Parametric study of the breaking scenarios during the loss of vacuum accident for CFETR

In the China Fusion Engineering Test Reactor (CFETR), the occurrence of a Loss of Vacuum Accident (LOVA) could result in high-velocity airflow entering the vacuum vessel, causing plasma disruption and potentially posing a significant safety hazard. In this study, the LOVA involving multiple small and minor breaches in the vacuum vessel (VV) of the CFETR is analyzed through modeling and simulation utilizing the ANSYS Fluent software. The study examines the influence of the initial pressure in VV, the total area, number, position, and distribution of breaking points on gas flow characteristics during the LOVA, based on the validation of the numerical model. The analysis includes the examination of the evolution and disappearance of the Mach disk resulting from supersonic fluid under the conditions of LOVA. With a constant total area, an increase in the number of distinct breaking points would result in a reduction of the critical mass flow rate of the jet. This decrease would decelerate the decline of the flow rate, consequently extending the necessary stability time. Moreover, the findings indicate that as the number of breaking points increases, the size of the Mach disk observed along the central flow axis diminishes, while the numerical value demonstrates a rising pattern.