U.S. Nuclear Tests

Between 16 July 1945 and 23 September 1992 the United States of America conducted (by official count) 1054 nuclear tests, and two nuclear attacks. The number of actual nuclear devices (aka "bombs") tested, and nuclear explosions is larger than this, but harder to establish precisely. Some devices that were tested failed to produce any noticeable explosion (some by design, some not), other "tests" (by official definition) were actually multiple device detonations. It is not clear whether all multiple device tests have yet been identified, and enumerated.

These pages focus principally (although not exclusively) on the period from 16 July 1945 to 4 November 1962, the era of atmospheric testing*. There are a number of reasons for this. These early years marked the height of the Cold War, when the U.S. nuclear weapons establishment came into being, when the major breakthroughs in weapon design occurred, and when the most severe effects of nuclear testing were felt around the world. During this period test series were grand operations, involving huge numbers of people, and each often with a set of clear objectives. The era of atmospheric testing is also the period for which the most information is available. When tests were exploded in the open, everyone could collect data on what was being tested. When the tests went underground, testing became routine, and information about what was being tested went underground too. There were actually a few surface tests included in the official test count conducted after 4 November 1962. These were a series of zero yield tests of plutonium dispersal conducted in 1963, known as Operation Roller Coaster.

Nuclear Testing and Health

Ever since nuclear testing began it has been very difficult to get a useful accounting of human exposures to the fallout from these tests. Partly this was motivated by military secrecy, partly by a desire to allay public fears (i.e public relations reasons), and partly by a fear of possible legal action by actual of potential victims. Some exposure related incidents have been revealed due to the impossibility of hiding them: namely the high radiation exposures of the Marshallese and the Japanese aboard the Fifth Lucky Dragon after the Castle Bravo disaster. But most information on this subject has been withheld, deliberated buried in obscure reports, or never collected (this is the principle of being careful not to learn what you don't want to know). This information has slowly come to light in bits and pieces over the last 20 years.

What is probably the most important study of the health effects of testing were announced by the National Cancer Institute in August of 1997, and released in October. The study report is now available on line: National Cancer Institute Study Estimating Thyroid Doses of I-131 Received by Americans From Nevada Atmospheric Nuclear Bomb Test.

The basic finding of the report is that internal exposures to radioiodine (I-131) in fallout from continental nucelar testing was the most serious health consequence. Radioiodine concentrates in milk when consumed by cows when grazing, and then concentrates in human thyroid glands when contaminated milk is ingested. This concentration effect is especially strong in children. The NCI study estimates that the average American alive at the time received a thyroid radiation exposure of 2 rads, with some people receiving up to 300 rads. The effect of these exposures is to boost the chance of contracting thyroid cancer some time during a lifetime. This cancer is normally not very rare, and is highly treatable (as cancers go). It is possible to estimate the overall effect of the total radiation exposure of the American population. From the 380 million person-rads of total exposure roughly 120,000 extra cases of thyroid cancer can be expected to develop, resulting in some 6,000 deaths [see box]. For comparison, the worst industrial disaster in history (Bhopal, India; 3 December 1984) killed about 3000 people and injured 150,000.

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NCI declined to provide estimates of how many cancers and deaths might result from this population exposure. I made the estimates given here (and on various test series pages accessible from this one) from material on the NCI site in the following way.

The incidence of thyroid cancer increases 7.7 fold for each 100 rad exposure. The base lifetime risk of contracting thyroid cancer is 0.47% (a likelihood of 0.0047) averaged over both men and women. 100 rads of exposure thus increases the risk to 3.62% (0.0362), which is an additional incidence of 3.15% (0.0315) due to the radiation. Making the standard assumption of linearity in biological response to radiation dose, the 380 million rad population exposure thus would result in 120,000 additional cases of thyroid cancer. The mortality rate of thyroid cancer is given as 5%, so about 6,000 deaths would result.

Now the 7.7 fold risk enhancement figure is actually for exposures to young children, so the estimate given here is probably something of an overestimate. However two factors should be kept in mind. First, these radiation exposures occurred at the height of the Baby Boom (the peak year was 1957), when the proportion of the population consisting of young children was extraordinarily large. Second, the principal route for radiation exposure was drinking contaminated milk. Children drink a disproportionate amount of milk and thus accumulated a large part of the total population radiation exposure.

No effort was made to systematically study the nationwide effects of atmospheric nuclear testing until congress ordered the study -- which was finally released 15 years later. In hearing held in September 1998, Bruce Wachholz, chief of the radiation effects branch of the National Cancer Institute, told a Senate hearing that the basic results were known as early as 1989 and a final draft report was completed in 1992 yet none of the information was made public for five more years.

The Nuclear Test Series

United States nuclear tests were conducted on an intermittent basis from July 1946 to October 1958. During this period, nuclear tests were conducted in groups known as "operations" or "test series", each series was a distinct operation that was organized and carried out independently of other operations.

On 31 October 1958, just after it concluded the largest test series to date, the United States entered into a unilateral testing moratorium announced by President Eisenhower with the understanding that the former Soviet Union also would refrain from conducting tests. The Soviet Union honored this moratorium initially, but secretly prepared for a massive testing campaign which commenced in September 1961, and included the largest nuclear tests ever conducted.

On September 15, 1961, the United States resumed testing at the Nevada Test Site (NTS) on a year-round basis with

Operation Nougat. From that time to the present, tests have principally been grouped for fiscal and reporting purposes into "operations" or "series" according to the fiscal year in which they took place. For example, fiscal year 1963 tests -- which began 1 July 1962 and extended through 30 June 1963 -- were in the Operation Storax series.

Important exceptions to this scheme were a number of test series conducted during 1962-63:

• Operation Dominic (which also been called Dominic I), conducted between 25 April and 4 November of 1962 (and thus overlapping Nougat and Storax); and which included the Department of Defense (DoD) Operation Fishbowl high-altitude tests in the Pacific.
• Operation Sunbeam (also known as Dominic II), four weapons effects tests conducted by the DoD at the NTS between 7 July and 17 July 1962 (concurrent with Storax)
• Operation Roller Coaster, four zero-yield tests conducted jointly by the US and UK at Nellis Air Force Range (NAFR) between 15 May and 9 June 1963 (concurrent with Storax).

Atmospheric testing concluded with the test Dominic/Fishbowl Tightrope on 4 November 1962. The signing of the Atmospheric Test Ban Treaty on 5 August 1963 in Moscow halted all further atmospheric testing by both superpowers.

The Fiscal Year based underground series was perturbed in 1976, when the federal government changed the fiscal year to begin on October 1 and end on September 30. Accordingly, the Fiscal Year 1976 series, Operation Anvil, did not end on June 30, but was extended through September 30, 1976 -- a period of 15 months.

On March 31, 1976, the Soviet Union and the United States agreed to limit the maximum yield of underground tests to 150 kt.

On October 2, 1992, the United States entered into another unilateral moratorium on nuclear weapons testing announced by President Bush. President Clinton extended this moratorium in July 1993, and again in March 1994 until September 1995. With the signing of the Comprehensive Test Ban Treaty in September 1996, the United States -- along with the other nuclear powers -- made a legal commitment never to test nuclear devices again, even though this treaty will likely never go into force due to the opposition of India.

The Atmospheric Test Series

Trinity - The First Nuclear Test

Operation	Year	Location	Number
Trinity	1945	Alamagordo New Mexico	1

The Post War Test Series

Operation	Year	Location	Number
Crossroads	1946	Bikini Atoll	2
Sandstone	1948	Enewetak Atoll	3
Ranger	1951	Nevada Test Site	5
Greenhouse	1951	Enewetak Atoll	4
Buster-Jangle	1951	Nevada Test Site	7
Tumbler-Snapper	1951	Nevada Test Site	7
Ivy	1952	Enewetak Atoll	2
Upshot-Knothole	1953	Nevada Test Site	11
Castle	1954	Bikini Atoll Enewetak Atoll	6
Teapot	1955	Nevada Test Site	14
Wigwam	1955	Pacific Ocean	1
Project 56	1955	Nevada Test Site	4
Redwing	1956	Bikini Atoll Enewetak Atoll	17
Plumbbob	1957	Nevada Test Site	30
Project 58	1957	Nevada Test Site	2
Project 58 A	1958	Nevada Test Site	2
Hardtack I	1958	Bikini Atoll Enewetak Atoll Johnston Island	35
Argus	1958	South Atlantic	3
Hardtack II	1958	Nevada Test Site	37
Nougat	1961-1962	Nevada Test Site	32
Dominic (with Fishbowl)	1962	Christmas Island Johnston Island Central Pacific	36
Storax (with Sunbeam and Roller Coaster)	1962-1963	Nevada Test Site Nellis Air Force Range	56

Underground Tests

The Nevada Test Site

The Nevada Test Site (NTS) is located in Nye County in southern Nevada; the southernmost point of the NTS is about 65 miles (105 kilometers) northwest of Las Vegas. The site contains 1,350 square miles (3,500 square kilometers) of federally owned land with restricted access, and varies from 28-35 miles (45-56 kilometers) in width (east-west) and from 40-55 miles (64-88 kilometers) in length (north-south).

The Nevada Test Site is bordered on three sides by 4,120 square miles (10,700 square kilometers) of land comprising the Nellis Air Force Range (NAFR), another federally owned, restricted area. This restricted area provides a buffer zone to the north and east between the test area and land that is open to the public, and varies in width from 15-65 miles (24-105 kilometers). A northwestern portion of the Nellis Air Force Range is occupied by the Tonopah Test Range, an area of 624 square miles (1,620 square kilometers), which is operated for the U.S. Dept. of Energy (DOE) by the Sandia Laboratories primarily for airdrop tests of ballistic shapes for nuclear weapons. The combination of the Tonopah Test Range, the Nellis Air Force Range, and the Nevada Test Site is one of the largest unpopulated land areas in the United States, comprising some 5,470 square miles (14,200 square kilometers).

From the end of World War II until 1951, five U.S. nuclear weapons tests were conducted at distant islands in the Pacific Ocean: two at Bikini atoll and three at Enewetak atoll. Testing at those sites required an extensive logistic effort and an inordinate amount of time. When the decision to accelerate the development of nuclear weapons was made in the late 1940s in response to national defense policy, it became apparent that weapons development lead times would be reduced and considerably less expense incurred if nuclear weapons, especially the lower yield weapons, could be tested safely within the continental boundaries. In addition security of the test operation could be ensured, a considerable concern at a time that a major land war was raging in Asia, and the possibility of direct conflict with China and the Soviet Union was feared.

Accordingly, a number of sites throughout the continental United States, including Alaska, were considered on the basis of low population density, safety, favorable year-round weather conditions, security, available labor sources, reasonable accessibility including transportation routes, and favorable geology. After review of known information about fallout, thermal, and blast effects, it was determined that an area within what is now the Nellis Air Force Range could be used for relatively low-yield nuclear detonations. The Southern Nevada site was selected from a list of five possibilities which included Alamogordo/White Sands, New Mexico; Dugway Proving Ground, Utah; Pamilco Sound/Camp Lejuene, North Carolina; and a 50-mile-wide strip between Fallon and Eureka, Nevada. Although the NTS originally was selected to meet criteria for atmospheric tests, it subsequently also was used for underground tests.

