COVER STORY | STEAM GENERATORS
Renewing the licence renewal
Diablo Canyon has won a reprieve from closure and the potential to operate until the mid 2040s. Now its life extension application is under initial assessment by the Nuclear Regulatory Commission
IN NOVEMBER, PACIFIC GAS AND Electric Company (PG&E) submitted an operating licence renewal application to the US Nuclear Regulatory Commission (NRC) for its two-unit Diablo Canyon nuclear power plant. It sought to add 20 years to the facility’s lifetime, so that Unit 1’s operating licence would be extended from midnight on 2 November 2024, to midnight on 2 November 2044, and Unit 2 would be extended from midnight on 26 August 2025, to midnight on 26 August 2045. The submission was a remarkable turnaround from the situation five years ago, when in April 2018 the NRC granted a request from PG&E to withdraw a licence extension application that had been submitted in November 2009. The company said the decision to withdraw the application at that time was based on the determination by California’s Public Utility Commission (CPUC) that continued baseload operation of the two units was not necessary to meet California’s projected energy demand. What had changed? In September 2022 California Governor Gavin Newsom signed a bill (Senate Bill No. 846 (Dodd)) that reversed the 2018 CPUC decision. PG&E notified the NRC of the intent to submit a new application by 31 December 2023. In response, NRC said the plant could continue to operate under its current licence, because “if Pacific Gas and Electric submits a license renewal
application no later than December 31, 2023, and if the NRC Staff finds it acceptable for docketing, the existing operating licenses for Diablo Canyon Power Plant, Units 1 and 2 will be in timely renewal under NRC regulations until the NRC has made a final determination on the license renewal application.”
Licence renewal application The letter came with a licence renewal application running to nearly 3,000 pages which is being reviewed by the NRC staff to determine whether it is sufficiently complete to begin the agency’s extensive safety and environmental reviews. The application is publicly available and the following abstracts regarding the steam generators give a flavour of its depth of detail. The Diablo Canyon steam generator aging management
programme (AMP) covers tubes, plugs, divider plate assemblies, tube-to-tubesheet welds, heads (interior surfaces of channel or lower/upper heads), tubesheets (primary side), and secondary side components within the steam generators. Steam generator tube integrity can be affected by
degradation of steam generator plugs, and secondary side internals. Non-destructive examination (NDE) techniques identify components with degradation that may need to
Above: Diablo Canyon has won a reprieve from closure and the potential to operate until the mid 2040s 14 | January 2024 |
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