ML22342B160
| ML22342B160 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 01/10/2023 |
| From: | Jennifer Dixon-Herrity Plant Licensing Branch IV |
| To: | Entergy Operations |
| Wengert T | |
| References | |
| EPID L-2022-LLR-0022, EPID L-2022-LLR-0023, EPID L-2022-LLR-0024, EPID L-2022-LLR-0025, EPID L-2022-LLR-0026, EPID L-2022-LLR-0027 | |
| Download: ML22342B160 (1) | |
Text
January 10, 2023 ANO Site Vice President Arkansas Nuclear One Entergy Operations, Inc.
N-TSB-58 1448 S.R. 333 Russellville, AR 72802
SUBJECT:
ARKANSAS NUCLEAR ONE, UNIT 2 - REQUESTS FOR RELIEF ANO2-ISI-023, -024, -025, -026, -027, AND -028 TO PERMIT REDUCTION OF INSPECTION AREA DUE TO INTERFERENCE (EPID L-2022-LLR-0022, EPID L-2022-LLR-0023, EPID L-2022 LLR-0024, EPID L 2022-LLR-0025, EPID L-2022-LLR-0026, AND EPID L-2022-LLR-0027)
Dear Sir or Madam:
By letter dated February 24, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22055B120), as supplemented by letter dated July 20, 2022 (ML22201A433), Entergy Operations, Inc. (the licensee) submitted to the U.S. Nuclear Regulatory Commission (NRC) Relief Requests ANO2-ISI-023, ANO2-ISI-024, ANO2-ISI-025, ANO2-ISI-026, ANO2-ISI-027, and ANO2-ISI-028, for relief from certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI requirements at Arkansas Nuclear One, Unit 2 (ANO-2).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii) the licensee requested relief pertaining to the 10-year update of the ANO-2 inservice inspection (ISI) program items on the basis the code requirement is impractical. The licensees proposed reliefs are for the fourth ANO-2, 10-year ISI interval, second and third periods. The interval started on March 26, 2010, and was scheduled to end on August 1, 2020. The second period started on March 26, 2013, and ended March 25, 2017. The third period started March 26, 2017, and was scheduled to end on August 1, 2020, however the licensee subsequently extended the interval to end on March 25, 2021.
As set forth in the enclosed Safety Evaluations, the NRC staff determines that it is impractical for the licensee to comply with the ASME Code,Section XI requirements, that the proposed weld examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds, and that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i). Therefore, the NRC staff grants Relief Requests ANO2-ISI-023, ANO2-ISI-024, ANO2-ISI-025, ANO2-ISI-026, ANO2-ISI-027, and ANO2-ISI-028 for the fourth 10-year ISI interval, which commenced on March 26, 2010, and ended on March 25, 2021.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.
If you have any questions, please contact Thomas Wengert at (301) 415-4037 or by email at Thomas.Wengert@nrc.gov.
Sincerely, Jennifer L. Dixon-Herrity, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-368
Enclosures:
- 1. Safety Evaluation for ANO-ISI-023
- 2. Safety Evaluation for ANO-ISI-024 and ANO-ISI-028
- 3. Safety Evaluation for ANO-ISI-025 and ANO-ISI-026
- 4. Safety Evaluation for ANO-ISI-027 cc: Listserv Jennifer L.
Dixon-Herrity Digitally signed by Jennifer L. Dixon-Herrity Date: 2023.01.10 16:00:15 -05'00'
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST ANO2-ISI-023 REGARDING WELD EXAMINATION COVERAGE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-368
1.0 INTRODUCTION
By letter dated February 24, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22055B120), as supplemented by letter dated July 20, 2022 (ML22201A433), Entergy Operations, Inc., (the licensee) requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components. Relief Request ANO2-ISI-023 pertains to the examination coverage of Class 1 and 2 vessel and pipe welds in the fourth 10-year inservice inspection (ISI) interval at Arkansas Nuclear One, Unit 2 (ANO-2).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),
ISI program update: Notification of impractical ISI Code requirements, the licensee requested relief from the required examination coverage and to use alternative requirements (if necessary), for ISI of the vessel and pipe welds on the basis that the ASME Code requirements are impractical.
2.0 REGULATORY EVALUATION
Pursuant to 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice inspection requirements, set forth in ASME Code,Section XI.
Pursuant to 10 CFR 50.55a(g)(4)(ii), Applicable ISI Code: Successive 120-month intervals, inservice examination of components and system pressure tests conducted during successive 120-month inspection intervals must comply with the requirements of the latest edition and addenda of the ASME Code incorporated by reference in paragraph (a) of 10 CFR 50.55a 18 months before start of the 120-month inspection interval (or the optional ASME Code Cases listed in Regulatory Guide (RG) 1.147, Inservice Inspection Code Case Acceptability, ASME
Section XI, Division 1, Revision 20 (ML21181A222), when using ASME Code,Section XI as incorporated by reference in paragraph (a)(3)(ii) of 10 CFR 50.55a), subject to the conditions listed in paragraph (b) of 10 CFR 50.55a.
Pursuant to 10 CFR 50.55a(b)(2)(xv),Section XI condition: appendix VIII specimen set and qualification requirements, licensees using appendix VIII in the 2001 Edition of the ASME Code may elect to comply with all of the provisions in paragraphs (b)(2)(xv)(A) through (M) of 10 CFR 50.55a, except for paragraph (b)(2)(xv)(F) of 10 CFR 50.55a, which may be used at the licensees option. Licensees using editions and addenda after 2001 Edition through the 2006 Addenda must use the 2001 Edition of appendix VIII and may elect to comply with all of the provisions in paragraphs (b)(2)(xv)(A) through (M) of 10 CFR 50.55a, except for paragraph (b)(2)(xv)(F) of 10 CFR 50.55a, which may be used at the licensee's option.
Pursuant to 10 CFR 50.55a(g)(5)(iii), if the licensee has determined that conformance with an ASME Code requirement is impractical for its facility, the licensee must notify the NRC and submit, as specified in 10 CFR 50.4, Written communications, information to support the determinations. Determinations of impracticality in accordance with 10 CFR 50.55a must be based on the demonstrated limitations experienced when attempting to comply with the ASME Code requirements during the ISI interval for which the request is being submitted. Requests for relief made in accordance with 10 CFR 50.55a must be submitted to the U.S. Nuclear Regulatory Commission (NRC) no later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought.
Pursuant to 10 CFR 50.55a(g)(6)(i), Impractical ISI requirements: Granting of relief, the Commission will evaluate determinations under paragraph (g)(5) of 10 CFR 50.55a that ASME Code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, and will not endanger life or property or the common defense and security, and are otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC to grant the relief requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1
Applicable Code Edition and Addenda
The code of record for the fourth 10-year ISI interval was the 2001 Edition through 2003 Addenda of Section XI of the ASME Code.
The licensee stated that by safety evaluation dated July 12, 2017 (ML17174B144), the NRC approved use of the 2007 Edition with 2008 Addenda of Section XI of the ASME Code for activities associated with repair/replacement, pressure testing, and nondestructive examination (NDE) during the remainder of the fourth 10-year ISI interval of ANO-2. Therefore, in the 26th (fall 2018) and 27th (spring 2020) refueling outages of the fourth 10-year ISI interval, the licensee performed the pressure testing and NDE activities in accordance with the 2007 Edition with 2008 Addenda of Section XI of the ASME Code. Prior to the 26th refueling outage in the fourth 10-year ISI interval, the licensee performed the pressure testing and NDE activities in accordance with the 2001 Edition through 2003 Addenda of Section XI of the ASME Code.
3.2 Duration of Relief Request The licensee submitted the subject relief request for the fourth 10-year ISI interval, which started on March 26, 2010, and ended on March 25, 2021. The licensee stated that the extensions from March 25, 2020 to August 1, 2020, and from August 1, 2020 to March 25, 2021, were applied to the fourth 10-year ISI interval in accordance with ASME Code,Section XI, IWA-2430, Inspection Intervals, and all applicable requirements in IWA-2430 had been met.
