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Tokaimura nuclear accident
The Tokaimura nuclear accident was a serious nuclear radiation accident in Japan. It took place at a uranium-reprocessing facility in Tokaimura, northeast of Tokyo, Japan, on 30 September, 1999. The accident occurred in a very small fuel preparation plant operated by JCO.
The direct cause of the accident was some workers putting uranyl nitrate solution containing about 16.6 kg of uranium, which exceeded the critical mass, into a precipitation tank. The tank was not designed to dissolve this type of solution and was not designed to prevent such accidents to happen. As a result, three workers were exposed to neutron radiation doses in excess of allowable limits. Two of these workers later died.
Many emergency workers and nearby residents were hospitalized and hundreds of thousands of others were forced to remain indoors for 24 hours.
- Tokaimura Criticality Accident: Nuclear Issues Briefing Paper #52, June 2000
- In The Wake of Tokaimura, Japan Rethinks its Nuclear Picture