Risk-Based Radiological Site Investigation and Assessment Methodology for the Sellafield Site, Cumbria, UK

A preliminary assessment of the Sellafield site in Cumbria was undertaken to provide the information for the hazard identification stage in the environmental risk assessment process. This preliminary investigation has been crucial to understanding the site’s history, the zones of potential risk and for the design of a site investigation. The formalised assessment strategy that has subsequently been developed by BNFL for the Sellafield study has drawn upon UK and international guidance to take into account the size of the site and the anticipated complexity of issues. The approach presented represents an advance on existing working practices in contaminated land investigations. The use of a generic list of Features, Events and Processes (FEPs) has been adopted to ensure the systematic and comprehensive appraisal of all relevant uncertainties and sources of risk. Proforma have also been developed to provide a data management and retrieval system that is transparent for quality assurance purposes. This unique approach facilitates the development of conceptual site models as new data become available during the site investigation. It also aids in the development and justification of alternative site conceptualisations and in the early identification of data and interpretative uncertainty.