3D modelling of long-term sulfide corrosion of copper canisters in a spent nuclear fuel repository

Copper canisters are a central component in the safety of Finnish spent fuel repository concept (KBS-3), where main corrodent potentially affecting canister integrity is sulfide. In this study, 3D numerical model developed to assess evolution sulfide fluxes and spatially resolved corrosion depths for nuclear concept. The backfilled tunnel disposal hole implemented using geometries, with being produced at their interface rock (excavation damaged zone) by sulfate reducing bacteria (SRB). Recent experimental findings regarding microbial reduction process as well scavenging via iron (oxy)hydroxides incorporated reactive transport model. Long-term simulations performed, predicting heterogeneous max. depth 1.3 mm bottom corner after one million years. shows two phases, depending on source sulfate: first supplied dissolution gypsum from bentonite barriers, followed steady, low-level supply groundwater. Sensitivity cases demonstrate that both organic carbon Fe(III) oxide contents critical evolution, electron donor SRB activities major scavenger bentonite, respectively. contributes little flux corrosive due attenuation Fe(III)-oxides/hydroxides but induces notable into hole.