ML22276A249
| ML22276A249 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 10/25/2022 |
| From: | Stone Z NRC/NRR/DORL/LPL2-1 |
| To: | Simril T Duke Energy Carolinas |
| Stone Z, NRR/DORL/LPL2-1 | |
| References | |
| EPID L-2022-LRO-0050 | |
| Download: ML22276A249 (1) | |
Text
October 25, 2022 Mr. Tom Simril Site Vice President Duke Energy Carolinas, LLC Catawba Nuclear Station 4800 Concord Road York, SC 29745
SUBJECT:
CATAWBA NUCLEAR STATION, UNITS 1 AND 2 - COMPLETION OF LICENSE RENEWAL COMMITMENT NO. 10, AGING MANAGEMENT OF ENVIRONMENTALLY ASSISTED FATIGUE (EPID L-2022-LRO-0050)
Dear Mr. Simril:
By letter dated April 21, 2022, as supplemented by letter dated June 29, 2022, Duke Energy Carolinas, LLC (Duke Energy, the licensee), submitted information to the U.S. Nuclear Regulatory Commission (NRC) which proposed Duke Energys inspection plan for License Renewal Commitment (LRC) No. 10. Specifically, the letter documents Duke Energys proposed use of flaw tolerance evaluations and inspections of the safety injection nozzle welds for Catawba Nuclear Station, Units 1 and 2, to address LRC No. 10, environmentally assisted fatigue (EAF) aging management program.
The NRC staff has completed its review of the submittal and finds that the licensees proposed method is sufficient to manage cracking and the EAF aging management program is acceptable for the extended period of operation. The NRC considers LRC No. 10 closed. The enclosure documents the NRC staffs review of the submittal.
If you have any questions, please contact me at 301-415-0615 or via email at Zackary.Stone@nrc.gov.
Sincerely, Zackary R. Stone, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-413 and 50-414
Enclosure:
Review of Environmentally Assisted Fatigue Aging Management Program cc: Listserv Zackary R.
Stone Digitally signed by Zackary R. Stone Date: 2022.10.25 13:24:13 -04'00'
Enclosure U.S. NUCLEAR REGULATORY COMMISSION LICENSE RENEWAL COMMITMENT NO. 10 ENVIRONMENTALLY ASSISTED FATIGUE AGING MANAGEMENT PROGRAM DUKE ENERGY CAROLINAS, LLC CATAWBA NUCLEAR STATION, UNITS 1 AND 2 DOCKET NO. 50-413 AND 50-414
1.0 INTRODUCTION
By letter dated April 21, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22111A297), as supplemented by letter dated June 29, 2022 (ML22180A002), Duke Energy Carolinas, LLC (Duke Energy, the licensee) submitted information to the U.S. Nuclear Regulatory Commission (NRC) which documented Duke Energys proposal to meet License Renewal Commitment (LRC) No. 10 (ML030850237, NUREG-1772, Appendix D), by providing an environmentally assisted fatigue (EAF) aging management program for the safety injection nozzle welds. Specifically, the letter documents Duke Energys proposed use of a proposed method for flaw tolerance evaluations and inspections of the safety injection nozzle welds for Catawba Nuclear Station (Catawba), Units 1 and 2.
The licensees submittal, RA-22-0115, is in response to LRC No. 10 in the license renewal safety evaluation for Catawba, Units 1 and 2, that is described in NUREG-1772, Safety Evaluation Report Related to the License Renewal of McGuire Nuclear Station, Units 1 and 2, and Catawba Nuclear Station, Units 1 and 2 (ML030850251).
In Section 4.3.2 of NUREG-1772, the NRC staff states that Duke Energy agreed not to use flaw tolerance and inspection procedures specified in Note 1 unless such procedures have been accepted by the NRC staff. Accordingly, the licensee submitted the request for NRC staffs review of the proposed commitment change regarding this analytical method for flaw tolerance evaluation and inservice inspection (ISI) plan.
2.0 REGULATORY EVALUATION
Title 10 of the Code of Federal Regulations (10 CFR) CFR Part 54, Requirements for renewal of operating licenses for nuclear power plants, addresses the requirements for plant license renewal process. The regulation at 10 CFR 54.21, Contents of application - technical information, requires that each application for license renewal contain an integrated plant assessment (IPA) and an evaluation of time-limited aging analyses. The plant-specific IPA shall identify and list those structures and components subject to an aging management review and demonstrate that the effects of aging will be adequately managed so that their intended functions will be maintained consistent with the current licensing basis for the period of extended operations.
