ML19101A293

Relief Request RR-4-22, Request for Alternative to Implement Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping.

ML19101A293
Person / Time
Site:	Summer
Issue date:	04/10/2019
From:	Lippard G South Carolina Electric & Gas Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
19-181
Download: ML19101A293 (34)

Text

A SCANA COMPANY April 10, 2019 U. S. Nuclear Regulatory Commission Serial No.19-181 Attention: Document Control Desk VCS LIC/HK/Rev 0 Washington, DC 20555 Docket No. 50-395 License No. NPF-12 Page 1 of 2 SOUTH CAROLINA ELECTRIC & GAS COMPANY VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 RELIEF REQUEST RR-4-22, REQUEST FOR ALTERNATIVE TO IMPLEMENT CODE CASE N-513-4, "EVALUATION CRITERIA FOR TEMPORARY ACCEPTANCE OF FLAWS IN MODERATE ENERGY CLASS 2 OR 3 PIPING" In accordance with the provisions of 10 CFR 50.55a(z)(2), South Carolina Electric & Gas Company (SCE&G), acting for itself and as an agent for South Carolina Public Service Authority (Santee Cooper) requests an emergency relief request to use Code Case N-513-4, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1" for the temporary acceptance of a through-wall leak identified in a Class 3 Service Water branch tee.

SCE&G is requesting this relief until the conclusion of the Virgil C. Summer Nuclear Station (VCSNS), Unit 1 Spring 2020 refueling outage (RF-25). The repair will be implemented no later than the completion of RF-25 or before exceeding the temporary acceptance criteria specified in this relief request, whichever comes first.

On April 9, 2019, at approximately 02:00, a pinhole leak was discovered in the Service Water (SW) system on the branch tee connection below field weld FW-1, downstream of XVB03123B-SW - Component Cooling Water (CC) Heat Exchanger B SW Return Valve. SCE&G requests the use of Code Case N-513-4 for the analysis of this branch tee connection to allow continued operation.

Enclosed is the relief request.

SCE&G requests NRC approval of the proposed alternative by close of business on April 11, 2019.

Should you have any questions, please call Michael Moore at 803-345-4752.

V. C. Summer Nuclear Station, P. 0. Box 88, Jenkinsville, South Carolina, 29065

• F(803) 941-9776

• www.sceg.com

Serial No.19-181 Docket No. 50-395 Page 2 of 2 Sincerely, V.C. Summer Nuclear Station Commitments contained in this Jetter: None

Enclosures:

1) VCSNS Relief Request RR-4-22

2) Design Calculation SW002/05

3) Design Agent's Qualification Letter cc:

C. Haney S. A. Williams NRC Resident Inspector G. J. Lindamood S. E. Jenkins

Serial No.19-181 Enclosure 1 Page 1 of6 South Carolina Electric & Gas Co. (SCE&G)

Virgil C. Summer Nuclear Station Unit 1 (VCSNS)

Relief Request RR-4-22

1. ASME Code Component(s) Affected A pinhole leak was identified in the Service Water (SW) System branch tee located in the 20-inch diameter piping downstream of the 'B' Component Cooling Water (CC) Heat Exchanger B SW Return Valve (XVB03123sB-SW) below field weld FW-1. The affected piping provides a return path for the safety related cooling water from the 'B' Component Cooling Water Heat Exchanger back to the SW Pond. This Moderate Energy (ME) piping is designed to ASME Section Ill Sub-Section ND (Code Class 3) criteria and is required to meet all ASME requirements (TS 4.0.5).

The branch tee material is SA-234 WPB.

2. Applicable Code Edition and Addenda ASME Code Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components,"

2007 Edition through 2008 Addenda. The station is in its 4th 10 year interval effective from January 1, 2014, through and including December 31, 2023.

3. Applicable Code Requirement ASME Code Section XI, 2007 Edition through 2008 Addenda, Article IWA-4000, Repair/Replacement Activities.

4. Reason for Request On April 9, 2019, at approximately 02:00, a pinhole leak was discovered in a branch connection below field weld FW-1, downstream of XVB03123B-SW. At the time of discovery, leakage was estimated to be approximately 7 ml/minute (0.0018 gpm). This leaking location does not meet ASME Section Ill Sub-Section ND Class 3 requirements because it is a localized flaw that violates the minimum allowed wall thickness criteria for this piping. This degraded condition is not in compliance with ASME Section XI, 2007 Edition through 2008 Addenda, IWA-4000.

As a result, a number of limiting conditions for operation (LCOs) of the plant technical specifications are not met, including, but not limited to, LCO 3.7.4, "Service Water System". The action statement requires that with only one SW loop OPERABLE, restore at least two loops to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

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," provides criteria to allow temporary acceptance of flaws, including through-wall flaws in moderate energy Class 2 or 3 piping without performing repair or replacement activities. Code Case N-513-3, (Revision 3, January 26, 2009) is approved for generic use by licensees in Nuclear Regulatory Commission (NRC) Regulatory Guide 1.147, "lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1, Revision 18" (ADAMS Accession No. ML16321A336), with the condition that the repair or replacement activity be temporarily deferred under the provisions of this Code Case shall be performed during the next scheduled outage.

ASME Code Case N-513-3 does not address the evaluation of flaws in certain locations of moderate energy piping components, such as elbows, bent pipe, reducers, expanders, and branch tees. ASME Code Case N-513-4, "Evaluation Criteria for Temporary Acceptance of Flaws

Serial No.19-181 Enclosure 1 Page 2 of 6 in Moderate Energy Class 2 or 3 Piping ,Section XI, Division 1," (Revision 4, May 7, 2014) contains several revisions to ASME Code Case N-513-3 including expanding the applicability of the Code Case beyond straight pipe to include elbows, bent pipe, reducers, expanders, and branch tees .

ASM E Code Case N-513-4, Reference 4, has not been approved by the NRC for generic use by licensees. Use of ASME Code Case N-513-4 is proposed to allow temporary acceptance of the through-wall flaw, which is in a moderate energy Class 3 piping branch tee without performing repair or replacement activities, and thereby avoid a plant shutdown . Use of this alternative evaluation method in lieu of immediate action for such a degraded condition would allow time for safe and orderly long-term repair actions.

Code repair is considered a hardship without a compensating increase in the level of quality and safety. A Code repair would require a plant shutdown . The branch tee is located between valve XVB03123B-SW and the SW pond. The piping cannot be isolated from other portions of the SW system.

Plant shutdown activities result in additional plant risk. Such a shutdown would be inappropriate when an affected ASME Code component in a degraded condition is demonstrated to retain adequate margin to fulfill the component's function. Accordingly, compliance with the current code requirements results in a hardship without a compensating increase in the level of quality and safety.

5. Proposed Alternative and Basis for Use In accordance with 10 CFR 50.55a(g)(4), this safety-related piping must meet the requirements applicable to components which are classified as ASME Code Class 3. V.C . Summer proposes a relief request from ASME Code Section XI, IWA 4000 by using the methodology described in Code Case N-513-4 for temporary acceptance of flaws. V.C. Summer will follow all requirements of the Code Case and will take no exceptions. This relief request is not valid if the total leakage rate exceeds 51.7 gpm.

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 allows temporary 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 considering effects of 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 approved by the ASME to expand it for use at these locations and to revise several other areas of the Code Case.

Significant changes in Code Case N-513-4 when compared to NRC approved Code Case N-513-3 are discussed in Reference 5, "Technical Basis for Proposed Fourth Revision to ASME Code Case N-513." to this letter contains the evaluation of the acceptability of the through-wall leak using the UT inspection results. The UT inspection results were obtained by a Quality Control inspector who was qualified as a UT Level II inspector. In addition, Enclosure 3 to this letter contains the evaluation for the acceptability of the PMCap adjacent to the thinned region around the discovered pinhole leak. This PMCap was installed during the previous refueling outage in the fall of 2018 to repair previously identified thin wall areas and pinhole leaks within the subject tee fitting.

