Study of the Thermal and Fluid Dynamical Effects on the Heat Removal in the Vicinity of Spacers for Supporting a Fuel Rod in a Nuclear Reactor

核反应堆燃料棒支撑垫片附近散热的热和流体动力学效应研究

基本信息

批准号：
01550149
负责人：
FUKANO Tohru
金额：
$ 1.22万
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 (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

In order to make clear the fluid dynamical mechanisms causing the liquid film breakdown on the fuel rod in BWR, the following two kinds of fundamental investigation were made.1. The effect of the thermocapillary convection on the breakdown of a horizontal thin water layer, with its surface locally heated, was examined. We made a visual observation by using the tracer method and proposed an analytical model. In the case that the thickness of the layer is larger than 2 mm, both the observed and calculated results showed that vortices are induced in the layer and the surface profile changes transiently. On the other hand if the layer thickness is much less than 2 mm, the liquid cannot flow into the position just below the locally heated surface, causing the thinning of the layer at that position. This phenomenon, which was shown by calculation only, has the effect of promoting the film breakdown.2. To simulate a spacer supporting a fuel rod in BWR, a flat-plate-type obstacle was set in an air-water stratified flow in the horizontal and inclined ducts with rectangular cross section and the effects of the flat plate on the film breakdown was experimentally investigated. The results are as follows : The plate itself does not promote the liquid film breakdown but the projection connected on the lower side of the plate has a strong effect on it. In the case of the gas flow velocity of 60 - 70 m/s, film breakdown occurred in front of the projection due to the leading edge down-wash of the stream and due also to the rejection of water by gravitational force in the case of the upward flow in the inclined duct. It also occurred just downstream of the projection in the case of the lower gas velocity. By setting a hole in front of the projection the occurrence of the dry patch formation was delayed.

为了清除BWR中液体棒杆的流体动力学机制，进行了以下两种基本研究。1。研究了热毛细血管对流对局部加热水平薄水层的分解的影响。我们使用示踪剂方法进行了视觉观察，并提出了一个分析模型。在层的厚度大于2 mm的情况下，观察到的结果和计算结果都表明涡旋在层中诱导，表面曲线会瞬时变化。另一方面，如果层厚度小于2 mm，则液体不能流入局部加热表面以下的位置，从而导致该位置的层变薄。这种现象仅通过计算显示，具有促进薄膜崩溃的作用。2。为了模拟支撑BWR中燃料杆的间隔物，在水平水分分层的水平和倾斜导管中设置了扁平式式障碍物，并具有矩形横截面，并且经过实验研究了平板对薄膜崩溃的影响。结果如下：板本身不会促进液体膜的崩溃，但是在板的下侧连接的投影对其具有很强的影响。在60-70 m/s的气流速度的情况下，由于溪流的前缘向下冲洗，在投影前发生了薄膜崩溃，并且由于引力在倾斜导管中的向上流动而被重力排斥。在较低的气体速度的情况下，它也发生在投影的下游。通过在投影的前面设置一个孔，延迟了干斑形成的发生。