Axial Flow Induced Vibration of Nuclear Power Plant Components (Non-Homogeneous Pressure Field).

Abstract

This work examines the vibrations, caused by axial turbulent flow, of long slender beam-like nuclear power plant components, such as tubes in a steam generator or fuel rods in a nuclear reactor, taking into account the hydrodynamic interaction among them. To accomodate probabilistic vibration analysis, we developed a mathematical model for non-homogeneous cross spectral density of fluctuating wall-pressure caused by flow spoilers such as grid assembly in a reactor and support plate in a steam generator. We have shown that the root-mean-square values of rod displacement calculated with this model agree well with measured values. A mathematical model has been developed to reduce the complexity in the vibration analysis of hydrodynamically coupled rod arrays. Based on this model, we investigated the hydrodynamic coupling effect on the root mean square value of rod displacement, which shows that ignoring the hydrodynamic coupling effect may not lead to a conservative prediction of rod displacement if driving forces on different rods are correlated with each other. Various axial mode contributions to the vibration of multispanned steam generator tube have been investigated in terms of joint- and cross-acceptance. It is observed that higher mode contributions to the root-mean-square displacement of tube and bending stress at tube ends are more significant than those in single-span tube in the low frequency region.