3.3 Relief Request ANO2-ISI-023 3.3.1 Component Affected ASME Code Class 1, Examination Category B-D, Item No. B3.130 welds in table IWB-2500-1 of ASME Code,Section XI, are affected. The licensee stated that it categorized ANO-2s steam generator (SG) primary outlet and inlet nozzle-to-extension piece circumferential welds as Examination Category B-D, Item No. B3.130. In table 1 of attachment 1 to Relief Request ANO2-ISI-023, the licensee provides additional information including the components identification, description, examination method, limitations, materials of construction, and the percent examination coverage that was obtained. The SG nozzle and extension piece are made of carbon steel with stainless steel cladding on the inside surface.
ASME Code Class 1, Examination Category B-D, Item No. B3.110 welds in table IWB-2500-1 of ASME Code,Section XI, are affected. The licensee stated that it categorized ANO-2s pressurizer surge nozzle-to-head circumferential weld as Examination Category B-D, Item No. B3.110. In table 1 of attachment 1 to Relief Request ANO2-ISI-023, the licensee provides additional information including the components identification, description, examination method, limitations, materials of construction, and percent examination coverage that was obtained. Both the pressurizer nozzle and head are carbon steel with stainless steel cladding on the inside surface.
ASME Code Class 1, Examination Category B-D, Item No. B3.140 welds in table IWB-2500-1 of ASME Code,Section XI, are affected. The licensee stated that it categorized ANO-2s SG B primary outlet nozzle inner radii as Examination Category B-D, Item No. B3.140. In table 1 of attachment 1 to Relief Request ANO2-ISI-023, the licensee provides additional information including the components identification, description, examination method, limitations, materials of construction, and the percent examination coverage that was obtained. Both the SG B nozzle and head are carbon steel with stainless steel cladding on the inside surface.
ASME Code Class 1, Examination Category B-D, Item No. B3.90 welds in table IWB-2500-1 of ASME Code,Section XI, affected. The licensee stated that it categorized ANO-2s reactor pressure vessel (RPV) nozzle-to-vessel weld as Examination Category B-D, Item No. B3.90. In table 1 of attachment 1 to Relief Request ANO2-ISI-023, the licensee provides additional information including the components identification, description, examination method, limitations, materials of construction, and the percent examination coverage that was obtained.
Both the RPV nozzle and vessel are carbon steel with stainless steel cladding on the inside surface.
3.3.2 ASME Code Requirement The ASME Code requirements applicable to Class 1 welds originate in table IWB-2500-1 of Section XI to the ASME Code. Examination Category B-D, Item Nos. B3.90, B3.110, B3.130 and B3.140 welds are required to be volumetrically examined each 10-year ISI interval. The extent of required examination coverage is defined to be essentially 100 percent (i.e., greater than 90 percent coverage) by ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 welds,Section XI. This code case has been incorporated by reference into 10 CFR 50.55a via inclusion in RG 1.147, Revision 20.
3.3.3 Impracticality of Compliance The licensee stated that it was not possible to obtain greater than 90 percent of the ASME Code required examination volume due to the geometric configuration of the components, which limited scan paths of the ultrasonic probes. The ultrasonic testing (UT) was a single-sided examination. In table 1 and figures 1, 2, 2a, 3, 3a, 4, 4a, 5, 5a, 6, 6a, 7, 7a, 8, 8a, and 8b of attachment 1 to Relief Request ANO2-ISI-023, the licensee described and illustrated the limitations that prevented ultrasonic scanning of the subject components. The licensee stated that the radiographic testing is not practical because the weld configurations prevent the placement of radiation source and film.
The licensee further stated that the burden caused by compliance would include major modification of plant components, which would include the redesign and replacement of the welds and associated components.
3.3.4 Basis for Relief The licensee stated that it scanned the subject welds in the axial and circumferential directions using the beam angles, as described in table 1 of attachment 1 to Relief Request ANO2-ISI-023. The UT was performed to the maximum extent possible utilizing personnel qualified and procedures demonstrated in accordance with Entergy procedure CEP-NDE-0497, Manual Ultrasonic Examination of Welds in Vessels (Non-APP. VIII [ASME Code,Section XI, appendix VIII]), which is consistent with the applicable requirements of the 2007 Edition through 2008 Addenda of ASME Code,Section V, Nondestructive Examination. No unacceptable indications were identified in the volume examined.
In addition, the welds had been subjected to the ASME Code system leakage test and associated visual examination (VT-2) in the fourth 10-year ISI interval. No through-wall leakage was identified in any of the welds.
3.3.5 Proposed Alternative In table 1 of attachment 1 to Relief Request ANO2-ISI-023, the licensee reported the percent coverage achieved for each SG nozzle weld examined. Table 1 below shows the examination coverage obtained.
Table 1 - ASME Code Coverage for Examination Category B-D, Item No. B3.130, SG Primary Outlet and Inlet Nozzle-to-Extension Piece Circumferential Welds Component ID Coverage Obtained (Percent)03-005 86.65 03-006 86.65 04-005 88.44 04-006 88.44 04-007 87.21 Table 2 - ASME Code Coverage for Examination Category B-D, Item No. B3.110, Pressurizer Surge Nozzle-to-Head Circumferential Welds Component ID Coverage Obtained (Percent)05-009 67.51 Table 3 - ASME Code Coverage for Examination Category B-D, Item No. B3.140, Steam Generator B Primary Outlet Nozzle Inner Radii Component ID Coverage Obtained (Percent) 04-005IR 89.03 04-006IR 89.03 Table 4 - ASME Code Coverage for Examination Category B-D, Item No. B3.90, RPV Nozzle-to-Vessel Welds Component ID Coverage Obtained (Percent)01-021 73.83 01-024 73.83 The licensee proposed the above alternative coverage in lieu of the required essentially 100 percent coverage.
3.4
NRC Staff Evaluation
Examination Category B-D, Item No. B3.130 The NRC staff evaluated Relief Request ANO2-ISI-023 pursuant to 10 CFR 50.55a(g)(6)(i). The NRC staffs evaluation focused on: (1) whether a technical justification exists to support the determination that the ASME Code requirement is impractical, (2) whether the imposition of the Code-required inspections would result in a burden to the licensee, and (3) whether the licensees proposed alternative (accepting the reduced inspection coverage in this case) provides reasonable assurance of structural integrity and leak tightness of the subject welds.
The NRC staff finds that if these three criteria are met, the requirements of 10 CFR 50.55a(g)(6)(i) (i.e., granting the requested relief will not endanger life or property or the common defense and security, and are otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility) will also be met.
As described in the licensees application, as supplemented, the predominant limitation that prevented the licensees UT to achieve essentially 100 percent coverage of the ASME Code-required volume was the geometric nozzle-to-extension piece configurations. From review of figures 2, 2a, 3, 3a, 4, 4a, 5, 5a, 6, and 6a of attachment 1 to Relief Request ANO2-ISI-023, the NRC staff confirmed that each welds configuration prevented the licensee from fully scanning the welds. Therefore, the NRC staff finds that a technical justification exists to support the determination that achieving essentially 100 percent coverage is impractical.
The licensee proposed that making the welds fully accessible for inspection would require replacement or significant design modification to the welds and their associated components.
The NRC staff finds that replacing or reconfiguring the components of the subject welds is the only reasonable means to achieve essentially 100 percent coverage of these welds and that replacement or reconfiguration of the nozzle, SG vessel, and extension piece constitutes a burden on the licensee without a commensurate increase in safety.
The NRC staff considered whether the licensees proposed alternative provided reasonable assurance of structural integrity and leak tightness of the subject welds based on: (1) the examination coverage achieved, and (2) safety significance of unexamined volumes and unachievable coverage (e.g., the presence or absence of known active degradation mechanisms and essentially 100 coverage achieved for similar welds in similar environments subject to similar degradation mechanisms).
In evaluating the licensees proposed alternative coverage, the NRC staff assessed whether the licensee obtained as much coverage as reasonably possible, and the methods used for achieving the reported coverage. From review of the licensees application, the NRC staff verified that:
The welds were examined using the appropriate equipment, ultrasonic modes of propagation, probe angles, frequencies, and scanning directions to obtain maximum coverage.
