Numerical simulation on leaking water vapor and helium mixture gas dispersion in a closed vessel

Terada, Atsuhiko  ; Thwe Thwe, A.  ; Nagaishi, Ryuji 

Under the long-term storage of wet radioactive waste materials, hydrogen (H) is generated by radiolysis of water, and the reduction of the risk of explosion and combustion plays an important role. Since water vapor condenses on the walls of storage vessel, the behavior of H is mainly in H-air-steam (water vapor) atmosphere inside of storage vessel. Therefore, it is important to understand the condensation process of water vapor accurately and grasp the change of H concentration. In this study, CFD simulation method for estimating the amount of condensation of water vapor based on the heat-mass transfer analogy was used when the introduced gas was set to helium (He). An evaluation based on the comparison between the analytical results and the experimental values was carried out. As a result, it was found that the reproducibility of the experimental results was improved by using the condensation model considering the simple liquid film behavior.