Numerical Simulation On Asymmetrical Three-Dimensional Thermal Characteristics Of Sodium Pool Under A Primary Pump Stuck Accident In CEFR

The structure of pool-type sodium-cooled is complex,the structure size difference is large,and the operating temperature of sodium in the sodium pool is high.There are many supporting plates and pipes in the cold pool,which make the flow and heat transfer between the cold and hot sodium pools complicated.The flow of coolant in sodium pool is complex.The complex structure of pool-type sodium-cooled fast reactor may lead to the uncertainty and asymmetry of the flow and temperature field distributions under a primary pump stuck accident.Backflow may occurs in the reactor core,the pressure tube and the intermediate heat exchanger of the failure loop.In order to evaluate the safety of sodium-cooled fast reactor,it is necessary to understand the three-dimensional thermal hydraulic characteristics of sodium-cooled fast reactor.Based on China Experimental Fast Reactor(CEFR),a large number of engineering experiments and numerical simulations of key components in CEFR have been carried out in recent years,but the thermal hydraulic parameters of CEFR are still unknown.The complex structure of the pool-type sodium-cooled fast reactor may lead to the uncertainty and asymmetry of the flow and temperature field distributions under a primary pump stuck accident.This phenomenon has obvious three-dimensional thermal hydraulic characteristics and cannot be analyzed by one-dimensional or two-dimensional models,previous research have been limited and result in lacking of three dimensional numerical data.In addition,previous numerical simulations lack of experimental verification.Therefore,it is necessary to carry out the three-dimensional numerical simulation of the whole reactor thermal and hydraulic characteristics of a primary pump stuck accident,and carry out the experimental verification work.In this paper,the commercial CFD software ANSYS is used to conduct numerical simulation of the thermal hydraulic characteristics of the PLANDTL-DHX test device by using the key technology of "partition decoupling modeling&total coupling calculation".The feasibility and accuracy of the calculation method of"partition decoupling modeling&total coupling calculation" are verified by comparing the three-dimensional steady-state calculation results with the experimental results.The key technology of "partition decoupling modeling&total coupling calculation" is used to simulate the steady-state condition of CEFR,and the parameters of CEFR operating at 100%power are obtained.The accuracy of the"partition decoupling modeling&total coupling calculation" method for CEFR model is verified by comparing with the design value of CEFR.Taking the three-dimensional thermal hydraulic parameters of CEFR under steady-state condition as the initial input to calculate the transient accident condition of one pump stuck in primary loop,the long-term transient calculation of the whole reactor under the accident condition of one pump stuck in primary loop is completed.The results show that the flow field in sodium pool is asymmetric under the accident of a primary loop pump stuck.Backflow occurs in the reactor core,the pressure tube of the failure loop and the intermediate heat exchanger.The ratio of the flow rate of the main pump pressure pipe in the intact loop,the flow rate into the core and the flow rate of the main pump pressure pipe in the failure loop is always kept at 3:2:1.The cold and hot sodium pool has obvious thermal stratification and asymmetric temperature distribution.Comparing the outlet of the intermediate heat exchanger between the failure loop and the intact loop,a temperature difference of more than 90℃ occurred within a few minutes after the accident.The temperature difference between the upper and lower areas of the baffles along the vertical direction is 20℃-105℃.Due to the obstruction of the vertical baffles,the maximum temperature difference along the annular direction of the cold sodium pool is 85℃.The key technology of "partition decoupling modeling&total coupling calculation"provided in this paper can provide technical support for full-scale coupled transient three-dimensional numerical simulation of complex models with huge structural size differences.This paper provides an important three-dimensional quantitative parameter for CEFR under the pump stuck accident in primary loop,and provides an important reference for the design and safety analysis of sodium-cooled fast reactor.