ML12334A701
| ML12334A701 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 04/30/2011 |
| From: | Nuclear Energy Institute |
| To: | Atomic Safety and Licensing Board Panel |
| SECY RAS | |
| References | |
| RAS 21566, 50-247-LR, 50-286-LR, ASLBP 07-858-03-LR-BD01 | |
| Download: ML12334A701 (20) | |
Text
United States Nuclear Regulatory Commission Official Hearing Exhibit NYS000169 Entergy Nuclear Operations, Inc. Submitted: December 16, 2011 In the Matter of:
(Indian Point Nuclear Generating Units 2 and 3)
V\..~P.R REG(J<.q)<o ASLBP #: 07-858-03-LR-BD01 l~\
Docket #: 05000247 l 05000286
" 0'!:
Exhibit #: NYS000169-00-BD01 Identified: 10/15/2012
'" ~ Admitted: 10/15/2012 Withdrawn: April 2011
~
'1"'....1-: 0' i Rejected: Stricken:
" .*** .. " Other:
Industry Guidance for the Development of Inspe~tion Plans for Buried Piping Prepared by: Buried PiP,e,,~~~rity Task Force
April 2011 TABLE OF CONTENTS 1.0 Preface ................................................................................................................. 4 2.0 Purpose ................................................................................................................ 4 3.0 Background ......................................................................................................... 4 4.0 Terms and Definitions .............................................................................. 6 5.0 Buried Piping Reasonable Assurance Flow Chart-Description .. .... .
6.0 References ........................................................................................ .
3 IPEG PA OAG0023180
April 2011 1.0 Preface This document provides industry guidance for the determination of reasonable assurance for structural and/or leakage integrity for buried piping. The criteria and guidelines presented in this document were developed as a consistent basis for establishment of what is necessary to provide "reasonable assurance of integrity".
2.0 Purpose The purpose of this document is to provide a technically based approach {pr<<>
development of inspection plans that establish reasonable assurance of st~~tufal and/or leakage integrity of buried piping through the application of the p~sults of both indirect inspections and direct examinations. The approach is prQ§r~-rn~~tically founded in the precepts established in the "Recommendations for an Effe~~~¥~Program to Control the Degradation of Buried and Underground Piping abgTariks (EPRI 1016456, Revision 1) and utility site specific program documents. TQi§!QQt'ument is intended to establish reasonable assurance for scoped buried piping~~~t~ms; optimizing the inspection scope, while not requiring 100% inspection:>
3.0 Background Reasonable assurance is an industry met~Qe~idgy used to achieve increased confidence in the capability of a structure,:§yst~fn or component (SSC) to perform its intended function. Reasonable assu~~P1~~dbes not equate to absolute assurance or confidence. Rather, reasonable assui)~mce collects appropriate data/insights/information to ~1::I~port the establishment of increased confidence.
Situations may occur where~yffiefent data cannot be easily collected; in these cases, the available data may b~$bppremented with additional insights to bolster a technical foundation of reasoJ}~bf~>§~§urance. If available information (even with supplemental insights) is insuffi~~~ntlb~upport a conclusion of reasonable assurance, then additional actions must .~>~ tak~ffto achieve reasonable assurance. Ultimately, the establishment of reasonabl~.>?s~urance is the obligation of the owner. This guideline provides insights to achiev~ :fb6$lstency among industry users to identify what actions are generally nec~s~f3~.Ja.>establish reasonable assurance for structural and/or leakage integrity for b4(1~d/pl~i~g .
Reasonable assurance of integrity in buried piping systems containing licensed material or non-licensed material is obtained when activities such as an engineering evaluation (including a Fitness-for-Service assessment), indirect inspections of underground components, direct examination and remediation (if necessary), are performed. Such a combination of activities will provide a high level of confidence that the structural and leak integrity of the buried piping systems, will be managed and effectively maintained.
