Numerical Analysis on Characteristic of Hydrogen Mixing and Stratification in a Containment Model

Hydrogen explosion is one of the severe threats to the integrity of containment for nuclear power plant which has drawn many experts attention to make great efforts on hydrogen related issues, espeically after the Fukushima Dai-ichi nuclear power station accident took place. However, the issue of hydrogen distribution hasn’t been closed as a result of related complex process of hydrogen transport and the particular design of each kind of facility. In the present study, CFD method has been applied to the pre-analysis on the characteristic of hydrogen mixing and stratification in a computational containment model for the sake of probable phenomena identification and instrumentaion design of experimental study in the next phase. Firstly, physical models have been verified by the experimental data from THAI HM2. Based on the determined numerical models, five typical groups of cases have been simulated, considering the effect of initial momentum, injection location, and injection direction. During the cases, only helium has been released in the vessel isothermally, on behalf of hydrogen. The results show that the backflow from the wall to the main stream in the dome and the buoyancy force may strongly dominate the helium flow, thus affacting the mixing and stratification. The eccentric injection and horizontal injection may also influence the helium distribution, in which the wall effects and rapid shifting may play important roles. However, the inference will be examined in the experiments later. All the work will be helpful for safety design and analysis of newly-built containment in China.