CNL-25-057, Response to Request for Confirmation of Information - TVA LAR to Revised Sequoyah Nuclear Plant, Units 1 and 2 and Watts Bar Nuclear Plant, Units 1 and 2, TS LCO 3.5.2, Note 1
| ML25112A281 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar, Sequoyah  |
| Issue date: | 04/22/2025 |
| From: | Hulvey K Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| EPID L-2024-LLA-0152, CNL-25-057 | |
| Download: ML25112A281 (1) | |
Text
1101 Market Street, Chattanooga, Tennessee 37402 CNL-25-057 April 22, 2025 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-77 and DPR-79 NRC Docket Nos. 50-327 and 50-328 Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating License Nos. NPF-90 and NPF-96 NRC Docket Nos. 50-390 and 50-391
Subject:
Response to Request for Confirmation of Information - TVA LAR to Revised Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Units 1 and 2, TS LCO 3.5.2, Note 1 (EPID L-2024-LLA-0152)
References:
- 1. TVA letter to NRC, CNL-24-021, Application to Revise Technical Specification Limiting Condition of Operation 3.5.2, ECCS - Operating, Note 1 to Include Residual Heat Removal Pump Flow Paths for the Sequoyah Nuclear Plant and Watts Bar Nuclear Plant (SQN-TS-23-04 and WBN-TS-23-020), dated November 12, 2024 (ML24317A243)
- 2. NRC electronic mail to TVA, Request for Confirmation of Information
- TVA LAR to Revised Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Units 1 and 2, TS LCO 3.5.2, Note 1 (EPID L-2024-LLA-0152), dated March 25, 2025 (ML25085A273)
In Reference 1, Tennessee Valley Authority (TVA) submitted a request for an amendment to Renewed Facility Operating License Nos. DPR-77 and DPR-79 for the Sequoyah Nuclear Plant (SQN), Units 1 and 2 and Facility Operating License Nos. NPF-90 and NPF-96 for Watts Bar Nuclear (WBN), Units 1 and 2. The proposed license amendment would revise SQN Units 1 and 2 and WBN Units 1 and 2 Technical Specification (TS) Limiting Condition of Operation (LCO) 3.5.2, ECCS - Operating, Note 1 to include residual heat removal (RHR) pump flow paths as follows.
In MODE 3, both safety injection (SI) pump flow paths and one residual heat removal (RHR) pump flow path may be isolated by closing the isolation valves for up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to perform pressure isolation valve testing per SR 3.4.14.1.
U.S. Nuclear Regulatory Commission CNL-25-057 Page 2 April 22, 2025 In Reference 2, the Nuclear Regulatory Commission (NRC) issued a request for confirmation of information (RCI) and requested that TVA provide a response by April 24, 2025. The Enclosure to this submittal provides a response to the RCI.
This submittal does not change the no significant hazards consideration or the environmental consideration contained in Reference 1. In accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.91, Notice for public comment; State consultation, a copy of this supplement is being provided to the Tennessee Department of Environment and Conservation.
There are no new regulatory commitments contained in this letter. Please address any questions regarding this request to Amber V. Aboulfaida, Senior Manager, Fleet Licensing, at avaboulfaida@tva.gov.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 22nd day of April 2025.
Respectfully, Kimberly D. Hulvey General Manager, Nuclear Regulatory Affairs & Emergency Preparedness Enclosure Response to Nuclear Regulatory Commission Request for Confirmation of Information cc (Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant NRC Project Manager - Sequoyah Nuclear Plant NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant Director, Division of Radiological Health - Tennessee Department of Environment and Conservation Digitally signed by Edmondson, Carla Date: 2025.04.22 13:35:56
-04'00'
Enclosure CNL-25-057 E-1 of 3 Response to Nuclear Regulatory Commission Request for Confirmation of Information
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Introduction:==
By application dated November 12, 2024, (Agencywide Documents Access and Management System Accession No. ML24317A243), Tennessee Valley Authority (TVA, the licensee) submitted a license amendment request (LAR) requesting a change to the Technical Specifications (TS) for Sequoyah Nuclear Plant (SQN), Units 1 and 2, and Watts Bar Nuclear Plant (WBN), Units 1 and 2. The proposed amendments would revise SQN, Units 1 and 2, and WBN, Units 1 and 2, TS Limiting Condition for Operation (LCO) 3.5.2, ECCS - Operating, Note 1 to add one residual heat removal (RHR) pump flow path to the emergency core cooling system (ECCS) flow paths allowed to be isolated for up to two hours to perform pressure isolation valve testing per Surveillance Requirement (SR) 3.4.14.1.
The U.S. Nuclear Regulatory Commission (NRC) staff is currently reviewing the LAR and has identified areas where confirmation of information is needed to complete its review. The requests for confirmation of information (RCIs) are identified below.
