View source for RS-23-114, Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds

{{Adams
| number = ML23305A069
| issue date = 11/01/2023
| title = Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds
| author name = Lueshen K
| author affiliation = Constellation Energy Generation, LLC
| addressee name = 
| addressee affiliation = NRC/NRR, NRC/Document Control Desk
| docket = 05000456, 05000457, 05000454, 05000455
| license number = NPF-072, NPF-077, NPF-037, NPF-066
| contact person = 
| case reference number = RS-23-114
| document type = Letter type:RS
| page count = 56
}}

=Text=
{{#Wiki_filter:200 Exelon Way Kennett Square, PA 19348 www.constellation.com 10 CFR 50.55a RS-23-114 November 1, 2023 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455

==Subject:==
Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds

==References:==
: 1) Letter from D. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds, dated May 12, 2021 (ML21133A297).
: 2) Letter from D. Gudger (Constellation Energy Generation, LLC) to U.S.
Nuclear Regulatory Commission, Supplemental Information - Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds, dated April 8, 2022 (ML22098A179).
: 3) Letter from N. Salgado (U.S. Nuclear Regulatory Commission) to D.
Rhoades (Constellation Energy Generation), Braidwood Station, Units 1 and 2 and Bryon Station, Unit Nos. 1 and 2 - Proposed Alternative to the Requirements of the American Society of Mechanical Engineers Boiler &
Pressure Vessel Code (EPIDS L-2021-LLR-0035 and L-2021-LLR-0036),
dated November 10, 2022 (ML22307A246).
: 4) SECY-23-0061, Clarification of the Staffs Position on Certain American Society of Mechanical Engineers Code Alternatives for More than One 10-Year Inservice Inspection Interval Under Title 10 Code of Federal Regulations 50.55a, dated July 21, 2023 (ML23094A178).

Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds November 1, 2023 Page 2 In the Reference 1 letter, Constellation Energy Generation, LLC (Constellation) requested relief from the examination of pressurizer circumferential and longitudinal shell-to-head welds and nozzle-to-vessel welds for Braidwood Generating Station (Braidwood), Units 1 and 2 and Byron Generating Station (Byron), Units 1 and 2. In this letter, Constellation requested approval for the remainder of the currently approved operating licenses. In the Reference 2 letter, Constellation supplemented the Reference 1 letter with a performance monitoring plan.
In the Reference 3 letter, the U.S. Nuclear Regulatory Commission (NRC) approved the proposed alternative for only the current fourth inservice inspection interval at Braidwood and Byron based on the NRC policy to not grant relief beyond the current interval. As discussed in the Reference 3 letter, Since the ASME Code requirements beyond the fourth 10-year ISI intervals at Braidwood and Byron have not yet been established in accordance with 10 CFR 50.55a(g)(4)(ii), no authorization can be made at this time for subsequent ISI intervals following the fourth ISI interval.
In Reference 4, which was issued after approval of the proposed alternative for Braidwood and Byron, the NRC reinstated its policy of granting proposed alternatives for the full operating license. Reference 4 (SECY-23-0061) was issued to inform the Commission of a regulatory practice concerning the staffs approval of certain American Society of Mechanical Engineers (ASME) Code alternatives for more than one 10-year inservice inspection (ISI) interval under Title 10 of the Code of Federal Regulations (10CFR) 50.55a, Codes and standards. SECY-23-0061 concludes by stating that the staff intends to continue to implement its regulatory practice concerning the approval of certain ASME Code alternatives for more than one 10-year ISI interval on a limited, case-by-case basis when the technical bases supporting the requested alternative ensure that an acceptable level of quality and safety will be maintained.
In the Reference 2 letter, Constellation committed to completing performance monitoring examinations during the fifth inservice inspection interval (by 2034) at Byron Unit 2, which is the duration of approval being requested in the attached proposed alternative. The Reference 3 safety evaluation states the NRC staff determined that the proposed inspections, indication resolution, and inspection expansions proposed together support an acceptable performance monitoring plan.
Therefore, in accordance with 10 CFR 50.55a(z)(1) and SECY-23-0061, Constellation hereby requests NRC approval of Revision 1 of the Reference 1 proposed alternative for the fifth inservice inspection interval at Braidwood, Units 1 and 2, and Byron, Units 1 and 2 on the basis that the proposed alternative provides an acceptable level of quality and safety. Specifically, Constellation is requesting an alternative to volumetric examination of pressurizer circumferential and longitudinal shell-to-head welds and nozzle-to-shell welds for the fifth inservice inspection interval during which time the performance monitoring examinations committed to in Reference 2 will be performed at Byron Unit 2.
Proposed Alternative I4R-15 Revision 1 for Braidwood and I4R-21 Revision 1 for Byron, is provided in Attachment 2. Constellation requests approval of the proposed alternative by October 1, 2024, to support the Byron fifth interval code of record update, which will include scheduling of the performance monitoring examinations committed to in the Reference 2 letter.

Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds November 1, 2023 Page 3 This submittal contains a regulatory commitment provided in Attachment 1. This commitment is consistent with the Reference 2 commitment. Attachment 2 contains Revision 1 of the proposed alternative.
Should you have any questions concerning this matter, please contact Tom Loomis at (267-533-5669).
Respectfully, Lueshen,                Digitally signed by Lueshen, Kevin Kevin                   Date: 2023.11.01 07:03:16
                              -05'00' Kevin Lueshen Director, Licensing Constellation Energy Generation, LLC

==Attachment:==
: 1) Summary of Commitments
: 2) 10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 cc:     Regional Administrator - NRC Region III NRC Senior Resident Inspector - Braidwood Station NRC Senior Resident Inspector - Byron Station NRC Project Manager - Braidwood Station NRC Project Manager - Byron Station Illinois Emergency Management Agency - Division of Nuclear Safety

Attachment 1 Summary of Commitments

Summary of Commitments Page 1 of 1 Attachment 1 Summary of Commitments The following table identifies commitments made in this document. (Any other actions discussed in the submittal represent intended or planned actions. They are described to the NRC for the NRCs information and are not regulatory commitments.)
COMMITMENT TYPE COMMITTED DATE          ONE-TIME COMMITMENT                                                           Programmatic OR OUTAGE            ACTION (Yes/No)
(Yes/No)
As part of the performance monitoring plan,      The required            Yes         No Constellation will examine the following         examinations will be components at Byron Station, Unit 2 to the       completed by the maximum extent possible:                         end of 2034 to
* One (1) Category B-B, Item B2.11           ensure that no more top head circumferential weld            than 20 years
* One (1) Category B-B, Item B2.12           elapses between the top head longitudinal weld               performance of an
* Five (5) Category B-D, Item B3.110         ASME XI nozzle to vessel welds consisting of:    examination for the o One (1) spray nozzle              Category B-B and o One (1) relief nozzle             B-D components o Three (3) safety nozzles          covered by the proposed alternative.
The components to be examined are provided in the Table below.
Any new unacceptable indications identified as part of the performance monitoring plan at Byron Unit 2 will result in the same population of welds being examined at Byron Unit 1 and Braidwood Unit 1 and 2 during the next regularly scheduled refueling outage.
ASME ASME Unit                             Component ID             Component Description Category Item 2      B-B      B2.11         2RY-01-S/PC-05              Shell - Upper Head 2      B-B      B2.12          2RY-01-S/PL-04           Upper Longitudinal Weld 2      B-D     B3.110         2RY-01-S/PN-02                  Spray Nozzle 2      B-D     B3.110         2RY-01-S/PN-03                  Relief Nozzle 2      B-D     B3.110         2RY-01-S/PN-04                  Safety Nozzle 2      B-D     B3.110         2RY-01-S/PN-05                  Safety Nozzle 2      B-D     B3.110         2RY-01-S/PN-06                  Safety Nozzle

Attachment 2 10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 1 of 50)
Proposed Alternative for Examination of Pressurizer Shell-to-Head and Nozzle-to-Shell Welds (Examination Categories B-B and B-D)
In Accordance with 10 CFR 50.55a(z)(1) 1    ASME Code Component(s) Affected Code Class:              Class 1

== Description:==
Pressurizer Shell-to-Head and Nozzle-to-Vessel Welds Examination Categories:  Category B-B, Pressure-Retaining Welds in Vessels Other Than Reactor Vessels Category B-D, Full Penetration Welded Nozzles in Vessels Item Numbers:            B2.11 - Pressurizer, Shell-to-Head Welds, Circumferential B2.12 - Pressurizer, Shell-to-Head Welds, Longitudinal B3.110 - Pressurizer, Nozzle-to-Vessel Welds Braidwood Component IDs:
ASME       ASME Unit                           Component ID             Component Description Category     Item 1      B-B      B2.11         1PZR-01-08A                Shell - Lower Head 1      B-B      B2.11         1PZR-01-08E                Shell - Upper Head 2      B-B      B2.11         2PZR-01-08A                Shell - Lower Head 2      B-B      B2.11         2PZR-01-08E                Shell - Upper Head 1      B-B      B2.12         1PZR-01-09A               Shell Longitudinal Weld 1      B-B      B2.12         1PZR-01-09D               Shell Longitudinal Weld 2      B-B      B2.12         2PZR-01-09A               Shell Longitudinal Weld 2      B-B      B2.12         2PZR-01-09D               Shell Longitudinal Weld 1      B-D      B3.110         1PZR-01-N1                    Surge Nozzle 1      B-D      B3.110         1PZR-01-N2                    Spray Nozzle 1      B-D      B3.110         1PZR-01-N3                    Relief Nozzle 1      B-D      B3.110        1PZR-01-N4A                    Safety Nozzle 1      B-D      B3.110        1PZR-01-N4B                    Safety Nozzle 1      B-D      B3.110        1PZR-01-N4C                    Safety Nozzle 2      B-D      B3.110         2PZR-01-N1                    Surge Nozzle 2      B-D      B3.110         2PZR-01-N2                    Spray Nozzle 2      B-D      B3.110         2PZR-01-N3                    Relief Nozzle 2      B-D      B3.110        2PZR-01-N4A                    Safety Nozzle 2      B-D      B3.110        2PZR-01-N4B                    Safety Nozzle 2      B-D      B3.110        2PZR-01-N4C                    Safety Nozzle

