ML23354A003
| ML23354A003 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point, Limerick  |
| Issue date: | 01/19/2024 |
| From: | Jeffrey Whited NRC/NRR/DORL/LPL3 |
| To: | Rhoades D Constellation Energy Generation, Constellation Nuclear |
| Wall S, NRR/DORL/LPL3 | |
| References | |
| EPID L-2023-LLR-0046 | |
| Download: ML23354A003 (1) | |
Text
January 19, 2024 LIMERICK GENERATING STATION, UNIT 1, AND NINE MILE POINT NUCLEAR STATION, UNIT 2 - AUTHORIZATION AND SAFETY EVALUATION FOR ALTERNATIVE REQUEST ASSOCIATED WITH SUCCESSIVE INSPECTIONS FOR GENERIC LETTER 88-01 /
BWRVIP-75-A AUGMENTED EXAMINATIONS (EPID L-2023-LLR-0046)
LICENSEE INFORMATION Recipients Name and Address:
Mr. David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Rd Warrenville, IL 60555 Licensee:
Constellation Energy Generation, LLC Plant Name(s) and Unit(s):
Limerick Generating Station, Unit 1 Nine Mile Point Nuclear Station, Unit 2 Docket No(s).:
50-362 50-410 APPLICATION INFORMATION Submittal Date: August 25, 2023 Submittal Agencywide Documents Access and Management System (ADAMS)
Accession No.: ML23237A737 Applicable Inservice Inspection (ISI) Program Interval and Interval Start/End Dates:
Limerick Generating Station (Limerick) Unit 1: Fourth 10-year ISI program interval, which began on February 1, 2017, and is currently scheduled to end on January 31, 2027.
Nine Mile Point Nuclear Station (Nine Mile Point), Unit 2: Fourth 10-year ISI program interval, which began on October 6, 2018, and is currently scheduled to end on August 22, 2028.
Alternative Provision: The applicant requested an alternative under Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(z)(1)
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Applicable Code Edition and Addenda===
Limerick, Unit 1: 2007 Edition of the American Society of Mechanical Engineers (ASME)
Code,Section XI, with the 2008 Addenda.
Nine Mile Point, Unit 2: 2011 Edition of the ASME Code,Section XI.
Applicable Code Requirements:
ASME Code,Section XI IWB-2420(b) that requires the subsequent examination of flaws found acceptable by analytical evaluation. This requirement was invoked by the identification of flaws in an augmented ISI program examination that were unacceptable per the ASME Code,Section XI, Subparagraph IWB-3514.4 and mandated by 10 CFR 50.55a(g)(4) to utilize the ASME Code to address all flaws identified in inservice inspections, including augmented inspections, of ASME Class 1, 2 and 3 structures, systems, and components.
ASME Code,Section XI, Paragraph IWB-3514 contains the flaw acceptance standards applicable to Examination Category R-A, Item Number R1.16.
Brief Description of the Proposed Alternative:
The licensee is requesting an alternative to the successive inspection requirements of ASME Code,Section XI, IWB-2420(b) for the remainder of the current fourth interval and until the next required inspection is performed per the requirements of Boiling Water Reactor (BWR) Vessel and Internals Project (BWRVIP)-75-A, Technical Basis for Revisions to Generic Letter 88-01 Inspection Schedules, in the fifth interval at both Limerick, Unit 1, and Nine Mile Point, Unit 2.
This alternative is technically based on the previously submitted analytical evaluations for the subject flaws in submittals dated April 9, 2020, for Nine Mile Point, Unit 2 (ML20100F682), and April 15, 2020, for Limerick, Unit 1 (ML20106E828).
For additional details on the licensees request, please refer to the documents located at the ADAMS accession numbers identified above.
REGULATORY EVALUATION Regulatory Basis: 10 CFR 50.55a(z)(1)
Adherence to Section XI of the ASME Code is mandated by 10 CFR 50.55a(g)(4), which states, in part, that ASME Code Class 1, 2, and 3 components will meet the requirements set forth in the ASME Code,Section XI.
Paragraph 10 CFR 50.55a(z) states, in part, that alternatives to the requirements of 10 CFR 50.55a(b)-(h) may be used, when authorized by the Director, Office of Nuclear Reactor Regulation, if (1) the proposed alternatives would provide 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 licensee has submitted this request on the basis that a proposed alternative would provide an acceptable level of quality and safety.
STAFF EVALUATION The two welds which are the subject of the proposed alternative are the Core Spray Injection Nozzle-to-Safe End Weld, Weld No. DCA-319-1 N5A at Limerick, Unit 1 and the Reactor Coolant System Inlet Nozzle N2J-to-Safe End Weld, Weld No. 2RPV-KB11 at Nine Mile Point, Unit 2.
