Do-Hee Ahn

Fabrication of UO2 Porous Pellets on a Scale of 30 kg-U/Batch at the PRIDE Facility

In the pyroprocess integrated inactive demonstration (PRIDE) facility at the Korea Atomic Energy Research Institute (KAERI), UO2 porous pellets were fabricated as a feed material for electrolytic reduction on an engineering scale of 30 kg-U/batch. To increase the batch size, we designed and modified the corresponding equipment for unit processes based on ceramic processing. In the course of pellet fabrication, the correlation between the green density and sintered density was investigated within a compaction pressure range of 106–206 MPa, in terms of the optimization of processing parameters. Analysis of the microstructures of the produced UO2 porous pellets suggested that the pellets were suitable for feed material in the subsequent electrolytic reduction process in pyroprocessing. This research puts forth modifications to the process and equipment to allow the safe mass production of UO2 porous pellets; we believe these results will have immense practical interest.

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.

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.

Electrolytic reduction rate of porous UO2 pellets

The electrolytic reduction rate of porous UO2 pellets in a LiCl salt was investigated for various applied charges. The degree of reduction (α) value was evaluated from the ratios of cross-sectional areas of the reduced and oxide parts. An analysis of the experimental results revealed that the first-order reaction model is the best geometry function to describe the reduction reaction. An electrolytic reduction rate equation was proposed using the first-order model, although it was available in a limited region of (0≤α≤0.56). A power law based reaction rate equation was also suggested for the whole range of α, and the reaction time for a complete reduction, estimated using the power law equation, was confirmed through the experimental results. Changes in the Li-Li2O concentration around the reduced pellets for various applied charges were also measured, which increased up to 23 wt% with increasing α.

Recovery of uranium using electrorefining with an anode-liquid cathode module (ALCM) in molten LiCl–KCl–UCl3–NdCl3 and cadmium distillation

A laboratory-scale anode-liquid cathode module was used to recover uranium (U) from molten LiCl–KCl salt bearing uranium (U) and neodymium (Nd). The influences of the salt composition and the anodic reaction on the amount of U and Nd recovered from the liquid Cd cathode (LCC) were examined. The anode type did not affect the U/Nd ratio in the LCC product significantly when the ratio of U/Nd in the salt was 1.2–1.5. The eight process runs led to the recovery of U in high yield, with 2–5 wt% of co-deposited Nd.

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.

Performance of a Depleted Uranium Bed for a Nuclear Fusion Fuel Cycle

Abstract The Tritium Storage & Delivery System (SDS) is part of a tokamak-type nuclear fusion reactor fuel cycle. For the safety of this cycle, the hydrogen isotopes are stored in a metal hydride form in the SDS. Depleted uranium (DU) was chosen as the storage material. DU hydride can be heated to very high temperatures that are sufficient for pumping hydrogen isotopes without using gas pumps. The 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 and dehydriding of hydrogen. The DU bed is a vertical double-cylinder type with sintered metal filters. The bed is composed of primary and secondary vessels. The primary vessel contains DU, and a vacuum layer is formed between the primary and secondary vessels. In this study, recent experimental results on the pretreatment (activation and powderization) of DU and the direct hydrogen recovery and delivery of a DU bed are presented. In addition, the relationship between hydrogen pressure and temperature in the DU bed is obtained.

Engineering Design of a Voloxidizer with a Double Reactor for the Hull Separation of Spent Nuclear Fuel Rods

A voloxidizer with a double reactor capable of processing several tens of kilograms of HM/batch of nuclear spent fuel has been developed for the decladding and voloxidation of rod-cuts into hulls and pellets through the conversion of UO2 pellets to U3O8 powder. In this study, we optimized the engineering design of this voloxidizer to improve its hull-recovery ratio. First, we tested the oxidation performance of the device prototype and evaluated the effectiveness of various mechanical and chemical voloxidizing methods. On the basis of the results, we selected the screw-and-rotation method for the double rotary drum. Next, we derived a theoretical equation for calculating the optimal reactor volume for various rod-cut weights and lengths and then validated the equation using centimeter-scale acryl reactors and hulls. Subsequently, we modularized the main components such as the heater, utility, motor, reactor, valve, and structure. The double reactor was subject to preliminary separation tests of hulls and powder. Moreover, the hull-separation performance of the voloxidizer reactor was tested at a loading of 50 kg HM/batch. Finally, the remote assembling and disassembling possibility of the modules were experimentally optimized.

Chlorination reaction kinetics of CsI under cladding hull waste treatment condition: a TGA study

The reaction between cesium iodide (CsI) and chlorine gas was quantitatively investigated using a thermo-gravimetric analysis system. A comparison between calculated and experimental results on the chlorine molar flow rate revealed that the reaction lies within the gas phase diffusion limited region under the condition of this work. Using the experimental data, the second-order nucleation and growth model was identified as the best geometry function to describe the morphological changes of CsI during the chlorination reaction. Combining the gas phase diffusion equation and geometry function, a reaction rate equation was proposed for the reaction between CsI and Cl2.