WorldWideScience

Sample records for actinide complexes

  1. Kinetics of actinide complexation reactions

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

  2. Actinide cation-cation complexes

    The +5 oxidation state of U, Np, Pu, and Am is a linear dioxo cation (AnO2+) with a formal charge of +1. These cations form complexes with a variety of other cations, including actinide cations. Other oxidation states of actinides do not form these cation-cation complexes with any cation other than AnO2+; therefore, cation-cation complexes indicate something unique about AnO2+ cations compared to actinide cations in general. The first cation-cation complex, NpO2+·UO22+, was reported by Sullivan, Hindman, and Zielen in 1961. Of the four actinides that form AnO2+ species, the cation-cation complexes of NpO2+ have been studied most extensively while the other actinides have not. The only PuO2+ cation-cation complexes that have been studied are with Fe3+ and Cr3+ and neither one has had its equilibrium constant measured. Actinides have small molar absorptivities and cation-cation complexes have small equilibrium constants; therefore, to overcome these obstacles a sensitive technique is required. Spectroscopic techniques are used most often to study cation-cation complexes. Laser-Induced Photacoustic Spectroscopy equilibrium constants for the complexes NpO2+·UO22+, NpO2+·Th4+, PuO2+·UO22+, and PuO2+·Th4+ at an ionic strength of 6 M using LIPAS are 2.4 ± 0.2, 1.8 ± 0.9, 2.2 ± 1.5, and ∼0.8 M-1

  3. Actinide phosphonate complexes in aqueous solutions

    Complexes formed by actinides with carboxylic acids, polycarboxylic acids, and aminopolycarboxylic acids play a central role in both the basic and process chemistry of the actinides. Recent studies of f-element complexes with phosphonic acid ligands indicate that new ligands incorporating doubly ionizable phosphonate groups (-PO3H2) have many properties which are unique chemically, and promise more efficient separation processes for waste cleanup and environmental restoration. Simple diphosphonate ligands form much stronger complexes than isostructural carboxylates, often exhibiting higher solubility as well. In this manuscript recent studies of the thermodynamics and kinetics of f-element complexation by 1,1 and 1,2 diphosphonic acid ligands are described

  4. Actinide halides and their complexes

    Papers are reviewed published since late 1967 to middle 1970. Problems involving the availability of actinoid halogenides with oxidation degrees from +6 to +2, actinoid oxihalogenides, and also halogenous actinoid complexes with oxidation degrees from +6 to +3, oxihalogenous actinoid complexes with valencies from +6 to -6. The NpF+L5, BKF4, CfF4, BKF3, CfF3 BKBr3, PaF5.2H2O and Pa2OF8 compounds with rhombic pseudocell with the parameters of a0=6.894A, b0=4.014A, c0=4.143A have been obtained for the first time. The process is described of the hew- synthesised ThOF with the face-centered lattice (a0=5.68A), hydrated U(5)-MU2F12 complexes where M=Co, Mi, Cu, and also MUF7 complexes where M=K1Rb, Cs. Csub(s)UFsub(7) is characterized by cubic symmetry with a0=5.54A. The crystal structure of the formally-divalent actinoid compound, ThI2, has been examined. In fact, this compound should be regarded as Th4+(e-)2I2. An interesting method for obtaining UOCl3 through a reaction between UO3 and MoCl5; UOF2.H2O from aqueous solution, and also a simple method for obtaining UCl5 by UO3 reduction with the silicon tetrachloride. The results of investigation of infrared spectra of halogenous and oxihalogenous actinoid complexes (valency from +6 to +4) with donor ligands

  5. Supercritical fluid extraction of actinide element complexes. II. SCF of actinide complexes with β-diketones

    Data on solubility of β-diketones complexes with uranium (VI), plutonium, neptunium, and americium in supercritical carbon dioxide (SC-CO2) are presented. It is established that content of actinide complexes with β-diketones in SC-CO2 can achieve 10-100 g/l. Complexes with dipivaloylmethane, trifluoroacetylacetone and hexafluoroacetylacetone and adducts with tributylphosphate and water in particular are the most highly soluble in it. Residues of complexes after dissolution in SC-CO2 are investigated spectroscopically

  6. Hydrophilic actinide complexation studied by solvent extraction radiotracer technique

    Actinide migration in the ground water is enhanced by the formation of water soluble complexes. It is essential to the risk analysis of a wet repository to know the concentration of central atoms and the ligands in the ground water, and the stability of complexes formed between them. Because the chemical behavior at trace concentrations often differ from that at macro concentrations, it is important to know the chemical behavior of actinides at trace concentrations in ground water. One method used for such investigations is the solvent extraction radiotracer (SXRT) technique. This report describes the SXRT technique in some detail. A particular reason for this analysis is the claim that complex formation constants obtained by SXRT are less reliable than results obtained by other techniques. It is true that several difficulties are encountered in the application of SXRT technique to actinide solution, such as redox instability, hydrophilic complexation by side reactions and sorption, but it is also shown that a careful application of the SXRT technique yields results as reliable as by any other technique. The report contains a literature survey on solvent extraction studies of actinide complexes formed in aqueous solutions, particularly by using the organic reagent thenoyltrifluoroacetone (TTA) dissolved in benzene or chloroform. Hydrolysis constants obtained by solvent extraction are listed as well as all actinide complexes studied by SX with inorganic and organic ligands. 116 refs, 11 tabs

  7. XAFS study on electronic structure analysis of actinide complexes

    Structures and electronic states of actinide complexes in solution were reviewed in relation to chemical separation required from nuclear fuel processing and nuclear waste disposal. Actinide complexes formed from organic compounds were studied in respect of solvent extraction in a wet method for nuclear fuel reprocessing. Particular attention was paid to the experiments by XAFS using synchrotron radiation. A Fourier transformation form of EXAFS oscillation was shown for a U(VI)-amide complex in dodecane solution. The structure radial function of Uranium-DH2EHA (N, N-dihyxyl-2-ethylhexanamice) in solution was determined by EXAFS, and the contributions of two oxygens in an axial direction and of ligand atoms coordinated in an equatorial plane, which combined with a central uranium ion, were indicated in the structure radial function. Structure parameters for U-, Np- and Pu-TBP(Tributyl phosphate) complexes, and for U-amide complexes were listed in Table. A theory predicted a systematic increase of covalency for complexes formed from UO22+∼PO22+ and TEP with an increase of atomic number of actinides, but for U-amide and U∼Pu-TBP complexes the effect of covalency was not reflected in interatomic distances. Some correlations between distribution ratios and different substituents were found in the interatomic distances between uranium and ligand atoms-Distribution ratios of U(VI) depended on interatomic distances between actinide atoms and oxygen ions in carbonyl and in nitric acid. Similarity of chemical bonds in all U-amide complexes except DH2EHA was indicated from XANES spectra of U LIII absorption edge. Three structures for Np(V)-carbon complexes were shown in a ball-and-stick model, and the structure parameters determined by EXAFS were also summarized in Table. Separation of trivalent actinide from the same valent lanthanide was described in connection with soft donors, which have donors such as sulfur and nitrogen atoms. (Kazumata, Y.)

  8. Lanthanide and actinide complexation studies with tetradentate 'N' donor ligands

    Because of their similar charge and chemical behaviour separation of trivalent actinides and lanthanides is an important and challenging task in nuclear fuel cycle. Soft (S,N) donor ligands show selectivity towards the trivalent actinides over the lanthanides. Out of various 'N' donor ligands studied, bis(1,2,4)triazinyl bipyridine (BTBP) and bis(1,2,4)triazinyl phenanthroline (BTPhen) were found to be most promising. In order to understand the separation behaviour of these ligands, their complexation studies with these 'f' block elements are essential. In the present work, complexation studies of various lanthanide ions (La3+, Eu3+ and Er3+) was studied with ethyl derivatives of BTBP (C2BTBP) and BTBPhen (C2BTPhen) and pentyl derivative of BTBP (C5BTBP) in acetonitrile medium using UV-Vis spectrophotometry, fluorescence spectroscopy and solution calorimetry. Computational studies were also carried out to understand the experimental results

  9. Actinides and rare earths complexation with adenosine phosphate nucleotides

    Organophosphorus compounds are important molecules in both nuclear industry and living systems fields. Indeed, several extractants of organophosphorus compounds (such as TBP, HDEHP) are used in the nuclear fuel cycle reprocessing and in the biological field. For instance, the nucleotides are organophosphates which play a very important role in various metabolic processes. Although the literature on the interactions of actinides with inorganic phosphate is abundant, published studies with organophosphate compounds are generally limited to macroscopic and / or physiological approaches. The objective of this thesis is to study the structure of several organophosphorus compounds with actinides to reach a better understanding and develop new specific buildings blocks. The family of the chosen molecules for this procedure consists of three adenine nucleotides mono, bi and triphosphate (AMP, adenosine monophosphate - ADP, adenosine diphosphate - ATP, adenosine triphosphate) and an amino-alkylphosphate (AEP O-phosphoryl-ethanolamine). Complexes synthesis was conducted in aqueous and weakly acidic medium (2.8-4) for several lanthanides (III) (Lu, Yb, Eu) and actinides (U (VI), Th (IV) and Am (III)). Several analytical and spectroscopic techniques have been used to describe the organization of the synthesized complexes: spectrometric analysis performed by FTIR and NMR were used to identify the functional groups involved in the complexation, analysis by ESI-MS and pH-metric titration were used to determine the solution speciation and EXAFS analyzes were performed on Mars beamline of the SOLEIL synchrotron, have described the local cation environment, for both solution and solid compounds. Some theoretical approaches of DFT were conducted to identify stable structures in purpose of completing the experimental studies. All solid complexes (AMP, ADP, ATP and AEP) have polynuclear structures, while soluble ATP complexes are mononuclear. For all synthesized complexes, it has been

  10. Complexation of lanthanides and actinides with humic acids. Appendix II

    Natural waters are the main transport medium for radionuclides in the geosphere in case of an accidental release of radioactivity from a nuclear waste disposal. Complexation studies of radionuclides with natural organic substances present in aquifers are important to perform in order to predict their behaviour in natural systems. Interactions of two trivalent elements, curium and dysprosium, representative respectively for actinides and lanthanides, have been investigated by Time-Resolved Laser-Induced Spectrofluorometry (TRLIS) allowing to work at low concentrations of cations (10-6 M-10-8 M). By using a 'Fluorescence titration' method, complexing capacities and interaction constants are obtained over a broad pH range (4 to 7) at a constant ionic strength (0.1 M). The complexing behaviour of Cm and Dy is analysed. Data are discussed and compared with existing literature data. (orig.)

  11. New insights into formation of trivalent actinides complexes with DTPA

    Complexation of trivalent actinides with DTPA (diethylenetriamine pentaacetic acid) was studied as a function of pcH and temperature in (Na,H)Cl medium of 0.1 M ionic strength. Formation constants of both complexes AnHDTPA- and AnDTPA2- (where An stands for Am, Cm, and Cf) were determined by TRLFS, CE-ICP-MS, spectrophotometry, and solvent extraction. The values of formation constants obtained from the different techniques are coherent and consistent with reinterpreted literature data, showing a higher stability of Cf complexes than Am and Cm complexes. The effect of temperature indicates that formation constants of protonated and non protonated complexes are exothermic with a high positive entropic contribution. DFT calculations were also performed on the An/DTPA system. Geometry optimizations were conducted on AnDTPA2- and AnHDTPA- considering all possible protonation sites. For both complexes, one and two water molecules in the first coordination sphere of curium were also considered. DFT calculations indicate that the lowest energy structures correspond to protonation on oxygen that is not involved in An-DTPA bonds and that the structures with two water molecules are not stable. (authors)

  12. The electronic g matrix of some actinide complexes

    Complete text of publication follows: The molecular g-factors are crucial parameters in Electron Paramagnetic Resonance (EPR) spectroscopy. They parametrize the Zeeman effect that involves the interaction of a spin magnetic moment with a magnetic field. Before the 90's, g-factors were mostly calculated by semi-empirical methods while in the last decade, ab initio techniques have been developed based on wave functions or density functional theories either using a sum over states (SOS) expansion or using response theory [1]. We have recently proposed an alternative method based on wave function theory including spin-orbit effects by the SO-RASSI method [2]. This method has been applied with success to small molecules containing atoms until the third series of the transition metals and to a mixed-valence bimetallic complex[3] and in this work, it is applied to actinide complexes with a 5f1 configuration. To our knowledge, only few attempts have been made to calculate g-factors of actinide complexes from first principles [4, 5]. Relativistic effects in actinide complexes are important, so the deviation of g-factors from the value of the free electron is large and can even become negative. Most of the experiments measuring magnetic properties of actinide complexes date from the sixties. EPR and magnetic susceptibilities give the absolute values of the g-factors while experiment using circularly polarized light provide the sign of the product of the three factors. Magnetic properties of these compounds are easily understood using ligand field theory models. In the first part of this presentation, we will discuss the arbitrary character of the g-matrix and specially of the effect of phase factors and of the choice of the spin quantification axis and we will show that only the G tensor gg* has a physical significance. In the second part, equilibrium distances, excitation energies and g-factors of the AnXq-6 series with An = Pa,U,Np and X = F,Cl,Br are calculated using the

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

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

    1983-07-01

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

  14. Actinide coordination sphere in various U, Np and Pu nitrato coordination complexes

    Waste management of nuclear fuel represents one of the major environmental concerns of the decade. To recycle fissile valuable materials, intimate knowledge of complexation mechanisms involved in the solvent extraction processes is indispensable. Evolution of the actinide coordination sphere of AnO2(NO3)2TBP-type complexes (an = U, Np, Pu; TBP = tributylphosphate) with the actinide valence state have been probed by XAS at the metal LIII edge. Dramatic changes in the actinide coordination sphere appeared when the An(VI) metal is reduced to An(IV). However, no significant evolution in the actinide environment has been noticed across the series UO22+, NpO22+ and PuO22+. (au)

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

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

    2010-02-24

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

  16. Thermally unstable complexants/phosphate mineralization of actinides

    Nash, K. [Argonne National Lab., IL (United States)

    1996-10-01

    In situ immobilization is an approach to isolation of radionuclides from the hydrosphere that is receiving increasing attention. Rather than removing the actinides from contaminated soils, this approach transforms the actinides into intrinsically insoluble mineral phases resistant to leaching by groundwater. The principal advangates of this concept are the low cost and low risk of operator exposure and/or dispersion of the radionuclides to the wider environment. The challenge of this approach is toe accomplish the immobilization without causing collateral damage to the environment (the cure shouldn`t be worse than the disease) and verification of system performance.

  17. Thermally unstable complexants/phosphate mineralization of actinides

    In situ immobilization is an approach to isolation of radionuclides from the hydrosphere that is receiving increasing attention. Rather than removing the actinides from contaminated soils, this approach transforms the actinides into intrinsically insoluble mineral phases resistant to leaching by groundwater. The principal advangates of this concept are the low cost and low risk of operator exposure and/or dispersion of the radionuclides to the wider environment. The challenge of this approach is toe accomplish the immobilization without causing collateral damage to the environment (the cure shouldn't be worse than the disease) and verification of system performance

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

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

    2009-11-01

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

  19. The complex formation of selected actinides (U, Np, Cm) with microbial ligands

    One of the urgent tasks in the field of nuclear technology is the final storage of radioactive substances. As a part of the safety requirements the protection of humans and the environment from the danger of radioactive substances in case of the release from the final storage is essential. For performing long-term safety calculations the detailed understanding of the physico-chemical effects and influences which cause the mobilisation and transport of actinides are necessary. The presented work was a discrete part of a project, which was focused on the clarification of the influence of microorganisms on the migration of actinides in case of the release of actinides from a final storage. The influence of microbial produced substances on the mobilisation of selected actinides was studied thereby. The microbial produced substances studied in this project were synthesized by bacteria from the Pseudomonas genus under special conditions. Fluorescent Pseudomonads secrete bacterial pyoverdin-type siderophores with a high potential to complex and transport metals, especially iron(III). The aim of the project was to determine how and under which conditions the bioligands are able to complex also radioactive substances and therefore to transport them. For this work the alpha-emitting actinides uranium, curium and neptunium were chosen because their long-life cycle and their radiotoxicity are a matter of particular interest. This work dealed with the interaction of the actinides U(VI), Np(V) and Cm(III) with model ligands simulating the functionality of the pyoverdins. So, such bioligands can essentially influence the behaviour of actinides in the environment. The results of this work contribute to a better understanding and assessment of the influence of the microbial ligands to the mobilisation and migration of the radionuclides. The outcomes could be used to quantify the actinide-mobilising effect of the bioligands, which are released, for example, in the vicinity of a

  20. Effects of humic substances on the migration of radionuclides: Complexation of actinides with humic substances. 1. progress report

    The aim of the present research programme is to study the complexation behaviour of actinide ions with humic substances in natural aquifer systems and hence to quantify the effect of humic substances on the actinide migration. Aquatic humic substances commonly found in all groundwaters in different concentrations have a strong tendency towards complexation with actinide ions. This is one of the major geochemical reactions but hitherto least quantified. Therefore, the effect of humic substances on the actinide migration is poorly understood. In the present research programme the complexation of actinide ions with humic substances will be described thermodynamically. This description will be based on a model being as simple as possible to allow an easy introduction of the resulting constants into geochemical modelling of the actinide migration. This programme is a continuation of the activities of the COCO group in the second phase of the CEC-MIRAGE project. (orig.)

  1. Studies on fluoride complexing of hexavalent actinides using a fluoride ion selective electrode

    Complex formation between actinide(VI) and fluoride ions in aqueous solutions was investigated using a fluoride ion selective electrode (F-ISE). As fairly high acidity used to suppress hydrolysis of the actinide(VI) ions, significant liquid junction potentials (Esub(j)) existed in the system. An iterative procedure was developed for computing free hydrogen ion concentration [Hsup(+)] as it colud not be measured directly, using data obtained with F-ISE. Esub(j) values were estimated from known [Hsup(+)] and the stability constants of fluoride complexes of actinide(VI) ions were calculated following King and Gallagher's method using a computer program. The stability constants were found to follow the order U(VI)>Np(VI)>Pu(VI). (author)

  2. Correlation of retention of lanthanide and actinide complexes with stability constants and their speciation

    Datta, A.; Sivaraman, N.; Viswanathan, K.S.; Ghosh, Suddhasattwa; Srinivasan, T.G.; Vasudeva Rao, P.R. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Chemistry Group

    2013-03-01

    The present study describes a correlation that is developed from retention of lanthanide and actinide complexes with the stability constant. In these studies, an ion-pairing reagent, camphor-10-sulphonic acid (CSA) was used as the modifier and organic acids such as {alpha}-hydroxy isobutyric acid ({alpha}-HIBA), mandelic acid, lactic acid and tartaric acid were used as complexing reagent for elution. From these studies, a correlation has been established between capacity factor of a metal ion, concentration of ion-pairing reagent and complexing agent with the stability constant of metal complex. Based on these studies, it has been shown that the stability constant of lanthanide and actinide complexes can be estimated using a single lanthanide calibrant. Validation of the method was carried out with the complexing agents such as {alpha}-HIBA and lactic acid. It was also demonstrated that data from a single chromatogram can be used for estimation of stability constant at various ionic strengths. These studies also demonstrated that the method can be applied for estimation of stability constant of actinides with a ligand whose value is not reported yet, e.g., ligands of importance in the lanthanide-actinide separations, chelation therapy etc. The chromatographic separation method is fast and the estimation of stability constant can be done in a very short time, which is a significant advantage especially in dealing with radioactive elements. The stability constant data was used to derive speciation data of plutonium in different oxidation states as well as that of americium with {alpha}-HIBA. The elution behavior of actinides such as Pu and Am from reversed phase chromatographic technique could be explained based on these studies. (orig.)

  3. Synthesis and Characterization of Templated Ion Exchange Resins for the Selective Complexation of Actinide Ions

    Uy, O. Manual

    2001-03-01

    The purpose of this research is to develop a polymeric extractant for the selective complexation of uranyl ions (and subsequently other actinyl and actinide ions) from aqueous solutions (lakes, streams, waste tanks and even body fluids). Chemical insights into what makes a good complexation site will be used to synthesize reagents tailor-made for the complexation of uranyl and other actinide ions. These insights, derived from studies of molecular recognition include ion coordination number and geometry, ionic size and ionic shape, as well as ion to ligand thermodynamic affinity. Selectivity for a specific actinide ion will be 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 metal ion. These cavity-containing polymers will be produced by using a specific ion (or surrogate) as a template around which monomeric complexing ligands will be polymerized. The complexing ligands will be ones containing functional groups known to form stable complexes with a specific ion and less stable complexes with other cations. Prior investigator's approaches for making templated resins for metal ions have had marginal success. We have extended and amended these methodologies in our work with Pb(II) and uranyl ion, by changing the order of the steps, by the inclusion of sonication, by using higher complex loading, and the selection of functional groups with better complexation constants. This has resulted in significant improvements to selectivity. The unusual shape of the uranyl ion suggests that this approach will result in even greater selectivities than already observed for Pb(II). Preliminary data obtained for uranyl templated polymers shows unprecedented selectivity and has resulted in the first ion selective electrode for uranyl ion.

  4. Actinides(3)/lanthanides(3) separation by nano-filtration assisted by complexation; Separation actinides(3)lanthanides(3) par nanofiltration assistee par complexation

    Sorin, A

    2006-07-01

    In France, one of the research trend concerning the reprocessing of spent nuclear fuel consists to separate selectively the very radio-toxic elements with a long life to be recycled (Pu) or transmuted (Am, Cm, Np). The aim of this thesis concerns the last theme about actinides(III)/lanthanides(III) separation by a process of nano-filtration assisted by complexation. Thus, a pilot of tangential membrane filtration was designed and established in a glove box at the ATALANTE place of CEA-Marcoule. Physico-chemical characterisation of the Desal GH membrane (OSMONICS), selected to carry out actinides(III)/lanthanides(III) separation, was realized to determine the zeta potential of the active layer and its resistance to ionizing radiations. Moreover, a parametric study was also carried out to optimize the selectivity of complexation, and the operating conditions of complex retention (influences of the transmembrane pressure, solute concentration, tangential velocity and temperature). Finally, the separation of traces of Am(III) contained in a mixture of lanthanides(III), simulating the real load coming from a reprocessing cycle, was evaluated with several chelating agents such as poly-amino-carboxylic acids according to the solution acidity and the [Ligand]/[Cation(III)] ratio. (author)

  5. Thermodynamics and Structure of Actinide(IV) Complexes with Nitrilotriacetic Acid

    Nitrilotriacetic acid, commonly known as NITA (N(CH2CO2H)3), can be considered a representative of the polyamino-carboxylic family. The results presented in this paper describe the thermodynamical complexation and structural investigation of An(IV) complexes with NTA in aqueous solution. In the first part, the stability constants of the An(IV) complexes (An = Pu, Np, U, and Th) have been determined by spectrophotometry. In the second part, the coordination spheres of the actinide cation in these complexes have been described using extended X-ray absorption fine structure spectroscopy and compared to the solid-state structure of (Hpy)2[U(NTA)2].H2O. These data are further compared to quantum chemical calculations, and their evolution across the actinide series is discussed. In particular, an interpretation of the role of the nitrogen atom in the coordination mode is proposed. These results are considered to be model behavior of polyamino-carboxylic ligands such as diethylenetriamine pentaacetic acid, which is nowadays the best candidate for a chelating agent in the framework of actinide decorporation for the human body. (authors)

  6. Effect of the structure of amido-poly-nitrogen molecules on the complexation of actinides

    The complexation and solvent extraction of Eu(III) and actinides in different oxidation states (Am(III), Pu(IV), Np(V)) by bi-topic molecules with a dipyridyl-phenanthroline cycle as nitrogen unit and one or two amido functions are described. The complexation has been studied in methanol-water solution with hydrophilic molecules to enhance knowledge about this new family of ligands and to identify the most interesting structural effect. Some extraction tests have been performed with lipophilic molecules of the family to check the possible utility of the new class of ligands under representative fuel reprocessing conditions. These first studies have demonstrated that the presence of a pre-organized N-donors unit like dipyridyl-phenanthroline improves the ligand's affinity for actinides and its An/Ln selectivity. (authors)

  7. NMR study of rare earth and actinide complexes

    Proton magnetic resonance studies of lanthanide shift reagents with olefin-transition metal complexes, monoamines and diamines as substrates are described. Shift reagents for olefins are reported: Lnsup(III)(fod)3 can induce substantial shifts in the nmr spectra of a variety of olefins when silver 1-heptafluororobutyrate is used to complex the olefin. The preparation, properties and efficiency of such systems are described. Configurational aspects and exchange processes of Lnsup(III)(fod)3 complexes with secondary and tertiary monoamines are analysed by means of dynamic nmr. Factors influencing the stability and the stoichiometry of these complexes and various processes such as nitrogen inversion and ligand exchange are discussed. At low temperature, ring inversion can be slow on an nmr time-scale for Lnsup(III)(fod)3-diamino chelates. Barriers to ring inversion in substituted ethylenediamines and propanediamines are obtained. Steric factors appear to play an important role in the stability and kinetics of these bidentate species. The synthesis of uranium-IV crown-ether and cryptate complexes is described. A conformational study of these compounds show evidence of an insertion of the paramagnetic cation as witnessed by the large induced shifts observed. The insertion of uranium in the macrocyclic ligand of a UCl4-dicyclohexyl-18-crown-6 complex is confirmed by an X-ray structural determination

  8. Influence of humic acid size on actinide complexation

    The complexation of Am(III) and Eu(III) with humic acid of different molecular sizes was measured and the data for the ≥300kD and ≥10kD sized HA at pcH 4.0 and 6.0 was analyzed by the Charge Neutralization Model (CNM) and the Polyelectrolyte Model (PM). For the PM, solvent extraction was used to obtain the stability constants of 241Am at tracer concentration. For the CNM, ultrafiltration was used to determine the loading capacity and the stability constants for Eu(III) at macro concentrations. There was a difference of 1-2 orders of magnitude in the stability constants from the two models. The 5D0-7F0 excitation spectra of Eu(III) as a function of loading of HA was found to have a shift in wavenumbers of the peak maximum, indicating that the coordination environment of Eu(III) varied with pH, presumably due to variation in the number of functional groups of the humate bound to the metal ion

  9. Coordination Chemistry of Homoleptic Actinide(IV)-Thiocyanate Complexes.

    Carter, Tyler J; Wilson, Richard E

    2015-10-26

    The synthesis, X-ray crystal structure, vibrational and optical spectroscopy for the eight-coordinate thiocyanate compounds, [Et4 N]4 [Pu(IV) (NCS)8 ], [Et4 N]4 [Th(IV) (NCS)8 ], and [Et4 N]4 [Ce(III) (NCS)7 (H2 O)] are reported. Thiocyanate was found to rapidly reduce plutonium to Pu(III) in acidic solutions (pHthiocyanate complex [Et4 N]4 [Pu(IV) (NCS)8 ] was crystallized when a large excess of [Et4 N][NCS] was present. This compound, along with its U(IV) analogue, maintains inner-sphere thiocyanate coordination in acetonitrile based on the observation of intense ligand-to-metal charge-transfer bands. Spectroscopic and crystallographic data do not support the interaction of the metal orbitals with the ligand π system, but support an enhanced An(IV) -NCS interaction, as the Lewis acidity of the metal ion increases from Th to Pu. PMID:26493880

