Synthesis of vibration studies on a three loop PWR internals model

The flow induced vibrations problems are of complex nature. While it is easy to measure the global effects on the structures, it is often difficult to understand the phenomena mechanisms, because the various excitation sources, cause of the structures motion, do not act separately, but in a combined way. In the case of reactor internal structures, the authors have carried out a relatively complete study, based on a three loop PWR 1/8 internals model, the SAFRAN test model. Methods and specific means of calculation were associated in this experimental tool, allowing thus the understanding of the phenomena and their extrapolation to the full scale reactor. Experimental tests in air, and in still water were carried out, to determine structures frequencies, mode shapes and generalized coefficients. Flow tests were made to measure the random response of internal structures, and to get information about the fluctuating pressure field acting on the system. (Auth.)