RA-23-0136, Duke Energy Response to Request for Additional Information Regarding Proposed Alternative for Steam Generator Welds in Accordance with 10 CFR 50.55a(z)(1): Difference between revisions

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{{#Wiki_filter:Ryan Treadway General Manager (Acting)
{{#Wiki_filter:Ryan Treadway General Manager (Acting)
Nuclear Regulatory Affairs, Policy &
Nuclear Regulatory Affairs, Policy &
Emergency Preparedness Duke Energy 526 South Church St., EC08F Charlotte, NC 28202 980-373-5873 Ryan.Treadway@duke-energy.com Serial: RA-23-0136                                                                 10 CFR 50.55a July 20, 2023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Catawba Nuclear Station, Unit Nos. 1 and 2 Docket Nos. 50-413, 50-414 / Renewed License Nos. NPF-35 and NPF-52 Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400 / Renewed License No. NPF-63 McGuire Nuclear Station, Unit Nos. 1 and 2 Docket Nos. 50-369, 50-370 / Renewed License Nos. NPF-9 and NPF-17 Oconee Nuclear Station, Unit Nos. 1, 2, and 3 Docket Nos. 50-269, 50-270, and 50-287 / Renewed License Nos. DPR-38, DPR-47, and DPR-55 H. B. Robinson Steam Electric Plant, Unit No. 2 Docket No. 50-261 / Renewed License No. DPR-23
Emergency Preparedness
 
Duke Energy 526 South Church St., EC08F Charlotte, NC 28202
 
980-373-5873 Ryan.Treadway@duke-energy.com
 
Serial: RA-23-0136 10 CFR 50.55a July 20, 2023
 
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
 
Catawba Nuclear Station, Unit Nos. 1 and 2 Docket Nos. 50-413, 50-414 / Renewed License Nos. NPF-35 and NPF-52
 
Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400 / Renewed License No. N PF-63
 
McGuire Nuclear Station, Unit Nos. 1 and 2 Docket Nos. 50-369, 50-370 / Renewed License Nos. NPF-9 and NPF-17
 
Oconee Nuclear Station, Unit Nos. 1, 2, and 3 Docket Nos. 50-269, 50-270, and 50-287 / Renewed License Nos. DPR-38, DPR-47, and DPR-55
 
H. B. Robinson Steam Electric Plant, Unit No. 2 Docket No. 50-261 / Renewed License No. DPR-23


==SUBJECT:==
==SUBJECT:==
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U.S. Nuclear Regulatory Commission RA-23-0136 Page 2 In Reference 2, the NRC staff provided a request for additional information (RAI) regarding Reference 1. Enclosure 1 provides Duke Energys response to the Reference 2 RAI.
U.S. Nuclear Regulatory Commission RA-23-0136 Page 2 In Reference 2, the NRC staff provided a request for additional information (RAI) regarding Reference 1. Enclosure 1 provides Duke Energys response to the Reference 2 RAI.
Should you have any question concerning this letter and its enclosure, please contact Ryan Treadway, Director - Nuclear Fleet Licensing at (980) 373-5873.
Should you have any question concerning this letter and its enclosure, please contact Ryan Treadway, Director - Nuclear Fleet Licensing at (980) 373-5873.
No new regulatory commitments have been made in this submittal.
No new regulatory commitments have been made in this submittal.
Sincerely, Ryan Treadway General Manager (Acting) - Nuclear Regulatory Affairs, Policy & Emergency Preparedness
 
Sincerely,
 
Ryan Treadway General Manager (Acting) - Nuclear Regulatory Affairs, Policy & Emergency Preparedness


==Enclosure:==
==Enclosure:==
: 1. Response to Request for Additional Information cc:
: 1. Response to Request for Additional Information
 
cc:
L. Dudes, USNRC, Region II Regional Administrator N. Jordan, USNRC NRR Project Manager for Duke Fleet M. Mahoney, USNRC NRR Project Manager for HNP J. Klos, USNRC NRR Project Manager for MNS S. Williams, USNRC NRR Project Manager for ONS and CNS L. Haeg, USNRC NRR Project Manager for RNP D. Rivard, USNRC Senior Resident Inspector for CNS P. Boguszewski, USNRC Senior Resident Inspector for HNP C. Safouri, USNRC Senior Resident Inspector for MNS J. Nadel, USNRC Senior Resident Inspector for ONS J. Zeiler, USNRC Senior Resident Inspector for RNP
L. Dudes, USNRC, Region II Regional Administrator N. Jordan, USNRC NRR Project Manager for Duke Fleet M. Mahoney, USNRC NRR Project Manager for HNP J. Klos, USNRC NRR Project Manager for MNS S. Williams, USNRC NRR Project Manager for ONS and CNS L. Haeg, USNRC NRR Project Manager for RNP D. Rivard, USNRC Senior Resident Inspector for CNS P. Boguszewski, USNRC Senior Resident Inspector for HNP C. Safouri, USNRC Senior Resident Inspector for MNS J. Nadel, USNRC Senior Resident Inspector for ONS J. Zeiler, USNRC Senior Resident Inspector for RNP


Enclosure 1 RA-23-0136 Enclosure 1 Response to Request for Additional Information
Enclosure 1 RA-23-0136
 
Enclosure 1 Response to Request for Additional Information
 
Enclosure 1 RA-23-0136 Page 1 of 14
 
Request for Additional Information (RAI)-1
 
Issue
 
The licensee referenced probabilistic and deterministic analyses in the above EPRI reports to estimate potential fatigue crack growth in the subject SG welds and to justify application of these analyses to the proposed examination elimination for the welds and nozzle inner radius locations. The licensee presented plant-specific information to demonstrate that the referenced analyses in the EPRI reports would bound the subject SG welds, including the ISI history of the welds.


Enclosure 1 RA-23-0136 Page 1 of 14 Request for Additional Information (RAI)-1 Issue The licensee referenced probabilistic and deterministic analyses in the above EPRI reports to estimate potential fatigue crack growth in the subject SG welds and to justify application of these analyses to the proposed examination elimination for the welds and nozzle inner radius locations. The licensee presented plant-specific information to demonstrate that the referenced analyses in the EPRI reports would bound the subject SG welds, including the ISI history of the welds.
Leveraging PFM analyses to define the basis for risk-informing inspection requirements requires knowledge of both the current and future behavior of the material degradation and the associated uncertainties applicable to the subject SG welds. Confidence in the results of these analyses hinges on the assurance that the PFM model adequately represents, and will continue to represent, the degradation behavior in the subject SG welds. The NRC staff has determined that, when considering proposed elimination of examinations, adequate performance monitoring through inspections is needed to ensure that the assumptions of the PFM model remain valid, and that novel or unexpected degradation is detected and dispositioned in a timely fashion.
Leveraging PFM analyses to define the basis for risk-informing inspection requirements requires knowledge of both the current and future behavior of the material degradation and the associated uncertainties applicable to the subject SG welds. Confidence in the results of these analyses hinges on the assurance that the PFM model adequately represents, and will continue to represent, the degradation behavior in the subject SG welds. The NRC staff has determined that, when considering proposed elimination of examinations, adequate performance monitoring through inspections is needed to ensure that the assumptions of the PFM model remain valid, and that novel or unexpected degradation is detected and dispositioned in a timely fashion.
Further, the staff has communicated concepts that licensees can implement on a fleet-wide basis to develop a performance monitoring plan and bolster the technical basis for alternative requests (see slide packages dated January 30, 2023, and April 27, 2023 at ML23033A667 and ML23114A034, respectively). In Section 5.0 of the submittal, the licensee described the various plant-specific examination scenarios and the proposed elimination of examinations. The licensee stated that the proposed alternative results in a maximum time period of approximately 20 years from the end of the interval in which the Section XI requirements were met in full until the end of the proposed alternative. The licensee did not provide a performance monitoring schema for the subject welds and nozzle inner radius locations.
Further, the staff has communicated concepts that licensees can implement on a fleet-wide basis to develop a performance monitoring plan and bolster the technical basis for alternative requests (see slide packages dated January 30, 2023, and April 27, 2023 at ML23033A667 and ML23114A034, respectively). In Section 5.0 of the submittal, the licensee described the various plant-specific examination scenarios and the proposed elimination of examinations. The licensee stated that the proposed alternative results in a maximum time period of approximately 20 years from the end of the interval in which the Section XI requirements were met in full until the end of the proposed alternative. The licensee did not provide a performance monitoring schema for the subject welds and nozzle inner radius locations.
The licensee discusses the system leakage test as providing further assurance of safety for the proposed alternative. However, the NRC staff notes that the visual examinations performed during system leakage tests may not provide sufficient information to ensure that the PFM model continues to predict the material behavior and that emergent degradation is discovered and dispositioned in a timely fashion. Specifically, visual examinations may not directly detect the presence or extent of degradation; may not provide direct detection of aging effects prior to potential loss of structure or intended function; and do not provide sufficient validating data necessary to confirm the modeling of degradation behavior in the subject welds and nozzle inner radius locations.
The licensee discusses the system leakage test as providing further assurance of safety for the proposed alternative. However, the NRC staff notes that the visual examinations performed during system leakage tests may not provide sufficient information to ensure that the PFM model continues to predict the material behavior and that emergent degradation is discovered and dispositioned in a timely fashion. Specifically, visual examinations may not directly detect the presence or extent of degradation; may not provide direct detection of aging effects prior to potential loss of structure or intended function; and do not provide sufficient validating data necessary to confirm the modeling of degradation behavior in the subject welds and nozzle inner radius locations.
Request
Request
: a. Describe the performance monitoring that will be implemented with this proposed alternative to ensure that the PFM model adequately represents, and will continue to represent the degradation behavior in the subject components commensurate with the duration of the requested alternative.
: a. Describe the performance monitoring that will be implemented with this proposed alternative to ensure that the PFM model adequately represents, and will continue to represent the degradation behavior in the subject components commensurate with the duration of the requested alternative.
: b. Explain how this performance monitoring will provide, over the extended examination interval, (1) direct evidence of the presence and extent of degradation, (2) validation and confirmation of the continued adequacy of the PFM model; and (3) timely detection of novel or unexpected degradation.
: b. Explain how this performance monitoring will provide, over the extended examination interval, (1) direct evidence of the presence and extent of degradation, (2) validation and confirmation of the continued adequacy of the PFM model; and (3) timely detection of novel or unexpected degradation.
Enclosure 1 RA-23-0136 Page 2 of 14
Enclosure 1 RA-23-0136 Page 2 of 14
: c. If through this performance monitoring indications are detected that exceed the acceptance standards of ASME Code, Section XI, IWB-3500, confirm that they will be evaluated as required by ASME Code, Section XI (which includes requirements for successive inspections and additional examinations) and describe other actions (if any) specified in the plants corrective action program to ensure that the integrity of the component is adequately maintained.
: c. If through this performance monitoring indications are detected that exceed the acceptance standards of ASME Code, Section XI, IWB-3500, confirm that they will be evaluated as required by ASME Code, Section XI (which includes requirements for successive inspections and additional examinations) and describe other actions (if any) specified in the plants corrective action program to ensure that the integrity of the component is adequately maintained.
: d. If through this performance monitoring indications are detected that exceed the acceptance standards of ASME Code, Section XI, IWB-3500, then scope expansion may be appropriate to assess extent of condition. Furthermore, if this performance monitoring plan or industry-wide operating experience indicates that a new or novel degradation mechanism is possible in SG welds or nozzle inner radii, scope expansion may be appropriate to ensure that no such mechanism is occurring in the subject plants. Discuss the detailed scope expansion plans for these scenarios.
: d. If through this performance monitoring indications are detected that exceed the acceptance standards of ASME Code, Section XI, IWB-3500, then scope expansion may be appropriate to assess extent of condition. Furthermore, if this performance monitoring plan or industry-wide operating experience indicates that a new or novel degradation mechanism is possible in SG welds or nozzle inner radii, scope expansion may be appropriate to ensure that no such mechanism is occurring in the subject plants. Discuss the detailed scope expansion plans for these scenarios.
Duke Energy Response to RAI-1:
Duke Energy Response to RAI-1:
: a. Performance monitoring supporting this Alternative Request began with the Fourth Inspection Intervals for Catawba, Units 1&2, McGuire, Units 1&2, and Shearon Harris, Unit 1 and with the Fifth Inspection Intervals for H.B. Robinson, Unit 2 and Oconee, Units 1, 2, &3.
: a. Performance monitoring supporting this Alternative Request began with the Fourth Inspection Intervals for Catawba, Units 1&2, McGuire, Units 1&2, and Shearon Harris, Unit 1 and with the Fifth Inspection Intervals for H.B. Robinson, Unit 2 and Oconee, Units 1, 2, &3.
As documented in Table 1-2 below, the requested deferral lengths for Catawba, Units 1&2, McGuire, Units 1 &2, and Shearon Harris, Unit 1 range from 12.9 years up to 28.3 years.
As documented in Table 1-2 below, the requested deferral lengths for Catawba, Units 1&2, McGuire, Units 1 &2, and Shearon Harris, Unit 1 range from 12.9 years up to 28.3 years.
Therefore, a performance monitoring plan for these plants is described in detail below. All ASME code required exams have been completed for the 5th Intervals at H.B. Robinson, Unit 2 and Oconee, Units 1 & 3. Oconee Unit 2 has completed all required exams except for one C-A, C1.30 exam scheduled for the upcoming Fall 2023 outage (last outage the 5th Interval). The requested deferral lengths between exams for H.B. Robinson, Unit 2 and Oconee, Units 1, 2, & 3 range from 9.7 years to 16.2 years. Therefore, requested deferrals for all welds and components associated with H.B. Robinson, Unit 2 and Oconee, Units 1, 2,
Therefore, a performance monitoring plan for these plants is described in detail below. All ASME code required exams have been completed for the 5th Intervals at H.B. Robinson, Unit 2 and Oconee, Units 1 & 3. Oconee Unit 2 has completed all required exams except for one C-A, C1.30 exam scheduled for the upcoming Fall 2023 outage (last outage the 5th Interval). The requested deferral lengths between exams for H.B. Robinson, Unit 2 and Oconee, Units 1, 2, & 3 range from 9.7 years to 16.2 years. Therefore, requested deferrals for all welds and components associated with H.B. Robinson, Unit 2 and Oconee, Units 1, 2,
  &3 are below 20 years between examinations and as such do not require any performance monitoring. This is consistent with prior precedent where U.S. licensees have sought examination relief from prescriptive ASME Section XI requirements.
&3 are below 20 years between examinations and as such do not require any performance monitoring. This is consistent with prior precedent where U.S. licensees have sought examination relief from prescriptive ASME Section XI requirements.
As shown in the Inspection History Tables from Reference 1, a significant number of 4th Interval examinations have been completed across Catawba, Units 1&2 and Shearon Harris, Unit 1. Specifically, 10 of the required 19 Steam Generator Welds for the interval have been inspected with no relevant indications identified. All of these 4th Interval examinations utilized phased array ultrasonic testing (UT) techniques with component specific Non-Destructive Examination (NDE) modeling (when available) to maximum coverage obtained. These modern UT techniques are far superior at detecting near surface or surface breaking flaws and obtained greater coverage compared to earlier interval PSI/ISI exams. These completed examinations (10/19 53% of the total number of required exams) across all three stations are credited for performance monitoring during remainder of the current 4th Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1.
As shown in the Inspection History Tables from Reference 1, a significant number of 4th Interval examinations have been completed across Catawba, Units 1&2 and Shearon Harris, Unit 1. Specifically, 10 of the required 19 Steam Generator Welds for the interval have been inspected with no relevant indications identified. All of these 4th Interval examinations utilized phased array ultrasonic testing (UT) techniques with component specific Non-Destructive Examination (NDE) modeling (when available) to maximum coverage obtained. These modern UT techniques are far superior at detecting near surface or surface breaking flaws and obtained greater coverage compared to earlier interval PSI/ISI exams. These completed examinations (10/19 53% of the total number of required exams) across all three stations are credited for performance monitoring during remainder of the current 4th Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1.
Additionally, the 6-inch nominal diameter Auxiliary Feedwater nozzle-to-shell welds have been examined during the current 4th Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1. These examinations consisted of volumetric UT and magnetic particle testing (MT) examinations in accordance with code requirements (Item No. C2.21). Full 100% coverage was obtained for each exam and no rejectable indications were identified. Although the
 
