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Critics cite 'severe seismic risk' at California nuclear power plants

State and federal legislators voice concerns about the earthquake risk at two California nuclear power plants – as well as the adequacy of safety protocols in place there.

By Staff writer / March 22, 2011

A March 17 aerial view of the Diablo Canyon Nuclear Power Plant, which sits on the edge of the Pacific Ocean in California's San Luis Obispo County. State and federal lawmakers have challenged the earthquake preparedness California's two nuclear power plants, as recent evidence indicates that both are in regions more seismically active than previously believed.

Mark Ralston / AFP Photo / Newscom

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Los Angeles

California legislators at the state and federal levels are ratcheting up pressure on the Golden State’s two operating nuclear power plants – both, like Japan’s stricken Fukushima I, located in seismically active regions near the Pacific coastline.

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California’s nuclear power plants – one in San Onofre, just north of San Diego, and the other in Diablo Canyon, near San Luis Obispo – together provide nearly 15 percent of the state’s electricity. Scientists and nuclear industry watchdogs note that the aging facilities began operations in the 1980s and have both been cited for maintenance and safety issues in recent years.

At a legislative hearing Monday, state lawmakers challenged what they called the overconfidence of engineers and plant employees, pointing out that Japan’s earthquake was many times worse than Fukushima’s safety measures had been designed to withstand. They also raised concerns that recent geological evidence indicated a higher earthquake risk for both plants than their designers anticipated.

In the wake of the Fukushima I disaster, “we really need to go back and take a hard look at safety assumptions for systems and safety practices in the plants themselves,” says Naj Meshkati, a professor of civil and environmental engineering at the University of Southern California Viterbi School of Engineering.

Japanese plants, like US plants, are designed to withstand extreme events based on projections from past quake and tsunami action in the affected regions, he notes. Engineering for Fukushima I anticipated a maximum 7.8 quake and 6.5 meters (21 feet) wave height. “But of course, the quake was much more powerful and the waves came in half a meter higher than the plant design,” says Professor Meshkati.

US Sens. Barbara Boxer and Dianne Feinstein, both California Democrats, sent a letter on March 16 to the Nuclear Regulatory Commission calling for a “thorough inspection” of the two plants and asking detailed questions about the plants’ preparedness as well as the NRC’s oversight and enforcement of known concerns.

“New information about the severe seismic risk at the San Onofre Nuclear Generating Station and the Diablo Canyon Power Plant make clear that these two plants require immediate attention in light of the catastrophic events in Japan,” said Senator Boxer in a statement.

The NRC "will be working on short term and long term analysis of the information we gather from the Japan incident," writes spokeswoman Lara Uselding in an e-mail.

“US nuclear power plants are built to withstand environmental hazards, including earthquakes and tsunamis,” adds Ms. Uselding. “The NRC requires that safety-significant structures, systems, and components be designed to take into account the most severe natural phenomena historically reported for the site and surrounding area.”

Sacramento hearing

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