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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.

为了弄清沸水堆燃料棒液膜击穿的流体动力学机理，进行了以下两类基础研究。研究了热毛细对流对表面局部受热的水平薄水层破裂的影响。我们用示踪法进行了目视观察，并提出了分析模型。当层厚大于2 mm时，观测和计算结果均表明，层内会产生涡，表面廓形会发生瞬态变化。另一方面，如果层厚远小于2毫米，则液体无法流入局部受热表面下方的位置，导致该位置的层变薄。这一现象仅通过计算表明，有促进薄膜破裂的作用。为了模拟沸水堆中支撑燃料棒的隔板，在横截面为矩形的水平和倾斜管道中，在空气-水分层流动中设置平板型障碍物，实验研究了平板对膜击穿的影响。结果表明：平板本身对液膜击穿没有促进作用，但连接在平板下侧的投影对液膜击穿有较强的影响。在气流速度为60 ~ 70 m/s的情况下，由于气流前缘的下冲作用，以及倾斜风道内向上流动时重力对水的排斥作用，在投影前发生了膜层破裂。在气体速度较低的情况下，它也发生在投影的下游。通过在投影前设置一个孔，可以延迟干斑地层的发生。