ML20087G307

ASME Section XI Inservice Inspection Program Proposed Inservice Inspection Alternative N1-I5-NDE-003

ML20087G307
Person / Time
Site:	North Anna
Issue date:	03/19/2020
From:	Mark D. Sartain Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML20087G300	List: ML20087G307
References
20-028
Download: ML20087G307 (51)

Text

PROPRIETARY INFORMATION -WITHHOLD UNDER 10 CFR 2.390 VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 March 19, 2020 U.S. Nuclear Regulatory Commission Serial No.: 20-028 Attention: Document Control Desk NRNENC: RO Washington, DC 20555 Docket Nos.: 50-338 License Nos.: NPF-4 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)

NORTH ANNA POWER STATION UNIT 1 ASME SECTION XI INSERVICE INSPECTION PROGRAM PROPOSED INSERVICE INSPECTION ALTERNATIVE N1-I5-NDE-003 Pursuant to 10 CFR 50.55a(z)(1), Virginia Electric and Power Company (Dominion Energy Virginia) proposes as an alternative to the requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code,Section XI, a one-time extension of the volumetric examination requirements stated in ASME Code Case N-770-2, Table 1, Inspection Item B, from an interval not to exceed seven years to a one-time interval of six nominal 18-month fuel cycles, approximately nine years, for North Anna Power Station Unit 1 (NAPS1).

Specifically, alternative request N1-I5-NDE-003, included in Attachment 1, proposes an extension of the volumetric examination inspection interval for the Steam Generator (SG)

Cold Leg Nozzle to Safe End Dissimilar Metal (OM) welds of two operating cycles, approximately 36 months, to the spring refueling outage (RFO) in 2024 (N1R30). The extension would allow examination of the SG Cold Leg Nozzle to Safe End OM welds in conjunction with the SG Hot Leg Nozzle to Safe End weld required during N1R30.

Coordination of the SG cold leg nozzle and SG hot leg nozzle examinations promotes industrial and radiological safety and results in a more efficient use of station resources while providing an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1).

Supporting calculation C-4520-00-02, "Crack Growth Analysis for NAPS Unit 1 Steam Generator Outlet Nozzles," Revision 1 [Attachment 2], contains information proprietary to Westinghouse. An affidavit signed by Westinghouse, the owner of the information, is included in Attachment 4 detailing the basis on which the information may be withheld from public disclosure by the Nuclear Regulatory Commission (NRC) and addresses with specificity the considerations listed in (b)(4) of 10 CFR 2.390. Accordingly, it is respectfully requested that the information, which is proprietary to Westinghouse, be Attachment 2 contains information that is being withheld from public disclosure under 10 CFR 2.390. Upon separation from Attachment 2, this letter is decontrolled.

Serial No.: 20-028 Docket Nos.: 50-338 Page 2 of 3 withheld from public disclosure in accordance with 10 CFR 2.390. A non-proprietary version of the calculation is provided in Attachment 3.

Pursuant to 10 CFR 50.55a(z), the proposed alternative request requires NRC review and approval before implementation. Dominion Energy Virginia requests NRC approval of this alternative request by March 1, 2021 to support the next scheduled NAPS1 RFO.

If you have any questions or require additional information, please contact Erica Combs at (804)-273-3386.

Sincerely, Mark D. Sartain Vice President - Nuclear Engineering and Fleet Support Attachments:

1. Relief Request N1-I5-NDE-003, "Steam Generator Cold Leg Nozzle to Safe End Dissimilar Metal Welds Examination Extension"

2. Calculation C-4520-00-02, "Crack Growth Analysis for NAPS Unit 1 Steam Generator

• Outlet Nozzles," Revision 1. [Proprietary Version]

3. Calculation C-4520-00-02-NP, "Crack Growth Analysis for NAPS Unit 1 Steam Generator Outlet Nozzles," Revision 1. [Non-Proprietary Version]

4. Westinghouse Affidavit Pursuant to 10 CFR 2.390 Commitments made in this letter: None

Serial No.: 20-028 Docket Nos.: 50-338 Page 3 of 3 cc: Regional Administrator, Region II (w/o attachments)

U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, Georgia 30303-1257 G. E. Miller NRC Senior Project Manager - North Anna Power Station U. S. Nuclear Regulatory Commission Mail Stop 09 E-3 One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 Mr. Marcus Harris (w/o attachments)

Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.

Suite 300 Glen Allen, Virginia 23060 NRC Senior Resident Inspector (w/o attachments)

North Anna Power Station

Serial No.: 20-028 Attachment 1 Relief Request N1-I5-NDE-003 Steam Generator Cold Leg Nozzle to Safe End Dissimilar Metal Welds Examination Extension Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Unit 1

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 1 of 10 North Anna Power Station Unit 1 10 CFR 50.55a Request Relief Request N1-I5-NDE-003 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1)

--Alternative Provides Acceptable Level of Quality and Safety--

1. American Society of Mechanical Engineers {ASME) Code Components Affected The affected components are ASME Class 1 Steam Generator (SG) Cold Leg Nozzle to Safe End Dissimilar Metal (OM) welds on the North Anna Power Station Unit 1 (NAPS1) A, B, and C SG Cold Legs.

SG Cold Leg Nozzle to Safe End DM Welds 8-F 85.70 31-RC-2 / N-SE31 IN A Cold Leg Low Alloy Steel2 Cold Leg Nozzle nominal, 31-RC-5 / N-SE31 IN B Cold Leg 27.5 inch Alloy 82/182 Weld 31-RC-8 / N-SE31 IN C Cold Leg Stainless Steel3 Safe End 1Inside Diameter 2

Low Alloy Steel: SA-508, Class 3 3

Stainless Steel: SA-336, Class F316LN

2. Applicable Code Edition and Addenda

The applicable Code for the NAPS1 fifth 10-year inservice inspection (ISi) interval and ISi Program is the ASME Boiler and Pressure Vessel (BPV) Code,Section XI, 2013 Edition with no Addenda [Reference 1]. The NAPS1 fifth interval started May 1, 2019 and ends April 30, 2029.

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 2 of 10

3. Applicable Code Requirement

10 CFR 50.55a(g)(6)(ii)(F)(1) requires licensees of existing, operating Pressurized Water Reactors (PWRs) to implement the requirements of ASME Code Case N-770-2, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated with UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities,"Section XI, Division 1, (Approval Date: June 9, 2011) as follows:

• Inspection Item "B", Unmitigated Butt Weld at Cold Leg Operating Temperature (-241O) 2! 525°F (274 °C) and < 580° F (304° C) requires visual examination once per interval and volumetric examination every second inspection period not to exceed 7 years.

Note that this relief request will apply to future versions of Code Case N-770 that may be incorporated in 10 CFR 50.55a(g)(6)(ii)(F)(1) provided the Item B maximum examination frequency continues to be less than 10 years.

4. Reason for Request

Dominion requests to extend the SG cold leg nozzle weld inspections by two operating cycles (approximately 36 months) to the spring 2024 Refueling Outage (RFO) (N1 R30). The total requested interval from the time of the previous volumetric examination of these locations is six nominal 18-month fuel cycles.

The requested extension would allow the next volumetric examination of the SG cold leg nozzle welds to be performed during the same RFO as the next required volumetric examination of the SG hot leg nozzle weld. Coordinating the volumetric examination of the SG hot leg and cold leg nozzle welds supports As Low As Reasonably Achievable (ALARA) practices resulting in dose savings to station personnel performing the work associated with these activities.

Electric Power Research Institute (EPRI) report Materials Reliability Program: PWR Reactor Coolant System Cold-Loop Dissimilar Metal Butt Weld Reexamination Interval Extension (MRP-349) [Reference 2] and a plant-specific crack growth evaluation for NAPS1 [Reference 3] included in Attachment 2 provide the basis for extension of the current volumetric examination interval for the SG cold leg nozzle Alloy 82/182 OM welds. This technical basis demonstrates that the reexamination interval can be extended to the requested interval length while maintaining an acceptable level of quality and safety. The NAPS1 SG primary loop nozzles are Alloy 82/182 butter welds (Figure 1).

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 3 of 10

5. Proposed Alternative and Basis for Use Pursuant to 10 CFR 50.55a(z)(1), Dominion proposes as an alternative to the ASME Code requirements stated above a one-time extension to the requirements of ASME Code Case N-770-2, Table 1, Inspection Item B, volumetric examinations from an interval not to exceed 7 years to a one-time interval of six nominal 18-month fuel cycles, approximately 9 years, for NAPS1. A baseline volumetric examination of each of the three SG cold leg nozzle Alloy 82/182 welds was performed during the spring 2015 RFO (N1R24). The requested extension would allow examination of the SG cold leg nozzle welds coincident with the SG hot leg nozzle weld required during the spring 2024 RFO (N1R30) resulting in personnel dose savings.

