AP1000主蒸汽管道与蒸汽发生器连接。根据设计要求，主蒸汽管道与蒸汽发生器管嘴连接的焊缝需要进行役前和在役检查，同时位于安全壳内的主蒸汽管道需要满足先漏后破原则。为了满足上述设计和运行要求，主蒸汽管道需要进行镗孔加工并且满足镗孔后的最小壁厚要求。通过分析设计给出的主蒸汽管道外径及公差和蒸汽发生器管嘴内径及公差要求，发现主蒸汽管道镗孔后其壁厚可能无法满足设计要求，从而判断设计要求自身耦合出现偏差，建议修正主蒸汽管道外径公差值。%The main steam pipe of AP1000 connects with the nozzle of steam generator ( SG) .According to the design requirements ,the weld between the main steam pipeline and SG nozzle is required to imple-ment pre-service and in-service inspection ,at the same time the main steam pipe in the containment vessel needs to obey the principles of Leak Before Break (LBB).In order to meet the above-mentioned requirements on design and operation ,the main steam pipe needs to be bored with a minimum pipe wall thickness after boring .By analyzing the design dimension and tolerance of the main steam pipe outside di-ameter and the SG nozzle inside diameter ,it is discovered that the pipe wall thickness of main steam pipe after boring may be unable to meet the design requirements ,so a suggestion is proposed to modify the tol-erance of main steam pipe outside diameter .
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