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Title: Molecular Characterization of Actinide Oxocations from Protactinium to Plutonium

Abstract

This presentation addresses the structural characterization by EXAFS of actinide cations at oxidation states (V) and (VI) as one walks across the periodic table from Z = 91 (protactinium) to Z = 94 (plutonium). A structural comparison between Pa, U, Np and Pu oxocations in aqueous solution at formal oxidation states (V) and (VI) is carried out. These results are corroborated by quantum chemical and molecular dynamics calculations.

Authors:
; ; ;  [1]; ; ; ;  [2]; ;  [3];  [4];  [5]
  1. CEA Marcoule, DEN/DRCP/SCPS, 30207 Bagnols sur Ceze Cedex (France)
  2. IPN Orsay, 91405 Orsay Cedex (France)
  3. Forshungszentrum Rossendorf, Institute of Radiochemistry, P.O. Box 510119, D-01314 Dresden (Germany)
  4. (France)
  5. LANL, Los Alamos, NM87545, NM (United States)
Publication Date:
OSTI Identifier:
21054588
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644468; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; AQUEOUS SOLUTIONS; CATIONS; COMPARATIVE EVALUATIONS; FINE STRUCTURE; MOLECULAR DYNAMICS METHOD; NEPTUNIUM IONS; OXIDATION; PLUTONIUM; PLUTONIUM IONS; PROTACTINIUM; URANIUM IONS; VALENCE; X-RAY SPECTROSCOPY

