The FUVIAN4 code for fuel seismic analysis with various non-linear damping mechanisms

It is generally known that the vibrational characteristics of fuels (damping and natural frequency) are strongly dependent on the amplitude. So the ordinary linear treatment of constant damping and frequency is not sufficient to analize precisely the dynamic behaviors of fuels in the range of large amplitude. The non-linear damping mechanisms on fuels were experimentally investigated and the analytical model for FUVIAN code which could deal with structural and hydraulic non-linear damping were developed. The adequacy of the new models were confirmed by the vibration tests and impact tests which were performed on full scaled fuel assemblies taking special interest to the large amplitude behaviors and the effect of water surrounding fuels. (orig.)