Steam Generator Fretting-Wear Damage: A Summary of Recent Findings

1999 ◽  
Vol 121 (3) ◽  
pp. 304-310 ◽  
Author(s):  
F. M. Gue´rout ◽  
N. J. Fisher
Keyword(s):  
Steam Generator ◽  
Wear Test ◽  
Operating Conditions ◽  
Fretting Wear ◽  
Measuring System ◽  
Effect Of Temperature ◽  
Design Parameters ◽  
Wear Depth ◽  
Alloy 800 ◽  
Wear Damage

Flow-induced vibration of steam generator (SG) tubes may sometimes result in fretting-wear damage at the tube-to-support locations. Fretting-wear damage predictions are largely based on experimental data obtained at representative test conditions. Fretting-wear of SG materials has been studied at the Chalk River Laboratories for two decades. Tests are conducted in fretting-wear test machines that simulate SG environmental conditions and tube-to-support dynamic interactions. A new high-temperature force and displacement measuring system was developed to monitor tube-to-support interaction (i.e., work-rate) at operating conditions. This improvement in experimental fretting-wear technology was used to perform a comprehensive study of the effect of various environment and design parameters on SG tube wear damage. This paper summarizes the results of tests performed over the past 4 yr to study the effect of temperature, water chemistry, support geometry and tube material on fretting-wear. The results show a significant effect of temperature on tube wear damage. Therefore fretting-wear. The results show a significant effect of temperature or tube wear damage. Therefore, fretting-wear tests must be performed at operating temperatures in order to be relevant. No significant effect of the type of water treatment on tube wear damage was observed. For predominantly impacting motion, the wear of SG tubes in contact with 410 stainless steel is similar regardless of whether Alloy 690 or Alloy 800 is used as tubing material or whether lattice bars or broached hole supports are used. Based on results presented in this paper, an average wear coefficient value is recommended that is used for the prediction of SG tube wear depth versus time.

An Evaluation of Fuel Rod Fretting Wear in Spacer Grid With Conformal Shape

2006 ◽  
Author(s):  
Young Ki Jang ◽  
Nam Kyu Park ◽  
Jae Ik Kim ◽  
Kyu Tae Kim ◽  
Chong Chul Lee ◽  
...  
Keyword(s):  
Nuclear Fuel ◽  
Calculation Method ◽  
Power Plants ◽  
Failure Time ◽  
Fretting Wear ◽  
Measuring System ◽  
Wear Volume ◽  
Wear Depth ◽  
Volume Calculation ◽  
Fuel Rod

Turbulent flow-induced vibration in nuclear fuel may cause fretting wear of fuel rod at grid support locations. An advanced nuclear fuel for Korean PWR standard nuclear power plants (KSNPs), has been developed to get higher performance comparing to the current fuel considering the safety and economy. One of the significant features of the advanced fuel is the conformal shape in mid grid springs and dimples, which are developed to diminish the fretting wear failure. Long-term hydraulic tests have been performed to evaluate the fretting wear of the fuel rod with the conformal springs and dimples. Wear volume is a measure to predict the fretting wear performance. The shapes of a lot of scars are non-uniform such as wedge shapes, and axially non-symmetric shapes, etc., depending on the contact angle between fuel rod and springs/dimples. In addition, conformal springs and dimples make wear scars wide and thin comparing to conventional ones with convex shape. It is found that wear volumes of these kinds of non-uniform wear scars are over-predicted when the traditionally used wear depth-dependent volume calculation method is employed. In order to predict wear volume more accurately, therefore, the measuring system with high accuracy has been used and verified by the known wear volumes of standard specimens. The wear volumes of the various wear scars have been generated by the measuring system and used for predicting the fretting wear-induced failure time. Based on new evaluation method, it is considered that the fretting wear-induced fuel failure duration with this conformal grid has increased up to 8 times compared to the traditionally used wear depth-dependent volume calculation method.

