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.

Actinide migration in Johnston Atoll soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolf, S. F.; Bates, J. K.; Buck, E. C.

1997-02-01

Characterization of the actinide content of a sample of contaminated coral soil from Johnston Atoll, the site of three non-nuclear destructs of nuclear warhead-carrying THOR missiles in 1962, revealed that >99% of the total actinide content is associated with discrete bomb fragments. After removal of these fragments, there was an inverse correlation between actinide content and soil particle size in particles from 43 to 0.4 {micro}m diameter. Detailed analyses of this remaining soil revealed no discrete actinide phase in these soil particles, despite measurable actinide content. Observations indicate that exposure to the environment has caused the conversion of relatively insolublemore » actinide oxides to the more soluble actinyl oxides and actinyl carbonate coordinated complexes. This process has led to dissolution of actinides from discrete particles and migration to the surrounding soil surfaces, resulting in a dispersion greater than would be expected by physical transport of discrete particles alone.« less

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)

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.

Flammability Analysis For Actinide Oxides Packaged In 9975 Shipping Containers

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 ofmore » 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.« less

Actinides-1981

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 thatmore » other redox active components may have on the oxidation of Am III. Experimental findings indicated that Ce III, Np V, and Ru II are oxidized by peroxydisulfate, but there are no indications that the presence of Ce III, Np V, and Ru II affected the rate or extent of americium oxidation at the concentrations of peroxydisulfate being used.« less

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.

The inverse-trans-influence in tetravalent lanthanide and actinide bis(carbene) complexes

NASA Astrophysics Data System (ADS)

Gregson, Matthew; Lu, Erli; Mills, David P.; Tuna, Floriana; McInnes, Eric J. L.; Hennig, Christoph; Scheinost, Andreas C.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Kerridge, Andrew; Liddle, Stephen T.

2017-02-01

Across the periodic table the trans-influence operates, whereby tightly bonded ligands selectively lengthen mutually trans metal-ligand bonds. Conversely, in high oxidation state actinide complexes the inverse-trans-influence operates, where normally cis strongly donating ligands instead reside trans and actually reinforce each other. However, because the inverse-trans-influence is restricted to high-valent actinyls and a few uranium(V/VI) complexes, it has had limited scope in an area with few unifying rules. Here we report tetravalent cerium, uranium and thorium bis(carbene) complexes with trans C=M=C cores where experimental and theoretical data suggest the presence of an inverse-trans-influence. Studies of hypothetical praseodymium(IV) and terbium(IV) analogues suggest the inverse-trans-influence may extend to these ions but it also diminishes significantly as the 4f orbitals are populated. This work suggests that the inverse-trans-influence may occur beyond high oxidation state 5f metals and hence could encompass mid-range oxidation state actinides and lanthanides. Thus, the inverse-trans-influence might be a more general f-block principle.

The inverse-trans-influence in tetravalent lanthanide and actinide bis(carbene) complexes.

PubMed

Gregson, Matthew; Lu, Erli; Mills, David P; Tuna, Floriana; McInnes, Eric J L; Hennig, Christoph; Scheinost, Andreas C; McMaster, Jonathan; Lewis, William; Blake, Alexander J; Kerridge, Andrew; Liddle, Stephen T

2017-02-03

Across the periodic table the trans-influence operates, whereby tightly bonded ligands selectively lengthen mutually trans metal-ligand bonds. Conversely, in high oxidation state actinide complexes the inverse-trans-influence operates, where normally cis strongly donating ligands instead reside trans and actually reinforce each other. However, because the inverse-trans-influence is restricted to high-valent actinyls and a few uranium(V/VI) complexes, it has had limited scope in an area with few unifying rules. Here we report tetravalent cerium, uranium and thorium bis(carbene) complexes with trans C=M=C cores where experimental and theoretical data suggest the presence of an inverse-trans-influence. Studies of hypothetical praseodymium(IV) and terbium(IV) analogues suggest the inverse-trans-influence may extend to these ions but it also diminishes significantly as the 4f orbitals are populated. This work suggests that the inverse-trans-influence may occur beyond high oxidation state 5f metals and hence could encompass mid-range oxidation state actinides and lanthanides. Thus, the inverse-trans-influence might be a more general f-block principle.

The inverse-trans-influence in tetravalent lanthanide and actinide bis(carbene) complexes

PubMed Central

Gregson, Matthew; Lu, Erli; Mills, David P.; Tuna, Floriana; McInnes, Eric J. L.; Hennig, Christoph; Scheinost, Andreas C.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Kerridge, Andrew; Liddle, Stephen T.

2017-01-01

Across the periodic table the trans-influence operates, whereby tightly bonded ligands selectively lengthen mutually trans metal–ligand bonds. Conversely, in high oxidation state actinide complexes the inverse-trans-influence operates, where normally cis strongly donating ligands instead reside trans and actually reinforce each other. However, because the inverse-trans-influence is restricted to high-valent actinyls and a few uranium(V/VI) complexes, it has had limited scope in an area with few unifying rules. Here we report tetravalent cerium, uranium and thorium bis(carbene) complexes with trans C=M=C cores where experimental and theoretical data suggest the presence of an inverse-trans-influence. Studies of hypothetical praseodymium(IV) and terbium(IV) analogues suggest the inverse-trans-influence may extend to these ions but it also diminishes significantly as the 4f orbitals are populated. This work suggests that the inverse-trans-influence may occur beyond high oxidation state 5f metals and hence could encompass mid-range oxidation state actinides and lanthanides. Thus, the inverse-trans-influence might be a more general f-block principle. PMID:28155857

Sigma Team for Advanced Actinide Recycle FY2015 Accomplishments and Directions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moyer, Bruce A.

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 researchmore » 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

Aqueous Electrochemical Mechanisms in Actinide Residue Processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, David E.; Burns, Carol J.; Smith, Wayne H.

2000-12-31

as the Catalyzed Electrochemical Plutonium Oxide Dissolution (CEPOD) process pioneered by workers at Pacific Northwest National Laboratory in the mid-1970s [2]. The basis for most of these mediated electrochemical oxidation/reduction (MEO/R) processes is the generation of a dissolved electrochemical catalyst, such as Ag2+, which is capable of oxidizing or reducing solid-phase actinide species or actinide sorbates via 7 heterogeneous electron transfer to oxidation states that have significantly greater solubilities (e.g., PuO2(s) to PuO2 2+ (dissolved)). The solubilized actinide can then be recovered by ion exchange or other mechanisms. These aqueous electrochemical methods for residue treatment have been considered in many of the ''trade studies'' to evaluate options for stabilization of the various categories of residue materials. While some concerns generally arise (e.g., large secondary waste volumes could results since the process stream normally goes th rough anion exchange or precipitation steps to remove the actinide), the real utility and versatility of these methods should not be overlooked. They are low temperature, ambient pressure processes that operate in a non-corrosive environment. In principle, they can be designed to be highly selective for the actinides (i.e., no substrate degradation occurs), they can be utilized for many categories of residue materials with little or no modification in hardware or operating conditions, and they can conceivably be engineered to minimize secondary waste stream volume. However, some fundamental questions remain concerning the mechanisms through which these processes act, and how the processes might be optimized to maximize efficiency while minimizing secondary waste. In addition, given the success achieved to date on the limited set of residues, further research is merited to extend the range of applicability of these electrochemical methods to other residue and waste streams. The principal goal of the work described

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)

Physical and chemical characterization of actinides in soil from Johnston Atoll

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolf, S.F.; Bates, J.K.; Buck, E.C.

1997-02-01

Characterization of the actinide content of a sample of contaminated coral soil from Johnston Atoll, the site of three non-nuclear destructs of nuclear warhead-carrying THOR missiles in 1962, revealed that >99% of the total actinide content is associated with discrete bomb fragments. After removal of these fragments, there was an inverse correlation between actinide content and soil particle size in particles from 43 to 0.4 {mu}m diameter. Detailed analyses of this remaining soil revealed no discrete actinide phase in these soil particles, despite measurable actinide content. Observations indicate that exposure to the environment has caused the conversion of relatively insolublemore » actinide oxides to the more soluble actinyl oxides and actinyl carbonate coordinated complexes. This process has led to dissolution of actinides from discrete particles and migration to the surrounding soil surfaces, resulting in a dispersion greater than would be expected by physical transport of discrete particles alone. 26 refs., 4 figs., 1 tab.« less

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.

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.

Actinides in the Geosphere

NASA Astrophysics Data System (ADS)

Runde, Wolfgang; Neu, Mary P.

Since the 1950s actinides have been used to benefit industry, science, health, and national security. The largest industrial application, electricity generation from uranium and thorium fuels, is growing worldwide. Thus, more actinides are being mined, produced, used and processed than ever before. The future of nuclear energy hinges on how these increasing amounts of actinides are contained in each stage of the fuel cycle, including disposition. In addition, uranium and plutonium were built up during the Cold War between the United States and the Former Soviet Union for defense purposes and nuclear energy.

A Multireference Density Functional Approach to the Calculation of the Excited States of Uranium Ions

DTIC Science & Technology

2007-03-01

approach. xiv A MULTIREFERENCE DENSITY FUNCTIONAL APPROACH TO THE CALCULATION OF THE EXCITED STATES OF URANIUM IONS I. Introduction Actinide chemistry, in...oxidation state of the uranium atom. Uranium, like most early actinides , can possess a wide range of oxidation states, ranging from +3 to +6, due in part...in predicting the electronic spectra for heavy element compounds. The first difficulty is that relativistic effects for actinides are significant

Higher Americium Oxidation State Research Roadmap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mincher, Bruce J.; Law, Jack D.; Goff, George S.

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.« less

Preparation of actinide boride materials via solid-state metathesis reactions and actinide dicarbollide precursors

NASA Astrophysics Data System (ADS)

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

2000-07-01

Information gaps exist in the knowledge base needed for choosing among the alternate processes to be used in the safe conversion of fissile materials to optimal forms for safe interim storage, long-term storage, and ultimate disposition. The current baseline storage technology for various wastes uses borosilicate glasses.1 The focus of this paper is the synthesis of actinide-containing ceramic materials at low and moderate temperatures (200 °C-1000 °C) using molecular and polymeric actinide borane and carborane complexes.

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

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

DOE PAGES

Cary, Samantha K.; Vasiliu, Monica; Baumbach, Ryan 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, 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

Actinide geochemistry: from the molecular level to the real system.

PubMed

Geckeis, Horst; Rabung, Thomas

2008-12-12

Geochemical processes leading to either mobilization or retention of radionuclides in an aquifer system are significantly influenced by their interaction with rock, sediment and colloid surfaces. Therefore, a sound safety assessment of nuclear waste disposal requires the elucidation and quantification of those processes. State-of-the-art analytical techniques as e.g. laser- and X-ray spectroscopy are increasingly applied to study solid-liquid interface reactions to obtain molecular level speciation insight. We have studied the sorption of trivalent lanthanides and actinides onto aluminium oxides, hydroxides and purified clay minerals by the time-resolved laser fluorescence spectroscopy and X-ray-absorption spectroscopy. Chemical constitution and structure of surface bound actinides are proposed based on spectroscopic information. Open questions still remain with regard to the exact nature of mineral surface ligands and the mineral/water interface. Similarities of spectroscopic data obtained for M(III) sorbed onto gamma-alumina, and clay minerals suggest the formation of very comparable inner-sphere surface complexes such as S-O-An(III)(OH)x(2-x)(H2O)5-x at pH > 5. Those speciation data are found consistent with those predicted by surface complexation modelling. The applicability of data obtained for pure mineral phases to actinide sorption onto heterogeneously composed natural clay rock is examined by experiments and by geochemical modelling. Good agreement of experiment and model calculations is found for U(VI) and trivalent actinide/lanthanide sorption to natural clay rock. The agreement of spectroscopy, geochemical modelling and batch experiments with natural rock samples and purified minerals increases the reliability in model predictions. The assessment of colloid borne actinide migration observed in various laboratory and field studies calls for detailed information on actinide-colloid interaction. Kinetic stabilization of colloid bound actinides can be due

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.

Heptavalent Actinide Tetroxides NpO 4 – and PuO 4 –: Oxidation of Pu(V) to Pu(VII) by Adding an Electron to PuO 4

DOE PAGES

Gibson, John K.; de Jong, Wibe A.; Dau, Phuong D.; ...

2017-11-14

The highest known actinide oxidation states are Np(VII) and Pu(VII), both of which have been identified in solution and solid compounds. Recently a molecular Np(VII) complex, NpO 3(NO 3) 2-, was prepared and characterized in the gas phase. In accord with the lower stability of heptavalent Pu, no Pu(VII) molecular species has been identified. Reported here are the gas-phase syntheses and characterizations of NpO 4 - and PuO 4 -. Reactivity studies and density functional theory computations indicate the heptavalent metal oxidation state in both. This is the first instance of Pu(VII) in the absence of stabilizing effects due tomore » condensed phase solvation or crystal fields. Here, the results indicate that addition of an electron to neutral PuO 4, which has a computed electron affinity of 2.56 eV, counterintuitively results in oxidation of Pu(V) to Pu(VII), concomitant with superoxide reduction.« less

Heptavalent Actinide Tetroxides NpO 4 – and PuO 4 –: Oxidation of Pu(V) to Pu(VII) by Adding an Electron to PuO 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gibson, John K.; de Jong, Wibe A.; Dau, Phuong D.

The highest known actinide oxidation states are Np(VII) and Pu(VII), both of which have been identified in solution and solid compounds. Recently a molecular Np(VII) complex, NpO 3(NO 3) 2-, was prepared and characterized in the gas phase. In accord with the lower stability of heptavalent Pu, no Pu(VII) molecular species has been identified. Reported here are the gas-phase syntheses and characterizations of NpO 4 - and PuO 4 -. Reactivity studies and density functional theory computations indicate the heptavalent metal oxidation state in both. This is the first instance of Pu(VII) in the absence of stabilizing effects due tomore » condensed phase solvation or crystal fields. Here, the results indicate that addition of an electron to neutral PuO 4, which has a computed electron affinity of 2.56 eV, counterintuitively results in oxidation of Pu(V) to Pu(VII), concomitant with superoxide reduction.« less

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.

CHARACTERIZATION OF ACTINIDES IN SIMULATED ALKALINE TANK WASTE SLUDGES AND LEACHATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nash, Kenneth L.

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 actinidesmore » 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.« less

Coordination Chemistry of a Strongly-Donating Hydroxylamine with Early Actinides: An Investigation of Redox Properties and Electronic Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

McSkimming, Alex; Su, Jing; Cheisson, Thibault

Separations of f-block elements are a critical aspect of nuclear waste processing. Redox-based separations offer promise, but challenges remain in stabilizing and differentiating actinides in high oxidation states. The investigation of new ligand types that provide thermodynamic stabilization to high-valent actinides is essential for expanding their fundamental chemistry and to elaborate new separation techniques and storage methods. We report herein the preparation and characterization of Th and U complexes of the pyridyl-hydroxylamine ligand, N-tert-butyl-N-(pyridin-2-yl)hydroxylamine (pyNO–). Electrochemical studies performed on the homoleptic complexes [M(pyNO) 4] (M = Th, U) revealed significant stabilization of the U complex upon one-electron oxidation. The saltmore » [U(pyNO) 4] + was isolated by chemical oxidation of [U(pyNO) 4]; spectroscopic and computational data support assignment as a U V cation.« less

Coordination Chemistry of a Strongly-Donating Hydroxylamine with Early Actinides: An Investigation of Redox Properties and Electronic Structure

DOE PAGES

McSkimming, Alex; Su, Jing; Cheisson, Thibault; ...

2018-03-23

Separations of f-block elements are a critical aspect of nuclear waste processing. Redox-based separations offer promise, but challenges remain in stabilizing and differentiating actinides in high oxidation states. The investigation of new ligand types that provide thermodynamic stabilization to high-valent actinides is essential for expanding their fundamental chemistry and to elaborate new separation techniques and storage methods. We report herein the preparation and characterization of Th and U complexes of the pyridyl-hydroxylamine ligand, N-tert-butyl-N-(pyridin-2-yl)hydroxylamine (pyNO–). Electrochemical studies performed on the homoleptic complexes [M(pyNO) 4] (M = Th, U) revealed significant stabilization of the U complex upon one-electron oxidation. The saltmore » [U(pyNO) 4] + was isolated by chemical oxidation of [U(pyNO) 4]; spectroscopic and computational data support assignment as a U V cation.« less

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.

Actinide Solubility and Speciation in the WIPP [PowerPoint

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 repositorymore » 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.« less

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.

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 onmore » 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.« less

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.

JOWOG 22/2 - Actinide Chemical Technology (July 9-13, 2012)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, Jay M.; Lopez, Jacquelyn C.; Wayne, David 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 amore » 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.« less

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.

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.

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.

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.

The separation of lanthanides and actinides in supercritical fluid carbon dioxide

DOE PAGES

Mincher, Bruce J.; Wai, Chien M.; Fox, Robert V.; ...

2015-10-28

Supercritical fluid carbon dioxide presents an attractive alternative to conventional solvents for recovery of the actinides and lanthanides. Carbon dioxide is a good solvent for fluorine and phosphate-containing ligands, including the traditional tributylphosphate ligand used in process-scale uranium separations. Actinide and lanthanide oxides may even be directly dissolved in carbon dioxide containing the complexes formed between these ligands and mineral acids, obviating the need for large volumes of acids for leaching and dissolution, and the corresponding organic liquid–liquid solvent extraction solutions. As a result, examples of the application of this novel technology for actinide and lanthanide separations are presented.

Chelation and stabilization of berkelium in oxidation state +IV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deblonde, Gauthier J. -P.; Sturzbecher-Hoehne, Manuel; Rupert, Peter B.

Berkelium (Bk) has been predicted to be the only transplutonium element able to exhibit both +III and +IV oxidation states in solution, but evidence of a stable oxidized Bk chelate has so far remained elusive. Here, in this work, we describe the stabilization of the heaviest 4+ ion of the periodic table, under mild aqueous conditions, using a siderophore derivative. The resulting Bk(IV) complex exhibits luminescence via sensitization through an intramolecular antenna effect. This neutral Bk(IV) coordination compound is not sequestered by the protein siderocalin - a mammalian metal transporter - in contrast to the negatively charged species obtained withmore » neighbouring trivalent actinides americium, curium and californium (Cf). The corresponding Cf(III)-ligand-protein ternary adduct was characterized by X-ray diffraction analysis. Finally, combined with theoretical predictions, these data add significant insight to the field of transplutonium chemistry, and may lead to innovative Bk separation and purification processes.« less

Chelation and stabilization of berkelium in oxidation state +IV

DOE PAGES

Deblonde, Gauthier J. -P.; Sturzbecher-Hoehne, Manuel; Rupert, Peter B.; ...

2017-04-10

Berkelium (Bk) has been predicted to be the only transplutonium element able to exhibit both +III and +IV oxidation states in solution, but evidence of a stable oxidized Bk chelate has so far remained elusive. Here, in this work, we describe the stabilization of the heaviest 4+ ion of the periodic table, under mild aqueous conditions, using a siderophore derivative. The resulting Bk(IV) complex exhibits luminescence via sensitization through an intramolecular antenna effect. This neutral Bk(IV) coordination compound is not sequestered by the protein siderocalin - a mammalian metal transporter - in contrast to the negatively charged species obtained withmore » neighbouring trivalent actinides americium, curium and californium (Cf). The corresponding Cf(III)-ligand-protein ternary adduct was characterized by X-ray diffraction analysis. Finally, combined with theoretical predictions, these data add significant insight to the field of transplutonium chemistry, and may lead to innovative Bk separation and purification processes.« less

Crystal growth methods dedicated to low solubility actinide oxalates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamain, C., E-mail: christelle.tamain@cea.fr; Arab-Chapelet, B.; Rivenet, M.

Two novel crystal growth syntheses dedicated to low solubility actinide-oxalate systems and adapted to glove box handling are described. These methods based on the use of precursors of either actinide metal or oxalic acid have been optimized on lanthanide systems (analogue of actinides(III)) and then assessed on real actinide systems. They allow the synthesis of several actinide oxalate single crystals, Am{sub 2}(C{sub 2}O{sub 4}){sub 3}(H{sub 2}O){sub 3}·xH{sub 2}O, Th(C{sub 2}O{sub 4}){sub 2}·6H{sub 2}O, M{sub 2+x}[Pu{sup IV}{sub 2−x}Pu{sup III}{sub x}(C{sub 2}O{sub 4}){sub 5}]·nH{sub 2}O and M{sub 1−x}[Pu{sup III}{sub 1−x}Pu{sup IV}{sub x}(C{sub 2}O{sub 4}){sub 2}·H{sub 2}O]·nH{sub 2}O. It is the first timemore » that these well-known compounds are formed by crystal growth methods, thus enabling direct structural studies on transuranic element systems and acquisition of basic data beyond deductions from isomorphic (or not) lanthanide compounds. Characterizations by X-ray diffraction, UV–visible solid spectroscopy, demonstrate the potentialities of these two crystal growth methods to obtain oxalate compounds. - Graphical abstract: Two new single crystal growth methods dedicated to actinide oxalate compounds. - Highlights: • Use of diester as oxalate precursor for crystal growth of actinide oxalates. • Use of actinide oxide as precursor for crystal growth of actinide oxalates. • Crystal growth of Pu(III) and Am(III) oxalates. • Crystal growth of mixed Pu(III)/Pu(IV) oxalates.« less

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).

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).

Study on the leaching behavior of actinides from nuclear fuel debris

NASA Astrophysics Data System (ADS)

Kirishima, Akira; Hirano, Masahiko; Akiyama, Daisuke; Sasaki, Takayuki; Sato, Nobuaki

2018-04-01

For the prediction of the leaching behavior of actinides contained in the nuclear fuel debris generated by the Fukushima Daiichi nuclear power plant accident in Japan, simulated fuel debris consisting of a UO2-ZrO2 solid solution doped with 137Cs, 237Np, 236Pu, and 241Am tracers was synthesized and investigated. The synthesis of the debris was carried out by heat treatment at 1200 °C at different oxygen partial pressures, and the samples were subsequently used for leaching tests with Milli-Q water and seawater. The results of the leaching tests indicate that the leaching of actinides depends on the redox conditions under which the debris was generated; for example, debris generated under oxidative conditions releases more actinide nuclides to water than that generated under reductive conditions. Furthermore, we found that, as Zr(IV) increasingly substituted U(IV) in the fluorite crystal structure of the debris, the actinide leaching from the debris decreased. In addition, we found that seawater leached more actinides from the debris than pure water, which seems to be caused by the complexation of actinides by carbonate ions in seawater.

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.

Room temperature electrodeposition of actinides from ionic solutions

DOEpatents

Hatchett, David W.; Czerwinski, Kenneth R.; Droessler, Janelle; Kinyanjui, John

2017-04-25

Uranic and transuranic metals and metal oxides are first dissolved in ozone compositions. The resulting solution in ozone can be further dissolved in ionic liquids to form a second solution. The metals in the second solution are then electrochemically deposited from the second solutions as room temperature ionic liquid (RTIL), tri-methyl-n-butyl ammonium n-bis(trifluoromethansulfonylimide) [Me.sub.3N.sup.nBu][TFSI] providing an alternative non-aqueous system for the extraction and reclamation of actinides from reprocessed fuel materials. Deposition of U metal is achieved using TFSI complexes of U(III) and U(IV) containing the anion common to the RTIL. TFSI complexes of uranium were produced to ensure solubility of the species in the ionic liquid. The methods provide a first measure of the thermodynamic properties of U metal deposition using Uranium complexes with different oxidation states from RTIL solution at room temperature.

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.

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 metalmore » 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.« less

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Aaron T.; Nash, Kenneth L.

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 HNO 3 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 amore » 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).« less

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

DOE PAGES

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 HNO 3 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 amore » 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).« less

Hydrothermal Synthesis and Crystal Structures of Actinide Compounds

NASA Astrophysics Data System (ADS)

Runde, Wolfgang; Neu, Mary P.

Since the 1950s actinides have been used to benefit industry, science, health, and national security. The largest industrial application, electricity generation from uranium and thorium fuels, is growing worldwide. Thus, more actinides are being mined, produced, used and processed than ever before. The future of nuclear energy hinges on how these increasing amounts of actinides are contained in each stage of the fuel cycle, including disposition. In addition, uranium and plutonium were built up during the Cold War between the United States and the Former Soviet Union for defense purposes and nuclear energy. These stockpiles have been significantly reduced in the last decade.

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

DOEpatents

Lupinetti, Anthony J [Los Alamos, NM; Garcia, Eduardo [Los Alamos, NM; Abney, Kent D [Los Alamos, NM

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.

Actinide Sputtering Induced by Fission with Ultra-cold Neutrons

NASA Astrophysics Data System (ADS)

Venuti, Michael; Shi, Tan; Fellers, Deion; Morris, Christopher; Makela, Mark

2017-09-01

Understanding the effects of actinide sputtering due to nuclear fission is important for a wide range of applications, including nuclear fuel storage, 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. By controlling the energy of UCN, it is possible to induce fission at the sample surface within a well-defined depth. It is therefore an ideal tool for studying the effects of fission-induced sputtering as a function of interaction depth. Since the mechanism for fission-induced surface damage is not well understood, especially for samples with a surface oxide layer, this work has the potential to separate the various damage mechanisms proposed in previous works. During the irradiation with UCN, fission events are monitored by coincidence counting between prompt gamma rays using NaI detectors. Alpha spectroscopy of the ejected actinide material is performed in a custom-built ionization chamber to determine the amount of sputtered material. Actinide samples with various sample properties and surface conditions are irradiated and analyzed. In this presentation, we will discuss our experimental setup and present the preliminary results.

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)

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.

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.

Pocket formula for nuclear deformations of actinides

NASA Astrophysics Data System (ADS)

Manjunatha, H. C.; Sridhar, K. N.

2018-06-01

We have formulated a pocket formula for quadrupole (β2), octupole (β3), hexadecapole (β4) and hexacontatetrapole (β6) deformation of the nuclear ground state of all isotopes of actinide nuclei (89 < Z < 103). This formula is first of its kind and produces a nuclear deformation of all isotopes actinide nuclei 89 < Z < 103 with simple inputs of Z and A. Hence, this formula is useful in the fields of nuclear physics to study the structure and interaction of nuclei.

Thermodynamic constants for actinide oxides and oxyhydroxides relevant to actinide volatility calculations for thermal oxidation processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebbinghaus, B.B.; Krikorian, O.H.

The purpose of this report is to provide input of thermodynamic data on actinide volatilities to EERC for use in their computer code for modeling of metal volatilities in incinerators. It is also anticipated that the data may be documented later in an EPA sponsored ``Metals Bible.`` It should be noted that only upper limits for the volatility of PuO{sub 2}(s) due to PuO{sub 3}(g) and PuO{sub 2}(OH){sub 2}(g) and the volatility of AmO{sub 2} in PuO{sub 2}(s) due to AmO{sub 3}(g) and AmO{sub 2}(OH){sub 2}(g) could be set. The data on the americium vapor species are intended for calculationsmore » where AmO{sub 2} is present as a solid solution in PuO{sub 2}(s).« less

Theory of Photoemission in Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Svane, Axel

2008-07-01

A theory is presented which describes the photoemission spectra of actinide compounds starting from the atomic limit of isolated actinide ions. The multiplets of the ion are calculated and an additional term is introduced to describe the interaction with the sea of conduction electrons. This leads to complex mixed-valent ground states, which describes well the rich spectrum observed for PuSe. In particular, the three-peak feature, which is often seen in Pu and Pu compounds in the vicinity of the Fermi level originates from f{sup 6} {yields} f{sup 5} emission. The theory is further applied to PuSb, PuCoGa{sub 5} and Am.more » (author)« less

Protactinium and the intersection of actinide and transition metal chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, Richard E.; De Sio, Stephanie; Vallet, Valérie

The role of the 5f and 6d orbitals in the chemistry of the actinide elements has been of considerable interest since their discovery and synthesis. Relativistic effects cause the energetics of the 5f and 6d orbitals to change as the actinide series is traversed left to right imparting a rich and complex chemistry. The 5f and 6d atomic states cross in energy at protactinium (Pa), making it a potential intersection between transition metal and actinide chemistries. Herein, we report the synthesis of a Pa-peroxo cluster, A(6)(Pa4O(O-2)(6)F-12) [A = Rb, Cs, (CH3)(4)N], formed in pursuit of an actinide polyoxometalate. Quantum chemicalmore » calculations at the density functional theory level demonstrate equal 5f and 6d orbital participation in the chemistry of Pa and increasing 5f orbital participation for the heavier actinides. Periodic changes in orbital character to the bonding in the early actinides highlights the influence of the 5f orbitals in their reactivity and chemical structure.« less

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.

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.

Remarkably High Stability of Late Actinide Dioxide Cations: Extending Chemistry to Pentavalent Berkelium and Californium.

PubMed

Dau, Phuong D; Vasiliu, Monica; Peterson, Kirk A; Dixon, David A; Gibson, John K

2017-12-06

Actinyl chemistry is extended beyond Cm to BkO 2 + and CfO 2 + through transfer of an O atom from NO 2 to BkO + or CfO + , establishing a surprisingly high lower limit of 73 kcal mol -1 for the dissociation energies, D[O-(BkO + )] and D[O-(CfO + )]. CCSD(T) computations are in accord with the observed reactions, and characterize the newly observed dioxide ions as linear pentavalent actinyls; these being the first Bk and Cf species with oxidation states above IV. Computations of actinide dioxide cations AnO 2 + for An=Pa to Lr reveal an unexpected minimum for D[O-(CmO + )]. For CmO 2 + , and AnO 2 + beyond EsO 2 + , the most stable structure has side-on bonded η 2 -(O 2 ), as An III peroxides for An=Cm and Lr, and as An II superoxides for An=Fm, Md, and No. It is predicted that the most stable structure of EsO 2 + is linear [O=Es V =O] + , einsteinyl, and that FmO 2 + and MdO 2 + , like CmO 2 + , also have actinyl(V) structures as local energy minima. The results expand actinide oxidation state chemistry, the realm of the distinctive actinyl moiety, and the non-periodic character towards the end of the periodic table. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

DISTRIBUTION OF ACTINIDES BETWEEN THE AQUEOUS AND ORGANIC PHASES IN THE TALSPEAK PROCESS

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 amore » 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

Evaluation of actinide biosorption by microorganisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 maymore » 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.« less

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.

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.

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.

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

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghumman, S. S.

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.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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 f0 actinyl series (UO22+, NpO23+, PuO24+), the isoelectronic NUN, and thorium (ThO, ThO2+) and nobelium (NoO, NoO2) oxides are studied.

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.

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.

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.

Electronic Structure of Actinides under Pressure

NASA Astrophysics Data System (ADS)

Johansson, Borje

2006-03-01

The series of heavy radioactive elements known as the actinides all have similar elemental properties. However, when the volume per atom in the condensed phase is illustrated as a function of atomic number, perhaps the most dramatic anomaly in the periodic table becomes apparent. The atomic volume of americium is almost 50% larger than it is for the preceding element plutonium. For the element after americium, curium, the atomic volume is very close to that of americium. The same holds also for the next elements berkelium and californium. Accordingly from americium and onwards the actinides behave very similar to the corresponding rare-earth elements - a second lanthanide series of metallic elements can be identified. This view is strongly supported by the fact that all these elements adopt the dhcp structure, a structure typical for the lanthanides. The reason for this behavior is found in the behavior of the 5f electrons. For the earlier actinides, up to and including plutonium, the 5f electrons form metallic states and contribute most significantly to the bonding. In Np and Pu they even dominate the bonding, while all of a sudden they become localized in Am, very much like the 4f electrons in the lanthanide series, and contribute no longer to the cohesion. This withdrawal of 5f bonding gives rise to the large volume expansion between plutonium and americium. This difference between the light and heavy actinide suggests that it would be most worthwhile to strongly compress the transplutonium elements, thereby forcing the individual 5f electron wave functions into strong contact with each other (overlap). Recently high pressure experiments have been performed for americium and curium and dramatic crystal structure changes have been observed. These results and other high pressure data will be discussed in relation to the basic electronic structure of these elements.

Comparative Photoemission Study of Actinide (Am, Pu, Np and U) Metals, Nitrides, and Hydrides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gouder, Thomas; Seibert, Alice; Rebizant, Jean

2007-07-01

Core-level and valence-band spectra of Pu and the other early actinide compounds show remarkable systematics, which can be understood in the framework of final state screening. We compare the early actinide (U, Np, Pu and Am) metals, nitrides and hydrides and a few other specific compounds (PuSe, PuS, PuCx, PuSix) prepared as thin films by sputter deposition. In choosing these systems, we combine inherent 5f band narrowing, due to 5f orbital contraction throughout the actinide series, with variations of the chemical environment in the compounds. Goal of this work was to learn more on the electronic structure of the earlymore » actinide systems and to achieve the correct interpretation of their photoemission spectra. The highly correlated nature of the 5f states in systems, which are on the verge to localization, makes this a challenging task, because of the peculiar interplay between ground state DOS and final-state effects. Their influence can be estimated by doing systematic studies on systems with different (5f) bandwidths. We conclude on the basis of such systematic experiments that final-state effects due to strong e-e correlations in narrow 5f-band systems lead to multiplet like structures, analogous to those observed in the case of systems with localized electron states. Such observations in essentially band-like 5f-systems was first surprising, but the astonishing similarity of photoemission spectra of very different chemical systems (e.g. PuSe, Pu{sub 2}C{sub 3}..) points to a common origin, relating them to atomic features rather than material dependent density of states (DOS) features. (authors)« less

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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

2016-03-07

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.

On the Suitability of Lanthanides as Actinide Analogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szigethy, Geza; Raymond, Kenneth N.

2008-04-11

With the current level of actinide materials used in civilian power generation and the need for safe and efficient methods for the chemical separation of these species from their daughter products and for long-term storage requirements, a detailed understanding of actinide chemistry is of great importance. Due to the unique bonding properties of the f-elements, the lanthanides are commonly used as structural and chemical models for the actinides, but differences in the bonding between these 4f and 5f elements has become a question of immediate applicability to separations technology. This brief overview of actinide coordination chemistry in the Raymond groupmore » at UC Berkeley/LBNL examines the validity of using lanthanide analogs as structural models for the actinides, with particular attention paid to single crystal X-ray diffraction structures. Although lanthanides are commonly accepted as reasonable analogs for the actinides, these comparisons suggest the careful study of actinide materials independent of their lanthanide analogs to be of utmost importance to present and future efforts in nuclear industries.« less

On the suitability of lanthanides as actinide analogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raymond, Kenneth; Szigethy, Geza

2008-07-01

With the current level of actinide materials used in civilian power generation and the need for safe and efficient methods for the chemical separation of these species from their daughter products and for long-term storage requirements, a detailed understanding of actinide chemistry is of great importance. Due to the unique bonding properties of the f-elements, the lanthanides are commonly used as structural and chemical models for the actinides, but differences in the bonding between these 4f and 5f elements has become a question of immediate applicability to separations technology. This brief overview of actinide coordination chemistry in the Raymond groupmore » at UC Berkeley/LBNL examines the validity of using lanthanide analogs as structural models for the actinides, with particular attention paid to single crystal X-ray diffraction structures. Although lanthanides are commonly accepted as reasonable analogs for the actinides, these comparisons suggest the careful study of actinide materials independent of their lanthanide analogs to be of utmost importance to present and future efforts in nuclear industries. (authors)« less

Chemical bonds and vibrational properties of ordered (U, Np, Pu) mixed oxides

NASA Astrophysics Data System (ADS)

Yang, Yu; Zhang, Ping

2013-01-01

We use density functional theory +U to investigate the chemical bonding characters and vibrational properties of the ordered (U, Np, Pu) mixed oxides (MOXs), UNpO4,NpPuO4, and UPuO4. It is found that the 5f electronic states of different actinide elements keep their localized characters in all three MOXs. The occupied 5f electronic states of different actinide elements do not overlap with each other and tend to distribute over the energy band gap of the other actinide element's 5f states. As a result, the three ordered MOXs all show smaller band gaps than those of the component dioxides, with values of 0.91, 1.47, and 0.19 eV for UNpO4,NpPuO4, and UPuO4, respectively. Through careful charge density analysis, we further show that the U-O and Pu-O bonds in MOXs show more ionic character than in UO2 and PuO2, while the Np-O bonds show more covalent character than in NpO2. The change in covalencies in the chemical bonds leads to vibrational frequencies of oxygen atoms that are different in MOXs.

Ground-state configurations and theoretical soft-x-ray emission of highly charged actinide ions

NASA Astrophysics Data System (ADS)

Sheil, J.; Kilbane, D.; O'Sullivan, G.; Liu, L.; Suzuki, C.

2017-12-01

It is well known that the lanthanide and actinide elements are formed by the filling of 4 f and 5 f subshells which occurs after the filling of 5 d and 6 d subshells, respectively, has begun. With increasing ionization one expects the energy levels to eventually regroup to their hydrogenic ordering, i.e., in terms of principal quantum number. In the lanthanides, the 4 f electron binding energy overtakes that of 5 p near the 6th or 7th ion stage and 5 s near the 14th or 15th ion stage, leading to dramatic rearrangements of ground-state configurations. In this paper we report on the results of a study to explore the effects of increasing ionization on the ground-state configurations of actinide ions as a result of 5 f and 6 p or 6 s level crossings. It is seen that the effects generally occur later and are more strongly influenced by spin-orbit splitting than in the lanthanides. The near degeneracies of 5 f and 6 l energies in these stages lead to configuration interaction (CI) amongst configurations with variable numbers of 5 f and 6 p electrons. The effects of CI on the level complexity are explored for ions along the Rn I sequence and are found to lead to the formation of "compound states" as predicted for the lanthanides. The extreme ultraviolet and soft x-ray spectra of medium and highly charged lanthanides are dominated by emission from unresolved transition arrays (UTAs) of the type Δ n =0 , 4 p64 dN +1-4 p54 dN +2+4 p64 dN4 f , which, in general, overlap in adjacent ion stages of a particular element. Here, the corresponding Δ n =0 , 5 p65 dN +1-5 p55 dN +2+5 p65 dN5 f UTAs have been studied theoretically with the aid of Hartree-Fock with configuration interaction calculations. As well as predicting the wavelengths and spectral details of the anticipated features, the calculations show that the effects of configuration interaction are quite different for the two different families of Δ n =0 transitions and, once more, spin-orbit interactions play a major

Actinide bioimaging in tissues: Comparison of emulsion and solid track autoradiography techniques with the iQID camera

PubMed Central

Miller, Brian W.; Van der Meeren, Anne; Tazrart, Anissa; Angulo, Jaime F.; Griffiths, Nina M.

2017-01-01

This work presents a comparison of three autoradiography techniques for imaging biological samples contaminated with actinides: emulsion-based, plastic-based autoradiography and a quantitative digital technique, the iQID camera, based on the numerical analysis of light from a scintillator screen. In radiation toxicology it has been important to develop means of imaging actinide distribution in tissues as these radionuclides may be heterogeneously distributed within and between tissues after internal contamination. Actinide distribution determines which cells are exposed to alpha radiation and is thus potentially critical for assessing absorbed dose. The comparison was carried out by generating autoradiographs of the same biological samples contaminated with actinides with the three autoradiography techniques. These samples were cell preparations or tissue sections collected from animals contaminated with different physico-chemical forms of actinides. The autoradiograph characteristics and the performances of the techniques were evaluated and discussed mainly in terms of acquisition process, activity distribution patterns, spatial resolution and feasibility of activity quantification. The obtained autoradiographs presented similar actinide distribution at low magnification. Out of the three techniques, emulsion autoradiography is the only one to provide a highly-resolved image of the actinide distribution inherently superimposed on the biological sample. Emulsion autoradiography is hence best interpreted at higher magnifications. However, this technique is destructive for the biological sample. Both emulsion- and plastic-based autoradiography record alpha tracks and thus enabled the differentiation between ionized forms of actinides and oxide particles. This feature can help in the evaluation of decorporation therapy efficacy. The most recent technique, the iQID camera, presents several additional features: real-time imaging, separate imaging of alpha particles and

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

Gas core reactors for actinide transmutation. [uranium hexafluoride

NASA Technical Reports Server (NTRS)

Clement, J. D.; Rust, J. H.; Wan, P. T.; Chow, S.

1979-01-01

The preliminary design of a uranium hexafluoride actinide transmutation reactor to convert long-lived actinide wastes to shorter-lived fission product wastes was analyzed. It is shown that externally moderated gas core reactors are ideal radiators. They provide an abundant supply of thermal neutrons and are insensitive to composition changes in the blanket. For the present reactor, an initial load of 6 metric tons of actinides is loaded. This is equivalent to the quantity produced by 300 LWR-years of operation. At the beginning, the core produces 2000 MWt while the blanket generates only 239 MWt. After four years of irradiation, the actinide mass is reduced to 3.9 metric tonnes. During this time, the blanket is becoming more fissile and its power rapidly approaches 1600 MWt. At the end of four years, continuous refueling of actinides is carried out and the actinide mass is held constant. Equilibrium is essentially achieved at the end of eight years. At equilibrium, the core is producing 1400 MWt and the blanket 1600 MWt. At this power level, the actinide destruction rate is equal to the production rate from 32 LWRs.

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.

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.

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)

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

Rapid determination of actinides in seawater samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, Sherrod L.; Culligan, Brian K.; Hutchison, Jay B.

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 usedmore » 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.« less

Separation of actinides from lanthanides utilizing molten salt electrorefining

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grimmett, D.L.; Fusselman, S.P.; Roy, J.J.

1996-10-01

TRUMP-S (TRansUranic Management through Pyropartitioning Separation) is a pyrochemical process being developed to separate actinides form fission products in nuclear waste. A key process step involving molten salt electrorefining to separate actinides from lanthanides has been studied on a laboratory scale. Electrorefining of U, Np, Pu, Am, and lanthanide mixtures from molten cadmium at 450 C to a solid cathode utilizing a molten chloride electrolyte resulted in > 99% removal of actinides from the molten cadmium and salt phases. Removal of the last few percent of actinides is accompanied by lowered cathodic current efficiency and some lanthanide codeposition. Actinide/lanthanide separationmore » ratios on the cathode are ordered U > Np > Pu > Am and are consistent with predictions based on equilibrium potentials.« less

Prompt fission neutron spectra of actinides

DOE PAGES

Capote, R.; Chen, Y. -J.; Hambsch, F. -J.; ...

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.

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.

Single crystal structures and theoretical calculations of uranium endohedral metallofullerenes (U@C2n , 2n = 74, 82) show cage isomer dependent oxidation states for U.

PubMed

Cai, Wenting; Morales-Martínez, Roser; Zhang, Xingxing; Najera, Daniel; Romero, Elkin L; Metta-Magaña, Alejandro; Rodríguez-Fortea, Antonio; Fortier, Skye; Chen, Ning; Poblet, Josep M; Echegoyen, Luis

2017-08-01

Charge transfer is a general phenomenon observed for all endohedral mono-metallofullerenes. Since the detection of the first endohedral metallofullerene (EMF), La@C 82 , in 1991, it has always been observed that the oxidation state of a given encapsulated metal is always the same, regardless of the cage size. No crystallographic data exist for any early actinide endohedrals and little is known about the oxidation states for the few compounds that have been reported. Here we report the X-ray structures of three uranium metallofullerenes, U@ D 3h -C 74 , U@ C 2 (5)-C 82 and U@ C 2v (9)-C 82 , and provide theoretical evidence for cage isomer dependent charge transfer states for U. Results from DFT calculations show that U@ D 3h -C 74 and U@ C 2 (5)-C 82 have tetravalent electronic configurations corresponding to U 4+ @ D 3h -C 74 4- and U 4+ @ C 2 (5)-C 82 4- . Surprisingly, the isomeric U@ C 2v (9)-C 82 has a trivalent electronic configuration corresponding to U 3+ @ C 2v (9)-C 82 3- . These are the first X-ray crystallographic structures of uranium EMFs and this is first observation of metal oxidation state dependence on carbon cage isomerism for mono-EMFs.

Fusion barrier characteristics of actinides

NASA Astrophysics Data System (ADS)

Manjunatha, H. C.; Sridhar, K. N.

2018-03-01

We have studied fusion barrier characteristics of actinide compound nuclei with atomic number range 89 ≤ Z ≤ 103 for all projectile target combinations. After the calculation of fusion barrier heights and positions, we have searched for their parameterization. We have achieved the empirical formula for fusion barrier heights (VB), positions (RB), curvature of the inverted parabola (ħω) of actinide compound nuclei with atomic number range 89 ≤ Z ≤ 103 for all projectile target combinations (6 actinides with the simple inputs of mass number (A) and atomic number (Z) of projectile-targets.

Standard Materials for Microbeam Analysis of Lanthanides and Actinides

NASA Astrophysics Data System (ADS)

Ellis, I.; Gorton, M.; Rucklidge, J. C.

2010-12-01

redox conditions that favour Ce+3, Th+4, and U+4 instead of higher oxidation states. The absence of any cations other than those deliberately added permits positive control of cation mixtures in starting materials. The synthetic pathway—condensation of POx units--provides ideal conditions for the homogeneous distribution of cations including those with different charges. We present the results of synthesis, elemental analysis and imaging by XRF and SEM-EDX for mixed lanthanide-actinide phosphate materials.

Analysis of large soil samples for actinides

DOEpatents

Maxwell, III; Sherrod, L [Aiken, SC

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.