The NUREG-1800, Standard Review Plan for the Review of License [SRP-LR] Renewal Applications for Nuclear Power Plants, Revision 2, Appendix A, (ML103490036) provides guidance on how programs and activities that are credited for managing a certain aging effect for a specific structure or component should be described.
3.0 NRC STAFF EVALUATION 3.1 Flaw Tolerance Evaluation The licensee proposed a method to manage the aging effect due to EAF in the safety injection nozzle by using flaw tolerance evaluation and associated periodic inspections that will be performed once every 10 years. The licensee explained that the flaw tolerance evaluation of the safety injection nozzle is consistent with the approach documented in ASME Boiler and Pressure Vessel Code (ASME BPV Code),Section XI, Non-Mandatory Appendix L, Operating Plant Fatigue Assessment. Specifically, the licensee stated that the flaw tolerance evaluation was performed in accordance with the 2013 Edition of the ASME BPV Code,Section XI, Appendix L.
The NRC staff finds that the licensees use of the 2013 Edition of the ASME BPV Code,Section XI, Appendix L for the flaw tolerance evaluation is acceptable because the 2013 Edition of the Code has been incorporated by reference into 10 CFR 50.55a. Codes and Standards.
Table 1 of the licensees letter dated April 21, 2022, describes the specific locations evaluated in the flaw tolerance evaluation, which are subject to the bounding stresses of the safety injection nozzle. The licensee explained that the locations in the safety injection nozzle weld region will be periodically examined in accordance with L-3420 of ASME BPV Code,Section XI, Appendix L. In letter dated June 29, 2022, the licensee clarified that the flaw tolerance evaluation assumed the initial flaw depths and lengths in accordance with L-3210 of ASME BPV Code,Section XI, Appendix L. In addition, the acceptable flaw size after crack growth was determined in accordance with L-3000 of ASME BPV Code,Section XI, Appendix L. The NRC staff finds that the periodic inspections, initial flaw size assumption and acceptable flaw size determination rely on the relevant provisions of ASME BPV Code,Section XI, Appendix L, and are, therefore, acceptable.
In the flaw tolerance evaluation, the licensee also used the fatigue crack growth rates described in Code Case N-809, which are based on the latest fatigue crack growth data. The NRC staff finds that the use of Code Case N-809 is acceptable because Regulatory Guide 1.147, lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1, Revision 20, (ML21181A222) identifies the Code Case as an acceptable Code Case without condition.
As summarized in Table 1 of the licensees request, the 60-year flaw depth of the safety nozzle injection is less than the acceptable flaw depth for axial and circumferential flaw orientations.
The NRC staff finds that the flaw growth for 60 years is conservative because it assumes a pre-existing fatigue crack even at the beginning of the plant operation. Based on the above, the NRC staff finds that the flaw tolerance evaluation results support the results indicating that the aging effect of EAF does not affect the structural integrity of the safety injection nozzle for 60 years of operation and is, therefore, acceptable.
3.2 Aging Management Program In conjunction with the flaw tolerance evaluation, the licensee also proposed to perform periodic inspections once every 10 years in accordance with table L-3420 of ASME BPV Code,Section XI, Appendix L, as previously discussed. The NRC staffs evaluation of the proposed Safety Injection Nozzle Inspection Program is further documented below.
3.2.1 Scope of Program Table 2 of the licensees request lists the safety injection nozzle welds that will be examined in the Safety Injection Nozzle Inspection Program. These inspections are also part of the Catawba Risk-Informed Inservice Inspection Program that is consistent with ASME BPV Code,Section XI, Code Case N-716-1. The licensee indicated that the aging effect managed with these inspections is cracking due to EAF. The licensee will perform volumetric examination on the eight safety injection nozzle welds (four per unit) in each 10-year ISI interval during the period of extended operation. In the letter dated June 29, 2022, the licensee explained that the safety injection nozzle welds are subject to examination Item Number R1.11 (welds subject to thermal fatigue) in accordance with Code Case N-716-1.
The licensee stated that the scope of program program includes: (1) the scope of the program program element clearly identifying cracking due to EAF in the safety injection nozzle welds as the aging effect to be managed and associated components for aging management, and (2) the program element consistent with the guidance in SRP-LR, Section A.1.2.3.1.
The NRC staff finds that the scope of program acceptable because it follows the expectations of scope and method.
3.2.2 Preventive Actions In its letter dated April 21, 2022, the licensee stated that there are no specific preventive actions under the program to prevent the effect of aging.
