ANALYSIS ON THE DYNAMIC BUCKLING BEHAVIOR OF THE SPACER GRID STRUCTURE

The spacer grid is a key element of the fuel assembly used in the Pressurized water reactor. Due to its structural complexity, the analysis and the design of the spacer grid structure is difficult. This paper discusses the 5x5 cell size partial grid analysis including the detailed grid structural elements, through which, the impact force, the rebound velocity and the time history of acceleration and as well as other mechanical properties of grid under different initial impact velocity were obtained. This paper carried out the dynamic buckling criterion studies, and determined the dynamic buckling load of the 5x5 cell size partial spacer grid. Based on assuming the impact process is simple harmonic vibration, the method to determine the dynamic stiffness of the spacer grid was proposed. The experiments were also performed for the comparison with the analytical results. It is found that the analytical results are in good agreement with the experimental results. As a result, we can conclude that the analysis model including detailed grid elements is able to yield accurate analytical results.