Nonlinear flow effects on immersed spent nuclear racks

• Autor(a) principal: Moreira, Miguel
• Data de Publicação: 2004
• Outros Autores: Antunes, J.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.26/4579
• topic: Fluid-structure interaction; Nonlinear flow effects; Squeeze-film; Spent fuel storage racks; Seismic response; Differential-algebraic equations

Fluid-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.