Numerical Simulation And Experimental Verification Of Coolant Temperature Oscillation At Core Outlet Of Fast Reactor

In the sodium-cooled fast reactor,the calorific value of different fuel rods in each fuel assembly is different and the coolant flow distribution is not uniform,which leads to the different coolant temperature in different fuel assembly.When the coolant flows out of the fuel assembly,the coolant of different temperatures will intermix at the core outlet and produce temperature oscillations.As the coolant flows upwards,temperature oscillations are transmitted to the head area under the central measuring column.Under the influence of temperature oscillation for a long time,thermal fatigue and thermal aging may occur to the central measuring column and reactor internal components,which will affect the safety performance of the reactor.Therefore,it is of great engineering value to study the temperature oscillation of coolant in sodium cooled fast reactor.In recent years,extensive research has been carried out on the temperature oscillation in reactors at home and abroad,but the research on the coolant temperature oscillation at the core outlet of sodium cooled fast reactor is less.In the previous numerical simulation studies,some scholars have used the operator head model for calculation,but there is a lack of research on the applicability of turbulence model and sensitivity analysis of different parameter Settings of turbulence model.In addition,the correctness of the numerical simulation results also needs to be further verified by experiments.At the same time,in the previous experimental studies,the parallel double nozzle model,the parallel three nozzle model,the coaxial nozzle model and the T-shaped tee tube model were mostly used,and the experimental study on the temperature oscillation phenomenon in the reactor was lack of using the operating head model.Aiming at the above problems,the applicability and parameter sensitivity of the turbulence model in the numerical simulation of coolant temperature oscillation at the core outlet of fast reactor with three sets of operating head models were studied in this study.Meanwhile,the correctness of the numerical simulation method was analyzed and evaluated by using experimental data.It is found that the selection of turbulence model and parameters in numerical simulation has a very important effect on the calculation results,and the large eddy simulation,Smagorinsky-Lilly sublattice stress model and Cs value of 0.1 are the best numerical simulation results.At the same time,the transient temperature field and velocity field distribution of the whole model are obtained by numerical simulation.By analyzing the experimental data,the distribution law of temperature oscillation along the height direction and along the horizontal direction in the area of the operator head and the near wall area of the head under the central column was obtained.It was found that the most intense temperature oscillation along the height direction was mainly located at the interface of cold and hot fluids at the height of the sixth monitoring point.Along the horizontal direction,the temperature oscillations at the positions of No.2 and No.3 monitoring points are the most intense.The amplitude of temperature oscillation at the two most severe locations can reach about 12K,and the main frequency of temperature oscillation concentrates within 10Hz.It is found that in the area near the wall of the head under the central column,the temperature oscillation is the most severe along the height direction at the height of the fourth monitoring point,the temperature oscillation amplitude can reach 8K,and the temperature oscillation frequency is within 5Hz.Along the horizontal direction,the most severe temperature oscillation is located at the No.1 monitoring point,with the temperature oscillation amplitude of about 7K and the oscillation frequency within 5Hz.At the same time,numerical simulation and experiment for the temperature oscillation curve,power spectral density,and the standard deviation curve contrast,the average temperature of the statistics of the simulation and experiment relative error and relative error maximum temperature difference,found between simulation and experimental data inosculation and high reliability is high,the correctness of the numerical simulation method and experimental method to get the mutual authentication.