Application of Low Melting Metals for Separation of Uranium and Zirconium in a “Fused Chloride—Liquid Alloy” System

Closeness of electrochemical properties of uranium and zirconium makes separation of these metals in pyroelectrochemical reprocessing of spent nuclear fuels a challenging task. Varying electrode material can change metals’ deposition potentials. The study was aimed at assessing the effect of the cathode material on deposition potentials of zirconium and uranium from 3LiCl–2KCl based melts. Solid (tungsten) and liquid (gallium, zinc, Ga–Zn, Ga–Sn and Ga–In alloy) working electrodes were tested at 532–637 °C. Galvanostatic cathodic polarization was employed and the applied cathodic current varied from 0.0001 to 1 A. Gallium–zinc eutectic alloy demonstrated the largest difference of zirconium and uranium deposition potentials. Zirconium/uranium separation factors were experimentally determined in a “molten salt—liquid metal” system for gallium and Ga–Zn eutectic based alloys.

Numerical Simulation of Formation of Melt Jets in Melt-Coolant Interactions

Fragmentation of molten metal droplets is an important process in steam explosions caused by melt-coolant interactions. Ciccarelli and Frost (1994) found the formation of melt jets (or spikes) in hot melt drops immersed in water. In order to gain insight into this mechanism, they carried out experiments where melt jets were formed in a stratified water/liquid metal system with local generation of high-pressure vapor at the interface. This paper is dedicated to investigating how melt jets are formed in this mechanism when a stratified water/liquid metal system is analyzed. Also, a study of the most significant parameters in this process is performed. A 2D computational fluid dynamics (CFD) simulation is carried out using ANSYS Fluent software to study these phenomena by having water above hot liquid metal, a vapor film in between and a pressure pulse in the vapor film. The results show that the larger the pressure or density, the greater the melt jet length. In order to confirm this, deep neural network algorithm created by TensorFlow library was implemented to facilitate the understanding of the studied phenomena. The formation of melt jets observed in Ciccarelli and Frost’s experiments is also observed in current simulation.

Thermodynamic Modeling of Phase Equilibrium in Fe-Y-Cr-C-O Liquid Metal System

The thermodynamic characteristics of processes in the liquid metal system Fe–Y–Cr–C–O are considered as applied to low-carbon and low-alloy metal. The critical parameters for the state diagram of the oxide system Y2O3–Cr2O3 were established based on the values quoted in literature. The temperature dependence of the melting reaction constant Y2O3·Cr2O3 was determined. The coordinates of eutectic transformation points for the system Y2O3–Cr2O3 were calculated. In accordance with subregular solution theory, the energetic parameters which are necessary to calculate the activities Cr2O3 and Y2O3 of oxide melts in the system Y2O3–Cr2O3 were determined. The energetic parameters of subregular solution theories for the oxide system FeO–Cr2O3–Y2O3 were determined based on the values for the binary systems FeO–Y2O3, FeO–Cr2O3 and Y2O3–Cr2O3. The view of this diagram, as coupled with the existence domain of liquid metal within the framework of the quaternary system Fe–Y–Cr–O–С, suggests that low-carbon chromic liquid metal when injected with yttrium can form the following non-metallic inclusions: |Cr2O3|, |Y2O3|, |FeO·Cr2O3|, |Y2O3·Cr2O3| or oxide melt (FeO, Y2O3, Cr2O3). Oxide melt may contain up to 2 % of divalent chrome (Cr2+). The equilibrium constants for the main reactions of steel deoxidation with the formation of liquid, solid and gas products of chemical reactions were also established. The activity of components dissolved in metal was calculated using interaction parameters. The set of derived expressions for the activity of components and the dependences of equilibrium constants of chemical reactions and phase transformations allowed us to diagram the surface of component solubility in liquid metal (SCSM). SCSM diagrams show the compositions of liquid metal and indicate oxide phases which are in equilibrium with liquid metal.