Abstract
When a depressurization accident occurs in the Very-High-Temperature Reactor (VHTR), a mixing process of different kind of gases occurs. Then, in order to research mixing process of two component gases and flow characteristics of localized natural convection, we have carried out the numerical analysis using three dimensional CFD code. The numerical model was consisted of a reverse U-shaped vertical slot and a storage tank. The left side slot was consisted of a heated wall and a cooled wall. The right side slot was consisted of two cooled walls. The heavy gas was transported to the slot by the molecular diffusion and localized natural convection. And then, natural circulation generated through the reverse U-shaped slot. As a result of three dimensional analysis, gas mixture was promoted by flow of depth direction and natural circulation generated faster than that of two dimensional analysis.
