Study of spent nuclear fuel components distribution in a "liquid metal – molten salt" system with a variable composition of the liquid metal phase

Объектом исследования являются жидкометаллические двухфазные (Ж+ИМС) и гомогенные сплавы урана с эвтектическими расплавами Ga-Al и Ga-In. Целью настоящей работы является комплексное изучение поведения и экспериментальное определение основных термодинамических характеристик компонентов облученного ядерного топлива, в частности урана, а также изучение процессов распределения и селективного извлечения компонентов ОЯТ в системе «жидкометаллический сплав – солевой расплав» с неэвтектическим составом жидкометаллической фазы, в широком температурном диапазоне (423 – 973 К).The object of this study are two-phase liquid-metal (L + IMC ) and homogeneous alloys of uranium with eutectic melts of Ga-Al and Ga-In. The purpose of this study is to conduct a comprehensive study and experimental determination of the basic thermodynamic characteristics of the components of spent nuclear fuel, including uranium, as well as the study of the processes of distribution and selective extraction of components of spent nuclear fuel in the "liquid metal alloy - molten salt" with noneutectic composition of the liquid metal phase in a wide temperature range (423 - 973K).Программа развития УрФУ на 2013 год (п.1.2.2.3

Lanthanum Activity in La–U–Ga–X Systems (X = Al or In)

Lanthanum activity was determined for the first time in La–U–Ga–X (X = Al or In) alloys. Ga–In and Ga–Al alloys were taken in the eutectic composition (21.8 wt.% In and 1.6 wt.% Al, respectively). Measurements were performed between 573 and 1073 K employing the e.m.f. method. Keywords: Lanthanum; Uranium; Gallium-Indium Eutectic; Gallium-Aluminium Eutectic; Activity; Thermodynamics

The effect of fission product elements on the behavior of uranyl species in alkali chloride melts: A contribution towards reprocessing spent oxide fuels

The reactions of uranyl(VI) containing chloride melts with molybdenum, niobium, zirconium and palladium were studied using high temperature electronic absorption spectroscopy. Depending on the nature of the added element uranium is reduced to uranyl(V) and uranium(IV) chloro-species and UO2. Palladium, niobium and zirconium can all be removed from a uranyl(VI)-containing melt using molybdenum metal and the melt can then be purified from Mo(III) ions by bubbling Cl2 gas. Such approach can be employed for removal a number of fission product elements from molten chloride baths during reprocessing spent oxide fuels. ©The Electrochemical Society.Physical and Analytical Electrochemistry;Electrodeposition;Energy Technolog

Structure and Phase Composition of Zirconium Fuel Claddings in Initial State and after Creep Tests

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Quasiperiodic functions theory and the superlattice potentials for a two-dimensional electron gas

We consider Novikov problem of the classification of level curves of quasiperiodic functions on the plane and its connection with the conductivity of two-dimensional electron gas in the presence of both orthogonal magnetic field and the superlattice potentials of special type. We show that the modulation techniques used in the recent papers on the 2D heterostructures permit to obtain the general quasiperiodic potentials for 2D electron gas and consider the asymptotic limit of conductivity when $\tau \to \infty$. Using the theory of quasiperiodic functions we introduce here the topological characteristics of such potentials observable in the conductivity. The corresponding characteristics are the direct analog of the "topological numbers" introduced previously in the conductivity of normal metals.Comment: Revtex, 16 pages, 12 figure

On the formation of uranium(V) species in alkali chloride melts

Uranyl(V) species are normally unstable in solutions but are here shown to be stable in high-temperature chloride melts. Reactions leading to the formation of UO2Cl4 3- ions were studied, including thermal decomposition and chemical reduction of uranyl(VI) chlorospecies in various alkali chloride melts (LiCl, 3LiCl-2KCl, NaCl-KCl, and NaCl-2CsCl) at 550-850 °C. Decomposition of UO2Cl4 2- species under reduced pressure, with inert gas bubbling through the melt or using zirconium getter in the atmosphere results in the formation of UO 2Cl4 3- and UO2. Elemental tellurium, palladium, silver, molybdenum, niobium, zirconium, and hydrogen, as well as niobium and zirconium ions were tested as the reducing agents. The outcome of the reaction depends on the reductant used and its electrochemical properties: uranyl(VI) species can be reduced to uranyl(V) and uranium(IV) ions, and to uranium dioxide. © 2010 IUPAC

Study of uranium solubility in gallium-indium eutectic alloy by emf method

Activity, activity coefficients and solubility of uranium in Ga-In eutectic alloy as well as activity of uranium in U-Ga and U-In alloys were determined between 573 and 1073 K using electromotive force (emf) method. © 2013 Pleiades Publishing, Ltd

Electrode and redox potentials of molybdenum and stability of molybdenum chloro-species in alkali chloride melts

Molybdenum electrode and Mo(III)/(IV) redox potentials were measured in fused alkali chlorides. Experiments were performed in individual salts (LiCl, NaCl, KCl, RbCl and CsCl) and in several binary and ternary eutectic or low-melting mixtures between 633 and 1173 K (depending on the melting point of the solvent salt). Formal standard electrode potentials E∗ Mo/Mo(III) and redox potentials E∗ Mo(III)/Mo(IV) in respect to Cl-/Cl2 couple and Gibbs free energy change of formation of molybdenum(III) chloride in alkali chloride melts were calculated. Electronic absorption spectra of Mo(III) ions were recorded, and spectroscopic parameters of MoCl6 3- complex ions determined. High temperature spectroscopy measurements were used to study the stability of Mo(III) chloro-species in fused chlorides and the reaction rates of Mo(III) ions disproportionation were also determined. Diffusion coefficients of molybdenum ions in LiCl-KCl-CsCl and NaCl-CsCl eutectic based melts were determined from the results of electrochemical measurements. © The Author(s) 2017

Electronic structure study of YNbTiO6_6 vs. CaNb2_2O6_6 with U, Pu and minor actinide substitutions using compound-tunable embedding potential method

The compound-tunable embedding potential (CTEP) method is applied to study actinide substitutions in the niobate crystals YNbTiO$_6$ and CaNb$_2$O$_6$. Two one-center clusters centered on Ca and Y are built and 20 substitutions of Ca and Y with U, Np, Pu, Am, and Cm in four different oxidation states were made for each cluster. Geometry relaxation is performed for each resulting structure, and electronic properties are analyzed by evaluating the spin density distribution and X-ray emission spectra chemical shifts. Though the studied embedded clusters with actinides having the same oxidation state are found in general to yield similar local structure distortions, for Am and Cm in high "starting" oxidation states the electron transfer from the environment was found, resulting in decrease of their oxidation states, while for "starting" U$^{\rm III}$ state the electron transfer goes in the opposite direction, resulting in increase of its oxidation state to U$^{\rm IV}$. The U substitutions are additionally studied with the use of multi-center models, which can provide both more structural and electronic relaxation and also include charge-compensating vacancies. For "starting" U$^{\rm VI}$ case, the decrease in oxidation state similar to that of Am$^{\rm VI}$ and Cm$^{\rm VI}$ in one-center clusters is observed in our calculations but in a different way. Since the really synthesized YNbTiO$_6$ structures can not be considered as perfect (periodic) crystals because the Nb and Ti atoms are statistically distributed within them occupying the same Wyckoff positions, different Ti $\leftrightarrow$ Nb substitutions are studied and corresponding structural changes are estimated