Seong-Won Park

An Electrochemical Reduction of Uranium Oxide in the Advanced Spent-Fuel Conditioning Process

Abstract The Korea Atomic Energy Research Institute is currently developing the Advanced Spent-Fuel Conditioning Process (ACP) based on a pyrochemical process. An electrochemical reduction process has been developed as a key unit of the ACP. In this work, an electrochemical reduction of U3O8 powder in a LiCl-Li2O molten salt has been investigated in an electrochemical cell with a unique cathode assembly, which consists of a porous magnesia membrane, oxide powder, and a solid electricity conductor. The experimental results suggest successful demonstration of this process, exhibiting a reduction conversion of U3O8 of >99% for a batch.

Application of Graphite as a Cathode Material for Electrorefining of Uranium

Abstract The conventional electrorefiners to treat a metallic spent fuel equipped with a steel cathode have a sticking characteristic that hinders their overall processing efficiency. The critical question in order to enhance their throughput is how to decrease the sticking coefficient of the cathode. In order to realize this purpose, the conventional steel cathode was replaced with a graphite one. The graphite cathode exhibited self-scraping behavior in which the electrodeposited uranium dendrite falls from the cathode surface on its own without any kind of mechanical operation such as a scraping and rotation of the electrode. This self-scraping phenomenon of the graphite cathode was interpreted to be due to the formation of a uranium graphite intercalation compound. In this self-scraping mechanism, uranium atoms elongate at the graphite’s outermost layer by an intercalation reaction, so the deposited uranium dendrite falls off spontaneously as the gravitational force exceeds the bonding strength of the layers. Based on our preliminary work, a self-scraping should increase the efficiency of an electrorefiner due to the elimination of a mechanical scraping as well as the electrolytic stripping steps of the cathode.

Assessment of a High-Throughput Electrorefining Concept for a Spent Metallic Nuclear Fuel—I: Computational Fluid Dynamics Analysis

Numerical assessment of a high-throughput electrorefining concept for a spent metallic fuel was carried out by using a commercial computational fluid dynamics code, CFX. An electrorefiner concept equipped with a graphite cathode bundle was designed to recover a high-purity uranium product continuously without a noble metal contamination. The performance of the process for the decontamination of a noble metal in a uranium product was evaluated as a function of the process parameters, such as the rotation speeds of the stirrer and the anode basket. The effects of the void fraction of the anode basket cavity and the morphology of the uranium dendrite on the molten-salt flow and collection behavior were also evaluated with the calculated results.

Corrosion behavior of Ni−Base alloys in a hot lithium molten salt under an oxidizing atmosphere

The electrolytic reduction of a spent oxide fuel involves the liberation of the oxygen in molten LiCl electrolyte, which is a chemically aggressive environment that is excessively corrosive for typical structural materials. Accordingly, it is essential to choose the optimum material for the processing equipment that handles the molten salt. In this study, the corrosion behaviors of Haynes 263, Haynes 75, Inconel 718 and Inconel X-750 in a molten LiCl−Li2O salt under an oxidizing atmosphere were investigated at 650°C for 72 to 216 hrs. The Haynes 263 alloy showed the best corrosion resistance among the examined alloys. The corrosion products of Haynes 263 were Li(Ni,Co)O2 and LiTiO2; those of Haynes 75 were Cr2O3, NiFe2O4, LiNiO2 and Li2FiFe2O4; while Cr2O3, NiFe2O4 and CrNbO4 were identified as the corrosion products of Inconel 718. Inconel X-750 produced Cr2O3, NiFe2O4 and (Cr, Nb, Ti)O2 as its corrosion products. Haynes 263 showed a localized corrosion behavior while Haynes 75, Inconel 718 and Inconel X-750 showed a uniform corrosion behavior.

Assessment of a High-Throughput Electrorefining Concept for a Spent Metallic Nuclear Fuel - II: Electrohydrodynamic Analysis and Validation

Abstract Assessment of a high-throughput electrorefiner for a spent metallic fuel was carried out by using a commercial computational fluid dynamics code, CFX, and its performance was validated experimentally with a surrogate material. An electrorefiner equipped with a graphite cathode bundle was designed to continuously recover a high-purity uranium product without a noble metal contamination. The performance of the process for a decontamination of a noble metal in a uranium product was evaluated numerically as a function of the process parameters such as the rotation speed of the stirrer and the anode basket, and was validated experimentally. The distributions of the electric field and the electrodeposition behavior were also evaluated numerically, and an optimum electrode configuration was suggested.