The fast reactor (FR) core, immersed in liquid coolant, consists of hundreds of assemblies with millimeter-scale gaps. The core inevitably has inter-assembly collisions during seismic events. Thus, multi-angle collisions and fluid-structure interaction are two key points for the seismic safety evaluation of the entire core. This study presents an efficient dynamic analysis code of fast reactor assemblies (DAFA) for simulation of seismic behavior of a core. The developed contact model decouples the complex nonlinear multi-assembly system into a series of independent linear single-assembly systems, enabling parallel computation and avoiding the core's degenerate modes. A simple fluid added mass coefficient is proposed to characterize the fluid effect on the vibration behavior of non-uniform assembly. Validation against benchmark tests and other classical codes from International Atomic Energy Agency (IAEA) confirms the accuracy and feasibility of developed DAFA code. Results demonstrate that analysis results remain consistent and robust across different spike boundaries, as long as meeting assembly's natural frequencies in air/water. • An efficient dynamic analysis code of FR core assemblies is proposed for simulation of seismic behavior of a large-scale core. • Validation against RAPSODIE/PEC tests and other codes confirms the accuracy and feasibility of developed DAFA code. • Contact model decouples a large-scale core's system into independent single-assembly systems for the ability of parallel computation. • A simplified fluid added mass coefficient quantifies the fluid effects on the vibration of non-uniform assemblies. • Analysis results remain consistent and robust across various spike boundaries when meeting assembly's natural frequencies.
Liu et al. (Fri,) studied this question.