ML20198M682

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Alternate Request RR-05-06 - Inspection Interval Extension for Steam Generator Pressure Retaining Welds and Full-Penetration Welded Nozzles
ML20198M682
Person / Time
Site: Millstone Dominion icon.png
Issue date: 07/15/2020
From: Mark D. Sartain
Dominion Energy Nuclear Connecticut
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
20-167
Download: ML20198M682 (39)
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Text

Dominion Energy Nuclear Connecticut, Inc.

5000 Dominion Boulevard, Glen Allen, VA 23060 Dominion DominionEnergy.com Energy July 15, 2020 U.S. Nuclear Regulatory Commission Serial No.20-167 Attention: Document Control Desk NRA/SS RO Washington, DC 20555 Docket No. 50-336 License No. DPR-65 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2 ALTERNATIVE REQUEST RR-05 INSPECTION INTERVAL EXTENSION FOR STEAM GENERATOR PRESSURE-RETAINING WELDS AND FULL-PENETRATION WELDED NOZZLES In accordance with 10 CFR 50.55a(z)(1 ), Dominion Energy Nuclear Connecticut, Inc.

(DENC) hereby requests Nuclear Regulatory Commission (NRC) approval of proposed alternative request RR-05-06 for Millstone Power Station Unit 2 (MPS2). This proposed alternative requests to extend the inspection interval for ASME Section XI, Table IWB-2500-1, Examination Category B-B and B-D and Table IWC-2500-1, Examination Category C-A and C-B, component exams from 10 years to 30 years.

The proposed alternative request RR-05-06, which includes a summary of the key aspects of the technical basis for this extension request, is provided in Attachment 1.

The plant-specific applicability of the technical basis to MPS2 and the MPS2 inspection history is provided in Attachments 2 and 3, respectively. Lastly, the inspection history for these components, as obtained from an industry survey, is presented in Attachment 4.

The duration of the proposed alternative is requested for the remainder of the current fifth 10-year inservice inspection interval and through the following sixth 10-year inspection interval, currently scheduled to end on March 31, 2040.

NRC review and approval of the proposed alternative request is respectfully requested by August 1, 2021.

If you have any questions or require additional information, please contact Shayan Sinha at (804) 273-4687.

Sincerely, Mark D. Sartain Vice President- Nuclear Engineering & Fleet Support

Serial No.20-167 Docket No. 50-336 Page 2 of 2 Attachments:

1. Alternative Request RR-05 Inspection Interval Extension for Steam Generator Pressure-Retaining Welds and Full Penetration Welded Nozzles
2. Plant-Specific Applicability
3. Millstone Unit 2 Inspection History for the Third and Fourth 10-Year Inspection Intervals
4. Results of Industry Survey Commitments made in this letter: None cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 R. V. Guzman Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08-C 2 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No.20-167 Docket No. 50-336 ATTACHMENT 1 ALTERNATIVE REQUEST RR-05-06 INSPECTION INTERVAL EXTENSION FOR STEAM GENERATOR PRESSURE-RETAINING WELDS AND FULL PENETRATION WELDED NOZZLES MILLSTONE POWER STATION UNIT 2 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 1 of 9 Alternative Request RR-05-06 Proposed Alternative In Accordance with 10 CFR 50.55a(z)(1)

--Acceptable Level of Quality and Safety--

1.0 ASME CODE COMPONENTS AFFECTED:

Code Class: Class 1 and Class 2

Description:

Steam generator (SG) pressure-retaining welds and full penetration welded nozzles Examination Categories: Class 1, Category B-B, pressure-retaining welds in vessels other than reactor vessels Class 1, Category B-D, full penetration welded nozzles in vessels Class 2, Category C-A, pressure-retaining welds in pressure vessels Class 2, Category C-B, pressure-retaining nozzle welds in vessels Item Numbers: B2.31 - Steam generators (primary side), head welds, circumferential B2.40 - Steam generators (primary side), tubesheet-to-head weld B3.130 - Steam generators (primary side), nozzle-to-vessel welds C1.10- Shell circumferential welds C1 .20 - Head circumferential welds C1 .30 - Tubesheet-to-shell weld C2.21 - Nozzle-to-shell (nozzle-to-head or nozzle-to-nozzle) welds C2.22 - Nozzle inside radius sections Component IDs:

Millstone Unit 2, Steam Generator 1 ASMEltem Component ID Component Description No.

SG-1-BHC-1-A Stay Cylinder Base to Hemisphere (Head} B2.31 SG-1-TSS-3-A Stay Cylinder to Tube Sheet B2.31 SG-1-BHC-2-A Hemisphere (Head) to Tube Sheet B2.40 SG-1-NH-2-A Loop 1A Cold Leg Nozzle to Hemisphere (Head} B3.130 SG-1-NH-4-A Hot Leg Nozzle to Hemisphere B3.130 SG-1-NH-5-A Loop 1B Cold Leg Nozzle to Hemisphere (Head) B3.130

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 2 of 9 Millstone Unit 2, Steam Generator 1 ASMEltem Component ID Component Description No.

1-SC-2A Lower Cone to Shell Weld Cl.10 1-SC-3 Cone to Upper Shell Weld Cl.10 1-SC-4 Hand Hole Ring to Shell Circumferential Weld Cl.10 1-SC-5 Upper Shell to Lower Shell Circumferential Weld Cl.10 1-SC-6 Lower Cone to Upper Cone Cl.10 SG-1-THS-1 Secondary Head Circumferential Weld to Shell Cl.20 SG-1-THS-2 Head Circumferential Weld Cl.20 1-BHSC-2A Hand Hole Ring to Tube Sheet Circumferential Weld Cl.30 SG-1-FW-1 Feed Water Nozzle to Shell Weld C2.21 SG-1-MS-1 Main Steam Nozzle to Head Weld C2.21 SG-1-FW-IR-1 Feed Water Nozzle Inside Radius Section C2.22 SG-1-MS-IR-1 Main Steam Nozzle Inside Radius Section C2.22 Millstone Unit 2, Steam Generator 2 ASMEltem Component ID Component Description No.

