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Relief Request Number EN-17-RR-1 - Proposed Alternative to Use ASME Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate-Energy Class 2 or 3 Piping, Section XI, Division 1
	ML17321B081
Person / Time
Site:	Palisades, Indian Point, Grand Gulf, Pilgrim, Arkansas Nuclear, River Bend, Waterford
Issue date:	11/17/2017
From:	Halter M; Entergy Nuclear Operations, Entergy Operations
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	17-RR-1, CNRO-2017-00022
	Download: ML17321B081 (45)
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Director, Nuclear Licensing CNRO-2017-00022 November 17, 2017 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Relief Request Number EN-17-RR Proposed Alternative to Use ASME Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate-Energy Class 2 or 3 Piping, Section XI, Division 1" Arkansas Nuclear One, Units 1 & 2 Indian Point Energy Center, Units 2 & 3 Docket Nos. 50-313 & 50-368 Docket Nos. 50-247 & 50-286 License Nos. DPR-51 & NPF-6 License Nos. DPR-26 & DPR-64 Grand Gulf Nuclear Station, Unit 1 Palisades Nuclear Plant Docket No. 50-416 Docket 50-255 License No. NPF-29 License No. DPR-20 River Bend Station, Unit 1 Pilgrim Nuclear Power Station Docket No. 50-458 Docket No. 50-293 License No. NPF-47 License No. DPR-35 Waterford 3 Steam Electric Station Docket No. 50-382 License No. NPF-38

Dear Sir or Madam:

Pursuant to 10 CFR 50.55a(z)(2), Hardship without a compensating increase in quality and safety, Entergy Operations, Inc. and Entergy Nuclear Operations, Inc. (hereafter referred to collectively as Entergy) request NRC authorization of a proposed alternative to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," on the basis that the current code requirements result in hardship and/or unusual difficulty without a compensating increase in quality and safety. The proposed alternative is provided in the attachment to this letter.

Specifically, Entergy is requesting to utilize ASME Code Case N-513-4, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1,"

to evaluate and temporarily accept flaws in Class 2 and 3 moderate energy piping including elbows, bent pipe, reducers, expanders, and branch tees in lieu of specified ASME Code requirements.

This alternative is proposed for the 10-year Inservice Inspection (ISI) intervals for the plants as identified in Section 2 of the attached relief request.

CNRO-2017-00022 Page 2 of 3

Entergy requests NRC approval of this multi-site request as soon as possible or by November 17, 2018.

This letter contains no new or revised commitments.

If you have any questions, please contact Mr. John Giddens, Senior Manager, Fleet Regulatory Assurance, at (601) 368-5756.

Sincerely,

Mandy Halter Director, Nuclear Licensing MH/JMG/gpn

Attachment:

Relief Request EN-17-RR-1 cc: C. Bakken (ECH)

J. Elnitsky (ECH)

J. Ventosa (ECH)

C. Costanzo (ECH)

L. Coyle (ECH)

D. Jacobs (ECH)

L. Martin (ECH)

R. Anderson (ANO)

E. Larson (GGNS)

W. Maguire (RBS)

J. Dinelli (WF3)

T. Vitale (IPEC)

B. Sullivan (PIL)

C. Arnone (PAL)

B. Ford (ECH)

J. Giddens (ECH)

All above w/o attachments NRC Region I Administrator NRC Region III Administrator NRC Region IV Administrator NRC Project Manager (ANO)

NRC Project Manager (GGNS)

NRC Project Manager (RBS)

NRC Project Manager (WF3)

NRC Project Manager (IPEC)

NRC Project Manager (PIL)

NRC Project Manager (PAL)

NRC Senior Resident Inspector (ANO)

NRC Senior Resident Inspector (GGNS)

CNRO-2017-00022 Page 3 of 3

NRC Senior Resident Inspector (RBS)

NRC Senior Resident Inspector (WF3)

NRC Senior Resident Inspector (IPEC)

NRC Senior Resident Inspector (PIL)

NRC Senior Resident Inspector (PAL)

Ms. Margaret OBanion, Project Manager, NRC/NRR/DORL

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All American Society of Mechanical Engineers (ASME), Section XI, Class 2 and 3 components that meet the operational and configuration limitations of Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping, Section XI, Division 1, paragraphs 1(a), 1(b), 1(c), and 1(d).

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Arkansas Nuclear 5th 2007 Edition through May 31, May 30, One, Unit 1 2008 Addenda 2017 2027 Arkansas Nuclear 4th 2001 Edition through March 26, March 25, One, Unit 2 2003 Addenda 2010 2020 Grand Gulf Nuclear 4th 2007 Edition through December 1, November 30, Station 2008 Addenda 2017 2027 Indian Point Energy 5th 2007 Edition through June 1, May 31, Center, Unit 2 2008 Addenda 2016 2026 Indian Point Energy 4th 2001 Edition through July 21, July 20, Center, Unit 3 2003 Addenda 2009 2020 Palisades 5th 2007 Edition through December 13, December 12, 2008 Addenda 2015 2025 Pilgrim Nuclear 5th 2007 Edition through July 1, June 30, Power Station 2008 Addenda 2015 2025 River Bend Station 4th 2007 Edition through December 1, November 30, 2008 Addenda 2017 2027 Waterford Unit 3 4th 2007 Edition through December 1, November 30, 2008 Addenda 2017 2027

The table above identifies the ASME Section XI Code of Record for performance of Inservice Inspections (ISI) at each Entergy nuclear plant effective December 1, 2017.

However, it should be noted that all Entergy plants perform ISI-related activities such as nondestructive examinations (NDE), pressure testing (PT), and repair/replacement (R&R) activities in accordance with standardized programs based on a common Edition / Addenda of ASME Section XI which, at present, is the 2001 Edition / 2003 Addenda. Entergy plans to update the Code of Record for these programs to the 2007 Edition / 2008 Addenda on December 1, 2017.

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ASME Code, Section XI, IWC-3120 and IWC-3130 require that flaws exceeding the defined acceptance criteria be corrected by repair/replacement activities or evaluated and accepted by analytical evaluation. ASME Code, Section XI, lWD-3120(b) requires that components exceeding the acceptance standards of IWD-3400 be subject to supplemental examination, or to a repair/replacement activity.

Attachment to CNRO-2017-00022 Page 2 of 5

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In accordance with 10 CFR 50.55a(z)(2), Entergy Operations, Inc. and Entergy Nuclear Operations, Inc. (hereafter referred to collectively as Entergy) is requesting a proposed alternative from the requirement to perform repair/replacement activities for degraded Class 2 and 3 piping whose maximum operating temperature does not exceed 200°F and whose maximum operating pressure does not exceed 275 psig. Moderately degraded piping could require a plant shutdown within the required action statement timeframes to repair observed degradation. Plant shutdown activities result in additional dose and plant risk that would be inappropriate when a degraded condition is demonstrated to retain adequate margin to complete the components function. The use of an acceptable alternative analysis method in lieu of immediate action for a degraded condition will allow Entergy to perform additional extent of condition examinations on the affected systems while allowing time for safe and orderly long term repair actions if necessary. Actions to remove degraded piping from service could have a detrimental overall risk impact by requiring a plant shutdown, thus requiring use of a system that is in standby during normal operation. Accordingly, compliance with the current code requirements results in a hardship without a compensating increase in the level of quality and safety.

ASME Code Case N-513-3 does not allow evaluation of flaws located away from attaching circumferential piping welds that are in elbows, bent pipe, reducers, expanders, and branch tees. ASME Code Case N-513-3 also does not allow evaluation of flaws located in heat exchanger external tubing or piping. ASME Code Case N-513-4 provides rules for evaluation of flaws in these locations.

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Entergy is requesting approval to apply the evaluation methods of ASME Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1," to Class 2 and 3 components that meet the operational and configuration limitations of Code Case N-513-4, paragraphs 1(a), 1(b), 1(c), and 1(d) in order to avoid accruing additional personnel radiation exposure and increased plant risk associated with a plant shutdown to comply with the cited Code requirements.

The NRC issued Generic Letter 90-05 (Reference 1), Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping (Generic Letter 90-05)," to address the acceptability of limited degradation in moderate energy piping. The generic letter defines conditions that would be acceptable to utilize temporary non-code repairs with NRC approval. The ASME recognized that relatively small flaws could remain in service without risk to the structural integrity of a piping system and developed Code Case N-513.

NRC approval of Code Case N-513 versions in Regulatory Guide 1.147, "lnservice Inspection Code Case Acceptability, ASME Section Xl, Division 1," allows acceptance of partial through-wall or through-wall leaks for an operating cycle provided all conditions of the Code Case and NRC conditions are met. The Code Case also requires the Owner to demonstrate system operability due to leakage.

The ASME recognized that the limitations in Code Case N-513-3 were preventing needed use in piping components such as elbows, bent pipe, reducers, expanders, and branch tees and external tubing or piping attached to heat exchangers. Code Case N-513-4 was

Attachment to CNRO-2017-00022 Page 3 of 5 approved by the ASME to expand use on these locations and to revise several other areas of the Code Case. Enclosure 1 of this Attachment provides a marked-up N-513-3 version of the Code Case to highlight the changes compared to the NRC approved N-513-3 version.

Enclosure 2 of this Attachment provides the ASME approved Code Case N-513-4. The following provides a high level overview of the Code Case N-513-4 changes:

1. Revised the maximum allowed time of use from no longer than 26 months to the next scheduled refueling outage.

2. Added applicability to piping elbows, bent pipe, reducers, expanders, and branch tees where the flaw is located more than (Rot)1/2 from the centerline of the attaching circumferential piping weld.

3. Expanded use to external tubing or piping attached to heat exchangers.

4. Revised to limit the use to liquid systems.

5. Revised to clarify treatment of Service Level load combinations.

6. Revised to address treatment of flaws in austenitic pipe flux welds.

7. Revised to require minimum wall thickness acceptance criteria to consider longitudinal stress in addition to hoop stress.

8. Other minor editorial changes to improve the clarity of the Code Case.

The technical basis for ASME Code Case N-513-4 when compared to NRC approved Code Case N-513-3 is provided in Enclosure 3 of this Attachment.

The design basis is considered for each leak and evaluated using the Entergy Operability Evaluation process. The evaluation process must consider requirements or commitments established for the system, continued degradation and potential consequences, operating experience, and engineering judgment. As required by the Code Case, the evaluation process considers but is not limited to system make-up capacity, containment integrity with the leak not isolated, effects on adjacent equipment, and the potential for room flooding.

Leakage rate is not typically a good indicator of overall structural stability in moderate energy systems, where the allowable through-wall flaw sizes are often on the order of inches (Relief Requests, identified by ADAMS Accession Numbers ML14240A603, ML14316A167, ML15070A428, support the preceding statement). The periodic inspection interval defined using paragraph 2(e) of Code Case N-513-4 provides evidence that a leaking flaw continues to meet the flaw acceptance criteria and that the flaw growth rate is such that the flaw will not grow to an unacceptable size.