Technical Basis The overall basis used to demonstrate the acceptability of extending the inspection interval for Code Case N-770-2, Inspection Item B components is contained in MRP-349 and the site-specific flaw evaluation performed for NAPS1. In summary, the basis for extending the inspection is:

(1) There has been no service experience with Pressurized Water Stress Corrosion Cracking (PWSCC) found in any main loop Alloy 82/182 cold leg DM welds in PWRs; (2) Crack growth rates in Alloy 82/182 cold leg DM welds are relatively slow, about a factor of 4 lower than comparative hot leg DM welds, based on the temperature dependence of the PWSCC crack growth equation; (3) The likelihood of initial cracking, crack growth, and a subsequent through-wall leak is very small in SG cold leg DM welds, particularly with the relatively thick

(~4.8 inches) welds for the NAPS1 cold leg nozzle welds; and (4) The NAPS1 specific axial and circumferential flaw evaluation shows any indications detected during the 2012 and 2015 RFO examinations, as well as any flaw size which could have been reasonably missed during the nozzle to safe end weld examinations, would not grow to the allowable size flaw specified by ASME Section XI rules over the timeframe of the requested inspection interval.

This technical basis demonstrates that the re-examination interval can be extended while maintaining an acceptable level of quality and safety.

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 4 of 10 Service Experience Ultrasonic (UT) examination of the NAPS1 SG Cold Leg Nozzle to Safe End Welds was last performed during the spring 2015 RFO (N1R24). The examination technique used was encoded phased array ultrasonic testing that met AMSE Section XI, Appendix VIII, requirements including an examination volume of essentially 100%.

No indications exhibiting characteristics indicative of Stress Corrosion Cracking (SCC) were noted during the evaluation of the recorded UT Data for Cold Leg A.

Four indications attributed to embedded fabrication flaws were recorded and compared to historical examination results with acceptable evaluation results.

No indications exhibiting characteristics indicative of SCC were noted during the evaluation of the recorded UT Data for Cold Leg B. Two indications attributed to embedded fabrication flaws were recorded and compared to historical examination results with acceptable evaluation results.

No indications exhibiting characteristics indicative of SCC were noted during the evaluation of the recorded UT Data for Cold Leg C. Eight indications attributed to embedded fabrication flaws were recorded and compared to historical examination results with acceptable evaluation results.

All recordable subsurface indications were acceptable per IWB-3514 of ASME Section XI, 2004 Edition.

Third interval examination of Cold Leg B was performed during the fall 2001 RFO (N2R15) with 79% coverage identifying no reportable indications. Cold Leg B was examined again during the spring 2009 RFO (N1R20) using phased array for full coverage identifying no indications indicative of PWSCC. Third interval examinations of Cold Leg A and C were also performed during the spring 2009 RFO (N1R20) with no indications indicative of PWSCC.

Plant-Specific Crack Growth Evaluation Crack growth calculations were performed considering the specific geometry and loads applicable to the NAPS1 SG outlet nozzles, including the weld residual stress (WRS) analysis results documented in C-4520-00-01, Rev. 0 [Reference 5]. These calculations applied the common deterministic approach for unmitigated Alloy 82/182 piping butt welds in PWRs. The results of these crack growth calculations demonstrate the acceptability of the following alternative volumetric reexamination interval (once per Section XI interval, nominally 10 years) specified by ASME Code

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 5 of 10 Case N-770-5 per Inspection Item B-2 for unmitigated cold-leg butt weld locations NPS [nominal pipe size] 14 or larger.

The crack growth calculations presented below demonstrate that these alternative volumetric examination frequencies are sufficient to provide reasonable assurance of the structural integrity of the cold leg piping at NAPS1. Hence, the alternative frequency provides an acceptable level of quality and safety.

The key results of the crack growth calculations are as follows:

• The crack growth rate for axial cracks was found to be greater than for circumferential cracks due to the total (residual plus operating) hoop stresses being greater than the total axial stresses. Thus, the analysis for growth rate of axial cracks are the limiting cases.

• The limiting case for the calculated time for a crack to grow from 10% through wall to the allowable depth is 10.3 years. In the limiting case, an axial crack growing to an allowable 75% through-wall depth, an additional 2.8 years is calculated for the axial crack to penetrate through the remaining 25% of the wall thickness.

• The relatively large thickness of the subject Alloy 82/182 weld (4.813 inches) compared to other Alloy 82/182 butt welds in U.S. PWRs is a major factor in these calculated crack growth times. As the wall thickness increases, the distance for the crack to grow increases.

These limiting axial crack growth calculation results reflect some key conservatisms that tend to provide increased assurance of the structural integrity of the cold leg piping at NAPS1:

• The limiting crack growth result is for axial flaws, which are not a credible concern for becoming unstable and causing rupture of the pressure boundary.

This is because the critical flaw length of a through-wall axial flaw for causing unstable rupture in this case is much greater than the axial width of Alloy 82/182 weld metal susceptible to PWSCC. For the limiting case, the calculated time for a flaw detectable via UT to grow though the weld thickness and cause leakage is 13.1 years using a 10% through-wall initial depth.

• A universal weight function method was applied to accurately calculate the stress intensity factor resulting from the through-wall stress distribution. This approach does not fit a polynomial to approximate the stress profile, as is often the case when applying published solutions such as the method of influence coefficients. Fitting the stress profile to a polynomial can introduce a significant source of modeling uncertainty depending on the accuracy of the fit obtained.

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 6 of 10 Assuming the same through-wall WRS profile is present along the entire length of the modeled axial crack is conservative.

• For modeling axial cracks, the stress intensity factor calculation conservatively does not credit the effect of flaw total-length-to-depth aspect ratios (2c/a) below

1. Because of the lack of published solutions for this range of aspect ratios, a conservatism is introduced by assuming 2cla = 1 in the stress intensity factor calculations when 2cla < 1. This results in stress intensity factors at the deepest point on the crack somewhat greater than the true stress intensity factor corresponding to the true aspect ratio with identical crack loading. The end result is a conservatism in the calculated crack growth time, since the axial crack growth occurs with 2cla < 1 during most of the time.

Conclusions There are significant radiological, industrial safety, and mobilization cost benefits in aligning the SG cold leg nozzle examinations with the SG hot leg nozzle examinations. The mitigated SG hot leg examinations are required once per interval (10 years) and are usually coordinated with the cold leg nozzles which are required to be examined within 7 years. Otherwise, there is remobilization for the cold leg nozzle exams on a different frequency of 6 years (with 18-month cycles) and again for the hot leg nozzle at 9 years. Both alternatives increase dose, outage scheduling, and resource costs. Increasing the cold leg nozzle exams from 7 years to once per interval (effectively 9 years) allows alignment of the cold leg and hot leg examinations, therefore improving radiological and industrial safety and resource efficiencies while maintaining an acceptable level of quality and safety.

Conclusions from MRP-349 technical basis include:

(1) All known incidents of cracking in large bore Alloy 82/182 piping welds have occurred in locations operating at hot leg temperatures or higher; (2) No safety or structural integrity concern has resulted from cold leg butt weld PWSCC to date; (3) The flaw tolerance analyses performed to date have shown that the critical crack sizes in large-diameter butt welds operating at cold leg temperatures are very large, and those that initiate take a very long time to grow to critical size; (4) Analyses performed to calculate the probability of failure for Alloy 82/182 welds using both probabilistic fracture mechanics and statistical methods have shown that the likelihood of cracking or through-wall leaks in large diameter

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 7 of 10 cold leg welds is very small. Sensitivity studies performed using probabilistic fracture mechanics have shown that even for the more limiting high temperature locations, more frequent inspections than required by Section XI, such as that in MRP-139 or Code Case N-770, have only a small benefit in terms of risk. While the increased inspection frequency from Code Case N-770 may be needed for the more susceptible hot leg locations, it is not necessary to maintain an acceptable level of safety and quality for the cold legs.

The plant-specific crack growth evaluation concluded that more than 10 years is required for crack growth from the standard detectability limit to the allowable size per the ASME Section XI IWB-3640 flaw evaluation procedure.

The flaw evaluation procedure also concluded that the crack growth rate for axial cracks was greater than for circumferential cracks, and axial flaws are bounding of the growth time and not a credible concern for causing pipe rupture.

The reexamination interval can be extended from 7 years as required by Code Case N-770 to the requested interval length of once per interval (10 years) while maintaining an acceptable level of quality and safety. For these reasons, it is requested that the NRC authorize this proposed alternative in accordance with 10 CFR 50.55a(z)(1).

6. Duration of Proposed Alternative

The provisions of this alternative are applicable to the fifth 10-year inservice inspection interval for NAPS1 which commenced on May 1, 2019 and ends on April 30, 2029, until the welds are examined during the spring 2024 RFO (N1R30).

7. Precedents

Similar proposed alternatives for unmitigated Alloy 82/182 piping butt welds were previously approved by the NRC for the following licensees:

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 8 of 10 NRC ADAMS Accession No.

