Nuclear risksSeismic faults make Diablo Canyon a nuclear catastrophe in waiting: Experts

Michael Peck, a senior instructor at the Nuclear Regulatory Commission’s (NRC) Technical Training Center in Tennessee, and who for five years was the lead on-site inspector at California’s Diablo Canyon, the state’s last operating nuclear plant, has urged regulators to shut down the plant until it can be determine whether the facility’s nearly 30-year-old twin reactors can withstand shaking from any one of several nearby earthquake faults.

ABC Newsreports that in a forty-two-page confidential report obtained by the AP, Peck says that the NRC has not been applying the safety rules it once set out for the plant’s operation, even though the agency acknowledges that it has become clear that earthquakes pose a risk to the plant. Continuing to run the reactors, Peck writes, “challenges the presumption of nuclear safety.”

In 2008 authorities discovered the Shoreline fault, which lies about 650 yards from the plant’s reactors. Surveys have mapped a network of other faults around the reactors. According to Peck’s filing, Diablo Canyon’s owner Pacific Gas and Electric Co. released research in 2011 that determined that any of the three nearby faults — the Shoreline, Los Osos, and San Luis Bay — is capable of producing significantly more shaking during an earthquake than was accounted for in the design of the plant’s most vulnerable equipment.

After reviewing the PG&E research, Peck urged the NRC to shut the facility until operators can prove that piping, reactor cooling, and other systems can meet higher stress levels, or until the NRC can approve exemptions that would allow the plant to operate.

The NRC allowed the plant to operate without assessing the new findings, and in response, Peck filed a formal objection, calling PG&E to be cited for violating safety standards. Within weeks, the NRC refuted Peck’s filings, saying the plant was being operated safely. In 2012 the NRC endorsed preliminary findings that found shaking from the Shoreline fault would not pose additional risk for the plant’s reactors. The agency added that those greater ground motions were “at or below those for which the plant was evaluated previously,” referring to the Hosgri fault, which had been discovered in the 1970s, about three miles away, after the plant’s construction permits had been issued. In 2013, Peck filed another objection.

Diablo Canyon produces electricity for more than three million people annually and supporters who want to keep the plant open fear that closing the plant for upgrades would be too costly, and may lead to permanent closure. The Humboldt Bay plant in Northern California, which was within 3,000 yards of three faults, was closed in 1976 to refuel and reinforce its ability to withstand earthquakes, but restarting it became more difficult and costly than projected, so it never reopened.

PG&E spokesman Blair Jones assures that the NRC has confirmed Diablo Canyon as “seismically safe,” noting that the core issue involving earthquake ground motions was resolved in the late 1970s with seismic retrofitting. After Japan’s 2011 Fukushima Dai-ichi nuclear plant disaster in which a magnitude-9 earthquake and tsunami destroyed the plant’s power and cooling systems, the NRC has since ordered U.S. nuclear plants to reevaluate seismic risks, and to report their findings by March 2015.

Sunday’s magnitude-6 earthquake in Northern California has renewed focus on the dangers of Diablo Canyon, considered by many as a nuclear catastrophe in waiting. The plant, located halfway between Los Angeles and San Francisco, is within fifty miles of 500,000 people.