The Demolition of the Sellafield Pile 1 Chimney - 22434

A significant seismic risk was identified with the highly contaminated redundant Sellafield Pile 1 chimney which initiated its demolition. A comprehensive characterisation programme of the structure confirmed that the concrete was classified as Low Activity Low Level Waste (LALLW). The radiological properties of the concrete did not meet the criteria stipulated in the Conditions for Acceptance (CfA) for the onsite disposal facility, the Calder Landfill Extension Segregated Area (CLESA). To enable the waste to be disposed of to the CLESA, large scale decontamination of the internal surface of the concrete structure was anticipated. Alternative disposal facilities were available, these being an off-site specified landfill 126 miles away from the Sellafield site and as Low Level Waste at the UK's Low Level Waste Repository (LLWR). Both options would require packaging the waste into more than 74 Half Height Isofreight (HHISO) containers and transporting them accordingly. In collaboration with various stakeholders it was decided that the waste management Best Available Technique (BAT) was to dispose of the waste via the onsite landfill. This required modification of the Environmental Safety Case to increase the specific activity limit to 200 Bq/g. A reassurance characterisation programme was initiated which demonstrated that 217 out of the 238 blocks removed to date, are compliant with the CLESA CfA. The non-compliant concrete blocks will be remediated in order to further reduce the volume of LLW presented for final disposal at the LLWR. Modification of the, CLESA's Environmental Safety Case (ESC) prevented the need for large scale decontamination and a reduction of circa 8,900 miles in transport and preserved valuable capacity in the National Low-Level Waste Repository. (authors)