FEBEX (Full-scale Engineered Barrier Experiment in Crystalline Host Rock) is a research and demonstration project that was initiated by ENRESA (Spain). The aim of the project is to study the behaviour of near-field components in a repository for high-level radioactive waste in granite formations. The main objectives of the project may be grouped in two areas: demonstration of the feasibility of constructing the engineered barrier system in a horizontal configuration according to the Spanish concept for deep geological storage (AGP-abbreviation in Spanish), and analysis of the technical problems to be solved for this type of disposal method to develop a better understanding of the thermo-hydro-mechanical (THM) and thermo-hydrogeochemical (THG) processes in the near-field, and development and validation of the modelling tools required for interpretation and prediction of the evolution of such processes. The project consists of two large-scale tests (see Fig. 1-1) – "in situ" and "mock-up" (the latter is managed by CIEMAT in Spain) –, a series of laboratory tests, and THM and THG modelling tasks.