The Nuclear Regulatory Commission (NRC) on Dec. 24 formally issued a Notice of Violation to Southern California Edison (SCE) for failing to properly vet the design of replacement steam generators at the San Onofre Nuclear Generating Station in California. The steam generators later developed excessive tube wear, forcing SCE to shut down the plant in early 2012. It retired San Onofre for good this past June after concluding that further efforts at repair and restart would be too expensive.
Previous investigations had found that Mitsubishi Heavy Industries (MHI), which supplied the steam generators, used a flawed computer model that did not adequately predict tube vibration. In a draft of the proposed enforcement action released in September, NRC officials found that during the design process in the early 2000s, SCE personnel repeatedly questioned “the results from and appropriateness of using” the model but ultimately accepted the design anyway, even though MHI never adequately addressed the concerns SCE engineers had raised. “As a result,” the NRC said, “replacement steam generators were installed at San Onofre with a significant design deficiency, resulting in rapid tube wear of a type never before seen in recirculating steam generators.” The final decision to issue the Notice of Violation came last week.
Though the notice carries with it no fines or penalties, the action is sure to complicate the ongoing wrangling over SONGS’s decommissioning. SCE is locked in battles with both MHI over its warranty claim for the faulty steam generators and the California Public Utility Commission (CPUC) over recovery of costs stemming from the 2012 shutdown. The CPUC in November proposed ordering a nearly $100 million refund to ratepayers after finding that SCE’s “single-minded” drive to restart the plant “was the result of an unsound decision-making process.” Further refunds—which may run into hundreds of millions of dollars, according to a CPUC statement—are still under review.
SCE spent more than $1 billion on inspections, repairs, and replacement power after Unit 3 was forced to shut down following a tube rupture in January 2012. It has thus far argued that it was the victim of faulty components supplied by MHI, but the NRC action spreads the blame across both companies.
SCE has 30 days to respond to the Notice of Violation.
—Thomas W. Overton, JD, gas technology editor (@thomas_overton, @POWERmagazine)