Additionally, the 6-inch nominal diameter Auxiliary Feedwater nozzle-to-shell welds have been examined during the current 4th Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1. These examinations consisted of volumetric UT and magnetic particle testing (MT) examinations in accordance with code requirements (Item No. C2.21). Full 100% coverage was obtained for each exam and no rejectable indications were identified. Although the Enclosure 1 RA-23-0136 Page 3 of 14


Enclosure 1 RA-23-0136 Page 3 of 14 Auxiliary Feedwater nozzles were not included in the scope of Alternative RA-22-0256, these completed examinations ensure direct detection of aging affects prior to the potential loss of structure or intended function. The UT/MT exams provide additional validating data to confirm the absence of degradation behavior in Steam Generator welds.
Auxiliary Feedwater nozzles were not included in the scope of Alternative RA-22-0256, these completed examinations ensure direct detection of aging affects prior to the potential loss of structure or intended function. The UT/MT exams provide additional validating data to confirm the absence of degradation behavior in Steam Generator welds.
The performance monitoring plan covering the 5th Interval for Catawba, Units 1&2, and Shearon Harris, Unit 1 and the 5th/6th Intervals at McGuire, Units 1&2 will examine one weld from each Item Number across all five Units. Specifically, over a given inspection interval a total of five (5) Steam Generators would be examined comprised of 29 welds/component exams. The proposed performance monitoring plan is to inspect a total of seven (7) different welds/components across all five Units that covers each Item No. and weld/component configuration. Note, the design of the CNS2 Steam Generators differs from CNS1, MNS1, MNS2, and HNP, since CNS2 has original Westinghouse Model D-5 Steam Generators.
The performance monitoring plan covering the 5th Interval for Catawba, Units 1&2, and Shearon Harris, Unit 1 and the 5th/6th Intervals at McGuire, Units 1&2 will examine one weld from each Item Number across all five Units. Specifically, over a given inspection interval a total of five (5) Steam Generators would be examined comprised of 29 welds/component exams. The proposed performance monitoring plan is to inspect a total of seven (7) different welds/components across all five Units that covers each Item No. and weld/component configuration. Note, the design of the CNS2 Steam Generators differs from CNS1, MNS1, MNS2, and HNP, since CNS2 has original Westinghouse Model D-5 Steam Generators.
Therefore, only CNS2 has C1.10 welds and a Main Steam (MS) nozzle-to-shell (C2.21) weld. The proposed performance monitoring plan ensures those weld configurations unique to CNS2 are selected. Finally, at least one weld/component at each Unit is selected for examination for even distribution. This ensures a diverse sampling across the Duke PWR Fleet rather than monitoring individual welds on a repetitive basis or a single Steam Generator at only one Unit. The proposed performance monitoring plan selects the most time-limited welds since the last inspection, to the extent practical. The components to be examined are described in Table 1-1 below. Also, a visual representation of the past inspection interval history including the proposed performance monitoring schedule is shown in Figure 1-1.
Therefore, only CNS2 has C1.10 welds and a Main Steam (MS) nozzle-to-shell (C2.21) weld. The proposed performance monitoring plan ensures those weld configurations unique to CNS2 are selected. Finally, at least one weld/component at each Unit is selected for examination for even distribution. This ensures a diverse sampling across the Duke PWR Fleet rather than monitoring individual welds on a repetitive basis or a single Steam Generator at only one Unit. The proposed performance monitoring plan selects the most time-limited welds since the last inspection, to the extent practical. The components to be examined are described in Table 1-1 below. Also, a visual representation of the past inspection interval history including the proposed performance monitoring schedule is shown in Figure 1-1.
Enclosure 1 RA-23-0136 Page 4 of 14
Table 1-1: Proposed Performance Monitoring Plan


Enclosure 1 RA-23-0136 Page 4 of 14 Table 1-1: Proposed Performance Monitoring Plan Station/Unit             ASME       ASME       Description               Number and Type of       Proposed Schedule     Approximate Category   Item No.                             Exam                     (Year)2               Length of Time Since Last Exam (Years)
Station/Unit ASME ASME Description Number and Type of Proposed Schedule Approximate Category Item No. Exam (Year)2 Length of Time Since Last Exam (Years)
Catawba / Unit 1         C-B         C2.21       FW Nozzle-to-Shell       1 Volumetric (UT) &     Interval 5, Period 1       18 Weld                     1 Surface (MT or PT)     (Spring 2029)
Catawba / Unit 1 C-B C2.21 FW Nozzle-to-Shell 1 Volumetric (UT) & Interval 5, Period 1 18 Weld 1 Surface (MT or PT) (Spring 2029)
Catawba / Unit 1         C-B         C2.22       FW Inside Radius         1 Volumetric (UT)       Interval 5, Period 1       10.5 (Spring 2029) 1 Catawba / Unit 2         C-A         C1.10       Shell Circumferential     1 Volumetric (UT)       Interval 5, Period 3       16.5 Weld                                               (Fall 2034) 1 Catawba / Unit 2         C-B         C2.21       MS Nozzle-to-Shell       1 Volumetric (UT) &     Interval 5, Period 2       16.5 Weld                     1 Surface (MT or PT)     (Fall 2031)
Catawba / Unit 1 C-B C2.22 FW Inside Radius 1 Volumetric (UT) Interval 5, Period 1 10.5 (Spring 2029) 1Catawba / Unit 2 C-A C1.10 Shell Circumferential 1 Volumetric (UT) Interval 5, Period 3 16.5 Weld (Fall 2034) 1Catawba / Unit 2 C-B C2.21 MS Nozzle-to-Shell 1 Volumetric (UT) & Interval 5, Period 2 16.5 Weld 1 Surface (MT or PT) (Fall 2031)
McGuire / Unit 1         C-A         C1.20       Head Circumferential     1 Volumetric (UT)       Interval 5, Period 3       16.5 Weld                                               (Fall 2029)
McGuire / Unit 1 C-A C1.20 Head Circumferential 1 Volumetric (UT) Interval 5, Period 3 16.5 Weld (Fall 2029)
McGuire / Unit 2         C-A         C1.30       Tubesheet-to-Shell       1 Volumetric (UT)       Interval 5, Period 3       18 Weld                                               (Fall 2033)
McGuire / Unit 2 C-A C1.30 Tubesheet-to-Shell 1 Volumetric (UT) Interval 5, Period 3 18 Weld (Fall 2033)
Shearon Harris / Unit 1   B-B         B2.40       Tubesheet-to Head         1 Volumetric (UT)       Interval 5, Period 2       19 Weld                                               (Fall 2031)
Shearon Harris / Unit 1 B-B B2.40 Tubesheet-to Head 1 Volumetric (UT) Interval 5, Period 2 19 Weld (Fall 2031)
Notes:
Notes:
: 1. Catawba Unit 2 has original Westinghouse Model D-5 Steam Generators. Therefore, it is the only Unit from the performance monitoring plan with C1.10 welds and a Main Steam nozzle-to-shell weld.
: 1. Catawba Unit 2 has original Westinghouse Model D-5 Steam Generators. Therefore, it is the only Unit from the performance monitoring plan with C1.10 welds and a Main Steam nozzle-to-shell weld.
: 2. The proposed year is subject to change in accordance with IWA-2430(c)(1) or +/- one outage from the proposed schedule not to exceed the overall end date of 2035. This allows for possible unit transitions from an 18-month fuel cycle to a 24-month fuel cycle or other unforeseen plant radiation exposure limits or exam support issues. The proposed performance monitoring plan will be completed by the end of 2035.
: 2. The proposed year is subject to change in accordance with IWA-2430(c)(1) or +/- one outage from the proposed schedule not to exceed the overall end date of 2035. This allows for possible unit transitions from an 18-month fuel cycle to a 24-month fuel cycle or other unforeseen plant radiation exposure limits or exam support issues. The proposed performance monitoring plan will be completed by the end of 2035.