The coverage was calculated in a reasonable manner.
The personnel and UT procedures utilized for the examination were qualified as required by the ASME Code,Section XI.
The coverage was limited by geometric configuration of the components that limited access to the required examination volume.
No unacceptable indications were identified.
Therefore, the NRC staff found that the licensee made a significant effort to obtain as much coverage as reasonably possible with the ASME Code-required UT.
In addition to the coverage analysis described above, the NRC staff evaluated the safety significance of the unexamined volumes of welds and unachievable coverage. From review of the licensees application, as supplemented, the NRC staff verified that the licensees UT has covered, to the extent possible, the regions (i.e., the weld root and the heat affected zone of the base material near the inside diameter surface of the joint) that are typically susceptible to
higher stresses and, therefore, potential degradation. No unacceptable indications were detected in the volumes examined.
Therefore, the NRC staff determined that based on the coverage achieved by the qualified UT and the examination of the weld root and its heat affected zone to the extent possible, it is reasonable to conclude that if significant service-induced degradation had occurred, evidence of it would have been detected by the examinations that the licensee performed.
In this analysis, the NRC staff also found that, in addition to the required volumetric examinations, the subject welds received the ASME Code,Section XI, table IWB-2500-1, Examination Category B-P-required system leakage test. Despite reduced coverage of the required examination volume, the NRC staff finds that this inspection will provide additional assurance that any pattern of degradation, if it were to occur, would be detected and the licensee would have sufficient time to take appropriate correction actions.
Therefore, the NRC staff finds that the volumetric examinations performed to the extent possible provide reasonable assurance of structural integrity and leak tightness of the SG primary outlet and inlet nozzle-to-extension piece circumferential welds. Compliance with the ASME Code requirements for these welds would be a burden on the licensee, without a commensurate increase in safety.
Examination Category B-D, Item No. B3.90, B3.110, and B3.140 The NRC staff evaluated the components classified as Examination Category B-D, Item Nos. B3.90, B3.110, and B3.140 welds within Relief Request ANO2-ISI-023 pursuant to 10 CFR 50.55a(g)(6)(i). The NRC staffs evaluation focused on: (1) whether a technical justification exists to support the determination that the ASME Code requirement is impractical, (2) whether the imposition of the Code-required inspections would result in a burden to the licensee, and (3) whether the licensees proposed alternative (accepting the reduced inspection coverage in this case) provides reasonable assurance of structural integrity and leak tightness of the subject welds. The NRC staff finds that if these three criteria are met, the requirements of 10 CFR 50.55a(g)(6)(i) (i.e., granting the requested relief will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility) will also be met.
As described in the licensees application, as supplemented, the predominant limitation that prevented the licensees UT to achieve essentially 100 percent coverage of the ASME Code-required volume was the geometric nozzle configuration for subject welds in Examination Category B-D, Item No. B3.90, B3.110, and B3.140. From review of figures 1, 1a, 7, 7a, 8, 8a, and 8b of attachment 1 to Relief Request ANO2-ISI-023, the NRC staff confirmed that each nozzle configuration prevented the licensee from fully scanning the respective welds. Therefore, the NRC staff finds that a technical justification exists to support the determination that achieving essentially 100 percent coverage is impractical.
The licensee stated that making the welds fully accessible for inspection would require replacement or significant design modification to the welds and their associated components.
The NRC staff finds that replacing or reconfiguring the components of the subject welds is the only reasonable means to achieve essentially 100 percent coverage for these welds and that replacement or reconfiguration of the subject welds in Examination Category B-D, Item
Nos. B3.90, B3.110, and B3.140 constitutes a burden on the licensee without a commensurate increase in safety.
The NRC staff considered whether the licensees achieved examination coverage for the subject welds in Examination Category B-D, Item Nos. B3.90, B3.110, and B3.140, provides reasonable assurance of structural integrity and leak tightness of the subject welds based on:
(1) the examination coverage achieved, and (2) the safety significance of unexamined volumes and unachievable coverage (e.g., the presence or absence of known active degradation mechanisms and essentially 100 percent coverage achieved for similar welds in similar environments subject to similar degradation mechanisms).
In evaluating the licensees achieved examination coverage, the NRC staff assessed:
(1) whether the licensee obtained as much coverage as reasonably possible, and (2) the methods used for achieving the reported coverage. From review of the licensees application, as supplemented, the NRC staff verified that:
The welds were examined using the appropriate equipment, ultrasonic modes of propagation, probe angles, frequencies, and scanning directions to obtain maximum coverage.
The coverage was calculated in a reasonable manner.
The personnel and UT procedures utilized for the examination were qualified as required by the ASME Code,Section XI.
The coverage was limited by geometric configuration of the components that limited access to the required examination volume.
No unacceptable indications were identified.
Therefore, the NRC staff found that the licensee made a significant effort to obtain as much coverage as reasonably possible with the ASME Code-required UT. In addition to the coverage analysis described above, the NRC staff evaluated the safety significance of the unexamined volumes of welds and unachievable coverage. Based on its review of the application, the NRC staff verified that the licensees UT has covered, to the extent possible, the regions that are typically susceptible to higher stresses and, therefore, potential degradation. No unacceptable indications were detected in the volumes examined. Therefore, the NRC staff determined that based on the coverage achieved by the qualified UT and the examination of the subject welds to the extent possible, the NRC staff finds it reasonable that if significant service-induced degradation had occurred, evidence of it would have been detected by the examinations that the licensee performed.
In this analysis, the NRC staff also found that, in addition to the required volumetric examinations, the subject welds have received the ASME Code,Section XI, table IWB-2500-1, Examination Category B-P-required system leakage test. Despite reduced coverage of the required examination volume, the NRC staff finds that this inspection will provide additional assurance that any pattern of degradation, if it were to occur, would be detected and the licensee would have sufficient time to take appropriate correction actions.
Therefore, the NRC staff finds that the volumetric examinations performed to the extent possible provide reasonable assurance of structural integrity and leak tightness of the subject welds in Examination Category B-D, Item Nos. B3.90, B3.110, and B3.140. Compliance with the ASME Code requirements for these welds would be a burden on the licensee without a commensurate increase in safety.
4.0 CONCLUSION
As set forth above, the NRC staff determines that it is impractical for the licensee to comply with the ASME Code,Section XI requirements, that the proposed weld examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds, and that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i). Therefore, the NRC staff grants Relief Request ANO2-ISI-023 at ANO-2 for the fourth 10-year ISI interval, which commenced on March 26, 2010, and ended on March 25, 2021.
All other ASME Code,Section XI requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributors: O. Yee, NRR A. Rezai, NRR Date: January 10, 2023
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUESTS ANO2-ISI-024 AND ANO2-ISI-028 REGARDING WELD EXAMINATION COVERAGE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-368
1.0 INTRODUCTION
By letter dated February 24, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22055B120), as supplemented by letter dated July 20, 2022 (ML22201A433), Entergy Operations, Inc. (the licensee) requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components. Relief Requests ANO2-ISI-024 and ANO2-ISI-028 pertain to the examination coverage of Class 1 piping welds in the fourth 10-year inservice inspection (ISI) interval at Arkansas Nuclear One, Unit 2 (ANO-2).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),
ISI program update: Notification of impractical ISI Code requirements, the licensee requested relief from the required examination coverage and to use alternative requirements (if necessary) for ISI of the piping welds on the basis that the ASME Code requirements are impractical.
2.0 REGULATORY EVALUATION
Pursuant to 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice inspection requirements, set forth in ASME Code,Section XI.
