[en] Windscale Piles 1 and 2 in Cumbria in the UK were constructed in the early 1950s. They were not intended to produce electricity but were for military purposes only. They were graphite-moderated, air-cooled reactors with horizontal fuel channels fuelled with uranium rods clad in finned aluminium. In October 1957, Windscale Pile 1 suffered a core fire during a planned release of Wigner energy and both Piles were subsequently closed down. Following the fire, Pile 2 was defuelled entirely and as much fuel as was possible was removed from Pile 1. However, it is estimated that up to 15 Te of fuel remains in the core, a large proportion of which is located in the central Fire Affected Zone (FAZ). The condition of the fuel and graphite moderator in the FAZ is not known. It is possible that the moderator could contain voidage, greatly reduced density graphite and fused materials in a disordered matrix. It is probable that there is residual Wigner energy in the graphite. Use of water as part of the attempt to extinguish the fire, together with the possibility that the solidification of molten materials or other local sealing mechanisms could have excluded air mean that uranium hydrides, carbides and other pyrophorics may be present within the core. Pile 1 is now being decommissioned and a considerable amount of preparatory work has already been carried out during Phase 1. Phase 2 decommissioning, which will remove the residual fuel, the moderator and associated steelwork, condition the wastes and place them in a purpose built store is now underway. This work will be carried out for the site licensee, the United Kingdom Energy Authority, by a consortium of British Nuclear Fuels plc, Rolls Royce and NUKEM. This paper will describe the methods to be used to decommission Pile 1 and the systems and procedures which will be used to ensure that it is done safely and with the lowest reasonably practicable environmental impact. It will also describe the methods which will be used to ensure that the radiation doses received by the decommissioning workers will be as low as reasonably practicable. (author)