Localized Corrosion of Nuclear Grade Alloy 800 Under Steam Generator Layup, Startup and Operating Conditions

2012 ◽  
Vol 1 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Y. Lu
Keyword(s):  
Corrosion Resistance ◽  
Steam Generator ◽  
Elevated Temperatures ◽  
Chloride Concentration ◽  
Operating Conditions ◽  
Nuclear Grade ◽  
Localized Corrosion ◽  
Pitting Potential ◽  
Alloy 800 ◽  
Secondary Side

The localized corrosion resistance of nuclear-grade Alloy 800, which is one of the preferred steam generator (SG) heat exchange tube materials of CANDU and PWR reactors, was studied under simulated SG secondary side crevice chemistry conditions at ambient temperature as well as at elevated temperatures. Series of cyclic potentiodynamic polarization tests were performed to study the localized corrosion resistance of Alloy 800 as a function of chloride ion concentration in the SG crevice solution at 40°C, 150°C and 300°C. Based on the experimental results, empirical equations were provided for calculating the pitting potential of nuclear grade Alloy 800 in the SG secondary side crevice chemistries with different levels of chloride concentration at SG layup, startup and operating temperatures.

Experimental Fretting-Wear Studies of Steam Generator Materials

1995 ◽  
Vol 117 (4) ◽  
pp. 312-320 ◽  
Author(s):  
N. J. Fisher ◽  
A. B. Chow ◽  
M. K. Weckwerth
Keyword(s):  
Steam Generator ◽  
Contact Force ◽  
Environmental Conditions ◽  
Analytical Techniques ◽  
Work Rate ◽  
Fretting Wear ◽  
Flow Induced Vibration ◽  
Dynamic Interactions ◽  
Support Materials ◽  
Wear Damage

Flow-induced vibration of steam generator tubes results in fretting-wear damage due to impacting and rubbing of the tubes against their supports. This damage can be predicted by computing tube response to flow-induced excitation forces using analytical techniques, and then relating this response to resultant wear damage using experimentally derived wear coefficients. Fretting-wear of steam generator materials has been studied experimentally at Chalk River Laboratories for two decades. Tests are conducted in machines that simulate steam generator environmental conditions and tube-to-support dynamic interactions. Different tube and support materials, tube-to-support clearances, and tube support geometries have been studied. The effect of environmental conditions, such as temperature, oxygen content, pH and chemistry control additive, have been investigated as well. Early studies showed that damage was related to contact force as long as other parameters, such as geometry and motion, were held constant. Later studies have shown that damage is related to a parameter called work-rate, which combines both contact force and sliding distance. Results of short and long-term fretting-wear tests for CANDU steam generator materials at realistic environmental conditions are presented. These results demonstrate that work-rate is an appropriate correlating parameter for impact-sliding interaction.

Probabilistic Assessment of Fretting Wear in Steam Generator Tubes Under Flow Induced Vibrations

2003 ◽  
Author(s):  
Greg D. Morandin ◽  
Richard G. Sauve´
Keyword(s):  
Steam Generator ◽  
Degradation Mechanism ◽  
Probabilistic Methods ◽  
Fretting Wear ◽  
Nonlinear Flow ◽  
Impact Wear ◽  
Steam Generators ◽  
Flow Induced Vibration ◽  
Wear Damage ◽  
The Impact

Successful life management of steam generators requires an ongoing operational assessment plan to monitor and address all potential degradation mechanisms. A degradation mechanism of concern is tube fretting as a result of flow-induced vibration. Flow induced vibration predictive methods routinely used for design purposes are based on deterministic nonlinear structural analysis techniques. In previous work, the authors have proposed the application of probabilistic techniques to better understand and assess the risk associated with operating power generating stations that have aging re-circulating steam generators. Probabilistic methods are better suited to address the variability of the parameters in operating steam generators, e.g., flow regime, support clearances, manufacturing tolerances, tube to support interactions, and material properties. In this work, an application of a Monte Carlo simulation to predict the propensity for fretting wear in an operating re-circulation steam generator is described. Tube wear damage is evaluated under steady-state conditions using two wear damage correlation models based on the tube-to-support impact force time histories and work rates obtained from nonlinear flow induced vibration analyses. Review of the tube motion in the supports and the impact/sliding criterion shows that significant tube damage at the U-bend supports is a result of impact wear. The results of this work provide the upper bound predictions of wear damage in the steam generators. The EPRI wear correlations for sliding wear and impact wear indicate good agreement with the observed damage and, given the preponderance of wear sites subject to impact, should form the basis of future predictions.

