Plutonium

 

Properties of Plutonium

Symbol Pu
Atomic number 94
Atomic weight 244
Group in periodic table IIIb
Boiling point 5,850°F (3,232°C)
Melting point 1,183.1°F (639.5°C)
Specific gravity 19.84

                                                                                                                        Electron Configuration: [Rn]7s25f6

 

 

Overview

 

Plutonium will be with us for a long time, and not only because it has a radioactive half-life of 24,000 years and therefore is dangerous for more than 200,000 years. Plutonium will be with us because nuclear weapon states are deeply devoted to having it as a military presence, the global nuclear power establishment is deeply devoted to pushing it as the fuel of the future, and the personal and political opinions of scientists often carry more weight than their scientific opinions.

 

This emphasis on the military use of plutonium suggests that without the military applications, support for “peaceful uses” of plutonium 239 would be meager. Plutonium may be a nuclear weapons physicists’ dream (see sidebar), but the dreams of physicists do not always come true, as is evident in the case of the now defunct Superconducting Super Collider project of the 1980's.  

 

So while the pro-plutonium inertia is powerful, it is not omnipotent and the future of this element and other special nuclear weapons materials is not set in stone. As the debate continues to unfurl, it is important for people to know that this most secret of elements is the most complex metal in the periodic table; and its presence in deployed nuclear weapons threatens life as we know it.



 

Select an element from the periodic table.

Group

1

2

 

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Period

 

1

1
H

 

2
He

2

3
Li

4
Be

 

5
B

6
C

7
N

8
O

9
F

10
Ne

3

11
Na

12
Mg

 

13
Al

14
Si

15
P

16
S

17
Cl

18
Ar

4

19
K

20
Ca

 

21
Sc

22
Ti

23
V

24
Cr

25
Mn

26
Fe

27
Co

28
Ni

29
Cu

30
Zn

31
Ga

32
Ge

33
As

34
Se

35
Br

36
Kr

5

37
Rb

38
Sr

 

39
Y

40
Zr

41
Nb

42
Mo

43
Tc

44
Ru

45
Rh

46
Pd

47
Ag

48
Cd

49
In

50
Sn

51
Sb

52
Te

53
I

54
Xe

6

55
Cs

56
Ba

*

71
Lu

72
Hf

73
Ta

74
W

75
Re

76
Os

77
Ir

78
Pt

79
Au

80
Hg

81
Tl

82
Pb

83
Bi

84
Po

85
At

86
Rn

7

87
Fr

88
Ra

**

103
Lr

104
Rf

105
Db

106
Sg

107
Bh

108
Hs

109
Mt

110
Uun

111
Uuu

112
Uub

113
Uut

114
Uuq

115
Uup

116
Uuh

117
Uus

118
Uuo

 

 

*Lanthanoids

*

57
La

58
Ce

59
Pr

60
Nd

61
Pm

62
Sm

63
Eu

64
Gd

65
Tb

66
Dy

67
Ho

68
Er

69
Tm

70
Yb

 

 

**Actinoids

**

89
Ac

90
Th

91
Pa

92
U

93
Np

94
Pu

95
Am

96
Cm

97
Bk

98
Cf

99
Es

100
Fm

101
Md

102
No

 

 

 

Historical Aspect

 

Plutonium belongs to the class of elements called transuranic elements whose atomic number is higher than 92, the atomic number of uranium.  Plutonium, named after the planet Pluto, was the second transuranium element of the actinide series to be discovered in 1940 by Glenn Seaborg, Joseph Kennedy and Arthur Wahl, by deuteron bombardment of uranium in the 60-inch cyclotron at Berkeley, California.  Provided below is a short history of the discovery of Plutonium.

 

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Discovery of the Neutron (1932)

The story begins in 1932, with the discovery of the neutron by Sir James Chadwick, an English physicist.  Until 1932, the atom was known to consist of a positively charged nucleus surrounded by enough negatively charged electrons to make the atom electrically neutral. Most of the atom was empty space, with its mass concentrated in a tiny nucleus. The nucleus was thought to contain both protons and electrons because the proton (otherwise known as the hydrogen ion, H+) was the lightest known nucleus and because electrons were emitted by the nucleus in beta decay. In addition to the beta particles, certain radioactive nuclei emitted positively charged alpha particles and neutral gamma radiation. The symbols for these emissions are b - or –1e0, a 2+ or 24He2+, and 00g .

Twelve years earlier, Lord Ernest Rutherford, a pioneer in atomic structure, had postulated the existence of a neutral particle, with the approximate mass of a proton, that could result from the capture of an electron by a proton. This postulation stimulated a search for the particle. However, its electrical neutrality complicated the search because almost all experimental techniques of this period measured charged particles.

In 1928, a German physicist, Walter Bothe, and his student, Herbert Becker, took the initial step in the search. They bombarded beryllium with alpha particles emitted from polonium and found that it gave off a penetrating, electrically neutral radiation, which they interpreted to be high-energy gamma photons.

In 1932, Irene Joliot-Curie, one of Madame Curie’s daughters, and her husband, Frederic Joliot-Curie, decided to use their strong polonium alpha source to further investigate Bothe’s penetrating radiation. They found that this radiation ejected protons from a paraffin target. This discovery was amazing because photons have no mass. However, the Joliot-Curies interpreted the results as the action of photons on the hydrogen atoms in paraffin. They used the analogy of the Compton Effect, in which photons impinging on a metal surface eject electrons. The trouble was that the electron was 1,836 times lighter than the proton and, therefore, recoiled much more easily than the heavier proton after a collision with a gamma photon. We now know that gamma photons do not have enough energy to eject protons from paraffin

The Compton Effect

When James Chadwick reported to Lord Rutherford on the Joliot-Curies’ results, Lord Rutherford exclaimed, "I do not believe it!" Chadwick immediately repeated the experiments at the Cavendish Laboratory in Cambridge, England. He not only bombarded the hydrogen atoms in paraffin with the beryllium emissions, but also used helium, nitrogen, and other elements as targets. By comparing the energies of recoiling charged particles from different targets, he proved that the beryllium emissions contained a neutral component with a mass approximately equal to that of the proton. He called it the neutron in a paper published in the February 17, 1932, issue of Nature. In 1935, Sir James Chadwick received the Nobel Prize in physics for this work. It is interesting to note that the Joliot-Curies’ misinterpretation of their results cost them the Nobel Prize. (Not to worry; in 1935, they received the Nobel Prize in chemistry for their discovery of artificial radioactivity.)

Chadwick's Apparatus

The search was over. Chadwick had found a new elementary particle, the third basic component of the nucleus. It increased the mass of elements without adding electrical charge. Two protons and 2 neutrons made a helium nucleus while 92 protons and 146 (or 143) neutrons made uranium, the heaviest known element. This not only changed our view of the nucleus, but also provided a new, relatively inexpensive means of probing the nucleus. Because the neutron was relatively massive but neutral, it was scarcely affected by the cloud of electrons surrounding the nucleus or by the positive electrical barrier of the nucleus itself; thus it could penetrate the nucleus of any element.

 

Twelve years earlier, Lord Ernest Rutherford, a pioneer in atomic structure, had postulated the existence of a neutral particle, with the approximate mass of a proton, that could result from the capture of an electron by a proton. This postulation stimulated a search for the particle. However, its electrical neutrality complicated the search because almost all experimental techniques of this period measured charged particles.

In 1928, a German physicist, Walter Bothe, and his student, Herbert Becker, took the initial step in the search. They bombarded beryllium with alpha particles emitted from polonium and found that it gave off a penetrating, electrically neutral radiation, which they interpreted to be high-energy gamma photons.

Playing with Neutrons (1934-38)

In addition to the discovery of the neutron, 1932 was the year that the Joliot-Curies first created new radioactive isotopes of nitrogen and phosphorus by bombarding boron and aluminum with alpha particles. The announcement of artificial radioactivity created much excitement in the scientific community. In the case of aluminum, the initial reaction with alpha particles produced a radioactive isotope of phosphorus that then underwent positron emission to produce silicon-30.

 

27Al13 + 4He22+         --->       30P15 + 1n0

The new radioactive isotopes were separated from the target materials by radiochemical methods. Yields of the radioactive isotopes were small because most of the alpha particles were repelled by the positively charged nuclei.

 

In 1934, it occurred to Enrico Fermi, an Italian physicist, to use neutrons to produce radioactivity instead of alpha particles, which are repelled by the positive charge of the target nuclei. In Rome, his group obtained a strong radon/beryllium neutron source and began to bombard the elements in order of increasing atomic number, beginning with hydrogen. Bombardment of the first elements in the periodic chart produced no radioactivity, but finally a fluorine (Z = 9) target gave a radioactive product. In the next 3 years, the group identified 40 new radioactive isotopes. This work was important to the advancement of nuclear theory and provided radioactive tracers for practically all of the elements. The use of these tracers would later revolutionize chemical and biological techniques

 

The group observed that when the target nuclei absorbed neutrons, they emitted particles (alphas, betas, positrons, or protons) as well as energy, in the form of gamma radiation. Thus, these nuclear reactions produced isotopes of elements in the neighborhood of the target element. When Fermi's group reached the heaviest known element, uranium, they expected that neutron bombardment would produce transuranic elements (new elements heavier than uranium) with properties similar to rhenium, osmium, iridium, and platinum. Beta radiation from the products and an absence of products that could be assigned to elements of atomic number between lead and uranium validated their hypothesis. Thus, the products were assumed to be transuranium elements.

In 1935, Otto Hahn, Lise Meitner, and Fritz Strassmann, in Berlin, confirmed the uranium experiments of Fermi's group and also identified the presence of U-239 as a beta emitter with a half-life of 23 minutes. The Joliot-Curies also confirmed Fermi’s work and, in 1938, identified a 3.5-hour radioactive isotope that had the chemical properties of lanthanum, an element with an atomic number much lower than that of uranium. They did not realize that it was, indeed, La141, a fission product. Another Nobel Prize blown!

These results indicated that the nuclear reactions were complex and that the Italians’ speculation of transuranium products might not have been entirely correct. Furthermore, in 1934, Ida Noddack (a German chemist who, with her husband Walter, had discovered the element rhenium) had warned Fermi’s group to compare the chemistry of the "new" transuranium elements with all known elements, not just those in the immediate neighborhood of uranium. Noddack suggested that "when heavy nuclei are bombarded by neutrons, it is conceivable that the nucleus breaks up into several large fragments, which would, of course, be isotopes of known elements, but would not be neighbors." The physics community ignored her warning, and she herself did not follow up with experiments.

The Italian group made one more important discovery in 1934. They found, by chance and intelligent observation, that neutrons passed through a paraffin block before reaching the target element were more effective in producing nuclear reactions than those emerging directly from the neutron source. Fermi concluded that the neutrons were slowed by elastic collisions within the paraffin and that these slow neutrons were more effective than faster ones in producing certain nuclear reactions.

It is ironic that in 1938, while Fermi was accepting his Nobel prize in Sweden, in Berlin, Hahn and Strassmann were discovering nuclear fission. This work clarified the mysterious results obtained from neutron bombardment of uranium and was the genesis of the atomic bomb. It is interesting to reflect on what world history might have been had the Italians recognized uranium fission in 1934.

The Discovery of Fission (1938)

By 1938, Hahn, Strassmann, and Meitner had identified at least 10 radioactive products resulting from the neutron bombardment of uranium, many more than Fermi’s group had observed initially. They assumed that these substances were new transuranic elements or isotopes of uranium. The Joliot-Curies had also performed this experiment and thought that they had observed thorium and actinium (elements below, not beyond, uranium in the periodic chart). These differences with Fermi’s results led both groups to continue their investigations.

 

Early in December 1938, Hahn and Strassmann thought that they had established the nuclear reactions that yielded the products observed by the Joliot-Curies. Presumably, isotopes of radium produced by the initial neutron bombardment of uranium decayed to thorium and actinium. To be absolutely certain, Hahn and Strassmann decided to identify the ‘radium’ isotopes by chemical means. (The chemical separation is shown below.) The suspected radioisotope of 'radium' is indicated as 'Ra'. Since radium and barium are group IIA elements, having the same chemical properties, barium was added as a carrier to facilitate the chemical isolation of the small amounts of the suspected 'radium'.

The final step in this procedure was a fractional crystallization to separate the barium carrier from the suspected 'radium'. Hahn and Strassmann were unable to separate the radioactivity of the 'Ra' from that of the barium fractions and thus confirmed that one of the products of neutron bombardment of uranium was not neighboring radium, but distant barium. Could Ida Noddack’s hypothesis be correct? Had the uranium atoms split into fragments of approximately equal mass?

Hahn and Strassmann repeated the experiment numerous times and were never able to isolate the ‘radium’ from barium. They reported their results as follows: "As chemists, we must actually say the new particles do not behave like radium but, in fact, like barium; as nuclear physicists, we cannot make this conclusion, which is in conflict with all experience in nuclear physics." Hahn, the chemist, was reluctant to go against the ideas of respected nuclear physicists, despite clear chemical evidence of barium

Hahn then turned to his colleague, Lise Meitner, for an explanation. Meitner was a physicist who had recently fled to Sweden to escape the Nazi regime. During Christmas 1939, Meitner and her nephew Otto Frisch, a physicist also banished from Germany, read Hahn’s letters reporting, with amazement, the barium results. As Meitner and Frisch searched for an explanation, it dawned on them that when the uranium nucleus absorbs a neutron, it might become unstable and split into two particles of approximately equal mass (e.g., barium and krypton). They used Bohr’s earlier model, which treated the nucleus as a large drop of liquid. In this model, the absorption of a neutron could cause the uranium nucleus to become unstable and divide into two smaller drops. If this division takes place, the resulting drops (nuclear fragments) would be repelled by their respective positive charges. This process, termed fission by Meitner and Frisch, would create a large amount of energy, as well as additional neutrons. They calculated the energy associated with pushing the two positively charged nuclear fragments apart to be approximately 200 million electron volts (MeV) per uranium atom. By comparison, the most energetic chemical reactions release approximately 5 eV per atom.

From where was the energy required to separate the uranium nucleus coming? Existing data on the masses of the elements showed that the sum of the masses of the smaller product nuclei was less than the mass of uranium. Meitner used Einstein’s famous E = mc2 equation to calculate the energy associated with this mass difference (nuclear binding energy) and the energy associated with pushing the two fission fragments apart. His calculations revealed that energy equivalent to the mass difference was equal to 200 MeV! Frisch quickly returned to his laboratory at the Neils Bohr Institute in Copenhagen to experimentally verify this hypothesis.

The scientific community was excited by the discovery of this new source of energy. When Frisch presented his explanation to Bohr, Bohr is said to have struck his forehead and exclaimed, "What idiots we have all been! Oh but this is wonderful! It just must be!" Energy from fission was at least eight orders of magnitude greater than the energy released in chemical reactions involving an equal number of atoms.

Furthermore, fission raised the possibility of a nuclear chain reaction. Radioactive fission products have excess neutrons, compared with stable (nonradioactive) nuclei of the same mass number. They can eliminate the excess neutrons by beta decay, a slow process that increases the atomic number by one, or by direct neutron emission. In the latter case, the secondary neutrons may be used to produce new fissions and if a sufficient number of fissions occur, they will produce enough neutrons to sustain a chain reaction.

It was theorized that if such a chain reaction could be controlled, one would have a tremendous source of power. Scientists began to speculate on the potential of nuclear power plants. But if the chain reaction were to occur in a violent, uncontrolled manner, one would have an atomic bomb. Scientists also began to worry about the potential for nuclear weapons. It is interesting to note that the science fiction writer H. G. Wells had written about the potential of nuclear power in "The World Set Free", published in 1914.

One scientist, Leo Szilard, began to worry about the potential for nuclear weapons in the face of the growing hostility of Germany and the likelihood of massive, technically based warfare.

Szilard, the Hungarian expatriate physicist, deduced that the discovery of fission would lead either Germany or the Allies to high energy weapons.  He sought an audience with President Franklin Roosevelt but he was rebuffed.  But Szilard got assurance that a letter from Einstein would be delivered to Roosevelt.  Szilard went to Einstein, who prepared the letter shown below.slide10.gif (16274 bytes)

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One final question remained concerning the fission of uranium. In 1935, Arthur Dempster, a Canadian-born chemist working at the University of Chicago, used a mass spectrometer to find a heretofore unknown isotope of mass 235 hidden in natural uranium, the overall mass of which was approximately 238. Three years later, Alfred Nier used a mass spectrometer to measure the ratio of U-235 to U-238 in natural uranium as 1:139, which meant that U-235 was present to the extent of 0.7%.

Meanwhile, at Princeton University, Niels Bohr and John Wheeler theorized that U-238 only underwent fission with fast, high-energy neutrons, while slow, thermal neutrons would produce fission only in U-235. John Dunning, a physicist working with Fermi at Columbia University, decided to test the Bohr-Wheeler theory and made a deal with Nier to obtain a few micrograms of pure U-235. Using this small sample, Dunning’s group proved the Bohr-Wheeler hypothesis. Until this discovery, the lighter isotope was not considered of importance in nuclear reactions because of its low concentration. Now, to make a uranium bomb, it would be necessary to separate U-235 from U-238, which is a difficult task. Physical, not chemical, methods have to be used for the separation, since the two isotopes have identical chemical properties.

The Discovery and Isolation of Plutonium

 

The cyclotron at the University of California, Berkeley
 

The transuranium element, plutonium, was the first synthetic element to be produced on a large scale. In addition to being fissionable, it has interesting and unusual chemical and metallurgical properties. The story of its discovery and isolation is among the most fascinating in the history of science. The distinction between discovery and isolation is significant. Discovery refers to the first nuclear and chemical proof of the existence of atoms of a new element, while isolation is the procurement of the first weighable amount in pure form. There was often a considerable amount of time between the discovery and isolation of the transuranium elements.

 

The search for transuranium elements initiated by Fermi continued unabated. In the spring of 1940, Edward McMillan and Philip Abelson, working at the University of California Berkeley (UCB), exposed a natural uranium target to 12 Mev neutrons produced by bombarding Be with cyclotron-accelerated deuterons (2H1).


238U92 + 1n0 --> 239U92 + g


239U92 t ˝ = 23.5 min.--> 239Np93 + b -

McMillan and Abelson were able to prove that the chemical and nuclear properties of the product of the U-239 beta decay were unique and thus discovered the first transuranium element, atomic number 93. It was named neptunium (Np) after Neptune, the planet immediately beyond Uranus. However, the first isolation of Np did not occur until October 1944.

(Courtesy of the University of California, Berkeley)

In the summer of 1940, Glen Seaborg, Arthur Wahl, and Joseph Kennedy, a group of chemists at UCB, began a search for the next transuranium element, 94, which they thought to be a decay product (daughter) of Np-239.


239Np93 t ˝ = 2.3 days -1ß - --> 239?94

Continuing the search for element 94 in the winter of 1941, they bombarded uranium oxide with 16 Mev deuterons from the Berkeley cyclotron. They chemically identified another isotope of neptunium, Np-238, which decayed by beta emission to an isotope of element 94 (plutonium) that then emitted alpha particles.

238U92 + 2H1 -->   238Np93 + 21n0

 

238Np93 t 1/2 = 2.12 days -->  238Pu94 + b -

 

238Pu94 t1/2 = 90 years --> a 2+ + 236U92

 

The Pu alpha particle emitter was separated chemically from U, Np, and other reaction products and oxidized with potassium peroxydisulfate, K2S2O8, to a fluoride-soluble oxidation state. The other products of this neutron bombardment did not undergo oxidation with K2S2O8 and thus remained insoluble. The alpha activity (400 counts per minute) used to trace Pu was concentrated in the resulting solution. The Pu in solution was then reduced to a lower oxidation state with SO2 and precipitated as a fluoride using Ce3+ and La3+ as carriers. This chemistry, based on oxidation, reduction, and precipitation reactions, would later prove the basis for the large-scale production of plutonium. The alpha particle energy and activity was unique and thus indicated a new element. At this time, Seaborg and Wahl could not identify which Pu isotope produced the alpha activity. It was later identified as Pu-238.

Plutonium solutions
(Courtesy of the University of California, Berkeley)

Seaborg remarked, "During this time, a great deal was learned about the chemistry of plutonium. It was established that plutonium in its higher oxidation state was not carried by lanthanum fluoride or cerium fluoride, in contrast to plutonium in the lower state, which was quantitatively coprecipitated with these compounds. The lower state could be oxidized to the higher state with oxidizing agents such as persulfate, dichromate, permanganate, or periodate ions, and then reduced by treatment with sulfur dioxide or bromide ion to the lower oxidation state."

Later in the spring of 1941, another more important isotope of plutonium, Pu-239, was produced using neutrons from the Berkeley cyclotron to target a uranium compound surrounded by paraffin. As Fermi’s group had discovered, the paraffin acted as a moderator to slow the neutrons and thus increase the chances of interaction with the target. This new Pu isotope, an alpha emitter with a half life of about 24,000 years, was separated from other reaction products using the same chemistry as that used to isolate Pu-238. However, the longer half-life of Pu-239 reduced its activity, making it more difficult to detect than Pu-238.

238U92 + 1n0 -->   239U92 + g

 

239U92 t 1/2 = 23.5 min. --> 239Np93 + b -

 

239Np93 t 1/2 = 2.35 days -->  239Pu94 + b -

 

239Pu93 t 1/2 = 24,110 yrs. --> 235U92 + a 2+

 

In March 1941, Seaborg’s group irradiated a sample estimated to contain 0.25 mg of Pu-239 surrounded by paraffin with neutrons produced in the cyclotron. Under these conditions, this isotope appeared to undergo fission. When the Pu was replaced with a sample containing approximately 0.5 mg U-235, the other known fissionable material, neutron-induced fission was also observed, but at a rate approximately half that of Pu-239. This discovery raised the possibility of using a controlled chain reaction to produce quantities of Pu-239 sufficient for nuclear weapons. The product Pu-239 would have to be separated from the unreacted uranium and fission products by chemical means. It now became important to investigate the chemistry of plutonium to develop large-scale separation procedures.

However, in the summer of 1942, the cyclotron was the only means of producing plutonium, and the amounts produced were so small that they could not be seen or weighed with existing balances. Calculations showed that long periods of neutron bombardment of uranium in the cyclotron would produce only a few micrograms of Pu-239, much less than that normally required to determine the physical and chemical properties of a new element. The preparation and measurement of such small quantities of plutonium required the development of "ultramicrochemical" techniques and equipment.

The first weighing of a plutonium compound occurred in September of 1942, when 2.77 mg of PuO2 was placed on a balance especially designed for small masses and calibrated with platinum wire. Liquid volumes in the range of 0.10 to 10-5 mL were delivered with an error of less than one percent using calibrated capillary pipettes. Glassware, such as beakers and test tubes, was made from capillary tubing and handled under a microscope with micromanipulators. In November 1943, the first pure plutonium metal was prepared by reducing 35 mg of PuF4 with barium metal at 1,400o C. The plutonium metal appeared as silvery globules weighing about 3 mg each and having an estimated density of 16 g/mL.

Although the Pu-239 isotope had the potential to be fissionable material for bombs or power generation, realization of this potential required larger amounts of this isotope. Large-scale production of Pu-239 required a controlled nuclear chain reaction of uranium, a feat that would soon be achieved by Enrico Fermi and Leo Szilard in Chicago.

Chain Reaction (December 2, 1942)

By early 1942, it was known that the two naturally occurring isotopes of uranium reacted with neutrons as follows:

235U92 +   1n0    -->   fission products + (2.5)1n0   +  200 MeV Energy

238U92   1n0    -->  239U92   

239U92       -->  239Np93   +    ß-1       t1/2=23.5 min. 

239Np93     --->  239Pu94+   ß-1         t1/2=2.33 days

Each U-235 that undergoes fission produces an average of 2.5 neutrons. In contrast, some U-238 nuclei capture neutrons, become U-239, and subsequently emit two beta particles to produce Pu-239. The times are half-lives for the successive beta emissions.

The first generations of a nuclear chain reaction

The answers to two questions were critical to the production of plutonium for atomic bombs. Is it possible, using natural uranium (99.3% U-238 and 0.7% U-235), to achieve a controlled chain reaction on a large scale? If so, some of the excess neutrons produced by the fission of U-235 would be absorbed by U-238 and produce fissionable Pu-239. The second question concerned how to separate (in a reasonable period of time) the relatively small quantities of Pu-239 from the unreacted uranium and the highly radioactive fission-product elements.

Although fission had been observed on a small scale in many laboratories, noone had carried out a controlled chain reaction. Fermi thought that he could achieve a controlled chain reaction using natural uranium. He had started this work with Leo Szilard at Columbia University, but moved to the University of Chicago in early 1942. The nuclear reactor, called a pile, was composed of 80,590 lbs. of uranium oxide, 12,400 lbs. of uranium, and 771,000 lbs. of ultrapure graphite arranged in a manner to maximize neutron propagation. On December 2, 1942, the first controlled nuclear chain reaction occurred in a squash court under the football field at the University of Chicago. At around 2:20 p.m. the reactor went critical; that is, it produced one neutron for every neutron absorbed by the uranium nuclei. Fermi allowed the reaction to continue for the next 27 minutes before inserting neutron-absorbing cadmium control rods. In addition to excess neutrons and energy, the pile also produced a small amount of Pu-239, the other known fissionable material.

The achievement of the first sustained nuclear reaction was the beginning of a new age in nuclear physics and the study of the atom. Humankind could now use the tremendous potential energy contained in the nucleus of the atom. However, while a controlled chain reaction was achieved with natural uranium, it would be necessary to separate U-235 from U-238 to build a uranium bomb. On December 28, 1942, upon reviewing a report from his advisors, President Roosevelt recommended building full-scale plants to produce both U-235 and Pu-239. This changed the effort to develop nuclear weapons from experimental work in academic laboratories administered by the U.S. Office of Scientific Research and Development to a huge effort by private industry. This work, supervised by the U.S. Army Corps of Engineers, was codenamed the Manhattan Project. It spread throughout the entire United States, with the facilities for uranium and plutonium production being located at Oak Ridge, Tennessee, and Hanford, Washington, respectively. Work on plutonium production continued at the University of Chicago, at what became known as the Metallurgical Laboratory or Met Lab. A new laboratory at Los Alamos, New Mexico, became the focal point for development of the uranium and plutonium bombs.