The effects of leakage may impact the operability determination or the plant flooding analyses specified in paragraph 1(f) of Code Case N-513-4. For a leaking flaw, the allowable leakage rate will be determined by dividing the critical leakage rate by a safety factor of four (4). The critical leakage rate is determined as the lowest leakage rate that can be tolerated and may be based on the allowable loss of inventory or the maximum leakage that can be tolerated relative to room flooding, among others. The safety factor of four (4) on leakage is based upon Code Case N-705 (Reference 3), which is accepted without condition in Regulatory Guide 1.147, Revision 17 (Reference 4). Paragraph 2.2(e) of N-705 requires a

Attachment to CNRO-2017-00022 Page 4 of 5 safety factor of two (2) on flaw size when estimating the flaw size from the leakage rate. This corresponds to a safety factor of four (4) on leakage for nonplanar flaws. Although the use of a safety factor for determination of an unknown flaw is considered conservative when the actual flaw size is known, this approach is deemed acceptable based upon the precedent of Code Case N-705. Note that the alternative herein does not propose to use any portion of Code Case N-705 and that citation of N-705 is intended only to provide technical basis for the safety factor on leakage.

During the temporary acceptance period, leaking flaws will be monitored daily as required by paragraph 2(f) of Code Case N-513-4 to confirm the analysis conditions used in the evaluation remain valid. Significant change in the leakage rate is reason to question that the analysis conditions remain valid, and would require re-inspection per paragraph 2(f) of the Code Case. Any re-inspection must be performed in accordance with paragraph 2(a) of the Code Case.

The leakage limit provides quantitative measurable limits which ensure the operability of the system and early identification of issues that could erode defense-in-depth and lead to adverse consequences.

In summary, Entergy will only apply ASME Code Case N-513-4 to the evaluation of Class 2 and 3 components that are within the scope of the Code Case. Code Case N-513-4 utilizes technical evaluation approaches that are based on principals that are accepted in other Code documents already acceptable to the NRC. The application of this code case, in concert with safety factors on leakage limits, will maintain acceptable structural and leakage integrity while minimizing plant risk and personnel exposure by minimizing the number of plant transients that could be incurred if degradation is required to be repaired based on ASME Section XI acceptance criteria only.

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The proposed alternative is for use of Code Case N-513-4 for Class 2 and Class 3 components within the scope of the Code Case. A Section XI compliant repair/replacement will be completed prior to exceeding the next refueling outage or allowable flaw size, whichever comes first. This relief request will be applied for the duration of the inservice inspection intervals defined in Section 2 of this relief request or such time as the NRC approves Code Case N-513-4 in Regulatory Guide 1.147 or other document. If a flaw is evaluated near the end of the interval for one of the plants in Section 2 and the next refueling outage is in the subsequent interval, the flaw may remain in service under this relief request until the next refueling outage.

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NRC letter to Exelon Generation Company, LLC, Exelon Generation Company, LLC - Fleet Request for Proposed Alternative to Use ASME Code Case N-513-4 (CAC Nos.

MF7301-MF7322), dated September 6, 2016, (ADAMS Accession No. ML16230A237)

Attachment to CNRO-2017-00022 Page 5 of 5

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1) NRC Generic Letter 90-05, "Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping (Generic Letter 90-05)," dated June 15, 1990 (ADAMS Accession No. 12339A442)

2) Letter from Exelon Generation Company, LLC letter number RS-16-41 to NRC, "Proposed Alternative to Utilize Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1,"

dated January 28, 2016 (ADAMS Accession No. ML16029A003)

3) ASME Boiler and Pressure Vessel Code, Code Case N-705, "Evaluation Criteria for Temporary Acceptance of Degradation in Moderate Energy Class 2 or 3 Vessels and Tanks Section XI, Division 1," October 12, 2006.

4) NRC Regulatory Guide 1.147, "lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1," Revision 17

5) NRC letter to Exelon Generation Company, LLC, Exelon Generation Company, LLC -

Fleet Request for Proposed Alternative to Use ASME Code Case N-513-4 (CAC Nos.

MF7301-MF7322), dated September 6, 2016, (ADAMS Accession No. ML16230A237)

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II Record # 12-841 CASE I CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J Approval Date: January 26, 2009 Code Cases will remain available for use until annulled by the applicable Standards Committee.

Case N-513-~~ (e) The piping design Code shall be used in Evaluation Criteria for Temporary Acceptance of determining the stress indices B I and B), and stress Flaws in Moderate Energy Class 2 or 3 Piping intensification factor, i, for flaw evaluation following Section XI, Division 1 Code applicability limits in terms of component geometry, such as DoL!nom ratio. If the piping design Inquiry: What requirements may be used for Code does not provide stress indices, Section III, 2004 temporary acceptance of flaws, including through-wall Edition or later Editions and Addenda may be used to flaws, in moderate energy Class 2 or 3 piping including define B I and B 1.~

elbows, bent pipe, reducers, expanders, and branch tees, ([d) The provisions of this Case demonstrate the without performing a repair/replacement activity? integrity of the item and not the consequences of leakage. It is the responsibility of the Owner to Reply: It is the opinion of the Committee that the del'H:eastrate systefl'l epentbility considerffig effects of following requirements may be used to accept flaws, leakage in demonstrating system operability and including through-wall flaws, in moderate energy Class performing plant flooding analyses .

2 or 3 piping including elbows, bent pipe, reducers, (e) The evalHatiea peried, Ttt~JeW, is the eperatieaal expanders, and branch tees, without performing a tifl'le fer whieh the tel'H:perary aeeeptaaee eriteria are repair/replacement activity for a limited time, not satisfied bt1t aet eJf:eeediag 26 l'H:eaths frefl'l the iaitial exceeding the evalHatiea peried as defiaed ia this diseevery ef the eeaditiea.

G-asetime to the next scheduled refueling outage.

2 PROCEDURE 1 SCOPE (a) The flaw geometry shall be characterized by (a) These requirements apply to the ASME Section volumetric inspection methods or by physical III, ANSI B31.1, and ANSI B31. 7 piping, classified by measurement. The full pipe circumference at the flaw the Owner as Class 2 or 3 that is accessible for location shall be inspected to characterize the length and inspection. The provisions of this Case do not apply to depth of all flaws in the pipe section.

the following: (b) Flaw shall be classified as planar or nonplanar.

(1) pumps, valves, expansion joints,_ and heat (c) When multiple flaws, including irregular exchangers, except as provided in (b) ; (compound) shape flaws, are detected, the interaction (2) weld metal of socket welded joints; and combined area loss of flaws in a given pipe section (3) leakage through a flange joint; shall be accounted for in the flaw evaluation.

(4) threaded connections employing (d) A flaw evaluation shall be performed to nonstructural seal welds for leakage protection. determine the conditions for flaw acceptance. Section 3 (b) This Case may be applied to heat exchanger provides accepted methods for conducting the required external tubing or piping, provided the flaw is analysis.

characterized in accordance with 2(a) and leakage is (e) Frequent periodic inspections of no more than monitored. 30 day intervals shall be used to determine if flaws are (f.e) The provisions of this Case apply to Class 2 or growing and to establish the time.,.--'fe~~ew;-_at which the 3 piping in liquid systems whose maximum operating detected flaw will reach the allowable size.

temperature does not exceed 200°F (93 °C) and whose Alternatively, a flaw growth evaluation may be maximum operating pressure does not exceed 275 psig performed to predict the time.,.......-Te~~ew-, at which the (1.9 MPa). detected flaw will grow to the allowable size. The flaw (d_e) The following flaw evaluation criteria are growth analysis shall consider the relevant growth permitted for pipe and tube including elbows, bent pipe, mechanisms such as general corrosion or wastage, reducers, expanders, and branch tees. The straight pipe fatigue, or stress corrosion cracking. When a flaw flaw evaluation criteria are permitted for adjoining growth analysis is used to establish the allowable time fittings and flanges to a distance of (Rat) Yz from the weld for temporary operation, periodic examinations of no centerline. more than 90 day intervals shall be conducted to verify the flaw growth analysis predictions.

Draft 15 (05/05/14)

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J (f) For through-wall leaking flaws, leakage shall be When through-wall axial flaws are evaluated, the eeserved bymonitored daily wallEdevffls to confirm the allowable flaw length is:

analysis conditions used in the evaluation remain valid.

(g) If examinations reveal flaw growth rate to be unacceptable, a repair-er-Lreplacement activity shall be performed.

(h) Repair---er---Lreplacement activities shall be performed no later than when the predicted flaw size from either periodic inspection or by flaw growth analysis exceeds the acceptance criteria of 4, or during where the next scheduled refueling outage, whichever occurs p =pressure for the loading condition Note: Z has been first. Repair---er---Lreplacement activities shall be in added to equation D 0 =pipe outside diameter accordance with IWA-4000 er P.VA 7000, respeetively, (1).

CJ! = flow stress in Editiens and Addenda prier te the 1991 Addenda; Sy = Code specified yield strength and, in the 1991 Addenda and later, in aeeerdanee with Su = Code specified ultimate tensile strength and IVll\: 4000.

SFm = structural factor on primary membrane stress (i) Evaluations and examination shall be as specified in C-2622 documented in accordance with IWA-6300. The Owner Z = load multiplier for ductile flaw extension shall document the use of this Case on the applicable (equal to 1.0 when using limit load criteria) data report form.

Material properties at the temperature of interest 3 FLAW EVALUATION shall be used.

Planar flaws in straight pipe shall be evaluated in FIG.1 THROUGH-WALL FLAW GEOMETRY accordance with the requirements in 3 .1. Nonplanar flaws in straight pipe shall be evaluated in accordance with the requirements in 3.2. Through-wall flaws in elbows and bent pipe shall be evaluated in accordance with the requirements in 3.3. Through-wall flaws in reducers, expanders, and branch tees shall be evaluated in accordance with the requirements in 3.4 and 3.5, respectively. Flaw growth evaluation shall be performed in accordance with the requirements in 3.§.J. Nonferrous (c) For planar flaws in ferritic piping, the evaluation materials shall be evaluated in accordance with the procedure of Appendix C shall be used. Flaw depths up requirements in 3.14. to 100% of wall thickness may be evaluated. Flaw For all flaw evaluations, all Service Level load depth, a, is defined in Figures C-4310-1 and C-4310-2.

combinations shall be evaluated to determine the most When through-wall circumferential flaws are evaluated limiting allowable flaw size. in accordance with C-5300 or C-6300, the flaw depth to thickness ratio, a/t, shall be set to unity. When applying 3.1 Planar Flaws in Straight Pipe the Appendix C screening criteria for through-wall axial (a) For planar flaws, the flaw shall be bounded by a flaws, a/t shall be set to unity, and the reference limit rectangular or circumferential planar area in accordance load hoop stress, a1, shall be defined as cry!M 2 . When with the methods described in Appendix C. IWA-3300 through-wall axial flaws are evaluated in accordance shall be used to determine when multiple proximate with C-5400 or C-6400, the allowable length is defined flaws are to be evaluated as a single flaw. The geometry by eqs. (1) through (3), with the appropriate structural of a through-wall planar flaw is shown in Fig. 1. factors from Appendix C, C-2622. When through-wall (b) For planar flaws in austenitic piping, the flaws are evaluated in accordance with C-7300 or C-evaluation procedure in Appendix C shall be used. Flaw 7400, the formulas for evaluation given in C-4300 may depths up to 100% of wall thickness may be evaluated. be used, but with values for Fm, Fb, and F applicable to When through-wall circumferential flaws are evaluated, through-wall flaws. Relations for F m, Fb, and F that take the formulas for evaluation given in C-5320 or C-6320, into account flaw shape and pipe geometry (R/t ratio) as applicable, of Appendix C may be used, with the flaw shall be used. The appendix to this Case provides depth to thickness ratio, a/t, equal to unity. equations for Fm, Fb, and F for a selected range of R/t.

