蒸汽发生器传热管凹陷复合缺陷涡流信号分析

Analysis of composite eddy current signals of denting with defect in steam generator tubes

以CPR1000核电机组蒸汽发生器传热管为例,针对蒸汽发生器管板上部因硬质泥渣沉积后挤压传热管致使其产生凹陷,进而可能诱发应力腐蚀开裂的问题,利用三种不同类型的涡流探头,开展传热管凹陷与缺陷复合信号的分析。试验结果表明:凹陷对复合信号中裂纹的识别有较大的影响;当凹陷处的裂纹类缺陷深度增加至40%T(T为壁厚)时,Bobbin探头在信号特征上有较明显变化,使用MRPC探头可有效识别;阵列探头可有效识别局部小变形凹陷与20%T裂纹的复合信号;对比三种类型的探头,阵列探头对凹陷复合缺陷具有更好的检测能力。

Taking the steam generator tube of CPR1000 nuclear power unit for example,regarding the issue of denting on the upper part of tubesheet caused by hard sludge which might induced stress corrosion cracking in steam generator tubes,this paper used three different types of eddy current probes to study the composite signal of denting with defect.Experimental results revealed that denting would impact on the detection of crack in the composite signal.When the depth of crack increased to 40%wall thickness in the composite signals,Bobbin probe showed significant changes in signal characteristics and MRPC probe could detect it effectively.Array probe would be better to detect the composite signals of local small denting with 20%T crack.Compared to the three types of probes,array probe had better detection ability for composite signals of denting with crack.