Hunterston B, a nuclear power plant in North Ayrshire, Scotland, has become the first of the UK’s seven advanced gas-cooled reactor (AGR) facilities to complete defueling, marking a key step toward decommissioning. Operator EDF Energy announced that the process, covering both reactors, was completed on time and within budget, following thorough inspections by EDF and the Office for Nuclear Regulation (ONR).

The plant consists of two 490 MWe AGRs, Reactor 3 and Reactor 4. Reactor 3 began operating in February 1976 and was shut down in November 2021, while Reactor 4 started in March 1977 and ceased operation in January 2023. Originally designed for a 25-year lifespan, both reactors operated for over 45 years. Defueling, which took two years and 10 months, involved removing 4,880 used fuel elements, processed and packaged into nearly 350 specialized flasks. Reactor 3’s defueling began in May 2022 and took 16 months, while Reactor 4’s started in November 2023 and lasted 14 months. The fuel was transported by rail to Sellafield, Cumbria, for long-term storage.

Next year, the nuclear site license for Hunterston B will transfer from EDF Energy to Nuclear Restoration Services (NRS), a subsidiary of the Nuclear Decommissioning Authority (NDA), which will oversee the site’s decommissioning. This process will involve dismantling and demolishing the plant and its buildings. Hunterston B Station Director Andy Dalling stated: “Defueling the station on time and on budget has been down to the hard work and commitment of everyone involved and we are proud to have been able to deliver such an exceptional performance. We are now fully focused on getting the station ready to transfer from EDF to NRS for decommissioning in around a year’s time.”

NDA Group CEO David Peattie added: “This is a significant achievement, and I want to congratulate EDF, the staff at Hunterston B, and all those involved from the NDA group who worked tirelessly in partnership to make this happen. We look forward to welcoming Hunterston B into our group.” He emphasized NRS’s expertise in nuclear decommissioning and waste management, which will support the site’s transition.

Hunterston B is one of seven AGR plants in the UK, alongside Torness, Dungeness B, Hartlepool, Heysham 1, Heysham 2, and Hinkley Point B, all scheduled to cease operations this decade. In June 2021, EDF and the UK government agreed to streamline AGR decommissioning, with EDF focusing on rapid defueling before transferring sites to the NDA. Currently, Hinkley Point B and Dungeness B are in the defueling stage, while Hartlepool, Heysham 1, Heysham 2, and Torness remain operational, with expected closures between March 2026 and March 2030.