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1、Electric Power Research Institute 3420 Hillview Avenue, Palo Alto, California 94304-1338 PO Box 10412, Palo Alto, California 94303-0813 USA 800.313.3774 650.855.2121 Electric Power Research Institute 3420 Hillview Avenue, Palo Alto, California 94304-1338 PO Box 10412, Palo Alto, California 94303-0
2、813 USA 800.313.3774 650.855.2121 Recommendations for an Effective Flow-Accelerated Corrosion Program (NSAC-202L-R3) Non-Proprietary Version Effective December 6, 2006, this report has been made publicly available in accordance with Section 734.3(b)(3) and published in accordance with Section 734.
3、7 of the U.S. Export Administration Regulations. As a result of this publication, this report is subject to only copyright protection and does not require any license agreement from EPRI. This notice supersedes the export control restrictions and any proprietary licensed material notices embedded in
4、 the document prior to publication. EPRI Project Manager S. Findlan ELECTRIC POWER RESEARCH INSTITUTE 3420 Hillview Avenue, Palo Alto, California 94304-1338 PO Box 10412, Palo Alto, California 94303-0813 USA 800.313.3774 650.855.2121 Recommendations for an Effective Flow-Accelerated Corrosion Prog
5、ram (NSAC-202L-R3) Non-Proprietary Version 1015425 Final Report, August 2007 DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES THIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC. (EPRI). NEIT
6、HER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) BELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM: (A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN TH
7、IS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTYS INTELLECTUAL PROPERTY, OR (III) THAT THIS DOCUMENT IS SUITABLE TO ANY PARTICULAR USERS CIRCUMSTANCE; OR (B) ASSUMES R
8、ESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMI
9、LAR ITEM DISCLOSED IN THIS DOCUMENT. ORGANIZATION(S) THAT PREPARED THIS DOCUMENT Munson Harold Crockett, EPRI Solutions, Inc.; James Bennetch and Chris Hooper, Dominion Generation; and Omair Naeem, Ontario Power Generation. x CONTENTS 1 INTRODUCTION 1-1 1.1 Background.1-2 1.2 Industry Status 1-3 2 E
10、LEMENTS OF AN EFFECTIVE FAC PROGRAM .2-1 2.1 Corporate Commitment.2-1 2.2 Analysis.2-2 2.3 Operating Experience2-3 2.4 Inspections2-3 2.5 Training and Engineering Judgment .2-4 2.6 Long-Term Strategy 2-4 3 PROCEDURES AND DOCUMENTATION.3-1 3.1 Governing Document 3-1 3.2 Implementing Procedures .3-1 3
11、.3 Other Program Documentation .3-2 3.4 Records of Component and Line Replacements.3-3 4 RECOMMENDATIONS FOR FAC TASKS 4-1 4.1 Definitions .4-1 4.2 Identifying Susceptible Systems4-3 4.2.1 Potential Susceptible Systems4-3 4.2.2 Exclusion of Systems from Evaluation 4-3 4.3 Performing FAC Analysis4-5
12、4.3.1 FAC Analysis and Power Uprates.4-5 4.4 Selecting and Scheduling Components for Inspection4-5 4.5 Performing Inspections4-11 4.5.1 Inspection Technique for Piping4-11 xi 4.5.2 Grid Coverage for Piping Components4-12 4.5.3 Grid Size for Piping Components4-14 4.5.4 Use of RT to Inspect Large-Bore
13、 Piping4-15 4.5.5 Inspection of Cross-Around Piping4-15 4.5.6 Inspection of Valves 4-16 4.5.7 Measuring Trace Alloy Content.4-16 4.6 Evaluating Inspection Data4-17 4.6.1 Evaluation Process4-17 4.6.2 Data Reduction4-17 4.6.3 Determining Initial Thickness and Measured Wear.4-18 4.6.3.1 Band Method .4-
14、18 4.6.3.2 Averaged Band Method.4-19 4.6.3.3 Area Method 4-20 4.6.3.4 Moving Blanket Method .4-20 4.6.3.5 Point-to-Point Method4-21 4.6.3.6 Summary4-22 4.7 Evaluating Worn Components.4-22 4.7.1 Acceptable Wall Thickness4-22 4.7.2 Maximum Wear Rate.4-23 4.7.3 Remaining Service Life4-25 4.8 Repairing
15、and Replacing Components4-26 4.9 Determination of the Safety Factor4-27 5 DEVELOPMENT OF A LONG-TERM STRATEGY5-1 5.1 Need for a Long-Term Strategy.5-1 5.2 FAC-Resistant Materials .5-2 5.3 Water Chemistry5-3 5.3.1 PWR Plants.5-3 5.3.1.1 Effect of pH and Amines on FAC.5-3 5.3.1.2 Effect of Hydrazine o
16、n FAC .5-4 5.3.2 BWR Plants.5-6 5.3.2.1 Feedwater Side Oxygen 5-6 5.3.2.2 Steam Side Oxygen.5-7 5.4 System Design Changes.5-7 5.5 Summary.5-8 xii 6 REFERENCES .6-1 A RECOMMENDATIONS FOR AN EFFECTIVE FAC PROGRAM FOR SMALL-BORE PIPINGA-1 A.1 Introduction A-1 A.2 Identifying Susceptible Systems A-1 A.3
17、 Evaluating Susceptible Systems for Consequence of Failure . A-1 A.4 Approaches for Mitigating FAC in Small-Bore Piping A-5 A.5 Guidelines for Selecting Inspection Locations in Small-Bore Piping A-6 A.5.1 Category 1 Piping. A-6 A.5.2 Category 2 Piping. A-6 A.6 Selecting Components for Initial Inspec
18、tion. A-6 A.6.1 Grouping Piping Lines into Sub-Systems. A-6 A.6.2 Selecting Components for Inspection A-6 A.7 Performing Inspections A-8 A.7.1 Radiography Techniques (RT). A-8 A.7.2 Ultrasonic Techniques (UT) . A-8 A.7.3 Thermography A-8 A.8 Evaluating Inspection Results A-8 A.9 Disposition of Sub-S
