The California Public Utilities Commission (CPUC) has agreed to allow the Diablo Canyon NPP to operate for an additional five years, despite calls from environmental groups for its closure. The CPUC voted to extend the shutdown date to 2030 instead of closing it in 2025 as previously agreed. The US Nuclear Regulatory Commission (NRC) still needs to conduct a safety review. 

Three commissioners voted in favour, one abstained and one was absent. CPUC acknowledged that the costs of an extension were still unknown but were expected to exceed $6bn. The commissioners said the extension should serve as a bridge to renewable energy and that the plant should not operate beyond 2030.

The two 1,100 MWe pressurised water reactors at Diablo Canyon began operation in 1985 and 1986, and produce 9% of the state's electricity. Plant owner Pacific Gas & Electric Company (PG&E) in 2016 proposed closing Diablo Canyon when the two units reached the end of their current operating licences in 2024 and 2025. This was approved by CPUC in 2018. All other nuclear plants in California had already closed. Units 2&3 at Southern California Edison's San Onofre nuclear generating station (SONGS) were prematurely retired in 2013.

However, in September 2022, California lawmakers voted to extend the operating life of Diablo Canyon by five years, in part by giving PG&E a $1.4bn forgivable loan to be repaid with federal funding. In November, the Department of Energy (DOE) announced the conditional selection of the Diablo Canyon to receive the first round of funding from the first round of the $6bn Civil Nuclear Credit (CNC) programme, funded by President Biden’s Bipartisan Infrastructure Law.

In March, NRC approved an exemption request from PG&E to allow continued operation of the Diablo Canyon NPP. This allows PG&E to continue operating both units while the company's Licence Renewal Application (LRA) is under review. PG&E intends to submit a new LRA by the end of 2023. NRC’s approval followed a unanimous vote by the California Energy Commission (CEC) to adopt a report finding that extending operations until at least 2030 would be prudent. The analysis found that the state's electricity forecasts for 2024-2030 show potential for reliability deficiencies if Diablo Canyon’s operation is not extended. The report was developed in consultation with the CPUC.

CPUC’s decision comes in the wake of ongoing pressure from environmentalist groups to close the plant. A state judge in August rejected a lawsuit filed by Friends of the Earth aimed at preventing the plant’s continued operation. Then, in October, NRC rejected a request from environmental groups for the immediate closure of one unit. immediately shut down one of two reactors.

Ken Cook, President of the Environmental Working Group said CPUC’s “ill-conceived decision” would “further escalate financial strain on California ratepayers and extend the threat of a catastrophe at Diablo Canyon”.

However, American Nuclear Society (ANS) President Kenneth Petersen welcomed the decision. “The American Nuclear Society applauds the decision by the California Public Utilities Commission to extend the operations of Diablo Canyon nuclear power plant through 2030,” he said in a statement. “The California PUC commissioners made the right choice in preserving California’s largest and most reliable clean energy source, Diablo Canyon nuclear power plant. Keeping California’s lights on requires keeping Diablo Canyon online.”

Image: Diablo Canyon nuclear power plant (courtesy of PG&E)