Abundance of live 244Pu in deep-sea reservoirs on Earth points to rarity of actinide nucleosynthesis

PubMed Central

Wallner, A.; Faestermann, T.; Feige, J.; Feldstein, C.; Knie, K.; Korschinek, G.; Kutschera, W.; Ofan, A.; Paul, M.; Quinto, F.; Rugel, G.; Steier, P.

2015-01-01

Half of the heavy elements including all actinides are produced in r-process nucleosynthesis, whose sites and history remain a mystery. If continuously produced, the Interstellar Medium is expected to build-up a quasi-steady state of abundances of short-lived nuclides (with half-lives ≤100 My), including actinides produced in r-process nucleosynthesis. Their existence in today’s interstellar medium would serve as a radioactive clock and would establish that their production was recent. In particular 244Pu, a radioactive actinide nuclide (half-life=81 My), can place strong constraints on recent r-process frequency and production yield. Here we report the detection of live interstellar 244Pu, archived in Earth’s deep-sea floor during the last 25 My, at abundances lower than expected from continuous production in the Galaxy by about 2 orders of magnitude. This large discrepancy may signal a rarity of actinide r-process nucleosynthesis sites, compatible with neutron-star mergers or with a small subset of actinide-producing supernovae. PMID:25601158

Trivalent Actinide Uptake by Iron (Hydr)oxides.

PubMed

Finck, Nicolas; Nedel, Sorin; Dideriksen, Knud; Schlegel, Michel L

2016-10-04

The retention of Am(III) by coprecipitation with or adsorption onto preformed magnetite was investigated by X-ray diffraction (XRD), solution chemistry, and X-ray absorption spectroscopy (XAS). In the coprecipitation experiment, XAS data indicated the presence of seven O atoms at 2.44(1) Å, and can be explained by an Am incorporation at Fe structural sites at the magnetite surface. Next-nearest Fe were detected at distances suggesting that Am and Fe polyhedra share corners in geometries ranging from bent to close to linear Am-O-Fe bonds. After aging for two years, the coordination number and the distance to the first O shell significantly decreased, and atomic shells were detected at higher distances. These data suggest a structural reorganization and an increase in structural order around sorbed Am. Upon contact with preformed Fe 3 O 4 , Am(III) forms surface complexes with cosorbed Fe at the surface of magnetite, a possible consequence of the high concentration of dissolved Fe. In a separate experiment, chloride green rust (GR) was synthesized in the presence of Am(III), and subsequently converted to Fe(OH) 2 (s) intermixed with magnetite. XAS data indicated that the actinide is successively located first at octahedral brucite-like sites in the GR precursor, then in Fe(OH) 2 (s), an environment markedly distinct from that of Am(III) in Fe 3 O 4 . The findings indicate that the magnetite formation pathway dictates the magnitude of Am(III) incorporation within this solid.

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.

Impact of minor actinide recycling on sustainable fuel cycle options

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heidet, F.; Kim, T. K.; Taiwo, T. A.

The recent Evaluation and Screening study chartered by the U.S. Department of Energy, Office of Nuclear Energy, has identified four fuel cycle options as being the most promising. Among these four options, the two single-stage fuel cycles rely on a fast reactor and are differing in the fact that in one case only uranium and plutonium are recycled while in the other case minor actinides are also recycled. The two other fuel cycles are two-stage and rely on both fast and thermal reactors. They also differ in the fact that in one case only uranium and plutonium are recycled whilemore » in the other case minor actinides are also recycled. The current study assesses the impact of recycling minor actinides on the reactor core design, its performance characteristics, and the characteristics of the recycled material and waste material. The recycling of minor actinides is found not to affect the reactor core performance, as long as the same cycle length, core layout and specific power are being used. One notable difference is that the required transuranics (TRU) content is slightly increased when minor actinides are recycled. The mass flows are mostly unchanged given a same specific power and cycle length. Although the material mass flows and reactor performance characteristics are hardly affected by recycling minor actinides, some differences are observed in the waste characteristics between the two fuel cycles considered. The absence of minor actinides in the waste results in a different buildup of decay products, and in somewhat different behaviors depending on the characteristic and time frame considered. Recycling of minor actinides is found to result in a reduction of the waste characteristics ranging from 10% to 90%. These results are consistent with previous studies in this domain and depending on the time frame considered, packaging conditions, repository site, repository strategy, the differences observed in the waste characteristics could be beneficial and help

Phytosiderophore effects on subsurface actinide contaminants: potential for phytostabilization and phytoextraction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruggiero, C. E.; Twary, S. N.; Deladurantaye, E.

2003-01-01

In recognition of the need for a safe, effective technology for long term Pu/Th/Actinide stabilization or removal from soils, we have begun an investigation of the potential for phytoremediation (phytostabilization and/or phytoextraction) of Pu and other actinide soil contaminants at DOE sites using phytosiderophore producing plants, and are investigating the contribution of phytosiderophores to actinide mobility in the subsurface environment. Phytoremediation and Phytostabilization have been proven to be a cost-effective, safe, efficient, and publicly acceptable technology for clean up and/or stabilization of contaminant metals . However, no phyto-based technologies have been developed for stabilization or removal of plutonium from soilsmore » and groundwater, and very few have been investigated for other actinides . Current metal-phytostabilization and phytoremediation techniques, predominately based around lead, nickel, and other soft-metal phytoextraction, will almost certainly be inadequate for plutonium due its distinct chemical properties . Phytosiderophore-based phytoremediation may provide technically and financially practical methods for remediation and long-term stewardship of soils that have low to moderate, near surface actinide contamination . We plan to demonstrate potential benefits of phytosiderophore-producing plants for long-term actinide contaminant stabilization by the plant's prevention of soil erosion and actinide migration through hydraulic control and/or through actinide removal through phytoextraction . We may also show possible harm caused by these plants through increased presence of actinide chelators that could increase actinide mobilization and migration in the subsurface environment. This information can then be directly applied by either removal of harmful plants, or be used to develop plant-based soil stabilization/remediation technologies .« less

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.

Covalent bonding in heavy metal oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagus, Paul S.; Nelin, Connie J.; Hrovat, Dave A.

Novel theoretical methods were used to quantify the magnitude and the energetic contributions of 4f/5f-O2p and 5d/6d-O2p interactions to covalent bonding in lanthanide and actinide oxides. Although many analyses have neglected the involvement of the frontier d orbitals, the present study shows that f and d covalency are of comparable importance. Two trends are identified. As is expected, the covalent mixing is larger when the nominal oxidation state is higher. More subtly, the importance of the nf covalent mixing decreases sharply relative to (n+1)d as the nf occupation increases. Atomic properties of the metal cations that drive these trends aremore » identified.« less

Rapid determination of actinides in asphalt samples

DOE PAGES

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

The chemical state of defective uranium-plutonium oxide fuel pins irradiated in sodium cooled reactors

NASA Astrophysics Data System (ADS)

Kleykamp, H.

1997-09-01

Steady-state irradiation experiments were conducted in the sodium loop of the Siloe reactor on artificially failed mixed oxide pins that had been pre-irradiated in fast reactors up to 11.5% burnup. The formation of the predominant reaction product Na 3(U,Pu)O 4 starts on the fuel surface and is terminated when a lower O/(U + Pu) threshold of the fuel is attained. The axial extent of the reaction product depends on the size of the initial cladding defect. The occurrence of secondary cracks is possible. Na(U,Pu)O 3 forms at higher fuel temperatures. The existence of Na 3U 1- xPu xO 4 is shown in pre-irradiated blanket pins after artificial defect formation. Caesium in the oxocompounds is reduced to the metallic state and is dissolved in the coolant. Evidence of a very low chemical potential of oxygen in defective fuel pins is sustained by the occurrence of actinide-platinum metal phases formed by coupled reduction of hypostoichiometric fuel with ɛ-(Mo,Tc,Ru,Rh,Pd) precipitates. Continued operation of defective pins is not hazardous by easy precautions.

Enhancing the actinide sciences in Europe through hot laboratories networking and pooling: from ACTINET to TALISMAN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourg, S.; Poinssot, C.

2013-07-01

Since 2004, Europe supports the strengthening of the European actinides sciences scientific community through the funding of dedicated networks: (i) from 2004 to 2008, the ACTINET6 network of excellence (6. Framework Programme) gathered major laboratories involved in nuclear research and a wide range of academic research organisations and universities with the specific aims of funding and implementing joint research projects to be performed within the network of pooled facilities; (ii) from 2009 to 2013, the ACTINET-I3 integrated infrastructure initiative (I3) supports the cost of access of any academics in the pooled EU hot laboratories. In this continuation, TALISMAN (Trans-national Accessmore » to Large Infrastructures for a Safe Management of Actinides) gathers now the main European hot laboratories in actinides sciences in order to promote their opening to academics and universities and strengthen the EU-skills in actinides sciences. Furthermore, a specific focus is set on the development of advanced cutting-edge experimental and spectroscopic capabilities, the combination of state-of-the art experimental with theoretical first-principle methods on a quantum mechanical level and to benefit from the synergy between the different scientific and technical communities. ACTINET-I3 and TALISMAN attach a great importance and promote the Education and Training of the young generation of actinides scientists in the Trans-national access but also by organizing Schools (general Summer Schools or Theoretical User Lab Schools) or by granting students to attend International Conference on actinide sciences. (authors)« less

Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal–Organic Frameworks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolgopolova, Ekaterina A.; Ejegbavwo, Otega A.; Martin, Corey R.

Growing necessity for efficient nuclear waste management is a driving force for development of alternative architectures towards fundamental understanding of mechanisms involved in actinide integration inside extended structures. In this manuscript, metal-organic frameworks (MOFs) were investigated as a model system for engineering radionuclide containing materials through utilization of unprecedented MOF modularity, which cannot be replicated in any other type of materials. Through the implementation of recent synthetic advances in the MOF field, hierarchical complexity of An-materials were built stepwise, which was only feasible due to preparation of the first examples of actinide-based frameworks with “unsaturated” metal nodes. The first successfulmore » attempts of solid-state metathesis and metal node extension in An-MOFs are reported, and the results of the former approach revealed drastic differences in chemical behavior of extended structures versus molecular species. Successful utilization of MOF modularity also allowed us to structurally characterize the first example of bimetallic An-An nodes. To the best of our knowledge, through combination of solid-state metathesis, guest incorporation, and capping linker installation, we were able to achieve the highest Th wt% in mono- and bi-actinide frameworks with minimal structural density. Overall, combination of a multistep synthetic approach with homogeneous actinide distribution and moderate solvothermal conditions could make MOFs an exceptionally powerful tool to address fundamental questions responsible for chemical behavior of An-based extended structures, and therefore, shed light on possible optimization of nuclear waste administration.« less

Growth control of the oxidation state in vanadium oxide thin films

DOE PAGES

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

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

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.

A Summary of Actinide Enrichment Technologies and Capability Gaps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patton, Bradley D.; Robinson, Sharon M.

2017-01-01

The evaluation performed in this study indicates that a new program is needed to efficiently provide a national actinide radioisotope enrichment capability to produce milligram-to-gram quantities of unique materials for user communities. This program should leverage past actinide enrichment, the recent advances in stable isotope enrichment, and assessments of the future requirements to cost effectively develop this capability while establishing an experience base for a new generation of researchers in this vital area. Preliminary evaluations indicate that an electromagnetic isotope separation (EMIS) device would have the capability to meet the future needs of the user community for enriched actinides. Themore » EMIS technology could be potentially coupled with other enrichment technologies, such as irradiation, as pre-enrichment and/or post-enrichment systems to increase the throughput, reduce losses of material, and/or reduce operational costs of the base EMIS system. Past actinide enrichment experience and advances in the EMIS technology applied in stable isotope separations should be leveraged with this new evaluation information to assist in the establishment of a domestic actinide radioisotope enrichment capability.« less

Growth control of the oxidation state in vanadium oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Shinbuhm; Meyer, Tricia L.; Lee, Ho Nyung, E-mail: hnlee@ornl.gov

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 puremore » 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.« less

Actinide targets for the synthesis of super-heavy elements

DOE PAGES

Roberto, J.; Alexander, Charles W.; Boll, Rose Ann; ...

2015-06-18

Since 2000, six new super-heavy elements with atomic numbers 113 through 118 have been synthesized in hot fusion reactions of 48Ca beams on actinide targets. These target materials, including 242Pu, 244Pu, 243Am, 245Cm, 248Cm, 249Cf, and 249Bk, are available in very limited quantities and require specialized production and processing facilities resident in only a few research centers worldwide. This report describes the production and chemical processing of heavy actinide materials for super-heavy element research, current availabilities of these materials, and related target fabrication techniques. The impact of actinide materials in super-heavy element discovery is reviewed, and strategies for enhancing themore » production of rare actinides including 249Bk, 251Cf, and 254Es are described.« less

Impact of Including Higher Actinides in Fast Reactor Transmutation Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

B. Forget; M. Asgari; R. Ferrer

2007-09-01

Previous fast reactor transmutation studies generally disregarded higher mass minor actinides beyond Cm-246 due to various considerations including deficiencies in nuclear cross-section data. Although omission of these higher mass actinides does not significantly impact the neutronic calculations and fuel cycle performance parameters follow-on neutron dose calculations related to fuel recycling, transportation and handling are significantly impacted. This report shows that including the minor actinides in the equilibrium fast reactor calculations will increase the predicted neutron emission by about 30%. In addition a sensitivity study was initiated by comparing the impact of different cross-section evaluation file for representing these minor actinides.

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

Actinide and lanthanide separation process (ALSEP)

DOEpatents

Guelis, Artem V.

2013-01-15

The process of the invention is the separation of minor actinides from lanthanides in a fluid mixture comprising, fission products, lanthanides, minor actinides, rare earth elements, nitric acid and water by addition of an organic chelating aid to the fluid; extracting the fluid with a solvent comprising a first extractant, a second extractant and an organic diluent to form an organic extractant stream and an aqueous raffinate. Scrubbing the organic stream with a dicarboxylic acid and a chelating agent to form a scrubber discharge. The scrubber discharge is stripped with a simple buffering agent and a second chelating agent in the pH range of 2.5 to 6.1 to produce actinide and lanthanide streams and spent organic diluents. The first extractant is selected from bis(2-ethylhexyl)hydrogen phosphate (HDEHP) and mono(2-ethylhexyl)2-ethylhexyl phosphonate (HEH(EHP)) and the second extractant is selected from N,N,N,N-tetra-2-ethylhexyl diglycol amide (TEHDGA) and N,N,N',N'-tetraoctyl-3-oxapentanediamide (TODGA).

Fuel Sustainability And Actinide Production Of Doping Minor Actinide In Water-Cooled Thorium Reactor

NASA Astrophysics Data System (ADS)

Permana, Sidik

2017-07-01

Fuel sustainability of nuclear energy is coming from an optimum fuel utilization of the reactor and fuel breeding program. Fuel cycle option becomes more important for fuel cycle utilization as well as fuel sustainability capability of the reactor. One of the important issues for recycle fuel option is nuclear proliferation resistance issue due to production plutonium. To reduce the proliferation resistance level, some barriers were used such as matrial barrier of nuclear fuel based on isotopic composition of even mass number of plutonium isotope. Analysis on nuclear fuel sustainability and actinide production composition based on water-cooled thorium reactor system has been done and all actinide composition are recycled into the reactor as a basic fuel cycle scheme. Some important parameters are evaluated such as doping composition of minor actinide (MA) and volume ratio of moderator to fuel (MFR). Some feasible parameters of breeding gains have been obtained by additional MA doping and some less moderation to fuel ratios (MFR). The system shows that plutonium and MA are obtained low compositions and it obtains some higher productions of even mass plutonium, which is mainly Pu-238 composition, as a control material to protect plutonium to be used as explosive devices.

Siderocalin-mediated recognition, sensitization, and cellular uptake of actinides.

PubMed

Allred, Benjamin E; Rupert, Peter B; Gauny, Stacey S; An, Dahlia D; Ralston, Corie Y; Sturzbecher-Hoehne, Manuel; Strong, Roland K; Abergel, Rebecca J

2015-08-18

Synthetic radionuclides, such as the transuranic actinides plutonium, americium, and curium, present severe health threats as contaminants, and understanding the scope of the biochemical interactions involved in actinide transport is instrumental in managing human contamination. Here we show that siderocalin, a mammalian siderophore-binding protein from the lipocalin family, specifically binds lanthanide and actinide complexes through molecular recognition of the ligands chelating the metal ions. Using crystallography, we structurally characterized the resulting siderocalin-transuranic actinide complexes, providing unprecedented insights into the biological coordination of heavy radioelements. In controlled in vitro assays, we found that intracellular plutonium uptake can occur through siderocalin-mediated endocytosis. We also demonstrated that siderocalin can act as a synergistic antenna to sensitize the luminescence of trivalent lanthanide and actinide ions in ternary protein-ligand complexes, dramatically increasing the brightness and efficiency of intramolecular energy transfer processes that give rise to metal luminescence. Our results identify siderocalin as a potential player in the biological trafficking of f elements, but through a secondary ligand-based metal sequestration mechanism. Beyond elucidating contamination pathways, this work is a starting point for the design of two-stage biomimetic platforms for photoluminescence, separation, and transport applications.

Crystal growth methods dedicated to low solubility actinide oxalates

NASA Astrophysics Data System (ADS)

Tamain, C.; Arab-Chapelet, B.; Rivenet, M.; Grandjean, S.; Abraham, F.

2016-04-01

Two novel crystal growth syntheses dedicated to low solubility actinide-oxalate systems and adapted to glove box handling are described. These methods based on the use of precursors of either actinide metal or oxalic acid have been optimized on lanthanide systems (analogue of actinides(III)) and then assessed on real actinide systems. They allow the synthesis of several actinide oxalate single crystals, Am2(C2O4)3(H2O)3·xH2O, Th(C2O4)2·6H2O, M2+x[PuIV2-xPuIIIx(C2O4)5]·nH2O and M1-x[PuIII1-xPuIVx(C2O4)2·H2O]·nH2O. It is the first time that these well-known compounds are formed by crystal growth methods, thus enabling direct structural studies on transuranic element systems and acquisition of basic data beyond deductions from isomorphic (or not) lanthanide compounds. Characterizations by X-ray diffraction, UV-visible solid spectroscopy, demonstrate the potentialities of these two crystal growth methods to obtain oxalate compounds.

Siderocalin-mediated recognition, sensitization, and cellular uptake of actinides

PubMed Central

Allred, Benjamin E.; Rupert, Peter B.; Gauny, Stacey S.; An, Dahlia D.; Ralston, Corie Y.; Sturzbecher-Hoehne, Manuel; Strong, Roland K.; Abergel, Rebecca J.

2015-01-01

Synthetic radionuclides, such as the transuranic actinides plutonium, americium, and curium, present severe health threats as contaminants, and understanding the scope of the biochemical interactions involved in actinide transport is instrumental in managing human contamination. Here we show that siderocalin, a mammalian siderophore-binding protein from the lipocalin family, specifically binds lanthanide and actinide complexes through molecular recognition of the ligands chelating the metal ions. Using crystallography, we structurally characterized the resulting siderocalin–transuranic actinide complexes, providing unprecedented insights into the biological coordination of heavy radioelements. In controlled in vitro assays, we found that intracellular plutonium uptake can occur through siderocalin-mediated endocytosis. We also demonstrated that siderocalin can act as a synergistic antenna to sensitize the luminescence of trivalent lanthanide and actinide ions in ternary protein–ligand complexes, dramatically increasing the brightness and efficiency of intramolecular energy transfer processes that give rise to metal luminescence. Our results identify siderocalin as a potential player in the biological trafficking of f elements, but through a secondary ligand-based metal sequestration mechanism. Beyond elucidating contamination pathways, this work is a starting point for the design of two-stage biomimetic platforms for photoluminescence, separation, and transport applications. PMID:26240330

Process to remove actinides from soil using magnetic separation

DOEpatents

Avens, Larry R.; Hill, Dallas D.; Prenger, F. Coyne; Stewart, Walter F.; Tolt, Thomas L.; Worl, Laura A.

1996-01-01

A process of separating actinide-containing components from an admixture including forming a slurry including actinide-containing components within an admixture, said slurry including a dispersion-promoting surfactant, adjusting the pH of the slurry to within a desired range, and, passing said slurry through a pretreated matrix material, said matrix material adapted to generate high magnetic field gradients upon the application of a strong magnetic field exceeding about 0.1 Tesla whereupon a portion of said actinide-containing components are separated from said slurry and remain adhered upon said matrix material is provided.

Electronic structure of free and doped actinides: N and Z dependences of energy levels and electronic structure parameters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulagin, N.

2005-02-15

Theoretical study of electronic structure of antinide ions and its dependence on N and Z are presented in this paper. The main 5f{sup N} and excited 5f{sup N}n'l'{sup N'} configurations of actinides have been studied using Hartree-Fock-Pauli approximation. Results of calculations of radial integrals and the energy of X-ray lines for all 5f ions with electronic state AC{sup +1}-AC{sup +4} show approximate dependence on N and Z. A square of N and cubic of Z are ewalized for the primary electronic parameters of the actinides. Theoretical values of radial integrals for free actinides and for ions in a cluster AC{supmore » +n}:[L]{sub k} are compared, too.« less

THERMODYNAMICS OF THE ACTINIDES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cunningham, Burris B.

1962-04-01

Recent work on the thermodynamic properties of the transplutonium elements is presented and discussed in relation to trends in thermodynamic properties of the actinide series. Accurate values are given for room temperature lattice parameters of two crystallographic forms, (facecentred cubic) fcc and dhcp (double-hexagonal closepacked), of americium metal and for the coefficients of thermal expansion between 157 and 878 deg K (dhcp) and 295 to 633 deg K (fcc). The meiting point of the metal, and its magnetic susceptibility between 77 and 823 deg K are reported and the latter compared with theoretical values for the tripositive ion calculated frommore » spectroscopic data. Similar data (crystallography, meiting point and magnetic susceptibility) are given for metallic curium. A value for the heat of formation of americium monoxide is reported in conjunction with crystallographic data on the monoxide and mononitride. A revision is made in the current value for the heat of formation of Am/O/sub 2/ and for the potential of the Am(III)-Am(IV) couple. The crystal structures and lattice parameters are reported for the trichloride, oxychloride and oxides of californium. (auth)« less

Systematization of actinides using cluster analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

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.

Novel Separation of Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mariella, R

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 physicalmore » 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.« less

Metal oxidation states in biological water splitting.

PubMed

Krewald, Vera; Retegan, Marius; Cox, Nicholas; Messinger, Johannes; Lubitz, Wolfgang; DeBeer, Serena; Neese, Frank; Pantazis, Dimitrios A

2015-03-01

A central question in biological water splitting concerns the oxidation states of the manganese ions that comprise the oxygen-evolving complex of photosystem II. Understanding the nature and order of oxidation events that occur during the catalytic cycle of five S i states ( i = 0-4) is of fundamental importance both for the natural system and for artificial water oxidation catalysts. Despite the widespread adoption of the so-called "high-valent scheme"-where, for example, the Mn oxidation states in the S 2 state are assigned as III, IV, IV, IV-the competing "low-valent scheme" that differs by a total of two metal unpaired electrons ( i.e. III, III, III, IV in the S 2 state) is favored by several recent studies for the biological catalyst. The question of the correct oxidation state assignment is addressed here by a detailed computational comparison of the two schemes using a common structural platform and theoretical approach. Models based on crystallographic constraints were constructed for all conceivable oxidation state assignments in the four (semi)stable S states of the oxygen evolving complex, sampling various protonation levels and patterns to ensure comprehensive coverage. The models are evaluated with respect to their geometric, energetic, electronic, and spectroscopic properties against available experimental EXAFS, XFEL-XRD, EPR, ENDOR and Mn K pre-edge XANES data. New 2.5 K 55 Mn ENDOR data of the S 2 state are also reported. Our results conclusively show that the entire S state phenomenology can only be accommodated within the high-valent scheme by adopting a single motif and protonation pattern that progresses smoothly from S 0 (III, III, III, IV) to S 3 (IV, IV, IV, IV), satisfying all experimental constraints and reproducing all observables. By contrast, it was impossible to construct a consistent cycle based on the low-valent scheme for all S states. Instead, the low-valent models developed here may provide new insight into the over-reduced S

Gas core reactors for actinide transmutation and breeder applications

NASA Technical Reports Server (NTRS)

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

1978-01-01

This work consists of design power plant studies for four types of reactor systems: uranium plasma core breeder, uranium plasma core actinide transmuter, UF6 breeder and UF6 actinide transmuter. The plasma core systems can be coupled to MHD generators to obtain high efficiency electrical power generation. A 1074 MWt UF6 breeder reactor was designed with a breeding ratio of 1.002 to guard against diversion of fuel. Using molten salt technology and a superheated steam cycle, an efficiency of 39.2% was obtained for the plant and the U233 inventory in the core and heat exchangers was limited to 105 Kg. It was found that the UF6 reactor can produce high fluxes (10 to the 14th power n/sq cm-sec) necessary for efficient burnup of actinide. However, the buildup of fissile isotopes posed severe heat transfer problems. Therefore, the flux in the actinide region must be decreased with time. Consequently, only beginning-of-life conditions were considered for the power plant design. A 577 MWt UF6 actinide transmutation reactor power plant was designed to operate with 39.3% efficiency and 102 Kg of U233 in the core and heat exchanger for beginning-of-life conditions.

Predictive Modeling in Actinide Chemistry and Catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ping

2016-05-16

These are slides from a presentation on predictive modeling in actinide chemistry and catalysis. The following topics are covered in these slides: Structures, bonding, and reactivity (bonding can be quantified by optical probes and theory, and electronic structures and reaction mechanisms of actinide complexes); Magnetic resonance properties (transition metal catalysts with multi-nuclear centers, and NMR/EPR parameters); Moving to more complex systems (surface chemistry of nanomaterials, and interactions of ligands with nanoparticles); Path forward and conclusions.

On-line Monitoring of Actinide Concentrations in Molten Salt Electrolyte

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtis W. Johnson; Mary Lou Dunzik-Gougar; Shelly X. Li

2006-11-01

Pyroprocessing, a treatment method for spent nuclear fuel (SNF), is currently being studied at the Idaho National Laboratory. The key operation of pyroprocessing which takes place in an electrorefiner is the electrochemical separation of actinides from other constituents in spent fuel. Efficient operation of the electrorefiner requires online monitoring of actinide concentrations in the molten salt electrolyte. Square-wave voltammetry (SWV) and normal pulse voltammetry (NPV) are being investigated to assess their applicability to the measurement of actinide concentrations in the electrorefiner.

Understanding Release from Actinide Targets -- Recent Results from RIB Development

NASA Astrophysics Data System (ADS)

Kronenberg, Andreas; Carter, H. K.; Spejewski, E. H.; Stracener, D. W.

2006-10-01

Development of ion beams of short-lived isotopes is crucial for modern nuclear structure and nuclear astrophysics. The Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory uses the ISOL (Isotope Separation Online) technique to provide radioactive ion beams. So far, uranium carbide has been used as a target to produce neutron-rich fission fragments. Thermodynamic calculations indicate the possibility of in-situ chemical side band formations of volatile species of refractory metals, such as V and Re. These elements release out of oxide targets after production in a nuclear reaction, and can occur only through in-situ formation of their volatile oxide. These have been confirmed experimentally. The results from recent, more detailed investigations of ThO2, UB4 and other actinide targets as well as conclusions from systematic studies will be presented. This research was sponsored by the NNSA under Stewardship Science Academic Alliance program through DOE Cooperative Agreement # DE-FC03-3NA00143.

Colloid-borne forms of tetravalent actinides: A brief review

NASA Astrophysics Data System (ADS)

Zänker, Harald; Hennig, Christoph

2014-02-01

Tetravalent actinides, An(IV), are usually assumed to be little mobile in near-neutral environmental waters because of their low solubility. However, there are certain geochemical scenarios during which mobilization of An(IV) in a colloid-borne (waterborne) form cannot be ruled out. A compilation of colloid-borne forms of tetravalent actinides described so far for laboratory experiments together with several examples of An(IV) colloids observed in field experiments and real-world scenarios are given. They are intended to be a knowledge base and a tool for those who have to interpret actinide behavior under environmental conditions. Synthetic colloids containing structural An(IV) and synthetic colloids carrying adsorbed An(IV) are considered. Their behavior is compared with the behavior of An(IV) colloids observed after the intentional or unintentional release of actinides into the environment. A list of knowledge gaps as to the behavior of An(IV) colloids is provided and items which need further research are highlighted.

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)

Towards Synthesis and Usage of Actinide-Bearing REE Phosphate age Standards: A Progress Report

NASA Astrophysics Data System (ADS)

Pyle, J. M.; Cherniak, D. J.

2006-05-01

Electron microprobe (EMP) dates result from a concentration-time unit conversion, so use of a concentration- based (rather than isotope-ratio based) fictive age standard is warranted. This observation has motivated our mineral synthesis program, aimed at producing actinide-doped REE phosphate EMP dating standards that meet the following criteria: 1) known concentrations of U, Th, and Pb; 2) homogeneous intragrain distribution of all components; 3) of suitable size, either as a single-crystal or polycrystalline sintered ceramic. Single-crystal synthesis of actinide-doped LaPO4 by flux-growth methods results in disproportionation of lanthanide and flux, alkali, and actinide components into phosphate and oxide phases, respectively, and flux- growth methods were abandoned. Actinide-doped La phosphate is successfully prepared by high-T annealing and hydrothermal processing of microcrystalline phosphate; both homogeneity and charge-balance of (Ca, Th, Pb)-bearing LaPO4 increase with increasing solvent acidity during cold-seal hydrothermal synthesis. A combination of pressing and high-T (1400° C) sintering transforms fine-grained (0.1-10 μm) run- products to ceramic pellets with 90-95% theoretical density. Our most recent runs focused on a target composition of La80(CaTh)17(CaU)2(PbTh)1PO4 processed with 6% 2M HCl at 820° C, 0.75 kbar for 1 week. The run products are 0.1-2 μm crystals identified by XRD as La-actinide phosphate solid solution. 2 μm grains (N=16) give a composition (mean±2 sd) of La79.77(1.26)(CaTh)17.87(1.00)(CaU)1.53(0.42)(PbTh)0.82(0.09)PO4. Th (8.07-9.13 wt. %) is homogeneous at the level of analytical precision, and the Pb concentration range (3500-4350 ppm) is restricted relative to untreated precipitate. Uranium concentration values are more variable (6500-10000 ppm). This run yields a fictive age of 702±4 Ma (mean±2 se), compared to the fictive age of 794 Ma for the target composition.

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

DOE PAGES

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

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 Zr 1+, Zr 2+, and Zr 3+ as non-equilibrium oxidation states, in addition to Zr 4+ in the stoichiometric ZrO 2. This finding resolves the long-debated question of whether it is possible to form any valence states between Zr 0 and Zr 4+ at the metal-oxide interface. As a result, themore » 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.« less

Reduction in the Band Gap of Manganese-Doped Zinc Oxide: Role of the Oxidation State

NASA Astrophysics Data System (ADS)

Sharma, Sonia; Ramesh, Pranith; Swaminathan, P.

2015-12-01

Manganese-doped zinc oxide powders were synthesized by solid state reaction of the respective oxides. The high-temperature conditions were chosen such that multiple valence states of manganese were doped in the host zinc oxide lattice. Structural characterization was carried out to confirm the doping and to find the maximum amount of manganese that can be incorporated. Diffuse reflectance spectroscopy was used to measure the optical band gap of the doped sample and the lowering with respect to pure ZnO was attributed to the presence of higher oxidation states of manganese. The presence of these oxidation states was confirmed using x-ray photoelectron spectroscopy. The study shows that a solid state reaction is a viable route for synthesizing doped metal oxides with desired optical properties.

An optimization methodology for heterogeneous minor actinides transmutation

NASA Astrophysics Data System (ADS)

Kooyman, Timothée; Buiron, Laurent; Rimpault, Gérald

2018-04-01

In the case of a closed fuel cycle, minor actinides transmutation can lead to a strong reduction in spent fuel radiotoxicity and decay heat. In the heterogeneous approach, minor actinides are loaded in dedicated targets located at the core periphery so that long-lived minor actinides undergo fission and are turned in shorter-lived fission products. However, such targets require a specific design process due to high helium production in the fuel, high flux gradient at the core periphery and low power production. Additionally, the targets are generally manufactured with a high content in minor actinides in order to compensate for the low flux level at the core periphery. This leads to negative impacts on the fuel cycle in terms of neutron source and decay heat of the irradiated targets, which penalize their handling and reprocessing. In this paper, a simplified methodology for the design of targets is coupled with a method for the optimization of transmutation which takes into account both transmutation performances and fuel cycle impacts. The uncertainties and performances of this methodology are evaluated and shown to be sufficient to carry out scoping studies. An illustration is then made by considering the use of moderating material in the targets, which has a positive impact on the minor actinides consumption but a negative impact both on fuel cycle constraints (higher decay heat and neutron) and on assembly design (higher helium production and lower fuel volume fraction). It is shown that the use of moderating material is an optimal solution of the transmutation problem with regards to consumption and fuel cycle impacts, even when taking geometrical design considerations into account.

Statistical analysis of excitation energies in actinide and rare-earth nuclei

NASA Astrophysics Data System (ADS)

Levon, A. I.; Magner, A. G.; Radionov, S. V.

2018-04-01

Statistical analysis of distributions of the collective states in actinide and rare-earth nuclei is performed in terms of the nearest-neighbor spacing distribution (NNSD). Several approximations, such as the linear approach to the level repulsion density and that suggested by Brody to the NNSDs were applied for the analysis. We found an intermediate character of the experimental spectra between the order and the chaos for a number of rare-earth and actinide nuclei. The spectra are closer to the Wigner distribution for energies limited by 3 MeV, and to the Poisson distribution for data including higher excitation energies and higher spins. The latter result is in agreement with the theoretical calculations. These features are confirmed by the cumulative distributions, where the Wigner contribution dominates at smaller spacings while the Poisson one is more important at larger spacings, and our linear approach improves the comparison with experimental data at all desired spacings.

High-pressure synthesis and characterization of new actinide borates, AnB4O8 (An=Th, U).

PubMed

Hinteregger, Ernst; Hofer, Thomas S; Heymann, Gunter; Perfler, Lukas; Kraus, Florian; Huppertz, Hubert

2013-11-18

New actinide borates ThB4O8 and UB4O8 were synthesized under high-pressure, high-temperature conditions (5.5 GPa/1100 °C for thorium borate, 10.5 GPa/1100 °C for the isotypic uranium borate) in a Walker-type multianvil apparatus from their corresponding actinide oxide and boron oxide. The crystal structure was determined on basis of single-crystal X-ray diffraction data that were collected at room temperature. Both compounds crystallized in the monoclinic space group C2/c (Z=4). Lattice parameters for ThB4O8: a=1611.3(3), b=419.86(8), c=730.6(2) pm; β=114.70(3)°; V=449.0(2) Å(3); R1=0.0255, wR2=0.0653 (all data). Lattice parameters for UB4O8: a=1589.7(3), b=422.14(8), c=723.4(2) pm; β=114.13(3)°; V=443.1(2) Å(3); R1=0.0227, wR2=0.0372 (all data). The new AnB4O8 (An=Th, U) structure type is constructed from corner-sharing BO4 tetrahedra, which form layers in the bc plane. One of the four independent oxygen atoms is threefold-coordinated. The actinide cations are located between the boron-oxygen layers. In addition to Raman spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands. © 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This isan open access article under the terms of the Creative Commons AttributionLicense, which permits use, distribution and reproduction in any medium,provided the original work is properly cited.

Separation of actinides using capillary extraction chromatography-inductively coupled plasma mass spectrometry.

PubMed

Peterson, Dominic S; Montoya, Velma M

2009-08-01

Trace levels of actinides have been separated on capillary extraction chromatography columns. Detection of the actinides was achieved using an inductively coupled plasma mass spectrometer, which was coupled with the extraction chromatography system. In this study, we compare 30-cm long, 4.6 mm i.d. columns to capillary columns (750 microm i.d.) with lengths from 30 cm up to 150 cm. The columns that were tested were packed with TRU resin. We were able to separate a mixture of five actinides ((232)Th, (238)U, (237)Np, (239)Pu, and (241)Am). This work has application to rapid bioassay as well as automated separations of actinide materials.

Synthesis and Characterization of Templated Ion Exchange Resins for the Selective Complexion of Actinide Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murrray, George M.; Uy, O. Manuel

The purpose of this research is to develop polymeric extractants for the selective complexation of uranyl ions (and subsequently other actinyl and actinide ions) from aqueous solutions. Selectivity for a specific actinide ion is obtained by providing the polymers with cavities lined with complexing ligands so arranged as to match the charge, coordination number, coordination geometry, and size of the actinide ion. These cavity-containing polymers are produced by using a specific actinide ion (or surrogate) as a template around which monomeric complexing ligands are polymerized. The polymers provide useful sequestering agents for removing actinide ions from wastes and will formmore » the basis for a variety of analytical techniques for actinide determination.« less

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.

Seventeen-Coordinate Actinide Helium Complexes.

PubMed

Kaltsoyannis, Nikolas

2017-06-12

The geometries and electronic structures of molecular ions featuring He atoms complexed to actinide cations are explored computationally using density functional and coupled cluster theories. A new record coordination number is established, as AcHe 17 3+ , ThHe 17 4+ , and PaHe 17 4+ are all found to be true geometric minima, with the He atoms clearly located in the first shell around the actinide. Analysis of AcHe n 3+ (n=1-17) using the quantum theory of atoms in molecules (QTAIM) confirms these systems as having closed shell, charge-induced dipole bonding. Excellent correlations (R 2 >0.95) are found between QTAIM metrics (bond critical point electron densities and delocalization indices) and the average Ac-He distances, and also with the incremental He binding energies. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Managing Zirconium Chemistry and Phase Compatibility in Combined Process Separations for Minor Actinide Partitioning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wall, Nathalie; Nash, Ken; Martin, Leigh

In response to the NEUP Program Supporting Fuel Cycle R&D Separations and Waste Forms call DEFOA- 0000799, this report describes the results of an R&D project focusing on streamlining separation processes for advanced fuel cycles. An example of such a process relevant to the U.S. DOE FCR&D program would be one combining the functions of the TRUEX process for partitioning of lanthanides and minor actinides from PUREX(UREX) raffinates with that of the TALSPEAK process for separating transplutonium actinides from fission product lanthanides. A fully-developed PUREX(UREX)/TRUEX/TALSPEAK suite would generate actinides as product(s) for reuse (or transmutation) and fission products as waste.more » As standalone, consecutive unit-operations, TRUEX and TALSPEAK employ different extractant solutions (solvating (CMPO, octyl(phenyl)-N,Ndiisobutylcarbamoylmethylphosphine oxide) vs. cation exchanging (HDEHP, di-2(ethyl)hexylphosphoric acid) extractants), and distinct aqueous phases (2-4 M HNO 3 vs. concentrated pH 3.5 carboxylic acid buffers containing actinide selective chelating agents). The separate processes may also operate with different phase transfer kinetic constraints. Experience teaches (and it has been demonstrated at the lab scale) that, with proper control, multiple process separation systems can operate successfully. However, it is also recognized that considerable economies of scale could be achieved if multiple operations could be merged into a single process based on a combined extractant solvent. The task of accountability of nuclear materials through the process(es) also becomes more robust with fewer steps, providing that the processes can be accurately modeled. Work is underway in the U.S. and Europe on developing several new options for combined processes (TRUSPEAK, ALSEP, SANEX, GANEX, ExAm are examples). There are unique challenges associated with the operation of such processes, some relating to organic phase chemistry, others arising from the

Extraction processes and solvents for recovery of cesium, strontium, rare earth elements, technetium and actinides from liquid radioactive waste

DOEpatents

Zaitsev, Boris N.; Esimantovskiy, Vyacheslav M.; Lazarev, Leonard N.; Dzekun, Evgeniy G.; Romanovskiy, Valeriy N.; Todd, Terry A.; Brewer, Ken N.; Herbst, Ronald S.; Law, Jack D.

2001-01-01

Cesium and strontium are extracted from aqueous acidic radioactive waste containing rare earth elements, technetium and actinides, by contacting the waste with a composition of a complex organoboron compound and polyethylene glycol in an organofluorine diluent mixture. In a preferred embodiment the complex organoboron compound is chlorinated cobalt dicarbollide, the polyethylene glycol has the formula RC.sub.6 H.sub.4 (OCH.sub.2 CH.sub.2).sub.n OH, and the organofluorine diluent is a mixture of bis-tetrafluoropropyl ether of diethylene glycol with at least one of bis-tetrafluoropropyl ether of ethylene glycol and bis-tetrafluoropropyl formal. The rare earths, technetium and the actinides (especially uranium, plutonium and americium), are extracted from the aqueous phase using a phosphine oxide in a hydrocarbon diluent, and reextracted from the resulting organic phase into an aqueous phase by using a suitable strip reagent.

Method for digesting spent ion exchange resins and recovering actinides therefrom using microwave radiation

DOEpatents

Maxwell, III, Sherrod L.; Nichols, Sheldon T.

1999-01-01

The present invention relates to methods for digesting diphosphonic acid substituted cation exchange resins that have become loaded with actinides, rare earth metals, or heavy metals, in a way that allows for downstream chromatographic analysis of the adsorbed species without damage to or inadequate elution from the downstream chromatographic resins. The methods of the present invention involve contacting the loaded diphosphonic acid resin with concentrated oxidizing acid in a closed vessel, and irradiating this mixture with microwave radiation. This efficiently increases the temperature of the mixture to a level suitable for digestion of the resin without the use of dehydrating acids that can damage downstream analytical resins. In order to ensure more complete digestion, the irradiated mixture can be mixed with hydrogen peroxide or other oxidant, and reirradiated with microwave radiation.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jernigan, Glenn Geoffrey

1994-10-01

Carbon monoxide oxidation was performed over the three different oxidation states of copper -- metallic (Cu), copper (I) oxide (Cu 2O), 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 2O > CuO) and the activation energy increased with increasing oxidation state (Cu, 9 kcal/molmore » < Cu 2O, 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 2 and CO 2. At the end of each reaction, the catalyst was found to be Cu 2O. There is a need to study the kinetics of this reaction over the different oxidation states of copper.« less

Characterization of a transient +2 sulfur oxidation state intermediate from the oxidation of aqueous sulfide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vairavmurthy, M.A.; Zhou, Weiqing

1995-04-01

The oxidation H{sub 2}S to sulfate involves a net transfer of eight electrons and occurs through the formation of several partially oxidized intermediates with oxidation states ranging from {minus}1 to +5. Known intermediates include elemental sulfur (oxidation state 0), polysulfides (outer sulfur: {minus}1, inner sulfur: 0), sulfite (+4) and thiosulfate (outer sulfur: {minus}1, inner sulfur: +5). A noticeable gap in this series of intermediates is that of a +2 sulfur oxidation state oxoacid/oxoanion species, which was never detected experimentally. Here, we present evidence of the transient existence of +2 oxidation state intermediate in the Ni(II)-catalyzed oxidation of aqueous sulfide. X-raymore » absorption near-edge structure (XANES) spectroscopy and Fourier-transform-infrared (FT-IR) spectroscopy were used to characterize this species; they suggest that it has a sulfoxylate ion (SO{sub 2}{sup 2{minus}}) structure.« less

Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal-Organic Frameworks.

PubMed

Dolgopolova, Ekaterina A; Ejegbavwo, Otega A; Martin, Corey R; Smith, Mark D; Setyawan, Wahyu; Karakalos, Stavros G; Henager, Charles H; Zur Loye, Hans-Conrad; Shustova, Natalia B

2017-11-22

Growing necessity for efficient nuclear waste management is a driving force for development of alternative architectures toward fundamental understanding of mechanisms involved in actinide (An) integration inside extended structures. In this manuscript, metal-organic frameworks (MOFs) were investigated as a model system for engineering radionuclide containing materials through utilization of unprecedented MOF modularity, which cannot be replicated in any other type of materials. Through the implementation of recent synthetic advances in the MOF field, hierarchical complexity of An-materials was built stepwise, which was only feasible due to preparation of the first examples of actinide-based frameworks with "unsaturated" metal nodes. The first successful attempts of solid-state metathesis and metal node extension in An-MOFs are reported, and the results of the former approach revealed drastic differences in chemical behavior of extended structures versus molecular species. Successful utilization of MOF modularity also allowed us to structurally characterize the first example of bimetallic An-An nodes. To the best of our knowledge, through combination of solid-state metathesis, guest incorporation, and capping linker installation, we were able to achieve the highest Th wt % in mono- and biactinide frameworks with minimal structural density. Overall, the combination of a multistep synthetic approach with homogeneous actinide distribution and moderate solvothermal conditions could make MOFs an exceptionally powerful tool to address fundamental questions responsible for chemical behavior of An-based extended structures and, therefore, shed light on possible optimization of nuclear waste administration.

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.

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.

