Document Type

Article

Publication Date

4-5-2024

Department

Department of Materials Science and Engineering

Abstract

One major factor impeding the design of nuclear waste glasses with enhanced waste loadings is our insufficient understanding of their composition–structure–durability relationships, specifically in the environments the waste form is expected to encounter in a geological repository. In particular, the high field-strength cations (HFSCs) are an integral component of most waste streams. However, their impact on the long-term performance of the glassy waste form remains mostly undeciphered. In this context, the present study aims to understand the impact of some HFSCs (i.e., Nb5+, Zr4+, Ti4+, and La3+) on the dissolution behavior of alkali/alkaline-earth aluminoborosilicate-based model nuclear waste glasses in hyper-alkaline media. At pH = 13, the studied glasses dissolve through the dissolution–reprecipitation mechanism, with Ca precipitation being the most vital step to passivation. In Ca-free glasses, although the HFSCs slow down the forward rate, they do not seem to impact the residual rate behavior of glasses. The presence of Ca2+, however, initiates the rapid precipitation of network polymerizing HFSCs (i.e., Nb5+, Zr4+, and Ti4+) into a Ca2+/HFSCs-based passivating layer, thus suggesting a synergy between Ca2+ and HFSCs that contributes to the enhanced long-term durability of the glasses. Such synergy is not strongly evident for La3+, but instead, a potential La/Si affinity is observed upon the formation of the alteration layer.

Publisher's Statement

© 2024 The Authors. Journal of the American Ceramic Society published by Wiley Periodicals LLC on behalf of American Ceramic Society. Publisher’s version of record: https://doi.org/10.1111/jace.19806

Publication Title

Journal of the American Ceramic Society

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