ML24250A078
| ML24250A078 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 10/22/2024 |
| From: | Markley M Plant Licensing Branch II |
| To: | Carr E Dominion Energy South Carolina |
| Miller, GE | |
| References | |
| EPID L-2023-LLR-0067 | |
| Download: ML24250A078 (1) | |
Text
October 22, 2024 Eric S. Carr Senior Vice President and Chief Nuclear Officer Innsbrook Technical Center 5000 Dominion Blvd.
Glen Allen, VA 23060-6711
SUBJECT:
VIRGIL C. SUMMER NUCLEAR STATION, UNIT NO. 1 - RE: RELIEF REQUEST RR-5-V1 REGARDING SERVICE WATER RETURN HEADER CHECK VALVES (EPID L-2023-LLR-0067)
Dear Eric Carr:
By letter dated December 21, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML23361A104), Dominion Energy South Carolina (Dominion, the licensee), submitted a request for the Virgil C. Summer Nuclear Station, Unit No. 1 (Summer), to the U.S. Nuclear Regulatory Commission (NRC or Commission) for a proposed alternative to certain American Society of Mechanical Engineers (ASME) Operations and Maintenance (OM)
Code.
Specifically, Dominion requested relief from ASME OM Code Subsection ISTC-3522, Category C Check Valves, and Subsection ISTC-5221, Check Valve Obturator Movement, on the basis that conformance with certain inservice testing (IST) OM Code requirements is impractical.
The NRC staff has reviewed the alternative request and concludes, as set forth in the enclosed safety evaluation, that Dominion has demonstrated under 10 CFR 50.55a(f)(5) that conformance with the Code requirements is impractical, and the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(f)(5)(iii). Therefore, the NRC grants the requested relief pursuant to 10 CFR 50.55a(f)(6)(i) for the Fifth IST Interval that begins on January 1, 2025. All other ASME Code requirements for which relief was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
If you have any questions, please contact the Project Manager, Ed Miller at 301-415-2481 or via e-mail at Ed.Miller@nrc.gov.
Sincerely, Michael T. Markley, Chief Plant Licensing Branch 2-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-395
Enclosure:
Safety Evaluation cc: Listserv MICHAEL MARKLEY Digitally signed by MICHAEL MARKLEY Date: 2024.10.22 12:42:52 -04'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SERVICE WATER RETURN HEADER CHECK VALVES RR-5-V1 DOMINION ENERGY SOUTH CAROLINA VIRGIL C. SUMMER NUCLEAR STATION, UNIT 1 DOCKET NO. 50-395
1.0 INTRODUCTION
By letter dated December 21, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML23361A104), Dominion Energy South Carolina (Dominion, the licensee), submitted a request for the Virgil C. Summer Nuclear Station, Unit No. 1 (Summer), to the U.S. Nuclear Regulatory Commission (NRC or Commission) for a proposed alternative to certain American Society of Mechanical Engineers (ASME) Operations and Maintenance (OM)
Code.
Specifically, Dominion requested relief from ASME OM Code Subsection ISTC-3522, Category C Check Valves, and Subsection ISTC-5221, Check Valve Obturator Movement, on the basis that conformance with certain inservice testing (IST) OM Code requirements is impractical
2.0 REGULATORY EVALUATION
The NRC regulations in 10 CFR 50.55a(f)(4), Inservice testing standards requirement for operating plants, state, in part, that throughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the inservice testing requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in 10 CFR 50.55a(f)(2) and (3) and that are incorporated by reference in 10 CFR 50.55a(a)(1)(iv), to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The NRC regulations in 10 CFR 50.55a(f)(5), Requirements for updating IST programs, state, in part, that:
(iii) IST program update: Notification of impractical IST Code requirements. If the licensee has determined that conformance with certain Code requirements is
impractical for its facility, the licensee must notify the Commission and submit, as specified in § 50.4, information to support the determination.
(iv) IST program update: Schedule for completing impracticality determinations.
Where a pump or valve test requirement by the Code or addenda is determined to be impractical by the licensee and is not included in the revised inservice test program (as permitted by paragraph (f)(4) of this section), the basis for this determination must be submitted for NRC review and approval not later than 12 months after the expiration of the initial 120-month [inservice examination and test] interval of operation from the start of facility commercial operation and each subsequent 120-month [inservice examination and test] interval of operation during which the test is determined to be impractical.
The NRC regulations in 10 CFR 50.55a(f)(6), Actions by the Commission for evaluating impractical and augmented IST Code requirements, state in part:
(i) Impractical IST requirements: Granting of relief. The Commission will evaluate determinations under paragraph (f)(5) of this section that code requirements are impractical. The Commission may grant relief and may impose such alternative requirements as it determines are authorized by law, will not endanger life or property or the common defense and security, and are 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
ASME OM Code Components Affected The following plant equipment within the scope of this request are:
Table 1 Component ID Component Description Code Class Code Category XVC03130A-SW Service Water (SW) Pond SW Return Header A Inlet Check Valve 3
C XVC03130B-SW SW Pond SW Return Header B Inlet Check Valve 3
C Applicable ASME OM Code Requirements The IST requirements in the ASME OM Code as incorporated by reference in 10 CFR 50.55a related to relief request RR-5-V1 are as follows:
ASME OM Code, Subsection ISTC, Inservice Testing of Valves in Water-Cooled Reactor Nuclear Power Plants, paragraph ISTC-3522, Category C Check Valves, in subparagraph (a) states, in part, that:
During operation at power, each check valve shall be exercised or examined in a manner that verifies obturator travel by using the methods in ISTC-5221. Each check valve exercise test shall include open and close tests.
