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Reed DT, Lucchini JF, Aase SB, Kropf AJ. Reduction of plutonium(VI) in brine under subsurface conditions. RADIOCHIM ACTA 2009. [DOI: 10.1524/ract.2006.94.9-11.591] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The redox stability of PuO2
2+ was investigated in brine under subsurface conditions. In simulated brines, when no reducing agent was present, 0.1 mM concentrations of plutonium(VI) were stable as regards to reduction for over two years, which was the duration of the experiments performed. In these systems, the plutonyl existed as a carbonate or hydroxy-chloride species. The introduction of reducing agents (e.g. steel coupons, and aqueous Fe2+) typically present in a subsurface repository, however, led to the destabilization of the plutonium(VI) complexes and the subsequent reduction to Pu(IV) under most conditions investigated. X-ray Absorption Near-Edge Spectroscopy (XANES) confirmed that the final oxidation state in these systems was Pu(IV). This reduction lowered the overall steady state concentration of plutonium in the brine by 3−4 orders of magnitude. These results show the importance of considering repository constituents in evaluating subsurface actinide solubility/mobility and provide further evidence of the effectiveness of reduced iron species in the reduction and immobilization of higher-valent plutonium species.
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Ding M, Conca JL, Auwer CD, Gabitov RI, Hess NJ, Paviet-Hartmann P, Palmer PD, LoPresti V, Conradson SD. Chemical speciation of heterogeneously reduced Pu in synthetic brines. RADIOCHIM ACTA 2009. [DOI: 10.1524/ract.2006.94.5.249] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
SummaryX-ray absorption fine structure (XAFS) spectroscopy has been used to determine the speciation of Pu precipitates prepared by the heterogeneous reduction of Pu(VI) with Al and Fe in 5 M NaCl and an ERDA-6 brine, a simulant from the Waste Isolation Pilot Plant in Carlsbad, New Mexico. NaOCl was added to some of these solutions to determine its effect on Pu speciation. Analysis of the PuLIIIspectra showed that all solids consisted of PuO2+x-y(OH)2y·zH2O, compounds with characteristics identical to those prepared by hydrolysis and with Pu-O and Pu-Pu distances identical to those treated at elevated temperature. Additionally, reduction with Al gave compounds with different site distributions than reduction with Fe, and reduction with Al or the addition of NaOCl appeared to suppress the formation of oxo groups and their associated Pu(V) sites.
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Speciation and transformations of sorbed Pu on geologic materials: Wet chemical and spectroscopic observations. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s1569-4860(01)80012-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Subsurface interactions of actinide species and microorganisms: Implications for the bioremediation of actinide-organic mixtures. J Radioanal Nucl Chem 1999. [DOI: 10.1007/bf02347481] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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