ML23130A390
| ML23130A390 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 05/12/2023 |
| From: | Perry Buckberg NRC/NRR/DORL/LPL2-2 |
| To: | Krakuszeski J Duke Energy Progress |
| References | |
| EPID L-2022-LLR-0089 | |
| Download: ML23130A390 (12) | |
Text
May 12, 2023 Mr. John A. Krakuszeski Site Vice President Brunswick Steam Electric Plant Duke Energy Progress, LLC 8470 River Rd., SE (M/C BNP001)
Southport, NC 28461
SUBJECT:
BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS. 1 AND 2 -
REGULATORY AUDIT PLAN IN SUPPORT OF ALTERNATIVE REQUEST RA-22-0308 FOR INSERVICE INSPECTION OF THE TORUS METALLIC LINER (EPID L-2022-LLR-0089)
Dear Mr. Krakuszeski:
By letter dated December 15, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22349A655), Duke Energy Progress, LLC (Duke Energy) requested an alternative (RA-22-0308) to certain requirements of the 2007 Edition through 2008 Addenda of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, Subsection IWE to conduct alternative visual examinations of the torus metallic liner at Brunswick Steam Electric Plant, Unit Nos. 1 and 2 (Brunswick).
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed Duke Energys request and determined that a regulatory audit would assist in the timely completion of the review. The NRC staff will conduct a regulatory audit to support its review in accordance with the enclosed audit plan. A regulatory audit is a planned activity that includes the examination and evaluation of primarily non-docketed information.
The NRC staff will conduct the audit to increase its understanding of the request and identify information that will require docketing to support the NRC staffs regulatory findings. The NRC staff will conduct the audit virtually June 5 to June 15, 2023.
J. Krakuszeski If you have any questions, please contact me at (301) 415-1383 or by email at Perry.Buckberg@nrc.gov.
Sincerely,
/RA by Michael Mahoney for/
Perry H. Buckberg, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-325 and 50-324
Enclosure:
Audit Plan cc: Listserv
Enclosure REGULATORY AUDIT PLAN BY THE OFFICE OF NUCLEAR REACTOR REGULATION IN SUPPORT OF ALTERNATIVE REQUEST RR-22-0308 FOR INSERVICE INSPECTION OF THE TORUS METALLIC LINER DUKE ENERGY PROGRESS, LLC BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-325 AND 50-324
1.0 BACKGROUND
By letter dated December 15, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22349A655), Duke Energy Progress, LLC (Duke Energy, the licensee) requested an alternative (request RA-22-0308) to certain requirements of the 2007 Edition through 2008 Addenda of American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code,Section XI, Subsection IWE to conduct alternative visual examinations of the torus metallic liner at Brunswick Steam Electric Plant, Unit Nos. 1 and 2 (Brunswick).
The U.S. Nuclear Regulatory Commission (NRC) staff has determined the need for a regulatory audit to be conducted in accordance with Office of Nuclear Reactor Regulation Office Instruction LIC-111, Regulatory Audits (ML19226A274), for the NRC staff to examine the licensees non-docketed information with the intent to gain a better understanding of the alternative request, to verify information, and to identify information that may require docketing to support the basis of the NRC staffs regulatory decision.
2.0 REGULATORY AUDIT BASIS The NRC staff (i.e., audit team) will perform the audit to support its evaluation of whether the licensees request meets the requirements of Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55(a)(z), Alternatives to codes and standards requirements. The audit will assist the NRC staff with understanding the licensees proposed alternatives.
3.0 REGULATORY AUDIT SCOPE AND METHODOLOGY The audit team will review the licensees records, analyses, and calculations related to proposed alternative examinations required by ASME Code, subsection IWE, for visual examination of the metallic liner surrounding each torus suppression chamber (torus) of Brunswick, Unit Nos. 1 and 2. The audit team will determine whether any additional information contained in the records, analyses, and calculations, will need to be submitted or supplemented to the request to support or develop conclusions for the NRC staffs safety evaluation.
