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INSTABILITY OF TWO PHASE FLOW IN A 3-D NATURAL CIRCULATION COOLED NUCLEAR REACTOR SYSTEM

三维自然循环冷却核反应堆系统中两相流的不稳定性

基本信息

批准号：
09480103
负责人：
FUKUDA Kenji
金额：
$ 3.65万
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：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

To assure the passive-safety of the SBWR cooled by natural circulation its possible instabilities are examined with using a small scale experimental apparatus. This is a 1+3 dimensional system, composed of a glass container with three heater parallel channels, and a chimney volume on the top half of the container.Experiments were performed for various number of channels to observe closely the instabilities : the geysering and the density wave oscillation. It was clarified that the geyserings are initiated either from the top or the bottom of the heated channels, with accelerated propagation of the boiling front due to the gravity-governed self-evaporation. On the other hand the feedback effect between the driving force of the natural circulation and the movement of the bubbles plays the dominant role. It was very often to observe these two type instabilities occur simultaneously. These observations were simulated with using a newly developed time-domain computer code.Experiments were also performed with using a larger container with higher chimney volume. Although with a higher chimney, it was observed that the natural circulation flow rate unchanged. This was because, the secondary circulation in the chimney volume makes the pressure drop uniform, which declines the driving force of the natural circulation in the chimney part. This indicates that dividing of the chimney with several vertical segments is advisable. This observation was verified by analyses with a computer code using the drift-flux model.

为了保证自然循环冷却SBWR的被动安全性，利用小型实验装置研究了SBWR可能出现的不稳定性。这是一个1+3维系统，由一个带有三个平行加热通道的玻璃容器和一个位于容器上半部的烟囱组成，对不同数量的通道进行了实验，以密切观察不稳定性：间歇泉和密度波振荡。有人澄清，间歇泉是从顶部或底部的加热通道，加速传播的沸腾前，由于重力支配的自我蒸发。另一方面，自然循环的驱动力和气泡运动之间的反馈作用起主导作用。这两种类型的不稳定性经常同时发生。利用一个新开发的时域计算机程序模拟了这些观测结果，并在一个具有较大烟囱容积的较大容器中进行了实验。虽然烟囱较高，但观察到自然循环流量不变。这是因为烟囱内的二次循环使压力降均匀，降低了烟囱部分自然循环的推动力。这表明将烟囱分成几个垂直段是可取的。这一观测结果得到了使用漂移通量模型的计算机代码分析的验证。