Actinide Sputtering Induced by Fission with Ultra-cold Neutrons

NASA Astrophysics Data System (ADS)

Shi, Tan; Venuti, Michael; Fellers, Deion; Martin, Sean; Morris, Chris; Makela, Mark

2017-09-01

Understanding the effects of actinide sputtering due to nuclear fission is important for a wide range of applications, including nuclear fuel storage, 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. By controlling the UCN energy, it is possible to induce fission at the sample surface within a well-defined depth. It is therefore an ideal tool for studying the effects of fission-induced sputtering as a function of interaction depth. Since the mechanism for fission-induced surface damage is not well understood, this work has the potential to deconvolve the various damage mechanisms. During the irradiation with UCN, NaI detectors are used to monitor the fission events and were calibrated by monitoring fission fragments with an organic scintillator. Alpha spectroscopy of the ejected actinide material is performed in an ion chamber to determine the amount of sputtered material. Actinide samples with various sample properties and surface conditions are irradiated and analyzed. In this talk, I will discuss our experimental setup and present the preliminary results from the testing of multiple samples. This work has been supported by Los Alamos National Laboratory and Seaborg Summer Research Fellowship.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pelatt, Brian D.; Kokenyesi, Robert S.; Ravichandran, Ram

2015-11-15

The atomic solid state energy (SSE) scale originates from a plot of the electron affinity (EA) and ionization potential (IP) versus band gap (E{sub G}). 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 IPmore » versus E{sub G} 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. - Highlights: • Atomic solid-state energies are estimated for 64 elements from experimental data. • The relationship between atomic SSEs and oxidation state is assessed. • Cations are positioned above and absolute energy of −4.5 eV and anions below.« less

Electronic Structure of Transition Metal Clusters, Actinide Complexes and Their Reactivities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnan Balasubramanian

2009-07-18

critical to the environmental management of high-level nuclear wastes. In collaboration with experimental colleague Prof Hieno Nitsche (Berkeley) and Dr. Pat Allen (Livermore, EXAFS) we have studied the uranyl complexes with silicates and carbonates. It should be stressed that although our computed ionization potential of uranium oxide was in conflict with the existing experimental data at the time, a subsequent gas-phase experimental work by Prof Mike Haven and coworkers published as communication in JACS confirmed our computed result to within 0.1 eV. This provides considerable confidence that the computed results in large basis sets with highly-correlated wave functions have excellent accuracies and they have the capabilities to predict the excited states also with great accuracy. Computations of actinide complexes (Uranyl and plutonyl complexes) are critical to management of high-level nuclear wastes.« less

Dehydration of plutonium or neptunium trichloride hydrate

DOEpatents

Foropoulos, Jr., Jerry; Avens, Larry R.; Trujillo, Eddie A.

1992-01-01

A process of preparing anhydrous actinide metal trichlorides of plutonium or neptunium by reacting an aqueous solution of an actinide metal trichloride selected from the group consisting of plutonium trichloride or neptunium trichloride with a reducing agent capable of converting the actinide metal from an oxidation state of +4 to +3 in a resultant solution, evaporating essentially all the solvent from the resultant solution to yield an actinide trichloride hydrate material, dehydrating the actinide trichloride hydrate material by heating the material in admixture with excess thionyl chloride, and recovering anhydrous actinide trichloride is provided.

Dehydration of plutonium or neptunium trichloride hydrate

DOEpatents

Foropoulos, J. Jr.; Avens, L.R.; Trujillo, E.A.

1992-03-24

A process is described for preparing anhydrous actinide metal trichlorides of plutonium or neptunium by reacting an aqueous solution of an actinide metal trichloride selected from the group consisting of plutonium trichloride or neptunium trichloride with a reducing agent capable of converting the actinide metal from an oxidation state of +4 to +3 in a resultant solution, evaporating essentially all the solvent from the resultant solution to yield an actinide trichloride hydrate material, dehydrating the actinide trichloride hydrate material by heating the material in admixture with excess thionyl chloride, and recovering anhydrous actinide trichloride.

Association of actinides with microorganisms and clay: Implications for radionuclide migration from waste-repository sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohnuki, T.; Francis, A.; Kozai, N.

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 uraniummore » 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

Photochemical route to actinide-transition metal bonds: synthesis, characterization and reactivity of a series of thorium and uranium heterobimetallic complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Ashleigh; Lukens, Wayne; Lu, Connie

2014-04-01

A series of actinide-transition metal heterobimetallics has been prepared, featuring thorium, uranium and cobalt. Complexes incorporating the binucleating ligand N[-(NHCH2PiPr2)C6H4]3 and Th(IV) (4) or U(IV) (5) with a carbonyl bridged [Co(CO)4]- unit were synthesized from the corresponding actinide chlorides (Th: 2; U: 3) and Na[Co(CO)4]. Irradiation of the isocarbonyls with ultraviolet light resulted in the formation of new species containing actinide-metal bonds in good yields (Th: 6; U: 7); this photolysis method provides a new approach to a relatively rare class of complexes. Characterization by single-crystal X-ray diffraction revealed that elimination of the bridging carbonyl is accompanied by coordination ofmore » a phosphine arm from the N4P3 ligand to the cobalt center. Additionally, actinide-cobalt bonds of 3.0771(5) and 3.0319(7) for the thorium and uranium complexes, respectively, were observed. The solution state behavior of the thorium complexes was evaluated using 1H, 1H-1H COSY, 31P and variable-temperature NMR spectroscopy. IR, UV-Vis/NIR, and variable-temperature magnetic susceptibility measurements are also reported.« less

The nature of chemical bonding in actinide and lanthanide ferrocyanides determined by X-ray absorption spectroscopy and density functional theory.

PubMed

Dumas, Thomas; Guillaumont, Dominique; Fillaux, Clara; Scheinost, Andreas; Moisy, Philippe; Petit, Sébastien; Shuh, David K; Tyliszczak, Tolek; Den Auwer, Christophe

2016-01-28

The electronic properties of actinide cations are of fundamental interest to describe intramolecular interactions and chemical bonding in the context of nuclear waste reprocessing or direct storage. The 5f and 6d orbitals are the first partially or totally vacant states in these elements, and the nature of the actinide ligand bonds is related to their ability to overlap with ligand orbitals. Because of its chemical and orbital selectivities, X-ray absorption spectroscopy (XAS) is an effective probe of actinide species frontier orbitals and for understanding actinide cation reactivity toward chelating ligands. The soft X-ray probes of the light elements provide better resolution than actinide L3-edges to obtain electronic information from the ligand. Thus coupling simulations to experimental soft X-ray spectral measurements and complementary quantum chemical calculations yields quantitative information on chemical bonding. In this study, soft X-ray XAS at the K-edges of C and N, and the L2,3-edges of Fe was used to investigate the electronic structures of the well-known ferrocyanide complexes K4Fe(II)(CN)6, thorium hexacyanoferrate Th(IV)Fe(II)(CN)6, and neodymium hexacyanoferrate KNd(III)Fe(II)(CN)6. The soft X-ray spectra were simulated based on quantum chemical calculations. Our results highlight the orbital overlapping effects and atomic effective charges in the Fe(II)(CN)6 building block. In addition to providing a detailed description of the electronic structure of the ferrocyanide complex (K4Fe(II)(CN)6), the results strongly contribute to confirming the actinide 5f and 6d orbital oddity in comparison to lanthanide 4f and 5d.

The nature of chemical bonding in actinide and lanthanide ferrocyanides determined by X-ray absorption spectroscopy and density functional theory

DOE PAGES

Dumas, Thomas; Guillaumont, Dominique; Fillaux, Clara; ...

2016-01-01

The electronic properties of actinide cations are of fundamental interest to describe intramolecular interactions and chemical bonding in the context of nuclear waste reprocessing or direct storage. The 5f and 6d orbitals are the first partially or totally vacant states in these elements, and the nature of the actinide ligand bonds is related to their ability to overlap with ligand orbitals. Because of its chemical and orbital selectivities, X-ray absorption spectroscopy (XAS) is an effective probe of actinide species frontier orbitals and for understanding actinide cation reactivity toward chelating ligands. The soft X-ray probes of the light elements provide bettermore » resolution than actinide L 3 -edges to obtain electronic information from the ligand. Thus coupling simulations to experimental soft X-ray spectral measurements and complementary quantum chemical calculations yields quantitative information on chemical bonding. In this study, soft X-ray XAS at the K-edges of C and N, and the L 2,3 -edges of Fe was used to investigate the electronic structures of the well-known ferrocyanide complexes K 4 Fe II (CN) 6 , thorium hexacyanoferrate Th IV Fe II (CN) 6 , and neodymium hexacyanoferrate KNd III Fe II (CN) 6 . The soft X-ray spectra were simulated based on quantum chemical calculations. Our results highlight the orbital overlapping effects and atomic effective charges in the Fe II (CN) 6 building block. In addition to providing a detailed description of the electronic structure of the ferrocyanide complex (K 4 Fe II (CN) 6 ), the results strongly contribute to confirming the actinide 5f and 6d orbital oddity in comparison to lanthanide 4f and 5d.« less

Advancing the scientific basis of trivalent actinide-lanthanide separations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nash, K.L.

For advanced fuel cycles designed to support transmutation of transplutonium actinides, several options have been demonstrated for process-scale aqueous separations for U, Np, Pu management and for partitioning of trivalent actinides and fission product lanthanides away from other fission products. The more difficult mutual separation of Am/Cm from La-Tb remains the subject of considerable fundamental and applied research. The chemical separations literature teaches that the most productive alternatives to pursue are those based on ligand donor atoms less electronegative than O, specifically N- and S-containing complexants and chloride ion (Cl{sup -}). These 'soft-donor' atoms have exhibited usable selectivity in theirmore » bonding interactions with trivalent actinides relative to lanthanides. In this report, selected features of soft donor reagent design, characterization and application development will be discussed. The roles of thiocyanate, aminopoly-carboxylic acids and lactate in separation processes are detailed. (authors)« less

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.

Minor actinide transmutation in thorium and uranium matrices in heavy water moderated reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatti, Zaki; Hyland, B.; Edwards, G.W.R.

2013-07-01

The irradiation of Th{sup 232} breeds fewer of the problematic minor actinides (Np, Am, Cm) than the irradiation of U{sup 238}. This characteristic makes thorium an attractive potential matrix for the transmutation of these minor actinides, as these species can be transmuted without the creation of new actinides as is the case with a uranium fuel matrix. Minor actinides are the main contributors to long term decay heat and radiotoxicity of spent fuel, so reducing their concentration can greatly increase the capacity of a long term deep geological repository. Mixing minor actinides with thorium, three times more common in themore » Earth's crust than natural uranium, has the additional advantage of improving the sustainability of the fuel cycle. In this work, lattice cell calculations have been performed to determine the results of transmuting minor actinides from light water reactor spent fuel in a thorium matrix. 15-year-cooled group-extracted transuranic elements (Np, Pu, Am, Cm) from light water reactor (LWR) spent fuel were used as the fissile component in a thorium-based fuel in a heavy water moderated reactor (HWR). The minor actinide (MA) transmutation rates, spent fuel activity, decay heat and radiotoxicity, are compared with those obtained when the MA were mixed instead with natural uranium and taken to the same burnup. Each bundle contained a central pin containing a burnable neutron absorber whose initial concentration was adjusted to have the same reactivity response (in units of the delayed neutron fraction β) for coolant voiding as standard NU fuel. (authors)« less

Requirements for Predictive Density Functional Theory Methods for Heavy Materials Equation of State

NASA Astrophysics Data System (ADS)

Mattsson, Ann E.; Wills, John M.

2012-02-01

The difficulties in experimentally determining the Equation of State of actinide and lanthanide materials has driven the development of many computational approaches with varying degree of empiricism and predictive power. While Density Functional Theory (DFT) based on the Schr"odinger Equation (possibly with relativistic corrections including the scalar relativistic approach) combined with local and semi-local functionals has proven to be a successful and predictive approach for many materials, it is not giving enough accuracy, or even is a complete failure, for the actinides. To remedy this failure both an improved fundamental description based on the Dirac Equation (DE) and improved functionals are needed. Based on results obtained using the appropriate fundamental approach of DFT based on the DE we discuss the performance of available semi-local functionals, the requirements for improved functionals for actinide/lanthanide materials, and the similarities in how functionals behave in transition metal oxides. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Uranium oxide fuel cycle analysis in VVER-1000 with VISTA simulation code

NASA Astrophysics Data System (ADS)

Mirekhtiary, Seyedeh Fatemeh; Abbasi, Akbar

2018-02-01

The VVER-1000 Nuclear power plant generates about 20-25 tons of spent fuel per year. In this research, the fuel transmutation of Uranium Oxide (UOX) fuel was calculated by using of nuclear fuel cycle simulation system (VISTA) code. In this simulation, we evaluated the back end components fuel cycle. The back end component calculations are Spent Fuel (SF), Actinide Inventory (AI) and Fission Product (FP) radioisotopes. The SF, AI and FP values were obtained 23.792178 ton/y, 22.811139 ton/y, 0.981039 ton/y, respectively. The obtained value of spent fuel, major actinide, and minor actinide and fission products were 23.8 ton/year, 22.795 ton/year, 0.024 ton/year and 0.981 ton/year, respectively.

Nuclear waste disposal—pyrochlore (A2B2O7): Nuclear waste form for the immobilization of plutonium and "minor" actinides

NASA Astrophysics Data System (ADS)

Ewing, Rodney C.; Weber, William J.; Lian, Jie

2004-06-01

During the past half-century, the nuclear fuel cycle has generated approximately 1400 metric tons of plutonium and substantial quantities of the "minor" actinides, such as Np, Am, and Cm. The successful disposition of these actinides has an important impact on the strategy for developing advanced nuclear fuel cycles, weapons proliferation, and the geologic disposal of high-level radioactive waste. During the last decade, there has been substantial interest in the use of the isometric pyrochlore structure-type, A2B2O7, for the immobilization of actinides. Most of the interest has focused on titanate-pyrochlore because of its chemical durability; however, these compositions experience a radiation-induced transition from the crystalline-to-aperiodic state due to radiation damage from the alpha-decay of actinides. Depending on the actinide concentration, the titanate pyrochlore will become amorphous in less than 1000 years of storage. Recently, systematic ion beam irradiations of a variety of pyrochlore compositions has revealed that many zirconate pyrochlores do not become amorphous, but remain crystalline as a defect fluorite structure-type due to disordering of the A- and B-site cations. The zirconate pyrochlores will remain crystalline even to very high doses, greater than 100 displacements per atom. Systematic experimental studies of actinide-doped and ion beam-irradiated pyrochlore, analyses of natural U- and Th-bearing pyrochlore, and simulations of the energetics of the disordering process now provide a rather detailed understanding of the structural and chemical controls on the response of pyrochlore to radiation. These results provide a solid basis for predicting the behavior and durability of pyrochlore used to immobilize plutonium.

Magnetic susceptibilities of actinide 3d-metal intermetallic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muniz, R.B.; d'Albuquerque e Castro, J.; Troper, A.

1988-04-15

We have numerically calculated the magnetic susceptibilities which appear in the Hartree--Fock instability criterion for actinide 3d transition-metal intermetallic compounds. This calculation is based on a previous tight-binding description of these actinide-based compounds (A. Troper and A. A. Gomes, Phys. Rev. B 34, 6487 (1986)). The parameters of the calculation, which starts from simple tight-binding d and f bands are (i) occupation numbers, (ii) ratio of d-f hybridization to d bandwidth, and (iii) electron-electron Coulomb-type interactions.

Method for extracting lanthanides and actinides from acid solutions

DOEpatents

Horwitz, E. Philip; Kalina, Dale G.; Kaplan, Louis; Mason, George W.

1985-01-01

A process for the recovery of actinide and lanthanide values from aqueous acidic solutions with an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms. 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.

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.

Actinide targets for fundamental research in nuclear physics

NASA Astrophysics Data System (ADS)

Eberhardt, K.; Düllmann, Ch. E.; Haas, R.; Mokry, Ch.; Runke, J.; Thörle-Pospiech, P.; Trautmann, N.

2018-05-01

Thin actinide layers deposited on various substrates are widely used as calibration sources in nuclear spectroscopy. Other applications include fundamental research in nuclear chemistry and -physics, e.g., the chemical and physical properties of super-heavy elements (SHE, Z > 103) or nuclear reaction studies with heavy ions. For the design of future nuclear reactors like fast-fission reactors and accelerator-driven systems for transmutation of nuclear waste, precise data for neutron absorption as well as neutron-induced fission cross section data for 242Pu with neutrons of different energies are of particular importance, requiring suitable Pu-targets. Another application includes studies of nuclear transitions in 229Th harvested as α-decay recoil product from a thin layer of its 233U precursor. For this, a thin and very smooth layer of 233U is used. We report here on the production of actinide layers mostly obtained by Molecular Plating (MP). MP is currently the only fabrication method in cases where the desired actinide material is available only in very limited amounts or possesses a high specific activity. Here, deposition is performed from organic solution applying a current density of 1-2 mA/cm2. Under these conditions target thicknesses of 500-1000 μg/cm2 are possible applying a single deposition step with deposition yields approaching 100 %. For yield determination α-particle spectroscopy, γ-spectroscopy and Neutron Activation Analysis is routinely used. Layer homogeneity is checked with Radiographic Imaging. As an alternative technique to MP the production of thin lanthanide and actinide layers by the so-called "Drop on Demand"-technique applied e.g., in ink-jet printing is currently under investigation.

Properties of pure single crystals of actinide compounds

NASA Astrophysics Data System (ADS)

Vogt, O.

1989-07-01

Actinide research started with substances of poor quality and a multitude of "unexplainable" results mostly found on powder samples of doubtful quality exerted some pressure on the crystal growers. As an example we may mention the measurements on UP. Type I antiferromagnetism was found below 123 K by neutron diffraction experiments on powdered samples. At 23 K another transition becomes apparent in susceptibility measurements. The change of the magnetic moments associated with this transition remained unexplained. It was only after the discovery of multi k structures in other actinide compounds that the need was seen to perform even inelastic neutron diffraction experiments on single crystals so that finally the true nature of the transition in UP could be revealed. NpAs is another illustrative example for the fact that sometimes it takes decades to get a clear understanding for things even so simple as macroscopic magnetic properties. The main reason for the need of single crystals is certainly the anisotropy of the magnetic moment encountered in all actinide compounds. Self-heating effects may prevent research on big crystals or might call for isotopic purity of certain samples.

Photochemical route to actinide-transition metal bonds: synthesis, characterization and reactivity of a series of thorium and uranium heterobimetallic complexes.

PubMed

Ward, Ashleigh L; Lukens, Wayne W; Lu, Connie C; Arnold, John

2014-03-05

A series of actinide-transition metal heterobimetallics has been prepared, featuring thorium, uranium, and cobalt. Complexes incorporating the binucleating ligand N[ο-(NHCH2P(i)Pr2)C6H4]3 with either Th(IV) (4) or U(IV) (5) and a carbonyl bridged [Co(CO)4](-) unit were synthesized from the corresponding actinide chlorides (Th: 2; U: 3) and Na[Co(CO)4]. Irradiation of the resulting isocarbonyls with ultraviolet light resulted in the formation of new species containing actinide-metal bonds in good yields (Th: 6; U: 7); this photolysis method provides a new approach to a relatively unusual class of complexes. Characterization by single-crystal X-ray diffraction revealed that elimination of the bridging carbonyl and formation of the metal-metal bond is accompanied by coordination of a phosphine arm from the N4P3 ligand to the cobalt center. Additionally, actinide-cobalt bonds of 3.0771(5) Å and 3.0319(7) Å for the thorium and uranium complexes, respectively, were observed. The solution-state behavior of the thorium complexes was evaluated using (1)H, (1)H-(1)H COSY, (31)P, and variable-temperature NMR spectroscopy. IR, UV-vis/NIR, and variable-temperature magnetic susceptibility measurements are also reported.

High-resolution X-ray absorption spectroscopy as a probe of crystal-field and covalency effects in actinide compounds

DOE PAGES

Butorin, Sergei M.; Kvashnina, Kristina O.; Vegelius, Johan R.; ...

2016-07-01

Applying the high-energy resolution fluorescence-detection (HERFD) mode of X-ray absorption spectroscopy (XAS), we were able to probe, for the first time to our knowledge, the crystalline electric field (CEF) splittings of the 5f shell directly in the HERFD-XAS spectra of actinides. Using ThO 2 as an example, data measured at the Th 3d edge were interpreted within the framework of the Anderson impurity model. Because the charge-transfer satellites were also resolved in the HERFD-XAS spectra, the analysis of these satellites revealed that ThO 2 is not an ionic compound as previously believed. The Th 6d occupancy in the ground statemore » was estimated to be twice that of the Th 5f states. Here, we demonstrate that HERFD-XAS allows for characterization of the CEF interaction and degree of covalency in the ground state of actinide compounds as it is extensively done for 3d transition metal systems.« less

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.

Exploiting the Reactivity of Actinide Fluoride Bonds for the Synthesis of a New Class of Bis(azide) Uranium Complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erickson, Karla A.; Lichtscheidl, Alejandro G.; Monreal, Marisa Jennifer

The terminal actinide fluoride bonds in (C 5Me 5) 2ThF 2(py) (py = pyridine) and (C 5Me 5) 2UF 2(O=PR 3) (R = Me, Ph) react with two equivalents of Me 3SiN 3 in toluene to form the polymeric thorium bis(azide), [(C 5Me 5) 2Th(N 3)2] ∞, and a new class of monometallic uranium bis(azide) complexes, (C 5Me 5) 2U(N 3)2(O=PR 3), respectively. Full characterization of the novel complexes (C 5Me 5) 2ThF 2(py) and (C 5Me 5) 2UF 2(O=PR 3) are reported, including the solid-state structures of (C 5Me 5) 2ThF 2(py) and (C 5Me 5) 2U(N 3) 2(O=PPhmore » 3). Lastly, electronic absorption spectral data are also reported for (C 5Me 5) 2AnF 2(py) (An = Th, U) and (C 5Me 5) 2U(N 3) 2(O=PR 3) to confirm metal oxidation state and enable elucidation of the fluoride and azide ligand bonding in these complexes.« less

Exploiting the Reactivity of Actinide Fluoride Bonds for the Synthesis of a New Class of Bis(azide) Uranium Complexes

DOE PAGES

Erickson, Karla A.; Lichtscheidl, Alejandro G.; Monreal, Marisa Jennifer; ...

2017-11-04

The terminal actinide fluoride bonds in (C 5Me 5) 2ThF 2(py) (py = pyridine) and (C 5Me 5) 2UF 2(O=PR 3) (R = Me, Ph) react with two equivalents of Me 3SiN 3 in toluene to form the polymeric thorium bis(azide), [(C 5Me 5) 2Th(N 3)2] ∞, and a new class of monometallic uranium bis(azide) complexes, (C 5Me 5) 2U(N 3)2(O=PR 3), respectively. Full characterization of the novel complexes (C 5Me 5) 2ThF 2(py) and (C 5Me 5) 2UF 2(O=PR 3) are reported, including the solid-state structures of (C 5Me 5) 2ThF 2(py) and (C 5Me 5) 2U(N 3) 2(O=PPhmore » 3). Lastly, electronic absorption spectral data are also reported for (C 5Me 5) 2AnF 2(py) (An = Th, U) and (C 5Me 5) 2U(N 3) 2(O=PR 3) to confirm metal oxidation state and enable elucidation of the fluoride and azide ligand bonding in these complexes.« less

Method for fluorination of actinide fluorides and oxyfluorides using O/sub 2/F/sub 2/

DOEpatents

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

1984-08-01

The present invention relates generally to methods of fluorination and more particularly to the use of O/sub 2/F/sub 2/ for the preparation of actinide hexafluorides, and for the extraction of deposited actinides and fluorides and oxyfluorides thereof from reaction vessels. The experiments set forth hereinabove demonstrate that the room temperature or below use of O/sub 2/F/sub 2/ will be highly beneficial for the preparation of pure actinide hexafluorides from their respective tetrafluorides without traces of HF being present as occurs using other fluorinating agents: and decontamination of equipment previously exposed to actinides: e.g., walls, feed lines, etc.

β4 systematics in rare-earth and actinide nuclei: sdg interacting boson model description

NASA Astrophysics Data System (ADS)

Devi, Y. D.; Kota, V. K. B.

1992-07-01

The observed variation of hexadecupole deformation parameter β4 with mass number A in rare-earth and actinide nuclei is studied in the sdg interacting boson model (IBM) using single j-shell Otsuka-Arima-Iachello mapped and IBM-2 to IBM-1 projected hexadecupole transition operator together with SUsdg(3) and SUsdg(5) coherent states. The SUsdg(3) limit is found to provide a good description of data.

The role of the 5f valence orbitals of early actinides in chemical bonding

PubMed Central

Vitova, T.; Pidchenko, I.; Fellhauer, D.; Bagus, P. S.; Joly, Y.; Pruessmann, T.; Bahl, S.; Gonzalez-Robles, E.; Rothe, J.; Altmaier, M.; Denecke, M. A.; Geckeis, H.

2017-01-01

One of the long standing debates in actinide chemistry is the level of localization and participation of the actinide 5f valence orbitals in covalent bonds across the actinide series. Here we illuminate the role of the 5f valence orbitals of uranium, neptunium and plutonium in chemical bonding using advanced spectroscopies: actinide M4,5 HR-XANES and 3d4f RIXS. Results reveal that the 5f orbitals are active in the chemical bonding for uranium and neptunium, shown by significant variations in the level of their localization evidenced in the spectra. In contrast, the 5f orbitals of plutonium appear localized and surprisingly insensitive to different bonding environments. We envisage that this report of using relative energy differences between the 5fδ/ϕ and 5fπ*/5fσ* orbitals as a qualitative measure of overlap-driven actinyl bond covalency will spark activity, and extend to numerous applications of RIXS and HR-XANES to gain new insights into the electronic structures of the actinide elements. PMID:28681848

The role of the 5f valence orbitals of early actinides in chemical bonding

NASA Astrophysics Data System (ADS)

Vitova, T.; Pidchenko, I.; Fellhauer, D.; Bagus, P. S.; Joly, Y.; Pruessmann, T.; Bahl, S.; Gonzalez-Robles, E.; Rothe, J.; Altmaier, M.; Denecke, M. A.; Geckeis, H.

2017-07-01

One of the long standing debates in actinide chemistry is the level of localization and participation of the actinide 5f valence orbitals in covalent bonds across the actinide series. Here we illuminate the role of the 5f valence orbitals of uranium, neptunium and plutonium in chemical bonding using advanced spectroscopies: actinide M4,5 HR-XANES and 3d4f RIXS. Results reveal that the 5f orbitals are active in the chemical bonding for uranium and neptunium, shown by significant variations in the level of their localization evidenced in the spectra. In contrast, the 5f orbitals of plutonium appear localized and surprisingly insensitive to different bonding environments. We envisage that this report of using relative energy differences between the 5fδ/φ and 5fπ*/5fσ* orbitals as a qualitative measure of overlap-driven actinyl bond covalency will spark activity, and extend to numerous applications of RIXS and HR-XANES to gain new insights into the electronic structures of the actinide elements.

Crystalline matrices for the immobilization of plutonium and actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, E.B.; Burakov, E.E.; Galkin, Ya.B.

1996-05-01

The management of weapon plutonium, disengaged as a result of conversion, is considered together with the problem of the actinide fraction of long-lived high level radioactive wastes. It is proposed to use polymineral ceramics based on crystalline host-phases: zircon ZrSiO{sub 4} and zirconium dioxide ZrO{sub 2}, for various variants of the management of plutonium and actinides (including the purposes of long-term safe storage or final disposal from the human activity sphere). It is shown that plutonium and actinides are able to form with these phases on ZrSiO{sub 4} and ZrO{sub 2} was done on laboratory level by the hot pressingmore » method, using the plasmochemical calcination technology. To incorporate simulators of plutonium into the structure of ZrSiO{sub 4} and ZrO{sub 2} in the course of synthesis, an original method developed by the authors as a result of studying the high-uranium zircon (Zr,U) SiO{sub 4} form Chernobyl {open_quotes}lavas{close_quotes} was used.« less

Actinide electronic structure and atomic forces

NASA Astrophysics Data System (ADS)

Albers, R. C.; Rudin, Sven P.; Trinkle, Dallas R.; Jones, M. D.

2000-07-01

We have developed a new method[1] of fitting tight-binding parameterizations based on functional forms developed at the Naval Research Laboratory.[2] We have applied these methods to actinide metals and report our success using them (see below). The fitting procedure uses first-principles local-density-approximation (LDA) linear augmented plane-wave (LAPW) band structure techniques[3] to first calculate an electronic-structure band structure and total energy for fcc, bcc, and simple cubic crystal structures for the actinide of interest. The tight-binding parameterization is then chosen to fit the detailed energy eigenvalues of the bands along symmetry directions, and the symmetry of the parameterization is constrained to agree with the correct symmetry of the LDA band structure at each eigenvalue and k-vector that is fit to. By fitting to a range of different volumes and the three different crystal structures, we find that the resulting parameterization is robust and appears to accurately calculate other crystal structures and properties of interest.

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.

Joint Actinide Shock Physics Experimental Research - JASPER

ScienceCinema

None

2018-01-16

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.

Fission of actinide nuclei using multi-nucleon transfer reactions

NASA Astrophysics Data System (ADS)

Léguillon, Romain; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Makii, Hiroyuki; Nishinaka, Ichiro; Ishii, Tetsuro; Tsukada, Kazuaki; Asai, Masato; Chiba, Satoshi; Ohtsuki, Tsutomu; Araki, Shohei; Watanabe, Yukinobu; Tatsuzawa, Ryotaro; Takaki, Naoyuki

2014-09-01

We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. Present study is supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan.

Testing actinide fission yield treatment in CINDER90 for use in MCNP6 burnup calculations

DOE PAGES

Fensin, Michael Lorne; Umbel, Marissa

2015-09-18

Most of the development of the MCNPX/6 burnup capability focused on features that were applied to the Boltzman transport or used to prepare coefficients for use in CINDER90, with little change to CINDER90 or the CINDER90 data. Though a scheme exists for best solving the coupled Boltzman and Bateman equations, the most significant approximation is that the employed nuclear data are correct and complete. Thus, the CINDER90 library file contains 60 different actinide fission yields encompassing 36 fissionable actinides (thermal, fast, high energy and spontaneous fission). Fission reaction data exists for more than 60 actinides and as a result, fissionmore » yield data must be approximated for actinides that do not possess fission yield information. Several types of approximations are used for estimating fission yields for actinides which do not possess explicit fission yield data. The objective of this study is to test whether or not certain approximations of fission yield selection have any impact on predictability of major actinides and fission products. Further we assess which other fission products, available in MCNP6 Tier 3, result in the largest difference in production. Because the CINDER90 library file is in ASCII format and therefore easily amendable, we assess reasons for choosing, as well as compare actinide and major fission product prediction for the H. B. Robinson benchmark for, three separate fission yield selection methods: (1) the current CINDER90 library file method (Base); (2) the element method (Element); and (3) the isobar method (Isobar). Results show that the three methods tested result in similar prediction of major actinides, Tc-99 and Cs-137; however, certain fission products resulted in significantly different production depending on the method of choice.« less

Analogue Study of Actinide Transport at Sites in Russia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novikov, A P; Simmons, A M; Halsey, W G

2003-02-12

The U. S. Department of Energy (DOE) and the Russian Academy of Sciences (RAS) are engaged in a three-year cooperative study to observe the behavior of actinides in the natural environment at selected disposal sites and/or contamination sites in Russia. The purpose is to develop experimental data and models for actinide speciation, mobilization and transport processes in support of geologic repository design, safety and performance analyses. Currently at the mid-point of the study, the accomplishments to date include: evaluation of existing data and data needs, site screening and selection, initial data acquisition, and development of preliminary conceptual models.

Development of ion beam sputtering techniques for actinide target preparation

NASA Astrophysics Data System (ADS)

Aaron, W. S.; Zevenbergen, L. A.; Adair, H. L.

1985-06-01

Ion beam sputtering is a routine method for the preparation of thin films used as targets because it allows the use of a minimum quantity of starting material, and losses are much lower than most other vacuum deposition techniques. Work is underway in the Isotope Research Materials Laboratory (IRML) at ORNL to develop the techniques that will make the preparation of actinide targets up to 100 μg/cm 2 by ion beam sputtering a routinely available service from IRML. The preparation of the actinide material in a form suitable for sputtering is a key to this technique, as is designing a sputtering system that allows the flexibility required for custom-ordered target production. At present, development work is being conducted on low-activity actinides in a bench-top system. The system will then be installed in a hood or glove box approved for radioactive materials handling where processing of radium, actinium, and plutonium isotopes among others will be performed.

Development of Metallic Fuels for Actinide Transmutation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, Steven Lowe; Fielding, Randall Sidney; Benson, Michael Timothy

between 10 and 60%. In general, the performance of all of these substantially disparate metallic fuel alloys has been observed to be excellent, and their irradiation behaviors are generally consistent with historic norms for metallic fuels without minor actinide additions and having lower Pu or Zr contents. Future work is being undertaken with a view toward increasing the burnup potential of metallic fuels even more. Design innovations under investigation include: 1) lowering the fuel smear density in order to accommodate more swelling, 2) annular fuel geometry to eliminate the need for a sodium bond, 3) minor alloy additions to stabilize lanthanide fission products inside the fuel and prevent their transport to the cladding where they can participate in fuel-cladding chemical interaction (FCCI), and 4) coatings/liners on the cladding inner surface to mitigate FCCI and enable higher temperature operation. This paper will present the current state of development of metallic fuels for actinide transmutation in the US. Highlights will include recent results from metallic fuel casting experiments, experiments to identify alloy additions to immobilize lanthanide fission products, and postirradiation examinations of annular metallic fuels at low burnup.« less

Zirconium behaviour during electrorefining of actinide-zirconium alloy in molten LiCl-KCl on aluminium cathodes

NASA Astrophysics Data System (ADS)

Meier, R.; Souček, P.; Malmbeck, R.; Krachler, M.; Rodrigues, A.; Claux, B.; Glatz, J.-P.; Fanghänel, Th.

2016-04-01

A pyrochemical electrorefining process for the recovery of actinides from metallic nuclear fuel based on actinide-zirconium alloys (An-Zr) in a molten salt is being investigated. In this process actinides are group-selectively recovered on solid aluminium cathodes as An-Al alloys using a LiCl-KCl eutectic melt at a temperature of 450 °C. In the present study the electrochemical behaviour of zirconium during electrorefining was investigated. The maximum amount of actinides that can be oxidised without anodic co-dissolution of zirconium was determined at a selected constant cathodic current density. The experiment consisted of three steps to assess the different stages of the electrorefining process, each of which employing a fresh aluminium cathode. The results indicate that almost a complete dissolution of the actinides without co-dissolution of zirconium is possible under the applied experimental conditions.

Oxidation State Discrimination in the Atomic Layer Deposition of Vanadium Oxides

DOE PAGES

Weimer, Matthew S.; Kim, In Soo; Guo, Peijun; ...

2017-06-02

We describe the use of a vanadium 3+ precursor for atomic layer deposition (ALD) of thin films that span the common oxidation states of vanadium oxides. Self-limiting surface synthesis of V 2O 3, VO 2, and V 2O 5 are realized via four distinct reaction mechanisms accessed via judicious choice of oxygen ALD partners. In situ quartz crystal microbalance and quadrupole mass spectrometry were used to study the reaction mechanism of the vanadium precursor with O 3, H 2O 2, H 2O/O 2, and H 2O 2/H 2. A clear distinction between non-oxidative protic ligand exchange and metal oxidation ismore » demonstrated through sequential surface reactions with different non-metal precursors. This synergistic effect, provides greater control of the resultant metal species in the film, as well as reactive surface species during growth. In an extension of this approach, we introduce oxidation state control through reducing equivalents of H 2 gas. When H 2 is dosed after H 2O 2 during growth, amorphous films of VO 2 are deposited that are readily crystallized with a low temperature anneal. These VO 2 films show a temperature dependent Raman spectroscopy response in the expected range and consistent with the well-known phase-change behavior of VO 2.« less

Using X-ray absorption to probe sulfur oxidation states in complex molecules

NASA Astrophysics Data System (ADS)

Vairavamurthy, A.

1998-10-01

X-ray absorption near-edge structure (XANES) spectroscopy offers an important non-destructive tool for determining oxidation states and for characterizing chemical speciation. The technique was used to experimentally verify the oxidation states of sulfur in different types of complex molecules because there are irregularities and uncertainties in assigning the values traditionally. The usual practice of determining oxidation states involves using a set of conventional rules. The oxidation state is an important control in the chemical speciation of sulfur, ranging from -2 to +6 in its different compounds. Experimental oxidation-state values for various types of sulfur compounds, using their XANES peak-energy positions, were assigned from a scale in which elemental sulfur and sulfate are designated as 0 and +6, respectively. Because these XANES-based values differed considerably from conventionally determined oxidation states for most sulfur compounds, a new term 'oxidation index' was coined to describe them. The experimental values were closer to those conventional values obtained by assigning shared electrons to the more electronegative atoms than to those based on other customary rules for assigning them. Because the oxidation index is distinct and characteristic for each different type of sulfur functionality, it becomes an important parameter for characterizing sulfur species, and for experimentally verifying uncertain oxidation states.

Correlation consistent basis sets for actinides. I. The Th and U atoms.

PubMed

Peterson, Kirk A

2015-02-21

New correlation consistent basis sets based on both pseudopotential (PP) and all-electron Douglas-Kroll-Hess (DKH) Hamiltonians have been developed from double- to quadruple-zeta quality for the actinide atoms thorium and uranium. Sets for valence electron correlation (5f6s6p6d), cc - pV nZ - PP and cc - pV nZ - DK3, as well as outer-core correlation (valence + 5s5p5d), cc - pwCV nZ - PP and cc - pwCV nZ - DK3, are reported (n = D, T, Q). The -PP sets are constructed in conjunction with small-core, 60-electron PPs, while the -DK3 sets utilized the 3rd-order Douglas-Kroll-Hess scalar relativistic Hamiltonian. Both series of basis sets show systematic convergence towards the complete basis set limit, both at the Hartree-Fock and correlated levels of theory, making them amenable to standard basis set extrapolation techniques. To assess the utility of the new basis sets, extensive coupled cluster composite thermochemistry calculations of ThFn (n = 2 - 4), ThO2, and UFn (n = 4 - 6) have been carried out. After accurately accounting for valence and outer-core correlation, spin-orbit coupling, and even Lamb shift effects, the final 298 K atomization enthalpies of ThF4, ThF3, ThF2, and ThO2 are all within their experimental uncertainties. Bond dissociation energies of ThF4 and ThF3, as well as UF6 and UF5, were similarly accurate. The derived enthalpies of formation for these species also showed a very satisfactory agreement with experiment, demonstrating that the new basis sets allow for the use of accurate composite schemes just as in molecular systems composed only of lighter atoms. The differences between the PP and DK3 approaches were found to increase with the change in formal oxidation state on the actinide atom, approaching 5-6 kcal/mol for the atomization enthalpies of ThF4 and ThO2. The DKH3 atomization energy of ThO2 was calculated to be smaller than the DKH2 value by ∼1 kcal/mol.

Recovery of actinides from actinide-aluminium alloys by chlorination: Part III - Chlorination with HCl(g)

NASA Astrophysics Data System (ADS)

Meier, Roland; Souček, Pavel; Walter, Olaf; Malmbeck, Rikard; Rodrigues, Alcide; Glatz, Jean-Paul; Fanghänel, Thomas

2018-01-01

Two steps of a pyrochemical route for the recovery of actinides from spent metallic nuclear fuel are being investigated at JRC-Karlsruhe. The first step consists in electrorefining the fuel in molten salt medium implying aluminium cathodes. The second step is a chlorination process for the separation of actinides (An) from An-Al alloys formed on the cathodes. The chlorination process, in turn, consists of three steps; the distillation of adhered salt (1), the chlorination of An-Al by HCl/Cl2 under formation of AlCl3 and An chlorides (2), and the subsequent sublimation of AlCl3 (3). In the present work UAl2, UAl3, NpAl2, and PuAl2 were chlorinated with HCl(g) in a temperature range between 300 and 400 °C forming UCl4, NpCl4 or PuCl3 as the major An containing phases, respectively. Thermodynamic calculations were carried out to support the experimental work. The results showed a high chlorination efficiency for all used starting materials and indicated that the sublimation step may not be necessary when using HCl(g).

Crystal Growth and Characterization of THO2 and UxTh1-xO2

DTIC Science & Technology

2013-03-01

bulk actinide crystals would open up new possibilities for the detection of weapons of mass destruction, the study of the effect of aging on...way of growing bulk actinide materials of optical quality. These refractory oxide single crystals offer potential applications in thorium nuclear...fuel technology, wide-band-gap uranium-based direct-conversion solid state neutron detectors, and understanding how actinide fuels age with time. ThO2

Method for fluorination of actinide fluorides and oxyfluorides thereof using O.sub.2 F.sub.2

DOEpatents

Eller, Phillip G.; Malm, John G.; Penneman, Robert A.

1988-01-01

Method for fluorination of actinides and fluorides and oxyfluorides thereof using O.sub.2 F.sub.2 which generates actinide hexafluorides, and for removal of actinides and compounds thereof from surfaces upon which they appear as unwanted deposits. The fluorinating agent, O.sub.2 F.sub.2, has been observed to readily 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 thereby not destroyed by high temperature reactions with the walls of the reaction vessel. Dioxygen difluoride is easily prepared, stored and transferred to the desired place of reaction.

Method for fluorination of actinide fluorides and oxyfluorides thereof using O[sub 2]F[sub 2

DOEpatents

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

1988-11-08

Method is described for fluorination of actinides and fluorides and oxyfluorides thereof using O[sub 2]F[sub 2] which generates actinide hexafluorides, and for removal of actinides and compounds thereof from surfaces upon which they appear as unwanted deposits. The fluorinating agent, O[sub 2]F[sub 2], has been observed to readily 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 thereby not destroyed by high temperature reactions with the walls of the reaction vessel. Dioxygen difluoride is easily prepared, stored and transferred to the desired place of reaction.

Trivalent Lanthanide/Actinide Separation Using Aqueous-Modified TALSPEAK Chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Travis S. Grimes; Richard D. Tillotson; Leigh R. Martin

TALSPEAK is a liquid/liquid extraction process designed to separate trivalent lanthanides (Ln3+) from minor actinides (MAs) Am3+ and Cm3+. Traditional TALSPEAK organic phase is comprised of a monoacidic dialkyl bis(2-ethylhexyl)phosphoric acid extractant (HDEHP) in diisopropyl benzene (DIPB). The aqueous phase contains a soluble aminopolycarboxylate diethylenetriamine-N,N,N’,N”,N”-pentaacetic acid (DTPA) in a concentrated (1.0-2.0 M) lactic acid (HL) buffer with the aqueous acidity typically adjusted to pH 3.0. TALSPEAK balances the selective complexation of the actinides by DTPA against the electrostatic attraction of the lanthanides by the HDEHP extractant to achieve the desired trivalent lanthanide/actinide group separation. Although TALSPEAK is considered a successfulmore » separations scheme, recent fundamental studies have highlighted complex chemical interactions occurring in the aqueous and organic phases during the extraction process. Previous attempts to model the system have shown thermodynamic models do not accurately predict the observed extraction trends in the p[H+] range 2.5-4.8. In this study, the aqueous phase is modified by replacing the lactic acid buffer with a variety of simple and longer-chain amino acid buffers. The results show successful trivalent lanthanide/actinide group separation with the aqueous-modified TALSPEAK process at pH 2. The amino acid buffer concentrations were reduced to 0.5 M (at pH 2) and separations were performed without any effect on phase transfer kinetics. Successful modeling of the aqueous-modified TALSPEAK process (p[H+] 1.6-3.1) using a simplified thermodynamic model and an internally consistent set of thermodynamic data is presented.« less

SOLVENT EXTRACTION PROCESS FOR SEPARATING ACTINIDE AND LANTHANIDE METAL VALUES

DOEpatents

Hildebrandt, R.A.; Hyman, H.H.; Vogler, S.

1962-08-14

A process of countercurrently extracting an aqueous mineral acid feed solution for the separation of actinides from lanthanides dissolved therern is described. The feed solution is made acid-defrcient with alkali metal hydroxide prior to.contact with acid extractant; during extraction, however, acid is transferred from organic to aqueous solution and the aqueous solution gradually becomes acid. The acid-deficient phase ' of the process promotes the extraction of the actinides, while the latter acid phase'' of the process improves retention of the lanthanides in the aqueous solution. This provides for an improved separation. (AEC)

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

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

Trends in the short-term release of fission products and actinides to aqueous solution from used CANDU fuels at elevated temperature

NASA Astrophysics Data System (ADS)

Stroes-Gascoyne, S.

1992-08-01

A large number of short-term leaching experiments has been performed to determine fission product and actinide release from used CANDU (CANada Deuterium Uranium) fuels and to establish which factors affect release. Results are reported after30 ± 10 d leaching at 100-150°C under oxidizing (air) or reducing (Ar-3% H 2 or Ar) conditions, in various synthetic groundwaters. Cesium-137 release (0.007-6%) was positively correlated with increases in fuel power, leachant temperature and ionic strength. Strontium-90 release (0.0003-0.3%) generally increased with ionic strength, higher temperature and redox conditions. Actinide and Tc concentrations were compared to ranges calculated with a thermodynamic equilibrium model, that accounts for the uncertain geochemical parameters of a nuclear waste vault by calculating concentration ranges based on 40000 hypothetical cases. Experimental U concentrations (10 -8.5 to 10 -3 mol/kg) were higher than the model range, probably because of higher redox potentials in the experiments. Measured Pu concentrations (10 -12.5 to 10 -7 mol/kg) were at the low end of the calculated range. Americium and Cm concentrations (10 -12.5 to 10 -7 and 10 -15 to 10 -9 mol/kg, respectively) were highest under oxidizing conditions and higher temperatures. Technetium-99 concentrations (10 -5.5 to 10 -10.5 mol/kg) covered a much narrower range than calculated by the model.