Serial No.19-181 Enclosure 1 Page 3 of6 A flaw evaluation using the "Through-Wall Flaws in Branch Tees" approach from Code Case N-513-4 determined the flaw was acceptable in its current configuration . The observed pinhole leak was determined to be a non-planar through-wall leak with a surrounding thinned region . Per Code Case N-513-4, the non-planar through-wall flaw is allowed to be evaluated as two independent planar through-wall flaws, one in the axial direction, and one in the circumferential direction. The Code Case evaluation contained in Enclosure 2 conservatively assumes a degraded area of 8 inches axially and 2.5 inches circumferentially (from run pipe) in which the entire area is assumed to be a through-wall flaw. This is conservative as only a small pinhole leak has currently formed.

The pinhole was also demonstrated to be outside the area of reinforcement of both the branch run of the tee and the PMCap. Note that for conservatism the stress allowables from the ASME Section Ill Code of Record (1971 with Summer 1973 Addenda) were used in the Code Case evaluation, whereas use of a newer code year would provide additional margin .

The two independent planar flaws were evaluated based on the acceptance criteria of ASME Section XI, Appendix C, Linear Elastic Fracture Mechanics (LEFM) which conservatively assumes brittle fracture as the failure mechanism. The LEFM evaluation utilized a reasonable lower bound fracture toughness of K1c=95.9 ksi-in°* 5 for the carbon steel tee based on the operating temperature of the Service Water System. The results of the LEFM evaluation demonstrated that a through-wall flaw in the axial direction up to 21 inches meets the acceptance criteria of ASME Section XI. Similarly, a through-wall flaw in the circumferential direction up to 2.7 inches meets the acceptance criteria of ASME Section XI. Therefore, the assumed through-wall flaw with an area of 8 inches axially and 2.5 inches circumferentially meets the acceptance criteria of Code Case N-513-4.

In addition to the LEFM evaluation, Code Case N-513-4, Paragraph 3.2(c) also requires that the remaining ligament average thickness over the degraded area be sufficient to resist pressure blowout. Per Enclosure 2 the required average ligament thickness for a 5 inch diameter is 0.06 inch, which is bounded by the observed thinning. Further degradation is acceptable as long as the average thickness of the remaining material outside the hole is greater than 0.06 inch within a diameter of 5 inches of the hole. The thinned area will be reexamined monthly according to the Code Case requirements and the inspection results will be compared to the Code Case evaluation to ensure the evaluation remains bounding .

Additional evaluations were performed to consider the effects of leakage in demonstrating system operability and flooding analysis. A compensatory action of daily walkdowns of the area will be completed to quantify the leakage. UT examinations of no more than 30-day intervals will be performed around the degraded area to characterize flaw growth. The monitoring plan will remain in place until the system is removed from service and repaired . A code compliant repair will be completed during the next refueling outage which is scheduled for the spring of 2020.

5.1 Flaw Characterization : The flaw was characterized by ultrasonic inspection (UT) under WO# 1907703-001. The UT inspection found a thin area around the pinhole, which is bounded by a degraded area of approximately 8 inches axially and 2.5 inches circumferentially. The flaw has been classified as non-planar through-wall and no evidence was found to indicate a "crack" type indication.

5.2 Structural Integrity: Per VCSNS Unit 1 Technical Specification (TS) 4.0.5, the structural integrity of an ASME component is determined in accordance with either the original construction code or the ASME Section XI Code, approved Code Cases or regulatory-approved methods of evaluation . No NRC approved methodology exists that allows for temporary acceptance of flaws or non-welded repairs for this condition. A flaw evaluation

Serial No.19-181 Enclosure 1 Page 4 of 6 using the "Through-Wall Flaws in Branch Tees" approach from Code Case N-513-4 determined the flaw was acceptable in its current configuration.

Design Calculation SW002/05 Rev. 1 was conducted to evaluate the acceptability of the through-wall leak. The evaluation results show the existing defect is structurally acceptable per Code Case N-513-4. Design Calculation SW002/05 Rev. 1 conservatively assumed a through-wall leak that encompassed the thinned region adjacent to the pinhole leak. Further degradation is acceptable if the measured values remain within the evaluated criteria.

5.3 SW System Flow Margin: The pinhole leak is located downstream of the 'B' Component Cooling Water Heat Exchangers downstream of the discharge valve XVB03123B-SW on the discharge line to the SW pond. Therefore, a leak at this location does not affect the ability to provide cooling water to the CC Heat Exchangers. The inlet and discharge valves XVB03122B-SW and XVB03123B-SW are routinely manipulated in support of heat exchanger backflush activities. The valves are returned to the approximate normal operating position (XVB03122B-SW full open and XVB03123B-SW throttled) to maintain the required CC Heat Exchanger design flow range.

The SW pump is designed to supply 16,800 gpm of flow. A flow of 51 .7 gpm from the leakage would not have a significant effect on the performance of the pump. A recent routine code check valve test from STP-230.006J , "Service Water System Refuel Frequency Testing of XVC03130A-SW, XVC03130B-SW, XVC03115A-SW, XVC03115B-SW, AND XVC03115C-SW', on the SW 'B' Train measured the total system flow to be 13,036 gpm (STTS# 1711400). The design minimum required post-accident flow for a train of SW is 12,237 gpm (SW DBD). This check valve testing alignment is comparable to the post-accident SW system alignment. Therefore, there is a flow margin of approximately of 799 gpm. A postulated leakage of 51 .7 gpm would not adversely affect SW system flow margin .

This is a conservative approach since the 51.7 gpm leak would be located downstream of all cool ing loads and throttle valves. Therefore, it would have an insignificant effect on cooling load flow.

The SW pond contains approximately 38.5 x 106 gallons of water and has the capability of being filled by a cross-tie valve from the circulating water system if water level drops below the alarm limit. A postulated leak of 51.7 gpm would not significantly affect the SW pond level.

5.4 Spray Effects: The current stream from the pinhole leak is directed toward the middle of the Intermediate Building (18) 412' room and is spraying at a distance of approximately 3 feet.

There is no equipment in the spray path that would be impacted by the leakage. From visual observation , the closest equipment in the path of the spray is RML0002A (liquid rad monitor, component cooling) , located approximately 20 feet away from the pinhole leak. At the current diameter opening , the spray cannot reach RML0002A and if the pinhole were to further develop, the spray would travel an even shorter distance. Furthermore, the Radiation Monitor is raised above the 18 floor which would prevent potential impacts from spray pooling .

5.5 Building Flooding : Calculation DC03490-003 Rev 1 provides the Intermediate Building flood ing evaluation . The design margin for flooding in the Intermediate Build ing 412' is 271 gpm leakage for the Service Water System. When a safety factor of 4 is applied to the total margin of 271 gpm, the maximum allowable leak rate is 67.75 gpm. The Relief Request, for conservatism, is not valid for total leakage exceeding 51 .7 gpm for all flaws and will require

Serial No.19-181 Enclosure 1 Page 5 of6 reevaluation. Daily monitoring and periodic UTs will be performed to monitor the leakage and flaws.

5.6 Ongoing Mitigation Efforts: Through the application of ASME Code Case N-513-4 for previous flaws on both 'A' and 'B' trains of SW Return from the CCW Heat Exchanger, a majority of the 'B' pipe tee was ultrasonically inspected between June and October of 2018.

For each flaw on the 'B' Train, half inch spacing was used local to the flaw, as well as a circumferential scan in the plane of each flaw. UT readings around the flaw and Code Case N-513-4 requirements would dictate how far the examination extended past the immediate area (nominally 3 inch diameter around flaw). Circumferential scans were taken by qualified UT personnel in such a way that readings below nominal wall thickness would be recorded.

There were no low readings found during circumferential UT measurements that required further analysis of the area. It should be noted that the current flaw location was not directly examined as a part of the volumetric inspections.

