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Public Safety

San Onofre Operators Begin Study On Earthquake Risk

San Onofre Nuclear Generating Station
Nuclear Regulatory Commission
San Onofre Nuclear Generating Station

Operators of the San Onofre Nuclear Generating Station are about to embark on a costly study on earthquake risk that could determine the future of the plant, it was reported today.

Southern California Edison, which operates the troubled plant just north of Camp Pendleton, is expected to spend $64 million on the seismic study, U-T San Diego reported. The study will focus on little-understood offshore faults and the risks they pose to the plant's aging reactors, which have been shut down since earlier this year.

San Onofre's two reactors, referred to as Unit 2 and Unit 3, have been offline since late January. Unit 1 was in operation from 1968 to 1992, when it was shut down over fears it would not withstand a major earthquake.


Unit 2 was taken down for planned maintenance Jan. 9 and Unit 3 was shut down abruptly on Jan. 31 after a small leak in one of the reactor's steam generator tubes was detected. The leak resulted in a small release of radioactive gas, according to Edison officials, who said neither plant workers nor the public were endangered.

Since the leak, Edison has been working with the U.S. Nuclear Regulatory Commission to complete certain benchmark inspections before the commission will allow the units to be restarted.

The impending seismic study at San Onofre comes as the regulatory commission is in the process of drafting new industry guidelines for re- evaluating earthquake risk in the aftermath of last year's meltdown at the Fukushima Daiichi plant in Japan following a massive earthquake and tsunami.

A seismic study similar to the one that will be conducted at San Onofre by Southern California Edison is already underway at the coastal Diablo Canyon plant in San Luis Obispo County. It is being conducted by Pacific Gas & Electric.

Both studies should help decide if California's two active nuclear plants are safe enough to operate into the 2040s, U-T San Diego reported. Currently, Southern California Edison is considering whether to re-license or shut down San Onofre after 2022.

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