Federal regulators and Southern California Edison officials met publicly for a second time Tuesday to discuss Edison's restart proposal for the San Onofre nuclear plant, which has been out of service for more than 10 months because of unexpected equipment problems.
Edison has proposed to restart one of the plant's two reactor units at 70% power. The company argues that running the unit at reduced power would alleviate conditions that led to unusual wear on tubes carrying radioactive water.
It will be months before the NRC decides whether to allow restart. A tentative NRC timeline posted on the agency's website said it would be March at the earliest before the agency decides whether to sign off on Edison's plan.
During Tuesday's meeting in Maryland, regulators posed questions on a variety of aspects of the proposal. Among other things, NRC senior materials engineer Emmett Murphy questioned whether some of the 510 tubes in reactor Unit 2 that have been deactivated and plugged could eventually pose problems.
Some of the tubes, Murphy pointed out, "are adjacent to a retainer bar that vibrates, and this vibration was the cause of wear in some tubes." In the long term, he said, the plugged tubes could wear through and break, damaging other tubes.
Edison officials promised to address the concern in their response to the NRC questions.
Regulators also posed questions about an upgraded loose parts monitoring system that Edison has proposed to install. Richard Stattel of the NRC's instrumentation and controls branch said it was unclear how the system would contribute to added safety, since it is only capable of historical analysis and unable to detect tube wear as it occurs. Mike Short, a consultant for Edison, responded that the company had not intended to characterize the system as performing a preventive safety function.
Edison officials promised that they would prepare a response to the questions posed by commission staff by mid-January.
Another meeting between regulators and the company is tentatively scheduled for mid-February.
This story was reported by Times Staff Writer Abby Sewell.