Moreira, MiguelAntunes, J.2013-07-242013-07-242004M. Moreira, J. Antunes, "Nonlinear Flow effects on Immersed Spent Nuclear Racks", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Seventh International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 88, 2004. doi:10.4203/ccp.79.88http://hdl.handle.net/10400.26/4579Fluid-coupling effects lead to a complex dynamical behavior of immersed spent fuel assembly storage racks. Predicting their responses under strong earthquakes is of prime importance for the safety of nuclear plant facilities. In the near-past we introduced a simplified linearized model for the vibrations of such systems, in which gap-averaged velocity and pressure fields were described analytically in terms of a single space-coordinate for each fluid inter-rack channel. Using such approach it was possible to generate and assemble a complete set of differentialalgebraic equations describing the multi-rack fluid coupled system dynamics. Because of the linearization assumptions, we achieved computation of the flowstructure coupled modes, but also time-domain simulations of the system responses. However, nonlinear squeeze-film and dissipative flow effects, connected with very large amplitude responses and/or relatively small water gaps, cannot be properly accounted unless the linearization assumption is relaxed. Such was the aim of a previous paper. Here, our nonlinear model is introduced and tested in order to expose the significance of the squeeze-film and dissipative effects. The response of a fuel storage pool with several racks submitted to strong seismic excitations applied in different directions are also presented and discussed.engFluid-structure interactionNonlinear flow effectsSqueeze-filmSpent fuel storage racksSeismic responseDifferential-algebraic equationspreprint