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Sample records for actinide oxidation state

  1. Stabilization of actinides and lanthanides in unusually high oxidation states

    SciTech Connect

    Eller, P.G.; Penneman, R.A.

    1986-01-01

    Chemical environments can be chosen which stabilize actinides and lanthanides in unusually high or low oxidation states and in unusual coordination. In many cases, one can rationalize the observed species as resulting from strong charge/size influences provided by specific sites in host lattices (e.g., Tb(IV) in BaTbO/sub 3/ or Am(IV) in polytungstate anions). In other cases, the unusual species can be considered from an acid-base viewpoint (e.g., U(III) in AsF/sub 5//HF solution or Pu(VII) in Li/sub 5/PuO/sub 6/). In still other cases, an interplay of steric and redox effects can lead to interesting comparisons (e.g., instability of double fluoride salts of Pu(V) and Pu(VI) relative to U, Np, and Am analogues). Generalized ways to rationalize compounds containing actinides and lanthanides in unusual valences (particularly high valences), including the above and numerous other examples, will form the focus of this paper. Recently developed methods for synthesizing high valent f-element fluorides using superoxidizers and superacids at low temperatures will also be described. 65 refs., 8 figs., 9 tabs.

  2. Patterns in the stability of the lower oxidation states of the actinides and lanthanides

    SciTech Connect

    Mikheev, N.B.; Auerman, L.N.; Ionova, G.V.; Korshunov, B.G.; Spitsyn, V.I.

    1986-09-01

    The authors compare the first half of the lanthanides and the second half of the actinides by considering the specifics of the electronic structure of the valence atoms of the f-, d-, and s-orbitals, consisting of he following: The lanthanides from praseodymium to europium and from dysprosium to ytterbium, as well as the actinides from californium to nobelium, have the same electronic configuration f /SUP n/ s/sub 2/ in the state of free neutral atoms, which corresponds to their divalent state. On the basis of a consideration of the energy characteristics of the valence orbitals of the elements of the lanthanide and actinide famililies and as a result of an experimental determination of the standard oxidation potential of these elements, the authors consider the profound similarity between the elements of the first half of the lanthanide family and the second half of the actinide family to be established.

  3. Density Functional Theory Studies of the Electronic Structure of Solid State Actinide Oxides

    SciTech Connect

    Wen, Xiaodong; Martin, Richard L.; Henderson, Thomas M.; Scuseria, Gustavo E.

    2013-02-13

    The actinide oxides have been extensively studied in the context of the nuclear fuel cycle. They are also of fundamental interest as members of a class of strongly correlated materials, the Mott insulators. Their complex physical and chemical properties make them challenging systems to characterize, both experimentally and theoretically. Chiefly, this is because actinide oxides can exhibit both electronic localization and electronic delocalization and have partially occupied f orbitals, which can lead to multiple possibilities for ground states. Of particular concern for theoretical work is that the large number of competing states display strong correlations which are dffcult to capture with computationally tractable methods.

  4. Influence of microorganisms on the oxidation state distribution of multivalent actinides under anoxic conditions

    SciTech Connect

    Reed, Donald Timothy; Borkowski, Marian; Lucchini, Jean - Francois; Ams, David; Richmann, M. K.; Khaing, H.; Swanson, J. S.

    2010-12-10

    The fate and potential mobility of multivalent actinides in the subsurface is receiving increased attention as the DOE looks to cleanup the many legacy nuclear waste sites and associated subsurface contamination. Plutonium, uranium and neptunium are the near-surface multivalent contaminants of concern and are also key contaminants for the deep geologic disposal of nuclear waste. Their mobility is highly dependent on their redox distribution at their contamination source as well as along their potential migration pathways. This redox distribution is often controlled, especially in the near-surface where organic/inorganic contaminants often coexist, by the direct and indirect effects of microbial activity. Under anoxic conditions, indirect and direct bioreduction mechanisms exist that promote the prevalence of lower-valent species for multivalent actinides. Oxidation-state-specific biosorption is also an important consideration for long-term migration and can influence oxidation state distribution. Results of ongoing studies to explore and establish the oxidation-state specific interactions of soil bacteria (metal reducers and sulfate reducers) as well as halo-tolerant bacteria and Archaea for uranium, neptunium and plutonium will be presented. Enzymatic reduction is a key process in the bioreduction of plutonium and uranium, but co-enzymatic processes predominate in neptunium systems. Strong sorptive interactions can occur for most actinide oxidation states but are likely a factor in the stabilization of lower-valent species when more than one oxidation state can persist under anaerobic microbiologically-active conditions. These results for microbiologically active systems are interpreted in the context of their overall importance in defining the potential migration of multivalent actinides in the subsurface.

  5. Effect of oxidation state and ionic strength on sorption of actinides (Th, U, Np, Am) to geologic media

    SciTech Connect

    Dittrich, Timothy M.; Richmann, Michael K.; Reed, Donald T.

    2015-10-30

    The degree of conservatism in the estimated sorption partition coefficients (Kds) used in a performance assessment model is being evaluated based on a complementary batch and column method. The main focus of this work is to investigate the role of ionic strength, solution chemistry, and oxidation state (III-VI) in actinide sorption to dolomite rock. Based on redox conditions and solution chemistry expected at the WIPP, possible actinide species include Pu(III), Pu(IV), U(IV), U(VI), Np(IV), Np(V), Am(III), and Th(IV).

  6. Electrochemical and spectroscopic studies of some less stable oxidation states of selected lanthanide and actinide elements

    SciTech Connect

    Hobart, D. E.

    1981-06-01

    Simultaneous observation of electrochemical and spectroscopic properties (spectroelectrochemistry) at optically transparent electrodes (OTE's) was used to study some less stable oxidation states of selected lanthanide and actinide elements. Cyclic voltammetry at microelectrodes was used in conjunction with spectroelectrochemistry for the study of redox couples. Additional analytical techniques were used. The formal reduction potential (E/sup 0/') values of the M(III)/M(II) redox couples in 1 M KCl at pH 6 were -0.34 +- 0.01 V for Eu, -1.18 +- 0.01 V for Yb, and -1.50 +- 0.01 V for Sm. Spectropotentiostatic determination of E/sup 0/' for the Eu(III)/Eu(II) redox couple yielded a value of -0.391 +- 0.005 V. Spectropotentiostatic measurement of the Ce(IV)/Ce(III) redox couple in concentrated carbonate solution gave E/sup 0/' equal to 0.051 +- 0.005 V, which is about 1.7 V less positive than the E/sup 0/' value in noncomplexing solution. This same difference in potential was observed for the E/sup 0/' values of the Pr(IV)/Pr(III) and Tb(IV)/Tb(III) redox couples in carbonate solution, and thus Pr(IV) and Tb(IV) were stabilized in this medium. The U(VI)/U(V)/U(IV) and U(IV)/U(III) redox couples were studied in 1 M KCl at OTE's. Spectropotentiostatic measurement of the Np(VI)/Np(V) redox couple in 1 M HClO/sub 4/ gave an E/sup 0/' value of 1.140 +- 0.005 V. An E/sup 0/' value of 0.46 +- 0.01 V for the Np(VII)/Np(VI) couple was found by voltammetry. Oxidation of Am(III) was studied in concentrated carbonate solution, and a reversible cyclic voltammogram for the Am(IV)/Am(III) couple yielded E/sup 0/' = 0.92 +- 0.01 V in this medium; this value was used to estimate the standard reduction potential (E/sup 0/) of the couple as 2.62 +- 0.01 V. Attempts to oxidize Cm(III) in concentrated carbonate solution were not successful which suggests that the predicted E/sup 0/ value for the Cm(IV)/Cm(III) redox couple may be in error.

  7. rapid separation of higher actinide elements by cocrystallization using lower oxidation states

    SciTech Connect

    Kamenskaya, A.N.; Konovalova, N.A.; Kulyukhin, S.A.; Mikheev, N.B.

    1986-07-01

    An express method has been developed for the separation of higher actinides based on their cocrystallization with alkali metal halides. By carrying out reduction with the dichlorides of europium, ytterbium, and samarium it was possible to separate mendelevium from fermium, einsteinium, and californium, fermium from einsteinium and californium, and californium with einsteinium from trivalent actinides in turn. A practically complete purification from lanthanides was achieved in this way. Separation was carried in aqueous ethanol solutions by cocrystallization with NaCl resulting from salting out with ethanol. The purification coefficient of actinides from accompanying elements was 10/sup 3/ to 10/sup 4/. The yield on separation was about 90%. The duration of the separation process was 3-5 min.

  8. Sample preparation for actinide solid state research

    NASA Astrophysics Data System (ADS)

    Spirlet, J. C.

    1982-09-01

    The actinide elements (5f elements) and their compounds constitute a very interesting group for solid state research. The electronic properties of the 5f elements show intermediate behavior between the well-understood, completely localized 4f system (lanthanides) and the 3d system (transition elements). The possibility of understanding some unexplained properties of the 3d elements through a systematic investigation of the electronic structures of the actinides considerably increased interest in samples with well-defined composition and structure and with well-known purity. In some cases, single crystals of low defect densities and high purity levels are needed to allow sophisticated investigations of physical properties. Actinide compounds are easily obtained at a high purity level by direct synthesis from pure elements using noncontaminating techniques. Examples of these techniques are the reaction of the actinide metal powder with the vapor of an oxidant in a sealed quartz ampoule, leviation melting on a water-cooled pedestal or melting in a Huking crucible. Actinide metals are produced by metallothermic reduction of commercially available oxides or carbides or by the van Arkel purification process. The metals are refined to the desired purity level by evaporation in vacuum for the more volatile elements (Ac, Pu, Am, Cm, Bk) and by the van Arkel process for the metals with low vapor pressure. Single crystals of actinide compounds have been grown by chemical vapor transport methods (oxides, chalcogenides), high temperature solution growth techniques (oxides), and pulling from the melt by the Czochralski method (oxides, intermetallics). Thin solid films have been prepared by vacuum evaporation or by focused ion-beam sputtering. The materials are analyzed for trace-level impurity content by inductively-coupled plasma spectroscopy, by spark source mass spectroscopy and by secondary-ion mass spectroscopy. The chemical composition of the compounds is determined by

  9. Understanding the Chemistry of Uncommon Americium Oxidation States for Application to Actinide/Lanthanide Separations

    SciTech Connect

    Leigh Martin; Bruce J. Mincher; Nicholas C. Schmitt

    2007-09-01

    A spectroscopic study of the stability of Am(V) and Am(VI) produced by oxidizing Am(III) with sodium bismuthate is presented, varying the initial americium concentration, temperature and length of the oxidation was seen to have profound effects on the resultant solutions.

  10. Decontamination of matrices containing actinide oxides

    SciTech Connect

    Villarreal, Robert

    1997-12-01

    There is provided a method for removing actinides and actinide oxides, particularly fired actinides, from soil and other contaminated matrices, comprising: (a) contacting a contaminated material with a solution of at least one inhibited fluoride and an acid to form a mixture; (b) heating the mixture of contaminated material and solution to a temperature in the range from about 30 C to about 90 C while stirring; (c) separating the solution from any undissolved matrix material in the mixture; (d) washing the undissolved matrix material to remove any residual materials; and (e) drying and returning the treated matrix material to the environment.

  11. Electronic structure and ionicity of actinide oxides from first principles

    NASA Astrophysics Data System (ADS)

    Petit, L.; Svane, A.; Szotek, Z.; Temmerman, W. M.; Stocks, G. M.

    2010-01-01

    The ground-state electronic structures of the actinide oxides AO , A2O3 , and AO2 ( A=U , Np, Pu, Am, Cm, Bk, and Cf) are determined from first-principles calculations, using the self-interaction corrected local spin-density approximation. Emphasis is put on the degree of f -electron localization, which for AO2 and A2O3 is found to follow the stoichiometry, namely, corresponding to A4+ ions in the dioxide and A3+ ions in the sesquioxides. In contrast, the A2+ ionic configuration is not favorable in the monoxides, which therefore become metallic. The energetics of the oxidation and reduction in the actinide dioxides is discussed, and it is found that the dioxide is the most stable oxide for the actinides from Np onward. Our study reveals a strong link between preferred oxidation number and degree of localization which is confirmed by comparing to the ground-state configurations of the corresponding lanthanide oxides. The ionic nature of the actinide oxides emerges from the fact that only those compounds will form where the calculated ground-state valency agrees with the nominal valency expected from a simple charge counting.

  12. Application of powerful oxidizers in the synthesis of new high-oxidation state actinide and related species

    SciTech Connect

    Yeh, S.M.

    1984-11-01

    The fluorinating and oxide scavenging ability of XeF/sub 6/ have been studied by bringing XeF/sub 6/ into interaction with oxide-fluoride compounds of the third-transition-series elements (W, Re and Os) and uranium, in their highest oxidation states. A/sup +/MOF/sub 5//sup -/ and A/sup +/M/sub 2/O/sub 2/F/sub 9//sup -/ (A = K or Cs, M = W or U) were converted to A/sup +/MF/sub 7//sup -/ by XeF/sub 6/, but the rhenium and osmium compounds, K/sup +/ReO/sub 2/F/sub 4//sup -/ and XeF/sub 5//sup +/OsO/sub 3/F/sub 3//sup -/, resisted interaction with XeF/sub 6/. Strong interactions between XeF/sub 2/ or KrF/sub 2/ and the solvent have been observed for their solutions in anhydrous HF. Both XeF/sub 2/ and KrF/sub 2/ are seen to be effective in breaking up the polymeric (HF)/sub n/ chains. Only weak interactions occur between cations and anions of KrF/sup +/AuF/sub 6//sup -/ and Kr/sub 2/F/sub 3//sup +/AuF/sub 6//sup -/ in HF. The AuF/sub 6//sup -/ anions are slightly distorted from O/sub h/ symmetry. Kr/sub 2/F/sub 3//sup +/ cations in HF have the same dissymmetric V-shape which occurs in crystalline salts. A low-temperature orthorhombic form, ..beta..-ReF/sub 6//sup +/SbF/sub 6//sup -/, a high-temperature rhombohedral form, ..cap alpha..-ReF/sub 6//sup +/SbF/sub 6//sup -/, and a ReF/sub 6//sup +/AuF/sub 6//sup -/ have been prepared. These compounds possess only kinetic stability at ambient temperature and at approx. 20/sup 0/C are best represented as ReF/sub 6//sup +/ReF/sub 7/MF/sub 6//sup -/MF/sub 5/. Thermochemical energy evaluations indicate that the ionization potential of ReF/sub 6/ is 261 kcal mole/sup -1/ and that the fluoride-ion affinity of ReF/sub 6//sup +/ is -214 kcal mole/sup -1/. This is more exothermal than the corresponding process for IF/sub 6//sup +/ (-208 kcal mole/sup -1/). In contrast, ReOF/sub 5/ is shown to be a better fluoro-base than IOF/sub 5/ and also is a better base than ReF/sub 7/. ReOF/sub 4//sup +/MF/sub 6//sup -/ (M = Sb, Au and As

  13. Actinides in Hanford Tank Waste Simulants: Chemistry of Selected Species in Oxidizing Alkaline Solutions

    SciTech Connect

    Nash, Kenneth L.; Laszak, Ivan; Borkowski, Marian; Hancock, Melissa; Rao, Linfeng; Reed, Wendy

    2004-03-30

    To enhance removal of selected troublesome nonradioactive matrix elements (P, Cr, Al, S) from the sludges in radioactive waste tanks at the Hanford site, various chemical washing procedures have been evaluated. It is intended that leaching should leave the actinides in the residual sludge phase for direct vitrification. Oxidative treatment with strongly alkaline solutions has emerged as the best approach to accomplishing this feat. However, because the most important actinide ions in the sludge can exist in multiple oxidation states, it is conceivable that changes in actinide oxidation state speciation could interfere with hopes and plans for actinide insolubility. In this presentation, we discuss both the impact of oxidative alkaline leachants on actinide oxidation state speciation and the chemistry of oxidized actinide species in the solution phase. Actinide oxidation does occur during leaching, but the solubility behavior is complex. Mixed ligand complexes may dominate solution phase speciation of actinides under some circumstances. This work was supported by the U.S. Department of Energy, Offices of Science and Waste Management, Environmental Management Science Program under Contract DEAC03- 76SF0098 at Lawrence Berkeley National Laboratory and Contract W-31-109- ENG-38 at Argonne National Laboratory.

  14. Irradiaton of Metallic and Oxide Fuels for Actinide Transmutation in the ATR

    SciTech Connect

    Heather J. MacLean; Steven L. Hayes

    2007-09-01

    Metallic fuels containing minor actinides and rare earth additions have been fabricated and are prepared for irradiation in the ATR, scheduled to begin during the summer of 2007. Oxide fuels containing minor actinides are being fabricated and will be ready for irradiation in ATR, scheduled to begin during the summer of 2008. Fabrication and irradiation of these fuels will provide detailed studies of actinide transmutation in support of the Global Nuclear Energy Partnership. These fuel irradiations include new fuel compositions that have never before been tested. Results from these tests will provide fundamental data on fuel irradiation performance and will advance the state of knowledge for transmutation fuels.

  15. Actinide thermodynamic predictions. 3. Thermodynamics of compounds and aquo ions of the 2+, 3+ and 4+ oxidation states and standard electrode potentials at 298. 15 K

    SciTech Connect

    Bratsch, S.G.; Lagowski, J.J.

    1986-01-16

    A modified ionic model is applied to selected actinide thermodynamic measurements to allow the evaluation of gas-phase ion thermodynamics across the actinide series. These are used to predict the thermodynamic properties of a number of actinide compounds and aquo ions at 298.15 K. General guidelines are offered for predicting the relative stabilities of actinide(II), -(III), and -(IV) compounds in various chemical environments. 40 references, 6 figures, 8 tables.

  16. Fusion Techniques for the Oxidation of Refractory Actinide Oxides

    SciTech Connect

    Rudisill, T.S.

    1999-04-15

    Small-scale experiments were performed to demonstrate the feasibility of fusing refractory actinide oxides with a series of materials commonly used to decompose minerals, glasses, and other refractories as a pretreatment to dissolution and subsequent recovery operations. In these experiments, 1-2 g of plutonium or neptunium oxide (PuO2 or NpO2) were calcined at 900 degrees Celsius, mixed and heated with the fusing reagent(s), and dissolved. For refractory PuO2, the most effective material tested was a lithium carbonate (Li2CO3)/sodium tetraborate (Na2B4O7) mixture which aided in the recovery of 90 percent of the plutonium. The fused product was identified as a lithium plutonate (Li3PuO4) by x-ray diffraction. The use of a Li2CO3/Na2B4O7 mixture to solubilize high-fired NpO2 was not as effective as demonstrated for refractory PuO2. In a small-scale experiment, 25 percent of the NpO2 was oxidized to a neptunium (VI) species that dissolved in nitric acid. The remaining neptunium was then easily recovered from the residue by fusing with sodium peroxide (Na2O2). Approximately 70 percent of the neptunium dissolved in water to yield a basic solution of neptunium (VII). The remainder was recovered as a neptunium (VI) solution by dissolving the residue in 8M nitric acid. In subsequent experiments with Na2O2, the ratio of neptunium (VII) to (VI) was shown to be a function of the fusion temperature, with higher temperatures (greater than approximately 400 degrees C) favoring the formation of neptunium (VII). The fusion of an actual plutonium-containing residue with Na2O2 and subsequent dissolution was performed to demonstrate the feasibility of a pretreatment process on a larger scale. Sodium peroxide was chosen due

  17. Solid-state actinide acid phosphites from phosphorous acid melts

    NASA Astrophysics Data System (ADS)

    Oh, George N.; Burns, Peter C.

    2014-07-01

    The reaction of UO3 and H3PO3 at 100 °C and subsequent reaction with dimethylformamide (DMF) produces crystals of the compound (NH2(CH3)2)[UO2(HPO2OH)(HPO3)]. This compound crystallizes in space group P21/n and consists of layers of uranyl pentagonal bipyramids that share equatorial vertices with phosphite units, separated by dimethylammonium. In contrast, the reaction of phosphorous acid and actinide oxides at 210 °C produces a viscous syrup. Subsequent dilution in solvents and use of standard solution-state methods results in the crystallization of two polymorphs of the actinide acid phosphites An(HPO2OH)4 (An=U, Th) and of the mixed acid phosphite-phosphite U(HPO3)(HPO2OH)2(H2O)·2(H2O). α- and β-An(HPO2OH)4 crystallize in space groups C2/c and P21/n, respectively, and comprise a three-dimensional network of An4+ cations in square antiprismatic coordination corner-sharing with protonated phosphite units, whereas U(HPO3)(HPO2OH)2(H2O)2·(H2O) crystallizes in a layered structure in space group Pbca that is composed of An4+ cations in square antiprismatic coordination corner-sharing with protonated phosphites and water ligands. We discuss our findings in using solid inorganic reagents to produce a solution-workable precursor from which solid-state compounds can be crystallized.

  18. Advances in actinide solid-state and coordination chemistry

    SciTech Connect

    Burns, Peter C; Ikeda, Y.; Czerwinski, K.

    2011-01-31

    Actinide solid-state and coordination chemistry has advanced through unexpected results that have further revealed the complex nature of the 5f elements. Nanoscale control of actinide materials is emerging, as shown by the creation of a considerable range of cluster and tubular topologies. Departures from established structural trends for actinyl ions are provided by cation-cation interactions in which an O atom of one actinyl ion is an equatorial ligand of a bipyramid of another actinyl ion. The solid-state structural complexity of actinide materials has been further demonstrated by open framework materials with interesting properties. The U(VI) tetraoxide core has been added to this cation's repertoire of coordination possibilities. The emergence of pentavalent uranium solid-state and coordination chemistry has resulted from the prudent selection of ligands. Finally, analogues of the uranyl ion have challenged our understanding of this normally unreactive functional group.

  19. SURFACE COMPLEXATION OF ACTINIDES WITH IRON OXIDES: IMPLICATIONS FOR RADIONUCLIDE TRANSPORT IN NEAR-SURFACE AQUIFERS

    SciTech Connect

    J.L. Jerden Jr.; A.J. Kropf; Y. Tsai

    2005-08-25

    The surface complexation of actinides with iron oxides plays a key role in actinide transport and retardation in geosphere-biosphere systems. The development of accurate actinide transport models therefore requires a mechanistic understanding of surface complexation reactions (i.e. knowledge of chemical speciation at mineral/fluid interfaces). Iron oxides are particularly important actinide sorbents due to their pH dependent surface charges, relatively high surface areas and ubiquity in oxic and suboxic near-surface systems. In this paper we present results from field and laboratory investigations that elucidate the mechanisms involved in binding uranium and neptunium to iron oxide mineral substrates in near neutral groundwaters. The field study involved sampling and characterizing uranium-bearing groundwaters and solids from a saprolite aquifer overlying an unmined uranium deposit in the Virginia Piedmont. The groundwaters were analyzed by inductively coupled mass spectrometry and ion chromatography and the aquifer solids were analyzed by electron microprobe. The laboratory study involved a series of batch sorption tests in which U(VI) and Np(V) were reacted with goethite, hematite and magnetite in simulated groundwaters. The pH, ionic strength, aging time, and sorbent/sorbate ratios were varied in these experiments. The oxidation state and coordination environment of neptunium in solutions and sorbents from the batch tests were characterized by X-ray absorption spectroscopy (XAS) at the Advanced Photon Source, Argonne National Laboratory. Results from this work indicate that, in oxidizing near-surface aquifers, the dissolved concentration of uranium may be limited to less than 30 parts per billion due to uptake by iron oxide mineral coatings and the precipitation of sparingly soluble U(VI) phosphate minerals. Results from the batch adsorption tests showed that, in near neutral groundwaters, a significant fraction of the uranium and neptunium adsorbed as strongly

  20. Flammability Analysis For Actinide Oxides Packaged In 9975 Shipping Containers

    SciTech Connect

    Laurinat, James E.; Askew, Neal M.; Hensel, Steve J.

    2013-03-21

    Packaging options are evaluated for compliance with safety requirements for shipment of mixed actinide oxides packaged in a 9975 Primary Containment Vessel (PCV). Radiolytic gas generation rates, PCV internal gas pressures, and shipping windows (times to reach unacceptable gas compositions or pressures after closure of the PCV) are calculated for shipment of a 9975 PCV containing a plastic bottle filled with plutonium and uranium oxides with a selected isotopic composition. G-values for radiolytic hydrogen generation from adsorbed moisture are estimated from the results of gas generation tests for plutonium oxide and uranium oxide doped with curium-244. The radiolytic generation of hydrogen from the plastic bottle is calculated using a geometric model for alpha particle deposition in the bottle wall. The temperature of the PCV during shipment is estimated from the results of finite element heat transfer analyses.

  1. Gas Generation from Actinide Oxide Materials

    SciTech Connect

    George Bailey; Elizabeth Bluhm; John Lyman; Richard Mason; Mark Paffett; Gary Polansky; G. D. Roberson; Martin Sherman; Kirk Veirs; Laura Worl

    2000-12-01

    This document captures relevant work performed in support of stabilization, packaging, and long term storage of plutonium metals and oxides. It concentrates on the issue of gas generation with specific emphasis on gas pressure and composition. Even more specifically, it summarizes the basis for asserting that materials loaded into a 3013 container according to the requirements of the 3013 Standard (DOE-STD-3013-2000) cannot exceed the container design pressure within the time frames or environmental conditions of either storage or transportation. Presently, materials stabilized and packaged according to the 3013 Standard are to be transported in certified packages (the certification process for the 9975 and the SAFKEG has yet to be completed) that do not rely on the containment capabilities of the 3013 container. Even though no reliance is placed on that container, this document shows that it is highly likely that the containment function will be maintained not only in storage but also during transportation, including hypothetical accident conditions. Further, this document, by summarizing materials-related data on gas generation, can point those involved in preparing Safety Analysis Reports for Packages (SARPs) to additional information needed to assess the ability of the primary containment vessel to contain the contents and any reaction products that might reasonably be produced by the contents.

  2. A Screened Hybrid DFT Study of Actinide Oxides, Nitrides, and Carbides

    SciTech Connect

    Wen, Xiaodong; Martin, Richard L.; Scuseria, Gustavo E.; Rudin, Sven P.; Batista, Enrique R.

    2013-06-27

    A systematic study of the structural, electronic, and magnetic properties of actinide oxides, nitrides, and carbides (AnX1–2 with X = C, N, O) is performed using the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional. Our computed results show that the screened hybrid HSE functional gives a good description of the electronic and structural properties of actinide dioxides (strongly correlated insulators) when compared with available experimental data. However, there are still some problems reproducing the electronic properties of actinide nitrides and carbides (strongly correlated metals). In addition, in order to compare with the results by HSE, the structures, electronic, and magnetic properties of these actinide compounds are also investigated in the PBE and PBE+U approximation. Interestingly, the density of states of UN obtained with PBE compares well with the experimental photoemission spectra, in contrast to the hybrid approximation. This is presumably related to the need of additional screening in the Hartree–Fock exchange term of the metallic phases.

  3. The Thermodynamic Properties of the f-Elements and their Compounds. Part 2. The Lanthanide and Actinide Oxides

    SciTech Connect

    Konings, Rudy J. M. Beneš, Ondrej; Kovács, Attila; Manara, Dario; Sedmidubský, David; Gorokhov, Lev; Iorish, Vladimir S.; Yungman, Vladimir; Shenyavskaya, E.; Osina, E.

    2014-03-15

    A comprehensive review of the thermodynamic properties of the oxide compounds of the lanthanide and actinide elements is presented. The available literature data for the solid, liquid, and gaseous state have been analysed and recommended values are presented. In case experimental data are missing, estimates have been made based on the trends in the two series, which are extensively discussed.

  4. Research in actinide chemistry

    SciTech Connect

    Choppin, G.R.

    1993-01-01

    This research studies the behavior of the actinide elements in aqueous solution. The high radioactivity of the transuranium actinides limits the concentrations which can be studied and, consequently, limits the experimental techniques. However, oxidation state analogs (trivalent lanthanides, tetravalent thorium, and hexavalent uranium) do not suffer from these limitations. Behavior of actinides in the environment are a major USDOE concern, whether in connection with long-term releases from a repository, releases from stored defense wastes or accidental releases in reprocessing, etc. Principal goal of our research was expand the thermodynamic data base on complexation of actinides by natural ligands (e.g., OH[sup [minus

  5. Synthesis of actinide nitrides, phosphides, sulfides and oxides

    DOEpatents

    Van Der Sluys, William G.; Burns, Carol J.; Smith, David C.

    1992-01-01

    A process of preparing an actinide compound of the formula An.sub.x Z.sub.y wherein An is an actinide metal atom selected from the group consisting of thorium, uranium, plutonium, neptunium, and americium, x is selected from the group consisting of one, two or three, Z is a main group element atom selected from the group consisting of nitrogen, phosphorus, oxygen and sulfur and y is selected from the group consisting of one, two, three or four, by admixing an actinide organometallic precursor wherein said actinide is selected from the group consisting of thorium, uranium, plutonium, neptunium, and americium, a suitable solvent and a protic Lewis base selected from the group consisting of ammonia, phosphine, hydrogen sulfide and water, at temperatures and for time sufficient to form an intermediate actinide complex, heating said intermediate actinide complex at temperatures and for time sufficient to form the actinide compound, and a process of depositing a thin film of such an actinide compound, e.g., uranium mononitride, by subliming an actinide organometallic precursor, e.g., a uranium amide precursor, in the presence of an effectgive amount of a protic Lewis base, e.g., ammonia, within a reactor at temperatures and for time sufficient to form a thin film of the actinide compound, are disclosed.

  6. Oxidative dissolution of actinide oxides in H 2O 2 containing aqueous solution - A preliminary study

    NASA Astrophysics Data System (ADS)

    Pehrman, Reijo; Amme, Marcus; Roth, Olivia; Ekeroth, Ella; Jonsson, Mats

    2010-02-01

    Oxidative dissolution of spent nuclear fuel is an important issue in the safety assessment of a future geological repository for spent nuclear fuel. Although UO 2 constitutes, in terms of mass, the majority of the spent fuel material, its main radiotoxicity is (after extended storage times) contained in actinides with half lives shorter than that of 238-uranium, such as isotopes of Np and Pu. Relatively little information is available on the dissolution behavior of Np and Pu in comparable environments. This work investigates the oxidative dissolution of NpO 2 and PuO 2 in non-complexing aqueous solutions containing H 2O 2 and compares their behavior with that of UO 2. We have found that oxidative dissolution takes place for all three actinides in the presence of H 2O 2. Based on the obtained dissolution rates, we would not expect the dissolution of the actinides to be congruent. Instead, in a system without complexing agent, the release rates of Np and Pu are expected to be lower than the U release rate.

  7. Application of chemical structure and bonding of actinide oxide materials for forensic science

    SciTech Connect

    Wilkerson, Marianne Perry

    2010-01-01

    We are interested in applying our understanding of actinide chemical structure and bonding to broaden the suite of analytical tools available for nuclear forensic analyses. Uranium- and plutonium-oxide systems form under a variety of conditions, and these chemical species exhibit some of the most complex behavior of metal oxide systems known. No less intriguing is the ability of AnO{sub 2} (An: U, Pu) to form non-stoichiometric species described as AnO{sub 2+x}. Environmental studies have shown the value of utilizing the chemical signatures of these actinide oxide materials to understand transport following release into the environment. Chemical speciation of actinide-oxide samples may also provide clues as to the age, source, or process history of the material. The scientific challenge is to identify, measure and understand those aspects of speciation of actinide analytes that carry information about material origin and history most relevant to forensics. Here, we will describe our efforts in material synthesis and analytical methods development that we will use to provide the fundamental science to characterize actinide oxide molecular structures for forensic science. Structural properties and initial results to measure structural variability of uranium oxide samples using synchrotron-based X-ray Absorption Fine Structure will be discussed.

  8. Actinide Oxidation State and O/M Ratio in Hypostoichiometric Uranium-Plutonium-Americium U0.750Pu0.246Am0.004O2-x Mixed Oxides.

    PubMed

    Vauchy, Romain; Belin, Renaud C; Robisson, Anne-Charlotte; Lebreton, Florent; Aufore, Laurence; Scheinost, Andreas C; Martin, Philippe M

    2016-03-01

    Innovative americium-bearing uranium-plutonium mixed oxides U1-yPuyO2-x are envisioned as nuclear fuel for sodium-cooled fast neutron reactors (SFRs). The oxygen-to-metal (O/M) ratio, directly related to the oxidation state of cations, affects many of the fuel properties. Thus, a thorough knowledge of its variation with the sintering conditions is essential. The aim of this work is to follow the oxidation state of uranium, plutonium, and americium, and so the O/M ratio, in U0.750Pu0.246Am0.004O2-x samples sintered for 4 h at 2023 K in various Ar + 5% H2 + z vpm H2O (z = ∼ 15, ∼ 90, and ∼ 200) gas mixtures. The O/M ratios were determined by gravimetry, XAS, and XRD and evidenced a partial oxidation of the samples at room temperature. Finally, by comparing XANES and EXAFS results to that of a previous study, we demonstrate that the presence of uranium does not influence the interactions between americium and plutonium and that the differences in the O/M ratio between the investigated conditions is controlled by the reduction of plutonium. We also discuss the role of the homogeneity of cation distribution, as determined by EPMA, on the mechanisms involved in the reduction process. PMID:26907589

  9. METHOD FOR THE PREPARATION OF STABLE ACTINIDE METAL OXIDE-CONTAINING SLURRIES AND OF THE OXIDES THEREFOR

    DOEpatents

    Hansen, R.S.; Minturn, R.E.

    1958-02-25

    This patent deals with a method of preparing actinide metal oxides of a very fine particle size and of forming stable suspensions therefrom. The process consists of dissolving the nitrate of the actinide element in a combustible organic solvent, converting the solution obtained into a spray, and igniting the spray whereby an oxide powder is obtained. The oxide powder is then slurried in an aqueous soiution of a substance which is adsorbable by said oxides, dspersed in a colloid mill whereby a suspension is obtained, and electrodialyzed until a low spectiic conductance is reached.

  10. Actinide metal processing

    DOEpatents

    Sauer, Nancy N.; Watkin, John G.

    1992-01-01

    A process of converting an actinide metal such as thorium, uranium, or plnium to an actinide oxide material by admixing the actinide metal in an aqueous medium with a hypochlorite as an oxidizing agent for sufficient time to form the actinide oxide material and recovering the actinide oxide material is provided together with a low temperature process of preparing an actinide oxide nitrate such as uranyl nitrte. Additionally, a composition of matter comprising the reaction product of uranium metal and sodium hypochlorite is provided, the reaction product being an essentially insoluble uranium oxide material suitable for disposal or long term storage.

  11. Actinide metal processing

    SciTech Connect

    Sauer, N.N.; Watkin, J.G.

    1992-03-24

    A process for converting an actinide metal such as thorium, uranium, or plutonium to an actinide oxide material by admixing the actinide metal in an aqueous medium with a hypochlorite as an oxidizing agent for sufficient time to form the actinide oxide material and recovering the actinide oxide material is described together with a low temperature process for preparing an actinide oxide nitrate such as uranyl nitrate. Additionally, a composition of matter comprising the reaction product of uranium metal and sodium hypochlorite is provided, the reaction product being an essentially insoluble uranium oxide material suitable for disposal or long term storage.

  12. Actinide metal processing

    SciTech Connect

    Sauer, N.N.; Watkin, J.G.

    1991-04-05

    This invention is comprised of a process of converting an actinide metal such as thorium, uranium, or plutonium to an actinide oxide material by admixing the actinide metal in an aqueous medium with a hypochlorite as an oxidizing agent for sufficient time to form the actinide oxide material and recovering the actinide oxide material is provided together with a low temperature process of preparing an actinide oxide nitrate such as uranyl nitrate. Additionally, a composition of matter comprising the reaction product of uranium metal and sodium hypochlorite is provided, the reaction product being an essentially insoluble uranium oxide material suitable for disposal or long term storage.

  13. FINAL REPORT. ACTINIDE-ALUMINATE SPECIATION IN ALKALINE RADIOACTIVE WASTE

    EPA Science Inventory

    Investigation of behavior of actinides in alkaline media containing Al(III) showed that no aluminate complexes of actinides in oxidation states (III-VII) were formed in alkaline solutions. At alkaline precipitation (pH 10-14) of actinides in presence of Al(III) formation of alumi...

  14. Literature review of United States utilities computer codes for calculating actinide isotope content in irradiated fuel

    SciTech Connect

    Horak, W.C.; Lu, Ming-Shih

    1991-12-01

    This paper reviews the accuracy and precision of methods used by United States electric utilities to determine the actinide isotopic and element content of irradiated fuel. After an extensive literature search, three key code suites were selected for review. Two suites of computer codes, CASMO and ARMP, are used for reactor physics calculations; the ORIGEN code is used for spent fuel calculations. They are also the most widely used codes in the nuclear industry throughout the world. Although none of these codes calculate actinide isotopics as their primary variables intended for safeguards applications, accurate calculation of actinide isotopic content is necessary to fulfill their function.

  15. Strontium and Actinides Removal from Savannah River Site Actual Waste Samples by Freshly Precipitated Manganese Oxide

    SciTech Connect

    Barnes, M.J.

    2003-10-30

    The authors investigated the performance of freshly precipitated manganese oxide and monosodium titanate (MST) for the removal of strontium (Sr) and actinides from actual high-level waste. Manganese oxide precipitation occurs upon addition of a reductant such as formate (HCO2-) or peroxide (H2O2) to a waste solution containing permanganate (MnO4-). Tests described in this document address the capability of manganese oxide treatment to remove Rs, Pu, and Np from actual high-level waste containing elevated concentrations of Pu. Additionally, tests investigate MST (using two unique batches) performance with the same waste for direct comparison to the manganese oxide performance.

  16. Actinides-1981

    SciTech Connect

    Not Available

    1981-09-01

    Abstracts of 134 papers which were presented at the Actinides-1981 conference are presented. Approximately half of these papers deal with electronic structure of the actinides. Others deal with solid state chemistry, nuclear physic, thermodynamic properties, solution chemistry, and applied chemistry.

  17. Probing the population of the spin-orbit split levels in the actinide 5f states

    SciTech Connect

    Moore, K; der Laan, G v; Tobin, J; Chung, B; Wall, M; Schwartz, A

    2004-07-14

    Spin-orbit interaction in the 5f states is believed to strongly influence exotic behaviors observed in actinides metals and compounds. Understanding these interactions and how they relate to the actinide series is of considerable importance. To address this issue, the branching ratio of the white-line peaks of the N4,5 edges for the light actinide metals, {alpha}-Th, {alpha}-U, and {alpha}-Pu were recorded using electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM) and synchrotron-radiation-based x-ray absorption spectroscopy (XAS). Using the spin-orbit sum rule and the branching ratios from both experimental spectra and many-electron atomic spectral calculations, accurate values of the spin-orbit interaction, and thus the relative occupation of the j = 5/2 and 7/2 levels, are determined for the actinide 5f states. Results show that the spin-orbit sum rule works very well with both EELS and XAS spectra, needing little or no correction. This is important, since the high spatial resolution of a TEM can be used to overcome the problems of single crystal growth often encountered with actinide metals, allowing acquisition of EELS spectra, and subsequent spin-orbit analysis, from nm-sized regions. The relative occupation numbers obtained by our method have been compared with recent theoretical results and show a good agreement in their trend.

  18. Analysis and spectral assignments of mixed actinide oxide samples using laser-induced breakdown spectroscopy (LIBS).

    PubMed

    Barefield, James E; Judge, Elizabeth J; Berg, John M; Willson, Stephen P; Le, Loan A; Lopez, Leon N

    2013-04-01

    In this paper, we report for the first time the identification and assignments of complex atomic emission spectra of mixed actinide oxides using laser-induced plasma spectroscopy or laser-induced breakdown spectroscopy (LIBS). Preliminary results of LIBS measurements on samples of uranium dioxide (UO2)/plutonium dioxide (PuO2) and UO2/PuO2/americium dioxide (AmO2)/neptunium dioxide (NpO2) simulated fuel pellets (or mixed actinide oxide samples) are reported and discussed. We have identified and assigned >800 atomic emission lines for a UO2/PuO2/AmO2/NpO2 fuel pellet thus far. The identification and assignments of spectral emission lines for U, Pu, and Am are consistent with wavelength data from the literature. However, only a few emission lines have been assigned with a high degree of confidence for Np compared with atomic emission data from the literature. We also indicate where atomic emission lines for Cm would most likely appear in the spectral regions shown. Finally, we demonstrate that a LIBS system with a resolving power of approximately 20,000 is adequate for analyzing complex mixtures of actinide elements within the same sample. PMID:23601543

  19. Method for recovery of actinides from refractory oxides thereof using O.sub. F.sub.2

    DOEpatents

    Asprey, Larned B.; Eller, Phillip G.

    1988-01-01

    Method for recovery of actinides from nuclear waste material containing sintered and other oxides thereof using O.sub.2 F.sub.2 to generate the hexafluorides of the actinides present therein. The fluorinating agent, O.sub.2 F.sub.2, has been observed to perform the above-described tasks at sufficiently low temperatures that there is virtually no damage to the containment vessels. Moreover, the resulting actinide hexafluorides are not destroyed by high temperature reactions with the walls of the reaction vessel. Dioxygen difluoride is readily prepared, stored and transferred to the place of reaction.

  20. Subsurface interactions of actinide species and microorganisms : implications for the bioremediation of actinide-organic mixtures.

    SciTech Connect

    Banaszak, J.E.; Reed, D.T.; Rittmann, B.E.

    1999-02-12

    By reviewing how microorganisms interact with actinides in subsurface environments, we assess how bioremediation controls the fate of actinides. Actinides often are co-contaminants with strong organic chelators, chlorinated solvents, and fuel hydrocarbons. Bioremediation can immobilize the actinides, biodegrade the co-contaminants, or both. Actinides at the IV oxidation state are the least soluble, and microorganisms accelerate precipitation by altering the actinide's oxidation state or its speciation. We describe how microorganisms directly oxidize or reduce actinides and how microbiological reactions that biodegrade strong organic chelators, alter the pH, and consume or produce precipitating anions strongly affect actinide speciation and, therefore, mobility. We explain why inhibition caused by chemical or radiolytic toxicities uniquely affects microbial reactions. Due to the complex interactions of the microbiological and chemical phenomena, mathematical modeling is an essential tool for research on and application of bioremediation involving co-contamination with actinides. We describe the development of mathematical models that link microbiological and geochemical reactions. Throughout, we identify the key research needs.

  1. Comparative electronic structure of a lanthanide and actinide diatomic oxide: Nd versus U

    NASA Astrophysics Data System (ADS)

    Krauss, M.; Stevens, W. J.

    2003-01-01

    Using a modified version of the Alchemy electronic structure code and relativistic pseudopotentials, the electronic structure of the ground and low lying excited states of UO, NdO, and NdO + have been calculated at the Hartree-Fock (HF) and multiconfiguration self-consistent field (MCSCF) levels of theory. Including results from an earlier study of UO + this provides the information for a comparative analysis of a lanthanide and an actinide diatomic oxide. UO and NdO are both described formally as M +2 O -2 and the cations as M +3 O -2 , but the HF and MCSCF calculations show that these systems are considerably less ionic due to large charge back-transfer in the πorbitals. The electronic states putatively arise from the ligand field (oxygen anion) perturbed f 4 , sf 3 , df 3 , sdf 2 , or s 2 f 2 states of M +2 and f 3 , sf 2 or df 2 states of M +3 . Molecular orbital results show a substantial stabilization of the sf 3 or s 2 f 2 configurations relative to the f 4 or df 3 configurations that are the even or odd parity ground states in the M +2 free ion. The compact f and d orbitals are more destabilized by the anion field than the diffuse s orbital. The ground states of the neutral species are dominated by orbitals arising from the M +2 sf 3 term, and all the potential energy curves arising from this configuration are similar, which allows an estimate of the vibrational frequencies for UO and NdO of 862 cm -1 and 836 cm -1 , respectively. For NdO + and UO + the excitation energies for the Ωstates were calculated with a valence configuration interaction method using ab initio effective spin-orbit operators to couple the molecular orbital configurations. The results for NdO + are very comparable with the results for UO + , and show the vibrational and electronic states to be interleaved.

  2. Oxidation State 10 Exists.

    PubMed

    Yu, Haoyu S; Truhlar, Donald G

    2016-07-25

    In a recent paper, Wang et al. found an iridium-containing compound with a formal oxidation state of 9. This is the highest oxidation state ever found in a stable compound. To learn if this is the highest chemical oxidation state possible, Kohn-Sham density functional theory was used to study various compounds, including PdO4 (2+) , PtO4 (2+) , PtO3 F2 (2+) , PtO4 OH(+) , PtO5 , and PtO4 SH(+) , in which the metal has an oxidation state of 10. It was found that PtO4 (2+) has a metastable state that is kinetically stable with a barrier height for decomposition of 31 kcal mol(-1) and a calculated lifetime of 0.9 years. All other compounds studied would readily decompose to lower oxidation states. PMID:27273799

  3. f-state luminescence of lanthanide and actinide ions in solution

    SciTech Connect

    Beitz, J.V.

    1993-09-01

    Detailed studies of the luminescence of aquated Am{sup 3+} are presented in the context of prior lanthanide and actinide ion work. The luminescing state of aquated Am{sup 3+} is confirmed to be {sup 5}D{sub l} based on observed emission and excitation spectra. The luminescence lifetime of Am{sup 3+} in H{sub 2}O solution is (22 {plus_minus} 3) ns and (155 {plus_minus} 4) ns in D{sub 2}O solution at 295 K. Judd-Ofelt transition intensity theory qualitatively describes the observed Am{sup 3+} relative integrated fluorescence intensities. Recent luminescence studies on complexed trivalent f-element ions in solution are reviewed as to the similarities and differences between lanthanide ion 4f state and actinide ion 5f state properties.

  4. Recent progress on minor-actinide-bearing oxide fuel fabrication at CEA Marcoule

    NASA Astrophysics Data System (ADS)

    Lebreton, Florent; Prieur, Damien; Horlait, Denis; Delahaye, Thibaud; Jankowiak, Aurélien; Léorier, Caroline; Jorion, Frédéric; Gavilan, Elisabeth; Desmoulière, François

    2013-07-01

    Partitioning and transmutation (P&T) of minor actinides (MA: americium, neptunium and curium) in fast neutron reactors or accelerator-driven systems is a route envisaged to reduce nuclear waste inventory. Over the years, several modes of P&T were proposed, each being based on the use of dedicated fuels such as inert-matrix fuels, MA-bearing MOX or MA-bearing blankets. In this context, progress on the manufacturing of such fuels is a key-challenge in order to render P&T viable at the industrial scale. Here, MA-bearing oxide fuel fabrication and characterization conducted in the CEA Marcoule Atalante facility is reviewed. A particular attention is also given to the research conducted on uranium-americium mixed-oxides fuels, which are now considered the reference fuels for MA transmutation in France.

  5. THEORY FOR THE XPS OF ACTINIDES

    SciTech Connect

    Bagus, Paul S.; Ilton, Eugene S.

    2013-08-01

    Two aspects of the electronic structure of actinide oxides that significantly affect the XPS spectra are described; these aspects are also important for the materials properties of the oxides. The two aspects considered are: (1) The spin-orbit coupling of the open 5f shell electrons in actinide cations and how this coupling affects the electronic structure. And, (2) the covalent character of the metal oxygen interaction in actinide compounds. Because of this covalent character, there are strong departures from the nominal oxidation states that are significantly larger in core-hole states than in the ground state. The consequences for the XPS of this covalent character are examined. A proper understanding of the way in which they influence the XPS makes it possible to use the XPS to correctly characterize the electronic structure of the oxides.

  6. Synthesis of Functionalized Superparamagnetic Iron Oxide Nanoparticles from a Common Precursor and their Application as Heavy Metal and Actinide Sorbents

    SciTech Connect

    Warner, Marvin G.; Warner, Cynthia L.; Addleman, Raymond S.; Droubay, Timothy C.; Engelhard, Mark H.; Davidson, Joseph D.; Cinson, Anthony D.; Nash, Michael A.; Yantasee, Wassana

    2009-10-12

    We describe the use of a simple and versatile technique to generate a series of ligand stabilized iron oxide nanoparticles containing different functionalities with specificities toward heavy metals and actinides at the periphery of the stabilizing ligand shell from a common, easy to synthesize precursor nanoparticle. The resulting nanoparticles are designed to contain affinity ligands that make them excellent sorbent materials for a variety of heavy metals from contaminated aqueous systems such as river water and ground water as well as actinides from clinical samples such as blood and urine. Functionalized superparamagnetic nanoparticles make ideal reagents for extraction of heavy metal and actinide contaminants from environmental and clinical samples since they are easily removed from the media once bound to the contaminant by simply applying a magnetic field. In addition, these engineered nanomaterials have an inherently high active surface area (often > 100 m2/g) making them ideal sorbent materials for these types of applications

  7. Actinide recovery process

    DOEpatents

    Muscatello, Anthony C.; Navratil, James D.; Saba, Mark T.

    1987-07-28

    Process for the removal of plutonium polymer and ionic actinides from aqueous solutions by absorption onto a solid extractant loaded on a solid inert support such as polystyrenedivinylbenzene. The absorbed actinides can then be recovered by incineration, by stripping with organic solvents, or by acid digestion. Preferred solid extractants are trioctylphosphine oxide and octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide and the like.

  8. Bidentate organophosphorus solvent extraction process for actinide recovery and partition

    DOEpatents

    Schulz, Wallace W.

    1976-01-01

    A liquid-liquid extraction process for the recovery and partitioning of actinide values from acidic nuclear waste aqueous solutions, the actinide values including trivalent, tetravalent and hexavalent oxidation states is provided and includes the steps of contacting the aqueous solution with a bidentate organophosphorous extractant to extract essentially all of the actinide values into the organic phase. Thereafter the respective actinide fractions are selectively partitioned into separate aqueous solutions by contact with dilute nitric or nitric-hydrofluoric acid solutions. The hexavalent uranium is finally removed from the organic phase by contact with a dilute sodium carbonate solution.

  9. Fundamental aspects of actinide-zirconium pyrochlore oxides: Systematic comparison of the Pu, Am, Cm, Bk and Cf systems

    NASA Astrophysics Data System (ADS)

    Haire, R. G.; Raison, P. E.

    2000-07-01

    Zirconium- and hafnium-based oxide materials have gained attraction for various nuclear applications. These materials have features in common with one of the early, well-publicized inorganic ceramics for immobilizing nuclear waste. Our interests have addressed the fundamental structural and chemical properties of these oxide systems. We pursued both the crystal chemical constraints of the oxide matrices, as well as the importance of the chemistry of the f-elements. By incorporating five actinide elements in our studies, we were able to compare systematically the materials science of these materials with the fundamental chemistry and electronic configurations of these actinides employed. It is expected that this basic information will be useful technologically in the realm of tailor-made materials for different applications.

  10. Spectroscopy of high-lying states in actinide nuclei

    SciTech Connect

    Ahmad, I.; Back, B.B.; Betts, R.R.

    1995-08-01

    In the course of studying positron-electron production during the collisions of uranium beams and tantalum targets, a careful measurement of the emitted gamma radiation was made using large Ge detectors. Many new high energy gamma rays were found, associated both with U-like and Ta-like fragments. To determine the origin of these gamma rays, a dedicated set of improved gamma-ray studies were carried out. The studies used four large (> 55%) Ge detectors mounted in the APEX chamber. States in {sup 238}U and {sup 232}Th were Coulomb excited using a {sup 208}Pb beam of 5.8 MeV/u. Heavy ions were detected in the large-area APEX multiwire proportional counters. The extensive beam monitoring of the APEX setup allowed precise normalization and accurate cross-section determinations. The Doppler shifts from upstream and downstream detectors permitted a precise confirmation of the incident beam energy to less than 0.05 MeV/A. A spectrum of gamma rays, corrected assuming emission from {sup 238}U.

  11. Proton Single-Particle States In The Heaviest Actinide Nuclei

    SciTech Connect

    Ahmad, I.; Kondev, F.G.; Moore, E.F.; Chasman, R.R.; Carpenter, M.P.; Greene, J.P.; Janssens, R.V.F.; Lauritsen, T.; Lister, C.J.; Seweryniak, D.; Hoff, R.W.; Evans, J.E.; Lougheed, R.W.; Porter, C.E.; Felker, L.K.

    2005-04-05

    The level structure of 249Bk has been investigated by measuring the {gamma}-ray spectra following the {alpha} decay of a chemically and isotopically pure 253Es sample. Alpha-gamma coincidence measurement was performed using a Si detector for {alpha} particles and a 25% Ge detector for {gamma} rays. A gamma-gamma coincidence measurement was performed with the Gammasphere spectrometer. The Es sample was obtained by extracting the 253Es which grew in a 253Cf source material produced in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Additional information on the 249Bk levels was obtained from the study of {gamma} rays produced in the {beta}- decay of 249Cm. The 249Cm sample was produced by neutron irradiation of 248Cm. Using the results of the present study and the results of previous 248Cm({alpha},t) and 248Cm(3He,d) reaction spectra, the following single-particle states have been identified in 249Bk: 7/2+[633], 0.0 keV; 3/2-[521], 8.78 keV; 1/2+[400], 377.55 keV: 5/2+[642], 389.17 keV; 1/2-[530], 569.19 keV; 1/2-[521], 643.0 keV; 5/2-[523], 672.8 keV; 9/2+[624], 1075.1 keV. Four vibrational bands were identified at 767.9, 932.2, 1150.7 and 1223.0 keV with tentative assignments of {l_brace}7/2+[633]x1-{r_brace}9/2-, {l_brace}7/2+[633]x0-{r_brace}7/2-, {l_brace}7/2+[633]x1-{r_brace}5/2- and {l_brace}7/2+[633]x0+{r_brace}7/2+, respectively.

  12. Low-Temperature Synthesis of Actinide Tetraborides by Solid-State Metathesis Reactions

    SciTech Connect

    Lupinetti, Anthony J.; Garcia, Eduardo; Abney, Kent D.

    2004-12-14

    The synthesis of actinide tetraborides including uranium tetraboride (UB,), plutonium tetraboride (PUB,) and thorium tetraboride (ThB{sub 4}) by a solid-state metathesis reaction are demonstrated. The present method significantly lowers the temperature required to {approx_equal}850 C. As an example, when UCl{sub 4}, is reacted with an excess of MgB{sub 2}, at 850 C, crystalline UB, is formed. Powder X-ray diffraction and ICP-AES data support the reduction of UCl{sub 3}, as the initial step in the reaction. The UB, product is purified by washing water and drying.

  13. Overview of actinide chemistry in the WIPP

    SciTech Connect

    Borkowski, Marian; Lucchini, Jean - Francois; Richmann, Michael K; Reed, Donald T; Khaing, Hnin; Swanson, Juliet

    2009-01-01

    The year 2009 celebrates 10 years of safe operations at the Waste Isolation Pilot Plant (WIPP), the only nuclear waste repository designated to dispose defense-related transuranic (TRU) waste in the United States. Many elements contributed to the success of this one-of-the-kind facility. One of the most important of these is the chemistry of the actinides under WIPP repository conditions. A reliable understanding of the potential release of actinides from the site to the accessible environment is important to the WIPP performance assessment (PA). The environmental chemistry of the major actinides disposed at the WIPP continues to be investigated as part of the ongoing recertification efforts of the WIPP project. This presentation provides an overview of the actinide chemistry for the WIPP repository conditions. The WIPP is a salt-based repository; therefore, the inflow of brine into the repository is minimized, due to the natural tendency of excavated salt to re-seal. Reducing anoxic conditions are expected in WIPP because of microbial activity and metal corrosion processes that consume the oxygen initially present. Should brine be introduced through an intrusion scenario, these same processes will re-establish reducing conditions. In the case of an intrusion scenario involving brine, the solubilization of actinides in brine is considered as a potential source of release to the accessible environment. The following key factors establish the concentrations of dissolved actinides under subsurface conditions: (1) Redox chemistry - The solubility of reduced actinides (III and IV oxidation states) is known to be significantly lower than the oxidized forms (V and/or VI oxidation states). In this context, the reducing conditions in the WIPP and the strong coupling of the chemistry for reduced metals and microbiological processes with actinides are important. (2) Complexation - For the anoxic, reducing and mildly basic brine systems in the WIPP, the most important

  14. Actinide cation-cation complexes

    SciTech Connect

    Stoyer, N.J.; Seaborg, G.T.

    1994-12-01

    The +5 oxidation state of U, Np, Pu, and Am is a linear dioxo cation (AnO{sub 2}{sup +}) with a formal charge of +1. These cations form complexes with a variety of other cations, including actinide cations. Other oxidation states of actinides do not form these cation-cation complexes with any cation other than AnO{sub 2}{sup +}; therefore, cation-cation complexes indicate something unique about AnO{sub 2}{sup +} cations compared to actinide cations in general. The first cation-cation complex, NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, was reported by Sullivan, Hindman, and Zielen in 1961. Of the four actinides that form AnO{sub 2}{sup +} species, the cation-cation complexes of NpO{sub 2}{sup +} have been studied most extensively while the other actinides have not. The only PuO{sub 2}{sup +} cation-cation complexes that have been studied are with Fe{sup 3+} and Cr{sup 3+} and neither one has had its equilibrium constant measured. Actinides have small molar absorptivities and cation-cation complexes have small equilibrium constants; therefore, to overcome these obstacles a sensitive technique is required. Spectroscopic techniques are used most often to study cation-cation complexes. Laser-Induced Photacoustic Spectroscopy equilibrium constants for the complexes NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, NpO{sub 2}{sup +}{center_dot}Th{sup 4+}, PuO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, and PuO{sub 2}{sup +}{center_dot}Th{sup 4+} at an ionic strength of 6 M using LIPAS are 2.4 {plus_minus} 0.2, 1.8 {plus_minus} 0.9, 2.2 {plus_minus} 1.5, and {approx}0.8 M{sup {minus}1}.

  15. Higher Americium Oxidation State Research Roadmap

    SciTech Connect

    Mincher, Bruce J.; Law, Jack D.; Goff, George S.; Moyer, Bruce A.; Burns, Jon D.; Lumetta, Gregg J.; Sinkov, Sergey I.; Shehee, Thomas C.; Hobbs, David T.

    2015-12-18

    -solvent-extraction separations are also under investigation. The first would separate Am(VI) by co-crystallization with uranium and the other oxidizable actinides as their nitrate salts. This novel idea has been successful in lab scale testing, and merits further investigation. Similarly, success has been achieved in separations using inorganic or hybrid ion exchange materials to sorb the lanthanides and actinides, while allowing pentavalent americium to elute. This is the only technique currently investigating Am(V), despite the advantages of this oxidation state with regard to its higher stability. The ultimate destination for this roadmap is to develop an americium separation that can be applied under process conditions, preferably affording a co-separation of the actinyl (VI) ions. Toward that end, emphasis is given here to selection of a solvent extraction flowsheet for testing in the INL centrifugal contactor hot test bed during FY16. A solvent extraction process will be tested mainly because solvent extraction separations of Am(VI) are relatively mature and the test bed currently exists in a configuration to support them. Thus, a major goal of FY16 is to select the oxidant/ligand combination to run such a test using the contactors. The only ligands under consideration are DAAP and DEHBA. This is not to say that ion exchange and co-crystallization techniques are unimportant. They merit continued investigation, but are not mature enough for hot test bed testing at this time.

  16. Magnetic measurements of the transuranium elements and charge state characterization of actinides in monazite. Progress report

    SciTech Connect

    Huray, P. G.

    1980-01-01

    A micromagnetic susceptometer for the purpose of measuring extremely small sample quantities (on the microgram level) was designed, constructed, and calibrated in previous years. (The 1979 progress report gives details of its operation.) This device has operated without significant downtime in this funding period, and much progress has been made in the magnetic characterization of elements beyond Am in the periodic table. This program has roughly doubled man's knowledge of magnetism in Cm, Bk, and Cf, and includes the only Es magnetic measurements to date. The incorporation of an automatic data collection system in this period has made analysis much more accurate, and has allowed quicker turnaround of compounds and metals for study. Results obtained for the compounds and metals studied this year are summarized. The lanthanide orthophosphates are being investigated as an alternate means of primary containment for high-level actinide wastes. Researchers at the Oak Ridge National Laboratory are involved in preparation of actinide-doped compounds for all of the lanthanide transition series (La through Lu) for a study of leaching characteristics and E.S.R. classification. To aid this study the charge state of /sup 237/Np or /sup 57/Fe has been identified, either in the as-prepared compounds or following radioactive decay of /sup 241/Am via the Moessbauer Effect. The final charge state will be an influential variable in the immobilization characteristics of the waste products stored in this synthetic monazite form. 10 figures, 1 table. (RWR)

  17. Kinetics of actinide complexation reactions

    SciTech Connect

    Nash, K.L.; Sullivan, J.C.

    1997-09-01

    Though the literature records extensive compilations of the thermodynamics of actinide complexation reactions, the kinetics of complex formation and dissociation reactions of actinide ions in aqueous solutions have not been extensively investigated. In light of the central role played by such reactions in actinide process and environmental chemistry, this situation is somewhat surprising. The authors report herein a summary of what is known about actinide complexation kinetics. The systems include actinide ions in the four principal oxidation states (III, IV, V, and VI) and complex formation and dissociation rates with both simple and complex ligands. Most of the work reported was conducted in acidic media, but a few address reactions in neutral and alkaline solutions. Complex formation reactions tend in general to be rapid, accessible only to rapid-scan and equilibrium perturbation techniques. Complex dissociation reactions exhibit a wider range of rates and are generally more accessible using standard analytical methods. Literature results are described and correlated with the known properties of the individual ions.

  18. Charged defects during alpha-irradiation of actinide oxides as revealed by Raman and luminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Mohun, R.; Desgranges, L.; Léchelle, J.; Simon, P.; Guimbretière, G.; Canizarès, A.; Duval, F.; Jegou, C.; Magnin, M.; Clavier, N.; Dacheux, N.; Valot, C.; Vauchy, R.

    2016-05-01

    We have recently evidenced an original Raman signature of alpha irradiation-induced defects in UO2. In this study, we aim to determine whether the same signature also exists in different actinide oxides, namely ThO2 and PuO2. Sintered UO2 and ThO2 were initially irradiated with 21 MeV He2+ ions using a cyclotron device and were subjected to an in situ luminescence experiment followed by Raman analysis. In addition, a PuO2 sample which had accumulated self-irradiation damage due to alpha particles was investigated only by Raman measurement. Results obtained for the initially white ThO2 showed that a blue color appeared in the irradiated areas as well as luminescence signals during irradiation. However, Raman spectroscopic analysis showed the absence of Raman signature in ThO2. In contrast, the irradiated UO2 and PuO2 confirmed the presence of the Raman signature but no luminescence peaks were observed. The proposed mechanism involves electronic defects in ThO2, while a coupling between electronic defects and phonons is required to explain the Raman spectra for UO2 and PuO2.

  19. Advanced Aqueous Separation Systems for Actinide Partitioning

    SciTech Connect

    Nash, Kenneth L.; Clark, Sue; Meier, G Patrick; Alexandratos, Spiro; Paine, Robert; Hancock, Robert; Ensor, Dale

    2012-03-21

    One of the most challenging aspects of advanced processing of spent nuclear fuel is the need to isolate transuranium elements from fission product lanthanides. This project expanded the scope of earlier investigations of americium (Am) partitioning from the lanthanides with the synthesis of new separations materials and a centralized focus on radiochemical characterization of the separation systems that could be developed based on these new materials. The primary objective of this program was to explore alternative materials for actinide separations and to link the design of new reagents for actinide separations to characterizations based on actinide chemistry. In the predominant trivalent oxidation state, the chemistry of lanthanides overlaps substantially with that of the trivalent actinides and their mutual separation is quite challenging.

  20. Experimental findings on actinide recovery utilizing oxidation by peroxydisulfate followed by ion exchange: Fuel cycle research & development

    SciTech Connect

    Hobbs, D. T.; Shehee, T. C.

    2015-08-31

    Our research seeks to determine if inorganic ion-exchange materials can be exploited to provide effective minor actinide (Am, Cm) separation from lanthanides. Previous work has established that a number of inorganic and UMOF ion-exchange materials exhibit varying affinities for actinides and lanthanides, which may be exploited for effective separations. During FY15, experimental work focused on investigating methods to oxidize americium in dilute nitric and perchloric acid with subsequent ion-exchange performance measurements of ion exchangers with the oxidized americium in dilute nitric acid. Ion-exchange materials tested included a variety of alkali titanates. Americium oxidation testing sought to determine the influence that other redox active components may have on the oxidation of AmIII. Experimental findings indicated that CeIII, NpV, and RuII are oxidized by peroxydisulfate, but there are no indications that the presence of CeIII, NpV, and RuII affected the rate or extent of americium oxidation at the concentrations of peroxydisulfate being used.

  1. Experimental findings on actinide recovery utilizing oxidation by peroxydisulfate followed by ion exchange: Fuel cycle research & development

    SciTech Connect

    Hobbs, D. T.; Shehee, T. C.

    2015-08-31

    Our research seeks to determine if inorganic ion-exchange materials can be exploited to provide effective minor actinide (Am, Cm) separation from lanthanides. Previous work has established that a number of inorganic and UMOF ion-exchange materials exhibit varying affinities for actinides and lanthanides, which may be exploited for effective separations. During FY15, experimental work focused on investigating methods to oxidize americium in dilute nitric and perchloric acid with subsequent ion-exchange performance measurements of ion exchangers with the oxidized americium in dilute nitric acid. Ion-exchange materials tested included a variety of alkali titanates. Americium oxidation testing sought to determine the influence that other redox active components may have on the oxidation of AmIII. Experimental findings indicated that CeIII, NpV, and RuII are oxidized by peroxydisulfate, but there are no indications that the presence of CeIII, NpV, and RuII affected the rate or extent of americium oxidation at the concentrations of peroxydisulfate being used.

  2. Environmental speciation of actinides.

    PubMed

    Maher, Kate; Bargar, John R; Brown, Gordon E

    2013-04-01

    Although minor in abundance in Earth's crust (U, 2-4 ppm; Th, 10-15 ppm) and in seawater (U, 0.003 ppm; Th, 0.0007 ppm), light actinides (Th, Pa, U, Np, Pu, Am, and Cm) are important environmental contaminants associated with anthropogenic activities such as the mining and milling of uranium ores, generation of nuclear energy, and storage of legacy waste resulting from the manufacturing and testing of nuclear weapons. In this review, we discuss the abundance, production, and environmental sources of naturally occurring and some man-made light actinides. As is the case with other environmental contaminants, the solubility, transport properties, bioavailability, and toxicity of actinides are dependent on their speciation (composition, oxidation state, molecular-level structure, and nature of the phase in which the contaminant element or molecule occurs). We review the aqueous speciation of U, Np, and Pu as a function of pH and Eh, their interaction with common inorganic and organic ligands in natural waters, and some of the common U-containing minerals. We also discuss the interaction of U, Np, Pu, and Am solution complexes with common Earth materials, including minerals, colloids, gels, natural organic matter (NOM), and microbial organisms, based on simplified model system studies. These surface interactions can inhibit (e.g., sorption to mineral surfaces, formation of insoluble biominerals) or enhance (e.g., colloid-facilitated transport) the dispersal of light actinides in the biosphere and in some cases (e.g., interaction with dissimilatory metal-reducing bacteria, NOM, or Mn- and Fe-containing minerals) can modify the oxidation states and, consequently, the behavior of redox-sensitive light actinides (U, Np, and Pu). Finally, we review the speciation of U and Pu, their chemical transformations, and cleanup histories at several U.S. Department of Energy field sites that have been used to mill U ores, produce fissile materials for reactors and weapons, and store

  3. Low-temperature synthesis of actinide tetraborides by solid-state metathesis reactions

    DOEpatents

    Lupinetti, Anthony J.; Garcia, Eduardo; Abney, Kent D.

    2004-12-14

    The synthesis of actinide tetraborides including uranium tetraboride (UB.sub.4), plutonium tetraboride (PuB.sub.4) and thorium tetraboride (ThB.sub.4) by a solid-state metathesis reaction are demonstrated. The present method significantly lowers the temperature required to .ltoreq.850.degree. C. As an example, when UCl.sub.4 is reacted with an excess of MgB.sub.2, at 850.degree. C., crystalline UB.sub.4 is formed. Powder X-ray diffraction and ICP-AES data support the reduction of UCl.sub.3 as the initial step in the reaction. The UB.sub.4 product is purified by washing water and drying.

  4. PRODUCTION OF ACTINIDE METAL

    DOEpatents

    Knighton, J.B.

    1963-11-01

    A process of reducing actinide oxide to the metal with magnesium-zinc alloy in a flux of 5 mole% of magnesium fluoride and 95 mole% of magnesium chloride plus lithium, sodium, potassium, calcium, strontium, or barium chloride is presented. The flux contains at least 14 mole% of magnesium cation at 600-- 900 deg C in air. The formed magnesium-zinc-actinide alloy is separated from the magnesium-oxide-containing flux. (AEC)

  5. Actinide recovery process

    DOEpatents

    Muscatello, A.C.; Navratil, J.D.; Saba, M.T.