Spin State Control of the Perovskite Rh/Co Oxides

PubMed Central

Terasaki, Ichiro; Shibasaki, Soichiro; Yoshida, Shin; Kobayashi, Wataru

2010-01-01

We show why and how the spin state of transition-metal ions affects the thermoelectric properties of transition-metal oxides by investigating two perovskite-related oxides. In the A-site ordered cobalt oxide Sr3YCo4O10.5, partial substitution of Ca for Sr acts as chemical pressure, which compresses the unit cell volume to drive the spin state crossover, and concomitantly changes the magnetization and thermopower. In the perovskite rhodium oxide LaRhO3, partial substitution of Sr for La acts as hole-doping, and the resistivity and thermopower decrease systematically with the Sr concentration. The thermopower remains large values at high temperatures (>150 μV/K at 800 K), which makes a remarkable contrast to La1−xSrxCoO3. We associate this with the stability of the low spin state of the Rh3+ ions.

Georgia Institute of Technology research on the Gas Core Actinide Transmutation Reactor (GCATR)

NASA Technical Reports Server (NTRS)

Clement, J. D.; Rust, J. H.; Schneider, A.; Hohl, F.

1976-01-01

The program reviewed is a study of the feasibility, design, and optimization of the GCATR. The program is designed to take advantage of initial results and to continue work carried out on the Gas Core Breeder Reactor. The program complements NASA's program of developing UF6 fueled cavity reactors for power, nuclear pumped lasers, and other advanced technology applications. The program comprises: (1) General Studies--Parametric survey calculations performed to examine the effects of reactor spectrum and flux level on the actinide transmutation for GCATR conditions. The sensitivity of the results to neutron cross sections are to be assessed. Specifically, the parametric calculations of the actinide transmutation are to include the mass, isotope composition, fission and capture rates, reactivity effects, and neutron activity of recycled actinides. (2) GCATR Design Studies--This task is a major thrust of the proposed research program. Several subtasks are considered: optimization criteria studies of the blanket and fuel reprocessing, the actinide insertion and recirculation system, and the system integration. A brief review of the background of the GCATR and ongoing research is presented.

Supercritical Fluid Extraction and Separation of Uranium from Other Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2014-06-01

This paper investigates the feasibility of separating uranium from other actinides by using supercritical fluid carbon dioxide (sc-CO2) as a solvent modified with tri-n-butylphosphate (TBP) for the development of an extraction and counter current stripping technique, which would be a more efficient and environmentally benign technology for used nuclear fuel reprocessing compared to traditional solvent extraction. Several actinides (U(VI), Np(VI), Pu(IV), and Am(III)) 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, the separation of uraniummore » from plutonium in sc-CO2 modified with TBP was successful at nitric acid concentrations of less than 3 M in the presence of acetohydroxamic acid or oxalic acid, and the separation of uranium from neptunium was successful at nitric acid concentrations of less than 1 M in the presence of acetohydroxamic acid, oxalic acid, or sodium nitrite.« less

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]).

Complexation of lanthanides and actinides by acetohydroxamic acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, R.J.; Sinkov, S.I.; Choppin, G.R.

2008-07-01

Acetohydroxamic acid (AHA) has been proposed as a suitable reagent for the complexant-based, as opposed to reductive, stripping of plutonium and neptunium ions from the tributylphosphate solvent phase in advanced PUREX or UREX processes designed for future nuclear-fuel reprocessing. Stripping is achieved by the formation of strong hydrophilic complexes with the tetravalent actinides in nitric acid solutions. To underpin such applications, knowledge of the complexation constants of AHA with all relevant actinide (5f) and lanthanide (4f) ions is therefore important. This paper reports the determination of stability constants of AHA with the heavier lanthanide ions (Dy-Yb) and also U(IV) andmore » Th(IV) ions. Comparisons with our previously published AHA stability-constant data for 4f and 5f ions are made. (authors)« less

LLNL SFA OBER SBR FY17 Program Management and Performance Report: Subsurface Biogeochemistry of Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kersting, Annie B.

A major scientific challenge in environmental sciences is to identify the dominant processes controlling actinide transport in the environment. It is estimated that currently, over 2200 metric tons of anthropogenic plutonium (Pu) has accumulated worldwide, a number that increases yearly with additional spent nuclear fuel (Ewing et al., 2010). Plutonium has been shown to migrate on the scale of kilometers, giving way to a critical concern that the fundamental biogeochemical processes that control its behavior in the subsurface are not well understood (Kersting et al. 1999; Novikov et al. 2006; Santschi et al. 2002). Neptunium (Np) is less prevalent inmore » the environment; however, it is predicted to be a significant long-term dose contributor in high-level nuclear waste. Our focus on Np chemistry in this Science Plan is intended to help formulate a better understanding of Pu redox transformations in the environment and clarify the differences between the two long-lived actinides. The research approach of our Science Plan combines (1) Fundamental Mechanistic Studies that identify and quantify biogeochemical processes that control actinide behavior in solution and on solids, (2) Field Integration Studies that investigate the transport characteristics of Pu and test our conceptual understanding of actinide transport, and (3) Actinide Research Capabilities that allow us to achieve the objectives of this Scientific Focus Area (SFA) and provide new opportunities for advancing actinide environmental chemistry. These three Research Thrusts form the basis of our SFA Science Program.« less

Increased retention of americium in kidneys as compared with plutonium in an actinide wound contamination model in the rat.

PubMed

Griffiths, Nina M; Coudert, Sylvie; Molina, Thibaut; Wilk, Jean-Claude; Renault, Daniel; Berard, Philippe; Van der Meeren, Anne

2014-11-01

Americium-241 ((241)Am) presents a potential risk for nuclear industry workers associated with reactor decommissioning and aging combustible materials. The purpose of this study was to investigate Am renal retention after actinide contamination by wounding in the rat. Anesthetized rats were contaminated with Mixed Oxide (MOX) (7.1% Plutonium [Pu] by mass and containing 27% Am as % total alpha activity), Pu or Am nitrate following an incision wound of the hind leg. Times of euthanasia ranged from 2 hours to 5 months after contamination. Pu and Am levels were quantified following radiochemistry and alpha-spectrophotometry. Initial data show that over the experimental period the proportion of Am in kidneys as a fraction of total kidney alpha activity was elevated as compared to MOX powder indicating a specific retention in this organ. The percentage of Pu was similar to the powder. After MOX contamination, kidney to liver ratios appeared to increase more markedly for Am (from 0.2 at 7 days to 0.6 at 90 days) as compared with Pu (0.1 at 7 days to 0.2 at 90 days). In accordance with tissue actinide retention the dose from Am to the kidney increases with time. For comparison, the ratio of estimated equivalent doses due to Am to kidney is 1.5-fold greater than for Pu (around 90 versus 60 mSv). After actinide contamination of wounds, Am is concentrated in the kidneys as compared to Pu leading to potential exposure of renal tissue to both alpha particles and gamma radiation.

Local structure in solid solutions of stabilised zirconia with actinide dioxides (UO{sub 2}, NpO{sub 2})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walter, Marcus, E-mail: marcus.walter@vkta.d; Somers, Joseph; Bouexiere, Daniel

2011-04-15

The local structure of (Zr,Lu,U)O{sub 2-x} and (Zr,Y,Np)O{sub 2-x} solid solutions has been investigated by extended X-ray absorption fine structure (EXAFS). Samples were prepared by mixing reactive (Zr,Lu)O{sub 2-x} and (Zr,Y)O{sub 2-x} precursor materials with the actinide oxide powders, respectively. Sintering at 1600 {sup o}C in Ar/H{sub 2} yields a fluorite structure with U(IV) and Np(IV). As typical for stabilised zirconia the metal-oxygen and metal-metal distances are characteristic for the different metal ions. The bond lengths increase with actinide concentration, whereas highest adaptation to the bulk stabilised zirconia structure was observed for U---O and Np---O bonds. The Zr---O bond showsmore » only a slight increase from 2.14 A at 6 mol% actinide to 2.18 A at infinite dilution in UO{sub 2} and NpO{sub 2}. The short interatomic distance between Zr and the surrounding oxygen and metal atoms indicate a low relaxation of Zr with respect to the bulk structure, i.e. a strong Pauling behaviour. -- Graphical abstract: Metal-oxygen bond distances in (Zr,Lu,U)O{sub 2-x} solid solutions with different oxygen vacancy concentrations (Lu/Zr=1 and Lu/Zr=0.5). Display Omitted Research Highlights: {yields} EXAFS indicates high U and Np adaption to the bulk structure of stabilised zirconia. {yields} Zr---O bond length is 2.18 A at infinite Zr dilution in UO{sub 2} and NpO{sub 2}. {yields} Low relaxation (strong Pauling behaviour) of Zr explains its low solubility in UO{sub 2}.« less

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.

Thermal NF3 fluorination/oxidation of cobalt, yttrium, zirconium, and selected lanthanide oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheele, Randall D.; McNamara, Bruce K.; Casella, Andrew M.

2013-02-01

This paper presents results of our continuing investigation on the use of nitrogen trifluoride as a fluorination or fluorination/oxidation agent for separating valuable constituents from used nuclear fuels by exploiting the different volatilities of the constituent fission product and actinide fluorides. This article focuses on fission products that do not have volatile fluorides or oxyfluorides at expected operations temperatures. Our thermodynamic calculations show that nitrogen trifluoride has the potential to completely fluorinate fission product oxides to their fluorides. Simultaneous thermogravimetric and differential thermal analyses show that the oxides of cobalt, zirconium, and the lanthanides are fluorinated but do not formmore » volatile fluorides when treated with nitrogen trifluoride at temperatures up to 550°C. Our studies of gadolinium-doped commercial nuclear fuel indicate that nitrogen trifluoride can extract uranium from the non-volatile gadolinium.« less

An Approach for Validating Actinide and Fission Product Burnup Credit Criticality Safety Analyses: Criticality (k eff) Predictions

DOE PAGES

Scaglione, John M.; Mueller, Don E.; Wagner, John C.

2014-12-01

One of the most important remaining challenges associated with expanded implementation of burnup credit in the United States is the validation of depletion and criticality calculations used in the safety evaluation—in particular, the availability and use of applicable measured data to support validation, especially for fission products (FPs). Applicants and regulatory reviewers have been constrained by both a scarcity of data and a lack of clear technical basis or approach for use of the data. In this study, this paper describes a validation approach for commercial spent nuclear fuel (SNF) criticality safety (k eff) evaluations based on best-available data andmore » methods and applies the approach for representative SNF storage and transport configurations/conditions to demonstrate its usage and applicability, as well as to provide reference bias results. The criticality validation approach utilizes not only available laboratory critical experiment (LCE) data from the International Handbook of Evaluated Criticality Safety Benchmark Experiments and the French Haut Taux de Combustion program to support validation of the principal actinides but also calculated sensitivities, nuclear data uncertainties, and limited available FP LCE data to predict and verify individual biases for relevant minor actinides and FPs. The results demonstrate that (a) sufficient critical experiment data exist to adequately validate k eff calculations via conventional validation approaches for the primary actinides, (b) sensitivity-based critical experiment selection is more appropriate for generating accurate application model bias and uncertainty, and (c) calculated sensitivities and nuclear data uncertainties can be used for generating conservative estimates of bias for minor actinides and FPs. Results based on the SCALE 6.1 and the ENDF/B-VII.0 cross-section libraries indicate that a conservative estimate of the bias for the minor actinides and FPs is 1.5% of their worth within the

Ionic Interactions in Actinide Tetrahalides

NASA Astrophysics Data System (ADS)

Akdeniz, Z.; Karaman, A.; Tosi, M. P.

2001-05-01

We determine a model of the ionic interactions in AX 4 compounds (where A is an atom in the actinide series from Th to Am and X = F, Cl, Br or I) by an analysis of data on the static and dynamic structure of their molecular monomers. The potential energy function that we adopt is taken from earlier work on rare-earth trihalides [Z. Akdeniz, Z. Q q e k and M. P. Tosi, Z. Naturforsch. 55a, 861 (2000)] and in particular allows for the electronic polarizability of the actinide ion. This polarizability quantitatively determines the antisymmetric-bending vibrational mode, but its magnitude remains compatible with a symmetric tetrahedral shape of the molecule at equilibrium. The fluorides have an especially high degree of ionic character, and the interionic-force parameters for each halide of the U, Np, Pu and Am series show regular trends, suggesting that extrapolations to the other transuranic-element halides may usefully be made. The Th compounds show some deviations from these trends, and the interionic-force model that we determine for ThCl4 differs somewhat from that obtained in a previous study. We therefore return on the evaluation of the relative stability of charged oligomers of ThCl4 and ZrCl4 and find confirmation of our earlier results on this problem.

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

PubMed Central

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

2015-01-01

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. PMID:26056725

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szymanski, Craig J.; Munusamy, Prabhakaran; Mihai, Cosmin

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 quantifiedmore » 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.« less

Benchmark Evaluation of Dounreay Prototype Fast Reactor Minor Actinide Depletion Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hess, J. D.; Gauld, I. C.; Gulliford, J.

2017-01-01

Historic measurements of actinide samples in the Dounreay Prototype Fast Reactor (PFR) are of interest for modern nuclear data and simulation validation. Samples of various higher-actinide isotopes were irradiated for 492 effective full-power days and radiochemically assayed at Oak Ridge National Laboratory (ORNL) and Japan Atomic Energy Research Institute (JAERI). Limited data were available regarding the PFR irradiation; a six-group neutron spectra was available with some power history data to support a burnup depletion analysis validation study. Under the guidance of the Organisation for Economic Co-Operation and Development Nuclear Energy Agency (OECD NEA), the International Reactor Physics Experiment Evaluation Projectmore » (IRPhEP) and Spent Fuel Isotopic Composition (SFCOMPO) Project are collaborating to recover all measurement data pertaining to these measurements, including collaboration with the United Kingdom to obtain pertinent reactor physics design and operational history data. These activities will produce internationally peer-reviewed benchmark data to support validation of minor actinide cross section data and modern neutronic simulation of fast reactors with accompanying fuel cycle activities such as transportation, recycling, storage, and criticality safety.« less

Dynamical approach to heavy-ion induced fusion using actinide target

NASA Astrophysics Data System (ADS)

Aritomo, Y.; Hagino, K.; Chiba, S.; Nishio, K.

2012-10-01

To treat heavy-ion reactions using actinide target nucleus, we propose a model which takes into account the coupling to the collective states of interacting nuclei in the penetration of the Coulomb barrier and the dynamical evolution of nuclear shape from the contact configuration. A fluctuation-dissipation model (Langevin equation) was applied in the dynamical calculation, where effect of nuclear orientation at the initial impact on the prolately deformed target nucleus was considered. Using this model, we analyzed the experimental data for the mass distribution of fission fragments (MDFF) in the reaction of 36S+238U at several incident energies. Fusion-fission, quasifission and deep-quasi-fission are separated as different trajectories on the potential energy surface. We estimated the fusion cross section of the reaction.

Correlation consistent basis sets for actinides. I. The Th and U atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, Kirk A., E-mail: kipeters@wsu.edu

New correlation consistent basis sets based on both pseudopotential (PP) and all-electron Douglas-Kroll-Hess (DKH) Hamiltonians have been developed from double- to quadruple-zeta quality for the actinide atoms thorium and uranium. Sets for valence electron correlation (5f6s6p6d), cc − pV nZ − PP and cc − pV nZ − DK3, as well as outer-core correlation (valence + 5s5p5d), cc − pwCV nZ − PP and cc − pwCV nZ − DK3, are reported (n = D, T, Q). The -PP sets are constructed in conjunction with small-core, 60-electron PPs, while the -DK3 sets utilized the 3rd-order Douglas-Kroll-Hess scalar relativistic Hamiltonian. Bothmore » series of basis sets show systematic convergence towards the complete basis set limit, both at the Hartree-Fock and correlated levels of theory, making them amenable to standard basis set extrapolation techniques. To assess the utility of the new basis sets, extensive coupled cluster composite thermochemistry calculations of ThF{sub n} (n = 2 − 4), ThO{sub 2}, and UF{sub n} (n = 4 − 6) have been carried out. After accurately accounting for valence and outer-core correlation, spin-orbit coupling, and even Lamb shift effects, the final 298 K atomization enthalpies of ThF{sub 4}, ThF{sub 3}, ThF{sub 2}, and ThO{sub 2} are all within their experimental uncertainties. Bond dissociation energies of ThF{sub 4} and ThF{sub 3}, as well as UF{sub 6} and UF{sub 5}, were similarly accurate. The derived enthalpies of formation for these species also showed a very satisfactory agreement with experiment, demonstrating that the new basis sets allow for the use of accurate composite schemes just as in molecular systems composed only of lighter atoms. The differences between the PP and DK3 approaches were found to increase with the change in formal oxidation state on the actinide atom, approaching 5-6 kcal/mol for the atomization enthalpies of ThF{sub 4} and ThO{sub 2}. The DKH3 atomization energy of ThO{sub 2} was calculated to be smaller than

Accuracy Improvement of Neutron Nuclear Data on Minor Actinides

NASA Astrophysics Data System (ADS)

Harada, Hideo; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Terada, Kazushi; Nakao, Taro; Nakamura, Shoji; Mizuyama, Kazuhito; Igashira, Masayuki; Katabuchi, Tatsuya; Sano, Tadafumi; Takahashi, Yoshiyuki; Takamiya, Koichi; Pyeon, Cheol Ho; Fukutani, Satoshi; Fujii, Toshiyuki; Hori, Jun-ichi; Yagi, Takahiro; Yashima, Hiroshi

2015-05-01

Improvement of accuracy of neutron nuclear data for minor actinides (MAs) and long-lived fission products (LLFPs) is required for developing innovative nuclear system transmuting these nuclei. In order to meet the requirement, the project entitled as "Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMAC)" has been started as one of the "Innovative Nuclear Research and Development Program" in Japan at October 2013. The AIMAC project team is composed of researchers in four different fields: differential nuclear data measurement, integral nuclear data measurement, nuclear chemistry, and nuclear data evaluation. By integrating all of the forefront knowledge and techniques in these fields, the team aims at improving the accuracy of the data. The background and research plan of the AIMAC project are presented.

Solar r-process-constrained actinide production in neutrino-driven winds of supernovae

NASA Astrophysics Data System (ADS)

Goriely, S.; Janka, H.-Th.

2016-07-01

Long-lived radioactive nuclei play an important role as nucleo-cosmochronometers and as cosmic tracers of nucleosynthetic source activity. In particular, nuclei in the actinide region like thorium, uranium, and plutonium can testify to the enrichment of an environment by the still enigmatic astrophysical sources that are responsible for the production of neutron-rich nuclei by the rapid neutron-capture process (r-process). Supernovae and merging neutron-star (NS) or NS-black hole binaries are considered as most likely sources of the r-nuclei. But arguments in favour of one or the other or both are indirect and make use of assumptions; they are based on theoretical models with remaining simplifications and shortcomings. An unambiguous observational determination of a production event is still missing. In order to facilitate searches in this direction, e.g. by looking for radioactive tracers in stellar envelopes, the interstellar medium or terrestrial reservoirs, we provide improved theoretical estimates and corresponding uncertainty ranges for the actinide production (232Th, 235, 236, 238U, 237Np, 244Pu, and 247Cm) in neutrino-driven winds of core-collapse supernovae. Since state-of-the-art supernova models do not yield r-process viable conditions - but still lack, for example, the effects of strong magnetic fields - we base our investigation on a simple analytical, Newtonian, adiabatic and steady-state wind model and consider the superposition of a large number of contributing components, whose nucleosynthesis-relevant parameters (mass weight, entropy, expansion time-scale, and neutron excess) are constrained by the assumption that the integrated wind nucleosynthesis closely reproduces the Solar system distribution of r-process elements. We also test the influence of uncertain nuclear physics.

GGA + U studies of the early actinide mononitrides and dinitrides

NASA Astrophysics Data System (ADS)

Obodo, K. O.; Chetty, N.

2013-11-01

We present a detailed comparative study of the electronic and mechanical properties of the early actinide mononitrides and dinitrides within the framework of the Perdew-Burke-Ernzerhof generalized gradient approximation (GGA [PBE]) and GGA + U implementations of density functional theory with the inclusion of spin-orbit coupling. The dependence of selected observables of these materials on the effective U-parameter is investigated in detail. The properties include the lattice constant, bulk modulus, charge density distribution, hybridization of the atomic orbitals, energy of formation and the lattice dynamics. The inclusion of the Hubbard U parameter results in a proper description of the 5f electrons, and is subsequently used in the determination of the structural and electronic properties of these compounds. The mononitrides and dinitrides of the early actinides are metallic except for UN2, which is a semiconductor. These actinide nitrides are non-magnetic with the exception of UN, NpN, PuN, NpN2 and PuN2 that are magnetic systems with orbital-dependent magnetic moments oriented in the z-axis. We observed that ThN2 is elastically unstable to isotropic pressure. We discovered that UN2 is thermodynamically unstable, but may be stabilized by N vacancy formation.

LIBS Spectral Data for a Mixed Actinide Fuel Pellet Containing Uranium, Plutonium, Neptunium and Americium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Judge, Elizabeth J.; Berg, John M.; Le, Loan A.

2012-06-18

interactions occurring within the plasma, such as collisional energy transfer, that might be a factor in the reduction in neptunium emission lines. Neptunium has to be analyzed alone using LIBS to further understand the dynamics that may be occurring in the plasma of the mixed actinide fuel pellet sample. The LIBS data suggests that the emission spectrum for the mixed actinide fuel pellet is not simply the sum of the emission spectra of the pure samples but is dependent on the species present in the plasma and the interactions and reactions that occur within the plasma. Finally, many of the neptunium lines are in the near infrared region which is drastically reduced in intensity by the current optical setup and possibly the sensitivity of the emission detector in the spectral region. Once the optics are replaced and the optical collection system is modified and optimized, the probability of observing emission lines for neptunium might be increased significantly. The mixed actinide fuel pellet was analyzed under the experimental conditions listed in Table 1. The LIBS spectra of the fuel pellet are shown in Figures 1-49. The spectra are labeled with the observed wavelength and atomic species (both neutral (I) and ionic (II)). Table 2 is a complete list of the observed and literature based emission wavelengths. The literature wavelengths have references including NIST Atomic Spectra Database (NIST), B.A. Palmer et al. 'An Atlas of Uranium Emission Intensities in a Hollow Cathode Discharge' taken at the Kitt Peak National Observatory (KPNO), R.L. Kurucz 1995 Atomic Line Data from the Smithsonian Astrophysical Observatory (SAO), J. Blaise et al. 'The Atomic Spectrum of Plutonium' from Argonne National Laboratory (BFG), and M. Fred and F.S. Tomkins, 'Preliminary Term Analysis of Am I and Am II Spectra' (FT). The dash (-) shown under Ionic State indicates that the ionic state of the transition was not available. In the spectra, the dash (-) is replaced with a question mark (?). Peaks

Theoretical study of actinide monocarbides (ThC, UC, PuC, and AmC)

NASA Astrophysics Data System (ADS)

Pogány, Peter; Kovács, Attila; Visscher, Lucas; Konings, Rudy J. M.

2016-12-01

A study of four representative actinide monocarbides, ThC, UC, PuC, and AmC, has been performed with relativistic quantum chemical calculations. The two applied methods were multireference complete active space second-order perturbation theory (CASPT2) including the Douglas-Kroll-Hess Hamiltonian with all-electron basis sets and density functional theory with the B3LYP exchange-correlation functional in conjunction with relativistic pseudopotentials. Beside the ground electronic states, the excited states up to 17 000 cm-1 have been determined. The molecular properties explored included the ground-state geometries, bonding properties, and the electronic absorption spectra. According to the occupation of the bonding orbitals, the calculated electronic states were classified into three groups, each leading to a characteristic bond distance range for the equilibrium geometry. The ground states of ThC, UC, and PuC have two doubly occupied π orbitals resulting in short bond distances between 1.8 and 2.0 Å, whereas the ground state of AmC has significant occupation of the antibonding orbitals, causing a bond distance of 2.15 Å.

Study of uranium oxidation states in geological material.

PubMed

Pidchenko, I; Salminen-Paatero, S; Rothe, J; Suksi, J

2013-10-01

A wet chemical method to determine uranium (U) oxidation states in geological material has been developed and tested. The problem faced in oxidation state determinations with wet chemical methods is that U redox state may change when extracted from the sample material, thereby leading to erroneous results. In order to quantify and monitor U redox behavior during the acidic extraction in the procedure, an analysis of added isotopic redox tracers, (236)U(VI) and (232)U(IV), and of variations in natural uranium isotope ratio ((234)U/(238)U) of indigenous U(IV) and U(VI) fractions was performed. Two sample materials with varying redox activity, U bearing rock and U-rich clayey lignite sediment, were used for the tests. The Fe(II)/Fe(III) redox-pair of the mineral phases was postulated as a potentially disturbing redox agent. The impact of Fe(III) on U was studied by reducing Fe(III) with ascorbic acid, which was added to the extraction solution. We observed that ascorbic acid protected most of the U from oxidation. The measured (234)U/(238)U ratio in U(IV) and U(VI) fractions in the sediment samples provided a unique tool to quantify U oxidation caused by Fe(III). Annealing (sample heating) to temperatures above 500 °C was supposed to heal ionizing radiation induced defects in the material that can disturb U redox state during extraction. Good agreement between two independent methods was obtained for DL-1a material: an average 38% of U(IV) determined by redox tracer corrected wet chemistry and 45% for XANES. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mapping the Iron Oxidation State in Martian Meteorites

NASA Technical Reports Server (NTRS)

Martin, A. M.; Treimann, A. H.; Righter, K.

2017-01-01

Several types of Martian igneous meteorites have been identified: clinopyroxenites (nakhlites), basaltic shergottites, peridotitic shergottites, dunites (chassignites) and orthopyroxenites [1,2]. In order to constrain the heterogeneity of the Martian mantle and crust, and their evolution through time, numerous studies have been performed on the iron oxidation state of these meteorites [3,4,5,6,7,8,9]. The calculated fO2 values all lie within the FMQ-5 to FMQ+0.5 range (FMQ representing the Fayalite = Magnetite + Quartz buffer); however, discrepancies appear between the various studies, which are either attributed to the choice of the minerals/melts used, or to the precision of the analytical/calculation method. The redox record in volcanic samples is primarily related to the oxidation state in the mantle source(s). However, it is also influenced by several deep processes: melting, crystallization, magma mixing [10], assimilation and degassing [11]. In addition, the oxidation state in Martian meteorites is potentially affected by several surface processes: assimilation of sediment/ crust during lava flowing at Mars' surface, low temperature micro-crystallization [10], weathering at the surface of Mars and low temperature reequilibration, impact processes (i.e. high pressure phase transitions, mechanical mixing, shock degassing and melting), space weathering, and weathering on Earth (at atmospheric conditions different from Mars). Decoding the redox record of Martian meteorites, therefore, requires large-scale quantitative analysis methods, as well as a perfect understanding of oxidation processes.

The R-Process Alliance: 2MASS J09544277+5246414, the Most Actinide-enhanced R-II Star Known

NASA Astrophysics Data System (ADS)

Holmbeck, Erika M.; Beers, Timothy C.; Roederer, Ian U.; Placco, Vinicius M.; Hansen, Terese T.; Sakari, Charli M.; Sneden, Christopher; Liu, Chao; Lee, Young Sun; Cowan, John J.; Frebel, Anna

2018-06-01

We report the discovery of a new actinide-boost star, 2MASS J09544277+5246414, originally identified as a very bright (V = 10.1), extremely metal-poor ([Fe/H] = ‑2.99) K giant in the LAMOST survey, and found to be highly r-process-enhanced (r-II; [Eu/Fe] = +1.28]), during the snapshot phase of the R-Process Alliance (RPA). Based on a high signal-to-noise ratio (S/N), high-resolution spectrum obtained with the Harlan J. Smith 2.7 m telescope, this star is the first confirmed actinide-boost star found by RPA efforts. With an enhancement of [Th/Eu] = +0.37, 2MASS J09544277+5246414 is also the most actinide-enhanced r-II star yet discovered, and only the sixth metal-poor star with a measured uranium abundance ([U/Fe] = +1.40). Using the Th/U chronometer, we estimate an age of 13.0 ± 4.7 Gyr for this star. The unambiguous actinide-boost signature of this extremely metal-poor star, combined with additional r-process-enhanced and actinide-boost stars identified by the RPA, will provide strong constraints on the nature and origin of the r-process at early times.

Aqueous and pyrochemical reprocessing of actinide fuels

NASA Astrophysics Data System (ADS)

Toth, L. Mac; Bond, Walter D.; Avens, Larry R.

1993-02-01

Processing of the nuclear fuel actinides has developed in two independent directions—aqueous processing and pyroprocessing. Similarities in the two processes, their goals, and restraints are indicated in brief parallel descriptions along with distinguishing advantages and areas of future development. It is suggested that from a technical viewpoint, the ultimate process might be a hybrid which incorporates the best steps of each process.

Oxidative Stress and Heart Failure in Altered Thyroid States

PubMed Central

Mishra, Pallavi; Samanta, Luna

2012-01-01

Increased or reduced action of thyroid hormone on certain molecular pathways in the heart and vasculature causes relevant cardiovascular derangements. It is well established that hyperthyroidism induces a hyperdynamic cardiovascular state, which is associated with a faster heart rate, enhanced left ventricular systolic and diastolic function whereas hypothyroidism is characterized by the opposite changes. Hyperthyroidism and hypothyroidism represent opposite clinical conditions, albeit not mirror images. Recent experimental and clinical studies have suggested the involvement of ROS tissue damage under altered thyroid status. Altered-thyroid state-linked changes in heart modify their susceptibility to oxidants and the extent of the oxidative damage they suffer following oxidative challenge. Chronic increase in the cellular levels of ROS can lead to a catastrophic cycle of DNA damage, mitochondrial dysfunction, further ROS generation and cellular injury. Thus, these cellular events might play an important role in the development and progression of myocardial remodeling and heart failure in altered thyroid states (hypo- and hyper-thyroidism). The present review aims at elucidating the various signaling pathways mediated via ROS and their modulation under altered thyroid state and the possibility of antioxidant therapy. PMID:22649319

Utilization of Minor Actinides as a Fuel Component for Ultra-Long Life Bhr Configurations: Designs, Advantages and Limitations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dr. Pavel V. Tsvetkov

2009-05-20

This project assessed the advantages and limitations of using minor actinides as a fuel component to achieve ultra-long life Very High Temperature Reactor (VHTR) configurations. Researchers considered and compared the capabilities of pebble-bed and prismatic core designs with advanced actinide fuels to achieve ultra-long operation without refueling. Since both core designs permit flexibility in component configuration, fuel utilization, and fuel management, it is possible to improve fissile properties of minor actinides by neutron spectrum shifting through configuration adjustments. The project studied advanced actinide fuels, which could reduce the long-term radio-toxicity and heat load of high-level waste sent to a geologicmore » repository and enable recovery of the energy contained in spent fuel. The ultra-long core life autonomous approach may reduce the technical need for additional repositories and is capable to improve marketability of the Generation IV VHTR by allowing worldwide deployment, including remote regions and regions with limited industrial resources. Utilization of minor actinides in nuclear reactors facilitates developments of new fuel cycles towards sustainable nuclear energy scenarios.« less

U(IV) chalcogenolates synthesized via oxidation of uranium metal by dichalcogenides.

PubMed

Gaunt, Andrew J; Scott, Brian L; Neu, Mary P

2006-09-04

Treatment of uranium metal with dichalcogenides in the presence of a catalytic amount of iodine in pyridine affords molecular U(IV) chalcogenolates that do not require stabilizing ancillary ligands. Oxidation of U(0) by PhEEPh yields monomeric seven-coordinate U(EPh)4(py)3 (E = S(1), Se(2)). The dimeric eight-coordinate complexes [U(EPh)2(mu2-EPh)2(CH3CN)2]2 (E = S(3), Se(4)) are obtained by crystallization from solutions of 1 and 2 dissolved in acetonitrile. Oxidation of U(0) by pySSpy and crystallization from thf yields nine-coordinate U(Spy)4(thf) (5). Incorporation of elemental selenium into the oxidation of U(0) by PhSeSePh results in the isolation of [U(py)2(SePh)(mu3-Se)(mu2-SePh)]4.4py (6), a tetrameric cluster in which each U(IV) ion is eight-coordinate and the U4Se4 core forms a distorted cube. The compounds were analyzed spectroscopically and the single-crystal X-ray structures of 1 and 3-6 were determined. The isolation of 1-6 represents six new examples of actinide chalcogenolates and allows insight into the nature of "hard" actinide ion-"soft" chalcogen donor interactions.

Electric dipole moments of actinide atoms and RaO molecule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flambaum, V. V.

We have calculated the atomic electric dipole moments (EDMs) induced in {sup 229}Pa and {sup 225}Ac by their respective nuclear Schiff moments S. The results are d({sup 229}Pa)=-9.5x10{sup -17} [S/(e fm)]e cm=-1.1x10{sup -20}{eta} e cm and d({sup 225}Ac)=-8.6x10{sup -17} [S/(e fm)]e cm=-0.8x10{sup -21}{eta} e cm. EDM of {sup 229}Pa is 3x10{sup 4} times larger than {sup 199}Hg EDM and 40 times larger than {sup 225}Ra EDM. Possible use of actinides in solid state experiments is also discussed. The (T,P)-odd spin-axis interaction in RaO molecule is 500 times larger than in TlF.

Solution thermodynamic stability of complexes formed with the octadentate hydroxypyridinonate ligand 3,4,3-LI(1,2-HOPO): A critical feature for efficient chelation of lanthanide(IV) and actinide(IV) ions

PubMed Central

Deblonde, Gauthier J-P.; Sturzbecher-Hoehne, Manuel; Abergel, Rebecca J.

2013-01-01

The solution thermodynamics of water soluble complexes formed between Ce(III), Ce(IV), Th(IV) and the octadentate chelating agent 3,4,3-LI(1,2-HOPO) were investigated. Several techniques including spectrofluorimetric and automated spectrophotometric titrations were used to overcome the slow spontaneous oxidation of Ce(III) complexes yielding to stability constants of log β110 = 17.4 ± 0.5, log β11-1 = 8.3 ± 0.4 and log β111 = 21.2 ± 0.4 for [Ce(III)(3,4,3-LI(1,2-HOPO))]−, [Ce(III)(3,4,3-LI(1,2-HOPO)(OH)]2− and [Ce(III)(3,4,3-LI(1,2-HOPO)H], respectively. Using the spectral properties of the hydroxypyridinonate chelator in ligand competition titrations against nitrilotriacetic acid, the stability constant log β110 = 41.5 ± 0.5 was determined for [Ce(IV)(3,4,3-LI(1,2-HOPO))]. Finally, the extraordinarily stable complex [Ce(IV)(3,4,3-LI(1,2-HOPO))] was used in Th(IV) competition titrations, resulting in a stability constant of log β110 = 40.1 ± 0.5 for [Th(IV)3,4,3-LI(1,2-HOPO))]. These experimental values are in excellent agreement with previous estimates, they are discussed with respect to the ionic radius and oxidation state of each cationic metal and allow predictions on the stability of other actinide complexes including [U(IV)(3,4,3-LI(1,2-HOPO))], [Np(IV)(3,4,3-LI(1,2-HOPO))] and [Pu(IV)(3,4,3-LI(1,2-HOPO))]. Comparisons with the standard ligand diethylenetriamine pentaacetic acid (DTPA) provide a thermodynamic basis for the observed significantly higher efficacy of 3,4,3-LI(1,2-HOPO) as an in vivo actinide decorporation agent. PMID:23855806

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.

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.

A Pyridine Alkoxide Chelate Ligand That Promotes Both Unusually High Oxidation States and Water-Oxidation Catalysis

DOE PAGES

Michaelos, Thoe K.; Shopov, Dimitar Y.; Sinha, Shashi Bhushan; ...

2017-03-08

Here, water-oxidation catalysis is a critical bottleneck in the direct generation of solar fuels by artificial photosynthesis. Catalytic oxidation of difficult substrates such as water requires harsh conditions, so that the ligand must be designed both to stabilize high oxidation states of the metal center and to strenuously resist ligand degradation. Typical ligand choices either lack sufficient electron donor power or fail to stand up to the oxidizing conditions. This research on Ir-based water-oxidation catalysts (WOCs) has led us to identify a ligand, 2-(2'-pyridyl)-2-propanoate or “pyalk” that fulfills these requirements.

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.

Electrochemistry of actinides and fission products in molten salts-Data review

NASA Astrophysics Data System (ADS)

Zhang, Jinsuo

2014-04-01

The thermodynamic and electrochemical properties of actinides and fission products in the molten salt determine the pyroprocessing separation performance. Extensive measurements have been carried out to provide fundamental data for evaluating the separation efficiency and technology feasibility of pyroprocessing although the technology has been very well developed in laboratory. The state of the art of fundamental data for substance or materials involved in pyropocessing will be reviewed in the present article. The available data will be summarized and reanalyzed. New correlations, which extend the available data to a broad range of applications, will be developed based on available data from different measurements. Further research topics on providing fundamental data that is needed for scaling the current laboratory technology to industrial applications are identified.

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…

Superabsorbing gel for actinide, lanthanide, and fission product decontamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaminski, Michael D.; Mertz, Carol J.

The present invention provides an aqueous gel composition for removing actinide ions, lanthanide ions, fission product ions, or a combination thereof from a porous surface contaminated therewith. The composition comprises a polymer mixture comprising a gel forming cross-linked polymer and a linear polymer. The linear polymer is present at a concentration that is less than the concentration of the cross-linked polymer. The polymer mixture is at least about 95% hydrated with an aqueous solution comprising about 0.1 to about 3 percent by weight (wt %) of a multi-dentate organic acid chelating agent, and about 0.02 to about 0.6 molar (M)more » carbonate salt, to form a gel. When applied to a porous surface contaminated with actinide ions, lanthanide ions, and/or other fission product ions, the aqueous gel absorbs contaminating ions from the surface.« less

Natural Variation in the Carbon Oxidation State and Oxidative Ratio of a Deciduous Forest

NASA Astrophysics Data System (ADS)

Masiello, C. A.; Calligan, L. J.; Gallagher, M. E.; Hockaday, W. C.; Robertson, G. P.

2007-12-01

Here we report natural variability in the oxidative ratio (OR) and carbon oxidation state (Cox) of a temperate, deciduous forest measured on an annual basis via elemental analysis of leaf litter. The OR of the terrestrial biosphere is a key component in O2 -based calculations of the biosphere's uptake of fossil fuel CO2 (eg [ Keeling, et al., 1996]). Ecosystem OR has been assumed to be invariant; however, small OR variations may cause significant shifts in the calculated size of the terrestrial biospheric C sink [ Randerson, et al., 2006]. Accurate measurements of OR are necessary for the accurate apportionment of fossil fuel CO2 between the atmosphere, oceans, and terrestrial biosphere. Ecosystem OR is linearly related to Cox, a parameter which can be easily measured via elemental analysis, calorimetry, or solid state nuclear magnetic resonance [ Masiello, et al., 2007]. We are measuring Cox and OR at the three deciduous forest sites within the Kellogg Biological Station NSF LTER (lter.kbs.msu.edu). We report OR from litter collected from three forest sites from 1998-2003, a time series which covers periods of both normal and low precipitation. We also report error introduced in the Cox to OR conversion via a range of plausible assumptions about ecosystem N cycling. Keeling, R. F., et al. (1996), Global and hemispheric CO2 sinks deduced from changes in atmospheric O2 concentration, Nature, 381, 218-221. Masiello, C.A. et al. (in review 2007) Two new approaches for measuring ecosystem carbon oxidation state and oxidative ratio. J.G.R. Biogeosciences. Randerson, J. T., et al. (2006), Is carbon within the global terrestrial biosphere becoming more oxidized? Implications for trends in atmospheric O2, Global Change Biology, 12, 260-271.

Electronic, structural, and thermodynamic properties of mixed actinide dioxides (U, Pu, Am) O2 from hybrid density functional theory

NASA Astrophysics Data System (ADS)

Ma, Li; Ray, Asok K.

2010-03-01

As a continuation of our studies of pure actinide metals using hybrid density functional theory,footnotetextR. Atta-Fynn and A. K. Ray, Europhysics Letters, 85, 27008-p1- p6 (2009); Chemical Physics Letters, 482, 223-227 (2009). we present here a systematic study of the electronic and geometric structure properties of mixed actinide dioxides, U0.5Pu0.5O2, U0.5Am0.5O2, Pu0.5Am0.5 O2 and U0.8Pu0.2O2. The fraction of exact Hartree-Fock exchange used was 40%. To investigate the effect of spin-orbit coupling on the ground state electronic and geometric structure properties, computations have been carried out at two theoretical levels, one at the scalar-relativistic level with no spin-orbit coupling and one at the fully relativistic level with spin-orbit coupling. Thermodynamic properties have been calculated by a coupling of first-principles calculation and lattice dynamics.

Extracting metals directly from metal oxides

DOEpatents

Wai, Chien M.; Smart, Neil G.; Phelps, Cindy

1997-01-01

A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of .beta.-diketones, halogenated .beta.-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process.

Extracting metals directly from metal oxides

DOEpatents

Wai, C.M.; Smart, N.G.; Phelps, C.

1997-02-25

A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of {beta}-diketones, halogenated {beta}-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process. 4 figs.

About structural phase state of coating based on zirconium oxide formed by microplasma oxidation method

NASA Astrophysics Data System (ADS)

Gubaidulina, Tatiana A.; Sergeev, Viktor P.; Kuzmin, Oleg S.; Fedorischeva, Marina V.; Kalashnikov, Mark P.

2017-12-01

The oxide-ceramic coating based of zirconium oxide is formed by the method of microplasma oxidation. The producing modes of the oxide layers on E110 zirconium alloy are under testing. It was found that using microplasma treatment of E110 zirconium in aluminosilicate electrolyte makes possible the formation of porous oxide-ceramic coatings based on zirconium alloyed by aluminum and niobium. The study is focused on the modes how to form heat-shielding coatings with controlled porosity and minimal amount of microcracks. The structural-phase state of the coating is studied by X-ray diffraction analysis and scanning electron microscopy (SEM). It was found that the ratio of the monoclinic and tetragonal phases changes with the change occurring in the coating formation modes.

Applications of time-resolved laser fluorescence spectroscopy to the environmental biogeochemistry of actinides.

PubMed

Collins, Richard N; Saito, Takumi; Aoyagi, Noboru; Payne, Timothy E; Kimura, Takaumi; Waite, T David

2011-01-01

Time-resolved laser fluorescence spectroscopy (TRLFS) is a useful means of identifying certain actinide species resulting from various biogeochemical processes. In general, TRLFS differentiates chemical species of a fluorescent metal ion through analysis of different excitation and emission spectra and decay lifetimes. Although this spectroscopic technique has largely been applied to the analysis of actinide and lanthanide ions having fluorescence decay lifetimes on the order of microseconds, such as UO , Cm, and Eu, continuing development of ultra-fast and cryogenic TRLFS systems offers the possibility to obtain speciation information on metal ions having room-temperature fluorescence decay lifetimes on the order of nanoseconds to picoseconds. The main advantage of TRLFS over other advanced spectroscopic techniques is the ability to determine in situ metal speciation at environmentally relevant micromolar to picomolar concentrations. In the context of environmental biogeochemistry, TRLFS has principally been applied to studies of (i) metal speciation in aqueous and solid phases and (ii) the coordination environment of metal ions sorbed to mineral and bacterial surfaces. In this review, the principles of TRLFS are described, and the literature reporting the application of this methodology to the speciation of actinides in systems of biogeochemical interest is assessed. Significant developments in TRLFS methodology and advanced data analysis are highlighted, and we outline how these developments have the potential to further our mechanistic understanding of actinide biogeochemistry. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Conjugates of magnetic nanoparticle-actinide specific chelator for radioactive waste separation.

PubMed

Kaur, Maninder; Zhang, Huijin; Martin, Leigh; Todd, Terry; Qiang, You

2013-01-01

A novel nanotechnology for the separation of radioactive waste that uses magnetic nanoparticles (MNPs) conjugated with actinide specific chelators (MNP-Che) is reviewed with a focus on design and process development. The MNP-Che separation process is an effective way of separating heat generating minor actinides (Np, Am, Cm) from spent nuclear fuel solution to reduce the radiological hazard. It utilizes coated MNPs to selectively adsorb the contaminants onto their surfaces, after which the loaded particles are collected using a magnetic field. The MNP-Che conjugates can be recycled by stripping contaminates into a separate, smaller volume of solution, and then become the final waste form for disposal after reusing number of times. Due to the highly selective chelators, this remediation method could be both simple and versatile while allowing the valuable actinides to be recovered and recycled. Key issues standing in the way of large-scale application are stability of the conjugates and their dispersion in solution to maintain their unique properties, especially large surface area, of MNPs. With substantial research progress made on MNPs and their surface functionalization, as well as development of environmentally benign chelators, this method could become very flexible and cost-effective for recycling used fuel. Finally, the development of this nanotechnology is summarized and its future direction is discussed.

Hardening neutron spectrum for advanced actinide transmutation experiments in the ATR.

