5×5 small-scale test fuel assembly was manufactured to carry out flow-induced vibration tests, aiming to obtain the vibration responses of new designed grid subjected to axial-flowing water. This test was carried out in a hydraulic loop with the maximum flow rate of 65 m3/h and room temperature and pressure. Laser vibrometer was used to measure the vibrating velocity of grid straps. The vibration peaks were generally distributed in three domains of the frequency spectrum. The first domain is from zero to decades of Hz, in which the vibration may be turbulence-buffeting-induced test assembly vibration as an integer entity. The second domain is from decades to hundreds of Hz, in which the vibration may also be test assembly vibration as an integer entity due to turbopump-induced pressure wave. The third domain is above 1000Hz, in which the vibration may be local strap vibration mainly due to vortex shedding along the edges of the straps. Series of tests were accomplished to figure out the characteristics of the trend of maximum high-frequency vibration velocity and related frequency with increasing flow rate. The high-frequency vibration characteristics of the grid in axial-flowing water are crucial for the fuel assembly designers when evaluating the anti-abrasion performance of fuel rods under reactor flow rate conditions.

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