    1985-06-13

    Process for the removal of plutonium polymer and ionic actinides from aqueous solutions by absorption onto a solid extractant loaded on a solid inert support such as polystyrene-divinylbenzene. The absorbed actinides can then be recovered by incineration, by stripping with organic solvents, or by acid digestion. Preferred solid extractants are trioctylphosphine oxide and octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide and the like. 2 tabs.

  6. Experiments with Unusual Oxidation States

    ERIC Educational Resources Information Center

    Kauffman, G. B.

    1975-01-01

    Describes four synthesis experiments, adapted for the general chemistry laboratory, in which compounds in unusual oxidation are prepared. The abnormal oxidation states involved in the synthesis products are: silver (II), chromium (II), lead (IV), and bromine (I). (MLH)

  7. Extraction of actinides into aqueous polyethylene glycol solutions from carbonate media in the presence of alizarin complexone

    SciTech Connect

    Molochnikova, N.P.; Frenkel', V.Ya.; Myasoedov, B.F.; Shkinev, V.M.; Spivakov, B.Ya.; Zolotov, Yu.A.

    1987-01-01

    Actinide extraction in a two-phase aqueous system based on polyethylene glycol from carbonate solutions of various compositions in presence of alizarin complexone is studied. It is shown that the nature of the alkali metals affects actinide extraction into the polyethylene glycol phase. Tri- and tetravalent actinides are extracted maximally from sodium carbonate solutions. Separation of actinides in different oxidation states is more effective in potassium carbonate solutions. The behavior of americium in different oxidation states in the system carbonate-polyethylene glycol-complexone is studied. The possibility of extraction separation of microamount of americium(V) from curium in carbonate solutions in presence of alizarin complexone is shown.

  8. Research in actinide chemistry. Progress report, 1990--1993

    SciTech Connect

    Choppin, G.R.

    1993-04-01

    This research studies the behavior of the actinide elements in aqueous solution. The high radioactivity of the transuranium actinides limits the concentrations which can be studied and, consequently, limits the experimental techniques. However, oxidation state analogs (trivalent lanthanides, tetravalent thorium, and hexavalent uranium) do not suffer from these limitations. Behavior of actinides in the environment are a major USDOE concern, whether in connection with long-term releases from a repository, releases from stored defense wastes or accidental releases in reprocessing, etc. Principal goal of our research was expand the thermodynamic data base on complexation of actinides by natural ligands (e.g., OH{sup {minus}}, CO{sub 3}{sup 2{minus}}, PO{sub 4}{sup 3{minus}}, humates). The research undertakes fundamental studies of actinide complexes which can increase understanding of the environmental behavior of these elements.

  9. Actinide-Aluminate Speciation in Alkaline Radioactive Waste

    SciTech Connect

    Dr. David L. Clark; Dr. Alexander M. Fedosseev

    2001-12-21

    Investigation of behavior of actinides in alkaline media containing AL(III) showed that no aluminate complexes of actinides in oxidation states (IIII-VIII) were formed in alkaline solutions. At alkaline precipitation IPH (10-14) of actinides in presence of AL(III) formation of aluminate compounds is not observed. However, in precipitates contained actinides (IIV)<(VI), and to a lesser degree actinides (III), some interference of components takes place that is reflected in change of solid phase properties in comparison with pure components or their mechanical mixture. The interference decreases with rise of precipitation PH and at PH 14 is exhibited very feebly. In the case of NP(VII) the individual compound with AL(III) is obtained, however it is not aluminate of neptunium(VII), but neptunate of aluminium(III) similar to neptunates of other metals obtained earlier.

  10. Recent progress in actinide borate chemistry

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2011-01-01

    The use of molten boric acid as a reactive flux for synthesizing actinide borates has been developed in the past two years providing access to a remarkable array of exotic materials with both unusual structures and unprecedented properties. [ThB₅O₆(OH)₆][BO(OH)₂]·2.5H₂O possesses a cationic supertetrahedral structure and displays remarkable anion exchange properties with high selectivity for TcO4- Uranyl borates form noncentrosymmetric structures with extraordinarily rich topological relationships. Neptunium borates are often mixed-valent and yield rare examples of compounds with one metal in three different oxidation states. Plutonium borates display new coordination chemistry for trivalent actinides. Finally, americium borates show a dramatic departure from plutonium borates, and there are scant examples of families of actinides compounds that extend past plutonium to examine the bonding of later actinides. There are several grand challenges that this work addresses. The foremost of these challenges is the development of structure-property relationships in transuranium materials. A deep understanding of the materials chemistry of actinides will likely lead to the development of advanced waste forms for radionuclides present in nuclear waste that prevent their transport in the environment. This work may have also uncovered the solubility-limiting phases of actinides in some repositories, and allows for measurements on the stability of these materials.

  11. Recent progress in actinide borate chemistry.

    PubMed

    Wang, Shuao; Alekseev, Evgeny V; Depmeier, Wulf; Albrecht-Schmitt, Thomas E

    2011-10-21

    The use of molten boric acid as a reactive flux for synthesizing actinide borates has been developed in the past two years providing access to a remarkable array of exotic materials with both unusual structures and unprecedented properties. [ThB(5)O(6)(OH)(6)][BO(OH)(2)]·2.5H(2)O possesses a cationic supertetrahedral structure and displays remarkable anion exchange properties with high selectivity for TcO(4)(-). Uranyl borates form noncentrosymmetric structures with extraordinarily rich topological relationships. Neptunium borates are often mixed-valent and yield rare examples of compounds with one metal in three different oxidation states. Plutonium borates display new coordination chemistry for trivalent actinides. Finally, americium borates show a dramatic departure from plutonium borates, and there are scant examples of families of actinides compounds that extend past plutonium to examine the bonding of later actinides. There are several grand challenges that this work addresses. The foremost of these challenges is the development of structure-property relationships in transuranium materials. A deep understanding of the materials chemistry of actinides will likely lead to the development of advanced waste forms for radionuclides present in nuclear waste that prevent their transport in the environment. This work may have also uncovered the solubility-limiting phases of actinides in some repositories, and allows for measurements on the stability of these materials. PMID:21915396

  12. Rhodium oxides in unusual oxidation states

    NASA Astrophysics Data System (ADS)

    Reisner, Barbara Alice

    Mixed valence RhIII/RhIV oxides have been proposed as a promising class of candidate compounds for superconductivity. Unfortunately, it is difficult to stabilize rhodates with a formal oxidation state approaching RhIV, as other techniques used for the synthesis of rhodium. oxides favor the most commonly observed formal oxidation state, RhIII. One technique which has been used to stabilize metal oxides in high formal oxidation states is crystallization from molten hydroxides. This thesis explores the use of molten hydroxides to enhance the reactivity of rhodium oxides in order to synthesize rhodates with high formal oxidation states. K0.5RhO2, Rb0.2RhO2, and CsxRhO2 were synthesized from pure alkali metal hydroxides. All crystallized with a previously unobserved polytype in the alkali metal rhodate system. Due to the low activity of dissolved oxygen species in LiOH and NaOH, LiRhO2 and NaRhO2 cannot be crystallized. The formal oxidation state of rhodium in AxRhO2 (A = K, Rb, Cs) is a function of the alkali metal hydroxide used to synthesize these oxides. These materials exhibit remarkable stability for layered metal oxides containing the heavier alkali metals, but all phases are susceptible to intercalation by water. The synthesis, structural characterization, magnetic susceptibility, and reactivity of these oxides are reported. Sr2RhO4 and a new rhodate were crystallized from a KOH-Sr(OH)2 flux. The synthesis and characterization of these materials is reported. Efforts to substitute platinum for rhodium in Sr 2RhO4 are also discussed. Mixed alkali metal-alkaline earth metal hydroxide fluxes were used to crystallize LiSr3RhO6, and NaSr3RhO 6. The synthesis of LiSr3RhO6 and NaSr3RhO 6 represents the first example of the stabilization of a rhodium oxide with a formal oxidation state approaching RhV. X-ray diffraction, electron beam microprobe analysis, thermogravimetric analysis, potentiometric titrations, X-ray photoelectron spectroscopy, and magnetic susceptibility

  13. A conceptual performance assessment model of the dissolved actinide source term for the WIPP

    SciTech Connect

    Weiner, R.F.; Stockman, C.T.; Wang, Y.; Novak, C.F.

    1996-12-31

    This paper presents a performance assessment model of dissolved actinide concentrations for the Waste Isolation Pilot Plant (WIPP). The model assesses the concentration of each actinide oxidation state and combines these concentrations with an oxidation state distribution. The chemical behavior of actinides in the same oxidation state is presumed to be very similar for almost all situations, but exceptions arising from experimental evidence are accommodated. The code BRAGFLO calculates the gas pressure, brine mass, gas volume, and mass of remaining Fe and cellulosics for each time step and computational cell. The total CO{sub 2} in the repository and dissolved Ca(OH){sub 2} is estimated. Lookup tables are constructed for pmH and f(CO{sub 2}) as a function of brine type and volume, moles of CO{sub 2}, and Ca(OH){sub 2}. Amounts of five soluble complexants are considered. A model based on the formulation of Harvie et al. produces tables of solubilities for each actinide oxidation state as a function of pmH, f(CO{sub 2}), brine composition, and complexant. Experimental data yield lookup tables of fractions of Th, U, Np, Pu, and Am in each oxidation state as a function of f(CO{sub 2}) and complexant. The tables are then used to provide a concentration of a particular actinide at particular values of pmH and f(CO{sub 2}). Under steady-state conditions, the oxidation state of each actinide that is most stable in the particular chemical environment controls the concentration of that actinide in solution. In the absence of steady-state conditions, the oxidation state distribution of interest is that of the dissolved actinide, and the oxidation states may be treated as if they were separate compounds.

  14. In-beam studies of high-spin states of actinide nuclei

    SciTech Connect

    Stoyer, M.A. . Nuclear Science Div. California Univ., Berkeley, CA . Dept. of Chemistry)

    1990-11-15

    High-spin states in the actinides have been studied using Coulomb- excitation, inelastic excitation reactions, and one-neutron transfer reactions. Experimental data are presented for states in {sup 232}U, {sup 233}U, {sup 234}U, {sup 235}U, {sup 238}Pu and {sup 239}Pu from a variety of reactions. Energy levels, moments-of-inertia, aligned angular momentum, Routhians, gamma-ray intensities, and cross-sections are presented for most cases. Additional spectroscopic information (magnetic moments, M{sub 1}/E{sub 2} mixing ratios, and g-factors) is presented for {sup 233}U. One- and two-neutron transfer reaction mechanisms and the possibility of band crossings (backbending) are discussed. A discussion of odd-A band fitting and Cranking calculations is presented to aid in the interpretation of rotational energy levels and alignment. In addition, several theoretical calculations of rotational populations for inelastic excitation and neutron transfer are compared to the data. Intratheory comparisons between the Sudden Approximation, Semi-Classical, and Alder-Winther-DeBoer methods are made. In connection with the theory development, the possible signature for the nuclear SQUID effect is discussed. 98 refs., 61 figs., 21 tabs.

  15. Elevated concentrations of actinides in mono lake.

    PubMed

    Anderson, R F; Bacon, M P; Brewer, P G

    1982-04-30

    Tetravalent thorium, pentavalent protactinium, hexavalent uranium, and plutonium (oxidation state uncertain) are present in much higher concentrations in Mono Lake, a saline, alkaline lake in eastern central California, than in seawater. Low ratios of actinium to protactinium and of americium to plutonium indicate that the concentrations of trivalent actinides are not similarly enhanced. The elevated concentrations of the ordinarily very insoluble actinides are maintained in solution by natural ligands, which inhibit their chemical removal from the water column, rather than by an unusually large rate of supply. PMID:17735740

  16. Elevated concentrations of actinides in Mono Lake

    SciTech Connect

    Anderson, R.F.; Bacon, M.P.; Brewer, P.G.

    1982-04-30

    Tetravalent thorium, pentavalent protactinium, hexavalent uranium, and plutonium (oxidation state uncertain) are present in much higher concentrations in Mono Lake, a saline, alkaline lake in eastern central California, than in seawater. Low ratios of actinium to protactinium and of americium to plutonium indicate that the concentrations of trivalent actinides are not similarly enhanced. The elevated concentrations of the ordinarily very insoluble actinides are maintained in solution by natural ligands, which inhibit their chemical removal from the water column, rather than by an unusually large rate of supply.

  17. DISSOLUTION OF METAL OXIDES AND SEPARATION OF URANIUM FROM LANTHANIDES AND ACTINIDES IN SUPERCRITICAL CARBON DIOXIDE

    SciTech Connect

    Donna L. Quach; Bruce J. Mincher; Chien M. Wai

    2013-10-01

    This paper investigates the feasibility of extracting and separating uranium from lanthanides and other actinides by using supercritical fluid carbon dioxide (sc-CO2) as a solvent modified with tri-n-butylphosphate (TBP) for the development of a counter current stripping technique, which would be a more efficient and environmentally benign technology for spent nuclear fuel reprocessing compared to traditional solvent extraction. Several actinides (U, Pu, and Np) and europium were extracted in sc-CO2 modified with TBP over a range of nitric acid concentrations and then the actinides were exposed to reducing and complexing agents to suppress their extractability. According to this study, uranium/europium and uranium/plutonium extraction and separation in sc-CO2 modified with TBP is successful at nitric acid concentrations of less than 6 M and at nitric acid concentrations of less than 3 M with acetohydroxamic acid or oxalic acid, respectively. A scheme for recycling uranium from spent nuclear fuel by using sc-CO2 and counter current stripping columns is presented.

  18. Dissolution of metal oxides and separation of uranium from lanthanides and actinides in supercritical carbon dioxide

    SciTech Connect

    Quach, D.L.; Wai, C.M.; Mincher, B.J.

    2013-07-01

    This paper investigates the feasibility of extracting and separating uranium from lanthanides and other actinides by using supercritical fluid carbon dioxide (sc-CO{sub 2}) as a solvent modified with tri-n-butylphosphate (TBP) for the development of a counter current stripping technique, which would be a more efficient and environmentally benign technology for spent nuclear fuel reprocessing compared to traditional solvent extraction. Several actinides (U, Pu, and Np) and europium were extracted in sc-CO{sub 2} modified with TBP over a range of nitric acid concentrations and then the actinides were exposed to reducing and complexing agents to suppress their extractability. According to this study, uranium/europium and uranium/plutonium extraction and separation in sc-CO{sub 2} modified with TBP is successful at nitric acid concentrations of less than 6 M and at nitric acid concentrations of less than 3 M with acetohydroxamic acid or oxalic acid, respectively. A scheme for recycling uranium from spent nuclear fuel by using sc-CO{sub 2} and counter current stripping columns is presented. (authors)

  19. Actinide chemistry in ionic liquids.

    PubMed

    Takao, Koichiro; Bell, Thomas James; Ikeda, Yasuhisa

    2013-04-01

    This Forum Article provides an overview of the reported studies on the actinide chemistry in ionic liquids (ILs) with a particular focus on several fundamental chemical aspects: (i) complex formation, (ii) electrochemistry, and (iii) extraction behavior. The majority of investigations have been dedicated to uranium, especially for the 6+ oxidation state (UO2(2+)), because the chemistry of uranium in ordinary solvents has been well investigated and uranium is the most abundant element in the actual nuclear fuel cycles. Other actinides such as thorium, neptunium, plutonium, americium, and curiumm, although less studied, are also of importance in fully understanding the nuclear fuel engineering process and the safe geological disposal of radioactive wastes. PMID:22873132

  20. Actinide (III) solubility in WIPP Brine: data summary and recommendations

    SciTech Connect

    Borkowski, Marian; Lucchini, Jean-Francois; Richmann, Michael K.; Reed, Donald T.

    2009-09-01

    The solubility of actinides in the +3 oxidation state is an important input into the Waste Isolation Pilot Plant (WIPP) performance assessment (PA) models that calculate potential actinide release from the WIPP repository. In this context, the solubility of neodymium(III) was determined as a function of pH, carbonate concentration, and WIPP brine composition. Additionally, we conducted a literature review on the solubility of +3 actinides under WIPP-related conditions. Neodymium(III) was used as a redox-invariant analog for the +3 oxidation state of americium and plutonium, which is the oxidation state that accounts for over 90% of the potential release from the WIPP through the dissolved brine release (DBR) mechanism, based on current WIPP performance assessment assumptions. These solubility data extend past studies to brine compositions that are more WIPP-relevant and cover a broader range of experimental conditions than past studies.

  1. Thin extractive membrane for monitoring actinides in aqueous streams.

    PubMed

    Chavan, Vivek; Paul, Sumana; Pandey, Ashok K; Kalsi, P C; Goswami, A

    2013-09-15

    Alpha spectrometry and solid state nuclear track detectors (SSNTDs) are used for monitoring ultra-trace amount of alpha emitting actinides in different aqueous streams. However, these techniques have limitations i.e. alpha spectrometry requires a preconcentration step and SSNTDs are not chemically selective. Therefore, a thin polymer inclusion membrane (PIM) supported on silanized glass was developed for preconcentraion and determination of ultra-trace concentration of actinides by α-spectrometry and SSNTDs. PIMs were formed by spin coating on hydrophobic glass slide or solvent casting to form thin and self-supported membranes, respectively. Sorption experiments indicated that uptakes of actinides in the PIM were highly dependent on acidity of solution i.e. Am(III) sorbed up to 0.1 molL(-1) HNO₃, U(VI) up to 0.5 molL(-1) HNO₃ and Pu(IV) from HNO₃ concentration as high as 4 molL(-1). A scheme was developed for selective sorption of target actinide in the PIM by adjusting acidity and oxidation state of actinide. The actinides sorbed in PIMs were quantified by alpha spectrometry and SSNTDs. For SSNTDs, neutron induced fission-fragment tracks and α-particle tracks were registered in Garware polyester and CR-39 for quantifications of natural uranium and α-emitting actinides ((241)Am/(239)Pu/(233)U), respectively. Finally, the membranes were tested to quantify Pu in 4 molL(-1) HNO3 solutions and synthetic urine samples. PMID:23747462

  2. Atomistic modeling of the solid-state chemistry of actinide materials

    NASA Astrophysics Data System (ADS)

    Shuller, Lindsay C.

    Materials that incorporate actinides are critical to the nuclear fuel cycle, either as nuclear fuels or nuclear waste forms. In this thesis, I examine four materials: i) ThO2-UO2 solid solutions, ii) binary ThO2-CeO2-ZrO2 solid solutions, iii) Np-doped studtite, iv) Np-doped boltwoodite. Computational methods, particularly density functional theory (DFT) calculations and Monte-Carlo (MC) simulations, are used to determine the energetics and structures of these actinide-bearing materials. The solid-solution behavior of nuclear fuels and nuclear waste forms indicate the thermodynamic stability of the material, which is important for understanding the in-reactor fuel properties and long-term stability of used fuel. The ThxU1-xO2 and ThxCe 1-xO2 binaries are almost completely miscible; however, DeltaGmix reveals a small tendency for the systems to exsolve (e.g., DeltaEexsoln(Th xU1-xO2) = 0.13 kJ/(mol cations) at 750 K). Kinetic hindrances (e.g., interfacial energy) may inhibit exsolution, especially at the low temperatures necessary to stabilize the nanoscale exsolution lamellae observed in the ThxU1-xO2 and Ce xZr1-xO2 binaries. Miscibility in the Zr-bearing binaries is limited. At 1400 °C, only 3.6 and 0.09 mol% ZrO2 is miscible in CeO2 and ThO2, respectively. The incorporation of minor amounts of Np5+,6+ into uranium alteration phases, e.g., studtite [UO2O2 (H2O)4] or boltwoodite [K(UO2)(SiO 3OH)(H2O)1.5] , may limit the mobility of aqueous neptunyl complexes released from oxidized nuclear fuels. Np6+-incorporation into studtite requires less energy than Np5+-incorporation (e.g., with source/sink = Np2O5/UO 3 DeltaEincorp(Np6+) = 0.42 eV and DeltaEincorp(Np5+) = 1.12 eV). In addition, Np6+ is completely miscible in studtite at room temperature with respect to a hypothetical Np6+-studtite. Electronic structure calculations provide insight into Np-bonding in studtite. The Np 5f orbitals are within the band gap of studtite, resulting in the narrowing of the band gap

  3. Zinc in +III oxidation state

    NASA Astrophysics Data System (ADS)

    Samanta, Devleena; Jena, Puru

    2012-02-01

    The possibility of Group 12 elements, such as Zn, Cd, and Hg existing in an oxidation state of +III or higher has fascinated chemists for decades. Significant efforts have been made in the past to achieve higher oxidation states for the heavier congener mercury (since the 3^rd ionization potential of the elements decrease as we go down the periodic table). It took nearly 20 years before experiment could confirm the theoretical prediction that Hg indeed can exist in an oxidation state of +IV. While this unusual property of Hg is attributed to the relativistic effects, Zn being much lighter than Hg has not been expected to have an oxidation state higher than +II. Using density functional theory we show that an oxidation state of +III for Zn can be realized by choosing specific ligands with large electron affinities i.e. superhalogens. We demonstrate this by a systematic study of the interaction of Zn with F, BO2, and AuF6 ligands whose electron affinities are progressively higher, namely, 3.4 eV, 4.4 eV, and 8.4 eV, respectively. Discovery of higher oxidation states of elements can help in the formulation of new reactions and hence in the development of new chemistry.

  4. Partitioning of actinides from high level waste of PUREX origin using octylphenyl-N,N{prime}-diisobutylcarbamoylmethyl phosphine oxide (CMPO)-based supported liquid membrane

    SciTech Connect

    Ramanujam, A.; Dhami, P.S.; Gopalakrishnan, V.; Dudwadkar, N.L.; Chitnis, R.R.; Mathur, J.N.

    1999-06-01

    The present studies deal with the application of the supported liquid membrane (SLM) technique for partitioning of actinides from high level waste of PUREX origin. The process uses a solution of octylphenyl-N,N{prime}-diisobutylcarbamoylmethyl phosphine oxide (CMPO) in n-dodecane as a carrier with a polytetrafluoroethylene support and a mixture of citric acid, formic acid, and hydrazine hydrate as the receiving phase. The studies involve the investigation of such parameters as carrier concentration in SLM, acidity of the feed, and the feed composition. The studies indicated good transport of actinides like neptunium, americium, and plutonium across the membrane from nitric acid medium. A high concentration of uranium in the feed retards the transport of americium, suggesting the need for prior removal of uranium from the waste. The separation of actinides from uranium-lean simulated samples as well as actual high level waste has been found to be feasible using the above technique.

  5. PROCESS OF PRODUCING ACTINIDE METALS

    DOEpatents

    Magel, T.T.

    1959-07-14

    The preparation of actinide metals in workable, coherent form is described. In general, the objects of the invention are achieved by heating a mixture of an oxide and a halide of an actinide metal such as uranium with an alkali metal on alkaline earth metal reducing agent in the presence of iodine.

  6. Spectroscopic investigations of neptunium`s and plutonium`s oxidation states in sol-gel glasses as a function of initial valance and thermal history

    SciTech Connect

    Stump, N.A.; Haire, R.G.; Dai, S.

    1996-12-01

    Several oxidation states of neptunium and plutonium, Pu(III),Pu (IV), PU(VI), Np(IV), Np(V) and Np (VI), were studied in glasses prepared by a sol-gel technology. The oxidation state of these actinides was determined primarily by absorption spectrometry and followed as a function of the solidification process, subsequent aging and thermal treatments. It was determined that the initial oxidation state of the actinides in the starting solutions was essentially maintained through the solidification process to form the glasses. However, during densification and removal of residual solvents at elevated temperatures, both actinides in the different sol-gel products converted completely to their tetravalent states. These results are discussed in terms of our findings in comparable studies that only the tetravalent states of plutonium and neptunium are formed in glasses prepared by dissolving their dioxides in different molten- glass formulations.

  7. Americium separation from nuclear fuel dissolution using higher oxidation states.

    SciTech Connect

    Bruce J. Mincher

    2009-09-01

    Much of the complexity in current AFCI proposals is driven by the need to separate the minor actinides from the lanthanides. Partitioning and recycling Am, but not Cm, would allow for significant simplification because Am has redox chemistry that may be exploited while Cm does not. Here, we have explored methods based on higher oxidation states of Am (AmV and AmVI) to partition Am from the lanthanides. In a separate but related approach we have also initiated an investigation of the utility of TRUEX Am extraction from thiocyanate solution. The stripping of loaded TRUEX by Am oxidation or SCN- has not yet proved successful; however, the partitioning of inextractable AmV by TRUEX shows promise.

  8. Study on Equilibrium Characteristics of Thorium-Plutonium-Minor Actinides Mixed Oxides Fuel in PWR

    SciTech Connect

    Waris, A.; Permana, S.; Kurniadi, R.; Su'ud, Z.; Sekimoto, H.

    2010-06-22

    A study on characteristics of thorium-plutonium-minor actinides utilization in the pressurized water reactor (PWR) with the equilibrium burnup model has been conducted. For a comprehensive evaluation, several fuel cycles scenario have been included in the present study with the variation of moderator-to-fuel volume ratio (MFR) of PWR core design. The results obviously exhibit that the neutron spectra grow to be harder with decreasing of the MFR. Moreover, the neutron spectra also turn into harder with the rising number of confined heavy nuclides. The required {sup 233}U concentration for criticality of reactor augments with the increasing of MFR for all heavy nuclides confinement and thorium and uranium confinement in PWR.

  9. Study on Equilibrium Characteristics of Thorium-Plutonium-Minor Actinides Mixed Oxides Fuel in PWR

    NASA Astrophysics Data System (ADS)

    Waris, A.; Permana, S.; Kurniadi, R.; Su'ud, Z.; Sekimoto, H.

    2010-06-01

    A study on characteristics of thorium-plutonium-minor actinides utilization in the pressurized water reactor (PWR) with the equilibrium burnup model has been conducted. For a comprehensive evaluation, several fuel cycles scenario have been included in the present study with the variation of moderator-to-fuel volume ratio (MFR) of PWR core design. The results obviously exhibit that the neutron spectra grow to be harder with decreasing of the MFR. Moreover, the neutron spectra also turn into harder with the rising number of confined heavy nuclides. The required 233U concentration for criticality of reactor augments with the increasing of MFR for all heavy nuclides confinement and thorium & uranium confinement in PWR.

  10. The reduced transition probabilities for excited states of rare-earths and actinide even-even nuclei

    SciTech Connect

    Ghumman, S. S.

    2015-08-28

    The theoretical B(E2) ratios have been calculated on DF, DR and Krutov models. A simple method based on the work of Arima and Iachello is used to calculate the reduced transition probabilities within SU(3) limit of IBA-I framework. The reduced E2 transition probabilities from second excited states of rare-earths and actinide even–even nuclei calculated from experimental energies and intensities from recent data, have been found to compare better with those calculated on the Krutov model and the SU(3) limit of IBA than the DR and DF models.

  11. Actinide behavior in a freshwater pond

    SciTech Connect

    Trabalka, J.R.; Bogle, M.A.; Scott, T.G.

    1983-01-01

    Long-term investigations of solution chemistry in an alkaline freshwater pond have revealed that actinide oxidation state behavior, particularly that of plutonium, is complex. The Pu(V,VI) fraction was predominant in solution, but it varied over the entire range reported from other natural aquatic environments, in this case, as a result of intrinsic biological and chemical cycles (redox and pH-dependent phenomena). A strong positive correlation between plutonium (Pu), but not uranium (U), and hydroxyl ion over the observation period, especially when both were known to be in higher oxidation states, was particularly notable. Coupled with other examples of divergent U and Pu behavior, this result suggests that Pu(V), or perhaps a mixture of Pu(V,VI), was the prevalent oxidation state in solution. Observations of trivalent actinide sorption behavior during an algal bloom, coupled with the association with a high-molecular weight (nominally 6000 to 10,000 mol wt) organic fraction in solution, indicate that solution-detritus cycling of organic carbon, in turn, may be the primary mechanism in amercium-curium (Am-Cm) cycling. Sorption by sedimentary materials appears to predominate over other factors controlling effective actinide solubility and may explain, at least partially, the absence of an expected strong positive correlation between carbonate and dissolved U. 49 references, 6 figures, 12 tables.

  12. Understanding the Chemistry of the Actinides in HL Waste Tank Systems: Actinide Speciation in Oxalic Acid Solutions in the Presence of Significant Quantities of Aluminum, Iron, and Manganese

    SciTech Connect

    Clark, Sue

    2006-07-30

    The overall goal of this research plan is to provide a thermodynamic basis for describing actinide speciation over a range of tank-like conditions, including elevated temperature, elevated OH- concentrations, and the presence of various organic ligands. With support from DOE�s EMSP program, we have made significant progress towards measuring thermodynamic parameters for actinide complexation as a function of temperature. We have used the needs of the ESP modelers to guide our work to date, and we have made important progress defining the effect of temperature for actinide complexation by organic, and for hydrolysis of the hexa- and pentvalent oxidation states.

  13. Molecular solids of actinide hexacyanoferrate: Structure and bonding

    NASA Astrophysics Data System (ADS)

    Dupouy, G.; Dumas, T.; Fillaux, C.; Guillaumont, D.; Moisy, P.; Den Auwer, C.; Le Naour, C.; Simoni, E.; Fuster, E. G.; Papalardo, R.; Sanchez Marcos, E.; Hennig, C.; Scheinost, A.; Conradson, S. D.; Shuh, D. K.; Tyliszczak, T.

    2010-03-01

    The hexacyanometallate family is well known in transition metal chemistry because the remarkable electronic delocalization along the metal-cyano-metal bond can be tuned in order to design systems that undergo a reversible and controlled change of their physical properties. We have been working for few years on the description of the molecular and electronic structure of materials formed with [Fe(CN)6]n- building blocks and actinide ions (An = Th, U, Np, Pu, Am) and have compared these new materials to those obtained with lanthanide cations at oxidation state +III. In order to evaluate the influence of the actinide coordination polyhedron on the three-dimensional molecular structure, both atomic number and formal oxidation state have been varied : oxidation states +III, +IV. EXAFS at both iron K edge and actinide LIII edge is the dedicated structural probe to obtain structural information on these systems. Data at both edges have been combined to obtain a three-dimensional model. In addition, qualitative electronic information has been gathered with two spectroscopic tools : UV-Near IR spectrophotometry and low energy XANES data that can probe each atom of the structural unit : Fe, C, N and An. Coupling these spectroscopic tools to theoretical calculations will lead in the future to a better description of bonding in these molecular solids. Of primary interest is the actinide cation ability to form ionic — covalent bonding as 5f orbitals are being filled by modification of oxidation state and/or atomic number.

  14. Molecular Characterization of Actinide Oxocations from Protactinium to Plutonium

    NASA Astrophysics Data System (ADS)

    Den Auwer, C.; Guilbaud, P.; Guillaumont, D.; Moisy, P.; Digandomenico, V.; Le Naour, C.; Trubert, D.; Simoni, E.; Hennig, C.; Scheinost, A.; Conradson, S. D.

    2007-02-01

    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.

  15. Molecular Characterization of Actinide Oxocations from Protactinium to Plutonium

    SciTech Connect

    Den Auwer, C.; Guilbaud, P.; Guillaumont, D.; Moisy, P.; Hennig, C.; Scheinost, A.; Conradson, S. D.

    2007-02-02

    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.

  16. Conversion of actinide and RE oxides into nitrates and their recovery into fluids

    SciTech Connect

    Bondin, V.V.; Bychkov, S.I.; Efremov, I.G.; Revenko, Y.A.; Babain, V.A.; Murzin, A.A.; Romanovsky, V.N; Fedorov, Y.S.; Shadrin, A.Y.; Ryabkova, N.V.; Li, E.N.

    2007-07-01

    The conditions for uranium oxides completely convert into uranyl nitrate hexahydrate in nitrogen tetra-oxide media (75 deg. C, 0,5-3,0 MPa, [UO{sub x}]:[H{sub 2}O]:[NO{sub 2}]=1:8:6) were found out. The conversion of Pu contained simulator of oxide spent nuclear fuel of thermal reactors was successfully demonstrated. The possibility of uranium recovery up to 95% from TR SNF without plutonium separation from FP is practically showed, what corresponds with Non-proliferation Treaty. (authors)

  17. Actinide Burning in CANDU Reactors

    SciTech Connect

    Hyland, B.; Dyck, G.R.

    2007-07-01

    Actinide burning in CANDU reactors has been studied as a method of reducing the actinide content of spent nuclear fuel from light water reactors, and thereby decreasing the associated long term decay heat load. In this work simulations were performed of actinides mixed with natural uranium to form a mixed oxide (MOX) fuel, and also mixed with silicon carbide to form an inert matrix (IMF) fuel. Both of these fuels were taken to a higher burnup than has previously been studied. The total transuranic element destruction calculated was 40% for the MOX fuel and 71% for the IMF. (authors)

  18. Selection of Actinide Chemical Analogues for WIPP Tests: Potential Nonradioactive Sorbing and Nonsorbing Tracers for Study of Ion Transport in the Environment

    SciTech Connect

    Dale Spall; Robert Villarreal

    1998-08-01

    Chemical characteristics of the actinides (Th, U, Np, Pu, Am) have been studied relative to nonradioactive chemical elements that have similar characteristics in an attempt to identify a group of actinide chemical analogues that are nonradioactive. In general, the chemistries of the actinides, especially U, Np, Pu, and Am, are very complex and attempts to identify a single chemical analogue for each oxidation state were not successful. However, the rationale for selecting a group of chemical analogues that would mimic the actinides as a group is provided. The categorization of possible chemical analogues (tracers) with similar chemical properties was based on the following criteria. Categorization was studied according.

  19. X-Ray Absorption Spectroscopy of the Actinides

    NASA Astrophysics Data System (ADS)

    Antonio, Mark R.; Soderholm, Lynda

    The recent availability of synchrotron radiation has revolutionized actinide chemistry. This is particularly true in environmental studies, where heterogeneous samples add to the already multifaceted chemistry exhibited by these ions. Environmental samples are often inhomogeneous, chemically diverse, and amorphous or poorly crystalline. Even surrogates prepared in the laboratory to simplify the natural complexity are plagued by multiple oxidation state and varied coordination polyhedra that are a reflection of inherent 5f chemistry. For example, plutonium can be found as Pu3+ Pu4+ Pu(V)O2 +, and Pu(VI)O2 2 + within naturally occurring pH-Eh conditions, consequently complex equilibria are found between these oxidation states in one solution. In addition, dissolved actinides have significant affinities for various mineral surfaces, to which they can adsorb with or without concomitant reduction-oxidation (redox) activity, depending on details of the solution and surface conditions.

  20. Selection of actinide chemical analogues for WIPP tests

    SciTech Connect

    Villarreal, R.; Spall, D.

    1995-07-05

    The Department of Energy must demonstrate the effectiveness of the Waste Isolation Pilot Plant (WIPP) as a permanent repository for the disposal of transuranic (TRU) waste. Performance assessments of the WIPP require that estimates of the transportability and outcome of the radionuclides (actinides) be determined from disposal rooms that may become either partially or completely filled with brine. Federal regulations limit the amount of radioactivity that may be unintentionally released to the accessible environment by any mechanism during the post closure phase up to 10,000 years. Thermodynamic models have been developed to predict the concentrations of actinides in the WIPP disposal rooms under various situations and chemical conditions. These models are based on empirical and theoretical projections of the chemistry that might be present in and around the disposal room zone for both near and long-term periods. The actinides that are known to be present in the TRU wastes (and are included in the model) are Th, U, Np, Pu, and Am. Knowledge of the chemistry that might occur in the disposal rooms when the waste comes in contact with brine is important in understanding the range of oxidation states that might be present under different conditions. There is a need to establish the mechanisms and resultant rate of transport, migration, or effective retardation of actinides beyond the disposal rooms to the boundary of the accessible environment. The influence of the bulk salt rock, clay sediments and other geologic matrices on the transport behavior of actinides must be determined to establish the overall performance and capability of the WIPP in isolating waste from the environment. Tests to determine the capabilities of the WIPP geologic formations in retarding actinide species in several projected oxidation states would provide a means to demonstrate the effectiveness of the WIPP in retaining TRU wastes.

  1. Raman and absorption spectrophotometric studies of selected lanthanide, californium-doped lanthanide, and actinide trihalides in the solid state

    SciTech Connect

    Wilmarth, W.R.

    1988-03-01

    The solid-state absorption spectra of Cf(III) ions as a dopant in lanthanide trihalide hosts (LnCl/sub 3/: Ln = Ce, Sm, and Y; LnBr/sub 3/: Ln = Ce, Sm, Tb, and Y; LnI/sub 3/: Ln = Ce and Y) have been recorded. The spectra of Cf(III) have been correlated with the various crystal structures. The phonon Raman spectra and solid-state absorption spectra of PmF/sub 3/, PmCl/sub 3/, PmBr/sub 3/, and two crystal modifications of PmI/sub 3/ have been recorded. Symmetry assignments have been made for the Raman-active bands for these trihalides and also the sesquioxide. The room-temperature absorption spectra have been correlated to crystal field effects. The symmetry assignments of the Raman-active phonon modes have been made based on polarized Raman spectra from single crystals of YF/sub 3/-type orthorhombic TbF/sub 3/ and PuBr/sub 3/-type orthorhombic NdBr/sub 3/. Raman spectra of other isostructural lanthanide compounds have been recorded and compared. Symmetry assignments for these compounds have been made by analogy to the single-crystal assignments. Raman spectra have been obtained and catalogued for a number of actinide compounds. Symmetry assignments have been made for the observed Raman-active phonon bands in this work based on the assignments made for isostructural lanthanide compounds. 29 figs., 22 tabs.

  2. Oxidation-state speciation of

    PubMed

    Hu; Heineman

    2000-06-01

    The analytical utility of chemically modified microelectrodes for oxidation-state speciation of redox couples by cyclic voltammetry has been explored. [Re(I)(DMPE)3]+/[Re(II)(DMPE)3]2+, where DMPE = 1,2-bis(dimethylphosphino)ethane, was studied at carbon-fiber microelectrodes of approximately 5 microm in radius coated with Nafion-entrapped solgel-derived silica (Nafion-silica) composite. The results are compared with cyclic voltammetry of [Fe(CN)6]3-/[Fe(CN)6]4- at bare carbon-fiber microelectrodes. At both microelectrodes, the cathodic and anodic limiting currents are linearly proportional to the concentrations of the reducible and oxidizable species of a redox couple, respectively. The shape of the cyclic voltammogram and the magnitude of the steady-state limiting current are not affected by the potential at which the scan starts. Speciation of both forms of a redox couple could be achieved voltammetrically at the microelectrodes. However, a considerably slower scan rate was required to achieve steady state at the modified electrode because of the smaller diffusion coefficients of [Re(I)(DMPE)3]+ and [Re(II)(DMPE)3]2+ in the Nafion-silica composite. The detection limit at the modified electrode was considerably lower (5 x 10(-9) M for [Re(I)(DMPE)3]+) than at the bare electrode (6 x 10(-5) M for [Fe(CN)6]3- and [Fe(CN)6]4-) because of the substantial preconcentration of [Re(I)(DMPE)3]+ by the Nafion-silica composite. PMID:10857611

  3. Rapid determination of alpha emitters using Actinide resin.

    PubMed

    Navarro, N; Rodriguez, L; Alvarez, A; Sancho, C

    2004-01-01

    The European Commission has recently published the recommended radiological protection criteria for the clearance of building and building rubble from the dismantling of nuclear installations. Radionuclide specific clearance levels for actinides are very low (between 0.1 and 1 Bq g(-1)). The prevalence of natural radionuclides in rubble materials makes the verification of these levels by direct alpha counting impossible. The capability of Actinide resin (Eichrom Industries, Inc.) for extracting plutonium and americium from rubble samples has been tested in this work. Besides a strong affinity for actinides in the tri, tetra and hexavalent oxidation states, this extraction chromatographic resin presents an easy recovery of absorbed radionuclides. The retention capability was evaluated on rubble samples spiked with certified radionuclide standards (239Pu and 241Am). Samples were leached with nitric acid, passed through a chromatographic column containing the resin and the elution fraction was measured by LSC. Actinide retention varies from 60% to 80%. Based on these results, a rapid method for the verification of clearance levels for actinides in rubble samples is proposed. PMID:15177360

  4. Research in actinide chemistry

    SciTech Connect

    Not Available

    1989-01-01

    Research continued to be focused broadly on the chemistry of the actinide cations in solution. While the direct concern is the actinide elements, their radioactivity limits the techniques which can be applied to their study. A major area of interest continues to be the thermodynamics of interaction of the f-elements with a broad spectrum of inorganic and organic ligands. Solvent extraction (for tracer levels), potentiometric and calorimetric titration and absorption spectrometry have been used to obtain stability constants and the associated enthalpy and entropy changes for complexation. A number of studies were performed to provide a better data base and a better understanding of the more significant species determining the behavior of actinides in natural waters (e.g., hydrolysis and silicate interaction). A second major area has been kinetics. NpO{sub 2}{sup 2+} reduction by hydroxy and carboxylic acids was studied to obtain an understanding of how such functional groups in humic substances may influence actinyl redox. The kinetics of dissociation of UO{sub 2}{sup 2+} and Ln{sup 3+} (La{sup 3+} = lanthanide element cations) from synthetic polyelectrolytes and humics provided significantly increased understanding of actinide complexation by these macromolecules. A third area of activity used laser induced fluorescence to study the hydration state of Eu(III) in a number of systems. Finally, several other studies, not in these major areas, were conducted. These included investigation of NpO{sub 2}{sup +} cation-cation complexes, the extraction of Am(III) by MX (M = Li, Na, NH{sub 4}{sup +}, K{sup +}; X = ClO{sub 4}{sup {minus}}, Cl{sup {minus}}, NO{sub 3}{sup {minus}}, BrO{sub 3}{sup {minus}}) over a concentration range from 0.01 M to saturated and the thermodynamics of synergistic extraction of actinides by crown ethers and {beta}-diketonates. 23 refs., 1 fig.

  5. Paving the way for the synthesis of a series of divalent actinide complexes: a theoretical perspective.

    PubMed

    Wu, Q-Y; Lan, J-H; Wang, C-Z; Cheng, Z-P; Chai, Z-F; Gibson, J K; Shi, W-Q

    2016-02-21

    Recently, the +2 formal oxidation state in soluble molecular complexes for lanthanides (La-Nd, Sm-Lu) and actinides (Th and U) has been discovered [W. J. Evans, et al., J. Am. Chem. Soc., 2011, 133, 15914; J. Am. Chem. Soc., 2012, 134, 8420; J. Am. Chem. Soc., 2013, 135, 13310; Chem. Sci., 2015, 6, 517]. To explore the nature of the bonding and stabilities of the low-valent actinide complexes, a series of divalent actinide species, [AnCp'3](-) (An[double bond, length as m-dash]Th-Am, Cp' = [η(5)-C5H4(SiMe3)](-)) have been investigated in THF solution using scalar relativistic density functional theory. The electronic structures and electron affinity properties were systematically studied to identify the interactions between the +2 actinide ions and Cp' ligands. The ground state electron configurations for the [AnCp'3](-) species are [ThCp'3](-) 6d(2), [PaCp'3](-) 5f(2)6d(1), [UCp'3](-) 5f(3)6d(1), [NpCp'3](-) 5f(5), [PuCp'3](-) 5f(6), and [AmCp'3](-) 5f(7), respectively, according to the MO analysis. The total bonding energy decreases from the Th- to the Am-complex and the electrostatic interactions mainly dominate the bonding between the actinide atom and ligands. The electron affinity analysis suggests that the reduction reaction of AnCp'3→ [AnCp'3](-) should become increasingly facile across the actinide series from Th to Am, in accord with the known An(iii/ii) reduction potentials. This work expands the knowledge on the low oxidation state chemistry of actinides, and further motivates and guides the synthesis of related low oxidation state compounds of 5f elements. PMID:26777518

  6. Advanced Aqueous Separation Systems for Actinide Partitioning

    SciTech Connect

    Nash, Ken; Martin, Leigh; Lumetta, Gregg

    2015-04-02

    One of the most challenging aspects of advanced processing of used nuclear fuel is the separation of transplutonium actinides from fission product lanthanides. This separation is essential if actinide transmutation options are to be pursued in advanced fuel cycles, as lanthanides compete with actinides for neutrons in both thermal and fast reactors, thus limiting efficiency. The separation is difficult because the chemistry of Am3+ and Cm3+ is nearly identical to that of the trivalent lanthanides (Ln3+). The prior literature teaches that two approaches offer the greatest probability of devising a successful group separation process based on aqueous processes: 1) the application of complexing agents containing ligand donor atoms that are softer than oxygen (N, S, Cl-) or 2) changing the oxidation state of Am to the IV, V, or VI state to increase the essential differences between Am and lanthanide chemistry (an approach utilized in the PUREX process to selectively remove Pu4+ and UO22+ from fission products). The latter approach offers the additional benefit of enabling a separation of Am from Cm, as Cm(III) is resistant to oxidation and so can easily be made to follow the lanthanides. The fundamental limitations of these approaches are that 1) the soft(er) donor atoms that interact more strongly with actinide cations than lanthanides form substantially weaker bonds than oxygen atoms, thus necessitating modification of extraction conditions for adequate phase transfer efficiency, 2) soft donor reagents have been seen to suffer slow phase transfer kinetics and hydro-/radiolytic stability limitations and 3) the upper oxidation states of Am are all moderately strong oxidants, hence of only transient stability in media representative of conventional aqueous separations systems. There are examples in the literature of both approaches having been described. However, it is not clear at present that any extant process is sufficiently robust for application at the scale

  7. Alternating-parity collective states of yrast and nonyrast bands in lanthanide and actinide nuclei

    SciTech Connect

    Nadirbekov, M. S. Yuldasheva, G. A.; Denisov, V. Yu.

    2015-03-15

    Excited collective states of even-even nuclei featuring quadrupole and octupole deformations are studied within a nonadiabatic collective model with a Gaussian potential energy. Rotational states of the yrast band and vibrational-rotational states of nonyrast bands are considered in detail. The energies of alternating-parity excited states of the yrast band in the {sup 164}Er, {sup 220}Ra, and {sup 224}Th nuclei; the yrast and first nonyrast bands in the {sup 154}Sm and {sup 160}Gd nuclei; and the yrast, first nonyrast, and second nonyrast bands in the {sup 224}Ra and {sup 240}Pu nuclei are described well on the basis of the proposed model.

  8. Gas-phase energetics of actinide oxides: an assessment of neutral and cationic monoxides and dioxides from thorium to curium.

    PubMed

    Marçalo, Joaquim; Gibson, John K

    2009-11-12

    An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and with condensed-phase thermochemistry. PMID:19725530

  9. Gas-Phase Energetics of Actinide Oxides: An Assessment of Neutral and Cationic Monoxides and Dioxides from Thorium to Curium

    NASA Astrophysics Data System (ADS)

    Marçalo, Joaquim; Gibson, John K.

    2009-09-01

    An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and with condensed-phase thermochemistry.

  10. Gas-phase energies of actinide oxides -- an assessment of neutral and cationic monoxides and dioxides from thorium to curium

    SciTech Connect

    Marcalo, Joaquim; Gibson, John K.

    2009-08-10

    An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and with condensed-phase thermochemistry.

  11. Nonaqueous method for dissolving lanthanide and actinide metals

    DOEpatents

    Crisler, L.R.

    1975-11-11

    Lanthanide and actinide beta-diketonate complex molecular compounds are produced by reacting a beta-diketone compound with a lanthanide or actinide element in the elemental metallic state in a mixture of carbon tetrachloride and methanol.

  12. Actinide Speciation and Solubility in a Salt Repository (Invited)

    NASA Astrophysics Data System (ADS)

    Reed, D.; Borkowski, M.; Richmann, M.; Lucchini, J.; Khaing, H.; Swanson, J.

    2009-12-01

    The use of bedded salt deposits for the permanent disposal of nuclear waste continues to receive much attention in the United States and internationally. This is largely based on the highly successful Waste Isolation Pilot Plant (WIPP) transuranic waste repository that was opened in 1999 in Southeastern New Mexico. A bedded salt formation, such as the one in which the WIPP is located, has many advantages that make it an ideal geology for permanent disposal of nuclear waste. This includes well established mining techniques, self-sealing that lead to a naturally-induced geologic isolation, a relatively dry environment, and a favorable chemistry. Herein we report on recent progress in our investigations, as part of ongoing recertification effort for the operating WIPP repository, to establish the redox distribution and overall solubility of actinides in brine. The overall ranking of actinides, from the perspective of potential contribution to release from the WIPP, is: Pu ~ Am >>U > Th >> Np, Cm. Our recent research emphasis has centered on the redox chemistry of multivalent actinides (e.g., U, Pu and Np) with the use of oxidation-state-invariant analogs (Th and Nd) to establish the solubilities. Under a wide range of conditions investigated, the predominant oxidation states established are Pu(III) and Pu(IV) for plutonium, U(IV) and U(VI) for uranium, and Am (III) for americium. Reduction pathways for plutonium include reaction with organics, reaction with reduced iron, and bioreduction by halophiles under anaerobic conditions. Uranium(VI) can also be reduced to U(IV) by reduced iron and microbial processes. Solubility data for neodymium (+3 analog), Uranium (+6 analog) and thorium (+4 analog) in brine are also reported. These data extend our past understanding of WIPP-specific actinide chemistry and show the WIPP, and salt-based repositories in general, to be a robust repository design from the perspective of actinide containment and immobilization.

  13. MICROBIAL TRANSFORMATIONS OF PLUTONIUM AND OTHER ACTINIDES IN TRANSURANIC AND MIXED WASTES.

    SciTech Connect

    FRANCIS,A.J.

    2003-07-06

    The presence of the actinides Th, U, Np, Pu, and Am in transuranic (TRU) and mixed wastes is a major concern because of their potential for migration from the waste repositories and long-term contamination of the environment. The toxicity of the actinide elements and the long half-lives of their isotopes are the primary causes for concern. In addition to the radionuclides the TRU waste consists a variety of organic materials (cellulose, plastic, rubber, chelating agents) and inorganic compounds (nitrate and sulfate). Significant microbial activity is expected in the waste because of the presence of organic compounds and nitrate, which serve as carbon and nitrogen sources and in the absence of oxygen the microbes can use nitrate and sulfate as alternate electron acceptors. Biodegradation of the TRU waste can result in gas generation and pressurization of containment areas, and waste volume reduction and subsidence in the repository. Although the physical, chemical, and geochemical processes affecting dissolution, precipitation, and mobilization of actinides have been investigated, we have only limited information on the effects of microbial processes. Microbial activity could affect the chemical nature of the actinides by altering the speciation, solubility and sorption properties and thus could increase or decrease the concentrations of actinides in solution. Under appropriate conditions, dissolution or immobilization of actinides is brought about by direct enzymatic or indirect non-enzymatic actions of microorganisms. Dissolution of actinides by microorganisms is brought about by changes in the Eh and pH of the medium, by their production of organic acids, such as citric acid, siderophores and extracellular metabolites. Immobilization or precipitation of actinides is due to changes in the Eh of the environment, enzymatic reductive precipitation (reduction from higher to lower oxidation state), biosorption, bioaccumulation, biotransformation of actinides complexed

  14. Research in actinide chemistry. Final report, March 1, 1993--February 28, 1996

    SciTech Connect

    Choppin, G R

    1997-01-01

    The present three-year grant period has been a fruitful one for the laboratory as research entered some new areas while continuing in others in which the group has been successful. As in past grant periods, the principal focus has been on complexation of actinide elements with inorganic and organic ligands. The ligands to study have been chosen for their value (known or potential) in actinide separations or for their potential role in environmental behavior of the actinides. Since the radioactivity of some actinides limits the variety of techniques which can be used in their study, we have used {open_quotes}oxidation state analogs{close_quotes}. These analogs have the same oxidation state and very similar chemical behavior but are stable or very long-lived. Also, the analogs are chosen for their redox stability to avoid uncertainties in interpretation of systems in which several oxidations may coexist (e.g., in the case of Pu). Examples of such analogs which we have used are: Nd(III), Eu(III) for Pu(III), Am(III), Cm(III); Th(IV) for U(IV), Pu(IV); NpO{sub 2}{sup +} for PuO{sub 2}{sup +}; UO{sub 2}{sup 2+} for NpO{sub 2}{sup 2+}, PuO{sub 2}{sup 2+}. These analogs have allowed use of techniques which can increase significantly our understanding of actinide complexation.

  15. Chemical state of complex uranium oxides.

    PubMed

    Kvashnina, K O; Butorin, S M; Martin, P; Glatzel, P

    2013-12-20

    We report here the first direct observation of U(V) in uranium binary oxides and analyze the gradual conversion of the U oxidation state in the mixed uranium systems. Our finding clarifies previous contradicting results and provides important input for the geological disposal of spent fuel, recycling applications, and chemistry of uranium species. PMID:24483742

  16. Actinide co-conversion by internal gelation

    SciTech Connect

    Robisson, Anne-Charlotte; Dauby, Jacques; Dumont-Shintu, Corinne; Machon, Estelle; Grandjean, Stephane

    2007-07-01

    Suitable microstructures and homogenous microspheres of actinide compounds are of interest for future nuclear fuel or transmutation target concepts to prevent the generation and dispersal of actinide powder. Sol-gel routes are being investigated as one of the possible solutions for producing these compounds. Preliminary work is described involving internal gelation to synthesize mixed compounds including minor actinides, particularly mixed actinide or mixed actinide-inert element compounds. A parameter study is discussed to highlight the importance of the initial broth composition for obtaining gel microspheres without major defects (cracks, craters, etc.). In particular, conditions are defined to produce gel beads from Zr(IV)/Y(III)/Ce(III) or Zr(IV)/An(III) systems. After gelation, the heat treatment of these microspheres is described for the purpose of better understanding the formation of cracks after calcination and verifying the effective synthesis of an oxide solid-solution. (authors)

  17. 33rd Actinide Separations Conference

    SciTech Connect

    McDonald, L M; Wilk, P A

    2009-05-04

    Welcome to the 33rd Actinide Separations Conference hosted this year by the Lawrence Livermore National Laboratory. This annual conference is centered on the idea of networking and communication with scientists from throughout the United States, Britain, France and Japan who have expertise in nuclear material processing. This conference forum provides an excellent opportunity for bringing together experts in the fields of chemistry, nuclear and chemical engineering, and actinide processing to present and discuss experiences, research results, testing and application of actinide separation processes. The exchange of information that will take place between you, and other subject matter experts from around the nation and across the international boundaries, is a critical tool to assist in solving both national and international problems associated with the processing of nuclear materials used for both defense and energy purposes, as well as for the safe disposition of excess nuclear material. Granlibakken is a dedicated conference facility and training campus that is set up to provide the venue that supports communication between scientists and engineers attending the 33rd Actinide Separations Conference. We believe that you will find that Granlibakken and the Lake Tahoe views provide an atmosphere that is stimulating for fruitful discussions between participants from both government and private industry. We thank the Lawrence Livermore National Laboratory and the United States Department of Energy for their support of this conference. We especially thank you, the participants and subject matter experts, for your involvement in the 33rd Actinide Separations Conference.

  18. Chemical aspects of actinides in the geosphere: towards a rational nuclear materials management

    SciTech Connect

    Allen, P; Sylwester, E

    2001-02-09

    A complete understanding of actinide interactions in the geosphere is paramount for developing a rational Nuclear and Environmental Materials Management Policy. One of the key challenges towards understanding the fate and transport of actinides is determining their speciation (i.e., oxidation state and structure). Since an element's speciation directly dictates physical properties such as toxicity and solubility, this information is critical for evaluating and controlling the evolution of an actinide element through the environment. Specific areas within nuclear and environmental management programs where speciation is important are (1) waste processing and separations; (2) wasteform materials for long-term disposition; and (3) aqueous geochemistry. The goal of this project was to develop Actinide X-ray Absorption Spectroscopy ( U S ) as a core capability at LLNL and integrate it with existing facilities, providing a multi-technique approach to actinide speciation. XAS is an element-specific structural probe which determines the oxidation state and structure for most atoms. XAS can be more incisive than other spectroscopies because it originates from an atomic process and the information is always attainable, regardless of an element's speciation. Despite the utility, XAS is relatively complex due to the need for synchrotron radiation and significant expertise with data acquisition and analysis. The coupling of these technical hurdles with the safe handling of actinides at a general user synchrotron facility such as the Stanford Synchrotron Radiation Facility (SSRL) make such experiments even more difficult. As a result, XAS has been underutilized by programs that could benefit by its application. We achieved our project goals by implementing key state-of-the-art Actinide XAS instrumentation at SSRL (Ge detector and remote positioning equipment), and by determining the chemical speciation of actinides (Th, U, and Np) in aqueous solutions, wasteform cements, and

  19. Process for making a ceramic composition for immobilization of actinides

    DOEpatents

    Ebbinghaus, Bartley B.; Van Konynenburg, Richard A.; Vance, Eric R.; Stewart, Martin W.; Walls, Philip A.; Brummond, William Allen; Armantrout, Guy A.; Herman, Connie Cicero; Hobson, Beverly F.; Herman, David Thomas; Curtis, Paul G.; Farmer, Joseph

    2001-01-01

    Disclosed is a process for making a ceramic composition for the immobilization of actinides, particularly uranium and plutonium. The ceramic is a titanate material comprising pyrochlore, brannerite and rutile. The process comprises oxidizing the actinides, milling the oxides to a powder, blending them with ceramic precursors, cold pressing the blend and sintering the pressed material.

  20. Process for Making a Ceramic Composition for Immobilization of Actinides

    SciTech Connect

    Ebbinghaus, Bartley B.; Van Konynenburg, Richard A.; Vance, Eric R.; Stewart, Martin W.; Walls, Philip A.; Brummond, William Allen; Armantrout, Guy A.; Curtis, Paul G.; Hobson, Beverly F.; Farmer, Joseph; Herman, Connie Cicero; Herman, David Thomas

    1999-06-22

    Disclosed is a process for making a ceramic composition for the immobilization of actinides, particularly uranium and plutonium. The ceramic is a titanate material comprising pyrochlore, brannerite and rutile. The process comprises oxidizing the actinides, milling the oxides to a powder, blending them with ceramic precursors, cold pressing the blend and sintering the pressed material.

  1. Experimental studies of actinides in molten salts

    SciTech Connect

    Reavis, J.G.

    1985-06-01

    This review stresses techniques used in studies of molten salts containing multigram amounts of actinides exhibiting intense alpha activity but little or no penetrating gamma radiation. The preponderance of studies have used halides because oxygen-containing actinide compounds (other than oxides) are generally unstable at high temperatures. Topics discussed here include special enclosures, materials problems, preparation and purification of actinide elements and compounds, and measurements of various properties of the molten volts. Property measurements discussed are phase relationships, vapor pressure, density, viscosity, absorption spectra, electromotive force, and conductance. 188 refs., 17 figs., 6 tabs.

  2. Iron oxidation state in hydrous rhyolites

    NASA Astrophysics Data System (ADS)

    Humphreys, M.; Brooker, R.; Fraser, D.; Smith, V. C.

    2012-12-01

    Recent studies have suggested that the Earth's mantle at subduction zones is oxidized relative to that at mid-ocean ridges. One possible origin of the oxidation is thought to be hydrous fluids, which are released into the mantle from the down-going slab during subduction. However, this is controversial; other studies have concluded that there is no intrinsic difference in oxidation state. One potential problem in determining primary oxidation states is that magmas produced by partial melting of the sub-arc mantle undergo significant degassing and crystallisation near the earth's surface, which may overprint the oxidation state of the primary melt. H2O contents of melt inclusions may be affected by partial re-equilibration. The effect of H2O on Fe oxidation state is unclear, although theoretical arguments typically predict increasing Fe3+/ΣFe during shallow degassing as a result of preferential diffusion of H2 out of the melt: FeO (m) + H2O (m) = Fe2O3 (m) + H2 (g) [1] We used XANES to measure Fe3+/Fe2+ in cylinders of rhyolitic obsidian that had been hydrated in gold capsules in cold-seal apparatus. Runs were performed at 850-900 °C under H2O-saturated conditions for short run times (20-80 minutes). Surprisingly, we find a positive correlation between Fe3+/ΣFe and H2O content of the glass. This is inconsistent with the effects of reaction [1], but can be explained by considering the acid-base properties of the hydrous melt. In particular, basic behaviour of FeO but amphoteric behaviour of Fe2O3, and changes in melt basicity relating to dissolution of H2O, can explain increasing Fe3+/Fe2+ with increasing H2O. We discuss the implications of these results for using melt compositions to infer the oxidation state of the earth's mantle.

  3. Theoretical Studies of the Electronic Structure of the Compounds of the Actinide Elements

    SciTech Connect

    Kaltsoyannis, Nikolas; Hay, P. Jeffrey; Li, Jun; Blaudeau, Jean-Philippe; Bursten, Bruce E.

    2006-02-02

    In this chapter, we will present an overview of the theoretical and computational developments that have increased our understanding of the electronic structure of actinide-containing molecules and ions. The application of modern electronic structure methodologies to actinide systems remains one of the great challenges in quantum chemistry; indeed, as will be discussed below, there is no other portion of the periodic table that leads to the confluence of complexity with respect to the calculation of ground- and excited-state energies, bonding descriptions, and molecular properties. But there is also no place in the periodic table in which effective computational modeling of electronic structure can be more useful. The difficulties in creating, isolating, and handling many of the actinide elements provide an opportunity for computational chemistry to be an unusually important partner in developing the chemistry of these elements. The importance of actinide electronic structure begins with the earliest studies of uranium chemistry and predates the discovery of quantum mechanics. The fluorescence of uranyl compounds was observed as early as 1833 (Jørgensen and Reisfeld, 1983), a presage of the development of actinometry as a tool for measuring photochemical quantum yields. Interest in nuclear fuels has stimulated tremendous interest in understanding the properties, including electronic properties, of small actinide-containing molecules and ions, especially the oxides and halides of uranium and plutonium. The synthesis of uranocene in 1968 (Streitwieser and Mu¨ ller-Westerhoff, 1968) led to the flurry of activity in the organometallic chemistry of the actinides that continues today. Actinide organometallics (or organoactinides) are nearly always molecular systems and are often volatile, which makes them amenable to an arsenal of experimental probes of molecular and electronic structure (Marks and Fischer, 1979). Theoretical and computational studies of the electronic

  4. Actinide halide complexes

    DOEpatents

    Avens, L.R.; Zwick, B.D.; Sattelberger, A.P.; Clark, D.L.; Watkin, J.G.

    1992-11-24

    A compound is described of the formula MX[sub n]L[sub m] wherein M is a metal atom selected from the group consisting of thorium, plutonium, neptunium or americium, X is a halide atom, n is an integer selected from the group of three or four, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is an integer selected from the group of three or four for monodentate ligands or is the integer two for bidentate ligands, where the sum of n+m equals seven or eight for monodentate ligands or five or six for bidentate ligands. A compound of the formula MX[sub n] wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds are described including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant.

  5. Actinide halide complexes

    DOEpatents

    Avens, Larry R.; Zwick, Bill D.; Sattelberger, Alfred P.; Clark, David L.; Watkin, John G.

    1992-01-01

    A compound of the formula MX.sub.n L.sub.m wherein M is a metal atom selected from the group consisting of thorium, plutonium, neptunium or americium, X is a halide atom, n is an integer selected from the group of three or four, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is an integer selected from the group of three or four for monodentate ligands or is the integer two for bidentate ligands, where the sum of n+m equals seven or eight for monodentate ligands or five or six for bidentate ligands, a compound of the formula MX.sub.n wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant, are provided.

  6. PREPARATION OF ACTINIDE-ALUMINUM ALLOYS

    DOEpatents

    Moore, R.H.

    1962-09-01

    BS>A process is given for preparing alloys of aluminum with plutonium, uranium, and/or thorium by chlorinating actinide oxide dissolved in molten alkali metal chloride with hydrochloric acid, chlorine, and/or phosgene, adding aluminum metal, and passing air and/or water vapor through the mass. Actinide metal is formed and alloyed with the aluminum. After cooling to solidification, the alloy is separated from the salt. (AEC)

  7. Actinide sulfite tetrahydrate and actinide oxysulfite tetrahydrate

    SciTech Connect

    Baugh, D.; Watt, G.

    1980-07-08

    A compound is prepared that comprises an actinide sulfite tetrahydrate selected from the group consisting of uranium (IV) sulfite tetrahydrate and plutonium (IV) sulfite tetrahydrate. A compound is also prepared that comprises an actinide oxysulfite tetrahydrate selected from the group consisting of uranium (IV) oxysulfite tetrahydrate and plutonium (IV) oxysulfite tetrahydrate

  8. MINOR ACTINIDE SEPARATIONS USING ION EXCHANGERS OR IONIC LIQUIDS

    SciTech Connect

    Hobbs, D.; Visser, A.; Bridges, N.

    2011-09-20

    This project seeks to determine if (1) inorganic-based ion exchange materials or (2) electrochemical methods in ionic liquids can be exploited to provide effective Am and Cm separations. Specifically, we seek to understand the fundamental structural and chemical factors responsible for the selectivity of inorganic-based ion-exchange materials for actinide and lanthanide ions. Furthermore, we seek to determine whether ionic liquids can serve as the electrolyte that would enable formation of higher oxidation states of Am and other actinides. Experiments indicated that pH, presence of complexants and Am oxidation state exhibit significant influence on the uptake of actinides and lanthanides by layered sodium titanate and hybrid zirconium and tin phosphonate ion exchangers. The affinity of the ion exchangers increased with increasing pH. Greater selectivity among Ln(III) ions with sodium titanate materials occurs at a pH close to the isoelectric potential of the ion exchanger. The addition of DTPA decreased uptake of Am and Ln, whereas the addition of TPEN generally increases uptake of Am and Ln ions by sodium titanate. Testing confirmed two different methods for producing Am(IV) by oxidation of Am(III) in ionic liquids (ILs). Experimental results suggest that the unique coordination environment of ionic liquids inhibits the direct electrochemical oxidation of Am(III). The non-coordinating environment increases the oxidation potential to a higher value, while making it difficult to remove the inner coordination of water. Both confirmed cases of Am(IV) were from the in-situ formation of strong chemical oxidizers.

  9. Actinide Solubility and Speciation in the WIPP

    SciTech Connect

    Reed, Donald T.

    2015-11-02

    The presentation begins with the role and need for nuclear repositories (overall concept, international updates (Sweden, Finland, France, China), US approach and current status), then moves on to the WIPP TRU repository concept (design, current status--safety incidents of February 5 and 14, 2014, path forward), and finally considers the WIPP safety case: dissolved actinide concentrations (overall approach, oxidation state distribution and redox control, solubility of actinides, colloidal contribution and microbial effects). The following conclusions are set forth: (1) International programs are moving forward, but at a very slow and somewhat sporadic pace. (2) In the United States, the Salt repository concept, from the perspective of the long-term safety case, remains a viable option for nuclear waste management despite the current operational issues/concerns. (3) Current model/PA prediction (WIPP example) are built on redundant conservatisms. These conservatisms are being addressed in the ongoing and future research to fill existing data gaps--redox control of plutonium by Fe(0, II), thorium (analog) solubility studies in simulated brine, contribution of intrinsic and biocolloids to the mobile concentration, and clarification of microbial ecology and effects.

  10. Oxidation state of the mantle

    SciTech Connect

    Saxena, S.K. Graduate Center, New York, NY )

    1989-01-01

    Phase equilibrium relations are established in a system Mg-Fe-Si-H-O, with and without C, at high pressures and temperatures. High pressure-temperature equations of state for the fluids including non-ideal mixing are used in the calculations. The computed equilibrium data show that an olivine of appropriate mantle composition is stable over a wide range of temperature and oxygen fugacities in the carbon-free system. If C is introduced, such that the equilibrium assemblage may contain graphite or diamond, the fluid phase in the peridotite + water system consists mostly of H{sub 2}O and little CO{sub 2} and CH{sub 4}. However, the fluid composition is strongly affected by the Fe content of the system. If Fe is increased from undersaturation to that of saturation the CH{sub 4} content of the fluid changes from a low of 1% to a high of 89%. The calculated results show a fluid with as much as 75% methane could be in equilibrium with olivine without metallic Fe as a coexisting phase. The fO{sub 2} of the primitive mantle with such a fluid composition would be several log units below that of the quartz-fayalite-magnetite buffer.

  11. Chemical properties of the heavier actinides and transactinides

    SciTech Connect

    Hulet, E.K.