4.0 INFORMATION AND OTHER MATERIAL NECESSARY FOR THE REGULATORY AUDIT The attached Audit Items List includes questions the Audit Team intends to discuss during the audit and includes information to be audited. The Audit Team requests that the information on the Audit Items List be readily available and accessible for the Audit Teams review via a Web-based portal to be established by Duke Energy. Information accessed through the licensees portal will not be held or retained in any way by the NRC staff. Based on the audit of information on the Audit Items List, the Audit Team will determine whether it needs to request any additional documents be made available via the portal or whether additional information needs to be submitted on the docket for the staff to complete the review of the alternative request. Throughout the audit, the NRC staff may supplement the Audit Items List as needed so that the licensee can better prepare for audit discussions which will be scheduled as needed.
The NRC staff will provide the final Audit Items List as an enclosure to the Audit Summary Report, which will be publicly available.
5.0 TEAM ASSIGNMENTS The audit team will consist of the following NRC staff from the Office of Nuclear Reactor Regulation (NRR).
Perry Buckberg, Senior Project Manager and Audit Team Lead, Division of Operating Reactor Licensing, Plant Licensing Branch 2-2 (LPL2-2)
Ata Istar, Civil Engineer, Division of Engineering and External Hazards, Structural, Civil, Geotech Engineering Branch (ESEB)
Brian Lee, Safety and Plant Systems Engineer, Division of Safety Systems, Containment and Plant Systems Branch (SCPB)
John Tsao, Senior Materials Engineer, Division of New and Renewed Licenses, Vessels and Internals Branch (NVIB)
Dan Widrevitz, Materials Engineer, NVIB 6.0 LOGISTICS The audit will be conducted from June 5 to June 15, 2023, through the online portal. Duke Energy will provide Audit Team members access to the online portal and access may be terminated after completion of the audit at a time agreed between the Audit Team and Duke Energy.
On or about June 5 2023, the Audit and the licensee team will conduct a virtual Audit Entrance Meeting with the licensee for the purpose of introducing the team, discussing the scope of the audit, and describing the information to be made available on the portal. The audit team will also confirm with the licensee if the information made available on the portal contains any sensitive or proprietary information. During the audit period, the Audit Team may request that the licensee respond to questions related to information provided on the portal at mutually agreeable days and times by virtual and/or telephone meetings. It is important that licensee staff who are knowledgeable about the alternative request and topics in the Audit Items List be available during the audit period.
7.0 SPECIAL REQUESTS The following conditions associated with the portal must be maintained while the NRC staff have access to the online portal:
The online portal will be password-protected. A separate password will be assigned or to each member of the NRC staff participating in the audit.
The online portal will prevent the audit team from printing, saving, downloading, or collecting any information directly from the portal.
Conditions of use of the portal will be displayed on the login screen and will require acknowledgment by each user.
Username and password information should be provided directly to members of the audit team.
The audit team lead will provide the licensee any needed contact information for the audit team.
All other communications should be coordinated through the audit team lead.
8.0 DELIVERABLES An audit summary, which will be publicly available, will be prepared within 60 days of the completion of the audit. If the NRC staff identifies information during the audit that is needed to support its regulatory decision, the NRC staff will issue requests for additional information to the licensee.
Enclosure Audit Items List ITEM #
AUDIT REQUEST R1 ESEB It is not clear how the licensee determined the acceptable minimum thicknesses (tmin) for local substrate pit corrosion and for general area corrosion.
Provide engineering evaluation(s) and/or a description that justifies the statement that the torus metallic liner remains fully capable of performing its intended design function with local substrate pit corrosion that does not result in a remaining wall thickness of less than 187 one thousandth of an inch (mils) (tmin =
3/16 or 50% nominal wall thickness) and with general area corrosion that does not result in a remaining wall thickness of less than 250 mils (tmin = 1/4 or 66%
nominal wall thickness).
R2 ESEB It is not clear how the licensee established the acceptance criteria that substrate corrosive degradation less than 90 mils in the submerged surfaces of the torus containment metallic liners for continued service without engineering evaluation or correction by repair/replacement or other applicable code corrective measures.
