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Solubility and speciation results from over- and undersaturation experiments on neptunium, plutonium, and americium in water from Yucca Mountain region well UE-25p {number_sign}1

Technical Report ·
DOI:https://doi.org/10.2172/171272· OSTI ID:171272
; ; ; ; ; ;  [1]
  1. Lawrence Berkeley Lab., CA (United States). Earth Sciences Div.
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Solubility and speciation are important in understanding aqueous radionuclide transport through the geosphere. Results are compared from solubility and speciation experiments from oversaturation and undersaturation of {sup 237}NpO{sub 2{sup +}}, {sup 239}Pu{sup 4+}, and {sup 241}Am{sup 3+}/Nd{sup 3+} in a modified UE-25p-1 groundwater (from the Yucca Mountain region, Nevada, which is being investigated as a potential high-level nuclear waste disposal site) at 60 C and three pH values (6.0, 7.0, 8.5). In the oversaturation experiments, the solubility-controlling steady-state solids were identified and the speciation and/or oxidation states present in the supernatant solutions were determined. The characterized solids were then reintroduced into fresh solutions of the modified UE-25p-1 groundwater to approach the steady state from undersaturation. For the undersaturation experiments, the solubility-controlling steady-state solids were also identified and the speciation and/or oxidation states present in the supernatant solutions were determined. The Np solubility decreased with increasing pH in both the over- and undersaturation experiments. The steady-state concentrations from the two experiments agreed to within an order of magnitude. Pu concentrations from over- and undersaturation agree very well in the pH 6 and 7 experiments. The pH 8.5 oversaturation experiment resulted in a steady-state concentration one order of magnitude above its undersaturation counterpart. For the Am/Nd solutions, the pH 6 and pH 7 experiments resulted in equivalent steady-state concentrations from both over and undersaturation. The pH 8.5 oversaturation experiment was 100 times more soluble than its undersaturation counterpart. 48 refs.
Research Organization:
Los Alamos National Lab., NM (United States)
Sponsoring Organization:
USDOE, Washington, DC (United States)
DOE Contract Number:
W-7405-ENG-36
OSTI ID:
171272
Report Number(s):
LA--13017-MS; ON: DE96003989
Country of Publication:
United States
Language:
English

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Related Subjects

05 NUCLEAR FUELS
54 ENVIRONMENTAL SCIENCES
AMERICIUM COMPOUNDS
EXPERIMENTAL DATA
GROUND WATER
HIGH-LEVEL RADIOACTIVE WASTES
HYDROLOGY
NEODYMIUM COMPOUNDS
NEPTUNIUM OXIDES
PLUTONIUM COMPOUNDS
RADIOACTIVE WASTE DISPOSAL
RADIONUCLIDE MIGRATION
SATURATION
SITE CHARACTERIZATION
SOLUBILITY
TEST FACILITIES
VALENCE
WATER WELLS
YUCCA MOUNTAIN