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Tokai JCO Criticality Accident

Serious nuclear accident at Tokai

30 September 1999

The nuclear accident at a test facility in the JCO Ltd.'s uranium processing plant, Tokai took place in 10:35 am Japanese Standard Time (+900) on 30 SEP 99.

Initially an atmospheric radiation count of 0.84 mSv/hour (4000 times of the annual limits of intake) was monitored, but the local government says now the count is back to normal. A criticality accident is suspected.

Three workers were exposed because of the accident, and the exposed workers taken to the hospital were then transferred by helicopter to the Science and Technology Agency's radiological center in order to treat the acute radiation injuries. One of the three is reported to be in a critical condition.

The facility in which the accident occurred is a commercial plant where enriched UF6 gas is converted to UO2 powder for further processing. The pellet fabrication is to be done in another plant nearby.

Police has declared a provisional 200m radius off-limit zone, around the site. People are told to shut all the windows and not to go outside. The cause and details of the accident has not yet been disclosed.


Citizens' Nuclear Information Center
Akebonobashi Co-op 2F-B, 8-5 Sumiyoshi-cho,
Shinjuku-ku, Tokyo, 162-0065, Japan