Text

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)
	v • d • e

(QWHUJ\\2SHUDWLRQV,QF

(QWHUJ\\1XFOHDU2SHUDWLRQV,QF

1340 Echelon Parkway Jackson, MS 39213 0DQG\\+DOWHU

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 Docket Nos. 50-313 & 50-368 License Nos. DPR-51 & NPF-6 Indian Point Energy Center, Units 2 & 3 Docket Nos. 50-247 & 50-286 License Nos. DPR-26 & DPR-64 Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 License No. NPF-29 Palisades Nuclear Plant Docket 50-255 License No. DPR-20 River Bend Station, Unit 1 Docket No. 50-458 License No. NPF-47 Pilgrim Nuclear Power Station Docket No. 50-293 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

$77$&+0(17

&152

5(/,()5(48(67(155

Attachment to CNRO-2017-00022 Page 1 of 5 5(/,()5(48(67(155

$60(&RGH&RPSRQHQWV$IIHFWHG

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).

$SSOLFDEOH&RGH(GLWLRQDQG$GGHQGD

3ODQW

,6,

,QWHUYDO

$60(6HFWLRQ;,

&RGHRI5HFRUG

,QWHUYDO

6WDUW

,QWHUYDO

(QG

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

$SSOLFDEOH&RGH5HTXLUHPHQW

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

5HDVRQIRU5HTXHVW

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.

3URSRVHG$OWHUQDWLYHDQG%DVLVIRU8VH

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. 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.

'XUDWLRQRI3URSRVHG$OWHUQDWLYH

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.

3UHFHGHQW

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

5HIHUHQFHV

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 TanksSection 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)

(QFORVXUH

1) Mark-up Version of ASME Code Case N-513-3, (YDOXDWLRQ&ULWHULDIRU7HPSRUDU\\

$FFHSWDQFHRI)ODZVLQ0RGHUDWH(QHUJ\\&ODVVRU3LSLQJ6HFWLRQ;,'LYLVLRQ

2) ASME Code Case N-513-4, (YDOXDWLRQ&ULWHULDIRU7HPSRUDU\\$FFHSWDQFHRI)ODZVLQ

0RGHUDWH(QHUJ\\&ODVVRU3LSLQJ6HFWLRQ;,'LYLVLRQ

3) Technical Basis for Proposed Fourth Revision to ASME Code Case N-513

&152

5(/,()5(48(67(155

(1&/2685(2)$77$&+0(17

0DUNXS9HUVLRQRI$60(&RGH&DVH1(YDOXDWLRQ&ULWHULDIRU

7HPSRUDU\\$FFHSWDQFHRI)ODZVLQ0RGHUDWH(QHUJ\\&ODVVRU

3LSLQJ6HFWLRQ;,'LYLVLRQ

II Record # 12-841 I

CASES OF ASME BOILER AND PRESSURE VESSEL CODE CASE 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-~~

Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1 Inquiry: What requirements may be used for temporary acceptance of flaws, including through-wall flaws, in moderate energy Class 2 or 3 piping including elbows, bent pipe, reducers, expanders, and branch tees, without performing a repair/replacement activity?

Reply: It is the opinion of the Committee that the following requirements may be used to accept flaws, including through-wall flaws, in moderate energy Class 2 or 3 piping including elbows, bent pipe, reducers, expanders, and branch tees, without performing a repair/replacement activity for a limited time, not exceeding the evalHatiea peried as defiaed ia this G-asetime to the next scheduled refueling outage.

1 SCOPE (a) These requirements apply to the ASME Section III, ANSI B31.1, and ANSI B31. 7 piping, classified by the Owner as Class 2 or 3 that is accessible for inspection. The provisions of this Case do not apply to the following:

(1) pumps, valves, expansion joints,_ and heat exchangers, except as provided in (b) ;

(2) weld metal of socket welded joints; (3) leakage through a flange joint; (4) threaded connections employing nonstructural seal welds for leakage protection.

(b) This Case may be applied to heat exchanger external tubing or piping, provided the flaw is characterized in accordance with 2(a) and leakage is monitored.

(f.e) The provisions of this Case apply to Class 2 or 3 piping in liquid systems whose maximum operating temperature does not exceed 200°F (93 °C) and whose maximum operating pressure does not exceed 275 psig (1.9 MPa).

(d_e) The following flaw evaluation criteria are permitted for pipe and tube including elbows, bent pipe, reducers, expanders, and branch tees. The straight pipe flaw evaluation criteria are permitted for adjoining fittings and flanges to a distance of (Rat) Yz from the weld centerline.

Draft 15 (05/05/14)

(e) The piping design Code shall be used in determining the stress indices B I and B), and stress intensification factor, i, for flaw evaluation following Code applicability limits in terms of component geometry, such as DoL!nom ratio. If the piping design Code does not provide stress indices,Section III, 2004 Edition or later Editions and Addenda may be used to define B I and B 1.~

([d) The provisions of this Case demonstrate the integrity of the item and not the consequences of leakage. It is the responsibility of the Owner to del'H:eastrate systefl'l epentbility considerffig effects of leakage in demonstrating system operability and performing plant flooding analyses.

(e) The evalHatiea peried, Ttt~JeW, is the eperatieaal tifl'le fer whieh the tel'H:perary aeeeptaaee eriteria are satisfied bt1t aet eJf:eeediag 26 l'H:eaths frefl'l the iaitial diseevery ef the eeaditiea.

2 PROCEDURE (a) The flaw geometry shall be characterized by volumetric inspection methods or by physical measurement. The full pipe circumference at the flaw location shall be inspected to characterize the length and depth of all flaws in the pipe section.

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

(c)

When multiple flaws, including irregular (compound) shape flaws, are detected, the interaction and combined area loss of flaws in a given pipe section shall be accounted for in the flaw evaluation.

(d) A flaw evaluation shall be performed to determine the conditions for flaw acceptance. Section 3 provides accepted methods for conducting the required analysis.

(e) Frequent periodic inspections of no more than 30 day intervals shall be used to determine if flaws are growing and to establish the time.,.--'fe~~ew;-_at which the detected flaw will reach the allowable size.

Alternatively, a flaw growth evaluation may be performed to predict the time.,.......-Te~~ew-, at which the detected flaw will grow to the allowable size. The flaw growth analysis shall consider the relevant growth mechanisms such as general corrosion or wastage, fatigue, or stress corrosion cracking. When a flaw growth analysis is used to establish the allowable time for temporary operation, periodic examinations of no more than 90 day intervals shall be conducted to verify the flaw growth analysis predictions.

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J (f) For through-wall leaking flaws, leakage shall be eeserved bymonitored daily wallEdevffls to confirm the 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 the next scheduled refueling outage, whichever occurs first. Repair---er---Lreplacement activities shall be in accordance with IWA-4000 er P.VA 7000, respeetively, in Editiens and Addenda prier te the 1991 Addenda; and, in the 1991 Addenda and later, in aeeerdanee with IVll\\: 4000.

(i)

Evaluations and examination shall be documented in accordance with IWA-6300. The Owner shall document the use of this Case on the applicable data report form.

3 FLAW EVALUATION Planar flaws in straight pipe shall be evaluated in accordance with the requirements in 3.1. Non planar 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 materials shall be evaluated in accordance with the requirements in 3.14.

For all flaw evaluations, all Service Level load combinations shall be evaluated to determine the most limiting allowable flaw size.

3.1 Planar Flaws in Straight Pipe (a) For planar flaws, the flaw shall be bounded by a rectangular or circumferential planar area in accordance with the methods described in Appendix C. IW A-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 Fig. 1.

(b) For planar flaws in austenitic piping, the evaluation procedure in Appendix C shall be used. Flaw depths up to 100% of wall thickness may be evaluated.