Enclosure 1 RA-23-0136 Page 5 of 14 Year Replacement Steam Generator Year Plant               2012     2013     2014   2015   2016   2017   2018     2019   2020 2021 2022 2023     2024     2025     2026   2027 2028     2029         2030 2031 2032 2033   2034 2035   2036     2037     2038   2039   2040         2041   2042       2043 2044 2045       2046 1
Enclosure 1 RA-23-0136 Page 5 of 14
1996         Catawba 1       3rd Interval                                 4th Interval                     4th Interval             5th Interval           X                                                  6th Interval ASME Code SG Requirements Resume           12/5/2043 Original SGs         Catawba 2       3rd Interval                                 4th Interval                             4th Interval                       5th Interval             X               X             6th Interval ASME Code SG Requirements Resume           12/5/2043 1984     H.B Robinson 2                                       5th Interval                                                       6th Interval                       7/31/2030 1997         McGuire 1                               4th Interval                                                   5th Interval                             X                                         6th Interval                                   6/12/2041 1997         McGuire 2   3rd Interval                                     4th Interval                                                             5th Interval                           X                                     6th Interval                               3/3/2043 2003 2004       Oconee 1, 2, 3 4th Interval                                     5th Interval                                                             6th Interval                               #
 
2001   Shearon Harris 1               3rd Interval                                 4th Interval                         4th Interval                       5th Interval         X                                                       6th Interval ASME Code SG Requirements Resume           10/24/2046 Notes:
Replacement Steam Year Generator Year Plant 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046
 
1996 Catawba 1 3rd Interval 4th Interval 4th Interval 5th Interval X1 6th Interval ASME Code SG Requirements Resume 12/5/2043
 
Original SGs Catawba 2 3rd Interval 4th Interval 4th Interval 5th Interval X X 6th Interval ASME Code SG Requirements Resume 12/5/2043
 
1984 H.B Robinson 2 5th Interval 6th Interval 7/31/2030
 
1997 McGuire 1 4th Interval 5th Interval X 6th Interval 6/12/2041 1997 McGuire 2 3rd Interval 4th Interval 5th Interval X 6th Interval 3/3/2043
 
2003 2004 Oconee 1, 2, 3 4th Interval 5th Interval 6th Interval #
 
2001 Shearon Harris 1 3rd Interval 4th Interval 4th Interval 5th Interval X 6th Interval ASME Code SG Requirements Resume 10/24/2046
 
Notes:
: 1. Two exams item numbers are scheduled, to ensure both the Main Feedwater nozzle-to-shell weld (C2.21) and associated inner radius (C2.22) exams are performed during the same refueling outage.
: 1. Two exams item numbers are scheduled, to ensure both the Main Feedwater nozzle-to-shell weld (C2.21) and associated inner radius (C2.22) exams are performed during the same refueling outage.
LEGEND Inspection Interval prior to Alternative RA-22-0256 X        Scheduled Performance Monitoring Exam Deferral Period per RA-22-0256 Subsequent Inspection Interval: Reverts Back to ASME Code Requirements Current License Period End Date
                                                                                            #        Oconee Current License Period End Date: Unit 1 - 2/6/2033; Unit 2 - 10/6/2033; Unit 3 - 7/19/2034 Figure 1-1: Inservice Inspection Interval History and Performance Monitoring Schedule


Enclosure 1 RA-23-0136 Page 6 of 14 The proposed performance monitoring plan for Duke Energy, will be performed by the end of 2035. This will ensure that no more than 20 years elapses between the performance of an ASME Code, Section XI, examination for each weld/component item number on a Steam Generator subject to examination requirements. Following completion of the proposed performance monitoring plan by 2035, none of the Duke Energy units covered by the proposed alternative will have operated more than 20 years between exams of each item number being performed at least once amongst the fleet. Following completion of the performance monitoring plan and the Fifth Inspection Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1, ASME Section XI Code required Steam Generator examinations for these plants will resume with the start of the Sixth Inspection Intervals as required per 10 CFR 50.55a(g)(4)(ii). These code required examinations satisfy the performance monitoring for McGuire, Units 1&2 thru the end of its current operating license.
Figure 1-1: Inservice Inspection Interval History and Performance Monitoring Schedule
 
Enclosure 1 RA-23-0136 Page 6 of 14
 
The proposed performance monitoring plan for Duke Energy, will be performed by the end of 2035. This will ensure that no more than 20 years elapses between the performance of an ASME Code, Section XI, examination for each weld/component item number on a Steam Generator subject to examination requirements. Following completion of the proposed performance monitoring plan by 2035, none of the Duke Energy units covered by the proposed alternative will have operated more than 20 years between exams of each item number being performed at least once amongst the fleet. Following completion of the performance monitoring plan and the Fifth Inspection Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1, ASME Section XI Code required Steam Generator examinations for these plants will resume with the start of the Sixth Inspection Intervals as required per 10 CFR 50.55a(g)(4)(ii). These code required examinations satisfy the performance monitoring for McGuire, Units 1&2 thru the end of its current operating license.


Enclosure 1 RA-23-0136 Page 7 of 14 Table 1-2: Summary of Inspection Deferrals in Proposed Alternative RA-22-0256 End of ASME      Item                                          Date of Last                    Length of Station Unit                              Description                                  Proposed Category    No.                                          Inspection                    Time1 (Years)
Enclosure 1 RA-23-0136 Page 7 of 14
Alternative Catawba    1    B-B    B2.40  Steam generators (primary side),        05/09/2017        End of 5th    18.2 tubesheet-to-head weld                                      Interval, C-A    C1.20  Steam generators (secondary side),      05/06/2011      Scheduled to    24.2 Head circumferential welds                                    End C-A    C1.30  Steam generators (secondary side),      05/09/2017        06/28/2035      18.2 Tubesheet-to-shell weld C-B    C2.21  FW Nozzle-to-shell weld                  05/12/2011                        24.1 C-B    C2.22  FW Nozzle inside radius section          11/25/2018                        16.6 Catawba    2    B-B    B2.40  Steam generators (primary side),        04/19/2021        End of 5th    14.3 tubesheet-to-head weld                                      Interval, C-A    C1.10  Steam generators (secondary side),      03/25/2018      Scheduled to    17.4 Shell circumferential welds                                    End C-A    C1.10  Steam generators (secondary side),      03/27/2009        08/18/2036      26.4 Shell circumferential welds C-A    C1.10  Steam generators (secondary side),      03/25/2009                        26.4 Shell circumferential welds C-A    C1.20  Steam generators (secondary side),      09/25/2022                        12.9 Head circumferential welds C-A    C1.30  Steam generators (secondary side),      03/23/2018                        17.4 Tubesheet-to-shell weld C-B    C2.21  FW Nozzle-to-shell weld                  03/25/2018                        17.4 C-B    C2.21  MS Nozzle-to-shell weld                  03/10/2015                        20.5 C-B    C2.22  FW Nozzle inside radius section          03/17/2015                        20.4


Enclosure 1 RA-23-0136 Page 8 of 14 End of ASME    Item                                    Date of Last              Length of Station Unit                            Description                        Proposed Category  No.                                      Inspection              Time1 (Years)
Table 1-2: Summary of Inspection Deferrals in Proposed Alternative RA-22-0256
Alternative H.B        2    B-B    B2.40 Steam generators (primary side),  06/01/2015    End of        15.2 Robinson                      tubesheet-to-head weld                            Current C-A    C1.10 Steam generators (secondary side), 10/09/2018    Licensed      11.8 Shell circumferential welds                      Period, C-A    C1.10 Steam generators (secondary side), 10/11/2018  07/31/2030      11.8 Shell circumferential welds C-A    C1.10 Steam generators (secondary side), 11/25/2020                    9.7 Shell circumferential welds C-A    C1.20 Steam generators (secondary side), 11/24/2020                    9.7 Head circumferential welds C-A    C1.30 Steam generators (secondary side), 06/02/2015                  15.2 Tubesheet-to-shell weld C-B    C2.21 FW Nozzle-to-shell weld            05/26/2015                  15.2 C-B    C2.21 MS Nozzle-to-shell weld            06/01/2015                  15.2 C-B    C2.22 FW Nozzle inside radius section    11/17/2020                    9.7 C-B    C2.22 MS Nozzle inside radius section    10/11/2018                  11.8 McGuire  1      B-B    B2.40 Steam generators (primary side),  03/31/2019    End of        22.2 tubesheet-to-head weld                            Current C-A    C1.20 Steam generators (secondary side), 03/24/2013    Licensed      28.2 Head circumferential welds                        Period, C-A    C1.30 Steam generators (secondary side), 03/20/2013  06/12/2041      28.3 Tubesheet-to-shell weld C-B    C2.21 FW Nozzle-to-shell weld            10/03/2014                  26.7 C-B    C2.22 FW Nozzle inside radius section    10/03/2014                  26.7 McGuire  2      B-B    B2.40 Steam generators (primary side),  03/29/2020    End of        22.9 tubesheet-to-head weld                            Current C-A    C1.20 Steam generators (secondary side), 03/04/2023    Licensed      20.0 Head circumferential welds                        Period, C-A    C1.30 Steam generators (secondary side), 09/23/2015  03/03/2043      27.5 Tubesheet-to-shell weld C-B    C2.21 FW Nozzle-to-shell weld            09/24/2015                  27.5 C-B    C2.22 FW Nozzle inside radius section    04/07/2017                  25.9 Oconee    1      B-B    B2.40 Steam generators (primary side),    11/3/2018    End of        14.3 tubesheet-to-head weld                            Current


