The Nuclear Regulatory Commission's latest analysis of faults near the Diablo Canyon nuclear power plant in California continues to conclude the plant’s design would withstand earthquakes near the site.
The NRC's work is laid out in Research Information Letter (RIL) 12-01, "Confirmatory Analysis Of Seismic Hazard At The Diablo Canyon Power Plant From The Shoreline Fault Zone." The RIL, part of the ongoing effort to better understand earthquake sources near Diablo Canyon, focuses on the latest identified source, the "Shoreline fault" about a kilometer offshore from the plant. The letter will be available in the NRC’s electronic document database, ADAMS, by entering "ML121230035" in the ADAMS search engine.
Pacific Gas & Electric (PG&E), which operates the plant 12 miles southwest of San Luis Obispo, Calif., first notified the NRC in November 2008 about the Shoreline fault. PG&E updated that information in early 2011, and a team of NRC staff visited the site 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. 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.
Diablo Canyon must still carry out additional earthquake evaluations, as well as a “walkdown” to identify any near-term actions for enhancing earthquake resistance. These measures are included in the NRC’s recent information request to all U.S. nuclear power plants as the agency implements lessons learned from the Fukushima Dai-ichi nuclear accident