When through-wall circumferential flaws are evaluated, the formulas for evaluation given in C-5320 or C-6320, as applicable, of Appendix C may be used, with the flaw depth to thickness ratio, a/t, equal to unity.

Draft 15 (05/05/14)

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

where p

=pressure for the loading condition Note: Z has been D 0 =pipe outside diameter added to equation CJ!

= flow stress (1).

Sy = Code specified yield strength Su

= Code specified ultimate tensile strength and SF m = structural factor on primary membrane stress as specified in C-2622 Z

= load multiplier for ductile flaw extension (equal to 1.0 when using limit load criteria)

Material properties at the temperature of interest shall be used.

FIG.1 THROUGH-WALL FLAW GEOMETRY (c) For planar flaws in ferritic piping, the evaluation procedure of Appendix C shall be used. Flaw depths up to 100% of wall thickness may be evaluated. Flaw depth, a, is defined in Figures C-4310-1 and C-4310-2.

When through-wall circumferential flaws are evaluated in accordance with C-5300 or C-6300, the flaw depth to thickness ratio, a/t, shall be set to unity. When applying the Appendix C screening criteria for through-wall axial flaws, a/t shall be set to unity, and the reference limit load hoop stress, a1, shall be defined as cry! M2. When through-wall axial flaws are evaluated in accordance with C-5400 or C-6400, the allowable length is defined by eqs. (1) through (3), with the appropriate structural factors from Appendix C, C-2622. When through-wall flaws are evaluated in accordance with C-7300 or C-7400, the formulas for evaluation given in C-4300 may be used, but with values for Fm, Fb, and F applicable to through-wall flaws. Relations for F m, Fb, and F that take into account flaw shape and pipe geometry (R/t ratio) shall be used. The appendix to this Case provides equations for Fm, Fb, and F for a selected range of R/t.

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

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

__ (a) The evaluation shall consider the depth and extent of the affected area and require that the wall thickness exceed tmin for a distance that is the greater of 2.5,fRtnom or 2Lm,avg between adjacent thinned regions, where R is the mean radius of the piping item based on 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 considered a single thinned region in the evaluation.

__ (b) For nonplanar flaws, the pipe is acceptable when either (b)(l) and (b)(2), or (b)(2) and (b)(3) are met.

(1) Tthe remaining pipe thickness (tp) is greater than or equal to the minimum wall thickness tmin:

(4) 2(S+0.4p) where p

= maximum operating pressure at flaw location S

= allowable stress at operating temperature (2) The remaining degraded pipe section meets the longitudinal stress limits in the design Code for the P.!P.ill&.

(3) As an alternative to (b)(l)Altematively, an evaluation of the remaining pipe thickness (t£}_may be performed as given below. The evaluation procedure is a function of the depth and the extent of the affected area as illustrated in Fig. 3.

(i:l) When Wm is less than or equal to 0.5 (R 0t)l!2, where Ra is the outside radius and Wm is defined in Fig. 3, the flaw can be classified as a planar flaw and evaluated in accordance with 3.1(a) through 3.1(c),

above. When the above requirement is not satisfied,

(.Jjj.) shall be met.

(fJ..J) When Lm(t) is not greater than (Ratmin )l!2, taloc is determined from Curve 1 of Fig. 4, where Lm(t) is Draft 15 (05/05/14) defined in Fig. 3. When the above requirement is not satisfied, (;iii) shall be met.

(jii;) When Lm is less than or equal to 2.65 (Ratmin)l!2 and tnom is greater than 1.13 tmin, tatoc is determined by satisfying both of the following equations:

t 1.5 ~[ t

]

....E.!!!E...."2_

\\fl'-olmin 1-~ +1.0 t min L

t min

[aloe 0.353Lm

->----:::=====-

tmin -

~ROt min (5)

(6)

When the above requirements are not satisfied,

( 4iJ!..) shall be met.

(iJ!..4) When the requirements of (.f.t), (.JfJ.), and

(;iii) above are not satisfied, taloc is determined from Curve 2 of Fig. 4. In addition, trtiee shall satisfy the following equation:

[min 1.8 where B'lJ. is the nominal pipe longitudinal bending stress resulting from all Serviee Level B primary pipe loadings.

(c) When there is through-wall leakage along a portion of the thinned wall, as illustrated in Fig. 5, the flaw may be evaluated by the branch reinforcement method. The thinned area including the through-wall opening shall be represented by a circular penetration at the flaw location. Only the portion of the flaw lying within tadJ need be considered as illustrated in Fig. 6.

When evaluating multiple flaws in accordance with 3.2(a), only the portions of the flaws contained within tadJ need be considered.

3

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 3.ILLUSTRATlON OF NONPLANAIR FLAW ()~

IE TO WALL THINNING Axial direction Draft 15 (05/05/14)

Transv,erse lei rcu mfere ntia II d irectJion Editor's Note: This Figure 3 is to be deleted and replaced with the Figure 3 on the following page.

4

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J FIG. 3 ILLUSTRATION OF NONPLANAR FLAW DUE TO WALL THINNING Axial direction Lm(a)-

l l...m(t) 1 Transverse (circumferential) direction FIG. 4 ALLOWABLE WALL THICK I~ SS AND ILENGTI-li OF LOCALLY l HINNED AREA 0 ~----~----~------~----~------------~----~----~

0 2

3 Draft 15 (05/05/14) 4

.Lmft1JI~

5 6

7 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 Axial d1rectJ1on Draft 15 (05/05/14)

Thro IJI g h-wa II I

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

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 Axial direction Draft 15 (05/05/14)

Through-wall

--- Laxial--+l l

Lcirc l

Transverse (circumferential) direction 7

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J The m1mmum wall thickness,

tmin, shall be determined by eq. ( 4). For evaluation purposes, the adjusted wall thickness, tadJ, is a postulated thickness as shown in Fig. 6. The pipe wall thickness is defined as the thickness of the pipe in the non-degraded region as 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 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:

1.5 fRtd (t d - t. )

d

\\J 1 u adj a y rmn adj -

{min (1&)

The remammg ligament average thickness, tc,avg' over the degraded area bounded by dadJ shall satisfy:

(~9)

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 in flaw dimensions shall consider the degradation mechanisms as relevant to the application. The flaw is acceptable when there is sufficient thickness in the degraded area to provide the required area reinforcement.

(d) Alternatively, if there is a through-wall opening along a portion of the thinned wall as illustrated in Fig.

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.

The minimum wall thickness tmin, shall be determined by eq. ( 4). The allowable through-wall lengths in the axial and circumferential directions shall be determined by varying tadJ shown in Fig. 5 from tnam to tmin* The allowable through-wall flaw lengths based on tadJ shall be greater than or equal to the corresponding Laxial and 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).

3.3 Through-wall Flaws in Elbows and Bent Pipe Through-wall flaws in elbows and bent pipe may be 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) are adjusted, to account for the geometry differences, as described below. Alternative methods may be used to calculate the stresses used in evaluation.

The hoop stress, CJh, for elbow and bent pipe evaluation shall be:

(5 = (pDa )[ 2Rbend + Ra sin¢ ] + (1.95) RaMb _i2}

h 2t 2( Rbend + Ra sin¢)

h 213 I

Rbend

= elbow or bent pipe bend radius

¢

= circumferential angle defined in Figure 7 h

= flexibility characteristic Mb

= resultant primary bending moment I

= moment of inertia based on evaluation wall thickness, t Equation 9 is only applicable for elbows and bent pipe where h > 0.1.

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

where B 1 is a primary stress index as defined in Section III for the piping item. B 1 shall be equal to 0.5 for elbows and bent pipe.

The axial bending stress, CJb, for elbow and bent pipe evaluation shall be:

(5

- B (-Da_M_b)

(11) b -

2 2I

'.~~~

where B? is a primary stress index as defined in Section III for the piping item.

