

Nuclear Regulatory Commission Chairman Gregory Jaczko, who toured the shuttered San Onofre nuclear plant Friday, assured reporters that the plant would not restart until officials understand the root cause of the cause of systems failures that forced the plant's closure.

Jaczko made a trip, accompanied by Sen. Dianne Feinstein and Rep. Darrell Issa (R-Vista), to tour the plant and talk to Edison officials about the unexpected wear in steam generator tubes that carry radioactive water in the plant's two working reactor units.

The steam generators at both of the plant's reactor units were installed within the last two years, at a cost of $671 million.

"The issue of the steam generators is a very serious issue, we take it seriously, and after some very frank discussions today, I can say that Southern California Edison takes it seriously, too," Jaczko told reporters.

The plant has been out of commission since a tube in the Unit 3 reactor, where the steam generators were installed about a year ago, sprung a leak and released a small amount of radioactive steam. Since then, Edison, the plant's operator, has found unexpected wear in more tubes at both of the reactor units, and eight tubes in the Unit 3 reactor have failed pressure tests.

The tubes in Unit 2, which was already offline for planned maintenance when the issues were discovered, also showed wear, and 192 were taken out of service.

Jaczko called the wear, particularly in Unit 3, highly unusual for such new equipment.

"It's certainly a very unique phenomenon, and particularly in Unit 3," he said.