About 105 gallons of coolant water containing radioactive material leaked from an inactive nuclear power reactor in western Japan, but there was no danger of radiation escaping the plant, its operator said Tuesday.

The leak was discovered by a worker who rushed to the scene after an alarm went off Tuesday afternoon at Reactor No. 3 of the Mihama nuclear power plant, about 200 miles west of Tokyo, according to Kansai Electric Power Co. spokesman Hiroshi Toshikiyo.

CountryWatch: Japan

The water spilled from the primary coolant tank into a catchment area, and seven gallons then spilled onto the surrounding floor, Toshikiyo said.

No radiation leaked outside the compound, and no one was exposed to radiation, Toshikiyo said.

The cause of the leak was under investigation, but it appeared that workers had improperly attached a pipe to the tank, Toshikiyo said.

The reactor has been closed since August 2004 after a corroded pipe ruptured and sprayed plant workers with boiling water and steam, killing five and injuring six others in the country's worst nuclear plant accident. There was no radiation leak then.

The government in December said Kansai Electric could restart the reactor, saying the pipe had been repaired in line with government safety standards. The energy company has been carrying out checks since then, but the plant has yet to resume operations.

Resource-poor Japan is heavily dependent on its nuclear program, with the country's 52 active nuclear reactors supplying 35 percent of its electricity. The government has said it wants to raise the figure to nearly 40 percent by 2010.

But the public has grown increasingly wary of the nuclear power industry following a series of safety problems, shutdowns and cover-ups.

In 1999, an accident at a reprocessing plant north of Tokyo killed two workers and exposed hundreds to radioactivity. That accident was caused by two workers who tried to save time by mixing excessive amounts of uranium in buckets instead of using special mechanized tanks.