Yoon-sang Lee

Concentrations of CsCl and SrCl2 from a Simulated LiCl Salt Waste Generated by Pyroprocessing by Using Czochralski Method

Separation of CsCl and SrCl2 from LiCl was carried out by using a separation technology, the Czochralski crystallization method. It was experimentally confirmed that Cs as well as Sr could be separated simultaneously from a LiCl molten salt by the suggested crystallization process without any additive or adsorption medium. The concentrations of Cs and Sr in LiCl decreased from 1.81 and 4.18 wt% in the initial salt to minimum values of 114 and 36 ppm in the grown LiCl crystal, respectively. The separation mechanism of Cs and Sr is described by the solubility difference of the solutes between the molten and solid states. It is expected that the total amount of salt waste will decrease drastically, because most of LiCl could be recovered by recycling with an electroreduction process.

Investigation of Electron Beam Welding Characteristics Using AA6061-T6 for Nuclear Plate-Type Fuel Assembly

This study was carried out to establish an electron beam welding process for nuclear plate-type fuel assembly fabrication. A preliminary investigation for plate fuel fabrication was conducted with a consideration of the weld performance using AA6061-T6 aluminum alloy made through the EBW (Electron Beam Welding) process. The optimum welding parameters for the plate-type fuel assembly were obtained in terms of the accelerating voltage, beam current and welding time. The welds made by the optimum parameters showed slightly lower tensile strengths than those of the un-welded specimens. The integrity of the welds by the EBW process was confirmed by the results of the tensile test, an examination of the macro-cross sections and the fracture surfaces of the welded specimens.Copyright

Development of Electron Beam Welding Technology Using AA6061-T6 Aluminum Alloy for Nuclear Fuel Plate Assembly

This study was carried out to establish the electron beam welding process for a nuclear fuel plate assembly fabrication. A preliminary investigation for plate fuel fabrication was conducted with a consideration of weld performance using AA6061-T6 aluminum alloy made by the EBW (Electron Beam Welding) process. The optimum welding parameters for the fuel plate assembly were obtained in terms of the accelerating voltage, beam current and welding time. The welds made by the optimum parameters showed slightly lower tensile strengths than those of the un-welded specimens. The integrity of the welds by the EBW process was confirmed by the results of the tensile test, an examination of the macro-cross sections and the fracture surfaces of the welded specimens.Copyright

Fabrication of Uranium Dispersion Targets for Mo-99 Production

Uranium metal dispersion particles have been proposed as targets for Mo-99 production to improve the radioisotope production efficiency of conventional low enriched uranium targets. In this study, uranium powders were produced by centrifugal atomization, and miniature targets were fabricated containing uranium particles in an aluminum matrix with uranium densities up to 9 g-U/cm3. Additional heat treatment was applied to convert the uranium particles into UAlx compounds by chemical reaction of the uranium particles and aluminum matrix. Thus, these targets could be treated with the same alkaline dissolution process that is used for conventional UAlx dispersion targets.

Fundamental study of Nd:YAG laser beam welding for lower end plug using HT9 alloy cladding tube

Various welding processes are now available for the end plug closure of a nuclear fuel element such as gas tungsten arc welding (GTAW), magnetic resistance welding, and Nd:YAG laser beam welding (LBW). Even though the resistance and GTAW processes are widely used for manufacturing commercial fuel elements, they cannot be recommended for the precise end plug welding of fuel elements owing to the complexity of a tungsten electrode alignment, wide heat-affected-zone (HAZ) and concave shapes and large heat input for thin cladding tubes. Therefore, Nd:YAG LBW using optical fiber transmission was selected for lower end plug welding using an HT9 alloy cladding tube. To establish the LBW process, and satisfy weld quality requirements, preliminary experiments for optimizing the welding conditions which used test specimens with a lower end plug of the cladding tube were performed. This paper describes the experimental results of the LB welded specimens using lower end plugs, along with the measurements of weld profiles and metallographic examinations. Furthermore, the effect of undercut depth and penetration depth after lower end plug welding was also investigated by changing the laser welding parameters and various dimensional configurations.Various welding processes are now available for the end plug closure of a nuclear fuel element such as gas tungsten arc welding (GTAW), magnetic resistance welding, and Nd:YAG laser beam welding (LBW). Even though the resistance and GTAW processes are widely used for manufacturing commercial fuel elements, they cannot be recommended for the precise end plug welding of fuel elements owing to the complexity of a tungsten electrode alignment, wide heat-affected-zone (HAZ) and concave shapes and large heat input for thin cladding tubes. Therefore, Nd:YAG LBW using optical fiber transmission was selected for lower end plug welding using an HT9 alloy cladding tube. To establish the LBW process, and satisfy weld quality requirements, preliminary experiments for optimizing the welding conditions which used test specimens with a lower end plug of the cladding tube were performed. This paper describes the experimental results of the LB welded specimens using lower end plugs, along with the measurements of weld prof...

Laser welding of seal tubes for an instrumented fuel irradiation test

This work was carried out to obtain sound welds using FIBER laser and to select the most suitable binary metal joint seal tubes linking three combinations, STS316L to Inconel600, Inconel600 to Ti, and Ti to Zircaloy-4 for the instrumented fuel irradiation test. To do this, the Taguchi experimental method was employed to optimize the experimental data. In addition, metallographic examinations, micro-focus X-ray radiography, and a micro-hardness test were also conducted to examine the welds. Visually, the penetration depth and bead width as well as from the standpoint of the weld defects, the laser welding of STS316L to Inconel600, Inconel600 to Ti, and Ti to Zircaloy-4 joint combinations is characterized. The investigating weld conditions are reviewed for a circumferential joining between the seal tubes and the MI (Mineral Insulator) cable on the instrumentation.This work was carried out to obtain sound welds using FIBER laser and to select the most suitable binary metal joint seal tubes linking three combinations, STS316L to Inconel600, Inconel600 to Ti, and Ti to Zircaloy-4 for the instrumented fuel irradiation test. To do this, the Taguchi experimental method was employed to optimize the experimental data. In addition, metallographic examinations, micro-focus X-ray radiography, and a micro-hardness test were also conducted to examine the welds. Visually, the penetration depth and bead width as well as from the standpoint of the weld defects, the laser welding of STS316L to Inconel600, Inconel600 to Ti, and Ti to Zircaloy-4 joint combinations is characterized. The investigating weld conditions are reviewed for a circumferential joining between the seal tubes and the MI (Mineral Insulator) cable on the instrumentation.