ML24351A242
| ML24351A242 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/19/2024 |
| From: | Richard Guzman NRC/NRR/DORL/LPL1 |
| To: | Carr E Dominion Energy Nuclear Connecticut |
| References | |
| EPID L-2023-LRO-0092 | |
| Download: ML24351A242 (1) | |
Text
December 19, 2024 Eric S. Carr President - Nuclear Operations and Chief Nuclear Officer Dominion Energy Nuclear Connecticut, Inc.
Millstone Power Station Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711
SUBJECT:
MILLSTONE POWER STATION, UNIT NO. 3 REACTOR COOLANT SYSTEM ALLOY 600 INSPECTION PROGRAM FOR LICENSE RENEWAL COMMITMENT NO. 15 (EPID L-2023-LRO-0092)
Dear Eric Carr:
By letter dated November 20, 2023, Dominion Energy Nuclear Connecticut, Inc. (the licensee),
submitted its response to a commitment related to renewal of the operating license for Millstone Power Station, Unit No. 3 (Millstone Unit 3). Specifically, the licensee committed to submit a revised aging management program description for the management of nickel-based alloy 600 components, no later than two years before Millstone Unit 3 enters its period of extended operation. This is designated as license renewal commitment no. 15.
The Nuclear Regulatory Commission (NRC) staff has reviewed the licensees Alloy 600 Program as a plant-specific program and finds that it meets the commitments made by the applicant and the requirements established in the Standard Review Plan for License Renewal for structures and/or components made of nickel alloy material. Based on its review, the NRC staff concludes the licensee has demonstrated that effects of aging will be adequately managed at Millstone Unit 3 so that the intended functions will be maintained consistent with the current licensing basis for the period of extended operation, as required by Title 10 of the Code of Federal Regulations Section 54.21(a)(3).
If you have any questions, please contact me at (301) 415-1030 or by email at Richard.Guzman@nrc.gov.
Sincerely,
/RA/
Richard Guzman, Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-423
Enclosure:
Safety Evaluation cc: Listserv
Enclosure STAFF EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REACTOR COOLANT SYSTEM ALLOY 600 AGING MANAGEMENT PROGRAM SUBMITTAL RELATED TO LICENSE RENEWAL COMMITMENT 15 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 3 DOCKET NO. 50-423
1.0 INTRODUCTION
By letter dated November 20, 2023 (Agencywide Documents Access and Management System Accession No. ML23324A430), as supplemented by letter dated May 20, 2024 (ML24141A243),
Dominion Energy Nuclear Connecticut, Inc. (the licensee) submitted a description of its revised aging management program (AMP) for management of nickel-based alloy 600 components for Millstone Power Station, Unit No. 3 (Millstone Unit 3). The document was submitted in accordance with Commitment Item No. 15 of NUREG-1838, the safety evaluation report for the renewed operating license for Millstone Unit 3.
The Millstone license renewal application for compliance with the requirements of Title 10 of the Code of Federal Regulations (10 CFR), Part 54, "Requirements for Renewal of Operating Licenses for Nuclear Power Plants," was authorized by the Nuclear Regulatory Commission (NRC) through NUREG-1838, "Safety Evaluation Report Related to the License Renewal of the Millstone Power Station, Units 2 and 3," in October 2005 as Volume 1 (ML053270483) and Volume 2 (ML053290180). Commitment Item No. 15 of NUREG-1838 for Millstone Unit 3 requires the submission of a revised aging management program (AMP) description for the management of nickel-based alloy (also referred to as Alloy 600) components to the NRC:
Millstone will follow the industry efforts investigating the aging effects applicable to nickel-based alloys (i.e., PWSCC [Primary Water Stress Corrosion Cracking]
in Alloy 600 base metal and Alloy 82/182 weld metals) and identifying the appropriate aging management activities and will implement the appropriate recommendations resulting from this guidance. The revised program description will be submitted at least two years prior to the period of extended operation for staff review and approval to determine if the program demonstrates the ability to manage the effects of aging in nickel based components per 10 CFR 54.21(a)(3).
