Chugoku Electric Power Co. announced March 30 that it failed to conduct routine checks on 123 components of its Shimane nuclear power plant in Matsue — 74 in the No. 1 reactor and 49 in the No. 2 reactor. Some components, such as valves in piping and an emergency diesel power generator, had not been checked since 1988. The omission of these checks is serious negligence on the part of the firm. It is thought more similar cases may emerge.

The government classifies nuclear power plant components into four categories, depending on their importance for ensuring safety. Of the 123 components unchecked at the Shimae plant, 57 fall in the “most important” category. It is appalling that the firm failed to check a component in the emergency core cooling system of the No. 1 reactor — a system that would pour a large amount of water into the reactor core to prevent a meltdown.

The No. 1 reactor has been shut down since March 31 (the No. 2 reactor was already idled for routine inspection.) This is the first time a reactor has been shut down due to omitted inspections.

Evidently, communication between sections and general attitude toward safety checks at the plant were problematic. A motor that drives a piping valve was to have been replaced in 2006, but continued to be used because the firm placed an incorrect order with the manufacturer. The situation was not reported to supervisors, who thought that the motor had been replaced. Only in June 2009, when the correct new motor arrived from the manufacturer, did the supervisors realize what had happened. Nonetheless, they neglected to tell the inspections section of the situation until January.

The power industry hopes to raise the operation rate of nuclear power plants from the current rate of less than 70 percent and increase the use of MOX (plutonium-uranium mixed oxide) fuel. But these shocking revelations about operations at Chugoku Electric Power Co. will increase people’s concerns about the safety of nuclear power.

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