The thermal expansion stress, CJe, for elbow and bent pipe evaluation shall be:

(5 = i(DoMe)

(12) e 2I

~~:..t.~

= stress intensification factor as defined in the design Code for the piping item Me = resultant thermal expansion moment 8

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J 3.4 Through-wall Flaws in Reducers and Expanders Through-wall flaws in reducers and expanders may be evaluated using the straight pipe procedures given in 3.1 or 3.2( d), provided the stresses 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.

Fig. 8 illustrates the reducer and expander zones discussed below. Evaluation of flaws in the small end transition zone is outside the scope of this Case.

The hoop stress, ah, and axial membrane pressure stress, am, for reducer or expander evaluation shall be:

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

(} = B (pDO)

(14) m I

2t

'.-':o.....:..L where Dais the small end OD for flaws in the small end and the large end OD for all other flaws.

The axial bending stress, ab, and thermal expansion stress, ae, for reducer or expander evaluation shall be:

(} = i(DoMe)

(16) e 2/

>.~.:;...:;:....L-where I is based on the degraded section.

3.5 Through-wall Flaws in Branch Tees Branch reinforcement requirements shall be met in accordance with the design Code. If the design Code did not require reinforcement, for evaluation pumoses, a reinforcement region is defined as a region of radius Df of the branch pipe from the center of the branch connection. Through-wall flaws in branch tees outside of the reinforcement region may be evaluated using the straight pipe procedures given in 3.1 or 3.2( d), provided the stresses 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 reinforcement is outside the scope of this Case.

The hoop stress, ah, and axial membrane pressure stress, am, for branch tee evaluation shall be determined from eq. (13) and eq. (14), respectively. The outside diameter for each of these equations shall be for the branch or run pipe, depending on the flaw location.

Draft 15 (05/05/14)

The axial bending stress, ab, and thermal expansion stress, ae, for branch tee evaluation shall be determined from eq. (15) and eq. (16), respectively.

3..§.J. Flaw Growth Evaluation If a flaw growth analysis is performed, the growth analysis shall consider both corrosion and crack-growth mechanisms as relevant to the application.

In performing a flaw growth analysis, the procedures in C-3000 may be used as guidance.

Relevant growth rate mechanisms shall be considered.

When stress corrosion cracking (SCC) is active, the following growth rate equation shall be used:

where da/dt is flaw growth rate in inches/hour, Kmax is the maximum stress intensity factor under long-term steady state conditions in ksi in.0*5, ST is a temperature correction factor, and C and n are material constants.

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

200°F (93°C).

C

=1.79xl0-8 ST

= 1 n

=2.161 For transgranular SCC in austenitic steels, where T :::;

200°F (93°C).

C

= 1.79 X 10-7 ST

= 3.71 X 108 [10(0.01842 T-12.25)]

n

= 2.161 The temperature, T, is the metal temperature in degrees Fahrenheit. The flaw growth rate curves for the above SCC growth mechanisms are shown in Figs. 2.+

and 10&. Other growth rate parameters in eq. (11(}) may be used, provided they are supported by appropriate data.

3.14 Nonferrous Materials For nonferrous materials, nonplanar and planar flaws may be evaluated following the general approach of 3.1 through 3.§.J.. For planar flaws in ductile materials, the approach given iR 3.1 (b) aRd 3.3 for austenitic pipe may be used; otherwise, the approach given iR 3.l(e) aRd 3.3for ferritic pipe should be applied. Structural factors provided in 4 shall be used. It is the responsibility of the evaluator to establish conservative estimates of strength and fracture toughness for the piping material.

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;, n lsdj

_+

~~¥-------------\\.

T Pipe

"""'"-""--"'--"'--"--"'---"""-+--------+-----"--"'~...........,......:0' 1 wall I

I I

I l.aJ Ad~usted WaH fhl.ckpess Shift figure (b) to the right so that dadj tm;n width lines up with Ti*

I

. t

.___fig_ur_e_ca_). ___

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

l.oe dsdj~

FIG. 7 CIRCUMFERENTIAL ANGLE DEFINED extrados

<t:>

_i~t~~o~~

Draft 15 (05/05/1 4) 10

CASES OF ASME BOILER AND PRESSURE VESSEL CODE FIG. 8 ZONES OF A REDUCER OR EXPANDER

¢.-----~

GENERAL NOTE:

Smalt end transition zon e Central conical section CASE (continued)

N-513-4J Transftio~ zones extend from the point on the ends where the diameter begins to change to the pomt on the central cone where the cone angle is constant.

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 I

H AuslonHiol'lplog

~ :;D:if

~

1.(£..(]4

..... ~-

~

~ =

/

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

.;'/

.c 'i Cl

.!j

/

I' 0 HE: -Del

.)/

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 1!1 a:

1.[E'..I]4

!, [E'..I]El r!i.

- E HA C E: I"S[

Draft 15 (05/05/14)

El AU'S'Iwti!G PlpllliJ J":ii~if

~

J"*il[if

/

.r v

/

i"

/ v

..;' ~

l/'

/

v

/

I T* IIJ[if I II]

n'L. ~*

13

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-513-4J 4

ACCEPTANCE CRITERIA Piping containing a circumferential planar flaw is acceptable for temporary service when flaw evaluation provides a margin using the structural factors in Appendix C, C-2621. For axial planar flaws, the structural factors for temporary acceptance are as specified in Appendix C, C-2622. Straight p.P.ip~ffig containing a nonplanar part:-through-wall flaw is acceptable for temporary service if the remaining pipe section meets the longitudinal stress limits in the design Code for the piping and tP 2:

talac, where taloc is determined from 3.2(b ). Straight pPip~ffig containing a nonplanar through-wall flaw is acceptable for temporary service when the flaw conditions of 3.2(c) or 3.2(d) are satisfied. An elbow or bent pipe containing a nonplanar through-wall flaw is acceptable for temporary service if the flaw conditions of 3.3 are satisfied. A reducer or expander containing a nonplanar through-wall flaw is acceptable for temporary service if the flaw conditions of 3.4 are satisfied. A branch tee containing a non planar through-wall flaw is acceptable for temporary service if the flaw conditions of3.5 are satisfied.

5 AUGMENTED EXAMINATION An augmented volumetric examination or physical measurement to assess degradation of the affected system shall be performed as follows:

(a) From the engineering evaluation, the most susceptible locations shall be identified. A sample size of at least five of the most susceptible and accessible locations, or, if fewer than five, all susceptible and accessible locations shall be examined within 30 days of detecting the flaw.

(b) When a flaw is detected, an additional sample of the same size as defined in 5(a) shall be examined.

(c) This process shall be repeated within 15 days for each successive sample, until no significant flaw is detected or until 100% of susceptible and accessible locations have been examined.

