Modal properties of the flexural vibrating package of rods linked by spacer grids

Abstract

The paper deals with the modelling and modal analysis of the large package of identical parallel rods linked by transverse springs (spacer grids) placed on several level spacings. The rod discretization by FEM is based on Rayleigh beam theory. For cyclic and central symmetric package of rods (such as fuel rods in nuclear fuel assembly) the system decomposition on the identical revolved rod segments was applied. A modal synthesis method with condensation is used for modelling of the whole system. The presented method is the first step of modelling the nuclear fuel assembly vibration caused by excitation determined by the support plate motion of the reactor core.