19、ystems. A-9 A.9.1 Low Wear Sub-Systems. A-9 A.9.2 High Wear Sub-Systems A-9 A.10 Long Term Strategy. A-10 B RECOMMENDED INSPECTION PROGRAM FOR VESSELS AND EQUIPMENT .B-1 B.1 Recommended Inspection Program for Feedwater Heaters B-1 B.1.1 Inspection of Feedwater Heater Shells and Nozzles . B-1 B.1.2 I
20、nspection of Internal Elements B-4 B.2 Recommended Inspection Program for Other Vessels and Equipment B-4 C MOST SIGNIFICANT FAC EXPERIENCE EVENTS THROUGH 12/2005.C-1 D HISTORICAL BACKGROUND.D-1 xiii xv LIST OF FIGURES Figure 2-1 An Effective FAC Program is Founded on Interrelated Elements.2-1 Figur
21、e 4-1 Grid Layout for an Elbow4-13 Figure 4-2 Example of Band Method .4-19 Figure 4-3 Example of Area Method4-20 Figure 4-4 Example of Moving Blanket Method.4-21 Figure 4-5 Predicted Thickness Profile4-23 Figure 4-6 Potential for Error when Using Average Wear Rate Based on Inspection Data.4-24 Figur
22、e 4-7 Danger of Using Wear Rate Based on Inspection Data from Two Inspections4-25 Figure 5-1 Expected Trends for Inspections Over a Plants Life5-1 Figure 5-2 Impact of Change in pH Level on FAC (As Predicted by CHECWORKS)5-3 Figure 5-3 Amine Comparison Typical Conditions at the Same Cold pH .5-4 Fig
23、ure 5-4 Effects of BWR Steam Line Oxygen Concentration .5-7 Figure A-1 Small Bore Piping FAC Program. A-2 Figure B-1 Recommended Feedwater Heater Coverage, Circumferential Direction B-3 Figure B-2 Recommended Feedwater Heater Coverage, Longitudinal Direction. B-4 LIST OF TABLES Table 4-1 Maximum Gri
24、d Sizes for Standard Pipe Sizes.4-15 Table 5-1 Performance of Common FAC-Resistant Alloys5-2 Table 5-2 Effect of Oxygen on Typical Feedwater Wear Rates.5-6 xvii 1 INTRODUCTION In December 1986, an elbow in the condensate system ruptured at the Surry Power Station. The failure caused four fatalities
25、and tens of millions of dollars in repair costs and lost revenue. Flow- accelerated corrosion (FAC)1 was found to be the cause of the failure.2 Subsequent to this failure, EPRI developed the CHEC family of computer codes (the current version of this technology is called the CHECWORKS Steam/Feedwater
26、 Application, hereinafter called CHECWORKS - reference 9). CHECWORKS was developed as a predictive tool to assist utilities in planning inspections and evaluating the inspection data to prevent piping failures caused by FAC. EPRI has also conducted many technology transfer workshops and user group m
27、eetings to promote the exchange of information among utility personnel and to help utilities address this issue. These technology and information exchanges have greatly reduced the incidence of FAC-caused leaks and failures. Nevertheless, instances of severe thinning, leaks, and ruptures still occur
28、. The most significant examples of recent failures occurred at Fort Calhoun in April 1997, at the H. A. Wagner fossil power plant in July 2002, at Mihama Unit 3 (Japan) in August 20043, and at the Edwards fossil plant in March 2005. A more complete listing of significant FAC-related piping and equip
29、ment failures is provided in Appendix C. The continuing occurrence of FAC failures is evidence that plant programs to mitigate FAC should be maintained and improved as necessary as industry knowledge evolves and more operating and plant data become available. The CHECWORKS Users Group (CHUG), an ind
30、ustry-sponsored group formed to deal with FAC-induced wall thinning, authorized and provided major funding for EPRI to conduct a series of plant visits in the early 1990s to understand how the technology, plant experience, and engineering know-how were being used. One result of these visits was that
31、 a need was identified for a set of recommendations to help utility personnel develop and effectively implement a comprehensive FAC program. Later revisions to this document have been based on successful utility experiences as well as improvements to FAC technology and understanding of the phenomena
32、. This document describes the organization and activities necessary to implement a successful FAC program. Typical elements of an effective FAC program are identified, and recommendations for implementation are made. This document is written to be of use to all utilities, irrespective of the predict
33、ive analytical methodology being used. 1 Flow-accelerated corrosion is sometimes, but incorrectly, called erosion-corrosion. Erosion, it should be noted, is not part of the degradation mechanism. 2 This was not the first instance that a rupture was caused by FAC, but it did bring the issue to promin
34、ence. 3 It should be noted that CHECWORKS and this document were not in use at Mihama Unit 3 or at the Wagner and Edwards fossil plants, at the time of the failures. 1-1 Introduction This document is directed at wall thinning caused by FAC. It is primarily directed at wall thinning in large-bore pip
