Study on flow-induced-vibration evaluation of the large-diameter pipings in a sodium-cooled fast reactor. (3) Random vibration analysis method based on turbulence energy calculated by CFD

The design in a Japan sodium-cooled fast reactor (JSFR) requires increase in primary coolant velocity and enlarging the diameter of piping, so that a flow-induced-vibration issue is raised. Flow-induced-vibration tests were performed by using 1/3-scaled elbow test section, which simulates a hot-leg. In the tests, the pressure fluctuation and their correlation length were measured. A computer fluid dynamics (CFD) simulation using the Reynolds stress model was performed to evaluate turbulence-induced forces. The turbulence energy by the CFD was compared with the pressure fluctuation distributions test results. The profile of turbulence energy showed reasonably good agreement with that of the pressure fluctuation. Therefore the magnitude of pressure fluctuation can be estimated from the calculated turbulence energy multiplied by a certain coefficient. In the vibration analysis, the PSDs of the pressure fluctuation were derived from the measured normalized PSD multiplied by the coefficient. The vibration analysis method was proposed based on the PSDs and correlation lengths. The analysis results of vibration response showed reasonably good agreement with the results. (author)