PMCaps, an ASME Code approved repair, were installed on both 'A' and 'B' train based on NOE and flaw characterization information for each train as a permanent repair strategy to encompass the degraded regions. The work that was performed during RF-24 involved cutting out the flawed area, performing UT measurements around the cut-out area, visually inspecting the inside of the pipe through the cut-out area (borescope inspection), installing an erosion plate over the cut-out area, and then installing the PM Cap over the erosion plate.

The area that was cut out for 'B' train was roughly 2.5 inches by 6 inches. The ultrasonically tested area extended 4 inches above and below the cut-out, 5.5 inches to the left, and 2.5 inches to the right of the cut-out. These UTs were performed in one-half inch grid spacing, and no additional flaw zones were noted. The visual inspection did not indicate obvious signs of additional wear zones. After identification of the current leak additional review of borescope inspection from RF-24, indicated a wear area in the vicinity of the leak. Following the visual inspection, the erosion plate and the PMCap were installed and appropriate NOE was performed on welds and plate to verify proper integrity. Yearly repetitive tasks were established for UT examinations in a 3 inch band around the PMCaps. First time performance is scheduled for September 2019.

A Plant Issue Management team was formed in the summer of 2018 as a result of the SW leakage. This team typically meets weekly to address the causes of the SW system leakage.

This includes actions to address chemical addition strategies and CCW HX inleUoutlet throttling to address cavitation concerns. In parallel, a troubleshooting plan was developed to throttle the CCW HX inlet/outlet butterfly valves in a manner such that cavitation is reduced or eliminated. The degradation mechanism has been determined to be cavitation induced erosion/corrosion based on independent causal evaluation and metallurgical analysis of removed samples. In addition, cavitation is audible downstream of the throttled butterfly valves. Troubleshooting performance is currently scheduled for May 2019. The results will be used to evaluate permanent corrective actions going forward.

5.7 Extent of Condition: An Augmented Examination will be performed in accordance with Section 5.0 of Code Case N-513-4.

5.8 Compensatory Monitoring Plan:

• Leakage quantification to be performed daily

• NOE flaw characterization every 30-days

• Augmented examination for extent of condition

• Perform comprehensive UT scans of affected SW branch tees within 90-days

Serial No.19-181 Enclosure 1 Page 6 of 6 5.9 Conclusion : Although the structural integrity of the degraded pipe cannot be demonstrated in accordance with a regulatory-approved methodology, it is concluded that the integrity and functional requirements of the pipe will be maintained. SW will continue to be capable of providing required cooling water flow to meet the required cooling loads including the Component Cooling Water Heat Exchangers. There will be no adverse impact on neighboring equipment due to either spray or flooding .

VCSNS will implement the compensatory monitoring plan above to ensure any growth of the flaw is identified and assessed for its impact on structural integrity. A code compliant repair will be completed during the next refueling outage which is scheduled for the spring of 2020.

6. Duration of Proposed Alternative:

A code compliant repair will be performed no later than the completion of the next refueling outage which is scheduled for the spring of 2020.

7. Precedents:

There have been several submittals approved for N-513-4 in specific applications. The table below lists several Safety Evaluation Reports as precedents for use of Code Case N-513-4.

SER Accession No Plant Application Additional Requirement ML18296A111 V. C. Summer Leaking Branch Tee 50 .3 qpm leakage limit ML17270A030 Perrv Leakinq Elbow None ML15070A428 ANO Leaking Sweepolet 5 gpm leakage limit ML14231B310 Fort Calhoun Leaking Elbow None ML14335A551 Peach Bottom Leakinq Elbow 5 qpm leakaqe limit

8.

References:

1. ASME Code Section XI, Division 1, 2007 Edition through 2008 Addenda

2. Regulatory Guide 1.147, "lnservice Inspection Code Case Acceptability, ASME Section XI ,

Division 1," Revision 18, March 2017. (ADAMS Accession No. ML16321A336)

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

4. Code Case N-513-4, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping",Section XI , Division 1, May 7, 2014. (Previously enclosed in ML 17232AOOO)

5. Technical Basis for Proposed Fourth Revision to ASME Code Case N-513 . (Previously enclosed in ML 17232AOOO)

6. VCSNS Design Basis Document, "Service Water System (SW)", Revision 15.

Serial No.19-181 Enclosure 2 Page 1 of 23 VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 ENCLOSURE 2 DESIGN CALCULATION SW002/05 REVISION 1 "THROUGH WALL LEAK EVALUATION"

ES-0412 ATTACHMENT I PAGE 1 OF 2 REVISION 5 Subject Code SOUTH CAROLINA ELECTRIC AND GAS COMPANY 560 CALCULATION RECORD Pa~e1 of18 Calculation Title Calculation Number Revision Status THROUGH WALL LEAK EVALUATION SW002/05 1 A 2s:, ~/10/1, Parent Document System Safety Class 0Partial Cale. Revision ECR-50933G SW DNN DOR ~SR ~Complete Cale. Revision Originator Discipline Organization I Date I XREF Number Schwab, Zach PS SCE&G- DE 4/10/2019 1900475.301 CALCULATION INFORMATION Content

Description:

This calculation contains the evaluation performed by Structural Integrity Associates of the acceptability of a through wall leak in the 20" Service Water line downstream of valve XV8031238-SW.

Affected Components/Calculations/Documents:

SW002 Piping Reconciliation Completed per QA-CAR-0089-18: 0This Revision D Previous Revision ~ N/A Contains Preliminary Data/Assumptions: ~No D Yes, Affected Pages:

Computer Program Used: ~ No D Yes, Validated per computer program validation process (others) vendors name D Yes, Validated in accordance with _ _ (Ref. 3.11)

D Yes, Validated [ES-0412]

D Computer Program Validation Calculation VERIFICATION D Continued, Attachment Scope:

Review administrative revision of Design Agents' calculation to assign VCS calculation number in accordance with ES-110 and ES-412.

Verifier: Kevin Wise Assigned by: Doug Mauldin Zach Schwab z-?,~~

Engineering Personnel /Date 04/10/2019 A

Owner's Acceptance Review Kevin Wise J.1w1;/

Ve1i!ie1/Date/d'f,J 4-/,o/zoi"t 4 ~ 1/4oko1~ Nathan Glunt ~~ Lf..(lo/A Responsible Engineer/Date R.,e..J 1(.we.r Required for all engineering work performed by contractor personnel not enrolled in the VCSNS Engineering Training Program Doug Mauldin Aooroval/Date p '1-(ltJ /._ZPl'J To Records Mgmt RECORDS Initials/Date Distribution: Cale File (Original)

ES-0412 ATTACHMENT I PAGE 2 OF 2 REVISION 5 SOUTH CAROLINA ELECTRIC & GAS COMPANY REVISION

SUMMARY

I Page 2 of 18 Calculation Number SW002/05 Revision Number Summary Description 0 Initial Issue of Vendor File No. 1900475.301 1 This calculation is being entered into the V.C. Summer system in accordance with ES-412.

SW002/05 REVISION 1 PAGE 3 OF 18 File No.: 1900475.301 Project No.: 1900475 13 Structural Integrity Quality Program Type: [8J Nuclear D Commercial Associates, Inc.