Approval Plant NRC Safety Date Relief Request Evaluation Comanche Peak Unit 1 ML15300A013 ML16074A001 03/14/2016 Farley Units 1 and 2 ML14084A203 ML14262A317 12/05/2014 Indian Point Unit 2 ML13064A299 ML13310A575 11/14/2013 Indian Point Unit 3 ML14017A054 ML14199A444 08/04/2014 McGuire Unit 1 ML15083A045 ML15232A543 08/27/2015 South Texas Project Unit 1 ML15133A130 ML15218A367 08/21/2015 South Texas Project Unit 2 ML16076A319 ML16174A091 06/30/2016 North Anna Unit 2 ML18093B076 ML19039A236 02/14/2019

8. References

1. ASME Boiler and Pressure Vessel Code,Section XI, 2013 Edition.

2. Materials Reliability Program: PWR Reactor Coolant System Cold.:.Loop Dissimilar Metal Butt Weld Reexamination Interval Extension (MRP-349): A Basis for Revision to the Requirements of MRP-139 and American Society of Mechanical Engineers Code Case N-770 for Large-Diameter Welds at Cold-Leg Temperatures. EPRI, Palo Alto, CA: 2012. 1025852. [Freely available at www.epri.com]

3. Dominion Engineering, Inc., "Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles," Calculation No. C-4520-00-02-NP, Rev. 0.

[Attachment 2]

4. Dominion Engineering, Inc., "Crack Growth Analysis for NAPS Unit 1 Steam Generator Outlet Nozzles," Calculation No. C-4520-00-02, Rev. 0. [Attachment 3]

5. Dominion Engineering, Inc., "Welding Residual Stress Calculation for North Anna Steam Generator DMW," Calculation No. C-4520-00-01, Rev. 0, dated December 20, 2017.

6. Materials Reliability Program: Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Alloy 82, 182, and 132 Welds (MRP-115). EPRI, Palo Alto, CA: 2004. 1006696. [Freely available at www.epri.com]

Serial # 20-028 Docket No. 50-338 SG Cold Leg Interval Extension Page 9 of 10

7. Materials Reliability Program: Primary Water Stress Corrosion Cracking (PWSCC) Flaw Evaluation Guidance (MRP-287), EPRI, Palo Alto, CA: 2010.

1021023. [Freely available at www.epri.com]

8. ASME Code Case N-770-5, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated with UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities,"Section XI, Division 1."

. I# 20-028 Sena Doc ket No. 50-338 SG Cold Leg lnte I Extension

ge 10 of 10 FIGURE 1

Serial No.: 20-028 Attachment 3 Calculation C-4520-00-02-NP, "Crack Growth Analysis for NAPS Unit 1 Steam Generator Outlet Nozzles" [Non-Proprietary Version]

Revision 1 Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Unit 1

Dominion fninmin No:--:-PROPRIET.-\RY VERSI(l:\

CALCULATION

1/

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 1 of 32 RECORD OF REVISIONS Prepared by Checked by Reviewed by Approved by Rev. Description Date Date Date Date 12/20/2017 12/20/2017 12/20/2017 12/20/2017 0 Original Issue M Burkardt G Lener GA While GA. White Associate Engint:er Engincl.!r Principal Engrnca Pnncipal Engineer I Added stress intensity factor t1. 3,.,1..,,,d, G. 1.L.-* / f\.V\ &,l>r.

profiles for axial and circumferential crack growth calculation.

"'" ii, ?.,Ol 0 M. Burkard!

I /16/2020 G Lenci J*\ \\b(io GA While v>

,t\fD Semor Engineer Senior Engineer Principal Engineer Prmcipal Engineer The last revision number to reflect any changes for each section of the calculation is shown in the Table of Contents. The last revision numbers to reflect any changes for tables and figures are shown in the List of Tables and the List of Figures. Changes made in the latest revision. except for Rev. 0 and revisions which change the calculation in its entirety. are indicated by a double line in the right hand margin as shown here.

NON-PROPRIETARY VERSION 12100 Sunrise Valley Drive, Suite 220

• Reston, VA 20191

• PH 703.657.7300

• FX 703.657.7301

Dominion fnineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 2 of 32 TABLE OF CONTENTS Last Mod.

Section Page Rev.

1 PURPOSE ..................................................................................................................................... 4 0 2

SUMMARY

OF RESULTS ................................................................................................................. 4 0 3 INPUT REQUIREMENTS .................................................................................................................. 6 0 4 ASSUMPTIONS .............................................................................................................................. 7 0 5 ANALYSIS ..................................................................................................................................... 9 0 5.1 Stress Intensity Factor Calculation ................................................................................. 9 0 5.1.1 Loads and Stresses ......................................................................................... 9 1 5.1.2 Universal Weight Function Method ................................................................ 12 0 5.2 Crack Growth Calculation ............................................................................................. 16 0 5.2.1 Approach........................................................................................................ 16 0 5.2.2 Results ........................................................................................................... 18 1 5.3 Software Usage ............................................................................................................ 19 0 6 REFERENCES ............................................................................................................................. 19 0 A CONTENTS OF DATA DISK D-4520-00-02..................................................................................... 29 0 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion Enineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 3 of 32 LIST OF TABLES Last Mod.

Table No. Rev.

Table 1. Crack Growth Results 0 Table A-1. Software Usage Records 0 LIST OF FIGURES Last Mod.

Figure No. Rev.

Figure 1. Annotated Drawing Indicating Wall Thickness and Average Weld Width (Average 0 of Maximum and Minimum Widths)

Figure 2. Residual Plus Operating Stress Profiles Applied for PWSCC Crack Growth 0 Calculations using 360 ° 45% Through-Wall ID Weld Repair Figure 3. Residual Plus Operating Stress Profiles Applied for PWSCC Crack Growth 0 Calculations using No Weld Repair Figure 4. Axial Crack Depth, alt, as a Function of Time 0 Figure 5. Circumferential Crack Depth, alt, as a Function of Time 0 Figure 6. Axial Crack Half-Length on ID, c, as a Function of Time 0 Figure 7. Circumferential Crack Half-Length on ID, c, as a Function of Time 0 Figure 8. Axial Crack Aspect Ratio, 2cla, as a Function of Time 0 Figure 9. Circumferential Crack Aspect Ratio, 2cla, as a Function of Time 0 Figure 10. Axial Crack Stress Intensity Factor at Deepest Point, Kgo, as a Function of Crack 1 Depth Figure 11. Circumferential Crack Stress Intensity Factor at Deepest Point, Kgo, as a 1 Function of Crack Depth Figure 12. Axial Crack Stress Intensity Factor at Surface Point, Ko, as a Function of Crack Depth Figure 13. Circumferential Crack Stress Intensity Factor at Surface Point, Ko, as a Function 1 of Crack Depth 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion fnineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 4 of 32 1 PURPOSE The steam generator outlet nozzles at North Anna Power Station (NAPS) Unit 1 are joined to stainless steel safe ends with Alloy 82/182 double V-groove butt welds [1]. Requirements for periodic examination of Alloy 82/182 butt welds in pressurized water reactor (PWR) primary system piping are currently specified by ASME Code Case N-770-2 [2], which is mandated with conditions by U.S.

Nuclear Regulatory Commission (NRC) per 10 CPR 50.55a(g)(6)(ii)(F). This code case requires that a volumetric examination be performed of unmitigated cold-leg butt weld locations such as the NAPS Unit 1 steam generator outlet nozzles every second inspection period (as defined by ASME Section XI), not to exceed 7 years.

This calculation provides a technical basis for an alternative volumetric reexamination interval for the NAPS Unit 1 steam generator outlet nozzles. Specifically, the crack growth calculation demonstrates the acceptability of a volumetric reexamination interval of once per ASME Section XI interval, which is nominally 10 years. This is the interval specified by ASME Code Cases N-770-3 [3] and N-770-4

[4] per Inspection Item B-2 for unmitigated cold-leg butt weld locations nominal pipe size (NPS) 14 or larger. The NAPS Unit 1 steam generator outlet nozzles would be categorized under Inspection Item B-2 of these code case versions, which are not currently approved by NRC.

2

SUMMARY

OF RESULTS Crack growth calculations were performed considering the specific geometry and loads applicable to the NAPS Unit 1 steam generator outlet nozzles, including the weld residual stress (WRS) analysis results documented in C-4520-00-01, Rev. 0 [5]. These calculations applied the common deterministic approach for unmitigated Alloy 82/182 piping butt welds in PWRs. The results of these crack growth calculations demonstrate the acceptability of the alternative volumetric reexamination interval (once per Section XI interval, nominally 10 years) specified by ASME Code Cases N-770-3 [3] and N-770-4

[4] per Inspection Item B-2 for unmitigated cold-leg butt weld locations NPS 14 or larger.

The crack growth calculations presented below demonstrate that the alternative frequency of volumetric examinations is sufficient to provide reasonable assurance of the structural integrity of the cold-leg piping at NAPS Unit 1. Hence, the alternative frequency provides an acceptable level of quality and safety.

12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion fnineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 5 of 32 The key results of the crack growth calculations are as follows:

• The crack growth rate for axial cracks was found to be greater than for circumferential cracks, due to the total (residual plus operating) hoop stresses being greater than the total axial stresses.

Thus, the analysis cases for axial cracks are the limiting cases.

• The limiting case for the calculated time for a crack to grow from 10% through-wall to the allowable depth is 10.3 years. The limiting case is for an axial crack growing to an allowable depth of 75% through-wall. In this limiting case, an additional 2.8 years is calculated for the axial crack to penetrate through the remaining 25% of the wall thickness.

