Investigation of Natural Helium Circulation Inside Dual Channels Prismatic Modular Reactor

Natural helium circulation inside a dual-channel prismatic modular reactor was numerically investigated to comprehend the passive safety features using the new RHYS/ASYST VER4 package. The natural circulation was studied at Depressurized Cooldown (DC) at heat fluxes of 860–2293 W/m2 with a pressure of 413.7 kPa and Pressurized Cooldown (PC) at pressures of 413.47–689.12 kPa with a flux of 1720 W/m2. A reversal of the heat transfer near the riser exit was seen, combined with a decrease in helium and riser wall temperatures due to the end effect. The pressure has an inverse effect on the heat transfer, where the temperature decreases by 19 % as the pressure increases from 413.47 to 689.12 kPa. The heat transfer was studied under the DC and PC. Both entrance and end effects are introduced with the heat transfer coefficient. Also, the nondimensional groups (Nu, Gr, Pr, and Ra) were discussed.