CALCULATION PACKAGE PROJECT NAME:

V.C. Summer Code Case N-513-4 Evaluation on Leaking Tee CONTRACT NO.:

NU-02NN773515 CLIENT: PLANT:

SCANA Corporation Virgil C. Summer Nuclear Generating Station CALCULATION TITLE:

Code Case N-513-4 Evaluation of Thinned Service Water Tee Downstream of XVB-03123B-SW Project Manager Preparer(s) &

Document Affected Revision Description Approval Checker(s)

Revision Pages Sionature & Date Sionatures & Date 0 1 - 16 Initial Issue S4/~~ S4/~~

Stephen Parker Stephen Parker SMP 4/10/19 SMP 4/10/19

~ II+/-:-

Eric Houston EJH 4/10/19

SW002/05 REVISION 1 PAGE 4 OF 18 Table of Contents 1.0 OBJECTIVE ... ................... .. ..... ... .. ............ .. ....... .................... .. ...... ... ....... .............. ... 3 2.0 METHODOLOGY ........................................................... ... .. ............. .. .......... ............. 3 3.0 DESIGN INPUTS .. ............. ....... .. ....... ... ................. ... .. ............. ... ........ .. ................... ..4 4.0 ASSUMPTIONS ........................................... .. .......... ... ....... .... ........... ............. ....... .. .. 7 5.0 CALCULATIONS .......... .. .............. .. .. ..... .......... .. ............ .... .. .. ....................... ..... ........ 7 5.1 Branch Reinforcement Area Check ................................................................ 8 5.2 Applied Loads .............................................................................................. 11

52. 1 Hoop Stress ......... ......... .. ........ ... ........................... .... .. ....... ........ .. ...... ... .. ... .. 11 52.2 Axial Stresses .............. .. ..... .... .... ............ ..... ... .. .. ........ .. ....................... ... ..... 11 5.3 Stress Intensity Factor Calculations ................................................... .. ........ 12 5.4 Critical Fracture Toughness Determination ............. .. .... .. ............................. 13 6.0 RESULTS OF ANALYSIS ........... .. ................. .. ....... .. .......... ..................................... 14

7.0 CONCLUSION

S AND DISCUSSION ..................... .... .. .. .... .. ... ........... ...................... 15

8.0 REFERENCES

................................................. ...... .. .... ......... ......... ...... ........ .. ......... 16 List of Tables Table 1: Moments at Thinning Location .................. .. ... .. .. ..... .... .... ................................................... 7 Table 2: Required Thicknesses Relative to Distance from Branch ............ .. .. ...... ........ ................... 1O Table 3: Load Combinations ................................................ .. .. .... ... ............................................... 13 Table 4: Allowable Axial Through-Wall Flaw ...... ......... .. ..... .. ..... .. ................................................... 14 Table 5: Allowable Circumferential Through-Wall Flaw .. ............... .. ........................................... .... 14 Table 6: Pressure Blowout Check .... .. ........ .... .... ......... .... ....... ...... ... ... ..... ....................................... 14 List of Figures Figure 1. Micro Grid Thickness Values ................................ ...... ....................................................... 5 Figure 2. Micro Grid Around Leak Downstream of XVB-03123B-SW ................... ........... .. .. .. ..... ...... 6 Figure 3: ASME Code Section Ill , Figure ND-3643.3(c)(1)-1 , Reinforcement of Branch Connections9 Figure 4: Required Reinforcement Area and Dimensions ...... .. .. ..... .. ........ .. ................................... 10

SW002/05 REVISION 1 PAGE 5 OF 18 1.0 OBJECTIVE A through-wall leak was recently discovered in the Service Water system at Virgil C. Summer Nuclear Generating Station (Summer). The through-wall leak is in a 20-inch square tee downstream of valve XVB-03123B-SW. The 20-inch carbon steel line is safety related Class 3 piping. The objective of this calculation is to demonstrate suitability for continued operation in accordance with ASME Code Case N-513-4 [1] .

2.0 METHODOLOGY The flaw evaluation herein is based on the criteria prescribed in ASME Code Case N-513-4, which allows for the temporary acceptance of part-wall and through-wall flaws in moderate energy Class 2 or Class 3 piping, including tees.

The observed leaking flaw is a non-planar through-wall flaw. The Code Case allows non-planar through-wall flaws to be characterized and evaluated as two independent planar (i.e., crack-like) through-wall flaws; one in the axial direction and circumferential direction. Allowable through-wall flaw sizes in the axial and circumferential directions are calculated and are shown to bound the observed flaw. The measured wall thickness val.Jes in the pipe section containing the flaw are bounded by a thinner analyzed thickness (i.e.,

the wall thickness surrounding the flaw is assumed to be uniformly thinned to the analyzed thickness, tadj).

This conservatively ignores the load carrying capacity of the pipe wall that is greater than tadj, Code Case N-513-4 evaluation criteria rely on the methods given in ASME Section XI , Appendix C [2] .

Linear Elastic Fracture Mechanics (LEFM) criteria are conservatively employed as described in Article C-7000. Equations for through-wall stress intensity factor parameters Fm, Fb and Fare given in Appendix I of the Code Case. Allowable flaw lengths are determined iteratively through comparison of the calculated stress intensity factors to a critical fracture toughness defined in C-7200 of Section XI, Appendix C.

The U.S. Nuclear Regulatory Commission (NRC) has not generically reviewed and approved N-513-4 in the current edition of Regulatory Guide 1.147 [3]. Summer will need to submit a request for relief to the NRC in order to use the code case for this evaluation.

File No. : 1900475.301 Page 3 of 16 Revision: 0 F0306-01R3 e

Structural Integrity Associates, Inc. inlo.slructint.com a 1-877-451-POWER C9 structint.com ~

SW002/05 REVISION 1 PAGE 6 OF 18 3.0 DESIGN INPUTS The following design inputs are used in the evaluation :

1. Tee Design: Standard Butt-Welded Tee per ASME 816.9 [4]

2. Nominal Pipe Size = 20-inch [5]

3. Outside diameter= 20.0 inches [5]

4. Nominal wall thickness = 0.375-inch [5]

5. Normal operating temperature= 124°F [6]

6. Upset operating temperature= 130°F [6]

7. Maximum operating pressure= 20 psig [6]

8. Code of Construction : ASME Section 1111971 Edition through the Summer 1973 Addenda [4, 7]

9. Pipe Material: SA-234 Grade WPB [8]

10. Young's modulus= 27,900 ksi [7, Appendix I, Table 1-6.0]

11. Material allowable stress= 15,000 psi [7, Appendix I, Table 1-7.1]

The NDE inspection results [9] provide the thickness data characterizing the localized wall loss.

Measurements in Reference [9] are taken in a 0.5-inch grid with a 22-inch axial by 9-inch circumferential extent around area of localized thinning , as shown in Figure 1. This data set indicates that the through-wall location is at grid L23 where the measurement is taken as 0.17-inch.

Figure 1 provides a visual representation of the thinning profile based on the gridded NDE data in Reference [9]. The through-wall leak is a pinhole leak with a characterized extent of 0.5-inch square. The average thickness of the examined area of the tee including the butt weld (Row 1O through 43) is 0.573-inch. Rows 10 and 11 represent the pipe-to-tee butt weld and row 12 is the first row of measured data in the tee.

For the purposes of the structural evaluation, the through-wall flaw is conservatively characterized as 8.0 inches axial by 2.5 inches circumferential as shown in the red outlined grid in Figure 1. For the structural stability evaluation , the entire region within the red outlined grid is considered to be a through-wall flaw. In addition , a surround ing thickness of 0.470-inch is selected for the structural evaluation. Use of this surrounding thickness is conservative as it is less than the average thickness of the measured pipe wall and the adjacent wall thickness around the characterized through-wall extent as shown in Figure 1.

Figure 2 shows the location of interest and the relative location of the grid on the run pipe of the tee.

Column R of the micro grid is adjacent to the PM Cap repair.

