Workers at the former research site at Dounreay, Scotland, are preparing to break open and remotely dismantle equipment within a used nuclear fuel reprocessing plant.
Redundant equipment and controls from the exterior of the plant have already been removed by a three-year operation. The next stage is to tackle the 'labyrinth' of pipework within the plant's 150-cm-thick concrete walls.
Highly radioactive used nuclear fuel from Dounreay's Materials Test Reactor and similar units built abroad was reprocessed at the facility from the 1950s to 1996. The chemical process separated the high-enriched uranium used by the reactors, which was valuable and suitable for recycling, from a much smaller stream of waste for disposal.
Decommissioning such a facility poses many engineering problems, particularly because of the high levels of radiation that were present in the used nuclear fuel and the dangerous and corrosive nature of chemicals used in the separation process. Site operator the UK Atomic Energy Authority said that the pipework had been cleaned out with an 'aggressive' cleaning fluid.
Because of the levels of radiation that remain within the building, the pipework will be dismantled using robots. Before this can happen, workers must break open the 150-cm-thick reinforced concrete containment structure.
In addition to the main plant, a cooling pond that held the used fuel before reprocessing is being cleaned out in preparation for demolition. The overall decommissioning process began in 2000 and is expected to be complete by 2010 at a cost of £15 million ($29 million).
The Dounreay site is operated by the UKAEA under the ownership of the Nuclear Decommissioning Authority which has developed the program of work required to decommission the UK nuclear facilities left over from previous national programs.