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 2 of 50)
Byron Component IDs:
ASME         ASME Unit                                       Component ID                    Component Description Category        Item 1        B-B         B2.11               1RY-01-S/PC-01                       Shell - Bottom Head 1        B-B         B2.11               1RY-01-S/PC-05                       Shell - Upper Head 2        B-B         B2.11               2RY-01-S/PC-01                       Shell - Bottom Head 2        B-B         B2.11               2RY-01-S/PC-05                       Shell - Upper Head 1        B-B         B2.12               1RY-01-S/PL-01                    Lower Longitudinal Weld 1        B-B         B2.12               1RY-01-S/PL-04                    Upper Longitudinal Weld 2        B-B         B2.12               2RY-01-S/PL-01                    Lower Longitudinal Weld 2        B-B         B2.12               2RY-01-S/PL-04                    Upper Longitudinal Weld 1        B-D        B3.110               1RY-01-S/PN-01                          Surge Nozzle 1        B-D        B3.110               1RY-01-S/PN-02                          Spray Nozzle 1        B-D        B3.110               1RY-01-S/PN-03                          Relief Nozzle 1        B-D        B3.110               1RY-01-S/PN-04                          Safety Nozzle 1        B-D        B3.110               1RY-01-S/PN-05                          Safety Nozzle 1        B-D        B3.110               1RY-01-S/PN-06                          Safety Nozzle 2        B-D        B3.110               2RY-01-S/PN-01                          Surge Nozzle 2        B-D        B3.110               2RY-01-S/PN-02                          Spray Nozzle 2        B-D        B3.110               2RY-01-S/PN-03                          Relief Nozzle 2        B-D        B3.110               2RY-01-S/PN-04                          Safety Nozzle 2        B-D        B3.110               2RY-01-S/PN-05                          Safety Nozzle 2        B-D        B3.110               2RY-01-S/PN-06                          Safety Nozzle 2      Applicable Code Edition and Addenda The following table identifies the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel (B&PV) Section XI Code of Record for performing Inservice Inspection (ISI) activities at Braidwood and Byron:
PLANT         INTERVAL             EDITION                      START1                         END1 Braidwood Station,                                            August 29, 2018 (Unit1)        July 28, 2028 (Unit 1)
Fourth           2013 Edition Units 1 and 2                                              November 5, 2018 (unit 2) October 16, 2028 (Unit 2)
Established 18 months prior to 5th interval start   July 29, 2028 (Unit 1)        July 28, 2038 (Unit 1)
Braidwood Station, Fifth       date in accordance Units 1 and 2                                              October  17, 2028 (Unit 2)   October 16, 2038 (Unit 2) with 10 CFR 50.55a(g)(4)(ii)
Byron Station,                  2007 Edition, through Fourth                                       July 16, 2016                 July 15, 2025 Units 1 and 2                      2008 Addenda Byron Station, Fifth           2019 Edition                July 16, 2025                 July 15, 2035 Units 1 and 2 Note 1: The fifth interval start and end dates are estimates based on the current interval.
Interval start and end dates may be adjusted as allowed by ASME Section XI.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 3 of 50)
The 2019 Edition of ASME Section XI, Table G-2110-1 will be utilized to extend the use of Figure G-2110-1, Reference Critical Stress Intensity Factor for Material, to material SA-533 Grade A, Class 2. (Note: The 2019 Edition of ASME Section XI is approved in 10 CFR 50.55a.)
3    Applicable Code Requirement ASME Code, Section XI, IWB-2500(a), Table IWB-2500-1, Examination Category B-B, requires examination of the applicable Item Numbers as follows:
Item No. B2.11 - Volumetric examination of both Circumferential Shell-to-Head welds during each inspection interval. The examination volume is shown in Figure IWB-2500-1.
Item No. B2.12 - Volumetric examination of one foot of one Longitudinal Shell-to-Head weld intersecting the circumferential weld per head each inspection interval. The examination volume is shown in Figure IWB-2500-2.
ASME Code, Section XI, IWB-2500(a), Table IWB-2500-1, Examination Category B-D, requires examination of the applicable Item Number as follows:
Item No. B3.110 - Volumetric examination of all Full Penetration Nozzle-to-Vessel welds during each inspection interval. The examination volume is shown in Figures IWB-2500-7(a), (b), (c), and (d).
4    Reason for Request The Electric Power Research Institute (EPRI) performed assessments in Reference
[1] of the basis for the ASME Section XI examination requirements specified for the above-listed ASME Code, Section XI, Division 1 (ASME Section XI) Examination Categories and Item Numbers for pressurizer welds. The assessments include a survey of inspection results from 74 units as well as flaw tolerance evaluations using probabilistic fracture mechanics (PFM) and deterministic fracture mechanics (DFM). The Reference [1] report results indicate that the current ASME Section XI inspection frequency of ten years for these welds can be increased with no impact to plant safety. It is upon the basis of those results that an alternate inspection frequency is requested.
5    Proposed Alternative and Basis for Use Constellation requests an inspection alternative to the examination requirements of ASME Section XI, Table IWB-2500-1, for Examination Categories B-B and B-D, Item Numbers B2.11, B2.12, and B3.110. The proposed alternative is to defer inspection of these Item Numbers through the end of the fifth inservice inspection interval for Braidwood Station (Braidwood), Units 1 and 2, and Byron Station (Byron), Units 1 and 2 as summarized in Table 1.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 4 of 50)
This proposed alternative includes the performance monitoring plan previously committed to in the RAI response [17] to Revision 0 of the proposed alternative which is summarized below for reference.
As a performance monitoring plan, Constellation will examine the following components at Byron Station, Unit 2 to the maximum extent possible:
* One (1) Category B-B, Item B2.11 top head shell-to-head circumferential weld
* One (1) Category B-B, Item B2.12 top head shell-to-head longitudinal weld
* Five (5) Category B-D, Item B3.110 nozzle-to-vessel welds consisting of:
o One (1) spray nozzle o One (1) relief nozzle o Three (3) safety nozzles The components to be examined as part of this performance monitoring plan are provided in the table below for reference. The proposed performance monitoring plan for Bryon Unit 2 will be performed by the end of 2034. This will ensure that no more than 20 years elapses between the performance of an ASME XI examination for the Category B-B and B-D components included in the performance monitoring plan.
In the unlikely event of any new unacceptable indications (i.e., indications exceeding the acceptance standards of IWB-3500, that are accepted by Repair/Replacement Activity or Analytical Evaluation) are identified during the performance monitoring plan at Byron Unit 2, these indications will be evaluated as required by ASME Section XI and the corrective action program. The additional examination and successive inspection requirements of ASME Section XI also apply. Any new unacceptable indications identified as part of the performance monitoring plan at Byron Unit 2 will result in the same population of welds being examined at Byron Unit 1 and Braidwood Units 1 and 2 during the next regularly scheduled refueling outage.
The absence of any new unacceptable indications in the Byron Unit 2 components selected for examination as part of the performance monitoring plan and the absence of any unexpected degradation across the operating fleet, provides validation that the assumptions and methods of the PFM Model used in the EPRI Report are adequate to predict the future behavior of the subject components. The strong technical basis provided by the results of the PFM Model and EPRI Report along with the implementation of the proposed performance monitoring plan,

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 5 of 50) including scope expansion criteria, will provide additional assurance that the pressurizer welds at Byron and Braidwood can operate safely through the end of the fifth inspection interval and will continue to provide an acceptable level of quality and safety.
Upon completion of the fifth inspection interval, the ASME Section XI examination requirements for the subject components would again become applicable. If Braidwood or Byron desires to use a similar proposed alternative for the sixth inspection interval, it is required to be addressed in a separate proposed alternative submitted in accordance with 10 CFR 50.55a(z).

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 6 of 50)
Table 1. Summary of Inspection Deferrals in this Proposed Alternative End of 5th ASME         Item                                         Date of Last Station     Unit                                    Description                                  Inspection Category       No.                                          Inspection Interval1 Braidwood      1        B-B       B2.11       Pressurizer, Shell-to-Head         10/12/2019        7/28/2038 Welds, Circumferential B-B       B2.12       Pressurizer, shell-to-Head         10/12/2019 Welds, Longitudinal B-D       B3.110     Pressurizer, Nozzle-to-Vessel        4/8/2021 Welds Braidwood      2        B-B       B2.11       Pressurizer, Shell-to-Head         10/11/2018       10/16/2038 Welds, Circumferential B-B       B2.12       Pressurizer, shell-to-Head         10/11/2018 Welds, Longitudinal B-D       B3.110     Pressurizer, Nozzle-to-Vessel       10/11/2018 Welds Byron        1        B-B       B2.11       Pressurizer, Shell-to-Head          9/18/2015        7/15/2035 Welds, Circumferential B-B       B2.12       Pressurizer, shell-to-Head          9/18/2015 Welds, Longitudinal B-D       B3.110     Pressurizer, Nozzle-to-Vessel        9/14/2018 Welds Byron        2        B-B       B2.11       Pressurizer, Shell-to-Head          10/6/2014        7/15/2035 Welds, Circumferential B-B       B2.12       Pressurizer, shell-to-Head          10/6/2014 Welds, Longitudinal B-D       B3.110     Pressurizer, Nozzle-to-Vessel        4/13/2019 Welds Note 1: The fifth inspection interval end dates are estimates based on the current fourth interval end dates. The interval end dates may be adjusted as allowed by ASME XI.
The key aspects of the technical basis for this request are summarized below. The applicability of the technical basis to Braidwood and Byron is shown in Appendix A.
It is noted that the inputs for transients and cycle counting remain valid for this Revision 1 submittal.
Degradation Mechanism Evaluation An evaluation of degradation mechanisms that could potentially impact the reliability of the pressurizer welds was performed in Reference [1]. Evaluated mechanisms included stress corrosion cracking (SCC), environmental assisted fatigue (EAF),
microbiologically influenced corrosion (MIC), pitting, crevice corrosion, erosion-cavitation, erosion, flow accelerated corrosion (FAC), general corrosion, galvanic corrosion, and mechanical/ thermal fatigue. Other than the potential for EAF and mechanical/thermal fatigue, there are no active degradation mechanisms identified that significantly affect the long-term structural integrity of the pressurizer welds.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 7 of 50)
Stress Analysis Finite element analyses (FEA) were performed in Reference [1] to determine the stresses in the subject pressurizer welds. The analyses were performed using representative pressurized water reactor (PWR) geometries, representative transients, and typical material properties. The results of the stress analyses were used to produce flaw tolerance evaluations. The applicability of the FEA to Braidwood and Byron in accordance with Section 9 of Reference [1] is shown in Appendix A and confirms that all plant-specific applicability requirements are satisfied. Therefore, the evaluation results and conclusions of Reference [1] are applicable to Braidwood and Byron.
Flaw Tolerance Evaluation Flaw tolerance evaluations were performed in Reference [1] consisting of PFM and DFM evaluations. The results of the PFM analyses indicate that, after a preservice inspection (PSI), no other inspections are required for up to 60 years of plant operation to meet the U.S. Nuclear Regulatory Commissions (NRCs) safety goal of 10-6 failures per year. For the case of Braidwood and Byron, PSI was followed by three full 10-year interval inspections, which have been performed on the subject pressurizer welds. Table 8-12 of Reference [1] indicates that if PSI are followed by at least three full 10-year interval inspections subsequent examinations do not need to be performed for up to 80 years of plant operation, and they will still meet the NRC safety goal (with considerable margin). The DFM evaluations confirm the PFM results by demonstrating that it takes approximately 400 years for a postulated flaw with an initial depth equal to the ASME Section XI acceptance standards to grow to 80% of the wall thickness without exceeding the ASME Section XI allowable fracture toughness.
Inspection History Plant operating experience (including examinations performed to-date, examination findings, inspection coverage, and previously submitted Proposed Alternatives) is summarized in Tables 2 and 3. As shown in these tables, some previous examinations for the subject welds had limited coverage because of limited volumetric examination scan access due to existing plant obstructions.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 8 of 50)
Table 2. Braidwood Station, Units 1 and 2, Pressurizer Welds Inspection History Weld ID                            PSI1                          Interval 1               Interval 2            Interval 3       Interval 4 Unit   Summary Number                 Ultrasonic Test (UT)                (Date/Outage,           (Date/Outage,          (Date/Outage,     (Date/Outage, Exam Cat, Item Number         (Date, Coverage/Results)            Coverage/Results)        Coverage/Results)      Coverage/Results) Coverage/Results) 1PZR-01-08E                          8-1985 10-1995/A1R05              4-2006/A1R12          9-2016/A1R19    Not required per 1      BRW-1-B02.11.0005     Coverage was not documented; but 100%/NRI                  100%/NRI             98.5%/NRI       ML22307A246 B-B/B2.11                 obstructions noted/NRI 1PZR-01-08A 8-1985                     10-1989/A1R01             9-1998/A1R07          4-2009/A1R14     10-2019/A1R21 1      BRW-1-B02.11.0006 100%/Laminar type flaws noted               100%/NRI                95.3%/NRI             95.3%/NRI         95.3%/NRI B-B/B2.11 1PZR-01-09A 8-1985                     10-1989/A1R01           10-1998/A1R07           4-2009/A1R14     10-2019/A1R21 1      BRW-1-B02.12.0005 100%/Laminations/slag                  100%/NRI                 100%/NRI              100%/NRI         100%/NRI B-B/B2.12 1PZR-01-09D 8-1985                     10-1995/A1R05             4-2006/A1R12          9-2016/A1R19    Not required per 1      BRW-1-B02.12.0006 100%/NRI                        100%/NRI                 100%/NRI              100%/NRI       ML22307A246 B-B/B2.12 1PZR-01-N4A                          8-1985                    10-1995/A1R053             4-2006/A1R12 9-2016/A1R19    Not required per 1     BRW-1-B03.110.0013        Coverage was not documented;           Coverage was not      100% Shell Side only due 68.7%/NRI       ML22307A246 B-D/B3.110           limitations due to Geometry/NRI         documented/NRI             to config/NRI 8-1985 1PZR-01-N4B Coverage was not documented;             10-1995/A1R05           10-2004/A1R11           4-2015/A1R18    Not required per 1     BRW-1-B03.110.0014 limitations due to Geometry/Laminar             100%/NRI               92.66%/NRI             90.9%/NRI       ML22307A246 B-D/B3.110 flaw 1PZR-01-N1                          8-1985                          A1R06 10-2007/A1R132          9-2016/A1R192   Not required per 1     BRW-1-B03.110.0015        Coverage was not documented;        (VT-2 per Relief Request 59.2%/NRI             74.7%/NRI       ML22307A246 B-D/B3.110           limitations due to Geometry/NRI             per NR-24) 9-1998/A1R073 1PZR-01-N2                          8-1985                    10-1989/A1R013 Coverage was not        10-2010/A1R15      4-2021/A1R22 1     BRW-1-B03.110.0016        Coverage was not documented;           Coverage was not documented; geometry         56.56%/NRI       56.43%/NRI B-D/B3.110           limitations due to Geometry/NRI         documented/NRI limitations/NRI 9-1998/A1R073 1PZR-01-N3                          8-1985                    10-1989/A1R01  3 Coverage was not        10-2010/A1R15      4-2021/A1R22 1     BRW-1-B03.110.0017        Coverage was not documented;           Coverage was not documented; geometry         60.92%/NRI         60%/NRI B-D/B3.110           limitations due to Geometry/NRI         documented/NRI limitations/NRI 10-1995/A1R053 1PZR-01-N4C                          8-1985 Coverage was not          10-2004/A1R11           4-2015/A1R18    Not required per 1     BRW-1-B03.110.0018        Coverage was not documented; documented; geometry           92.66%/NRI             90.9%/NRI       ML22307A246 B-D/B3.110           limitations due to Geometry/NRI limitations/NRI 1-1987 2PZR-01-08A                                                      4-1990/A2R013            5-1999/A2R07 Coverage was not documented;                                                            10-2009/A2R14    Not required per 2      BRW-2-B02.11.0005 limitations due to obstructions/
Coverage was not        99.85%/Laminations 95.57%/NRI      ML22307A246 B-B/B2.11                                                    documented/NRI                  noted Laminar and Planar flaws noted 12-1986 2PZR-01-08E Coverage was not documented;              4-1996/A2R05           10-2006/A2R12          10-2018/A2R20    Not required per 2      BRW-2-B02.11.0006 obstructions noted/Laminar and               100%/NRI                 100%/NRI              100%/NRI       ML22307A246 B-B/B2.11 Planar flaws noted

