Technischer Bericht NTB 96-03

Endlager für schwach- und mittelaktive Abfälle (Endlager SMA) Zwischenbericht über die Untersuchungen 1994/95 am Standort Wellenberg (Gemeinde Wolfenschiessen, NW)

Following submission of the application for a general licence by GNW in June 1994, Nagra continued as planned with the field work at the Wellenberg site and with analysis of available data. In view of the delay in procedure brought about by the cantonal vote of 25th June 1995, the Federal Office of Energy requested GNW to review the geological content of the general licence application in the light of more recent investigation results in order to give HSK (the Swiss Federal Nuclear Safety Inspectorate) access to the most up-to-date information when preparing its opinion. This is the purpose of the present report, which discusses the current status of ongoing analyses. The report concentrates on the main results only and is correspondingly concise; it is in no way intended to anticipate the final report on the Wellenberg investigations.

The report begins by outlining the aims of the site investigations of 1994/95 and goes on to discuss the field work performed at the site. The raw data available from the field investigations are also presented.

The main section of the report discusses the first analyses of the data; these are then summarised into a set of geological conclusions which are complemented by a preliminary safety analysis. The resulting conceptualisations and parameter values clearly lie within the confines of the geological dataset used for the general licence application.

It can therefore be concluded that the field investigations and complementary studies performed since the submission of the general licence application confirm the validity of the basic findings of the reference reports which formed the background to the application: the selected site is suitable for continuing investigations with a view to construction of a L/ILW repository.