By Angela Lau UNION-TRIBUNE STAFF WRITER

SAN ONOFRE – The nuclear power plant shut down its nuclear reactors this week after discovering faulty gaskets in some of its backup water tanks used to cool reactors in an emergency.

No leaks of radioactive material occurred, and the power plant's electricity customers continued to receive power from backup sources in and out of California, San Onofre Power Plant spokesman Ray Golden said. No blackouts were necessary.

The San Onofre Power Plant supplies 2,100 megawatts of electricity each day to 2 million households in San Diego, Orange and Los Angeles counties, he said.

Yesterday, Nuclear Regulatory Commission spokesman Victor Dricks said such gasket failures happen from time to time at nuclear power plants and are not a cause for concern if they are detected and repaired.

At San Onofre, crews noticed a faulty gasket on Monday in a backup water tank to one of the power plant's two reactors. That reactor had been shut down since January for refueling and maintenance.

Each reactor has four backup water tanks. Each tank carries 13,000 gallons of water, with 600 pounds of nitrogen gas on top to keep the water down in the tank. The backup water is released only when reactors run low on water because of leaks and need the backup to cool them down, Golden said.

After discovering the first worn gasket, San Onofre workers checked the other three backup water tanks and found their gaskets slightly worn. The plant abandoned plans to restart that reactor on its scheduled day, Tuesday, until it has replaced all four gaskets, Golden said. It will restart in a week or so.

As a precaution, the plant also shut down the other reactor at 4:30 a.m. Wednesday. It already was scheduled for a 30-day maintenance shut-down at the end of next month, to prepare for peak summer demand, Golden said.

Just last month, San Onofre was in the news when a contractor's tanker carrying radioactive wastewater from San Onofre to a Utah dump site leaked at a Utah truck stop because of a faulty gasket. An investigation is continuing.

Angela Lau: (760) 476-8240; angela.lau@uniontrib.com

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