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USA: NRC inspector warns of Diablo Canyon seismic risks

Nuclear Monitor Issue: 

The former top Nuclear Regulatory Commission on-site inspector at the Diablo Canyon reactors in California, nuclear engineer Dr Michael Peck, has recommended to the NRC that those reactors be shut down until their ability to withstand earthquakes is fully assessed. This should have been the big news a year ago: Peck wrote his recommendation − in the form of a formal Differing Professional Opinion − in July 2013. But the NRC still hasn't taken action, or even responded to it.

There are several major earthquake faults around Diablo Canyon. And not only has our understanding of earthquakes evolved dramatically since construction of the first reactor at Diablo was authorized in 1968, but at least two major faults − the Hosgri and the Shoreline faults − hadn't even been discovered then.

According to the Associated Press: "The NRC says the Hosgri fault line presents the greatest earthquake risk and that Diablo Canyon's reactors can withstand the largest projected quake on it. In his analysis, Peck wrote that after officials learned of the Hosgri fault's potential shaking power, the NRC never changed the requirements for the structural strength of many systems and components in the plant."

And the NRC has done only a preliminary assessment of the possible effects of the Shoreline fault. Diablo's owner, Pacific Gas & Electric, claims the reactors would withstand any possible earthquake from any of the faults, but given that this is the same utility that built the second unit at Diablo in a mirror image of its blueprints, it doesn't hold a lot of credibility. Pacific Gas & Electric has not only been insisting that its two Diablo Canyon reactors are safe, 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.

Peck, on the other hand, who still works for NRC but not at Diablo, does have credibility. In his Differing Professional Opinion, 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."

Peck writes in NRC bureaucratic language, but what he is saying can easily be summed up in plain English: 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.

Peck asked that his Differing Professional Opinion be made public, but the NRC has not released it. And despite the NRC's requirement that Differing Professional Opinions are to be ruled on within 120 days of filing, the NRC has not ruled on Peck's July 2013 opinion.

Friends of the Earth has filed a petition with the NRC charging that the plant is in violation of its license and must be closed immediately pending public hearings to prove it is safe. The petition charges that despite having new information that earthquake faults surrounding Diablo Canyon are capable of ground motion far greater than the reactors were designed and licensed to withstand, both Pacific Gas and Electric and the NRC have failed to close the plant pending the completion of a rigorous safety analysis and licensing review required by the NRC's rules.

The Senate Environment and Public Works Committee has announced it will hold hearings into the NRC's suppression of Dr Peck's Differing Professional Opinion. Committee chair Sen. Barbara Boxer said: "The NRC's failure to act constitutes an abdication of its responsibility to protect public health and safety."

Michael Peck, July 2013, 'Differing Professional Opinion − Diablo Canyon Seismic Issues'

Associated Press, 25 Aug 2014, 'Hearings Planned After Call for Nuke-Plant Closure',

Friends of the Earth petition to the NRC:

Other sources:

Diablo Canyon 1Diablo Canyon 2