Towards modeling of Grid to Rod and the effect of its nonlinear dynamic behaviors on grid-to-rod fretting wear

Abstract

The grid-to-rod fretting (GTRF) wear is always a significant cause of fuel failure. The dynamic behavior of fuel rods during actual operation is complex, so understanding the dynamic mechanism of the grid-to-rod system is essential for wear analysis. This paper developed a mathematical model of a fuel rod subjected to sinusoidal excitation loads with gap constraint. The partial differential equation was discretized by the Galerkin method and solved by Runge–Kutta scheme. The vibration response and the wear rate of cladding in the possible gap range under numerous hypothetical cases were studied. The result shows that the nonlinear vibration motion significantly impacts GTRF wear. The wear rate changes are linear under harmonic and low-period vibration, and most high-period movement significantly affects the wear rate. Some exciting and fresh results allow us to understand better GTRF wear propagation and optimize fuel assembly design.