CNL-24-075, Response to Request for Additional Information for Application to Revise Function 5 of Technical Specification Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, for the Sequoyah and Watts Bar (SQN-TSTS-23-02 and W
| ML24332A140 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah, Watts Bar  |
| Issue date: | 11/27/2024 |
| From: | Hulvey K Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| EPID L-2023-LLA-0175, CNL-24-075 | |
| Download: ML24332A140 (1) | |
Text
1101 Market Street, Chattanooga, Tennessee 37402 CNL-24-075 November 27, 2024 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 Additional Information for Application to Revise Function 5 of Technical Specification Table 3.3.2-1, "Engineered Safety Feature Actuation System Instrumentation," for the Sequoyah Nuclear Plant and Watts Bar Nuclear Plant (SQN-TS-23-02 and WBN-TS-23-08) (EPID L-2023-LLA-0175)
References:
- 1. TVA letter to NRC, CNL-23-036, Application to Revise Function 5 of Technical Specification Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, for the Sequoyah Nuclear Plant and Watts Bar Nuclear Plant (SQN TS 23-02 and WBN TS 23-08), dated December 18, 2023 (ML23352A298)
- 2. TVA letter to NRC, CNL-24-061, Supplement to Application to Revise Function 5 of Technical Specification Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, for the Sequoyah Nuclear Plant and Watts Bar Nuclear Plant (SQN-TS-23-02 and WBN-TS-23-08),
(EPID L-2023-LLA-0175), dated August 19, 2024 (ML24232A071)
- 3. NRC electronic mail to TVA, Request for Additional Information - TVA LAR to Revised Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Units 1 and 2 re TS Table 3.3.2-1, Function 5 (EPID L-2023-LLA-0175), dated November 1, 2024 (ML24309A055)
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 the Watts Bar Nuclear Plant (WBN), Units 1 and 2, respectively.
The proposed license amendment would add the following Note to SQN Units 1 and 2 and WBN Units 1 and 2 Technical Specification (TS) 3.3.2, Engineered Safety Feature
U.S. Nuclear Regulatory Commission CNL-24-075 Page 2 November 27, 2024 Actuation System (ESFAS) Instrumentation, Table 3.3.2-1, Functions 5.a and 5.b, Turbine Trip and Feedwater Isolation.
Turbine trip function is not required when all turbine stop valves or all governor valves are closed and are incapable of opening.
The proposed change also revises Note (f) of WBN Unit 1 TS Table 3.3.2-1, Functions 5.a and 5.b and Note (h) of WBN Unit 2 TS Table 3.3.2-1, Functions 5.a and 5.b to be consistent with Note (i) of SQN Unit 1 TS Table 3.3.2-1, Functions 5.a and 5.b and Note (j) of SQN Unit 2 TS Table 3.3.2-1, Functions 5.a and 5.b and the corresponding Note and Table in Westinghouse Standard TS (NUREG-1431, Revision 5.0).
In Reference 2, TVA provided a supplement to the license amendment request. In Reference 3, the Nuclear Regulatory Commission issued a Request for Additional Information (RAI) and requested that TVA provide a response by December 2, 2024. The enclosure to this submittal provides a response to the RAI.
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 27th day of November 2024.
Respectfully, Kimberly D. Hulvey General Manager, Nuclear Regulatory Affairs & Emergency Preparedness
Enclosure:
Response to Nuclear Regulatory Commission Request for Additional Information cc (Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Sequoyah 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: 2024.11.27 12:47:48 -05'00'
Enclosure CNL-24-075 E1 of 9 Response to Nuclear Regulatory Commission Request for Additional Information NRC Introduction By \
letter dated December 18, 2023 (Agencywide Documents Access and Management System Accession No. ML23352A298), as supplemented by \
letter dated August 19, 2024 (ML24232A071), the Tennessee Valley Authority (TVA) submitted license amendment requests (LAR) for the Sequoyah Nuclear Plant (Sequoyah), Units 1 and 2, and the Watts Bar Nuclear Plant (Watts Bar), Units 1 and 2. Specifically, the proposed amendments would revise Sequoyah and Watts Bar Technical Specification (TS) Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, by adding a note to Functions 5.a and 5.b related to the turbine trip function. The amendments for Watts Bar, Units 1 and 2, would also revise note (f) of Watts Bar, Unit 1, TS Table 3.3.2-1 and note (h) of Watts Bar, Unit 2, TS Table 3.3.2-1 to be consistent with the corresponding note in Sequoyah, Units 1 and 2, TS Table 3.3.2-1.
The U.S. Nuclear Regulatory Commission (NRC or Commission) is reviewing the LAR, and has identified an area where additional information is needed to complete its review. The requested information is identified below.
