CFD investigating thermal-hydraulic characteristics and hydrogen generation from graphite–water reaction after SG tube rupture in HTR-10 reactor

With inherent safety performance and high conversion efficiency, high-temperature gas-cooled reactors are the possible candidates for next-generation energy sources. A transient three-dimensional compressible CFD model is developed to investigate the thermal-hydraulic characteristics within the core under steady-state and accident conditions. The HTR-10, a graphite-moderated and helium-cooled reactor with a pebble bed core is selected for the present simulations. Four postulated accidents, with ruptures in one and two SG tubes, respectively, are investigated. In accidents, water is released into the core and reacts with graphite on fuel surface, causing H2 and CO generation. Calculation results reveal that the concentration of H2, produced by the chemical reaction of carbon with water, is not sufficient to induce hydrogen explosion during the postulated accidents. In addition, the peak coolant temperatures during the transients are predicted to be lower than the limiting value, confirming safety of the HTR-10 core in these accidents.