SG-2-BHC-1-A Stay Cylinder Base to Hemisphere (Head} B2.31 SG-2-TSS-3-A Stay Cylinder to Tube Sheet B2.31 SG-2-BHC-2-A Hemisphere (Head} to Tube Sheet B2.40 SG-2-NH-2-A Loop 2A Cold Leg Nozzle to Hemisphere (Head} B3.130 SG-2-NH-4-A Hot Leg Nozzle to Hemisphere (Head} B3.130 SG-2-NH-5-A Loop 2B Cold Leg Nozzle to Hemisphere (Head} B3.130 2-SC-6 Lower Cone to Upper Cone Cl.10 2-SC-2A Lower Cone to Shell Weld Cl.10 2-SC-3 Cone to Upper Shell Weld Cl.10 2-SC-4 Hand Hole Ring to Shell Circumferential Weld Cl.10 2-SC-5 Upper Shell to Lower Shell Circumferential Weld Cl.10 SG-2-THS-1 Secondary Head Circumferential Weld to Shell Cl.20 SG-2-THS-2 Head Circumferential Weld Cl.20 2-BHSC-2A Hand Hole Ring to Tube Sheet Circumferential Weld Cl.30 SG-2-FW-1 Feed Water Nozzle to Shell Weld C2.21 SG-2-MS-1 Main Steam Nozzle to Head Weld C2.21 SG-2-FW-IR-1 Feed Water Nozzle Inside Radius Section C2.22 SG-2-MS-IR-1 Main Steam Nozzle Inside Radius Section C2.22 2.0 REQUESTED APPROVAL DATE:

Approval is requested no later than August 1, 2021.

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 3 of 9 3.0 APPLICABLE CODE EDITION AND ADDENDA:

The fifth 10-year inservice inspection interval Code of record for Millstone Power Station Unit 2 (MPS2) is the 2013 Edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components."

4.0 APPLICABLE CODE REQUIREMENT:

ASME Section XI IWB-2500(a), Table IWB-2500-1, examination Categories B-B and B-D and IWC-2500(a), Table IWC-2500-1, Examination Categories C-A and C-B require examination of the following Item Nos.:

Item No. B2.31 - Volumetric examination of essentially 100% of the weld length of all welds during the first Section XI inspection interval. For successive inspection intervals the examination may be limited to one vessel among the group of vessels performing a similar function. The examination volume is shown in Figure IWB-2500-3.

Item No. B2.40 - Volumetric examination of essentially 100% of the weld length of all welds during the first Section XI inspection interval. For successive inspection intervals the examination may be limited to one vessel among the group of vessels performing a similar function. The examination volume is shown in Figure IWB-2500-6.

Item No. B3.130 - Volumetric examination of all nozzles during each Section XI inspection interval. The examination volume is shown in Figures IWB-2500-?(a), (b), (c) and (d).

Item No. C1 .1 0 - Volumetric examination of essentially 100% of the weld length of the cylindrical-shell-to-conical shell-junction welds and shell (or head)-to-flange welds during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination volume is shown in Figure IWC-2500-1.

Item No. C1 .20 - Volumetric examination of essentially 100% of the weld length of the head-to-shell weld during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination volume is shown in Figure IWC-2500-1.

Item No. C1 .30 - Volumetric examination of essentially 100% of the weld length of the tubesheet-to-shell welds during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination volume is shown in Figure IWC-2500-2.

Item No. C2.21 - Volumetric and surface examination of all nozzle welds at terminal ends of piping runs during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 4 of 9 among the vessels. The examination area and volume are shown in Figures IWC-2500-4(a), (b), or (d).

Item No. C2.22 - Volumetric examination of all nozzle inside radius sections at terminal ends of piping runs during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination volume is shown in Figures IWC-2500-4(a), (b), or (d).

5.0 REASON FOR REQUEST:

Electric Power Research Institute (EPRI) performed assessments in References [1-1]

and [1-2] of the basis for the ASME Section XI examination requirements specified for the above listed ASME Section XI, Division 1 examination categories for steam generator welds and components. The assessments include a survey of inspection results from 74 domestic and international nuclear units and flaw tolerance evaluations using probabilistic fracture mechanics (PFM) and deterministic fracture mechanics (DFM). The Reference [1-1] and [1-2] reports concluded that the current ASME Code Section XI inspection interval of ten years can be increased significantly with no impact to plant safety. Based on the conclusions of the two EPRI reports, Dominion Energy Nuclear Connecticut, Inc. (DENG) is requesting an alternate inspection interval for the subject welds. The Reference [1-1] and [1-2] reports were developed consistent with the recommendations provided in EPRl's White Paper on PFM [1-12].

6.0 PROPOSED ALTERNATIVE AND BASIS FOR USE:

DENG is requesting an inspection alternative to the examination requirements of ASME Section XI, Tables IWB-2500-1 and IWC-2500-1 for the following examination categories and item numbers:

ASME Item No. Description Catego~

B-B B2.31 Steam generators (primary side), head welds, circumferential B-B B2.40 Steam generators (primary side), tubesheet-to-head weld B-D B3.130 Steam generators (primary side), nozzle-to-vessel welds C-A Cl.10 Shell circumferential welds C-A Cl.20 Head circumferential welds C-A Cl.30 Tubesheet-to-shell weld C-B (2.21 Nozzle-to-shell (nozzle to head or nozzle to nozzle) welds C-B (2.22 Nozzle inside radius sections The proposed alternative is to increase the inspection interval for these examination items to 30 years (from the current ASM E Code Section XI 10-year requirement) for the remainder of the fifth 10-year inspection interval and through the following sixth 10-year inspection interval, which is currently scheduled to end on March 31, 2040. A summary of the key aspects of the technical basis for this request is provided below. The applicability of the technical basis to MPS2 is demonstrated in Attachment 2.

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 5 of 9 Degradation Mechanism Evaluation An evaluation of degradation mechanisms that could potentially impact the reliability of the SG welds and components was performed in References [1-1] and [1-2]. The degradation mechanisms that were evaluated included stress corrosion cracking (SCC),

environmental assisted fatigue (EAF), microbiologically influenced corrosion (MIC),

pitting, crevice corrosion, erosion-cavitation, erosion, flow accelerated corrosion (FAC),

general corrosion, galvanic corrosion, and mechanical/thermal fatigue. Other than the potential for EAF and mechanical/thermal fatigue, there were no active degradation mechanisms identified that significantly affect the long-term structural integrity of the SG welds and components covered in this request. Therefore, these fatigue-related mechanisms were considered in the PFM and DFM evaluations in References [1-1] and

[1-2].

Stress Analysis Finite element analyses (FEA) were performed in References [1-1] and [1-2] to determine the stresses in the SG welds and components covered in this request. The analyses were performed using representative pressurized water reactor (PWR) geometries, bounding transients, and typical material properties. The results of the stress analyses were used in a flaw tolerance evaluation. The applicability of the FEA analysis to MPS2 is demonstrated in Attachment 2 and confirms that all plant-specific requirements are met. Therefore, the evaluation results and conclusions of References

[1-1] and [1-2] are applicable to MPS2.