Wear Scar Progression of Impact-Fretting at Elevated Temperature for Steam Generator Tubes in Nuclear Power Plants

2006 ◽  
Vol 326-328 ◽  
pp. 1251-1254 ◽  
Author(s):  
Chi Yong Park ◽  
Jeong Keun Lee
Keyword(s):  
Steam Generator ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Operating Conditions ◽  
Wear Scar ◽  
Fretting Wear ◽  
Test Material ◽  
The Impact ◽  
Steam Generator Tubes

Fretting wear generated by flow induced vibration is one of the important degradation mechanisms of steam generator tubes in the nuclear power plants. Understanding of tube wear characteristics is very important to keep the integrity of the steam generator tubes to secure the safety of the nuclear power plants. Experimental examination has been performed for the purpose of investigating the impact fretting. Test material is alloy 690 tube and 409 stainless steel tube supports. From the results of experiments, wear scar progression is investigated in the case of impact-fretting wear test of steam generator tubes under plant operating conditions such as pressure of 15MPa, high temperature of 290C and low dissolved oxygen. Hammer imprint that is actual damaged wear pattern, has been observed on the worn surface. From investigation of wear scar pattern, wear mechanism was initially the delamination wear due to cracking the hard oxide film and finally transferred to the stable impact-fretting pattern.

Crack Initiation Factor by Impact Fretting Wear at INCONEL Alloy for Steam Generator Tube in Nuclear Power Plants

2007 ◽  
Vol 26-28 ◽  
pp. 1269-1272
Author(s):  
Chi Yong Park ◽  
Jeong Kun Kim ◽  
Tae Ryong Kim ◽  
Sun Young Cho ◽  
Hyun Ik Jeon
Keyword(s):  
Steam Generator ◽  
Wear Mechanism ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Operating Conditions ◽  
Fretting Wear ◽  
Steam Generator Tube ◽  
Inconel Alloy ◽  
The Impact

Inconel alloy such as alloy 600 and alloy 690 is widely used as the steam generator tube materials in the nuclear power plants. The impact fretting wear tests were performed to investigate wear mechanism between tube alloy and 409 stainless steel tube support plates in the simulated steam generator operating conditions, pressure of 15MPa, high temperature water of 290°C and low dissolved oxygen(<10 ppb). From investigation of wear test specimens by the SEM and EDS analysis, hammer imprint, which is known to be an actual damaged wear pattern, has been observed on the worn surface, and fretting wear mechanism was investigated. Wear progression of impact-fretting wear also has been examined. It was observed that titanium rich phase contributes to the formation of voids and cracks in sub-layer of fretting wear damage by impact fretting wear.

Development of Wear Test System for Steam Generator Tubes in Nuclear Power Plants

2005 ◽  
Vol 297-300 ◽  
pp. 1418-1423 ◽  
Author(s):  
Chi Yong Park ◽  
Yong Sung Lee ◽  
Myung Hwan Boo
Keyword(s):  
Steam Generator ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Wear Test ◽  
Test System ◽  
Fretting Wear ◽  
Stable Operation ◽  
Test Results ◽  
Steam Generator Tubes