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SW002/05 REVISION 1 PAGE 7 OF 18 Circumferential II A F G H I J K L M N 0 p R 12 0.489 0.484 0.466 0.48 0.477 0.473 0.463 0.473 0.466 0.465 0.459 0.432 0.435 0.458 cu 13 0.521 0.498 0.501 0.475 0.4741 0.493 0.47 2.5" .489 0.48rl 0.466 0.46 0.469 0.527

~ 14 0.521 0.51 0.497 0.484 0.49 0.511 0.50 .499 0.5 0.475 0.482 0.483 0.506 15 0.549 0.538 0.534 0.531 0.529 0.522 0.474 0.281 0.294 0.426 0.528 0.513 3 0.486 0.5 0.533 16 0.518 0.53 0.542 0.557 0.554 0.544 0.527 0.635 0.539 0.529 0.416 0.535 0.538 0.531 0.526 0.514 0.541 17 0.552 0.57 0.565 0.579 0.556 0.553 0.299 0.302 0.567 0.557 0.555 0.526 0.537 0.57 18 0.581 0.608 0.59 0.612 Location of 0.573 0.605 0.529 0.614 0.593 0.579 0.569 through-wall 19 0.589 0.608 0.593 0.611 0.137 0.291 0.595 0.585 0.588 0.583 0.569 leak 20 0.591 0.625 0.599 0.596 0.57 0.581 0.604 0.586 0.573 0.543 0.581 21 0.643 0.64 0.639 0.61 0.311 0.466 0.567 0.556 0.583 22 0.602 0.643 0.63 0.568 0.584 0.587 23 0.634 0.657 0.654 0.48 0.583 0.59 24 0.655 0.631 0.63 0.488 0,192 0.534 0.565 0.604 0.583 25 0.617 0.63 0.64 0.51 0.366 0.546 0.577 0.548 0.571 0.575 26 0.637 0.638 0.646 0.635 0.621 0.558 0.41 0.165 0.284 0.569 0.558 0.56 0.572 27 0.626 0.664 0.619 0.631 0.633 0.576 0.574 0.305 0.52 0.572 0.538 0.565 0.57 28 0.623 0.649 0.619 0.643 0.649 0.626 0.616 0.625 0.614 0.566 0.461 0.56 0.556 0.56 0.545 0.566 0.628 0.627 0.611 0.64 0.649 0,658 0.626 0.612 0.588 0.392 0.442 0.619 0.55 0.579 0.553 0.545 0.627 0.615 0.624 0.628 0.624 0.634 0.629 0.628 0.588 0.373 0.536 0.481 0.507 0.555 0.573 0.571 31 0.622 0.626 0.625 0.643 0.654 0.632 0.646 0.625 0.6 0.596 0.584 0.573 0.569 0.582 0.547 0.572 0.55 0.585 32 0.623 0.618 0.638 0.638 0 .615 0.63 0.625 0.63 0.688 0.613 0.591 0.428 0.579 0.468 0.399 0.581 0.605 0.615 33 0.619 0.629' 0.644 0.645 0.598 0.641 0.63 0.633 0.63 0.624 0.581 0.539 0.572 0.579 0.581 0.593 0.586 0.587 Figure 1. Micro Grid Thickness Values Note: measurements in inches, grids are 1/2-inch square File No.: 1900475.301 Page 5 of 16 Revision: 0 F0306-01R3 tt Structural Integrity info.structint.com a 1-877-4SI-POWER '9 structint.com (ffi)

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SW002/05 REVISION 1 PAGE 8 OF 18

. . I Figure 2. Micro Grid Around Leak Downstream of XVB-03123B-SW File No.: 1900475.301 Page 6 of 16 Revision: 0 F0306-01R3 e

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SW002/05 REVISION 1 PAGE 9 OF 18 Determination of the fracture toughness, J1c, used in the evaluation is based on Section XI, Appendix C, C-8320 [2], which specifies that 'reasonable lower bound fracture toughness data' may be used to determine the allowable stress intensity factor, Kie- Beginning with the 2013 Edition,Section XI, Appendix C contains guidance for the temperature for the onset of upper-shelf behavior [10, Table C-8321-2]. Note that the NRC has approved the 2013 Edition of Section XI, Appendix C without exception

[11]. Based on the guidance in [10, Table C-8321-2], upper shelf material toughness is expected at temperatures greater than 76°F (interpolated upper shelf temperature for 0.529-inch wall thickness), which is less than the normal operating temperature of 124°F. Therefore, J1c is taken as 300 in-lb/in 2 in the evaluation for both the axial and circumferential directions [2 , Table C-8321-1 and C8322-1].

Nodal moments at the flaw location from the piping design stress report [12] are shown in Table 1 (note that all values are given as positive within the table). The nodal range of the run pipe of the tee is between Node 25 and 27, with the center of the tee at Node 26 [5, 12]. The bounding nodal moments are taken from Node 26 and 27.

Table 1: Moments at Thinning Location Component Moments (ft-lbs) MsRss Load Node MsRss (ft-lbs)

Bend 1 Bend 2 Torsion (in-lbs) ow 26 654 2854 158 2932 35,187 Upset 27 9495 6935 1660 11,875 142,495 (OBE)

Emergency 27 12,274 8775 2150 15,241 182,887 (SSE)

Thermal 27 5655 144,491 2598 144,625 1,735,499 4.0 ASSUMPTIONS

1. Poisson's ratio is assumed to be 0.3, which is a typical value for carbon steel.

2. A corrosion allowance is not considered in the evaluation. The ongoing inspection requirements in Code Case N-513-4 address the possibility of flaw growth during the temporary acceptance period.

3. Adjacent to the through-wall leak is a PMCap repair, as shown in Figure 2. To account for this discontinuity, it is conservatively assumed that this repair is a branch connection to the run pipe.

Calculations are performed to demonstrate that the extent of thinning does not violate the branch reinforcement requirements of ASME Section Ill, Subparagraph NC-3643.3 [7].

5.0 CALCULATIONS The following subsections describe calculations performed to determine the allowable flaw sizes in accordance with ASM E Code Case N-513-4 [1] as well as a check to confirm that the through-wall thinning is outside of the area of branch reinforcement for the branch connection of the tee. The results of this check are also conservatively used to demonstrate that the thinning is outside of the area of reinforcement for the adjacent discontinuity PMCap repair (See Assumption 3).

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SW002/05 REVISION 1 PAGE100F18 5.1 Branch Reinforcement Area Check Per Section 3.5 of Code Case N-513-4, the "branch reinforcement requirements shall be met in accordance with the design Code .... Through-wall flaws in branch tees outside of the reinforcement region may be evaluated using the straight pipe procedures ... "

In order to apply the straight pipe procedures detailed in the Code Case, the location of thinning relative to the branch reinforcement area needs to be determined.

ASME Section Ill, Subparagraph NC-3643.3 [7] defines the required reinforcement area of the run pipe due to the loss of wall thickness created by the branch connection penetration. For right angle connections, the required reinforcement area is calculated as:

where:

tmh = required minimum wall thickness of the header, in d1 = inside diameter of the branch, in As shown in Figure NC-3643.3(a)-1, the reinforcement area can be achieved from additional material in four different locations. A1 is excess wall in the header, A2 is excess wall in the branch, and A3 and~ are weld metal reinforcement. This calculation is performed conservatively assuming that the required reinforcement area only is achieved by excess wall thickness in the header, or area A1. The required area at each cross-section 360° around the branch connection is calculated as.

AReq A=-

1 2 A portion of NC-3643.3(a)-1 is reproduced in Figure 3 of this report for clarity. Using the input data provided in Section 3.0 of this report, the resulting required reinforcement area is equal to 0.278 in 2. Per Reference [8], the repair has an extent of 11 inches by 8 inches, which results in a maximum extent of 13.6 inches. As all other input for determination of the reinforcement area is the same, the required reinforcement area for the 20-inch branch connection can be conservatively used for the PM Cap repair.

For this calculation, area A1 is defined by a thickness and length dimension, tex and l, respectively. The thickness, tex, is calculated parametrically based on multiple lengths measured from the inner diameter of the branch pipe (See Figure 4). The product of tex and l is equal to A1. The relationship is such that increasing values for l will result in decreasing the required values for tex, The length l cannot be easily measured as it starts at the ID of the branch connection. The length ladi is introduced in order to facilitate physical measurement from the OD surface of the tee. See Figure 4 for a diagram of these areas and dimensions with respect to the header and branch pipe.

The required header thickness surrounding the branch connection, tReq, is equal to the sum of the excess wall thickness in the header, tex, and the pressure based minimum required wall thickness of the header, tmh, as determined using NC-3641.1, Equation 3. Per Reference [8, Attachment 3], the pressure based File No.: 1900475.301 Page 8 of 16 Revision: 0 F0306-01R3 SJ Structural Integrity info.structint.com m 1-877-4SI-POWER. structint.com G Associates, Inc.

