ML23054A290
| ML23054A290 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 03/13/2023 |
| From: | David Wrona Plant Licensing Branch II |
| To: | Jim Barstow Tennessee Valley Authority |
| Green K | |
| References | |
| EPID L-2022-LLR-0049 | |
| Download: ML23054A290 (1) | |
Text
March 13, 2023 Mr. James Barstow Vice President, Nuclear Regulatory Affairs and Support Services Tennessee Valley Authority 1101 Market Street, LP 4A-C Chattanooga, TN 37402-2801
SUBJECT:
BROWNS FERRY NUCLEAR PLANT, UNIT 2 - REQUEST FOR RELIEF FROM THE REQUIREMENTS OF THE ASME BOILER AND PRESSURE VESSEL CODE REGARDING WELD EXAMINATION COVERAGE (EPID L-2022-LLR-0049)
Dear Mr. Barstow:
By letter dated May 24, 2022, the Tennessee Valley Authority (TVA, the licensee) submitted a request to the U. S. Nuclear Regulatory Commission (NRC) for relief from certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code,Section XI requirements at Browns Ferry Nuclear Plant (Browns Ferry), Unit 2.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),
TVA requested relief and to use alternative requirements for inservice inspection (ISI) items on the basis that the code requirement is impractical.
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluations, that granting relief is authorized by law, 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 of the regulatory requirements set forth in the regulations at 10 CFR 50.55a(g)(5)(iii). Therefore, the NRC staff grants relief from the ASME BPV Code examination requirements for the welds included in BFN-2-ISI-003 for Browns Ferry, Unit 2, for the fourth 10-year ISI interval, which began on May 11, 2011, and ended on May 24, 2021.
J. Barstow All other ASME BPV Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
If you have any questions, please contact Ms. Kimberly Green at 301-415-1627 or via email at Kimberly.Green@nrc.gov.
Sincerely, Digitally signed by David J.
David J. Wrona Date: 2023.03.13 13:34:59 Wrona -04'00' David J. Wrona, Branch Chief Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-260
Enclosure:
Safety Evaluation cc: Listserv
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST BFN-2-ISI-003 REGARDING WELD EXAMINATION COVERAGE TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-260
1.0 INTRODUCTION
By letter dated May 24, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22144A138), the Tennessee Valley Authority (TVA or the licensee),
submitted Relief Request BFN-2-ISI-003 to the U.S. Nuclear Regulatory Commission (NRC or Commission) for the fourth 10-year inservice inspection (ISI) interval at Browns Ferry Nuclear Plant (Browns Ferry), Unit 2. 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 BPV Code), applicable to certain ASME Code Class 1 component welds.
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 BPV Code-required volumetric examination coverage for the subject welds in Relief Request BFN-2-ISI-003 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, Class 2, and Class 3 must meet the requirements, except design and access provisions and preservice examination requirements set forth in Section XI of editions and addenda of the ASME BPV 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 Enclosure
Acceptability, ASME Section XI, Division 1, when using ASME BPV 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), ISI Program Update: Notification of impractical ISI Code requirements, 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, 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 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 10 CFR 50.55a(g)(5) that ASME BPV 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 Relief Request BFN-2-ISI-003 is for multiple ASME BPV Code Class 1 component welds associated with ASME BPV Code, Examination Categories B-D and R-A, for Browns Ferry, Unit 2. The licensee stated that for the subject welds in Relief Request BFN-2-ISI-003, it was impractical to meet the ASME BPV Code-required examination coverage. Specifically, due to component design configurations or interference by other items, it was not possible to perform examinations to the extent required by the ASME BPV Code.
The licensee stated that using radiography as an alternative would result in numerous work-related stoppages and increased radiation exposure due to the shutdown and startup of other work in the areas. The licensee stated that water may need to be drained from some systems or components where radiography is performed, which increases the radiation dose rates over a much broader area than the weld being examined. Therefore, the licensee determined there is significant impracticality associated with the performance of weld or area modifications or the use of radiography in order to increase the examination coverage. Additionally, the licensee indicated that it performed the ASME BPV Code-required examinations to the maximum extent possible. Due to design limitations, there are no viable alternative volumetric examination techniques currently available to increase the coverage.
