Analysis of Onset Time of Natural Circulation Process and Influence Factor in Air Ingress Accident of HTR

Air ingress accident is a kind of beyond design basis accident in HTR, and the onset time of the stable natural circulation is concerned in this accident. Professor Takeda suggested that the local natural convection in the core played an important role in this phenomenon in 2013, and an experiment was carried out to prove it. FLUENT code was used to simulate this experiment, showing good agreement with it, which verified the ability of FLUENT to solve problems of this kind. On the other hand, analysis of influence factors (such as temperature, resistance and geometry) is much convenient with CFD code. The results provide basement to the further analysis of air ingress accident of HTR.