Development and testing of radionuclide transport models for fractured rock: examples from the Nagra/JNC Radionuclide Migration Programme in the Grimsel Test Site, Switzerland

The joint Swiss National Go-operative for the Disposal of Radioactive Waste (Nagra)/Japan Nuclear Cycle Development Institute (JNC) Radionuclide Migra tion Programme has now been on-going for over a decade in Nagra's Grimsel T est Site (GTS). The main aim of the programme has been the direct testing o f radionuclide transport models in as realistic manner as possible. Althoug h it will never be possible to fully test these models due to the large tim e and distance scales involved, tests of the model assumptions in scaled do wn but otherwise realistic conditions will contribute to developing confide nce in the predictive power of the models. In this paper, the Nagra/JNC approach is highlighted with examples from a l arge programme of field, laboratory and natural analogue studies based arou nd the GTS. The successes and failures are discussed as in the general appr oach to the thorough testing of predictive transport codes which will be us ed in repository performance assessment (PA). Some of the work is still on- going and this represents the first presentation of a unique set of results and conclusions. (C) 2001 Elsevier Science B.V. All rights reserved.