President Harry S. Truman approved the establishment of the NPG on 11 January 1951, and on 27 January 1951 the first atmospheric test was detonated at 1,060 feet above the surface of Frenchman Flat. Public Land Order 805, dated 19 February 1952, identified 680 square miles (1,800 square kilometers) for nuclear testing purposes from an area used by the Air Force as a bombing and gunnery range; this area now comprises approximately the eastern half of the present Nevada Test Site. The predominant geological features of this area are the closed drainage basins of Frenchman Flat and Yucca Flat where the early atmospheric tests were conducted. The main Control Point has remained on the crest of Yucca Pass between these two basins. Additional land was added to the site in 1958, 1961, 1964, and 1967, thereby enlarging the site to its present size of about 1,350 square miles (3,500 square kilometers).

Testing Goes Underground

The first true underground test of a nuclear explosive, with the blast entirely contained underground, was the 1.7 kt Plumbob Rainier (16:59:59.5 19 September 1957 at Area 12 of NTS). Operation Nougat (September 1961 - April 1962) was the first test series to be conducted underground. After 1962 no further atmospheric testing was conducted, and all tests henceforth were underground tests.

Although underground testing was the rule after August 1963, it is not exactly true that no radioactivity was released into the atmosphere after that date. First, there were five Plowshare cratering tests conducted underground, but designed to breach the surface (see below). These released a total of 984 kilocuries of I-131 (radioiodine) into the atmosphere. Containment failures for for a few dozen other tests that were supposed to be entirely underground released another 123 kilocuries (two-thirds of this was due to Baneberry, with Des Moines, and Bandicoot accounting for nearly all of the rest). For comparison, Trinity released about 3200 kilocuries of radioiodine. The total population exposure to radioiodine from all 'underground' tests amounted to 9.1 million person-rads of thryoid tissue exposure (about 2% of all exposure due to continental nuclear tests). This can be expected to eventually cause about 2800 cases of thyroid cancer, leading to some 140 deaths. Chart of fallout exposures from "underground tests" (63 K, 539x577). From National Cancer Institute Study Estimating Thyroid Doses of I-131 Received by Americans From Nevada Atmospheric Nuclear Bomb Test, 1997. To go to the National Cancer Institute and get the full report, click here.

Underground testing often leaves visible evidence on the surface in the form of subsidence craters. These are depressions on the surface that come about when the roof of the blast cavity collapses in to the void left by the explosion. This creates a new roof, which can also shear off into the new, larger, but partially rubble-filled cavity. A chain reaction of successive roof collapses forms a "chimney" that works its way to the surface.

The "Underground" Plowshare Cratering Shots

Test Series	Test Name	Time and Date (GMT)	Location	Test Type	Height (m)	Yield (kt)	Sponsor	Purpose	Comments
Whetstone	Sulky	19:35 18-Dec-64 (GMT)	NTS Area 18d)	Shaft	-30 m	0.092	LLNL	11th Plowshare	Explore cratering mechanics in hard, dry rock and study dispersal pattern of airborne radionuclides
Whetstone	Sulky	19:35:00.09 18-Dec-64 (GMT)	NTS Area 18d)	Shaft	-30 m	0.092	LLNL	11th Plowshare	Explore cratering mechanics in hard, dry rock and study dispersal pattern of airborne radionuclides; released 13 kilocuries of I-131
Whetstone	Palanquin	13:14.00.11 14-Apr-65 (GMT)	NTS Area 20k	Crater	-85 m	4.3	LLNL	12th Plowshare	Explore cratering mechanics in hard, dry rock and study dispersal pattern of airborne radionuclides; crater produced was 240 feet by 70 feet; released 910 kilocuries of I-131
Crosstie	Cabriolet	16:00.00.11 1-Jan-68 (GMT)	NTS Area 20l	Crater	-20 m	2.3	LLNL	20th Plowshare	Study effects and phenomenology of cratering in hard rock (rhyolite); crater produced was 360 feet by 120 feet; released 6 kilocuries of I-131
Crosstie	Buggy	17:04.00.11 12-Mar-68 (GMT)	NTS Area 30	Shaft	-40 m	5.4	LLNL	21st Plowshare	Trench cratering experiment, five 1.1 kt charges detonated 150 feet apart, produced crater 850 ft long, 250 ft wide, and 65 ft deep; released 40 kilocuries of I-131
Bowline	Schooner	16:00.00.14 8-Dec-68 (GMT)	NTS Area 20u	Crater	-100 m	30	LLNL	23rd Plowshare	Study effects and phenomenology of cratering in hard rock (tuff); crater produced was 800 feet by 270 feet; probably used tungsten-rhenium alloy fission tamper, U-235 core (based on radioisotope releases), released 15 kilocuries of I-131

Nevada Test Site From Space

As of the end of 1992, there had been a total of 925 announced tests at NTS, 825 of them underground. This has left the Nevada Test Site pock-marked with subsidence craters, some of the more heavily used test areas are so heavily fractured that they are almost unusable for further testing.

 Official List of Underground Nuclear Explosions (UNEs) in Nevada from Sandia National Laboratories (July, 1994).

U.S. Test Locations

The first test of a nuclear weapon was in the atmosphere on July 16, 1945, in a remote part of New Mexico on what was then the Alamogordo Bombing Range, and is now the White Sands Missile Range. The site is 55 miles northwest of Alamogordo, New Mexico. At various times between June 1946 and November 1962, atmospheric and underground tests were conducted by the United States in the Marshall Islands (known as the Pacific Proving Grounds or PPG), Christmas Island, Johnston Atoll in the Pacific Ocean, and over the South Atlantic Ocean. Between January 1951 and July 1962, atmospheric and underground nuclear tests were conducted in Nevada at the Nevada Test Site (NTS, originally called the Nevada Proving Grounds or NPG).

Since July 1962, all nuclear tests conducted in the United States have been underground, and most of them have been at the NTS. Some tests were conducted on the Nellis Air Force Range (NAFR); in central and northwestern Nevada; in Colorado, New Mexico, and Mississippi; and on Amchitka, one of the Aleutian Islands off the coast of Alaska.

The 100 Ton Test

 

Before Trinity: The 100 Ton Test

May 7, 1945:

To help in preparing the instrumentation for the Trinity shot the "100 Ton Test" was fired on 7 May 1945. This test detonated 108 tons of TNT stacked on a wooden platform 800 yards from Trinity ground zero. The pile of high explosive was threaded with tubes containing 1000 curies of reactor fission products. This is the largest instrumented explosion conducted up to this date. The test allowed the calibration of instruments to measure the blast wave, and gave some indication of how fission products might be distributed by the explosion.

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Trinity

16 July 1945

The first nuclear explosion in history took place in New Mexico, at the Alamogordo Test Range, on the Jornada del Muerto (Journey of Death) desert, in the test named Trinity.

This test was intended to prove the radical new implosion weapon design that had been developed at Los Alamos during the previous year. This design, embodied in the test device called Gadget, involved a new technology that could not be adequately evaluated without a full scale test. The gun-type uranium bomb, in contrast, was certain to be effective and did not merit testing. In addition, since no nuclear explosion had ever occurred on Earth, it seemed advisible that at least one should be set off with careful monitoring to test whether all of the theoretical predictions held.

The origin of the name Trinity for this event is uncertain. It is commonly thought that Robert Oppenheimer provided the name, which would seem logical, but even this is not definitely known. A leading theory is that Oppenhimer did select it, and that he did so with reference to the divine Hindu trinity of Brahma (the Creator), Vishnu (the Preserver), and Shiva (the Destroyer). Oppenheimer had an avid interest in Sanskrit literature (which he had taught himself to read), and following the Trinity test is reported to have recited the passage from the Bhagavad-Gita that opens this page.

The Trinity Test

July 16 1945, 5:29:45 A.M. (Mountain War Time)
Trinity Site Zero, Alamogordo Test Range,
Jornada del Muerto desert.

Yield: 20-22 Kilotons

First Glance Expanded fireball 16 milliseconds after detonation

Mushroom Cloud

Trinity Crater

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Operation Crossroads

1946

The Crossroads Series tests were the first nuclear explosions since World War II, and the first nuclear weapon tests since Trinity. These were the first "weapons effects" tests ever conducted - tests designed specifically to study hhow nuclear explosions affect other things - rather than tests of the behavior of a weapon design (as was Trinity). The purpose of the tests was to examine the effects of nuclear explosions on naval vessels, planes, and animals.

A fleet of 71 surplus and captured ships anchored in the Bikini Atoll lagoon in the Marshall Islands were used as targets. This fleet included a number of famous Allied and Axis vessels such as the aircraft carrier USS Saratoga, the battleships USS Nevada, Pennsylvania, Arkansas, and New York; the German cruiser Prinz Eugen and Japanese battleshp Nagato.

The weapons used were Mk 3A ("Model 1561") Fat Man-type atomic bombs, essentially unmodified from the wartime designs.

Test:	Able
Time:	22:00:34 30 June 1946 (GMT) 09:00:34 1 July 1946 (local)
Location:	Bikini Atoll lagoon, Marshall Islands
Test Height and Type:	Airburst, Altitude 520 ft (160 m)
Yield:	23 Kt

History's fourth atomic explosion. A standard Fat Man type Mk 3A fission bomb, dropped by B-29 "Dave's Dream", was used in test. The bomb fell 980 ft short and 1870 ft left of target, perhaps due to a collapsed tail fin. The USS Gilliam was sunk, and four other vessels were either sunk or severly damaged. The misplaced bomb resulted in a government investigation of the flight crew.

As seen from Eneu Island As seen from the air

Test:	Baker
Time:	21:35:00 24 July 1946 (GMT) 08:35:00 23 July 1946 (local)
Location:	Bikini Atoll lagoon, Marshall Islands
Test Height and Type:	Sub-surface burst, Depth -90 ft (-27.5 m)
Yield:	23 Kt

History's fifth atomic explosion. A standard Fat Man type Mk 3A fission bomb was used in test. The bomb was encased in a watertight steel caisson, and suspended beneath landing ship LSM-60. The closest ship to surface zero was the USS Saratoga. Eight ships were sunk or capsized, eight more were severly damaged. Sunk vessels were the USS Saratoga, USS Arkansas, the Nagato, LSM-60 (obviously), the submarines USS Apogon and USS Pilotfish, the concrete dry dock ARDC-13, and the barge YO-160.

Serious radioactive contamination of the lagoon occurred, radiation exposure at the surface near the detonation point amounted to a lethal 730 R in the first 24 hours. Bikini Island, some three miles from surface zero could not be safely landed on until a week had passed.

Beginning 4 milliseconds after the explosion, the shock wave reaching the surface throws up a "spray dome", rising at an initial speed of 2500 ft/sec (mach 2.5), in advance of the rapidly expanding bubble of hot gases. This picture shows the spray dome development a few milliseconds later. The light from the sub-surface fireball is clearly visible.

 

Baker Spray Dome

Once the fireball bubble (consisting of water vapor and bomb debris) reaches the surface a huge hollow column of water is thrown up, with the intensely radioactive gas in the bubble being vented through the center of the column.

The low pressure rarefaction zone behind the advancing shock wave causes water droplets to condense out of the moisture laden tropical air producing the "Wilson Cloud Chamber" effect.

Below, the Wilson condensation cloud is prominent. It hides the growing water column, which is only visible by the "crown" of the column protruding through the top of the cloud. The location of the shock front can be seen by the white zone on the water (called the "crack") surrounding the cloud.

Wilson Cloud Chamber Effect

The condensation cloud is beginning to dissipate, it has vanished close to the ocean surface revealing the hollow water column (or stem) and target fleet, but leaving a cloud layer that still obscures most of the developing mushroom head.

