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Tokai JCO Criticality Accident

Worst Ever Accident Within Japan at Tokai, Ibaraki

Tokai accident information part 3

The radiation count is still high and not even JCO workers can enter the site. No one is aware of the situation inside the plant and nothing is being done. Thus it is very likely that the criticality condition is still in progress.

Latest news as of 9 p.m.

1) Ibaraki prefecture has advised the residents of 10km radius of the plant to stay indoors.
2) Government has set up a committee head by Obuchi prime minister to respond to the situation. The cabinet organization will be put off for the moment to fully cope with this situation.
3) Atmospheric radiation count was 0.7milisievert per hour (mSv/h) at 3 p.m. Normal count is 1milisievert per year (mSv/y).
4) Two of the three workers hospitalized are suspected to have been seriously exposed due to a sudden increase of white blood corpuscle experienced by both of them.
5) 160 people have evacuated to a community center. The evacuees will have to spend the night at the center.

Tokai accident information, part 2

According to T.V. news around 6 p.m., the head of Tokai village stressed three points at a press conference.

1) The atmospheric radiation count has not decreased around the site.
2) There is a possibility that nuclear fission is still occurring at the moment.
3) The plant's structure is intact.

Information Part 1
30 September 1999

There was a nuclear accident at a test facility in the JCO Ltd.'s uranium processing plant located in Tokai, Ibaraki. It happened at 10:35 am Japanese Standard Time (+900) on 30 September, 1999.

Initially, an atmospheric radiation count of 0.84 mSv/hour (10,000 times of the annual dose limit) was monitored, but the local government has announced that the radiation count is back to normal. The Science and Technology Agency (STA) has announced that it was a criticality accident.

Three workers were exposed because of the accident, and the exposed workers taken to a local hospital were later transferred by a helicopter to the National Institute of Radiological Sciences in Chiba City, east of Tokyo, in order to treat the acute radiation injuries. They seem to have inhaled high concentration uranium gas. Two of the three exposed workers are reported to be in a critical condition.

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

Police has declared the area of 200m radius of the site to be an off-limit zone. The local government (Tokai-mura administration) issued an evacuation request to the residents of the surrounding 350m radius of the site. All the villagers residing outside the 350m radius were asked to stay indoors. School children are ordered not to go home, but remain indoors at each school. Naka-machi, a town next to Tokai mura, also advised the residents to remain indoors.

The cause and details of the accident has not yet been disclosed. CNIC will release a statement as soon as enough materials are collected, however, we will keep people post on any further details gathered.


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