ML24225A213
| ML24225A213 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/26/2024 |
| From: | Jeffrey Whited Plant Licensing Branch III |
| To: | Rhoades D Constellation Energy Generation |
| Arora, S | |
| References | |
| EPID L-2023-LLR-0063 | |
| Download: ML24225A213 (14) | |
Text
September 26, 2024
David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3 - RELIEF REQUEST REGARDING EXAMINATION COVERAGE FOR THE FIFTH INSERVICE INSPECTION INTERVAL (EPID L-2023-LLR-0063)
Dear David Rhoades:
By letter dated November 8, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23312A092), as supplemented by letters dated April 2, 2024 (ML24093A204), and June 14, 2024 (ML24166A103), Constellation Energy Generation, LLC (the licensee) submitted relief request I5R-22 to the U.S. Nuclear Regulatory Commission (NRC), requesting relief from the requirement s of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Plant Components, for the fifth inservice inspection (ISI) interval at Dresden Nuclear Power Station (DNPS), Units 2 and 3.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR), 50.55a(g)(5)(iii),
the licensee requested relief from the essentia lly 100% volumetric and/or surface examination coverage requirements of the ASME Code, section XI, for reactor pressure vessel (RPV), RPV nozzle, isolation condenser, and piping welds, on the basis that the compliance with the requirement is impractical.
The NRC staff has reviewed the subject relief request and concluded that granting the relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Additionally, the NRC sta ff concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject components. Accordingly, the NRC staff conclu des that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii) and grants relief pursuant to 10 CFR 50.55a(g)(6)(i) for the examinations of the subject components contained in RR I5R-22, for the fifth 10-year ISI interval at DNPS, Units 2 and 3.
All other ASME Code, section XI, requirements for which relief was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
D. Rhoades
If you have any questions on this action, plea se contact the NRC Project Manager Surinder Arora at 301-415-1421 or via e-mail at Surinder.Arora@nrc.gov.
Sincerely,
Jeffrey A. Whited, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Docket Nos. 50-237 and 50-249
Enclosure:
Safety Evaluation
cc: Listserv
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
RELIEF REQUEST I5R-22
LIMITED EXAMINATION COVERAGE
FIFTH INSERVICE INSPECTION INTERVAL
CONSTELLATION ENERGY GENERATION, LLC
DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3
DOCKET NOS. 50-237 AND 50-249
1.0 INTRODUCTION
By letter dated November 8, 2023 (ML23312A092), as supplemented by letters dated April 2, 2024 (ML24093A204), and June 14, 2024 (ML24166A103), Constellation Energy Generation, LLC (the licensee) submitted Request Relief (RR) I5R-22 to the U.S. Nuclear Regulatory Commission (NRC or Commission), r equesting relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),
section XI, Rules for Inservice Inspection [ISI] of Nuclear Power Plant Components, for the fifth ISI interval at Dresden Nuclear Power Station (DNPS), Units 2 and 3.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),
the licensee requested relief from the essentia lly 100% volumetric and/or surface examination coverage requirements of ASME Code, section XI, for reactor pressure vessel (RPV) welds, RPV nozzle welds, isolation condenser welds, and piping welds, on the basis that compliance with the requirement is impractical.
2.0 REGULATORY EVALUATION
Section 50.55a(g)(4) to 10 CFR, states that ASME Code, Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set fort h 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 require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of section XI of the ASME Code, which was incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. Section 50.55a(g)(5)(iii) to 10 CFR, states, in part, that licensees may determine that conformance with certain ASME Code requirements is impractical, and that the licensee shall notify the Commission and submit information in support of the determination. Determination of impracticality in accordance
Enclosure
with this section must be based on the demonstrated limitations experience when attempting to comply with the code requirements during the ISI interval for which the request is being submitted. The RRs made in accordance with this section must be submitted to the NRC no later than 12 months after the expiration of the initial 120-month inspection interval or subsequent 120-month inspection interval for which relief is sought.
Section 50.55a(g)(6)(i) to 10 CFR, states that the NRC will evaluate determinations under paragraph (g)(5) of this section that code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
3.0 TECHNICAL EVALUATION
The NRC staff evaluated the vessel welds (i.e., in the RPV and isolation condenser shell) and piping welds in RR I5R-22 separately as documented below.
