Theoretical Study of the Reactivity of Mixed Manganese and Silver Oxides on Hydrogen Simulating Tritium for the Limitation of Outgassing from Waste Drums

The oxide mixture MnO₂/Ag₂O has been identified as one of the best materials to oxidize hydrogen under ambient temperature and atmospheric pressure conditions. Studies have been carried out within the scope of the mitigation of hydrogen risk in fusion reactors and the optimal composition of this mixture has been determined by Chaudron as MnO₂/Ag₂O 10% wt. Using Maruéjouls' experiments, a model, previously developed to explain the oxidation of hydrogen by copper oxide for helium purification purpose, has been adapted and its simulation capability tested. To achieve this point, an exploratory experiment with a thin MnO₂/Ag₂O bed has been carried out under low hydrogen initial concentration (130 Vppm) in order to simulate tritium degassing. Although a very good global agreement between the calculations and the experimental points, the model is unable to account for the behaviour of hydrogen breakthrough at the beginning of the experimentation. Thus, enhancements of this model are presented in this paper. Finally, Scanning Electron Microscopy (SEM) analyses confirm the coherence of some assumptions used to solve the model equations.