Geometry of a through-wall crack is shown in Fig. 1.

Draft 15 (05/05/14) 2

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 2 SEPARATION REQUIREMENTS FOR ADJACENT THINNED AREAS 3.2 Nonplanar Flaws in Straight Pipe defined in Fig. 3. When the above requirement is not

__ (a) The evaluation shall consider the depth and satisfied, (;iii) shall be met.

extent of the affected area and require that the wall (jii;) When Lm is less than or equal to 2.65 thickness exceed tmin for a distance that is the greater of (Ratmin)l!2 and tnom is greater than 1.13 tmin , tatoc is 2.5 ,fRtnom or 2Lm,avg between adjacent thinned regions, determined by satisfying both of the following where R is the mean radius of the piping item based on equations:

nominal wall thickness and Lm,avg is the average of the extent of Lm below tmin for adjacent areas (see Fig. 2).

Alternatively, the adjacent thinned regions shall be t

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1.5 \fl'-olmin t ] +1.0 (5) considered a single thinned region in the evaluation. tmin L tmin

__ (b) For nonplanar flaws, the pipe is acceptable when either (b)(l) and (b)(2), or (b)(2) and (b)(3) are [aloe 0.353Lm (6)

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met. tmin - ~ROtmin (1) Tthe remaining pipe thickness (tp) is greater than or equal to the minimum wall thickness tmin:

When the above requirements are not satisfied, (4iJ!..) shall be met.

(4) (iJ!..4) When the requirements of (.f.t), (.JfJ.), and 2(S+0.4p) (;iii) above are not satisfied, taloc is determined from Curve 2 of Fig. 4. In addition, trtiee shall satisfy the where following equation:

p = maximum operating pressure at flaw location S = allowable stress at operating temperature (2) The remaining degraded pipe section meets the [min 1.8 longitudinal stress limits in the design Code for the P.!P.ill&. where B'lJ. is the nominal pipe longitudinal bending stress (3) As an alternative to (b)(l)Altematively, an resulting from all Serviee Level B primary pipe evaluation of the remaining pipe thickness (t£}_may be loadings.

performed as given below. The evaluation procedure is (c) When there is through-wall leakage along a a function of the depth and the extent of the affected portion of the thinned wall, as illustrated in Fig. 5, the area as illustrated in Fig. 3. flaw may be evaluated by the branch reinforcement (i:l) When Wm is less than or equal to 0.5 method. The thinned area including the through-wall (R 0 t)l!2, where Ra is the outside radius and Wm is defined opening shall be represented by a circular penetration at in Fig. 3, the flaw can be classified as a planar flaw and the flaw location. Only the portion of the flaw lying evaluated in accordance with 3.1(a) through 3.1(c), within tadJ need be considered as illustrated in Fig. 6.

above. When the above requirement is not satisfied, When evaluating multiple flaws in accordance with

(.Jjj.) shall be met. 3.2(a), only the portions of the flaws contained within (fJ..J) When Lm(t) is not greater than (Ratmin )l!2, tadJ need be considered.

taloc is determined from Curve 1 of Fig. 4, where Lm(t) is Draft 15 (05/05/14) 3

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 3 .ILLUSTRATlON OF NONPLANAIR FLAW ()~ IE TO WALL THINNING Tra nsv,erse lei rcu mfere ntia II Axial d irectJion di rection Editor's Note: This Figure 3 is to be deleted and replaced with the Figure 3 on the following page.

Draft 15 (05/05/14) 4

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 3 ILLUSTRATION OF NONPLANAR FLAW DUE TO WALL THINNING

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Transverse (circumferential)

Axial direction direction 1

FIG. 4 ALLOWABLE WALL THICK I~ SS AND IL ENGT I-li OF LOCALLY l HINNED AREA 0 ~----~----~------~----~------------~----~----~

0 2 3 4 5 6 7

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Draft 15 (05/05/14) 5

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. S ILlUSTRATION OF lHR10UGHI-WALL NO IP'LA AR FlAW DUE TO WAlL THIIN lNG Thro IJI g h-wa II opening I

Transverse (c'i rcumfe rentia n Axia l direction d1rectJ1on Editor's Note: This Figure 5 is to be deleted and replaced with the Figure 5 on the following page.

Draft 15 (05/05/14) 6

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 5 ILLUSTRATION OF THROUGH-WALL NONPLANAR FLAW DUE TO WALL THINNING Through-wall

- - - Laxial - - +l l

Lcirc Transverse (circumferential)

Axial direction l direction Draft 15 (05/05/14) 7

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J The m1mmum wall thickness, tmin, shall be are adjusted, to account for the geometry differences, as determined by eq. (4). For evaluation purposes, the described below. Alternative methods may be used to adjusted wall thickness, tadJ, is a postulated thickness as calculate the stresses used in evaluation.

shown in Fig. 6. The pipe wall thickness is defined as The hoop stress, CJh, for elbow and bent pipe the thickness of the pipe in the non-degraded region as evaluation shall be:

shown in Fig. 6(a). The diameter of the opening is equal to dadJ as defined by tadJ as shown in Fig. 6(a). The postulated value for tadJ shall be greater than tmin and (5 = (pDa )[ 2Rbend + Ra sin¢ ] + (1.95) RaMb _i2}

2 13 h 2t 2( Rbend + Ra sin¢) h I shall not exceed the pipe wall thickness. The tadJ value may be varied between tmin and the pipe wall thickness to determine whether there is a combination of tadJ and dadJ that satisfies the branch reinforcement requirements.

The values of tadJ and dadJ of Fig. 6(b) shall satisfy: Rbend = elbow or bent pipe bend radius

¢ = circumferential angle defined in Figure 7 d < 1.5 \JfRtd 1

u adj (t ady - trmn. ) h = flexibility characteristic (1&)

adj - {min Mb = resultant primary bending moment I = moment of inertia based on evaluation wall thickness, t The remammg ligament average thickness, tc,avg' over the degraded area bounded by dadJ shall satisfy:

Equation 9 is only applicable for elbows and bent pipe where h > 0.1.

(~9)

The axial membrane pressure stress, CJm, for elbow and bent pipe evaluation shall be:

In addition, the pme section including the equivalent hole representation shall meet the longitudinal stress limits in the design Code for the illP!!!&

__If a flaw growth analysis is performed, the growth where B 1 is a primary stress index as defined in Section in flaw dimensions shall consider the degradation III for the piping item. B 1 shall be equal to 0.5 for mechanisms as relevant to the application. The flaw is elbows and bent pipe.

acceptable when there is sufficient thickness in the The axial bending stress, CJb, for elbow and bent degraded area to provide the required area pipe evaluation shall be:

reinforcement.

(d) Alternatively, if there is a through-wall opening (5 - B2 (-Da_M_b) 2I -------'.~~~

(11) along a portion of the thinned wall as illustrated in Fig. - b -

5 the flaw may be evaluated as two independent planar through-wall flaws, one oriented in the axial direction and the other oriented in the circumferential direction. where B ? is a primary stress index as defined in Section The minimum wall thickness tmin, shall be determined III for the piping item.

by eq. (4). The allowable through-wall lengths in the The thermal expansion stress, CJe, for elbow and axial and circumferential directions shall be determined bent pipe evaluation shall be:

by varying tadJ shown in Fig. 5 from tnam to tmin* The allowable through-wall flaw lengths based on tadJ shall (5 = i(DoMe) (12) be greater than or equal to the corresponding Laxial and --- e 2I --------~~:..t.~

Lcirc (see Fig. 5) as determined from 3.l(a) and 3.l(b) or 3.1 (c), as appropriate. The remaining ligament average thickness, tc,avg, over the degraded area bounded by Laxial and Lcirc shall satisfy eq. (~9).

= stress intensification factor as defined in the design Code for the piping item 3.3 Through-wall Flaws in Elbows and Bent Pipe Through-wall flaws in elbows and bent pipe may be Me = resultant thermal expansion moment evaluated using the straight pipe procedures given in 3.1 or 3.2(d), provided the stresses used in the evaluation Draft 15 (05/05/14) 8

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J 3.4 Through-wall Flaws in Reducers and The axial bending stress, ab, and thermal expansion Expanders stress, ae, for branch tee evaluation shall be determined Through-wall flaws in reducers and expanders may from eq. (15) and eq. (16), respectively.

be evaluated using the straight pipe procedures given in 3.1 or 3 .2(d), provided the stresses used in the 3 ..§.J. Flaw Growth Evaluation evaluation are adjusted, to account for the geometry If a flaw growth analysis is performed, the growth differences, as described below. Alternative methods analysis shall consider both corrosion and crack-growth may be used to calculate the stresses used in evaluation. mechanisms as relevant to the application.

Fig. 8 illustrates the reducer and expander zones In performing a flaw growth analysis, the discussed below. Evaluation of flaws in the small end procedures in C-3000 may be used as guidance.

transition zone is outside the scope of this Case. Relevant growth rate mechanisms shall be considered.

The hoop stress, ah, and axial membrane pressure When stress corrosion cracking (SCC) is active, the stress, am, for reducer or expander evaluation shall be: following growth rate equation shall be used:

~=(p~") ------------~(~13~)

where da/dt is flaw growth rate in inches/hour, Kmax is

(} = B (pDO) 2t (14) the maximum stress intensity factor under long-term steady state conditions in ksi in. 0*5, ST is a temperature

m I ---------'.-':o.....:..L where Dais the small end OD for flaws in the small end correction factor, and C and n are material constants.

and the large end OD for all other flaws.

The axial bending stress, ab, and thermal expansion For intergranular SCC in austenitic steels, where T :::;

stress, ae, for reducer or expander evaluation shall be: 200°F (93°C).

C =1.79xl0-8 ST = 1 n =2.161

(} =

e i(DoMe) 2/

(16)

>.~.:;...:;:....L-For transgranular SCC in austenitic steels, where T :::;

200°F (93°C).

where I is based on the degraded section.

C = 1.79 X 10-7 3.5 Through-wall Flaws in Branch Tees ST = 3.71 X 108 [10(0.01842 T-12.25)]

Branch reinforcement requirements shall be met in n = 2.161 accordance with the design Code. If the design Code did not require reinforcement, for evaluation pumoses, a The temperature, T, is the metal temperature in reinforcement region is defined as a region of radius Df degrees Fahrenheit. The flaw growth rate curves for the of the branch pipe from the center of the branch above SCC growth mechanisms are shown in Figs. 2.+

connection. Through-wall flaws in branch tees outside and 10&. Other growth rate parameters in eq. (11(}) may of the reinforcement region may be evaluated using the be used, provided they are supported by appropriate straight pipe procedures given in 3.1 or 3 .2( d), provided data.

the stresses used in the evaluation are adjusted, to account for the geometry differences, as described 3.14 Nonferrous Materials below. Alternative methods may be used to calculate the For nonferrous materials, nonplanar and planar stresses used in evaluation. Evaluation of flaws in the flaws may be evaluated following the general approach region of branch reinforcement is outside the scope of of 3.1 through 3 .§.J.. For planar flaws in ductile this Case. materials, the approach given iR 3.1 (b) aRd 3.3 for The hoop stress, ah, and axial membrane pressure austenitic pipe may be used; otherwise, the approach stress, am, for branch tee evaluation shall be determined given iR 3.l(e) aRd 3.3for ferritic pipe should be from eq. (13) and eq. (14), respectively. The outside applied. Structural factors provided in 4 shall be used. It diameter for each of these equations shall be for the is the responsibility of the evaluator to establish branch or run pipe, depending on the flaw location. conservative estimates of strength and fracture toughness for the piping material.

