Characterization of Secondary Phases forming from Weathering of Waste Glasses
EMSL Project ID
1649
Abstract
A performance assessment is underway to evaluate the suitability of the unsaturated sediments at the Hanford Site for long-term disposal of vitrified low-activity waste. Previous analyses show that groundwater transport presents the greatest potential for long-term dose uptake by humans, and have shown that the key risk drivers at the proposed disposal site include 129I, 237Np, 79Se, 99Tc, and 233,235,238U. Several studies have shown that formation of zeolitic and smectitic secondary crystalline minerals as a product of chemical weathering is a common phenomena. Lliterature on isomorphous substitution in zeolites and smectites suggest radionuclides that are in waste forms could upon chemical weathering be sequestered in these secondary crystalline mineral structures. Because zeolites and smectites have significantly lower solubilities than glass waste forms, the aqueous phase activities of isomorphically substituted radionuclides would be significantly decreased. Experiments evaluated potential incorporation of radionuclides in secondary mineral phases that form from weathering vitrified nuclear waste glasses, and generate data on radionuclide mobilization and transport in a near-field environment of disposed vitrified wastes. Study will characterize secondary crystalline phases that form and assess the extent these crystalline phases sequester some of the key radionuclides. (1) Identify/characterize ( XRD, SEM/EDS) the secondary minerals from chemical weathering of waste glass samples of known composition in contact with Hanford groundwater; (2) determine the degree of radionuclide sequestration; (3) determine kinetics of dissolution and equilibrium activities in aqueous phase in contact with radionuclide-bearing secondary minerals.
Project Details
Project type
Exploratory Research
Start Date
1999-08-18
End Date
2001-04-01
Status
Closed
Released Data Link
Team
Principal Investigator