Simulation of the Incident Helium Ingress into the Cryostat of the DEMO Fusion Reactor

During a helium leak accident the cryostat is filled with helium gas, which causes the cryostat to cool down due to the heat transferred through the helium between the cryostat and the cryogenic magnet system. The scenario considered in this study assumes that the cryostat thermal shield (CTS) remains actively cooled at 80 K. Hence, only the heat transferred by natural convection of helium between the warm cryostat walls and the cold CTS is considered in the analysis. The helium natural convection in the isolated compartment between the CTS and the cryostat has been simulated to determine the heat transfer and temperature distributions on the cryostat walls, on the outside surrounded by the air at room temperature. The ANSYS-CFX code was used to run the steady-state simulations. The 2015 DEMO geometry with 18 equatorial port is used for the purpose of this study.