page_title: Nuclear power
section_title: Accidents
hierarchical_section_title: Nuclear power / Accidents, attacks and safety / Accidents
caption_attribution_description: English: Graph of Decay heat as fraction of full power from a SCRAMed operating power reactor. Two models are displayed in the graph, one being Retran, which uses a 11 group exponential decay, the other being Todreas and Kazimi from published work in 1990, which was adapted from previous empirical correlations. The Retran model inputs no assumptions of operating history, and the Todreas model requires the operating time before shutdown, which was assumed to be 2 years for this application.
context_page_description: Nuclear power is the use of nuclear reactions that release nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by nuclear fission of uranium and plutonium. Nuclear decay processes are used in niche applications such as radioisotope thermoelectric generators. Generating electricity from fusion power remains at the focus of international research.
  Civilian nuclear power supplied 2,563 terawatt hours of electricity in 2018, equivalent to about 10% of global electricity generation, and was the second largest low-carbon power source after hydroelectricity. As of December 2019, there are 443 civilian fission reactors in the world, with a combined electrical capacity of 395 gigawatt. There are also 56 nuclear power reactors under construction and 109 reactors planned, with a combined capacity of 60 GW and 120 GW, respectively.
context_section_description: Some serious nuclear and radiation accidents have occurred.
  The severity of nuclear accidents is generally classified using the International Nuclear Event Scale (INES) introduced by the International Atomic Energy Agency (IAEA).
  The scale ranks anomalous events or accidents on a scale from 0 (a deviation from normal operation that poses no safety risk) to 7 (a major accident with widespread effects).
  There have been 3 accidents of level 5 or higher in the civilian nuclear power industry, two of which, the Chernobyl accident and the Fukushima accident, are ranked at level 7.
  The Chernobyl accident in 1986 caused approximately 50 deaths from direct and indirect effects, and some temporary serious injuries.
  The future predicted mortality from cancer increases, is usually estimated at some 4000 in the decades to come. A higher number of the routinely treatable Thyroid cancer, set to be the only type of causal cancer, will likely be seen in future large studies.
  The Fukushima Daiichi nuclear accident was caused by the 2011 Tohoku earthquake and tsunami.
  The accident has not caused any radiation-related deaths, but resulted in radioactive contamination of surrounding areas.
  The difficult Fukushima disaster cleanup will take 40 or more years, and is expected to cost tens of billions of dollars.
  The Three Mile Island accident in 1979 was a smaller scale accident, rated at INES level 5.
  There were no direct or indirect deaths caused by the accident.
  According to Benjamin K. Sovacool, fission energy accidents ranked first among energy sources in terms of their total economic cost, accounting for 41 percent of all property damage attributed to energy accidents.
  Another analysis presented in the international journal Human and Ecological Risk Assessment found that coal, oil, Liquid petroleum gas and hydroelectric accidents (primarily due to the Banqiao dam burst) have resulted in greater economic impacts than nuclear power accidents. Comparing Nuclear's latent cancer deaths, such as cancer with other energy sources immediate deaths per unit of energy generated(GWeyr). This study does not include Fossil fuel related cancer and other indirect deaths created by the use of fossil fuel consumption in its "severe accident", an accident with more than 5 fatalities, classification.</ref>
  Nuclear power works under an insurance framework that limits or structures accident liabilities in accordance with the Paris convention on nuclear third-party liability, the Brussels supplementary convention, the Vienna convention on civil liability for nuclear damage and the Price-Anderson Act in the United States.
  It is often argued that this potential shortfall in liability represents an external cost not included in the cost of nuclear electricity; but the cost is small, amounting to about 0.1% of the levelized cost of electricity, according to a CBO study.
  These beyond-regular-insurance costs for worst-case scenarios are not unique to nuclear power, as hydroelectric power plants are similarly not fully insured against a catastrophic event such as the Banqiao Dam disaster, where 11 million people lost their homes and from 30,000 to 200,000 people died, or large dam failures in general. As private insurers base dam insurance premiums on limited scenarios, major disaster insurance in this sector is likewise provided by the state.
caption: Reactor decay heat as a fraction of full power after the reactor shutdown, using two different correlations. To remove the decay heat, reactors need cooling after the shutdown of the fission reactions. A loss of the ability to remove decay heat caused the Fukushima accident.
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