As aftershocks of the 6.0 Napa earthquake that occurred Sunday in California continued, the Associated Press revealed a secret government report pointing to major earthquake vulnerabilities at the Diablo Canyon nuclear plants which are a little more than 200 miles away and sitting amid a webwork of earthquake faults.

It’s apparent to any visitor to the stretch of California where the two Diablo Canyon plants are sited that it is geologically hot. A major tourist feature of the area: hot spas.

“Welcome to the Avila Hot Springs”, declares the website of one, noting how “historic Avila Hot Springs” was “discovered in 1907 by at the time unlucky oil drillers and established” as a “popular visitor-serving natural artesian mineral hot springs.”

Nevertheless, Pacific Gas & Electric had no problem in 1965 picking the area along the California coast, north of Avila Beach, as a location for two nuclear plants.

Geology rocks!

It was known that the San Andreas Fault was inland 45 miles away. But in 1971, with construction already under way, oil company geologists discovered another earthquake fault – the Hosgri Fault, just three miles out in the Pacific from the plant site and linked to the San Andreas Fault.

In 2008 yet another fault was discovered, the Shoreline Fault – just 650 yards from the Diablo Canyon plants.

The Shoreline Fault, and concerns about the vulnerability of nuclear plants to earthquakes in the wake of the 2011 Fukushima Daiichi disaster, are integral to a 42-page report written by Dr. Michael Peck.

For five years Peck was the lead inspector on-site for the US Nuclear Regulatory Commission at Diablo Canyon. He’s still with the NRC, a trainer at its Technical Training Center in Chattanooga, Tennessee.

Peck’s report was obtained by the Associated Press, which has done excellent journalism in recent years investigating the dangers of nuclear power, and they issued their story on Monday. In the report

Peck writes: “The new seismic information resulted in a condition outside of the bounds of the existing Diablo Canyon design basis and safety analysis. Continued reactor operation outside the bounds of the NRC approved safety analyses challenges the presumption of nuclear safety.”

“The Shoreline [Fault] Scenario results in SSC [acronym in the nuclear field for Structures, Systems and Components] seismic stress beyond the plant SSE [Safe Shutdown Earthquake] qualification basis. Exposure to higher levels of stress results in an increase[d] likelihood of a malfunction of SSCs. The change also increases the likelihood of a malfunction of SSCs important to safety…”

A ‘reasonable assurance of safety’?

Peck notes that the “prevailing” NRC staff view is that “potential ground motions from the Shoreline fault are at or below those levels for which the plant was previously evaluated and demonstrated to have a ‘reasonable assurance of safety’.”

He disagrees, noting that the NRC staff “also failed to address the Los Osos and San Luis Bay faults”, faults that the Shoreline Fault are seen as potentially interacting with, and that “new seismic information” concludes that “these faults were also capable of producing ground motions.”

In addition, “The prevailing staff view that ‘operability’ may be demonstrated independent of existing facility design basis and safety analyses requirements establishes a new industry precedent. Power reactor licensees may apply this precedent to other nonconforming and unanalyzed conditions.”

“What’s striking about Peck’s analysis”, says AP, “is that it comes from within the NRC itself, and gives a rare look at a dispute within the agency. At issue are whether the plant’s mechanical guts could survive a big jolt, and what yardsticks should be used to measure the ability of the equipment to withstand the potentially strong vibrations that could result.”

It continues: “Environmentalists have long depicted Diablo Canyon – the state’s last nuclear plant after the 2013 closure of the San Onofre reactors in Southern California – as a nuclear catastrophe in waiting.

“In many ways, the history of the plant, located halfway between Los Angeles and San Francisco … and within 50 miles of 500,000 people, has been a costly fight against nature, involving questions and repairs connected to its design and structural strength.”

Nuclear secrecy

Calling the Peck report “explosive”, the environmental group Friends of the Earth this week described it as having been “kept secret for a year.”

According to Damon Moglen, senior strategy advisor at Friends of the Earth, “Inspector Peck is the canary in the coal mine, warning us of a possible catastrophe at Diablo Canyon before it’s too late. We agree with him that Diablo Canyon is vulnerable to earthquakes and must be shut down immediately.”

“Given the overwhelming risk of earthquakes, federal and state authorities would never allow nuclear reactors on this site now. Are PG&E and the NRC putting the industry’s profits before the health and safety of millions of Californians.”

“Rather than the NRC keeping this a secret, there must be a thorough investigation with public hearings to determine whether these reactors can operate safely.”

Can Diablo Canyon survive an earthquake?

Michael Mariotte, president of the Nuclear Information & Resource Service, commented Monday that in “plain English” what Peck’s report acknowledges is:

“The NRC does not know whether Diablo Canyon could survive an earthquake, within the realm of the possible, at any of the faults around Diablo Canyon. And the reactors should shut down until the NRC does know one way or the other.

“Of course, if the reactors cannot survive a postulated earthquake, the obvious conclusion is that they must close permanently. The question is whether the NRC will ever act on Peck’s recommendation or whether the agency will continue to sit on it until after the next earthquake.”

Mariotte adds: “The irony is that this should have been the big news a year ago; Peck wrote his recommendation – in the form of a formal Differing Professional Opionion – in July 2013. And the NRC still hasn’t taken action or even responded to it.”

In his report Peck also states that the NRC is supposed to be committed to a “standard of safety” and “safety means avoiding undue risk or providing reasonable assurance of adequate protection for the public.”

PG&E’s response? Apply to extend the licenses

Meanwhile, PG&E has not only been insisting that its Diablo Canyon plants are safe, despite the earthquake threat, but has filed with the NRC to extend the 40 year licenses given for their operations another 20 years – to 2044 for Diablo Canyon 1 and to 2045 for Diablo Canyon 2.

An analysis done in 1982 by Sandia National Laboratories for the NRC, titled ‘Calculations for Reactor Accident Consequences 2‘, evaluated the impacts of a meltdown with “breach of containment” at every nuclear plant in the US – what happened at the Fukushima Daiichi nuclear plants as a result of an earthquake.

For the Diablo Canyon nuclear plants, it projected 10,000 “peak early fatalities” for each of the plants and $155 billion in property damages for Diablo Canyon 1 and $158 billion for Diablo Canyon 2 – in 1980 dollars.

Karl Grossman is professor of journalism at the State University of New York/College at Old Westbury, and the author of ‘Cover Up: What You Are Not Supposed to Know About Nuclear Power’ and host of the nationally-aired TV program ‘EnviroCloseup‘.