4 IPEG PA OAG0023181
April 2011 A reasonable assurance of integrity process is based on defining systems that are in scope, risk ranking these systems, and then identifying a sample of locations in these systems for inspections. It relies on engineering analyses, expert judgment, operating experience, and groundwater protection program data to determine what regions of the buried pipes are vulnerable to degradation and adequately characterizing the vulnerability so that, if necessary, appropriate corrective actions may be taken. This process is based on risk identification and inspection sampling intended to greatly reduce the potential for unacceptable leakage or failures in the most susceptible systems.
Engineering evaluation is an important part of the "reasonable assuranCe'~grity" process. The engineering evaluation will consider but not limited to ite~s such as high consequence and/or likelihood areas, previous inspection results,;fq5rj~Jlion practices, material type, backfill, coating, soil condition, water levels, water~~.a' s6il chemistry, cathodic protection, operational history, industry operating e~~riente, site operating experience and groundwater protection program data. Thi~>~Qalneering evaluation will identify the risk of potential leakage, the most probablelp~~Ubns, and/or areas of likely susceptibility. The evaluation will also identify the pgtel'1tial consequences that could result if a leak occurred. With this information, ag. i6;pection plan can be developed and implemented that provides information regardIQ~~t9~'~ondition of the structure, system or component. The inspections can be indiIe~tJ~that they will provide information on the condition of the pipe remotely - from~r~~na>level or from an exposed section of pipe that is distant or remote from th~gi~'r&cation of interest. Inspections include a direct examination of the pipe wall an~.a visual inspection of the outer surface coating to determine coating integrity. Qir.ect examination can also be achieved using an in-line vehicle (or Pipeline Inspecti~~'>GatJge "PIG") deployed with demonstrated direct examination equipment'tapable of detecting degradation that is possible at the location of interest large enough to challenge structural or leakage integrity if present.
The specific j;~~ctions and examinations that are performed will be based on the type of degrad§,lib~" ~bserved or expected, the susceptibility of the pipe to leakage, the consequ~Q6e~ of a leak, and the location of the pipe. The scheduling of re-inspection agd'r:e:~~J'~ination is also dependent on the engineering determination of susceptibility, cori~~quences, and the results of the initial inspection or examination.
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April 2011 4.0 Terms and Definitions 4.1. Adverse Inspection Findings - Indications from inspections that require immediate repairs or repairs within one cycle.
4.2. Baseline Inspections - Inspection of new or replaced pipe or compolJ@nts that have not previously been involved in plant operations.
4.3. Corrosion Rate (CR) is the rate of corrosion occurring over a<~~;;~~d period of time.
4.4. Direct Examination - A Nondestructive Evaluation (NQE~;~amination where the NDE sensor(s) is in immediate contact withQr in<~o~e proximity to the section of the component being examined. Resl{ft§provide some degree of quantitative measurement of wall thickness (Pf <;di~continuity size. Direct examinations can be performed from .111~.fr\terior or exterior surface.
Detection and characterization capabiliti~sW~fY by NDE method as well as by specific NDE technique. Examples of.NID>E*?methods include ultrasonics, eddy current, radiography, visual and ){arj~bs electromagnetic techniques. Visual examinations need to be supp}e~~flted with NDE or engineering judgment that addresses the conditiqR.(:lth:~~pi~e wall.
4.5. Fitness-far-Service (FFS~(:' :'technical evaluation of direct examination data to determine~~eptable flaw size, degradation rate, remaining life, and the time to the nexfilJ~pection or repair/replacement/mitigation.
4.6. Highest §<Y~~~~~:~I: Locations are the highest likelihood and consequence risk raij~edHiries, segments or zones as defined in the buried piping sus~epti6It.tYanalysis and risk ranking database.
4.7. l.Q~;;t Inspection - Survey techniques used to assess the likelihood of
}(a~g~adation without having direct access to the section of the component being examined. These inspections typically measure surrounding conditions that may be indicative of corrosion or damage. Results are typically qualitative and less accurate than direct examinations. Examples of indirect inspection methods include over-the-line surveys and for the purpose of this document, long range guided wave.