  10. Temperature and ionic strength influences on actinide(VI)/(V) redox potentials for carbonate limiting complexes

    Actinide behaviour was studied in two limiting aqueous solutions: acidic and carbonate. Cyclic voltametry was validated with well-known U redox system. SIT was used to account for I influence. Taylor's series expansions to the second order were used to account for T influence. Redox potentials of actinide couples had previously been measured in non complexing media. The above data treatments give standard values for redox potential E0, for the corresponding entropy ΔS0, enthalpy ΔH0 and heat capacity ΔCp0 changes, and also for the corresponding excess values (i.e. the variation of these thermodynamic constants with ionic strength). This methodology was here used in carbonate media to measure the potential of the redox couple PuO2(CO3)34-/PuO2(CO3)35- from 5 to 70 degC and from I = 0.5 to 4.5 M in Na2CO3, NaClO4 media. Experimental details and full results are given for Pu. Only final results are given for Np. Previous and/or published data for U and Am are discussed. E and ΔS variations with T or I were enough to be measured. The values obtained for the fitted SIT coefficients Δε, and for ΔS and ΔCp are similar for U, Np and Pu redox reactions. Using this analogy for Am missing data is discussed. β3V/β3VI formation constant ratio of the carbonate limiting complexes were deduced from the potential shift from complexing to non complexing media for the Actinide(VI)/Actinide(V) redox couples. β3V(U and Pu) and β3VI(Np) were finally proposed using published β3VI(U and Pu) and β3V(Np). For Am, this data treatment was used to discuss the AmO22+/ AmO2+ redox potential

  11. Theoretical study of the structure and reactivity of lanthanide and actinide based organometallic complexes

    In this PhD thesis, lanthanide and actinide based organometallic complexes are studied using quantum chemistry methods. In a first part, the catalytic properties of organo-lanthanide compounds are evaluated by studying two types of reactions: the catalytic hydro-functionalization of olefins and the polymerisation of polar monomers. The reaction mechanisms are theoretically determined and validated, and the influence of possible secondary non productive reactions is envisaged. A second part focuses on uranium-based complexes. Firstly, the electronic structure of uranium metallocenes is analysed. An analogy with the uranyl compounds is proposed. In a second chapter, two isoelectronic complexes of uranium IV are studied. After validating the use of DFT methods for describing the electronic structure and the reactivity of these compounds, it is shown that their reactivity difference can be related to a different nature of chemical bonding in these complexes. (author)

  12. Study of the factors supporting the selective complexation of the trivalent lanthanide and actinide ions; Etude des facteurs favorisant la complexation selective des ions lanthanides et actinides trivalents

    Mehdoui, T

    2005-09-15

    In order to obtain clear-cut information on the factors which favour the discrimination between trivalent actinides and lanthanides, we investigated the complexation of the tris(cyclopentadienyl) Ce(III) and U(III) compounds, (RCp)3M (R = tBu, SiMe3), with a series of monocyclic azines with distinct Lewis basicity and reduction potential. Coordination of pyrazine and 4,4' and 2,2'-bipyridines on the (RCp)3M complexes has also been studied. Of major interest is the reversible oxidation of the (RCp)3U species into the uranium(IV) [(RCp)3U]2(pyz) complexes by pyrazine. The presence of cooperativity in the binding of the cyclopentadienyl groups by U(III), due to late appearance of back-bonding, leads to a greater stabilization of the uranium(III) complexes. Complexation of the species Cp*2MI (M = Ce, U) by 2,2'-bipyridine, phenanthroline and ter-pyridine affords the adducts [Cp*2M(L)]I. For L = bipy and terpy, these compounds are reduced into Cp*2M(L). The magnetic data for [Cp*2M(terpy)]I and Cp*2M(terpy) are consistent with Ce(III) and U(III) species, with the formulation Cp*2MIII(terpy). An electron transfer reaction between these species was observed in NMR. Reactions of the [Cp*2M(terpy)]I and Cp*2M(terpy) complexes with H and H{sup +} donor reagents lead to a clear differentiation of these trivalent ions. We studied the coordination of the stable N-heterocyclic carbene and isonitrile molecules on (RCp)3M and Cp*2MI; competition reactions and comparison of the crystal structures of the carbene compounds reveal the much better affinity of the NHC and tBuNC ligands for the 5f rather than for the 4f ion. (authors)

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

    Graves, Christopher R [Los Alamos National Laboratory; Vaughn, Anthony E [Los Alamos National Laboratory; Morris, David E [Los Alamos National Laboratory; Kiplinger, Jaqueline L [Los Alamos National Laboratory

    2008-01-01

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

  14. Actinides(3)/lanthanides(3) separation by nano-filtration assisted by complexation

    In France, one of the research trend concerning the reprocessing of spent nuclear fuel consists to separate selectively the very radio-toxic elements with a long life to be recycled (Pu) or transmuted (Am, Cm, Np). The aim of this thesis concerns the last theme about actinides(III)/lanthanides(III) separation by a process of nano-filtration assisted by complexation. Thus, a pilot of tangential membrane filtration was designed and established in a glove box at the ATALANTE place of CEA-Marcoule. Physico-chemical characterisation of the Desal GH membrane (OSMONICS), selected to carry out actinides(III)/lanthanides(III) separation, was realized to determine the zeta potential of the active layer and its resistance to ionizing radiations. Moreover, a parametric study was also carried out to optimize the selectivity of complexation, and the operating conditions of complex retention (influences of the transmembrane pressure, solute concentration, tangential velocity and temperature). Finally, the separation of traces of Am(III) contained in a mixture of lanthanides(III), simulating the real load coming from a reprocessing cycle, was evaluated with several chelating agents such as poly-amino-carboxylic acids according to the solution acidity and the [Ligand]/[Cation(III)] ratio. (author)

  15. Mass spectrometric studies of the complexing behaviour of actinide ions in solution

    As the long-term radiotoxicity of spent nuclear fuel is governed by Plutonium and the Minor Actinides, these elements are focussed on for investigations in the framework of safety assessment for nuclear waste repositories. To shed more light on the selectivity of the partitioning ligands BTP and BTBP towards the extraction of trivalent actinides, the complexes these ligands form with lanthanides in octanolic solution were characterized. The differences in the extraction efficiencies among the different lanthanides were traced back to the varying preferential formation of Ln(BTP)3 complexes, depending on the ionic radius of the lanthanides. Additionally it was shown that depending on the sterical demand of BTBP ligands nitrate anions coordinate in the first coordination shell of Eu(BTBP)2-complexes. As the behavior of Plutonium under geochemical conditions is of particular interest for the safety assessment of potential nuclear waste repositories, the second part of the thesis focuses on the hydrolysis and colloid formation behavior of aqueous Plutonium solutions. The solution species of Zirconium(IV) as analogue for Plutonium(IV) as well as of Uranium(VI) and Plutonium(VI) were characterized and quantified by means of electrospray ionization mass spectrometry. Moreover the colloid-induced reduction of Pu(V) to Pu(IV) and the subsequent formation of colloidal species was investigated.

  16. Lanthanides and trivalent actinides complexation by tripyridyl triazine, applications to liquid-liquid extraction

    The protonation constants of TPTZ (tripyridyl (2) - 2,4,6 triazine 1,3,5) have been measured: pKa1 = 3.8 and pKa2 = 2.7. (I = 1M, KCl). TPTZ can be autoassociated as (HTPTZ)sub(x)sup(x+) (x=3 or 4). The Am TPTZ3+ formation constant (log β = 4.22) is more stable than the lanthanides ones: log β1 = 2.23/3.16/2.81/3.35/3.11/3.00/2.50/2.43/2.43/2.03./2.00/2.09 and 2.3 respectively for La/Pr/Nd/Sm/Eu/Gd/Tb/Dy/Ho/Er/Tm/Yb and Lu. The selectivity of TPTZ is applied to investigate the groups separation actinides (III)-lanthanides by a liquid-liquid extraction procedure, from nitric acid into several diluents. Acidic extractants dibutylthiophosphoric, di-2 ethylhexyldithiophosphoric, α-bromocapric (H α B Cr10) or dinonylnaphtalensulfonic (HDNNS) acid were used to insure the organic complexes electroneutrality. Am(III) and Cm(III) and lanthanides are extracted into decanol as M(α Br C10)3 and MTPZ (α Br C10)3 this last complex is more stable with actinides (III) than with lanthanides (log Kew = -3,1 and -3,9 respectively). HDNNS-TPTZ mixtures form inverted micelles in t-butylbenzene and can extract the actinides 20 times better than the lanthanides from 0.3 M HNO3. We explained qualitatively and quantitatively the extraction data, by assuming that HDNNS-TPTZ micelles behave like a 3rd phase

  17. Synthesis and evaluation structure/extracting and complexing properties of new bi-topic ligands for group actinides extraction

    The aim of this project is to design and study new extractants for spent nuclear fuel reprocessing. To decrease the long-term radiotoxicity of the waste, the GANEX process is an option to homogeneously recycle actinides. All actinides (U, Np, Pu, Am, Cm) would be extracted together from a highly acidic media and separated from fission products (especially from lanthanides). In this context, fourteen new bi-topic ligands constituted of a nitrogen poly-aromatic unit from the dipyridyl-phenanthroline and dipyridyl-1,3,5-triazine families and functionalized by amid groups were synthesized. Extraction studies performed with some of these ligands confirmed their interest to selectively separate actinides at different oxidation states from an aqueous solution 3M HNO3. To determine the influence of ligands structure on cation complexation, a study in a homogenous media (MeOH/H2O) has been carried out. Electro-spray ionization mass spectrometry have been used to characterize the complexes stoichiometries formed with several cations (Eu3+, Nd3+, Am3+, Pu4+ and NpO2+). Stability constants, evaluated by UV-Visible spectrophotometry, confirm the selectivity of these ligands toward actinides. Lanthanides and actinides complexes have also been characterized in the solid state by infra-red spectroscopy and X-Ray diffraction. Associated to nuclear magnetic resonance experiments and DFT calculations (Density Functional Theory), a better knowledge of their coordination mode was achieved. (author)

  18. Coupling of terminal alkynes and isonitriles by organo-actinide complexes: Scope and mechanistic insights

    The coupling reaction of terminal alkynes with several isonitriles, catalyzed by the neutral organo-actinide complexes Cp*2AnMe2 (Cp* = C5Me5, An = Th, U) or the cationic complex [(Et2N)3U][BPh4], yielded substituted α, β-acetylenic aldimines, in good to excellent yields. The reaction proceeded via a 1,1-insertion of the isonitrile carbon into a metal-acetylide bond, followed by a protonolysis by the acidic proton of the terminal alkyne. Additional insertion products were obtained by altering the catalyst and the reactant ratios. A plausible mechanism for the catalytic reaction is also presented, based on kinetics measurements and thermodynamic studies of the coupling reaction with Cp*2ThMe2 or [(Et2N)3U][BPh4] as catalysts. The reaction is first-order in catalyst and isonitrile and zero-order in alkyne. (authors)

  19. Complexation of the actinides (III, IV and V) with organic acids

    A thorough knowledge of the chemical properties of actinides is now required in a wide variety of fields: extraction processes involved in spent fuel reprocessing, groundwater in the vicinity of radioactive waste packages, environmental and biological media in the case of accidental release of radionuclides. In this context, the present work has been focused on the complexation of Am(III), Cm(III), Cf(III), Pu(IV) and Pa(V) with organic ligands: DTPA, NTA and citric acid. The complexation of pentavalent protactinium with citric and nitrilotriacetic acids was studied using liquid-liquid extraction with the element at tracer scale (CPa ≤ 10-10M). The order and the mean charge of each complex were determined from the analysis of the systematic variations of the distribution coefficient of Pa(V) as function of ligand and proton concentration. Then, the apparent formation constants related of the so-identified complexes were calculated. The complexation of trivalent actinides with DTPA was studied by fluorescence spectroscopy (TRLFS) and capillary electrophoresis (CE-ICP-MS). The coexistence of the mono-protonated and non-protonated complexes (AnHDTPA- and AnDTPA2-) in acidic media (1.5 ≤ pH ≤ 3.5) was shown unambiguously. Literature data have been reinterpreted by taking into account both complexes and a consistent set of formation constants of An(III)-DTPA has been obtained. The experimental study was completed by theoretical calculations (DFT) on Cm-DTPA system. The coordination geometry of Cm in CmDTPA2- and CmHDTPA- including water molecules in the first coordination sphere has been determined as well as interatomic distances. Finally, a study on the complexation of Pu(IV) with DTPA was initiated in order to more closely mimic physiological conditions. A three-step approach was proposed to avoid plutonium hydrolysis: i/ complexation of Pu(IV) with (NTA) in order to protect Pu(IV) from hydrolysis (at low pH) ii/ increase of pH toward neutral conditions and iii

  20. Characterization of partitioning relevant lanthanide and actinide complexes by NMR spectroscopy

    In the present work the interaction of N-donor ligands, such as 2,6-Bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (nPrBTP) and 2,6-Bis(5-(2,2-dimethylpropyl)1H-pyrazol)-3-yl-pyridine (C5-BPP), with trivalent lanthanide and actinide ions was studied. Ligands of this type show a high selectivity for the separation of trivalent actinide ions over lanthanides from nitric acid solutions. However, the reason for this selectivity, which is crucial for future partitioning and transmutation strategies for radioactive wastes, is still unknown. So far, the selectivity of some N-donor ligands is supposed to be an effect of an increased covalency in the actinide-ligand bond, compared to the lanthanide compounds. NMR spectroscopy on paramagnetic metal complexes is an excellent tool for the elucidation of bonding modes. The overall paramagnetic chemical shift consists of two contributions, the Fermi Contact Shift (FCS), due to electron spin delocalisation through covalent bonds, and the Pseudo Contact Shift (PCS), which describes the dipolar coupling of the electron magnetic moment and the nuclear spin. By assessing the FCS share in the paramagnetic shift, the degree of covalency in the metal-ligand bond can be gauged. Several methods to discriminate FCS and PCS have been used on the data of the nPrBTP- and C5-BPP-complexes and were evaluated regarding their applicability on lanthanide and actinide complexes with N-donor ligands. The study comprised the synthesis of all Ln(III) complexes with the exceptions of Pm(III) and Gd(III) as well as the Am(III) complex as a representative of the actinide series with both ligands. All complexes were fully characterised (1H, 13C and 15N spectra) using NMR spectroscopy. By isotope enrichment with the NMR-active 15N in positions 8 and 9 in both ligands, resonance signals of these nitrogen atoms were detected for all complexes. The Bleaneymethod relies on different temperature dependencies for FCS (T-1) and PCS (T-2) that occur upon description

  1. On the synthesis of actinide complexes with neutral organic phosphorus compounds

    The complexes of uranium (6) and (4) nitrates with trialkyl-phosphine oxides (TAPO) have been synthetized, and qeneral methods of their synthesis, separation and purification described. It has been found that, whatever the method of preparation, each compound of the synthesized homologous series of complexes corresponds only to disolvate stoichiometry of a qeneral formula, UO2(NO3)2 x 2(Csub(n)Hsub(2n+1))3PO and U(NO3)4 x 2(Csub(n)Hsub(2n+1))3PO. It is shown that the complexes prepared do not contain water and nitric acid. The absence of water and acid in the complex composition, as well as the possibility of preparing the same compounds by the methods where no nitric acid is used, make it possible to believe that formation of acidocomplexes is unlikely. The described methods pf complex synthesis may be of use for preparative and analytical purposes in separating (quantitatively, in some cases) complexes of actinide, rare-earth, noble, transplutonium, and other elements with phosphates, phosphinates, phosphine oxides, di- and polyoxides, as well as with other organic ligands. The experimental data on the thermal properties of the complexes separated are presented

  2. Complex formation of the lanthanides and actinides in lower oxidation states

    The coordination chemistry of the lanthanides (ln) and actinides (An) in lower oxidation states is discussed, including the hydration-solvation properties of Ln2+ and An2+ in aqueous and aqueous-ethanolic solutions and the formation of complexes with the tetraphenylborate ion and crown ethers. Some physicochemical properties of a number of novel compounds with crown ethers are reported. In this paper the difference in the properties of Ln2+ and An2+ with an fnd0 and fn-1d1 configuration and the ability of the fn-1 d1 compounds to form mixed condensed clusters with Gd2Cl3 are discussed. The properties of Ln and An elements in various oxidation states are compared with those of elements of other groups in the periodic table

  3. Stability constants of the fluoride complexes of actinides in aqueous solution and their correlation with fundamental properties

    Stability constants of the fluoride complexes of the actinides in different oxidation states measured by potentiometric method using fluoride ion selective electrode have been presented. Procedure and precautions required to overcome certain difficulties particular to actinide ions have been discussed. Literature data from various sources have been compiled. In order to have a reasonable comparison the stability constant (β1) values obtained in diverse ionic strength media are converted to thermodynamic stability constant, β10, using Davies equation (a modification of Debye-Huckel equation). A correlation of the β10 values with the fundamental properties of the actinide ions using various models available in the literature has been attempted. A semiempirical relation recently developed by Brown, Sylva and Ellis (BSE equation) appears to be most suitable. Using the values of ionic radii and best available values of the stability constants of a large number of metal ions from recent compilations a comparative study of the various models or relations available in the literature has been tried. For metal ions in general, the best correlation is obtained with the BSE equation. In an attempt to accommodate the unusual trend in the stability constants of the tetravalent actinides a modification in a parameter of the BSE equation has been proposed. Good agreement between the theoretically calculated and experimentally determined values for actinides in different oxidation states is then obtained in most of the cases. (author)

  4. Study of the factors supporting the selective complexation of the trivalent lanthanide and actinide ions

    In order to obtain clear-cut information on the factors which favour the discrimination between trivalent actinides and lanthanides, we investigated the complexation of the tris(cyclopentadienyl) Ce(III) and U(III) compounds, (RCp)3M (R = tBu, SiMe3), with a series of monocyclic azines with distinct Lewis basicity and reduction potential. Coordination of pyrazine and 4,4' and 2,2'-bipyridines on the (RCp)3M complexes has also been studied. Of major interest is the reversible oxidation of the (RCp)3U species into the uranium(IV) [(RCp)3U]2(pyz) complexes by pyrazine. The presence of cooperativity in the binding of the cyclopentadienyl groups by U(III), due to late appearance of back-bonding, leads to a greater stabilization of the uranium(III) complexes. Complexation of the species Cp*2MI (M = Ce, U) by 2,2'-bipyridine, phenanthroline and ter-pyridine affords the adducts [Cp*2M(L)]I. For L = bipy and terpy, these compounds are reduced into Cp*2M(L). The magnetic data for [Cp*2M(terpy)]I and Cp*2M(terpy) are consistent with Ce(III) and U(III) species, with the formulation Cp*2MIII(terpy). An electron transfer reaction between these species was observed in NMR. Reactions of the [Cp*2M(terpy)]I and Cp*2M(terpy) complexes with H and H+ donor reagents lead to a clear differentiation of these trivalent ions. We studied the coordination of the stable N-heterocyclic carbene and isonitrile molecules on (RCp)3M and Cp*2MI; competition reactions and comparison of the crystal structures of the carbene compounds reveal the much better affinity of the NHC and tBuNC ligands for the 5f rather than for the 4f ion. (authors)

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

    This is a continuing DOE-BES funded project on transition metal and actinide containing species, aimed at the electronic structure and spectroscopy of transition metal and actinide containing species. While a long term connection of these species is to catalysis and environmental management of high-level nuclear wastes, the immediate relevance is directly to other DOE-BES funded experimental projects at DOE-National labs and universities. There are a number of ongoing gas-phase spectroscopic studies of these species at various places, and our computational work has been inspired by these experimental studies and we have also inspired other experimental and theoretical studies. Thus our studies have varied from spectroscopy of diatomic transition metal carbides to large complexes containing transition metals, and actinide complexes that are critical to the environment. In addition, we are continuing to make code enhancements and modernization of ALCHEMY II set of codes and its interface with relativistic configuration interaction (RCI). At present these codes can carry out multi-reference computations that included up to 60 million configurations and multiple states from each such CI expansion. ALCHEMY II codes have been modernized and converted to a variety of platforms such as Windows XP, and Linux. We have revamped the symbolic CI code to automate the MRSDCI technique so that the references are automatically chosen with a given cutoff from the CASSCF and thus we are doing accurate MRSDCI computations with 10,000 or larger reference space of configurations. The RCI code can also handle a large number of reference configurations, which include up to 10,000 reference configurations. Another major progress is in routinely including larger basis sets up to 5g functions in thee computations. Of course higher angular momenta functions can also be handled using Gaussian and other codes with other methods such as DFT, MP2, CCSD(T), etc. We have also calibrated our RECP

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

    Krishnan Balasubramanian

    2009-07-18

    This is a continuing DOE-BES funded project on transition metal and actinide containing species, aimed at the electronic structure and spectroscopy of transition metal and actinide containing species. While a long term connection of these species is to catalysis and environmental management of high-level nuclear wastes, the immediate relevance is directly to other DOE-BES funded experimental projects at DOE-National labs and universities. There are a number of ongoing gas-phase spectroscopic studies of these species at various places, and our computational work has been inspired by these experimental studies and we have also inspired other experimental and theoretical studies. Thus our studies have varied from spectroscopy of diatomic transition metal carbides to large complexes containing transition metals, and actinide complexes that are critical to the environment. In addition, we are continuing to make code enhancements and modernization of ALCHEMY II set of codes and its interface with relativistic configuration interaction (RCI). At present these codes can carry out multi-reference computations that included up to 60 million configurations and multiple states from each such CI expansion. ALCHEMY II codes have been modernized and converted to a variety of platforms such as Windows XP, and Linux. We have revamped the symbolic CI code to automate the MRSDCI technique so that the references are automatically chosen with a given cutoff from the CASSCF and thus we are doing accurate MRSDCI computations with 10,000 or larger reference space of configurations. The RCI code can also handle a large number of reference configurations, which include up to 10,000 reference configurations. Another major progress is in routinely including larger basis sets up to 5g functions in thee computations. Of course higher angular momenta functions can also be handled using Gaussian and other codes with other methods such as DFT, MP2, CCSD(T), etc. We have also calibrated our RECP

  7. Investigation of the complexation and the migration of actinides and non-radioactive substances with humic acids under geogenic conditions. Complexation of humic acids with actinides in the ocidation state IV Th, U, Np

    Sachs, S.; Schmeide, K.; Brendler, V.; Krepelova, A.; Mibus, J.; Geipel, G.; Heise, K.H.; Bernhard, G.

    2004-03-01

    Objective of this project was the study of basic interaction and migration processes of actinides in the environment in presence of humic acids (HA). To obtain more basic knowledge on these interaction processes synthetic HA with specific functional properties as well as {sup 14}C-labeled HA were synthesized and applied in comparison to the natural HA Aldrich. One focus of the work was on the synthesis of HA with distinct redox functionalities. The obtained synthetic products that are characterized by significantly higher Fe(III) redox capacities than Aldrich HA were applied to study the redox properties of HA and the redox stability of U(VI) humate complexes. It was confirmed that phenolic OH groups play an important role for the redox properties of HA. However, the results indicate that there are also other processes than the single oxidation of phenolic OH groups and/or other functional groups contributing to the redox behavior of HA. A first direct-spectroscopic proof for the reduction of U(VI) by synthetic HA with distinct redox functionality was obtained. The complexation behavior of synthetic and natural HA with actinides (Th, Np, Pu) was studied. Structural parameters of Pu(III), Th(IV), Np(IV) and Np(V) humates were determined by X-ray absorption spectroscopy (XAS). The results show that carboxylate groups dominate the interaction between HA and actinide ions. These are predominant monodentately bound. The influence of phenolic OH groups on the Np(V) complexation by HA was studied with modified HA (blocked phenolic OH groups). The blocking of phenolic OH groups induces a decrease of the number of maximal available complexing sites of HA, whereas complex stability constant and Np(V) near-neighbor surrounding are not affected. The effects of HA on the sorption and migration behavior of actinides was studied in batch and column experiments. Th(IV) sorption onto quartz and Np(V) sorption onto granite and its mineral constituents are affected by the pH value

  8. Investigation of the complexation and the migration of actinides and non-radioactive substances with humic acids under geogenic conditions. Complexation of humic acids with actinides in the oxidation state IV Th, U, Np

    Objective of this project was the study of basic interaction and migration processes of actinides in the environment in presence of humic acids (HA). To obtain more basic knowledge on these interaction processes synthetic HA with specific functional properties as well as 14C-labeled HA were synthesized and applied in comparison to the natural HA Aldrich. One focus of the work was on the synthesis of HA with distinct redox functionalities. The obtained synthetic products that are characterized by significantly higher Fe(III) redox capacities than Aldrich HA were applied to study the redox properties of HA and the redox stability of U(VI) humate complexes. It was confirmed that phenolic OH groups play an important role for the redox properties of HA. However, the results indicate that there are also other processes than the single oxidation of phenolic OH groups and/or other functional groups contributing to the redox behavior of HA. A first direct-spectroscopic proof for the reduction of U(VI) by synthetic HA with distinct redox functionality was obtained. The complexation behavior of synthetic and natural HA with actinides (Th, Np, Pu) was studied. Structural parameters of Pu(III), Th(IV), Np(IV) and Np(V) humates were determined by X-ray absorption spectroscopy (XAS). The results show that carboxylate groups dominate the interaction between HA and actinide ions. These are predominant monodentately bound. The influence of phenolic OH groups on the Np(V) complexation by HA was studied with modified HA (blocked phenolic OH groups). The blocking of phenolic OH groups induces a decrease of the number of maximal available complexing sites of HA, whereas complex stability constant and Np(V) near-neighbor surrounding are not affected. The effects of HA on the sorption and migration behavior of actinides was studied in batch and column experiments. Th(IV) sorption onto quartz and Np(V) sorption onto granite and its mineral constituents are affected by the pH value and the

  9. Design, synthesis, and evaluation of polyhydroxamate chelators for selective complexation of actinides

    Specific chelating polymers targeted for actinides have much relevance to problems involving remediation of nuclear waste. Goal is to develop polymer supported, ion specific extraction systems for removing actinides and other hazardous metal ions from wastewaters. This is part of an effort to develop chelators for removing actinide ions such as Pu from soils and waste streams. Selected ligands are being attached to polymeric backbones to create novel chelating polymers. These polymers and other water soluble and insoluble polymers have been synthesized and are being evaluated for ability to selectively remove target metal ions from process waste streams

  10. Complexation studies of actinides (U, Pu, Am) with linear polyamino-carboxylate ligands and sidero-chelates

    As part of our research endeavour aimed at developing and improving decontamination processes of wastewater containing alpha emitters, physico-chemical complexation studies of actinides (U, Pu, Am) with organic open-chain ligands such as poly-aminocarboxylic acids (H4EDTA) and sidero-chelates (di-hydroxamic acids and desferrioxamine B) have been carried out. Gaining a clear understanding of the coordination properties of the targeted actinides is an essential step towards the selection of the most appropriate chelating agents that will exhibit high uptake efficiencies. EXAFS (Extended X-ray Absorption Fine Structure) measurements at the ESRF synchrotron enabled to elucidate the coordination scheme of uranium and plutonium complexes. Solution thermodynamic investigations were intended to provide valuable information about the nature and the stability of the uranium(VI) and americium(III) complexes prevailing at a given pH in solution. The set of stability constants determined from potentiometric and UV-visible spectrophotometric titrations, allowed to predict the speciation of the selected actinides in presence of the aforementioned ligands and to determine the pH range required for achieving 'ultimate' decontamination. (author)

  11. Rare-earth metal π-complexes of reduced arenes, alkenes, and alkynes: Bonding, electronic structure, and comparison with actinides and other electropositive metals

    Huang, W.; Diaconescu, PL

    2015-01-01

    © 2015 The Royal Society of Chemistry. Rare-earth metal complexes of reduced π ligands are reviewed with an emphasis on their electronic structure and bonding interactions. This perspective discusses reduced carbocyclic and acyclic π ligands; in certain categories, when no example of a rare-earth metal complex is available, a closely related actinide analogue is discussed. In general, rare-earth metals have a lower tendency to form covalent interactions with π ligands compared to actinides, m...

