Abstract
Due to the design of deep pool, the deep pool-type nuclear reactor has a higher coolant temperature at the core outlet compared to the general pool-type research reactor. And it shows good economics when used in district heating, industrial refrigeration and seawater desalination. In the case of loss-of-flow accident happened in deep pool-type nuclear reactor, the natural circulation gradually established in pool to remove the residual heat after the flap valve opens. In this paper, a simulation model is developed based on the RELAP5 program. And the thermal-hydraulic behaviors of natural circulation established in pool of deep pool-type nuclear reactor are analyzed. According to the simulation results, four natural circulation flow modes (single-phase natural circulation, geysering with small oscillation amplitude, steady two-phase natural circulation and geysering with large oscillation amplitude) are observed by decreasing the coolant subcooling degree at core inlet. The characteristics and mechanism of the above flow modes are also analyzed. In addition, the effects of the flow resistance coefficient in flap valve on the natural circulation flow are also analyzed. The research in this paper can provide a reference for the design and optimization of deep pool-type nuclear reactor.