• The relatively large thickness of the subject Alloy 82/182 weld (4.813 inches) compared to other Alloy 82/182 butt welds in U.S. PWRs is a main factor in these calculated crack growth times.

As the wall thickness increases, the distance for the crack to grow increases.

These limiting axial crack growth calculation results reflect some key conservatisms that tend to provide increased assurance of the structural integrity of the cold-leg piping at NAPS Unit 1:

• The limiting crack growth result is for axial flaws, which are not a credible concern for becoming unstable and causing rupture of the pressure boundary. This is because the critical flaw length of a through-wall axial flaw for causing unstable rupture in this case is much greater than the axial width of Alloy 82/182 weld metal susceptible to primary water stress corrosion cracking (PWSCC) (see Section 5.2.2). For the limiting case, the calculated time for a flaw detectable via ultrasonic testing (UT), i.e., initial depth of 10% through-wall, to grow though the weld thickness and cause leakage is 13.1 years.

• As discussed in Section 5.1.2, a universal weight function method was applied to calculate accurately the stress intensity factor resulting from the through-wall stress distribution. This approach does not fit a polynomial to approximate the stress profile, as is often the case when applying published solutions such as the method of influence coefficients. Fitting the stress profile to a polynomial can introduce a significant source of modeling uncertainty depending on the accuracy of the fit obtained. Conservatism results from assuming that the same through-wall WRS profile is present along the entire length of the modeled axial crack.

• For modeling axial cracks, the stress intensity factor calculation conservatively does not credit the effect of flaw total-length-to-depth aspect ratios (2c/a) below 1. Because of the lack of published solutions for this range of aspect ratios, a conservatism is introduced by assuming 2c/a = 1 in the stress intensity factor calculations when 2c/a < 1. This results in stress intensity factors at the deepest point on the crack somewhat greater than the true stress intensity factor corresponding to the true aspect ratio with identical crack loading. The end result is a conservatism in the calculated crack growth time since the axial crack growth occurs with 2c/a < 1 during most of the time (see Figure 8).

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Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 6 of 32 3 INPUT REQUIREMENTS The following inputs were used in support of this calculation:

1. Key dimensions required for the crack growth calculation are as follows:

a. Dissimilar metal weld (DMW) region machined ID: 3 1.03 in. [1, Figure 4]

b. Wall Thickness: 4.8 13 in. (at centerline of double-V groove, as shown in Figure 1) [1, Figure 4]

2. The DMW for the steam generator outlet nozzle is fabricated using Alloy 182 and/or Alloy 82 [I]

3. The crack growth rates for Alloy 182 are evaluated per the MRP- 1 15 [6] crack growth rate disposition curve, which is also specified in Nonmandatory Appendix C of ASME Section XI [7]

4. The operating temperature of the steam generator outlet nozzle is: 549 °F [8]

5. The operating pressure, P, is 2235 psig [1, Table 4]

6. The operating stress profiles are defined in C-4520-00-01 RO [5]

a. Cold-leg hoop stress profile for 45% weld repair

b. Cold-leg axial stress profile for 45% weld repair

c. Cold-leg hoop stress profile for no weld repair I

d. Cold-leg axial stress profile for no weld repair

7. Nozzle operating forces are as follows [1, Table 6] (tensile forces are positive):

Corifidential I

I Commercial Information I

8. Nozzle operating moments due to normal thermal expansion are as follows [1, Table 6]:

Confidential Commercial Information I l

9. Nozzle operating moments due to pressure are as follows [l, Table 6]:

Confidential Commercial Information I l

10. Nozzle operating moments due to dead weight are as follows [l, Table 6]:

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11. Influence coefficients used in the stress intensity factor calculation were obtained from API 579-1 I ASME FFS-1 [9, Table C.12 and Table C.14]

4 ASSUMPTIONS

1. In accordance with the standard approach of the nonmandatory appendices of ASME Section XI

([7], [10]), circumferential and axial surface flaws evaluated in this subcritical growth calculation are modeled to have semi-elliptical shape.

2. The weld material is reported in technical documentation as Alloy 182 or Alloy 82 [1]. The standard deterministic crack growth rate for Alloy 182 per MRP-115 [6] and Nonmandatory Appendix C of ASME Section XI [7] is conservatively applied for the weld material as it is higher than the corresponding crack growth rate for Alloy 82 per these standard references.

3. For the axial crack growth calculation, the double V-groove weld cross-sectional geometry is approximated as a rectangular geometry with a constant width equal to the average width of the double V-groove weld. This width limits the axial extent of the modeled axial crack. This average weld width (average of maximum and minimum weld width as shown in Figure 1) is 1.6 in. [1, Figure 4].

4. An initial flaw depth of 10% through-wall (alt = 0. l) is applied on the basis that this is the minimum flaw depth covered by the ASME Section XI Appendix VIII, Supplement 10 qualifications for UT flaw detection [11].

5. As cracking degradation in piping butt welds is dominated by PWSCC, fatigue crack growth is not modeled in this calculation. Accordingly, the effects of transient loading are not considered to be significant, and are thus not modeled. The dominance of PWSCC growth is illustrated by the crack growth results of Reference [12] for the NAPS Unit 2 steam generator inlet and outlet nozzles.

6. For axial cracks, the maximum length of the flaw is limited to the axial extent of the Alloy 82/182 weld. It is widely accepted that the PWSCC growth mechanism does not have a significant effect in stainless or low-alloy steels for a normal primary water environment relative to PWSCC growth in the Alloy 82/182 weld [13]. The subject DMWs are exposed to flowing primary water and not stagnant conditions where impurity ions or oxygen could concentrate. The experience for the leaking reactor vessel outlet nozzle weld at V.C. Summer Station illustrates the expected behavior. The leak in this weld was caused by an axial crack extending over most of the weld cross section without penetrating a significant distance into the low-alloy steel nozzle or stainless steel pipe materials [14]. For circumferential cracks, the maximum length of the flaw remains less than the inner circumference of the DMW. Thus, the maximum circumferential flaw length does not need to be limited in this analysis.

7. For axial flaws, an initial aspect ratio (2c/a) of 2 is appropriate because the axial flaw growth due to PWSCC is limited to the axial length of the dissimilar metal weld (as indicated in Assumption 6). For circumferential flaws, an initial aspect ratio (2c/a) of 10 is conservatively applied.

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8. When calculating the effective bending moment and OD bending stress, circumferential cracks are conservatively assumed to be centered at the point of maximum bending tensile stress.

9. Each component (Mx, My, and Mz) of the effective bending moment is calculated conservatively using the maximum between the absolute value of the sum of the "max" and that of the "min" moment contributions (NTE, pressure, DW) for the same moment component, as in Equation

[4-1]. The effective bending moment (Meff) is then determined as a combination of the bending and torsional moments based on a Von Mises stress approach:

[4-1]

10. Values for Go and G1 influence coefficients are obtained by interpolating or extrapolating from tables in API Standard 579-1/ASME FFS-1 [9, Table C.12 and Table C.14]. For input parameters outside the domains provided in the tables, extrapolation is performed following Assumption 11.

For input parameters inside those domains, influence coefficients are determined through log linear interpolation in tlRi and in ale, and linear interpolation in alt.

11. Solutions for influence coefficients Go and G1 are provided in API Standard 579-1/ASME FFS-1

[9] only for alt ::S 0.8 and for ale 0.125 (for the tlRi values of interest). In order to predict the time to through-wall growth, the influence coefficients are linearly extrapolated for the range 0.8 <alt<1.0. Extrapolation of influence coefficients for alt> 0.8 is considered to be standard practice, and has also been applied in probabilistic fracture mechanics codes such as xLPR (Etremely 1.ow .r_robability of Rupture) [15]. Furthermore, the time required for a crack to grow from 10% through-wall to through-wall (which is affected by this extrapolation for alt> 0.8) is considered to be a secondary result of this calculation. The time required for a crack to grow from 10% through-wall to the allowable depth (no greater than 75% through-wall), which is the primary result of this calculation, remains unaffected by this assumption. The influence coefficients are log-linearly extrapolated for ale<0.125 because there are no influence coefficients available in this range in API Standard 579-11ASME FFS-1 for the tlRi values of interest. It would be nonconservative to apply influence coefficients for ale = 0.125 when calculating stress intensity factors for ale<0.125.

12. As recommended by Rudland, et al. [15], the influence coefficients and the flaw shape parameter are evaluated consistently with the available influence functions. For crack aspect ratios ale> 2.0 (2c/a < 1), a crack aspect ratio of ale = 2.0 (2c/a = 1) is applied in evaluating the influence coefficients and flaw shape parameter.

13. A plant capacity factor of 0.93 is applied to account for time in which the plant is not operating (e.g., due to refueling outages). This assumption is considered to be conservative.

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14. The residual stress profile is represented as a piecewise linear stress profile, as defined within C-4520-00-01 RO [5]. Defining a piecewise linear stress profile with a relatively fine spatial resolution of 2.5% through-wall (TW) as done here is considered appropriate for stresses output from finite-element analyses at discrete locations through the thickness of the weld ([10], [16]).