NUREG-1838 included nickel-based alloy aging management in the lnservice Inspection Program: Systems, Components, and Supports AMP. After considering industry developments and operating experience, the licensee developed a separate, new AMP to address nickel-based alloy aging management. In accordance with Commitment Item No. 15, the nickel-based alloy AMP inspection program is based on industry guidance and addresses the ten program elements of NUREG-1801. The Millstone Unit 3 Alloy 600 AMP description was provided for NRC review and approval per 10 CFR 54.21(a)(3).
2.0 REGULATORY EVALUATION
In accordance with 10 CFR 54.21(a)(3), "For each structure and component identified in paragraph (a)(1) of this section, the licensee shall demonstrate that the effects of aging will be adequately managed so that the intended function(s) will be maintained consistent with the current licensing basis (CLB) for the period of extended operation."
As documented in NUREG-1838, the staff reviewed the information included in the License Renewal Application regarding the applicant's demonstration of the Reactor Coolant System Alloy 600 Inspection Program to ensure that the effects of aging will be adequately managed so that the intended functions will be maintained consistent with the CLB throughout the period of extended operation.
At the time NUREG-1838 was being finalized, the industry was still developing a long-term Alloy 600 management plan. The applicant committed to develop and submit the Reactor Coolant System Alloy 600 Inspection Program to the U.S. Nuclear Regulatory Commission (NRC) for staff review and approval 24 to 36 months prior to the period of extended operation.
As documented in NUREG-1838, the staff concluded that this program attribute was acceptable.
By letter dated November 20, 2023, as supplemented by letter dated May 20, 2024, the licensee submitted a response to the above commitment by providing the details for Millstone Unit 3 Alloy 600 Inspection Program as part of the license renewal process.
3.0 TECHNICAL EVALUATION
In accordance with 10 CFR 54.21(a)(3), the NRC staff reviewed the information in the licensees submittal to meet Commitment Item No. 15 in Table 19.6-1 of the Millstone Unit 3 Final Safety Analysis Report to ensure that the effects of aging will be adequately managed for each component so that the intended function(s) will be maintained consistent with the current licensing basis for the period of extended operation.
The NRC staff focused its review on the Dominion Nuclear Fleet Alloy 600 Management Plan, which manages cracking due to PWSCC for nickel alloy component locations. The licensee noted that this program is currently consistent with the Nickel Alloy Nozzles and Penetrations AMP described in Chapter XI of the Generic Aging Lessons Learned (GALL) Report (NUREG-1801), Rev. 0, with two enhancements.
- 1. The program scope has been enhanced according to industry guidelines to include all Alloy 600/82/182 components in the primary system.
- 2. The inspection requirements have been updated to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME) Code,Section XI Code Cases N-722-1, N-729-6 and N-770-5 and MRP-335, Revision 3-A, Materials Reliability Program: Topical Report for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement, November 2016.
The licensee explained that at the time NUREG-1838 was being finalized (2005), the industry was still developing a long-term Alloy 600 management plan and reactor vessel head inspections were being performed in accordance with the First Revised Order EA-03-009. As such, at the time of the licensees license renewal request, the licensees program was consistent with the Nickel Alloy Nozzles and Penetrations AMP described in Chapter XI of NUREG-1801, Rev. 0 with one exception. The exception concerned reactor vessel top head inspections and hence, the license renewal Commitment Item No. 15 followed. NRC staff confirmed this was a basis for original approval of the LRA for Millstone Unit 3 in Section 3.0.3.2.13 of NUREG-1838.
Given the only exception was the reactor vessel top head inspection program inclusion within a long-term plan from the original LRA approved by NUREG-1838, the NRC staff confirmed an acceptable program to address reactor vessel top head inspections was included in the current program. As noted above, the licensees program is enhanced by the incorporation of ASME Code Case N-729-6 entitled, Alternative Examination Requirements for PWR [pressurized water reactor] Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds. The NRC currently mandates the use of ASME Code Case N-729-6 through 10 CFR 50.55a(g)(6)(ii)(D), Augmented ISI requirements: Reactor vessel head inspections. Therefore, the NRC staff notes the previous exception has been addressed in the licensees program and the NRC regulations for an augmented inservice inspection program to address reactor vessel top head inspections. Since the license renewal commitment included a revised program for NRC review and approval, the NRC staff also reviewed the licensees Alloy 600 Program AMP.