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            Plutonium also exists in trace quantities in naturally occurring uranium ores. It is formed in much the same manner as neptunium, by irradiation of natural uranium with the neutrons which are present.

Plutonium has assumed the position of dominant importance among the trasuranium elements because of its successful use as an explosive ingredient in nuclear weapons and the place which it holds as a key material in the development of industrial use of nuclear power. One kilogram is equivalent to about 22 million kilowatt hours of heat energy. The complete detonation of a kilogram of plutonium produces an explosion equal to about 20,000 tons of chemical explosive. Its importance depends on the nuclear property of being readily fissionable with neutrons and its availability in quantity. The world's nuclear-power reactors are now producing about 20,000 kg of plutonium/yr. By 1982 it was estimated that about 300,000 kg had accumulated. The various nuclear applications of plutonium are well known. 238Pu has been used in the Apollo lunar missions to power seismic and other equipment on the lunar surface. As with neptunium and uranium, plutonium metal can be prepared by reduction of the trifluoride with alkaline-earth metals.

Plutonium creation

Plutonium is created when non-fissionable uranium (U-238) absorbs a neutron released by the fission process. In the first instance this produces uranium-239 which quickly sheds an electron to turn into neptunium-239, rapidly followed by the loss of a further electron which results in the creation of plutonium-239 (Pu-239), see figure 1. Plutonium-239 is a fissile material so, as the chain reaction in a reactor continues, some of the Pu-239 splits, releasing energy. Up to about half the energy generated by a uranium-fuelled nuclear reactor is produced from plutonium fission.

 

Not all of the plutonium undergoes fission. A Pu-239 atom which has escaped fission may absorb a second neutron and another isotope of plutonium, Pu-240, which has different physical properties from Pu-239, is then produced.   After some time, commonly about three years, the reduction in fissionable uranium content and the accumulation of the products of fission make the fuel unsuitable for continued use. Spent nuclear fuel is replaced with new fuel, much as the spent battery in a torch is replaced with a new one. The spent fuel still has great energy potential. In addition to unused uranium, it contains Pu-239 which has not yet been fissioned.

                       

The most important isotope of plutonium is Pu-239. It's virtually nonexistent in nature. It is produced by bombarding uranium-238 with slow neutrons. This forms neptunium-239, which in turn emits a beta particle and forms plutonium-239. Plutonium-239's principal mode of decay is alpha decay. Various sources give slightly different figures for the half-life. The values found include 24,360, 24,400, 24,110, and 24,000 years. None of theses measurements agree. It is because there are many factors that can affect the accuracy of this measurement. Plutonium-239 is produced artificially, and every time it is produced, it is mixed with varying amounts of other isotopes, notably plutonium-240, plutonium-241 and plutonium-242. Since all the isotopes have nearly the same chemical characteristics, it is very difficult to separate isotopes from each other by chemical techniques. This means, it is virtually impossible to study the properties of pure Plutonium-239. Therefore, the results might be the average half-life of it being mixed with a small amount of the other isotopes. And there will be a slight difference in the density and purity of it every time it is being produced, depending upon the amount of reactants used in the process of its production. In addition, a little spontaneous fission occurs in most plutonium isotopes. So while some of the Plutonium-239 atoms are undergoing decay, a small number of them are splitting into less-massive nuclei. The rate of fission is not a constant.

Physical, Nuclear, and Chemical, Properties of Plutonium

Plutonium-239 is one of the two fissile materials used for the production of nuclear weapons and in some nuclear reactors as a source of energy. The other fissile material is uranium-235. Plutonium-239 is virtually nonexistent in nature. It is made by bombarding uranium-238 with neutrons in a nuclear reactor. Uranium-238 is present in quantity in most reactor fuel; hence plutonium-239 is continuously made in these reactors. Since plutonium-239 can itself be split by neutrons to release energy, plutonium-239 provides a portion of the energy generation in a nuclear reactor.

The physical properties of plutonium metal are summarized in Table 1.

TABLE 1.

Physical Characteristics of Plutonium Metal

Color:

 

 

 

 

Silver

Melting point:

641 deg. C

Boiling point:

3232 deg. C

Density:

16 to 20 grams/cubic centimeter

Nuclear Properties of Plutonium

Only two plutonium isotopes have commercial and military applications. Plutonium-238, which is made in nuclear reactors from neptunium-237, is used to make compact thermoelectric generators; plutonium-239 is used for nuclear weapons and for energy; plutonium-241, although fissile, (see next paragraph) is impractical both as a nuclear fuel and a material for nuclear warheads. Some of the reasons are far higher cost , shorter half-life, and higher radioactivity than plutonium-239. Isotopes of plutonium with mass numbers 240 through 242 are made along with plutonium-239 in nuclear reactors, but they are contaminants with no commercial applications. I will focus on civilian and military plutonium (which are interchangeable in practice--see Table 5), which consist mainly of plutonium-239 mixed with varying amounts of other isotopes, notably plutonium-240, -241, and -242.

 

Plutonium-239 and plutonium-241 are fissile materials. This means that they can be split by both slow (ideally zero-energy) and fast neutrons into two new nuclei (with the concomitant release of energy) and more neutrons. Each fission of plutonium-239 resulting from a slow neutron absorption results in the production of a little more than two neutrons on the average. If at least one of these neutrons, on average, splits another plutonium nucleus, a sustained chain reaction is achieved.

 

The even isotopes, plutonium-238, -240, and -242 are not fissile but yet aare fissionable--that is, they can only be split by high energy neutrons. Generally, fissionable but non-fissile isotopes cannot sustain chain reactions; plutonium-240 is an exception to that rule.

 

The minimum amount of material necessary to sustain a chain reaction is called the critical mass. A supercritical mass is bigger than a critical mass, and is capable of achieving a growing chain reaction where the amount of energy released increases with time.   The amount of material necessary to achieve a critical mass depends on the geometry and the density of the material, among other factors. The critical mass of a bare sphere of plutonium-239 metal is about 10 kilograms. It can be considerably lowered in various ways.   The amount of plutonium used in fission weapons is in the 3 to 5 kilograms range.  Nuclear weapons with a destructive power of 1 kiloton can be built with as little as 1 kilogram of weapon grade plutonium. The smallest theoretical critical mass of plutonium-239 is only a few hundred grams.

 

In contrast to nuclear weapons, nuclear reactors are designed to release energy in a sustained fashion over a long period of time. This means that the chain reaction must be controlled--that is, the number of neutrons produced needs to equal the number of neutrons absorbed. This balance is achieved by ensuring that each fission produces exactly one other fission.

 

All isotopes of plutonium are radioactive, but they have widely varying half-lives. The half-life is the time it takes for half the atoms of an element to decay. For instance, plutonium-239 has a half-life of 24, 110 years while plutonium-241 has a half-life of 14.4 years. The various isotopes also have different principal decay modes. The isotopes present in commercial or military plutonium-239 are plutonium-240, -241, and -242. Table 2 shows a summary of the radiological properties of five plutonium isotopes.

 

The isotopes of plutonium that are relevant to the nuclear and commercial industries decay by the emission of alpha particles, beta particles, or spontaneous fission. Gamma radiation, which is penetrating electromagnetic radiation, is often associated with alpha and beta decays.

 

TABLE 2.

Radiological Properties of Important Plutonium Isotopes

Pu-238

Pu-239

Pu-240

Pu-241

Pu-242

Half-life(in years)

87.74

24,110

6537

14.4

376,000

Specific activity(curies/gram)

17.3

.063

.23

104

.004

Principal decay mode

alpha

alpha

alpha
some spontaneous fission(a)

Beta

Alpha

Decay energy(MeV)

5.593

5.244

5.255

.021

4.983

Radiological hazards

alpha, weak gamma

alpha, weak gamma

alpha, weak gamma

beta, weak gamma(b)

alpha, weak gamma


a) Source of neutrons causing added radiation dose to workers in nuclear facilities. A little spontaneous fission occurs in most plutonium isotopes.
b) Plutonium-241 decays into Americium-241, which is an intense gamma-emitter.

 

Half-Life of Plutonium

 

During radioactive decay, the time in which the strength of a radioactive source decays to half its original value. In theory, the decay process is never complete and there is always some residual radioactivity. For this reason, the half-life of a radioactive isotope is measured, rather than the total decay time. It may vary from millionths of a second to billions of years.

 

Radioactive substances decay exponentially; thus the time taken for the first 50% of the isotope to decay will be the same as the time taken by the next 25%, and by the 12.5% after that, and so on.

For example, carbon-14 takes about 5,730 years for half the material to decay; another 5,730 for half of the remaining half to decay; then 5,730 years for half of that remaining half to decay, and so on. Plutonium-239, one of the most toxic of all radioactive substances, has a half-life of about 24,000 years.

 

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Rutherford's Discovery of Half-Life - Transcript of Ernest Rutherford's paper describing his discovery of the half life of radioactive materials. The paper entitled A Radioactive Substance emitted from Thorium Compounds first appeared in the Philosophical Magazine in January 1900. The reproduction of it is complete with several diagrams and all the relevant equations.

A Radioactive Substance emitted from Thorium
Compounds

by E. RUTHERFORD, M.A., B.SC.,
Macdonald Professor of Physics, McGill University, Montreal


From the Philosophical Magazine for January 1900, ser. 5, xlix, pp. 1-14
Communicated by Professor J. J. Thomson, F.R.S.


Note: the page numbering is take from "The Collected Works of Lord Rutherford of Nelson," vol. I

220

It has been shown by Schmidt* that thorium compounds give out a type of radiation similar in its photographic and electrical actions to uranium and Röntgen radiation. In addition to this ordinary radiation, I have found that thorium compounds continuously emit radioactive particles of some kind, which retain their radioactive powers for several minutes. This 'emanation', as it will be termed for shortness, has the power of ionizing the gas in its neighbourhood and of passing through thin layers of metals, and, with great ease, through considerable thicknesses of paper.

 

In order to make clear the evidence of the existence of a radioactive emanation, an account will first be given of the anomalous behaviour of thorium compounds compared with those of uranium. Thorium oxide has been employed in most of the experiments, as it exhibits the 'emanation' property to a greater degree than the other compounds; but what is true for the oxide is also true, but to a less extent, of the other thorium compounds examined, viz. the nitrate, sulphate, acetate, and oxalate.

 

In a previous paper** the author has shown that the radiation from thorium is of a more penetrating character than the radiation from uranium. Attention was also directed to the inconstancy of thorium as a source of radiation. Owens*** has investigated in more detail the radiation from thorium compounds. He has shown that the radiations from the different compounds are of the same kind, and, with the exception of thorium oxide in thick layers, approximately homogeneous in character.

 

The intensity of thoriurn radiation, when examined by means of the electrical discharge produced, is found to be very variable; and this inconstancy is due to slow currents of air produced in an open room. When the apparatus is placed in a closed vessel, to do away with air currcnts, the intensity is found to be practically constant. The sensitiveness of thorium oxide to

221

slight currents of air is very remarkable. The movement of the air caused by the opening or closing of a door at the end of the room opposite to where the apparatus is placed, is often sufficient to considerably diminish the rate of discharge. In this respect thorium compounds differ from those of uranium, which are not appreciably affected by slight currents of air. Another anomaly that thorium compounds exhibit is the ease with which the radiation apparently passes through paper. The following table is an example of the way the rate of leak between two parallel plates, one of which is covered with a thick layer of thorium oxide, varies with the number of layers of ordinary foolscap paper placed over the radioactive substance.

 

TABLE I

Thickness of each Layer of Paper = 0.008 cm. 50 volts between plates

Number of Layers of
Paper

Rate of Disharge

0

1

1

0.74

2

0.74

5

0.72

10

0.67

20

0.55

 

In the above table the rate of leak with the thorium oxide uncovered is taken as unity. It will be observed that the first layer reduced the rate of leak to 0.74, and the five succeeding layers produce very little effect. The action, however, is quite different if we use a thin* layer of thorium oxide. With one layer of paper, the rate of discharge is then reduced to less than 1/16 of its value. At first sight it appears as if the thorium oxide gave out two types of radiation, one of which is readily absorbed by paper, and the other to only a slight extent. If we examine the radiation given out by

 

TABLE II

Thickness of Paper = 0.0027 cm.

Number of Layers of Thin Paper

Rate of Discharge

0

1

1

0.37

2

0.16

3

0.08

 

* To produce a thin layer on a plate, the oxide, in the form of a fine powder, was sprinkled by means of a fine gauze, so as to cover the plate to a very small depth. By a thick layer is meant a layer of oxide over a millimetre in thickness.

222

a thin layer of thorium oxide, by placing successive layers of thin paper upon it, we find the radiation is approximately homogeneous, as the Table II (p. 221) shows.

 

The rate of leak of the bare salt is taken as unity. If the radiation is of one kind, we should expect the rate of discharge (which is proportional to the intensity of the radiation) to diminish in geometrical progression with the addition of equal thicknesses of paper. The above figures show that this is approximately the case. With a thick layer of thorium oxide, by adding successive layers of thin paper, we find the rate of discharge gradually diminish, till after a few layers it reaches a constant value. The amount that is cut off by the first layer of foolscap paper (see Table I) is of the same kind of radiation as that which is emitted by a thin layer of oxide.

On directing a slight current of air between the test plates, the rate of discharge due to a thick layer of thorium oxide is greatly diminished. The amount of diminution is to a great extent independent of the electromotive force acting between the plates. Under similar conditions with uranium, the rate of leak is not appreciably affected. With a thin layer of oxide, the diminution of the rate of leak is small; but with a thick layer of oxide, the rate of leak may be reduced to less than one-third of its previous value. If two thicknesses of foolscap paper are placed over the thorium oxide, the resulting rate of leak between the plates may be diminished to less than 1/10 of its value by a slight continuous blast of air from a gasometer or bellows.

 

The phenomena exhibited by thorium compounds receive a complete explanation if we suppose that, in addition to the ordinary radiation, a large number of radioactive particles are given out from the mass of the active substance. This 'emanation' can pass through considerable thicknesses of paper. The radioactive particles emitted by the thorium compounds gradually diffuse through the gas in its neighbourhood and become centres of ionization throughout the gas. The fact that the effect of air currents is only observed to a slight extent with thin layers of thorium oxide is due to the preponderance, in that case, of the rate of leak due to the ordinary radiation over that due to the emanation. With a thick layer of thorium oxide, the rate of leak due to the ordinary radiation is practically that due to a thin surface layer, as the radiation can only penetrate a short distance through the salt. On the other hand, the 'emanation' is able to diffuse from a distance of several millimetres below the surface of the compound, and the rate of leak due to it becomes much greater than that due to the radiation alone.

 

The explanation of the action of slight currents of air is clear on the 'emanation' theory. Since the radioactive particles are not affected by an electrical field, extremely minute motions of air, if continuous, remove many of the radioactive centres from between the plates. It will be shown shortly that the emanation continues to ionize the gas in its neighbourhood for several minutes, so that the removal of the particles from between the plates diminishes the rate of discharge between the plates.

223

Duration of the Radioactivity of the Emanation

 

The emanation gradually loses its radioactive power. The following method was adopted to determine the rate of decay of the intensity of the radiation of the radioactive particles emitted by thorium oxide. A thick layer of thorium oxide was enclosed in a narrow rectangular paper vessel A (Fig. 1), made up of two thicknesses of foolscap paper. The paper cut off the regular radiation almost entirely, but allowed the emanation to pass through. The thorium thus enclosed was placed inside a long metal tube B.

 

One end of the tube was connected to a large insulated cylindrical vessel C, which had a number of small holes in the end for the passage of air. Inside C was fixed an insulated electrode, D, connected with one pair of quadrants of a Thomson electrometer. The cylinder, C, was connected to one terminal of a battery of 100 volts, the other terminal of which was connected to earth.

 

A slow current of air from an aspirator or gasometer, which had been freed from dust by its passage through a plug of cotton-wool, was passed through the apparatus. The current of air, in its passage by the thorium oxide, carried away the radioactive particles with it, and these were gradually conveyed into the large cylinder C. The electrometer needle showed no sign of movement until the radioactive particles were carried into C. In consequence of the ionization of the gas in the cylinder by the radioactive particles, a current passed between the electrodes C and D. The value of the current was the same whether C was connected with the positive or negative pole of the battery. When the current of air had been flowing for some minutes, the current between C and D reached a constant value. The flow of air was then stopped, and the rate of leak between C and D observed at regular intervals. It was found that the current between C and D persisted for over ten minutes.

224

The following is a series of observations.

TABLE III
Potential Difference 100 volts

Time in seconds

Current

0

1

28

0.69

62

0.51

118

0.23

155

0.14

210

0.067

272

0.041

360

0.018

 

Fig. 2, curve A, shows the relation existing between the current through the gas and the time. The current, just before the flow of air is stopped, is taken as unity. It will be observed that the current through the gas diminishes in a geometrical progression with the time. It can easily be shown, by the theory of ionization, that the current through the gas is proportional to the intensity of the radiation emitted by the radioactive particles. We therefore see that the intensity of the radiation given out by the radioactive particles falls off in a geometrical progression with the time. The result shows that the intensity of the radiation has fallen to one-half its value after an interval of about one

225

minute. The rate of leak due to the emanation was too small for measurement after an interval of ten minutes.

If the ionized gas had been produced from a uranium compound, the duration of the conductivity, for voltages such as were used, would only have been a fraction of a second.

 

The rate of decay of intensity is independent of the electromotive force acting on the gas. This shows that the radioactive particles are not destroyed by the electric field. The current through the gas at any particular instant, after stoppage of the flow of air, was found to be the same whether the electromotive force had been acting the whole time or just applied for the time of the test.

The current through the gas in the cylinder depends on the electromotive force in the same way as the current through a gas made conducting by Röntgen rays. The current at first increases nearly in proportion to the electromotive force, but soon reaches an approximate 'saturation' value.

 

The duration of the radioactivity was also tested by another method. The paper vessel containing the thorium oxide was placed inside a long brass cylinder over 200 cm. in length. A slow current of air (with a velocity of about 2 cm. per sec. along the tube) was passed over the thorium oxide along the tube, and then between two insulated concentric cylinders. The rate of leak between the two concentric cylinders (potential difference 270 volts) was observed when the air had been passing sufficiently long to produce a steady state. The rates of leak were observed for varying positions of the thorium oxide along the tube. Knowing the velocity of the current of air along the tube, the time taken to carry the radioactive particles to the testing apparatus could be determined. In this way it was found that the rate of decay was about the same as determined by the first method, i.e. the intensity fell to half its value in about one minute.

 

In this apparatus experiments were also tried to see whether the radioactive particles moved in an electric field. The experiments on the effect of a current of air on the rate of discharge naturally suggest that possibly one of the ions was so large that it moved extremely slowly even in strong electric fields. The results obtained showed that the particles did not move with a greater velocity than 1/100,000 cm. per sec. for a potential gradient of one volt per centimetre; and it is probable that the partides do not move at all in an electric field. By blowing the emanation into an inductor, no evidence of any charge in the emanation could be detected. We may therefore conclude that the emanation is uncharged, and is not appreciably affected by an electric field.

 

Properties of the Emanation

 

The emanation passes through a plug of cotton-wool without any loss of its radioactive powers. It is also unaffected by bubbling through hot or cold water, weak or strong sulphuric acid. In this respect it acts like an ordinary gas.

226

An ion, on the other hand, is not able to pass through a plug of cotton-wool, or to bubble through water, without losing its charge.

The emanation is similar to uranium in its photographic and electrical actions. It can ionize the gas in its neighbourhood, and can affect a photographic plate in the dark after several days' exposure. Russell* has shown that the active agent in producing photographic action in the case of metals, paper, etc., is due to hydrogen peroxide. Hydrogen peroxide apparently has the power of passing in some way through considerable thicknesses of special substances, and in this respect the emanation resembles it. Hydrogen peroxide, however, does not ionize the gas in its neighbourhood. The action of hydrogen peroxide on the photographic plate is purely a chemical one; but it is the radiation from the emanation, and not the emanation itself, that produces ionizing and photographic actions.

 

The radioactive emanation passes through all metals if sufficiently thin. In order to make certain that the emanation passed through the material to be examined and did not diffuse round the edges, the radioactive substance was placed in a square groove of a thick lead plate. Two layers of paper were pasted tightly over the opening to cut off the regular radiation. The material to be tested was then firmly waxed down on the lead plate. The following numbers illustrate the effect of different metals. The rate of discharge, due to the emanation between two parallel plates 4 cm. apart, was observed.

 

Aluminium Foil, thickness = 0.0008 cm.

Number of Layers

Rate of Discharge

0

1

1

0.66

3

0.42

6

0.16

Cardboard, thickness 0.08 cm.

Layers

Rate of Discharge

0

1

1

0.40

2

0.21

 

The emanation passed readily through several thicknesses of gold- and silver-leaf. A plate of mica, thickness 0.006 cm., was completely impervious to the emanation.

 

When a thick layer of thorium oxide, covered over with several thicknesses of paper, is placed inside a closed vessel, the rate of discharge due to the emanation is small at first, bue gradually increases, until after a few minutes a steady state is reached.

* Proc. Roy. Soc., 1897.

227

These results are to be expected, for the emanation can only slowly diffuse through the paper and the surrounding air. A steady state is reached when the rate of loss of intensity due to the gradual decay of the radioactivity of the emanation is recompensed by the number of new radioactive centres supplied from the thorium compound.

Let n = number of ions produced per second by the radioactive particles between the plates.
Let q = number of ions supplied per second by the emanation diffusing from the thorium.

The rate of variation of the number of ions at any time t is given by

dn / dt = q - ln

where l is a constant.

 

The results given in Table III show that the rate of diminution of the number of ions is proportional to the number present.

Solving the equation, it is seen that

loge (q - ln) = - lt + A

where A is a constant.

When

t = 0, n = 0

therefore

A = loge q

Thus

n = (q / l) (1 - eŻlt)

With a large potential difference between the test plates the current i through the gas at any time is given by

i = ne

where e is the charge on an ion.

When a steady state is reached, dn / dt = 0; and the maximum number N of ions produced per second by the radioactive particles between the plates is given by

N = q / l

and the maximum current I is given by

I = Ne

Therefore

i / I = 1 - eŻlt

228

The current thus increases according to the same law as a current of electricity rises in a circuit of constant inductance.

This result is confirmed by an experiment on the rise of the current between two concentric cylinders. The thorium oxide enclosed in paper was placed inside the cylinder. A current of air was sent between the cylinders in order to remove the emanation as rapidly as it was formed. The current of air was then stopped and the current between the two cylinders observed, by means of an electrometer, for successive intervals after the current of air ceased. Table IV gives the results obtained.

 

TABLE IV
Length of cylinder = 30 cm.
Internal diameter outer cylinder = 5.5 cm
External diameter inner cylinder = 0.8 cm
100 volts between cylinders.

Time in seconds

Current in Scale Divisions
per second

0

2.4

7.5

3.3

2.3*

6.5

4.0

10.0

5.3

12.5

6.7

13.8

9.6

17.1

12.5

19.4

18.4

22.7

24.4

25.3

30.4

25.6

48.4

25.6

 

The results are expressed in Fig. 2, curve B, where the ordinate represents current and the abscissa time. It will be observed that the curve of rise of the current is similar in form to the rise of an electric current in a circuit of constant inductance. The current reaches half its value about one minute after the current of air has stopped-a result which agrees with the equation given, for eŻlt = 1/2 when t = 60 sec. (see Table IV). At the instant of stopping the current of air the current has a definite value, since most of the ions given off by the emanation, before it is blown out of the cylinders, reach the electrodes. When the source of the emanation is removed, q = 0, and the decay of the number of ions produced by the emanation is given by the equation

dn / dt = Żln

* Editor's Footnote: - This and the following figures in the same column should read: 23, 40, 53, etc. This, and similar minor errors, left as in original.

229

If n = N when t = 0, it is easily seen that

n / N = eŻlt

or

i / I = eŻlt

i.e. the current through the gas diminishes in a geometrical progression. After 20 minutes the current through the gas is only about one millionth part of its initial value. It has been shown that eŻlt = 1/2 when t = 60 sec.

Therefore

l = 1 / 86

and

N = q / l = 86q

or the total number of ions produced per second when a steady state is reached is 86 times the number of ions supplied per second by the emanation.

 

The amount of emanation from thorium oxide increases with the thickness of the layer. When 1 gramme of thorium oxide was spread over a surface of 25 cm.2, the amount of discharge due to the ordinary radiation had practically reached a maximum. The rate of leak due to the emanation for the same thickness was small. With 9 grammes of oxide spread over the same area, the rate of leak due to the emanation had reached about half its maximum value, which for that case corresponded to four times the rate of leak caused by the ordinary radiation. The emanation thus still preserves its radioactive properties after diffusing through several millimetres of thorium compound.

 

The emanation is given out whatever the gas by which the thorium is surrounded. The action is very similar whether air, oxygen, hydrogen, or carbonic acid is used.

 

The rate of discharge due to the emanation diminishes with lowering of the pressure of the air surrounding it. Only a few observations have been made, but the results seem to point to a uniform rate of emission of the emanation at all pressures; but since the intensity of the ionization of the gas varies directly as the pressure, the rate of leak decreases with lowering of the pressure.

 

The amount of the emanation, so far as the experiments have gone, is also independent of the quantity of water-vapour present.

The power of emitting radioactive particles is not possessed to any appreciable extent by other radioactive substances besides thorium. All the compounds of thorium examined possess it to a marked degree, and it is especially large in the oxide. Two different specimens of the oxide have been used, one obtained from Schuchart of Germany, and the other from Eimer and Amend of New York. The oxide is prepared by the latter by igniting thorium nitrate obtained from monazite sand.

230

The amount of discharge caused by the emanation is increased several times by the conversion of the nitrate into the oxide; but at the same time, the rate of discharge due to the ordinary radiation emitted by the thorium is increased in about an equal ratio. The conversion of the nitrate into the oxide took place below a red heat. On heating in a muffle for some time at white heat, the amount of emanation continually diminished, till after four hours' exposure to the heat, the rate of discharge due to the emanation was only of the value immediately after its conversion into oxide.

 

Both thorium oxalate and sulphate act in a similar manner to the nitrate; but the emanation is still given off to a considerable extent after continued heating.

