PLANS have been unveiled for Europe’s deepest nuclear clean-up at the decommissioned Dounreay plant in Caithness.
Work is expected to start next year on the huge task of removing an estimated 1,500 tonnes of radioactive waste from two underground facilities at the Caithness nuclear complex – a 213ft-deep vertical shaft and a nearby vault set 30ft below the surface.
The water-filled shaft was first used to store intermediate level waste from some of Britain’s earliest nuclear energy experiments in 1957. The silo – a shallow reinforced concrete bunker – was built in 1971 to store nuclear waste from the plant.
A report published in 1996 revealed that waste contaminated with sodium continued to be buried in the underground silo despite an explosion in 1977 caused by a cocktail of sodium, potassium and water.
The 1977 blast demolished seven metres of fencing, damaged asbestos walls, threw five concrete slabs weighing five tonnes each up to two metres away and blew a concrete and steel lid, weighing 12.5 tonnes, several metres into the air.
The vertical shaft, 15ft in diameter, contains about 750m of intermediate level waste. The silo was used to dispose of 500 metres of intermediate waste until it was closed in 1998.
Plans for the £100 million clean-up operation, due to be completed by 2021, are now to go on public display in nearby Thurso ahead of an application for the work being submitted next month to Highland Council by Dounreay Site Restoration Ltd, the site licence company acquired earlier this by the Babcock Dounreay Partnership.
A spokesman for the company said: “This will be Europe’s deepest nuclear clean-up. An estimated 1,500 tonnes of radioactive waste was consigned to the two facilities between 1957 and 1998. Radiation levels are too high for man-entry to either facility, so robotic equipment will be used to retrieve, analyse, shred and package the waste.
“A 60-strong team is now working on the project, with employment levels expected to peak at about 200 during the construction phase in 2013-16.”
The plan involves the construction of waste processing facilities above each storage facility where the retrieved waste will be treated and packaged before being transported to an onsite store.
The spokesman said: “The project team is looking wherever possible to use technology already proven elsewhere such as remote vehicles, shredders, remotely-operated grabs, water treatment and monitoring.
“They will solidify the processed waste in a type of container that is new to Dounreay but proven by the nuclear industry in other parts of the world.”
He added: “The use of boxes made from steel, lead and concrete will provide shielding from harmful radiation and remove the need to build a heavily-shielded store for the previous design of containers. This will save tens of millions of pounds.”
Bo Wier, the project director, said: “Emptying the shaft and silo at Dounreay is one of the biggest clean-up challenges in Europe and one of the priorities for the Nuclear Decommissioning Authority (NDA) in the UK.
“We believe we can deliver the decommissioning on an earlier timescale and at lower cost than previously thought by combining proven technology with innovation in design.
“By 2021, we aim to have all the waste safely packaged for long-term storage above ground and both facilities left in a condition that do not pose a hazard to future generations.”