Draft 15 (05/05/14) 9

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 61LLUSTRATION OF ADJUSTED WALL THICKNESS AND EQUIVALENT HOLE DIAMETERS Th roug1h-wa II tm;,

nlsdj T

Pipe

_+ * ~~¥-------------\.

" "'"-" - "'- "'- "- "'- -" "-+--------+- -' - "- "'~. . . . . .,. . . :0'1 wall I I I I l.aJ Ad~ usted WaH fh l.ckpess Shift figure (b) to the right so that dadj width lines up with Ti* .;

t m;n

+--t------------ 1~~t ....

I >: . t .___fig_ur_e_ca_)._ _ ____,

l.oe dsdj ~

FIG. 7 CIRCUMFERENTIAL ANGLE DEFINED extrados

- - - -- - - - -- - <t:>

_i~t~~o~ ~

Draft 15 (05/05/1 4) 10

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 8 ZONES OF A REDUCER OR EXPANDER Cent ral conical section Smalt end transition zon e

¢.-----~

GENERAL NOTE:

Transftio~ zones extend from the point on the ends w here the diameter begins to change to the pomt on the cent ral cone where the cone angle is con stant.

Draft 15 (05/05/14) 11

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. ~7 FLAW GROWTH RATE FOR IGSCC IN AUSTENITIC PIPING H AuslonHiol'lplog

~ :;D:if I

~

..... ~-

1.(£..(]4

~

~ .....

=

/ "

1'1 1.1..""E:..IE

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a:

.c

'i Cl

.!j / ""'

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v

/

f "

/

1*1 '1*:(1 Etr~ lnllli"EEt'i AiP:tor, ~ ln. I

. E E~ D l'i[ m : 'lJJ 1 r - 7.

L[l" ~~ ; 'L.o . - 'l .!J ~ P.il.

Draft 15 (05/05/14) 12

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 108 FLAW GROWTH RATE FOR TGSCC IN AUSTENITIC PIPING El AU'S'Iwti!G Pl pllliJ J":ii~if

~

l/'

/

1. [E'..I]4 v

/ /

~ J"*il[if 1!1 /

a: / /

I I

!r!i ,. [E'..I]El / / T* IIJ[if

.r v

/

i"

/

v II]

- E HA C E: I"S[ n'L . ~* .

Draft 15 (05/05/14) 13

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J 4 ACCEPTANCE CRITERIA nondimensional stress intensity factor for through-wall circumferential flaw under Piping containing a circumferential planar flaw is membrane stress acceptable for temporary service when flaw evaluation I moment of inertia based on evaluation provides a margin using the structural factors in thickness, t Appendix C, C-2621. For axial planar flaws, the maximum stress intensity factor under structural factors for temporary acceptance are as long term steady state conditions specified in Appendix C, C-2622. Straight p.P.ip~ffig L maximum extent of a local thinned area containing a nonplanar part: -through-wall flaw is with t < tnom acceptable for temporary service if the remaining pipe Laxial length of idealized through-wall planar section meets the longitudinal stress limits in the design flaw opening in the axial direction of the Code for the piping and tP 2: talac, where taloc is pipe, as illustrated in Fig. 5 determined from 3 .2(b ). Straight pPip~ffig containing a length of idealized through-wall planar nonplanar through-wall flaw is acceptable for temporary flaw opening in the circumferential service when the flaw conditions of 3.2(c) or 3.2(d) are direction of the pipe, as illustrated in Fig. 5 satisfied. An elbow or bent pipe containing a nonplanar maximum extent of a local thinned area through-wall flaw is acceptable for temporary service if with t < tmin the flaw conditions of 3.3 are satisfied. A reducer or Lm(a) axial extent of wall thinning below tmin expander containing a nonplanar through-wall flaw is Lm (t) circumferential extent of wall thinning acceptable for temporary service if the flaw conditions below tmin of 3.4 are satisfied. A branch tee containing a nonplanar Lm,avg average of the extent of Lm below through-wall flaw is acceptable for temporary service if tmin for adjacent thinned areas the flaw conditions of3.5 are satisfied. Lm,i maximum extent of thinned area, i M2 bulging factor for axial flaw 5 AUGMENTED EXAMINATION Mn:___....!;r..:::.e:::..:su:::::.:lc::.:ta:::.!n~t'-"p::..!;r~im=ary~..:::.b.::;en~d~i~n~g)...;!m=o~m~e::..!;n~t Me_ _ _....!;r..:::.e:::..:su:::::.:lc::.:ta:::.!n~t~t~h.::;er::..!:m=al!...,;e::::..!x~p;::.!a:!:!.n~s~io:::..::n~m;.!.:o::..!m=en=t An augmented volumetric examination or physical R mean pipe radius measurement to assess degradation of the affected &end.------=-e=lb<--'=o'-'w..:........oeoe!...r-"b'-"e~n-=-t""P..:.~ip:<...!e"-c"'-'e"-!n~t.!::;er:c..:l=in;.!.:e"-b=e::::..!n=d~ra""d:::.!i=us system shall be performed as follows: Ra outside pipe radius (a) From the engineering evaluation, the most S allowable stress at operating temperature susceptible locations shall be identified. A sample size SFm structural factor on primary membrane of at least five of the most susceptible and accessible stress locations, or, if fewer than five, all susceptible and coefficient for temperature dependence in accessible locations shall be examined within 30 days of the crack growth relationship detecting the flaw. Code-specified ultimate tensile strength (b) When a flaw is detected, an additional sample Code-specified yield strength of the same size as defined in 5(a) shall be examined. metal temperature (c) This process shall be repeated within 15 days maximum extent of a local thinned area for each successive sample, until no significant flaw is perpendicular to Lm with t < tmin detected or until 100% of susceptible and accessible ~.j minimum distance between thinned areas i locations have been examined. andj z load multiplier for ductile flaw extension 6 NOMENCLATURE a flaw depth c half crack length

.!l.1Jb.-=---=S-=-e=ct=i=on==I=II:.....lp~='-'r=im=a:=...ry.J-,....::.s=tr-=-e=ss::.....=in=d=i=ce=s da/dt flaw growth rate for stress corrosiOn C coefficient in the crack growth relationship cracking Dt:----=in=s=id=e:::.....l='-p..:.~iP::....:e:.....d=i=a=m=e"-"t=er diameter equivalent circular hole at tadJ Da outside pipe diameter diameter of equivalent circular hole at F nondimensional stress intensity factor for lmin through-wall axial flaw under hoop stress h flexibility characteristic nondimensional stress intensity factor for stress intensification factor through-wall circumferential flaw under e total crack length = 2c pipe bending stress eall allowable axial through-wall flaw length n exponent in the crack growth relationship Draft 15 (05/05/14) 14

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J p maximum operating pressure at flaw location evaluation wall thickness, surrounding the degraded area tadJ adjusted wall thickness which is varied for evaluation purposes in the evaluation of a through-wall nonplanar flaw fatoc allowable local thickness for a nonplanar flaw tc,avg average remaining wall thickness covering degraded area with through-wall leak bounded by dadJ fmtn minimum wall thickness required for pressure loading tnam nominal wall thickness tP minimum remaining wall thickness a maximum cone angle at the center of a reducer

'A nondimensional half crack length for through-wall axial flaw

¢ circumferential angle from elbow or bend flank Qb axial bending stress for primary loading Qe axial thermal expansion stress CJ! material flow stress CJh pipe hoop stress due to pressure and bending moment (for elbows and bent pipe) 66 nominal longitudinal bending stress for primary loading without stress intensifi eation faetor CJ1 reference limit load hoop stress

!lm axial pressure stress CJy material yield strength at temperature, as defined in C-4300 "ftt~JeW time reqt~ired for the detested flaw to grow to the allowable flaw size, but not eReeeding 26 months from the initial diseovery of the eondition e half crack angle for through-wall circumferential flaw 7 APPLICABILITY This Case is applieable from the 19g3 Edition with the \Vinter 19g5 Addenda, through the 2007 Edition with the 200g Addenda. Reference to Appendix C in Editor's Note: For Applicability Index, this Case shall apply to Appendix C of the 2004 Edition applicability is from 1996 Addenda to or later editions or addenda. For editions and-or addenda 2013 Edition.

prior to the 2004 Edition, Class 1 pipe flaw evaluation procedures may be used for other piping classes. As a matter of definition, the current term "structural factor" is equivalent to the term "safety factor," which is used in earlier editions and addenda.

Draft 15 (05/05/14) 15

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J MANDATORY APPENDIX I RELATIONS FORFm, Fb, AND FFOR THROUGH-WALL FLAWS I-1 DEFINITIONS Ab = -3.26543 + 1.52784 (R/t)- 0.072698 (Rit )2

+ 0.0016011 (R/t) 3 For through-wall flaws, the crack depth_,_-fa_,J will Eb = 11.36322-3.91412 (R/t) + 0.18619 (Rit )2 be replaced with half crack length,_--fc,J in the stress - 0.004099 (R/t) 3 intensity factor equations in C-7300 and C-7400 of cb = -3.18609 + 3.84763 3 (Rit)- 0.18304 (Rit )2 Section XI, Appendix C. Also, Q will be set equal to + 0.00403 (R/t) unity in C-7400.

Equations for Fm and Fb are accurate for R/t between 5 I-2 CIRCUMFERENTIAL FLAWS and 20 and become increasingly conservative for R/t greater than 20. Alternative solutions for Fm and Fb may For a range of R/t between 5 and 20, the following be used when R/t is greater than 20.

equations for Fm and Fb may be used:

I-3 AXIAL FLAWS Fm = 1 +Am (B!tr)u +Em (B!tr) 2 *5 + Cm (B!tr) 3*5 Fb = 1 + Ab (B!tr)u + Eb (B!trf 5 + Cb (B!tr) 3 *5 For internal pressure loading, the following equation for F may be used:

where F = 1 + 0.072449A + 0.64856A2 - 0.2327 A3 8 = half crack angle = c/R + 0.038154 A4 - 0.0023487 A5 R = mean pipe radius t = evaluation ~wall thickness where and Am = -2.02917 + 1.67763 (R/t)- 0.07987 (Rit )2 c = half crack length

+ 0.00176 (R/t) 3 A= c/(Rt)l/2 Em = 7.09987-4.42394 (R/t) + 0.21036 (Rit )2 The equation for F is accurate for A between 0 and 5.

- 0.00463 (R/t) 3 Alternative solutions for F may be used when A is Cm = 7.79661 + 5.16676 (R/t)- 0.24577 (Rit )2 greater than 5.

+ 0.00541 (R/t) 3 Draft 15 (05/05/14) 16

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CASE ASME BPVC.CC.NC-2015 N-513-4 Approval Date: May 7, 2014 Code Cases will remain available for use until annulled by the applicable Standards Committee.

