A Japanese nuclear power plant -- the world's biggest -- may be shut down for more than a year while a safety study is made after an earthquake caused radiation leaks and showed that the plant was built above an active fault.
Fears about the safety of Japan's nuclear industry have been renewed by radiation leaks into the ocean and atmosphere from Tokyo Electric Power's (TEPCO) plant in the northwestern city of Kashiwazaki, hard hit by a 6.8 magnitude quake on Monday.
The trade minster and a local mayor have already said the Kashiwazaki-Kariwa plant, closed since the quake that flattened homes and killed 10 people, cannot reopen until safety is assured.
On Thursday, the Nikkei business newspaper said the government might order TEPCO to keep the plant shut for more than a year while a safety study is conducted, raising questions about possible power cuts and the hefty cost to TEPCO of firing up other mothballed power stations to meet heavy summer demand.
If the earthquake resistance study shows the facility needs to be reinforced, it might take much longer than a year before operations can resume, the newspaper added.
TEPCO spokesman Jun Oshima said the utility was unclear when it could restart the plant. "The priority is on being able to say that the facility is safe," he said.
TEPCO has acknowledged that Monday's quake was stronger than the tremors that the plant, whose first reactor came on stream more than 20 years ago, had been designed to withstand.
International Atomic Energy Agency chief Mohamed ElBaradei has said that the firm had misjudged the seismic risks.
TEPCO's Oshima said that the firm now assumes that fault that caused this week's tremor was the same one found during research in 1979-1980, before the plant's second unit was built, but it had not caused concern because it had not been expected to cause a big quake.
Japan accounts for about 20% of the world's earthquakes of magnitude 6 or greater and every year there are up to 2,000 quakes that can be felt by people.
Japan's nuclear power industry has been tarnished by cover-ups of accidents and fudged safety records, and the dribble of bad news since Monday has done nothing to ease concerns.
Tadao Yabe, a local Kashiwazaki lawmaker, said the latest developments would boost anti-nuclear opposition among residents. "I think people are really fed up. When they saw flames rising from that fire, they must have said: 'That's it.'," Yabe told Reuters this week.
Quake-proofing regulations for nuclear power stations -- which supply about one-third of the resource-poor country's electricity -- were tightened last year, requiring utilities to reassess risks to the nation's 17 nuclear power plants.
"The latest earthquake has underscored the need for power companies to review in earnest their nuclear-power plants ability to withstand seismic tremors," said the Japan Times newspaper. "Their reviews must proceed with public transparency."
TEPCO first said there had been no radiation leaks from the quake, which caused a small fire, but later revealed that 1,200 litres (317 U.S. gallons) of radioactive water had leaked into the ocean.
On Tuesday, it said there had been about 50 problems including a minor radiation leak into the atmosphere.
Then on Wednesday, the utility revised up the amount of radiation in the leaked water, but added that the amounts were still too small to harm people or the environment.
Anti-nuclear activists have charged for decades that the Kashiwazaki-Kariwa plant was unsafe.
In 2005, the Tokyo High Court rejected a demand by residents that a 1977 permit to build the first reactor at the plant be revoked because a safety review had been insufficient and there was an active fault nearby.
TEPCO has asked six utilities for electricity to help replace lost production, but media said power cuts were possible later in the summer as the plant was unlikely to be back in action soon.
TEPCO said supplies were sufficient for now, especially since the weather has been unseasonably cool, but that the utility might restart unused thermal plants if needed.
"We would like to ask for as much electricity as possible from each utility," Kaoru Yoshida, TEPCO's corporate communications manager told reporters.
TEPCO added it would consider asking other utilities for help. The six companies it has already asked are: Tohoku Electric Power Co., Kyushu Electric Power Co., Chugoku Electric Power
Co., Shikoku Electric Power Co., Chubu Electric Power Co. and Kansai Electric Power Co.