Citation Formats

Den Auwer, C., Guilbaud, P., Guillaumont, D., Moisy, P., Digandomenico, V., Le Naour, C., Trubert, D., Simoni, E., Hennig, C., Scheinost, A., Rossendorf Beamline at the European Synchrotron Radiation Facility, F-38043 Grenoble, and Conradson, S. D. Molecular Characterization of Actinide Oxocations from Protactinium to Plutonium. United States: N. p., 2007. Web. doi:10.1063/1.2644468.
Den Auwer, C., Guilbaud, P., Guillaumont, D., Moisy, P., Digandomenico, V., Le Naour, C., Trubert, D., Simoni, E., Hennig, C., Scheinost, A., Rossendorf Beamline at the European Synchrotron Radiation Facility, F-38043 Grenoble, & Conradson, S. D. Molecular Characterization of Actinide Oxocations from Protactinium to Plutonium. United States. doi:10.1063/1.2644468.
Den Auwer, C., Guilbaud, P., Guillaumont, D., Moisy, P., Digandomenico, V., Le Naour, C., Trubert, D., Simoni, E., Hennig, C., Scheinost, A., Rossendorf Beamline at the European Synchrotron Radiation Facility, F-38043 Grenoble, and Conradson, S. D. Fri . "Molecular Characterization of Actinide Oxocations from Protactinium to Plutonium". United States. doi:10.1063/1.2644468.
@article{osti_21054588,
title = {Molecular Characterization of Actinide Oxocations from Protactinium to Plutonium},
author = {Den Auwer, C. and Guilbaud, P. and Guillaumont, D. and Moisy, P. and Digandomenico, V. and Le Naour, C. and Trubert, D. and Simoni, E. and Hennig, C. and Scheinost, A. and Rossendorf Beamline at the European Synchrotron Radiation Facility, F-38043 Grenoble and Conradson, S. D.},
abstractNote = {This presentation addresses the structural characterization by EXAFS of actinide cations at oxidation states (V) and (VI) as one walks across the periodic table from Z = 91 (protactinium) to Z = 94 (plutonium). A structural comparison between Pa, U, Np and Pu oxocations in aqueous solution at formal oxidation states (V) and (VI) is carried out. These results are corroborated by quantum chemical and molecular dynamics calculations.},
doi = {10.1063/1.2644468},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}
  • No abstract prepared.
  • Single crystals of Na8Pu2(O2)2(CO3)6•12H2O, exhibiting mu2, eta2-O2 ligands in unprecedented Pu(IV) dimeric units, were obtained at ambient temperature from aqueous Plutonium(IV) peroxide carbonate solution.
  • Several synthetic procedures have been developed for the preparation of early actinide aryloxide complexes. Simple alcoholysis of the actinide metallacycle [l brace][(Me[sub 3]Si)[sub 2]N][sub 2][ovr An(CH[sub 2]SiMe[sub 2]N]SiMe[sub 3])[r brace] [An = Th (1), U (2)] using 1 equiv of 2,6-disubstituted phenol results in the protonation of the An-C bond to form mono(aryloxide) complexes An(O-2,6-R[sub 2]C[sub 6]H[sub 3])[N(SiMe[sub 3])[sub 2]][sub 3] [An = U; R = t-Bu (3), i-Pr (4). An = Th; R = t-Bu (5), Me (6)] in essentially quantitative yield. For An = Th, further stepwise substitution products, the bis(aryloxide) or tris(aryloxide) complexes Th(O-2,6-t-Bu[sub 2]C[sub 6]H[sub 3])[submore » 2][N(SiMe[sub 3])[sub 2]][sub 2] (7) and Th(O-2,6-t-Bu[sub 2]C[sub 6]H[sub 3])[sub 3][N(SiMe[sub 3])[sub 2]] (8), are readily isolated depending on the stoichiometry of added phenol. Prolonged (36 h) reflux with excess 2,6-di-tert-butylphenol fails to provide the homoleptic Th(O-2,6-t-Bu[sub 2]C[sub 6]H[sub 3])[sub 4] via this simple protonolysis reaction. Thorium metallacycle 1 reacts with 4 equiv of HO-4-t-BuC[sub 6]H[sub 4] to produce polymeric [Th(O-4-t-BuC[sub 6]H[sub 4])[sub 4]][sub x], addition of pyridine to which yields the monomeric adduct Th(O-4-t-BuC[sub 6]H[sub 4])[sub 4](py)[sub 3] (10). For alcoholysis reactions employing the uranium metallacycle (2), addition of slightly greater than 4 equiv of HO-2,6-t-Bu[sub 2]C[sub 6]H[sub 3] in refluxing toluene for 6 h provides U(O-2,6-R[sub 2]C[sub 6]H[sub 3])[sub 4] [R = t-Bu (11), i-Pr (12)]. While alcoholysis fails to provide the homoleptic Th(O-2,6-t-Bu[sub 2]C[sub 6]H[sub 3])[sub 4] (9), the authors can prepare this complex via a metathetical procedure. Reaction of ThI[sub 4](THF)[sub 4] with 4 equiv of KO-2,6-t-Bu[sub 2]C[sub 6]H[sub 3] in THF provides 9 in high yield.« less
  • The presence of halide anions in four types of wastes arising from the pyrochemical reprocessing of plutonium required an immobilization process to be developed in which not only the actinide cations but also the halide anions were immobilized in a durable waste form. At AWE, we have developed such a process using Ca3(PO4)2 as the host material. Successful trials of the process with actinide- and Cl-bearing Type I waste were carried out at PNNL where the immobilization of the waste in a form resistant to aqueous leaching was confirmed. Normalized mass losses determined at 40°C and 28 days were 12more » x 10-6 g∙m-2 and 2.7 x 10-3 g∙m-2 for Pu and Cl, respectively. Accelerated radiation-induced damage effects are being determined with specimens containing 238Pu. No changes in the crystalline lattice have been detected with XRD after the 239Pu equivalent of 400 years ageing. Confirmation of the process for Type II waste (a oxyhydroxide-based waste) is currently underway at PNNL. Differences in the ionic state of Pu in the four types of waste have required different surrogates to be used. Samarium chloride was used successfully as a surrogate for both Pu(III) and Am(III) chlorides. Initial investigations into the use of HfO2 as the surrogate for Pu(IV) oxide in Type II waste indicated no significant differences.« less