Oxidative alteration of uraninite at the Nopal I deposit, Mexico: Possible contaminant transport and source term constraints for the proposed repository at Yucca Mountain
- Southwest Research Institute, San Antonio, TX (United States)
The Nopal I uranium deposit at Pena Blanca, Mexico is being studied as a natural analog of the proposed high-level nuclear waste repository at Yucca Mountain. Identification of secondary uranium phases at Nopal I, and the sequence of their formation after uraninite oxidation, provides insight into the source term for uranium, and suggests that uranophane may control uranium release and transport in a silici, tuffaceous, chemically oxidizing, and hydrologically unsaturated environment. Possible constraints on contaminant transport at Nopal I are derived from the spatial distribution of uranium and from measurements of {sup 238}U decay-series isotopes. The analyses indicate that flow of U-bearing fluids was influenced strongly by fracture density, but that the flow of these fluids was not restricted to fractures. Gamma spectroscopic measurements of {sup 238}U decay-series isotopes indicates secular equilibrium, which suggests undetectable U transport under present conditions.
- OSTI ID:
- 62239
- Report Number(s):
- CONF-921101--Vol.294; CNN: Contract NRC-02-88-005
- Country of Publication:
- United States
- Language:
- English
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