Edison, consultant spar over blame for San Onofre shutdown
A document released Monday by the U.S. Nuclear Regulatory Commission shows that Southern California Edison informed the federal agency of a number of planned design changes before it replaced the plant's four steam generators.
A consultant who has alleged that Edison sidestepped review of the design changes said, however, that the document left out some key points.
The new steam generators, installed in the last couple of years at an estimated price tag of $671 million, have become a major source of issues in recent months. On Jan. 31, a tube carrying radioactive water sprang a leak. The plant was powered down and has remained offline since.
Inspections have since found that hundreds of other tubes were wearing out more quickly than they should. More than 1,300 of the plant's nearly 39,000 tubes have been taken out of service because of excessive wear, apparently caused by the tubes vibrating and rubbing against support structures and other tubes.
A report by consultant Arnie Gundersen, commissioned by the environmental group Friends of the Earth, argued that the problems were a result of design changes and that Edison sidestepped a thorough review of the replacement project by misleading the NRC about the extent of those changes.
He argued that the decision to increase the number of tubes in each steam generator by 377 led to a series of "cascading design changes" that resulted in the excessive vibration that apparently caused the tube wear.
Edison officials have insisted that they kept the NRC fully informed.
In the document released Monday, part of a presentation at a June 2006 meeting between Edison and NRC officials about the steam generator replacement, the utility company outlined several design changes, including the increased number of tubes, a change in the metal used to make the tubes and larger surface area.
Gundersen said the report omitted the fact that the stay cylinder, a support pillar, was removed and that the walls of the tubesheet, a metal cylinder near the bottom of the steam generator, were thickened. He said the changes were significant and the NRC should have been informed.
"It looks like from the slide [Edison] mentioned all the good news and weren't telling the bad news," he said.
An Edison spokesperson said the utility followed established guidelines and Nuclear Regulatory Commission regulations and was "rigorous" in making sure those regulations were met.
NRC spokesman Victor Dricks said Edison had informed the agency of the steam generator design change and that NRC inspectors had reviewed portions of the engineering design change evaluation and observed the installation and testing of the steam generators.
He added that a "primary objective" of a special NRC inspection team that was dispatched to San Onofre after the tube wear issues surfaced is to "review the steam generator design changes to ensure they were properly reviewed and approved by the agency."
-- Abby Sewell
Photo: A surfer stands near the San Onofre nuclear plant. Credit: Los Angeles Times