Case N-513-4 (e) The piping design Code shall be used in determin-Evaluation Criteria for Temporary Acceptance of Flaws ing the stress indices B 1 and B 2 , and stress intensification in Moderate Energy Class 2 or 3 Piping factor, i, for flaw evaluation following Code applicability Section XI, Division 1 limits in terms of component geometry, such as D 0 ftnom ratio. If the piping design Code does not provide stress in-Inquiry: What requirements may be used for temporary dices, Section III, 2004 Edition or later Editions and Ad-acceptance of flaws, including through-wall flaws, in mod- denda may be used to define B 1 and B 2 .

erate energy Class 2 or 3 piping including elbows, bent [J) The provisions of this Case demonstrate the integ-pipe, reducers, expanders, and branch tees, without per- rity of the item and not the consequences of leakage. It forming a repair /replacement activity? is the responsibility of the Owner to consider effects of leakage in demonstrating system operability and per-forming plant flooding analyses.

Reply: It is the opinion of the Committee that the follow-ing requirements may be used to accept flaws, including through-wall flaws, in moderate energy Class 2 or 3 pip-ing including elbows, bent pipe, reducers, expanders, 2 PROCEDURE and branch tees, without performing a repair /replace- (a) The flaw geometry shall be characterized by volu-ment activity for a limited time, not exceeding the time metric inspection methods or by physical measurement.

to the next scheduled refueling outage. The full pipe circumference at the flaw location shall be inspected to characterize the length and depth of all flaws in the pipe section.

1 SCOPE (b) Flaw shall be classified as planar or non planar.

(a) These requirements apply to the ASME Section III, (c) When multiple flaws, including irregular (com-ANSI B31.1, and ANSI B31.7 piping, classified by the Own- pound) shape flaws, are detected, the interaction and er as Class 2 or 3 that is accessible for inspection. The pro- combined area loss of flaws in a given pipe section shall visions of this Case do not apply to the following: be accounted for in the flaw evaluation.

(1) pumps, valves, expansion joints, and heat exchan- (d) A flaw evaluation shall be performed to determine gers, except as provided in (b) the conditions for flaw acceptance. Section 3 provides ac-(2) weld metal of socket welded joints cepted methods for conducting the required analysis.

(3) leakage through a flange joints (e) Frequent periodic inspections of no more than (4) threaded connections employing nonstructural 30 day intervals shall be used to determine if flaws are seal welds for leakage protection growing and to establish the time, at which the detected (b) This Case may be applied to heat exchanger exter- flaw will reach the allowable size. Alternatively, a flaw nal tubing or piping, provided the flaw is characterized growth evaluation may be performed to predict the time in accordance with 2(a) and leakage is monitored. at which the detected flaw will grow to the allowable size.

(c) The provisions of this Case apply to Class 2 or 3 pip- The flaw growth analysis shall consider the relevant ing in liquid systems whose maximum operating tem- growth mechanisms such as general corrosion or wa-perature does not exceed 200°F (93°C) and whose stage, fatigue, or stress corrosion cracking. When a flaw maximum operating pressure does not exceed 275 psig growth analysis is used to establish the allowable time (1.9 MPa). for temporary operation, periodic examinations of no (d) The following flaw evaluation criteria are permitted more than 90 day intervals shall be conducted to verify for pipe and tube including elbows, bent pipe, reducers, the flaw growth analysis predictions.

expanders, and branch tees. The straight pipe flaw evalua- [J) For through-wall leaking flaws, leakage shall be tion criteria are permitted for adjoining fittings and monitored daily to confirm the analysis conditions used flanges to a distance of (R 0 t) 1 / 2 from the weld centerline. in the evaluation remain valid.

The Committee's function is to establish rules of safety, relating only to pressure integrity, governing the construction of boilers, pressure vessels, transport tanks and nuclear components, and inservice inspection for pressure integrity of nuclear components and transport tanks, and to interpret these rules when questions arise regarding their intent. This Code does not address other safety issues relating to the construction of boilers, pressure vessels, transport tanks and nuclear components, and the inservice inspection of nuclear components and transport tanks. The user of the Code should refer to other pertinent codes, standards, laws, regulations or other relevant documents.

1 (N-513-4)

CASE (continued)

N-513-4 ASME BPVC.CC.NC-2015

[g) If examinations reveal flaw growth rate to be unac-ceptable, a repair /replacement activity shall be (3) performed.

(h) Repair /replacement activities shall be performed where no later than when the predicted flaw size from either D 0 = pipe outside diameter periodic inspection or by flaw growth analysis exceeds p = pressure for the loading condition the acceptance criteria of 4, or during the next scheduled SF m = structural factor on primary membrane stress as refueling outage, whichever occurs first. Repair /replace- specified in C-2622 ment activities shall be in accordance with IWA-4000. S u = Code specified ultimate tensile strength

[i) Evaluations and examination shall be documented Sy = Code specified yield strength in accordance with IWA-6300. The Owner shall document CJ 1 = flow stress the use of this Case on the applicable data report form. Z = load multiplier for ductile flaw extension (equal to 1.0 when using limit load criteria)

Material properties at the temperature of interest shall 3 FLAW EVALUATION be used.

Planar flaws in straight pipe shall be evaluated in accor-dance with the requirements in 3.1. Nonplanar flaws in straight pipe shall be evaluated in accordance with the re-quirements in 3.2. Through-wall flaws in elbows and bent pipe shall be evaluated in accordance with the require-ments in 3.3. Through-wall flaws in reducers, expanders, Figure I and branch tees shall be evaluated in accordance with the Through-Wall Flaw Geometry requirements in 3.4 and 3.5, respectively. Flaw growth evaluation shall be performed in accordance with the re-quirements in 3.6. Nonferrous materials shall be evalu-ated in accordance with the requirements in 3. 7.

For all flaw evaluations, all Service Level load combina-tions shall be evaluated to determine the most limiting al-lowable flaw size.

3.1 PLANAR FLAWS IN STRAIGHT PIPE (a) For planar flaws, the flaw shall be bounded by a rec-tangular or circumferential planar area in accordance with the methods described in Section XI Nonmandatory Appendix C. IWA-3300 shall be used to determine when multiple proximate flaws are to be evaluated as a single flaw. The geometry of a through-wall planar flaw is shown in Figure 1.

(E) (b) For planar flaws in austenitic piping, the evaluation (a) Circumferential Flaw procedure in Nonmandatory Appendix C shall be used.

Flaw depths up to 100% of wall thickness may be evalu-ated. When through-wall circumferential flaws are evalu-ated, the formulas for evaluation given in C-5 320 or C-6320, as applicable, of Nonmandatory Appendix C may be used, with the flaw depth to thickness ratio, a I t, equal to unity.

When through-wall axial flaws are evaluated, the allow-able flaw length is:

(1)

(2) (b) Axial Flaw 2 (N-513-4)

CASE (continued)

ASME BPVC.CC.NC-2015 N-513-4 (E) (c) For planar flaws in ferritic piping, the evaluation (-a) When W m is less than or equal to 0.5 (R 0 t) 1 12 ,

procedure of Nonmandatory Appendix C shall be used. where R 0 is the outside radius and W m is defined in Flaw depths up to 100% of wall thickness may be evalu- Figure 3, the flaw can be classified as a planar flaw and ated. Flaw depth, a, is defined in Figures C-431 0-1 and evaluated in accordance with 3.1(a) through 3.1(c),

C-4310-2. When through-wall circumferential flaws are above. When the above requirement is not satisfied, (-b) evaluated in accordance with C-5300 or C-6300, the flaw shall be met.

depth to thickness ratio, a It, shall be set to unity. When (-b) When Lm{tJ is not greater than (R 0 tmin) 112 ,

applying the Nonmandatory Appendix C screening criter- taloc is determined from Curve 1 of Figure 4, where ia for through-wall axial flaws, a It shall be set to unity, Lm{tJ is defined in Figure 3. When the above requirement and the reference limit load hoop stress, CJ 1, shall be de- is not satisfied, (-c) shall be met.

fined as CJY I M 2 . When through-wall axial flaws are evalu-(-c) When L m is less than or equal to 2.65 ated in accordance with C-5400 or C-6400, the allowable X (Rotmin) 112 and tnom is greater than 1.13tminJ taloc length is defined by eqs. (b)(1) through (b)(3), with the is determined by satisfying both of the following appropriate structural factors from Nonmandatory equations:

Appendix C, C-2622. When through-wall flaws are evalu-ated in accordance with C-7300 or C-7400, the formulas for evaluation given in C-4300 may be used, but with val- -taloc 2: l.S.J Ratmin [ 1 - - tnom]

- + 1.0 (5) ues for Fm' Fb, and F applicable to through-wall flaws. Re- tmin L tmin lations for Fm' Fb, and F that take into account flaw shape and pipe geometry (Rit ratio) shall be used. The appen-dix to this Case provides equations for Fm' Fb' and F for taloc > 0.353Lm ( )

6 a selected range of Rlt. Geometry of a through-wall crack tmin - .J Ratmin is shown in Figure 1.

When the above requirements are not satisfied, (-d) shall be met.

3.2 NONPLANAR FLAWS IN STRAIGHT PIPE (-d) When the requirements of (-a), (-b), and (-c) above are not satisfied, taloc is determined from Curve (a) The evaluation shall consider the depth and extent 2 of Figure 4.

of the affected area and require that the wall thickness ex-(c) When there is through-wall leakage along a portion ceed tm in for a distance that is the greater of 2.5 -J Rtnom of the thinned wall, as illustrated in Figure 5, the flaw may or 2L m,a vg between adjacent thinned regions, where R is be evaluated by the branch reinforcement method. The the mean radius of the piping item based on nominal wall thinned area including the through-wall opening shall thickness and L m, a vg is the average of the extent of L m be represented by a circular penetration at the flaw loca-below tmin for adjacent areas (see Figure 2). Alterna- tion. Only the portion of the flaw lying within tad i need be tively, the adjacent thinned regions shall be considered considered as illustrated in Figure 6. When evaluating a single thinned region in the evaluation. multiple flaws in accordance with (a), only the portions (E) (b) For nonplanar flaws, the pipe is acceptable when of the flaws contained within tadi need be considered.

either (1) and (2), or (2) and (3) are met. The minimum wall thickness, tmin' shall be determined (1) The remaining pipe thickness, tp, is greater than by (b)(1), eq. (4). For evaluation purposes, the adjusted or equal to the minimum wall thickness t min: wall thickness, tadi' is a postulated thickness as shown in Figure 6. The pipe wall thickness is defined as the thick-t . - pDo ness of the pipe in the non-degraded region as shown in (4) mm - 2(5 + 0.4p) Figure 6, illustration (a). The diameter of the opening is equal to d adi as defined by tadJ as shown in Figure 6, il-lustration (a). The postulated value for tadi shall be great-where er than tmin and shall not exceed the pipe wall thickness.

p = maximum operating pressure at flaw location The tadi value may be varied between tmin and the pipe S = allowable stress at operating temperature wall thickness to determine whether there is a combina-tion of tadi and d adi that satisfies the branch reinforce-(2) The remaining degraded pipe section meets the ment requirements.

longitudinal stress limits in the design Code for the piping. The values of tadi and dadi of Figure 6, illustration (b) shall satisfy:

(3) As an alternative to (1 ), an evaluation of the re-maining pipe thickness, tP, may be performed as given be-low. The evaluation procedure is a function of the depth l.S~Rtadj (tadj- tminJ dadj ::; - - - ' - - - - - - - - (7) and the extent of the affected area as illustrated in Figure tmin 3.

