Development And Verification Of Sub-channel Analysis Code For Sodium-cooled Fast Reactor Under Nature Cycle

With the rapid development of world science,people’s demand for energy is increasing.China takes "carbon peaking and carbon neutralization" as a key development task,and the most important thing is to reform China’s energy structure.As a clean energy with the most development prospects,nuclear energy is the only choice for future energy development.Considering the requirements of safety,sustainability,reliability and economy of nuclear energy,sodium cooled fast reactor is one of the Generation-four nuclear reactors proposed by IAEA.Sodium cooled fast reactor has a safety system design.After an emergency shutdown,natural circulation through the core is the only way to cool the core fuel assembly.Therefore,accurate prediction of the flow and temperature distribution of sodium flow in the core under natural circulation is of great significance for the design of PRHRS of sodium cooled fast reactor.In this paper,based on the experimental facility of sodium cooled fast reactor in the laboratory of liquid metal technology of Tsinghua University,the relationship of friction pressure drop applicable to low Reynolds number wire wound bundle fuel assembly is studied,and the subchannel analysis program for thermal hydraulic analysis of single box fuel assembly with natural circulation under accident condition of sodium cooled fast reactor is developed.The geometric model and flow field model in the assembly are established,and the physical parameter model,mixing model and transverse heat conduction model involved in the calculation process are investigated to solve the flow field model;Comparing the results of different formulas which are suitable for calculating the friction resistance of wire wound fuel assemblies in low Reynolds number flow,the better formula is selected to be used in the subchannel analysis program;The accuracy of the subchannel analysis program is verified by comparing the calculated results of the axial and radial temperature distributions with the experimental data.The results show that the calculation results of the subchannel analysis program are in good agreement with the experimental data.By comparing the calculation results of several friction resistance calculation formulas,it is found that the calculation results of the subchannel analysis program are most consistent with the experimental data when using the UCTD calculation formula.It is considered that the UCTD calculation formula has better calculation performance under the natural cycle condition.Compared with the experimental data,it is found that the calculated results are in good agreement with the experimental data under the low power condition,and there is a deviation between the calculated results and the experimental data under the high power condition.It is considered that under the high power condition,the re of the sodium flow in the wire wound bundle assembly is higher,and the turbulent mixing in the sodium flow between the sub channels plays a role.