SW002/05 REVISION 1 PAGE 11 OF 18 minimum required thickness for the tee is equal to 0.013-inch. This minimum required thickness is also applicable when calculating tReq for the PM Cap repair. For both the branch and PMCap repair, tReq is calculated as:

f Req = !ex + t mh The required header thickness needed to meet the branch reinforcement rules is determined parametrically for several adjusted lengths, l actj, in Table 2. The tReq for each distance of l actj is applicable to both the PMCap and the branch connection, where l acti is measured from the outer surface.

Excess wall in branch/ y tmb t

Example A Explanation of areas:

Required reinfo rcement area Area A, - Excess w all in hea der I Area A2 - Excess wall in branch Figure 3: ASME Code Section 111, Figure ND-3643.3(c)(1)-1, Reinforcement of Branch Connections File No.: 1900475.301 Page 9 of 16 Revision: O F0306-01R3 SJ Structural Integrity info.structint.com m 1-877-4SI-POWER C9 structint.com @

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SW002/05 REVISION 1 PAGE 12 OF 18 I

Bra,-ich tmh tReq tex %1/.

//~ A1

/

~ ~

/,/

/,/

A1 / / /~ /

l Run Figure 4: Required Reinforcement Area and Dimensions Table 2: Required Thicknesses Relative to Distance from Branch lad] tReq (in) (in) 0.5 0.284 1.0 0.150 1.5 0.105 2.0 0.082 Reference [13] indicates that the through-wall leak is measured to be 3.56 inches away from the PM Cap repair, which is closer to the leak than the branch connection. Figure 2 and the NDE report [9] show that Column R is directly adjacent to the PMCap. The minimum wall thickness from cell 012 through R43 in the NDE data , which are measured values of the tee wall thickness between the characterized thinning and the PMcap , is 0.399 inch. This thickness is well above all tReq thicknesses in Table 2. Therefore, the branch reinforcement requirements are met and the through-wall leak is outside of the reinforcement area .

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SW002/05 REVISION 1 PAGE 13 OF 18 5.2 Applied Loads Axial and circumferential (i.e., hoop) stresses used in this evaluation are calculated from the evaluated wall thickness (tadj), the nodal stresses in Table 1, and the maximum operating pressure. The evaluated wall thickness is used to determine the section properties in the flaw evaluation .

5.2. 1 Hoop Stress For the allowable axial flaw length, the hoop stress, oh, may be determined as:

pDo er=--

" 2t where:

p = maximum operating pressure, psig Do = outside diameter, in t = evaluated wall thickness =tadj, in The hoop stress is calculated as 426 psi based on tadj.

5.2.2 Axial Stresses For the allowable circumferential flaw length, the axial stress due to pressure, deadweight, seismic, and thermal loading is presented below. For axial membrane stress due to pressure, Gm, Equation 14 of N-513-4 is used . Note that there is a typo in the original published version of this equation; the equation has been corrected by errata and is:

- B pDo (Jm - 1 2t 81 is the primary stress index for pressure loading. As allowed by the Code Case, the primary stress indices 81 and 82 are taken from a more recent edition of the ASME Code [14, Table ND-3673.2(b)-1]. For welded tees, 81 is 0.5.

For axial bending stress, Ob, due to deadweight and seismic moments, Equation 15 of N-513-4 may be used:

where:

Mb = resultant primary bending moment, in-lbs.

I = moment of inertia based on evaluated wall thickness, in 4 The coefficient 82 for welded tees is defined as [14, Table ND-3673.2(b)-1]:

r 2/3 B2 = 0.5 (-)

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SW002/05 REVISION 1 PAGE 14 OF 18 where:

r = mean radius of run pipe, in tn = nominal wall thickness of run pipe, in For axial bending stress, Oe, due to thermal expansion, Equation 16 of N-513-4 may be used:

CJe = l. DoMe 21 where:

i = stress intensification factor Me = resultant thermal expansion moment, in-lbs.

The stress intensification factor is calculated based on a welding tee as [14, Table ND-3673.2(b)-1]:

. 0.9 L = JiZ/3 where:

h = fl ex1'b'I' 11ty c haractenst1c

. . = --

4.4tn r

5.3 Stress Intensity Factor Calculations For LEFM analysis, the stress intensity factor, Kr, for an axial flaw is taken from Article C-7000 [2] as prescribed by N-513-4 and is given below:

where:

SFm= structural factor for membrane stress (see [2, C-2620])

F = through-wall stress intensity factor parameter for an axial flaw under hoop stress (given in Appendix I of N-513-4) oh = hoop stress, ksi a = flaw depth (taken as half flaw length for through-wall flaw per Appendix I of N-513-4), in Q = flaw shape parameter (unity per Appendix I of N-513-4)

K1r = Kr from residual stresses at flaw location (assumed negligible as the flaw is in the base metal)

Only the hoop stress influences the allowable axial flaw length.

For LEFM analysis, the stress intensity factor, Kr, for a circumferential flaw is taken from Article C-7000 [2]

as prescribed by N-513-4 and is given below:

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SW002/05 REVISION 1 PAGE150F18 K,m = SF,11F,11(5111 J;i; K,b = [SF;,C5b+C5e]F;, ~

where:

Fm = through-wall stress intensity factor parameter for a circumferential flaw under membrane stress (given in Appendix I of N-513-4)

Om = membrane stress, ksi SFb = structural factor for bending stress (see [2 , C-2620])

ab = bending stress, ksi Ge = thermal stress, ksi Fb = through-wall stress intensity factor parameter for a circumferential flaw under bending stress (given in Appendix I of N-513-4)

K,r = K, from residual stresses at flaw location (assumed negligible as the flaw is in the base metal)

Note that the through-wall flaw stress intensity factor parameters are a function of flaw length.

Table 3 shows the specific load combinations considered herein for the allowable circumferential flaw calculations. Note that Service Level Dis bounded by Service Level C and is not explicitly evaluated.

Table 3: Load Combinations Load Combination Service Level P+DW+TH A P+DW+OBE+ TH B P+DW+SSE+ TH C 5.4 Critical Fracture Toughness Determination For LEFM analysis, the static fracture toughness for crack initiation under plane strain conditions, Kie, is taken from Article C-7000 [2] as prescribed by N-513-4 and is given below:

K = l1cE '

Jc 1000 E' =_§_2 1-v where:

J,c = material toughness, in-lb/in 2 E = Young's modulus, ksi v = Poisson 's ratio Based on the design input listed above, K,c = 95.9 ksi-in°*5 . The allowable flaw lengths are determined iteratively by increasing flaw length until the stress intensity factor is equal to the static fracture toughness.

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SW002/05 REVISION 1 PAGE 16 OF 18 6.0 RESULTS OF ANALYSIS Based on inputs in Section 3.0 and using equations from Section 5.0, the allowable through-wall flaw lengths in the axial and circumferential direction are calculated for each Service Level. For a surrounding wall thickness of 0.470-inch, the allowable through-wall flaw in the axial direction is 21 inches as shown in Table 4 for all Service Levels. The allowable through-wall flaw in the circumferential direction is 2.7 inches as shown in Table 5 for Service Level B. Based on the inspection data given in Reference [9], the analyzed thickness and allowable flaw lengths bound the observed thinning. Thus, the acceptance criteria of Code Case N-513-4 are met for structural stability.

