PG&E Gears Up for License Extension at Diablo Canyon

In response to growing concerns about the aging infrastructure at Diablo Canyon, California’s last operational nuclear power plant, Pacific Gas & Electric (PG&E) has initiated several safety measures.

Originally projected to cease operations by 2025, the facility received a state legislative extension that permits it to remain functional until 2030. Additionally PG&E has reportedly filed for a 20-year license extension, with hopes of operational continuity until 2044 and 2045.

Mothers For Peace—a non-profit organization advocating against nuclear energy and waste since the 1970s—wrote a letter last month to the CEO of PG&E expressing heightened worries regarding the plant’s current safety standards. The group urged for immediate shutdown and testing of one of Diablo Canyon’s reactor vessels due to potential embrittlement — a condition that can lead to hazardous operational failures if left unaddressed.

PG&E states it is preparing for a planned and scheduled refueling and maintenance outage for Unit 1 at Diablo Canyon. Refueling and maintenance outages are scheduled years in advance, and are performed on each unit approximately every 18 months. To support the scope of work, they have hired approximately 1,000 temporary additional workers.

The outage for Unit 1 will last approximately one month, and at the conclusion of the outage, the unit will be brought back into service to generate electricity for California. Unit 2 will remain online until its next scheduled refueling and maintenance outage in the fall of this year, PG&E stated.

“To ensure the continued safety and integrity of Diablo Canyon’s reactor vessels, we perform ultrasonic testing and visual inspections of the reactor vessel and core. We also conduct extensive computer modeling and testing of metal discs called ‘coupons’ that are made of the same material as our reactor vessel. These coupons provide data that help us monitor the strength of the vessel and ensure safe plant operations,” PG&E stated.

As part of license renewal process, PG&E obtained approval from the Nuclear Regulatory Commission (NRC) to remove coupons from Unit 1 during either its 2023 or 2025 refueling outage. Limited access prevented the removal of the coupons during the 2023 outage.

Following the plan approved by PG&E’s regulator, they will remove them during the upcoming refueling and maintenance outage later this month, as there will be better access to them. Once the coupons are removed, they will be shipped to an independent laboratory for extensive metallurgical analysis.

This analysis of the coupons takes between 12-18 months and the results will be sent to the NRC for further evaluation and are part of the public record.

[Ed Note: This article has been updated with clarifying information and a statement provided by PG&E]