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Bruce J Mincher – One of the best experts on this subject based on the ideXlab platform.

  • Kinetics of the Autoreduction of Hexavalent Americium in Aqueous Nitric Acid.
    Inorganic chemistry, 2017
    Co-Authors: Travis S. Grimes, Gregory P. Horne, Christopher J. Dares, Simon M. Pimblott, Stephen P. Mezyk, Bruce J Mincher


    The rate of reduction of hexavalent 243Am due to self-radiolysis was measured across a range of total Americium and nitric acid concentrations. These so-called autoreduction rates exhibited zero-order kinetics with respect to the concentration of hexavalent Americium, and pseudo-first-order kinetics with respect to the total concentration of Americium. However, the rate constants did vary with nitric acid concentration, resulting in values of 0.0048 ± 0.0003, 0.0075 ± 0.0005, and 0.0054 ± 0.0003 h–1 for 1.0, 3.0, and 6.5 M HNO3, respectively. This indicates that reduction is due to reaction of hexavalent Americium with the radiolysis products of total Americium decay. The concentration changes of Am(III), Am(V), and Am(VI) were determined by UV–vis spectroscopy. The Am(III) molar extinction coefficients are known; however, the unknown values for the Am(V) and Am(VI) absorbances across the studied range of nitric acid concentrations were determined by sensitivity analysis in which a mass balance with the k…

  • minor actinide separation in the reprocessing of spent nuclear fuels recent advances in the united states
    Reprocessing and Recycling of Spent Nuclear Fuel, 2015
    Co-Authors: Bruce A Moyer, Gregg J Lumetta, Bruce J Mincher


    Essential for realizing the goal of a fully closed nuclear fuel cycle, separations of minor actinides are being pursued in the United States at the level of fundamental research through demonstration of process concepts. Research entails developing a concept for achieving a separation of Americium and curium from fission products (FPs) using a single solvent system for the combined extraction of trivalent actinides and lanthanides together with selective complexants for stripping Americium and curium. An alternative line of research addresses the question concerning the possibility of exploiting the higher oxidation states of Americium to achieve its selective separation from FPs and curium.

  • tributylphosphate extraction behavior of bismuthate oxidized Americium
    Inorganic Chemistry, 2008
    Co-Authors: Bruce J Mincher, Leigh R Martin, Nicholas C Schmitt


    Higher oxidation states of Americium have long been known; however, options for their preparation in acidic solution are limited. The conventional choice, silver-catalyzed peroxydisulfate, is not useful at nitric acid concentrations above about 0.3 M. We investigated the use of sodium bismuthate as an oxidant for Am3+ in acidic solution. Room-temperature oxidation produced AmO22+ quantitatively, whereas oxidation at 80 °C produced AmO2+ quantitatively. The efficacy of the method for the production of oxidized Americium was verified by fluoride precipitation and by spectroscopic absorbance measurements. We performed absorbance measurements using a conventional 1 cm cell for high Americium concentrations and a 100 cm liquid waveguide capillary cell for low Americium concentrations. Extinction coefficients for the absorbance of Am3+ at 503 nm, AmO2+ at 514 nm, and AmO22+ at 666 nm in 0.1 M nitric acid are reported. We also performed solvent extraction experiments with the hexavalent Americium using the commo…

Ralf Sudowe – One of the best experts on this subject based on the ideXlab platform.

  • separation of Americium in high oxidation states from curium utilizing sodium bismuthate
    Analytical Chemistry, 2016
    Co-Authors: Jason M. Richards, Ralf Sudowe


    A simple separation of Americium from curium would support closure of the nuclear fuel cycle, assist in nuclear forensic analysis, and allow for more accurate measurement of neutron capture properties of 241Am. Methods for the separation of Americium from curium are however complicated and time-consuming due to the similar chemical properties of these elements. In this work a novel method for the separation of Americium from curium in nitric acid media was developed using sodium bismuthate to perform both the oxidation and separation. Sodium bismuthate is shown to be a promising material for performing a simple and rapid separation. Curium is more strongly retained than Americium on the undissolved sodium bismuthate at nitric acid concentrations below 1.0 M. A separation factor of ∼90 was obtained in 0.1 M nitric acid. This separation factor is achieved within the first minute of contact and is maintained for at least 2 h of contact. Separations using sodium bismuthate were performed using solid–liquid ex…

Thibaud Delahaye – One of the best experts on this subject based on the ideXlab platform.