The NRC staff finds that the preventive actions program element is acceptable because: (1) a condition monitoring programs may not rely on preventive actions and thus the information for preventive actions need not be provided, as discussed in SRP-LR, Section A.1.2.3.2, and (2) the licensees program relies on periodic inspections in conjunction with the flaw tolerance analysis for aging management rather than preventive actions 3.2.3 Parameters Monitored or Inspected In its letter dated April 21, 2022, the licensee stated that volumetric examinations will be performed on the safety injection nozzle welds as described in Table 2. The volumetric examination will be conducted in accordance with the examination requirements of ASME BPV Code,Section XI, IWA-2000 and Code Case N-716-1.
The NRC staff finds that the parameters monitored or inspected program element is acceptable because: (1) the periodic volumetric inspections in accordance with the examination provisions of ASME BPV code are sufficient to detect and monitor cracks in the safety inspection nozzle welds, and (2) relevant inspection results, including crack sizes, are evaluated to perform corrective actions, as needed (e.g., repair or replacement of affected welds),
consistent with the guidance in SRP-LR, Section A.1.2.3.3.
3.2.4 Detection of Aging Effects The aging effect managed for the safety injection nozzle welds is cracking due to EAF. The licensee stated that the aging management will be accomplished by performing periodic volumetric examinations. The frequency of the volumetric examinations (i.e., once every 10 years) is based on the flaw tolerance evaluation in accordance with ASME BPV Code Section XI, Appendix L.
As described in Table 1 of the licensees request, the flaw tolerance analysis confirms that the fatigue crack growth of a postulated flaw takes more than 60 years to reach the maximum allowable flaw size, which is significantly greater than the 10-year inspection interval for the safety injection nozzle welds. Therefore, the NRC staff finds that the analysis results demonstrate that the 10-year inspection interval is sufficient to manage cracking due to EAF for the safety injection nozzle.
The NRC staff finds that the detection of aging effects program element is acceptable because: (1) the volumetric examinations are sufficient to detect cracking due to EAF in the safety injection nozzle welds, (2) the program uses an adequate inspection frequency (once every 10 years) based on the Appendix L flaw tolerance evaluation, and (3) the program element specifically identifies cracking due to EAF as the aging effect to be managed and how the aging effect will be detected and managed (i.e., detection of aging effect through periodic inspections based on the flaw tolerance evaluation), consistent with the guidance in SRP-LR, Section A.1.2.3.4.
3.2.5 Monitoring and Trending In addition to the periodic examinations discussed above, subparagraph 6(a)(2) of Code Case N-716-1, which the licensees inspection program relies on, specifies successive examination requirements. If the examined welds are accepted for continued service by analytical evaluation of flaws in accordance with ASME BPV Code,Section XI, IWB-3132.3, the areas containing flaws are required to be reexamined during the next three inspection periods.
The analytical evaluation of flaws and successive inspections also follow ASME BPV Code,Section XI, IWB-3600. The licensee further explained that, if a flaw is identified in the safety injection nozzle, it will evaluate the flaw to assess the effect of EAF and to determine impacts on the EAF analysis.
The NRC staff finds that the monitoring and trending program element is acceptable because:
(1) the periodic volumetric examinations and their frequency, once every 10 years based on the flaw tolerance analysis, are adequate to monitor and trend cracking due to EAF in the safety injection nozzles, (2) detected flaws are evaluated against the acceptance standards specified in ASME BPV Code,Section XI, IWB-3500, (3) if the examined welds are accepted for continued service based on analytical evaluation of flaws, successive examinations will be conducted in accordance with the provisions of ASME BPV Code,Section XI, IWB-3600 and Code Case N-716-1, (4) if flaws are identified in the welds during the examinations, the examination results will be also evaluated to assess the impacts of the degradation on the licensees EAF analysis for Class 1 components and piping, and (5) the licensees approach is consistent with the guidance in SRP-LR, Section A.1.2.3.5, that the program element includes an evaluation of the results against the acceptance criteria and a prediction regarding the rate of degradation in order to ensure that the next scheduled inspection will occur before a loss of the components intended function.
3.2.6 Acceptance Criteria In the evaluation of detected flaws, the licensees inspection program uses the acceptance standards specified in ASME BPV Code,Section XI, IWB-3500.
The NRC staff finds that the acceptance criteria program element is acceptable because:
(1) the periodic volumetric examinations evaluate relevant indications of degradation in accordance with the acceptance standards specified in IWB-3500 of ASME BPV Code,Section XI, (2) the acceptance standards of the ASME BPV Code are sufficient to evaluate relevant indications and initiate corrective actions, consistent with the current licensing basis, and (3) the licensees approach is consistent with the guidance in SRP-LR, Section A.1.2.3.6, which allows the current licensing basis acceptance criteria such as code standards to be used.
