Final decommissioning of the former active handling Building A59 at UKAEA Winfrith

RWE NUKEM has been decommissioning the former active handling Building A59 at Winfrith since July 2000 for the site owners and nuclear site licence holders UKAEA, following a competitive tendering process. Following recent government changes the UK's Nuclear Decommissioning Authority has contracts with UKAEA for delivery of the site clean-up programme. Decommissioning work has centred upon two heavily shielded suites of caves originally used to carry out remote examination of irradiated nuclear fuel elements although other supporting facilities are also involved. Starting activity and contamination levels were extremely high in the two cave lines but decommissioning operations have steadily advanced and both facilities have now been decontaminated such that they are ready for demolition. The processes used to achieve this objective involved mainly standard off-the-shelf equipment but the work has demonstrated the importance of undertaking the task with the right tooling and lessons learnt will be described for the benefit of other operators. The essential challenge is always to achieve these objectives in a safe and cost-effective way whilst ensuring that the radiation exposure of the operators is kept as low as reasonably practicable (ALARP). This paper describes how the approach to cave line demolition had to be amended from the original plan owing to features of the original building design which provide structural support for the main fabric from the concrete cave line walls. As a result, the original plan to demolish the cave lines first could not be undertaken economically and the building itself will now be cleared, decontaminated and demolished ahead of these two major facilities. Considerable benefits have flowed from this decision and the paper will set out the advantages that have been gained, which may be of benefit to others carrying out similar tasks. Finally, the paper will explain how the achievement of cost-effective and safe solutions to all these problems has been greatly assisted by the employment of a non-adversary team-working approach between client and contractor. The decommissioning programme remains on schedule and has been achieved in a safe and efficient manner, demonstrating the worth of adopting this co-operative approach for mutual benefit. (authors)