There have been several nuclear and radiation accidents involving fatalities, including nuclear power plant accidents, nuclear submarine accidents, and radiotherapy incidents.

List of accidents FatalitiesIncidentINES levelDateDetails200+ (short-term)Kyshtym disaster6 1957, September 29An improperly stored underground tank of high-level radioactive waste exploded. Death count unknown, estimates range from more than 200 immediate deaths.31-60 (short-term)4,000-16,000+(long-term, disputed)Chernobyl disaster71986, April 2631 are believed to have been directly killed by the disaster (2 in the explosion and 29 due to radioactivity, 28 during the event and one in 2005). There are varying estimates of increased mortality over subsequent decades from 4,000-16,000. An additional 19 workers subsequently died between 1987 and 2004, which may be related. (see Deaths due to the Chernobyl disaster).Windscale fire5 1957, October 8A 1988 UK government estimate estimated that there would be around 100 deaths by 2007 as a result of exposure to radioactive material from the fire. Subsequent epidemiological studies have failed to find any such rise in cancer cases, and criticised earlier estimates as lacking sound evidentiary basis. Fukushima nuclear disaster72011 MarchIn 2018, 1 cancer death of a man who worked at the plant at the time of the accident was attributed to radiation exposure by a Japanese government panel. The government of Japan states that 51 people died due to the evacuation.Government of Japan (2014). WG3 Question 2, Submission 6, Official Communication.17Instituto Oncológico Nacional of Panama 2000 August – 2001 MarchPatients receiving treatment for prostate cancer and cancer of the cervix received lethal doses of radiation.13Radiotherapy accident in Costa Rica1996114 patients received an overdose of radiation from a cobalt-60 source that was being used for radiotherapy.11Radiotherapy accident in Zaragoza, Spain1990 DecemberCancer patients receiving radiotherapy; 11 fatalities and 27 patients were injured.Strengthening the Safety of Radiation Sources p. 15.10Soviet submarine K-431 reactor accident1985, August 10Reactor lid and control rods were lifted too far while adjusting position, resulting in criticality excursion. 49 people suffered radiation injuries.10Columbus radiotherapy accident1974–197688 injuries resulting in 10 fatalities from cobalt-60 source due to incorrect calibration of a teletherapy unit.9Soviet submarine K-27 reactor accident1968, May 2483 people were injured due to uneven cooling of the reactor core, resulting in fuel element failures and multiple ruptures.8Soviet submarine K-19 reactor accident1961, July 4More than 30 people were over-exposed to radiation when the starboard reactor cooling system failed and the reactor temp rose uncontrollably. Emergency repairs ordered by the captain successfully cooled the reactor and avoided meltdown, but exposed the workers to high levels of radiation.Strengthening the Safety of Radiation Sources p. 14.8Radiation accident in Morocco1984 MarchAt least 8 people died when an iridium-192 source used to radiograph welds became separated from its shielded container.7Houston radiotherapy accident1980An accident involving yttrium-90 in nuclear medicine therapy caused 7 deaths.5Lost radiation source, Baku, Azerbaijan, USSR1982, October 5A caesium-137 orphan source was carried by an individual in a clothes pocket, exposing several individuals. Five people suffered radiation burns and died; at least one other person suffered acute radiation sickness, and twelve others were exposed.4Goiânia accident51987, September 13249 people received a large radiation dose from a lost radiotherapy source.The Radiological Accident in Goiania p. 2.4Radiation accident in Mexico City1962Exposure to a cobalt-60 orphan source from an industrial radiographic device.3SL-1 accident (US Army)1961, January 3All three of the experimental reactor crew died when the reactor went prompt critical and the core explosively vaporized.3Samut Prakan radiation accident2000 FebruaryThree deaths and ten injuries resulted when a radiation-therapy unit was dismantled.Pallava Bagla. "Radiation Accident a 'Wake-Up Call' For India's Scientific Community" Science, Vol. 328, 7 May 2010, p. 679.2Tokaimura nuclear accident, Japan41999, September 30Two fatalities, and 667 people suffered exposure. during a criticality accident at a fuel reprocessing facility, due to improper handling of liquid uranium fuel.Benjamin K. Sovacool. A Critical Evaluation of Nuclear Power and Renewable Electricity in Asia, Journal of Contemporary Asia, Vol. 40, No. 3, August 2010, p. 399.2Meet Halfa, Qalyubiyya Governorate, Egypt2000 MayTwo fatalities, five injuries, and seventy six others treated for changes to their blood, due to an iridium-192 orphan source.1Mayapuri radiological accident, India2010 AprilEight hospitalized, with one fatality, from exposure to a cobalt-60 orphan source.1Daigo Fukuryū Maru1954, March 1Crewman of a Japanese fishing boat exposed to nuclear fallout from the Castle Bravo test.1Louis Slotin 1946, May 21Criticality accident at Los Alamos National Laboratory in New Mexico with same plutonium bomb core as the Daghlian accident, known as the "demon core".1Harry Daghlian1945, August 21Criticality accident at Los Alamos National Laboratory in New Mexico with a plutonium bomb core, known as the "demon core".1Cecil Kelley criticality accident1958, December 30Criticality accident at Los Alamos National Laboratory.1Wood River Junction, Rhode Island1964Operator error at nuclear facility while recovering highly enriched uranium; Robert Peabody died 49 hours later.1Constituyentes Atomic Center1983, September 23Malfunction INES level 4 at RA2 reactor in Argentina, operator Osvaldo Rogulich died days later.1San Salvador, El Salvador1989One fatality due to violation of safety rules at 60Co irradiation facility.1Tammiku, Estonia1994One fatality from disposed 137Cs source.1Sarov, Russia1997 JuneOne fatality due to violation of safety rules.1Lia radiological accident, Tsalenjikha, Samegrelo-Zemo Svaneti, Georgia2001, December 2One fatality due to unknowing exposure to a Soviet-era radioisotope thermoelectric generator.

