Seismic Showdown Coming at Diablo Canyon

Environmental groups have successfully petitioned for “enforcement action” by the US Nuclear Regulatory Commission (NRC) to conduct a review of the earthquake risks and the potential nuclear accident threat with the continued operation of California’s two-unit Diablo Canyon nuclear power plant near San Luis Obispo. The March 4, 2024 petition  was filed to the NRC Commissioners’ Office calling for the revocation of the nuke’s operating license by Mothers For Peace, the Environmental Working Group and Friends of the Earth. The May 15, 2024 initial assessment by an impaneled NRC Petition Review Board (under 10 CFR 2.206) was that the petition should be denied because it did not present significant new information. Enough information was provided however that the Board offered the Petitioners the opportunity for a pre-hearing meeting to supplement their request.

On July 17, 2024, the Petitioners’ presented their seismic expert, Dr. Peter Bird, Professor Emeritus of Geosciences at UCLA, who in testimony to the NRC argued that Pacific Gas & Electric’s (PG&E) most recent publicly-cited seismic risk analysis was seriously deficient. Dr. Bird’s testimony finds that PG&E’s 2018 Seismic Probabilistic Risk Assessment for Diablo Canyon’s “seismic core damage frequency” (SCDF) is currently estimated to be 3×10-5, when it should be 1.4×10-3 per year.

Dr. Bird warns that PG&E has significantly underestimated the earthquake-related nuclear accident frequency because of flawed assumptions that the Diablo Canyon meltdown risk chiefly comes from strike-slip earthquakes.  Dr. Bird charges that PG&E’s analysis disregards the more recent January 1, 2024 earthquake in Japan.  He asserts that the earthquake centered on the Noto Peninsula (7.5 Magnitude) is a dramatic demonstration and analogous to the significant risk contribution from the “thrust fault” earthquake potential underneath the Diablo Canyon reactor site and in the adjacent Irish Hills.

Based on Dr. Bird’s supplemental information and testimony, the NRC Petition Review Board announced on August 27, 2024 that it reconsidered its preliminary judgment and “As provided by 10 CFR 2.206, we will take action on your request within a reasonable time.”