4.8. Initial Inspection - The inspection of pipe or components that have been in service but have not been previously inspected.
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April 2011 4.9. Inspection Program - A systematic evaluation of in-scope components using various techniques (e.g., ultrasonic testing (UT), radiographic testing (RT),
visual testing (VT), leak testing (LT), eddy current testing (ET)).
4.10. Lg - is the total length of piping associated with a group of lines.
4.11. L indirect - is the total length of pipe associated with a group of pipe lines that have been indirectly inspected.
4.12. Line Grouping - is a process that may be used to optimize inspebti§fj$cope and schedule duration. Lines/segments/zones are grouped ba§~2 o.~ various attributes, such as but not limited to process fluid, pipe mjaterial,* coatings,
~at:::
depth, age, soil/backfill, etc.
4.13. Next Scheduled Inspection (NSI) - is the until another inspection of the pipe line group is required.
4.14. Opportunistic Inspection - An inspecti6!1~~rfOrmed when buried or underground components are exposedori:~xbavated due to another activity providing an opportunity to inspect apddJtument the results for a program 4.15. :~:::n::gment _ Portions >>~s:: piping systems that are grouped together for risk ranking P~FPOS~~> based on similarities such as installation, manufacture, or environmefltal conditions. Some risk ranking methods may use other terms to piping segments, such as zones.
4.16. Post Asses~.m~Vt an assessment of all indirect and direct examination results ilJdtl~in~ a FFS evaluation that will determine the projected structural and leaR~gefntegrity of a pipe.
4.17. R~in~: Life (RL) is defined as the time period until the pipe wall ttli~hess is no longer acceptable.
- ~ ~sual Inspections involve direct observation by inspectors or by the use of remote visual inspection devices.
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April 2011 Figure 5-1 Buried Piping Inspection Reasonable Assurance (RA) Flow Chart 8
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April 2011 Figure 5-2 Buried Piping Inspection Reasonable Assurance (RA) Flow Chart 9
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April 2011 5.0 Buried Piping Inspection RA Flow Chart-Description 5.1 Buried Piping Program Susceptibility Analysis and Risk Ranking
- 1. Susceptibility Analysis and Risk Ranking are used to determine the overall likelihood and consequence of a line, segment or zone failure.
- 2. This evaluation is based on detailed site specific information and provides a risk assessment of all piping within the program scope. /<> >.
- 3. The following potential exclusions from the program sco8e>rt1a~be considered in the susceptibility and risk ranking process. Th.t ba.$i;i6r the exclusion should be documented:
- a. Segments or zones constructed of materials not s.ysceptible to the associated 10 and 00 degradation mechanism>s<<lik~ titanium and super austenitic stainless (e.g., AL6XN or 254 SM6,:/
- b. Segments or zones of materials fully bae~f:illed<Dsing controlled low strength material (flowable backfill) in acgQ~9gnce with NACE SP0169-2007, unless the pipe is susceptible tol~>a¢g~adation.
- c. Piping sections that are hydrostati0~.I,~t~sted in accordance with 49 CFR 195 subpart E on an to exceed 5 years.
5.2 Create Line Groupings
- 1. The purpose for the 9rou~if1g~~~jl"les is to be able to extrapolate inspection results from one or more e~~~jnations to the rest of the group, optimizing the number of excavations.
