Letters to the Editor

Seismic and tsunami safety a priority for Diablo Canyon

Diablo Canyon Power Plant plays a major role in helping PG&E generate and deliver to its customers some of the nation’s cleanest electricity. And there’s nothing more important to the company and the 1,500 employees who work at the plant and live with their families in the community than its safe operation.

We understand we have been given a special trust to operate the plant and we work to keep that trust by putting safety first each and every day.

Of course when it comes to safety, the question I often get asked is: Can the plant withstand earthquakes and other forces nature may throw our way? My answer is yes, and it’s based on how the plant is designed and our vigilant efforts to continue studying how earthquakes and tsunamis may impact the plant.

When it comes to the plant’s earthquake design, it’s important to remember that it is built to a higher safety standard than other commercial buildings. Unlike those buildings — built to hold up for occupants to escape after an earthquake — Diablo Canyon’s structures were designed to remain intact, with key safety systems continuing to operate, after a major seismic jolt.

Our commitment to plant safety also extends to ensuring it can withstand offshore and weather events, which is why flooding and tsunami protection was also at the forefront in the design of the facility.

Seismic and tsunami safety, however, wasn’t simply a one-shot deal with the original design and construction of the power plant. We constantly work to ensure the facility can withstand such events — an ongoing process that puts us on the cutting edge of research and solidifies Diablo Canyon as an industry leader in these important areas.

Through our unique long-term seismic safety research program, we’ve continued to gather additional information on how earthquakes behave locally and around the world, and have applied that information to ensure plant safety. We have shared those results with local government and infrastructure operators to increase safety in our community.

Our safety focus has also led us to continue our study of tsunamis, including how they are generated, their source and what impact they might have to the facility.

These topics took on even more importance in 2011 following the events at the Fukushima Dai-ichi nuclear plant in Japan. While the plant there stood up very well in the face of a major earthquake, the resulting tsunami that impacted the facility caused a series of events that led to the accident.

Plant operators around the world continue to study Fukushima’s event, and the U.S. Nuclear Regulatory Commission (NRC) and the industry have implemented numerous changes to ensure all U.S. facilities, including Diablo Canyon, can withstand extreme events. This includes adding additional layers of back-up equipment to provide continuous electricity and cooling at all times to protect the facility.

Going further, the NRC also required all U.S. plants to re-evaluate the potential hazard that earthquakes and flooding pose to their facilities.

We recently completed a reassessment of these hazards, and the results reflect well for Diablo Canyon. The extensive scientific analyses, using new regulatory processes, independent expertise and sitespecific information, continue to show that the plant can safely withstand earthquakes, as well as large waves and flooding that could potentially occur in the region.

Under the NRC’s seismic hazard re-evaluation process, independent experts publicly analyzed existing and new seismic information, including how earthquakes occurring on individual and multiple geologic faults could potentially impact the facility. Their work also utilized insight gained from the advanced seismic studies recently completed near Diablo Canyon.

In addition, input on the advanced seismic studies provided by the California Public Utilities Commission’s Independent Peer Review Panel was considered in the seismic hazard re-evaluation process.

The result of this effort is a thorough assessment of the seismic hazard, confirming the plant continues to be seismically safe.

Our flooding and tsunami hazard update involved the use of the latest NRC guidance and methodologies to determine the maximum potential waves and rainfall that could impact the site.

The re-evaluation, using independent expertise, determined that the plant’s key safety systems and components continue to be safe from tsunamis, including those generated from underwater landslides and earthquakes.

The plant’s design is also deemed appropriate to withstand expected storm flooding. In addition, measures were identified and implemented to address a rare, theoretical event of excessive rainfall and a quick build-up of water in some plant locations that greatly exceeds any known precipitation event recorded in the site’s history.

These robust assessments will now be reviewed by the NRC and are available to researchers and the public who are interested in learning more about the findings.

While these important updates demonstrate that the plant’s design is safe, our work doesn’t stop there. Our commitment to safe operations and always protecting public health and safety will continue to be reflected in our ongoing study and evaluation of the areas. You, our customers and our neighbors expect no less.

We encourage anyone who wants to learn more about the plant and our commitment to safety to take one of our public tours. For more information, please visit http://www.diablocanyonpge.com.