Enclosure 1 RA-23-0136 Page 9 of 14 End of ASME   Item                                     Date of Last                 Length of Station Unit                             Description                          Proposed Category No.                                     Inspection               Time1 (Years)
ASME Item Date of Last End of Length of Station Unit Category No. Description Inspection Proposed Time1 (Years)
Alternative B-B   B2.40 Steam generators (primary side),   11/21/2016    Licensed      16.2 tubesheet-to-head weld                               Period, C-A   C1.30 Steam generators (secondary side), 10/30/2020    02/06/2033      12.3 Tubesheet-to-shell weld C-A   C1.30 Steam generators (secondary side), 10/29/2020                    12.3 Tubesheet-to-shell weld C-B   C2.21 MS Nozzle-to-shell weld             11/13/2016                    16.2 C-B   C2.21 MS Nozzle-to-shell weld            10/29/2018                   14.3 Oconee    2     B-B   B2.40 Steam generators (primary side),   11/21/2019      End of       13.9 tubesheet-to-head weld                             Current B-B    B2.40 Steam generators (primary side),    11/21/2019    Licensed      13.9 tubesheet-to-head weld                              Period, C-A   C1.30 Steam generators (secondary side), 11/16/2021    10/06/2033      13.9 Tubesheet-to-shell weld C-A   C1.30 Steam generators (secondary side), 10/23/2013,                  10.0 Tubesheet-to-shell weld            Scheduled for O2R31 (Fall 2023)2 C-B    C2.21 MS Nozzle-to-shell weld            11/19/2019                    13.9 C-B    C2.21 MS Nozzle-to-shell weld            11/19/2019                    13.9 Oconee    3      B-B    B2.40 Steam generators (primary side),     5/21/2022      End of      12.2 tubesheet-to-head weld                              Current B-B    B2.40 Steam generators (primary side),    4/20/2020    Licensed      14.3 tubesheet-to-head weld                              Period, C-A   C1.30 Steam generators (secondary side),   5/20/2022   07/19/2034      12.2 Tubesheet-to-shell weld C-A   C1.30 Steam generators (secondary side),   4/20/2020                    14.3 Tubesheet-to-shell weld C-B   C2.21 MS Nozzle-to-shell weld             4/29/2018                   16.2 C-B   C2.21 MS Nozzle-to-shell weld             4/30/2018                    16.2 Shearon  1      B-B   B2.40 Steam generators (primary side),    5/4/2012      End of 5th    25.0 Harris                        tubesheet-to-head weld                              Interval, C-A    C1.20 Steam generators (secondary side),  4/23/2015  Scheduled to    22.0 Head circumferential welds
Alternative Catawba 1 B-B B2.40 Steam generators (primary side), 05/09/2017 End of 5th 18.2 tubesheet-to-head weld Interval, C-A C1.20 Steam generators (secondary side), 05/06/2011 Scheduled to 24.2 Head circumferential welds End C-A C1.30 Steam generators (secondary side), 05/09/2017 06/28/2035 18.2 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 05/12/2011 24.1 C-B C2.22 FW Nozzle inside radius section 11/25/2018 16.6 Catawba 2 B-B B2.40 Steam generators (primary side), 04/19/2021 End of 5th 14.3 tubesheet-to-head weld Interval, C-A C1.10 Steam generators (secondary side), 03/25/2018 Scheduled to 17.4 Shell circumferential welds End C-A C1.10 Steam generators (secondary side), 03/27/2009 08/18/2036 26.4 Shell circumferential welds C-A C1.10 Steam generators (secondary side), 03/25/2009 26.4 Shell circumferential welds C-A C1.20 Steam generators (secondary side), 09/25/2022 12.9 Head circumferential welds C-A C1.30 Steam generators (secondary side), 03/23/2018 17.4 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 03/25/2018 17.4 C-B C2.21 MS Nozzle-to-shell weld 03/10/2015 20.5 C-B C2.22 FW Nozzle inside radius section 03/17/2015 20.4 Enclosure 1 RA-23-0136 Page 8 of 14


Enclosure 1 RA-23-0136 Page 10 of 14 End of ASME       Item                                             Date of Last                       Length of Station   Unit                                   Description                                      Proposed Category     No.                                               Inspection                     Time1 (Years)
ASME Item Date of Last End of Length of Station Unit Category No. Description Inspection Proposed Time1 (Years)
Alternative C-A     C1.30 Steam generators (secondary side),             4/18/2015           End           22.0 Tubesheet-to-shell weld                                         05/01/2037 C-B     C2.21 FW Nozzle-to-shell weld                       5/3/2021                           16.0 C-B     C2.22 FW Nozzle inside radius section               5/5/2012                           25.0 Notes:
Alternative H.B 2 B-B B2.40 Steam generators (primary side), 06/01/2015 End of 15.2 Robinson tubesheet-to-head weld Current C-A C1.10 Steam generators (secondary side), 10/09/2018 Licensed 11.8 Shell circumferential welds Period, C-A C1.10 Steam generators (secondary side), 10/11/2018 07/31/2030 11.8 Shell circumferential welds C-A C1.10 Steam generators (secondary side), 11/25/2020 9.7 Shell circumferential welds C-A C1.20 Steam generators (secondary side), 11/24/2020 9.7 Head circumferential welds C-A C1.30 Steam generators (secondary side), 06/02/2015 15.2 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 05/26/2015 15.2 C-B C2.21 MS Nozzle-to-shell weld 06/01/2015 15.2 C-B C2.22 FW Nozzle inside radius section 11/17/2020 9.7 C-B C2.22 MS Nozzle inside radius section 10/11/2018 11.8 McGuire 1 B-B B2.40 Steam generators (primary side), 03/31/2019 End of 22.2 tubesheet-to-head weld Current C-A C1.20 Steam generators (secondary side), 03/24/2013 Licensed 28.2 Head circumferential welds Period, C-A C1.30 Steam generators (secondary side), 03/20/2013 06/12/2041 28.3 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 10/03/2014 26.7 C-B C2.22 FW Nozzle inside radius section 10/03/2014 26.7 McGuire 2 B-B B2.40 Steam generators (primary side), 03/29/2020 End of 22.9 tubesheet-to-head weld Current C-A C1.20 Steam generators (secondary side), 03/04/2023 Licensed 20.0 Head circumferential welds Period, C-A C1.30 Steam generators (secondary side), 09/23/2015 03/03/2043 27.5 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 09/24/2015 27.5 C-B C2.22 FW Nozzle inside radius section 04/07/2017 25.9 Oconee 1 B-B B2.40 Steam generators (primary side), 11/3/2018 End of 14.3 tubesheet-to-head weld Current Enclosure 1 RA-23-0136 Page 9 of 14
 
ASME Item Date of Last End of Length of Station Unit Category No. Description Inspection Proposed Time1 (Years)
Alternative B-B B2.40 Steam generators (primary side), 11/21/2016 Licensed 16.2 tubesheet-to-head weld Period, C-A C1.30 Steam generators (secondary side), 10/30/2020 02/06/2033 12.3 Tubesheet-to-shell weld C-A C1.30 Steam generators (secondary side), 10/29/2020 12.3 Tubesheet-to-shell weld C-B C2.21 MS Nozzle-to-shell weld 11/13/2016 16.2 C-B C2.21 MS Nozzle-to-shell weld 10/29/2018 14.3 Oconee 2 B-B B2.40 Steam generators (primary side), 11/21/2019 End of 13.9 tubesheet-to-head weld Current B-B B2.40 Steam generators (primary side), 11/21/2019 Licensed 13.9 tubesheet-to-head weld Period, C-A C1.30 Steam generators (secondary side), 11/16/2021 10/06/2033 13.9 Tubesheet-to-shell weld C-A C1.30 Steam generators (secondary side), 10/23/2013, 10.0 Tubesheet-to-shell weld Scheduled for O2R31 (Fall 2023)2 C-B C2.21 MS Nozzle-to-shell weld 11/19/2019 13.9 C-B C2.21 MS Nozzle-to-shell weld 11/19/2019 13.9 Oconee 3 B-B B2.40 Steam generators (primary side), 5/21/2022 End of 12.2 tubesheet-to-head weld Current B-B B2.40 Steam generators (primary side), 4/20/2020 Licensed 14.3 tubesheet-to-head weld Period, C-A C1.30 Steam generators (secondary side), 5/20/2022 07/19/2034 12.2 Tubesheet-to-shell weld C-A C1.30 Steam generators (secondary side), 4/20/2020 14.3 Tubesheet-to-shell weld C-B C2.21 MS Nozzle-to-shell weld 4/29/2018 16.2 C-B C2.21 MS Nozzle-to-shell weld 4/30/2018 16.2 Shearon 1 B-B B2.40 Steam generators (primary side), 5/4/2012 End of 5th 25.0 Harris tubesheet-to-head weld Interval, C-A C1.20 Steam generators (secondary side), 4/23/2015 Scheduled to 22.0 Head circumferential welds Enclosure 1 RA-23-0136 Page 10 of 14
 
ASME Item Date of Last End of Length of Station Unit Category No. Description Inspection Proposed Time1 (Years)
Alternative C-A C1.30 Steam generators (secondary side), 4/18/2015 End 22.0 Tubesheet-to-shell weld 05/01/2037 C-B C2.21 FW Nozzle-to-shell weld 5/3/2021 16.0 C-B C2.22 FW Nozzle inside radius section 5/5/2012 25.0
 
