ML24155A004
| ML24155A004 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/18/2024 |
| From: | Kimberly Green Plant Licensing Branch II |
| To: | Jim Barstow Tennessee Valley Authority |
| Green K | |
| References | |
| EPID L-2023-LLR-0034 AR 0-ISI-47 | |
| Download: ML24155A004 (1) | |
Text
June 18, 2024
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, UNITS 1, 2, AND 3 - PROPOSED ALTERNATIVE TO THE REQUIREMENTS OF THE ASME CODE (REVISED ALTERNATIVE REQUEST 0-ISI-47) (EPID L-2023-LLR-0034)
Dear James Barstow:
By letter dated July 3, 2023, as supplemented by letters dated January 11 and May 15, 2024, the Tennessee Valley Authority (TVA) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use an alternative to certain American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (BPV Code), Sect ion XI requirements at Browns Ferry Nuclear Plant, Units 1, 2, and 3.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), TVA requested to use the proposed alternative on the basis that the alternative provides an acceptable level of quality and safety.
The NRC staff has reviewed the subject request and conc ludes, as set forth in the enclosed safety evaluation, that TVA has adequately addressed all of the regulatory requirements specified in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorizes the use of the proposed revised alternative Request No. 0-ISI-47 at Browns Ferry Nuclear Plant, Units 1, 2, and 3 for the duration of the third, fifth, and fourth, respectively, 10-year inservice inspection intervals. All other ASME BPV Code,Section XI, requirements for which an alternative was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
J. Barstow
If you have any questions, please contact the Project Manager, Kimberly Green, at 301-415-1627 or Kimberly.Green@nrc.gov .
Sincerely,
David Wrona, Chief Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Docket Nos. 50-259, 50-260, and 50-296
Enclosure:
Safety Evaluation
cc: Listserv SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
PROPOSED REVISED ALTERNATIVE REQUEST 0-ISI-47 REGARDING
ASME CODE, SECTION XI, CLASS 1, EXAMINATION CATEGORIES B-N-1 AND B-N-2
TENNESSEE VALLEY AUTHORITY
BROWNS FERRY NUCLEAR PLANT, UNITS 1, 2, AND 3
DOCKET NOS. 50-259, 50-260, AND 50-296
1.0 INTRODUCTION
By letter dated July 3, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23184A142), as supplemented by letters dated January 11, 2024 (ML24011A288), and May 15, 2024 (ML24136A154), Tennessee Valley Authority (the licensee) submitted revised alternative request 0-ISI-47 for the Browns Ferry Nuclear Plant, Units 1, 2, and 3 (Browns Ferry).
Pursuant to section 50.55a(z)(1), Acceptable level of quality and safety, of Title 10 of the Code of Federal Regulations (10 CFR), the licensee requested to utilize the requirements of the Boiling Water Reactor Vessel and Internals Project (BWRVIP) Inspection and Evaluation (I&E) guidelines in lieu of the requirements of the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (BPV Code),Section XI, examination requirements for Examination Categories B-N-1 and B-N-2, as mandated in 10 CFR 50.55a, Codes and Standards. Specifically, the licensee requested the use of the BWRVIP I&E guidelines in lieu of the requirements of ASME BPV Code,Section XI, Table IWB-2500-1, Examination Item Numbers B13.10 (vessel interior), B13.20 (interior attachments within beltline region), B13.30 (interior attachments beyond beltline region), and B13.40 (core support structure) in the two examination categories above.
By letter dated February 28, 2020 (ML20059N637), as supplemented by letters dated August 10 and September 10, 2020 (ML20223A366 and ML20255A150, respectively), the licensee submitted original alternative request 0-ISI-47 regarding the use of BWRVIP guidelines in lieu of the ASME BPV Code,Section XI requirements. The U.S. Nuclear Regulatory Commission (NRC) authorized the alternative request by letter dated September 23, 2020 (ML20253A181).
The authorized alternative request refers to the use of BWRVIP-03, Revision 19, BWRVIP-25, BWRVIP-41, Revision 3, BWRVIP-48-A, and BWRVIP-94, Revision 2.
