The Hamaoka nuclear plant, which sits near a major fault line in Shizuoka prefecture, is considered Japan's most vulnerable nuclear facility


The operator of Japan's "most dangerous" nuclear plant said on Monday it would comply with a government request to temporarily close the facility and carry out work to improve its ability to withstand earthquakes and tsunamis.

Chubu Electric had been asked to close the Hamaoka nuclear plant in Shizuoka prefecture, central Japan, which is thought to be the country's most vulnerable nuclear facility.

The firm's executives agreed to halt the plant's working reactors as soon as possible at an emergency board meeting, according to Japanese media.

Located 125 miles west of Tokyo, Hamaoka sits near a major fault line in a region where seismologists say there is an 87% chance of an earthquake of magnitude 8.0 or higher striking in the next 30 years.

Fears are mounting in the wake of the Fukushima Daiichi crisis that another large quake and tsunami could cause radiation leaks that, depending on wind direction, could have a serious impact on the capital.

The issue of the Hamaoka plant was raised as concern grows over a dramatic rise in the temperature inside a reactor building at Fukushima Daiichi, scene of the world's worst nuclear accident since Chernobyl.

The temperature inside the pressure vessel of the No 3 reactor rose to 217C on Sunday evening from 163C on Saturday morning. But the plant's operator, Tokyo Electric Power (Tepco), said that was still lower than the 286C observed during normal operations, adding that it would continue to monitor the unit.

The No 3 reactor is of particular concern because it contains plutonium-uranium mixed oxide fuel - or MOX - and would release highly toxic plutonium in the event of a meltdown.

Japan's prime minister, Naoto Kan, has bowed to pressure from the public and key scientific advisers and asked Chubu Electric to immediately shut down Hamaoka's two working reactors. A third reactor has been shut down for inspection and two others are being decommissioned.

The plant is expected to remain closed while a tsunami-resistant wall is built and emergency backup generators installed to improve its ability to function after a natural disaster.

Company officials estimate it will take two to three years to build a 12-metre-high tsunami wall stretching nearly a mile along the Pacific coast. At present the plant is protected by sand hills high enough to withstand an 8m tsunami.

The waves that knocked out the power at Fukushima Daiichi were at least 14m high.

About 79,800 people live within a 6-mile (10km) radius of the Hamaoka plant.

While Kan's order is not legally binding, few expected Chubu Electric to resist, despite concerns that the closure of its only nuclear plant could cause power shortages in central Japan this summer.

The three functioning reactors at Hamaoka, which supplies power to 16 million people, including the nearby headquarters of carmakers Toyota and Suzuki, account for more than 10% of its power supply.

Chubu Electric estimates peak demand this summer will run at about 26m kilowatts, with output at 30m kilowatts provided the reactors are running.

The firm is examining the possibility of boosting output from gas, oil and coal fired plants, as well as buying in power from other utilities. Chubu Electric's chairman, Toshio Mita, is in Qatar to discuss the possible provision of liquefied natural gas to help cover the shortfall.

The government indicated over the weekend that Japan was committed to nuclear power, despite the Fukushima Daiichi accident and growing public disquiet.

Kan said the proposed Hamaoka shutdown was an "exceptional case" given its vulnerability to quake and tsunami damage. "If an accident occurs at Hamaoka, it could have serious consequences," he said, adding there were no plans to shut any more of Japan's 54 nuclear reactors.

"Our energy policy is to stick to nuclear power," Yoshito Sengoku, the deputy chief cabinet secretary, told reporters.

Tepco, meanwhile, appears to making progress in reaching its self-imposed deadline of between six and nine months to stabilise the Fukushima Daiichi plant and achieve "cold shutdown".

Workers could soon be able to enter the No 1 reactor building to install new cooling systems, the company said, after readings showed a drop in radiation levels.

Contamination levels inside the building have fallen sufficiently to allow workers in protective clothing to enter for short periods, the country's nuclear safety agency said, adding that the doors to the building were opened Sunday night to promote ventilation.

Workers entered early Monday morning to check radiation levels ahead of a decision on whether to proceed with work to install cooling systems.

• Japan disaster
• Japan
• Nuclear power

Justin McCurry

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