<P> One of the worst nuclear accidents to date was the Chernobyl disaster which occurred in 1986 in Ukraine . The accident killed 31 people directly and damaged approximately $7 billion of property . A study published in 2005 estimates that there will eventually be up to 4,000 additional cancer deaths related to the accident among those exposed to significant radiation levels . Radioactive fallout from the accident was concentrated in areas of Belarus, Ukraine and Russia . Other studies have estimated as many as over a million eventual cancer deaths from Chernobyl . Estimates of eventual deaths from cancer are highly contested . Industry, UN and DOE agencies claim low numbers of legally provable cancer deaths will be traceable to the disaster . The UN, DOE and industry agencies all use the limits of the epidemiological resolvable deaths as the cutoff below which they cannot be legally proven to come from the disaster . Independent studies statistically calculate fatal cancers from dose and population, even though the number of additional cancers will be below the epidemiological threshold of measurement of around 1% . These are two very different concepts and lead to the huge variations in estimates . Both are reasonable projections with different meanings . Approximately 350,000 people were forcibly resettled away from these areas soon after the accident . </P> <P> Social scientist and energy policy expert, Benjamin K. Sovacool has reported that worldwide there have been 99 accidents at nuclear power plants from 1952 to 2009 (defined as incidents that either resulted in the loss of human life or more than US $50,000 of property damage, the amount the US federal government uses to define major energy accidents that must be reported), totaling US $20.5 billion in property damages . Fifty - seven accidents have occurred since the Chernobyl disaster, and almost two - thirds (56 out of 99) of all nuclear - related accidents have occurred in the US . There have been comparatively few fatalities associated with nuclear power plant accidents . </P> <Table> Nuclear power plant accidents and incidents with multiple fatalities and / or more than US $100 million in property damage, 1952 - 2011 <Tr> <Th> Date </Th> <Th> Location of accident </Th> <Th> Description of accident or incident </Th> <Th> Dead </Th> <Th> Cost ($US millions 2006) </Th> <Th> INES level </Th> </Tr> <Tr> <Td> 000000001957 - 09 - 29 - 0000 September 29, 1957 </Td> <Td> Mayak, Kyshtym, Russia </Td> <Td> The Kyshtym disaster was a radiation contamination incident that occurred at Mayak, a Nuclear fuel reprocessing plant in the Soviet Union . </Td> <Td> </Td> <Td> </Td> <Td> 6 </Td> </Tr> <Tr> <Td> 000000001957 - 07 - 26 - 0000 July 26, 1957 </Td> <Td> Simi Valley, California, United States </Td> <Td> Partial core meltdown at Santa Susana Field Laboratory's Sodium Reactor Experiment . </Td> <Td> 0 </Td> <Td> 32 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001957 - 10 - 10 - 0000 October 10, 1957 </Td> <Td> Sellafield aka Windscale fire, Cumberland, United Kingdom </Td> <Td> A fire at the British atomic bomb project destroyed the core and released an estimated 740 terabecquerels of iodine - 131 into the environment . A rudimentary smoke filter constructed over the main outlet chimney successfully prevented a far worse radiation leak and ensured minimal damage . </Td> <Td> 0 </Td> <Td> </Td> <Td> 5 </Td> </Tr> <Tr> <Td> 000000001961 - 01 - 03 - 0000 January 3, 1961 </Td> <Td> Idaho Falls, Idaho, United States </Td> <Td> Explosion at SL - 1 prototype at the National Reactor Testing Station . All 3 operators were killed when a control rod was removed too far . </Td> <Td> </Td> <Td> 22 