• Kyodo

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Police on Wednesday arrested six former executives and current employees of JCO Co. on suspicion of professional negligence resulting in death in connection with the nation’s worst-ever nuclear power accident last year in Tokai, Ibaraki Prefecture.

Those arrested included Kenzo Koshijima, 54, head of the plant at the time of the accident; Hiromasa Kato, 61, then chief of the production department; and Yutaka Yokokawa, 55, who was exposed to radiation in the accident along with two other workers who later died — Hisashi Ouchi and Masato Shinohara.

The six have reportedly admitted the police charges brought against them.

Police suspect that systematic violations at JCO — such as inadequate safety training and illegal operations — were to blame for the accident, which occurred at the firm’s nuclear fuel processing plant in the village of Tokai, some 120 km northeast of Tokyo, on Sept. 30, 1999.

Police said that on the day of the accident, Ouchi and Shinohara bypassed normal procedures by using buckets to transfer uranium when producing a uranium solution.

They poured an excessive amount of uranium from the buckets into a tank not designed to hold the substance, the police investigation indicates.

Ouchi, 35, died in December while Shinohara, 40, died in April.

Police believe that JCO executives and employees in the production department were aware of the danger of the illegal operations but did not provide the necessary safety instructions, the sources said.

The Sumitomo Metal Mining Co. subsidiary reportedly started taking the shortcuts in 1993, and in 1996 compiled an unofficial manual that suggested using buckets to make uranium solution. The manual was used thereafter as if it were an officially authorized manual, according to the investigation.

JCO did not seek or obtain approval to change the production method, as is required by law, the sources said.

The arrests mark the end of the Ibaraki Prefectural Police investigation, which began three days after the accident.

At least 439 people, including 207 Tokai residents, were exposed to radiation as a result of the accident.

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