AN ADVANCED TUBE WEAR AND FATIGUE WORKSTATION TO PREDICT FLOW INDUCED VIBRATIONS OF STEAM GENERATOR TUBES

摘要

Flow induced tube vibration damage is a major concern for designers and operators of nuclear power plant steam generators (SG). Although a tube bundle has been correctly designed for nominal conditions, its vibratory behavior may vary significantly, due to a modification of operating conditions or an alteration of the structural system or tube supporting device. In this case, the operating flow-induced vibrational behavior has to be estimated accurately to allow a precise evaluation of the new safety margins in order to optimize the maintenance policy. For this purpose, an industrial “Tube Wear and Fatigue Workstation”, called "GEVIBUS Workstation" and based on an advanced methodology for predictive analysis of flow-induced vibration of tube bundles subject to cross-flow has been developed at Electricité de France. The GEVIBUS Workstation can be briefly described as an interactive processor, which links modules as : SG thermal-hydraulic computation, parametric finite element builder, interface between finite element model, thermal-hydraulic code and vibratory response computations, refined modelling of fluidelastic and random forces, linear and non-linear dynamic response of the coupled fluid-structure system, evaluation of tube damage due to fatigue and wear, graphical outputs. Two practical applications are also presented in this paper. The first simulation refers to an experimental set-up consisting of a straight tube bundle subject to water cross-flow. The second one deals with an industrial configuration observed in some operating steam generators. For these two applications, computational results are compared to experimental or plant data in terms of flow-induced damage.