Experimental Study On Sodium Droplet Combustion Rate And The Spatial Temperature Distribution Characteristics

The sodium-cooled fasted reactor(SFR)is a more realistic type of reactor in the forth generation advanced reactors.Liquid sodium is used as a coolant in the SFR for its excellent thermo-dynamical properties than water.However,the particular disadvantage of liquid sodium is its high chemical reactivity with the atmosphere and the leakage of high temperature sodium would cause serious fire accidents.The combustion of sodium droplet is the baise of different sodium fire accidents.In this paper,the combustion and spatial temperature distribution characteristics at the different distances(10mm-40mm)from the center of droplet and the different angles(0°-30°)were studied by carrying out the experiments of the oxidation and combustion under different conditions of initial temperatures(200?-350?)of sodium droplet,oxygen concentrations(12-21%)and ambient atmosphere temperatures(80? and 180?).The combustion behaviors were recorded by high-speed camera.According the experiment video and result,the process of the sodium droplet combustion can be divided into 3 stages: surface oxidation,pre-ignition and combustion.The different initial temperature of the sodium droplet and the oxygen concentration of the ambient atmostphere could change the combustion characteristics.The different combustion model adopts to the different stages and the combustion rate is influenced relatively large by the oxygen concentration.The ambient atmosphere temperature(80? and 180?)will not change the three stages of the sodium droplet combustion(surface oxidation,pre-ignition and combustion)but will change the characteristics in every stage.When the ambient atmosphere temperature is low(80?),the columnar oxides is relatively obvious and the temperature of sodium change slowly,then the temperature rises suddenly after exceeding the ignition point.When the ambient atmosphere temperature is high(180?),the columnar oxides is not obvious and the time of combustion is shorter.The peak temperatures are all relatively close.When the ambient atmosphere temperature is relatively high(180 ?),the spatial temperature in different distances from the center of the sodium droplet and at different angles change more are all relativiliyt large.However when the ambient atmosphere temperature is relatively low(80?),the spatial temperature is relatively small.The peak temperature of sodium droplet sufficient combustion is between 560? and 1000?.The temperature of sodium droplet begins to increase after the gas supplied,and the spatial temperature begin to increase substantially after the sodium temperature exceeds the characteristic temperature The spatial temperatures change greatly at 10 mm from droplet,and because of the relative velocity,the temperatures in the 0° direction is highest at 10 mm from droplet.In the distance of 10mm-20 mm,the spatial temperatures change gradually,and at 20 mm away from droplet,the spatial fitting temperatures at different angles almost level off to a stable value.The results provide the technical support on the evaluation and analysis of the various forms of sodium fire accidents.