Describe how the acceptance criterion of 90 mils was established by providing engineering calculation(s) justifying for the torus containment metallic liners for the continued service without engineering evaluation or correction by repair/replacement or other applicable code corrective measures.
R3 ESEB It is not clear how the licensee determined the acceptance criteria of 145% design minimum allowable as the relevant condition provides adequate design margin and reasonable assurance that the torus metallic liner submerged surfaces remain fully capable of performing their intended design function(s) until the next scheduled containment inspection in accordance with Table IWE-2500-1, Examination Category E-A, Item Number E1.12.
Provide the engineering assessment with applicable code(s) and regulatory bases for choosing the acceptance criteria of 145% design minimum allowable and as the relevant condition, provides adequate design margin and reasonable assurance that the torus metallic liner submerged surfaces remain fully capable of performing their intended design function(s) until the next scheduled containment inspection in accordance with Table IWE-2500-1, Examination Category E-A, Item Number E1.12.
R4 ESEB The efficacy of these protective coatings is not clear to the staff on existing degradation in the submerged surfaces of the torus containment liners. The staff is also unclear about the life-expectancy of the protective coating.
(1) Provide information (procedure(s), technical document(s), etc.) describing how the applications and restorations of coatings on the submerged surfaces of the torus containment liners are performed. Describe how the application and restoration of coatings would arrest degradation for the remainder of the current inspection interval and until the subsequent scheduled visual (VT-3) examination during the successive containment inspection interval, as well as provide reasonable assurance that the existing degradations of these submerged surfaces of the torus containment liners have been arrested and/or mitigated. (2)
Describe how long the protective coating is expected last. Provide a basis for the ITEM #
AUDIT REQUEST life-expectancy of the protective coating materials and whether debris from protective coating failure could cause operational concerns.
R5 ESEB The request did not include a discussion related to visual examination procedures and effectiveness of diver(s) in detecting substrate pit corrosion and general area degradation of the torus metallic liners.
Provide the visual examination procedure(s) (describing applicable acceptance criteria) and justify the effectiveness of diver(s) in their detection of substrate pit corrosion and general area degradation on the torus containment metallic liners.
R6 NVIB The licensee submitted alternative request RA-22-0308 pursuant to 10 CFR 50.55a(z)(1) which permits the implementation of an alternative that provides an acceptable level of quality and safety. The regulation of 10 CFR 50.55a(z)(2) permits an alternative that demonstrates that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. To submit under 10 CFR 50.55a(z)(1), the alternative request typically contains extensive analyses and testing to demonstrate the level of quality and safety of the proposed alternative is equivalent to the requirements of the ASME Code,Section XI. To use 10 CFR 50.55a(z)(2), the alternative request typically demonstrates show hardship or unusual difficulty without a compensating increase in the level of quality and safety. The proposed alternative does not provide extensive analyses and testing to demonstrate its equivalent level of quality and safety. Therefore, it is not clear why the proposed alternative was submitted under 10 CFR 50.55a(z)(1).
Explain/further justify why the proposed alternative was submitted under 10 CFR 50.55a(z)(1) in lieu of 10 CFR 50.55a(z)(2).
R7 NVIB Section 4.1 of the request states, in part, that The Brunswick Units 1 and 2 Suppression Chamber (torus) containment metallic liner plate is 3/8-inch (375 mils) nominal thickness and backed by reinforced concrete Attachment 1 to the request presents two diagrams of the torus arrangement. However, the diagrams do not show how the reinforced concrete is joined with the torus shell metal plates.
(1) Discuss whether a gap or annulus exists between the torus shell metal plate (i.e., liner) and the reinforced concrete such that the leaking coolant, if leakage occurs, could be drained away from the torus metal shell; (2) If a through wall leak does occur at a torus shell liner, discuss how the leakage can be detected and how soon the operator could be notified (e.g., hours, days, etc.); (3) Discuss the consequence if the torus shell incurred a 100% through wall flaw and the coolant leaks into the interface between the metal shell and the reinforced concrete without timely detection; and (4) Provide a sketch or diagram of the joint configuration between the torus shell plate and the reinforced concrete similar to Figure IWE-2500-1 of the 2007 Edition of the ASME Code,Section XI.