3 (N-513-4)

CASE (continued)

N-513-4 ASME BPVC.CC.NC-2015 Figure 2 Separation Requirements for Adjacent Thinned Areas t ~ tmin in surrounding area Area 3 tp, 3 < tmin Legend:

Lm, avj = 0.5 (Lm, ; + Lm, 1 ) X;, 1 = minimum distance between areas i andj L m, ; = maximum extent of thinned area i GENERAL NOTE: Combination of adjacent areas into an equivalent single area shall be based on dimensions and extents prior to combination.

The remaining ligament average thickness, tc,avg, over 3.1(a) and 3.1(b) or 3.1(c), as appropriate. The remaining the degraded area bounded by d adi shall satisfy: ligament average thickness, tc,a vg* over the degraded area bounded by Laxial and Lcirc shall satisfy (c), eq. (8).

rp tc avg ~ 0.353dadJ. 1- (8)

, ~ 'J s 3.3 THROUGH-WALL FLAWS IN ELBOWS AND BENT PIPE In addition, the pipe section including the equivalent Through-wall flaws in elbows and bent pipe may be hole representation shall meet the longitudinal stress lim-evaluated using the straight pipe procedures given in its in the design Code for the piping.

3.1 or 3.2(d), provided the stresses used in the evaluation If a flaw growth analysis is performed, the growth in are adjusted, to account for the geometry differences, as flaw dimensions shall consider the degradation mechan- described below. Alternative methods may be used to cal-isms as relevant to the application. The flaw is acceptable culate the stresses used in evaluation.

when there is sufficient thickness in the degraded area to The hoop stress, a h, for elbow and bent pipe evaluation provide the required area reinforcement.

shall be as follows:

(d) Alternatively, if there is a through-wall opening along a portion of the thinned wall as illustrated in Figure 5 the flaw may be evaluated as two independent planar a = [PD h Zt 0 I 2Rbend + R0 2(Rbend sincp] + [ 1.95 J R

+ R0 sin¢ h2/3 0

I Mb (9) through-wall flaws, one oriented in the axial direction and the other oriented in the circumferential direction.

where The minimum wall thickness tmin* shall be determined by (b)(l), eq. (4). The allowable through-wall lengths in h = flexibility characteristic the axial and circumferential directions shall be deter- I = moment of inertia based on evaluation wall mined by varying tadi shown in Figure 5 from tnom to thickness, t tmin* The allowable through-wall flaw lengths based on Mb = resultant primary bending moment t a dj shall be greater than or equal to the corresponding Rbend = elbow or bent pipe bend radius Laxial and Lcirc (see Figure 5) as determined from ¢ = circumferential angle defined in Figure 7 4 (N-513-4)

CASE (continued)

ASME BPVC.CC.NC-2015 N-513-4 Figure 3 (E)

Illustration of Nonplanar Flaw Due to Wall Thinning Transverse (circumferential)

Axial direction direction Equation (9) is only applicable for elbows and bent The thermal expansion stress, a e* for elbow and bent pipe where h ~ 0.1. pipe evaluation shall be as follows:

The axial membrane pressure stress, a m* for elbow and bent pipe evaluation shall be as follows: (12)

(10) where stress intensification factor as defined in the design where Code for the piping item 8 1 = primary stress index as defined in Section III for the Me resultant thermal expansion moment piping item 3.4 THROUGH-WALL FLAWS IN REDUCERS AND (E)

= 0.5 for elbows and bent pipe EXPANDERS The axial bending stress, a b* for elbow and bent pipe Through-wall flaws in reducers and expanders may be evaluation shall be as follows: evaluated using the straight pipe procedures given in 3.1 or 3.2(d), provided the stresses used in the evaluation are (11) adjusted, to account for the geometry differences, as de-scribed below. Alternative methods may be used to calcu-late the stresses used in evaluation. Figure 8 illustrates where the reducer and expander zones discussed below. Evalua-82 = primary stress index as defined in Section III for the tion of flaws in the small end transition zone is outside the piping item scope of this Case.

5 (N-513-4)

CASE (continued)

N-513-4 ASME BPVC.CC.NC-2015 Figure 4 Allowable Wall Thickness and Length of Locally Thinned Area 1.0

~

0.8 0.6 I

~

~(0

/ ~})

~ ---- ------

I /

c J'-'

0

.3 0.4 I I 0.2 0

0 2 3 5 6 7 8 The hoop stress, CJ h, and axial membrane pressure the branch pipe from the center of the branch connection.

stress, CJ m, for reducer or expander evaluation shall be Through-wall flaws in branch tees outside of the rein-as follows: forcement region may be evaluated using the straight pipe procedures given in 3.1 or 3.2(d), provided the stres-(13) ses used in the evaluation are adjusted, to account for the geometry differences, as described below. Alternative methods may be used to calculate the stresses used in evaluation. Evaluation of flaws in the region of branch re-(14) inforcement is outside the scope of this Case.

The hoop stress, CJ h, and axial membrane pressure where stress, CJ m, for branch tee evaluation shall be determined from eq. 3.4(13) and eq. 3.4(14), respectively. The outside D0 = small-end O.D. for flaws in the small-end and the diameter for each of these equations shall be for the large-end O.D. for all other flaws branch or run pipe, depending on the flaw location.

The axial bending stress, CJ b* and thermal expansion The axial bending stress, CJ b* and thermal expansion stress, CJ e

for reducer or expander evaluation shall be stress, CJ e

for branch tee evaluation shall be determined as follows: from eq. 3.4(15) and eq. 3.4(16) respectively.

(15) 3.6 FLAW GROWTH EVALUATION (16) If a flaw growth analysis is performed, the growth ana-lysis shall consider both corrosion and crack-growth me-chanisms as relevant to the application.

where In performing a flaw growth analysis, the procedures in I = moment of inertia based on degraded section Article C-3000 may be used as guidance. Relevant growth rate mechanisms shall be considered. When stress corro-3.5 THROUGH-WALL FLAWS IN BRANCH TEES sion cracking (SCC) is active, the following growth rate Branch reinforcement requirements shall be met in ac- equation shall be used:

cordance with the design Code. If the design Code did not require reinforcement, for evaluation purposes, a rein- dajdt = SyCK~ax (17) forcement region is defined as a region of radius D i of 6 (N-513-4)

CASE (continued)

ASME BPVC.CC.NC-2015 N-513-4 Figure 5 (E)

Illustration of Through-Wall Nonplanar Flaw Due to Wall Thinning Through-wall

~-- Laxial - - - + !

Transverse (circumferential)

Axial direction direction where dajdt is flaw growth rate in inches/hour, Kmax is and 10. Other growth rate parameters in eq. (17) may the maximum stress intensity factor under long-term be used, provided they are supported by appropriate steady state conditions in ksi in. 0*5, S T is a temperature data.

correction factor, and C and n are material constants.

For intergranular SCC in austenitic steels, where T : :;

3.7 NONFERROUS MATERIALS 200°F (93°C). For nonferrous materials, nonplanar and planar flaws may be evaluated following the general approach of 3.1

[ 1.79 X 10- 8 through 3.6. For planar flaws in ductile materials, the ap-n 2.161 proach given for austenitic pipe may be used; otherwise, Sr 1 the approach given for ferritic pipe should be applied.

Structural factors provided in 4 shall be used. It is the re-For transgranular SCC in austenitic steels, where T : :; sponsibility of the evaluator to establish conservative es-200°F (93°C). timates of strength and fracture toughness for the piping

[ 1.79 X 10-? material.

n 2.161 5T 3.71 X 108 [10(0.01842 T- 12.25)]

4 ACCEPTANCE CRITERIA The temperature, T, is the metal temperature in de- Piping containing a circumferential planar flaw is ac-grees Fahrenheit. The flaw growth rate curves for the ceptable for temporary service when flaw evaluation pro-above SCC growth mechanisms are shown in Figures 9 vides a margin using the structural factors in 7 (N-513-4)

CASE (continued)

N-513-4 ASME BPVC.CC.NC-2015 Figure 6 Illustration of Adjusted Wall Thickness and Equivalent Hole Diameter tmin rt tadj T

Pipe

-~ \~~¥------------<."

~~+----~~~tall (a) Adjusted Wall Thickness (b) Equivalent Hole Representation Nonmandatory Appendix C, C-2621. For axial planar nonplanar through-wall flaw is acceptable for temporary flaws, the structural factors for temporary acceptance service if the flaw conditions of 3.3 are satisfied. A redu-are as specified in Nonmandatory Appendix C, C-2622. cer or expander containing a non planar through-wall flaw Straight pipe containing a nonplanar part through-wall is acceptable for temporary service if the flaw conditions flaw is acceptable for temporary service if the remaining of 3.4 are satisfied. A branch tee containing a nonplanar pipe section meets the longitudinal stress limits in the de- through-wall flaw is acceptable for temporary service if sign Code for the piping and tP :?: taloc* where t aloc is de- the flaw conditions of 3.5 are satisfied.

termined from 3.2(b) . Straight pipe containing a nonplanar part through-wall flaw is acceptable for tem-porary service when the flaw conditions of 3.2 (c) or 3.2(d) are satisfied. An elbow or bent pipe containing a Figure 7 Circumferential Angle Defined extrados (Y-____ ~

intrados 8 (N-513-4)

CASE (continued)

ASME BPVC.CC.NC-2015 N-513-4 Figure 8 Zones of a Reducer or Expander Centr_al conical sect1on

/

t - - - - - - - - - - - - - - - - - - - - - - - - - - -*

GENERAL NOTE: Transition zones extend from the point on the ends where the diameter begins to change to the point on the central cone where the cone angle is constant.

5 AUGMENTED EXAMINATION Fb nondimensional stress intensity factor for through-wall circumferential flaw under pipe An augmented volumetric examination or physical bending stress measurement to assess degradation of the affected sys- Fm nondimensional stress intensity factor for tem shall be performed as follows: through-wall circumferential flaw under mem-(a) From the engineering evaluation, the most suscepti- brane stress ble locations shall be identified. A sample size of at least h flexibility characteristic five of the most susceptible and accessible locations, or, stress intensification factor if fewer than five, all susceptible and accessible locations I moment of inertia based on evaluation thick-shall be examined within 30 days of detecting the flaw. ness, t (b) When a flaw is detected, an additional sample of the Kmax maximum stress intensity factor under long same size as defined in (a) shall be examined. term steady state conditions L maximum extent of a local thinned area with t (c) This process shall be repeated within 15 days for

< tnom each successive sample, until no significant flaw is de-Laxial length of idealized through-wall planar flaw tected or until 100% of susceptible and accessible loca-opening in the axial direction of the pipe, as il-tions have been examined.

lustrated in Figure 5 Lcirc length of idealized through-wall planar flaw opening in the circumferential direction of the pipe, as illustrated in Figure 5 6 NOMENCLATURE Lm maximum extent of a local thinned area with t < tmin a flaw depth axial extent of wall thinning below t min Lm{a) 81, Bz Section III primary stress indices circumferential extent of wall thinning below Lm{t) c half crack length tmin c coefficient in the crack growth relationship Lm,avg average of the extent of L m below tmin for ad-dajdt flaw growth rate for stress corrosion cracking jacent thinned areas dadj diameter equivalent circular hole at tadi maximum extent of thinned area, i Di inside pipe diameter bulging factor for axial flaw dmin diameter of equivalent circular hole at t min resultant primary bending moment Do outside pipe diameter resultant thermal expansion moment F nondimensional stress intensity factor for n exponent in the crack growth relationship through-wall axial flaw under hoop stress 9 (N-513-4)

CASE (continued)

N-513-4 ASME BPVC.CC.NC-2015 Figure 9 Flaw Growth Rate for IGSCC in Austenitic Piping 1.0 E- 02 f---

Austenitic Piping f--- T ::; 200°F 1.0 E-03

/

~;'

//

1.0 E-04 sc /

t v

/

~

ico c::

1.0 E- 05

/v

/

..c

~ /

2 /

(.9

~

/

(.)