- 2. Separate segmen~;bf:.;wnes by process fluid (e.g., Tritiated, Service Water,
& Oil lines wouI9>6@~~~uped separately; Corrosive vs. non-corrosive fluid, for instance cheglit'ifeed would be grouped separately from condensate and separat~{Yff:~;:ntritiated circulating water piping)
- 3. Further*~~B~rate or create groups of lines with similar physical attributes by thet~!!owihg order of importance:
Material (e.g., Carbon Steel, Stainless Steel, Plastic, Fiberglass, and Aluminum would be grouped separately)
- b. Coating type/age
- i. 10 coating, type/age ii. 00 coating, type/age
- c. Line depth (the basis for this grouping is the effect of live loads, and overburden):
- i. < 10ft below grade -- Can see the effects of live loads 10 IPEG PA OAG0023187
April 2011 ii. > 10ft below grade
- d. Pipe Age (e.g., Inspections on newer lines should not be used to justify reasonable assurance on older lines).
- e. Location in similar soil conditions (e.g., Lines in close proximity to one another in the same underground path/fill trench, backfill)
- f. Cathodic protection availability and operating history
- g. Operating Conditions
- i. Temperature (e.g., lines that undergo temperature changes and/or are >100F would g rou ped with ambient temperature lines).
ii. Operating frequency, and continuous vs.
infrequent/outage only)
.;
- h. Pipe joining methods (e.g., §Qbk~t vs butt welds or threaded connections & could be ag~n;!!aeration for the adequacy of the external coating applicatiQQJf ***
- 4. It is not required to separate or't~ new groups for each category listed in 5.2.3 above.
- 5. Each segment or zone be included in a Line Group.
- 6. Documentation is reguired to support the basis for each line grouping.
- 7. Inspections would~.~~erformed on the highest susceptible locations in each group.
5.3 Indire,f<I~~~~ction 1.lhqir;~~>>i~spections, when feasible, are the best approach for determining C';;t~e<~umber and location of direct examinations that are required.
Indirect inspections are not required and the owner can go straight to direct examinations.
- 3. Indirect Inspection Selection is based on the highest susceptible locations in a line group.
- 4. Review each of the Indirect Inspection techniques per station or industry examination guidelines for determining applicable or optimum methods for each grouping or individual segments/zones.
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April 2011
- 5. Review historical cathodic protection survey data and segment or zone location accessibility in order to refine the inspection selection areas.
- 6. Review the Groundwater Protection Program data.
- 7. Indirect inspection measurements should be referenced to precise geographic locations and documented so that inspection results c~il pe used for excavation and direct examinations. Indications from<.ips:g~t16ns should be aligned with other results, drawings and structure~,<
- 8. Verification of the indirect inspections should be done1~sing the direct examination results. At least one direct examinati.0f1~e performed in each high risk line grouping.
5.4 Classify Indirect Inspection Results
- 1. Criteria for classifying indirect inspectr6hresults must be established.
- 2. The criteria for classifying the ~J~rity of indications should take into account the indirect inspectj~ri;t~chniques used and the conditions surrounding the pipe segllJ~ht~:<"e following general classifications may be used:
- Severe - indication~(h~~in~ the highest likelihood of active corrosion activity;
- Moderate JQd~sjble pipeline corrosion activity; or
- Minor - t~~I~west likelihood of active corrosion activity.
- 3. The c~Ra~iiifr:and accuracy of the inspection method used must be con~id~;~d<~s part of the engineering evaluation.
5.5 Dir~::~~ination Initial Sample Size
<~~~n indirect inspections (for example a combination of Guided Wave and Above Ground Coating Surveys), covered greater than 50% of total (group) length including the highest susceptibility locations and where no severe indication (Section 5.4) is identified; one direct examination of the highest susceptible location to confirm the indirect inspection results would be required for each high risk line grouping, irrespective of the total line length. If an acceptable direct examination was achieved (i.e., Post Examination Assessment), then reasonable assurance could be demonstrated.
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April 2011
- 2. When indirect inspections covered less than 50% of total length of a pipe group and where no severe indication is identified:
- a. For those High Risk Ranked lines that are safety related or contain Licensed Material or are known to be contaminated, that have pipe groups with total lengths of piping less than approximately 500' (ft) ,
then one direct examination of the highest susceptible location, with acceptable results, may be sufficient to demonstrate reasqtjable assurance. In selecting the location of the direct ~~aQJil?:l~tibn, consideration can be given to the accessibility q! e~~rl1fhation locations.
