Natural analogues in SKB safety assessments

On the behalf of the Swedish nuclear energy producers the Swedish Nuclear Fuel and Waste Management Co is responsible for the management of radioactive wastes outside the power stations. The start of the construction of the final disposal facility for spent fuel is planned for the year 2010. During the early 1990-ies a few sites will be selected for detailed geological investigation from repository depth, the conceptual design of the engineered barrier system will be selected in mid 1990-ies and an application for siting the repository will be made around year 2000. Seen from the safety assessors point of view a favorable development has taken place during the last 5 year period both in investigations of natural analogues and in applying them to long term safety of repositories. Areas in need for further development through international cooperation are now seen to be coupled to the use of the results. How should the measure of validity be expressed. What is the level of validity required