Regulatory Basis:
Appendix A, General Design Criteria [GDC] for Nuclear Power Plants, to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, establishes the minimum requirements for the principal design criteria for water-cooled nuclear power plants. The principal design criteria establish the necessary design, fabrication, construction, testing, and performance requirements for structures, systems, and components important to safety. GDC 35 states:
A system to provide abundant emergency core cooling shall be provided. The system safety function shall be to transfer heat from the reactor core following any loss of reactor coolant at a rate such that (1) fuel and clad damage that could interfere with continued effective core cooling is prevented and (2) clad metal-water reaction is limited to negligible amounts. Suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.
The regulation at 10 CFR 50.46, Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors, provides specific criteria in implementation of the general requirements set forth in 10 CFR Part 50 (including GDC 35) with respect to ECCS performance and design.
Requests for Confirmation of Information SNSB-RCI 1 Section 3.0 of the LAR cites various pressurized-water reactor shutdown loss-of-coolant accident (LOCA) studies, which concluded that the likelihood of occurrence of a large-break LOCA in shutdown conditions is extremely remote, and determined required operator responses and timelines would ensure that the acceptance criteria of 10 CFR 50.46 would remain met in the event of a small-break LOCA occurring from shutdown conditions. In summarizing the relevant conclusions of the most recent shutdown LOCA study, the LAR states:
Enclosure CNL-25-057 E-2 of 3 The result was the conclusion that for a Westinghouse four-loop nuclear steam supply system (NSSS), the initiation of a safety injection within 10 minutes of indication of the LOCA precluded any meaningful reactor core uncovery and, as a result, no significant core heatup occurred and the 10 CFR 50.46 criteria would be met.
In order to provide assurance that the criteria of 10 CFR 50.46 will be met should a small-break LOCA occur, confirm that procedural guidance exists, or will exist, for both SQN and WBN such that operators can initiate the necessary ECCS flow within the assumed timeframes (i.e., with 10 minutes) as described in the LAR and the cited shutdown LOCA studies, including when initial conditions are representative of those that will be present when SR 3.4.14.1 testing is being undertaken per the proposed Note 1 of LCO 3.5.2 (i.e., in Mode 3 with both safety injection (SI) flow paths and one RHR flow path isolated, and testing in progress).
TVA Response TVA confirms that procedural guidance will exist for SQN and WBN such that operators can initiate the necessary ECCS flow within the assumed timeframes, including when initial conditions are representative of those that will be present when SR 3.4.14.1 testing is being undertaken per the proposed Note 1 of LCO 3.5.2.
SNSB-RCI 2 Section 3.0 of the LAR states:
Because of the plant configuration during the RCS [reactor coolant system]
pressure isolation valve leakage surveillance, when a SI is initiated the ECCS flow would automatically be available from two centrifugal charging pumps injecting into all four cold legs and one RHR pump initially injecting into two of the cold legs. For both WBN and SQN, in Mode 3 the RHR pump suction would be aligned to the RWST [refueling water storage tank]. If the pressure isolation valve surveillance test were to occur in Mode 3 at an RCS pressure of 1000 psi
[pounds per square inch] or greater then the accumulators are operable and available to inject during a LOCA. If the pressure isolation valve surveillance were to occur at an RCS pressure of less than 1000 psi then the accumulators cannot be assumed to be available. Regardless of availability of the accumulators, at both WBN and SQN substantially more ECCS flow would be provided in ten minutes due to the availability of all the ECCS pumps and injection paths than assumed in the various Mode 3 LOCA evaluations which do not credit accumulator injection at reduced RCS pressures.
Operability of ECCS accumulators is addressed under LCO 3.5.1, Accumulators, rather than LCO 3.5.2, ECCS - Operating; thus, the proposed change to Note 1 of LCO 3.5.2 will not ensure that ECCS accumulators are operable, when required by the Applicability of LCO 3.5.1 during Mode 3, while invoking the provisions of that Note. Similarly, the proposed changes to Note 1 of LCO 3.5.2 do not involve the centrifugal charging (CC) subsystems; as such, no assurance is provided that the CC subsystems will remain operable for the 2-hour period during which the SI and RHR subsystems are inoperable. Note that, in addition to both SI subsystems being isolated and rendered inoperable per Note 1, isolation of one RHR flow path per the proposed Note 1 will render both RHR subsystems inoperable, since neither subsystem will be capable of injecting into all four cold loops.
Enclosure CNL-25-057 E-3 of 3 In order to provide assurance that abundant emergency core cooling will remain capable of being provided, confirm that procedural guidance for both SQN and WBN exists, or will exist, to verify operability/availability of the ECCS subsystems (i.e., CC subsystems, ECCS accumulators > 1000 psig) that are assumed to be available and are otherwise unaffected by the proposed note prior to the initiation of, and for the duration of, SR 3.4.14.1 pressure isolation valve testing undertaken in accordance with the proposed Note 1.
TVA Response TVA confirms that procedural guidance for SQN and WBN will exist to verify operability/availability of the ECCS subsystems that are assumed to be available and are otherwise unaffected by the proposed note prior to the initiation of, and for the duration of, SR 3.4.14.1 pressure isolation valve testing undertaken in accordance with the proposed Note 1 of LCO 3.5.2.