Numerical simulation of seismic response of spent fuel pool considering structure-fluid-structure interaction

Abstract

The objective of the paper is to assess approaches to include the effect of fluid–structure along with equipment-fluid–structure interaction by evaluating the response of a typical spent fuel pool found in Westinghouse type Pressurized water reactor auxiliary building to earthquake loading, as well as to derive the seismic demand in critical structural members for the needs of a seismic fragility analysis. Different approaches are presented to account for fluid–structure interaction during the dynamic nature of seismic loading. All structural key aspects considered relevant are included in the analyses: the concrete box structure, the outlining stainless-steel liner, its connections, the submerged rack’s structure, and the containing fluid.

Three numerical models were developed and tested with the finite element code LS-Dyna with different implementations considering the fluid–structure interaction to demonstrate the robustness of the structure against earthquakes. Mechanical analogue adopted in codes with spring-mass system representation of the fluid attached to the structure and explicit modelling of the domain representing the water considering the two-way interaction between structure and fluid.

It is of great importance to include all the effects of fluid–structure interaction, as they increase the response and load of the structure. Both approaches considered for fluid representation were found to capture accurately the global response of the structure. The lattice structure of the racks exerts extra damping in the fluid motion and the pressure loading on the tank walls in near vicinity during earthquake excitation. The explicit modelling approach for the fluid elements could possibly result in lowering the racks critical displacements.