An advanced seismic study conducted by utility PG&E to determine the safety of California's Diablo Canyon nuclear power plant has found that the facility is "designed to withstand and perform [its] safety functions during and after a major seismic event." The Central Coastal California Seismic Imaging Project report was submitted to the Nuclear Regulatory Commission (NRC) by PG&E and released last week.

The report finds that "the plant is designed to withstand the ground motions that would be produced by potential earthquakes from faults in the vicinity of the [Diablo Canyon Power Plant]."

The timing of the report (executive summary here) does raise questions about NRC's licensing, relicensing and review processes at the last operating civilian nuclear plant in California.

The earthquake study concludes that the Diablo Canyon plant is "seismically safe," according to Ed Halpin, PG&E's chief nuclear officer. In a release, Halpin said that recent 3-D seismic studies "provide scientists and regulators an unprecedented scientific analysis of the seismic characteristics near Diablo Canyon." He emphasized that "these studies are unprecedented and unlike anything that has been done at any other nuclear power plant in the nation and likely the world."

The studies are "unlike anything that has been done" because it's rare for nuclear power plant operators to detect three new faults within miles of the facility -- after the plant has been built, commissioned and operated. The 3-D mapping studies are plotting the Hosgri and San Simeon faults, as well as the more recently detected Shoreline, Los Osos and San Luis Bay faults. (You can read the conclusions of the report here.) PG&E has provided these reports to the California Public Utilities Commission’s Independent Peer Review Panel, as well as to the U.S. NRC.

PG&E began its advanced seismic research in 2010. The most recent fault was identified in 2008. Plant construction began in 1968.

The PG&E report arrives amidst accusations that a formal dissent by a Diablo Canyon power plant nuclear official might have been mishandled. This has prompted renewed protest by anti-nuclear groups, as well as a call for Senate hearings.

Anti-nuclear organization Friends of the Earth claims "the NRC suppressed [the] dissent for almost a year."

"Differing professional opinion" prompts Senate hearings

A document, acquired and verified by The Associated Press and authored by Dr. Michael Peck, the former senior resident inspector at Diablo Canyon for the NRC, claims that "three of the nearby faults (Shoreline, Los Osos and San Luis Bay) are capable of generating earthquakes stronger than the reactors were designed to withstand."

The document is a Differing Professional Opinion (DPO), and it reveals part of the inner workings of formal dissent process within the NRC. The procedure from the NRC: "All routine DPO cases are expected to be completed within 60 days of acceptance of the issue as a DPO, and all complex cases within 120 days."

Peck submitted his DPO in July of last year.

Continuing to operate the plant, Peck writes, "challenges the presumption of nuclear safety," according to the AP report. Peck asserts, "Diablo Canyon is operating outside the conditions of its license and should be shut down until PG&E can prove that the reactors can withstand potential earthquakes on these faults." 

The AP notes that Peck "does not say the plant itself is unsafe. Instead, according to Peck's analysis, no one knows whether the facility's key equipment can withstand strong shaking from those faults -- the potential for which was realized decades after the facility was built."

U.S. Sen. Barbara Boxer, the chair of the Environment and Public Works Committee, pledged to call public hearings on earthquake risks at Diablo Canyon after AP disclosed the Peck report.

An SF Gate article quoted Sen. Boxer as saying, "A year ago, a qualified NRC inspector informed the NRC that the Diablo Canyon nuclear power plant should be shut down until it is clear that the plant can withstand the kind of earthquake that has been predicted for the area. I am alarmed that the NRC has not followed this recommendation and has not required actions to protect the 500,000 people who live near the site."

Friends of the Earth disagrees with the PG&E findings

The founding of the organization Friends of the Earth in 1969 was prompted by safety concerns at the then-proposed Diablo Canyon plant, according to its website. Almost fifty years later, Friends of the Earth now suggests, "More information about the seismic activity near the two aging reactors has made it increasingly clear that Diablo Canyon should never have been built on its current site. The tremendous and unnecessary risk these reactors pose to public health and the environment necessitates that they be shut down."

The organization reports, "At the time of construction it was known that Diablo Canyon was at risk from two earthquake faults: the San Andreas, 45 miles inland, and the Rinconada, 20 miles inland. Since then, it has become increasingly clear that Diablo Canyon is surrounded by faults capable of creating ground motion beyond that for which the reactors and their components were tested and licensed."

“Decrepit reactors on an array of active seismic faults is a recipe for disaster,” said Damon Moglen, senior strategic advisor at Friends of the Earth. “PG&E is trying to spin the facts and asking the public to blindly trust them. But the facts are clear: the plant’s two aging reactors -- designed in the 1960s and built in the 1970s -- are surrounded by dangerous earthquake faults that were unknown at the time of construction, and these faults are capable of far stronger shaking than the plant was designed and built to withstand.”

"It has taken six years for PG&E to acknowledge the risks of the Shoreline Fault first identified in 2008. Why has the utility withheld this information for years when it involves such dramatic risk to the public?” asked David Freeman, a nuclear power expert who has served in high-ranking roles at the federal Tennessee Valley Authority, the Los Angeles Department of Water and Power, and the Sacramento Municipal Utility District, and who is now a special advisor to Friends of the Earth.

Freeman added: “Unfortunately, this seems very much in character for the company responsible for the safety failures that led to the San Bruno natural gas line disaster. This is a ‘safety’ report by a company that has been indicted by the federal government for its corporate disregard for safety.” According to Freeman, Diablo Canyon and the since-closed San Onofre nuclear plant are both "disasters waiting to happen: aging, unreliable reactors sitting near earthquake fault zones on the fragile Pacific Coast, with millions or hundreds of thousands of Californians living nearby."

The Union of Concerned Scientists is concerned about the seismic safety of the plant.

Operating licenses and San Onofre

Diablo Canyon's reactors became operable in 1985 and 1986 and their licenses expire in 2024 and 2025. PG&E was applying to the NRC for a twenty-year license extension, but Japan's Fukushima disaster put the extension on hold until this latest seismic study and its submittal to the NRC and CPUC.

Friends of the Earth is employing similar maneuvers in its effort to close Diablo Canyon as it used in its successful campaign to close Southern California's 2,200-megawatt San Onofre Nuclear Generating Station power plant in 2012: filing a petition with the NRC to shut down the reactor since the new earthquake data means the facility is no longer in compliance with its license.

Replacing the 2,200 megawatts of the shuttered SONGS plant or the potential loss of Diablo Canyon will require new natural-gas-fired power plants, as well as a meaningful supply of renewables and energy storage.  

The PG&E study now gets peer-reviewed by two independent scientific panels, one named by the CPUC and another named by the NRC. Results are expected in 2015.

Diablo Canyon Nuclear Power Plant facts  

  • Owned and operated by PG&E
  • Location: 12 miles west southwest of San Luis Obispo, California on 900 acres west of Avila Beach
  • Commission date for the 1,118-megawatt Unit 1: May 7, 1985. 
  • Commission date for the 1,122-megawatt Unit 2: March 13, 1986. 
  • Reactor type: Westinghouse four-loop pressurized-water nuclear reactors
  • There are more than 1,000 PG&E employees of PG&E and 200 subcontractor employees at the Diablo Canyon site.
  • The 2010 U.S. population within 10 miles of Diablo Canyon was 26,123. The 2010 U.S. population within 50 miles was 465,521.

Sources: NRC, DOE, PG&E

Diablo Canyon Power Plant photo by Doc Searls, CC

PG&E's electricity mix