35、ing, although small-bore piping and FAC-susceptible equipment are also addressed. It does not cover other thinning mechanisms, such as cavitation, microbiologically-influenced corrosion (MIC), and erosive wear. It is planned that this document will be periodically updated to reflect the advances mad
36、e in FAC mitigation. 1.1 Background Flow-accelerated corrosion (FAC) is sometimes referred to as flow-assisted corrosion or erosion-corrosion. FAC leads to wall thinning (metal loss) of steel piping exposed to flowing water or wet steam. The rate of metal loss depends on a complex interplay of many
37、parameters including water chemistry, material composition, and hydrodynamics. FAC damage to plant piping can lead to costly outages and repairs and can affect plant reliability, plant safety and personnel safety. Pipe wall thinning rates as high as 0.120 inch/year (3 mm/year) have occurred. Pipe ru
38、ptures and leaks caused by FAC have occurred at fossil plants, nuclear plants, and industrial processing plants. Carbon-steel piping and vessels that carry wet steam are especially susceptible to FAC and represent an industry-wide problem. Although there were limited FAC programs in place before the
39、 Surry pipe rupture, it was not until after this accident that utilities expanded their inspection programs to reduce the risk of pipe ruptures caused by FAC. Since the Surry incident in December 1986, the industry has worked steadily to develop or refine their monitoring programs to prevent the fai
40、lure of piping due to FAC. Additional historical background on FAC and development of the CHECWORKS technology is provided in Appendix D. In July 1989, EPRI formed the CHEC/CHECMATE Users Group, since renamed the CHECWORKS Users Group, CHUG. The key purpose of this group is to provide a forum for th
41、e exchange of information pertaining to FAC issues, to provide user support, maintenance, and enhancements for CHECWORKS, and to support research into the causes, detection, and mitigation of FAC. Other organizations have also provided guidance and criteria for mitigating FAC. They include: The Amer
42、ican Society of Mechanical Engineers (ASME), which published Code Case N-597-2, “Requirements for Analytical Evaluation of Pipe Wall Thinning” 15, which provides structural acceptance criteria for Class 1, 2, and 3 piping components that have experienced wall thinning4, and Non-mandatory Appendix IV
43、 to the B31.1 Code, “Corrosion Control for ASME B31.1 Power Piping Systems” 14. The Institute of Nuclear Plant Operations (INPO), which issued Significant Operating Experience Report (SOER) 87-3 in March 1987 2 and published Engineering Program Guide FAC 25. The U.S. Nuclear Regulatory Commission (N
44、RC), which released Generic Letter 89-08 in 1989 4 and Inspection Procedure 49001, “Inspection of Erosion-Corrosion/Flow- Accelerated-Corrosion Monitoring Programs” 26 in 1998. 4 Some organizations are also using Code Case N-597 to evaluate ANSI B31.1 piping for FAC-related wall thinning. 1-2 Introd
45、uction 1.2 Industry Status Following the failure of a separator drain line at Millstone 3 in December 1990, EPRI conducted a series of visits to nuclear power plants to ascertain how well FAC programs had been implemented. The goal was to review the scope, implementation, current status, and effecti
46、veness of individual FAC programs. It was found that, although the utilities had a common goal of preventing leaks and ruptures, their approaches and rates of success in attaining this goal varied. The recommendations in this document are provided to aid utilities in implementing an effective monito
47、ring program at their plants and to establish a uniform industry approach toward mitigating FAC damage. It is believed that the implementation of these recommendations will prove to be a cost-effective method of increasing personnel safety, plant safety, and plant availability. These recommendations
48、 also have the potential to reduce forced outages and thus increase the capacity factor, while helping to reduce the cost of plant operations and maintenance. The implementation of recommendations found in this document should greatly reduce the probability of a consequential leak or a rupture occur
49、ring. However, since the approach is based on inspection of a prioritized sample of susceptible locations, it is recognized that it will never be possible to prevent all FAC-related leaks and ruptures from occurring. The guidance contained in this document supersedes that contained in EPRI Report NP-3944 1 and all prior versions of this document 38. 1-3 2 ELEMENTS OF AN EFFECTIVE FAC PROGRAM Six key and interrelated element
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