R8 NVIB Section 4.1 of the request states, in part, that The torus metallic liner remains fully capable of performing its intended design function with local substrate pit corrosion that does not result in a remaining wall thickness of less than 187 mils (tmin=3/16 or 50% nominal wall thickness) and with general area corrosion that ITEM #
AUDIT REQUEST does not result in a remaining wall thickness of less than 250 mils (tmin = 1/4 or 66% nominal wall thickness) The proposed alternative does not provide technical basis to support the claim that 50% and 66% nominal wall thickness for the local substrate pit corrosion and the general area corrosion, respectively, would maintain the design function. Also, the proposed alternative does not provide the definition of local pit corrosion and general corrosion e.g., what is the dimension of the surface area that would be considered as local pit corrosion vs.
general area corrosion.
(1) Discuss the technical basis of 50% and 66% nominal wall thickness for the local pit corrosion and the general area corrosion, respectively, that would support the design function of the torus; and (2) Define the general area corrosion and local substrate pit corrosion in term of surface area of the torus.
R9 NVIB Section 4.2.2 of the request states, in part, that the licensee applied protective coating on the submerged surface of all 16 torus bays at Unit 2 during the second CISI [containment inservice inspection] (March 2015). Section 4.3.2 of the request states, in part, that in the third CISI inspection which began in May 2018, a corroded area that exceeded the 10% metal loss acceptance criterion was detected in a torus bay. It appears that the protective coating that was applied to the torus interior surface in 2015 did not arrest or prevent the corrosion at that corroded area. In addition, the proposed alternative does not provide data on the corrosion rate (mils per month or year).
(1) Discuss why the protective coating did not arrest or prevent corrosion at the corroded area on a torus bay of Unit 2; (2) Discuss the effectiveness of the protective coating, e.g., how many years the protective coating can protect the torus shell from growth of an existing corroded area or from a new corrosion to occur on the torus metal shell surface?; and (3) Discuss the maximum and average corrosion rate (mils per month or year) of the corroded areas detected in Units 1 and 2.
R10 NVIB Section 4.4.2 of the request states, in part, that For Brunswick Unit 1 torus submerged surfaces with substrate pit corrosion areas left uncoated during the second inspection interval (Brunswick Unit 1, March 2016), the engineering evaluation, proposed alternative visual (VT-3) examination acceptance criteria (Section 5.1), and the scheduled visual examinations during the next two refueling outages of the current third containment inspection interval It is not clear why the corroded areas have not been applied with protective recoating restoration during the second CISI of Unit 1 even though protective coating was applied on the torus bays of Unit 2. It is not clear whether the uncoated corroded areas will be visually examined during each of the two refueling outages, or will be divided between the two refueling outages in the third CISI.
(1) Discuss why the uncoated corroded areas of the Unit 1 torus were not applied with protective coating during the second CISI to minimize further corrosion; (2) If the uncoated corroded areas on the torus shells of Unit 1 have grown during the inspections in the next two refueling outages of the third CISI, discuss the corrective actions; and (3) Discuss whether all the uncoated corroded torus areas of Unit 1 will be visually examined in each of the two refueling outages, or will be divided between the two refueling outages in the third CISI.
ITEM #
AUDIT REQUEST R11 NVIB Section 4.4.2 of the request states, in part, that During Brunswick Unit 1 third containment inspection interval, there are three (3) remaining refueling outages.