The BWRVIP has issued newer revisions of these documents, specifically BWRVIP-03, Revision 20, BWRVIP-25, Revision 1-A, BWRVIP-41, Revision 4-A, BWRVIP-48, Revision 2, and BWRVIP-94, Revision 4. Additionally, the BWRVIP has issued BWRVIP-62, Revision 2,
Enclosure
which was not included in the NRC approval of the original alternative request 0-ISI-47. In the case of BWRVIP-25 and BWRVIP-41, the newer revisions have been approved by the NRC. In the case of BWRVIP-03, BWRVIP-48, BWRVIP-62, and BWRVIP-94, the latest revisions have not been reviewed and approved by the NRC, but have been evaluated in accordance with NEI 03-08, Revision 3, Guideline for the Management of Materials Issues, Appendix C, Document Screening (ML19079A256) to determine that the revised guidance may be implemented without NRC review and approval.
The licensee revised alternative request 0-ISI-47 to allow for use of BWRVIP-03, Revision 20, BWRVIP-25, Revision 1-A, BWRVIP-41, Revision 4-A, BWRVIP-48, Revision 2, BWRVIP-62, Revision 2, and BWRVIP-94, Revision 4 rather than the former revisions as previously approved. No other changes to the previously approved request for alternative are proposed.
2.0 REGULATORY EVALUATION
The regulations in 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, state, in part, that ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in Section XI of the applicable editions and addenda of the ASME BPV Code to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The regulations in 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state, in part, that alternatives to the requirements in paragraphs (b) through (h) of 10 CFR 50.55a may be authorized by the NRC if the licensee demonstrates that: (1) the proposed alternative provides an acceptable level of quality and safety, or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
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 authorize, the alternative requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1 Licensees Proposed Alternatives
The licensee requested NRC authorization to use the updated guidance in BWRVIP-03, Revision 20, BWRVIP-25, Revision 1-A, BWRVIP-41, Revision 4-A, BWRVIP-48, Revision 2, and BWRVIP-94, Revision 4, as well as commencing use of BWRVIP-62, Revision 2. The BWRVIP I&E guidelines will continue to be used for the third, fifth, and fourth 10-year inservice inspection (ISI) intervals at Browns Ferry Units 1, 2, and 3, respectively, as an alternative to the examination requirements in ASME BPV Code,Section XI, for Examination Categories B-N-1 and B-N-2.
The licensee stated that third, fifth, and fourth 10-year ISI intervals at Browns Ferry Units 1, 2, and 3, respectively, all have a start date of February 1, 2016, and an end date of January 31, 2026.
3.2 NRC Staff Evaluation
The NRC staff previously approved BWRVIP-25, Revision 1-A (ML20290A784), and BWRVIP-41, Revision 4-A (ML19297G484) for generic use, so the NRC staff finds it acceptable to utilize the NRC-approved versions as an alternat ive to the examination requirements of the ASME BPV Code,Section XI Examination Categories B-N-1, and B-N-2.
The NRC staff has neither reviewed nor approved BWRVIP-03, Revision 20 or BWRVIP-94, Revision 4 for generic use. However, the NRC staff notes that BWRVIP-03 and BWRVIP-94 do not contain I&E guidelines for any specific components. Rather, BWRVIP-03, in general:
(1) provides an overview of the structure of the BWRVIP, and (2) includes guideline documents that establish protocols to follow in order to gain access to BWRVIP-owned mockups; to perform formal demonstrations of nondestructive examinations (NDE) techniques using BWRVIP mockups; and to perform their own demonstrations of NDE techniques or inspection tooling in an acceptable manner. BWRVIP-94, Revision 4 establishes a framework for structuring and strengthening existing BWR vessel and internals programs to ensure consistent application of guidelines by BWRVIP members. The NRC staff notes that these two documents are integral to the implementation of the BWRVIP l&E guidelines, including those associated with the licensees submittal.
The NRC staff has neither reviewed nor approved BWRVIP-48, Revision 2 or BWRVIP-62, Revision 2 for generic use. As such, as part of evaluating the current submittal, the NRC staff has evaluated the use of BWRVIP-48, Revision 2 and BWRVIP-62, Revision 2 at Browns Ferry, as discussed below.
3.2.1 Plant-Specific Evaluation of BWRVIP-48, Revision 2 Guidelines
In the supplemental letter dated January 11, 2024, the licensee described technical details of the BWRVIP-48, Revision 2 guidance and additional technical justification for its use specific to the core spray piping bracket attachments, the steam dryer support bracket attachments, and the jet pump riser brace attachments.
