AGRs were the second generation of nuclear reactors to be built in the UK – the first being Magnox reactors. They use carbon dioxide as coolant and have been the backbone of the UK’s nuclear power fleet since the 1980s.

Seven AGR stations comprised of fourteen reactors (two at each station) were built between the 1960s and 1980s – Hunterston B, Hinkley Point B, Dungeness B, Heysham 1, Hartlepool, Heysham 2 and Torness.

But there are now just four reactors still operating, which are all expected to be closed by the end of the decade.

In 2020, EDF announced it would close Hunterston B the following year, two years earlier than planned, after various fractures were found in about 10 per cent of the graphite bricks in the reactor core.

The defuelling of Hunterston B’s Reactor 3 took around 16 months and work is now due to start on the station’s second reactor.

The aim is to have the second reactor defuelled and all spent fuel sent to Sellafield by mid-2025...