1952

Dec. 12, Chalk River, nr. Ottawa, Canada: a partial meltdown of the reactor's uranium fuel core resulted after the accidental removal of four control rods. Although millions of gallons of radioactive water accumulated inside the reactor, there were no injuries.

1953

Love Canal, nr. Niagara Falls, N.Y.: was destroyed by waste from chemical plants. By the 1990s, the town had been cleaned up enough for families to begin moving back to the area.

1957

Oct. 7, Windscale Pile No. 1, north of Liverpool, England: fire in a graphite-cooled reactor spewed radiation over the countryside, contaminating a 200-square-mile area.

South Ural Mountains: explosion of radioactive wastes at Soviet nuclear weapons factory 12 mi from city of Kyshtym forced the evacuation of over 10,000 people from a contaminated area. No casualties were reported by Soviet officials.

1976

nr. Greifswald, East Germany: radioactive core of reactor in the Lubmin nuclear power plant nearly melted down due to the failure of safety systems during a fire.

1979

March 28, Three Mile Island, nr. Harrisburg, Pa.: one of two reactors lost its coolant, which caused overheating and partial meltdown of its uranium core. Some radioactive water and gases were released. This was the worst accident in U.S. nuclear-reactor history.

1984

Dec. 3, Bhopal, India: toxic gas, methyl isocyanate, seeped from Union Carbide insecticide plant, killing more than 2,000 and injuring about 150,000.

1986

April 26, Chernobyl, nr. Kiev, Ukraine: explosion and fire in the graphite core of one of four reactors released radioactive material that spread over part of the Soviet Union, eastern Europe, Scandinavia, and later western Europe. 31 claimed dead. Total casualties are unknown. Worst such accident to date.

1987

Sept. 18, Goiânia, Brazil: 244 people contaminated with cesium-137 from a cancer-therapy machine that had been sold as scrap. Four people died in worst radiation disaster in Western Hemisphere.

1999

Sept. 30, Tokaimura, Japan: uncontrolled chain reaction in a uranium-processing nuclear fuel plant spewed high levels of radioactive gas into the air, killing two workers and seriously injuring one other.

2004

Aug. 9, Mihama, Japan: nonradioactive steam leaked from a nuclear power plant, killing four workers and severely burning seven others.

2007

July 17, Kashiwazaki, Japan: radiation leaks, burst pipes, and fires at a major nuclear power plant followed a 6.8 magnitude earthquake near Niigata. Japanese officials, frustrated at the plant operators' delay in reporting the damage, closed the plant a week later until its safety could be confirmed. Further investigation revealed that the plant had unknowingly been built directly on top of an active seismic fault.

2008

February 7, Port Wentworth, Georgia: an explosion fueled by combustible sugar dust killed 13 people and injured several others at the Imperial Sugar plant near Savannah.

2011

March 12, Fukushima Daiichi Nuclear Power Station, Japan: an explosion in reactor No. 1 caused one of the buildings to crumble to the ground. The cooling system at the reactor failed shortly after the earthquake and tsunami hit Japan. By Tuesday, March 15, two more explosions and a fire had officials and workers at the plant struggling to regain control of four reactors. The fire, which happened at reactor No. 4, was contained by noon on Tuesday, but not before the incident released radioactivity directly into the atmosphere.

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