PubMed

Chang, G S; Ambrosek, R G

2005-01-01

The most effective method for transmuting long-lived isotopes contained in spent nuclear fuel into shorter-lived fission products is in a fast neutron spectrum reactor. In the absence of a fast test reactor in the United States, initial irradiation testing of candidate fuels can be performed in a thermal test reactor that has been modified to produce a test region with a hardened neutron spectrum. Such a test facility, with a spectrum similar but somewhat softer than that of the liquid-metal fast breeder reactor (LMFBR), has been constructed in the INEEL's Advanced Test Reactor (ATR). The radial fission power distribution of the actinide fuel pin, which is an important parameter in fission gas release modelling, needs to be accurately predicted and the hardened neutron spectrum in the ATR and the LMFBR fast neutron spectrum is compared. The comparison analyses in this study are performed using MCWO, a well-developed tool that couples the Monte Carlo transport code MCNP with the isotope depletion and build-up code ORIGEN-2. MCWO analysis yields time-dependent and neutron-spectrum-dependent minor actinide and Pu concentrations and detailed radial fission power profile calculations for a typical fast reactor (LMFBR) neutron spectrum and the hardened neutron spectrum test region in the ATR. The MCWO-calculated results indicate that the cadmium basket used in the advanced fuel test assembly in the ATR can effectively depress the linear heat generation rate in the experimental fuels and harden the neutron spectrum in the test region.

From carbon to actinides: A new universal 1MV accelerator mass spectrometer at ANSTO

NASA Astrophysics Data System (ADS)

Wilcken, K. M.; Hotchkis, M.; Levchenko, V.; Fink, D.; Hauser, T.; Kitchen, R.

2015-10-01

A new 1 MV NEC pelletron AMS system at ANSTO is presented. The spectrometer comprises large radius magnets for actinide measurements. A novel feature of the system is fast switching between isotopes both at low and high energy sections allowing measurements of up to 8 isotopes within a single sequence. Technical details and layout of the spectrometer is presented. Performance data for 14C, 10Be, 26Al and actinides demonstrate the system is ready for routine AMS measurements.

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.

Lanthanide/Actinide Opacities

NASA Astrophysics Data System (ADS)

Hungerford, Aimee; Fontes, Christopher J.

2018-06-01

Gravitational wave observations benefit from accompanying electromagnetic signals in order to accurately determine the sky positions of the sources. The ejecta of neutron star mergers are expected to produce such electromagnetic transients, called macronovae (e.g. the recent and unprecedented observation of GW170817). Characteristics of the ejecta include large velocity gradients and the presence of heavy r-process elements, which pose significant challenges to the accurate calculation of radiative opacities and radiation transport. Opacities include a dense forest of bound-bound features arising from near-neutral lanthanide and actinide elements. Here we present an overview of current theoretical opacity determinations that are used by neutron star merger light curve modelers. We will touch on atomic physics and plasma modeling codes that are used to generate these opacities, as well as the limited body of laboratory experiments that may serve as points of validation for these complex atomic physics calculations.

Vaporisation of candidate nuclear fuels and targets for transmutation of minor actinides

NASA Astrophysics Data System (ADS)

Gotcu-Freis, P.; Hiernaut, J.-P.; Colle, J.-Y.; Nästrén, C.; Carretero, A. Fernandez; Konings, R. J. M.

2011-04-01

The thermal stability and high temperature behaviour of candidate fuels and targets for transmutation of minor actinides has been investigated. Zirconia-based solid solution, MgO-based CERCER and molybdenum-based CERMET fuels containing Am and/or Pu in various concentrations were heated up to 2700 K in a Knudsen cell coupled with a quadrupole mass spectrometer, to measure their vapour pressure and vapour composition. The results reveal that the vaporisation of the actinides from the samples is not only determined by the thermodynamics of the system but is also related to the dynamic evolution of multi-component mixtures with complex composition or microstructure.

Rapid method to determine actinides and 89/90Sr in limestone and marble samples

DOE PAGES

Maxwell, Sherrod L.; Culligan, Brian; Hutchison, Jay B.; ...

2016-04-12

A new method for the determination of actinides and radiostrontium in limestone and marble samples has been developed that utilizes a rapid sodium hydroxide fusion to digest the sample. Following rapid pre-concentration steps to remove sample matrix interferences, the actinides and 89/90Sr are separated using extraction chromatographic resins and measured radiometrically. The advantages of sodium hydroxide fusion versus other fusion techniques will be discussed. Lastly, this approach has a sample preparation time for limestone and marble samples of <4 hours.

Matrix infrared spectra and electronic structure calculations of the first actinide borylene: FB=ThF(2).

PubMed

Wang, Xuefeng; Roos, Björn O; Andrews, Lester

2010-03-14

Laser-ablated Th atoms react with BF(3) during condensation in excess argon at 6 K to form the first actinide borylene (FB=ThF(2)) and actinide-boron multiple bond. Three new product absorptions in the B-F and Th-F stretching regions of matrix infrared spectra are assigned to FB=ThF(2) from comparison to theoretically predicted vibrational frequencies.

Oxide films state analysis by IR spectroscopy based on the simple oscillator approximation

NASA Astrophysics Data System (ADS)

Volkov, N. V.; Yakutkina, T. V.; Karpova, V. V.

2017-05-01

Stabilization of structure-phase state in a wide temperature range is one of the most important problems of improving properties of oxide compounds. As such, the search of new effective methods for obtaining metal oxides with desired physic-chemical, electro-physical and thermal properties and their control is important and relevant. The aim of this work is identification features state of the oxide films of some metals Be, Al, Fe, Cu, Zr on the metal surface of the polycrystalline samples by infrared spectroscopy. To identify the resonance emission bands the algorithm of IR-spectra processing was developed and realized on the basis of table processor EXCEL-2010, which allow revealing characteristic resonance bands successfully and identification of inorganic chemical compounds. In the frame of simple oscillator model, resonance frequencies of normal vibrations of water and some inorganic compounds: metal oxides - Be, Al, Fe, Cu, Zr were calculated and characteristic frequencies for different states (aggregate, deformation, phase) were specified. By means of IR-spectroscopy fundamental possibility of revealing oxides films on metal substrate features state is shown, that allow development and optimization of the technology for production of the oxide films with desired properties.

On the Use of Thermal NF3 as the Fluorination and Oxidation Agent in Treatment of Used Nuclear Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheele, Randall D.; McNamara, Bruce K.; Casella, Andrew M.

2012-05-01

This paper presents results of our investigation on the use of nitrogen trifluoride as the fluorination or fluorination/oxidation agent for use in a process for separating valuable constituents from used nuclear fuels by employing the volatility of many transition metal and actinide fluorides. Nitrogen trifluoride is less chemically and reactively hazardous than the hazardous and aggressive fluorinating agents used to prepare uranium hexafluoride and considered for fluoride volatility based nuclear fuels reprocessing. In addition, nitrogen trifluoride’s less aggressive character may be used to separate the volatile fluorides from used fuel and from themselves based on the fluorination reaction’s temperature sensitivitymore » (thermal tunability) rather than relying on differences in sublimation/boiling temperature and sorbents. Our thermodynamic calculations found that nitrogen trifluoride has the potential to produce volatile fission product and actinide fluorides from candidate oxides and metals. Our simultaneous thermogravimetric and differential thermal analyses found that the oxides of lanthanum, cerium, rhodium, and plutonium fluorinated but did not form volatile fluorides and that depending on temperature volatile fluorides formed from the oxides of niobium, molybdenum, ruthenium, tellurium, uranium, and neptunium. We also demonstrated near-quantitative removal of uranium from plutonium in a mixed oxide.« less

Detection of the actinides and cesium from environmental samples

NASA Astrophysics Data System (ADS)

Snow, Mathew Spencer

Detection of the actinides and cesium in the environment is important for a variety of applications ranging from environmental remediation to safeguards and nuclear forensics. The utilization of multiple different elemental concentrations and isotopic ratios together can significantly improve the ability to attribute contamination to a unique source term and/or generation process; however, the utilization of multiple elemental "signatures" together from environmental samples requires knowledge of the impact of chemical fractionation for various elements under a variety of environmental conditions (including predominantly aqueous versus arid conditions). The research reported in this dissertation focuses on three major areas: 1. Improving the understanding of actinide-mineral interactions at ultra-low concentrations. Chapter 2 reports a batch sorption and modeling study of Np(V) sorption to the mineral goethite from attomolar to micromolar concentrations. 2. Improving the detection capabilities for Thermal Ionization Mass Spectrometry (TIMS) analyses of ultra-trace cesium from environmental samples. Chapter 4 reports a new method which significantly improves the chemical yields, purification, sample processing time, and ultimately, the detection limits for TIMS analyses of femtogram quantities of cesium from a variety of environmental sample matrices. 3. Demonstrating how actinide and cesium concentrations and isotopic ratios from environmental samples can be utilized together to determine a wealth of information including environmental transport mechanisms (e.g. aqueous versus arid transport) and information on the processes which generated the original material. Chapters1, 3 and 5 demonstrate these principles using Pu, Am, Np, and Cs concentrations and isotopic ratios from contaminated soils taken near the Subsurface Disposal Area (SDA) of Idaho National Laboratory (INL) (a low level radioactive waste disposal site in southeastern Idaho).

A spontaneous change in the oxidation states of Pd/WO3 toward an active phase during catalytic cycles of CO oxidation

NASA Astrophysics Data System (ADS)

Jeon, Byungwook; Kim, Ansoon; Lee, Young-Ahn; Seo, Hyungtak; Kim, Yu Kwon

2017-11-01

CO oxidation over Pd/WO3 films prepared on a glass substrate has been examined at the substrate temperature of 150 - 250 °C and pressures less than 1 Torr with a stoichiometric mixture of CO and O2. Under the given reaction condition, the chemical states of the Pd/WO3 film gradually change into the most catalytically active form with the highest saturation reaction rate regardless of the initial oxidation states. The measured CO oxidation rate over the Pd/WO3 is strongly dependent on the chemical states of Pd and W. Either metallic Pd or fully oxidized PdO phase is not as catalytically active as the active form with mixed metallic Pd and thin PdO layers supported on WO3 with partially reduced W5+ state which is spontaneously obtained during the catalytic reaction cycles. Our results indicate that the facile oxygen transfer between Pd and WO3 layers not only facilitate the spontaneous changes into the active form, but also act as a promotional role in CO oxidation over the Pd layer.

Differentiation of Sclerotinia minor depends on thiol redox state and oxidative stress.

PubMed

Patsoukis, Nikolaos; Georgiou, Christos D

2008-01-01

Sclerotial differentiation in Sclerotinia minor is associated with oxidative stress and thiol redox state. The significance of oxidative stress to sclerotial differentiation was revealed by the higher oxidative stress of S. minor compared with a nonsclerotiogenic counterpart. The effect of thiol redox state on sclerotial differentiation was shown by the antioxidant action of the thiol (-SH) group of N-acetylcysteine and cysteine and by an unknown (not antioxidant) role of glutathione (GSH) on S. minor. The nonantioxidant role of GSH was indicated by the differentiation-inhibiting and differentiation-noninhibiting actions of the GSH biosynthesis inhibitor L-buthionine-S,R-sulfoximine and the GSH biosynthesis inducer L-2-oxo-thiazolidine-4-carboxylate, respectively, and by the increase of oxidative stress they caused during the transition from the undifferentiated to differentiated state of S. minor. Moreover, N-acetylcysteine can be used as a potent nontoxic fungicide against this phytopathogenic fungus by acting as a growth-inhibiting cytotoxic oxidant and by sustaining the fungus in the undifferentiated hyphal stage, which is vulnerable to degradation by soil microorganisms.

Heterogeneous Oxidation of Atmospheric Organic Aerosol: Kinetics of Changes to the Amount and Oxidation State of Particle-Phase Organic Carbon.

PubMed

Kroll, Jesse H; Lim, Christopher Y; Kessler, Sean H; Wilson, Kevin R

2015-11-05

Atmospheric oxidation reactions are known to affect the chemical composition of organic aerosol (OA) particles over timescales of several days, but the details of such oxidative aging reactions are poorly understood. In this study we examine the rates and products of a key class of aging reaction, the heterogeneous oxidation of particle-phase organic species by the gas-phase hydroxyl radical (OH). We compile and reanalyze a number of previous studies from our laboratories involving the oxidation of single-component organic particles. All kinetic and product data are described on a common basis, enabling a straightforward comparison among different chemical systems and experimental conditions. Oxidation chemistry is described in terms of changes to key ensemble properties of the OA, rather than to its detailed molecular composition, focusing on two quantities in particular, the amount and the oxidation state of the particle-phase carbon. Heterogeneous oxidation increases the oxidation state of particulate carbon, with the rate of increase determined by the detailed chemical mechanism. At the same time, the amount of particle-phase carbon decreases with oxidation, due to fragmentation (C-C scission) reactions that form small, volatile products that escape to the gas phase. In contrast to the oxidation state increase, the rate of carbon loss is nearly uniform among most systems studied. Extrapolation of these results to atmospheric conditions indicates that heterogeneous oxidation can have a substantial effect on the amount and composition of atmospheric OA over timescales of several days, a prediction that is broadly in line with available measurements of OA evolution over such long timescales. In particular, 3-13% of particle-phase carbon is lost to the gas phase after one week of heterogeneous oxidation. Our results indicate that oxidative aging represents an important sink for particulate organic carbon, and more generally that fragmentation reactions play a major

Actinides in deer tissues at the rocky flats environmental technology site.

PubMed

Todd, Andrew S; Sattelberg, R Mark

2005-11-01

Limited hunting of deer at the future Rocky Flats National Wildlife Refuge has been proposed in U.S. Fish and Wildlife planning documents as a compatible wildlife-dependent public use. Historically, Rocky Flats site activities resulted in the contamination of surface environmental media with actinides, including isotopes of americium, plutonium, and uranium. In this study, measurements of actinides [Americium-241 (241Am); Plutonium-238 (238Pu); Plutonium-239,240 (239,240Pu); uranium-233,244 (233,234U); uranium-235,236 (235,236U); and uranium-238 (238U)] were completed on select liver, muscle, lung, bone, and kidney tissue samples harvested from resident Rocky Flats deer (N = 26) and control deer (N = 1). In total, only 17 of the more than 450 individual isotopic analyses conducted on Rocky Flats deer tissue samples measured actinide concentrations above method detection limits. Of these 17 detects, only 2 analyses, with analytical uncertainty values added, exceeded threshold values calculated around a 1 x 10(-6) risk level (isotopic americium, 0.01 pCi/g; isotopic plutonium, 0.02 pCi/g; isotopic uranium, 0.2 pCi/g). Subsequent, conservative risk calculations suggest minimal human risk associated with ingestion of these edible deer tissues. The maximum calculated risk level in this study (4.73 x 10(-6)) is at the low end of the U.S. Environmental Protection Agency's acceptable risk range.

Actinide management with commercial fast reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohki, Shigeo

The capability of plutonium-breeding and minor-actinide (MA) transmutation in the Japanese commercial sodium-cooled fast reactor offers one of practical solutions for obtaining sustainable energy resources as well as reducing radioactive toxicity and inventory. The reference core design meets the requirement of flexible breeding ratio from 1.03 to 1.2. The MA transmutation amount has been evaluated as 50-100 kg/GW{sub e}y if the MA content in fresh fuel is 3-5 wt%, where about 30-40% of initial MA can be transmuted in the discharged fuel.

On the use of thermal NF3 as the fluorination and oxidation agent in treatment of used nuclear fuels

NASA Astrophysics Data System (ADS)

Scheele, Randall; McNamara, Bruce; Casella, Andrew M.; Kozelisky, Anne

2012-05-01

This paper presents results of our investigation on the use of nitrogen trifluoride as a fluorination or fluorination/oxidation agent for separating valuable constituents from used nuclear fuels by exploiting the different volatilities of the constituent fission product and actinide fluorides. Our thermodynamic calculations show that nitrogen trifluoride has the potential to produce volatile fission product and actinide fluorides from oxides and metals that can form volatile fluorides. Simultaneous thermogravimetric and differential thermal analyses show that the oxides of lanthanum, cerium, rhodium, and plutonium are fluorinated but do not form volatile fluorides when treated with nitrogen trifluoride at temperatures up to 550 °C. However, depending on temperature, volatile fluorides or oxyfluorides can form from nitrogen trifluoride treatment of the oxides of niobium, molybdenum, ruthenium, tellurium, uranium, and neptunium. Thermoanalytical studies demonstrate near-quantitative separation of uranium from plutonium in a mixed 80% uranium and 20% plutonium oxide. Our studies of neat oxides and metals suggest that the reactivity of nitrogen trifluoride may be adjusted by temperature to selectively separate the major volatile fuel constituent uranium from minor volatile constituents, such as Mo, Tc, Ru and from the non-volatile fuel constituents based on differences in their reaction temperatures and kinetic behaviors. This reactivity is novel with respect to that reported for other fluorinating reagents F2, BrF5, ClF3.

Controlling Hexavalent Americium – A Centerpiece to a Compact Nuclear Fuel Cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shafer /Braley, Jenifer; Nash, Kenneth L; Lumetta, Gregg

2014-10-01

Closing the nuclear fuel cycle could be simplified by recovering the actinides U through Am as a group. This could be achieved by converting U, Np, Pu and Am to the hexavalent state. Uranium, Np and Pu are readily oxidized to the hexavalent state. Generation of hexavalent Am in acidic solutions is more difficult, as the standard reduction potential of the Am(VI) /Am(III) couple (+1.68 V in 1 M HClO4) is well outside of the electrochemical stability window of water. While the oxidation and separation of Am has been demonstrated under laboratory conditions, several issues could plague scale up andmore » implementation of this separation with used fuel. Two primary concerns are considered. The first issue concerns the stability of the oxidized Am. The second involves the undesirable co-extraction of tetravalent f-elements with the hexavalent actinides. To address the first concern regarding Am redox instability, Am reduction will be monitored under a variety of different conditions to establish the means of improving the stability of Am(VI) in the organic phase. Identifying the components contributing most significantly to its reduction will allow thoughtful modification of the process. To address the second concern, we propose to apply branched chain extractants to separate hexavalent actinides from tetravalent f-elements. Both branched monoamide and organophosphorus extractants have demonstrated significant selectivity for UO22+ versus Th4+, with separation factors generally on the order of 100. The efforts of this two-pronged research program should represent a significant step forward in the development of aqueous separations approaches designed to recover the U-Am actinides based on the availability of the hexavalent oxidation state. For the purposes of this proposal, separations based on this approach will be called SAn(VI) separations, indicating the Separation of An(VI).« less

Microanalysis of iron oxidation states in earth and planetary materials

NASA Astrophysics Data System (ADS)

Bajt, S.; Sutton, S. R.; Delaney, J. S.

1995-02-01

Initial studies have been made on quantifying Fe oxidation states in different iron-bearing minerals using K-edge XANES. The energy of a weak pre-edge peak in the XANES spectrum due to 1s-3d electron transition was used to quantify ferric/ferrous ratios with microprobe spatial resolution. The estimated accuracy of the technique was +/- 10% in terms of Fe3+/((Fe2+ + Fe3+)). The detection limit was ~ 100 ppm with a synchrotron beam of ~ 100 μm in diameter. The pre-edge peak energy in well-characterized samples with known Fe oxidation states was found to be a linear function of the ferric/(ferrous) ratio. The technique was applied to altered magnetics (ideally Fe3O4), and various silicates and oxides from meteorites.

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.

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.

Trap States of the Oxide Thin Film Transistor

NASA Astrophysics Data System (ADS)

Yu, Kyeong Min; Yuh, Jin Tae; Park, Sang Hee Ko; Ryu, Min Ki; Yun, Eui Jung; Bae, Byung Seong

2013-10-01

We investigated the temperature dependent recovery of the threshold voltage shift observed in both ZnO and indium gallium zinc oxide (IGZO) thin film transistors (TFTs) after application of gate bias and light illumination. Two types of recovery were observed for both the ZnO and IGZO TFTs; low temperature recovery (below 110 °C) which is attributed to the trapped charge and high temperature recovery (over 110 °C) which is related to the annihilation of trap states generated during stresses. From a comparison study of the recovery rate with the analysis of hydrogen diffusion isochronal annealing, a similar behavior was observed for both TFT recovery and hydrogen diffusion. This result suggests that hydrogen plays an important role in the generation and annihilation of trap states in oxide TFTs under gate bias or light illumination stresses.

Analysis and optimization of minor actinides transmutation blankets with regards to neutron and gamma sources

NASA Astrophysics Data System (ADS)

Kooymana, Timothée; Buiron, Laurent; Rimpault, Gérald

2017-09-01

Heterogeneous loading of minor actinides in radial blankets is a potential solution to implement minor actinides transmutation in fast reactors. However, to compensate for the lower flux level experienced by the blankets, the fraction of minor actinides to be loaded in the blankets must be increased to maintain acceptable performances. This severely increases the decay heat and neutron source of the blanket assemblies, both before and after irradiation, by more than an order of magnitude in the case of neutron source for instance. We propose here to implement an optimization methodology of the blankets design with regards to various parameters such as the local spectrum or the mass to be loaded, with the objective of minimizing the final neutron source of the spent assembly while maximizing the transmutation performances of the blankets. In a first stage, an analysis of the various contributors to long and short term neutron and gamma source is carried out while in a second stage, relevant estimators are designed for use in the effective optimization process, which is done in the last step. A comparison with core calculations is finally done for completeness and validation purposes. It is found that the use of a moderated spectrum in the blankets can be beneficial in terms of final neutron and gamma source without impacting minor actinides transmutation performances compared to more energetic spectrum that could be achieved using metallic fuel for instance. It is also confirmed that, if possible, the use of hydrides as moderating material in the blankets is a promising option to limit the total minor actinides inventory in the fuel cycle. If not, it appears that focus should be put upon an increased residence time for the blankets rather than an increase in the acceptable neutron source for handling and reprocessing.

Control of cerium oxidation state through metal complex secondary structures

DOE PAGES

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

2015-08-11

A series of alkali metal cerium diphenylhydrazido complexes, M x(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. Reductionmore » 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.« less

Nuclear Forensics: Measurements of Uranium Oxides Using Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)

DTIC Science & Technology

2010-03-01

Isotope Ratio Analysis of Actinides , Fission Products, and Geolocators by High- efficiency Multi-collector Thermal Ionization Mass Spectrometry...Information, 1999. Hou, Xiaolin, and Per Roos. “ Critical Comparison of radiometric and Mass Spectrometric Methods for the Determination of...NUCLEAR FORENSICS: MEASUREMENTS OF URANIUM OXIDES USING TIME-OF-FLIGHT SECONDARY ION MASS

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.

Dissolution behavior of MgO based inert matrix fuel for the transmutation of minor actinides

NASA Astrophysics Data System (ADS)

Mühr-Ebert, E. L.; Lichte, E.; Bukaemskiy, A.; Finkeldei, S.; Klinkenberg, M.; Brandt, F.; Bosbach, D.; Modolo, G.

2018-07-01

This study explores the dissolution properties of magnesia-based inert matrix nuclear fuel (IMF) containing transuranium elements (TRU). Pure MgO pellets as well as MgO pellets containing CeO2, as surrogate for TRU oxides, and are considered as model systems for genuine magnesia based inert matrix fuel were fabricated. The aim of this study is to identify conditions at which the matrix material can be selectively dissolved during the head-end reprocessing step, allowing a separation of MgO from the actinides, whereas the actinides remain undissolved. The dissolution behavior was studied in macroscopic batch experiments as a function of nitric acid concentration, dissolution medium volume, temperature, stirring velocity, and pellet density (85, 90, 96, and 99%TD). To mimic pellets with various burn-ups the density of the here fabricated pellets was varied. MgO is soluble even under mild conditions (RT, 2.5 mol/L HNO3). The dissolution rates of MgO at different acid concentrations are rather similar, whereas the dissolution rate is strongly dependent on the temperature. Via a microscopic approach, a model was developed to describe the evolution of the pellet surface area during dissolution and determine a surface normalized dissolution rate. Moreover, dissolution rates of the inert matrix fuel containing CeO2 were determined as a function of the acid concentration and temperature. During the dissolution of MgO/CeO2 pellets the MgO dissolves completely, while CeO2 (>99%) remains undissolved. This study intends to provide a profound understanding of the chemical performance of magnesia based IMF containing fissile material. The feasibility of the dissolution of magnesia based IMF with nitric acid is discussed.

Lanthanide and actinide chemistry at high C/O ratios in the solar nebula

NASA Technical Reports Server (NTRS)

Lodders, Katharina; Fegley, Bruce, Jr.

1993-01-01

Chemical equilibrium calculations were performed to study the condensation chemistry of the REE and actinides under the highly reducing conditions which are necessary for the formation of the enstatite chondrites. Our calculations confirm that the REE and actinides condensed into oldhamite (CaS), the major REE and actinide host phase in enstatite chondrites, at a carbon-oxygen (C/O) ratio not less than 1 in an otherwise solar gas. Five basic types of REE abundance patterns, several of which are analogous to REE abundance patterns observed in the Ca, Al-rich inclusions in carbonaceous chondrites, are predicted to occur in meteoritic oldhamites. All of the reported REE patterns in oldhamites in enstatite chondrites can be interpreted in terms of our condensation calculations. The observed patterns fall into three of the five predicted categories. The reported Th and U enrichments and ratios in meteoritic oldhamites are also consistent with predictions of the condensation calculations. Pure REE sulfides are predicted to condense in the 10 exp -6 to 10 exp -9 bar range and may be found in enstatite chondrites if they formed in this pressure range.

Extraction Selectivity of a Quaternary Alkylammonium Salt for Trivalent Actinides over Trivalent Lanthanides: Does Extractant Aggregation Play a Role?

DOE PAGES

Knight, Andrew W.; Chiarizia, Renato; Soderholm, L.

2017-05-10

In this paper, the extraction behavior of a quaternary alkylammonium salt extractant was investigated for its selectivity for trivalent actinides over trivalent lanthanides in nitrate and thiocyanate media. The selectivity was evaluated by solvent extraction experiments through radiochemical analysis of 241Am and 152/154Eu. Solvent extraction distribution and slope-analysis experiments were performed with americium(III) and europium(III) with respect to the ligand (nitrate and thiocyanate), extractant, and metal (europium only) concentrations. Further evaluation of the equilibrium expression that governs the extraction process indicated the appropriate use of the saturation method for estimation of the aggregation state of quaternary ammonium extractants in themore » organic phase. From the saturation method, we observed an average aggregation number of 5.4 ± 0.8 and 8.5 ± 0.9 monomers/aggregate for nitrate and thiocyanate, respectively. Through a side-by-side comparison of the nitrate and thiocyanate forms, we discuss the potential role of the aggregation in the increased selectivity for trivalent actinides over trivalent lanthanides in thiocyanate media.« less

Extraction Selectivity of a Quaternary Alkylammonium Salt for Trivalent Actinides over Trivalent Lanthanides: Does Extractant Aggregation Play a Role?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knight, Andrew W.; Chiarizia, Renato; Soderholm, L.

In this paper, the extraction behavior of a quaternary alkylammonium salt extractant was investigated for its selectivity for trivalent actinides over trivalent lanthanides in nitrate and thiocyanate media. The selectivity was evaluated by solvent extraction experiments through radiochemical analysis of 241Am and 152/154Eu. Solvent extraction distribution and slope-analysis experiments were performed with americium(III) and europium(III) with respect to the ligand (nitrate and thiocyanate), extractant, and metal (europium only) concentrations. Further evaluation of the equilibrium expression that governs the extraction process indicated the appropriate use of the saturation method for estimation of the aggregation state of quaternary ammonium extractants in themore » organic phase. From the saturation method, we observed an average aggregation number of 5.4 ± 0.8 and 8.5 ± 0.9 monomers/aggregate for nitrate and thiocyanate, respectively. Through a side-by-side comparison of the nitrate and thiocyanate forms, we discuss the potential role of the aggregation in the increased selectivity for trivalent actinides over trivalent lanthanides in thiocyanate media.« less

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.

Oxidation of extracellular cysteine/cystine redox state in bleomycin-induced lung fibrosis

PubMed Central

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 (Eh Cys/CySS) is oxidized in association with age and smoking, known risk factors for IPF. Furthermore, oxidized Eh 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 Eh GSH/glutathione disulfide (GSSG). We observed distinct effects on plasma GSH and Cys redox systems during the progression of bleomycin-induced lung injury. Plasma Eh GSH/GSSG was selectively oxidized during the proinflammatory phase, whereas oxidation of Eh Cys/CySS occurred at the fibrotic phase. In the epithelial lining fluid, oxidation of Eh 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

Supercritical fluid extraction and separation of uranium from other actinides.

PubMed

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

2014-06-15

The feasibility of separating U from nitric acid solutions of mixed actinides using tri-n-butylphosphate (TBP)-modified supercritical fluid carbon dioxide (sc-CO2) was investigated. The actinides U, Np, Pu, and Am were extracted into sc-CO2 modified with TBP from a range of nitric acid concentrations, in the absence of, or in the presence of, a number of traditional reducing and/or complexing agents to demonstrate the separation of these metals from U under sc-CO2 conditions. The separation of U from Pu using sc-CO2 was successful at nitric acid concentrations of less than 3M in the presence of acetohydroxamic acid (AHA) or oxalic acid (OA) to mitigate Pu extraction, and the separation of U from Np was successful at nitric acid concentrations of less than 1M in the presence of AHA, OA, or sodium nitrite to mitigate Np extraction. Americium was not well extracted under any condition studied. Copyright © 2014 Elsevier B.V. All rights reserved.

Complete recovery of actinides from UREX-like raffinates using a combination of hard and soft donor ligands. II. soft donor structure variation

DOE PAGES

Zalupski, Peter R.; Klaehn, John R.; Peterman, Dean R.

2015-07-30

The feasibility of simultaneous separation of uranium, neptunium, plutonium, americium, and curium from a simulated dissolved used fuel simulant adjusted to 1.0 M nitric acid is investigated using a mixture of the soft donor bis(bis-3,5-trifluoromethyl)phenyl) dithiophosphinic acid (“0”) and the hard donor synergist trioctylphosphine oxide (TOPO) dissolved in toluene. The results reported in this work are compared to our recent demonstration of a complete actinide recovery from a simulated dissolved fuel solution using a synergistic combination of bis(o-trifluoromethylphenyl)dithiophosphinic acid (“1”) and TOPO dissolved in either toluene or trifluoromethylphenyl sulfone. While the extraction efficiency of americium was enhanced for the liquid-liquidmore » system containing “0”, enabling to accomplish a trivalent An/Ln separation at 1.0 M HNO3, the extraction of neptunium was drastically diminished, relative to “1”. The partitioning behavior of curium was also negatively impacted, introducing an effective opportunity for americium/curium separation. Radiometric and spectrophotometric studies demonstrate that the complete actinide recovery using the solvent based upon “0” and TOPO is not feasible. Additionally, the importance of radiolytic degradation processes is discussed through the comparisons of extraction properties of liquid-liquid systems based on both soft donor reagents.« less

RAPID DETERMINATION OF ACTINIDES IN URINE BY INDUCTIVELY-COUPLED PLASMA MASS SPECTROMETRY AND ALPHA SPECTROMETRY: A HYBRID APPROACH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, S.; Jones, V.

2009-05-27

A new rapid separation method that allows separation and preconcentration of actinides in urine samples was developed for the measurement of longer lived actinides by inductively coupled plasma mass spectrometry (ICP-MS) and short-lived actinides by alpha spectrometry; a hybrid approach. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration, if required, is performed using a streamlined calcium phosphate precipitation. Similar technology has been applied to separate actinides prior to measurement by alpha spectrometry, but this new method has been developed with elution reagents now compatible with ICP-MS as well. Purified solutions are splitmore » between ICP-MS and alpha spectrometry so that long- and short-lived actinide isotopes can be measured successfully. The method allows for simultaneous extraction of 24 samples (including QC samples) in less than 3 h. Simultaneous sample preparation can offer significant time savings over sequential sample preparation. For example, sequential sample preparation of 24 samples taking just 15 min each requires 6 h to complete. The simplicity and speed of this new method makes it attractive for radiological emergency response. If preconcentration is applied, the method is applicable to larger sample aliquots for occupational exposures as well. The chemical recoveries are typically greater than 90%, in contrast to other reported methods using flow injection separation techniques for urine samples where plutonium yields were 70-80%. This method allows measurement of both long-lived and short-lived actinide isotopes. 239Pu, 242Pu, 237Np, 243Am, 234U, 235U and 238U were measured by ICP-MS, while 236Pu, 238Pu, 239Pu, 241Am, 243Am and 244Cm were measured by alpha spectrometry. The method can also be adapted so that the separation of uranium isotopes for assay is not required, if uranium assay by direct dilution of the urine sample is preferred

Quantification of Cation Sorption to Engineered Barrier Materials Under Extreme Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Brian; Schlautman, Mark; Rao, Linfeng

The objective of this research is to examine mechanisms and thermodynamics of actinide sorption to engineered barrier materials (iron (oxyhydr)oxides and bentonite clay) for nuclear waste repositories under high temperature and high ionic strength conditions using a suite of macroscopic and microscopic techniques which will be coupled with interfacial reaction models. Gaining a mechanistic understanding of interfacial processes governing the sorption/sequestration of actinides at mineral-water interfaces is fundamental for the accurate prediction of actinide behavior in waste repositories. Although macroscale sorption data and various spectroscopic techniques have provided valuable information regarding speciation of actinides at solid-water interfaces, significant knowledge gapsmore » still exist with respect to sorption mechanisms and the ability to quantify sorption, particularly at high temperatures and ionic strengths. This objective is addressed through three major tasks: (1) influence of oxidation state on actinide sorption to iron oxides and clay minerals at elevated temperatures and ionic strengths; (2) calorimetric titrations of actinide-mineral suspensions; (3) evaluation of bentonite performance under repository conditions. The results of the work will include a qualitative conceptual model and a quantitative thermodynamic speciation model describing actinide partitioning to minerals and sediments, which is based upon a mechanistic understanding of specific sorption processes as determined from both micro-scale and macroscale experimental techniques. The speciation model will be a thermodynamic aqueous and surface complexation model of actinide interactions with mineral surfaces that is self-consistent with macroscopic batch sorption data, calorimetric and potentiometric titrations, X-ray absorption Spectroscopy (XAS, mainly Extended X-ray Absorption Fine Structure (EXAFS)), and electron microscopy analyses. The novelty of the proposed work lies

Sub-barrier quasifission in heavy element formation reactions with deformed actinide target nuclei

NASA Astrophysics Data System (ADS)

Hinde, D. J.; Jeung, D. Y.; Prasad, E.; Wakhle, A.; Dasgupta, M.; Evers, M.; Luong, D. H.; du Rietz, R.; Simenel, C.; Simpson, E. C.; Williams, E.

2018-02-01

Background: The formation of superheavy elements (SHEs) by fusion of two massive nuclei is severely inhibited by the competing quasifission process. Low excitation energies favor SHE survival against fusion-fission competition. In "cold" fusion with spherical target nuclei near 208Pb, SHE yields are largest at beam energies significantly below the average capture barrier. In "hot" fusion with statically deformed actinide nuclei, this is not the case. Here the elongated deformation-aligned configurations in sub-barrier capture reactions inhibits fusion (formation of a compact compound nucleus), instead favoring rapid reseparation through quasifission. Purpose: To determine the probabilities of fast and slow quasifission in reactions with prolate statically deformed actinide nuclei, through measurement and quantitative analysis of the dependence of quasifission characteristics at beam energies spanning the average capture barrier energy. Methods: The Australian National University Heavy Ion Accelerator Facility and CUBE fission spectrometer have been used to measure fission and quasifission mass and angle distributions for reactions with projectiles from C to S, bombarding Th and U target nuclei. Results: Mass-asymmetric quasifission occurring on a fast time scale, associated with collisions with the tips of the prolate actinide nuclei, shows a rapid increase in probability with increasing projectile charge, the transition being centered around projectile atomic number ZP=14 . For mass-symmetric fission events, deviations of angular anisotropies from expectations for fusion fission, indicating a component of slower quasifission, suggest a similar transition, but centered around ZP˜8 . Conclusions: Collisions with the tips of statically deformed prolate actinide nuclei show evidence for two distinct quasifission processes of different time scales. Their probabilities both increase rapidly with the projectile charge. The probability of fusion can be severely

Ferric Iron Production in Magma Oceans and Evolution of Mantle Oxidation State

NASA Astrophysics Data System (ADS)

Schaefer, L.; Elkins-Tanton, L. T.; Pahlevan, K.

2018-05-01

Self-oxidation of the magma ocean by ferric iron production at high pressure may explain the mantle oxidation state of the Earth. Partitioning during fractional crystallization can further increase the mantle oxygen fugacity during solidification.

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

Octupole deformation in neutron-rich actinides and superheavy nuclei and the role of nodal structure of single-particle wavefunctions in extremely deformed structures of light nuclei

NASA Astrophysics Data System (ADS)

Afanasjev, A. V.; Abusara, H.; Agbemava, S. E.

2018-03-01

Octupole deformed shapes in neutron-rich actinides and superheavy nuclei as well as extremely deformed shapes of the N∼ Z light nuclei have been investigated within the framework of covariant density functional theory. We confirmed the presence of new region of octupole deformation in neutron-rich actinides with the center around Z∼ 96,N∼ 196 but our calculations do not predict octupole deformation in the ground states of superheavy Z≥slant 108 nuclei. As exemplified by the study of 36Ar, the nodal structure of the wavefunction of occupied single-particle orbitals in extremely deformed structures allows to understand the formation of the α-clusters in very light nuclei, the suppression of the α-clusterization with the increase of mass number, the formation of ellipsoidal mean-field type structures and nuclear molecules.

A moving target: responding to magnetic and structural disorder in lanthanide- and actinide-based superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, Eric D; Mitchell, Jeremy N; Booth, C H

2009-01-01

The effects of various chemical substitutions and induced lattice disorder in the Ce- and Pu-based 115 superconductors are reviewed, with particular emphasis on results from x-ray absorption fine structure (XAFS) measurements. The competition between spin, charge, and lattice interactions is at the heart of many of the strongly-correlated ground states in materials of current interest, such as in colossal magnetoresistors and high-temperature superconductors. This relationship is particularly strong in the CeTIn{sub 5} and PuTGa{sub 5} series (T = Co, Rh, Ir) of heavy-fermion superconductors. In these systems (figure 1), competition between bulk magnetic and non-magnetic ground states, as well asmore » between superconducting and normal states, are directly related to local properties around the lanthanide or actinide ion, such as the nearest-neighbor bond lengths and the local density of states at the Fermi level. Tiny changes in the latter values can easily tip the balance from one ground state to another. This paper reviews recent work by the authors exploring the relationship between local crystal and electronic structure and ground state magnetic and conducting properties in the Ce- and Pu-based 115 materials.« less

On the valence fluctuation in the early actinide metals

DOE PAGES

Soderlind, P.; Landa, A.; Tobin, J. G.; ...

2015-12-15

In this study, recent X-ray measurements suggest a degree of valence fluctuation in plutonium and uranium intermetallics. We are applying a novel scheme, in conjunction with density functional theory, to predict 5f configuration fractions of states with valence fluctuations for the early actinide metals. For this purpose we perform constrained integer f-occupation calculations for the α phases of uranium, neptunium, and plutonium metals. For plutonium we also investigate the δ phase. The model predicts uranium and neptunium to be dominated by the f 3 and f 4 configurations, respectively, with only minor contributions from other configurations. For plutonium (both αmore » and δ phase) the scenario is dramatically different. Here, the calculations predict a relatively even distribution between three valence configurations. The δ phase has a greater configuration fraction of f 6 compared to that of the α phase. The theory is consistent with the interpretations of modern X-ray experiments and we present resonant X-ray emission spectroscopy results for α-uranium.« less

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

Physical nature of longevity of light actinides in dynamic failure phenomenon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uchaev, A. Ya., E-mail: uchaev@expd.vniief.ru; Punin, V. T.; Selchenkova, N. I.

It is shown in this work that the physical nature of the longevity of light actinides under extreme conditions in a range of nonequilibrium states of t ∼ 10{sup –6}–10{sup –10} s is determined by the time needed for the formation of a critical concentration of a cascade of failure centers, which changes connectivity of the body. These centers form a percolation cluster. The longevity is composed of waiting time t{sub w} for the appearance of failure centers and clusterization time t{sub c} of cascade of failure centers, when connectivity in the system of failure centers and the percolation clustermore » arise. A unique mechanism of the dynamic failure process, a unique order parameter, and an equal dimensionality of the space in which the process occurs determine the physical nature of the longevity of metals, including fissionable materials.« less

MRI based on iron oxide nanoparticles contrast agents: effect of oxidation state and architecture

NASA Astrophysics Data System (ADS)

Javed, Yasir; Akhtar, Kanwal; Anwar, Hafeez; Jamil, Yasir

2017-11-01

Iron oxide nanoparticles (IONPs) extensively employed beyond regenerative medicines to imaging disciplines because of their great constituents for magneto-responsive nano-systems. The unique superparamagnetic behavior makes IONPs very suitable for hyperthermia and imaging applications. From the last decade, versatile functionalization with surface capabilities, efficient contrast properties and biocompatibilities make IONPs an essential imaging contrast agent for magnetic resonance imaging (MRI). IONPs have shown signals for both longitudinal relaxation and transverse relaxation; therefore, negative contrast as well as dual contrast can be used for imaging in MRI. In the current review, we have focused on different oxidation state of iron oxides, i.e., magnetite, maghemite and hematite for their T1 and T2 contrast enhancement properties. We have also discussed different factors (synthesis protocols, biocompatibility, toxicity, architecture, etc.) that can affect the contrast properties of the IONPs. [Figure not available: see fulltext.

Method for extracting lanthanides and actinides from acid solutions by modification of purex solvent

DOEpatents

Horwitz, E. Philip; Kalina, Dale G.

1986-01-01

A process for the recovery of actinide and lanthanide values from aqueous solutions with an extraction solution containing an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms and phase modifiers in a water-immiscible hydrocarbon diluent. 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.

Importance of strong-correlation on the lattice dynamics of light-actinides Th-Pa alloy

NASA Astrophysics Data System (ADS)

de La Peã+/-A Seaman, Omar; Heid, Rolf; Bohnen, Klaus-Peter

We have studied the structural, electronic, and lattice dynamics of the Th1-xPax actinide alloy. This system have been analyzed within the framework of density functional perturbation theory, using a mixed-basis pseudopotential method and the virtual crystal approximation (VCA) for modeling the alloy. In particular, the energetics is analyzed as the ground-state crystal structure is changed form fcc to bct, as well as the electronic density of states (DOS), and the phonon frequencies. Such properties have been calculated with and without strong correlations effects through the LDA+U formalism. Although the strong-correlation does not influence on a great manner the Th properties, such effects are more important as the content increases towards Pa, affecting even the definition of the ground-state crystal structure for Pa (experimentally determined as bct). The evolution of the density of states at the Fermi level (N (EF)) and the phonon frequencies as a function of Pa-content are presented and discussed in detail, aiming to understand their influence on the electron-phonon coupling for the Th-Pa alloy. This research was supported by Conacyt-México under project No. CB2013-221807-F.

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.

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

Evaluation of possible physical-chemical processes that might lead to separations of actinides in ORNL waste tanks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Del Cul, G.D.; Toth, L.M.; Bond, W.D.

The concern that there might be some physical-chemical process which would lead to a separation of the poisoning actinides ({sup 232}Th, {sup 238}U) from the fissionable ones ({sup 239}Pu, {sup 235}U) in waste storage tanks at Oak Ridge National Laboratory has led to a paper study of potential separations processes involving these elements. At the relatively high pH values (>8), the actinides are normally present as precipitated hydroxides. Mechanisms that might then selectively dissolve and reprecipitate the actinides through thermal processes or additions of reagents were addressed. Although redox reactions, pH changes, and complexation reactions were all considered, only themore » last type was regarded as having any significant probability. Furthermore, only carbonate accumulation, through continual unmonitored air sparging of the tank contents, could credibly account for gross transport and separation of the actinide components. From the large amount of equilibrium data in the literature, concentration differences in Th, U, and Pu due to carbonate complexation as a function of pH have been presented to demonstrate this phenomenon. While the carbonate effect does represent a potential separations process, control of long-term air sparging and solution pH, accompanied by routine determinations of soluble carbonate concentration, should ensure that this separations process does not occur.« less

The mitochondrial oxidoreductase CHCHD4 is present in a semi-oxidized state in vivo.

PubMed

Erdogan, Alican J; Ali, Muna; Habich, Markus; Salscheider, Silja L; Schu, Laura; Petrungaro, Carmelina; Thomas, Luke W; Ashcroft, Margaret; Leichert, Lars I; Roma, Leticia Prates; Riemer, Jan

2018-07-01

Disulfide formation in the mitochondrial intermembrane space is an essential process catalyzed by a disulfide relay machinery. In mammalian cells, the key enzyme in this machinery is the oxidoreductase CHCHD4/Mia40. Here, we determined the in vivo CHCHD4 redox state, which is the major determinant of its cellular activity. We found that under basal conditions, endogenous CHCHD4 redox state in cultured cells and mouse tissues was predominantly oxidized, however, degrees of oxidation in different tissues varied from 70% to 90% oxidized. To test whether differences in the ratio between CHCHD4 and ALR might explain tissue-specific differences in the CHCHD4 redox state, we determined the molar ratio of both proteins in different mouse tissues. Surprisingly, ALR is superstoichiometric over CHCHD4 in most tissues. However, the levels of CHCHD4 and the ratio of ALR over CHCHD4 appear to correlate only weakly with the redox state, and although ALR is present in superstoichiometric amounts, it does not lead to fully oxidized CHCHD4. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

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

DOEpatents

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

1986-03-04

A process is described for the recovery of actinide and lanthanide values from aqueous solutions with an extraction solution containing an organic extractant having the formula as shown in a diagram where [phi] is phenyl, R[sup 1] is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R[sup 2] is an alkyl containing from 3 to 6 carbon atoms and phase modifiers in a water-immiscible hydrocarbon diluent. 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. 6 figs.

