中国实验快堆热钠池热分层现象研究

中国实验快堆(CEFR)在紧急停堆工况下,会在热钠池上部空间形成热分层现象。热分层出现后,由于上腔室底部存在大量的冷钠(相对而言),这将延缓一回路自然循环的建立。同时,冷钠的存在还会降低自然循环的流量,并对事故停堆后堆芯的冷却产生不利影响。因此,热分层现象应当引起广泛注意。从设备结构的完整性分析上看,快堆热分层现象的出现对堆容器和部分堆内构件是不利的,会使这些部件在结构内部形成明显的热应力,对堆的安全运行构成隐患。本文调研了国内外在该领域的研究状况,分析国外已有的实验研究和理论计算进展,并结合快堆现有的计算分析程序,对CEFR的热分层现象进行深入和较为全面的计算分析。通过计算分析可以看到,在全厂断电工况下,在热钠池的上部会初步形成稳定的热分层,分层界面位于中间热交换器入口的下方,但是热分层现象不会对堆的自然循环构成影响。

Thermal stratificaiton studies in the upper plenum of CEFR

The thermal stratification can be formed in the upper plenum during the reactor scram transient of CEFR which is the first LMFRR in our country.This will bring a bad effect on the natural circulation of the coolant sodium in the primary circuit because it delay the buildup of the ciucualtion for the cold coolant in the outlet of the reactor core.On the other hand,the thermal stratification in the hot pool can also bring the therrmal stress to the reactor vessel and compents.Based on the detail investigation to this phenonena,the numerical analysis have been performed by using commercial CFD code STAR-CD.From the result,it can be seen that the thermal stratificaiton can be formed after the accident of station blackout.The interface of the clear stratification is located in the level of the upper window of the IHX,but it will never stop the buildup of the natural circulation of the primary circuit.