Pursuant to 10 CFR 50.55a(g)(4)(ii), Applicable ISI Code: Successive 120-month intervals, inservice examination of components and system pressure tests conducted during successive 120-month inspection intervals must comply with the requirements of the latest edition and addenda of the ASME Code incorporated by reference in paragraph (a) of 10 CFR 50.55a 18 months before start of the 120-month inspection interval (or the optional ASME Code Cases listed in Regulatory Guide (RG) 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, Revision 20 (ML21181A222), when using ASME Code,Section XI, as
incorporated by reference in paragraph (a)(3)(ii) of 10 CFR 50.55a), subject to the conditions listed in paragraph (b) of 10 CFR 50.55a.
Pursuant to 10 CFR 50.55a(b)(2)(xv),Section XI condition: appendix VIII specimen set and qualification requirements, licensees using appendix VIII in the 2001 Edition of the ASME Code may elect to comply with all of the provisions in paragraphs (b)(2)(xv)(A) through (M) of 10 CFR 50.55a. Licensees using editions and addenda after the 2001 Edition through the 2006 Addenda must use the 2001 Edition of appendix VIII and may elect to comply with all the provisions in paragraphs (b)(2)(xv)(A) through (M) of 10 CFR 50.55a, except for paragraph (b)(2)(xv)(F) of 10 CFR 50.55a, which may be used at the licensee's option.
Pursuant to 10 CFR 50.55a(g)(5)(iii), if the licensee determined that conformance with an ASME Code requirement is impractical for its facility, the licensee must notify the U.S. Nuclear Regulatory Commission (NRC) and submit, as specified in 10 CFR 50.4, Written communications, information to support the determinations. Determinations of impracticality in accordance with 10 CFR 50.55a must be based on the demonstrated limitations experienced when attempting to comply with the ASME Code requirements during the ISI interval for which the request is being submitted. Requests for relief made in accordance with 10 CFR 50.55a must be submitted to the NRC no later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought.
Pursuant to 10 CFR 50.55a(g)(6)(i), Impractical ISI requirements: Granting of relief, the Commission will evaluate determinations under paragraph (g)(5) of 10 CFR 50.55a that ASME Code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, will not endanger life or property or the common defense and security, and are otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC to grant the relief requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1
Applicable Code Edition and Addenda
The code of record for the fourth 10-year ISI interval was the 2001 Edition through 2003 Addenda of the ASME Code,Section XI.
The licensee stated that in a safety evaluation dated July 12, 2017 (ML17174B144), the NRC approved use of the 2007 Edition with 2008 Addenda of the ASME Code,Section XI for activities associated with repair/replacement, pressure testing, and nondestructive examination (NDE) during the remainder of the fourth 10-year ISI interval of ANO-2. Therefore, in the 26th (fall 2018) and 27th (spring 2020) refueling outages of the fourth 10-year ISI interval, the licensee performed the pressure testing and NDE activities in accordance with the 2007 Edition with 2008 Addenda of the ASME Code,Section XI. Prior to the 26th (fall 2018) refueling outage in the fourth 10-year ISI interval, the licensee performed the pressure testing and NDE activities in accordance with the 2001 Edition through 2003 Addenda of the ASME Code,Section XI.
3.2 Duration of Relief Request The licensee submitted the subject relief requests for the fourth 10-year ISI interval, which started on March 26, 2010, and ended on March 25, 2021. The licensee stated that the extensions from March 25, 2020 to August 1, 2020, and from August 1, 2020 to March 25, 2021, were applied to the fourth 10-year ISI interval in accordance with ASME Code,Section XI, subsubarticle IWA-2430, Inspection Intervals, and all applicable requirements in subsubarticle IWA-2430 had been met.
3.3 Relief Request ANO2-ISI-024 3.3.1. Components Affected The licensee categorized the ANO-2 reactor vessel control element drive mechanism (CEDM) housing pressure boundary welds as ASME Code,Section XI, table IWB-2500-1, Examination Category B-O, Item No. B14.10. The ANO-2 CEDM housing is shown in figure 1 of attachment 2 to Relief Request ANO2-ISI-024, which contains four pressure boundary welds that are labeled as W, X, Y, and Z. Table 1 of attachment 2 to Relief Request ANO2-ISI-024 provides additional information including component identifications, descriptions, examination methods, limitations, and percent examination coverage obtained.
3.3.2 ASME Code Requirement The ASME Code requirements applicable to Class 1 welds of the ANO-2 reactor vessel CEDM housing originate in ASME Code,Section XI, table IWB-2500-1, Examination Category B-O, Item No. B14.10, which requires a surface examination or a volumetric examination of the pressure-retaining welds in 10 percent of peripheral CEDM housings, as depicted in figure IWB-2500-18, during each 10-year ISI interval. The extent of the required examination coverage is defined to be essentially 100 percent (i.e., greater than 90 percent coverage) by ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 welds,Section XI. This code case has been incorporated by reference into 10 CFR 50.55a via inclusion in RG 1.147, Revision 20.
3.3.3 Impracticality of Compliance The licensee stated that a cooling shroud was designed and installed around the ANO-2 reactor vessel CEDMs, as shown in figures 2 and 3 of attachment 2 to Relief Request ANO2-ISI-024.
This modification impacted access to the peripheral CEDM housing welds to perform the required examination. To gain access to the CEDM housing welds, a significant design modification would have to be made. It was not possible to obtain greater than 90 percent coverage of the ASME Code-required examination of the surface or volume of pressure-retaining welds in 10 percent of peripheral CEDM housings due to access limitation caused by the cooling shroud assembly configuration and interferences. In table 1 and figures 1, 2, 3, 4, 5, and 6 of attachment 2 to the Relief Request ANO2-ISI-024 submittal, the licensee described and illustrated the limitations that prevented the liquid penetrant testing (PT) of the required examination area. A surface examination by eddy current testing or volumetric examination by ultrasonic testing (UT) could not be performed because of limited access and tight space.
The licensee stated that the burden caused by compliance would include major modification of plant components including redesign of the CEDM housing welds and cooling shroud assembly.
3.3.4 Basis for Relief The licensee stated that to comply with the ASME Code-required examination (i.e., essentially 100 percent surface examination coverage of the pressure-retaining welds in 10 percent of peripheral CEDM housings), four pressure-boundary welds (i.e., X, Y, W, and Z) in three CEDM housings must be examined each 10-year ISI interval. The licensee chose the welds in CEDM housings 57, 69, and 80 to inspect. The W and Z welds in each CEDM housing were successfully examined with essentially 100 percent coverage, but no coverage was obtained for the X and Y welds. The licensee performed a supplemental remote visual examination, VT-1, of both X and Y housing welds with no limitations and did not identify any unacceptable indications.
The licensee stated that it performed the PT to the maximum extent possible utilizing personnel qualified and procedures demonstrated in accordance with ASME Code,Section V, Nondestructive Examination. No unacceptable indications were identified in the surface area examined.
The licensee stated that a bare metal visual examination, VE, in accordance with ASME Code Case N-729, Alternative Examination Requirements for PWR [Pressurized-Water Reactor]
Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division1, as mandated by 10 CFR 50.55a(g)(6)(ii) and a visual examination, VT-2, in accordance with ASME Code,Section XI, table IWB-2500-1 of the reactor vessel closure head (RVCH) including the CEDM housings has been performed every refueling outage. No evidence of leakage or relevant conditions have been observed during the performance of the VT-2 or VE.
3.3.5 Proposed Alternative In table 1 of attachment 2 to Relief Request ANO2-ISI-024, the licensee reported the percent coverage of the required examination area achieved for the welds W, X, Y, and Z in CEDM housings 57, 69, and 80. Table 1 below shows the percent coverage obtained for each CEDM housing weld including the combined percent coverage for each CEDM housing.
Table 1-ASME Code Coverage for Examination Category B-O, Item No. B14.10, CEDM Housing Welds Component ID Housing Welds in each CEDM, as Shown in Figure 1 Coverage Obtained in each Housing Weld, as Shown in Figure 1 (Percent)
Total Coverage Obtained (Percent)
CEDM-057 W, X, Y, Z 100, 0, 0, 100 50 CEDM-069 W, X, Y, Z 100, 0, 0, 100 50 CEDM-080 W, X, Y, Z 100, 0, 0, 100 50 The licensee proposed the above alternative coverage in lieu of the required essentially 100 percent coverage.
