Degree of complexity of geohydrological models used in performance assessment

A proposal for the use of selected degrees of complexity of models is discussed. It is shown that 3-D models are needed in an early stage to determine the geochemical zones through which radionuclides will pass after release from a deep-lying repository. For a wide range of flow tubes produced by 3-D models, transport calculations based on 1-D models are required to explore relevant geochemical processes. This should reciprocally lead to an optimal program in terms of quality and costs of laboratory and field experiments