The Bacchus backfill experiment at the Hades underground research facility at Mol, Belgium: Final report

BACCHUS is the acronym for BACkfilling Control experiment for High level wastes in Undergroud Storage. This large scale experiment is considering a compacted clay-based material around a heater implanted in the host clay in order to investigate the thermal behaviour of the Boom clay as well as the thermal and hydraulic transfers through a highly compacted material. It was developed jointly with CEA/DRDD in Fontenay. Beside the experiment itself and its original design, material characterization and instrumentation survey were important aspects in which considerable experience has been gained. In this respect, the development of specific sensors (thermal shock and Time Domain reflectometry probes) adapted to the particular experimental conditions is worth mentioning. In-situ investigations from the Hades facility have been running from November 1988 (implementation in clay) to August 1990 (end of the 5 months heating phase). Most of the data could be reproduced using the computer code available at CEN/SCK but some important limitations have to be overcome in the future, as for example the behaviour of partially saturated materials.