 

In considering the question of the origin and nature of the emanation, two possible explanations naturally suggest themselves, viz.:

(1) That the emanation may be due to fine dust particles of the radioactive substance emitted by the thorium compounds.

(2) That the emanation may be a vapour given off from thorium compounds.

The fact that the emanation can pass through metals and large thicknesses of paper and through plugs of cotton-wool, is strong evidence against the dust hypothesis. Special experiments, however, were tried to settle the question. The experiments of Aitken and Wilson* have shown that ordinary air can be completely freed from dust particles by repeated small expansions of the air over a water surface. The dust particles act as nuclei for the formation of small drops, and are removed from the gas by the action of gravity.

 

The experiment was repeated with thorium oxide present in the vessel. The oxide was enclosed in a paper cylinder, which allowed the emanation to pass through it. After repeated expansions no cloud was formed, showing that for the expansions used the particles of the emanation were too small to become centres of condensation of the water-vapour. We may therefore conclude, from this experiment, that the emanation does not consist of dust particles of thorium oxide.

 

It would be of interest to examine the behaviour of the emanation for greater and more sudden expansions, after the manner employed by C. T. R. Wilson** in his experiments on the action of ions as centres of condensation.

 

The emanation may possibly be a vapour of thorium. There is reason to believe that all metals and substances give off vapour to some degree. If the radioactive power of thorium is possessed by the molecules of the substance, it would be expected that the vapour of the substance would be itself radioactive for a short time, but the radioactive power would diminish in consequence of the rapid radiation of energy. Some information on this point could probably be obtained by observation of the rate of diffusion of the emanation into gases. It is hoped that experimental data of this kind will lead to an approximate determination of the molecular weight of the emanation.

 

* Trans. Roy. Soc., 1897.
**
Phil. Trans. Roy. Soc., clxxxix, 1897.

231

Experiments have been tried to see if the amount of the emanation from thorium oxide is sufficient to appreciably alter the pressure of the gas in an exhausted tube. The oxide was placed in a bulb connected with a Plücker spectroscopic tube. The whole was exhausted, and the pressure noted by a McLeod gauge. The bulb of thorium oxide was disconnected from the main tube by means of a stopcock. The Plücker tube was refilled and exhausted again to the same pressure. On connecting the two tubes together again, no appreciable difference in the pressure or in the appearance of the discharge from an induction coil was observed. The spectrum of the gas was unchanged.

 

Experiments, which are still in progress, show that the emanation possesses a very remarkable property. I have found that the positive ion produced in a gas by the emanation possesses the power of producing radioactivity in all substances on which it falls. This power of giving forth a radiation lasts for several days. The radiation is of a more penetrating character than that given out by thorium or uranium. The emanation from thorium compounds thus has properties which the thorium itself does not possess. A more complete account of the results obtained is reserved for a later communication.

McGill University, Montreal
September 13, 1899

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Half-Life of Plutonium-239

 

 The half life of plutonium-239 is 24,110 years. 

Of an original mass of 100 g, how much remains

after 96,440 years?

 

 ˝ life = 24,110 yrs

 

96440 yrs x 1 half life = 4 half lives

                 24110 yrs

 

100 g   ŕ             50 g      ŕ         25 g  ŕ  12.5 g  ŕ  6.25 g 

    1 half-life                2 half-lives     3 half-lives      4 half-lives

  

6.25 g remain after 96,440 yrs.

 


Chemical properties and hazards of plutonium.

Table 3 describes the chemical properties of plutonium in air. These properties are important because they affect the safety of storage and of operation during processing of plutonium. The oxidation of plutonium represents a health hazard since the resulting stable compound, plutonium dioxide is in particulate form that can be easily inhaled. It tends to stay in the lungs for long periods, and is also transported to other parts of the body. Ingestion of plutonium is considerably less dangerous since very little is absorbed while the rest passes through the digestive system.

 

TABLE 3.

How Plutonium Metal Reacts in Air

Forms and Ambient Conditions:

Reaction:

Non-divided metal at room temperature (corrodes)

relatively inert, slowly oxidizes

Divided metal at room temperature (PuO2)

readily reacts to form plutonium dioxide

Finely divided particles under about
1 millimeter diameter

particles over about
1 millimeter diameter

spontaneously ignites at about 150 C

spontaneously ignites at about 500 C.

Humid, elevated temperatures (PuO2)

readily reacts to form plutonium dioxide

Important Plutonium Compounds and their Uses

Plutonium combines with oxygen, carbon, and fluorine to form compounds which are used in the nuclear industry, either directly or as intermediates.   Table 4 shows some important plutonium compounds. Plutonium metal is insoluble in nitric acid and plutonium is slightly soluble in hot, concentrated nitric acid. However, when plutonium dioxide and uranium dioxide form a solid mixture, as in spent fuel from nuclear reactors, then the solubility of plutonium dioxide in nitric acid is enhanced due to the fact that uranium dioxide is soluble in nitric acid. This property is used when reprocessing irradiated nuclear fuels.

 

TABLE 4.

Important Plutonium Compounds and Their Uses

Compound:

Use:

Oxides
Plutonium Dioxide(PuO2)

can be mixed with uranium dioxide (UO2) for use as reactor fuel

Carbides
Plutonium Carbide(PuC)
Plutonium Dicarbide(PuC2)
Diplutonium Tricarbide(Pu2C3)

all three carbides can potentially be used as fuel in breeder reactors

Fluorides
Plutonium Trifluoride(PuF3)
Plutonium Tetrafluoride(PuF4)

both fluorides are intermediate compounds in the production of plutonium metal

Nitrates
Plutonium Nitrates [Pu(NO3)4]
and [Pu(NO3)3]

no use, but it is a product of reprocessing (extraction of plutonium from used nuclear fuel).

Formation and Grades of Plutonium-239

Plutonium-239 is formed in both civilian and military reactors from uranium-238.

 

The subsequent absorption of a neutron by plutonium-239 results in the formation of plutonium-240. Absorption of another neutron by plutonium-240 yields plutonium-241. The higher isotopes are formed in the same way. Since plutonium-239 is the first in a string of plutonium isotopes created from uranium-238 in a reactor, the longer a sample of uranium-238 is irradiated, the greater the percentage of heavier isotopes. Plutonium must be chemically separated from the fission products and remaining uranium in the irradiated reactor fuel. This chemical separation is called reprocessing.

 

Fuel in power reactors is irradiated for longer periods at higher power levels, called high "burn-up", because it is fuel irradiation that generates the heat required for power production. If the goal is production of plutonium for military purposes then the "burn-up" is kept low so that the plutonium-239 produced is as pure as possible, that is, the formation of the higher isotopes, particularly plutonium-240, is kept to a minimum.

 

Plutonium has been classified into grades by the Department of Energy (DOE) as depicted in Table 5.

 

It is important to remember that this classification of plutonium according to grades is somewhat arbitrary. For example, although "fuel grade" and "reactor grade" are less suitable as weapons material than "weapon grade" plutonium, they can also be made into a nuclear weapon, although the yields are less predictable because of unwanted neutrons from spontaneous fission. The ability of countries to build nuclear arsenals from reactor grade plutonium is not just a theoretical construct.  In 1962 the United States conducted a successful test with "reactor grade" plutonium. All grades of plutonium can be used as weapons of radiological warfare which involve weapons that disperse radioactivity without a nuclear explosion.

 

TABLE 5.

Grades of Plutonium

Grades

Pu-240 Content

Supergrade

2-3 %

Weapon grade

< 7 %

Fuel grade

7-19 %

Reactor grade

19 % or greater

Isotopes

Plutonium has 16 known isotopes (Pu-238 was discovered in 1992), with mass numbers ranging from 232 to 246.  All isotopes of plutonium are radioactive, but they have widely varying half-lives. The half-life is the time it takes for half the atoms of an element to decay. The various isotopes also have different principal decay modes.

 

 

Isotopes of Plutonium

Click on an isotope to get more information about its decay

Isotope

Half-life

Spin Parity

Decay Mode(s) or Abundance

228Pu

4 ms

0+

%A=100

229Pu

 

 

%A=?

230Pu

 

0+

%A=?

231Pu

 

 

 

232Pu

34.1 m

0+

%EC=77 6, %A=23 6

233Pu

20.9 m

 

%EC+%B+=99.88 5, %A=0.12 5

234Pu

8.8 h

0+

%EC ~ 94, %A ~ 6

234m1Pu

3 ns

 

 

235Pu

25.3 m

(5/2+)

%EC+%B+=99.9973 5, %A=0.0027 5

235m1Pu

25 ns

 

 

236Pu

2.858 y

0+

%A=100, %SF=1.37E-7 7

236m1Pu

37 ps

(0+)

 

236m2Pu

34 ns

 

 

237Pu

45.2 d

7/2-

%A=0.0042 4, %EC=99.9958 4

237m1Pu

0.18 s

1/2+

%IT=100

237m2Pu

85 ns

 

 

237m3Pu

1.1 us

 

 

238Pu

87.7 y

0+

%A=100, %SF=1.85E-7 4, %MG ~ 6E-15, %SI ~ 1.4E-14

238m1Pu

0.6 ns

 

 

238m2Pu

6.0 ns

(0+)

 

239Pu

24110 y

1/2+

%A=100, %SF=3.0E-10 8

239m1Pu

7.5 us

(5/2+)

 

239m2Pu

2.6 ns

(9/2-)

 

240Pu

6563 y

0+

%A=100 , %SF=5.75E-6 5

241Pu

14.35 y

5/2+

%B-=99.998, %A=0.00245 2, %SF ~ 2.4E-14

241m1Pu

21 us

 

 

241m2Pu

32 ns

 

 

242Pu

3.733e+5 y

0+

%A=100 , %SF=5.54E-4 6

243Pu

4.956 h

7/2+

%B-=100

243m1Pu

45 ns

 

 

244Pu

8.08e+7 y

0+

%A=99.879 4, %SF=0.121 4, %BB < 3E-11

245Pu

10.5 h

(9/2-)

%B-=100

245m1Pu

90 ns

 

 

246Pu

10.84 d

0+

%B-=100

247Pu

2.27 d

 

%B-=100

By far of greatest importance is the isotope 239Pu, with a half-life of 24,100 years, produced in extensive quantities in nuclear reactors from natural uranium: 238U(n, gamma) --> 239U--(beta) --> 239Np--(beta) --> <239Pu.

Plutonium also exhibits four ionic valence states in aqueous solutions: Pu+3 (blue lavender), Pu+4 (yellow brown), PuO+ (pink?), and PuO+2 (pink-orange). The ion PuO+ is unstable in aqueous solutions, disproportionating into Pu+4 and PuO+2. The Pu+4 thus formed, however, oxidizes the PuO+ into PuO+2, itself being reduced to Pu+3, giving finally Pu+3 and PuO+2. Plutonium forms binary compounds with oxygen: PuO, PuO2, and intermediate oxides of variable composition; with the halides: PuF3, PuF4, PuCl3, PuBr3, PuI3; with carbon, nitrogen, and silicon: PuC, PuN, PuSi2. Oxyhalides are also well known: PuOCl, PuOBr, PuOI.

Shown as isotope, half-life, and natural abundance (if available).

                228Pu               4 milliseconds
229Pu
230Pu
231Pu
232Pu               34.1 minutes
233Pu               20.9 minutes
234Pu               8.8 hours
234m1Pu           3 nanoseconds
235Pu               25.3 minutes
235m1Pu           25 nanoseconds
236Pu               2.858 years
236m1Pu           37 picoseconds
236m2Pu           34 nanoseconds
237Pu               45.2 days
237m1Pu           0.18 seconds
237m2Pu           85 nanoseconds
237m3Pu           1.1 microseconds
238Pu               87.7 years
238m1Pu           0.6 nanoseconds
238m2Pu           6.0 nanoseconds
239Pu               24110 years
239m1Pu           7.5 microseconds
239m2Pu           2.6 nanoseconds
240Pu               6563 years
241Pu               14.35 years
241m1Pu           21 microseconds
241m2Pu           32 nanoseconds
242Pu               3.733 X 105 years
243Pu               4.956 hours
243m1Pu           45 nanoseconds
244Pu               8.08 X 107 years
245Pu               10.5 hours
245m1Pu           90 nanoseconds
246Pu               10.84 days
247Pu               2.27 days

Properties of Plutonium Isotopes

The plutonium isotopes listed below are "fissionable," which means that the nuclei can be split into two fragments, called fission products. In addition to being fissionable, plutonium-239 and plutonium-241 are "fissile" - that is, they can be split by neutrons of very low (ideally zero) energy. This means that they can be assembled into a critical mass, and hence can sustain a chain reaction without an external source of neutrons.

 

Important Radiological Properties of Plutonium Isotopes

 

Pu-238

Pu-239

Pu-240

Pu-241

Pu-242

Half-life (in years)

87.74

24,110

6,537

14.4

376,000

Specific activity (curies/gram)

17.3

0.063

0.23

104

0.004

Principal decay mode

Alpha

alpha

alpha and some spontaneous fission1

beta

alpha

Decay energy (MeV)

5.593

5.244

5.255

0.021

4.983

Radiological hazards

alpha and weak gamma

alpha and weak gamma

alpha and weak gamma

beta and weak gamma2

alpha and weak gamma

How isotope is produced

nuclear reactors

nuclear reactors

nuclear reactors

nuclear reactors

nuclear reactors

Main uses

Production of thermoelectric power used in nuclear weapons, satallites, and heart pacemakers

Fissile material for nuclear weapons, and for the production of energy

none

none

none

1Source of neutrons causing added radiation dose to workers in nuclear facilities.
2Plutonium-241 decays into Americium-241, which is an intense gamma emitter.

Properties

The metal has a silvery appearance and takes on a yellow tarnish when slightly oxidized. It is chemically reactive. A relatively large piece of plutonium is warm to the touch because of the energy given off in alpha decay. Larger pieces will produce enough heat to boil water. The metal readily dissolves in concentrated hydrochloric acid, hydroiodic acid, or perchloric acid. The metal exhibits six allotropic modifications having various crystalline structures. The densities of these vary from 16.00 to 19.86 g/cm3.

Plutonium is toxic if ingested but the problems associated with the toxicity of plutonium are no different in type from those presented by a whole range of industrial substances, such as heavy metals. There are other substances found in nature which are more toxic than plutonium, and there are many well known substances in everyday use which, like plutonium, are very toxic if they are not handled properly.

 

Very strict protection measures are taken at each stage of the handling process. For ease of handling plutonium is generally kept in the form of one of its oxides, which are virtually insoluble in bodily fluids and so essentially non-toxic. Plutonium used in the manufacture of MOX fuel is in the form of solid pellets made from oxide powder.   In commercial power plant or research applications, plutonium generally exists as the compound plutonium dioxide (PuO2), a very stable ceramic material which is extremely insoluble in water or body fluids, reducing the chemical toxicity to negligible levels, unless inhaled.

 

Plutonium is radioactive but the main type of radiation it emits (alpha particles) does not penetrate even very thin layers of materials. This means that a pair of gloves can protect against the radiation from plutonium. Precautions are taken in the handling of plutonium in order to prevent harm to the work force and to the general public. These have proved effective for more than 30 years.

 


Picture

U-235 captures slow neutrons much more frequently than fast neutrons. Fission produces fast neutrons. These lose energy in bouncing against moderator nuclei and emerge as slow neutrons to split more U-235 nuclei.

 

----------------------------------------------------------------------------------

Plutonium in Nuclear Explosives

Plutonium-239 is a fissile material well-known for its use as the primary trigger in most nuclear explosives (Figure 1-1). All grades of plutonium (see Table 2-1) are considered useable in nuclear explosives, but weapon-grade plutonium--which contains more than 92% plutonium-239--is preferred for nuclear weapon arsenals because lower amounts of plutonium-239 found in fuel and reactor grade pose a much higher risk of “pre-initiation” of the trigger due to corresponding higher amounts of plutonium-240. Use of lower grades also makes fabrication of the plutonium trigger, or pit, more difficult.iii Because of its use in weapons of mass destruction, plutonium accounting is conducted to the level of grams, and large security forces are necessary to guard it.

However, the use of fuel or reactor grade plutonium is considered an easier path for a nonweapons state or a terrorist group because: easiest way to make a nuclear weapon is with reactor-grade plutonium because:

 

Figure 1-1. A simplified illustration of how a precise detonation of chemical high explosives surrounding a subcritical mass of fissile materials generates enough force to initiate, or trigger, the nuclear detonation.

 

Plutonium Chemical Complexity


If anything contributes to plutonium’s demise as a military tool it will be its inherent chemical instability. The future of the plutonium triggers in the U.S. nuclear weapons stockpile is the focus of intense debate both internally and externally to the weapons labs and in the Pentagon. In particular, the lack of understanding of how plutonium ages is driving calls for renewed large-scale pit production. Lawrence Livermore National Laboratory spins it this way, “predicting kinetics is crucial to avoiding surprise requirements for large-scale refurbishment and remanufacture of weapons components.”v

Plutonium is cited by the nuclear weapons labs as the most complex metal in the periodic table and continues to baffle people who best understand it (see sidebar). U.S. and Russian weapons scientists do not even agree on the “phase diagram” for the easily machinable delta-phase plutonium that dominates nuclear weapons stockpiles.vi Its traits are commonly described as unstable, unpredictable, anomalous, and dramatically variable in the open literature. The litany of difficulties includes:

Figure 1-2. This diagram is commonly used to illustrate plutonium complexity, showing the contrasts between the dramatic and abrupt six phase changes of plutonium as it is heated compared to the stability of iron. Some of the key traits of the different phrases include:

·                                                                                
Alpha-phrase plutonium is brittle and difficult to machine, like cast iron.


· Small amounts of aluminum alloyed with delta-phase plutonium stabilize the plutonium and produces a metal as machinable as aluminum. However, because aluminum emits neutrons upon absorbing alpha particles from the decay of plutonium, it raises the risk of pre-initiation, or early criticality, of the plutonium trigger.
· Gallium alloyed with delta-phase plutonium retains the benefit of a product nearly machinable as aluminum and far less prone to plutonium oxidation without raising the risk of pre-initiation, and therefore the plutonium-gallium alloy is the most common in plutonium pits.
To make plutonium fuel, DOE intends to destabilize plutonium by removing gallium during purification.

 

Plutonium Hazards

The combination of radioactivity and chemical instability makes plutonium in the workplace an inherently unsafe enterprise even after it is produced and separated.

Add to this the need for precise accounting to the gram level and large protective forces to guard vaults and other storage areas, and the costs of dealing with plutonium become exorbitant.

Primary among the numerous aspects of the plutonium radiation hazard is the fact that it takes 24,400 years for it to lose one half of its radioactivity, meaning that it will remain dangerous for hundreds of thousands of years and react adversely when exposed to common environments.

 

Alpha Radiation and Decay

 

Plutonium-239 emits high levels of alpha radiation (Figure 1-3). Although alpha radiation can be stopped with paper, it causes damage in many ways and from several phenomenon.

 

Figure 1-3. The first part of the plutonium-239 decay chain. Plutonium decays to Uranium 238 by emitting an alpha particle, in this case a helium nucleus. The energy from this process drives several reactions that are poorly understood.

1.         Damage to the plutonium over time. The recoil energy from the decay generates 85 kilo-electron-volts of kinetic energy in the uranium nucleus, of which 60 keV remains when the nucleus collides within the matrix and displaces plutonium atoms in the metal.ix Over the course of decades, this action can damage plutonium enough to keep weapons designers leery of the “reliability” of the plutonium triggers.

The helium nucleus has far more energy when released, 5 million-electron-volts, but this is said to lose all but 0.1 percent of its energy through collisions with electrons before capturing a few electrons and “settling in” as a helium atom.x Over the course of decades, helium atoms accumulate to the point of creating bubbles, another grave concern of weapons designers. Helium buildup also poses a health and safety risk. For example, in 1963 a plutonium pit tube broke during a weapon disassembly process at Pantex and contaminated workers and the facility with plutonium contaminated helium gas.

2.         Damage to other metals over time. Plutonium decay basically damages everything in its path, and this impact is most measurable on elements that experience “void swelling” from radiation, meaning they swell in size over time.xi The effects of this over the course of decades is poorly understood because plutonium has never been allowed to age for decades, but some implications are obvious:

·         Beryllium, which is used as a neutron tamper within pits and as cladding on many plutonium pits (see Part III) serving to protect the plutonium from oxidizing, experiences “gas-driven” swelling;.

·         Aluminum, which is used in cladding on some pits, suffers from void swelling.

·         Iron, Chromium, and Nickel, the key ingredients in stainless steel used for plutonium storage cans, experiences void swelling;

·         Zirconium, used to clad nuclear fuel, experiences void swelling.

3.         Damage to live tissues. If the uranium nuclei from decay damages metal as dense as plutonium, the impacts on living tissue are quite obvious. Plutonium is said to be “harmless” if ingested as a metal, but this is an obvious fallacy since even plutonium metal has a layer of plutonium oxide present at all times,xii oxides are always present to some degree on metals, and the chemical reactions with common materials that worry metallurgists and weapons designers are certainly a concern inside the human body.

Plutonium is most hazardous in a powder form. Much debate has occurred over how much plutonium oxide can cause lung cancer within a few decades, with estimates ranging from a few micrograms to 30-60 micrograms to 2 milligrams. There seems to be little debate over how much will kill a person:

·         Ingestion of 500 milligrams, or one half of a gram, is considered the acute lethal dose;

·         Inhalation of 20 milligrams is considered the acute lethal dose;xiii

A good scale for reference is a typical Sweet N’ Low packet which contains one million micrograms of sugar substitute.

 

4.         Radiolysis of common materials. Alpha particles react with materials such as air and water to cause “radiolysis” of common materials (Figure 1-4). Plutonium metal oxidizes readily in air and plutonium oxide generates gases that can rupture storage containers. Plutonium is most hazardous in a powder form.

Figure 1-4. Simplified illustration showing various reactions brought about by alpha decay.

The literature is filled with reports about ruptured containers and massive oxidation of entire metal pieces. For example, in 1983 Los Alamos reported the formation of a black powdered suboxide in “casting skulls” left over from plutonium pit fabrication, and when containers of skulls were opened, the plutonium suboxide would ignite “almost explosively.”xiv

To avoid these undesirable reactions, DOE finally established a long-term storage standard for plutonium in 1994, but has had trouble meeting that standard (see Part II, Section B.) Called the 3013 standard, it requires that plutonium metals and oxides be stored in two sealed metal containers free of organic materials. Reaching this standard requires heating of oxides to temperatures greater than 900 degrees Celsius.

A few near-term implications of this chemical fact include:

1. Nitric acid processing, which DOE plans to use to purify plutonium oxide as the first step towards making plutonium MOX, greatly increases the likelihood of explosions, spills, and criticality events. The plutonium pit disassembly and conversion facility is planned as the main source of plutonium oxide for a plutonium fuel (MOX) factory. Early plans for the PDCF require the plutonium oxide product to meet the long term plutonium storage (3013) standard.xv

2. The dangers of nitric acid plutonium processing are aggravated if the plutonium oxide was produced or treated at temperatures greater than 600 degrees Celsius. Oxides heated to temperatures between 600 and 1000 C “require somewhat more stringent procedures” when dissolving in acids, and plutonium oxide powder heated to temperatures over 1000 Celsius “require extreme measures.”xvi
Since the long-term storage standard requires plutonium to be heated at temperatures well above 600 degrees C,xvii it is incompatible with the needs of plutonium fuel production.

 

Aging Plutonium and Americium-241


Plutonium-241, which is present in all grades of plutonium, decays into the more radioactive and dangerous americium-241, an intense gamma ray emitter that is 100 times more toxic than plutonium 239. Weapons plutonium was routinely purified to eliminate americium, which of course produced stockpiles of americium. If plutonium decay is allowed to run its course, radiation levels in U.S. plutonium will peak in the next 38 to 60 years (Figure 1-4).


Figure 1-4. As plutonium-241 decays to Americium-241, weapon grade plutonium becomes more hazardous and radioactive. Americium levels peak after 70 years.

One fact that has become increasingly clear is that the plutonium hazard has more depth and breadth. Not only is plutonium useable in nuclear weapons at the scale of kilograms and acutely toxic at the scale of milligrams, it is also has the most complex chemistry in the Periodic Table of the Elements (Pages 1.3 to 1.6). DOE officials who have told the public countless times that alpha radiation can be blocked by a piece of paper have failed to inform people that alpha radiation from the decay of plutonium 239 causes, over the course of decades to centuries, damage to plutonium metal, any metal in contact or near contact with plutonium, and adverse chemical reactions with our most common elements, oxygen and hydrogen. All these things also make keeping track of plutonium much more difficult.

If the alpha particles from the decay of plutonium 239 can damage the densest metal on earth, the impacts of alpha radiation from plutonium ingested or inhaled n the human body is obviously detrimental. Plutonium is often said to be “harmless” if ingested as a metal, but this is an obvious fallacy since it turns out that plutonium metal has a microscopic layer of plutonium oxide present at all times. The chemical reactions with common materials that worry metallurgists and weapons designers are certainly a concern inside the human body.

Plutonium is most hazardous in an oxide powder form., with inhalation of only 20 milligrams enough to kill someone quickly (Page 1.6) and 30 to 60 micrograms easily enough to greatly raise the risk of cancer. Yet, DOE is planning to truck 3 metric tonnes of plutonium oxide from Rocky Flats to Savannah River Site this year in its politically motivated rush to close Rocky Flats as soon as possible.

Although the revelations about plutonium complexity has forced DOE to finally establish a long term plutonium storage standard, it is pursuing projects at odds with its own standards. The best example is DOE’s zealous pursuit of a plutonium MOX fuel factory that utilizes surplus weapon-grade plutonium found in plutonium pits.

To make this fuel requires nitric acid based plutonium processing that has generated tremendous radioactive waste problems in the past, a process that greatly increases the likelihood of explosions, spills, and accidental criticality. Yet, the plutonium storage standard requires plutonium oxide to be heated to temperatures that make nitric acid processing even more dangerous. (Page 1.7). Instead of recognizing that plutonium fuel production from weapons plutonium is incompatible with its own storage standard, DOE seems intent on neglecting its commitment to safe storage in favor of its devotion to plutonium fuel.

