A-Plant Foes Urge More Study on Quake Safety

Homeowners and merchants were still cleaning up broken glass and plaster Monday in the wake of Southern California’s latest earthquake--while an anti-nuclear group and one state geologist called for more study of the chance that a future temblor might damage the nuclear power plant at San Onofre.

San Diego County authorities said Sunday’s earthquake, centered in the Pacific 28 miles southwest of Oceanside, cost about $720,000 in broken windows, ruined merchandise and cracked walls, but seemed to have done no major damage to structures.

Opponents of the San Onofre nuclear plant were not reassured, however.

“This affirms what we’ve been saying for years,” said Marion Pack, director of the Orange County chapter of Alliance for Survival, an anti-nuclear group. “Putting a nuclear power plant on a major fault line is not wise.”

Found No Damage

Officials of Southern California Edison, the plant’s majority owner and operator, declared that the quake fell far short of damaging the plant and changed nothing in the utility’s assessment of the plant’s vulnerability to earthquakes.

But Michael P. Kennedy, a senior marine geologist with the state Division of Mines and Geology who has argued in the past that the entire area off Southern California’s coast is more prone to quakes than the San Onofre plant’s owners are willing to admit, said Sunday’s earthquake supports research done by him and others at the division’s La Jolla office.

“It’s very important to take another look at these faults, and to maybe not take some of the data we’ve put forward so lightly as some of the consultants did at the time of San Onofre’s licensing,” Kennedy said.

Harold Ray, Southern California Edison vice president and manager of the San Onofre plant, said the quake, which measured 5.3 on the Richter scale, was centered too far from the plant to raise much concern.

Ray said the plant, just south of San Clemente, is built to withstand a quake of 7.0 magnitude five miles offshore.

He said Sunday’s quake, and the unrelated 5.9 temblor earlier in the week near Palm Springs, set off a series of carefully planned actions by plant operators.

On Sunday, Ray said, an “unusual event” was declared at San Onofre at 7:02 a.m.--just 16 minutes after the quake struck. (An unusual event is the lowest form of emergency that can be declared at the plant; it calls for the notification of surrounding cities and counties and the federal Nuclear Regulatory Commission that there is chance of a “degradation” in plant safety.)

At Full Power

At the time of the quake, San Onofre Unit 2 was at full power and Unit 3 was at 94%. Unit 1, the oldest reactor and the one considered by critics to be most vulnerable to quakes, was shut down for repairs.

Ray said a technician in the control room immediately moved to a panel of red and orange lights that alert operators in case vibrations in the plant approach the levels the reactors were built to withstand. If the movements reach about 90% of those levels, the plant is shut down automatically.

In this case (as in all other quakes ever felt at the plant) none of the lights flashed, meaning that the vibrations did not reach even half the level for which the plant was built. An engineer later calculated that the strongest movements were between 2% and 3% of the normal force of gravity, Ray said. The plant is designed to withstand movements 30 times stronger.

Water Level Monitored

After checking for vibrations, operators monitored the level of water in the plant’s key coolant systems. Decreasing water levels in the pressurizer just outside the reactor core, for example, would be a sign that there might be a serious leak; alternatively, water levels rising in sumps at the bottom of the containment area would also indicate that a pipe had burst. On Sunday, all water levels remained normal and no leaks were detected, Ray said.

The last step in the inspection calls for workers to check seismic supports for any damage. But no damage was found Sunday, he said.

The unusual-event alert was called off at 8:01 a.m., Ray said.

Meanwhile, authorities increased the number of injuries attributable to Sunday’s quake from 15 to 29, most of them minor. Anthony Cima, 87, who was trapped for 11 hours under thousands of books that toppled on him in his room at a downtown San Diego residential hotel, was in serious but improved condition at the University of California, San Diego, Medical Center.

One death was attributed to Sunday’s temblor: Arless Wilson, 55, of Chula Vista, suffered a heart attack during the quake and died shortly after.

Seismic experts said Sunday’s quake was followed over the next 27 hours by 16 aftershocks and was preceded by a milder temblor centered about two miles north of Chula Vista.