Feds: Calif. Nuke Plant to Remain Shut for Probe The troubled San Onofre nuclear plant in Southern California will remain shut down until federal regulators can determine why tubes carrying radioactive water in the plant's massive generators are rapidly decaying. The announcement Tuesday formalized an agreement with operator Southern California Edison on the same day that a report commissioned by an environmental group claimed the utility misled the Nuclear Regulatory Commission about design changes that are the likely culprit in excessive tube wear. A four-page letter from NRC Regional Administrator Elmo E. Collins laid out a series of steps Edison must take before restarting the seaside reactors located 45 miles north of San Diego. Elmo wrote that the problems in the generators must be resolved and fixed and "until we are satisfied that has been done, the plant will not be permitted to restart." The plant's four steam generators each contain nearly 10,000 alloy tubes that carry hot, pressurized water from the reactors. The Unit 3 reactor was shut down as a precaution in January after a tube break, and extensive wear was found on similar tubing in its twin, Unit 2, which has been shut down for maintenance. Authorities in California have been scrambling to find additional power in case the reactors remain off-line through summer, when energy use typically peaks. That could include restarting retired plants in Huntington Beach in northern Orange County. FILE - This file photo taken June 30, 2011, shows beach-goers walking on the sand near the San Onofre nuclear power plant in San Clemente , Calif. The utility that runs California's San Onofre nuclear plant misled federal regulators about equipment and design changes that are the likely cause of problems with tubing that carries radioactive water, a report commissioned by an environmental group claimed Tuesday March 27,2012. (AP Photo, Lenny Ignelzi, File) Close The company has found that the tube wear is being caused by vibration and friction with adjacent tubes and bracing, however investigators don't know why that's happening. The company "has been committed from the beginning to not returning Unit 2 or Unit 3 to service until we are satisfied it is safe to do so," SCE spokeswoman Jennifer Manfre said in a statement. The problems have raised questions about the integrity and safety of replacement generators the company installed at the two reactors in a multimillion-dollar makeover in 2009 and 2010. The report by nuclear consultants Fairewinds Associates warned that a more detailed study is needed on the alloy tubing in the generators before the reactors are restarted. The study was produced for nuclear watchdog Friends of the Earth and was authored by engineer Arnie Gundersen, a former nuclear industry executive who was a licensed reactor operator. A series of equipment and design changes to the generators "created a large risk of tube failure at the San Onofre reactors," the report found, citing a review of publicly available records. It said the rapid tube wear can raise the potential for an accident that could release radioactivity. Among the modifications, the report said the tube alloy was changed, bracing was redesigned and more tubes were added. It said the company never disclosed that such extensive changes were made, instead describing it as an exchange of similar equipment that allowed SCE "to avoid the requisite NRC oversight of a steam generator replacement." Manfre, the company spokeswoman, said SCE provided "open and transparent information" to the NRC. Agency spokesman Scott Burnell said in a statement that the agency was aware of the design changes.