1、 1 Item No. 24252 NACE International Publication 41013 This Technical Committee Report has been prepared by NACE International Task Group (TG) 404,* “Nuclear Buried Piping.” State-of-the-Art Report: External Corrosion, Assessment, and Control of Buried Piping Systems in Nuclear Power Plants December
2、 2013, NACE International This NACE International (NACE) technical committee report represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone from manufacturing, marketing, purchasing, or usin
3、g products, processes, or procedures not included in this report. Nothing contained in this NACE report is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by letters patent, or as indemnifyi
4、ng or protecting anyone against liability for infringement of letters patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all cases relating to the subject. Unpredictable c
5、ircumstances may negate the usefulness of this report in specific instances. NACE assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE report are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and f
6、or determining their applicability in relation to this report prior to its use. This NACE report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this report
7、. Users of this NACE report are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of t
8、his report. CAUTIONARY NOTICE: The user is cautioned to obtain the latest edition of this report. NACE reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NACE reports are automatically withdrawn if more than 10 years old. Purchasers of NACE repo
9、rts may receive current information on all NACE International publications by contacting the NACE FirstService Department, 15835 Park Ten Place, Houston, Texas 77084-5145 (telephone +1 281-228-6200). Foreword Recent operating experience from nuclear power plants, particularly those located in the Un
10、ited States, many of which are between 30 and 40 years old, indicates that degradation of buried piping is occurring in at least some plants and represents an issue requiring the attention of the nuclear industry. Degradation in a variety of forms has been observed on both the external and internal
11、surfaces of the pipe. In most cases to date, the degradation was not detected until a leak was identified. Some of these leaks have resulted in the release of radioisotopes (normally tritium) and materials that may be harmful to the environment (hereafter, “environmentally sensitive material”). Thes
12、e events (a) have not resulted in the loss of the intended safety function of any component or system; (b) have not resulted in off-site exposure to radiation in excess of regulatory limits; (c) constitute only about 10% of the leaks of tritium containing water into the environment; and (d) have att
13、racted significant public attention. It is the intent of this NACE International technical committee report to provide an overview of issues associated with buried piping that might be applicable worldwide. This report, however, is written from the perspective of experiences in the United States. Th
14、is approach was taken primarily because of a lack of publicly available international information concerning this topic. _ *Chair Gabriel Ogundele, Kinectrics, Inc., Toronto, ON. NACE International 2 This report addresses a subset of the operating experience described above. It includes only topics
15、related to the external corrosion of buried piping, i.e., piping that is in direct contact with soil or concrete. It does not include topics related to internal corrosion of buried piping. Additionally, it does not include topics related to the corrosion of buried tanks, such as those in contact wit
16、h soil, concrete, or underground piping and tanks, i.e., those enclosed in a vault or trench. As with all NACE state-of-the-art reports, it is not the intent of this report to be a complete treatise on the subject of degradation, corrosion prevention, or corrosion mitigation of buried piping. Rather
17、, it is the intent of this report to identify issues for corrosion professionals to consider when addressing degradation of buried piping in nuclear power plants. The report introduces subjects and identifies applicable reference material on the subject. When a specific issue related to buried pipin
18、g degradation is found to be unique to nuclear power plants, and when ample reference material is not available, this report provides additional text concerning the issue. The length of the sections of this report correlate with the uniqueness, not the importance, of the topic considered with respec