15. The WRS profile applied in the stress intensity factor calculations resulting in the limiting crack growth times assumes the presence of a 360° 45% through-wall weld repair on the inner diameter (ID) surface from plant construction. As a detailed review of the weld fabrication records for NAPS Unit 1 [17] shows that such a 360° weld repair conservatively bounds the actual ID weld repair depth affecting the NAPS Unit 1 steam generator outlet nozzle Alloy 82/182 welds (up to 41.6% ), this weld repair case was applied instead of the general default assumption of a 50%

through-wall weld repair on the ID surface.

16. A time step of 1 month is applied for the crack growth calculation. This time step is appropriately refined to yield converged results given the time-scale over which a crack grows through the thickness of the weld (i.e., greater than 10 years).

17. Numerical integration for the weight function integral is performed using 10,000 bins, and a value of y = 0.57. These values were selected using sensitivity studies to ensure appropriate numerical convergence of the stress intensity factors resulting from the weight function integrals.

5 ANALYSIS The purpose of this section is to describe the stress intensity factor calculations (Section 5.1) and crack growth calculations (Section 5.2) performed for the North Anna Unit 1 steam generator outlet nozzle dissimilar metal welds. Deterministic crack growth calculations that are documented in this section are used to determine the time required for axial and circumferential cracks to grow (1) to a depth of 75%

through-wall (maximum allowable depth when flaw stability is not limiting [7]) or (2) through the thickness of the weld.

5.1 Stress Intensity Factor Calculation 5.1.1 Loads and Stresses Tensile stresses are one of the key factors influencing PWSCC. For the purposes of crack growth calculations, separate stresses are considered in the hoop direction (which drive axial crack growth) and the axial direction (which drive circumferential crack growth).

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Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 10 of 32 This calculation appropriately considers weld residual stresses, operating pressure stresses, operating temperature stresses, and piping loads due to dead weight, pressure, and thermal expansion. The effect of transient stresses is not significant, as discussed in Assumption 5.

Weld residual stresses, operating pressure stresses, and operating temperature stresses were calculated using finite-element analyses that are documented in C-4520-00-01 [5]. In the finite-element model, the final length of the safe end (weld center-line to weld center-line) is 8.31 inches. The through-wall operating stress profile considering these load sources was determined in C-4520-00-01 [5] and is shown in Figure 2 (45% through-wall ID weld repair case) and Figure 3 (no weld repair case). The axial operating stress profile is given as (jop,a(x/t), and the hoop operating stress profile is given as (iop,h(X/t).

Piping loads due to dead weight, pressure, and normal thermal expansion act to create a longitudinal force component, a torsion moment, and two orthogonal bending moments. These loads have a null or negligible effect on the hoop stress. The axial membrane stresses due to dead weight and normal thermal expansion are calculated as follows:

[5-1]

FNTE,x (jNTE,a =--

A ' [5-2]

where Fow;x and FNTE;x are the axial forces due to dead weight and normal thermal expansion, respectively, and A is the axial cross-sectional area of the weld. The axial membrane stress due to the end cap pressure loading is included in the axial operating stress profile (jop,a(x/t) from the finite element analysis.

The axial bending stress is calculated using the bending moment and torsion components of the dead weight, pressure, and normal thermal expansion piping loads. An effective bending moment (Meff) is determined as a combination of the bending and torsional moments based on a Von Mises stress approach:

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2 2 2 MX J [5-3]

As discussed in Assumption 9, when calculating the effective bending moment, the inputs describing the "max" and "min" values for dead weight, pressure, and normal thermal expansion are used to calculate a conservative effective bending moment according to Equation [4-1]. Based on the moments specified in Inputs 8, 9, and 10, an effective bending moment of 13,053 in-kips (1,474.8 kN-m) is calculated. The outer diameter (OD) bending stress at the point of maximum bending is then calculated as:

[5-4]

[5-5]

where R0 is the weld outer radius and Jis the moment of inertia of the weld cross-sectional area.

For both axial and circumferential cracks, a membrane stress accounting for the effect of crack face pressure, P, equal to the operating pressure acting on the crack face is also considered.

As the principle of superposition applies for linear-elastic fracture mechanics, the individual membrane stress contributions defined above are superimposed to obtain a total stress profile. The resulting total axial stress profile is defined as:

O"tot,a ( X) = O"op,a ( X) + O"DW,a + O"NTE,a + p *

[5-6]

For circumferential cracks, the global bending stress, UB, is applied separately in the K calculation.

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Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 12 of 32 The resulting total hoop stress profile is defined as:

(Ttot,h ( X) = (Top,h ( X) + p *

[5-7]

5.1.2 Universal Weight Function Method Given the total hoop and axial stress profiles defined in Section 5 .1.1, along with the orientation, depth, and aspect ratio of the crack, stress intensity factors can be calculated. To facilitate flexibility in total stress profile applied to the crack face, instead of fitting a polynomial to the stress profile and applying the influence coefficient method, the universal weight function method is applied. The general form of the mode I stress intensity factor calculation by way of the universal weight function method is given by [9]:

a KI= Jo r h(x, a)a-tot ix)dx' [5-8]

where:

K1 = mode I stress intensity factor (MPam)

X = distance from the ID surface (m) a = crack depth (m), and h(x,a) = weight function.

For circumferential cracks, there is an additional contribution to the mode I stress intensity factor due to a global bending moment. With this additional term, the form of the stress intensity factor for circumferential cracks is given by:

K, = c,B G, + J: h(x, )c,w.,,(x)dx, a

[5-9]

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Gs = influence coefficient for the effect of global bending on a circumferential flaw centered at the point of maximum bending stress Q = flaw shape parameter defined below in Equation [ 5-18]

In general, the weight function, h(x,a) is a function of the influence coefficients, Go and G1. For the purpose of modeling crack growth under the semi-elliptical crack shape approximation (Assumption 1), the universal weight function method is applied to calculate separate stress intensity factors for the deepest point and the surface point of the semi-elliptical flaw.

For the deepest point, the influence coefficients Go and G1 are determined as:

G90,i = LA,,,;

n=O

[5-10]

and for the surface point, the influence coefficients Go and G1 are determined as:

Go.=LI ..

,I -L-'Q,1

[5-11l The individual An,i and Ao,i fitting coefficients are obtained from linear-elastic finite element analyses.

These fitting coefficients are tabulated in API 579-1 I ASME FFS-1 [9, Table C.12 and Table C.14] for specific combinations of the ratio of the weld thickness to inner radius (tlRi), the ratio of the crack depth to crack half-length (ale), and the ratio of the crack depth to the weld thickness (alt).

Values from tables of Go and G1 influence coefficients are interpolated in tlRi, ale, and alt to obtain values of Go and G1 specific to the crack geometry. This is accomplished by performing interpolation of the influence coefficients (Assumption 10):

1. Log-linear interpolation in t/Ri

2. Log-linear interpolation in ale

a. If ale> 2.0, evaluate using ale = 2.0 (Assumption 12)

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3. Linear interpolation in alt

a. If alt> 0.8, linearly extrapolate up to alt = 1.0 (Assumption 11).

Crack-geometry-specific Go and G1 influence coefficients are then applied to compute the weight function coefficients, U (for the deepest point) and Ni (for the surface point) [9, Section C.14.2]:

21r 24 Ml= Mn ( 3G901* -G90*0 ) --

v2 Q s [5-12]

M2- -3

[5-13]

61r (

M3 = r,:;;::;

) +-8 v2 Q G90

• 0 -2G901* s [5-14]

[5-15]

[5-16]

[5-17]

where the flaw shape parameter, Q, is applied using the definition in API 579-1 I ASME FFS-1 [9, Section C.3.4.1] modified according to Assumption 12:

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( r 65 c

Q= l.0+l.464 : for 2.0 :2: ale> 1.0.

( r [5-18]

65 l.0+l.464 for ale >2.0 2 r For the deepest point ofa semi-elliptical surface crack, the weight function, h90, is then defined as [9]:

= ,j [1+M (1- x) +M2 (1- x)+M3 (I- x)312 2

112

].

h,,(x, a ) a a a [5-19]

2Jr(a-x) 1 Similarly, for the surface point ofthe crack, the weight function, ho, is defined as [9]:

[5-20]

The integrals for the stress intensity factors (Equations [5-8] and [5-9]) are numerically evaluated for each individual time step using open extended formulas and using strategies to obtain accurate solutions despite the integrable power-law singularities at their lower or upper limits [I 8].

The following identity is applied ifthere is a singularity at the lower limit ofthe integral (as is the case when evaluating Ko):

r f(x)dx=-l-t -af' t lr 1(/r +a\+ (b>a).

b a I-r o r [5-21]

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ra I-r o b

f(x)dx=-l-t -atr t lrt(b-t lr}t (b>a).

[5-22]

The right-hand side integrals in Equations [5-21] and [5-22] are solved by dividing the integration domain into 10,000 intervals, using a value of y = 0.57 (Assumption 17), and applying the open numerical integration expression shown below [I 8]:

The resulting stress intensity factors are then input into the crack growth calculation, which is detailed in Section 5.2.

5.2 Crack Growth Calculation 5.2.1 Approach The crack growth rates for axial and circumferential cracks in the Alloy 82/182 weld metal are calculated considering the PWSCC growth mechanism. Per Assumption 5, as cracking degradation in the subject weld is dominated by PWSCC, fatigue crack growth is not modeled in this calculation.