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 9 of 50)
Table 2. Braidwood Station, Units 1 and 2, Pressurizer Welds Inspection History Weld ID                            PSI1                         Interval 1              Interval 2              Interval 3             Interval 4 Unit       Summary Number                   Ultrasonic Test (UT)              (Date/Outage,           (Date/Outage,           (Date/Outage,          (Date/Outage, Exam Cat, Item Number             (Date, Coverage/Results)           Coverage/Results)       Coverage/Results)       Coverage/Results)     Coverage/Results) 2PZR-01-09A 1-1987                     4-1990/A2R01            5-1999/A2R07            10-2009/A2R14         Not required per 2         BRW-2-B02.12.0005 100%/NRI                        100%/NRI                100%/NRI                100%/NRI            ML22307A246 B-B/B2.12 2PZR-01-09D 12-1986                    4-1996/A2R05           10-2006/A2R12            10-2018/A2R20         Not required per 2          BRW-2-B02.12.0006 100%/Laminar type flaws noted             100%/NRI                100%/NRI                100%/NRI            ML22307A246 B-B/B2.12 2PZR-01-N1                                                          A2R06 1-1987                                             5-2008/A2R13            4-2017/A2R192         Not required per 2         BRW-2-B03.110.0013                                             (VT-2 per Relief Request 100%/NRI                                               59.2%/NRI               59.2%/NRI            ML22307A246 B-D/B3.110                                                         NR-24) 2PZR-01-N2 12-1986                    4-1996/A2R05            4-1999/A2R07            4-2011/A2R15          Not required per 2         BRW-2-B03.110.0014 100%/NRI                        100%/NRI               88.5%/NRI               88.5%/NRI            ML22307A246 B-D/B3.110 4-1990/A2R013 2PZR-01-N3                           12-1986 Coverage was not          4-1999/A2R07            4-2011/A2R15           10-2021/A2R22 2         BRW-2-B03.110.0015          Coverage was not documented; documented; geometry          88.5%/NRI               88.5%/NRI               71.6%/NRI B-D/B3.110                 geometry limitations/NRI limitations /NRI 4-1990/A2R013 2PZR-01-N4A                           12-1986 Coverage was not         10-2006/A2R12            10-2018/A2R20         Not required per 2         BRW-2-B03.110.0016          Coverage was not documented; documented; geometry          91.5%/NRI               91.5%/NRI            ML22307A246 B-D/B3.110             nozzle geometry limitations/NRI limitations /NRI 12-1986                    3-1996/A2R053 2PZR-01-N4B Coverage was not documented;          Coverage was not         11-2003/A2R10            5-2014/A2R17          Not required per 2         BRW-2-B03.110.0017 nozzle geometry limitations /Laminar documented; geometry           88.5%/NRI               88.5%/NRI            ML22307A246 B-D/B3.110 type flaw                  limitations /NRI 3-1996/A2R053          11-2003/A2R103 2PZR-01-N4C                           12-1986 Coverage was not        Coverage was not          5-2014/A2R17          Not required per 2         BRW-2-B03.110.0018          Coverage was not documented; documented; geometry    documented; geometry          88.5%/NRI            ML22307A246 B-D/B3.110             nozzle geometry limitations /NRI limitations /NRI        limitations/NRI Notes:
: 1. PSI included radiographic (RT) examinations per Section III and ultrasonic (UT) examinations per Section XI. Together, these examinations constituted PSI examination in Reference [1], and 100% coverage was assumed because such coverage was required by Section III for the RT exams, and the RT exams were successfully completed for the subject pressurizer welds for both Braidwood, Units 1 and 2.
: 2. The increase in examination coverage from the Second Interval to the Third Interval for weld 1PZR-01-N1 was not a result of a change in physical limitations, but was due to a change in the methods of calculating coverage. For Unit 1 the actual coverage reported in 2007 (A1R13) utilized the most conservative angle for the total coverage (60&deg; axial = 59.2%). In 2016 (A1R19) the coverage utilized an aggregate of all angles 0&deg;, 45&deg; axial and circumferential and 60&deg; axial and circumferential to achieve 74.7% coverage. For Unit 2 during the exam in 2017 (A2R19) for the similar weld, 2PZR-01-N1, coverage was not recalculated, and the same coverage was recorded as the prior interval examination. The limitations are the same between Unit 1 and Unit 2 and the reported Third Interval coverage for weld 2PZR-01-N1 should be similar to the Unit 1 Third Interval coverage at 74.7%.
: 3. Constellation has reviewed the missing coverages for the examinations in the First and Second Intervals and has concluded that the NDE code requirements and equipment for early interval examinations would not have resulted in an examination coverage lower than the minimum achieved coverage of 56.43%. In addition, there have been no design configuration changes that would alter examination access for any of the welds.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 10 of 50)
During the Fourth Interval, the Braidwood, Unit 1, pressurizer spray nozzle weld 1PZR-01-N2 had the minimum coverage of 56.43%. Section 8.3.5 and Table 8-33 of Reference [1] discuss the limited coverage and show that the conclusions of the report are applicable to components with limited coverage as low as 50%. The minimum coverage of 56.43% for this weld is higher than the 50% minimum coverage assumed in the sensitivity study of the base case in the EPRI report; therefore, the sensitivity results from the EPRI report are bounding for application to Braidwood, Units 1 and 2.
No flaws that exceeded the ASME Section XI acceptance standards were identified during any prior examinations for Braidwood.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 11 of 50)
Table 3. Byron Station, Units 1 and 2, Pressurizer Welds Inspection History Weld ID PSI1                          Interval 1                  Interval 2                Interval 3             Interval 4 Summary Number Unit Exam Cat, Item            Ultrasonic Test (UT)                 (Date/Outage,               (Date/Outage,            (Date/Outage,            (Date/Outage, (Date, Coverage/Results)              Coverage/Results)            Coverage/Results)        Coverage/Results)       Coverage/Results)
Number 4-1987 & 4-1987/B1R014 Coverage was not documented; scan limitations 8-1983               due to sampling nozzles and 3-2002/B1R11 Coverage was not documented;                X axis plates/
92%/5 embedded scan limitations (welded pads)        Resizing of 5 subsurface indications identified (1 1RY-01-S/PC-012             were identified/            indications identified in PSI with 45&deg; and 4 with 60&deg;)       3-2011/B1R17           Not required per 1    BYR-1-B2.11.0001   2 rejectable 45&deg; indications and ML22307A246 B-B/B2.11                                                                                                             92%/NRI 3 rejectable 60&deg; indications              1-1990/B1R03 Fourth exam showed (total of 5 indications that did      Resizing of 5 subsurface no change in indication not meet the requirements of     indications identified in B1R01 sizes.
ASME Section XI, IWB-3511 4-1996/B1R07 Resizing of 5 subsurface indications identified in B1R03 8-1982 1RY-01-S/PC-05 Coverage was not documented;                 4-1996/B1R07               3-2005/B1R13              9-2015/B1R20           Not required per 1    BYR-1-B2.11.0002 ML22307A246 B-B/B2.11        scan limitations (welded pads)                 96%/NRI                    96%/NRI                  95.47%/NRI were identified/NRI 8-1982 1RY-01-S/PL-01                                                 4-1987/B1R01 Coverage was not documented;                                            3-2002/B1R11              3-2011/B1R17           Not required per 1    BYR-1-B2.12.0001                                          90% - limited by sample ML22307A246 B-B/B2.12           no scan limitations were                                              100%/NRI                   100%/NRI nozzles and axis plates/NRI identified/NRI 8-1982 1RY-01-S/PL-04 Coverage was not documented;                 4-1996/B1R07               3-2005/B1R13              9-2015/B1R20           Not required per 1    BYR-1-B2.12.0002 ML22307A246 B-B/B2.12           no scan limitations were                   100%/NRI                   100%/NRI                   100%/NRI identified/NRI 9-2018/B1R223 7-1982                                                                             9-2006/B1R143 1RY-01-S/PN-01                                                                                                                            72.03% - limited by Coverage was not documented;      B1R07 (VT-2 per Relief Request B1R11 (VT-2 per Relief       40% - limited by nozzle 1   BYR-1-B3.110.0001 NR-19)                 Request I2R-03) nozzle configuration B-D/B3.110          no scan limitations were                                                                 configuration and heater and heater identified/NRI                                                                        penetrations/NRI penetrations/NRI

