ML20253A181
| ML20253A181 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/23/2020 |
| From: | Undine Shoop Plant Licensing Branch II |
| To: | Jim Barstow Tennessee Valley Authority |
| Wentzel M | |
| References | |
| EPID L-2019-LLR-0034 | |
| Download: ML20253A181 (10) | |
Text
September 23, 2020 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, UNITS 1, 2, AND 3 - PROPOSED ALTERATIVE TO THE REQUIREMENTS OF THE ASME CODE (EPID L-2019-LLR-0034)
Dear Mr. Barstow:
By letter dated February 28, 2020, as supplemented by letters dated August 10 and September 10, 2020, the Tennessee Valley Authority (the licensee) submitted Alternative Request No. 0-ISI-47 to the U.S. Nuclear Regulatory Commission (NRC) for the use of an alternative to certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code),Section 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), the licensee 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 concludes, as set forth in the enclosed safety evaluation, that the Tennessee Valley Authority has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55(z)(1). Therefore, the NRC staff authorizes the use of the licensees proposed alternative in 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 interval. All other ASME BPV Code,Section XI, requirements for which relief 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, Michael Wentzel, at 301-415-6459 or michael.wentzel@nrc.gov.
Sincerely, Undine Shoop, 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
Enclosures:
Safety Evaluation cc: Listserv Undine S.
Shoop Digitally signed by Undine S. Shoop Date: 2020.09.23 14:34:58 -04'00'
- by e-mail OFFICE NRR/DORL/LPLII-2/PM NRR/DORL/LPLII-2/LA*
NRR/DNRL/NVIB/BC NAME MWentzel BAbeywickrama HGonzalez (GCheruvenki for)
DATE 09/14/2020 09/09/2020 09/04/2020 OFFICE NRR/DORL/LPLII-2/BC NAME UShoop DATE 09/23/2020
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE REQUEST NO. 0-ISI-47 FOR THIRD, FIFTH AND FOURTH 10-YEAR INSERVICE INSPECTION INTERVALS 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 February 28, 2020, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20059N637) as supplemented by letters dated August 10 and September 10, 2020 (ADAMS Accession Nos. ML20223A366 and ML20255A150, respectively),
the Tennessee Valley Authority (the licensee) requested relief from the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code) for the Browns Ferry Nuclear Plant (Browns Ferry), Units 1, 2, and 3. The licensee proposed to use Boiling Water Reactor Vessel and Internals Project (BWRVIP) guidelines as an alternative to certain requirements of Section XI of the ASME BPV Code for the inservice inspection (ISI) of reactor pressure vessel interior surfaces, attachments, and core support structures. Pursuant to Paragraph 50.55a(z)(1) of Title 10 of the Code of Federal Regulations (10 CFR), the licensee requested to use the proposed alternative on the basis that the alternative provides an acceptable level of quality and safety.
2.0 REGULATORY REQUIREMENTS The regulations at 10 CFR 50.55a(g)(4) state, in part, that ASME BPV 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 interior accessible areas, welded attachments, and the welded core support structures in the reactor pressure vessel are categorized as ASME BPV Code Class 1 components. Therefore, per 10 CFR 50.55a(g)(4), ISI of these areas and components must be performed in accordance with Section XI of the applicable edition and addenda of the ASME BPV Code.
The regulations at 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state:
Alternatives to the requirements of paragraphs (b) through (h) of this section
[50.55a] or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation. The applicant or licensee must demonstrate that:
(1)
Acceptable Level of Quality and Safety. The proposed alternative would provide an acceptable level of quality and safety; or (2)
Hardship without a Compensating Increase in Quality and Safety.
Compliance with the specified requirements of this section [50.55a] 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 the licensee may propose an alternative to ASME BPV Code,Section XI, and the NRC staff has the regulatory authority to authorize the licensee's proposed alternative.
3.0 LICENSEES EVALUATION In this safety evaluation (SE), the term RVI components include reactor pressure vessel interior surfaces, attachments, and core support structures.
The Components for Which an Alternative is Requested ASME Code,Section XI, Class 1, Examination Categories B-N-1 and B-N-2, Code 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).
Applicable ASME BPV Code Edition The applicable Code of Record for the third, fifth and fourth 10-year ISI intervals at Browns Ferry, Units 1, 2, and 3, respectively, is the ASME BPV Code,Section XI, 2007 Edition with the 2008 Addenda.
Examination Requirements for Which an Alternative is Requested ASME Code, Section Xl requires the visual examination (VT) of certain RVI components. These examinations are included in Table IWB-2500-1, Categories B-N-1 and B-N-2, and identified with the following item numbers:
B13.10 - Examine accessible areas of the reactor vessel interior each period using a technique which meets the requirements for a VT-3 examination. This includes only those spaces above and below the core made accessible by removal of components during normal refueling outages.
