Accelerated Leach Testing of GLASS (ALTGLASS): I. Informatics approach to high level waste glass gel formation and aging

Abstract Glass corrosion data from the ALTGLASS ^™ database were used to determine if gel compositions, which evolve as glass systems corrode, are correlated with the generation of zeolites and subsequent increase in the glass dissolution rate at long times. The gel compositions were estimated based on the difference between the elemental glass starting compositions and the measured elemental leachate concentrations from the long‐term product consistency tests (ASTM C1285) at various stages of dissolution, ie, reaction progress. A well‐characterized subset of high level waste glasses from the database was selected: these glasses had been leached for 15‐20 years at reaction progresses up to ~80%. The gel composition data, at various reaction progresses, were subjected to a step‐wise regression, which demonstrated that hydrogel compositions with Si ^* /Al ^* ratios of <1.0 did not generate zeolites and maintained low dissolution rates for the duration of the experiments. Glasses that formed hydrogel compositions with Si^*/Al^* ratios ≥1, generated zeolites accompanied by a resumption in the glass dissolution rate. The role of the gel Si/Al ratio, and the interactions with the leachate, provides the fundamental understanding needed to predict if and when the glass dissolution rate will increase due to zeolitization.