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U.S. Department of Energy
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Radionuclide solubility and speciation studies for the Yucca Mountain site characterization project

Conference ·
OSTI ID:145529

Yucca Mountain, Nevada, U.S.A., is being investigated for its suitability as a potential site for a geologic nuclear waste repository. As part of the site characterization studies, actinide solubilities and speciations were studied at pH 6, 7, and 8.5 at 25{degrees} and 60{degrees}C in two different groundwaters from the vicinity of Yucca Mountain. The groundwaters differ substantially in total dissolved carbonate concentration, and to a lesser extent in ionic strength. In the waters with higher carbonate content, the solubilities of neptunium(V) decreased, whereas those of americium (III) increased at 25{degrees}C and decreased at 60{degrees}C. The solids formed were sodium neptunium carbonates and americium hydroxycarbonates. Plutonium solubilities did not significantly change with changing water composition because the solubility-controlling solids were mostly amorphous Pu(IV) polymers that contained only small amounts of carbonate.

Research Organization:
American Nuclear Society, La Grange Park, IL (United States); American Society of Civil Engineers, New York, NY (United States)
OSTI ID:
145529
Report Number(s):
CONF-930408--Vol.2
Country of Publication:
United States
Language:
English