核电站核一级BOSS头焊缝缺陷的处理

经排查国内压水堆核电站一回路压力边界核一级BOSS头焊缝存在大量未熔合、夹渣、气孔等缺陷。对BOSS头焊缝缺陷的类型、位置、原因进行分析,制定了打磨+补焊和切割+更换两种处理方案,设计并开发了专用工具,攻克了打磨剩余壁厚控制、切割防异物控制和焊缝背面充氩保护等技术难题,在宁德、福清、防城港和昌江等核电站成功应用,较好地完成了核电站核一级BOSS头焊缝缺陷处理工作,为核电站BOSS头及类似结构焊接缺陷的处理提供参考依据。

Treatment and research on the defect of level 1 BOSS weld in nuclear power plant

Defects have been found on the class 1 BOSS welds in Loop 1 pressure boundary in domestic PWRs,such as,incomplete fusion,slag inclusion,blowhole and so on. an analysis is made from the aspects of the type,position and reason of the defects,two treatment solutions are formulated,one is grinding and repairing,one is cutting and replacing. Through the design and development of special tools,the technical difficulties,including the control for grinding residual wall thickness,the control for cutting to prevent foreign matters and the argon protection for weld back,have been conquered. All of these are successfully applied in Ningde,Fuqing,Fang Chenggang and Changjiang NPPs,which provide reference for the treatments of the welding defects of BOSS and other similar structures.