ML24358A183
| ML24358A183 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point, Limerick, LaSalle  |
| Issue date: | 01/07/2025 |
| From: | Ilka Berrios NRC/NRR/DORL/LPL3 |
| To: | Rhoades D Constellation Energy Generation, Constellation Nuclear |
| Wall S, NRR/DORL/LPL3 | |
| References | |
| EPID L-2024-LLR-0031 | |
| Download: ML24358A183 (1) | |
Text
January 7, 2025 David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
LASALLE COUNTY STATION, UNITS 1 AND 2; LIMERICK GENERATING STATION, UNITS 1 AND 2; AND NINE MILE POINT NUCLEAR STATION, UNIT 2 - ISSUANCE OF RELIEF RE: PROPOSED ALTERNATIVE REQUEST ASSOCIATED WITH ULTRASONIC EXAMINATION OF REACTOR PRESSURE VESSEL CIRCUMFERENTIAL SHELL WELDS (EPID L-2024-LLR-0031)
Dear David Rhoades:
By letter dated May 2, 2024 (Agencywide Documents Access and Management System Accession No. ML24123A119), as supplemented by letter dated September 12, 2024 (ML24257A032), Constellation Energy Generation, LLC (CEG, the licensee) submitted a request for LaSalle County Station (LaSalle), Units 1 and 2; Limerick Generating Station (Limerick), Units 1 and 2; and Nine Mile Point Nuclear Station, Unit 2 (NMP-2) (collectively, the CEG facilities), to the U.S. Nuclear Regulatory Commission (NRC)for a proposed alternative to certain requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code (ASME Code),Section XI.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) section 50.55a(z)(1), Acceptable level of quality and safety, the licensee requested extension of permanent relief from the required ultrasonic examinations of the reactor pressure vessel (RPV) circumferential welds from the current ASME Code,Section XI requirements until the end of the extended operating licenses for the CEG facilities. The regulation in 10 CFR 50.55a(z)(1) requires the licensee to demonstrate that the proposed alternatives provide an acceptable level of quality and safety.
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorized the use of the proposed alternative for the CEG facilities for the remainder of their currently approved operating license, currently scheduled to end on April 17, 2042 (LaSalle, Unit 1), December 16, 2043 (LaSalle, Unit 2), October 26, 2044 (Limerick, Unit 1), June 22, 2049 (Limerick, Unit 2), and October 31, 2046 (NMP-2).
All other ASME BPV Code,Section XI, requirements for which relief was not specifically requested and approved in this alternative request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
If you have any questions, please contact the Senior Project Manager, Scott Wall, at 301-415-2855 or email at Scott.Wall@nrc.gov.
Sincerely, Ilka Berrios, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-373, 50-374, 50-352, 50-353, and 50-410
Enclosure:
Safety Evaluation cc: Listserv ILKA BERRIOS Digitally signed by ILKA BERRIOS Date: 2025.01.07 07:39:34 -05'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR ALTERNATIVE REGARDING ULTRASONIC EXAMINATION OF REACTOR PRESSURE VESSEL CIRCUMFERENTIAL SHELL WELDS CONSTELLATION ENERGY GENERATION, LLC LASALLE COUNTY STATION, UNITS 1 AND 2 LIMERICK GENERATING STATION, UNITS 1 AND 2 NINE MILE POINT NUCLEAR STATION, UNIT 2 DOCKET NOS. 50-373, 50-374, 50-352, 50-353, AND 50-410 INTRODUCTION By letter dated May 2, 2024 (Agencywide Documents Access and Management System Accession No. ML24123A119), as supplemented by letter dated September 12, 2024 (ML24257A032), Constellation Energy Generation, LLC (CEG, the licensee) submitted a request for LaSalle County Station (LaSalle), Units 1 and 2; Limerick Generating Station (Limerick), Units 1 and 2; and Nine Mile Point Nuclear Station, Unit 2 (NMP-2) (collectively, the CEG facilities), to the U.S. Nuclear Regulatory Commission (NRC or Commission) for a proposed alternative to certain requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code (ASME Code),Section XI.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) section 50.55a(z)(1), Acceptable level of quality and safety, the licensee requested extension of permanent relief from the required ultrasonic examinations of the reactor pressure vessel (RPV) circumferential welds from the current ASME Code,Section XI requirements until the end of the extended operating licenses for the CEG facilities. The proposed alternative utilizes the methodology and technical basis of Boiling Water Reactor (BWR) Vessel and Internals Project (BWRVIP)-329-A, Updated Probabilistic Fracture Mechanics Analyses for BWR RPV Welds to Address Extended Operations, dated August 22, 2019 (ML19238A075). BWRVIP-329-A was approved by the NRC on April 21, 2021 (ML21084A088).
