日本文殊原型快堆堆芯出口腔室热分层现象数值模拟

本文利用商业CFD程序STAR-CCM+，采用合理的网格生成技术及物理模型，对日本文殊原型快堆堆芯出口腔室建立近似1∶1的模型，模拟分析40%额定功率停堆过程中堆芯出口腔室的瞬态工况，获得腔室内较为完整的热分层进程。结果表明：停堆2 min后腔室内出现稳定热分层现象；10～21 min时热分层通过上升桶桶顶位置；10～140 min热分层处于上升筒顶端位置附近期间，腔室内流型不稳定；140 min后热分层完全处于上升桶顶，桶内流型稳定且接近于停堆前。模拟结果与实验数据对比表明，停堆初期4 min内两者符合较好，表明本文模拟方法适用于停堆工况堆芯出口腔室热分层进程模拟；之后模拟进程明显快于实验，分析其偏差主要来自模拟边界及结构与实际的差异。

Numerical Simulation of Thermal Stratification in Reactor Upper Plenum of Monju Prototype Fast Reactor

Using a commercial CFD code STAR-CCM+ and adopting rational meshing technology and physical models, an approximate 1∶1 scale numerical simulation model for Monju Prototype Fast Reactor upper plenum was established, a numerical investigation of thermal-hydraulic phenomenon under 40% rated power output condition was carried out, and the relatively complete process of thermal stratification within upper plenum was studied. The results show that the steady thermal stratification is set up at 2 min after reactor shutdown and gets across the top of the up-flow barrel during 10-21 min, the flow pattern is unstable during 10-140 min when thermal stratification locates near the top of the up-flow barrel, and stable flow pattern close to that before reactor shutdown is resumed at 140 min after reactor shutdown. By comparing with test result, it is shown that a good agreement is achieved at an early stage of the transient (0-4 min), which can be concluded that the present numerical simulation is applicable to investigate the thermal stratification phenomena. It is also demonstrated that the elevation of the interface of the thermal stratification is overestimated after 4 min from the reactor trip, which is largely due to the difference of simulation boundaries and structure with the reality.