Fluidelastic instability on Super Phenix LMFBR weir system: A survey

The work helped to find and validate a solution for the instability for SPX 1 reactor situation. This was achieved by changing the nominal hydraulic conditions of the reactor, in order to be in a stable zone in the weir system fall height - flow rate diagram. The effective confrontation of the stability thresholds analysis procedure derived from the theoretical model with the experimental observations, had a second important consequence. This is for the design of similar weir systems, where the help of scale mock-ups is limited. In fact, limit conditions on weir shell bottom are difficult to represent on a scaled mock-up as well as dissipative-damping effects. These two parameters are of importance respectively, in the definition of the resonance frequencies involved in the instability, and in the possibility to get it. The instability thresholds analysis procedure can overcome these difficulties for design purposes. The steady regime vibratory analysis shows the ability of a non-linear theoretical model to understand and quantify the behaviour of a complex fluid-structure interaction problem including flow. (orig./HP)