Cognition was appointed as Principal Contractor by Magnox to undertake remediation works, which related primarily to radiological contamination associated with the operation of the Harwell Liquid Effluent Treatment Plant. The remediation involved the demolition of underground structures and excavation of made ground within defined ‘Remediation Zones’, each zone having a different type and level of radiological contamination. All materials processed from the remediation area including concrete, steel rebar and subsoil had to be excavated, segregated, and loaded into 0.9m3 bulk bags for radiological monitoring. Once assayed these bags were then allocated as in-scope (active material) or out-of-scope (clean material). In-scope material was loaded into articulated lorries ready for transport, processing and storage at specialised facilities. Out-of-scope material (clean soils) were removed from site for disposal to landfill.

During the course of the works, Cognition processed a total of 78,549 bulk bags of material. Overall, this project has been the largest nuclear decommissioning and delicensing project in the UK.

After almost four years of demolition, excavation, radiological assessment, disposal and verification, the decommissioning works at Harwell LETP is finally complete. The site is now progressing through the delicensing route and will be reprofiled for future redevelopment. The detailed investigations, innovative assay, meticulous planning and materials management during the works has been challenging but the approach to decommissioning the site has received the praise of the client. This project has demonstrated how radiologically impacted sites can be delicensed and be given a new lease of life.