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 12 of 50)
Table 3. Byron Station, Units 1 and 2, Pressurizer Welds Inspection History Weld ID PSI1                        Interval 1               Interval 2                Interval 3             Interval 4 Summary Number Unit Exam Cat, Item            Ultrasonic Test (UT)              (Date/Outage,             (Date/Outage,             (Date/Outage,           (Date/Outage, (Date, Coverage/Results)          Coverage/Results)          Coverage/Results)        Coverage/Results)        Coverage/Results)
Number 7-1982 Coverage was not documented;             1-1990/B1R03 1RY-01-S/PN-02                                                                      11-1997/B1R08               9-2006/B1R14 no scan limitations were        75% - limited by nozzle                                                        Not required per 1   BYR-1-B3.110.0002                                                                  73% - limited by nozzle  77% - limited by nozzle ML22307A246 B-D/B3.110                   identified/         configuration/NRI with 0&deg; and configuration/NRI         configuration/NRI Indications - appears to be ID   45&deg;. ID Geometry with 60&deg; geometry 7-1982 1RY-01-S/PN-03                                                                      11-1997/B1R08               9-2006/B1R14 Coverage was not documented;             3-1987/B1R01                                                              Not required per 1   BYR-1-B3.110.0003                                                                  69% - limited by nozzle  77% - limited by nozzle ML22307A246 B-D/B3.110           no scan limitations were                100%/NRI configuration/NRI         configuration/NRI identified/NRI 7-1982 Coverage was not documented;             1-1990/B1R03 1RY-01-S/PN-04                                                                       3-2002/B1R11               9-2015/B1R20 no scan limitations were        75% - limited by nozzle                                                        Not required per 1   BYR-1-B3.110.0004                                                                  66% - limited by nozzle 64.93% - limited by nozzle ML22307A246 B-D/B3.110                   identified          configuration/NRI with 0&deg; and configuration/NRI         configuration/NRI Indications - appears to be ID   45&deg;. ID Geometry with 60&deg; geometry 9-2006/B1R14 68% - limited by nozzle 7-1982 1RY-01-S/PN-05                                                                      11-1997/B1R08            configuration/NRI Coverage was not documented;             4-1996/B1R07                                                              Not required per 1   BYR-1-B3.110.0005                                                                  73% - limited by nozzle ML22307A246 B-D/B3.110           no scan limitations were                100%/NRI configuration/NRI            9-2015/B1R20 identified/NRI 64.93% - limited by nozzle configuration/NRI 7-1982 Coverage was not documented;             9-1988/B1R02 1RY-01-S/PN-06         no scan limitations were    76% (0&deg;) 75% (45&deg;), 75% (60&deg;)    11-1997/B1R08               9-2006/B1R14 Not required per 1   BYR-1-B3.110.0006                identified/                  limited due to       73% - limited by nozzle  77% - limited by nozzle ML22307A246 B-D/B3.110        Indications - appears to be ID configuration/Spot indication   configuration/NRI         configuration/NRI geometry and one spot indication          similar to PSI (seen with 45&deg;)
1-1989/B2R014 10-1985                                              3-2004/B2R11 Coverage was not 2RY-01-S/PC-01     Coverage was not documented;                                  92% - scan limitations documented; scan limitations                                10-2014/B2R18          Not required per 2    BYR-2-B2.11.0001     scan limitations (welded pads,                                   (welded pads, ML22307A246 B-B/B2.11                                           (welded pads, sampling                                       94%/NRI sampling nozzle and skirt) were                                sampling nozzle and nozzle and skirt) were identified/NRI                                             skirt)/NRI identified/NRI

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 13 of 50)
Table 3. Byron Station, Units 1 and 2, Pressurizer Welds Inspection History Weld ID PSI1                          Interval 1                 Interval 2               Interval 3              Interval 4 Summary Number Unit Exam Cat, Item              Ultrasonic Test (UT)                  (Date/Outage,              (Date/Outage,            (Date/Outage,           (Date/Outage, (Date, Coverage/Results)              Coverage/Results)           Coverage/Results)       Coverage/Results)        Coverage/Results)
Number 3-1995/B2R054 10-1985 2RY-01-S/PC-05                                                 Coverage was not Coverage was not documented;                                            9-2005/B2R12              4-2010/B2R15          Not required per 2    BYR-2-B2.11.0002                                         documented; scan limitations ML22307A246 B-B/B2.11          scan limitations (welded pads)                                             96%/NRI                  96%/NRI (welded pads) were were identified/NRI identified/NRI 10-1985 Coverage was not documented; no scan limitations were                1-1989/B2R014 2RY-01-S/PL-01 identified/                  Coverage    was not          3-2004/B2R11             10-2014/B2R18          Not required per 2    BYR-2-B2.12.0001 ML22307A246 B-B/B2.12            Indications - 0&deg; identified 4         documented; no scan               100%/NRI                 100%/NRI embedded indications, 45&deg; was NRI, limitations were identified/NRI 60&deg; identified 2 embedded indications.
10-1985                      3-1995/B2R054 2RY-01-S/PL-04 Coverage was not documented; no              Coverage was not             9-2005/B2R12              4-2010/B2R15          Not required per 2    BYR-2-B2.12.0002 ML22307A246 B-B/B2.12                scan limitations were             documented; no scan               100%/NRI                 100%/NRI identified/NRI           limitations were identified/NRI 10-1985 Coverage was not documented; no                                                                                             4-2019/B2R213 4-2007/B2R133 2RY-01-S/PN-01      scan limitations were identified/                                      11-1999/B2R08                                     40% - limited by 2-1989/B2R01                                    40% - limited by nozzle 2   BYR-2-B3.110.0001       Indications - 0&deg; was NRI, 45&deg; (VT-2 per Relief Request NR-19)
(VT-2 per Relief                                nozzle configuration Request I2R-03)      configuration and heater B-D/B3.110       identified 1 embedded indication,                                                                                            and heater 60&deg; identified 1 embedded                                                                   penetrations/NRI penetrations/NRI indication.
9-1993/B2R044              3-2004/B2R11 2RY-01-S/PN-02                     10-1985                                                                            4-2010/B2R15 Coverage was not           62.3% - limited by                                Not required per 2   BYR-2-B3.110.0002   Coverage was not documented; no                                                               62.3% - limited by nozzle ML22307A246 documented; no scan                 nozzle B-D/B3.110     scan limitations were identified/NRI                                                              configuration/NRI limitations were identified/NRI   configuration/NRI 2RY-01-S/PN-03                     10-1985                       10-1990/B2R02              4-2001/B2R09              4-2010/B2R15 Not required per 2   BYR-2-B3.110.0003   Coverage was not documented; no           75% - limited by nozzle     66% - limited by nozzle 66.3% - limited by nozzle ML22307A246 B-D/B3.110     scan limitations were identified/NRI          configuration/NRI          configuration/NRI        configuration/NRI 9-1993/B2R044 2RY-01-S/PN-04                     10-1985                                                  3-2004/B2R11             10-2014/B2R18 Coverage was not                                                             Not required per 2   BYR-2-B3.110.0004   Coverage was not documented; no                                       62% - limited by nozzle 62.5% - limited by nozzle ML22307A246 B-D/B3.110                                                 documented; no scan scan limitations were identified/NRI                                     configuration/NRI        configuration/NRI limitations were identified/NRI

