Modelling the three-dimensional behaviour of a prototype nuclear waste repository

This paper presents a study of the full three-dimensional thermo/hydro/mechanical behaviour of SKB's Prototype Repository experiment. In particular, the three-dimensional interaction of the multiple barrier system, which includes MX-80 bentonite buffer with the host rock is investigated. These materials are subjected to a steep thermal gradient representing the heat produced by high-level nuclear waste. A hydraulic gradient is also present due to the host rock acting as a source of water. The simulation is achieved via the application of the numerical code, COMPASS, which implements a coupled thermo/hydro/mechanical approach to model the behaviour of saturated/unsaturated media. These patterns of behaviour require a large three-dimensional model in order to represent the non-symmetrical, complex geometry of the proposed repository. A range of simulation results is presented detailing the thermal-hydraulic-mechanical behaviour of the Prototype Repository. Attention has also been given to the micro-macro interaction occurring within the MX-80 bentonite buffer as the material begins to saturate and swell.