  12. Actinide environmental chemistry

    In order to predict release and transport rates, as well as design cleanup and containment methods, it is essential to understand the chemical reactions and forms of the actinides under aqueous environmental conditions. Four important processes that can occur with the actinide cations are: precipitation, complexation, sorption and colloid formation. Precipitation of a solid phase will limit the amount of actinide in solution near the solid phase and have a retarding effect on release and transport rates. Complexation increases the amount of actinide in solution and tends to increase release and migration rates. Actinides can sorb on to mineral or rock surfaces which tends to retard migration. Actinide ions can form or become associated with colloidal sized particles which can, depending on the nature of the colloid and the solution conditions, enhance or retard migration of the actinide. The degree to which these four processes progress is strongly dependent on the oxidation state of the actinide and tends to be similar for actinides in the same oxidation state. In order to obtain information on the speciation of actinides in solution, i.e., oxidation state, complexation form, dissolved or colloidal forms, the use of absorption spectroscopy has become a method of choice. The advent of the ultrasensitive, laser induced photothermal and fluorescence spectroscopies has made possible the detection and study of actinide ions at the parts per billion level. With the availability of third generation synchrotrons and the development of new fluorescence detectors, X-ray absorption spectroscopy (XAS) is becoming a powerful technique to study the speciation of actinides in the environment, particularly for reactions at the solid/solution interfaces. (orig.)

  13. Research in actinide chemistry

    1991-01-01

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

  14. Thermodynamic study on the complexation of Trivalent actinide and lanthanide cation by N-donor ligands in homogeneous conditions; Etude thermodynamique de la complexation des ions actinide (III) et lanthanide (III) par des ligands polyazotes en milieu homogene

    Miguirditchian, M

    2004-07-01

    Polydentate N-donor ligands, alone or combined with a synergic acid, may selectively extract minor actinides(III) from lanthanide(III) ions, allowing to develop separation processes of long-live radioelements. The aim of the researches carried out during this thesis was to better understand the chemical mechanisms of the complexation of f-elements by Adptz, a tridentate N-donor ligand, in homogeneous conditions. A thermodynamic approach was retained in order to estimate, from an energetic point of view, the influence of the different contributions to the reaction, and to acquire a complete set of thermodynamic data on this reaction. First, the influence of the nature of the cation on the thermodynamics was considered. The stability constants of the 1/1 complexes were systematically determined by UV-visible spectrophotometry for every lanthanide ion (except promethium) and for yttrium in a mixed solvent methanol/water in volume proportions 75/25%. The thermodynamic parameters ({delta}H{sup 0} {delta}{sup S}) of complexation were estimated by the van't Hoff method and by micro-calorimetry. The trends of the variations across the lanthanide series are compared with similar studies. The same methods were applied to the study of three actinide(III) cations: plutonium, americium and curium. The comparison of these values with those obtained for the lanthanides highlights the increase of stability of these complexes by a factor of 20 in favor of the actinide cations. This gap is explained by a more exothermic reaction and is associated, in the data interpretation, to a higher covalency of the actinide(III)-nitrogen bond. Then, the influence of the change of solvent composition on the thermodynamic of complexation was studied. The thermodynamic parameters of the complexation of europium(III) by Adptz were determined for several fractions of methanol. The stability of the complex formed increases with the percentage of methanol in the mixed solvent, owing to an

  15. Effects of humic substances on the migration of radionuclides: Complexation of actinides with humic substances. Appendix V

    The complexation of Eu(III) with humic substances was studied by using Time Resolved Laser Induced Fluorescence. Most of the work concentrated on the investigation of competition effects. Actinides in aquatic environments coexist with major and minor components of natural waters, usually present at much higher concentration levels. The competition effect was found to be larger for ions of identical oxidation state, suggesting therefore binding to the same sorption sites. Spectroscopic measurements were made in the system Eu/HA/Cr by looking at the decrease of the fluorescence signal of the pre-formed EuHA complex with increasing concentrations of the non-fluorescent Cr(III) ions. (orig.)

  16. A quantum chemistry study of actinide(III) and lanthanide(III) complexes with tridentate nitrogen ligands

    The structure and bonding in large complexes of actinide(III) and lanthanide(III) with tridentate N-donor ligands and water molecules have been investigated through quantum chemistry calculations in order to characterize the nature of the lanthanide-ligand and actinide-ligand bonds. Calculations have been performed using relativistic density functional theory on [M(L)(H2O)6]3+, [M(L)(H2O)5Cl]2+ and [M(H2O)9]3+ clusters where M = La, Ce, Nd, U, Pu, Am or Cm and L = 2,2':6'2''ter-pyridine (Terpy) or 2,6-bis(5,6-di-methyl-1,2,4-triazine-3-yl)pyridine (MeBtp). The calculated evolution of the M-L bond as a function of the cation shows that lanthanide-ligand distances decrease with the diminution of the ionic radius, whereas the actinide-ligand distances increase from uranium to americium and are shorter than Ln-N distances. These trends are explained by the presence of covalent effects in the metal-ligand decreasing in the order U > Pu > Am ≅ Cm ≅ Ln. (author)

  17. Research in actinide chemistry

    This research studies the behavior of the actinide elements in aqueous solution. The high radioactivity of the transuranium actinides limits the concentrations which can be studied and, consequently, limits the experimental techniques. However, oxidation state analogs (trivalent lanthanides, tetravalent thorium, and hexavalent uranium) do not suffer from these limitations. Behavior of actinides in the environment are a major USDOE concern, whether in connection with long-term releases from a repository, releases from stored defense wastes or accidental releases in reprocessing, etc. Principal goal of our research was expand the thermodynamic data base on complexation of actinides by natural ligands (e.g., OH-, CO32-, PO43-, humates). The research undertakes fundamental studies of actinide complexes which can increase understanding of the environmental behavior of these elements

  18. Complexation parameters for the actinides(IV)-humic acid system: a search for consistency and application to laboratory and field observations

    The coherence of actinide(IV) complexation by humic substances (HS) is reviewed and new data are proposed. In a first attempt, the values of independent data from literature on Th(IV), U(IV), and Pu(IV) are collected, selected, and compiled. The data obtained follow the ''classical'' trend of increasing conditional formation ''constants'' with pH, led both by the increasing ionisation of HS and by the extensive hydrolysis of the tetravalent actinides. Even though a fair agreement is evident, the experimental uncertainties do not permit a full analogy between the actinides(IV) to be ascertained. In a second attempt, the experiments from which the original data are available were reinterpreted using only one hydrolysis constant set for U(IV) as an example, considering that all actinides(IV) have analogous humic complexation behaviour. Hence, the obtained evolution of conditional formation ''constants'' is much more coherent and the uncertainties do not permit to distinguish an actinide(IV) from one another. The obtained data are then applied to independent laboratory and in situ experiments in order to delimit the domain of possible applicability. This exercise demonstrates the treatment of data through analogy in the case of actinides(IV) and would permit to limit and orientate the number of necessary, but difficult, experiment with redox sensitive elements like U, Np, or Pu. It also demonstrates that complexation-only mechanisms may not be sufficient to understand field observations. (orig.)

  19. Theoretical study of the structure and reactivity of lanthanide and actinide based organometallic complexes; Etude theorique de la structure et de la reactivite de complexes organometalliques de lanthanides et d'actinides

    Barros, N

    2007-06-15

    In this PhD thesis, lanthanide and actinide based organometallic complexes are studied using quantum chemistry methods. In a first part, the catalytic properties of organo-lanthanide compounds are evaluated by studying two types of reactions: the catalytic hydro-functionalization of olefins and the polymerisation of polar monomers. The reaction mechanisms are theoretically determined and validated, and the influence of possible secondary non productive reactions is envisaged. A second part focuses on uranium-based complexes. Firstly, the electronic structure of uranium metallocenes is analysed. An analogy with the uranyl compounds is proposed. In a second chapter, two isoelectronic complexes of uranium IV are studied. After validating the use of DFT methods for describing the electronic structure and the reactivity of these compounds, it is shown that their reactivity difference can be related to a different nature of chemical bonding in these complexes. (author)

  20. A novel CMPO-functionalized task specific ionic liquid: synthesis, extraction and spectroscopic investigations of actinide and lanthanide complexes.

    Mohapatra, Prasanta K; Kandwal, Pankaj; Iqbal, Mudassir; Huskens, Jurriaan; Murali, Mallekav S; Verboom, Willem

    2013-04-01

    A novel CMPO (carbamoylmethylphosphine oxide) based task specific ionic liquid (TSIL) with an NTf(2)(-) counter anion was synthesized and evaluated for actinide/lanthanide extraction from acidic feed solutions using several room temperature ionic liquids (RTILs). The extraction data were compared with those obtained with CMPO in the same set of RTILs and also in the molecular diluent, n-dodecane. The extracted species were analyzed by the conventional slope analysis method and the extraction followed an ion-exchange mechanism. The nature of bonding in the extracted complexes was investigated by various spectroscopic techniques such as FT-IR and UV-visible spectroscopy. PMID:23403959

  1. [U(III) {N(SiMe2 tBu)2 }3 ]: a structurally authenticated trigonal planar actinide complex.

    Goodwin, Conrad A P; Tuna, Floriana; McInnes, Eric J L; Liddle, Stephen T; McMaster, Jonathan; Vitorica-Yrezabal, Inigo J; Mills, David P

    2014-11-01

    We report the synthesis and characterization of the uranium(III) triamide complex [U(III) (N**)3 ] [1, N**=N(SiMe2 tBu)2 (-) ]. Surprisingly, complex 1 exhibits a trigonal planar geometry in the solid state, which is unprecedented for three-coordinate actinide complexes that have exclusively adopted trigonal pyramidal geometries to date. The characterization data for [U(III) (N**)3 ] were compared with the prototypical trigonal pyramidal uranium(III) triamide complex [U(III) (N")3 ] (N"=N(SiMe3 )2 (-) ), and taken together with theoretical calculations it was concluded that pyramidalization results in net stabilization for [U(III) (N")3 ], but this can be overcome with very sterically demanding ligands, such as N**. The planarity of 1 leads to favorable magnetic dynamics, which may be considered in the future design of U(III) single-molecule magnets. PMID:25241882

  2. Effects of humic substances on the migration of radionuclides: complexation of actinides with humic substances. A commission of the European Communities program

    The aim of the research program is to study the complexation behavior of actinide ions with humic substances in natural aquifer systems and hence to quantify the effect of humic substances on the actinide migration. In the present research program the complexation of actinide ions with humic substances will be described thermodynamically. This description will be based on a simple model which will allow an easy introduction of the resulting reaction constants into geochemical modeling of actinide migration. To achieve the desired goal, the program is divided into three task; complexation reactions of actinide ions with well characterized reference and site-specific humic and fulvic acids, competition reactions with major cations in natural groundwaters, and validation of the complexation data in natural aquatic systems by comparison of calculation with spectroscopic experiment. This program is a continuation of the activities of the colloid and complexation (COCO) group in the second phase of the CEC-MIRAGE project. (authors). 39 refs., 5 figs., 4 tabs

  3. Apparent formation constants of actinide complexes with humic substances determined by solvent extraction

    Apparent formation constants of Pu(IV) with two kinds of humic substances (HSs) were determined in 0.1M NaClO4 at 25°C using a back-solvent extraction method. The effect of solution conditions, such as the pH, the initial metal and HS concentrations, and the ionic strength, on the formation constants was investigated. The obtained data were compared with the other actinide series. (author)

  4. Synthesis and Structural Examination of Complexes of Am(IV) and Other Tetravalent Actinides with Lacunary Heteropolyanion α2-P2W17O6110-

    This study concerns the formation of complexes with actinides at oxidation state +IV, from Th to Am, through a lacunary heteropolyanion ligand P2W17O6110-. The preparation of original single crystals of complexes with 1:2 stoichiometry provided structural data through single-crystal X-ray diffraction for the entire An(IV) series, An(IV) atoms in these complexes have a coordination number of 8, and their coordination polyhedron is a distorted square anti-prism. The data were used to compute a mean (An-O) interatomic distance for each actinide. When the interatomic distance is plotted versus the inverse ionic radius of these tetravalent actinides, it appears that the simple electrostatic model is not suitable for Am(IV) and Pu(IV), although this trend must be confirmed by further investigation with other examples from the An(IV) series. (authors)

  5. Thermodynamics and speciation: Carbonate complexation of Am(III) and speciation of actinides by pulsed laser spectroscopies

    The report includes the carbonate complexation of Am(III) and speciation of actinides by pulsed laser spectroscopies. Part A describes the carbonate complexation behaviour of Am3+ in aqueous solution under 1% CO2 partial pressure, investigated by solubility and spectroscopic experiments. The average constants determined by the two methods are: log Ksp (Am2(CO3)3)=-29.7 ± 0.6, log β1=6.3 ± 0.3 and log β2 = 9.7 ± 0.6. Part B presents speciation capabilities of three different pulsed laser spectroscopies: laser-induced photoacoustic spectroscopy (LPAS), time-resolved laser-induced fluorescence spectroscopy (TRLFS) and photoacoustic detection of light scattering (PALS). Examples for the speciation of Am(III) and Cm(III) in different aquatic media are presented. (orig.)

  6. Study of strontium extraction as cryptate complex in view to 102 element separation from the actinides

    In the present report is studied in detail the extraction of strontium, in tracer amounts, as cryptate and its separation from the lanthanides and transplutonium elements with a high degree of purification. Influence of different parameters: pH of the aqueous phase, cryptant concentration, counteranion concentration, nature of the solvent are investigated. It is intended to use this method to separate the 102 element from actinides in the study of the isotope 102 259 produced in irradiation of a curium 248 target by oxygen 18 ions

  7. Actinide-to-carbon bonds in Cp2An(alkyl)2, -(butadiene), -(metallacyclopentadiene), and -(cyclobutadiene) complexes

    The electronic structure of actinide bis(cyclopentadienyl)dialkyl, -butadiene, -metallacyclopentadiene, and -cyclobutadiene complexes is examined. Some Cp*2Th(alkyl)2 complexes display an interesting structural deformation in which a Th-C-C(alkyl) angle (α) opens up considerably. A molecular orbital analysis of Cp2Th(C2H5)2 traces the deformation to the characteristic shape of the d/sub σ/ fragment orbital of Cp2Th(C2H5)+. The potential energy curve for the ethyl pivoting was found to be very soft, with a shallow minimum at α ∼ 1600. Nonrigidity of the ethyl orientation indicates that not only an α hydrogen but also a β hydrogen can come close to Th without a loss of Th-C bond strength; the discussion should provide a theoretical basis for understanding important aspects of C-H activation chemistry involving actinide centers. The Cp2An(s-cis-C4H6) complex was calculated to be 0.74 eV (Th) or 0.42 eV (U) more stable than its s-trans-C4H6 isomer, in contrast to the analogous Cp2Zr(C4H6) complex where the stability of the two geometrical isomers was well-balanced. The σ2,π character of the s-cis-C4H6 coordination to An is somewhat less pronounced than that in the Zr congener, in harmony with the X-ray structures, while highly negative charges are accumulated on the s-cis-C4H6 terminal carbons

  8. Trivalent lanthanide and actinide extraction by functionalized calixarenes study of the structure of complexes in solution by nuclear magnetic resonance

    The behaviour of different lanthanides and actinides with respect to their complexation by various ligands (in particular functionalized calixarenes) carrying acetamide-phosphine oxide groups (CMPO calixarenes) has been studied. These calixarenes allow the selective extraction of light lanthanides. A size effect of the cations has been evidenced. The substituents present on the lower and upper edges of the calixarene influence the extraction and its selectiveness. Studies of experimental conditions improvement have been carried out. It is shown that the de-extraction of trivalent cations extracted by CMPO calixarenes is possible using a very low concentration nitric acid solution. This requires the use of a chlorinated or alcoholic diluent. Transport experiments using this re-extraction phase slightly acidified have shown identical separation properties to those detected in liquid-liquid extraction. Nuclear magnetic resonance (NMR) is a spectroscopic method used to identify some structural parameters in solution. The NMR nuclei relaxation theory allows to link different physical data to the relaxation time of the nuclei of a molecule. The influence of the presence of paramagnetic lanthanide and actinide cations on different nuclei of the CMPO calixarene molecule has been studied. The determination of their respective relaxation time can lead to the average distances between the cation and these nuclei. This work has led to the determination of the correlation times and to a first evaluation of the average position of the cations. (J.S.)

  9. Computational Tools for Predictive Modeling of Properties in Complex Actinide Systems

    Autschbach, Jochen; Govind, Niranjan; Atta Fynn, Raymond; Bylaska, Eric J.; Weare, John H.; de Jong, Wibe A.

    2015-03-30

    In this chapter we focus on methodological and computational aspects that are key to accurately modeling the spectroscopic and thermodynamic properties of molecular systems containing actinides within the density functional theory (DFT) framework. Our focus is on properties that require either an accurate relativistic all-electron description or an accurate description of the dynamical behavior of actinide species in an environment at finite temperature, or both. The implementation of the methods and the calculations discussed in this chapter were done with the NWChem software suite (Valiev et al. 2010). In the first two sections we discuss two methods that account for relativistic effects, the ZORA and the X2C Hamiltonian. Section 1.2.1 discusses the implementation of the approximate relativistic ZORA Hamiltonian and its extension to magnetic properties. Section 1.3 focuses on the exact X2C Hamiltonian and the application of this methodology to obtain accurate molecular properties. In Section 1.4 we examine the role of a dynamical environment at finite temperature as well as the presence of other ions on the thermodynamics of hydrolysis and exchange reaction mechanisms. Finally, Section 1.5 discusses the modeling of XAS (EXAFS, XANES) properties in realistic environments accounting for both the dynamics of the system and (for XANES) the relativistic effects.

  10. Actinide oxalate complexes formation as a function of temperature by capillary electrophoresis coupled with inductively coupled plasma mass spectrometry

    Brunel, Benoit; Mendes, Mickael; Aupiais, Jean [CEA, DAM, DIF, Arpajon (France); Philippini, Violaine [Nice Univ. Sophia Antipolis (France). Inst. de Chimie de Nice

    2015-05-01

    Complexation of various actinides (U(VI), Np(V), Pu(V), Am(III)) by oxalato ligand was studied by capillary electrophoresis (ICPMS detection) in 0.1 mol L{sup -1} NaClO{sub 4} ionic strength solutions at various temperatures (15, 25, 35, 45 and 55 C). For each solution a unique peak was observed as a result of a fast equilibrium between the free ions and the complexes (labile systems). The results confirmed the formation of the 1:1, 1:2 and 1:3 complexes for U(VI) and Am(III); the formation of the 1:1 and 1:2 complexes for Np(V) and the formation of only 1 complex for Pu(V). For each complex, the thermodynamic parameters (the Gibbs energy Δ{sub r}G(T), the molar entropy change Δ{sub r}S(T) and the molar enthalpy change Δ{sub r}H(T{sup 0})) were fitted to the experimental data. The effect of the ionic medium was treated using the specific ion interaction theory and the thermodynamic parameters at zero ionic strength were compared to previously published data.

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

    Ward, Ashleigh; Lukens, Wayne; Lu, Connie; Arnold, John

    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 of 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.

  12. Polymeric Structure of Oxalato-Bridged Complexes of Tetravalent Actinides Th, U, Np and Pu

    A series of isostructural oxalates of Th, U, Np, and Pu have been synthesized. The crystal structure of {C(NH2)3}4[An(C2O4)4].2H2O comprises infinite [An(C2O4)4]4n- chains, guanidinium cations and water molecules. Each An atom is connected to five oxalate anions, two of which act as bridging tetradentate ligands, while the other three function as terminating bidentate ligands. Electron and IR spectra of the compounds as well as the results of thermal analysis correlate with their structure. An actinide contraction effect is demonstrated by a decrease in the An-O interatomic distances and the volumes of An atom coordination polyhedra and Voronoi-Dirichlet polyhedra. Ten-coordinate An oxalates are discussed in terms of continuous shape measures approach. (authors)

  13. A specific alpha laboratory dedicated to structural and thermodynamic studies on actinide complexes

    The main scope of the LN1 laboratory in ATALANTE facility is the chemical and physico-chemical study of transuranic samples to understand the behavior of compounds of actinide with selective ligands at a molecular scale. The main techniques implemented in this laboratory are the following ones: Nuclear Magnetic Resonance spectrometer (400 MHz shielded magnetic field), a four circle X-ray diffractometer for single crystals, a microcalorimeter to the measurement of low heats of reactions, a Time Resolved Laser-induced spectro-fluorimeter, vibrational spectrometers: FTIR and Raman, an Electro-spray Ionisation Mass spectrometer. Specific glove boxes have been built for each technique to work on radio elements with safety conditions and allow the analysis of samples in different states (aqueous and organic liquids, gels, solids). (authors)

  14. Complexation of Nd(III) with tetraborate ion and its effect on actinide(III) solubility in WIPP brine

    The potential importance of tetraborate complexation on lanthanide(III) and actinide(III) solubility is recognized in the literature but a systematic study of f-element complexation has not been performed. In neodymium solubility studies in WIPP brines, the carbonate complexation effect is not observed since tetraborate ions form a moderately strong complex with neodymium(III). The existence of these tetraborate complexes was established for low and high ionic strength solutions. Changes in neodymium(III) concentrations in undersaturation experiments were used to determine the neodymium with tetraborate stability constants as a function of NaCl ionic strength. As very low Nd(III) concentrations have to be measured, it was necessary to use an extraction pre-concentration step combined with ICP-MS analysis to extend the detection limit by a factor of 50. The determined Nd(III) with borate stability constants at infinite dilution and 25 C are equal to log β1 = 4.55 ± 0.06 using the SIT approach, equal to log β1 = 4.99 ± 0.30 using the Pitzer approach, with an apparent log β1 = 4.06 ± 0.15 (in molal units) at I = 5.6 m NaCl. Pitzer ion-interaction parameters for neodymium with tetraborate and SIT interaction coefficients were also determined and reported. (orig.)

  15. Critical analysis of the data on complexation of lanthanides and actinides by natural organic matter: particular case of humic substances; Analyse critique des donnees de complexation des lanthanides et actinides par la matiere organique naturelle: cas des substances humiques

    Reiller, P.

    2010-07-01

    This document proposes a critical analysis of the models that describe the actinides and lanthanides complexation by natural organic matter in general and by humic substances in particular. In order to better delimit the particular properties of these substances the most influent physical and chemical properties on complexation are recalled as a preamble. Models as well as data that has been used are reviewed, compiled, and eventually compared to independent data in order to identify (i) their application domain, (ii) the possible simplifications which permit to obtain operational models, (iii) the conditions in which simplifications cannot be ascertained yet, and (iv) the data or fields of knowledge which are still too uncertain. A comparison between the different models is proposed in order to adapt parameters from one model to another minimising the experimental acquisitions, or at least to focus on missing data. Usually, data on the complexation of free ions M{sup z+} are reliable; as soon as hydrolysis, or competition with another ligand in general, in at stake data are much less reliable. Predictions from models are much more uncertain: formation of mixed complexes with hydroxide or carbonate anions is not univocal whatever the modelling strategy. Hints for transfer functions between models which are believed to be incompatible could be explored in order to justify necessary simplifications for using operational modelling. Influence on the solubility of oxides could be quantified, but it is difficult to clearly separate it from colloidal particles stabilisation. The account of the competition between cations by the models has also been tested. In view of the small number of available experimental data there still lie some uncertainties especially for the media that are close to neutrality and in the case of competition with magnesium, but overall in the case of the competition with aluminium and iron. The influence of redox activity of humic substances is

  16. Actinides-1981

    1981-09-01

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

  17. Actinides-1981

    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

  18. Critical analysis of the data on complexation of lanthanides and actinides by natural organic matter: particular case of humic substances

    This document proposes a critical analysis of the models that describe the actinides and lanthanides complexation by natural organic matter in general and by humic substances in particular. In order to better delimit the particular properties of these substances the most influent physical and chemical properties on complexation are recalled as a preamble. Models as well as data that has been used are reviewed, compiled, and eventually compared to independent data in order to identify (i) their application domain, (ii) the possible simplifications which permit to obtain operational models, (iii) the conditions in which simplifications cannot be ascertained yet, and (iv) the data or fields of knowledge which are still too uncertain. A comparison between the different models is proposed in order to adapt parameters from one model to another minimising the experimental acquisitions, or at least to focus on missing data. Usually, data on the complexation of free ions Mz+ are reliable; as soon as hydrolysis, or competition with another ligand in general, in at stake data are much less reliable. Predictions from models are much more uncertain: formation of mixed complexes with hydroxide or carbonate anions is not univocal whatever the modelling strategy. Hints for transfer functions between models which are believed to be incompatible could be explored in order to justify necessary simplifications for using operational modelling. Influence on the solubility of oxides could be quantified, but it is difficult to clearly separate it from colloidal particles stabilisation. The account of the competition between cations by the models has also been tested. In view of the small number of available experimental data there still lie some uncertainties especially for the media that are close to neutrality and in the case of competition with magnesium, but overall in the case of the competition with aluminium and iron. The influence of redox activity of humic substances is also

  19. DISTRIBUTION OF LANTHANIDE AND ACTINIDE ELEMENTS BETWEEN BIS-(2-ETHYLHEXYL)PHOSPHORIC ACID AND BUFFERED LACTATE SOLUTIONS CONTAINING SELECTED COMPLEXANTS

    Rudisill, Tracy S.; Diprete, David P.; Thompson, Major C.

