Geochemical simulation of dissolution of West Valley and DWPF [Defense Waste Product Facility] glasses in J-13 water at 90{sup 0}C.

Abstract

Dissolution of West Valley and Defense Waste Product Facility (DWPF) glasses in J-13 water at 90{sup 0}C at the candidate Yucca Mountain, Nevada repository was simulated using the EQ3/6 computer code package. The objectives of the study were to attempt to predict the concentrations of radionuclides and other glass components in solution resulting from glass dissolution, and to identify potential precipitates that sequester glass components. Modified projected inventories of 10,000 year-old West Valley and DWPF SRL-165 frit glasses were used as starting glass compositions. J-13 water was considered to be representative of groundwater at Yucca Mountain. A total of 10 grams of each glass was assumed to dissolve congruently into a kilogram of J-13 water in a closed system. No inhibitions to precipitation, except for crystalline SiO{sub 2} polymorphs, were assumed to exist. Radiolysis and materials interactions were not considered. Simulation results predict that radionuclides and other glass components precipitate predominantly in the form of oxides and hydroxides, together with carbonates, silicates and phosphates. Precipitates appear to be effective in limiting the concentrations of radionuclides and other elements in solution. The general compositional trends in precipitates and solution chemistry are the same in the West Valley and DWPF simulations, except for variations arising from differences in glass chemistry. 20 refs., 7 figs., 3 tabs.