A nuclear and radiation accident is defined by the International Atomic Energy Agency (IAEA) as "an event that has led to significant consequences to people, the environment or the facility." Examples include lethal effects to individuals, large radioactivity release to the environment, or a reactor core melt. The prime example of a "major nuclear accident" is one in which a reactor core is damaged and significant amounts of radioactive isotopes are released, such as in the Chernobyl disaster in 1986 and the Fukushima nuclear accident in 2011. The impact of nuclear accidents has been a topic of debate since the first nuclear reactors were constructed in 1954 and has been a key factor in public concern about nuclear facilities. Technical measures to reduce the risk of accidents or to minimize the amount of radioactivity released to the environment have been adopted; however, human error remains, and there have been many accidents with varying impacts as well as near misses and incidents. As of 2014, there have been more than 100 serious nuclear accidents and incidents from the use of nuclear power. Fifty-seven accidents or severe incidents have occurred since the Chernobyl disaster, and about 60% of all nuclear-related accidents/severe incidents have occurred in the United States. Serious nuclear power plant accidents include the Fukushima nuclear accident (2011), the Chernobyl disaster (1986), the Three Mile Island accident (1979), and the SL-1 accident (1961). Nuclear power accidents can involve loss of life and large monetary costs for remediation work. Nuclear submarine accidents include the K-19 (1961), K-11 (1965), K-27 (1968), K-140 (1968), K-429 (1970), K-222 (1980), and K-431 (1985) accidents. Serious radiation incidents and accidents include the Kyshtym disaster, the Windscale fire, the radiotherapy accident in Costa Rica, the radiotherapy accident in Zaragoza, the radiation accident in Morocco, the Goiania accident, the radiation accident in Mexico City, the Samut Prakan radiation accident, and the Mayapuri radiological accident in India. The IAEA maintains a website reporting recent nuclear accidents. In 2020, the WHO stated that "Lessons learned from past radiological and nuclear accidents have demonstrated that the mental health and psychosocial consequences can outweigh the direct physical health impacts of radiation exposure.""
Nuclear plant accidents
The world's first nuclear reactor meltdown was the NRX reactor at Chalk River Laboratories, Ontario, Canada in 1952. The worst nuclear accident is the Chernobyl disaster which occurred in 1986 in the Ukrainian SSR, now Ukraine. The accident killed approximately 30 people directly and damaged approximately $7 billion of property. A study published in 2005 by the World Health Organization estimates that there may 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. 6,000 people were involved in cleaning Chernobyl and 10,800 square miles (28,000 km2) were contaminated.
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. There have been comparatively few fatalities associated with nuclear power plant accidents. An academic review of many reactor accident and the phenomena of these events was published by Mark Foreman.
List of nuclear plant accidents and incidents
Nuclear reactor attacks
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![Nuclear and radiation accidents and incidents: Following the 2011 Japanese Fukushima nuclear accident, authorities shut down the nation's 54 nuclear power plants. The Fukushima site remains radioactive, with about 30,000 evacuees still living in temporary housing, although nobody has died or is expected to die from radiation effects.[1] The difficult cleanup job will take 40 or more years, and cost tens of billions of dollars.[2][3]](https://upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Fukushima_I_by_Digital_Globe.jpg/1280px-Fukushima_I_by_Digital_Globe.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)

![Nuclear and radiation accidents and incidents: The Kashiwazaki-Kariwa Nuclear Power Plant, a Japanese nuclear plant with seven units, the largest single nuclear power station in the world, was shut down for 21 months following an earthquake in 2007. Safety-critical systems were found to be undamaged by the earthquake.[27][28]](https://upload.wikimedia.org/wikipedia/commons/thumb/2/24/Kashiwazaki_Kariwa-April_2011.jpg/500px-Kashiwazaki_Kariwa-April_2011.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)
![Nuclear and radiation accidents and incidents: Dr. Joseph G. Hamilton was the primary researcher for the human plutonium experiments done at U.C. San Francisco from 1944 to 1947.[59] Hamilton wrote a memo in 1950 discouraging further human experiments because the AEC would be left open "to considerable criticism" since the experiments as proposed had "a little of the Buchenwald touch."[60]](https://upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Joseph_Hamilton_with_radio_sodium_experiment_97401413.jpeg/1280px-Joseph_Hamilton_with_radio_sodium_experiment_97401413.jpeg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)
