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Oxidative Alteration of Uraninite at the Nopal I Deposit, Mexico: Possible Contaminant Transport and Source Term Constraints for the Proposed Repository at Yucca Mountain

Published online by Cambridge University Press:  01 January 1992

Bret W. Leslie ,
English C. Pearcy  and
James D. Prikryl
Bret W. Leslie
Affiliation:
Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228-0510
English C. Pearcy
Affiliation:
Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228-0510
James D. Prikryl
Affiliation:
Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228-0510
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Abstract

The Nopal I uranium deposit at Pefla 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 silicic, 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 238U 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 238U decay-series isotopes indicate secular equilibrium, which suggests undetectable U transport under present conditions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 294: Symposium V – Scientific Basis for Nuclear Waste Management XVI , 1992 , 505
Copyright
Copyright © Materials Research Society 1993

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References

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