FINITE-ELEMENT MODELING AND ANALYSIS OF NONLINEAR IMPACT AND FRICTIONAL MOTION RESPONSES INCLUDING FLUID-STRUCTURE COUPLING EFFECTS

A nonlinear three dimensional (3D) single rack model and a nonlinear 3 0 whole pool multi-rack model are developed for the spent fuel storage racks of a nuclear power plant (NPP) to determine impacts and frictio nal motion responses when subjected to 30 excitations from the support ing building floor The submerged free standing rack system and surroun ding water are coupled due to hydrodynamic fluid-structure interaction (FSI) using potential theory. The models developed have features that allow consideration of geometric and material nonlinearities includin g (I) the impacts of fuel assemblies to rack cells, a rack to adjacent racks or pool walls, and rack support legs to the pool floor; (2) the hydrodynamic coupling of fuel assemblies with their storing racks, an d of a rack with adjacent racks, pool walls, and the pool floor; and ( 3) the dynamic motion behavior of rocking, twisting, and frictional sl iding of rack modules. Using these models 30 nonlinear time history dy namic analyses are performed per the U.S. Nuclear Regulatory Commissio n (USNRC) criteria. Since few such modeling, analyses, and results usi ng both the 30 single and whole pool multiple rack models are availabl e in the literature, this paper emphasizes description of modeling and analysis techniques using the SOLVIA general purpose nonlinear finite element code. Typical response results with different Coulomb frictio n coefficients are presented and discussed.