CFD Analysis of Singular Pressure Losses due to Tube Support Plate Flow Blockage in Steam Generators
Résumé
Corrosion product deposits in the secondary side of nuclear plant steam generators may result in tube support plate flow blockage, and tube fouling. As deposition phenomena are very sensitive to parameters such as pressure and velocity, notable enhancement of the deposit models may be obtained from a better knowledge of local thermal-hydraulic profiles. Tube support plate flow blockage can be induced by the sudden contraction due to the broach holes. Recirculation zones and sudden pressure drops are expected. These physical phenomena can encourage specific particle deposition mechanisms or the precipitation of soluble species. The “flashing” deposition mecha- nism for instance shows high sensitivity to pressure drops. CFD calculations may capture and quantify the local and sudden change of thermal-hydraulic parameters at the inlet of broach holes. In this paper, CFD calculations are performed by EDF’s open-source Code Saturne CFD code. The initial concern of this study is to better understand local thermal-hydraulics. It does not cover the modelling of particle deposition or precipitation of soluble species. Plant observations such as TV inspections of steam generators have allowed to determine best estimate profiles for tube support plate flow blockage. Several blockage rates and fluid velocities are investigated. The results are compared to experimental pressure loss data. The global trends are in agreement with experimental results. The limits of this initial CFD calculation series and the strategy to model the effect of local recirculation on deposition are discussed.