The influence of a noncondensable gas on the collapse of a bubble in a stratified steam explosion at NPP

Abstract

In the present work, the effect of a noncondensable gas on the collapse of a hot bubble in cold water was studied. It is assumed that the bubble consists of a gas mixture of steam, which can condense on cold water, and a noncondensable gas. The dynamics of the bubble was modeled by the integral equations of mass and energy supplemented by the steam diffusion equation. The steam condensation rate was determined by heat fluxes on the interfacial surface from the steam and water sides. It was used a one-dimensional spherically symmetric approach. The water surrounding the bubble was considered as an incompressible fluid, the flow of which was described by the Rayleigh-Plesset. Heat transfer in water is described by a one-dimensional heat equation, which takes into account conductive and convective mechanisms of heat transfer. Calculations performed using this model showed that the presence of a noncondensable gas in a bubble does not significantly affect its collapse in cold water. This means that the noncondensable gas cannot significantly weaken the impact of water on the melt, which occurs when a bubble collapses near the interface, which leads to a stratified steam explosion.