gineering Failure Analysis 37(2014)29-41 Contents lists available at ScienceDirect ENGINEERING Engineering Failure Analysis ELSEVIER journalhomepagewww.elsevier.com/locate/engfailanal Failure analysis on abnormal wall thinning of heat-transfer Cross Mark titanium tubes of condensers in nuclear power plant Part 1: Corrosion and wear Fei-Jun Chen, Cheng Yao, Zhen-Guo Yang Department of Materials Science, Fudan University, Shanghai 200433, PR China ARTICLE IN FO A BSTRACT Titanium tubes used in condensers in a nuclear power plant in China encountered abnor ACcepable 24 March 20 mal wall thinning, and was thus forced to temporarily stop operation or it could bring 19 November 2013 online 4 December 2013 about catastrophic safety problems. Most of the wall thinning happened at quite regula positions on the tubes and these failure tubes were located similarly in the condensers, indicating some common problems. To find out the root cause and mechanism of the thin- ning failure, we conducted surface deposit analysis, appearance inspection, microstructure hinning nalysis and composition analysis of the diffraction(XRD). ste. reo microscope, scanning electron microscope( SEM)and Energy Dispersive Spect (EDS). The results revealed that the wall thinning was primarily caused by eccent Failure analysis tact wear and three-body contact wear rooted in processing defect of internal boril rosion products deposit and sagging, and foreign particles. Finally, countermeasure proposed for repair and preventio e 2013 Elsevier Ltd. All rights reserved. 1 Introduction Under the background of power crisis, people are relentlessly looking for new and highly effective powers among which nuclear power is the most popular and feasible one. So the safety of nuclear power stations has ever become the priority of ll China has over a dozen of nuclear power stations under operation, one of which located in the southeast has two 700 Mw CANDU units(unit 1 and unit 2) imported from Atomic Energy of Canada Limited(AECL), the only two pressurized heavy water reactor(PHWR)units in the country. Each unit has a vertical structure with four condensers, shown in Fig. 1. The med- ia inside and outside the tubes (also called tube side and shell side)in the condenser are sea water and high purity water steam respectively. Each condenser has two independent shells connected by steam balance channel. within each shell there are two separated horizontal rows of one way heat transfer tube bundles, each of which has independent water inlet and utlet chambers as well as inlet and outlet dynamoelectric isolation valves. So each tube bundle can be isolated for main- tenance and leak emergency treatment. the working parameters of the condensers are listed in Table 1 Each condenser has 9922 heat transfer tubes that fit together as a tower-like structure shown in Fig. 2. The tubes are made of industrial pure titanium in correspondence to Chinese brand TAl, with the length of 17, 370 mm, and specifications of 25. 4 mm x 0.5 mm(outside diameter x wall thickness). Corresponding author. Tel: +86 21 65642523: fax: +86 21 65103056 1350-6307/s- see front matter o 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.engfailanal.2013.11.003Failure analysis on abnormal wall thinning of heat-transfer titanium tubes of condensers in nuclear power plant Part I: Corrosion and wear Fei-Jun Chen, Cheng Yao, Zhen-Guo Yang ⇑ Department of Materials Science, Fudan University, Shanghai 200433, PR China article info Article history: Received 24 March 2013 Accepted 19 November 2013 Available online 4 December 2013 Keywords: Titanium tube Wall thinning Corrosion Wear Failure analysis abstract Titanium tubes used in condensers in a nuclear power plant in China encountered abnor￾mal wall thinning, and was thus forced to temporarily stop operation or it could bring about catastrophic safety problems. Most of the wall thinning happened at quite regular positions on the tubes and these failure tubes were located similarly in the condensers, indicating some common problems. To find out the root cause and mechanism of the thin￾ning failure, we conducted surface deposit analysis, appearance inspection, microstructure analysis and composition analysis of the samples by means of X-ray diffraction (XRD), ste￾reo microscope, scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). The results revealed that the wall thinning was primarily caused by eccentric con￾tact wear and three-body contact wear rooted in processing defect of internal borings, cor￾rosion products deposit and sagging, and foreign particles. Finally, countermeasures were proposed for repair and prevention. 2013 Elsevier Ltd. All rights reserved. 1. Introduction Under the background of power crisis, people are relentlessly looking for new and highly effective powers among which nuclear power is the most popular and feasible one. So the safety of nuclear power stations has ever become the priority of all concerns. China has over a dozen of nuclear power stations under operation, one of which located in the southeast has two 700 MW CANDU units (unit 1 and unit 2) imported from Atomic Energy of Canada Limited (AECL), the only two pressurized heavy water reactor (PHWR) units in the country. Each unit has a vertical structure with four condensers, shown in Fig. 1. The med￾ia inside and outside the tubes (also called tube side and shell side) in the condenser are sea water and high purity water steam respectively. Each condenser has two independent shells connected by steam balance channel. Within each shell there are two separated horizontal rows of one way heat transfer tube bundles, each of which has independent water inlet and outlet chambers as well as inlet and outlet dynamoelectric isolation valves. So each tube bundle can be isolated for main￾tenance and leak emergency treatment. The working parameters of the condensers are listed in Table 1. Each condenser has 9922 heat transfer tubes that fit together as a tower-like structure, shown in Fig. 2. The tubes are made of industrial pure titanium in correspondence to Chinese brand TA1, with the length of 17,370 mm, and specifications of 25.4 mm 0.5 mm (outside diameter wall thickness). 1350-6307/$ - see front matter 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.engfailanal.2013.11.003 ⇑ Corresponding author. Tel.: +86 21 65642523; fax: +86 21 65103056. E-mail address: zgyang@fudan.edu.cn (Z.-G. Yang). Engineering Failure Analysis 37 (2014) 29–41 Contents lists available at ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal