NRC says Shoreline Fault not a significant threat to Diablo Canyon

October 15, 2012

The Nuclear Regulatory Commission released a letter Friday stating that the earthquake potential of the recently discovered Shoreline Fault does not exceed the maximum amount of seismic shifting the Diablo Canyon Power Plant can handle.

PG&E safety measures have prepared the nuclear power plant to safely survive a maximum earthquake on the nearby Hosgri fault of magnitude 7.5

In 2008, PG&E discovered another fault line less than one mile offshore from Diablo Canyon, which it named the Shoreline Fault. Following the meltdown of the Japanese Fukushima nuclear reactors in March 2011, PG&E decided to conduct seismic testing of the Shoreline Fault, which is schedule to begin next month.

Yet, the NRC letter, which discusses a report that reviewed new data on the Shoreline Fault, confirmed the agency’s previous finding that the Shoreline Fault cannot generate as large of a maximum earthquake as the Hosgri. Thus, the agency does not consider the Shoreline Fault a safety threat that requires any more preparations by PG&E.

“Staff has concluded that the Shoreline scenario should be considered as a lesser included case under the Hosgri evaluation,” the letter reads. “The licensee should update the final safety analysis report, as necessary, to include the Shoreline scenario.”

Despite the NRC’s lack of concern over seismic potential near Diablo Canyon and public outcry over the possibility of major harm to sea life in the area, PG&E plans to begin seismic testing in mid-November.

Although the NRC did not state that the seismic mapping is necessary, it said in the letter that it expects PG&E to report back any new information it gathers in the process suggesting that the Shoreline Fault has greater seismic potential than previously determined or that other fault lines exist in the area.

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Did Japanese geologists quantify the probability of the 9.0 Tohoku earthquake & tsunami (March 11, 2011) prior to the event? The quake was 43 miles offshore & 20 miles deep under water. Of course it wasn’t expected.

Yet we’re spending untold amounts of energy, money, ecological damage, public rancor and professional expertise trying to quantify a mostly known risk (Hosgri+Shoreline) while betting that we won’t be caught with our pants down when the inevitable happens at a previously-unknown fault location or at a known location (San Andreas?) but at a fantastic scale.

Two things are constant:

Man’s arrogance & folly


Nature’s surprises