3.4
NRC Staff Evaluation
The NRC staff evaluated Relief Request ANO2-ISI-024 pursuant to 10 CFR 50.55a(g)(6)(i). The NRC staffs evaluation focused on: (1) whether a technical justification exists to support the
determination that the ASME Code requirement is impractical, (2) whether the imposition of the Code-required inspections would result in a burden to the licensee, and (3) whether the licensees proposed alternative (accepting the reduced inspection coverage in this case) provides reasonable assurance of structural integrity and leak tightness of the subject welds.
The NRC staff finds that if these three criteria are met that the requirements of 10 CFR 50.55a(g)(6)(i), (i.e., granting the requested relief will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility) will also be met.
As described in the licensees application, as supplemented, the predominant limitation that prevented the licensees PT from achieving essentially 100 percent coverage of the ASME Code-required area was access limitation caused by the cooling shroud assembly. From review of figures 1 through 6 in attachment 2 to ANO2-ISI-024, the NRC staff confirmed that access to the CEDM housing welds X and Y was not possible. Other examination techniques such as eddy current testing or UT were not practical due to access limitations. Therefore, the NRC staff finds that a technical justification exists to support the determination that achieving essentially 100 percent coverage is impractical.
The licensee stated that making the CEDM housing welds X and Y accessible for inspection would require replacement or significant design modification to the welds and their associated components. The NRC staff finds that replacing or reconfiguring the components of the subject welds are the only reasonable means to achieve the required examination coverage of these welds and that replacement or reconfiguration of the CEDM housing welds and/or cooling shroud assembly constitutes a burden on the licensee without a commensurate increase in safety.
The NRC staff considered whether the licensees proposed alternative provided reasonable assurance of structural integrity and leak tightness of the subject CEDM housing welds based on: (1) the examination coverage achieved, and (2) safety significance of unexamined areas and unachievable coverage (e.g., the presence or absence of known active degradation mechanisms and essentially 100 coverage achieved for similar welds in similar environments subject to similar degradation mechanisms).
In evaluating the licensees proposed alternative coverage, the NRC staff assessed whether the licensee obtained as much coverage as reasonably possible, and the methods used for achieving the reported coverage. From review of the licensees application, the NRC staff verified that:
The welds were examined by PT using the appropriate equipment and procedures to obtain maximum coverage.
The coverage was calculated in a reasonable manner.
The personnel and PT procedures utilized for the surface examination were qualified as required by the ASME Code,Section XI.
The examination coverage of the CEDM housing welds X and Y was limited due to access to these welds. However, the 100 percent coverage of the required examination area was obtained for the CEDM housing welds W and Z.
No unacceptable indications were identified in the area examined by PT.
Therefore, the NRC staff found that the licensee made a significant effort to obtain as much coverage as reasonably possible with the ASME Code-required PT.
In addition to the coverage analysis described above, the NRC staff evaluated the safety significance of the unexamined areas of welds and unachievable coverage. From review of licensees application and table 1 in attachment 2 to Relief Request ANO2-ISI-024, the NRC staff verified that:
The licensee performed a supplemental remote visual examination, VT-1, on the X and Y CEDM housing welds with no unacceptable indications identified.
A visual examination, VT-2, performed in accordance with the ASME Code,Section XI, table IWB-2500-1 of the RVCH and the CEDM housings every refueling outage did not identify any evidence of leakage from the CEDM housing welds.
A bare metal visual examination, VE, of the RVCH performed every refueling outage in accordance with ASME Code Case N-729 as part of augmented inspections mandated by 10 CFR 50.55a(g)(6)(ii) did not observe any evidence or relevant conditions indicating leakage from the CEDM housing welds.
Therefore, the NRC staff determined that based on the coverage achieved by the qualified PT and the additional VT-1, VT-2, and VE visual examinations, it is reasonable to conclude that if significant service-induced degradation had occurred in the CEDM housing welds, evidence of it would have been detected by the examinations that the licensee performed.
Therefore, the NRC staff finds that the surface examinations performed to the extent possible provide a reasonable assurance of structural integrity and leak tightness of the reactor vessel CEDM housing pressure boundary welds. Compliance with the ASME Code requirements for the CEDM housing welds would be a burden on the licensee without a commensurate increase in safety.
3.5 Relief Request ANO2-ISI-028 3.5.1 Components Affected ASME Code Case N-716-1, Alternative Piping Classification and Examination Requirements,Section XI, Division 1, table 1, Examination Category R-A, Item No. R1.11 welds (i.e., subject to thermal fatigue), R1.16 welds (i.e., subject to intergranular stress corrosion cracking (IGSCC) or transgranular stress corrosion cracking (TGSCC)), and R1.20 welds (i.e., not subject to a degradation mechanism) are affected. ASME Code Case N-716-1 has been incorporated by reference into 10 CFR 50.55a via inclusion in RG 1.147, Revision 20. The licensee identified eleven ASME Code Class 1 welds in three piping systems as follows:
Four welds in the chemical and volume control system (CVCS) piping: 37-028,37-029, 37-030, and 40-001.
Five welds in the reactor coolant system (RCS) piping: 43-031,43-033, 28-041,28-042, and 29-056.
Two welds in the safety injection (SI) system piping: 21-007 and 21-001A.
Table 1 of attachment 6 to Relief Request ANO2-ISI-028 contains additional information about the affected welds, which include the component identifications, descriptions, examination methods, limitations, materials of construction, and the percent examination coverage obtained.
3.5.2 ASME Code Requirement The ASME Code requirements applicable to Class 1 welds originate in ASME Code,Section XI, table IWB-2500-1, Examination Categories B-F and B-J. The licensee utilized alternative risk-informed ISI program in accordance with ASME Code Case N-716-1 in lieu of the ASME Code requirements. The requirements of ASME Code Case N-716-1, table 1, Examination Category R-A are as follows: Item Nos. R1.11, 16, and 20 welds shall be subjected to volumetric examination, and the extent of examination volume is depicted in ASME Code,Section XI, figures IWB-2500-8(c), -9, -10, and -11.
Note (3) of table 1 in ASME Code Case N-716-1 states, in part, that the extent of examination is essentially 100 percent (i.e., greater than 90 percent) coverage of the required examination volume or area.
Note (10) of table 1 in ASME Code Case N-716-1 states that the visual examination, VT-2, shall be conducted according to ASME Code,Section XI, Examination Category B-P during a system pressure test.
3.5.3 Impracticality of Compliance The licensee stated that it was not possible to obtain greater than 90 percent of the ASME Code required examination volume due to the geometric configuration and material type of the components, which limited scan paths of the ultrasonic probes. The UT was a single-sided examination for all welds except two (welds28-041 and 28-042). In table 1 and figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 of attachment 6 to Relief Request ANO2-ISI-028, the licensee described and illustrated the limitations that prevented ultrasonic scanning of the pipe-to-valve, tee-to-pipe, elbow-to-valve, valve-to-pipe, tee-to-reducer, elbow-to-tee, pipe-to-tree, and elbow-to-safe end welds. The licensee stated that the burden caused by compliance would include major modification of plant components, which would include redesign and replacement of the welds and associated components.
3.5.4 Basis for Relief The licensee stated that it scanned each weld in the axial and circumferential directions using the ultrasonic probe angles of 45, 60, and/or 70 degrees (i.e., insonification angles) and the ultrasonic wave modes (i.e., refracted shear and longitudinal waves) as shown in table 1 of attachment 6 to Relief Request ANO2-ISI-028. The UT was performed to the maximum extent possible utilizing personnel qualified and procedures demonstrated in accordance with ASME Code,Section XI, appendix VIII, Performance Demonstration for Ultrasonic Examination Systems, Supplement 2, Qualification Requirements for Wrought Austenitic Piping Welds. No unacceptable indications were identified in the volume examined.
The licensee stated that although it extended the beam path into the volume on the opposite side of the weld centerline (far-side) to examine to the extent practical the other side of the weld, no credit was claimed for this percent coverage obtained and was not included in the percent
coverage reported in table 1 of attachment 6 to Relief Request ANO2-ISI-028. No unacceptable indications were identified in the far-side volume examined.