In the past five years, DOE has reneged on nearly every one of its plutonium management decisions (see sidebar on Page iii) that did not involve spreading the liability at Rocky Flats around the country as quickly as possible or pursuing the dream of stuffing aging nuclear reactors one-third full of plutonium fuel. While underfunding the most fundamental mission-safe and secure storage-it has spent millions of dollars on unnecessary projects like gallium removal experiments and an irrelevant MOX fuel test in Canada.

DOE has not released updated plutonium inventory figures in five years and has even silently carved away bits and pieces of the declared surplus:

---In November 1999, DOE removed 3.8 (MMMMMMMT) of surplus plutonium found in unirradiated nuclear fuel in Idaho (Page 2.9) which forced the planning team for the plutonium immobilization plant at SRS to issue its third design; and another 0.6 to 0.8 MT of un-irradiated nuclear fuel at Hanford was removed for “possible programmatic use.”

---In 1998 an undisclosed number of surrplus plutonium pits were recategorized as “national security assets;” (Page 3.3)

---In 1998 the nuclear weapons program aaaat Los Alamos received “permission from the politicians” to divert some “nickel-sized” pieces of plutonium from its pit disassembly and conversion demonstration project for plutonium aging studies in support of nuclear weapons stockpile stewardship; (Page 2-12).

DOE matched this failure to be up-front with its numbers with an aversion to being up-front about the hazards of its proposals. During the Surplus Plutonium Disposition Environmental Impact Statement process, DOE attempted to hide the fact that plutonium pit disassembly and conversion involved tritium and beryllium processing that would have meant a 10,000 fold increase in radioactive air pollutants at Pantex and will mean that SRS will become a certifiable beryllium site.

Broken Promises, Abandoned Decisions


The Department of Energy has proven adept at canceling major projects that formed the foundation of its plutonium program and were included in major Records of Decision by the Secretary of Energy:


In 1997 DOE canceled its effort to repackage 12,000 plutonium pits in “state-of-the-art” AT-400A shipping and storage containers at Pantex. After spending $50 million on research and development, the plug was pulled after a mere 20 plutonium pits were repackaged. (Page 3.14)


In December 1997 DOE abandoned its efforts to upgrade Building 12-66 at Pantex for surplus plutonium pit storage after completing the preconceptual design work. (Page 3.15)


In 1999 DOE abruptly canceled construction of a new plutonium storage and stabilization facility at Savannah River Site after spending $70 million on its design and nearly completing excavation work. Two years later, DOE still does not have a long- term storage plan for non-pit plutonium at SRS, but still plans to truck about 9 metric tonnes from Rocky Flats to SRS. (Page 2. ).


In fiscal year 2000 DOE quietly stopped funding the plutonium pit reuse project at Pantex, a program designed to avoid costly and environmentally damaging plutonium pit fabrication. (Page 3-12).


In 1997 DOE ceased plutonium stabilization efforts at Los Alamos in favor of pursuing the ARIES project, which has turned out to be an essential pre-cursor to plutonium pit production.


In 1999 DOE began shipping plutonium residues called “sands, slags, and crucibles” from Rocky Flats to SRS, then abruptly quit and decided to send the material to WIPP.


Higher on the list was DOE’s selection of a nitric-acid based plutonium conversion process for making Mixed Oxide (MOX) plutonium fuel in 1997. Unfortunately, DOE did not inform the public of its decision until late in 1999 and then grossly underestimated the impacts of the operations.

But the most egregious example of dishonesty was the public presentation of plutonium disposition facilities as nonproliferation missions while DOE officials, at the urging of the Pentagon and Congress, secretly crafted a parallel plan to produce new plutonium warheads. The possibility of SRS dismantling plutonium pits for a few years and then putting new ones together is very real. (Pages 3.15 to 3.19).

The list includes internal stonewalling, drastic funding cuts on fundamental programs, constant redesign and “rebaselining,” and a plethora of contradictions:


As a result of this investigation, BREDL is making the following recommendations to the new administration in the hopes that health and safety will take precedent over political expediency, that the fundamental issue of safe and secure storage receives the highest priority, and that no more huge sums of money are squandered:

1. There must be a renewed attitude towards increased openness and honesty in the U.S. nuclear weapons complex and a reversal of the current trend against openness.

2. DOE must publish its latest inventories of plutonium, uranium, and other special nuclear materials and disclose any information suggesting that diversion of materials has occurred. BREDL is making the following estimates based on DOE’s figures in various reports, showing the sheer volume of plutonium “items,” requiring individual handling at some point in time:


Plutonium Inventory

 

Plutonium Form

# Items

Plutonium Content, MT

 

Non-Pit Plutonium

Solutions



43,000 Liters



0.5

Metals

6,361

8.6

Oxides

12,537

6.35

Residues

29,530

6.35

Unirradiated Fuel

52,000

4.4

 

Plutonium Pits

20,000

66.1

Irradiated Fuel

 

7.5

Total

120,528

99.8 to 100.0


3. Insure that DOE lives up to its promises and commitments made in Environmental Impact Statements and in implementation Plans to the Defense Nuclear Facilities Safety Board.

4. Make safe and secure storage of plutonium the number one priority in the weapons complex.

5. Cease all efforts to pursue full-scale plutonium pit production and a plutonium fuel economy and focus on reducing the plutonium hazard.

6. The inherent chemical instability of plutonium should be an added incentive to make drastic cuts in the nuclear weapons arsenal.



 

 

 

 

 

 

 

 

 

 

 

 

 

 

-----------------------------------

Effective Nuclear Fuel Utilisation by DUPIC Cycle

A PWR is charged with fresh fuel of about 3.5% enrichment, which is burned down to about 1.5% fissile content (0.9% U-235 and 0.6% Pu). It is then discharged from the core at its end-of-life. The 0.9% residual U-235 enrichment is still higher than the natural U-235 concentration of 0.71%.

A normal CANDU reactor is loaded with natural uranium fuel, in which the U-235 concentration is 0.71%. In contrast, the U-235 enrichment concentration in PWR spent fuel is 0.9%, in addition to 0.6% newly generated plutonium. Needless to say, we are also dealing with considerable amounts of fission products, which are detrimental to reactivity maintenance and radiation control.

Research is, therefore, being directed at making use of this valuable unburnt fissile material in PWR spent fuel, by linking it with the CANDU reactor system. This research is entitled DUPIC, which is an acronym for Direct Use of PWR spent fuel In CANDU. The project is being conducted by a tripartite group consisting of US, Canadian and Korean partners.

In Japan, there is a saying associated with business administration, that is used to convey a desire to improve overall productivity: "Further squeeze the dry floorcloth until you get the last drop out of it." One could say that DUPIC resembles this dry floorcloth-squeezing endeavour. One main difference, of course, is that LWR spent fuel is not dry, but very wet, with lots of fissile nuclides in it. There is a lot of juice to extract.

As you can see in Figure 1 below, the nuclide composition of fissionable materials in CANDU spent fuel is 0.2% U-235 and 0.3% Pu. This represents a significant squeeze of the fissile nuclides from PWR spent fuel, that at the outset contained 0.9% U-235 and 0.6% Pu. The advantages of the DUPIC fuel cycle include the following:

Figure 1: PWR-CANDU tandem fuel cycle by DUPIC

 

On the other hand, the following must be borne in mind as we attempt to bring the DUPIC concept to reality:

Plutonium as fuel

Unused uranium and plutonium can be extracted from spent fuel by reprocessing, and recycled to produce more energy. This is being done in a number of countries. The separated plutonium can be incorporated into new, mixed oxide (MOX) fuel which is a combination of plutonium dioxide and uranium dioxide.

 

A number of facilities, including Sellafield in the UK and La Hague in France, separate uranium and plutonium from spent fuel by chemical reprocessing. Several countries, including Belgium, France, Germany and the UK, have developed the technology to make the plutonium into MOX fuel. Currently, there are 34 reactors licensed to use MOX fuel and 25 others are in the licensing process. In addition, in OECD (Organisation for Economic Co-operation and Development) countries, there are 165 more reactors where licensing for MOX fuel is considered to be technically feasible.

 

Since 1963 some 400 tonnes of MOX fuel has been loaded into reactors around the world. The principal benefits of the MOX option are conservation of uranium, minimisation of high level waste volumes and reduction of the world's separated plutonium inventory. Substitution of MOX for uranium in nuclear fuel can result in a net reduction in plutonium, since spent MOX fuel contains about one quarter less plutonium than the original loading. A substantial part of this plutonium will be Pu-240, rendering the mixture unsuitable for weapons.

 

After the uranium and plutonium have been separated by reprocessing, there remain some radioactive wastes. These are stored to allow their radioactivity to decay before permanent disposal, for example in an underground repository.

Plutonium security

Since nuclear fuel remains in a reactor for several years, plutonium extracted from the spent fuel from nuclear power stations is unsuitable for weapons manufacture. This is because it contains significant quantities of Pu-240, which has physical properties that make the plutonium unsuitable for use in nuclear weapons. By the time the fuel is removed from a power reactor, as much as 40% of the plutonium it contains is Pu-240. Plutonium for weapons is made in special reactors under conditions which do not lead to the formation of more than a small amount of Pu-240.

Safeguarding of plutonium in the nuclear power industry, which ensures that the material is not diverted to nuclear weapons production, has built up an impressive record. To demonstrate that they are not manufacturing nuclear weapons, essentially all countries with nuclear power programs subject their nuclear facilities to the International Atomic Energy Agency (IAEA) safeguards system. A function similar to that of the IAEA is performed by the Euratom nuclear safeguards system. All commercial nuclear material in the European Union is subject to active Euratom safeguards inspections.

Plutonium inventory

Overview

 

The US National Academy of Sciences estimated that in 1992 there were 1100 tonnes of plutonium in total from all types and sources, including plutonium which has not been separated from spent fuel. This is equivalent in energy potential to more than one billion tons of oil.   It is estimated that within the world's total plutonium inventory there is of the order of 200 tonnes of separated, weapons-grade material.    Over the past few years, the dismantlement of excess nuclear warheads has left the United States and Russia with large stocks of plutonium and highly enriched uranium (HEU). These surpluses have re-ignited the debates around the world about the use of plutonium as an energy source and provided new arguments for continued assistance to on-going plutonium projects. This article reviews the basic facts regarding plutonium use and provides some cost and technical analysis of the issue.

About one-third of this is in the USA and about two thirds in the former USSR. In addition, there are less than 100 tonnes of separated, reactor grade plutonium. As a result of existing arms-control reduction commitments, approximately 100 tonnes of weapons-grade plutonium are expected to become surplus to military needs.

 

--------------

In 1996 the Department of Energy (DOE) in which the U.S. declared it had acquired 111.4 metric tonnes (MT) from four sources:

·         103.4 MT from government-owned plutonium production reactors (36.1 MT at Savannah River Site (SRS) and 67.3 MT at Hanford);

·         0.6 MT from government-owned nonproduction reactions;

·         1.7 MT from commercial U.S. nuclear reactors that was primarily received from West Valley, N.Y. reprocessing plant;

·         5.7 MT from foreign countries.

The active military plutonium inventory held by DOE and the Department of Defense (DoD) was declared to be 99.6 metric tonnes (MT), broken down into 3 categories.xviii (Table 1-1).

 

 

Table 2-1. Declared Inventory, 1996.

 

Grade

% Plutonium-240

Total Pu, Metric Tonnes

Weapons Grade

< 7%

85.1

Fuel Grade

7-19%

13.2

Reactor Grade

>19%

1.3

 

Total Plutonium

99.6 MT

This 99.6MT can be further broken down into three major categories: the plutonium in nuclear weapons triggers called plutonium pits, within irradiated nuclear fuel, or in non-pit form..

Table 2-2. Plutonium Inventory.

 

Category

Weapon Grade

Fuel Grade

Reactor Grade

Total

Pits

66.1

0

0

66.1

Irradiated Fuel

0.6

6.6

0.3

7.5

Non-pit

18.4

7.6

0

26.0

Total

85.1

14.5

0.3

99.6

Nonpit plutonium breakdown is based on these three assumptions
(1) Assumes all plutonium in pits are weapon-grade, since U.S. is not known to have developed plutonium weapons from non-weapon grade plutonium (although it did test such weapons).
(2) Assumes that there is no non-surplus plutonium in irradiated fuel.
(3) DOE Plutonium vulnerability report cited 26.0 MT of non-pit Pu in DOE complex.

Noting that due to “rounding” its figures did not always match up, DOE claimed that 12.0 MT of plutonium has been “lost” or sent abroad, so the active inventory is the acquired plutonium minus the following (note that DOE admitted that due to rounding its figures did not always add up):

·         3.4 MT “expended” in wartime and nuclear weapons testing;

·         2.8 MT of plutonium DOE cannot account for called “inventory differences;”xix

·         3.4 MT of plutonium in waste forms described as “normal operating losses.”

·         1.2 MT of plutonium lost during nuclear reactor operations described as “fission” and “transmutation”;

·         0.4 MT of plutonium that decayed to Americium 241 and uranium 237.

·         0.1 MT of plutonium now in the hands of the U.S. civilian industry;

·         0.7 MT of plutonium sent to foreign countries under “agreements for cooperation,” i.e. the Atoms-For-Peace program;

Changes Since 1996

 

Last year DOE submitted a report to Congress called the Integrated Nuclear Materials Management Plan. The active inventory declared was the same as that of 1996. This is unlikely to be the case for the following reasons:

1. Contractors operating DOE plutonium sites are required to conduct inventories on all Special Nuclear Materials (SNM) and report updated inventory differences. For example, at Savannah River Site (SRS), the Materials Controls and Accounting (MC&A) department is directed to “reconcile SRS nuclear material records with NMMSS (U.S. Nuclear Materials Management Safeguard System) semiannually” and “provide to OSS (Office of Security and Safeguards) semi-annual reports on statistical analyses of inventory differences.”xx Therefore the Department has updated figures on material-unaccounted-for (MUF), now known as “inventory differences.”
The question that remains is: Does DOE still have 2.8 MT of unaccounted-for plutonium?

2. In response to an investigation by the Institute for Energy and Environmental Research (IEER), DOE acknowledged there is more buried plutonium waste at Idaho, SRS, RFETS, and Hanford.xxi Therefore, the amount of plutonium in waste is also likely to be higher, which would mean lower inventory differences.

3. DOE has changed how it classifies waste vs. non-waste plutonium,xxii and now appears intent on trying to send as much plutonium as waste to the Waste Isolation Pilot Plant (WIPP) in New Mexico as possible.

4. Plutonium has done nothing but decay the last five years, so more has been lost.

5. Stabilization efforts of non-pit plutonium should have led to better estimates, especially considering the advances in technology for materials accounting.

6. DOE opened a new plutonium storage site, the Waste Isolation Pilot Plant, in New Mexico; where it intends to bury more than ten metric tonnes of plutonium as waste.


Non-Pit Plutonium

 

The amount of non-pit plutonium is complicated by several factors:

·         the inherent difficulty of measuring and accounting for plutonium;

·         the fact that many materials with 10-30% plutonium content are poorly characterized;

·         the changes in U.S. policy regarding waste vs. recoverable materials;

·         whether plutonium in pits was a part of the declassified inventory at Rocky Flats and SRS

·         The ownership of the plutonium within the DOE bureaucracy and the lack of final decisions regarding the fate of numerous materials.

Confusion about Nuclear Materials


The flow and storage of SNM [Special Nuclear Material], including tritium, throughout the DOE complex [prior to 1990] was fairly complicated and could be somewhat confusing to the unitiated observer. In fact, it could be somewhat confusing to an experienced observer as well.”
Albert Abey, Lawrence Livermore National Laboratory. UCRL-ID-111061. 1992.

When Production Stopped

Prior to 1990, when nuclear weapons production was in high gear, “the vast majority of fissile material scrap and materials from retired weapons was recycled. It was less costly to recover fissile materials from high assay scrap and retired weapons than to produce new material. As a result, very little scrap containing fissile material was considered surplus. Consequently, these materials were designated, handled, and packaged for short-term storage.”

In 1989, when the U.S. stopped producing special nuclear materials and numerous facilities were shut down, there was no long-term standard for storing plutonium. In fact, not much thought was even given to storage until it became a problem:

“the halt in weapons production that began in 1989 froze the manufacturing pipeline, leaving it in a state that posed significant risks. High quantities of fissile materials (approximately 13 tons of plutonium metals and oxides, 400,000 liters of plutonium solutions, 130 tons of plutonium residues, HEU, and special isotopes) needed attention.” xxiii


By 1994 DOE had finally developed a standard for long-term storage-up to 50 years-of non-pit plutonium metals and oxides, commonly called the 3013 Standard. However, between 1989 and 1994 DOE made insignificant progress resolving the actual problem.

Change began in April 1994 when the Defense Nuclear Facilities Safety Board (DNFSB) issued its first Technical Report. Plutonium Storage Safety at Major Department of Energy Facilities
addressed all unencapsulated, separated plutonium., leaving out plutonium in pits, unirradiated nuclear fuel, and sealed sources. The report chastised the DOE for not clearly recognizing many of the hazards associated with plutonium storage, such as potential fires, explosions, and pressurization of containers.xxiv (Three years later a major chemical explosion forced Hanford to shut down its Plutonium Finishing Plant.)

A month later the Board issued Recommendation 94-1 for this plutonium and other special nuclear materials. At the top of the list of nine recommendations encompassed within 94-1 was the recommendation to:

“convert within two to three years the materials...to forms or conditions suitable for safe interim storage. The plan should include a provision that, within a reasonable period of time (such as eight years), all storage of plutonium metal and oxide should be in conformance with the draft DOE Standard on storage of plutonium now being made final.” xxv


Also in 1994 the DOE conducted a detailed plutonium vulnerability investigation and published a landmark document of the results, including the detailing of plutonium holdings down to the gram level at numerous “small holding” sites documenting approximately 26.0 MT of non-pit separated plutonium.. In February 1995, a few months after publishing the vulnerability report, the Department sent its first plan with new plutonium estimates (Table 1-3) for implementing Recommendation 94-1 to the Defense Board, and acknowledged the urgency of the issue:

“The Department acknowledges and shares the Board's concerns and has developed this integrated program plan to address these urgent problems.”xxvi

Table 2-3: Differences in separated, unencapsulated Plutonium Inventory between DOE's Implementation Plan for Recommendation 94-1 and DOE's Plutonium Vulnerability Report

 

Plutonium Form

MT of Pu
94-1 Implementation

MT of Pu
Vulnerability Report

Oxide

6.21

3.3 (1)

Metal

8.95

13.0 (1)

Scrap/Residues

6.34 (2)

8.7

Solutions

0.49 (2)

0.7

Sealed Sources

not reported

0.05

Other Forms

not reported (3)

0.24

Total

21.7

26.0

 

(1) These figures included plutonium in unirradiated nuclear fuel.
(2) The actual amount of plutonium by form at SRS was classified in the first 94-1 implementation plan, although DOE reported 2.1 MT at SRS in 1994. Since then DOE has reported 0.490 MT in metals, and DNFSB reported approximately 0.8 MT in oxides and 0.4 MT of in residues at SRS in January, 2001. The estimate for Pu in solutions remains classified, the number in this table is an estimate based on the various numbers reported for SRS and the complex.
(3) Other forms may be encompassed within 94.1, but are not reported.

Not included in DOE's 94-1 implementation plan were 4.4 to 4.6 MT of plutonium in unirradiated fuel:

· 0.6 MT of plutonium in unused FFTF mixed oxxide fuel clad in 17,000 MOX fuel pins at Hanford;
· 0.2 MT to 0.4 MT of plutonium in unclad FFTF fuel pellets at Hanford;
· 0.3 MT of unused ZPPR fuel in 21,000 pins of mixed oxide fuel in Idaho (Figure 2-2)
· 3.5 MT of unused ZPPR plates within 29,000 plates of metal alloy fuel (Figure 2-3);

This provides more evidence that the 26.0 MT in the vulnerability report at sites other than Pantex was non-pit plutonium and did not include plutonium in pits, meaning that the original inventory at Rocky Flats was closer to 16.0 MT.

Implementation of DOE's nuclear materials stabilization plan has been hindered by several factors, many of them political:

· The political decision to "accelerate closure"at Rocky Flats, with an artificial deadline for closing all plutonium facilities by 2006;
· The political decision to pursue disposition of surplus plutonium through the "dual-strategy" of both plutonium fuel use and immobilization;
· The lack of commitment to safe and secure storage within the Department of Energy;
· The issue of who "owns" this plutonium, as it is managed by four DOE departments Offices of Nuclear Energy, Defense Programs, Environmental Management, and Fissile Materials Disposition.
· DOE's hopelessly fragmented approach to implementing the National Environmental Policy Act (NEPA), with the total plutonium program being addressed in several environmental impact statements.
· The 3013 standard has changed three times (3013-96, 30-13-99, and 3013-00).
· The nature of the materials, especially since the amount of plutonium contained in the complex was minor compared to the total quantities of materials that contained plutonium. (Figure 1-x_) .
· In 1999 DOE stopped construction of a cornerstone of its implementation plan, the Actinide Packaging and Stabilization Facility (APSF), leaving a gaping hole in the ground at Savannah River Site where excavation work was almost complete.

The fate of most of these materials remains unclear. One option is to dispose more plutonium as a waste at the Waste Isolation Pilot Plant (WIPP) in New Mexico. A more recent scheme proposed by the National Laboratories is to truck hundreds of tonnes of residues to SRS and separate and purify the plutonium. in the SRS canyons. The goal would be to increase-by 6-7 tonnes-:the amount of weapons grade plutonium and improve our negotiating stance with Russia." xxvii

Because of the variations in DOE reporting, the actual inventory remains murky. Following are BREDL's estimates for the total number of items containing plutonium, and the plutonium content within those items.

 

 

 

 

Figure 2-1. This graphic illustrates the quantity of materials compared to the plutonium in those materials. Much of the non-pit plutonium is not weapons-usable, yet the necessity to stabilize these materials from a health and safety standpoint results in weapons-usable plutonium. Source: DOE/ID-10631, Plutonium Focus Area. 1995.

 

Plutonium in Solutions

 

In the plutonium vulnerability report, DOE estimated a total of 700 kilograms (0.7 MT) of plutonium contained in various concentrations within 400,000 liters of solutions with high risks of criticality, explosions, and leaks:

· 143 kilograms at Rocky Flats
· 360 kilograms at Hanford
· a classified amount--estimated at approximately 200 kilograms--at Savannah River Site;

DOE's contractors have stabilized 90% of the plutonium solutions in terms of total volume, but only about 30 % of the solutions in terms of plutonium content:

· 43 kilograms of plutonium remains at Rocky Flats in 2,000 liters of solution in piping in 6 facilities;
· An estimated 110 kilograms of plutonium remains in H-Canyon at SRS in 34,000 liters of solution;*
· 341 kilograms of plutonium remains at Hanford's Plutonium Finishing Plant in 4,270 liters of solution
· A total of 494 kilograms, or approximately 0.5 MT, of plutonium in 40,270 liters of solutions.

Figure 2-2. Plutonium Ingots.

 

Plutonium Metal

 

As of June 2000, DOE reported 8,951.3 kilograms (8.951 MT) of plutonium metal contained in 6,361 items at 9 different sites:

· 6600 kilograms (6.6 MT) in 3403 containers at Rocky Flats;
· 700 kilograms (0.7 MT) in 475 containers in Hanford's Plutonium Finishing Plant
· 1133 kilograms (1.133 MT) in 2060 containers at Los Alamos
· 490 kilograms (0.49 MT) in 230 containers at SRS
· 0.45 kilograms (0.00045 MT) in 210 containers at Argonne East National Laboratory in Chicago;
· 20 kilograms (0.020 MT) in 50 containers at LLNL.
· 0.855 kilograms (0.00085 MT) in 20 containers at the Mound Plant in Ohio
· 0.3013 KG (0.0003 MT) in 30 containers at Oak Ridge;
· 6.7 kg (0.0067 MT) in 5 containers at Sandia National Laboratory. .

About 7.6 MT of this material is considered surplus, based on 28.9 MT of metals declared surplus minus the 21.3 MT of surplus plutonium in pits at Pantex.

1.0 MT of this material is categorized as fuel-grade plutonium. In all likelihood this includes the the 275 plutonium-aluminum alloy items at Hanford.

Table 2.4. Plutonium in Metals

 

Site

Pu Content in Metals, KG

# of Pu Metal Items

Rocky Flats

6600.00

3403

Hanford

700.00

339

Los Alamos

1133.00

2060

SRS

490.00

203

Argonne-East

0.45

210

Livermore

20.00

91

Mound

0.86

20

Oak Ridge

0.30

30

Sandia

6.70

5

Total

8591

6361


Plutonium Oxide

Figure 2-3. A can of plutonium oxide powder at Rocky Flats.

 

DOE has approximately 12,540 items of plutonium oxides with greater than 50% plutonium content, for a total of 6.35 MT of plutonium. Virtually none of this plutonium meets the long-term 3013 storage standard:

· 3,200 kilograms (3.2 MT) of plutonium within 3,296 items content at Rocky Flats;
· 1,500 kilograms (1.5 MT) of plutonium in 2,800 Pu oxide items and 2,300 plutonium-uranium oxide items at Hanford
· 800 kilograms (0.8 MT) of plutonium in 800 containers of Pu oxide at SRS;
· 721 kilograms (0.721 MT) of plutonium in more than 2,000 Pu oxide containers at Los Alamos;
· 102 kilograms (0.102 MT) in 92 containers at LLNL;
· 28.1 kilograms (0.0028 MT) in 107 containers at Mound;
· 1.706 kilograms (0.0017 MT) in 83 containers at Oak Ridge;
· 1.4 kilograms (0.0014 MT) in 10 containers at Sandia National Laboratory; and
· 0.014 kilograms in 354 items at Lawrence Berkeley Laboratory.

Table 2.5 Plutonium in Oxides

 

Site

Pu Content, KG

# of Items

Rocky Flats

3200

3296

Hanford

1500

5100

Los Alamos

721

2000

SRS

800

800

Argonne-East

0.48

695

Livermore

102

92

Mound

28

107

Oak Ridge

1.7

83

Sandia

1.4

10

Lawrence-Berkeley

0.014

354

Total

6355

12537

Plutonium in Unirradiated Nuclear Fuel

Figure 2-4. 21,000 ZPPR Fuel Pins like the one pictured here are stored at Argonne National Laboratory West, Idaho and contain a reported 0.3 MT of fuel-grade plutonium mixed with uranium oxide to make Mixed Oxide (MOX) fuel.