Notes:
: 1. This column represents the length of time between the date of the last completed code inspection and the end of the proposed alternative.
: 1. This column represents the length of time between the date of the last completed code inspection and the end of the proposed alternative.
: 2. This C1.30 is scheduled for O2R31 (Fall 2023) and required to be completed for ASME 5th Interval code compliance (last outage of the 5th Interval for ONS Unit 2). This alternative is only applicable to Oconee 6th Interval exams through the current licensed period for Oconee Units 1, 2, and 3.
: 2. This C1.30 is scheduled for O2R31 (Fall 2023) and required to be completed for ASME 5th Interval code compliance (last outage of the 5th Interval for ONS Unit 2). This alternative is only applicable to Oconee 6th Interval exams through the current licensed period for Oconee Units 1, 2, and 3.
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Enclosure 1 RA-23-0136 Page 11 of 14
Enclosure 1 RA-23-0136 Page 11 of 14
: b. (1) The performance monitoring plan provided in the response above includes sampled inspections using Volumetric/Surface exam methods that will provide direct evidence of the presence and extent of any degradation over the extended examination interval for these welds.
: b. (1) The performance monitoring plan provided in the response above includes sampled inspections using Volumetric/Surface exam methods that will provide direct evidence of the presence and extent of any degradation over the extended examination interval for these welds.
(2) The components in the proposed alternative have operated for a minimum of 21.8 years and up to a maximum of 36.9 years without the identification through inspection of any service-induced degradation. This excellent operating history is validation and confirmation of the conservative nature of the PFM and DFM models used in the EPRI Technical Reports 3002015906 and 3002014590 (References 2 & 3). This also shows that the models will predict future behavior conservatively. The proposed performance monitoring plan includes sampling of examinations across different weld types located at different plants. This ensures the inspection data is representative of the Duke Fleet and is sufficient to demonstrate continued adequacy of the modeling.
(2) The components in the proposed alternative have operated for a minimum of 21.8 years and up to a maximum of 36.9 years without the identification through inspection of any service-induced degradation. This excellent operating history is validation and confirmation of the conservative nature of the PFM and DFM models used in the EPRI Technical Reports 3002015906 and 3002014590 (References 2 & 3). This also shows that the models will predict future behavior conservatively. The proposed performance monitoring plan includes sampling of examinations across different weld types located at different plants. This ensures the inspection data is representative of the Duke Fleet and is sufficient to demonstrate continued adequacy of the modeling.
(3) The performance monitoring schedule described above will provide timely detection of any novel or unexpected degradation in these components.
(3) The performance monitoring schedule described above will provide timely detection of any novel or unexpected degradation in these components.
: c. If during the performance monitoring schedule described above, indications are detected that exceed the applicable ASME Code, Section XI acceptance standards of IWB-3500 or IWC-3500, then the indications will be addressed as required by ASME Code Section XI, and the Duke Energy Corrective Action Program. The additional examination and successive inspection requirements of ASME Code, Section XI, also apply during the current outage. The number of additional exams shall be the number of performance monitoring exams included in the inspection item number that were scheduled to be performed during the present inspection period. If additional examinations reveal indications exceeding acceptance standards of IWB-3500 or IWC-3500, the examinations shall be further extended to include all remaining welds/components in the inspection item number.
: c. If during the performance monitoring schedule described above, indications are detected that exceed the applicable ASME Code, Section XI acceptance standards of IWB-3500 or IWC-3500, then the indications will be addressed as required by ASME Code Section XI, and the Duke Energy Corrective Action Program. The additional examination and successive inspection requirements of ASME Code, Section XI, also apply during the current outage. The number of additional exams shall be the number of performance monitoring exams included in the inspection item number that were scheduled to be performed during the present inspection period. If additional examinations reveal indications exceeding acceptance standards of IWB-3500 or IWC-3500, the examinations shall be further extended to include all remaining welds/components in the inspection item number.
: d. Additionally, any unacceptable indication(s) identified as part of the performance monitoring plan will result in the same number of weld(s) to be examined at all the remaining plants (Catawba, Units 1&2, McGuire, Units 1&2, and Shearon Harris, Unit 1). The expanded scope shall include the same rejected weld/component1. These exams shall be completed no later than the first or second refueling outage following discovery of the initial indication(s). This expanded scope is performed in addition to the established performance monitoring plan and cannot be dual credited. Additional and successive inspection requirements of ASME Code, Section XI apply for all newly identified unacceptable indications.
: d. Additionally, any unacceptable indication(s) identified as part of the performance monitoring plan will result in the same number of weld(s) to be examined at all the remaining plants (Catawba, Units 1&2, McGuire, Units 1&2, and Shearon Harris, Unit 1). The expanded scope shall include the same rejected weld/component1. These exams shall be completed no later than the first or second refueling outage following discovery of the initial indication(s). This expanded scope is performed in addition to the established performance monitoring plan and cannot be dual credited. Additional and successive inspection requirements of ASME Code, Section XI apply for all newly identified unacceptable indications.
1 The same rejected weld shall be examined at each of the remaining plants. For example, if a C2.21 Main Feedwater nozzle-to-shell weld at CNS1 was found with a rejectable indication exceeding the acceptance standard of IWC-3500, then the same Main Feedwater nozzle-to-shell weld at CNS2, MNS1&2, and HNP1 shall be examined in either the 1st or 2nd outage following the initial indication.
1 The same rejected weld shall be examined at each of the remaining plants. For example, if a C2.21 Main Feedwater nozzle-to-shell weld at CNS1 was found with a rejectable indication exceeding the acceptance standard of IWC-3500, then the same Main Feedwater nozzle-to-shell weld at CNS2, MNS1&2, and HNP1 shall be examined in either the 1st or 2nd outage following the initial indication.
However, if a C1.10 shell circumferential weld at CNS2 was found with a rejectable indication exceeding the acceptance standard of IWC-3500, then similar welds C1.20 or C1.30 welds at CNS1, MNS1&2, and HNP1 shall be examined in either the 1st or 2nd outage following the initial indication. CNS2 has original Westinghouse Model D-5 Steam Generators and the only Steam Generators within the Performance Monitoring Plan scope with C1.10 shell circumferential welds.
However, if a C1.10 shell circumferential weld at CNS2 was found with a rejectable indication exceeding the acceptance standard of IWC-3500, then similar welds C1.20 or C1.30 welds at CNS1, MNS1&2, and HNP1 shall be examined in either the 1st or 2nd outage following the initial indication. CNS2 has original Westinghouse Model D-5 Steam Generators and the only Steam Generators within the Performance Monitoring Plan scope with C1.10 shell circumferential welds.
Enclosure 1 RA-23-0136 Page 12 of 14


Enclosure 1 RA-23-0136 Page 12 of 14 In addition to the direct evidence provided by the proposed Duke Energy performance monitoring plan, examination of steam generator welds and components is expected to continue to be performed by other units across the domestic and international PWR fleet.
In addition to the direct evidence provided by the proposed Duke Energy performance monitoring plan, examination of steam generator welds and components is expected to continue to be performed by other units across the domestic and international PWR fleet.
Any new unacceptable indications identified will be entered into the Duke Energy Corrective Action Program to evaluate operating experience and determine if additional examinations are required across the Duke Fleet. If a new degradation mechanism is identified during continued industry examinations, Duke Energy will follow the industry guidance to address the new degradation mechanism.
Any new unacceptable indications identified will be entered into the Duke Energy Corrective Action Program to evaluate operating experience and determine if additional examinations are required across the Duke Fleet. If a new degradation mechanism is identified during continued industry examinations, Duke Energy will follow the industry guidance to address the new degradation mechanism.


===RAI-1===
===RAI-1===
==References:==
==References:==
: 1. Letter from K.M. Ellis (Duke Energy) to the U.S. NRC, Proposed Alternative for Steam Generator Welds in Accordance with 10 CFR 50.55a(z)(1), Serial No. RA-22-0256, dated January 23, 2023, ADAMS Accession No. ML23023A093.
: 1. Letter from K.M. Ellis (Duke Energy) to the U.S. NRC, Proposed Alternative for Steam Generator Welds in Accordance with 10 CFR 50.55a(z)(1), Serial No. RA-22-0256, dated January 23, 2023, ADAMS Accession No. ML23023A093.
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===RAI-2===
===RAI-2===
Issue Table 6-4 in Attachment 6 of the submittal noted Value not available for the 60-year projected cycles for the Loss of Power transient at H.B. Robinson Steam Electric Plant.
Issue
Request Confirm that the 60 cycles analyzed in EPRI report 14590 for the Loss of Power transient reasonably bound any occurrence of the transient that might occur or could have occurred at H.B. Robinson Steam Electric Plant.
 
Table 6-4 in Attachment 6 of the submittal noted Value not available for the 60-year projected cycles for the Loss of Power transient at H.B. Robinson Steam Electric Plant.
 
Request
 
Confirm that the 60 cycles analyzed in EPRI report 14590 for the Loss of Power transient reasonably bound any occurrence of the transient that might occur or could have occurred at H.B. Robinson Steam Electric Plant.
 
Duke Energy Response to RAI-2:
Duke Energy Response to RAI-2:
The Loss of Power transient at H.B. Robinson Steam Electric Plant (Robinson) is tracked by the site Fatigue Monitoring Program, which is administered by plant procedure PLP-109, Cycle and Transient Monitoring. PLP-109 Attachment 1, Transient Accounting Summary is routinely completed by the Program Owner to update the records of primary system cycles and transients resulting from normal, test, and upset operating conditions. The most recently-performed (completed and vaulted as QA record) Transient Accounting Summary which included the period up to Robinson refueling outage 31 (30 September 2018) indicates that two (2) Loss of Power transients occurred in the period from 1970 to 9/30/2018 (a total of 48 years). Projecting to 60 years of plant operation will result in a total of three (3) Loss of Power transient cycles.
The Loss of Power transient at H.B. Robinson Steam Electric Plant (Robinson) is tracked by the site Fatigue Monitoring Program, which is administered by plant procedure PLP-109, Cycle and Transient Monitoring. PLP-109 Attachment 1, Transient Accounting Summary is routinely completed by the Program Owner to update the records of primary system cycles and transients resulting from normal, test, and upset operating conditions. The most recently-performed (completed and vaulted as QA record) Transient Accounting Summary which included the period up to Robinson refueling outage 31 (30 September 2018) indicates that two (2) Loss of Power transients occurred in the period from 1970 to 9/30/2018 (a total of 48 years). Projecting to 60 years of plant operation will result in a total of three (3) Loss of Power transient cycles.
Therefore, the 60 cycles analyzed in EPRI report 14590 (Reference 1) for the Loss of Power transient conservatively bound the projected Loss of Power transient cycles at H.B. Robinson over 60-year period.
Therefore, the 60 cycles analyzed in EPRI report 14590 (Reference 1) for the Loss of Power transient conservatively bound the projected Loss of Power transient cycles at H.B. Robinson over 60-year period.


===RAI-2===
===RAI-2===
==References:==
==References:==
: 1. ADAMS Accession No. ML19347B107, EPRI Technical Report 3002014590, "Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Nozzle Inside Radius Sections," Palo Alto, California, 2019.
: 1. ADAMS Accession No. ML19347B107, EPRI Technical Report 3002014590, "Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Nozzle Inside Radius Sections," Palo Alto, California, 2019.
Line 134: Line 205:


===RAI-3===
===RAI-3===
Issue An ISI interval at a particular plant site may be extended, within certain limitations, per IWA-2430 or similar provisions of Section XI. As such, interval dates may extend beyond the end of the operating license for the plant. The NRC may not approve a proposed alternative beyond the end of the current license.
Issue
Request Confirm that the proposed alternative does not apply beyond the current licenses of the subject plants.
 
An ISI interval at a particular plant site may be extended, within certain limitations, per IWA-2430 or similar provisions of Section XI. As such, interval dates may extend beyond the end of the operating license for the plant. The NRC may not approve a proposed alternative beyond the end of the current license.
 
Request
 
Confirm that the proposed alternative does not apply beyond the current licenses of the subject plants.
 
