California governor says power needed beyond 2025 to ward off possible blackouts.

A US court has denied a challenge to a licence renewal application extension granted by the federal government for the two-unit Diablo Canyon nuclear power station in California.

Three climate groups – Mothers for Peace, Environmental Working Group, and Friends of the Earth – filed a motion asking for the immediate closure of Diablo Canyon based on it posing an “unacceptable safety risk”.

The groups claimed the US Nuclear Regulatory Commission had ignored risks to the public and the environment.

In an opinion written by US circuit judge Consuelo Callahan, the three-judge panel found that the NRC had not acted arbitrarily nor capriciously. The agency “adequately explained why California’s changing energy needs constitute a special circumstance, and why the record supported its findings of no undue risk to the public health and safety”.

The three groups said following the ruling this week that they would consider asking for an en banc review – a special decision where all judges of a particular court hear a case – of the decision.

The current operating licences for Units 1 and 2, both Westinghouse pressurised water reactors, were set to expire in 2024 and 2025.

Diablo Canyon owner and operator Pacific Gas and Electric is planning to keep Unit 1 operational until 31 October 2029 and Unit 2 until 31 October 2030.

California governor Gavin Newsom, a Democrat, signed legislation in 2022 that reversed an agreement between the state, PG&E and environmental groups to retire the facility.

Newsom, once a leading voice to close the facility, said Diablo Canyon’s power is needed beyond 2025 to ward off possible blackouts as California moves to solar and other renewable energy sources.

Newsom’s administration has cited “unprecedented stress” on the state’s energy system as a reason for keeping open Diablo Canyon, which alone accounts for 9% of the state’s generation and 17% of its electricity from carbon-free sources.