2.0 REGULATORY EVALUATION
The RPV circumferential welds nozzles at the subject CEG units are ASME Code Class 1 and Class 2 components, whose inservice inspections (ISIs) are performed in accordance with the applicable edition of Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, of the ASME Code, as required by 10 CFR 50.55a(g).
The regulations in 10 CFR 50.55a(g)(4) state, in part, that components that are classified as ASME Code Class 1, 2, and 3 must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, 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 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.
3.0 TECHNICAL EVALUATION
3.1 Licensees Proposed Alternative Request 3.1.1 Applicable Code Edition and Addenda The current ISI interval and associated codes of record for the subject plants are summarized in Table 1, below.
Table 1: Section XI Codes of Record for Subject Plants Plant Interval Edition Start End LaSalle, Units 1 and 2 Fourth 2007 Edition, through 2008 Addenda October 1, 2017 September 30, 2027 Limerick, Units 1 and 2 Fourth 2007 Edition, through 2008 Addenda February 1, 2017 January 31, 2027 NMP-2 Fourth 2013 Edition October 6, 2018 August 22, 2028 3.1.2 ASME Code Components Affected ASME Code Class:
Class 1 Examination Category:
B-A, Pressure Retaining Welds in Reactor Vessel Item Numbers:
B1.11 for the circumferential welds 3.1.3 Applicable Code Requirements For ASME Code Class 1 welds listed above, the ISI requirements are those specified in Subarticle IWB-2500 of the ASME Code,Section XI, which requires the licensee to perform volumetric examinations as specified in ASME Code,Section XI, Table IWB-2500-1, for the Examination Category and Item No. listed below once every 10-year ISI interval.
The NRC staff confirmed that the ASME Code ISI requirements listed above did not change in the latest edition of ASME Code,Section XI incorporated by reference in 10 CFR 50.55a.
3.1.4 Reason for Proposed Alternative In Section 4 of the attachment to the submittal, the licensee stated that it has previously utilized BWRVIP-74-A, BWR Vessel and Internals Project BWR Reactor Pressure Vessel Inspection and Flaw Evaluation Guidelines for License Renewal, or BWRVIP-05, BWR Vessel and Internals Project, BWR Reactor Pressure Vessel Shell Weld Inspection Recommendations, to obtain examination relief of RPV beltline circumferential welds and to address embrittlement of RPV beltline axial welds during extended plant operation. The NRC safety evaluation (SE) of BWRVIP-74-A (ML012920549) specified actions to obtain examination relief of RPV beltline circumferential welds and to monitor embrittlement of RPV beltline axial welds, both of which were based on results of probabilistic fracture mechanics (PFM) analyses in the staffs SE and supplemental SE of BWRVIP-05 (ML20236V550 and ML031430372, respectfully). As stated in BWRVIP-329-A, the objective of the report is to use NRC safety goals and PFM analysis procedures that have been developed since the publication of BWRVIP-05 to update the evaluation procedure and acceptance criteria specified in BWRVIP-74-A for providing relief from examination of RPV circumferential welds and assessing axial weld integrity.
3.1.5 Proposed Alternative and Basis for Use In Section 5 of the attachment to the submittal, the licensee described the proposed request, summarized as follows:
The licensee is requesting relief (i.e., an alternative) from the ultrasonic examination requirements of the ASME Code,Section XI for RPV circumferential welds, described above.
The proposed alternative is to the end of the extended operating licenses for LaSalle, Units 1 and 2; Limerick, Units 1 and 2; and NMP-2 for 54, 57, and 54 effective full power years (EFPYs), respectively. The request is based upon the PFM analysis, methodology, and conclusions in BWRVIP-329-A. The licensee used the implementation from Section 5 of BWRVIP-329-A to provide a means to verify that the PFM analysis is applicable to each BWR RPV, provided in Table 1 of the attachment to the submittal (repeated as Table 2 below); and that the plant-specific limiting RPV beltline mean reference temperature at the vessel inner surface (RTMAX) values for each subject unit are less than the limiting RTMAX values analyzed in BWRVIP-329-A, provided in Tables 2 through 6 of the attachment to the submittal (repeated as Tables 3 to 7 below without the table notes).
