Japanese nuclear incidents

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This is a list of Japanese atomic, nuclear and radiological accidents, incidents and disasters.


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 nuked 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 nuked Nagasaki. More than 39,000 fatalities were estimated.

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.

The 2011 Fukushima Daiichi nuclear disaster, the worst nuclear accident in 25 years, displaced 50,000 households after radiation leaked into the air, soil and sea.[15]

List of plants affected by 2011 Tōhoku earthquake and tsunami[edit]

Hiroshima Explosion of Nuclear Bomb

See also[edit]


  1. ^ CNN (1998). "Cold War: Broken Arrows (1960e)". CNN. Archived from the original on 27 March 2007. Retrieved 17 June 2007. 
  2. ^ "1980s accidents". Nuclearfiles.org. Retrieved 19 April 2012. 
  3. ^ "Criticality accident during periodic inspection | Nuclear power in Europe". Climatesceptics.org. Retrieved 19 April 2012. 
  4. ^ Japanese utility to shut reactor after admitting accident cover-up
  5. ^ "Tokaimura Criticality Accident". World-nuclear.org. Retrieved 19 April 2012. 
  6. ^ "Tokaimura Criticality Accident Nuclear Issues Briefing Paper # 52". Web.archive.org. 3 March 2008. Archived from the original on 3 March 2008. Retrieved 19 April 2012. 
  7. ^ "Chronology and Press Reports of the Tokaimura Criticality". Isis-online.org. Retrieved 19 April 2012. 
  8. ^ "Timeline: Nuclear plant accidents". BBC News. 11 July 2006. Retrieved 19 April 2012. 
  9. ^ "Japan Earthquake: NEI Updates for Saturday, March 12". Nuclear Energy Institute. Retrieved 2 April 2011. [permanent dead link]
  10. ^ "Japan initiates emergency protocol after earthquake". Nuclear Engineering International. 11 March 2011. Archived from the original on 14 March 2011. Retrieved 11 March 2011. 
  11. ^ Sumit Paul-Choudhury, Rowan Hooper (13 March 2011). "Japanese nuclear crisis spreads to two more plants". NewScientist. 
  12. ^ Pete Norman (13 March 2011). "Japan: 200,000 Evacuated From Near Reactors". Sky News. Archived from the original on 15 March 2011. 
  13. ^ IAEA, Fukushima 2011 March 15 update (accessed 20 March 2011)
  14. ^ Ministry of Economy, Trade, and Industry of Japan/NISA: INES (the International Nuclear and Radiological Event Scale) Rating on the Events in Fukushima Dai-ichi Nuclear Power Station by the Tohoku District – off the Pacific Ocean Earthquake Archived 23 July 2012 at WebCite (12 April 2011)
  15. ^ Tomoko Yamazaki and Shunichi Ozasa (27 June 2011). "Fukushima Retiree Leads Anti-Nuclear Shareholders at Tepco Annual Meeting". Bloomberg.