Affect of recombiner location on its performance in closed containment under dry and steam conditions

Abstract

Hydrogen has been the major cause of fire in almost all of the biggest nuclear accidents witnessed by world so far. Many approaches have been investigated and developed worldwide to mitigate the consequences of hydrogen buildup inside the containment of Nuclear Power Plants (NPPs) under severe accident scenarios. One such most promising method is to deploy Passive Catalytic Recombiner Devices (PCRDs). They work on the principle of recombining hydrogen with oxygen from ambient air on catalytic surfaces to form steam and release of the exothermic heat of reaction. The present work describes the development, validation and application of a CFD based detailed 3D model for hydrogen recombination inside PCRD using the governing mass, momentum, energy and species conservation equations from first principle. The model has been integrated into the CFD code FLUIDYN-MP to capture the associated multi-physics phenomena. The integrated tool has been used to assess the most suitable location within a closed geometry for placing the PCRD so as to improve its performance and efficiency. Simulations were performed for different PCRD positions within a closed vessel under dry as well as steam laden conditions. The findings reveal that PCRD location in closed geometry plays important role in its performance. Moreover lower PCRD position helps in more natural convective mixing causing better hydrogen transport towards PCRD inlet and hence more hydrogen consumption.