Initial Dissolution Rate of the International Simple Glass as a Function of pH and Temperature Measured Using Microchannel Flow‐Through Test Method

International simple glass (ISG) is a six‐component alumino‐borosilicate glass developed as a reference benchmark glass for six nations collaborating study on high‐level nuclear waste glass dissolution/corrosion mechanism. In this study, aqueous dissolution tests were performed for the ISG using microchannel flow‐through (MCFT) method to evaluate the initial dissolution rate of glass matrix, r 0 , precisely and systematically as a function of solution pH and temperature. The test results indicated that the r 0 shows a “V‐shaped” pH dependence with a bottom at around pH 4 at each temperature. Compared with Japanese reference glass of P0798, for which the r 0 showed a “U‐shaped” pH dependence with a bottom at around pH6 in our previous study, the ISG shows the higher dissolution rate at basic pH, and lower dissolution rate at neutral to acidic pH . The results also indicated that the r 0 increases with temperature according to an Arrhenius law, and the apparent activation energy evaluated from Arrhenius relation is 62–77 [kJ/mol] at any pH from 3 to 10, which suggests the initial dissolution of ISG proceeds controlled by a surface‐reaction mechanism in this pH range.