    2013-04-15

    With the renewed interest in the closure of the nuclear fuel cycle, the TALSPEAK process is being considered for the separation of Am and Cm from the lanthanide fission products in a next generation reprocessing plant. However, an efficient separation requires tight control of the pH which likely will be difficult to achieve on a large scale. To address this issue, we measured the distribution of lanthanide and actinide elements between aqueous and organic phases in the presence of complexants which were potentially less sensitive to pH control than the diethylenetriaminepentaacetic (DTPA) used in the process. To perform the extractions, a rapid and accurate method was developed for measuring distribution coefficients based on the preparation of lanthanide tracers in the Savannah River National Laboratory neutron activation analysis facility. The complexants tested included aceto-, benzo-, and salicylhydroxamic acids, N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), and ammonium thiocyanate (NH{sub 4}SCN). The hydroxamic acids were the least effective of the complexants tested. The separation factors for TPEN and NH{sub 4}SCN were higher, especially for the heaviest lanthanides in the series; however, no conditions were identified which resulted in separations factors which consistently approached those measured for the use of DTPA.

  20. Distribution Of Lanthanide And Actinide Elements Between BIS-(2-Ethylhexyl)Phosphoric Acid And Buffered Lactate Solutions Containing Selected Complexants

    With the renewed interest in the closure of the nuclear fuel cycle, the TALSPEAK process is being considered for the separation of Am and Cm from the lanthanide fission products in a next generation reprocessing plant. However, an efficient separation requires tight control of the pH which likely will be difficult to achieve on a large scale. To address this issue, we measured the distribution of lanthanide and actinide elements between aqueous and organic phases in the presence of complexants which were potentially less sensitive to pH control than the diethylenetriaminepentaacetic (DTPA) used in the process. To perform the extractions, a rapid and accurate method was developed for measuring distribution coefficients based on the preparation of lanthanide tracers in the Savannah River National Laboratory neutron activation analysis facility. The complexants tested included aceto-, benzo-, and salicylhydroxamic acids, N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), and ammonium thiocyanate (NH4SCN). The hydroxamic acids were the least effective of the complexants tested. The separation factors for TPEN and NH4SCN were higher, especially for the heaviest lanthanides in the series; however, no conditions were identified which resulted in separations factors which consistently approached those measured for the use of DTPA

  1. Specific sequestering agents for the actinides. VI. Synthetic and structural chemistry of tetrakis(N-alkylalkanehydroxamato)thorium(IV) complexes

    Hydroxamate complexes of the actinides have been investigated as structural archetypes in the design of actinide-specific sequestering agents. The complexes Th[(CH3)2CHN(O)O(O)R]4 have been prepared (R = C(CH3)3 (1) or CH2C(CH3)3 (2) The uranium(IV) analogue of 1 was also prepared. The tert-butyl groups of 1 dominate the stereochemistry of the complex by assuming a tetrahedral disposition around the metal. The coordination polyhedron of 1, which has 4 (S4) crystallographic symmetry, is nearly cubic. The localization of charge on the nitrogen oxygen of the hydroxamate group makes this ligand unsymmetrical, and this gives rise to a 0.14-A difference in R(Th-O/sub N/) [2.357(3) A] and R(Th-O/sub C/) [2.492 (3) A]. The sterically less constrained neopentyl derivative 2 shows a more typical eight-coordinate geometry - the D/sub 2d/ trigonal-faced (mmmm) dodecahedron. The average R(Th-O/sub N/) [2.36 (1) A] is again shorter than R(Th-O/sub C/) [2.46 (2) A]. There is apparently no sorting of sites by ligand charge, since the O/sub N/ and O/sub C/ atoms are equally distributed between the A and B sites of the dodecahedron. Crystals of 1 conform to space group I41/a with a = 17.338 (4) A and c = 12.706 (4) A. For 4 formula units per cell the calculated density d/sub calcd/ is 1.50 g cm-3 and d/sub obsd/ is 1.50 (1) g cm-3. Crystals of 2 conform to space group P1 with a = 9.777 (2) A, b = 14.633 (2) A, c = 18.515 (1) A, α = 74.0610 (8), β = 88.41 (1)0, and γ = 74.71 (2)0. For 2 formula units per cell d/sub calcd/ = 1.30 g cm-3 and d/sub obsd/ = 1.19 g cm-3. Full-matrix least-squares refinement of both structures using all averaged, independent data with F2 > 3sigma(F)2 gave for 1 with 1798 data and 117 variables R = 0.027 and R/sub w/ = 0.032 and for 2 with 6978 data and 467 variables R = 0.034, R/sub w/ = 0.042. 10 figures, 11 tables

  2. Lanthanides(III)/Actinides(III) separation by nano-filtration-complexation

    The aim of this work is to evaluate the lanthanides (III) separation by nano-filtration complexation according to the pH (1.0-4.0) with poly-amino-carboxylic acids as complexing agent. The experimental Ln(III) complex rejections were then compared to Ln(III)-Ligand system speciation calculated using the protonation and thermodynamic stability constants. Some differences were revealed for lower (pH 1.0) and higher (pH 4.0) Ln(III) complex rejections. These differences of the Ln(III) complex rejections could be explained by a combination of both steric exclusion and surface force interactions. At pH 1.0, the initial experimental rejection of the free Ln(III) reaches 6% in absence of complexation because the membrane is positively charged. In order to limit the escape in Ln(III) complexes at pH 4.0, the influence of the operating parameters was studied. At pH 5.8 and for an operational pressure of 3 bars, a complex concentration of 0.4 mM, a tangential velocity of 145 mm.s-1 and a temperature of 15 deg C, the Gd(III) complex rejection reached more than 99% and thus the total Gd(III) complex in the feed is rejected. (authors)

  3. Plutonium(IV) complexation by diglycolamide ligands - coordination chemistry insight into TODGA-based actinide separations

    Reilly, S.D.; Gaunt, A.J.; Scott, B.L.; Modolo, G.; Iqbal, M.; Verboom, W.; Sarsfield, M.J.

    2012-01-01

    Complexation of Pu(IV) with TMDGA, TEDGA, and TODGA diglycolamide ligands was followed by vis-NIR spectroscopy. A crystal structure determination reveals that TMDGA forms a 1:3 homoleptic Pu(IV) complex with the nitrate anions forced into the outer coordination sphere

  4. Determination of nonmetallic elements in actinide complexes by oxygen flask combustion (OFC) (Part 2). Sulphur

    This report describes the determination of sulphur in metallic complexes by oxygen flask combustion followed by conductivity titration with standard barium acetate solution in alcoholic medium and lead electrode titration using a lead ion sensitive electrode. Various organic ligands and uranyl and plutonyl synergistic complexes have been analysed by both these methods and the precision and accuracy of the results have been found to be satisfactory. (author). 12 refs., 12 tabs

  5. Computational Study of Covalency and Complexation in Actinides using Static and Dynamic Simulation and Topological Density Analysis

    Kirker, I. D. J.

    2013-01-01

    The separation of minor actinides such as americium and curium from other actinide and lanthanide-bearing components of used nuclear fuel is a necessary part of post-processing and recycling this fuel into storable components and new fuel material. Separation ratios can be optimised using a comprehensive understanding of the differences between these elements and their aqueous chemistry. This work uses computational simulation to investigate bonding behaviour and covalency differences between...

  6. Effects of humic substances on the migration of radionuclides: Complexation of actinides with humic substances. (6th progress report, project summary). Period covered: January 1994 - July 1994

    The goal of the research project is to examine the complexation behaviour of actinide ions with humic substances and thermodynamically describe the binding based upon a simple complexation model. This program is a continuation of the activities of the colloid and complexation group (COCO) in the second phase of the EC-MIRAGE project. A number of different experimental methods are used to determine speciation. The metal ions examined are the trivalent lanthanides, UO22+, NpO2+, Am3+, and Cm3+. The project is divided into three tasks: Task 1: complexation reactions of actinide ions with well characterized reference and site-specific humic and fulvic acids, Task 2: complexation reactions with major cations in natural groundwaters; Task 3: validation of the complexation data in natural aquatic systems by comparison of calculation with spectroscopic experiment. Five European community laboratories participated in the program: Technische Universitaet Muenchen, Commissariat a l'Energie Atomique Fontenay-Aux-Roses and Saclay, Universitaet Mainz, Katolieke Universiteit Leuven, and Joint Research Centre, Ispra. The evaluated stability constants are similar for all laboratories when the same humic substance complexation model is applied. Humic acid is shown to reduce NpO2+ to Np4+, while no reduction of UO22+ is observed. Temperature effects are seen on the Np humate complex. Competition is observed between NpO2+ and Ca2+, but not between the trivalent lanthanides and Ca2+. No influence of humic acid purification on the evaluated stability constants is seen. Using the evaluated constants, calculations are conducted for natural water systems which indicate the trivalent actinide humate complex to be an important species. (orig.)

  7. Actinide complexation kinetics: rate and mechanism of dioxoneptunium (V) reaction with chlorophosphonazo III

    Rates of complex formation and dissociation in NpO2+- Chlorophosphonazo III (2,7-bis(4-chloro-2-phosphonobenzeneazo)-1,8- dihydroxynapthalene-3,6-disulfonic acid)(CLIII) were investigated by stopped-flow spectrophotometry. Also, limited studies were made of the rates of reaction of La3+, Eu3+, Dy3+, and Fe3+ with CLIII. Rate determining step in each system is an intramolecular process, the NpO2+-CLIII reaction proceeding by a first order approach to equilibrium in the acid range from 0.1 to 1.0 M. Complex formation occurs independent of acidity, while both acid dependent and independent dissociation pathways are observed. Activation parameters for the complex formation reaction are ΔH=46.2±0.3 kJ/m and ΔS=7± J/mK (I=1.0 M); these for the acid dependent and independent dissociation pathways are ΔH=38.8±0.6 kJ/m, ΔS=-96±18 J/mK, ΔH=70.0± kJ/m, and ΔS=17±1 J/mK, respectively. An isokinetic relationship is observed between the activation parameters for CLIII complex formation with NpO2+, UO22+, Th4+, and Zr4+. Rates of CLIII complex formation reactions for Fe3+, Zr4+, NpO2+, UO22+, Th4+, La3+, Eu3+, and Dy3+ correlate with cation radius rather than charge/radius ratio

  8. Supercritical fluid extraction (SFE) of actinide complexes. Communication 1. SFE of uranyl trifluoroacetylacetonate adduct with pyridine

    Comparison of some methods of ascertaining the solubility of metal complexes in supercritical carbon dioxide (SC-CO2) was made. It is shown that solubility of uranyl trifluoroacetylacetonate adduct with pyridine exceeds 100 g/l (36 mg of uranium per ml) of SC-CO2 under the pressure of 300 atm and temperature of 60 deg C. Partial degrading of the uranyl trifluoroacetylacetonate adduct with pyridine is pointed out

  9. Study of the selectivity of poly-nitrogenous extracting molecules in the complexation of actinides (III) and lanthanides (III) in solution in anhydrous pyridine

    The aim of this work is to better understand the factors which contribute to the separation of lanthanides(III) and actinides(III). Polydentate nitrogenous molecules present an interesting selectivity. A thermodynamic study of the complexation in pyridine of lanthanide and uranium by the bipyridine ligand (bipy) has been carried out. The formation constants and the thermodynamic values of the different complexes have been determined. It has been shown that the bipy complexes formation is controlled by the enthalpy and unfavored by the entropy. The conductometry has revealed too a significant difference in the uranium and lanthanides complexation by the bipyridine ligand. The use of the phenanthroline ligand induces a better complexation of the metallic ions but the selectivity is not improved. On the other hand, the decrease of the basicity and the increase of the ligand denticity (for instance in the case of the use of ter-pyridine) favour the selectivity without improving the complexation. The selectivity difference for the complexation of actinides(III) and lanthanides(III) by the different studied ligands (independent systems) has been confirmed by experiments of inter-metals competition. (O.M.)

  10. Complexation thermodynamics and structural studies of trivalent actinide and lanthanide complexes with DTPA, MS-325 and HMDTPA

    The protonation constants of DTPA (diethylenetriaminepentaacetic acid) and two derivatives of DTPA, 1-R(4,4-diphenyl cyclohexyl-phosphonyl-methyl diethylenentriaminepentaacetic acid) (MS-325) and (R)-hydroxymethyl-diethylenentriaminepentaacetic acid (HMDTPA) were determined by potentiometric titration in 0.1 M NaClO4. The formation of 1: 1 complexes of Am3+, Cm3+ and Ln3+ cations with these three ligands were investigated by potentiometric titration with competition by ethylenediaminetetraacetic acid (EDTA) and the solvent extraction method in aqueous solutions of I=0.10 M NaClO4. The thermodynamic data of complexation were determined by the temperature dependence of the stability constants and by calorimetry. The complexation is exothermic and becomes weaker with increase in temperature. The complexation strength of these ligands follows the order: DTPA ∼ HMDTPA > MS-325. Eu3+/Cm3+ luminescence, EXAFS (Extended X-ray Absorption Fine Structure) and DFT (Density Functional Theory) calculations suggest that all three ligands are octadentate in the complex. In the complex, M(L)2- (L = DTPA, MS-325 and HMDTPA). The M3+ binds via five carboxylates oxygen atoms, three nitrogen atoms, and the complex contains one water of hydration. (orig.)

  11. An apparatus for the determination of molecular weights of actinide complexes

    This report describes the fabrication and standardisation of an apparatus called, 'Osmistor' for molecular weight determinations. The set up uses a matched pair of thermistors as temperature sensing device and is based on the principles of relative lowering of vapour pressure of a solution with respect to the solvent exposed to the same temperature. The instrument was calibrated using standard solution (0.01 to 0.08 M) of A.R. benzil in three different solvents, viz, benzene, acetone and chloroform at a temperature of 38.0, 25.0 and 25.0 +-0.01deg C respectively and the calibration constant K was determined. The molecular weight of naphthalene in the above solvents was determined with a precision and accuracy of +- 3%. Also, the molecular weights of a few synergistic uranyl complexes were determined with an accuracy of about 5%. (author)

  12. Complexation modelling of uranium and other actinides by organic compounds of natural or synthetic origin

    The future of nuclear wastes raises a lot of questions. Their resolution require an accurate knowledge of the physical, chemical and biological processes which affect the properties of radioelements constituting the wastes. 3 research themes have been approached. The experimental methods used are: neutronic activation analysis, UV-visible spectrophotometry and time-resolved induced laser spectro-fluorimetry. A part of the phenomena has been modelled by ionic strength correction models (as Davies or MSA). The main results have revealed: 1)the bio-sorption capacities of the microorganism (Mycobacterium phlei) for UO22+ and NpO2+ (in conditions where the specific adsorption capacities Qe(UO22+)=60 and Qe(NpO2+)=444 moles cations/g dry biomass 2)the retention capacities, in various leaching conditions, by this bacteria of the ions initially adsorbed 3)the complexation properties of 2 siderophores for the cations UO22+, U4+ and Th4+. The thermodynamical equilibrium constants were determined for one of the siderophore: the pyoverdine A; they were such that KUO22+≤KU4+≤KTh4+ 4)in very acidic media (HCl and HClO4 until 12 M), the behaviour of the acylisoxazolone HPBI (1-phenyl-4-benzoyl-5-isoxazolone) and the value of its acidity thermodynamical constant is such that 0.13≤KATh≤0.32 at 25 degrees Celsius 5)the variations of the fluorescence properties of the uranyl cation in terms of the acidity of the concentrated media (HClO4 and CF3SO3H) in which they are in solution; it seems that a complexation between the uranyl ion and the counter-ions present in solution occur. (O.M.)

  13. Diphosphine dioxides as extractants for actinides (in connection with the problem of anomalous aryl strengthening of complexes)

    Extraction study of uranylnitrate, plutonium in trivalent, tetravalent and gexavalent states and trivalent americium, curium, praseodymium and promethium by alkyl, aromatic and mixed diphosphine dioxides is briefly outlined. The influence of diphosphine dioxide structures on their extraction capacity and, in particular, the problem of anomalous aryl strengthening of compounds, both of entropy and binding character, are considered. Perchlorate media, as opposed to nitrate ones, are characteristic for their high distribution coefficients and extraction equilibrium constants. Anomalous aryl strengthening of trivalent lanthanides and actinides can be applied, at the minimum, for solution purifications from the traces of actinides and lanthanides

  14. Actinide recycle

    A multitude of studies and assessments of actinide partitioning and transmutation were carried out in the late 1970s and early 1980s. Probably the most comprehensive of these was a study coordinated by Oak Ridge National Laboratory. The conclusions of this study were that only rather weak economic and safety incentives existed for partitioning and transmuting the actinides for waste management purposes, due to the facts that (1) partitioning processes were complicated and expensive, and (2) the geologic repository was assumed to contain actinides for hundreds of thousands of years. Much has changed in the few years since then. A variety of developments now combine to warrant a renewed assessment of the actinide recycle. First of all, it has become increasingly difficult to provide to all parties the necessary assurance that the repository will contain essentially all radioactive materials until they have decayed. Assurance can almost certainly be provided to regulatory agencies by sound technical arguments, but it is difficult to convince the general public that the behavior of wastes stored in the ground can be modeled and predicted for even a few thousand years. From this point of view alone there would seem to be a clear benefit in reducing the long-term toxicity of the high-level wastes placed in the repository

  15. Research on the chemical speciation of actinides

    A demand for the safe and effective management of spent nuclear fuel and radioactive waste generated from nuclear power plant draws increasing attention with the growth of nuclear power industry. The objective of this project is to establish the basis of research on the actinide chemistry by using advanced laser-based highly sensitive spectroscopic systems. Researches on the chemical speciation of actinides are prerequisite for the development of technologies related to nuclear fuel cycles, especially, such as the safe management of high level radioactive wastes and the chemical examination of irradiated nuclear fuels. For supporting these technologies, laser-based spectroscopies have been performed for the chemical speciation of actinide in an aqueous solutions and the quantitative analysis of actinide isotopes in spent nuclear fuels. In this report, results on the following subjects have been summarized. (1) Development of TRLFS technology for chemical speciation of actinides, (2) Development of LIBD technology for measuring solubility of actinides, (3) Chemical speciation of plutonium complexes by using a LWCC system, (4) Development of LIBS technology for the quantitative analysis of actinides, (5) Development of technology for the chemical speciation of actinides by CE, (6) Evaluation on the chemical reactions between actinides and humic substances, (7) Chemical speciation of actinides adsorbed on metal oxides surfaces, (8) Determination of actinide source terms of spent nuclear fuel

  16. New reagents for actinide-lanthanide group separations

    Organic extractants which possess nitrogen or sulfur donor atoms preferentially complex the trivalent actinide. They are potential reagents for actinide lanthanide group separations, which can be performed at low pH without the addition of inorganic salts

  17. Study of the selectivity of poly-nitrogenous extracting molecules in the complexation of actinides (III) and lanthanides (III) in solution in anhydrous pyridine; Etude de la selectivite de molecules extractantes polyazotees dans la complexation des actinides (III) et des lanthanides (III) en solution dans la pyridine anhydre

    Riviere, Ch

    2000-10-05

    The aim of this work is to better understand the factors which contribute to the separation of lanthanides(III) and actinides(III). Polydentate nitrogenous molecules present an interesting selectivity. A thermodynamic study of the complexation in pyridine of lanthanide and uranium by the bipyridine ligand (bipy) has been carried out. The formation constants and the thermodynamic values of the different complexes have been determined. It has been shown that the bipy complexes formation is controlled by the enthalpy and unfavored by the entropy. The conductometry has revealed too a significant difference in the uranium and lanthanides complexation by the bipyridine ligand. The use of the phenanthroline ligand induces a better complexation of the metallic ions but the selectivity is not improved. On the other hand, the decrease of the basicity and the increase of the ligand denticity (for instance in the case of the use of ter-pyridine) favour the selectivity without improving the complexation. The selectivity difference for the complexation of actinides(III) and lanthanides(III) by the different studied ligands (independent systems) has been confirmed by experiments of inter-metals competition. (O.M.)

  18. Chemistry of actinides and fission products

    This task is concerned primarily with the fundamental chemistry of the actinide and fission product elements. Special efforts are made to develop research programs in collaboration with researchers at universities and in industry who have need of national laboratory facilities. Specific areas currently under investigation include: (1) spectroscopy and photochemistry of actinides in low-temperature matrices; (2) small-angle scattering studies of hydrous actinide and fission product polymers in aqueous and nonaqueous solvents; (3) kinetic and thermodynamic studies of complexation reactions in aqueous and nonaqueous solutions; and (4) the development of inorganic ion exchange materials for actinide and lanthanide separations. Recent results from work in these areas are summarized here

  19. Actinide Waste Forms and Radiation Effects

    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

  20. Research on the chemical speciation of actinides

    A demand for the safe and effective management of spent nuclear fuel and radioactive waste generated from nuclear power plant draws increasing attention with the growth of nuclear power industry. The objective of this project is to establish the basis of research on the actinide chemistry by using highly sensitive and advanced laser-based spectroscopic systems. Researches on the chemical speciation of actinides are prerequisite for the development of technologies related to nuclear fuel cycles, especially, such as the safe management of high level radioactive wastes and the chemical examination of irradiated nuclear fuels. For supporting these technologies, laser-based spectroscopies have been applied for the chemical speciation of actinide in aqueous solutions and the quantitative analysis of actinide isotopes in spent nuclear fuels. In this report, results on the following subjects have been summarized. Development of TRLFS technology for the chemical speciation of actinides, Development of laser-induced photo-acoustic spectroscopy (LPAS) system, Application of LIBD technology to investigate dynamic behaviors of actinides dissolution reactions, Development of nanoparticle analysis technology in groundwater using LIBD, Chemical speciation of plutonium complexes by using a LWCC system, Development of LIBS technology for the quantitative analysis of actinides, Evaluation on the chemical reactions between actinides and humic substances, Spectroscopic speciation of uranium-ligand complexes in aqueous solution, Chemical speciation of actinides adsorbed on metal oxides surfaces

  1. Complexation of lanthanide(III) and actinide(III) cations with tridentate nitrogen-donor ligands: A luminescence and spectro photometric study

    Miguirditchian, M.; Guillaneux, D.; Fran is, N.; Airvault, S.; Ducros, S.; Thauvin, D. [CEA-Valrho, DEN/DRCP/SCPS, B.P. 17171, 30207 Bagnols-sur-Ceze Cedex (France); Madic, C. [CEA-Saclay, DEN/DDIN, 91191 Gif-sur-Yvette (France); Illemassene, M.; Lagarde, G.; Krupa, J.C. [Groupe de Radiochimie, Institut de Physique Nucleaire, 91405 Orsay (France)

    2006-07-01

    The complexation of lanthanide(III) (lanthanum, europium, and lutetium) and americium (III) by four tridentate nitrogen-donor ligands was investigated in homogeneous methanol/water solutions by using structural and thermodynamic approaches. The stoichiometry and inner-sphere hydration state of the europium complexes formed were determined by time-resolved laser-induced fluorimetry. The stability constants and in some cases the thermodynamic parameters were measured by ultraviolet-visible spectrophotometry and the van't Hoff method. The comparison of the stability constant of americium complexes with lanthanide complexes shows better stability for the actinide species. The strong affinity for these ligands toward Am{sup 3+} is confirmed by the formation of higher complexes, especially in the case of 2,6-bis-(5,6-dimethyl-1,2,4-triazine-3-yl)-pyridine (MeBTP), the only ligand able to form a 1:3 complex. The influence of the solvent composition on the complexation thermodynamics highlights the effect of the solvent reorganization on the reaction. (authors)

  2. Synthesis, chemistry, and catalytic activity of complexes of lanthanide and actinide metals in unusual oxidation states and coordination environments. Progress report, February 1, 1981-January 31, 1982

    The objectives of this research project are: (1) to demonstrate experimentally that the lanthanide and actinide metals have a more extensive chemistry than is presently known; (2) to develop a better understanding of the special features of the f orbital elements which will allow the design of f orbital complexes possessing unique chemical and physical properties; (3) to provide a basis for seeking unusual catalytic transformations involving these elements; and (4) to synthesize and explore the chemical and physical properties of mixed metal complexes which contain both lanthanide and transition metals. During the past year progress was made in each area. Some of the specific results are: (1) the first activation of CO by an organolanthanide complex was demonstrated; (2) the first, crystallograhically characterized, molecular lanthanide hydride complexes, the bridged dimers, [(C5H4R)2LnH(THF)]2 (R=H, CH3; Ln=Lu, Er, Y), were synthesized by hydrogenolysis of the appropriate (C5H4R)2Ln(C(CH3)3)(THF) complex; (3) [(C5H5)2(THF)ErH]2 was found to catalyze the homogeneous hydrogenation of alkynes; (4) the first trimetallic organolanthanide complex was synthesized; (5) the first polyhydridic organolanthanide complex was synthesized; (6) U(III) hydride was found to catalytically activate molecular hydrogen in alkene and alkyne hydrogenation reactions

  3. Use of tetraaza-macrocycles for complexation of actinides in aqueous solutions. Validation of the process for the treatment of waste waters

    This report makes one's contribution to the study of the reactivity of free or fixed tetraaza-macrocycles. The major interest of this work concerns the following key-points: - Synthesis, spectral characterization and X-ray diffraction study of tetraaza-macrocycles N-tetra-functionalized, - Synthesis, physicochemical, chemicals and X-ray studies of macrocyclic complex in lanthanides and actinides series, - Synthesis and characterization of tetraaza-macrocycles grafted on organic and inorganic polymers, - Reactivity of macrocyclic ligands grafted on Merrifield's resin or silica gel in cerium, europium, uranium, plutonium and americium series, - Extraction of heavy metals in a solid-liquid process and measurements of a pilot. (author)

  4. Characterization of partitioning relevant lanthanide and actinide complexes by NMR spectroscopy; Charakterisierung von partitioningrelevanten Lanthaniden- und Actinidenkomplexen mittels NMR-Spektroskopie

    Adam, Christian

    2016-01-15

    In the present work the interaction of N-donor ligands, such as 2,6-Bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (nPrBTP) and 2,6-Bis(5-(2,2-dimethylpropyl)1H-pyrazol)-3-yl-pyridine (C5-BPP), with trivalent lanthanide and actinide ions was studied. Ligands of this type show a high selectivity for the separation of trivalent actinide ions over lanthanides from nitric acid solutions. However, the reason for this selectivity, which is crucial for future partitioning and transmutation strategies for radioactive wastes, is still unknown. So far, the selectivity of some N-donor ligands is supposed to be an effect of an increased covalency in the actinide-ligand bond, compared to the lanthanide compounds. NMR spectroscopy on paramagnetic metal complexes is an excellent tool for the elucidation of bonding modes. The overall paramagnetic chemical shift consists of two contributions, the Fermi Contact Shift (FCS), due to electron spin delocalisation through covalent bonds, and the Pseudo Contact Shift (PCS), which describes the dipolar coupling of the electron magnetic moment and the nuclear spin. By assessing the FCS share in the paramagnetic shift, the degree of covalency in the metal-ligand bond can be gauged. Several methods to discriminate FCS and PCS have been used on the data of the nPrBTP- and C5-BPP-complexes and were evaluated regarding their applicability on lanthanide and actinide complexes with N-donor ligands. The study comprised the synthesis of all Ln(III) complexes with the exceptions of Pm(III) and Gd(III) as well as the Am(III) complex as a representative of the actinide series with both ligands. All complexes were fully characterised ({sup 1}H, {sup 13}C and {sup 15}N spectra) using NMR spectroscopy. By isotope enrichment with the NMR-active {sup 15}N in positions 8 and 9 in both ligands, resonance signals of these nitrogen atoms were detected for all complexes. The Bleaneymethod relies on different temperature dependencies for FCS (T{sup -1}) and PCS (T

  5. Density and wave function analysis of actinide complexes: What can fuzzy atom, atoms-in-molecules, Mulliken, Löwdin, and natural population analysis tell us?

