As aftershocks of the 6.0 Napa earthquake that occurred Sunday in California continued, the Associated Press this week 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." www.avilahotsprings.com
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.
It was known that the San Andreas Fault was inland 45 miles away. Then, in 1971, with construction underway, 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--but 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 the lead inspector on-site for the U.S. Nuclear Regulatory Commission at Diablo Canyon.
Peck's report was obtained by the Associated Press, which has done excellent journalism in recent years investigating the dangers of nuclear power, and the AP issued a story Monday on 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."
He also states: "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..."
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 and says 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"
Also, he says: "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 the AP story, "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." click here
The AP story also says, "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."
Calling the Peck report "explosive," the environmental group Friends of the Earth this week described it as having been "kept secret for a year."