Analysis of temperature fluctuation characteristics in liquid metal fast reactor three-jet flows

In a liquid metal fast reactor, the mixing of coolant from the core outlet in the upper plenum induces temperature fluctuations in the adjacent wall temperature field, which can lead to thermal fatigue of structural components. This study uses computational fluid dynamics (CFD) software and employs large eddy simulation (LES) to numerically simulate temperature fluctuations in a parallel three-nozzle model. The accuracy of the simulation method is first validated against existing experimental data. A subsequent comparative analysis examines the frequency and amplitude of temperature fluctuations for three liquid metal coolants: lead-bismuth eutectic (LBE), liquid lead (Pb), and liquid sodium (Na). The results show that, in the parallel three-nozzle model, temperature fluctuations are more pronounced for lead-based coolants, increasing the risk of thermal fatigue in structural components.