 

As of June 2000, DOE had more than 50,000 items of clad, unused, unirradiated fuel containing a total of 4.4 to 4.6 MT of plutonium.

DOE's Office of Nuclear Energy retains control this plutonium. Until November 1999, the ZPPR fuels (Figures 2-4, 2-5) and FFTF Mixed Oxide (MOX) fuel (not pictured) were scheduled to be processed at the Plutonium Immobilization Plant at Savannah River Site. This idea was withdrawn in November 1999.

 

 

Figure 2-5. ZPPR Fuel Plates. 22,000 of these plates containing a reported 3.5 MT of plutonium are presently stored at Argonne National Laboratory-West within the Idaho National Engineering and Environmental Laboratory. The ZPPR fuel contains varying percentages of uranium and plutonium alloyed with either aluminum or molybdenum to make a material that is resistant to oxidation. Some plates are coated with nickel to increase the resistance to oxidation. Source: UCRL-ID-131608, Rev. 3, PIP-00-035

 

Processing 50,000 pieces of old unused fuel with high concentrations of americium-241 necessitated planning for remotely controlled processing of these materials. Plans for dealing with such highly radioactive materials greatly contributed to increased costs of a plutonium immobilization plant.

The cost of abandoning this path has not been determined. DOE is now considering calling the ZPPR fuel a "national asset material" but has yet to determine a future use.xxviii

 

Figure 2-6. Projected Feed for Plutonium Disposition.

 

Several assumptions lie within the "nominal planning figures (figure 2-6):

 

· materials will be pre-processed before the disposition steps begin. In other words, the planning figures are based on expected conditions, not real conditions.
· included was 7.0 MT of metals "anticipated" to be surplus if START II induced more weapons dismantlement;
· not included was the 7.5 MT of plutonium in irradiated fuel.

 

 

Figure 2-7. Office of Fissile Materials Disposition

 


Figure 2-8. Office of Environmental Management.

 

Plutonium Residues

 

Residues is a catch all phrase for "material containing plutonium that was generated during the separation and purification of plutonium or during the manufacture of plutonium-bearing components for nuclear weapons."xxix In 1990 these materials were assumed to have enough plutonium remaining to be recoverable for future operations. Today, the plutonium cannot be used in weapons without substantial processing and purification and it is mostly being treated as waste.

Residues currently consist of an estimated 6.350 MT of plutonium in 29,530 items:

· 3000 kilograms (3.0 MT) in 20,532 items totaling more than 100 metric tonnes of materials in Buildings 371 and 707 at Rocky Flats, of which nearly 10,000 items remain to be stabilized;
· 1,500 MT in 1300 containers at Hanford;
· 1,400 kg in nearly 6,000 items at LANL;
· 400 kilograms of plutonium in 1306 items of miscellaneous residues in the F-Area at the Savannah River Site;xxx
· 35 kilograms in 202 items at LLNL;(114 cans of ash)
· 3 kilograms in 39 items at Mound;
· less than 1 kilogram in 12 items at Argonne East;
· 0.1 kg in 12 items at Oak Ridge;
· less than 1 kg in 250 items at Lawrence Berkeley;

This is the least certain and most poorly defined of all categories for the following reasons:

1. With a few exceptions, this should be categorized as plutonium waste by U.S. standards, since DOE intends to "dilute" most of the residues to attain less than 10% plutonium by weight and therefore meet WIPP acceptance criteria. The desire to "bury" nearly 7 MT of plutonium that would be recycled under Russian policy clearly undermines claims made by U.S. plutonium fuel advocates that Russia opposes the U.S. burying plutonium, and therefore the U.S. must pursue the MOX plutonium fuel option.

2. Decommissioning of plutonium facilities across the nuclear weapons complex will result in more plutonium wastes. This is because the category called "holdup"-plutonium in pipes, glove boxes, ductwork, etc-has never been quantified and is considered part of the unaccounted-for plutonium.

3. A recent proposal by DOE and its labs, called the 2025 vision, holds open the prospects of processing much of the residues at the canyons at SRS in order to increase weapons grade plutonium inventories.

 

Table 2-6. Plutonium in Residues

 

Plutonium in Residues

 

Site

Pu Content, KG

# of Items

Rocky Flats

3000

20532

Hanford

1500

1313

Los Alamos

1400

5900

SRS

400

1270

Argonne-East

0

12

Livermore

35

202

Mound

3

39

Oak Ridge

12

12

Sandia

0

0

Lawrence-Berkeley

0

250

Total

6350

29530

 

Plutonium in Waste:


In 1996 DOE estimated 3.4 MT of plutonium as "lost" through normal operations and categorized as plutonium wastes (not including plutonium released through smokestacks or in wastewater either routinely or by accident) that are buried or stored at 8 sites:

· 1.522 MT buried or stored at Hanford;
· 1.108 MT buried or stored at Idaho National Engineering Laboratory; with 0.002 MT of this credited to ANLW;
· 0.610 MT buried or stored at Los Alamos;
· 0.575 MT buried or stored at SRS;
· 0.047 MT buried or stored at Rocky Flats;
· 0.016 MT stored at Nevada Test Site from past nuclear weapons accidents;

U.S. Surplus Plutonium


U.S. surplus plutonium figures have changed substantially, although these changes are obscured by unclear management plans. In 1996 the U.S. declared 38.2 MT of weapon-grade plutonium to be surplus. The common belief is that the U.S. has 50 metric tonnes of surplus plutonium, but at no time did the U.S. declare an active inventory of 50 metric tonnes of weapons-usable plutonium.

2.1 MT of the non-pit weapon-grade plutonium is estimated to be nonsurplus based on the following:

· DOE declared 21.3 MT of plutonium at Pantex to be surplus, leaving 44.8 MT of plutonium in pit form as stockpile plutonium;
· DOE declared 38.2 MT of weapon-grade plutonium to be surplus, leaving 46.9 MT of weapon-grade plutonium as nonsurplus;

The Nominal 50 MT

 

This confusion is a function of DOE planning efforts. The Office of Fissile Materials Disposition spent five years conducting environmental impact statements (EIS) on the plutonium disposition options. The EIS processes consistently used 50.0 metric tonnes of surplus plutonium as a "nominal planning figure,"xxxi broken down as:

· 31.8 MT of "clean metal," mostly plutonium contained in weapon components (pits), designated to the MOX route;
· 18.2 MT of plutonium contained in an array of forms considered physically unsuitable or economically unfeasible to separate and purify for use in MOX and designated for the immobilization disposition route.

 

The Real Surplus


DOE did report approximately 52.5 metric tonnes (MT) of surplus plutonium (see Table 1-5) that included:

· 38.2 MT of weapons-grade plutonium and 14.3 MT of fuel-grade plutonium.
· A net amount of surplus weapons-usable plutonium in the existing inventory of 43.0 MT.xxxii

The 9.5 MT of plutonium not weapons-usable in its present state, broken down as:

· 7.5 MT of plutonium contained in irradiated mixed-oxide (MOX) and metal alloy fuel that already met the spent fuel standard.
· 2.0 MT of material commonly known as "residues" with low concentrations of plutonium for "which extraction of plutonium would not be practical and which is expected to be processed and repackaged for disposal as TRU [transuranic] waste" at the Waste Isolation Pilot Plant in New Mexico.

 

The Changing Surplus


The following changes have occurred since the surplus inventory was announced:

1. There is now 3.0 MT of plutonium in residues scheduled for disposal at WIPP and this material is identified as weapon-grade plutonium.. The addition of 1.0 MT to this route occurred when DOE rescinded its decision to send 1.0 MT of plutonium in Rocky Flats "Sands, Slags, and Crucibles" to the reprocessing canyons at SRS.

2. In 1997 Lawrence Livermore National Laboratory reported only 51.3 MT as the "latest estimate"xxxiii of surplus plutonium within a table identical to one in 1997,xxxiv with the difference being the removal of 1.2 MT of plutonium in the following forms:

· 0.8 tonnes of fuel-grade plutonium in irradiated fuel;
· 0.2 MT tonnes of fuel-grade plutonium in unirradiated reactor fuel;
· 0.1 MT of fuel-grade plutonium oxide;
· 0.1 MT of weapon-grade plutonium metal;

The reasons for this change are unknown and have not been explained by DOE. However, in 1998 plutonium pits were reclassified (see Part 3) and some surplus pits were reidentified as "national assets." Also, in 1998 Los Alamos received "permission from the politicians" to divert some "nickel-sized" pieces of plutonium from its pit disassembly and conversion "disposition" demonstration project to its nuclear weapons program for plutonium aging studies.xxxv

3. In November 1999, prior to issuing a Record of Decision on the SPDEIS in January 2000, but after finishing the final SPDEIS, DOE removed the unirradiated ZPPR fuel plates and oxides pins from the surplus inventory and declared it "Programmatic Use material."xxxvi DOE failed to mention this change in its Record of Decision and apparently did not inform the designers of the Immobilization Facility until after January 1, 2000.xxxvii

In June 2000 DOE submitted its Integrated Nuclear Materials to Congress in which they described an active surplus plutonium inventory of 52.5 MT but added the disclaimer that "a majority of the excess, approximately 48 MT, has no programmatic use." DOE then described how it removed more than 4 MT from the surplus inventory:

"A small portion of the 52.5 MT supports programmatic uses such as basic scientific research, criticality research, and production of medical isotopes. Most of this is in the form of fuel for the Zero Power Physics Reactor (ZPPR) and Fast Flux Test Facility (FFTF)."

"The Department is now considering retaining the ZPPR fuel as a national resource at ANL-W. The Department is currently preparing a Programmatic Environmental Impact Statement (PEIS) (DOE, 1999i) to consider the potential impacts of expanded nuclear facilities to accommodate new civilian nuclear energy research and development efforts and isotope production missions, including the role of the FFTF."xxxviii

Table 2-3 of this document identifies the ZPPR fuel as "in storage pending future use."

 

The U.S. Russian Agreement


Adding to the confusion is the U.S./Russian bilateral plutonium disposition agreement signed on September 1, 2000. Plutonium "disposition" is a catchphrase for putting plutonium in a highly irradiated storage environment. Instead of 50 MT to be "disposed," the agreement calls for only disposing 34.5 MT. DOE has continued to incorrectly declare 52.5 MT of surplus plutonium in the active inventory (see Figures 2-7 and 2-8 on following page).

One unfortunate consistency in plutonium management has been overlapping and poorly integrated bureaucracies. DOE's Office of Fissile Materials Disposition (OFMD) and the Office of Environmental Management (EM) have never presented a cohesive plan for managing non-pit plutonium to the public, and they can't seem to agree on the numbers:

· EM incorrectly described the 14.3 MT of non-weapon grade plutonium as "non-weapon-capable" even though DOE defines weapons-usable as "all plutonium except that present in spent [irradiated] fuel and plutonium which contains greater than 10% plutonium 238."xxxix

· Although WIPP was never said to be part of the fissile materials disposition program in terms of surplus plutonium, both parties show 3.1 MT of weapons-grade plutonium being disposed of at WIPP. OFMD's chart states the material will be "diluted in waste" and sent to WIPP; whereas the EM chart simply shows this waste being sent to WIPP;
· EM inaccurately claimed that 4.8 MT of reactor fuel was surplus.

Table 2.7. Non-pit Plutonium Inventory

 

Plutonium Form

# Items

Plutonium Content, MT

Metals

6,361

8.59

Oxides

12,537

6.35

Residues

29,530

6.35

Unirradiated Fuel

52,000

4.6

Total

100,528

25.9

 

 

Table 2-8. DOE's Variety of Surplus Plutonium Numbers

 

Form

DOE's Official Estimate of
Surplus Pu

Weapon-
Grade

Fuel-
Grade

Total*

"Planning" Estimate of Surplus Pu Total **

Amount for Disposition under U.S./Russia Agreement

 

Metal

27.8

1.0

28.9

(1) 36.2

27.8

Oxide

3.1

1.3

4.4

9.0

3.1

Reactor Fuel

0.2

4.4

4.6

4.8

0.0

Irradiated Fuel

0.6

6.9

7.5

0

0.0

Other Forms

6.4

0.7

7.1

0

4.6

Totals

38.2

14.3

52.5

50.0

34.5

 

*Metal includes plutonium in pits, ingots, and buttons; Oxide refers to plutonium oxide, reactor fuel refers to prepared but unused MOX fuel, metal-alloy fuel elements, pellets, and MOX powder; and "other forms" refers to uranium/plutonium oxides and "residues" from the fabrication of weapon components.

(1) This includes 7.0 MT "that may be declared surplus in the future."(2) In 1997 DOE reported that 0.223 MT of plutonium/uranium fuel material that had not been fabricated into finished fuel components is part of the 4.8 MT total of unirradiated fuel and therefore accounted for an additional 0.2 MT of reactor fuel in the planned category; xl

 

Table 2-9. BREDL's Estimate of Active U.S. Plutonium Stockpile

 

Form

BREDL's Current Estimate of Surplus Pu

Weapon-
Grade

Fuel-
Grade

Total *

Stockpile Pu

wg

fg

 

Amount for Disposition under U.S./Russia Agreement

 

Metal in Pits

21.2

0

21.2

44.9

0

44.9

21.2

Clean Metal


Oxide

3.7


3.1

0


1.6

3.7


4.7



2.1

0


0



2.1

3.7


4.7

Impure Metal

2.8

1.0

3.87

0

0

0

2.8

Reactor Fuel

0

0.0

0.0

0.2

4.2

4.4

0.0

Irradiated Fuel

0.6

6.1

6.7

0

0.8

0.8

0.0

Residues

6.5

0.7

7.2

0

0

0

0.4

Totals

37.9

9.4

47.3

47.2

5.0

52.2

31.8

 

Nuclear Site

Total Plutonium Inventory, in Metric Tonnes (1.1 English Ton = 1.0 metric tonne) and
by material

Metal

Oxide

Residues

Solutions

Reactor Fuel

Irradiated Fuel

Total

 

Hanford (1)

0.7

1.5

1.5

0.343

0.6

6.6

11.243

ANLW

0.1

0

0

0

3.8

0.1

4.0

INEEL

0

0

0

0

0

0.5

0.5

SRS (2)

0.490

0.800

0.400

0.110

0

0.3

2.1

PANTEX (3)

66.1

0

0

0

0

0

66.1

LANL (4)

1.1

0.7

1.4

0

0

0

3.2

LLNL (5)

0.020

0.102

0.035

0

0

0

0.4

RFETS (6)

6.6

3.2

3.0

0.043

0

0

12.9

TOTALS (7)

75.13

6.35

6.35

0.496

4.4

7.5

100.2

 

(1) DOE reported 11.0 MT in 1996. The plutonium in solutions may be double counted.
(2) Does not reflect plutonium received from Rocky Flats, which could bring total as high as 2.5 MT.
(3) This is total plutonium at Pantex plus in weapons stored or deployed. There are 12,000+ plutonium pits presently in storage, with approximate on-site inventory of 35 to 40 MT. The total inventory of plutonium in pits has probably been reduced by up to 0.5 MT due to stockpile surveillance and pit disassembly and conversation demonstration project at Los Alamos.
(4) Does not reflect the plutonium Los Alamos has from Rocky Flats and from Pantex.
(5) Probably reflects plutonium shipped from Rocky Flats.
(6) 1,200 plutonium pits were transferred to Pantex with no decrease in inventory means that plutonium in pits were not part of declassified inventory at RFETS. 0.1 MT of Pu in solutions were converted to oxides, not reflected here.
(7) Higher total may mean that plutonium in solutions is double counted and reported as oxide or metal by DOE. Other sites include Sandia, Oak Ridge, Mound, Argonne-East, and Lawrence Berkeley Laboratory, and amount to <0.1 MT.

 

Plutonium In Pits

Figure 3-1. Simplified illustration of a plutonium trigger, or "pit", with storage "AL-R8" storage container. Source: U.S. Department of Energy (DOE), Office of Fissile Materials Disposition (OFMD). http://www.md.doe.gov

Plutonium pits are finished weapon components and comprised of numerous parts, including metal cladding, welds, a pit tube, neutron tamper(s), and plutonium hemispheres (usually hollow-cored). The sealed pit tube carries deuterium-tritium gas into hollow-core pits in order to boost the nuclear explosive power of weapons.

This illustration shows stainless steel as the outer cladding, but some pit types are also clad with beryllium, aluminum, and possibly vanadium; and there are experimental designs called "not war-reserve like" pits stored at Rocky Flats in Colorado.

There are more than 12,000 plutonium pits stored at the Pantex Nuclear Weapons Plant near Amarillo, Texas - - of which 7,000 to 8,000 are "surplus"- - and another 8-10,000 stored in nuclear weapons, both deployed and stored.

Plutonium Pit Basics

Describing Pits, No. 1

"Pits can generally be characterized as nested shells of materials in different configurations and constructed by different methods." Los Alamos National Laboratory. ARIES Fact Sheet. 1997.

Plutonium pits are the triggers in most nuclear explosives. Pits are sealed weapon components containing plutonium and other materials and came into being in 1956, replacing the plutonium "capsule" trigger design.xli Pits are surrounded by carefully machined high explosive spheres. When the high explosives are detonated the plutonium is compressed and imploded, thus triggering the nuclear detonation (see Figure 1-1).

Describing Pits, No. 2

Rocky Flats described pits as a "pressure vessel designed to withstand, without yielding, the boost gas or other operational pressures which vary from weapon to weapon but are in the range of hundreds of psi." Pits are also "designed to provide containment of the radioactive materials to prevent the release of contamination or other unsafe conditions." Other features of pits include:

· all metal construction generally using three joint welds at the "equator," the tube pinch-off, and the tube to shell brazed joint;
· an absence of o-rings, seals, or other non-metallic components which are sensitive to either heat or cold.

Source: Safety Analysis Report for the AL-R8 Container. Rocky Flats Plant. 1990.

Pits were fabricated at the Rocky Flats plant in Colorado from about 1954 to 1989, when safety and environmental problems forced a production shutdown. Rocky Flats is infamous for thirty five years of unsafe operations and costly accidents resulting in massive radiological contamination, but in the nuclear weapons complex it is equally known for producing high quality, "diamond-stamped" plutonium pits considered the most durable and resilient parts of nuclear weapons.

There are about 48 different types of pits (see Table 3-1), each designed for use in specific nuclear weapon systems and to be stored for 20 years or more inside a weapon environment. Long-term storage (more than five years) of pits outside of weapons is a program filled with uncertainties. Designers and weaponeers within DOE refer to the variety of designs in terms of "pit families,"with some more important variations including:

· shape and mass of the plutonium within the pit;
· the presence or absence of highly enriched uranium;
· the presence or absence of tritium;
· the type of metal cladding;
· bonded vs. nonbonded.

Pit numbers and DOE management terminology

Normal operations coupled with START I treaty between the U.S. and Russia turned the Pantex nuclear weapons plant into a disassembly facility in the 1990's (Figure 3-2). 11, 875 weapons were dismantled, with most of the plutonium pits being sent to "Zone 4" for "interim" storage.xlii More than 11,000 plutonium pits accumulated at Pantex during this time, (Figure 3-2).

About 1200 pits were shipped to Pantex between 1997 and 1999 from Rocky Flats, and another 60 pits were shipped from SRS to Pantex in 1998. Pantex in turn shipped about 20 pits/year to Los Alamos for its surveillance/inspection program, and an undisclosed amount (but less than 100) to Los Alamos for plutonium pit disassembly and conversion demonstration program, leaving more than 12,000 pits at Pantex today.xliii

Figure 3-2. Weapons Dismantlement at Pantex, 1990's.
(427 dismantlements were scheduled for Year 2000).

 DOE now categorizes pits as surplus to military needs or as "national security assets" (NSA), the latter a category concocted in 1998 and composed of:

· strategic reserve pits, including surplus pits considered defense program "assets;"
· "enduring stockpile" pits that belong to existing weapon systems;
· "enhanced surveillance" pits that may include surplus pits.xliv

National Asset pits are scheduled to be stored indefinitely at Pantex in retrofitted Building 2-116, possibly the most robust facility at Pantex but not one without problems. At least one "national security asset" pit, the problematic W-48, is not allowed in 12-116 because of heat concerns; and there is no funding to move the national asset pits into 12-116 this fiscal year.xlv

The list of NSA pits is not constant, and the "design agencies"-Lawrence Livermore and Los Alamos National Laboratories--have failed to update their list of national security assets since February 1999, leaving Pantex in the dark:

"an updated list has been requested by letter, in briefings, and verbally to the person in charge of the list. To date, an update has not been received. This is an open issue." xlvi

The total amount of plutonium in surplus pits was declared to be 21.3 MT in 1996. DOE maintains this number is current, but the reclassification of some surplus pits as "national assets" leaves this questionable. If START II arms reductions are implemented, another 7.0 MT of surplus plutonium in about 2,000 to 2,500 pits is likely to be declared.

Surplus pits are scheduled to remain in Zone 4 at Pantex (see Pit Storage at Pantex, page 3. )
until they are sent to a Plutonium Pit Disassembly and Conversion Facility (PDCF) scheduled to open later this decade at Savannah River Site. (SRS). Plutonium pit disassembly and conversion refers to "the removal of the plutonium from the nuclear weapon pit and conversion [of the plutonium and other parts] to an unclassified form that is verifiable in the sense that, containing no classified information, the form can be examined by inspectors from other nations." xlvii Size, shape, mass and isotopic composition of the plutonium and other parts are considered traits in need of declassification at the PDCF.

Table 3.1 Plutonium Pit Types in U.S. Nuclear Weapons "Enduring Stockpile."

 

Designer
Laboratory

Warhead

Pit Type
(# ID) xlviii xlix

Container

Unique Properties and/or Safety Issues

 

Los Alamos National Laboratory

B61-3,4,10

B61-7,11




123

125




2040

2040



Present container unsuitable for long-term storage. (See Pit Storage, Page 3). B61-4 also reported as Pit Type 118

W76

116

2030

Most heat sensitive LANL design

W78

117

2030

 

W80

124

2030

Responsibility being transferred to LLNL

W80

119

2030

 

W88

126

2030

 

Lawrence Livermore
National Laboratory

B83




MC3350



MODF




Heaviest Pit l, Fire Resistant Pit

W62

MC2406

2030

 

W84

(1)

unknown

Fire Resistant Pit

W87

MC3737

2040

Fire Resistant Pit. Unsuitable container.

 

Container refers to the AL-R8 Subtype.li There are no replacements for the 2040 at this time. Pit type ID's were determined from 1990 Rocky Flats Safety Analysis Report for AL-R8's and from Dow and Salazar. Re: Storage Facility Environmental Requirements for Pits and CSA's. August 22, 1995.
(1) One high numbered LLNL pit, the MC 3650, was reported by Rocky Flats to have the highest heat load of any pit, including surplus pits. This could be the W84.

 

Table 3.1.B: Plutonium Pit types from retired weapon systems.

 

Design Lab

Warhead

Pit Type

Container

Unique Properties and/or Safety Issues

Los
Alamos

B28

83

2030

 

 

B28-0

93

2030

minimum decay heat load lii

 

B43

79

unknown

Beryllium cladding

 

B43-1

101

2030

Beryllium cladding

 

W33

unknown

unknown

 

 

W44

74

2030

Beryllium cladding

 

W44-1

100

2030

Beryllium cladding

 

W-50-1

103

2030

 

 

B54

81

2030

Pits require cleaning liii

 

B54-1

96

2030

Pits require cleaning

 

B57

104

2030

 

 

W59

90

unknown

 

 

B61-0

110

2030

 

 

B61-2,5

114

2040

Unsuitable container, no replacement yet

 

W66

112

unknown

 

 

W69

111

2030

 

 

W85

128

2030

 

Lawrence
Livermore
National
Laboratory

W48

MC1397

2030

Beryllium clad pits, require cleaning prior to LTS

 

W55

MC1324

2030

Suspected to be beryllium clad

 

W56

MC1801

2040

High radiation pits, require cleaning prior to LTS

 

W68

MC1978

2030

 

 

W70-0

MC2381

2030

 

 

W70-1

MC2381a

2030

 

 

W70-2

MC2381b

2040

Unsuitable container with no replacement yet

 

W70-3

MC2381c

2060

Suitability of container

 

W71

Unknown

Unknown

Pits require cleaning

 

W79

MC2574

2030

Suspected to be beryllium clad

Plutonium Mass, Beryllium, and HEU

Figure 3-3. Plutonium mass in pits is reduced through the use of neutron tampers. Source: An Introduction to Nuclear Weapons. 1972.

The amount, or mass, of plutonium that is inside of a pit varies and even the average amount remains classified. But enough evidence exists to declare a range of 1 to 6 kilograms (2.2 to 13.2 pounds) of plutonium mass in pits. Only one kilogram of plutonium is necessary for a 1 kiloton explosion,liv and Los Alamos defined a maximum material weight of 6 kilograms in pit shipping containers.lv Considering there is 66.1 MT of plutonium in approximately 20,000 plutonium pits, the average plutonium content is just over 3.0 kilograms per pit, or 6.6. pounds.

Two design variations can be used to decrease the plutonium mass:

1. Neutron tampers (Figure 3-3) are used to scatter escaping neutrons back into the plutonium or HEU core after the nuclear chain reaction starts.lvi One of the more common neutron tampers is beryllium, a highly toxic light metal. Because classified nonnuclear pit parts will be "declassified" at a PDCF by using furnaces to melt down the classified shapes,lvii this operation poses extreme workplace hazards when the tamper is high-purity beryllium (Figure 3-4).

Figure 3-4. How Toxic is Beryllium?
According to the Lawrence Livermore National Laboratory Health and Safety Internet Site, "some people are very susceptible to getting Chronic Beryllium Disease" when inhaling small amounts of beryllium dust. Acute Beryllium Disease can "cause toxic reaction to the whole body " if large amounts are inhaled.
(http://www-training.llnl.gov/wbt/hc/Be/Hazards.html)

2. The use of Highly Enriched Uranium (HEU), also known as "Oralloy, in pits creates what are referred to as "composite cores" and were a "major advance" in weapons design that reduced the probability of pre-initiation of the nuclear explosive, and allowed for a reduction in the amount of plutonium in the pit.lviii As a result, "the pits in the US stockpile can be generally grouped into two types: (1) those containing weapons-grade plutonium and (2) those containing weapons-grade plutonium and highly enriched uranium."lix

The presence of HEU in pits poses accounting, handling, and classification problems at a PDCF.

