Experimental Study On The Surface Reaction Characteristics Of Liquid Sodium-water Vapor In Sodium-cooled Fast Reactor

The Sodium-cooled fast reactor(SFR)is one of the easiest reactors in the fourthgeneration reactor to achieve nuclear fuel proliferation and closed fuel cycle.In a sodiumcooled fast reactor steam generator(SG),a rupture of a heat transfer tube can cause the sodiumwater reaction accident.The surface reaction between liquid sodium and water vapor is an important subject in the research of sodium water reaction accidents.The effects of different initial temperature and water vapor fraction of liquid sodium on reaction temperature,interface state and average mass loss rate of liquid sodium were analyzed.The experimental results show that: The interface state of the liquid sodium-water vapor surface reaction is divided into three stages: solid film stage,liquid film stage and smooth stage.The surface reaction is affected by the change of interface state.The transition between different phases is related to the initial temperature of liquid sodium and the mass fraction of water vapor.The dimensionless number Ma was calculated by the average temperature difference between the inside and outside of liquid sodium during the reaction period,and it was found that marangoni-benard pair was unstable on the surface of liquid sodium.The convection on the surface was in transition flow state.The surface reaction has little effect on the space temperature.With the increase of the initial temperature of liquid sodium(250℃～450℃),the average temperature in the reaction period showed an upward trend,and the average temperature increment was within 10℃.With the increase of the mass fraction of water vapor(10%～90%),the peak temperature of liquid sodium was significantly different,with an average temperature rise difference of about 30℃.At low water vapor mass fraction(10%),liquid sodium tends to stabilize after temperature rise;at high water vapor mass fractions(50% and 90%),the temperature of the liquid sodium continues to rise;under the condition of high water vapor mass fraction,the influence of initial temperature on temperature rise is more significant.By measuring the reaction time under different conditions,it was found that the reaction time under high water vapor mass fraction was twice as long as that under low water vapor mass fraction.The average mass loss rate calculated using reaction time and initial mass of liquid sodium was between 0.0005g/s and 0.006g/s.As the initial temperature of liquid sodium and the mass fraction of water vapor increase,the average mass loss rate will gradually increase.This indicates that both the mass transfer by water vapor and the initial temperature of the reaction are important factors controlling the reaction rate of sodium water,and the finite reaction rate model based on chemical kinetics is more reasonable for surface reaction calculation.These studies can provide necessary basic data and theoretical support for the study of liquid natrium-water vapor surface reaction.