Decommissioning of a liquid effluent treatment R&D facility

Abstract

The United Kingdom Atomic Energy Authority (UKAEA) is responsible for managing the decommissioning of the nuclear reactors and other radioactive facilities used for the UKAEA nuclear research and development programme in a safe and environmentally responsible manner with the objective of restoring the sites for conventional use. It is also responsible for input to the European fusion research programme and for maximizing the income from the land and buildings at its sites at Dounreay in Scotland, Windscale in Cumbria, Harwell and Culham in Oxfordshire and Winfrith in Dorset. Building 336.28 typified the problems encountered during the removal of redundant facilities from the liquid effluent treatment plant at Harwell. The building was constructed in the late 1940s, was lined with asbestos limpet and contained a range of poorly characterized liabilities that had been ‘mothballed’ after use. Decommissioning was carried out following competitive tender. The work involved the removal of radioactive liquids and wastes, the dismantling and removal of contaminated tanks, vessels, glove boxes and test rigs and the demolition of the building. There were uncertainties associated with the radioactive inventory, the extent of the contamination beneath the floor slab and the processing requirements for the waste ion-exchange resins. These were addressed by a combination of characterization surveys (carried out by UKAEA at the pre-tender stage) and the use of unit work rates within the contract for some activities. In addition, the flexible approach by both the client (UKAEA) and the implementation contractor (NNC Limited) enabled the project end-point to be redefined to manage the widespread low-level contamination discovered beneath the floor slab.