Anti-nuclear groups demand ‘immediate shutdown’ of Diablo Canyon. Why PG&E disagrees

In a petition filed earlier this month, two anti-nuclear groups demand that the U.S. Nuclear Regulatory Commission order PG&E to shut down Diablo Canyon nuclear power plant due to what they say is overdue testing on the safety of the facility — a risk the utility disputes.

The petition, filed by Mothers for Peace and Friends of the Earth on Sept. 14, alleges that PG&E has delayed testing on the Diablo Canyon Power Plant’s Unit 1 pressure vessel for 20 years, according to a news release by the groups.

“The pressure vessel may be the most important component of the reactor because it encases water on the highly radioactive reactor core,” the Sept. 14 news released said. “Failure of the reactor vessel could cause a catastrophic meltdown.”

Immediately powering down Diablo Canyon Power Plant, located just north of Avila Beach, should happen while PG&E inspects the pressure vessel, the groups’ petition states.

Additionally, the groups requested that the NRC reconsider its decision to allow PG&E an extension on inspecting the pressure vessel until 2025.

“This petition is part of a comprehensive legal strategy to ensure that people and the planet are not put at risk of a nuclear meltdown while PG&E profits in the billions,” said Hallie Templeton, legal director for Friends of the Earth, in a prepared statement. “We will not sit idly by while PG&E cuts corners on Unit 1’s safety and the NRC rubber stamps operation with a dangerously deteriorating pressure vessel.”

PG&E spokesperson Carina Corral said the utility company conducted an ultrasonic inspection on Diablo Canyon Power Plant’s Unit 1 in 2014.

That test “confirmed there were no reportable indications of cracking,” Corral wrote in an email to The Tribune.

PG&E has also inspected the reactor vessel through withdrawing a “surveillance capsule,” or “coupon,” to check for any damage, Corral added.

The last time that test was conducted was in May 2002.

PG&E was originally scheduled to withdraw a surveillance capsule from the Unit 1 vessel in 2022. The NRC had approved that testing date while PG&E applied for license renewal of the nuclear power plant in 2009.

However, PG&E withdrew its application for license renewal in 2018 and was then expected to cease operation of the power plant by 2025.

“Because the Unit 1 capsule removal was to support (Diablo Canyon) license renewal, it was not removed in 2022,” Corral wrote in her email.

PG&E is now working on its application for license renewal to potentially operate the power plant through at least 2030, following direction from the State Legislature under Senate Bill 846 signed last September by Gov. Gavin Newsom.

“The Nuclear Regulatory Commission (NRC) has approved PG&E’s schedule to withdraw a test capsule from Unit 1 for inspection and testing during either the Fall 2023 or the following Spring 2025 refueling outage,” Corral wrote in her email. “PG&E also plans to complete another ultrasonic inspection of the Unit 1 reactor vessel prior to May 6, 2025.”

The fall 2023 outage at Diablo Canyon nuclear power plant is scheduled for this weekend, according to Corral. Whether the test capsule inspection will happen during the outage is yet to be determined, she added.

Anti-nuclear groups want Diablo Canyon testing moved up

In their petition, Mothers for Peace and Friends of the Earth maintain that waiting until 2025 is too late.

Citing an analysis by Digby Macdonald, a staff researcher at UC Berkeley’s Department of Nuclear Engineering, the groups allege in their petition that the “Unit 1 pressure vessel could reach an unacceptable level of embrittlement” by late 2023.

Embrittlement occurs when operation of the nuclear reactor causes power plant materials exposed to radiation to become more susceptible to potential breaks.

“These indications of embrittlement should have caused PG&E to seek additional data for an adequate understanding of the condition of the pressure vessel,” the petition said. “Instead, over the past 20 years, PG&E has repeatedly postponed additional surveillance and testing of the pressure vessel.”

Such delays mean the power plant is operating unsafely and should be shut down immediately, according to the petition and Macdonald’s analysis.

“Now we are at a watershed moment where the safety risks created by PG&E’s failure to conduct any surveillance of capsules from the Unit 1 pressure vessels or ultrasound testing of the pressure vessel’s beltline welds are extremely grave,” Macdonald said in his Sept. 14 analysis.

Macdonald was retained by Mothers for Peace and Friends of the Earth to evaluate PG&E’s inspection of the reactor vessel.

Despite the allegations from Macdonald, Mothers for Peace and Friends of the Earth, PG&E continues to assert that it operates Diablo Canyon nuclear power plant safely.

“Analysis has demonstrated that the reactor vessels for both Units 1 and 2 currently meet the NRC’s acceptance criteria (10 CFR 50.61),” Corral wrote in her email to The Tribune. “Reflecting our focus on safety, we are in full compliance with industry guidance and regulatory standards regarding our program to monitor, evaluate and ensure reactor vessel safety.”