Operational behavior of a passive auto-catalytic recombiner under low pressure conditions

International audienceIn the case of a severe accident inside a water-cooled fusion facility, like ITER, there exist several scenarios in which hydrogen may be produced and released into the suppression tank. Assuming the accidental ingress of air, the formation of flammable gas mixtures may lead to explosions and severe component failure. One option to mitigate such hypothetical scenarios is the installation of passive auto-catalytic recombiners (PARs), which are presently used as safety devices inside the containments of nuclear fission reactors. PARs convert hydrogen into water vapor by means of passive mechanisms and support the prevention of large accumulations of combustible gases. Experimental investigations of PAR operation have been performed with a scaled-down model of a conventional PAR inside the REKO-4 facility (JÜLICH), a pressure vessel with a volume of 5.3 m3. A first low-pressure test series has been performed with absolute pressures between 0.2 and 1 bar (a), and hydrogen concentrations of up to 6 vol.%. The test results show a strong dependence of the pressure on the PAR start-up behavior. The start-up delay is proportional to the pressure level. Furthermore, the recombination rate is significantly reduced with decreasing pressure. © 2017 The Author