Environmental groups demand shutdown of Diablo Canyon reactor

September 18, 2023

Statement from Mothers for Peace and Friends of the Earth

The environmental advocacy groups Mothers for Peace and Friends of the Earth have jointly filed a petition calling on NRC commissioners to order the immediate shutdown of Diablo Canyon Unit 1 for tests and inspections of its pressure vessel that have been delayed for twenty years.

The pressure vessel may be the most important component of the reactor because it encases water on the highly radioactive reactor core. Failure of the reactor vessel could cause a catastrophic meltdown.

That risk is increased by Diablo Canyon’s proximity to a web of earthquake faults if vessel failure were to occur coincidently with a major earthquake that might breach containment. Yet, Pacific Gas and Electric Co. (PG&E) has repeatedly postponed essential metallurgical tests and ultrasound inspections over the past two decades.

The last inspections of the Unit 1 pressure vessel were conducted in 2003-2005. Alarmingly, despite serious indications of embrittlement, PG&E declared key test results “not credible.” They postponed further testing, claiming that the results from tests on what are called “sister” reactors —  those of similar design and materials and that have similar operating characteristics (e.g., maximum operating power, temperature, etc.) — were sufficient to justify continued operation.

Dr. Digby Macdonald, UC Berkeley Professor in Residence, Departments of Nuclear Engineering and Materials Science and Engineering, retained by the groups to evaluate the status of Unit 1, argues in his petition that the Charpy impact fracture test results conducted in 2003-2005 were credible and should have caused PG&E to inquire further rather than postpone the next scheduled inspections.

He dismissed PG&E’s decades-long reliance on data from similar pressure vessels, saying that “even if two nuclear plants are identical in every respect (“sister” nuclear reactors never are), each soon becomes individualized by unique operating conditions and histories.”

Macdonald also pointed out that PG&E was already warned that Unit 1 should be closely watched, given the discovery during reactor construction of defects due to excessive copper and nickel content. These defects “require more, not less, testing,” he said.

“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 added.

Diane Curran, attorney for Mothers for Peace, said the groups’ extensive investigation had  revealed an unprecedented and persistent pattern of neglect by PG&E and the NRC technical staff of their regulatory responsibilities for the condition of the Unit 1 pressure vessel.”

Curran underscored that the groups were appealing to the Commissioners, as the top officials in the agency, to take charge of the situation, reverse the regulatory lapse of the technical staff, and ensure that the required tests and inspections are conducted immediately. Additionally, Curran asserted that Unit 1 must be shut down immediately and remain closed until PG&E and the NRC technical staff had thoroughly evaluated the condition of the Unit 1 pressure vessel and justified continued operation in a public hearing.

Hallie Templeton, Legal Director for Friends of the Earth, said, “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. 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.”

Linda Seeley, spokesperson for Mothers for Peace, denounced the NRC’s lack of oversight and transparency over the past decade, leaving San Luis Obispo residents unaware of lurking safety risks. She warned, “The California State legislature, which decided a year ago to extend the operation of Diablo Canyon, should be worried that the federal government agency on which they are relying for the safety of the plant has been complicit in a very serious safety lapse.”