The Office for Nuclear Regulation has permissioned EDF's post-defuelling safety case (PDSC) for the Hunterston B site.
This marks the first such approval to be granted across EDF's Advanced Gas-Cooled Reactor fleet and constitutes a significant milestone at Hunterston B as it progresses to the next phase of its lifecycle.
In a further significant development, ONR has also approved a revision to the site's emergency plan in recognition of the significantly-reduced hazard at the North Ayrshire site in Scotland.
This comes after EDF successfully completed the defuelling of both reactors at Hunterston B, transferred all nuclear fuel off-site, and successfully completed comprehensive fuel-free verification activities.
Tom Eagleton, ONR Superintending Inspector, said: "Our specialist inspectors have conducted a thorough assessment of the safety case, and we are satisfied that it meets the high regulatory standards expected.
“As an enabling regulator, we are committed to working with EDF and Nuclear Restoration Services, who will assume operational responsibility for the site in 2026, in progressing the vital decommissioning work safely.
"This regulatory approval will enable EDF to progress these essential activities.
“Additionally, the extensive work undertaken in recent years to defuel Hunterston B has significantly reduced the nuclear hazard on the site, and we are therefore satisfied that it is appropriate for the emergency plan to be updated accordingly."
Hunterston B began operating in 1976 and stopped generation in 2022, during which time it produced almost 300TWh of electricity.
In April 2025, the site was declared fuel free.
During the next 15 years, the site will undergo decommissioning activities to prepare it for a prolonged period of care and maintenance for approximately 85 years before final site clearance work takes place.
ONR will maintain appropriate regulatory oversight of the site and will continue to conduct regular inspections to ensure all work is carried out safely and in accordance with regulatory requirements.
Further information about our regulation of decommissioning sites is available on our website.