§:>
- b. For those High Risk Ranked lines that are ~afElty~~lated or contain Licensed Material or are known to be conta~iD~t~d, that have pipe groups with total lengths of piping grea't~{> thah approximately 500' (ft), but less than 2500' (ft), two direct>~~~minations of the highest susceptible locations, with accept~t5I~ . tesults, may be sufficient to demonstrate reasonable assur§.!:ibe~ In selecting the location of the direct examination, conside~~t£Pry; can be given to the accessibility of examination locations ... /~>NNN
- c. For those High RiSk'~~~ ;'ines that are safety related or contain Licensed Material~Ill~~ known to be contaminated, that have pipe groups with total t~ngths of piping greater than approximately 2500' (ft) , three direct examinations of the highest susceptible locations, with a~~.~~table results, may be sufficient to demonstrate reasofl:abl~/ assurance. In selecting the location of the direct
~~a~;rl§tion, consideration can be given to the accessibility of
.*.*********. ei~rriination locations.
For those lines that are High Risk Ranked and are not safety related, do not contain Licensed Material or are not known to be contaminated that have pipe groups with total lengths less than approximately 500 ft, one direct examination of the highest susceptible location, with acceptable results, may be sufficient to demonstrate reasonable assurance. In selecting the location of the direct examination, consideration can be given to the accessibility of examination locations.
- e. For those lines that are High Risk Ranked and are not safety related, do not contain Licensed Material or are not known to be contaminated that have pipe groups with total lengths greater than 13 IPEG PA OAG0023190
April 2011 approximately 500 ft, two direct examinations of the highest susceptible locations, with acceptable results, may be sufficient to demonstrate reasonable assurance. In selecting the location of the direct examination, consideration can be given to the accessibility of examination locations ..
- f. For those lines that are Medium and Low Risk Ranked, a monitoring plan should be established and direct examinplibns performed on an opportunistic basis to determine /.(ep~f1able assurance.
- 3. For indirect inspections that indicate severe levels of~rrosion activity, categorize locations for direct examination and pro~ee:d>f~<§ection 5.6.
- 4. For indirect inspections that indicate mOd<\'fIll;in;/ minor levels of corrosion activity the direct examination or~~~wlnations in section 5.5.2 would be focused on the highest area of indiciated degradation.
- 5. Where indirect inspections that ev?,~~'~:all thickness are performed at the most susceptible location§ .. in . ~> group, and the results of such inspections indicate NO orMI~9R likelihood of corrosion activity, then confirmation of the indirect\:iri~p~ttion results may be obtained from a direct examination of?ry~~h~~/ indirect inspection location in the same group (where the sam~>inspection technique was used). This can be allowed whel>>eccessibility issues exist for conducting a direct examination.
Using !b""~:elow to illustrate this concept; a guided wave shot is tak~ri~~~~avation 1 showing only "minor" indications at "8" and "0".
di~@~t.~xam is performed that validates these results, and the remaining acceptable. A second set of guided wave shots is taken through a penetration (highest susceptible location), showing minor indications "A" and "e". The pipe condition and indications at "A" and "e" would be considered validated by the direct examination completed in Excavation 1 with an acceptable remaining life. A second excavation would not be required to validate indications "A" and "e". To provide additional assurance of pipe integrity for all of these indications; one or more of the monitoring activities listed in section 5.8-3 should be periodically performed.
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April 2011 Tndk:-:>. -tk/': B
':r",:r:::T" 5.6 Direct Examination Selection The objective of direct examination is to asse~~ihe extent of corrosion activity for line segments selected for examination<ba~ed on the risk assessment and indirect inspections, when performed, :;W~en no significant degradation is found from a direct examination there~?ining service life and next scheduled inspection should be calculated uSi6gth~ guidance in the following sections.