With the conservatism applied by the engineering evaluation to establish visual (VT-3) examination acceptance criteria and design minimum allowable thickness for the torus metallic liner, additional remaining service life may be attained and applied through additional design analysis. This additional analysis may allow extending the current scheduled visual examinations and protective coating restorations to the third remaining refueling outage of the current Brunswick Unit 1 current third containment inspection interval Section 5.2 of the request states, in part, that On Brunswick Unit 1, visual (VT-3) examinations and protective coatings restoration of submerged surfaces in the remaining twelve (12) torus bays will continue during the current third inspection interval in accordance with Table IWE-2500-1, Examination Category E-A, Item Number E1.12. These twelve (12) torus bays did not receive protective coating restoration during the third period of the previous second containment inspection interval. Visual (VT-3) examinations during the current third containment inspection interval and engineering evaluation facilitate the monitoring of degradation of these torus metallic liner submerged surfaces. Duke Energy proposes that the engineering evaluation provides reasonable assurance that these submerged surfaces remain fully capable of performing its intended design function(s) during the current third containment inspection interval and until the next visual (VT-3) examination during the next two refueling outages of the current inspection interval It is not clear which is the third remaining refueling outage of the third CISI. It is not clear whether corroded areas were or were not detected in the 12 Unit 1 torus bays. Therefore, coating restoration was not needed, or there were corroded areas detected but the licensee made the decision not to restore the corroded areas. It is not clear whether the 16 Unit 1 torus bays, including the 12 bays mentioned above, have been applied with protected recoating. It seems that the proposed examination extension for Unit 1 is predicated on the protective coating restoration of the torus bays. However, it is not clear whether torus bays for Unit 1 have been restored with protective coating. It appears that the licensee requests NRC approval of the proposed examination extension before the protective coating is being restored in the Unit 1 torus.
(1) For Unit 1, discuss whether corroded areas were detected in the 12 torus bays during the inspection performed in the third period of the second CISI. If corroded areas were detected, discuss why the protective coating restoration was not performed on the corroded areas of the 12 torus bays; (2) Clarify whether these remaining 12 torus bays were re-examined during the first period of the third CISI.
If re-examined, discuss whether new corroded areas were detected and whether the existing corroded areas have grown. If not re-examined, discuss when the next examination of the 12 bays would occur; (3) Discuss whether the protective coating restoration will be applied to all 16 Unit 1 torus bays during the third remaining refueling outage of the third CISI. If not restored, provide justification; (4) Confirm that the third remaining refueling outage of the third CISI is the last refueling outage before the end of third CISI on May 10, 2028; and (5) Discuss ITEM #
AUDIT REQUEST and/or provide the design analysis and corrosion test data that allows for examination extension and protective coating restorations of the uncoated corroded areas to the third remaining refueling outage of the third CISI for the Unit 1 torus. That is, justify why the examination extension (inspection every three periods) could be applied to the Unit 1 torus bays that have not implemented protective coating restoration to the corroded areas.
R12 NVIB Section 5.1 of the request states, in part, that As an alternative to the 10% loss of nominal wall thickness specified in IWE-3513(a), Duke Energy proposes visual (VT-3) examinations revealing substrate pitting or other corrosive degradation that results in a remaining wall thickness of less than 145% of the design minimum allowable for substrate pit corrosion of the metallic liner nominal wall thickness will be considered relevant conditions Subarticle IWE-3513(a) of the 2007 Edition of the ASME Code,Section XI, discusses relevant conditions include corrosion that exceeds 10% of the nominal wall thickness. The NRC staff noted that 10% loss of nominal torus wall thickness is 0.0375 inches for the torus of both Unit Nos. 1 and 2. The NRC staff noted that the request does not provide the design minimum allowable thickness; therefore, it is not clear how the proposed alternative criterion of 145% of the design minimum allowable thickness is compared to the acceptance criterion of IWE-3513(a).
(1) Provide the proposed alternative converted remaining wall thickness of less than 145% of the design minimum allowable to the percentage of metal loss of the torus nominal wall thickness; (2) Discuss the technical basis, including analyses and corrosion test data, of the acceptance criterion of 145% of the design minimum allowable; (3) Provide the value of the design minimum allowable thickness and its derivation; and (4) Discuss the corrective actions that would be taken if a corroded area exceeds the proposed acceptance criterion.
