Estimates of post-closure risk in regulatory decision making: environment agency issues and options

The Environment Agency of England and Wales (the Agency) is responsible for the authorization of radioactive waste disposal under the Radioactive Substances Act 1993. British Nuclear Fuels plc (BNFL) is currently authorised to dispose of solid low-level radioactive waste at a disposal facility near the village of Drigg on the Cumbrian coast, in north-west England. In accordance with Government Policy, the Agency periodically reviews authorizations for the disposal of radioactive waste. The Agency intends to commence its next review of the Drigg authorization in 2003/4. To inform its decision making, the Agency required BNFL to submit new safety cases for the Drigg disposal facility in September 2002. These have been received from BNFL and made publicly available (via national public registers): - The Operational Environmental Safety Case considers the impacts of the facility on the environment and the public in the period whilst the site remains operational and under institutional control, which BNFL estimates might be 2150. - The Post-Closure Safety Case considers the long-term environmental impacts of the facility after 2150 and includes a Post-Closure Radiological Safety Assessment, which is a risk assessment. This paper deals with estimates of post-closure risk, it specifically excludes the operational phase and regulatory controls thereon. The paper summarises work undertaken by the Agency to consider potential regulatory actions against different levels of risk in relation to the risk target set out in the published regulatory guidance. The work was undertaken principally in preparation for review of BNFL's Drigg post-closure safety case and authorization. (authors)