Duke Energy Response to RAI-3:
Duke Energy Response to RAI-3:
The duration for the proposed alternative does not apply beyond the current licenses of the subject plants listed in Table 3-1 below.
The duration for the proposed alternative does not apply beyond the current licenses of the subject plants listed in Table 3-1 below.
Table 3-1: Plants Included in This Request for Alternative and Their Current License End Date Current License Period End Plant/Unit                       Duration of Proposed Alternative1 Date Catawba Nuclear Station,       Remainder of 4th Interval through the end of the 5th Unit 1                                 Interval, scheduled to end on 06/28/2035               12/05/2043 Catawba Nuclear Station,       Remainder of 4th Interval through the end of the 5th Unit 2                                 Interval, scheduled to end on 08/18/2036               12/05/2043 H.B. Robinson Steam               6th Interval not to exceed current License Period Electric Plant, Unit 2                                   End Date                             07/31/2030 McGuire Nuclear Station,         5th and 6th Intervals not to exceed current License Unit 1                                               Period End Date                           06/12/2041 McGuire Nuclear Station,         5th and 6th Intervals not to exceed current License Unit 2                                               Period End Date                           03/03/2043 Oconee Nuclear Station,           6th Interval not to exceed current License Period Unit 1                                                   End Date                             02/06/2033 Oconee Nuclear Station,           6th Interval not to exceed current License Period Unit 2                                                   End Date                             10/06/2033 Oconee Nuclear Station,           6th Interval not to exceed current License Period Unit 3                                                   End Date                             07/19/2034 Shearon Harris Nuclear         Remainder of 4th Interval through the end of the 5th Plant, Unit 1                         Interval, scheduled to end on 05/01/2037.               10/24/2046 Notes:
 
Table 3-1: Plants Included in This Request for Alternative and Their Current License End Date Plant/Unit Duration of Proposed Alternative1 Current License Period End Date Catawba Nuclear Station, Remainder of 4th Interval through the end of the 5th Unit 1 Interval, scheduled to end on 06/28/2035 12/05/2043 Catawba Nuclear Station, Remainder of 4th Interval through the end of the 5th Unit 2 Interval, scheduled to end on 08/18/2036 12/05/2043 H.B. Robinson Steam 6th Interval not to exceed current License Period Electric Plant, Unit 2 End Date 07/31/2030 McGuire Nuclear Station, 5th and 6th Intervals not to exceed current License Unit 1 Period End Date 06/12/2041 McGuire Nuclear Station, 5th and 6th Intervals not to exceed current License Unit 2 Period End Date 03/03/2043 Oconee Nuclear Station, 6th Interval not to exceed current License Period Unit 1 End Date 02/06/2033 Oconee Nuclear Station, 6th Interval not to exceed current License Period Unit 2 End Date 10/06/2033 Oconee Nuclear Station, 6th Interval not to exceed current License Period Unit 3 End Date 07/19/2034 Shearon Harris Nuclear Remainder of 4th Interval through the end of the 5th Plant, Unit 1 Interval, scheduled to end on 05/01/2037. 10/24/2046 Notes:
: 1. The Interval End Date is subject to change in accordance with IWA-2430(c)(1) or an NRC endorsed ASME Code Case. In no case will the proposed alternative exceed the current license period end date.}}
: 1. The Interval End Date is subject to change in accordance with IWA-2430(c)(1) or an NRC endorsed ASME Code Case. In no case will the proposed alternative exceed the current license period end date.}}

Revision as of 18:28, 13 November 2024

Duke Energy Response to Request for Additional Information Regarding Proposed Alternative for Steam Generator Welds in Accordance with 10 CFR 50.55a(z)(1)
ML23201A140
Person / Time
Site: Oconee, Mcguire, Catawba, Harris, Robinson, McGuire  Duke Energy icon.png
Issue date: 07/20/2023
From: Treadway R
Duke Energy Carolinas, Duke Energy Progress
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
RA-23-0136
Download: ML23201A140 (1)
v • d • e


Text

Ryan Treadway General Manager (Acting)

Nuclear Regulatory Affairs, Policy &

Emergency Preparedness

Duke Energy 526 South Church St., EC08F Charlotte, NC 28202

980-373-5873 Ryan.Treadway@duke-energy.com

Serial: RA-23-0136 10 CFR 50.55a July 20, 2023

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Catawba Nuclear Station, Unit Nos. 1 and 2 Docket Nos. 50-413, 50-414 / Renewed License Nos. NPF-35 and NPF-52

Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400 / Renewed License No. N PF-63

McGuire Nuclear Station, Unit Nos. 1 and 2 Docket Nos. 50-369, 50-370 / Renewed License Nos. NPF-9 and NPF-17

Oconee Nuclear Station, Unit Nos. 1, 2, and 3 Docket Nos. 50-269, 50-270, and 50-287 / Renewed License Nos. DPR-38, DPR-47, and DPR-55

H. B. Robinson Steam Electric Plant, Unit No. 2 Docket No. 50-261 / Renewed License No. DPR-23

SUBJECT:

Response to Request for Additional Information Regarding Proposed Alternative for Steam Generator Welds in Accordance with 10 CFR 50.55a(z)(1)

REFERENCES:

1. Duke Energy letter, Proposed Alternative for Steam Generator Welds in Accordance with 10 CFR 50.55a(z)(1), dated January 23, 2023 (ADAMS Accession No. ML23023A093)
2. NRC email, Duke Fleet - Request for Additional Information RE: Proposed Alternative for Steam Generator Welds in Accordance with 10 CFR 50.55a(z)(1) (EPID L-2023-LLR-0003), dated May 22, 2023 (ADAMS Accession No. ML23142A273)

Ladies and Gentlemen:

In Reference 1, Duke Energy Carolinas, LLC and Duke Energy Progress, LLC (collectively referred to as Duke Energy) requested U.S. Nuclear Regulatory Commission (NRC) approval of a proposed alternative to certain requirements of the American Society of Mechanical Engineers (ASME) Code,Section XI for certain Steam Generator welds at Catawba Nuclear Station Units 1 and 2 (CNS), McGuire Nuclear Station Units 1 and 2 (MNS), Oconee Nuclear Station Units 1, 2, and 3 (ONS), Shearon Harris Nuclear Power Plant, Unit 1 (HNP), and H. B. Robinson Steam Electric Plant, Unit 2 (RNP).

U.S. Nuclear Regulatory Commission RA-23-0136 Page 2 In Reference 2, the NRC staff provided a request for additional information (RAI) regarding Reference 1. Enclosure 1 provides Duke Energys response to the Reference 2 RAI.

Should you have any question concerning this letter and its enclosure, please contact Ryan Treadway, Director - Nuclear Fleet Licensing at (980) 373-5873.

No new regulatory commitments have been made in this submittal.

Sincerely,

Ryan Treadway General Manager (Acting) - Nuclear Regulatory Affairs, Policy & Emergency Preparedness

Enclosure:

1. Response to Request for Additional Information

cc:

L. Dudes, USNRC, Region II Regional Administrator N. Jordan, USNRC NRR Project Manager for Duke Fleet M. Mahoney, USNRC NRR Project Manager for HNP J. Klos, USNRC NRR Project Manager for MNS S. Williams, USNRC NRR Project Manager for ONS and CNS L. Haeg, USNRC NRR Project Manager for RNP D. Rivard, USNRC Senior Resident Inspector for CNS P. Boguszewski, USNRC Senior Resident Inspector for HNP C. Safouri, USNRC Senior Resident Inspector for MNS J. Nadel, USNRC Senior Resident Inspector for ONS J. Zeiler, USNRC Senior Resident Inspector for RNP

Enclosure 1 RA-23-0136

Enclosure 1 Response to Request for Additional Information

Enclosure 1 RA-23-0136 Page 1 of 14

Request for Additional Information (RAI)-1

Issue

The licensee referenced probabilistic and deterministic analyses in the above EPRI reports to estimate potential fatigue crack growth in the subject SG welds and to justify application of these analyses to the proposed examination elimination for the welds and nozzle inner radius locations. The licensee presented plant-specific information to demonstrate that the referenced analyses in the EPRI reports would bound the subject SG welds, including the ISI history of the welds.

Leveraging PFM analyses to define the basis for risk-informing inspection requirements requires knowledge of both the current and future behavior of the material degradation and the associated uncertainties applicable to the subject SG welds. Confidence in the results of these analyses hinges on the assurance that the PFM model adequately represents, and will continue to represent, the degradation behavior in the subject SG welds. The NRC staff has determined that, when considering proposed elimination of examinations, adequate performance monitoring through inspections is needed to ensure that the assumptions of the PFM model remain valid, and that novel or unexpected degradation is detected and dispositioned in a timely fashion.

Further, the staff has communicated concepts that licensees can implement on a fleet-wide basis to develop a performance monitoring plan and bolster the technical basis for alternative requests (see slide packages dated January 30, 2023, and April 27, 2023 at ML23033A667 and ML23114A034, respectively). In Section 5.0 of the submittal, the licensee described the various plant-specific examination scenarios and the proposed elimination of examinations. The licensee stated that the proposed alternative results in a maximum time period of approximately 20 years from the end of the interval in which the Section XI requirements were met in full until the end of the proposed alternative. The licensee did not provide a performance monitoring schema for the subject welds and nozzle inner radius locations.

The licensee discusses the system leakage test as providing further assurance of safety for the proposed alternative. However, the NRC staff notes that the visual examinations performed during system leakage tests may not provide sufficient information to ensure that the PFM model continues to predict the material behavior and that emergent degradation is discovered and dispositioned in a timely fashion. Specifically, visual examinations may not directly detect the presence or extent of degradation; may not provide direct detection of aging effects prior to potential loss of structure or intended function; and do not provide sufficient validating data necessary to confirm the modeling of degradation behavior in the subject welds and nozzle inner radius locations.

Request

a. Describe the performance monitoring that will be implemented with this proposed alternative to ensure that the PFM model adequately represents, and will continue to represent the degradation behavior in the subject components commensurate with the duration of the requested alternative.
b. Explain how this performance monitoring will provide, over the extended examination interval, (1) direct evidence of the presence and extent of degradation, (2) validation and confirmation of the continued adequacy of the PFM model; and (3) timely detection of novel or unexpected degradation.

Enclosure 1 RA-23-0136 Page 2 of 14

c. If through this performance monitoring indications are detected that exceed the acceptance standards of ASME Code,Section XI, IWB-3500, confirm that they will be evaluated as required by ASME Code,Section XI (which includes requirements for successive inspections and additional examinations) and describe other actions (if any) specified in the plants corrective action program to ensure that the integrity of the component is adequately maintained.
d. If through this performance monitoring indications are detected that exceed the acceptance standards of ASME Code,Section XI, IWB-3500, then scope expansion may be appropriate to assess extent of condition. Furthermore, if this performance monitoring plan or industry-wide operating experience indicates that a new or novel degradation mechanism is possible in SG welds or nozzle inner radii, scope expansion may be appropriate to ensure that no such mechanism is occurring in the subject plants. Discuss the detailed scope expansion plans for these scenarios.

Duke Energy Response to RAI-1:

a. Performance monitoring supporting this Alternative Request began with the Fourth Inspection Intervals for Catawba, Units 1&2, McGuire, Units 1&2, and Shearon Harris, Unit 1 and with the Fifth Inspection Intervals for H.B. Robinson, Unit 2 and Oconee, Units 1, 2, &3.

As documented in Table 1-2 below, the requested deferral lengths for Catawba, Units 1&2, McGuire, Units 1 &2, and Shearon Harris, Unit 1 range from 12.9 years up to 28.3 years.

