Nuclear accidents
Nuclear accidents refer to unplanned events that lead to the release of radioactive materials into the environment, raising significant public concern about the safety of nuclear power. Despite a generally good safety record in the nuclear industry, incidents have occurred and are often fueled by fears of potential catastrophic events. Key factors that can lead to accidents include equipment failures, operator errors, and external events such as natural disasters. Notable accidents include the Three Mile Island incident in the United States in 1979, which resulted in significant fuel melting, and the catastrophic events at Chernobyl in 1986 and Fukushima in 2011.
These incidents highlight the risks associated with nuclear reactors, particularly the possibility of breaching containment structures, which could disperse dangerous radioactive materials. Regulations by authorities such as the U.S. Nuclear Regulatory Commission aim to enforce safety standards, yet ongoing concerns about safety equipment failures and near misses persist. Proponents of nuclear energy argue that the industry's safety measures are effective, while critics emphasize the potential for severe accidents and the historical frequency of safety-related incidents. Additionally, there is a global dimension to nuclear safety, with significant concerns regarding older reactor designs in other countries, as well as less stringent public disclosure regulations regarding incidents outside the United States. The International Atomic Energy Agency categorizes nuclear accidents based on severity, with only Chernobyl and Fukushima reaching major accident status.
Subject Terms
Nuclear accidents
DEFINITION: Unplanned events involving the release of radioactive materials into the environment
Public concern about reactor safety and the risk of accidents remains an important reason the expansion of nuclear power has stalled in the United States and many other nations. Although the industry’s safety record has generally been good, safety lapses and near accidents are sometimes reported, and the public has become increasingly aware that a severe accident could have widespread consequences.
The accident in nuclear power plants lies in the possibility that a malfunction caused by equipment failure, operator error, or external events will disrupt the flow of vital cooling water to the intensely hot, dangerously radioactive reactor core, a situation that could result in the fuel melting. Possible problematic external events include natural disasters such as the massive earthquake and subsequent tsunami that damaged reactors at Japan’s Fukushima 1 nuclear power plant in March 2011. In the unlikely event that both the huge steel vessel holding the fuel and the massive concrete containment structure surrounding the reactor are breached, large quantities of dangerous radioactive materials could be dispersed to the environment.
The US Nuclear Regulatory Commission (NRC) is the federal agency that sets the safety requirements that plant owners must meet in the construction and operation of nuclear power reactors in the United States. NRC regulations and technical specifications cover a wide range of areas, including design requirements, safety systems, equipment quality, record keeping, and operator training.
Incidents in the United States
The worst nuclear accident to have occurred in the United States took place in 1979 at the Three Mile Island (TMI) Unit 2 plant in Pennsylvania, resulting in more than one-half of the fuel melting and the total loss of the reactor. Recurring incidents and near accidents over the years have led to some disquiet among the public and among nuclear regulators. Among these have been the 1975 fire at the Brown’s Ferry plant in Alabama that burned for seven hours, during which it took plant personnel several hours to shut down the reactor; the 1983 unexpected failure of the Salem reactor in New Jersey to shut down after a safety system was activated; and the 1985 incident at the Davis-Besse plant in Ohio when multiple equipment failures caused a loss of cooling water that could have initiated a core meltdown if plant operators had not responded quickly. At some plants, it has been discovered that important safety equipment has been inoperable for years. The NRC has kept a number of US reactors shut down for long periods until safety-related equipment problems or operator lapses could be corrected.
Proponents of nuclear energy argue that, despite recurrent mishaps, the US industry’s overall safety record has been excellent. They assert that the events at TMI showed that systems designed to contain an accident worked. They claim that an accident similar to the one that occurred at Chernobyl in 1986 could not occur in the United States because the design of the older, Soviet-designed Chernobyl-style plants is flawed and permits a severe accident to occur far more easily than in US-designed plants. They note that the number of safety-related occurrences per year at U.S. reactors has declined since the TMI accident. Finally, they point to government-sponsored studies that have concluded that there is a very low probability of a severe accident occurring with significant off-site property damage and injuries to the public.
