A major demolition project is under way on one of the tallest hazards at Sellafield.

A chimney on top of the nuclear site's first generation reprocessing plant is being taken down as it does not meet modern safety standards.

At 61m in height and sitting on top of a 61m building, the stack was the tallest structure on the nuclear site until a modern replacement was built.

Now it is being deconstructed at a rate of one metre a week, in a project that will run until 2020 and change the Sellafield skyline.

When in operation, the stack provided ventilation for a fleet of reprocessing plants.

But the 60-year-old structure no longer meets seismic safety standards so it must be removed as a priority.

Because the chimney is in a crowded area of the site, conventional demolition techniques like explosives and cranes cannot be used on it.

Instead, Sellafield Ltd has worked with Nuvia Ltd and steeplejacks Delta International.

A self-climbing platform has been designed, engineered and installed to act as a podium so that workers can safely access the 650 tonne chimney.

Using handheld tools like drills, hydraulic breakers, concrete crunching jaws and plasma steel cutting torches, workers will remove each piece of concrete and steel from the stack by hand to a waiting waste skip.

The demolition started in October, with workers accessing it from the circular platform, which is held in place by friction, and moves up and down the barrel of the stack.

The preparation work for the project saw Nuvia win the Technology Innovation Implementation award at the 2017 NDA Estate Supply Chain Awards.

Stuart Latham, head of remediation at Sellafield Ltd, said: “Cleaning up our legacy facilities safely, quickly and cost-effectively is our absolute priority, so are delighted to now see the stack coming down after four years of preparation.

“Given the structural integrity of the stack, its location in the heart of the site and the fact that this new technique has never been used here before, the planning has been comprehensive. The project demonstrates the challenges of decommissioning the Sellafield site.

“We couldn’t move a crumb of this chimney without building a modern replacement first, so this has been a complicated project, made easier by working closely with our supply chain.

“Safety is the number one priority, so thorough testing has helped us ensure everything works as it should.”

Mina Golshan, director of the Office for Nuclear Regulation's Sellafield, decommissioning, fuel and waste division, said: "Starting demolition of this redundant stack is a key achievement by Sellafield and another important step towards reducing the risk and hazard posed by legacy facilities on site in order to further enhance safety. This is the focus of our regulatory strategy for the site.

"Our inspectors have engaged with Sellafield Ltd during the design, build, testing and commissioning phases and gathered evidence that assured us of the suitability of the proposed demolition activity and Sellafield’s supporting safety case."