Numerical Simulation Of Sodium Fire In Confined Space

Compared with the third generations,the fourth generation of reactors puts forward higher requirements for the effective use of nuclear resources,nuclear energy sustainability,safety,and non-proliferation and physical protection.Sodium-cooled fast reactors are the fastest-growing,fourth-generation nuclear reactors who are closest to meeting the needs of commercial nuclear power plants.In the sodium-cooled fast reactor,liquid metal sodium penetrates from the sodium circuit and will touch the air,which is in a state of intense combustion.The combustion may bring large-scale radioactive sodium oxide,and it will be in a short time.The inside brings a large thermal shock to the surrounding equipment,which poses a greater threat to the safety facilities and system security in this room.Therefore,this study combines the concrete sodium fire experiment of Harbin University to simulate the sodium fire in confined space.The simulation model of this paper is based on the existing 3D spray sodium fire and column flow sodium fire simulation experience,and completes the sodium fire simulation calculation by means of Computational Fluid Dynamics software FLUENT.By limiting the initial operating temperature of liquid sodium,the mass of liquid sodium leaked,the concentration of oxygen in the space,and the size of the fracture,a confined space with a height of 1 m,a confined space with a height of 2 m,and a limited height of 3 m are completed to simulation of sodium fire in space.According to the simulation results,the lower the height of the defined space at the same initial operating temperature can cause the higher the peak temperature of the monitoring points in the space,but the peak temperature of the monitoring points between the three is not much different with the intial operating temperature improved.Under the condition that the same amount of liquid sodium is leaked,the higher the height of the defined space can cause the higher the peak temperature it reaches.As the quality of the leaked liquid sodium continues to increase,the difference in peak temperature in each height-limited space will become smaller and smaller.When the quality of the leaked liquid sodium is not large enough,the effect of the leakage liquid sodium increased mass on the sodium fire with the height in the confined space,but when it is increased to a certain size,the difference between the three will be small.Under the same oxygen concentration,the peak temperature of the central monitoring point increases with the height of the defined space,and the increase of the peak temperature of the central monitoring point decreases as the height of the defined space increases.Changing the oxygen concentration has a more pronounced effect on sodium fire in a low height confined space.At the same fracture scale,the peak temperature of the central monitoring point increases as the height of the defined space increases,but the magnitude of this addition decreases with increasing height.These analyses have a little reference to the occurrence of sodium fire accidents in rooms of different heights in the sodium fast reactor.