The Belgian HLW repository design and associated R&D on the behaviour of the host rock and EBS

In Belgium， Repositories of HLW are designed on the basis of a multiple barrier system between the HLW and the biosphere. The Boom clay has been investigated for more than 20 years as the reference host rock. An URL (HADES) in Boom clay formation at a depth of about 223 m at Mol site was built to investigate the feasibility of the disposal concepts and to provide reliable date on the performance of repository . Among numerous experiments carried out in HADES，several tests were designed to study the THM behaviour of the host rock and the engineered barriers，e.g. CACTUS，ATLAS，BACCHUS，and RESEAL，etc. The construction of the underground research facility(URF，shaft and gallery) using the industrial technique gave us an opportunity to extend our knowledge on the hydro-mechanical(HM) behaviour of host rock clay(CLIPEX project)，on the excavation damaged zone due to tunnelling works(SELFRAC project)，the mock-up test allowed to investigate the THM behaviour of the bentonite buffer material. A large-scale in-situ heater test(PRACLAY experiments) will start in 2006 for a period about 10 years. This paper will give a brief description on the Belgian repository design for HLW，then a review on the performed tests ，finally a general presentation on the PRACLAY experiments.