Suddhasattwa Ghosh

PRAGAMAN: A Computer Code for Simulation of Electrotransport During Molten Salt Electrorefining

Abstract The computer code PRAGAMAN has been developed for numerical simulation of electrotransport during molten salt electrorefining of spent metallic fuels. The code is based on the thermodynamic equilibriums among pairs of elements and their chlorides that exist at the anode-electrolyte salt and cathode-electrolyte salt interfaces. It uses nonlinear and linear equations to arrive at real solutions for all 16 possible conditions that could be envisaged with respect to the solubilities of U and Pu at the anode and cathode. It can handle the electrotransport of eight elements representing typical actinides, minor actinides, and fission products, as well as potential dependent electrotransport of U and Pu.

Exchange Current Density and Diffusion Layer Thickness in Molten LiCl-KCl Eutectic: A Modeling Perspective for Pyroprocessing of Metal Fuels

Abstract The DIFAC (DIFfusion of Actinides in EleCtrorefiner) computer code for pyroprocessing, developed earlier by the authors, is modified in the present work to model electrorefining at the liquid cadmium electrode. The modeling of electrorefining of metal fuels requires accurate knowledge of two important kinetic parameters: exchange current density io and diffusion layer thickness δ. These are estimated in the present work by polarization methods and employing Tafel and Allen-Hickling analysis for Gd3+/Gd, U3+/U, and Zr2+/Zr couples in LiCl-KCl eutectic at 773 K for an inert cathode and compared with literature data, wherever possible. The equilibrium potentials for these couples at an inert electrode are found to be –1.94, –1.52, and –1.22 V, respectively, at 773 K. Electrochemical studies are also carried out in LiCl-KCl eutectic to estimate io and δ for the anodic dissolution of Na-bonded U-Zr and Gd-U-Zr alloy and are compared with the anodic dissolution of U-Pu-Zr alloy. The equilibrium potential of Na-bonded U-Zr alloy in LiCl-KCl-UCl3 was found to be –1.46 V, and those for Gd-U-Zr alloy in blank LiCl-KCl and LiCl-KCl-UCl3 were –1.56 and –1.34 V, respectively, at 773 K. The exchange current densities of Na-bonded U-Zr and Gd-U-Zr alloy were found to be in the range of 40.1 to 46.5 mA · cm−2 and 16.8 to 27.3 mA · cm−2 at 773 K, respectively. A preliminary design of the liquid cadmium electrode suitable for laboratory-scale experiments on uranium- and plutonium-based systems is also reported in the present work. The io and δ of gadolinium, uranium, and zirconium are subsequently estimated at the liquid cadmium electrode at 773 K. The equilibrium potentials for Gd3+/Cd6Gd, U3+/[U]Cd, and Zr2+/Cd3Zr couples in LiCl-KCl eutectic at 773 K for the liquid cadmium electrode are found to be –1.35, –1.13, and −1.12 V, respectively. Finally, a few algorithms are proposed for modeling electrorefining data at the liquid cadmium electrode for multicomponent systems.

Modeling the Anodic Behavior of U, Zr, and U-Zr Alloy in Molten LiCl-KCl Eutectic

Abstract The DIFfusion of Actinides in EleCtrorefiner (DIFAC) computer code has been developed and is used to calculate the variation of the anode potential with time during constant current anodic dissolution of U, Zr, and U-Zr alloy in molten LiCl-KCl eutectic. A few algorithms are proposed within the framework of the DIFAC code for modeling the activation and concentration overpotentials during anodic dissolution. These algorithms are based on an iterative search procedure and would later be applied to modeling the electrorefining of a multicomponent metallic fuel system.