위상잠금 적외선열화상을 이용한 원전배관 감육결함 검사기술 개발

Abstract

Recently, the safety problem of nuclear power plants (NPPs) has emerged as a global concern. As a result, NPP safety problems have become a global concern. Piping of aged NPPs has wall-thinned defects due to corrosion and fatigue. Wall-thinned defects have often been found in carbon steel pipes. These wall-thinned defects are a major cause of reduced pipe integrity. Serious accidents can occur when the integrity of a pipe is damaged by wall-thinned defects. Therefore, it is important to inspect piping in advance to detect defects before damage occurs. For these reasons, NDT for checking the integrity of the secondary system equipment is performed. The infrared (IR) thermography is one of the NDT. Among them, Thermal imaging technology through real-time imaging temperature changes detected by a copy of the object surface energy is a technology that can determine the presence of defects. IR thermography has been applied to many areas of defect inspection for composite structures, the deterioration diagnosis of power equipment, and military fields. However, it has not been applied to the piping systems of NPPs. IR thermography inspection is expected to show a higher utilization in the field of NPPs. In particular, IR thermography using a lock-in technique for inspection is expected to be able to clearly detect the boundaries between non-defective parts and defective parts, which will allow it to be extensively utilized in industrial fields. In this study, we developed a lock-in infrared (IR) thermography technique to detect wall-thinned defects in the small diameter pipes of a NPP’s secondary systems during normal operation. For experiments, a mock-up loop was constructed that contained artificially generated defects. The fluid inside the loop was maintained at a temperature similar to the operating conditions of a NPP. Based on the results of experiments where lock-in IR thermography was applied, it is expected to be possible to detect wall-thinned defects in piping during normal operation, shorten the maintenance time of NPPs, and improve the work efficiency of the inspector.