ML24254A255
| ML24254A255 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 09/25/2024 |
| From: | Hipolito Gonzalez Plant Licensing Branch 1 |
| To: | Coffey B Florida Power & Light Co |
| Poole J, NRR/DORL/LPLI, 415-2048 | |
| References | |
| EPID L-2024-LLR-0019 | |
| Download: ML24254A255 (1) | |
Text
September 25, 2024 Bob Coffey Executive Vice President, Nuclear Division and Chief Nuclear Officer Florida Power & Light Company Mail Stop: EX/JB 700 Universe Blvd.
Juno Beach, FL 33408
SUBJECT:
SEABROOK STATION, UNIT NO. 1 - ALTERNATIVE REQUEST NO. 4A-01 FOR THE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL (EPID L-2024-LLR-0019)
Dear Bob Coffey:
By letter dated February 28, 2024, (Agencywide Documents Access and Management System Accession No. ML24151A187, NextEra Energy Seabrook, LLC (the licensee) requested relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME BPV Code) for the Seabrook Nuclear Plant (Seabrook), Unit 1.
The licensee proposed to perform an enhanced visual examination as an alternative to the liquid penetrant (PT) examination required by the original Code of Construction for the final seal weld overlay (WOL) when reinstalling the canopy seal weld for reactor vessel closure head (RVCH) middle control rod drive mechanism (CRDM) housing H-4.
The Nuclear Regulatory Commission (NRC) staff has determined that complying with the specified requirements described in the licensees request referenced above would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components. Therefore, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in Title 10 of the Code of Federal Regulations Paragraph 50.55a(z)(2). The NRC staff authorizes the use of proposed alternative 4A-01, Revision 1 at Seabrook Unit 1 starting with the Fall 2024 Outage and for the duration of the fourth 10-year ISI.
All other ASME BPV Code,Section XI requirements for which an alternative was not specifically requested and authorized remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
If you have any question please contact V.Sreenivas at 301-415-2597 or email v.sreenivas@nrc.gov.
Sincerely, Hipólito González, Branch Chief Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-443
Enclosure:
Safety Evaluation cc: Listserv HIPOLITO GONZALEZ Digitally signed by HIPOLITO GONZALEZ Date: 2024.09.25 14:52:54 -04'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE REQUEST NO. 4A-01 FOR THE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL NEXTERA ENERGY SEABROOK, LLC SEABROOK NUCLEAR PLANT UNIT 1 DOCKET NO. 50-443
1.0 INTRODUCTION
By letter dated February 28, 2024, (Agencywide Documents Access and Management System Accession No. ML24151A187), NextEra Energy Seabrook, LLC (the licensee) requested relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME BPV Code) for the Seabrook Nuclear Plant (Seabrook), Unit 1.
The licensee proposed to perform an enhanced visual examination as an alternative to the liquid penetrant (PT) examination required by the original Code of Construction for the final seal weld overlay (WOL) when reinstalling the canopy seal weld for reactor vessel closure head (RVCH) middle control rod drive mechanism (CRDM) housing H-4. Pursuant to Paragraph 50.55a(z)(2) of Title 10 of the Code of Federal Regulations (10 CFR), the licensee requested to use the proposed alternative on the basis that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
2.0 REGULATORY EVALUATION
The regulations at 10 CFR 50.55a(g), Preservice and inservice inspection requirements, require, in part, that inservice inspection (ISI) of the ASME BPV Code Class 1, 2, and 3 components be performed in accordance with Section XI of the ASME BPV Code and applicable addenda as a means of detecting anomalies and indications of degradation so that structural integrity of these components can be maintained.
The regulations at 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state, in part, that alternatives to the requirements of paragraphs (b) through (h) of 10 CFR 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) the proposed alternative would provide an acceptable level of quality and safety, or (2) compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
3.0 TECHNICAL EVALUATION
3.1 Licensees Alternative Request No. 4A-01, Revision 1 3.1.1 Applicable Inservice Inspection (ISI) Program Interval and Interval End Date Fourth 10-year ISI interval which began August 19, 2020, and ends on August 18, 2030.