Basis:
The Commissions regulatory requirements related to the content of TSs are set forth in Title 10 of the Code of Federal Regulations (10 CFR), Section 50.36, Technical Specifications, which require, in pertinent part, that the TSs include: (1) safety limits, limiting safety system settings, and limiting control settings; (2) limiting conditions for operation; (3) surveillance requirements; (4) design features; and (5) administrative controls.
NUREG-14311, contains improved Standard Technical Specifications (STS) for Westinghouse plants. The NUREG encourages licensees to upgrade their TSs consistent with those criteria and conforming, to the practical extent, to Revision 5 of the improved STS.
In the STS for Westinghouse plants (i.e., NUREG-1431), for note k to Table 3.3.2-1, it states:
(k) Except when all MFIVs, MFRVs, [and associated bypass valves] are closed and [de-activated] [or isolated by a closed manual valve].
As noted in TSTF-GG-05-01, Writers Guide for Plant-Specific Improved Technical Specifications, brackets are typically used in the generic TSs and Bases to indicate where plant-specific input is needed. Bracketed values or requirements in STS are those that are based on plant-specific design, analysis, or licensing basis.
TVA is requesting the removal of the words associated bypass valves and and deactivated, and the addition of the words, MFRV bypass valves, and stated in the LAR that the proposed changes are administrative in nature in that they are consistent with Note (i) of Sequoyah Units 1 and 2, TS Table 3.3.2-1, Functions 5.a and 5.b; however, TVA has not provided a plant-specific reason for the changes.
1 U.S. Nuclear Regulatory Commission, Standard Technical Specifications, Westinghouse Plants, NUREG-1431, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21259A155 and ML21259A159, respectively).
Enclosure CNL-24-075 E2 of 9 Watts Bar Dual-Unit Updated Final Safety Analysis Report (UFSAR) Figure 10.4-8 (ML23346A225) shows the main feedwater isolation valves (MFIVs) and main feedwater regulator valves (MFRVs) on the 16-inch main feedwater line, and the MFIV bypass and MFRV bypass valves on the 6-inch startup flow feedwater line. The NRC staff notes that the feedwater configuration at Watts Bar is not consistent with the feedwater configuration at Sequoyah.
The NRC staff also notes that TS Table 3.3.2-1, notes (f) and (h) for Watts Bar Units 1 and 2, respectively, apply to the main steam valve vault rooms level switches for level high. According to the Watts Bar TS Bases for TS 3.7.3 (ML23312A013), the MFIVs and bypass MFIVs are located in the main steam valve vault close to containment.
Request:
Based on its review of information in the UFSAR, the NRC staff was unable to determine if the subject valves do not need to be deactivated nor could the staff determine if all the subject valves could be isolated by a closed manual valve.
Provide the plant-specific justification for the requested addition and removal of the noted words as they relate to Functions 5.a, 5.b, 5.d, and 5.e.
TVA Response Currently Note (f) of WBN Unit 1 TS Table 3.3.2-1 and Note (h) of Watts Bar Nuclear Plant (WBN) Unit 2 TS Table 3.3.2-1 state:
Except when all MFIVs, MFRVs, and associated bypass valves are closed and de-activated or isolated by a closed manual valve.
The proposed change revises this Note as follows:
Except when all MFIVs, MFRVs, and MFRV associated bypass valves are closed and de-activated or isolated by a closed manual valve.
The above change to Notes (f) and (h) apply to Functions 5.a and 5.b of WBN Units 1 and 2 TS Table 3.3.2-1 for the Turbine Trip and Feedwater Isolation, Automatic Actuation Logic and Actuation Relays and SG Water Level - High High (P-14), respectively. Notes (f) and (h) also apply to Functions 5.d and 5.e of WBN Units 1 and 2 TS Table 3.3.2-1 for the Turbine Trip and Feedwater Isolation, North and South MSV Vault Room Water Level - High, respectively.
As noted in Part 4 of 8 to Reference 1, the purpose of the TS Table 3.3.2-1 Functions 5.a and 5.b Applicability is to provide an exception to clarify that the Turbine Trip and Feedwater Isolation Steam Generator Water Level - High High (P-14) instrumentation and the Turbine Trip and Feedwater Isolation Automatic Actuation Logic and Actuation Relays are not required when all MFIVs, MFRVs, and MFRV bypass valves are closed or isolated by a closed manual valve.
In this condition, the function will not be needed because the valves are in a position that supports the safety analyses. This change is acceptable because the requirements continue to ensure that the structures, systems, and components are maintained in the Modes and other specified conditions assumed in the safety analyses and licensing basis. When the MFIVs, MFRVs, and MFRV bypass valves are in the closed position, they are in their assumed accident position.
