Dounreay Prototype Fast Reactor Coming Apart

17th January 2007

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Work to pull apart Dounreay's Prototype Fast Reactor (PFR) is rapidly advancing with more and more large items of redundant equipment being ripped out of the former reactor complex as the plant is dismantled.

Dounreay is at the leading edge of world-wide clean-up of former nuclear facilities, and as demolition progresses removal of massive and extremely heavy steel structures presents a challenging task to the site.

This phase of pulling apart the plant has seen the removal of the largest amount of steelwork from the facility since decommissioning began and has resulted in the first visible external impact of the reactor demolition by leaving a noticeable gap on the Dounreay skyline.

This £1m project is major progress for PFR. The project involves the strip-out of the steam generating building and the three secondary sodium circuits, with the associated redundant plant and equipment being removed for disposal. One of the major items size reduced and removed was the twenty-seven metre high main steam stack, weighing thirteen tonnes, which was cut into five sections using the 'PetroGen' hot cutting technique. These sections were carefully and slowly raised through the roof of the former turbine hall, using the tallest crane since the construction of the
facility forty years ago, towering some 126 metres over the steam generating building. The two remaining forty tonne steam boilers were also size reduced and removed.

A pioneering cold diamond wire cutting technique is also being used to size reduce the eight thirty-two tonne secondary circuit heat exchanger tube bundles. The diamond wire resembles a thick diamond encrusted cheese slice, which drives its way through lumps of redundant steel with minimal waste generation as no coolant is required to cool the wire.

John Lehew, head of the site decommissioning programme, said: "This is another historic milestone in the restoration of the Dounreay site on behalf of the Nuclear Decommissioning Authority. Removal of redundant equipment from our plants is crucial to enable the decommissioning programme to proceed. UKAEA's project manager, Rashid Abdulla, and his team, have worked extremely hard to ensure the safe and successful stripping out of this area in order to proceed with the redundant plant dismantling."

Following its shutdown in 1994, PFR is undergoing a 30-year decommissioning programme. The facility presents hazards associated with forty year old construction materials, heavy plant and specialised mechanical equipment, combined with radiological issues and the major hazards associated with removal of the sodium liquid metal coolant.

Dr Jim McCafferty, PFR decommissioning manager, has paid credit to Nukem Ltd, Baker Dougan Ltd, Caithness Scaffolding (Contractors) Ltd, Sureclean and Hugh Simpson (Contractors) Ltd, who were all involved with this work: "This is a great team effort, UKAEA and its contractors have worked tirelessly to ensure the safe stripping out of this area in order to proceed with dismantling the PFR facility."

Note
PFR operated for twenty years from 1974 until 1994. 1500 tonnes of liquid sodium metal was used as the coolant to transfer the heat from the reactor core through to the three secondary circuits to a steam-generating plant for electricity production. All the nuclear fuel was removed from the reactor following its closure and the next phase of decommissioning is to complete the disposal of the remaining sodium using the revolutionary Water Vapour Nitrogen process (WVN) process following the destruction of the majority of the sodium via the sodium disposal plant. PFR had the dual role of providing power to the national grid and offering unique research and development facilities. PFR provided information for the future design and operation of large commercial fast reactor stations and had an electrical output of 250 MW, which was enough electricity to supply a city the size of Aberdeen.

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