Keeping Tabs on Diablo Canyon’s Evolving Seismic Situation

Lara Uselding
Public Affairs Officer
Region IV

diabloThe NRC has added two items to the growing list of documents on seismic issues related to the Diablo Canyon Power Plant, near San Luis Obispo, Calif. Our Region IV office in Arlington, Texas, sent the plant operator, PG&E, an inspection report and our headquarters Office of Nuclear Reactor Regulation in Rockville, Md. sent PG&E a letter about the plant’s seismic hazard reevaluation due in March 2015.

The Region IV inspection report discusses the agency’s independent assessment of the operability determination completed by PG&E associated with its September report on the Shoreline and other faults near the plant. PG&E provided the report to the state under California Assembly Bill 1632. That bill required the report so the California Energy Commission could assess if California’s largest baseload power plants are vulnerable to a seismic event as those plants age.

The NRC did not request this analysis, but PG&E committed to keep us updated on any new information that would indicate the Shoreline fault is more energetic or capable than was presented in the January 2011 Shoreline Fault Report. PG&E further committed to provide the NRC with an interim analysis of any new Shoreline-related information before the post-Fukushima evaluations are due in March 2015.

Our regional review of PG&E’s operability determination indicates there is considerable design margin for the plant’s systems, structure, and components. The staff did not identify any concerns with PG&E’s determination that the plant is operable. The analysis adds to the evidence that the plant’s systems, structures, and components would function properly after an earthquake and not pose undue risk to public health and safety.

Our letter from headquarters confirms PG&E will incorporate the September report’s findings into its ongoing, post-Fukushima, full seismic re-analysis due in March 2015. The NRC believes this more rigorous analysis will provide the most accurate assessment of faults affecting the site.

The bottom line is that the effect of earthquakes has been extensively evaluated during the construction, licensing, and operation of the plant. Diablo Canyon’s systems, structures, and components are designed to withstand the area’s earthquakes and perform their safety functions.

Southern California Fire Puts Spotlight on NRC Regs

Victor Dricks
Senior Public Affairs Officer
Region IV
 

 A wildfire broke out on the Camp Pendleton Marine Base north of San Diego last Wednesday. The smoke could be seen by staff at the San Onofre Nuclear Generating Station and a handful of non-essential plant workers were sent home as a precaution.

 Firefighters from Camp Pendleton, in California, work to douse a wildfire.

Firefighters from Camp Pendleton, in California, work to douse a wildfire.

Members of the plant’s fire department responded to the event and sprayed water on vegetation at the plant’s South Yard to retard the fire’s progress. San Onofre also dispatched some of its personnel to Camp Pendleton to assist base personnel with firefighting efforts on the ground, while helicopters from the Marine base dropped buckets of water on the fire.

The blaze, which was sparked by an accident on Interstate 5, was brought under control in a few hours and never got closer than a half-mile from the owner-controlled area of the plant.

The San Onofre nuclear plant is shut down and preparing to decommission, and remained stable throughout the event. An NRC inspector onsite verified plant conditions and monitored the licensee’s response to the fire from the plant’s control room, relaying information to the NRC’s Region IV office in Arlington, Texas. Because the fire never reached the site or disrupted offsite power to the plant, no emergency declaration was necessary.

But the fire – and the start of the fire season in the West – does highlight NRC regulations related to natural disasters. As a part of their emergency preparedness plans, nuclear power plants are required by the NRC to be able to respond to a variety of natural disasters – hurricanes, tornadoes, tsunamis, earthquakes and fires — which can disrupt offsite power needed for vital plant equipment, interfere with access to the site and cause damage to equipment and threaten the safety of personnel.

NRC requires that all nuclear plants have personnel who have been specially trained and are qualified to respond to fires. Some plants, like Diablo Canyon, maintain on-site fire departments. Others, like San Onofre, have arrangements with off-site fire departments or organizations like Camp Pendleton to supplement their initial response. NRC inspects these response plans to ensure their adequacy and effectiveness.

On Wednesday, we saw those plans put into action. It might not be the last time this year. The need for vigilance will continue in the months ahead for plants located in areas where a prolonged drought is raising concerns about the upcoming summer wildfire season.