Study on the sliding, collision, and rocking behavior of free-standing spent fuel storage and transport baskets under seismic loading

Abstract

To improve the efficiency of spent fuel transportation, a new free-standing storage and transport basket (hereafter referred to as the basket) has been developed. This basket uses a 3 × 3 storage cell layout, which makes it slimmer than the traditional 7 × 6 layout of spent fuel storage racks (hereafter referred to as the rack). Consequently, it exhibits more significant rocking motion during earthquakes. To enhance stability, 24 baskets are connected using dovetail grooves to form a 4 × 6 basket group. Since this type of connection has not been previously employed in spent fuel storage, a specialized seismic safety analysis is required. Previous experimental results indicate that under seismic loading, the baskets exhibit rocking, and occasionally the base plates interlock, preventing them from returning to their original positions. However, existing seismic analysis methods fail to accurately simulate the underwater rocking behavior of multiple baskets connected by dovetail grooves. To explore ways to reduce the rocking angle and to investigate the principle of baseplate interlock, a finite element model is developed. The model employs gap-spring elements to simulate collisions between baskets and fuel assemblies, and simplifies the dovetail connections into spring elements. It also represents fluid-structure interaction as an added mass matrix. Numerical results demonstrate good agreement with experimental data, validating the model's reliability. The influence of the vertical position of dovetail grooves on basket rocking angles and sliding displacements is investigated. The research content can provide important reference for reducing the rocking angle of the basket under earthquake and optimizing the design of the basket.