Analysis of hydrogen depletion using a scaled passive autocatalytic recombiner

Passive autocatalytic recombiners (PARs) are being considered by the nuclear power industry as a combustible gas control system in operating plants and advanced light water reactor containments for design-basis events. PARs do not require a source of power; instead, they use a catalyst to recombine hydrogen and oxygen gases into water vapor upon contact with the catalyst. At low hydrogen concentrations, energy from the recombination of hydrogen with oxygen is released at a relatively slow (but continuous) rate into the containment. The heat produced creates strong buoyancy effects, which increase the influx of the surrounding gases to the recombiner. These natural convective flow currents promote mixing of combustible gases in the containment. The recombination rate of the PAR system needs to be great enough to keep the concentration of hydrogen below acceptable levels. There are several catalytic recombiner concepts under development worldwide. The objective of this paper was to determine the hydrogen depletion rate of a PAR that has been developed by the NIS Company, in Hanau, Germany