A federal report Tuesday concluded that the Nuclear Regulatory Commission missed opportunities to spot potential trouble with an equipment swap that led to the installation of faulty machinery in a Southern California nuclear power plant.
The San Onofre plant, located between Los Angeles and San Diego, was closed for good last year by Southern California Edison after a battle over whether it was safe to restart. The plant had been idle since January 2012, after a small radiation leak led to the discovery of unusual damage to hundreds of tubes inside virtually new steam generators.
In a 55-page report, the NRC's Inspector General said a 2009 agency inspection failed to recognize "shortcomings" in the way the replacement of the huge steam generators was evaluated. It also raised questions about why Edison was allowed to install the new generators without seeking a change in its federal operating license.
Edison installed the generators under a frequently used rule that allows plant operators to replace equipment without prior NRC approval, provided they can show the switch doesn't cause significant changes to plant operation or safety.
The generators that were installed during a $670 million overhaul in 2009 and 2010. After the plant was shut down, tests found some generator tubes were so badly worn that they could fail and possibly release radiation, a stunning finding inside the nearly new equipment.
The report noted that NRC experts, who reviewed how the swap was evaluated after the plant was shut down, questioned whether there was sufficient evidence to sidestep a license amendment, which can involve a thicket of hearings, appeals and commission actions on safety and design issues that can take months or years to complete.
Although some details remain unclear, the report said there is "no assurance the NRC reached the correct conclusion" in its 2009 inspection that a license amendment wasn't needed to replace the generators.
Edison is reviewing the report and had no immediate comment.
The former top NRC official in the West, ex-Regional Administrator Elmo Collins, told inspectors that given what is now known the "steam generators as designed were basically licensable. We wouldn't approve them."
Sen. Barbara Boxer, a California Democrat who chairs the Environment and Public Works Committee, faulted both the agency and the company.
"When Southern California Edison decided to completely replace their steam generators in order to increase their profit margin, they failed to apply for an amended license as they are required to do, and NRC stood by and did nothing," she said in a statement.
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 stood 65 feet high and weighted 1.3 million pounds.