6 NOMENCLATURE

.!l.1Jb.-=---=S-=-e=ct=i=on==I=II:.....lp~='-'r=im=a:=...ry.J-,....::.s=tr-=-e=ss::.....=in=d=i=ce=s C

coefficient in the crack growth relationship Dt:----=in=s=id=e:::.....l='-p..:.~iP::....:e:.....d=i=a=m=e"-"t=er D a outside pipe diameter F

nondimensional stress intensity factor for through-wall axial flaw under hoop stress nondimensional stress intensity factor for through-wall circumferential flaw under pipe bending stress Draft 15 (05/05/14)

I L

Laxial Lm(a)

Lm(t)

Lm,avg nondimensional stress intensity factor for through-wall circumferential flaw under membrane stress moment of inertia based on evaluation thickness, t maximum stress intensity factor under long term steady state conditions maximum extent of a local thinned area with t < tnom length of idealized through-wall planar flaw opening in the axial direction of the pipe, as illustrated in Fig. 5 length of idealized through-wall planar flaw opening in the circumferential direction of the pipe, as illustrated in Fig. 5 maximum extent of a local thinned area with t < tmin axial extent of wall thinning below tmin circumferential extent of wall thinning below tmin average of the extent of Lm below tmin for adjacent thinned areas Lm,i maximum extent of thinned area, i M2 bulging factor for axial flaw 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 R

mean pipe radius

&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 Ra outside pipe radius S

allowable stress at operating temperature SF m structural factor on primary membrane stress

~.j z

a c

da/dt h

e e

all n

coefficient for temperature dependence in the crack growth relationship Code-specified ultimate tensile strength Code-specified yield strength metal temperature maximum extent of a local thinned area perpendicular to Lm with t < tmin minimum distance between thinned areas i andj load multiplier for ductile flaw extension flaw depth half crack length flaw growth rate for stress corrosiOn cracking diameter equivalent circular hole at tadJ diameter of equivalent circular hole at lmin flexibility characteristic stress intensification factor total crack length = 2c allowable axial through-wall flaw length exponent in the crack growth relationship 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) 6 6 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 this Case shall apply to Appendix C of the 2004 Edition or later editions or addenda. For editions and-or addenda 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)

Editor's Note: For Applicability Index, applicability is from 1996 Addenda to 2013 Edition.

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 For through-wall flaws, the crack depth_,_ -fa_,J will be replaced with half crack length,_ --fc,J in the stress intensity factor equations in C-7300 and C-7400 of Section XI, Appendix C. Also, Q will be set equal to unity in C-7400.

I-2 CIRCUMFERENTIAL FLAWS For a range of R/t between 5 and 20, the following equations for Fm and Fb may be used:

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 where 8 = half crack angle = c/R R = mean pipe radius t = evaluation ~wall thickness and Am

= -2.02917 + 1.67763 (R/t)- 0.07987 (Rit )

2

+ 0.00176 (R/t)3 Em

= 7.09987-4.42394 (R/t) + 0.21036 (Rit )

2

- 0.00463 (R/t)3 Cm

= 7.79661 + 5.16676 (R/t)- 0.24577 (Rit )2

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

Ab

= -3.26543 + 1.52784 (R/t)- 0.072698 (Rit )

2

+ 0.0016011 (R/t)3 Eb

= 11.36322-3.91412 (R/t) + 0.18619 (Rit )2

- 0.004099 (R/t)3 cb

= -3.18609 + 3.84763 (Rit)- 0.18304 (Rit )2

+ 0.00403 (R/t)3 Equations for Fm and Fb are accurate for R/t between 5 and 20 and become increasingly conservative for R/t greater than 20. Alternative solutions for Fm and Fb may be used when R/t is greater than 20.

I-3 AXIAL FLAWS For internal pressure loading, the following equation for F may be used:

F = 1 + 0.072449A + 0.64856A2 - 0.2327 A3

+ 0.038154 A4 - 0.0023487 A5 where c = half crack length A= c/(Rt)l/2 The equation for F is accurate for A between 0 and 5.

Alternative solutions for F may be used when A is greater than 5.

16

&152

5(/,()5(48(67(155

(1&/2685(2)$77$&+0(17

$60(&RGH&DVH1(YDOXDWLRQ&ULWHULDIRU7HPSRUDU\\

$FFHSWDQFHRI)ODZVLQ0RGHUDWH(QHUJ\\&ODVVRU3LSLQJ

6HFWLRQ;,'LYLVLRQ

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 Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1 Inquiry: What requirements may be used for temporary acceptance of flaws, including through-wall flaws, in mod-erate energy Class 2 or 3 piping including elbows, bent pipe, reducers, expanders, and branch tees, without per-forming a repair /replacement activity?

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, and branch tees, without performing a repair /replace-ment activity for a limited time, not exceeding the time to the next scheduled refueling outage.

1 SCOPE (a) These requirements apply to the ASME Section III, ANSI B31.1, and ANSI B31.7 piping, classified by the Own-er as Class 2 or 3 that is accessible for inspection. The pro-visions of this Case do not apply to the following:

(1) pumps, valves, expansion joints, and heat exchan-gers, except as provided in (b)

(2) weld metal of socket welded joints (3) leakage through a flange joints (4) threaded connections employing nonstructural seal welds for leakage protection (b) This Case may be applied to heat exchanger exter-nal tubing or piping, provided the flaw is characterized in accordance with 2(a) and leakage is monitored.

(c) The provisions of this Case apply to Class 2 or 3 pip-ing in liquid systems whose maximum operating tem-perature does not exceed 200°F (93°C) and whose maximum operating pressure does not exceed 275 psig (1.9 MPa).

(d) The following flaw evaluation criteria are permitted for pipe and tube including elbows, bent pipe, reducers, expanders, and branch tees. The straight pipe flaw evalua-tion criteria are permitted for adjoining fittings and flanges to a distance of (R 0 t) 1/ 2 from the weld centerline.

(e) The piping design Code shall be used in determin-ing the stress indices B 1 and B 2, and stress intensification factor, i, for flaw evaluation following Code applicability limits in terms of component geometry, such as D 0 ftnom ratio. If the piping design Code does not provide stress in-dices,Section III, 2004 Edition or later Editions and Ad-denda may be used to define B 1 and B 2.

[J) The provisions of this Case demonstrate the integ-rity of the item and not the consequences of leakage. It is the responsibility of the Owner to consider effects of leakage in demonstrating system operability and per-forming plant flooding analyses.

2 PROCEDURE (a) The flaw geometry shall be characterized by volu-metric inspection methods or by physical measurement.

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

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

(c) When multiple flaws, including irregular (com-pound) shape flaws, are detected, the interaction and combined area loss of flaws in a given pipe section shall be accounted for in the flaw evaluation.

(d) A flaw evaluation shall be performed to determine the conditions for flaw acceptance. Section 3 provides ac-cepted methods for conducting the required analysis.

(e) Frequent periodic inspections of no more than 30 day intervals shall be used to determine if flaws are growing and to establish the time, at which the detected flaw will reach the allowable size. Alternatively, a flaw growth evaluation may be performed to predict the time at which the detected flaw will grow to the allowable size.

The flaw growth analysis shall consider the relevant growth mechanisms such as general corrosion or wa-stage, fatigue, or stress corrosion cracking. When a flaw growth analysis is used to establish the allowable time for temporary operation, periodic examinations of no more than 90 day intervals shall be conducted to verify the flaw growth analysis predictions.

[J) For through-wall leaking flaws, leakage shall be monitored daily to confirm the analysis conditions used 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 performed.

(h) Repair /replacement 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 the next scheduled refueling outage, whichever occurs first. Repair /replace-ment activities shall be in accordance with IWA-4000.

[i) Evaluations and examination shall be documented in accordance with IWA-6300. The Owner shall document the use of this Case on the applicable data report form.

3 FLAW EVALUATION 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, 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 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 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)

(3) where D 0 = pipe outside diameter p = pressure for the loading condition SF m = structural factor on primary membrane stress as specified in C-2622 S u = Code specified ultimate tensile strength S y = Code specified yield strength CJ 1 = flow stress Z = load multiplier for ductile flaw extension (equal to 1.0 when using limit load criteria)

Material properties at the temperature of interest shall be used.

Figure I Through-Wall Flaw Geometry (a) Circumferential Flaw (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) 112, where R0 is the outside radius and W m is defined in Figure 3, the flaw can be classified as a planar flaw and evaluated in accordance with 3.1(a) through 3.1(c),

above. When the above requirement is not satisfied, (-b) shall be met.

(E) procedure of N onmandatory Appendix C shall be used.

