In all nuclear power generating countries, spent nuclear fuel and long lived radioactive-waste management is an important environmental issue today. Disposal in deep clay geological formations is one of the promising options to dispose of these waste. An important item for the long-term safety of underground disposal is the proper evaluation of the Damaged Zone (DZ) in the clay host rock. The DZ is first initiated during the repository construction. Its behaviour is a dynamic problem, dependent on changing conditions that vary from open-drift period, to initial closure period, to the entire heating-cooling cycle of the decaying waste. Other factors concern the even longer-term issues of chemical reactions and biological activities. The TIMODAZ project will focus on the study of the combined effect of the EDZ (Excavation Damaged Zone) and the thermal impact. The influence of the temperature increase on the EDZ evolution as well as the possible additional damage created by the thermal load will be studied. Three types of clay will be investigated: the Boom Clay, the Opalinus Clay and the Callovo-Oxfordian argilite. To assess the impact of the different repository evolution stages on the host rock, numerical tools will be developed allowing a good prognosis of the THMC host rock behaviour at the time and spatial scale of a repository. These developments will build on an experimental programme including laboratory and in-situ tests. The knowledge gained within the project will allow an assessment of the significance of the TDZ (Thermal Damaged Zone) in the safety case for disposal in clay host rock and to provide direct feedback to repository design teams. In order to ensure appropriate and continuous linkage between the end-users' needs and the priorities of the project, an end-users' group that will be active throughout the duration of the project has been constituted. The end-user group will consist of mainly national agencies for management of radioactive waste.
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Funding SchemeSTREP - Specific Targeted Research Project