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 14 of 50)
Table 3. Byron Station, Units 1 and 2, Pressurizer Welds Inspection History Weld ID PSI1                            Interval 1                   Interval 2               Interval 3             Interval 4 Summary Number Unit Exam Cat, Item                 Ultrasonic Test (UT)                  (Date/Outage,                (Date/Outage,            (Date/Outage,           (Date/Outage, (Date, Coverage/Results)               Coverage/Results)            Coverage/Results)        Coverage/Results)        Coverage/Results)
Number 3-1995/B2R054                                                                  4-2019/B2R21 2RY-01-S/PN-05                    10-1985                                                      4-2001/B2R09             10-2014/B2R18 Coverage was not                                                                66% - limited by 2     BYR-2-B3.110.0005    Coverage was not documented; no                                      66.3% - limited by nozzle 62.5% - limited by nozzle documented; no scan                                                                    nozzle B-D/B3.110       scan limitations were identified/NRI                                     configuration/NRI        configuration/NRI limitations were identified/NRI                                                       configuration/NRI 3-1995/B2R05 4 4-2019/B2R21 2RY-01-S/PN-06                    10-1985                                                      4-2001/B2R09              4-2010/B2R15 Coverage was not                                                                62% - limited by 2     BYR-2-B3.110.0006    Coverage was not documented; no                                       66% - limited by nozzle  66.3% - limited by nozzle documented; no scan                                                                    nozzle B-D/B3.110       scan limitations were identified/NRI                                     configuration/NRI        configuration/NRI limitations were identified/NRI                                                       configuration/NRI Notes:
: 1. PSI included radiographic (RT) examinations per Section III and ultrasonic (UT) examinations per Section XI. Together, these examinations constituted PSI examination in Reference [1], and 100% coverage was assumed because such coverage was required by Section III for the RT exams, and the RT exams were successfully completed for the subject pressurizer welds for both Byron units.
: 2. Indications were found in weld 1RY-01-S/PC-01 that did not meet the acceptance standards of IWB-3511 during the initial PSI examination, but were accepted by engineering evaluation per IWB-3600 and three successive examinations were performed in B1R01, B1R03, and B1R07, which showed no changes in the flaw sizes.
: 3. The increase in examination coverage from the Third Interval to the Fourth Interval for weld 1RY-01-S/PN-01 was not a result of a change in physical limitations, but was due to a change in the methods of calculating coverage. For Unit 1 in 2018 (B1R22) the coverage calculated included the axial coverage of the examination which increased the coverage to 72.03%. For Unit 2 the exam in 2019 (B2R21) did not recalculate the coverage and conservatively assumed the same coverages as the 2007 (B2R13) exam, which did not include the axial coverage. The limitations are the same between Unit 1 and Unit 2 and the reported Fourth Interval coverage for weld 2RY-01-S/PN-01 should be similar to the Unit 1 Fourth Interval coverage at 72.03%.
: 4. Constellation has reviewed the missing coverages for the examinations in the First Interval and has concluded that the Code NDE requirements and equipment for early interval examinations would not have resulted in an examination coverage lower than the minimum documented coverage of 40%. In addition, there have been no design configuration changes that would alter examination access for any of the welds.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 15 of 50)
During Interval 3, the Byron, Units 1 and 2 pressurizer surge nozzle welds 1RY    S/PN-01 and 2RY-01-S/PN-01 had the minimum documented coverage of 40%.
During Interval 4, the Byron, Unit 2 pressurizer surge nozzle weld 2RY-01-S/PN-01 again had a minimum documented coverage of 40%. (Note: The subsequent B1R22 examination for Weld ID 1RY-01-S/PN-01 recorded significantly more coverage at 72.03%, which was calculated by including the axial examination. The change in coverage was not a result of changes to physical limitations. The limitations are the same between Unit 1 and Unit 2 and the reported Fourth Interval coverage for weld 2RY-01-S/PN-01 should be similar to the Unit 1 Fourth Interval coverage at 72.03%). During the First and Second Intervals Relief Requests NR-19 and I2R-03 were approved by the NRC to perform VT-2 examination in lieu of UT for welds 1RY-01-S/PN-01 (Outage B1R07 and B1R11) and 2RY-01-S/PN-01 (Outages B2R01 and B2R08). Since the minimum coverage was identified for the surge line nozzle welds, a review of the probability of leakage and rupture for various sensitivity studies from Reference [1] was done for leak path PRNV-BW-1C, which is applicable to welds 1RY-01-S/PN-01 and 2RY-01-S/PN-01 as follows:
* Section 8.3.4.1.1 and Table 8-11 of Reference [1] discuss the probability of rupture and leakage for the case study if only PSI exams are performed.
The most limiting crack path for the surge line nozzle welds (PRNV-BW-1C),
yielded a probability of leakage of 6.25x10-9 after 80 years and a probability of rupture of 1.25x10-9 after 80 years. The probability of leakage and the probability of rupture for this Case ID listed in Table 8-11 are approximately three orders of magnitude below the acceptance criteria utilized in Reference [1], Section 8.3.2.9, of 10-6 failures per year. Additionally, the impact of performing more examinations than the PSI-only case study, even with limited coverage, which was the case for welds 1RY-01-S/PN-01 and 2RY-01-S/PN-01, would reduce the probability of rupture and leakage.
Furthermore, as discussed in Section 8.3.4.1.1 of Reference [1], leakage of the pressure boundary is detectable by plant operators and plant procedures allow for safe plant shutdown under leaking conditions.
Probabilities of rupture values are maintained well below the acceptance criterion for 80 years of operation even considering only PSI inspection. The examination results with coverage as low as 40% for welds 1RY-01-S/PN-01 and 2RY-01-S/PN-01 at Byron are bounded by the PSI-only case study in Reference [1] and the failure frequency for these welds would be below the NRC acceptance criteria of 10-6 failures per year.
* Section 8.3.5 and Table 8-33 of Reference [1] discuss the probability of leakage for the case study where only 50% coverage was achieved. For the leak path most applicable to welds 1RY-01-S/PN-01 and 2RY-01-S/PN-01, PRNV-BW-1C was evaluated to have a probability of leakage of 3.75x10-9 after 80 years. This was an increase of 2.5x10-9 compared to the base case where 100% coverage was achieved. This increase in the probability of leakage is small in comparison to the acceptance criteria of 10-6 failures per year. The sensitivity studies performed in Reference [1], including the Inspection Coverage case study, show that probabilities of rupture and leakage are not significantly affected by using a range of values for most of the input variables.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 16 of 50)
Considering all of the findings from Reference [1] it can be concluded that the probability of failure is below 10-6 failures per year for welds 1RY-01-S/PN-01 and 2RY-01-S/PN-01.
At Byron, weld 1RY-01-S/PC-01 had five indications that did not meet acceptance standards of IWB-3511 during the PSI examination, but all five indications were accepted through engineering evaluation in accordance with IWB-3600 of Section XI. Successive examinations were performed in B1R01 (1987), B1R03 (1990), and B1R07 (1996) which showed no change in the five indications. The most recent examination performed on weld 1RY-01-S/PC-01 during B1R17 (2011) did not identify any recordable indications. The absence of indications in this latest examination is due to improved NDE techniques and changes to sizing requirements. Therefore, the B1R17 examination determined that the previously reported indications meet the acceptance standards of ASME Section XI.
Based on the discussions above, the results of the EPRI report are applicable to Byron, Units 1 and 2.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 17 of 50)
Conclusion Based on the results of Reference [1] and its demonstrated applicability to Braidwood and Byron, the subject pressurizer welds contained in this proposed alternative are very flaw tolerant. PFM and DFM evaluations performed as part of the technical basis in Reference [1] demonstrate that, after PSI, no other inspections are required for up to 60 years of operation to meet the NRC safety goal of 10-6 failures per reactor year. Plant-specific applicability of the technical basis to Braidwood and Byron is demonstrated in Appendix A. While the technical bases demonstrate longer inspection intervals are possible, Constellation considers that deferral of these inspections until the end of the fifth inspection interval, with the performance monitoring plan previously committed to in the Revision 0 RAI response [17] , is justified and provides an acceptable level of quality and safety.
The PWR fleet inspection history for the applicable components (obtained from an EPRI industry survey) is presented in Appendix B. The results of the survey indicate that these components are very flaw tolerant and prior instances of flaw detection are minimal.
Constellation operating and examination experience demonstrates that these welds have performed with very high reliability, mainly due to their robust designs and structural margins. As shown in the Tables 2 and 3, to-date, Constellation has performed over 150 inspections (PSI and ISI) of the subject pressurizer welds at Braidwood and Byron, with only one of these welds found to have recordable indications. The sizes of these indications have not increased since PSI. As indicated in the inspection history Tables 2 and 3, some of the examinations involved limited coverage of as low as 40%. However, due to the robust fabrication of these components and the intensive pre-service examinations performed, Reference [1] was able to conclude that performing only the PSI examination without any other follow-on ISI examinations is acceptable for up to 80 years of operation while still maintaining plant safety. In addition, it is important to note that all other inspection activities, including the ASME Section XI, Examination Category B-P system leakage test conducted during each refueling outage, will continue to be performed, providing further assurance of safety.
Finally, as discussed in Reference [2], for situations where no active degradation mechanism is present, it was concluded that subsequent inservice inspections do not provide additional value after the PSI has been performed. Braidwood and Byron pressurizer welds have received the required PSI examinations along with nearly 120 subsequent inservice inspections with no service-induced indications documented.
Therefore, Constellation requests that the NRC authorize this proposed alternative for the Braidwood and Byron in accordance with 10 CFR 50.55a(z)(1).
6    Duration of Proposed Alternative The proposed alternative is requested for Braidwood and Byron for the fifth inservice inspection interval. The current estimated start and end dates for the fifth inservice inspection interval are provided in Section 2 of the proposed alternative.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 18 of 50)
The interval start and end dates may be adjusted as allowed by ASME Section XI.
7    Precedent
* Letter from N. Salgado (U.S. Nuclear Regulatory Commission) to D. Rhoades (Constellation Energy Generation), Braidwood Station, Units 1 and 2 and Bryon Station, Unit Nos. 1 and 2 - Proposed Alternative to the Requirements of the American Society of Mechanical Engineers Boiler & Pressure Vessel Code (EPIDS L-2021-LLR-0035 and L-2021-LLR-0036), dated November 10, 2022, ADAMS Accession No. ML22307A246.
* NRC Safety Evaluation Report, Calvert Cliffs Nuclear Power Plant, Units 1 and 2 - Authorization and Safety Evaluation for Alternative Request No. ISI-05-016 (EPID L-2021-LLR-0036), dated January 3, 2023, ADAMS Accession No. ML22195A025.
* NRC Safety Evaluation Report, Catawba Nuclear Station, Unit Nos. 1 and 2; Shearon Harris Nuclear Power Plant, Unit No. 1; McGuire Nuclear Station, Unit Nos. 1 and 2; Oconee Nuclear Station, Unit Nos. 1, 2, and 3; and H. B.
Robinson Steam Electric Plant, Unit No. 2 - Issuance of Alternative to Pressurizer Welds (EPID L-2023-LLR-0020), dated October 19, 2023, ADAMS Accession No. ML23264A853.
In addition, other studies have been performed by the industry to extend the inspection interval for various components and have been accepted by the NRC.
* Based on studies presented in Reference [11], the NRC approved extending the SG vessel and nozzle welds from 10 to 30 years for Vogtle in Reference
[12].
* Based on studies presented in Reference [3], the NRC approved extending PWR reactor vessel nozzle-to-shell welds from 10 to 20 years in Reference
[4].
* Based on work performed in BWRVIP-108, Reference [5], and BWRVIP-241, Reference [7], the NRC approved the reduction of BWR vessel nozzle-to-shell weld examinations (Item No. B3.90 for BWRs from 100% to a 25%
sample of each nozzle type every 10 years) in References [6] and [8]. The work performed in BWRVIP-108 and BWRVIP-241 provided the technical basis for ASME Code Case N-702, Reference [9], which has been conditionally approved by the NRC in Revision 18 of Regulatory Guide 1.147, Reference [10].

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 19 of 50) 8  Acronyms ASME        American Society of Mechanical Engineers B&W         Babcock and Wilcox BWR         Boiling Water Reactor BWRVIP      Boiling Water Reactor Vessel and Internals Program CE          Combustion Engineering CFR         Code of Federal Regulations DFM         Deterministic fracture mechanics EAF         Environmentally assisted fatigue EPRI        Electric Power Research Institute FAC         Flow accelerated corrosion FEA         Finite element analysis ISI         Inservice Inspection MIC         Microbiologically influenced corrosion NPS         Nominal pipe size NRC         Nuclear Regulatory Commission NSSS        Nuclear steam supply system PFM         Probabilistic fracture mechanics PWR         Pressurized Water Reactor SCC         Stress corrosion cracking 9    

==REFERENCES:==
: 1. Technical Bases for Inspection Requirements for PWR Pressurizer Head, Shell-to- Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905, ADAMS Accession No. ML21021A271.
: 2. American Society of Mechanical Engineers, Risk-Based Inspection: Development of Guidelines, Volume 2-Part 1 and Volume 2-Part 2, Light Water Reactor (LWR) Nuclear Power Plant Components. CRTD-Vols. 20-2 and 20-4, ASME Research Task Force on Risk-Based Inspection Guidelines, Washington, D.C., 1992 and 1998.
: 3. B. A. Bishop, C. Boggess, N. Palm, Risk-Informed extension of the Reactor Vessel In-Service Inspection Interval, WCAP-16168-NP-A, Rev. 3, October 2011.
: 4. U.S. NRC, Revised Final Safety Evaluation by the Office of Nuclear Reactor Regulation; Topical Report WCAP-16168-NP-A, Revision 2, Risk-Informed Extension of the Reactor Vessel In-service Inspection Interval, Pressurized Water Reactor Owners Group, Project No. 694, July 26, 2011, ADAMS Accession No. ML111600303.
: 5. BWRVIP-108: BWR Vessels and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Shell Welds and Nozzle Blend Radii, EPRI, Palo Alto, CA 2002. 1003557.
: 6. U.S. NRC, Safety Evaluation of Proprietary EPRI Report, BWR Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radius (BWRVIP-108),
December 19, 2007, ADAMS Accession No. ML073600374.
: 7. BWRVIP-241: BWR Vessels and Internals Project, Probabilistic Fracture Mechanics Evaluation for the Boiling Water Reactor Nozzle-to-Shell Welds and Nozzle Blend Radii, EPRI, Palo Alto, CA 2010. 1021005.
: 8. U.S. NRC, Safety Evaluation of Proprietary EPRI Report, BWR Vessel and Internals Project, Probabilistic Fracture Mechanics Evaluation for the Boiling Water Reactor Nozzle-to-Shell Welds and Nozzle Blend Radii (BWRVIP-241), April 19, 2013, ADAMS Accession Nos. ML13071A240 and ML13071A233.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 20 of 50)
: 9. Code Case N-702, Alternate Requirements for Boiling Water Reactor (BWR) Nozzle Inner Radius and Nozzle-to-Shell Welds, ASME Code Section XI, Division 1, Approval Date: February 20, 2004.
: 10. U.S. NRC Regulatory Guide 1.147, Revision 19, Inservice Inspection Code Case Acceptability, ASME Code Section XI, Division 1, October 2019.
: 11. Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds. EPRI, Palo Alto, CA: 2019. 3002015906.
: 12. U.S. NRC, Vogtle Electric Generating Plant, Units 1 and 2 - Relief Request for Proposed Inservice Inspection Alternative VEGP-ISI-ALT-04-04 to the Requirements of the ASME Code (EPID L-2020-LLR-0109), January 11, 2021, ADAMS Accession No. ML20352A155.
: 13. American Society of Mechanical Engineers, Section XI Rules for Inservice Inspection of Nuclear Power Plant Components, 2007 Edition with 2008 Addenda, 2013 Edition, and 2019 Edition.
: 14. U.S. NRC, Vogtle Electric Generating Plant, Units 1 and 2 - Audit Report for the Promise Version 1.0 Probabilistic Fracture Mechanics Software Used in Relief Request VEGP-ISI-ALT-04-04 (EPID L-2019-LLR-0109), December 10, 2020, ADAMS Accession No. ML20258A002.
: 15. U.S. NRC Regulatory Federal Register Volume 86, Issue 57, March 26, 2021.
: 16. Letter from D. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds, dated May 12, 2021, ADAMS Accession No. ML21133A297.
: 17. Letter from D. Gudger (Constellation Energy Generation, LLC) to U.S. Nuclear Regulatory Commission, Supplemental Information - Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds, dated April 8, 2022, ADAMS Accession No. ML22098A179.
: 18. Letter from N. Salgado (U.S. Nuclear Regulatory Commission) to D. Rhoades (Constellation Energy Generation), Braidwood Station, Units 1 and 2 and Byron Station, Units Nos. 1 and 2 - Proposed Alternative to the Requirements of the American Society of Mechanical Engineers Boiler & Pressure Vessel Code (EPIDS L-2021-LLR-0035 and L-2021-LLR-0036), dated November 10, 2022, ADAMS Accession No. ML22307A246.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 21 of 50)
APPENDIX A Plant-Specific Applicability