    1981-01-01

    The chemical properties of each of the elements 99 (Es) through 105 are reviewed and their properties correlated with the electronic structure expected for 5f and 6d elements. A major feature of the heavier actinides, which differentiates them from the comparable lanthanides, is the increasing stability of the divalent oxidation state with increasing atomic number. The divalent oxidation state first becomes observable in the anhydrous halides of californium and increases in stability through the series to nobelium, where this valency becomes predominant in aqueous solution. In comparison with the analogous 4f electrons, the 5f electrons in the latter part of the series are more tightly bound. Thus, there is a lowering of the 5f energy levels with respect to the Fermi level as the atomic number increases. The metallic state of the heavier actinides has not been investigated except from the viewpoint of the relative volatility among members of the series. In aqueous solutions, ions of these elements behave as a normal trivalent actinides and lanthanides (except for nobelium). Their ionic radii decrease with increasing nuclear charge which is moderated because of increased screening of the outer 6p electrons by the 5f electrons. The actinide series of elements is completed with the element lawrencium (Lr) in which the electronic configuration is 5f/sup 14/7s/sup 2/7p. From Mendeleev's periodicity and Dirac-Fock calculations, the next group of elements is expected to be a d-transition series corresponding to the elements Hf through Hg. The chemical properties of elements 104 and 105 only have been studied and they indeed appear to show the properties expected of eka-Hf and eka-Ta. However, their nuclear lifetimes are so short and so few atoms can be produced that a rich variety of chemical information is probably unobtainable.

  12. Predicting thermo-mechanical behaviour of high minor actinide content composite oxide fuel in a dedicated transmutation facility

    NASA Astrophysics Data System (ADS)

    Lemehov, S. E.; Sobolev, V. P.; Verwerft, M.

    2011-09-01

    The European Facility for Industrial Transmutation (EFIT) of the minor actinides (MA), from LWR spent fuel is being developed in the integrated project EUROTRANS within the 6th Framework Program of EURATOM. Two composite uranium-free fuel systems, containing a large fraction of MA, are proposed as the main candidates: a CERCER with magnesia matrix hosting (Pu,MA)O 2-x particles, and a CERMET with metallic molybdenum matrix. The long-term thermal and mechanical behaviour of the fuel under the expected EFIT operating conditions is one of the critical issues in the core design. To make a reliable prediction of long-term thermo-mechanical behaviour of the hottest fuel rods in the lead-cooled version of EFIT with thermal power of 400 MW, different fuel performance codes have been used. This study describes the main results of modelling the thermo-mechanical behaviour of the hottest CERCER fuel rods with the fuel performance code MACROS which indicate that the CERCER fuel residence time can safely reach at least 4-5 effective full power years.

  13. Extraction studies of selected actinide ions from aqueous solutions with 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione and tri-n-octylphosphine oxide

    SciTech Connect

    Hannink, N.J.; Hoffman, D.C. |; Smith, B.F.

    1991-11-01

    The first measurements of distribution coefficients (K{sub d}) for Cm(III), Bk(III), Cf(III), Es(III), and Fm(III) between aqueous perchlorate solutions and solutions of 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (BMPPT) and the synergist tri-n-octylphosphine oxide (TOPO) in toluene are reported. Curium-243, berkelium-250, californium-249, einsteinium-254, and fermium-253 were used in these studies. The K{sub d} for {sup 241}Am was also measured and is in agreement with previously published results. Our new results show that the K{sub d}`s decrease gradually with increasing atomic number for the actinides with a dip at Cf. In general, the K{sub d}`s for these actinides are about a factor of 5 to 10 greater than the K{sub d}`s for the homologous lanthanides at a pH of 2.9, a BMPPT concentration of 0.2 M, and a TOPO concentration of 0.04 M. The larger K{sub d}`s for the actinides are consistent with greater covalent bonding between the actinide metal ion and the sulfur bonding site in the ligand.

  14. Extraction studies of selected actinide ions from aqueous solutions with 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione and tri-n-octylphosphine oxide

    SciTech Connect

    Hannink, N.J.; Hoffman, D.C. California Univ., Berkeley, CA . Dept. of Chemistry); Smith, B.F. )

    1991-11-01

    The first measurements of distribution coefficients (K{sub d}) for Cm(III), Bk(III), Cf(III), Es(III), and Fm(III) between aqueous perchlorate solutions and solutions of 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (BMPPT) and the synergist tri-n-octylphosphine oxide (TOPO) in toluene are reported. Curium-243, berkelium-250, californium-249, einsteinium-254, and fermium-253 were used in these studies. The K{sub d} for {sup 241}Am was also measured and is in agreement with previously published results. Our new results show that the K{sub d}'s decrease gradually with increasing atomic number for the actinides with a dip at Cf. In general, the K{sub d}'s for these actinides are about a factor of 5 to 10 greater than the K{sub d}'s for the homologous lanthanides at a pH of 2.9, a BMPPT concentration of 0.2 M, and a TOPO concentration of 0.04 M. The larger K{sub d}'s for the actinides are consistent with greater covalent bonding between the actinide metal ion and the sulfur bonding site in the ligand.

  15. Extraction studies of selected actinide ions from aqueous solutions with 4-benzoyl-2,4-Dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione and Tri-n-octylphosphine oxide

    SciTech Connect

    Hannink, N.J.; Hoffman, D.C.; Smith, B.F.

    1992-07-01

    The first measurements of distribution coefficients (k{sub d}) for Cm(III), Bk(III), Cf(III), Es(III), and Fm(III) between aqueous perchlorate solutions and solutions of 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (BMPPT) and the synergist tri-n-octylphosphine oxide (TOPO) in toluene are reported. Curium-243, berkelium-250, californium-249, einsteinium-254, and fermium-253 were used in these studies. The K{sub d} for {sup 241}Am was also measured and is in agreement with previously published results. Our new results show that the K{sub d}`s decrease gradually with increasing atomic number for the actinides with a dip at Cf. In general, the K{sub d}`s for these actinides are about about a factor of 10 greater than the K{sub d}`s for the homologous lanthanides at a pH of 2.9, a BMPPT concentration of 0.2 M, and a TOPO concentration of 0.04 M. The larger K{sub d}`s for the actinides are consistent with greater covalent bonding between the actinide metal ion and the sulfur bonding site in the ligand. 9 refs., 2 figs., 1 tab.

  16. Expanded Definition of the Oxidation State

    ERIC Educational Resources Information Center

    Loock, Hans-Peter

    2011-01-01

    A proposal to define the oxidation state of an atom in a compound as the hypothetical charge of the corresponding atomic ion that is obtained by heterolytically cleaving its bonds such that the atom with the higher electronegativity in a bond is allocated all electrons in the bond. Bonds between like atoms are cleaved homolytically. This…

  17. Stability of tetravalent actinides in perovskites

    SciTech Connect

    Williams, C.W.; Morss, L.R.; Choi, I.K.

    1983-01-01

    This paper reports the first determination of the enthalpy of formation of a complex actinide(IV) oxide: ..delta..H/sup 0//sub f/ (BaUO/sub 3/, s, 298 K) = -1690 +- 10 kJ mol/sup -1/. The preparation and properties of this and other actinide(IV) complex oxides are described and are compared with other perovskites BaMO/sub 3/. The relative stabilities of tetravalent and hexavalent uranium in various environments are compared in terms of the oxidation-reduction behavior of uranium in geological nuclear waste storage media; in perovskite, uranium(IV) is very unstable in comparison with uranium(VI).

  18. Actinide-ion sensor

    DOEpatents

    Li, Shelly X; Jue, Jan-fong; Herbst, Ronald Scott; Herrmann, Steven Douglas

    2015-01-13

    An apparatus for the real-time, in-situ monitoring of actinide-ion concentrations. A working electrolyte is positioned within the interior of a container. The working electrolyte is separated from a reference electrolyte by a separator. A working electrode is at least partially in contact with the working electrolyte. A reference electrode is at least partially in contact with the reference electrolyte. A voltmeter is electrically connected to the working electrode and the reference electrode. The working electrolyte comprises an actinide-ion of interest. The separator is ionically conductive to the actinide-ion of interest. The separator comprises an actinide, Zr, and Nb. Preferably, the actinide of the separator is Am or Np, more preferably Pu. In one embodiment, the actinide of the separator is the actinide of interest. In another embodiment, the separator further comprises P and O.

  19. Average oxidation state of carbon in proteins

    PubMed Central

    Dick, Jeffrey M.

    2014-01-01

    The formal oxidation state of carbon atoms in organic molecules depends on the covalent structure. In proteins, the average oxidation state of carbon (ZC) can be calculated as an elemental ratio from the chemical formula. To investigate oxidation–reduction (redox) patterns, groups of proteins from different subcellular locations and phylogenetic groups were selected for comparison. Extracellular proteins of yeast have a relatively high oxidation state of carbon, corresponding with oxidizing conditions outside of the cell. However, an inverse relationship between ZC and redox potential occurs between the endoplasmic reticulum and cytoplasm. This trend provides support for the hypothesis that protein transport and turnover are ultimately coupled to the maintenance of different glutathione redox potentials in subcellular compartments. There are broad changes in ZC in whole-genome protein compositions in microbes from different environments, and in Rubisco homologues, lower ZC tends to occur in organisms with higher optimal growth temperature. Energetic costs calculated from thermodynamic models are consistent with the notion that thermophilic organisms exhibit molecular adaptation to not only high temperature but also the reducing nature of many hydrothermal fluids. Further characterization of the material requirements of protein metabolism in terms of the chemical conditions of cells and environments may help to reveal other linkages among biochemical processes with implications for changes on evolutionary time scales. PMID:25165594

  20. Oxidation state of marine manganese nodules

    USGS Publications Warehouse

    Piper, D.Z.; Basler, J.R.; Bischoff, J.L.

    1984-01-01

    Analyses of the bulk oxidation state of marine manganese nodules indicates that more than 98% of the Mn in deep ocean nodules is present as Mn(IV). The samples were collected from three quite different areas: the hemipelagic environment of the Guatemala Basin, the pelagic area of the North Pacific, and seamounts in the central Pacific. Results of the study suggest that todorokite in marine nodules is fully oxidized and has the following stoichiometry: (K, Na, Ca, Ba).33(Mg, Cu, Ni).76Mn5O22(H2O)3.2. ?? 1984.

  1. Modelling the behaviour of oxide fuels containing minor actinides with urania, thoria and zirconia matrices in an accelerator-driven system

    NASA Astrophysics Data System (ADS)

    Sobolev, V.; Lemehov, S.; Messaoudi, N.; Van Uffelen, P.; Aı̈t Abderrahim, H.

    2003-06-01

    The Belgian Nuclear Research Centre, SCK • CEN, is currently working on the pre-design of the multipurpose accelerator-driven system (ADS) MYRRHA. A demonstration of the possibility of transmutation of minor actinides and long-lived fission products with a realistic design of experimental fuel targets and prognosis of their behaviour under typical ADS conditions is an important task in the MYRRHA project. In the present article, the irradiation behaviour of three different oxide fuel mixtures, containing americium and plutonium - (Am,Pu,U)O 2- x with urania matrix, (Am,Pu,Th)O 2- x with thoria matrix and (Am,Y,Pu,Zr)O 2- x with inert zirconia matrix stabilised by yttria - were simulated with the new fuel performance code MACROS, which is under development and testing at the SCK • CEN. All the fuel rods were considered to be of the same design and sizes: annular fuel pellets, helium bounded with the stainless steel cladding, and a large gas plenum. The liquid lead-bismuth eutectic was used as coolant. Typical irradiation conditions of the hottest fuel assembly of the MYRRHA subcritical core were pre-calculated with the MCNPX code and used in the following calculations as the input data. The results of prediction of the thermo-mechanical behaviour of the designed rods with the considered fuels during three irradiation cycles of 90 EFPD are presented and discussed.

  2. Emergence of californium as the second transitional element in the actinide series

    SciTech Connect

    Cary, Samantha K.; Vasiliu, Monica; Baumbach, Ryan E.; Stritzinger, Jared T.; Green, Thomas D.; Diefenbach, Kariem; Cross, Justin N.; Knappenberger, Kenneth L.; Liu, Guokui; Silver, Mark A.; DePrince, A. Eugene; Polinski, Matthew J.; Van Cleve, Shelley M.; House, Jane H.; Kikugawa, Naoki; Gallagher, Andrew; Arico, Alexandra A.; Dixon, David A.; Albrecht-Schmitt, Thomas E.

    2015-04-16

    A break in periodicity occurs in the actinide series between plutonium and americium as the result of the localization of 5f electrons. The subsequent chemistry of later actinides is thought to closely parallel lanthanides in that bonding is expected to be ionic and complexation should not substantially alter the electronic structure of the metal ions. Here we demonstrate that ligation of californium(III) by a pyridine derivative results in significant deviations in the properties of the resultant complex with respect to that predicted for the free ion. We expand on this by characterizing the americium and curium analogues for comparison, and show that these pronounced effects result from a second transition in periodicity in the actinide series that occurs, in part, because of the stabilization of the divalent oxidation state. As a result, the metastability of californium(II) is responsible for many of the unusual properties of californium including the green photoluminescence.

  3. Emergence of californium as the second transitional element in the actinide series

    DOE PAGESBeta

    Cary, Samantha K.; Vasiliu, Monica; Baumbach, Ryan E.; Stritzinger, Jared T.; Green, Thomas D.; Diefenbach, Kariem; Cross, Justin N.; Knappenberger, Kenneth L.; Liu, Guokui; Silver, Mark A.; et al

    2015-04-16

    A break in periodicity occurs in the actinide series between plutonium and americium as the result of the localization of 5f electrons. The subsequent chemistry of later actinides is thought to closely parallel lanthanides in that bonding is expected to be ionic and complexation should not substantially alter the electronic structure of the metal ions. Here we demonstrate that ligation of californium(III) by a pyridine derivative results in significant deviations in the properties of the resultant complex with respect to that predicted for the free ion. We expand on this by characterizing the americium and curium analogues for comparison, andmore » show that these pronounced effects result from a second transition in periodicity in the actinide series that occurs, in part, because of the stabilization of the divalent oxidation state. As a result, the metastability of californium(II) is responsible for many of the unusual properties of californium including the green photoluminescence.« less

  4. Emergence of californium as the second transitional element in the actinide series.

    PubMed

    Cary, Samantha K; Vasiliu, Monica; Baumbach, Ryan E; Stritzinger, Jared T; Green, Thomas D; Diefenbach, Kariem; Cross, Justin N; Knappenberger, Kenneth L; Liu, Guokui; Silver, Mark A; DePrince, A Eugene; Polinski, Matthew J; Van Cleve, Shelley M; House, Jane H; Kikugawa, Naoki; Gallagher, Andrew; Arico, Alexandra A; Dixon, David A; Albrecht-Schmitt, Thomas E

    2015-01-01

    A break in periodicity occurs in the actinide series between plutonium and americium as the result of the localization of 5f electrons. The subsequent chemistry of later actinides is thought to closely parallel lanthanides in that bonding is expected to be ionic and complexation should not substantially alter the electronic structure of the metal ions. Here we demonstrate that ligation of californium(III) by a pyridine derivative results in significant deviations in the properties of the resultant complex with respect to that predicted for the free ion. We expand on this by characterizing the americium and curium analogues for comparison, and show that these pronounced effects result from a second transition in periodicity in the actinide series that occurs, in part, because of the stabilization of the divalent oxidation state. The metastability of californium(II) is responsible for many of the unusual properties of californium including the green photoluminescence. PMID:25880116

  5. Emergence of californium as the second transitional element in the actinide series

    PubMed Central

    Cary, Samantha K.; Vasiliu, Monica; Baumbach, Ryan E.; Stritzinger, Jared T.; Green, Thomas D.; Diefenbach, Kariem; Cross, Justin N.; Knappenberger, Kenneth L.; Liu, Guokui; Silver, Mark A.; DePrince, A. Eugene; Polinski, Matthew J.; Van Cleve, Shelley M.; House, Jane H.; Kikugawa, Naoki; Gallagher, Andrew; Arico, Alexandra A.; Dixon, David A.; Albrecht-Schmitt, Thomas E.

    2015-01-01

    A break in periodicity occurs in the actinide series between plutonium and americium as the result of the localization of 5f electrons. The subsequent chemistry of later actinides is thought to closely parallel lanthanides in that bonding is expected to be ionic and complexation should not substantially alter the electronic structure of the metal ions. Here we demonstrate that ligation of californium(III) by a pyridine derivative results in significant deviations in the properties of the resultant complex with respect to that predicted for the free ion. We expand on this by characterizing the americium and curium analogues for comparison, and show that these pronounced effects result from a second transition in periodicity in the actinide series that occurs, in part, because of the stabilization of the divalent oxidation state. The metastability of californium(II) is responsible for many of the unusual properties of californium including the green photoluminescence. PMID:25880116

  6. Microscopic theory of the insulating electronic ground states of the actinide dioxides AnO2 (An = U, Np, Pu, Am, and Cm)

    NASA Astrophysics Data System (ADS)

    Suzuki, M.-T.; Magnani, N.; Oppeneer, P. M.

    2013-11-01

    The electronic states of the actinide dioxides AnO2 (with An = U, Np, Pu, Am, and Cm) are investigated employing first-principles calculations within the framework of the local density approximation +U (LDA+U) approach, implemented in a full-potential linearized augmented plane-wave scheme. A systematic analysis of the An-5f states is performed which provides intuitive connections between the electronic structures and the local crystalline fields of the f states in the AnO2 series. Particularly the mechanisms leading to the experimentally observed insulating ground states are investigated. These are found to be caused by the strong spin-orbit and Coulomb interactions of the 5f orbitals; however, as a result of the different configurations, this mechanism works in distinctly different ways for each of the AnO2 compounds. In agreement with experimental observations, the nonmagnetic states of plutonium and curium dioxide are computed to be insulating, whereas those of uranium, neptunium, and americium dioxides require additional symmetry breaking to reproduce the insulator ground states, a condition which is met with magnetic phase transitions. We show that the occupancy of the An-f orbitals is closely connected to each of the appearing insulating mechanisms. We furthermore investigate the detailed constitution of the noncollinear multipolar moments for transverse 3q magnetic ordered states in UO2 and longitudinal 3q high-rank multipolar ordered states in NpO2 and AmO2.

  7. Performance of Thorium-Based Mixed Oxide Fuels for the Consumption of Plutonium and Minor Actinides in Current and Advanced Reactors

    SciTech Connect

    Weaver, Kevan Dean; Herring, James Stephen

    2002-06-01

    A renewed interest in thorium-based fuels has arisen lately based on the need for proliferation resistance, longer fuel cycles, higher burnup and improved wasteform characteristics. Recent studies have been directed toward homogeneously mixed, heterogeneously mixed, and seed-and-blanket thorium-uranium fuel cycles that rely on "in situ" use of the bred-in U-233. However, due to the higher initial enrichment required to achieve acceptable burnups, these fuels are encountering economic constraints. Thorium can nevertheless play a large role in the nuclear fuel cycle; particularly in the reduction of plutonium. While uranium-based mixedoxide (MOX) fuel will decrease the amount of plutonium, the reduction is limited due to the breeding of more plutonium (and higher actinides) from the U-238. Here we present calculational results and a comparison of the potential burnup of a thorium-based and uranium-based mixed oxide fuel in a light water reactor (LWR). Although the uranium-based fuels outperformed the thorium-based fuels in achievable burnup, a depletion comparison of the initially charged plutonium (both reactor and weapons grade) showed that the thorium-based fuels outperformed the uranium-based fuels by more that a factor of 2; where more than 70% of the total plutonium in the thorium-based fuel is consumed during the cycle. This is significant considering that the achievable burnup of the thorium-based fuels were 1.4 to 4.6 times less than the uranium-based fuels. Furthermore, use of a thorium-based fuel could also be used as a strategy for reducing the amount of long-lived nuclides (including the minor actinides), and thus the radiotoxicity in spent nuclear fuel. Although the breeding of U-233 is a concern, the presence of U-232 and its daughter products can aid in making this fuel self-protecting, and/or enough U-238 can be added to denature the fissile uranium. From these calculations, it appears that thorium-based fuel for plutonium incineration is superior as

  8. Structural and magnetic characterization of actinide materials

    SciTech Connect

    Cort, B.; Allen, T.H.; Lawson, A.C.

    1998-12-31

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors have successfully used neutron scattering techniques to investigate physicochemical properties of elements, compounds, and alloys of the light actinides. The focus of this work is to extend the fundamental research capability and to address questions of practical importance to stockpile integrity and long-term storage of nuclear material. Specific subject areas are developing neutron diffraction techniques for smaller actinide samples; modeling of inelastic scattering data for actinide metal hydrides; characterizing actinide oxide structures; and investigating aging effects in actinides. These studies utilize neutron scattering supported by equilibrium studies, kinetics, and x-ray diffraction. Major accomplishments include (1) development of encapsulation techniques for small actinide samples and neutron diffraction studies of AmD{sub 2.4} and PuO{sub 2.3}; (2) refinement of lattice dynamics model to elucidate hydrogen-hydrogen and hydrogen-metal interactions in rare-earth and actinide hydrides; (3) kinetic studies with PuO{sub 2} indicating that the recombination reaction is faster than radiolytic decomposition of adsorbed water but a chemical reaction produces H{sub 2}; (4) PVT studies of the reaction between PuO{sub 2} and water demonstrate that PuO{sub 2+x} and H{sub 2} form and that PuO{sub 2} is not the thermodynamically stable form of the oxide in air; and (5) model calculations of helium in growth in aged plutonium predicting bubble formation only at grain boundaries at room temperature. The work performed in this project has application to fundamental properties of actinides, aging, and long-term storage of plutonium.

  9. The effective oxidation state of a peatland

    NASA Astrophysics Data System (ADS)

    Worrall, Fred; Clay, Gareth D.; Moody, Catherine S.; Burt, Tim P.; Rose, Rob

    2016-01-01

    The oxidative ratio (OR) of the organic matter of the terrestrial biosphere is a key parameter in the understanding of the magnitude of the carbon sink represented both by the terrestrial biosphere and by the global oceans. However, no study has considered the oxidation state of all the organic pools and fluxes within one environment. In this study all organic matter pathways (dissolved organic matter, particulate organic matter, CO2, and CH4) were measured within an upland peat ecosystem in northern England. The study showed the following: (1) The peat soil of ecosystem was accumulating oxygen at a rate of between -16 and -73 t O km-2 yr-1; (2) Although there was no significant variation in oxidation state in the peat profile, there was a significant increase in degree of unsaturation with depth; (3) The dissolved organic matter leaving the ecosystem was significantly more oxidized than the other carbon pools analyzed while the particulate organic matter was not significantly different from the peat soil profile; and (4) Assuming that all carbon flux from the site was as CO2, the OR of the ecosystem was 1.07; when the nature and speciation of the release pathways were considered, the ecosystem OR was 1.04. At the global scale, correcting for the speciation of carbon fluxes means that the annual global fluxes of carbon to land = 1.49 ± 0.003 Gt C/yr and to the oceans = 2.01 ± 0.004 Gt C/yr.

  10. Separation of actinides from lanthanides

    DOEpatents

    Smith, Barbara F.; Jarvinen, Gordon D.; Ryan, Robert R.

    1989-01-01

    An organic extracting solution and an extraction method useful for separating elements of the actinide series of the periodic table from elements of the lanthanide series, where both are in trivalent form. The extracting solution consists of a primary ligand and a secondary ligand, preferably in an organic solvent. The primary ligand is a substituted monothio-1,3-dicarbonyl, which includes a substituted 4-acyl-2-pyrazolin-5-thione, such as 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (BMPPT). The secondary ligand is a substituted phosphine oxide, such as trioctylphosphine oxide (TOPO).

  11. Separation of actinides from lanthanides

    DOEpatents

    Smith, B.F.; Jarvinen, G.D.; Ryan, R.R.

    1988-03-31

    An organic extracting solution and an extraction method useful for separating elements of the actinide series of the periodic table from elements of the lanthanide series, where both are in trivalent form is described. The extracting solution consists of a primary ligand and a secondary ligand, preferably in an organic solvent. The primary ligand is a substituted monothio-1,3-dicarbonyl, which includes a substituted 4-acyl-2-pyrazolin-5-thione, such as 4-benzoyl-2,4- dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (BMPPT). The secondary ligand is a substituted phosphine oxide, such as trioctylphosphine oxide (TOPO).

  12. Actinide extraction methods

    DOEpatents

    Peterman, Dean R [Idaho Falls, ID; Klaehn, John R [Idaho Falls, ID; Harrup, Mason K [Idaho Falls, ID; Tillotson, Richard D [Moore, ID; Law, Jack D [Pocatello, ID

    2010-09-21

    Methods of separating actinides from lanthanides are disclosed. A regio-specific/stereo-specific dithiophosphinic acid having organic moieties is provided in an organic solvent that is then contacted with an acidic medium containing an actinide and a lanthanide. The method can extend to separating actinides from one another. Actinides are extracted as a complex with the dithiophosphinic acid. Separation compositions include an aqueous phase, an organic phase, dithiophosphinic acid, and at least one actinide. The compositions may include additional actinides and/or lanthanides. A method of producing a dithiophosphinic acid comprising at least two organic moieties selected from aromatics and alkyls, each moiety having at least one functional group is also disclosed. A source of sulfur is reacted with a halophosphine. An ammonium salt of the dithiophosphinic acid product is precipitated out of the reaction mixture. The precipitated salt is dissolved in ether. The ether is removed to yield the dithiophosphinic acid.

  13. Actinide Studies with Ultracold Neutrons

    NASA Astrophysics Data System (ADS)

    Broussard, Leah

    2014-03-01

    Understanding the effects of sputtering due to nuclear fission is crucial to the nuclear industry and has wide-reaching applications, including nuclear energy, space science, and national defense. A new program at the Los Alamos Neutron Science Center uses ultracold neutrons (UCN) to induce fission in actinides such as uranium and plutonium. UCN are an ideal tool for finely controlling induced fission as a function of depth in an actinide sample. The mechanism for fission-induced surface damage is not well understood, especially regarding the effect of a surface oxide layer. We will discuss our experimental strategy for studies of UCN-induced fission and the ejected material, and present preliminary data from enriched and depleted uranium. We gratefully acknowledge the support of the G. T. Seaborg Institute for Transactinium Science and the U.S. Department of Energy through the LANL/LDRD Program for this work.

  14. Multiplet splitting for the XPS of heavy elements: Dependence on oxidation state

    NASA Astrophysics Data System (ADS)

    Bagus, Paul S.; Nelin, Connie J.; Al-Salik, Yahya; Ilton, Eugene S.; Idriss, Hicham

    2016-01-01

    Multiplet splittings in X-ray Photo-electron Spectroscopy, XPS, are a means of distinguishing different open shell occupations, or different oxidation states, in a material being studied. Indeed, especially for 3d transition metal complexes, they have provided fingerprints of the metal oxidation state. The present work provides theoretical and experimental evidence that it may also be possible to use multiplets to characterize the oxidation state of heavy metal, lanthanide and actinide, cations in complexes. However, it is important to make a proper choice of the XPS region to study in order to obtain large multiplet splittings. We identify a low binding energy, BE, peak that had been observed for Ce(III) in CeOx as a high spin coupled multiplet. Furthermore, we show that a low BE feature with reasonable intensity is characteristic of other XPS regions and of other metals. This feature arises from a high spin multiplet and serves as a fingerprint to distinguish closed shell from open shell cations. Evidence is presented that it may also be possible to distinguish different open shell occupations.

  15. Improved method for extracting lanthanides and actinides from acid solutions

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.; Kaplan, L.; Mason, G.W.

    1983-07-26

    A process for the recovery of actinide and lanthanide values from aqueous acidic solutions uses a new series of neutral bi-functional extractants, the alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high-level nuclear reprocessing waste solutions.

  16. Study of actinide chemistry in saturated potassium fluoride solution

    NASA Technical Reports Server (NTRS)

    Cohen, D.; Thalmayer, C. E.

    1969-01-01

    Study concerning the chemistry of actinides in saturated KF solution included work with neptunium, uranium, and americium. Solubilities, absorption spectra, oxidation-reduction reactions, and solid compounds which can be produced in KF solution were examined. The information is used for preparation of various materials from salts of the actinides.

  17. Final Project Report for ER15351 “A Study of New Actinide Zintl Ion Materials”

    SciTech Connect

    Peter K. Dorhout

    2007-11-12

    The structural chemistry of actinide main-group metal materials provides the fundamental basis for the understanding of structural coordination chemistry and the formation of materials with desired or predicted structural features. The main-group metal building blocks, comprising sulfur-group, phosphorous-group, or silicon-group elements, have shown versatility in oxidation state, coordination, and bonding preferences. These building blocks have allowed us to elucidate a series of structures that are unique to the actinide elements, although we can find structural relationships to transition metal and 4f-element materials. In the past year, we investigated controlled metathesis and self-propagating reactions between actinide metal halides and alkali metal salts of main-group metal chalcogenides such as K-P-S salts. Ternary plutonium thiophosphates have resulted from these reactions at low temperature in sealed ampules. we have also focused efforts to examine reactions of Th, U, and Pu halide salts with other alkali metal salts such as Na-Ge-S and Na-Si-Se and copper chloride to identify if self-propagating reactions may be used as a viable reaction to prepare new actinide materials and we prepared a series of U and Th copper chalcogenide materials. Magnetic measurements continued to be a focus of actinide materials prepared in our laboratory. We also contributed to the XANES work at Los Alamos by preparing materials for study and for comparison with environmental samples.

  18. Oxidation state of Mn in the Mn oxide produced by Leptothrix discophora SS-1

    NASA Astrophysics Data System (ADS)

    Adams, Lee F.; Ghiorse, William C.

    1988-08-01

    Leptothrix discophora SS-1 excretes at least one Mn 2+-oxidizing protein that, in association with acidic exopolymers, catalyzes a rapid oxidation of Mn 2+. Iodometric titration of Mn oxide product showed that the oxidation state of Mn increased with age of the oxide from 3.32 in samples 11 hours old to 3.62 in samples formed over a period of 30 days. Electron diffraction of 90-day old samples showed evidence of poorly crystalline Mn(IV) oxides. Simultaneous measurement of oxygen consumption and Mn oxide formation during 15 min reaction periods indicated that the initial Mn product possessed an average oxidation state no greater than 3.6. Results suggest that the Mn 2+-oxidizing system of Leptothrix discophora SS-1 first generates Mn oxide with an average oxidation state close to Mn(III). Aging increases this oxidation state to give the mixed Mn(III, IV) oxide product observed in older samples.

  19. Hybrid functional for correlated electrons in the projector augmented-wave formalism: Study of multiple minima for actinide oxides

    NASA Astrophysics Data System (ADS)

    Jollet, F.; Jomard, G.; Amadon, B.; Crocombette, J. P.; Torumba, D.

    2009-12-01

    Exact (Hartree-Fock) exchange for correlated electrons is implemented to describe correlated orbitals in the projector augmented-waves (PAW) framework, as suggested recently in another context [P. Novák , Phys. Status Solidi B 243, 563 (2006)]. Hartree-Fock exchange energy is applied to strongly correlated electrons only inside the PAW atomic spheres. This allows the use of PBE0 hybrid exchange-correlation functional for correlated electrons. This method is tested on NiO and results agree well with already published results and generalized gradient approximation, GGA+U calculations. It is then applied to plutonium oxides and UO2 for which the results are comparable with the ones of GGA+U calculations but without adjustable parameter. As evidenced in the uranium oxide case, the occurrence of multiple energy minima may lead to very different results depending on the initial electronic configurations and on the symmetries taken into account in the calculation.

  20. Actinides in Solution: Disproportionation, Strong Correlations, and Emergence

    NASA Astrophysics Data System (ADS)

    Marston, Brad; Horowitz, Steven

    2010-03-01

    Plutonium in acid solutions can be found in oxidation states III through VI. There is a striking near perfect degeneracy of the reduction-oxidation (redox) potentials, each being about 1 volt. Neptunium is the only other element that approaches this degree of degeneracy. One consequence of the redox degeneracy is a marked tendency of plutonium ions to disproportionate; up to four different oxidation states can coexist simultaneously in the same solution, greatly complicating the environmental chemistry of the element. While the degeneracy could simply be a coincidence, it could also be the manifestation of a higher-level organizing principle at work. Other systems that exhibit disproportionation raise the possibility of an emergent negative-U attractive interaction. The hypothesis is tested by combining first-principles relativistic density-functional calculations using the Amsterdam Density Functional (ADF) package with exact diagonalizations of Hubbard-like models of the strong correlations between the actinide 5f electrons.

  1. Hydrophilic Clicked 2,6-Bis-triazolyl-pyridines Endowed with High Actinide Selectivity and Radiochemical Stability: Toward a Closed Nuclear Fuel Cycle.

    PubMed

    Macerata, Elena; Mossini, Eros; Scaravaggi, Stefano; Mariani, Mario; Mele, Andrea; Panzeri, Walter; Boubals, Nathalie; Berthon, Laurence; Charbonnel, Marie-Christine; Sansone, Francesco; Arduini, Arturo; Casnati, Alessandro

    2016-06-15

    There is still an evident need for selective and stable ligands able to separate actinide(III) from lanthanide(III) metal ions in view of the treatment of the accumulated radioactive waste and of the recycling of minor actinides. We have herein demonstrated that hydrophilic 2,6-bis-triazolyl-pyridines are able to strip all actinides in all the different oxidation states from a diglycolamide-containing kerosene solution into an acidic aqueous phase. The ascertained high actinide selectivity, efficiency, extraction kinetics, and chemical/radiolytic stability spotlight this hydrophilic class of ligands as exceptional candidates for advanced separation processes fundamental for closing the nuclear fuel cycle and solving the environmental issues related to the management of existing nuclear waste. PMID:27203357

  2. Extraction of actinides and fission products by octyl(phenyl)-N,N-diisobutylcarbamoylmethyl-phosphine oxide from nitric acid media.

    PubMed

    Mathur, J N; Murali, M S; Natarajan, P R; Badheka, L P; Banerji, A

    1992-05-01

    Extraction of promethium(III), uranium(VI), plutonium(IV), americium(III), zirconium(IV), ruthenium(III), iron(III) and palladium(II) has been carried out with a mixture of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and tributyl phosphate (TBP) in dodecane. The effects of nitric acid, TBP and CMPO concentrations on the extraction of these metal ions have been studied. The nature of the species of the above metal ions extracted into the organic phase has been suggested. PMID:18965406

  3. A literature review of actinide-carbonate mineral interactions

    SciTech Connect

    Stout, D.L.; Carroll, S.A.

    1993-10-01

    Chemical retardation of actinides in groundwater systems is a potentially important mechanism for assessing the performance of the Waste Isolation Pilot Plant (WIPP), a facility intended to demonstrate safe disposal of transuranic waste. Rigorous estimation of chemical retardation during transport through the Culebra Dolomite, a water-bearing unit overlying the WIPP, requires a mechanistic understanding of chemical reactions between dissolved elements and mineral surfaces. This report represents a first step toward this goal by examining the literature for pertinent experimental studies of actinide-carbonate interactions. A summary of existing models is given, along with the types of experiments on which these models are based. Articles pertaining to research into actinide interactions with carbonate minerals are summarized. Select articles involving trace element-carbonate mineral interactions are also reviewed and may serve as templates for future research. A bibliography of related articles is included. Americium(III), and its nonradioactive analog neodymium(III), partition strongly from aqueous solutions into carbonate minerals. Recent thermodynamic, kinetic, and surface studies show that Nd is preferentially removed from solution, forming a Nd-Ca carbonate solid solution. Neptunium(V) is rapidly removed from solution by carbonates. Plutonium incorporation into carbonates is complicated by multiple oxidation states. Little research has been done on the radium(H) and thorium(IV) carbonate systems. Removal of uranyl ion from solution by calcite is limited to monolayer surface coverage.

  4. Thermodynamic Properties of Actinides and Actinide Compounds

    NASA Astrophysics Data System (ADS)

    Konings, Rudy J. M.; Morss, Lester R.; Fuger, Jean

    The necessity of obtaining accurate thermodynamic quantities for the actinide elements and their compounds was recognized at the outset of the Manhattan Project, when a dedicated team of scientists and engineers initiated the program to exploit nuclear energy for military purposes. Since the end of World War II, both fundamental and applied objectives have motivated a great deal of further study of actinide thermodynamics. This chapter brings together many research papers and critical reviews on this subject. It also seeks to assess, to systematize, and to predict important properties of the actinide elements, ions, and compounds, especially for species in which there is significant interest and for which there is an experimental basis for the prediction.

  5. Photochemical oxidants: state of the science.

    PubMed

    Kley, D; Kleinmann, M; Sanderman, H; Krupa, S

    1999-01-01

    Atmospheric photochemical processes resulting in the production of tropospheric ozone (O(3)) and other oxidants are described. The spatial and temporal variabilities in the occurrence of surface level oxidants and their relationships to air pollution meteorology are discussed. Models of photooxidant formation are reviewed in the context of control strategies and comparisons are provided of the air concentrations of O(3) at select geographic locations around the world. This overall oxidant (O(3)) climatology is coupled to human health and ecological effects. The discussion of the effects includes both acute and chronic responses, mechanisms of action, human epidemiological and plant population studies and briefly, efforts to establish cause-effect relationships through numerical modeling. A short synopsis is provided of the interactive effects of O(3) with other abiotic and biotic factors. The overall emphasis of the paper is on identifying the current uncertainties and gaps in our understanding of the state of the science and some suggestions as to how they may be addressed. PMID:15093111

  6. Simultaneous recovery of all actinides from spent nuclear fuel by carbamoyl-methylphosphine oxide in fluorinated diluents

    SciTech Connect

    Ozawa, M.; Iwai, T.; Babain, V.; Shadrin, A.

    2008-07-01

    Bifunctional organophosphorus extractants dissolved in polar fluorinated diluents were studied, aiming at directly recovering all f-elements from the dissolver solution of spent nuclear fuel. Octyl(phenyl)-N,N-diisobutyl-carbamoyl-methylphosphine oxide (0{phi}D[iB] CMPO, 0.2-0.8 M) with 30% TBP dissolved in meta-nitrobenzotrifluoride (Fluoropole-732) dramatically expanded its extraction region without splitting out a heterogeneous third phase. Distribution ratios of U, Np, and Pu were sufficiently high for 0.4-0.8 M CMPO in this solvent system. Combination of salt-free, methylamine carbonate (MAC), citric acid, and hydrazine reagents were evaluated to obtain fractional stripping of f-elements such as TRU group and U. Static multistage extraction using artificial FBR dissolver solution supported the process feasibility. When all f-elements are extracted simultaneously, and TRU and U recovered separately with a single extraction cycle, the new extraction process, named ORGA-process, can be expected to be highly proliferation-resistant and systematically and economically advantageous. (authors)

  7. Method for preparing actinide nitrides

    DOEpatents

    Bryan, G.H.; Cleveland, J.M.; Heiple, C.R.

    1975-12-01

    Actinide nitrides, and particularly plutonium and uranium nitrides, are prepared by reacting an ammonia solution of an actinide compound with an ammonia solution of a reactant or reductant metal, to form finely divided actinide nitride precipitate which may then be appropriately separated from the solution. The actinide nitride precipitate is particularly suitable for forming nuclear fuels.

  8. Novel complexing agents for the efficient separation of actinides and remediation of actinide-contaminated sites

    SciTech Connect

    Baisden, P.; Kadkhodayan, B.

    1996-03-15

    Research into the coordination chemistry of transactinide elements should provide us with new fundamental knowledge about structure, geometry, and stability of these metal complexes. Our approach involves the design, synthesis, and characterization of {open_quotes}expanded porphyrin{close_quotes} macrocyclic ligands which coordinate the actinide metal cations with high thermodynamic affinity and kinetic stability. We can use the knowledge from understanding the fundamental coordination chemistry of these elements as a stepping stone to heavy metal detoxification, radioactive waste cleanup, and possibly radioactive isotope separation. The critical components of this research endeavor, along with the viability of metal complex formation, will be correlated to ring size and core geometry of the ligand and, the atomic radius, oxidation state, coordination geometry and coordination number of the transactinium metal ion. These chelating agents may have certain applications to the solution of some radioactive waste problems if they can be attached to polymer supports and used to chemically separate the radioactive components in waste.

  9. Actinide removal from spent salts

    DOEpatents

    Hsu, Peter C.; von Holtz, Erica H.; Hipple, David L.; Summers, Leslie J.; Adamson, Martyn G.

    2002-01-01

    A method for removing actinide contaminants (uranium and thorium) from the spent salt of a molten salt oxidation (MSO) reactor is described. Spent salt is removed from the reactor and analyzed to determine the contaminants present and the carbonate concentration. The salt is dissolved in water, and one or more reagents are added to precipitate the thorium as thorium oxide and/or the uranium as either uranium oxide or as a diuranate salt. The precipitated materials are filtered, dried and packaged for disposal as radioactive waste. About 90% of the thorium and/or uranium present is removed by filtration. After filtration, salt solutions having a carbonate concentration >20% can be dried and returned to the reactor for re-use. Salt solutions containing a carbonate concentration <20% require further clean-up using an ion exchange column, which yields salt solutions that contain less than 0.1 ppm of thorium or uranium.

  10. Strong correlations in actinide redox reactions

    NASA Astrophysics Data System (ADS)

    Horowitz, S. E.; Marston, J. B.

    2011-02-01

    Reduction-oxidation (redox) reactions of the redox couples An(VI)/An(V), An(V)/An(IV), and An(IV)/An(III), where An is an element in the family of early actinides (U, Np, and Pu), as well as Am(VI)/Am(V) and Am(V)/Am(III), are modeled by combining density functional theory with a generalized Anderson impurity model that accounts for the strong correlations between the 5f electrons. Diagonalization of the Anderson impurity model yields improved estimates for the redox potentials and the propensity of the actinide complexes to disproportionate.

  11. Sigma Team for Advanced Actinide Recycle FY2015 Accomplishments and Directions

    SciTech Connect

    Moyer, Bruce A.

    2015-09-30

    The Sigma Team for Minor Actinide Recycle (STAAR) has made notable progress in FY 2015 toward the overarching goal to develop more efficient separation methods for actinides in support of the United States Department of Energy (USDOE) objective of sustainable fuel cycles. Research in STAAR has been emphasizing the separation of americium and other minor actinides (MAs) to enable closed nuclear fuel recycle options mainly within the paradigm of aqueous reprocessing of used oxide nuclear fuel dissolved in nitric acid. Its major scientific challenge concerns achieving selectivity for trivalent actinides vs lanthanides. Not only is this challenge yielding to research advances, but technology concepts such as ALSEP (Actinide Lanthanide Separation) are maturing toward demonstration readiness. Efforts are organized in five task areas: 1) combining bifunctional neutral extractants with an acidic extractant to form a single process solvent, developing a process flowsheet, and demonstrating it at bench scale; 2) oxidation of Am(III) to Am(VI) and subsequent separation with other multivalent actinides; 3) developing an effective soft-donor solvent system for An(III) selective extraction using mixed N,O-donor or all-N donor extractants such as triazinyl pyridine compounds; 4) testing of inorganic and hybrid-type ion exchange materials for MA separations; and 5) computer-aided molecular design to identify altogether new extractants and complexants and theory-based experimental data interpretation. Within these tasks, two strategies are employed, one involving oxidation of americium to its pentavalent or hexavalent state and one that seeks to selectively complex trivalent americium either in the aqueous phase or the solvent phase. Solvent extraction represents the primary separation method employed, though ion exchange and crystallization play an important role. Highlights of accomplishments include: Confirmation of the first-ever electrolytic oxidation of Am(III) in a

  12. Raman spectroscopy characterization of actinide oxides (U 1-yPu y)O 2: Resistance to oxidation by the laser beam and examination of defects

    NASA Astrophysics Data System (ADS)

    Jégou, C.; Caraballo, R.; Peuget, S.; Roudil, D.; Desgranges, L.; Magnin, M.

    2010-10-01

    Structural changes in four (U 1-yPu y)O 2 materials with very different plutonium concentrations (0 ⩽ y ⩽ 1) and damage levels (up to 110 dpa) were studied by Raman spectroscopy. The novel experimental approach developed for this purpose consisted in using a laser beam as a heat source to assess the reactivity and structural changes of these materials according to the power supplied locally by the laser. The experiments were carried out in air and in water with or without hydrogen peroxide. As expected, the material response to oxidation in air depends on the plutonium content of the test oxide. At the highest power levels U 3O 8 generally forms with UO 2 whereas no significant change in the spectra indicating oxidation is observed for samples with high plutonium content ( 239PuO 2). Samples containing 25 wt.% plutonium exhibit intermediate behavior, typified mainly by a higher-intensity 632 cm -1 peak and the disappearance of the 1LO peak at 575 cm -1. This can be attributed to the presence of anion sublattice defects without any formation of higher oxides. The range of materials examined also allowed us to distinguish partly the chemical effects of alpha self-irradiation. The results obtained with water and hydrogen peroxide (a water radiolysis product) on a severely damaged 238PuO 2 specimen highlight a specific behavior, observed for the first time.

  13. Research in actinide chemistry

    SciTech Connect

    Not Available

    1991-01-01

    This report contains research results on studies of inorganic and organic complexes of actinide and lanthanide elements. Special attention is given to complexes of humic acids and to spectroscopic studies.

  14. Thermochemistry of the actinides

    SciTech Connect

    Kleinschmidt, P.D.

    1993-10-01

    The measurement of equilibria by Knudsen effusion techniques and the enthalpy of formation of the actinide atoms is briefly discussed. Thermochemical data on the sublimation of the actinide fluorides is used to calculate the enthalpies of formation and entropies of the gaseous species. Estimates are made for enthalpies and entropies of the tetrafluorides and trifluorides for those systems where data is not available. The pressure of important species in the tetrafluoride sublimation processes is calculated based on this thermochemical data.

  15. Actinides and Rare Earths Topical Conference (Code AC)

    SciTech Connect

    Tobin, J G

    2009-11-24

    Actinide and the Rare Earth materials exhibit many unique and diverse physical, chemical and magnetic properties, in large part because of the complexity of their f electronic structure. This Topical Conference will focus upon the chemistry, physics and materials science in Lanthanide and Actinide materials, driven by 4f and 5f electronic structure. Particular emphasis will be placed upon 4f/5f magnetic structure, surface science and thin film properties. For the actinides, fundamental actinide science and its role in resolving technical challenges posed by actinide materials will be stressed. Both basic and applied experimental approaches, including synchrotron-radiation-based investigations, as well as theoretical modeling and computational simulations, are planned to be part of the Topical Conference. Of particular importance are the issues related to the potential renaissance in Nuclear Fuels, including synthesis, oxidation, corrosion, intermixing, stability in extreme environments, prediction of properties via benchmarked simulations, separation science, environmental impact and disposal of waste products.

  16. Chemical and physical consequences of. cap alpha. and. beta. /sup -/ decay in the solid state

    SciTech Connect

    Young, J.P.; Haire, R.G.; Peterson, J.R.; Ensor, D.D.

    1984-01-01

    Interesting chemical and structural phenomena can occur when radioactive materials are stored in the solid state. Extensive studies have been made of both the chemical and physical status of progeny species that result from the ..cap alpha.. or ..beta.. /sup -/ day of actinide ions in several different compounds. The samples have been both initially pure actinide compounds - halides, oxides, etc. and actinides incorporated into other non-radioactive host materials, for example lanthanide halides. In general, the oxidation state of the actinide progeny is controlled by the oxidation state of its parent (a result of heredity). The structure of the progeny compound seems to be controlled by its host (a result of environment). These conclusions are drawn from solid state absorption spectral studies, and where possible, from x-ray diffraction studies of multi-microgram sized samples. 13 references, 4 figures, 4 tables.

  17. Engineering the Ground State of Complex Oxides

    NASA Astrophysics Data System (ADS)

    Meyers, Derek Joseph

    Transition metal oxides featuring strong electron-electron interactions have been at the forefront of condensed matter physics research in the past few decades due to the myriad of novel and exciting phases derived from their competing interactions. Beyond their numerous intriguing properties displayed in the bulk they have also shown to be quite susceptible to externally applied perturbation in various forms. The dominant theme of this work is the exploration of three emerging methods for engineering the ground states of these materials to access both their applicability and their deficiencies. The first of the three methods involves a relatively new set of compounds which adhere to a unique paradigm in chemical doping, a-site ordered perovskites. These compounds are iso-structural, i.e. constant symmetry, despite changing the dopant ions. We find that these materials, featuring Cu at the doped A-site, display the Zhang-Rice state, to varying degrees, found in high temperature superconducting cuprates, with the choice of B-site allowing "self-doping" within the material. Further, we find that within CaCu3Ir 4O12 the Cu gains a localized magnetic moment and leads to the experimentally observed heavy fermion state in the materials, one of only two such non-f-electron heavy fermion materials. Next, epitaxial constraint is used to modify the ground state of the rare-earth nickelates in ultra thin film form. Application of compressive (tensile) strain is found to suppress (maintain) the temperature at which the material goes through a Mott metal-insulator transition. Further, while for EuNiO3 thin films the typical bulk-like magnetic and charge ordering is found to occur, epitaxial strain is found to suppress the charge ordering in NdNiO3 thin films due to pinning to the substrate and the relatively weak tendency to monoclinically distort. Finally, the creation of superlattices of EuNiO3 and LaNiO3 was shown to not only allow the selection of the temperature at which

  18. Nonaqueous actinide hydride dissolution and production of actinide $beta$- diketonates

    DOEpatents

    Crisler, L.R.

    1975-11-11

    Actinide beta-diketonate complex molecular compounds are produced by reacting a beta-diketone compound with a hydride of the actinide material in a mixture of carbon tetrachloride and methanol. (auth)

  19. Synthesis of nanoscale silicon oxide oxidation state distributions: The transformation from hydrophilicity to hydrophobicity

    NASA Astrophysics Data System (ADS)

    Laminack, William; Gole, James L.; White, Mark G.; Ozdemir, Serdar; Ogden, Andrew G.; Martin, Holly J.; Fang, Zongtang; Wang, Tsang-Hsiu; Dixon, David A.

    2016-06-01

    Silicon oxide nanostructures which span the range from hydrophilic to hydrophobic have been synthesized. The surface chemistry of these silicon-based nanostructures was analyzed using a combination of X-ray photoelectron spectroscopy, reflectance infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The dominant oxidation state for the nanostructured oxides shifts from an average oxidation state of +III to a combination of +II and +III oxidation states. A correlation of the ability to adsorb water with variations in the surface Si:O ratios was observed showing a transition from hydrophilic to hydrophobic character.

  20. Oxidation state of Mn in the Mn oxide produced by Leptothrix discophora SS-1

    SciTech Connect

    Adams, L.F.; Ghiorse, W.C. )

    1988-08-01

    Leptothrix discophora SS-1 excretes at least one Mn{sup 2+}-oxidizing protein that, in association with acidic exopolymers, catalyzes a rapid oxidation of Mn{sup 2+}. Iodometric titration of Mn oxide product showed that the oxidation state of Mn increased with age of the oxide from 3.32 in samples 11 hours old to 3.62 in samples formed over a period of 30 days. Electron diffraction of 90-day old samples showed evidence of poorly crystalline Mn(IV) oxides. Simultaneous measurement of oxygen consumption and Mn oxide formation during 15 min reaction periods indicated that the initial Mn product possessed an average oxidation state no greater than 3.6. Results suggest that the Mn{sup 2+}-oxidizing system of Leptothrix discophora SS-1 first generates Mn oxide with an average oxidation state close to Mn(III). Aging increases this oxidation state to give the mixed Mn(III, IV) oxide product observed in older samples.

  1. Final Report on Actinide Glass Scintillators for Fast Neutron Detection

    SciTech Connect

    Bliss, Mary; Stave, Jean A.

    2012-10-01

    This is the final report of an experimental investigation of actinide glass scintillators for fast-neutron detection. It covers work performed during FY2012. This supplements a previous report, PNNL-20854 “Initial Characterization of Thorium-loaded Glasses for Fast Neutron Detection” (October 2011). The work in FY2012 was done with funding remaining from FY2011. As noted in PNNL-20854, the glasses tested prior to July 2011 were erroneously identified as scintillators. The decision was then made to start from “scratch” with a literature survey and some test melts with a non-radioactive glass composition that could later be fabricated with select actinides, most likely thorium. The normal stand-in for thorium in radioactive waste glasses is cerium in the same oxidation state. Since cerium in the 3+ state is used as the light emitter in many scintillating glasses, the next most common substitute was used: hafnium. Three hafnium glasses were melted. Two melts were colored amber and a third was clear. It barely scintillated when exposed to alpha particles. The uses and applications for a scintillating fast neutron detector are important enough that the search for such a material should not be totally abandoned. This current effort focused on actinides that have very high neutron capture energy releases but low neutron capture cross sections. This results in very long counting times and poor signal to noise when working with sealed sources. These materials are best for high flux applications and access to neutron generators or reactors would enable better test scenarios. The total energy of the neutron capture reaction is not the only factor to focus on in isotope selection. Many neutron capture reactions result in energetic gamma rays that require large volumes or high densities to detect. If the scintillator is to separate neutrons from gamma rays, the capture reactions should produce heavy particles and few gamma rays. This would improve the detection of a

  2. Use of two-phase aqueous systems based on water-soluble polymers in thin-layer and extraction chromatography for recovery and separtion of actinides

    SciTech Connect

    Molochnikova, N.P.; Shkinev, V.M.; Myasoedov, B.F.

    1995-11-01

    The feasibility has been demonstrated of using two-phase aqueous systems based on water-soluble polymers, polyethylene glycol and dextran sulfate, in thin-layer and extraction chromatography for recovery and separation of actinides. A convenient method has been proposed for continuous recovery of {sup 239}Np from {sup 243}Am, originating from differences in sorption of tri- and pentavalent actinides from sulfate solutions containing potassium phosphotungstate by silica gel impregnated with polyethylene glycol. New plates for thin-layer chromatography using water-soluble polymers have been developed. These plates were used to study behavior of americium in various oxidation states in thin sorbent layers.

  3. Carbon monoxide oxidation over three different states of copper: Development of a model metal oxide catalyst

    SciTech Connect

    Jernigan, G G

    1994-10-01

    Carbon monoxide oxidation was performed over the three different oxidation states of copper -- metallic (Cu), copper (I) oxide (Cu{sub 2}O), and copper (II) oxide (CuO) as a test case for developing a model metal oxide catalyst amenable to study by the methods of modern surface science and catalysis. Copper was deposited and oxidized on oxidized supports of aluminum, silicon, molybdenum, tantalum, stainless steel, and iron as well as on graphite. The catalytic activity was found to decrease with increasing oxidation state (Cu > Cu{sub 2}O > CuO) and the activation energy increased with increasing oxidation state (Cu, 9 kcal/mol < Cu{sub 2}O, 14 kcal/mol < CuO, 17 kcal/mol). Reaction mechanisms were determined for the different oxidation states. Lastly, NO reduction by CO was studied. A Cu and CuO catalyst were exposed to an equal mixture of CO and NO at 300--350 C to observe the production of N{sub 2} and CO{sub 2}. At the end of each reaction, the catalyst was found to be Cu{sub 2}O. There is a need to study the kinetics of this reaction over the different oxidation states of copper.

  4. Probing the Electronic Structure and Chemical Bonding of Mono-Uranium Oxides with Different Oxidation States: UOx(-) and UOx (x = 3-5).

    PubMed

    Su, Jing; Li, Wei-Li; Lopez, Gary V; Jian, Tian; Cao, Guo-Jin; Li, Wan-Lu; Schwarz, W H Eugen; Wang, Lai-Sheng; Li, Jun

    2016-02-25

    Uranium oxide clusters UOx(-) (x = 3-5) were produced by laser vaporization and characterized by photoelectron spectroscopy and quantum theory. Photoelectron spectra were obtained for UOx(-) at various photon energies with well-resolved detachment transitions and vibrational resolution for x = 3 and 4. The electron affinities of UOx were measured as 1.12, 3.60, and 4.02 eV for x = 3, 4, and 5, respectively. The geometric and electronic structures of both the anions and the corresponding neutrals were investigated by quasi-relativistic electron-correlation quantum theory to interpret the photoelectron spectra and to provide insight into their chemical bonding. For UOx clusters with x ≤ 3, the O atoms appear as divalent closed-shell anions around the U atom, which is in various oxidation states from U(II)(fds)(4) in UO to U(VI)(fds)(0) in UO3. For x > 3, there are no longer sufficient valence electrons from the U atom to fill the O(2p) shell, resulting in fractionally charged and multicenter delocalized valence states for the O ligands as well as η(1)- or η(2)-bonded O2 units, with unusual spin couplings and complicated electron correlations in the unfilled poly oxo shell. The present work expands our understanding of both the bonding capacities of actinide elements with extended spdf valence shells as well as the multitude of oxygen's charge and bonding states. PMID:26825216

  5. Silicon radiation detectors with oxide charge state compensation

    NASA Technical Reports Server (NTRS)

    Walton, J. T.; Goulding, F. S.

    1987-01-01

    This paper discusses the use of boron implantation on high resistivity P type silicon before oxide growth to compensate for the presence of charge states in the oxide and oxide/silicon interface. The presence of these charge states on high resistivity P type silicon produces an inversion layer which causes high leakage currents on N(+)P junctions and high surface conductance. Compensating the surface region by boron implantation is shown to result in oxide passivated N(+)P junctions with very low leakage currents and with low surface conductance.

  6. Characterization of actinide metallofullerenes

    NASA Astrophysics Data System (ADS)

    Akiyama, K.; Sueki, K.; Zhao, Y.-L.; Haba, H.; Tsukada, K.; Kodama, T.; Kikuchi, K.; Ohtsuki, T.; Nagame, Y.; Nakahara, H.; Katada, M.

    2001-10-01

    In this paper, the characterization of a number of actinoid metallofullerenes is reported. From the similarity of the HPLC elution behavior and identification by mass spectroscopy we observe that the electronic structures of U, Np, and Am metallofullerenes are extremely similar to that of Ce@C82 and that the oxidation states of encapsulated Th and Pa have the value +3 or 4.

  7. Method for recovery of actinides from actinide-bearing scrap and waste nuclear material using O/sub 2/F/sub 2/

    DOEpatents

    Asprey, L.B.; Eller, P.G.

    1984-09-12

    Method for recovery of actinides from nuclear waste material containing sintered and other oxides thereof and from scrap materials containing the metal actinides using O/sub 2/F/sub 2/ to generate the hexafluorides of the actinides present therein. The fluorinating agent, O/sub 2/F/sub 2/, has been observed to perform the above-described tasks at sufficiently low temperatures that there is virtually no damage to the containment vessels. Moreover, the resulting actinide hexafluorides are not detroyed by high temperature reactions with the walls of the reaction vessel. Dioxygen difluoride is readily prepared, stored and transferred to the place of reaction.

  8. Imaging the Formation of High-Energy Dispersion Anomalies in the Actinide UCoGa5

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy; Durakiewicz, Tomasz; Zhu, Jian-Xin; Joyce, John J.; Sarrao, John L.; Graf, Matthias J.

    2012-10-01

    We use angle-resolved photoemission spectroscopy to image the emergence of substantial dispersion and spectral-weight anomalies in the electronic renormalization of the actinide compound UCoGa5 that was presumed to belong to a conventional Fermi-liquid family. Kinks or abrupt breaks in the slope of the quasiparticle dispersion are detected both at low (approximately 130 meV) and high (approximately 1 eV) binding energies below the Fermi energy, ruling out any significant contribution of phonons. We perform numerical calculations to demonstrate that the anomalies are adequately described by coupling between itinerant fermions and spin fluctuations arising from the particle-hole continuum of the spin-orbit-split 5f states of uranium. These anomalies resemble the “waterfall” phenomenon of the high-temperature copper-oxide superconductors, suggesting that spin fluctuations are a generic route toward multiform electronic phases in correlated materials as different as high-temperature superconductors and actinides.

  9. Advanced Extraction Methods for Actinide/Lanthanide Separations

    SciTech Connect

    Scott, M.J.

    2005-12-01

    The separation of An(III) ions from chemically similar Ln(III) ions is perhaps one of the most difficult problems encountered during the processing of nuclear waste. In the 3+ oxidation states, the metal ions have an identical charge and roughly the same ionic radius. They differ strictly in the relative energies of their f- and d-orbitals, and to separate these metal ions, ligands will need to be developed that take advantage of this small but important distinction. The extraction of uranium and plutonium from nitric acid solution can be performed quantitatively by the extraction with the TBP (tributyl phosphate). Commercially, this process has found wide use in the PUREX (plutonium uranium extraction) reprocessing method. The TRUEX (transuranium extraction) process is further used to coextract the trivalent lanthanides and actinides ions from HLLW generated during PUREX extraction. This method uses CMPO [(N, N-diisobutylcarbamoylmethyl) octylphenylphosphineoxide] intermixed with TBP as a synergistic agent. However, the final separation of trivalent actinides from trivalent lanthanides still remains a challenging task. In TRUEX nitric acid solution, the Am(III) ion is coordinated by three CMPO molecules and three nitrate anions. Taking inspiration from this data and previous work with calix[4]arene systems, researchers on this project have developed a C3-symmetric tris-CMPO ligand system using a triphenoxymethane platform as a base. The triphenoxymethane ligand systems have many advantages for the preparation of complex ligand systems. The compounds are very easy to prepare. The steric and solubility properties can be tuned through an extreme range by the inclusion of different alkoxy and alkyl groups such as methyoxy, ethoxy, t-butoxy, methyl, octyl, t-pentyl, or even t-pentyl at the ortho- and para-positions of the aryl rings. The triphenoxymethane ligand system shows promise as an improved extractant for both tetravalent and trivalent actinide recoveries form

  10. Comparative Study of f-Element Electronic Structure across a Series of Multimetallic Actinide, Lanthanide-Actinide and Lanthanum-Actinide Complexes Possessing Redox-Active Bridging Ligands

    SciTech Connect

    Schelter, Eric J.; Wu, Ruilian; Veauthier, Jacqueline M.; Bauer, Eric D.; Booth, Corwin H.; Thomson, Robert K.; Graves, Christopher R.; John, Kevin D.; Scott, Brian L.; Thompson, Joe D.; Morris, David E.; Kiplinger, Jaqueline L.

    2010-02-24

    A comparative examination of the electronic interactions across a series of trimetallic actinide and mixed lanthanide-actinide and lanthanum-actinide complexes is presented. Using reduced, radical terpyridyl ligands as conduits in a bridging framework to promote intramolecular metal-metal communication, studies containing structural, electrochemical, and X-ray absorption spectroscopy are presented for (C{sub 5}Me{sub 5}){sub 2}An[-N=C(Bn)(tpy-M{l_brace}C{sub 5}Me4R{r_brace}{sub 2})]{sub 2} (where An = Th{sup IV}, U{sup IV}; Bn = CH{sub 2}C{sub 6}H{sub 5}; M = La{sup III}, Sm{sup III}, Yb{sup III}, U{sup III}; R = H, Me, Et) to reveal effects dependent on the identities of the metal ions and R-groups. The electrochemical results show differences in redox energetics at the peripheral 'M' site between complexes and significant wave splitting of the metal- and ligand-based processes indicating substantial electronic interactions between multiple redox sites across the actinide-containing bridge. Most striking is the appearance of strong electronic coupling for the trimetallic Yb{sup III}-U{sup IV}-Yb{sup III}, Sm{sup III}-U{sup IV}-Sm{sup III}, and La{sup III}-U{sup IV}-La{sup III} complexes, [8]{sup -}, [9b]{sup -} and [10b]{sup -}, respectively, whose calculated comproportionation constant K{sub c} is slightly larger than that reported for the benchmark Creutz-Taube ion. X-ray absorption studies for monometallic metallocene complexes of U{sup III}, U{sup IV}, and U{sup V} reveal small but detectable energy differences in the 'white-line' feature of the uranium L{sub III}-edges consistent with these variations in nominal oxidation state. The sum of this data provides evidence of 5f/6d-orbital participation in bonding and electronic delocalization in these multimetallic f-element complexes. An improved, high-yielding synthesis of 4{prime}-cyano-2,2{prime}:6{prime},2{double_prime}-terpyridine is also reported.

  11. Method for the concentration and separation of actinides from biological and environmental samples

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1989-01-01

    A method and apparatus for the quantitative recover of actinide values from biological and environmental sample by passing appropriately prepared samples in a mineral acid solution through a separation column of a dialkyl(phenyl)-N,N-dialylcarbamoylmethylphosphine oxide dissolved in tri-n-butyl phosphate on an inert substrate which selectively extracts the actinide values. The actinide values can be eluted either as a group or individually and their presence quantitatively detected by alpha counting.

  12. Method for the concentration and separation of actinides from biological and environmental samples

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1989-05-30

    A method and apparatus for the quantitative recover of actinide values from biological and environmental sample by passing appropriately prepared samples in a mineral acid solution through a separation column of a dialkyl(phenyl)-N,N-dialylcarbamoylmethylphosphine oxide dissolved in tri-n-butyl phosphate on an inert substrate which selectively extracts the actinide values. The actinide values can be eluted either as a group or individually and their presence quantitatively detected by alpha counting. 3 figs.

  13. Oxidation state and local structure of plutonium reacted with magnetite, mackinawite, and chukanovite.

    PubMed

    Kirsch, Regina; Fellhauer, David; Altmaier, Marcus; Neck, Volker; Rossberg, Andre; Fanghänel, Thomas; Charlet, Laurent; Scheinost, Andreas C

    2011-09-01

    Due to their redox reactivity, surface sorption characteristics, and ubiquity as corrosion products or as minerals in natural sediments, iron(II)-bearing minerals control to a large extent the environmental fate of actinides. Pu-L(III)-edge XANES and EXAFS spectra were used to investigate reaction products of aqueous (242)Pu(III) and (242)Pu(V) reacted with magnetite, mackinawite, and chukanovite under anoxic conditions. As Pu concentrations in the liquid phase were rapidly below detection limit, oxidation state and local structure of Pu were determined for Pu associated with the solid mineral phase. Pu(V) was reduced in the presence of all three minerals. A newly identified, highly specific Pu(III)-sorption complex formed with magnetite. Solid PuO(2) phases formed in the presence of mackinawite and chukanovite; in the case of chukanovite, up to one-third of plutonium was also present as Pu(III). This highlights the necessity to consider, under reducing anoxic conditions, Pu(III) species in addition to tetravalent PuO(2) for environmental risk assessment. Our results also demonstrate the necessity to support thermodynamic calculations with spectroscopic data. PMID:21755920

  14. Ion Exchange Separation of the Oxidation State of Vanadium.

    ERIC Educational Resources Information Center

    Cornelius, Richard

    1980-01-01

    Describes an experiment that emphasizes the discrete nature of the different oxidation states of vanadium by the separation of ammonium metavanadate into all four species by ion exchange chromatography. (CS)

  15. Towards a Predictive Thermodynamic Model of Oxidation States of Uranium Incorporated in Fe (hydr) oxides

    SciTech Connect

    Bagus, Paul S.

    2013-01-01

    The theoretical research in this project has been directed toward the interpretation of core-level spectroscopies for systems relevant to the project. For the initial efforts, the focus of our theoretical simulations has been the interpretation of laboratory and synchrotron X-Ray Photoemission Spectra, XPS. In more recent efforts, an increasing emphasis has been placed on developing transparent understandings of X-Ray Adsorption Spectra, XAS . For the XAS, the principal concern is for the near-edge features, either just below or just above, an ionization limit or edge, which are described as Near-Edge X-Ray Adsorption Fine Structure, NEXAFS. In particular, a priority has involved the analysis and interpretation of XPS and NEXAFS spectra, especially of Fe and U systems, as measured by our PNNL collaborators. The overall objective of our theoretical studies is to establish connections between features of the spectra and their origin in the electronic structure of the materials. The efforts for the analysis of XPS have been reviewed in a paper by the PI, C. J. Nelin, and E. S. Ilton from PNNL on “The interpretation of XPS spectra: Insights into materials properties”, Surf. Sci. Reports, 68, 273 (2013). Two materials properties of special interest have been the degree of ionicity and the character of the covalent bonding in a range of oxides formed with transition metal, lanthanide, and actinide cations. Since the systems treated have electrons in open shells, it has been necessary to determine the energetics and the character of the angular momentum coupling of the open shell electrons. In particular, we have established methods for the treatment of the “intermediate coupling” which arises when the system is between the limit of Russell-Saunders multiplets, and the limit of j-j coupling where the spin-orbit splittings of single electrons dominate. A recent paper by the PI, and M. J. Sassi, and K. M. Rosso, (both at PNNL) “Intermediate Coupling For Core

  16. XPS determination of Mn oxidation states in Mn (hydr)oxides

    NASA Astrophysics Data System (ADS)

    Ilton, Eugene S.; Post, Jeffrey E.; Heaney, Peter J.; Ling, Florence T.; Kerisit, Sebastien N.

    2016-03-01

    Hydrous manganese oxides are an important class of minerals that help regulate the geochemical redox cycle in near-surface environments and are also considered to be promising catalysts for energy applications such as the oxidation of water. A complete characterization of these minerals is required to better understand their catalytic and redox activity. In this contribution an empirical methodology using X-ray photoelectron spectroscopy (XPS) is developed to quantify the oxidation state of hydrous multivalent manganese oxides with an emphasis on birnessite, a layered structure that occurs commonly in soils but is also the oxidized endmember in biomimetic water-oxidation catalysts. The Mn2p3/2, Mn3p, and Mn3s lines of near monovalent Mn(II), Mn(III), and Mn(IV) oxides were fit with component peaks; after the best fit was obtained the relative widths, heights and binding energies of the components were fixed. Unknown multivalent samples were fit such that binding energies, intensities, and peak-widths of each oxidation state, composed of a packet of correlated component peaks, were allowed to vary. Peak-widths were constrained to maintain the difference between the standards. Both average and individual mole fraction oxidation states for all three energy levels were strongly correlated, with close agreement between Mn3s and Mn3p analyses, whereas calculations based on the Mn2p3/2 spectra gave systematically more reduced results. Limited stoichiometric analyses were consistent with Mn3p and Mn3s. Further, evidence indicates the shape of the Mn3p line was less sensitive to the bonding environment than that for Mn2p. Consequently, fitting the Mn3p and Mn3s lines yielded robust quantification of oxidation states over a range of Mn (hydr)oxide phases. In contrast, a common method for determining oxidation states that utilizes the multiplet splitting of the Mn3s line was found to be not appropriate for birnessites.