Mushroom Cloud

This close-up view of the stem from Eneu Island, 10 seconds after detonation, shows water starting to escape the stem and fall back toward the surface. At its greatest extent, the water column was 2000 feet (600 m) across, with walls 300 feet (100 m) thick, and 6000 feet (2 km) tall, holding a million tons of water.

As water falls back from the stem, it forms a dense highly radioactive cloud called the "base surge". Stern of the USS Saratoga can be seen rising 43 feet on the crest of the first wave (94 feet high and 1000 feet from surface zero). Waves 6 feet high were seen 22,000 feet (7 km) from the explosion.

 

 

 

Closer View of Stem and Cloud

Cloud Stem

 At this point the mushroom cloud head is 6000 feet across (2000 meters). It rose to 10,000 feet (~3000 meters before dispersing). The base surge is prominent. Expanding outward initially at over 60 mph, it rapidly rose to a height of 900 feet (300 meters). The expanding surge formed a doughnut shaped ring 3.5 miles (5 km) across and 1800 feet high 4 minutes after the explosion.

 

Base Surge Forming

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Operation Sandstone

A series of improvements for the implosion bomb were envisioned and under development at Los Alamos even before Trinity, the first nuclear test, the end of the war had derailed these efforts. With the Cold War rapidly developing, an urgent need was felt to bring these improvements to the U.S. weapon stockpile.

On 27 June 1947 President Harry Truman authorized a new test series for weapons development for the following year. Operation Sandstone was conducted at Enewetak Atoll in the Marshall Islands in 1948 to test the first new weapon designs since World War II. The massive operation involved 10,200 personnel

Up until this time, all four implosion bombs that had been exploded (the Trinity Gadget, the Fat Man bomb used on Nagasaki, and the two bombs used during Operation Crossroads ) had all been identical, based on a conservative wartime design. The Sandstone test series intoduced a second generation of weapon design by evaluating several new design principles. In addition a number of design parameters were varied to evaluate their effects on performance.

The original Fat Man pit design used a Christy solid plutonium core, surrounded by a close fitting natural uranium tamper. The Sandstone devices all replaced the contiguous tamper-core approach with a "levitated core" in which the core was suspended within a larger hollow space within the tamper so that a gap existed between them. The collision between the tamper and core would create more efficient compression of the core than the explosive-driven shock in the watime design. They apparently retained a solid core however.

These devices also abandoned the use of a pure plutonium core since oralloy (uranium hihgly enriched in U-235) production exceeded plutonium production by a factor of over 3-to-1. The first test, X-Ray, used a composite oralloy-plutonium core. Both Yoke and Zebra used an all oralloy core. The pits (tamper plus core) for all three devices weighed about the same.

Other tested features included:

• varying the tamper thickness (which had been fixed at 7 cm in earlier devices)
• varying the amount of fissile material in the core
• the effect of using a "minimum strength" polonium-beryllium Urchin neutron initiator.

Previously, Urchins containing the full load of 50 curies of Po-210 had been used in tested bombs. Guidelines permitted the use of initiators with as little as 12 curies, but the adequacy of these had never been put to an actual test. Given the very short 138.4 day half life of Po-210, this was an important question for maintaining a ready stockpile.

Although the Sandstone tests continued to use the Mk 3 implosion system, they proof tested components that led to the fielding of the Mk 4 bomb. The Mk 3 bomb used for the Sandstone devices was 60 inches in diameter and weighed 10,500 lb total; the explosive, core and firing system weighed 7,600 lb.

Both the principle of levitation and the use of oralloy-plutonium composite cores had been under development at Los Alamos during the war. If it had continued into the fall of 1945, both of these innovations would have been introduced to increase the size and efficiency of the stockpile. Now, the confrontation with the Soviet Union impelled the inclusion of these innovations in deployed weapons. The results of Sandstone led to the immediate stockpiling of both X-Ray and Zebra core designs, replacing all other designs. Taken together, this lead to an immediate increase in total stockpile yield of 75%.

Test:	X-Ray
Time:	18:17 14 April 1948 (GMT) 0617 15 April 1948 (local)
Location:	Island Engebi ("Janet"), Enewetak Atoll
Test Height and Type:	200 foot Tower Shot
Yield:	37 kt

The X-Ray device used a uranium-plutonium composite Type B levitated pit. The uranium-to-plutonium ratio by weight was on the order of 2:1 or greater. Efficiency of utilization of the plutonium in this core was around 35%; uranium utilization was in excess of 25%. Taken together this indicates a core containing about 2.5 kg of Pu, and 5 kt of U-235. This was the highest yield device tested to date.

Yoke Testing

Test:	Zebra
Time:	18:04 14 May 1948 (GMT) 0604 15 May 1948 (local)
Location:	Island Runit ("Yvonne"), Enewetak Atoll
Test Height and Type:	200 foot Tower Shot
Yield:	18 kt

The Zebra device also used only highly enriched uranium in the levitated pit. Despite its lower yield than Yoke, it apparently had superior efficiency (at least for its size).

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Operation Ranger

1951

The intensifying Cold War, which spread into direct nuclear competition in 1949 with the first Soviet atomic test, spurred the U.S. to expand its efforts to produce more and better nuclear weapons. For the first time true mass production of nuclear weapons began with the Mk 4 in 1950 which, though much improved in reliability and ease of stockpiling, was basically equivalent in weight and yield to the wartime Fat Man. By late 1950, programs were in full swing to increase the yield, and to reduce the weight and size of nuclear weapons.

These new designs were planned for testing in the Pacific Proving Ground at Enewetak Atoll in a series to be called Greenhouse, planned for April-May 1951. As preparations proceeded, two concerns were raised:

·         With the outbreak of the Korean War in 25 June 1950, fears developed of a wider war that would make operations in the Pacific impossible;

·         Weapon designers began to feel that insufficient technical data was available and that a systematic series of atomic tests was called for to study how various parameters affected yield in fission weapons.

The first concern led to the selection of an alternate testing ground in the continental United States - Frenchman Flat in the Las Vegas Bombing and Gunnery Range (now part of the Nevada Test Site, or NTS). The second led to Operation Ranger, a hastily organized test operation to collect data in preparation for Greenhouse.

Operation Ranger carried out the first tests in the United States proper since the Trinity test in 1945. It was proposed during technical discussions at Los Alamos on 6 and 11 December 1950. Approval was requested by LASL Director Norris Bradbury on 22 December, Preidential approval was received on 11 January 1951. The first Ranger test shot was 16 days later. All five were fired in just eight days.

The Ranger test devices were mostly Mark 4 bomb designs modified to test the effects of various design parameters on yield. The last shot was a test of a new bomb design (the Mk 6) and proof tested the Fox composite core.

All of the test devices weighed 10,800 lb and were 60 inches in diameter (essentially identical to the Fat Man bomb); the explosive, core and firing systems of each device weighed 7100 lb.

All test devices were dropped over Frenchman Flat by a B-50 bomber (a re-engined B-29, which was the type of aircraft used in the atomic attacks against Japan).

 

Ranger released about 6000 kilocuries of radioiodine (I-131) into the atmosphere (for comparison, Trinity released about 3200 kilocuries of radioiodine). This produced total civilian radiation exposures amounting to 160 thousand person-rads of thyroid tissue exposure (about 0.04% of all exposure due to continental nuclear tests).

 

 

 

 

 

Test:	Able
Time:	13:45 27 January 1951 (GMT) 5:45 27 January 1951 (local)
Location:	Frenchman Flat (NTS), Nevada
Test Height and Type:	1060 foot Air Burst
Yield:	1 kt

The Able device was a compression vs critical mass test using an all-oralloy core. Used a type D pit, in a Mk 4 high explosive assembly. A yield of 1.3 kt was predicted before the shot. This test configuration was used again repeatedly in weapon effects tests in later years when an accurate, predictable 1 kt yield was desired.

Test:	Baker-1
Time:	13:52 28 January 1951 (GMT) 5:52 28 January 1951 (local)
Location:	Frenchman Flat (NTS), Nevada
Test Height and Type:	1080 foot Air Burst
Yield:	8 kt

The Baker-1 device was a "fractional crit" test. A core with less than one critical mass of material (at normal density) was imploded to supercriticality by high implosion pressure. For comparison, the Fat Man bomb contained 1.3 critical masses. Used a type D pit, was used in a Mk 4 high explosive assembly. Was the first use of the TOM initiator (a more advanced design than the wartime Urchin). Predicted yield was 9 kt.

Test:	Easy
Time:	13:47 1 February 1951 (GMT) 5:47 1 February 1951 (local)
Location:	Frenchman Flat (NTS), Nevada
Test Height and Type:	1080 foot Air Burst
Yield:	1 kt

The Easy device was another compression vs critical mass test to obtain a different point on the compression vs yield curve. Presumably an all-oralloy core was used as in the Able test. Easy used a type D pit in a Mk 4 high explosive assembly. A yield of 0.6 kt was predicted before the shot.

Test:	Baker-2
Time:	13:49 2 February 1951 (GMT) 5:49 2 February 1951 (local)
Location:	Frenchman Flat (NTS), Nevada
Test Height and Type:	1100 foot Air Burst
Yield:	8 kt

A test of the reproducibility of weapon performance. The test device was identical to Baker-1.

Test:	Fox
Time:	13:47 6 February 1951 (GMT) 5:47 6 February 1951 (local)
Location:	Frenchman Flat (NTS), Nevada
Test Height and Type:	1435 foot Air Burst
Yield:	22 kt

This shot proof-tested a Fox composite core in a Type D pit, using the Mk 6 HOW double prime high explosive assembly. The test device was named "Freddy". Predicted yield was 34 kt. At this time Fox cores, which were expected to be more efficient than X-Ray cores (tested in Operation Sandstone), were being rapidly stockpiled.

MK6

Operation Greenhouse

1951

The Greenhouse Test Series was conducted at Enewetok Atoll in April and May of 1951. It consisted of four relatively high yield tests (by the standards of the time) - Dog, Easy , George, and Item. Dog and Easy were proof tests of two new strategic bombs the Mk 6 and Mk 5 respectively. George and Item were the first true tests of thermonuclear fusion - the release of fusion energy from therrmally excited nuclei. George was a research experiment that studied deuterium-fusion burning when heated by thermal radiation. Item was the first test of the principle of fusion boosting of fission devices.

Test: Dog

Time: 18:34 7 April 1951 (GMT)
06:34 8 April 1951 (local)

Location: Island Runit ("Yvonne"), Enewetak Atoll Test Height and

Type: 300 foot Tower Shot

Yield: 81 kt

 

 

Dog was a proof test of Mk 6 strategic bomb. This was the highest yield test up to that time (superseded by George a month later), and evaluated the stockpiled MK 6 weapon with a "How Double Prime" composite uranium-plutonium core. The explosion lifted 250,000 tons of soil to an altitude of approximately 35,000 feet. The Mk 6 was a improved large "Fat Man-style" weapon, with a 60 inch diameter, a length of 128 inches, and a weight of 8500 lb (later reduced to 7600 lb) a reduction from the earlier 10900 lb Mk 4. The Mk 6 had an improved 60 point implosion system (the Mk 4 had a 32 point system) that provided greater compression and higher efficiency. The Mk 6 was the first nuclear weapon stockpiled in large numbers by the U.S. (over 1000 eventually produced). Stockpiling of the MK 6 on an emergency basis was underway at the time of the test.

