The Influences of Key Factors on the Gas Diffusion in the Material Irradiation Test Based on the Regulation of Gas Composition

Abstract Material irradiation test requires to design device structure to ensure that the specimen temperature can meet requirements. Gas composition regulation is one of the main temperature control methods. Temperature gradient is established through the gas gap between the specimens and coolant, and the thermal conductivity of gap can be changed by regulating the gas composition, thereby controlling the specimen temperature. The study takes the annular gas gap of a typical material irradiation device as the research object, adopts computational fluid dynamics (CFD) method to simulate the gas diffusion process, and analyzes the influences of key factors such as type of gas inflated, gas inflation rate and volume on gas diffusion behavior during the process of gas composition regulation. Helium floats because of its lower density than the mixed gas, and argon sinks because of its higher density. For the same working conditions, argon will diffuse to a farther location under the action of greater inertial force. The higher the gas inflation rate, the wider the range of gas diffusion to the surroundings at the bottom of the device, the faster the diffusion rate in the gas gap, and the longer the diffusion distance. The volume of only affects the final diffusion state. The higher the gas inflation volume, the mole fraction of the corresponding gas will continue to increase.