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Study on Fiber Laser Welding Conditions for the Fabrication of a Nuclear Fuel Rod
Hong, Jintae,Joung, Chang-Young,Kim, Ka-Hye,Heo, Sung-Ho,Kim, Hyun-Gil 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.4
To verify the performance of nuclear fuel, a test rig needs to be fabricated to place the nuclear fuel and carry out irradiation tests. Welding is one of the most frequently used processes in fabricating a test rig, and a fiber laser welding system that enables assembling the components with various volumes has been developed in this study. A case study was then carried out for a nuclear fuel rod made of Zircaloy-4 by changing the process variables such as the focal length, frequency of laser pulse, peak laser power, and shield gas. From the case studies, a suitable welding condition with which a fuel rod can be completely welded regardless of the shield gas (He or Ar) should be achieved. By inspection of SEM and an immersion test, it was verified that Ar is useful as a shield gas in fabricating a nuclear fuel rod with a fiber laser welding system.
홍진태(Jintae Hong),정황영(Hwang-Young Jeong),안성호(Sung-Ho Ahn),정창용(Chang-Young Joung) Korean Society for Precision Engineering 2013 한국정밀공학회지 Vol.30 No.2
When a new nuclear fuel is developed, an irradiation test needs to be carried out in the research reactor to analyze the performance of the new nuclear fuel. In order to check the performance of a nuclear fuel during the irradiation test in the test loop of a research reactor, sensors need to be attached in and out of the fuel rod and connect them with instrumentation cables to the measuring device located outside of the reactor pool. In particular, to check the temporary temperature change at the center of a nuclear fuel during the irradiation test, a thermocouple should be instrumented at the center of the fuel rod. Therefore, a hole needs to be made at the center of fuel pellet to put in the thermocouple. However, because the hardness and the density of a sintered UO<SUB>2</SUB> pellet are very high, it is difficult to make a small fine hole on a sintered UO2 pellet using a simple drilling machine even though we use a diamond drill bit made by electro deposition. In this study, an automated drilling mach ne using a CVD diamond drill has been developed to make a fine hole in a fuel pellet without changing tools or breakage of workpiece. A sintered alumina (Al<SUB>2</SUB>O<SUB>3</SUB>) block which has a higher hardness than a sintered UO<SUB>2</SUB> pellet is used as a test specimen. Then, it is verified that a precise hole can be drilled off without breakage of the drill bit in a short time.