Effect of cement water contacting an aged cementitious grout on the dissolution rates of inactive nuclear glass SON68

Abstract The long‐term behavior of high‐level radioactive waste glass depends on the mineralogical and geochemical interactions between the various components of the multibarrier system, under geological repository conditions. The present study focuses on SON68 glass alteration in synthetic cement water and at 50°C and 70°C. While pH > 10, the glass dissolution rates were lower when contacting synthetic cement water than deionized water. This effect stems from the high Ca concentration and the presence of Si in the porewater. The initial dissolution rates at low reaction progress (3.4 ± 1.0 × 10 −2 g m −2 d −1 at 50°C and 1.9 ± 0.8 × 10 −2 g m −2 day −1 at 70°C) and the long‐term dissolution rates at high reaction progress (1.5 ± 0.5 × 10 −5 g m −2 day −1 at 50°C and 6.7 ± 1.0 × 10 −5 g m −2 day −1 at 70°C), were two times to one order of magnitude lower than the rates determined in deionized water. The cement water has a beneficial effect on glass dissolution rates which were dependent on pH, Si, and Ca concentrations.