A comparative computational fluid dynamics (CFD) study was conducted on the three different types of pressurized water reactor (PWR) upper plenum, named TYPE 1 (support columns (SCs) and control rod guide tubes (CRGTs) with two large windows), TYPE 2 (SCs and CRGTs without windows), and TYPE 3 (two parallel perforated barrel shells and CRGTs). First, three types of upper plenum geometry information were collected, simplified, and adopted into the BORA facility, which is a 1/5 scale system of the four-loop PWR reactor. Then, the geometry, including the upper half core, upper plenum region, and hot legs, was built using the Salome platform. After that, an unsteady calculation to simulate the reactor balance operation at hot full power scenario was performed. Finally, the differences of flowrate distribution at the core outlet and temperature distribution and transverse velocity inside the hot legs with different upper plenum internals were compared. The results suggest that TYPE 1 upper plenum internals cause the largest flowrate difference at the core outlet while TYPE 3 leads to the most even distributed flowrate. The distribution and evolution pattern of the tangential velocity inside hot legs is highly dependent on the upper plenum internals. Two counter-rotating swirls exist inside the TYPE 1 hot leg and only one swirl revolving around the hog leg axis exist inside the TYPE 2 hot leg. For TYPE 3, two swirls like that of TYPE 1 rotating around the hot leg axis significantly increase the temperature homogenization speed. This research provides meaningful guidelines for the future optimization and design of advanced PWR upper plenum internal structures.

对三种不同类型的压水反应堆（PWR）上气室进行了比较计算流体力学（CFD）研究，其名称为TYPE 1（支撑柱（SC）和带有两个大窗口的控制杆导管（CRGT）），TYPE 2个（不带窗口的SC和CRGT）和TYPE 3（两个平行的带孔枪管弹壳和CRGT）。首先，收集，简化了三种类型的上气室几何信息，并将其用于BORA设施，该设施是四回路PWR反应堆的1/5比例系统。然后，使用Salome构建包括上半部核心，上充气区和热腿在内的几何体平台。此后，进行了非稳态计算来模拟热全功率情况下的反应堆平衡运行。最后，比较了在具有不同上增压内部的热腿内部的流量分布与温度分布和横向速度之间的差异。结果表明，类型1的上通风系统内部导致芯出口处的流量差异最大，而类型3导致最均匀的分布流量。热腿内部切线速度的分布和演变模式高度依赖于上充气室内部。1型热腿内部存在两个反向旋转的旋流，而2型热腿内部仅存在一个绕生猪腿轴线旋转的旋流。对于TYPE 3，绕热腿轴旋转的两种旋涡（如1型旋涡）显着提高了温度均质化速度。该研究为高级压水堆上部气室内部结构的未来优化和设计提供了有意义的指导。