Hybrid Empirical - Theoretical Approach to Modeling Uranium Adsorption
An estimated 330 metric tons of U are buried in the radioactive waste Subsurface Disposal Area (SDA) at the Idaho National Engineering and Environmental Laboratory (INEEL). An assessment of U transport parameters is being performed to decrease the uncertainty in risk and dose predictions derived from computer simulations of U fate and transport to the underlying Snake River Plain Aquifer. Uranium adsorption isotherms were measured for 14 sediment samples collected from sedimentary interbeds underlying the SDA. The adsorption data were fit with a Freundlich isotherm. The Freundlich n parameter is statistically identical for all 14 sediment samples and the Freundlich Kf parameter is correlated to sediment surface area (r2=0.80). These findings suggest an efficient approach to material characterization and implementation of a spatially variable reactive transport model that requires only the measurement of sediment surface area. To expand the potential applicability of the measured isotherms, a model is derived from the empirical observations by incorporating concepts from surface complexation theory to account for the effects of solution chemistry. The resulting model is then used to predict the range of adsorption conditions to be expected in the vadose zone at the SDA based on the range in measured pore water chemistry. Adsorption in the deep vadose zone is predicted to be stronger than in near-surface sediments because the total dissolved carbonate decreases with depth.
- Research Organization:
- Idaho National Laboratory (INL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC07-99ID13727
- OSTI ID:
- 911992
- Report Number(s):
- INEEL/JOU-02-01431
- Journal Information:
- Applied Geochemistry, Journal Name: Applied Geochemistry Journal Issue: 5 Vol. 19; ISSN 0883-2927; ISSN APPGEY
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ADSORPTION
ADSORPTION ISOTHERMS
CARBONATES
CHEMISTRY
COMPUTERIZED SIMULATION
Hybrid empirical
IMPLEMENTATION
INEEL
ISOTHERMS
METRICS
RADIOACTIVE WASTES
SDA
SEDIMENTS
SNAKE RIVER PLAIN
SURFACE AREA
Snake River Plain Aquifer
TRANSPORT
URANIUM
WATER CHEMISTRY
adsorption
uranium