Non-Destructive Examination of PWR Steam Generator Tube-Tube Plate Welds After Repairing Melting Damage

Abstract

The tube-tube plate weld is the boundary weld that separates the primary and secondary circuits of the Pressurized Water Reactor (PWR) Steam Generator and is the weakest link of the Steam Generator. If the weld leaks, the media that may be contaminated by radiation in the primary circuit may flow into the secondary circuit, resulting in a nuclear leakage event. Therefore, the welding quality of the weld is directly related to the safety of the nuclear power site and requires special attention during the manufacturing process. The tube-tube plate weld of the PWR Steam Generator generally uses non-filled wire self-fusion welding technology. In addition to common welding defects such as pores, incomplete penetration, and cracks during the welding process, melting damage may sometimes occur due to improper operation. Since the melt loss repair involves both the tube plate surfacing layer and the tube-to-tube plate sealing weld, the repair process is much more complicated. There is little experience in the successful implementation of non-destructive inspection after melting damage repair. How to remove the defects? Which non-destructive examination methods should be selected in the repair process to ensure the defect removal effect? How to weld repair after the defect removal? Which nondestructive examination techniques should be selected during the repair process to ensure the repair effect? How to conduct final non-destructive testing after repair to confirm Rework quality? These are urgent issues. In this paper, by using tube-tube plate weld samples to carry out melting damage repair simulation experiments. After repairing, the penetration examination and the radiographic examination have been successfully implemented, and good results have been achieved.