Research On FCI Characteristics Of Sodium Cooled Fast Reactor Under Severe Accident

Sodium-cooled fast reactor is most likely to achieve commercial operation in the generation IV of advanced reactors,with large power density,good passive shutdown potential and excellent safety characteristics.However,in the progression of core disruptive accidents?CDA?,after molten corium-coolant interaction,the degree of fragmentation of the alloy formed by low-temperature metallurgical reactions of the metal fuel with the cladding and molten fuel directly affects the re-cooling capacity of the accident core.In this paper,a series of experimental studies have been carried out on the molten-coolant interaction?FCI?.The experimental conditions is the initial mass of aluminum and copper is 10g and 20g⁵0g respectively,the instantaneous contact interface temperature is 579??T_i?834?and 906??T_i?1282?respectively.The aluminum as a simulant of eutectic alloy fuel,copper as a simulant of metallic fuel.At the same time,in order to make up for the invisible defects of sodium-related FCI,and compare with the melt fragmentation progression under light water reactor serious accidents,the experiments of Wood metal-water interaction at different temperatures and mass were carried out,the initial mass of wood metal is 1¹0g,the instantaneous contact interface temperature is 65??T_i?313?;The study found that with the higher temperature of the melt,the overall extent of droplet fragmentation more and more finely.When T_i<728?,the fragment degree of aluminum droplet is mainly affected by the temperature of the melt,the overall distribution of the mass median diameter D_m and dimensionless number D_m/D₀ of aluminum droplet is dispersion;when T_i>728?,with the aluminum temperature goes up,the debris size of aluminum droplet has little change.T_i=1066?and T_i=1069?is the turning point temperature when the initial mass of copper is 20g and 50g respectively,when the temperature of T_i is less than the turning point temperature,the fragmentation degree of molten copper droplets is greatly affected by the temperature;When T_i is greater than the turning point temperature,the mass median diameter D_m and the dimensionless number D_m/D₀ are almost have no change,it also founds no matter how the initial mass change,the fragment degree of copper almost keep same under same experimental condition.Comparing with the experimental results of single droplet,it founds that when T_i is less than the turning point temperature,the fragmentation degree of continuous droplet is more finely than single droplet under the same thermal and hydraulic conditions;When T_i is greater than the turning point temperature,the fragmentation degree of melt has no business with the different drop modes.T_i=100?is turning point temperature of wood metal,When T_i<100?,the mass is the mainly factor affects the droplet fragmentation;when T_i>100?,the mass has a little impact on the droplet size.However,when T_i?313??water homogeneous nucleation temperature?,the temperature and mass almost has no impact on fragmentation.By analyzing the typical fragments of aluminum and copper and the Wood-Water interaction fragmentation process,it is shown that the molten droplet fragmentation mechanism is consistent with the sodium entrainment model proposed by Sugiyama.These studies can provide some technical support and references for estimating the re-cooling capacity and safety design of sodium-cooled reactor core,...