ML21039A636
| ML21039A636 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs, Byron, Braidwood, Ginna  |
| Issue date: | 02/17/2021 |
| From: | Nancy Salgado Plant Licensing Branch III |
| To: | Rhoades D Exelon Generation Co, Exelon Nuclear |
| Purnell B A-301-415-1380 | |
| References | |
| EPID L-2020-LLR-0069 | |
| Download: ML21039A636 (9) | |
Text
February 17, 2021 Mr. David P. Rhoades Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer (CNO)
Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
BRAIDWOOD STATION, UNITS 1 AND 2; BYRON STATION, UNIT NOS. 1 AND 2; CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2; AND R. E. GINNA NUCLEAR POWER PLANT PROPOSED ALTERNATIVE TO USE THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS BOILER AND PRESSURE VESSEL CODE CASE N-885 (EPID L-2020-LLR-0069)
Dear Mr. Rhoades:
By application dated April 28, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20119B061), as supplemented by letter dated February 1, 2021 (ADAMS Accession No. ML21032A173), Exelon Generation Company, LLC (Exelon) submitted a request in accordance with paragraph 50.55a(z)(2) of Title 10 of the Code of Federal Regulations (10 CFR) for a proposed alternative to certain requirements of 10 CFR 50.55a, Codes and standards, at Braidwood Station, Units 1 and 2 (Braidwood); Byron Station, Unit Nos. 1 and 2 (Byron); Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (Calvert Cliffs); and R. E. Ginna Nuclear Power Plant (Ginna). The proposed alternative would allow Exelon to use the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV))
Code Case N-885, Alternative Requirements for Table IWB-2500-1, Examination Category B-N-1, Interior of Reactor Vessel, Category B-N-2, Welded Core Support Structures and Interior Attachments to Reactor Vessels, Category B-N-3, Removable Core Support Structures:
Section XI, Division 1, at these facilities.
The regulations in 10 CFR 50.55a(z) state, in part, that alternatives to the requirements in paragraphs (b) through (h) of 10 CFR 50.55a may be authorized by the U.S. Nuclear Regulatory Commission (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.
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that Exelon has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorizes Exelon to use the proposed alternative described in its application at Braidwood, Byron, Calvert Cliffs, and Ginna. This authorization is for the remainder of the current 10-year inservice inspection interval for each of these facilities.
The NRC approval of this alternative does not imply or infer the NRC approval of Code Case N-885 for generic use. All other ASME BPV Code requirements for which relief was not been specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
If you have any questions, please contact Blake Purnell at 301-415-1380 or via e-mail at Blake.Purnell@nrc.gov.
Sincerely, Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-456, STN 50-457, STN 50-454, STN 50-455, 50-317, 50-318, and 50-244
Enclosure:
Safety Evaluation cc: ListServ Nancy L.
Salgado Digitally signed by Nancy L. Salgado Date: 2021.02.17 11:19:19 -05'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE TO USE ASME CODE CASE N-885 BRAIDWOOD STATION, UNITS 1 AND 2 BYRON STATION, UNIT NOS. 1 AND 2 CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2 AND R. E. GINNA NUCLEAR POWER PLANT EXELON GENERATION COMPANY, LLC DOCKET NOS. STN 50-456, STN 50-457, STN 50-454, STN 50-455, 50-317, 50-318, AND 50-244
1.0 INTRODUCTION
By application dated April 28, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20119B061), as supplemented by letter dated February 1, 2021 (ADAMS Accession No. ML21032A173), Exelon Generation Company, LLC (Exelon) submitted a request in accordance with paragraph 50.55a(z)(2) of Title 10 of the Code of Federal Regulations (10 CFR) for a proposed alternative to certain requirements of 10 CFR 50.55a, Codes and standards, at Braidwood Station, Units 1 and 2 (Braidwood); Byron Station, Unit Nos. 1 and 2 (Byron); Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (Calvert Cliffs); and R. E. Ginna Nuclear Power Plant (Ginna). The proposed alternative would allow Exelon to use the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code Case N-885, Alternative Requirements for Table IWB-2500-1, Examination Category B-N-1, Interior of Reactor Vessel, Category B-N-2, Welded Core Support Structures and Interior Attachments to Reactor Vessels, Category B-N-3, Removable Core Support Structures:
Section XI, Division 1, at these facilities.