Method of forming high density oxide pellets by hot pressing at 50$sup 0$ to 100$sup 0$C above the cubic to monoclinic phase transformation temperature

DOEpatents

Pasto, A.E.

1975-08-01

A process for low temperature sintering of rare earth and actinide oxides which have a cubic to monoclinic transformation is described. The process involves hot pressing a powder compact at a temperature just above the transformation temperature. (auth)

Solid oxide fuel cells fueled with reducible oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chuang, Steven S.; Fan, Liang Shih

A direct-electrochemical-oxidation fuel cell for generating electrical energy includes a cathode provided with an electrochemical-reduction catalyst that promotes formation of oxygen ions from an oxygen-containing source at the cathode, a solid-state reduced metal, a solid-state anode provided with an electrochemical-oxidation catalyst that promotes direct electrochemical oxidation of the solid-state reduced metal in the presence of the oxygen ions to produce electrical energy, and an electrolyte disposed to transmit the oxygen ions from the cathode to the solid-state anode. A method of operating a solid oxide fuel cell includes providing a direct-electrochemical-oxidation fuel cell comprising a solid-state reduced metal, oxidizing themore » solid-state reduced metal in the presence of oxygen ions through direct-electrochemical-oxidation to obtain a solid-state reducible metal oxide, and reducing the solid-state reducible metal oxide to obtain the solid-state reduced metal.« less

Fundamental Studies of Irradiation-Induced Defect Formation and Fission Product Dynamics in Oxide Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stubbins, James

2012-12-19

The objective of this research program is to address major nuclear fuels performance issues for the design and use of oxide-type fuels in the current and advanced nuclear reactor applications. Fuel performance is a major issue for extending fuel burn-up which has the added advantage of reducing the used fuel waste stream. It will also be a significant issue with respect to developing advanced fuel cycle processes where it may be possible to incorporate minor actinides in various fuel forms so that they can be 'burned' rather than join the used fuel waste stream. The potential to fission or transmutemore » minor actinides and certain long-lived fission product isotopes would transform the high level waste storage strategy by removing the need to consider fuel storage on the millennium time scale.« less

Formation of unprecedented actinidecarbon triple bonds in uranium methylidyne molecules

PubMed Central

Lyon, Jonathan T.; Hu, Han-Shi; Andrews, Lester; Li, Jun

2007-01-01

Chemistry of the actinide elements represents a challenging yet vital scientific frontier. Development of actinide chemistry requires fundamental understanding of the relative roles of actinide valence-region orbitals and the nature of their chemical bonding. We report here an experimental and theoretical investigation of the uranium methylidyne molecules X3UCH (X = F, Cl, Br), F2ClUCH, and F3UCF formed through reactions of laser-ablated uranium atoms and trihalomethanes or carbon tetrafluoride in excess argon. By using matrix infrared spectroscopy and relativistic quantum chemistry calculations, we have shown that these actinide complexes possess relatively strong UC triple bonds between the U 6d-5f hybrid orbitals and carbon 2s-2p orbitals. Electron-withdrawing ligands are critical in stabilizing the U(VI) oxidation state and sustaining the formation of uranium multiple bonds. These unique UC-bearing molecules are examples of the long-sought actinide-alkylidynes. This discovery opens the door to the rational synthesis of triple-bonded actinidecarbon compounds. PMID:18024591

Arsenic (+3 Oxidation State) Methyltransferase and the Methylation of Arsenicals

PubMed Central

Thomas, David J.; Li, Jiaxin; Waters, Stephen B.; Xing, Weibing; Adair, Blakely M.; Drobna, Zuzana; Devesa, Vicenta; Styblo, Miroslav

2008-01-01

Metabolic conversion of inorganic arsenic into methylated products is a multistep process that yields mono-, di-, and trimethylated arsenicals. In recent years, it has become apparent that formation of methylated metabolites of inorganic arsenic is not necessarily a detoxification process. Intermediates and products formed in this pathway may be more reactive and toxic than inorganic arsenic. Like all metabolic pathways, understanding the pathway for arsenic methylation involves identification of each individual step in the process and the characterization of the molecules which participate in each step. Among several arsenic methyltransferases that have been identified, arsenic (+3 oxidation state) methyltransferase is the one best characterized at the genetic and functional levels. This review focuses on phylogenetic relationships in the deuterostomal lineage for this enzyme and on the relation between genotype for arsenic (+3 oxidation state) methyltransferase and phenotype for conversion of inorganic arsenic to methylated metabolites. Two conceptual models for function of arsenic (+3 oxidation state) methyltransferase which posit different roles for cellular reductants in the conversion of inorganic arsenic to methylated metabolites are compared. Although each model accurately represents some aspects of enzyme’s role in the pathway for arsenic methylation, neither model is a fully satisfactory representation of all the steps in this metabolic pathway. Additional information on the structure and function of the enzyme will be needed to develop a more comprehensive model for this pathway. PMID:17202581

GaAs-oxide interface states - Gigantic photoionization via Auger-like process

NASA Technical Reports Server (NTRS)

Lagowski, J.; Kazior, T. E.; Gatos, H. C.; Walukiewicz, W.; Siejka, J.

1981-01-01

Spectral and transient responses of photostimulated current in MOS structures were employed for the study of GaAs-anodic oxide interface states. Discrete deep traps at 0.7 and 0.85 eV below the conduction band were found with concentrations of 5 x 10 to the 12th/sq cm and 7 x 10 to the 11th/sq cm, respectively. These traps coincide with interface states induced on clean GaAs surfaces by oxygen and/or metal adatoms (submonolayer coverage). In contrast to surfaces with low oxygen coverage, the GaAs-thick oxide interfaces exhibited a high density (about 10 to the 14th/sq cm) of shallow donors and acceptors. Photoexcitation of these donor-acceptor pairs led to a gigantic photoionization of deep interface states with rates 1000 times greater than direct transitions into the conduction band. The gigantic photoionization is explained on the basis of energy transfer from excited donor-acceptor pairs to deep states.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagus, Paul S.

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 hasmore » 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

Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide

DOE PAGES

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 (V O n; n=0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta 2O 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 O n of all oxidation states preferentially segregate at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta 2O 5, V O 0 are characterized by structural contractionmore » and electron density localization, while V O 2+ promote structural expansion and are depleted of electron density. In contrast, interfacial V O 0 and V O 2+ show nearly indistinguishable ionic and electronic signatures indicative of a reduced V O center. Interfacial V O 2+ extract electron density from metallic Ta indicating V O 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.« less

Model for determination of mid-gap states in amorphous metal oxides from thin film transistors

NASA Astrophysics Data System (ADS)

Bubel, S.; Chabinyc, M. L.

2013-06-01

The electronic density of states in metal oxide semiconductors like amorphous zinc oxide (a-ZnO) and its ternary and quaternary oxide alloys with indium, gallium, tin, or aluminum are different from amorphous silicon, or disordered materials such as pentacene, or P3HT. Many ZnO based semiconductors exhibit a steep decaying density of acceptor tail states (trap DOS) and a Fermi level (EF) close to the conduction band energy (EC). Considering thin film transistor (TFT) operation in accumulation mode, the quasi Fermi level for electrons (Eq) moves even closer to EC. Classic analytic TFT simulations use the simplification EC-EF> `several'kT and cannot reproduce exponential tail states with a characteristic energy smaller than 1/2 kT. We demonstrate an analytic model for tail and deep acceptor states, valid for all amorphous metal oxides and include the effect of trap assisted hopping instead of simpler percolation or mobility edge models, to account for the observed field dependent mobility.

An optical potential for the statically deformed actinide nuclei derived from a global spherical potential

NASA Astrophysics Data System (ADS)

Al-Rawashdeh, S. M.; Jaghoub, M. I.

2018-04-01

In this work we test the hypothesis that a properly deformed spherical optical potential, used within a channel-coupling scheme, provides a good description for the scattering data corresponding to neutron induced reactions on the heavy, statically deformed actinides and other lighter deformed nuclei. To accomplish our goal, we have deformed the Koning-Delaroche spherical global potential and then used it in a channel-coupling scheme. The ground-state is coupled to a sufficient number of inelastic rotational channels belonging to the ground-state band to ensure convergence. The predicted total cross sections, elastic and inelastic angular distributions are in good agreement with the experimental data. As a further test, we compare our results to those obtained by a global channel-coupled optical model whose parameters were obtained by fitting elastic and inelastic angular distributions in addition to total cross sections. Our results compare quite well with those obtained by the fitted, channel-coupled optical model. Below neutron incident energies of about 1MeV, our results show that scattering into the rotational excited states of the ground-state band plays a significant role in the scattering process and must be explicitly accounted for using a channel-coupling scheme.

Actinide Sorption in Rainier Mesa Tunnel Waters from the Nevada Test Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, P; Zavarin, M; Leif, R

2007-12-17

The sorption behavior of americium (Am), plutonium (Pu), neptunium (Np), and uranium (U) in perched Rainier Mesa tunnel water was investigated. Both volcanic zeolitized tuff samples and groundwater samples were collected from Rainier Mesa, Nevada Test Site, NV for a series of batch sorption experiments. Sorption in groundwater with and without the presence of dissolved organic matter (DOM) was investigated. Am(III) and Pu(IV) are more soluble in groundwater that has high concentrations of DOM. The sorption K{sub d} for Am(III) and Pu(IV) on volcanic zeolitized tuff was up to two orders of magnitude lower in samples with high DOM (15more » to 19 mg C/L) compared to samples with DOM removed (< 0.4 mg C/L) or samples with naturally low DOM (0.2 mg C/L). In contrast, Np(V) and U(VI) sorption to zeolitized tuff was much less affected by the presence of DOM. The Np(V) and U(VI) sorption Kds were low under all conditions. Importantly, the DOM was not found to significantly sorb to the zeolitized tuff during these experiment. The concentration of DOM in groundwater affects the transport behavior of actinides in the subsurface. The mobility of Am(III) and Pu(IV) is significantly higher in groundwater with elevated levels of DOM resulting in potentially enhanced transport. To accurately model the transport behavior of actinides in groundwater at Rainier Mesa, the low actinide Kd values measured in groundwater with high DOM concentrations must be incorporated in predictive transport models.« less

Crystallographic studies of [NiFe]-hydrogenase mutants: towards consensus structures for the elusive unready oxidized states.

PubMed

Volbeda, Anne; Martin, Lydie; Barbier, Elodie; Gutiérrez-Sanz, Oscar; De Lacey, Antonio L; Liebgott, Pierre-Pol; Dementin, Sébastien; Rousset, Marc; Fontecilla-Camps, Juan C

2015-01-01

Catalytically inactive oxidized O2-sensitive [NiFe]-hydrogenases are characterized by a mixture of the paramagnetic Ni-A and Ni-B states. Upon O2 exposure, enzymes in a partially reduced state preferentially form the unready Ni-A state. Because partial O2 reduction should generate a peroxide intermediate, this species was previously assigned to the elongated Ni-Fe bridging electron density observed for preparations of [NiFe]-hydrogenases known to contain the Ni-A state. However, this proposition has been challenged based on the stability of this state to UV light exposure and the possibility of generating it anaerobically under either chemical or electrochemical oxidizing conditions. Consequently, we have considered alternative structures for the Ni-A species including oxidation of thiolate ligands to either sulfenate or sulfenic acid. Here, we report both new and revised [NiFe]-hydrogenases structures and conclude, taking into account corresponding characterizations by Fourier transform infrared spectroscopy (FTIR), that the Ni-A species contains oxidized cysteine and bridging hydroxide ligands instead of the peroxide ligand we proposed earlier. Our analysis was rendered difficult by the typical formation of mixtures of unready oxidized states that, furthermore, can be reduced by X-ray induced photoelectrons. The present study could be carried out thanks to the use of Desulfovibrio fructosovorans [NiFe]-hydrogenase mutants with special properties. In addition to the Ni-A state, crystallographic results are also reported for two diamagnetic unready states, allowing the proposal of a revised oxidized inactive Ni-SU model and a new structure characterized by a persulfide ion that is assigned to an Ni-'Sox' species.

The oxidation state of sulfur in apatite: A new oxybarometer?

NASA Astrophysics Data System (ADS)

Fiege, A.; Konecke, B.; Kim, Y.; Simon, A. C.; Becker, U.; Parat, F.

2016-12-01

Oxygen fugacity (fO2) of magmatic and hydrothermal systems influences, for instance, crystallization and degassing processes as well as metal solubilities in melts and fluids. Apatite is a ubiquitous mineral in magmatic and hydrothermal environments that can record and preserve volatile zonation. It can contain several thousand μg/g of the redox sensitive element sulfur (S), making S-in-apatite a potential fO2 sensor. Despite the polyvalent properties of S (e.g., S2-, S4+, S6+), the oxidation state and incorporation mechanisms of S in the apatite structure are poorly understood. In this study, the oxidation state of S-in-apatite as a function of fO2 is investigated using X-ray absorption near-edge structures (XANES) spectroscopy at the S K-edge. Apatites crystallized from lamproitic melts at 1000°C, 300 MPa and over a broad range of fO2 and sulfur fugacities (fS2) were measured. Peaks corresponding to S6+ ( 2482 eV), S4+ ( 2478 eV) and S2- ( 2470 eV) were identified in apatite. The integrated S6+/STotal (STotal = S6+ + S4+ + S2-) peak area ratios show a distinct positive correlation with fO2, increasing from 0.17 at FMQ+0 to 0.96 at FMQ+3. Ab-initio calculations were performed to further understand the energetics and geometry of incorporation of S6+, S4+ and S2- into the apatite (F-, Cl-, OH-) end-members. The results confirm that apatite can contain three different oxidations states of S (S6+, S4+, S2-) as a function of fO2. This makes apatite probably the first geologically relevant mineral to incorporate reduced (S2-), intermediate (S4+), and oxidized (S6+) S in variable proportions. We emphasize that the strong dependence of the S oxidation state in apatite as a function of fO2 is also coupled with changing S content of apatite and co-existing melt (i.e., with changing fS2), resulting in a complex correlation between [1] apatite-melt (or fluid) partitioning, [2] redox conditions and [3] the melt and/or fluid composition, making the application of previously

Characterization of Intermediate Oxidation States in CO2 Activation

NASA Astrophysics Data System (ADS)

Dodson, Leah G.; Thompson, Michael C.; Weber, J. Mathias

2018-04-01

Redox chemistry during the activation of carbon dioxide involves changing the charge state in a CO2 molecular unit. However, such changes are usually not well described by integer formal charges, and one can think of COO functional units as being in intermediate oxidation states. In this article, we discuss the properties of CO2 and CO2-based functional units in various charge states. Besides covering isolated CO2 and its ions, we describe the CO2-based ionic species formate, oxalate, and carbonate. Finally, we provide an overview of CO2-based functional groups and ligands in clusters and metal-organic complexes.

BAGHEERA: A new experimental facility at CEA / Valduc for actinides studies under high dynamic loading

NASA Astrophysics Data System (ADS)

Roy, G.; Llorca, F.; Lanier, G.; Lamalle, S.; Beaulieu, J.; Antoine, P.; Martinuzzi, P.

2006-08-01

This paper is a technical presentation about a new experimental facility recently developed at CEA/Valduc, BAGHEERA, a French acronym for “Hopkinson And High Speed Experiments Glove Box”. This facility is used since mid-2003 to characterize the physical and mechanical behaviour of actinides under high dynamic loadings. For this purpose, four basic experimental devices are confined inside a single glove box: a 50 mm bore diameter single stage light gas gun, two compression and torsion split Hopkinson bars (SHPB and TSHB respectively) and a Taylor test device (TTD). Design and technical data on the experimental equipment are addressed, with a particular emphasis on the gas gun specific features due to actinide applications.

Energetics and Defect Interactions of Complex Oxides for Energy Applications

NASA Astrophysics Data System (ADS)

Solomon, Jonathan Michael

investigated based on the present results and previous computational and experimental thermochemical studies of rare earth substituted fluorite oxides. A consistent trend towards increased energetic stability with larger size mismatch between the smaller host tetravalent cation and the larger rare earth trivalent cation is found for both actinide and non-actinide fluorite oxide systems where aliovalent substitution of M cations is compensated by oxygen vacancies. However, the large exothermic oxidation enthalpy in the UO2 based systems favors compositions with higher oxygen-to-metal ratios where charge compensation occurs through the formation of uranium cations with higher oxidation states.

Conformational Toggling of Yeast Iso-1-Cytochrome c in the Oxidized and Reduced States

PubMed Central

Yang, Zhongzheng; Zhu, Jing; Ying, Tianlei; Jiang, Xianwang; Zhang, Xu; Wu, Houming; Liu, Maili; Tan, Xiangshi; Cao, Chunyang; Huang, Zhong-Xian

2011-01-01

To convert cyt c into a peroxidase-like metalloenzyme, the P71H mutant was designed to introduce a distal histidine. Unexpectedly, its peroxidase activity was found even lower than that of the native, and that the axial ligation of heme iron was changed to His71/His18 in the oxidized state, while to Met80/His18 in the reduced state, characterized by UV-visible, circular dichroism, and resonance Raman spectroscopy. To further probe the functional importance of Pro71 in oxidation state dependent conformational changes occurred in cyt c, the solution structures of P71H mutant in both oxidation states were determined. The structures indicate that the half molecule of cyt c (aa 50–102) presents a kind of “zigzag riveting ruler” structure, residues at certain positions of this region such as Pro71, Lys73 can move a big distance by altering the tertiary structure while maintaining the secondary structures. This finding provides a molecular insight into conformational toggling in different oxidation states of cyt c that is principle significance to its biological functions in electron transfer and apoptosis. Structural analysis also reveals that Pro71 functions as a key hydrophobic patch in the folding of the polypeptide of the region (aa 50–102), to prevent heme pocket from the solvent. PMID:22087268

An Advanced TALSPEAK Concept for Separating Minor Actinides. Part 1. Process Optimization and Flowsheet Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lumetta, Gregg J.; Levitskaia, Tatiana G.; Wilden, Andreas

A system is being developed to separate trivalent actinides from lanthanide fission product elements that uses 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester to extract the lanthanide ions into an organic phase, while the actinide ions are held in the citrate-buffered aqueous phase by complexation to N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA). Earlier investigations of this system using a 2-cm centrifugal contactor revealed that the relatively slow extraction of Sm3+, Eu3+, and Gd3+ resulted in low separation factors from Am3+. In the work reported here, adjustments to the aqueous phase chemistry were made to improve the extraction rates. The results suggest that increasing the concentration ofmore » the citric acid buffer from 0.2 to 0.6 mol/L, and lowering the pH from 3.1 to 2.6, significantly improved lanthanide extraction rates resulting in an actinide/lanthanide separation system suitable for deployment in centrifugal contactors. Experiments performed to evaluate whether the lanthanide extraction rates can be improved by replacing aqueous HEDTA with nitrilotriacetic acid (NTA) exhibited promising results. However, NTA exhibited an unsatisfactorily high distribution value for Am3+ under the extraction conditions examined.« less

ADS Model in the TIRELIRE-STRATEGIE Fuel Cycle Simulation Code Application to Minor Actinides Transmutation Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garzenne, Claude; Massara, Simone; Tetart, Philippe

2006-07-01

Accelerator Driven Systems offer the advantage, thanks to the core sub-criticality, to burn highly radioactive elements such as americium and curium in a dedicated stratum, and then to avoid polluting with these elements the main part of the nuclear fleet, which is optimized for electricity production. This paper presents firstly the ADS model implemented in the fuel cycle simulation code TIRELIRE-STRATEGIE that we developed at EDF R and D Division for nuclear power scenario studies. Then we show and comment the results of TIRELIRE-STRATEGIE calculation of a transition scenario between the current French nuclear fleet, and a fast reactor fleetmore » entirely deployed towards the end of the 21. century, consistently with the EDF prospective view, with 3 options for the minor actinides management:1) vitrified with fission products to be sent to the final disposal; 2) extracted together with plutonium from the spent fuel to be transmuted in Generation IV fast reactors; 3) eventually extracted separately from plutonium to be incinerated in a ADSs double stratum. The comparison of nuclear fuel cycle material fluxes and inventories between these options shows that ADSs are not more efficient than critical fast reactors for reducing the high level waste radio-toxicity; that minor actinides inventory and fluxes in the fuel cycle are more than twice as high in case of a double ADSs stratum than in case of minor actinides transmutation in Generation IV FBRs; and that about fourteen 400 MWth ADS are necessary to incinerate minor actinides issued from a 60 GWe Generation IV fast reactor fleet, corresponding to the current French nuclear fleet installed power. (authors)« less

Angle-resolved photoemission spectroscopy studies of metallic surface and interface states of oxide insulators

NASA Astrophysics Data System (ADS)

Plumb, Nicholas C.; Radović, Milan

2017-11-01

Over the last decade, conducting states embedded in insulating transition metal oxides (TMOs) have served as gateways to discovering and probing surprising phenomena that can emerge in complex oxides, while also opening opportunities for engineering advanced devices. These states are commonly realized at thin film interfaces, such as the well-known case of LaAlO3 (LAO) grown on SrTiO3 (STO). In recent years, the use of angle-resolved photoemission spectroscopy (ARPES) to investigate the k-space electronic structure of such materials led to the discovery that metallic states can also be formed on the bare surfaces of certain TMOs. In this topical review, we report on recent studies of low-dimensional metallic states confined at insulating oxide surfaces and interfaces as seen from the perspective of ARPES, which provides a direct view of the occupied band structure. While offering a fairly broad survey of progress in the field, we draw particular attention to STO, whose surface is so far the best-studied, and whose electronic structure is probably of the most immediate interest, given the ubiquitous use of STO substrates as the basis for conducting oxide interfaces. The ARPES studies provide crucial insights into the electronic band structure, orbital character, dimensionality/confinement, spin structure, and collective excitations in STO surfaces and related oxide surface/interface systems. The obtained knowledge increases our understanding of these complex materials and gives new perspectives on how to manipulate their properties.

Electrodeposition of actinide compounds from an aqueous ammonium acetate matrix. Experimental development and optimization

DOE PAGES

Boll, Rose Ann; Matos, Milan; Torrico, Matthew N.

2015-03-27

Electrodeposition is a technique that is routinely employed in nuclear research for the preparation of thin solid films of actinide materials which can be used in accelerator beam bombardments, irradiation studies, or as radioactive sources. The present study investigates the deposition of both lanthanides and actinides from an aqueous ammonium acetate electrolyte matrix. Electrodepositions were performed primarily on stainless steel disks; with yield analysis evaluated using -spectroscopy. Experimental parameters were studied and modified in order to optimize the uniformity and adherence of the deposition while maximizing the yield. The initial development utilized samarium as the plating material, with and withoutmore » a radioactive tracer. As a result, surface characterization studies were performed by scanning electron microscopy, electron microprobe analysis, radiographic imaging, and x-ray diffraction.« less

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.

The impact of degassing on the oxidation state of basaltic magmas: A case study of Kīlauea volcano

NASA Astrophysics Data System (ADS)

Moussallam, Yves; Edmonds, Marie; Scaillet, Bruno; Peters, Nial; Gennaro, Emanuela; Sides, Issy; Oppenheimer, Clive

2016-09-01

Volcanic emissions link the oxidation state of the Earth's mantle to the composition of the atmosphere. Whether the oxidation state of an ascending magma follows a redox buffer - hence preserving mantle conditions - or deviates as a consequence of degassing remains under debate. Thus, further progress is required before erupted basalts can be used to infer the redox state of the upper mantle or the composition of their co-emitted gases to the atmosphere. Here we present the results of X-ray absorption near-edge structure (XANES) spectroscopy at the iron K-edge carried out for a series of melt inclusions and matrix glasses from ejecta associated with three eruptions of Kīlauea volcano (Hawai'i). We show that the oxidation state of these melts is strongly correlated with their volatile content, particularly in respect of water and sulfur contents. We argue that sulfur degassing has played a major role in the observed reduction of iron in the melt, while the degassing of H2O and CO2 appears to have had a negligible effect on the melt oxidation state under the conditions investigated. Using gas-melt equilibrium degassing models, we relate the oxidation state of the melt to the composition of the gases emitted at Kīlauea. Our measurements and modelling yield a lower constraint on the oxygen fugacity of the mantle source beneath Kīlauea volcano, which we infer to be near the nickel nickel-oxide (NNO) buffer. Our findings should be widely applicable to other basaltic systems and we predict that the oxidation state of the mantle underneath most hotspot volcanoes is more oxidised than that of the associated lavas. We also suggest that whether the oxidation states of a basalt (in particular MORB) reflects that of its source, is primarily determined by the extent of sulfur degassing.

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 ...

Selective Separation of Trivalent Actinides from Lanthanides by Aqueous Processing with Introduction of Soft Donor Atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenneth L. Nash

2009-09-22

Implementation of a closed loop nuclear fuel cycle requires the utilization of Pu-containing MOX fuels with the important side effect of increased production of the transplutonium actinides, most importantly isotopes of Am and Cm. Because the presence of these isotopes significantly impacts the long-term radiotoxicity of high level waste, it is important that effective methods for their isolation and/or transmutation be developed. Furthermore, since transmutation is most efficiently done in the absence of lanthanide fission products (high yield species with large thermal neutron absorption cross sections) it is important to have efficient procedures for the mutual separation of Am andmore » Cm from the lanthanides. The chemistries of these elements are nearly identical, differing only in the slightly stronger strength of interaction of trivalent actinides with ligand donor atoms softer than O (N, Cl-, S). Research being conducted around the world has led to the development of new reagents and processes with considerable potential for this task. However, pilot scale testing of these reagents and processes has demonstrated the susceptibility of the new classes of reagents to radiolytic and hydrolytic degradation. In this project, separations of trivalent actinides from fission product lanthanides have been investigated in studies of 1) the extraction and chemical stability properties of a class of soft-donor extractants that are adapted from water-soluble analogs, 2) the application of water soluble soft-donor complexing agents in tandem with conventional extractant molecules emphasizing fundamental studies of the TALSPEAK Process. This research was conducted principally in radiochemistry laboratories at Washington State University. Collaborators at the Radiological Processing Laboratory (RPL) at the Pacific Northwest National Laboratory (PNNL) have contributed their unique facilities and capabilities, and have supported student internships at PNNL to broaden their

United States Transuranium and Uranium Registries. Annual report February 1, 2000--January 31, 2001

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehrhart, Susan M.; Filipy, Ronald E.

2001-07-01

The United States Transuranium and Uranium Registries (USTUR) comprise a human tissue research program studying the deposition, biokinetics and dosimetry of the actinide elements in humans with the primary goals of providing data fundamental to the verification, refinement, or future development of radiation protection standards for these and other radionuclides, and of determining possible bioeffects on both a macro and subcellular level attributable to exposure to the actinides. This report covers USTUR activities during the year from February 2000 through January 2001.

United States Transuranium and Uranium Registries. Annual report October 1, 1994 - September 30, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kathren, R.L.; Harwick, L.A.; Markel, M.J.

1996-07-01

The United States Transuranium and Uranium Registries (USTUR) comprise a human tissue research program studying the deposition, biokinetics and dosimetry of the actinide elements in humans with the primary goals of providing data fundamental to the verification, refinement, or future development of radiation protection standards for these and other radionuclides, and of determining possible bioeffects on both a macro and subcellular level attributable to exposure to the actinides. This report covers USTUR activities during the year from October 1994 through September 1995.

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pacold, J. I.; Lukens, W. W.; Booth, C. H.

Nuclear weapons testing generates large volumes of glassy materials that influence the transport of dispersed actinides in the environment and may carry information on the composition of the detonated device. We determine the oxidation state of U and Fe (which is known to buffer the oxidation state of actinide elements and to affect the redox state of groundwater) in samples of melt glass collected from three U.S. nuclear weapons tests. For selected samples, we also determine the coordination geometry of U and Fe, and we report the oxidation state of Pu from one melt glass sample. We find significant variationsmore » among the melt glass samples and, in particular, find a clear deviation in one sample from the expected buffering effect of Fe(II)/Fe(III) on the oxidation state of uranium. In the first direct measurement of Pu oxidation state in a nuclear test melt glass, we obtain a result consistent with existing literature that proposes Pu is primarily present as Pu(IV) in post-detonation material. In addition, our measurements imply that highly mobile U(VI) may be produced in significant quantities when melt glass is quenched rapidly following a nuclear detonation, though these products may remain immobile in the vitrified matrices. The observed differences in chemical state among the three samples show that redox conditions can vary dramatically across different nuclear test conditions. The local soil composition, associated device materials, and the rate of quenching are all likely to affect the final redox state of the glass. The resulting variations in glass chemistry are significant for understanding and interpreting debris chemistry and the later environmental mobility of dispersed material.« less

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

NASA Astrophysics Data System (ADS)

Pacold, J. I.; Lukens, W. W.; Booth, C. H.; Shuh, D. K.; Knight, K. B.; Eppich, G. R.; Holliday, K. S.

2016-05-01

Nuclear weapons testing generates large volumes of glassy materials that influence the transport of dispersed actinides in the environment and may carry information on the composition of the detonated device. We determine the oxidation state of U and Fe (which is known to buffer the oxidation state of actinide elements and to affect the redox state of groundwater) in samples of melt glass collected from three U.S. nuclear weapons tests. For selected samples, we also determine the coordination geometry of U and Fe, and we report the oxidation state of Pu from one melt glass sample. We find significant variations among the melt glass samples and, in particular, find a clear deviation in one sample from the expected buffering effect of Fe(II)/Fe(III) on the oxidation state of uranium. In the first direct measurement of Pu oxidation state in a nuclear test melt glass, we obtain a result consistent with existing literature that proposes Pu is primarily present as Pu(IV) in post-detonation material. In addition, our measurements imply that highly mobile U(VI) may be produced in significant quantities when melt glass is quenched rapidly following a nuclear detonation, though these products may remain immobile in the vitrified matrices. The observed differences in chemical state among the three samples show that redox conditions can vary dramatically across different nuclear test conditions. The local soil composition, associated device materials, and the rate of quenching are all likely to affect the final redox state of the glass. The resulting variations in glass chemistry are significant for understanding and interpreting debris chemistry and the later environmental mobility of dispersed material.

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…

Oxidation-state dependence of rheology in peralkaline glasses of phonolitic composition

NASA Astrophysics Data System (ADS)

Scherrer, M. C.; Hess, K.-U.; Fehr, K. T.; Dingwell, D. B.

2012-04-01

The precise description of magmatic melts rheology at the glass transition is crucial in understanding dynamic processes in volcanology. The glass transition has been described to scale with the viscosity of the material according to Maxwell's relaxation theory for viscoelastic liquids (Dingwell and Webb, 1989). The temperature dependence of the viscosity of multi-component systems can adequately be calculated using empirical models such as Hess et al. (1996), Giordano et al. (2008) and Hui and Zhang (2008); yet, within these calculations, the influence of oxidation state has been so far considered minor and was consequently neglected. The rheological behavior of some iron-rich silicate melts has shown noteworthy oxidation state-dependent variations (Cukierman and Uhlmann 1974, Dingwell and Virgo 1987). The focus of our study is to improve the viscosity models by investigating the necessity of an additional redox-parameter. Thirteen re-melted glass samples of natural phonolitic composition (peralkaline lavas with 8.5 wt. % FeOtot) were produced under different oxygen fugacity (fO2) conditions in a CO/CO2 gas-mixing furnace. Their oxidation-state (Fe3+/Fetot) ranges from 0.44 to 0.93 (±0.05). The viscosity above the liquidus was recorded via the concentric cylinder technique at a constant temperature of 1186 ° C. Additionally, viscosities were measured in the interval of 107to 1011Pa swith temperatures up to 900 ° C at ambient pressure via a BAEHR micro-penetration viscometer. Glass transition temperatures (Tg) have been determined with a constant heating/cooling rate of 10K/min on a SETARAM Sensys evo DSC using the peak of the specific heat capacity curve. Under a constant temperature in the super-liquidus state, the viscosity increases strongly with increasing fO2. In the sub-liquidus state, the measured calorimetric Tgis shifted to lower temperatures as the ratio of ferrous/total iron decreases from 638 ° C to 610 ° C. However, there is no equivalent

Facile solid-state synthesis of oxidation-resistant metal nanoparticles at ambient conditions

NASA Astrophysics Data System (ADS)

Lee, Kyu Hyung; Jung, Hyuk Joon; Lee, Ju Hee; Kim, Kyungtae; Lee, Byeongno; Nam, Dohyun; Kim, Chung Man; Jung, Myung-Hwa; Hur, Nam Hwi

2018-05-01

A simple and scalable method for the synthesis of metal nanoparticles in the solid-state was developed, which can produce nanoparticles in the absence of solvents. Nanoparticles of coinage metals were synthesized by grinding solid hydrazine and the metal precursors in their acetates and oxides at 25 °C. The silver and gold acetates converted completely within 6 min into Ag and Au nanoparticles, respectively, while complete conversion of the copper acetate to the Cu sub-micrometer particles took about 2 h. Metal oxide precursors were also converted into metal nanoparticles by grinding alone. The resulting particles exhibit distinctive crystalline lattice fringes, indicating the formation of highly crystalline phases. The Cu sub-micrometer particles are better resistant to oxidation and exhibit higher conductivity compared to conventional Cu nanoparticles. This solid-state method was also applied for the synthesis of platinum group metals and intermetallic Cu3Au, which can be further extended to synthesize other metal nanoparticles.

Determination of Uncertainties for +III and +IV Actinide Solubilities in the WIPP Geochemistry Model for the 2009 Compliance Recertification Application

NASA Astrophysics Data System (ADS)

Ismail, A. E.; Xiong, Y.; Nowak, E. J.; Brush, L. H.

2009-12-01

The Waste Isolation Pilot Plant (WIPP) is a U.S. Department of Energy (DOE) repository in southeast New Mexico for defense-related transuranic (TRU) waste. Every five years, the DOE is required to submit an application to the Environmental Protection Agency (EPA) demonstrating the WIPP’s continuing compliance with the applicable EPA regulations governing the repository. Part of this recertification effort involves a performance assessment—a probabilistic evaluation of the repository performance with respect to regulatory limits on the amount of releases from the repository to the accessible environment. One of the models used as part of the performance assessment process is a geochemistry model, which predicts solubilities of the radionuclides in the brines that may enter the repository in the different scenarios considered by the performance assessment. The dissolved actinide source term comprises actinide solubilities, which are input parameters for modeling the transport of radionuclides as a result of brine flow through and from the repository. During a performance assessment, the solubilities are modeled as the product of a “base” solubility determined from calculations based on the chemical conditions expected in the repository, and an uncertainty factor that describes the potential deviations of the model from expected behavior. We will focus here on a discussion of the uncertainties. To compute a cumulative distribution function (CDF) for the uncertainties, we compare published, experimentally measured solubility data to predictions made using the established WIPP geochemistry model. The differences between the solubilities observed for a given experiment and the calculated solubilities from the model are used to form the overall CDF, which is then sampled as part of the performance assessment. We will discuss the methodology used to update the CDF’s for the +III actinides, obtained from data for Nd, Am, and Cm, and the +IV actinides, obtained

Experimental and theoretical identification of the Fe(vii) oxidation state in FeO4.

PubMed

Lu, Jun-Bo; Jian, Jiwen; Huang, Wei; Lin, Hailu; Li, Jun; Zhou, Mingfei

2016-11-16

The experimentally known highest oxidation state of iron has been determined to be Fe(vi) so far. Here we report a combined matrix-isolation infrared spectroscopic and theoretical study of two interconvertible iron oxide anions: a dioxoiron peroxide complex [(η 2 -O 2 )FeO 2 ] - with a C 2v -structure and a tetroxide FeO 4 - with a D 2d tetrahedral structure, which are formed by co-condensation of laser-ablated iron atoms and electrons with O 2 /Ar mixtures at 4 K. Quantum chemistry theoretical studies indicate that the Jahn-Teller distorted tetroxide FeO 4 - anion is a d 1 species with hereto the highest iron formal oxidation state Fe(vii).

Steady-state voltammetry of hydroxide ion oxidation in aqueous solutions containing ammonia.

PubMed

Daniele, Salvatore; Baldo, M Antonietta; Bragato, Carlo; Abdelsalam, Mamdouh Elsayed; Denuault, Guy

2002-07-15

An oxidation process observed in dilute aqueous solutions of ammonia was investigated under steady-state conditions with gold microelectrodes with radii in the range 2.5-30 microm. Over the ammonia concentration range 0.1-10 mM, a well-defined voltammetric wave was observed at approximately 1.4 V versus Ag/AgCl. It was attributed to the oxidation of hydroxide ions that arise from the dissociation of the weak base. The steady-state limiting current was found to depend on the concentration of supporting electrolyte, and in solution with low electrolyte, it was enhanced by migration contribution, as expected for a negatively charged species that oxidizes on a positively charged electrode. In addition, the steady-state limiting current was proportional to both the ammonia concentration and the electrode radius. The overall electrode process was analyzed in terms of a CE mechanism (homogeneous chemical reaction preceding the heterogeneous electron transfer) with a fast chemical reaction when measurements were carried out in solutions containing NH3 at < or = 5 mM and with electrodes having a radius of > or = 5 microm. This was ascertained by comparing experimental and theoretical data obtained by simulation. The formation of the soluble complex species Au(NH3)2+ was also considered as a possible alternative to explain the presence of the oxidation wave. This process however was ruled out, as the experimental data did not fit theoretical predictions in any of the conditions employed in the investigation. Instead, the direct oxidation of NH3, probably to N2O, was invoked to explain the anomalous currents found when the CE process was strongly kinetically hindered. Throughout this study, a parallel was made between the CE mechanism investigated here and that known to occur during the hydrogen evolution reaction from weak acids.

An objective alternative to IUPAC's approach to assign oxidation states.

PubMed

Postils, Verònica; Delgado-Alonso, Carlos; Luis, Josep M; Salvador, Pedro

2018-05-22

The IUPAC has recently clarified the term Oxidation State (OS), and provided algorithms for its determination based on the ionic approximation (IA) of the bonds supported by atomic electronegativities (EN). Unfortunately, there are a number of exceptions and ambiguities in IUPAC's algorithms when it comes to practical applications. Our comprehensive study reveals the critical role of the chemical environment on establishing the OS, which cannot always be properly predicted using fix atomic EN values. By identifying what we define here as subsystems of enhanced stability within the molecular system, OS can be safely assigned in many cases without invoking exceptions. New insights about the effect of local aromaticity upon OS are revealed. Moreover, we prove that there are intrinsic limitations of the IA that cannot be overcome. In this context, the effective oxidation state (EOS) analysis arises as a robust and general scheme to derive OS without any external guidance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

URANIUM SEPARATION PROCESS

DOEpatents

Lyon, W.L.

1962-04-17

A method of separating uranium oxides from PuO/sub 2/, ThO/sub 2/, and other actinide oxides is described. The oxide mixture is suspended in a fused salt melt and a chlorinating agent such as chlorine gas or phosgene is sparged through the suspension. Uranium oxides are selectively chlorinated and dissolve in the melt, which may then be filtered to remove the unchlorinated oxides of the other actinides. (AEC)

Study on separation of minor actinides from HLLW with new extractant of TODGA-DHOA/Kerosene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Guo-an; Zhu, Wen-bin; Li, Feng-feng

2013-07-01

The extraction behavior of U, Np, Pu, Am, rare earth elements and Sr from nitric acid solutions by TODGA/dodecan, DHOA/dodecane and TODGA-DHOA/dodecane were investigated, respectively. Based on experimental results, a separation process was proposed for minor actinide isolation from high level liquid waste (HLLW): the TODGA-DHOA/kerosene system. The multi-stage counter-current cascade experiments were carried out for the purpose by 0.1 mol/l TODGA-1.0 mol/l DHOA/kerosene with miniature mixer- settler contactor rigs (8 stages for extraction, 6 stages for scrubbing, 8 stages for first stripping, 8 stages for second stripping). The results show that the recovery efficiencies of the actinides and lanthanidesmore » are more than 99.9%, whereas less than 1% Sr was extracted by 0.1 mol/l TODGA - 1.0 mol/l DHOA/kerosene. The stripping efficiencies of U, Np and Pu are more than 95% in the first stripping step by 0.5 mol/l HNO{sub 3} + 0.5 mol/l AHA(aceto-hydroxamic acid), all of the remained actinides and lanthanides can be stripped by 0.01 mol/l HNO{sub 3} in the second stripping step. 99% Sr was extracted by 0.1 mol/l TODGA/kerosene, so Sr can be recovered efficiently directly from the raffinate by 0.1 mol/l TODGA/kerosene. (authors)« less

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).

Development and Testing of Diglycolamide Functionalized Mesoporous Silica for Sorption of Trivalent Actinides and Lanthanides

DOE PAGES

Shusterman, Jennifer A.; Mason, Harris E.; Bowers, Jon; ...

2015-09-03

Sequestration of trivalent actinides and lanthanides present in used nuclear fuel and legacy wastes is necessary for appropriate long-term stewardship of these metals, particularly to prevent their release into the environment. Organically modified mesoporous silica is an efficient material for recovery and potential subsequent separation of actinides and lanthanides because of its high surface area, tunable ligand selection, and chemically robust substrate. Here, we have synthesized the first novel hybrid material composed of SBA-15 type mesoporous silica functionalized with diglycolamide ligands (DGA-SBA). Because of the high surface area substrate, the DGA-SBA was found to have the highest Eu capacity reportedmore » so far in the literature of all DGA solid-phase extractants. The sorption behavior of europium and americium on DGA-SBA in nitric and hydrochloric acid media was tested in batch contact experiments. DGA-SBA was found to have high sorption of Am and Eu in pH 1, 1 M, and 3 M nitric and hydrochloric acid concentrations, which makes it promising for sequestration of these metals from used nuclear fuel or legacy waste. The kinetics of Eu sorption were found to be two times slower than that for Am in 1 M HNO 3. Additionally, the short-term susceptibility of DGA-SBA to degradation in the presence of acid was probed using 29Si and 13C solid-state NMR spectroscopy. Finally, the material was found to be relatively stable under these conditions, with the ligand remaining intact after 24 h of contact with 1 M HNO 3, an important consideration in use of the DGA-SBA as an extractant from acidic media.« less

Development and Testing of Diglycolamide Functionalized Mesoporous Silica for Sorption of Trivalent Actinides and Lanthanides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shusterman, Jennifer A.; Mason, Harris E.; Bowers, Jon

Sequestration of trivalent actinides and lanthanides present in used nuclear fuel and legacy wastes is necessary for appropriate long-term stewardship of these metals, particularly to prevent their release into the environment. Organically modified mesoporous silica is an efficient material for recovery and potential subsequent separation of actinides and lanthanides because of its high surface area, tunable ligand selection, and chemically robust substrate. Here, we have synthesized the first novel hybrid material composed of SBA-15 type mesoporous silica functionalized with diglycolamide ligands (DGA-SBA). Because of the high surface area substrate, the DGA-SBA was found to have the highest Eu capacity reportedmore » so far in the literature of all DGA solid-phase extractants. The sorption behavior of europium and americium on DGA-SBA in nitric and hydrochloric acid media was tested in batch contact experiments. DGA-SBA was found to have high sorption of Am and Eu in pH 1, 1 M, and 3 M nitric and hydrochloric acid concentrations, which makes it promising for sequestration of these metals from used nuclear fuel or legacy waste. The kinetics of Eu sorption were found to be two times slower than that for Am in 1 M HNO 3. Additionally, the short-term susceptibility of DGA-SBA to degradation in the presence of acid was probed using 29Si and 13C solid-state NMR spectroscopy. Finally, the material was found to be relatively stable under these conditions, with the ligand remaining intact after 24 h of contact with 1 M HNO 3, an important consideration in use of the DGA-SBA as an extractant from acidic media.« less

Actinide-contaminated Skin: Comparing Decontamination Efficacy of Water, Cleansing Gels, and DTPA Gels.

PubMed

Tazrart, A; Bolzinger, M A; Lamart, S; Coudert, S; Angulo, J F; Jandard, V; Briançon, S; Griffiths, N M

2018-07-01

Skin contamination by alpha-emitting actinides is a risk to workers during nuclear fuel production and reactor decommissioning. Also, the list of items for potential use in radiological dispersal devices includes plutonium and americium. The actinide chemical form is important and solvents such as tributyl phosphate, used to extract plutonium, can influence plutonium behavior. This study investigated skin fixation and efficacy of decontamination products for these actinide forms using viable pig skin in the Franz cell diffusion system. Commonly used or recommended decontamination products such as water, cleansing gel, diethylenetriamine pentaacetic acid, or octadentate hydroxypyridinone compound 3,4,3-LI(1,2-HOPO), as well as diethylenetriamine pentaacetic acid hydrogel formulations, were tested after a 2-h contact time with the contaminant. Analysis of skin samples demonstrated that more plutonium nitrate is bound to skin as compared to plutonium-tributyl phosphate, and fixation of americium to skin was also significant. The data show that for plutonium-tributyl phosphate all the products are effective ranging from 80 to 90% removal of this contaminant. This may be associated with damage to the skin by this complex and suggests a mechanical/wash-out action rather than chelation. For removal of americium and plutonium, both Trait Rouge cleansing gel and diethylenetriamine pentaacetic acid are better than water, and diethylenetriamine pentaacetic acid hydrogel is better than Osmogel. The different treatments, however, did not significantly affect the activity in deeper skin layers, which suggests a need for further improvement of decontamination procedures. The new diethylenetriamine pentaacetic acid hydrogel preparation was effective in removing americium, plutonium, and plutonium-tributyl phosphate from skin; such a formulation offers advantages and thus merits further assessment.