Enclosure CNL-24-075 E3 of 9 Additional information in response to the NRC Request for Additional Information (RAI) and questions raised during the NRC clarification call on this RAI is provided below:
Based on its review of information in the UFSAR, the NRC staff was unable to determine all the subject valves that could be isolated by a closed manual valve.
Associated bypass valves and MFRV bypass valves are synonymous with each other.
SQN has one 16 main feedwater (MFW) line providing flow to each steam generator (SG) as shown below:
WBN differs from SQN in that it not only has a 16 MFW line, but also a 6 MFW bypass line providing flow to each SG. Both of these lines are able to be isolated by a manual valve. WBN also differs from SQN in that the manual valve for the 16 MFW line has a motor operator; the manual valve for the 6 MFW bypass line does not have a motor operator. The manual valve for the 16 MFW line does not have any associated automatic controls, and it is only operated by a local hand-switch or the valves handwheel, which would be used if the motor operator failed.
Color coding is used to distinguish the valves associated with the 16 MFW line and 6 MFW bypass lines providing flow to the WBN SGs as shown in Figure 1.
Figure 1 Excerpt from Feedwater Flow Diagram Showing the Valves Associated with the 16 MFW Line and 6 MFW Bypass Lines
Enclosure CNL-24-075 E4 of 9 The color coded valves highlighted in the WBN print excerpt are listed with their nomenclature below.
Flow control valves for the 6 MFW bypass line 1,2-FCV-3-35A Bypass Feedwater Regulation Valve 1,2-FCV-3-48A Bypass Feedwater Regulation Valve 1,2-FCV-3-90A Bypass Feedwater Regulation Valve 1,2-FCV-3-103A Bypass Feedwater Regulation Valve Flow control valves for the 16 MFW line 1,2-FCV-3-35 Main Feedwater Regulation Valve 1,2-FCV-3-48 Main Feedwater Regulation Valve 1,2-FCV-3-90 Main Feedwater Regulation Valve 1,2-FCV-3-103 Main Feedwater Regulation Valve Main Feedwater Isolation Valves for the 6 MFW bypass line 1,2-FCV-3-236 Bypass Feedwater Isolation 1,2-FCV-3-239 Bypass Feedwater Isolation 1,2-FCV-3-242 Bypass Feedwater Isolation 1,2-FCV-3-245 Bypass Feedwater Isolation Main Feedwater Isolation Valves for the 16 MFW line 1,2-FCV-3-33 Main Feedwater Isolation 1,2-FCV-3-47 Main Feedwater Isolation 1,2-FCV-3-87 Main Feedwater Isolation 1,2-FCV-3-100 Main Feedwater Isolation Manual valves capable of isolating the 6 MFW bypass line 1,2-IBV-3-532 Bypass Regulation Valve Isolation 1,2-IBV-3-533 Bypass Regulation Valve Isolation 1,2-IBV-3-534 Bypass Regulation Valve Isolation 1,2-IBV-3-535 Bypass Regulation Valve Isolation Manual valves capable of isolating the 16 MFW line 1,2-FCV-3-250 Main Feedwater Regulation Valve Isolation 1,2-FCV-3-251 Main Feedwater Regulation Valve Isolation 1,2-FCV-3-252 Main Feedwater Regulation Valve Isolation 1,2-FCV-3-253 Main Feedwater Regulation Valve Isolation The operation of the manual valves capable of isolating the 16 MFW line is shown in Figure 2.
Enclosure CNL-24-075 E5 of 9 Figure 2 Except from the Wiring Diagram for the Main and Auxiliary Feedwater System As shown in Figure 2, the 16 MFW regulation valve isolation valves have no automatic features. The valves are located in the turbine hall, away from the valve vault rooms. Once closed by a field operator, the valve stays closed until further operator action is taken to open it.
The valves are located in a mild environment in the turbine hall, directly upstream of the MFRVs.
Enclosure CNL-24-075 E6 of 9 Do the isolation valves once closed need to be deactivated The MFRVs isolate the 16 MFW line from the SGs following a high energy line break (HELB).
Similarly, the bypass MFRVs isolate the 6 MFW bypass line from the SGs under the same circumstances. The safety related function of the MFIVs is to provide the second isolation of MFW flow to the secondary side of the steam generators following an HELB. There are MFIVs provided for both the 16 MFW line and the 6 MFW bypass line. The MFIV associated with the 16 MFW line is a motor-operated valve. The MFIV associated with the 6 MFW bypass line is an air-operated valve. Figure 1 shows that there are no bypass paths around the MFIVs for either the 6 or 16 lines. Closure of the MFIVs and associated bypass valves or MFRVs and associated bypass valves terminates feedwater flow to the SGs. The consequences of events occurring in the main steam lines or in the MFW lines downstream from the MFIVs will be mitigated by their closure.
