March 8 (Bloomberg) -- Kansai Electric Power Co., Japan's second-biggest utility, said it closed the No. 3 reactor at its Ohi nuclear power plant today after a water leak was found.

The 1,180-megawatt reactor was shut down at 5:02 a.m. local time, spokesman Kimihito Kawabata said in a telephone interview.

``The water may have been radioactive,'' Kawabata said. ``We're going to check that out and find where the leak originated by closing the unit.''

Staff at the Osaka-based utility found the leak in the coolant drain-tank room of the reactor's containment vessel at about 3:50 p.m. yesterday, he said. None of the water leaked outside the reactor.

Separately, Kansai Electric plans to restart the No. 1 reactor at its Mihama plant at about 10 p.m. today, Kawabata said. The 340-megawatt reactor was closed on Feb. 4 after a water leak was discovered in the unit's turbine room.

Kansai Electric has 11 nuclear reactors at three power plants in Japan's central prefecture of Fukui, on the Japan Sea coast.

To contact the reporter on this story: Meggan Richard in Tokyo at mrichard3@bloomberg.net.

Last Updated: March 7, 2005 20:28 EST