ASME OM Code, Subsection ISTC, paragraph ISTC-5221, Valve Obturator Movement, subparagraph (a) specifies:
The necessary valve obturator movement during exercise testing shall be demonstrated by performing both an open and a close test.
ASME OM Code, Subsection ISTC, paragraph ISTC-5221(a)(2), states:
Check valves that have a safety function in only the open direction shall be exercised by initiating flow and observing that the obturator has traveled either [to] the fully open position or to the position required to perform its intended function(s) (see ISTA-1100), and verify closure.
Licensees Notification of Impractical Code Requirement Pursuant to 10 CFR 50.55a(f)(5)(iii)
The licensee stated:
Most of the VCSNS Unit 1 SW return piping is underground, including the SW system discharge check valves, without direct access. The system configuration does not provide a means to employ non-intrusive test methods or disassembly to confirm valve closure. To comply with the Code open and close testing requirements, either routine excavations or a system modification would be required. Since the valves are buried without direct access, excavation would be required every outage to allow access to the valves to facilitate valve disassembly and inspection or to employ non-intrusive test methods.
Alternatively, a design modification would be required to allow routine access to the valves to allow testing of the valves in the closed direction using non-intrusive test methods or system operation.
Licensees Proposed Relief In its letter dated December 21, 2023, the licensee stated:
This Relief Request proposes to test by verifying these check valves in the open position instead of testing/verifying both open and close positions as stated in the Code requirement, i.e., VCSNS will exercise these check valves and verify the valves to be in the safety related fully open position during refueling outages without performing verification of the non-safety related closed position.
The design close function of these check valves is to prevent siphoning of the pond in the event of a postulated crack of a large diameter pipe in the SW system piping and to prevent inadvertent flooding during SW system maintenance from an incorrect valve lineup. The SW piping is moderate energy piping. Therefore, the design rules require that cracks, not breaks, must be postulated. Calculations for the postulated crack project a leak flow range less than the capacities of the sump pumps in the affected areas.
Due to the relatively small size of the resulting crack, the existing plant can easily handle a leak without requiring the valves to shut. Therefore, the back-seat function has been
determined to not be required since the SW system and the Auxiliary and Intermediate buildings are designed to accommodate all postulated cracks. Also, due to the design of the valve (duo-disc), age related degradation of the valve would not affect the valve's ability to perform its safety related function. Using the provisions of this request, open testing/verification will provide reasonable assurance of the SW system discharge check valves' operational readiness.
Based on the absence of a safety function in the closed position, elimination of bidirectional reverse flow closure testing has no safety impact. DESC requests approval of the relief request from the specific ISTC requirements identified in this request.
NRC Staff Evaluation of Request RR-5-V1 The ASME OM Code as incorporated by reference in 10 CFR 50.55a requires that safety-related check valves be exercise tested in both the open and closed direction quarterly (bi-directional testing). If exercising is not practical during plant operation, the ASME OM Code requires that exercising shall be performed during cold shutdown. If exercising is not practical during plant operation or cold shutdowns, the ASME OM Code requires that exercising shall be performed during RFOs.
At VCSNS Unit 1, two normally open SW system discharge check valves perform an active safety function in the open position to allow SW return flow to the SW pond. These check valves do not perform a safety function in the closed position. The SW system discharge check valves at VCSNS Unit 1 are buried underground without direct access.
The licensee asserts that it is impractical to test the SW system discharge check valves in the closed direction due to the design of the SW system that does not provide direct access to the valves or the capability to test the valves in the closed direction using non-intrusive test methods or system operation. The licensee requests relief from the bi-directional exercise testing requirements specified in ASME OM Code, Subsection ISTC, paragraphs ISTC-3522(a) and ISTC-5221(a), for the specified SW system discharge check valves at VCSNS Unit 1. In Request RR-5-V1, as an alternative, the licensee proposes to verify that these check valves move to the open position rather than testing both open and close positions as required by the ASME OM Code. This approach will exercise these check valves and verify the valves can reach their safety-related fully open position during RFOs without performing verification of the non-safety-related closed position.
Given that the approach will continue to verify the ability of the valve to reach its safety-related position, the NRC staff finds that the licensees request for relief may be granted pursuant to 10 CFR 50.55a(f)(6)(i) on the basis that compliance with the ASME OM Code requirements is impractical. Therefore, the NRC staff finds that the licensee's proposed alternative to full stroke exercising of the valves to the safety-related open position without performing bi-directional exercise testing to the non-safety-related closed position will provide reasonable assurance of the operational readiness of the SW system discharge check valves in light of the impracticality of the close test. The NRC staff finds that granting the relief 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.
4.0 CONCLUSION
As set forth above, the NRC staff has determined that the required testing is impractical and, that Request RR-5-V1 has met the applicable requirements for relief to specific ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for the applicable components within the scope of these requests at VCSNS Unit 1. Further, the proposed IST approach described in the request provide reasonable assurance that the applicable components at VCSNS Unit 1 will be available to perform their safety functions in lieu of the specified ASME OM Code requirements. Therefore, the NRC staff grants Relief Request RR-5-V1 for the Fifth Interval IST Program at VCSNS Unit 1, which will begin on January 1, 2025.
All other ASME Code 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 Contributor: M. Breach, NRR T. Scarbrough, NRR Date: October 22, 2024
- Via SE Input OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DEX/EMIB/BC NRR/DORL/LPL2-1/BC NAME GEMiller KGoldstein TScarbrough for SBailey* MMarkley DATE 9/6/2024 09/06/2024 8/30/2024 10/22/2024 OFFICE NRR/DORL/LPL2-1/PM NAME GEMiller DATE 10/22/2024