Selection of models for hydrogen distribution calculations in the containment using CFD codes

Full text: Hydrogen mixing/distribution in nuclear reactor containment atmosphere is one of the important safety issues under accident conditions. It is therefore necessary to predict the hydrogen distribution accurately. Computational Fluid Dynamics (CFD) codes are increasingly used for this purpose. However, the commercially available CFD codes do not have the condensation models and one has to incorporate these models before applying these codes for this purpose as condensation of steam affects the distribution of the hydrogen. Further, during accident conditions, release of hydrogen into the containment may form combustible mixtures and which can pose a threat to the containment integrity. Re-combiners are placed in the containment to mitigate such risk by removing hydrogen from the containment atmosphere by catalytic reaction. Hence, re-combiner models also need to be implemented in the CFD codes to predict the hydrogen distribution. Finally, the turbulence models play a key role in dictating the convective diffusive behavior of hydrogen transport. The present paper systematically describes the selection of the condensation and re-combiner models to be implemented based on the model capabilities, applicability and their validation aspects. In addition, it also brings out the most competitive turbulence model in terms of accuracy and computational speed