19、t to buried piping at nuclear power plants. This state-of-the-art technical committee report was prepared by NACE Task Group (TG) 404, “Nuclear Buried Piping.” TG 404 is administered by Specific Technology Group (STG) 41, “Electric Utility Generation, Transmission, and Distribution.” It is sponsored
20、 by STG 03, “Coatings and Linings, ProtectiveImmersion and Buried Service”; STG 05, “Cathodic/Anodic Protection”; and STG 35, “Pipelines, Tanks, and Well Casings.” This technical committee report is issued by NACE under the auspices of STG 41. NACE technical committee reports are intended to convey
21、technical information or state-of-the-art knowledge regarding corrosion. In many cases, they discuss specific applications of corrosion mitigation technology, whether considered successful or not. Statements used to convey this information are factual and are provided to the reader as input and guid
22、ance for consideration when applying this technology in the future. However, these statements are not intended to be recommendations for general application of this technology, and must not be construed as such. Table of Contents Introduction . 3 Definitions for Underground and Buried Piping 3 Recen
23、t Nuclear Buried Piping Activities and Publications 4 Relevant Issues Regarding Buried Piping at Nuclear Power Plants 6 Materials of Construction 7 Carbon Steel and Cast Iron 7 300 Series Stainless Steels 8 Super Austenitic Stainless Steels (6% Molybdenum Stainless Steels) 8 Titanium 8 Copper Alloys
24、 8 Aluminum 9 Prestressed Concrete Cylinder Pipe (PCCP) . 9 High-Density Polyethylene (HDPE) 9 Coatings 10 Cathodic Protection . 10 Impact of System Grounding on Corrosion and Current Demand 11 Impact of Congestion on Anode Design . 12 Isolating Devices . 12 Test Stations . 12 Inspection Options 13
25、Indirect Inspections . 13 Direct Examinations 14 Gaps 15 Operating Experience . 15 Inspection Gaps 15 Coating Material/System Gaps . 15 Cathodic Protection Gaps . 15 References 16 NACE International 3 Introduction Recent operating experience from nuclear power plants, particularly those located in t
26、he United States, many of which are between 30 and 40 years old, indicates that degradation of buried piping is occurring in at least some plants and represents an issue requiring the attention of the nuclear industry. Degradation in a variety of forms has been observed on both the external and inte
27、rnal surfaces of the pipe. In most cases to date, the degradation was not detected until a leak was identified. Some of these leaks have resulted in the release of radioisotopes (normally tritium) and materials that may be harmful to the environment (environmentally sensitive material). These events
28、: (a) have not resulted in the loss of the intended safety function of any component or system; (b) have not resulted in off-site exposure to radiation in excess of regulatory limits; (c) constitute only about 10% of the leaks of tritium containing water into the environment;1and (d) have attracted
29、significant public attention.1Buried piping in nuclear power plants includes safety-related piping (required to attain or maintain plant shutdown), generally ASME International (ASME)(1)Class 3, and nonsafety-related piping. Although the number of piping systems that are wholly or partially buried v
30、aries from plant to plant, more than 30 different systems have been identified as being at least partially buried at several plants. Typical systems that are at least partially buried include service water (generally raw water used to cool safety and nonsafety-related components), fuel oil, lube oil
31、, compressed air, circulating water, and fire protection. Additionally, other systems that carry gases, such as oxygen, hydrogen, and nitrogen, may be buried. The following is a list of events from the U.S. Nuclear Regulatory Commission (NRC)(2)NUREG-1801, Generic Aging Lessons Learned (GALL) Report
32、 Revision 2, Aging Management Program (AMP) XI.M41,2that provides some indication of the range of recent occurrences. (a) In February 2005, a leak was detected in a 4 in (102 mm) condensate storage supply line. The cause of the leak was microbiologically influenced corrosion (MIC) or under-deposit c
33、orrosion. The leak was repaired in accordance with the ASME Boiler for the remainder of this report, the NRC GALL Report buried pipe definition is used unless otherwise specified. Recent Nuclear Buried Piping Activities and Publications Significant actions in response to the degradation of buried pi
34、ping have been taken by the NRC and the nuclear industry, primarily the NEI and the Electric Power Research Institute (EPRI).(5)These actions are described in the paragraphs below. The NRCs actions have been focused on plants that have or will be applying for a renewed operating license as permitted
