Study On Fluid Induced Vibration Characteristics Of Pwr Fuel Assembly Grid

Based on the flow induced vibration(FIV)mechanism and theory analysis,this paper manly focus on the FIV analysis of grid which is the key component of fuel assembly.Through grid CFD simulation,5×5 small scaled fuel assembly high frequency FIV test,full scaled fuel assembly FIV test,the methodology consisting analysis and test is developed to evaluate the FIV characteristic of PWR fuel assembly.Turbulence excitation and vortex shedding are selected as the major causes of the fuel assembly grid flow induced vibration.Based on the study of the grid FIV characteristic,the flow induced vibration of fuel assemblies is mainly caused by turbulence excitation and vortex shedding.The mixing vane,spring and dimple will produce larger vortex and transverse flow,which will cause the fuel assembly vibration.5×5 small scaled fuel assembly FIV test results show that the high frequency vibration is caused by vortex shedding.The full scaled fuel assembly test shows that the vibration of the assembly belongs to the low frequency small amplitude vibration,which is mainly caused by the turbulence excitation at the grid position.This paper builds a methodology based on the analysis of the CFD analysis,5×5 small scaled and full scaled fuel assembly FIV test.By comparing the flow field of vortex and transverse flow,vibration amplitude,high frequency vibration amplitude,the FIV performance of CAP1400 fuel assembly grid is fully demonstrated.