Papers by Author: Chang Hee Lee

Abstract: The irradiation induced defects of irradiated reactor pressure vessel(RPV) steel were investigated by a small angle neutron scattering. The degradation of the mechanical properties of RPV steels during an irradiation in a nuclear power plant is closely related to the irradiation induced defects. The size of these defects is known to be a few nanometers, and the small angle neutron scattering technique is regarded as the best non destructive technique to characterize the nano sized inhomogeneities in bulk samples. The RPV steel was irradiated in the HANARO reactor in KAERI. The small angle neutron scattering experiments were performed at SANS instrument in the HANARO reactor. Both unirradiated and irradiated RPV steels were measured and the SANS data of both steels were compared. The nano sized irradiation induced defects were quantitatively analyzed by SANS. The type of defects was also analyzed based on the SANS results, and the effect of the chemical composition of the RPV steel on the irradiation induced defects was discussed.

Abstract: In this study, a diffusion bonding of aluminium alloy A6061 was preformed using an Ag-28Cu filler metal in order to conduct eutectic brazing. Melting mechanism was surveyed. Interface behaviors of the brazed joints were observed after brazing and T6 solution treatment. Also, tensile property of the brazed joints was examined. During diffusion bonding of Al6061 alloys with Ag-28Cu filler metal, eutectic melts were formed by eutectic reaction between Al6061 and Ag-28Cu filler metal. It was found that the reaction layer consist of two phases formed at the interface between AA6061 and Ag-28Cu filler metal. EPMA analysis revealed that two phases in the reaction layers consist of Ag-rich phase and Cu-rich phase. Tensile strength was 300 MPa after ageing treatment at 175°C.