Test:	Easy
Time:	18:26 20 April 1951 (GMT) 06:26 21 April 1951 (local)
Location:	Island Enjebi ("Janet"), Enewetak Atoll
Test Height and Type:	300 foot Tower Shot
Yield:	47 kt

Proof test of the TX-5D bomb, a major advance in weight reduction for implosion bombs. Weight was 2700 lb with a 40 inch diameter, compared to 10,000 lb and a 60 inch diameter for earlier designs. Used a 92 point (lens) implosion system and a composite (plutonium/oralloy) core. This design was used as the primary in the first thermonuclear bomb test, Ivy Mike. This test was also used to test weapon effects on various military structures. These structures were erected on Enjebi and nearby Mijakadrek Island.

Test:	George
Time:	21:30 8 May June 1951 (GMT) 09:30 9 May 1951 (local)
Location:	Island Eberiru ("Ruby"), Enewetak Atoll
Test Height and Type:	200 foot Tower Shot
Yield:	225 kt

George was the largest nuclear explosion to date (a record that stood until the first thermonuclear device test, Ivy Mike, 17 months later). George was a thermonuclear physics experiment, and used a purely experimental device design unsuitable for use as a weapon. The test device, named the CYLINDER, consisted of an enriched uranium core which was imploded using a unique cylindrical implosion system. This device may have been the first to use external initiation to begin the fission chain reaction.

Fireball of George

The device was a disk about 8 ft across and 2 feet thick perforated by an axial hole. The hole, compressed to a narrow channel by the implosion, conducted thermal radiation to a small beryllium oxide chamber containing several grams of cryogenic deuterim-tritium mixture. The thermal radiation not only heated the fuel chamber to fusion temperatures, the pressure in the BeO wall caused it to implode and compress the fusion fuel, accelerating its combustion. The thermal radiation arrived ahead of the shock front of the fission explosion, allowing time for a reaction to occur before being engulfed by the expanding fission fireball. The yield of the fusion reaction was negligible compared to the fission device.

The thermonuclear portion of the experiment was largely developed by Edward Teller, the Cylinder may have been based on a design by physicist George Gamow. The progress of the fusion burn was observed by measuring the thermal X-rays emitted by the fusion plasma. This required instruments that were shielded from the thermal X-rays and the gamma rays of the fission bomb, and were far enough away from the explosion to be able to measure and transmit data while the fusion burn was in progress. This part of the experiment was designed by Hugh Bradner and Hebert York. The measurements were made by recording the fluorescence of a set of K-edge filters located at the base of the shot tower. X-rays from the fusion chamber reached the instruments through vacuum filled pipes that were inside a 4 ft. diameter lead pipe that blocked out extraneous X-rays and gammas, and weighed 235 tons. The total weight of diagnostic equipment was 283 tons.

The test was originally planned to study the ignition concept for the "Classical Super" thermonuclear weapon design (which had already been shown to be infeasible). The test fortuitously provided useful data on radiation implosion, an essential element of the Teller-Ulam design which had been devised just two months prior. George left a large shallow crater in the coral and sand atoll - 1140 feet across and 10 feet deep (such wide shallow craters were typical of atoll tower shots).

In the sequence of three Rapatronic camera pictures below the development of the "Mach stem" can be seen as the fireball shock wave reflects off the ground. The Mach stem is a belt of intensified shock pressure at the base of the shock front. Since in this phase of growth the temperature (and hence brightness) of the fireball is determined by the strength of the shock wave, a bright band can be seen where the Mach stem is located

Test:	Item
Time:	18:17 24 May 1951 (GMT) 06:17 25 May 1951 (local)
Location:	Island Enjebi ("Janet"), Enewetak Atoll
Test Height and Type:	200 foot Tower Shot
Yield:	45.5 kt

First test of the principle of "fusion boosting", the use of a thermonuclear fusion reaction to inject neutrons into a fission core to boost efficiency. The Item device used a cryogenic deuterium-tritium mixture inside an enriched uranium core. The boosting approximately doubled the yield over its expected unboosted value.

Unidentified Greenhouse Shot

********************

Operation Buster-Jangle

1951

The Cold-War inspired accelerating tempo of nuclear weapons activity led to the inauguration of more complex joint test operations between the Department of Defense and the nuclear weapons labs (at this time consisting only of Los Alamos). The previous test series had either been run by the DOD (Crossroads) or Los Alamos (Sandstone, Ranger, and Greenhouse). In late 1951 two test series were held together for the first time - Operation Buster (conducted by Los Alaamos) and Operation Jangle (conducted by the DOD). 7800 DOD personnel participated in Buster-Jangle, 6500 of them troops who conducted field exercises in conjunction with the tests. These were the first such field exercises conducted in the United States proper.

Buster-Jangle was held at the Nevada Proving Ground (later NTS) and had a number of objectives. The Buster series was primarily a weapon development effort. A number of pit configurations were fired in a Mk-4 high explosive assembly to collect data for weapons design. In addition the TX-7E design was proof fired (leading to the deployment of the Mk7 light weight bomb). The DOD also particpated in one of the Buster tests conducting the Desert Rock I exercise during the Dog shot. The Jangle series evaluated the usefulness of atomic weapons in cratering using ground-level and sub-surface bursts. The Desert Rock II and III troop exercises were held in conjunction with these tests. The purpose of the Desert Rock exercises was to gain experience in operations Conducted in a nuclear combat environment

Buster-Jangle released about 10,500 kilocuries of radioiodine (I-131) into the atmosphere (for comparison, Trinity released about 3200 kilocuries of radioiodine). This produced total civilian radiation exposures amounting to 7.4 million person-rads of thyroid tissue exposure (about 2% of all exposure due to continental nuclear tests). This can be expected to eventually cause about 2300 cases of thyroid cancer, leading to some 120 deaths.

 

 

Operation Buster

Test:	Able
Time:	14:00 22 October 1951 (GMT) 6:00 22 October 1951 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	100 foot Tower Shot
Yield:

This was a test of the Petite Plutonium fission bomb, designed by Ted Taylor. It consisted of a standard 60 inch, 10,000 lb. implosion system with the plutonium core reduced to what was estimated to be close to the minimum amount of fissile material for an appreciable yield. This was the lowest yield design yet tested, with a predicted yield of only 200 tons. It was a fizzle - the first actual failure of any U.S. nuclear device (the 18th exploded by the U.S.), and the first known failure of any nuclear device. Rather than being a sign of ineptness, this failure was indicative of the increasingly aggressive (and thus risky) U.S. experimental approach to weapon development. It established a close lower bound on the minimum amount of plutonium that could be used in a weapon to produce a significant yield, an important benchmark in weapon design.

This was inadvertently a "zero yield" test. The device achieved super criticality and produced detectable nuclear output, but the energy produced was negligible compared to the high explosive used. The tower was damaged but largely intact from the test.

The first attempt to fire this device (on 19 October) was a true failure - nothing happened. The problem was traced to the control circuitry.

 

Test:	Baker
Time:	15:20 28 October 1951 (GMT) 7:20 28 October 1951 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	1118 Foot Airdrop from B-50
Yield:	3.5 kt

The test device, designated "LT", was a Mk 4 bomb assembly consisting of a plutonium core without a uranium tamper. The expected yield was 3-8 kt.

Test:	Charlie
Time:	15:00 30 October 1951 (GMT) 7:00 30 October 1951 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	1132 Foot Airdrop from B-50
Yield:	14 kt

The test device, designated "PC", was a Mk 4 bomb assembly of a composite uranium-plutonium core. The expected yield was 12-15 kt.

 

 

Test:	Dog
Time:	15:30 1 November 1951 (GMT) 7:30 1 November 1951 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	1417 Foot Airdrop from B-50
Yield:	21 kt

The test device, designated "NF", was a Mk 4 bomb assembly of a composite uranium-plutonium core. The expected yield was 18-25 kt.

Desert Rock I - the first U.S. nuclear field exercise on land was conducted in association with the Dog shot. In the weeks before the shot the assembled troops (from the 188th Airborne, 127th Engineer Battalion, and the 546th Field Artillery Battalion) dug field emplacements to simulate a defensive deployment southwest of the shot location. The troops observed the shot from a point six miles from ground zero, were transported to the defensive emplacements to view the weapon effects, and then conducted maneuvers in the area. Since this shot was an airburst there was no local fallout, although some neutron-induced radioactivity existed.

Buster Easy

Test:	Easy
Time:	16:30 5 November 1951 (GMT) 8:30 5 November 1951 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	1314 Foot Airdrop from B-45
Yield:	31 kt

This was a test of the TX-7E , a Mk-7 bomb prototype. With a weight of only 1800 lb and a diameter of 30 inches this bomb represented a drastic size reduction over its Fat Man-size (10,000 lb, 60 inch diameter) predecessors. The design used an 800 lb. assembly of high explosive (primarily Octol 75/25), with a composite uranium-plutonium core. The predicted yield was 22-35 kt.

********************

Operation Jangle

Test:	Sugar
Time:	17:00 19 November 1951 (GMT) 9:00 19 November 1951 (local)
Location:	Nevada Test Site (NTS), Area 9
Test Height and Type:	Surface Burst (bomb center 3.5 ft. above surface)
Yield:	1.2 kt

This was a weapons effect test of a surface burst. Up to this time no surface burst had ever been fired (the fact that the center of the 60 inch diameter bomb was actually slightly above the surface later complicated attempts at analysis). This was the only surface test ever conducted in the United States proper (although sub-surface shots were subsequently fired at NTS that produced surface craters).

The device used (desigated "Johnny") was identical to the Ranger Able device, chosen for its predictibility and its limited yield (to minimize contamination). It was Mk-6 bomb using an all uranium core. The test name (Sugar) was a mnemonic code for "surface".

The test left a crater 21 feet deep and 90 feet wide. At this time an 83 kt surface burst implosion bomb was being considered for use as a cratering and bunker-buster weapon. The test indicated that such a weapon would produce a crater 300 feet in diameter and 70 feet deep.

Desert Rock II was conducted in conjunction with Sugar. The troops observed the detonation at a distance of 5 miles. Due to the intense local radioactivity from the ground burst, the maneuvers were conducted at a considerable distance from ground zero.

 

Test:	Uncle
Time:	19:59:59.7 29 November 1951 (GMT) 11:59:59.7 29 November 1951 (local)
Location:	Nevada Test Site (NTS), Area 10
Test Height and Type:	Sub-surface Burst -17 ft.
Yield:	1.2 kt

This was a weapons effect test of a sub-surface burst.

The device used (desigated "Frankie") was identical to the Ranger Able device. The test name (Uncle) was a mnemonic code for "underground".

The test left a crater 53 feet deep and 260 feet wide. The 17 foot depth of burial was designed as a scaled down test of a 23 kt ground penetrating gun-type weapon also being considered as a cratering and bunker-buster weapon. The test indicated that such a weapon would leave a crater 700 feet in diameter and 140 feet deep.

Desert Rock III was conducted in conjunction with Uncle. As with Sugar, the troops observed the detonation at a distance of 5 miles and did not closely approach ground zero. Near ground zero the radiation level was 5000 roentgens/hour at one hour after the test, with levels of 1000 R/hr extending up to 1200 yards from the burst point. Hazardous levels of 100 R/hr extended past 5000 yards in some areas.

 

Operation Tumbler-Snapper

1952 - Nevada Proving Ground

As the Korean War raged, the high tempo of Cold-War nuclear weapons tests continued with a second combined test operation being conducted at the Nevada Proving Ground (later NTS) scarcely four months after the last joint operation (Buster-Jangle). Operations at the NPG were beginning to resemble non-stop testing.

With the U.S. preoccupied by Korea, and by the possibility of a general asian land war erupting, both parts of Tumbler-Snapper were focused on developing tactical nuclear weapons - both the weapons themselves and the knowledge and experience necessary for their operational use.