B13.20 - Examine interior attachment welds within the beltline region each interval using a technique which meets the requirements for a VT-1 examination.
B13.30 - Examine interior attachment welds beyond the beltline region each interval using a technique which meets the requirements for a VT-3 examination.
B13.40 - Examine surfaces of the core support structure each interval using a technique which meets the requirements for a VT-3 examination These examinations are performed to assess the structural integrity of the reactor pressure vessel interior surfaces, its welded attachments, and the welded core support structures.
Licensees Basis for Requesting an Alternative and Justification for Granting Relief In proposed Alternative Request No.0-ISI-47, the licensee submitted an alternative inspection program per the BWRVIP guidelines in lieu of ASME Section XI, Code requirements for B-N-1 and B-N-2 reactor pressure vessel interior surfaces, attachments, and core support structures at Browns Ferry, Units 1, 2, and 3. The licensee stated that implementation of the alternative inspection program will maintain an acceptable level of quality and safety of the affected welds and components. The proposed alternative includes examination methods, examination volume, frequency, training, successive and additional examinations, flaw evaluations, and reporting. The BWRVIP guidelines were developed based on inspection data gathered during many inspections across the BWR industry. The Proposed Alternative is requested for the third, fifth and fourth 10-year ISI intervals for Browns Ferry, Units 1, 2, and 3, respectively.
Alternative Examination The licensee proposes to apply the BWRVIP Inspection and Evaluation (I&E) guidelines listed below to the affected ASME Code components identified in Table 1 of its submittal, in lieu of the requirements of ASME Code,Section XI, paragraph IWB-2500(a), and Table IWB-2500-1, including the examination method, examination volume, frequency, training, successive and additional examinations, flaw evaluations, and reporting.
BWRVIP-03, Reactor Pressure Vessel and Internal Examination Guidelines BWRVIP-06, Safety Assessment of BWR Internals BWRVIP-14, BWR Evaluation of Crack Growth in BWR Stainless Steel RPV Internals BWRVIP-18, BWR Core Spray Internals Inspection and Flaw Evaluation Guidelines BWRVIP-25, BWR Core Plate Inspection and Flaw Evaluation Guidelines BWRVIP-26, BWR Top Guide Inspection and Flaw Evaluation Guidelines BWRVIP-27, BWR Standby Liquid Control System/Core Plate P Inspection and Flaw Evaluation Guidelines BWRVIP-38, BWR Shroud Support Inspection and Flaw Evaluation Guidelines BWRVIP-41, BWR Jet Pump Assembly Inspection and Flaw Evaluation Guidelines BWRVIP-47, BWR Lower Plenum Inspection and Flaw Evaluation Guidelines BWRVIP-48, Vessel ID Attachment Weld Inspection and Flaw Evaluation Guidelines BWRVIP-49, Instrument Penetration Inspection and Flaw Evaluation Guidelines BWRVIP-74, BWR Reactor Vessel Inspection and Flaw Evaluation Guidelines BWRVIP-76, BWR Core Shroud Inspection and Flaw Evaluation Guidelines BWRVIP-94, BWR Vessel and Internals Project Program Implementation Guide BWRVIP-100, Updated Assessment of the Fracture Toughness of Irradiated Stainless Steel for BWR Core Shrouds BWRVIP-138, Updated Jet Pump Beam Inspection and Flaw Evaluation Guidelines BWRVIP-180, Access Hole Cover Inspection and Flaw Evaluation Guidelines BWRVIP-183, Top Guide Grid Beam Inspection and Flaw Evaluation Guidelines The licensee further indicated that the BWRVIP has established reporting protocol for examination results and deviations, and that the NRC has agreed with the BWRVIP approach in principle and has issued SEs for many of these guidelines.
In Table 1 of the Proposed Alternative, the licensee provided a comparison of the ASME Code,Section XI, examination requirements for B-N-1 and B-N-2 Categories of the reactor pressure vessel interior surfaces, attachments, and core support structures with the applicable current BWRVIP I&E Guidelines above. In the Enclosure to the Proposed Alternative, the licensee provided additional information regarding the BWRVIP inspection guidelines for the following components of the reactor pressure vessel interior surfaces, attachments, and core support structures and their subcomponents representing each of the ASME Code,Section XI, Item Numbers B13.10, B13.20, B13.30, and B13.40:
Reactor Vessel Interior (B13.10)
Interior Attachments within Beltline (B13.20)
Interior Attachments beyond Beltline (B13.30)
Core Support Structure (B13.40)
For the components included in the above examination categories, the licensee stated that the inspection techniques that are recommended by the BWRVIP inspection guidelines meet or exceed the inspection techniques mandated by the ASME Code,Section XI ISI program and in many instances include components that are not part of the ASME BPV Code,Section XI, jurisdiction. The licensee also stated the BWRVIP guidelines focus on specific and susceptible components, specify appropriate inspection methods capable of identifying known or potential degradation mechanisms, and required reexamination at appropriate intervals. The licensee concluded that implementation of the BWRVIP inspection guidelines for the Browns Ferry, Units 1, 2, and 3 reactor pressure vessel interior surfaces, attachments, and core support structures would provide an acceptable level of quality and safety while avoiding duplicate or unnecessary inspections and conserving radiological dose.
