Judges question environmentalists’ legal recourse in fight about Diablo Canyon Unit 1 vessel

Federal judges on Monday worried that the owner of California’s last nuclear power plant has not checked the condition of a reactor core for more than a decade but questioned whether environmentalists had grounds to force such a check.

“Your argument from practicality and so on is really disturbing,” Marsha Berzon, a senior judge in the U.S. Ninth Circuit Court of Appeals in Phoenix, told Dianne Curran, a lawyer for San Luis Obispo Mothers for Peace. However, Berzon said during oral arguments, Curran seemed to have a “problem finding” where the Nuclear Regulatory Commission broke the law.

Mothers for Peace say NRC illegally amended Pacific Gas & Electric Co.’s (PG&E) operating license for the Diablo Canyon Nuclear Power Plant by not requiring the utility to collect a proxy sample of the reactor’s vessel’s steel structure.

The environmental group said that by declining to force PG&E to collect this sample, from a capsule inside the Unit 1 reactor, NRC in 2008 effectively modified a 2006 license amendment granted to PG&E after the utility installed the capsule, known as capsule b. The agency subsequently made identical de facto amendments, most recently in November 2023, when it refused Mothers for Peace’s request to force a check, the group said.

Mothers for Peace appealed that denial to the Ninth Circuit, calling it the latest illegal license amendment. The utility at one point imagined it would remove the capsule in 2009 but has since obtained NRC’s permission to wait until 2025.

Capsule b could potentially prove or disprove an academic researcher’s theory, presented to the NRC by Mothers for Peace as part of a broad effort to prevent a relicensing of Diablo Canyon’s two reactors, that Unit 1’s reactor vessel is unacceptably brittle.

On Monday, Erich Michel, NRC’s lawyer, told the circuit judges that NRC “did not inadvertently create a license amendment proceeding or issue a license amendment” by declining to make PG&E remove capsule b.

For that reason, Mothers for Peace had no right to a hearing before the agency, said Michel. On the other hand, Michel said, refusing a hearing in November does not “is not at all about shutting the door on petitioners’ concerns or preventing them from raising their health and safety issue.”

Mothers for Peace can still advance their argument about potential reactor brittleness during NRC staff’s review of PG&E’s license extension request, said Michel.

PG&E’s operating licenses for Unit 1 expired on Nov. 2, but NRC has allowed the reactor to stay online while staff vet the utility’s license renewal application. Unit 2’s license will lapse on Aug. 26 2025. Commission staff have said they could finish reviewing the renewal application in August 2025 or so.