A nuclear reactor at San Onofre Nuclear Generating Station remained off-line today due to an equipment problem that sent a small, non-hazardous amount of radioactive gas into an auxiliary building and possibly into the atmosphere, authorities said.
The leak in a steam-generator tube in Unit 3 at the power plant just north of Camp Pendleton was detected about 6 p.m. Tuesday, according to the U.S. Nuclear Regulatory Commission.
An alarm alerted station personnel to the presence of radioactivity in the ancillary structure, and they immediately began shutting down the reactor, NRC spokesman Victor Dricks said.
Since the equipment-housing building into which the gas leaked is not airtight, it is possible a "very, very low level'' of radioactivity escaped into the environment, according to Dricks, who said those traces would be "barely measurable against (existing) background levels'' and would pose no danger to the public.
SONGS crews will fully evaluate the cause of the mishap and the steps required to repair it before resuming operations, according to Southern California Edison, which operates the facility.
Once the problem is resolved, it will likely take several days for the reactor to be restarted, the Rosemead-based utility advised.
At the time of the accident, the other reactor at the plant already was powered down for routine maintenance, refueling and technology upgrades. Still, the utility had ample reserve power to meet customer needs, according to SCE officials.