• Journal of Welding and Joining
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• 제15권6호
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• pp.85-95
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• 1997

This study is to investigate the optimum conditions of Nd:YAG laser beam welding for Zircaloy-4 end cap closure by optical fiber transmission. Laser welding parameters which affect the penetration depth and bead width were experimentally examined using the various beam radius by the beam quality analyzer, joint geometries of end cap and the laser parameters which mean pulse width, repetition rate and pulse energy. Also, an optimum welding speed and the effect of assistant gas with varying the flow rate of He were investigated. We found that the laser average power for the end cap welding will be 230W and rotation speed must not exceed 8 RPM, the best position of focus using optical fiber with 600.mu.m will be 2 to 3mm below the surface of the material.

• Journal of Welding and Joining
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• 제21권6호
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• pp.20-25
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• 2003

Various welding methods such as Gas Tungsten Arc Welding(GTAW), magnetic force electrical resistance welding and Laser Beam Welding(LBW) are now available for end cap closure of nuclear fuel rods. Even though the resistance and GTA welding processes are widely used in manufacturing commercial fuel rods, they can not be recommended for the remote seal welding of fuel rods in the hot cell Facility due to the complexity of the electrode alignment, the difficulty in replacing parts in a remote manner and the large heat input for the thin sheath. Therefore, the Nd:YAG laser system using optical fiber transmission was selected for the end cap welding of irradiation fuel rods in the hot cell. The remote laser welding apparatus in the hot cell Facility was developed using a pulsed Nd:YAG laser of 500 watt average power with an optical fiber transmission. The weldment quality such as microstructure and mechanical strength was satisfactory. The optimum conditions of laser welding for encapsulating irradiation fuel rods in the hot cell were obtained.

• Journal of Welding and Joining
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• 제34권5호
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• pp.54-60
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• 2016

In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of three types of austenitic stainless steels (type 310: A mode, type 316-A: AF mode, type 316-B: FA mode solidifications), the laser beam welding (LBW) transverse-Varestraint tests consisted of multi-mode fiber laser, welding robot and hydraulic pressure system were performed. As the welding speed increased from 1.67 to 40.0 mm/s, the solidification brittle temperature range (BTR) of laser welds for type 316 stainless steels enlarged (316-A: from 37 to 46 K, 316-B: from 14 to 40 K), while the BTR for type 310 stainless steel reduced from 146 to 120 K. In other words, it founds that solidification cracking susceptibility could not be simply mitigated through application of LBW process, and the BTR variation behavior is quite different upon solidification mode of austenitic stainless steels.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.39-41
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• 2006

The weld quality of spacer grids in Pressurized Water Reactors(PWR) fuel is extremely important for the fuel assembly performance in the nuclear renter. The spacer grid welds are currently evaluated mainly by the metallographic examination although it reveals only cross-points which are welded by the laser beam. This experiment is also to compare the weldability of Zircaloy-4 spacer grids using by the GTA and laser beam. The effect of node geometries of spacer grids for GTAW and LBW has been studied and optimum conditions of spacer grid welding have been found. Microstructures and micro-hardness of GTA and laser beam welded zones have been also compared.

• Journal of Welding and Joining
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• 제24권5호
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• pp.22-28
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• 2006

A spacer grid assembly, which is an interconnected array of slotted grid straps and is welded at the intersections to form an egg crate structure, is one of the main structural components of the nuclear fuel assembly for Pressurized Water Reactors (PWRs). The weld quality of spacer grids in PWRs fuel is extremely important for the fuel assembly performance in the nuclear renter. The spacer grid welds are currently evaluated mainly by the metallographic examination although it reveals only cross-points which are welded by the laser beam. This experiment is also to compare the weldability of Zircaloy-4 spacer grids using by the GTA and LB. The effect of node geometries of spacer grids for the GTAW and LBW has been studied and optimum conditions of spacer grid welding have been found. Microstructures and micro-hardness of the GTA and LB welded zones have been also compared.

• Journal of Welding and Joining
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• 제27권3호
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• pp.44-51
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• 2009

In this study, welding distortion analysis is performed for various design of tube shape structures which are assembled with aluminum sheet metal. Aluminum 5052 plates of 1mm thickness are used to analyze. An efficient keyhole model, as a welding heat source, is used for the prediction of full penetration weld size and shape which is required for the thermal analysis. The thermal and mechanical material properties are considered as temperature dependent functions, due to the high temperature variations during the welding. The numerical model is calculated by using a commercial software and evaluated with the experiments. The calculation results could make a comparative study in the view of distortion for the various size and shape of structure.