3.1 RPV and Isolation Condenser Shell Welds
3.1.1 Licensees Relief Request
ASME Code Components Affected
Code Class: Class 1 and 2
Examination Category: B-A, Pressure Retaining Welds in Reactor Vessels B-D, Full Penetration Welded Nozzles in Vessels B-K, Welded Attachments for Vessels, Piping, Pumps, and Valves C-B, Pressure Retaining Nozzle Welds in Pressure Vessels
Item Numbers: B1.12, Longitudinal Shell Welds B3.90, Reactor Vessel Nozzle-to-Vessel Welds B10.10 and B10.20, Pressure Vessels and Piping C2.21, Nozzle-to-Shell Welds
Component IDs: See Tables 3.1.1 and 3.1.2 of this safety evaluation
ASME Code Edition and Addenda
The licensee stated that the fifth 10-year ISI interval of DNPS ended on January 19, 2023, and was based on the ASME Code,Section XI, 2007 Edition with the 2008 Addenda.
ASME Code Requirement
IWA-2200(c) requires that All nondestructive exam inations of the required examination surface or volume shall be conducted to the maximum extent practical. When performing VT-1, surface, radiographic, or ultrasonic examination on a component with defined surface or volume, essentially 100% of the required surface or volume shall be examined. Essentially 100%
coverage is achieved when the applicable examination coverage is greater than
90%; however, in no case shall the examination be terminated when greater than 90%coverage is achieved, if additional coverage of the required examination surface or volume is practical.
Table IWB-2500-1 of ASME Code, section XI, Examination Category B-A, Item No. B1.12, requires a volumetric examination of the RPV longitudinal percent of the required examination volume, as specified in IWA-2200(c).
Table IWB-2500-1, Examination Category B-D, Item No. B3.90, requires a volumetric examination of the Reactor Vessel nozzle-to-vessel welds in accordance with Figure IWB-2500-7. The extent of examination is essent ially 100% of the required examination volume, as specified in IWA-2200(c).
Table IWB-2500-1, Examination Category B-K, Item No. B10.10, requires a surface examination of welded attachments to pressure vessels in accordance with Figure IWB-2500-13, Figure IWB-2500-14, or Figure IWB-2500-15. The extent of examination is essentially 100% of the required surface, as specified in IWA-2200(c).
Table IWB-2500-1, Examination Category B-K, Item Number B10.20, requires a surface examination of welded attachments to piping in accordance with Figure IWB-2500-13, Figure IWB-2500-14, or Figure IWB-2500-15. The extent of examination is essentially 100% of the required surface, as specified in IWA-2200(c).
Table IWC-2500-1, Examination Category C-B, Item Number C2.21, requires a surface and volumetric examination of pressure retaining nozzle welds in vessels in accordance with Figure IWC-2500-4(a), (b), (c), or (d). The extent of examination is essentially 100% of the required surface and volume, as specified in IWA-2200(c).
Relief Request
The licensee achieved the examination coverages shown in tables 3.1.1 and 3.1.2 for the subject Examination Category B-A, B-D, B-K, and C-B welds. Only the volumetric examination coverages are shown in the tables for the Examination Category C-B welds, which require both volumetric and surface examinations. The licensee achieved 100% surface examination coverage with no recordable indications for the Examination Category C-B welds. The licensee stated that in accordance with 10 CFR 50.55a(g)(5)(iii), relief is requested on the basis that conformance with the ASME Code, section XI, r equirements is impractical since conformance would require extensive structural modifications to the component or the surrounding structure.
The licensee also stated that compliance with the applicable ASME Code, section XI, volumetric and surface examination requirements can only be accomplished by redesigning and refabricating the subject and/or surrounding components. The licensee summarized the limitations for each subject Examination Category B-A, B-D, B-K, and C-B weld in tables A and B, in the Attachment to the submittal and included corresponding details in Enclosures 1 and 2 to the submittal.
