ML23090A130
| ML23090A130 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 03/31/2023 |
| From: | Richard Guzman NRC/NRR/DORL/LPL1 |
| To: | Tom Loomis Constellation Energy Generation |
| References | |
| EPID L-2023-LLR-0011 | |
| Download: ML23090A130 (1) | |
Text
From: Richard Guzman To: Loomis, Thomas R:(Constellation Nuclear)
Cc: Reynolds, Ronnie J:(Constellation Nuclear); Hipo Gonzalez
Subject:
Verbal Authorization for NMP1 Proposed Alternative Weld Overlay N2E Safe-end to nozzle DM Weld (EPID L-2023-LLR-0011)
Date: Friday, March 31, 2023 9:59:45 AM Attachments: image001.png
Mr. Loomis,
In accordance with NRR Office Instruction LIC-102, Review of Relief Requests, Proposed Alternatives, and Requests to Use Later Code Editions and Addenda, (ADAMS Accession No. ML18351A218) the NRR staff has provided verbal authorization for Nine Mile Point Nuclear Station, Unit 1 (NMP1) Relief Request I5R-11 as described in Constellation Energy Generation, LLC (CEG, the licensee) letter dated March 24, 2023 (ML23083B991), as supplemented by letters dated March 27, March 29, and March 30, 2023 (ML23086C088, ML23088A165, and ML23089A230, respectively). The proposed alternative, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), requested to perform a weld overlay to act as a leakage barrier on recirculation inlet nozzle N2E safe end to nozzle dissimilar metal weld, in lieu of repairing as required by American Society of Mechanical Engineers (ASME) Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plants.
Below is the script for the verbal authorization of Relief Request I5R-11 that was provided at approximately 9:30am EDT on March 31, 2023, by Matthew Mitchell and Hipolito Gonzalez and a list of attendees on the call. As was communicated, the NRC staff finds that the licensees proposed alternative I5R-11 will provide an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1). Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1).Therefore, as of March 31, 2023, the NRC authorizes the use of Relief Request I5R-11 at NMP1 until the end of the next refueling outage (N1R28).
This e-mail communication will be added to ADAMS as a publicly available official agency record, documenting the staffs approval. The NRC staffs formal safety evaluation will be transmitted via separate correspondence within approximately 150 days.
Please contact me if you have any questions regarding this licensing action.
Richard V. Guzman Senior Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission
Docket No. 50-220
Enclosure:
Verbal Authorization Script and List of Attendees
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VERBAL AUTHORIZATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
RELIEF REQUEST I5R-11 PROPOSED ALTERNATIVE ASME CODE REPAIR OF RECIRCULATION INLET NOZZLE
N2E SAFE END-TO-NOZZLE DISSIMILAR METAL WELD REPAIR NINE MILE POINT NUCLEAR STATION, UNIT 1
CONSTELLATION ENERGY GENERATION, LLC DOCKET NO. 50-220
Technical Evaluation read by Matthew Mitchell, Chief of the Piping and Head Penetrations Branch, Division of New and Renewed Licenses, NRR
By letter dated March 24, 2023, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23083B991), as supplemented by letters dated March 27, March 29 and March 30, 2023 (ADAMS Accession Nos.ML23086C088, ML23088A165 and ML23089A230, respectively), Constellation Energy Generation, LLC (CEG, the licensee) requested an alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Power Plants, IWA-4411(a), IWA-4411(b), IWA-4412, IWA-4611, and IWB-3640 at Nine Mile Point Nuclear Station, Unit 1 (NMP 1). The licensee submitted Relief Request I5R-11 for U.S. Nuclear Regulatory Commission (NRC) review and approval to support performing a weld overlay to act as a leakage barrier on the recirculation inlet nozzle N2E safe end-to-nozzle dissimilar metal weld in lieu of repairing as required by ASME Code,Section XI. Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), the licensee submitted Relief Request I5R-11 on the basis that it will provide an acceptable level of quality and safety for the units next cycle of operation.
On March 18, 2023, during automated ultrasonic examination of the N2E safe end-to-nozzle weld, the licensee discovered an axially-oriented, 83 percent through-wall flaw.