The licensee stated that the welds had been subjected to the ASME Code system leakage test and associated visual examination, VT-2, in the fourth 10-year ISI interval. No through-wall leak was identified in any of the welds examined.
3.5.5 Proposed Alternative In table 1 of attachment 6 to Relief Request ANO2-ISI-028, the licensee reported the percent coverage achieved for each weld examined. Table 1 below shows the percent coverage obtained.
Table 1. ASME Code Coverage for Examination Category R-A Welds System Component ID Coverage Obtained (Percent)
CVCS37-028 63 CVCS37-029 50 CVCS37-030 50 CVCS40-001 50 RCS43-031 50 RCS43-033 50 RCS28-041 84.8 RCS28-042 88 RCS29-056 50 SI 21-007 50 SI 21-001A 50 The licensee proposed the above alternative coverage in lieu of the required essentially 100 percent coverage.
3.6
NRC Staff Evaluation
The NRC staff evaluated Relief Request ANO2-ISI-028 pursuant to 10 CFR 50.55a(g)(6)(i). The NRC staffs evaluation focused on: (1) whether a technical justification exists to support the determination that the ASME Code requirement is impractical, (2) whether the imposition of the Code-required inspections would result in a burden to the licensee without a commensurate increase in safety, and (3) whether the licensees proposed alternative (accepting the reduced inspection coverage in this case) provides reasonable assurance of structural integrity and leak tightness of the subject welds. The NRC staff finds that if these three criteria are met that the requirements of 10 CFR 50.55a(g)(6)(i), (i.e., granting the requested relief will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility) will also be met.
As described in the licensees application and shown in figures 1 through 11 of attachment 6 to Relief Request ANO2-ISI-028, the predominant limitation that prevented the licensees UT from achieving essentially 100 percent coverage of the ASME Code-required volume were the design and configuration of the weld and associated components. As an example, pipe-to-valve,
tee-to-pipe, elbow-to-valve, and elbow-to-safe end weld configurations restricted the UT to single-sided scanning only. Although tee-to-reducer and elbow-to-tee weld configurations were examined by the dual-sided scanning, the intrados of the tee limited the required examination coverage. Radiographic testing was not practical due to the weld configurations. Therefore, the NRC staff finds that a technical justification exists to support the determination that achieving essentially 100 percent coverage is impractical.
The licensee proposed that making the weld accessible for inspection from both sides would require replacement or significant modification of the weld and associated components. The NRC staff finds that replacing or reconfiguring the components is the only reasonable means to achieve the required coverage of these welds, and that replacement or reconfiguration of the components constitutes a burden on the licensee without a commensurate increase in safety.
The NRC staff considered whether the licensees proposed alternative provided reasonable assurance of structural integrity and leak tightness of the welds in table 1 based on: (1) the examination coverage achieved, and (2) the safety significance of unexamined areas and unachievable coverage (e.g., the presence or absence of known active degradation mechanisms and essentially 100 coverage achieved for similar welds in similar environments subject to similar degradation mechanisms).
In evaluating the licensees proposed alternative coverage, the NRC staff assessed whether the licensee obtained as much coverage as reasonably possible, and the methods used for achieving the reported coverage. From the review of the application, as supplemented, the NRC staff verified that:
The welds were examined using the appropriate equipment, ultrasonic modes of propagation, probe angles, frequencies, and scanning directions to obtain maximum coverage.
The coverage was calculated in a reasonable manner.
The personnel and UT procedures utilized for the examination were qualified as required by the ASME Code,Section XI.
The coverage was limited by geometric configuration of the components that limited access to the required examination volume.
No unacceptable indications were identified in the volume scanned by UT.
Therefore, the NRC staff found that the licensee made a significant effort to obtain as much coverage as reasonably possible with the ASME Code-required UT.
In addition to the coverage analysis described above, the NRC staff evaluated the safety significance of the unexamined areas of welds and unachievable coverage. From review of figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and table 1 of attachment 6 to Relief Request ANO2-ISI-028, the NRC staff verified that:
The licensees UT covered, to the extent possible, the regions (i.e., the weld root and the heat affected zone of the base material near the inner diameter surface of the joint) that are typically susceptible to higher stresses and, therefore, potential degradation.
For the stainless steel welds, the coverage obtained was limited to the volume up to the weld centerline (near-side). The NRC staff notes that claiming coverage for the volume on the opposite side of the weld centerline (far-side) requires meeting the 10 CFR 50.55a(b)(2)(xv)(A)(2) far-side UT qualifications, which has not been demonstrated in any qualification attempts to date. The licensees UT inspected the far-side volume by the Best Effort examination and did not identify any unacceptable indications in the volume scanned. The licensee did not take credit for the coverage achieved from the Best Effort examination.
Therefore, the NRC staff determined that based on the coverage achieved by the qualified UT to the extent possible, the supplemental Best Effort examinations, and the examination of the weld root and its heat affected zone to the extent possible, it is reasonable to conclude that if significant service induced degradation had occurred, evidence of it would have been detected by the examinations that the licensee performed.
In this analysis, the NRC staff also found that, in addition to the required volumetric examinations, the subject welds received the ASME Code,Section XI, table IWB-2500-1, Examination Category B-P required system leakage test and associated visual examination, VT-2, every refueling outage. Despite reduced coverage of the required examination volume, the NRC staff finds that this inspection will provide additional assurance that any pattern of degradation, if it were to occur, would be detected and the licensee would have sufficient time to take appropriate correction actions.
Therefore, the NRC staff finds that the volumetric examinations performed to the extent possible provide reasonable assurance of structural integrity and leak tightness of the subject welds.
Compliance with the ASME Code requirements for these welds would be a burden on the licensee without a commensurate increase in safety.
4.0 CONCLUSION
As set forth above, the NRC staff determines that it is impractical for the licensee to comply with the ASME Code,Section XI requirements, that the proposed weld examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds, and that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i). Therefore, the NRC staff grants Relief Requests ANO2-ISI-024 and ANO2-ISI-028 at ANO-2 for the fourth 10-year ISI interval which commenced on March 26, 2010, and ended on March 25, 2021.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: A. Rezai, NRR Date: January 10, 2023
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUESTS ANO2-ISI-025 AND ANO2-ISI-026 INSERVICE INSPECTION IMPRACTICALITY FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-368
1.0 INTRODUCTION
By letter dated February 24, 2022 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML22055B120), as supplemented by letter dated July 20, 2022 (ML22201A433), Entergy Operations, Inc. (the licensee) submitted relief requests ANO2-ISI-025 and ANO2-ISI-026 for U.S. Nuclear Regulatory Commission (NRC) review and approval for the fourth 10-year Inservice Inspection (ISI) interval for Arkansas Nuclear One, Unit 2 (ANO2).
Relief is requested due to the impracticality of satisfying a specific requirement of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for lnservice Inspection of Nuclear Power Plant Components, for the fourth 10-year ISI interval.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),
the licensee requested relief on the basis that achieving the ASME Code required examination coverage for the components and welds identified in Relief Requests ANO2-ISI-025 and ANO2-ISI-026 are impractical.
2.0 REGULATORY EVALUATION
The NRC staff considered the following regulatory requirements and guidance in its evaluation.
Pursuant to 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, components that are classified as ASME Code Class 1, 2, and 3 must meet the requirements, except the design and access provisions and preservice examination requirements, as set forth in Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(a) 12 months prior to the start of the 120-month interval, subject to the conditions listed in 10 CFR 50.55a(b) throughout the service life of a pressurized water-cooled nuclear power facility.
The regulation at 10 CFR 50.55a(g)(5)(iv), ISI program update: Schedule for completing impracticality determinations, states that:
Where the licensee determines that an examination required by Code edition or addenda is impractical, the basis for this determination must be submitted for NRC review and approval not later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought.
