This paper presents the safety assessment exercise "REGIME" (Repository Evaluation performed by GRS and IRSN through a Modelling Exercise) performed jointly by GRS and IRSN. The main objective of the project is to test the ability of integrated modelling to contribute to site selection and repository conception in the context of high-level radioactive waste disposal. The project is divided in two parts. Phase 1 consisted in studying different flow patterns in a given geological context. The selected hydrogeological contexts and three site locations potentially favourable for hosting a repository are described. Phase 2, under progress, aims at evaluating the role of limitation of releases played by the different components of the disposal system taking into account possible dysfunctions. The main issues to be addressed in phase 2, the modelling outline and the scenarios to be studied are presented.