Flaw Tolerance Evaluation Flaw tolerance evaluations were performed in References [1-1] and [1-2] consisting of PFM evaluations and confirmatory DFM evaluations. The results of the PFM analyses indicate that, after a preservice inspection (PSI), no other inspections are required for up to 80 years of plant operation to meet the U.S. Nuclear Regulatory Commission's (NRC's) safety goal of 1o-s failures per year.

For the specific case of MPS2 where PSI, followed by four 10-year interval inspections have been performed, Table 8-10 of References [1-1] and [1-2] indicates that if the inspection interval is increased to 30 years after these previous inspections, the NRC safety goal is met (with considerable margin) for up to 80 years of plant operation. The DFM evaluations provide verification of the PFM results by demonstrating that it takes approximately 80 years for a postulated flaw with an initial depth equal to the ASME Code Section XI acceptance standards to grow to a depth where the maximum stress intensity factor (K) exceeds the ASME Code Section XI allowable fracture toughness.

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 6 of 9 Inspection History Plant operating experience (including examinations performed to-date, examination findings, examination coverage, and relief requests) is presented in Attachment 3. As shown in the attachment, some of the weld/component examinations had limited coverage. Also, as shown in Attachment 3, no flaws that exceeded the ASME Code,Section XI acceptance standards were identified during any examinations.

The inspection history for these components (as obtained from an industry survey) is presented in Attachment 4. The results of the survey indicate that these components are very flaw tolerant.

Conclusion It is concluded that the SG pressure-retaining welds and full penetration welded nozzles are very flaw tolerant. PFM and DFM evaluations performed as part of the technical basis reports [1-1] and [1-2] demonstrate that, after PSI, no other inspections are required until 80 years to meet the NRC safety goal of 10-5 failures per reactor year.

Plant-specific applicability of the technical basis to MPS2 is demonstrated in Attachment

2. An alternate inspection interval of 30 years provides an acceptable level of quality and safety in lieu of the current ASME Section XI 10-year inspection frequency.

Operating and examination history demonstrates that these components have performed with very high reliability, mainly due to their robust design. Attachment 3 shows the examination history for the SG welds examined in the third and fourth 10-year inspection intervals.

In 1992 (second inspection interval) both steam generators were replaced. The upper portions of the generators were reused, as identified on Figure A 1. The welds and components in the upper portions of the steam generators received the required PSI examinations followed by inservice inspection (ISi) examinations through the first four inspection intervals. The new welds and components of the lower portions of the steam generators received the required PSI examinations in the second inspection interval followed by ISi examinations through the last three inspection intervals.

In addition to the required PSI examinations for these SG welds and components, DENG has performed 65 ISi examinations of the welds and components addressed by this request at MPS2 through the first four 10-year inspection intervals. No flaws that exceeded the ASME Code,Section XI acceptance standards were identified during any examinations, as shown in Attachment 3. Some of the examinations listed in involved limited coverage ranging from 49% to 99%. Section 8.3.5 of Reference [1-1] and Section 8.2.5 of Reference [1-2] discuss limited coverage and determine that the conclusions of the report are applicable to components with limited coverage. In addition, it is important to note that all other inspection activities, including the system leakage test (Examination Categories B-P and C-H) will continue to be performed in accordance with the ASME Section XI requirements, providing further assurance of safety.

Finally, as discussed in Reference [1-3], for situations where no active degradation mechanism is present, it was concluded that subsequent ISi examinations do not provide additional value after PSI has been performed and the inspection volumes examined have been confirmed to be free of defects. As previously noted, the MPS2

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 7 of 9 SG welds and components covered by this request have received the required PSI examinations and follow-on ISi examinations through the first four 10-year inspection intervals found no flaws that exceeded the ASME Code,Section XI acceptance standards.

Therefore, DENG requests the NRC grant this proposed alternative in accordance with 10 CFR 50.55a(z)(1).

7.0 DURATION OF PROPOSED ALTERNATIVE:

The proposed alternative is requested for the remainder of the fifth 10-year inspection interval and through the following sixth 10-year inspection interval for MPS2. The sixth 10-year inspection interval is currently scheduled to end on March 31, 2040, recognizing that the existing 60-year license expires July 31, 2035.

8.0 PRECEDENT

No previous submittals have been approved to provide relief from the ASME Section XI Examination Categories B-B, B-D, C-A, and C-B (Item Nos. B2.31, B2.40, B3.130, C1.10, C1 .20, C1 .30, C2.21, and C2.22) surface and volumetric examinations based on Reference [1-1] and [1-2] technical basis reports. However, the following is a list of approved actions (including relief requests and topical reports) related to inspections of SG welds and components:

  • Letter from J. W. Clifford (NRC) to S. E. Scace (Northeast Nuclear Energy Company), "Safety Evaluation of the Relief Request Associated with the First and Second 10-Year Interval of the lnservice Inspection (ISi) Plan, Millstone Nuclear Power Station, Unit 3 (TAC No. MA 5446)," dated July 24, 2000, ADAMS Accession No. ML003730922.
  • Letter from R. L. Emch (NRC) to J. B. Beasley, Jr. (SNOC), "Second 10-Year Interval lnservice Inspection Program Plan Requests for Relief 13, 14, 15, 21 and 33 for Vogtle Electric Generating Plant, Units 1 and 2 (TAC No. MB0603 and MB0604)," dated June 20, 2001, ADAMS Accession No. ML011640178.
  • Letter from M. Khanna (NRC) to D. A. Heacock (Dominion Nuclear Connecticut Inc.), Millstone Power Plant Unit No. 2 - Issuance of Relief Requests RR-89-69 Through RR-89-78 Regarding Third 10-Year Interval lnservice Inspection Plan (TAC Nos. ME5998 Through ME6006)," dated March 12, 2012, ADAMS Accession No. ML120541062.
  • Letter from R. J. Pascarelli (NRC) to E. D. Halpin (PG&E), "Diablo Canyon Plant, Units 1 and 2 - Relief Request; NOE SG-MS-IR, Main Steam Nozzle Inner Radius Examination Impracticality, Third 10-Year Interval, American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, lnservice Inspection Program (CAC Nos. MF6646 and MF6647)," dated December 8, 2015, ADAMS Accession No. ML15337A021.

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 8 of 9 In addition, there are precedents related to similar topical reports that justify relief for Class 1 nozzles:

  • Based on studies presented in Reference [1-4], the NRC approved extending PWR reactor vessel nozzle-to-shell welds from 10 to 20 years in Reference [1-5].

