The Probability of a Nuclear Accident

Feature story - May 20, 2003
The nuclear industry and the Nuclear Regulatory Commission (NRC) have always maintained that the probability of an accident was low. However, neither the nuclear industry nor the NRC has been very good at estimating the probability of an accident.

The nuclear industry and the Nuclear Regulatory Commission (NRC) have always maintained that the probability of an accident was low. Even if we were to take the nuclear industry or the NRC at its word, the risk of a meltdown would still be great because the consequences of such an event are potentially so devastating. However, neither the nuclear industry nor the NRC has been very good at estimating the probability of an accident.

On March 9, 1979, the NRC staff produced a memo for then Commissioner Peter Bradford entitled, "Probabilities That The Next Major Accident Occurs Within Prescribed Intervals." The memorandum states that:

  1. The probability is less than .5 that the next (i.e., the first) major accident occurs within the next 400 reactor years.
  2. The probability is less than .05 that the next major accident occurs within the next 21 reactor years.
  3. The probability is larger than .5 that the next major accident occurs after the next 400 reactor years. This is equivalent to statement (a).34 (Note: one nuclear reactor operating for one year equals a reactor year.)

Less than three weeks later, the unit 2 reactor at Three Mile Island suffered a meltdown of the radioactive fuel in the reactor core.

The Nuclear Regulatory Commission ignores the fact that meltdowns have occurred at U.S. nuclear reactors. The NRC's latest risk assessments don't even account for the meltdown at Three Mile Island or the earlier meltdowns at Fermi-1 and other test reactors. The U.S. nuclear reactors that have experienced partial core melt accidents include:

  • EBR-1 (Experimental Breeder Reactor) 11/29/55 Idaho Falls, ID
  • WTR (Westinghouse Testing Reactor) 04/03/60 Waltz Mill, PA
  • SL-1 (Stationary Low Power Reactor) 01/03/61 Idaho Falls, ID
  • Fermi-1 10/05/66 Lagoona Beach, MI
  • Three Mile Island 03/28/79 Harrisburg, PA35

Even if you exclude the core-melt accidents at the test reactors, the U.S. commercial nuclear industry has melted down two nuclear reactors in less than 3000 reactor years. This reality makes nuclear power anything but "safe." However, it wasn't until after the Chernobyl disaster that the Nuclear Regulatory Commission acknowledged the risk posed by nuclear reactors in the United States.

In the wake of the 1986 accident at Chernobyl, the U.S. Nuclear Regulatory Commission was asked to testify before Congress concerning the potential for severe accident in the U.S. According to NRC Commissioner James K. Asselstine:

...given the present level of safety being achieved by the operating nuclear power plants in this country, we can expect to see a core meltdown accident with in the next 20 years...36

The U.S. nuclear industry was quick to point out that you can't have a "Chernobyl" here. Public pronouncements by nuclear industry officials included assertions that Soviet technology was so different from U.S. commercial reactors that the causes and consequences of the Chernobyl accident had little relevance. 37 The American Nuclear Society's fact sheet on nuclear energy stated that,."Because of major differences in technology, a Chernobyl-type accident can not occur in a light water reactor such as those in the U.S. A reactor similar to the Chernobyl design could not be licensed in the U.S. either now or before the accident." 38

Unfortunately, the nuclear industry was merely playing with words. Their protestations rely on the fact that there are no reactors of Chernobyl's design operating here in the United States, but that's not the point. The reality is that a nuclear accident can occur at a U.S. nuclear power plant that would have off-site releases of radiation comparable to that of Chernobyl. Again in testimony before Congress in 1986, NRC Commissioner James Asselstine stated that:

While we hope that their occurrence is unlikely, there are accident sequences for U.S. plants that can lead to rupture or bypassing of containment in U.S. reactors which would result in the off-site release of fission products comparable or worse than the releases estimated by the NRC staff to have taken place during the Chernobyl accident.