4.0 STAFF EVALUATION The NRC staff reviewed the information provided by the licensee in its submittal dated February 28, 2020, as supplemented by letters dated August 10 and September 10, 2020, regarding its proposed alternative to the ASME Code,Section XI ISI requirements and the technical bases for the licensees proposed alternative. The NRC staff found the referenced BWRVIP reports to be acceptable, along with any additional conditions associated with the implementation of the subject BWRVIP reports outlined in the corresponding staff SE for that report.
Examination of Reactor Vessel Interior (Item B13.10)
The ASME Code requires a VT-3 examination of the reactor vessel interior which is above and below the core beltline, and which is made accessible during normal refueling outages. For the first inspection interval, the ASME Code requires inspection at the first refueling outage and at approximately 3-year intervals thereafter. For the second and successive inspection intervals, the ASME Code requires inspection once each inspection period.
Portions of the various examinations required by the applicable BWRVIP Guidelines (referenced in Section 3.0 of this SE) require access to the accessible areas of the reactor vessel during each refueling outage. According to the licensee, BWRVIP examination of core spray piping and spargers, top guide, shroud support, jet pump welds and components, low-pressure coolant injection couplings lower plenum components, interior attachments, core shroud welds, access hole cover, and top guide beams provides access to the ASME Code defined Item B13.10 reactor vessel interior. The licensee stated that no inspections of the lower plenum components are planned for the third, fifth and fourth ISI intervals (for Browns Ferry, Units 1, 2, and 3, respectively) because there is no access to the lower plenum without removal of components such as control guide tubes or jet pump mixers. But the licensee also stated that if the lower plenum welds become accessible, inspections will be performed to the extent possible during the refueling outage. This meets the requirement of the BWRVIP-47-A which only requires examination of accessible lower plenum welds.
The licensee stated that the remote camera systems used in these BWRVIP examinations provide an equivalent method of visual examination than that required by the ASME Code.
During the BWRVIP examinations, evidence of wear, structural degradation, loose, missing or displaced parts, foreign materials, and corrosion product buildup can be observed. The licensee concluded that the specified BWRVIP Guideline requirements meet or exceed the ASME Code requirements for Item B13.10 examination of the reactor vessel interior.
There is a correlation between the chemical mitigation program implemented and the inspection frequency specified by the BWRVIP alternatives. The licensee stated in its letter dated August 11, 2020 that it uses Online Noble ChemTM (OLNC) to mitigate the effects of Inter-Granular Stress Corrosion Cracking (IGSCC) at Browns Ferry, Units 1, 2, and 3.
BWRVIP-62-A provides the technical basis for the inspection relief in the BWR Vessel Internals (BWRVI) and ISI Programs that is permitted when hydrogen water chemistry, noble metal chemical addition, or OLNC are effectively implemented. Browns Ferry, Units 1, 2, and 3 currently do not claim inspection relief. The licensee stated that if inspection relief credit is taken in the future, it plans to do so in accordance with BWRVIP-62-A and Nuclear Energy Institute (NEI) 03-08, Guideline for the Management of Materials Issues.
The NRC staff verified that the specified BWRVIP Guideline requirements meet or exceed the ASME Code requirements for Item B13.10 examination of the reactor vessel interiors and finds that the licensees proposed alternative provides an acceptable level of quality and safety for the Item B13.10 components.
Examination of Interior Attachments within Beltline (Item B13.20)
The ASME Code requires a VT-1 examination of accessible reactor vessel interior attachment welds within the beltline during each inspection interval.
The licensee specifically lists the jet pump riser braces and lower surveillance specimen holder brackets as Item B13.20 components which are to be examined in accordance with BWRVIP-48-A. BWRVIP-48-A requires the lower surveillance specimen holder bracket attachment to be examined by VT-1 each inspection interval, which is the same level of inspection and frequency as required by the ASME Code. However, BWRVIP-48-A requires an enhanced VT-1 (EVT-1) examination of 100% of the jet pump riser brace attachments during the first 12 years, and then 25% EVT-1 examination during each subsequent 6 years. The BWRVIP EVT-1 exams require the same character resolution as the ASME Code VT-1 exams, but with a more stringent viewing angle for remote video examination and the performance of a cleaning assessment and cleaning as necessary. The licensee states that the BWRVIP-required examination provides an acceptable level of quality and safety for the Item B13.20 components despite the frequency of the BWRVIP examination which is less than the frequency of the ASME Section XI examination.
