Processing of vanadium and niobium electrodeposited from alkali chloride melts

The methods of hydrometallurgical treatment of cathodic deposits obtained by electrorefining vanadium and niobium metals in chloride melts were studied. The effectiveness of employing nitric acid was demonstrated. The optimal conditions of leaching trapped salt were determined: HNO3 concentration of 2.5 wt. % for vanadium and 5 wt. % for niobium; solid-to-liquid ratio 1:10 for both metals. The effect of increasing duration of a washing cycle on number of process stages was investigated. The methods of final washing and drying metallic powders were considered. ©The Electrochemical Society.Physical and Analytical Electrochemistry;Electrodeposition;Energy Technolog

Study of causes of film formation on the electrolyte surface during niobium electrorefining

Formation of a conducting film on the surface of fused electrolyte during electrorefining of niobium in chloride melts was investigated. It was found that this film has metallic nature and is formed as a result of disproportionation of niobium(III) ions at a liquid-gas interface. Decreasing temperature gradient along the heated part of the electrolyser can be used to limit the influence of the disproportionation onto film formation. The metal film formation on solid ceramics can be used for creation of conducting layers on various oxide materials. copyright The Electrochemical Society.Electrochemical Society, Phys. Anal. Electrochem. Div.;Electrochemical Society, Electrodeposition Division;Electrochemical Society, High Temperature Materials Division;Electrochemical Society, Battery Division;Electrochemical Society, Energy Technology Divisio

Behaviour of rare earth elements in molten salts in relation to pyrochemical reprocessing of spent nuclear fuels

The kinetics of chlorination of lanthanide oxides (by Cl2 and HCl) and precipitation of lanthanide phosphates was studied by in situ electronic absorption spectroscopy in 3LiC1-2KC1 and NaCl-KCl melts at 400-750°C Products of the chlorination are the corresponding hexachlorospecies, LnCl63-, and the rate of chlorination increases with increasing temperature. Composition of the precipitated phosphates depends on the melt composition and 1.5-5 fold excess of phosphate, depending on the nature of lanthanide, is needed for the complete removal of the lanthanides from the melt. Over three hours are required for completing the reaction of phosphate precipitation. copyright The Electrochemical Society.Electrochemical Society, Phys. Anal. Electrochem. Div.;Electrochemical Society, Electrodeposition Division;Electrochemical Society, High Temperature Materials Division;Electrochemical Society, Battery Division;Electrochemical Society, Energy Technology Divisio

Effect of melt composition on the reaction of uranium dioxide with hydrogen chloride in molten alkali chlorides

The reaction of uranium dioxide with excess hydrogen chloride in alkali chloride melts (LiCl, 3LiCl-2KCl, NaCl-KCl and NaCl-2CsCl) has been studied between 450 and 750°C, and the reaction products were characterized by electronic absorption and X-ray absorption spectroscopy. Uranium(V), [UO 2Cl4]3-, and uranium(IV), [UCl 6]2-, species were formed. They depended upon the temperature and the radius of the alkali cations present. Uranium(V) ions predominated in melts with small cations (LiCl and 3LiCl-2KCl). © 2007 Verlag der Zeitschrift für Naturforschung

Study of the Electrochemical Behavior of Vanadium Ions in Chloride Melts Using Voltammetry Methods

The electrode processes involving vanadium species were studied at 690-860 oC in NaCl-KCl-based melts employing various electrochemical methods. Analysis of the red-ox processes in chloride melts showed that V(II) and V(III) complex chloride ions are stable in these media

Research and Development of the pyrochemical processing for the mixed nitride uranium-plutonium fuel

A mixed nitride U-Pu SNF pyrochemical reprocessing technology was suggested. It includes the following basic operations: dissolution of key components using the CdCl2 or PbCl2 oxidizer in chloride melt and their subsequent deposition as oxides. The obtained product, which is a mixture of actinides and rare-earth metals, may be additionally purified using hydrometallurgical processes (combined technology) or using pyrochemical methods. The mixture of actinides oxides is reduced to metal ("metallization"), additionally purified from fission products during electrorefining and then Am and Cm are separated using the potentiostatic electrolysis in order to obtain products that may be used for pure fuel fabrication. © 2020 IOP Publishing Ltd. All rights reserved

Polymorphs of Rb3ScF6: X-ray and Neutron Diffraction, Solid-State NMR, and Density Functional Theory Calculations Study

The crystal structures of three polymorphs of Rb3ScF6 have been determined through a combination of synchrotron, laboratory X-ray, and neutron powder diffraction, electron diffraction, and multinuclear high-field solid-state NMR studies. The room temperature (RT; α) and medium-temperature (β) structures are tetragonal, with space groups I41/a (Z = 80) and I4/m (Z = 10) and lattice parameters a = 20.2561(4) Å, c = 36.5160(0) Å and a = 14.4093(2) Å, c = 9.2015(1) Å at RT and 187 °C, respectively. The high-temperature (γ) structure is cubic space group Fm3¯ m (Z = 4) with a = 9.1944(1) Å at 250 °C. The temperatures of the phase transitions were measured at 141 and 201 °C. The three α, β, and γRb3ScF6 phases are isostructural with the α, β, and δforms of the potassium cryolite. Detailed structural characterizations were performed by density functional theory as well as NMR. In the case of the β polymorph, the dynamic rotations of the ScF6 octahedra of both Sc crystallographic sites have been detailed. © 2021 American Chemical Society.For DFT calculations, we thank the “Centre de Calcul Scientifique en region Centre” (Orléans, France). We acknowledge the Interface, Confinement, Materials and Nanostructures (Orléans, France) for access to their transmission electron microscope. Financial support from the IR-RMN-THC Fr3050 CNRS for conducting the research is gratefully acknowledged. This study was also financially supported by VEGA-2/0060/18 and ITMS project (code 313021T081, Research & Innovation Operational Programme funded by the ERDF). We thank also Dr. F. Vivet, Dr. F. Fayon, and Dr. D. Massiot for useful discussions

CORROSION, MECHANICAL AND THERMOPHYSICALPROPERTIES OF THE NEW ALLOY ON THE BASIS OF THE SYSTEM «Ni-Cr-Mo» WITH A LOW CARBON CONTENT

The mechanical and thermophysical properties as well as the tendency to intergranular corrosion of the new nickel alloy with low carbon content were investigated. It was found that Physical and mechanical properties of the prepared alloy under high temperature conditions are influenced by changes of structure and composition. In separate series of experiments corrosion resistance of the material was studied in a wide temperature range (450 – 650 °C) in the molten chloroaluminate melts. The rates and the mechanisms of corrosion of the studied materials were determined. The processes taking place during the interaction between metals and melts were investigated

CORROSION, MECHANICAL AND THERMOPHYSICAL PROPERTIES OF THE NEW ALLOY KHN62M

The mechanical and thermophysical properties as well as the tendency to intergranular corrosion of the new nickel alloy with low carbon content were investigated. It was found that physical and mechanical properties of the prepared alloy under high temperature conditions are influenced by changes of structure and composition. In separate series of experiments corrosion resistance of the material was studied in a wide temperature range (450 – 650 °C) in the molten chloroaluminate melts. The rates and the mechanisms of corrosion of the studied materials were determined. The processes taking place during the interaction between metals and melts were investigated