A new incorporation mechanism for trivalent actinides into bioapatite: a TRLFS and EXAFS study.

PubMed

Holliday, Kiel; Handley-Sidhu, Stephanie; Dardenne, Kathy; Renshaw, Joanna; Macaskie, Lynne; Walther, Clemens; Stumpf, Thorsten

2012-02-28

One of the most toxic byproducts of nuclear power and weapons production is the transuranics, which have a high radiotoxicity and long biological half-life due to their tendency to accumulate in the skeletal system. This accumulation is inhomogeneous and has been associated with the chemical properties and structure of the bone material rather than its location or function. This suggests a chemical driving force to incorporation and requires an atomic scale mechanistic understanding of the incorporation process. Here we propose a new incorporation mechanism for trivalent actinides and lanthanides into synthetic and biologically produced hydroxyapatite. Time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure have been used to demonstrate that trivalent actinides and lanthanides incorporate into the amorphous grain boundaries of apatite. This incorporation site can be used to explain patterns in uptake and distribution of radionuclides in the mammalian skeletal system. © 2012 American Chemical Society

Demonstration of the TRUEX process for partitioning of actinides from actual ICPP tank waste using centrifugal contactors in a shielded cell facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Law, J.D.; Brewer, K.N.; Herbst, R.S.

1996-09-01

TRUEX is being evaluated at Idaho Chemical Processing Plant (ICPP) for separating actinides from acidic radioactive waste stored at ICPP; efforts have culminated in a recent demonstration with actual tank waste. A continuous countercurrent flowsheet test was successfully completed at ICPP using waste from tank WM-183. This demonstration was performed using 24 states of 2-cm dia centrifugal contactors in the shielded hot cell at the ICPP Remote Analytical Laboratory. The flowsheet had 8 extraction stages, 5 scrub stages, 6 strip stages, 3 solvent wash stages, and 2 acid rinse stages. A centrifugal contactor stage in the scrub section was notmore » working during testing, and the scrub feed (aqueous) solution followed the solvent into the strip section, eliminating the scrub section in the flowsheet. An overall removal efficiency of 99.97% was obtained for the actinides, reducing the activity from 457 nCi/g in the feed to 0.12 nCi/g in the aqueous raffinate, well below the NRC Class A LLW requirement of 10 nCi/g for non-TRU waste.The 0.04 M HEDPA strip section back-extracted 99.9998% of the actinide from the TRUEX solvent. Removal efficiencies of >99. 90, 99.96, 99.98, >98.89, 93.3, and 89% were obtained for {sup 241}Am, {sup 238}Pu, {sup 239}Pu, {sup 235}U, {sup 238}U, and {sup 99}Tc. Fe was partially extracted by the TRUEX solvent, resulting in 23% of the Fe exiting in the strip product. Hg was also extracted by the TRUEX solvent (73%) and stripped from the solvent in the 0.25 M Na2CO3 wash section. Only 1.4% of the Hg exited with the high activity waste strip product.« less

The interaction of human serum albumin with selected lanthanide and actinide ions: Binding affinities, protein unfolding and conformational changes.

PubMed

Ali, Manjoor; Kumar, Amit; Kumar, Mukesh; Pandey, Badri N

2016-04-01

Human serum albumin (HSA), the most abundant soluble protein in blood plays critical roles in transportation of biomolecules and maintenance of osmotic pressure. In view of increasing applications of lanthanides- and actinides-based materials in nuclear energy, space, industries and medical applications, the risk of exposure with these metal ions is a growing concern for human health. In present study, binding interaction of actinides/lanthanides [thorium: Th(IV), uranium: U(VI), lanthanum: La(III), cerium: Ce(III) and (IV)] with HSA and its structural consequences have been investigated. Ultraviolet-visible, Fourier transform-infrared, Raman, Fluorescence and Circular dichroism spectroscopic techniques were applied to study the site of metal ions interaction, binding affinity determination and the effect of metal ions on protein unfolding and HSA conformation. Results showed that these metal ions interacted with carbonyl (CO..:)/amide(N..-H) groups and induced exposure of aromatic residues of HSA. The fluorescence analysis indicated that the actinide binding altered the microenvironment around Trp214 in the subdomain IIA. Binding affinity of U(VI) to HSA was slightly higher than that of Th(IV). Actinides and Ce(IV) altered the secondary conformation of HSA with a significant decrease of α-helix and an increase of β-sheet, turn and random coil structures, indicating a partial unfolding of HSA. A correlation was observed between metal ion's ability to alter HSA conformation and protein unfolding. Both cationic effects and coordination ability of metal ions seemed to determine the consequences of their interaction with HSA. Present study improves our understanding about the protein interaction of these heavy ions and their impact on its secondary structure. In addition, binding characteristics may have important implications for the development of rational antidote for the medical management of health effects of actinides and lanthanides. Copyright © 2016 Elsevier

Solid-State Diffusional Behaviors of Functional Metal Oxides at Atomic Scale.

PubMed

Chen, Jui-Yuan; Huang, Chun-Wei; Wu, Wen-Wei

2018-02-01

Metal/metal oxides have attracted extensive research interest because of their combination of functional properties and compatibility with industry. Diffusion and thermal reliability have become essential issues that require detailed study to develop atomic-scaled functional devices. In this work, the diffusional reaction behavior that transforms piezoelectric ZnO into magnetic Fe 3 O 4 is investigated at the atomic scale. The growth kinetics of metal oxides are systematically studied through macro- and microanalyses. The growth rates are evaluated by morphology changes, which determine whether the growth behavior was a diffusion- or reaction-controlled process. Furthermore, atom attachment on the kink step is observed at the atomic scale, which has important implications for the thermodynamics of functional metal oxides. Faster growth planes simultaneously decrease, which result in the predominance of low surface energy planes. These results directly reveal the atomic formation process of metal oxide via solid-state diffusion. In addition, the nanofabricated method provides a novel approach to investigate metal oxide evolution and sheds light on diffusional reaction behavior. More importantly, the results and phenomena of this study provide considerable inspiration to enhance the material stability and reliability of metal/oxide-based devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pacold, J. I.; Lukens, W. W.; Booth, C. H.

We report that nuclear weapons testing generates large volumes of glassy materials that influence the transport of dispersed actinides in the environment and may carry information on the composition of the detonated device. We determine the oxidation state of U and Fe (which is known to buffer the oxidation state of actinide elements and to affect the redox state of groundwater) in samples of melt glass collected from three U.S. nuclear weapons tests. For selected samples, we also determine the coordination geometry of U and Fe, and we report the oxidation state of Pu from one melt glass sample. Wemore » find significant variations among the melt glass samples and, in particular, find a clear deviation in one sample from the expected buffering effect of Fe(II)/Fe(III) on the oxidation state of uranium. In the first direct measurement of Pu oxidation state in a nuclear test melt glass, we obtain a result consistent with existing literature that proposes Pu is primarily present as Pu(IV) in post-detonation material. In addition, our measurements imply that highly mobile U(VI) may be produced in significant quantities when melt glass is quenched rapidly following a nuclear detonation, though these products may remain immobile in the vitrified matrices. The observed differences in chemical state among the three samples show that redox conditions can vary dramatically across different nuclear test conditions. The local soil composition, associated device materials, and the rate of quenching are all likely to affect the final redox state of the glass. Lastly, the resulting variations in glass chemistry are significant for understanding and interpreting debris chemistry and the later environmental mobility of dispersed material.« less

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

DOE PAGES

Pacold, J. I.; Lukens, W. W.; Booth, C. H.; ...

2016-05-18

We report that nuclear weapons testing generates large volumes of glassy materials that influence the transport of dispersed actinides in the environment and may carry information on the composition of the detonated device. We determine the oxidation state of U and Fe (which is known to buffer the oxidation state of actinide elements and to affect the redox state of groundwater) in samples of melt glass collected from three U.S. nuclear weapons tests. For selected samples, we also determine the coordination geometry of U and Fe, and we report the oxidation state of Pu from one melt glass sample. Wemore » find significant variations among the melt glass samples and, in particular, find a clear deviation in one sample from the expected buffering effect of Fe(II)/Fe(III) on the oxidation state of uranium. In the first direct measurement of Pu oxidation state in a nuclear test melt glass, we obtain a result consistent with existing literature that proposes Pu is primarily present as Pu(IV) in post-detonation material. In addition, our measurements imply that highly mobile U(VI) may be produced in significant quantities when melt glass is quenched rapidly following a nuclear detonation, though these products may remain immobile in the vitrified matrices. The observed differences in chemical state among the three samples show that redox conditions can vary dramatically across different nuclear test conditions. The local soil composition, associated device materials, and the rate of quenching are all likely to affect the final redox state of the glass. Lastly, the resulting variations in glass chemistry are significant for understanding and interpreting debris chemistry and the later environmental mobility of dispersed material.« less

Structural differences between the ready and unready oxidized states of [NiFe] hydrogenases.

PubMed

Volbeda, Anne; Martin, Lydie; Cavazza, Christine; Matho, Michaël; Faber, Bart W; Roseboom, Winfried; Albracht, Simon P J; Garcin, Elsa; Rousset, Marc; Fontecilla-Camps, Juan C

2005-05-01

[NiFe] hydrogenases catalyze the reversible heterolytic cleavage of molecular hydrogen. Several oxidized, inactive states of these enzymes are known that are distinguishable by their very different activation properties. So far, the structural basis for this difference has not been understood because of lack of relevant crystallographic data. Here, we present the crystal structure of the ready Ni-B state of Desulfovibrio fructosovorans [NiFe] hydrogenase and show it to have a putative mu-hydroxo Ni-Fe bridging ligand at the active site. On the other hand, a new, improved refinement procedure of the X-ray diffraction data obtained for putative unready Ni-A/Ni-SU states resulted in a more elongated electron density for the bridging ligand, suggesting that it is a diatomic species. The slow activation of the Ni-A state, compared with the rapid activation of the Ni-B state, is therefore proposed to result from the different chemical nature of the ligands in the two oxidized species. Our results along with very recent electrochemical studies suggest that the diatomic ligand could be hydro-peroxide.

Ceramification: A plutonium immobilization process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rask, W.C.; Phillips, A.G.

1996-05-01

This paper describes a low temperature technique for stabilizing and immobilizing actinide compounds using a combination process/storage vessel of stainless steel, in which measured amounts of actinide nitrate solutions and actinide oxides (and/or residues) are systematically treated to yield a solid article. The chemical ceramic process is based on a coating technology that produces rare earth oxide coatings for defense applications involving plutonium. The final product of this application is a solid, coherent actinide oxide with process-generated encapsulation that has long-term environmental stability. Actinide compounds can be stabilized as pure materials for ease of re-use or as intimate mixtures withmore » additives such as rare earth oxides to increase their degree of proliferation resistance. Starting materials for the process can include nitrate solutions, powders, aggregates, sludges, incinerator ashes, and others. Agents such as cerium oxide or zirconium oxide may be added as powders or precursors to enhance the properties of the resulting solid product. Additives may be included to produce a final product suitable for use in nuclear fuel pellet production. The process is simple and reduces the time and expense for stabilizing plutonium compounds. It requires a very low equipment expenditure and can be readily implemented into existing gloveboxes. The process is easily conducted with less associated risk than proposed alternative technologies.« less

Forcing Cesium into Higher Oxidation States Using Useful hard x-ray Induced Chemistry under High Pressure

NASA Astrophysics Data System (ADS)

Sneed, D.; Pravica, M.; Kim, E.; Chen, N.; Park, C.; White, M.

2017-10-01

This paper discusses our attempt to synthesize higher oxidation forms of cesium fluoride by pressurizing cesium fluoride in a fluorine-rich environment created via the x-ray decomposition of potassium tetrafluoroborate. This was done in order to confirm recent theoretical predictions of higher oxidation forms of CsFn. We discuss the development of a technique to produce molecular fluorine in situ via useful hard x-ray photochemistry, and the attempt to utilize this technique to form higher oxidation states of cesium fluoride. In order to verify the formation of the novel stoichiometric species of CsFn. X-ray Absorption Near Edge Spectroscopy (XANES) centered on the cesium K-edge was performed to probe the oxidation state of cesium as well as the local molecular coordination around Cs.

Method for forming an extraction agent for the separation of actinides from lanthanides

DOEpatents

Klaehn, John R.; Harrup, Mason K.; Law, Jack D.; Peterman, Dean R.

2010-04-27

An extraction agent for the separation of trivalent actinides from lanthanides in an acidic media and a method for forming same are described, and wherein the methodology produces a stable regiospecific and/or stereospecific dithiophosphinic acid that can operate in an acidic media having a pH of less than about 7.

Influence of a Heterocyclic Nitrogen-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by Aminopolycarboxylate Complexants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grimes, Travis S.; Heathman, Colt R.; Jansone-Popova, Santa

Here, the novel metal chelator N-2-(pyridylmethyl)diethylenetriamine- N,N',N",N"-tetraacetic acid (DTTA-PyM) was designed to replace a single oxygen-donor acetate group of the well-known aminopolycarboxylate complexant diethylenetriamine- N,N,N',N",N"-pentaacetic acid (DTPA) with a nitrogen-donor 2-pyridylmethyl. Potentiometric, spectroscopic, computational, and radioisotope distribution methods show distinct differences for the 4f and 5f coordination environments and enhanced actinide binding due to the nitrogen-bearing heterocyclic moiety. The Am 3+, Cm 3+, and Ln 3+ complexation studies for DTTA-PyM reveal an enhanced preference, relative to DTPA, for trivalent actinide binding. Fluorescence studies indicate no changes to the octadentate coordination of trivalent curium, while evidence of heptadentate complexation of trivalentmore » europium is found in mixtures containing EuHL (aq) complexes at the same aqueous acidity. The denticity change observed for Eu 3+ suggests that complex protonation occurs on the pyridyl nitrogen. Formation of the CmHL (aq) complex is likely due to the protonation of an available carboxylate group because the carbonyl oxygen can maintain octadentate coordination through a rotation. The observed suppressed protonation of the pyridyl nitrogen in the curium complexes may be attributed to stronger trivalent actinide binding by DTTA-PyM. Density functional theory calculations indicate that added stabilization of the actinide complexes with DTTA-PyM may originate from π-back-bonding interactions between singly occupied 5f orbitals of Am 3+ and the pyridyl nitrogen. The differences between the stabilities of trivalent actinide chelates (Am 3+, Cm 3+) and trivalent lanthanide chelates (La 3+–Lu 3+) are observed in liquid–liquid extraction systems, yielding unprecedented 4f/5f differentiation when using DTTA-PyM as an aqueous holdback reagent. In addition, the enhanced nitrogen-donor softness of the new DTTA-PyM chelator was perturbed

Mixed Metal Phosphonate- Phosphate Resins for Separation of Lanthanides from Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clearfield, Abraham

As indicated in the previous annual report the goals of this project are to develop procedures for efficient separation of lanthanides from actinides and curium from americium. These processes are required for the nuclear fuel cycle to minimize the waste and recover the valuable actinides. The basis for our study is that we have prepared a group of compounds that are porous and favor the uptake of ions with charges 3+ and 4+ over ions of lesser charge. The general formula for these materials is M(O 3PC 6H 4PO 3) 1-x/2(APO 4)x·nH 2O: where M=Zr 4+, Sn 4+, A=H, Na,more » or K and X=O, 0.5, 0.8, 1.0, 1.33 and 1.61-3. One of our tasks is to determine which members of this group of compounds are effective in carrying out the required separations. A difficulty in obtaining this required information is that the compounds are amorphous. That is they are not crystalline, therefore we need to resort to synchrotron data to obtain structural data which will be presented in detail. This information will be provided as a separate section.« less

The use of MOX caramel fuel mixed with 241Am, 242mAm and 243Am as burnable absorber actinides for the MTR research reactors.

PubMed

Shaaban, Ismail; Albarhoum, Mohamad

2017-07-01

The MOX (UO 2 &PuO 2 ) caramel fuel mixed with 241 Am, 242m Am and 243 Am as burnable absorber actinides was proposed as a fuel of the MTR-22MW reactor. The MCNP4C code was used to simulate the MTR-22MW reactor and estimate the criticality and the neutronic parameters, and the power peaking factors before and after replacing its original fuel (U 3 O 8 -Al) by the MOX caramel fuel mixed with 241 Am, 242m Am and 243 Am actinides. The obtained results of the criticality, the neutronic parameters, and the power peaking factors for the MOX caramel fuel mixed with 241 Am, 242m Am and 243 Am actinides were compared with the same parameters of the U 3 O 8 -Al original fuel and a maximum difference is -6.18% was found. Additionally, by recycling 2.65% and 2.71% plutonium and 241 Am, 242m Am and 243 Am actinides in the MTR-22MW reactor, the level of 235 U enrichment is reduced from 4.48% to 3% and 2.8%, respectively. This also results in the reduction of the 235 U loading by 32.75% and 37.22% for the 2.65%, the 2.71% plutonium and 241 Am, 242m Am and 243 Am actinides, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

An Approach for Validating Actinide and Fission Product Burnup Credit Criticality Safety Analyses--Criticality (keff) Predictions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scaglione, John M; Mueller, Don; Wagner, John C

2011-01-01

One of the most significant remaining challenges associated with expanded implementation of burnup credit in the United States is the validation of depletion and criticality calculations used in the safety evaluation - in particular, the availability and use of applicable measured data to support validation, especially for fission products. Applicants and regulatory reviewers have been constrained by both a scarcity of data and a lack of clear technical basis or approach for use of the data. U.S. Nuclear Regulatory Commission (NRC) staff have noted that the rationale for restricting their Interim Staff Guidance on burnup credit (ISG-8) to actinide-only ismore » based largely on the lack of clear, definitive experiments that can be used to estimate the bias and uncertainty for computational analyses associated with using burnup credit. To address the issue of validation, the NRC initiated a project with the Oak Ridge National Laboratory to (1) develop and establish a technically sound validation approach (both depletion and criticality) for commercial spent nuclear fuel (SNF) criticality safety evaluations based on best-available data and methods and (2) apply the approach for representative SNF storage and transport configurations/conditions to demonstrate its usage and applicability, as well as to provide reference bias results. The purpose of this paper is to describe the criticality (k{sub eff}) validation approach, and resulting observations and recommendations. Validation of the isotopic composition (depletion) calculations is addressed in a companion paper at this conference. For criticality validation, the approach is to utilize (1) available laboratory critical experiment (LCE) data from the International Handbook of Evaluated Criticality Safety Benchmark Experiments and the French Haut Taux de Combustion (HTC) program to support validation of the principal actinides and (2) calculated sensitivities, nuclear data uncertainties, and the limited available

Correlation consistent basis sets for actinides. II. The atoms Ac and Np-Lr

NASA Astrophysics Data System (ADS)

Feng, Rulin; Peterson, Kirk A.

2017-08-01

New correlation consistent basis sets optimized using the all-electron third-order Douglas-Kroll-Hess (DKH3) scalar relativistic Hamiltonian are reported for the actinide elements Ac and Np through Lr. These complete the series of sets reported previously for Th-U [K. A. Peterson, J. Chem. Phys. 142, 074105 (2015); M. Vasiliu et al., J. Phys. Chem. A 119, 11422 (2015)]. The new sets range in size from double- to quadruple-zeta and encompass both those optimized for valence (6s6p5f7s6d) and outer-core electron correlations (valence + 5s5p5d). The final sets have been contracted for both the DKH3 and eXact 2-component (X2C) Hamiltonians, yielding cc-pVnZ-DK3/cc-pVnZ-X2C sets for valence correlation and cc-pwCVnZ-DK3/cc-pwCVnZ-X2C sets for outer-core correlation (n = D, T, Q in each case). In order to test the effectiveness of the new basis sets, both atomic and molecular benchmark calculations have been carried out. In the first case, the first three atomic ionization potentials (IPs) of all the actinide elements Ac-Lr have been calculated using the Feller-Peterson-Dixon (FPD) composite approach, primarily with the multireference configuration interaction (MRCI) method. Excellent convergence towards the respective complete basis set (CBS) limits is achieved with the new sets, leading to good agreement with experiment, where these exist, after accurately accounting for spin-orbit effects using the 4-component Dirac-Hartree-Fock method. For a molecular test, the IP and atomization energy (AE) of PuO2 have been calculated also using the FPD method but using a coupled cluster approach with spin-orbit coupling accounted for using the 4-component MRCI. The present calculations yield an IP0 for PuO2 of 159.8 kcal/mol, which is in excellent agreement with the experimental electron transfer bracketing value of 162 ± 3 kcal/mol. Likewise, the calculated 0 K AE of 305.6 kcal/mol is in very good agreement with the currently accepted experimental value of 303.1 ± 5 kcal

Correlation consistent basis sets for actinides. II. The atoms Ac and Np-Lr.

PubMed

Feng, Rulin; Peterson, Kirk A

2017-08-28

New correlation consistent basis sets optimized using the all-electron third-order Douglas-Kroll-Hess (DKH3) scalar relativistic Hamiltonian are reported for the actinide elements Ac and Np through Lr. These complete the series of sets reported previously for Th-U [K. A. Peterson, J. Chem. Phys. 142, 074105 (2015); M. Vasiliu et al., J. Phys. Chem. A 119, 11422 (2015)]. The new sets range in size from double- to quadruple-zeta and encompass both those optimized for valence (6s6p5f7s6d) and outer-core electron correlations (valence + 5s5p5d). The final sets have been contracted for both the DKH3 and eXact 2-component (X2C) Hamiltonians, yielding cc-pVnZ-DK3/cc-pVnZ-X2C sets for valence correlation and cc-pwCVnZ-DK3/cc-pwCVnZ-X2C sets for outer-core correlation (n = D, T, Q in each case). In order to test the effectiveness of the new basis sets, both atomic and molecular benchmark calculations have been carried out. In the first case, the first three atomic ionization potentials (IPs) of all the actinide elements Ac-Lr have been calculated using the Feller-Peterson-Dixon (FPD) composite approach, primarily with the multireference configuration interaction (MRCI) method. Excellent convergence towards the respective complete basis set (CBS) limits is achieved with the new sets, leading to good agreement with experiment, where these exist, after accurately accounting for spin-orbit effects using the 4-component Dirac-Hartree-Fock method. For a molecular test, the IP and atomization energy (AE) of PuO 2 have been calculated also using the FPD method but using a coupled cluster approach with spin-orbit coupling accounted for using the 4-component MRCI. The present calculations yield an IP 0 for PuO 2 of 159.8 kcal/mol, which is in excellent agreement with the experimental electron transfer bracketing value of 162 ± 3 kcal/mol. Likewise, the calculated 0 K AE of 305.6 kcal/mol is in very good agreement with the currently accepted experimental value of 303.1 ± 5 kcal

Impact of the cation distribution homogeneity on the americium oxidation state in the U0.54Pu0.45Am0.01O2-x mixed oxide

NASA Astrophysics Data System (ADS)

Vauchy, Romain; Robisson, Anne-Charlotte; Martin, Philippe M.; Belin, Renaud C.; Aufore, Laurence; Scheinost, Andreas C.; Hodaj, Fiqiri

2015-01-01

The impact of the cation distribution homogeneity of the U0.54Pu0.45Am0.01O2-x mixed oxide on the americium oxidation state was studied by coupling X-ray diffraction (XRD), electron probe micro analysis (EPMA) and X-ray absorption spectroscopy (XAS). Oxygen-hypostoichiometric Am-bearing uranium-plutonium mixed oxide pellets were fabricated by two different co-milling based processes in order to obtain different cation distribution homogeneities. The americium was generated from β- decay of 241Pu. The XRD analysis of the obtained compounds did not reveal any structural difference between the samples. EPMA, however, revealed a high homogeneity in the cation distribution for one sample, and substantial heterogeneity of the U-Pu (so Am) distribution for the other. The difference in cation distribution was linked to a difference in Am chemistry as investigated by XAS, with Am being present at mixed +III/+IV oxidation state in the heterogeneous compound, whereas only Am(IV) was observed in the homogeneous compound. Previously reported discrepancies on Am oxidation states can hence be explained by cation distribution homogeneity effects.

SRNL Development of Recovery Processes for Mark-18A Heavy Actinide Targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allender, Jeffrey S.; Bridges, Nicholas J.; Loftin, Bradley M.

2015-07-14

Savannah River National Laboratory (SRNL) and Oak Ridge National Laboratory (ORNL) are developing plans for the recovery of rare and unique isotopes contained within heavy-actinide target assemblies, specifically the Mark-18A. Mark-18A assemblies were irradiated in Savannah River Site (SRS) reactors in the 1970s under extremely high neutron-flux conditions and produced, virtually, the world's supply of plutonium-244, an isotope of key importance to high-precision actinide measurement and other scientific and nonproliferation uses; and curium highly enriched in heavy isotopes (e.g., curium-246 and curium-248). In 2015 and 2016, SRNL is pursuing tasks that would reduce program risk and budget requirements, including furthermore » characterization of unprocessed targets; engineering studies for the use of the SRNL Shielded Cells Facility (SCF) for recovery; and development of onsite and offsite shipping methods including a replacement for the heavy (70 ton) cask previously used for onsite transfer of irradiated items at SRS. A status update is provided for the characterization, including modeling using the Monte Carlo N-Particle Transport Code (MCNP); direct non-destructive assay measurements; and cask design.« less

Developing an in-situ Detector of Neutron-Induced Fission for Actinide Sputtering Characterization

NASA Astrophysics Data System (ADS)

Fellers, Deion

2016-09-01

The physical mechanism describing the transfer of large amounts of energy due to fission in a material is not well understood and represents one of the modern challenges facing nuclear scientists, with applications including nuclear energy and national defense. Fission fragments cause damage to the material from sputtering of matter as they pass through or near the material's surface. We have developed a new technique at the Los Alamos Neutron Science Center for characterizing the ejecta by using ultracold neutrons (neutrons with kinetic energy less than 300 neV) to induce fission at finely controlled depths in an actinide. This program will ultimately provide a detailed description of the properties of the sputtered particles as a function of the depth of the fission in the material. A key component of this project is accurately quantifying the number of neutron induced fissions in the sample. This poster depicts the development of an in-situ detector of neutron-induced fission for the AShES (Actinide Sputtering from ultracold neutron Exposure at the Surface) experiment.

Separation of uranium from (U, Th)O 2 and (U, Pu)O 2 by solid state reactions route

NASA Astrophysics Data System (ADS)

Keskar, Meera; Mudher, K. D. Singh; Venugopal, V.

2005-01-01

Solid state reactions of UO 2, ThO 2, PuO 2 and their mixed oxides (U, Th)O 2 and (U, Pu)O 2 were carried out with sodium nitrate upto 900 °C, to study the formation of various phases at different temperatures, which are amenable for easy dissolution and separation of the actinide elements in dilute acid. Products formed by reacting unsintered as well as sintered UO 2 with NaNO 3 above 500 °C were readily soluble in 2 M HNO 3, whereas ThO 2 and PuO 2 did not react with NaNO 3 to form any soluble products. Thus reactions of mixed oxides (U, Th)O 2 and (U, Pu)O 2 with NaNO 3 were carried out to study the quantitative separation of U from (U, Th)O 2 and (U, Pu)O 2. X-ray diffraction, X-ray fluorescence, thermal analysis and chemical analysis techniques were used for the characterization of the products formed during the reactions.

Forcing Cesium into Higher Oxidation States Using Useful hard x-ray Induced Chemistry under High Pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sneed, D.; Pravica, M.; Kim, E.

This paper discusses our attempt to synthesize higher oxidation forms of cesium fluoride by pressurizing cesium fluoride in a fluorine-rich environment created via the x-ray decomposition of potassium tetrafluoroborate. This was done in order to confirm recent theoretical predictions of higher oxidation forms of CsFn. We discuss the development of a technique to produce molecular fluorine in situ via useful hard x-ray photochemistry, and the attempt to utilize this technique to form higher oxidation states of cesium fluoride. In order to verify the formation of the novel stoichiometric species of CsFn. X-ray Absorption Near Edge Spectroscopy (XANES) centered on themore » cesium K-edge was performed to probe the oxidation state of cesium as well as the local molecular coordination around Cs.« less

Plant Mounds as Concentration and Stabilization Agents for Actinide Soil Contaminants in Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

D.S. Shafer; J. Gommes

Plant mounds or blow-sand mounds are accumulations of soil particles and plant debris around the base of shrubs and are common features in deserts in the southwestern United States. An important factor in their formation is that shrubs create surface roughness that causes wind-suspended particles to be deposited and resist further suspension. Shrub mounds occur in some plant communities on the Nevada Test Site, the Nevada Test and Training Range (NTTR), and Tonopah Test Range (TTR), including areas of surface soil contamination from past nuclear testing. In the 1970s as part of early studies to understand properties of actinides inmore » the environment, the Nevada Applied Ecology Group (NAEG) examined the accumulation of isotopes of Pu, 241Am, and U in plant mounds at safety experiment and storage-transportation test sites of nuclear devices. Although aerial concentrations of these contaminants were highest in the intershrub or desert pavement areas, the concentration in mounds were higher than in equal volumes of intershrub or desert pavement soil. The NAEG studies found the ratio of contaminant concentration of actinides in soil to be greater (1.6 to 2.0) in shrub mounds than in the surrounding areas of desert pavement. At Project 57 on the NTTR, 17 percent of the area was covered in mounds while at Clean Slate III on the TTR, 32 percent of the area was covered in mounds. If equivalent volumes of contaminated soil were compared between mounds and desert pavement areas at these sites, then the former might contain as much as 34 and 62 percent of the contaminant inventory, respectively. Not accounting for radionuclides associated with shrub mounds would cause the inventory of contaminants and potential exposure to be underestimated. In addition, preservation of shrub mounds could be important part of long-term stewardship if these sites are closed by fencing and posting with administrative controls.« less

Actinide Corroles: Synthesis and Characterization of Thorium(IV) and Uranium(IV) bis(-chloride) Dimers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Ashleigh L.; Buckley, Heather L.; Gryko, Daniel T.

2013-12-01

The first synthesis and structural characterization of actinide corroles is presented. Thorium(IV) and uranium(IV) macrocycles of Mes2(p-OMePh)corrole were synthesised and characterized by single-crystal X-ray diffraction, UV-Visible spectroscopy, variable-temperature 1H NMR, ESI mass spectrometry and cyclic voltammetry.

Revealing the role of oxidation state in interaction between nitro/amino-derived particulate matter and blood proteins

PubMed Central

Liu, Zhen; Li, Ping; Bian, Weiwei; Yu, Jingkai; Zhan, Jinhua

2016-01-01

Surface oxidation states of ultrafine particulate matter can influence the proinflammatory responses and reactive oxygen species levels in tissue. Surface active species of vehicle-emission soot can serve as electron transfer-mediators in mitochondrion. Revealing the role of surface oxidation state in particles-proteins interaction will promote the understanding on metabolism and toxicity. Here, the surface oxidation state was modeled by nitro/amino ligands on nanoparticles, the interaction with blood proteins were evaluated by capillary electrophoresis quantitatively. The nitro shown larger affinity than amino. On the other hand, the affinity to hemoglobin is 103 times larger than that to BSA. Further, molecular docking indicated the difference of binding intensity were mainly determined by hydrophobic forces and hydrogen bonds. These will deepen the quantitative understanding of protein-nanoparticles interaction from the perspective of surface chemical state. PMID:27181651

Spectroscopic characterization of zinc oxide nanorods synthesized by solid-state reaction

NASA Astrophysics Data System (ADS)

Prasad, Virendra; D'Souza, Charlene; Yadav, Deepti; Shaikh, A. J.; Vigneshwaran, Nadanathangam

2006-09-01

Well-crystallized zinc oxide nanorods have been fabricated by single step solid-state reaction using zinc acetate and sodium hydroxide, at room temperature. The sodium lauryl sulfate (SLS) stabilized zinc oxide nanorods were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. The X-ray diffraction revealed the wurtzite structure of zinc oxide. The size estimation by XRD and TEM confirmed that the ZnO nanorods are made of single crystals. The growth of zinc oxide crystals into rod shape was found to be closely related to its hexagonal nature. The mass ratio of SLS:ZnO in the nanorods was found to be 1:10 based on the thermogravimetric analysis. Blue shift of photoluminescence emission was noticed in the ZnO nanorods when compared to that of ZnO bulk. FT-IR analysis confirmed the binding of SLS with ZnO nanorods. Apart from ease of preparation, this method has the advantage of eco-friendliness since the solvent and other harmful chemicals were eliminated in the synthesis protocol.

Site preferences of actinide cations in [NZP] compounds

NASA Astrophysics Data System (ADS)

Hawkins, H. T.; Spearing, D. R.; Smith, D. M.; Hampel, F. G.; Veirs, D. K.; Scheetz, B. E.

2000-07-01

Compounds adopting the sodium dizirconium tris(phosphate) (NaZr2(PO4)3) structure type belong to the [NZP] structural family of compounds. [NZP] compounds possess desirable properties that would permit their application as hosts for the actinides. These properties include compositional flexibility (i.e., three structural sites that can accommodate a variety of different cations), high thermal stability, negligible thermal expansion, and resistance to radiation damage. Experimental data indicate that [NZP] compounds resist dissolution and release of constituents over a wide range of experimental conditions. Moreover, [NZP] compounds may be synthesized by both conventional and novel methods and may be heat treated or sintered at modest temperatures (800 °C-1350 °C) in open or restricted systems.

Method of loading organic materials with group III plus lanthanide and actinide elements

DOEpatents

Bell, Zane W [Oak Ridge, TN; Huei-Ho, Chuen [Oak Ridge, TN; Brown, Gilbert M [Knoxville, TN; Hurlbut, Charles [Sweetwater, TX

2003-04-08

Disclosed is a composition of matter comprising a tributyl phosphate complex of a group 3, lanthanide, actinide, or group 13 salt in an organic carrier and a method of making the complex. These materials are suitable for use in solid or liquid organic scintillators, as in x-ray absorption standards, x-ray fluorescence standards, and neutron detector calibration standards.

The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System.

PubMed

Angelini, Francesco; Pagano, Francesca; Bordin, Antonella; Milan, Marika; Chimenti, Isotta; Peruzzi, Mariangela; Valenti, Valentina; Marullo, Antonino; Schirone, Leonardo; Palmerio, Silvia; Sciarretta, Sebastiano; Murdoch, Colin E; Frati, Giacomo; De Falco, Elena

2017-01-01

Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS) in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human's current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject's profile will be discussed.

The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System

PubMed Central

Angelini, Francesco; Pagano, Francesca; Bordin, Antonella; Milan, Marika; Valenti, Valentina; Marullo, Antonino; Schirone, Leonardo; Palmerio, Silvia; Sciarretta, Sebastiano; Frati, Giacomo

2017-01-01

Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS) in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human's current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject's profile will be discussed. PMID:28607629

On the link between hygroscopicity, volatility, and oxidation state of ambient and water-soluble aerosol in the Southeastern United States

NASA Astrophysics Data System (ADS)

Cerully, K. M.; Bougiatioti, A.; Hite, J. R., Jr.; Guo, H.; Xu, L.; Ng, N. L.; Weber, R.; Nenes, A.

2014-12-01

The formation of secondary organic aerosol (SOA) combined with the partitioning of semi-volatile organic components can impact numerous aerosol properties including cloud condensation nuclei (CCN) activity, hygroscopicity and volatility. During the summer 2013 Southern Oxidant and Aerosol Study (SOAS) field campaign in a rural site in the Southeastern United States, a suite of instruments including a CCN counter, a thermodenuder (TD) and a high resolution time-of-flight aerosol mass spectrometer (AMS) were used to measure CCN activity, aerosol volatility, composition and oxidation state. Particles were either sampled directly from ambient or through a Particle Into Liquid Sampler (PILS), allowing the investigation of the water-soluble aerosol component. Ambient aerosol exhibited size-dependent composition with larger particles being more hygroscopic. The hygroscopicity of thermally-denuded aerosol was similar between ambient and PILS-generated aerosol and showed limited dependence on volatilization. Results of AMS 3-factor Positive Matrix Factorization (PMF) analysis for the PILS-generated aerosol showed that the most hygroscopic components are most likely the most and the least volatile features of the aerosol. No clear relationship was found between organic hygroscopicity and oxygen-to-carbon ratio; in fact, Isoprene organic aerosol (Isoprene-OA) was found to be the most hygroscopic factor, while at the same time being the least oxidized and likely most volatile of all PMF factors. Considering the diurnal variation of each PMF factor and its associated hygroscopicity, Isoprene-OA and More Oxidized - Oxidized Oxygenated Organic Aerosol (MO-OOA) are the prime contributors to hygroscopicity and covary with Less Oxidized - Oxidized Oxygenated Organic Aerosol (LO-OOA) in a way that induces the observed diurnal invariance in total organic hygroscopicity. Biomass Burning Organic Aerosol (BBOA) contributed little to aerosol hygroscopicity, which is expected since there

Microbial utilization of low molecular weight organic substrates in soil depends on their carbon oxidation state

NASA Astrophysics Data System (ADS)

Gunina, Anna; Smith, Andrew; Jones, Davey; Kuzyakov, Yakov

2017-04-01

Removal of low molecular weight organic substances (LMWOS), originating from plants and microorganisms, from soil solution is regulated by microbial uptake. In addition to the concentration of LMWOS in soil solution, the chemical properties of each substance (e.g. C oxidation state, number of C atoms, number of -COOH groups) can affect their uptake and subsequent partitioning of C within the soil microbial community. The aim of this study was to trace the initial fate of three dominant classes of LMWOS in soil (sugars, carboxylic and amino acids), including their removal from solution and utilization by microorganisms, and to reveal the effect of substance chemical properties on these processes. Soil solution, spiked at natural abundance levels with 14C-labelled glucose, fructose, malate, succinate, formate, alanine or glycine, was added to the soil and 14C was traced in the dissolved organic carbon (DOC), CO2, cytosol and soil organic carbon (SOC) over 24 hours. The half-life time of all LMWOS in the DOC (T1 /2-solution) varied between 0.6-5.0 min showing extremely fast initial uptake of LMWOS. The T1 /2-solution of substances was dependent on C oxidation state, indicating that less oxidized organic substances (with C oxidation state "0") were retained longer in soil solution than oxidized substances. The LMWOS-C T1 /2-fast, characterizing the half-life time of 14C in the fast mineralization pool, ranged between 30 and 80 min, with the T1 /2-fast of carboxylic acids (malic acid) being the fastest and the T1 /2-fast of amino acids (glycine) being the slowest. An absence of correlation between T1 /2-fast and either C oxidation state, number of C atoms, or number of -COOH groups suggests that intercellular metabolic pathways are more important for LMWOS transformation in soil than their basic chemical properties. The CO2 release during LMWOS mineralization accounted for 20-90% of 14C applied. Mineralization of LMWOS was the least for sugars and the greatest for

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

Influence of Organic Ligands on the Surface Oxidation State and Magnetic Properties of Iron Oxide Particles

NASA Astrophysics Data System (ADS)

Goroncy, Christian; Saloga, Patrick E. J.; Gruner, Mathias; Schmudde, Madlen; Vonnemann, Jonathan; Otero, Edwige; Haag, Rainer; Graf, Christina

2018-05-01

For the application of iron oxide nanoparticles from thermal decomposition approaches as contrast agents in magnetic resonance imaging (MRI), their initial hydrophobic ligands have to be replaced by hydrophilic ones. This exchange can influence the surface oxidation state and the magnetic properties of the particles. Here, the effect of the anchor group of three organic ligands, citric acid and two catechols, dihydrocaffeic acid and its nitrated derivative nitro dihydrocaffeic acid on iron oxide nanoparticles is evaluated. The oleate ligands of Fe3O4/γ-Fe2O3 nanoparticles prepared by the thermal decomposition of iron oleate were exchanged against the hydrophilic ligands. X-ray absorption spectroscopy, especially X-ray magnetic circular dichroism (XMCD) measurements in the total electron yield (TEY) mode was used to investigate local magnetic and electronic properties of the particles' surface region before and after the ligand exchange. XMCD was combined with charge transfer multiplet calculations which provide information on the contributions of Fe2+ and Fe3+ at different lattice sites, i.e. either in tetrahedral or octahedral environment. The obtained data demonstrate that nitro hydrocaffeic acid leads to least reduction of the magnetizability of the surface region of the iron oxide nanoparticles compared to the two other ligands. For all hydrophilic samples, the proportion of Fe3+ ions in octahedral sites increases at the expense of the Fe2+ in octahedral sites whereas the percentage of Fe3+ in tetrahedral sites hardly changes. These observations suggest that an oxidation process took place, but a selective decrease of the Fe2+ ions in octahedral sites ions due to surface dissolution processes is unlikely. The citrate ligand has the least oxidative effect, whereas the degree of oxidation was similar for both catechol ligands regardless of the nitro group. Twenty-four hours of incubation in isotonic saline has nearly no influences on the magnetic properties of

Chromium oxidation state mapping in human cells

NASA Astrophysics Data System (ADS)

Ortega, R.; Fayard, B.; Salomé, M.; Devès, G.; Susini, J.

2003-03-01

The widespread use of chromium in industrial applications such as chemical production of pigments, refractory brick production, tanning, metallurgy, electroplating, and combustion of fuels has lead to human occupational exposure and to its increased introduction into the environment. Hexavalent chromium compounds are established carcinogens but their mechanism of cell transformation is not known. Up to now, no microanalytical technique was sensitive enough to allow the observation of chromium distribution, and oxidation state identification, within isolated cells at carcinogenic concentrations. In this experiment, we used successfully the ID-21 X-ray microscope to map Cr(VI) and total Cr distributions in cells exposed in vitro to soluble, and insoluble, Cr(VI) compounds. Exposure to soluble compounds, weak carcinogens, resulted in a homogeneous intracellular distribution of Cr, confirming by in situ measurement that Cr is present in the cell nucleus. Cr(VI) was never detected in cells which suggests a mechanism of rapid intracellular reducticn. On the other hand, exposure to insoluble compounds, strong carcinogens, also resulted in a homogeneous distribution of reduced forms of Cr in cells, and their nucleus. However, in this case, Cr(VI)-rich structures were observed into the cells suggesting that carcinogenicity is enhanced when oxidation reactions due to Cr(VI) chronic exposure are associated to Cr-DNA alterations.

Composition and oxidation state of sulfur in atmospheric particulate matter

NASA Astrophysics Data System (ADS)

Longo, Amelia F.; Vine, David J.; King, Laura E.; Oakes, Michelle; Weber, Rodney J.; Huey, Lewis Gregory; Russell, Armistead G.; Ingall, Ellery D.

2016-10-01

The chemical and physical speciation of atmospheric sulfur was investigated in ambient aerosol samples using a combination of sulfur near-edge x-ray fluorescence spectroscopy (S-NEXFS) and X-ray fluorescence (XRF) microscopy. These techniques were used to determine the composition and oxidation state of sulfur in common primary emission sources and ambient particulate matter collected from the greater Atlanta area. Ambient particulate matter samples contained two oxidation states: S0 and S+VI. Ninety-five percent of the individual aerosol particles (> 1 µm) analyzed contain S0. Linear combination fitting revealed that S+VI in ambient aerosol was dominated by ammonium sulfate as well as metal sulfates. The finding of metal sulfates provides further evidence for acidic reactions that solubilize metals, such as iron, during atmospheric transport. Emission sources, including biomass burning, coal fly ash, gasoline, diesel, volcanic ash, and aerosolized Atlanta soil, and the commercially available bacterium Bacillus subtilis, contained only S+VI. A commercially available Azotobacter vinelandii sample contained approximately equal proportions of S0 and S+VI. S0 in individual aerosol particles most likely originates from primary emission sources, such as aerosolized bacteria or incomplete combustion.

Oxidized Nitrogen Balance over 15 Months at Rural and Urban New York State Locations

NASA Astrophysics Data System (ADS)

Schwab, J. J.; Ninneman, M.; Marto, J.; Edgerton, E. S.; Blanchard, C. L.; Shaw, S. L.

2017-12-01

Continuous measurements of oxidized nitrogen species (NO, NO2, and HNO3), families of species (NOy, alkyl nitrates [or ANs], and peroxyacetyl nitrates [or PANs]), and particle nitrate (pNO3) were carried out for a fifteen-month period from August 2016 through October 2017 at two locations in New York State. The two sites were a rural research station at Pinnacle State Park in Addison, NY and an urban research station at Queens College in New York City. Four different chemiluminescence analyzers with various converters and denuders were employed to make these measurements. Instrumentation used for the study will be described, as well as some of the challenges created by combining data from these independent analyzers to address the oxidized nitrogen budget at the two sites. The Pinnacle State Park site often experiences quite clean air with low ppb levels of total NOy and a greater fraction of oxidized nitrogen products (NOz species). This contrasts with the urban Queens College location, which experiences stronger NOx sources. Seasonal differences in the NOx/NOy and NOz/NOy ratios, and the makeup of the NOz species, are also significant and will be explored in the presentation.

