Aqueous dissolution rate of nuclear waste glasses as a function of aqueous Si concentration and pH

• Dissolution rate was measured for nuclear waste glasses as a function of aqueous Si concentration. • The dissolution tests were performed by using MCFT method with Si isotopes. • The glass dissolution rate decreased with an increase in the Si concentration at pH9. • The glass dissolution rate was increased slightly with an increase in the Si concentration at pH4. • The glass dissolution mechanism changes sensitively depending on pH. The aqueous dissolution rate was measured precisely for two kinds of reference nuclear waste glasses, ISG and P0798, as a function of aqueous Si concentration and pH of a solution by using the micro-channel flow-through test method with Si isotopes. The glass dissolution rate determined from the Si dissolution rate decreased with increasing aqueous Si concentration at pH 9. In contrast, the dissolution rate at pH 4 was not affected by the Si concentration or increased slightly with an increase in the Si concentration. Therefore, the glass dissolution mechanism with the altered surface properties depended sensitively on pH, causing large changes in the glass dissolution kinetics.