Successful clean-up of radiological contamination

The Harwell Nuclear Licensed Site in Oxfordshire has successfully cleaned up and delicensed part of the site. The site was a former RAF airfield before it was used for research associated with the development of nuclear power in the UK. The original licensed site was 113 hectares, containing four research reactors. A phased approach to delicensing was adopted based on the programme for decommissioning the facilities. In 1992 five hectares were delicensed and in 2006 a further seven hectares, originally containing 43 buildings, were delicensed. Ten of the buildings had been used for work involving radioactivity. The facilities were decommissioned and the land and buildings certified free of ionising radiation and available for non­nuclear development. A further five hectares, including the former site of the research reactor GLEEP (the graphite low energy experimental pile), were delicensed in 2011. In this instance, all the buildings were demolished and some concrete foundations were left. The case for delicensing a further five hectares has been submitted. Experience gained in the delicensing work was that it is important to pay attention to detail and to work with the ONR as far as possible. It is best practice to build delicensing require­ments into decommissioning and land remediation works and to keep good decommissioning and remediation records. Often it is important to demon­strate the absence of something, for example that the section of drain is not there any more.

Since 1984, a programme of monitoring for radioactive objects has been carried out on beaches in the vicinity of the Sellafield site in West Cumbria. During this programme, over 650 radioactive objects were identified and removed up to the summer of 2009, comprising particles with sizes smaller or similar to grains of sand and also contaminated pebbles and stones. These objects have a much higher activity content that can be easily distinguished from the ambient homogeneous levels of contamination on the beaches. The source of these objects is not known but there have been a number of known events in the past that have resulted in release of radioactive parti­cles into the environment, including early operation of the Windscale piles (1952 to 1957), the Windscale fire in 1957 and the beach incident in 1983. Hence the management strategy for the clean-up of the beaches has to consider a wider context than just the beaches, e. g., the terrestrial and marine environment.

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