Quality monitoring of end plug resistance weldment for nuclear fuel rods by electrode displacement

Abstract

The welds on the fuel rods in a nuclear power fuel assembly are the most likely places to leak during combustion, and therefore, the integrity of the welds is critical. The end plug welding method used for the nuclear fuel rod was upset butt resistance welding, and the welding time was a very short 1 cycle. The purpose of this research was to investigate factors that could be used to monitor the welding quality of end plug welds on nuclear fuel rods. In this study, to assess the integrity of the nuclear fuel rod welds, the waveform of the variables during the short welding time was measured using a waveform measurement device, and the quality assessment factors that can impact the welding quality were determined. To deduce the quality assessment factors, this study chose to use instantaneous displacement, which was calculated from electrode displacement. To observe electrode movements resulting from instantaneous thermal expansion on welds, a displacement sensor was installed on the welding machine, and physical phenomena were analyzed per half-cycle by measuring displacement signals during welding. In addition, damage to major components of the welding equipment was simulated. Welding testing was carried out to determine the waveforms, and the quality assessment factor values here were compared with the values corresponding to a normal welding condition. Through this study, the major components of welding equipment were monitored to ensure the integrity of the welding.