Environmental group faults design changes in San Onofre shutdown
An environmental watchdog group is alleging that unusual wear in the San Onofre nuclear power plant's steam generator tubes stems from design changes that were made in order to fit more tubes into each steam generator.
The group's second report on the situation at the nuclear plant came a day after plant operator Southern California Edison said that some tubes in both of the plant's reactor units are showing the same pattern of wear, apparently caused by tubes vibrating and rubbing against each other.
Officials had previously said that the cause of the tube wear in the two units appeared to be different, although tubes in both units showed deterioration that wouldn't be expected, since the current steam generators were installed in the last two years.
Because of the tube issues, which federal officials said could pose a safety threat if the plant continued to operate, San Onofre has been shuttered since Jan. 31.
The Friends of the Earth report, written by consulting group Fairewinds Associates, argues that a series of "cascading design changes" resulted from the decision to add 377 more tubes into each steam generator, including modifications to the support structures for the tubes and changes to the pressure and rate of water flow.
The alloy used in the tubes was also changed, but the report noted that the alloy currently being used is common in newer steam generators and generally extends the life of the tubes.
The group alleged that Edison sidestepped a full U.S. Nuclear Regulatory Commission review of the changes by representing the new steam generators as being essentially like the ones they replaced. Edison and Nuclear Regulatory Commission officials have said the design changes were disclosed.