9.0 ACRONYMS

ASME American Society of Mechanical Engineers B&W Babcock and Wilcox BWR Boiling Water Reactor BWRVIP Boiling Water Reactor Vessel and Internals Program CE Combustion Engineering CFR Code of Federal Regulations DENC Dominion Energy Nuclear Connecticut, Inc.

DFM Deterministic fracture mechanics EAF Environmentally assisted fatigue EPRI Electric Power Research Institute FAC Flow accelerated corrosion FEA Finite element analysis FW Feedwater ISi lnservice Inspection MIC Microbiologically influenced corrosion MPS2 Millstone Power Station Unit 2 MS Main Steam NPS Nominal pipe size NRC Nuclear Regulatory Commission NSSS Nuclear steam supply system PFM Probabilistic fracture mechanics PSI Preservice Inspection PWR Pressurized Water Reactor sec Stress corrosion cracking SG Steam Generator

Serial No.20-167 Docket No. 50-336 Attachment 1, Page 9 of 9

10.0 REFERENCES

1-1 Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds. EPRI, Palo Alto, CA: 2019.

3002015906.

1-2 Technical Bases for Inspection requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Inside Radius Sections.

EPRI, Palo Alto, CA: 2019. 3002014590.

1-3 American Society of Mechanical Engineers, Risk-Based Inspection: Development of Guidelines, Volume 2-Part 1 and Volume 2-Part 2, Light Water Reactor (LWR)

Nuclear Power Plant Components. CRTD-Vols. 20-2 and 20-4, ASME Research Task Force on Risk-Based Inspection Guidelines, Washington, D.C., 1992 and 1998.

1-4 B. A. Bishop, C. Boggess, N. Palm, "Risk-Informed Extension of the Reactor Vessel In-Service Inspection Interval," WCAP-16168-NP-A, Rev. 3, October 2011.

1-5 US NRC, "Revised Safety Evaluation by the Office of Nuclear Reactor Regulation; Topical Report WCAP-16168-NP-A, Revision 2, 'Risk-Informed Extension of the Reactor Vessel In-service Inspection Interval,' Pressurized Water Reactor Owners Group, Project No. 694," July 26, 2011, ADAMS Accession No. ML111600303.

1-6 BWRVIP-108: BWR Vessels and Internals Project, Technical Basis for the Reduction of Inspection Requirements for tlie Boiling Water Reactor Nozzle-to-Shell Welds and Nozzle Blend Radii, EPRI, Palo Alto, CA 2002. 1003557.

1-7 US NRC, Safety Evaluation of Proprietary EPRI Report, "BWR Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radius (BWRVIP-108)," December 19, 2007, ADAMS Accession No. ML073600374.

1-8 BWRVIP-241: BWR Vessels and Internals Project, Probabilistic Fracture Mechanics Evaluation for the Boiling Water Reactor Nozzle-to-Shell Welds and Nozzle Blend Radii, EPRI, Palo Alto, CA 2010. 1021005.

1-9 US NRC, Safety Evaluation of Proprietary EPRI Report, "BWR Vessel and Internals Project, Probabilistic Fracture Mechanics Evaluation for the Boiling Water Reactor Nozzle-to-Shell Welds and Nozzle Blend Radii (BWRVIP-241),"

April 19, 2013, ADAMS Accession Nos. ML13071A240 and ML13071A233.

1-10 Code Case N-702, "Alternate Requirements for Boiling Water Reactor (BWR)

Nozzle Inner Radius and Nozzle-to-Shell Welds," ASME Code Section XI, Division 1, Approval Date: February 20, 2004.

1-11 U. S. NRC Regulatory Guide 1.147, Revision 19, "lnservice Inspection Code Case Acceptability, ASME Code Section XI, Division 1," dated March 2020.

1-12 N. Palm (EPRI), BWR Vessel & Internals Project (BWRVIP) Memo No. 2019-016, "White Paper on Suggested Content for PFM Submittals to the NRC,"

February 27, 2019, ADAMS Accession No. ML19241A545.

Serial No.20-167 Docket No. 50-336 ATTACHMENT 2 PLANT-SPECIFIC APPLICABILITY MILLSTONE POWER STATION UNIT 2 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 1 of 18 Plant-Specific Applicability Section 9 of References [2-1] and [2-2] provide requirements that must be demonstrated in order to apply the representative stress and flaw tolerance analyses to a specific plant. Plant-specific evaluation of these requirements for Millstone Power Station Unit 2 (MPS2) is provided in Table A1.

Table A 1 indicates that all plant-specific requirements are met for MPS2. Therefore, the results and conclusions of the EPRI reports are applicable to MPS2.

Table A1 Plant-Specific Applicability of References [2-1] and [2-2] Representative Analyses to MPS2 Items Nos. 82.31 and 82.40 (SG Primary Side Shell Welds)

Category Requirement from Reference [2-1] Applicability to MPS2 General The Loss of Power transient (involving MPS2 has not experienced a Requirements unheated auxiliary feedwater being introduced loss of power transient into a hot SG that has been boiled dry resulting in unheated following blackout, resulting in thermal shock auxiliary feedwater being of portion of the vessel) is not considered in introduced into a hot SG that this evaluation due to its rarity. In the event has been boiled dry following that such a significant thermal event occurs at blackout, resulting in thermal a plant, its impact on the Kie (material fracture shock of portion of the toughness) value may require more frequent vessel.

examinations and other plant actions outside the scope of this report's guidance.

The materials of the SG shell, FW nozzles, and The MPS2 SG vessel heads, MS nozzles must be low alloy ferritic steels tubesheet and nozzles are which conform to the requirements of ASME fabricated of SA-508, Class 3 Code,Section XI, Appendix G, Paragraph G- material, and the SG vessel 2110. shell is fabricated from SA-533, Gr. B, Cl. 1 material.

Both of these materials conform to the requirements of ASME Code,Section XI, Appendix G, Paragraph G-2110 (Reference [2-3] and [2-4]}.

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 2 of 18 Category Requirement from Reference (2-1) Applicability to MPS2 Specific The weld configurations must conform to those The MPS2 weld Requirements shown in Figures 1-1 and Figure 1-2 of configurations are shown in Reference [2-1] Figure A2, and conform to Figure 1-1 and Figure 1-2 of Reference [2-1].

The SG vessel dimensions must be within 10% The MPS2 SG vessel percent of the upper and lower bounds of the dimensions are as follows:

values provided in the table in Section 9.4.3 of Reference [2-1].