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001966 - 10 - 05 - 0000 October 5, 1966 </Td> <Td> Frenchtown Charter Township, Michigan, United States </Td> <Td> Partial core meltdown of the Fermi 1 Reactor at the Enrico Fermi Nuclear Generating Station . No radiation leakage into the environment . </Td> <Td> 0 </Td> <Td> 132 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001969 - 01 - 21 - 0000 January 21, 1969 </Td> <Td> Lucens reactor, Vaud, Switzerland </Td> <Td> On January 21, 1969, it suffered a loss - of - coolant accident, leading to a partial core meltdown and massive radioactive contamination of the cavern, which was then sealed . </Td> <Td> 0 </Td> <Td> </Td> <Td> 5 </Td> </Tr> <Tr> <Td> 000000001975 - 01 - 01 - 0000 1975 </Td> <Td> Sosnovyi Bor, Leningrad Oblast, Russia </Td> <Td> There was reportedly a partial nuclear meltdown in Leningrad nuclear power plant reactor unit 1 . </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001975 - 12 - 07 - 0000 December 7, 1975 </Td> <Td> Greifswald, East Germany </Td> <Td> Electrical error causes fire in the main trough that destroys control lines and five main coolant pumps </Td> <Td> 0 </Td> <Td> 443 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001976 - 01 - 05 - 0000 January 5, 1976 </Td> <Td> Jaslovské Bohunice, Czechoslovakia </Td> <Td> Malfunction during fuel replacement . Fuel rod ejected from reactor into the reactor hall by coolant (CO). </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001977 - 02 - 22 - 0000 February 22, 1977 </Td> <Td> Jaslovské Bohunice, Czechoslovakia </Td> <Td> Severe corrosion of reactor and release of radioactivity into the plant area, necessitating total decommission </Td> <Td> 0 </Td> <Td> 1,700 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001979 - 03 - 28 - 0000 March 28, 1979 </Td> <Td> Three Mile Island, Pennsylvania, United States </Td> <Td> Loss of coolant and partial core meltdown due to operator errors . There is a small release of radioactive gases . See also Three Mile Island accident health effects . </Td> <Td> 0 </Td> <Td> 2,400 </Td> <Td> 5 </Td> </Tr> <Tr> <Td> 000000001984 - 09 - 15 - 0000 September 15, 1984 </Td> <Td> Athens, Alabama, United States </Td> <Td> Safety violations, operator error, and design problems force a six - year outage at Browns Ferry Unit 2 . </Td> <Td> 0 </Td> <Td> 110 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001985 - 03 - 09 - 0000 March 9, 1985 </Td> <Td> Athens, Alabama, United States </Td> <Td> Instrumentation systems malfunction during startup, which led to suspension of operations at all three Browns Ferry Units </Td> <Td> 0 </Td> <Td> 1,830 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001986 - 04 - 11 - 0000 April 11, 1986 </Td> <Td> Plymouth, Massachusetts, United States </Td> <Td> Recurring equipment problems force emergency shutdown of Boston Edison's Pilgrim Nuclear Power Plant </Td> <Td> 0 </Td> <Td> 1,001 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001986 - 04 - 26 - 0000 April 26, 1986 </Td> <Td> Chernobyl, Chernobyl Raion (Now Ivankiv Raion), Kiev Oblast, Ukraininan SSR, Soviet Union </Td> <Td> Overheating, steam explosion, fire, and meltdown, necessitating the evacuation of 300,000 people from Chernobyl and dispersing radioactive material across Europe (see Effects of the Chernobyl disaster) </Td> <Td> 30 direct, 19 not entirely related and 15 minors due to thyroid cancer, as of 2008. (3) </Td> <Td> 6,700 </Td> <Td> 7 </Td> </Tr> <Tr> <Td> 000000001986 - 05 - 04 - 0000 May 4, 1986 </Td> <Td> Hamm - Uentrop, West Germany </Td> <Td> Experimental THTR - 300 reactor releases small amounts of fission products (0.1 GBq Co-60, Cs - 137, Pa - 233) to surrounding area </Td> <Td> 0 </Td> <Td> 267 