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Tokai JCO Criticality Accident

Report [16]11/11/99 16:40

STA Inspects Conversion Building on October 26th and 27th

The Science and Technology Agency (STA) inspected the JCO uranium conversion building on October 26th and 27th. According to the STA, pictures were taken on the 26th to determine the condition of the area of the accident which was left as it was since the accident. The pictures revealed that the uranium solution was left in the stainless steel bucket used to mix the uranium solution, and a beaker, also made of stainless steel, with a handle. Thus on the 27th, 50ml each of the solutions left in the bucket and the beaker were taken as a sample.

The following five fission products were found in the beaker.

zirconium 95
ruthenium 103
neodymium 147
iodine 131
barium 140

The following three fission products were found in the bucket.

zirconium 95
ruthenium 103
iodine 131

The 2 day operation to investigate JCO uranium plant exposed JCO workers to radiation of 31 -109 microSv.

Concrete Blocks to be Piled Up

Upon requests from the prefecture and towns of the vicinity of the JCO plant, JCO employees are now piling up concrete blocks around the conversion building and all along the boundary of the site. The concrete blocks were piled up to 3 meters height around the conversion building, and piled up to 2 - 3 meters height along the boundary.


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