In 1998 the ability to perform adequate materials control and accounting measurements on incoming pits was found to pose a technically high risk at the planned PDCF.lx This risk is higher with HEU pits since there are no "proven techniques for measurement" of this type. lxi

Having HEU parts in plutonium pits also necessitates decontamination of the HEU to levels that meet strict acceptance criteria at the Y-12 plant at Oak Ridge, Tennessee. The Y-12 plant is responsible for all storing all military HEU, it is not a plutonium processing site, and designation as such would meet stiff and justifiable resistance from the state and local communities.

Los Alamos encountered difficulties meeting the previous criteria of 20 disintegrations per minute of plutonium 239 in HEU metal, "with 30% of the shipped parts presently being returned." However, the new limit for plutonium contamination in HEU-oxide form has changed to 2.7 parts-per-million, allowing plutonium levels "several orders of magnitude" higher than the metal standard.lxii

Because of this issue, the final form of the HEU at a pit disassembly and conversion plant was undecided as of a year ago. The decontamination methods under consideration include:

· electrolytic etching, the current method at LANL that has achieved marginal success at meeting metal acceptance criteria at Y-12 but generates less waste;
· Acid spray-leach; the historical process that involves spraying parts with acid and then soaking in a diluted acid solution for up to three hours, producing large volumes of liquid waste; or
· brushing of parts with a wire brush or blasting parts with "some medium," both of which "are not expected to achieve the Y-12 acceptance criteria." lxiii

Plutonium Shape

Because the critical mass for a spherical shape is "less than for any other geometrical form of the given material,"lxiv most pits are reported said to be spherical in shape. It is unlikely that plutonium in pits are only spherical:

· Passive NMIS measurement systems are in development to estimate the shape of plutonium assemblies inside of containers.lxv
· DOE continues to censor the discussion of shape of critical masses in the sanitized version of Introduction to Nuclear Weapons (Section 1.22).lxvi
· Criticality experiments at Rocky Flats in the 1960's included cylindrical shapes of plutonium.lxvii

Isotopic Composition

The amount of Plutonium-240 is the key isotopic variable in weapon-grade plutonium because its high rate of spontaneous fission poses a higher risk of "pre-initiation," or an early chain reaction, of the fissile material. Higher quantities of plutonium-240 mean increases in critical mass requirements, and therefore costs more to design, develop, and produce the warhead.lxviii

Early weapons had plutonium-240 content as low to 1.5% but more commonly 4-7%; and in 1972 the Pu-240 content in most stockpile weapons was said to be about 6%.lxix The isotopic composition varied slightly according to the source of the plutonium (Figure 3-5) and the design of the pit.

Figure 3-5. Variation in average isotopic composition by source.
From: An Introduction to Nuclear Weapons. 1972.


During five years of Environmental Impact Statements, DOE never informed the public that declassification of pits included declassifying the isotopic composition. One month after the January 2000 Record of Decision to build a PDCF at SRS was signed, the "blending" of plutonium oxides from two or more pit types was required to declassify the isotopic composition of the powder.lxx It is unclear whether this requirement is an artifact of the Atomic Energy Act or a requirement for the plutonium fuel factory.

Cladding and Beryllium Problems

The W-48

The pit for the W-48 nuclear artillery shell is a clad with beryllium, and has created great problems at Pantex. In 1992 a W48 pit cracked during a Pantex weapon disassembly operation that required rapid cooling followed by rapid heating during removal of the high explosives. The crack of 0.025 inch wide and 8.0 long in the outer beryllium shell resulted in airborne plutonium contamination and was one of the rare accidents involving pits. Afterward, a summer temperature limit of 150 degrees was established for W-48's. In spite of these problems, DOE is retaining an undisclosed number of W-48 pits as National Security Assets.


Plutonium pits have an outer cladding of beryllium, aluminum, or stainless steel. Vanadium is another cladding element, but it is unknown whether it is just experimental or in use. Vanadium was used in 1993 during the W89 pit re-use program at Pantex as a fire resistant cladding on W68 pits being converted for use as W89 pits,lxxi and the classified plutonium part inventory at RFETS presently includes six Pu/Vanadium hemishells.lxxii

At least seven pit types are known or suspected to be clad with beryllium. (Table 3.1.B),lxxiii posing the most significant problems with storage and dismantlement of pits:

· pit disassembly can expose workers to highly toxic beryllium dust and fumes;
· beryllium clad pits appear to be more likely to require cleaning (see Table 3.1.B to remove any potentially corrosive organic materials, and pit cleaning can expose workers to airborne beryllium;
· higher sensitivity to temperature fluctuations;
· increased risk of corrosion from chlorides and moisture which are found in storage containers;
· pits clad with beryllium "are more vulnerable to fracture under impact loading."lxxiv

Pits as a Heat Source

Pits that Heat Up


"Because of natural radioactive decay, each plutonium pit is an intrinsic heat source, producing as much as roughly 18 watts in heat load. Currently, magazine heat loads at Pantex can reach as high as a few kilowatts-an amount sufficient to raise internal magazine temperatures well above ambient. Elevated magazine temperatures are a cause of concern because of corresponding elevations in pit temperatures. Because the AL-R8 containers are primarily designed to keep heat from external sources from entering the pit and to protect the pit in the event of a fire, their design also serves to prevent heat produced by the pit from escaping. Thus, depending on pit wattage, relatively high differences in temperature (ATs) from pit to can can occur. Some high-wattage pits, with average temperatures greater than 50 degrees C, are known to have reached temperatures near 150 C while stored in Zone 4." Source. Pit Storage Monitoring. 1995.

Many pits are sensitive to temperatures, particularly those clad with beryllium. Los Alamos and Lawrence Livermore have expressed major concerns over heating of pits since early this decade.lxxv In 1995 Lawrence Livermore and Los Alamos National Laboratories recommended temperatures between 65 and 75 degrees Fahrenheit for storage buildings with strategic reserve pits, and less stringent recommendations for "surplus" plutonium pits.lxxvi

In August 1998 an estimated thirty plutonium "W76" pits were moved from one Pantex Zone 4 "bunker" to another "due to potential temperature concerns during the recent heat wave."lxxvii The W76 pits are part of the large "strategic reserve"of pits scheduled to be stored indefinitely at Pantex.

Tritium in Pits

In 1998 Los Alamos released a fact sheet that stated:

"A significant number of pits processed by the ARIES facility will contain tritium."lxxviii

The "fact that tritium is associated with some unspecified pits" was declassified in 1992.lxxix During the Environmental Impact Statements for plutonium disposition, DOE vaguely admitted that some plutonium pits were "contaminated" with tritium and that these pits would have to be decontaminated; but finally acknowledged that some pits contain tritium by writing:

"DOE knows how many pits contain tritium."lxxx

The reason for having tritium in pits by design is unknown but the impacts of this design on the disassembly of plutonium pits are now more open.

Pits that contain tritium must be processed up-front in a highly secretive "Special Recovery Line" where plutonium "is separated from highly enriched uranium (HEU) and other parts and then processed in a vacuum furnace that drives off tritium and produces a metal ingot. The tritium is captured and packaged as a low level waste. The resulting plutonium ingot is assayed and then reprocessed if it still contains tritium."lxxxi This process was sufficiently difficult enough to dissuade Los Alamos from processing pits containing tritium in its original ARIES demonstration project when only 40 pits were planned for disassembly and conversion.lxxxii

The major environmental impact of this process is tritium air pollutants. In the June 1998 Environmental Assessment for the plutonium pit demonstration project at Los Alamos involving 250 plutonium pits over a four year period, DOE reported air emissions of "up to 69 curies of tritium each year." In the 1998 Draft SPDEIS, DOE buried the impacts in a source document by choosing to omit a small table occupying less than a half-page reporting that 1100 curies of tritium will be emitted annually at a PDCF.lxxxiii

Tritium Contamination vs. Pits that contain tritium


"Hydride corrosion of uranium and plutonium may have significant implications for the lifetime of uranium [and plutonium] in nuclear weapons."

A Model for the Initiation and Growth of Metal Hydride Corrosion. LA-UR-00-5496.


Pits could become contaminated if they contain tritium by design, or if they become contaminated with tritium by accident. In any case, any kind of hydrogen-plutonium reaction is undesirable because it could induce hydride corrosion of the plutonium metal, causing pitting and a growth of hydride film along the surface,"lxxxiv as well as producing a pyrophoric plutonium hydride compound.

Bonded vs. NonBonded Pits


DOE had declassified information about bonded weapon components prior to 1996.lxxxv A 1998 Technical Risk Assessment of the Plutonium Pit Disassembly and Conversion Facility identified the implications of this distinct design variable when it identified an option with the least technical risk for disassembly and conversion of most plutonium pit types. The Metal-Only Option was suggested to process only "nonproblem pits" to produce only a metal plutonium product and no plutonium oxide. This was because "many of the pits, perhaps as many as 80%, can bypass the hydride/dehydride (conversion to metal) module as the plutonium metal can be mechanically separated from the pits."lxxxvi

The pit types where plutonium metal can be mechanically separated using a lathe are called "non-bonded" pits; whereas the pits that require chemical processing-either pyrochemical or liquid-to separate the plutonium in the pit from other pit parts are called "Bonded" pits. In bonded pits, the the plutonium is bonded to other metals in the pit, such as stainless steel, beryllium, and/or uranium.lxxxvii At least one Los Alamos source reports that all Russian plutonium pits are nonbonded.lxxxviii

Figure 3-6. Plutonium Pit Bisector.
"The prototype bisector was designed and tested at Livermore. Using a chipless cutting wheel, it can separate weapon pits into two half-shells in less than 30 minutes so that the plutonium in them can be recovered for disposition." Science and Technology Review. April 1997. Lawrence Livermore National Laboratory.


Bonding and Pit Disassembly and Conversion Issues


To avoid liquid acid "aqueous" processing of pits, Lawrence Livermore National Laboratory developed the ARIES system that included a pit "bisector" for cutting plutonium pits in half (Figure 3-6) --which suggests that most or all bonded pits are of Livermore design.lxxxix The bisector is the front end the Advanced Resource Integrated Extraction System (ARIES) that DOE chose as a major part of the pit disassembly and conversion process while it was still in the design and experimental phase.


Following the pit bisection, the plutonium must the be chemically separated from the pit cladding and other pit parts. The two experimental technologies proposed are hydride-dehydride, which recasts the plutonium as a metal, and HYDOX, which utilizes the reaction of plutonium with hydrogen to produce a plutonium oxide powder.

Do Bonded Pits Lack Tritium?


It is evident that bonded pits are "problem pits" since the metals-only option would defer processing these pits and simplify the plutonium disposition process; although considerable evidence also points to an absence of tritium in bonded pits:

a. Pits containing tritium were not "selected as part of the ARIES pilot demonstration because of the difficulties associated with handling tritium;"
b. The original ARIES demonstration line involved only 40 pits and 7 pit types, and the Special Recovery Line was not required for these pit types;
c. The pit bisector in the ARIES process was specially designed to take "into account the dimensions, encapsulation methods, construction materials, and manufacturing techniques of these pits in order to incorporate the representative configurations that will be processed through ARIES." (Gray, 1995. Lawrence Livermore National Laboratory).
d. Chemical processing is unnecessary to separate plutonium from other pit parts in nonbonded pits, so HYDOX was designed for bonded pits as well

 

Pit Tubes and Pit Re-Use at Pantex


While DOE pursues plutonium pit fabrication at Los Alamos and possibly SRS, it has abandoned, at least for now, the plutonium pit re-use project planned for Pantex. A pit-re-use project occurred at Pantex in the early 1990's when Rocky Flats was shut down. This project allowed DOE to proceed to complete the W-89 weapon program by re-using W68 pits and converting them to fire-resistant pits by cladding them with vanadium. Heralded then as an innovative approach that avoided messy pit fabrication, the latest plan for pit-re-use went unfunded in fiscal year 2000,xc and there is no indication that DOE plans to pursue this work, indicating a preference for new pit production at SRS.

One of the sticking points regarding pit-re-use involves pit tubes. Plutonium pit tubes are designed to carry the booster tritium gas from the tritium reservoir to the hollow core of the pit at the time of detonation. According to pit-tube fabrication experts, pit tubes:

· are constructed of annealed type 304 stainless steel that is "very ductile" and able to take severe deformation without cracking or leaking;
· are placed at assembly within tightly fitting slots in the high explosive and must be straight and within true position within 0.02 in 1 inch.
· are usually of 0.12 inch diameter, for pressure testing, evacuation and filling.
· are attached to stainless steel shell by TIG welding or electron beam welding and to beryllium and aluminum shells by high temperature braze xci
.
Pit re-use was always described as "non-intrusive" during the Environmental Impact Statement process. After Pantex was selected for the pit re-use mission, the mission was renamed "pit requalification" and changed from non-intrusive to intrusive because it included pit tube replacement and refurbishment:

"SNM Requalification at PANTEX for FY 98 has been as continuation of the original
effort and has included an increase in scope to address pre-screening, tube replacement and reacceptance...tube replacement is a capability that was utilized at Rocky Flats. A similar capability is being supported as a part of the Pit Rebuild program at LANL" xcii

Figure 3-7. Sun-Woo, Characterization of Stainless Steel 304 Tubing.

 Pit tube replacement was being advocated by Los Alamos prior to the funding cutoff for this program. Because pit tubes are bent to very specific configurations and there is no record of the number of times they have been bent, Los Alamos wanted to replace all pit tubes. However, a LLNL report discussing the stainless steel used in W87 pits reported that the tube would need to be bent at least ten times to pose a great risk of failing (Figure 3-7). xciii

PLUTONIUM STORAGE AT PANTEX: Stockpile Negligence?


Plutonium pits are multimillion dollar weapon components being stored in substandard conditions.

Most pits are stored in the AL-R8 container (Figure 3-11) which is unsuitable for long-term storage. Designed by Dow Chemical in the 1960's. AL-R8's are unsealed and pits stored in them:
· require extra humidity and temperature controls
· are prone to corrosion because the internal celotex packing-sugar cane, paper, starch, and wax--is a source of chlorides and moisture that can lead to corrosion of the pit cladding.
· do not meet all safety criteria-specifically the 1100 pound dynamic crush test.
· provide poor radiation shielding.

There are about 2,000 corroded AL-R8's at Pantex because they were procured without the corrosion resistant liner.

Figure 3-8. AL-R8.

 

THE AT-400A Fiasco

DOE spent $50,000,000 designing and developing the
AT-400-A (Figure 3-9) dual-use shipping and storage container for plutonium pits. Its advantages included:
· a sealed, inert gas environment that would prevent corrosion and other degradation of pits
· better radioactive shielding;
· a 50-year design life.

It's disadvantages included cost ($8,000/unit) and problems associated with the weld-possible burn through of the containment vessel.

DOE estimated that 2,000 plutonium pits per year could be repackaged in the AT-400A, leaving pits in the safest container within a five year period. After the repackaging startup was delayed by more than a year, 20 pits were repackaged in a pilot run before DOE pulled the plug on the entire program. Twenty W-48 pits remain in AT-400A's.

Figure 3-9. AT-400A



The Sealed Insert

Figure 3-10. AL-R8 with Sealed Insert, 2030 model. There is still a need for 2040 models for several pit types, including national asset pits


DOE replaced the AT-400A with the AL-R8 Sealed Insert (Figure 3-10). It is a significant improvement over the AL-R8 because of the sealed, bolted, stainless steel inner container, but is still not considered worthy of shipping certification. Problems now plaguing this program include xciv :

· a lack of funding to buy new containers at a cost of $2800/unit.
· the need to certify larger "2040-type"AL-R8 sealed inserts for about several pit types ome pits, including most stockpile pits;

?
Figure 3-11. DOE still has no pit shipping container


· the lack of a pit cleaning station for 1500 pits too dirty for long term storage, so Pantex is having to double-handle some pits;
· a lack of funding for labor, so Pantex is not able to run two shifts;
· a lack of funding for monitoring;
· limited funds for dealing with another cracked pit.
· DOE has only 300 shipping containers called FL's, the certification for the FL's expires in 2002, and more than 200 of these were recently found to not match design drawings;

Figure 3-12. Zone 4 Bunkers at Pantex. Plutonium pits are literally stacked to the ceilings in these WWII and 1960's vintage bunkers. All but a few of these facilities lack required humidity or temperature controls, and are unlikely to withstand an aircraft crash - a serious issue due to the proximity of Amarillo International Airport. Pantex has little space for additional pits.


· DOE has made no reported progress developing a new shipping container (Figure 3-11) to replace the FL and AT-400A.;
· a planned upgrade to Building 12-66 at Pantex was abandoned after the design work was complete, leaving decades-old bunkers as the main storage buildings. (Figure 3-12) These facilities were not supposed to be used after the Year 2000, but will be used indefinitely.

DOE's Dirty Plutonium Secret
Plutonium Pit Production at Savannah River Site


In the newly downsized U.S. Nuclear Weapons Production Complex, Savannah River Site is the only remaining major plutonium processing site in the country and is in line for three new facilities promoted as "nonproliferation" missions:

a Plutonium Pit Disassembly and Conversion Facility that will process surplus plutonium pits and convert the plutonium in those pits to an unclassified plutonium oxide powder.
b Mixed Oxide (MOX) Fuel Fabrication Facility where "pure" or nearly pure surplus plutonium will be purified using liquid acid processing and then mixed with uranium to make MOX plutonium fuel for nuclear reactors;
c. A Plutonium Immobilization Plant (PIP) where impure and very difficult to purify surplus plutonium will be mixed with uranium and a "titanate" ceramic to make ceramic "pucks." (See below for explanation of can in canister)

Tritium production and recycling is said to be the only nuclear weapons production mission at SRS. However, because Rocky Flats no longer produces nuclear weapons triggers called plutonium pits, new pit production is slated for SRS, and this would inevitably involve the PDCF, making it a dual-use facility:

Plutonium Aging and ARIES as a Weapon Program

In 1998 the Government Accounting Office reported that:

"DOD was concerned that the aging of pits was not clearly identified in our report as
a driving force of pit-production requirements. DOD said that it could not give detailed pit-manufacturing requirements until the lifetime of pits is specified more clearly by DOE."

DOE plans to spend over $1.1 billion through fiscal year 2007 to establish a 20-pits-per-year capacity. But this budget does not include disassembly work xcv which is clearly being funded by OFMD under the ARIES development. In addition, plutonium pit enhanced surveillance program, a SSM program, ARIES was identified as a "pertinent task" for the "Pit Focus Program."
material property data from pits dismantled in the ARIES process in order to expand the age-
correlated database of applied plutonium properties.xcvi

Chairman Spence and the Foster Panel


In 1996 Chairman of the House National Security Committee Floyd Spence (R-South Carolina) issued a report titled "The Clinton Administration and Stockpile Stewardship: Erosion by Design," in which he wrote that,"Unprecedented reductions and disruptive reorganizations in the nuclear weapons scientific and industrial base have compromised the ability to maintain a safe and reliable nuclear stockpile...unlike Russia or China, the United States no longer retains the capacity for large-scale plutonium "pit" production and DOE's plans to reconstitute such a capacity may be inadequate."

In December 1999 a congressional panel called the Foster Panel published "FY 1999 Report of the Panel to Assess the Reliability, Safety, and Security of the United States Nuclear Stockpile,"
recommending that DOE:

"immediately begin the conceptual design phase of a pit production facility adequate to meet national security needs." xcvii

The Chiles Commission


Another vote for pit production was cast by the Chiles Commission, which was established to review the nuclear weapons workforce and determine needs and priorities. The Commission concluded in 1998 report that, "large numbers of workers are reaching retirement and a new generation of workers must be hired and trained in order to preserve essential skills." One of these essential skills is the machining of "materials unique to nuclear weapons," such as plutonium, highly enriched uranium, and beryllium. Their recommendations called for a renewed emphasis on plutonium pit production:

"DOE needs to give a much higher priority to detailed planning for the production of replacement weapons components. In the absence of such planning, the sizing of the nuclear weapons workforce at the production facilities is left unnecessarily uncertain" xcviii

The SRS Strategic Plan


The Savannah River Site is very explicit about its potential pit production mission within some documents but does not publicize its intentions in an up-front manner. The Savannah River Site Strategic Plan: A Strategic Plan for 2000 and Beyond xcix lists three focus areas for SRS:

· Nuclear Weapons Stockpile Stewardship
· Nuclear Materials Stewardship
· Environmental Stewardship

The plan states that Nuclear Weapons Stockpile Stewardship "emphasizes science-based maintenance of the nuclear weapons stockpile. SRS supports the stockpile by ensuring the safe and reliable recycle, delivery, and management of tritium resources; by contributing to the stockpile surveillance program; and by our ability to assist in the development of alternatives for large-scale pit production capability, if required. associated with products and services essential to achieving the Department of Energy's (DOE) goals."c Under Goals, Objectives, and Strategies, the strategic plan states as a goal:

"Consolidate existing facilities and plan, design, and construct new facilities to support current and future stockpile requirements."

Within this goal is the objective to:

"Support the development of contingency plans for a new pit production facility to meet future stockpile requirements as national needs emerge."
Within this objective is the strategy to:

"Develop partnerships with the national weapons laboratories and Oak Ridge Y-12 Plant to outline roles for each organization in a large- scale pit manufacturing project."

Preparing for Pit Production at SRS?

Several operations at SRS suggest that the site is quietly and surreptitiously implementing its strategic plan as it relates to large-scale plutonium pit production:

1. Developing Plutonium Casting Capability. An essential part of plutonium pit fabrication is "casting plutonium metal feed ingots after adding gallium to the plutonium metal and shape-casting the feed ingots into hemishells."

The Los Alamos Perspective


Stephen Younger, the Associate Laboratory Director for Nuclear Weapons at Los Alamos National Laboratory, which is operated by the University of California under contract to DOE. recently wrote, in Nuclear Weapons in the Twenty-First Century that

"Plutonium pit production can be maintained at a small rate at Los Alamos, but any stockpile above about one thousand weapons will require the construction of a new large production plant to replace the Rocky Flats facility, which ceased production in 1989."
"In the case of DOE, an extensive infrastructure of laboratories and plants is required for the Stockpile Stewardship program, including a new manufacturing capability for plutonium pits"

Yet, even under START III conditions, "the U.S. has offered to begin negotiations on ceilings of 2,000 to 2,500 weapons immediately upon Russian ratification of the START II treaty" Obviously, as long as the U.S. intends to maintain more than 1,000 nuclear warheads, then demands for large-scale pit production will be made.


In 1998 SRS developed the capability to recast plutonium metal in the FB-Line "using an M-18 reduction furnace with a new casting chamber." Plutonium metal is recast by charging a standard FB-Line magnesia crucible and placing the charge in the casting chamber. In October 1998, "a [plutonium] button was produced by combining plutonium and gallium metals to produce an alloy in which the plutonium is stabilized in the d phase. Delta (d ) phase metal is not susceptible to low temperature induced phase changes like a phase metal." ci

This effort was portrayed by SRS only as a contingency for plutonium metal storage and not as a dual-purpose program that integrated storage goals with pit production goals:

The capability to produce d stabilized metal in FB-Line would provide a contingency for plutonium metal storage at the SRS in the event that experimental programs show that the a to b phase transition (and resulting decrease in density) has the potential to create harmful mechanical stresses in storage containers. The continued use of the casting process for the declassification and consolidation of plutonium from weapons components also provides a disposition path for classified metal parts and alloys currently stored at the RFETS." cii

2. Measuring Plutonium Density in Pits. Another capability SRS has developed is a new measurement system for determining plutonium density in finished plutonium pits. The Savannah River Technology Center (SRTC) and Los Alamos undertook a collaborative research project in which SRTC designed, fabricated, and tested a gas pycnometer "to be used to measure densities of surrogate [plutonium pit] parts." The project's objective was to find a more environmentally friendly method for measuring the density of plutonium hemishells in pits. ciii

The plutonium density project is not a dual-use program, and is only necessary for plutonium pit fabrication. Although the project occurred prior to the issuance of the SRS strategic plan, it clearly is an example of collaborating with the national laboratories to define roles for pit production.

3. The Plutonium Pit Disassembly and Conversion Facility. Every analysis of plutonium pit production lists pit disassembly as the first step in the process. For example, a joint paper issued by Lawrence Livermore and Los Alamos National Laboratories specified the first two steps of pit fabrication as:

· dismantlement of the pit;
· conversion of the metal through hydride and oxidize to plutonium oxide (HYDOX) or hydride and reduce to metallic plutonium (HYDEC); civ

4. The Plutonium MOX Fuel Factory. The capability to purify plutonium for pit fabrication is the missing ingredient in the current version of the PDCF is plutonium purification processing. However, the planned plutonium fuel factory will have the capability to purify plutonium oxide powder.

 

 

Endnotes


i. For in-depth overviews of plutonium and other special nuclear materials, see:

International Physicians for the Prevention of Nuclear War. 1992. Plutonium, Deadly Gold of the Nuclear Age. (Second Printing with Corrections in 1995).

Nuclear Wastelands.



ii. Avens, Larry R. and P. Gary Eller. 2000. A Vision for Environmentally Conscious Plutonium Processing. Los Alamos National Laboratory. In: Challenges in Plutonium Science. Los Alamos Science. Number 26. 2000. Page 436.

iii. Minutes of the Plutonium Information Meeting. Rocky Flats Plant. January 29-30, 1959. Sanitized version from DOE Archives.


