Effects of the up-comer width on the PCCS heat removal

Based on the outside cooling of the Passive Containment Cooling System (PCCS), a simplified containment outside model was built and was then numerically solved. Air circulation driven by natural forces for a steady state along with the coupled thermal-hydraulic phenomena was then obtained and analyzed. For the PCCS, there are two encountered opposed forces. The density difference between the atmosphere and the channel is the driving force and the structure contributes to the drag forces. Thus, Variations of up-comer structure width between the steel wall and the buffer plate was carried out. The effects of its width on the residual heat removal, on the air temperature and on the air velocity during nuclear accident were obtained and discussed. The conclusion is important for PCCS flow and heat removal analysis. (author)