  17. Device for Detecting Actinides, Method for Detecting Actinides

    SciTech Connect

    Stevens, Fred J.; Wilkins-Stevens, Priscilla

    1998-10-29

    A heavy metal detector is provided comprising a first molecule and a second molecule, whereby the first and second molecules interact in a predetermined manner; a first region on the first molecule adapted to interact with an actinide; and a second region on the second molecule adapted to interact with the actinide, whereby the interactions of the actinide with the regions effect the predetermined manner of interaction between the molecules.

  18. Growth control of the oxidation state in vanadium oxide thin films

    SciTech Connect

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; Lee, Ho Nyung

    2014-12-05

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research, but also technological applications that utilize the subtle change in the physical properties originating from the metalinsulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V₂⁺²O₃, V⁺⁴O₂, and V₂⁺⁵O₅. A well pronounced MIT was only observed in VO₂ films grown in a very narrow range of oxygen partial pressure P(O₂). The films grown either in lower (< 10 mTorr) or higher P(O₂) (> 25 mTorr) result in V₂O₃ and V₂O₅ phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO₂ thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an 3 improved MIT behavior.

  19. Growth control of the oxidation state in vanadium oxide thin films

    DOE PAGESBeta

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; Lee, Ho Nyung

    2014-12-05

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research, but also technological applications that utilize the subtle change in the physical properties originating from the metalinsulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase puremore » epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V₂⁺²O₃, V⁺⁴O₂, and V₂⁺⁵O₅. A well pronounced MIT was only observed in VO₂ films grown in a very narrow range of oxygen partial pressure P(O₂). The films grown either in lower (< 10 mTorr) or higher P(O₂) (> 25 mTorr) result in V₂O₃ and V₂O₅ phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO₂ thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an 3 improved MIT behavior.« less

  20. Growth control of the oxidation state in vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; Egami, Takeshi; Lee, Ho Nyung

    2014-12-01

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V2 + 3 O 3 , V + 4 O 2 , and V2 + 5 O 5 . A well pronounced MIT was only observed in VO2 films grown in a very narrow range of oxygen partial pressure P(O2). The films grown either in lower (<10 mTorr) or higher P(O2) (>25 mTorr) result in V2O3 and V2O5 phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO2 thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.

  1. Growth control of the oxidation state in vanadium oxide thin films

    SciTech Connect

    Lee, Shinbuhm; Meyer, Tricia L.; Lee, Ho Nyung; Park, Sungkyun; Egami, Takeshi

    2014-12-01

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V{sub 2}{sup +3}O{sub 3}, V{sup +4}O{sub 2}, and V{sub 2}{sup +5}O{sub 5}. A well pronounced MIT was only observed in VO{sub 2} films grown in a very narrow range of oxygen partial pressure P(O{sub 2}). The films grown either in lower (<10 mTorr) or higher P(O{sub 2}) (>25 mTorr) result in V{sub 2}O{sub 3} and V{sub 2}O{sub 5} phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO{sub 2} thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.

  2. Novel Separation of Actinides

    SciTech Connect

    Mariella, R

    2011-02-17

    The separation of actinides and other elements of interest for nuclear forensics and threat reduction is currently performed using decades-old chemistries and ion-exchange columns. We propose to determine the technical feasibility of a novel method for separating actinide ions in solution. This method is based upon isotachophoresis (ITP), which has been applied in the purification of pharmaceuticals and other biochemical applications. This technique has the potential to separate inorganic ions more effectively than existing methods, which is key to analyzing very small samples. We will perform a quantitative assessment of the effectiveness of specific isotachophoretic approaches including predicting the physical and chemical properties, such as ion mobility, of inorganic ions under specific solvent conditions using a combination of ab initio calculations and semi-empirical methods. We expect to obtain a thorough understanding of the analytical systems parameters under which ITP is most effective for the separation of inorganic samples, including the influence of the double layer surrounding actinide ions, the Debye length for different ions and ion complexes, and Debye-Hueckel limits. Inorganic separations are key to nuclear forensics for countering terrorism and nuclear proliferation. If found to be feasible and potentially superior to currently used separation approaches, ITP could provide the conceptual basis for an improved means to separate samples of nuclear explosion debris for nuclear forensic analysis, in support of the Laboratory's missions in homeland and national security.

  3. A comparative study of actinide complexation in three ligand systems with increasing complexity

    NASA Astrophysics Data System (ADS)

    Jeanson, A.; Dahou, S.; Guillaumont, D.; Moisy, P.; Den Auwer, C.; Scheinost, A.; Hennig, C.; Vidaud, C.; Subra, G.; Solari, P. L.

    2009-11-01

    The complexation of thorium, neptunium and plutonium at oxidation state +IV with three ligands of increasing complexity has been investigated. These ligands are relevant for bio inorganic systems. The first ligand is the small nitrilotriacetic acid that often play the role of protecting ligands against hydrolysis. EXAFS results for the Th to Pu series have been correlated to quantum chemical calculations and show an homogeneous behavior of the actinide at oxidation state +IV. For larger ligands, steric effects may become significant and one can ask how the ligand may accommodate the large actinide cation coordination sphere. Model pentapeptides have been synthesized and tested as complexing agents. Comparison with NTA shows that the molecular arrangements are radically different. The third ligand system is transferrin, a diferric metalloptrotein that is well known to coordinate a large variety of cations from transition metals of f-elements. Metalloproteins bear primary, secondary and tertiary structures that all play a crucial role in bonding. At a given oxidation state (+IV), but for various atomic numbers (Th, Np, Pu) EXAFS data at the cation LIII edge exhibit significant coordination discrepancies that are related to a changes in protein geometry. In that sense, the metalloprotein may be viewed as a complex system.

  4. Non-equilibrium oxidation states of zirconium during early stages of metal oxidation

    SciTech Connect

    Ma, Wen; Yildiz, Bilge; Herbert, F. William; Senanayake, Sanjaya D.

    2015-03-09

    The chemical state of Zr during the initial, self-limiting stage of oxidation on single crystal zirconium (0001), with oxide thickness on the order of 1 nm, was probed by synchrotron x-ray photoelectron spectroscopy. Quantitative analysis of the Zr 3d spectrum by the spectrum reconstruction method demonstrated the formation of Zr{sup 1+}, Zr{sup 2+}, and Zr{sup 3+} as non-equilibrium oxidation states, in addition to Zr{sup 4+} in the stoichiometric ZrO{sub 2}. This finding resolves the long-debated question of whether it is possible to form any valence states between Zr{sup 0} and Zr{sup 4+} at the metal-oxide interface. The presence of local strong electric fields and the minimization of interfacial energy are assessed and demonstrated as mechanisms that can drive the formation of these non-equilibrium valence states of Zr.

  5. Non-equilibrium oxidation states of zirconium during early stages of metal oxidation

    DOE PAGESBeta

    Ma, Wen; Senanayake, Sanjaya D.; Herbert, F. William; Yildiz, Bilge

    2015-03-11

    The chemical state of Zr during the initial, self-limiting stage of oxidation on single crystal zirconium (0001), with oxide thickness on the order of 1 nm, was probed by synchrotron x-ray photoelectron spectroscopy. Quantitative analysis of the Zr 3d spectrum by the spectrum reconstruction method demonstrated the formation of Zr1+, Zr2+, and Zr3+ as non-equilibrium oxidation states, in addition to Zr4+ in the stoichiometric ZrO2. This finding resolves the long-debated question of whether it is possible to form any valence states between Zr0 and Zr4+ at the metal-oxide interface. As a result, the presence of local strong electric fields andmore » the minimization of interfacial energy are assessed and demonstrated as mechanisms that can drive the formation of these non-equilibrium valence states of Zr.« less

  6. Non-spin-flip ( 3He, t) charge-exchange and isobaric analog states of actinide nuclei studied at θ = 0°, E( 3He) = 76 MeV and 200 MeV

    NASA Astrophysics Data System (ADS)

    Jänecke, J.; Becchetti, F. D.; van den Berg, A. M.; Berg, G. P. A.; Brouwer, G.; Greenfield, M. B.; Harakeh, M. N.; Hofstee, M. A.; Nadasen, A.; Roberts, D. A.; Sawafta, R.; Schippers, J. M.; Stephenson, E. J.; Stewart, D. P.; van der Werf, S. Y.

    1991-04-01

    The ( 3He, t) charge-exchange reaction has been studied at θ = 0° and bombarding energies of E( 3He) = 76.5 MeV and 200 MeV. Spectra were measured using magnetic analysis for target nuclei of 12, 13C, 16O, 19F, 28, 29, 30Si, 90Zr, 117, 120Sn, natTa, natW, 197Au, 208Pb, 230, 232Th, 234, 236, 238U and 244Pu. The measurements at 76.5 MeV concentrated on the isobaric analog states of several actinide nuclei, particularly on their widths and the branching ratios for proton decay. Cross sections, Q-values and total widths were determined for the transitions to the isobaric analog states. Coulomb displacement energies derived from the measured Q-values display the influence of deformed nuclear shapes. Escape widths Γ ↑ and spreading widths Γ ↓ of the isobaric analog states in five actinide nuclei were deduced from the measured proton-decay branching ratios. They were found to be in agreement with predictions which postulate isospin mixing via the Coulomb force with the ( T0-1)-component of the isovector giant monopole resonance. The measurements at 200 MeV were concerned with transitions to isobaric analog states in both light and heavy nuclei, including several actinide nuclei, but Gamow-Teller resonances and transitions to numerous other states were also observed. The measured cross sections for several transitions to isobaric analog states from 30Si to 208Pb were used to extract the effective interaction Vτ for non-spin-flip ( 3He, t) charge exchange at E( 3He) ≈ 200 MeV. The interaction strength Vτ decreases by a factor 0.6 when compared to previously measured values for the energy range E( 3He) = 65 to 90 MeV. An angular distribution from θτ = 0° to 16° for the transition to the isobaric analog state in 120Sb measured at E( 3He) = 200 MeV was found to be in very good agreement with microscopic calculations.

  7. Analysis of the Gas Core Actinide Transmutation Reactor (GCATR)

    NASA Technical Reports Server (NTRS)

    Clement, J. D.; Rust, J. H.

    1977-01-01

    Design power plant studies were carried out for two applications of the plasma core reactor: (1) As a breeder reactor, (2) As a reactor able to transmute actinides effectively. In addition to the above applications the reactor produced electrical power with a high efficiency. A reactor subsystem was designed for each of the two applications. For the breeder reactor, neutronics calculations were carried out for a U-233 plasma core with a molten salt breeding blanket. A reactor was designed with a low critical mass (less than a few hundred kilograms U-233) and a breeding ratio of 1.01. The plasma core actinide transmutation reactor was designed to transmute the nuclear waste from conventional LWR's. The spent fuel is reprocessed during which 100% of Np, Am, Cm, and higher actinides are separated from the other components. These actinides are then manufactured as oxides into zirconium clad fuel rods and charged as fuel assemblies in the reflector region of the plasma core actinide transmutation reactor. In the equilibrium cycle, about 7% of the actinides are directly fissioned away, while about 31% are removed by reprocessing.

  8. Potentiometric Sensor for Real-Time Remote Surveillance of Actinides in Molten Salts

    SciTech Connect

    Natalie J. Gese; Jan-Fong Jue; Brenda E. Serrano; Guy L. Fredrickson

    2012-07-01

    A potentiometric sensor is being developed at the Idaho National Laboratory for real-time remote surveillance of actinides during electrorefining of spent nuclear fuel. During electrorefining, fuel in metallic form is oxidized at the anode while refined uranium metal is reduced at the cathode in a high temperature electrochemical cell containing LiCl-KCl-UCl3 electrolyte. Actinides present in the fuel chemically react with UCl3 and form stable metal chlorides that accumulate in the electrolyte. This sensor will be used for process control and safeguarding of activities in the electrorefiner by monitoring the concentrations of actinides in the electrolyte. The work presented focuses on developing a solid-state cation conducting ceramic sensor for detecting varying concentrations of trivalent actinide metal cations in eutectic LiCl-KCl molten salt. To understand the basic mechanisms for actinide sensor applications in molten salts, gadolinium was used as a surrogate for actinides. The ß?-Al2O3 was selected as the solid-state electrolyte for sensor fabrication based on cationic conductivity and other factors. In the present work Gd3+-ß?-Al2O3 was prepared by ion exchange reactions between trivalent Gd3+ from GdCl3 and K+-, Na+-, and Sr2+-ß?-Al2O3 precursors. Scanning electron microscopy (SEM) was used for characterization of Gd3+-ß?-Al2O3 samples. Microfocus X-ray Diffraction (µ-XRD) was used in conjunction with SEM energy dispersive X-ray spectroscopy (EDS) to identify phase content and elemental composition. The Gd3+-ß?-Al2O3 materials were tested for mechanical and chemical stability by exposing them to molten LiCl-KCl based salts. The effect of annealing on the exchanged material was studied to determine improvements in material integrity post ion exchange. The stability of the ß?-Al2O3 phase after annealing was verified by µ-XRD. Preliminary sensor tests with different assembly designs will also be presented.

  9. Direct determination of the intracellular oxidation state of plutonium.

    PubMed

    Gorman-Lewis, Drew; Aryal, Baikuntha P; Paunesku, Tatjana; Vogt, Stefan; Lai, Barry; Woloschak, Gayle E; Jensen, Mark P

    2011-08-15

    Microprobe X-ray absorption near edge structure (μ-XANES) measurements were used to determine directly, for the first time, the oxidation state of intracellular plutonium in individual 0.1-μm(2) areas within single rat pheochromocytoma cells (PC12). The living cells were incubated in vitro for 3 h in the presence of Pu added to the media in different oxidation states (Pu(III), Pu(IV), and Pu(VI)) and in different chemical forms. Regardless of the initial oxidation state or chemical form of Pu presented to the cells, the XANES spectra of the intracellular Pu deposits were always consistent with tetravalent Pu even though the intracellular milieu is generally reducing. PMID:21755934

  10. Direct Determination of the Intracellular Oxidation State of Plutonium

    PubMed Central

    Gorman-Lewis, Drew; Aryal, Baikuntha P.; Paunesku, Tatjana; Vogt, Stefan; Lai, Barry; Woloschak, Gayle E.; Jensen, Mark P.

    2013-01-01

    Microprobe X-ray absorption near edge structure (μ-XANES) measurements were used to determine directly, for the first time, the oxidation state of intracellular plutonium in individual 0.1 μm2 areas within single rat pheochromocytoma cells (PC12). The living cells were incubated in vitro for 3 hours in the presence of Pu added to the media in different oxidation states (Pu(III), Pu(IV), and Pu(VI)) and in different chemical forms. Regardless of the initial oxidation state or chemical form of Pu presented to the cells, the XANES spectra of the intracellular Pu deposits was always consistent with tetravalent Pu even though the intracellular milieu is generally reducing. PMID:21755934

  11. First-principles investigation of higher oxides of uranium and neptunium: U3O8 and Np2O5

    NASA Astrophysics Data System (ADS)

    Yun, Y.; Rusz, J.; Suzuki, M.-T.; Oppeneer, P. M.

    2011-02-01

    A computational study is presented of the structural, electronic, and magnetic properties of U3O8 and Np2O5, which are actinide oxides in a higher oxidation state than the tetravalent state of the common dioxide phases, UO2 and NpO2. The calculations are based on the density functional theory+U approach, in which additional Coulomb correlations on the actinide atom are taken into account. The calculated properties of these two higher oxidized actinide oxides are analyzed and compared to those of their tetravalent analogs. The optimized structural parameters of these noncubic oxides are found to be in reasonable agreement with available experimental data. U3O8 is predicted to be a magnetic insulator, having one U atom in a hexavalent oxidation state and two U atoms in a pentavalent oxidation state. For Np2O5, which is also predicted to be an insulator, a complicated noncollinear magnetic structure is computed, leading to a nonzero overall magnetization with a slight antiferromagnetic canting. The calculated electronic structures are presented and the variation of the U 5f or Np 5f-O 2p hybridization with the oxidation state is analyzed. With increasing oxygen content, the nearly localized 5f electrons of the actinide elements are more positioned near the Fermi level and the hybridization between 5f and 2p states is markedly increased.

  12. New density functional theory approaches for enabling prediction of chemical and physical properties of plutonium and other actinides.

    SciTech Connect

    Mattsson, Ann Elisabet

    2012-01-01

    functional the Harmonic Oscillator Gas is providing the necessary reference system for the strong correlation and localization occurring in actinides. Preliminary testing shows that the new Hao-Armiento-Mattsson (HAM) functional gives a trend towards improved results for the crystalline copper oxide test system we have chosen. This test system exhibits the same exchange-correlation physics as the actinide systems do, but without the relativistic effects, giving access to a pure testing ground for functionals. During the work important insights have been gained. An example is that currently available functionals, contrary to common belief, make large errors in so called hybridization regions where electrons from different ions interact and form new states. Together with the new understanding of functional issues, the Dirac implementation into the RSPt code will permit us to gain more fundamental understanding, both quantitatively and qualitatively, of materials of importance for Sandia and the rest of the Nuclear Weapons complex.

  13. Oxygenic Photosynthesis and the Oxidation State of Mars

    NASA Technical Reports Server (NTRS)

    Hartman, Hyman; McKay, Christopher P.

    1995-01-01

    The oxidation state of the Earth's surface is one of the most obvious indications of the effect of life on this planet. The surface of Mars is highly oxidized, as evidenced by its red color, but the connection to life is less apparent. Two possibilities can be considered. First, the oxidant may be photochemically produced in the atmosphere. In this case the fundamental source of O2 is the loss of H2 to space and the oxidant produced is H2O2. This oxidant would accumulate on the surface and thereby destroy any organic material and other reductants to some depth. Recent models suggest that diffusion limits this depth to a few meters. An alternative source of oxygen is biological oxygen production followed by sequestration of organic material in sediments - as on the Earth. In this case, the net oxidation of the surface was determined billions of years ago when Mars was a more habitable planet and oxidative conditions could persist to great depths, over 100 m. Below this must be a compensating layer of biogenic organic material. Insight into the nature of past sources of oxidation on Mars will require searching for organics in the martian subsurface and sediments.

  14. Solid state potentiometric gaseous oxide sensor

    NASA Technical Reports Server (NTRS)

    Wachsman, Eric D. (Inventor); Azad, Abdul Majeed (Inventor)

    2003-01-01

    A solid state electrochemical cell (10a) for measuring the concentration of a component of a gas mixture (12) includes first semiconductor electrode (14) and second semiconductor electrode (16) formed from first and second semiconductor materials, respectively. The materials are selected so as to undergo a change in resistivity upon contacting a gas component, such as CO or NO. An electrolyte (18) is provided in contact with the first and second semiconductor electrodes. A reference cell can be included in contact with the electrolyte. Preferably, a voltage response of the first semiconductor electrode is opposite in slope direction to that of the second semiconductor electrode to produce a voltage response equal to the sum of the absolute values of the control system uses measured pollutant concentrations to direct adjustment of engine combustion conditions.

  15. Changes in magmatic oxidation state induced by degassing

    NASA Astrophysics Data System (ADS)

    Brounce, M. N.; Stolper, E. M.; Eiler, J. M.

    2015-12-01

    Temporal variations in the oxygen fugacity (fO2) of the mantle may have been transmitted to Earth's atmosphere and oceans by volcanic degassing. However, it is unclear how redox states of volatiles relate to their source magmas because degassing and assimilation can impact fO2 before or during eruption. To explore this, we present µ-XANES measurements of the oxidation states of Fe and S and laser fluorination measurements of 18O/16O ratios in submarine glasses from two settings where degassing is recorded: 1) submarine glasses from the Reykjanes Ridge as it shoals to Iceland, including subglacial glasses from the Reykjanes Peninsula; and 2) submarine glasses from Mauna Kea recovered by the Hawaii Shield Drilling Program (HSDP). Glasses from both settings are basalts with 5.5-9.9 wt% MgO and 350-1790 ppm S. Submarine Reykjanes glasses are sulfide saturated. Subglacial Reykjanes and HSDP glasses are not sulfide saturated, and S and H2O contents are consistent with S+H2O degassing. Submarine Reykjanes glasses have 18O/16O indistinguishable from MORB and become progressively 18O-depleted as MgO decreases. Subglacial glasses have lower 18O/16O than submarine glasses at a given MgO, but both sample types project to a common 18O/16O near 10 wt% MgO, suggesting that 18O-depletion in these lavas is generated by fractional crystallization and assimilation of an 18O-depleted crustal component. The oxidation state of Fe increases only slightly as 18O/16O decrease, suggesting that the assimilant is not oxidized enough to change magmatic fO2. Fe and S do not oxidize or reduce with decreasing S or H2O, suggesting that relatively reduced magmas at depth degassed S+H2O without changing magmatic fO2, and that the fO2 of these lavas reflect the fO2of their mantle source. The oxidation states of Fe and S in HSDP glasses are broadly correlated and samples with the highest S concentrations are the most oxidized. Both Fe and S reduce with decreasing S and H2O contents. This suggests

  16. RAPID MEASUREMENTS OF NEPTUNIUM OXIDATION STATES USING CHROMATOGRAPHIC RESINS

    SciTech Connect

    Diprete, D; C Diprete, C; Mira Malek, M; Eddie Kyser, E

    2009-03-24

    The Savannah River Site's (SRS) H-Canyon facility uses ceric ammonium nitrate (CAN) to separate impure neptunium (Np) from a high sulfate feed stream. The material is processed using a two-pass solvent extraction purification which relies on CAN to oxidize neptunium to Np(VI) during the first pass prior to extraction. Spectrophotometric oxidation-state analyses normally used to validate successful oxidation to Np(VI) prior to extraction were compromised by this feed stream matrix. Therefore, a rapid chromatographic method to validate successful Np oxidation was developed using Eichrom Industries TRU and TEVA{reg_sign} resins. The method was validated and subsequently transferred to existing operations in the process analytical laboratories.

  17. Metabolism and dosimetry of actinide elements in occupationally-exposed personnel of Russia and the United States: A summary progress report

    SciTech Connect

    Khokhryakov, V.F.; Suslova, K.G.; Filipy, R.E.; Alldredge, J.R.; Aladova, E.E.; Glover, S.E.; Vostrotin, V.V.

    2000-07-01

    The US Transuranium and Uranium Registries (USTUR) and the Dosimetry Registry of the Mayak Industrial Association (DRMIA) have been independently collecting tissues at autopsy of plutonium workers in their respective countries for nearly 30 y. The tissues are analyzed radiochemically and the analytical data are used to develop, modify, or refine biokinetic models that describe the depositions and translocations of plutonium and transplutonium elements in the human body. The purpose of this collaborative research project is to combine the unique information on humans, gathered by the two Registries, into a joint database and perform analyses of the data. A series of project tasks are directly concerned with dosimetry in Mayak workers and involve biokinetic modeling for actinide elements. Transportability coefficients derived from in-vitro solubility measurements of actinide-containing aerosols (as measured by the DRMIA) were related to specific workplaces within Mayak facilities. The transportability coefficients of inhaled aerosols significantly affected the translocation rates of plutonium from the respiratory tract to the systemic circulation. Parameters for a simplified lung model, used by Branch No. 1, Federal Research Center Institute of Biophysics (FIB-1) and the Mayak Production Association for dose assessment at long times after inhalation of plutonium-containing aerosols, were developed on the basis of joint USTUR and DRMIA data. This model has separate sets of deposition and transfer parameters for three aerosol transportability groups, allowing work histories of the workers to be considered in the dose-assessment process. FIB-1 biokinetic models were extended to include the distributions of actinide elements in systemic organs of workers, and a relationship between the health of individual workers and plutonium distribution in tissues was determined. Workers who suffered from liver diseases generally had a smaller fraction of systemic plutonium in the

  18. Density functional theory calculations of the redox potentials of actinide(VI)/actinide(V) couple in water.

    PubMed

    Steele, Helen M; Guillaumont, Dominique; Moisy, Philippe

    2013-05-30

    The measured redox potential of an actinide at an electrode surface involves the transfer of a single electron from the electrode surface on to the actinide center. Before electron transfer takes place, the complexing ligands and molecules of solvation need to become structurally arranged such that the electron transfer is at its most favorable. Following the electron transfer, there is further rearrangement to obtain the minimum energy structure for the reduced state. As such, there are three parts to the total energy cycle required to take the complex from its ground state oxidized form to its ground state reduced form. The first part of the energy comes from the structural rearrangement and solvation energies of the actinide species before the electron transfer or charge transfer process; the second part, the energy of the electron transfer; the third part, the energy required to reorganize the ligands and molecules of solvation around the reduced species. The time resolution of electrochemical techniques such as cyclic voltammetry is inadequate to determine to what extent bond and solvation rearrangement occurs before or after electron transfer; only for a couple to be classed as reversible is it fast in terms of the experimental time. Consequently, the partitioning of the energy theoretically is of importance to obtain good experimental agreement. Here we investigate the magnitude of the instantaneous charge transfer through calculating the fast one electron reduction energies of AnO2(H2O)n(2+), where An = U, Np, and Pu, for n = 4-6, in solution without inclusion of the structural optimization energy of the reduced form. These calculations have been performed using a number of DFT functionals, including the recently developed functionals of Zhao and Truhlar. The results obtained for calculated electron affinities in the aqueous phase for the AnO2(H2O)5(2+/+) couples are within 0.04 V of accepted experimental redox potentials, nearly an order of magnitude

  19. IDENTIFYING CRITICAL CYSTEINE RESIDUES IN ARSENIC (+3 OXIDATION STATE) METHYLTRANSFERASE

    EPA Science Inventory

    Arsenic (+3 oxidation state) methyltransferase (AS3MT) catalyzes methylation of inorganic arsenic to mono, di, and trimethylated arsenicals. Orthologous AS3MT genes in genomes ranging from simple echinoderm to human predict a protein with five conserved cysteine (C) residues. In ...

  20. Soft X-ray scanning transmission X-ray microscopy (STXM) of actinide particles.

    PubMed

    Nilsson, Hans J; Tyliszczak, Tolek; Wilson, Richard E; Werme, Lars; Shuh, David K

    2005-09-01

    A descriptive account is given of our most recent research on the actinide dioxides with the Advanced Light Source Molecular Environmental Science (ALS-MES) Beamline 11.0.2 soft X-ray scanning transmission X-ray microscope (STXM) at the Lawrence Berkeley National Laboratory (LBNL). The ALS-MES STXM permits near-edge X-ray absorption fine structure (NEXAFS) and imaging with 30-nm spatial resolution. The first STXM spectromicroscopy NEXAFS spectra at the actinide 4d5/2 edges of the imaged transuranic particles, NpO2 and PuO2, have been obtained. Radiation damage induced by the STXM was observed in the investigation of a mixed oxidation state particle (Np(V,VI)) and was minimized during collection of the actual spectra at the 4d5/2 edge of the Np(V,VI) solid. A plutonium elemental map was obtained from an irregular PuO2 particle with the dimensions of 650 x 650 nm. The Pu 4d5/2 NEXAFS spectra were collected at several different locations from the PuO2 particle and were identical. A representative oxygen K-edge spectrum from UO2 was collected and resembles the oxygen K-edge from the bulk material. The unique and current performance of the ALS-MES STXM at extremely low energies (ca. 100 eV) that may permit the successful measurement of the actinide 5d edge is documented. Finally, the potential of STXM as a tool for actinide investigations is briefly discussed. PMID:16021423

  1. Shifts in oxidation states of cerium oxide nanoparticles detected inside intact hydrated cells and organelles

    SciTech Connect

    Szymanski, Craig J.; Munusamy, Prabhakaran; Mihai, Cosmin; Xie, Yumei; Hu, Dehong; Gilles, Marry K.; Tyliszczak, T.; Thevuthasan, Suntharampillai; Baer, Donald R.; Orr, Galya

    2015-09-01

    Cerium oxide nanoparticles (CNPs) have been shown to induce diverse biological effects, ranging from toxic to beneficial. The beneficial effects have been attributed to the potential antioxidant activity of CNPs via certain redox reactions, depending on their oxidation state or Ce3+/Ce4+ ratio. However, this ratio is strongly dependent on the environment and age of the nanoparticles and it is unclear whether and how the complex intracellular environment impacts this ratio and the possible redox reactions of CNPs. To identify any changes in the oxidation state of CNPs in the intracellular environment and better understand their intracellular reactions, we directly quantified the oxidation states of CNPs outside and inside intact hydrated cells and organelles using correlated scanning transmission x-ray and super resolution fluorescence microscopies. By analyzing hundreds of small CNP aggregates, we detected a shift to a higher Ce3+/Ce4+ ratio in CNPs inside versus outside the cells, indicating a net reduction of CNPs in the intracellular environment. We further found a similar ratio in the cytoplasm and in the lysosomes, indicating that the net reduction occurs earlier in the internalization pathway. Together with oxidative stress and toxicity measurements, our observations identify a net reduction of CNPs in the intracellular environment, which is consistent with their involvement in potentially beneficial oxidation reactions, but also point to interactions that can negatively impact the health of cells.

  2. Actinide-specific complexing agents: their structural and solution chemistry

    SciTech Connect

    Raymond, K.N.; Freeman, G.E.; Kappel, M.J.

    1983-07-01

    The synthesis of a series of tetracatecholate ligands designed to be specific for Pu(IV) and other actinide(IV) ions has been achieved. Although these compounds are very effective as in vivo plutonium removal agents, potentiometric and voltammetric data indicate that at neutral pH full complexation of the Pu(IV) ion by all four catecholate groups does not occur. Spectroscopic results indicate that the tetracatecholates, 3,4,3-LICAMS and 3,4,3-LICAMC, complex Am(III). The Am(IV)/(III)-catecholate couple (where catecholate = 3,4,3-LICAMS or 3,4,3-LICAMC) is not observed, but may not be observable due to the large currents associated with ligand oxidation. However, within the potential range where ligand oxidation does not occur, these experiments indicate that the reduction potential of free Am(IV)/(III) is probably greater than or equal to + 2.6 V vs NHE or higher. Proof of the complexation of americium in the trivalent oxidation state by 3,4,3-LICAMS and 3,4,3-LICAMC elimates the possibility of tetracatholates stabilizing Am(IV) in vivo.

  3. Extraction of trivalent lanthanides and actinides by ``CMPO-like`` calixarenes

    SciTech Connect

    Delmau, L.H.; Simon, N.; Schwing-Weill, M.J.

    1999-04-01

    Extractive properties of calix[4]arenes bearing carbamoylmethylphosphine oxide moieties on their upper rim toward trivalent lanthanide and actinide cations were investigated. The study revealed that these molecules selectively extract light lanthanides and actinides from heavy lanthanides. All parameters present in the extraction system were varied to determine the origin of the selectivity. It was found that this selectivity requires a calix[4]arene platform and acetamidophosphine oxide groups containing phenyl substituents on the four phosphorus atoms.

  4. Managing Inventories of Heavy Actinides

    SciTech Connect

    Wham, Robert M; Patton, Bradley D

    2011-01-01

    The Department of Energy (DOE) has stored a limited inventory of heavy actinides contained in irradiated targets, some partially processed, at the Savannah River Site (SRS) and Oak Ridge National Laboratory (ORNL). The 'heavy actinides' of interest include plutonium, americium, and curium isotopes; specifically 242Pu and 244Pu, 243Am, and 244/246/248Cm. No alternate supplies of these heavy actinides and no other capabilities for producing them are currently available. Some of these heavy actinide materials are important for use as feedstock for producing heavy isotopes and elements needed for research and commercial application. The rare isotope 244Pu is valuable for research, environmental safeguards, and nuclear forensics. Because the production of these heavy actinides was made possible only by the enormous investment of time and money associated with defense production efforts, the remaining inventories of these rare nuclear materials are an important part of the legacy of the Nuclear Weapons Program. Significant unique heavy actinide inventories reside in irradiated Mark-18A and Mark-42 targets at SRS and ORNL, with no plans to separate and store the isotopes for future use. Although the costs of preserving these heavy actinide materials would be considerable, for all practical purposes they are irreplaceable. The effort required to reproduce these heavy actinides today would likely cost billions of dollars and encompass a series of irradiation and chemical separation cycles for at least 50 years; thus, reproduction is virtually impossible. DOE has a limited window of opportunity to recover and preserve these heavy actinides before they are disposed of as waste. A path forward is presented to recover and manage these irreplaceable National Asset materials for future use in research, nuclear forensics, and other potential applications.

  5. FTICR/MS studies of gas-phase actinide ion reactions: fundamental chemical and physical properties of atomic and molecular actinide ions and neutrals

    NASA Astrophysics Data System (ADS)

    Gibson, J. K.; Haire, R. G.; Marçalo, J.; Santos, M.; Leal, J. P.; Pires de Matos, A.; Tyagi, R.; Mrozik, M. K.; Pitzer, R. M.; Bursten, B. E.

    2007-10-01

    Fundamental aspects of the chemical and physical properties of atomic and molecular actinide ions and neutrals are being examined by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS). To date, gas-phase reactivity studies of bare and ligated An+ and An2+ ions, where An = Th, Pa, U, Np, Pu, Am, and Cm, with oxidants and with hydrocarbons have been performed. Among the information that has been deduced from these studies are thermodynamic properties of neutral and ionic actinide oxide molecules and the role of the 5f electrons in actinide chemistry. Parallel theoretical studies of selected actinide molecular ions have also been carried out to substantiate the interpretation of the experimental observations.

  6. Actinide Dioxides in Water: Interactions at the Interface

    SciTech Connect

    Alexandrov, Vitaly; Shvareva, Tatiana Y.; Hayun, Shmuel; Asta, Mark; Navrotsky, Alexandra

    2011-12-15

    A comprehensive understanding of chemical interactions between water and actinide dioxide surfaces is critical for safe operation and storage of nuclear fuels. Despite substantial previous research, understanding the nature of these interactions remains incomplete. In this work, we combine accurate calorimetric measurements with first-principles computational studies to characterize surface energies and adsorption enthalpies of water on two fluorite-structured compounds, ThO₂ and CeO₂, that are relevant for understanding the behavior of water on actinide oxide surfaces more generally. We determine coverage-dependent adsorption enthalpies and demonstrate a mixed molecular and dissociative structure for the first hydration layer. The results show a correlation between the magnitude of the anhydrous surface energy and the water adsorption enthalpy. Further, they suggest a structural model featuring one adsorbed water molecule per one surface cation on the most stable facet that is expected to be a common structural signature of water adsorbed on actinide dioxide compounds.

  7. Crystalline state and acoustic properties of zinc oxide films

    SciTech Connect

    Kal'naya, G.I.; Pryadko, I.F.; Yarovoi, Yu.A.

    1988-08-01

    We study the effect of the crystalline state of zinc oxide films, prepared by magnetron sputtering, on the efficiency of SAW transducers based on the layered system textured ZnO film-interdigital transducer (IDT)-fused quartz substrate. The crystalline perfection of the ZnO films was studied by the x-ray method using a DRON-2.0 diffractometer. The acoustic properties of the layered system fused quartz substrate-IDT-zinc oxide film were evaluated based on the squared electromechanical coupling constant K/sup 2/ for strip filters. It was found that K/sup 2/ depends on the magnitude of the mechanical stresses. When zinc oxide films are deposited by the method of magnetron deposition on fused quartz substrates, depending on the process conditions limitations can arise on the rate of deposition owing to mechanical stresses, which significantly degrade the efficiency of SAW transducers based on them, in the ZnO films.

  8. Photofission of Actinides with Linearly Polarized Photons

    SciTech Connect

    Dale, D. S.; Cole, P. L.; Conn, A.; Forest, T. A.; Kosinov, O.; Setiniyaz, S.; Shapovlov, R.; Starovoitova, V.; Swanson, J.; Bodily, R.; Kelley, K.

    2010-08-04

    Idaho State University and the Idaho Accelerator Center are developing a polarized photon facility in the 10 MeV region using the off axis bremsstrahlung technique. Initial tests have been performed with the aim of using the high analyzing power of the photodisintegration of the deuteron to measure the beam polarization. A program is currently underway to measure the potential angular asymmetries of neutrons arising from the angular distribution of the fission fragments from photofission with linearly polarized photons. In this paper, we describe the Idaho State University Polarized Photon Facility, present results of commissioning runs, and describe potential application of polarized photofission in detecting actinides for homeland security and safeguards applications.

  9. Environmental research on actinide elements

    SciTech Connect

    Pinder, J.E. III; Alberts, J.J.; McLeod, K.W.; Schreckhise, R.G.

    1987-08-01

    The papers synthesize the results of research sponsored by DOE's Office of Health and Environmental Research on the behavior of transuranic and actinide elements in the environment. Separate abstracts have been prepared for the 21 individual papers. (ACR)

  10. Non-equilibrium oxidation states of zirconium during early stages of metal oxidation

    SciTech Connect

    Ma, Wen; Senanayake, Sanjaya D.; Herbert, F. William; Yildiz, Bilge

    2015-03-11

    The chemical state of Zr during the initial, self-limiting stage of oxidation on single crystal zirconium (0001), with oxide thickness on the order of 1 nm, was probed by synchrotron x-ray photoelectron spectroscopy. Quantitative analysis of the Zr 3d spectrum by the spectrum reconstruction method demonstrated the formation of Zr1+, Zr2+, and Zr3+ as non-equilibrium oxidation states, in addition to Zr4+ in the stoichiometric ZrO2. This finding resolves the long-debated question of whether it is possible to form any valence states between Zr0 and Zr4+ at the metal-oxide interface. As a result, the presence of local strong electric fields and the minimization of interfacial energy are assessed and demonstrated as mechanisms that can drive the formation of these non-equilibrium valence states of Zr.

  11. Control of cerium oxidation state through metal complex secondary structures

    SciTech Connect

    Levin, Jessica R.; Dorfner, Walter L.; Carroll, Patrick J.; Schelter, Eric J.

    2015-08-11

    A series of alkali metal cerium diphenylhydrazido complexes, Mx(py)y[Ce(PhNNPh)4], M = Li, Na, and K, x = 4 (Li and Na) or 5 (K), and y = 4 (Li), 8 (Na), or 7 (K), were synthesized to probe how a secondary coordination sphere would modulate electronic structures at a cerium cation. The resulting electronic structures of the heterobimetallic cerium diphenylhydrazido complexes were found to be strongly dependent on the identity of the alkali metal cations. When M = Li+ or Na+, the cerium(III) starting material was oxidized with concomitant reduction of 1,2-diphenylhydrazine to aniline. Reduction of 1,2-diphenylhydrazine was not observed when M = K+, and the complex remained in the cerium(III) oxidation state. Oxidation of the cerium(III) diphenylhydrazido complex to the Ce(IV) diphenylhydrazido one was achieved through a simple cation exchange reaction of the alkali metals. As a result, UV-Vis spectroscopy, FTIR spectroscopy, electrochemistry, magnetic susceptibility, and DFT studies were used to probe the oxidation state and the electronic changes that occurred at the metal centre.

  12. Control of cerium oxidation state through metal complex secondary structures

    DOE PAGESBeta

    Levin, Jessica R.; Dorfner, Walter L.; Carroll, Patrick J.; Schelter, Eric J.

    2015-08-11

    A series of alkali metal cerium diphenylhydrazido complexes, Mx(py)y[Ce(PhNNPh)4], M = Li, Na, and K, x = 4 (Li and Na) or 5 (K), and y = 4 (Li), 8 (Na), or 7 (K), were synthesized to probe how a secondary coordination sphere would modulate electronic structures at a cerium cation. The resulting electronic structures of the heterobimetallic cerium diphenylhydrazido complexes were found to be strongly dependent on the identity of the alkali metal cations. When M = Li+ or Na+, the cerium(III) starting material was oxidized with concomitant reduction of 1,2-diphenylhydrazine to aniline. Reduction of 1,2-diphenylhydrazine was not observedmore » when M = K+, and the complex remained in the cerium(III) oxidation state. Oxidation of the cerium(III) diphenylhydrazido complex to the Ce(IV) diphenylhydrazido one was achieved through a simple cation exchange reaction of the alkali metals. As a result, UV-Vis spectroscopy, FTIR spectroscopy, electrochemistry, magnetic susceptibility, and DFT studies were used to probe the oxidation state and the electronic changes that occurred at the metal centre.« less

  13. Evolution of the Oxidation State of the Earth's Mantle

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Righter, K.; Keller, L.; Christoffersen, E.; Rahman, Z.

    2015-01-01

    The oxidation state of the Earth's mantle during formation remains an unresolved question, whether it was constant throughout planetary accretion, transitioned from reduced to oxidized, or from oxidized to reduced. We investigate the stability of Fe3(+) at depth, in order to constrain processes (water, late accretion, dissociation of FeO) which may reduce or oxidize the Earth's mantle. In our previous experiments on shergottite compositions, variable fO2, T, and P less than 4 GPa, Fe3(+)/sigma Fe decreased slightly with increasing P, similar to terrestrial basalt. For oxidizing experiments less than 7GPa, Fe3(+)/sigma Fe decreased as well, but it's unclear from previous modelling whether the deeper mantle could retain significant Fe3(+). Our current experiments expand our pressure range deeper into the Earth's mantle and focus on compositions and conditions relevant to the early Earth. Preliminary multi-anvil experiments with Knippa basalt as the starting composition were conducted at 5-7 GPa and 1800 C, using a molybdenum capsule to set the fO2 near IW, by buffering with Mo-MoO3. TEM and EELS analyses revealed the run products quenched to polycrystalline phases, with the major phase pyroxene containing approximately equal to Fe3(+)/2(+). Experiments are underway to produce glassy samples that can be measured by EELS and XANES, and are conducted at higher pressures.

  14. Rigorous Definition of Oxidation States of Ions in Solids

    NASA Astrophysics Data System (ADS)

    Jiang, Lai; Levchenko, Sergey V.; Rappe, Andrew M.

    2012-04-01

    We present justification and a rigorous procedure for electron partitioning among atoms in extended systems. The method is based on wave-function topology and the modern theory of polarization, rather than charge density partitioning or wave-function projection, and, as such, reformulates the concept of oxidation state without assuming real-space charge transfer between atoms. This formulation provides rigorous electrostatics of finite-extent solids, including films and nanowires.

  15. Pentavalent Uranium Chemistry - Synthetic Pursuit Of A Rare Oxidation State

    SciTech Connect

    Graves, Christopher R; Kiplinger, Jaqueline L

    2009-01-01

    This feature article presents a comprehensive overview of pentavalent uranium systems in non-aqueous solution with a focus on the various synthetic avenues employed to access this unusual and very important oxidation state. Selected characterization data and theoretical aspects are also included. The purpose is to provide a perspective on this rapidly evolving field and identify new possibilities for future developments in pentavalent uranium chemistry.

  16. Systematic view of optical absorption spectra in the actinide series

    SciTech Connect

    Carnall, W.T.

    1985-01-01

    In recent years sufficient new spectra of actinides in their numerous valence states have been measured to encourage a broader scale analysis effort than was attempted in the past. Theoretical modelling in terms of effective operators has also undergone development. Well established electronic structure parameters for the trivalent actinides are being used as a basis for estimating parameters in other valence states and relationships to atomic spectra are being extended. Recent contributions to our understanding of the spectra of 4+ actinides have been particularly revealing and supportive of a developing general effort to progress beyond a preoccupation with modelling structure to consideration of the much broader area of structure-bonding relationships. We summarize here both the developments in modelling electronic structure and the interpretation of apparent trends in bonding. 60 refs., 9 figs., 1 tab.

  17. FY2010 Annual Report for the Actinide Isomer Detection Project

    SciTech Connect

    Warren, Glen A.; Francy, Christopher J.; Ressler, Jennifer J.; Erikson, Luke E.; Miller, Erin A.; Hatarik, R.

    2011-01-01

    This project seeks to identify a new signature for actinide element detection in active interrogation. This technique works by exciting and identifying long-lived nuclear excited states (isomers) in the actinide isotopes and/or primary fission products. Observation of isomers in the fission products will provide a signature for fissile material. For the actinide isomers, the decay time and energy of the isomeric state is unique to a particular isotope, providing an unambiguous signature for Special Nuclear Materials (SNM). Future work will include a follow-up measurement scheduled for December 2010 at LBNL. Lessons learned from the July 2010 measurements will be incorporated into these new measurements. Analysis of both the July and December experiments will be completed in a few months. A research paper to be submitted to a peer-reviewed journal will be drafted if the conclusions from the measurements warrant publication.

  18. Oxidation states of uranium in depleted uranium particles from Kuwait.

    PubMed

    Salbu, B; Janssens, K; Lind, O C; Proost, K; Gijsels, L; Danesi, P R

    2005-01-01

    The oxidation states of uranium in depleted uranium (DU) particles were determined by synchrotron radiation based mu-XANES, applied to individual particles isolated from selected samples collected at different sites in Kuwait. Based on scanning electron microscopy with X-ray microanalysis prior to mu-XANES, DU particles ranging from submicrons to several hundred micrometers were observed. The median particle size depended on sources and sampling sites; small-sized particles (median 13 microm) were identified in swipes taken from the inside of DU penetrators holes in tanks and in sandy soil collected below DU penetrators, while larger particles (median 44 microm) were associated with fire in a DU ammunition storage facility. Furthermore, the (236)U/(235)U ratios obtained from accelerator mass spectrometry demonstrated that uranium in the DU particles originated from reprocessed fuel (about 10(-2) in DU from the ammunition facility, about 10(-3) for DU in swipes). Compared to well-defined standards, all investigated DU particles were oxidized. Uranium particles collected from swipes were characterized as UO(2), U(3)O(8) or a mixture of these oxidized forms, similar to that observed in DU affected areas in Kosovo. Uranium particles formed during fire in the DU ammunition facility were, however, present as oxidation state +5 and +6, with XANES spectra similar to solid uranyl standards. Environmental or health impact assessments for areas affected by DU munitions should therefore take into account the presence of respiratory UO(2), U(3)O(8) and even UO(3) particles, their corresponding weathering rates and the subsequent mobilisation of U from oxidized DU particles. PMID:15511555

  19. Atomic solid state energy scale: Universality and periodic trends in oxidation state

    NASA Astrophysics Data System (ADS)

    Pelatt, Brian D.; Kokenyesi, Robert S.; Ravichandran, Ram; Pereira, Clifford B.; Wager, John F.; Keszler, Douglas A.

    2015-11-01

    The atomic solid state energy (SSE) scale originates from a plot of the electron affinity (EA) and ionization potential (IP) versus band gap (EG). SSE is estimated for a given atom by assessing an average EA (for a cation) or an average IP (for an anion) for binary inorganic compounds having that specific atom as a constituent. Physically, SSE is an experimentally-derived average frontier orbital energy referenced to the vacuum level. In its original formulation, 69 binary closed-shell inorganic semiconductors and insulators were employed as a database, providing SSE estimates for 40 elements. In this contribution, EA and IP versus EG are plotted for an additional 92 compounds, thus yielding SSE estimates for a total of 64 elements from the s-, p-, d-, and f-blocks of the periodic table. Additionally, SSE is refined to account for its dependence on oxidation state. Although most cations within the SSE database are found to occur in a single oxidation state, data are available for nine d-block transition metals and one p-block main group metal in more than one oxidation state. SSE is deeper in energy for a higher cation oxidation state. Two p-block main group non-metals within the SSE database are found to exist in both positive and negative oxidation states so that they can function as a cation or anion. SSEs for most cations are positioned above -4.5 eV with respect to the vacuum level, and SSEs for all anions are positioned below. Hence, the energy -4.5 eV, equal to the hydrogen donor/acceptor ionization energy ε(+/-) or equivalently the standard hydrogen electrode energy, is considered to be an absolute energy reference for chemical bonding in the solid state.

  20. Optoelectronic properties of valence-state-controlled amorphous niobium oxide

    NASA Astrophysics Data System (ADS)

    Onozato, Takaki; Katase, Takayoshi; Yamamoto, Akira; Katayama, Shota; Matsushima, Koichi; Itagaki, Naho; Yoshida, Hisao; Ohta, Hiromichi

    2016-06-01

    In order to understand the optoelectronic properties of amorphous niobium oxide (a-NbO x ), we have investigated the valence states, local structures, electrical resistivity, and optical absorption of a-NbO x thin films with various oxygen contents. It was found that the valence states of Nb ion in a-NbO x films can be controlled from 5+  to 4+  by reducing oxygen pressure during film deposition at room temperature, together with changing the oxide-ion arrangement around Nb ion from Nb2O5-like to NbO2-like local structure. As a result, a four orders of magnitude reduction in the electrical resistivity of a-NbO x films was observed with decreasing oxygen content, due to the carrier generation caused by the appearance and increase of an oxygen-vacancy-related subgap state working as an electron donor. The tunable optoelectronic properties of a-NbO x films by valence-state-control with oxygen-vacancy formation will be useful for potential flexible optoelectronic device applications.

  1. Optoelectronic properties of valence-state-controlled amorphous niobium oxide.

    PubMed

    Onozato, Takaki; Katase, Takayoshi; Yamamoto, Akira; Katayama, Shota; Matsushima, Koichi; Itagaki, Naho; Yoshida, Hisao; Ohta, Hiromichi

    2016-06-29

    In order to understand the optoelectronic properties of amorphous niobium oxide (a-NbO x ), we have investigated the valence states, local structures, electrical resistivity, and optical absorption of a-NbO x thin films with various oxygen contents. It was found that the valence states of Nb ion in a-NbO x films can be controlled from 5+  to 4+  by reducing oxygen pressure during film deposition at room temperature, together with changing the oxide-ion arrangement around Nb ion from Nb2O5-like to NbO2-like local structure. As a result, a four orders of magnitude reduction in the electrical resistivity of a-NbO x films was observed with decreasing oxygen content, due to the carrier generation caused by the appearance and increase of an oxygen-vacancy-related subgap state working as an electron donor. The tunable optoelectronic properties of a-NbO x films by valence-state-control with oxygen-vacancy formation will be useful for potential flexible optoelectronic device applications. PMID:27168317

  2. Simultaneous separation and detection of actinides in acidic solutions using an extractive scintillating resin.

    PubMed

    Roane, J E; DeVol, T A

    2002-11-01

    An extractive scintillating resin was evaluated for the simultaneous separation and detection of actinides in acidic solutions. The transuranic extractive scintillating (TRU-ES) resin is composed of an inert macroporous polystyrene core impregnated with organic fluors (diphenyloxazole and 1,4-bis-(4-methyl-5-phenyl-2-oxazolyl)benzene) and an extractant (octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide in tributyl phosphate). The TRU-ES resin was packed into FEP Teflon tubing to produce a flow cell (0.2-mL free column volume), which is placed into a scintillation detection system to obtain pulse height spectra and time series data during loading and elution of actinides onto/from the resin. The alpha-particle absolute detection efficiencies ranged from 77% to 96.5%, depending on the alpha energy and quench. In addition to the on-line analyses, off-line analyses of the effluent can be conducted using conventional detection methods. The TRU-ES resin was applied to the quantification of a mixed radionuclide solution and two actual waste samples. The on-line characterization of the mixed radionuclide solution was within 10% of the reported activities whereas the agreement with the waste samples was not as good due to sorption onto the sample container walls and the oxidation state of plutonium. Agreement between the on-line and off-line analyses was within 35% of one another for both waste samples. PMID:12433098

  3. Arsenic removal from water using flame-synthesized iron oxide nanoparticles with variable oxidation states

    PubMed Central

    Abid, Aamir D.; Kanematsu, Masakazu; Young, Thomas M.; Kennedy, Ian M.

    2013-01-01

    We utilized gas-phase diffusion flame synthesis, which has potential for large-scale production of metal oxide nanoparticles, to produce iron oxide nanoparticles (IONPs) with variable oxidation states. The efficacy of these materials in removal of arsenate (As(V) ) from water was assessed. Two different flame configurations, a diffusion flame (DF) and an inverse diffusion flame (IDF), were employed to synthesize six different IONPs by controlling flame conditions. The IONPs produced in the IDF configuration (IDF-IONPs) had smaller particle diameters (4.8 – 8.2 nm) and larger surface areas (141–213 m2/g) than the IONPs produced in the DF configuration (29 nm, 36 m2/g), which resulted in their higher adsorption capacities. As(V) adsorption capacities of the IDF-IONPs increased when the IONPs were synthesized in more oxidizing conditions. The fully oxidized IDF-IONPs, maghemite (γ-Fe2O3), showed the highest As(V) adsorption capacity, comparable to that of magnetite nanocrystals synthesized by thermal decomposition of iron pentacarbonyl and equivalent to three to four times higher capacity than that of a commonly used goethite-based adsorbent. All IONPs were magnetically responsive, which is of great importance for solid−liquid separation. This study demonstrates that the IONPs synthesized in gas-phase flame, particularly IDF-IONPs, are excellent adsorbents because of their high As(V) sorption capacity, potential for large-scale production, and useful magnetic property. PMID:23645964

  4. Evaluating tantalum oxide stoichiometry and oxidation states for optimal memristor performance

    SciTech Connect

    Brumbach, Michael T. Mickel, Patrick R.; Lohn, Andrew J.; Mirabal, Alex J.; Kalan, Michael A.; Stevens, James E.; Marinella, Matthew J.

    2014-09-01

    Tantalum oxide has shown promising electrical switching characteristics for memristor devices. Consequently, a number of reports have investigated the electrical behavior of TaO{sub x} thin films. Some effort has been made to characterize the composition of the TaO{sub x} films and it is known that there must be an optimal stoichiometry of TaO{sub x} where forming and switching behavior are optimized. However, many previous reports lack details on the methodology used for identifying the chemistry of the films. X-ray photoelectron spectroscopy has been the most commonly used technique; however, peak fitting routines vary widely among reports and a native surface oxide of Ta{sub 2}O{sub 5} often confounds the analysis. In this report a series of large area TaO{sub x} films were deposited via sputtering with controlled O{sub 2} partial pressures in the sputtering gas, resulting in tunable oxide compositions. Spectra from numerous samples from each wafer spanning a range of oxide stoichiometries were used to develop a highly constrained peak fitting routine. This procedure allowed for the composition of the TaO{sub x} films to be identified with greater detail than elemental ratios alone. Additionally, the peak fitting routine was used to evaluate uniformity of deposition across individual wafers. The appearance of a greater contribution of Ta{sup 4+} oxidation states in the oxygen starved films are believed to relate to films with optimal forming characteristics.

  5. Electronic Structure of AC-Clusters and High-Resolution X-ray Spectra of Actinides in Solids

    SciTech Connect

    Kulagin, Nicolay Alex

    2007-07-01

    Ab initio calculations using SCF approach for and analysis of results of investigation of the electronic structure of the clusters RAn+:[L]k with rare earths or actinides were carried out for the clusters in solids and liquids. Theoretical results for the electronic structure, radial integrals and energy of X- ray lines are presented for AC ions with unoccupied 5f-shell in the clusters in oxides, chlorides and fluorides environment. Possibility of collapse of nf-shell for the separate clusters and identification of electronic state of ions with unstable nuclei, are discussed, too. (author)

  6. Photoelectron spectroscopy and theoretical studies of gaseous uranium hexachlorides in different oxidation states: UCl6 (q-) (q = 0-2).

    PubMed

    Su, Jing; Dau, Phuong D; Liu, Hong-Tao; Huang, Dao-Ling; Wei, Fan; Schwarz, W H E; Li, Jun; Wang, Lai-Sheng

    2015-04-01

    Uranium chlorides are important in actinide chemistry and nuclear industries, but their chemical bonding and many physical and chemical properties are not well understood yet. Here, we report the first experimental observation of two gaseous uranium hexachloride anions, UCl6 (-) and UCl6 (2-), which are probed by photoelectron spectroscopy in conjunction with quantum chemistry calculations. The electron affinity of UCl6 is measured for the first time as +5.3 eV; its second electron affinity is measured to be +0.60 eV from the photoelectron spectra of UCl6 (2-). We observe that the detachment cross sections of the 5f electrons are extremely weak in the visible and UV energy ranges. It is found that the one-electron one-determinental molecular orbital picture and Koopmans' theorem break down for the strongly internally correlated U-5f(2) valence shell of tetravalent U(+4) in UCl6 (2-). The calculated adiabatic and vertical electron detachment energies from ab initio calculations agree well with the experimental observations. Electronic structure and chemical bonding in the uranium hexachloride species UCl6 (2-) to UCl6 are discussed as a function of the oxidation state of U. PMID:25854244

  7. Photoelectron spectroscopy and theoretical studies of gaseous uranium hexachlorides in different oxidation states: UCl6q- (q = 0-2)

    NASA Astrophysics Data System (ADS)

    Su, Jing; Dau, Phuong D.; Liu, Hong-Tao; Huang, Dao-Ling; Wei, Fan; Schwarz, W. H. E.; Li, Jun; Wang, Lai-Sheng

    2015-04-01

    Uranium chlorides are important in actinide chemistry and nuclear industries, but their chemical bonding and many physical and chemical properties are not well understood yet. Here, we report the first experimental observation of two gaseous uranium hexachloride anions, UCl6- and UCl62-, which are probed by photoelectron spectroscopy in conjunction with quantum chemistry calculations. The electron affinity of UCl6 is measured for the first time as +5.3 eV; its second electron affinity is measured to be +0.60 eV from the photoelectron spectra of UCl62-. We observe that the detachment cross sections of the 5f electrons are extremely weak in the visible and UV energy ranges. It is found that the one-electron one-determinental molecular orbital picture and Koopmans' theorem break down for the strongly internally correlated U-5f2 valence shell of tetravalent U+4 in UCl62-. The calculated adiabatic and vertical electron detachment energies from ab initio calculations agree well with the experimental observations. Electronic structure and chemical bonding in the uranium hexachloride species UCl62- to UCl6 are discussed as a function of the oxidation state of U.

  8. Features of the Thermodynamics of Trivalent Lanthanide/Actinide Distribution Reactions by Tri-n-Octylphosphine Oxide and Bis(2-EthylHexyl) Phosphoric Acid

    SciTech Connect

    Travis S. Grimes; Peter R. Zalupski

    2014-11-01

    A new methodology has been developed to study the thermochemical features of the biphasic transfer reactions of trisnitrato complexes of lanthanides and americium by a mono-functional solvating ligand (tri-n-octyl phosphine oxide - TOPO). Stability constants for successive nitrato complexes (M(NO3)x3-x (aq) where M is Eu3+, Am3+ or Cm3+) were determined to assist in the calculation of the extraction constant, Kex, for the metal ions under study. Enthalpies of extraction (?Hextr) for the lanthanide series (excluding Pm3+) and Am3+ by TOPO have been measured using isothermal titration calorimetry. The observed ?Hextr were found to be constant at ~29 kJ mol-1across the series from La3+-Er3+, with a slight decrease observed from Tm3+-Lu3+. These heats were found to be consistent with enthalpies determined using van ’t Hoff analysis of temperature dependent extraction studies. A complete set of thermodynamic parameters (?G, ?H, ?S) was calculated for Eu(NO3)3, Am(NO3)3 and Cm(NO3)3 extraction by TOPO and Am3+ and Cm3+ extraction by bis(2-ethylhexyl) phosphoric acid (HDEHP). A discussion comparing the energetics of these systems is offered. The measured biphasic extraction heats for the transplutonium elements, ?Hextr, presented in these studies are the first ever direct measurements offered using two-phase calorimetric techniques.

  9. Actinides and Life's Origins

    NASA Astrophysics Data System (ADS)

    Adam, Zachary

    2007-12-01

    There are growing indications that life began in a radioactive beach environment. A geologic framework for the origin or support of life in a Hadean heavy mineral placer beach has been developed, based on the unique chemical properties of the lower-electronic actinides, which act as nuclear fissile and fertile fuels, radiolytic energy sources, oligomer catalysts, and coordinating ions (along with mineralogically associated lanthanides) for prototypical prebiotic homonuclear and dinuclear metalloenzymes. A four-factor nuclear reactor model was constructed to estimate how much uranium would have been required to initiate a sustainable fission reaction within a placer beach sand 4.3 billion years ago. It was calculated that about 1-8 weight percent of the sand would have to have been uraninite, depending on the weight percent, uranium enrichment, and quantity of neutron poisons present within the remaining placer minerals. Radiolysis experiments were conducted with various solvents with the use of uranium- and thorium-rich minerals (metatorbernite and monazite, respectively) as proxies for radioactive beach sand in contact with different carbon, hydrogen, oxygen, and nitrogen reactants. Radiation bombardment ranged in duration of exposure from 3 weeks to 6 months. Low levels of acetonitrile (estimated to be on the order of parts per billion in concentration) were conclusively identified in 2 setups and tentatively indicated in a 3rd by gas chromatography/mass spectrometry. These low levels have been interpreted within the context of a Hadean placer beach prebiotic framework to demonstrate the promise of investigating natural nuclear reactors as power production sites that might have assisted the origins of life on young rocky planets with a sufficiently differentiated crust/mantle structure. Future investigations are recommended to better quantify the complex relationships between energy release, radioactive grain size, fissionability, reactant phase, phosphorus

  10. Actinides and Life's Origins.

    PubMed

    Adam, Zachary

    2007-12-01

    There are growing indications that life began in a radioactive beach environment. A geologic framework for the origin or support of life in a Hadean heavy mineral placer beach has been developed, based on the unique chemical properties of the lower-electronic actinides, which act as nuclear fissile and fertile fuels, radiolytic energy sources, oligomer catalysts, and coordinating ions (along with mineralogically associated lanthanides) for prototypical prebiotic homonuclear and dinuclear metalloenzymes. A four-factor nuclear reactor model was constructed to estimate how much uranium would have been required to initiate a sustainable fission reaction within a placer beach sand 4.3 billion years ago. It was calculated that about 1-8 weight percent of the sand would have to have been uraninite, depending on the weight percent, uranium enrichment, and quantity of neutron poisons present within the remaining placer minerals. Radiolysis experiments were conducted with various solvents with the use of uraniumand thorium-rich minerals (metatorbernite and monazite, respectively) as proxies for radioactive beach sand in contact with different carbon, hydrogen, oxygen, and nitrogen reactants. Radiation bombardment ranged in duration of exposure from 3 weeks to 6 months. Low levels of acetonitrile (estimated to be on the order of parts per billion in concentration) were conclusively identified in 2 setups and tentatively indicated in a 3(rd) by gas chromatography/mass spectrometry. These low levels have been interpreted within the context of a Hadean placer beach prebiotic framework to demonstrate the promise of investigating natural nuclear reactors as power production sites that might have assisted the origins of life on young rocky planets with a sufficiently differentiated crust/mantle structure. Future investigations are recommended to better quantify the complex relationships between energy release, radioactive grain size, fissionability, reactant phase, phosphorus

  11. Hydrothermal method of preparation of actinide(IV) phosphate hydrogenphosphate hydrates and study of their conversion into actinide(IV) phosphate diphosphate solid solutions.

    PubMed

    Dacheux, N; Grandjean, S; Rousselle, J; Clavier, N

    2007-11-26

    Several compositions of Th2-x/2AnIVx/2(PO4)2(HPO4).H2O (An=U, Np, Pu) were prepared through hydrothermal precipitation from a mixture of nitric solutions containing cations and concentrated phosphoric acid. All the samples were fully characterized by X-ray diffraction, UV-vis, and infrared spectroscopies to check for the existence of thorium-actinide(IV) phosphate hydrogenphosphate hydrates solid solutions. Such compounds were obtained as single phases, up to x=4 for uranium, x=2 for neptunium, and x<4 for plutonium, the cations being fully maintained in the tetravalent oxidation state. In a second step, the samples obtained after heating crystallized precursors at high temperature (1100 degrees C) were characterized. Single-phase thorium-actinide(IV) phosphate-diphosphate solid solutions were obtained up to x=0.8 for Np(IV) and x=1.6 for Pu(IV). For higher substitution rates, polyphase systems composed by beta-TAnPD, An2O(PO4)2, and/or alpha-AnP2O7 were formed. Finally, this hydrothermal route of preparation was applied successfully to the synthesis of an original phosphate-based compound incorporating simultaneously tetravalent uranium, neptunium and plutonium. PMID:17973479

  12. Evaluation of actinide biosorption by microorganisms

    SciTech Connect

    Happel, A.M.

    1996-06-01

    Conventional methods for removing metals from aqueous solutions include chemical precipitation, chemical oxidation or reduction, ion exchange, reverse osmosis, electrochemical treatment and evaporation. The removal of radionuclides from aqueous waste streams has largely relied on ion exchange methods which can be prohibitively costly given increasingly stringent regulatory effluent limits. The use of microbial cells as biosorbants for heavy metals offers a potential alternative to existing methods for decontamination or recovery of heavy metals from a variety of industrial waste streams and contaminated ground waters. The toxicity and the extreme and variable conditions present in many radionuclide containing waste streams may preclude the use of living microorganisms and favor the use of non-living biomass for the removal of actinides from these waste streams. In the work presented here, we have examined the biosorption of uranium by non-living, non-metabolizing microbial biomass thus avoiding the problems associated with living systems. We are investigating biosorption with the long term goal of developing microbial technologies for the remediation of actinides.

  13. Effect of microorganisms on the plutonium oxidation states.

    PubMed

    Lukšienė, Benedikta; Druteikienė, Rūta; Pečiulytė, Dalia; Baltrūnas, Dalis; Remeikis, Vidmantas; Paškevičius, Algimantas

    2012-03-01

    Particular microbes from substrates at the low-level radioactive waste repository in the Ignalina NPP territory were exposed to (239)Pu (IV) at low pH under aerobic conditions. Pu(III) and Pu(IV) were separated and quantitatively evaluated using the modified anion exchange method and alpha spectrometry. Tested bacteria Bacillus mycoides and Serratia marcescens were more effective in Pu reduction than Rhodococcus fascians. Fungi Paecillomyces lilacinus and Absidia spinosa var. spinosa as well as bacterium Rhodococcus fascians did not alter the plutonium oxidation state. PMID:22112595

  14. Nuclear waste forms for actinides

    PubMed Central

    Ewing, Rodney C.

    1999-01-01

    The disposition of actinides, most recently 239Pu from dismantled nuclear weapons, requires effective containment of waste generated by the nuclear fuel cycle. Because actinides (e.g., 239Pu and 237Np) are long-lived, they have a major impact on risk assessments of geologic repositories. Thus, demonstrable, long-term chemical and mechanical durability are essential properties of waste forms for the immobilization of actinides. Mineralogic and geologic studies provide excellent candidate phases for immobilization and a unique database that cannot be duplicated by a purely materials science approach. The “mineralogic approach” is illustrated by a discussion of zircon as a phase for the immobilization of excess weapons plutonium. PMID:10097054

  15. Features of the thermodynamics of trivalent lanthanide/actinide distribution reactions by tri-n-octylphosphine oxide and bis(2-ethylhexyl) phosphoric acid.

