Japan Press Weekly

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2007 March 14 - 20 [SOCIAL ISSUES]

Nuclear reactor’s criticality accident covered up

On March 15, it was revealed that Hokuriku Electric Power Co. had a critical accident in 1999 at its No.1 reactor at the Shika nuclear power plant in Ishikawa Prefecture, but that the company concealed this serious accident for eight years.

The company on the same day reported the accident to the Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade, and Industry. The Agency ordered the company to suspend its operation of the nuclear reactor and investigate the accident.

On June 18, 1999, during a regular inspection, three out of 89 reactor control rods of the reactor slipped out of the reactor core due to operational errors, causing the reactor to activate. It did not automatically shut down and the self-sustained nuclear fission chain reaction continued for about 15 minutes until the rods were reinserted manually. At that time, the lids of the containment vessels and the pressure vessels were kept open for the inspection.

No radiation leaked, and no worker was exposed to radiation, according to Hokuriku Electric Power Co.

The company failed not only to report the accident to the government but also to keep records of the accident.

Ishikawa Prefectural Governor Tanimoto Masanori said at a press conference on March 15, “It was very regrettable that the company had failed to report the accident to the prefectural government,” adding, “This could radically undermine residents’ confidence [in the nuclear plant].”

It has recently been revealed that Tokyo Electric Power Co. and Tohoku Electric Power Co. also concealed emergency shutdowns of their nuclear reactors in the past.