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Japanese utility co. begins to shut down reactors

TOKYO — The operator of a nuclear power plant in central Japan began Friday the process of shutting down its reactors as part of an agreement with the government to temporarily suspend operations until it strengthens tsunami protections.

Prime Minister Naoto Kan requested the temporary shutdown amid concerns an earthquake with a magnitude of 8 or higher could strike central Japan sometime within 30 years. The Hamaoka facility sits above a major fault line and has long been considered Japan's riskiest nuclear power plant.

The government has said it will not seek similar shutdowns of any other reactors in the country. Its decision came after evaluating Japan's 54 reactors for quake and tsunami vulnerability after the March 11 disasters that crippled the Fukushima Dai-ichi nuclear plant in northeast Japan, which is still leaking radiation.

Complete coverage: Disaster in Japan

Chubu Electric Co. said work to idle the No. 4 reactor at the Hamaoka plant started Friday morning. The company expects to begin halting the No. 5 reactor — its second operational reactor — on Saturday.

Chubu Electric President Akihisa Mizuno agreed to cooperate with the government during a nationally televised news conference Monday, describing Kan's request as carrying immense weight.

The company will also indefinitely delay a planned resumption of the No. 3 reactor, which has been shut down for regular maintenance since late last year.

The plant's non-operating No. 1 and No. 2 reactors were slated for decommission before the tsunami.

Nuclear energy provides more than one-third of Japan's electricity, and shutting the Hamaoka plant is likely to exacerbate power shortages expected this summer. The three reactors account for more than 10 percent of Chubu's power supply.

Chubu Electric inserted neutron-absorbing control rods into the No. 4 reactor to slow nuclear fission, spokesman Koki Saguchi said. It stopped producing power at 10 a.m. and is expected to reach cold shutdown — when the reactor temperature drops below 100 degrees Celsius — sometime Saturday.