- 1. Indirect inspections re"~}~'::: be used in determining the priority of direct examinations. B~(9W is an example of criteria used for prioritizing direct examinatiqps based on the severity of indications from the indirect
- ,s::~:r:: (~~:'ons Initiate Direct Examination Plan with qe~:tj~g~ncies for Mitigating Action for:
Severe indications in close proximity Severe indications in a region with multiple moderate indications Isolated severe indications in a high risk region or area Indications known to be actively corroding Moderate indications in a region of high risk, prior leaks or severe corrosion
- b. Moderate Indications - Scheduled Action Required
- i. Isolated severe indication in a low risk region ii. Groups of moderate indications iii. Groups of minor indications in a medium risk region iv. Groups of minor indications in close proximity 15 IPEG PA OAG0023192
April 2011
- c. Minor Indications - Monitor
- i. All remaining indication scenarios
- 2. If no Indirect Inspections were performed for a group, then selection of the direct examination locations is based on the highest susceptible location of each line group considering location accessibility. Review historical cathodic protection survey data or other relevant parameters to refi~~>!re direct examination area.
- 3. Direct examinations resulting from excavations should coatings inspections by a person trained and experienced in~2ating condition assessment.
- 4. At least one Direct Examination is required fore:~ch igh Risk Line Group in order to establish reasonable assurance~~!Group.
- 5. A Direct Examination at an individual exea~.ation will assess a minimum 10 feet length of pipe, if feasible. is more than 1 pipeline in an excavation, each pipeline that an examination accounts for a separate direct examination.
5.7 Inspection Sample Expa~<;!,nsiderations
<::/<-- ~/
When a pipe segmenJ or zohe has degradation detected by direct examination that ~~:C~~os the acceptance criteria in section 5.8 and 5.9:
- 1. Determine.t"¢:~te~t of the corrosion by mapping the axial and transverse lengthS<@rlijejepths of the corroded area.
- 2. R.e~ii~*. .t~le5indirect inspection results for the affected segment or zone
~h.q determine if additional excavation is required to perform direct
<(3.~cffnination of other areas with severe or moderate indications.
Determine any segments or zones that share the same corrosion susceptibility characteristics and schedule additional direct examinations.
The timing of the additional examinations should be based on the severity of the degradation identified and should be commensurate with the consequence of a leak or loss of function.
- 4. Scope expansion must be sufficient to provide confidence that the extent of condition reasonably bounds the degradation.
- 5. Document the findings and actions in the appropriate corrective action program.
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April 2011 5.8 Post Examination Assessment The purpose of the post assessment process is to define the inspection interval (time to Next Scheduled Inspection or NSI), assess the effectiveness of the program, and then feed the results back to the pre-assessment step to revise the risk ranking of buried pipe segments or zones as a continuous improvement process. The cumulative goal of the evaluations for a piping>
group is to complete a post assessment; including a fitness for se~){iqt>
evaluation, that determines the remaining life and next schedul~d i~sp~dion interval to provide quantitative reasonable assurance for that g~dijg:<.>/
§:>
- 1. The assessment of the examination results ShQt;;Ilq<5:made using a Fitness-for-Service (FFS) assessment. Any degr~4~fJO'~ found during a direct examination should be appropriately dod~went~d.
- 2. The FFS evaluation performed will apply the group.
'!j~~' segments, or zones in
- a. When direct wall thickness m~~~~;~~ent meets tmin & tmeas is >87.5%
of tnom no FFS evaluatiol7i~j~h~quired, >>>,,'/
unless active degradation is identified.
- b. When direct wall thi~~:~S measurement meets tmin & tmeas is <87.5%
of tnom : ,&>; ';>,
- i. Perf~,hiai1 F FS ii. E\[aty~re cause of degradation (consider all variables-backfill,
"**;",.. ~oJtlhgs, installation, etc.)
