Hydrogen Ignition Risk by Passive Autocatalytic Recombiners (PARs) in a PWR-KWU reactor type during a SBO sequence

The hydrogen combustion in a post-accident containment represents one of the most significant hazards for the integrity of the containment. The implementation of Passive Autocatalytic Recombiners (PARs) to reduce the concentration of hydrogen during severe accident sequences is under study in many nuclear power plants. The behaviour of the PARs under extreme conditions reached should be studied in depth to avoid impaired performance, malfunction of the PARs in their mitigation function, or even the ignition of the mixture due to the heat induced by the recombiner performance. A reference PAR configuration was implemented in a GOTHIC8.1 model of PWRKWU containment. The auto-ignition for each PAR unit in each time step was separately evaluated, analyzing if the recombiner reached ignition conditions.