COSMOS: Concept, design and use of the experimental infrastructure

Geological disposal of nuclear waste into clay host rocks is considered as a reliable and feasible option. However, as more and more studies indicate that microbiological activity is detected and can have a serious impact on the physico-chemical properties of many geological environments, the possibility of microbes interacting with a future geological disposal system for radioactive waste, cannot be ignored. In Belgium, such a disposal system could be located in poorly indurated clay hosts, such as the Boom Clay or the Ypresian clays. Because of the high plasticity of Boom Clay (and of the Ypresian clays), it is expected that voids and fractures will fill and close rapidly and that consolidation will bring back the soil density close to its initial state in a very short time period. Hence, porosity will be a parameter that returns relatively fast (close) to its initial state. Therefore it is likely that space/transport restriction will be among the first physico-chemical conditions to have an effect on the microbiological presence and activity. COSMOS, “Consolidation by Oedometers Shifting Microbiological Optimum towards Stress”, aims to study the impact of (re)consolidation on the microbiological community that is found in the solutions of filters of the piezometers installed in the Boom Clay.