That is why the Commission told Congress recently that it could not rule out a commercial nuclear power plant accident in the United States resulting in tens of billions of dollars of property losses and injuries to the public. 39

In 1990, the Nuclear Regulatory Commission was again asked the probability of a severe core melt accident at a U.S. nuclear reactor. However, the NRC refused to provide the National Academy of Science's National Research Council with the number they were seeking. In the Nuclear Regulatory Commission's response to the National Research Council, the agency stated that it "would strongly encourage your committee not to use any number based on assuming an average severe core damage frequency…." Rather, the NRC suggested that the National Research Council state that "there is reasonable assurance that the health and safety of the public are adequately protected." 40

At least on member of the NRC's Advisory Committee on Reactor Safeguards (ACRS), doesn't hold the same overly optimistic view espoused by the Commission. Hal Lewis, a former member of the NRC's Advisory Committee on Reactor Safeguards, critiqued the Commission's position when the ACRS was addressing the renewal of nuclear reactor licenses, noting that:

The Commission certainly doesn't know that its current regulatory process provides adequate protection to the public. It has declared that it does, and it's the operating definition, but the Commission has also promulgated safety goals and the commission doesn't know that the current licensing basis will meet the safety goals, although it believes it to be the case. 41

The public should not be lulled into a false sense of security by the mere fact that the U.S. nuclear power industry has not melted down a reactor since Three Mile Island. Operating without a meltdown for a finite period of time does not mean that safety is adequate. Again, Mr. Lewis, of the NRC's Advisory Committee on Reactor Safeguards, recognized this fallacy. Mr. Lewis stated that:

The general argument that the fact that one has operated safely for a finite period of time proves that the safety level is adequate is just not statistically right, because there isn't that much history in the industry. And it's a trap. Because other agencies, for example, people have used the argument that they had 24 successful Shuttle flights, to show the level of safety was adequate. And in retrospect, after one disaster, it turned out not to be. The Soviets, after Chernobyl, suddenly discovered that the level of safety they had before Chernobyl was not adequate. But the day before Chernobyl they would have said it was adequate on the basis of operating history..So it is a general trap, a psychological trap, to believe that because something has not happened, you are doing just fine. 42

The NRC and the nuclear industry have already fallen into the trap. The NRC and the NEI have already begun to deregulate nuclear safety regulations, including those dealing with the security of nuclear reactors, based upon the limited operating history of reactors in the U.S. The risk posed by nuclear power plants was significant before September 11 th . When we take into consideration the terrorist threat to nuclear power plants their continued operation is unacceptable.

As NRC Commissioner Asselstine pointed out, U.S. nuclear reactors are capable of releasing enormous amounts of radiation into the environment. Since each reactor has the potential for a Chernobyl sized release of radiation, it is important to recognize the consequences of such an accident.

In 1990, the Wall Street Journal reported on a study conducted by a Soviet nuclear industry economist on the continuing economic disaster of the Chernobyl accident. The study found that the cost of the disaster had originally been underestimated. Yuri Koryakin, chief economist of the Research and Development Institute of Power Engineering, the institute that originally designed the Chernobyl reactor, found that the accident may cost 20 times more than Moscow's original estimates. By 2000, the report estimated that the Chernobyl accident would cost the country between 170 and 215 billion rubles from contaminated farm land, lost electricity production and other economic fall-out. The accident contaminated approximately 31,000 square kilometers or 12,400 square miles. When the Wall Street Journal article was published in 1990, the contaminated land was considered a total loss for at least two generations. 43

The Wall Street Journal article concludes that, "The total bill suggests that the Soviet Union may have been better off if they had never begun building nuclear reactors in the first place." 44

The Nuclear Energy Institute (NEI) attempt to down play the impact of the disaster. According to NEI:

The accident destroyed the reactor in Unit 4, killed 31 people (one immediately and 30 within three months) and contaminated large areas of Belarus (formerly Byelorussia), Ukraine and the Russian Federation. In addition, one person has subsequently died from a confirmed diagnosis of acute radiation syndrome, and three children have died from thyroid cancer. 45

The consequences of the accident are severely understated by NEI. According to an article published by

the Associated Press the consequences of the Chernobyl disaster are "grimly visible."

an estimated 4,000 deaths among those who took part in the hasty and poorly organized cleanup; 70,000 people disabled by radiation, according to government figures. Overall, about 3.4 million of Ukraine's 50 million people, including some 1.26 million children, are considered affected by Chernobyl, and many may not show the affects for years. 46

The grim reality of the Chernobyl accident will be with the people of the former Soviet Union for generations.