  • SG Lower Head diameter

=165 inches

  • SG Upper Shell diameter

=240 inches These dimensions are within 10% of those specified in Table 9-2 in Section 9.4.3 of Reference [2-1] for CE plants (Reference [2-5] and [2-6]}.

The component must experience transients As shown in Table A2, the and cycles bounded by those shown in Table 5- MPS2 transients and number 7 of Reference [2-1] over a 60-year operating of cycles projected to occur life. over a 60-year life are bounded by those shown in Table 5-7 of Reference [2-1]

for CE plants.

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 3 of 18 Item No. 83.130 (SG Primary Inlet/Outlet Nozzles)

Category Requirement from Reference [2-1] Applicability to MPS2 General The Loss of Power transient (involving unheated MPS2 has not experienced a Requirements auxiliary feedwater being introduced into a hot SG loss of power transient that has been boiled dry following blackout, resulting in unheated resulting in thermal shock of portion of the vessel) auxiliary feedwater being is not considered in this evaluation due to its rarity. introduced into a hot SG that In the event that such a significant thermal event has been boiled dry following occurs at a plant, its impact on the Kie (material blackout, resulting in thermal fracture toughness) value may require more shock of portion of the frequent examinations and other plant actions vessel.

outside the scope of this report's guidance.

The materials of the SG shell and nozzles must be The MPS2 SG vessel primary low alloy ferritic steels which conform to the head, tubesheet and primary requirements of ASME Code,Section XI, Appendix nozzles are fabricated of SA-G, Paragraph G-2110. 508, Class 3 material, and the SG vessel shell is fabricated from SA-533, Gr. B, Cl. 1 material. Both of these materials conform to the requirements of ASME Code,Section XI, Appendix G, Paragraph G-2110.

(References [2-3] and [2-4])

Specific The weld configurations must conform to those The MPS2 weld Requirements shown in Figures 1-3 through 1-5 of Reference [2- configurations are shown in 1] Figure A3, and conform to Figure 1-5 of Reference [2-1].

The piping attached to the primary inlet and outlet The MPS2 primary nozzles (RCS piping) for the various designs must inlet/outlet nozzle and piping be within 10% percent of the values provided in dimensions are as follows:

the table in Section 9.4.2 of Reference [2-1].

  • SG primary side inlet nozzle= 42 inches NPS
  • SG primary side outlet nozzle= 30 inches NPS These dimensions are within

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 4 of 18 Category Requirement from Reference [2-1] Applicability to MPS2 10% of those specified in Table 9-1 in Section 9.4.2 of Reference [2-1] for CE plants.

(Reference [2-8])

The component must experience transients and As shown in Table A2, the cycles bounded by those shown in Table 5-7 of MPS2 transients and number Reference [2-1] over a 60-year operating life. of cycles projected to occur over a 60-year life are bounded by those shown in Table 5-7 of Reference [2-1]

for CE plants.

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 5 of 18 Items Nos. C1.10, C1.20 and C1.30 (SG Secondary Side Shell Welds)

Category Requirement from Reference (2-1] Applicability to MPS2 General The Loss of Power transient (involving unheated MPS2 has not experienced a Requirements auxiliary feedwater being introduced into a hot SG loss of power transient that has been boiled dry following blackout, resulting in unheated auxiliary resulting in thermal shock of portion of the vessel) feedwater being introduced is not considered in this evaluation due to its into a hot SG that has been rarity. In the event that such a significant thermal boiled dry following blackout, event occurs at a plant, its impact on the Kie resulting in thermal shock of (material fracture toughness) value may require portion of the vessel.

more frequent examinations and other plant actions outside the scope of this report's guidance.

The materials of the SG shell, FW nozzles, and MS The MPS2 SG vessel heads, nozzles must be low alloy ferritic steels which tubesheet and nozzles are conform to the requirements of ASME Code, fabricated of SA-508, Class 3 Section XI, Appendix G, Paragraph G-2110. material, and the SG vessel shell is fabricated from SA-533, Gr. B, Cl. 1 material.

Both of these materia Is conform to the requirements of ASM E Code,Section XI, Appendix G, Paragraph G-2110 (References [2-3] and [2-41).

Specific The weld configurations must conform to those The MPS2 weld configurations Requirements shown in Figure 1-7 and Figure 1-8 of Reference are shown in Figures A4-1 and

[2-1]. A4-2, and conform to Figure 1-7 and Figure 1-8 of Reference [2-1].

The SG vessel dimensions must be within 10% The M PS2 SG vessel percent of the upper and lower bounds of the dimensions are as follows:

values provided in the table in Section 9.4.4 of Reference [2-1].

  • SG Lower Head diameter

= 165 inches

  • SG Upper Shell diameter=

240 inches These dimensions are within

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 6 of 18 Category Requirement from Reference [2-1] Applicability to MPS2 10% of those specified in Table 9-3 in Section 9.4.4 of Reference [2-1] for CE plants (References [2-5] and [2-6]}.

The component must experience transients and As shown in Table A3, the cycles bounded by those shown in Table 5-9 of MPS2 transients and number Reference [2-1] over a 60-year operating life. of cycles projected to occur over a 60-year life are bounded by those shown in Table 5-9 of Reference [2-1].

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 7 of 18 Items Nos. C2.21 and C2.22 (MS and FW Nozzle to Shell Welds and Inside Radius Sections)

Requirement from Category Applicability to MPS2 Reference [2-2]

General Requirements The nozzle-to-shell weld shall be The MPS2 MS and FW nozzles one of the configurations shown are shown in Figures AS and in Figure 1-1 or Figure 1-2 of A6 and are representative of Reference (2-2]. the configuration shown in Figure 1-2 of Reference (2-2].

The materials of the SG shell, FW The MPS2 MS and FW nozzles nozzles, and MS nozzle must be are fabricated of SA-508, low alloy ferritic steels which Class 2 material, the SG conform to the requirements of vessel secondary head is ASM E Code,Section XI, Appendix fabricated from SA-516 Gr 70 G, Paragraph G-2110. and upper secondary cylinder is fabricated from SA-533, Gr.

B, Cl. 1 material. These materials conform to the requirements of ASME Code,Section XI, Appendix G, Paragraph G-2110 (References (2-9] and (2-10]).

The SG must not experience more As shown in Table A4, the than the number of all transients MPS2 SG is not projected to shown in Table 5-5 of Reference experience more than the (2-2] over a 60-year operating life. number of the transients shown in Table 5-5 of Reference (2-2]).

SG Feedwater Nozzle The piping attached to the FW The MPS2 FW piping lines are nozzle must be 14-inch to 18-inch 18-inch NPS {18"-EBB-6 on NPS. Reference (2-11]).

