Liquified hydrogen is considered a new energy resource to replace conventional fossil fuels due to environmental regulations by the IMO. When building tank for the storage and transportation of liquified hydrogen, materials need to withstand temperatures of -253°C, which is even lower than that of LNG (-163°C). Austenitic stainless steel mainly used to build liquified hydrogen tank. When building the tanks, both the base material and welding zone need to have excellent strength in cryogenic condition, however, manual arc welding has several issues due to prolonged exposure of the base material to high temperatures. Laser welding, which has some benefits like short period of exposure time and decrease of thermal affected zone, is used many industries. In this study, laser bead on plate welding was conducted to determine the laser butt welding conditions for STS 304 and STS 316L steels. After the BOP test, cross-section observations were conducted to measure and compare four bead parameters. These tendency result of laser BOP test can be used as conditions laser butt welding of STS 304 and STS 316L steel.

To precisely assemble the fuel test rod, an orbital TIG welding system was designed and developed to accurately conduct orbital TIG welding for the nuclear fuel test rod. Using this system, a welding process needs to confirm the welding properties for orbital TIG welding. Therefore, preliminary weld tests were performed on the cladding tubes under various conditions, and the results show that the width and depth of HAZ of the cladding specimen welded using identical power during an orbital TIG welding cycle was continuously increased from a welded start-point to a welded end-point because of heat accumulation. The performance tests were conducted under the welding conditions considered through preliminary welding tests, and the properties of the specimens were conformed through surface and microstructure analyses.

To conduct a nuclear fuel irradiation test, the inside of the nuclear fuel rod must be assembled along with the test fuel, several different parts, and sensors, and then filled with high-pressure and high-purityhelium gas. Therefore, it is necessary to develop helium gas filling techniques that can achieve exact TIG (Tungsten Inert Gas) spot welding at a pin-hole of the nuclear fuel rod to fill helium gas into the nuclear fuel test rod. However, previous apparatuses do not have repeatability for TIG spot welding as they lack an electrode position control jig to exactly fix a TIG electrode in a high-pressure chamber, and they consume a large amount of helium gas. Therefore, a TIG spot welding apparatus was developed to easily and accurately conduct TIG spot welding and significantly reduce the gas consumption. In addition, the optimum welding conditions of this welding apparatus were established through various weld tests.

This study presents an experimental study of the structural behavior for steel plate-concrete column-to-steel girder connections. Experiments were carried out to investigate the moment-rotation characteristics, failure behavior and ultimate moment capacity of these connections. The results of this experimental study involving three welded moment-resisting connections subjected to cyclic loading are presented. The specimens were fabricated at full scale to evaluate their hysteretic behavior. A description of the test specimens, the details of the joint, the test system and the testing methods are described. The test results showed that the structural behavior of these composite connections was influenced by the connection details.