Japan shuts units at top nuclear plant after quake

TOKYO (Reuters) - Tokyo Electric Power Co. shut down three major generators at the world's biggest nuclear power plant after a powerful earthquake in Japan on Monday caused a brief fire in one of the units, company officials said.

TEPCO, Asia's biggest utility, added that 1.5 liters of water containing radioactive materials had leaked from a unit closed for maintenance at the Kashiwazaki-Kariwa nuclear power plant.

The contaminated water was released into the ocean and had had no effect on the environment, TEPCO said in a statement. The company had previously said there had been no radiation leaks at the plant, where reactors automatically shut down for checks.

The leak was from the shut-down No.6 unit, which has a capacity of 1.356 million kilowatts. The fire had been sparked in a transformer linked to another unit, No.3.

TEPCO could not say when the three units that had tripped offline after the quake would be restarted, but an official said it had no immediate plans to increase operations at oil- or gas-fired power plants to make up for the lost capacity.

"We have plenty of power supplies to cover needs for this week between Tuesday and Sunday," a company official said. "We'll study the situation closely to decide on our plans beyond next week."

Restarting other power units could boost oil, gas or coal consumption by Japan's power industry, which is closely watched by energy traders after maintenance scandals forced a series of nuclear shutdowns that increased use of other fuels.

The magnitude 6.8 quake struck at 10:13 a.m. (0113 GMT) on a holiday Monday in Japan, killing at least four people in the same area as a tremor three years ago that killed 65 people.

The No.3, No.4 and No.7 power generation units at the plant, located near the centre of the quake some 250 km (155 miles) northwest of Tokyo, shut down automatically. The No.3 unit alone has a capacity of 1.1 million kilowatts.

Four more units at Kashiwazaki-Kariwa, which the company says is the world's biggest such facility, were not operating as they had been shut for maintenance, TEPCO said.

The outage comes at a time when Japan's nuclear sector, which generates about a third of its power, is already operating at unusually low levels for the peak demand summer period.

Nuclear plants at the country's 10 generators operated at an average 62.4 percent in June, up from a seven-month low of 61.9 percent in May, data by the Federation of Electric Power Companies of Japan showed last week.

But it was 7.5 percentage point lower than in June 2006, while overall power consumption rose to its highest on record for the month.

It was the weakest rate for the month of June since 2003, when the sector was in the grips of a safety scandal that forced top utility TEPCO to shut its entire fleet, causing a spike in oil consumption as back-up power plants fired up.

A new batch of safety lapses revealed this year has forced power companies to shut for additional checks this spring, dragging down utilization rates -- excluding Japan Atomic Power Co. -- to their lowest in over two and a half years in May.