Optimal Experimental Environment for Flow-induced High Frequency Vibration Test Facility

The coolant in a reactor transfers generated heat from the nuclear fuel assemblies to the coolant flow. The average velocity of the coolant is approximately 5 m/sec, and the coolant is affected by severe turbulence, with a value of hundreds of thousands of the Reynolds number. Nuclear fuel rods are exposed to coolant flow, and fuel rod vibration occurs due to this flow. Excessive vibration caused by turbulence induced fluctuating forces is the main source of fretting wear, which is a major cause of mechanical failure for fuel rods. The grid structure in the fuel assembly has a large pressure drop, and disturbs the coolant flow, and increases vibration due to fluid-structure interaction. The incidence of vibration is dependent on the structure of the grid design. It can also be simultaneously affected by vortex and turbulence. Thus it is necessary to investigate the characteristics of grid assembly vibration in the development and design verification phase, because the grid assembly can cause fluid-elastic instability to the fuel assembly. This paper presents an optimal experimental environment for a flow-induced high frequency vibration test facility