San Onofre Unit 1, Restarted After Refueling, Requires More Repairs

Unit 1 of the San Onofre nuclear power plant was shut down for repairs just a day after it was restarted after months of refueling and scrutiny, a spokesman said Sunday.

The reactor, shut down shortly before midnight Friday, is one of three at the coastal plant in northern San Diego County, said David Barron of Southern California Edison, which operates the plant.

Faulty sensors that measure the water level in the steam generator will be adjusted over the next three weeks, he said.

“It’s new instrumentation that we added while the plant was shut down,” Barron said. “It’s a system that we couldn’t test completely until we restarted.”

Unit 1 had only been on line since just after midnight Thursday, he said.

The unit was first shut down in November for replacement of its nuclear fuel and remained out of operation over concerns about possibly cracked bolts in the thermal shield, a steel cylinder inside the reactor that is designed to protect its main wall from radiation, Barron said. Three of the 36 bolts were found to be cracked.

“The NRC (Nuclear Regulatory Commission) analyzed it and a decision was made that it would not be a hazard” and no repairs were made, Barron said.

A second reactor, Unit 2, has been shut down for about 10 days while technicians trace leaks in some of the thousands of tubes that shuttle water between the reactor and steam generator, Barron said.

Some radioactive water leaked into pipes that usually handle non-radioactive water from the steam generator, but no radiation escaped the plant, he said. The Unit 2 reactor is expected to be restarted in about two weeks.

Unit 3 reactor remains on line.