DISMANTLING OF A CONCRETE SHIELDED FACILITY

Decommissioning processes have been developed for a small but heavily contaminated, concreteshielded remote handling cave as a precursor to operations on two much larger facilities within one building at the United Kingdom Atomic Energy Authority's (UKAEA) Winfrith Technology Centre. Techniques have been developed to maximise the amounts of contaminated materials that can be removed from the cave remotely in order to minimise operator dose uptake. This has been achieved using both shielded flasks and other semi-shielded containers together with setting of maximum dose-rates on removed items. Man entries with well established cleaning techniques have been used to reduce the contamination levels such that the whole structure can be dismantled. Particular attention has been paid to provision of a safe lifting arrangement for five 40Te concrete shielding blocks, which form a major part of the structure. Additionally, methods are being developed to demolish 36 cubic metres of steel-reinforced concrete in a simple and cost-effective manner. Finally, a protocol has been developed for the removal of paints and contamination from the large concrete blocks and many other items with the objective of achieving free-release disposal, thereby saving considerable sums of money for the contractor and ultimately the client. A commercially based shot blasting technique will be utilised here to achieve the required levels of cleanliness demanded by the appropriate regulatory authorities.