Kansai Electric to manually shut Mihama nuclear unit

December 07, 2011


Kansai Electric Power Co. will manually halt its Mihama No. 2 nuclear reactor as a safety precaution after it discovered unusual levels of coolant leaking from a valve inside the containment vessel, but there have been no radiation leaks, a company spokesman said on Dec. 7.

Japan's second-largest power utility said the problem at the 500 megawatt reactor in western Japan had not affected pressure inside the reactor vessel or the operation of the unit.

"We're checking the cause of the trouble," the spokesman said.

Mihama No. 2, which was due to be taken down for maintenance on Dec. 18, is Japan's fourth-oldest nuclear reactor and one of only nine still operating after the Fukushima crisis in March stirred fears over atomic power safety.

A valve connected to the reactor's pressuriser, which maintains pressure inside the reactor vessel to prevent water from boiling, was leaking greater amounts of water than usual, leading the utility to decide to shut the reactor.

A spokesman at the Nuclear and Industrial Safety Agency, Japan's nuclear watchdog, said it had been notified of the incident.

"As we understand it, this is not due to a failure in the pressuriser," he said.

More than four-fifths of Japan's 54 commercial nuclear reactors are offline, some knocked out by the March 11 earthquake and tsunami that triggered the world's worst nuclear disaster in a quarter century at Tokyo Electric Power Co's Fukushima No. 1 nuclear power plant.

Most have gone down for routine maintenance, however, and are unable to restart as fears about nuclear safety in the wake of the Fukushima crisis leave local communities reluctant to let them go back into operation.

A nuclear reactor at Kyushu Electric Power Co's Genkai plant in southern Japan was restarted last month despite public opposition, however, after it automatically shut down the month before due to a cooling system problem.

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Mihama nuclear power plant (Asahi Shimbun file photo)

Mihama nuclear power plant (Asahi Shimbun file photo)

  • Mihama nuclear power plant (Asahi Shimbun file photo)

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