Temperature fluctuation characteristics for liquid lead-bismuth in complex circulation structure

Abstract: [Background] LBE (Lead-Bismuth Eutectic) alloy exhibits high thermal conductivity, substantial heat capacity, and the capability to operate under normal pressure at elevated temperatures. These properties render it a primary candidate for use as a coolant in fourth-generation reactors. [Purpose] This study aims to reveal the temperature fluctuation characteristics for LBE in complex circulation by combining experimental data and Large-Eddy Simulation (LES) model. [Methods] Firstly, the suitability of various turbulence models for simulating temperature fluctuations was validated using experimental data from liquid sodium tests conducted under a parallel three-nozzle configuration. Secondly, comparisons were made between the temperature fluctuation intensities of liquid sodium and LBE to illustrate the thermal similarity of these two liquid metal. Finally, under an artificial engineering boundary conditions, the LES model was employed to analyze the temperature fluctuation characteristics of LBE within the reactor upper plenum structure. [Results] The temperature fluctuation intensity of LBE is 1~10 Hz, indicative of typical low-frequency fluctuations. The most pronounced temperature fluctuations occur at approximately three-quarters of the height between the reactor core outlet and the heat pipe section. At the far end of the reactor core outlet, the temperature fluctuation intensity diminishes significantly due to relatively effective mixing of non-isothermal LBE. [Conclusions] The research provide valuable insights for assessing material thermal fatigue and optimizing the placement of measurement points within the LBE reactor upper plenum.