Technischer Bericht NTB 93-26

Endlager für kurzlebige schwach- und mittelaktive Abfälle (Endlager SMA)Beurteilung der Langzeitsicherheit des Endlagers SMA am Standort Wellenberg (Gemeinde Wolfenschiessen)

This report was prepared as part of the documentation justifying the choice of Wellenberg as the proposed site for a low- and intermediate-level waste repository. The aim of the report is to provide information which will serve as a basis for comparing Wellenberg with the other three potential sites which were evaluated, and to document the deliberations and calculations which formed part of the safety analysis of Wellenberg as a potential repository site.

A conservative approach is adopted in the performance assessment, in that not all of those features of the site which potentially increase the achievable safety levels are considered and pessimistic assumptions are made in the event of uncertainties in the data.

The performance assessment results indicate that the site offers a sufficient degree of long-term safety. For the base case, which is founded on realistic-conservative assumptions, predicted radiation doses lie well below the dose limit of 0.1 mSv/a specified in the official protection objective of the Swiss authorities. Even for the wide range of parameter variations considered, the resulting radiation doses remain below the official protection objective – although the safety margins are smaller.

The results of the performance assessment therefore lead to the conclusion that there is sufficient justification for preparing an application for a general license for the Wellenberg site and for continuing investigation work in connection with construction of a L/ILW repository.