Antinuclear activists point to numerous recurring safety-related incidents and problems at US reactors, including some cases in which serious accidents were narrowly averted. They argue that the TMI incident showed that a serious accident is not as improbable as the industry claims. While critics acknowledge the design superiority of US reactors compared to the Chernobyl plant, they note that an NRC commissioner testified before Congress in 1986 that an accident at a US reactor with off-site releases equal to or worse than what occurred at Chernobyl could occur under conditions regarded as improbable but not impossible. Critics have also attacked the assumptions and methodology of the government’s major nuclear accident risk studies. Finally, opponents observe that those same studies indicate that if a low-probability catastrophic accident should nonetheless occur, it could result in tens of thousands of deaths and injuries, tens of billions of dollars in property damage, and widespread, long-lived radioactive contamination.
The Price-Anderson Act limits the liability of nuclear power plant owners and equipment vendors in the event of a severe accident. This legislation was passed in 1957 after private companies made it clear that they would not participate in the development of nuclear energy without liability protection. Critics argue that the nuclear industry’s continuing insistence that such protection is required is inconsistent with its denial of the possibility of a catastrophic accident.
Incidents in Other Nations
Much less information is generally available about nuclear accidents and incidents with serious safety implications in countries other than the United States because the public disclosure requirements of most nations are less stringent than US requirements. Worrisome accidents and equipment malfunctions are known to have occurred at reactors in many nations, including Japan, India, and the countries of the former Soviet Union. In Europe, grave concern remains about older Soviet-designed reactors, including some Chernobyl-style plants, still operating in the countries of Eastern Europe and the former Soviet Union. Western nations have provided some funding for safety improvements and have sought the eventual permanent closure of many of these plants.
A number of nuclear accidents have occurred at noncommercial facilities, some of which resulted in serious environmental consequences. In 1952 a fuel melt and explosion severely damaged an experimental Canadian reactor at Chalk River, Ontario. In 1957 an explosion at a site at the then-secret Chelyabinsk complex near the city of Kyshtym in Russia contaminated hundreds of square miles of the surrounding countryside. Also in 1957, a fire occurred in England at the Windscale reactor (an atypical plant used to produce plutonium for the United Kingdom’s weapons program); the surrounding countryside was contaminated, and radioactive fallout drifted into several neighboring countries.
The International Atomic Energy Agency (IAEA) rates nuclear accidents on a scale of one to seven, with one classified as an anomaly and seven as a major accident. Since the International Nuclear and Radiological Event Scale (INES) was implemented, only two events—Chernobyl and Fukushima—have been classified as major accidents. Three Mile Island was a level five event, an accident with wider consequences. The Kyshtym disaster in 1957 was rated a level six, a serious accident.
Bibliography
"About NRC." Nuclear Regulatory Commission, 5 July 2024, www.nrc.gov/about-nrc.html. Accessed 19 July 2024.
Arceneaux, H. “NUREG/CR-7293 "The Price-Anderson Act: 2021 Report to Congress, Public Liability Insurance and Indemnity Requirements for a Evolving Commercial Nuclear Industry.” Nuclear Regulatory Commission, 31 Dec. 2021, www.nrc.gov/docs/ML2133/ML21335A064.pdf. Accessed 19 July 2024.
Bodansky, David. Nuclear Energy: Principles, Practices, and Prospects. 2d ed. New York: Springer, 2004.
Cooper, John R., Keith Randle, and Ranjeet S. Sokhi. Radioactive Releases in the Environment: Impact and Assessment. Hoboken, N.J.: John Wiley & Sons, 2003.
Garwin, Richard L., and Georges Charpak. “Safety, Nuclear Accidents, and Industrial Hazards.” In Megawatts and Megatons: The Future of Nuclear Power and Nuclear Weapons. Chicago: University of Chicago Press, 2001.
"International Nuclear and Radiological Event Scale (INES)." International Atomic Energy Agency, 2024, www.iaea.org/resources/databases/international-nuclear-and-radiological-event-scale. Accessed 19 July 2024.
Savchenko, V. K. The Ecology of the Chernobyl Catastrophe. New York: Informa Healthcare, 1995.
Wolfson, Richard. Nuclear Choices: A Citizen’s Guide to Nuclear Technology. Rev. ed. Cambridge, Mass.: MIT Press, 1993.