S. Paek

Properties of titanium sponge bed for tritium storage

ABSTRACT A TRF (Tritium Removal Facility) will be constructed at Wolsong Nuclear Generating station to remove the tritium from heavy water. Titanium sponge has been selected as suitable material for tritium product immobilization. This paper is a summary of the experimental results conducted for the various properties of the reaction between titanium sponge and hydrogen isotopes. The conditions for activation, hydriding and dehydriding were investigated. The factors such as initial gas pressure and the helium content in the gas stream influencing the hydriding rate of the bed were examined.

Development of an anode structure consisting of graphite tubes and a SiC shroud for the electrowinning process in molten salt

In a molten chloride salt-based electrolysis, chloride evolution at an anode needs to be considered in terms of potential fluctuation, capture, and corrosion problems. Here, we demonstrate an anode structure consisting of graphite tubes and a SiC shroud to be applied to the electrowinning process. A large surface area as well as high corrosion resistivity was achieved through the use of inert graphite tubes. The Cl2 (g) capture was enhanced by the employment of a porous SiC shroud. It also allows an efficient contact of the electrode surface to the LiCl–KCl eutectic melt for an anodic evolution. No significant effects of the use of a SiC shroud on the anode overpotential and cell potential were found during the U deposition test.

Tritium Activities in Korea

ABSTRACT An overview of the tritium related research and activities presently undertaken in Korea is presented. These activities encompass the Wolsong Tritium Removal Facility (WTRF) in KHNP, isotope separation, storage and biology in KAERI, KEPRI and KAIST. The design status of the WTRF that serves four CANDU reactors is described. It is made up of three parts; liquid phase catalytic exchange (LPCE), cryogenic distillation, and metal hydride storage. Results from the technological R&D of tritium processing for the WTRF and biology are summarized.

Performance of 500kCi Tritium Storage Vessel for WTRF

A prototype TSV (Tritide Storage Vessel) has been manufactured for the long-term storage of tritium of the WTRF (Wolsong Tritium Removal Facility). A performance test was carried out to demonstrate that the TSV could hold a minimum of 500kCi of tritium. This experiment was conducted by a batch type hydriding reaction. Hydrogen gas equivalent to 50kCi of tritium was reacted with the titanium sponge in a batch reaction. Experimental results for 10 batches show that the TSV has enough capacity to store 500kCi of tritium.

Preparation, characterization, and reactivity of Pt/SDBC catalysts for the hydrogen - water isotopic exchange reaction

Pt/SDBC catalysts, which are used for the hydrogen-water isotopic exchange reaction, were prepared. TGA experiments showed that the treatment temperature of Pt/SDBC catalysts in inert gas is limited to 400 °C and the maximum allowable heat treatment temperature in oxygen is 200 °C. From nitrogen adsorption and hydrogen chemisorption measurements, it was shown that the dispersion of platinum particles depended on the physical properties, i.e., specific surface area and pore structure of SDBC. It was found that the heat treatment could not impact the structure of SDBC and the oxygen treatment at 150 °C improved the platinum dispersion. It was shown by XPS analysis that the oxygen treatment of impregnated Pt/SDBC increased the fraction of platinum metal state and platinum dispersion. As the supported platinum area increases, the catalytic activity of Pt/SDBC for the hydrogen-water vapor isotopic exchange reaction increases. It indicates that the hydrogen chemisorption measurement can be used to estimate the catalytic activities of Pt/SDBC catalysts. It was not observed that the particle size of supported platinum affected the specific reaction rate at 60 °C. It implies that this reaction is structure insensitive.

Detritiation Technology Development for Environmental Protection

Abstract Korea is operating 24 nuclear power plants and a highly advanced neutron application reactor HANARO (High-flux Advanced Neutron Application Reactor). In addition, Korea is designing a tritium storage and delivery system (SDS) for ITER. We have been developing detritiation and tritium storage technologies since the operation of Wolsong CANDU (Canada Deuterium-Uranium) station in 1983. The Wolsong Tritium Removal System (TRF) was designed to remove tritium generated in heavy water of the moderator and heat transport. Catalysts transfer tritium from the tritiated heavy water to gaseous tritiated deuterium. The hydrogen isotopes, including tritium, are transported to a cryogenic distillation system where the tritium is removed for safe storage. Conventional high-pressure storage tanks can be dangerous for the storage of radioactive tritium gas. We have been studying various kinds of metal hydride, such as titanium, zirconium cobalt, and depleted uranium. Titanium was proven to store tritium safely and efficiently for a long period of time. Zirconium cobalt, meanwhile, incorporates tritium safely and compactly, and temporarily holds large quantities that can be recovered easily under safe, controlled conditions. However owing to the disproportionation characteristics of zirconium cobalt, we are now developing depleted uranium hydride safe handling technologies. In this technical note, we present the details of the recent development progress of these tritium systems.

