Research On Simulation Model Of Sodium Fire In A Columnar Flow Of Sodium-cooled Fast Reactor

Compared to the fourth generation nuclear reactors,the third generation nuclear reactors make more efficient use of nuclear resources,and the safety of reactors has been further improved.In a variety of alternative types of the fourth generation reactors,the sodium-cooled fast reactors are most likely to meet the requirements of the commercial operation.However,when the liquid sodium leak from coolant systems,it can react violently with water and oxygen and pose a risk for potentially dangerous consequences.As a result,the sodium fire could cause a serious security problem to the safe operation of the nuclear reactors.So in this paper,the detailed study on simulation model of sodium fire in a columnar flow is carried out.Combined with the existing experimental research of sodium fire in a columnar flow,and using the liquid jet theory,liquid sodium combustion model,the extended model of liquid pool and other mature theoretical model,the simulation models of sodium fire in a columnar flow is completed.Then the secondary development of the CFD software FLUENT basing on the simulation model is also finished,and the software is used to complete the final calculation of the simulation model and the gain the temperature field parameters,oxygen concentration distribution and combustion rate,etc.In order to verify the simulation model,the simulation results and experimental data of sodium columnar fire are compared.According to the comparisons,the simulation model for the central combustion zone has high precision,and the prediction error of the maximum temperature of the combustion zone is not more than 10%.In addition,by varying the initial conditions of simulation calculations,the factors affecting the sodium fire in a columnar flow including the initial environmental oxygen concentration,temperature and flow rate of liquid sodium are studied and analyzed.According to the simulation results,when the sodium fire in a columnar flow occurs,the concentrated spray combustion will lead to a rapid increase of the temperature in the combustion area.But due to the restriction of the oxygen concentration in the combustion area,the burning rate will be reduced as the oxygen is consumed.Eventually the temperature in the combustion area will come down after reaching a peak.In order to study the factors affecting the sodium fire in a columnar flow,the combustion characteristic is simulated under different initial temperature(250-500?),initial environmental oxygen concentration(10-20%)and flow rate of liquid sodium(0.1-0.3kg/s).The simulation results also show that the main factors making an impact on the sodium fire in a columnar flow is the oxygen concentration of the surrounding environment and the flow rate of liquid sodium.Reducing the initial oxygen concentration of the surrounding environment can significantly decrease the burning rate and the maximum temperature.when the oxygen concentration decreased to 10%,the peak temperature of sodium fire is only about 600?.In addition,when the flow rate increases from 0.1 kg/s to 0.2 kg/s,the initial burning rate rises by a double.Due to the limitation of the oxygen concentration,when the flow rate increases from 0.2 kg/s to 0.3 kg/s,the initial burning rate rises by one fifth,and the central maximum temperature is about 1000?.