  • peculiar behavior of u am o2 δ compounds for high Americium contents evidenced by xrd xas and raman spectroscopy
    Inorganic Chemistry, 2015
    Co-Authors: Florent Lebreton, Denis Horlait, Richard Caraballo, Philippe Martin, Andreas C Scheinost, Andre Rossberg, Christophe Jegou, Thibaud Delahaye


    In U1–xAmxO2±δ compounds with low Americium content (x ≤ 20 atom %) and oxygen-to-metal (O/M) ratios close to 2.0, AmIII+ cations are charge-balanced by an equivalent amount of UV+ cations while the fluorite structure of pure UIV+O2 is maintained. Up to now, it is unknown whether this observation also holds for higher Americium contents. In this study, we combined X-ray diffraction with Raman and X-ray absorption spectroscopies to investigate a U0.5Am0.5O2±δ compound. Our results indicate that Americium is again only present as AmIII+, while UV+ remains below the amount required for charge balance. Unlike lower Americium contents, this leads to an overall oxygen hypostoichiometry with an average O/M ratio of 1.92(2). The cationic sublattice is only slightly affected by the coexistence of large amounts of reduced (AmIII+) and oxidized (UV+) cations, whereas significant deviations from the fluorite structure are evidenced by both extended X-ray absorption fine structure and Raman spectroscopies in the oxyge…

  • Application of Weak Acid Resin process to the production of spherical and calibrated oxide precursor bearing uranium and Americium overview of 10 years research at CEA
    , 2015
    Co-Authors: S. Picart, Thibaud Delahaye, Jean-pierre Bayle, A. Gauthé, I. Jobelin, J. Dauby, Elisabeth Remy, P. Parant, M. Caisso, H. Mokhtari


    Mixed uranium-Americium oxides are one of the materials envisaged for Americium Bearing Blankets dedicated to Americium transmutation in fast neutron reactor. Recently, several processes have been developed in order to improve and validate fabrication in terms of material specifications such as density and homogeneity. The challenge is also to propose simplifications for lowering industrial costs and hazards linked to dust generation of highly contaminating and irradiating compounds such as Am based oxides which presence complicates grinding and milling operations commonly encountered in conventional powder metallurgy processes. Our goal was then to develop an innovative and dust-free process for synthetizing uranium-Americium mixed oxide in the form of spherules of the size of hundreds microns in order to facilitate remote handling operations and reduce fine dust dispersion. In this way, the Weak Acid Resin route (WAR), originally dedicated to uranium carbide kernel synthesis, was selected and adapted to mixed oxide fabrication incorporating uranium and Americium. This process is based on the fixation of actinide cations in acrylic resin beads and the subsequent mineralization in air of the metal loaded resin into oxide microspheres. A final reducing thermal treatment is then necessary to adjust oxygen stoichiometry and form the mixed oxide phase. This process has been tested and validated for many oxide compounds such as single lanthanide or uranium oxide but also for mixed uranium and lanthanides or Americium compounds. Therefore, this contribution aims at describing the development of WAR process for oxide synthesis during recent years at CEA Marcoule and will detail particularly the synthesis and characterization of U0.9Am0.1O2±x mixed oxide precursor. The current study of pelletization and sintering of such precursors, known as Calcined Resin Microsphere Pelletization process (CRMP), will be also presented and will illustrate the application of WAR spherule metallurgy to the fabrication of uranium and Americium containing materials.

  • Application of Weak Acid Resin process to the production of spherical and calibrated oxide precursor bearing uranium and Americiumoverview of 10 years research at CEA
    , 2015
    Co-Authors: S. Picart, Thibaud Delahaye, Jean-pierre Bayle, A. Gauthé, I. Jobelin, J. Dauby, P. Parant, M. Caisso, E. Remy, H. Mokhtari


    This paper is dedicated to the adaptation of the Weak Acid Resin process (WAR) to the elaboration of uranium-Americium mixed oxide microspheres as precursors for the fabrication of Americium Bearing Blankets (AmBB). It describes successive developments of WAR process from lanthanide simple oxide synthesis to actinide(s) bearing mixed oxide preparation. Recent studies demonstrated the scientific feasibility of the preparation of a dense uranium-Americium mixed oxide pellets with 10 $_{at}$% of Am vs heavy metal and with 95 % of theoretical density (TD) from those innovative microsphere precursors