The licensee stated that it will continue to comply with all other applicable ASME Code,Section XI examination requirements associated with the RPVs, including inspection of the RPV vertical (i.e., axial) pressure retaining welds (Category B-A, Item No. B1.12) and performance of the Class 1 system leakage test (Category B-P, Item Nos. B15.10 & B15.20) each refueling outage.
Table 2: Site-Specific Information for Verification of Vessel Dimensions Dimension LaSalle Unit 1 LaSalle Unit 2 Limerick Unit 1 Limerick Unit 2 NMP-2 Reactor Vessel Inside Radius to CBMI, in.
127.0 126.7 126.7 126.7 126.7 Base Metal Wall Thickness, in.
6.1 6.4 6.4 6.4 6.4 Radius /
thickness 20.7 19.7 19.7 19.7 19.7 Cladding Thickness, in.
5/16 3/16 3/16 3/16 3/16 Table 3: LaSalle, Unit 1 Parameter Verification LaSalle, Unit 1 Parameter Limiting Plate Limiting Circumferential Weld Limiting Axial Weld Heat/Lot Identification Number C6345-1 6329637 1P3571 Copper Content (wt. %)
0.14 0.205 0.21 Nickel Content (wt. %)
0.54 0.105 0.75 Chemistry Factor (CF)
(°F) 152 98 440 EOI Neutron Fluence (f) (n/cm2) 9.77E+17 8.45E+17 8.23E+17 RTNDT(U) (°F)
-20
-50
-30 EOI RTNDT (°F) 63 38 167 EOI RTMAX (°F) 43
-12 137 Category 1 Vessel Limiting RTMAX (°F)
See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 EOI RTMAX < Limiting RTMAX?
Yes Yes Yes Table 4: LaSalle, Unit 2 Parameter Verification LaSalle, Unit 2 Parameter Limiting Plate Limiting Circumferential Weld Limiting Axial Weld Heat/Lot Identification Number C9404-2 5P6771/342 3P4966/1214 Copper Content (wt. %)
0.07 0.034 0.025 Nickel Content (wt. %)
0.49 0.934 0.913 Chemistry Factor (CF)
(°F) 44 46 34 EOI Neutron Fluence (f) (n/cm2) 1.07E+18 9.11E+17 1.01E+18 RTNDT(U) (°F) 52
-34
-6 EOI RTNDT (°F) 19 18 14 EOI RTMAX (°F) 71
-16 8
Category 1 Vessel Limiting RTMAX (°F)
See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 EOI RTMAX < Limiting RTMAX?
Yes Yes Yes Table 5: Limerick, Unit 1 Parameter Verification Limerick, Unit 1 Parameter Limiting Plate Limiting Circumferential Weld Limiting Axial Weld Heat/Lot Identification Number C7677-1 07L857/B101A27A 662A746/H013A27A Copper Content (wt.
%)
0.11 0.03 0.03 Nickel Content (wt. %)
0.50 0.97 0.88 Chemistry Factor (CF)
(°F) 73 41 41 EOI Neutron Fluence (f) (n/cm2) 1.09E+18 8.08E+17 8.89E+17 RTNDT(U) (°F) 20
-6
-20 EOI RTNDT (°F) 32 15 16 EOI RTMAX (°F) 52 9
-4 Category 2 Vessel Limiting RTMAX (°F)
See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 EOI RTMAX < Limiting RTMAX?
Yes Yes Yes Table 6: Limerick, Unit 2 Parameter Verification Limerick, Unit 2 Parameter Limiting Plate Limiting Circumferential Weld Limiting Axial Weld Heat/Lot Identification Number B3416-1 07L857/B101A27A 432A2671/
H019A27A Copper Content (wt. %)
0.14 0.03 0.04 Nickel Content (wt. %)
0.65 0.97 1.08 Chemistry Factor (CF)
(°F) 101 41 54 EOI Neutron Fluence (f) (n/cm2) 7.69E+17 7.69E+17 8.71E+17 RTNDT(U) (°F) 40
-6
-12 EOI RTNDT (°F) 37 15 21 EOI RTMAX (°F) 77 9
9 Category 2 Vessel Limiting RTMAX (°F)
See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 EOI RTMAX < Limiting RTMAX?