Therefore, pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief on the basis that achieving the ASME BPV Code-required examination coverage for the subject components in BFN-2-ISI-003 is impractical.
During the Browns Ferry, Unit 2 fourth 10-year ISI interval, the applicable ASME Code is ASME Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, 2004 Edition, subject to the limitations and modifications of 10 CFR 50.55a(b)(2). The Appendix VIII requirements and use of the performance demonstration initiative (PDI) requirements at Browns Ferry, Unit 2 were in accordance with the ASME Code,Section XI, 2004 Edition, as modified by 10 CFR 50.55a(b)(2) for the limited examinations contained in this request.
The licensee cited the following ASME Code cases, which are approved or conditionally approved for use in Regulatory Guide (RG) 1.147, Revision 20, Inservice Inspection Code Case Acceptability (ML21181A222):
ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds,Section XI, Division 1. This Code Case defines essentially 100 percent, as greater than 90 percent coverage of the examination volume or surface area, as applicable.
ASME Code Case N-648-1, Alternative Requirements for Inner Radius Examination of Class 1 Reactor Vessel Nozzles,Section XI, Division 1, for Item Number B3.100 components.
ASME Code Case N-613-1, Ultrasonic Examination of Full Penetration Nozzles in Vessels, Examination Category B-D, Item Nos. B3.10 and B3.90, Reactor Nozzle-To-Vessel Welds, Figs. IWB-2500-7(a), (b), and (c),Section XI, Division I for Item Number B3.90 components. This Code Case permits a reduced examination volume, specified in the Code Case, in lieu of the examination volumes required in accordance with Figures IWB-2500-7 (a), (b), and (c) of ASME Code,Section XI.
ASME Code N-577, Risk-Informed Requirements for Class 1, 2, or 3 Piping, Method A,Section XI, Division 1.
For Browns Ferry, Unit 2, the fourth 10-year ISI interval ended on May 24, 2021.
For clarity, the NRC staffs evaluation of BFN-2-ISI-003 is documented according to each of the applicable ASME BPV Code-required examination categories.
3.2 Examination Category B-D, Full Penetration Welded Nozzles in Welds 3.2.1 Applicable ASME Code Requirements The examination requirements for ASME Code Class 1, Examination Category B-D, Item Number B3.90, Nozzle-to-Vessel Welds, as delineated in ASME BPV Code,Section XI, Table IWB-2500-1, require the volumetric examination coverage of all nozzle-to-vessel welds. The examination volumes shall conform to the applicable Figures IWB-2500-7(a) through (d). The subject welds included a 4-inch jet pump instrumentation nozzle-to-shell weld, 28-inch reactor water recirculation outlet nozzle-to-shell weld, and a 12-inch reactor feedwater nozzle-to-shell weld.
The examination requirements for ASME Code Class 1, Examination Category B-D, Item Number B3.100, Nozzle Inside Radius Section, as delineated in ASME BPV Code,Section XI, Table IWB-2500-1, require volumetric examination of all nozzle inside radius section welds.
Examination volumes shall conform to the applicable figure shown in Figures IWB-2500-7(a) through (d). The subject welds were 4-inch jet pump instrumentation nozzle inside radius welds.
Table 1 below provides a summary of the examinations for Examination Category B-D welds for which the licensee is seeking relief in which there were examination limitations from obtaining essentially 100 percent examination coverage due to other components and geometric nozzle configuration.
