Experimental investigation on quenching behavior across spacer grid during reflooding transient

IF 1.9 3区工程技术 Q1 NUCLEAR SCIENCE & TECHNOLOGY

Nuclear Engineering and Design Pub Date : 2025-04-04 DOI:10.1016/j.nucengdes.2025.114042

Long Ji , Xiaojing Liu , Wei Xu , Wei Zeng , Jie Wang , Hui He

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Abstract

During a Loss Of Coolant Accident (LOCA), the reflooding transient involves complex two-phase flow heat transfer process betweeen dispersed liquid phase, continuous vapor phase and high-temperature wall. The presence of spacer grids along the entire rod bundle has significant effects on the reflooding heat transfer phenomena during reflooding transients by interacting with entrained droplets. Quenching behavior in different regions of the spacer grid during the reflooding transient is studied experimentally using the 2 × 2 rod bundle test facility. The axial and circumferential quenching behaviors of the heater rods upstream and downstream of the spacer grid are analyzed for different reflooding velocities and linear power densities. Experimental results show that earlier occurrence of quenching downstream of the grid spacer is observed under low reflooding velocities and high linear power densities due to the mechanism of droplet breakup by dry spacer grid. On the other hand, at high reflooding velocity and low linear power density, a wetted grid results in increased downstream droplet size and decreased heat transfer performance, causing the linear change of the quench front curve. The experimental results also indicate that the circumferential quenching process of the heater rod upstream and downstream of the spacer grid is inconsistent due to the influence of the inhomogeneous flow pattern and spacer grid wetting conditions. The experimental data is used to support the development and validation of the model of film boiling heat transfer coefficient considering droplet breakup. The comparison results show that the boron equilibrium model can predict the performance of the boron concentration in the rod bundle channel with an accuracy of 5 %.

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重新注水瞬态过程中隔栅淬火行为的实验研究

在失冷事故（LOCA）中，再注瞬态是一个复杂的分散液相、连续气相和高温壁之间的两相流动换热过程。沿整个棒束存在的间隔栅通过与夹带液滴的相互作用对再注水瞬态传热现象有显著影响。利用2 × 2杆束试验装置，研究了再注水瞬态过程中间隔栅不同区域的淬火行为。分析了不同回流速度和线功率密度下间隔栅上下游加热棒的轴向和周向淬火行为。实验结果表明，在低回流速度和高线性功率密度条件下，由于液滴被干燥间隔栅破碎的机理，栅格间隔栅下游发生的淬灭较早。另一方面，在高回流速度和低线性功率密度下，湿润的网格导致下游液滴尺寸增大，传热性能下降，导致淬火前曲线线性变化。实验结果还表明，受非均匀流型和间隔栅润湿条件的影响，间隔栅上下游加热棒的周向淬火过程不一致。实验数据支持了考虑液滴破碎的膜沸腾换热系数模型的建立和验证。结果表明，硼平衡模型能较好地预测棒束通道中硼浓度的变化，预测精度为5%。

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来源期刊

Nuclear Engineering and Design 工程技术-核科学技术

CiteScore

3.40

自引率

11.80%

发文量

377

审稿时长

5 months

期刊介绍： Nuclear Engineering and Design covers the wide range of disciplines involved in the engineering, design, safety and construction of nuclear fission reactors. The Editors welcome papers both on applied and innovative aspects and developments in nuclear science and technology. Fundamentals of Reactor Design include: • Thermal-Hydraulics and Core Physics • Safety Analysis, Risk Assessment (PSA) • Structural and Mechanical Engineering • Materials Science • Fuel Behavior and Design • Structural Plant Design • Engineering of Reactor Components • Experiments Aspects beyond fundamentals of Reactor Design covered: • Accident Mitigation Measures • Reactor Control Systems • Licensing Issues • Safeguard Engineering • Economy of Plants • Reprocessing / Waste Disposal • Applications of Nuclear Energy • Maintenance • Decommissioning Papers on new reactor ideas and developments (Generation IV reactors) such as inherently safe modular HTRs, High Performance LWRs/HWRs and LMFBs/GFR will be considered; Actinide Burners, Accelerator Driven Systems, Energy Amplifiers and other special designs of power and research reactors and their applications are also encouraged.