Conceptual designs for a Spanish deep geological repository for high level waste in different media

Studies undertaken by the Empresa Nacional de Residuos Radiactivos, SA (ENRESA), during the last two years have been recently concluded with the selection of a reference repository concept for the final disposal of spent fuel and other high activity wastes in deep geological formations. Two non-site-specific preliminary designs, at a conceptual level, have been elaborated: one considers granite as the host rock and the other rock salt formations. The Spanish General Radioactive Waste Plan also considers clay as a potential host rock for deep disposal of HLW; conceptualization for a deep repository in clay is in its initial phase of development. The guiding principles followed for the selection of the reference concepts and repository designs have been to: ensure high safety performance of the repository during the operational phase; ascertain long term performance based on the multiple barrier principle; use proven techniques and methods for the design, wherever possible; devise repository facilities flexible enough to be easily adapted to possible variations in waste quantities, waste forms and repository operational time schedules; and optimize the global cost of the back end of the nuclear fuel cycle. The granite repository concept contemplates the disposal of the HLW in carbon steel canisters, embedded in a 0.8 m thick buffer of swelling smectite clay, in the drifts of an underground facility excavated at a depth of 500 m. The salt repository concept contemplates the disposal of the HLW in self-shielding casks emplaced in the drifts of an underground facility excavated at a depth of 850 m. (author). 6 figs