Installation of the PRACLAY Seal and Heater

In 2011 the last phase in the installation of the PRACLAY In-Situ Experiment in the underground research facility HADES was completed. The main goal of the experiment is to perform a large-scale in-situ Heater Test. The Heater Test will examine the effect of the thermal load generated by heat-emitting waste on Boom Clay, currently considered as a potential host rock in the Belgian R&D programme for geological disposal. In 2007 the PRACLAY gallery was constructed to host the Heater Test. In 2010 a bentonite-based hydraulic seal was installed in this gallery, isolating the heated part from the non-heated part of the PRACLAY gallery. The primary objective of the seal is to provide undrained hydraulic boundary conditions for the Heater Test. As the performance of the seal is crucial to the Heater Test, it has been instrumented accordingly. The seal also provides an opportunity to gather additional information on the in-situ behaviour of bentonite-based repository structures. Finally the placement of a heating system and water-saturated sand in the heated section of the PRACLAY gallery completed the experiment installation. The water-saturated backfill sand has to assure undrained hydraulic boundary conditions at the interface between the clay and the gallery lining.