Objective The BACCHUS 2 (BACkfilling Control Experiment for High level wastes in Underground Storage) experiment aims at the optimization and the demonstration of an installation procedure, material processes and capabilities.2 (BACkfilling Control Experiment for High level wastes in Underground Storage2 (BACkfilling Control Experiment for High level wastes in Underground Storage The backfill material will consist of a mixture of high density pellets and powder.2 (BACkfilling Control Experiment for High level wastes in Underground Storage The instrumentation of the experiment will be optimized in such a way that it can be used as a validation experiment for the hydro-mechanical model developed under contract FI2W-CT90-0033.2 (BACkfilling Control Experiment for High level wastes in Underground Storage The BACCHUS 2 project also includes the characterisation of the granular backfill and the retrieval and the expertise of the BACCHUS 1 test mock up.Compacted expansive clays are proposed as engineered barriers in reference concepts for the disposal of heat-emitting nuclear waste in granite and clay.The backfill material of the BACCHUS 2 test consists of a mixture of high density pellets and powder. This granular backfill material was characterized. The hydraulic conductivity and swelling pressure was measured as a function of the dry density. X-ray tomography has been applied successfully to measure the evolution of the density distribution during hydartion.The installation procedure, materials and techniques used in the BACCHUS 2 were close to realistic industrial processes and capabilities. To gain more confidence in the hydromechanical model for unsaturated clay-based materials, BACCHUS 2 was instrumented so that it can be used as a validation experiment.The instrumentation (including total stress, pore-water pressure and water content measurements) of the backfill material and of the surrounding clay massif has allowed observation of the hydration process. The measured parameters in the backfill show clearly the hydration effect (ie a strong increase in water content, pore-water pressure and a redistribution of the mechanical stresses). Results of the natural hydration modelling are in good agreement with the in situ measurements.Work programme:1. Study and optimization of the backfill materialThe sealing material will consist in a mixture of clay pellets and clay powder. The ratio powder/pellets and the density, size and water content of the pellets will be used as parameters in the optimization process.Fundamental properties of this mixture such as the hydraulic conductivity and the swelling pressure will be measured.2. Recuperation of the BACCHUS 1 experimentThe BACCHUS 1 mock-up installed in '88 will be retrieved by over coring. The aspects and hydro-mechanical properties of the retrieved Boom clay seal and the FoCa-bentonite buffer will be studied.3. In-situ demonstration of the application of the backfill material The demonstration will consist in the sealing of the large borehole (50 cm diameter) left after the retrieval of the BACCHUS 1 mock-up. The backfill material developed under 1 will be installed around a central filter tube which will also be used as support and access tube for the instrumentation.Probes for water content measurement, based on the experience gained by CEA in the BACCHUS 1 project, will be embedded in the backfill material. Also the instrumentation installed previously in the host clay around the BACCHUS 1 mock-up, can be further used for monitoring the host clay behaviour. Fields of science engineering and technologyother engineering and technologiesnuclear engineeringnuclear waste management Programme(s) FP2-RADWASTOM 4C - Specific research and technical development programme (Euratom) in the field of management and storage of radioactive waste, 1990-1994 Topic(s) B.2 - The underground facility HADES in the argillaceous layer under the Mol Site (B) Call for proposal Data not available Funding Scheme CSC - Cost-sharing contracts Coordinator BELGIAN NUCLEAR RESEARCH CENTRE EU contribution No data Address 200,Herrmann Debrouxlaan 40-42 1160 BRUXELLES Belgium See on map Total cost No data Participants (2) Sort alphabetically Sort by EU Contribution Expand all Collapse all EMPRESA NACIONAL DE RESIDUOS RADIOACTIVOS S.A. Spain EU contribution No data Address 7,Emilio Vargas 7 28043 MADRID See on map Total cost No data NATIONAL RADIOACTIVE WASTE MANAGEMENT AGENCY OF FRANCE France EU contribution No data Address Rue Jean Monnet 1-7 92298 CHATENAY MALABRY See on map Total cost No data
