NRC says Shoreline Fault isn't threatening



The federal agency that oversees the country’s nuclear industry released a report saying a recently discovered fault doesn’t present an imminent danger to the Diablo Canyon nuclear power plant.

On Oct. 12, the Nuclear Regulatory Commission announced that the agency had recently completed an analysis of seismic faults near the plant and concluded it could withstand the ground motion from a possible temblor caused by the newly discovered Shoreline Fault.

The Shoreline was discovered by the U.S. Geological Survey and subsequently reported to the NRC by plant operator PG&E in November 2008. PG&E updated its preliminary information to the NRC in 2011, which sent inspectors to the plant in October 2011.

“Based on the available information and the site visit, the NRC team analyzed ground motion from earthquakes the Shoreline fault could potentially generate,” an NRC statement reads. “All of those ground motions fell within Diablo Canyon’s existing design limits, which are based on ground motion associated with an earthquake from the larger Hosgri Fault near the plant.”

The Hosgri Fault is believed to be capable of producing up to a 7.3-magnitude earthquake. The plant is designed to withstand the ground motion of up to a 7.5 quake.

According to the NRC, the plant must still carry out additional seismic evaluations for “enhancing earthquake resistance” to keep in step with a separate NRC mandate to all U.S. nuclear plants as the industry attempts to compile a “lessons learned” document following the Fukushima Dai-ichi incident in Japan in March 2011.

And despite the Shoreline report and the information being compiled for the NRC mandate, PG&E is additionally set to begin high-energy 3-D offshore seismic to glean additional information about the nearby faults.

That survey is scheduled to begin in mid-November, but depends upon a number of outstanding regulatory permits.

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