No timetable has been set for the restart of the San Onofre Nuclear Generating Station (SONGS) despite “erroneous reports” in the media that referred to June dates, Nuclear Regulatory Commission (NRC) Chair Gregory Jaczko said on Monday.
“We have yet to receive the utility’s written response documenting their completion of actions described in the March 27 Confirmatory Action Letter, so any discussion of a date for the restart of Unit 2 or Unit 3 is clearly premature,” Jaczko said in a statement on Monday. “Once we receive their response, we will take whatever time is necessary to conduct a thorough safety review.”
Southern California Edison (SCE) reaffirmed the NRC head’s statement in a separate report, issued jointly with regional grid operator the California Independent System Operator Corporation (ISO). “Those dates were provided by SCE to the ISO as a purely administrative matter in March of 2012 because, for long-range planning purposes, ISO requires an estimated return to service date to be posted. These dates are for planning purposes only and are subject to change,” it said.
SONGS Unit 2 was taken out of service for a planned outage on Jan. 9. Unit 3 had been shut down since Jan. 31, when it was safely taken off line after station operators detected a leak in one of the unit’s steam generator tubes. Inspections of some of the tubes inside the Unit 2 and 3 steam generators showed areas of tube wear.
In a more recent update, SCE said it identified a wear mechanism caused by tubes that were vibrating and rubbing against adjacent tubes. “Tube wear was also observed where tubes had rubbed against certain supports in both units. The company continues to analyze inspection and test data, and is conducting additional inspections to determine why these wear mechanisms are occurring,” SCE said.
To date, SCE has conducted in-situ pressure testing on 129 tubes in Unit 3 after initial inspections identified tube-to-tube wear. A total of eight tubes failed certain tests, and additional tube wear was identified in two of the 19,454 tubes in the Unit 2 generators that was similar to the type of wear previously seen in Unit 3. The company has plugged a total of 510 tubes in Unit 2 steam generators and a total of 807 tubes in Unit 3.
Sources: POWERnews, NRC, SCE, CAISO