| The fast reactor primary container is an important nuclear safety equipment,which contains argon gas and sodium coolant.During reactor operation,the sodium liquid continuously transfers heat to the conical cover,which serves as the pressure boundary.The temperature distribution of the pressure boundary is an important basis for evaluating its structural integrity.The structure within the argon gas space is complex,with many thin-walled structures,and convective and radiative heat transfer is coupled.The argon gas exhibits different flow and heat transfer characteristics at different locations in the structure.At present,although domestic and foreign scholars use numerical simulation methods to study the flow characteristics and heat transfer characteristics of the covered gas space,there are still uncertainties in the choice of models(such as turbulence model,radiation model,etc.),and no comparison with experiments has been made.Therefore,it is of great academic and engineering significance to carry out research on the heat transfer characteristics of argon gas space.This article is based on a three-dimensional computational fluid dynamics method to conduct numerical simulations of the thermal-hydraulic characteristics of the argon gas space in the CFR600 model.First,a local model was established based on the Heattransfer Experimental Facility for Argon space at the top of the main vessel to carry out the calculation.and the results were compared with the experimental data.The results show that the numerical method is correct.Secondly,th’e calculated argon flow characteristics are qualitatively analyzed with the numerical simulation results of other simplified models established by other scholars,which verifies that the complex model established in this paper can more accurately reflect the argon flow characteristics inside the argon space,which is closer to the argon space flow state of the main container of the fast reactor during actual operation,and on this basis,the spatial temperature distribution of argon in the roof slab is obtained.The simulation results show that the internal temperature distribution of argon space is basically symmetrical,and at the same time,due to the particularity of the channel shielding structure,argon is actively convective heat exchange at the channel shield,and the temperature is obvious temperature stratification at the channel shield,boss and hoist material change channel,The highest temperature on the metal layer is about 428.5 ℃,and the local temperature exceeds the creep temperature of the selected material(427℃).In order to reduce creep caused by excessive temperature caused by heat transfer on the roof slab,the effectiveness of radial heat shielding structure of the heat transfer optimization scheme of the main vessel is analyzed.The calculation model of CFR600 with and without radial shield was established,and the results were compared and analyzed.The results show that the presence of radial shield significantly reduces the temperature of the cone top cover,The maximum metal layer temperature of the cone top is 383℃,which is lower than the maximum material creep temperature.The Rayleigh number reaches 106 in the large space of argon between the radial shield and the bottom sodium liquid surface,the Nussel number is in the range of 100-1000,the convection is more active,the natural convection characteristics are obvious,the Rayleigh number in the narrow channel area outside the radial shield is small,the Nussel number is in the range of 0-100,the natural convection has less influence,the temperature distribution is more uniform,and the heat exchange mainly relies on radiation and heat conduction.The results of this calculation have positive significance for reactor safety and can provide key parameters for strength analysis stress assessment under the temperature load of the main vessel. |
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