The Standard Review Plan for License Renewal (SRP LR), NUREG-1800, Rev. 2 contains the staff's generic evaluation of existing plant programs and documents the technical basis for determining where existing programs are adequate without modification for the extended period of operation. Guidance for a generic review of an aging management program such as the licensees Alloy 600 Program is provided in Section A.1, Aging Management Review, of the SRP LR. The staff reviewed the licensees Alloy 600 Program against the AMP elements found in Section A.1.2.3 based on the licensees submittal.
(1)
Scope of the Program -the licensees Alloy 600 Program will manage cracking due to PWSCC for the following nickel alloy component locations:
Reactor Vessel (RV) o Closure head 78 Alloy 600 control rod drive mechanisms head penetrations 1 Alloy 600 vent line nozzle Alloy 82/182 J-groove welds for above o Bottom Head 58 Bottom Mounted Instrumentation Nozzles Alloy 82/182 J-groove welds for above o 4 Hot Leg Nozzle-to-Safe End Alloy 82/182 Welds mitigated with water jet peening o 4 Cold Leg Nozzle-to-Safe End Alloy 82/182 Welds Pressurizer o 3 Safety Line Nozzle-to-Safe End Welds mitigated with weld overlays o 1 Relief Line Nozzle-to-Safe End Weld mitigated with weld overlays o 1 Spray Line Nozzle-to-Safe End Weld mitigated with weld overlays o 1 Surge Line Nozzle-to-Safe End Weld mitigated with weld overlays RV Flange Leakage Monitor Tube (Exempt from Code Case N-722-1)
RV Core Guide Lugs/Welds RV Core Guide Lug Shell Cladding Clevis Inserts and Lock Keys Steam Generators o 4 Channel Head Drain Lines (Alloy 600 Nozzles and 82/182 Welds) o Steam Generator Tubes Alloy 600 Thermally Treated (TT) o Steam Generator Tubesheet Cladding o Steam Generator Tube-Tubesheet Autogenous Weld o Steam Generator Partition Divider Plate: Stub Runner/Divider Plate o Steam Generator Stub Runner to Divider Plate Weld o Steam Generator Divider Plate to Tube Sheet Cladding Weld; Divider Plate to Channel Head Cladding Weld The NRC staff notes that these nickel alloy components are managed under several other programs such as 10 CFR 50.55a which specifiesSection XI requirements of the ASME Code, license renewal programs such as LR-AMP-005-BAC, Boric Acid Corrosion Program, and several Code Cases, such as N-722-1, N-729-6 and N-770-5.
The staff confirms that the scope of the program program element satisfies the criterion defined in SRP LR Section A.1.2.3.1. The staff finds this program element acceptable.
(2)
Preventive Actions - The plan is an inspection program and is designated condition monitoring. As such, the plan does not include preventive actions. The plan relies on the inservice inspection (ISI) Program: Systems, Components and Supports; the S/G Structural Integrity Program; and the Boric Acid Corrosion AMPs for inspections.
Preventive action is provided by the Chemistry Control for Primary Systems AMP.
The NRC staff notes though that peening is a preventive action to proactively mitigate components for PWSCC initiation, and was performed on the Millstone Unit 3 reactor vessel head penetration nozzles and associated partial penetration welds and the reactor vessel hot leg dissimilar metal welds in accordance with MRP-335, Revision 3-A.
Based on this review, the NRC staff confirms that the preventive actions program element satisfies the guidance in SRP LR Section A.1.2.3.2. The staff finds this program element acceptable.
(3)
Parameters Monitored or Inspected - The plan monitors for indications of cracking due to PWSCC in Alloy 600 components in the Millstone Unit 3 primary system.
The staff notes that the licensees Alloy 600 Program uses the appropriate volumetric, surface and visual NDE techniques for detection of degradation of the components identified in the scope of the program as required by ASME Code and industry guidance.
