Pacific Gas & Electric (PG&E) can operate the two-unit Diablo Canyon nuclear power plant in California beyond the expiry of their current licences (2024 and 2025, respectively) following the acceptance of PG&E's licence renewal application by the US Nuclear Regulatory Commission (NRC).

PG&E filed the application on 7 November, seeking to extend the plant's operating licences by an additional 20 years.

"The NRC staff has determined the application contains sufficient information to formally docket the application and begin its detailed safety and environmental reviews," the NRC said on 19 December. "With the docketing of the application, the reactors' licences will remain in effect under an exemption to agency regulations until the agency's review is complete."

PG&E originally applied to renew the licences in November 2009, but withdrew the application in 2018 after agreeing to close the plant at the end of its current licences. At that time, it was thought that the plant's output would no longer be required as California focused on an energy policy centred on efficiency, renewables and storage. However, in September 2022 - as California's energy grid saw its highest-ever peak demand during a record-breaking heatwave - the state passed a law allowing the units to continue to operate until 2030 to ensure a reliable energy system.

Normally, NRC regulations allow a reactor's operating licence to remain in effect beyond its expiry date provided that the licensee has already applied for a renewal at least five years prior to expiration, which the NRC calls "timely renewal".

PG&E asked the NRC to resume its review of the licence renewal application, but in January the regulator ruled that a new application would need to be submitted. This meant that PG&E could not meet the timely renewal requirement, and therefore it needed to seek the exemption. Such an exemption, allowing the two units to continue operating while the NRC considers PG&E's application to renew the plant's licence, was granted in early March.

Last week, Californian regulators agreed to extending the operations of the Diablo Canyon plant for an additional five years, to 2030. The California Public Utilities Commission's (CPUC's) approval is subject to three conditions: the NRC must continue to authorise the plant to operate; a USD1.4 billion federal loan agreement must not be terminated; and that the CPUC does not make a future determination that extended plant operations "are imprudent or unreasonable".

"PG&E remains committed to complying with energy policies to ensure the state has the option to keep DCPP online past 2025 to ensure electricity reliability as California continues toward its clean energy future," said Maureen Zawalick, DCPP Vice President. "We are grateful for the opportunity to continue providing homes and businesses across California with safe, clean, and affordable power."