Yes Yes Yes Table 7: NMP-2 Parameter Verification NMP-2 Parameter Limiting Plate Limiting Circumferential Weld Limiting Axial Weld Heat/Lot Identification Number C3147-1 4P7216(S)/0751 5P5657(S)/0931 Copper Content (wt. %)
0.11 0.045 0.07 Nickel Content (wt. %)
0.63 0.80 0.71 Chemistry Factor (CF)
(°F) 74.5 61 95 EOI Neutron Fluence (f) (n/cm2) 1.62E+18 1.58E+18 1.62E+18 RTNDT(U) (°F) 0
-50
-60 EOI RTNDT (°F) 39 32 50 EOI RTMAX (°F) 39
-18
-10 Category 1 Vessel Limiting RTMAX (°F)
See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 See BWRVIP-329-A Table 5-2 EOI RTMAX < Limiting RTMAX?
Yes Yes Yes 3.1.6 Duration of Proposed Alternative In Section 6 of the Attachment to the submittal, the licensee stated that the proposed alternatives are requested for the CEG facilities for the remainder of their currently approved operating license, currently scheduled to end on April 17, 2042 (LaSalle, Unit 1),
December 16, 2043 (LaSalle, Unit 2), October 26, 2044 (Limerick, Unit 1), June 22, 2049 (Limerick, Unit 2), and October 31, 2046 (NMP-2). The end of extended operating license and analyzed EFPYs for the subject plants are summarized in Table 8, below.
Table 8: End of Extended Operating License Plant End of Extended Operating License EFPYs LaSalle, Unit 1 April 17, 2042 54 LaSalle, Unit 2 December 16, 2043 54 Limerick, Unit 1 October 26, 2044 57 Limerick, Unit 2 June 22, 2049 57 NMP-2 October 31, 2046 54 3.2 Staff Evaluation Pursuant to 10 CFR 50.55a(z)(1), the proposed alternative is in regard to the requirements of the ASME Code,Section XI, Table IWB-2500-1, Examination Category B-A, pertaining to the RPV circumferential shell welds at LaSalle Units 1 and 2, Limerick Units 1 and 2, and NMP-2.
The licensee referenced the PFM analysis in BWRVIP-329-A as the technical basis for its proposed alternative. Section 5 of the NRC staffs SE for BWRVIP-329-A describes the use and referencing of BWRVIP-329-A for plant-specific implementation. The NRC staffs SE for BWRVIP-329-A states that if applicability of the analysis in the report is demonstrated for a specific BWR RPV, and the plant-specific limiting RPV beltline RTMAX values are demonstrated to be less than the limiting RTMAX values analyzed in the report, the demonstration would (1) provide an acceptable technical basis for a relief request, i.e., a request for alternative pursuant to 10 CFR 50.55(a)(z)(1), from the ASME Code,Section XI examinations for the RPV circumferential weld beyond the initial license renewal period; and (2) provide an acceptable technical evaluation (not relief) of the embrittlement of RPV axial welds beyond the initial license renewal period.
Table 5-1 in Section 5 of BWRVIP-329-A provides a template to verify that plant-specific RPV dimensions are enveloped by the PFM analysis. The licensee provided this verification in Table 1 of the attachment to the submittal (repeated as Table 1 of this SE).
Table 5-2 in Section 5 of BWRVIP-329-A provides a template to verify that plant-specific limiting RPV beltline RTMAX values are less than the limiting RTMAX values determined in BWRVIP-329-A. The licensee provided this verification in Tables 2 through 6 of the attachment to the submittal (repeated as Tables 3 to 7 of this SE without the table notes).
The NRC staff evaluated the plant-specific RPV dimensions and the plant-specific end-of-interval RTMAX values to verify that the RPVs of the subject units are within the envelope of limiting RTMAX values established in BWRVIP-329-A. The staff confirmed that the plant-specific end-of-interval RTMAX values were calculated based on the material properties of the subject RPVs (e.g., initial RTNDT, weight percent Cu, weight percent Ni, chemistry factor) and neutron fluence values that are consistent with current licensing basis values for each unit, i.e.,
based on the NRC-approved values through each units respective end of extended operating license. The NRC staff also confirmed the licensees calculations of the shift in nil-ductility reference temperature (RTNDT) values.
