Uranium-series constraints on subrepository water flow at yucca mountain, nevada
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Abstract
Mineral abundances and whole-rock chemical and uranium-series isotopic compositions were measured in unfractured and rubble core samples from borehole USW SD-9 in the same layers of variably zeolitized tuffs that underlie the proposed nuclear waste repository at Yucca Mountain, Nevada. Uranium concentrations and isotopic compositions also were measured in pore water from core samples from the same rock units and rock leachates representing loosely bound U adsorbed on mineral surfaces or contained in readily soluble secondary minerals. The chemical and isotopic data were used to evaluate differences in water-rock interaction between fractured and unfractured rock and between fracture surfaces and rock matrix. Samples of unfractured and rubble (fragments about 1 centimeter) core and material from fracture surfaces show similar amounts of uranium-series disequilibrium, recording a complex history of sorption and loss of uranium over the past 1 million years. The data indicate that fractures in zeolitized tuffs may not have had greater amounts of water-rock interaction than the rock matrix. The data also show that rock matrix from subrepository units is capable of scavenging uranium with elevated uranium-234/uranium-238 from percolating water and that retardation of radionuclides and dose reduction may be greater than currently credited to this aspect of the natural barrier. Uranium concentrations of pore water and the rock leachates are used to estimate long-term in situ uranium partition coefficient values greater than 7 milliliters per gram.
Suggested Citation
Neymark, L., Chipera, S., Paces, J., Vaniman, D.T., 2006, Uranium-series constraints on subrepository water flow at yucca mountain, nevada, in Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM, v. 2006, Las Vegas, NV, 30 April 2006 through 4 May 2006, p. 82-88.
| Publication type | Conference Paper |
|---|---|
| Publication Subtype | Conference Paper |
| Title | Uranium-series constraints on subrepository water flow at yucca mountain, nevada |
| ISBN | 0894486918; 9780894486913 |
| Volume | 2006 |
| Year Published | 2006 |
| Language | English |
| Larger Work Title | Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM |
| First page | 82 |
| Last page | 88 |
| Conference Title | 11th International High Level Radioactive Waste Management Conference |
| Conference Location | Las Vegas, NV |
| Conference Date | 30 April 2006 through 4 May 2006 |