Since hydrogen risk remains an important safety issue for current and future PWR (Pressurized Water Reactors), the CEA and IRSN have developed a code which covers all the phenomena related to hydrogen distribution processes : complex 3D flow, natural convection, heat transfer by condensation on walls and effect of mitigation devices. Combustion phenomena can also be modelled in this code. At the same time, the MISTRA coupled effect test facility was built at CEA to cover some of the validation needs for such a code.
The paper presents a validation case based on steady-state air/steam flows in MISTRA, for two positions of the steam injector: centered (M2 test) and off-centered (M3 test). We give a comparison between experimental data, a lumped parameter approach and CFD calculations, 2D axisymmetrical and 3D.