Thermalhydraulic Analysis of Steam Generators: Application of the Thirst Code to Vibration Analyses
Flow-induced vibration concerns may be avoided by analysis, which requires the knowledge of flow patterns and the flow distribution in steam generators (SG). Typically, the distributions of flow velocity, fluid density, and, in the case of two-phase flow, distributions of steam quality and two-phase flow regime are needed. Generating this data is not straightforward because of the 3-dimensional nature of flow, complex steam generator geometry, and uncertainties associated with two-phase flow modelling. In this paper, the main features of THIRST, a thermalhydraulic code for recirculating SGs, are described. In addition, the effects of thermalhydraulic modelling and design features on velocity distributions and gap flow velocity needed for flow-induced vibration and fretting-wear calculations are discussed. These include an anisotropic resistance model in the U-bend region, design modifications in the U-bend region to reduce tube vibration, and the prediction of two-phase flow regimes.