Therefore, a performance monitoring plan for these plants is described in detail below. All ASME code required exams have been completed for the 5th Intervals at H.B. Robinson, Unit 2 and Oconee, Units 1 & 3. Oconee Unit 2 has completed all required exams except for one C-A, C1.30 exam scheduled for the upcoming Fall 2023 outage (last outage the 5th Interval). The requested deferral lengths between exams for H.B. Robinson, Unit 2 and Oconee, Units 1, 2, & 3 range from 9.7 years to 16.2 years. Therefore, requested deferrals for all welds and components associated with H.B. Robinson, Unit 2 and Oconee, Units 1, 2,

&3 are below 20 years between examinations and as such do not require any performance monitoring. This is consistent with prior precedent where U.S. licensees have sought examination relief from prescriptive ASME Section XI requirements.

As shown in the Inspection History Tables from Reference 1, a significant number of 4th Interval examinations have been completed across Catawba, Units 1&2 and Shearon Harris, Unit 1. Specifically, 10 of the required 19 Steam Generator Welds for the interval have been inspected with no relevant indications identified. All of these 4th Interval examinations utilized phased array ultrasonic testing (UT) techniques with component specific Non-Destructive Examination (NDE) modeling (when available) to maximum coverage obtained. These modern UT techniques are far superior at detecting near surface or surface breaking flaws and obtained greater coverage compared to earlier interval PSI/ISI exams. These completed examinations (10/19 53% of the total number of required exams) across all three stations are credited for performance monitoring during remainder of the current 4th Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1.

Additionally, the 6-inch nominal diameter Auxiliary Feedwater nozzle-to-shell welds have been examined during the current 4th Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1. These examinations consisted of volumetric UT and magnetic particle testing (MT) examinations in accordance with code requirements (Item No. C2.21). Full 100% coverage was obtained for each exam and no rejectable indications were identified. Although the Enclosure 1 RA-23-0136 Page 3 of 14

Auxiliary Feedwater nozzles were not included in the scope of Alternative RA-22-0256, these completed examinations ensure direct detection of aging affects prior to the potential loss of structure or intended function. The UT/MT exams provide additional validating data to confirm the absence of degradation behavior in Steam Generator welds.

The performance monitoring plan covering the 5th Interval for Catawba, Units 1&2, and Shearon Harris, Unit 1 and the 5th/6th Intervals at McGuire, Units 1&2 will examine one weld from each Item Number across all five Units. Specifically, over a given inspection interval a total of five (5) Steam Generators would be examined comprised of 29 welds/component exams. The proposed performance monitoring plan is to inspect a total of seven (7) different welds/components across all five Units that covers each Item No. and weld/component configuration. Note, the design of the CNS2 Steam Generators differs from CNS1, MNS1, MNS2, and HNP, since CNS2 has original Westinghouse Model D-5 Steam Generators.

Therefore, only CNS2 has C1.10 welds and a Main Steam (MS) nozzle-to-shell (C2.21) weld. The proposed performance monitoring plan ensures those weld configurations unique to CNS2 are selected. Finally, at least one weld/component at each Unit is selected for examination for even distribution. This ensures a diverse sampling across the Duke PWR Fleet rather than monitoring individual welds on a repetitive basis or a single Steam Generator at only one Unit. The proposed performance monitoring plan selects the most time-limited welds since the last inspection, to the extent practical. The components to be examined are described in Table 1-1 below. Also, a visual representation of the past inspection interval history including the proposed performance monitoring schedule is shown in Figure 1-1.

Enclosure 1 RA-23-0136 Page 4 of 14

Table 1-1: Proposed Performance Monitoring Plan

Station/Unit ASME ASME Description Number and Type of Proposed Schedule Approximate Category Item No. Exam (Year)2 Length of Time Since Last Exam (Years)

Catawba / Unit 1 C-B C2.21 FW Nozzle-to-Shell 1 Volumetric (UT) & Interval 5, Period 1 18 Weld 1 Surface (MT or PT) (Spring 2029)

Catawba / Unit 1 C-B C2.22 FW Inside Radius 1 Volumetric (UT) Interval 5, Period 1 10.5 (Spring 2029) 1Catawba / Unit 2 C-A C1.10 Shell Circumferential 1 Volumetric (UT) Interval 5, Period 3 16.5 Weld (Fall 2034) 1Catawba / Unit 2 C-B C2.21 MS Nozzle-to-Shell 1 Volumetric (UT) & Interval 5, Period 2 16.5 Weld 1 Surface (MT or PT) (Fall 2031)

McGuire / Unit 1 C-A C1.20 Head Circumferential 1 Volumetric (UT) Interval 5, Period 3 16.5 Weld (Fall 2029)

McGuire / Unit 2 C-A C1.30 Tubesheet-to-Shell 1 Volumetric (UT) Interval 5, Period 3 18 Weld (Fall 2033)

Shearon Harris / Unit 1 B-B B2.40 Tubesheet-to Head 1 Volumetric (UT) Interval 5, Period 2 19 Weld (Fall 2031)

Notes:

1. Catawba Unit 2 has original Westinghouse Model D-5 Steam Generators. Therefore, it is the only Unit from the performance monitoring plan with C1.10 welds and a Main Steam nozzle-to-shell weld.
2. The proposed year is subject to change in accordance with IWA-2430(c)(1) or +/- one outage from the proposed schedule not to exceed the overall end date of 2035. This allows for possible unit transitions from an 18-month fuel cycle to a 24-month fuel cycle or other unforeseen plant radiation exposure limits or exam support issues. The proposed performance monitoring plan will be completed by the end of 2035.

Enclosure 1 RA-23-0136 Page 5 of 14

Replacement Steam Year Generator Year Plant 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046

1996 Catawba 1 3rd Interval 4th Interval 4th Interval 5th Interval X1 6th Interval ASME Code SG Requirements Resume 12/5/2043

Original SGs Catawba 2 3rd Interval 4th Interval 4th Interval 5th Interval X X 6th Interval ASME Code SG Requirements Resume 12/5/2043

1984 H.B Robinson 2 5th Interval 6th Interval 7/31/2030

1997 McGuire 1 4th Interval 5th Interval X 6th Interval 6/12/2041 1997 McGuire 2 3rd Interval 4th Interval 5th Interval X 6th Interval 3/3/2043

2003 2004 Oconee 1, 2, 3 4th Interval 5th Interval 6th Interval #

2001 Shearon Harris 1 3rd Interval 4th Interval 4th Interval 5th Interval X 6th Interval ASME Code SG Requirements Resume 10/24/2046

Notes:

1. Two exams item numbers are scheduled, to ensure both the Main Feedwater nozzle-to-shell weld (C2.21) and associated inner radius (C2.22) exams are performed during the same refueling outage.

Figure 1-1: Inservice Inspection Interval History and Performance Monitoring Schedule

Enclosure 1 RA-23-0136 Page 6 of 14

The proposed performance monitoring plan for Duke Energy, will be performed by the end of 2035. This will ensure that no more than 20 years elapses between the performance of an ASME Code,Section XI, examination for each weld/component item number on a Steam Generator subject to examination requirements. Following completion of the proposed performance monitoring plan by 2035, none of the Duke Energy units covered by the proposed alternative will have operated more than 20 years between exams of each item number being performed at least once amongst the fleet. Following completion of the performance monitoring plan and the Fifth Inspection Intervals at Catawba, Units 1&2 and Shearon Harris, Unit 1, ASME Section XI Code required Steam Generator examinations for these plants will resume with the start of the Sixth Inspection Intervals as required per 10 CFR 50.55a(g)(4)(ii). These code required examinations satisfy the performance monitoring for McGuire, Units 1&2 thru the end of its current operating license.

Enclosure 1 RA-23-0136 Page 7 of 14

Table 1-2: Summary of Inspection Deferrals in Proposed Alternative RA-22-0256

ASME Item Date of Last End of Length of Station Unit Category No. Description Inspection Proposed Time1 (Years)

Alternative Catawba 1 B-B B2.40 Steam generators (primary side), 05/09/2017 End of 5th 18.2 tubesheet-to-head weld Interval, C-A C1.20 Steam generators (secondary side), 05/06/2011 Scheduled to 24.2 Head circumferential welds End C-A C1.30 Steam generators (secondary side), 05/09/2017 06/28/2035 18.2 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 05/12/2011 24.1 C-B C2.22 FW Nozzle inside radius section 11/25/2018 16.6 Catawba 2 B-B B2.40 Steam generators (primary side), 04/19/2021 End of 5th 14.3 tubesheet-to-head weld Interval, C-A C1.10 Steam generators (secondary side), 03/25/2018 Scheduled to 17.4 Shell circumferential welds End C-A C1.10 Steam generators (secondary side), 03/27/2009 08/18/2036 26.4 Shell circumferential welds C-A C1.10 Steam generators (secondary side), 03/25/2009 26.4 Shell circumferential welds C-A C1.20 Steam generators (secondary side), 09/25/2022 12.9 Head circumferential welds C-A C1.30 Steam generators (secondary side), 03/23/2018 17.4 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 03/25/2018 17.4 C-B C2.21 MS Nozzle-to-shell weld 03/10/2015 20.5 C-B C2.22 FW Nozzle inside radius section 03/17/2015 20.4 Enclosure 1 RA-23-0136 Page 8 of 14

ASME Item Date of Last End of Length of Station Unit Category No. Description Inspection Proposed Time1 (Years)

Alternative H.B 2 B-B B2.40 Steam generators (primary side), 06/01/2015 End of 15.2 Robinson tubesheet-to-head weld Current C-A C1.10 Steam generators (secondary side), 10/09/2018 Licensed 11.8 Shell circumferential welds Period, C-A C1.10 Steam generators (secondary side), 10/11/2018 07/31/2030 11.8 Shell circumferential welds C-A C1.10 Steam generators (secondary side), 11/25/2020 9.7 Shell circumferential welds C-A C1.20 Steam generators (secondary side), 11/24/2020 9.7 Head circumferential welds C-A C1.30 Steam generators (secondary side), 06/02/2015 15.2 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 05/26/2015 15.2 C-B C2.21 MS Nozzle-to-shell weld 06/01/2015 15.2 C-B C2.22 FW Nozzle inside radius section 11/17/2020 9.7 C-B C2.22 MS Nozzle inside radius section 10/11/2018 11.8 McGuire 1 B-B B2.40 Steam generators (primary side), 03/31/2019 End of 22.2 tubesheet-to-head weld Current C-A C1.20 Steam generators (secondary side), 03/24/2013 Licensed 28.2 Head circumferential welds Period, C-A C1.30 Steam generators (secondary side), 03/20/2013 06/12/2041 28.3 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 10/03/2014 26.7 C-B C2.22 FW Nozzle inside radius section 10/03/2014 26.7 McGuire 2 B-B B2.40 Steam generators (primary side), 03/29/2020 End of 22.9 tubesheet-to-head weld Current C-A C1.20 Steam generators (secondary side), 03/04/2023 Licensed 20.0 Head circumferential welds Period, C-A C1.30 Steam generators (secondary side), 09/23/2015 03/03/2043 27.5 Tubesheet-to-shell weld C-B C2.21 FW Nozzle-to-shell weld 09/24/2015 27.5 C-B C2.22 FW Nozzle inside radius section 04/07/2017 25.9 Oconee 1 B-B B2.40 Steam generators (primary side), 11/3/2018 End of 14.3 tubesheet-to-head weld Current Enclosure 1 RA-23-0136 Page 9 of 14

