Byung Heung Park

AN EXPERIMENTAL STUDY ON AN ELECTROCHEMICAL REDUCTION OF AN OXIDE MIXTURE IN THE ADVANCED SPENT-FUEL CONDITIONING PROCESS

An electrochemical reduction of a mixture of metal oxides was conducted in a LiCl molten salt containing 3 wt% Li₂O at 650℃. The oxide reduction was carried out by applying a current to an electrolysis cell, and the Li₂O concentration was analyzed during each run. The concentration of Li₂O in the electrolyte bulk phase gradually decreases according to Faraday’s law due to a slow diffusion of the O₂- ions. A hindrance effect of the unreduced metal oxides was observed for the reduction of the uranium oxide. Cs, Sr, and Ba of high heat-load fission products were diffused into and accumulated in the salt phase as predicted with thermodynamic consideration.

Advances in the ACP Facility Electrochemical Reduction Process

Abstract The Advanced Spent Fuel Conditioning Process (ACP) has been proposed and developed by the Korea Atomic Energy Research Institute (KAERI) to treat oxide spent fuels (SFs) from light water reactors to reduce the volume, heat load, and radiotoxicity of processed SFs. In the ACP, an electrochemical reduction process has been developed, and an electroreducer with a maximum 20 kg/batch scale has been installed in the KAERI ACP facility. In this study, electrochemical reduction runs were carried out with 10 kg/batch of SIMFUEL at 923 K under current controlled conditions. The electrochemical reduction processes adopted LiCl molten salt as the electrolyte, and initially, 3.0 or 4.9 wt% of Li2O was dissolved to increase the oxygen ion activity in this work. A porous MgO basket was used to contain the powder-type test fuels; the basket and fuels along with a metal conductor as the current lead comprise a packed bed reactor where reduction takes place. During the three runs of reduction, the Li2O concentration was decreased with the applied current, and it was found that Ar bubbling in the bulk phase accelerated the depletion rate. Alkali and alkaline earth metal elements from the test fuels had dissolved and accumulated in the molten salt. The reduced metal was recovered after the runs, and sampled products exhibited >90% reduction yields with respect to their positions in the MgO basket. In addition to the experimental study, a three-dimensional model was developed to analyze respective phases in a reactor by using commercial tools. Streamlines of the fluids, the temperature distribution, and the oxygen partial pressure were obtained for the gas phase in motion, and the potential field calculation was carried out to reveal that most of the potential was applied to the cathode side because of the low electrical conductivities of the constituents.

Volumetric properties of binary mixtures of 1-butyl-3-methylimidazolium halides with water, methanol or ethanol at 293.15 to 318.15 K

Densities of nine binary solutions made of one of three 1-butyl-3-methylimidazolium ([bmim]) halides with water, methanol, or ethanol were measured at atmospheric pressure. The compositions of an ionic liquid ([bmim]Cl, [bmim]Br, or [bmim]I) were increased up to 0.4 as a mole fraction at a given temperature within a range of 293.15 to 318.15 K. The measured values were correlated by a quadratic equation to obtain a temperature dependency of the respective systems. Furthermore, the equation was used to obtain the volume expansivity, which would be used for a pressure-volume-temperature behavior of a condensed phase. The apparent molar volumes were also calculated from the experimental data. The remarkable distinction of the volumetric property behavior between aqueous and nonaqueous solutions was found and attributed to strong ion–solvent interactions in the aqueous systems.

Reactive Extraction of Propionic Acid Using Tri-n-octylamine

Propionic acid has been received increasing attention due to its various usages as an antifungal agent in food and a chemical in the production of several chemical products. In order to develop an alternative production process of propionic acid such as fermentation of glycerol, the cost effective recovery process of propionic acid from its fermentation broth is needed. Differently from conventional physical extraction, long chain amine (TOA)-based extraction is the separation process using reactions between amine and materials extracted. The equilibrium distribution of propionic acid increased with amine concentration and decreased with increase of n-heptane composition in mixed diluents. From the loading values with TOA concentrations, it was found that the stoichiometries of acid-amine-1-octanol complex were (1,1) and (1,1,1). From this study, amine-based extraction can be promising separation process for the recovery of propionic acid.

Electrochemical behavior of chalcogen and halogen fission products in pyro-electrochemical reduction process

An electrochemical process using a molten LiCl has been developed to reduce metal oxides from spent fuel (SF) from nuclear power plants, under the name of an electrolytic reduction process as a part of pyroprocessing. The researches on the electrolytic reduction have been investigated to determine the process conditions such as the shape of cathode, the form of feed material, and cell configuration. SF contains various kinds of oxides and chalcogen and halogen (group VIB and VIIB) compounds are expected to be dissolved into LiCl which is adopted as an electrolyte of the electrolytic reduction process. However, the behaviors of such compounds have not been experimentally clarified yet. In this work, the chemical and electrochemical behaviors of chalcogen and halogen compounds during the electrolytic reduction process were thermodynamically analyzed to understand their stability and final forms. LPP diagrams were used to determine the probable compounds on cathode and anode, respectively. Chemical and electrochemical calculations were carried out to find that it is required to suppress the reactions associated with chalcogens to protect anode and increase current efficiency.Graphical Abstract

Analysis of thermophysical property data of HIx components for I2 crystallizer design in sulfur-iodine process to produce hydrogen

I2 crystallization could be a technical option in HI decomposition section of SI thermochemical water splitting process to increase process efficiency. Design of a crystallizer requires experimental data as well as corresponding equations for thermophysical properties of HIx solution, which is a named ternary solution of H2O, HI, and I2. However, so far, there are no available analyses on them. We collected experimental data and corresponding equations with temperature parameters and compared the equations with the data to analyze their accuracy and credibility. Thermal conductivity was updated in this work while keeping a structure of a corresponding equation. Relative deviations were estimated for liquid density, thermal conductivity, viscosity, and heat capacity and summarized with temperature for H2O, HI, and I2. Solution density and viscosity of binary H2O-HI solution were also analyzed with an empirical equation under a limited condition and with predictable methods exhibiting satisfactory consistency.

Composition and Pressure Estimation on Salt Distillation Process after Electrorefining for Spent Nuclear Fuel

A pyroprocessing technology has been developed to process spent nuclear fuels with decreased waste and increased proliferation resistance. A main process of the pyroprocessing is an electrorefining which requires a post-treatment for recovered uranium. A distillation approach is adopted to remove an electrolyte salt residue on the uranium. In this work, the vapor composition of the distillation process and the total pressure were estimated to obtain basic data for process design and integration. Six chlorides including KCl, LiCl, UCl3, PuCl3, CeCl3, and YCl3 were considered to understand the behavior of the representative components of actinides and lanthanides. It was found that small amount of the actinides and lanthanides would be accompanied by the electrolyte salts (KCl and LiCl) during the distillation under high vacuum.