The international hydrocoin project - Groundwater hydrology modelling strategies for performance assessment of nuclear waste disposal

The international cooperation project HYDROCOIN for studying groundwater flow modelling in the context of radioactive waste disposal was initiated in 1984. Thirteen organisations from ten countries and two international organisations have participated in the project which has been managed by the Swedish Nuclear Power Inspectorate, SKI. This report summarises the results from the third phase of HYDROCOIN, Level 3, which has addressed the issues of uncertainty and sensitivity analysis of groundwater flow problems and how uncertainties affect the modelling results. Seven test cases were selected for the project, representing a variety of flow situations in different media, as well as variety of temporal and spatial scales. These test cases were tackled by the participating organisations (Project Teams) using a number of different codes. An overview of the methodologies used in uncertainty and sensitivity analysis is given. Results from the various Teams attempting the Test Cases are presented and conclusions are drawn as to the applicability of the results obtained to the test cases being analysed as well as the general applicability of the results. The importance of making uncertainty and sensitivity analysis as part of a performance analysis of the safety of a nuclear waste repository is stressed. The conclusion is drawn that the HYDROCOIN Level 3 study has greatly contributed to the understanding of these issues. 42 refs., 159 figs., 61 tabs