Failure Analysis for Wires of Coordinate Location Sensor for Control Rod in Reactors
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摘要: 某核电厂某机组的控制棒位置传感器出现故障,为找出故障原因,对传感器进行拆解检查,发现位置传感器上的12根导线在同一位置均有1个小角度弯曲,其中1根导线弯曲的顶点部位断开,导致位置传感器失效。为分析导线失效原因,对该断开导线、弯曲导线和正常导线分别进行了扫描电镜分析、能谱分析和金相检查。分析结果显示导线材料长期在堆内高温、高压环境下产生应力腐蚀,导致导线材料脆化产生裂纹并扩展,最终在因热膨胀系数的差异形成的拉应力作用下断开。Abstract: The coordinate location sensor of control rod of XX Nuclear Power Plant failed during operation.In order to analyze the reason,it is necessary to take apart of the coordinate location sensor.Each coordinate sensor has 12 wires and each wire has a V flexure at the same position.And one wire is fractured at the top of the V flexure.In order to study the fracture reason of the wire,the microstructures of fractured,flexural and normal wires were investigated by using scanning electron microscope（SEM）,energy dispersive X ray spectrometer（EDS）,and optical microscopy（OM）.The results indicate that the wires are stress corroded,and the grain boundary became rather weak in the high temperature and high pressure environment in the reactor.Finally the wire is broken at the top of the V flexure due to tensile stress which caused by the differential heat expansion coefficient of the material.
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Key words:
- Wire of coordinate location sensor /
- Brittle fracture /
- Residual stress /
- Tensile stress
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