Op-ed: Remembering the Chernobyl catastrophe

M V Ramana

The most important lesson of Chernobyl is simply that such a catastrophic accident occurred. Officials in the nuclear programs around the world, South Asia especially, often make confident and glib statements about how safe nuclear technologies are. The reality is quite different

According to the United Nations Scientific Committee on the Effects of Atomic Radiation the roughly 1800 thyroid cancers observed in individuals exposed in childhood “is considerably greater than expected based on previous knowledge... If the current trend continues, additional thyroid cancers can be expected to occur, especially in those who were exposed at young ages.”

In June 1983 the Bulletin of the International Atomic Energy Agency (IAEA), the head of the IAEA’s safety division claimed: “a serious loss of coolant accident is practically impossible... the safety of nuclear power plants in the Soviet Union is assured by a very wide spectrum of measures...” (emphasis added) Less than three years after this announcement and seventeen years ago this week, on 26 April 1986, Unit 4 of the Chernobyl nuclear power station was destroyed by a loss of coolant accident, the most catastrophic in the annals of the nuclear energy industry.

The Chernobyl Power Complex is about 130 km north of Kiev, Ukraine, and about 20 km south of the border with Belarus, and consisted of four nuclear reactors. Unit 4 was to be shutdown for routine maintenance on 25 April 1986. Reactor operators decided to take advantage of this shutdown to run a test to determine whether, in the event of a loss of station power, the emergency equipment could be operated until the diesel emergency power supply became operative. As part of the experiment a number of safety features were disabled. According to the OECD’s Nuclear Energy Agency, “This course of actions was compounded by the existence of significant drawbacks in the reactor design which made the plant potentially unstable and easily susceptible to loss of control in case of operational errors. The combination of these factors provoked a sudden and uncontrollable power surge which resulted in violent explosions and almost total destruction of the reactor.”

The amount of radioactive materials released was enormous, and involved a large fraction of the radioactive product inventory in the reactor. The duration of the release was also unexpectedly long: over 10 days. Carried by the wind, the radioactive materials released spread far and wide. Practically every country in the Northern Hemisphere received some radioactive fallout. The accident had social, psychological, economic (valued by some at over $300 billion) and, above all, health impacts.

In terms of health impacts from radiation exposure, the most affected were the 600 workers present on the site on 26 April; 134 of them received high doses and suffered from radiation sickness. Of these, 28 died in the first three months and another 2 soon afterwards. About 200,000 recovery operation workers also received significant radiation doses.

Among the general population who lived in the area, many, especially children, received radiation doses to the thyroid gland because they drank milk contaminated by radioiodine from the accident. This has resulted in a virtual explosion in thyroid cancers. According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR 2000), “the number of thyroid cancers (about 1,800) in individuals exposed in childhood, in particular in the severely contaminated areas of the three affected countries, is considerably greater than expected based on previous knowledge. The high incidence and the short induction period are unusual... If the current trend continues, additional thyroid cancers can be expected to occur, especially in those who were exposed at young ages.” Fortunately thyroid cancer is treatable and only a small fraction of the people diagnosed with the disease actually die from it.

UNSCEAR finds no evidence of an increase in other kinds of cancers but suggests that “weaknesses in the scientific studies, the uncertainties in the dose estimates, the latency period of around 10 years and the protracted nature of the exposures probably explain why no radiation-associated cancers have been noticed so far.” Of course, not being noticed does not mean that they do not exist, just that they are hard to distinguish from cancers induced by other factors.

What lessons about nuclear safety can we learn from the Chernobyl accident? Nuclear energy advocates have focused on two factors responsible for the accident. The first is operator error — i.e., it was all the fault of the low-paid operators who were carrying out an unauthorized test. Attributing accident to operator error, however, implies that as long as humans operate reactors they will continue to be susceptible to accidents.

The second factor is a design flaw in the Chernobyl reactor that made it unstable. They have also focused on the absence of a containment building, which would be a barrier to the release of radioactivity to the environment, at Chernobyl. Neither of these features holds true in the case of Western designs and hence, the argument, goes, American and European designs are “safe”.

These have been disputed at many levels. D G Arnott and Rob Greene provocatively argued that the lack of containment at Chernobyl may have even been a safety valve because a containment would have made the fuel core stay together for a longer period, thereby amplifying the energy release from the explosion and increasing the radioactive inventory expelled. The related issue is whether any containment structure could have actually been strong enough to hold the amount of energy released at the Chernobyl accident.

And finally, while Western reactor designs may be safer, they are not without risks. As a 1990 study by the Union of Concerned Scientists concluded: “Regardless of the attention to design, construction, operation, and management of nuclear reactors, there is always something that could be done (or not done) to render the reactor dangerous. The degree to which this is true varies from design to design, but we believe that our general conclusion is correct.”

The most important lesson of Chernobyl is simply that such a catastrophic accident occurred. It renders assurances like the one quoted at the beginning of this article meaningless. Officials in the nuclear programs around the world, South Asia especially, often make confident and glib statements about how safe nuclear technologies are. The reality is quite different. Because of their complex nature and the very fast time scales of the underlying physical processes, nuclear reactors are inherently prone to catastrophic accidents. Societal decisions about such technologies must be made with full cognisance of these hazards and involving the populations that are at risk from potential accidents.

M V Ramana is a physicist and research staff member at Princeton University’s Program on Science and Global Security and co-editor of Prisoners of the Nuclear Dream

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