The BWRVIP-48-A examination guidance for the core spray piping bracket attachments relevant to Browns Ferry is to perform an enhanced visual test (EVT-1) of 100 percent of the subject components every 8 years. Although the guidelines in BWRVIP-48, Revision 2 include a reduction in periodicity and sample size required for the core spray piping bracket attachments, Browns Ferry also implements the NRC-approved guidance in BWRVIP-18, Revision 2-A, and thus, inspects 100 percent of these components by EVT-1 every 10 years to satisfy both BWRVIP-18, Revision 2-A and BWRVIP-48, Revision 2 simultaneously. This sample size and periodicity are the same as the 10-year interval required in ASME BPV Code,Section XI, thereby providing an acceptable level of quality and safety.
The BWRVIP-48, Revision 2 examination guidance for the steam dryer support bracket attachments is EVT-1 for 100 percent of the population every 12 years in lieu of the BWRVIP-48-A guidance to perform EVT-1 for 100 percent of the population every 10 years. The BWRVIP-48, Revision 2 examination guidance for reinspection of the jet pump riser brace attachments is EVT-1 for 25 percent of the population every 12 years in lieu of the BWRVIP-48-A guidance to reinspect 25 percent of the population every 6 years. The technical justification for lengthening the inspection frequency for the steam dryer support bracket attachments and the jet pump riser brace attachments is contained in BWRVIP-48, Revision 2, Appendix G, Section G.4, Qualitative Risk Assessment for BWRVIP-48, Rev. 2, and
Section G.5, Summary of Inspection Program Revisions. Appendix G of BWRVIP-48, Revision 2 can be found in letter dated June 8, 2023 (ML23159A230, non-proprietary) (ML23159A231, proprietary).
Examination data at all three Browns Ferry units for the components listed were reviewed by the licensee to assess whether site-specific data was reflective of the data identified in the conclusions drawn from the qualitative risk asse ssment in BWRVIP-48, Revision 2, Appendix G.
The licensee confirmed that 72 EVT-1 examinations of the core spray piping bracket attachment welds, 31 EVT-1 examinations of the steam dryer support bracket attachments, and 228 EVT-1 examinations of the jet pump riser brace attachments have been performed since 1997 with the establishment of the BWRVIP program. For the core spray piping bracket attachment welds, jet pump riser brace attachments, and steam dryer support bracket attachments, this represents a full baseline examination of the entire population with at least one full reinspection of the entire population for these components at all three Browns Ferry units. The weld inspections are rotated in such a way that the entire population of the welds are examined, with the welds that were examined the farthest in the past being selected for the next examination campaign and so forth.
Of those examinations, the licensee reported one indication of a cracked core spray piping bracket tack weld and four steam dryer support bracket wear locations. The licensee stated that none of these indications are associated with any reported degradation of the attachment welds to the vessel. The indications identified are typical of tack weld flaws and the wear found is commensurate with wear described as common industry occurrence to the steam dryer support brackets in the qualitative risk assessment. Furthermore, no indications representative of vessel attachment weld degradation have been reported for any attachment covered by the July 3, 2023, alternative request for any Browns Ferry unit. The licensees review of Browns Ferry examinations confirms that the data collected by Electric Power Research Institute is comparable to the specific results at Browns Ferry and supports the applicability of the technical justification presented in the qualitative risk assessment of BWRVIP-48, Revision 2, Appendix G.
The NRC staff noted that, when components are inspected at frequencies less than specified in Section XI of the ASME BPV Code or BWRVIP-48-A, the licensee will sample the components in accordance with the process described in BWRVIP-48, Revision 2 and BWRVIP-41, Revision 4-A. When periodic inspections specify that only a fraction of the population is required during the specified interval, the licensee will select attachment welds for the Browns Ferry units based on accumulated service time since the weld was last inspected. Weld selection is rotated through the entire population before any specific weld is selected a second time. When 100 percent of the population of a component is to be inspected at an interval greater than the 10-year ISI interval specified in the ASME BPV Code, the licensee may examine the entire population at one time, or they may split the inspections over the entire interval.
The NRC staff determines that the plant-specific operating experience of these welds, the fleet-wide operating experience of these welds, and the results of the qualitative risk assessment provided in BWRVIP-48, Revision 2 taken together provide appropriate technical justification for the use of BWRVIP-48, Revision 2 at Browns Ferry in lieu of the requirements of ASME Code BVP,Section XI. The NRC staff finds that BWRVIP-48, Revision 2 demonstrates an acceptable level of quality and safety to justify the alternative requested.
