A monitoring plan is an important part of a disposal programme. Monitoring a deep geological repository for the disposal of radioactive waste faces several challenges. These may arise from the technically demanding environment in which the monitoring equipment must operate or from the potentially long period of time during which they must operate. Over the past decades, a lot of experience has been gained in monitoring experiments in underground research laboratories (URL).
Since the HADES URL became operational in the 1980s, thousands of sensors have been installed. To document the experience gained in this context, ONDRAF/NIRAS launched a research project to evaluate the performance of the monitoring equipment implemented in the HADES URL. This required developing a method to assess the performance of sensors in a consistent way. The methodology is explained in this paper and illustrated for the instruments installed to monitor the THM response of Boom Clay to the large scale PRACLAY
In Situ
Experiment.
Demonstrating the feasibility of constructing tunnels in deep clay formations is an important goal of the Belgian RD&D programme on the geological disposal of radioactive waste. In 2002 a major achievement was reached when the HADES Underground Research Laboratory (URL) in Boom Clay was extended with the construction of the Connecting Gallery. This demonstrated that it is feasible to construct galleries in poorly indurated clays using industrial techniques. To monitor the mechanical behaviour of the gallery and assess its stability, strain gauges were embedded in the segmental gallery lining and prisms were installed on the segments. These sensors provide valuable information that will support the design of future galleries. This paper presents the acquired 20 years of monitoring data in the Connecting gallery and a first analysis of these data in term of Boom Clay behaviour. In addition, the key findings are compared to those of a similar analysis performed by Andra (the French Radioactive Waste Agency) at the Meuse/Haute-Marne URL. The latter URL is excavated in the Callovo-Oxfordian claystone (COX). The comparison identifies general trends and highlights similarities between the behaviour of tunnels in poorly indurated clay (Boom Clay) and in claystone (COX).
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