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Mechanisms of Burnout Generation due to the Instability and the Transient Change of Boiling Two-Phase Flow near a Flow Obstacle simulating a Spacer of a BWR

模拟沸水堆隔板流动障碍附近沸腾两相流的不稳定性和瞬态变化引起的烧毁机理

基本信息

批准号：
12450076
负责人：
FUKANO Tohru
金额：
$ 9.66万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

A cylindrical flow obstruction which simulates a spacer supporting nuclear fuel rods in BWR was installed in the vertical annular channel. Flow patterns, especially the generation of drypatch and burnout, were carefully observed by a high speed video camera. The time variations of temperature on the heating tube surface were simultaneously measured near the spacer at six axially different location under the experimental conditions of transiently changing flow caused by the sudden change in the heart flux, the inlet quality, the mass flow rate. The effect of flow instability on the generation of burnout was also investigated. The results are summarized as follow.(1) In the transient change of flow caused by the sharp increase of heat flux or decrease of mass flow rate, the effect of transition on the generation of burnout is small and the burnout was occurred only when the heating condition, i.e., the heat flux after the change is as large as the burnout heat flux in steady operation. I … More n low flow rate condition j_L=0.1 m/s burnout is triggered by the generation of the drypatch in the location neither in or upstream of the spacer. The burnout dose not generate downstream of the spacer.(2) The quick reduction of heat flux causes the large scale drypatch extending in the spacer and also reached to the point upstream of the spacer. The temperature increase reaches up to 20 K〜30 K.(3)The drastic increase in the inlet quality causes the flow stably change to a new flow condition. On the other hand the drastic decrease in the heat flux causes the generation of burnout near the spacer due to decreasing the passing frequency of the disturbance waves.(4)The change in flow pattern, in which the velocity increases and shear stress increases, is stable. On the other hand if the change causes the decrease in the velocity the burnout occurs even if the heat flux is less than the steady burnout.(5)The general rule found in the present research is that the passing frequency of disturbance waves is the controlling factor to couse the generation of burn out. That is If the interbal of the passing of disturbance wave becomes long the burnout is easy to occur. Less

在垂直环形通道中安装了一个圆柱形流动障碍物，模拟了沸水堆中支撑核燃料棒的间隔件。利用高速摄像机对流动形态，特别是干斑和燃尽的产生进行了细致的观察。在心脏流量、进气品质、质量流量突变引起的流量瞬变的实验条件下，同时测量了加热管近间隔件处6个轴向不同位置的温度随时间的变化。流动的不稳定性对产生的燃尽的影响进行了研究。结果总结如下。(1)在热流密度急剧增加或质量流量下降引起的流动瞬态变化中，过渡对燃烬的产生影响很小，仅在加热条件，即，变化后的热通量与稳定运行时的燃尽热通量一样大。我 ...更多信息在低流速条件下，j_L=0.1 m/s，在间隔器内或上游的位置产生干斑会触发燃尽。在间隔物的下游不会产生烧坏。(2)热通量的快速减小导致大规模的干板在间隔件中延伸，并且也到达间隔件的上游点。温度升高可达20 K ~ 30 K。（3）进口品质的急剧增加使流动稳定地改变到新的流动状态。另一方面，热通量的急剧下降导致由于降低了扰动波的通过频率而在间隔件附近产生烧毁。（4）流速增大、切应力增大的流型变化是稳定的。另一方面，如果变化导致速度降低，即使热通量小于稳定燃尽，也会发生燃尽。（5）研究发现，扰动波的通过频率是导致烧损发生的控制因素。即干扰波通过的间隔时间过长，容易发生烧毁。少