低压低干度自然循环流量漂移分析

Analysis of Flow Excursion in a Natural Circulation System with Low Pressure and Low Steam Quality

在 5MW核供热堆全尺寸全参数模拟试验回路HRTL 5上进行的实验中 ,观察到在一定条件下系统发生静态流量漂移的同时 ,伴随动态流量振荡。本文总结了HRTL 5模拟试验回路上的实验研究结果 ,分析了低压低干度自然循环系统的特点、欠热沸腾和闪蒸的作用机理 ,较完整地描述了自然循环流量漂移的整个过程。分析结果表明 :1 )在自然循环系统中 ,欠热沸腾和闪蒸对流动稳定性具有重要作用 ;2 )自然循环流量漂移是一个长热工过程 ,动态振荡也可以发生在静态流量漂移过程中 ;3 )在静态流量漂移的发生、发展并向动态振荡转变的过程中 ,先是欠热沸腾占主导地位 ,然后逐渐转变为闪蒸占主导地位 ,最后主要表现为密度波振荡的形式。自然循环流量漂移对 5MW堆的设计、安全分析以及升级开发具有重要价值。

A series of experments were perforned on the test loop (HRTL 5),which simulates the geometry and system design of the 5 MW nuclear heating reactor.The flow excursion accompanied with flow oscillation was observed under certain conditions.Some experimental results have been summarized in the natural circulation with low pressure and low steam quality.The mechanism of sub cooled boiling and flashing is analyzed,and an entire process of flow excursion is described too.The analysis shows:1)Sub cooled boiling and flashing play an important role on the flow instabilities in a natural circulation system.2)The static flow excursion in the natural circulation is a rather long thermo hydraulic process,which can be accompanied by the dynamic flow oscillation.3)In the course of the flow excursion's beginning,developing and gradually converting to the flow oscillation ,the flow instability is first dominated by sub cooled boiling ,then is dominated by void flashing,last is mainly the density wave oscillation.The investigation on flow excursion in the natural circulation is important for the design and accident analysis and upgrading development of the 5MW nuclear heating reactor.