In steam generators of nuclear power plants, flow-induced vibration (FIV) can lead to tube damage by fretting-wear occurred due to impact and sliding movement between the tubes and their supports. There have been many studies and test results on wear damage of steam generator tubes but they were not reflected the mechanical and chemical conditions accurately. KEPRI nuclear power laboratory developed a wear test system, which is able to control the motion of impact and sliding simultaneously in the pressurized high temperature water-chemistry conditions. Some wear tests were performed to verify the stable operation for the wear test. This wear test system with new concepts was described briefly, and some data for verifying its performance have been shown in the cases of the selected some test results. In the test, Alloy 690 was used for tube materials and 409 stainless steel for support plates. A little data deviation was obtained and stability of system operation was investigated.

scholarly journals An ad-hoc fretting wear tribotester design for thin steel wires

2018 ◽  
Vol 165 ◽  
pp. 22018
Author(s):  
Iñigo Llavori ◽  
Alaitz Zabala ◽  
Mikel Aingeru Urchegui ◽  
Wilson Tato ◽  
Andrea Aginagalde ◽  
...  
Keyword(s):  
Ad Hoc ◽  
Steel Wire ◽  
Wear Test ◽  
Fretting Wear ◽  
Maximum Diameter ◽  
Test Machine ◽  
Wire Ropes ◽  
Thin Wires ◽  
Wear Damage ◽  
Contacting Force

Steel wire ropes experience fretting wear damage when the rope runs over a sheave promoting an oscillatory motion between the wires. Consequently, wear scars appear between the contacting wires leading to an increase of the stress field and the following rupture of the wires due to fatigue. That is why the understanding and prediction of the fretting wear phenomena of thin wires is fundamental in order to improve the performance of steel wire ropes. The present research deals with the design of an ad-hoc fretting wear test machine for thin wires. The test apparatus is designed for testing thin wires with a maximum diameter of 1.0 mm, at slip amplitudes ranging from 5 to 300 μm, crossing angle between 0-90°, and contacting force ranging from 0,5 to 5 N. The working principle of displacement amplitude and contacting force as well as the crossing angle between the wires are described. Preliminary studies for understanding the fretting wear characteristics are presented, analysing 0.45 mm diameter cold-drawn eutectoid carbon steel (0.8% C) wires (tensile strength higher than 3000 MPa).

scholarly journals Dynamic Analysis of a Bladed Disk With Friction and Fretting-Wear in Blade Attachments

2009 ◽  
Author(s):  
Loi¨c Salles ◽  
Laurent Blanc ◽  
Fabrice Thouverez ◽  
Aleksander M. Gouskov ◽  
Pierrick Jean
Keyword(s):  
Jacobian Matrix ◽  
Relative Displacement ◽  
Correction Method ◽  
Fretting Wear ◽  
Wear Depth ◽  
Industrial Plants ◽  
Friction Dampers ◽  
Coulomb’S Friction ◽  
Bladed Disk ◽  
Wear Damage

Assembled bladed disks have many contact interfaces (blade-disk joint, blade shrouds, friction dampers...). Because of relative displacements at these interfaces, fretting-wear occurs, which affects negatively the lifetime of the structure. Methods exist to predict fretting-wear in quasi-static analysis. However they don’t predict all the phenomena observed in blade attachments on real industrial plants. This paper studies the assumption of a responsibility of dynamics for fretting-wear damage. A numerical treatment of fretting-wear under vibratory loading is proposed. The method is based on the Dynamical Lagrangian Frequency Time method. It models unilateral contact through Coulomb’s friction law. The basic idea is to separate time in two scales, slow scale for tribological phenomena and fast scale for dynamics. For a chosen number of periods of vibration, a steady state is assumed and the variables are decomposed in Fourier series. An Alternating Frequency Time procedure is performed to calculate the non-linear forces. Then, a Hybrid Powell’s algorithm is used as solver. A quasi-analytical expression of the Jacobian matrix decreases the duration of calculations. This expression is also used to predict new relative displacement at the interfaces due to the increase of wear depth. This method is similar to a prediction-correction method, with wear depth as the term of continuation. Numerical investigations on a bladed-disk with friction contact interfaces illustrate the performances of this method and show the coupling between dynamical and tribological phenomena.

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