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 22 of 50)
Plant-Specific Applicability for Braidwood Station Section 9 of Reference [A1] provides applicability requirements that must be demonstrated in order to apply the representative stress and flaw tolerance analyses to a specific plant. Plant-specific evaluation of these requirements for Braidwood is provided in Table A-1.
Table A-1 indicates that all plant-specific requirements are met for Braidwood. Therefore, the results and conclusions of the EPRI report are applicable to Braidwood.
Table A-1 Plant-Specific Applicability of Reference [A1] Representative Analyses to Braidwood Station, Units 1 and 2 Pressurizer Shell-to-Head Welds (Circumferential and Longitudinal) and Nozzle-to-Shell Welds (Item Numbers B2.11, B2.12, and B3.110)
Requirement from Category                                     Applicability to Braidwood Station, Units 1 and 2 Reference [A1]
General      The plant-specific          In Appendix C of this proposed alternative, the number Requirements    pressurizer general         and type of the Braidwood, Units 1 and 2 general transients and cycles       transients are compared to the transients listed in must be bounded by          Table 5-6 of Reference [A1]. As shown in Table C-2, the those shown in Table 5-     Braidwood, Units 1 and 2 transients are bounded by the 6 for a 60- year            transients listed in Table 5-6 of Reference [A1].
operating life. It should be noted that the number of cycles were extrapolated to 80 years in the evaluations.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 23 of 50)
Requirement from Category                                   Applicability to Braidwood Station, Units 1 and 2 Reference [A1]
The materials of the        The Braidwood, Units 1 and 2, pressurizer upper and pressurizer shell and       lower heads are fabricated of SA-533 Grade A, Class 2, nozzles must be low         to meet ASME Nuclear Vessels Code Section III.
alloy ferritic steels which SA-533 Grade A, Class 2 material is not specifically conform to the listed in ASME Code, Section XI, Appendix G. However, requirements of ASME SA-533 Grade A, Class 2 material has similar toughness Code, Section XI, and chemical composition to SA-533, Grade B, Class 1, Appendix G, Paragraph SA-508-1, SA-508-2, and SA-508-3. SA-533 Grade A, G-2110.
Class 2 has a specified minimum yield strength at room temperature of 70 ksi (which is greater than 50 ksi), and the maximum RTNDT values for the Braidwood pressurizer bottom head materials are 60&deg;F or less (so the RTNDT of 60&deg;F used in the EPRI report is bounding).
Appendix G, Table G-2110-1, of the 2019 Edition of ASME Section XI acknowledges that Figure G-2210-1 is applicable to material SA-533 Grade A, Class 2.
Therefore, it can be concluded that the EPRI report is applicable to material SA-533 Grade A, Class 2.
Also, material properties in SA-533 Grade A, Class 2 material are identical compared to the SA-533 Grade B Class 1 material used in the FEA in the EPRI report as is shown Table 5-2 of Reference [A1]. Therefore, by comparison, SA-533 Grade A, Class 2 material is consistent with the requirements of ASME Code, Section XI, Appendix G and satisfies the requirements for application of the EPRI report.
The Braidwood, Units 1 and 2, pressurizer shells are fabricated from SA-533 Grade A, Class 2, material. The Braidwood, Units 1 and 2, pressurizer Surge, Spray, and Safety-Relief valve nozzles are all fabricated from SA-508, Class 2, material.
The materials for the pressurizer shells conform to the requirements of ASME Code, Section XI, Appendix G, Paragraph G-2110.
Specific   The plant-specific          The Braidwood, Units 1 and 2, pressurizer shell-to-head Requirements pressurizer surge nozzle    and nozzle-to-vessel weld configurations included in this and bottom head weld        request are shown in Figures A-1, A-2, A-3, and A-4 and configurations must         show conformance with the figures shown in Reference conform to those shown      [A1].
in Figure 1-1 (Item No.
B2.11), Figure 1-2 (Item No. B2.12) and Figures 1-4 and 1-5 (Item No.
B3.110) of Reference
[A1].

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 24 of 50)
Requirement from Category                                 Applicability to Braidwood Station, Units 1 and 2 Reference [A1]
The plant-specific         The comparison of the Braidwood, Units 1 and 2, dimensions of the          pressurizer shell dimensions with those in Table 9-1 of pressurizer shell and the  Reference [A1] is provided in Table A-2. The surge nozzle must be       comparison shows that the Braidwood, Units 1 and 2 within the range of        configurations are within the range of values shown in values listed in Table 9-1 Table 9-1 of Reference [A1].
of Reference [A1].
The plant-specific         In Appendix D of this proposed alternative, the Insurge/Outsurge           Braidwood, Units 1 and 2, Insurge/Outsurge transients transient definitions      are compared to the number and type of transients (temperature difference    listed in Table 5-10 of Reference [A1]. As can be seen between the pressurizer    from Table D-2, the Braidwood, Units 1 and 2, transients shell and the pressurizer  are bounded by those transients listed in Table 5-10 of surge nozzle fluid         Reference [A1].
temperature and associated number of cycles) must be bounded by those shown in Table 5-10 for a Westinghouse/CE plant of Reference [A1].

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 25 of 50)
Table A-2 Range of Geometric Parameters for which the Evaluation is Applicable in Comparison with Braidwood Station, Units 1 and 2 Braidwood Station, Component        Geometric Parameter       For a Westinghouse Plant      Units 1 and 2 Dimensions Pressurizer Inside Diameter (in)    Must be between 80 and 88        84 [A3]
Shell NPS of piping or component (e.g., reducer)
Surge Nozzle                               Must be between 12 and 18        14 [A2]
attached to nozzle safe-end (in)
NPS of piping or Safety/Relief  component (e.g., reducer)
Must be between 4 and 8          6 [A2]
Nozzle        attached to nozzle safe-end (in)
NPS of piping or component (e.g., reducer)
Spray Nozzle                                Must be between 4 and 6          4 [A2]
attached to nozzle safe-end (in)
REFERENCES A1. Technical Bases for Inspection Requirements for PWR Pressurizer Vessel Head, Shell-to- Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905, ADAMS Accession No. ML21021A271.
A2. Westinghouse Electric Corporation Drawing No. 1100J48, Outline: Pressurizer 1800 Cu.
Ft. [50.96].
A3. Westinghouse Electric Corporation Drawing No. 1101J22, General Arrangement:
Pressurizer 1800 Cu. Ft. [50.96].
A4. Braidwood Station, Drawings 1PZR-01 and 2PZR-01, Inspection Identification Drawing Inservice Inspection for Pressurizer NC. 1RY01S and 2RY01S.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 26 of 50)
Figure A-1: Braidwood Station, Unit 1 Pressurizer Vessel Weld Locations [A4]

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 27 of 50)
Figure A-2: Braidwood Station, Unit 2 Pressurizer Vessel Weld Locations [A4]

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 28 of 50)
Figure A-3: Braidwood Station, Units 1 and 2 Typical Pressurizer Nozzle-to-Shell Weld Details

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 29 of 50)
Figure A-4: Braidwood Station, Units 1 and 2 Typical Shell and Head Weld Details [A3]

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2 Revision 1 (Page 30 of 50)
Plant-Specific Applicability for Byron Station Section 9 of Reference [A5] provides applicability requirements that must be demonstrated in order to apply the representative stress and flaw tolerance analyses to a specific plant. Plant-specific evaluation of these requirements for Byron is provided in Table A-3.
Table A-3 indicates that all plant-specific requirements are met for Byron. Therefore, the results and conclusions of the EPRI report are applicable Byron.
Table A-3 Plant-Specific Applicability of Reference [A5] Representative Analyses to Byron Station, Units 1 and 2 Pressurizer Shell-to-Head Welds (Circumferential and Longitudinal) and Nozzle-to-Shell Welds (Item Numbers B2.11, B2.12, and B3.110)
Requirement from Category                                        Applicability to Byron Station, Units 1 and 2 Reference [A5]
General      The plant-specific           In Appendix C of this proposed alternative, the number Requirements    pressurizer general          and type of the Byron, Units 1 and 2 general transients transients and cycles        are compared to the transients listed in Table 5-6 of must be bounded by           Reference [A5]. As shown in Table C-4, the Byron, Units those shown in Table 5-      1 and 2 transients are bounded by the transients listed 6 for a 60- year             in Table 5-6 of Reference [A5].
operating life. It should be noted that the number of cycles were extrapolated to 80 years in the evaluations.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2 Revision 1 (Page 31 of 50)
Requirement from Category                                      Applicability to Byron Station, Units 1 and 2 Reference [A5]
The materials of the        The Byron, Units 1 and 2, pressurizer upper and lower pressurizer shell and       heads are fabricated of carbon steel casting SA-533 nozzles must be low         Grade A, Class 2, to meet ASME Nuclear Vessels Code alloy ferritic steels which Section III.
conform to the SA-533 Grade A, Class 2 material is not specifically requirements of ASME listed in ASME Code, Section XI, Appendix G. However, Code, Section XI, SA-533 Grade A, Class 2 material has similar toughness Appendix G, Paragraph and chemical composition to SA-533, Grade B, Class 1, G-2110.
SA-508-1, SA-508-2, and SA-508-3. SA-533 Grade A, Class 2 has a specified minimum yield strength at room temperature of 70 ksi (which is greater than 50 ksi), and the maximum RTNDT values for the Byron pressurizer bottom head materials are 60&deg;F or less (so the RTNDT of 60&deg;F used in the EPRI report is bounding). Appendix G, Table G-2110-1, of the 2019 Edition of ASME Section XI acknowledges that Figure G-2210-1 is applicable to material SA-533 Grade A, Class 2. Therefore, it can be concluded that the EPRI report is applicable to material SA-533 Grade A, Class 2.
Also, material properties in SA-533 Grade A, Class 2 material is identical compared to the SA-533 Grade B Class 1 material used in the FEA in the EPRI report as is shown Table 5-2 of Reference [A5]. Therefore, by comparison, SA-533 Grade A, Class 2 material is consistent with the requirements of ASME Code, Section XI, Appendix G and satisfies the requirements for application of the EPRI report.
The Byron, Units 1 and 2, pressurizer shells are fabricated from SA-533 Grade A, Class 2, material. The Byron, Units 1 and 2 pressurizer Surge, Spray, and Safety-Relief valve nozzles are all fabricated from SA-508, Class 2, material.
The materials for the pressurizer shells conform to the requirements of ASME Code, Section XI, Appendix G, Paragraph G-2110.
Specific   The plant-specific          The Byron, Units 1 and 2, pressurizer shell-to-head and Requirements pressurizer surge nozzle    nozzle-to-vessel weld configurations included in this and bottom head weld        request are shown in Figures A-5, A-6, A-7, and A-8 and configurations must         show conformance with the figures shown in Reference conform to those shown      [A5].
in Figure 1-1 (Item No.
B2.11), Figure 1-2 (Item No. B2.12) and Figures 1-4 and 1-5 (Item No.
B3.110) of Reference
[A5].

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2 Revision 1 (Page 32 of 50)
Requirement from Category                                    Applicability to Byron Station, Units 1 and 2 Reference [A5]
The plant-specific         The comparison of the Byron, Units 1 and 2, pressurizer dimensions of the          shell dimensions with those in Table 9-1 of Reference pressurizer shell and the  [A5] is provided in Table A-4. The comparison shows surge nozzle must be       that the Byron, Units 1 and 2, configurations are within within the range of        the range of values shown in Table 9-1 of Reference values listed in Table 9-1 [A5].
of Reference [A5].
The plant-specific         In Appendix D of this proposed alternative, the Byron, Insurge/Outsurge           Units 1 and 2, Insurge/Outsurge transients are transient definitions      compared to the number and type of transients listed in (temperature difference    Table 5-10 of Reference [A5]. As can be seen from between the pressurizer    Table D-4, the Byron, Units 1 and 2, transients are shell and the pressurizer  bounded by those transients listed in Table 5-10 of surge nozzle fluid         Reference [A5].
temperature and associated number of cycles) must be bounded by those shown in Table 5-10 for a Westinghouse/CE plant of Reference [A5].

