Design modification and shaking table test of the drain pipes of steam generator for vibration reduction

Abstract

Abstract The drain pipe of the steam generators in nuclear power plants is designed to remove the remaining reactor coolant when the nuclear power plant stops. In the normal electricity generating condition of the nuclear power plant, the drain pipe acts as the pressure boundary between the primary coolant system and outside, which forbids the radioactive coolant to be leaked. Therefore, it is important to assure the structural integrity of the drain pipe, which is closely related with the vibration characteristics of the drain pipe. In this paper, the vibration characteristics of the previous and newly designed drain pipes are investigated by simulation and measurement with the shaking table test. The purpose of the new design was to suppress the excessive vibration in the interested low and high frequency ranges, which were observed in the power uprating of plants. From the measured results, in y direction, the first three modal frequencies are increased by 5, 18, and 50 Hz in the low frequency region, and the higher order modes are excluded in the interested high frequency region with the adoption of the new design. Further design modification is required to reduce the high frequency vibration in x direction with other approaches. In general, it is expected from the result that the newly designed drain pipe is more robust to the existing vibration compared with the previous one.