Table 3.1.1 ASME Code,Section XI, Examination Coverages (Unit 2)
ASME Percent Code Component ID Weld Description Coverage Item Obtained Examination Category B-A B1.12 2/1/RPV SHELL/2-SC1A-VERT RPV Shell Weld 89 B1.12 2/1/RPV SHELL/2-SC1B-VERT RPV Shell Weld 40.2 B1.12 2/1/RPV SHELL/2-SC1C-VERT RPV Shell Weld 41.4 B1.12 2/1/RPV SHELL/2-SC1D-VERT RPV Shell Weld 82.7 B1.12 2/1/RPV SHELL/2-SC2A-VERT RPV Shell Weld 77.9 B1.12 2/1/RPV SHELL/2-SC2B-VERT RPV Shell Weld 85.7 B1.12 2/1/RPV SHELL/2-SC2C-VERT RPV Shell Weld 87.7 B1.12 2/1/RPV SHELL/2-SC3A-VERT RPV Shell Weld 74.4 B1.12 2/1/RPV SHELL/2-SC3B-VERT RPV Shell Weld 71.1 B1.12 2/1/RPV SHELL/2-SC3C-VERT RPV Shell Weld 75.0 B1.12 2/1/RPV SHELL/2-SC3D-VERT RPV Shell Weld 81.2 B1.12 2/1/RPV SHELL/2-SC3E-VERT RPV Shell Weld 73.7 B1.12 2/1/RPV SHELL/2-SC4C-VERT RPV Shell Weld 85.0 Examination Category B-D B3.90 2/1/RPV Shell/N1A-2 RPV Nozzle Weld 64.9 B3.90 2/1/RPV Shell/N1B-2 RPV Nozzle Weld 64.9 B3.90 2/1/RPV Shell/N2C-2 RPV Nozzle Weld 74.2 B3.90 2/1/RPV Shell/N2F-2 RPV Nozzle Weld 74.2 B3.90 2/1/RPV Shell/N2H-2 RPV Nozzle Weld 74.2 B3.90 2/1/RPV Shell/N5B-2 RPV Nozzle Weld 62.8 B3.90 2/1/RPV SHELL/N19A-2 RPV Nozzle Weld 70.7 B3.90 2/1/RPV SHELL/N4A-2 RPV Nozzle Weld 74 B3.90 2/1/RPV SHELL/N4B-2 RPV Nozzle Weld 74 B3.90 2/1/RPV SHELL/N4C-2 RPV Nozzle Weld 74 B3.90 2/1/RPV SHELL/N4D-2 RPV Nozzle Weld 74 B3.90 2/1/RPV SHELL/N3C-2 RPV-to-Nozzle Weld 70.1 B3.90 2/1/RPV SHELL/N5A-2 RPV-to-Nozzle Weld 69.7 B3.90 2/1/RPV UPP HD/N18A-2 RPV Head-to-Nozzle Weld 88.0 Examination Category B-K
B10.10 2/1/RPV SHELL/M-1175D-1 (IWA) Stabilizer Bracket Welded Attachment to Reactor Vessel 56
B10.20 2/1/1506-16/M-1164D-296 (IWA) Support Plate Welded Attachment to Piping (LPCI) 55 Examination Category C-B C2.21 2/2/1302B-12/12-8 Nozzle-to-Shell Weld (ISCO) 58.55 C2.21 2/2/1303A-8/8-9 Nozzle-to-Shell Weld (ISCO) 59.3
Table 3.1.1 ASME Code,Section XI, Examination Coverages (Unit 2)
ASME Percent Code Component ID Weld Description Coverage Item Obtained C2.21 2/2/1303B-8/8-8 Nozzle-to-Shell Weld (ISCO) 59.3
Table 3.1.2 ASME Code,Section XI, Examination Coverages (Unit 3)
ASME Percent Code Component ID Weld Description Coverage Item Obtained Examination Category B-A B1.12 3/1/RPV SHELL/3-SC1B-VERT Longitudinal Shell Weld 42.3 B1.12 3/1/RPV SHELL/3-SC2A-VERT Longitudinal Shell Weld 70.9 B1.12 3/1/RPV SHELL/3-SC3A-VERT Longitudinal Shell Weld 23.5 B1.12 3/1/RPV SHELL/3-SC3B-VERT Longitudinal Shell Weld 67.9 B1.12 3/1/RPV SHELL/3-SC3C-VERT Longitudinal Shell Weld 67.0 B1.12 3/1/RPV SHELL/3-SC3D-VERT Longitudinal Shell Weld 78.1 B1.12 3/1/RPV SHELL/3-SC4B-VERT Longitudinal Shell Weld 88.5 Examination Category B-D B3.90 3/1/RPV SHELL/ N19B-2 RPV Nozzle Weld 74.6 B3.90 3/1/RPV SHELL/N1A-2 RPV Nozzle Weld 70.0 B3.90 3/1/RPV SHELL/N2D-2 RPV Nozzle Weld 80.9 B3.90 3/1/RPV SHELL/ N2E-2 RPV Nozzle Weld 80.9 B3.90 3/1/RPV SHELL/ N3C-2 RPV Nozzle Weld 70.0 B3.90 3/1/RPV SHELL/ N5B-2 RPV Nozzle Weld 62.9 B3.90 3/1/RPV SHELL/ N9-2 RPV Nozzle Weld 73.0 B3.90 3/1/RPV UPP HD/N18A-2 Nozzle-to-Head Weld 84.1 B3.90 3/1/RPV UPP HD/N18B-2 Nozzle-to-Head Weld 84.1 B3.90 