.

iv. DoD Militarily Critical Technologies list. Nuclear Weapons Technology. Section 5.

v. Lawrence Livermore National Laboratory. Stockpile Stewardship Program. UCRL-LR-129261. 9781

vi. Hecker, Sigfried. 2000. Los Alamos Science. Number 26, and Plutonium Aging: From Mystery to Enigma. LA-UR-99-5821. 1999.

vii. Condit, R.H. 1993. Plutonium: An Introduction. Lawrence Livermore National Laboratory. UCRL-JC-115357. Prepared for submittal to the Plutonium Primer Workshop. DOE Office of Arms Control and Proliferation in Washington, D.C. on September 29, 1993.

viii. U.S. DOE. Plutonium, the First Fifty Years; 1996; and Declassification of Plutonium Inventory at Rocky Flats, Colorado, 1994.

ix. Radiation Effects in Plutonium. Los Alamos Science. Number 26.

x. Ibid.

xi. Ibid.

xii. Haschke, John. 2000. The Surface Corrosion of Plutonium. Los Alamos Science. No. 26.

xiii. Condit, R.H. 1993. Plutonium: An Introduction; and Plutonium Storage by John
M. Haschke and Joseph C. Martz.

xiv. LA-3542. Plutonium Processing at LANL. 1983.

xv. Westinghouse Savannah River Company. 2000. Facility Design Description for Pit Disassembly and Conversion Facility. February 24, 2000. Page 55.

xvi. Plutonium Processing at LANL . 1983.

xvii. DOE Standard 3013.

xviii. U.S. Department of Energy. Plutonium. The First 50 Years. DOE actually declared 99.5 MT but this did not include 0.1 MT of “classified transactions.”

xix. Inventory Differences used to be called “Materials Unaccounted For”

xx.Savannah River Site FY 2001 Annual Operating Plan. Summary Task Description Sheet. SOXX. MC&A.

xxi. http://www.ieer.org

xxii. This graphic illustrates the fine line between “waste” and “residues.” Historically much of what is now called “residues” would have been recovered by purifying the plutonium. Russia’s policy is to recover plutonium from all forms until there is less than 200 ppm of plutonium remaining. Only then does it become a waste.


Integrated Nuclear Materials Management Plan. June 2000.


xxiii. DOE/ID-10631. Revision 0 October 1998 Plutonium Focus Area

xxiv. Defense Nuclear Facilities Safety Board. Technical Report 1. Plutonium Storage Safety at Defense Nuclear Facilities. April 1994.

xxv. Defense Nuclear Facilities Safety Board. Recommendation 94-1. May 26, 1994.

xxvi. U.S. DOE. Implementation Plan for DNFSB Recommendation 94-1. February, 1995.

xxvii. Christenson, et al. 2000. Managing the Nation’s Nuclear Materials. The 2025 Vision for the Department of Energy. LA-UR-00-3489. http://lib-www.lanl.gov/la-pubs/00393665.pdf.
.
xxviii. U.S. DOE. 2000. Integrated Nuclear Materials Management Plan. Submitted to Congress, June 2000.

xxix. DOE 94-1 Implemnetation Plan. Revision 3.

xxx. DNFSB. Recommendation 2000-1.

xxxi. U.S. DOE. Office of Fissile Materials Disposition. Draft and Final Surplus Plutonium Disposition Environmental Impact Statements (SPDEIS), 1997-1999.

xxxii. U.S. DOE. Office of Fissile Materials Disposition. 1997. Feed Materials Planning Basis for Surplus Weapons-Usable Plutonium Disposition. April 1997.
.
xxxiii.



xxxiv



xxxv. Olivas. Plutonium Aging.

xxxvi. Letter, William D. Magwood, DOE, Office of Nuclear Energy, to Laura S. H. Holgate, DOE, Office of Fissile Materials Disposition, "Zero Power Physics Reactor (ZPPR) Plutonium Fuel," November 12, 1999. Referred to in the November 2000 SRS Pu Storage Plan.

xxxvii. Design Only Conceptual Design Report for Plutonium Immobilization Plant. February 2000. Revision 1.

xxxviii. Integrated Materials Plan. Page 2-4.

xxxix. Gray, L.W. et al. 1999. The Blending Strategy for the Plutonium Immobilization Program.
Paper prepared for submittal to the Waste Management ‘99 Symposium, Tuscon, Arizona. February 28-March 4, 1999. UCRL-JC-133279. Lawrence Livermore National Laboratory.

xl

xli. U.S. Atomic Energy Commission Nuclear Safety Working Group. 1956. A Preliminary Consideration of the Hazards of Sealed Pit Weapons. Sanitized Version from DOE Archives.

xlii. Pantex was selected as the long-term storage (up to 50 years) facility for plutonium pits in the January 1997 Record of Decision for the Programmatic Environmental Impact Statement for Storage and Disposition of Weapons-Usable Fissile Materials; and under the Pantex Plant Sitewide Environmental Impact Statement (January 1997), up to 20,000 plutonium pits can be stored there.

xliii. Pantex now claims that total pit numbers are classified.

xliv. Mason and Hanger Corporation. 2000. Pantex Pit Management Plan. Final Revision 3. October 27, 2000. Pantex Nuclear Materials Department. Page 38.

xlv. Ibid. Page 42.

xlvi. Ibid. Page 43.

xlvii. Toevs, 1997. LA-UR-97-4113. Surplus Weapons Plutonium: Technologies for Pit Disassembly and Conversion and MOX fuel Fabrication.
.
xlviii.

xlix. Ibid. All pit type ID’s obtained from this source or otherwise noted.

l. Rocky Flats Safety Analysis Report for the AL-R8 Container. 1990.

li. Ibid.

lii. Ibid.

liii. Mason and Hanger Corporation. 2000. Pantex Pit Management Plan.

liv. Institute for Energy and Environmental Research. Plutonium Fact Sheet.

lv. Data Call for Stockpile Stewardship Management Programmatic Environmental Impact Statement. Los Alamos Plutonium Pit Production. 1995.

lvi. Glasstone and Redman. An Introduction to Nuclear Weapons. June 1972. Atomic Energy Agency. Sanitized Version from DOE Archives.

lvii. Westinghouse Savannah River Company. 2000. Facility Design Description for Pit Disassembly and Conversion Facility. February 24, 2000. Page 55.

lviii. Glasstone and Redman. An Introduction to Nuclear Weapons.

lix. LA-UR-00-504 January 2000 Safeguards and Security Program Quarterly Activity Summary October 1-December 31, 1999.

lx. Ibid.

lxi. Ibid.

lxii. Wedman, Douglas E. and Steven D. McKee. Uranium Disposition Options for a Pit Disassembly Facility. LA-UR-00-128. February 200.

lxiii. Ibid.

lxiv. Glasstone and Redman. An Introduction to Nuclear Weapons.

lxv. Mattingly, et al. 1998. Passive NMIS Measurements to Estimate the Shape of Plutonium Assemblies (Slide Presentation.) Y-12 Oak Ridge Plant. November 25, 1998. Y/LB-15,998.

lxvi. Glasstone and Redman. An Introduction to Nuclear Weapons.

lxvii. Minutes of Plutonium Information Meeting. Rocky Flats Plant. June 29-30, 1959. Issued August 7, 1959. DOE Archives. Sanitized Version.

lxviii. Glasstone and Redman. An Introduction to Nuclear Weapons.

lxix. Glasstone and Redman. An Introduction to Nuclear Weapons

lxx. Westinghouse Savannah River Company. 2000. Facility Design Description for Pit Disassembly and Conversion Facility. February 24, 2000. Page 55.

lxxi. Pit Resuse Station. 1993.

lxxii. 3/26/99 letter from DOE to DNFSB: Classified Plutonium at Rocky Flats.

lxxiii. Pits are “suspected to be clad with beryllium” in this report if they were separated from the high explosives using similar technologies as the W-48.

lxxiv. Rocky Flats Safety Analysis Report for the AL-R8 Container. 1990.

lxxv. Buntain, G., et al 1995. Pit Storage Monitoring. LA-12907 UC-721 April 1995.

lxxvi. Dow, Jerry (LLNL) and Lou Salazar (LANL). Letter to Department of Energy. Re: Storage Facility Environmental Requirements for Pits and CSA’s. August 22, 1995.

lxxvii. Defense Nuclear Facilities Safety Board. Pantex Plant Activity Report for Week Ending July 10, 1998.

lxxviii. ARIES Source Term Fact Sheet (LALP-97-24, Rev. 3, April 24, 1998).

lxxix. http://www.osti.gov/html/osti/opennet/document/rdd-1/drwcrtf3.html#ZZ1

lxxx. SPDEIS. Page 3-923.

lxxxi. Los Alamos National Laboratory and Fluor Daniel, Inc. 1997. Design-Only Conceptual Design Report for the Pit Disassembly and Conversion Facility. Project No. 99-D-141. Prepared for the DOE Office of Fissile Materials Disposition. December 12, 1997.

lxxxii. ARIES Source Term Fact Sheet (LALP-97-24, Rev. 3, April 24, 1998).

lxxxiii. The tritium data was contained in Pit Disassembly and Conversion Facility EIS Data Report. LA-UR-97-2909. The Draft SPDEIS referred to this document on Page 3-4.

lxxxiv. Tanksi, John A. 2000. A Model for the Initiation and Growth of Metal Hydride Corrosion. LA-UR-00-5496. 23rd DOE Aging, Compatibility, and Stockpile Stewardship Conference. November 14-16, 2000.

lxxxv. http://www.osti.gov/html/osti/opennet/document/rdd-1/drwcrtf3.html#ZZ1
1) Fact that bonding of plutonium or enriched uranium to materials other than themselves is a weapon production process. (93-2)
(2) Fact that such bonding occurs or may occur to specific unclassified tamper, alpha-barrier or fire resistant materials in unspecified pits or weapons. (93-2)
(3) Fact that plutonium and uranium may be bonded to each other in unspecified pits or weapons. (93-2)
(4) Fact that such bonding may be diffusion bonding accomplished in an autoclave or may be accomplished by sputtering. (93-2)
(5) Fact that pit bonding/sputtering is done to ensure a more robust weapon or pit. (93-2) (6) The use of autoclaves in pit production. (93-2)
(7) The fact that plutonium is processed in autoclaves. (93-2)
(8) The fact that sputtering of fissile materials is done at or for any Department of Energy facility as a
production process. (93-2)
(9) The fact of a weapons interest in producing a metallurgical bond between beryllium and plutonium. (93-2)
(10) The fact that beryllium and plutonium are bonded together in unspecified pits or weapons. (93-2)
(11) Routine data concerning concentrations of beryllium in plutonium higher than 100 ppm. (93-2)

lxxxvi. Kidinger, John, ARES Corporation, John Darby and Desmond Stack, Los Alamos National Laboratory. 1997. Technical Risk Assessment for the Department of Energy Pit Disassembly and Conversion Facility Final Report. September, 1997. LA-UR-97-2236. (TRA or Technical Assessment)

lxxxvii. Toevs, 1997. LA-UR-97-4113. Surplus Weapons Plutonium: Technologies for Pit Disassembly and Conversion and MOX fuel Fabrication

lxxxviii. Ibid.

lxxxix. The list of problem pits, like the list of weapons with disassembly problems, seems to be dominated by LLNL designs. Three of the four pit types requiring cleaning are LLNL designs, as is the most problematic pit, the W-48. The only remaining weapons systems to dismantle under START I are LLNL designs-the W79, the W56, which have both been problematic programs.

xc. Pantex Work Authorization Directives. Fiscal Year 2000.

xci. Rocky Flats Safety Analysis Report for the AL-R8. 1990.

xcii. Khalil, Nazir, Bill Bish, and Ken Franklin. 1998. Process development implementation plan for pits, LA-UR-98-5047. Page 2.

xciii. Sun-Woo, A.J., M.A. Brooks, and J.E. Kervin. 1995. Characterization of Stainless Steel 304 Tubing. UCRL-ID-122234. October 16, 1995.

xciv. Mason and Hanger Corporation. 2000. Pantex Pit Management Plan.

xcv. Khail, et al. Process development implementation plan for pits.

xcvi. Stockpile Stewardship Enhanced Surveillance Program. 1998.

xcvii. The unclassified version of the report can be downloaded in the “Public Documents” section at http://www.dp.doe.gov.

xcviii. Commission on Maintaining United States Nuclear Weapons Expertise. Report to the Congress and Secretary of Energy Pursuant to the National Defense Authorization Acts of 1997 and 1998. March 1, 1999

xcix. Savannah River Site Strategic Plan. http://www.srs.gov

c. Ibid.

ci. Rudisill, T.S. and M.L. Crowder. 1999. Characterization of d Phase Plutonium Metal WSRC-TR-99-00448. Westinghouse Savannah River Company

cii. Ibid.

ciii. Collins, Susan, and Henry Randolph. 1997. Gas Pycnometry for Density Determination of Plutonium Parts. Westinghouse Savannah River Company. WSRC-MS-97-00636. Document prepared for the 21st Aging, Compatibility, and Stockpile Stewardship Conference, Albuquerque, NM. 9/30/97 to 10/2/97.

civ. Hart, Mark. M, Warren Wood, and J. David Olivas. Plutonioum Pit Manufacturing and Unit Process Separation Options for Rapid Reconstitution. A Joint Position Paper of LLNL and LANL. September 6, 1996. .

 

Plutonium as an Energy Source

 

Over the past few years, the dismantlement of excess nuclear warheads has left the United States and Russia with large stocks of plutonium and highly enriched uranium (HEU). These surpluses have re-ignited the debates around the world about the use of plutonium as an energy source and provided new arguments for continued assistance to on-going plutonium projects. This article reviews the basic facts regarding plutonium use and provides some cost and technical analysis of the issue.

 


1. All figures are rounded either to one significant figure or to the nearest 5 metric tons. The total is not rounded further.

2. Separated commercial plutonium is owned by the only countries that are currently reprocessing: France, Britain, Japan, Russian, India. In addition, countries that have no current reprocessing have contracts for reprocessing with France and Britain, and also own substantial commercial plutonium stocks. They are: Germany, Belgium, Holland, Italy, and Switzerland. The United States also has a relatively small stock of commercial plutonium from its West Valley reprocessing plant in New York, which was shut down in 1972.

3. No country besides the U.S. has released historical military plutonium production data. All other military data are rough estimates. We have assumed a figure of 150 metric tons of military plutonium for Russia in the 1990 and 1995 totals. Recent data form Russia indicate that the figure may be lower, at about 130 metric tons (rounded).

Source: Arjun Makhijani and Scott Saleska, The Nuclear Power Deception (Takoma Park, Maryland: Institute for Energy and Environmental Research, 1996.)

Uranium and plutonium resource basics

For all practical purposes, uranium-235 is the only naturally-occurring fissile material (one that can sustain a chain reaction and can fuel nuclear reactors). However, uranium-235 makes up only about 0.7 percent of natural uranium ore. Almost all the rest is another isotope, uranium-238, which cannot sustain a chain reaction.

But although uranium-238 is not a fissile material, it can be converted into fissile plutonium-239 in a nuclear reactor. This property has led nuclear proponents to see uranium-238 as the key to the long-term future of nuclear energy. In fact, reactors can be designed so that they produce more fissile material from uranium-238 in the form of plutonium than they consume in the course of power production. Such reactors have come to be called "breeder reactors" and uranium-238 a "fertile" material. Promoters of nuclear power have used the expression "magical energy source" to describe a breeder reactor electricity production system because the amount of fuel at the end of production would be greater than at the beginning.1

In the 1950s and 1960s, uranium was thought to be a very scarce resource. Scientists realized that uranium resource requirements for a power system based on breeder reactors would be far lower than for one based on once-through use of uranium. For instance, the amount of natural uranium needed over the life of a 1,000 megawatt 2 power plant with a light water reactor (LWR-the most common nuclear reactor), is roughly 4,000 metric tons. By contrast, only about 40 metric tons are required for a breeder reactor of the same size. This hundred-fold theoretical reduction in resource requirements convinced proponents of nuclear power that breeder reactors, along with the recovery of plutonium from irradiated reactor fuel (reprocessing), would be at the heart of the magical nuclear energy future, when nuclear power would be "too cheap to meter."3 At that time, projections of nuclear power use were very high. In the early 1970s, the U.S. expected an installed nuclear capacity by the year 2000 of 1,000,000 megawatts. However, U.S. capacity is now only 10% of those projections (about 100,000 megawatts) and will not increase by the year 2000 (see Table 3 for additional data).

Nuclear Power and its Role in Global Electricity and Energy

compiled by Anita Seth


Table 1 (below) lists countries in order of the percentage of electricity they derive from nuclear power. This table actually contains two separate measures of electricity: capacity and production. Capacity refers to the manufactured rating of the generation equiptment installed in a country, and is measured in megawatts (MW). Generation refers to the energy output over a given period of time (in this case, one year) and is measured in kilowatt-hours (kWh). Table 1 and Table 2 measure gross electricity, including transmission and distribution losses.

 

Table 1: Nuclear Power (1993)

Country

Nuclear as Percentage of Gross Electricity Generation (rounded)

Gross
Electricity
Generation (million kWh)

Gross Capacity (MW)

France

78%

368,188

59,020

Belgium

60%

41,927

5,485

Sweden

43%

61,395

9,912

Spain

36%

56,060

7,020

S. Korea

36%

58,138

7,616

Ukraine

33%

75,243

12,818

Germany

29%

153,476

22,657

Japan

28%

249,256

38,541

United Kingdom

28%

89,353

11,894

United States

19%

610,365

99,061

Canada

18%

94,823

15,437

Russia

12%

119,186

21,242

World Totals*

18%

2,167,515</B.< td>

340,911

* World totals include countries not individually listed.

Source: Energy Studies Yearbook: 1993 (New York: United Nations, 1995).

 

Table 2 compares nuclear power to other sources of electricity. While thermal-generated electricity is by far the most common, representing over 60 percent of world-wise electricity, on a regional basis, other energy sources can supply a majority of the electricity. In South America, hydro-electricity accounts for 80 percent of all electricity produced, over four times as much as thermal electricity, and over fifty times as much as nuclear power.

 

Table 2: Global Electricity Generation - by Type
(in million kWhe)

 

FOSSIL FUEL

HYDRO

NUCLEAR

GEOTHERMAL and OTHER

TOTAL

World

7,669,958

2,376,106

2,167,515

47,131

12,260,710

 

Africa

281,518

50,531

7,200

340

339,589

 

N.America

2,491,646

641,208

709,994

30,195

3,873,043

USA

2,236,388

276,463

610,365

22,676

3,145,892

 

S.America

97,291

410,479

8,192

-

515,962

 

Asia

2,403,166

526,107

351,498

9,356

3,290,127

China

685,153

151,800

2,500

-

839,453

India

279,000

70,667

6,800

52

356,519

Japan

550,181

105,470

249,256

1,798

906,705

 

Europe

2,237,226

708,654

1,090,631

5,640

4,042,151

France

35,366

67,894

368,188

-

471,448

Germany

350,656

21,465

153,476

124

525,721

Russia

662,199

175,174

119,186

28

956,587

Source: Energy Studies Yearbook: 1993 (New York: United Nations, 1995).

Table 3 looks at the broader context of not just electricity production, but all commercial energy consumption. The 700 million people of Africa, representing about 15 percent of world population, only consumed 3 percent of the world's commercial energy in 1993. By contrast, North America and Europe, where about one-fifth of the world's people live, accounted for almost half of all commercial energy consumption.

Among commercial energy sources, the reliance on fossil fuels is clear. Ninety percent of energy in the world comes from fossil fuels (mainly coal, petroleum, and natural gas). However, certain countries obtain a very significant percentage of their energy from nuclear power. In France, for example, nuclear power accounts for about 44% of total energy consumption.

Table 3: Global Commercial Energy Comsumption (1993)
(in petajoules)*

 

SOLIDS

LIQUIDS

NATURAL GAS

NUCLEAR**

OTHER ELECTRICITY

TOTAL

World

93,981

119,407

77,921

23,599

9,966

324,873

 

Africa

3,130

3,859

1,548

78

195

8,805

 

N.America

20,056

40,070

26,474

7,730

3,266

97,598

USA

18,863

32,093

22,362

6,645

1,684

81,751

 

S.America

616

5,456

2,461

89

1478

10,095

 

Asia

42,131

34,132

13,443

3,827

2,260

95,830

China

23,540

4,886

661

27

547

29,679

India

6,281

2,264

460

74

255

9,338

Japan

3,545

8,579

2,223

2,714

443

17,505

 

Europe

26,231

34,095

33,109

11,874

2,560

107,852

France

610

3,204

1,307

4,009

224

9,153

Germany

4,115

5,158

2,699

1,671

78

13,724

Russia

6,636

6,802

14,745

1,298

631

30,042

* Solids include hard coal, lignite, peat, and oil shale. Liquids includecrude petroleum and natural gas liquids. Other electricity is primarily hydro-electricity, but also included geothermal, wind, tide, wave, and solar sources. Nuclear electricity has been converted to thermal energy equivalent using a factor of 1,000 kWh (electrical) = 0.372 metric tons coal.

** Does not include imports and exports.

NOTE: Table 3 lists energy inputs (consumption of primary energy), while Table 2 lists energy outputs (in the form of electricity). This is the reason for the apparent disparity between the figures in the "Nuclear" and "Other Electricity" (primarily hydro-electricity) columns in this table,and those in the "Hydro" and "Nuclear" columns in Table 2. Electricity generation from heat energy (like nuclear) is only about one-third as efficient as electricity generation from mechanical energy (like hydro). While the amount of electricity produced from nuclear and hydro power sources are about equal, the nuclear inputs are three times greater than the hydro inputs. To make energy figures comparable, the "Other" column should be increased to about 27,000 petajoules.

Source: Energy Statistics Yearbook: 1993 (New York: United Nations, 1995).

Numbers in Tables 1-3 are based on the most recent United Nations data available. These tables take into account only commercial energy use, and thus leave out traditional sources of energy, such as wood, animal dung and crop residues (collectively known as biomass) which are used for cooking and heating. Biomass burning accounts for almost 15 percent of the world's energy consumption. In the developing world, reliance on biomass for energy is even greater: biomass burning is the largest source of energy, making up about 38 percent of total energy use. Because these fuels are non-monetized, their value and the extent of their use are often overlooked. Yet it is the only available energy source for hundreds of millions of people. One crucial energy source not included in these numbers is the energy intake by draft animals, which plays an especially significant role in Asia.

Biomass burning in its current form (Table 4) is inefficient compared to fossil fuels, and creates health and environmental problems. With some investment of money and research, biomass fuels could be converted into modern energy forms which would provide a cleaner, more efficient, and renewable base of energy, and hence preferable to fossil fuels and nuclear energy.

 


 

Table 4: Energy from Biomass Burning (1985)

 

petajoules

percentage of total energy

World

54,800

14.7%

Industrialized Countries*

6,900

2.8%

Developing Countries*

48,000

38.1%

* The catagory "Industrialized Countries" includes U.S./Canada, Europe, Japan, Australia and New Zealand, and the former Soviet Union. The heading "Developing Countries" includes Latin America, Africa, Asia (minus Japan), and Oceania (minus Australia and New Zealand).

Source: Thomas B. Johansson, Henry Kelly, Amulya K. N. Reddy, and Robert H. Williams, Renewable Energy: Sources for Fuels and Electricity (Washington, DC: Island Press, 1993), pp. 594-5.

 

 

Units of Measure

WATT

A metric unit used to measure the rate of energy generation or consumption. One horsepower is equal to 746 watts.

MEGAWATT

(MW) A common measure of generating capacity for large power plants.

JOULE

A metric unit of energy, equal to one watt of power operating for one second.

KILOWATT-HOUR

(kWh) A unit of energy equal to 3.6 million joules. It is the amount of energy generated by a one-kilowatt source operating for one hour.

PETAJOULE

Energy use on a large scale is often measured in petajoules. One metric ton of coal equivalent (U.N. standard) is approximately 29 billion joules, therefore one petajoule is equivalent to about 34,500 metric tons of coal.

PREFIXES:

kilo -- One thousand
mega -- One million
giga -- One billion (or 109)
tera -- One trillion (or 1012)
peta -- One thousand trillion (or 1015)
exa -- One million million (or 1018)

 

 

Theoretical arguments in favor of breeder reactors still provide inspiration to nuclear establishments all over the world. But technical, economic, political, environmental, and military realities have all combined to make a plutonium-based energy system economically impractical, environmentally dangerous, diplomatically difficult, and militarily risky.

Technical and economic complications

Discussion in this article focuses on the sodium-cooled breeder reactor (also called a fast neutron reactor)-the main breeder reactor design that has been developed. Tens of billions of dollars have been spent on research, development, and demonstration of this technology in a number of countries, including the United States, Russia, France, Britain, India, Japan, and Germany. But the technology has not yet reached the commercial stage of even moderately reliable power production and breeding of fuel. Breeder reactors total a capacity of roughly 2,600 megawatts, which is only 0.8 percent of the world's nuclear power capacity of about 340,000 megawatts (see pie chart).

 

*Pressurized Water reactors (PWRs) account for 219,391 MWe and boiling water reactors (BWRs) for 75,519 MWe.
** A small amount of electrical capacity (less than 0.1%) is accounted for by other types of reactors.

Sources: Uranium Institute website (http://www.uilondon.org/reastats.html). The figure for fast breeder reactors is taken from Nuclear Power Reactors in the World (Vienna: international Atomic Energy Agency, April 1995). 280 MWe have been added to account for the Monju reactor in Japan which began operating in April 1995 but is now shut.

In turn, nuclear power plants account for 12 percent of the world's total electrical capacity. Not only have "breeder" reactors produced only a miniscule fraction of nuclear electricity; they have also failed to produce a significant amount of net fissile material. Indeed, it is possible that "breeder" reactors have so far been net consumers of fissile material.

Almost half of the world's breeder reactor capacity is in a single reactor, the Superphčnix in France, which has faced serious operating problems and is not currently run as a breeder reactor. Rather, it is now a net burner of fissile material, used mainly as a research facility for studying the fission of plutonium and other similar elements called actinides. Another 10 percent of breeder capacity is in the 280-megawatt Monju reactor in Japan, which had an accident in December 1995, only eight months after its start up. (See graphic below.)

 

A cut-away view of the Japanese "Monju" fast breeder reactor. The two circuits contain sodium coolant with the secondary, non-radioactive loop drawing heat from the primary loop. The December, 1995 sodium leak occurred in the secondary circuit.

Most breeder reactors outside of France and Japan have operated on uranium fuel rather than the more difficult plutonium fuel. Russia's BN600 sodium-cooled reactor has been fueled primarily with highly enriched uranium and the BN350 in Kazakhstan now runs on medium-enriched uranium.