Based on this review, the NRC staff confirms that the parameters monitored or inspected program element satisfies the guidance in SRP LR Section A.1.2.3.3. The staff finds this program element acceptable.
(4)
Detection of Aging Effects - The licensees Alloy 600 Program uses the ASME Code Section XI inspection regulatory requirements for augmented ISI and various industry guidance programs. The NRC has approved, in accordance with 10 CFR 50.55a, the specific techniques and frequencies for monitoring nickel alloy components, which are prescribed by ASME Code Section XI for those components examined in accordance with the ISI program. In addition, for other items included in the scope of the licensees Alloy 600 Program, the methods and frequencies of examination are recommended in industry guidance. These include the guidance of MRP-126, Materials Reliability Program: Generic Guidance for Alloy 600 Management, ASME Section XI Code Cases N-722-1, N-729-6, and N-770-5, and MRP-335, Revision 3-A. These inspections are performed as directed by the augmented ISI program, the Steam Generator Program, or the Boric Acid Corrosion Program. Each of these programs for the detection of aging effects has been analyzed by the NRC to provide adequate detection capability.
Based on this review, the NRC staff confirms that the licensees commitment in the detection of aging effects program element satisfies the guidance in SRP LR Section A.1.2.3.4. The staff finds this program element acceptable.
(5)
Monitoring and Trending - The licensees Alloy 600 Program relies on periodic inspections performed by the ISI program, the S/G Structural Integrity Program, and the Boric Acid Corrosion Control Program to detect and address degradation. The Chemistry Control for Primary Systems also monitors and trends results to provide timely indication of abnormal chemistry conditions. The augmented ISI program directs Alloy 600 inspections according to the regulatory requirements of 10 CFR 50.55a and industry guidance including Code Cases N-722-1, N-729-6, and N-770-5.
Based on this review, the NRC staff confirms that the monitoring and trending program element satisfies the guidance in SRP LR Section A.1.2.3.5. The staff finds this program element acceptable.
(6)
Acceptance Criteria - The licensees Alloy 600 Program uses the ASME Code,Section XI inspection requirements ISI and staff accepted industry guidance. In general, the acceptance criteria of Alloy 600 component inspection programs are based on the scope and reporting requirements established by the ASME Code as required by 10 CFR 50.55a. Each of the required augmented ISI ASME Code Cases have specific acceptance criteria. Further, the licensee explains the Steam Generator Structural Integrity Programs acceptance criteria are in accordance with the requirements of Millstone Unit 3s Technical Specifications, the guidance of NEI 97-06, Steam Generator Program Guidelines and the EPRI Steam Generator Guidelines. The Boric Acid Corrosion Control Programs acceptance criteria meets the requirements of NRC Generic Letter 88-05 and other industry guidelines. The Chemistry Control for Primary Systems has Action Level criteria based on the EPRI PWR Primary Water Chemistry Guideline.
Based on this review, the NRC staff confirms that the acceptance criteria program element satisfies the guidance in SRP LR Section A.1.2.3.6. The staff finds this program element acceptable.
(7)
Corrective Actions - The licensee notes in the Alloy 600 Program several repair alternatives that address corrective actions to address PWSCC aging effects of Ni-based alloys. Specifically, the licensees Alloy 600 Program uses the repair and replacement requirements of ASME Code,Section XI for ISI and staff accepted industry guidance.
The NRC endorses the use of these repair and replacement activities through incorporation into the requirements of 10 CFR 50.55a.
The licensee credits four programs for managing the effect of cracking due to PWSCC. These four programs are ISI unresolved relevant indications, S/G eddy current tub degradation, boric acid corrosion control and primary system chemistry corrective actions.
Based on this review, the NRC staff confirms that the corrective actions program element satisfies the guidance in SRP LR Section A.1.2.3.7. The staff finds this program element acceptable.
(8)
Confirmation Process - The confirmation process for the licensees Alloy 600 Program uses Site quality assurance procedures, review and approval processes, and administrative controls. These are implemented in accordance with the requirements of 10 CFR Part 50, Appendix B.