ASME Code,Section XI, IWB-3640 requires that a flaw may not exceed 75 percent through wall. In lieu of performing an ASME Code,Section XI repair in accordance with IWA-4000, the licensee proposed to perform a weld overlay to ensure continued leak tightness until a full structural weld overlay can be completed during refueling outage N1R28.
After the weld overlay is applied, the licensee will demonstrate, prior to restart, that the flaw is less than 75 percent through wall, taking into account the thickness of the weld overlay applied over the original weld. However, during the next NMP 1 operating cycle, the flaw may grow and exceed 75 percent through wall. Therefore, the licensee requested an alternative to potentially not meet the requirements of IWB-3640 at some point during the next cycle of operation. Although the flaw may grow to greater that 75 percent through wall, the licensee has shown by analytical evaluation (Structural Integrity Report No.
2300376.401), that the flaw will not challenge the structural integrity of weld and will maintain significant margin to structural failure through the next cycle of operation. The licensee will also volumetrically examine essentially 100% of the overlay installed during refueling outage N1R27.
The NRC staff has determined that the proposed alternative is acceptable because the weld flaw will be less than 75 percent through-wall at the time that the plant begins operation following the N1R27 refueling outage. Therefore, the staff finds the licensees requested alternatives to ASME Code,Section XI, IWA-4411(a), IWA-4411(b), IWA-4412, and IWA-4611 to be acceptable.
In the event that the flaw becomes greater than 75 percent through-wall prior to the next refueling outage (N1R28), the licensee has shown by analysis that structural integrity of the subject weld will be maintained. Therefore, the staff finds the licensees requested alternative to potentially not meet IWB-3640 during the next NMP 1 cycle of operation to be acceptable. In addition, in the event that the flaw grows through the original weld thickness, the licensee has shown by analysis that growth of the flaw into the Alloy 52 overlay material will have sufficient margin for one cycle of operation and thus leak tightness will be maintained.
The portion of the weld overlay on the low alloy steel nozzle requires temper bead welding.
The licensee proposed to perform temper bead welding in accordance with ASME Code Case N-638-10, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1, with the exception that surface and volumetric examinations may be performed on the completed weld prior to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the completion of the three tempering weld layers. The staff finds the licensees exception to be acceptable. The weld overlay is being applied with the machine gas tungsten arc welding process which produces welds with very low diffusible hydrogen when compared to welding processes that use flux. Therefore, hydrogen induced cracking is not likely to occur, making the 48-hour time requirement unnecessary. In addition, the NRC staff is unaware of any instances of hydrogen induced cracking out of the numerous weld overlays that have been completed by the nuclear industry using any of the revisions of Code Case N-638.
Based on the above evaluation, the NRC staff finds that the licensees proposed alternative I5R-11 will provide an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1).
Authorization read by Hipolito Gonzalez, Chief of Plant Licensing Branch I, Division of Operating Reactor Licensing, NRR
As chief of the Plant Licensing Branch I, Office of Nuclear Reactor Regulation, I concur with the conclusions of the Piping and Head Penetrations Branch.
As set forth above, the NRC staff determines that the proposed alternative provides acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, as of March 31, 2023, the NRC authorizes the use of Relief Request I5R-11 at Nine Mile Nuclear Station Unit 1 until the end of the next refueling outage (N1R28).
All other requirements in ASME Code,Section XI, for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
This verbal authorization does not preclude the NRC staff from asking additional clarification question(s) regarding the proposed alternative while preparing the subsequent written safety evaluation.
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NRC Participants Hipo Gonzalez Matthew Mitchell Richard Guzman Robert Davis Jay Collins Elena Herrera Torres Omar Khan
Constellation Energy Group Participants Thomas Loomis Mathew Rice Jason Pulliam Michael Salley Mark Weis Richard Hall David Gudger Jacqueline Graham Jacky Shoulders Matthew Rossi Sailaja Mokkapati Dick Mattson Mark Ferlisi Vasilios Peter Zeppos Heather Malikowski Darani Reddick Jim Axline Kemper Young Jennifer Bianculli