    PubMed

    Grimes, Travis S; Zalupski, Peter R; Martin, Leigh R

    2014-11-01

    A new methodology has been developed to study the thermochemical features of the biphasic transfer reactions of trisnitrato complexes of lanthanides and americium by a monofunctional solvating ligand (tri-n-octylphosphine oxide, TOPO). Stability constants for successive nitrato complexes (M(NO3)x(3-x)(aq) where M is Eu(3+), Am(3+), or Cm(3+)) were determined to assist in the calculation of the extraction constant, K(ex), for the metal ions under study. Enthalpies of extraction (ΔH(extr)) for the lanthanide series (excluding Pm(3+)) and Am(3+) by TOPO have been measured using isothermal titration calorimetry. The observed ΔH(extr) were found to be constant at ~29 kJ mol(-1) across the series from La(3+) to Er(3+), with a slight decrease observed from Tm(3+) to Lu(3+). These heats were found to be consistent with enthalpies determined using van't Hoff analysis of temperature dependent extraction studies. A complete set of thermodynamic parameters (ΔG, ΔH, ΔS) was calculated for Eu(NO3)3, Am(NO3)3, and Cm(NO3)3 extraction by TOPO and Am(3+) and Cm(3+) extraction by bis(2-ethylhexyl) phosphoric acid (HDEHP). A discussion comparing the energetics of these systems is offered. The measured biphasic extraction heats for the transplutonium elements, ΔH(extr), presented in these studies are the first ever direct measurements offered using two-phase calorimetric techniques. PMID:25315891

  16. Interface controlled oxidation states in layered cobalt oxide nanoislands on gold.

    PubMed

    Walton, Alex S; Fester, Jakob; Bajdich, Michal; Arman, Mohammad A; Osiecki, Jacek; Knudsen, Jan; Vojvodic, Aleksandra; Lauritsen, Jeppe V

    2015-03-24

    Layered cobalt oxides have been shown to be highly active catalysts for the oxygen evolution reaction (OER; half of the catalytic "water splitting" reaction), particularly when promoted with gold. However, the surface chemistry of cobalt oxides and in particular the nature of the synergistic effect of gold contact are only understood on a rudimentary level, which at present prevents further exploration. We have synthesized a model system of flat, layered cobalt oxide nanoislands supported on a single crystal gold (111) substrate. By using a combination of atom-resolved scanning tunneling microscopy, X-ray photoelectron and absorption spectroscopies and density functional theory calculations, we provide a detailed analysis of the relationship between the atomic-scale structure of the nanoislands, Co oxidation states and substrate induced charge transfer effects in response to the synthesis oxygen pressure. We reveal that conversion from Co(2+) to Co(3+) can occur by a facile incorporation of oxygen at the interface between the nanoisland and gold, changing the islands from a Co-O bilayer to an O-Co-O trilayer. The O-Co-O trilayer islands have the structure of a single layer of β-CoOOH, proposed to be the active phase for the OER, making this system a valuable model in understanding of the active sites for OER. The Co oxides adopt related island morphologies without significant structural reorganization, and our results directly demonstrate that nanosized Co oxide islands have a much higher structural flexibility than could be predicted from bulk properties. Furthermore, it is clear that the gold/nanoparticle interface has a profound effect on the structure of the nanoislands, suggesting a possible promotion mechanism. PMID:25693621

  17. Oxidation states of uranium in DU particles from Kosovo.

    PubMed

    Salbu, B; Janssens, K; Lind, O C; Proost, K; Danesi, P R

    2003-01-01

    The oxidation states of uranium contained in depleted uranium (DU) particles were determined by synchrotron radiation based micro-XANES, applied to individual particles in soil samples collected at Ceja Mountain, Kosovo. Based on scanning electron microscopy (SEM) with XRMA prior to micro-XANES, DU particles ranging from submicrons to about 30 microm (average size: 2 microm or less) were identified. Compared to well-defined standards, all investigated DU particles were oxidized. About 50% of the DU particles were characterized as UO2, the remaining DU particles present were U3O8 or a mixture of oxidized forms (ca. 2/3 UO2, 1/3 U3O8). Since the particle weathering rate is expected to be higher for U3O8 than for UO2, the presence of respiratory U3O8 and UO2 particles, their corresponding weathering rates and subsequent remobilisation of U from DU particles should be included in the environmental or health impact assessments. PMID:12500803

  18. Actinide Thermodynamics at Elevated Temperatures

    SciTech Connect

    Friese, Judah I.; Rao, Linfeng; Xia, Yuanxian; Bachelor, Paula P.; Tian, Guoxin

    2007-11-16

    The postclosure chemical environment in the proposed Yucca Mountain repository is expected to experience elevated temperatures. Predicting migration of actinides is possible if sufficient, reliable thermodynamic data on hydrolysis and complexation are available for these temperatures. Data are scarce and scattered for 25 degrees C, and nonexistent for elevated temperatures. This collaborative project between LBNL and PNNL collects thermodynamic data at elevated temperatures on actinide complexes with inorganic ligands that may be present in Yucca Mountain. The ligands include hydroxide, fluoride, sulfate, phosphate and carbonate. Thermodynamic parameters of complexation, including stability constants, enthalpy, entropy and heat capacity of complexation, are measured with a variety of techniques including solvent extraction, potentiometry, spectrophotometry and calorimetry

  19. New cubic structure compounds as actinide host phases

    NASA Astrophysics Data System (ADS)

    Stefanovsky, S. V.; Yudintsev, S. V.; Livshits, T. S.

    2010-03-01

    structure oxide as an extra phase have leach and radiation resistance similar to the other well-known actinide waste forms.

  20. The Oxidation State of Europium in Halide Glasses

    PubMed Central

    Weber, J.K.R.; Vu, M.; Paßlick, C.; Schweizer, S.; Brown, D.E.; Johnson, C.E.; Johnson, J.A.

    2012-01-01

    The luminescent properties of divalent europium ions can be exploited to produce storage phosphors for x-ray imaging applications. The relatively high cost and limited availability of divalent europium halides makes it desirable to synthesize them from the readily available trivalent salts. In this work, samples of pure EuCl3 and fluoride glass melts doped with EuCl3 were processed at 700-800 °C in an inert atmosphere furnace. The Eu oxidation state in the resulting materials was determined using fluorescence and Mössbauer spectroscopy. Heat treatment of pure EuCl3 for 10 minutes at 710 °C resulted in a material comprising approximately equal amounts of Eu2+ and Eu3+. Glasses made using mixtures of EuCl2 and EuCl3 in the starting material contained both oxidation states. This paper describes the sample preparation and analysis and discusses the results in the context of chemical equilibria in the melts. PMID:22101252

  1. Crystal structures of human peroxiredoxin 6 in different oxidation states.

    PubMed

    Kim, Kyung Hee; Lee, Weontae; Kim, Eunice EunKyeong

    2016-09-01

    Peroxiredoxins (Prxs) are a family of antioxidant enzymes found ubiquitously. Prxs function not only as H2O2 scavengers but also as highly sensitive H2O2 sensors and signal transducers. Since reactive oxygen species are involved in many cellular metabolic and signaling processes, Prxs play important roles in various diseases. Prxs can be hyperoxidized to the sulfinic acid (SO2H) or sulfonic acid (SO3H) forms in the presence of high concentrations of H2O2. It is known that oligomerization of Prx is changed accompanying oxidation states, and linked to the function. Among the six Prxs in mammals, Prx6 is the only 1-Cys Prx. It is found in all organs in humans, unlike some 2-Cys Prxs, and is present in all species from bacteria to humans. In addition, Prx6 has Ca(2+)-independent phospholipase A2 (PLA2) activity. Thus far only the crystal structure of Prx in the oxidized state has been reported. In this study, we present the crystal structures of human Prx6 in the reduced (SH) and the sulfinic acid (SO2H) forms. PMID:27353378

  2. Andreev bound state at a strongly correlated oxide interface

    NASA Astrophysics Data System (ADS)

    Cheng, Guanglei; Tomczyk, Michelle; Tacla, Alexandre; Daley, Andrew; Lu, Shicheng; Veazey, Josh; Huang, Mengchen; Irvin, Patrick; Ryu, Sangwoo; Lee, Hyungwoo; Eom, Chang-Beom; Pekker, David; Levy, Jeremy

    Strongly correlated electrons at oxide interfaces give rise to a set of novel physics phenomena including superconductivity and magnetism. At the LaAlO3/SrTiO3 (LAO/STO) interface, signatures of strong electron pairing persist even for conditions where superconductivity is suppressed. Meanwhile, an Andreev bound state (ABS) is a single quasiparticle excitation that mediates pair transport in confined superconductor-normal systems. Here we report a transition from pair resonant transport to ABS in sketched single electron transistors at the LAO/STO interface. This transition is consistent with a change of electron-electron interaction from attractive to repulsive, occurring at or near the Lifshitz transition. Such new electronically tunable electron-electron interaction may be useful for quantum simulation and engineering of novel quantum states in oxide materials. We gratefully acknowledge support from AFOSR FA9550-10-1-0524 (JL, CBE), AFOSR FA9550-12-1-0057 (JL, CBE, AD), NSF DMR-1104191 (JL), ONR N00014-15-1-2847 (JL).

  3. Preparation and properties of a compound containing nickel in highest oxidation states

    SciTech Connect

    Nikol'skii, V.A.; Bekreneva, L.A.; Garmash, L.A.; Makashev, Yu.A.; Mikhailova, K.A.; Raikhel'son, L.B.; Shchelkunova, L.I.

    1986-04-10

    The purpose of this paper is to obtain nickel hydroxide oxide of the optimal composition both by chemical and by electrochemical oxidation for use as the cathode material in alkaline batteries. The authors selected the oxidation conditions (oxidant, component ratio) for production of gamma-NiOOH; hydrogen peroxide, potassium permanganate, and potassium persulfate were used as oxidants. Gamma-NiOOH was also obtained by electrochemical oxidation of nickel (II) oxide hydrate in alkaline solutions. In samples obtained by electrochemical oxidation virtually 100% of the nickel is in the highly oxidized state. It is shown that gamma-NiOOH obtained by both chemical and electrochemical oxidation is a complex individual compound containing nickel and in the highest oxidation states, Ni/sup 3 +/ and Ni/sup 4 +/, together with salt-forming potassium ions and water molecules. The gamma-NiOOH obtained may be used with success in galvanic cells.

  4. Oxidation states of Fe and Ti in blue sapphire

    NASA Astrophysics Data System (ADS)

    Wongrawang, P.; Monarumit, N.; Thammajak, N.; Wathanakul, P.; Wongkokua, W.

    2016-02-01

    X-ray absorption near-edge spectroscopy (XANES) can be used to study the oxidation state of a dilute system such as transition metal defects in solid-state samples. In blue sapphire, Fe and Ti are defects that cause the blue color. Inter-valence charge transfer (IVCT) between Fe2+ and Ti4+ has been proposed to describe the optical color’s origin. However, the existence of divalent iron cations has not been thoroughly investigated. Fluorescent XANES is therefore employed to study K-edge absorptions of Fe and Ti cations in various blue sapphire samples including natural, synthetic, diffused and heat-treated sapphires. All the samples showed an Fe absorption edge at 7124 eV, corresponding to the Fe3+ state; and Ti at 4984 eV, corresponding to Ti4+. From these results, we propose Fe3+-Ti4+ mixed acceptor states located at 1.75 eV and 2.14 eV above the valence band of corundum, that correspond to 710 nm and 580 nm bands of UV-vis absorption spectra, to describe the cause of the color of blue sapphire.

  5. Internal contamination by actinides after wounding: a robust rodent model for assessment of local and distant actinide retention.

    PubMed

    Griffiths, N M; Wilk, J C; Abram, M C; Renault, D; Chau, Q; Helfer, N; Guichet, C; Van der Meeren, A

    2012-08-01

    Internal contamination by actinides following wounding may occur in nuclear fuel industry workers or subsequent to terrorist activities, causing dissemination of radioactive elements. Contamination by alpha particle emitting actinides can result in pathological effects, either local or distant from the site of entry. The objective of the present study was to develop a robust experimental approach in the rat for short- and long- term actinide contamination following wounding by incision of the skin and muscles of the hind limb. Anesthetized rats were contaminated with Mixed OXide (MOX, uranium, plutonium oxides containing 7.1% plutonium) or plutonium nitrate (Pu nitrate) following wounding by deep incision of the hind leg. Actinide excretion and tissue levels were measured as well as histological changes from 2 h to 3 mo. Humid swabs were used for rapid evaluation of contamination levels and proved to be an initial guide for contamination levels. Although the activity transferred from wound to blood is higher after contamination with a moderately soluble form of plutonium (nitrate), at 7 d most of the MOX (98%) or Pu nitrate (87%) was retained at the wound site. Rapid actinide retention in liver and bone was observed within 24 h, which increased up to 3 mo. After MOX contamination, a more rapid initial urinary excretion of americium was observed compared with plutonium. At 3 mo, around 95% of activity remained at the wound site, and excretion of Pu and Am was extremely low. This experimental approach could be applied to other situations involving contamination following wounding including rupture of the dermal, vascular, and muscle barriers. PMID:22951478

  6. Oxidative state and oxidative metabolism of the heart from rats with adjuvant-induced arthritis.

    PubMed

    Schubert, Amanda Caroline; Wendt, Mariana Marques Nogueira; de Sá-Nakanishi, Anacharis Babeto; Amado, Ciomar Aparecida Bersani; Peralta, Rosane Marina; Comar, Jurandir Fernando; Bracht, Adelar

    2016-06-01

    The aim of the present work was to investigate, in a more extensive way, the oxidative state and parameters related to energy metabolism of the heart tissue of rats using the model of adjuvant-induced arthritis. The latter is a model for the human arthritic disease. Measurements were done in the total tissue homogenate, isolated mitochondria and cytosolic fraction. The adjuvant-induced arthritis caused several modifications in the oxidative state of the heart which, in general, indicate an increased oxidative stress (+80% reactive oxygen species), protein damage (+53% protein carbonyls) and lipid damage (+63% peroxidation) in the whole tissue. The distribution of these changes over the various cell compartments was frequently unequal. For example, protein carbonyls were increased in the whole tissue and in the cytosol, but not in the mitochondria. No changes in GSH content of the whole tissue were found, but it was increased in the mitochondria (+33%) and decreased in the cytosol (-19%). The activity of succinate dehydrogenase was 77% stimulated by arthritis; the activities of glutamate dehydrogenase, isocitrate dehydrogenase and cytochrome c oxidase were diminished by 31, 25 and 35.3%, respectively. In spite of these alterations, no changes in the mitochondrial respiratory activity and in the efficiency of energy transduction were found. It can be concluded that the adjuvant-induced arthritis in rats causes oxidative damage to the heart with an unequal intracellular distribution. Compared to the liver and brain the modifications caused by arthritis in the heart are less pronounced on variables such as GSH levels and protein integrity. Possibly this occurs because the antioxidant system of the heart is less impaired by arthritis than that reported for the former tissues. Even so, the modifications caused by arthritis represent an imbalanced situation that probably contributes to the cardiac symptoms of the arthritis disease. PMID:27032477

  7. Determination of actinides in urine and fecal samples

    SciTech Connect

    McKibbin, T.T.

    1992-12-31

    A method of determining the radioactivity of specific actinides that are carried in urine or fecal sample material is disclosed. The samples are ashed in a muffle furnace, dissolved in an acid, and then treated in a series of steps of reduction, oxidation, dissolution, and precipitation, including a unique step of passing a solution through a chloride form anion exchange resin for separation of uranium and plutonium from americium.

  8. Determination of actinides in urine and fecal samples

    DOEpatents

    McKibbin, Terry T.

    1993-01-01

    A method of determining the radioactivity of specific actinides that are carried in urine or fecal sample material is disclosed. The samples are ashed in a muffle furnace, dissolved in an acid, and then treated in a series of steps of reduction, oxidation, dissolution, and precipitation, including a unique step of passing a solution through a chloride form anion exchange resin for separation of uranium and plutonium from americium.

  9. Determination of actinides in urine and fecal samples

    DOEpatents

    McKibbin, T.T.

    1993-03-02

    A method of determining the radioactivity of specific actinides that are carried in urine or fecal sample material is disclosed. The samples are ashed in a muffle furnace, dissolved in an acid, and then treated in a series of steps of reduction, oxidation, dissolution, and precipitation, including a unique step of passing a solution through a chloride form anion exchange resin for separation of uranium and plutonium from americium.

  10. Separations of actinides, lanthanides and other metals

    DOEpatents

    Smith, Barbara F.; Jarvinen, Gordon D.; Ensor, Dale D.

    1995-01-01

    An organic extracting solution comprised of a bis(acylpyrazolone or a substituted bis(acylpyrazolone) and an extraction method useful for separating certain elements of the actinide series of the periodic table having a valence of four from one other, and also from one or more of the substances in a group consisting of hexavalent actinides, trivalent actinides, trivalent lanthanides, trivalent iron, trivalent aluminum, divalent metals, and monovalent metals and also from one or more of the substances in a group consisting of hexavalent actinides, trivalent actinides, trivalent lanthanides, trivalent iron, trivalent aluminum, divalent metals, and monovalent metals and also useful for separating hexavalent actinides from one or more of the substances in a group consisting of trivalent actinides, trivalent lanthanides, trivalent iron, trivalent aluminum, divalent metals, and monovalent metals.

  11. Determination of the oxidation states of metals and metalloids: An analytical review

    NASA Astrophysics Data System (ADS)

    Vodyanitskii, Yu. N.

    2013-12-01

    The hazard of many heavy metals/metalloids in the soil depends on their oxidation state. The problem of determining the oxidation state has been solved due to the use of synchrotron radiation methods with the analysis of the X-ray absorption near-edge structure (XANES). The determination of the oxidation state is of special importance for some hazardous heavy elements (arsenic, antimony, selenium, chromium, uranium, and vanadium). The mobility and hazard of each of these elements depend on its oxidation state. The mobilities are higher at lower oxidation states of As, Cr, V, and Se and at higher oxidation states of Sb and U. The determination of the oxidation state of arsenic has allowed revealing its fixation features in the rhizosphere of hydrophytes. The known oxidation states of chromium and uranium are used for the retention of these elements on geochemical barriers. Different oxidation states have been established for vanadium displacing iron in goethite. The determination of the oxidation state of manganese in the rhizosphere and the photosynthetic apparatus of plants is of special importance for agricultural chemists.

  12. Thermodynamic and Structural Investigation of Synthetic Actinide-Peptide Scaffolds.

    PubMed

    Safi, Samir; Jeanson, Aurélie; Roques, Jérome; Solari, Pier Lorenzo; Charnay-Pouget, Florence; Den Auwer, Christophe; Creff, Gaëlle; Aitken, David J; Simoni, Eric

    2016-01-19

    The complexation of uranium and europium, in oxidation states +VI and +III, respectively, was investigated with pertinent bio-inorganic systems. Three aspartate-rich pentapeptides with different structural properties were selected for study to rationalize the structure-affinity relationships. Thermodynamic results, crosschecked by both isothermal titration calorimetry and time-resolved laser fluorescence spectroscopy, showed different affinity depending on the peptide for both Eu(III) and U(VI). The thermodynamic aspects were correlated to structural predictions, which were acquired by density functional theory quantum chemical calculations and from IR and extended X-ray absorption fine structure experiments. The combination of these microscopic properties revealed that carbonyl-metal interactions affected the entropy in the case of europium, while the larger uranyl cation was mostly affected by preorganization and steric effects, so that the affinity was enhanced through enthalpy. The approach described here revealed various microscopic aspects governing peptide actinide affinity. Highlighting these mechanisms should certainly contribute to the rational synthesis of higher affinity biomimetic aspartic ligands. PMID:26727631

  13. Oxidation state determination of uranium in various uranium oxides: Photoacoustic spectroscopy complimented by photoluminescence studies

    NASA Astrophysics Data System (ADS)

    Gupta, Santosh K.; Dhobale, A. R.; Kumar, M.; Godbole, S. V.; Natarajan, V.

    2015-03-01

    Photoacoustic spectroscopy (PAS) has been utilized for the determination of U(IV). Initial experiments were carried out for determination of U(IV) in uranium tetra fluoride, and were further extended to the determination of U(IV) in uranium oxide samples having various O/M ratios like UO2.00, UO2.17, U3O8, and U3O7. All these oxides, since dark gray/black in color, were having featureless spectra in the visible region, hence solid state reaction of uranium oxide with ammonium bi-fluoride was utilized for the formation of U(IV) and U(VI) oxyfluorides, having narrow well resolved spectra, prior to estimation by Photoacoustic spectroscopy technique. The strong absorption for U(IV) complex at 630 nm was monitored using a He-Ne laser resulting in good sensitivity for determination of U(IV). It was observed that fluorinated uranium dioxide (UO2) is having spectra similar to U(IV); fluorinated uranium trioxide (UO3) is having spectra of uranyl only whereas Triuranium octoxide (U3O8) spectra consist of both U(IV) and uranyl component. This was further supported by photoluminescence studies.

  14. Heterogeneous magnetic state in nanocrystalline cupric oxide CuO

    NASA Astrophysics Data System (ADS)

    Yermakov, A. Ye.; Uimin, M. A.; Korolyov, A. V.; Mikhalev, K. N.; Pirogov, A. N.; Teplykh, A. E.; Shchegoleva, N. N.; Gaviko, V. S.; Byzov, I. V.; Maikov, V. V.

    2015-02-01

    This paper presents the results of investigations of the structural state and magnetic properties of nanocrystalline cupric oxide samples with average particle sizes of approximately 40 and 13 nm, which were synthesized by the electric explosion and gas phase methods, respectively. The samples have been studied using X-ray diffraction, neutron diffraction, magnetic measurements, high-resolution transmission electron microscopy, and copper nuclear magnetic resonance. It has been shown that, in the initial state, regardless of the synthesis method, CuO nanoparticles are characterized by a heterogeneous magnetic state, i.e., by the existence of long-range antiferromagnetic order, spontaneous magnetization, especially at low temperatures, and paramagnetic centers in the material. The ferromagnetic contribution is probably caused by the formation of magnetic polaron states due to the phase separation induced in the system by excess charge carriers as a result of the existence of point defects (vacancies in the anion sublattice) in the nanocrystalline state. In this state, there is an inhomogeneously broadened nuclear magnetic resonance spectrum, which is a superposition of the spectrum of the initial antiferromagnetic matrix and the spectrum of ferromagnetically ordered regions. At high concentrations of ferromagnetically ordered regions, the antiferromagnetic matrix exhibits a nuclear magnetic resonance spectrum of CuO nanoparticles, predominantly from regions with the ferromagnetic phase. The appearance of magnetization can also be partly due to the frustration of spins in CuO, and this state is presumably localized near the most imperfect surface of the nanoparticles. The magnetic susceptibility of nanoparticles in the initial state in strong magnetic fields is significantly higher than that for the annealed samples, which, most likely, is associated with the influence of the high concentration of magnetic polarons. No correlation between the ferromagnetic

  15. Molybdenum Catalyzed Ammonia Borane Dehydrogenation: Oxidation State Specific Mechanisms

    PubMed Central

    2015-01-01

    Though numerous catalysts for the dehydrogenation of ammonia borane (AB) are known, those that release >2 equiv of H2 are uncommon. Herein, we report the synthesis of Mo complexes supported by a para-terphenyl diphosphine ligand, 1, displaying metal–arene interactions. Both a Mo0 N2 complex, 5, and a MoII bis(acetonitrile) complex, 4, exhibit high levels of AB dehydrogenation, releasing over 2.0 equiv of H2. The reaction rate, extent of dehydrogenation, and reaction mechanism vary as a function of the precatalyst oxidation state. Several Mo hydrides (MoII(H)2, [MoII(H)]+, and [MoIV(H)3]+) relevant to AB chemistry were characterized. PMID:25034459

  16. Fusion-Fission Burner for Transuranic Actinides

    NASA Astrophysics Data System (ADS)

    Choi, Chan

    2013-10-01

    The 14-MeV DT fusion neutron spectrum from mirror confinement fusion can provide a unique capability to transmute the transuranic isotopes from light water reactors (LWR). The transuranic (TRU) actinides, high-level radioactive wastes, from spent LWR fuel pose serious worldwide problem with long-term decay heat and radiotoxicity. However, ``transmuted'' TRU actinides can not only reduce the inventory of the TRU in the spent fuel repository but also generate additional energy. Typical commercial LWR fuel assemblies for BWR (boiling water reactor) and PWR (pressurized water reactor) measure its assembly lengths with 4.470 m and 4.059 m, respectively, while its corresponding fuel rod lengths are 4.064 m and 3.851 m. Mirror-based fusion reactor has inherently simple geometry for transmutation blanket with steady-state reactor operation. Recent development of gas-dynamic mirror configuration has additional attractive feature with reduced size in central plasma chamber, thus providing a unique capability for incorporating the spent fuel assemblies into transmutation blanket designs. The system parameters for the gas-dynamic mirror-based hybrid burner will be discussed.

  17. Proteomic indicators of oxidation and hydration state in colorectal cancer

    PubMed Central

    2016-01-01

    New integrative approaches are needed to harness the potential of rapidly growing datasets of protein expression and microbial community composition in colorectal cancer. Chemical and thermodynamic models offer theoretical tools to describe populations of biomacromolecules and their relative potential for formation in different microenvironmental conditions. The average oxidation state of carbon (ZC) can be calculated as an elemental ratio from the chemical formulas of proteins, and water demand per residue (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}${\\overline{n}}_{{\\mathrm{H}}_{2}\\mathrm{O}}$\\end{document}n¯H2O) is computed by writing the overall formation reactions of proteins from basis species. Using results reported in proteomic studies of clinical samples, many datasets exhibit higher mean ZC or \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}${\\overline{n}}_{{\\mathrm{H}}_{2}\\mathrm{O}}$\\end{document}n¯H2O of proteins in carcinoma or adenoma compared to normal tissue. In contrast, average protein compositions in bacterial genomes often have lower ZC for bacteria enriched in fecal samples from cancer patients compared to healthy donors. In thermodynamic calculations, the potential for formation of the cancer-related proteins is energetically favored by changes in the chemical activity of H2O and fugacity of O2 that reflect the compositional differences. The compositional analysis suggests that a systematic change in chemical composition is an essential feature of cancer proteomes, and the thermodynamic descriptions show that the observed proteomic

  18. Manganese oxidation state mediates toxicity in PC12 cells

    SciTech Connect

    Reaney, S.H. . E-mail: stevereaney@hotmail.com; Smith, D.R.

    2005-06-15

    The role of the manganese (Mn) oxidation state on cellular Mn uptake and toxicity is not well understood. Therefore, undifferentiated PC12 cells were exposed to 0-200 {mu}M Mn(II)-chloride or Mn(III)-pyrophosphate for 24 h, after which cellular manganese levels were measured along with measures of cell viability, function, and cytotoxicity (trypan blue exclusion, medium lactate dehydrogenase (LDH), 8-isoprostanes, cellular ATP, dopamine, serotonin, H-ferritin, transferrin receptor (TfR), Mn-superoxide dismutase (MnSOD), and copper-zinc superoxide dismutase (CuZnSOD) protein levels). Exposures to Mn(III) >10 {mu}M produced 2- to 5-fold higher cellular manganese levels than equimolar exposures to Mn(II). Cell viability and ATP levels both decreased at the highest Mn(II) and Mn(III) exposures (150-200 {mu}M), while Mn(III) exposures produced increases in LDH activity at lower exposures ({>=}50 {mu}M) than did Mn(II) (200 {mu}M only). Mn(II) reduced cellular dopamine levels more than Mn(III), especially at the highest exposures (50% reduced at 200 {mu}M Mn(II)). In contrast, Mn(III) produced a >70% reduction in cellular serotonin at all exposures compared to Mn(II). Different cellular responses to Mn(II) exposures compared to Mn(III) were also observed for H-ferritin, TfR, and MnSOD protein levels. Notably, these differential effects of Mn(II) versus Mn(III) exposures on cellular toxicity could not simply be accounted for by the different cellular levels of manganese. These results suggest that the oxidation state of manganese exposures plays an important role in mediating manganese cytotoxicity.

  19. CHARACTERIZATION OF ACTINIDES IN SIMULATED ALKALINE TANK WASTE SLUDGES AND LEACHATES

    SciTech Connect

    Nash, Kenneth L.

    2008-11-20

    In this project, both the fundamental chemistry of actinides in alkaline solutions (relevant to those present in Hanford-style waste storage tanks), and their dissolution from sludge simulants (and interactions with supernatants) have been investigated under representative sludge leaching procedures. The leaching protocols were designed to go beyond conventional alkaline sludge leaching limits, including the application of acidic leachants, oxidants and complexing agents. The simulant leaching studies confirm in most cases the basic premise that actinides will remain in the sludge during leaching with 2-3 M NaOH caustic leach solutions. However, they also confirm significant chances for increased mobility of actinides under oxidative leaching conditions. Thermodynamic data generated improves the general level of experiemental information available to predict actinide speciation in leach solutions. Additional information indicates that improved Al removal can be achieved with even dilute acid leaching and that acidic Al(NO3)3 solutions can be decontaminated of co-mobilized actinides using conventional separations methods. Both complexing agents and acidic leaching solutions have significant potential to improve the effectiveness of conventional alkaline leaching protocols. The prime objective of this program was to provide adequate insight into actinide behavior under these conditions to enable prudent decision making as tank waste treatment protocols develop.

  20. METHOD OF MAINTAINING PLUTONIUM IN A HIGHER STATE OF OXIDATION DURING PROCESSING

    DOEpatents

    Thompson, S.G.; Miller, D.R.

    1959-06-30

    This patent deals with the oxidation of tetravalent plutonium contained in an aqueous acid solution together with fission products to the hexavalent state, prior to selective fission product precipitation, by adding to the solution bismuthate or ceric ions as the oxidant and a water-soluble dichromate as a holding oxidant. Both oxidant and holding oxidant are preferably added in greater than stoichiometric quantities with regard to the plutonium present.

  1. Redox state of plutonium in irradiated mixed oxide fuels

    NASA Astrophysics Data System (ADS)

    Degueldre, C.; Pin, S.; Poonoosamy, J.; Kulik, D. A.

    2014-03-01

    Nowadays, MOX fuels are used in about 20 nuclear power plants around the world. After irradiation, plutonium co-exists with uranium oxide. Due to the redox sensitive nature of UO2 other plutonium oxides than PuO2 potentially present in the fuel may interact with the matrix. The aim of this study is to determine which plutonium species are present in heterogeneous and homogeneous MOX. The results provided by X-ray Absorption Near Edge Spectroscopy (XANES) for non-irradiated as well as irradiated (center and periphery) homogeneous MOX fuel were published earlier and are completed by Extended X-ray Fine Structure (EXAFS) analysis in this work. The EXAFS signals have been extracted using the ATHENA code and the analyses were carried using EXCURE98 as performed earlier for an analogous element. EXAFS shows that plutonium redox state remains tetravalent in the solid solution and that the minor fraction of trivalent Pu must be below 10%. Independently, the study of homogeneous MOX was also approached by thermodynamics of solid solution of (U,Pu)O2. Such solid solutions were modeled using the Gibbs Energy Minimisation (GEM)-Selektor code (developed at LES, NES, PSI) supported by the literature data on such solid solutions. A comparative study was performed showing which plutonium oxides in their respective mole fractions are more likely to occur in (U,Pu)O2. In the modeling, these oxides were set as ideal and non-ideal solid solutions, as well as separate pure phases. Pu exists mainly as PuO2 in the case of separate phases, but can exist under its reduced forms, PuO1.61 and PuO1.5 in minor fraction i.e. ~15% in ideal solid solution (unlikely) and ~10% in non-ideal solid solution (likely) and at temperature around 1300 K. This combined thermodynamic and EXAFS studies confirm independently the results obtained so far by Pu XANES for the same MOX samples.

  2. Lessons Learned from Characterization, Performance Assessment, and EPA Regulatory Review of the 1996 Actinide Source Term for the Waste Isolation Pilot Plant

    SciTech Connect

    Larson, K.W.; Moore, R.C.; Nowak, E.J.; Papenguth, H.W.; Jow, H.

    1999-03-22

    The Waste Isolation Pilot Plant (WIPP) is a US Department of Energy (DOE) facility for the permanent disposal of transuranic waste from defense activities. In 1996, the DOE submitted the Title 40 CFR Part 191 Compliance Certification Application for the Waste Isolation Pilot Plant (CCA) to the US Environmental Protection Agency (EPA). The CCA included a probabilistic performance assessment (PA) conducted by Sandia National Laboratories to establish compliance with the quantitative release limits defined in 40 CFR 191.13. An experimental program to collect data relevant to the actinide source term began around 1989, which eventually supported the 1996 CCA PA actinide source term model. The actinide source term provided an estimate of mobile dissolved and colloidal Pu, Am, U, Th, and Np concentrations in their stable oxidation states, and accounted for effects of uncertainty in the chemistry of brines in waste disposal areas. The experimental program and the actinide source term included in the CCA PA underwent EPA review lasting more than 1 year. Experiments were initially conducted to develop data relevant to the wide range of potential future conditions in waste disposal areas. Interim, preliminary performance assessments and actinide source term models provided insight allowing refinement of experiments and models. Expert peer review provided additional feedback and confidence in the evolving experimental program. By 1995, the chemical database and PA predictions of WIPP performance were considered reliable enough to support the decision to add an MgO backfill to waste rooms to control chemical conditions and reduce uncertainty in actinide concentrations, especially for Pu and Am. Important lessons learned through the characterization, PA modeling, and regulatory review of the actinide source term are (1) experimental characterization and PA should evolve together, with neither activity completely dominating the other, (2) the understanding of physical processes

  3. Method for the recovery of actinide elements from nuclear reactor waste

    DOEpatents

    Horwitz, E. Philip; Delphin, Walter H.; Mason, George W.

    1979-01-01

    A process for partitioning and recovering actinide values from acidic waste solutions resulting from reprocessing of irradiated nuclear fuels by adding hydroxylammonium nitrate and hydrazine to the waste solution to adjust the valence of the neptunium and plutonium values in the solution to the +4 oxidation state, thus forming a feed solution and contacting the feed solution with an extractant of dihexoxyethyl phosphoric acid in an organic diluent whereby the actinide values, most of the rare earth values and some fission product values are taken up by the extractant. Separation is achieved by contacting the loaded extractant with two aqueous strip solutions, a nitric acid solution to selectively strip the americium, curium and rare earth values and an oxalate solution of tetramethylammonium hydrogen oxalate and oxalic acid or trimethylammonium hydrogen oxalate to selectively strip the neptunium, plutonium and fission product values. Uranium values remain in the extractant and may be recovered with a phosphoric acid strip. The neptunium and plutonium values are recovered from the oxalate by adding sufficient nitric acid to destroy the complexing ability of the oxalate, forming a second feed, and contacting the second feed with a second extractant of tricaprylmethylammonium nitrate in an inert diluent whereby the neptunium and plutonium values are selectively extracted. The values are recovered from the extractant with formic acid.

  4. Fission-product data analysis from actinide samples exposed in the Dounreay Prototype Fast Reactor

    SciTech Connect

    Murphy, B.D.; Dickens, J.K.; Walker, R.L.; Newton, T.D.

    1994-12-31

    Since 1979 a cooperative agreement has been in effect between the United States and the United Kingdom to investigate the irradiation of various actinide species placed in the core of the Dounreay Prototype Fast Reactor (PFR). The irradiated species were isotopes of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium. A set of actinide samples (mg quantities) was exposed to about 490 effective full power days (EFPD) of reactor operations. The fission-product results are reported here. The actinide results will be report elsewhere.

  5. "Computational Modeling of Actinide Complexes"

    SciTech Connect

    Balasubramanian, K

    2007-03-07

    We will present our recent studies on computational actinide chemistry of complexes which are not only interesting from the standpoint of actinide coordination chemistry but also of relevance to environmental management of high-level nuclear wastes. We will be discussing our recent collaborative efforts with Professor Heino Nitsche of LBNL whose research group has been actively carrying out experimental studies on these species. Computations of actinide complexes are also quintessential to our understanding of the complexes found in geochemical, biochemical environments and actinide chemistry relevant to advanced nuclear systems. In particular we have been studying uranyl, plutonyl, and Cm(III) complexes are in aqueous solution. These studies are made with a variety of relativistic methods such as coupled cluster methods, DFT, and complete active space multi-configuration self-consistent-field (CASSCF) followed by large-scale CI computations and relativistic CI (RCI) computations up to 60 million configurations. Our computational studies on actinide complexes were motivated by ongoing EXAFS studies of speciated complexes in geo and biochemical environments carried out by Prof Heino Nitsche's group at Berkeley, Dr. David Clark at Los Alamos and Dr. Gibson's work on small actinide molecules at ORNL. The hydrolysis reactions of urnayl, neputyl and plutonyl complexes have received considerable attention due to their geochemical and biochemical importance but the results of free energies in solution and the mechanism of deprotonation have been topic of considerable uncertainty. We have computed deprotonating and migration of one water molecule from the first solvation shell to the second shell in UO{sub 2}(H{sub 2}O){sub 5}{sup 2+}, UO{sub 2}(H{sub 2}O){sub 5}{sup 2+}NpO{sub 2}(H{sub 2}O){sub 6}{sup +}, and PuO{sub 2}(H{sub 2}O){sub 5}{sup 2+} complexes. Our computed Gibbs free energy(7.27 kcal/m) in solution for the first time agrees with the experiment (7.1 kcal

  6. Measurement of soil carbon oxidation state and oxidative ratio by 13C nuclear magnetic resonance

    USGS Publications Warehouse

    Hockaday, W.C.; Masiello, C.A.; Randerson, J.T.; Smernik, R.J.; Baldock, J.A.; Chadwick, O.A.; Harden, J.W.

    2009-01-01

    The oxidative ratio (OR) of the net ecosystem carbon balance is the ratio of net O2 and CO2 fluxes resulting from photosynthesis, respiration, decomposition, and other lateral and vertical carbon flows. The OR of the terrestrial biosphere must be well characterized to accurately estimate the terrestrial CO2 sink using atmospheric measurements of changing O2 and CO2 levels. To estimate the OR of the terrestrial biosphere, measurements are needed of changes in the OR of aboveground and belowground carbon pools associated with decadal timescale disturbances (e.g., land use change and fire). The OR of aboveground pools can be measured using conventional approaches including elemental analysis. However, measuring the OR of soil carbon pools is technically challenging, and few soil OR data are available. In this paper we test three solid-state nuclear magnetic resonance (NMR) techniques for measuring soil OR, all based on measurements of the closely related parameter, organic carbon oxidation state (Cox). Two of the three techniques make use of a molecular mixing model which converts NMR spectra into concentrations of a standard suite of biological molecules of known C ox. The third technique assigns Cox values to each peak in the NMR spectrum. We assess error associated with each technique using pure chemical compounds and plant biomass standards whose Cox and OR values can be directly measured by elemental analyses. The most accurate technique, direct polarization solid-state 13C NMR with the molecular mixing model, agrees with elemental analyses to ??0.036 Cox units (??0.009 OR units). Using this technique, we show a large natural variability in soil Cox and OR values. Soil Cox values have a mean of -0.26 and a range from -0.45 to 0.30, corresponding to OR values of 1.08 ?? 0.06 and a range from 0.96 to 1.22. We also estimate the OR of the carbon flux from a boreal forest fire. Analysis of soils from nearby intact soil profiles imply that soil carbon losses associated

  7. Measurement of soil carbon oxidation state and oxidative ratio by 13C nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Hockaday, W. C.; Masiello, C. A.; Randerson, J. T.; Smernik, R. J.; Baldock, J. A.; Chadwick, O. A.; Harden, J. W.

    2009-06-01

    The oxidative ratio (OR) of the net ecosystem carbon balance is the ratio of net O2 and CO2 fluxes resulting from photosynthesis, respiration, decomposition, and other lateral and vertical carbon flows. The OR of the terrestrial biosphere must be well characterized to accurately estimate the terrestrial CO2 sink using atmospheric measurements of changing O2 and CO2 levels. To estimate the OR of the terrestrial biosphere, measurements are needed of changes in the OR of aboveground and belowground carbon pools associated with decadal timescale disturbances (e.g., land use change and fire). The OR of aboveground pools can be measured using conventional approaches including elemental analysis. However, measuring the OR of soil carbon pools is technically challenging, and few soil OR data are available. In this paper we test three solid-state nuclear magnetic resonance (NMR) techniques for measuring soil OR, all based on measurements of the closely related parameter, organic carbon oxidation state (Cox). Two of the three techniques make use of a molecular mixing model which converts NMR spectra into concentrations of a standard suite of biological molecules of known Cox. The third technique assigns Cox values to each peak in the NMR spectrum. We assess error associated with each technique using pure chemical compounds and plant biomass standards whose Cox and OR values can be directly measured by elemental analyses. The most accurate technique, direct polarization solid-state 13C NMR with the molecular mixing model, agrees with elemental analyses to ±0.036 Cox units (±0.009 OR units). Using this technique, we show a large natural variability in soil Cox and OR values. Soil Cox values have a mean of -0.26 and a range from -0.45 to 0.30, corresponding to OR values of 1.08 ± 0.06 and a range from 0.96 to 1.22. We also estimate the OR of the carbon flux from a boreal forest fire. Analysis of soils from nearby intact soil profiles imply that soil carbon losses associated

  8. Iron Partitioning and Oxidation State in Earth's Lower Mantle

    NASA Astrophysics Data System (ADS)

    Piet, H.; Badro, J.; Nabiei, F.; Dennenwaldt, T.; Shim, S. H. D.; Cantoni, M.; Hébert, C.; Gillet, P.

    2015-12-01

    Valence state and concentrations of iron in lower mantle phases have strong effects on their chemical and physical properties. Experimental studies have reported stark differences in iron partitioning between bridgmanite (Brg) and ferropericlase (Fp) for San Carlos olivine [1] and pyrolite [2] systems. We recently performed experiments at lower mantle conditions for an Al-rich olivine system [3] and observed an iron enrichment of the silicate phase very similar to that in pyrolite. Mössbauer studies [4] have shown that in the presence of aluminum non negligible amounts of Fe3+ could be incorporated in bridgmanite explaining the observed iron enrichment. Non negligible amounts of Fe3+ in the lower mantle could influence transport properties of the phases [5]. The evaluation of ferrous and ferric iron concentrations in lower mantle mineral assemblages is then key to a thorough understanding of geophysical observations and associated mantle dynamics. We used electron energy loss spectroscopy technique to quantify the proportions of Fe2+ and Fe3+ iron in Brg and Fp phases previously synthesized from Al-rich olivine composition [3]. The oxidation state of iron in the lower mantle will be discussed as well as ensuing implications on transport properties for relevant lower mantle compositions. References [1] Sakai et al., 2009 [2] Prescher et al., 2014 [3] Piet et al., submitted [4] McCammon et al., 1996 [5] Xu et al., 1998

  9. The Concept of Oxidation States in Metal Complexes

    ERIC Educational Resources Information Center

    Steinborn, Dirk

    2004-01-01

    The concepts of oxidation numbers when applied means electrons that are shared between atoms in molecules are assigned to a specific atom. Oxidation numbers are assigned from the Lewis structure of a molecule, with knowledge of the electronegativities of elements.

  10. Process for recovering actinide values

    DOEpatents

    Horwitz, E. Philip; Mason, George W.

    1980-01-01

    A process for rendering actinide values recoverable from sodium carbonate scrub waste solutions containing these and other values along with organic compounds resulting from the radiolytic and hydrolytic degradation of neutral organophosphorous extractants such as tri-n butyl phosphate (TBP) and dihexyl-N,N-diethyl carbamylmethylene phosphonate (DHDECAMP) which have been used in the reprocessing of irradiated nuclear reactor fuels. The scrub waste solution is preferably made acidic with mineral acid, to form a feed solution which is then contacted with a water-immiscible, highly polar organic extractant which selectively extracts the degradation products from the feed solution. The feed solution can then be processed to recover the actinides for storage or recycled back into the high-level waste process stream. The extractant is recycled after stripping the degradation products with a neutral sodium carbonate solution.

  11. Actinide abundances in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Hagee, B.; Bernatowicz, T. J.; Podosek, F. A.; Johnson, M. L.; Burnett, D. S.

    1990-01-01

    Measurements of actinide and light REE (LREE) abundances and of phosphate abundances in equilibrated ordinary chondrites were obtained and were used to define the Pu abundance in the solar system and to determine the degree of variation of actinide and LREE abundances. The results were also used to compare directly the Pu/U ratio with the earlier obtained ratio determined indirectly, as (Pu/Nd)x(Nd/U), assuming that Pu behaves chemically as a LREE. The data, combined with high-accuracy isotope-dilution data from the literature, show that the degree of gram-scale variability of the Th, U, and LREE abundances for equilibrated ordinary chondrites is a factor of 2-3 for absolute abundances and up to 50 percent for relative abundances. The observed variations are interpreted as reflecting the differences in the compositions and/or proportions of solar nebula components accreted to ordinary chondrite parent bodies.

  12. Actinide partitioning-transmutation program final report. IV. Miscellaneous aspects. [Transport; fuel fabrication; decay; policy; economics

    SciTech Connect

    Alexander, C.W.; Croff, A.G.

    1980-09-01

    This report discusses seven aspects of actinide partitioning-transmutation (P-T) which are important in any complete evaluation of this waste treatment option but which do not fall within other major topical areas concerning P-T. The so-called miscellaneous aspects considered are (1) the conceptual design of a shipping cask for highly neutron-active fresh and spent P-T fuels, (2) the possible impacts of P-T on mixed-oxide fuel fabrication, (3) alternatives for handling the existing and to-be-produced spent fuel and/or wastes until implementation of P-T, (4) the decay and dose characteristics of P-T and standard reactor fuels, (5) the implications of P-T on currently existing nuclear policy in the United States, (6) the summary costs of P-T, and (7) methods for comparing the risks, costs, and benefits of P-T.

  13. Actinide chemistry using singlet-paired coupled cluster and its combinations with density functionals.

    PubMed

    Garza, Alejandro J; Sousa Alencar, Ana G; Scuseria, Gustavo E

    2015-12-28

    Singlet-paired coupled cluster doubles (CCD0) is a simplification of CCD that relinquishes a fraction of dynamic correlation in order to be able to describe static correlation. Combinations of CCD0 with density functionals that recover specifically the dynamic correlation missing in the former have also been developed recently. Here, we assess the accuracy of CCD0 and CCD0+DFT (and variants of these using Brueckner orbitals) as compared to well-established quantum chemical methods for describing ground-state properties of singlet actinide molecules. The f(0) actinyl series (UO2(2+), NpO2(3+), PuO2(4+)), the isoelectronic NUN, and thorium (ThO, ThO(2+)) and nobelium (NoO, NoO2) oxides are studied. PMID:26723650

  14. Actinide Waste Forms and Radiation Effects

    NASA Astrophysics Data System (ADS)

    Ewing, R. C.; Weber, W. J.

    Over the past few decades, many studies of actinides in glasses and ceramics have been conducted that have contributed substantially to the increased understanding of actinide incorporation in solids and radiation effects due to actinide decay. These studies have included fundamental research on actinides in solids and applied research and development related to the immobilization of the high level wastes (HLW) from commercial nuclear power plants and processing of nuclear weapons materials, environmental restoration in the nuclear weapons complex, and the immobilization of weapons-grade plutonium as a result of disarmament activities. Thus, the immobilization of actinides has become a pressing issue for the twenty-first century (Ewing, 1999), and plutonium immobilization, in particular, has received considerable attention in the USA (Muller et al., 2002; Muller and Weber, 2001). The investigation of actinides and

  15. Actinide recovery techniques utilizing electromechanical processes

    SciTech Connect

    Westphal, B.R.; Benedict, R.W.

    1994-01-01

    Under certain conditions, the separation of actinides using electromechanical techniques may be an effective means of residue processing. The separation of granular mixtures of actinides and other materials discussed in this report is based on appreciable differences in the magnetic and electrical properties of the actinide elements. In addition, the high density of actinides, particularly uranium and plutonium, may render a simultaneous separation based on mutually complementary parameters. Both high intensity magnetic separation and electrostatic separation have been investigated for the concentration of an actinide waste stream. Waste stream constituents include an actinide metal alloy and broken quartz shards. The investigation of these techniques is in support of the Integral Fast Reactor (IFR) concept currently being developed at Argonne National Laboratory under the auspices of the Department of Energy.

  16. Highly Oxidizing Excited States of One-Electron Oxidized Guanine in DNA: Wavelength and pH Dependence

    PubMed Central

    Khanduri, Deepti; Adhikary, Amitava; Sevilla, Michael D.

    2011-01-01

    Excited states of one-electron oxidized guanine in DNA are known to induce hole transfer to the sugar moiety and on deprotonation result in neutral sugar radicals that are precursors of DNA-strand breaks. This work carried out in homogeneous aqueous glass (7.5 M LiCl) at low temperatures (77 to 175 K) shows the extent of photoconversion of one-electron oxidized guanine and the associated yields of individual sugar radicals and are crucially controlled by photon energy, protonation state, and strandedness of the oligomer. In addition to forming sugar radicals, highly oxidizing excited states of one-electron oxidized guanine are produced with 405 nm light at pH 5 and below that are able to oxidize chloride ion in the surrounding solution to form Cl2•− via an excited state hole transfer process. Among the various DNA model systems studied in this work, the maximum amount of Cl2•− is produced with ds (double stranded) DNA where the one-electron oxidized guanine exists in its cation radical (G•+:C) form. Thus, via excited state hole transfer, the dsDNA is apparently able to protect itself from cation radical excited states by transfer of damage to the surrounding environment. PMID:21381665

  17. The Dirac equation in electronic structure calculations: Accurate evaluation of DFT predictions for actinides

    SciTech Connect

    Wills, John M; Mattsson, Ann E

    2012-06-06

    Brooks, Johansson, and Skriver, using the LMTO-ASA method and considerable insight, were able to explain many of the ground state properties of the actinides. In the many years since this work was done, electronic structure calculations of increasing sophistication have been applied to actinide elements and compounds, attempting to quantify the applicability of DFT to actinides and actinide compounds and to try to incorporate other methodologies (i.e. DMFT) into DFT calculations. Through these calculations, the limits of both available density functionals and ad hoc methodologies are starting to become clear. However, it has also become clear that approximations used to incorporate relativity are not adequate to provide rigorous tests of the underlying equations of DFT, not to mention ad hoc additions. In this talk, we describe the result of full-potential LMTO calculations for the elemental actinides, comparing results obtained with a full Dirac basis with those obtained from scalar-relativistic bases, with and without variational spin-orbit. This comparison shows that the scalar relativistic treatment of actinides does not have sufficient accuracy to provide a rigorous test of theory and that variational spin-orbit introduces uncontrolled errors in the results of electronic structure calculations on actinide elements.

  18. Forest soil carbon oxidation state and oxidative ratio responses to elevated CO2

    NASA Astrophysics Data System (ADS)

    Hockaday, William C.; Gallagher, Morgan E.; Masiello, Caroline A.; Baldock, Jeffrey A.; Iversen, Colleen M.; Norby, Richard J.

    2015-09-01

    The oxidative ratio (OR) of the biosphere is the stoichiometric ratio (O2/CO2) of gas exchange by photosynthesis and respiration—a key parameter in budgeting calculations of the land and ocean carbon sinks. Carbon cycle-climate feedbacks could alter the OR of the biosphere by affecting the quantity and quality of organic matter in plant biomass and soil carbon pools. This study considers the effect of elevated atmospheric carbon dioxide concentrations ([CO2]) on the OR of a hardwood forest after nine growing seasons of Free-Air CO2 Enrichment. We measured changes in the carbon oxidation state (Cox) of biomass and soil carbon pools as a proxy for the ecosystem OR. The OR of net primary production, 1.039, was not affected by elevated [CO2]. However, the Cox of the soil carbon pool was 40% higher at elevated [CO2], and the estimated OR values for soil respiration increased from 1.006 at ambient [CO2] to 1.054 at elevated [CO2]. A biochemical inventory of the soil organic matter ascribed the increases in Cox and OR to faster turnover of reduced substrates, lignin and lipids, at elevated [CO2]. This implicates the heterotrophic soil community response to elevated [CO2] as a driver of disequilibrium in the ecosystem OR. The oxidation of soil carbon pool constitutes an unexpected terrestrial O2 sink. Carbon budgets constructed under the assumption of OR equilibrium would equate such a terrestrial O2 sink to CO2 uptake by the ocean. The potential for climate-driven disequilibriua in the cycling of O2 and CO2 warrants further investigation.

  19. Sigma Team for Minor Actinide Separation: PNNL FY 2010 Status Report

    SciTech Connect

    Lumetta, Gregg J.; Sinkov, Sergey I.; Neiner, Doinita; Levitskaia, Tatiana G.; Braley, Jenifer C.; Carter, Jennifer C.; Warner, Marvin G.; Pittman, Jonathan W.; Rapko, Brian M.

    2010-08-24

    Work conducted at Pacific Northwest National Laboratory (PNNL) in FY 2010 addressed two lines of inquiry. The two hypotheses put forth were: 1. The extractants from the TRUEX( ) process (CMPO)( ) and from the TALSPEAK( ) process (HDEHP)( ) can be combined into a single process solvent to separate 1) the lanthanides and actinides from acidic high-level waste and 2) the actinides from the lanthanides in a single solvent extraction process. (Note: This combined process will hereafter be referred to as the TRUSPEAK process.) A series of empirical measurements performed (both at PNNL and Argonne National Laboratory) in FY 2009 supported this hypothesis, but also indicated some nuances to the chemistry. Lanthanide/americium separation factors of 12 and higher were obtained with a prototypic TRUSPEAK solvent when extracting the lanthanides from a citrate-buffered DTPA( ) solution. Although the observed separation factors are sufficiently high to design an actinide/lanthanide separation process, a better understanding of the chemistry is expected to lead to improved solvent formulations and improved process performance. Work in FY 2010 focused on understanding the synergistic extraction behavior observed for Nd(III) and Am(III) when extracted into mixtures of CMPO and HDEHP. The interaction between CMPO and HDEHP in dodecane was investigated by 31P NMR spectroscopy, and an adduct of the type CMPO•HDEHP was found to form. The formation of this adduct will reduce the effective extractant concentrations and must be taken into account when modeling metal ion extraction data in this system. Studies were also initiated to determine the Pitzer parameters for Nd(III) in lactate media. 2. Higher oxidation states (e.g., +5 and +6) of Am can be stabilized in solution by complexation with uranophilic ligands, and this chemistry can be exploited to separate Am from Cm. To test this hypothesis, the previously reported stereognostic uranophilic ligands NPB( ) and ETAC(e) were

  20. Oxidation State of Nakhlites as inferred from Fe-Ti oxide Equilibria and Augite/Melt Europium Partitioning

    NASA Technical Reports Server (NTRS)

    Makishima, J.; McKay, G.; Le, L.; Miyamoto, M.; Mikouchi, T.

    2007-01-01

    Recent studies have shown that Martian magmas had wide range of oxygen fugacities (fO2) and that this variation is correlated with the variation of La/Yb ratio and isotopic characteristics of the Martian basalts, shergottite meteorites. The origin of this correlation must have important information about mantle sources and Martian evolution. In order to understand this correlation, it is necessary to know accurate value of oxidation state of other Martian meteorite groups. Nakhlites, cumulate clinopyroxenites, are another major group of Martian meteorites and have distinctly different trace element and isotopic characteristics from shergottites. Thus, estimates of oxidation state of nakhlites will give us important insight into the mantle source in general. Several workers have estimated oxidation state of nakhlites by using Fe-Ti oxide equilibrium. However, Fe-Ti oxides may not record the oxidation state of the parent melt of the nakhlite because it is a late-stage mineral. Furthermore, there is no comprehensive study which analyzed all nakhlite samples at the same time. Therefore, in this study (1) we reduced the uncertainty of the estimate using the same electron microprobe and the same standards under the same condition for Fe-Ti oxide in 6 nakhlites and (2) we also performed crystallization experiments to measure partition coefficients of Eu into pyroxene in the nakhlite system in order to estimate fO2 when the pyroxene core formed (i.e. Eu oxybarometer [e.g. 2,6]).

  1. Actinide Binding by Kläui Ligands: REDOX Speciation and Sorption on an Extraction Chromatography Resin

    SciTech Connect

    Levitskaia, Tatiana G.; Sinkov, Sergey I.; Lumetta, Gregg J.

    2008-12-01

    The sorption of Eu(III) and actinide ions in various oxidation states from nitric acid solutions by an extraction chromatography resin containing 1 wt% of the Kläui ligand Cp*Co[P(O)(OR)2]3– [Cp* = pentamethylcyclopentadienyl, R = –CH2 CH2CH3] on Amberlite® XAD-7HP was examined. At 0.3 M HNO3 and a metal-to-ligand ratio of 0.07, the relative affinity of the resin for the ions investigated followed the order: tetravalent >> hexavalent > trivalent > pentavalent; however, the relative affinity for the trivalent and hexavalent ions can be reversed, depending on the extent of ligand loading and the nitric acid concentration. The sorption of the tetravalent ions was exceptionally strong in the entire range of nitric acid concentration examined (0.2 to 8 M HNO3). Resin samples loaded with various actinide ions were examined spectrophotometrically. No Np(V) and Pu(III) species were identified on the resin; rather, reduction-oxidation (REDOX) reactions occurred during equilibration, resulting in their complete conversion to M(IV) species bound by the Kläui ligand. Similarly, the sorption behavior of Pu(VI) and Np(VI) was complicated by their reduction to M(IV) upon sorption. The observed REDOX processes were apparently driven by the extremely high affinity of the Kläui ligand for the tetravalent ions. The acid-base properties of the methyl derivative of the Kläui ligand were investigated in aqueous solution, and its pKa was found to be highly dependent upon the solution ionic strength. The binding constants of this ligand with various actinide ions measured in a mixed methanol/carbon tetrachloride solvent exhibited qualitative agreement with the sorption selectivity trends.

  2. Indium tin oxide for solid-state image sensors

    NASA Astrophysics Data System (ADS)

    Weijtens, Christianus Hermanus L.

    Solid State Image Sensors (SSIS) which convert light into an electrical signal are introduced and transparent conductive materials and their deposition methods are reviewed as a solution to imager problems. The development of basic tools to enable replacement of poly-Si by Indium Tin Oxide (ITO) in SSIS is addressed. The installation and optimization of deposition equipment, the development of deposition and process technology of ITO, and the implementation and application of ITO in an image sensor are studied. Deposition rate and homogeneity and morphology and parameters like gas composition, power, pressure and substrate temperature are considered. Scope is limited to a first generation frame transfer imager with only one ITO layer although some concepts of an all ITO imager are discussed. The sensor used is a redesign of the accordion imager. All requirements imposed on ITO were met and the usefulness of the developed technology was demonstrated by implementing ITO in an imager. The characteristics of a constructed frame-transfer image sensor in which half the gates in the light sensitive part were replaced by ITO gates are discussed.

  3. Effects of iron oxidation state on viscosity, lunar composition 15555

    NASA Technical Reports Server (NTRS)

    Cukierman, M.; Uhlmann, D. R.

    1974-01-01

    The viscous flow behavior of a 9.6-kg lunar rock containing 22.5 wt.% FeO was studied in the temperature ranges from 620 to 700 C and from 1215 to 1400 C. The material was synthesized under mildy reducing conditions to simulate the Fe(2+)/total Fe ratio of the lunar environment. The effect of iron oxidation state on flow behavior in the high viscosity region is studied for specimens of the 15555 composition with Fe(2+) concentration ratios of 0.94, 0.76, and 0.20. A change in ratio from 0.94 to 0.76 had no observable effect on viscosity, whereas a change from 0.76 to 0.20 was accompanied by a drastic increase in viscosity (some three orders of magnitude) at a given temperature, but without changing the form of the variation of viscosity with temperature. The flow behavior is analyzed as a function of the structural features of the glasses.

  4. Mixed monofunctional extractants for trivalent actinide/lanthanide separations: TALSPEAK-MME

    DOE PAGESBeta

    Johnson, Aaron T.; Nash, Kenneth L.

    2015-08-20

    The basic features of an f-element extraction process based on a solvent composed of equimolar mixtures of Cyanex-923 (a mixed trialkyl phosphine oxide) and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) extractants in n-dodecane are investigated in this report. This system, which combines features of the TRPO and TALSPEAK processes, is based on co-extraction of trivalent lanthanides and actinides from 0.1 to 1.0 M HNO3 followed by application of a buffered aminopolycarboxylate solution strip to accomplish a Reverse TALSPEAK selective removal of actinides. This mixed-extractant medium could enable a simplified approach to selective trivalent f-element extraction and actinide partitioning in a singlemore » process. As compared with other combined process applications in development for more compact actinide partitioning processes (DIAMEX-SANEX, GANEX, TRUSPEAK, ALSEP), this combination features only monofunctional extractants with high solubility limits and comparatively low molar mass. Selective actinide stripping from the loaded extractant phase is done using a glycine-buffered solution containing N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) or triethylenetetramine-N,N,N',N'',N''',N'''-hexaacetic acid (TTHA). Lastly, the results reported provide evidence for simplified interactions between the two extractants and demonstrate a pathway toward using mixed monofunctional extractants to separate trivalent actinides (An) from fission product lanthanides (Ln).« less

  5. Mixed monofunctional extractants for trivalent actinide/lanthanide separations: TALSPEAK-MME

    SciTech Connect

    Johnson, Aaron T.; Nash, Kenneth L.

    2015-08-20

    The basic features of an f-element extraction process based on a solvent composed of equimolar mixtures of Cyanex-923 (a mixed trialkyl phosphine oxide) and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) extractants in n-dodecane are investigated in this report. This system, which combines features of the TRPO and TALSPEAK processes, is based on co-extraction of trivalent lanthanides and actinides from 0.1 to 1.0 M HNO3 followed by application of a buffered aminopolycarboxylate solution strip to accomplish a Reverse TALSPEAK selective removal of actinides. This mixed-extractant medium could enable a simplified approach to selective trivalent f-element extraction and actinide partitioning in a single process. As compared with other combined process applications in development for more compact actinide partitioning processes (DIAMEX-SANEX, GANEX, TRUSPEAK, ALSEP), this combination features only monofunctional extractants with high solubility limits and comparatively low molar mass. Selective actinide stripping from the loaded extractant phase is done using a glycine-buffered solution containing N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) or triethylenetetramine-N,N,N',N'',N''',N'''-hexaacetic acid (TTHA). Lastly, the results reported provide evidence for simplified interactions between the two extractants and demonstrate a pathway toward using mixed monofunctional extractants to separate trivalent actinides (An) from fission product lanthanides (Ln).

  6. Uranium in granites from the southwestern United States: actinide parent-daughter systems, sites and mobilization. Second year report. National Uranium Resource Evaluation

    SciTech Connect

    Silver, L.T.; Woodhead, J.A.; Williams, I.S.; Chappell, B.W.

    1984-09-01

    Results of detailed field and laboratory studies are reported on the primary distribution of uranium (and thorium and lead) in the radioactive minerals of five radioactive granite bodies in Arizona and California. This distribution was examined in a granite pluton. Granites with uranium concentrations ranging from 4 to 47 ppM, thorium concentrations from 11 to 181 ppM, and Th/U ratios of 0.6 to 16.0 were compared. Evidence for secondary mobilization, migration, fixation and/or loss of uranium, thorium and radiogenic leads was explored. Uranium distribution in radioactive granites is hosted in a far greater diversity of sites than has previously been known. Uranium and thorium distribution in primary minerals of granites is almost entirely a disequilibrium product involving local fractionation processes during magmatic crystallization. Every radioactive granite studied contains minerals that contain uranium and/or thorium as major stoichiometric components. When the granites are subject to secondary geochemical events and processes, the behavior of uranium is determined by the stability fields of the different radioactive minerals in the rocks. The two most powerful tools for evaluating uranium migration in a granite are (a) isotope dilution mass spectrometry and (b) the electron microprobe. Uranium mobilization and loss is a common feature in radioactive granites of the southwestern United States. A model for the evaluation of uranium loss from granites has been developed. The mineral zircon can be used as an independent indicator of uranium and thorium endowment. The weathering products show surprising differences in the response of different granites in arid region settings. Significant losses of primary uranium (up to 70%) has been a common occurrence. Uranium, thorium and radiogenic lead exist in labile (movable) form on surfaces of cleavages, fractures and grain boundaries in granites.

  7. Interconversion, reactivity and thermal stability of polyaniline in selected oxidation states

    SciTech Connect

    Masters, J.G.

    1992-01-01

    The objectives of this study were: (i) to determine if the base form of the conducting polymer, polyaniline, existed in a continuum of oxidation states ranging from the completely reduced leucoemeraldine oxidation state, (1 [minus] y) = 0, to the completely oxidized pernigraniline oxidation state, (1 [minus] y = 1). (ii) To investigate a novel type of reductive ring amination reaction of protonated polyaniline, of oxidation state 1 [minus] y = 0.50. (iii) Tascertain whether certain forms of polyaniline exhibited thermochromic behavior. (iv) To study factors responsible for enhancing the thermal/oxidative stability of [open quotes]doped[close quotes] polyaniline. (v) To study the reaction between polyaniline and C[sub 60]. The significant results and conclusions are: (a) In the oxidation state range between 1 [minus] y = 0.0 and 1 [minus] y = 1.0, polyaniline base exists in only three discrete oxidation states at the molecular level in the solid state and also in N-methylpyrrolidinone (NMP) solution. (b) Equimolar quantities of the two extreme oxidation states of polyaniline in the base form, leucoemeraldine, (1 [minus] y = 0.0), and pernigraniline, (1 [minus] y = 1.0), undergo a [open quotes]mutual[close quotes] oxidation and reduction when mixed in NMP solution. (c) In the oxidation state range between 1 [minus] y = 0.0 and 1 [minus] y = 0.50, only two species are observed in NMP solution of the polymer after the addition of excess aq. HCl, viz., fully protonated emeraldine salt and non-protonated leucoemeraldine base. (d) Protonation of emeraldine base, (1 [minus] y = 0.50), with nonvolatile acids has allowed the determination of the intrinsic thermal stability of the [open quotes]doped[close quotes] polymer. (e) A new reaction between emeraldine HCl and anhydrous amines results in reductive ring amination to produce leucoemeraldine base derivatives. (f) Reactions of the bases gave reversible thermochromic behavior and the formation of insoluble fullerenes.

  8. Correlation and relativistic effects in actinide ions

    SciTech Connect

    Safronova, U. I.; Safronova, M. S.

    2011-11-15

    Wavelengths, line strengths, and transition rates are calculated for the multipole (E1, M1, E2, M2, E3, and M3) transitions between the excited 6s{sup 2}6p{sup 5}nl and 6s6p{sup 6}nl states and the ground 6s{sup 2}6p{sup 6} state in Ac{sup 3+}, Th{sup 4+}, and U{sup 6+} Rn-like ions. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate energies and transition rates for multipole transitions in these hole-particle systems. The RMBPT method agrees with multiconfigurational Dirac-Fock (MCDF) calculations in lowest order, includes all second-order correlation corrections, and includes corrections from negative-energy states. The calculations start from a [Xe]4f{sup 14}5d{sup 10}6s{sup 2}6p{sup 6} Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and second-order RMBPT is used to determine the matrix elements. Evaluated multipole matrix elements for transitions from excited states to the ground states are used to determine the line strengths, transition rates, and multipole polarizabilities. This work provides a number of yet unmeasured properties of these actinide ions for various applications and for benchmark tests of theory and experiment.

  9. Analysis of large soil samples for actinides

    DOEpatents

    Maxwell, III; Sherrod L.

    2009-03-24

    A method of analyzing relatively large soil samples for actinides by employing a separation process that includes cerium fluoride precipitation for removing the soil matrix and precipitates plutonium, americium, and curium with cerium and hydrofluoric acid followed by separating these actinides using chromatography cartridges.

  10. Prompt fission neutron spectra of actinides

    DOE PAGESBeta

    Capote, R.; Chen, Y. -J.; Hambsch, F. -J.; Kornilov, N. V.; Lestone, J. P.; Litaize, O.; Morillon, B.; Neudecker, D.; Oberstedt, S.; Ohsawa, T.; et al

    2016-01-06

    Here, the energy spectrum of prompt neutrons emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) "Evaluation of Prompt Fission Neutron Spectra of Actinides" was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei.

  11. Minor Actinides Recycling in PWRs

    SciTech Connect

    Delpech, M.; Golfier, H.; Vasile, A.; Varaine, F.; Boucher, L.; Greneche, D.

    2006-07-01

    Recycling of minor actinides in current and near future PWR is considered as one of the options of the general waste management strategy. This paper presents the analysis of this option both from the core physics and fuel cycle point of view. A first indicator of the efficiency of different neutron spectra for transmutation purposes is the capture to fission cross sections ratio which is less favourable by a factor between 5 to 10 in PWRs compared to fast reactors. Another indicator presented is the production of high ranking isotopes like Curium, Berkelium or Californium in the thermal or epithermal spectrum conditions of PWR cores by successive neutron captures. The impact of the accumulation of this elements on the fabrication process of such PWR fuels strongly penalizes this option. The main constraint on minor actinides loadings in PWR (or fast reactors) fuels are related to their direct impact (or the impact of their transmutation products) on the reactivity coefficients, the reactivity control means and the core kinetics parameters. The main fuel cycle physical parameters like the neutron source, the alpha decay power, the gamma and neutrons dose rate and the criticality aspects are also affected. Recent neutronic calculations based on a reference core of the Evolutionary Pressurized Reactor (EPR), indicates typical maximum values of 1 % loadings. Different fuel design options for minor actinides transmutation purposes in PWRs are presented: UOX and MOX, homogeneous and heterogeneous assemblies. In this later case, Americium loading is concentrated in specific pins of a standard UOX assembly. Recycling of Neptunium in UOX and MOX fuels was also studied to improve the proliferation resistance of the fuel. The impact on the core physics and penalties on Uranium enrichment were underlined in this case. (authors)

  12. Actinide abundances in ordinary chondrites

    USGS Publications Warehouse

    Hagee, B.; Bernatowicz, T.J.; Podosek, F.A.; Johnson, M.L.; Burnett, D.S.; Tatsumoto, M.

