Numerical method to simulate detonative combustion of hydrogen-air mixture in a containment

Abstract

During an accident accompanied by core damage in a water-cooled nuclear reactor, a large amount of hydrogen is generated by fuel clad oxidation and released into the reactor containment. Hydrogen mitigation in the containment during a severe accident is important because the integrity of the structures important to safety could be threatened by an explosive combustion of the hydrogen. Even when equipped with a hydrogen mitigation system, if a highly concentrated hydrogen mixture cloud is developed in a compartment of the containment, the compartment integrity with a pressure load from a local detonation must be evaluated. In this study, a reliable numerical method to simulate the detonation of a hydrogen-air mixture was developed for the evaluation of a pressure load from a detonation. The numerical method has the capability to capture shocks robustly as well as resolve combustion phenomena stably. The Euler equations of mass, momentum, energy and gas species are employed as the governing equations of detonation. A central-upwind scheme was adopted as a shock capturing scheme and a reduced chemical kinetic model was applied for combustion. The numerical method was validated by solving experimental cases and applied for understanding detonation shock behaviour in a generic containment.