Sulfide-induced corrosion is considered to be the main long-term mode of degradation of the copper-based waste canister for disposal of spent nuclear fuel in Sweden. Detailed understanding of the mechanism of this process will aid in the proper safety analysis, as well as in the design, of the planned deep geological repositories (DGR) for nuclear waste in Sweden and around the world. Although the anode side of the corrosion reaction is considered well understood, questions remain regarding the active site and the reactant of the cathode reaction:

 

HX + e^– → ½H₂(g) + X^–, X = OH, HS, or S^–

 

Will H₂S/HS^– or H₂O donate the proton in the reaction above? Will the Cu₂S corrosion film support the cathode reaction, or will it take place at Cu exposed in the pore bottoms of the porous film? The answers to these questions could have implications for the expected corrosion behavior of copper in the DGR. Using computational chemistry methods, we have compared the cathodic reaction rates for H₂S/HS^– versus H₂O, and Cu versus Cu₂S. On our poster we will present results indicating that the most probable situation, based on our model systems, under DGR conditions is that H₂O acts as proton-donor and that Cu, if sufficiently large areas are exposed, is the site of reaction [1].

 

[1] JH Stenlid, E Campos dos Santos, AJ Johansson, LGM Pettersson, J. Electrochem. Soc., 166, C196-C208 (2019)

Souhaitez-vous présenter une affiche ?DFT modeling, copper corrosion, cathode reaction, sulfide7th International Workshop on Long-term Prediction of Corrosion Damage in Nuclear Waste Systems (LTC 2019)