Study On Ignition Effect Of Hydrogen Recombiner In PWRs

During a core meltdown accident in a pressurized water reactor（PWR）,the re-leased hydrogen through reactor breaks would induce the hydrogen detonation.Among the existing hydrogen control methods,the hydrogen passive automatic recombiner（PAR）is widely implemented in the nuclear industry as a major way to ensure the containment hydrogen safety for its passive capability,low starting threshold and easy installation.Hydrogen PAR eliminates hydrogen in the containment through a catalytic hydrogen-oxygen recombination reaction.However,ignition could be triggered by the released reaction heat in high hydrogen mole fraction conditions,causing temperature and pressure abrupt increase.As a result,it is essential to study this effect with experi-ments and computational simulation.This thesis aims at the computation fluid dynamic（CFD）simulation of the PAR model with the in-house code CYCAS.Benchmark experiments of hydrogen recom-biner research are modeled for the verification and validation.The ignition effect of PARs is studied through simulation.Guidelines are drawn for the installation and ar-rangement of PARs in reactor containments.The simulation results show good agreement with experimental validation tests.In term of ignition effects,the simulation results show a flammability limit of 6.7 vol%H₂in condition without steam,corresponding to the experimental results.A peak pressure of 2-3 bar and a peak temperature of 1300-1800 K are detected during the simulation corresponding to a hydrogen mole fraction of 7-9 vol%,proving that the PAR induced ignition causes certain temperature and pressure loads.