Design and Analysis of a Full Structural Weld Overlay for a Feedwater Nozzle-to-Safe End Dissimilar Metal Butt Weld
Design and Analysis of a Full Structural Weld Overlay for a Feedwater Nozzle-to-Safe End Dissimilar Metal Butt Weld
复制标题
给水喷嘴至安全端异种金属对接焊缝全结构堆焊的设计与分析
DOI：
--
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
C. Krause
中科院分区：
文献类型：
--
作者：
R. Engel;J. Heldt;C. Krause
2012年秋季，瑞士莱布施塔特核电站（Leibstadt Nuclear Power Plant）在换料和维修中断期间，通过无损检测，在给水喷嘴到安全端焊缝（反应堆压力容器的N-5喷嘴）处发现了一个深轴向平面指示。该指示位于不同的金属周向对接焊缝附近的一个内表面焊缝修复。其轴向长度受限于黄油，由Alloy 182材料制成，并与Alloy 82焊缝堆焊。焊缝缺陷连接到内表面。指示的深度超过壁厚的75%，因此根据ASME规范第XI节，IWB-3640, 1类部件是不可接受的。因此，在工厂重新启动之前，有缺陷的焊缝需要修复。工厂决定根据ASME规范案例N-740-2在受影响的给水喷嘴处执行全结构焊缝覆盖修复方法。瑞士监管机构最初批准这次维修作为临时维修措施，直到2015年停电。在此日期之后继续运作将受到额外的审查。本文的目的是总结所有结构和断裂力学评估的结果，根据上述规范案例进行焊接覆盖层的设计和分析。从分析结果和自20世纪80年代中期以来一直使用的焊缝覆盖修复的良好操作经验来看，可以得出结论，所讨论的覆盖给水喷嘴到安全端焊缝提供了完整的结构裕度，可以被视为长期修复。
During the refueling and maintenance outage in the Fall of 2012 at Leibstadt Nuclear Power Plant in Switzerland, a deep axially-oriented planar indication was detected by nondestructive examination in a feedwater nozzle-to-safe end weld (N-5 nozzle at the reactor pressure vessel). The indication was located in the dissimilar metal circumferential butt weld in the vicinity of an inside surface weld repair. Its axial length was restricted to the butter, made of Alloy 182 material, and the Alloy 82 weld deposits. The weld defect was connected to the inside surface. The depth of the indication exceeded 75% of the wall thickness and was thus not acceptable according to ASME Code Section XI, IWB-3640 for Class 1 components. Therefore, the defective weld required repair prior to the restart of the plant. The plant decided to perform the full structural weld overlay repair method according to ASME Code Case N-740-2 at the affected feedwater nozzle. The Swiss regulatory authority initially approved this repair as a temporary repair measure until the 2015 outage. Continued operation beyond this date is subject to additional review. The objective of the present paper is to summarize the results of all structure and fracture mechanics evaluations performed for the design and analysis of the weld overlay according to the Code Case mentioned above. From the results of the analyses and the fact that weld overlay repairs have been used with excellent operational experience since the mid 1980s, it has been concluded that the overlaid feedwater nozzle-to-safe end weld in question provides full structural margins and can be considered a long-term repair.