Flaw depths up to 100% of wall thickness may be evalu-ated. Flaw depth, a, is defined in Figures C-431 0-1 and C-4310-2. When through-wall circumferential flaws are evaluated in accordance with C-5300 or C-6300, the flaw depth to thickness ratio, a It, shall be set to unity. When applying the Nonmandatory Appendix C screening criter-ia for through-wall axial flaws, a It shall be set to unity, and the reference limit load hoop stress, CJ 1, shall be de-fined as CJ Y I M 2. When through-wall axial flaws are evalu-ated in accordance with C-5400 or C-6400, the allowable length is defined by eqs. (b)(1) through (b)(3), with the appropriate structural factors from Nonmandatory 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-ues for F m' F b, and F applicable to through-wall flaws. Re-lations for F m' F b, 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 F m' F b' and F for a selected range of Rlt. Geometry of a through-wall crack is shown in Figure 1.

3.2 NONPLANAR FLAWS IN STRAIGHT PIPE (a) The evaluation shall consider the depth and extent of the affected area and require that the wall thickness ex-ceed tm in for a distance that is the greater of 2.5 -J Rtnom or 2L m,a vg between adjacent thinned regions, where R is the mean radius of the piping item based on nominal wall thickness and L m, a vg is the average of the extent of L m below tmin for adjacent areas (see Figure 2). Alterna-tively, the adjacent thinned regions shall be considered a single thinned region in the evaluation.

(b) For nonplanar flaws, the pipe is acceptable when either (1) and (2), or (2) and (3) are met.

(1) The remaining pipe thickness, tp, is greater than or equal to the minimum wall thickness t min:

t. -

pDo mm -

2(5 + 0.4p) where p = maximum operating pressure at flaw location S = allowable stress at operating temperature (4)

(2) The remaining degraded pipe section meets the longitudinal stress limits in the design Code for the piping.

(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 and the extent of the affected area as illustrated in Figure

3.

(-b) When Lm{tJ is not greater than (R 0 tmin) 112, taloc is determined from Curve 1 of Figure 4, where Lm{tJ is defined in Figure 3. When the above requirement is not satisfied, (-c) shall be met.

(-c) When L m is less than or equal to 2.65 X (Rotmin) 112 and tnom is greater than 1.13tminJ taloc is determined by satisfying both of the following equations:

taloc l.S.J Ratmin [

tnom]

2:

1 - -- + 1.0 (5) tmin L

tmin taloc > 0.353Lm (6) tmin -.J Ratmin When the above requirements are not satisfied, (-d) shall be met.

(-d) When the requirements of (-a), (-b), and (-c) above are not satisfied, taloc is determined from Curve 2 of Figure 4.

(c) When there is through-wall leakage along a portion of the thinned wall, as illustrated in Figure 5, the flaw may be evaluated by the branch reinforcement method. The thinned area including the through-wall opening shall be represented by a circular penetration at the flaw loca-tion. Only the portion of the flaw lying within tad i need be considered as illustrated in Figure 6. When evaluating multiple flaws in accordance with (a), only the portions of the flaws contained within tadi need be considered.

The minimum wall thickness, tmin' shall be determined by (b)(1), eq. (4). For evaluation purposes, the adjusted wall thickness, tadi' is a postulated thickness as shown in Figure 6. The pipe wall thickness is defined as the thick-ness of the pipe in the non-degraded region as shown in 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-er than tmin and shall not exceed the pipe wall thickness.

The tadi value may be varied between tmin and the pipe wall thickness to determine whether there is a combina-tion of tadi and d adi that satisfies the branch reinforce-ment requirements.

The values of tadi and dadi of Figure 6, illustration (b) shall satisfy:

l.S~Rtadj (tadj-tminJ dadj ::; ---'--------

tmin (7) 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 the degraded area bounded by d adi shall satisfy:

rp tc avg ~ 0.353dadJ. 1-

~

'J s (8)

In addition, the pipe section including the equivalent hole representation shall meet the longitudinal stress lim-its in the design Code for the piping.

If a flaw growth analysis is performed, the growth in flaw dimensions shall consider the degradation mechan-isms as relevant to the application. The flaw is acceptable when there is sufficient thickness in the degraded area to provide the required area reinforcement.

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

The minimum wall thickness tmin* shall be determined by (b)(l), eq. (4). The allowable through-wall lengths in the axial and circumferential directions shall be deter-mined by varying tadi shown in Figure 5 from tnom to tmin* The allowable through-wall flaw lengths based on t a dj shall be greater than or equal to the corresponding Laxial and Lcirc (see Figure 5) as determined from 3.1(a) and 3.1(b) or 3.1(c), as appropriate. The remaining ligament average thickness, tc,a vg* over the degraded area bounded by Laxial and Lcirc shall satisfy (c), eq. (8).

3.3 THROUGH-WALL FLAWS IN ELBOWS AND BENT PIPE Through-wall flaws in elbows and bent pipe may be evaluated using the straight pipe procedures given in 3.1 or 3.2(d), provided the stresses used in the evaluation are adjusted, to account for the geometry differences, as described below. Alternative methods may be used to cal-culate the stresses used in evaluation.

The hoop stress, a h, for elbow and bent pipe evaluation shall be as follows:

a = [PD0I 2Rbend + R0 sincp] + [ 1.95 J R0 Mb (9) h Zt 2(Rbend + R0 sin¢ h2/3 I

where h = flexibility characteristic I = moment of inertia based on evaluation wall thickness, t Mb = resultant primary bending moment Rbend = elbow or bent pipe bend radius

¢ = circumferential angle defined in Figure 7 4 (N-513-4)

CASE (continued)

ASME BPVC.CC.NC-2015 N-513-4 Figure 3 Illustration of Nonplanar Flaw Due to Wall Thinning Axial direction Equation (9) is only applicable for elbows and bent pipe where h ~ 0.1.

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

(10) where Transverse (circumferential) direction The thermal expansion stress, a e* for elbow and bent pipe evaluation shall be as follows:

where (12) stress intensification factor as defined in the design Code for the piping item Me resultant thermal expansion moment (E) 8 1 = primary stress index as defined in Section III for the piping item 3.4 THROUGH-WALL FLAWS IN REDUCERS AND (E)

= 0.5 for elbows and bent pipe The axial bending stress, a b* for elbow and bent pipe evaluation shall be as follows:

(11) where 8 2 = primary stress index as defined in Section III for the piping item EXPANDERS Through-wall flaws in reducers and expanders may be evaluated using the straight pipe procedures given in 3.1 or 3.2(d), provided the stresses used in the evaluation are 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 the reducer and expander zones discussed below. Evalua-tion of flaws in the small end transition zone is outside the 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 c

0.6 J

0

.3 0.4

~

I

~(0

~

~})

/

I /

I I 0.2 0

0 2

3 The hoop stress, CJ h, and axial membrane pressure stress, CJ m, for reducer or expander evaluation shall be as follows:

(13)

(14) where D 0 = small-end O.D. for flaws in the small-end and the large-end O.D. for all other flaws The axial bending stress, CJ b* and thermal expansion stress, CJ e

for reducer or expander evaluation shall be as follows:

(15)

(16) where I = moment of inertia based on degraded section 3.5 THROUGH-WALL FLAWS IN BRANCH TEES Branch reinforcement requirements shall be met in ac-cordance with the design Code. If the design Code did not require reinforcement, for evaluation purposes, a rein-forcement region is defined as a region of radius D i of

~

5 6

7 8

the branch pipe from the center of the branch connection.

Through-wall flaws in branch tees outside of the rein-forcement region may be evaluated using the straight pipe procedures given in 3.1 or 3.2(d), provided the stres-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-inforcement is outside the scope of this Case.

The hoop stress, CJ h, and axial membrane pressure stress, CJ m, for branch tee evaluation shall be determined from eq. 3.4(13) and eq. 3.4(14), respectively. The outside diameter for each of these equations shall be for the branch or run pipe, depending on the flaw location.

