Multi-dimensional simulation of hydrogen mixing and transport in the containment using CFD codes

Oxidation of the metallic components of the reactor core and the interaction of core/concrete will produce hydrogen under severe accident. Hydrogen combustion in the containment building may threaten the integrity of the containment. It is important to predict hydrogen transport and mixing in the containment, in order to determine whether the mixture can locally reach flammability limits. GASFLOW and FLUENT are two CFD codes available to analyze hydrogen mixing and transport in the containment. The main goal of the investigation is to assess the capability of the GASFLOW code to predict hydrogen concentration distributions and velocity fields for a variety of physical conditions. The assessment relied on the comparison with the results obtained using the commercial computational fluid dynamics code FLUENT. FLUENT calculation results with standard kε. model and laminar model showed nearly the same hydrogen concentration distributions. But in the much coarser grid in GASFLOW, large differences exist between the turbulence and laminar simulation. Calculation using laminar flow assumption in the investigated grid is very misleading, and the effects of turbulence and mass diffusion can not be neglected in the present GASFLOW grid. (authors)