Computational electrochemo-fluid dynamics modeling in a uranium electrowinning cell

A computational electrochemo-fluid dynamics model has been developed to describe the electrowinning behavior in an electrolyte stream through a planar electrode cell system. Electrode reaction of the uranium electrowinning process from a molten-salt electrolyte stream was modeled to illustrate the details of the flow-assisted mass transport of ions to the cathode. This modeling approach makes it possible to represent variations of the convective diffusion limited current density by taking into account the concentration profile at the electrode surface as a function of the flow characteristics and applied current density in a commercially available computational fluid dynamics platform. It was possible to predict the conventional current–voltage relation in addition to details of electrolyte fluid dynamics and electrochemical variables, such as the flow field, species concentrations, potential, and current distributions throughout the galvanostatic electrolysis cell.

Development of Tritium Technologies at KAERI

Abstract Tritium is formed by neutrons captured from deuterium. If left to accumulate, tritium oxide will become a hazard to the operating staff and public. The primary purpose of a Tritium Removal Facility (TRF) is to reduce tritium concentration in a heavy water moderator. In Korea, operation of a TRF commenced at the Wolsong Nuclear Power Site on July 26th, 2007. Nowadays, KAERI is developing a Very High Temperature Gas Cooled Reactor (VHTR). We have developed a tritium behavior analysis code for the VHTR. We also developed analytical methods for the measurement of food stuffs. Korea shared in the construction of the ITER fuel cycle plant with the EU, Japan, and the US, and is responsible for the supply of an SDS (Tritium Storage and Delivery System). We present the recent progress in the development of tritium storage technology, and safety features of the related system. KAERI has been developing tritium technologies related to the Wolsong TRF, HANARO, VHTR, and nuclear fusion fuel systems. We thus present details on the recent development progress of these tritium systems.

Development of the anode-liquid cathode module (ALCM) for a high-throughput electrowinner

The employment of multiple electrode pairs is one of the ways to achieve a high-throughput electrowinner. In order to improve the U/TRU recovery rate and also to obtain economic advantages for a molten salt electrowinning process, which is a major step in pyroprocessing, the development of an electrode module having a compact structure is required. Here, we designed an anode-liquid cathode module (ALCM), where two graphite anodes are symmetrically arranged centering on a liquid Cd cathode with a mesh stirrer to prevent the growth of U dendrites, to be applied to the electrowinning process. As a preliminary study, basic electrochemical characterization of the designed electrode module was conducted and its capability for U recovery was evaluated in the ALCM-employed lab-scale electrowinner including LiCl–KCl-UCl3 at 500xa0°C. Also, the morphology and component of the recovered U residue by distillation of the cathode product was examined by FE-SEM and EDS analyses.

Direct Delivery of Hydrogen Isotopes from a DU Hydride Bed

A tritium plant for nuclear fusion power plants consists of an SDS (Storage and Delivery System), an ISS (Hydrogen Isotope Separation System), a TEP (Tokamak Exhaust Processing system), and an ANS (tritium plant Analytical System). Korea has been developing an SDS. The main purpose of this tritium storage and delivery system is to store and supply the D-T gas needed for DT plasma operation and to provide the necessary infrastructure for short- and long-term storage of large amounts of tritium. We have been developing tritium storage beds for the SDS. The primary role of the metal hydride beds in the SDS is to store and supply D-T fuel during DT plasma operation. ZrCo and depleted uranium (DU) have been extensively studied. Compared to the use of ZrCo, which is disproportionate at temperatures of higher than 350°C, DU hydride can be heated up to very high temperatures sufficient to pump hydrogen isotopes without using gas compressors. Our experimental apparatus used to test the experimental DU bed consists of a tank that stores and measures the hydrogen, and a DU bed used for the hydriding/dehydriding of hydrogen. Our DU bed is a horizontal double-cylinder type with sintered metal filters. The bed is composed of primary and secondary vessels. The primary vessel contains a DU, and a vacuum layer is formed between the primary and secondary vessels. In this study, we present our recent experimental results on the direct delivery of hydrogen isotopes from a DU hydride bed. We also present the effect of the initial bed temperature and impurity gas on the hydriding rates.