TOKYO (Kyodo) — The Nuclear Regulation Authority said Wednesday that it assessed the severity of a nuclear exposure accident in June in eastern Japan provisionally as level 2 on the zero-to-seven international scale.
The June 6 accident at the Japan Atomic Energy Agency’s Oarai Research and Development Center in Ibaraki Prefecture, east of Tokyo, left five workers internally exposed to radiation although no harmful consequences were detected for the surrounding environment.
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It was estimated one of the workers will be internally exposed to a radiation dose from 100 to 200 millisieverts in total over 50 years, a level that could slightly increase the risk of cancer.
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Japan previously assessed as level 2 a critical-state accident at the No. 1 reactor of Hokuriku Electric Power Co.’s Shika nuclear plant in 1999. The utility hid the accident, which occurred while the unit’s operation was suspended for regular checkups, until 2007.
Tokyo also rated as level 2 a 1991 accident at the No. 2 reactor in the Mihama plant run by Kansai Electric Power Co., in which one of a steam generator’s tubes snapped, activating the emergency core-cooling system for the first time in the country.
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