The Sorption/Desorption Behavior of Uranium in Transport Studies Using Yucca Mountain Alluvium
- Univ. of New Mexico, Albuquerque, NM (United States)
Yucca Mountain, Nevada is the proposed site of a geologic repository for the disposal of spent nuclear fuel and high-level radioactive waste in the United States. In the event repository engineered barriers fail, the saturated alluvium located south of Yucca Mountain is expected to serve as a natural barrier to the migration of radionuclides to the accessible environment. The purpose of this study is to improve the characterization of uranium retardation in the saturated zone at Yucca Mountain to support refinement of an assessment model. The distribution of uranium desorption rates from alluvium obtained from Nye County bore holes EWDP-19IM1, EWDP-10SA, EWDP-22SA were studied to address inconsistencies between results from batch sorption and column transport experiments. The alluvium and groundwater were characterized to better understand the underlying mechanisms of the observed behavior. Desorption rate constants were obtained using an activity based mass balance equation and column desorption experiments were analyzed using a mathematical model utilizing multiple sorption sites with different first-order forward and reverse reaction rates. The uranium desorption rate constants decreased over time, suggesting that the alluvium has multiple types of active sorption sites with different affinities for uranium. While a significant fraction of the initially sorbed uranium desorbed from the alluvium quite rapidly, a roughly equivalent amount remained sorbed after several months of testing. The information obtained through this research suggests that uranium may experience greater effective retardation in the alluvium than simple batch sorption experiments would suggest. Electron Probe Microanalysis shows that uranium is associated with both clay minerals and iron oxides after sorption to alluvial material. These results provide further evidence that the alluvium contains multiple sorption sites for uranium.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 881276
- Report Number(s):
- LA-14271-T; TRN: US0602904
- Country of Publication:
- United States
- Language:
- English
Similar Records
Estimates of ambient groundwater velocity in the alluvium south of Yucca Mountain from single-well tracer tests.
SATURATED ZONE IN-SITU TESTING
Related Subjects
07 ISOTOPES AND RADIATION SOURCES
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
58 GEOSCIENCES
CLAYS
DESORPTION
ELECTRON PROBES
HIGH-LEVEL RADIOACTIVE WASTES
IRON OXIDES
MASS BALANCE
MATHEMATICAL MODELS
MICROANALYSIS
NUCLEAR FUELS
RADIOISOTOPES
REACTION KINETICS
SORPTION
TESTING
URANIUM
URANIUM 228
YUCCA MOUNTAIN