Analysis of Modal Characteristics and Dynamic Response of Branch Pipe in Nuclear Power Plants

With the extension of operating life of nuclear power plants, the vibration fatigue of the small branch pipes becomes more and more prominent, which poses a threat to the safety and economic of nuclear power plants. Therefore, to ensure the safe operation of nuclear power plants, it is necessary to reconstruct the constraint of the sensitive pipes. In this paper, a branch pipe of a nuclear power plant was taken as the research object, and experimental and numerical studies were performed to obtain the modal characteristics of the pipe. Spectrum analysis was conducted to calculate the vibration response of the pipe in the operation condition. The calculation results showed that the fatigue stress of the branch pipe exceeds the allowable alternating stress of fatigue, that is, the branch pipe is a sensitive pipe. According to the numerical analysis, not only the sensitive pipe was accurately judged, but also the theoretical basis was provided for the reconstruction and optimization of the constrained structure of subsequent branch pipe. (authors)