The FW nozzle design must have The M PS2 FW nozzle an integrally attached thermal configuration has an sleeve. integrally attached thermal sleeve (Reference (2-12]).

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 8 of 18 Requirement from Category Applicability to MPS2 Reference [2-2]

Auxiliary feedwater nozzles N/A for MPS2.

connected directly to the SG are not covered in this evaluation.

SG Main Steam Nozzle For Westinghouse and CE plants, MPS2 is a CE 2-loop PWR.

the piping attached to the SG MS The MPS2 MS piping lines are nozzle must be 28-inch to 36-inch both 34-inch NPS {34" -EBB-2 NPS. on Reference [2-11]}.

For B&W SGs, the piping attached N/A for MPS2 since it is a CE to the main steam nozzle must be 2-loop unit.

22-inch to 26-inch NPS.

The SG must have one main steam MPS2 has one MS nozzle per nozzle that exits the top dome of SG that exits the top dome of the SG. each SG as shown in Figure Al.

The main steam nozzle shall not The MPS2 MS nozzle significantly protrude into the SG configuration {shown in

{e.g., see Figure 4-7 of Reference Figure A6} does not protrude

[2-2]} or have a unique nozzle significantly into the SG as weld configuration {e.g., see shown in Figure 4-7 of Figure 4-6 of Reference [2-2]}. Reference [2-2] and does not have a unique weld configuration as shown in Figure 4-6 of Reference [2-2)

{Reference [2-10]}.

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 9 of 18 111 i----

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Serial No.20-167 Docket No. 50-336 Attachment 2, Page 10 of 18

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Serial No.20-167 Docket No. 50-336 Attachment 2, Page 11 of 18 I

SEE ~£TAIL '0' NII IN.ET t-()ZZLE WELD OUTLEl NOZZL~S WELD Figure A3. Millstone Unit 2 SG Primary Side Inlet/Outlet Nozzle Configuration

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 12 of 18 Cone to Upper Shell And Cone to Cone Figure A4-1. Millstone Unit 2 SG Secondary Side Shell Welds Configuration

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 13 of 18

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Figure A4-2. Millstone Unit 2 SG Secondary Side Shell Welds Configuration

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 14 of 18 Figure A5. Millstone Unit 2 SG Feedwater Nozzle Configuration

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 15 of 18 Figure AG. Millstone Unit 2 SG Main Steam Nozzle Configuration

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 16 of 18 Table A2 - MPS2 Data for Thermal Transients for Stress Analysis of the PWR SG Primary-Side Head Welds (Comparison to Table 5-7 of Reference [2-11)

Transient MaxThot Min Thot Max Min Tcold Max Min Press 60-Year OF OF Tcold °F OF Press PSIG Cycles PSIG Heatup/Cooldown 545 70 545 70 2235 0 300 EPRI Report 3002015906 Heatup/Cooldown 535 70 535 70 2235 0 121 MP2 Plant Loading/ 610 550 550 545 2300 2300 5000 Unloading EPRI Report 3002015906 Plant Loading/ Not typical operation, not counted - See Note 1 Unloading MP2 Reactor Trip EPRI 615 530 565 530 2435 1700 360 Report 3002015906 Reactor Trip MP2 595 535 550 530 2250 1900 216 Note 1 Load following operation not typical. Plant Loading/ Unloading transients not counted per Report SIR-03-062 Table 2-2

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 17 of 18 Table A3 MPS2 Data for Thermal Transients for Stress analysis of the PWR SG Secondary-Side Vessel Welds (Comparison to Table 5-9 of Reference [2-1])

Transient Max Tss °F Min Tss °F Max Press Min Press 60-Year PSIG PSIG Cycles Heatup/Cooldown 545 70 1000 0 300 EPRI Report 3002015906 Heatup/Cooldown 530 70 850 0 121 MP2 Plant Loading/ 610 550 2300 2300 5000 Unloading EPRI Report 3002015906 Plant Loading/ Not typical Operation, not counted - See Note 1 Unloading MP2 Reactor Trip EPRI 555 530 1130 1000 360 Report 3002015906 Reactor Trip MP2 535 520 910 800 216 Note 1 Load following operation not typical. Plant Loading/

Unloading transients not counted per Report SIR-03-062 Table 2-2 Table A4 - MPS2 Data for Thermal Transients Applicable to PWR SG Feedwater and Main Steam Nozzles (Comparison to Table 5-5 of Reference [2-2])

Transient Cycles from Table 5-5 Millstone Unit 2 60-year Millstone Unit 2 60-of EPRI Report projected cycles from year allowable cycles 3002014590 calculation NCFM- from calculation 04321M2 Rev 3 NCFM-04321M2 Rev Attachment E 3 Attachment E Heatup/Cooldown 300 121 500 Plant Loading Not Typical/ Not 5000 15000 - Note 1 Plant Unloading Counted - Note 1 Loss of Load 360 8 40 Loss of Power 60 0 40 Note 1 Load following operation not typical. Plant Loading/ Unloading transients not counted per Report SIR-03-062 Table 2-2

Serial No.20-167 Docket No. 50-336 Attachment 2, Page 18 of 18

REFERENCES:

2-1 Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds. EPRI, Palo Alto, CA: 2019.

3002015906.

2-2 Technical Bases for Inspection requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Inside Radius Sections.

EPRI, Palo Alto, CA: 2019. 3002014590.

2-3 BWC-7612-SR-2, Revision 0, "Replacement Steam Generators Transient Analysis Stress Report. Section 4.0, pp. 1 and 12.

2-4 Drawing No. 25203-29145, Sheet 313, "Material and Parts List," Revision 2.

2-5 Drawing No. 25203-29145, Sheet 296, "Lower Replacement Steam Generator Sub Assembly," Revision 1.

2-6 Drawing No. 25203-29145, Sheet 3, "General Arrangement and Assembly Elevation Steam Generator," Revision 6.

2-7 Millstone Calculation No. NCFM-04321M2, "2010 FatiguePro Data Evaluation for Millstone Unit 2," Revision 3 2-8 Drawing No. 25203-26014, Sheet 1, "Piping and Instrumentation Diagram Reactor Coolant System," Revision 41 2-9 CENC-1176, "Analytical Report for MP2 Steam Generator," Revision 0, pp. A2, A17, and A20.

2-10 Drawing No. 25203-29145, Sheet 13, "Nozzle Detail Steam Generator," Revision 7.

2-11 Drawing No. 25203-26002, Sheet 1, "Piping and Instrumentation Diagram Main Steam from Generators," Revision 88.

