Research Needs in HLW Disposal Programmes

ABSTRACTA repository for high-level radioactive waste (HLW) will not be in operation in Switzerland (or elsewhere) before the turn of the century. However, extensive investigations for disposal in specific regions or sites are ongoing and formal safety analyses have been performed in many countries. Broadly speaking, these analyses show the feasibility of the chosen options for deep geological disposal. At the present stage, before a licensing application, performance assessments have another important application: to identify further needs to improve system understanding, and to guide the necessary research activities. Performance assessments are thus indispensable tools for focussing in on research requirements and discriminating between necessary, and merely desirable or interesting, research projects.Based on experience from assessments of HLW disposal in the crystalline of Northern Switzerland (Project Gewähr, KRISTALLIN-I) we consider in detail the chain of models resulting from a scenario analysis. For each model block (e.g., engineered barrier performance, hydrology, radionuclide transport), the adequacy of understanding is addressed and the necessary research needs pointed out. These needs cover a wide span, from a requirement for more reliable input numbers (example: long-term corrosion rate of glass) to a better understanding of important features (example: excavation-damaged-zone) and key mechanisms (example: sorption).