Novel Portland cement matrices incorporating a gamma -MnO2 /Ag2O hydrogen/tritium getter -structure changes and trapping performance
Résumé
This study investigates novel Portland cement-based mortars, developed for hydrogen/tritium trapping and radioactive waste immobilization. They incorporate a γ-MnO2/Ag2O getter powder at 10% wt (i.e. 6.8 to 7.1% vol). Compared to former patented materials, no drying or heat treatment of the materials is needed.
Complementarily to X Ray Diffractometry (XRD) and thermo-gravimetry analysis (TGA), 27Al and 29Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) evidences that the structure of the Portland cement solids (i.e. the C-A-S-H) is not impacted by the presence of getter, even after several month curing. Yet, Scanning Electron Microscopy coupled to Energy Dispersive Spectroscopy (SEM+EDS) shows that calcium is significantly present at the surface of the getter grains; this could affect trapping efficiency.
However, after gamma irradiation with cumulated doses of 491 or 997 kGy (i.e. 23 to 46 days at 900 Gy.h−1), all mortars made with getter have a hydrogen trapping efficiency of between 77 and 96%, when compared to the irradiation of mortars made with a non-trapping γ-MnO2 powder, or to the irradiation of pure water considered alone.
This means that the developed mortars display excellent hydrogen trapping efficiency, without any impact on their solid structure.