HYDROGEOLOGICAL PERFORMANCE OF THE PLANNED FRENCH GEOLOGICAL RADIOACTIVE WASTES REPOSITORY SITE - CIGEO

摘要

Safety assessment of a deep geological repository for radioactive wastes (IHLLW) requires identification of potential flow paths and the associated travel times for radionuclides originating at repository depth. The planned French repository will be located at great depths in the Callovo-Oxfordian clay formation of the multi-layered system of Paris Basin. Hydrogeological performance of the planned radioactive waste repository relies on analysis and assessment of the geodynamic evolution impact on groundwater flow behaviour in the multi-layered aquifer system through the next million of years. Numerical simulations coupling the geodynamic evolution and the groundwater flow describe how the tectonic uplift and erosion/sedimentation processes affect (i) the long term transient flow behaviour and (ii) the hydrogeological performance measures. Hydrogeological performance assessment of the potential repository site is performed by the use of particles transport model using a 3D transient flow field induced by: (i) deformation of the multi-layered aquifer system resulting from the differential tectonic uplift, (ii) evolution of the outcrop zones governed by erosion and incision of the geological layers and (Hi) the climate changes. Outlets of the hydrogeological system are located and the associated transit times from the repository are estimated.