    1990-01-01

    Measurements of 244Pu fission Xe, U, Th, and light REE (LREE) abundances, along with modal petrographic determinations of phosphate abundances, were carried out on equilibrated ordinary chondrites in order to define better the solar system Pu abundance and to determine the degree of variation of actinide and LREE abundances. Our data permit comparison of the directly measured Pu/ U ratio with that determined indirectly as (Pu/Nd) ?? (Nd/U) assuming that Pu behaves chemically as a LREE. Except for Guaren??a, and perhaps H chondrites in general, Pu concentrations are similar to that determined previously for St. Se??verin, although less precise because of higher trapped Xe contents. Trapped 130Xe 136Xe ratios appear to vary from meteorite to meteorite, but, relative to AVCC, all are similar in the sense of having less of the interstellar heavy Xe found in carbonaceous chondrite acid residues. The Pu/U and Pu/Nd ratios are consistent with previous data for St. Se??verin, but both tend to be slightly higher than those inferred from previous data on Angra dos Reis. Although significant variations exist, the distribution of our Th/U ratios, along with other precise isotope dilution data for ordinary chondrites, is rather symmetric about the CI chondrite value; however, actinide/(LREE) ratios are systematically lower than the CI value. Variations in actinide or LREE absolute and relative abundances are interpreted as reflecting differences in the proportions and/or compositions of more primitive components (chondrules and CAI materials?) incorporated into different regions of the ordinary chondrite parent bodies. The observed variations of Th/U, Nd/U, or Ce/U suggest that measurements of Pu/U on any single equilibrated ordinary chondrite specimen, such as St. Se??verin, should statistically be within ??20-30% of the average solar system value, although it is also clear that anomalous samples exist. ?? 1990.

  13. Prediction of dissolved actinide concentrations in concentrated electrolyte solutions: a conceptual model and model results for the Waste Isolation Pilot Plant (WIPP)

    SciTech Connect

    Novak, C.F.; Moore, R.C.; Bynum, R.V.

    1996-10-25

    The conceptual model for WIPP dissolved concentrations is a description of the complex natural and artificial chemical conditions expected to influence dissolved actinide concentrations in the repository. By a set of physical and chemical assumptions regarding chemical kinetics, sorption substrates, and waste-brine interactions, the system was simplified to be amenable to mathematical description. The analysis indicated that an equilibrium thermodynamic model for describing actinide solubilities in brines would be tractable and scientifically supportable. This paper summarizes the conceptualization and modeling approach and the computational results as used in the WIPP application for certification of compliance with relevant regulations for nuclear waste repositories. The WIPP site contains complex natural brines ranging from sea water to 10x more concentrated than sea water. Data bases for predicting solubility of Am(III) (as well as Pu(III) and Nd(III)), Th(IV), and Np(V) in these brines under potential repository conditions have been developed, focusing on chemical interactions with Na, K, Mg, Cl, SO{sub 4}, and CO{sub 3} ions, and the organic acid anions acetate, citrate, EDTA, and oxalate. The laboratory and modeling effort augmented the Harvie et al. parameterization of the Pitzer activity coefficient model so that it could be applied to the actinides and oxidation states important to the WIPP system.

  14. Probing the chemistry, electronic structure and redox energetics in pentavalent organometallic actinide complexes

    SciTech Connect

    Graves, Christopher R; Vaughn, Anthony E; Morris, David E; Kiplinger, Jaqueline L

    2008-01-01

    Complexes of the early actinides (Th-Pu) have gained considerable prominence in organometallic chemistry as they have been shown to undergo chemistries not observed with their transition- or lanthanide metal counterparts. Further, while bonding in f-element complexes has historically been considered to be ionic, the issue of covalence remains a subject of debate in the area of actinide science, and studies aimed at elucidating key bonding interactions with 5f-orbitals continue to garner attention. Towards this end, our interests have focused on the role that metal oxidation state plays in the structure, reactivity and spectral properties of organouranium complexes. We report our progress in the synthesis of substituted U{sup V}-imido complexes using various routes: (1) Direct oxidation of U{sup IV}-imido complexes with copper(I) salts; (2) Salt metathesis with U{sup V}-imido halides; (3) Protonolysis and insertion of an U{sup V}-imido alkyl or aryl complex with H-N{double_bond}CPh{sub 2} or N{triple_bond}C-Ph, respectively, to form a U{sup V}-imido ketimide complex. Further, we report and compare the crystallographic, electrochemical, spectroscopic and magnetic characterization of the pentavalent uranium (C{sub 5}Me{sub 5}){sub 2}U({double_bond}N-Ar)(Y) series (Y = OTf, SPh, C{triple_bond}C-Ph, NPh{sub 2}, OPh, N{double_bond}CPh{sub 2}) to further interrogate the molecular, electronic, and magnetic structures of this new class of uranium complexes.

  15. Exploring actinide materials through synchrotron radiation techniques.

    PubMed

    Shi, Wei-Qun; Yuan, Li-Yong; Wang, Cong-Zhi; Wang, Lin; Mei, Lei; Xiao, Cheng-Liang; Zhang, Li; Li, Zi-Jie; Zhao, Yu-Liang; Chai, Zhi-Fang

    2014-12-10

    Synchrotron radiation (SR) based techniques have been utilized with increasing frequency in the past decade to explore the brilliant and challenging sciences of actinide-based materials. This trend is partially driven by the basic needs for multi-scale actinide speciation and bonding information and also the realistic needs for nuclear energy research. In this review, recent research progresses on actinide related materials by means of various SR techniques were selectively highlighted and summarized, with the emphasis on X-ray absorption spectroscopy, X-ray diffraction and scattering spectroscopy, which are powerful tools to characterize actinide materials. In addition, advanced SR techniques for exploring future advanced nuclear fuel cycles dealing with actinides are illustrated as well. PMID:25169914

  16. Actinide ion sensor for pyroprocess monitoring

    DOEpatents

    Jue, Jan-fong; Li, Shelly X.

    2014-06-03

    An apparatus for real-time, in-situ monitoring of actinide ion concentrations which comprises a working electrode, a reference electrode, a container, a working electrolyte, a separator, a reference electrolyte, and a voltmeter. The container holds the working electrolyte. The voltmeter is electrically connected to the working electrode and the reference electrode and measures the voltage between those electrodes. The working electrode contacts the working electrolyte. The working electrolyte comprises an actinide ion of interest. The reference electrode contacts the reference electrolyte. The reference electrolyte is separated from the working electrolyte by the separator. The separator contacts both the working electrolyte and the reference electrolyte. The separator is ionically conductive to the actinide ion of interest. The reference electrolyte comprises a known concentration of the actinide ion of interest. The separator comprises a beta double prime alumina exchanged with the actinide ion of interest.

  17. Status of development of actinide blanket processing flowsheets for accelerator transmutation of nuclear waste

    SciTech Connect

    Dewey, H.J.; Jarvinen, G.D.; Marsh, S.F.; Schroeder, N.C.; Smith, B.F.; Villarreal, R.; Walker, R.B.; Yarbro, S.L.; Yates, M.A.

    1993-09-01

    An accelerator-driven subcritical nuclear system is briefly described that transmutes actinides and selected long-lived fission products. An application of this accelerator transmutation of nuclear waste (ATW) concept to spent fuel from a commercial nuclear power plant is presented as an example. The emphasis here is on a possible aqueous processing flowsheet to separate the actinides and selected long-lived fission products from the remaining fission products within the transmutation system. In the proposed system the actinides circulate through the thermal neutron flux as a slurry of oxide particles in heavy water in two loops with different average residence times: one loop for neptunium and plutonium and one for americium and curium. Material from the Np/Pu loop is processed with a short cooling time (5-10 days) because of the need to keep the total actinide inventory, low for this particular ATW application. The high radiation and thermal load from the irradiated material places severe constraints on the separation processes that can be used. The oxide particles are dissolved in nitric acid and a quarternary, ammonium anion exchanger is used to extract neptunium, plutonium, technetium, and palladium. After further cooling (about 90 days), the Am, Cm and higher actinides are extracted using a TALSPEAK-type process. The proposed operations were chosen because they have been successfully tested for processing high-level radioactive fuels or wastes in gram to kilogram quantities.

  18. The oxidation state of nanophase Fe particles in lunar soil: Implications for space weathering

    NASA Astrophysics Data System (ADS)

    Thompson, Michelle S.; Zega, Thomas J.; Becerra, Patricio; Keane, James T.; Byrne, Shane

    2016-05-01

    We report measurements of the oxidation state of Fe nanoparticles within lunar soils that experienced varied degrees of space weathering. We measured >100 particles from immature, submature, and mature lunar samples using electron energy-loss spectroscopy (EELS) coupled to an aberration-corrected transmission electron microscope. The EELS measurements show that the nanoparticles are composed of a mixture of Fe0, Fe2+, and Fe3+ oxidation states, and exhibit a trend of increasing oxidation state with higher maturity. We hypothesize that the oxidation is driven by the diffusion of O atoms to the surface of the Fe nanoparticles from the oxygen-rich matrix that surrounds them. The oxidation state of Fe in the nanoparticles has an effect on modeled reflectance properties of lunar soil. These results are relevant to remote sensing data for the Moon and to the remote determination of relative soil maturities for various regions of the lunar surface.

  19. The oxidation state of nanophase Fe particles in lunar soil: Implications for space weathering

    NASA Astrophysics Data System (ADS)

    Thompson, Michelle S.; Zega, Thomas J.; Becerra, Patricio; Keane, James T.; Byrne, Shane

    2016-06-01

    We report measurements of the oxidation state of Fe nanoparticles within lunar soils that experienced varied degrees of space weathering. We measured >100 particles from immature, submature, and mature lunar samples using electron energy-loss spectroscopy (EELS) coupled to an aberration-corrected transmission electron microscope. The EELS measurements show that the nanoparticles are composed of a mixture of Fe0, Fe2+, and Fe3+ oxidation states, and exhibit a trend of increasing oxidation state with higher maturity. We hypothesize that the oxidation is driven by the diffusion of O atoms to the surface of the Fe nanoparticles from the oxygen-rich matrix that surrounds them. The oxidation state of Fe in the nanoparticles has an effect on modeled reflectance properties of lunar soil. These results are relevant to remote sensing data for the Moon and to the remote determination of relative soil maturities for various regions of the lunar surface.

  20. Solid State, Surface and Catalytic Studies of Oxides

    SciTech Connect

    Kung, H. H.

    2004-11-23

    This project investigates the catalytic properties of oxides for the selective oxidative dehydrogenation of light alkanes and for hydrocarbon reduction of NO{sub x}. Various vanadium oxide based catalysts were investigated to elucidate the relationship between the chemical and structural properties of the catalysts and their selectivity for the formation of alkenes. It was found that vanadium oxide units that are less reducible give higher selectivities. For hydrocarbon reduction of NO{sub x}, it was found that alumina-based catalysts can be effective at higher temperatures than the corresponding zeolite-based catalysts. On some catalysts, such as SnO{sub 2}/Al{sub 2}O{sub 3}. Ag/Al{sub 2}O{sub 3}, the alumina participates directly in the reaction, making the catalyst bifunctional. These results are useful in research to improve the performance of this stress of catalysts.

  1. Three Dimensional Mapping of Nicle Oxidation States Using Full Field Xray Absorption Near Edge Structure Nanotomography

    SciTech Connect

    Nelson, G.J.; Chu, Y.; Harris, W.M.; Izzo, J.R.; Grew, K.N., Chiu, W.K.S.; Yi, J.; Andrews, J.C.; Liu, Y., Pierro, P.

    2011-04-28

    The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.

  2. Rapid actinide-separation methods

    SciTech Connect

    Maxwell, S.L. III

    1997-12-31

    New high-speed actinide-separation methods have been developed by the Savannah River Site Central Laboratory that can be applied to nuclear materials process samples, waste solutions and environmental samples. As part of a reengineering effort to improve efficiencies and reduce operating costs, solvent extraction methods (TTA, Hexone, TBP and TIOA) used for over thirty years in the SRS Central Laboratory were replaced with new rapid extraction column methods able to handle a variety of difficult sample matrices and actinide levels. Significant costs savings were realized and costly mixed-waste controls were avoided by using applied vacuum and 50-100 micron particle-size resins from Eichrom Industries. TEVA Resin{reg_sign}, UTEVA Resin{reg_sign}, and TRU Resin{reg_sign} columns are used with flow rates of approximately two to three milliliters per minute to minimize sample turnaround times. Single-column, dual-column and sequential-cartridge methods for plutonium, uranium, neptunium, americium and curium were developed that enable rapid, cost-effective separations prior to alpha-particle counting, thermal ionization and inductively coupled plasma mass spectrometry, and laser phosphorescence measurements.

  3. The Effects of Decomposition on the Oxidative Ratio and Carbon Oxidation State of Organic Matter

    NASA Astrophysics Data System (ADS)

    Gallagher, M. E.; Masiello, C. A.; Clark, N.; Randerson, J. T.; Robertson, G. P.

    2006-12-01

    Ecosystem oxidative ratio (OR) and the related parameter carbon oxidation state (Cox) are critical in the apportionment of anthropogenic CO2 between the terrestrial biosphere and ocean reservoirs. OR is the ratio of O2 to CO2 in gas exchange fluxes between the biosphere and the atmosphere (Fba and Fab). Accurate measurements of OR have been challenging (Seibt et al. 2004); instead we approach the problem by measuring Cox and calculating OR from biomass reservoirs. Cox can range from -4 to +4 (CH4 to CO2) and is driven by photosynthesis, respiration, and decomposition. The net OR of the biosphere varies with ecosystem type, and this can affect the apportionment of anthropogenic CO2 between the terrestrial biosphere and ocean reservoirs (Randerson et al. 2006). This makes it essential to constrain ecosystem Cox and OR values. Although small variations in global ecosystem OR have the potential to cause shifts in atmospheric O2 concentrations, no whole ecosystem measurements of Cox yet exist. To constrain ORba and ORab, and improve our understanding of how decomposition affects Cox, we performed a litter bag experiment at the Kellogg Biological Station-Long Term Ecological Research (KBS-LTER) in Michigan at the end of the 2005 agricultural season. We placed 15 corn biomass litter bags in an agricultural field and collected 3 bags at 2, 4, 7, 26, and 29 weeks. These samples were analyzed for %C, %H, %N, and %O via elemental analysis, and these data were used to calculate Cox. Aboveground Cox was measured similarly. We anticipated that the Cox of the corn litter would become more reduced with decomposition, as the percentage of carbohydrates would decrease with time, while that of protein, lignin, and lipids would increase (Baldock et al. 2004). We report differences between the Cox of biomass fixation and biomass degradation from our experiments. Using simple assumptions about ecosystem nitrogen cycling, we convert Cox to OR and report the existence or absence of a

  4. Predictions of Actinide Solubilities under Near-Field Conditions Expected in the WIPP

    NASA Astrophysics Data System (ADS)

    Brush, L. H.; Xiong, Y.

    2009-12-01

    , EDTA, and oxalate in TRU waste. The oxidation-state analogy was then used to extend the +III model to Pu(III), and the +IV model to Pu(IV), U(IV), and Np(IV). The solubility of U(VI) was estimated. For the recent WIPP Compliance Recertification Application PA Baseline Calculations, we calculated actinide solubilities with fCO2 buffered at 3.14 × 10-6 atm by the brucite-hydromagnesite carbonation reaction, with pH maintained at ~9 by the brucite dissolution-precipitation reaction, and with estimated concentrations of the organic ligands in brines from the Salado and the Castile Fm., which underlies the Salado. The calculated +III, +IV, and +V solubilities are 1.56 × 10-6, 5.64 × 10-8, and 4.07 × 10-7 M, respectively, in Salado brine; and 1.51 × 10-6, 6.98 × 10-8, and 8.75 × 10-7 M in Castile brine. The U(VI) solubility estimated for both brines is 1 × 10-3 M. This research is funded by WIPP programs administered by the U.S. Department of Energy. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

  5. Characterization of Actinides in Simulated Alkaline Tank Waste Sludges and Leachates

    SciTech Connect

    Nash, Kenneth L.

    2005-06-01

    Removal of waste-limiting components of sludge (Al, Cr, S, P) in underground tanks at Hanford by treatment with concentrated alkali has proven less efficacious for Al and Cr removal than had been hoped. More aggressive treatments of sludges, for example, contact with oxidants targeting Cr(III), have been tested in a limited number of samples and found to improve leaching efficiency for Cr. Oxidative alkaline leaching can be expected to have at best a secondary influence on the mobilization of Al. Our earlier explorations of Al leaching from sludge simulants indicated acidic and complexometric leaching can improve Al dissolution. Unfortunately, treatments of sludge samples with oxidative alkaline, acidic or complexing leachates produce conditions under which normally insoluble actinide ions (e.g., Am3+, Pu4+, Np4+) can be mobilized to the solution phase. Few experimental or meaningful theoretical studies of actinide chemistry in strongly alkaline, strongly oxidizing solutions have been completed. Unfortunately, extrapolation of the more abundant acid phase thermodynamic data to these radically different conditions provides limited reliable guidance for predicting actinide speciation in highly salted alkaline solutions. In this project, we are investigating the fundamental chemistry of actinides and important sludge components in sludge simulants and supernatants under representative oxidative leaching conditions. We are examining the potential impact of acidic or complexometric leaching with concurrent secondary separations on Al removal from sludges. Finally, a portion of our research is directed at the control of polyvalent anions (SO4=, CrO4=, PO43-) in waste streams destined for vitrification. Our primary objective is to provide adequate insight into actinide behavior under these conditions to enable prudent decision making as tank waste treatment protocols develop. We expect to identify those components of sludges that are likely to be problematic in the

  6. CHARACTERIZATION OF ACTINIDES IN SIMULATED ALKALINE TANK WASTE SLUDGES AND LEACHATES

    EPA Science Inventory

    During sludge washing procedures associated with tank waste remediation, actinide ions are expected to remain with the insoluble metal oxide/hydroxide residue as the sludges are scrubbed to remove Cr, P, Al, S, and thus to be transmitted conveniently to the vitrification plant. ...

  7. The oxidation state of the surface of Venus. [Abstract only

    NASA Technical Reports Server (NTRS)

    Fegley, B., Jr.; Klingelhofer, G.; Brackett, R. A.; Izenberg, N.

    1994-01-01

    We present experimental results showing that basalt is oxidized in CO-CO2 gas mixtures having CO number densities close to those (approximately 2 times higher) at the surface of Venus. The results suggest that the red color observed by Pieters et al at the Venera 9 and 10 landing sites is due to subaerial oxidation of Fe(2+)-bearing basalt on the surface of Venus, and that hematite, instead of magnetite, is present on the surface of Venus. Well-characterized basalt powder was iosthermally heated in 1000 ppm CO-CO2 gas mixtures at atmospheric pressure for several days. The starting material and reacted samples were analyzed by Mossbauer spectroscopy to determine the amount of Fe(2+) and Fe(3+) in the samples. X-ray diffraction and optical microscopy were also used to characterize samples. The basalt oxidation occurs because the CO and CO2 do not equilibrate in the gas mixture at the low temperatures used. Thus, the basalt reacts with the more abundant CO2 and is oxidized. We propose that the red color of the surface of Venus is due to failure of CO and CO2 to equilibrate with one another in the near-surface atmosphere of Venus, leading to subaerial oxidation of erupted Fe(2+)-bearing basalts. Our interpretation is supported by our studies of magnetite oxidation, which show that synthetic magnetite powders are oxidized to hematite in CO-CO2 gas mixtures inside the magnetite stability field, by our studies of pyrite decomposition, and by independent work on CO-CO2 equilibration in furnace gases.

  8. Organic nature of colloidal actinides transported in surface water environments.

    PubMed

    Santschi, Peter H; Roberts, Kimberly A; Guo, Laodong

    2002-09-01

    Elevated levels of (239,240)Pu and 241Am have been present in surficial soils of the Rocky Flats Environmental Technology Site (RFETS), CO, since the 1960s, when soils were locally contaminated in the 1960s by leaking drums stored on the 903 Pad. Further dispersion of contaminated soil particles was by wind and water. From 1998 until 2001, we examined actinide ((239,240)Pu and 241Am) concentrations and phase speciation in the surface environment at RFETS through field studies and laboratory experiments. Measurements of total (239,240)Pu and 241Am concentrations in storm runoff and pond discharge samples, collected during spring and summer times in 1998-2000, demonstrate that most of the (239,240)Pu and 241Am transported from contaminated soils to streams occurred in the particulate (> or = 0.45 microm; 40-90%) and colloidal (approximately 2 nm or 3 kDa to 0.45 microm; 10-60%) phases. Controlled laboratory investigations of soil resuspension, which simulated storm and erosion events, confirmed that most of the Pu in the 0.45 microm filter-passing phase was in the colloidal phase (> or = 80%) and that remobilization of colloid-bound Pu during soil erosion events can be greatly enhanced by humic and fulvic acids present in these soils. Most importantly, isoelectric focusing experiments of radiolabeled colloidal matter extracted from RFETS soils revealed that colloidal Pu is in the four-valent state and is mostly associated with a negatively charged organic macromolecule with a pH(IEP) of 3.1 and a molecular weight of 10-15 kDa, rather than with the more abundant inorganic (iron oxide and clay) colloids. This finding has important ramifications for possible remediation, erosion controls, and land-management strategies. PMID:12322742

  9. Oxidation state of multivalent elements in high-level nuclear waste glass

    SciTech Connect

    Reynolds, J.G.

    2007-07-01

    Nuclear waste contains many different elements that have more than one oxidation state. When the nuclear waste is treated by vitrification, the behavior of the element in the melter and resulting glass product depends on the stable oxidation state. The stable oxidation state in any medium can be calculated from the standard potential in that medium. Consequently, the standard potential of multi-valent elements has been measured in many silicate-melts, including ones relevant to nuclear waste treatment. In this study, the relationship between the standard potential in molten nuclear waste glass and the standard potential in water will be quantified so that the standard potential of elements that have not been measured in glass can be estimated. The regression equation was found to have an R{sup 2} statistic of 0.96 or 0.83 depending on the number of electrons transferred in the reaction. The Nernst equation was then used to calculate the oxidation state of other relevant multi-valent elements in nuclear waste glass from these standard potentials and the measured ferrous to ferric iron ratio. The calculated oxidation states were consistent with all oxidation state measurements available. The calculated oxidation states were used to rationalize the behavior of many of the multi-valent elements. For instance, chromium increases glass crystallization because it is in the trivalent-state, iodine volatilises from the melter because it is in the volatile zero-valent state, and the leaching behavior of arsenic is driven by its oxidation state. Thus, these thermodynamic calculations explain the behavior of many trace elements during the vitrification process. (authors)

  10. Identification of an iridium-containing compound with a formal oxidation state of IX.

    PubMed

    Wang, Guanjun; Zhou, Mingfei; Goettel, James T; Schrobilgen, Gary J; Su, Jing; Li, Jun; Schlöder, Tobias; Riedel, Sebastian

    2014-10-23

    One of the most important classifications in chemistry and within the periodic table is the concept of formal oxidation states. The preparation and characterization of compounds containing elements with unusual oxidation states is of great interest to chemists. The highest experimentally known formal oxidation state of any chemical element is at present VIII, although higher oxidation states have been postulated. Compounds with oxidation state VIII include several xenon compounds (for example XeO4 and XeO3F2) and the well-characterized species RuO4 and OsO4 (refs 2-4). Iridium, which has nine valence electrons, is predicted to have the greatest chance of being oxidized beyond the VIII oxidation state. In recent matrix-isolation experiments, the IrO4 molecule was characterized as an isolated molecule in rare-gas matrices. The valence electron configuration of iridium in IrO4 is 5d(1), with a formal oxidation state of VIII. Removal of the remaining d electron from IrO4 would lead to the iridium tetroxide cation ([IrO4](+)), which was recently predicted to be stable and in which iridium is in a formal oxidation state of IX. There has been some speculation about the formation of [IrO4](+) species, but these experimental observations have not been structurally confirmed. Here we report the formation of [IrO4](+) and its identification by infrared photodissociation spectroscopy. Quantum-chemical calculations were carried out at the highest level of theory that is available today, and predict that the iridium tetroxide cation, with a Td-symmetrical structure and a d(0) electron configuration, is the most stable of all possible [IrO4](+) isomers. PMID:25341786

  11. Identification of an iridium-containing compound with a formal oxidation state of IX

    NASA Astrophysics Data System (ADS)

    Wang, Guanjun; Zhou, Mingfei; Goettel, James T.; Schrobilgen, Gary J.; Su, Jing; Li, Jun; Schlöder, Tobias; Riedel, Sebastian

    2014-10-01

    One of the most important classifications in chemistry and within the periodic table is the concept of formal oxidation states. The preparation and characterization of compounds containing elements with unusual oxidation states is of great interest to chemists. The highest experimentally known formal oxidation state of any chemical element is at present VIII, although higher oxidation states have been postulated. Compounds with oxidation state VIII include several xenon compounds (for example XeO4 and XeO3F2) and the well-characterized species RuO4 and OsO4 (refs 2, 3, 4). Iridium, which has nine valence electrons, is predicted to have the greatest chance of being oxidized beyond the VIII oxidation state. In recent matrix-isolation experiments, the IrO4 molecule was characterized as an isolated molecule in rare-gas matrices. The valence electron configuration of iridium in IrO4 is 5d1, with a formal oxidation state of VIII. Removal of the remaining d electron from IrO4 would lead to the iridium tetroxide cation ([IrO4]+), which was recently predicted to be stable and in which iridium is in a formal oxidation state of IX. There has been some speculation about the formation of [IrO4]+ species, but these experimental observations have not been structurally confirmed. Here we report the formation of [IrO4]+ and its identification by infrared photodissociation spectroscopy. Quantum-chemical calculations were carried out at the highest level of theory that is available today, and predict that the iridium tetroxide cation, with a Td-symmetrical structure and a d0 electron configuration, is the most stable of all possible [IrO4]+ isomers.

  12. Method for extracting lanthanides and actinides from acid solutions by modification of Purex solvent

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.

    1984-05-21

    A process has been developed for the extraction of multivalent lanthanide and actinide values from acidic waste solutions, and for the separation of these values from fission product and other values, which utilizes a new series of neutral bi-functional extractants, the alkyl(phenyl)-N, N-dialkylcarbamoylmethylphosphine oxides, in combination with a phase modifier to form an extraction solution. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions.

  13. Photoelectron spectroscopy and theoretical studies of gaseous uranium hexachlorides in different oxidation states: UCl{sub 6}{sup q−} (q = 0–2)

    SciTech Connect

    Su, Jing; Dau, Phuong D.; Huang, Dao-Ling; Wang, Lai-Sheng; Liu, Hong-Tao; Wei, Fan; Schwarz, W. H. E.; Li, Jun

    2015-04-07

    Uranium chlorides are important in actinide chemistry and nuclear industries, but their chemical bonding and many physical and chemical properties are not well understood yet. Here, we report the first experimental observation of two gaseous uranium hexachloride anions, UCl{sub 6}{sup −} and UCl{sub 6}{sup 2−}, which are probed by photoelectron spectroscopy in conjunction with quantum chemistry calculations. The electron affinity of UCl{sub 6} is measured for the first time as +5.3 eV; its second electron affinity is measured to be +0.60 eV from the photoelectron spectra of UCl{sub 6}{sup 2−}. We observe that the detachment cross sections of the 5f electrons are extremely weak in the visible and UV energy ranges. It is found that the one-electron one-determinental molecular orbital picture and Koopmans’ theorem break down for the strongly internally correlated U-5f{sup 2} valence shell of tetravalent U{sup +4} in UCl{sub 6}{sup 2−}. The calculated adiabatic and vertical electron detachment energies from ab initio calculations agree well with the experimental observations. Electronic structure and chemical bonding in the uranium hexachloride species UCl{sub 6}{sup 2−} to UCl{sub 6} are discussed as a function of the oxidation state of U.

  14. PF-4 actinide disposition strategy

    SciTech Connect

    Margevicius, Robert W

    2010-05-28

    The dwindling amount of Security Category I processing and storage space across the DOE Complex has driven the need for more effective storage of nuclear materials at LANL's Plutonium Facility's (PF-4's) vault. An effort was begun in 2009 to create a strategy, a roadmap, to identify all accountable nuclear material and determine their disposition paths, the PF-4 Actinide Disposition Strategy (PADS). Approximately seventy bins of nuclear materials with similar characteristics - in terms of isotope, chemical form, impurities, disposition location, etc. - were established in a database. The ultimate disposition paths include the material to remain at LANL, disposition to other DOE sites, and disposition to waste. If all the actions described in the document were taken, over half of the containers currently in the PF-4 vault would been eliminated. The actual amount of projected vault space will depend on budget and competing mission requirements, however, clearly a significant portion of the current LANL inventory can be either dispositioned or consolidated.

  15. Arsenic (+3 oxidation state) methyltransferase and the methylation of arsenicals in the invertebrate chordate Ciona intestinalis

    EPA Science Inventory

    The biotransformation of inorganic arsenic (iAs) involves methylation by an arsenic (+3 oxidation state) methyltransferase (AS3MT), yielding methyl arsenic (MA), dimethyl arsenic (DMA), and trimethylarsenic (TMA). To identify molecular mechanisms that coordinate arsenic biotra...

  16. Arsenic (+3 oxidation state) methyltransferase and the methylation of arsenicals in the invertebrate chordate Ciona intestinalis

    EPA Science Inventory

    Biotransformation of inorganic arsenic (iAs) involves methylation catalyzed by arsenic (+3 oxidation state) methyltransferase (As3mt), yielding mono- , di- , and trimethylated arsenicals. To investigate the evolution of molecular mechanisms that mediate arsenic biotransformation,...

  17. *Arsenic (+3 oxidation state) methyltransferase and the methylation of arsenicals in the invertebrate chordate ciona intestinalis

    EPA Science Inventory

    Biotransformation of inorganic arsenic (iAs) involves methylation catalyzed by arsenic (+3 oxidation state) methyltransferase (As3mt) , yielding mono-, di-, and trimethylated arsenicals. A comparative genomic approach focused on Ciona intestinaJis, an invertebrate chordate, was u...

  18. Carotenoid Excited State Kinetics in Bacterial RCs with the Primary Electron Donor Oxidized

    NASA Astrophysics Data System (ADS)

    Lin, Su; Katilius, Evaldas; Woodbury, Neal W.

    Carotenoid singlet excited state kinetics in wild type reaction centers from Rhodobacter sphaeroides was investigated using ultrafast laser spectroscopy under conditions where the primary electron donor is either neutral or oxidized.

  19. Studies of Nuclear Structure and Decay Properties of Actinide Nuclei

    SciTech Connect

    Kondev, F. G.; Ahmad, I.; Carpenter, M. P.; Chiara, C. J.; Greene, J. P.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Lister, C. J.; Moore, E. F.; Seweryniak, D.; Zhu, S.; Kellett, M. A.; Nichols, A. L.

    2009-01-28

    The identification of single-particle states in heavy actinide nuclei by means of studying their decay schemes plays a seminal role in understanding the structure of the heaviest elements and testing the predictive power of modern theoretical models. The heaviest odd-mass nuclides available in sufficient quantity for detailed decay spectroscopic studies are 20-h {sup 255} Fm(for neutrons) and 20-d {sup 253}Es(for protons). Decay spectra of these isotopes, together with those for the odd-odd 276-d {sup 254}Es nuclide, were measured using a variety of {alpha}-particle and {gamma}-ray spectroscopy techniques. Well-defined decay data are also essential pre-requisites for the detection and accurate characterization of fissile radionuclides. The parameters of greatest relevance include actinide half-lives, branching fractions, and {alpha}-particle and {gamma}-ray energies and emission probabilities. Their quantification to good accuracy provides the means of monitoring their presence, behavior and transport in nuclear facilities as well as any clandestine movement and usage. As a consequence of recommendations made at recent IAEA research coordination meetings on 'Updated Decay Data Library for Actinides,' measurements were undertaken to determine specific decay data of the more inadequately defined radionuclides.

  20. Determination of actinides in environmental and biological samples using high-performance chelation ion chromatography coupled to sector-field inductively coupled plasma mass spectrometry.

    PubMed

    Truscott, J B; Jones, P; Fairman, B E; Evans, E H

    2001-08-31

    High-performance chelation ion chromatography, using a neutral polystyrene substrate dynamically loaded with 0.1 mM dipicolinic acid, coupled with sector-field inductively coupled plasma mass spectrometry has been successfully used for the separation of the actinides thorium, uranium, americium, neptunium and plutonium. Using this column it was possible to separate the various actinides from each other and from a complex sample matrix. In particular, it was possible to separate plutonium and uranium to facilitate the detection of the former free of spectral interference. The column also exhibited some selectivity for different oxidation states of Np, Pu and U. Two oxidation states each for plutonium and neptunium were found, tentatively identified as Np(V) and Pu(III) eluting at the solvent front, and Np(IV) and Pu(IV) eluting much later. Detection limits were 12, 8, and 4 fg for 237Np, 239Pu, and 241Am, respectively, for a 0.5 ml injection. The system was successfully used for the determination of 239Pu in NIST 4251 Human Lung and 4353 Rocky Flats Soil, with results of 570+/-29 and 2939+/-226 fg g(-1), respectively, compared with a certified range of 227-951 fg g(-1) for the former and a value of 3307+/-248 fg g(-1) for the latter. PMID:11589474

  1. Chemical reduction of actinides probed by resonant inelastic X-ray scattering.

    PubMed

    Butorin, Sergei M; Shuh, David K; Kvashnina, Kristina O; Guo, Jinghua; Werme, Lars; Nordgren, Joseph

    2013-12-01

    The study addresses the possibilities of immobilizing the mobile species of actinides in the geosphere using metallic iron. Sorption on corroding iron is well-known, but there have been uncertainties with regard to the possibilities of reducing the actinyl species to sparingly soluble oxides and, thereby, permanently immobilizing them. Resonant inelastic X-ray scattering (RIXS) measurements at the actinide 5d edges on Fe foils exposed to uranium(VI) and neptunium(V) solutions in groundwater unambigiously indicate reduction of actinides to, respectively, uranium(IV) and neptunium(IV) on iron surfaces. The reduction manifests itself in an appearance of distinct specific signatures of uranium(IV) and neptunium(IV) in the RIXS profile of 5f-5f excitations. Such signatures and RIXS intensity/cross-section behavior with varying energy of incident photons can be reproduced by model atomic-multiplet calculations of the RIXS spectra. By normalizing the RIXS signal of corresponding 5f-5f excitations to core-to-core 6p-to-5d characteristic fluorescence transitions of actinides, their reduction rates on Fe samples with different exposure to actinide solutions can be estimated. Observed reduction implies similar processes in the nuclear waste canister thus suggesting reduced probability of nuclear waste release with ground waters from the canister. PMID:24187957

  2. Structural evolution and valence electron-state change during ultra thin silicon-oxide growth

    NASA Astrophysics Data System (ADS)

    Shimizu, A.; Abe, S.; Nakayama, H.; Nishino, T.; Iida, S.

    2000-06-01

    We have studied valence electron-state changes of Si during initial oxidation of Si(111) clean surface, HF-treated Si(001) and Si(111) surfaces by Auger valence electron spectroscopy (AVES). The results showed that the valence electron-state changes during initial oxidation were sensitively reflected in Si[2s,2p,V] (V=3s,3p) AVES spectra and that they depended on both initial surface treatment and surface orientation. The local valence electron-states, local density of states in other words, showed the characteristic-structure evolution depending on the initial surface treatment and surface orientation.

  3. Clay-mediated reactions of HCN oligomers - The effect of the oxidation state of the clay

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Alwis, K. W.; Edelson, E. H.; Mount, N.; Hagan, W. J., Jr.

    1981-01-01

    Montmorillonite clays which contain Fe(III) inhibit the oligomerization of aqueous solutions of HCN. The inhibitory effect is due to the rapid oxidation of diaminomaleonitrile, a key intermediate in HCN oligomerization, by the Fe(III) incorporated into the aluminosilicate lattice of the clay. The Fe(III) oxidizes diaminomaleonitrile to diiminosuccinonitrile, a compound which is rapidly hydrolyzed to HCN and oxalic acid derivatives. Diaminomaleonitrile is not oxidized when Fe(III) in the montmorillonite is reduced with hydrazine. The oxidation state of the clay is an important variable in experiments designed to simulate clay catalysis on the primitive earth.

  4. Electronic structure and correlation effects in actinides

    SciTech Connect

    Albers, R.C.

    1998-12-01

    This report consists of the vugraphs given at a conference on electronic structure. Topics discussed are electronic structure, f-bonding, crystal structure, and crystal structure stability of the actinides and how they are inter-related.

  5. BWR Assembly Optimization for Minor Actinide Recycling

    SciTech Connect

    G. Ivan Maldonado; John M. Christenson; J.P. Renier; T.F. Marcille; J. Casal

    2010-03-22

    The Primary objective of the proposed project is to apply and extend the latest advancements in LWR fuel management optimization to the design of advanced boiling water reactor (BWR) fuel assemblies specifically for the recycling of minor actinides (MAs).

  6. Joint Actinide Shock Physics Experimental Research - JASPER

    ScienceCinema

    None

    2015-01-09

    Commonly known as JASPER the Joint Actinide Shock Physics Experimental Research facility is a two stage light gas gun used to study the behavior of plutonium and other materials under high pressures, temperatures, and strain rates.

  7. Joint Actinide Shock Physics Experimental Research - JASPER

    SciTech Connect

    2014-10-31

    Commonly known as JASPER the Joint Actinide Shock Physics Experimental Research facility is a two stage light gas gun used to study the behavior of plutonium and other materials under high pressures, temperatures, and strain rates.

  8. Preparation of actinide targets by electrodeposition

    NASA Astrophysics Data System (ADS)

    Trautmann, N.; Folger, H.

    1989-10-01

    Actinide targets with varying thicknesses on different substrates have been prepared by electrodeposition either from aqueous solutions or from solutions of their nitrates in isopropyl alcohol. With these techniques the actinides can be deposited almost quantitatively on various backing materials within 15 to 30 min. Targets of thorium, uranium, neptunium, plutonium, americium, curium and californium with areal densities from almost carrier-free up to 1.4 mg/cm 2 on thin beryllium, carbon, titanium, tantalum and platinum foils have been prepared. In most cases, prior to the deposition, the actinides had to be purified chemically and for some of them, due to the limited amount of material available, recycling procedures were required. Applications of actinide targets in heavy-ion reactions are briefly discussed.

  9. SOLID STATE ENERGY CONVERSION ALLIANCE DELPHI SOLID OXIDE FUEL CELL

    SciTech Connect

    Steven Shaffer; Sean Kelly; Subhasish Mukerjee; David Schumann; Gail Geiger; Kevin Keegan; John Noetzel; Larry Chick

    2003-12-08

    The objective of Phase I under this project is to develop a 5 kW Solid Oxide Fuel Cell power system for a range of fuels and applications. During Phase I, the following will be accomplished: Develop and demonstrate technology transfer efforts on a 5 kW stationary distributed power generation system that incorporates steam reforming of natural gas with the option of piped-in water (Demonstration System A). Initiate development of a 5 kW system for later mass-market automotive auxiliary power unit application, which will incorporate Catalytic Partial Oxidation (CPO) reforming of gasoline, with anode exhaust gas injected into an ultra-lean burn internal combustion engine. This technical progress report covers work performed by Delphi from January 1, 2003 to June 30, 2003, under Department of Energy Cooperative Agreement DE-FC-02NT41246. This report highlights technical results of the work performed under the following tasks: Task 1 System Design and Integration; Task 2 Solid Oxide Fuel Cell Stack Developments; Task 3 Reformer Developments; Task 4 Development of Balance of Plant (BOP) Components; Task 5 Manufacturing Development (Privately Funded); Task 6 System Fabrication; Task 7 System Testing; Task 8 Program Management; and Task 9 Stack Testing with Coal-Based Reformate.

  10. Transmutation of actinides in power reactors.

    PubMed

    Bergelson, B R; Gerasimov, A S; Tikhomirov, G V

    2005-01-01

    Power reactors can be used for partial short-term transmutation of radwaste. This transmutation is beneficial in terms of subsequent storage conditions for spent fuel in long-term storage facilities. CANDU-type reactors can transmute the main minor actinides from two or three reactors of the VVER-1000 type. A VVER-1000-type reactor can operate in a self-service mode with transmutation of its own actinides. PMID:16604724

  11. Synergism of trivalent actinides and lanthanides

    SciTech Connect

    Mathur, J.N.

    1983-01-01

    The synergism of trivalent actinides and lanthanides has been reviewed critically. Different systems including ..beta..-di-ketones and several other chelating agents with various neutral donors have been discussed. The thermodynamic parameters, effect of diluents, auto-synergism and synergism with eutectic mixtures have been discussed in the case of trivalent actinides and lanthanides. Also the mechanism of synergism and the various possible uses of this phenomenon have been referred to with the possible data available. 160 references, 4 tables.

  12. Rapid determination of actinides in seawater samples

    DOE PAGESBeta

    Maxwell, Sherrod L.; Culligan, Brian K.; Hutchison, Jay B.; Utsey, Robin C.; McAlister, Daniel R.

    2014-03-09

    A new rapid method for the determination of actinides in seawater samples has been developed at the Savannah River National Laboratory. The actinides can be measured by alpha spectrometry or inductively-coupled plasma mass spectrometry. The new method employs novel pre-concentration steps to collect the actinide isotopes quickly from 80 L or more of seawater. Actinides are co-precipitated using an iron hydroxide co-precipitation step enhanced with Ti+3 reductant, followed by lanthanum fluoride co-precipitation. Stacked TEVA Resin and TRU Resin cartridges are used to rapidly separate Pu, U, and Np isotopes from seawater samples. TEVA Resin and DGA Resin were used tomore » separate and measure Pu, Am and Cm isotopes in seawater volumes up to 80 L. This robust method is ideal for emergency seawater samples following a radiological incident. It can also be used, however, for the routine analysis of seawater samples for oceanographic studies to enhance efficiency and productivity. In contrast, many current methods to determine actinides in seawater can take 1–2 weeks and provide chemical yields of ~30–60 %. This new sample preparation method can be performed in 4–8 h with tracer yields of ~85–95 %. By employing a rapid, robust sample preparation method with high chemical yields, less seawater is needed to achieve lower or comparable detection limits for actinide isotopes with less time and effort.« less

  13. Rapid determination of actinides in seawater samples

    SciTech Connect

    Maxwell, Sherrod L.; Culligan, Brian K.; Hutchison, Jay B.; Utsey, Robin C.; McAlister, Daniel R.

    2014-03-09

    A new rapid method for the determination of actinides in seawater samples has been developed at the Savannah River National Laboratory. The actinides can be measured by alpha spectrometry or inductively-coupled plasma mass spectrometry. The new method employs novel pre-concentration steps to collect the actinide isotopes quickly from 80 L or more of seawater. Actinides are co-precipitated using an iron hydroxide co-precipitation step enhanced with Ti+3 reductant, followed by lanthanum fluoride co-precipitation. Stacked TEVA Resin and TRU Resin cartridges are used to rapidly separate Pu, U, and Np isotopes from seawater samples. TEVA Resin and DGA Resin were used to separate and measure Pu, Am and Cm isotopes in seawater volumes up to 80 L. This robust method is ideal for emergency seawater samples following a radiological incident. It can also be used, however, for the routine analysis of seawater samples for oceanographic studies to enhance efficiency and productivity. In contrast, many current methods to determine actinides in seawater can take 1–2 weeks and provide chemical yields of ~30–60 %. This new sample preparation method can be performed in 4–8 h with tracer yields of ~85–95 %. By employing a rapid, robust sample preparation method with high chemical yields, less seawater is needed to achieve lower or comparable detection limits for actinide isotopes with less time and effort.

  14. Microbially-Promoted Solubilization of Steel Corrosion Products and Fate of Associated Actinides

    SciTech Connect

    Gill Geesey; Timothy Magnuson; Andrew Neal

    2002-06-15

    Microorganisms have the capacity to modify iron oxides during anaerobic respiration. When the dissimilatory sulfate-reducing bacterium Desulfovibrio desulfuricans G20 respires soluble sulfate during colonization of the solid-phase iron oxide hematite, the sulfide product reacts with the iron to produce the insoluble iron sulfide, pyrrhotite. When soluble uranium is present as uranyl ion, these microorganisms reduce the U(VI) to U(IV) as insoluble uraninite on the hematite surface. There is also evidence that a stable form of U is produced under these conditions that displays an oxidation state between U(VI) and U(iv). The dissimilatory iron reducing bacterium, Shewanella oneidensis MR1 can utilize insoluble hematite as the sole electron acceptor for anaerobic respiration during growth and biofilm development on the mineral. The growth rate, maximum cell density and detachment rate for this bacterium are significantly greater on hematite than on magnetite (111) and (100). The difference could not be attributed to iron site density in the iron oxide. A gene (ferA) encoding a c-tyoe cytochrome involved in dissimulatory iron reduction in the bacterium Geobacter sulfurreducens was completed sequenced and characterized. The sequence information was used to develop an in-situ reverse transcriptase polymerase chain reaction assay that could detect expression of the gene during growth and biofilm development on ferrihydrite at the single cell and microcolony level. X-ray photoelectron spectroscopic analysis revealed that the ferrihydrite was reduced during expression of this gene. The assay was extended to detect expression of genes involved in sulfate reduction and hydrogen reduction in sulfate-reducing bacteria. This assay will be useful to assess mechanisms of biotransformation of minerals including corrosion products on buried metal containers containing radionuclide waste. In summary, the research has shown that dissimilatory sulfate and iron reducing bacteria can

  15. Reduction Rates for Higher Americium Oxidation States in Nitric Acid

    SciTech Connect

    Grimes, Travis Shane; Mincher, Bruce Jay; Schmitt, Nicholas C

    2015-09-30

    The stability of hexavalent americium was measured using multiple americium concentrations and nitric acid concentrations after contact with the strong oxidant sodium bismuthate. Contrary to our hypotheses Am(VI) was not reduced faster at higher americium concentrations, and the reduction was only zero-order at short time scales. Attempts to model the reduction kinetics using zero order kinetic models showed Am(VI) reduction in nitric acid is more complex than the autoreduction processes reported by others in perchloric acid. The classical zero-order reduction of Am(VI) was found here only for short times on the order of a few hours. We did show that the rate of Am(V) production was less than the rate of Am(VI) reduction, indicating that some Am(VI) undergoes two electron-reduction to Am(IV). We also monitored the Am(VI) reduction in contact with the organic diluent dodecane. A direct comparison of these results with those in the absence of the organic diluent showed the reduction rates for Am(VI) were not statistically different for both systems. Additional americium oxidations conducted in the presence of Ce(IV)/Ce(III) ions showed that Am(VI) is reduced without the typical growth of Am(V) observed in the systems sans Ce ion. This was an interesting result which suggests a potential new reduction/oxidation pathway for Am in the presence of Ce; however, these results were very preliminary, and will require additional experiments to understand the mechanism by which this occurs. Overall, these studies have shown that hexavalent americium is fundamentally stable enough in nitric acid to run a separations process. However, the complicated nature of the reduction pathways based on the system components is far from being rigorously understood.

  16. SOLID STATE ENERGY CONVERSION ALLIANCE DELPHI SOLID OXIDE FUEL CELL

    SciTech Connect

    Steven Shaffer; Sean Kelly; Subhasish Mukerjee; David Schumann; Gail Geiger; Kevin Keegan; Larry Chick

    2004-05-07

    The objective of this project is to develop a 5 kW Solid Oxide Fuel Cell power system for a range of fuels and applications. During Phase I, the following will be accomplished: Develop and demonstrate technology transfer efforts on a 5 kW stationary distributed power generation system that incorporates steam reforming of natural gas with the option of piped-in water (Demonstration System A). Initiate development of a 5 kW system for later mass-market automotive auxiliary power unit application, which will incorporate Catalytic Partial Oxidation (CPO) reforming of gasoline, with anode exhaust gas injected into an ultra-lean burn internal combustion engine. This technical progress report covers work performed by Delphi from July 1, 2003 to December 31, 2003, under Department of Energy Cooperative Agreement DE-FC-02NT41246. This report highlights technical results of the work performed under the following tasks: Task 1 System Design and Integration; Task 2 Solid Oxide Fuel Cell Stack Developments; Task 3 Reformer Developments; Task 4 Development of Balance of Plant (BOP) Components; Task 5 Manufacturing Development (Privately Funded); Task 6 System Fabrication; Task 7 System Testing; Task 8 Program Management; Task 9 Stack Testing with Coal-Based Reformate; and Task 10 Technology Transfer from SECA CORE Technology Program. In this reporting period, unless otherwise noted Task 6--System Fabrication and Task 7--System Testing will be reported within Task 1 System Design and Integration. Task 8--Program Management, Task 9--Stack Testing with Coal Based Reformate, and Task 10--Technology Transfer from SECA CORE Technology Program will be reported on in the Executive Summary section of this report.

  17. Monomethylioarsenicals are substratres for human arsenic (+3 oxidation state) methyltransferase

    EPA Science Inventory

    Monomethylthioarsenicals are substrates for human arsenic (+3 oxida1tion state) methyltransferase Methylated thioarsenicals are structural analogs of methylated oxyarsenic in which one or more oxygen atom bound t...

  18. Water and the Oxidation State of Subduction Zone Magmas

    SciTech Connect

    Kelley, K.; Cottrell, E

    2009-01-01

    Mantle oxygen fugacity exerts a primary control on mass exchange between Earth's surface and interior at subduction zones, but the major factors controlling mantle oxygen fugacity (such as volatiles and phase assemblages) and how tectonic cycles drive its secular evolution are still debated. We present integrated measurements of redox-sensitive ratios of oxidized iron to total iron (Fe{sup 3+}/{Sigma}Fe), determined with Fe K-edge micro-x-ray absorption near-edge structure spectroscopy, and pre-eruptive magmatic H{sub 2}O contents of a global sampling of primitive undegassed basaltic glasses and melt inclusions covering a range of plate tectonic settings. Magmatic Fe{sup 3+}/{Sigma}Fe ratios increase toward subduction zones (at ridges, 0.13 to 0.17; at back arcs, 0.15 to 0.19; and at arcs, 0.18 to 0.32) and correlate linearly with H{sub 2}O content and element tracers of slab-derived fluids. These observations indicate a direct link between mass transfer from the subducted plate and oxidation of the mantle wedge.

  19. Arsenic (+3 oxidation state) methyltransferase genotype affects steady-state distribution and clearance of arsenic in arsenate-treated mice

    EPA Science Inventory

    Arsenic (+3 oxidation state) methyltransferase (As3mt) catalyzes formation of mono-, di-, and tri-methylated metabolites of inorganic arsenic. Distribution and retention of arsenic were compared in adult female As3mt knockout mice and wild-type C57BL/6 mice using a regimen in whi...

  20. Mantle redox evolution and the oxidation state of the Archean atmosphere

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.; Eggler, D. H.; Raeburn, S. P.

    1993-01-01

    Current models predict that the early atmosphere consisted mostly of CO2, N2, and H2O, along with traces of H2 and CO. Such models are based on the assumption that the redox state of the upper mantle has not changed, so that volcanic gas composition has remained approximately constant with time. We argue here that this assumption is probably incorrect: the upper mantle was originally more reduced than today, although not as reduced as the metal arrest level, and has become progressively more oxidized as a consequence of the release of reduced volcanic gases and the subduction of hydrated, oxidized seafloor. Data on the redox state of sulfide and chromite inclusions in diamonds imply that the process of mantle oxidation was slow, so that reduced conditions could have prevailed for as much as half of the earth's history. To be sure, other oxybarometers of ancient rocks give different results, so the question of when the mantle redox state has changed remains unresolved. Mantle redox evolution is intimately linked to the oxidation state of the primitive atmosphere: A reduced Archean atmosphere would have had a high hydrogen escape rate and should correspond to a changing mantle redox state; an oxidized Archean atmosphere should be associated with a constant mantle redox state. The converses of these statements are also true. Finally, our theory of mantle redox evolution may explain why the Archean atmosphere remained oxygen-deficient until approximately 2.0 billion years ago (Ga) despite a probable early origin for photosynthesis.

  1. The effect of the existing state of Y on high temperature oxidation properties of magnesium alloys

    NASA Astrophysics Data System (ADS)

    Yu, Xiaowen; Shen, Shijun; Jiang, Bin; Jiang, Zhongtao; Yang, Hong; Pan, Fusheng

    2016-05-01

    This paper studies the effect of the existing state of Y element on the high temperature oxidation resistance of magnesium alloys. Different levels of Al element were added into Mg-2.5Y alloy to obtain different existing state of Y. The oxidation rate of Mg-2.5Y-2.5Al alloy is the highest among Mg-2.5Y, Mg-2.5Y-2.5Al and Mg-2.5Y-4.2Al alloys at 500 °C. An effective and protective Y2O3/MgO composite oxide film was formed on the surface of Mg-2.5Y alloy after oxidized at 500 °C for 360 min. The results show that the dissolved Y element in the matrix was beneficial to improve the oxidation resistance of magnesium alloys. Once Y element transformed to the high temperature stable Al2Y compound, its ability in preventing oxidation would disappear. The formation of Al2Y compound severely deteriorated the oxidation resistance of Mg-2.5Y alloy. In addition, the dissolved Al can also cause the rise of oxidation resistance at a certain extent.

  2. Investigation of oxygen states and reactivities on a nanostructured cupric oxide surface

    NASA Astrophysics Data System (ADS)

    Svintsitskiy, D. A.; Stadnichenko, A. I.; Demidov, D. V.; Koscheev, S. V.; Boronin, A. I.

    2011-08-01

    Nanostructured copper (II) oxide was formed on clean copper foil at room temperature using activated oxygen produced by RF discharge. CuO particles of approximately 10-20 nm were observed on the surface by Scanning Tunneling Microscopy (STM). The copper states and oxygen species of the model cupric oxide were studied by means of X-ray Photoelectron Spectroscopy (XPS). These oxide particles demonstrated abnormally high reactivity with carbon monoxide (CO) at temperatures below 100 °C. The XPS data showed that the interaction of CO with the nanostructured cupric oxide resulted in reduction of the CuO particles to Cu 2O species. The reactivity of the nanostructured cupric oxide to CO was studied at 80 °C using XPS in step-by-step mode. The initial reactivity was estimated to be 5 × 10 -5 and was steadily reduced down to 5 × 10 -9 as the exposure was increased. O1s spectral analysis allowed us to propose that the high initial reactivity was caused by the presence of non-lattice oxygen states on the surface of the nanostructured CuO. We established that reoxidation of the partially reduced nanostructured cupric oxide by molecular oxygen O 2 restored the highly reactive oxygen form on the surface. These results allowed us to propose that the nanostructured cupric oxide could be used for low temperature catalytic CO oxidation. Some hypotheses concerning the nature of the non-lattice oxygen species with high reactivity are also discussed.

  3. Effect of environment on iodine oxidation state and reactivity with aluminum.

    PubMed

    Smith, Dylan K; McCollum, Jena; Pantoya, Michelle L

    2016-04-28

    Iodine oxide is a highly reactive solid oxidizer and with its abundant generation of iodine gas during reaction, this oxidizer also shows great potential as a biocidal agent. A problem with using I2O5 in an energetic mixture is its highly variable reactive behavior. This study isolates the variable reactivity associated with I2O5 as a function of its chemical reaction in various environments. Specifically, aluminum fuel and iodine oxide powder are combined using a carrier fluid to aid intermixing. The carrier fluid is shown to significantly affect the oxidation state of iodine oxide, thereby affecting the reactivity of the mixture. Four carrier fluids were investigated ranging in polarity and water miscibility in increasing order from hexane < acetone < isopropanol < water as well as untreated, dry-mixed reactants. Oxidation state and reactivity were examined with experimental techniques including X-ray photoelectric spectroscopy (XPS) and differential scanning calorimetry (DSC). Results are compared with thermal equilibrium simulations. Flame speeds increased with polarity of the fluid used to intermix the powder and ranged from 180 to 1202 m s(-1). The I2O5 processed in the polar fluids formed hydrated states of iodine oxide: HIO3 and HI3O8; and, the nonpolar and dry-mixed samples formed: I2O4 and I4O9. During combustion, the hydrated iodine oxides rapidly dehydrated from HIO3 to HI3O8 and from HI3O8 to I2O5. Both steps release 25% of their mass as vapor during combustion. Increased gas generation enhances convective energy transport and accounts for the increase in reactivity seen in the mixtures processed in polar fluids. These results explain the chemical mechanisms underlying the variable reactivity of I2O5 that are a function of the oxide's highly reactive nature with its surrounding environment. These results will significantly impact the selection of carrier fluid in the synthesis approach for iodine containing reactive mixtures. PMID:27052472

  4. Quantum Chemical Studies of Actinides and Lanthanides: From Small Molecules to Nanoclusters

    NASA Astrophysics Data System (ADS)

    Vlaisavljevich, Bess

    Research into actinides is of high interest because of their potential applications as an energy source and for the environmental implications therein. Global concern has arisen since the development of the actinide concept in the 1940s led to the industrial scale use of the commercial nuclear energy cycle and nuclear weapons production. Large quantities of waste have been generated from these processes inspiring efforts to address fundamental questions in actinide science. In this regard, the objective of this work is to use theory to provide insight and predictions into actinide chemistry, where experimental work is extremely challenging because of the intrinsic difficulties of the experiments themselves and the safety issues associated with this type of chemistry. This thesis is a collection of theoretical studies of actinide chemistry falling into three categories: quantum chemical and matrix isolation studies of small molecules, the electronic structure of organoactinide systems, and uranyl peroxide nanoclusters and other solid state actinide compounds. The work herein not only spans a wide range of systems size but also investigates a range of chemical problems. Various quantum chemical approaches have been employed. Wave function-based methods have been used to study the electronic structure of actinide containing molecules of small to middle-size. Among these methods, the complete active space self consistent field (CASSCF) approach with corrections from second-order perturbation theory (CASPT2), the generalized active space SCF (GASSCF) approach, and Moller-Plesset second-order perturbation theory (MP2) have been employed. Likewise, density functional theory (DFT) has been used along with analysis tools like bond energy decomposition, bond orders, and Bader's Atoms in Molecules. From these quantum chemical results, comparison with experimentally obtained structures and spectra are made.

  5. Actinide sequestration using self-assembled monolayers on mesoporous supports.

    PubMed

    Fryxell, Glen E; Lin, Yuehe; Fiskum, Sandy; Birnbaum, Jerome C; Wu, Hong; Kemner, Ken; Kelly, Shelley

    2005-03-01

    Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometalate anions, and radionuclides. Details addressing the design, synthesis, and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental cleanup necessary after 40 years of weapons-grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented. PMID:15787373

  6. Actinide Sequestration Using Self-Assembled Monolayers on Mesoporous Supports

    SciTech Connect

    Fryxell, Glen E.; Lin, Yuehe; Fiskum, Sandra K.; Birnbaum, Jerome C.; Wu, Hong; Kemner, K. M.; Kelly, Shelley

    2005-03-01

    Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents, whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometallate anions and radionuclides. Details addressing the design, synthesis and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental clean-up necessary after 40 years of weapons grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented.

  7. Autodetachment spectroscopy of the aluminum oxide anion dipole bound state

    SciTech Connect

    Mascaritolo, Kyle J.; Gardner, Adrian M.; Heaven, Michael C.

    2015-09-21

    The {sup 1}Σ{sup +}←X{sup 1}Σ{sup +} ground state to dipole bound state (DBS) electronic transition of AlO{sup −} has been studied by means of autodetachment spectroscopy. Vibrational and rotational molecular constants for AlO{sup −} have been determined for both the ground state (υ″ = 0, 1) and the excited DBS (υ′ = 0, 1). These data provide an improved determination of the electron affinity for AlO (2.6110(7) eV) that is consistent with an earlier measurement. The electron binding energy of the DBS was found to be 52 ± 6 cm{sup −1}. Experimental results are compared with the predictions from high level ab initio calculations.

  8. Approaches to Determining the Oxidation State of Nitrogen and Carbon Atoms in Organic Compounds for High School Students

    ERIC Educational Resources Information Center

    Jurowski, Kamil; Krzeczkowska, Malgorzata Krystyna; Jurowska, Anna

    2015-01-01

    The concept of oxidation state (or oxidation number) and related issues have always been difficult for students. In addition, there are misunderstandings and obscurities, which can cause improper balancing of the chemical equations (mostly in organic reactions). In particular, these problems are related to determination of the oxidation state of…

  9. Topological and unconventional magnetic states in transition metal oxides

    NASA Astrophysics Data System (ADS)

    Fiete, Gregory

    In this talk I describe some recent work on unusual correlated phases that may be found in bulk transition metal oxides with strong spin-orbit coupling. I will focus on model Hamiltonian studies that are motivated by the pyrocholore iridates, though the correlated topological phases described may appear in a much broader class of materials. I will describe a variety of fractionalized topological phases protected by time-reversal and crystalline symmetries: The weak topological Mott insulator (WTMI), the TI* phase, and the topological crystalline Mott insulator (TCMI). If time permits, I will also discuss closely related heterostructures of pyrochlore iridates in a bilayer and trilayer film geometry. These quasi-two dimensional systems may exhibit a number of interesting topological and magnetic phases. This work is generously funded by the ARO, DARPA, and the NSF.

  10. Method for decontamination of nickel-fluoride-coated nickel containing actinide-metal fluorides

    DOEpatents

    Windt, Norman F.; Williams, Joe L.

    1983-01-01

    The invention is a process for decontaminating particulate nickel contaminated with actinide-metal fluorides. In one aspect, the invention comprises contacting nickel-fluoride-coated nickel with gaseous ammonia at a temperature effecting nickel-catalyzed dissociation thereof and effecting hydrogen-reduction of the nickel fluoride. The resulting nickel is heated to form a melt and a slag and to effect transfer of actinide metals from the melt into the slag. The melt and slag are then separated. In another aspect, nickel containing nickel oxide and actinide metals is contacted with ammonia at a temperature effecting nickel-catalyzed dissociation to effect conversion of the nickel oxide to the metal. The resulting nickel is then melted and separated as described. In another aspect nickel-fluoride-coated nickel containing actinide-metal fluorides is contacted with both steam and ammonia. The resulting nickel then is melted and separated as described. The invention is characterized by higher nickel recovery, efficient use of ammonia, a substantial decrease in slag formation and fuming, and a valuable increase in the service life of the furnace liners used for melting.

  11. Oxidation-resistive copper nanoparticles: photoreduction synthesis and their oxidation state measurements by XAFS and HRTEM

    NASA Astrophysics Data System (ADS)

    Tanaka, H.; Aoki, T.; Yonemura, M.; Miyagawa, M.; Okumura, K.

    2016-05-01

    We examined the synthesis of copper nanoparticles by photoreduction, and characterized them using optical spectroscopy, XAFS measurement, and electron microscopy. Ethanol solution of copper acetate with TiO2 nanoparticles was photoirradated. Optical absorption observation indicated that copper nanoparticles were formed in the solution. XAFS measurement indicated that the nanoparticles were metallic, not oxidized. Electron microscopy observation exhibited that the nanoparticles kept metallic even under exposure to air.

  12. Microanalysis of iron oxidation state in iron oxides using X Ray Absorption Near Edge Structure (XANES)

    NASA Technical Reports Server (NTRS)

    Sutton, S. R.; Delaney, J.; Bajt, S.; Rivers, M. L.; Smith, J. V.

    1993-01-01

    An exploratory application of x ray absorption near edge structure (XANES) analysis using the synchrotron x ray microprobe was undertaken to obtain Fe XANES spectra on individual sub-millimeter grains in conventional polished sections. The experiments concentrated on determinations of Fe valence in a suite of iron oxide minerals for which independent estimates of the iron speciation could be made by electron microprobe analysis and x ray diffraction.

  13. Characterizing Oxidation State using Bader Analysis, Maximally Localized Wannier Functions and Atomic Orbitals Projection

    NASA Astrophysics Data System (ADS)

    Reeves, Kyle; Kanai, Yosuke

    2013-03-01

    The concept of oxidation state of atoms in molecules and materials is widely used to predict and understand chemical and physical properties. This concept is perhaps driven more empirically than by any rigorous criteria differentiating one oxidation state from another. Within the oxidation state framework, an integer number of electrons is assigned to the nuclei within a system. In practice, a distribution of electron density makes it difficult to quantify such discrete assignments without some ambiguities. We explore three different charge analysis approaches in density functional theory calculations for addressing the oxidation state of important organometallic molecules [Ru(bpy)3]2+ and [Ru(bpy)3]3+, which are widely used for solar energy conversion applications. Bader charge analysis, Wannier function analysis, and atomic orbital projection are employed in this work. Given the highly-localized nature of the d-electrons of the ruthenium atom, the charge analysis methods are also compared with Hubbard-U correction. We also discuss how the solvation by water molecules influences the oxidation state characterization for these organometallic complexes.

  14. Theoretical study of the structures of flavin in different oxidation and protonation states

    SciTech Connect

    Zheng, Y.J.; Ornstein, R.L.

    1996-10-02

    Ab initio molecular orbital theory was used to investigate the structure of flavin in different oxidation and protonation states using lumiflavin as a model compound. According to our study. oxidized flavin is planar no matter what its protonation state or whether it participates in hydrogen bonding. The structures of flavin semiquinone radicals are planar or very close to planar, but the reduced flavin H{sub 3}Fl{sub red} (9) is bent with a ring puckering angle of 27.3{degree} along the N5 and N10 axis. The calculations indicate that N1 is the site of protonation for oxidized flavin, which is in agreement with several crystallographic studies. The calculated spin density distribution for flavin semiquinone radicals is also consistent with experimental results. Electrostatic potential derived charges at the RHF/6-31G{sup *} level of theory are also provided for both oxidized and reduced flavins. 34 refs., 4 figs., 5 tabs.

  15. DIAMIDE DERIVATIVES OF DIPICOLINIC ACID AS ACTINIDE AND LANTHANIDE EXTRACTANTS IN A VARIATION OF THE UNEX PROCESS

    SciTech Connect

    D. R. Peterman; R. S. Herbst; J. D. Law; R. D. Tillotson; T. G. Garn; T. A. Todd; V. N. Romanovskiy; V. A. Babain; M. Yu. Alyapyshev; I. V. Smirnov

    2007-09-01

    The Universal Extraction (UNEX) process has been developed for simultaneous extraction of cesium, strontium, and actinides from acidic solutions. This process utilizes an extractant consisting of 0.08 M chlorinated cobalt dicarbollide (HCCD), 0.007-0.02 M polyethylene glycol (PEG-400), and 0.02 M diphenyl-N,N-di-n-butylcarbamoylmethylphosphine oxide (Ph2CMPO) in the diluent trifluoromethylphenyl sulfone (CF3C6H5SO2, designated FS-13) and provides simultaneous extraction of Cs, Sr, actinides, and lanthanides from HNO3 solutions. The UNEX process is of limited utility for processing acidic solutions containing large quantities of lanthanides and/or actinides, such as dissolved spent nuclear fuel solutions. These constraints are primarily attributed to the limited concentrations of CMPO (a maximum of ~0.02 M) in the organic phase and limited solubility of the CMPO-metal complexes. As a result, alternative actinide and lanthanide extractants are being investigated for use with HCCD as an improvement for waste processing and for applications where higher concentrations of the metals are present. Our preliminary results indicate that diamide derivatives of dipicolinic acid may function as efficient actinide and lanthanide extractants. The results to be presented indicate that, of the numerous diamides studied to date, the tetrabutyldiamide of dipicolinic acid, TBDPA, shows the most promise as an alternative actinide/lanthanide extractant in the UNEX process.

  16. Manifestation of cluster effects in the structure of actinides

    NASA Astrophysics Data System (ADS)

    Shneidman, T. M.; Adamian, G. G.; Antonenko, N. V.; Jolos, R. V.; Zhou, Shan-Gui

    2016-01-01

    We developed a cluster model which allows to take into account both shape deformation parameters and cluster degrees of freedom. The model is based on the assumption that the wave function of nucleus can be treated as a superposition of a mononucleus and two-cluster configurations. The model is applied to describe the multiple negative-parity bands in deformed actinides. Special emphasis is made on the investigation of the recently measured positive parity 0+2 rotational band of reflection-asymmetric nature in 240Pu. The results suggest that this band might be understood as the one built on the lowest excited state in mass asymmetry degree of freedom.

  17. Determining the Oxidation States of Manganese in NT2 Cells and Cultured Astrocytes

    SciTech Connect

    Gunter,K.; Aschner, M.; Miller, L.; Eliseev, R.; Salter, J.; Andersen, K.; Gunter, T.

    2006-01-01

    Excessive brain manganese (Mn) can produce a syndrome called 'manganism', which correlates with loss of striatal dopamine and cell death in the striatum and globus pallidus. The prevalent hypothesis for the cause of this syndrome has been oxidation of cell components by the strong oxidizing agent, Mn{sup 3+}, either formed by oxidation of intracellular Mn{sup 2+} or transported into the cell as Mn{sup 3+}. We have recently used X-ray absorption near edge structure spectroscopy (XANES) to determine the oxidation states of manganese complexes in brain and liver mitochondria and in nerve growth factor (NGF)-induced and non-induced PC12 cells. No evidence was found for stabilization or accumulation of Mn{sup 3+} complexes because of oxidation of Mn{sup 2+} by reactive oxygen species in these tissues. Here we extend these studies of manganese oxidation state to cells of brain origin, human neuroteratocarcinoma (NT2) cells and primary cultures of rat astrocytes. Again we find no evidence for stabilization or accumulation of any Mn{sup 3+} complex derived from oxidation of Mn{sup 2+} under a range of conditions.

  18. TUCS/phosphate mineralization of actinides

    SciTech Connect

    Nash, K.L.