3.2.2 Plant-Specific Evaluation of BWRVIP-62, Revision 2 Guidelines
BWRVIP-62-A provides guidelines regarding the noble metal chemical addition (NMCA) process and Hydrogen Water Chemistry, moderate process, and implementation in accordance with BWRVIP-62-A has been accepted as a basis for claiming relief from certain BWRVIP inspections. The NRC staff SE for BWRVIP-62 (ML081840747) accepted for use the following three criteria that plants applying NMCA must meet to demonstrate mitigation of intergranular stress corrosion cracking:
- 1) Measured electrochemical potential less than or equal to -230 millivolts (mV).
- 2) Measured hydrogen-to-oxygen molar ratio greater than or equal to 3.
- 3) Measured catalyst loading greater than or equal to a specific proprietary value.
BWRVIP-62-A does not address the use of Online Noble Metal Chemistry (OLNC), which is currently in use at the Browns Ferry units. By letter dated January 24, 2018 (ML18033A323),
BWRVIP issued interim guidance that states plants utilizing OLNC shall meet the Category 3a NMCA parameters and implementation steps (including platinum loading) of Tables 3-5 and 3-8 of BWRVIP-62-A. The NRC staff reviewed this guidance and provided a supplemental safety evaluation for BWRVIP-62-A (ML18107A613, non-public) that concluded that plants applying OLNC which meet the criteria of a Category 3a plant in BWRVIP-62-A may claim inspection credit afforded by other sources that reference BWRVIP-62-A.
In the licensees supplement dated May 15, 2024, it confirmed that the Browns Ferry water chemistry program meets the criteria for Category 3a plants specified in accordance with BWRVIP-62-A and that there are no programmatic differences between BWRVIP-62, Revision 2 and BWRVIP-62-A that will be employed by Browns Ferry. The licensee also confirmed that it will implement BWRVIP-62, Revision 2 (both Volume 1 and Volume 2) at Browns Ferry.
The NRC staff determined that the licensee may use BWRVIP-62, Revision 2 because the Browns Ferry water chemistry program satisfies BWRVIP-62-A and there is no programmatic difference between BWRVIP-62, Revision 2 and BWRVIP-62-A at Browns Ferry.
3.2.3 NRC Staff Summary
In summary, the NRC staff reviewed the updated examination guidance for the ASME BPV Code,Section XI, Table IWB-2500-1, Examination Item Numbers B13.10, B13.20, B13.30, and B13.40 for the plant-specific cases of Browns Ferry, Units 1, 2, and 3. Based on the above evaluation, the NRC staff finds that the licensee may use the updated guidance in BWRVIP-03, Revision 20, BWRVIP-25, Revision 1-A, BWRVIP-41, Revision 4-A, BWRVIP-48, Revision 2, BWRVIP-62, Revision 2 and BWRVIP-94, Revision 4 for the third, fifth, and fourth 10-year ISI intervals at Browns Ferry Units 1, 2, and 3, respectively.
4.0 CONCLUSION
As set forth above, the NRC staff determines that the revised request for alternative 0-ISI-47 will provide an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorizes the use of the revised request for
- 6 -
alternative 0-ISI-47 at Browns Ferry Units, 1, 2, and 3 for the duration of the third, fifth, and fourth 10-year ISI intervals, respectively.
This SE approves only the use of those versions of the BWRVIP I&E guidelines that were requested in the licensees submittal dated July 3, 2023, as supplemented by letters dated January 11, 2024, and May 15, 2024. Use of later versions of the subject BWRVIP I&E guidelines that are not discussed in the submittal at Browns Ferry, Units 1, 2, and 3 for the third, fifth and fourth 10-year ISI intervals, respectively, requires the licensee to submit a request for approval.
All other requirements of ASME BPV Code,Section XI, for which an alternative was not specifically requested and authorized by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear In-Service Inspector.
The NRC approval of the specific use of topical reports BWRVIP-03, Revision 20, BWRVIP-48, Revision 2, BWRVIP-94, Revision 4 and BWRVIP-62, Revision 2 at Browns Ferry Units 1, 2, and 3 does not imply or infer the NRCs approval of those BWRVIP I&E guidelines for generic use.
Principal Contributors: S. Levitus, NRR M. Benson, NRR
Date: June 18, 2024
ML24155A004 OFFICE NRR/DORL/LPLII-2/PM NRR/DORL/LPLII-2/LA NRR/DNRL/NVIB/BC NRR/DORL/LPLII-2/BC NAME KGreen ABaxter ABuford (JTsao for) DWrona DATE 05/31/24 06/05/24 05/13/24 06/18/24