Innovative hydrogen recombiner concept for severe accident management in nuclear power plants

Excursion of catalyst surface temperature is an important safety concern in deployment of a passive catalytic recombiner device in the nuclear reactor containment. In order to minimize the temperature on the catalyst surface, heat transfer from the surface has to be enhanced. In the present paper, a conceptual design of an innovative PAR is presented. This recombiner uses pool boiling of water to enhance heat transfer from the catalyst surface and limit its temperature. Numerical studies are presented to demonstrate the efficacy of this design. An in-house numerical code called HDS that couples CFD techniques with models for reaction kinetics and water pool boiling heat transfer is used in the analysis. It is shown that unlike conventional recombiner designs, the present design limits the surface temperature even at very high hydrogen mole fractions. The recombiner ensures passive and safe operation for hydrogen mole fraction as high as 16% and for the duration in which high hydrogen concentration is expected. The recombiner can be installed in areas such as the fuelling machine vault and pump room, where high hydrogen concentration is expected.