3.1.2 ISI Requirement The Fourth Ten Year ISI interval Code of record for Seabrook Unit 1 is ASME Code,Section XI, 2013 Edition.
3.1.3 Applicable Code Edition and Addenda The manufacturing Code for the Seabrook Unit 1 RVCH CRDMs is ASME Code, Section Ill, Rules for Construction of Nuclear Power Plant Components, Division 1, 1974 Edition through and including the Winter 1974 Addenda.
3.1.4 Reason for Request Seabrook Unit 1 seeks relief from ASME Code,Section XI requirements that repairs/replacement be performed in accordance with the owners original code of construction for the component or system, or later editions and addenda of the Code. The original code of construction for RVCH CRDM canopy seal welds at Seabrook Unit 1 is ASME Code,Section III, Division 1, 1974 Edition through and including Winter 1974 Addenda, which in Subsection NB-5270/NB-5271 requires performance of a PT surface examination for the repair/replacement of the Seabrook Unit 1 RVCH CRDM Housing H-4 canopy seal weld. Replacement of the CRDM requires cutting and re-welding the canopy seal weld. Although the seal weld does not perform a pressure retaining function for this threaded connection, it is essential for leak prevention. Seabrook Unit 1 will also install a seal WOL over the re-welded canopy seal weld on CRDM housing H-4 to provide additional assurance of leak prevention.
Seabrook proposes using enhanced remote visual examination instead of PT due to difficulty of accessing the weld area, which is subject to high radiation levels and limited access. Performing PT would require significant additional support, increasing radiation exposure and industrial safety risks. The alternative methods comply with ASME Code,Section XI and relevant codes, addressing potential flaws and ensuring safety. Relief is requested under 10 CFR 50.55a(z)(2) due to the significant hardship and safety concerns associated with complying with the standard examination requirements.
Proposed Alternative Seabrook proposes to perform an enhanced remote visual examination of the repair/replacement of the CRDM housing H-4 middle canopy seal weld and installing of the seal WOL in lieu of ASME Code surface examination PT, as required by ASME Code,Section III, Division 1, 1974 Edition through and including Winter 1974 Addenda, paragraph NB-5270/NB-5271. The minimum seal WOL thickness is designed to provide additional margin over the original canopy seal weld thickness to account for corrosion and fatigue analyses and will be the new secondary leak barrier. The design includes a postulated through wall flaw in the existing canopy seal weld, and the fatigue and corrosion crack growth analysis that supports 60 years of service from the time of installation, well beyond the current license. Because of limited access and high dose rates, compliance with the ASME Code requirement to perform a surface examination would not meet the intent of the sites as low as reasonably achievable (ALARA) radiological control program and, therefore, presents a hardship to the utility and workers.
The proposed remote enhanced visual examination will be conducted using a video camera with a minimum of 5X magnification. Lighting and acuity will be verified using ASME Code,Section XI, Table IWA-2211-1 requirements for VT-1 note (2). The licensee requested the proposed alternative for the remainder of the Fourth 10-year ISI interval.
For additional details on the licensees request, please refer to the documents located at the ADAMS Accession No. identified above.
3.2
NRC Staff Evaluation
Article IWA-4000 of the ASME Code,Section XI requires that repairs be performed in accordance with the owner's original construction code for the component or system, or later editions and addenda of the Code. The original construction code for CRDM housings at Seabrook Unit 1 is the ASME Code,Section III Division 1, 1974 Edition through and including Winter 1974 Addenda, and repair or replacement of canopy seal weld would require surface examination and removal of indications followed by another surface examination to ensure that rejectable indications have been removed. Seabrook Unit 1 has experienced control rod slipping in the H-04 CRDM attributed to crud miss-stepping as the likely cause. Although no leak or flaw was detected in the canopy seal weld, a postulated through wall flaw is assumed in the existing canopy seal weld for the design of the seal WOL. The seal WOL repair was designed under the requirements of ASME Code,Section XI, 2013 Edition, Paragraph IWB-3640, Evaluation Procedures and Acceptance Criteria for Flaws in Austenitic and Ferritic piping, and Appendix C, Evaluation of Flaws in Piping, which will be used as an alternative repair method.
