反应堆下腔室涡流引起堆芯流动不稳定性试验研究

Experimental Study on Core Flow Instability Caused by Vortex Flow in Reactor Lower Plenum

压水反应堆各个环路中的冷却剂在下腔室发生剧烈湍流交混,下腔室腔体内产生大量涡流,会导致堆芯燃料组件入口流量随机震荡,引发堆芯瞬态流动不稳定性,可能影响到反应堆热工、结构安全或传热性能。本文对反应堆内燃料组件区域流动特性开展研究,通过水力学试验手段获得反应堆堆芯在多种运行工况下,下腔室安装流量分配裙和不安装流量分配裙时的堆芯燃料组件入口流量脉动数据,试验结果表明,流量分配裙对下腔室涡流的抑制效果明显,在碎涡整流作用下,堆芯流量脉动明显降低;随着运行环路数的减少,下腔室流场对称性降低,涡流增强,堆芯流量脉动明显增大;下腔室涡流还会对堆芯入口流量分配均匀度造成不利影响,流量脉动偏大区域对应的流量分配因子明显较小。

Strong turbulent mixing of coolant in each loop of the PWR occurs in the lower plenum,and a large number of vertex are generated in the lower plenum,which can lead to random fluctuation of the fuel assembly inlet flow and trigger transient flow instability in the core,thus affecting the reactor thermal safety,structural safety or heat transfer performance.In this paper,the flow characteristics of the fuel assembly area in the reactor are studied,and the flow pulsation data of the fuel assembly inlet with and without flow distribution skirt in the lower plenum are obtained by hydraulic test under various operating conditions.The experimental results show that the lower plenum flow distribution skirt has obvious effect on restraining vortex,and the core flow pulsation is obviously reduced under the action of vortex breaking rectification.With the decrease of the number of operating loops,the symmetry of the flow field in the lower plenum decreases,the vertex flow increases,and the flow pulsation in the core increases obviously.The vortex in the lower chamber will also adversely affect the uniformity of flow distribution at the inlet of the core,and the flow distribution factor corresponding to the area with large flow pulsation is obviously small.