| Date |
Incident level |
Location |
Type |
| Description |
Notes |
| 6 August 1945 |
Nuclear bombing |
Hiroshima |
Bomb flown in on airplane and dropped over urban area; 13kt explosion |
|
United States of America aviators detonated nuclear bomb over Hiroshima. More than 70,000 fatalities were estimated. |
|
| 9 August 1945 |
Nuclear bombing |
Nagasaki |
Bomb flown in on airplane and dropped over urban area; 21kt explosion |
|
United States of America aviators detonated nuclear bomb over Nagasaki. More than 39,000 fatalities were estimated. |
|
| 1 March 1954 |
Nuclear weapons test |
Bikini Atoll |
Nuclear test poisoned crew of Japanese fishing boat; 15Mt explosion |
|
United States high yield nuclear test Castle Bravo contaminated crew of Japanese tuna fishing boat Daigo Fukuryū Maru giving them acute radiation syndrome. One crew member died of complications. |
|
| 5 December 1965 |
Broken arrow |
coast of Japan |
Loss of a nuclear bomb |
|
A US Navy aircraft with one B43 nuclear bomb fell off the aircraft carrier Ticonderoga into 16,200 feet (4,900 m) of water while the ship was underway from Vietnam to Yokosuka, Japan. The weapon was never recovered. Navy documents show it happened about 80 miles (130 km) from the Amami Islands and 200 miles (320 km) from Okinawa.[1] |
|
| March 1981 |
INES Level 2 |
Tsuruga |
Overexposure of workers |
| More than 100 workers were exposed to doses of up to 155 millirem per day radiation during repairs of a nuclear power plant.[2] |
|
| June 1999 |
INES Level 2[3] |
Shika plant, Ishikawa Prefecture |
Control rod malfunction |
| Operators attempting to insert one control rod accidentally withdrew three causing a 15-minute uncontrolled sustained reaction at the number 1 reactor of Shika Nuclear Power Plant.[4] |
|
| 30 September 1999 |
INES Level 4 |
Ibaraki Prefecture |
Accidental criticality |
|
During preparation of a uranyl nitrate solution, uranium in solution exceeded the critical mass, at a uranium reprocessing facility in Tokai-mura northeast of Tokyo, Japan. Three workers were exposed to (neutron) radiation doses in excess of allowable limits. Two of these workers died. 116 other workers received lesser doses of 1 mSv or greater though not in excess of the allowable limit.[5][6][7][8] |
|
| 11–15 March 2011 |
INES Level 3[citation needed] |
Fukushima II Nuclear Power Plant, Fukushima Prefecture |
Earthquake/tsunami damage, overheating, possible radioactivity emergency |
|
After the 2011 Tōhoku earthquake and tsunami of 11 March, the cooling systems for three reactors (numbers 1, 2 and 4) of the Fukushima II (Fukushima Dai-ni) nuclear power plant were compromised due to damage from the tsunami.[9] Nuclear Engineering International reported that all four units were successfully automatically shut down, but emergency diesel generators at the site were out of order.[10] People were evacuated around 10 kilometres (6.2 mi) from the plant, due to possible radioactive contamination.[11][12] By 15 March, all four reactors at Daini were reported shutdown, cold and safe.[13] |
|
| 11 March 2011 – onwards |
INES Level 7[14] |
Fukushima Daiichi Nuclear Power Plant, Fukushima Prefecture |
Earthquake/tsunami damage, multiple meltdowns, core breaches, explosions, radiological releases, cooling failures |
|
After the 2011 Tōhoku earthquake and tsunami of 11 March, the cooling systems for multiple reactors (units 1, 2, 3) and spent fuel cooling ponds (all 6 units and central pool) of the Fukushima I (Fukushima Dai-ichi) nuclear power plant were compromised due to damage from the tsunami. |
|
