Uncertainty and sensitivity analysis within the post closure Performance and Safety Assessment of the French deep geological radwaste disposal: methodology, tool and examples of results

Within the framework of the December 30, 1991 french act, Andra submitted to the French Parliament in December 2005 a report on the feasibility of a high-level and long-lived radwaste disposal in the Callovo-Oxfodien clay layer (Meuse/Haute-Marne site). Further to 2006 french act, Andra is now involved in licensing of the reversible disposal up to 2015, which requires a great scientific and technical knowledge. Studies are based on many years of research carried out in France, in particular in Andra’s Meuse/Haute-Marne Underground Research Laboratory (MHM URL), and international programs on radwastes, engineered barriers and deep clay formations. Intensive programs on hydraulic, solute transfer and radionuclides behaviour (solubility, retention) were and are carried out on Callovo-Oxfordian argilites (undisturbed and damaged), concrete materials and swelling clay based material, in order to provide a sound database. All these data allowed to perform firstly a sound description of the expected phenomenological evolution of the repository and its geological environment (including release and migration of radionuclides) from operating period to post closure period up to one million years, secondly a sound post-closure performance and safety assessment covering the different waste types (ILLW, HLW).