A number of problems have plagued the design and operation of breeder reactors:

  • Breeder reactors are more difficult to control than light water reactors because runaway nuclear reactions (including complete loss of control, or "prompt criticalities") can occur far more easily in fast breeder reactors than in light water and other reactors that use slow neutrons for the chain reaction.
  • Sodium, while it is an excellent coolant, reacts violently with air and explodes on contact with water. These and other properties raise severe safety issues, design complications, and operating difficulties. For instance, air and moisture must be kept out of the two necessary sodium loops.
  • The presence of plutonium as a fuel in breeder reactors raises security risks that require more safeguards than are necessary with LWRs.
  • Fabrication of plutonium fuel is far more costly than fabrication of uranium fuel due to higher radioactivity of, and safeguards requirements for plutonium.
  • Extraction of plutonium from reactor fuel to enable its reuse in reactors (reprocessing), is costly and raises many safety, security, and environmental issues. [Reprocessing is covered in the January 1997 issue of Energy & Security.]
  • The greater risk of catastrophic accidents and the more serious potential consequences of such accidents necessitate greater safety measures.

Most breeder reactor programs are now suspended or stopped due to the high capital costs and operating problems discussed above. They have been abandoned or cut back to a low-level research stage in the United States, Germany, and Britain. The Japanese program has had a severe setback due to the December 1995 sodium-leak accident at the Monju plant. The plant is not expected to be on line for several years, if ever. There are no current plans for new breeder reactors in France. Britain and Germany have pulled out of the European Breeder Reactor project. India's program has so far produced only a small pilot plant. Russian plans for breeder reactors are stalled for lack of money.

The expense and technical difficulties of breeder reactors, reprocessing, and plutonium fuel fabrication have led to far higher net costs for breeder reactors than for reactors that load only uranium as a fuel. Moreover, uranium is far more abundant than was presumed in the 1950s and 1960s. Instead of rising, uranium prices have, on the average, declined in real terms over the last several decades ( table below).

 

Contract Price for Uranium Ore in 1995 Dollars

(all figures are rounded*)

Year

Price U.S.$ per kg U

1960

100

1970

50

1980

90

1990

60

* We have used the producer price index for converting current uranium prices to 1995 dollars.

 

Furthermore, in the past ten years, spot market prices (the open market price at any given time) have been significantly lower than contract prices. For instance, in 1990 spot prices were about $30 per kilogram of uranium (in 1995 dollars)-just half of the contract price. In the past couple of years spot prices have ranged between $20 and $40 per kilogram. Low uranium prices are also partly due to reduced demand because the number of nuclear power reactors built has been far fewer than projected.

 

Value and cost of plutonium

 

While electricity systems based on breeder reactors have not been built, it is still possible to use plutonium as a fuel in light water and other power reactors not designed to breed plutonium. In any case, about one-fourth to one-third of the energy in an LWR is derived from plutonium created in the course of reactor operation from the uranium-238 in the fuel rods. Further, the spent fuel rods from LWRs typically contain about 0.7 percent fissile isotopes of plutonium. This plutonium, while far less than the amount of fissile material used in the reactor, can be re-extracted for use as fuel.

 

However, most reactors are not designed to operate on pure plutonium. The total amount of fissile material (uranium-235 plus fissile isotopes of plutonium) must be kept below the design level -- in the vicinity of five percent for most LWRs. The plutonium is put into oxide form, mixed with depleted uranium oxide (mainly uranium-238 with about 0.2 percent uranium-235) to make a mixed oxide fuel ("MOX fuel"). Thus, it would appear that even without breeder reactors, plutonium can be useful as a nuclear reactor fuel.

 

While this argument is theoretically correct from the point of view of physics, it fails on economic grounds. To determine a practical economic value for plutonium, we must take into account the costs of processing and fabricating it into usable fuel and compare them to the costs of other fuels. The most detailed, recent independent analysis done on this subject was a study of reactor options for plutonium disposition published by the U.S. National Academy of Sciences (NAS) in 1995.

 

The NAS report estimated the cost of processing and fabricating low enriched uranium oxide reactor fuel (4.4 percent enrichment) at about $1,400 per kilogram in 1992 dollars, assuming a natural uranium price of $55 per kilogram. The costs of MOX fuel fabrication, assuming that the plutonium was free (that is, obtained as surplus from the nuclear weapons program), would be about $1,900 per kilogram in 1992 dollars, exclusive of taxes and insurance. 4 The higher cost of MOX means that annual fuel costs for a full MOX core would be approximately $15 million more than uranium fuel per year for a 1,000 megawatt reactor, or about $450 million over its operating life (in 1992 dollars), even if the plutonium were free. This amounts to about $500 millon in 1995 dollars. Further, the costs of disposing of MOX spent fuel are likely to be higher than those for uranium spent fuel because the MOX spent fuel will be more radioactive and contain two to three times more residual plutonium than uranium spent fuel.

 

It is clear that so long as uranium prices are relatively low, the use of MOX fuel is uneconomical even under the most favorable circumstances: when the plutonium itself is free and uranium is assumed to be more expensive than current spot market prices. The cost difference is even greater when the cost of reprocessing is taken into account, because reprocessing would add hundreds of millions of dollars to lifetime fuel costs for each reactor.

 

As the NAS pointed out in a 1994 study, the fact that plutonium has a fuel value in physical terms does not make it economically practical. The oil present in shale rock also has a physical fuel value. It is the cost of extracting oil from shale relative to petroleum in oil fields that precludes oil shale, like plutonium, from having an economic value as a fuel. In addition, plutonium poses some proliferation liability which, although difficult to quantify, is a serious cost.

 

Proliferation Dangers

 

Although civilian plutonium has a different isotopic composition from plutonium that has been produced for weapons, it can be used to make a nuclear explosive, as demonstrated in a successful 1962 test by the United States Atomic Energy Commission. Continued reprocessing and use of plutonium pose a two-fold proliferation danger. First, growing stockpiles of commercial separated plutonium undermine disarmament commitments under international treaties. Even if carried out for commercial reasons, reprocessing of plutonium can be perceived as simply adding to weapons-usable materials stockpiles. In the short-term, this could undermine effective global negotiations on a fissile material cut-off, and in the long-term, the Non-Proliferation Treaty, in which, under Article VI, signatories commit to "pursue negotiations in good faith on effective measures relating to the cessation of the arms race at an early date and to nuclear disarmament . . ."

 

Second is the danger of plutonium being diverted to a black market. The fuel value of plutonium is determined by the price of uranium. Assuming a price of $40 per kilogram of natural uranium, uranium-235 is worth about $5,600 per kilogram. Since the energy per fission from plutonium-239 and uranium-235 is about the same, the theoretical fuel value of fissile plutonium can be put at $5,600 per kilogram. Reactor-grade plutonium also contains non-fissile isotopes, reducing its value to about $4,400 per kilogram. 5 Six to ten kilograms of reactor-grade plutonium would suffice to make a nuclear bomb, making the fuel value of one bomb's worth of plutonium between $26,400 and $44,000. However, the value of the plutonium would undoubtedly be far greater than this on a potential black market where the objective would be to make a weapon. The danger of plutonium diversion to a black market is particularly acute in Russia where the weakening of central control, combined with the rise of organized crime and poor economic conditions heighten the chances of diversion.

 

From Reactors to Weapons

The size of the plutonium core in the bomb that exploded over Nagasaki would fit easily into an adult's hand.

The current amount of separated commercial plutonium is enough to make 20,000 to 30,000 crude but highly effective nuclear weapons.

By the year 2000, the total amount of separated plutonium in the civilian sector is expected to surpass the total amount of plutonium in the world's nuclear arsenals.

 

Long-term energy issues

 

The economic facts regarding plutonium are now so clear that they are not in serious dispute so far as short- and medium-term energy issues are concerned. But supporters of plutonium as an energy source cite long-term energy needs as a reason to create and maintain an infrastructure for the use of plutonium.

Current estimates of uranium resources at $80 per kilogram of uranium (still well below the price at which MOX fuel may be competitive) are estimated at about 3.3 million metric tons, enough for about six or seven decades of once-through fuel use at present levels of nuclear power production. These estimates do not take into account the intense exploratory activity that accompanies real increases in prices. The history of petroleum and natural gas exploration is instructive. The price increases in 1973-74 resulted from production-limiting and price-fixing policies adopted by the Organization of Oil Exporting Countries (OPEC). However, the price jump spurred new exploration activity, and the number of oil exporting countries and oil availability increased so substantially that the real price of petroleum is lower today than it was in 1974. Uranium prices have tended to decline in real terms (with the exception of a period in the 1970s, when uranium prices followed the upward trend of oil prices), and so current estimates of uranium resources may be biased downwards.

 

Whatever one's views about the future of nuclear power, it makes little sense to invest huge amounts of money in using plutonium as a fuel today, when any potential economic use is many decades away, at best. Plutonium use makes even less sense when viewed in the context of scarce economic resources, which can be invested in areas with better environmental and security characteristics and a higher return, such as natural gas- or biomass-fueled power plants, natural gas-assisted solar electricity generation, and improved efficiency of energy use.

ENDNOTES

  1. A similar production of fuel is possible by converting non-fissile thorium-232 into fissile uranium-233 (which does not occur in nature in significant quantities), but development of uranium-233 breeders is even less advanced than that of plutonium breeders. For more technical information on nuclear power reactors, see Arjun Makhijani and Scott Saleska, The Nuclear Power Deception, Institute for Energy and Environmental Research, Takoma Park, Maryland, 1996.
  2. All figures for reactor capacity are in megawatts electrical unless otherwise specified. A 30-year life and 70 percent capacity factor is assumed. Figures are rounded and adapted from John R. Lamarsh, Introduction to Nuclear Engineering, Second Edition (Reading, Massachusetts: Addison-Wesley Publishing Company, 1983).
  3. The idea of nuclear energy which would be "too cheap to meter" was actually Cold War propaganda. Even in the 1950s nuclear engineers never believed that nuclear power could be made truly cheap. See IEER report, The Nuclear Power Deception.
  4. Panel on Reactor-Related Options for the Disposition of Excess Weapons Plutonium. Committee on International Security and Arms Control, Management and Disposition of Excess Weapons Plutonium--Reactor-Related Options (Washington, DC: National Academy Press, 1995), pp. 290, 294.

Typical LWR spent fuel contains about 0.2 percent non-fissile plutonium isotopes and 0.7 percent fissile isotopes.

Disposing of Surplus U.S. Plutonium

The United States declared over 50 metric tons of plutonium surplus to defense needs.

 


BACK

The NNSA is pursuing a hybrid disposition strategy to eliminate the surplus.

- - - - - - - - - - - - - - - - - - - - -  - - -

DOE Press Release: R-97-001 January 14, 1997

DOE ANNOUNCES DECISION ON THE STORAGE AND DISPOSITION OF SURPLUS NUCLEAR WEAPONS MATERIALS

Secretary of Energy Hazel R. O’Leary today signed a Record of Decision finalizing a dual-track strategy to irreversibly dispose of the Nation’s surplus plutonium and to reduce from seven to three the number of sites where surplus nuclear weapons materials are stored. The strategy, first announced on December 9, 1996, allows for immobilizing plutonium in glass or ceramic forms and burning plutonium as mixed oxide fuel in existing reactors.

Today’s decision formally completes this phase of the program’s environmental review and is consistent with the preferred alternative identified in the Department’s final Environmental Impact Statement on Storage and Disposition of Nuclear Weapons Materials.

Secretary O’Leary said, "The Clinton administration believes that the dual-track approach for eliminating excess U.S. weapons plutonium stockpiles best serves our arms reduction and nonproliferation goals. Maintaining both the reactor and immobilization options will provide important insurance against possible difficulties with the implementation of either one and help ensure an early start to this important task. Furthermore, this approach will provide us the needed flexibility and leverage to work with Russia on the critical task of reducing Russian excess weapons plutonium stockpiles."

The Department of Energy (DOE) will consolidate the storage of plutonium by upgrading and expanding existing and planned facilities at the Pantex Pant in Texas and the Savannah River Site in South Carolina, and continue the storage of weapons-usable highly enriched uranium at DOE’s Y-12 Plant in Tennessee, in upgraded and consolidated facilities. After certain conditions are met, most plutonium now stored at the Rocky Flats Environmental Technology Site in Colorado will be moved to Pantex and the Savannah River Site. Plutonium currently stored at Hanford Site, the Idaho National Engineering Laboratory, and the Los Alamos National Laboratory will remain at those sites until disposition.

DOE will pursue a disposition approach that allows immobilization of surplus plutonium in glass or ceramic material for disposal in a geologic repository and burning of some of the surplus plutonium as mixed oxide (MOX) fuel in existing domestic, commercial reactors, with subsequent disposal of the spent fuel in a geologic repository. However, the Department has decided that at least 8 metric tons of surplus plutonium materials will be immobilized because they are not suitable for use in MOX fuel without extensive purification. The full extent to which either or both options are implemented will be determined by the results of technology demonstrations, additional environmental reviews and detailed cost proposals. The results of these efforts, as well as nonproliferation considerations and negotiations with Russia and other nations, will ultimately determine the timing and extent to which each technology is deployed.

Burning excess plutonium as MOX fuel in existing reactors would be consistent with U.S. nonproliferation policy because there would be no reprocessing and extraction of residual plutonium from the spent fuel. In addition, MOX fuel would be fabricated in a domestic, government-owned facility at a secure DOE site. The facility would be licensed and used only for the weapons plutonium disposition mission and would be shut down when this mission was complete.

The Department has also decided to retain the option of using MOX fuel in Canadian Deuterium Uranium (CANDU) reactors in Canada in the event a multilateral agreement to use CANDU reactors is negotiated among Russia, Canada and the United States.

Through these efforts, the President will be provided the basis and flexibility to begin disposition, either unilaterally as an example to Russia, or multilaterally or bilaterally with other nations. Proceeding in this way will serve as a strong statement of the United States’ commitment to nonproliferation and disarmament and encourage similar actions by Russia and other nations, and foster multilateral or bilateral disposition efforts and agreements.

- - - - - - - - - - - - - - - - - - - - - - - - -

Both approaches convert the surplus plutonium to the "spent fuel standard" so it cant be used to make a nuclear bomb.

 

As recommended by the National Academy of Sciences, weapon-grade plutonium is converted to forms as inaccessible and unattractive for retrieval and weapons use as the residual plutonium in spent fuel from commercial reactors. In this form, the surplus plutonium cannot be used in nuclear weapons without significant processing.

 

The NNSA plans to build three facilities at the Savannah River Site (SRS) in South Carolina to carry out the hybrid disposition strategy.

·         Pit Disassembly and Conversion Facility

Pit Disassembly and Conversion

About two-thirds of the surplus U.S. weapon-grade plutonium exists in classified nuclear weapons components called "pits". 

Pits, whose designs are classified, are the core component of a nuclear weapon. Pits are comprised of plutonium, hermetically sealed within a metallic shell that, when imploded by high explosives, initiates a thermonuclear reaction

The NNSA plans to build a Pit Disassembly and Conversion Facility at the Savannah River Site. The facility will use the Advanced Retrieval and Integrated Extraction System (ARIES) process to: 

University of California scientists and engineers have developed ARIES, the Advanced Recovery and Integrated Extraction System, at Los Alamos National Laboratory. This system separates plutonium from nuclear weapons components. The plutonium is declassified and packaged for future disposition.

ARIES exemplifies the commitment of the United States to remove 50 tons of weapons-grade plutonium, as agreed to by United States President Bill Clinton and Russian Federation President Boris Yeltsen on September 2, 1998.

Washington Group International is designing the facility. Design efforts are underway. In order to reduce the anticipated future year peak funding requirements, work on the pit disassembly and conversion facility is being delayed until the construction of the Mixed Oxide (MOX) Fuel Fabrication Facility is further along.

·         MOX Fuel Fabrication Facility; and

Irradiation of Mixed Oxide Fuel

The NNSA will irradiate surplus U.S. weapon-grade plutonium converted from classified weapon "pits" and clean metal as mixed oxide (MOX) fuel in domestic commercial reactors.

The NNSA plans to build a MOX Fuel Fabrication Facility at the Savannah River Site. The facility will use commercial processes similar to ones used in European facilities. The U.S. facility will:

Each MOX fuel assembly is approximately 8 inches square and just over 13 feet long, and contains 264 fuel pins. Each MOX fuel assembly will contain about 20 kilograms of surplus weapon-grade plutonium, and weigh about 1,100 pounds. Each domestic reactor will hold up to 40 complete MOX fuel assemblies during an irradiation cycle.

A consortium of Duke, COGEMA, Stone & Webster (DCS), located in Charlotte, North Carolina, is designing the facility, and may also construct and operate the facility. The U.S. Nuclear Regulatory Commission will regulate the construction and operation of the facility.

Duke Power Company will irradiate the mixed oxide fuel assemblies in commercial reactor facilities in North Carolina and South Carolina. Revised operating licenses from the Nuclear Regulatory Commission are necessary in order to irradiate mixed oxide fuel.

·         Plutonium Immobilization Facility.

Immobilization

The NNSA will immobilize surplus U.S. plutonium that exists as impure metal and oxides because these materials are unsuitable for irradiation as mixed oxide fuel without extensive purification.

The NNSA plans to build a Plutonium Immobilization Facility at the Savannah River Site (SRS). The facility will use a new process to:

The immobilization process is completed at the existing Defense Waste Processing Facility at the SRS, where molten high-level radioactive waste is poured into the canister to provide a radiation barrier for proliferation resistance.

 

Each 10-foot tall high-level waste canister will contain 28 steel cans, each containing 20 ceramic plutonium pucks. About 1 kilogram of plutonium is inside each steel can. When filled with vitrified high-level radioactive waste, each canister will weigh close to 5,500 pounds

 

Research and development on immobilization is supported by Lawrence Livermore National Laboratory, the SRS, Clemson University, Argonne National Laboratory, and the Pacific Northwest National Laboratory.

In order to reduce the anticipated future year peak funding requirements, work on immobilization is being suspended and will be resumed when construction of the Mixed Oxide (MOX) Fuel Fabrication Facility and the Pit Disassembly and Conversion Facility are further along. 

 

Surplus plutonium at various sites will be transported to the SRS for disposition.

 

 

 


Surplus U.S. Plutonium Disposition Method Graphic

 

Working with Russia to Dispose of Surplus Russian Plutonium

 

 

 

Russia has declared approximately 50 metric tons of plutonium surplus to their defense needs.

Russian President Boris Yeltsin made the first official declaration of excess Russian fissile materials in 1997, stating that up to 50 metric tons of weapons plutonium and up to 500 metric tons of highly enriched uranium excess to Russian defense needs.

Russia intends to dispose of their surplus plutonium in reactors by irradiating mixed oxide (MOX) fuel. They may immobilize small amounts that are unsuitable for use in reactors.

In 1998, the United States and Russia signed a Scientific and Technical Cooperation Agreement to conduct tests and demonstrations of plutonium disposition technologies.

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Scientific and Technical Cooperation Agreement

Signed by Vice President Gore and Prime Minister Kiriyenko in July 1998.

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Initial efforts focused on:

GOSATOMNADZOR (GAN) is the Federal Nuclear and Radiation Safety Authority of Russia. The Department of Energy is helping GAN develop the regulatory infrastructure required for licensing the design, construction, testing and operation of Russian Federation nuclear facilities for surplus weapons plutonium disposition. 

Specific help is provided to develop nuclear regulations and safety standards needed to license new or modified facilities for disposition, and to support review of license applications and granting of licenses and permits for the disposition facilities.

The National Nuclear Security Administration is supporting research and development of advanced reactors that might provide additional surplus weapon plutonium disposition capacity in Russia.

 

Advanced Reactors

The Gas Turbine-Modular Helium Reactor (GT-MHR) technology project could provide additional surplus weapon plutonium disposition capacity in Russia.

General Atomics worked with the Ministry of the Russian Federation of Atomic Energy (Minatom), Framatome from France, and Fuji Electric Corporation from Japan, to produce a conceptual design for a GT-MHR that would be used for plutonium disposition.

General Atomics and the Oak Ridge National Laboratory now provide technical support to many Russian organizations to design a plutonium -burning reactor for Seversk such as the Gas Turbine Modular Helium Reactor.

The GT-MHR project was integrated into the existing framework of the joint Scientific and Technical Cooperation Agreement.

 

The United States and Russia recently concluded a bilateral agreement on plutonium disposition. Under the agreement, both the United States and Russia will proceed with roughly parallel programs to dispose of 68 metric tons of surplus weapon-grade plutonium.

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White House Press Release September 1, 2000  

VICE PRESIDENT AL GORE SIGNS U. S. - RUSSIA PLUTONIUM MANAGEMENT AND DISPOSITION AGREEMENT

Washington, D.C. – Vice President Gore signed today the United States-Russian Federation Agreement for irreversibly transforming excess weapons plutonium into forms unusable for weapons, announced by President Clinton and President Putin at the June 4 Moscow Summit. With this act and Prime Minister Kasyanov’s signature, the Agreement shall be applied as of today’s date. This accomplishment advances the critical task of reducing stockpiles of excess weapons plutonium and contributes to key arms control and non-proliferation objectives.

The Agreement requires that 68 metric tons of weapons-grade plutonium, 34 tons for each Party, be disposed. This is enough plutonium for thousands of nuclear weapons. It will be disposed by irradiating it as fuel in reactors or by immobilizing it with high-level radioactive waste, rendering it suitable for geologic disposal. Implementation will require the construction of new industrial-scale facilities to convert and fabricate this plutonium into fuel in both countries, and to immobilize a portion of the U.S. material. The Agreement sets 2007 as the target date to begin operating such facilities with a minimum disposition goal of 2 metric tons per year and an obligation to seek to at least double that rate.

The Agreement establishes the goals, time lines, and conditions for ensuring that this plutonium can never again be used for weapons or any other military purposes. Both the process and the end products will be subject to monitoring and, thus, transparent. The Agreement bans reprocessing any of this plutonium prior to the disposition of all 34 metric tons. Reprocessing thereafter must be under mutual-agreed, effective monitoring measures. Plutonium immobilization under the program must never be separated from the immobilized forms. The Agreement allows plutonium that may be designated as excess to defense needs in the future to come under the surplus program.

As the Presidents’ Joint Statement noted, the Agreement will enable new cooperation to go forward between the United States and the Russian Federation. Thanks to the leadership of Senator Domenici and others in the U.S. Congress, $200 million has already been appropriated to help implement the Russian program.

Other G-8 countries have strongly endorsed and advanced this cooperation. The Untied States and Russian Federation have urged the G-8 leaders at their recent summit to accelerate this cooperation by directing development of necessary multilateral arrangements and an international financing process for assisting Russia’s program. The plan will consider both public and private sector financing mechanisms.

Also present to today’s signing was Michael Guhin, U.S. negotiator.

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Bilateral Agreement on Plutonium Disposition

A bilateral agreement on plutonium disposition calls for the United States and Russia to irreversibly dispose of surplus weapon-grade plutonium. Each country will:

Plutonium disposition in Russia requires substantial financial assistance from the international community.  An international financing plan and additional multi-lateral arrangements are being developed for the Genoa 2001 G-8 Summit.  The U.S. Department of State will lead U.S. efforts to finalize the plan. Several nations have already pledged significant resources for the plutonium disposition effort in Russia.

With the signing of the bilateral agreement on Plutonium disposition, Russia and the United States will accelerate and expand ongoing plutonium disposition research, development, and demonstration work under the Joint U.S.-Russian Scientific and Technical Cooperation Agreement.

 

Fabrication and Use of Mixed Oxide Fuel

The United States, France, Germany, Japan and others are collaborating with Russia on developing mixed oxide (MOX) fuel fabrication processes to irradiate surplus Russian weapon-grade plutonium.

o        Adapting proven European MOX fabrication experience to Russian fuel designs;

o        Assessing feasibility of either pelletized fuel fabricated at the Mayak Production Association in Ozersk or vibro-compacted fuel fabricated at the Research Institute of Atomic Reactors (RIAR) in Dmitrovgrad;

o        Working with AIDA-MOX on a parallel development effort with France and Germany; and

o        Fabricating test fuel for irradiation in a research reactor and lead test assemblies.

Russia will build a mixed oxide fuel fabrication facility at either the Mayak Production Association in Ozersk or at the Mining and Chemical Combine in Zheleznogorsk (the closed city formerly known as Krasnoyarsk-26).

Rosenergoatom, the Russian utility that operates nuclear power reactors, is involved in the effort as the ultimate user of the MOX fuel. Final fabrication and use of the fuel is subject to approval by Gosatomnadzor, which will license the use of MOX fuel in Russian reactors.

Russia will use two types of existing nuclear power plants to irradiate mixed oxide fuel:

VVER is the Russian version of the Pressurized Water Reactor (PWR). There are 3 standard designs - two 6 loop- 440 Megawatt [440-230 (older) and 440-213 (newer)] and 4 loop-1000 Megawatt output designs. As with PWRs, annual refuelings are conducted with the plant shutdown. The VVER-1000 units at Balakovo and Kalinin Nuclear Power Plants will be used in the program.

 

Balakovo Nuclear Power Plant

Balakovo NPP, 1997

 

Unit 1

Unit 2

Unit 3

Unit 4

Type of reactor

VVER-1000

VVER-1000

VVER-1000

VVER-1000

Power, MWe

1000

1000

1000

1000

First Power

28.12.85

08.10.87

24.12.88

11.04.93

Generated electrical power, mln kW·h

5004,2

4302,2

2209,6

4938,0

In-house requirements, %

5,65

7,18

8,08

6,17

Reactor operational time, days

242

257

141

276

Reactor operational time, effective days

209

179

92

206

Load Factor, %

57,12

49,11

25,22

56,38

Kalinin Nuclear Power Plant

Kalinin NPP, 1997

 

Unit 1

Unit 2

Type of reactor

VVER-1000

VVER-1000

Power, MWe

1000

1000

First Power

09.05.84

03.12.86

Generated electrical power, mln kW·h

5496,2

4138,4

In-house requirements, %

5,61

6,38

Reactor operational time, days

258

255

Reactor operational time, effective days

229

172

Load Factor, %

62,74

47,26

Beloyarsk Nuclear Power Plant

Beloyarsk NPP, 1997

 

Unit 3

Type of reactor

BN-600

Power, MWe

600

First Power

08.04.80

Generated electrical power, mln kW·h

3835,4

In-house requirements, %

7,55

Reactor operational time, days

278

Reactor operational time, effective days

266

Load Factor, %

72,99

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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