2.0 REGULATORY EVALUATION
The regulations in 10 CFR 50.55a(g)(4) 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, Rules for Inservice Inspection of Nuclear Power Plant Components, 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) state, in part, that alternatives to the requirements in paragraphs (b) through (h) of 10 CFR 50.55a may be authorized by the U.S. Nuclear Regulatory Commission (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. Although the licensee requested the proposed alternative in accordance with 10 CFR 50.55a(z)(2), the NRC staff reviewed the proposed alternative against the criterion in 10 CFR 50.55a(z)(1).
3.0 TECHNICAL EVALUATION
3.1 Licensees Request 3.1.1 ASME Code Components Affected The components affected by this request are the accessible areas, welds, and surfaces associated with the reactor vessel interior that are included in Examination Categories B-N-1, B-N-2, and B-N-3, Item Nos. B13.10, B13.50, B13.60, and B13.70, of the ASME BPV Code,Section XI.
3.1.2 Applicable Code Edition and Addenda The licensee identified the currently applicable editions and addenda of the ASME BPV Code,Section XI, for each plant in its application, as shown in the table below. In addition, the table shows the current 10-year inservice inspection (ISI) interval, including the start and end dates, for each plant.
Table 1: Current ASME BPV Code,Section XI, Code of Record PLANT ISI INTERVAL SECTION XI EDITION START END Braidwood Unit 1 4th 2013 Edition 8/29/2018 7/28/2028 Braidwood Unit 2 4th 2013 Edition 11/5/2018 10/16/2028 Byron Units 1 and 2 4th 2007 Edition, through 2008 Addenda 7/16/2016 7/15/2025 Calvert Cliffs Units 1 and 2 5th 2013 Edition 7/1/2019 6/30/2029 Ginna 6th 2013 Edition 1/1/2020 12/31/2029 3.1.3 ASME BPV Code Requirements The ASME BPV Code,Section XI, identifies, in part, the following Examination Categories:
B-N-1, interior of reactor vessel; B-N-2, welded core support structures and interior attachments to reactor vessels; and B-N-3, removable core support structures. Table IWB-2500-1 (B-N-1, B-N-2, B-N-3), as required by paragraph IWB-2500(a), and paragraph IWB-3520 of the 2013 edition of Section XI specify the examination requirements, methods, and acceptance standards for Examination Categories B-N-1, B-N-2, and B-N-3. The 2007 edition, through 2008 addenda, of Section XI provides the same requirements, except it has a single Table IWB-2500-1 for all Examination Categories. However, to simplify the discussion, this SE references Table IWB-2500-1 (B-N-1, B-N-2, B-N-3) when referring to these requirements.
3.1.4 Proposed Alternative Braidwood, Byron, Calvert Cliffs, and Ginna are all pressurized-water reactors (PWRs). For PWRs, the components subject to the examination requirements in Table IWB-2500-1 (B-N-1, B-N-2, B-N-3) are identified as Item Nos. B13.10, B13.50, B13.60, and B13.70. The current PWR requirements for these examinations are summarized in Table 2 below. For the subject facilities, the licensee proposed to use Code Case N-885 as an alternative to the applicable requirements in Table IWB-2500-1 (B-N-1, B-N-2, B-N-3) and paragraph IWB-3520, of the ASME BPV Code,Section XI.
Code Case N-885 eliminates Examination Category B-N-1 and Item No. B13.10. Examination Categories B-N-2 and B-N-3 are combined into a single Examination Category B-N. The examination requirements for Examination Categories B-N-2 and B-N-3 (Item Nos. B13.50, B13.60, and B13.70) are retained, but the parts descriptions and numbering are revised. The acceptance standard for VT-1 visual examination is retained, but renumbered. The acceptance standard for VT-3 visual examination is revised and renumbered. The PWR requirements for the new Examination Category B-N in Code Case N-885 are summarized in Table 3 below.
Table 2: Summary of Current PWR Requirements for Examination Categories B-N-1, B-N-2, and B-N-3 Item No.
Parts Examined Examination Requirements and Method Acceptance Standard B13.10 Vessel Interior (B-N-1)
VT-3 visual examination of accessible areas IWB-3520.2 B13.50 Interior attachments with beltline region (B-N-2)
VT-1 visual examination of accessible welds IWB-3520.1 B13.60 Interior attachments beyond beltline region (B-N-2)
VT-3 visual examination of accessible welds IWB-3520.2 B13.70 Core support structure (structure removed from reactor vessel for examination) (B-N-3)
VT-3 visual examination of accessible surfaces IWB-3520.2 Table 3: Summary of Code Case N-885 PWR Requirements for New Examination Category B-N Item No.