Table 4: Allowable Axial Through-Wall Flaw Service Hoop Stress Allowable Kim Kie SFm Level [psi] Flaw Size [in] [ksi-in°*5] [ksi-in°*5]

A 2.7 426 21 32.4 95.9 B 2.4 426 21 28 .8 95.9 C 1.8 426 21 21 .6 95 .9 Table 5: Allowable Circumferential Through-Wall Flaw Thermal Bending Allowable Service Membrane Bending K1 Kie SFb SFm Stress Flaw Size Level Stress [psi] Stress [ksi-in°*5] [ksi-in°*5]

[psi] [in]

rosil A 2.3 2.7 213 31,957 967 3.6 94.4 95.9 B 2.0 2.4 213 31,957 4,881 2.7 95.3 95.9 C 1.6 1.8 213 31 ,957 5,990 2.7 94.6 95.9 Code Case N-513-4, Paragraph 3.2( c) requires that the remaining ligament average thickness over the degraded area be sufficient to resist pressure blowout [1 , Equation 8]. Table 6 shows the required average thickness, tc,avg, as a function of the equivalent diameter of the circular hole, dactj, for which the wall thickness is less than tactj, Based on the inspection data given in Reference [9], the values in Table 6 bound the observed thinning. Thus, this Code Case requirement is met.

Table 6: Pressure Blowout Check dadj [in] tc,avg [in]

1.0 0.01 2.0 0.03 3.0 0.04 4.0 0.05 5.0 0.06 Code Case N-513-4, Paragraph 2(a) requires that the full pipe circumference at the location of the flaw be inspected . This inspection was performed and documented in Reference [9]; therefore, the requirement is met.

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SW002/05 REVISION 1 PAGE 17 OF 18

7.0 CONCLUSION

S AND DISCUSSION A through-wall pinhole leak in a 20-inch square tee downstream of valve XVB-03123B-SW has been identified in the Summer Service Water system. Allowable through-wall flaw lengths have been calculated in accordance with ASME Code Case N-513-4.

The allowable through-wall flaw in the axial direction is 21 inches. The allowable through-wall flaw in the circumferential direction is 2.7 inches. The allowable through-wall flaw lengths are based on an evaluated wall thickness of 0.470-inch. The allowable through-wall flaw sizes bound the conservatively characterized thinning that assumed a through-wall extent of 8 inches axially by 2.5 inches circumferentially. Table 6 shows the requirements to meet the Code Case pressure blowout limits.

The observed thinning is bounded by the results of the analysis; thus, the structural evaluation criteria of Code Case N-513-4 are met. The Code Case requires additional actions by the owner, such as:

• Volumetric reinspection: Paragraph 2(e)

• Augmented volumetric examinations: Paragraph 5

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SW002/05 REVISION 1 PAGE 18 OF 18

8.0 REFERENCES

1. ASME Boiler and Pressure Vessel Code, Code Case N-513-4, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1," May 7, 2014.

2. ASME Boiler and Pressure Vessel Code,Section XI, Appendix C, 2007 Edition with 2008 Addenda.

3. Regulatory Guide 1.147, "lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1," Revision 18, U.S. Nuclear Regulatory Commission , March 2017.

4. Email from Z. Schwab (SCANA) to S Parker (SI), April 4, 2019, Subject "RE: VC Summer - Service Water Pinhole Leak Information," SI File No. 1900475.208.

5. SCE&G Drawing No. C-314-251, Sheet 2, Revision 5, "Service Water- To & From Comp. Cooling Heat Exchanger 'B'," SI File No. 1900475.205.

6. SCE&G Drawing No. D-302-222, Sheet 2, Revision 5, "Service Water Cooling B - Train Outside RB," SI File No. 1900475.205.

7. ASME Boiler and Pressure Vessel Code, Section Ill, 1971 Edition with Addenda through Summer 1973.

8. SCE&G Calculation No. SW002, Revision 6.1, "Pipe Analysis SW002," SI File No. 1900475.201.

9. SCE&G Ultrasonic Thickness Determination Report, Work Request No. 1907703-001, April 9, 2019, SI File No. 1900475.203.

10. ASME Boiler and Pressure Vessel Code,Section XI, Appendix C, 2013 Edition.

11. Codes and standards, 10CFR 50.55a (February 16, 2018).

12. SCE&G Calculation No. SW002, Revision 6, "Pipe Analysis SW002," SI File No. 1900475.201 .

13. Email from Z. Schwab (SCANA) to S Parker (SI), April 4, 2019 1:06 PM MDT, Subject "RE: VC Summer- Service Water Pinhole Leak Information," Attachment "IMG_0929.jpg," SI File No.

1900475.208.

14. ASME Boiler and Pressure Vessel Code, Section Ill, 2010 Edition.

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ES-0110 ATTACHMENT XVI PAGE 1 OF2 REVISION 3 REVIEW CONSIDERATIONS: OWNER'S ACCEPTANCE REVIEW ECR/Document Number: 1900475.301 Project

Title:

Code Case N-513-4 Evaluation of Thinned Service Water Tee Downstream of XVB-031238-SW The following questions should be considered, as a minimum, during the performance of an Owner's Acceptance Review of vendor developed engineering documents.

Yes N/A

[gJ D Is the technical information/design complete, consistent, and correct for the activity under review?

[gJ D Were inputs, including codes, standards, and regulatory requirements correctly selected and applied?

[gJ D Are assumptions necessary to perform the design activity adequately described and reasonable? Where necessary, are the assumptions identified for subsequent re-verification when the detailed design activities are completed?

[gJ D Is the document/package developed in a clear and understandable manner?

[gJ D Is the plant design basis/criteria maintained?

[gJ D Are references properly identified and complete?

D ~ Were design considerations from EC-01, Attachment I and II adequately addressed/incorporated?

[gJ D Were technical, design, program or procedure requirements adequately addressed/incorporated?

[gJ D Have applicable construction and operating experiences been considered?

~ D Were designs developed in accordance with good engineering practices and established ES guidance documents?

D ~ Have impacted documents, databases (EC-02) and equipment changes been identified?

D ~ Is the document/pacl<age developed in accordance with applicable station procedures (e.g., SAP-0133, ES-0453, ES-0455)?

~ D Is the document/package developed in a clear and understandable manner as to not require recourse to the Originator?

ES-0110 ATTACHMENT XVI PAGE 2 OF 2 REVISION 3 Yes N/A D !X1 Does the design meet interfacing organizations operational/maintenance requirements?

[XJ D Is technical information adequate to perform the task?

[XJ D Is the acceptance criteria adequate for the activity under review?

D [XJ Is the post modification testing adequate to confirm the design?

D [XJ Has the 10CFR50.59/ 10CFR72.48 Review been completed, if required?

For work performed in accordance with VC Summer Nuclear Station Procedures, the procedure forms must be signed by the originator and if not qualified must be co-signed by a qualified person . Check the qualifications of the contractor personnel signing the procedure forms .

Yes No D [XJ Are contractor personnel signing the VCSNS procedure forms qualified under a vendor qualification program or the VCSNS Nuclear Training Manual for those procedures?

• This is a Review of Design Agent's calculation. A separate administrative revision will be completed to assign a VCSNS calculation number.

D [XJ If not have the VCSNS forms been co-signed by a person qualified to the applicable procedure?

• This is a Review of Design Agent's calculation. A separate administrative revision will be completed to assign a VCSNS calculation number.

Technical Reviews D Are all technical reviews complete and all comments resolved to the satisfaction of the commenter?

TECHNICAL REVIEW: Check all blocks that apply

[8J Princigal Piging Engineer D Princigal Engr Analysis Engineer 0 Princigal l&C Engineer

[8J Princigal Mechanical Engineer D Princigal Civil Engineer 0 Princigal PSA Engineer D Princigal Nuclear Fuels Engineer D Princigal Digital Engineer 0 Principal Electrical Engineer D Princigal EQ Engineer D Princigal Fire Protection Engineer 0 Princigal Security Engineer

[8J Zach Schwab D o _ ___ ____

[8J Kevin P. Wise D o_ _______

Nathan Glunt Reviewer's Printed Name Reviewer's Signature Date

SIA File No.: 1900475.301 Rev. 0 (Code Case N-513-4 Evaluation)

Page Section Comment +/- Comment Resolution 4 3 Second paragraph after references . Please Resolved .

state that the characterized extent is conservative. The actual through wall portion of the flaw is very small. Throughout the report +

it is important to explicitly identify any conservatisms. We have received these comment!'; in the n<>c:t 5 3 In figure 1 please identify that row 12 is the Resolved .

