ML23094A142
| ML23094A142 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 04/05/2023 |
| From: | Hipolito Gonzalez NRC/NRR/DORL/LPL1 |
| To: | Rhoades D Constellation Energy Generation |
| References | |
| EPID L-2023-LLR-0012 | |
| Download: ML23094A142 (1) | |
Text
April 5, 2023
NINE MILE POINT NUCLEAR STATION, UNIT NO. 1-APPROVAL OF ALTERNATIVE REQUEST I5R-13 TO UTILIZE SPECIFIC PROVISIONS OF CODE CASE N-716-3 (EPID: L-2023-LLR-0012)
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 and Unit: Nine Mile Point Nuclear Station, Unit No. 1
Docket No.: 50-220
APPLICATION INFORMATION
Application Date: March 29, 2023
Application Agencywide Documents Access and Management System (ADAMS)
Accession No.: ML23088A395
Supplement Date: April 3, 2023
Supplement ADAMS Accession No.: ML23093A178
Licensee Proposed Alternative No. or Identifier: I5R-13
Applicable Inservice Inspection (ISI) Program Interval and Interval Start/End Dates: The fifth 10-year ISI interval for Nine Mile Point Nuclear Station, Unit No. 1 (Nine Mile Point, Unit 1),
began on April 23, 2019, and is scheduled to conclude on August 22, 2029.
Alternative Provision: The applicant requested an alternative under Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(z)(1).
Applicable Code Edition and Addenda: 2013 Edition of the American Society of Mechanical Engineers (ASME) Code,Section XI.
Applicable Code Requirements:
The regulation at 10 CFR 50.55a(g)(4) requires that inservice examination of components conducted during the first 10-year inspection interval and subsequent 10-year inspection intervals comply with the requirements in the latest edition and addenda of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) incorporated by reference in 10 CFR 50.55a(b) twelve months prior to the start of the 120-month inspection interval, subject to the limitations and modifications listed therein.
The licensee is utilizing a Risk-Informed Inserv ice Inspection (RI-ISI) program based on ASME Code Case N-716-1, Alternative Classificati on and Examination RequirementsSection XI, Division 1. ASME Code Case N-716-1 Paragraph (6)(b)(2) states, "if the additional examinations required by 6(b)(1) reveal flaws or relevant conditions exceeding the acceptance standards of Table IWB-3410-1, Table IWC-3410-1, or IWD-3000 as applicable, the examinations shall be extended to include a se cond sample of additional examinations during the current outage."
Code Case N-716-1 Paragraphs (6)(b)(2)(a) states, "the second sample of additional inspection items to be examined shall include all remaining HSS [high safety significance] inspection items subject to the same degradation mechanism."
ASME Code,Section XI, Paragraph IWB-3514 contains the flaw acceptance standards applicable to Examination Category R-A, Item Number R1.16.
The proposed alternative is requested for the Nine Mile Point, Unit 1, Spring 2023 refueling outage, designated as N1R27.
Brief Description of the Proposed Alternative:
The licensee is requesting to use ASME Code Case N-716-3 Paragraphs 6(b)(3), 6(b)(4), and 6(b)(5) for defining additional examinations bas ed on the examination results during Nine Mile Point, Unit 1s, N1R27 refueling outage. The rules of Code Case N-716-3 allow for additional examinations for butt welds subject to Intergranular Stress Corrosion Cracking (IGSCC)
(defined as Item No. R1.16.1 in N-716-3 and equivalent to Item No. R1.16 in N-716-1) to be performed in accordance with the Owner's existing program. The licensees augmented inspection program is based upon the guidance of Generic Letter 88-01, NRC [U.S. Nuclear Regulatory Commission] Position on IGSCC in BWR [Boiling-Water Reactor] Austenitic Stainless Steel Piping and the inspection schedules of BWRVIP-75-A, BWR Vessel and Internals Project Technical Basis for Revisions to Generic Letter 88-01 Inspection Schedules.
The sample expansion requirements of BWRVIP-75-A for Category D welds are required "if cracking is detected." Identification of fabrication flaws, not attributed to IGSCC cracking, does not require any additional examinations in accordance with BWRVIP-75-A.
For additional details on the licensees submittal, please refer to the documents located at the ADAMS accession number 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 licensee is proposing to use ASME Code Case N-716-3 Paragraphs 6(b)(3), 6(b)(4), and 6(b)(5) in lieu of Code Case N-716-1, Paragraph 6(b)(2) to not have to further expand the required examinations during their N1R27 refueling outage. The NRC staff reviewed the submittal to evaluate the submittal to determine if the proposed alternative would provide an acceptable level of quality and safety.