The NRC staff finds that the licensee proposed alternative provides an acceptable level of quality and safety for the Item B13.20 components because the proposed alternate provides for equivalent or superior flaw detection and characterization than the ASME Code requirements.
Examination of Interior Attachments beyond Beltline (Item B13.30)
The ASME Code requires a VT-3 examination of accessible reactor vessel interior attachment welds beyond the beltline during each inspection interval.
The licensee specifically lists the core spray piping brackets, upper surveillance specimen holder brackets, feedwater sparger brackets, steam dryer support brackets, steam dryer hold down brackets, guide rod brackets, as Item B13.30 welded components which are to be examined in accordance with BWRVIP-48-A. The licensee also lists the shroud supports as Item B13.30 welded components which are to be examined in accordance with BWRVIP-38.
For the steam dryer hold-down brackets, the guide rod brackets, and the upper surveillance specimen holder brackets, the BWRVIP requires a VT-3 examination each inspection interval, which is the same level and frequency as required by the ASME Code. For the steam dryer support brackets and the feedwater sparger brackets, the BWRVIP requires an EVT-1 examination each inspection interval, which is an enhanced level of inspection, but at the same frequency as compared to the ASME Code. For the core spray piping brackets, the BWRVIP requires an EVT-1 examination every four cycles, which is an enhanced level of inspection and an increased frequency as compared to the ASME Code. For the shroud support welds, the BWRVIP requires either an EVT-1 examination every 6 years, or a UT examination, which is an enhanced level of inspection and the same or increased frequency as compared to the ASME Code. The licensee states that the BWRVIP required examination provides a level of quality and safety equivalent or superior to the ASME Code requirements for the Item B13.30 components.
The NRC staff finds that the licensee proposed alternative provides an acceptable level of quality and safety for the Item B13.30 components because the proposed alternate provides for equivalent or superior flaw detection and characterization with an examination frequency that is equivalent or more frequent than the ASME Code requirements.
Examination of Core Support Structure (Item B13.40)
The ASME Code requires a VT-3 examination of accessible surfaces of the core support structure during each inspection interval.
The licensee specifically lists the integrally welded core support structure (shroud support welds including gussetts), shroud horizontal welds, shroud vertical welds, and shroud repair tie-rods as Item B13.40 components which are to be examined according to the BWRVIP. For the shroud support, BWRVIP-38 requires either EVT-1 or UT based on as-found conditions, to a maximum 6 years for EVT-1, 10 years for UT where accessible.
For the core shroud horizontal and vertical welds, BWRVIP-76-R1-A requires either EVT-1 or UT, maximum of 10 years based on inspection of horizontal welds. Where the BWRVIP requires EVT-1 or UT examination of these components, these examination methods are more effective in identifying defects than the VT-3 examination prescribed in the ASME Code. The licensee also stated that tie rod repairs would be examined in accordance with BWRVIP-76-R1-A, Section 3.5.
For Item B13.40 components, the BWRVIP examination frequency is equivalent or more frequent than that provided by the ASME Code. The licensee states that the superior flaw detection and characterization capability, with an equivalent or more frequent examination frequency and the comparable flaw evaluation criteria, provides a level of quality and safety equivalent or superior to the ASME Code requirements for the Item B13.40 components.
The NRC staff finds that the licensee proposed alternative provides an acceptable level of quality and safety for the Item B13.40 components because the proposed alternate provides for equivalent or superior flaw detection and characterization with an examination frequency that is equivalent or more frequent than the ASME Code requirements.
5.0 CONCLUSION
As set forth above, the NRC staff determines that the licensees proposed alternative provides 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 proposed alternative in Request No. 0-ISI-47 at Browns Ferry, Units 1, 2, and 3 for the duration of the third, fifth and fourth 10-year ISI interval, respectively.
This SE approves only the use of those versions of the BWRVIP topical reports that were requested in the licensee submittal dated February 28, 2020 and supplemented by letters dated August 10 and September 10, 2020. Use of later versions of BWRVIP topical reports 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 Code,Section XI for which an alternative has not been specifically requested remain applicable, including third party review by the Authorized Nuclear In-service Inspector. Any ASME Code,Section XI, RVI components that are not included in this request for alternative will continue to be inspected in accordance with the ASME Code,Section XI requirements. The I&E guidelines addressed in the relevant BWRVIP reports should be implemented for the non-ASME Code,Section XI, RVI components at Browns Ferry, Units 1, 2, and 3.
Principal Contributor:
C. Fairbanks Date: September 23, 2020