3/1/RPV SHELL/N2B-2 RPV Nozzle Weld 76.0 B3.90 3/1/RPV SHELL/N4A-2 RPV Nozzle Weld 72.6 B3.90 3/1/RPV SHELL/N4B-2 RPV Nozzle Weld 72.6 B3.90 3/1/RPV SHELL/N4C-2 RPV Nozzle Weld 72.6 B3.90 3/1/RPV SHELL/N4D-2 RPV Nozzle Weld 72.6 Examination Category B-K B10.10 3/1/RPV SHELL/M-1211D-1 (IWA) Stabilizer Bracket Welded Attachment to Reactor Vessel 60 Examination Category C-B C2.21 3/2/1302A-12/12-8 Nozzle-to-Shell Weld (ISCO) 28.25 C2.21 3/2/1302B-12/12-9 Nozzle-to-Shell Weld (ISCO) 28.25 C2.21 3/2/1303A-8/8-8 Nozzle-to-Shell Weld (ISCO) 70.0 C2.21 3/2/1303B-8/8-9 Nozzle-to-Shell Weld (ISCO) 70.0
Basis for Relief Request
The licensee stated that DNPS, Units 2 and 3, performed the ASME Code, section XI, required examinations to the maximum extent practical, or best effort, which are documented in tables A and B in the Attachment to the submittal. Due to physical interferences or component geometry, the licensee stated that there were no other examination techniques available to increase examination coverage, and no cases in any of the listed examinations where the components outside diameter surface features could have been conditioned to obtain the required coverage without major modification to the components.
The licensee also stated that during the fifth ISI Interval, periodic system pressure tests that include VT-2 visual examinations were performed in accordance with ASME Code, section Xl, Table IWB-2500-1, Examination Category B-P for Class 1 pressure retaining welds and components and Table IWC-2500-1, Examination Category C-H for Class 2 pressure retaining welds and components, during each inspection during each refueling outage. The licensee stated that these periodic system pressure tests and VT-2 examinations provided additional assurance that the structural and leak-tight integrity of the subject components was maintained throughout the fifth ISI Interval.
3.1.2 NRC Staff Evaluation
For the subject Examination Categories B-A, B-D, and C-B welds, the licensee obtained the volumetric examination coverages summarized in tables 3.1.1 and 3.1.2 using procedures, equipment, and personnel qualified using ASME Code, section XI, appendix VIII, Performance Demonstration for Ultrasonic Examination Systems. For the subject examination Category B-K welds, the licensee performed surface examinat ions specified in ASME Code, section XI. The licensee achieved less than the required examination coverage due to geometric, material, and physical limitations that would entail modification of the associated components if the required coverage were to be obtained. The NRC staff confirmed from the examination diagrams included in Enclosures 2 and 3 to the submittal that the coverages obtained included regions near the inside surface where service-induced degradation could occur. The NRC staff also reviewed and verified the examination cover ages achieved. The NRC staff finds the stated limitations to be an acceptable basis for impracticality of conforming to the requirements and finds the modifications necessary to achieve the required coverage constitute a burden upon the licensee.