2-12 Drawing No. 25203-29145, Sheet 171, "F/W Thermal Sleeve Detail," Revision 1

Serial No.20-167 Docket No. 50-336 ATTACHMENT 3 MILLSTONE UNIT 2 INSPECTION HISTORY FOR THE THIRD AND FOURTH 10-YEAR INSPECTION INTERVALS MILLSTONE POWER STATION UNIT 2 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

Serial No.20-167 Docket No. 50-336 Attachment 3, Page 1 of 2 MILLSTONE UNIT 2 INSPECTION HISTORY SG Primary Side Shell Welds Item Examination Interval/Period Component Examination Relief Coverage No. Date (Outage) ID Results Request 3rd Interval/ 3rd Period 11/08/06 SG-2-BHC-1-A Acceptable 49.58% RR-89-14 (M2RF17)

RR-04-31 4th Interval / 3 rd Period 10/17/18 SG-1-BHC-l-A Acceptable 88.33% (In (M2RF25) progress)

B2.31 3rd Interval / 3rd Period 4/16/08 SG-1-BHC-1-A Acceptable 72.90% RR-89-14 (M2RF18) 4th Interval/ 3rd Period 10/16/18 SG-2-TSS-3-A Acceptable 100% N/A (M2RF25) rd rd 3 Interval/ 3 Period 11/07/06 SG-2-TSS-3-A Acceptable 100% N/A (M2RF17) rd rd 3 Interval/ 3 Period 11/07/06 SG-2-BHC-2-A Acceptable 99.59% N/A (M2RF17) th st 4 Interval/ 1 Period B2.40 4/10/11 SG-1-BHC-2-A Acceptable 99.60% N/A (M2RF20) 3rd Interval/ 1st Period 05/15/00 SG-1-BHC-2-A Acceptable 90.1% N/A (M2RF13)

SG Secondary Side Shell Welds Item Examination Interval/Period Component Examination Relief Coverage No. Date (Outage) ID Results Request 4th Interval/ 3rd Period 10/19/18 1-SC-2A Acceptable 99.55% N/A (M2RF25) 3rd Interval/ 3rd Period 4/23/08 1-SC-2A Acceptable 94.50% N/A (M2RF18)

Cl.10 th nd 4 Interval/ 2 Period 4/29/14 1-SC-3 Acceptable 100% N/A (M2RF22) rd rd 3 Interval/ 3 Period 4/22/08 1-SC-3 Acceptable 100% N/A (M2RF18) nd 4th Interval/ 2 Period 4/29/14 SG-1-THS-l Acceptable 100% N/A (M2RF22) 3rd Interval/ 2nd Period 10/29/03 SG-1-THS-l Acceptable 100% N/A (M2RF15)

Cl.20 4th Interval/ 2nd Period 4/29/14 SG-1-THS-2 Acceptable 100% N/A (M2RF22) 3rd Interval/ 2nd Period 10/28/03 SG-1-THS-2 Acceptable 98.60% N/A (M2RF15) 4th Interval/ 3rd Period 10/19/18 1-BHSC-2A Acceptable 97.53% N/A (M2RF25)

Cl.30 3rd Interval/ 3rd Period 4/16/08 1-BHSC-2A Acceptable 97.30% N/A (M2RF18)

Serial No.20-167 Docket No. 50-336 Attachment 3, Page 2 of 2 SG Primary Side Nozzles Item Examination Interval/Period Examination Relief Component ID Coverage No. Date (Outage) Results Request 4th Interval/ 2nd Period 4/19/14 SG-l-NH-2-A Acceptable 72.4% RR-04-28 (M2RF22) 3 rd Interval/ 2nd Period 4/21/05 SG-1-NH-2-A Acceptable 54% RR-89-70 (M2RF16) 4th Interval/ 2nd Period 4/19/14 SG-1-NH-4-A Acceptable 72.5% RR-04-28 (M2RF22) 3 rd Interval/ 2nd Period 4/19/05 SG-1-N H-4-A Acceptable 56% RR-89-70 (M2RF16) nd 4 th Interval/ 2 Period 4/19/14 SG-l-NH-5-A Acceptable 72.4% RR-04-28 (M2RF22) 3 rd Interval/ 2nd Period 4/25/05 SG-l-NH-5-A Acceptable 55% RR-89-70 (M2RF16) 83.130 4th Interval/ 1st Period 10/21/12 SG-2-NH-2-A Acceptable 73.3% RR-04-17 (M2RF21) 3rd Interval/ 1st Period 02/23/02 SG-2-N H-2-A Acceptable 100% N/A (M2RF14) 4th Interval/ 1st Period RR 10/21/12 SG-2-NH-4-A Acceptable 72.5%

(M2RF21) 17 3 rd Interval/ 1st Period 02/23/02 SG-2-N H-4-A Acceptable 100% N/A (M2RF14) 4th Interval /1 st Period RR 10/21/12 SG-2-NH-5-A Acceptable 72.4%

(M2RF21) 17 3 rd Interval/ 1st Period 02/23/02 SG-2-N H-5-A Acceptable 100% N/A (M2RF14)

SG Secondary Side Nozzles Item Examination Interval/Period Examination Relief Component ID Coverage No. Date (Outage) Results Request 4th Interval/ 2nd Period 4/29/14 SG-1-FW-1 Acceptable 88.8% RR-04-29 (M2RF22) 3 rd Interval/ 1st Period 3/02/02 SG-1-FW-1 Acceptable 74.7% RR-89-73 (M2RF14)

C2.21 4 th Interval/ 2nd Period 10/24/15 SG-2-MS-1 Acceptable 73.6% RR-04-29 (M2RF23) 3 rd Interval/ 2 nd Period 10/28/03 SG-2-MS-1 Acceptable 56.3% RR-89-73 (M2RF15) 4th Interval/ 2nd Period 4/29/14 SG-1-FW-IR-1 Acceptable 100% N/A (M2RF22) rd st 3 Interval/ 1 Period 03/02/02 SG-1-FW-IR-1 Acceptable 100% N/A (M2RF14)

C2.22 4th Interval/ 2nd Period 10/20/15 SG-2-MS-IR-1 Acceptable 100% N/A (M2RF23) 3 rd Interval/ 2nd Period 10/27/03 SG-2-MS-IR-1 Acceptable 100% N/A (M2RF15)

Serial No.20-167 Docket No. 50-336 ATTACHMENT 4 RESULTS OF INDUSTRY SURVEY MILLSTONE POWER STATION UNIT 2 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

Serial No.20-167 Docket No. 50-336 Attachment 4, Page 1 of 4 Overall Industry Inspection Summary for Code Items 82.31, 82.32, 82.40, 83.130, C1.10, C1.20, and C1.30 The results of an industry survey of past inspections of SG nozzle-to-shell welds, inside radius sections and shell welds are summarized in Reference [4-1]. Table C1 provides a summary of the combined survey results for Item Nos. 82.31, 82.32 (see Table Note 3), 82.40, 83.130, C1.10, C1.20, and C1.30. The results of the industry survey identified numerous steam generator (SG) examinations being performed with no service-induced flaws being detected.