    Clark, Aurora E.; Sonnenberg, Jason L.; Hay, P. Jeffrey; Martin, Richard L.

    2004-08-01

    Recent advances in computational methods have made it possible to calculate the wave functions for a wide variety of simple actinide complexes. Equally important is the ability to analyze the information contained therein and produce a chemically meaningful understanding of the electronic structure. Yet the performance of the most common wave function analyses for the calculation of atomic charge and bond order has not been thoroughly investigated for actinide systems. This is particularly relevant because the calculation of charge and bond order even in transition metal complexes is known to be fraught with difficulty. Here we use Mulliken, Löwdin, natural population analysis, atoms-in-molecules (AIM), and fuzzy atom techniques to determine the charges and bond orders of UO22+, PuO22+, UO2, UO2Cl42-, UO2(CO)52+, UO2(CO)42+, UO2(CN)53-, UO2(CN)42-, UO2(OH)53-, and UO2(OH)42-. This series exhibits a clear experimental and computational trend in bond lengths and vibrational frequencies. The results indicate that Mulliken and Löwdin populations and bond orders are unreliable for the actinyls. Natural population analysis performs well after modification of the partitioning of atomic orbitals to include the 6d in the valence space. The AIM topological partitioning is insensitive to the electron donating ability of the equatorial ligands and the relative atomic volume of the formally U(VI) center is counterintuitively larger than that of O2- in the UO22+ core. Lastly, the calibrated fuzzy atom method yields reasonable bond orders for the actinyls at significantly reduced computational cost relative to the AIM analysis.

  6. Subsurface interactions of actinide species and microorganisms. Implications for the bioremediation of actinide-organic mixtures

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

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

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

    1999-02-12

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

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

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

  9. One ligand fits all: lanthanide and actinide sandwich complexes comprising the 1,4-bis(trimethylsilyl)cyclo-octa-tetra-enyl (=COT'') ligand

    The series of anionic lanthanide(III) sandwich complexes of the type [Ln(COT'')2]- (COT'' = 1,4-bis(trimethylsilyl)cyclo-octa-tetra-enyl di-anion) has been largely extended by the synthesis of eight new derivatives ranging from lanthanum to lutetium. The new compounds [Li(DME)3][Ln(COT'')2] (Ln = Y (1), La (2), Pr (3), Gd (4), Tm (6), Lu (8)) and [Li(THF)4][Ln(COT'')2] (Ln = Ho (5), Tm (7)) were prepared in good yields following a straightforward synthetic protocol which involves the treatment of LnCl3 with 2 equiv. of in situ prepared Li2COT' in either DME (=1,2-dimethoxyethane) or THF. The neutral actinide sandwich complexes An(COT'')2 (An = Th (9), U (10)) and An(COT''')2 (COT''' = 1,3,6-tris(trimethylsilyl)cyclo-octa-tetra-enyl di-anion; An = Th (11), U (12)) were synthesized in a similar manner, starting from ThCl4 or UCl4, respectively. The COT'' ligand imparts excellent solubility even in low-polar solvents as well as excellent crystallinity to all new compounds studied. All twelve new f-element sandwich complexes have been structurally authenticated by single-crystal X-ray diffraction. All are nearly perfect sandwich complexes with little deviation from the coplanar arrangement of the substituted COT'' rings. Surprisingly, all six [Li(DME)3][Ln(COT)2] complexes covering the entire range of Ln3+ ionic radii from La3+ to Lu3+ are isostructural (space group P1-bar). % Compound 10 is the first uranocene derivative for which 13C NMR data are reported. (authors)

  10. The lanthanides and actinides

    This paper relates the chemical properties of the actinides to their position in the Mendeleev periodic system. The changes in the oxidation states of the actinides with increasing atomic number are similar to those of the 3d elements. Monovalent and divalent actinides are very similar to alkaline and alkaline earth elements; in the 3+ and 4+ oxidation states they resemble d elements in the respective oxidation states. However, in their highest oxidation states the actinides display their individual properties with only a slight resemblance to d elements. Finally, there is a profound similarity between the second half of the actinides and the first half of the lanthanides

  11. Actinide chemistry in the far field

    The environmental chemistry of the actinides is complicated due both to the extensive redox and coordination chemistry of the elements and also to the complexity of the reactive phases encountered in natural environments. In the far field, interactions with reactive surfaces, coatings and colloidal particles will play a crucial role in controlling actinide mobility. By virtue of both their abundance and reactivity; clays and other layer aluminosilicate minerals, hydrous oxides and organic matter (humic substances) are all identified as having the potential to react with actinide ions and some possible modes of interaction are described, together with experimental evidence for their occurrence. (author)

  12. Actinide co-ordination and discrimination by human transferrin

    The design and evaluation of synthetic chelating agents which are specific for the actinide(IV) ions are described. The initial approach has been based on the biological and chemical similarities of Pu(IV) and Fe(III). In particular, using a philosophy influenced by naturally occurring ferric ion chelating agents, tetracatechoylamide ligands have been developed for the actinides. The test of the degree to which there was an actinide-specific complexing agent has been based on studies using Pu4+ as a biological contaminant. For a chelating agent to be able to sequester actinides effectively, it must remove actinides from actinide(IV)-protein complexes. The complexation chemistry of Th(IV)-transferrin system is described. The evidence suggests that, based on a size criterion, Th(IV) may be a poor biological model for Pu(IV) in some cases, with U(IV) being a somewhat better model. (author)

  13. Effects of humic substances on the migration of radionuclides: Complexation of actinides with humic substances. 4. progress report

    In this report a number of methodical developments are in progress. The effective ligand concentration is one of the important parameters for the evaluation of the metal ion complexation behaviour of bulk polyelectrolytes like humic or fulvic acids. Studies by KUL and TUM show that the effective ligand concentration of humic acid is related to the protonation of the ion exchanging groups. For a precise evaluation of the complexation reaction, however, a direct measurement of the effective ligand capacity under given experimental conditions is neccessary. The humate complexation has been studied for pentavalent neptunium (UM), hexavalent uranium (TUM) and trivalent lanthanide ions (CEA, UM and KUL) under different experimental conditions. The pH is varied between 3.0 and 9.0, the ionic strength between 0.01 and 0.1 M with metal ion concentrations between 10-13 and 10-5 mol/L. Competition of Al3+, [Co(NH3)6]3+, Ca2+, Cu2+, Fe2+ and Na+ on the Eu humate interaction is investigated by KUL. CEA-FAR has studied the influence of temperature on the Dy(III) humate complexation as well as the Dy(III) complexation with EDTA for the purpose of comparison. Studies by KUL on the influence of different competing ligands show that in such a ternary system (metal ion, humic acid and competing ligand) mixed complexes are generated. (orig.)

  14. Effects of humic substances on the migration of radionuclides: Complexation of actinides with humic substances. 5. progress report

    The complexation study with Am(III) is conducted with humic acid concentrations between 2.5x10-5 mol/L and 3.8x10-5 mol/L ([HA(III)]). The Am(III) concentration is varied to give Am(III) to HA(III) concentration ratios between approximately 0.1 and 2.0. The excess Am concentration allows to determine the loading capacity of humic acid. Taking the loading capacity into account, the complexation constants of the two types of humic acid are evaluated. The loading capacities and the complexation constants do not differ from one another and agree well with previous results on the site specific COCO-group standard humic acid from the same groundwater (Gohy-573(HA)). The mean value of the Am(III) complexation constants for the natural and purified humic acids is found to be logβ=6.26±0.05. The results show that the purification of humic acid has no significant influence on its complexation behaviour with Am(III) and thus thermodynamic data from purified humic acid can be applied readily for geochemical modelling. (orig.)

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

    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.

  16. Coordination chemistry of actinide elements: preparation of new uranium complexes with schiff bases and their characterization (Preprint No. CT-31)

    The Schiff bases, o-vanillin semicarbazone (oVSC) and 2-pyridine carboxaldehyde isonicotinoyl hydrazone (PCINH) have been prepared and their novel complexes with dioxouranium(VI) have been synthesized and characterized by IR spectra, elemental analysis and other physico-chemical techniques. (author)

  17. Overview of actinide chemistry in the WIPP

    Borkowski, Marian [Los Alamos National Laboratory; Lucchini, Jean - Francois [Los Alamos National Laboratory; Richmann, Michael K [Los Alamos National Laboratory; Reed, Donald T [Los Alamos National Laboratory; Khaing, Hnin [Los Alamos National Laboratory; Swanson, Juliet [Los Alamos National Laboratory

    2009-01-01

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

  18. Actinide chemistry in ionic liquids.

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

    2013-04-01

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

  19. Separation of actinides with alkylpyridinium salts

    Various f-elements are separated as anionic complexes from both acidic and alkaline solutions by precipitation with alkylpyridinium salts. The precipitates are also cationic surfactants where the simple counter-ion (e.g. nitrate or chloride) is replaced by the negatively charged complex anion of an actinide or lanthanide. The low solubility of these precipitates is explained by a strong affinity of divalent complex counter-ions of f-elements to the quaternary nitrogen. Precipitations in solutions of nitric acid allow to separate tetravalent f-elements from other metals, in alkaline carbonate solutions tetravalent and hexavalent actinides are precipitated simultaneously. The last procedure yields precipitates, which are very intimate mixtures of hexavalent and tetravalent actinides. This allows to prepare mixed oxides in a simple way. (author) 6 refs.; 3 figs.; 3 tabs

  20. Aqueous complexes of lanthanides(III) and actinides(III) with the carbonate and sulphate ions. Thermodynamic study by time-resolved laser-induced fluorescence spectroscopy and electro-spray-ionisation mass spectrometry; Complexes aqueux de lanthanides (3) et actinides (3) avec les ions carbonate et sulfate. Etude thermodynamique par spectrofluorimetrie laser resolue en temps et spectrometrie de masse a ionisation electrospray

    Vercouter, Th

    2005-03-15

    The prediction of the environmental impact of a possible geological disposal of radioactive wastes is supported by the thermodynamic modelling of the radionuclides behaviour in the groundwater. In this framework, the analogy between lanthanides and actinides(III) is confirmed by a critical analysis of the literature and the comparison with experimental results obtained here. The limiting complex, Eu(CO{sub 3}){sub 3}{sup 3-}, is identified by solubility measurements in Na{sub 2}CO{sub 3} solutions. Then the formation constants of the complexes Eu(CO{sub 3}){sub i}{sup 3-2i} (i=1-3) and Eu(SO{sub 4}){sub i}{sup 3-2i} (i=1-2) are measured by TRLFS. The formation of aqueous LaSO{sub 4}{sup +} is studied by ESI-MS and is in good agreement with the expected speciation. The enthalpy and entropy of the reaction Cm(CO{sub 3}){sub 2}{sup -} + CO{sub 3}{sup 2-} {r_reversible} Cm(CO{sub 3}){sub 3}{sup 3-} are deduced from TRLFS measurements of the equilibrium constant between 10 and 70 C. The ionic strength effect is calculated using the SIT formula. (author)

  1. Subsurface Biogeochemistry of Actinides

    Kersting, Annie B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Univ. Relations and Science Education; Zavarin, Mavrik [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Glenn T. Seaborg Inst.

    2016-06-29

    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 plutonium (Pu) have been deposited in the subsurface 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 in 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 (Figure 1).

  2. Actinide elements in aquatic and terrestrial environments

    Progress is reported on the following research projects: water-sediment interactions of U, Pu, Am, and Cm; relative availability of actinide elements from abiotic to aquatic biota; comparative uptake of transuranic elements by biota bordering Pond 3513; metabolic reduction of 239Np from Np(V) to Np(IV) in cotton rats; evaluation of hazards associated with transuranium releases to the biosphere; predicting Pu in bone; adsorption--solubility--complexation phenomena in actinide partitioning between sorbents and solution; comparative soil extraction data; and comparative plant uptake data

  3. TUCS/phosphate mineralization of actinides

    Nash, K.L. [Argonne National Lab., IL (United States)

    1997-10-01

    This program has as its objective the development of a new technology that combines cation exchange and mineralization to reduce the concentration of heavy metals (in particular actinides) in groundwaters. The treatment regimen must be compatible with the groundwater and soil, potentially using groundwater/soil components to aid in the immobilization process. The delivery system (probably a water-soluble chelating agent) should first concentrate the radionuclides then release the precipitating anion, which forms thermodynamically stable mineral phases, either with the target metal ions alone or in combination with matrix cations. This approach should generate thermodynamically stable mineral phases resistant to weathering. The chelating agent should decompose spontaneously with time, release the mineralizing agent, and leave a residue that does not interfere with mineral formation. For the actinides, the ideal compound probably will release phosphate, as actinide phosphate mineral phases are among the least soluble species for these metals. The most promising means of delivering the precipitant would be to use a water-soluble, hydrolytically unstable complexant that functions in the initial stages as a cation exchanger to concentrate the metal ions. As it decomposes, the chelating agent releases phosphate to foster formation of crystalline mineral phases. Because it involves only the application of inexpensive reagents, the method of phosphate mineralization promises to be an economical alternative for in situ immobilization of radionuclides (actinides in particular). The method relies on the inherent (thermodynamic) stability of actinide mineral phases.

  4. Actinide isotopic analysis systems

    This manual provides instructions and procedures for using the Lawrence Livermore National Laboratory's two-detector actinide isotope analysis system to measure plutonium samples with other possible actinides (including uranium, americium, and neptunium) by gamma-ray spectrometry. The computer program that controls the system and analyzes the gamma-ray spectral data is driven by a menu of one-, two-, or three-letter options chosen by the operator. Provided in this manual are descriptions of these options and their functions, plus detailed instructions (operator dialog) for choosing among the options. Also provided are general instructions for calibrating the actinide isotropic analysis system and for monitoring its performance. The inventory measurement of a sample's total plutonium and other actinides content is determined by two nondestructive measurements. One is a calorimetry measurement of the sample's heat or power output, and the other is a gamma-ray spectrometry measurement of its relative isotopic abundances. The isotopic measurements needed to interpret the observed calorimetric power measurement are the relative abundances of various plutonium and uranium isotopes and americium-241. The actinide analysis system carries out these measurements. 8 figs

  5. Actinides and Life's Origins.

    Adam, Zachary

    2007-12-01

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

  6. Radiochemistry and actinide chemistry

    The analysis of trace amounts of actinide elements by means of radiochemistry, is discussed. The similarities between radiochemistry and actinide chemistry, in the case of species amount by cubic cm below 1012, are explained. The parameters which allow to define what are the observable chemical reactions, are given. The classification of radionuclides in micro or macrocomponents is considered. The validity of the mass action law and the partition function in the definition of the average number of species for trace amounts, is investigated. Examples illustrating the results are given

  7. The speciation of actinide ions in concentrated salt solutions

    Many separations of actinide ions involve concentrated solutions. There is additional interest in actinide behavior in brine solutions in the WIPP salt repository. Unfortunately, little understanding exists on the speciation of actinides in concentrated solutions. The author has studied the extraction distribution of Am(III) as a function of concentration of NX salts (N-, Li+, Na+, K+, NH4+ and X = ClO4-, Cl-, NO3-). Analyses of the distribution curves are discussed in terms of hydration, complexation, etc. effects on the Am(III). The variation of the calculated stability constants with ionic strength is compared with the expected variation using Specific-Ion Interaction Theory (SIT)

  8. Actinide separative chemistry

    Actinide separative chemistry has focused very heavy work during the last decades. The main was nuclear spent fuel reprocessing: solvent extraction processes appeared quickly a suitable, an efficient way to recover major actinides (uranium and plutonium), and an extensive research, concerning both process chemistry and chemical engineering technologies, allowed the industrial development in this field. We can observe for about half a century a succession of Purex plants which, if based on the same initial discovery (i.e. the outstanding properties of a molecule, the famous TBP), present huge improvements at each step, for a large part due to an increased mastery of the mechanisms involved. And actinide separation should still focus R and D in the near future: there is a real, an important need for this, even if reprocessing may appear as a mature industry. We can present three main reasons for this. First, actinide recycling appear as a key-issue for future nuclear fuel cycles, both for waste management optimization and for conservation of natural resource; and the need concerns not only major actinide but also so-called minor ones, thus enlarging the scope of the investigation. Second, extraction processes are not well mastered at microscopic scale: there is a real, great lack in fundamental knowledge, useful or even necessary for process optimization (for instance, how to design the best extracting molecule, taken into account the several notifications and constraints, from selectivity to radiolytic resistivity?); and such a need for a real optimization is to be more accurate with the search of always cheaper, cleaner processes. And then, there is room too for exploratory research, on new concepts-perhaps for processing quite new fuels- which could appear attractive and justify further developments to be properly assessed: pyro-processes first, but also others, like chemistry in 'extreme' or 'unusual' conditions (supercritical solvents, sono-chemistry, could be

  9. SPECIFIC SEQUESTERING AGENTS FOR THE ACTINIDES

    Raymond, Kenneth N.; Smith, William L.; Weitl, Frederick L.; Durbin, Patricia W.; Jones, E.Sarah; Abu-Dari, Kamal; Sofen, Stephen R.; Cooper, Stephen R.

    1979-09-01

    This paper summarizes the current status of a continuing project directed toward the synthesis and characterization of chelating agents which are specific for actinide ions - especially Pu(IV) - using a biomimetic approach that relies on the observation that Pu(IV) and Fe(III) has marked similarities that include their biological transport and distribution in mammals. Since the naturally-occurring Fe(III) sequestering agents produced by microbes commonly contain hydroxamate and catecholate functional groups, these groups should complex the actinides very strongly and macrocyclic ligands incorporating these moieties are being prepared. We have reported the isolation and structure analysis of an isostructural series of tetrakis(catecholato) complexes with the general stoichiometry Na{sub 4}[M(C{sub 6}H{sub 4}O{sub 2}){sub 4}] • 21 H{sub 2}O (M = Th, U, Ce, Hf). These complexes are structural archetypes for the cavity that must be formed if an actinide-specific sequestering agent is to conform ideally to the coordination requirements of the central metal ion. The [M(cat){sub 4}]{sup 4-} complexes have the D{sub 2d} symmetry of the trigonal-faced dodecahedron.. The complexes Th [R'C(0)N(O)R]{sub 4} have been prepared where R = isopropyl and R' = t-butyl or neopentyl. The neopentyl derivative is also relatively close to an idealized D{sub 2d} dodecahedron, while the sterically more hindered t-butyl compound is distorted toward a cubic geometry. The synthesis of a series of 2, 3-dihydroxy-benzoyl amide derivatives of linear and cyclic tetraaza- and diazaalkanes is reported. Sulfonation of these compounds improves the metal complexation and in vivo removal of plutonium from test animals. These results substantially exceed the capabilities of compounds presently used for the therapeutic treatment of actinide contamination.

  10. Actinide separation chemistry in nuclear waste streams and materials

    The separation of actinide elements from various waste materials, produced either in nuclear fuel cycles or in past nuclear weapons production, represents a significant issue facing developed countries. Improvements in the efficiencies of the separation processes can be expected to occur as a result of better knowledge of the elements in these complex matrices. The Nuclear Science Committee of the OECD/NEA has established a task force of experts in actinide separation chemistry to review current and developing separation techniques and chemical processes. The report consist of eight chapters. In Chapter 1 the importance of actinide separation chemistry in the fields of waste management and its background are summarized.In Chapter 2 the types of waste streams are classified according to their relative importance, by physical form and by source of actinides. The basic data of actinide chemical thermodynamics, such as oxidation states, hydrolysis, complexation, sorption, Gibbs energies of formation, and volatility, were collected and are presented in Chapter 3. Actinide analyses related to separation processes are also mentioned in this chapter. The state of the art of actinide separation chemistry is classified in three groups, including hydrometallurgy, pyrochemical process and process based on fields, and is described in Chapter 4 along with the relationship of kinetics to separations. In Chapter 5 basic chemistry research needs and the inherent limitation on separation processes are discussed. Prioritization of research and development is discussed in Chapter 6 in the context of several attributes of waste management problems. These attributes include: mass or volume of waste; concentration of the actinide in the waste; expected difficulty of treating the wastes; short-term hazard of the waste; long-term hazard of the waste; projected cost of treatment; amount of secondary waste. Based on the priority, recommendations were made for the direction of future research

  11. Synergistic extraction of actinides : Part I. Hexa-and pentavalent actinides

    A detailed discussion on the reported literature on the synergistic extraction of hexa- and pentavalent actinide ions, by different combinations of extractants and from different aqueous media, is presented. Structural aspects of the various complexes involved in synergism also are reviewed. A short account of the applications based on synergistic extraction is also given. (author)

  12. Interaction of actinides with amino acids: from peptides to proteins

    Structural information on complexes of actinides with molecules of biological interest is required to better understand the mechanisms of actinides transport in living organisms, and can contribute to develop new decorporation treatments. Our study is about Th(IV), Np(IV), Pu(IV) and uranyl(VI) cations, which have a high affinity for some protein domains, and Fe(III), which is the natural cation of these biological systems. In this work, chelation of actinides has been brought to light with UV-visible-Near Infra Red spectroscopy, NMR, EPR, and ultrafiltration. Determination of the structure of the complexation site has been undertaken with Exafs measurements, and of the tertiary structure of the protein with SANS measurements. The first approach was to describe the interaction modes between actinides and essential chemical functions of proteins. Thus, the Ac-AspAspProAspAsp-NH2 peptide was studied as a possible chelate of actinides. Polynuclear species with μ-oxo or μ-hydroxo bridges were identified. The iron complex is binuclear, and the actinide ones have a higher nuclearity. The second approach was to study a real case of complexation of actinide with a protein: transferrin. Results show that around physiological ph a mononuclear complex is formed with Np(IV) and Pu(IV), while transferrin does not complex Th(IV) in the same conditions. Characteristic distances of M-transferrin complexes (M = Fe, Np, Pu) were determined. Moreover, the protein seems to be in its close conformation with Pu(IV), and in its open form with Np(IV) and UO22+. (author)

  13. PF-4 actinide disposition strategy

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

  14. Photochemistry of the actinides

    It has been found that all three major actinides have a useful variety of photochemical reactions which could be used to achieve a separations process that requires fewer reagents. Several features merit enumerating: (1) Laser photochemistry is not now as uniquely important in fuel reprocessing as it is in isotopic enrichment. The photochemistry can be successfully accomplished with conventional light sources. (2) The easiest place to apply photo-reprocessing is on the three actinides U, Pu, and Np. The solutions are potentially cleaner and more amenable to photoreactions. (3) Organic-phase photoreactions are probably not worth much attention because of the troublesome solvent redox chemistry associated with the photochemical reaction. (4) Upstream process treatment on the raffinate (dissolver solution) may never be too attractive since the radiation intensity precludes the usage of many optical materials and the nature of the solution is such that light transmission into it might be totally impossible

  15. Recovering actinide values

    Actinide values are recovered from sodium carbonate scrub waste solutions containing these and other values along with organic compounds resulting from the radiolytic and hydrolytic degradation of neutral organophosphorus extractants such as tri-n butyl phosphate (TBP) and dihexyl-N, N-diethyl carbamylmethylene phosphonate (DHDECMP) which have been used in the reprocessing of irradiated nuclear reactor fuels. The scrub waste solution is 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 can be recycled after stripping the degradation products with a neutral sodium carbonate solution. (author)

  16. Actinides: why are they important biologically

    The following topics are discussed: actinide elements in energy systems; biological hazards of the actinides; radiation protection standards; and purposes of actinide biological research with regard to toxicity, metabolism, and therapeutic regimens

  17. Photoelectron spectra of actinide compounds

    A brief overview of the application of photoelectron spectroscopy is presented for the study of actinide materials. Phenomenology as well as specific materials are discussed with illustrative examples

  18. Sequential separation of actinides and lanthanides by extraction chromatography using a CMPO-TBP/XAD7 column

    CMPO/TBP sorbed on Amberlite XAD7 resin was used for the separation of actinides and lanthanides from nitric acid solutions by extraction chromatography. The distribution ratios of actinides and lanthanide fission products (Ce, Eu) as a function of acid concentration and some complexing agents were determined. In strong HNO3 medium (> 1 mol/l) the tri-, tetra- and hexavalent actinides as well as the lanthanides have shown great affinity for the CMPO/TBP/XAD7 sorbent. The same behavior was found in HCl medium except for trivalent actinides and lanthanides which show lower distribution values in the same acid range. The effect of some complexing agents as DTPA and ammonium oxalate were also investigated. In DTPA only hexavalent actinides showed higher distribution value. On the basis of these differences, an alternative procedure for actinide-lanthanide separation and actinides from each other is proposed. (author)

  19. Interaction of actinide cations with synthetic polyelectrolytes

    The binding of Am+3, Th+4 and UO2+2 to polymaleic acid, polyethylenemaleic acid and polymethylvinylethermaleic acid has been measured by a solvent extraction technique at 250C and either 0.02 or 0.10 M ionic strength. The solutions were buffered over a pH range such that the percent of carboxylate groups ionized ranged from 25 to 74%. The binding was described by two constants, β1 and β2, which were evaluated after correction for complexation of the actinide cations by acetate and hydrolysis. For comparable degrees of ionization, all three polyelectrolytes showed similar binding strengths. In general, these results indicated that the binding of actinides to these synthetic polyelectrolytes is basically similar to that of natural polyelectrolytes such as humic and fulvic acids. (orig.)