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

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

3.6 FLAW GROWTH EVALUATION 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.

In performing a flaw growth analysis, the procedures in Article C-3000 may be used as guidance. Relevant growth rate mechanisms shall be considered. When stress corro-sion cracking (SCC) is active, the following growth rate equation shall be used:

dajdt = SyCK~ax (17) 6 (N-513-4)

CASE (continued)

ASME BPVC.CC.NC-2015 N-513-4 Figure 5 Illustration of Through-Wall Nonplanar Flaw Due to Wall Thinning Through-wall

~-- Laxial ---+!

Axial direction where dajdt is flaw growth rate in inches/hour, Kmax is the maximum stress intensity factor under long-term steady state conditions in ksi in. 0*5, S T is a temperature correction factor, and C and n are material constants.

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

200°F (93°C).

[

1.79 X 10-8 n

2.161 Sr 1

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

200°F (93°C).

[

1.79 X 10-?

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

The temperature, T, is the metal temperature in de-grees Fahrenheit. The flaw growth rate curves for the above SCC growth mechanisms are shown in Figures 9 Transverse (circumferential) direction and 10. Other growth rate parameters in eq. (17) may be used, provided they are supported by appropriate data.

3.7 NONFERROUS MATERIALS For nonferrous materials, nonplanar and planar flaws may be evaluated following the general approach of 3.1 through 3.6. For planar flaws in ductile materials, the ap-proach given for austenitic pipe may be used; otherwise, the approach given for ferritic pipe should be applied.

Structural factors provided in 4 shall be used. It is the re-sponsibility of the evaluator to establish conservative es-timates of strength and fracture toughness for the piping material.

4 ACCEPTANCE CRITERIA Piping containing a circumferential planar flaw is ac-ceptable for temporary service when flaw evaluation pro-vides a margin using the structural factors in 7 (N-513-4)

(E)

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 flaws, the structural factors for temporary acceptance are as specified in Nonmandatory Appendix C, C-2622.

Straight pipe containing a nonplanar part through-wall flaw is acceptable for temporary service if the remaining pipe section meets the longitudinal stress limits in the de-sign Code for the piping and tP :?: taloc* where t aloc is de-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 nonplanar through-wall flaw is acceptable for temporary service if the flaw conditions of 3.3 are satisfied. A redu-cer or expander containing a non planar through-wall flaw is acceptable for temporary service if the flaw conditions of 3.4 are satisfied. A branch tee containing a nonplanar through-wall flaw is acceptable for temporary service if the flaw conditions of 3.5 are satisfied.

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 An augmented volumetric examination or physical measurement to assess degradation of the affected sys-tem shall be performed as follows:

(a) From the engineering evaluation, the most suscepti-ble locations shall be identified. A sample size of at least five of the most susceptible and accessible locations, or, if fewer than five, all susceptible and accessible locations shall be examined within 30 days of detecting the flaw.

(b) When a flaw is detected, an additional sample of the same size as defined in (a) shall be examined.

(c) This process shall be repeated within 15 days for each successive sample, until no significant flaw is de-tected or until 100% of susceptible and accessible loca-tions have been examined.

6 NOMENCLATURE a

81, Bz c

c dajdt dadj Di dmin Do F

flaw depth Section III primary stress indices half crack length coefficient in the crack growth relationship flaw growth rate for stress corrosion cracking diameter equivalent circular hole at tadi inside pipe diameter diameter of equivalent circular hole at t min outside pipe diameter nondimensional stress intensity factor for through-wall axial flaw under hoop stress F b nondimensional stress intensity factor for through-wall circumferential flaw under pipe bending stress F m nondimensional stress intensity factor for through-wall circumferential flaw under mem-brane stress h

flexibility characteristic stress intensification factor I

moment of inertia based on evaluation thick-ness, t Kmax maximum stress intensity factor under long term steady state conditions L

maximum extent of a local thinned area with t

< tnom Laxial length of idealized through-wall planar flaw opening in the axial direction of the pipe, as il-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 Lm maximum extent of a local thinned area with Lm{a)

Lm{t)

Lm,avg n

t < tmin axial extent of wall thinning below t min circumferential extent of wall thinning below tmin average of the extent of L m below tmin for ad-jacent thinned areas maximum extent of thinned area, i bulging factor for axial flaw resultant primary bending moment resultant thermal expansion moment exponent in the crack growth relationship 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

//

.... s c

/

t

~

i 1.0 E- 05 co v

/

/v c::

..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 MPa m 0*5 ; oc = [°F - 32]/1.8).

maximum operating pressure at flaw location mean pipe radius elbow or bent pipe centerline bend radius outside pipe radius allowable stress at operating temperature structural factor on primary membrane stress coefficient for temperature dependence in the crack growth relationship Code-specified ultimate tensile strength Code-specified yield strength metal temperature evaluation wall thickness, surrounding the de-graded area t a dj t a l o c t c,avg 10 (N-513-4)

= adjusted wall thickness which is varied for eva-luation purposes in the evaluation of a through-wall non planar flaw allowable local thickness for a nonplanar flaw average remaining wall thickness covering de-graded area with through-wall leak bounded by d a dj minimum wall thickness required for pressure loading nominal wall thickness minimum remaining wall thickness maximum extent of a local thinned area per-pendicular to Lm with t < tmin

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 1.0 E-03 T s 200°F

//

/

v 1.0 E-04

./

/

s

/

c t

1.0 E- 05

~

i co c:

/'

v

~

T 200°F

./

/

..c

~

1.0 E- 06 2

/

I T = 100°F I

(.9

..lo:

(.)

co

./

/

u

/

~"

1.0 E- 07

//

./

/

v 1.0 E-08

./

/

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 m0*5 ; oc = [°F - 32]/1.8).

Xi,J minimum distance between thinned areas i and}

Z load multiplier for ductile flaw extension

-1! = total crack length = 2c

-1! all allowable axial through-wall flaw length ct>

circumferential angle from elbow or bend flank a

maximum cone angle at the center of a reducer 8

half crack angle for through-wall circumferen-tial flaw A = nondimensional half crack length for through-wall axial flaw a b axial bending stress for primary loading a e axial thermal expansion stress a 1 = material flow stress a h pipe hoop stress due to pressure and bending moment (for elbows and bent pipe) a 1 reference limit load hoop stress am axial pressure stress a y material yield strength at temperature, as de-fined in C-4300 7 APPLICABILITY Reference to Nonmandatory Appendix C in this Case shall apply to Nonmandatory Appendix C of the 2004 Edi-tion or later editions or addenda. For editions or addenda 11 (N-513-4)

CASE (continued)

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

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 1-1 DEFINITIONS For through-wall flaws, the crack depth, a, will be re-placed with half crack length, c, in the stress intensity fac-tor equations in C-7300 and C-7400 of Section XI, Nonmandatory Appendix C. Also, Q will be set equal to unity in C-7 400.

1-2 CIRCUMFERENTIAL FLAWS For a range of R It between 5 and 20, the following equations for F m and F b may be used:

where Am = -2.02917 + 1.67763 (Rit)- 0.07987 (Rit) 2 +

0.00176 (Rit) 3 Bm = 7.09987-4.42394 (Rit) + 0.21036 (Rit) 2 -

0.00463 (Rit) 3 Cm = 7.79661 + 5.16676 (Rit)- 0.24577 (Rit) 2 +

0.00541 (Rit) 3 where Ab = -3.26543 + 1.52784 (Rit) - 0.072698 (Rfti +

0.0016011 (Rit) 3 Bb = 11.36322-3.91412 (Rit) + 0.18619 (Rit) 2 -

0.004099 (Rit) 3 Cb = -3.18609 + 3.84763 (Rit)- 0.18304 (Rit) 2 +

0.00403 (Rit) 3 In the above equations:

R = mean pipe radius t = evaluation wall thickness 8 = half crack angle = c I R Equations for F m and F b are accurate for R It between 5 and 20 and become increasingly conservative for Rlt greater than 20. Alternative solutions for F m and F b may be used when Rjt is greater than 20.