Events with disputed fatality counts

Chernobyl disaster

Estimates of the total number of deaths potentially resulting from the Chernobyl disaster vary enormously: A UNSCEAR report proposes 45 total confirmed deaths from the accident . This number includes 2 non-radiation related fatalities from the accident itself, 28 fatalities from radiation doses in the immediate following months and 15 fatalities due to thyroid cancer likely caused by iodine-131 contamination; it does not include 19 additional individuals initially diagnosed with acute radiation syndrome who had also died , but who are not believed to have died due to radiation doses. The World Health Organization (WHO) suggested in 2006 that cancer deaths could reach between 4,000 to 9,000 among the 600,000 most heavily exposed people, a group which includes emergency workers, nearby residents, evacuees, and residents of low-contaminated areas. A 2006 report, commissioned by the anti nuclear German political party The Greens and sponsored by the Altner Combecher Foundation, predicted 30,000 to 60,000 cancer deaths as a result of worldwide Chernobyl fallout by assuming a linear no-threshold model for very low doses. A Greenpeace report puts this figure at 200,000 or more. A disputed Russian publication, Chernobyl, concludes that 985,000 premature deaths occurred worldwide between 1986 and 2004 as a result of radioactive contamination from Chernobyl.

Kyshtym disaster The Kyshtym disaster, which occurred at Mayak in Russia on 29 September 1957, was rated as a level 6 on the International Nuclear Event Scale, the third most severe incident after Chernobyl and Fukushima. Because of the intense secrecy surrounding Mayak, it is difficult to estimate the death toll of Kyshtym. One book claims that "in 1992, a study conducted by the Institute of Biophysics at the former Soviet Health Ministry in Chelyabinsk found that 8,015 people had died within the preceding 32 years as a result of the accident." By contrast, only 6,000 death certificates have been found for residents of the Tech riverside between 1950 and 1982 from all causes of death, though perhaps the Soviet study considered a larger geographic area affected by the airborne plume. The most commonly quoted estimate is 200 deaths due to cancer, but the origin of this number is not clear. More recent epidemiological studies suggest that around 49 to 55 cancer deaths among riverside residents can be associated to radiation exposure. This would include the effects of all radioactive releases into the river, 98% of which happened long before the 1957 accident, but it would not include the effects of the airborne plume that was carried north-east. The area closest to the accident produced 66 diagnosed cases of chronic radiation syndrome, providing the bulk of the data about this condition.

Windscale fire The Windscale fire resulted when uranium metal fuel ignited inside plutonium production piles; surrounding dairy farms were contaminated. The severity of the incident was covered up at the time by the UK government, as Prime Minister Harold Macmillan feared that it would harm British nuclear relations with America, and so original reports on the disaster and its health impacts were subject to heavy censorship. The severity of the radioactive fallout was played down, and the release of a highly dangerous isotope during the fire, Polonium-210, was covered up at the time.

Partly because of this, consensus on the precise number of cancer deaths caused in the long term as a result of the radiation leak has changed over time as more information on the incident has come to light. Taking into account the impact of the release of Polonium-210 for the first time, a 1983 UK government report estimated at least 33 cancer fatalities as a result of the incident. An updated 1988 UK government report estimated that 100 fatalities "probably" resulted from cancers as a result of the releases over 40 to 50 years. In 2007, the 50-year anniversary of the fire, new academic research into the health effects of the incident was published by Richard Wakeford, a visiting professor at the University of Manchester's Dalton Nuclear Institute, and by former UK Atomic Energy Authority researcher, John Garland. Their study concluded that because the actual amount of radiation released in the fire could be double the previous estimates, and that the radioactive plume actually travelled further east, there could have been 240 cases of cancer resulting in 100 fatalities in the long term as a result of the fire. However, subsequent epidemiological studies have failed to find any such increase in cancer linked to the fire. A 2024 study criticised earlier estimates as lacking sound evidentiary basis.

Fukushima disaster

In a 2013 report, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) stated the overall health risks from the Fukushima disaster to be far lower than those of Chernobyl. There have been no observed or expected deterministic effects. In pregnancies, there has been no expected increase in spontaneous abortions, miscarriages, perinatal mortality, birth defects, or cognitive impairment. Finally, there was no expected discernible increase in heritable disease or discernible radiation-related increases in any cancers, with the possible exception of thyroid cancer. However, the high detection rates of thyroid nodules, cysts, and cancer may be a consequence of intensive screening. In a 2015 white paper, UNSCEAR stated its findings from 2013 remain valid and largely unaffected by new information, and the new information further supports the statement that high thyroid detection is likely due to more intensive screening.