Nuclear accidents
Two accidents have been rated level 7, the top of the IAEA's scale: Chernobyl and Fukushima Daiichi. They are not comparable events. Chernobyl killed 30 people acutely and displaced over 300,000; at Fukushima the radiation killed no one, while the evacuation ordered to protect people killed 2,313. Both facts sit uncomfortably with the arguments usually built on them.
Death tolls for the largest accidents are genuinely contested, and both exaggeration and dismissal are common. Every figure on these pages is stated with the body that produced it, usually UNSCEAR, the UN scientific committee, and where credible estimates disagree, that is said rather than resolved. Deaths caused by an evacuation are counted as such: not folded into radiation deaths, and not left out.
| Accident | INES | Date | Country | Facility | Immediate deaths |
|---|---|---|---|---|---|
| Chernobyl | 7retrospective | 1986-04-26 | Ukraine | power reactor | 30 |
| Fukushima Daiichi | 7 | 2011-03-11 | Japan | power reactor | 0 |
| Kyshtym (Mayak) | 6retrospective | 1957-09-29 | Russia | reprocessing | not established |
| Chalk River NRX | 5retrospective | 1952-12-12 | Canada | research reactor | 0 |
| Windscale Pile 1 fire | 5retrospective | 1957-10-10 | United Kingdom | research reactor | 0 |
| Three Mile Island Unit 2 | 5retrospective | 1979-03-28 | United States | power reactor | 0 |
| SL-1 | 4retrospective | 1961-01-03 | United States | research reactor | 3 |
| Lucens | 4retrospective | 1969-01-21 | Switzerland | power reactor | 0 |
| Saint-Laurent A1 fuel melt | 4retrospective | 1969-10-17 | France | power reactor | 0 |
| Bohunice A1 refuelling accident | 4retrospective | 1977-02-22 | Slovakia | power reactor | 0 |
| Saint-Laurent A2 fuel melt | 4retrospective | 1980-03-13 | France | power reactor | 0 |
| Tokaimura criticality accident | 4 | 1999-09-30 | Japan | fuel fabrication | 2 |
| Browns Ferry cable fire | 3retrospective | 1975-03-22 | United States | power reactor | 0 |
| Greifswald cable fire | 3retrospective | 1975-12-07 | Germany | power reactor | 0 |
| Vandellòs I turbine fire | 3retrospective | 1989-10-19 | Spain | power reactor | 0 |
| Tomsk-7 reprocessing explosion | 3 | 1993-04-06 | Russia | reprocessing | 0 |
| Davis-Besse vessel head corrosion | 3 | 2002-03-06 | United States | power reactor | 0 |
| Paks fuel cleaning accident | 3 | 2003-04-10 | Hungary | power reactor | 0 |
| Fukushima Daini | 3 | 2011-03-11 | Japan | power reactor | 0 |
The INES scale
The International Nuclear and Radiological Event Scale runs from 1 to 7 and is logarithmic: each step is roughly ten times more severe than the one below. Levels 1 to 3 are incidents, 4 to 7 are accidents.
| Level | Name | Meaning |
|---|---|---|
| 7 | Major accident | Major release, widespread health and environmental effects |
| 6 | Serious accident | Significant release, likely to require planned countermeasures |
| 5 | Accident with wider consequences | Limited release, or severe damage to the reactor core |
| 4 | Accident with local consequences | Minor release, at least one death from radiation |
| 3 | Serious incident | Severe contamination on site, or near-accident with defences remaining |
Sources
- IAEA International Nuclear and Radiological Event Scale
- UNSCEAR reports on Chernobyl (2018) and Fukushima (2013, 2020)
- World Nuclear Association safety of plants library
How these sources are used, including the corrections applied on top of them and what is deliberately left blank · download the underlying data