Guidance was also taken from ASME Code Case N-504-4 which was incorporated into 2007 Editon with 2008 addendum and later edition of ASME Code,Section XI, Article Q and NUREG-0313, Revision 2, Technical Report on Material Selection and Processing Guidelines for BWR Coolant Pressure Boundary Piping for the seal WOL design.
The NRC staff reviewed the licensees basis and justification for its repair/replacement and subsequent examination method, as stated in proposed alternative 4A-01, Revision 1. The NRC staff finds that the licensees assertion that compliance with the ASME Code requirements for the re-welding CRDM H-04 mid-canopy seal weld and installing of the seal WOL at Seabrook Unit 1 would result in hardship or unusual difficulty is acceptable on the basis that the subject components are located such that there is limited space and high radiation levels.
For this seal WOL, the licensee has proposed using a remote enhanced visual examination on the completed weld in lieu of the required ASME Code surface examinations. Additionally, visual and/or surface examination will be performed on the accessible disassembled mating surfaces to ensure they are suitable for performing the seal WOL.
As an added contingency if a defect is identified in the canopy seal weld or adjoining mating surface materials that cannot be removed due to accessibility or tooling limitations, the proposed design of the replacement seal WOL accounts for this with the assumption of a per-existing through wall flaw in the original seal weld secondary leak boundary. The minimum seal WOL thickness is designed to have additional margin over the original canopy seal weld thick to account for corrosion and fatigue analyses and will be the new secondary leak boundary.
The final seal WOL will be examined by the proposed remote enhanced visual means. The NRC staff notes that the structural components associated with the CRDMs are assembled by threaded connections. The CRDM assemblies and their threaded joints provide the primary pressure boundary and structural support for the CRDMs. The canopy seal WOL is intended for leak tight seal only and does not provide the primary pressure boundary or structural support.
The licensee provided a drawings and sketches that demonstrates the general configuration of a CRDM with the middle canopy seal weld and seal WOL.
The NRC staff also notes that it approved similar alternatives as identified in Section 7 of the submittal. There is no applicable ASME Code,Section XI Examination Category or Item Number associated with this configuration as canopy seal welds are not subject to Table IWB-2500-1 surface or volumetric examinations. Furthermore, a VT-2 in-service leakage examination is performed on the Class 1 pressure boundary at the conclusion of each refueling outage as required by ASME Code,Section XI, Table IWB-2500-1 Examination Category B-P, All Pressure Retaining Components. In addition, a leakage examination is performed through the reactor vessel head shroud plexiglass windows at the CRDM penetrations at the beginning of each refueling outage as part of the Seabrook Unit 1 Containment Leakage Reduction Program Surveillance and the Boric Acid Corrosion Control Program. In the unlikely event of leakage from the newly installed seal WOL, these examinations at Seabrook Unit 1 are designed to promptly identify and correct the issue.
In summary, the NRC staff reviewed the licensees submittal and finds that compliance with the ASME Code requirements for the re-installation of mid canopy seal welds and installation of the seal WOL would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Additionally, the NRC staff finds that proposed alternative will provide reasonable assurance of leak tightness: 1) the proposed repair follows the welding qualification requirements of the ASME Code,Section XI, 2) the proposed repair will meet the design requirements of ASME Code,Section III, 3) similar alternatives were approved and used previously, 4) structural integrity of the subject components will not be altered by the alternative, and 5) these components would be subject to the periodic system leakage testing requirements of the ASME Code,Section XI.
4.0 CONCLUSION
The NRC staff has determined that complying with the specified requirements described in the licensees request referenced above would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components.
Therefore, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2). The NRC staff authorizes the use of proposed alternative 4A-01, Rev.1 at Seabrook Unit 1 starting with the Fall 2024 Outage and for the duration of the fourth 10-year ISI.
All other ASME BPV Code,Section XI requirements for which an alternative was not specifically requested and authorized remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: O. Khan, NRR Date: September 25, 2024
- via email OFFICE DORL/LPL1/PM DORL/LPL1/LA DNRL/NPHPB/BC*
NAME VSreenivas KZeleznock MMitchell DATE 09/10/2024 09/13/2024 08/28/2024 OFFICE DORL/LPL1/BC NAME HGonzalez DATE 09/25/2024