Long-term thermal aging performance of welding structures in primary coolant pipes for nuclear power plants. (15th December 2020)

• Record Type: Journal Article
• Authors: Fan, Minyu; Chen, Mingya; Yu, Min; Jia, Wenqing; Li, Yuanfei; Cao, Yu; Xue, Fei; Yu, Weiwei
• Is Part Of: Annals of nuclear energy. Volume 149(2020)
• Publication Date: 2020-12-15
• Subjects: Long-term thermal aging performance -- Welding structures -- Impact energy -- Nanoindentation -- Spinodal decomposition -- Saturation; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2020.107793
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: Thermal aging experiment was performed on welding structures until 30, 000 h. A mottled structure and G-phases were observed in ferrite after thermal aging. Impact energy was still higher than initial design value until aging saturation. Thermal aging led to a decrease in impact energy and an increase in nanohardness. Abstract: Welding structures of primary coolant pipes were subjected on a series of accelerated thermal aging test at 400 °C until 30, 000 h to investigate the resulting microstructure, impact and nanoindentation properties change. The results indicated that after long-term thermal aging, a mottled structure and precipitated G-phases were observed in ferrite phases both of straight pipes and welded joints, leading to a decrease in impact energy and an increase in nanohardness. Moreover, until thermal aging saturation, impact energy of welding structures was still higher than initial design value (80 J), thus demonstrating a high toughness reserve, but saturated impact energy in welded joints was higher than that in straight pipes owing to lower ferrite content. Furthermore, there were higher-density spinodal decompositions and more precipitated G-phases in welded joints than those in straight pipes owing to micro-defects generated from welding process, resulting in a higher nanohardness in ferrite phases of welded joints.