The UK’s Hunterston B1 (Reactor 3) was permanently closed down on 26 November, marking the end of 46 years of operation for this 490MWe advanced gas-cooled reactor (AGR).
Hunterston B2 (Reactor 4, also a 490Mwe AGR) is scheduled to shut down in January. The Hunterston A plant, which is already closed, comprised two 180MWe Magnox reactors which began operation in 1964. Reactor 2 shut down in December 1989 and Reactor 1 in March 1990.
Construction of Hunterston B began in 1968 and reactors 3 and 4 began operating in February 1976 and March 1977. In 2012, EDF Energy extended the generating life of the plant to March 2023, with a two-year window either side of that date. Both units were taken offline in 2018 after cracks in their graphite cores were discovered during routine inspections. In August 2020, the UK Office for Nuclear Regulation (ONR) approved the restart of unit 2 in August 2020 followed by unit 1 in September 2020.
Huntrston NPP Director Paul Forrest noted that since unit 1 returned to service in September 2020 it “has had one of its best operating runs, experiencing no unplanned outages”. He added: “The exceptional performance of the unit to the end of its generating life is testament to the hard work and dedication of the people who work at the site."
Both reactors were taken offline earlier this year for further inspections of their graphite cores. In April, the ONR said the units could resume operation provided that inspection results were as expected. However, it limited operation to 16.7 terawatt days for unit 1 and 16.52 terawatt days for unit 2 - about six months of operation for each reactor. Unit 1 returned to service on 23 April and unit 2 on 5 June.
Forrest said: "The people here at Hunterston B are massively proud of the work they do. Every one of them has played a part in the success of the station and in supporting Reactor 3 generate enough zero-carbon electricity over its lifetime to power every home in Scotland for 15 years. While we will pause to reflect on this milestone, we are looking forward to the future. We will focus our efforts on the final six weeks of generation from Reactor 4 and ensuring the site is ready to start defuelling after that."
As soon as the nuclear power plant ceases operation, EDF will begin defuelling the station. EDF said preparations for defuelling have been under way for a long time and the process is expected to take a few years.
In June, the UK government and EDF agreed on improved arrangements to safely decommission the UK’s seven AGR nuclear plants that are scheduled to close this decade. The plants are Torness and Hunterston B in Scotland, Dungeness B in Kent, Hartlepool in Teesside, Heysham 1 and 2 in Lancashire and Hinkley Point B in Somerset. This followed an announcement by EDF that it had decided not to restart the first of the AGRs, Dungeness B, and to begin defuelling with immediate effect.
Photo: Inside Hunterston B (Photo: EDF Energy)