This article lists notable civilian accidents involving fissile nuclear material or nuclear reactors. Military accidents are listed at List of military nuclear accidents. Civil radiation accidents not involving fissile material are listed at List of civilian radiation accidents. For a general discussion of both civilian and military accidents, see Nuclear and radiation accidents.
Scope of this article In listing civilian nuclear accidents, the following criteria have been followed: Notably severe: there must be well-attested and substantial health damage, property damage or contamination; if an International Nuclear Event Scale (INES) level is available, of at least two. Nuclear aspect: the damage must be related directly to nuclear operations or materials; the event should involve fissile material or a reactor, not merely (for example) having occurred at the site of a nuclear power plant. Primarily civilian: the nuclear operation/material must be principally for non-military purposes.
1950s
Date Location INES Level Type Description 12 December 1952 Chalk River, Ontario, Canada 5 Partial meltdown A reactor shutoff rod failure, combined with several operator errors, led to a major power excursion of more than double the reactor's rated output at AECL's NRX reactor. The operators purged the reactor's heavy water moderator, and the reaction stopped in under 30 seconds. A subsequent cover gas system failure led to hydrogen explosions, which severely damaged the reactor core. The fission products from approximately of uranium were released through the reactor stack. Contaminated light water coolant leaked from the damaged coolant circuit into the reactor building; some were pumped via pipeline to a disposal area to avoid contamination of the Ottawa River. Subsequent monitoring of surrounding water sources revealed no contamination. After the incident, approximately 1202 people were involved in the two-year-long cleanup. No immediate fatalities or injuries resulted from the incident; a 1982 follow-up study of exposed workers showed no long-term health effects, though Atomic Energy of Canada Limited (AECL) dosimetry files were lost in a 1956 fire. Future U.S. President Jimmy Carter, then a lieutenant in the U.S. Navy, was among the cleanup crew. 24 May 1958 Chalk River, Ontario, Canada 5 Fuel damaged Due to inadequate cooling, a damaged uranium fuel rod caught fire and was torn in two as it was being removed from the core at the NRU reactor. The fire was extinguished, but not before radioactive combustion products contaminated the interior of the reactor building and, to a lesser degree, an area surrounding the laboratory site. Approximately 679 people were employed in the clean-up. A corporal named Bjarnie Hannibal Paulson who was at the cleanup did not die from his exposure but developed unusual skin cancers. Paulson had to testify at many hearings before he was awarded compensation for his radiation injuries. 25 October 1958 Vinča, Serbia (then Yugoslavia) 4 Criticality excursion, irradiation of personnel During a subcritical counting experiment, a power buildup went undetected at the Vinca Nuclear Institute's zero-power natural uranium heavy water-moderated research reactor. Saturation of radiation detection chambers gave the researchers false readings and the level of moderator in the reactor tank was raised, triggering a power excursion which a researcher detected from the smell of ozone. Six scientists received radiation doses of (p. 96). An experimental bone marrow transplant treatment was performed on all of them in France and five survived, despite the ultimate rejection of the marrow in all cases. A single woman among them later had a child without apparent complications. This was one of the first nuclear incidents investigated by then-newly formed IAEA. 30 December 1958 Los Alamos Criticality excursion Cecil Kelley, a chemical operator working on plutonium purification, switched on a stirrer on a large mixing tank, which created a vortex in the tank. The plutonium, dissolved in an organic solvent, flowed into the center of the vortex. Due to a procedural error, the mixture contained 3.27 kg of plutonium, which reached criticality for about 200 microseconds. Kelley received 3,900 to 4,900 rad (36.385 to 45.715 Sv) according to later estimates. The other operators reported seeing a bright flash of blue light and found Kelley outside, saying "I'm burning up! I'm burning up!" He died 35 hours later.The Cecil Kelley Criticality Accident 26 July 1959 Santa Susana Field Laboratory, California, United States 4 Partial meltdown A partial core meltdown took place when the Sodium Reactor Experiment (SRE) experienced a power excursion that caused severe overheating of the reactor core, resulting in the melting of one-third of the nuclear fuel and significant release of radioactive gases. The amount of radioactivity released is disputed, with it ranging from 28 Curies to as much as 240 to 260 times worse than Three Mile Island. Over the succeeding years, the site was cleaned up and all buildings and contamination removed. The soil was removed and other soil brought in and now forms a portion of an area near the Simi Valley Adventist Hospital.