    1997-10-01

    This program has as its objective the development of a new technology that combines cation exchange and mineralization to reduce the concentration of heavy metals (in particular actinides) in groundwaters. The treatment regimen must be compatible with the groundwater and soil, potentially using groundwater/soil components to aid in the immobilization process. The delivery system (probably a water-soluble chelating agent) should first concentrate the radionuclides then release the precipitating anion, which forms thermodynamically stable mineral phases, either with the target metal ions alone or in combination with matrix cations. This approach should generate thermodynamically stable mineral phases resistant to weathering. The chelating agent should decompose spontaneously with time, release the mineralizing agent, and leave a residue that does not interfere with mineral formation. For the actinides, the ideal compound probably will release phosphate, as actinide phosphate mineral phases are among the least soluble species for these metals. The most promising means of delivering the precipitant would be to use a water-soluble, hydrolytically unstable complexant that functions in the initial stages as a cation exchanger to concentrate the metal ions. As it decomposes, the chelating agent releases phosphate to foster formation of crystalline mineral phases. Because it involves only the application of inexpensive reagents, the method of phosphate mineralization promises to be an economical alternative for in situ immobilization of radionuclides (actinides in particular). The method relies on the inherent (thermodynamic) stability of actinide mineral phases.

  19. Actinide Sorption in a Brine/Dolomite Rock System: Evaluating the Degree of Conservatism in Kd Ranges used in Performance Assessment Modeling for the WIPP Nuclear Waste Repository

    NASA Astrophysics Data System (ADS)

    Dittrich, T. M.; Reed, D. T.

    2015-12-01

    The Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM is the only operating nuclear waste repository in the US and has been accepting transuranic (TRU) waste since 1999. The WIPP is located in a salt deposit approximately 650 m below the surface and performance assessment (PA) modeling for a 10,000 year period is required to recertify the operating license with the US EPA every five years. The main pathway of concern for environmental release of radioactivity is a human intrusion caused by drilling into a pressurized brine reservoir below the repository. This could result in the flooding of the repository and subsequent transport in the high transmissivity layer (dolomite-rich Culebra formation) above the waste disposal rooms. We evaluate the degree of conservatism in the estimated sorption partition coefficients (Kds) ranges used in the PA based on an approach developed with granite rock and actinides (Dittrich and Reimus, 2015; Dittrich et al., 2015). Sorption onto the waste storage material (Fe drums) may also play a role in mobile actinide concentrations. We will present (1) a conceptual overview of how Kds are used in the PA model, (2) technical background of the evolution of the ranges and (3) results from batch and column experiments and model predictions for Kds with WIPP dolomite and clays, brine with various actinides, and ligands (e.g., acetate, citrate, EDTA) that could promote transport. The current Kd ranges used in performance models are based on oxidation state and are 5-400, 0.5-10,000, 0.03-200, and 0.03-20 mL g-1 for elements with oxidation states of III, IV, V, and VI, respectively. Based on redox conditions predicted in the brines, possible actinide species include Pu(III), Pu(IV), U(IV), U(VI), Np(IV), Np(V), Am(III), and Th(IV). We will also discuss the challenges of upscaling from lab experiments to field scale predictions, the role of colloids, and the effect of engineered barrier materials (e.g., MgO) on transport conditions. Dittrich

  20. Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol

    SciTech Connect

    Massachusetts Institute of Technology; Kroll, Jesse H.; Donahue, Neil M.; Jimenez, Jose L.; Kessler, Sean H.; Canagaratna, Manjula R.; Wilson, Kevin R.; Altieri, Katye E.; Mazzoleni, Lynn R.; Wozniak, Andrew S.; Bluhm, Hendrik; Mysak, Erin R.; Smith, Jared D.; Kolb, Charles E.; Worsnop, Douglas R.

    2010-11-05

    A detailed understanding of the sources, transformations, and fates of organic species in the environment is crucial because of the central roles that organics play in human health, biogeochemical cycles, and Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state (OSC), a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of OSC , using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number (nC).

  1. Ab initio molecular dynamics simulation of aqueous solution of nitric oxide in different formal oxidation states

    NASA Astrophysics Data System (ADS)

    Venâncio, Mateus F.; Rocha, Willian R.

    2015-10-01

    Ab initio molecular dynamics simulations were used to investigate the early chemical events involved in the dynamics of nitric oxide (NOrad), nitrosonium cation (NO+) and nitroxide anion (NO-) in aqueous solution. The NO+ ion is very reactive in aqueous solution having a lifetime of ∼4 × 10-13 s, which is shorter than the value of 3 × 10-10 s predicted experimentally. The NO+ reacts generating the nitrous acid as an intermediate and the NO2- ion as the final product. The dynamics of NOrad revealed the reversibly formation of a transient anion radical species HONOrad -.

  2. Actinide-silicon multiradical bonding: infrared spectra and electronic structures of the Si(μ-X)AnF3 (An = Th, U; X = H, F) molecules.

    PubMed

    Hu, Han-Shi; Wei, Fan; Wang, Xuefeng; Andrews, Lester; Li, Jun

    2014-01-29

    We report a series of Si(μ-X)AnF3 (An = Th, U; X = H, F) complexes with silicon-actinide(IV) single bonds and unexpected multiradical features that form rare triplet silylenes. These bridged molecules have been prepared in microscopic scale through reactions of laser-ablated uranium and thorium atoms with silicon fluorides and identified from infrared spectra in argon and neon matrixes and relativistic quantum chemical calculations. Similar neon matrix experiments for the reactions of uranium with CF4 and CHF3 were carried out for comparison. Our density functional theory calculations show that the Si-U single-bonded species Si(μ-X)UF3 (X = H, F) with U(IV) oxidation state and the quasi-agostic bridge ligand of H or F are most stable among all the isomers, whereas the naively anticipated triple-bonded species XSi≡UF3 with U(VI) oxidation state and the double-bonded species XSi(•)═(•)UF3 with U(V) oxidation state lie markedly higher in energy. Similar thorium products from reactions with XSiF3 are also found to prefer the Si(μ-X)ThF3 structures with Si-Th single bonds and bridged H or F ligands. High level ab initio wave function theory calculations with the CCSD(T) and CASPT2 methods confirm that the ground states are quintet for Si(μ-X)UF3 and triplet for Si(μ-X)ThF3 with two unpaired electrons on the silylene group. These silicon-bearing molecules as the lowest-energy isomer of XSiAnF3 represent the first silicon-actinide systems with unusual "triplet" silylenes and Si-An single bonds with multiradical character. They are in dramatic contrast to the uranium-carbon analogs, XC≡UF3, which form triple-bonded singlet ground states with C3v symmetry. The calculated vibrational frequencies of the Si(μ-X)AnF3 complexes agree well with experimental observations. These results accentuate the critical difference of chemical bonding of 3p- and 2p-row main-group elements with actinides. The Lewis electron-pair model and the octet rule break down for these

  3. Optical spectra and electronic structure of actinide ions in compounds and in solution

    SciTech Connect

    Carnall, W.T.; Crosswhite, H.M.

    1985-08-01

    This report provides a summary of theoretical and experimental studies of actinide spectra in condensed phases. Much of the work was accomplished at Argonne National Laboratory, but references to related investigations by others are included. Spectroscopic studies of the trivlent actinides are emphasized, as is the use of energy level parameters, evaluated from experimental data, to investigate systematic trends in electronic structure and other properties. Some reference is made to correlations with atomic spectra, as well as with spectra of the (II), (IV), and higher valence states. 207 refs., 39 figs., 38 tabs.

  4. Evidence for oxidation-state-dependent conformational changes in human ferredoxin from multinuclear, multidimensional NMR spectroscopy.

    PubMed

    Xia, B; Volkman, B F; Markley, J L

    1998-03-17

    Human ferredoxin belongs to the vertebrate ferredoxin family which includes bovine adrenodoxin. It is a small (13.8 kDa) acidic protein with a [2Fe-2S] cluster. It functions as an electron shuttle in the cholesterol side-chain cleavage reaction which is the first step of steroid hormone biosynthesis. The protein studied here was produced in Escherichia coli and doubly labeled with 13C and 15N. The diamagnetic 15N, 13C', 13C alpha, 13C beta, 1H alpha, and 1HN resonances from about 70% of the 124 amino acid residues for oxidized human ferredoxin and 80% of those for the reduced protein have been assigned primarily on the basis of results from three-dimensional, triple-resonance experiments. Secondary structure features for human ferredoxin in its oxidized and reduced states have been identified from a combination of chemical shift index and NOE data. Comparison of NMR results from the protein in its oxidized and reduced states indicates that structural changes accompany the change in the oxidation state of the [2Fe-2S] cluster. Major differences are localized at two regions: residues 29-31 and residues 109-124; the latter stretch forms the C-terminal region of the protein. The possible functional significance of these oxidation-state-dependent structural changes is discussed. PMID:9521718

  5. Ultratrace analysis of transuranic actinides by laser-induced fluorescence

    DOEpatents

    Miller, S.M.

    1983-10-31

    Ultratrace quantities of transuranic actinides are detected indirectly by their effect on the fluorescent emissions of a preselected fluorescent species. Transuranic actinides in a sample are coprecipitated with a host lattice material containing at least one preselected fluorescent species. The actinide either quenches or enhances the laser-induced fluorescence of the preselected fluorescent species. The degree of enhancement or quenching is quantitatively related to the concentration of actinide in the sample.

  6. Ultratrace analysis of transuranic actinides by laser-induced fluorescence

    DOEpatents

    Miller, Steven M.

    1988-01-01

    Ultratrace quantities of transuranic actinides are detected indirectly by their effect on the fluorescent emissions of a preselected fluorescent species. Transuranic actinides in a sample are coprecipitated with a host lattice material containing at least one preselected fluorescent species. The actinide either quenches or enhances the laser-induced fluorescence of the preselected fluorescent species. The degree of enhancement or quenching is quantitatively related to the concentration of actinide in the sample.

  7. 99Tc and Re incorporated into metal oxide polyoxometalates: oxidation state stability elucidated by electrochemistry and theory.

    PubMed

    McGregor, Donna; Burton-Pye, Benjamin P; Mbomekalle, Israel M; Aparicio, Pablo A; Romo, Susanna; López, Xavier; Poblet, Josep M; Francesconi, Lynn C

    2012-08-20

    The radioactive element technetium-99 ((99)Tc, half-life = 2.1 × 10(5) years, β(-) of 253 keV), is a major byproduct of (235)U fission in the nuclear fuel cycle. (99)Tc is also found in radioactive waste tanks and in the environment at National Lab sites and fuel reprocessing centers. Separation and storage of the long-lived (99)Tc in an appropriate and stable waste-form is an important issue that needs to be addressed. Considering metal oxide solid-state materials as potential storage matrixes for Tc, we are examining the redox speciation of Tc on the molecular level using polyoxometalates (POMs) as models. In this study we investigate the electrochemistry of Tc complexes of the monovacant Wells-Dawson isomers, α(1)-P(2)W(17)O(61)(10-) (α1) and α(2)-P(2)W(17)O(61)(10-) (α2) to identify features of metal oxide materials that can stabilize the immobile Tc(IV) oxidation state accessed from the synthesized Tc(V)O species and to interrogate other possible oxidation states available to Tc within these materials. The experimental results are consistent with density functional theory (DFT) calculations. Electrochemistry of K(7-n)H(n)[Tc(V)O(α(1)-P(2)W(17)O(61))] (Tc(V)O-α1), K(7-n)H(n)[Tc(V)O(α(2)-P(2)W(17)O(61))] (Tc(V)O-α2) and their rhenium analogues as a function of pH show that the Tc-containing derivatives are always more readily reduced than their Re analogues. Both Tc and Re are reduced more readily in the lacunary α1 site as compared to the α2 site. The DFT calculations elucidate that the highest oxidation state attainable for Re is VII while, under the same electrochemistry conditions, the highest oxidation state for Tc is VI. The M(V)→ M(IV) reduction processes for Tc(V)O-α1 are not pH dependent or only slightly pH dependent suggesting that protonation does not accompany reduction of this species unlike the M(V)O-α2 (M = (99)Tc, Re) and Re(V)O-α1 where M(V/IV) reduction process must occur hand in hand with protonation of the terminal M═O to

  8. Evaluating two experimental approaches for measuring ecosystem carbon oxidation state and oxidative ratio

    NASA Astrophysics Data System (ADS)

    Masiello, C. A.; Gallagher, M. E.; Randerson, J. T.; Deco, R. M.; Chadwick, O. A.

    2008-09-01

    Degree of oxidation of organic carbon (Cox) is a fundamental property of the carbon cycle, reflecting the synthesis and decomposition of natural organic matter. Cox is also related to ecosystem oxidative ratio (OR), the molar ratio of O2 to CO2 fluxes associated with net ecosystem exchange (NEE). Here we compare two methods for measuring Cox and OR: (1) %C, %H, %N, and %O elemental analysis, and (2) heat of combustion (ΔHc) measured by means of bomb calorimetry coupled with %C elemental analysis (hereafter referred to as calorimetry). Compared with %C, %N, %H, and %O elemental analysis, calorimetry generates Cox and OR data more rapidly and cheaply. However, calorimetric measurements yield less accurate Cox and OR data. We additionally report Cox and OR data for a pair of biomass standards and a suite of biomass samples. The OR values we measured in these samples were less variable than OR data reported in the literature (generated by simultaneous measurement of ecosystem O2 and CO2 gas mixing ratios). Our biomass OR values had a mean of 1.03 and range of 0.99-1.06. These estimates are lower than the OR value of 1.10 that is often used to partition uptake of fossil fuel CO2 between the ocean and the terrestrial biosphere.

  9. DetOx: a program for determining anomalous scattering factors of mixed-oxidation-state species.

    PubMed

    Sutton, Karim J; Barnett, Sarah A; Christensen, Kirsten E; Nowell, Harriott; Thompson, Amber L; Allan, David R; Cooper, Richard I

    2013-01-01

    Overlapping absorption edges will occur when an element is present in multiple oxidation states within a material. DetOx is a program for partitioning overlapping X-ray absorption spectra into contributions from individual atomic species and computing the dependence of the anomalous scattering factors on X-ray energy. It is demonstrated how these results can be used in combination with X-ray diffraction data to determine the oxidation state of ions at specific sites in a mixed-valance material, GaCl(2). PMID:23254676

  10. How far can we go? Quantum-chemical investigations of oxidation state +IX.

    PubMed

    Himmel, Daniel; Knapp, Carsten; Patzschke, Michael; Riedel, Sebastian

    2010-03-15

    The highest known oxidation state of any element is +VIII. After the recent discovery of Ir(VIII)O(4) under cryogenic conditions, we have investigated the stability of cationic species [MO(4)](+) (M=Rh,Ir,Mt). Such compounds would formally represent the new oxidation state +IX, which is experimentally unknown so far for the whole periodic table. [IrO(4)](+) is predicted to be the most promising candidate. The calculated spin-orbit (SO) coupling shows only minor effects on the stability of the iridium species, whereas SO-coupling increases enormously for the corresponding Eka-Iridium (Meitnerium) complexes and destabilizes these. PMID:20127784

  11. Photoemission study of praseodymia in its highest oxidation state: The necessity of in situ plasma treatment

    SciTech Connect

    Schaefer, A.; Zielasek, V.; Baeumer, M.; Gevers, S.; Wollschlaeger, J.; Schroeder, T.; Falta, J.

    2011-02-07

    A cold radio frequency oxygen plasma treatment is demonstrated as a successful route to prepare clean, well-ordered, and stoichiometric PrO{sub 2} layers on silicon. High structural quality of these layers is shown by x-ray diffraction. So far unobserved spectral characteristics in Pr 3d x-ray photoelectron (XP) spectra of PrO{sub 2} are presented as a fingerprint for praseodymia in its highest oxidized state. They provide insight in the electronic ground state and the special role of praseodymia among the rare earth oxides. They also reveal that former XP studies suffered from a significant reduction at the surface.

  12. Corannulene reduction. Spectroscopic detection of all anionic oxidation states

    SciTech Connect

    Baumgarten, M.; Gherghel, L.; Wagner, M.; Weitz, A.; Rabinovitz, M. |; Cheng, P.C.; Scott, L.T.

    1995-06-14

    The reduction of corannulene (1) has been followed by parallel detection of optical absorption, electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopies. The major findings are the existence of a diamagnetic dianion that can be observed in NMR and negligible counterion influences in the mono- and dianion. The diamagnetic state of the dianion is also supported by vanishing EPR intensity and semiempirical calculations and exhibits one indistinguishable proton NMR resonance at -5.6 ppm for potassium and lithium as counterions, respectively. The NMR signal is strongly temperature dependent and can only be obtained at low temperature (T < 230 K) where the line width decreases with temperature. Further reduction to the trianion and tetraanion succeeds with Li as the reducing metal, but not with K even at ambient temperatures. The EPR spectra of the trianion show a pronounced temperature dependence with at least two Li cations being strongly coupled. 18 refs., 3 figs., 3 tabs.

  13. Oxidation of extracellular cysteine/cystine redox state in bleomycin-induced lung fibrosis.

    PubMed

    Iyer, Smita S; Ramirez, Allan M; Ritzenthaler, Jeffrey D; Torres-Gonzalez, Edilson; Roser-Page, Susanne; Mora, Ana L; Brigham, Kenneth L; Jones, Dean P; Roman, Jesse; Rojas, Mauricio

    2009-01-01

    Several lines of evidence indicate that depletion of glutathione (GSH), a critical thiol antioxidant, is associated with the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, GSH synthesis depends on the amino acid cysteine (Cys), and relatively little is known about the regulation of Cys in fibrosis. Cys and its disulfide, cystine (CySS), constitute the most abundant low-molecular weight thiol/disulfide redox couple in the plasma, and the Cys/CySS redox state (E(h) Cys/CySS) is oxidized in association with age and smoking, known risk factors for IPF. Furthermore, oxidized E(h) Cys/CySS in the culture media of lung fibroblasts stimulates proliferation and expression of transitional matrix components. The present study was undertaken to determine whether bleomycin-induced lung fibrosis is associated with a decrease in Cys and/or an oxidation of the Cys/CySS redox state and to determine whether these changes were associated with changes in E(h) GSH/glutathione disulfide (GSSG). We observed distinct effects on plasma GSH and Cys redox systems during the progression of bleomycin-induced lung injury. Plasma E(h) GSH/GSSG was selectively oxidized during the proinflammatory phase, whereas oxidation of E(h) Cys/CySS occurred at the fibrotic phase. In the epithelial lining fluid, oxidation of E(h) Cys/CySS was due to decreased food intake. Thus the data show that decreased precursor availability and enhanced oxidation of Cys each contribute to the oxidation of extracellular Cys/CySS redox state in bleomycin-induced lung fibrosis. PMID:18931052

  14. Minior Actinide Doppler Coefficient Measurement Assessment

    SciTech Connect

    Nolan E. Hertel; Dwayne Blaylock

    2008-04-10

    The "Minor Actinide Doppler Coefficient Measurement Assessment" was a Department of Energy (DOE) U-NERI funded project intended to assess the viability of using either the FLATTOP or the COMET critical assembly to measure high temperature Doppler coefficients. The goal of the project was to calculate using the MCNP5 code the gram amounts of Np-237, Pu-238, Pu-239, Pu-241, AM-241, AM-242m, Am-243, and CM-244 needed to produce a 1E-5 in reactivity for a change in operating temperature 800C to 1000C. After determining the viability of using the assemblies and calculating the amounts of each actinide an experiment will be designed to verify the calculated results. The calculations and any doncuted experiments are designed to support the Advanced Fuel Cycle Initiative in conducting safety analysis of advanced fast reactor or acceoerator-driven transmutation systems with fuel containing high minor actinide content.

  15. Preparation of actinide-metal research materials

    SciTech Connect

    Aaron, W.S.; Culpepper, C.A.; Campbell, K.B.

    1986-01-01

    The preparation of actinide-metal research materials is one of many functions of the Isotope Research Materials Laboratory (IRML) at Oak Ridge National Laboratory. Research samples of uranium, plutonium, americium, and curium, typically from milligram quantities up to approx. 100 g, are prepared as pure metals or alloys to customer specifications. Larger quantities, up to many kilograms, of the lower activity actinides, such as /sup 235/U, /sup 238/U, and /sup 232/Th, are also fabricated into custom research forms. Physical forms of these metals include rolled foils or sheets, castings (ingot, rod, or special shapes), and evaporated or sputtered films. The actinide-metal processing capabilities of the IRML are continuing to be improved and applied to a wide variety of custom material preparations to meet the needs of the world-wide research community.

  16. The Actinide-Lanthanide Separation Process

    SciTech Connect

    Lumetta, Gregg J.; Gelis, Artem V.; Carter, Jennifer C.; Niver, Cynthia M.; Smoot, Margaret R.

    2014-02-21

    The Actinide-Lanthanide SEParation (ALSEP) process is described. The process uses an extractant phase consisting of either N,N,N',N'-tetraoctyldiglycolamide (TODGA) or N,N,N',N'-tetra(2 ethylhexyl)diglycolamide (T2EHDGA) combined with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]). The neutral TODGA or T2EHDGA serves to co-extract the trivalent actinide and lanthanide ions from nitric acid media. Switching the aqueous phase chemistry to a citrate buffered diethylenetriaminepentaacetic acid (DTPA) solution at pH 2.5 to 4 results in selective transfer of the actinides to the aqueous phase, thus resulting in separation of these two groups of elements.

  17. Light-induced metastable states in ferroelectric oxides

    NASA Astrophysics Data System (ADS)

    Liu, G. K.; Vikhnin, V. S.; Kapphan, S. E.

    2007-07-01

    New Raman scattering lines (at 463 cm-1 and at 156 cm-1) induced by strong enough optical pumping in nominally pure KTaO3 crystals are manifested. The model of such effect is proposed. This model is based on the light-induced formation of metastable polar clusters constructed from bi-polaronic excitons - Charge Transfer Vibronic Excitons (CTVEs) with their high degree alignment. The CTVEs are caused by photo-carriers with high local concentration which are trapped to local potential wells related with long-range defect fields. CTVE formation are realized in these potential wells due to significant easing of charge transfer fluctuations induced by photo-carrier screening effects. This model is effective also for explanation of giant dielectric constant inducing by strong illumination which was detected recently in KTaO3 and SrTiO3 by Japanese investigators [M. Takesada, T. Yagi, M. Itoh, S. Koshihara, J. Phys. Soc. Jpn. 72 (2003) 37; T. Hasegawa, S. Mouri, Y. Yamada, K. Tanaka, J. Phys. Soc. Jpn. 72 (2003) 41; I. Katayama, Y. Ichikawa, K. Tanaka, Phys. Rev. B 67 (2003) 100102(R)]. Another aspect of the present study was specific recombination luminescence of CTVEs which was investigated here with respect to the influence of additional IR pumping. The present investigation has led to experimental evidence of new, mainly non-linear CTVE with good defined metastable behavior. Such an essentially anharmonic CTVE with respect to charge transfer and lattice displacements was predicted recently in our work [V.S. Vikhnin, Solid State Commun. 127 (2003) 283]. Here, we present experimental evidence of the existence of a new type of exciton state.

  18. RECOVERY OF ACTINIDES FROM AQUEOUS NITRIC ACID SOLUTIONS

    DOEpatents

    Ader, M.

    1963-11-19

    A process of recovering actinides is presented. Tetravalent actinides are extracted from rare earths in an aqueous nitric acid solution with a ketone and back-extracted from the ketone into an aqueous medium. The aqueous actinide solution thus obtained, prior to concentration by boiling, is sparged with steam to reduce its ketone to a maximum content of 3 grams per liter. (AEC)

  19. Complexation of Actinides in Solution: Thermodynamic Measurementsand Structural Characterization

    SciTech Connect

    Rao, L.

    2007-02-01

    This paper presents a brief introduction of the studies of actinide complexation in solution at Lawrence Berkeley National Laboratory. An integrated approach of thermodynamic measurements and structural characterization is taken to obtain fundamental understanding of actinide complexation in solution that is of importance in predicting the behavior of actinides in separation processes and environmental transport.

  20. Actinide Lanthanide Separation Process – ALSEP

    SciTech Connect

    Gelis, Artem V.; Lumetta, Gregg J.

    2014-01-29

    Separation of the minor actinides (Am, Cm) from the lanthanides at an industrial scale remains a significant technical challenge for closing the nuclear fuel cycle. To increase the safety of used nuclear fuel (UNF) reprocessing, as well as reduce associated costs, a novel solvent extraction process has been developed. The process allows for partitioning minor actinides, lanthanides and fission products following uranium/plutonium/neptunium removal; minimizing the number of separation steps, flowsheets, chemical consumption, and waste. This new process, Actinide Lanthanide SEParation (ALSEP), uses an organic solvent consisting of a neutral diglycolamide extractant, either N,N,N',N'-tetra(2 ethylhexyl)diglycolamide (T2EHDGA) or N,N,N',N'-tetraoctyldiglycolamide (TODGA), and an acidic extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]), dissolved in an aliphatic diluent (e.g. n-dodecane). The An/Ln co-extraction is conducted from moderate-to-strong nitric acid, while the selective stripping of the minor actinides from the lanthanides is carried out using a polyaminocarboxylic acid/citrate buffered solution at pH anywhere between 3 and 4.5. The extraction and separation of the actinides from the fission products is very effective in a wide range of HNO3 concentrations and the minimum separation factors for lanthanide/Am exceed 30 for Nd/Am, reaching > 60 for Eu/Am under some conditions. The experimental results presented here demonstrate the great potential for a combined system, consisting of a neutral extractant such as T2EHDGA or TODGA, and an acidic extractant such as HEH[EHP], for separating the minor actinides from the lanthanides.

  1. MOLECULAR SPECTROSCPY AND REACTIONS OF ACTINIDES IN THE GAS PHASE AND CRYOGENIC MATRICES

    SciTech Connect

    Heaven, Michael C.; Gibson, John K.; Marcalo, Joaquim

    2009-02-01

    temperature or below. For many spectroscopic measurements, low temperatures have been achieved by co-condensing the actinide vapor in rare gas or inert molecule host matrices. Spectra recorded in matrices are usually considered to be minimally perturbed. Trapping the products from gas-phase reactions that occur when trace quantities of reactants are added to the inert host gas has resulted in the discovery of many new actinide species. Selected aspects of the matrix isolation data were discussed in chapter 17. In the present chapter we review the spectroscopic matrix data in terms of its relationship to gas-phase measurements, and update the description of the new reaction products found in matrices to reflect the developments that have occurred during the past two years. Spectra recorded in matrix environments are usually considered to be minimally perturbed, and this expectation is borne out for many closed shell actinide molecules. However, there is growing evidence that significant perturbations can occur for open shell molecules, resulting in geometric distortions and/or electronic state reordering. Studies of actinide reactions in the gas phase provide an opportunity to probe the relationship between electronic structure and reactivity. Much of this work has focused on the reactions of ionic species, as these may be selected and controlled using various forms of mass spectrometry. As an example of the type of insight derived from reaction studies, it has been established that the reaction barriers for An+ ions are determined by the promotion energies required to achieve the 5fn6d7s configuration. Gas-phase reaction studies also provide fundamental thermodynamic properties such as bond dissociation and ionization energies. In recent years, an increased number of gas-phase ion chemistry studies of bare (atomic) and ligated (molecular) actinide ions have appeared, in which relevant contributions to fundamental actinide chemistry have been made. These studies were initiated

  2. Systematization of actinides using cluster analysis

    SciTech Connect

    Kopyrin, A.A.; Terent`eva, T.N.; Khramov, N.N.

    1994-11-01

    A representation of the actinides in multidimensional property space is proposed for systematization of these elements using cluster analysis. Literature data for their atomic properties are used. Owing to the wide variation of published ionization potentials, medians are used to estimate them. Vertical dendograms are used for classification on the basis of distances between the actinides in atomic-property space. The properties of actinium and lawrencium are furthest removed from the main group. Thorium and mendelevium exhibit individualized properties. A cluster based on the einsteinium-fermium pair is joined by californium.

  3. Preparation of actinide-metal research

    SciTech Connect

    Aaron, W.S.; Culpepper, C.A.; Campbell, K.B.

    1986-01-01

    The preparation of actinide-metal research materials is one of many functions of the Isotope Research Materials Laboratory (IRML) at Oak Ridge National Lab. Research samples of uranium, plutonium, americium, and curium, typically from milligram quantities up to approx. 100 g, are prepared as pure metals or alloys to customer specifications. Larger quantities, up to many kilograms, of the lower activity actinides, such as /sup 235/U, /sup 238/U, and /sup 232/Th, are also fabricated into custom research forms. Physical forms of these metals include rolled foils or sheets, castings (ingot, rod, or special shapes), and evaporated or sputtered films.

  4. Spin-orbit coupling in actinide cations

    NASA Astrophysics Data System (ADS)

    Bagus, Paul S.; Ilton, Eugene S.; Martin, Richard L.; Jensen, Hans Jørgen Aa.; Knecht, Stefan

    2012-09-01

    The limiting case of Russell-Saunders coupling, which leads to a maximum spin alignment for the open shell electrons, usually explains the properties of high spin ionic crystals with transition metals. For actinide compounds, the spin-orbit splitting is large enough to cause a significantly reduced spin alignment. Novel concepts are used to explain the dependence of the spin alignment on the 5f shell occupation. We present evidence that the XPS of ionic actinide materials may provide direct information about the angular momentum coupling within the 5f shell.

  5. Sulfur-Bridged Terthiophene Dimers: How Sulfur Oxidation State Controls Interchromophore Electronic Coupling.

    PubMed

    Cruz, Chad D; Christensen, Peter R; Chronister, Eric L; Casanova, David; Wolf, Michael O; Bardeen, Christopher J

    2015-10-01

    Symmetric dimers have the potential to optimize energy transfer and charge separation in optoelectronic devices. In this paper, a combination of optical spectroscopy (steady-state and time-resolved) and electronic structure theory is used to analyze the photophysics of sulfur-bridged terthiophene dimers. This class of dimers has the unique feature that the interchromophore (intradimer) electronic coupling can be modified by varying the oxidation state of the bridging sulfur from sulfide (S), to sulfoxide (SO), to sulfone (SO2). Photoexcitation leads to the formation of a delocalized charge resonance state (S1) that relaxes quickly (<10 ps) to a charge-transfer state (S1*). The amount of charge-transfer character in S1* can be enhanced by increasing the oxidation state of the bridging sulfur group as well as the solvent polarity. The S1* state has a decreased intersystem crossing rate when compared to monomeric terthiophene, leading to an enhanced photoluminescence quantum yield. Computational results indicate that electrostatic screening by the bridging sulfur electrons is the key parameter that controls the amount of charge-transfer character. Control of the sulfur bridge oxidation state provides the ability to tune interchromophore interactions in covalent assemblies without altering the molecular geometry or solvent polarity. This capability provides a new strategy for the design of functional supermolecules with applications in organic electronics. PMID:26331195

  6. Effect of oxidation state on Bi mineral speciation in oxidized and reduced granitoids from the Uetsu region, NE Japan

    NASA Astrophysics Data System (ADS)

    Izumino, Yuya; Maruoka, Teruyuki; Nakashima, Kazuo

    2016-06-01

    The relationship between bismuth (Bi) mineral speciation and redox state in three types of granitoids from the Uetsu region, northeast Japan is investigated. Electron microprobe analysis of Bi minerals, sphalerite, Mg-Fe-bearing carbonate minerals, and muscovite, as well as sulfur isotope analysis of sulfide minerals and microthermometric study of fluid inclusions reveal that Bi mineral speciation varies according to the redox state of the granitoids. For example, native bismuth and bismuthinite are abundant and Bi sulfosalts are rare in the lowest fS2 and fO2 mineralized zones of the reduced Iwafune granite (S-type, ilmenite-series) while Bi sulfosalts (Bi3+) are abundant and trace amounts of native bismuth (Bi0) and bismuthinite are found in the highest fS2 and fO2 mineralized zones of the oxidized Wasada granodiorite (I-type, magnetite-series). Bismuthinite is a major Bi mineral, and native bismuth and Bi sulfosalts occur in only minor amounts in the mineralized zones of the Nishitagawa granodiorite (I-type, ilmenite-series), which has intermediate fS2 and fO2 to that of the Iwafune and Wasada samples. Our study indicates that Bi mineral speciation related to granitic intrusive activity is controlled by the redox state of the magmatism, such that native bismuth is typical of reducing conditions, whereas Bi sulfosalts are typical of oxidizing conditions.

  7. Effect of oxidation state on Bi mineral speciation in oxidized and reduced granitoids from the Uetsu region, NE Japan

    NASA Astrophysics Data System (ADS)

    Izumino, Yuya; Maruoka, Teruyuki; Nakashima, Kazuo

    2015-12-01

    The relationship between bismuth (Bi) mineral speciation and redox state in three types of granitoids from the Uetsu region, northeast Japan is investigated. Electron microprobe analysis of Bi minerals, sphalerite, Mg-Fe-bearing carbonate minerals, and muscovite, as well as sulfur isotope analysis of sulfide minerals and microthermometric study of fluid inclusions reveal that Bi mineral speciation varies according to the redox state of the granitoids. For example, native bismuth and bismuthinite are abundant and Bi sulfosalts are rare in the lowest fS2 and fO2 mineralized zones of the reduced Iwafune granite (S-type, ilmenite-series) while Bi sulfosalts (Bi3+) are abundant and trace amounts of native bismuth (Bi0) and bismuthinite are found in the highest fS2 and fO2 mineralized zones of the oxidized Wasada granodiorite (I-type, magnetite-series). Bismuthinite is a major Bi mineral, and native bismuth and Bi sulfosalts occur in only minor amounts in the mineralized zones of the Nishitagawa granodiorite (I-type, ilmenite-series), which has intermediate fS2 and fO2 to that of the Iwafune and Wasada samples. Our study indicates that Bi mineral speciation related to granitic intrusive activity is controlled by the redox state of the magmatism, such that native bismuth is typical of reducing conditions, whereas Bi sulfosalts are typical of oxidizing conditions.

  8. ENHANCED CHEMICAL CLEANING OF SRS WASTE TANKS TO IMPROVE ACTINIDE SOLUBILITY

    SciTech Connect

    Rudisill, T.; Thompson, M.

    2011-09-20

    Processes for the removal of residual sludge from SRS waste tanks have historically used solutions containing up to 0.9 M oxalic acid to dissolve the remaining material following sludge removal. The selection of this process was based on a comparison of a number of studies performed to evaluate the dissolution of residual sludge. In contrast, the dissolution of the actinide mass, which represents a very small fraction of the waste, has not been extensively studied. The Pu, Np, and Am in the sludge is reported to be present as hydrated and crystalline oxides. To identify aqueous solutions which have the potential to increase the solubility of the actinides, the alkaline and mildly acidic test solutions shown below were selected as candidates for use in a series of solubility experiments. The efficiency of the solutions in solubilizing the actinides was evaluated using a simulated sludge prepared by neutralizing a HNO{sub 3} solution containing Pu, Np, and Am. The hydroxide concentration was adjusted to a 1.2 M excess and the solids were allowed to age for several weeks prior to starting the experiments. The sludge was washed with 0.01 M NaOH to prepare the solids for use. Following the addition of an equal portion of the solids to each test solution, the concentrations of Pu, Np, and Am were measured as a function of time over a 792 h (33 day) period to provide a direct comparison of the efficiency of each solution in solubilizing the actinide elements. Although the composition of the sludge was limited to the hydrated actinide oxides (and did not contain other components of demonstrated importance), the results of the study provides guidance for the selection of solutions which should be evaluated in subsequent tests with a more realistic surrogate sludge and actual tank waste.

  9. About the strain state of different metal oxide layers epitaxially grown on Si(1 1 1)

    NASA Astrophysics Data System (ADS)

    Zaumseil, P.; Schroeder, T.

    2011-02-01

    The strain state of metal oxides Pr2O3, Y2O3 and Sc2O3 used as buffer material in different heteroepitaxially grown semiconductor-oxide-Si(1 1 1) layer stacks was studied by x-ray diffraction techniques at room temperature (RT) and near the growth temperature of 625 °C. A broad spectrum of different strain states was found depending on preparation conditions, layer combination and layer thickness. Pr2O3 behaves differently from the other two investigated oxides as it grows in a hexagonal phase on Si(1 1 1) and must be transformed into the stable cubic phase by annealing processes. This transformation is accompanied by the creation of an amorphous silicate interface layer that leads to a decoupling of substrate and oxide lattices and finally to a partial relaxation of the cub-Pr2O3 layer only. High-temperature measurements demonstrate that there exists a measurable difference between the strain state at RT, where x-ray measurements are typically performed, and at growth temperature. The coefficient of thermal expansion of different metal oxides was measured in thin film structures for the first time. These coefficients are significantly higher compared with that of Si, which leads to an additional tensile strain component when the samples are cooled down to RT.

  10. In pursuit of homoleptic actinide alkyl complexes.

    PubMed

    Seaman, Lani A; Walensky, Justin R; Wu, Guang; Hayton, Trevor W

    2013-04-01

    This Forum Article describes the pursuit of isolable homoleptic actinide alkyl complexes, starting with the pioneering work of Gilman during the Manhattan project. The initial reports in this area suggested that homoleptic uranium alkyls were too unstable to be isolated, but Wilkinson demonstrated that tractable uranium alkyls could be generated by purposeful "ate" complex formation, which serves to saturate the uranium coordination sphere and provide the complexes with greater kinetic stability. More recently, we reported the solid-state molecular structures of several homoleptic uranium alkyl complexes, including [Li(THF)4][U(CH2(t)Bu)5], [Li(TMEDA)]2[UMe6], [K(THF)]3[K(THF)2][U(CH2Ph)6]2, and [Li(THF)4][U(CH2SiMe3)6], by employing Wilkinson's strategy. Herein, we describe our attempts to extend this chemistry to thorium. The treatment of ThCl4(DME)2 with 5 equiv of LiCH2(t)Bu or LiCH2SiMe3 at -25 °C in THF affords [Th(CH2(t)Bu)5] (1) and [Li(DME)2][Th(CH2SiMe3)5 (2), respectively, in moderate yields. Similarly, the treatment of ThCl4(DME)2 with 6 equiv of K(CH2Ph) produces [K(THF)]2[Th(CH2Ph)6] (3), in good yield. Complexes 1-3 have been fully characterized, while the structures of 1 and 3 were confirmed by X-ray crystallography. Additionally, the electronic properties of 1 and 3 were explored by density functional theory. PMID:22716022

  11. In-situ determination of the oxidation state of iron in Fe-bearing silicate melts

    NASA Astrophysics Data System (ADS)

    Courtial, P.; Wilke, M.; Potuzak, M.; Dingwell, D. B.

    2005-12-01

    Terrestrial lavas commonly contain up to 10 wt% of iron. Furthermore, rocks returned from the Moon indicate lunar lava containing up to 25 wt% of iron and planetary scientists estimated that the martian mantle has about 18 wt% of iron. An experimental challenge in dealing with Fe-bearing silicate melts is that the oxidation state, controlling the proportions of ferric and ferrous iron, is a function of composition, oxygen fugacity and temperature and may vary significantly. Further complications concerning iron originate from its potential to be either four-, six- or even five-fold coordinated in both valence states. Therefore, the oxidation state of iron was determined in air for various Fe-bearing silicate melts. Investigated samples were Na-disilicate (NS), one atmosphere anorthite-diopside eutectic (AD) and haplogranitic (HPG8) melts containing up to 20, 20 and 10 wt% of iron, respectively. XANES spectra at the Fe K-edge were collected for all the melts at beamline A1, HASYLAB, Hamburg, using a Si(111) 4-crystal monochromator. Spectra were collected for temperatures up to 1573 K using a Pt-Rh loop as heating device. The Fe oxidation state was determined from the centroid position of the pre-edge feature using the calibration of Wilke et al. (2004). XANES results suggest that oxidation state of iron does not change within error for NS melts with addition of Fe, while AD and HPG8 melts become more oxidised with increasing iron content. Furthermore, NS melts are well more oxidised than AD and HPG8 melts that exhibit relatively similar oxidation states for identical iron contents. The oxidation state of iron for NS melts appears to be slightly temperature-dependent within the temperature range investigated (1073-1573 K). However, this trend is stronger for AD and HPG8 melts. Assuming that glass reflects a picture of the homogeneous equilibria of the melt, the present in-situ Fe-oxidation states determined for these melts were compared to those obtained on quenched

  12. Bidentate organophosphorus compound management of actinide and lanthanide extraction by changing structure and diluent parameter

    SciTech Connect

    Rozen, A.M.; Volk, V.I.; Zakharkin, B.S.; Nikolotova, Z.I.; Kartasheva, N.A.; Bochvar, A.A.

    1995-12-31

    Extraction of actinides and lanthanides by bidentate organophosphorus compounds (diphosphine dioxides and carbamoylphosphine oxides) can be managed by varying the polarity of diluent DP* in the range of 2--5 and by introducing aryl groups (tolyl) into an extractant molecule which results in improved extraction ability due to bidentate coordination and effect of the anomalous aryl strengthening (AAS) of the complexes. Disappearance of AAS effect upon carbamoylphosphine oxide extraction at the lower polarity of diluent (not observed toy diphosphine dioxides) is explained by an increase of the solvate number to three and transfer from bidentate coordination to monodentate one. Due to AAS effect the above mentioned extractants can be used for deep purification of waste to remove actinides without any preliminary conditioning of solutions.

  13. Spectroscopy of Actinide Nuclei - Perspectives with Position Sensitive HPGe Detectors

    NASA Astrophysics Data System (ADS)

    Reiter, P.; Birkenbach, B.; Kotthaus, T.

    Recent advances in in-beam gamma-ray spectroscopy of actinide nuclei are based on highly efficient arrays of escape-suppressed spectrometers. The sensitivity of these detector arrays is greatly enhanced by the combination with powerful mass separators or particle detector systems. This technique is demonstrated by an experiment to investigate excited states in 234U after the one-neutron-transfer reaction 235U(d,t). In coincidence with the outgoing tritons, γ-rays were detected with the highly efficient MINIBALL spectrometer. In the near future an even enhanced sensitivity will be achieved by utilizing position sensitive HPGe detectors which will exploit the novel detection method of gamma-ray energy tracking in electrically segmented germanium detectors. An example for this novel approach is the investigation neutron-rich actinide Th and U nuclei after multi nucleon transfer reactions employing the AGATA demonstrator and PRISMA setup at LNL, Italy. A primary 136Xe beam hitting a 238U target was used to produce the nuclei of interest. Beam-like reaction products after neutron transfer were selected by the PRISMA spectrometer. Coincident γ-rays from excited states in beam and target like particles were measured with the position sensitive AGATA HPGe detectors. Improved Doppler correction and quality of the γ-spectra is based on the novel γ-ray tracking technique, which was successfully exploited in this region.

  14. Hybridization effects in selected actinides and their compounds

    NASA Astrophysics Data System (ADS)

    El-Khatib, Sami T.

    Many actinide systems exhibit 'unusual' phenomena that differ from the normal text-book behavior. This occurs because the 5f electrons of the actinides and their compounds experience a delicate balance between local-moment and itinerant magnetism. It is well established that strong-electron correlations affect the different properties in such systems. Even though the actinides and their compounds have been extensively studied in recent decades, both experimentally and theoretically, to date, no complete understanding of the full range of their properties has been achieved. My thesis focuses mainly on understanding the role of 5f electrons and their interactions with the electron states of the surrounding ligands. Particularly, the effect of the 5f-ligand hybridization in the development of bulk properties is investigated. The experimental studies utilized macroscopic techniques, such as magnetization, electrical-resistivity, specific-heat and resonant-ultrasound-spectroscopy measurements, as well as microscopic techniques, such as neutron-diffraction and muon-spin-resonance studies. The results are used to disentangle the importance of direct 5f--5f overlap and 5 f-ligand hybridization. The following features have been investigated in this thesis: (a) the dual nature of hybridization effects (magnetic moment reduction vs. exchange mediation) was studied for two isostructural uranium compounds U2Pd2Sn and U2Ni2 In; (b) the formation of complex magnetic structures and its connection to the hybridization effects was studied for UCuSn, UPdSn and UPdGe; (c) the tuning of the hybridization to critical values through substitutions was attempted for two single crystals of UCoAl1-xSn x and UNi1-xRh xAl alloys; (d) the effects of compositional deficiencies was studied for the copper-deficient compound in UCu1.5Sn 2; and finally, (e) the influence of strong electron correlations on the elastic properties was studied in the case of alpha-Pu.

  15. Photonuclear reactions of actinide and pre-actinide nuclei at intermediate energies

    SciTech Connect

    Mukhopadhyay, Tapan; Basu, D. N.

    2007-12-15

    Photonuclear reaction is described with an approach based on the quasideuteron nuclear photoabsorption model followed by the process of competition between light particle evaporation and fission for the excited nucleus. Thus fission process is considered as a decay mode. The evaporation-fission process of the compound nucleus is simulated in a Monte Carlo framework. Photofission reaction cross sections are analysed in a systematic manner in the energy range {approx}50-70 MeV for the actinides {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, and {sup 237}Np and the pre-actinide nuclei {sup 208}Pb and {sup 209}Bi. The study reproduces satisfactorily well the available experimental data of photofission cross sections at energies {approx}50-70 MeV and the increasing trend of nuclear fissility with the fissility parameter Z{sup 2}/A for the actinides and pre-actinides at intermediate energies ({approx}20-140 MeV)

  16. ENVIRONMENTAL VARIABLES CONTROLLING NITRIC OXIDE EMISSIONS FROM AGRICULTURAL SOILS IN THE SOUTHEAST UNITED STATES

    EPA Science Inventory

    Fluxes of nitric oxide (NO) were measured during the summer of 1994 (12 July to 11 August) in the Upper Coastal Plain of North Carolina in a continuing effort to characterize NO emissions from intensively managed agricultural soils in the southeastern United States. Previous work...

  17. Investigation of the oxidation states of Pu isotopes in a hydrochloric acid solution.

    PubMed

    Lee, M H; Kim, J Y; Kim, W H; Jung, E C; Jee, K Y

    2008-12-01

    The characteristics of the oxidation states of Pu in a hydrochloric acid solution were investigated and the results were applied to a separating of Pu isotopes from IAEA reference soils. The oxidation states of Pu(III) and Pu(IV) were prepared by adding hydroxylamine hydrochloride and sodium nitrite to a Pu stock solution, respectively. Also, the oxidation state of Pu(VI) was adjusted with concentrated HNO(3) and HClO(4). The stability of the various oxidation states of plutonium in a HCl solution with elapsed time after preparation were found to be in the following order: Pu(III) approximately Pu(VI)>Pu(IV)>Pu(V). The chemical recoveries of Pu(IV) in a 9M HCl solution with an anion exchange resin were similar to those of Pu(VI). This method for the determination of Pu isotopes with an anion exchange resin in a 9M HCl medium was applied to IAEA reference soils where the activity concentrations of (239,240)Pu and (238)Pu in IAEA-375 and IAEA-326 were consistent with the reference values reported by the IAEA. PMID:18674920

  18. The Silver Complexes of Porphyrins, Corroles, and Carbaporphyrins: Silver in the Oxidation States II and III

    ERIC Educational Resources Information Center

    Bruckner, Christian

    2004-01-01

    Studies in relation to the silver complexes of porphyrins, corroles and carbaporphyrins are presented especially with relation to silver in the oxidation states II and III. It is seen that the Ag(sub III) complex was electrochemically readily and reversibly reduced to the corresponding Ag(sub II) complex, thus indicating that the complex could be…

  19. Compositional and Oxidation State Zoning in Martian Pyroxene: Paradox or Process Indicator

    NASA Technical Reports Server (NTRS)

    Delaney, Jeremy S.; Dyar, M. D.

    2002-01-01

    Coordinated zoning studies of major, minor, trace elements and oxidation states in Martian minerals elucidate the magmatic evolution of QUE94201 and suggest an important role for olivine and volatile fluxing in a complex magmatic history. Additional information is contained in the original extended abstract.

  20. Regulation of Ca2+ release from mitochondria by the oxidation-reduction state of pyridine nucleotides.

    PubMed

    Lehninger, A L; Vercesi, A; Bababunmi, E A

    1978-04-01

    Mitochondria from normal rat liver and heart, and also Ehrlich tumor cells, respiring on succinate as energy source in the presence of rotenone (to prevent net electron flow to oxygen from the endogenous pyridine nucleotides), rapidly take up Ca(2+) and retain it so long as the pyridine nucleotides are kept in the reduced state. When acetoacetate is added to bring the pyridine nucleotides into a more oxidized state, Ca(2+) is released to the medium. A subsequent addition of a reductant of the pyridine nucleotides such as beta-hydroxybutyrate, glutamate, or isocitrate causes reuptake of the released Ca(2+). Successive cycles of Ca(2+) release and uptake can be induced by shifting the redox state of the pyridine nucleotides to more oxidized and more reduced states, respectively. Similar observations were made when succinate oxidation was replaced as energy source by ascorbate oxidation or by the hydrolysis of ATP. These and other observations form the basis of a hypothesis for feedback regulation of Ca(2+)-dependent substrate- or energy-mobilizing enzymatic reactions by the uptake or release of mitochondrial Ca(2+), mediated by the cytosolic phosphate potential and the ATP-dependent reduction of mitochondrial pyridine nucleotides by reversal of electron transport. PMID:25436

  1. Teaching the Properties of Chromium's Oxidation States with a Case Study Method

    ERIC Educational Resources Information Center

    Ozdilek, Zehra

    2015-01-01

    The purpose of this study was to investigate how a mixed-method case study affects pre-service science teachers' awareness of hexavalent chromium pollution and content knowledge about the properties of chromium's different oxidation states. The study was conducted in Turkey with 55 sophomores during the fall semester of 2013-2014. The…

  2. Oxidation States of GRIM Glasses in EET79001 Based on Vanadium Valence

    NASA Astrophysics Data System (ADS)

    Sutton, S. R.; Rao, M. N.; Nyquist, L. E.

    2010-03-01

    Mean vanadium valences determined by microXANES for gas-rich impact-melt (GRIM) glasses in EET79001 ranged from 3.0 to 3.6. Mean fO2 ranged from IW-1.2 to IW+1.4. Variable oxidation state is consistent with impact reduction of regolith precursors.

  3. Theoretical comparison of advanced methods for calculating nitrous oxide fluxes using non-steady state chambers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Several flux-calculation (FC) schemes are available for determining soil-to-atmosphere emissions of nitrous oxide (N2O) and other trace gases using data from non-steady-state flux chambers. Recently developed methods claim to provide more accuracy in estimating the true pre-deployment flux (f0) comp...

  4. Theory of the electronic and structural properties of solid state oxides

    SciTech Connect

    Chelikowsky, J.R.

    1990-01-01

    Studies on electronic and structural properties of solid state oxides continued. This quarter, studies have concentrated on silica. Progress is discussed in the following sections: interatomic potentials and the structural properties of silica; chemical reactivity and covalent/metallic bonding on Si clusters; and surface and thermodynamic interatomic forces fields for silicon. 64 refs., 20 figs., 5 tabs. (CBS)

  5. Regulation of Ca2+ release from mitochondria by the oxidation-reduction state of pyridine nucleotides

    PubMed Central

    Lehninger, Albert L.; Vercesi, Anibal; Bababunmi, Enitan A.

    1978-01-01

    Mitochondria from normal rat liver and heart, and also Ehrlich tumor cells, respiring on succinate as energy source in the presence of rotenone (to prevent net electron flow to oxygen from the endogenous pyridine nucleotides), rapidly take up Ca2+ and retain it so long as the pyridine nucleotides are kept in the reduced state. When acetoacetate is added to bring the pyridine nucleotides into a more oxidized state, Ca2+ is released to the medium. A subsequent addition of a reductant of the pyridine nucleotides such as β-hydroxybutyrate, glutamate, or isocitrate causes reuptake of the released Ca2+. Successive cycles of Ca2+ release and uptake can be induced by shifting the redox state of the pyridine nucleotides to more oxidized and more reduced states, respectively. Similar observations were made when succinate oxidation was replaced as energy source by ascorbate oxidation or by the hydrolysis of ATP. These and other observations form the basis of a hypothesis for feedback regulation of Ca2+-dependent substrate- or energy-mobilizing enzymatic reactions by the uptake or release of mitochondrial Ca2+, mediated by the cytosolic phosphate potential and the ATP-dependent reduction of mitochondrial pyridine nucleotides by reversal of electron transport. Images PMID:25436

  6. Using carbon oxidation state and ecosystem oxidative ratio to understand terrestrial ecosystem response to elevated CO2

    NASA Astrophysics Data System (ADS)

    Hockaday, W. C.; Masiello, C. A.; Gallagher, M. E.

    2015-12-01

    Here we show that an easily-measured biogeochemical tracer, carbon oxidation state (Cox) can be used to understand ecosystem response to elevated atmospheric CO2 concentrations. We briefly review the use of Cox in understanding C sink estimates, and its role in understanding the coupled nature of carbon and oxygen cycles, which derives from its relationship with ecosystem oxidative ratio (OR). The Cox of a carbon pool provides an integrated measure of all processes that create and destroy organic matter (e.g. photosynthesis, respiration, fire) and therefore, can be used to estimate the oxidative ratio (O2/CO2) of biosphere-atmosphere exchange. Our preliminary data suggest that the OR of temperate hardwood forest and grassland ecosystems are influenced by atmospheric CO2 concentration. The variation in ecosystem Cox with atmospheric CO2 concentration suggest that OR is not a conservative property of terrestrial ecosystems on annual or decadal timescales. In the grassland ecosystem, the Cox of plant biomass increased by as much as 50% across a CO2 concentration gradient of 190 ppm, but the response was highly dependent upon soil properties. In the temperate forest, the Cox of the soil C pool increased by 40% after 9 seasons of CO2 enrichment (by 175 ppm). We will discuss our interpretation of Cox as a proxy and its potential use in studies of coupled O2 and CO2 cycling.

  7. Assessment of SFR fuel pin performance codes under advanced fuel for minor actinide transmutation

    SciTech Connect

    Bouineau, V.; Lainet, M.; Chauvin, N.; Pelletier, M.

    2013-07-01

    Americium is a strong contributor to the long term radiotoxicity of high activity nuclear waste. Transmutation by irradiation in nuclear reactors of long-lived nuclides like {sup 241}Am is, therefore, an option for the reduction of radiotoxicity and residual power packages as well as the repository area. In the SUPERFACT Experiment four different oxide fuels containing high and low concentrations of {sup 237}Np and {sup 241}Am, representing the homogeneous and heterogeneous in-pile recycling concepts, were irradiated in the PHENIX reactor. The behavior of advanced fuel materials with minor actinide needs to be fully characterized, understood and modeled in order to optimize the design of this kind of fuel elements and to evaluate its performances. This paper assesses the current predictability of fuel performance codes TRANSURANUS and GERMINAL V2 on the basis of post irradiation examinations of the SUPERFACT experiment for pins with low minor actinide content. Their predictions have been compared to measured data in terms of geometrical changes of fuel and cladding, fission gases behavior and actinide and fission product distributions. The results are in good agreement with the experimental results, although improvements are also pointed out for further studies, especially if larger content of minor actinide will be taken into account in the codes. (authors)

  8. Chronopotentiometry of refractory metals, actinides and oxyanions in molten salts: A review

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1992-01-01

    The applications of chronopotentiometry to the study of electrochemical behavior of three technologically important areas of refractory metals, actinides, and oxyanions in molten salts are critically reviewed. Chronopotentiometry is a very versatile diagnostic tool to understand the reaction mechanism of the electrode processes for the electrochemical reduction/oxidation of these electroactive species in molten salt solutions. Well adherent, compact, and uniformly thick coatings of refractory metals may be electrodeposited from their solutions in molten salts.

  9. Dynamic tests for actinide/lanthanide separation by CMPO solvent in fluorinated diluents

    SciTech Connect

    Tkachenko, L.; Babain, V.; Alyapyshev, M.; Vizniy, A.; Il'in, A.; Shadrin, A.

    2013-07-01

    Actinide and lanthanide extraction by new solvent: 0.2 M phenyl-octyl-N,N-diiso-butylcarbamoyl-phosphine oxide (CMPO) + 30% TBP + formal of octafluoro-pentanol was studied. A dynamic test with this solvent was performed. It was shown that americium and lanthanides are effectively extracted from PUREX process raffinate. The separation of americium from light lanthanides was confirmed in the modified SETFICS flowsheet with this new solvent. (authors)

  10. International Workshop on Orbital and Spin Magnetism of Actinides (IWOSMA-3)

    SciTech Connect

    Temmerman, W; Tobin, J; der Laan, G v

    2006-11-08

    This International Workshop on Orbital and Spin Magnetism of Actinides (IWOSMA) is the third in a series. The first workshop took place in Daresbury in 1999 and the second in Berkeley, CA, USA in 2002. These workshops are informal gatherings of theoreticians and experimentalists addressing the latest issues in the electronic and magnetic properties of actinides. The magnetism of transition metal systems and lanthanide systems is now fairly well understood, where d and f electrons can be described in a delocalized and localized model, respectively. On the other hand, actinide systems do not fit in such a description. The localization of the 5f is in between that of the 3d and 4f and the strong spin-orbit interaction necessitates a relativistic approach. Furthermore, electron correlation effects play a major role in these compounds. Recently, it has become possible to determine element-specific magnetic moments using neutron diffraction and x-ray scattering and absorption. The latter technique makes it even possible to separate the orbital and spin contribution to the total magnetic moment. The results are very interesting but difficult to reproduce with present state-of-art calculations. Not only a very large orbital polarization but also a large magnetic dipole term has been measured in cubic compounds, such as US. This allows for severe testing of the extra terms included in band theory to account for orbital polarization. It is also clear that deeper insight in magnetism can be obtained by studying the unusual behavior of the actinides. The recent development and application of such techniques as DMFT could contribute to the understanding of magnetism in actinides. Despite the fact that actinides for health reasons will find less application in technological market products, the understanding of their magnetic and electronic properties will no doubt provide key elements for a general description of electron correlation and relativistic effects.

  11. Trends in actinide processing at Hanford

    SciTech Connect

    Harmon, H.D.

    1993-09-01

    In 1989, the mission at the Hanford Site began a dramatic and sometimes painful transition. The days of production--as we used to know it--are over. Our mission officially has become waste management and environmental cleanup. This mission change didn`t eliminate many jobs--in fact, budgets have grown dramatically to support the new mission. Most all of the same skilled crafts, engineers, and scientists are still required for the new mission. This change has not eliminated the need for actinide processing, but it has certainly changed the focus that our actinide chemists and process engineers have. The focus used to be on such things as increasing capacity, improving separations efficiency, and product purity. Minimizing waste had become a more important theme in recent years and it is still a very important concept in the waste management and environmental cleanup arena. However, at Hanford, a new set of words dominates the actinide process scene as we work to deal with actinides that still reside in a variety of forms at the Hanford Site. These words are repackage, stabilize, remove, store and dispose. Some key activities in each of these areas are described in this report.

  12. Optical properties of actinide and lanthanide ions

    SciTech Connect

    Hessler, J.P.; Carnall, W.T.

    1980-01-01

    This paper reviews some of the recent developments in this area of spectroscopy, emphasizing the optical properties of the tripositive lanthanide and actinide ions. In particular, the single ion properties of line positon, intensity, width, and fluorescence lifetime are discussed. 53 reference, 3 figures, 4 tables.

  13. Actinide valences in xenotime and monazite

    NASA Astrophysics Data System (ADS)

    Vance, E. R.; Zhang, Y.; McLeod, T.; Davis, J.

    2011-02-01

    Tetravalent U, Np and Pu can be substituted by ceramic methods into the rare earth site of xenotime and monazite in air atmospheres using Ca ions as charge compensators, while no evidence of penta- or hexavalent actinide ions was found. Some Pu 3+ and Np 3+ can be incorporated in xenotime samples fired in a reducing atmosphere.

  14. Rapid determination of actinides in asphalt samples

    SciTech Connect

    Maxwell, Sherrod L.; Culligan, Brian K.; Hutchison, Jay B.

    2014-01-12

    A new rapid method for the determination of actinides in asphalt samples has been developed that can be used in emergency response situations or for routine analysis If a radiological dispersive device (RDD), Improvised Nuclear Device (IND) or a nuclear accident such as the accident at the Fukushima Nuclear Power Plant in March, 2011 occurs, there will be an urgent need for rapid analyses of many different environmental matrices, including asphalt materials, to support dose mitigation and environmental clean up. The new method for the determination of actinides in asphalt utilizes a rapid furnace step to destroy bitumen and organics present in the asphalt and sodium hydroxide fusion to digest the remaining sample. Sample preconcentration steps are used to collect the actinides and a new stacked TRU Resin + DGA Resin column method is employed to separate the actinide isotopes in the asphalt samples. The TRU Resin plus DGA Resin separation approach, which allows sequential separation of plutonium, uranium, americium and curium isotopes in asphalt samples, can be applied to soil samples as well.

  15. COMPLEXANTS FOR ACTINIDE ELEMENT COORDINATION AND IMMOBILIZATION

    EPA Science Inventory

    We propose that inorganic clusters known as polyoxoanions (POAs) can be exploited as complexants for actinide (An) ion coordination and immobilization. Our objective is to develop rugged, stoichiometrically well-defined POAs that act as molecular containers of An elements. Poly...

  16. Actinide measurements by AMS using fluoride matrices

    NASA Astrophysics Data System (ADS)

    Cornett, R. J.; Kazi, Z. H.; Zhao, X.-L.; Chartrand, M. G.; Charles, R. J.; Kieser, W. E.

    2015-10-01

    Actinides can be measured by alpha spectroscopy (AS), mass spectroscopy or accelerator mass spectrometry (AMS). We tested a simple method to separate Pu and Am isotopes from the sample matrix using a single extraction chromatography column. The actinides in the column eluent were then measured by AS or AMS using a fluoride target matrix. Pu and Am were coprecipitated with NdF3. The strongest AMS beams of Pu and Am were produced when there was a large excess of fluoride donor atoms in the target and the NdF3 precipitates were diluted about 6-8 fold with PbF2. The measured concentrations of 239,240Pu and 241Am agreed with the concentrations in standards of known activity and with two IAEA certified reference materials. Measurements of 239,240Pu and 241Am made at A.E. Lalonde AMS Laboratory agree, within their statistical uncertainty, with independent measurements made using the IsoTrace AMS system. This work demonstrated that fluoride targets can produce reliable beams of actinide anions and that the measurement of actinides using fluorides agree with published values in certified reference materials.

  17. Actinide Targets for Neutron Cross Section Measurements

    SciTech Connect

    John D. Baker; Christopher A. McGrath

    2006-10-01

    The Advanced Fuel Cycle Initiative (AFCI) and the Generation IV Reactor Initiative have demonstrated a lack of detailed neutron cross-sections for certain "minor" actinides, those other than the most common (235U, 238U, and 239Pu). For some closed-fuel-cycle reactor designs more than 50% of reactivity will, at some point, be derived from "minor" actinides that currently have poorly known or in some cases not measured (n,?) and (n,f) cross sections. A program of measurements under AFCI has begun to correct this. One of the initial hurdles has been to produce well-characterized, highly isotopically enriched, and chemically pure actinide targets on thin backings. Using a combination of resurrected techniques and new developments, we have made a series of targets including highly enriched 239Pu, 240Pu, and 242Pu. Thus far, we have electrodeposited these actinide targets. In the future, we plan to study reductive distillation to achieve homogeneous, adherent targets on thin metal foils and polymer backings. As we move forward, separated isotopes become scarcer, and safety concerns become greater. The chemical purification and electodeposition techniques will be described.

  18. Rapid determination of actinides in asphalt samples

    DOE PAGESBeta

    Maxwell, Sherrod L.; Culligan, Brian K.; Hutchison, Jay B.

    2014-01-12

    A new rapid method for the determination of actinides in asphalt samples has been developed that can be used in emergency response situations or for routine analysis If a radiological dispersive device (RDD), Improvised Nuclear Device (IND) or a nuclear accident such as the accident at the Fukushima Nuclear Power Plant in March, 2011 occurs, there will be an urgent need for rapid analyses of many different environmental matrices, including asphalt materials, to support dose mitigation and environmental clean up. The new method for the determination of actinides in asphalt utilizes a rapid furnace step to destroy bitumen and organicsmore » present in the asphalt and sodium hydroxide fusion to digest the remaining sample. Sample preconcentration steps are used to collect the actinides and a new stacked TRU Resin + DGA Resin column method is employed to separate the actinide isotopes in the asphalt samples. The TRU Resin plus DGA Resin separation approach, which allows sequential separation of plutonium, uranium, americium and curium isotopes in asphalt samples, can be applied to soil samples as well.« less

  19. Cross sections for actinide burner reactors

    SciTech Connect

    Difilippo, F.C.

    1991-01-01

    Recent studies have shown the feasibility of burning higher actinides (i.e., transuranium (TRU) elements excluding plutonium) in ad hoc designed reactors (Actinide Burner Reactors: ABR) which, because of their hard neutron spectra, enhance the fission of TRU. The transmutation of long-lived radionuclides into stable or short-lived isotopes reduces considerably the burden of handling high-level waste from either LWR or Fast Breeder Reactors (FBR) fuels. Because of the large concentrations of higher actinides in these novel reactor designs the Doppler effect due to TRU materials is the most important temperature coefficient from the point of view of reactor safety. Here we report calculations of energy group-averaged capture and fission cross sections as function of temperature and dilution for higher actinides in the resolved and unresolved resonance regions. The calculations were done with the codes SAMMY in the resolved region and URR in the unresolved regions and compared with an independent calculation. 4 refs., 2 figs., 2 tabs.

  20. Gas-phase chemistry of bare and oxo-ligated protactinium ions: a contribution to a systematic understanding of actinide chemistry.

    PubMed

    Gibson, John K; Haire, Richard G

    2002-11-01

    Gas-phase chemistry of bare and oxo-ligated protactinium ions has been studied for the first time. Comparisons were made with thorium, uranium, and neptunium ion chemistry to further the systematic understanding of 5f elements. The rates of oxidation of Pa(+) and PaO(+) by ethylene oxide compared with those of the homologous uranium ions indicate that the first and second bond dissociation energies, BDE[Pa(+)-O] and BDE[OPa(+)-O], are approximately 800 kJ mol(-1). The relatively facile fluorination of Pa(+) to PaF(4)(+) by SF(6) is consistent with the high stability of the pentavalent oxidation state of Pa. Reactions with ethene, propene, 1-butene, and iso-butene revealed that Pa(+) is a very reactive metal ion. In analogy with U(+) chemistry, ethene was trimerized by Pa(+) to give PaC(6)H(6)(+). Reactions of Pa(+) with larger alkenes resulted in secondary and tertiary products not observed for U(+) or Np(+). The bare protactinium ion is significantly more reactive with organic substrates than are heavier actinide ions. The greatest difference between Pa and heavier actinide congeners was the exceptional dehydrogenation activity of PaO(+) with alkenes; UO(+) and NpO(+) were comparatively inert. The striking reactivity of PaO(+) is attributed to the distinctive electronic structure at the metal center in this oxide, which is considered to reflect the greater availability of the 5f electrons for participation in bonding, either directly or by promotion/hybridization with higher-energy valence orbitals. PMID:12401099

  1. Environmental Impact of the Nuclear Fuel Cycle: Fate of Actinides

    SciTech Connect

    Ewing, Rodney C.; Runde, W.; Albrecht-Schmitt, Thomas E.

    2011-01-31

    The resurgence of nuclear power as a strategy for reducing greenhouse gas (GHG) emissions has, in parallel, revived interest in the environmental impact of actinides. Just as GHG emissions are the main environmental impact of the combustion of fossil fuels, the fate of actinides, consumed and produced by nuclear reactions, determines whether nuclear power is viewed as an environmentally “friendly” source of energy. In this article, we summarize the sources of actinides in the nuclear fuel cycle, how actinides are separated by chemical processing, the development of actinide-bearing materials, and the behavior of actinides in the environment. At each stage, actinides present a unique and complicated behavior because of the 5f electronic configurations.

  2. Aqueous secondary organic aerosol (SOA) production from the oxidation of phenols by triplet excited state organics

    NASA Astrophysics Data System (ADS)

    Smith, J.; Yu, L.; Zhang, Q.; Anastasio, C.

    2011-12-01

    Recent literature has shown that atmospheric condensed-phase chemistry can play a significant role in the evolution of organic aerosols, including the formation of secondary organic aerosol (SOA). SOA formation from the oxidation of volatile organic compounds (VOCs) in the aqueous phase has largely focused on oxidations involving the hydroxyl radical and other oxidants, such as photochemically created triplet excited states, have not been fully investigated. Phenolic compounds are one of the primary carbon emission classes from biomass and wood combustion and have significant water solubility. Once in the aqueous phase, phenolic compounds can react with the triplet excited states of non-phenolic aromatic carbonyls (NPCs), particle-bound organics that are also emitted in large quantities from wood combustion. The oxidation of phenolic species in the condensed phase by triplet excited states can result in the production of SOA. A main goal of this study was to investigate bulk solution reaction kinetics under atmospherically relevant conditions in order to ascertain how these reactions can impact aqueous-phase SOA production. In our experiments, we studied the reactions of five phenols (phenol, guaiacol, syringol, catechol, and resorcinol) with the triplet state of 3,4-dimethoxybenzaldehyde (34-DMB) during simulated solar radiation. We have characterized the impacts of pH, ionic strength and reactant concentrations on the reaction behavior of this system. In addition, we analyzed the SOA formed using high-resolution aerosol mass spectrometry, ion chromatography, and liquid chromatography-mass spectrometry to infer the reaction mechanisms. Our evidence suggests that under atmospherically relevant conditions, triplet excited states can be the dominant oxidant of phenolics and contribute significantly to the total SOA budget.