~ /"'

u 1.0 E- 06 /

/

1/

1.0 E- 07 /

/

1.0 E-08 1 10 100 Stress Intensity Factor, K (ksi in.D.5)

GENERAL NOTE: (SI conversion: 1.0 in.jhr = 7.06 x 10- 3 mmjsec; 1.0 ksi in. 0 *5 = 1.099 MP a m 0 *5 ; oc = [°F - 32]/1.8).

maximum operating pressure at flaw location t a dj = adjusted wall thickness which is varied for eva-mean pipe radius luation purposes in the evaluation of a through-elbow or bent pipe centerline bend radius wall non planar flaw outside pipe radius t aloc allowable local thickness for a nonplanar flaw allowable stress at operating temperature t c, avg average remaining wall thickness covering de-structural factor on primary membrane stress graded area with through-wall leak bounded coefficient for temperature dependence in the by d a dj crack growth relationship minimum wall thickness required for pressure Code-specified ultimate tensile strength loading Code-specified yield strength nominal wall thickness metal temperature minimum remaining wall thickness evaluation wall thickness, surrounding the de- maximum extent of a local thinned area per-graded area pendicular to Lm with t < tmin 10 (N-513-4)

CASE (continued)

ASME BPVC.CC.NC-2015 N-513-4 Figure 10 Flaw Growth Rate for TGSCC in Austenitic Piping 1.0 E- 02

- /

- Austenitic Piping "

T s 200°F //

1.0 E-03

/

1.0 E-04 v

./

sc /

/

t 1.0 E- 05

~

/' v

~ T 200°F ,

./

ico /

c: / /

..c

/ / I T = 100°F I

~ 1.0 E- 06 2

(.9

..lo: ./ ./

(.)

co / /

u / ~"

//

1.0 E- 07

./

/

1.0 E-08 v

./

/

1.0 E-09 1 10 100 Stress Intensity Factor, K (ksi in.D.5)

GENERAL NOTE: (SI conversion: 1.0 in.jhr =7.06 x 10- 3 mmjsec; 1.0 ksi in. 0 *5 = 1.099 MPa m 0 *5 ; oc = [°F - 32]/1.8).

Xi,J minimum distance between thinned areas i ah pipe hoop stress due to pressure and bending and} moment (for elbows and bent pipe)

Z load multiplier for ductile flaw extension a1 reference limit load hoop stress

-1! = total crack length = 2c am axial pressure stress

-1! all allowable axial through-wall flaw length ay material yield strength at temperature, as de-ct> circumferential angle from elbow or bend flank fined in C-4300 a maximum cone angle at the center of a reducer 8 half crack angle for through-wall circumferen- 7 APPLICABILITY tial flaw Reference to Nonmandatory Appendix C in this Case A = nondimensional half crack length for through- shall apply to Nonmandatory Appendix C of the 2004 Edi-wall axial flaw tion or later editions or addenda. For editions or addenda ab axial bending stress for primary loading ae axial thermal expansion stress a1 = material flow stress 11 (N-513-4)

CASE (continued)

N-513-4 ASME BPVC.CC.NC-2015 prior to the 2004 Edition, Class 1 pipe flaw evaluation matter of definition, the current term "structural factor" procedures may be used for other piping classes. As a is equivalent to the term "safety factor," which is used in earlier editions and addenda.

12 (N-513-4)

CASE (continued)

ASME BPVC.CC.NC-2015 N-513-4 MANDATORY APPENDIX I RELATIONS FOR Fm, Fb, AND F FOR THROUGH-WALL FLAWS Bb = 11.36322- 3.91412 (Rit) + 0.18619 (Rit) 2 -

1-1 DEFINITIONS 0.004099 (Rit) 3 For through-wall flaws, the crack depth, a, will be re- Cb = -3.18609 + 3.84763 (Rit)- 0.18304 (Rit) 2 +

placed with half crack length, c, in the stress intensity fac- 0.00403 (Rit) 3 tor equations in C-7300 and C-7400 of Section XI, In the above equations:

Nonmandatory Appendix C. Also, Q will be set equal to unity in C-7 400. R = mean pipe radius t = evaluation wall thickness 8 = half crack angle = c I R 1-2 CIRCUMFERENTIAL FLAWS Equations for F m and F b are accurate for R It between For a range of R It between 5 and 20, the following 5 and 20 and become increasingly conservative for Rlt equations for F m and F b may be used: greater than 20. Alternative solutions for F m and F b may be used when Rjt is greater than 20.

where 1-3 AXIAL FLAWS Am = -2.02917 + 1.67763 (Rit)- 0.07987 (Rit) 2 + For internal pressure loading, the following equation 0.00176 (Rit) 3 for F may be used:

Bm = 7.09987- 4.42394 (Rit) + 0.21036 (Rit) 2 -

2 3 4 0.00463 (Rit) 3 F = 1 + 0.072449.A + 0.64856.A - 0.2327.A + 0.038154.A Cm = 7.79661 + 5.16676 (Rit)- 0.24577 (Rit) 2 + - o.0023487.A 5 0.00541 (Rit) 3 where c = half crack length A = ci(Rt) 112 where The equation for F is accurate for A between 0 and 5.

Ab = -3.26543 + 1.52784 (Rit) - 0.072698 (Rfti + Alternative solutions for F may be used when A is greater 0.0016011 (Rit) 3 than 5.

13 (N-513-4)

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Proceedings of the ASME 2014 Pressure Vessels & Piping Conference PVP2014 July 20-24, 2014, Anaheim, California, USA PVP2014-28355 TECHNICAL BASIS FOR PROPOSED FOURTH REVISION TO ASME CODE CASE N-513 Robert 0. McGill Guy DeBoo Structural Integrity Associates Exelon Generation Company San Jose, CA Warrenville, IL rmcgill@structint.com guy.deboo@exeloncorp.com Russell C. Cipolla Eric J. Houston lntertek AIM Structural Integrity Associates Sunnyvale, CA San Jose, CA russell.cipolla@intertek.com ehouston@structint.com ABSTRACT Resultant thermal expansion moment Elbow or bent pipe bend radius Code Case N-513 provides evaluation rules and criteria Outside radius for temporary acceptance of flaws, including through-wall Flexibility characteristic flaws, in moderate energy piping. The application of the Code Stress intensification factor as defined in the Code of Case is restricted to moderate energy, Class 2 and 3 systems, Record for the piping item so that safety issues regarding short-term, degraded system p Maximum operating pressure at flaw location operation are minimized. The first version of the Code Case Evaluation thickness was published in 1997. Since then, there have been three Axial bending stress revisions to augment and clarify the evaluation requirements Thermal expansion stress and acceptance criteria of the Code Case that have been Hoop stress published by ASME. The technical bases for the original Axial membrane stress version of the Code Case and the three revisions have been Circumferential angle previously published.

There is currently work underway to incorporate INTRODUCTION additional changes to the Code Case and this paper provides Background the technical basis for the changes proposed in a fourth revision. These changes include addressing the current Code Case N-513-3 [1] (currently approved revision) condition on the Code Case acceptance by the US Nuclear provides evaluation rules and criteria for the temporary Regulatory Commission (NRC), clarification of the Code Case acceptance of flaws, including through-wall flaws, in applicability limits and expansion of Code Case scope to moderate energy piping. The provisions of this Code Case are additional piping components. New flaw evaluation focused on preventing gross failure of the affected pipe for a procedures are given for through-wall flaws in elbows, bent temporary period. However, it also requires the piping system pipe, reducers, expanders and branch tees. These procedures and adjacent equipment functionality be demonstrated for lost evaluate flaws in the piping components as if in straight pipe fluid inventory, spraying and flooding caused by the leakage.

by adjusting hoop and axial stresses to account for the The Code Case provides rules for the evaluation of degraded geometry differences. These changes and their technical bases pipe and tube for a short operating period, with inspection and are described in this paper. monitoring requirements of the degraded condition as part of the overall integrity assessment. The application of the Code NOMENCLATURE Case is restricted to moderate energy Class 2 and Class 3 systems, so that the safety issues regarding short-term system B 1, B 2 Primary stress index defined in ASME Section III for operation are minimized. Moderate energy piping is defined the piping item as those piping systems where the maximum operating Da Outside diameter pressure and temperature do not exceed 275 psig (1.9 MPa)

I Moment of inertia based on t (degraded section) and 200°F (93°C), respectively.

Currently, the scope of the Code Case is limited to to accept flaws ... without performing a repair/replacement straight pipe with some provision for flaw evaluation into activity for a limited time, not exceeding the time to the next fittings for a short distance from the weld attachment to scheduled refueling outage." Note that the word "refueling" straight pipe. There have been many instances where through- has been added for further clarification regarding the nature wallleaks have been observed in pipe components (i.e., and duration of the plant outage.

elbows, reducers, expanders or branch tees) or bent pipe outside of the current Code Case scope. As a result, utilities This language is consistent with the introduction ofNRC are forced into taking alternate actions (e.g., repair, Generic Letter 90-05 [3] which the original N -513 was based.

replacement, or making requests for NRC relief) that can be The second paragraph of90-05 states: "Temporary non-code significantly more burdensome without any measurable repairs are applicable until the next scheduled outage increase in plant safety. The fourth revision of the Code Case exceeding 30 days, but no later than the next scheduled provides evaluation rules and criteria for the temporary refueling outage."

acceptance of flaws for these instances. In addition, other enhancements are included with the fourth revision as Flaw Evaluation Criteria for Piping Components and Bent summarized below. Pipe Evaluation and acceptance criteria have been added toN-Summary of Code Case N-513-4 Changes 513-4 for flaws in elbows, bent pipe, reducers, expanders and The list below summarizes the proposed changes included branch tees. A simplified approach has been adopted based on in Revision 4 of Code Case N-513. Note that a brief reason the evaluations and results from the Second International for each change is included in parenthesis. Piping Integrity Research Group (IPIRG-2) program reported in Reference [4]. The flaw evaluation for the piping

Temporary acceptance period redefined (addresses component is conducted as if in straight pipe by scaling hoop NRC condition given in Regulatory Guide 1.147 [2]) and axial stresses using ASME piping design code stress

Flaw evaluation criteria included for elbows, bent indices and stress intensification factors to account for the pipe, reducers, expanders and branch tees (scope stress variations caused by the geometric differences. In expansion) Reference [4], this approach was determined to be very

Allow flaw evaluation of heat exchanger tubing in conservative by comparing the failure moments predicted specific instances (scope expansion) using this approach to the measured failure moments from the

Daily walkdown requirement for through-wall leaks elbow tests for through-wall circumferential flaws. Details of provides additional flexibility for user the simplified approach are given in the following sections.

implementation (scope expansion)

Limit scope to only liquid systems (scope Flaw Evaluation in Elbows and Bent Pipe. Through-clarification) wall flaws in elbows and bent pipe may be evaluated using the

Treatment of Service Level load combinations (scope straight pipe procedures given in N-513-4 provided the clarification) stresses used in the evaluation are adjusted to account for geometry differences. The hoop stress for elbow and bent

Treatment of flaws in austenitic pipe flux welds pipe evaluation shall be (Equation 9 ofN-513-4):

(scope clarification)

Minimum wall thickness acceptance criteria to consider longitudinal stresses in addition to hoop stress (scope clarification)

(]" =

h (pDa 2t J[ 2Rbend + Ra sin¢ ] +(1.95] RaM b 2(Rbend + Ra sin¢) h 2 13 I

(9)

In addition, several editorial changes to improve the Equation 9 is only applicable for elbows and bent pipe clarity of the Code Case are included. where h 2: 0.1.