3.2.7 Corrective Actions The licensee will generate action requests in accordance with the Duke Corrective Action Program for flaws that exceed the acceptance criteria. Items with examination results that do not meet the acceptance criteria are subject to acceptance by analytical evaluation per ASME BVP Code,Section XI, IWB-3600 or acceptance by repair or replacement in accordance with IWA-4000.
The NRC staff finds that the corrective actions program element is acceptable because: (1) the flaws, which do not meet the acceptance criteria, will be repaired, replaced or analytically evaluated for continued service in accordance with the ASME BPV Code requirements, consistent with the current licensing basis, and (2) the licensees approach is consistent with the guidance in SRP-LR, Section A.1.2.3.7, that, if corrective actions permit analysis without repair or replacement, the analysis should ensure that the intended functions of the components are maintained, consistent with the current licensing basis.
3.2.8 Confirmation Process As discussed above, if degradation is identified in safety injection nozzle welds, the licensee will perform an engineering evaluation to determine if they are acceptable for continued service or if repair or replacement is required in accordance with the requirements of ASME BPV Code,Section XI. The licensee also stated that the engineering evaluation will include probable cause, the extent of degradation, the nature and frequency of additional examinations, and whether repair or replacement is required.
The licensee explained that the records of the examination procedures, results of activities, examination datasheets, and corrective actions taken or recommended will be maintained in accordance with the requirements of the Catawba Inservice Inspection Program and ASME BPV Code,Section XI. The licensee also indicted that it performs repair and replacement activities in accordance with the requirements of ASME BPV Code,Section XI, IWA-4000 as implemented by the Catawba administrative procedure for the Repair/Replacement Program.
The NRC staff finds that the confirmation process program element is acceptable because: (1) if degradation is identified in the safety injection nozzle welds, the licensee will determine the cause of degradation, the extent of degradation and additional examination, and the need for repair or replacement in accordance with the ASME BPV Code requirements and licensees administrative procedure for implementing and confirming corrective actions, and (2) the licensees approach is consistent with the guidance in SRP-LR, Section A.1.2.3.8, that, when corrective actions are necessary, there should be follow-up activities to confirm that the corrective actions have been completed and a root cause determination was performed.
3.2.9 Administrative Controls The licensee stated that the Catawba ISI Program will document the EAF inspection requirements for the safety injection nozzle welds under the ASME Section XI ISI Program. The licensee also stated that site quality assurance procedures, review and approval processes, and administrative controls are implemented in accordance with the requirements of 10 CFR Part 50, Appendix B, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants and will continue to be used for the period of extended operation.
The NRC staff finds that the administrative controls program element, which complies with the requirements of 10 CFR Part 50, Appendix B, is consistent with the guidance in SRP-LR, Section A.1.2.3.9, and, therefore, is acceptable.
3.2.10 Operating Experience The licensee stated that all safety injection nozzle welds were inspected in 2021 at Catawba, Units 1 and 2, and that the inspection results did not reveal any indication of cracking. The licensee also explained that the programmatic operating experience review activities in accordance with station procedures ensure adequate evaluation of operating experience on an ongoing basis to address age-related degradation and aging management for the safety injection nozzle.
The NRC staff finds that the operating experience program element and associated discussions are acceptable because (1) the previous inspection results on the safety injection nozzle welds at Catawba, Units 1 and 2, did not reveal any indications of cracking and (2) the licensee will continue to evaluate operating experience related to cracking due to EAF in the safety injection nozzle welds for aging management, consistent with the guidance in SRP-LR, Section A.1.2.3.10.
4.0 CONCLUSION
S As set forth above, the NRC staff determines that the licensee-proposed method for aging management is sufficient to manage cracking due to EAF for the safety injection nozzle at Catawba, Units 1 and 2, by using the flaw tolerance evaluations and periodic inspections for the period of extended operation. Therefore, the NRC staff approves the use of the proposed aging management method for the period of extended operation at Catawba, Units 1 and 2 (i.e., 40 to 60 years of operation). Based on the above, the NRC considers LRC No. 10 closed.
Principal Contributor: S. Min, NRR/DNRL/NPHP Date: October 25, 2022
ML22276A249 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DNRL/NPHP/BC NAME ZStone KGoldstein (KEntz for)
MMitchell DATE 9/30/2022 10/06/2022 9/27/2022 OFFICE NRR/DORL/LPL2-1/BC NRR/DORL/LPL2-1/PM NAME MMarkley ZStone DATE 10/25/2022 10/25/2022