1-3 AXIAL FLAWS For internal pressure loading, the following equation for F may be used:

F = 1 + 0.072449.A + 0.64856.A2 -

0.2327.A3 + 0.038154.A4 o.0023487.A5 where c = half crack length A = ci(Rt) 112 The equation for F is accurate for A between 0 and 5.

Alternative solutions for F may be used when A is greater than 5.

13 (N-513-4)

&152

5(/,()5(48(67(155

(1&/2685(2)$77$&+0(17

7HFKQLFDO%DVLVIRU3URSRVHG)RXUWK5HYLVLRQWR$60(

&RGH&DVH1

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 ABSTRACT Robert 0. McGill Structural Integrity Associates San Jose, CA rmcgill@structint.com Russell C. Cipolla lntertek AIM Sunnyvale, CA russell.cipolla@intertek.com Code Case N-513 provides evaluation rules and criteria for temporary acceptance of flaws, including through-wall flaws, in moderate energy piping. The application of the Code Case is restricted to moderate energy, Class 2 and 3 systems, so that safety issues regarding short-term, degraded system operation are minimized. The first version of the Code Case was published in 1997. Since then, there have been three revisions to augment and clarify the evaluation requirements and acceptance criteria of the Code Case that have been published by ASME. The technical bases for the original version of the Code Case and the three revisions have been previously published.

There is currently work underway to incorporate additional changes to the Code Case and this paper provides the technical basis for the changes proposed in a fourth revision. These changes include addressing the current condition on the Code Case acceptance by the US Nuclear Regulatory Commission (NRC), clarification of the Code Case applicability limits and expansion of Code Case scope to additional piping components. New flaw evaluation procedures are given for through-wall flaws in elbows, bent pipe, reducers, expanders and branch tees. These procedures evaluate flaws in the piping components as if in straight pipe by adjusting hoop and axial stresses to account for the geometry differences. These changes and their technical bases are described in this paper.

NOMENCLATURE B 1, B 2 Primary stress index defined in ASME Section III for the piping item D a Outside diameter I

Moment of inertia based on t (degraded section)

Mb Resultant primary bending moment p

Guy DeBoo Exelon Generation Company Warrenville, IL guy.deboo@exeloncorp.com Eric J. Houston Structural Integrity Associates San Jose, CA ehouston@structint.com Resultant thermal expansion moment Elbow or bent pipe bend radius Outside radius Flexibility characteristic Stress intensification factor as defined in the Code of Record for the piping item Maximum operating pressure at flaw location Evaluation thickness Axial bending stress Thermal expansion stress Hoop stress Axial membrane stress Circumferential angle INTRODUCTION

Background

Code Case N-513-3 [1] (currently approved revision) provides evaluation rules and criteria for the temporary acceptance of flaws, including through-wall flaws, in moderate energy piping. The provisions of this Code Case are focused on preventing gross failure of the affected pipe for a temporary period. However, it also requires the piping system and adjacent equipment functionality be demonstrated for lost fluid inventory, spraying and flooding caused by the leakage.

The Code Case provides rules for the evaluation of degraded pipe and tube for a short operating period, with inspection and monitoring requirements of the degraded condition as part of the overall integrity assessment. The application of the Code Case is restricted to moderate energy Class 2 and Class 3 systems, so that the safety issues regarding short-term system operation are minimized. Moderate energy piping is defined as those piping systems where the maximum operating pressure and temperature do not exceed 275 psig (1.9 MPa) and 200°F (93°C), respectively.

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. There have been many instances where through-wallleaks have been observed in pipe components (i.e.,

elbows, reducers, expanders or branch tees) or bent pipe outside of the current Code Case scope. As a result, utilities are forced into taking alternate actions (e.g., repair, replacement, or making requests for NRC relief) that can be significantly more burdensome without any measurable increase in plant safety. The fourth revision of the Code Case provides evaluation rules and criteria for the temporary acceptance of flaws for these instances. In addition, other enhancements are included with the fourth revision as summarized below.

Summary of Code Case N-513-4 Changes The list below summarizes the proposed changes included in Revision 4 of Code Case N-513. Note that a brief reason for each change is included in parenthesis.

Temporary acceptance period redefined (addresses NRC condition given in Regulatory Guide 1.147 [2])

Flaw evaluation criteria included for elbows, bent pipe, reducers, expanders and branch tees (scope expansion)

Allow flaw evaluation of heat exchanger tubing in specific instances (scope expansion)

Daily walkdown requirement for through-wall leaks provides additional flexibility for user implementation (scope expansion)

Limit scope to only liquid systems (scope clarification)

Treatment of Service Level load combinations (scope clarification)

Treatment of flaws in austenitic pipe flux welds (scope clarification)

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

In addition, several editorial changes to improve the clarity of the Code Case are included.

CODE CASE N-513-4 CHANGES AND TECHNICAL BASIS The following subsections provide details regarding each change and their technical basis.

Temporary Acceptance Period N-513-3 specifies a temporary acceptance period that could extent out to 26 months. The NRC did not endorse this maximum period length and in the latest revision of NRC Regulatory Guide 1.147, placed a condition on N-513-3 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 addresses this condition by removing the maximum duration limit and stating,"... the following requirements may be used 2

to accept flaws... without performing a repair/replacement activity for a limited time, not exceeding the time to the next scheduled refueling outage." Note that the word "refueling" has been added for further clarification regarding the nature and duration of the plant outage.

This language is consistent with the introduction ofNRC Generic Letter 90-05 [3] which the original N -513 was based.

The second paragraph of90-05 states: "Temporary non-code repairs are applicable until the next scheduled outage exceeding 30 days, but no later than the next scheduled refueling outage."

Flaw Evaluation Criteria for Piping Components and Bent Pipe Evaluation and acceptance criteria have been added toN-513-4 for flaws in elbows, bent pipe, reducers, expanders and branch tees. A simplified approach has been adopted based on the evaluations and results from the Second International Piping Integrity Research Group (IPIRG-2) program reported in Reference [ 4]. The flaw evaluation for the piping component is conducted as if in straight pipe by scaling hoop and axial stresses using ASME piping design code stress indices and stress intensification factors to account for the stress variations caused by the geometric differences. In Reference [ 4], this approach was determined to be very conservative by comparing the failure moments predicted using this approach to the measured failure moments from the elbow tests for through-wall circumferential flaws. Details of the simplified approach are given in the following sections.

Flaw Evaluation in Elbows and Bent Pipe. Through-wall flaws in elbows and bent pipe may be evaluated using the straight pipe procedures given in N-513-4 provided the stresses used in the evaluation are adjusted to account for geometry differences. The hoop stress for elbow and bent pipe evaluation shall be (Equation 9 ofN-513-4):

(]" = (pDa J[ 2Rbend + Ra sin¢ ] +(1.95] RaMb (9) h 2t 2(Rbend + Ra sin¢)

h 213 I

Equation 9 is only applicable for elbows and bent pipe where h 2: 0.1.

The axial membrane pressure stress for elbow and bent pipe evaluation shall be (Equation 10 ofN-513-4):

(]" =B(pDoJ m

I 2t B1 shall be equal to 0.5 for elbows and bent pipe.

The axial bending stress for elbow and bent pipe evaluation shall be (Equation 11 ofN-513-4):

(]" = B (RaMb J b

2 I

(10)

(11)

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.