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001987 - 03 - 31 - 0000 March 31, 1987 </Td> <Td> Delta, Pennsylvania, United States </Td> <Td> Peach Bottom units 2 and 3 shutdown due to cooling malfunctions and unexplained equipment problems </Td> <Td> 0 </Td> <Td> 400 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001987 - 12 - 19 - 0000 December 19, 1987 </Td> <Td> Lycoming, New York, United States </Td> <Td> Malfunctions force Niagara Mohawk Power Corporation to shut down Nine Mile Point Unit 1 </Td> <Td> 0 </Td> <Td> 150 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001989 - 03 - 17 - 0000 March 17, 1989 </Td> <Td> Lusby, Maryland, United States </Td> <Td> Inspections at Calvert Cliff Units 1 and 2 reveal cracks at pressurized heater sleeves, forcing extended shutdowns </Td> <Td> 0 </Td> <Td> 120 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001992 - 03 - 01 - 0000 March 1992 </Td> <Td> Sosnovyi Bor, Leningrad Oblast, Russia </Td> <Td> An accident at the Sosnovy Bor nuclear plant leaked radioactive gases and iodine into the air through a ruptured fuel channel . </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001996 - 02 - 20 - 0000 February 20, 1996 </Td> <Td> Waterford, Connecticut, United States </Td> <Td> Leaking valve forces shutdown Millstone Nuclear Power Plant Units 1 and 2, multiple equipment failures found </Td> <Td> 0 </Td> <Td> 254 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001996 - 09 - 02 - 0000 September 2, 1996 </Td> <Td> Crystal River, Florida, United States </Td> <Td> Balance - of - plant equipment malfunction forces shutdown and extensive repairs at Crystal River Unit 3 </Td> <Td> 0 </Td> <Td> 384 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000001999 - 09 - 30 - 0000 September 30, 1999 </Td> <Td> Ibaraki Prefecture, Japan </Td> <Td> Tokaimura nuclear accident killed two workers, and exposed one more to radiation levels above permissible limits . </Td> <Td> </Td> <Td> 54 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000002002 - 02 - 16 - 0000 February 16, 2002 </Td> <Td> Oak Harbor, Ohio, United States </Td> <Td> Severe corrosion of control rod forces 24 - month outage of Davis - Besse reactor </Td> <Td> 0 </Td> <Td> 143 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000002004 - 08 - 09 - 0000 August 9, 2004 </Td> <Td> Fukui Prefecture, Japan </Td> <Td> Steam explosion at Mihama Nuclear Power Plant kills 4 workers and injures 7 more </Td> <Td> </Td> <Td> 9 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000002006 - 07 - 25 - 0000 July 25, 2006 </Td> <Td> Forsmark, Sweden </Td> <Td> An electrical fault at Forsmark Nuclear Power Plant caused one reactor to be shut down </Td> <Td> 0 </Td> <Td> 100 </Td> <Td> </Td> </Tr> <Tr> <Td> 000000002011 - 03 - 11 - 0000 March 11, 2011 </Td> <Td> Fukushima, Japan </Td> <Td> A tsunami flooded and damaged the plant's 5 active reactors, drowning two workers . Loss of backup electrical power led to overheating, meltdowns, and evacuations . One man died suddenly while carrying equipment during the clean - up . The plant's 6th reactor was inactive at the time . </Td> <Td> 2 + </Td> <Td> </Td> <Td> 7 </Td> </Tr> <Tr> <Td> 12 September 2011 </Td> <Td> Marcoule, France </Td> <Td> One person was killed and four injured, one seriously, in a blast at the Marcoule Nuclear Site . The explosion took place in a furnace used to melt metallic waste . </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> </Table> <Tr> <Th> Date </Th> <Th> Location of accident </Th> <Th> Description of accident or incident </Th> <Th> Dead </Th> <Th> Cost ($US millions 2006) </Th> <Th> INES level </Th> </Tr>

Where was the most serious global nuclear power plant accident in 1986