Parts Examined Examination Requirements and Method Acceptance Standard B13.10 Interior welded attachments within beltline region VT-1 visual examination of accessible welds
-3520.1 B13.20 Interior welded attachments beyond beltline region VT-3 visual examination of accessible welds
-3520.2 B13.30 Welded core support structure (structure removed from reactor vessel for examination)
VT-3 visual examination of accessible surfaces
-3520.2 B13.40 Removable core support structure (structure removed from reactor vessel for examination)
VT-3 visual examination of accessible surfaces
-3520.2 3.1.5 Duration of the Proposed Alternative The licensees February 1, 2021, letter states that it would discontinue use of the proposed alternative at the end of the current 10-year ISI interval for each plant if the NRC has not approved Code Case N-885 for generic use.
3.2 NRC Staffs Evaluation For Braidwood, Byron, Calvert Cliffs, and Ginna, the license proposed to use Code Case N-885 as an alternative to the applicable requirements in Table IWB-2500-1 (B-N-1, B-N-2, B-N-3) and IWB-3520 of the ASME BPV Code,Section XI. The proposed alternative would eliminate the VT-3 visual examination of the accessible surfaces of the reactor vessel interiors (Examination Category B-N-1) at these facilities. The proposed alternative also changes the requirements for the current Examination Categories B-N-2 and B-N-3, which would be combined into a single Examination Category B-N. Although the licensee requested the proposed alternative in accordance with 10 CFR 50.55a(z)(2), the NRC staff reviewed the proposed alternative against the criterion in 10 CFR 50.55a(z)(1).
3.2.1 Elimination of Examination Category B-N-1 For the subject facilities, the proposed alternative would allow the licensee to eliminate the examinations currently required by the ASME BPV Code,Section XI, for Examination Category B-N-1. Specifically, the licensee would no longer be required to perform the VT-3 visual examinations of the reactor vessel interior (current Item No. B13.10) each inspection period.
The licensee stated, in part, that:
The concern for the effects of foreign material and debris within the reactor vessel are adequately addressed by the routine Core Verification and Foreign Object Search and Retrieval (FOSAR) activities that are performed during refueling outages. If foreign material or debris is observed, maintenance practices are established to either remove the foreign material, or evaluate the consequences if not removing, prior to the reactor vessel head closure. These activities occur each refueling which is more frequent than the current code requirement of each inspection period and provide appropriate processes to adequately address detrimental foreign material within the reactor vessel.
The licensee further stated that other examinations that occur during refueling outages, which are required by the ASME BPV Code,Section XI, or Code Case N-885, also provide opportunities for detecting adverse conditions in the interior of the reactor vessel.
The Electric Power Research Institute (EPRI) Report No. 3002012966, Evaluation of Basis for Periodic Visual Examination of Accessible Areas of Reactor Vessel Interior per Examination Category B-N-1 of ASME Section XI, Division 1, provides information that supports elimination of the VT-3 visual examination of the reactor vessel interior. As discussed in this report, the purpose of this examination is to detect foreign material and debris. The NRC staff determined that the status of the reactor vessel interior is frequently monitored by the plant personnel through core verification, FOSAR, and other examination activities. The FOSAR and core verification activities entail monitoring of the reactor vessel interior surfaces of the surrounding areas. The NRC staff determined that these activities are similar to the VT-3 visual examination of the reactor vessel interior, and, therefore, would provide similar results regarding the status of the vessel interior surface.
The periodic inspection of the reactor vessel interior attachments and removable core support structures would continue to be required under Code Case N-885. These inspections provide reasonable assurance to the NRC staff that the reactor vessel interior surfaces located near these components would also be monitored periodically.
Based on the activities discussed above, the NRC staff concludes that the elimination of the requirements for Examination Category B-N-1 would not compromise the quality and safety of the reactor vessel interior surfaces, because adverse conditions, such as the presence of foreign material or debris on the vessel interior surface, would be identified in a timely manner through core verification, FOSAR, and other examination activities. Therefore, the NRC staff finds it acceptable to eliminate the examinations currently required by the ASME BPV Code,Section XI, for Examination Category B-N-1 at Braidwood, Byron, Calvert Cliffs, and Ginna.
3.2.2 Requirements for the New Examination Category B-N The proposed alternative would combine the current Examination Categories B-N-2 and B-N-3 into a single new Examination Category B-N. The examination requirements for Examination Categories B-N-2 and B-N-3, Item Nos. B13.50, B13.60, and B13.70, are retained, but the parts descriptions and numbering are revised. The acceptance standard for VT-1 visual examination is retained, but renumbered. The NRC staff determined that these changes are acceptable because they do not affect the level of quality and safety of the reactor vessel internal components.
