Context

The NEPTUNE Project prepares a new generation of tools for multi-scale thermal-hydraulics computations in French PWR. A brief summary of NEPTUNE activities is available in the paper by Guelfi et al (NEPTUNE: a new software platform for advanced nuclear thermal-hydraulics, Nuclear Science Engineering, vol. 156, 2007). These codes will involve the system scale (real-time computation of the whole primary coolant circuit), the component scale (computation in cores and steam generators including obstacles, or equivalently CFD in porous medium) and the local CFD scale. Computations include safety analysis and thus predictions of severe accidents, such as the Loss Of Coolant Accident, and the Reflooding Phase. The latter case requires the computation of three-field models (in order to account for the dispersed liquid phase, the continuous liquid phase and the vapour phase, which is useful for instance for the reflooding phase). Up to now, the basic strategy to predict these unsteady three-field flows relies on the computation of three-phase single-pressur