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2 Revision 1 (Page 33 of 50)
Table A-4 Range of Geometric Parameters for which the Evaluation is Applicable in Comparison with Byron Station, Units 1 and 2 Byron Station, Units 1 Component        Geometric Parameter       For a Westinghouse Plant and 2 Dimensions Pressurizer Inside Diameter (in)    Must be between 80 and 88        84 [A7]
Shell NPS of piping or component (e.g., reducer)
Surge Nozzle                               Must be between 12 and 18        14 [A6]
attached to nozzle safe-end (in)
NPS of piping or Safety/Relief  component (e.g., reducer)
Must be between 4 and 8          6 [A6]
Nozzle        attached to nozzle safe-end (in)
NPS of piping or component (e.g., reducer)
Spray Nozzle                                Must be between 4 and 6          4 [A6]
attached to nozzle safe-end (in)
REFERENCES A5. Technical Bases for Inspection Requirements for PWR Pressurizer Vessel Head, Shell-to- Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905, ADAMS Accession No. ML21021A271.
A6. Westinghouse Electric Corporation Drawing No. 1100J48, Outline: Pressurizer 1800 Cu.
Ft. [50.96].
A7. Westinghouse Electric Corporation Drawing No. 1101J22, General Arrangement:
Pressurizer 1800 Cu. Ft. [50.96].
A8. Byron Station, Drawings 1PZR-1-ISI and 2PZR-1-ISI, Inspection Identification Drawing Inservice Inspection for Pressurizer No. 1RY01S and 2RY01S.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2 Revision 1 (Page 34 of 50)
Figure A-5: Byron Station, Unit 1 Pressurizer Vessel Weld Locations [A8]

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2 Revision 1 (Page 35 of 50)
Figure A-6: Byron Station, Unit 2 Pressurizer Vessel Weld Locations [A8]

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 36 of 50)
Figure A-7: Byron Station, Units 1 and 2 Typical Pressurizer Nozzle-to-Shell Weld Details

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 37 of 50)
Figure A-8: Byron Station, Units 1 and 2 Typical Shell and Head Weld Details [A5]

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 38 of 50)
APPENDIX B Results of Industry Survey

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 39 of 50)
Overall Industry Inspection Summary The results of an industry survey of past inspections of pressurizer welds are summarized in Reference
[B1]. Table B-1 provides a summary of the combined survey results for Item Numbers B2.11, B2.12, and B3.110. The results identify that pressurizer examination of the items adversely impact outage activities including worker exposure, personnel safety, and radwaste. A total of 47 domestic and international PWR units responded to the survey and provided information representing all PWR plant designs currently in operation in the U.S. This included 2-loop, 3-loop, and 4-loop PWR designs from each of the PWR nuclear steam supply system (NSSS) vendors (i.e., Babcock and Wilcox (B&W), Combustion Engineering (CE), and Westinghouse). A total of 1,128 examinations of components for the three affected Item Numbers included in this proposed alternative were conducted on PWR pressurizer components.
A small number of flaws were identified during these examinations which required flaw evaluation. None of these flaws were found to be service induced. Out of a total of 1,128 examinations identified by the plants that responded to the survey that have been performed on the above item numbers, only four examinations (for Item No. B2.11) at two units of a single plant site identified flaws exceeding the acceptance criteria of ASME Code, Section XI. Flaw evaluations were performed to show acceptability of these indications and follow on examinations showed no change in flaw sizes since the original inspections. No other indications were identified in any in-scope components.
Table B-1 Summary of Survey Results Item No.         No. of Examinations            No. of Reportable Indications B2.11                   269                                   4 (1)
B2.12                   269                                     0 B3.110                  590                                     0 Note:
: 1. Flaw evaluations were performed to show acceptability of these indications and follow on examinations showed no change in flaw sizes since the original inspections.
REFERENCE B1. Technical Bases for Inspection Requirements for PWR Pressurizer Vessel Head, Shell-to-Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905, ADAMS Accession No. ML21021A271.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 40 of 50)
APPENDIX C Comparison of Braidwood Station and Byron Station General Transients to the Transients Evaluated in EPRI Report

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 41 of 50)
Comparison of Braidwood Station, Units 1 and 2 General Transients to the Transients Evaluated in Reference [C1]
Braidwood general transients are tracked by Constellation and the number of cycles encountered as of 2020 for the transients relevant to this request are provided in Table C-1
[C2]. As indicated in Reference [C1], not all the transients tracked by Constellation for Braidwood are required for this request. Table 5-5 of Reference [C1] identified the significant cycles to be used in the evaluation based on expected cycles from a fleet fatigue monitoring review. The Reference [C1] report considered the heatup/coodown and loss of load. Leakage tests are conducted as an integral part of the plant heatup process; therefore, no additional cycles were included solely for leakage testing. Braidwood would also expect to perform operating leakage testing, instead of hydrostatic testing, following any potential Braidwood Units 1 and 2 pressurizer repairs required by Paragraph IWA-4540(a) of ASME Section XI, in the future. The report considered 300 heatup and cooldown transients for 60 years of operation. The loss of load condition was the most limiting transient, but the cycles were increased to account for other similar events (reactor trip, loss of flow, and loss of power) and thus increased the number of cycles to 360.
For comparison with Table 5-6 of Reference [C1], the actual number of cycles in Table C-1 were projected to 60 years. The comparison of Braidwood general transients to the requirements in Reference [C1] is shown in Table C-2.
Table C-1 Braidwood Station, Units 1 and 2, General Transients Applicable to This Request [C2-C7]
Braidwood Station, Unit 1                Braidwood Station, Unit 2 Maximum                               Maximum Transient Name         Up to      60-Year         Cycles        Up to     60-Year       Cycles 2020     Projected     (Controlling     2020     Projected   (Controlling Limit)                                Limit) 1       RCS Heat Up           40          72            200           43         79           200 2     RCS Cool Down           39          70            200           51         94           200 3   Pressurizer Cooldown      40          72            200           41         75           200 4       Reactor Trips          6          11            230           38         69           230 Reactor Trips 5      w/Subsequent           11          20            160            3          5           160 Cooldown Reactor Trip w/
6                              3           5             10            0          0            10 Subsequent SI 50% Step Load        See                                      See     See Steps See Steps      See Steps                            See Steps 7a, 7   Decrease with Steam Steps 7a,                                 Steps 7a, 7a, 7b, 7c, 7a, 7b, 7c, 7d 7a, 7b, 7c, 7d                          7b, 7c, 7d Dump (See Below) 7b, 7c, 7d                                  7b, 7c, 7d     7d 7a     Unload @5%/min         104         187           12240          86        158          13200

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 42 of 50)
Braidwood Station, Unit 1               Braidwood Station, Unit 2 Maximum                                Maximum Transient Name            Up to      60-Year       Cycles       Up to     60-Year        Cycles 2020      Projected   (Controlling     2020    Projected    (Controlling Limit)                                 Limit)
Step Load 10%
7b                               3            5          2000           5          9            2000 Decrease Unloading, 15%-0%
7c                              17           31           500          15         28             500 Power Large Step Load 7d                               2            4           200           1          2             200 Decrease 8       Loss of Load            1            2            80           1          2              80 Loss of Offsite AC 9                               1            2            40           2          4              40 Power See                                   See Loss of Flow in One RC               See Steps    See Steps               See Steps   See Steps 10a, 10                             Steps                                 Steps Loop Only (BRW below)                 10a, 10b     10a, 10b                10a, 10b          10b 10a, 10b                               10a, 10b 10a    Partial Loss of Flow       1            2            80           1          2              80 10b Complete Loss of Flow         0            0             5           1          2               5 Note:
: 1. Allowable limits and totals are from the Braidwood, Unit 1 and 2, Fatigue Monitoring Reports (December 2020) Work Orders 05107062 and 05107063 (Procedure BwVP 850-7).
: 2. 60-year projection is based on Braidwood, Unit 1 and 2, Semi-Annual Fatigue Monitoring Report (January 2021) under Work Orders 05064062 and 05064063.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 43 of 50)
Table C-2 Comparison of Braidwood Station, Units 1 and 2, General Transients to the Transients Evaluated in Reference [C1]
Number of        Braidwood Station,   Braidwood Station, Cycles for 60       Unit 1 60-Year       Unit 2 60-Year Transient              Years from        Projections from     Projections from Reference [C1]          Table C-1            Table C-1 Heatup / Cooldown             300                    72                  94 Loss of Load (Sum of Reactor Trips, 50%
Step Load Decrease with Steam Dump, Loss of Load,          360                   269                 281 Loss of Flow in One RC Loop Only, and Loss of Offsite AC Power Events)
REFERENCES C1. Technical Bases for Inspection Requirements for PWR Pressurizer Vessel Head, Shell-to-Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905, ADAMS Accession No. ML21021A271.
C2. Braidwood Station, Unit 1, December Fatigue Monitoring Report (Monthly), Work Order 05107062.
C3. Braidwood Station, Unit 2, December Fatigue Monitoring Report (Monthly), Work Order 05107063.
C4. Braidwood Station, Unit 1, Semi-Annual Report (January), Work Order 05064063.
C5. Braidwood Station, Unit 2, Semi-Annual Report (January), Work Order 05064062.
C6. Procedure BwVP 850-7, Operational Transient Cycle Counting.
C7. WCAP-15966, Evaluation of Pressurizer Insurge / Outsurge Transients for Byron and Braidwood, 2002.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 44 of 50)
Comparison of Byron Station, Units 1 and 2, General Transients to the Transients Evaluated in Reference [C8]
Byron general transients are tracked by Constellation and the number of cycles encountered as of 2020 for the transients relevant to this request are provided in Table C-3 [C9]. As indicated in Reference [C8], not all the transients tracked by Constellation for Byron are required for this request. Table 5-5 of Reference [C8] identified the significant cycles to be used in the evaluation based on expected cycles from a fleet fatigue monitoring review. The Reference [C8]
report considered the heatup/coodown and loss of load. Leakage tests are conducted as an integral part of the plant heatup process; therefore, no additional cycles were included solely for leakage testing. Byron would also expect to perform operating leakage testing, instead of hydrostatic testing, following any potential Byron Units 1 and 2 pressurizer repairs, required by Paragraph IWA-4540(a) of ASME Section XI, in the future. The report considered 300 heatup and cooldown transients for 60 years of operation. The loss of load condition was the most limiting transient, but the cycles were increased to account for other similar events (reactor trip, loss of flow, and loss of power) and thus increased the number of cycles to 360.
For comparison with Table 5-6 of Reference [C8], the actual number of cycles in Table C-3 were projected to 60 years. The comparison of Byron general transients to the requirements in Reference [C8] is shown in Table C-4.
Table C-3 Byron Station, Units 1 and 2, General Transients Applicable to This Request [C9]
Byron Station, Unit 1                   Byron Station, Unit 2 Maximum                                Maximum Cycles                                 Cycles Transient Name             Up to      60-Year                      Up to      60-Year (Controlling                            (Controlling 2020     Projected                     2020      Projected Limit)                                  Limit)
Heat Up@ <100&deg;F/hr             38          66            200           34          62            200 Cooldown@ <100&deg;F/hr             38          66            200           34          62            200 Reactor Trips               5           9            230            7          13            230 50% Step Load Decrease 2           4            200            3           6            200 with Steam Dump Loss of Load               3           6             80            1           2             80 Loss of Flow in One RC 0           0             80            0           0             80 Loop Only Loss of Offsite AC Power           1           2             40            3           6             40 Note:
: 1. Allowable limits and totals are from the Byron, Unit 1 and 2, Annual Fatigue Monitoring Report (2020),
EC 633359, Revision 0.
: 2. 60-year projection is based on Byron, Unit 1 and 2, Annual Fatigue Monitoring Report (2020), EC 633359, Revision 0.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 45 of 50)
Table C-4 Comparison of Byron Station, Units 1 and 2, General Transients to the Transients Evaluated in Reference [C8]
Number of        Byron Station, Unit  Byron Station, Unit Cycles for 60          1 60-Year            2 60-Year Transient              Years from        Projections from     Projections from Reference [C8]          Table C-3            Table C-3 Heatup / Cooldown              300                    66                   62 Loss of Load (Sum of Reactor Trips, 50%
Step Load Decrease with Steam Dump, Loss of Load,          360                    21                   27 Loss of Flow in One RC Loop Only, and Loss of Offsite AC Power Events)
REFERENCES C8. Technical Bases for Inspection Requirements for PWR Pressurizer Vessel Head, Shell-to-Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905, ADAMS Accession No. ML21021A271.
C9. EC 633359, Revision 0, Annual Fatigue Monitoring Report 2020 Unit 1 & Unit 2.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 46 of 50)
APPENDIX D Comparison of Braidwood Station and Byron Station Insurge/Outsurge Transients to the Insurge/Outsurge Transients Evaluated EPRI Report