Performing these examinations adversely impact outage activities including worker exposure, personnel safety, and radwaste. A total of 74 domestic and international boiling water reactor (BWR) and pressurized water reactor (PWR) units responded to the survey and provided information representing all PWR plant designs currently in operation in the United States. This included 2-loop, 3-loop, and 4-loop PWR designs from each of the PWR nuclear steam supply system (NSSS) vendors (i.e., Babcock and Wilcox (B&W), Combustion Engineering (CE), and Westinghouse). A total of 1324 examinations for the components of the affected Item Nos.

were conducted, with 1098 of these specifically for PWR components. The majority of the PWR examinations were performed on SG welds.

A relatively small number of flaws were identified during these examinations which required flaw evaluation. None of these flaws were found to be service-induced. For Item No. 82.40, examinations at two units at a single plant site identified multiple flaws exceeding the acceptance criteria of ASME Code Section XI; however, these were determined to be subsurface-embedded fabrication flaws and not service-induced (see Table Note 1). For Item No. C1 .20, two PWR units reported flaws exceeding the acceptance criteria of ASME Code,Section XI. In the first unit, a single flaw was identified, and was evaluated as an inner diameter surface imperfection. Reference [4-3] indicates that this was a spot indication with no measurable through-wall depth. This indication is therefore not considered to be service-induced but rather fabrication-related. A flaw evaluation per IWC-3600 was performed for this flaw and it was found to be acceptable for continued operation. In the second unit, multiple flaws were identified (see Table Note 2). As discussed in References [4-4] and [4-5], these flaws were most likely subsurface weld defects typical of thick vessel welds and not service-induced. A flaw evaluation per IWC-3600 was performed for these flaws and they were found to be acceptable for continued operation.

Serial No.20-167 Docket No. 50-336 Attachment 4, Page 2 of 4 Table C1 - Summary of Survey Results No. of Examinations No. of Reportable Indications Item No.

BWR PWR Total BWR PWR Total B2.31 0 30 30 0 0 0 B2.32 0 13 13 0 0 0 (Note 3)

B2.40 0 183 183 0 Note 1 Note 1 B3.130 0 135 135 0 0 0 Cl.10 140 305 445 0 0 0 Cl.20 54 319 373 0 Note 2 Note 2 Cl.30 32 113 145 0 0 0 Totals 226 1098 1324 0 Notes 1 and 2 Notes 1 and 2 Table Notes:

(1) Two PWR W-2 Loop units at a single plant reported multiple subsurface embedded fabrication flaws.

(2) A single PWR W-2 Loop unit reported multiple flaws [4-4, 4-5].

(3) Item No. 82.32 was evaluated in the Reference [4-1] technical basis and included in the industry survey, but is not contained in the scope of this alternative request.

Serial No.20-167 Docket No. 50-336 Attachment 4, Page 3 of 4 Overall Industry Inspection Summary for Code Items C2.21, C2.22, and C2.32 The results of an industry survey of past inspections of SG main steam (MS) and feedwater (FW) nozzles are summarized in Reference [4-2]. Table C2 provides a summary of the combined survey results for Item Nos. C2.21, C2.22, and C2.32 (see Table Note 1). The results of the industry survey identified numerous SG MS and FW Nozzle-to-Shell Welds and Nozzle Inside Radius Section examinations being performed with no service-induced flaws being detected. Performing these examinations adversely impact outage activities including worker exposure, personnel safety, and radwaste. A total of 74 domestic and international BWR and PWR units responded to the survey and provided information representing all PWR plant designs currently in operation in the United States. This included 2-loop, 3-loop, and 4-loop PWR designs from each of the PWR NSSS vendors (i.e., B&W, CE, and Westinghouse). A total of 727 examinations for Item Nos. C2.21, C2.22, and C2.32 (see Table Note 1) components were conducted, with 563 of these specifically for PWR components. The majority of the PWR examinations were performed on SG MS and FW nozzles. Only one PWR examination identified two (2) flaws that exceeded ASME Code Section XI acceptance criteria.

The flaws were linear indications of 0.3" and 0.5" in length and were detected in a MS nozzle-to-shell weld using magnetic particle examination techniques. The indications were dispositioned by light grinding (ADAMS Accession No. ML13217A093).

Table C2 - Summary of Survey Results Number of Plant Type . Number of Units Number of Examinations Reportable Indications BWR 27 164 0 PWR 47 563 2 727 Totals 74 2 (Note 1)

Table Note:

(1) Item No. C2.32 was evaluated in the Reference [4-2] technical basis and included in the industry survey, but is not contained in the scope of this alternative request.

Serial No.20-167 Docket No. 50-336 Attachment 4, Page 4 of 4

REFERENCES:

4-1 Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds. EPRI, Palo Alto, CA: 2019.

3002015906.

4-2 Technical Bases for Inspection requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Inside Radius Sections.

EPRI, Palo Alto, CA: 2019. 3002014590.

4-3 Letter from F. A. Kearney (Exelon) to U. S. NRG, "Byron Station Unit 2 90-Day lnservice Inspection Report for Interval 3, Period 3, (B2R17)," dated July 29, 2013, Docket No. 50-455, ADAMS Accession Number ML13217A093.

4-4 Letter from J. M. Sorensen (NMC) to U. S. NRG, "Unit 1 lnservice Inspection Summary Report, Interval 3, Period 3 Refueling Outage Dates 1-19-2001 to 2-25-2001 Cycle 20 I 05-26-99 to 02-25-2001," dated May 29, 2001, Docket Nos.

50-282 and 50-306, ADAMS Accession Number ML011550346.

4-5 Letter from J. P. Solymossy (NMC) to U. S. NRG, "Response to Opportunity For Comment On Task Interface Agreement (TIA) 2003-01, "Application of ASME Code Section XI, IWB-2430 Requirements Associated With Scope of Volumetric Weld Expansion at the Prairie Island Nuclear Generating Plant" (Tac Nos.

MB7294 and MB7295)," dated April 4, 2003, Docket Nos. 50-282 and 50-306, ADAMS Accession Number ML031040553.

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