Based on this review, the NRC staff confirms that the confirmation process program element satisfies the guidance in SRP LR Section A.1.2.3.8. The staff finds this program element acceptable.
(9)
Administrative Controls - The administrative controls for the licensees Alloy 600 Program are reviewed, approved and maintained as controlled documents in accordance with the procedure control process and the QA program.
Based on this review, the NRC staff confirms that the administrative controls program element satisfies the guidance in SRP LR Section A.1.2.3.9. The staff finds this program element acceptable.
(10)
Operating Experience - The licensees Alloy 600 Program provides industry experience regarding PWSCC and associated reactor coolant leakage incidents. Specifically, the licensee notes those components that have been replaced and mitigated at MSP3.
The program stated the Millstone Unit 3 would follow industry efforts investigating the aging effects applicable to nickel-based alloys, identify the appropriate aging management activities, and implement the appropriate recommendations resulting from this guidance. The licensee provided examples of operating experience to support that the licensees Alloy 600 Program has been, and will continue to be, effective in managing the aging effects of components within the scope of the program. The NRC staff notes the proactive peening mitigation of the Alloy 600 reactor vessel upper head penetration nozzles and associated partial penetration welds, as well as the reactor vessel hot leg dissimilar metal welds are strong examples of significant mitigation efforts to proactively address PWSCC in these components. Further the extension of performing full structural weld overlays to the remainder of the pressurizer nozzle welds demonstrates to the NRC staff an effective program at addressing the potential susceptibility of reactor coolant pressure boundary welds. As noted by the licensee, continued compliance with the requirements of Nuclear Energy Institute (NEI) 03-08, Guideline for the Management of Materials Issues, being mandated by the licensees programs ensures compliance with any future industrys lessons learned to address PWSCC. Beyond the requirements of NEI 03-08, the NRC staff finds the planned mitigation of the Steam Generator Head Drain demonstrates a proactive method to address a potentially age increased susceptible component through a review of international operating experience.
The NRC staff specifically reviewed the licensees actions regarding the implementation of Note 10 of Table 1 of ASME Code Case N-770-5 in regard to inspection of full structural weld overlays during the period of extended operation. The NRC staff found the licensees actions were in line with regulatory requirements for future planned examinations. The NRC staff also verified two recent NEI 03-08 guidance technical reports, issued in 2018 and 2019, were incorporated within the program, as well as NRC Regulatory Issue Summary 2018-06, Clarification of the Requirements for Reactor Pressure Vessel Upper Head Bare Metal Visual Examinations, issued on December 10, 2018 (ML18178A137). Verification of each of these items provides reasonable assurance that the licensees Alloy 600 Program is a well maintained aging management program.
Based on this review, the NRC staff confirms that the operating experience program element satisfies the guidance in SRP LR Section A.1.2.3.10. The staff finds this program element acceptable.
In addition to the above, the NRC staff finds that the requirements of 10 CFR 50.55a (including required Code Cases) are bounding with respect to the recommendations contained in the GALL report (irrespective of revision). Therefore, the NRC staff finds that adherence by the licensee to current regulatory requirements is sufficient to adequately manage the aging of the subject components in the licensees Alloy 600 Program.
4.0 CONCLUSION
The staff has reviewed the licensees Alloy 600 Program as a plant-specific program and finds that it meets the commitments made by the applicant and the requirements established in the SRP LR for structures and/or components made of nickel alloy material.
On the basis of its technical review of the licensees Alloy 600 Program, the staff concludes that the licensee has demonstrated that effects of aging will be adequately managed at Millstone Unit 3 so that the intended functions will be maintained consistent with the current licensing basis for the period of extended operation, as required by 10 CFR 54.21(a)(3).
Principal Contributor: J. Collins, NRR Date: December 19, 2024
ML24351A242 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DNRL/NPHP/BC NAME RGuzman KEntz MMitchell DATE 12/17/2024 12/19/2024 7/15/2024 OFFICE NRR/DORL/LPL1/BC NRR/DORL/LPL1/PM NAME HGonzález RGuzman DATE 12/19/2024 12/19/2024