Remediation of the Site of a Former Active Handling Building in the United Kingdom

In 2000, Nuvia Limited was contracted to carry out the decommissioning of a former Active Handling Building A59 on the United Kingdom Atomic Energy Authority (UKAEA) site at Winfrith in the UK. This is in support of UKAEA’s mission, which is to carry out environmental restoration of its nuclear sites and to put them to alternative uses wherever possible. Recently UKAEA has been reorganised and responsibility for the site lies with Research Sites Restoration Limited (RSRL) with funding provided by the National Decommissioning Authority (NDA). Following major decommissioning operations the main containment building structure and the two suites of concrete shielded caves were demolished between June 2006 and March 2007 leaving just the base slab for final removal and the site remediation operations undertaken. The base slab contained a quantity of encast, internally contaminated items including more than 100 steel mortuary tubes set up to 6.6m deep into the slab. At the outset it was suspected that some leakage of radioactive contamination had occurred into the ground although the precise location/s of the leakage was unknown. As a result the scope of the work required the underlying soil to be carefully monitored for the presence of radioactive contamination and, if detected, its remediation to an end state suitable for unrestricted use without planning or nuclear regulatory controls. These latter operations form the basis of this paper, which reviews some of the significant tasks undertaken during the process and describes the waste monitoring procedures utilised on the concrete and soil debris. Extensive dewatering was required to support the removal of the deeper mortuary tubes and the impact this had upon the operations and associated excavations will be described. Further, the demolition of an external active effluent tank and excavation and monitoring of the surrounding soils due to the presence of significant local contamination will be a key feature of the paper. A number of significant problems that were encountered during the operations will also be identified with a narrative about how these arose and were subsequently overcome. The use of Nuvia’s Groundhog™ system, a gamma radiation ground surveying and global positioning system, together with a well defined sampling grid enabled the footprint of the base slab to be surveyed and subsequently remediated to an agreed standard by the end of 2008 to allow infilling with non-calcareous soil ahead of final landscaping as the last step for completion of the project. One area of particular significance to the remediation process has been the use of office-based contaminated land assessment tools including ReCLAIM, a Microsoft Excel spreadsheet based tool used to assess current and future impacts of radiological contamination at nuclear licensed sites. This tool is particularly recommended to others working on similar projects.Copyright © 2009 by ASME