Table 1 - Examination Category B-D Welds with Limited Examination Coverage for Browns Ferry, Unit 2 Item Component ID and Limitation/Coverage Examination Results No. Description 1 N8A-IR Limited access due to Jet Pumps #5 and No Recordable B-D 4 Jet Pump Instrumentation #4, and the sensing lines. 50% coverage Indications B3.100 Nozzle Inside Radius 1 N8A-NV Geometric Nozzle Design Configuration No Recordable B-D 4 Jet Pump Instrumentation 84.2% coverage Indications B3.90 Nozzle to Shell Weld 1 N1A-NV Geometric Nozzle Design Configuration No Recordable B-D 28 Reactor Water 24.5% coverage Indications B3.90 Recirculation Outlet Nozzle to Shell Weld 1 N4A-NV Geometric Nozzle Design Configuration and No Recordable B-D 12 Reactor Feedwater lift off from circumferential weld C-3-4. Indications B3.90 Nozzle to Shell Weld 29.9% coverage 1 N4B-NV Geometric Nozzle Design Configuration and No Recordable B-D 12 Reactor Feedwater lift off from circumferential weld C-3-4. Indications B3.90 Nozzle to Shell Weld 29.9% coverage 1 N4C-NV Geometric Nozzle Design Configuration and No Recordable B-D 12 Reactor Feedwater lift off from circumferential weld C-3-4. Indications B3.90 Nozzle to Shell Weld 29.9% coverage 1 N4D-NV Geometric Nozzle Design Configuration and No Recordable B-D 12 Reactor Feedwater lift off from circumferential weld C-3-4. Indications B3.90 Nozzle to Shell Weld 29.9% coverage 1 N4E-NV Geometric Nozzle Design Configuration and No Recordable B-D 12 Reactor Feedwater lift off from circumferential weld C-3-4. Indications B3.90 Nozzle to Shell Weld 29.9% coverage 1 N4F-NV Geometric Nozzle Design Configuration and No Recordable B-D 12 Reactor Feedwater lift off from circumferential weld C-3-4. Indications B3.90 Nozzle to Shell Weld 29.9% coverage 3.2.2 Licensees Reason for Request Due to component design configuration and limitations, the licensee was unable to obtain the ASME BPV Code-required examination coverage for the components identified in its submittal.
The licensee stated that the subject welds were examined to the extent practical due to limited access. The licensee stated that its determination is based on actual demonstrated limitations experienced when attempting to comply with the ASME BPV Code examination coverage requirements. The licensee clarified that further coverage would require extensive design modifications.
The licensee also explained that Examination Category B-D Welds, Items B3.90 and B3.100 are Class 1 pressure retaining welds and that the examinations were limited due to the configuration of the geometric design of the components.
3.2.3 NRC Staffs Evaluation of Examination Category B-D Welds The NRC staff has evaluated Relief Request BFN-2-ISI-003 pursuant to 10 CFR 50.55a(g)(6)(i).
The NRC staffs evaluation focused on whether: (1) sufficient technical justification exists to support the determination that the ASME BPV Code requirements are impractical; (2) imposition of the Code-required examinations would result in a burden to the licensee; and (3) the licensees proposed alternative (i.e., accepting the reduced inspection coverage in these cases, periodic system pressure tests and VT-2 visual examinations performed during each refueling outage in accordance with Examination Category B-P of Table IWB-2500-1, and continual monitoring of reactor coolant system (RCS) boundary leakage) provides reasonable assurance of structural integrity and leak tightness of the subject welds. The NRC staff determined that if these three criteria are met, then the requirements of 10 CFR 50.55a(g)(6)(i) (i.e., that 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.
Impracticality of Compliance The design of Browns Ferry, Unit 2 provides access for examinations; however, component design configurations with conditions resulting in examination limitations (for example, those from support interference and/or geometric configurations of welds) did not allow for the full required examination volume coverage. The licensee explained that when examined, the welds listed in its submittal did not receive the required ASME BPV Code volume coverage due to their component design configurations or interference by other items. These conditions resulted in scanning access limitations that prohibited obtaining essentially 100-percent examination coverage (i.e., greater than 90 percent) of the required examination volumes. When this situation occurred, 100 percent of the accessible volumes of each weld were examined to the extent practicable. Consequently, according to the licensee, every weld was examined as required by applicable procedures and regulations to the extent practicable. The licensee documented these impediments to achieving the required volumetric examination coverages in diagrams provided in its submittal and illustrated the problematic geometry surrounding the subject welds.
