Handling of timescales in safety assessment: the swiss perspective

This paper is intended as a contribution to the discussion of current approaches to the handling of timescales in safety assessments within national waste management programmes. It makes full use of on-going work within Nagra's Project Entsorgungsnachweis. This project is based on a specific site; it considers a repository in the Opalinus Clay of the Zurcher Weinland region in northern Switzerland. The repository is designed for the disposal of spent fuel (SF), vitrified high-level waste (HLW) from the reprocessing of spent fuel, and long-lived intermediate-level waste (ILW) and is accessed via a ramp and a shaft. Emplacement of the wastes is in near-horizontal tunnels. Project Entsorgungsnachweis is divided into three sub-projects: a synthesis of information from geological investigations of the Opalinus Clay, an engineering feasibility study and an assessment of long-term safety. Project Entsorgungsnachweis is a milestone in the programme for the disposal of SF, HLW and ILW and addresses an evaluation of the feasibility of the disposal of these wastes in Switzerland. It is also a major step on the way towards repository implementation. The corresponding reports will be submitted to the Swiss Government at the end of the year 2002. (authors)