Numerical Investigation of Fluid – Structure Interaction (FSI) on Sodium Leakage Accident at Prototype Fast Breeder Reactor Monju

Abstract

This study presents a numerical investigation of fluid-structure interaction about sodium leakage accident at prototype fast breeder reactor Monju. The dynamic forces of sodium liquid flow acting on the thermowell are the main cause of fatigue failure, which leads to the occurrence of thermowell cracking due to intense stresses and high fatigue-cycle. Since the location and magnitude of these stresses are unknown, an analysis of the vibrational characteristics and stresses caused by FSI was performed by using ANSYS to prevent similar accidents in the future. The most dangerous case was found for FSI analysis by comparisons between the natural frequency of thermowell and vortex shedding frequency at several operating conditions. The results showed that a stress concentration location is similar to the location of broken thermowell, and the amplitude of stress is large enough for fatigue damage.