AP1000蒸汽发生器与主泵泵壳焊接接头无损检测问题分析

Analysis on NDE Problem of Weld Joint between AP1000 Steam Generator and Reactor Coolant Pump Casing

针对AP1000蒸汽发生器(SG)与主泵泵壳连接焊缝在工厂进行超声波检测(UT)时发现超标缺陷显示的问题,通过比较不同版本的UT规程的检测方法和验收标准,详细分析ASME第Ⅲ卷和第Ⅺ卷的检测灵敏度的差异,分析表明:混用ASME第Ⅺ卷役前检查的UT方法和ASME第Ⅲ卷制造阶段的验收标准是导致缺陷显示超标的直接原因。同时,通过增设UT试块的标定孔来设置检测灵敏度,并采用几个不同角度的UT探头进行复查,发现原先的操作人员误判了UT显示的缺陷性质,最终证明该焊缝满足ASME第Ⅲ卷的验收标准要求。

For the problems of unacceptable imperfection indications found in the weld joint between AP1000 Steam Generator and RCP Casing during Ultrasonic Examination （UT）, the comparison of UT inspection techniques have been demonstrated for different UT Procedures, and examination sensitivities difference have been analyzed between ASME Section XI and Section Ⅲ. It is proved that ASME Section XI inspection techniques of in-service inspection were mixed with Section Ⅲ acceptance standards of examination for fabrication, which is the immediate cause why imperfection indications were unacceptable. Furthermore, the re-UT was performed by several different degree probes with examination sensitivities established on an added hole reflector in the UT block. It is found that imperfection identity of UT indications were misidentified by original operators, and finally proved that this weld joint meet the requirement of acceptance standards of ASME Section Ⅲ.