시험용 핵연료집합체의 유동유발진동에 대한 실험적 연구

The Flow-Induced Vibration (FIV) test for the test fuel assembly was carried out to investigate FIV characteristics using the KAERI-devised hydraulic test loop. The motivation of this study was to evaluate the effect of Spacer Grid (SG)s design on the vibration of the fuel bundle and to understand the flow-induced dynamic characteristics of the test bundle. A test bundle consists of 2 guide tubes, 23 dummy fuel rods (embedded with Pb pellets), and 5 SGs with the mixing vane. The fuel bundle was mounted by clamping ends of the guide tubes on the test section. The test flow velocity range was about 2 m/s ~ 10 m/s of cold water (25℃) such that the test condition covered the operating flow range of 4.5 ㎧ to 5.5 ㎧. Two fuel rods were instrumented with embedded accelerometers, permitting measurement of vibration in two mutually perpendicular planes of motion. A non-contact vibrometer were also used to measure oscillating motion of the bundle. The FIV characteristics of the test bundle with the flow variation were p esented in terms of temporal and spectral functions. The test results will be used to develop theoretical model for FIV of nuclear fuel and help to determine the final design of the SGs for the commercial usage.