There was a security violation at the San Onofre power plant after operator Southern California Edison declined to contest the finding.
The company failed to develop procedures to monitor electronic devices related to security, but withheld further information because of security concerns, said the Nuclear Regulatory Commission (NRC).
The commission is still determining the appropriate response to the violation. Edison said it corrected the problem, which it reported in 2011 to regulators.
“We corrected this deficiency last year when we discovered it and have implemented best practices for information security to ensure it doesn’t happen again,” said Pete Dietrich, chief nuclear officer at the plant.
The NRC conducted an inspection at the plant in May to gather more information about the security lapse.
The San Onofre plant in northern San Diego County normally supplies about 20 percent of the region’s electricity but has been offline since January because of an equipment failure.
Right now, the tab to repair the San Onofre nuclear power plant in California is at $165 million and counting.
It could cost $25 million more to get one of the damaged reactors running at reduced power, officials said.
Financial records released by Edison International — the parent company of operator Southern California Edison — provided an assessment of the troubles at the seaside plant, where malfunctioning steam generators damaged scores of tubes that carry radioactive water. The plant has not produced power since January.
Edison International Chairman Ted Craver left open the possibility the heavily damaged generators in the Unit 3 reactor might end up scrapped. It’s also possible the plant will never return to its full output of electricity, unless they replace four generators.