PG&E receives preliminary NRC assessment on Diablo Canyon seismic safety study

February 1, 2016

AVILA BEACH, Calif.— In a recent letter to Pacific Gas and Electric Company (PG&E), the Nuclear Regulatory Commission (NRC) communicated that it has completed its preliminary review of a new earthquake study for Diablo Canyon Power Plant, and has determined that the information is suitable to use in performing the next phase of the NRC's regulatory process.

PG&E submitted the study to the NRC in March of 2015 following years of analysis by independent experts. The study re-evaluated earthquake potential in the vicinity of Diablo Canyon, which PG&E then compared against the plant’s design to ensure it is safe to operate.

"Safety is and always will be the top priority for PG&E and Diablo Canyon. That's why we continually examine the region surrounding the plant through a long term seismic research program. The NRC's action represents an important milestone in the review of this new seismic study, which provided additional verification of the plant’s ability to withstand seismic activity," said Ed Halpin, senior vice president of generation and chief nuclear officer at PG&E.

Next Regulatory Steps

In its communication to PG&E, the NRC stated that it will complete its evaluation of the study by September of this year. The NRC also confirmed that the utility is to use the updated seismic information in completing by September 2017 a risk evaluation that further examines how plant structures, systems and components could be affected by the revised seismic findings.

The NRC and PG&E announced last year that this work would take place, and similar efforts are being performed at other plants around the country. The NRC will review these efforts to determine if additional actions might be required to further enhance safety at plant sites.

Due to the robust seismic design of Diablo Canyon, and the safety margins built into the design, PG&E does not anticipate the need for any seismic-related enhancements.

Seismic Hazard Background

As part of its response to the Fukushima event in Japan in 2011, the NRC directed all U.S. nuclear utilities to perform an updated seismic hazard evaluation for their plant sites. Plants located in the eastern and Central U.S. completed such analyses and provided them to the NRC in 2014. Western plants submitted their assessments in March 2015.

The process to perform the Diablo Canyon seismic hazard re-evaluation involved the use of new regulatory guidance, the latest scientific methods and models, and independent experts who publicly re-examined existing and new seismic information.

The result of this in-depth study is a more thorough assessment of the seismic hazard facing Diablo Canyon, providing additional confirmation that the plant is seismically safe.

About PG&E

Pacific Gas and Electric Company, a subsidiary of PG&E Corporation (NYSE:PCG), is one of the largest combined natural gas and electric utilities in the United States. Based in San Francisco, with more than 20,000 employees, the company delivers some of the nation's cleanest energy to nearly 16 million people in Northern and Central California. For more information, visit and