Failure analysis on leaked titanium tubes of seawater heat exchangers in recirculating cooling water system of coastal nuclear power plant

• Published in: Engineering failure analysis Vol. 101; pp. 172 - 179
• Main Authors: Gong, Yi, Ma, Fu-Qiu, Xue, Yun, Jiao, Cai-Shan, Yang, Zhen-Guo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2019
• Subjects: Erosion and corrosion; Failure analysis; Nuclear power plant; Seawater heat exchanger; Titanium tubes; Titanium tubes; Nuclear power plant; Failure analysis; Seawater heat exchanger; Erosion and corrosion
• ISSN: 1350-6307; 1873-1961
• DOI: 10.1016/j.engfailanal.2019.03.018

Thanks to the superior resistance to corrosions, especially the chloride-induced pitting corrosion, titanium and its alloys are generally regarded ideal for application in the seawater environment. However in this paper, one failure case regarding leakage on the titanium tubes of the seawater heat exchangers in the recirculating cooling water system of one coastal nuclear power plant was reported. Actually, similar problem with severer extent on even a larger number of tubes in this equipment had already occurred before and been effectively solved, nevertheless it emerged again this time but merely affected several individual tubes. To avoid contamination of the moderator system, plugging was temporarily adopted for the leaked tubes, but undoubtedly root causes analysis of this failure was immediately necessitated to reduce both the safety risks and the economic losses. Hence, comprehensive investigation of the base materials, environmental media, defects morphologies and micro-area compositions etc. was carried out for identification of the failure causes, based on which the relevant mechanisms were discussed and the pertinent countermeasures were proposed. Achievement of this paper will not only help to solve the practical engineering problem for this sole nuclear equipment, but also lead to a better understanding of the degradation behaviors of titanium alloys under complex service conditions. •Investigated a repeatedly occurring leakage case on the titanium tubes of seawater heat exchanger in coastal nuclear reactor.•Discussed the detailed mechanism and demonstrated the typical morphology of liquid-solid two-phase erosion on straight tubes.•Vividly exhibited a failure case induced by improper operation during installation which was rarely taken into account.