Ultrasonic Inspection Design and Application for Maincoolant Pipes of Third-Generation Nuclear Power Plants

This paper reviews the global development of third-generation nuclear power plants and examines the evolving requirements for main pipe inspection processes in the in-service inspection standards. Third-generation nuclear plants offer significant improvements in design and safety over previous generations. However, with the continued advancement of nuclear technology, the inspection technologies for primary loop main pipes face increasingly complex challenges, especially the detection of narrow gap welds, which has become a critical technical issue for nuclear plant safety. Using the operational EPR and Hualong One nuclear power plants in China as examples, the paper analyzes the characteristics, specifications, layout, and inspection scope of narrow gap welds in the main pipes. The narrow gaps and complex layouts make it difficult for conventional inspection methods to fully cover the welds, particularly in confined spaces and irregular pipe structures. Achieving high-precision, high-efficiency inspections is a key challenge for engineers. Through an in-depth analysis of the surrounding environment and nuclear island facility layout, the paper highlights the spatial constraints in the design of main pipe inspection equipment. The compact arrangement of the reactor and auxiliary facilities further complicates inspection tasks. To address these challenges, the paper introduces a lightweight, high-load automatic ultrasonic scanner designed to improve inspection efficiency in complex environments. This scanner uses advanced ultrasonic testing technology to efficiently inspect welds in confined spaces. Its core components include a high-load probe holder and a remote control system for real-time data analysis. The paper also discusses the practical application of this technology at Taishan and Hualong One nuclear power plants, where the new equipment has significantly improved inspection accuracy and efficiency, supporting safe plant operations. Finally, the paper looks forward to the future development of main pipe inspection technology, emphasizing advancements in automation, data processing, and remote operation, which will enhance the safety and efficiency of nuclear plants, supporting the sustainable growth of the global nuclear industry.