Analysis for the dynamic buckling behavior of the spacer grid structure of PWR fuel assembly

The spacer grid is a key element of fuel assembly. Due to its structural complexity, the analysis and design of the spacer grid structure are difficult. This paper discusses the structural analysis of a 17 × 17 fuel assembly grid including the detailed grid structural elements, through which, the impact force, rebound velocity and time history of displacement and as well as other mechanical properties of the grid under different initial impact velocity were obtained. This paper carried out studies for the dynamic buckling criterion, and determined the dynamic buckling load of the spacer grid. Based on the assumption of simple harmonic vibration of the impact process, the methods to determine the dynamic stiffness and the equivalent viscous damping of the spacer grid were proposed. Experiments were also performed for comparison with analytical results. It found out that the analytical results are in good agreement with the experimental results. As a result, it can be concluded that the 17 × 17 fuel assembly model including detailed grid elements is able to yield accurate analytical results. (authors)