Two-Phase Flow Simulations for PTS Investigation by Means of Neptune_CFD Code

Two-dimensional axisymmetric simulations of pressurized thermal shock (PTS) phenomena through Neptune CFD module are presented aiming at two-phase models validation against experimental data. Because of PTS complexity, only some thermal-hydraulic aspects were considered. Two different flow configurations were studied, occurring when emergency core cooling (ECC) water is injected in an uncovered cold leg of a pressurized water reactor (PWR)-a plunging water jet entering a free surface, and a stratified steam-water flow. Some standard and new implemented models were tested: modified turbulent k-epsilon models with turbulence production induced by interfacial friction, models for the drag coefficient, and interfacial heat transfer models. Quite good agreement with experimental data was achieved with best performing models for both test cases, even if a further improvement in phase change modelling would be suitable for nuclear technology applications. Copyright (C) 2009 Maria Cristina Galassi et al.