Countercurrent Flow Limitation Calculation of Hot Leg Based On System Program

In the event of a Loss of Coolant Accident, a large amount of coolant is released from the reactor, and steam is generated inside the reactor, and then flows down the heat pipe into the steam generator. When a natural circulation is not established in a loop, the condensed liquid in the steam generator is returned to the core by gravity of the wall of the pipe through the hot leg. This countercurrent flow has important influence on reactor safety analysis. At present, many researches have been carried out in this field, but most of them focus on the study of the countercurrent flow characteristics of two-phase flow in vertical or horizontal pipes, there are few researches on the countercurrent flow in a complex. In this paper, the countercurrent flow of two-phase flow in the hot leg under the condition of Loss of Coolant Accident (LOCA) is modeled and calculated. The experimental loop is composed of vertical pipe, inclined pipe and horizontal pipe. It is found that the shape of the hot leg has a significant effect on the injection limit, and the data based on dimensionless square root of velocity is compared with Wallis’ vertical tube results. The effects of liquid viscosity, density of liquid phase and gas, and geometry of pipeline on flooding were also studied.