R13 NVIB Section 5.1 of the request states, in part, that This visual (VT-3) reexamination shall be performed during the successive inspection interval at a frequency not to exceed every third inspection period from the previously visual (VT-3) examination The submerged torus shell plates of both Units 1 and 2 contain re-coated corroded areas, corroded areas that have not been re-coated, and potential new corroded areas. It is not clear whether inspecting the torus shell every third inspection period is adequate for corroded areas with various degrees of degradation because the proposed alternative will result in a maximum inspection frequency of 10 years. In addition, the request does not provide the corrosion test and operating experience data and analyses to justify the proposed examination extension.
(1) Discuss the technical basis to support the proposed inspection frequency of every third period for each of the following degradations: (a) previously detected corroded areas that are not repaired, (b) the repaired corroded areas, (c) newly detected corroded areas during future examinations, and (d) areas that may degrade during every three inspection periods (i.e., 10 years). The technical basis should include analyses and corrosion test and operating experience data to demonstrate the adequacy of inspection every three periods; and (2) Clarify whether the proposed examination extension (every three periods) applies only to ITEM #
AUDIT REQUEST the re-coated corroded areas that have been repaired (i.e., protective coating restoration) or to all possible corrosion cases (i.e., aforementioned cases a, b, c, and d).
R14 NVIB Section 5.2 of the request states, in part, that On Brunswick Unit 2, visual (VT-3) examinations and protective coating restoration were performed on five (5) torus bays during the first period of the third containment inspection interval.
Augmented visual (VT-1) examinations were neither required nor performed during these containment liner inspections For these five (5) torus bays on Brunswick Unit 2, Duke Energy proposes that successive visual (VT-1) examination during the next inspection period will not be performed and the next scheduled visual (VT-3) examination will be performed during the fourth containment inspection interval The NRC staff notes that: (1) The 2007 edition of the ASME Code,Section XI, Table IWE-2500-1, Examination Category E-C, Item No. E4.11 requires a VT-1 examination be performed for the surface areas identified by IWE-1242 which refers to surface areas identified by IWE-1240, Surface Areas Requiring Augmented Examination. It is not clear why VT-1 examination is not performed when a detected corroded area exceeded the 10% metal loss acceptance criterion of IWE-3513(a) during the first period of the third CISI for Unit 2; and (2)
It is not clear why VT-1 examination will not be performed on the corroded areas during the inspection that will be performed in the fourth CISI for Unit 2.
(1) Discuss why augmented VT-1 examinations were neither required nor performed during the first period of the third CISI when corrosion areas were detected on the torus bays for Unit 2; and (2) Discuss why the VT-1 examination will not be performed on the corroded areas during the inspection for the fourth CISI for Unit 2.
R15 NVIB Sections 4 and 5 of the request discuss activities that have been and will be performed in various refueling outages and periods of the third CISI. However, it is not clear the exact timing of the activities that have been and will be performed with respect to the refueling outages and periods of the third CISI. Section 6 of the request states that the duration of the request is for the third CISI only.
For Units 1 and 2, provide a table and/or timeline showing the examination and repair activities with respect to the refueling outages and periods of the third CISI.
Specifically (a) provide the month and year of every refueling outage in the third CISI, (b) indicate activities (examination and/or coating restoration) that have been and will be performed in the refueling outage(s) in the third CISI, (c) indicate which refueling outage belongs to which period of the third CISI, (d) indicate the examination and potential repair activities that are scheduled for the refueling outage in the first period of the fourth CISI, and (e) confirm that the torus examination and repair activities beyond the third CISI are not covered by the subject request.
ML23130A390 NRR-106 OFFICE NRR/DORL/LPL2-2/PM NRR/DEX/ESEB/BC NRR/DSS/SCPB/BC NAME NJordan ITseng BWittick DATE 4/21/2023 4/21/2023 4/21/2023 OFFICE NRR/DNRL/NVIB/BC NRR/DORL/LPL2-2/LA NRR/DORL/LPL2-2/BC NAME ABuford RButler DWrona (PBuckberg for)
DATE 5/09/2023 5/11/2023 5/12/2023 OFFICE NRR/DORL/LPL2-2/PM NAME PBuckberg (MMahoney for)
DATE 5/12/2023