Numerical study on the thermal stratification characteristics in the upper plenum of sodium-cooled fast reactor (SFR)

In this paper, the IAEA benchmark, a trip transient scenario from 40% rated power of Monju reactor in Japan, was studied using CFD method. The reactor steady state and shutdown transient scenarios were simulated and the 3-D distributions of important thermal hydraulic parameters in the SFR upper plenum was achieved. The steady state calculated results agreed well with experimental data and acceptable deviations were obtained, which indicate the application and prediction accuracy of CFD method. The complex development of thermal stratification in the upper plenum of SFR under accident conditions were obtained. The detailed flow fields in the bottom of center measuring column and near with the through flow holes were revealed. The influence of different local structures on the thermal stratification in the SFR upper plenum were understood. This work could provide a certain basis for the SFR upper plenum structure design and operation strategy making.