  3. FY2011 Annual Report for the Actinide Isomer Detection Project

    SciTech Connect

    Warren, Glen A.; Francy, Christopher J.; Ressler, Jennifer J.; Erikson, Luke E.; Tatishvili, Gocha; Hatarik, R.

    2011-10-01

    This project seeks to identify a new signature for actinide element detection in active interrogation. This technique works by exciting and identifying long-lived nuclear excited states (isomers) in the actinide isotopes and/or primary fission products. Observation of isomers in the fission products will provide a signature for fissile material. For the actinide isomers, the decay time and energy of the isomeric state is unique to a particular isotope, providing an unambiguous signature for SNM. This project entails isomer identification and characterization and neutron population studies. This document summarizes activities from its third year - completion of the isomer identification characterization experiments and initialization of the neutron population experiments. The population and decay of the isomeric state in 235U remain elusive, although a number of candidate gamma rays have been identified. In the course of the experiments, a number of fission fragment isomers were populated and measured [Ressler 2010]. The decays from these isomers may also provide a suitable signature for the presence of fissile material. Several measurements were conducted throughout this project. This report focuses on the results of an experiment conducted collaboratively by PNNL, LLNL and LBNL in December 2010 at LBNL. The measurement involved measuring the gamma-rays emitted from an HEU target when bombarded with 11 MeV neutrons. This report discussed the analysis and resulting conclusions from those measurements. There was one strong candidate, at 1204 keV, of an isomeric signature of 235U. The half-life of the state is estimated to be 9.3 {mu}s. The measured time dependence fits the decay time structure very well. Other possible explanations for the 1204-keV state were investigated, but they could not explain the gamma ray. Unfortunately, the relatively limited statistics of the measurement limit, and the lack of understanding of some of the systematic of the experiment, limit

  4. Oxidation state of vanadium in glass and olivine from terrestrial and Martian basalts: Implications for oxygen fugacity estimates

    SciTech Connect

    Karner, J.M.; Sutton, S.R.; Papike, J.J.; Shearer, C.K.; Newville, M.

    2005-04-22

    Several studies have demonstrated the usefulness of synchrotron micro x-ray absorption near-edge structure ({mu}-XANES or SmX) spectroscopy in determining the oxidation state of elements in planetary materials. Delaney et al. used SmX to investigate the oxidation states of Fe, Cr, and V in extraterrestrial samples, and they later determined the oxidation state of V in experimental glasses as a function of oxygen fugacity. More recently, Sutton et al. studied the oxidation state of V in meteoritic fassaite and also in synthetic pyroxene. This report discusses our first results using SmX spectroscopy to determine the oxidation state of V in olivine and glass from a terrestrial ocean floor (OF) basalt and a martian basaltic shergottite meteorite, Dar Al Gani 476. The goal of this and future studies is to use V (and Cr, Fe) valence states to determine the oxygen fugacity of basalts from different planetary bodies.

  5. Reduction of the Mn cluster of the water-oxidizing enzyme by nitric oxide: formation of an S(-2) state.

    PubMed

    Schansker, Gert; Goussias, Charilaos; Petrouleas, Vasili; Rutherford, A William

    2002-03-01

    The manganese cluster of the oxygen-evolving enzyme of photosystem II is chemically reduced upon interaction with nitric oxide at -30 degrees C. The state formed gives rise to an S = 1/2 multiline EPR signal [Goussias, Ch., Ioannidis, N., and Petrouleas, V. (1997) Biochemistry 36, 9261] that is attributed to a Mn(II)- Mn(III) dimer [Sarrou, J., Ioannidis, N., Deligiannakis, Y., and Petrouleas, V. (1998) Biochemistry 37, 3581]. In this work, we sought to establish whether the state could be assigned to a specific, reduced S state by using flash oxymetry, chlorophyll a fluorescence, and electron paramagnetic resonance spectroscopy. With the Joliot-type O(2) electrode, the first maximum of oxygen evolution was observed on the sixth or seventh flash. Three saturating pre-flashes were required to convert the flash pattern characteristic of NO-reduced samples to that of the untreated control (i.e., O(2) evolution maximum on the third flash). Measurements of the S state-dependent level of chlorophyll fluorescence in NO-treated PSII showed a three-flash downshift compared to untreated controls. In the EPR study, the maximum S(2) multi-line EPR signal was observed after the fourth flash. The results from all three methods are consistent with the Mn cluster being in a redox state corresponding to an S(-2) state in a majority of centers after treatment with NO. We were unable to generate the Mn(II)-Mn(III) multi-line signal using hydrazine as a reductant; it appears that the valence distribution and possibly the structure of the Mn cluster in the S(-2) state are dependent on the nature of the reductant that is used. PMID:11863444

  6. Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

    SciTech Connect

    Liang, W.

    1994-11-01

    X-ray absorption spectroscopy (XAS) was performed on Photosystem II (PSII)-enriched membranes prepared from spinach to explore: (1) the correlation between structure and magnetic spin state of the Mn cluster in the oxygen evolving complex (OEC) in the S{sub 2} state; and (2) the oxidation state changes of the Mn cluster in the flash-induced S-states. The structure of the Mn cluster in the S{sub 2} state with the g{approx}4 electron paramagnetic resonance (EPR) signal (S{sub 2}-g4 state) was compared with that in the S{sub 2} state with multiline signal (S{sub 2}-MLS state) and the S{sub 1} state. The S{sub 2}-g4 state has a higher XAS inflection point energy than that of the S{sub 1} state, indicating the oxidation of Mn in the advance from the S{sub 1} to the S{sub 2}-g4 state. Differences in the edge shape and in the extended X-ray absorption fine structure (EXAFS) show that the structure of the Mn cluster in the S{sub 2}-g4 state is different from that in the S{sub 2}-MLS or the S{sub 1} state. In the S{sub 2}-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 {angstrom} and 2.85 {angstrom}. Very little distance disorder exists in the second shell of the S{sub 1} or S{sub 2}-MLS states. The third shell of the S{sub 2}-g4 state at about 3.3 {angstrom} also contains increased heterogeneity relative to that of the S{sub 2}-MLS or the S{sub 1} state. Various S-states were prepared at room-temperature by saturating, single-turnover flashes. The flash-dependent oscillation in the amplitude of the MLS was used to characterize the S-state composition and to construct {open_quotes}pure{close_quotes} S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S{sub 1} {yields} S{sub 2} transition.

  7. JOWOG 22/2 - Actinide Chemical Technology (July 9-13, 2012)

    SciTech Connect

    Jackson, Jay M.; Lopez, Jacquelyn C.; Wayne, David M.; Schulte, Louis D.; Finstad, Casey C.; Stroud, Mary Ann; Mulford, Roberta Nancy; MacDonald, John M.; Turner, Cameron J.; Lee, Sonya M.

    2012-07-05

    The Plutonium Science and Manufacturing Directorate provides world-class, safe, secure, and reliable special nuclear material research, process development, technology demonstration, and manufacturing capabilities that support the nation's defense, energy, and environmental needs. We safely and efficiently process plutonium, uranium, and other actinide materials to meet national program requirements, while expanding the scientific and engineering basis of nuclear weapons-based manufacturing, and while producing the next generation of nuclear engineers and scientists. Actinide Process Chemistry (NCO-2) safely and efficiently processes plutonium and other actinide compounds to meet the nation's nuclear defense program needs. All of our processing activities are done in a world class and highly regulated nuclear facility. NCO-2's plutonium processing activities consist of direct oxide reduction, metal chlorination, americium extraction, and electrorefining. In addition, NCO-2 uses hydrochloric and nitric acid dissolutions for both plutonium processing and reduction of hazardous components in the waste streams. Finally, NCO-2 is a key team member in the processing of plutonium oxide from disassembled pits and the subsequent stabilization of plutonium oxide for safe and stable long-term storage.

  8. DISTRIBUTION OF ACTINIDES BETWEEN THE AQUEOUS AND ORGANIC PHASES IN THE TALSPEAK PROCESS

    SciTech Connect

    Rudisill, T.; Kyser, E.

    2010-09-02

    One objective of the US Department of Energy's Office of Nuclear Energy (DOE-NE) is the development of sustainable nuclear fuel cycles which improve uranium resource utilization, maximize energy generation, minimize waste generation, improve safety, and complement institutional measures limiting proliferation risks. Activities in progress which support this objective include the development of advanced separation technologies to recover the actinides from used nuclear fuels. With the increased interest in the development of technology to allow closure of the nuclear fuel cycle, the TALSPEAK process is being considered for the separation of Am and Cm from the lanthanide fission products in a next generation reprocessing plant. However, at this time, the level of understanding associated with the chemistry and the control of the process variables is not acceptable for deployment of the process on an industrial scale. To address this issue, DOE-NE is supporting basic scientific studies focused on the TALSPEAK process through its Fuel Cycle Research and Development (R&D) program. One aspect of these studies is an experimental program at the Savannah River National Laboratory (SRNL) in which temperature-dependent distribution coefficients for the extraction of actinide elements in the TALSPEAK process were measured. The data were subsequently used to calculate conditional enthalpies and entropies of extraction by van't Hoff analysis to better understand the thermodynamic driving forces for the TALSPEAK process. In the SRNL studies, the distribution of Pu(III) in the TALSPEAK process was of particular interest. A small amount of Pu(III) would be present in the feed due to process losses and valence adjustment in prior recovery operations. Actinide elements such as Np and Pu have multiple stable oxidation states in aqueous solutions; therefore the oxidation state for these elements must be controlled in the TALSPEAK process, as the extraction chemistry is dependent upon

  9. Electronic Structure and Oxidation State Changes in the Mn4Ca Cluster of Photosystem II

    SciTech Connect

    Yano, Junko; Pushkar, Yulia; Messinger, Johannes; Bergmann, Uwe; Glatzel, Pieter; Yachandra, Vittal K

    2007-08-03

    Oxygen-evolving complex (Mn4Ca cluster) of Photosystem II cycles through five intermediate states (Si-states, i =0-4) before a molecule of dioxygen is released. During the S-state transitions, electrons are extracted from the OEC, either from Mn or alternatively from a Mn ligand. The oxidation state of Mn is widely accepted as Mn4(III2,IV2) and Mn4(III,IV3) for S1 and S2 states, while it is still controversial for the S0 and S3 states. We used resonant inelastic X-ray scattering (RIXS) to study the electronic structure of Mn4Ca complex in the OEC. The RIXS data yield two-dimensional plots that provide a significant advantage by obtaining both K-edge pre-edge and L-edge-like spectra (metal spin state) simultaneously. We have collected data from PSII samples in the each of the S-states and compared them with data from various inorganic Mncomplexes. The spectral changes in the Mn 1s2p3/2 RIXS spectra between the S-states were compared to those of the oxides of Mn and coordination complexes. The results indicate strong covalency for the electronic configuration in the OEC, and we conclude that the electron is transferred from a strongly delocalized orbital, compared to those in Mn oxides or coordination complexes. The magnitude for the S0 to S1, and S1 to S2 transitions is twice as large as that during the S2 to S3 transition, indicating that the electron for this transition is extracted from a highly delocalized orbital with little change in charge density at the Mn atoms.

  10. Electronic Structure and Oxidation State Changes in the Mn (4) Ca Cluster of Photosystem II

    SciTech Connect

    Yano, J.; Pushkar, Y.; Messinger, J.; Bergmann, U.; Glatzel, P.; Yachandra, V.K.; /SLAC

    2012-08-17

    Oxygen-evolving complex (Mn{sub 4}Ca cluster) of Photosystem II cycles through five intermediate states (S{sub i}-states, i = 0-4) before a molecule of dioxygen is released. During the S-state transitions, electrons are extracted from the OEC, either from Mn or alternatively from a Mn ligand. The oxidation state of Mn is widely accepted as Mn{sub 4}(III{sub 2},IV{sub 2}) and Mn{sub 4}(III,IV{sub 3}) for S{sub 1} and S{sub 2} states, while it is still controversial for the S{sub 0} and S{sub 3} states. We used resonant inelastic X-ray scattering (RIXS) to study the electronic structure of Mn{sub 4}Ca complex in the OEC. The RIXS data yield two-dimensional plots that provide a significant advantage by obtaining both K-edge pre-edge and L-edge-like spectra (metal spin state) simultaneously. We have collected data from PSII samples in the each of the S-states and compared them with data from various inorganic Mn complexes. The spectral changes in the Mn 1s2p{sub 3/2} RIXS spectra between the S-states were compared to those of the oxides of Mn and coordination complexes. The results indicate strong covalency for the electronic configuration in the OEC, and we conclude that the electron is transferred from a strongly delocalized orbital, compared to those in Mn oxides or coordination complexes. The magnitude for the S{sub 0} to S{sub 1}, and S{sub 1} to S{sub 2} transitions is twice as large as that during the S{sub 2} to S{sub 3} transition, indicating that the electron for this transition is extracted from a highly delocalized orbital with little change in charge density at the Mn atoms.

  11. Association of actinides with microorganisms and clay: Implications for radionuclide migration from waste-repository sites

    SciTech Connect

    Ohnuki, T.; Francis, A.; Kozai, N.; Sakamoto, F.; Ozaki, T.; Nankawa, T.; Suzuki, Y.

    2010-04-01

    We conducted a series of basic studies on the microbial accumulation of actinides to elucidate their migration behavior around backfill materials used in the geological disposal of radioactive wastes. We explored the interactions of U(VI) and Pu(VI) with Bacillus subtilis, kaolinite clay, and within a mixture of the two, directly analyzing their association with the bacterium in the mixture by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The accumulation of U by the mixture rose as the numbers of B. subtilis cells increased. Treating the kaolinite with potassium acetate (CH{sub 3}COOK) removed approximately 80% of the associated uranium while only 65% was removed in the presence of B. subtilis. TEM-EDS analysis confirmed that most of the U taken from solution was associated with B. subtilis. XANES analyses revealed that the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both was U(VI). The amount of Pu sorbed by B. subtilis increased with time, but did not reach equilibrium in 48 h; in kaolinite alone, equilibrium was attained within 8 h. After 48 h, the oxidation state of Pu in the solutions exposed to B. subtilis and to the mixture had changed to Pu(V), whereas the oxidation state of the Pu associated with both was Pu(IV). In contrast, there was no change in the oxidation state of Pu in the solution nor on kaolinite after exposure to Pu(VI). SEM-EDS analysis indicated that most of the Pu in the mixture was associated with the bacteria. These results suggest that U(VI) and Pu(VI) preferentially are sorbed to bacterial cells in the presence of kaolinite clay, and that the mechanism of accumulation of U and Pu differs. U(VI) is sorbed directly to the bacterial cells, whereas Pu(VI) first is reduced to Pu(V) and then to Pu(IV), and the latter is associated with the cells. These results have important implications on the migrations of radionuclides around the repository sites of

  12. Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen

    SciTech Connect

    Sallis, S.; Williams, D. S.; Butler, K. T.; Walsh, A.; Quackenbush, N. F.; Junda, M.; Podraza, N. J.; Fischer, D. A.; Woicik, J. C.; White, B. E.; Piper, L. F. J.

    2014-06-09

    The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

  13. Theory of the electronic and structural properties of solid state oxides. Annual technical report 1993

    SciTech Connect

    Chelikowsky, J.R.

    1993-06-01

    Emphasis has been on the electronic materials: silica, titania, and ruthenia. Fundamental interest centered on nature of microstructure of these solids in the amorphous state, or mixed oxide state. New theoretical techniques have been implemented to examine such issues, based on ab initio pseudopotential methods and interatomic potentials. Some areas examined under this project are: (1) Nature of the amorphization transformation of quartz under pressure. Specific focus is on the microscopic nature of the amorphous material and the driving forces for amorphization. (2) Equation of states of crystalline silica polymorphs. (3) Elastic anomalies in silica. In particular, the existence of a ``negative`` Poisson ratio in high temperature, low density forms of crystalline silica. (4) Optical and structural properties of titania and mixed oxides such as Ru{sub x}Ti{sub 1-x}O{sub 2}.

  14. Oxidation state, bioavailability & biochemical pathway define the fate of carbon in soil

    NASA Astrophysics Data System (ADS)

    Kuzyakov, Yakov; Apostel, Carolin; Gunina, Anna; Herrmann, Anke M.; Dippold, Michaela

    2015-04-01

    Numerous experiments under laboratory and field conditions analyzed microbial utilization and mean residence time (MRT) of carbon (C) from plant and microbial residues as well as root exudates in soil. Most of these studies tested the effects of various environmental factors, such as temperature, soil moisture, texture etc. on these parameters. However, only a few studies compared the properties of the substances themselves and there is no conceptual framework based on biochemical pathways. We hypothesize that the fate of C from organic substances in soil strongly depends on the first step of their microbial utilization, specifically, on biochemical pathway and initial C oxidation state, as well as its bioavailability in soils, defined by its hydrophobicity and molecular weight. Here we introduce and evaluate a new conceptual framework based on the following parameters: 1) C oxidation state, 2) molecular weight and hydrophobicity, 3) initial biochemical pathway of a substance class in microbial cells. To assess these parameters, two databases were prepared based on the literature and own studies. The first database included only the studies with 14C or 13C position specific labeled sugars, amino acids, carboxylic acids, phenols and lipids in soil. This database allowed us to analyze microbial utilization and mineralization of organics to CO2 depending on their C oxidation state (OS) and on functional groups. Additionally, we calculated data on the bond electronegativity of all compounds investigated in these studies. The second data base included the results of 14C and 13C studies with uniformly labeled substances of various classes. This database considered the free enthalpie (Delta H) per C unit from a variety of substrates differing in their aromaticity, hydrophobicity/electronegativity and location of the substance on the van Krevelen diagram. In addition, we calculated the hydrophobicity from the electronegativity of the individual bonds and recorded their

  15. Laboratory actinide partitioning - Whitlockite/liquid and influence of actinide concentration levels

    NASA Technical Reports Server (NTRS)

    Benjamin, T. M.; Jones, J. H.; Heuser, W. R.; Burnett, D. S.

    1983-01-01

    The partition coefficients between synthetic whitlockite (beta Ca-phosphate) and coexisting silicate melts are determined for the actinide elements Th, U and Pu. Experiments were performed at 1 bar pressure and 1250 C at oxygen fugacities from 10 to the -8.5 to 10 to the -0.7 bars, and partitioning was determined from trace element radiography combined with conventional electron microprobe analysis. Results show Pu to be more readily incorporated into crystalline phases than U or Th under reducing conditions, which is attributed to the observation that Pu exists primarily in the trivalent state, while U and Th are tetravalent. Corrected partition coefficients for whitlockite of 3.6, less than or equal to 0.6, 1.2, 0.5 and less than or equal to 0.002 are estimated for Pu(+3), Pu(+4), Th(+4), U(+4) and U(+6), respectively. Experiments performed at trace levels and percent levels of UO2 indicate that Si is involved in U substitution in whitlockite, and show a reduced partition coefficient at higher concentrations of U that can be explained by effects on melt structure or the fraction of tetravalent U.

  16. Separation techniques for low-level determination of actinides in soil samples.

    PubMed

    Eikenberg, J; Jäggi, M; Beer, H; Rüthi, M; Zumsteg, I

    2009-05-01

    The separation methods for soil samples applied at PSI are based on extraction chromatography and ion exchange. After sample leaching, the actinides are pre-concentrated via precipitation using oxalic acid. Besides the classical separation methods applying the extraction chromatographic resins U/TEVA (for U, Th), TRU (Pu, Am), new methods were recently implemented to increase the radiochemical recovery of particularly trivalent Am and Cm. These methods do not require initial reduction of Pu(IV) to Pu(III) but stabilize Pu on the tetravalent oxidation state using a mixture of NaNO(2)/H(2)O(2) in strong acidic medium. The Pu-fraction is then fixed along with Th onto Dowex AG 1-X2 anion exchanger resin. Th is eluted via complexation with 10M HCl, Pu via reduction with HI. The fractions of Am+Cm and U are loaded onto DGA resin. This resin shows extraordinary high distribution coefficients (k'-values) exceeding 10(4) (for Am) in strong nitric acid medium. The separation between U and Am is obtained quantitatively by decreasing the HNO(3) concentration from 3 to 0.25 M (stripping of the U-fraction) while Am can be easily eluted thereafter using 0.25 M HCl as complexation compound. PMID:19243967

  17. Observation of ultraviolet emission and effect of surface states on the luminescence from tin oxide nanowires

    NASA Astrophysics Data System (ADS)

    Kar, Ayan; Stroscio, Michael A.; Dutta, Mitra; Kumari, Jyoti; Meyyappan, M.

    2009-03-01

    Ultraviolet (UV) and orange emissions have been observed from vapor-liquid-solid grown SnO2 nanowires. From the luminescence, the donor and acceptor binding energies have been estimated. The dependence of the orange luminescence on the diameters of tin oxide nanowires has been observed and the wavelength of the UV luminescence is found to depend on the laser power. Both the shift in the UV and the intensity of the orange luminescence is found to be dependent on the surface states of the tin oxide nanowires.

  18. Electronic structures of cyclometalated palladium complexes in the higher oxidation states.

    PubMed

    Nguyen, Bao N; Adrio, Luis A; Albrecht, Tim; White, Andrew J P; Newton, Mark A; Nachtegaal, Maarten; Figueroa, Santiago J A; Hii, King Kuok Mimi

    2015-10-01

    The electronic and redox properties of a series of cyclometalated Pd complexes with oxidation states of +2, +3 and +4 were examined using a range of currently available spectroscopic and electrochemical techniques. Changes in metal-ligand bond lengths were established by X-ray crystallography and correctly predicted by DFT calculations, from which the frontier orbitals and partial atomic charges can be obtained. X-ray absorption spectroscopy (XAS) revealed interesting XANES features that suggest a synergistic relationship between metal-ligand interactions. The electrochemical study of the Pd(ii) dimer was found to contain two sequential oxidative potentials indicative of a weak metal-metal interaction. PMID:26332167

  19. Actinide incorporation in a zirconia based pyrochlore (Nd 1.8An0.2)Zr 2O 7+x ( An=Th, U, Np, Pu, Am)

    NASA Astrophysics Data System (ADS)

    Nästren, Catharina; Jardin, Regis; Somers, Joseph; Walter, Marcus; Brendebach, Boris

    2009-01-01

    Actinides (thorium, uranium, neptunium, plutonium, and americium) were infiltrated into a porous Nd 1.8Zr 2O 6.7 matrix, prepared by gel-supported precipitation. (Nd 1.8An0.2)Zr 2O 7+x pyrochlores were formed after sintering in Ar/H 2 and the pyrochlore structure remains during oxidation at 800 °C in air. X-ray diffraction reveals a linear relationship between the pyrochlore lattice parameter and the ionic radii of the actinides. EXAFS measurements on actinide L3-edge show a split shell of nearest neighbour oxygen atoms similar to that surrounding of Nd. The actinide-oxygen bond distances decrease with the actinide ionic radii, which verifies that these actinides adopt the Nd site in the (Nd 1.8An0.2)Zr 2O 7+x pyrochlore. The oxidation susceptibility of Np is related to the availability of oxygen vacancies and in contrast to stabilised zirconia Np(V) can be obtained in zirconia based pyrochlore.

  20. Relaxation of Actinide Surfaces: An All Electron Study

    NASA Astrophysics Data System (ADS)

    Atta-Fynn, Raymond; Dholabhai, Pratik; Ray, Asok

    2006-10-01

    Fully relativistic full potential density functional calculations with a linearized augmented plane wave plus local orbitals basis (LAPW + lo) have been performed to investigate the relaxations of heavy actinide surfaces, namely the (111) surface of fcc δ-Pu and the (0001) surface of dhcp Am using WIEN2k. This code uses the LAPW + lo method with the unit cell divided into non-overlapping atom-centered spheres and an interstitial region. The APW+lo basis is used to describe all s, p, d, and f states and LAPW basis to describe all higher angular momentum states. Each surface was modeled by a three-layer periodic slab separated by 60 Bohr vacuum with four atoms per surface unit cell. In general, we have found a contraction of the interlayer separations for both Pu and Am. We will report, in detail, the electronic and geometric structures of the relaxed surfaces and comparisons with the respective non-relaxed surfaces.

  1. Density functional calculations of Hubbard parameter in actinide series

    SciTech Connect

    Puri, A.; Sen, K.D.

    1993-05-01

    The calculations of Hubbard parameter, U, which defines the polar state formation energy of the reaction 2(5f{sup n} 6d{sup 1} 7d{sup 2}) {yields} 5f{sup n-1} 6d{sup 2}7s{sup 2} + 5f{sup n+1} 7s{sup 2} for the actinide atoms, Th-No, have been carried out using the self-interaction-corrected (SIC) quasi-relativistic local spin density (LSD) functional due to Perdew and Zunger. Based on the available bandwidth calculations for the 5f metals and its monotonically decreasing trend with increasing nuclear charge it is predicted that the 5f state is iterent in Th-Np beyond which it becomes localized. These calculations agree with the conclusions drawn earlier by Johansson using the semiempirical data.

  2. VUV and soft x-ray spectroscopy of actinides

    SciTech Connect

    Olson, C. G.; Joyce, J. J.; Durakiewicz, T.; Guziewicz, E.

    2004-01-01

    Optical and photoelectron spectroscopies using VUV and Soft X-ray photons are powerful tools for studies of elemental and compound actinides. Large changes in the relative atomic cross sections of the 5f, 6d and sp electrons allow decomposition of the character of the valence bands using photoemission. Resonant enhancement of photoelectrons and Auger electrons at the 5d core threshold further aids the decomposition and gives a measure of elemental specificity. Angle-resolved photoemission can be used to map the momentum dependence of the electronic states. The large changes in relative cross section with photon energy yields further details when the mapping is done at equivalent points in multiple zones. Spectra for well understood rare earth materials will be presented to establish spectral characteristics for known atomic character initial states. These signatures will be applied to the case of USb to investigate f-d hybridization near the Fermi level.

  3. Adsorption properties versus oxidation states of rutile TiO{sub 2}(110)

    SciTech Connect

    Martinez, Umberto; Hammer, Bjoerk

    2011-05-21

    Using density functional theory we have studied the adsorption properties of different atoms and molecules deposited on a stoichiometric, reduced, and oxidized rutile TiO{sub 2}(110) surface. Depending on the oxidation state of the surface, electrons can flow from or to the substrate and, therefore, negatively or positively charged species are expected. In particular, we have found that a charge transfer process from or to the surface always occurs for highly electronegative or highly electropositive species, respectively. For atoms or molecules with intermediate electron affinity, the direction of the charge flow depends on the oxidation state of the rutile surface and on the adsorption site. Generally, the charging effect leads to more stable complexes. However, the increase in the binding energy of the adsorbates is highly dependent on the electronic states of the surface prior to the adsorption event. In this work we have analyzed in details these mechanisms and we have also established a direct correlation between the enhanced binding energy of the adsorbates and the induced gap states.

  4. The role of actinide burning and the Integral Fast Reactor in the future of nuclear power

    SciTech Connect

    Hollaway, W.R.; Lidsky, L.M.; Miller, M.M.

    1990-12-01

    A preliminary assessment is made of the potential role of actinide burning and the Integral Fast Reactor (IFR) in the future of nuclear power. The development of a usable actinide burning strategy could be an important factor in the acceptance and implementation of a next generation of nuclear power. First, the need for nuclear generating capacity is established through the analysis of energy and electricity demand forecasting models which cover the spectrum of bias from anti-nuclear to pro-nuclear. The analyses take into account the issues of global warming and the potential for technological advances in energy efficiency. We conclude, as do many others, that there will almost certainly be a need for substantial nuclear power capacity in the 2000--2030 time frame. We point out also that any reprocessing scheme will open up proliferation-related questions which can only be assessed in very specific contexts. The focus of this report is on the fuel cycle impacts of actinide burning. Scenarios are developed for the deployment of future nuclear generating capacity which exploit the advantages of actinide partitioning and actinide burning. Three alternative reactor designs are utilized in these future scenarios: The Light Water Reactor (LWR); the Modular Gas-Cooled Reactor (MGR); and the Integral Fast Reactor (FR). Each of these alternative reactor designs is described in some detail, with specific emphasis on their spent fuel streams and the back-end of the nuclear fuel cycle. Four separation and partitioning processes are utilized in building the future nuclear power scenarios: Thermal reactor spent fuel preprocessing to reduce the ceramic oxide spent fuel to metallic form, the conventional PUREX process, the TRUEX process, and pyrometallurgical reprocessing.

  5. Morphology dependence of interfacial oxidation states of gallium arsenide under near ambient conditions

    SciTech Connect

    Zhang, Xueqiang; Lamere, Edward; Ptasinska, Sylwia; Liu, Xinyu; Furdyna, Jacek K.

    2014-05-05

    The manipulation of semiconductor surfaces by tuning their electronic properties and surface chemistry is an essential ingredient for key applications in areas such as electronics, sensors, and photovoltaic devices. Here, in-situ surface reactions on gallium arsenide (GaAs) are monitored for two morphologies: a simple planar crystalline surface with (100) orientation and an ensemble of GaAs nanowires, both exposed to oxygen environment. A variety of oxide surface species, with a significant enhancement in oxidation states in the case of nanowires, are detected via near ambient pressure X-ray photoelectron spectroscopy. This enhancement in oxidation of GaAs nanowires is due to their higher surface area and the existence of more active sites for O{sub 2} dissociation.

  6. CO Oxidation Facilitated by Robust Surface States on Au-Covered Topological Insulators

    SciTech Connect

    Chen, Hua; Zhu, Wenguang; Xiao, Di; Zhang, Zhenyu

    2011-01-01

    Surface states the electronic states emerging as a solid material terminates at a surface are usually vulnerable to contaminations and defects. The robust topological surface state(s) (TSS) on the three-dimensional topological insulators provide a perfect platform for exploiting surface states in less stringent environments. Employing first-principles density functional theory calculations, we demonstrate that the TSS can play a vital role in facilitating surface reactions by serving as an effective electron bath. We use CO oxidation on gold-covered Bi2Se3 as a prototype example, and show that the robust TSS can significantly enhance the adsorption energy of both CO and O2 molecules, by promoting different directions of electron transfer. The concept of TSS as an electron bath may lead to new design principles beyond the conventional d-band theory of heterogeneous catalysis.

  7. Interplay between strain, defect charge state, and functionality in complex oxides

    NASA Astrophysics Data System (ADS)

    Aschauer, Ulrich; Spaldin, Nicola A.

    2016-07-01

    We use first-principles calculations to investigate the interplay between strain and the charge state of point defect impurities in complex oxides. Our work is motivated by recent interest in using defects as active elements to provide novel functionality in coherent epitaxial films. Using oxygen vacancies as model point defects, and CaMnO3 and MnO as model materials, we calculate the changes in internal strain caused by changing the charge state of the vacancies, and conversely the effect of strain on charge-state stability. Our results show that the charge state is a degree of freedom that can be used to control the interaction of defects with strain and hence the concentration and location of defects in epitaxial films. We propose the use of field-effect gating to reversibly change the charge state of defects and hence the internal strain and corresponding strain-induced functionalities.

  8. Oxide-free InAs(111)A interface in metal-oxide-semiconductor structure with very low density of states prepared by anodic oxidation

    SciTech Connect

    Valisheva, N. A. Aksenov, M. S.; Golyashov, V. A.; Levtsova, T. A.; Kovchavtsev, A. P.; Gutakovskii, A. K.; Tereshchenko, O. E.; Khandarkhaeva, S. E.; Kalinkin, A. V.; Prosvirin, I. P.; Bukhtiyarov, V. I.

    2014-10-20

    In this letter, we present structural, compositional, and electrical characteristics of anodic oxide layer-based metal-oxide-semiconductor (MOS) capacitors on n-type InAs(111)A, along with the effect of a thin fluorinated interfacial passivation layer. Electrochemical oxidation in acid electrolyte with addition of fluorine (NH{sub 4}F) led to the formation of oxygen free well-ordered wide gap fluorinated interfacial layer at InAs(111)A with the fixed charge (Q{sub fix}) and density of interface states (D{sub it}) in the range of (4–6) × 10{sup 10 }cm{sup −2} and (2–12) × 10{sup 10 }eV{sup −1 }cm{sup −2}, respectively. We found that MOS capacitors showed excellent capacitance-voltage characteristics with very small frequency dispersion (<1% and <15 mV). Fluorinated interfacial layer consists of crystalline isostructural compound with the InAs substrate, which remains intact with the atomic smoothness and sharpness that explain unpinned behavior of the Fermi level.

  9. Coupled interactions between volatile activity and Fe oxidation state during arc crustal processes

    USGS Publications Warehouse

    Humphreys, Madeleine C.S.; Brooker, R; Fraser, D.C.; Burgisser, A; Mangan, Margaret T.; McCammon, C

    2015-01-01

    Arc magmas erupted at the Earth’s surface are commonly more oxidized than those produced at mid-ocean ridges. Possible explanations for this high oxidation state are that the transfer of fluids during the subduction process results in direct oxidation of the sub-arc mantle wedge, or that oxidation is caused by the effect of later crustal processes, including protracted fractionation and degassing of volatile-rich magmas. This study sets out to investigate the effect of disequilibrium crustal processes that may involve coupled changes in H2O content and Fe oxidation state, by examining the degassing and hydration of sulphur-free rhyolites. We show that experimentally hydrated melts record strong increases in Fe3+/∑Fe with increasing H2O concentration as a result of changes in water activity. This is relevant for the passage of H2O-undersaturated melts from the deep crust towards shallow crustal storage regions, and raises the possibility that vertical variations in fO2 might develop within arc crust. Conversely, degassing experiments produce an increase in Fe3+/∑Fe with decreasing H2O concentration. In this case the oxidation is explained by loss of H2 as well as H2O into bubbles during decompression, consistent with thermodynamic modelling, and is relevant for magmas undergoing shallow degassing en route to the surface. We discuss these results in the context of the possible controls on fO2 during the generation, storage and ascent of magmas in arc settings, in particular considering the timescales of equilibration relative to observation as this affects the quality of the petrological record of magmatic fO2.

  10. Metal Oxide Nanoparticles: The Importance of Size, Shape, Chemical Composition, and Valence State in Determining Toxicity

    NASA Astrophysics Data System (ADS)

    Dunnick, Katherine

    Nanoparticles, which are defined as a structure with at least one dimension between 1 and 100 nm, have the potential to be used in a variety of consumer products due to their improved functionality compared to similar particles of larger size. Their small size is associated with increased strength, improved catalytic properties, and increased reactivity; however, their size is also associated with increased toxicity in vitro and in vivo. Numerous toxicological studies have been conducted to determine the properties of nanomaterials that increase their toxicity in order to manufacture new nanomaterials with decreased toxicity. Data indicates that size, shape, chemical composition, and valence state of nanomaterials can dramatically alter their toxicity profile. Therefore, the purpose of this dissertation was to determine how altering the shape, size, and chemical composition of various metal oxide nanoparticles would affect their toxicity. Metal oxides are used in variety of consumer products, from spray-sun screens, to food coloring agents; thus, understanding the toxicity of metal oxides and determining which aspects affect their toxicity may provide safe alternatives nanomaterials for continued use in manufacturing. Tungstate nanoparticles toxicity was assessed in an in vitro model using RAW 264.7 cells. The size, shape, and chemical composition of these nanomaterials were altered and the effect on reactive oxygen species and general cytotoxicity was determined using a variety of techniques. Results demonstrate that shape was important in reactive oxygen species production as wires were able to induce significant reactive oxygen species compared to spheres. Shape, size, and chemical composition did not have much effect on the overall toxicity of these nanoparticles in RAW 264.7 cells over a 72 hour time course, implicating that the base material of the nanoparticles was not toxic in these cells. To further assess how chemical composition can affect toxicity

  11. Electrorecovery of actinides at room temperature

    SciTech Connect

    Stoll, Michael E; Oldham, Warren J; Costa, David A

    2008-01-01

    There are a large number of purification and processing operations involving actinide species that rely on high-temperature molten salts as the solvent medium. One such application is the electrorefining of impure actinide metals to provide high purity material for subsequent applications. There are some drawbacks to the electrodeposition of actinides in molten salts including relatively low yields, lack of accurate potential control, maintaining efficiency in a highly corrosive environment, and failed runs. With these issues in mind we have been investigating the electrodeposition of actinide metals, mainly uranium, from room temperature ionic liquids (RTILs) and relatively high-boiling organic solvents. The RTILs we have focused on are comprised of 1,3-dialkylimidazolium or quaternary ammonium cations and mainly the {sup -}N(SO{sub 2}CF{sub 3}){sub 2} anion [bis(trif1uoromethylsulfonyl)imide {equivalent_to} {sup -}NTf{sub 2}]. These materials represent a class of solvents that possess great potential for use in applications employing electrochemical procedures. In order to ascertain the feasibility of using RTILs for bulk electrodeposition of actinide metals our research team has been exploring the electron transfer behavior of simple coordination complexes of uranium dissolved in the RTIL solutions. More recently we have begun some fundamental electrochemical studies on the behavior of uranium and plutonium complexes in the organic solvents N-methylpyrrolidone (NMP) and dimethylsulfoxide (DMSO). Our most recent results concerning electrodeposition will be presented in this account. The electrochemical behavior of U(IV) and U(III) species in RTILs and the relatively low vapor pressure solvents NMP and DMSO is described. These studies have been ongoing in our laboratory to uncover conditions that will lead to the successful bulk electrodeposition of actinide metals at a working electrode surface at room temperature or slightly elevated temperatures. The RTILs we

  12. Characterization of Interface State in Silicon Carbide Metal Oxide Semiconductor Capacitors

    NASA Astrophysics Data System (ADS)

    Kao, Wei-Chieh

    Silicon carbide (SiC) has always been considered as an excellent material for high temperature and high power devices. Since SiC is the only compound semiconductor whose native oxide is silicon dioxide (SiO2), it puts SiC in a unique position. Although SiC metal oxide semiconductor (MOS) technology has made significant progress in recent years, there are still a number of issues to be overcome before more commercial SiC devices can enter the market. The prevailing issues surrounding SiC MOSFET devices are the low channel mobility, the low quality of the oxide layer and the high interface state density at the SiC/SiO2 interface. Consequently, there is a need for research to be performed in order to have a better understanding of the factors causing the poor SiC/SiO2 interface properties. In this work, we investigated the generation lifetime in SiC materials by using the pulsed metal oxide semiconductor (MOS) capacitor method and measured the interface state density distribution at the SiC/SiO2 interface by using the conductance measurement and the high-low frequency capacitance technique. These measurement techniques have been performed on n-type and p-type SiC MOS capacitors. In the course of our investigation, we observed fast interface states at semiconductor-dielectric interfaces in SiC MOS capacitors that underwent three different interface passivation processes, such states were detected in the nitrided samples but not observed in PSG-passivated samples. This result indicate that the lack of fast states at PSG-passivated interface is one of the main reasons for higher channel mobility in PSG MOSFETs. In addition, the effect of mobile ions in the oxide on the response time of interface states has been investigated. In the last chapter we propose additional methods of investigation that can help elucidate the origin of the particular interface states, enabling a more complete understanding of the SiC/SiO2 material system.

  13. Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide

    SciTech Connect

    Bondi, Robert J. Marinella, Matthew J.

    2015-02-28

    First-principles density-functional theory calculations are used to study the atomistic structure, structural energetics, and electron density near the O monovacancy (V{sub O}{sup n}; n = 0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta{sub 2}O{sub 5}), and also at vacuum and metallic Ta interfaces. We calculate multivariate vacancy formation energies to evaluate stability as a function of oxidation state, distance from interface plane, and Fermi energy. V{sub O}{sup n} of all oxidation states preferentially segregates at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta{sub 2}O{sub 5}, V{sub O}{sup 0} is characterized by structural contraction and electron density localization, while V{sub O}{sup 2+} promotes structural expansion and is depleted of electron density. In contrast, interfacial V{sub O}{sup 0} and V{sub O}{sup 2+} show nearly indistinguishable ionic and electronic signatures indicative of a reduced V{sub O} center. Interfacial V{sub O}{sup 2+} extracts electron density from metallic Ta, indicating that V{sub O}{sup 2+} is spontaneously reduced at the expense of the metal. This oxidation/reduction behavior suggests careful selection and processing of both oxide layer and metal electrodes for engineering memristor device operation.

  14. Ab initio quantum Monte Carlo calculations of ground-state properties of manganese's oxides

    NASA Astrophysics Data System (ADS)

    Sharma, Vinit; Krogel, Jaron T.; Kent, P. R. C.; Reboredo, Fernando A.

    One of the critical scientific challenges of contemporary research is to obtain an accurate theoretical description of the electronic properties of strongly correlated systems such as transition metal oxides and rare-earth compounds, since state-of-art ab-initio methods based on approximate density functionals are not always sufficiently accurate. Quantum Monte Carlo (QMC) methods, which use statistical sampling to evaluate many-body wave functions, have the potential to answer this challenge. Owing to the few fundamental approximations made and the direct treatment of electron correlation, QMC methods are among the most accurate electronic structure methods available to date. We assess the accuracy of the diffusion Monte Carlo method in the case of rocksalt manganese oxide (MnO). We study the electronic properties of this strongly-correlated oxide, which has been identified as a suitable candidate for many applications ranging from catalysts to electronic devices. ``This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.'' Ab initio quantum Monte Carlo calculations of ground-state properties of manganese's oxides.

  15. XANES studies of oxidation states of sulfur in aquatic and soil humic substances

    SciTech Connect

    Xia, K.; Weesner, F.; Bleam, W.F.; Helmke, P.A.; Bloom, P.R.; Skyllberg, U.L.

    1998-09-01

    Sulfur K-edge x-ray absorption near-edge structure spectroscopy (XANES) was used to identify multiple organic S oxidation states in aquatic and soil humic substances. The XANES results suggest that S in humic substances exists in four major oxidation groups similar to sulfate ester, sulfonate, sulfoxide, and thiol-sulfide. Thiol S cannot be separated from sulfide X and must be considered as a single thiol-sulfide peak. The second derivative spectra suggest the existence of thiophene and sulfone S. The relative quantities of each major S form in humic samples were estimated based on the integrated cross section of each s {r_arrow} p transition peak corresponding to different S oxidation states in the S K-edge XANES spectra. The XANES results of the four humic samples used in this study appear to reflect the environmental settings where the humic substances originally formed. The percentage of the most reduced organic S (thiol-sulfide and possibly thiophene) in humic substances follows the sequence:aquatic samples > organic soil sample > mineral soil sample. The percentage of most oxidized S (sulfate group) was the greatest in the humic substance from a mineral soil and the lowest in the aquatic humic substances.

  16. Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide

    DOE PAGESBeta

    Bondi, Robert J.; Marinella, Matthew J.

    2015-02-28

    First-principles density-functional theory (DFT) calculations are used to study the atomistic structure, structural energetics, and electron density near the O monovacancy (VOn; n=0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta2O5) and also at vacuum and metallic Ta interfaces. We calculate multivariate vacancy formation energies to evaluate stability as a function of oxidation state, distance from interface plane, and Fermi energy. VOn of all oxidation states preferentially segregate at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta2O5, VO0 are characterized by structural contraction and electron density localization, while VO2+ promote structural expansion andmore » are depleted of electron density. In contrast, interfacial VO0 and VO2+ show nearly indistinguishable ionic and electronic signatures indicative of a reduced VO center. Interfacial VO2+ extract electron density from metallic Ta indicating VO2+ is spontaneously reduced at the expense of the metal. This oxidation/reduction behavior suggests careful selection and processing of both oxide layer and metal electrodes for engineering memristor device operation.« less

  17. Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide

    SciTech Connect

    Bondi, Robert J.; Marinella, Matthew J.

    2015-02-28

    First-principles density-functional theory (DFT) calculations are used to study the atomistic structure, structural energetics, and electron density near the O monovacancy (VOn; n=0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta2O5) and also at vacuum and metallic Ta interfaces. We calculate multivariate vacancy formation energies to evaluate stability as a function of oxidation state, distance from interface plane, and Fermi energy. VOn of all oxidation states preferentially segregate at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta2O5, VO0 are characterized by structural contraction and electron density localization, while VO2+ promote structural expansion and are depleted of electron density. In contrast, interfacial VO0 and VO2+ show nearly indistinguishable ionic and electronic signatures indicative of a reduced VO center. Interfacial VO2+ extract electron density from metallic Ta indicating VO2+ is spontaneously reduced at the expense of the metal. This oxidation/reduction behavior suggests careful selection and processing of both oxide layer and metal electrodes for engineering memristor device operation.

  18. No effect of H2O degassing on the oxidation state of magmatic liquids

    NASA Astrophysics Data System (ADS)

    Waters, Laura E.; Lange, Rebecca A.

    2016-08-01

    The underlying cause for why subduction-zone magmas are systematically more oxidized than those formed at mid-ocean spreading ridges is a topic of vigorous debate. It is either a primary feature inherited from the subduction of oxidized oceanic crust into the mantle or a secondary feature that develops because of H2O degassing and/or magma differentiation. Low total iron contents and high melt H2O contents render rhyolites sensitive to any effect of H2O degassing on ferric-ferrous ratios. Here, pre-eruptive magmatic Fe2+ concentrations, measured using Fe-Ti oxides that co-crystallized with silicate phenocrysts under hydrous conditions, are compared with Fe2+ post-eruptive concentrations in ten crystal-poor, fully-degassed obsidian samples; five are microlite free. No effect of H2O degassing on the ferric-ferrous ratio is found. In addition, Fe-Ti oxide data from this study and the literature show that arc magmas are systematically more oxidized than both basalts and hydrous silicic melts from Iceland and Yellowstone prior to extensive degassing. Nor is there any evidence that differentiation (i.e., crystal fractionation, crustal assimilation) is the cause of the higher redox state of arc magmas relative to those of Iceland/Yellowstone rhyolites. Instead, the evidence points to subduction of oxidized crust and the release of an H2O-rich fluid and/or melt with a high oxygen fugacity (fO2), which plays a role during H2O-flux melting of the mantle in creating basalts that are relatively oxidized.

  19. Engineering the defect state and reducibility of ceria based nanoparticles for improved anti-oxidation performance

    NASA Astrophysics Data System (ADS)

    Wang, Yan-Jie; Dong, Hao; Lyu, Guang-Ming; Zhang, Huai-Yuan; Ke, Jun; Kang, Li-Qun; Teng, Jia-Li; Sun, Ling-Dong; Si, Rui; Zhang, Jing; Liu, Yan-Jun; Zhang, Ya-Wen; Huang, Yun-Hui; Yan, Chun-Hua

    2015-08-01

    Due to their excellent anti-oxidation performance, CeO2 nanoparticles receive wide attention in pharmacological application. Deep understanding of the anti-oxidation mechanism of CeO2 nanoparticles is extremely important to develop potent CeO2 nanomaterials for anti-oxidation application. Here, we report a detailed study on the anti-oxidation process of CeO2 nanoparticles. The valence state and coordination structure of Ce are characterized before and after the addition of H2O2 to understand the anti-oxidation mechanism of CeO2 nanoparticles. Adsorbed peroxide species are detected during the anti-oxidation process, which are responsible for the red-shifted UV-vis absorption spectra of CeO2 nanoparticles. Furthermore, the coordination number of Ce in the first coordination shell slightly increased after the addition of H2O2. On the basis of these experimental results, the reactivity of coordination sites for peroxide species is considered to play a key role in the anti-oxidation performance of CeO2 nanoparticles. Furthermore, we present a robust method to engineer the anti-oxidation performance of CeO2 nanoparticles through the modification of the defect state and reducibility by doping with Gd3+. Improved anti-oxidation performance is also observed in cell culture, where the biocompatible CeO2-based nanoparticles can protect INS-1 cells from oxidative stress induced by H2O2, suggesting the potential application of CeO2 nanoparticles in the treatment of diabetes.Due to their excellent anti-oxidation performance, CeO2 nanoparticles receive wide attention in pharmacological application. Deep understanding of the anti-oxidation mechanism of CeO2 nanoparticles is extremely important to develop potent CeO2 nanomaterials for anti-oxidation application. Here, we report a detailed study on the anti-oxidation process of CeO2 nanoparticles. The valence state and coordination structure of Ce are characterized before and after the addition of H2O2 to understand the anti-oxidation

  20. Ge Interface Engineering with Ozone-oxidation for Low Interface State Density

    SciTech Connect

    Kuzum, Duygu; Krishnamohan, T.; Pethe, Abhijit J.; Okyay, Ali, K.; Oshima, Yasuhiro; Sun, Yun; McVittie, Jim P.; Pianetta, Piero A.; McIntyre, Paul C.; Saraswat, Krishna C.; /Stanford U., CIS

    2008-06-02

    Passivation of Ge has been a critical issue for Ge MOS applications in future technology nodes. In this letter, we introduce ozone-oxidation to engineer Ge/insulator interface. Interface states (D{sub it}) values across the bandgap and close to conduction bandedge were extracted using conductance technique at low temperatures. D{sub it} dependency on growth conditions was studied. Minimum D{sub it} of 3 x 10{sup 11} cm{sup -2} V{sup -1} was demonstrated. Physical quality of the interface was investigated through Ge 3d spectra measurements. We found that the interface and D{sub it} is strongly affected by the distribution of oxidation states and quality of the suboxide.

  1. Reduction-oxidation state and protein degradation in skeletal muscle of fasted and refed rats

    NASA Technical Reports Server (NTRS)

    Fagan, Julie M.; Tischler, Marc E.

    1986-01-01

    Redox state and protein degradation were measured in isolated muscles of fasted (up to 10 d) and refed (up to 4 d) 7- to 14-wk-old rats. Protein degradation in the extensor digitorum longus muscle, but not in the soleus muscle, was greater in the fasted rats than in weight-matched muscle from fed rats. The NAD couple was more oxidized in incubated and fresh extensor digitorum longus muscles and in some incubated soleus muscles of fasted rats than in weight-matched muscle from fed rats. In the extensor digitorum longus muscle of refed or prolonged fasted rats, protein degradation was slower and the NAD couple was more reduced than in the fed state. Therefore, oxidation of the NAD couple was associated with increased muscle breakdown during fasting, whereas reduction of the NAD couple was associated with muscle conservation and deposition.

  2. Constraints on the Detection of the Solar Nebula's Oxidation State Through Asteroid Observations

    NASA Technical Reports Server (NTRS)

    Abell, P. A.; Gaffey, M. J.; Hardersen, P. S.

    2005-01-01

    Introduction: Asteroids represent the only in situ surviving population of planetesimals from the formation of the inner solar system and therefore include materials from the very earliest stages of solar system formation. Hence, these bodies can provide constraints on the processes and conditions that were present during this epoch and can be used to test current models and theories describing the late solar nebula, the early solar system and subsequent planetary accretion. From detailed knowledge of asteroid mineralogic compositions the probable starting materials, thermal histories, and oxidation states of asteroid parent bodies can be inferred. If such data can be obtained from specific mainbelt source regions, then this information can be used to map out the formation conditions of the late solar nebula within the inner solar system and possibly distinguish any trends in oxidation state that may be present.

  3. Oxygen Fugacity of Basalts From Earth and Mars: Implications for Oxidation States of Terrestrial Planet Interiors

    NASA Astrophysics Data System (ADS)

    Herd, C.

    2004-12-01

    The oxidation state of a planetary interior plays an important role in the partitioning of elements between the planet's core and mantle, the geophysical properties of the mantle, the phase equilibria of igneous rocks, and the speciation of gases in the planet's atmosphere. Determining the oxidation state of the interior of the Moon, Mars, and differentiated asteroids is difficult, because planetary samples are dominated by basaltic igneous rocks. Direct mantle samples, such as mantle xenoliths and diamond inclusions, as benefit studies on Earth, are lacking. The oxidation state of these planets' interiors is inferred from the oxygen fugacity recorded in the basaltic samples. Basalts from Mars (martian meteorites) record oxygen fugacity ranging from near the IW buffer to 3 log units above ( ˜QFM), by several methods. The range of igneous rocks on Earth overlaps, but ranges up to ˜7 log units above IW, with the most oxidized samples derived from island arcs. Studies of the relationship between the oxidation state of a basalt and that of its mantle source on the Earth provide potentially important contributions to the interpretation of martian basalt oxygen fugacity and the inferred oxidation state of the martian interior. Thermodynamic considerations of ferrous-ferric mineral equilibria in the spinel and garnet facies of the Earth's mantle dictate that the oxygen fugacity should decrease, relative to the QFM buffer, with increasing pressure. Ballhaus (1995) calculated a decrease of 0.6 log unit per GPa increase, assuming a constant bulk composition. In contrast, C-H-O equilibria have isopleths of opposing slope, such that fluid composition will be dominated by more reduced species (e.g., methane) at greater depths. Ballhaus and Frost (1994) argue that C-H-O buffering influences upwelling asthenosphere, particularly by the presence of graphite, and that the oxygen fugacity of a basalt at the surface depends on the depth at which first melting occurs. This depth is

  4. Determination of the oxidation state and coordination of a vanadium doped chalcogenide glass

    NASA Astrophysics Data System (ADS)

    Hughes, Mark A.; Curry, Richard J.; Hewak, Daniel W.

    2011-01-01

    Vanadium doped chalcogenide glass has potential as an active gain medium, particularly at telecommunications wavelengths. This dopant has three spin allowed absorption transitions at 1100, 737 and 578 nm, and a spin forbidden absorption transition at 1000 nm. X-ray photoelectron spectroscopy indicated the presence of vanadium in a range of oxidation states from V+ to V5+. Excitation of each absorption band resulted in the same characteristic emission spectrum and lifetime, indicating that only one oxidation state is optically active. Arguments based on Tanabe-Sugano analysis indicated that the configuration of the optically active vanadium ion was octahedral V2+. The calculated crystal field parameters (Dq/B, B and C/B) were 1.85, 485.1 and 4.55, respectively.

  5. Visible light photoreactivity from hybridization states between carbon nitride bandgap states and valence states in Nb and Ti oxides

    NASA Astrophysics Data System (ADS)

    Lee, Hosik; Ohno, Takahisa

    2013-03-01

    For better efficiency as photocatalysts, N-doping for visible light reactivity has been intensively studied in Lamellar niobic and titanic solid acids (HNb3O8, H2Ti4O9), and its microscopic structures have been debated in this decade. We calculate the layered solid acids' structures and bandgaps. Bandgap reduction by carbon nitride adsorption in interlayer space is observed computationally. It originates from localized nitrogen states which form delocalized top-valence states by hybridizing with the host oxygen states and can contribute to photo-current.

  6. Tributylphosphate Extraction Behavior of Bismuthate-Oxidized Americium

    SciTech Connect

    Mincher; Leigh R. Martin; Nicholas C. Schmitt

    2008-08-01

    Higher oxidation states of americium have long been known; however, options for their preparation in acidic solution are limited. The conventional choice, silver-catalyzed peroxydisulfate, is not useful at nitric acid concentrations above about 0.3 M. We investigated the use of sodium bismuthate as an oxidant for Am3+ in acidic solution. Room-temperature oxidation produced AmO2 2+ quantitatively, whereas oxidation at 80 °C produced AmO2+ quantitatively. The efficacy of the method for the production of oxidized americium was verified by fluoride precipitation and by spectroscopic absorbance measurements. We performed absorbance measurements using a conventional 1 cm cell for high americium concentrations and a 100 cm liquid waveguide capillary cell for low americium concentrations. Extinction coefficients for the absorbance of Am3+ at 503 nm, AmO2+ at 514 nm, and AmO2 2+ at 666 nm in 0.1 M nitric acid are reported. We also performed solvent extraction experiments with the hexavalent americium using the common actinide extraction ligand tributyl phosphate (TBP) for comparison to the other hexavalent actinides. Contact with 30% tributyl phosphate in dodecane reduced americium; it was nevertheless extracted using short contact times. The TBP extraction of AmO2 2+ over a range of nitric acid concentrations is shown for the first time and was found to be analogous to that of uranyl, neptunyl, and plutonyl ions.

  7. The oxidation state, and sulfur and Cu contents of arc magmas: implications for metallogeny

    NASA Astrophysics Data System (ADS)

    Richards, Jeremy P.

    2015-09-01

    Global data for measured Fe2O3/FeO ratios and Cu contents in unaltered volcanic and intrusive arc rocks indicate that, on average, they are slightly more oxidized than other magmas derived from depleted upper mantle (such as MORB), but contain similar Cu contents across their compositional ranges. Although Cu scatters to elevated values in some intermediate composition samples, the bulk of the data show a steady but gentle trend to lower concentrations with differentiation, reaching modal values of ~ 50-100 ppm in andesitic rocks. These data suggest that Cu is mildly compatible during partial melting and fractionation processes, likely reflecting minor degrees of sulfide saturation throughout the magmatic cycle. However, the volume of sulfides must be small such that significant proportions of the metal content remain in the magma during fractionation to intermediate compositions. Previous studies have shown that andesitic magmas containing ~ 50 ppm Cu can readily form large porphyry-type Cu deposits upon emplacement in the upper crust. A review of the literature suggests that the elevated oxidation state in the asthenospheric mantle wedge source of arc magmas (ΔFMQ ≈ + 1 ± 1) derives from the subduction of seawater-altered and oxidized oceanic crust, and is transmitted into the mantle wedge via prograde metamorphic dehydration fluids carrying sulfate and other oxidizing components. Progressive hydration and oxidation of the mantle wedge may take up to ~ 10 m.y. to reach a steady state from the onset of subduction, explaining the rarity of porphyry deposits in primitive island arcs, and the late formation of porphyries in continental arc magmatic cycles. Magmas generated from this metasomatized and moderately oxidized mantle source will be hydrous basalts containing high concentrations of sulfur, mainly dissolved as sulfate or sulfite. Some condensed sulfides (melt or minerals) may be present due to the high overall fS2, despite the moderately high oxidation

  8. Actinide phosphonate complexes in aqueous solutions

    SciTech Connect

    Nash, K.L.

    1993-10-01

    Complexes formed by actinides with carboxylic acids, polycarboxylic acids, and aminopolycarboxylic acids play a central role in both the basic and process chemistry of the actinides. Recent studies of f-element complexes with phosphonic acid ligands indicate that new ligands incorporating doubly ionizable phosphonate groups (-PO{sub 3}H{sub 2}) have many properties which are unique chemically, and promise more efficient separation processes for waste cleanup and environmental restoration. Simple diphosphonate ligands form much stronger complexes than isostructural carboxylates, often exhibiting higher solubility as well. In this manuscript recent studies of the thermodynamics and kinetics of f-element complexation by 1,1 and 1,2 diphosphonic acid ligands are described.

  9. Microbial Transformations of Actinides and Other Radionuclides

    SciTech Connect

    Francis,A.J.; Dodge, C. J.

    2009-01-07

    Microorganisms can affect the stability and mobility of the actinides and other radionuclides released from nuclear fuel cycle and from nuclear fuel reprocessing plants. Under appropriate conditions, microorganisms can alter the chemical speciation, solubility and sorption properties and thus could increase or decrease the concentrations of radionuclides in solution in the environment and the bioavailability. Dissolution or immobilization of radionuclides is brought about by direct enzymatic action or indirect non-enzymatic action of microorganisms. Although the physical, chemical, and geochemical processes affecting dissolution, precipitation, and mobilization of radionuclides have been extensively investigated, we have only limited information on the effects of microbial processes and biochemical mechanisms which affect the stability and mobility of radionuclides. The mechanisms of microbial transformations of the major and minor actinides U, Pu, Cm, Am, Np, the fission products and other radionuclides such as Ra, Tc, I, Cs, Sr, under aerobic and anaerobic conditions in the presence of electron donors and acceptors are reviewed.

  10. Method for decontamination of nickel-fluoride-coated nickel containing actinide-metal fluorides

    DOEpatents

    Windt, N.F.; Williams, J.L.

    In one aspect, the invention comprises contacting nickel-fluoride-coated nickel with gaseous ammonia at a temperature effecting nickel-catalyzed dissociation thereof and effecting hydrogen-reduction of the nickel fluoride. The resulting nickel is heated to form a melt and a slag and to effect transfer of actinide metals from the melt into the slag. The melt and slag are then separated. In another aspect, nickel contianing nickel oxide and actinide metals is contacted with ammonia at a temperature effecting nickel-catalyzed dissociation to effect conversion of the nickel oxide to the metal. The resulting nickel is then melted and separated as described. In another aspect nickel-fluoride-coated nickel containing actinide-metal fluorides is contacted with both steam and ammonia. The resulting nickel then is melted and separated as described. The invention is characterized by higher nickel recovery, efficient use of ammonia, a substantial decrease in slag formation and fuming, and a valuable increase in the service life of the furnace liners used for melting.

  11. Highly mobile and reactive state of hydrogen in metal oxide semiconductors at room temperature

    NASA Astrophysics Data System (ADS)

    Chen, Wan Ping; He, Ke Feng; Wang, Yu; Chan, Helen Lai Wah; Yan, Zijie

    2013-11-01

    Hydrogen in metal oxides usually strongly associates with a neighboring oxygen ion through an O-H bond and thus displays a high stability. Here we report a novel state of hydrogen with unusually high mobility and reactivity in metal oxides at room temperature. We show that freshly doped hydrogen in Nb2O5 and WO3 polycrystals via electrochemical hydrogenation can reduce Cu2+ ions into Cu0 if the polycrystals are immersed in a CuSO4 solution, while this would not happen if the hydrogenated polycrystals have been placed in air for several hours before the immersion. Time-dependent studies of electrochemically hydrogenated rutile single crystals reveal two distinct states of hydrogen: one as protons covalently bonded to oxygen ions, while the other one is highly unstable with a lifetime of just a few hours. Observation of this mobile and reactive state of hydrogen will provide new insight into numerous moderate and low temperature interactions between metal oxides and hydrogen.

  12. Quantitative evaluation of the effect of H2O degassing on the oxidation state of magmas

    NASA Astrophysics Data System (ADS)

    Lange, R. A.; Waters, L.

    2014-12-01

    The extent to which degassing of the H2O component affects the oxidation state of hydrous magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of various magmas, whereas our focus is on the H2O component. There are two ways that degassing of H2O by itself may cause oxidation: (1) the reaction: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt), and/or (2) if dissolved water preferentially enhances the activity of ferrous vs. ferric iron in magmatic liquids. In this study, a comparison is made between the pre-eruptive oxidation states of 14 crystal-poor, jet-black obsidian samples (obtained from two Fe-Ti oxides) and their post-eruptive values (analyzed with the Wilson 1960 titration method tested against USGS standards). The obsidians are from Medicine Lake (CA), Long Valley (CA), and the western Mexican arc; all have low FeOT (1.1-2.1 wt%), rendering their Fe2+/Fe3+ ratios highly sensitive to the possible effects of substantial H2O degassing. The Fe-Ti oxide thermometer/oxybarometer of Ghiorso and Evans, (2008) gave temperatures for the 14 samples that range for 720 to 940°C and ∆NNO values of -0.9 to +1.4. With temperature known, the plagioclase-liquid hygrometer was applied and show that ≤ 6.5 wt% H2O was dissolved in the melts prior to eruption. In addition, pre-eruptive Cl and S concentrations were constrained on the basis of apatite analyses (Webster et al., 2009) and sulfur concentrations needed for saturation with pyrrhotite (Clemente et al., 2004), respectively. Maximum pre-eruptive chlorine and sulfur contents are 6000 and 200 ppm, respectively. After eruption, the rhyolites lost nearly all of their volatiles. Our results indicate no detectable change between pre- and post-eruptive Fe2+ concentrations, with an average deviation of ± 0.1 wt % FeO. Although degassing of large concentrations of S and/or Cl may affect the oxidation state of magmas, at the pre-eruptive levels

  13. Do the higher oxidation states of the photosynthetic O2-evolving system contain bound H2O?

    NASA Technical Reports Server (NTRS)

    Radmer, R.; Ollinger, O.

    1986-01-01

    A modified mass spectrometer was used to determine whether the higher oxidation states of the photosynthetic O2-evolving system contain substrate water that is not freely exchangeable with the external medium. Our data indicated that the higher oxidation states contain no appreciable bound, non-exchangeable H2O. This suggests that H2O oxidation takes place via a rapid, concerted, all-or-none mechanism rather than by a mechanism involving stable, partially oxidized, H2O-derived intermediates. These findings set definite constraints on possible mechanisms of O2 evolution.

  14. PROCESS OF SECURING PLUTONIUM IN NITRIC ACID SOLUTIONS IN ITS TRIVALENT OXIDATION STATE

    DOEpatents

    Thomas, J.R.

    1958-08-26

    >Various processes for the recovery of plutonium require that the plutonium be obtalned and maintained in the reduced or trivalent state in solution. Ferrous ions are commonly used as the reducing agent for this purpose, but it is difficult to maintain the plutonium in a reduced state in nitric acid solutions due to the oxidizing effects of the acid. It has been found that the addition of a stabilizing or holding reductant to such solution prevents reoxidation of the plutonium. Sulfamate ions have been found to be ideally suitable as such a stabilizer even in the presence of nitric acid.

  15. Three-dimensional mapping of nickel oxidation states using full field x-ray absorption near edge structure nanotomography

    SciTech Connect

    Nelson, George J.; Harris, William M.; Izzo, John R. Jr.; Grew, Kyle N.; Chiu, Wilson K. S.; Chu, Yong S.; Yi, Jaemock; Andrews, Joy C.; Liu Yijin; Pianetta, Piero

    2011-04-25

    The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.

  16. Three-dimensional mapping of nickel oxidation states using full field x-ray absorption near edge structure nanotomography

    NASA Astrophysics Data System (ADS)

    Nelson, George J.; Harris, William M.; Izzo, John R.; Grew, Kyle N.; Chiu, Wilson K. S.; Chu, Yong S.; Yi, Jaemock; Andrews, Joy C.; Liu, Yijin; Pianetta, Piero

    2011-04-01

    The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.

  17. Relativistic density functional theory modeling of plutonium and americium higher oxide molecules.

    PubMed

    Zaitsevskii, Andréi; Mosyagin, Nikolai S; Titov, Anatoly V; Kiselev, Yuri M

    2013-07-21

    The results of electronic structure modeling of plutonium and americium higher oxide molecules (actinide oxidation states VI through VIII) by two-component relativistic density functional theory are presented. Ground-state equilibrium molecular structures, main features of charge distributions, and energetics of AnO3, AnO4, An2On (An=Pu, Am), and PuAmOn, n = 6-8, are determined. In all cases, molecular geometries of americium and mixed plutonium-americium oxides are similar to those of the corresponding plutonium compounds, though chemical bonding in americium oxides is markedly weaker. Relatively high stability of the mixed heptoxide PuAmO7 is noticed; the Pu(VIII) and especially Am(VIII) oxides are expected to be unstable. PMID:23883027

  18. Relativistic density functional theory modeling of plutonium and americium higher oxide molecules

    NASA Astrophysics Data System (ADS)

    Zaitsevskii, Andréi; Mosyagin, Nikolai S.; Titov, Anatoly V.; Kiselev, Yuri M.

    2013-07-01

    The results of electronic structure modeling of plutonium and americium higher oxide molecules (actinide oxidation states VI through VIII) by two-component relativistic density functional theory are presented. Ground-state equilibrium molecular structures, main features of charge distributions, and energetics of AnO3, AnO4, An2On (An=Pu, Am), and PuAmOn, n = 6-8, are determined. In all cases, molecular geometries of americium and mixed plutonium-americium oxides are similar to those of the corresponding plutonium compounds, though chemical bonding in americium oxides is markedly weaker. Relatively high stability of the mixed heptoxide PuAmO7 is noticed; the Pu(VIII) and especially Am(VIII) oxides are expected to be unstable.

  19. In vitro removal of actinide (IV) ions

    DOEpatents

    Weitl, Frederick L.; Raymond, Kenneth N.

    1982-01-01

    A compound of the formula: ##STR1## wherein X is hydrogen or a conventional electron-withdrawing group, particularly --SO.sub.3 H or a salt thereof; n is 2, 3, or 4; m is 2, 3, or 4; and p is 2 or 3. The present compounds are useful as specific sequestering agents for actinide (IV) ions. Also described is a method for the 2,3-dihydroxybenzamidation of azaalkanes.

  20. Separation of Californium from other Actinides

    DOEpatents

    Mailen, J C; Ferris, L M

    1973-09-25

    A method is provided for separating californium from a fused fluoride composition containing californium and at least one element selected from the group consisting of plutonium, americium, curium, uranium, thorium, and protactinium which comprises contacting said fluoride composition with a liquid bismuth phase containing sufficient lithium or thorium to effect transfer of said actinides to the bismuth phase and then contacting the liquid bismuth phase with molten LiCl to effect selective transfer of californium to the chloride phase.