Limerick, Unit 1: In Weld No. DCA-319-1 N5A, the licensee identified a subsurface or embedded circumferentially-oriented flaw in the weld material that was measured by ultrasonic testing to be approximately 2.0 inches long, 0.3 inches through-wall and had a surface separation distance of 0.35 inches from the inside surface. The licensee proposes that this subsurface flaw was a fabrication defect and the change in size was more likely due to improved non-destructive examination (NDE) of the flaw. The NRC staff finds that operating experience has shown variation in indications due to changes in NDE techniques and that the qualified automated phased array technique used by the licensee in the 2020 examination is a preferred technique for being more accurate. The NRC staff notes the indication was measured to be greater than the allowable ASME Code subsurface flaw depth for this weld under Table IWB-3514-2, therefore NRC regulations require the licensee to perform a flaw analysis and supplemental examinations for acceptance of the flaw for continued operation. The licensee chose to use a previous analysis for this flaw identified in the past. The NRC staff found the licensees identification of a very similar sized indication in two previous examinations of this area to be a reasonable conclusion that this is the same flaw and the previous analysis of both intergranular stress corrosion cracking growth and fatigue growth would be conservative to address the subsurface flaw identified in 2020. The NRC staff reviewed the licensees previous flaw evaluation for this indication (ML20106E828) and found it conservative to assess the 2020 sized flaw. Furthermore, the NRC staff continues to find the previous analysis utilized acceptable inputs and analysis techniques to show reasonable assurance that the 2020 sized flaw would not challenge the structural integrity of the weld for at least 10 more years.
Nine Mile Point, Unit 2: In Weld No. 2RPV-KB11, the licensee identified a subsurface or embedded circumferentially-oriented flaw in the weld measured by ultrasonic testing to be approximately 6.1 inches long, 0.3 inches through-wall and a surface separation distance of 0.5 inches from the outside surface. The licensee explained they identified this flaw in the previous two examinations of this weld as acceptable per the requirements of IWB-3514 of the ASME Code. The licensee proposes that this subsurface flaw was a fabrication defect and the change in size was more likely due to improved NDE of the flaw. The NRC staff finds that operating experience has shown variation in indications due to changes in NDE techniques and that the qualified automated phased array technique used by the licensee in the 2020 examination is a preferred technique for being more accurate. The NRC staff found the licensees identification of a very similar sized indication in the two previous examinations of this area to be a reasonable conclusion that this is the same flaw. The NRC staff reviewed the licensees fatigue flaw analysis (ML20100F682) in accordance with Paragraph IWB-3640 of Section XI of the ASME Code. The NRC staff found the licensees flaw evaluation methodology, inputs and assumptions were reasonable and conservative in addressing measurement uncertainties, material properties and plant parameters to address fatigue flaw growth.
Therefore, the NRC staff finds the 2020 flaw analysis continues to show reasonable assurance that the 2020 sized flaw would not challenge the structural integrity of the weld for at least 10 more years.
The NRC staff notes that the licensees proposed alternative for these welds is to utilize the re-examination frequency of BWRVIP-75-A in lieu of the examination requirements of Subparagraph IWB-2420(b) of Section XI of the ASME Code, which would require examinations in the next three inspection periods for both welds. Weld No. DCA-319-1 N5A, at Limerick, Unit 1 is a Category C weld under BWRVIP-75-A and Weld No. 2RPV-KB11 at Nine Mile Point, Unit 2 is a Category D weld under BWRVIP-75-A. Both welds have a reinspection frequency under the proprietary BWRVIP-75-A program for both categories within the 10-year bounding flaw analysis performed for both welds. Therefore, the NRC staff finds that the licensees proposed alternative provides reasonable assurance of structural integrity of the subject welds, and it would therefore provide an acceptable level of quality and safety.
CONCLUSION The NRC staff has determined that the proposed alternative in the licensees request referenced above would provide an acceptable level of quality and safety.
The NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1).
The NRC staff authorizes the use of proposed alternative dated August 25, 2023, under Constellation Letter No. NMP2L2851, at Limerick, Unit 1, and Nine Mile Point, Unit 2, until the next scheduled examination of the subject welds in accordance with BWRVIP-75-A.
All other ASME 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(s): Jay Collins, NRR Date: January 19, 2024 Jeffrey A. Whited, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation cc: Listserv Jeffrey A.
Whited Digitally signed by Jeffrey A. Whited Date: 2024.01.19 13:42:26 -05'00'
ML23354A003 NRR-028 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DNRL/NPHP/BC NAME SWall SRohrer (ABaxter for)
MMitchell DATE 12/19/2023 12/27/2023 12/18/2023 OFFICE NRR/DORL/LPL3/BC NAME JWhited DATE 01/19/2024