.iil. Etaluate the extent of degradation (localized verses global) i~:./ Evaluate the need for scope expansion direct wall thickness measurement does NOT meet tmin:
Evaluate cause and extent of degradation
- Inspection scope expansion (See section 5.7)
- Determine the Extent of Condition
- Repair degraded areas
- Evaluate potential mitigation strategies
- Enter into the corrective action program
- 3. Monitoring activities should be considered as part of the reasonable assurance programmatic or compensatory actions. Examples for the 17 IPEG PA OAG0023194
April 2011 justification of the scheduling/deferral of reasonable assurance direct examinations are:
- Increased Ground Water Initiative related well monitoring frequency
- Enhanced Cathodic Protection and/or Area Potential Earth Current (APEC) Surveys
- Soil Analysis
- Coating Scans
- Flow/pressure testing
- Guided Wave inspections
- Corrosion Probes
- Leak Testing (Acoustic monitoring, etc.)
5.9
- e::r:::e:i::e (F::~ ::11:::::: proces~~~~ provide guidelines for evaluating wall thickness degradation il1~~fety and non-safety related components. Engineering should use tp~~~guidelines, or other applicable methodologies, when establishing thea{fceptance criteria or refining the acceptance criteria when warrant~d~Whe projected life of the component, based on these calculations, is<..t~b:?; used to establish the interval between examinations. An enginee(ingf~~tini~al evaluation is required for any deferral of the next scheduled exarfil~aiibri*past the remaining life date.
a) Corrosion Rate It is re~';:£~;hat for buried piping, most degradation mechanisms arel!llpt.ll~ear with time. Any corrosion rate calculated from one Ift~pe¢tion is likely to have a large inaccuracy and could be either
}. coris~rvative (for inactive degradation mechanisms) or non-
<eonservative (for recently activated mechanisms). Whenever possible, external corrosion rates should be determined by directly comparing measured wall thickness changes over a known time interval.
Therefore, it is recommended to perform at least two inspections before a more accurate corrosion rate can be established.
When previous pipe wall thickness measurements or other data are not available, default corrosion or pitting rate may be used to determine re-inspection intervals. NACE recommends a default pitting rate of 16 mils/year. NACE further indicates that the default corrosion rate may be reduced by 24% (from the default 16 mils/year), provided that the Cathodic Protection (CP) levels of the pipeline segments being 18 IPEG PA OAG0023195
April 2011 evaluated have had at least 40 mV of polarization, considering the voltage drop, for a significant fraction of the time since installation. If the evaluated line can potentially be subjected to an internal corrosion process, such as Flow Accelerated Corrosion (FAC),
Erosion/Corrosion (E/C) or Microbiologic Influenced Corrosion (MIC),
effects of internal wall loss should also be considered.
For components with multiple examinations the corrosion rate more refined, as outlined in equation 1 below:
CR =(timemw,' - timemw, ' ) x SF I time .................. :*bfr~uation 1 Where:
CR = Corrosion rate, also referred time meas 1 = tmeas at 1st examinab~.n time meas2 = tmeas at 2nd or<<$~b~~quent examination at mea~b:~~~:lue same location t meas = The minimum SF = Safety Factor (f:~~g!J,mend at least 10%) = 1.10 time = The length5f:</trme between the (time meas 1 and time meas2) examination§/~~@~rs) b) Remaining Life (RL:?ai~~ti:
For the eX~/~ihation of a buried pipe component, the remaining life (RL) mgy~~d~lculated as per Equation 2 below:
~r~4~1:~' _tm;")I CR ...........................................Equation 2
- MV~:~~:
tmeas = The minimum measured value from the 1sl examination tmin = The minimum acceptable wall thickness for the current inspection required to meet Code requirements.
CR = Corrosion Rate (mils/year). Whenever possible external corrosion rates should be calculated from direct comparison of changes in wall thickness over time. However, for the initial examination the time period of active corrosion is unknown. In the absence of a known period of time from the initiation of corrosion, a default corrosion rate (CR) of 16 mils/year may be used.