For the subject Examination Categories B-A welds at DNPS, the volumetric examinations were limited due to the proximity of surrounding components, such as core shroud repair tie rods, guide rods, dryer support lug, core spray piping, feedwater spargers, jet pump diffusers and risers, and jet pump riser brace, as applicable. In tables A and B in the Attachment to the submittal (including associated enclosures) and the response to request for additional information (RAI) 2, the licensee reported that in some Item No. B1.12 welds, there were indications that were also detected in previous examinations. These indications were either subsurface (i.e., embedded), fabrication, or non-relevant, and acceptable per the ASME Code,Section XI. In weld 2/1/RPV SHELL/2-SC3D-VERT, the licensee reported 10 fabrication indications that are acceptable per the ASME Code, section XI. Eight of these indications were detected during the previous examination, and two additional indications were detected during this examination due to differences in procedure recording criteria. The eight indications were compared to previous examination results, and no changes were observed. In weld 2/1/RPV SHELL/2-SC3E-VERT, the licensee reported six f abrication indications that are acceptable per the ASME Code, section XI. Two of these indications were detected during the previous
examination, and four additional indications were detected during this examination due to differences in procedure recording criteria. The two indications were compared to previous examination results, and no changes were observed. For the other Item No. B1.12 welds, the licensee stated that no recordable indications were observed during the volumetric examinations.
For the subject Examination Category B-D welds at DNPS, the volumetric examinations were limited due to the configuration of the nozzles. The licensee did not detect any recordable indications in the welds.
For the subject Examination Category B-K welded attachments at DNPS, the surface examinations were limited due to the design of the attachments and the surrounding components. In tables A and B in the Attachment to the submittal (including associated enclosures) and the response to RAI 1, the licensee reported rounded indications in two attachments, Item Nos. B10.10 and B10.20. These indications were dispositioned in accordance with ASME Code, section XI, IWA-3100(b). Three of the five indications in 2/1/1506-16/M-1164D-296 were found to be acceptable in accordance with ASME Code, section III, NB-5352(b)(2). The other two indications in 2/1/1506-16/M-1164D-296 exceeded the NB-5352(b)(2) criteria and an Engineering Evaluation was conducted concluding that these indications were in portions of the weld that were not required by design and had no impact on function; regardless these two indications were corrected by ASME Code, section XI, Repair/Replacement in accordance with ASME Code, section XI, and original construction code requirements. Two further indications were noted for 3/1/RPV SHELL/M-1211D-1. Both of these indications were found acceptable in accordance with NB-5352(b)(2). For the other Examination Category B-K welded attachments, the licensee stated that no recordable indications were observed during the surface examinations.
For the subject Examination Category C-B welds at DNPS, the volumetric examinations were limited due to the configuration of the nozzles. In Table B in the Attachment to the submittal, the licensee reported that the volumetric examination for weld 3/2/1302A-12/12-8 detected two subsurface flaws that exceeded the allowable flaw size and that were previously detected during refueling outage D2R20. In the response to the RAI in the letter dated June 14, 2024, the licensee clarified that the two subsurface indications exceeded the acceptance criteria in Table IWC-3511-1 of the ASME Code, section XI, and that the two indications were fabrication indications and not service-induced indications. The licensee dispositioned the two subsurface indications in accordance with IWC-3121(a) and performed an analytical evaluation in accordance with IWC-3600 (per IWC-3122.3). The licensees analytical evaluation determined that the two subsurface indications were acceptable and would remain acceptable for the service life of the component. The licensee stated that the two subsurface indications have not changed in size compared to the previously recorded results. Lastly, the licensee determined that having met the criteria in ASME Code, section XI, Code Cases N-526 and N-586-1, successive and additional examinations are not required for the two subsurface indications. The NRC staff confirmed that Code Cases N-526 and N-586-1 are unconditionally approved in Regulatory Guide 1.147, Revision 20, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, and that the two subsurface indications met the criteria in the Code Cases. The licensee did not detect any recordable indications in the other Examination Category C-B welds.
