Research Needs in HLW Disposal Programmes
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RESEARCH NEEDS IN HLW DISPOSAL PROGRAMMES JOERG HADERMANN* AND CHARLES MCCOMBIE**
*Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland "**NationalCooperative for the Disposal of Radioactive Waste, CH-5430 Wettingen, Switzerland.
ABSTRACT
A 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 Gew'hr, 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).
INTRODUCTION
The ultimate aim of a repository performance assessment is to predict quantitatively the behaviour of disposal systems over periods far into the future. However, before their final application in the course of licensing, performance assessments have a further important role [1], namely to identify needs for further system understanding, and to guide the necessary research activities. In the Swiss high-level waste (HLW) management programme, this application of performance assessment [2] has been repeatedly used for project planning. Over the last ten years, intensive regional field investigations, laboratory experiments, and modelling work have been performed in the course of developing concepts for a HLW repository') in the crystalline basement of Northern Switzerland. At present, a new performance assessment, KRISTALLIN-I, is being done, with the aims of reevaluating the safety analyses of such a repository that were performed in Project Gewlihr 1985 [3], and of assessing needs for further investigations, especially with respect to the explorability of crystalline on a site-specific basis. The general methodology adopted for KRISTALLIN-I is fairly standard. First, a scenario analysis is performed, identifying and screening features, events, and processes. From the scenario analysis follows a set of model chains for consequence analysi
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