Responding To Changes in the Decommissioning Plans for Demolition of a Former Active Handling Building at The United Kingdom Atomic Energy Establishment Winfrith

The full decommissioning of the former Active Handling Building A59 at Winfrith in Dorset is being carried out by RWE NUKEM Limited under contract from the site owners and nuclear site licence holder, United Kingdom Atomic Energy Authority (UKAEA). Following recent government changes, the United Kingdom's Nuclear Decommissioning Authority (NDA) has now set up contracts with UKAEA for delivery of the site clean-up programme. The building contains two heavily shielded suites of caves originally used to carry out remote examination of irradiated nuclear fuel elements together with other supporting facilities. The original intention was to demolish the caves ahead of the building but after detailed consideration it was concluded that demolition of the building in advance of the caves was more operationally effective. As a result, the original decommissioning plan had to be reworked to reflect these changes. The paper briefly explains how this situation arose and the means by which the problems experienced were overcome by a complete revision to the decommissioning programme. The updated plan has been adopted by UKAEA and work is now proceeding apace to clear the building of redundant items, to complete decontamination of all remaining areas and facilities and to carry out detailed radiologicalmore » surveys to confirm that the building structure is clean and ready for demolition. Both cave lines have been completely decontaminated to low residual levels of activity and are essentially ready for controlled demolition. This paper describes some of the significant tasks undertaken during the past year with particular reference to the decommissioning techniques that gave the greatest success and the limitations of others originally considered. Some of these processes were aimed at minimising the volume of low level waste (LLW) generated by using standard off-the-shelf equipment to remove contamination from {approx}5 Ton concrete blocks recovered from both cave line structures. A novel hot-cutting technique used to remove steel coatings from sections of each block was also instrumental in assisting with achieving this objective. Finally, the paper sets out the plans that have been developed for the sequenced demolition of the building structure, the two heavily reinforced concrete cave lines and the base slab. This will include details of the means by which residually contaminated and partly inaccessible items will be recovered for disposal during the demolition process. The decommissioning programme remains on schedule and has been achieved by the employment of a non-adversarial team working approach between client and contractor. This has greatly assisted in developing cost-effective and safe solutions to a number of problems that have arisen during the programme, demonstrating the worth of adopting this co-operative approach for mutual benefit. (authors)« less