The NRC confirmed that all but one of the B-D weld configurations prevented the licensee from scanning the welds from the nozzle side. In the case of component N8A-IR, the limitation was caused by obstruction from Jet Pumps #4 and #5 and the sensing lines. The licensee adopted ASME Code Case N-648-1 to perform a visual examination for this component. Additionally, as shown in the sketches and technical descriptions included in the licensees submittal, the subject components have access limitations which resulted in reduced visual and volumetric examination coverage.
Based on its review of the submittal, including the provided diagrams, the NRC staff finds that due to geometric limitations associated with the aforementioned welds, it was impractical to meet the ASME BPV Code-required essentially 100 percent volumetric examination coverage for the subject welds during fourth 10-year ISI interval for Browns Ferry, Unit 2.
Burden of Compliance The licensee stated that for each weld in the scope of this request, it is not possible to obtain interrogation of greater than 90 percent of the required ASME BPV Code examination volume
without extensive weld or component design modifications and that examinations have been performed to the maximum extent possible. The licensee explained that using radiography as an alternative would result in numerous work-related stoppages and increased radiation exposure due to the shutdown and startup of other work in the areas. The licensee further explained that the water may need to be drained from some systems or components where radiography is performed, which increases the radiation dose rates over a much broader area than the weld being examined. The licensee determined there is significant impracticality associated with the performance of weld or area modifications or the use of radiography in order to increase the examination coverage.
The NRC staff finds that replacing, reconfiguring, or modifying the components of the subject welds, or the use of radiography in order to increase the examination coverage are the only reasonable means to achieve greater than 90 percent of the required ASME BPV Code examination volume and that replacement or reconfiguration, or use of radiography of the subject components constitutes a burden on the licensee.
Structural Integrity and Leak Tightness The NRC staffs review considered whether the licensees achieved examination coverage for the subject welds in Examination Category B-D, Item Numbers B3.90 and B3.100 provides reasonable assurance of structural integrity and leak tightness of the subject welds. This was based on: (1) the examination coverages achieved and (2) safety significance of unexamined volumes and unachievable coverages (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 whether the licensee obtained as much coverage as reasonably possible and the manner in which the licensee reported the coverage achieved. From review of submittal, the NRC staff determined that:
The welds were examined using the appropriate equipment, UT modes of propagation, probe angles, frequencies, and scanning directions 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 BPV Code,Section XI.
The coverage was limited due to physical limitations or access.
No unacceptable indications were identified.
The NRC staff reviewed the licensees figures for the included 4 jet pump instrumentation nozzle-to-shell weld, 28 reactor water recirculation outlet nozzle-to-shell weld, and 12 reactor feedwater nozzle-to-shell weld identified above in Table 1. Based on its review, the NRC staff determined that the licensee made every effort to obtain as much coverage as reasonably possible with the ASME BPV Code-required volumetric examinations. 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 submittal, the NRC staff determined that the licensees volumetric examinations have covered, to the extent possible, the regions that are typically susceptible to higher stresses and, therefore, more susceptible to potential degradation. No recordable indications were detected in the volumes examined by the licensee. Therefore, based on the coverage achieved by the qualified
inspection method 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.
The NRC staff determined that, based on the aggregate coverage obtained for the subject components, the extent of the examinations, and considering the licensees performance of essentially 100 percent examination coverage for the accessible portions of these welds, some evidence of potential unacceptable flaws would have been detected by the licensee. There were no recordable indications identified in the B-D welds in the submittal for Browns Ferry, Unit 2.
The licensee utilized multiple weld scans, including tangential scans, utilizing skews to maximize coverage. Visual examination of the accessible nozzle inner radius surface in addition to ultrasonic examination of the nozzle-to-vessel weld provides reasonable assurance that deep flaws are not present. Therefore, the NRC staff finds that the examinations performed provide reasonable assurance of the structural integrity and leak tightness of the subject welds and that full compliance with the ASME Code requirements for these welds would be an undue burden on the licensee.