Accordingly, the standard PWSCC crack growth rate equation for Alloy 182 ([6], [7]) is applied for the crack growth calculation (see Assumption 2):

da = exp [- Qg dt R T

(_!_- -J] 1 Tref aK1P

'90 [5-24]

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dt e= exp[- Qg R T (l_ __ l J]aKP Tref i,o , [5-25]

where da/dt = crack growth rate at the deepest point ofthe crack (m/s) dc/dt = crack growth rate at the surface point ofthe crack (mis)

Qg

= thermal activation energy for crack growth = 130 kJ/mol ([6], [7])

R = universal gas constant = 8.314x 10-3 kJ/mol-K T = absolute operating temperature at crack location = 560.4 K (Input 4)

Tref = absolute temperature (325° C) used to normalize crack growth data = 598.15 K ([6],

[7])

a = crack growth rate coefficient = l .5x 10- 12 at 325° C for mis and MPam ([6], [7])

K1,90 = stress intensity factor at the deepest point ofthe crack, calculated per Section 5.1.

(MPam)

K1,o = stress intensity factor at the surface point ofthe crack, calculated per Section 5.1.

(MPa m) f3 = crack growth rate exponent = 1.6 ([6], [7])

To model growth ofthe cracks over time, the crack growth rate is calculated and integrated to determine the new crack length and depth using one-month time steps (Assumption 16). The crack growth rates obtained in Equations [5-24] and [5-25] are multiplied by the plant capacity factor (Assumption 13) to account for calendar time in which the plant is not operating (e.g., due to refueling outages). Using this approach, the times required (1) to produce a flaw with a depth of75% through wall (maximum allowable depth when flaw stability is not limiting) and (2) for the flaw to penetrate through-wall (resulting in leakage) are calculated.

Initial conditions applied assume an initial depth of l 0% through-wall (Assumption 4), along with an initial aspect ratio (2c/a) of2 for axial flaws and an initial aspect ratio (2c/a) of10 for circumferential flaws (Assumption 7). Two WRS analysis cases were considered, assuming either no weld repair or a 360 ° 45% through-wall weld repair on the ID surface (Assumption 15).

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Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 18 of 32 5.2.2 Results The results of the crack growth calculations are summarized in Table 1 and shown in Figure 4 through Figure 9. Crack depth as a function of time is shown in Figure 4 and Figure 5 for axial and circumferential cracks, respectively. Figure 6 and Figure 7 show the crack half-length on the ID surface as a function of time for axial and circumferential cracks, respectively. Figure 8 and Figure 9 show the crack aspect ratio (2c/a) as a function of time for axial and circumferential cracks, respectively.

In addition, plots are provided showing the key intermediate result of the crack-tip stress intensity factors applied in the crack growth equation. Figure 10 and Figure 11 show the crack-tip stress intensity factor at the deepest point (K90) as a function of crack depth (alt), and Figure 12 and Figure 13 show the crack-tip stress intensity factor at the surface point (Ko) as a function of crack depth (alt),

for axial and circumferential cracks, respectively.

Allowable flaw size calculations [12] performed in accordance with ASME Section XI confirm that the allowable flaw depth limit for axial flaws is 75% through-wall. These calculations were performed for the NAPS Unit 2 steam generator inlet and outlet nozzles. However, for axial flaws, which are subject only to pressure load in the calculation, those results also directly apply to NAPS Unit 1. Reference

[12] reports an allowable depth of 75% through-wall for axial flaws with lengths up to at least 7.4 inches, which as expected bounds the lengths reported below in Figure 6. For circumferential cracks, Reference [12] reports an allowable depth of 75% through-wall for circumferential flaw lengths up to at least 40% of the circumference. For the circumferential crack growth cases resulting from the present work, the flaw depth and length (Figure 5 and Figure 7) remain within these allowable limits for at least 57.3 years. In the limiting circumferential flaw case, the total flaw length on the ID (2c) reaches 40% of the circumference (i.e., 40% of 97.5 in., or 39.0 in.) after 57.3 years and 75% through wall after 83.1 years. Although there are differences in the design loads applicable to circumferential cracks for the steam generator outlet nozzles at NAPS Unit 1 [1] versus the load inputs of Reference

[12] for NAPS Unit 2, the axial flaw geometry is clearly limiting with regard to the time to reaching the allowable flaw depth. After 10 years, the total length for the limiting 45% ID repair circumferential flaw case is calculated to be about 9.3 inches (see Figure 7), which is only about 10% of the circumference at the weld ID, and the corresponding flaw depth is less than 50% through-wall (see Figure 5). Conservatively assuming a constant-depth circumferential flaw geometry, these dimensions 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

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The times required for a flaw with an initial depth of 10% through-wall to grow (1) to a depth of 75%

through-wall (maximum allowable depth per ASME Section XI when flaw stability is not limiting [7])

and (2) through-wall are reported in Table 1. The limiting case for the time for a flaw to grow from an initial depth of 10% through-wall to the allowable depth per ASME Section XI is for an axial flaw. In this limiting case, the growth time is 10.3 years, the allowable flaw depth is 75% through-wall, and an additional 2.8 years is calculated for the axial crack to penetrate through the remaining 25% of the wall thickness.

5.3 Software Usage The following software, controlled in accordance with DEi's quality assurance program for nuclear safety-related work [19], was used in preparing this calculation.

The stress intensity factor and crack growth calculations used in this work were performed using Python 3.5 as a one-time-use engineering analysis computer program on a Dell Precision 5510 with an Intel Core i5-6300HQ processor and running Windows 7 Professional (Service Pack 1). The results from this one-time-use program were checked and reviewed in accordance with DEi's nuclear quality assurance (QA) program manual [19]. Each output from the one-time-use Python calculation is individually verified in Memo M-4520-00-02 [20]. The alternate calculation documented in the memo was performed using Excel 2010. Furthermore, the memo compares results obtained using the Python model with axial and circumferential crack growth calculations published in peer-reviewed papers for Alloy 82/182 piping butt welds. Native electronic files for the Software Usage Records associated with the above software use are included in the data disk that accompanies this calculation [21]. These files are listed in Appendix A of this calculation.

6 REFERENCES

1. Westinghouse Letter to Dominion Generation, LTR-SGDA-09-32, Dated March 13, 2009,

Subject:

Transmittal of Design Information for North Anna Unit 1 Model 51F Steam Generator Channel Head Primary Nozzles.

2. ASME Code Case N-770-2, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated With UNS N06082 or UNS 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

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Section XI, Division 1, American Society of Mechanical Engineers, New York, Approval Date:

June 9, 2011.

3. ASME Code Case N-770-3, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated With UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities,"

Section XI, Division 1, American Society of Mechanical Engineers, New York, Approval Date:

April 7, 2013.

4. ASME Code Case N-770-4, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated With UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities,"

Section XI, Division 1, American Society of Mechanical Engineers, New York, Approval Date:

May 7, 2014.

5. Dominion Engineering, Inc. Calculation C-4520-00-01, Revision 0, December 2017.

6. Materials Reliability Program Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Alloy 82, 182, and 132 Welds (MRP-115), EPRI, Palo Alto, CA: 2004. 1006696. [Freely available at www.epri.com]

7. ASME Boiler and Pressure Vessel Code,Section XI, Nonmandatory Appendix C. 2015 Edition.

8. Incoming Correspondence IC-4520-00-01, Rev. 0, "RE Nominal Operating Conditions," dated January 10, 2017.

9. API Standard 579-1/ASME FFS-1 Fitness for Service, 2007.

10. ASME Boiler and Pressure Vessel Code,Section XI, Nonmandatory Appendix A. 2015 Edition.

11. ASME Boiler and Pressure Vessel Code,Section XI, Mandatory Appendix VIII. 2015 Edition.

12. "Flaw Tolerance Evaluation of Steam Generator Hot Leg Inlet and Cold Leg Outlet Nozzle Dissimilar Metal Welds, North Anna Power Station, Unit 2," Structural Integrity Associates, Inc.,

Calculation File No. 1300532.315, Rev. 0, May 15, 2013.

13. EPRI Materials Degradation Matrix, Revision 3. EPRI, Palo Alto, CA: 2013. 3002000628.

14. G. Rao, G. Moffatt, and A. Mcllree, "Metallurgical Investigation of Cracking in the Reactor Vessel Alpha Loop Hot Leg Nozzle to Pipe Weld at the V.C. Summer Station," Proceedings of the International Symposium, Fontevraud V, September 23-27, 2002.

15. D. Rudland, D.-J. Shim, and S. Xu, "Simulating Natural Axial Crack Growth in Dissimilar Metal Welds due to Primary Water Stress Corrosion Cracking," Proceedings of ASME 2013 Pressure Vessels and Piping Conference, July 14-18, 2013, Paris, France, ASME, 2013. PVP2013-97188.