Based on the discussion above, the NRC staff finds that it is impractical to meet the ASME Code-required examination coverage for the subject Examination Categories B-A, B-D, B-K, and C-B, welds at DNPS, Units 2 and 3, because the identified design geometries and proximity
of integral vessel appurtenances that limited the examination coverage of the welds would need extensive modifications to obtain the required coverage. Furthermore, given the volumetric coverages obtained, the NRC staff determined that if significant service-induced degradation had occurred in the subject welds, evidence of it would have been detected by the examinations that were performed because the examined weld volume includes the most susceptible regions, is the same material as the unexamined volume, is under the same loading conditions, and is exposed to the same environment. Accordingly, the NRC staff determined that the coverages obtained provide reasonable assurance of structural integrity of the subject welds.
3.2 Piping Welds
3.2.1 Licensees Relief Request
ASME Code Components Affected
Code Class: Class 1
Examination Category: R-A, Risk-Informed Piping Examinations
Item Number: R1.11, Elements subject to thermal fatigue, and R1.20, Elements not subject to a damage mechanism
Component IDs: See Tables 3.2.1 and 3.2.2 of this safety evaluation
ASME Code Edition and Addenda
The licensee stated that the fifth 10-year ISI interval of DNPS ended on January 19, 2023, and was based on the ASME Code,Section XI, 2007 Edition with the 2008 Addenda.
ASME Code Requirement
Table 1 of ASME Code Case N-578-1, Risk-Informed Requirements for Class 1, 2 or 3 Piping, Method B,Section XI, Division 1, assigns Examination Category R-A, Item No. R1.11, to piping inspection elements subject to thermal fatigue an d Item No. R1.20 to piping inspection elements not subject to a known damage mechanism. This code case requires essentially 100% of the examination location volume, as described in Figures IWB-2500-8(c), 9, 10, or 11, as applicable, including an additional one half on an inch of base metal adjacent to the ASME Code volume, be completed for selected Class 1 and 2 piping welds.
Relief Request
The licensee achieved the volumetric examination coverages shown in Tables 3.2.1 (Unit 2) and 3.2.2 (Unit 3) for the subject Examination Category R-A welds. The licensee stated that in accordance with 10 CFR 50.55a(g)(5)(iii), relief is requested on the basis that conformance with these ASME Code,Section XI requirements, is impractical since conformance would require extensive structural modifications to the component or the surrounding structure. The licensee also stated that compliance with the applicable ASME Code, section XI, volumetric and surface examination requirements can only be accomplished by incurring significant engineering, material, and installation costs to perform modifications to physical component configuration, interference from permanent plant equipment, single-sided access, etc. without a compensating increase in level of quality and safety. The licensee summarized the limitations for each subject
Examination Category R-A weld in table A and B, in Attachment to the submittal and included corresponding details in Enclosure 1 and 2 to the submittal for Unit 2 and 3, respectively.
The licensee reported the following Examination Category R-A welds for DNPS, Unit 2.
Table 3.2.1 ASME Code,Section XI, Examination Category R-A (Unit 2)
ASME Percent Code Component ID Weld Description Coverage Item Obtained
R1.20 FW-1 (WELD 1) 2/1/1201-8/8-20A Pipe-to-Valve Weld (RWCU) 50
R1.20 FW-2 (WELD 2) 2/1/1201-8/8-12A Valve-to-Elbow Weld (RWCU) 48.2
The licensee reported the following Examination Category R-A welds for DNPS, Unit 3.
Table 3.2.2 ASME Code,Section XI, Examination Category R-A (Unit 3)
ASME Percent Code Component ID Weld Description Coverage Item Obtained R1.20 3/1/1302-14/14-9(A) Flued Head-to-Pipe Weld (ISCO) 50 R1.11 3/2/3204B-18/18-1 Valve-to-Tee Weld (FW) 78.95
Basis for Relief Request
The licensee stated that DNPS, Units 2 and 3, performed the ASME Code, section XI, required examinations to the maximum extent practical, or best effort, which are documented in tables A and B in Attachment to the submittal. Due to physical interferences or component geometry, the licensee stated that there were no other examination techniques available to increase examination coverage, and no cases in any of the listed examinations where the components outside diameter surface features could have been conditioned to obtain the required coverage without major modification to the components.
