某核电厂核级设备法兰泄漏监测管开裂原因

Cracking Causes of Leak Monitoring Tube of Nuclear-Grade Equipment Flange in a Nuclear Power Plant

在国内某核电厂运行1 a后的大修期间,发现核级设备法兰泄漏监测管发生开裂.采用化学成分分析、金相检验、拉伸性能测试、扫描电镜及能谱分析等方法,分析了泄漏监测管开裂的原因.结果表明:该泄漏监测管的开裂形式为应力腐蚀开裂;泄漏监测管在安装阶段冲洗不彻底,导致氯离子残留在管内,在氯离子聚集处首先形成腐蚀坑,在应力及腐蚀性介质的共同作用下,该处产生裂纹,裂纹不断扩展,最终导致泄漏监测管发生开裂.

During the overhaul period of a domestic nuclear power plant after 1 a operation,it was found that the flange leak monitoring tube of nuclear-grade equipment was cracked.The reasons for the cracking of leak monitoring tube were analyzed by chemical composition analysis,metallographic examination,tensile property test,scanning electron microscopy and energy spectrum analysis.The results showed that the cracking form of leak monitoring tube was stress corrosion cracking.During the installation stage,the flushing of leak monitoring tube was not complete,and caused chloride ions remaineing in the tube.Some corrosion pits first formed on the site of chloride ions aggregation.Under the combined action of stress and corrosive medium,cracks occurred there,and the crack continued to expand,eventually leading to leak monitoring tube cracked.