Shutdown Before Meltdown

The United States can avoid the next nuclear accident by phasing out the remaining 103 commercial nuclear reactors. Rather than coddling the nuclear industry with more taxpayer subsidies and less regulation the federal government should replace nuclear reactors with energy efficiency and other clean, renewable sources of electricity.

A study conducted by the five national energy laboratories in November 2000 for the U.S. Department of Energy found that renewable energy could supply at least 7.5 percent of U.S. electricity by 2010. 47 Such an expansion in renewable technologies would allow for the phase-out of the most dangerous.reactors in the U.S. When combined with increases in energy efficiency the potential to phase-out nuclear power is even greater.

According to the Union of Concerned Scientists' Clean Energy Blueprint, renewable energy could supply 20 percent of U.S. electricity by 2020. 48 Coupled with an increase in energy efficiency, this increase in renewable resources would produce enough electricity to supplant every nuclear reactor currently operating in the United States. 49

Rather than extending the licenses of nuclear reactors and thereby extending the duration of the threat posed by these reactors, the Bush/Cheney energy plan should heed the advice of its own government laboratories and increase our nation's energy efficiency and use of renewable sources of electricity.


34 U.S. Nuclear Regulatory Commission, Memorandum For: Commissioner Bradford, From: David Rubinstein, Applied Statistics Branch, Subject: Probabilities That The Next Major Accident Occurs Within Proscribed Intervals, March 9, 1979, p. 1..

35 Richard E. Webb, The Accident Hazards of Nuclear Power Plants, University of Massachusetts press, Appendix 2, (1976); U.S. Atomic Energy Commission, Operational Accidents and Radiation Exposure Experience 1943 -- 1975, pp. 29 -- 38, (1975); John May, The Greenpeace Book of the Nuclear Age, p. 173, (1989).

36 Testimony of NRC Commissioner James K. Asselstine before the Energy Conservation and Power Sub-committee of the House Committee on Energy and Commerce, May 22, 1986; Also Letter from NRC Commissioner James K. Asselstine to Carl Walske, President, Atomic Industrial Forum, Inc., July 15, 1986, p. 1.

37 (Donaldson, Lufkin & Jenrette, Chernobyl: Some Lessons and Implications for Lower Quality Electric Utilities, (1986.) p. 22.

38 American Nuclear Society, "Nuclear Energy Facts: Questions and Answers", 1988, p. 28.

39 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Conservation and Power, Hearing on Nuclear Reactor Safety, 99 th Cong., 2 nd Session, May 22 and July 16, 1986, p. 38.

40 U.S. Nuclear Regulatory Commission, Letter from: Chairman Kenneth M. Carr, To: Dr. Albert L. Babb, Chairman, Committee on Future Nuclear Power Development, Commission on Engineering and Technical Systems, National Research Council, June 14, 1990, p. 2.

41 U.S. Nuclear Regulatory Commission, Advisory Committee on Reactor Safeguards, Subcommittee on Regulatory Policies and Practices: License Renewal, ACRS-T-1789, March 26, 1990, pp. 165, 166.

42 Id. at 153, 154.

43 Richard L. Hudson, Cost of Chernobyl Nuclear Disaster Soars in New Study, Wall Street Journal, March 29, 1990, p. A-8.

44 Id. at p. A-8.

45 Nuclear Energy Institute, The Chernobyl Accident and Its Consequences, http://www.nei.org/doc.asp?catnum=3&catid=296, July 2000.

46 Associated Press, Ukrainians Honor "Chernobyl Heroes" Who Helped Others in the 1989 Disaster, St. Louis Post-Dispatch, April 27, 2000, p. A-10.

47 Interlaboratory Working Group, Scenarios for a Clean Energy Future (Oak Ridge, TN; Oak Ridge National Laboratory and Berkeley, CA; Lawrence Berkeley National Laboratory), ORNL/CON-476 and LBNL-44029, November 2000. http://www.ornl.gov/ORNL/Energy_Eff/CEF.htm

48 Clemmer, Donovan, Nogee & Deyette, Clean Energy Blueprint: A Smarter National Energy Policy for Today and the Future, Union of Concerned Scientists, Cambridge, Mass. October 2001.

49 Union of Concerned Scientists, Energy and Security Fact Sheet, 2001.

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