San Onofre

Because of continuing problems with internal leakage of radioactivity-contaminated water, newly designed seals will be installed on the cooler pumps of San Onofre Nuclear Generating Station Unit 3 reactor, which closed Tuesday for four weeks of maintenance work.

Unit 3 has four large reactor cooler pumps that circulate water, and each pump has a series of seals designed to keep the pump from leaking. These seals have been replaced six times in the last three years, said David Barron, communications representative for Southern California Edison Co.

“There’s leakage of water with radioactive contaminants within the pump and within the plant’s interior environment, but not the exterior environment,” Barron said. “There has been no exposure of radiation to plant employees or to the general public. This is not an accident condition. They simply reached the point where we needed to replace them.”

The station’s other two units will remain in service, and the closure of Unit 3 is not expected to affect the power supply in any way, Barron said.

“We are replacing the old seals with a new design of seals which we expect will last substantially longer,” Barron said. “We installed these newly designed seals on the Unit 2 reactor six months ago, and we haven’t had to replace them yet. We have every indication that they are much more reliable.”