16. S. Xu, D. Lee, D. Scarth, and R. Cipolla, "Closed-Form Relations for Stress Intensity Factor Influence Coefficients for Axial ID Surface Flaws in Cylinders for Appendix A of ASME Section XI," Proceedings of the ASME 2014 Pressure Vessels & Piping Conference, July 20-24, 2014, Anaheim, California, USA, 2014. PVP2014-28222.

12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion Enfineerinf, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 21 of 32

17. "Fabrication and Repair History of the Unit 1 Steam Generator Outlet Nozzles," Dominion Generation Engineering Technical Evaluation ETE-NA-2017-043, Revision 0, August 2017.

18. W. H. Press, S. A. Teukolsky, W. T. Vetterling, B. P. Flannery, Numerical Recipes. The Art of Scientific Computing. Second Edition. Cambridge University Press, Cambridge, UK, 1992.

19. Dominion Engineering, Inc. Quality Assurance Manual for Safety-Related Nuclear Work, DEI-002, Revision 18, November 2010.

20. Dominion Engineering, Inc. Memorandum M-4520-00-02, "Verification of One-Time Use Software Outputs for C-4520-00-02 RO and C-4520-00-03 RO." Revision 0, December 2017.

21. Dominion Engineering, Inc. Data Disk D-4520-00-02, Revision 0, December 2017.

12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion tnineerin, Inc NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 22 of 32 Table 1. Crack Growth Results t

Crack Weld Residual Stress Growth Time to I Growth Time to Orientation Profile Weld Material, 75% TW (yr) TW (yr)

Axial 45% ID Repair Cold Leg Alloy 182 10.3 13.1 Axial No_Repair Cold Leg Ally 12 129 15.3 CircumferentiaI 45 ID pair Cold Leg Alloy 18_2 83.1 102 Circumferential No Repair Cold Leg Alloy 182 118 130 Maximum weld width Wall thickness Minimum weld width Figure 1. Annotated Drawing Indicating Wall Thickness and Average Weld Width (Average of Maximum and Minimum Widths) 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion fnineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 23 of 32 600 ------------- - - - - - - -

400 i

..=

200 00

" 0

"'=

Q, 0

"'=

-200

5?

-400

-+-Hoop Stress

-+-Axial Stress 0% I 0% 20% 30% 40% 50% 60% 70% 80% 90% I 00%

Percent Through-Wall (x/t)

Figure 2. Residual Plus Operating Stress Profiles Applied for PWSCC Crack Growth Calculations using 360 ° 45% Through-Wall ID Weld Repair 600 ------------------- - -

i..

400 200 00

.5

" 0

"'=

Q, 0

"'=

-200 "0

-400

-+-Hoop Stress

-+-Axial Stress 0% I 0% 20% 30% 40% 50% 60% 70% 80% 90% I 00%

Percent Through-Wall (x/t)

Figure 3. Residual Plus Operating Stress Profiles Applied for PWSCC Crack Growth Calculations using No Weld Repair 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion fnineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 24 of 32 1---- ---------------

I I

,, I 0.9 ,,, ,I 0.8 ,

0.7 _ ,

Z' 3,0.6

..:.=

c; E 04 u

0.3 0.2 0.1 (,/

///,,/-------- 1 -----45% Repair I

- - - No Repair 0 +-'---'-++-'--'--+-+-'--'-+-+-'--'-+-t-'-'--i 0 2 4 6 8 10 12 14 16 18 Time (Years)

Figure 4. Axial Crack Depth, alt, as a Function of Time 1------ - - ----------

0.9 ,

/

I I

,' I 0.8 0.7 Z'

3,0.6

/...--***********

,/... --- -

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- - - No Repair 0 +-'--'-t--'--+.........,f--'-+-'---1 0 20 40 60 80 100 120 140 Time (Years)

Figure 5. Circumferential Crack Depth, alt, as a Function of Time 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion [nineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 25 of 32 1

0.9 0.8 I

-;-0.7 e,

£ 0.6 I

i 05 /

0.4 u OJ 0.2

---

45% Repair 0.1 1 I

- - - No Repair 0

0 2 4 6 8 IO 12 14 16 18 Time (Years)

Figure 6. Axial Crack Half-Length on ID, c, as a Function of Time 40 ----- - - ------------

35 30

=

'.:;'25 bl)

=

20 t 15 E

u IO 5 1 -----45% Repair

- - - No Repair I 0 +-'---+-'-+--'--+-'--+-.___._-'--l 0 20 40 60 80 100 120 140 Time (Years)

Figure 7. Circumferential Crack Half-Length on ID, c, as a Function of Time 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion [nineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 26 of 32 2.5 ----- ------------- - -

1 -----45% Repair I

- - - No Repair 2 / '\

\'

\

1. 5 c::

- \

<,; \

Q,.

,;;r, I "'i, ...

- - - - - - - - -..-=-: - - -......-

u '*<:............. ...... ... ... ... _

0.5 0 +-'--'-++-'--'-+-+-'--'-+-t-'-'-+-t-'-'-i 0 2 4 6 8 IO 12 14 16 18 Time (Years)

Figure 8. Axial Crack Aspect Ratio, 2c/a, as a Function of Time 20 ---------------------

18 16 .... \

,, I I

co

<i 14 .,,., ...... '

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12 ,

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---

45% Repair

- - - No Repair I 0 20 40 60 80 JOO 120 140 Time (Years)

Figure 9. Circumferential Crack Aspect Ratio, 2c/a, as a Function of Time 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion [nineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 27 of 32 140 120 100 ,, ,,, ,,'

0 I

=--

80 f'

r , ' ...... ,

'\.

\

'\Iii, ,,,. ,,,.

r

'-' 60

\ -

0 \

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---

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0 0.2 0.4 0.6 0.8 Crack Depth (a/t)

Figure 10. Axial Crack Stress Intensity Factor at Deepest Point, Kso, as a Function of Crack Depth 140 120 ------- 45% Repair  ;

- - - - No Repair ,f 100 ,:,:

"'0,-_ ,,

'I

!, 80 I

=-- ,:

6 60 ..... ,,

0 I/

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Figure 11. Circumferential Crack Stress Intensity Factor at Deepest Point, Kso, as a Function of Crack Depth 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion [nineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: Page 28 of 32 250 -,------------------------,

200 50 ------- 45% Repair

- - - - No Repair 0-+-------

0 0.2 0.4 0.6 0.8 Crack Depth (a/t)

Figure 12. Axial Crack Stress Intensity Factor at Surface Point, Ko, as a Function of Crack Depth 100 90 80 , ,,,.

,,,. , - - \.,,,',,,,'----......,\\, ..,,.

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60 I

I ,'

50 I ,'

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- - - - No Repair 10 0

0 0.2 0.4 0.6 0.8 Crack Depth (a/t)

Figure 13. Circumferential Crack Stress Intensity Factor at Surface Point, Ko, as a Function of Crack Depth 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion fnineerin, Inc NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 29 of 32 A CONTENTS OF DATA DISK D-452O-OO-O2 The following tables list the contents of Data Disk D-4520-00-02. The contents include Software Usage Records in their native electronic formats.

12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion fnineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 30 of 32 Table A-1. Software Usage Records Software Usage Records Folder File name

' Description Crackgrowth_coldleg_noinlay_O.py Python script that generates the output files CL_O_axial.csv Axial stress profile from FEA (MPa)

CL_O_hoop.csv Hoop stress profile from FEA (MPa)

TableC12_axial.txt API 579-1/ASME FFS-1 Table C.12 input data - axial TableC14_circ.txt API 579-1/AMSE FFS-1 Table C.14 input data - circ out_2c_over_a_ax.txt Output - 2c/a axial solution out_2c_over_a_ho.txt Output - 2c/a hoop solution out_a_over_t_ax.txt Output - a/t axial solution out_a_over_t_ho.txt Output - a/t hoop solution Case_O out_kO_ax.txt Output - KO axial solution out_kO_ho.txt Output - KO hoop solution out_k90_ax.txt Output - K90 axial solution out_k90_ho.txt Output - K90 hoop solution out_time_ax.txt Output - time axial solution (years) out_time_ho.txt Output - time hoop solution (years) out_timethroughwall_ax.txt Output - time for through-wall crack in axial solution (years) out_timethroughwall_ho.txt Output - time for through-wall crack in hoop solution (years) out_timeto75_ax.txt Output - time for 75% through-wall crack in axial solution (years) out_timeto75_ho.txt Output - time for 75% through-wall crack in hoop solution (years)

Crackgrowth_coldleg_noinlay_ 45.py Python script that generates the output files CL_45_axial.csv Axial stress profile from FEA (MPa)

CL_45_hoop.csv Hoop stress profile from FEA (MPa)