The intent of TS Limiting Condition for Operation (LCO) 3.3.2 (i.e., the engineered safety feature actuation system instrumentation for each Function in Table 3.3.2-1 shall be OPERABLE) is to ensure the above action takes place. Once the flow path is isolated, the circuitry is no longer necessary to ensure the assumptions of the safety analysis remain valid. This is consistent with the current TS Notes (f) and (h) and remains consistent with the proposed change to TS Notes (f) and (h). With the valves closed, they are performing their intended safety function.
Valve indication is readily available to operators in the main control room (MCR) and is verified post trip with contingency actions in place to mitigate a failure to isolate.
The MFRVs and bypass MFRVs are located in the turbine hall on elevation 729 while the MFIVs and bypass MFIVs are located in the north and south valve vault rooms. These valves receive a feedwater isolation signal and are verified closed via control room board indications.
As stated above, these actions are verified post trip with defined contingency actions in place to mitigate a failure. In the event that the feedwater isolation circuitry is rendered inoperable, actions required to mitigate an HELB cause operations to isolate the flow path putting the required valves in their required position (closed) to perform their design safety function. Once closed with their safety function met, the circuitry is no longer required. With the readily available indications in the control room of the flow paths isolation and the operator action required to reopen these valves, deactivation is unnecessary. Furthermore, discrete operator action is required to reopen these valves as illustrated by Figures 3 and 4.
Enclosure CNL-24-075 E7 of 9 Figure 3 Except from the Wiring Diagram for the Main and Auxiliary Feedwater System Showing the Motor Operated 16" FW Isolation Valve The MFW isolation valves (1,2-FCV-3-33, -47, -87, and -100) are train A (-33 and -87) or train B (-47 and -100) electric motor-operated fail as-is gate valves. These valves can be operated either from the MCR or the 480-V board room, and they will close on a feedwater (FW) isolation signal or a long cycle recirculation.
Figure 4 Except from the Wiring Diagram for the Main and Auxiliary Feedwater System Showing the Air Operated Valves
Enclosure CNL-24-075 E8 of 9 Figure 5 Additional Except from the Wiring Diagram for the Main and Auxiliary Feedwater System Showing the Air Operated Valves The MFW regulation valve (1,2-FCV-3-35, -48, -90, and -103) is a fail-closed, pneumatic, diaphragm-operated angle valve. Air supply to the flow control valve (FCV) is regulated by train A and train B solenoid valve assemblies [e.g., ASSY-3-35A (1,2-FSV-3-35AA and -35AB) and ASSY-3-35B (1,2-FSV-3-35BA and -35BB)], which deenergize on a MFW isolation signal.
An FW control signal from the distributed control system (DCS) automatic control system regulates these valves (Figures 4 and 5). Manual control of the valve is available in all modes of operation. Replacement solenoid control circuitry meets Class 1E qualifications and appropriate quality assurance requirements.
The MFW bypass regulation valves (1,2-FCV-3-35A, -48A, -90A, and -103A) are controlled by the DCS automatic low power FW control system or manually. For Unit 1, air to the valve is regulated by a solenoid valve assembly [e.g., 1-ASSY-3-35C (1-FSV-3-35C1, 1-FSV-3-35C2, and 1-SPV-3-35C)], which will cause the bypass valve to close on a train A (1-ASSY-3-48C and -103C) or train B (1-ASSY-3-35C and -90C) MFW isolation signal. For Unit 2, air to the valve is regulated by a solenoid valve assembly [e.g., 2-ASSY-3-35C (2-FSV-3-35C1, 2-FSV 35C2, and 2-SPV-3-35C)], which will cause the bypass valve to close on a train A (2-ASSY-3-48C and -103C) or train B (2-ASSY 35C and -90C) MFW isolation signal.
The bypass valves are air-operated, diaphragm-controlled, fail-closed globe valves. Manual control of the valve is possible in the modes of operation.
The MFW bypass isolation valves (1,2-FCV-3-236, -239, -242, -245) are fail-closed, pneumatic, diaphragm-operated globe valves. Air to the valve is controlled by two solenoid valves, one of which will stop air supply to the valve (i.e., close valve) on a train A MFW isolation signal, and the other will actuate on a train B signal. The FW isolation valves, FW bypass control valve, and FW bypass isolation valve control logic is designed so that upon reset of MFW isolation
Enclosure CNL-24-075 E9 of 9 signal, the valves will remain closed. Following an MFW isolation signal, these valves will be reset by two additional switches in the MCR.
References
- 1. TVA letter to NRC, Sequoyah Nuclear Plants, Units 1 and 2 Technical Specifications Conversion to NUREG-1431, Rev. 4.0 (SQN-TS-11-10) - Supplement 2, dated June 19, 2015 (ML15176A649 and ML15176A682)