35、 by the NRC, Title 10, Code of Federal Regulations (CFR) 54.31.6This authority is subject to paragraphs 10 CFR 54.29; 10 CFR 54.21(a)(1); and 10 CFR 54.4.6In combination, these paragraphs of the CFR permit the extension of an original 40 year license for a nuclear power plant by 20 years provided th
36、e aging of passive long-lived components is adequately managed. In an effort to assist licensees in preparing applications for license renewal consistent with the objectives of the regulations and provide consistency in the review of those applications, the NRC developed, and periodically revises, t
37、he GALL Report. The GALL Report addresses specific degradation effects that occur in components constructed from typical materials exposed to environments that typically occur in nuclear power plants. Additionally, the GALL Report contains Aging Management Programs (AMPs). These programs have been f
38、ound to be suitable by the NRC for managing the effects of aging of components under consideration. The latest revision of the GALL Report, Rev. 2, was published in December 2010. As part of Revision 2 to the GALL Report, the NRC reviewed the existing AMPs related to buried piping (GALL Rev. 17AMPs
39、XI.M28, Buried Piping and Tanks Surveillance, and XI.M34, Buried Piping and Tanks Inspection) and found them to be less than ideal approaches to the management of buried piping given the available operating experience. The revised AMP (GALL Rev. 2 XI.M41, Buried and Underground Piping and Tanks) emp
40、hasizes the use of preventive and mitigative actions (corrosion-resistant piping, coatings, and cathodic protection CP) and bases the number of inspections to be conducted on the significance of the pipe, the material of construction of the pipe, and the environment surrounding the pipe. The U.S. nu
41、clear industry has taken several actions related to the degradation of buried piping. These actions began in 2007. Unlike the action taken by the NRC, which is primarily directed toward license renewal, actions taken by the nuclear industry resulted in initiatives that are not mandated by regulation
42、, i.e., are voluntary relative to the NRC, but which are mandatory within the U.S. nuclear industry. These actions are summarized as follows: (a) In May 2007, EPRI conducted a Nuclear Power Plants Piping Integrity Workshop in which integrity of buried pipe was identified as one of the top priorities
43、. (4)Nuclear Energy Institute (NEI), 1776 I Street NW, Suite 400, Washington, DC 20006-3708. (5)Electric Power Research Institute (EPRI), 3420 Hillview Ave., Palo Alto, CA 94304. NACE International 5 (b) In October 2007, EPRI conducted a follow-up workshop on buried piping. At its conclusion, the ut
44、ility attendees unanimously recommended that EPRI sponsor the development of a recommendations document to assist plant engineers in preventing and mitigating degradation and leaks in buried pipes. The resulting Report No. 1016276,8 “An Assessment of Industry Needs for Control of Degradation in Buri
45、ed Pipe,” was issued in March 2008.(c) EPRI initiated the Buried Pipe Integrity Group (BPIG) in 2007; during this and subsequent years, the BPIG has met twice a year (February and July) to fulfill the following objectives: 1. Provide a forum for plant owners to discuss buried pipe issues and exchang
46、e experiences; 2. Provide a forum to obtain a consensus on industry issues; 3. Facilitate interaction between buried pipe vendors and related technology suppliers to understand capabilities from other industries; 4. Sponsor related research and development; 5. Provide technical support on buried pip
47、e degradation issues, as well as support for related products; and 6. Provide related training. (d) EPRI Report No.1016456,9“Recommendations for an Effective Program to Control the Degradation of Buried Pipe,” was issued in December 2008. (e) EPRI Report No. 1016687,10“Buried Pipe End-of-Expected-Li
48、fe Considerations and the Need for Planning,” was issued in December 2008. The purpose of this report was to alert nuclear power plant managers and component/system engineers of the point in life of buried piping systems when long-term planning or contingency planning is desirable to preclude end-of
49、-life failure or to make its impact manageable. (f) In 2008 and 2009 EPRI issued two risk ranking software programs, and other risk ranking software programs also were developed within the industry by several technology suppliers. (g) In November 2009, the NEIs Nuclear Strategic Issues Advisory Committee (NSIAC) unanimously agreed that an industry initiative on buried pipe was needed. The goal of the NEIs “Buried Piping Integrity Initiative” is to “provide reasonable assurance of structural and leakage integrity of all buried pipe with special emphasis o