TableC12_axial.txt API 579-1/ASME FFS-1 Table C.12 input data - axial TableC14_circ.txt API 579-1/AMSE FFS-1 Table C.14 input data - circ out_2c_over_a_ax.txt Output - 2c/a axial solution out_2c_over_a_ho.txt Output - 2c/a hoop solution out_a_over_t_ax.txt Output - a/t axial solution out_a_over_t_ho.txt Output - a/t hoop solution Case_45 out_kO_ax.txt Output - KO axial solution out_kO_ho.txt Output - KO hoop solution out_k90_ax.txt Output - K90 axial solution out_k90_ho.txt Output - K90 hoop solution out_time_ax.txt Output - time axial solution (years) out_time_ho.txt Output - time hoop solution (years) out_timethroughwall_ax.txt Output - time for through-wall crack in axial solution (years) out_timethroughwall_ho.txt Output - time for through-wall crack in hoop solution (years) out_timeto75_ax.txt Output - time for 75% through-wall crack in axial solution (years) out_timeto75_ho.txt Output - time for 75% through-wall crack in hoop solution (years) 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion fnineerin, Inc. NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 31 of 32 Table A-1. Software Usage Records (Continued)

Software Usage Records Folder Filename Description Crackgrowth_coldleg_noinlay_O.py Python script that generates the output files CL_O_axial.csv Axial stress profile from FEA (MPa)

CL_O_hoop.csv Hoop stress profile from FEA (MPa)

TableC12_axial.txt API 579-1/ASME FFS-1 Table C.12 input data - axial TableC14_circ.txt API 579-1/AMSE FFS-1 Table C.14 input data - circ out_2c_over_a_ax.txt Output - 2c/a axial solution out_2c_over_a_ho.txt Output - 2c/a hoop solution out_a_over_t_ax.txt Output - a/t axial solution out_a_over_t_ho.txt Output - a/t hoop solution Python_Closed_Form_Case_O out_kO_ax.txt Output - KO axial solution out_kO_ho.txt Output - KO hoop solution out_k90_ax.txt Output - K90 axial solution out_k90_ho.txt Output - K90 hoop solution out_time_ax.txt Output - time axial solution (years) out_time_ho.txt Output - time hoop solution (years) out_timethroughwall_ax.txt Output - time for through-wall crack in axial solution (years) out_timethroughwall_ho.txt Output - time for through-wall crack in hoop solution (years) out_timeto75_ax.txt Output - time for 75% through-wall crack in axial solution (years) out_timeto75_ho.txt Output - time for 75% through-wall crack in hoop solution (years)

Crackgrowth_coldleg_noinlay_45.py Python script that generates the output files CL_45_axial.csv Axial stress profile from FEA (MPa)

CL_45_hoop.csv Hoop stress profile from FEA (MPa)

TableC12_axial.txt API 579-1/ASME FFS-1 Table C.12 input data - axial TableC14_circ.txt API 579-1/AMSE FFS-1 Table C.14 input data - circ out_2c_over_a_ax.txt Output - 2c/a axial solution out_2c_over_a_ho.txt Output - 2c/a hoop solution out_a_over_t_ax.txt Output - a/t axial solution out_a_over_t_ho.txt Output - a/t hoop solution Python_Closed_Form_Case_ 45 out_kO_ax.txt Output - KO axial solution out_kO_ho.txt Output - KO hoop solution out_k90_ax.txt Output - K90 axial solution out_k90_ho.txt Output - K90 hoop solution out_time_ax.txt Output - time axial solution (years) out_time_ho.,txt Output - time hoop solution (years) out_timethroughwall_ax.txt Output - time for through-wall crack in axial solution (years) out_timethroughwall_ho.txt Output - time for through-wall crack in hoop solution (years) out_timeto75_ax.txt Output - time for 75% through-wall crack in axial solution (years) out_timeto75_ho.txt Output - time for 75% through-wall crack in hoop solution (years) 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Dominion Enineerin, Inc NON-PROPRIETARY VERSION

Title:

Crack Growth Analyses for NAPS Unit 1 Steam Generator Outlet Nozzles Calculation No.: C-4520-00-02-NP Revision No.: 1 Page 32 of 32 Table A-1. Software Usage Records (Continued)

Software Usage Records Folder File name Description Crackgrowth_coldleg_noinlay_O.py Python script that generates the output files CL_O_axial.csv Axial stress profile from paper (MPa)

TableC12_axial.txt API 579-1/ASME FFS-1 Table C.12 input data - axial TableC14_circ.txt API 579-1/AMSE FFS-1 Table C.14 input data - circ out_2c_over_a_ho.txt Output - 2c/a hoop solution J_pVP_Tech_Circ out_a_over_t_ho.txt Output - a/t hoop solution out_kO_ho.txt Output - KO hoop solution out_k90_ho.txt Output - K90 hoop solution out_time_ho.txt Output - time hoop solution (years) out_timethroughwall_ho.txt Output - time for through-wall crack in hoop solution (years) out_timeto75_ho.txt Output - time for 75% through-wall crack in hoop solution (years)

Crackgrowth_coldleg_noinlay_O.py Python script that generates the output files CL_O_hoop.csv Hoop stress profile from paper (MPa)

TableC12_axial.txt API 579-1/ASME FFS-1 Table C.12 input data - axial TableC14_circ.txt API 579-1/AMSE FFS-1 Table C.14 input data - circ out_2c_over_a_ax.txt Output - 2c/a axial solution PVP2009-77855_Axial out_a_over_t_ax.txt Output - a/t axial solution out_kO_ax.txt Output - KO axial solution out_k90_ax.txt Output - K90 axial solution out_time_ax.txt Output - time axial solution (years) out_timethroughwall_ax. txt Output - time for through-wall crack in axial solution (years) out_timeto75 ax.txt Output - time for 75% through-wall crack in axial solution (years)

Memo documenting alternate calculation for one-time use engineering analysis M-4520-00-02_RO M-4520-00-02 RO.pdf computer program.

NA Unit 1 (Axial 45%).xlsm Alternate calculation for axial crack 45% ID weld repair case NA Unit 1 (Axial 0%).xlsm Alternate calculation for axial crack no weld repair case Excel_Closed_Form NA Unit 1 (Circ 45%).xlsm Alternate calculation for circ. crack 45% ID weld repair case NA Unit 1 (Circ 0%).xlsm Alternate calculation for circ. crack no weld repair case 12100 Sunrise Valley Drive, Suite 220 Reston, VA 20191 PH 703.657.7300 FX 703.657.7301

Serial No.: 20-028 Attachment 4 Westinghouse Affidavit Pursuant to 10 CFR 2.390 Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Unit 1

Westinghouse Non-Proprietary Class 3 CAW-20-5000 Page 1 of 3 AFFIDAVIT COMMONWEALTH OF PENNSYLVANIA:

COUNTY OF BUTLER:

(1) I, Camille T. Zoztda, have been specifically delegated and authorized to apply for withholding and execute this Affidavit on behalf of Westinghouse Electric Company LLC (Westinghouse).

(2) I am requesting the proprietary portions of C-4520-00-02-P, Rev. 1 be withheld from public disclosure under 10 CFR 2.390.

(3 ) I have personal knowledge of the criteria and procedures utilized by Westinghouse in designating information as a trade secret, privileged, or as confidential commercial or financial information.

(4) Pursuant to 10 CFR 2.390, the following is furnished for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld.

(i) The information sought to be withheld from public disclosure is owned and has been held in confidence by Westinghouse and is not customarily disclosed to the public.

(ii) Public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Westinghouse because it would enhance the ability of competitors to provide similar technical evaluation justifications and licensing defense services for commercial power reactors without commensurate expenses.

Also, public disclosure of the information would enable others to use the information to meet NRC requirements for licensing documentation without purchasing the right to use the information.

Westinghouse Non-Proprietary Class 3 CAW-20-5000 Page 2 of3 AFFIDAVIT (5) Westinghouse has policies in place to identify proprietary information. Under that system, information is held in confidence ifit falls in one or more ofseveral types, the release of which might result in the loss ofan existing or potential competitive advantage, as follows:

(a) The information reveals the distinguishing aspects ofa process (or component, structure, tool, method, etc.) where prevention ofits use by any of Westinghouse's competitors without license from Westinghouse constitutes a competitive economic advantage over other companies.

( b) It consists ofsupporting data, including test data, relative to a process (or component, structure, tool, method, etc.), the application ofwhich data secures a competitive economic advantage (e.g., by optimization or improved marketability).

(c ) Its use by a competitor would reduce his expenditure ofresources or improve his competitive position in the design, manufacture, shipment, installation, assurance ofquality, or licensing a similar product.

(d) It reveals cost or price information, production capacities, budget levels, or commercial strategies ofWestinghouse, its customers or suppliers.

( e) It reveals aspects ofpast, present, or future Westinghouse or customer funded development plans and programs ofpotential commercial value to Westinghouse.

(f) It contains patentable ideas, for which patent protection may be desirable.

(6) The attached documents are bracketed and marked to indicate the bases for withholding. The justification for withholding is indicated in both versions by means oflower case letters (a) through (f) located as a superscript immediately following the brackets enclosing each item of information being identified as proprietary or in the margin opposite such information. These

Westinghouse Non-Proprietary Class 3 CAW-20-5000 Page 3 of 3 AFFIDAVIT lower case letters refer to the types of information Westinghouse customarily holds in confidence identified in Sections (S)(a) through (t) of this Affidavit.

I declare that the averments of fact set forth in this Affidavit are true and correct to the best of my knowledge, information, and belief.

I declare under penalty of perjury that the foregoing is true and correct.

/\ 10 /7 Executed on: \4Y-tWUJ-0 &,.JL( ():/ f.

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