  20. Aqueous complexes of lanthanides(III) and actinides(III) with the carbonate and sulphate ions. Thermodynamic study by time-resolved laser-induced fluorescence spectroscopy and electro-spray-ionisation mass spectrometry

    The prediction of the environmental impact of a possible geological disposal of radioactive wastes is supported by the thermodynamic modelling of the radionuclides behaviour in the groundwater. In this framework, the analogy between lanthanides and actinides(III) is confirmed by a critical analysis of the literature and the comparison with experimental results obtained here. The limiting complex, Eu(CO3)33-, is identified by solubility measurements in Na2CO3 solutions. Then the formation constants of the complexes Eu(CO3)i3-2i (i=1-3) and Eu(SO4)i3-2i (i=1-2) are measured by TRLFS. The formation of aqueous LaSO4+ is studied by ESI-MS and is in good agreement with the expected speciation. The enthalpy and entropy of the reaction Cm(CO3)2- + CO32- ↔ Cm(CO3)33- are deduced from TRLFS measurements of the equilibrium constant between 10 and 70 C. The ionic strength effect is calculated using the SIT formula. (author)

  1. Optical techniques for actinide research

    In recent years, substantial gains have been made in the development of spectroscopic techniques for electronic properties studies. These techniques have seen relatively small, but growing, application in the field of actinide research. Photoemission spectroscopies, reflectivity and absorption studies, and x-ray techniques will be discussed and illustrative examples of studies on actinide materials will be presented

  2. Characterization of actinides in simulated alkaline tank waste sludges and leach solutions

    Current plans call for an alkaline scrub of actinide-bearing sludges in the Hanford Waste tanks prior to their incorporation in glass waste forms. Though it is assumed that actinides will remain in the sludge phase during this procedure, this assumption is based on insufficient supporting thermodynamic and kinetic data. In this project the authors will investigate the fundamental chemistry of actinides in strongly alkaline solution and solid phases to strengthen the foundation and identify potential limitations of this approach. They will focus on the characterization of the leaching of actinides from simulated BiPO4, REDOX, and PUREX sludges, the identification of actinide mineral phases in the sludge simulants, and the possible solubilization of actinides by complexation and radiolysis effects. This program will provide new fundamental information on the chemical behavior and speciation of uranium, neptunium, plutonium, and americium in simulated alkaline tank waste sludges and alkaline scrub liquors. Sludge simulants will be prepared from the appropriate matrix components using published data for guidance. Actinide ions will be introduced in the oxidation states pertinent to process conditions. The authors will characterize the speciation of the actinides in the sludges using a variety of techniques. In parallel studies, they will address the chemistry of actinide ions in alkaline solutions, principally those containing chelating agents. The third critical element of this research will be to assess the impact of radiolysis on actinide behavior. By correlating actinide speciation in the solid and solution phases with sludge composition, it will be possible to predict conditions favoring mobilization (or immobilization) of actinide ions during sludge washing. The new information will increase predictability of actinide behavior during tank sludge washing, and so contribute to minimization of the volume of high level waste created

  3. The Actinide User Laboratory at ITU-Karlsruhe

    The interest in actinide materials arises mainly from their fundamental physics and chemistry and the complexity of their behaviour as illustrated through numerous papers of this conference. Such research also impacts on nuclear fuel technology and the problem of nuclear waste and long-term storage. Despite the great interest in the actinides the number of Laboratories equipped to handle these materials is steadily decreasing due to heavy and costly security requirements. The Institute for Transuranium Elements (ITU) is a Laboratory of the Joint Research Centre of the European Commission which addresses a large number of questions related to actinides, both basic and applied, and is the only non-classified Laboratory in Europe where research on appreciable quantities of transuranium materials is conducted across a wide range of chemistry and physics. In order to keep alive an essential and exciting field of research in physic and chemistry, we have decided to offer access to our facilities to external users through an Actinide User Laboratory. Materials preparation facilities and a suite of instruments, together with expert technical assistance, are available for conducting basic or applied research studies. The Actinide User Laboratory is selected as a user facility to participate in the European Community - Access to Research Infrastructures action of the Improving Human Potential Programme (IHP) which supports access to our actinide facility for the selected users teams, travel and subsistence fees of visiting scientists. The programme is open to EC users and to scientists of the associated states. (author)

  4. Actinide production in 136Xe bombardments of 249Cf

    The production cross sections for the actinide products from 136Xe bombardments of 249Cf at energies 1.02, 1.09, and 1.16 times the Coulomb barrier were determined. Fractions of the individual actinide elements were chemically separated from recoil catcher foils. The production cross sections of the actinide products were determined by measuring the radiations emitted from the nuclides within the chemical fractions. The chemical separation techniques used in this work are described in detail, and a description of the data analysis procedure is included. The actinide production cross section distributions from these 136Xe + 249Cf bombardments are compared with the production cross section distributions from other heavy ion bombardments of actinide targets, with emphasis on the comparison with the 136Xe + 248Cm reaction. A technique for modeling the final actinide cross section distributions has been developed and is presented. In this model, the initial (before deexcitation) cross section distribution with respect to the separation energy of a dinuclear complex and with respect to the Z of the target-like fragment is given by an empirical procedure. It is then assumed that the N/Z equilibration in the dinuclear complex occurs by the transfer of neutrons between the two participants in the dinuclear complex. The neutrons and the excitation energy are statistically distributed between the two fragments using a simple Fermi gas level density formalism. The resulting target-like fragment initial cross section distribution with respect to Z, N, and excitation energy is then allowed to deexcite by emission of neutrons in competition with fission. The result is a final cross section distribution with respect to Z and N for the actinide products. 68 refs., 33 figs., 6 tabs

  5. Quest for Environmentally-Benign Ligands for Actinide Separations: Thermodynamic, Spectroscopic, and Structural Characterization of U(VI) Complexes with Oxa-Diamide and Related Ligands

    Advanced Light Source; Tian, Guoxin; Rao, Linfeng; Teat, Simon J.; Liu, Guokui

    2009-01-05

    Complexation of U(VI) with N,N,N{prime},N{prime}-tetramethyl-3-oxa-glutaramide (TMOGA) and N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) was studied in comparison with their dicarboxylate analog, oxydiacetic acid (ODA). Thermodynamic parameters, including stability constants, enthalpy and entropy of complexation, were determined by spectrophotometry, potentiometry and calorimetry. Single-crystal X-ray diffractometry, EXAFS spectroscopy, FT-IR absorption and laser-induced luminescence spectroscopy were used to obtain structural information on the U(VI) complexes. Like ODA, TMOGA and DMOGA form tridentate U(VI) complexes, with three oxygen atoms (the amide, ether and/or carboxylate oxygen) coordinating to the linear UO{sub 2}{sup 2+} cation via the equatorial plane. The stability constants, enthalpy and entropy of complexation all decrease in the order ODA > DMOGA > TMOGA, showing that the complexation is entropy driven and the substitution of a carboxylate group with an amide group reduces the strength of complexation with U(VI) due to the decrease in the entropy of complexation. The trend in the thermodynamic stability of the complexes correlates very well with the structural and spectroscopic data obtained by single crystal XRD, FT-IR and laser-induced luminescence spectroscopy.

  6. Actinide behavior in a freshwater pond

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

  7. Study of actinides paramagnetism in solution by NMR

    Paramagnetism of actinides in solution was characterized by NMR according to two approaches. In the first approach, magnetic susceptibilities of the most stable ions in solution from uranium to californium, for various oxidation states (U(IV)-U(VI), Np(IV)-Np(V)-Np(VI), Pu(III)-Pu(IV)-Pu(VI), Am(III), Cm(III) et Cf(III)), were measured by NMR by using the Evans' method. In perchloric medium, the paramagnetic behavior of actinide cations showed significant deviations compared with lanthanides, particularly for cations at oxidation state (+III) and (+IV). In hydrochloric and nitric media, it was observed that actinide magnetic behaviors followed the order M4+ ≥ MO2+2 ≥ M3+ ≥ MO2+, corresponding to the generally admitted order concerning the complexing power of actinide cations. It was demonstrated that the presence of chloride and nitrate in solution could have an large impact on the magnetic behavior of these cations. In the second approach, chemical shifts of actinide(IV)-di-picolinate paramagnetic complexes were studied and analyzed in dimethylformamide. In these experimental conditions, the only presence of the oxidation state (+IV) in solution as well as the stability of the latter on the NMR analysis timescale were verified, in presence or not of the ligand. Paramagnetic chemical shifts of the 1:3 limit complex were studied at various temperatures. The method of separation of the contact and dipolar contributions usually used for lanthanide(III) complexes have proved not applicable in the case of actinide(IV) complexes. (author)

  8. Managing Inventories of Heavy Actinides

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

  9. Advanced Aqueous Separation Systems for Actinide Partitioning

    Nash, Ken [Washington State Univ., Pullman, WA (United States); Martin, Leigh [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lumetta, Gregg [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-04-02

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

  10. Concentration of actinides in the food chain

    Considerable concern is now being expressed over the discharge of actinides into the environment. This report presents a brief review of the chemistry of the actinides and examines the evidence for interaction of the actinides with some naturally-occurring chelating agents and other factors which might stimulate actinide concentration in the food chain of man. This report also reviews the evidence for concentration of actinides in plants and for uptake through the gastrointestinal tract. (author)

  11. Calorimetric assay of minor actinides

    Rudy, C.; Bracken, D.; Cremers, T.; Foster, L.A.; Ensslin, N.

    1996-12-31

    This paper reviews the principles of calorimetric assay and evaluates its potential application to the minor actinides (U-232-4, Am-241, Am- 243, Cm-245, Np-237). We conclude that calorimetry and high- resolution gamma-ray isotopic analysis can be used for the assay of minor actinides by adapting existing methodologies for Pu/Am-241 mixtures. In some cases, mixtures of special nuclear materials and minor actinides may require the development of new methodologies that involve a combination of destructive and nondestructive assay techniques.

  12. Calorimetric assay of minor actinides

    This paper reviews the principles of calorimetric assay and evaluates its potential application to the minor actinides (U-232-4, Am-241, Am- 243, Cm-245, Np-237). We conclude that calorimetry and high- resolution gamma-ray isotopic analysis can be used for the assay of minor actinides by adapting existing methodologies for Pu/Am-241 mixtures. In some cases, mixtures of special nuclear materials and minor actinides may require the development of new methodologies that involve a combination of destructive and nondestructive assay techniques

  13. Mathematical modelling of the effects of aerobic and anaerobic chelate biodegradation on actinide speciation

    Biodegradation of natural and anthropogenic chelating agents directly and indirectly affects the speciation, and hence, the mobility of actinides in subsurface environments. We combined mathematical modelling with laboratory experimentation to investigate the effects of aerobic and anaerobic chelate biodegradation on actinide [Np(IV/V), Pu(IV)] speciation. Under aerobic conditions, nitrilotriacetic acid (NTA) biodegradation rates were strongly influenced by the actinide concentration. Actinide-chelate complexation reduced the relative abundance of available growth substrate in solution and actinide species present or released during chelate degradation were toxic to the organisms. Aerobic bioutilization of the chelates as electron-donor substrates directly affected actinide speciation by releasing the radionuclides from complexed form into solution, where their fate was controlled by inorganic ligands in the system. Actinide speciation was also indirectly affected by pH changes caused by organic biodegradation. The two concurrent processes of organic biodegradation and actinide aqueous chemistry were accurately linked and described using CCBATCH, a computer model developed at Northwestern University to investigate the dynamics of coupled biological and chemical reactions in mixed waste subsurface environments. CCBATCH was then used to simulate the fate of Np during anaerobic citrate biodegradation. The modelling studies suggested that, under some conditions, chelate degradation can increase Np(IV) solubility due to carbonate complexation in closed aqueous systems. (orig.)

  14. Mathematical modeling of the effects of aerobic and anaerobic chelate biodegradation on actinide speciation

    Biodegradation of natural and anthropogenic chelating agents directly and indirectly affects the speciation, and, hence, the mobility of actinides in subsurface environments. We combined mathematical modeling with laboratory experimentation to investigate the effects of aerobic and anaerobic chelate biodegradation on actinide [Np(IV/V), Pu(IV)] speciation. Under aerobic conditions, nitrilotriacetic acid (NTA) biodegradation rates were strongly influenced by the actinide concentration. Actinide-chelate complexation reduced the relative abundance of available growth substrate in solution and actinide species present or released during chelate degradation were toxic to the organisms. Aerobic bio-utilization of the chelates as electron-donor substrates directly affected actinide speciation by releasing the radionuclides from complexed form into solution, where their fate was controlled by inorganic ligands in the system. Actinide speciation was also indirectly affected by pH changes caused by organic biodegradation. The two concurrent processes of organic biodegradation and actinide aqueous chemistry were accurately linked and described using CCBATCH, a computer model developed at Northwestern University to investigate the dynamics of coupled biological and chemical reactions in mixed waste subsurface environments. CCBATCH was then used to simulate the fate of Np during anaerobic citrate biodegradation. The modeling studies suggested that, under some conditions, chelate degradation can increase Np(IV) solubility due to carbonate complexation in closed aqueous systems

  15. Actinides and the environment

    The book combines in one volume the opinions of experts regarding the interaction of radionuclides with the environment and possible ways to immobilize and dispose of nuclear waste. The relevant areas span the spectrum from pure science, such as the fundamental physics and chemistry of the actinides, geology, environmental transport mechanisms, to engineering issues such as reactor operation and the design of nuclear waste repositories. The cross-fertilization between these various areas means that the material in the book will be accessible to seasoned scientists who may wish to obtain an overview of the current state of the art in the field of environmental remediation of radionuclides, as well as to beginning scientists embarking on a career in this field. refs

  16. Extraction of DBP and MBP from actinides: application to the recovery of actinides from TBP--Na2CO3 scrub solutions

    A flowsheet for the recovery of actinides from TBP--Na2CO3 scrub waste solutions has been developed, based on batch extraction data, and tested, using laboratory scale counter-current extraction techniques. The process utilizes 2-ethyl-1-hexanol (2-EHOH) to extract the TBP degradation products (HDBP and H2MBP) from acidified Na2CO3 scrub waste leaving the actinides in the aqueous phase. Dibutyl and monobutyl phosphoric acids are attached to the 2-EHOH molecules through hydrogen bonds. These hydrogen bonds also diminish the ability of the HDBP and H2MBP to complex actinides and thus all actinides remain in the aqueous raffinate. Dilute sodium hydroxide solutions can be used to back-extract the dibutyl and monobutyl phosphoric acid esters as their sodium salts. The 2-EHOH can then be recycled. After extraction of the acidified carbonate waste with 2-EHOH, the actinides may be readily extracted from the raffinate with DHDECMP or, in the case of tetra- and hexavalent actinides, with TBP. The alcohol extraction (ARALEX) process is relatively simple and involves inexpensive and readily available chemicals. The ARALEX process can also be applied to other actinide waste streams which contain appreciable concentrations of polar organic compounds that interfere with conventional actinide ion exchange and liquid--liquid extraction procedures

  17. Selective extraction of trivalent actinides from lanthanides with dithiophosphinic acids and tributylphosphate

    A variety of chemical systems have been developed to separate trivalent actinides from lanthanides based on the slightly stronger complexation of the trivalent actinides with ligands that contain soft donor atoms. The greater stability of the actinide complexes in these systems has often been attributed to a slightly greater covalent bonding component for the actinide ions relative to the lanthanide ions. The authors have investigated several synergistic extraction systems that use ligands with a combination of oxygen and sulfur donor atoms that achieve a good group separation of the trivalent actinides and lanthanides. For example, the combination of dicyclohexyldithiophosphinic acid and tributylphosphate has shown separation factors of up to 800 for americium over europium in a single extraction stage. Such systems could find application in advanced partitioning schemes for nuclear waste

  18. Environmental research on actinide elements

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

  19. Selective extraction of actinides from high level liquid wastes. Study of the possibilities offered by the Redox properties of actinides

    Partitioning of high level liquid wastes coming from nuclear fuel reprocessing by the PUREX process, consists in the elimination of minor actinides (Np, Am, and traces of Pu and U). Among the possible processes, the selective extraction of actinides with oxidation states higher than three is studied. First part of this work deals with a preliminary step; the elimination of the ruthenium from fission products solutions using the electrovolatilization of the RuO4 compound. The second part of this work concerns the complexation and oxidation reactions of the elements U, Np, Pu and Am in presence of a compound belonging to the insaturated polyanions family: the potassium phosphotungstate. For actinide ions with oxidation state (IV) complexed with phosphotungstate anion the extraction mechanism by dioctylamine was studied and the use of a chromatographic extraction technic permitted successful separations between tetravalents actinides and trivalents actinides. Finally, in accordance with the obtained results, the basis of a separation scheme for the management of fission products solutions is proposed

  20. Properties of minor actinide nitrides

    The present status of the research on properties of minor actinide nitrides for the development of an advanced nuclear fuel cycle based on nitride fuel and pyrochemical reprocessing is described. Some thermal stabilities of Am-based nitrides such as AmN and (Am, Zr)N were mainly investigated. Stabilization effect of ZrN was cleary confirmed for the vaporization and hydrolytic behaviors. New experimental equipments for measuring thermal properties of minor actinide nitrides were also introduced. (author)

  1. The first crystal structure of an actinide complex of the macrocyclic ligand DOTA: a two-dimensional uranyl-organic framework

    Reaction of excess uranyl nitrate with DOTA (H4L) under hydrothermal conditions gave the complex [(UO2)2(H2L)(C2O4)(H2O)2]· 6H2O (1), in which the oxalato ligand was generated in situ. Each H2L2- ligand is bound to four uranyl groups, further oxalato-bridging giving rise to corrugated layers. This result shows the interest of DOTA as a square assembler. (author)

  2. Modeling of retention of some fission products and actinides by ion-exchange chromatography with a complexing agent. Application to the determination of selectivity coefficients

    For an accurate determination of the isotopic and elemental composition of americium (Am), curium (Cm), neodymium (Nd) and cesium (Cs) in spent nuclear fuels, performed by Thermal Ionization Mass Spectrometry (TIMS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), it is necessary to separate these elements before analysis. This separation is mandatory because of isobaric interferences between americium and curium, neodymium and samarium (Sm) and between cesium and barium (Ba). This is the reason why Ba and Sm are analyzed with the other four elements. Separation is carried out by cation-exchange chromatography on a silica-based stationary phase in the presence of a complexing eluent. The complexing agent is 2-hydroxy-2-methyl butanoic acid (HMB), a monoprotic acid (HL) with a pKa of 3.6. Cations (Mn+) interact with it to form MLy(n-y)+ complexes. Optimization of chromatographic separation conditions requires monitoring of the pH and eluent composition. The influence of each parameter on metal ion retention and on selectivity was investigated. The first studies on standard solutions with Sm(III), Nd(III), Cs(I) and Ba(II) showed that four conditions allow efficient separation. However, only one allows good separation with a real solution of spent nuclear fuels. This condition is a chelating agent concentration of 0.1 mol.l-1 and a pH of 4.2. With the other conditions, co-elution is observed for Cs(I) and Am(III). The overall results were used to study the retention mechanisms. The aim of this modeling is a closer knowledge of the form in which (Mn+ and/or MLy(n-y)+...) each cationic element is extracted into the stationary phase. In fact, while cations can exist in the eluent in various forms depending on the analytical conditions, their forms may be different in the stationary phase. (authors)

  3. One ligand fits all: lanthanide and actinide sandwich complexes comprising the 1,4-bis(trimethylsilyl)cyclooctatetraenyl (=COT′′) ligand

    RAUSCH Janek; Apostolidis, Christos; WALTER OLAF; Lorenz, Volker; HRIB Cristian; Hilfert, Liane; KÜHLING Marcel; BUSSE Sabine; Edelmann, Frank

    2015-01-01

    The series of anionic lanthanide(III) sandwich complexes of the type [Ln(COT'')2]- (COT'' = 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion) has been largely extended by the synthesis of eight new derivatives ranging from lanthanum to lutetium. The new compounds [Li(DME)3][Ln(COT'')2] (Ln = Y (1), La (2), Pr (3), Gd (4), Tm (6), Lu (8)) and [Li(THF)4][Ln(COT'')2] (Ln = Ho (5), Tm (7)) were prepared in good yields following a straightforward synthetic protocol which involves treatment of LnC...

  4. Molecular and electronic structure of actinide hexa-cyanoferrates

    The goal of this work is to improve our knowledge on the actinide-ligand bond properties. To this end, the hexacyanoferrate entities have been used as pre-organized ligand. We have synthesized, using mild chemistry, the following series of complexes: AnIV[FeII(CN)6].xH2O (An = Th, U, Np, Pu); AmIII[FeIII(CN)6].xH2O; Pu III[CoIII(CN)6].xH2O and K(H?)AnIII[FeII(CN)6].xH2O (An = Pu, Am). The metal oxidation states have been obtained thanks to the νCN, stretching vibration and to the actinide LIII absorption edge studies. As Prussian Blue, the AnIV[FeII(CN)6].xH2O (An = Np, Pu) are class II of Robin and Day compounds. X-ray Diffraction has shown besides that these complexes crystallize in the P63/m space group, as the isomorphic LaKFe(CN)6.4H2O complex used as structural model. The EXAFS oscillations at the iron K edge and at the An LIII edge allowed to determine the An-N, An-O, Fe-C and Fe-N distances. The display of the multiple scattering paths for both edges explains the actinide contribution absence at the iron edge, whereas the iron signature is present at the actinide edge. We have shown that the actinide coordination sphere in actinides hexa-cyanoferrates is comparable to the one of lanthanides. However, the actinides typical behavior towards the lanthanides is brought to the fore by the AnIV versus LnIII ions presence in this family of complexes. Contrarily to the 4f electrons, the 5f electrons influence the electronic properties of the compounds of this family. However, the gap between the An-N and Ln-N distances towards the corresponding metals ionic radii do not show any covalence bond evolution between the actinide and lanthanide series. (author)

  5. Actinide structural studies. Pt. 17. The crystal and molecular structures of four uranyl(VI) complexes with N,N-dialkyldithiocarbamate ligands

    Alcock, N.W.; Pennington, M.

    1989-03-01

    The synthesis and crystal structures are reported of four dithiocarbamates of general formula (NR/sub 4/) (UO/sub 2/(dtc)/sub 3/): (1; R = Et, dtc N-tetramethylenedithiocarbamate (C/sub 4/H/sub 8/NCS/sub 2/)), (2; R = Et, dtc=N-pentamethylenedithiocarbamate (C/sub 5/H/sub 10/NCS/sub 2/)), (3; R=Et, dtc = N,N-dimethyldithiocarbamate (Me/sub 2/NCS/sub 2/)), (4; R = Me, dtc = N,N-diethyldithiocarbamate (Et/sub 2/NCS/sub 2/)). All four complexes exhibit hexagonal bipyramidal geometry about the central uranium atom, involving three bidentate dithiocarbamate molecules co-ordinated in the equatorial plane of the uranyl ion. The U-O(UO/sub 2//sup 2+/) bond lengths are in the range 1.734(11) - 1.862(12) A. The U-S distances are almost equal in all the complexes (2.946(2) A mean). The equatorial planes show significant puckering to accommodate the six sulphur atoms (maximum deviation 0.32(5) A). Intra-ligand S....S distances (ligand bite) are in the range 2.856(4)-2.891(4) A and inter-ligand distances are in the range 2.911(4)-3.109(4) A.

  6. Advancing the scientific basis of trivalent actinide-lanthanide separations

    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-). These 'soft-donor' atoms have exhibited usable selectivity in their 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)

  7. THERMODYNAMICS OF THE ACTINIDES

    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 from 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)

  8. Molecular and electronic structure of actinide hexa-cyanoferrates; Structure moleculaire et electronique des hexacyanoferrates d'actinides

    Bonhoure, I

    2001-07-01

    The goal of this work is to improve our knowledge on the actinide-ligand bond properties. To this end, the hexacyanoferrate entities have been used as pre-organized ligand. We have synthesized, using mild chemistry, the following series of complexes: An{sup IV}[Fe{sup II}(CN){sub 6}].xH{sub 2}O (An = Th, U, Np, Pu); Am{sup III}[Fe{sup III}(CN){sub 6}].xH{sub 2}O; Pu {sup III}[Co{sup III}(CN){sub 6}].xH{sub 2}O and K(H?)An{sup III}[Fe{sup II}(CN){sub 6}].xH{sub 2}O (An = Pu, Am). The metal oxidation states have been obtained thanks to the {nu}{sub CN}, stretching vibration and to the actinide L{sub III} absorption edge studies. As Prussian Blue, the An{sup IV}[Fe{sup II}(CN){sub 6}].xH{sub 2}O (An = Np, Pu) are class II of Robin and Day compounds. X-ray Diffraction has shown besides that these complexes crystallize in the P6{sub 3}/m space group, as the isomorphic LaKFe(CN){sub 6}.4H{sub 2}O complex used as structural model. The EXAFS oscillations at the iron K edge and at the An L{sub III} edge allowed to determine the An-N, An-O, Fe-C and Fe-N distances. The display of the multiple scattering paths for both edges explains the actinide contribution absence at the iron edge, whereas the iron signature is present at the actinide edge. We have shown that the actinide coordination sphere in actinides hexa-cyanoferrates is comparable to the one of lanthanides. However, the actinides typical behavior towards the lanthanides is brought to the fore by the An{sup IV} versus Ln{sup III} ions presence in this family of complexes. Contrarily to the 4f electrons, the 5f electrons influence the electronic properties of the compounds of this family. However, the gap between the An-N and Ln-N distances towards the corresponding metals ionic radii do not show any covalence bond evolution between the actinide and lanthanide series. (author)

  9. Effects of humic substances on the migration of raidionuclides : Complexation of actinides with humic substances in natural aquatic systems. Appendix IV

    The interaction constants obtained by the Dialysis Equilibrium Technique are smaller than those obtained by the Schubert Method. This difference is ascribed to the diffusion of organic matter through the membrane. This effects an overestimation of the free Eu concentration, and further results in an underestimation of the interaction constant. Corrections failed. However, by using a competitive ligand as e.g. oxalate it was proven that in the future interaction constants can be measured accurately using the Dialysis Technique. Both methods allowed to conclude the following: 1) By using the Eu complexation capacity, determined at the considered pH, as ligand concentration, the pH dependency seems to vanish. 2) A dependency of the interaction constant with the ionic strength cannot a priori be rejected. Lower ionic strength conditions result in higher interaction constants. 3) The interaction constants depend on the Eu occupancy below 1% Eu occupancy. Lower Europium loadings give rise to slightly higher interaction constants. At high Europium occupancy (Dialysis Equilibrium Technique), the occupancy dependency was clearly demonstrated. (orig.)

