三环路压水堆压力容器上腔室交混矩阵数值研究

Numerical Analysis of RPV Upper Plenum Mixing Matrix in Three Loop PWRs

使用STAR-CCM+软件对三环路压水堆压力容器上腔室流场进行了大规模、精细化三维数值模拟,并采用组分跟踪方法分别对157个燃料组件出口冷却剂流动进行计算,构造了一个具有3×157个元素的"上腔室交混矩阵",用该矩阵即可定量、精确地描述冷却剂从堆芯流出后,经上腔室内交混并再分配到各热管道的复杂流动过程。研究发现堆芯流出的冷却剂在压力容器上腔室内的交混是并不充分的,径向上不同位置燃料组件流出的冷却剂会在上腔室同热管道的接口区域存在明显的对应关系,而燃料组件径向功率分布的差异必然导致热管道中冷却剂热分层现象的产生。

A large-scale and refined three-dimensional numerical simulation of the upper plenum flow field of the pressure vessel of the three-loop pressurized water reactor is carried out by using the commercial CFD software STAR-CCM+ code. The coolant flow at the outlet of 157 fuel assemblies is calculated by the component tracking method. A mixing matrix of the upper plenum with 3×157 elements is constructed, which can be used to quantitatively and accurately describe the complex flow process of the coolant flowing out from the reactor core and mixing in the upper plenum and redistributing to the hot legs. It is found that the mixing of the coolant flowing from the core is not thorough and complete in the upper plenum of pressure vessel. The coolant flowing from fuel assembly at different positions in the radial direction is with obvious corresponding relationship in the interface area between the upper plenum and the hot legs, and the difference of the radial power distribution of fuel assembly will inevitably lead to the formation of the thermal stratification of the coolant in hot legs.