Results from the Long-Term Interaction and Modeling of SRL-131 Glass with Aqueous Solutions.

摘要

Leaching studies of SRL-131 simulated defense nuclear waste glass have been carried out to two years duration, in leachants that simulate groundwaters of different ionic strengths. The leachability of SRL-131 glass followed the trend: deionized water > silicate water > salt brine = simulated groundwater at 40 deg C and deionized water = simulated groundwater > silicate water > salt brine at 90 deg C. The results are in general agreement with calculations using the PHREEQE geochemical code and indicate a sometimes complex sequence temperature dependent of mineral precipitation and redissolution. The calculations done in this study have illustrated the complexity of the precipitation sequence of mineral phases as a function of reaction progress. Complex, temperature dependent, precipitation/dissolution sequences have also been observed in experiments using natural materials, such as sea water and basaltic glass. The results of this two-year study point to the need for further work in establishing the thermodynamics of the observed phases and the relationship of these phases to the thermodynamically favored suite of phases for any given waste form/host rock/groundwater system. In order to study these phases, very long-term experiments may be necessary so that the phases grow to sizes which can be studied. In addition, geochemical codes should be used to better understand the experiments, to design leach test matrices, and to help predict the long-term results of experiments. The combination of long-term experiments and geochemical codes should lead to an improved method for forecasting the long-term behavior of a nuclear waste repository. 15 refs., 3 figs., 4 tabs. (ERA citation 11:011060)