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HEAT REMOVAL FROM A HEATING TUBE SURFACE NEAR THE SPACER SUPPORTING NUCLEAR FUEL RODS IN BWR

沸水堆中核燃料棒支撑垫片附近加热管表面的散热

基本信息

批准号：
05452154
负责人：
FUKANO Tohru
金额：
$ 4.03万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

An experimental research have been made in order to make clear the mechanism to cause the dryout of liquid film on the heating surface near the spacers which support nuclear fuel rods. We used an experimental apparatus with an electrically heated tube with flat plate type spacers simulating the circular cell type spacer which is an typical spacer used in Boiling Water Reactor. Vapor- liquid two phase flow behavior in an annular gap between the outer surface of the heating tube and the inner surface of the co-axial glass tube was carefully observed by a high speed video recorder. As a result followings are obtained : (1) The spacer caused drypatch to occur in the limited region near the upstream end of the spader. Drypatches occur in also the limited flow pattern, the annular flow, when the liquid wave instantaneously flows downward due to gravity while large gas bubble passes by the spacer. (2) The dry patch disappeared intermittently when waves reached at the dried area on the heating surface, the temperature of the heating tube surface is possible to sharply increase causing the burnout of the heating tube. (3) The spacer pin interrupted water to flow downward and promoted the thinning of water film near the upstream end of the spacer. Accordingly the drypatch appeared at fist at the location just below the spacer pin. (4) The spacer promotes the occurrence of drypatch. On the other hand It plays an important roll of cooling the heating surface as a cooling pin.Close inspection of the out put signals such as void fraction, wall pressure and the wall temperature, reveals the followings. (5) The effect of the spacer on the mixing of vapor and liquid is effective to reduce the frypatch formation. Down ward flow due to gravity is also effectively reduced by the existence of the spacer. which results in the reduction of the frequency of the drypatch formation. The distance between the two spacers was optimum when it is about 500mm.

为了弄清核燃料棒支撑垫片附近受热面液膜干涸的机理，进行了实验研究。我们使用了一个实验装置与电加热管与平板型垫片模拟圆形细胞型垫片，这是一个典型的间隔在沸水堆中使用。利用高速摄像机对同轴玻璃管内壁与加热管外壁之间的环形间隙内的汽液两相流动行为进行了详细的观测。研究结果表明：（1）隔离物的存在使铲板上游端附近的有限区域内出现干粘现象。当大气泡通过隔离物时，液体波由于重力而瞬间向下流动时，也会在有限流型（环形流）中发生泄漏。(2)当波浪到达加热表面干燥区域时，干燥斑间歇性消失，加热管表面温度可能急剧升高，导致加热管烧毁。(3)间隔销阻断了水流的向下流动，促进了间隔件上游端附近水膜的减薄。因此，干片首先出现在定位销正下方的位置。(4)间隔物促进了干斑的发生。另一方面，它又起到了冷却壁面的重要作用。通过对空泡率、壁面压力和壁面温度等输出信号的分析，发现空泡率、壁面压力和壁面温度是影响空泡率、壁面温度的主要因素。(5)隔板对汽液混合的影响对减少碎片的形成是有效的。由于间隔件的存在，也有效地减少了由于重力引起的向下流动。这导致干斑形成的频率降低。当两个垫片之间的距离为500mm时，两个垫片之间的距离为最佳。