The regulation at 10 CFR 50.55a(g)(6)(i), Impractical ISI requirements: Granting of relief, states that:
The Commission will evaluate determinations under paragraph (g)(5) of
[10 CFR 50.55a], that [ASME] code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, will not endanger life or property or the common defense and security, and are otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC to grant the relief requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1 Licensees Relief Request 3.1.1 ASME Code Components Affected ANO2-ISI-025 ASME Code Class 2, Examination Category C-A, Item No. C1.10, Shell Circumferential Weld.
Table 1. ANO2-ISI-025 Subject Welds Item No.
Comp. ID Item Description C1.10 49-001 Channel Flange to Channel Shell Weld ANO2-ISI-026 ASME Code Class 2, Examination Category C-B, Item No. C2.21, Pressure Retaining Nozzle Welds in Vessel Table 2. ANO2-ISI-026 Subject Welds Item No.
Comp. ID Item Description C2.21 04-002 Steam Generator B Feedwater Nozzle to Shell Weld C2.21 48-013 2E35A Shutdown Cooling Heat Exchanger Channel Inlet Nozzle C2.21 48-014 2E35A Shutdown Cooling Heat Exchanger Channel Outlet Nozzle
3.1.2 Applicable Code Edition and Addenda The fourth 10-year interval of the ANO-2 ISI program started on March 26, 2010, and ended on March 25, 2021. The 2001 Edition with 2003 Addenda of ASME Code,Section XI was applied for the first two periods within this interval. The licensee applied and was approved to use the 2007 Edition with 2008 Addenda of ASME Code,Section XI for the third and fourth periods.
3.1.3 Applicable Code Requirement ANO2-ISI-025 The examination requirement for Examination Category C-A, Item No. C1.10, per ASME Code,Section XI, table IWC-2500-1 requires a volumetric examination of essentially 100 percent of the weld length for shell-circumferential welds as shown in ASME Code,Section XI, figure IWC-2500-1.
In addition, the licensee has adopted the NRC-approved ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds,Section XI, Division 1, which defines essentially 100 percent as greater than 90 percent coverage of the examination volume or surface area, as applicable. This code case has been incorporated by reference into 10 CFR 50.55a via inclusion in Regulatory Guide (RG) 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, Revision 20.
ANO2-ISI-026 The examination requirement for Examination Category C-B, Item No. C2.21, per ASME Code,Section XI, table IWC-2500-1 requires a volumetric examination of the weld length for nozzle-to-shell welds as shown in ASME Code,Section XI, figure IWC-2500-4(a), (b), or (d).
In addition, the licensee has adopted the NRC-approved ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds,Section XI, Division 1, which defines essentially 100 percent as greater than 90 percent coverage of the examination volume or surface area, as applicable. This code case has been incorporated by reference into 10 CFR 50.55a via inclusion in RG 1.147, Revision 20.
3.1.4 Licensees Reason for Request The licensee was unable to meet the Code exam requirements due to configuration/geometry limitations to the ultrasonic testing (UT). The limitations were illustrated in figures 1 and 1a of ANO2-ISI-025 and ANO2-ISI-026. The subject welds would have to be modified to perform a full Code required UT examination of the subject welds.
3.1.5 Licensees Proposed Alternative No alternative was proposed.
3.1.6 Duration of the Request The licensee submitted this request for the fourth 10-year ISI interval. The fourth ISI interval for ANO-2 ended on March 25, 2021.
3.2
NRC Staff Evaluation
The licensee has requested relief from the volumetric coverage requirements described in ASME Code,Section XI and its ISI program because the design configuration of the subject welds limits access for volumetric inspection. In order to effectively increase the examination coverage to meet ASME Code requirements, the components would require significant modifications.
The UT examination of the C1.10 channel flange-to-channel shell weld (49-001) was performed from the shell side only. The licensee has performed UT examination on this weld to the maximum extent feasible. The C1.10 channel flange to channel shell weld is near the flange itself, precluding dual-sided examination to geometric interference. The licensee documented the impediment to the examination in several diagrams, convincingly illustrating the problematic geometry surrounding the subject weld.
Similarly, the three subject C2.21 welds (04-002,48-013, and 48-014) were all single-sided examinations due to geometric constraints. For weld 04-002, the constraint consisted of an insulation bracket ring. For weld 48-013, the geometric constraint consisted of the nozzle configuration. The licensee has performed UT examination on these welds to the maximum extent feasible. The licensee documented the impediments to the examinations in several diagrams, convincingly illustrating the problematic geometry surrounding the subject weld.
Evidence of significant service-induced degradation in the welds, if it were to occur, would likely be detected in the portions of the welds that were examined, because the examined volume is the same material as the unexamined volume, is under the same loading conditions, and is exposed to the same reactor coolant environment. Based on operating experience at similar locations to date, the NRC staff finds that the likelihood that a degradation mechanism unique to these welds and located only in the unexamined portion of the welds is acceptably low. Because of the above, the NRC staff determined that the coverages achieved represent a sufficient sample, such that, if significant degradation were present in the welds, it is likely that the degradation would have been detected.
The licensee stated that it would be a burden to meet the ASME Code-required 100 percent volumetric examination coverage for the subject welds due to their design. The NRC staff concludes that relieving the nature of the impediments would require significant burden and would be impractical. Thus, Relief Requests ANO2-ISI-025 and ANO2-ISI-026 meet the requirements for relief for impracticality described in the regulations at 10 CFR 50.55a(g)(6)(i).
Therefore, the NRC staff concludes that modifying the subject components to increase coverage would be impractical. Based on the volumetric coverage obtained, the resistant material, and examination results, the NRC staff concludes that there is reasonable assurance of structural integrity of the subject component. In light of the above, the NRC staff concludes that relief should be granted from further action in examining these welds for the ANO fourth 10-year ISI interval because the coverage achieved was as high as practical, this coverage provides reasonable assurance that no general degradation mechanism is active within the weld, and that to improve coverage would require undue burden.
4.0 CONCLUSION
As set forth above, the NRC staff determines that it is impractical for the licensee to comply with the ASME Code,Section XI requirements, that the proposed weld examination coverage
provides reasonable assurance of structural integrity and leak tightness of the subject welds, and that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i). Therefore, the NRC staff grants Relief Requests ANO2-ISI-025 and ANO2-ISI-026 for the fourth 10-year ISI interval, which commenced on March 26, 2010, and ended on March 25, 2021.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: D. Widrevitz, NRR Date: January 10, 2023
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST ANO2-ISI-027 INSERVICE INSPECTION IMPRACTICALITY FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT NO. 2 DOCKET NO. 50-368
1.0 INTRODUCTION
By letter dated February 24, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22055B120), as supplemented by letter dated July 20, 2022 (ML22201A433), Entergy Operations, Inc. (Entergy), submitted Relief Request (RR)
ANO2-ISI-027 to the U.S. Nuclear Regulatory Commission (NRC) for the fourth 10-year inservice inspection (ISI) interval at Arkansas Nuclear One, Unit 2 (ANO2). With its submittal of ANO2-ISI-027, the licensee requested relief from the examination coverage requirements of Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),
ISI program update: Notification of impractical ISI Code requirements, the licensee requested relief on the basis that achieving the ASME Code-required surface examination coverage for the subject weld in ANO2-ISI-027 is impractical.
2.0 REGULATORY EVALUATION
Pursuant to 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, components (including supports) that are classified as ASME Code Class 1, 2, and 3 must meet the requirements in 10 CFR 50.55a throughout the service life of a pressurized water-reactor. The exception is the design and access provisions and preservice examination requirements set forth in Section XI of editions and addenda of the ASME Code that become effective subsequent to editions specified in paragraphs (g)(2) and (3) of 10 CFR 50.55a, which are incorporated by reference in paragraph (a)(1)(ii) of 10 CFR 50.55a to the extent practical within the limitations of design, geometry, and materials of construction of the components.
