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Plutonium Solubility and Speciation to be Applied to theSeparation of Hydrothermal Waste Treatment Effluent

Published online by Cambridge University Press:  03 September 2012

M. P. Neu ,
S. D. Reilly  and
W. H. Runde
M. P. Neu
Affiliation:
Chemical Science and Technology Division, Mail Stop G739, Los Alamos National Laboratory, Los Alamos, NM 87545, mneu@lanl.gov
S. D. Reilly
Affiliation:
Chemical Science and Technology Division, Mail Stop G739, Los Alamos National Laboratory, Los Alamos, NM 87545, mneu@lanl.gov
W. H. Runde
Affiliation:
Chemical Science and Technology Division, Mail Stop G739, Los Alamos National Laboratory, Los Alamos, NM 87545, mneu@lanl.gov
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Abstract

One of the most complex problems concerning nuclear waste management and therestoration of plutonium production sites is the treatment and dispositionof mixed and TRU wastes. Hydrothermal oxidation, which has been shown to beeffective in oxidizing a wide variety of organic material to CO2,water, salts and other nonhazardous oxides, is a promising new technologyfor the treatment and volume reduction of actinide-containing waste.Information on the speciation and solubility of plutonium under processeffluent conditions will facilitate the development of separation techniquesfor removing it from the treated solutions. Such a strongly oxidizingenvironment will generate plutonium(VT); and upon the destruction oforganics, hydrothermal reactor solutions will contain carbonate. We areinvestigating the solubility and speciation of the plutonium(VI) carbonatesystem as a function of ionic strength (0.1 to 5.0 M). Formation constantsfor the tris- and biscarbonato complexes of plutonium(IV) were determined tobe, log β130 = 17.7 and log β120 = 13.6, respectively,by spectrophotometry. These formation constants indicate that PuO2CO3(aq) is the plutonium (VI) carbonatesolution species with the largest relevant stability range. We prepared andcharacterized the corresponding solid using XRD, EXAFS, and diffusereflectance, and initiated solubility experiments in 0.1, 0.2, 0.5, 1,2, and5 M NaCl at 22±1°C under 100% CO2. Data collected thus far yieldthe solubility products, log Ksp mol2/kg2 =-12.9 (0.1 m NaCl), -12.4 (0.2 m NaCl), -12.5 (0.5 m NaCl), -12.3 (1 mNaCl), -12.2 (2 m NaCl), -12.3 (5 m NaCl).

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Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 465: Symposium II – Scienfific Basis for Nuclear Waste Management XX , 1996 , 759
Copyright
Copyright © Materials Research Society 1997

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References

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