The thermal expansion stress for elbow and bent pipe evaluation shall be (Equation 12 ofN-513-4):

u. = { R"~" )

(12)

The first term of Equation 9 accounts for the hoop membrane stress variation around the circumference of the elbow (higher at the intrados, lower at the extrados assuming a uniform wall thickness). The second term conservatively accounts for the through-wall bending in the hoop direction that results from elbow ovalization due to in-plane or out-of-plane bending and was taken from Reference [ 5]. Equations 10-12 are consistent with the piping design by rule approach in ASME Section III, NC/ND-3600 [6].

It is recognized in Reference [ 4] that the simplified flaw evaluation approach may be overly conservative in some instances. Thus, N-513-4 allows for alternate methods to be used to calculate stresses used in the flaw evaluation. For example, the French have developed a more comprehensive approach in analyzing flaws in cracked elbows. They have implemented finite element analysis based correlations to determine location specific stresses for flaw evaluation.

Reference [7] provides additional details.

Flaw Evaluation in Reducers and Expanders. Through-wall flaws in reducers and expanders may be evaluated using the straight pipe procedures given in N-513-4 provided the stresses used in the evaluation are adjusted to account for the geometry differences. Figure 8 ofN-513-4 illustrates the reducer and expander zones discussed below. Evaluation of flaws in the small end transition zone is outside the scope of N-513-4. The hoop stress and axial membrane pressure stress for reducer and expander evaluation shall be:

CY =(pDa) h 2t (13)

CY

= B (pDo) m I

2t (14)

Note that Do is either the small end OD for the small end or is the large end 0 D for the large end. For the large end transition zone and central conical section, Do is the large end OD. Also, if the piping design Code of Record does not provide a B1, it may be taken from the ASME Section III, 2004 Edition or later Editions and Addenda.

The axial bending stress and thermal expansion stress for reducer and expander evaluation shall be:

CY =B (DaMb) b 2

21 (15) 3 (J = i(DoMe) e 21 (16)

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 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.

Flaw Evaluation in Branch Tees. Branch reinforcement requirements shall be met in accordance with the Construction Code. If the Construction Code did not require reinforcement, a reinforcement region is defined as a region of radius Di of the branch pipe from the center of the branch connection for evaluation purposes. Through-wall flaws in branch tees outside of the reinforcement region may be evaluated using the straight pipe procedures given in N-513-4 provided the stresses used in the evaluation are adjusted as described below to account for the geometry differences. Evaluation of flaws in the region of branch reinforcement is outside the scope of this Case.

The hoop stress and axial membrane pressure stress for branch tee evaluation shall be determined from N-513-4 Equation 13 and 14, respectively. The outside diameter for each of these equations shall be for either the branch or run pipe depending on the flaw location. The axial bending stress and thermal expansion stress for branch tee evaluation shall be determined from N-513-4 Equation 15 and 16, respectively.

As discussed previously, Equations 13-16 are consistent with the piping design by rule approach in ASME Section III.

The limitation regarding flaw evaluation within the branch reinforcement region is consistent with guidance given in Code Case N-597-2. As with elbows and bent pipe, N-513-4 allows for alternate methods to be used to calculate stresses used in the flaw evaluation.

Flaw Evaluation of Heat Exchanger Tubing 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 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 tubing of air cooling coils. The heat exchangers being of plate-fin design could have tubing accessible for volumetric inspection.

Flexibility in Daily Walkdown Requirement N-513-4 changes the daily walkdown requirement for leaking flaws from"... leakage shall be observed by daily 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 walkdowns. Such techniques could include remote visual 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 leakage rates are changing.

Scope Limited to Liquid Systems Provisions ofN-513-4 are now specifically limited to only liquid systems. The methods ofN-513-4 should not be applied to the piping of air or other compressible fluid systems.

Treatment of Service Level Load Combinations N-513-4 now specifically requires all Service Level load combinations to be considered in flaw evaluations to determine the most limiting. N-513-3 was previously silent as to what Service Level loading to consider. However, this requirement was implied in previous Code Case revisions when it required the use of pipe flaw evaluation procedures specified in the referenced, non-mandatory appendices of ASME Section XI. Appendix C in the 2002 Addenda and later editions and addenda, and Appendix H for ferritic materials in earlier editions, required all operating conditions or Service Levels be evaluated.

Treatment of Flaws in Austenitic Pipe Flux Welds A reference to ASME Section XI, Appendix C, C-6320 has been added to paragraph 3.1 (b) to address the instance where a flaw in an austenitic pipe flux weld requires evaluation. Such a flaw would require the use of Elastic Plastic Fracture Mechanics (EPFM) criteria instead of Limit Load criteria. Equation 1 ofN-513-4 now includes a Z factor to account for this specific application.

When the original version ofN-513 was developed, Appendix C of ASME Section XI only included flaw evaluation criteria for austenitic piping. The change from N-513-1 to -2 included the reference changes to the new Appendix C that combined austenitic and ferritic flaw evaluation criteria. The need to reference EPFM criteria for an austenitic flux weld flaw evaluation was overlooked.

Minimum Wall Thickness Acceptance Criteria In establishing a minimum wall thickness acceptance criteria for paragraphs 3.2(b) and 3.2 (c) ofN-513-4, the requirement to consider longitudinal stresses in addition to hoop stress is added. While it is unlikely that a longitudinal stress based minimum wall thickness would be limiting compared to the hoop stress based minimum wall thickness, the user should be aware of this possibility and confirm an appropriate tmin as an acceptance criterion.

CONCLUSIONS 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

and branch tees. In addition, several other scope expansions and clarifications are included as well as editorial improvements. With these changes, it is believed the Code Case will be of even greater use to utilities in avoiding unscheduled plant shutdowns without negatively impacting plant safety.

ACKNOWLEDGEMENTS The development of Code Case N-513-4 was through the efforts of the Working Group on Pipe Flaw Evaluation. The authors wish to recognize the efforts of all Working Group members especially the Working Group Chair, Dr. Doug Scarth.

REFERENCES

1.

ASME Code Case N-513-3, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1," Cases of the ASME Boiler and Pressure Vessel Code, January 26,2009.

2.

Regulatory Guide 1.14 7, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1,"

Revision 16, October 2010.

3.

NRC Generic Letter 90-05, "Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping," (June 15, 1990).

4.

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

Olson, R., Scott, P., Brust, F., Ghadiali, N.,

Wilkowski, G., and Hopper, A., "Fracture Behavior of Circumferentially Surface-Cracked Elbows,"

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

5.

Moore, S.E., and Rodabaugh, E.C., "Background for Changes in the 1981 Edition of the ASME Nuclear Power Plant Components Code for Controlling Primary Loads in Piping Systems," Journal of Pressure Vessel Technology, Volume 104, pp. 351 -

361, November 1982.

6.

ASME Boiler and Pressure Vessel Code,Section III, NC/ND-3600, 2004 Edition.

7.

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

Drubay, B., Barthelet, B., Le-Delliou, P., Rougier, V., Naudin, C., Gilles, P., and Triay, M., "French RSE-M and RCC-MR Code Appendices for Flaw Analysis: Presentation of the Fracture Parameters Calculation-Part IV: Cracked Elbow," International Journal of Pressure Vessels and Piping 84, pp. 659-686, May 2007.

8.

ASME Code Case N-597-2, "Requirements for Analytical Evaluation of Pipe Wall Thinning,Section XI, Division 1," Cases of the ASME Boiler and Pressure Vessel Code, November 18, 2003.

v t e Letter Sequence Request
EPID:L-2017-LLR-0141, 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 (Open)
Initiation Request Acceptance Administration Questions Answers Results Approval Other:
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

Text

SUBJECT:

Dear Sir or Madam:

Attachment:

Background

Navigation menu

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

Text

SUBJECT:

Dear Sir or Madam:

Attachment:

Background

Navigation menu

Search