Glass dissolution mechanism under nearly saturated conditions; Current state and the future

Maeda, Toshikatsu; Yamaguchi, Tetsuji ; Bamba, Tsunetaka; Usui, Hideo

An experimental approach was proposed to understand the mechanism and model for slow dissolution of high-level radioactive waste glass under disposal conditions where silica is nearly saturated in contacting pore water. Based on an extended literature survey covering recent experimental results on glass dissolution, we have reached a hypothesis that the slow dissolution is limited by diffusion of oxonium ions in an altered layer formed on the glass surface. We suggested several experimental methods such as an elaborate and systematic diffusion experiment using thin glass membranes of tens-of-micrometer thickness to validate the hypothesis. Also pointed out was that dissolution model applicable to glass waste form performance evaluation takes into account the surface area evolution and stability of altered region of the waste form.