Nuclear Disasters & Incidents

Comprehensive documentation of major nuclear accidents throughout history, their causes, impacts, and lessons learned.

Fukushima Daiichi Nuclear Disaster

March 11, 2011
Ōkuma, Fukushima Prefecture, Japan
Level 7 (Major Accident)UPuCsI

Summary

Following a major earthquake and tsunami, the Fukushima Daiichi Nuclear Power Plant experienced equipment failures, nuclear meltdowns, and releases of radioactive materials.

Tokaimura Nuclear Accident

September 30, 1999
Tokaimura, Ibaraki Prefecture, Japan
Level 4 (Accident with Local Consequences)U

Summary

A criticality accident occurred at a uranium processing facility when workers manually mixed uranium in a precipitation tank, causing an uncontrolled nuclear chain reaction.

Goiânia Radioactive Contamination

September 13, 1987
Goiânia, Goiás, Brazil
Level 5 (Accident with Wider Consequences)Cs

Summary

A radioactive contamination accident occurred when a cesium-137 source from an abandoned radiotherapy clinic was stolen and broken open, spreading radioactive material.

Chernobyl Disaster

April 26, 1986
Pripyat, Ukrainian SSR, Soviet Union
Level 7 (Major Accident)UPuCsISr

Summary

The Chernobyl disaster was a nuclear accident that occurred at the Chernobyl Nuclear Power Plant. A safety test went catastrophically wrong, causing a reactor core meltdown and explosion that released massive amounts of radioactive material into the atmosphere.

Saint-Laurent Nuclear Accident

March 13, 1980
Saint-Laurent-Nouan, France
Level 4 (Accident with Local Consequences)U

Summary

A partial meltdown occurred in the Saint-Laurent Nuclear Power Plant when the cooling system failed, causing fuel to melt.

Church Rock Uranium Mill Spill

July 16, 1979
Church Rock, New Mexico, USA
Significant environmental disasterU

Summary

A uranium mill tailings dam failed, releasing radioactive water and solid waste into the Puerco River. It was the largest release of radioactive material in U.S. history.

Three Mile Island Accident

March 28, 1979
Dauphin County, Pennsylvania, USA
Level 5 (Accident with Wider Consequences)U

Summary

A partial meltdown of reactor unit 2 at the Three Mile Island Nuclear Generating Station. It was the most serious accident in U.S. commercial nuclear power plant history.

SL-1 Reactor Accident

January 3, 1961
Idaho Falls, Idaho, USA
Level 4 (Accident with Local Consequences)U

Summary

A steam explosion killed three military personnel during maintenance of the experimental SL-1 reactor. It was the first fatal nuclear reactor accident in the United States.

Windscale Fire

October 10, 1957
Windscale, Cumberland, England
Level 5 (Accident with Wider Consequences)UPuI

Summary

A fire in the Windscale nuclear reactor core released radioactive contamination into the surrounding area. It was the worst nuclear accident in Great Britain's history.

Kyshtym Disaster

September 29, 1957
Mayak, Chelyabinsk Oblast, Soviet Union
Level 6 (Serious Accident)PuSrCs

Summary

A massive explosion at the Mayak nuclear facility released radioactive material over a large area. It was kept secret for decades and is the third worst nuclear accident in history.

Chalk River Nuclear Accident

December 12, 1952
Chalk River, Ontario, Canada
Level 5 (Accident with Wider Consequences)U

Summary

A partial meltdown of the NRX reactor at Chalk River Laboratories. It was one of the first major nuclear reactor accidents and required a massive cleanup effort.