Operation Tumbler consisted of three air bursts conducted to gather detailed information about blast effects, the fourth test was also an airburst and technically part of both Tumbler and Snapper. The remaining four shots during Operation Snapper were tower shots and were weapons development tests of various kinds.

The Desert Rock IV field exercise was conducted during Tumbler-Snapper, with 7350 out of 8700 DOD participants conducting maneuvers in conjunction with test shots Charlie, Dog, and George, and observing during Fox. Although the radiation exposure dose limit was set at 3.0 rem a number of exposures in excess of that occurred - 48 with 3-5 rem, 9 with 5-10 rem, and 1 in excess of 10 rem (these exposures do not cause observable health effects, but do cause a small increase in cancer risk).

Tumber-Snapper released about 15,500 kilocuries of radioiodine (I-131) into the atmosphere (for comparison, Trinity released about 3200 kilocuries of radioiodine). Although this was only some 40% more than that released by Buster-Jangle, unfavorable weather patterns caused dramatically higher civilian radiation exposures (about 15-fold). The total thyroid tissue exposure amounted to 110 million person-rads, about 29% of all exposure due to continental nuclear tests. This can be expected to eventually cause about 34,000 cases of thyroid cancer, leading to some 1750 deaths.

Operation Tumbler

Previous test series (Sandstone, Greenhouse, and Buster) had revealed unexpected anomalies in blast over pressures and arrival times from airbursts, so Tumbler was conducted to gather detailed data on these effects. The first two tests were both 1 kt for convenience in developing scaling laws. All three air drops during Tumbler were from a B-50, which was a re-engined B-29. The test devices were all based on the large (60 inch diameter) heavy Mk 4 bomb, which was essentially the same size as the original Fat Man bomb, but with special core assemblies to obtain specific yields.

Test:	Able
Time:	17:00 1 April 1952 (GMT) 09:00 1 April 1952 (local)
Location:	Nevada Test Site (NTS), Area 5
Test Height and Type:	793 Foot Airdrop from B-50
Yield:	1 kt

This device used the same U-235 core design first tested in Ranger Able. This design had become something of an experimental benchmark due to its convenient low yield and high predictability, having also been used in Jangle Sugar and Jangle Uncle. The Mk 4 based test device weighed 10,800 lb.

 

 

Test:	Baker
Time:	17:30 15 April 1952 (GMT) 09:30 15 April 1952 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	1109 Foot Airdrop from B-50
Yield:	1 kt

This device also used the Ranger Able U-235 core in a Mk 4 based test device (weight 10,500 lb).

Test:	Charlie
Time:	17:30 22 April 1952 (GMT) 09:30 22 April 1952 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	3447 Foot Airdrop from B-50
Yield:	31 kt

This test combined a proof test of a new high-efficiency core with blast effects measurements. The predicted yield was 40-60 kt. This test was broadcast live on television (a first). The Mk 4 based test device weighed 10,440 lb.

Tumbler Charlie

Operation Snapper

This was an ambitious series to evaluate new weapon design principles and gather fundamental weapon design data. Among the new features tested included deuterium gas fusion boosting, external initiation, and the use of beryllium neutron reflector/tampers. Tests of new smaller implosion systems, and new schemes for achieving high core compression were also conducted. Other experiments calibrated the TOM internal neutron initiator, provided initiation time vs yield calibration data, and explored the curious "rope trick" effect seen with cable moored test devices.

Test:	Dog
Time:	16:30 1 May 1952 (GMT) 08:30 1 May 1952 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	1040 Foot Airdrop from B-45
Yield:	19 kt

Dog was a test of a modified TX-7 weapon (previously tested in Buster Easy). The device tested the usefulness of deuterium gas fusion boosting (not deuterium-tritium boosting!). The predicted yield was 15-20 kt.

Test:	Easy
Time:	12:15 7 May 1952 (GMT) 04:15 7 May 1952 (local)
Location:	Nevada Test Site (NTS), Area 1
Test Height and Type:	300 Foot Tower
Yield:	12 kt

This device (code named BROK-1) was a test of the TX-12, a Mk-12 bomb prototype. The Mk-12 was intended to be a slender, lightweight tactical bomb that could be carried externally by high speed fighter-bombers. It set a record at the time for small diameter and light weight, with an implosion system diameter of 22 inches weighing only 550 lb (a modest improvement over the Mk-7), yet retained good compression and efficiency. The total device weight was 625 lb, with a predicted yield of 9 kt.

 

Test:	Fox
Time:	12:00 25 May 1952 (GMT) 04:00 25 May 1952 (local)
Location:	Nevada Test Site (NTS), Area 4
Test Height and Type:	300 Foot Tower
Yield:	11 kt

This device (code named XR1) used a Mk 5 bomb assembly. The test was intended to gather data on the initiation time vs yield curve; it also served as a calibration test of the TOM polonium-beryllium internal neutron initiator. The test device had a diameter of 40 inches and weighed 2700 lb, the predicted yield was 15-18 kt.

Test:	George
Time:	11:55 1 June 1952 (GMT) 03:55 1 June 1952 (local)
Location:	Nevada Test Site (NTS), Area 3
Test Height and Type:	300 Foot Tower
Yield:	15 kt

This device (code named XR2) used a Mk 5 bomb assembly. The test was intended to gather additional data on the initiation time vs yield curve. A novel feature of this test was the use of an external initiator - in this case employing a device called a betatron (which is a circular electron accelerator). In this test the high energy electrons were used to generate high energy X-rays that induced photo-fission in the core to initiate the chain reaction. The betatron allowed very accurate control of initiation time. The test device had a diameter of 40 inches and weighed 2700 lb, the predicted yield was 30 kt.

Test:	How
Time:	11:55 5 June 1952 (GMT) 03:55 5 June 1952 (local)
Location:	Nevada Test Site (NTS), Area 2
Test Height and Type:	300 Foot Tower
Yield:	14 kt

This device (code named Scorpion) was designed in part by Ted Taylor. Snapper How was the first test to use a beryllium neutron reflector/tamper, which would become standard in later weapons. The test device used the same 22 inch implosion system as Snapper Easy, but the lightweight tamper cut 80 pounds off the implosion system weight. Predicted yield was 11 kt.

Operation Ivy

1952 - Enewetak Atoll, Marshall Islands

On 31 January 1950 Pres. Harry S. Truman publicly declared the U.S. intention to develop a hydrogen bomb. The primary motivations for this declaration was were two surprising revelations - the Soviet Union's first fission bomb during the previous fall; and the discovery of Klaus Fuchs' espionage activity of at Los Alamos, uncovered just days before. These combined shocks, added to the rapidly growing Cold War tensions, created grave concern at the highest levels of Washington about the United States being overtaken in a nuclear arms race by the Soviet Union.

From that time onward, the highest priority was placed on developing new and more potent strategic weapons - especially thermonuclear weapons (hydrogen bombs). At that time though no one had good ideas about how a practical thermonuclear weapon could be made, rendering Truman's declaration hollow. This raised new fears - that Truman's pronouncement may have spurred Soviet thermonuclear efforts onward even faster, and that they might have hit upon concepts not yet known in the U.S. Consequently a fallback strategy was pursued - developing the highest yield fission bbomb possible, a technical effort led by Theodore Taylor at Los Alamos. The conceptual breakthroughs of Stanslaw Ulam and Edward Teller the following January provided the needed insights to develop a thermonuclear device.

So from early 1951 onward, these two parallel efforts to develop high yield weapons were focused on a Pacific Proving Ground test series for late in 1952. This series - Operation Ivy - exploded the two largest bombs tested up to that time. It inaugurated the thermonuclear age with the first "true" thermonuclear test (code name Mike), which was considerably more powerful than all the high explosives used in two World Wars put together. Ivy also tested the highest yield pure fission weapon ever exploded.

It is part of my responsibility as Commander in Chief of the Armed forces to see to it that our country is able to defend itself against any possible aggressor. Accordingly, I have directed the AEC to continue its work on all forms of atomic weapons, including the so-called hydrogen or Super bomb.

President Harry S. Truman, 31 January 1950

Ivy Mike

Test:	Mike
Time:	19:14:59.4 31 October 1952 (GMT) 07:14:59.4 1 November 1952 (local)
Location:	Elugelab ("Flora") Island, Enewetak Atoll
Test Height and Type:	Surface burst
Yield:	10.4 Mt

The device detonated in the Mike ("m" for "megaton") test, called the Sausage, was the first "true" H-Bomb ever tested, that is - the first thermonuclear device built upon the Teller-Ulam principles of staged radiation implosion. The device was designed by the Panda Committee directed by J. Carson Mark at Los Alamos (Teller declined to play a role in its development).

The 10.4 megaton device was a two stage device using a TX-5 fission bomb as the primary stage, and a secondary stage consisting of liquid deuterium fusion fuel stored in a cylindrical Dewar (thermos) flask. Running down the center of the Dewar was a plutonium "spark plug" rod to ignite the fusion reaction. The Dewar was surrounded by a natural uranium pusher/tamper weighing more than 5 metric tons. The entire assembly was housed in an enormous steel casing, 80 inches wide and 244 inches long, with walls ~10-12 inches thick, the largest single forging made up to that time. The inside surface of the casing was lined with sheets of lead and polyethylene to form the radiation channel that conducted heat from the primary to the secondary. The entire device weighed 82 tons.

The enormous explosion was the 4th largest device ever tested by the U.S. 77% (8 megatons) of the yield was due to fast fission of the natural uranium pusher/tamper, with remainder (2.4 megatons) coming directly from fusion of the deuterium fuel. The island the test device was installed on, Elugelab (code named Flora), was entirely destroyed. The resulting crater was 6240 ft across and 164 ft deep. High levels of radiation blanketed much of the atoll following the test.

Various Images of Ivy Mike

Ivy Mike Fireball

 

Ivy Mike Mushroom Cloud

The mushroom cloud climbed to 57,000 feet in only 90 seconds, entering the stratosphere. One minute later it reached 108,000 feet, eventually stabilizing at a ceiling of 120,000 feet. Half an hour after the test the mushroom stretched 60 miles across, with the base of the mushroom head joining the stem at 45,000 feet.

The Aftermath

Elugelab Island, before and after

Powered mostly by fission, Mike showered high levels of radiation over the atoll. Below is a fallout map showing radiation intensities (in rads/hour) an hour after the test.

 

Ivy King

Test:	King
Time:	23:30 15 November 1952 (GMT) 11:30 16 November 1952 (local)
Location:	Runit ("Yvonne") Island, Enewetak Atoll
Test Height and Type:	1480 Foot Airburst
Yield:	500 kt

The device detonated in the King ("k" for "kiloton") test was dropped by a B-36H bomber flying out of Kwajalein Island. The detonation occured 20 feet lower than planned, with a circular bombing error of 570 feet +/- 35 feet. While perhaps not the largest deliverable fission bomb possible at the time, it was certainly pushing close to the practical limit.

This device was a prototype of the Mk 18 Super Oralloy bomb ("SOB"). The device consisted mostly of standard stockpiled components - it was based on the stockpiled Mk-6D bomb, but using the 92 point implosion system developed for the Mk-13. The pit (consisting of the reflector and core) was modified however. The normal uranium-plutonium composite core was replaced by a new design made up of approximately 60 kilograms of highly enriched uranium (oralloy) in a natural uranium tamper. The complete bomb weighed 8600 lb.