+

bottom of the unner tee to oioe weld .

7 5 Tvoo - "Code Case 514-4" shoult be 513-4 + Resolved.

10 5.1 The mimimum wall thickness given in the Resolved .

calculation (0.339 inch) is actually the minimum thickness in the pipe (which is inherantly thinner). If you are going to use it that's fine

+

but please state the conservatism of using the thinnest in the pipe. Or else use 0. 399 inch which is in the tee at grid point 032.

14 6 Final NDE data is on its way, please remove Resolved .

last paragraph or revise once recieved . +

15 7 In conclusion please restate that the analysis Resolved.

conservatively assumeed that the 2 .5"x8"

+

thinned region was a thru-wall flaw. See page 4 for where it is first stated.

"+" Incorporated, "-" Not Incorporated (Explain)

TECHNICAL WORK RECORD ES-104, ATIACHMENT I REVISION 3 Originator: Kevin P. Wise Date -04/10/2019 Change Document: ECR50933G System: SW Tab - KW43024-SW002/0S Page 1 of 1 Project

Title:

Through Wall Leak Evaluation

Subject:

Review Documentation Purpose The purpose of this TWR is to document the Review of calculation SW002/05 Revision 1, THROUGH WALL LEAi(

EVALUATION.

Review Scope This Review was performed in accordance with ES-110, Review and Verification of Controlled Documents, Revision 3A. ES-110 defines a Review as "a check on the technical comp leteness, consiste ncy, and correctness of the activity under review. Reviews also include a check on the adequacy of any design, program, or procedure interfaces that were a requirement of the activity being reviewed." Additionally, this review ensures that this complete calculation revision was developed in accordance with ES-412, Initiation and Control of Design Calculations, Revision SG .

Review Conclusion This calculation revision is an Administrative revision of a Design Agents' calculation to assign a new SCE&G calculation number (Ref. ES-412, section 6.5 .2}. The Design Agent, Structural Integrity Associates, Inc.,

developed and verified calculation 1900475.301 in accordance with the SI Quality Assurance (QA) Program, which is in compliance with the requirements of 10CFR50, Appendix B, 10CFR21, and ANSI/AS ME NQA-1-1989, 1994, 2008/A2009, and meets the intent of applicable portions of ANSI N45.2 as indicated in SI proposal 1900475 and VCS PO NU-02NN773515 . The Design Agent's calculation was Owner Reviewed in accordance with ES-110 which includ ed a technical review. Therefore, SW002/05 Revision 1 shall be reviewed in accordance with ES-110 for the administrative incorporation of the calculation (Ref. ES-412, section 6.6.3) .

This calculation revision was developed consistent with other similar through wall pipe leak evaluations documented in SW002/03 and SW002/04. The evaluation methodology used was determined to be appropriate for the application (ASME Code Case N-513-4) and the outputs of the calculation are appropriate given the inputs provided. An Owner's Acceptance Review of the Design Agents' calculation was completed and documented by a qualified individual in accordance with ES-110 and comments were incorporated satisfactorily.

The administrative calculation revision was developed in accordance with ES-412, Revision SG. No procedural deficiencies were identified during the review of the administrative calculation revision.

Kevin P. Wise Reviewer's Printed Name Reviewer's Signature Date Page 1 of 1

Serial No.19-181 Enclosure 3 Page 1 of 3 VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 ENCLOSURE 3 DESIGN AGENT'S QUALIFICATION LETTER

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rr PMC ENGINEERING 8

272 Grubb Rd

• Pottstown, PA 19465 1 1 tel. 610.495.9750 11 fax. 440.425 .9750 I www.pmceng inee ring.co111 April 10, 2019 Letter Report No. 201911-LR-01, RO South Carolina Electric & Gas Co. SCANA V.C. Summer Nuclear Station Unit 1 Hwy 215 N. Bradham Blvd Jenkinsville, SC 29065 ATIN: Jeff Lackovic, P.E, PMP I Project Manager

Subject:

South Carolina Electric & Gas Co.

V.C. Summer Nuclear Station, Unit 1 Fitness for Service Evaluation!

Service Water Train "B" TEE Submittal of Fitness for Service Letter Report

Dear Jeff:

A Fitness for Service evaluation was performed to determine the capability of Service Water Train "B" TEE to maintain ASME Code compliance during the rema inder of the current operating cycle. The TEE was previously restored and ASME Code compliance of the TEE in the as-restored condition was documented in PMC Engineering Design Report 201823-5-01, RO, "ASME Section Ill, Subsection ND, (Class 3), DESIGN REPORT for Service Water System "A" and "B" Train TEE Restorations". The Fitness for Service evaluation addresses the new found TEE areas of thinning and a pinhole leak at one location. The Conclusion from the evaluation is as follows:

• PMC Engineering has concluded that Service Water Train "B" TEE, located adjacent to and downstream of ValveXVB-31238-SW will maintain ASME Section VIII, Div. 1, 1974 Edition, including Addenda Summer 78, Code compliance with applicable stress criteria during operation for the remainder of the current operating cycle.

Evaluation Methodology and Acceptance Criteria The evaluation methodology and acceptance criteria associated with the Fitness for Service evaluation is the same as that used in PMC DESIGN REPORT PMC Engineering Design Report 201823-S-01, RO.

Assumptions and Clarifications

• Three locations in the TEE were each found to have associated as-found thickness values within1/2" x 1/2" areas of less than 0.190". These three areas were modeled as3/4" x 3/4" areas and considered as having no material within them that would contribute to the structural integrity of the TEE.

• 500 out of the 576 total new measured thickness values within the TEE were measured as greater than 0.500".

These areas were considered as 0.4375" thick at end of current operating cycle.

• All as=found thickness values less than 0.500" were considered to have a minimum Joss of metal of 0.063".

• 60 out of 168 total new measured thickness values within the pipe (0.375" nominal) at the weld line or above the TEE were measured as greater than 0.375" with the minimum value measures at 0.304" . All these areas were considered to be at 0.242" at end of current operating cycle.

201911-LR-01, RO Page 1 of 2

PMG EN61NEERING 272 Grubb Rd

• Pottstown, PA 19465 te l. 61 0.495.9750 fax. 440 .425.9750 www .pmceng inee ring .com

• Stresses in the TEE at the locations of new as-found thinning and at the pinhole leak were found to be low and well within ASME Code stress acceptance criteria for any stress combination evaluated. Below is a table of the calculated stresses in the thinned region of the TEE. All stresses are well below their allowables, with the minimum F.S. = 1.63 for the thermal load case:

Condition LC Calculat ed Stress Allowables F. S. F.S.

Pl , Pm 1, 4A, 4B 4743 20000 / 30000 4.22 (P m) 6.33 (Pl)

Pl , Pm 7A, 7B 5528 34070 I 51105 6.16 (P m) 9.24 (Pl)

Pl , Pm 3(THERM) 36880 60000 1.63 --- --- ---

Pl+Pb+Q 2, 3, 4A, 4B , 5A, 513 20112 68140 3.39 --- --- ---

S1+S2+S3 1, 4A, 4B 4706 80000 17.00 --- --- ---

S1+S2+S3 7A, 7B 4853 92000 18.96 --- --- ---

• High stress locations in the TEE are at the center of the TEE and at the PMCap restoration hardware to TEE weld juncture. Stresses at these locations were found to have increased over the previously as-restored stress values but are still within ASME Code acceptance criteria .

I hereby certify that to the best of my knowledge and belief that the evaluations performed to support the conclusions noted in this Letter Report were performed in accordance with the ASME Boiler and Pressure Vessel Code, Section Ill, Nuclear Power Plant Components, Subsection ND, Requirements for Class 3 Components, 1971 Edition through Summer 1973 Addenda Paul S. Manzon - Professional Engineer Commonwealth of Pennsylvania License No. PE024250-E April 10, 2019 201911-LR-01, RO Page 2 of 2