In the response to the NRC staffs request for additional information (RAI) in the supplement dated September 12, 2024 (ML24257A032), CEG referenced LaSalle, Units 1 and 2, relief from the circumferential weld ISI requirements by letter dated June 25, 2003 (ML031880829) and NRC staffs SE dated January 28, 2004 (ML033300147). Additionally, in the RAI response, CEG referenced NMP-2 relief from the circumferential weld ISI requirements by letter dated November 16, 2006 (ML063320461), as supplemented by letter dated April 20, 2007 (ML071210245), and NRC staffs SE dated November 5, 2007 (ML072830047). Criterion (2) of Generic Letter 98-05 (ML031430368) requires licensees to demonstrate that they have implemented operator training and established procedures that limit the frequency of cold overpressure events, and the licensee addressed this criterion for LaSalle, Units 1 and 2, and NMP-2 in the requests and associated NRC staffs SEs above, respectively. The licensee stated that for LaSalle, Units 1 and 2, and NMP-2, the operator training and procedures to limit the frequency of cold overpressure events will continue during the period of extended operation, through 54 EFPY. The NRC staff also noted in Section 4.2.6 of its SE for the Limerick license renewal application (ML14276A156), that the Limerick units will use the same operator procedures and training in the period of extended operation that has been the practice during the original licensing period. Therefore, the NRC staff finds that the operator training and procedures that limit the frequency of cold overpressure events will continue through the end of the licenses of the subject units.
In summary, based on the above discussion, the NRC staff finds that the licensee has adequately demonstrated that the conditional probability of failure values for the RPV circumferential welds of the subject units through the end of the current extended operating license of each subject unit are below the acceptance criteria defined in BWRVIP-329-A because the RTMAX values are bounded by limiting values defined in BWRVIP-329-A.
Additionally, the staff noted that the operator training and procedures that limit the frequency of cold overpressure events will continue through the end of the current extended operating license of each subject unit. Therefore, the NRC staff finds that the implementation of the proposed alternative at the CEG facilities provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1).
4.0 CONCLUSION
As set forth above, the NRC staff determined that the licensees proposed alternative to the ASME Code,Section XI ultrasonic examinations for the RPV circumferential welds of the subject units as discussed above provides an 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, the NRC staff authorized the use of the proposed alternative for the CEG facilities for the remainder of their currently approved operating license, currently scheduled to end on April 17, 2042 (LaSalle, Unit 1),
December 16, 2043 (LaSalle, Unit 2), October 26, 2044 (Limerick, Unit 1), June 22, 2049 (Limerick, Unit 2), and October 31, 2046 (NMP-2).
All other ASME Code,Section XI requirements for which relief has not been specifically requested and approved in this relief request remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
Principal Contributors: D. Dijamco, NRR E. Haywood, NRR Date: January 7, 2025
SUBJECT:
LASALLE COUNTY STATION, UNITS 1 AND 2; LIMERICK GENERATING STATION, UNITS 1 AND 2; AND NINE MILE POINT NUCLEAR STATION, UNIT 2 - ISSUANCE OF RELIEF RE: PROPOSED ALTERNATIVE REQUEST ASSOCIATED WITH ULTRASONIC EXAMINATION OF REACTOR PRESSURE VESSEL CIRCUMFERENTIAL SHELL WELDS (EPID L-2024-LLR-0031)
DATED JANUARY 7, 2025 DISTRIBUTION:
PUBLIC RidsNrrDorlLpl1 Resource RidsNrrDorlLpl3 Resource RidsRgn1MailCenter Resource RidsRgn3MailCenter Resource RidsNrrLASLent Resource RidsNrrLASRohrer Resource RidsNrrLAKEntz Resource RidsAcrs_MailCTR Resource RidsNrrPMConstellation Resource RidsNrrPMLaSalle Resource RidsNrrPMLimerick Resource RidsNrrPMNineMilePoint Resource RidsNrrDnrlNvib Resource DDijamco, NRR EHaywood, NRR Accession No.: ML24358A183
- via memo NRR-028 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DNRL/NVIB/BC*
NAME SWall SRohrer (SLent for)
ABuford DATE 12/20/2024 12/23/2024 12/18/2024 OFFICE NRR/DORL/LPL3/BC NRR/DORL/LPL3/PM NAME IBerrios SWall DATE 01/07/2025 01/07/2025 OFFICIAL RECORD COPY