[H-CG24] Nuclear Energy and Geoscience

[HCG24-09] Significance of clogging at the interface between engineered barrier materials in the radioactive waste disposal

*Tsutomu Sato¹ (1.Faculty of Engineering Hokkaido University)

Keywords:Metal silicate hydrates, Engineered barrier materials, Clogging

At the radioactive waste disposal site, various kinds of materials such as glass, carbon steel, bentonite, cementitious material will be installed as the engineered barrier materials. Due to the differences in their chemistry, processes such as dissolution of the materials, exchange of constituent elements, and subsequent alteration of the materials are unambiguously expected at the interface between the materials such as glass-steel, steel-bentonite, bentonite-cementitious materials. Some of the processes lead to material degradation, which in turn leads to degradation of their barrier performance. On the other hand, some of the other processes induce the precipitation of secondary minerals at the interface and the resulting clogging. This clogging at the interfaces is important to prevent further degradation of the barrier materials and to maintain the performance of each barrier material for a long time. Such clogging is well documented in the results of geochemical modeling at the interface, but there is little data to validate them. Furthermore, even though thermodynamically metastable phases play an important role in clogging in many cases, the formation conditions for these metastable phases are poorly understood.
In this context, this presentation will review the candidate metastable phases that cause clogging and their formation conditions.