The Mk-18 bomb was developed under the direction of Ted Taylor at Los Alamos. A major aspect of the development was developing safety mechanisms. With such a large amount of enriched uranium (more than 4 critical masses) the bomb was skirting the edge of criticality safety. Chains made of aluminium and boron filled the central portion of the bomb to absorb neutrons and prevent collapse (if, for example, the high explosives were detonated in an accident). The chains were pulled out before the bomb was dropped.

 

Images of Ivy King

Operation Upshot-Knothole

1953 - Nevada Proving Ground

 As the first faint streaks of dawn poked over the distant hills the blast came. A vivid flash of light pierced the desert darkness and lighted up the entire countryside. It lasted but a moment or two then was gone. All eyes turned toward the spot where the bomb had exploded. They saw a big ball of furiously churning fire, smoke, sand and debris rapidly rising from the ground in huge, rolling waves. The afterglow remained for several minutes while the mushroom cloud continued to rise then drift away and apart. Then sun was still below the horizon but daylight was coming fast. Broad streaks of sunlight slanted over the mountain tops like ghostly fingers clawing at the heavens. Rumbling of the shock wave continued for nearly five minutes, bouncing back and forth from one mountain wall to another.

By 1953 a pattern of test activity at the Nevada Proving Ground had emerged. Through the fifties, every year or (every other year if a pacific test series intervened) a series of several shots was fired at the NPG over a period of three or four months to address a wide variety of objectives. Upshot-Knothole was just such a scatter-shot effort. Technical information to assist in weapon design was obtained in several tests. Efforts to prepare the U.S. military for atomic combat continued with proof-tests of a number of new tactical weapons, including the first nuclear artillery shell. The tests provided additional experience and information for planning atomic combat operations. Important information was also obtained for civil defense efforts.

And critically important - Upshot-Knothole also tested the radiattion implosion systems for the world's first deployable thermonuclear weapons which would be proof-tested in Operation Castle the following year.

An estimated 18,000 DOD personnel participated in observer programs, tactical maneuvers, scientific studies, and support activities. Members of all four armed services participated in Exercise Desert Rock V.

This operation exposed exercise personnel to nuclear tests, and thus radiation, more aggressively than previous ones. Observation by troop formations were conducted at what was calculated to be the minimum safe separation distance, with many personnel being exposed to multiple tests. Under current occupational radiation exposure limits (0.3 rem/week and 5 rem/year) this would would limit maximum exposures to 3.3 rems over the 11 week operation. Approximately three thousand soldiers reached or exceeded this limit, with 84 exceeding the annual limit (the highest recorded exposure was 26.6 rem). These exposures do not produce observable symptoms, they simply increase the lifetime risk of cancer a small amount.

The effect on the downwind civilian population, taken together, was much worse. Uphot-Knothole released some 35,000 kilocuries of radioiodine (I-131) into the atmosphere (for comparison, Trinity released about 3200 kilocuries of radioiodine). This produced total civilian radiation exposures amounting to 89 million person-rads of thyroid tissue exposure (about 24% of all exposure due to continental nuclear tests). This can be expected to eventually cause about 28,000 cases of thyroid cancer, leading to some 1400 deaths.

Test:	Annie
Time:	13:20 17 March 1953 (GMT) 05:20 17 March 1953 (local)
Location:	Nevada Test Site (NTS), Area 3
Test Height and Type:	300 Foot Tower Shot
Yield:	16 kt

In an effort to calm public fears about weapons testing, Annie was an "open shot" - civilian reporters were permitted to view it from News Nob, 11 kilometers south of the shot-tower. Annie was a weapon development test, it was an experimental device (code named XR3) that provided additional information to normalize the yield-vs-initiation time curve. It was a Mk-5 HE assembly using a Type D pit, and used a betatron for external initiation (the third such test). Total device weight was 2700 lb, predicted yield was 15-20 kt.

 

 

Test:	Nancy
Time:	13:10 24 March 1953 (GMT) 05:10 24 March 1953 (local)
Location:	Nevada Test Site (NTS), Area 4
Test Height and Type:	300 Foot Tower Shot
Yield:	24 kt

This was a test of the TX-15 "Zombie" thermonuclear weapon design scheduled to be proof-tested at the Pacific Proving Grounds in 1954. The device, code named Nevada Zombie, tested both the RACER primary and the TX-15 radiation implosion system. The TX-15 appears to have been something of a transitional design between a radiation implosion fission bomb, and a optimized thermonuclear design. It was originally conceived as a two stage pure fission bomb using enriched uranium fuel, but matured into a thermonuclear system for improved yield as work progressed. It was lighter and had a smaller diameter than any of the other thermonuclear designs then under development. The Nevada Zombie weighed 11,000 lb., had a diameter of 35.4 inches, and a length of 122 inches. The RACER primary produced a yield below the predicted range of 35-40 kt, leading to a design modification for the Simon shot.

Test:	Ruth
Time:	13:00 31 March 1953 (GMT) 05:00 31 March 1953 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	300 Foot Tower Shot
Yield:	0.2 kt

 This was the first device to be tested by UCRL (University of California Radiation Laboratory, later Lawrence-Livermore) the new second weapons laboratory, established by Teller and Lawrence. The device, named Hydride I, was a fission bomb based on a enriched uranium hydride fuel. Like its sister device tested in the Ray shot 12 days later, Hydride I was intended for use as a primary in a compact thermonuclear system.

The uranium hydride fission bomb approach was considered during the days of the Manhattan Project as possible way for reducing the required critical mass of uranium. The hydrogen in the hydride compound (UH3) moderates the fast neutrons somewhat, which moves the energy spectrum down into a region where the average fission cross section of uranium is substantially higher giving a smaller effective critical mass. Unfortunately, bomb efficiency is very adversely affected by the slowing down of the neutrons since it gives the bomb core more time to blow apart. The concept (if it worked) would allow low yield bombs that, while inherently inefficient, also did not use up much fissile material.

The Manhattan Project had abandoned this idea as a practical bomb design, although uranium hydride systems proved quite valuable for criticality experiments when fissile material was scarce. The famous "Dragon" prompt criticality experiments where a chunk of fissile material was dropped through a subcritical mass to momentarily reach supercriticality used uranium hydride.

After the war Los Alamos physicists were skeptical of the usefulness of uranium hydride in weapons. Edward Teller remained interested in the concept though, and used his prominent position to push hydride weapon development when the UCRL weapons lab opened.

The Ruth shot was a fizzle. The predicted yield was 1.5 to 3 kt, while the 200 ton yield was a fraction of that. Especially embarrassing to UCRL was that only the top 100 feet of the 300 foot shot tower was vaporized (though much of the remainder was scattered across the desert). It was standard practice at that time for each test to totally erase all evidence associated with it (automatically "declassifying" the site), which Ruth failed to do.

Hydride I weighed 7400 lb, was 56 inches in diameter and was 66 inches long. A betatron was used for initiation.

Test:	Dixie
Time:	15:30 6 April 1953 (GMT) 07:30 6 April 1953 (local)
Location:	Nevada Test Site (NTS), Area 7
Test Height and Type:	6022 Foot Airdrop
Yield:	11 kt

B-50 bomber air drop, the detonation was 565 feet east, and 72 feet north of the designated ground zero. Dixie was a Mk-5D bomb proof test. The predicted yield was 8-12 kt. This test experimented with lithium deuteride as a means of fusion boosting. The device weight was 3260 lb, diameter was 60 inches, length was 128 inches.

Test:	Ray
Time:	12:45 11 April 1953 (GMT) 04:45 11 April 1953 (local)
Location:	Nevada Test Site (NTS), Area 4
Test Height and Type:	100 Foot Tower
Yield:	0.2 kt

This was the second test of a uranium hydride device, this time using the heavy isotope of hydrogen - deuterium. The uranium deuteride device was called Hydride II, and was otherwise basically identical to Hydride I. The predicted yield was 0.5-1 kt, the lower expected yield making a smaller gap with the same 200 ton yield as the first test. UCRL scientist Herbert York claims not to regard this test as a failure since it was lower than the predicted range by "only a factor of three". Legend has it that this shot was fired on a tower of only 100 feet (compared to 300 feet for Ruth) to ensure that the tower would be entirely destroyed.

Test:	Badger
Time:	12:35 18 April 1953 (GMT) 04:35 18 April 1953 (local)
Location:	Nevada Test Site (NTS), Area 2
Test Height and Type:	300 Foot Tower
Yield:	23 kt

This was a test of the TX-16 thermonuclear weapon design, the reduced size cryogenic weapon descended from the Sausage device tested in Ivy Mike. The test device was named Buzzard and used a deuterium gas boosted RACER primary. The expected yield was 35-40 kt. The device had a diameter of 56 inches, and weighed 7400 lb. The full scale thermonuclear version of this design was actually deployed on a limited scale for a short time as an "Emergency Capability" weapon in late 1953 and early 1954. The full scale version was never tested though due to the success of solid fueled weapon designs

Soviet Nuclear Test Summary

The Soviet Union became the second nation in the world to detonate a nuclear device on 29 August 1949 (the U.S. had previously exploded eight devices). Between that date, and 24 October 1990 (the date of the last Soviet, or Russian, test) the Soviet Union conducted 715 nuclear tests, by official count. As with the U.S., the term "test" may indicate the near simultaneous detonation of more than one nuclear exposive device, so the actual number of devices exploded is 969 (for comparison, the U.S. has conducted 1056 tests/explosions using at least 1151 devices).

Not included are "hydronuclear tests", what are tests involving fissile material with yields (by design) of less than 1 ton. The Soviet Union conducted about 100 of these tests, with the yields remaining below 100 kg. Explosive device fizzles with yields of less than 1 ton are included however.

The Soviet Union conducted 124 "peaceful nuclear explosions" compared to 35 such tests in the U.S Plowshare program.

From first to last test, the Soviet test program lasted 41 years, 1 month, and 26 days. During this period testing activity was not continuous. A gap of 2 years and 26 days separated the first and second tests, due to the problems experienced in developing the nuclear weapons infrastructure. Four voluntary moratoriums were observed. The first was from November 1958 to August 1961, when the U.S. and the U.K. also abstained form any testing. This moratorium was abrogated on 31 August 1961 by Khruschev, with nuclear testing commencing the next day. This test series was the largest in world history, as measured by explosive yield. The second moratorium lasted from 26 December 1962 to 14 March 1964, while the Atmospheric Test Ban was being negotiated (signed 5 August 1963), and to prepare the test program for large scale underground testing. The third and fourth moratoriums extended from August 1985 to October 1987, and from November 1989 to October 1990, as the Soviet Union under Gorbachev sought to reach accomodation with the U.S. The test program was terminated by a fifth moratorium, which has now been made permanent with the signing of the Comprehensive Test Ban Treaty (CTBT).

Remains of concrete Soviet test towers at the Semipalatinsk Test Range

*****************************************************************

Soviet Atmospheric Tests

This is a complete list of all Soviet nuclear tests conducted during the era of atmospheric testing. Not included are "hydronuclear tests", what are tests involving fissile material with yields (by design) of less than 1 ton. Explosive device fizzles with yields of less than 1 ton are included however.

Abbreviations

• FMS = fundamental and methodical studies of the phenomena of a nuclear explosion
• ME = military exercise with a real nuclear detonation
• MT = Moscow Time
• MTR = Missile Testing Range (near Kapustin Yar, Astrakhan region, Russian Federation)
• NTSNZ = Northern Test Site Novaya Zemlya (Arctic Ocean, Russian Federation)
• NWR = Nuclear Weapons Related (weapon development or modification)
• SAM = studies of accident modes and emergencies (i.e. safety tests)
• STS = Semipalatinsk Test Site (Kazakhstan)
• WIE = Weapons Effects Tests ("weapon injurious effects" studies)

When the exact yield of a test is known, the entries in the minimum and maximum yield columns are identical.