CODE CASE N-513-4 CHANGES AND TECHNICAL The axial membrane pressure stress for elbow and bent BASIS pipe evaluation shall be (Equation 10 ofN-513-4):

The following subsections provide details regarding each change and their technical basis.

(]"m =B(pDoJ I 2t (10)

Temporary Acceptance Period N-513-3 specifies a temporary acceptance period that B 1 shall be equal to 0.5 for elbows and bent pipe.

could extent out to 26 months. The NRC did not endorse this maximum period length and in the latest revision of NRC The axial bending stress for elbow and bent pipe Regulatory Guide 1.147, placed a condition on N-513-3 evaluation shall be (Equation 11 ofN-513-4):

stating, " ... repair or replacement activity temporarily deferred under the provisions of this Code Case shall be performed during the next scheduled outage." N-513-4 (]" =

b B (RaM b 2 I J (11) addresses this condition by removing the maximum duration limit and stating," ... the following requirements may be used 2 Copyright © 2014 by ASME Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 09/11/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use

Note that if the piping design Code of Record does not provide a B 2 , it may be taken from the ASME Section III, 2004 Edition or later Editions and Addenda. (J e

= i(Do21Me) (16)

The thermal expansion stress for elbow and bent pipe evaluation shall be (Equation 12 ofN-513-4): Equations 13-16 are consistent with the piping design by rule approach in ASME Section III. The reducer and expander zones shown in Figure 8 ofN-513-4 are consistent with those

u. ={ R"~" ) (12) shown in Code Case N-597-2 [8]. As with elbows and bent pipe, N-513-4 allows for alternate methods to be used to calculate stresses used in the flaw evaluation.

The first term of Equation 9 accounts for the hoop membrane stress variation around the circumference of the Flaw Evaluation in Branch Tees. Branch reinforcement elbow (higher at the intrados, lower at the extrados assuming a requirements shall be met in accordance with the Construction uniform wall thickness). The second term conservatively Code. If the Construction Code did not require reinforcement, accounts for the through-wall bending in the hoop direction a reinforcement region is defined as a region of radius Di of that results from elbow ovalization due to in-plane or out-of- the branch pipe from the center of the branch connection for plane bending and was taken from Reference [5]. Equations evaluation purposes. Through-wall flaws in branch tees 10-12 are consistent with the piping design by rule approach outside of the reinforcement region may be evaluated using in ASME Section III, NC/ND-3600 [6]. the straight pipe procedures given in N-513-4 provided the stresses used in the evaluation are adjusted as described below It is recognized in Reference [4] that the simplified flaw to account for the geometry differences. Evaluation of flaws evaluation approach may be overly conservative in some in the region of branch reinforcement is outside the scope of instances. Thus, N-513-4 allows for alternate methods to be this Case.

used to calculate stresses used in the flaw evaluation. For example, the French have developed a more comprehensive The hoop stress and axial membrane pressure stress for approach in analyzing flaws in cracked elbows. They have branch tee evaluation shall be determined from N-513-4 implemented finite element analysis based correlations to Equation 13 and 14, respectively. The outside diameter for determine location specific stresses for flaw evaluation. each of these equations shall be for either the branch or run Reference [7] provides additional details. pipe depending on the flaw location. The axial bending stress and thermal expansion stress for branch tee evaluation shall be Flaw Evaluation in Reducers and Expanders. Through- determined from N-513-4 Equation 15 and 16, respectively.

wall flaws in reducers and expanders may be evaluated using the straight pipe procedures given in N-513-4 provided the As discussed previously, Equations 13-16 are consistent stresses used in the evaluation are adjusted to account for the with the piping design by rule approach in ASME Section III.

geometry differences. Figure 8 ofN-513-4 illustrates the The limitation regarding flaw evaluation within the branch reducer and expander zones discussed below. Evaluation of reinforcement region is consistent with guidance given in flaws in the small end transition zone is outside the scope of Code Case N-597-2. As with elbows and bent pipe, N-513-4 N-513-4. The hoop stress and axial membrane pressure stress allows for alternate methods to be used to calculate stresses for reducer and expander evaluation shall be: used in the flaw evaluation.

Flaw Evaluation of Heat Exchanger Tubing CY =(pDa)2t (13) h N-513-4 allows for flaw evaluation in heat exchanger tubing provided the flaw can be characterized and the leakage monitored. The technical basis is that knowledge of flaw CY m

= B(pDo)

I 2t (14) geometry is needed to evaluate the structural integrity of the tubing containing the flaw. An example application from plant operating experience would be for leaks in nonferrous Note that Do is either the small end OD for the small end tubing of air cooling coils. The heat exchangers being of or is the large end 0 D for the large end. For the large end plate-fin design could have tubing accessible for volumetric transition zone and central conical section, Do is the large end inspection.

OD. Also, if the piping design Code of Record does not provide a B 1 , it may be taken from the ASME Section III, Flexibility in Daily Walkdown Requirement 2004 Edition or later Editions and Addenda.

N-513-4 changes the daily walkdown requirement for The axial bending stress and thermal expansion stress for leaking flaws from" ... leakage shall be observed by daily reducer and expander evaluation shall be: walkdowns ... "to" ... leakage shall be monitored daily ... "

This change allows for other techniques to be employed in meeting the intent of the requirement instead of only physical CY b

=B 2

(Da21Mb) (15) walkdowns. Such techniques could include remote visual 3 Copyright © 2014 by ASME Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 09/11/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use

equipment or leakage detection systems to determine if and branch tees. In addition, several other scope expansions leakage rates are changing. and clarifications are included as well as editorial improvements. With these changes, it is believed the Code Scope Limited to Liquid Systems Case will be of even greater use to utilities in avoiding unscheduled plant shutdowns without negatively impacting Provisions ofN-513-4 are now specifically limited to only plant safety.

liquid systems. The methods ofN-513-4 should not be applied to the piping of air or other compressible fluid ACKNOWLEDGEMENTS systems.

The development of Code Case N-513-4 was through the Treatment of Service Level Load Combinations efforts of the Working Group on Pipe Flaw Evaluation. The authors wish to recognize the efforts of all Working Group N-513-4 now specifically requires all Service Level load members especially the Working Group Chair, Dr. Doug combinations to be considered in flaw evaluations to Scarth.

determine the most limiting. N-513-3 was previously silent as to what Service Level loading to consider. However, this REFERENCES requirement was implied in previous Code Case revisions when it required the use of pipe flaw evaluation procedures 1. ASME Code Case N-513-3, "Evaluation Criteria for specified in the referenced, non-mandatory appendices of Temporary Acceptance of Flaws in Moderate Energy ASME Section XI. Appendix C in the 2002 Addenda and Class 2 or 3 Piping Section XI, Division 1," Cases of later editions and addenda, and Appendix H for ferritic the ASME Boiler and Pressure Vessel Code, January materials in earlier editions, required all operating conditions 26,2009.

or Service Levels be evaluated. 2. Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1,"

Treatment of Flaws in Austenitic Pipe Flux Welds Revision 16, October 2010.

3. NRC Generic Letter 90-05, "Guidance for A reference to ASME Section XI, Appendix C, C-6320 Performing Temporary Non-Code Repair of ASME has been added to paragraph 3.1 (b) to address the instance Code Class 1, 2, and 3 Piping," (June 15, 1990).

where a flaw in an austenitic pipe flux weld requires

4. Kilinski, T., Mohan, R., Rudland, D., Fleming, M.,

evaluation. Such a flaw would require the use of Elastic Olson, R., Scott, P., Brust, F., Ghadiali, N.,

Plastic Fracture Mechanics (EPFM) criteria instead of Limit Wilkowski, G., and Hopper, A., "Fracture Behavior Load criteria. Equation 1 ofN-513-4 now includes a Z factor of Circumferentially Surface-Cracked Elbows,"

to account for this specific application.

NUREG/CR-6444, BMI-2192, December 1996.

5. Moore, S.E., and Rodabaugh, E.C., "Background for When the original version ofN-513 was developed, Changes in the 1981 Edition of the ASME Nuclear Appendix C of ASME Section XI only included flaw Power Plant Components Code for Controlling evaluation criteria for austenitic piping. The change from N-Primary Loads in Piping Systems," Journal of 513-1 to -2 included the reference changes to the new Pressure Vessel Technology, Volume 104, pp. 351 -

Appendix C that combined austenitic and ferritic flaw 361, November 1982.

evaluation criteria. The need to reference EPFM criteria for

6. ASME Boiler and Pressure Vessel Code, Section III, an austenitic flux weld flaw evaluation was overlooked.

NC/ND-3600, 2004 Edition.

7. Marie, S., Chapuliot, S., Kayser, Y., Lacire, M.H.,

Minimum Wall Thickness Acceptance Criteria Drubay, B., Barthelet, B., Le-Delliou, P., Rougier, In establishing a minimum wall thickness acceptance V., Naudin, C., Gilles, P., and Triay, M., "French criteria for paragraphs 3.2(b) and 3.2 (c) ofN-513-4, the RSE-M and RCC-MR Code Appendices for Flaw requirement to consider longitudinal stresses in addition to Analysis: Presentation of the Fracture Parameters hoop stress is added. While it is unlikely that a longitudinal Calculation- Part IV: Cracked Elbow," International stress based minimum wall thickness would be limiting Journal of Pressure Vessels and Piping 84, pp. 659-compared to the hoop stress based minimum wall thickness, 686, May 2007.

the user should be aware of this possibility and confirm an 8. ASME Code Case N-597-2, "Requirements for appropriate tmin as an acceptance criterion. Analytical Evaluation of Pipe Wall Thinning, Section XI, Division 1," Cases of the ASME Boiler and CONCLUSIONS Pressure Vessel Code, November 18, 2003.

This document serves as the technical basis for the fourth revision of Code Case N -513. This Code Case provides evaluation rules and criteria for temporary acceptance of flaws, including through-wall flaws, in moderate energy Class 2 or Class 3 piping. Currently, the scope of the Code Case is limited to straight pipe with some provision for flaw evaluation into fittings for a short distance from the weld attachment to straight pipe. N-513-4 provides flaw evaluation rules and criteria for elbows, bent pipe, reducers, expanders 4 Copyright © 2014 by ASME Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 09/11/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use

v t e Letter Sequence Request
EPID:L-2017-LLR-0141, ASME Code Case N-513-4 (Open)
Initiation Request Acceptance Administration Questions Answers Results Approval... Other: ML18128A067
MONTHYEAR2017-12-08 [Table View]

CNRO-2017-00022, Relief Request Number EN-17-RR-1 - Proposed Alternative to Use ASME Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate-Energy Class 2 or 3 Piping, Section XI, Division 1

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CNRO-2017-00022, Relief Request Number EN-17-RR-1 - Proposed Alternative to Use ASME Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate-Energy Class 2 or 3 Piping, Section XI, Division 1

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