Federal regulators Tuesday disclosed they are considering changing requirements set last year to restart the San Onofre nuclear power plant in California, another potential hurdle for the company that wants to return the troubled plant to service.
The twin reactors between Los Angeles and San Diego haven't produced electricity since January 2012, when a tiny radiation leak led to the discovery of damage to hundreds of tubes that carry radioactive water.
The Nuclear Regulatory Commission last year outlined a series of steps operator Southern California Edison must take before a restart would be allowed, including determining how to stop damage to tubes in the plant's steam generators. Edison last fall year submitted a plan to restart one reactor and run it at reduced power in an effort to halt tube erosion.
But NRC Deputy Regional Administrator Art Howell said in a hearing in Dana Point the agency is considering changing those requirements "as needed." He didn't elaborate.
Meanwhile, the NRC announced it was preparing a fresh round of technical questions for the company about its restart proposal.
Edison spokeswoman Jennifer Manfre said in an email the company "will continue to respond to all questions and requests for information throughout this entire, thorough process."
Last year, federal officials blamed a botched computer analysis for design flaws that they said are largely to blame for unprecedented wear in tubes at the plant. They found a computer analysis by Mitsubishi Heavy Industries, which manufactured the generators, vastly misjudged how water and steam would flow in the reactors.
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Gradual wear is common in steam generator tubing, but the rate of erosion at San Onofre stunned officials because the equipment, installed in a $670 million overhaul in 2009 and 2010, is relatively new.
The NRC last week began investigating claims by Sen. Barbara Box, D-Calif., and Rep. Edward Markey, D-Mass., that Edison was aware of generator problems linked to the 2012 tube break. The company disputed the account.
The generators, which resemble massive steel fire hydrants, control heat in the reactors and operate something like a car radiator. At San Onofre, each one stands 65 feet high, weighs 1.3 million pounds and has 9,727 U-shaped tubes inside, each three-quarters of an inch in diameter.
Overall, NRC records show investigators found wear from friction and vibration in 15,000 places, in varying degrees, in 3,401 tubes inside the plant's four generators, two in each reactor.
The plant is owned by SCE, San Diego Gas & Electric and the city of Riverside.
