The U.S. Nuclear Regulatory Commission (NRC) and Pacific Gas & Electric (PG&E) gave not-unexpected thumbs up to the Diablo Canyon Power Plant in separate communications this week, which provided little consolation to critics who await independent, scientific peer-reviews of the facility’s seismic safety.

NRC Executive Director Mark Satorius responded (pdf) directly to safety issues raised by Michael Peck, its former senior inspector at Diablo Canyon. A year ago, Peck filed a report (pdf)―made public last month―that said the facility should be shut down until its operators can prove it is able to withstand a strong earthquake.      

Peck wrote that the Shoreline, Los Osmos and San Luis Bay earthquake faults, all within 3,000 yards of the facility, are capable of rocking the nuclear plant harder than it was designed to take and PG&E knows it. He called for more analysis but, according to Satorius, stopped short of declaring an impending disaster.

“A compelling basis for my conclusion is drawn from our meeting on July 30, 2014, when you and I agreed that there is not now nor has there been an immediate or significant safety concern associated with this Diablo Canyon issue,” Satorius wrote in his response to Peck.

Peck specifically wanted the plant closed until the Shoreline Fault, discovered in 2008, was looked at more closely and PG&E completed a public license amendment process. Satorius said it had been studied enough.

On Wednesday, PG&E released a four-year study which, the utility said, “demonstrates Diablo Canyon continues to be seismically safe.” PG&E used new technology to remap the five earthquake faults nearby and assessed what kind of G-force they would slam the plant with individually or linked together.

PG&E needed a work-around for some of its information after researchers for its study were denied permission by the California Coastal Commission to test for faults using high-energy blasts of sound. Environmentalists successfully raised concerns about their effect on marine life. PG&E fought hard for the testing, but in the end said it could fill the data gap from other sources.  

The report will be peer-reviewed by two independent scientific panels and are expected to finish their work next year. The NRC will pick one group and the California Public Utilities Commission (PUC) will pick the other.

A surprised San Luis Obispo County Supervisor Bruce Gibson, a seismologist who is serving on the PUC review panel, told the San Luis Obispo Tribune he thought PG&E agreed not to go public with the report until it had been reviewed.

PG&E started its study in 2010 in response to discovery of the Shoreline Fault. The NRC told operators of all the nation’s nuclear power plants to retest their facilities for seismic safety after an earthquake and tsunami devastated the plant at Fukushima, Japan in 2011.

–Ken Broder

To Learn More:

Diablo Canyon Nuclear Plant Can Handle Earthquakes, PG&E Says (by David Sneed, San Luis Obispo Tribune)

NRC Finds No Immediate Seismic Safety Issues at Diablo Canyon (by David Sneed, San Luis Obispo Tribune)

Regulators Reject Call for Nuke Plant Shutdown (by Michael R. Blood, Associated Press)

No Big Quake Safety Concern at California Nuclear Plant, Regulators Say (by Lauren Raab, Los Angeles Times)

Ex-Nuclear Inspector's Secret Report Urged Closure of Diablo Canyon Plant (by Ken Broder, Allgov California)

Memorandum Rejecting Diablo Seismic Warning (by Mark A. Satorius, Nuclear Regulatory Commission) (pdf)

Central Coastal California Seismic Imaging Project (Pacific Gas & Electric)