ASME Item Date of Last End of Length of Station Unit Category No. Description Inspection Proposed Time1 (Years)

Alternative B-B B2.40 Steam generators (primary side), 11/21/2016 Licensed 16.2 tubesheet-to-head weld Period, C-A C1.30 Steam generators (secondary side), 10/30/2020 02/06/2033 12.3 Tubesheet-to-shell weld C-A C1.30 Steam generators (secondary side), 10/29/2020 12.3 Tubesheet-to-shell weld C-B C2.21 MS Nozzle-to-shell weld 11/13/2016 16.2 C-B C2.21 MS Nozzle-to-shell weld 10/29/2018 14.3 Oconee 2 B-B B2.40 Steam generators (primary side), 11/21/2019 End of 13.9 tubesheet-to-head weld Current B-B B2.40 Steam generators (primary side), 11/21/2019 Licensed 13.9 tubesheet-to-head weld Period, C-A C1.30 Steam generators (secondary side), 11/16/2021 10/06/2033 13.9 Tubesheet-to-shell weld C-A C1.30 Steam generators (secondary side), 10/23/2013, 10.0 Tubesheet-to-shell weld Scheduled for O2R31 (Fall 2023)2 C-B C2.21 MS Nozzle-to-shell weld 11/19/2019 13.9 C-B C2.21 MS Nozzle-to-shell weld 11/19/2019 13.9 Oconee 3 B-B B2.40 Steam generators (primary side), 5/21/2022 End of 12.2 tubesheet-to-head weld Current B-B B2.40 Steam generators (primary side), 4/20/2020 Licensed 14.3 tubesheet-to-head weld Period, C-A C1.30 Steam generators (secondary side), 5/20/2022 07/19/2034 12.2 Tubesheet-to-shell weld C-A C1.30 Steam generators (secondary side), 4/20/2020 14.3 Tubesheet-to-shell weld C-B C2.21 MS Nozzle-to-shell weld 4/29/2018 16.2 C-B C2.21 MS Nozzle-to-shell weld 4/30/2018 16.2 Shearon 1 B-B B2.40 Steam generators (primary side), 5/4/2012 End of 5th 25.0 Harris tubesheet-to-head weld Interval, C-A C1.20 Steam generators (secondary side), 4/23/2015 Scheduled to 22.0 Head circumferential welds Enclosure 1 RA-23-0136 Page 10 of 14

ASME Item Date of Last End of Length of Station Unit Category No. Description Inspection Proposed Time1 (Years)

Alternative C-A C1.30 Steam generators (secondary side), 4/18/2015 End 22.0 Tubesheet-to-shell weld 05/01/2037 C-B C2.21 FW Nozzle-to-shell weld 5/3/2021 16.0 C-B C2.22 FW Nozzle inside radius section 5/5/2012 25.0

Notes:

1. This column represents the length of time between the date of the last completed code inspection and the end of the proposed alternative.
2. This C1.30 is scheduled for O2R31 (Fall 2023) and required to be completed for ASME 5th Interval code compliance (last outage of the 5th Interval for ONS Unit 2). This alternative is only applicable to Oconee 6th Interval exams through the current licensed period for Oconee Units 1, 2, and 3.

Enclosure 1 RA-23-0136 Page 11 of 14

b. (1) The performance monitoring plan provided in the response above includes sampled inspections using Volumetric/Surface exam methods that will provide direct evidence of the presence and extent of any degradation over the extended examination interval for these welds.

(2) The components in the proposed alternative have operated for a minimum of 21.8 years and up to a maximum of 36.9 years without the identification through inspection of any service-induced degradation. This excellent operating history is validation and confirmation of the conservative nature of the PFM and DFM models used in the EPRI Technical Reports 3002015906 and 3002014590 (References 2 & 3). This also shows that the models will predict future behavior conservatively. The proposed performance monitoring plan includes sampling of examinations across different weld types located at different plants. This ensures the inspection data is representative of the Duke Fleet and is sufficient to demonstrate continued adequacy of the modeling.

(3) The performance monitoring schedule described above will provide timely detection of any novel or unexpected degradation in these components.

c. If during the performance monitoring schedule described above, indications are detected that exceed the applicable ASME Code,Section XI acceptance standards of IWB-3500 or IWC-3500, then the indications will be addressed as required by ASME Code Section XI, and the Duke Energy Corrective Action Program. The additional examination and successive inspection requirements of ASME Code,Section XI, also apply during the current outage. The number of additional exams shall be the number of performance monitoring exams included in the inspection item number that were scheduled to be performed during the present inspection period. If additional examinations reveal indications exceeding acceptance standards of IWB-3500 or IWC-3500, the examinations shall be further extended to include all remaining welds/components in the inspection item number.
d. Additionally, any unacceptable indication(s) identified as part of the performance monitoring plan will result in the same number of weld(s) to be examined at all the remaining plants (Catawba, Units 1&2, McGuire, Units 1&2, and Shearon Harris, Unit 1). The expanded scope shall include the same rejected weld/component1. These exams shall be completed no later than the first or second refueling outage following discovery of the initial indication(s). This expanded scope is performed in addition to the established performance monitoring plan and cannot be dual credited. Additional and successive inspection requirements of ASME Code,Section XI apply for all newly identified unacceptable indications.

1 The same rejected weld shall be examined at each of the remaining plants. For example, if a C2.21 Main Feedwater nozzle-to-shell weld at CNS1 was found with a rejectable indication exceeding the acceptance standard of IWC-3500, then the same Main Feedwater nozzle-to-shell weld at CNS2, MNS1&2, and HNP1 shall be examined in either the 1st or 2nd outage following the initial indication.

However, if a C1.10 shell circumferential weld at CNS2 was found with a rejectable indication exceeding the acceptance standard of IWC-3500, then similar welds C1.20 or C1.30 welds at CNS1, MNS1&2, and HNP1 shall be examined in either the 1st or 2nd outage following the initial indication. CNS2 has original Westinghouse Model D-5 Steam Generators and the only Steam Generators within the Performance Monitoring Plan scope with C1.10 shell circumferential welds.

Enclosure 1 RA-23-0136 Page 12 of 14

In addition to the direct evidence provided by the proposed Duke Energy performance monitoring plan, examination of steam generator welds and components is expected to continue to be performed by other units across the domestic and international PWR fleet.

Any new unacceptable indications identified will be entered into the Duke Energy Corrective Action Program to evaluate operating experience and determine if additional examinations are required across the Duke Fleet. If a new degradation mechanism is identified during continued industry examinations, Duke Energy will follow the industry guidance to address the new degradation mechanism.

RAI-1

References:

1. Letter from K.M. Ellis (Duke Energy) to the U.S. NRC, Proposed Alternative for Steam Generator Welds in Accordance with 10 CFR 50.55a(z)(1), Serial No. RA-22-0256, dated January 23, 2023, ADAMS Accession No. ML23023A093.
2. ADAMS Accession No. ML20225A141, EPRI Technical Report 3002015906, "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," Palo Alto, California, 2019.
3. ADAMS Accession No. ML19347B107, EPRI Technical Report 3002014590, "Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Nozzle Inside Radius Sections," Palo Alto, California, 2019.

Enclosure 1 RA-23-0136 Page 13 of 14

RAI-2

Issue

Table 6-4 in Attachment 6 of the submittal noted Value not available for the 60-year projected cycles for the Loss of Power transient at H.B. Robinson Steam Electric Plant.

Request

Confirm that the 60 cycles analyzed in EPRI report 14590 for the Loss of Power transient reasonably bound any occurrence of the transient that might occur or could have occurred at H.B. Robinson Steam Electric Plant.

Duke Energy Response to RAI-2:

The Loss of Power transient at H.B. Robinson Steam Electric Plant (Robinson) is tracked by the site Fatigue Monitoring Program, which is administered by plant procedure PLP-109, Cycle and Transient Monitoring. PLP-109 Attachment 1, Transient Accounting Summary is routinely completed by the Program Owner to update the records of primary system cycles and transients resulting from normal, test, and upset operating conditions. The most recently-performed (completed and vaulted as QA record) Transient Accounting Summary which included the period up to Robinson refueling outage 31 (30 September 2018) indicates that two (2) Loss of Power transients occurred in the period from 1970 to 9/30/2018 (a total of 48 years). Projecting to 60 years of plant operation will result in a total of three (3) Loss of Power transient cycles.

Therefore, the 60 cycles analyzed in EPRI report 14590 (Reference 1) for the Loss of Power transient conservatively bound the projected Loss of Power transient cycles at H.B. Robinson over 60-year period.

RAI-2

References:

1. ADAMS Accession No. ML19347B107, EPRI Technical Report 3002014590, "Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Nozzle Inside Radius Sections," Palo Alto, California, 2019.

Enclosure 1 RA-23-0136 Page 14 of 14

RAI-3

Issue

An ISI interval at a particular plant site may be extended, within certain limitations, per IWA-2430 or similar provisions of Section XI. As such, interval dates may extend beyond the end of the operating license for the plant. The NRC may not approve a proposed alternative beyond the end of the current license.

Request

Confirm that the proposed alternative does not apply beyond the current licenses of the subject plants.

Duke Energy Response to RAI-3:

The duration for the proposed alternative does not apply beyond the current licenses of the subject plants listed in Table 3-1 below.

Table 3-1: Plants Included in This Request for Alternative and Their Current License End Date Plant/Unit Duration of Proposed Alternative1 Current License Period End Date Catawba Nuclear Station, Remainder of 4th Interval through the end of the 5th Unit 1 Interval, scheduled to end on 06/28/2035 12/05/2043 Catawba Nuclear Station, Remainder of 4th Interval through the end of the 5th Unit 2 Interval, scheduled to end on 08/18/2036 12/05/2043 H.B. Robinson Steam 6th Interval not to exceed current License Period Electric Plant, Unit 2 End Date 07/31/2030 McGuire Nuclear Station, 5th and 6th Intervals not to exceed current License Unit 1 Period End Date 06/12/2041 McGuire Nuclear Station, 5th and 6th Intervals not to exceed current License Unit 2 Period End Date 03/03/2043 Oconee Nuclear Station, 6th Interval not to exceed current License Period Unit 1 End Date 02/06/2033 Oconee Nuclear Station, 6th Interval not to exceed current License Period Unit 2 End Date 10/06/2033 Oconee Nuclear Station, 6th Interval not to exceed current License Period Unit 3 End Date 07/19/2034 Shearon Harris Nuclear Remainder of 4th Interval through the end of the 5th Plant, Unit 1 Interval, scheduled to end on 05/01/2037. 10/24/2046 Notes:

1. The Interval End Date is subject to change in accordance with IWA-2430(c)(1) or an NRC endorsed ASME Code Case. In no case will the proposed alternative exceed the current license period end date.
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