  10. Actinide burning and waste disposal

    Here we review technical and economic features of a new proposal for a synergistic waste-management system involving reprocessing the spent fuel otherwise destined for a U.S. high-level waste repository and transmuting the recovered actinides in a fast reactor. The proposal would require a U.S. fuel reprocessing plant, capable of recovering and recycling all actinides, including neptunium americium, and curium, from LWR spent fuel, at recoveries of 99.9% to 99.999%. The recovered transuranics would fuel the annual introduction of 14 GWe of actinide-burning liquid-metal fast reactors (ALMRs), beginning in the period 2005 to 2012. The new ALMRs would be accompanied by pyrochemical reprocessing facilities to recover and recycle all actinides from discharged ALMR fuel. By the year 2045 all of the LWR spent fuel now destined f a geologic repository would be reprocessed. Costs of constructing and operating these new reprocessing and reactor facilities would be borne by U.S. industry, from the sale of electrical energy produced. The ALMR program expects that ALMRs that burn actinides from LWR spent fuel will be more economical power producers than LWRs as early as 2005 to 2012, so that they can be prudently selected by electric utility companies for new construction of nuclear power plants in that era. Some leaders of DOE and its contractors argue that recovering actinides from spent fuel waste and burning them in fast reactors would reduce the life of the remaining waste to about 200-300 years, instead of 00,000 years. The waste could then be stored above ground until it dies out. Some argue that no geologic repositories would be needed. The current view expressed within the ALMR program is that actinide recycle technology would not replace the need for a geologic repository, but that removing actinides from the waste for even the first repository would simplify design and licensing of that repository. A second geologic repository would not be needed. Waste now planned

  11. 33rd Actinide Separations Conference

    McDonald, L M; Wilk, P A

    2009-05-04

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

  12. Reversible optical sensor for the analysis of actinides in solution

    In this work is presented a concept of reversible optical sensor for actinides. It is composed of a p doped conducing polymer support and of an anion complexing the actinides. The chosen conducing polymer is the thiophene-2,5-di-alkoxy-benzene whose solubility and conductivity are perfectly known. The actinides selective ligand is a lacunar poly-oxo-metallate such as P2W17O6110- or SiW11O398- which are strong anionic complexing agents of actinides at the oxidation state (IV) even in a very acid medium. The sensor is prepared by spin coating of the composite mixture 'polymer + ligand' on a conducing glass electrode and then tested towards its optical and electrochemical answer in presence of uranium (IV). The absorption change due to the formation of cations complexes by poly-oxo-metallate reveals the presence of uranium (IV). After the measurement, the sensor is regenerated by anodic polarization of the support and oxidation of the uranium (IV) into uranium (VI) which weakly interacts with the poly-oxo-metallate and is then released in solution. (O.M.)

  13. Thermal-hydraulics of actinide burner reactors

    As a part of conceptual study of actinide burner reactors, core thermal-hydraulic analyses were conducted for two types of reactor concepts, namely (1) sodium-cooled actinide alloy fuel reactor, and (2) helium-cooled particle-bed reactor, to examine the feasibility of high power-density cores for efficient transmutation of actinides within the maximum allowable temperature limits of fuel and cladding. In addition, calculations were made on cooling of actinide fuel assembly. (author)

  14. ALMR potential for actinide consumption

    The Advanced Liquid Metal Reactor (ALMR) is a US Department of Energy (DOE) sponsored fast reactor design based on the Power Reactor, Innovative Small Module (PRISM) concept originated by General Electric. This reactor combines a high degree of passive safety characteristics with a high level of modularity and factory fabrication to achieve attractive economics. The current reference design is a 471 MWt modular reactor fueled with ternary metal fuel. This paper discusses actinide transmutation core designs that fit the design envelope of the ALMR and utilize spent LWR fuel as startup material and for makeup. Actinide transmutation may be accomplished in the ALMR core by using either a breeding or burning configuration. Lifetime actinide mass consumption is calculated as well as changes in consumption behavior throughout the lifetime of the reactor. Impacts on system operational and safety performance are evaluated in a preliminary fashion. Waste disposal impacts are discussed. (author)

  15. Archetypes for actinide-specific chelating agents

    The complexes of uranium and thorium with monomeric hydroxamic acids can serve as archetypes for an optimized macrochelate designed for tetravalent actinides. The eight-coordinate complexes, Th(i-PrN(O)C(O)R)4, where R = tert-butyl or R = neopentyl, have been synthesized and their structures have been determined by x-ray diffraction. The bulky alkyl substituents impart remarkable volatility and hydrocarbon solubility to these complexes, and the steric interactions of these substituents largely determine the structures. When R = tert-butyl, the substituents occupy the corners of a tetrahedron and force the complex into a distorted cubic geometry with crystallographic S4 symmetry. Insertion of a methylene group between the carbonyl carbon and the tert-butyl group relaxes the steric requirements, and the coordination polyhedron of the neopentyl derivative is close to the mmmm isomer of the trigonal-faced dodecahedron. Uranium tetrachloride was quantitatively oxidized via an oxygen transfer reaction with two equivalents of N-phenylbenzohydroxamic acid anion (PBHA) in tetrahydrofuran (THF) to form UO2 Cl(PBHA)(THF)2 and benzanilide. The structure of the uranyl complex has been determined from x-ray diffraction data; the linear uranyl ion is surrounded by a planar pentagonal array composed of two hydroxamate oxygen atoms, a chloride ion and two THF oxygens, such that the chloride ion is opposite the hydroxamate group. That the THF and phenyl rings are twisted from this equatorial plane limits the molecular geometry to that of the C1 point group. Some aspects of the chemistry of hydroxamic acids and of their incorporation into molecules that may serve as precursors of tetravalent actinide specific sequestering agents have also been investigated

  16. Orbital effects in actinide systems

    Actinide magnetism presents a number of important challenges; in particular, the proximity of 5f band to the Fermi energy gives rise to strong interaction with both d and s like conduction electrons, and the extended nature of the 5f electrons means that they can interact with electron orbitals from neighboring atoms. Theory has recently addressed these problems. Often neglected, however, is the overwhelming evidence for large orbital contributions to the magnetic properties of actinides. Some experimental evidence for these effects are presented briefly in this paper. They point, clearly incorrectly, to a very localized picture for the 5f electrons. This dichotomy only enhances the nature of the challenge

  17. Fabrication of actinide mononitride fuel

    Fabrication of actinide mononitride fuel in JAERI is summarized. Actinide mononitride and their solid solutions were fabricated by carbothermic reduction of the oxides in N2 or N2-H2 mixed gas stream. Sintering study was also performed for the preparation of pellets for the property measurements and irradiation tests. The products were characterized to be high-purity mononitride with a single phase of NaCl-type structure. Moreover, fuel pins containing uranium-plutonium mixed nitride pellets were fabricated for the irradiation tests in JMTR and JOYO. (author)

  18. Phytosiderophore Effects on Subsurface Actinide Contaminants: Potential for Phytostabilization and Phytoextraction

    Ruggiero, Christy

    2005-06-01

    This project seeks to understand the influence of phytosiderophore-producing plants (grasses, including crops such as wheat and barley) on the biogeochemistry of actinide and other metal contaminants in the subsurface environment, and to determine the potential of phytosiderophore-producing plants for phytostabilization and phytoextraction of actinides and some metal soil contaminants. Phytosiderophores are secreted by graminaceous plants such as barley and wheat for the solubilization, mobilization and uptake of Fe and other essential nutrients from soils. The ability for these phytosiderophores to chelate and absorb actinides using the same uptake system as for Fe is being investigated though characterization of actinide-phytosiderophore complexes (independently of plants), and characterization of plant uptake of such complexes. We may also show possible harm caused by these plants through increased chelation of actinides that increase in actinide mobilization & migration in the subsurface environment. This information can then be directly applied by either removal of harmful plants, or can be used to develop plant-based soil stabilization/remediation technologies. Such technologies could be the low-cost, low risk solution to many DOE actinide contamination problems.

  19. Decorporation of inhaled actinides by chelation therapy

    This article describes recent work in NRPB laboratories that has identified some of the factors influencing the behaviour of plutonium, americium and curium compounds in the body after inhalation, together with a number of experimental approaches that are being developed to optimise their treatment with DTPA. It is concluded that the most effective treatment has yet to be developed, but progress must depend on a better understanding of the factors governing the transport of actinides in the body. It cannot be assumed that because the inhaled material is readily translocated to blood, that treatment regimens with Ca-DTPA based solely on previous understanding of the metabolic fate of soluble actinide complexes will be successful. In fact, depending on the nature of the material involved in the accident, inhalation alone or combined with prolonged infusion of DTPA may be more effective than the periodic intravenous injections of the chelating agent alone. For poorly transportable materials such as insoluble plutonium-239 dioxide, chelation treatment remains essentially ineffective. (U.K.)

  20. Interaction processes of tetravalent actinides in the system humic acid/quartz sand/solution

    In the present work the influence of HA on the interaction of tetravalent actinides onto quartz sand was investigated in batch and column experiments. HA can affect the sorption of actinides onto mineral surface as a complexing ligand for cations in solutions, and as an adsorbent by modifying the properties of the mineral surface. Batch experiments were performed with Th(IV) as stable tetravalent actinide element. Column experiments were carried out with uranium which is less stable in the tetravalent state under laboratory conditions. Results of the U(IV) migration were compared to the U(VI) migration. (orig.)

  1. The separation of lanthanides and actinides in supercritical fluid carbon dioxide

    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. Examples of the application of this novel technology for actinide and lanthanide separations are presented. (author)

  2. Redox-flow battery of actinide complexes

    Np battery and U battery were developed. We suggested that Np redox-flow battery should be (-)|Np3+,Np4+||NpO2+,NpO22+|(+), and U battery (-)|[UIIIT2]-,[UIVT2]0||[UVO2T]-,[UVIO2T]0|(+). The electromotive force at 50 % charge of Np and U battery is 1.10 V and 1.04 V, respectively. The energy efficiency of 70 mA/cm2 of Np and U battery shows 99 % and 98 %, respectively. V redox-flow battery, electrode reactions of An battery, Np battery, U battery and future of U battery are described. The concept of V redox-flow battery, comparison of energy efficiency of Np, U and V battery, oxidation state and ionic species of 3d transition metals and main An, Purbe diagram of Np and U aqueous solution, shift of redox potential of β-diketones by pKa, and specifications of three redox-flow batteries are reported. (S.Y.)

  3. Environmental research on actinide elements

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

    1987-08-01

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

  4. ENDF/B-V actinides

    This document summarizes the contents of the actinides part of the ENDF/B-V nuclear data library released by the US National Nuclear Data Center. This library or selective retrievals of it, are available from the IAEA Nuclear Data Section. (author)

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

    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

    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 resu...

  6. DAE-BRNS symposium on spectroscopy of lanthanides and actinides (SLA-99)

    Spectroscopy of lanthanides and actinides, due to the rich and complex interactions of the f electrons, is of immense interest to basic sciences and technology. This volume covers both basic and applied aspects of the spectroscopy of lanthanides and actinides and also include the recent developments and emerging areas. The papers have been classified in several broad categories namely theoretical studies, high resolution spectroscopy, laser spectroscopy, solid state spectroscopy, analytical spectroscopy, optics and instrumentation and applications. Papers relevant to INIS are indexed separately

  7. Actinide Biocolloid Formation in Brine by Halophilic Bacteria

    We examined the ability of a halophilic bacterium (WFP 1A) isolated from the Waste Isolation Pilot Plant (WIPP) site to accumulate uranium in order to determine the potential for biocolloid facilitated actinide transport. The bacterial cell Surface functional groups involved in the complexation of the actinide were determined by titration. Uranium, added as uranyl nitrate, was removed from solution at pH 5 by cells but at pH 7 and 9 very little uranium was removed due to its limited volubility. Although present as soluble species, uranyl citrate at pH 5, 7, and 9, and uranyl carbonate at pH 9 were not removed by the bacterium because they were not bioavailable due to their neutral or negative charge. Addition of uranyl EDTA to brine at pH 5, 7, and 9 resulted in the immediate precipitation of U. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) analysis revealed that uranium was not only associated with the cell surface but also accumulated intracellulary as uranium-enriched granules. Extended X-ray absorption fine structure (EXAFS) analysis, of the bacterial cells indicated the bulk sample contained more than one uranium phase. Nevertheless these results show the potential for the formation of actinide bearing bacterial biocolloids that are strictly regulated by the speciation and bioavailability of the actinide

  8. Program and presentations of the 33th Actinide Days

    The 'Journees des Actinides' (JDA) is an annual conference which provides a forum for discussions on all aspects related to the chemical and physical properties of the actinides. At the 2003 meeting, mainly the following properties were discussed of actinides and a number of actinide compounds and complexes: crystal structure, crystal-phase transformations and transformation temperatures; electrical properties including superconductivity and superconducting transition temperatures; magnetic properties; specific heat and other thermodynamic properties; electronic structure, especially in condensed matter; chemical and physico-chemical properties. The relevant experimental techniques were also dealt with, such as neutron diffraction; X-ray diffraction, in particular using synchrotron radiation; photoemission techniques, electron microscopy and spectroscopy, etc. Altogether 96 contributions were presented, of which 42 were oral presentations and 54 poster presentations. A program of the meeting and texts of both type of presentations were published in electronic form in the PDF format. All contributions were inputted to INIS; the full text of the program and the presentations has been incorporated into the INIS collection of non-conventional literature on CD-ROM. (A.K.)

  9. Innovative SANEX process for trivalent actinides separation from PUREX raffinate

    Sypula, Michal

    2013-07-01

    Recycling of nuclear spent fuel and reduction of its radiotoxicity by separation of long-lived radionuclides would definitely help to close the nuclear fuel cycle ensuring sustainability of the nuclear energy. Partitioning of the main radiotoxicity contributors followed by their conversion into short-lived radioisotopes is known as partitioning and transmutation strategy. To ensure efficient transmutation of the separated elements (minor actinides) the content of lanthanides in the irradiation targets has to be minimised. This objective can be attained by solvent extraction using highly selective ligands that are able to separate these two groups of elements from each other. The objective of this study was to develop a novel process allowing co-separation of minor actinides and lanthanides from a high active acidic feed solution with subsequent actinide recovery using just one cycle, so-called innovative SANEX process. The conditions of each step of the process were optimised to ensure high actinide separation efficiency. Additionally, screening tests of several novel lipophilic and hydrophilic ligands provided by University of Twente were performed. These tests were aiming in better understanding the influence of the extractant structural modifications onto An(III)/Ln(III) selectivity and complexation properties. Optimal conditions for minor actinides separation were found and a flow-sheet of a new innovative SANEX process was proposed. Tests using a single centrifugal contactor confirmed high Eu(III)/Am(III) separation factor of 15 while the lowest SF{sub Ln/Am} obtained was 6,5 (for neodymium). In addition, a new masking agent for zirconium was found as a substitution for oxalic acid. This new masking agent (CDTA) was also able to mask palladium without any negative influence on An(III)/Ln(III). Additional tests showed no influence of CDTA on plutonium present in the feed solution unlike oxalic acid which causes Pu precipitation. Therefore, CDTA was proposed as

  10. Innovative SANEX process for trivalent actinides separation from PUREX raffinate

    Recycling of nuclear spent fuel and reduction of its radiotoxicity by separation of long-lived radionuclides would definitely help to close the nuclear fuel cycle ensuring sustainability of the nuclear energy. Partitioning of the main radiotoxicity contributors followed by their conversion into short-lived radioisotopes is known as partitioning and transmutation strategy. To ensure efficient transmutation of the separated elements (minor actinides) the content of lanthanides in the irradiation targets has to be minimised. This objective can be attained by solvent extraction using highly selective ligands that are able to separate these two groups of elements from each other. The objective of this study was to develop a novel process allowing co-separation of minor actinides and lanthanides from a high active acidic feed solution with subsequent actinide recovery using just one cycle, so-called innovative SANEX process. The conditions of each step of the process were optimised to ensure high actinide separation efficiency. Additionally, screening tests of several novel lipophilic and hydrophilic ligands provided by University of Twente were performed. These tests were aiming in better understanding the influence of the extractant structural modifications onto An(III)/Ln(III) selectivity and complexation properties. Optimal conditions for minor actinides separation were found and a flow-sheet of a new innovative SANEX process was proposed. Tests using a single centrifugal contactor confirmed high Eu(III)/Am(III) separation factor of 15 while the lowest SFLn/Am obtained was 6,5 (for neodymium). In addition, a new masking agent for zirconium was found as a substitution for oxalic acid. This new masking agent (CDTA) was also able to mask palladium without any negative influence on An(III)/Ln(III). Additional tests showed no influence of CDTA on plutonium present in the feed solution unlike oxalic acid which causes Pu precipitation. Therefore, CDTA was proposed as a Zr

  11. Actinides recycling assessment in a thermal reactor

    Highlights: • Actinides recycling is assessed using BWR fuel assemblies. • Four fuel rods are substituted by minor actinides rods in a UO2 and in a MOX fuel assembly. • Performance of standard fuel assemblies and the ones with the substitution is compared. • Reduction of actinides is measured for the fuel assemblies containing minor actinides rods. • Thermal reactors can be used for actinides recycling. - Abstract: Actinides recycling have the potential to reduce the geological repository burden of the high-level radioactive waste that is produced in a nuclear power reactor. The core of a standard light water reactor is composed only by fuel assemblies and there are no specific positions to allocate any actinides blanket, in this assessment it is proposed to replace several fuel rods by actinides blankets inside some of the reactor core fuel assemblies. In the first part of this study, a single uranium standard fuel assembly is modeled and the amount of actinides generated during irradiation is quantified for use it as reference. Later, in the same fuel assembly four rods containing 6 w/o of minor actinides and using depleted uranium as matrix were replaced and depletion was simulated to obtain the net reduction of minor actinides. Other calculations were performed using MOX fuel lattices instead of uranium standard fuel to find out how much reduction is possible to obtain. Results show that a reduction of minor actinides is possible using thermal reactors and a higher reduction is obtained when the minor actinides are embedded in uranium fuel assemblies instead of MOX fuel assemblies

  12. Factors influencing the transport of actinides in the groundwater environment. Final report

    This report summarizes investigations of factors that significantly influence the transport of actinide cations in the groundwater environment. Briefly, measurements of diffusion coefficients for Am(III), Cm(III), and Np(V) in moist US soils indicated that diffusion is negligible compared to mass transport in flowing groundwater. Diffusion coefficients do, however, indicate that, in the absence of flowing water, actinide elements will migrate only a few centimeters in a thousand years. The remaining investigations were devoted to the determination of distribution ratios (K/sub d/s) for representative US soils, factors influencing them, and chemical and physical processes related to transport of actinides in groundwaters. The computer code GARD was modified to include complex formation to test the importance of humic acid complexing on the rate of transport of actinides in groundwaters. Use of the formation constant and a range of humic acid, even at rather low concentrations of 10-5 to 10-6 molar, significantly increases the actinide transport rate in a flowing aquifer. These computer calculations show that any strong complexing agent will have a similar effect on actinide transport in the groundwater environment. 32 references, 9 figures

  13. X-Ray Absorption Spectroscopy of the Actinides

    Antonio, Mark R.; Soderholm, Lynda

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

  14. Synergistic extraction of actinides : Part II. Tetra-and trivalent actinides

    A detailed discussion on the synergistic solvent extraction behaviour of tetra- and trivalent actinide ions is presented. Structural aspects of the natural donor adducts of the tetravalent actinide ion chelates involved in synergism are also discussed. (author)

  15. Spin Hamiltonians for actinide ions

    The breakdown of Russel Saunders coupling for correlated f-levels of actinide ions is due to both spin orbit coupling and the crystalline electric field (CEF). Experiments on curium, an S-state ion in the metal for which the CEF is weak indicate a g-factor close to the Russel-Saunders value. Spin-orbit coupling is therefore too weak to produce jj coupling. This suggests a model for magnetic actinide ions in which the CEF ground multiplet is well separated from higher levels, completely determining thermodynamic magnetic properties. On this basis simplified spin Hamiltonians are derived for GAMMA1-GAMMA5 ground states in order to interpret thermodynamic measurements and ordering phenomena. (author)

  16. Research in actinide chemistry. Progress report, March 1, 1980-February 28, 1981

    The primary purpose of this research is to study the behavior of actinide cations in aqueous solution. The interaction of trivalent actinides with a wide variety of both inorganic and organic ligands has been investigated with emphasis on the thermodynamics and kinetics of complexation at tracer concentrations using radiochemical techniques. In order to expand the scope of the experimental techniques, thereby obtaining additional understanding of the fundamental processes involved, non-radioactive experiments with the trivalent lanthanides have been conducted. Visible spectroscopy, nmr (11H, 613C, 57139La) spectroscopy, potentiometry, solvent extraction and calorimetry are examples of techniques for these lanthanide studies which have allowed much more thorough interpretation of the actinide tracer data due to the close chemical similarity of the lanthanide and actinide families of trivalent cations. The following were investigated: nmr shifts of 139La for both halate and chloroacetate complexes; interaction of Pu(VI) with carbonates and bicarbonates; Ca+2, UO2+2, and Th+4 reactions with halate and chloroacetate anions; complexation of the lanthanides by benzoic acid; thermodynamic formation constants for trivalent lanthanide ions with succinic, glutaric, and adipic acids; complexation of benzene polycarboxylates with lanthanides; complexation of lanthanide ions by AMP (adenosine monophosphate), ADP (adenosine diphosphate) and ATP (adenosine triphosphate); interaction of the actinides ions with humic acid; measurements of water and benzoic acid concentrations in several organic solvents by potentiometric and spectral methods; and plutonium and neptunium redox behavior in the presence of organic complexing agents

  17. Actinide recovery techniques utilizing electromechanical processes

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

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

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

  19. Anthropogenic Actinides in the Environment

    The use of nuclear energy and the testing of nuclear weapons have led to significant releases of anthropogenic isotopes, in particular a number of actinide isotopes generally not abundant in nature. Most prominent amongst these are 239Pu, 240Pu, and 236U. The study of these actinides in nature has been an active field of study ever since. Measurements of actinides are applied to nuclear safeguards, investigating the sources of contamination, and as a tracer for a number of erosion and hydrology studies. Accelerator Mass Spectrometry (AMS) is ideally suited for these studies and generally offers higher sensitivities than competing techniques, like ICP-MS or decay counting. Recent advances in AMS allow the study of “minor” plutonium isotopes (241Pu, 242Pu, and 244Pu). Furthermore, 236U can now be measured at the levels expected from the global stratospheric fall-out of the atmospheric nuclear weapon tests in the 1950s and 1960s. Even the pre-anthropogenic isotope ratios could be within reach. However, the distribution and abundance levels of these isotopes are not well known yet. I will present an overview of the field, and in detail two recent studies on minor plutonium isotopes and 236U, respectively.(author)

  20. Actinides in earth materials: the importance of natural analogues

    Predictions of the stability of waste forms designed for long-term storage of actinides require an accurate knowledge of the long-term properties of these actinides in their host matrix. One useful approach to address this issue involves comparison of structural and thermodynamic information derived from short time-scale experiments on synthetic samples with similar information from natural samples, including natural glasses and metamict minerals. These natural analogues of synthetic waste forms, although significantly different in structure, properties and composition from the synthetic samples, offer a number of examples of earth materials that have received large doses of radioactivity (mainly α events) over very long time periods (106-109 years). In this paper, we present a review of the co-ordination chemistry of actinides in natural deep-seated earth systems and their analogues (mostly glasses, melts and radiation-damaged minerals). Special emphasis is given to data analysis methods that are important in determining accurate XAFS-derived interatomic distances and co-ordination numbers for actinides in these complex materials, including anharmonicity, multi-electronic transitions, deconvolution procedures, and ab initio calculations of near-edge structure. The effects of anharmonicity and multi-electronic transitions are best studied using high-energy resolution spectrometers on third-generation synchrotron sources. Application of these methods to selected natural minerals (crystalline and radiation-damaged) is presented, together with a comprehensive list of unusual mineral structures that are known to incorporate relatively large amounts of actinides over long periods of geologic time in a stable manner. (authors)

  1. Sequestering agents for the removal of actinides from waste streams

    Raymond, K.N.; White, D.J.; Xu, Jide; Mohs, T.R. [Univ. of California, Berkeley, CA (United States)

    1997-10-01

    The goal of this project is to take a biomimetic approach toward developing new separation technologies for the removal of radioactive elements from contaminated DOE sites. To achieve this objective, the authors are investigating the fundamental chemistry of naturally occurring, highly specific metal ion sequestering agents and developing them into liquid/liquid and solid supported actinide extraction agents. Nature produces sideophores (e.g., Enterobactin and Desferrioxamine B) to selectivity sequester Lewis acidic metal ions, in particular Fe(III), from its surroundings. These chelating agents typically use multiple catechols or hydroxamic acids to form polydentate ligands that chelate the metal ion forming very stable complexes. The authors are investigating and developing analogous molecules into selective chelators targeting actinide(IV) ions, which display similar properties to Fe(III). By taking advantage of differences in charge, preferred coordination number, and pH stability range, the transition from nature to actinide sequestering agents has been applied to the development of new and highly selective actinide extraction technologies. Additionally, the authors have shown that these chelating ligands are versatile ligands for chelating U(VI). In particular, they have been studying their coordination chemistry and fundamental interactions with the uranyl ion [UO{sub 2}]{sup 2+}, the dominant form of uranium found in aqueous media. With an understanding of this chemistry, and results obtained from in vivo uranium sequestration studies, it should be possible to apply these actinide(IV) extraction technologies to the development of new extraction agents for the removal of uranium from waste streams.

  2. PWRs potentialities for minor actinides burning

    In the frame of the SPIN program at CEA, the impacts of the minor actinides (MA) incineration in PWRs are analysed. The aim is to reduce the mass, the potential radiotoxicity level. The recycling of all actinide elements is evaluated in a PWR nuclear yard. A sensitivity study is done to evaluate the incineration for each minor actinide element. This gives the most efficient way of incineration for each MA elements in a PWR and helps to design a PWR burner. This burner is disposed in a PWR nuclear system in which the actinides are recycled until equilibrium. (author)

  3. Long-term plant availability of actinides

    Environmental releases of actinide elements raise issues about which data are very limited. Quantitative information is required to assess the long-term behavior of actinides and their potential hazards resulting from the transport through food chains leading to man. Of special interest is the effect of time on the changes in the availability of actinide elements for uptake by plants from soil. This study provides valuable information on the effects of weathering and aging on the uptake of actinides from soil by range and crop plants grown under realistic field conditions

  4. Pharmacokinetic and pharmaco-technological approaches of actinides decorporation by an in vivo sequestering agent. Application to the development of new treatments; Approches pharmacocinetique et pharmacotechnique de la decorporation d'actinides par un agent complexant in vivo. Application a la mise au point de nouveaux traitements

    Phan, G.

    2005-05-24

    After internal contamination by transuranic actinides, diethylene-triamine-pentaacetic acid (DTPA) is the only treatment available to haste the decorporation i.e. the excretion from the body of these radio-contaminants by the natural pathways (urinary and faecal excretion). However, the effectiveness of DTPA is variable and seems to be limited to mobilize efficiently the radionuclides from their sites of deposit and retention which are mainly the liver and the skeleton. Indeed, this molecule displays unfavourable pharmacokinetics (a low tissue distribution and a high urinary excretion) which do not match with the distribution of the actinides in vivo. Moreover, because of its physicochemical properties, DTPA is not able to pass through the plasmic membranes and to penetrate in the cells. Consequently, the use of colloidal vectors such as liposomes could make it possible to modulate DTPA pharmacokinetics as well as to promote the access of the chelating agent to the intracellular compartment of the macrophages of the reticulo-endothelial system which also uptake the radionuclides. The objective of this thesis thus was to improve the treatment of decorporation treatments of transuranic actinides, in particular of plutonium (Pu) by the sequestering agent DTPA by a double approach. The strategy consisted in developing liposomes in order to encapsulate and to modify the distribution of DTPA in vivo. The encapsulation of the DTPA in large multi-lamellar (MLV) and conventional liposomes (composed of DOPC:CH:PG) and in stealth MLV liposomes (composed of DOPC:CH:DSPE-PEG) could modify DTPA pharmacokinetics by prolonging its circulation time and by increasing its distribution especially in the liver (conventional MLV) and in the skeleton (stealth MLV). These modifications of the distribution of DTPA were well correlated with an increased de-corporating effect on Pu in the rats. The reduction of the diameter of liposomes to approximately 100 nm made it possible to further

  5. Characterization Of Actinides In Simulated Alkaline Tank Waste Sludges And Leachates

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

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

    Nash, Kenneth L.

