Flow induced vibrations on nuclear pipings - comparison between vibration test and stochastic FE analysis with SYSTUS

Calculations can predict plastification under stochastic vibrations by computation of the mean value of the maximum stress. For low level of excitation (1 to 3 g R.M.S. and elastic behaviour), the R.M.S. deformation level is correctly estimated with modal damping ranging from 1% to 2%. R.M.S. acceleration measured during campaign 2 are used along with calculation employing previously described methodology in order to check acceptable level of vibration and service life duration for a third nozzle not equipped with strain gauges on the same piping system. For higher level (10 g R.M.S. and plastic behaviour), R.M.S. calculated deformations are conservative but service life durations calculated with 7% damping are of the same level as actual ones. A higher dissipation of energy occured and can be taken into account by an increase of modal damping. (orig./GL)