It is a critical safety issue of thermal fatigue in the core outlet of sodium cooled fast reactors (SFRs) due to the mixing phenomenon of coolant with different temperatures flowing from different assemblies. In this paper, the large eddy simulation (LES) method was employed to study the coolant mixing phenomenon of a simplified assembly head model of SFR. The coolant velocity and temperature fields with vortices of different scales were obtained and analyzed. It shows that the lateral velocity is more sensitive to the inlet velocity than to the inlet temperature difference. In addition, the normalized parameters of temperature in axial and radial measuring lines and temperature fluctuations at specific points were obtained. Results show that there is no obvious dominant frequency of the temperature fluctuations with the energy of temperature fluctuations distributed in the frequency range of 0–100 Hz. The results would be beneficial for the design and structure optimization of SFRs.

由于来自不同组件的不同温度的冷却剂的混合现象，这是钠冷却快堆（SFR）堆芯出口中热疲劳的关键安全问题。本文采用大涡模拟（LES）方法研究了SFR简化装配头模型的冷却液混合现象。获得并分析了具有不同尺度旋涡的冷却剂速度和温度场。它表明，横向速度对入口速度比对入口温度差更敏感。此外，还获得了轴向和径向测量线温度的标准化参数以及特定点的温度波动。结果表明，温度波动的能量分布在0-100 Hz的频率范围内，没有明显的温度波动主频。该结果对SFR的设计和结构优化将是有益的。