    2008-11-20

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

  7. Recovery of actinides from TBP-Na2Co3 scrub-waste solutions: the ARALEX process

    A flowsheet for the recovery of actinides from TBP-Na2CO3 scrub-waste solutions has been developed, based on batch extraction data, and tested, using laboratory-scale countercurrent extraction techniques. The process, called the ARALEX process, uses 2-ethyl-1-hexanol (2-EHOH) to extract the TBP degradation products (HDBP and H2MBP) from acidified Na2CO3 scrub waste leaving the actinides in the aqueous phase. Dibutyl and monobutyl phosphoric acids are attached to the 2-EHOH molecules through hydrogen bonds, which also diminish the ability of the HDBP and H2MBP to complex actinides. Thus all actinides remain in the aqueous raffinate. Dilute sodium hydroxide solutions can be used to back-extract the dibutyl and monobutyl phosphoric acid esters as their sodium salts. The 2-EHOH can then be recycled. After extraction of the acidified carbonate waste with 2-EHOH, the actinides may be readily extracted from the raffinate with DHDECMP or, in the case of tetra- and hexavalent actinides, with TBP. The ARALEX process can also be applied to other actinide waste streams which contain appreciable concentrations of polar organic compounds (e.g., detergents) that interfere with conventional actinide ion exchange and liquid-liquid extraction procedures. 20 figures, 6 tables

  8. Calculated Atomic Volumes of the Actinide Metals

    Skriver, H.; Andersen, O. K.; Johansson, B.

    1979-01-01

    The equilibrium atomic volume is calculated for the actinide metals. It is possible to account for the localization of the 5f electrons taking place in americium.......The equilibrium atomic volume is calculated for the actinide metals. It is possible to account for the localization of the 5f electrons taking place in americium....

  9. Environmental chemistry of the actinide elements

    The environmental chemistry of the actinide elements is a new branch of science developing with the application of nuclear energy on a larger and larger scale. Various aspects of the environmental chemistry of the actinide elements are briefly reviewed in this paper, such as its significance in the nuclear waste disposal, its coverage of research fields and possible directions for future study

  10. PIE analysis for minor actinide

    Minor actinide (MA) is generated in nuclear fuel during the operation of power reactor. For fuel design, reactivity decrease due to it should be considered. Out of reactors, MA plays key role to define the property of spent fuel (SF) such as α-radioactivity, neutron emission rate, and criticality of SF. In order to evaluate the calculation codes and libraries for predicting the amount of MA, comparison between calculation results and experimentally obtained data has been conducted. In this report, we will present the status of PIE data of MA taken by post irradiation examinations (PIE) and several calculation results. (author)

  11. Actinide co-conversion by internal gelation

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

  12. Actinides analysis by accelerator mass spectrometry

    At the ANTARES accelerator at ANSTO a new beamline has been commissioned, incorporating new magnetic and electrostatic analysers, to optimise the efficiency for Actinides detection by Accelerator Mass Spectrometry (AMS). The detection of Actinides, particularly the isotopic ratios of uranium and plutonium, provide unique signatures for nuclear safeguards purposes. We are currently engaged in a project to evaluate the application of AMS to the measurement of Actinides in environmental samples for nuclear safeguards. Levels of certain fission products, Actinides and other radioactive species can be used as indicators of undeclared nuclear facilities or activities, either on-going or in the past Other applications of ultra-sensitive detection of Actinides are also under consideration. neutron-attenuation images of a porous reservoir rock

  13. Actinide ion sensor for pyroprocess monitoring

    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.

  14. Gross actinide preconcentration using phosphonate-based ligand and cloud point extraction

    A procedure for the effective separation and determination of the most abundant actinides relevant to the nuclear industry (U, Th, Np, Pu and Am) was developed based on cloud point extraction (CPE) using H2DEH[MDP] (P,P-di-(2-ethylhexyl) methanediphosphonic acid) as a ligand. The extractability of actinides with varying concentrations of nitric acid and hydrochloric acid were assessed. The robustness of the method was demonstrated for environmental matrices such as reference materials and spiked liquid samples for the quantification of the gross actinide content. This analytical strategy may replace traditional sample preparation techniques used in radiological methods for gross measurements of radioactivity, and may act as a rapid screening tool in emergency situations. The developed method is a greener alternative to common radiochemical sample preparation techniques such as co-precipitation or evaporation. The formation of a small-volume surfactant-rich phase containing the complexed actinides enables rapid, highly selective and great enrichment of the analytes in this phase. The proposed method shows good extraction and separation yield compared to existing methods, since the surfactant-rich phase is soluble in water and can therefore be redispersed quantitatively in a medium compatible with mass spectrometry while providing fast isolation of the actinide content. Separation of actinides can be achieved after by wet ashing of the surfactant-rich phase obtained by CPE if coupled to the proper radiochemical separation scheme. (author)

  15. Actinide production in /sup 136/Xe bombardments of /sup 249/Cf

    Gregorich, K.E.

    1985-08-01

    The production cross sections for the actinide products from /sup 136/Xe bombardments of /sup 249/Cf at energies 1.02, 1.09, and 1.16 times the Coulomb barrier were determined. Fractions of the individual actinide elements were chemically separated from recoil catcher foils. The production cross sections of the actinide products were determined by measuring the radiations emitted from the nuclides within the chemical fractions. The chemical separation techniques used in this work are described in detail, and a description of the data analysis procedure is included. The actinide production cross section distributions from these /sup 136/Xe + /sup 249/Cf bombardments are compared with the production cross section distributions from other heavy ion bombardments of actinide targets, with emphasis on the comparison with the /sup 136/Xe + /sup 248/Cm reaction. A technique for modeling the final actinide cross section distributions has been developed and is presented. In this model, the initial (before deexcitation) cross section distribution with respect to the separation energy of a dinuclear complex and with respect to the Z of the target-like fragment is given by an empirical procedure. It is then assumed that the N/Z equilibration in the dinuclear complex occurs by the transfer of neutrons between the two participants in the dinuclear complex. The neutrons and the excitation energy are statistically distributed between the two fragments using a simple Fermi gas level density formalism. The resulting target-like fragment initial cross section distribution with respect to Z, N, and excitation energy is then allowed to deexcite by emission of neutrons in competition with fission. The result is a final cross section distribution with respect to Z and N for the actinide products. 68 refs., 33 figs., 6 tabs.

  16. Vitrification of actinide solutions in SRS separations facilities

    The actinide vitrification system being developed at SRS provides the capability to convert specialized or unique forms of nuclear material into a stable solid glass product that can be safely shipped, stored or reprocessed according to the DOE complex mission. This project is an application of technology developed through funds from the Office of Technology Development (OTD). This technology is ideally suited for vitrifying relatively small quantities of fissile or special nuclear material since it is designed to be critically safe. Successful demonstration of this system to safely vitrify radioactive material could open up numerous opportunities for transferring this technology to applications throughout the DOE complex

  17. The ALMR actinide burning system

    The advanced liquid-metal reactor (ALMR) actinide burning system is being developed under the sponsorship of the US Department of Energy to bring its unique capabilities to fruition for deployment in the early 21st century. The system consists of four major parts: the reactor plant, the metal fuel and its recycle, the processing of light water reactor (LWR) spent fuel to extract the actinides, and the development of a residual waste package. This paper addresses the status and outlook for each of these four major elements. The ALMR is being developed by an industrial group under the leadership of General Electric (GE) in a cost-sharing arrangement with the US Department of Energy. This effort is nearing completion of the advanced conceptual design phase and will enter the preliminary design phase in 1994. The innovative modular reactor design stresses simplicity, economics, reliability, and availability. The design has evolved from GE's PRISM design initiative and has progressed to the final stages of a prelicensing review by the US Nuclear Regulatory Commission (NRC); a safety evaluation report is expected by the end of 1993. All the major issues identified during this review process have been technically resolved. The next design phases will focus on implementation of the basic safety philosophy of passive shutdown to a safe, stable condition, even without scram, and passive decay heat removal. Economic projections to date show that it will be competitive with non- nuclear and advanced LWR nuclear alternatives

  18. The chemical thermodynamics of actinide elements and compounds

    This compilation forms the twelfth part of a comprehensive assessment and selection of actinide thermodynamic data. The other parts of the compilation deal mostly with actinide elements and compounds. This part, which is the last one to be published in this Series, concerns inorganic actinide complexes in aqueous solution. The properties considered include the stability constant as a function of ionic strength and temperature and, whenever possible, enthalpy and entropy values. The present assessment is based on a literature survey that was terminated in early 1989. In tabulating literature data, only experimental results were used; estimates as well as recalculated data were ignored. Unlike in previous assessments of this kind in this assessment the selection of a best value is discussed and justified, and reasons are given for the rejection of data. In addition, our estimates of the thermodynamic properties, based on interrelationships between analogous systems, are given when this can be done reliably. Another essential aim of this assessment is to indicate those areas in which additional research is required. Refs

  19. Sensitivity analysis for actinide production and depletion in fast reactors

    In sensitivity analysis of the actinide production and depletion in fast reactors, a mathematical method of calculating sensitivity coefficients is improved and simplified by combining the time-dependent generalized perturbation technique with the eigenvalue method. Numerical calculations show that the eigenvalue method is well applicable in solving the nuclide chain equation and its adjoint equation and the cylic chains in the decay scheme of the actinides can be interpreted by means of complex eigenvalues. The sensitivity coefficients of actinide production and depletion in a 1000 MWe fast reactor are strongly dependent on the type of Pu fuel used, i.e. Pu fuel from BWR or Pu fuel from the blanket of FBR. The sensitivity coefficients due to variations of capture cross sections, σsub(n,2n) of 238U, lambda sub(β) of 241Pu and lambda sub(α) of 242Cm are especially large. Sensitivity analyses for the 1000 MWe fast reactors show that higher priorily should be given to decay constants of 241Pu and 242Cm, capture cross sections of 237Np, 241Am, 243Am and 242Pu, and fission cross sections of 237Np, 242Pu, 241Am and sup(242m)Am. (author)

  20. Supercritical Fluid Extraction and Separation of Uranium from Other Actinides

    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 uranium 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.

  1. Behaviour of actinides in room temperature ionic liquids

    The room temperature ionic liquids are potentially interesting for the treatment of nuclear fuel. But the knowledge of the behaviour of actinides in the ionic liquids is fragmented because these solvents are new, young and many. In a first time, the ionic liquids [BuMeIm][Tf2N] and [MeBu3N][Tf2N] have been studied in α and γ irradiation with different atmosphere (argon and air) and concentrations of water. ESIMS, NMR and liquid chromatography coupled ESI-MS analysis demonstrate a multitude of degradation products but in very small quantities. This good radiolytic stability makes it a major advantage for the studies of actinides. In a second time, the interaction between an anionic complex of uranium (UCl62-) and the cation of the ionic liquid and too the study of the hydrolysis of An4+ (An uranium, neptunium, plutonium) were conducted in different ionic liquids ([MeBu3N][Tf2N], [BuMe2Im][Tf2N] and [BuMeIm][Tf2N]). The experimental results showed that the intensity of these interactions between UCl62- anion and the ionic liquid cation depends on the latter and follows the order: MeBu3N+ ∼ BuMe2Im+ ≤BuMeIm+. In addition, the results obtained by UV/Vis spectroscopy showed that the reaction of hydrolysis in the ionic liquids is slow, secondary compared to the oxidation or the disproportionation and that the amount of water in ionic liquid must be relatively large compared to the concentration of actinide. The results from the coupling of different analytical techniques (NMR, mass spectrometry, UV-Visible, Infra-red, Electrochemistry..) have allowed a first approach in the understanding of the actinides in the room temperature ionic liquids. (author)

  2. Experimental studies of actinides in molten salts

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

  3. Experimental studies of actinides in molten salts

    Reavis, J.G.

    1985-06-01

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

  4. Spin and orbital moments in actinide compounds

    Lebech, B.; Wulff, M.; Lander, G.H.

    1991-01-01

    -electron band-structure calculations, is that the orbital moments of the actinide 5f electrons are considerably reduced from the values anticipated by a simple application of Hund's rules. To test these ideas, and thus to obtain a measure of the hybridization, we have performed a series of neutron scattering...... experiments designed to determine the magnetic moments at the actinide and transition-metal sublattice sites in compounds such as UFe2, NpCo2, and PuFe2 and to separate the spin and orbital components at the actinide sites. The results show, indeed, that the ratio of the orbital to spin moment is reduced as...

  5. Electronic structure and magnetic properties of actinides

    The study of the actinide series shows the change between transition metal behavior and lanthanide behavior, between constant weak paramagnetism for thorium and strong Curie-Weiss paramagnetism for curium. Curium is shown to be the first metal of the actinide series to be magnetically ordered, its Neel temperature being 52K. The magnetic properties of the actinides depending on all the peripheral electrons, their electronic structure was studied and an attempt was made to determine it by means of a phenomenological model. Attempts were also made to interrelate the different physical properties which depend on the outer electronic structure

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

    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

  7. Semi-microdetermination of nitrogen in actinide compounds by Dumas method

    This report describes the application of the Dumas method for the semi-micro determination of nitrogen in actinide compounds and actinide complexes with organic ligands. The usual set up has been modified to make it adaptable for glove box operations. The carbon dioxide generator and nitrometer assemblies were located outside the glove box while the reaction tube and combustion furnaces were housed inside. The nitrogen gas collected in the nitrometer was read with the help of a travelling microscope with a vernier attachment fitted in front of the nitrometer burette. The set up was standardised using acetanilide and employed for the determination of nirtogen in various substances such as uranium nitride, and a variety of substituted quinoline and pyrazolone derivatives of actinides as well as some ternary uranium-PMBR-sulphoxide complexes. Full details of the technique and the analytical data obtained are contained in this report. (author)

  8. Investigations of actinides in the context of final disposal of high-level radioactive waste. Trivalent actinides in aqueous solution

    The speciation of redox sensitive trivalent actinides Pu(III), Np(III), and U(III) has been studied in aqueous solution. The redox preparation, stabilization, and speciation of these trivalent actinides in aqueous systems are discussed here. The reductants investigated were rongalite, hydroxylamine hydrochloride, and acetohydroxamic acid and the An(III) species have been characterized by UV-Vis and XANES spectroscopy. The results show that the effectiveness of stabilization decreases generally in the order Pu(III) > Np(III) > U(III) and that the effectiveness of each reducing agent depends on the experimental conditions. More than 80 % of Pu(III) aquo species have been stabilized up to pH 5.5, whereas the Np(III) aquo ion could be stabilized in a pH range 0-2.5, and U(III) aquo ion is sufficiently stable at pH 1.0 and below over time periods suitable for experiments. However, this study gives a basis for the characterisation of the trivalent lighter actinides involved in complexation, sorption, and solid formation reactions in the future. (author)

  9. Endohedral Fullerenes with Actinide-Actinide Bonds: Unwilling Bonding in U2@C80

    Foroutan-Nejad, C.; Patzschke, M.; Straka, Michal

    Opole: -, 2014. [MMNB 2014. Polish-Taiwanese Conference. From Molecular Modeling to Nano- and Biotechnology . 04.09.2014-06.09.2014, Opole] R&D Projects: GA ČR(CZ) GA14-03564S Grant ostatní: European Social Fund(XE) CZ.1.07/2.3.00/30.009 Institutional support: RVO:61388963 Keywords : endohedral actinide fullerene * U-U bonding * actinide-actinide bonding Subject RIV: CF - Physical ; Theoretical Chemistry

  10. Actinide recovery from pyrochemical residues

    We demonstrated a new process for recovering plutonium and americium from pyrochemical waste. The method is based on chloride solution anion exchange at low acidity, or acidity that eliminates corrosive HCl fumes. Developmental experiments of the process flow chart concentrated on molten salt extraction (MSE) residues and gave >95% plutonium and >90% americium recovery. The recovered plutonium contained 62- from high-chloride low-acid solution. Americium and other metals are washed from the ion exchange column with lN HNO3-4.8M NaCl. After elution, plutonium is recovered by hydroxide precipitation, and americium is recovered by NaHCO3 precipitation. All filtrates from the process can be discardable as low-level contaminated waste. Production-scale experiments are in progress for MSE residues. Flow charts for actinide recovery from electro-refining and direct oxide reduction residues are presented and discussed

  11. Reversible optical sensor for the analysis of actinides in solution; Capteur optique reversible pour l'analyse des actinides en solution

    Lesage, B.; Picard, S. [CEA Marcoule, Dept. de Radiochimie et Procedes, Service de Chimie des Procedes de Separation, Lab. de Chimie des Actinides, 30 (France); Serein-Spirau, F.; Lereporte, J.P. [Ecole Nationale Superieure de Chimie de Montpellier (ENSCM), CNRS UMR 5076, Lab. Heterochimie Moleculaire et Macromoleculaire, 34 - Montpellier (France)

    2007-07-01

    In this work is presented a concept of reversible optical sensor for actinides. It is composed of a p doped conducing polymer support and of an anion complexing the actinides. The chosen conducing polymer is the thiophene-2,5-di-alkoxy-benzene whose solubility and conductivity are perfectly known. The actinides selective ligand is a lacunar poly-oxo-metallate such as P{sub 2}W{sub 17}O{sub 61}{sup 10-} or SiW{sub 11}O{sub 39}{sup 8-} which are strong anionic complexing agents of actinides at the oxidation state (IV) even in a very acid medium. The sensor is prepared by spin coating of the composite mixture 'polymer + ligand' on a conducing glass electrode and then tested towards its optical and electrochemical answer in presence of uranium (IV). The absorption change due to the formation of cations complexes by poly-oxo-metallate reveals the presence of uranium (IV). After the measurement, the sensor is regenerated by anodic polarization of the support and oxidation of the uranium (IV) into uranium (VI) which weakly interacts with the poly-oxo-metallate and is then released in solution. (O.M.)

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

    The present three-year grant period has been a fruitful one for the laboratory as research entered some new areas while continuing in others in which the group has been successful. As in past grant periods, the principal focus has been on complexation of actinide elements with inorganic and organic ligands. The ligands to study have been chosen for their value (known or potential) in actinide separations or for their potential role in environmental behavior of the actinides. Since the radioactivity of some actinides limits the variety of techniques which can be used in their study, we have used open-quotes oxidation state analogsclose quotes. These analogs have the same oxidation state and very similar chemical behavior but are stable or very long-lived. Also, the analogs are chosen for their redox stability to avoid uncertainties in interpretation of systems in which several oxidations may coexist (e.g., in the case of Pu). Examples of such analogs which we have used are: Nd(III), Eu(III) for Pu(III), Am(III), Cm(III); Th(IV) for U(IV), Pu(IV); NpO2+ for PuO2+; UO22+ for NpO22+, PuO22+. These analogs have allowed use of techniques which can increase significantly our understanding of actinide complexation

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

    Choppin, G R

    1997-01-01

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

  14. PWRs potentialities for minor actinides burning

    In the frame of the SPIN program at CEA, the impacts of the Minor Actinides (MA) incineration in PWRs are analysed. The aim is to reduce the mass and the potential radiotoxicity level. This study is done separately one on the Plutonium recycling. But the plutonium is essential. Thus, the recycling of all Actinide elements is evaluated in a PWR nuclear yard. A sensitivity study is done to evaluate the incineration for each Minor Actinide element. This gives us the most efficient way of incineration for each MA element in a PWR and help us to design a PWR burner. This burner is disposed in a PWR nuclear system in which the Actinides are recycled until equilibrium. (authors). 2 refs

  15. Electronic structure and correlation effects in actinides

    Albers, R.C.

    1998-12-01

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

  16. Preparation of actinide targets by electrodeposition

    Trautmann, N.; Folger, H.

    1989-10-01

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

  17. Actinide research to solve some practical problems

    The following topics are discussed: generation of plutonium inventories by nuclear power plants; resettlement of the Marshallese Islanders into an actinide contaminated environment; high radiation background areas of the world; and radiation hazards to uranium miners

  18. Advanced Aqueous Separation Systems for Actinide Partitioning

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

    2012-03-21

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

  19. BWR Assembly Optimization for Minor Actinide Recycling

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

    2010-03-22

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

  20. Microbial transformations of actinides in the environment

    The diversity of microorganisms is still far from understood, although many examples of the microbial biotransformation of stable, pollutant and radioactive elements, involving Bacteria, Archaea and Fungi, are known. In estuarine sediments from the Irish Sea basin, which have been labelled by low level effluent discharges, there is evidence of an annual cycle in Pu solubility, and microcosm experiments have demonstrated both shifts in the bacterial community and changes in Pu solubility as a result of changes in redox conditions. In the laboratory, redox transformation of both U and Pu by Geobacter sulfurreducens has been demonstrated and EXAFS spectroscopy has been used to understand the inability of G. sufurreducens to reduce Np(V). Fungi promote corrosion of metallic U alloy through production of a range of carboxylic acid metabolites, and are capable of translocating the dissolved U before precipitating it externally to the hyphae, as U(VI) phosphate phases. These examples illustrate the far-reaching but complex effects which microorganisms can have on actinide behaviour.

  1. Molecular structure of actinides in biochemistry

    In case of internal contamination, drugs used for decorporation are scarce and do not act very specifically. For instance the sole de-corporating drug recommended for plutonium decontamination is a water-soluble ligand named DTPA (Diethylene-Triamino-Pentaacetate). The transport of DTPA to its organ-target and its bio-availability on the spot are not satisfactorily understood. The conventional method to develop new ligands is based on molecular approaches but it is not sufficient. A new method that combines methods from structural biochemistry with methods of bio-inorganic chemistry and with methods from physico-chemistry (particularly X-ray absorption spectroscopy) is so far the best way to understand molecular speciation and to detail the local arrangement of atoms around a cation for instance, which are valuable information to understand the behaviour of a ligand. EXAFS (Extended X-ray Absorption Fine structure Spectroscopy) measurements suggest that during the formation of a complex involving an actinide (An) and a ligand, the inter-atomic distance An-O decreases when the atomic number of the cation increases while it is the reverse in the case of An-N

  2. Sensitivity analysis of minor actinides transmutation to physical and technological parameters

    Kooyman Timothée

    2015-01-01

    . Estimators of interest that have been derived from this approach include the maximum neutron source and decay heat load acceptable at reprocessing and fabrication steps, which influence among other things the total minor actinides inventory, the overall complexity of the cycle and the size of the geological repository. Based on this analysis, a new methodology to assess transmutation strategies is proposed.

  3. Superconductivity in rare earth and actinide compounds

    Rare earth and actinide compounds and the extraordinary superconducting and magnetic phenomena they exhibit are surveyed. The rare earth and actinide compounds described belong to three classes of novel superconducting materials: high temperature, high field superconductors (intermetallics and layered cuprates); superconductors containing localized magnetic moments; heavy fermion superconductors. Recent experiments on the resistive upper critical field of high Tc cuprate superconductors and the peak effect in the critical current density of the f-electron superconductor CeRu2 are discussed. (orig.)

  4. Lanthanides and actinides in ionic liquids

    Binnemans, Koen

    2007-01-01

    This lecture gives an overview of the research possibilities offered by combining f-elements (lanthanides and actinides) with ionic liquids [1] Many ionic liquids are solvents with weakly coordinating anions. Solvation of lanthanide and actinide ions in these solvents is different from what is observed in conventional organic solvents and water. The poorly solvating behavior can also lead to the formation of coordination compounds with low coordination numbers. The solvation of f-elements can...

  5. New molecules to separate actinides: the picolinamides

    The reprocessing of spent fuel is made with the Purex process, funded on liquid-liquid extraction of uranium nitrates(VI) and plutonium nitrates(IV) by the BTP (tributyl phosphate). To improve this proceeding, we look for extractants which allow, beyond U and Pu extractions, these of actinides (II) and allow separation of the whole actinides from the fission products, which have an important fraction of lanthanides. A new family seems to give good results: the picolinamides

  6. Lattice effects in the light actinides

    The light actinides show a variety of lattice effects that do not normally appear in other regions of the periodic table. The article will cover the crystal structures of the light actinides, their atomic volumes, their thermal expansion behavior, and their elastic behavior as reflected in recent thermal vibration measurements made by neutron diffraction. A discussion of the melting points will be given in terms of the thermal vibration measurements. Pressure effects will be only briefly indicated

  7. Recent progress in actinide borate chemistry.

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

    2011-10-21

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

  8. Evaluation of actinide partitioning and transmutation

    After a few centuries of radioactive decay the long-lived actinides, the elements of atomic numbers 89-103, may constitute the main potential radiological health hazard in nuclear wastes. This is because all but a very few fission products (principally technetium-99 and iodine-129) have by then undergone radioactive decay to insignificant levels, leaving the actinides as the principal radionuclides remaining. It was therefore at first sight an attractive concept to recycle the actinides to nuclear reactors, so as to eliminate them by nuclear fission. Thus, investigations of the feasibility and potential benefits and hazards of the concept of 'actinide partitioning and transmutation' were started in numerous countries in the mid-1970s. This final report summarizes the results and conclusions of technical studies performed in connection with a four-year IAEA Co-ordinated Research Programme, started in 1976, on the ''Environmental Evaluation and Hazard Assessment of the Separation of Actinides from Nuclear Wastes followed by either Transmutation or Separate Disposal''. Although many related studies are still continuing, e.g. on waste disposal, long-term safety assessments, and waste actinide management (particularly for low and intermediate-level wastes), some firm conclusions on the overall concept were drawn by the programme participants, which are reflected in this report

  9. Geochemistry of actinides and fission products in natural aquifer systems

    The progress in the research area of the community project MIRAGE: 'Geochemistry of actinides and fission products in natural aquatic systems' has been reviewed. This programme belongs to a specific research and technical development programme for the European Atomic Energy Community in the field of management and storage of radioactive waste. The review summarizes research progresses in subject areas: complexation with organics, colloid generation in groundwater and basic retention mechanisms in the framework of the migration of radionuclides in the geosphere. The subject areas are being investigated by 23 laboratories under interlaboratory collaborations or independent studies. (orig.)

  10. Specific sequestering agents for iron and the actinides

    The transuranium actinide ions represent one unique environmental hazard associated with the waste of the nuclear power industry. A major component associated with that waste and a potential hazard is plutonium. The synthesis of metal-ion-specific complexing agents for ions such as Pu(IV) potentially represents a powerful new approach to many of the problems posed by waste treatment. This document is a progress report of a rational approach to the synthesis of such chelating agents based on the similarities of Pu(IV) and Fe(III), the structures of naturally-occurring complexing agents which are highly specific for Fe(III), and the incorporation of the same kinds of ligating groups present in the iron complexes to make octadentate complexes highly specific for plutonium. Both thermodynamic and animal test results indicate that a relatively high degree of success has already been achieved in this aim