1960s
Date Location INES Level Type Description 3 April 1960 Westmoreland County, Pennsylvania, United States 4 Partial meltdown A partial core meltdown occurred at the Westinghouse TR-2 research reactor (also known as the Westinghouse Test Reactor or Westinghouse Testing Reactor (WTR)) at their Waltz Mill site. One fuel element melted, believed due to manufacturing defects in the fuel element, resulting in fission products being released into the reactor coolant water and gaseous fission products being released to the environment. Two million gallons of contaminated water were generated during the accident and cleanup. At least a portion of the water was retained on-site in lagoons, a condition which eventually led to detectable 90Sr in groundwater plus contaminated soil. The site cleanup was completed in 2013. 24 July 1964 Wood River Junction, Richmond, Rhode Island, United States 2 Criticality accident A worker at a United Nuclear Corporation fuel facility caused an accidental criticality. Robert Peabody, believing he was using a diluted uranium solution, accidentally put concentrated solution into an agitation tank containing sodium carbonate. Peabody was exposed to of radiation and died two days later. Ninety minutes after the criticality, a plant manager and another administrator returned to the building and were exposed to , but suffered no ill effects.UNC death bazley.net McLaughlin et al. pp. 33-34 5 October 1966 Frenchtown Charter Township, Michigan, United States 4 Partial meltdown A sodium cooling system malfunction caused the meltdown of some fuel elements at the Fermi 1 fast breeder reactor. The accident was attributed to a zirconium fragment that obstructed a flow-guide in the sodium cooling system. Two of the 105 fuel assemblies melted during the accident, but no contamination was recorded outside the containment vessel. Winter 1966-1967 (date unknown) Location unknown 5 Loss of coolant, possible meltdown The Soviet icebreaker Lenin, the USSR's first nuclear-powered surface ship, suffered a major accident (possibly a nuclear meltdownexactly what happened remains a matter of controversy in the West) in one of its three reactors. To find the leak the crew broke through the concrete and steel radiation shield with sledgehammers, causing irreparable damage. It was rumored that around 30 of the crew were killed. The ship was abandoned for a year to allow radiation levels to drop before the three reactors were removed, to be dumped into the Tsivolko Fjord on the Kara Sea, along with 60% of the fuel elements packed in a separate container. The reactors were replaced with two new ones, and the ship reentered service in 1970, serving until 1989. May 1967 Dumfries and Galloway, Scotland, United Kingdom 4 Partial meltdown Graphite debris partially blocked a fuel channel causing a fuel element to melt and catch fire at the Chapelcross nuclear power station. Contamination was confined to the reactor core. The core was repaired and restarted in 1969, operating until the plant's shutdown in 2004. 21 January 1969 Lucens, Canton of Vaud, Switzerland 4 Explosion, partial meltdown A loss of coolant led to a meltdown of one fuel element and a steam explosion in the Lucens reactor, an experimental reactor in a large rock cavern at Lucens. The underground location of this reactor acted like a containment building and prevented any outside contamination. The cavern was contaminated and temporarily sealed. No injuries or fatalities resulted. Defueling and partial dismantling occurred from 1969 to 1973. In 1988, the lowest caverns were filled with concrete, and a regulatory permit was issued in December 1990. Currently, the archives of the Canton of Vaud are located in the upper caverns."Interface between Operator, Regulatory Body and Public" at IAEA.org
1970s
Date Location INES Level Type Description 6 February 1975 Leningrad Nuclear Power Plant Explosion of cooling circuit The secondary cooling circuit of Unit 1 ruptured, releasing contaminated water into the environment. Three people were killed. 7 December 1975 Greifswald, Germany (then East Germany) 3 Station blackout A fire in a cable duct after a short circuit disabled the electrical power supply for all feedwater and emergency core cooling pumps. A power supply was improvised by the operating personnel after several hours. 22 February 1977 Jaslovské Bohunice, Slovakia (then Czechoslovakia) 4 Fuel damaged Operators neglected to remove moisture-absorbing materials from a fuel rod assembly before loading it into the KS 150 reactor at power plant A-1. The accident resulted in damaged fuel integrity, extensive corrosion damage of fuel cladding and release of radioactivity into the plant area. The affected reactor was decommissioned following this accident. 28 March 1979 Middletown, Dauphin County, Pennsylvania, United States 5 Partial meltdown Equipment failures, poor user interface design, and worker mistakes contributed to a loss of coolant and a partial core meltdown at the Three Mile Island Nuclear Generating Station southeast of Harrisburg. While the reactor was extensively damaged, on-site radiation exposure was under 100 millirems (less than annual exposure due to natural sources). Residents living within 10 miles of the plant received an average total dose of 8 millirems (80 μSv), which is roughly the equivalent from receiving a chest x-ray. There were no fatalities. Follow-up radiological studies predict between zero and one long-term cancer fatality.
1980s