Study on Accident Mitigation and Cooling of Damaged Core during Severe Accidents of Right water Reactor (Possibility of Cooling by Penetrated Water into a Narrow Gap between a Reactor Pressure Vessel and Piled-up Debris of Damaged Core)

使用的设备是R-113闭环。试验截面为长240mm的厚壁铜管。外径100mm，内径34或36mm。在测试管道中插入一根玻璃管，形成0.5、1、2或5mm的垂直窄环流通道。根据Bond数标度，缺口大小由TMI-2事故中估计的反应堆压力容器与受损堆芯堆积碎片之间的缺口宽度确定。实验进行了(1)底封闭逆流和(2)底排水逆流的临界热流密度实验。流动状态记录在带有CCD相机和光纤示波器的VTR上。传热方式为成核沸腾。随着热流密度的增大，最终达到临界热流密度（CHF）。然而，没有观察到壁温突然升高。当热流密度进一步增大后，壁面温度急剧升高。在(1)和(2)实验中，在启动逆流限流（CCFL）以限制液体进入流道后，受热表面部分形成不稳定的间歇性干燥斑，达到CHF点。在这个阶段，壁面温度没有急剧升高。当热通量（即向上的蒸汽流）进一步升高后，液体穿透受到更大的限制，液体穿透速率小于蒸发速率，形成大稳定的干斑，壁面温度偏移开始。否。(1)和(2)实验中CHF热流密度q_<CHF>和温度偏移起始热流密度q_<EXC>存在差异。在本实验中，q_<CHF>的值比用现有相关性预测的值低得多，约为一个数量级。

The facility used was a R-113 closed-loop. The test section was a thick wall copper pipe of 240mm in length. 100mm in OD and 34 or 36mm in ID.A glass pipe was inserted into the test pipe to from a vertical-narrow-annular flow passage of 0.5,1,2 or 5mm gap. Following the Bond number scaling, the gap size was determined from the gap width between the reactor pressure vessel and the piled-up debris of the damaged core estimated in the TMI-2 accident. Experiments performed were the critical heat flux experiments of (1) bottom-closed counter-current flow and (2) bottom drainage counter-current flow. The flow state was recorded on a VTR with a CCD camera and a fiber scope.The mode of heat transfer was nucleate boiling. As the heat flux was increased, the critical heat flux (CHF) condition was eventually reached. However, no abrupt wall temperature increase was observed then. After the heat flux was increased more, the sharp increase in the wall temperature was perceived. In both (1) and (2) experiments, after the counter-current flow limiting (CCFL) was initiated to restrict the liquid penetration into the flow passage, unstable-intermittent dray patches were formed partially on the heated surface and the CHF point was reached. At this stage, there is no sharp wall temperature increase. After the heat flux (i.e.the upward vapor flow) was elevated more, that liquid penetration was testricted more and the liquid penetrating rate becomes less than the evaporation rate, large-stable dry-patches were created and the wall temperature excursion started. No.difference was observed between the (1) and (2) experiments in the CHF heat flux q_<CHF> and the temperature excursion initiation heat flux q_<EXC>. The values of q_<CHF> in the present experiments were much lower, approximately one order, than values predicted with existing correlations.