International audience ; The ONDRAF/NIRAS agency for radioactive waste and enriched fissile materials is in charge of the management of the radioactive wastes in Belgium. In the framework of the study of a new concept for the disposal of high level wastes, a project of a supercontainer has been considered and studied. The main goal of this study was to estimate the Thermo-Hydrological behaviour of the concrete buffer in service life. Water (liquid and vapour) and heat transfers were described through coupled differential equations by the means of the procedure THYDR developed at the Department of Physico-Chemistry of the French Commission for Atomic Energy (CEA/DPC) and implemented in the code CAST3M. Two different configurations for the concrete buffer were investigated: concrete cured with no water loss or partially dried. The simulations allowed the estimation of the evolution of both vapour pressure and liquid saturation.