Modeling flashing flows in a two fluid code

CATHARE is a 2-phase thermohydraulic code elaborated for the Pressurized Water Reactor safety analysis. It is a 1-Dimension 2-Fluid 6-Equation model with a mass, momentum and energy balance for each phase. The calculation of the critical mass flow rate through a break in the primary circuit requires the modelization of the flashing process. The liquid-interface heat flux which governs the phenomenon is experimentally determined in various test nozzles. First an essentially empirical correlation is presented. Then a survey of the physical mechanisms involved in the flashing process demonstrate the complexity of the problem (nucleation delay, turbulence effects, 2-dimensional effects, ...). Modelizations based on physical investigations are also discussed