The licensee also stated that during the fifth ISI Interval, periodic system pressure tests that include VT-2 visual examinations were performed in accordance with ASME Code, section Xl, Table IWB-2500-1, Examination Category B-P for Class 1 All Pressure Retaining Components, and Table IWC-2500-1, Examination Category C-H for Class 2 All Pressure Retaining Components during each refueling outage. The licensee stated that these periodic system pressure tests and VT-2 examinations provided additional assurance that the structural and leak-tight integrity of the subject components was maintained throughout the fifth ISI Interval.
3.2.2 NRC Staff Evaluation
For the subject Examination Category R-A welds, the licensee obtained the volumetric examination coverages summarized in Table 3.2.1 and Table 3.2.2 using procedures, equipment, and personnel qualified using ASME Code, section XI, appendix VIII, Performance Demonstration for Ultrasonic Examination S ystems. The licensee achieved less than the required volumetric examination coverage due to geometric, material, and physical limitations
that would entail modification of the associated components if the required coverage were to be obtained. The NRC staff finds the stated limitations to be an acceptable basis for impracticality of conforming to the requirements and finds the modification necessary to achieve the required coverage constitutes a burden upon the licensee.
The licensee examined the subject welds to the maximum extent practical using volumetric and surface examination. However, due to the noted limitations, the licensee was not able to achieve the required examination volumes for the subject welds. The NRC staff reviewed and verified the examination coverages achieved and determined that subject welds had acceptable results for both surface and volumetric pre-service inspections and satisfied the VT-2 system leakage test. The NRC staff finds the licensee's achieved coverages acceptable, given the noted limitations.
Given the examination results and coverage obtained, the NRC staff concludes that, if significant service-induced degradation had occurred in the subject welds, evidence of it would have been detected by the examinations performed by the licensee. Furthermore, the NRC staff determined that the examinations performed provide reasonable assurance of structural integrity of the subject welds.
The NRC staff also noted that the licensee assess ed the potential for additional or alternative welds for examination to supplement the reduced volumetric coverages, and that the licensee determined that no other welds could have been selected to achieve better coverage.
Based on the above discussion, the NRC staff determined that obtaining the ASME Code-required examination volume coverage for the subject DNPS, Units 2 and 3, Examination Category R-A welds is impractical because of the stated limitations and that the modifications necessary to obtain the required coverage would impose a burden upon the licensee. The NRC staff also determined that the volumetric examination performed to the maximum extent practical provides reasonable assurance of the structural integrity of the weld because: (1) the licensee identified no recordable indications; and (2) evidence of significant service-induced degradation in the welds, if it were to occur, would likely have been detected by the volumetric examination coverage obtained by the licensee, because the examined weld volume includes the most susceptible regions, is the same material as the unexamined volume, is under the same loading conditions, and is exposed to the same environment.
4.0 CONCLUSION
S
As set forth above, the NRC staff has determined that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Furthermore, the NRC staff concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject components.
Accordingly, the NRC staff concludes that t he licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii) and grants relief pursuant to 10 CFR 50.55a(g)(6)(i) for the examinations of the subject components contained in RR I5R-22, for the fifth 10-year ISI interval at DNPS, Units 2 and 3.
All other ASME Code, section XI, requirements for which relief was not specifically requested and approved in the subject requests for relief rema in applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal contributors: D. Dijamco (NRR)
D. Widrevitz (NRR)
O. Khan (NRR)
Date: September 26, 2024
ML24225A213 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DNRL/NVIB/BC NRR/DNRL/NPHP/BC NAME SArora SRohrer DWidrevitz for ABuford MMitchell DATE 8/2/2024 8/13/2024 7/16/2024 7/16/2024 OFFICE NRR/DORL/LPL3/BC NAME JWhited DATE 9/25/2024