The operator of the recently retired San Onofre Nuclear Generating Station has been cited by nuclear safety regulators for failing to properly check the design of faulty replacement steam generators that disabled the plant.
The violation notice from the Nuclear Regulatory Commission carries no explicit penalties but complicates efforts by Southern California Edison to recover an array of plant costs and remaining assets on behalf of its shareholders. The California Public Utilities Commission is considering an initial $94 million refund to customers of Edison and minority plant owner San Diego Gas & Electric, with more extensive plant costs still under review for additional and possibly larger refunds.
Edison has 30 days to appeal the nuclear commission’s determination.
“We will evaluate the final determination letter from the NRC and respond within 30 days with appropriate corrective actions,” Edison spokeswoman Maureen Brown said in an email.
The violation notice has the potential to undermine Edison’s assertions before the state utilities commission that it acted prudently and made no specific mistakes, said Matthew Freedman, attorney for The Utility Reform Network, a San Francisco-based consumer advocacy group.
“Edison is arguing with every fiber of their being that they are the victims and did nothing wrong,” Freedman said. “This kind of contradicts their version of events.
“If they are found to be imprudent, then there are a whole host of costs that can be disallowed. That’s the trigger for a billion-plus dollars of pain for them.”
San Onofre stopped producing power in January 2012 when a small radiation leak was detected and traced to rapid wear among steam generator tubes carrying radioactive water. The plant’s twin reactors were retired in June.
The Nuclear Regulatory Commission found that, contrary to regulations, “design control measures were not established to provide for verifying and checking the adequacy of certain designs.”
Edison has laid the blame for the plant’s problems on generator manufacturer Mitsubishi Heavy Industries of Japan and botched computer calculations that underestimated steam velocities within the generators, installed in 2010 and 2011.
Rosemead-based Edison is seeking damages from Mitsubishi through binding arbitration. Mitsubishi is defending the limits of its $137.5 million warranty for its four replacement generators. Attempted repairs, consultants and replacement power have raised disputed costs to well over $1 billion.
Nuclear commission spokesman Victor Dricks said the violation notice itself, first outlined in a September draft, carries no penalties or sanctions.
The plant shutdown was determined to be of “low to moderate safety significance” in the federal nuclear agency’s final assessment, following 16 months of on-site inspections and detailed analysis at regional commission offices in Texas and headquarters in Maryland.
U.S. representatives for Mitsubishi were not immediately available for comment. Mitsubishi was faulted by the commission in September in a “notice of nonconformance” related to flawed computer codes used in the design of the replacement generators.
Mitsubishi says a generator design team that included Edison experts believed that vibrations had been addressed by installing additional tube supports. Mitsubishi contends it could not have anticipated the unprecedented type of tube vibrations that occurred in the exceptionally large generators commissioned by Edison.
Warnings emerged as early as 1983 in research showing tube supports might not guard against the type of vibrations that turned up at San Onofre. Faults in Mitsubishi’s design code were applied at four other plants, with none showing the problems seen at San Onofre.
|Title||SPENT, BUT NOT GONE -- With no final destination, used nuclear material stays at San Onofre indefinitely|
|Keywords||Shut San Onofre|
|Media Type||Linked Article|
|Author Name Sortable|