Federal regulators say one of several batteries used to supply power to San Onofre nuclear power plant safety systems didn't work for four years. But the company that operates the plant says the other batteries would have powered the safety system. KPBS Environmental Reporter Ed Joyce explains.
The Nuclear Regulatory Commission says inadequate maintenance procedures were to blame and the lapse is troubling because the condition persisted for so long.
The NRC says the loss of even one emergency battery reduced the plant's safety margins.
The agency says the battery was inoperable from 2004 to 2008.
Southern California Edison spokesman Gil Alexander says the battery's connections were not tightened to federal standards.
Alexander: The battery is part of a system of nine batteries that provide backup power in the event that all other electricity on the site and to the San Onofre site is unavailable. This would be a catastrophic earthquake for example.
Alexander says there was no danger to the public or employees during the four years the connections to the battery were not as tight as required.
He says other emergency batteries were available to supply power to plant safety systems.
Ed Joyce, KPBS News.