Validation of the earl-age thermo-mechanical behaviour of SCC supercontainers for the disposal of high level radioactive waste

The Belgian concept for the disposal of high level waste and spent fuel assemblies is founded on the use of cylindrical concrete Supercontainers deeply stored inside geological clayey layers. This concept is based on a multiple barrier system where every component has its own specific safety function requirements. A self-compacting concrete (SCC) is being considered for the choice of the cementious buffer, enclosing the radwaste. The use of SCC will ease considerably the precast process and complies with all other requirements regarding strength, durability, chemical interactions, etc. A laboratory characterization program, in order to obtain the mechanical and thermal properties of the SCC, and 2.5 D thermal and crack modelling simulations are conducted to predict the early-age thermo-mechanical behaviour of the concrete buffer during the different construction stages, i.e. (i) the casting of the buffer, (ii) insertion of the high-level waste and (iii) closure of the Supercontainer. Large scale tests, with temperature measurements, displacement and deformation registrations, are performed for the validation of the simulation results of the early-age behaviour of the Supercontainer during the first construction stage. In this way the prediction of the avoidance of through-going cracks in the concrete buffer is ensured.