华龙一号反应堆上腔室及热段流热耦合场数值模拟

压水型反应堆(pressurized water reactor, PWR)系统主管道热段内冷却剂的温度和流量，直接反映了核功率和堆芯换热状态，是反应堆功率控制和安全保护的核心参数。为全面掌握“华龙一号”反应堆上腔室及热段内冷却剂流-热耦合场分布及演变规律，为核心参数测控提供参考，本文基于有限元分析(Finite Element Method, FEA)方法，对上腔室及热段冷却剂流域进行了计算流体力学(computational fluid dynamics, CFD)数值模拟。首先建立了合理简化后的“华龙一号”(Hualong One)反应堆上腔室及相连热段的3D几何结构模型。随后对模型计算域进行了离散化网格划分和网格敏感性分析。最后通过计算，获得了冷却剂非等温流动的稳态特性解，流量、温度与相关设计估算值、实际测量值的相对误差均小于2%。对稳态特性研究表明，高、低温冷却剂在上腔室垂直内壁附近的不充分换热导致热段入口冷却剂温度分布不均，存在14.0~16.3℃的温差。随冷却剂沿轴向流动，冷却剂温度场分布和流场分布均逐渐趋于均匀和稳定，且是热段内低温冷却剂的流动主导了冷却剂温度分布的变化。

Numerical simulation of flow-thermal coupling field inside upper plenum and hot legs of HPR1000

The temperature and flow rate of coolant in the hot legs of pressurized water reactor (PWR) systems directly reflect the nuclear power and the heat transfer state of the reactor core, and are key parameters for reactor power control and safety protection. In order to comprehensively understand the distribution and evolution of the coolant flow-thermal coupling field in the upper plenum and hot leg of the Hualong One, and provide references for the measurement and control of core parameters, the Finite Element Analysis (FEA) method was employed in this paper to conduct computational fluid dynamics (CFD) numerical simulations of the coolant flow region in the upper plenum and hot legs. Firstly, a reasonably simplified 3D geometrical model of the upper plenum and hot legs of the Hualong One was established. Subsequently, the computational domain of the model was discretized into meshes and a mesh sensitivity analysis was performed. Finally, through calculations, a steady-state solution of non-isothermal coolant flow was obtained, with relative errors between flow rate, temperature and related design estimates and actual measured values all less than 2%. Analysis of the steady-state characteristics indicates that an uneven coolant temperature distribution at the inlet of the hot legs is caused by insufficient heat exchange between high and low temperature coolants near the vertical inner wall of the upper plenum, with a temperature difference between 14.0℃ and 16.3℃. As the coolant flows along the axial direction, both the temperature and flow distribution gradually become uniform and stable. Furthermore, the variation of the coolant temperature distribution is dominated by the flow of the low temperature coolant inside the hot legs.