Test Number	Date (MT)	Location	Test Type	Yield (Kt)		Purpose	Comments
				Min.	Max.
1	29-Aug-49	STS	surface	22	22	NWR	First Soviet nuclear test
2	24-Sep-51	STS	surface	38	38	NWR
3	18-Oct-51	STS	air	42	42	NWR	First Soviet air test; aerial bomb drop
4	12-Aug-53	STS	surface	400	400	NWR	First Soviet thermonuclear explosion; highest yield surface nuclear explosion
5	23-Aug-53	STS	air	28	28	NWR
6	3-Sep-53	STS	air	5.8	5.8	NWR
7	8-Sep-53	STS	air	1.6	1.6	NWR
8	10-Sep-53	STS	air	4.9	4.9	NWR
9	14-Sep-54	Totsk	air	40	40	ME	"Military exercise with real nuclear detonation; at Totask, MoD test site, Orenburg Region"
10	29-Sep-54	STS	air	0.2	0.2	NWR
11	1-Oct-54	STS	air	0.03	0.03	NWR
12	3-Oct-54	STS	air	2	2	NWR
13	5-Oct-54	STS	surface	4	4	NWR
14	8-Oct-54	STS	air	0.8	0.8	NWR
15	19-Oct-54	STS	surface	0	0.001	NWR	First nuclear test failure
16	23-Oct-54	STS	air	62	62	NWR
17	26-Oct-54	STS	air	2.8	2.8	NWR
18	30-Oct-54	STS	surface	10	10	NWR	Air dropped bomb, but with a very low height of burst
19	29-Jul-55	STS	surface	1.3	1.3	NWR
20	2-Aug-55	STS	surface	12	12	NWR
21	5-Aug-55	STS	surface	1.2	1.2	NWR
22	21-Sep-55	NTSNZ	underwater	3.5	3.5	WIE	First test at NTSNZ
23	6-Nov-55	STS	air	250	250	NWR
24	22-Nov-55	STS	air	1600	1600	NWR	"First Soviet test of radiation implosion bomb, highest yield test at STS"
25	2-Feb-56	Aralsk	surface	0.3	0.3	WIE	First surface nuclear exploson (near Aralsk in Kazakhstan) from missile launch near MTR
26	16-Mar-56	STS	surface	14	14	NWR
27	25-Mar-56	STS	surface	5.5	5.5	NWR
28	24-Aug-56	STS	surface	27	27	NWR
29	30-Aug-56	STS	air	900	900	NWR
30	2-Sep-56	STS	air	51	51	NWR
31	10-Sep-56	STS	air	38	38	NWR
32	17-Nov-56	STS	air	900	900	NWR
33	14-Dec-56	STS	air	40	40	NWR
34	19-Jan-57	MTR	air	10	10	WIE	First air nuclear explosion with missile launch from MTR
35	8-Mar-57	STS	air	19	19	NWR
36	3-Apr-57	STS	air	42	42	NWR
37	6-Apr-57	STS	air	57	57	NWR
38	10-Apr-57	STS	air	680	680	NWR
39	12-Apr-57	STS	air	22	22	NWR
40	16-Apr-57	STS	air	320	320	NWR
41	22-Aug-57	STS	air	520	520	NWR
42	26-Aug-57	STS	air	0.1	0.1	SAM	First test for nuclear weapons safety
43	7-Sep-57	NTSNZ	surface	32	32	FMS	The only surface test at NTSNZ
44	13-Sep-57	STS	air	5.9	5.9	NWR
45	24-Sep-57	NTSNZ	air	1600	1600	NWR	First air test at NTSNZ; aerial bomb drop
46	26-Sep-57	STS	air	13	13	NWR
47	6-Oct-57	NTSNZ	air	2900	2900	NWR
48	10-Oct-57	NTSNZ	underwater	10	10	WIE
49	28-Dec-57	STS	air	12	12	NWR
50	4-Jan-58	STS	air	1.3	1.3	NWR
51	17-Jan-58	STS	air	0.5	0.5	NWR
52	23-Feb-58	NTSNZ	air	860	860	NWR
53	27-Feb-58	NTSNZ	air	250	250	NWR
54	27-Feb-58	NTSNZ	air	1500	1500	NWR
55	13-Mar-58	STS	air	1.2	1.2	NWR
56	14-Mar-58	STS	air	35	35	NWR
57	14-Mar-58	NTSNZ	air	40	40	FMS
58	15-Mar-58	STS	air	14	14	NWR
59	18-Mar-58	STS	air	0.16	0.16	FMS
60	20-Mar-58	STS	air	12	12	NWR
61	21-Mar-58	NTSNZ	air	650	650	NWR
62	22-Mar-58	STS	air	18	18	NWR
63	30-Sep-58	NTSNZ	air	1200	1200	NWR
64	30-Sep-58	NTSNZ	air	900	900	NWR
65	2-Oct-58	NTSNZ	air	290	290	NWR
66	2-Oct-58	NTSNZ	air	40	40	FMS
67	4-Oct-58	NTSNZ	air	9	9	NWR
68	5-Oct-58	NTSNZ	air	15	15	NWR
69	6-Oct-58	NTSNZ	air	5.5	5.5	NWR
70	10-Oct-58	NTSNZ	air	68	68	NWR
71	12-Oct-58	NTSNZ	air	1450	1450	NWR
72	15-Oct-58	NTSNZ	air	1500	1500	NWR
73	18-Oct-58	NTSNZ	air	2900	2900	NWR
74	19-Oct-58	NTSNZ	air	40	40	FMS
75	19-Oct-58	NTSNZ	air	0	0.001	NWR
76	20-Oct-58	NTSNZ	air	440	440	NWR
77	21-Oct-58	NTSNZ	air	2	2	NWR
78	22-Oct-58	NTSNZ	air	2800	2800	NWR
79	24-Oct-58	NTSNZ	air	1000	1000	NWR
80	25-Oct-58	NTSNZ	air	190	190	NWR
81	25-Oct-58	NTSNZ	air	0	0.1	FMS
82	1-Nov-58	MTR	air	10	10	WIE
83	3-Nov-58	MTR	air	10	10	WIE
84	1-Sep-61	STS	air	16	16	NWR
85	4-Sep-61	STS	air	9	9	NWR
86	5-Sep-61	STS	air	16	16	NWR
87	6-Sep-61	STS	air	1.1	1.1	NWR
88	6-Sep-61	MTR	air	11	11	WIE
89	9-Sep-61	STS	surface	0.38	0.38	SAM
90	10-Sep-61	NTSNZ	air	2700	2700	NWR
91	10-Sep-61	NTSNZ	air	12	12	NWR
92	10-Sep-61	STS	air	0.88	0.88	NWR
93	11-Sep-61	STS	air	0.3	0.3	NWR
94	12-Sep-61	NTSNZ	air	1150	1150	NWR
95	13-Sep-61	NTSNZ	air	6	6	NWR
96	13-Sep-61	STS	air	0.001	20	NWR
97	14-Sep-61	STS	surface	0.4	0.4	NWR
98	14-Sep-61	NTSNZ	air	1200	1200	NWR
99	16-Sep-61	NTSNZ	air	830	830	NWR
100	17-Sep-61	STS	air	20	150	NWR
101	18-Sep-61	NTSNZ	air	1000	1000	NWR
102	18-Sep-61	STS	surface	0.004	0.004	SAM
103	18-Sep-61	STS	air	0.75	0.75	NWR
104	19-Sep-61	STS	surface	0.03	0.03	SAM
105	20-Sep-61	STS	air	4.8	4.8	NWR
106	20-Sep-61	NTSNZ	air	150	1500	NWR
107	21-Sep-61	STS	air	0.8	0.8	NWR
108	22-Sep-61	NTSNZ	air	260	260	NWR
109	26-Sep-61	STS	air	1.2	1.2	NWR
110	1-Oct-61	STS	air	3	3	NWR
111	2-Oct-61	NTSNZ	air	250	250	NWR
112	4-Oct-61	STS	air	13	13	NWR
113	4-Oct-61	NTSNZ	air	1500	10000	NWR
114	6-Oct-61	NTSNZ	air	4000	4000	NWR
115	6-Oct-61	MTR	air	40	40	WIE
116	8-Oct-61	NTSNZ	air	15	15	NWR
117	11-Oct-61	STS	underground	1	1	FMS	First Soviet underground test
118	12-Oct-61	STS	air	15	15	NWR
119	17-Oct-61	STS	air	6.6	6.6	NWR
120	19-Oct-61	STS	air	0.001	20	NWR
121	20-Oct-61	NTSNZ	air	1450	1450	NWR
122	23-Oct-61	NTSNZ	underwater	4.8	4.8	WIE
123	23-Oct-61	NTSNZ	air	12500	12500	NWR
124	25-Oct-61	NTSNZ	air	300	300	NWR
125	25-Oct-61	STS	air	0.5	0.5	FMS
126	27-Oct-61	NTSNZ	water surface	16	16	WIE
127	27-Oct-61	MTR	space	1.2	1.2	WIE	First Soviet space test
128	27-Oct-61	MTR	space	1.2	1.2	WIE
129	30-Oct-61	STS	air	0.09	0.09	NWR
130	30-Oct-61	NTSNZ	air	50000	50000	NWR	The highest yield explosion ever detonated
131	31-Oct-61	NTSNZ	air	5000	5000	NWR
132	31-Oct-61	NTSNZ	air	150	1500	NWR
133	1-Nov-61	STS	air	2.7	2.7	NWR
134	2-Nov-61	NTSNZ	air	120	120	NWR
135	2-Nov-61	NTSNZ	air	280	280	NWR
136	2-Nov-61	STS	air	0.6	0.6	NWR
137	3-Nov-61	STS	surface	0	0.001	SAM
138	3-Nov-61	STS	air	0.9	0.9	NWR
139	4-Nov-61	NTSNZ	air	15	15	NWR
140	4-Nov-61	NTSNZ	air	150	1500	NWR
141	4-Nov-61	NTSNZ	air	6	6	NWR
142	4-Nov-61	STS	surface	0.2	0.2	NWR
143	2-Feb-62	STS	underground	0.001	20	WIE	Tunnel A-1; first Soviet underground test for WIE
144	1-Aug-62	STS	air	2.4	2.4	NWR
145	3-Aug-62	STS	air	1.6	1.6	NWR
146	4-Aug-62	STS	air	3.8	3.8	NWR
147	5-Aug-62	NTSNZ	air	21100	21100	NWR
148	7-Aug-62	STS		9.9	9.9	NWR
149	10-Aug-62	NTSNZ	air	150	1500	NWR
150	18-Aug-62	STS	air	7.4	7.4	NWR
151	18-Aug-62	STS	air	5.8	5.8	NWR
152	20-Aug-62	NTSNZ	air	2800	2800	NWR
153	21-Aug-62	STS	air	20	150	NWR
154	22-Aug-62	NTSNZ	air	1600	1600	NWR
155	22-Aug-62	NTSNZ		6	6	NWR
156	22-Aug-62	STS	air	3	3	NWR
157	23-Aug-62	STS	air	2.5	2.5	NWR
158	25-Aug-62	NTSNZ	air	1500	10000	NWR
159	25-Aug-62	STS	air	0.001	20	NWR
160	27-Aug-62	NTSNZ	air	4200	4200	NWR
161	27-Aug-62	STS	air	11	11	NWR
162	31-Aug-62	STS	air	2.7	2.7	FMS
163	2-Sep-62	NTSNZ	air	80	80	NWR
164	8-Sep-62	NTSNZ	air	1900	1900	NWR
165	15-Sep-62	NTSNZ	air	3100	3100	NWR
166	16-Sep-62	NTSNZ	air	3250	3250	NWR
167	18-Sep-62	NTSNZ	air	1350	1350	NWR
168	19-Sep-62	NTSNZ	air	1500	10000	NWR
169	21-Sep-62	NTSNZ	air	2400	2400	NWR
170	22-Sep-62	STS		0.21	0.21	SAM
171	24-Sep-62	STS	air	1.2	1.2	NWR
172	25-Sep-62	STS		7	7	NWR
173	25-Sep-62	NTSNZ	air	19100	19100	NWR
174	27-Sep-62	NTSNZ	air	10000	20000	NWR
175	28-Sep-62	STS	air	1.3	1.3	FMS
176	7-Oct-62	NTSNZ	air	320	320	NWR
177	9-Oct-62	STS	air	8	8	NWR
178	9-Oct-62	NTSNZ	air	15	15	NWR
179	10-Oct-62	STS	air	9.2	9.2	NWR
180	13-Oct-62	STS	air	4.9	4.9	NWR
181	14-Oct-62	STS	air	0.001	20	NWR
182	20-Oct-62	STS	air	6.7	6.7	NWR
183	22-Oct-62	NTSNZ	air	8200	8200	NWR
184	22-Oct-62	MTR		300	300	WIE
185	27-Oct-62	NTSNZ	air	260	260	NWR
186	28-Oct-62	STS	air	7.8	7.8	NWR
187	28-Oct-62	MTR		300	300	WIE
188	28-Oct-62	STS	air	7.8	7.8	NWR
189	29-Oct-62	NTSNZ	air	360	360	NWR
190	30-Oct-62	STS		1.2	1.2	NWR
191	30-Oct-62	NTSNZ	air	280	280	NWR
192	31-Oct-62	STS	air	10	10	NWR
193	1-Nov-62	STS	air	3	3	NWR
194	1-Nov-62	NTSNZ	air	240	240	NWR
195	1-Nov-62	MTR		300	300	WIE
196	3-Nov-62	NTSNZ	air	390	390	NWR
197	3-Nov-62	NTSNZ	air	45	45	NWR
198	3-Nov-62	STS	air	4.7	4.7	NWR
199	4-Nov-62	STS	air	8.4	8.4	NWR
200	5-Nov-62	STS		0.4	0.4	WIE
201	11-Nov-62	STS		0.1	0.1	NWR
202	13-Nov-62	STS		0	0.001	NWR
203	14-Nov-62	STS	air	12	12	NWR
204	17-Nov-62	STS	air	18	18	NWR
205	24-Nov-62	STS		0	0.001	SAM
206	26-Nov-62	STS		0.031	0.031	SAM
207	1-Dec-62	STS	air	2.4	2.4	NWR
208	18-Dec-62	NTSNZ	air	110	110	NWR
209	18-Dec-62	NTSNZ	air	69	69	FMS
210	20-Dec-62	NTSNZ	air	8.3	8.3	NWR
211	22-Dec-62	NTSNZ	air	6.3	6.3	NWR
212	23-Dec-62	NTSNZ	air	430	430	NWR
213	23-Dec-62	NTSNZ	air	8.3	8.3	NWR
214	23-Dec-62	NTSNZ	air	2.4	2.4	NWR
215	23-Dec-62	STS	surface	0	0.001	SAM
216	24-Dec-62	STS	surface	0.007	0.007	SAM
217	24-Dec-62	STS	surface	0.028	0.028	SAM
218	24-Dec-62	NTSNZ	air	1100	1100	NWR
219	24-Dec-62	NTSNZ	air	24200	24200	NWR
220	25-Dec-62	NTSNZ	air	3100	3100	NWR
221	25-Dec-62	NTSNZ	air	8.5	8.5	NWR	Last Soviet atmospheric test

