A Post-Closure Radiological Safety Assessment (PCRSA) was undertaken by British Nuclear Fuels plc (BNFL) to support the Post-Closure Safety Case produced in September 2002 for the low level radioactive waste disposal site at Drigg, Cumbria.

The PCRSA provided a qualitative and quantitative evaluation of the long-term radiological impacts from disposals at the Drigg site. A structured, iterative approach to the PCRSA was used to define the context and scenarios for consideration, to describe the engineered disposal system and its environment, to assess the impact through calculations and qualitative arguments and to feed back the results to the safety case and forward programme of technical work.

The results of the PCRSA have identified that the most important radionuclides in term's of radiological impact are disposed uranium and thorium and their daughter products. The key exposure pathways relating to future impacts are the migration of radionuclides in groundwater and release to future terrestrial environments, exposures resulting from the potential disruption of the site by natural events, such as coastal erosion and glaciation, and speculative inadvertent human intrusion into the site. The PCRSA results have been used to identify areas for potential future work to address key areas of uncertainty, as part of the iterative assessment approach.

Further focused analysis has enabled key pessimisms and uncertainties to be identified and assessed in support of the evaluation and development of options for the future management of the Drigg site.