Reliability verification of the laser vibrometer technique

Flow-induced vibration occurs when the fuel assembly is in high speed coolant, which may damage the grid and fuel cladding. High frequency vibration test of fuel assembly need to be carried out during fuel design. But, it is hard to measure the vibration responses directly using accelerometers, which is impossible to be mounted on the surfaces of grid strip in the water surroundings. While with the help of the laser vibrometer, it is easy to measure the vibration responses of grid strip indirectly, because the laser can easily passes through the flow housing and coolant. The above technique has been employed widely during fuel design abroad, and has good application prospect during fuel design in China. The laser vibrometer and traditional accelerometer are both used to measure the simulated fuel rod vibration under three different excitation frequencies in three different operation conditions simultaneously. Measured results comparison shows that the laser vibrometer has better accuracy. (authors)