Pursuant to 10 CFR 50.55a(g)(4)(ii), Applicable ISI Code: Successive 120-month intervals, in-service examination of components and system pressure tests conducted during successive 120-month inspection intervals must comply with the requirements of the latest edition and
addenda of the ASME Code incorporated by reference in paragraph (a) of 10 CFR 50.55a 18 months before the start of the 120-month inspection interval (or the optional ASME Code Cases listed in NRC Regulatory Guide (RG) 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI Division 1 (ML21181A222), when using ASME Code,Section XI, as incorporated by reference in paragraph (a)(3)(ii) of 10 CFR 50.55a), subject to the conditions listed in paragraph (b) of 10 CFR 50.55a.
Pursuant to 10 CFR 50.55a(g)(5)(iii), if the licensee has determined that conformance with a ASME Code requirement is impractical for its facility, the licensee must notify the NRC and submit, as specified in 10 CFR 50.4, Written communications, information to support the determinations. Determinations of impracticality in accordance with 10 CFR 50.55a(g)(5)(iii) must be based on the demonstrated limitations experienced when attempting to comply with the ASME Code requirements during the ISI interval for which the request is being submitted.
Requests for relief made in accordance with 10 CFR 50.55a(g)(5)(iii) must be submitted to the NRC no later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought.
Pursuant to 10 CFR 50.55a(g)(6)(i), Impractical ISI requirements: Granting of relief, the Commission will evaluate determinations under paragraph (g)(5) of 10 CFR 50.55a that ASME Code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, will not endanger life or property or the common defense and security, and are otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC to grant the relief requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1 Summary of Request The licensees relief request in ANO2-ISI-027 is associated with ASME Code Class 2 integral attachments for vessels, piping, pumps, and valves for ANO-2s fourth 10-year ISI interval.
The licensee indicated that for the subject weld in ANO2-ISI-027, it was impractical to meet the ASME Code-required examination coverage. Specifically, due to the configuration of integral attachment in ANO2-ISI-027 and associated hanger strap, access to the weld ends and surrounding base material examination is limited. The licensee stated that it is impractical to obtain greater examination coverage on these areas and to obtain additional coverage would necessitate modification and/or replacement of the component. Therefore, pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief on the basis that achieving the ASME Code-required examination coverage for the subject component in ANO2-ISI-027 is impractical.
The ASME Code of record at ANO-2 for the fourth 10-year ISI interval is the 2001 Edition through the 2003 Addenda of ASME Code,Section XI. The fourth 10-year ISI interval at ANO-2 began on March 26, 2010, and ended on March 25, 2021. Additionally, the licensee indicated that ANO-2 adopted ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds,Section XI, Division 1, which defines essentially 100 percent, as greater than 90 percent coverage of the examination volume or surface area, as applicable. ASME
Code Case N-460 provides NRC-approved alternatives that can be used by licensees, as referenced in Regulatory Guide 1.147, Revision 20, Inservice Inspection Code Case Acceptability.
3.2 Examination Category C-C, Welded Attachments for Vessels, Piping, Pumps, and Valves 3.2.1 Applicable ASME Code Requirements The examination requirement for Examination Category C-C, Item No. C3.10 is delineated in table IWC-2500-1, and requires the surface examination depicted in figure IWC-2500-5. Table 1 below provides a summary of the licensees examination of the Examination Category C-C weld for which the licensee is seeking relief and shows the weld examination coverage of 64 percent achieved by the licensee.
Table 1 - Examination Category C-C Welds with Limited Surface Examination Coverage Item No.
Component Identification and System Limitation/Coverage Materials Examination Results C3.10 04-009 - Steam Generator B South Key Bracket Component configuration and limited access to the lower portion of bracket due to permanent insulation support / 64%
coverage Vessel and Bracket -
Carbon Steel Rounded indications (weld porosity) were noted that were acceptable to construction code and ASME Section XI 3.2.2 Licensees Reason for Request The licensee explained that the configuration of this component is four 5/8-inch x 1-inch x 1-inch lugs, placed 4 1/16 inches apart end to end in pairs at 0 degrees and 180 degrees on the vertical pipe. The lugs are integrally welded to the pipe with full penetration welds. The two piece 4-inch wide hanger strap is positioned and bolted between the end to end lugs, contacting the upper lugs, which support the vertical pipe. ASME Code examination of this type of integral attachment weld requires a surface examination technique of the weld crown surface and 0.5 inches of base material on either side of the weld toes. The licensee stated that due to the configuration of this integral attachment and associated hanger strap, access to the weld ends and surrounding base material for examination purposes is limited. In order to perform additional or alternative ASME Code examinations, modification and/or replacement of the component would be necessary.
3.3 NRC Staff Evaluation of Examination Category C-C Welds The NRC staff reviewed the licensees pictures and figures for the steam generator B south key bracket (Component ID No.04-009) showing the location of the weld, the limitations of the examination due to the configuration of this integral attachment and associated hanger strap, and the coverage plot for the surface examination. This figure detailed the areas for which examination coverage to this component was possible due to accessibility. Based on its review, the NRC staff finds that the redesign of the steam generator B south key bracket (Component ID No.04-009) to obtain examination coverage of greater than 90 percent of the required code
examination area is impractical due to the extensive effort that would be required to modify or replace the component. The NRC staff finds that replacing or reconfiguring the components of the subject welds is the only reasonable means to achieve essentially 100 percent coverage for this weld and that replacement or reconfiguration of the subject weld for the steam generator B south key bracket (component ID# 04-009) constitutes a burden on the licensee without a commensurate increase in safety.
In evaluating the licensees achieved examination coverage, the NRC staff assessed whether the licensee obtained as much coverage as reasonably possible and the manner in which the licensee reported the coverage achieved. From review of the licensees application, the NRC staff verified that:
The welds were examined using the appropriate methods to obtain maximum coverage.
The coverage was calculated in a reasonable manner.
The personnel and procedures utilized for the examination were qualified as required by the ASME Code,Section XI.
The coverage was limited by geometric configuration of the components that limited access to the required examination area.
No unacceptable indications were identified.
Therefore, the NRC staff found that the licensee made a significant effort to obtain as much coverage as reasonably possible with the ASME Code-required surface examination. In addition to the coverage analysis described above, the NRC staff evaluated the safety significance of the unexamined area of the welds and unachievable coverage. Based on its review of the licensees application, the NRC staff verified that the licensees surface examination was performed, to the extent possible and there were no unacceptable indications detected in the examined weld length. Therefore, the NRC staff determined that based on the coverage achieved by the qualified personnel and the examination of the subject welds to the extent possible, the staff finds it reasonable that if significant service-induced degradation had occurred, evidence of it would have been detected by the examinations that the licensee performed.
Based on its review of the subject Examination Category C-C, Item No. C3.10, weld at ANO-2, the NRC staff finds that it is impractical to meet the ASME Code-required examination coverage for the subject weld due to the design configuration of the subject component. The NRC staff also determined that the examinations performed, despite the limited coverage obtained by the licensee, provide reasonable assurance of the structural integrity for the subject component weld. Furthermore, the examination performed on the available surface area of the subject weld would detect the presence of generic degradation, if it existed; hence, the NRC staff finds that the risk associated with granting the requested relief would be very low. Therefore, the NRC staff finds the licensees request acceptable.
4.0 CONCLUSION
As set forth above, the NRC staff determines that it is impractical for the licensee to comply with the ASME Code,Section XI requirements, that the proposed weld examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds,
and that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i). Therefore, the NRC staff grants Relief Request ANO2-ISI-027 for the fourth 10-year ISI interval, which commenced on March 26, 2010, and ended on March 25, 2021.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: O. Yee, NRR Date: January 10, 2023
- by email OFFICE NRR/DORL/LPL4/PM*
NRR/DORL/LPL4/PM*
NRR/DORL/LPL4/LA*
NAME TByrd TWengert PBlechman DATE 1/5/23 1/5/23 1/5/2023 OFFICE NRR/DNRL/NVIB/BC*
NRR/DNRL/NVIB/BC(A)*
NRR/DNRL/NPHP/BC*
NRR/DORL/LPL4/BC*
NAME ABuford DWidrevitz MMitchell JDixon-Herrity DATE 10/31/22 11/9/22 9/27/22 10/25/22 01/10/23