The ESDRED project: Engineering studies and demonstration of repository designs

The construction, operation and closure of a deep geological repository for spent fuel and long-lived radioactive waste in clay involves specific technologies. The demonstration of these techniques at an industrial scale is being carried out in the frame of a technological integrated project within the sixth Framework Programme of EURATOM. The Belgian design for high level waste disposal is based on the so-called Supercontainer concept. Within this concept, the waste is encased in a carbon steel overpack, which is consequently fitted into a 70 cm thick concrete shell, in its turn enveloped by a stainless steel liner. A Supercontainer measures about 2 m in diameter. In the design of the repository, the Supercontainers will be emplaced, one after the other, in disposal galleries. The space between the Supercontainers and the gallery lining needs to be filled up with a solid material. The most essential function of this component, referred to as backfill, is to prevent a collapse of the gallery. A secondary function is to limit the presence of free oxygen, to limit corrosion. In the ESDRED project EIG EURIDICE, together with SCK-CEN and ONDRAF/NIRAS, investigates technologies to apply the backfill. After testing two techniques to apply the backfill in 2007 at limited scale (unite with granular material and grouting with backfill mortar), grouting was selected as the preferred technique. This technique then should be tested at full-scale (30 m long mock-up). First, a full-scale structure needs to built, including an extensive instrumentation programme. In addition, the logistical needs to ensure a continuous backfill operation have to be worked out. The objective is to have the almost 100 m3 backfilled in 4 hours