At Dungeness B nuclear power station on a remote stretch of the Kent coast in south-east England, workers are making preparations to carefully remove thousands of radioactive fuel elements from its reactors and transfer them to a purpose-built pond for at least 90 days for cooling.

The spent fuel will later be packed into 53-tonne “flasks” fortified with 39cmthick steel walls before being transported across country by train to Sellafield in Cumbria.

The nuclear facility in north-west England is host to most of the radioactive remnants of Britain’s civil nuclear programme that dates back to the 1950s. These include highly toxic waste that will remain there until a suitable site is found for an underground repository where it will have to be stored for more than 100,000 years to make it safe.

Preparations for the “defuelling” of Dungeness B started with “immediate effect” on June 7 when its majority owner, French state-controlled utility EDF, announced it would close the plant seven years early. It had not been operational since September 2018 as engineers tried to fix problems, including corrosion and cracks in its pipework.

The 1.1GW plant is the first of seven built in the UK between the mid-1960s and late-1980s using advanced gas-cooled reactor (AGR) technology to come out of service. It will kickstart a decommissioning process spanning generations, which sceptics argue strikes at the heart of why no new nuclear plants should be built.

The remaining six AGR plants are due to be retired by the end of this decade at the latest, leaving the more modern Sizewell B plant in Suffolk, which uses pressurised water reactor technology, as the only one operational out of the existing fleet.

“[Decommissioning ofl many of these facilities will continue well into the 22nd century,” said Paul Dorfman of University College London’s Energy Institute. “The problem with decommissioning is it always turns out to be more complex than one had imagined.”