Radionuclide Solubility and Speciation Studies for the Yucca Mountain Site Characterization Project

by H. Nitsche, Univ of California, Berkeley, United States,
K. Roberts, Univ of California, Berkeley, United States,
T. Prussin, Univ of California, Berkeley, United States,
D. Keeney, Univ of California, Berkeley, United States,
S. A. Carpenter, Univ of California, Berkeley, United States,
K. Becraft, Univ of California, Berkeley, United States,
R. C. Gatti, Univ of California, Berkeley, United States,



Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1993

Abstract: 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° and 60°C in two different groundwaters from the vicinity of Yucca Mountain. The groundwater 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°C and decreased at 60°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.

Subject Headings: Solubility | Radioactive wastes | Carbonation | Radioactive materials | Groundwater | Site investigation | Sodium | Geology | Solid mechanics | Nevada | North America | United States

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