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

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.

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

At the live webcast Sacramento legislative hearing on Monday, California lawmakers grilled officials from both plants. The interchange drew sparks as state senators pushed hard for explanations about such safety issues as a plugged plant valve that went undetected at Diablo Canyon for 18 months. Plant officials defended their disaster-readiness plans, noting that the valve could have been opened by hand in an emergency.

Representatives from both facilities said they could withstand the maximum events predicted for their sites. But wary legislators weren’t buying such confidence.

"In light of the disaster in Japan, I think the average person's response is: We should be safer," said state Sen. Christine Kehoe (D) of San Diego. "They weren't expecting a 9.0 earthquake."

Pacific Gas and Electric (PG&E), which runs the Diablo plant, has begun its relicensing process, despite the fact that current NRC licenses for the two reactors don’t expire until 2024 and 2025.

That’s a bad move, considering the discovery two years ago of a previously unknown fault just a half mile from the plant, says state Sen. Sam Blakeslee (R) of San Luis Obispo, who wants the utility to withdraw its license application until new studies have assessed the potential damage from this new discovery.

"I'm concerned mostly about this culture of disregard of risk," Senator Blakeslee, who has a doctorate in geophysics, told the panel. "It's potentially putting my constituents in a place of great risk."

Lloyd Cluff, PG&E's director of earthquake risk management, defended the facility’s approach to as-yet-unknown dangers.

"There's uncertainty in everything," Mr. Cluff said, pointing out that their disaster modeling took unforeseen events into account. "We don't see a concern about the uncertainty," he added.

Senator Kehoe turned her fire on Southern California Edison, who run the San Onofre plant, in addressing what she considers complacency about the maximum events contemplated in the plant design.

While San Onofre is built to withstand a magnitude 7 earthquake, no reassessment had been done in light of a 7.2 quake – just across the Mexico border – in April 2010.

Caroline McAndrews, director of licensing for the San Onofre plant, says, "We do evaluate for the probability of those larger earthquakes," McAndrews said, "and we have confidence."

The NRC cited the San Onofre plant for “serious issues” two years ago, notes USC’s Meshkati, “and after people raised questions, they came up with what I call ‘reasonable’ or ‘satisfactory’ answers, but – satisfactory isn’t good enough. They have to go above and beyond.”

After such disasters as Three Mile Island and Chernobyl, the modern nuclear industry is exceptionally safe, with multiple redundancies and backup plans for emergencies, says Gwyneth Cravens, author of “Power to Save the World: The Truth About Nuclear Energy.” As the technology continues to improve, she says, the most pressing issue is human error. Wakeup calls, even though framed by such human tragedy as the events unfolding in Japan, are what the industry needs to further training.

“Human engineering is a big issue,” she says.

It is too early to assess all the lessons of the Fukushima crisis for the US nuclear industry, says Meshkati, who sat on a committee that oversaw the followup to the BP Gulf Oil disaster. But if he could point to one lesson that seems to run through disaster preparedness of all sorts, he says, it is “too much confidence.”