Mechanical environmental transport of actinides and ¹³⁷Cs from an arid radioactive waste disposal site.

PubMed

Snow, Mathew S; Clark, Sue B; Morrison, Samuel S; Watrous, Matthew G; Olson, John E; Snyder, Darin C

2015-10-01

Aeolian and pluvial processes represent important mechanisms for the movement of actinides and fission products at the Earth's surface. Soil samples taken in the early 1970's near a Department of Energy radioactive waste disposal site (the Subsurface Disposal Area, SDA, located in southeastern Idaho) provide a case study for studying the mechanisms and characteristics of environmental actinide and (137)Cs transport in an arid environment. Multi-component mixing models suggest actinide contamination within 2.5 km of the SDA can be described by mixing between 2 distinct SDA end members and regional nuclear weapons fallout. The absence of chemical fractionation between (241)Am and (239+240)Pu with depth for samples beyond the northeastern corner and lack of (241)Am in-growth over time (due to (241)Pu decay) suggest mechanical transport and mixing of discrete contaminated particles under arid conditions. Occasional samples northeast of the SDA (the direction of the prevailing winds) contain anomalously high concentrations of Pu with (240)Pu/(239)Pu isotopic ratios statistically identical to those in the northeastern corner. Taken together, these data suggest flooding resulted in mechanical transport of contaminated particles into the area between the SDA and a flood containment dike in the northeastern corner, following which subsequent contamination spreading in the northeastern direction resulted from wind transport of discrete particles. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of Pr Valence State on Interfacial Structure and Electrical Properties of Pr Oxide/PrON/Ge Gate Stack Structure

NASA Astrophysics Data System (ADS)

Kato, Kimihiko; Sakashita, Mitsuo; Takeuchi, Wakana; Kondo, Hiroki; Nakatsuka, Osamu; Zaima, Shigeaki

2011-04-01

In this study, we investigated the valence state and chemical bonding state of Pr in a Pr oxide/PrON/Ge structure. We clarified the relationship between the valence state of Pr and the Pr oxide/Ge interfacial reaction using Pr oxide/Ge and Pr oxide/PrON/Ge samples. We found the formation of three Pr oxide phases in Pr oxide films; hexagonal Pr2O3 (h-Pr2O3) (Pr3+), cubic Pr2O3 (c-Pr2O3) (Pr3+), and c-PrO2 (Pr4+). We also investigated the effect of a nitride interlayer on the interfacial reaction in Pr oxide/Ge gate stacks. In a sample with a nitride interlayer (Pr oxide/PrON/Ge), metallic Pr-Pr bonds are also formed in the c-Pr2O3 film. After annealing in H2 ambient, the diffusion of Ge into Pr oxide is not observed in this sample. Pr-Pr bonds probably prevent the interfacial reaction and Ge oxide formation, considering that the oxygen chemical potential of this film is lower than that of a GeO2/Ge system. On the other hand, the rapid thermal oxidation (RTO) treatment terminates the O vacancies and defects in c-Pr2O3. As a result, c-PrO2 with tetravalent Pr is formed in the Pr oxide/PrON/Ge sample with RTO. In this sample, the leakage current density is effectively decreased in comparison with the sample without RTO. Hydrogen termination works effectively in Pr oxide/PrON/Ge samples with and without RTO, and we can achieve an interface state density of as low as 4 ×1011 eV-1·cm-2.

Analysis on fuel breeding capability of FBR core region based on minor actinide recycling doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Permana, Sidik; Novitrian,; Waris, Abdul

Nuclear fuel breeding based on the capability of fuel conversion capability can be achieved by conversion ratio of some fertile materials into fissile materials during nuclear reaction processes such as main fissile materials of U-233, U-235, Pu-239 and Pu-241 and for fertile materials of Th-232, U-238, and Pu-240 as well as Pu-238. Minor actinide (MA) loading option which consists of neptunium, americium and curium will gives some additional contribution from converted MA into plutonium such as conversion Np-237 into Pu-238 and it's produced Pu-238 converts to Pu-239 via neutron capture. Increasing composition of Pu-238 can be used to produce fissilemore » material of Pu-239 as additional contribution. Trans-uranium (TRU) fuel (Mixed fuel loading of MOX (U-Pu) and MA composition) and mixed oxide (MOX) fuel compositions are analyzed for comparative analysis in order to show the effect of MA to the plutonium productions in core in term of reactor criticality condition and fuel breeding capability. In the present study, neptunium (Np) nuclide is used as a representative of MAin trans-uranium (TRU) fuel composition as Np-MOX fuel type. It was loaded into the core region gives significant contribution to reduce the excess reactivity in comparing to mixed oxide (MOX) fuel and in the same time it contributes to increase nuclear fuel breeding capability of the reactor. Neptunium fuel loading scheme in FBR core region gives significant production of Pu-238 as fertile material to absorp neutrons for reducing excess reactivity and additional contribution for fuel breeding.« less

Effect of surface state on the oxidation behavior of welded 308L in simulated nominal primary water of PWR

NASA Astrophysics Data System (ADS)

Ming, Hongliang; Zhang, Zhiming; Wang, Jiazhen; Zhu, Ruolin; Ding, Jie; Wang, Jianqiu; Han, En-Hou; Ke, Wei

2015-05-01

The oxidation behavior of 308L weld metal (WM) with different surface state in the simulated nominal primary water of pressurized water reactor (PWR) was studied by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analyzer and X-ray photoelectron spectroscopy (XPS). After 480 h immersion, a duplex oxide film composed of a Fe-rich outer layer (Fe3O4, Fe2O3 and a small amount of NiFe2O4, Ni(OH)2, Cr(OH)3 and (Ni, Fe)Cr2O4) and a Cr-rich inner layer (FeCr2O4 and NiCr2O4) can be formed on the 308L WM samples with different surface state. The surface state has no influence on the phase composition of the oxide films but obviously affects the thickness of the oxide films and the morphology of the oxides (number & size). With increasing the density of dislocations and subgrain boundaries in the cold-worked superficial layer, the thickness of the oxide film, the number and size of the oxides decrease.

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 state

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.

Adaptation of oxidative phosphorylation to photoperiod-induced seasonal metabolic states in migratory songbirds.

PubMed

Trivedi, Amit Kumar; Malik, Shalie; Rani, Sangeeta; Kumar, Vinod

2015-06-01

Eukaryotic cells produce chemical energy in the form of ATP by oxidative phosphorylation of metabolic fuels via a series of enzyme mediated biochemical reactions. We propose that the rates of these reactions are altered, as per energy needs of the seasonal metabolic states in avian migrants. To investigate this, blackheaded buntings were photoperiodically induced with non-migratory, premigratory, migratory and post-migratory phenotypes. High plasma levels of free fatty acids, citrate (an intermediate that begins the TCA cycle) and malate dehydrogenase (mdh, an enzyme involved at the end of the TCA cycle) confirmed increased availability of metabolic reserves and substrates to the TCA cycle during the premigratory and migratory states, respectively. Further, daily expression pattern of genes coding for enzymes involved in the oxidative decarboxylation of pyruvate to acetyl-CoA (pdc and pdk) and oxidative phosphorylation in the TCA cycle (cs, odgh, sdhd and mdh) was monitored in the hypothalamus and liver. Reciprocal relationship between pdc and pdk expressions conformed with the altered requirements of acetyl-CoA for the TCA cycle in different metabolic states. Except for pdk, all genes had a daily expression pattern, with high mRNA expression during the day in the premigratory/migratory phenotypes, and at night (cs, odhg, sdhd and mdh) in the nonmigratory phenotype. Differences in mRNA expression patterns of pdc, sdhd and mdh, but not of pdk, cs and odgh, between the hypothalamus and liver indicated a tissue dependent metabolism in buntings. These results suggest the adaptation of oxidative phosphorylation pathway(s) at gene levels to the seasonal alternations in metabolism in migratory songbirds. Copyright © 2015 Elsevier Inc. All rights reserved.

The influence of iridium chemical oxidation state on the performance and durability of oxygen evolution catalysts in PEM electrolysis

NASA Astrophysics Data System (ADS)

Siracusano, S.; Baglio, V.; Grigoriev, S. A.; Merlo, L.; Fateev, V. N.; Aricò, A. S.

2017-10-01

Nanosized Ir-black (3 nm) and Ir-oxide (5 nm) oxygen evolution electrocatalysts showing high performance in polymer electrolyte membrane (PEM) water electrolysis based on Aquivion® short-side chain ionomer membrane are investigated to understand the role of the Ir oxidation state on the electrocatalytic activity and stability. Despite the smaller mean crystallite size, the Ir-black electrocatalyst shows significantly lower initial performance than the Ir-oxide. During operation at high current density, the Ir-black shows a decrease of cell potential with time whereas the Ir-oxide catalyst shows increasing cell potential resulting in a degradation rate of about 10 μV/h, approaching 1000 h. The unusual behaviour of the Ir-black results from the oxidation of metallic Ir to IrOx. The Ir-oxide catalyst shows instead a hydrated structure on the surface and a negative shift of about 0.5 eV for the Ir 4f binding energy after 1000 h electrolysis operation. This corresponds to the formation of a sub-stoichiometric Ir-oxide on the surface. These results indicate that a hydrated IrO2 with high oxidation state on the surface is favourable in decreasing the oxygen evolution overpotential. Modifications of the Ir chemical oxidation state during operation can affect significantly the catalytic activity and durability of the electrolysis system.

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

GaAs-oxide interface states - A gigantic photoionization effect and its implications to the origin of these states

NASA Technical Reports Server (NTRS)

Lagowski, J.; Walukiewicz, W.; Kazior, T. E.; Gatos, H. C.; Siejka, J.

1981-01-01

Gigantic photoionization was discovered on GaAs-oxide interfaces leading to the discharge of deep surface states with rates exceeding 1000 times those of photoionization transitions to the conduction band. It exhibits a peak similar to acceptor-donor transitions and is explained as due to energy transfer from photo-excited donor-acceptor pairs to deep surface states. This new process indicates the presence of significant concentrations of shallow donor and acceptor levels not recognized in previous interface models.

The control of iron-induced oxidative damage in isolated rat-liver mitochondria by respiration state and ascorbate.

PubMed

Burkitt, M J; Gilbert, B C

1989-01-01

The reaction of iron (II) with H2O2 is believed to generate highly reactive species (e.g. .OH) capable of initiating biological damage. This study investigates the possibility that the severity of oxidative damage induced by iron in hepatic mitochondria is determined by the level of mitochondrial-H2O2 generation, which is believed to be particularly prominent in state-4 respiration. Iron-induced damage is found to be greater in state-4 than in state-3 respiration. Experiments using uncoupling agents and Ca++ to mimic state-3 conditions indicate that this effect reflects differences in the steady-state oxidation-level of the electron carriers of the respiratory chain (and hence the level of H2O2-generation), rather than changes in redox potential or transportation of the metal-ion. Evidence is also presented for a mechanism in which Fe(II) and H2O2 react inside the mitochondrial matrix. Ascorbate (vitamin C) is shown to be pro-oxidant in this system, except when present at very high concentration when it becomes antioxidant in nature.

Homoleptic Ce(III) and Ce(IV) Nitroxide Complexes: Significant Stabilization of the 4+ Oxidation State

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogart, Justin A.; Lewis, Andrew J.; Medling, Scott A.

2014-06-25

Electrochemical experiments performed on the complex Ce-IV[2-((BuNO)-Bu-t)py](4), where [2-((BuNO)-Bu-t)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(Bu4N)-Bu-n](2)[Ce(NO3)(6)] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with delta symmetry. The results speak to the behavior of CeO2 and related solid solutions inmore » oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.« less

Status in calculating electronic excited states in transition metal oxides from first principles.

PubMed

Bendavid, Leah Isseroff; Carter, Emily Ann

2014-01-01

Characterization of excitations in transition metal oxides is a crucial step in the development of these materials for photonic and optoelectronic applications. However, many transition metal oxides are considered to be strongly correlated materials, and their complex electronic structure is challenging to model with many established quantum mechanical techniques. We review state-of-the-art first-principles methods to calculate charged and neutral excited states in extended materials, and discuss their application to transition metal oxides. We briefly discuss developments in density functional theory (DFT) to calculate fundamental band gaps, and introduce time-dependent DFT, which can model neutral excitations. Charged excitations can be described within the framework of many-body perturbation theory based on Green's functions techniques, which predominantly employs the GW approximation to the self-energy to facilitate a feasible solution to the quasiparticle equations. We review the various implementations of the GW approximation and evaluate each approach in its calculation of fundamental band gaps of many transition metal oxides. We also briefly review the related Bethe-Salpeter equation (BSE), which introduces an electron-hole interaction between GW-derived quasiparticles to describe accurately neutral excitations. Embedded correlated wavefunction theory is another framework used to model localized neutral or charged excitations in extended materials. Here, the electronic structure of a small cluster is modeled within correlated wavefunction theory, while its coupling to its environment is represented by an embedding potential. We review a number of techniques to represent this background potential, including electrostatic representations and electron density-based methods, and evaluate their application to transition metal oxides.

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.

Technical and economic assessment of different options for minor actinide transmutation: the French case

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chabert, C.; Coquelet-Pascal, C.; Saturnin, A.

Studies have been performed to assess the industrial perspectives of partitioning and transmutation of long-lived elements. These studies were carried out in tight connection with GEN-IV systems development. The results include the technical and economic evaluation of fuel cycle scenarios along with different options for optimizing the processes between the minor actinide transmutation in fast neutron reactors, their interim storage and geological disposal of ultimate waste. The results are analysed through several criteria (impacts on waste, on waste repository, on fuel cycle plants, on radiological exposure of workers, on costs and on industrial risks). These scenario evaluations take place inmore » the French context which considers the deployment of the first Sodium-cooled Fast Reactor (SFR) in 2040. 3 management options of minor actinides have been studied: no transmutation, transmutation in SFR and transmutation in an accelerator-driven system (ADS). Concerning economics the study shows that the cost overrun related to the transmutation process could vary between 5 to 9% in SFR and 26 % in the case of ADS.« less

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...

Directed evolution of the periodic table: probing the electronic structure of late actinides.

PubMed

Marsh, M L; Albrecht-Schmitt, T E

2017-07-25

Recent investigations of the coordination chemistry and physical properties of berkelium (Z = 97) and californium (Z = 98) have revealed fundamental differences between post-curium elements and lighter members of the actinide series. This review highlights these developments and chronicles key findings and concepts from the last half-century that have helped usher in a new understanding of the evolution of electronic structure in the periodic table.

The Efficacy of Denaturing Actinide Elements as a Means of Decreasing Materials Attractiveness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hase, Kevin R.; Ebbinghaus, Bartley B.; Sleaford, Brad W.

2013-07-01

This paper is an extension to earlier studies that examined the attractiveness of materials mixtures containing special nuclear materials (SNM) and alternate nuclear materials (ANM). This study considers the concept of denaturing as applied to the actinide elements present in spent fuel as a means to reduce materials attractiveness. Highly attractive materials generally have low values of bare critical mass, heat content, and dose.

Visualizing chemical states and defects induced magnetism of graphene oxide by spatially-resolved-X-ray microscopy and spectroscopy.

PubMed

Wang, Y F; Singh, Shashi B; Limaye, Mukta V; Shao, Y C; Hsieh, S H; Chen, L Y; Hsueh, H C; Wang, H T; Chiou, J W; Yeh, Y C; Chen, C W; Chen, C H; Ray, Sekhar C; Wang, J; Pong, W F; Takagi, Y; Ohigashi, T; Yokoyama, T; Kosugi, N

2015-10-20

This investigation studies the various magnetic behaviors of graphene oxide (GO) and reduced graphene oxides (rGOs) and elucidates the relationship between the chemical states that involve defects therein and their magnetic behaviors in GO sheets. Magnetic hysteresis loop reveals that the GO is ferromagnetic whereas photo-thermal moderately reduced graphene oxide (M-rGO) and heavily reduced graphene oxide (H-rGO) gradually become paramagnetic behavior at room temperature. Scanning transmission X-ray microscopy and corresponding X-ray absorption near-edge structure spectroscopy were utilized to investigate thoroughly the variation of the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups, as well as the C 2p(σ*)-derived states in flat and wrinkle regions to clarify the relationship between the spatially-resolved chemical states and the magnetism of GO, M-rGO and H-rGO. The results of X-ray magnetic circular dichroism further support the finding that C 2p(σ*)-derived states are the main origin of the magnetism of GO. Based on experimental results and first-principles calculations, the variation in magnetic behavior from GO to M-rGO and to H-rGO is interpreted, and the origin of ferromagnetism is identified as the C 2p(σ*)-derived states that involve defects/vacancies rather than the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups on GO sheets.

Visualizing chemical states and defects induced magnetism of graphene oxide by spatially-resolved-X-ray microscopy and spectroscopy

PubMed Central

Wang, Y. F.; Singh, Shashi B.; Limaye, Mukta V.; Shao, Y. C.; Hsieh, S. H.; Chen, L. Y.; Hsueh, H. C.; Wang, H. T.; Chiou, J. W.; Yeh, Y. C.; Chen, C. W.; Chen, C. H.; Ray, Sekhar C.; Wang, J.; Pong, W. F.; Takagi, Y.; Ohigashi, T.; Yokoyama, T.; Kosugi, N.

2015-01-01

This investigation studies the various magnetic behaviors of graphene oxide (GO) and reduced graphene oxides (rGOs) and elucidates the relationship between the chemical states that involve defects therein and their magnetic behaviors in GO sheets. Magnetic hysteresis loop reveals that the GO is ferromagnetic whereas photo-thermal moderately reduced graphene oxide (M-rGO) and heavily reduced graphene oxide (H-rGO) gradually become paramagnetic behavior at room temperature. Scanning transmission X-ray microscopy and corresponding X-ray absorption near-edge structure spectroscopy were utilized to investigate thoroughly the variation of the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups, as well as the C 2p(σ*)-derived states in flat and wrinkle regions to clarify the relationship between the spatially-resolved chemical states and the magnetism of GO, M-rGO and H-rGO. The results of X-ray magnetic circular dichroism further support the finding that C 2p(σ*)-derived states are the main origin of the magnetism of GO. Based on experimental results and first-principles calculations, the variation in magnetic behavior from GO to M-rGO and to H-rGO is interpreted, and the origin of ferromagnetism is identified as the C 2p(σ*)-derived states that involve defects/vacancies rather than the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups on GO sheets. PMID:26481557

Assessing the oxidation states and structural stability of the Ce analogue of brannerite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aluri, Esther Rani; Bachiu, Lisa M.; Grosvenor, Andrew P.

2017-07-04

The Ce-containing analogue of brannerite (ie, UTi2O6) was previously considered to be stoichiometric (ie, CeTi2O6); however, it has recently been determined that the material is O deficient. This oxygen-deficient material has been suggested to be charged balanced by the presence of a minor concentration of Ce3+ or by the A-site being cation deficient with the Ce oxidation state being 4+. A variety of Ti-containing oxides (including brannerite) have been investigated as potential nuclear wasteforms, and it is necessary to understand the electronic structure of a proposed nuclear wasteform material as well as how the structure responds to radiation from incorporatedmore » waste elements. The radiation resistance of a material can be simulated by ion implantation. The objective of this study was to confirm the Ce oxidation state in the cation- and oxygen-deficient material (ie, Ce0.94Ti2O6 - δ) and to determine how radiation damage affects this material. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy were used to study Ce0.94Ti2O6 - δ before and after being implanted with 2 MeV Au- ions. Analysis of the Ce 3d XPS spectra from the as-synthesized samples by using a previously developed fitting method has unequivocally shown that Ce adopts both 4+ (major) and 3+ (minor) oxidation states, which was confirmed by examination of magnetic susceptibility data. Analysis of XPS and X-ray absorption near-edge spectroscopy spectra from ion-implanted materials showed that both Ce and Ti were reduced because of radiation damage and that the local coordination environments of the cations are greatly affected by radiation damage.« less

Obesity-Associated Oxidative Stress: Strategies Finalized to Improve Redox State

PubMed Central

Savini, Isabella; Catani, Maria Valeria; Evangelista, Daniela; Gasperi, Valeria; Avigliano, Luciana

2013-01-01

Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance. PMID:23698776

Support for Students and Young Scientists to Participate in the 2009 Actinides Conference to be held in San Francisco, CA, Sunday, 12 July 2009 -- Friday, 17 July 2009

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raymond, Kenneth N.

2011-04-08

Early career scientist were provided support to attend and participate in the Actinides 2009 (AN2009) International Conference held in San Francisco, California from 12-17 July 2011. This is the premier conference in the field of actinide chemistry, physics, and materials science of the actinide elements. Participation in the preeminent scientific meeting in actinide science keeps the U.S at the forefront of developments in this key field. The specific involvement of early career scientists combats the loss of expertise in the aforementioned critical areas related to f-element chemistry such as energy, homeland, and environmental security. Without these trained scientists, the U.S.more » will not be able to properly exploit nuclear technology to its fullest and will not be able to address its energy needs in either an environmentally safe or cost–effective manner nor will it be able to provide for its national defense. Furthermore, the early career scientists added greatly to the scientific content of the meeting and stimulates early career scientists to remain in the filed of actinide science. Providing support for participation in the AN2009 Conference via registration fee waivers, hotel cost support, and travel cost support, was extremely effective in securing the participation of early career scientists that would have not otherwise been able to attend.« less

Bolide impacts and the oxidation state of carbon in the earth's early atmosphere

NASA Technical Reports Server (NTRS)

Kasting, James F.

1990-01-01

A one-dimensional photochemical model was used to examine the effect of bolide impacts on the oxidation state of earth's primitive atmosphere. The impact rate should have been high prior to 3.8 Ga before present, based on evidence derived from the moon. Impacts of comets or carbonaceous asteroids should have enhanced the atmospheric CO/CO2 ratio by bringing in CO ice and/or organic carbon that can be oxidized to CO in the impact plume. Ordinary chondritic impactors would contain elemental iron that could have reacted with ambient CO2 to give CO. Nitric oxide (NO) should also have been produced by reaction between ambient CO2 and N2 in the hot impact plumes. High NO concentrations increase the atmospheric CO/CO2 ratio by increasing the rainout rate of oxidized gases. According to the model, atmospheric CO/CO2 ratios of unity or greater are possible during the first several hundred million years of earth's history, provided that dissolved CO was not rapidly oxidized to bicarbonate in the ocean.

Multidimensionally constrained relativistic mean-field study of triple-humped barriers in actinides

NASA Astrophysics Data System (ADS)

Zhao, Jie; Lu, Bing-Nan; Vretenar, Dario; Zhao, En-Guang; Zhou, Shan-Gui

2015-01-01

Background: Potential energy surfaces (PES's) of actinide nuclei are characterized by a two-humped barrier structure. At large deformations beyond the second barrier, the occurrence of a third barrier was predicted by macroscopic-microscopic model calculations in the 1970s, but contradictory results were later reported by a number of studies that used different methods. Purpose: Triple-humped barriers in actinide nuclei are investigated in the framework of covariant density functional theory (CDFT). Methods: Calculations are performed using the multidimensionally constrained relativistic mean field (MDC-RMF) model, with the nonlinear point-coupling functional PC-PK1 and the density-dependent meson exchange functional DD-ME2 in the particle-hole channel. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. Results: Two-dimensional PES's of 226,228,230,232Th and 232,235,236,238U are mapped and the third minima on these surfaces are located. Then one-dimensional potential energy curves along the fission path are analyzed in detail and the energies of the second barrier, the third minimum, and the third barrier are determined. The functional DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and 238U . The third minima in 230 ,232Th are very shallow, whereas those in 226 ,228Th and 238U are quite prominent. With the functional PC-PK1 a third barrier is found only in 226 ,228 ,230Th . Single-nucleon levels around the Fermi surface are analyzed in 226Th, and it is found that the formation of the third minimum is mainly due to the Z =90 proton energy gap at β20≈1.5 and β30≈0.7 . Conclusions: The possible occurrence of a third barrier on the PES's of actinide nuclei depends on the effective interaction used in multidimensional CDFT calculations. More pronounced minima are predicted by the DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third well in Th isotopes decreases

Study of GaAs-oxide interface by transient capacitance spectroscopy - Discrete energy interface states

NASA Technical Reports Server (NTRS)

Kamieniecki, E.; Kazior, T. E.; Lagowski, J.; Gatos, H. C.

1980-01-01

Interface states and bulk GaAs energy levels were simultaneously investigated in GaAs MOS structures prepared by anodic oxidation. These two types of energy levels were successfully distinguished by carrying out a comparative analysis of deep level transient capacitance spectra of the MOS structures and MS structures prepared on the same samples of epitaxially grown GaAs. The identification and study of the interface states and bulk levels was also performed by investigating the transient capacitance spectra as a function of the filling pulse magnitude. It was found that in the GaAs-anodic oxide interface there are states present with a discrete energy rather than with a continuous energy distribution. The value of the capture cross section of the interface states was found to be 10 to the 14th to 10 to the 15th/sq cm, which is more accurate than the extremely large values of 10 to the -8th to 10 to the -9th/sq cm reported on the basis of conductance measurements.

Chemistry of transuranium elements in salt-base repository

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borkowski, Marian; Reed, Donald T; Lucchini, Jean - Francois

2010-12-02

The mobility and potential release of actinides into the accessible environment continues to be the key performance assessment concern of nuclear repositories. Actinide, in particular plutonium speciation under the wide range of conditions that can exist in the subsurface is complex and depends strongly on the coupled effects of redox conditions, inorganic/organic complexation, and the extent/nature of aggregation. Understanding the key factors that define the potential for actinide migration is, in this context, an essential and critical part of making and sustaining a licensing case for a nuclear repository. Herein we report on recent progress in a concurrent modeling andmore » experimental study to determine the speciation of plutonium, uranium and americium in high ionic strength Na-CI-Mg brines. This is being done as part of the ongomg recertification effort m the Waste Isolation Pilot Plant (WIPP). The oxidation-state specific solubility of actinides were established in brine as function of pC{sub H+}, brine composition and the presence and absence of organic chelating agents and carbonate. An oxidation-state invariant analog approach using Nd{sup 3+} and Th{sup 4+} was used for An{sup 3+} and An{sup 4+} respectively. These results show that organic ligands and hydrolysis are key factors for An(III) solubility, hydrolysis at pC{sub H+} above 8 is predominate for An(IV) and carbonates are the key factor for U(VI) solubility. The effect of high ionic strength and brine components measured in absence of carbonates leads to measurable increased in overall solubility over analogous low ionic strength groundwater. Less is known about the bioreduction of actinides by halo-tolerant microorganisms, but there is now evidence that bioreduction does occur and is analogous, in many ways, to what occurs with soil bacteria. Results of solubility studies that focus on Pitzer parameter corrections, new species (e.g. borate complexation), and the thermodynamic parameters for

SNC Oxygen Fugacity Recorded in Pyroxenes and its Implications for the Oxidation State of the Martian Interior: An Experimental and Analytical Study

NASA Technical Reports Server (NTRS)

McCanta, M. C.; Rutherford, M. J.

2003-01-01

Knowledge of the oxidation state of a magma is critical as it is one of the parameters which controls the nature and composition of the resulting crystals. In terrestrial magmatic systems, oxygen fugacity (fo2) is known to vary by over nine orders of magnitude. With variations of this magnitude, understanding the compositional differences, phase changes, and crystallization sequence variations, caused by the magma fo2, is essential in deciphering the origin of all igneous rocks. Magmatic oxidation state is of great importance in that it reflects the degree of oxidation of the source region and can provide insight into magmatic processes, such as metasomatism, degassing, and assimilation, which may have changed them. Carmichael [1991] argues that most magmas are unlikely to have their redox states altered from those of their source region. This assumption allows for estimation of the oxidation state of planetary interiors. Conversely, it is known that the fo2 of the magma can be affected by other processes, which occur outside of the source region and therefore, the oxidation state may record those too. Processes which could overprint source region fugacities include melt dehydrogenation or other volatile loss, water or melt infiltration, or assimilation of oxidized or reduced wallrock. Understanding which of these processes is responsible for the redox state of a magma can provide crucial information regarding igneous processes and other forces active in the region. The composition of the SNC basalts and their widely varying proposed oxidation states raise some interesting questions. Do the SNC meteorites have an oxidized or reduced signature? What was the oxygen fugacity of the SNC source region at the time of melt generation? Is the fugacity calculated for the various SNC samples the fugacity of the magma source region or was it overprinted by later events? Are there different oxidation states in the Martian interior or a single one? This proposal seeks to

Multiscale structural characterizations of mixed U(iv)-An(iii) oxalates (An(iii) = Pu or Am) combining XAS and XRD measurements.

PubMed

Arab-Chapelet, B; Martin, P M; Costenoble, S; Delahaye, T; Scheinost, A C; Grandjean, S; Abraham, F

2016-04-28

Mixed actinide(III,IV) oxalates of the general formula M2.2UAn(C2O4)5·nH2O (An = Pu or Am and M = H3O(+) and N2H5(+)) have been quantitatively precipitated by oxalic precipitation in nitric acid medium (yield >99%). Thorough multiscale structural characterization using XRD and XAS measurements confirmed the existence of mixed actinide oxalate solid solutions. The XANES analysis confirmed that the oxidation states of the metallic cations, tetravalent for uranium and trivalent for plutonium and americium, are maintained during the precipitation step. EXAFS measurements show that the local environments around U(+IV), Pu(+III) and Am(+III) are comparable, and the actinides are surrounded by ten oxygen atoms from five bidentate oxalate anions. The mean metal-oxygen distances obtained by XAS measurements are in agreement with those calculated from XRD lattice parameters.

The relationship between skin aging and steady state ultraweak photon emission as an indicator of skin oxidative stress in vivo.

PubMed

Gabe, Y; Osanai, O; Takema, Y

2014-08-01

Ultraweak photon emission (UPE) is one potential method to evaluate the oxidative status of the skin in vivo. However, little is known about how the daily oxidative stress of the skin is related to skin aging-related alterations in vivo. We characterized the steady state UPE and performed a skin survey. We evaluated the skin oxidative status by UPE, skin elasticity, epidermal thickness and skin color on the inner upper arm, the outer forearm, and the buttock of 70 Japanese volunteers. The steady state UPE at the three skin sites increased with age. Correlation analysis revealed that the steady state UPE only from the buttock was related to skin elasticity, which showed age-dependent changes. Moreover, analysis by age group indicated that b* values of the inner upper arm of subjects in their 20s were inversely correlated with UPE as occurred in buttock skin. In contrast, photoaged skin did not show a clear relationship with steady state UPE because the accumulation of sun-exposure might influence the sensitivity to oxidative stress. These results suggest that steady state UPE reflects not only intrinsic skin aging and cutaneous color but also the current oxidative status independent of skin aging. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

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.

Arsenic in ground-water under oxidizing conditions, south-west United States

USGS Publications Warehouse

Robertson, F.N.

1989-01-01

Concentrations of dissolved arsenic in ground-water in alluvial basins of Arizona commonly exceed 50 ??g L-1 and reach values as large as 1,300 ??g L-1. Arsenic speciation analyses show that arsenic occurs in the fully oxidized state of plus 5 (As+5), most likely in the form of HAsO4???2, under existing oxidizing and pH conditions. Arsenic in source areas presumably is oxidized to soluble As before transport into the basin or, if after transport, before burial. Probable sources of arsenic are the sulphide and arsenide deposits in the mineralized areas of the mountains surrounding the basins. Arsenic content of alluvial material ranged from 2 to 88 ppm. Occurrence and removal of arsenic in ground-water are related to the pH and the redox condition of the ground-water, the oxidation state of arsenic, and sorption or exchange. Within basins, dissolved arsenic correlates (P<0.01) with dissolved molybdenum, selenium, vanadium, and fluoride and with pH, suggesting sorption of negative ions. The sorption hypothesis is further supported by enrichment of teachable arsenic in the basin-fill sediments by about tenfold relative to the crustal abundance and by as much as a thousandfold relative to concentrations found in ground-water. Silicate hydrolysis reactions, as defined within the alluvial basins, under closed conditions cause increases in pH basinward and would promote desorption. Within the region, large concentrations of arsenic are commonly associated with the central parts of basins whose chemistries evolve under closed conditions. Arsenic does not correlate with dissolved iron (r = 0.09) but may be partly controlled by iron in the solid phase. High solid-phase arsenic contents were found in red clay beds. Large concentrations of arsenic also were found in water associated with red clay beds. Basins that contain the larger concentrations are bounded primarily by basalt and andesite, suggesting that the iron content as well as the arsenic content of the basin fill may

Liquid-liquid extraction of actinides, lanthanides, and fission products by use of ionic liquids: from discovery to understanding.

PubMed

Billard, Isabelle; Ouadi, Ali; Gaillard, Clotilde

2011-06-01

Liquid-liquid extraction of actinides and lanthanides by use of ionic liquids is reviewed, considering, first, phenomenological aspects, then looking more deeply at the various mechanisms. Future trends in this developing field are presented.

Potentialities of mass spectrometry (ICP-MS) for actinides determination in urine.

PubMed

Bouvier-Capely, C; Ritt, J; Baglan, N; Cossonnet, C

2004-05-01

The applicability of inductively coupled plasma-mass spectrometry (ICP-MS) for determining actinides in urine was investigated. Performances of ICP-MS including detection limit and analysis time were studied and compared with alpha spectrometry performances. In the field of individual monitoring of workers, the comparison chart obtained in this study can be used as a guide for medical laboratories to select the most adequate procedure to be carried out depending on the case in question (the radioisotope to be measured, the required sensitivity, and the desired response time).

Cloud droplet activation through oxidation of organic aerosol influenced by temperature and particle phase state: CLOUD ACTIVATION BY AGED ORGANIC AEROSOL

DOE PAGES

Slade, Jonathan H.; Shiraiwa, Manabu; Arangio, Andrea; ...

2017-02-04

Chemical aging of organic aerosol (OA) through multiphase oxidation reactions can alter their cloud condensation nuclei (CCN) activity and hygroscopicity. However, the oxidation kinetics and OA reactivity depend strongly on the particle phase state, potentially influencing the hydrophobic-to-hydrophilic conversion rate of carbonaceous aerosol. Here, amorphous Suwannee River fulvic acid (SRFA) aerosol particles, a surrogate humic-like substance (HULIS) that contributes substantially to global OA mass, are oxidized by OH radicals at different temperatures and phase states. When oxidized at low temperature in a glassy solid state, the hygroscopicity of SRFA particles increased by almost a factor of two, whereas oxidation ofmore » liquid-like SRFA particles at higher temperatures did not affect CCN activity. Low-temperature oxidation appears to promote the formation of highly-oxygenated particle-bound fragmentation products with lower molar mass and greater CCN activity, underscoring the importance of chemical aging in the free troposphere and its influence on the CCN activity of OA.« less

Identification of ground-state spin ordering in antiferromagnetic transition metal oxides using the Ising model and a genetic algorithm

PubMed Central

Lee, Kyuhyun; Youn, Yong; Han, Seungwu

2017-01-01

Abstract We identify ground-state collinear spin ordering in various antiferromagnetic transition metal oxides by constructing the Ising model from first-principles results and applying a genetic algorithm to find its minimum energy state. The present method can correctly reproduce the ground state of well-known antiferromagnetic oxides such as NiO, Fe2O3, Cr2O3 and MnO2. Furthermore, we identify the ground-state spin ordering in more complicated materials such as Mn3O4 and CoCr2O4. PMID:28458746

Ageing of a phosphate ceramic used to immobilize chloride contaminated actinide waste

NASA Astrophysics Data System (ADS)

Metcalfe, B. L.; Donald, I. W.; Fong, S. K.; Gerrard, L. A.; Strachan, D. M.; Scheele, R. D.

2009-03-01

A process for the immobilization of intermediate level waste containing a significant quantity of chloride using Ca3(PO4)2 as the host material has been developed. Waste ions are incorporated into two phosphate-based phases, chlorapatite [Ca5(PO4)3Cl] and spodiosite [Ca2(PO4)Cl]. Non-active trials performed using Sm as the actinide surrogate demonstrated the durability of these phases in aqueous solution. Trials of the process, in which actinide-doped materials were used, were performed at PNNL which confirmed the wasteform resistant to aqueous leaching. Initial leach trials conducted on 239Pu/241Am loaded ceramic at 313 K/28 days gave normalized mass losses of 1.2 × 10-5 g m-2 and 2.7 × 10-3 g m-2 for Pu and Cl, respectively. In order to assess the response of the phases to radiation-induced damage, accelerated ageing trials were performed on samples in which the 239Pu was replaced with 238Pu. No changes to the crystalline structure of the waste were detected in the XRD spectra after the samples had experienced an α radiation fluence of 4 × 1018 g-1. Leach trials showed that there was an increase in the P and Ca release rates but no change in the Pu release rate.

Ageing of a phosphate ceramic used to immobilize chloride contaminated actinide waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metcalfe, Brian L.; Donald, Ian W.; Fong, Shirley K.

2009-03-31

AWE has developed a process for the immobilization of ILW waste containing a significant quantity of chloride using Ca3(PO4)2 as the host material. Waste ions are incorporated into two phosphate based phases, chlorapatite, Ca5(PO4)3Cl, and spodiosite, Ca2(PO4)Cl. Non-active trials performed at AWE using samarium as the actinide surrogate demonstrated the durability of these phases in aqueous solution. Trials of the process using actinide-doped material were performed at PNNL which confirmed the immobilized wasteform resistant to aqueous leaching. Initial leach trials conducted on 239Pu /241Am loaded ceramic at 40°C/28 days gave normalized mass losses of 1.2 x 10-5 g.m-2 and 2.7more » x 10-3 g.m-2 for Pu and Cl respectively. In order to assess the response of the phases to radiation-induced damage, accelerated ageing trials were performed on samples in which the 239Pu was replaced by 238Pu. No changes to the crystalline structure of the waste were detected using XRD after the samples had experienced a radiation dose of 4 x 1018 α.g-1. Leach trials showed that there had been an increase in the P and Ca release rates but no change in the Pu release rate.« less

Special Form Testing of Sealed Source Encapsulation for High-Alpha-Activity Actinide Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez, Oscar A

In the United States all transportation of radioactive material is regulated by the U.S. Department of Transportation (DOT). Beginning in 2008 a new type of sealed-source encapsulation package was developed and tested by Oak Ridge National Laboratory (ORNL). These packages contain high-alpha-activity actinides and are regulated and transported in accordance with the requirements for DOT Class 7 hazardous material. The DOT provides specific regulations pertaining to special form encapsulation designs. The special form designation indicates that the encapsulated radioactive contents have a very low probability of dispersion even when subjected to significant structural events. The special form designs have beenmore » shown to simplify the delivery, transport, acceptance, and receipt processes. It is intended for these sealed-source encapsulations to be shipped to various facilities making it very advantageous for them to be certified as special form. To this end, DOT Certificates of Competent Authority (CoCAs) have been sought for the design suitable for containing high-alpha-activity actinide materials. This design consists of the high-alpha-activity material encapsulated within a triangular zirconia canister, referred to as a ZipCan, tile that is then enclosed by a spherical shell. The spherical shell design, with ZipCan tile inside, was tested for compliance with the special form regulations found in 49 CFR 173.469. The spherical enclosure was subjected to 9-m impact, 1 m percussion, and 10-minute thermal tests at the Packaging Evaluation Facility located at the National Transportation Research Center in Knoxville, TN USA and operated by ORNL. Before and after each test, the test units were subjected to a helium leak check and a bubble test. The ZipCan tiles and core were also subjected to the tests required for ISO 2919:2012(E), including a Class IV impact test and heat test and subsequently subjected to helium leakage rate tests [49 CFR 173.469(a)(4)(i)]. The

Active three-way catalysis of rhodium particles with a low oxidation state maintained under an oxidative atmosphere on a La-containing ZrO2 support.

PubMed

Kawabata, Hisaya; Koda, Yuki; Sumida, Hirosuke; Shigetsu, Masahiko; Takami, Akihide; Inumaru, Kei

2013-05-11

Rhodium on a La-containing ZrO2 support effectively eliminated NOx from a synthetic auto exhaust gas under fluctuating oxygen conditions. Rhodium particles maintained a low oxidation state on the ZrO2-La2O3 mixed oxide even after treatment with 5% O2 at 773 K, highlighting the significant effect of the La addition.

A combined calorimetric and computational study of the energetics of rare earth substituted UO 2 systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Lei; Solomon, Jonathan M.; Asta, Mark

2015-09-01

The energetics of rare earth substituted UO2 solid solutions (U1-xLnxO2-0.5x+y, where Ln = La, Y, and Nd) are investigated employing a combination of calorimetric measurements and density functional theory based computations. Calculated and measured formation enthalpies agree within 10 kJ/mol for stoichiometric oxygen/metal compositions. To better understand the factors governing the stability and defect binding in rare earth substituted urania solid solutions, systematic trends in the energetics are investigated based on the present results and previous computational and experimental thermochemical studies of rare earth substituted fluorite oxides (A1-xLnxO2-0.5x, where A = Hf, Zr, Ce, and Th). A consistent trend towardsmore » increased energetic stability with larger size mismatch between the smaller host tetravalent cation and the larger rare earth trivalent cation is found for both actinide and non-actinide fluorite oxide systems where aliovalent substitution of Ln cations is compensated by oxygen vacancies. However, the large exothermic oxidation enthalpy in the UO2 based systems favors oxygen rich compositions where charge compensation occurs through the formation of uranium cations with higher oxidation states.« less

Forest soil carbon oxidation state and oxidative ratio responses to elevated CO 2

DOE PAGES

Hockaday, William C.; Gallagher, Morgan E.; Masiello, Caroline A.; ...

2015-09-21

The oxidative ratio (OR) of the biosphere is the stoichiometric ratio (O 2/CO 2) 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. Here, this study considers the effect of elevated atmospheric carbon dioxide concentrations ([CO 2]) on the OR of a hardwood forest after nine growing seasons of Free-Air CO 2 Enrichment. We measured changes in the carbon oxidation state (C ox)more » 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 [CO 2]. However, the C ox of the soil carbon pool was 40% higher at elevated [CO 2], and the estimated OR values for soil respiration increased from 1.006 at ambient [CO 2] to 1.054 at elevated [CO 2]. A biochemical inventory of the soil organic matter ascribed the increases in C ox and OR to faster turnover of reduced substrates, lignin and lipids, at elevated [CO 2]. This implicates the heterotrophic soil community response to elevated [CO 2] as a driver of disequilibrium in the ecosystem OR. The oxidation of soil carbon pool constitutes an unexpected terrestrial O 2 sink. Carbon budgets constructed under the assumption of OR equilibrium would equate such a terrestrial O 2 sink to CO 2 uptake by the ocean. We find that the potential for climate-driven disequilibriua in the cycling of O 2 and CO 2 warrants further investigation.« less

Visualizing different uranium oxidation states during the surface alteration of uraninite and uranium tetrachloride.

PubMed

Grossmann, Kay; Arnold, Thuro; Steudtner, Robin; Weiss, Stefan; Bernhard, Gert

2009-08-01

Low-temperature alteration reactions on uranium phases may lead to the mobilization of uranium and thereby poses a potential threat to humans living close to uranium-contaminated sites. In this study, the surface alteration of uraninite (UO(2)) and uranium tetrachloride (UCl(4)) in air atmosphere was studied by confocal laser scanning microscopy (CLSM) and laser-induced fluorescence spectroscopy using an excitation wavelength of 408 nm. It was found that within minutes the oxidation state on the surface of the uraninite and the uranium tetrachloride changed. During the surface alteration process U(IV) atoms on the uraninite and uranium tetrachloride surface became stepwise oxidized by a one-electron step at first to U(V) and then further to U(VI). These observed changes in the oxidation states of the uraninite surface were microscopically visualized and spectroscopically identified on the basis of their fluorescence emission signal. A fluorescence signal in the wavelength range of 415-475 nm was indicative for metastable uranium(V), and a fluorescence signal in the range of 480-560 nm was identified as uranium(VI). In addition, the oxidation process of tetravalent uranium in aqueous solution at pH 0.3 was visualized by CLSM and U(V) was fluorescence spectroscopically identified. The combination of microscopy and fluorescence spectroscopy provided a very convincing visualization of the brief presence of U(V) as a metastable reaction intermediate and of the simultaneous coexistence of the three states U(IV), U(V), and U(VI). These results have a significant importance for fundamental uranium redox chemistry and should contribute to a better understanding of the geochemical behavior of uranium in nature.

Transitions between strongly correlated and random steady-states for catalytic CO-oxidation on surfaces at high-pressure

DOE PAGES

Liu, Da -Jiang; Evans, James W.

2015-04-02

We explore simple lattice-gas reaction models for CO-oxidation on 1D and 2D periodic arrays of surface adsorption sites. The models are motivated by studies of CO-oxidation on RuO 2(110) at high-pressures. Although adspecies interactions are neglected, the effective absence of adspecies diffusion results in kinetically-induced spatial correlations. A transition occurs from a random mainly CO-populated steady-state at high CO-partial pressure p CO, to a strongly-correlated near-O-covered steady-state for low p CO as noted. In addition, we identify a second transition to a random near-O-covered steady-state at very low p CO.