Multiple Roles of Clays in Radioactive Waste Confinement
CONTAINS OPEN ACCESS
This Special Publication highlights the importance of clays and clayey material, and their multiple roles, in many national geological disposal facilities for higher activity radioactive wastes. Clays can be both the disposal facility host rock and part of its intrinsic engineered barriers, and may be present in the surrounding geological environment. Clays possess various characteristics that make them high-quality barriers to the migration of radionuclides and chemical contaminants, e.g. very little water movement, diffusive transport, retention capacity, self-sealing capacity, stability over millions of years, homogeneity and lateral continuity.
The 20 papers presented in this Special Publication cover a range of topics related to clays in radioactive waste confinement. Aspects of clay characterization and behaviour at various temporal and spatial scales relevant to the confinement of radionuclides in clay are discussed, from phenomenological processes to the overall understanding of the performance and safety of geological disposal facilities.
Safety concept, FEP catalogue and scenario development as fundamentals of a long-term safety demonstration for high-level waste repositories in German clay formations
Published:January 01, 2019
A. Lommerzheim, M. Jobmann, A. Meleshyn, S. Mrugalla, A. Rübel, L. Stark, 2019. "Safety concept, FEP catalogue and scenario development as fundamentals of a long-term safety demonstration for high-level waste repositories in German clay formations", Multiple Roles of Clays in Radioactive Waste Confinement, S. Norris, E.A.C. Neeft, M. Van Geet
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A safety concept and a safety demonstration concept for the disposal of high-level radioactive waste in German clay formations have been developed. The main safety objective is to retain the radionuclides inside a ‘Containment Providing Rock Zone’. Thus, the radionuclide transport should be restrained by adequate safety functions of the geological and geotechnical barriers. The compliance with legal dose constraints has to be demonstrated for probable evolutions and less probable evolutions.
As a basis for system analysis, generic geological reference models, disposal concepts and repository designs have been developed for northern and southern Germany. All data relevant for future system evolution were compiled in two FEP (features, events and processes) catalogues. They provide information on FEP characteristics, their probabilities of occurrence, their interactions and identify ‘initial FEP’ that impair the safety functions of relevant barriers. A probable reference scenario has been deduced systematically from the probable ‘initial FEP’, and from probable processes relevant for radionuclide mobilization and transport. Four different starting points to develop alternative scenarios (i.e. less probable evolutions) were identified.
The scenario development methodology is applicable to different kinds of host rock and therefore may be a basis for the preliminary safety analyses necessary in the future site selection process in Germany.