*********************************************************

Abbreviations

• FMS = fundamental and methodical studies of the phenomena of a nuclear explosion
• IE = industrial underground peaceful nuclear explosion (PNE)
• ME = military exercise with a real nuclear detonation
• MT = Moscow Time
• MTR = Missile Testing Range (near Kapustin Yar, Astrakhan region, Russian Federation)
• NTSNZ = Northern Test Site Novaya Zemlya (Arctic Ocean, Russian Federation)
• NWR = Nuclear Weapons Related (weapon development or modification)
• SAM = studies of accident modes and emergencies (i.e. safety tests)
• STS = Semipalatinsk Test Site (Kazakhstan)
• TIC = testing of industrial nuclear charges for peaceful activities
• WIE = Weapons Effects Tests ("weapon injurious effects" studies)

Nuclear Tests and Peaceful Nuclear Explosions by Calendar Year
Year	Number	Year	Number
1949	1	1970	16
1950	0	1971	23
1951	2	1972	24
1952	0	1973	17
1953	5	1974	21
1954	10	1975	19
1955	6	1976	21
1956	9	1977	24
1957	16	1978	31
1958	34	1979	31
1959	0	1980	24
1960	0	1981	21
1961	59	1982	19
1962	79	1983	25
1963	0	1984	27
1964	9	1985	10
1965	14	1986	0
1966	18	1987	23
1967	17	1988	16
1968	17	1989	7
1969	19	1990	1
Total Number of Nuclear Tests and PNEs: 715

 

 

 

First Lightning/"Joe-1": The First Soviet Atomic Explosion

Test:	First Lightning/"Joe-1"
Time:	07:00 29 August 1949 (local)
Location:	Semipalatinsk Test Site, Kazakhstan
Test Height and Type:	Tower
Yield:	22 Kt

The first Soviet nuclear test, code named "First Lightning", detonated a plutonium bomb, the RDS-1. The code designation RDS was actually arbitrary and meaningless, but various people on the project gave it a variety of interpretations, one popular one was "Reaktivnyi Dvigatel Stalina" (Stalin's Rocket Engine), another was "Russia Does It Alone". The whole focus of the Soviet program at this point was to set off a Soviet atomic blast at the earliest possible time whatever the cost. At Beria's insistence, this device was an exact copy of the U.S. Gadget/Fat Man design.

More than two years passed between the first and second Soviet atomic tests. The crash-program to produce an atomic bomb a quickly as possible had created a very inefficient and hazardous production system, and tremendous effort was required to rationalize the program and place it on a firmer basis.

"Joe-2" was exploded on 24 September 1951 with a yield of 38 Kt. This was an improved plutonium implosion bomb, incorporating some improvements that Beria had prevented from being used in Joe-1.

Soviet Test No. 4/"Joe-4": The Sloika ("Layer Cake") Design

Test:	Test No. 4/"Joe-4"
Time:	12 August 1953
Location:	Semipalatinsk Test Site, Kazakhstan
Test Height and Type:	Tower
Yield:	400 Kt

The detonation of the RDS-6s device, the fifth Soviet nuclear test (dubbed "Joe 4" in the west) demonstrated the use of fusion in a weaponizable design. Not a "true" hydrogen bomb, this device obtained nearly all of its yield from fission and was limited for practical purposes to yields of less than a megaton. It was never widely deployed.

The RDS-6s used a U-235 fissile core surrounded by alternating layers of fusion fuel (lithium-6 deuteride spiked with tritium), and fusion tamper (natural uranium) inside a high explosive implosion system. The small U-235 fission bomb acted as the trigger (about 40 kt). The total yield was 400 Kt, and 15-20% of the energy was released by fusion, and 90% due directly or indirectly to the fusion reaction.

 

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RDS-37: The First Soviet Superbomb ("True H-Bomb") Test

Test:	Test No. 24/RDS-37
Time:	22 November 1955
Location:	Semipalatinsk Test Site, Kazakhstan
Test Height and Type:	Air drop
Yield:	1.6 Megatons

This device, designated RDS-37, was the Soviet Union's first test of a two-stage radiation implosion (aka Sakharov's "Third Idea", and Teller-Ulam) design. This was also the world's first air-dropped fusion bomb test (and the 24th Soviet test overall). After this test the Soviet Union used radiation implosion exclusively instead of the Sloika ("Layer Cake") approach.

The bomb's yield was reduced from its design yield for the test by about half by replacing part of the Li-6 D fusion fuel with "a passive material" (probably ordinary lithium hydride). The yield was within 10% of the predicted value. Air dropped by a crew commanded by F. P. Golovashko (made Hero of the Soviet Union). The bomb exploded underneath an inversion layer, which focused the shock back toward the ground unexpectedly. This refracted shock wave did unanticipated collateral damage, killing three people from a building collapse.

The Hydrogren "Super" Test

Chagan: The First Soviet "Industrial" Test

Test:	Chagan
Time:	05:59:59 15 January 1965 (GMT)
Location:	Semipalatinsk Test Range, Kazakhstan; Balapan Test Area 49.89 deg N, 78.97 deg E
Test Height and Type:	Shaft #1004, -178 m
Yield:	140 Kt

 

 This was the Soviet Union's first "industrial nuclear explosion", the equivalent of the US "Plowshare" program for developing peaceful nuclear explosives (PNEs). This test was a near copy of the US Sedan test, a 104 Kt subsurface cratering experiment.

The site for the Chagan shot was the dry bed of the Chagan River on the edge of the Semipalatinsk Test Site (STS) in Kazakhstan. The shot location was chosen so that the crater lip would form a dam in the river during its period of high flow in the spring. The crater formed by the Chagan explosion had a diameter of 408 m and a depth of 100 m. A major lake (10,000,000 m 3 ) was quickly formed behind the 20-35 m high upraised lip. Shortly after the explosion, earthmoving equipment was used to cut a channel through the lip so that water from the river could enter the crater.

Spring melt soon filled the crater with 6.4 million m^3 of water, and the reservoir behind the crater was filled with 10 million m^3 of water. These reservoirs are known informally as Lake Chagan or Lake Balapan. Subsidence of the crater slopes subsequently reduced the crater storage capacity by about 25%. A few years later, a water-control structure was built on the left bank of the river to control water levels in the reservoirs. Both reservoirs exist today in substantially the same form and are still used to provide water for cattle in the area. Efrim P. Slavskiy, Minister of the Medium Machine Building Ministry (the ministry responsible for the entire Soviet nuclear weapons program)was reported to have been the first person to have taken a swim in the crater lake.

  

 

The nuclear explosive used for the Chagan test was reported to be a low-fission design, which had a pure thermonuclear secondary driven by a fission primary with a yield of about 5-7 kt. Approximately 20% of the radioactive products of the explosion escaped into the atmosphere, resulting in dose levels on the lip of the crater of 20-30 R/hr several days after the explosion, most of which was from Co 60 (5.26 year half-life). Today, the dose level on the lip is reported to be ~2.6 mR/hr. Beyond a restricted area 100-150 m from the lip, the dose rate is at background levels (15-20 microR/hr). Radioactivity levels in the lake water in the crater are reported to be about 300 pCi/liter.

Radioactivity from the Chagan test was detected over Japan by both the U.S. and Japan in apparent violation of the 1963 Limited Test Ban Treaty (LTBT). The U.S. complained to the Soviet Union about the explosion, interpreting it as an accidental venting of a high-yield weapons test and asking for an explanation. The Soviets responded that the explosion was carried out deep underground. The quantity of radioactive debris that leaked into the atmosphere was so insignificant that the possibility of its fallout outside the territorial limits of the Soviet Union should be excluded. After several subsequent interactions, the issue was closed without further explanation.