For the current Examination Categories B-N-2 and B-N-3, only the accessible welds and surfaces of the reactor vessel internals are subject the VT-3 visual examinations. The purpose of these examinations is to identify conditions that may impact the structural integrity or functionality of these components. Based on the review of the proposed alternative, the NRC staff determined that the licensee will continue to perform reactor vessel internals examinations at its facilities consistent with the current examination requirements for Examination Categories B-N-2 and B-N-3.
The acceptance standard for VT-3 visual examination is also revised and renumbered. The current acceptance standard for VT-3 visual examinations of components included under Examination Categories B-N-1, B-N-2, and B-N-3 (see Table 2) are specified in subparagraph IWB-3520.2 of the ASME BPV Code,Section XI. Subparagraph IWB-3520.2 identifies relevant conditions that, if identified during an examination, require corrective action before the component can be returned to service. The revised acceptance standard (-3520.2) for the VT-3 examination of components included under the new Examination Category B-N (see Table 3) is consistent with subparagraph IWB-3520.2, except that it does not explicitly require corrective action if foreign materials or accumulation of corrosion products that could interfere with control rod motion or could result in blockage of coolant flow through fuel are identified.
In its February 1, 2021, letter, the licensee indicated that the FOSAR, core verification, and other refueling outage activities provide more frequent opportunities to detect foreign materials and accumulation of corrosion products than the examinations for the current Examination Categories B-N-2 and B-N-3. Given the scope of the VT-3 visual examinations for the current Examination Categories B-N-2 and B-N-3, the NRC staff understands that these examinations are not likely to identify foreign materials or accumulation of corrosion products that could interfere with control rod motion or could result in blockage of coolant flow through fuel. The NRC staff determined that the licensees FOSAR, core verification, and other refueling outage activities provide a much more effective means of detecting foreign materials and accumulation of corrosion products within the reactor vessel than these VT-3 visual examinations.
In its February 1, 2021, letter, the licensee confirmed that the proposed alternative would not result in any modifications to its corrective action process. The licensee stated that this process meets Criterion XVI, Corrective Action, of 10 CFR Part 50, Appendix B, which requires conditions adverse to quality to be corrected. Additionally, the licensee stated that its corrective action process ensures compliance with technical specification requirements (e.g., operability definition, limiting conditions for operations, surveillance requirements) related to control rods, reactor fuel, and the emergency core cooling system. Therefore, the NRC staff has reasonable assurance that the licensee would continue to take appropriate corrective actions, in accordance with Criterion XVI of 10 CFR Part 50, Appendix B, if foreign materials or accumulation of corrosion products that could interfere with control rod motion or could result in blockage of coolant flow through fuel are discovered.
Based on the above, the NRC staff finds that the use of Code Case N-885 at the subject facilities, as an alternative to the current requirements for Examination Categories B-N-2 and B-N-3, will provide an acceptable level of quality and safety. The NRC staff determined that the licensee will continue to perform reactor vessel internals examinations at its facilities consistent with the current examination requirements for Examination Categories B-N-2 and B-N-3. The NRC staff also determined that the licensee (1) will continue to have effective means of detecting foreign materials and accumulation of corrosion products within the reactor vessel and (2) will continue to take appropriate corrective actions, in accordance with Criterion XVI of 10 CFR Part 50, Appendix B, if foreign materials or accumulation of corrosion products that could interfere with control rod motion or could result in blockage of coolant flow through fuel are discovered. Therefore, the NRC staff finds it acceptable to use Code Case N-885 at Braidwood, Byron, Calvert Cliffs, and Ginna as an alternative to the current requirements for Examination Categories B-N-2 and B-N-3.
4.0 CONCLUSION
As set forth above, the NRC staff determined that use of the proposed alternative will provide an acceptable level of quality and safety. Accordingly, the NRC staff concludes that Exelon has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorizes Exelon to use the proposed alternative described in its application, as supplemented, at Braidwood, Byron, Calvert Cliffs, and Ginna. This authorization is for the remainder of the current 10-year ISI interval for each of these facilities.
The NRC approval of this alternative does not imply or infer the NRC approval of Code Case N-885 for generic use. All other ASME BPV Code,Section XI, requirements for which an alternative was not been specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributors: G. Cheruvenki, NRR B. Purnell, NRR Date: February 17, 2021
ML21039A636 OFFICE DORL/LPL3/PM DORL/LPL3/LA DNRL/NVIB/BC NAME BPurnell SRohrer HGonzalez DATE 02/9/2021 02/9/2021 02/16/2021 OFFICE DORL/LPL3/BC NAME NSalgado DATE 02/17/2021