Engineering Mechanics

Proceedings Vol. 21 (2015)

ENGINEERING MECHANICS 2015

Copyright © 2015 Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic, v.v.i., Prague

 

Š. Dyk, V. Zeman
pages 56 - 57, full text

The paper deals with nonlinear phenomena occurring during vibration of nuclear fuel rod (FR). The FR is considered as a system consisting of two impact-interacting subsystems - FR cladding (zircalloy tube) and fuel pellets stack placed inside FR cladding. Between both subsystems, there is a small clearance. The FR is bottom-end fixed, and at eight equidistant levels, the FR cladding is supported by spacer grids (SG). Both subsystems are modelled by means of finite element method for one-dimensional Euler-Bernoulli continua. During fuel assembly (FA) motion caused by pressure pulsations of the coolant, the FR vibrates and impacts can possibly occur between FR cladding and fuel pellets stack. The paper focuses on qualitative change of vibration with change of bifurcation parameters - clearance between FR cladding and fuel pellets stack, stiffness of spacer grids cells and excitation frequency. The change of vibration quality is shown using extremes of relative radial displacements of both tubes in discretization nodes, and phase trajectories.

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