Sellafield chimney demolition to set new heights
By Lindsay Gale22 July 2014
The skyline at the UK’s pre-eminent nuclear facility of Sellafield is set to be altered forever when a 1950s vintage 61 m (200 ft) chimney that sits atop the 11 storey high fuel reprocessing centre is demolished. Its location means that the top of the chimney stands 122 m (400 ft) from the ground. Its location at the heart of the Sellafield complex rules out the use of explosives, so the team carrying out the work will use a climbing platform to dismantle the structure and bring the estimated 600 tonnes of concrete and rebar, and 25 tonnes of stainless steel that will result from the work to the ground.
Recent assessments of the 1950s stack have confirmed that it does not meet modern design standards and its removal is considered a high priority for Sellafield Ltd, the Nuclear Decommissioning Authority and the Office for Nuclear Regulation (ONR).
Work on site will soon begin to install an industrial lift and a roof bridge structure, allowing access to the base of the chimney. The lift and bridge will then be used for the removal of waste materials when demolition starts. The demolition will take several years to complete.
Project manager Matthew Hodgson said: “The job of bringing down the stack is going to be a delicate operation to ensure 100 per cent safety of all personnel and surrounding nuclear plants. We have employed Nuvia Limited who has been working with us and a number of other contractors, including Delta Steeplejacks, for the last three years on the demolition scheme.
“Obviously conventional demolition using explosives is not feasible therefore we will use an ingenious self-climbing platform which will bring the chimney down bit by bit in a controlled manner.”
This dismantling technique has recently been used in the demolition of the Battersea Power Station’s famous chimneys on the banks of the Thames River in London, which were then been re-built to preserve the appearance of the capital’s iconic building.
Matthew added: “A mini-replica of the tapered chimney will be built to test the methodology as the diameter of the chimney increases the lower you go down, so the platform will correspondingly have to increase in size. A specialist diamond wire cutting system will be used to remove large sections of the concrete structure and the internal metal flue, all of which will have to be lowered to the base of the stack for monitoring before disposal.”
Steve Slater, Head of Decommissioning said: “Demolishing this chimney will represent a very visual demonstration of our commitment to tackling one of the most guarded parts of Sellafield’s legacy.
“The plant was built in the shadow of the war to secretly produce nuclear materials for the UK’s defence programme. It reprocessed fuel from the pile reactors and was then later used for commercial fuel reprocessing before the Thorp reprocessing plant took over.
“It’s going to be out with the old and in with the new, with the new Separation Area Ventilation (SAV) stack taking over. Work to construct that new replacement stack is continuing.”