分类： 物理学 >> 核物理学 提交时间： 2025-03-10
摘要： To obtain a comprehensive understanding of the mechanisms underlying the thermal mixing phenomenon of coolant jet flowing from the core outlet in a Lead-cooled Fast Reactor (LFR), a systematic research project has been initiated recently under the collaboration between the Sun Yat-sen University and Harbin Engineering University in China. In the first stage of the project, experiments were conducted in the Thermal-hydraulic characteristics in Liquid Jet Mixing (TLJM) apparatus. Parallel twin water jets under various thermal and hydraulic conditions were mixed in a rectangular water pool and the mixing behavior was measured by using the Ultrasonic Doppler Velocimetry (UDV). The study analyzed the transient characteristics of water jets in the thermal mixing zone, including flow velocity, temperature as well as their fluctuation intensity distributions. Additionally, the impact of experimental parameters (e.g. inlet velocity, temperature, velocity ratio, and hydraulic diameter) on the velocity field, temperature field, and their fluctuation intensity distributions were also examined in detail. The results indicate that thermal mixing occurs in specific regions and follows distinct patterns with main fluctuation frequencies up to 10 Hz. Velocity fluctuations are tightly coupled with temperature fluctuations, as turbulence enhances thermal diffusion in the mixing zone. All experimental parameters are found to have noticeable influence on the mixing patterns. The study provides valuable insights and database on the thermal mixing mechanism and also verifies the applicability of UDV in transient velocity measurement. The obtained knowledge benefits the upcoming lead-bismuth experiments and ultimately contributes to future design and safety analysis of LFRs.
分类： 物理学 >> 核物理学 提交时间： 2025-05-15
TianZhi, Dr. Lv
Congxin, Prof. Yang
Yan, Dr. Wang
Xin, Miss Tan
Ye, Miss Jing
YanLei, Dr. Guo
Sen, Dr. Zhao
摘要： The advancement and deployment of lead-cooled fast reactors (LFRs) are significantly hindered by the corrosive nature of lead-bismuth eutectic (LBE) coolant, which adversely affects internal components, including the main coolant pump(MCP). This corrosion can lead to structural failures, posing serious risks to reactor operational safety. In this study, a computational fluid dynamics (CFD) based mathematical model of an axial flow pump in a lead-bismuth reactor was developed and validated using experimental data. Numerical simulations of the MCP were conducted under various operational conditions using the SST k-ω turbulence model. The results revealed that the blade surface skin friction coefficient (Cf) reaches its maximum at the blade inlet edge. Under standard operating conditions, the peak Cf at the blade leading edge is minimized; however, When under the operating conditions of 0.8Q0 and 1.2Q0, the peak value of Cf increased by approximately 36.3% and 72.7% respectively compared to the rated operating conditions. This will result in the MCP being unable to operate stably under eccentric working conditions.deviations from these conditions cause a rapid increase in Cf at this location. Additionally, Cf at the blade leading edge exhibited a positive correlation with the velocity gradient of the LBE. This study provides valuable insights for optimizing the hydraulic design of MCP in LFRs and for further investigation into the structural aspects of reactor flow channels.
分类： 物理学 >> 核物理学 提交时间： 2024-07-28
摘要： In the scenario of a steam generator tube rupture (SGTR) accident in a lead-cooled fast reactor (LFR), secondarycircuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel, wherea molten lead-based alloy (typically pure lead or lead bismuth eutectic (LBE)) is used as the coolant. To clarifythe pressure build-up characteristics under water jet injection, this study conducted several experiments by injectingpressurized water into a molten LBE pool at Sun Yat-sen University. To obtain a further understanding,several new experimental parameters were adopted, including the melt temperature, water subcooling, injectionpressure, injection duration, and nozzle diameter. Through detailed analyses, it was found that the pressureand temperature during the water-melt interaction exhibited a consistent variation trend with our previous waterdroplet injection mode LBE experiment. Similarly, the existence of a steam explosion was confirmed, whichtypically results in a much stronger pressure buildup. For the non-explosion cases, increasing the injectionpressure, melt-pool temperature, nozzle diameter, and water subcooling promoted pressure build-up in the meltpool. However, a limited enhancement effect was observed when increasing the injection duration, which maybe owing to the continually rising pressure in the interaction vessel or the isolation effect of the generated steamcavity. Regardless of whether a steam explosion occurred, the calculated mechanical and kinetic energy conversionefficiencies of the melt were relatively small (not exceeding 4.1% and 0.7%, respectively). Moreover, therange of the conversion efficiency was similar to that of previous water droplet experiments, although the upperlimit of the jet mode was slightly lower.
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