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 47 of 50)
Comparison of Braidwood Station, Units 1 and 2, Insurge/Outsurge Transients to the Insurge/Outsurge Transients Evaluated in Reference [D1]
Braidwood Insurge/Outsurge transients are provided in Table D-1 [D2-D7]. The temperature differences (Ts) identified in Table D-1 are combined conservatively by summing all the events into the 320&deg;F T bin. It should be noted that the transients in Table D-1 reflect 40 years of operation, so for comparison with Table 5-10 of Reference [D1], they are extrapolated to 60 years by multiplying by 1.5. With this conservative treatment of the Insurge/Outsurge transients, the comparison of Braidwood Insurge/Outsurge transients to the requirements in Reference [D1] is shown in Table D-2. The results of Table D-2 indicate that the Braidwood Insurge/Outsurge transients are bounded by those in Reference
[D1].
Table D-1 40-Year Insurge/Outsurge Transients for Braidwood Station, Units 1 and 2 [D2-D7]
Unit 1                                Unit 2 No.          Transient Name (1,2,3)
Up to 60-Year           Allowable        Up to 60-Year Allowable 2020 Projected               Limit       2020 Projected        Limit
[D2]      [D4](5)           [D7](4)      [D3]     [D5](5)     [D7](4) 1       PZR I/O SURGE MOPHU320                  4          10               56          4         10          56 2       PZR I/O SURGE MOPHU300                  2           5               20          0          0          20 3       PZR I/O SURGE MOPHU280                  3           8               21          0          0          21 4       PZR I/O SURGE MOPHU270                  9          23               70          6         16          70 5       PZR I/O SURGE MOPCD320                  0           0               41          0          0          41 6       PZR I/O SURGE MOPCD310                  0           0               15          0          0          15 7       PZR I/O SURGE MOPCD300                  1           3               20          2          5          20 8       PZR I/O SURGE MOPCD270                  1           3               76          0          0          76 9       PZR I/O SURGE MOPCD250                  4          10               15          8        21(6)        15 Notes:
: 1. The Transient Name is MOPXXnnn, where MOP = post Modified Operating Procedures, XX = HU for insurge/outsurge transients that occur during Heatup events, or CD for insurge/outsurge transients that occur during Cooldown events, and nnn = temperature difference, delta T, between the RCS piping at the beginning of the transient and pressurizer temperature at the end of the transient
: 2. Insurge/Outsurge determination is based on WCAP-15966
: 3. Braidwood does not explicitly monitor the breakdown of the transients shown in this table. Rather, the number of cycles shown in this table were used in the governing fatigue evaluations for the pressurizer surge nozzles.
Braidwood does NOT currently monitor the environmental fatigue usage factor for the surge nozzle but is expected to do so with implementation of WESTEMs as part of license renewal commitments for the station.
: 4. Per Note 2 (WCAP-15966) the allowable insurge/outsurge numbers were used to evaluate the stresses for Braidwood. As such, these numbers are the same for 40 years and 60 years.
: 5. 60-year projection is based on Braidwood, Unit 1 and 2, Semi-Annual Fatigue Monitoring Report (January 2021) under Work Orders 05064062 and 05064063.
: 6. In Reference [D5], PZR I/O SURGE MOPCD250 was identified as reaching 53.33% of the allowable limit for Unit 2, and was projected to exceed the allowable limit in 2033. This projection is skewed based on the occurrences in 2008 and 2009, when three of the events occurred during a refueling outage cool down. Except for one event in 2014 during the A2R17 refueling outage, there have been zero occurrences of the PZR I/O SURGE MOPCD250 events between 2010 and 2020. Based on the latest trend, the 60-Year Projected count should decrease as the plant reaches its PEO and the projected year to reach the limit will continue to increase beyond 2033.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 48 of 50)
Table D-2 Comparison of Braidwood Station, Units 1 and 2, Insurge/Outsurge Transient Temperature Differences and Numbers of Cycles with the Insurge/Outsurge Transient Date from Reference [D1]
60-Year No. of                                           Braidwood Station, Braidwood Station, Unit Cycles                                                    Unit 2 Cycles 1 Cycles Projected to 60 T (oF)(1)       From Reference                                            Projected to 60 Years Years of Operation
[D1]                                                    of Operation 330                 600                            0                                0 320                3,000                          62                               52 103                1,500                           0                                0 Notes:
: 1. T is the temperature difference between the pressurizer fluid temperature and the fluid temperature in the surge nozzle.
REFERENCES D1. Technical Bases for Inspection Requirements for PWR Pressurizer Vessel Head, Shell-to-Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905, ADAMS Accession No. ML21021A271.
D2. Braidwood Station, Unit 1, December Fatigue Monitoring Report (Monthly), Work Order 05107062.
D3. Braidwood Station, Unit 2, December Fatigue Monitoring Report (Monthly), Work Order 05107063.
D4. Braidwood Station, Unit 1, Semi-Annual Report (January), Work Order 05064063.
D5. Braidwood Station, Unit 2, Semi-Annual Report (January), Work Order 05064062.
D6. Procedure BwVP 850-7, Operational Transient Cycle Counting.
D7. WCAP-15966, Evaluation of Pressurizer Insurge / Outsurge Transients for Byron and Braidwood, 2002.

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 49 of 50)
Comparison of Byron Station, Units 1 and 2, Insurge/Outsurge Transients to the Insurge/Outsurge Transients Evaluated in Reference [D8]
Byron Insurge/Outsurge transients are provided in Table D-3 [D9-D14]. The temperature differences (Ts) identified in Table D-3 are combined conservatively by summing all the events into the 320&deg;F T bin. It should be noted that the transients in Table D-3 reflect 40 years of operation, so for comparison with Table 5-10 of Reference [D8], they are extrapolated to 60 years by multiplying by 1.5. With this conservative treatment of the Insurge/Outsurge transients, the comparison of Byron Insurge/Outsurge transients to the requirements in Reference [D8] is shown in Table D-4. The results of Table D-4 indicate that the Byron Insurge/Outsurge transients are bounded by those in Reference [D8].
Table D-3 40-Year Insurge/Outsurge Transients for Byron Station, Units 1 and 2 [D9-D14]
WCAP-                       Unit 1                                  Unit 2 No.       Transient Name (1,2) 15966 Past       Up to                     Allowable      Up to                 Allowable 60-Year                                  60-Year Total        2020                        Limit        2020                    Limit Projected  (3)                           Projected(3)
Count      [D11](2)                     [D10](4)    [D11](2)                 [D10](4)
[D10]
1    PZR I/O Surge-MOPHU320             10            3          20              35            3          20          35 2    PZR I/O Surge-MOPHU310              5            0           5              17            0           5          17 3    PZR I/O Surge-MOPHU300              5            1           9              17            1           9          17 4    PZR I/O Surge-MOPHU280             15            0          15              52            1          19          52 5    PZR I/O Surge-MOPHU270             12            2          19              42            0          12          42 6    PZR I/O Surge-MOPHU250             11            8          36              37           10          44          37 7    PZR I/O Surge-MOPCD320              7            0           7              24            1          11          24 8    PZR I/O Surge-MOPCD310              9            0           9              31            0           9          31 9    PZR I/O Surge-MOPCD300              9            0           9              31            0           9          31 10 PZR I/O Surge-MOPCD290                11            0          11              38            0          11          38 11 PZR I/O Surge-MOPCD280                 4            0           4              14            0           4          14 12 PZR I/O Surge-MOPCD270                11            0          11              38            1          15          38 13 PZR I/O Surge-MOPCD250                 7            3          17              24            6          27          24 Notes:
: 1. The Transient Name is PZR I/O Surge-MOP XX nnn, where XX = HU for insurge/outsurge transients that occur during Heatup events, or CD for insurge/outsurge transients that occur during Cooldown events, and nnn = the temperature difference, T, between the pressurizer fluid temperature and the fluid temperature in the surge nozzle.
: 2. Byron has explicitly monitored the breakdown of the transients shown in this table since May 2008, when BVP 900-3, Revision 6 [D11] was issued. This monitoring was implemented to confirm the MOP strategies recommended in WCAP-14950 [D14] are effective and to ensure that the projections in WCAP-15966 [D10] remain bounding.
: 3. The projection for the number of Insurge/Outsurge Transients over 60 years of operation is equal to the sum of the conservatively estimated past events as documented in WCAP-15966 [D10] and the number of events recorded between 2008 and 2020 [D9] increased to assume the same rate of occurrence until the end of the 60 year operating period.
: 4. The Allowable Limit is the sum of the conservatively estimated past events as documented in WCAP-15966 [D10] and the projected number of future MOP Heatup/Cooldown events assumed in WCAP-15966 [D10].

10 CFR 50.55a Proposed Alternative I4R-15 for Braidwood Station, Units 1 and 2, and Proposed Alternative I4R-21 for Byron Station, Units 1 and 2, Revision 1 (Page 50 of 50)
Table D-4 Comparison of Byron Station, Units 1 and 2, Insurge/Outsurge Transient Temperature Differences and Numbers of Cycles with the Insurge/Outsurge Transient Date from Reference
[D8]
Byron Unit 1             Byron Unit 2 60-Year No. of         Cycles Projected         Cycles Projected T (oF)(1)     Cycles from             to 60 Years of           to 60 Years of Reference [D8]             Operation                Operation (2)                       (2) 330                600                     27                       31 (3)                       (3) 320              3,000                    172                      195 (4)                       (4) 103              1,500                     53                       71 Notes:
: 1. T is the temperature difference between the pressurizer fluid temperature and the fluid temperature in the surge nozzle.
: 2. Byron has an administrative limit of 320&deg;F on system T. WCAP-15966 [D10] did identify a small number of events that exceeded 320&deg;F on system T and assumed those events to be 320&deg;F for the purposes of developing the system T distribution in the analysis. Based on this precedence, the number of cycles at T = 330&deg;F is conservatively considered to be equal to sum of all heatup and cooldown events in Table D-3 for T = 320&deg;F, since Byron does not specifically monitor for transients with a temperature difference of 330&deg;F.
: 3. The number of cycles at T = 320&deg;F is conservatively considered to be equal to sum of all events in Table D-3.
: 4. The number of cycles at T = 103&deg;F is conservatively considered to be equal to sum of the heatup and cooldown events in Table D-3 for T = 250&deg;F, since Byron does not specifically monitor for transients with a temperature difference of 103&deg;F. Byron does count any event with T >80&deg;F and 250&deg;F in as applicable 250&deg;F surge condition.
Therefore, the number of events in Table D-3 for T = 250&deg;F is conservatively bounding.
REFERENCES D8. Technical Bases for Inspection Requirements for PWR Pressurizer Vessel Head, Shell-to-Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905, ADAMS Accession No. ML21021A271.
D9. EC 633359, Revision 0, Annual Fatigue Monitoring Report 2020 Unit 1 & Unit 2.
D10. WCAP-15966, Evaluation of Pressurizer Insurge/Outsurge Transients for Byron and Braidwood, Rev. 0, dated December 2002.
D11. BVP 900-3, Documentation of Operating Plant/Component Cyclic or Transient Events, Rev.
6, issued May 9, 2008.
D12. BVP 900-3, Documentation of Operating Plant/Component Cyclic or Transient Events, Rev.
8 (current revision), issued February 27, 2012.
D13. Exelon Procedure ER-AA-470, Fatigue and Transient Monitoring Program, Rev. 8, issued January 30, 2019.
D14. WCAP-14950, Mitigation and Evaluation of Pressurizer Insurge/Outsurge Transients, February 1998.}}