Sellafield tallest chimney to be dismantled

The chimney (centre) is the tallest historical structure on the site

Sellafield's tallest structure is going to be dismantled in a "delicate operation" lasting a number of years.

The 200ft (61m) chimney was built in the 1950s on top of an 11-storey reprocessing plant on the nuclear site.

It no longer meets modern design standards and needs to be demolished, but owing to its location, the use of explosives has had to be ruled out.

Instead, a platform will be constructed and steeplejacks will dismantle the huge structure bit by bit from the top.

They will have to remove 600 tonnes of concrete and more than 25 tonnes of stainless steel.

A special self-climbing platform will be built at the top of the structure

Matthew Hodgson, the project manager, said: "The job of bringing down the stack is going to be a delicate operation to ensure 100% safety of all personnel and surrounding nuclear plants.

"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.

"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: "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."

The first phase of the work, to install an industrial lift and a roof bridge structure, allowing access to the base of the chimney, is about to begin.