Transient modelling of sulphide diffusion under conditions typical of a deep geological repository

ABSTRACTThe Canadian Nuclear Waste Management Organization (NWMO) has chosen a used fuel container (UFC) design that consists of an inner steel core and outer copper coating that resists corrosion in the anaerobic underground. However, in these anaerobic conditions, microbiologically influenced corrosion (MIC) can contribute to UFC corrosion if sulphides are present in the repository. Therefore, an engineered barrier system (EBS) consisting of bentonite blocks and pellets has been designed to inhibit production of sulphide by microorganisms and impede the movement of sulphides from the host rock to the UFC. Initially, the bentonite within the deep geological repository will contain no sulphides and it will take time for sulphide from the host rock to saturate the repository. To examine the transient effect of sulphide transport and the effectiveness of the EBS, a 3D numerical model was developed capable of simulating the diffusive transport of sulphide within the NWMO repository. The model was developed u...