19 IPEG PA OAG0023196
April 2011 If the evaluated line can be subjected to FAG, E/G, and/or MIG, then the effects of internal wall loss should be considered.
- 3. Time to Next Scheduled Inspection (NSI)
When t meas is found to be less than or equal to 50% of t nom , the re-examination interval should be taken as one-half the remaining life (RL) calculated in Equation 2. The examination interval may be increas~~>if it can be determined that the corrosion mechanism is inactive, fore¥~~pl~ a coating repair has been applied. When corrosion is less th~n 5b~o?bf t nom (i.e. t meas is greater than 0.5 t nom ), the re-inspection interval <Ma¥be taken as 75% of RL, as summarized below:
t meas </= 0.5 x t nom : NSI = 0.5 x RL ........... . ........... Equation 3 t meas > 0.5 x t nom : ................. Equation 4
- 4. Mitigation or Engineering Technicalij:.valuation a) A determination ShOUld~~;;~~:>to either mitigate directly or to perform additional engi~~~rillg technical evaluation/analysis if the remaining life dq~s rf~tsLpport the period of time until the pipe will be available for f~~M:ext>examination (e.g., refueling outage).
b) If more>t~~n a single line is in the group, the lines with no examination (lata need to be evaluated based on the examinations perf9~rrr~~for determination of condition. Additional examination
>IT:!?~>t:>&~equired based on this evaluation.
A~e~ermination should be made to repair, replace or implement compensatory actions.
All engineering evaluations should be performed and documented as required by station procedures.
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April 2011 6.0 References
- 1. "Recommendations for an Effective Program to Control the Degradation of Buried and Underground Piping and Tanks 1021175 (EPRI 1016456, Revision 1)
- 2. Radiological SSC Groundwater Initiative Risk Evaluation Criteria
- 3. A.P. Moser "Buried Pipe Design", McGraw Hill, 2nd Edition (Tabl.~
Loads").
- 4.Section XI, Div. 1 Class 2 and 3 Metallic Piping Buried in a Ba~k:~jite8: Trench, Inquiry, Draft "What Rules may be used to evaluate Class 2 9n~:gJass 3 metallic piping buried in a back-filled trench subjected to metal 1~~S :.Q:[j the internal and external surfaces of the pipe or fitting"
- 5. ASME B&PV Code,Section XI
- 6. ASME B&PC Code,Section III
- 7. ASME B31.1, "Power Piping"
- 8. ASME Standard B31.3, "Process Piping"/':~'
- 9. ASME B31-G, "Manual for Deter!'PiQI~~; ;he Remaining Strength of Corroded Pipelines" 10.American Petroleum Institute;:(A'P'i) Standard 510 Pressure Vessel Inspection Code: "Maintenance Im;pection;'Rating, Repair, and Alteration" 11.API Standard 570 Pi~;~'~~"rispection Code: "In-service Inspection, Rating, Repair, and Alteration of F>~pi~g<Systems"
- 12. AP I Standard5~~;'::~'~~nk Inspection, Repair, and Reconstruction" 13.ASMEco~~~.a~e N-597-1, "Requirements for Analytical Evaluation of Pipe Wall Thinnih~?:!~::Se~tion XI Div. 1.
14.A~:M~i:~6~e Case N-513, "Evaluation Criteria for temporary Acceptance of Flaws
.![1~.6aerate Energy Class 2 or 3 Piping",Section XI, Div. 1.
- ~1579-2/ASME FFS-2, "Fitness-For-Service"
. NACE Standard Practice SP0169-2007, Control of External Corrosion on Underground or Submerged Metallic Piping Systems, 2007.
17.NACE International Standard Recommended Practice, RP0502, Item No. 21097, "Pipeline External Corrosion Direct Assessment Methodology".