The NRC staff also determined that, in addition to the required examinations, the subject welds have received and will continue to receive 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 of the subject welds, the NRC staff finds that this system leakage test will provide additional assurance that any pattern of degradation, if it were to occur, would be detected and that the licensee will be able to take appropriate corrective actions.
Additionally, the staff noted that there is continuous monitoring instrumentation, which is required to be operable by Browns Ferry Technical Specification (TS) 3.4.5, RCS Leakage Detection Instrumentation, to assure that early detection of any RCS pressure boundary leakage is identified and meets Browns Ferry TS 3.4.4, RCS Operational Leakage.
The NRC staff determined that the examinations performed, despite the limited coverage obtained by the licensee, provide reasonable assurance of the structural integrity for the subject component welds in Examination Category B-D, Item Numbers B3.90 and B3.100. Furthermore, the continued performance of the periodic required VT-2 examinations during the system pressure tests provides additional assurance of structural integrity and leak tightness of the subject welds. Full compliance with the ASME BPV Code requirements for these welds would be a burden on the licensee without a commensurate increase in safety. Therefore, the NRC staff finds that the risk associated with granting the requested relief would be acceptably low and the licensees request is acceptable.
3.3 Examination Category R-A, Risk-Informed Piping Examinations 3.3.1 Applicable ASME Code Requirements The Class 1 piping welds in Examination Category R-A, for which the licensee is seeking relief, were selected for examination under the Browns Ferry Risk-Informed Inservice Inspection (RI-ISI) Program in accordance with ASME Code Case N-577. The examination requirements for Examination Category R-A, Item Number R1.16 are delineated in ASME BPV Code,Section XI, Nonmandatory Appendix R, Table R-2500-1, and require the volumetric examination coverage depicted in Figures IWB-2500-8(c) or IWB-2500-9, -10, -11.
Table 2 lists the affected welds and provides additional details including the limitations that prohibited licensee to obtain the required coverage of the examination volume and the percent coverage achieved for each weld.
Table 2 - Examination Category R-A Piping Weld with Limited Examinations Browns Ferry Unit 2 Class Weld Identification and Limitation/Code Coverage Examination Category Description Results Item No.
1 DRHR-2-03 Single Sided Exam due to weld No Recordable R-A 24 Valve to Flued Head configuration. Indications R1.16 Residual Heat Removal 51.4% coverage 1 RWCU-2-003-G003 Penetration to Pipe weld configuration No Recordable R-A 6 Penetration to Pipe presented single side access. Indications R1.16 Reactor Water Cleanup 75% coverage 1 RWC-2-001-G002 Single Sided Exam due to configuration. No Recordable R-A 4 Elbow to Valve Stainless Steel Valve to a Carbon Steel Indications R1.16 Reactor Water Cleanup Elbow Weld.
43.9% coverage 1 RWCU-2-003-070 Single Sided Exam due to configuration. No Recordable R-A 6 Pipe to Weld-o-let Butt Weld 73.7% coverage Indications R1.16 Reactor Water Cleanup 1 KR-2-25 Single Sided Exam due to configuration of No Recordable R-A 28 Pipe to Tee a wrought piping Tee Fitting. Indications R1.16 Reactor Water Recirculation 50% coverage 1 KR-2-03 Single Sided Exam due to configuration. No Recordable R-A 28 Pipe to Tee 83.86% coverage Indications R1.16 Reactor Water Recirculation 1 DCS-2-05 Single side access due to cast stainless No Recordable R-A 12 Pipe to Valve steel valve. Indications R1.16 Core Spray 50% coverage 1 DCS-2-14 Single side access due to cast stainless No Recordable R-A 12 Pipe to Valve steel valve. Indications R1.16 Core Spray 50% coverage 3.3.2 Licensees Reason for Request The licensee submitted the proposed alternative on the basis that due to the configuration and geometric scanning limitations previously stated in Table 2, it was impractical to meet the ASME Code-required essentially 100 percent volumetric examination coverage for the subject piping welds during the fourth 10-year inspection interval at Browns Ferry, Unit 2.
