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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.

为了弄清支撑核燃料棒的隔板附近受热面上液膜干涸的机理，进行了实验研究。我们使用了一台带有平板隔板的电加热管的实验装置，模拟了沸水反应堆中一种典型的隔板--圆形槽式隔板。利用高速录像机对加热管外表面与同轴玻璃管内表面之间环形缝隙内的汽液两相流动行为进行了详细观察。结果表明：(1)隔板在隔板上游端附近的有限区域内产生了干裂。当液体波由于重力而瞬间向下流动时，当大气泡通过隔板时，在有限流动模式下也会出现干涉器，即环状流。(2)当波到达加热面的干燥区时，干燥的斑块间歇性消失，加热管表面温度有可能急剧上升，导致加热管烧毁。(3)隔板销打断水向下流动，促进隔板上游端附近的水膜变薄。因此，密封片首先出现在间隔销正下方的位置。(4)间隔区促进了旱斑的发生。另一方面，它起到了冷却受热面的重要作用。仔细检查输出信号，如空泡率、壁面压力和壁面温度，可以发现以下几点。(5)间隔物对气液混合的影响有效地减少了裂隙的形成。间隔物的存在也有效地减少了重力引起的向下流动。这导致了干斑形成的频率降低。当隔板间距在500 mm左右时，隔板之间的距离最优。