During the N1R27 refueling outage, the licensee performed ultrasonic (UT) examination of components subject to IGSCC. During these examinations, an IGSCC flaw was identified in the N2E safe end-to-nozzle dissimilar metal (DM) weld (32-WD-208). Since IGSCC cracking was identified, additional examinations were performed in accordance with the requirements of Code Case N-716-1 and BWRVIP-75-A. This sample of additional examinations includes locations subject to the same postulated degradation mechanism as N2E, which is subject to IGSCC. The N1A nozzle-to-safe end DM weld (32-WD-002) and N1B nozzle-to-safe end DM weld (32-WD-045) were selected for examination as they are subject to the IGSCC, same component configuration, and are within the same system (reactor recirculation).
During UT examination of 32-WD-002, two axial indications were determined to be unacceptable when compared to the acceptance standards of Table IWB-3514-1. During UT examination of 32-WD-045, three axial indications were recorded, two of which were determined to be unacceptable when compared to the acceptance standards of Table IWB-3514-1. It is worth noting that the N1R27 refueling outage 2023 inspection was the first time the licensee used a Phased-Array Refracted Longitudinal UT procedure. Previous examinations of 32-WD-002 and 32-WD-045 used shear-wave examinations.
The change in recorded flaw sizes in the N1R27 refueling outage inspection was judged by the licensee to be due to a change in the UT technique and not due to service-induced growth of the flaws. Attachment 4 in the letter dated March 29, 2023, details the flaw evaluations that have determined the flaws are acceptable for continued service for at least two operating cycles
(4 years). Successive inspections of 32-WD-002 and 32-WD-045 will be performed during the next inspection period which includes the next two refueling outages.
The flaws in 32-WD-002 and 32-WD-045 have been detected in previous inspections. The flaws were previously detected in 32-WD-002 during inspections in May 1999, April 2009, and March 2019. The flaws in 32-WD-045 were previously detected in May 1999, April 2009, and in March 2015.
The flaws in 32-WD-002 and 32-WD-045 were determined to be fabrication flaws by the licensee based on the following:
The flaws have been sized consistently by shear-wave automated UT for several exam cycles, starting in 1999, by different vendors and different equipment, and shear-wave examinations in the current outage, and using the shear-wave UT examinations the flaws exhibited no growth in the N1R27 refueling outage inspection.
The flaw signals display a smooth, uniform response with limited faceting, which is not indicative of IGSCC.
The UT examinations have consistently determined that the flaws are not in the weld material and extend axially into the IGSCC-resistant material.
The NRC staff agrees that the indications are cons istent with fabrication flaws in the base material.
Code Case N-716-1, Paragraph 6(b)(2) states in part, if the additional examinations required by 6(b)(1) reveal flaws or relevant conditions exceeding the acceptance standards of Table IWB-3410-1, the examinations shall be extended to include a second sample of additional examinations during the current outage. Since the 32-WD-002 and 32-WD-045 nozzle-to-safe ends welds both contain flaws exceeding the acceptance standards of Table IWB-3514-1, a second sample of additional examinations is required.
The purpose of expanding examinations after a flaw is found is to determine if more components are affected by service-induced degradation, and not to find fabrication flaws.
ASME Code Case N-716-1 was revised to give licensees flexibility in dealing with fabrication flaws found during the additional examinations. N-716-3 Paragraph 6(b)(3) allows the licensee to use their owners program to develop the scope of the successive examination. N-716-3 Paragraph 6(b)(5) states that, The evaluation shall determine the cause of the flaws or relevant conditions and the appropriate method to be used as part of the additional examination scope.
These provisions allow the licensee to explicitly use the information that the flaws detected in 32-WD-002 and 32-WD-045 are fabrication flaws and determine that no additional examinations are required to detect service-induced degradation. N-716-3 Paragraph 6(b)(4) allows the successive inspections to resume their normal schedule if reexaminations show no change in the flaws.
The NRC staff has determined that there is no significant safety benefit to expanding the inspection scope based on the examinations finding fabrication flaws in the associated base material. There is reasonable assurance that the defects are fabrication flaws have been present in the base material since construction and are not service-induced or growing with
time. If the determination that these flaws are fabrication flaws is incorrect, the possible crack growth will be measurable in the successive examinations.
Based on the above considerations, the NRC staff therefore finds that the use of the proposed alternative I5R-13 to use ASME Code Case N-716-3 Paragraphs 6(b)(3), 6(b)(4), and 6(b)(5) provides reasonable assurance that the leak tightness and structural integrity of the welds will be maintained.
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 I5R-13 at Nine Mile Point, Unit 1, for the N1R27 refueling outage.
All other ASME Code,Section XI requirements for which an alternative was not specifically requested and approved in this proposed alternative remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: Stephen Cumblidge
Date: April 5, 2023
Hipólito J. González, Chief Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
cc: Listserv
ML23094A142 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DNRL/NPHP/BC NAME RGuzman KEntz MMitchell DATE 04/04/2023 04/05/2023 04/04/2023 OFFICE NRR/DORL/LPL1/BC NAME HGonzález DATE 04/05/2023