Periodic system pressure tests and VT-2 visual examinations on Class 1 pressure-retaining welds and items are required during each refueling outage in accordance with Examination Category B-P of ASME BPV Code,Section XI, Table IWB-2500-1. The licensee stated that the UT was conducted to the maximum extent possible in addition with continual monitoring instrumentation that is in place to detect any RCS pressure boundary leakage.
The licensee stated that for each weld in this request, it is not possible to obtain UT interrogation of greater than 90 percent of the required ASME BPV Code examination volume or surface areas without extensive weld or component design modifications.
The licensee stated that using radiography as an alternative would result in numerous work-related stoppages and increased radiation exposure due to the shutdown and startup of other work in the areas. The water may need to be drained from some systems or components where radiography is performed. There is significant impracticality associated with the performance of
weld or area modifications or the use of radiography in order to increase the examination coverage.
3.3.3 NRC Staffs Evaluation of Examination Category R-A Welds The NRC staff has evaluated Relief Request BFN-2-ISI-003 pursuant to 10 CFR 50.55a(g)(6)(i).
The NRC staff focused its evaluation: (1) whether a technical justification exists to support the determination that the ASME Code requirement is impractical, (2) that imposition of the ASME Code-required examinations would result in a burden to the licensee, and (3) that the licensees proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject welds. The NRC staff determined 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.
From review of Table 2 and figures in Relief Request BFN-2-ISI-003, the NRC staff notes that the licensee achieved less than the required volumetric examination coverage due to geometric, material, and physical limitations that would entail modification of the associated components if the required coverage were to be obtained. The staff noted that the ASME BPV Code-required volumetric examination coverage is limited due to geometry of the welds. It would be impractical for the licensee to have to redesign these welds in order to achieve the ASME BPV Code-required examination coverage. The NRC staff finds the stated limitations to be an acceptable basis for impracticality of complying with the requirements and finds the modification necessary to achieve the required coverage constitutes a burden upon the licensee.
The licensee examined the subject welds to the maximum extent practical using UT methods qualified in accordance with ASME BPV Code,Section XI, as well as applicable leakage monitoring and required system pressure tests with VT-2 visual examinations. The NRC staff determined that licensee performed system leakage test as required by ASME Code,Section XI, IWB-2500. The NRC staff finds the licensees achieved coverage acceptable, given the noted limitations.
Based on the above discussion, the NRC staff determined that obtaining the ASME Code-required examination volume coverage for the welds listed in Table 1 is impractical because of the stated limitations and that the modification necessary to obtain the required coverage would impose a burden upon the licensee. The staff also determined that the volumetric UT examination performed to the maximum extent practical provides reasonable assurance of structural integrity of the welds because the licensee performed limited examination as well as best effort examination with no recordable indications. While the best effort examination coverage does not meet the ASME Code,Section XI requirements to be able to detect small cracks, the NRC staff finds the examinations would have been able to detect significant cracking if such cracking had been present.
4.0 CONCLUSION
As set forth above, the NRC staff has determined that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law, will not endanger life or property or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Furthermore, the NRC staff concluded that the examinations performed to the extent practical provide reasonable
assurance of structural integrity of the subject components. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Therefore, the NRC staff grants relief from the ASME Code examination requirements for the welds included in Relief Request BFN-2-ISI-003 for Browns Ferry, Unit 2 for the fourth 10-year ISI interval, which ended on May 24, 2021.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributors: E. Haywood, NRR K. Sida, NRR O. Yee, NRR Date: March 13, 2023
ML23054A290 OFFICE NRR/DORL/LPLII-2/PM NRR/DORL/LPLII-2/LA NRR/DNRL/NVIB/BC(A)
NAME KGreen RButler DWidrevitz DATE 02/23/23 02/27/23 01/11/23 OFFICE NRR/DNRL/NPHP/BC NRR/DORL/LPLII-2/BC NAME MMitchell DWrona DATE 01/11/23 03/13/23