The effect of composition on the leaching of three nuclear waste glasses: R7T7, AVM and VRZ

Abstract

The influence of composition variations on long-term glass behavior was investigated for three nuclear glass composition domains: the French SON 68 (R7T7-type) glass, the Na–Mg borosilicate AVM glass and the aluminosilicate VRZ glass defined as part of the investigation of new containment matrices based on zirconolite (CaZrTi 2O 7). The initial alteration rates for glasses from different domains are comparable. Conversely, the alteration kinetics at advanced stages of reaction progress are very different, with decreases in the rates corresponding to different kinetic profiles, i.e. altered thickness versus time. The altered glass thickness can depend on the initial alteration rate and especially on the decrease in the rate, or it can be determined by the high residual alteration rate. The variation of the alteration rates over time appears to be related to the alteration film that forms on the surface of the material in particular the presence of any secondary crystalline phases. For AVM glass, the high residual rate is attributed to phyllosilicate phases rich in magnesium.