A Large-Scale Study on the Effect of Ambient Conditions on Hydrogen Recombiner Induced Ignition

Hydrogen recombiners (known in the nuclear industry as passive autocatalytic recombiners-PARs), in general, can be utilized for mitigation of hydrogen in controlled areas where there is potential for hydrogen release and ventilation is not practical. Recombiners are widely implemented in the nuclear industry, however there are other applications of recombiners outside the nuclear industry that have not yet been explored practically. The most notable benefit of recombiners over conventional hydrogen mitigation measures is their passive capability, where power or operator actions are not needed for the equipment to remove hydrogen when it is present.
One of most significant concerns regarding the use of hydrogen recombiners in industry is their potential to ignite hydrogen at elevated concentrations (>6 vol%). The catalyst, heated by the exothermal H2–O2 reaction, is known to be a potential ignition source to cause hydrogen burns. An experimental program utilizing a full-size PAR at the Large-Scale Vented Combustion Test Facility (LSVCTF) has been carried out by Canadian Nuclear Laboratories (CNL) to investigate and understand the behaviour of hydrogen combustion induced by a PAR on a large-scale basis. A number of parameters external to the PAR have been explored including the effect of ambient humidity (steam) and temperature. The various aspects of this investigation will be discussed in this paper and examples of results are provided.