CNL-25-028, Units 1 & 2, Watts Bar, Units 1 & 2, Supplement to Application to Revise Function 5 of Technical Specification Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, for (SQN-TS-23-02 & WBN-TS-23-08) (EPID L-2023-LLA-0
| ML25043A280 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah, Watts Bar  |
| Issue date: | 02/12/2025 |
| From: | Hulvey K Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| CNL-25-028, EPID L-2023-LLA-0175 | |
| Download: ML25043A280 (1) | |
Text
10 CFR 50.90 1101 Market Street, Chattanooga, Tennessee 37402 CNL-25-028 February 12, 2025 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:
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)
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.
TVA letter to NRC, 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 Nuclear Plant and Watts Bar Nuclear Plant (SQN-TS-23-02 and WBN-TS-23-08) (EPID L-2023-LLA-0175),
dated November 27, 2024 (ML24332A140)
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.
U.S. Nuclear Regulatory Commission CNL-25-028 Page 2 February 12, 2025 The proposed license amendment, in part, revises Note (f) of WBN Unit 1 Technical Specification (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 similar to Note (i) of SQN Units 1 and 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). Specifically, TVA proposed to revise 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 as follows:
Except when all MFIVs, MFRVs, and MFRVassociated bypass valves are closed and de-activated or isolated by a closed manual valve.
In Reference 2, TVA provided a supplement to the license amendment request, which contained a revised response to Question 1 of Section 4.3, No Significant Hazards Consideration Determination Analysis, of Reference 1. In Reference 3, TVA responded to a Nuclear Regulatory Commission Request for Additional Information (RAI) regarding the proposed change to 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.
After further review, TVA has decided to retain the current verbiage of associated bypass valves in 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 as follows:
Except when all MFIVs, MFRVs, and associated bypass valves are closed and de-activated or isolated by a closed manual valve.
The retention of the verbiage associated bypass valves is consistent with the current WBN TS Bases 3.3.2 and 3.7.3, Main Feedwater Isolation Valves (MFIVs) and Main Feedwater Regulation Valves (MFRVs) and Associated Bypass Valves. to this submittal provides a revision to Section 2.2, Reason for the Proposed Change, and Section 2.3, Description of the Proposed Change, of the Enclosure to Reference 1. Attachment 1 to Enclosure 1 of this submittal provides a revised marked-up version of the affected TS pages of WBN Units 1 and 2. Attachment 2 to Enclosure 1 of this submittal provides a revised marked-up version of the WBN Units 1 and 2 TS Bases.
Changes to the existing TS Bases are provided for information only and will be implemented under the Technical Specification Bases Control Program. Attachment 1 and 2 to of this submittal supersedes the corresponding WBN TS and Bases changes provided in Reference 1. The revised information is indicated by redline insertions and deletions and revision bars. to this submittal provides a partial revision to the RAI response of Reference 3.
The remaining information provided in Reference 3 remains valid to this license amendment request.
U.S. Nuclear Regulatory Commission CNL-25-028 Page 3 February 12, 2025 This submittal does not change the no significant hazards consideration in References 1 and 2 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 12th day of February 2025.
Respectfully, Kimberly D. Hulvey General Manager, Nuclear Regulatory Affairs & Emergency Preparedness
Enclosures:
1.
Revision to the Enclosure to Reference 1 2.
Partial Revision to the RAI Response of Reference 3 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: 2025.02.12 11:20:39
-05'00' Revision to the Enclosure to Reference 1 CNL-25-028 E1-1 of 2 2.2 Reason for the Proposed Change SQN and WBN TS Table 3.3.2-1, Function 5 requires two trains of the Turbine Trip Function to be operable in Mode 1 and in Modes 2 to 3 [except when all MFW isolation valves, MFW regulating valves (MFRV), and MFRV bypass valves are closed or isolated by a closed manual valve] except as stated in the corresponding footnotes. This function requires the four main turbine stop valves to be capable of closing within the time limit prescribed in SQN Updated Final Safety Analysis Report (UFSAR) Table 7.3.1-4, Engineered Safety Features Response Times, and the WBN Units 1 and 2 Technical Requirements Manuals Table 3.3.2-1, Engineered Safety Actuations System Response Times.
However, SQN and WBN TS 3.3.2 does not provide any specific condition/action for the turbine stop valves. Therefore, if one or more of the turbine stop valves is inoperable (e.g., fails to meet the required closure time while in Mode 1 during a pre-planned turbine trip as part of normal startup sequence), then both trains of the Turbine Trip Function must be declared inoperable, which requires entry into SQN and WBN TS Limiting Condition for Operation (LCO) 3.0.3 due to two trains inoperable with no applicable TS required action.
However, entry into LCO 3.0.3 is unnecessary if the turbine stop valves or governor valves are already closed (in the required turbine trip condition) and are incapable of opening (i.e., turbine tripped). With the proposed change to SQN and WBN TS Table 3.3.2-1, Function 5, during startup testing if a valve were to fail its time response testing, but was closed with the turbine tripped, entry into 3.0.3 would not be required. This would preclude an unnecessary mode change that could challenge plant equipment and burden the operating crews.
The proposed changes to Note (f) of WBN Unit 1 TS Table 3.3.2-1, Functions 5a and 5b and Note (h) of WBN Unit 2 TS Table 3.3.2-1, Functions 5a and 5b are administrative in nature in that they are consistent with the current WBN TS Bases 3.3.2, Engineered Safety Feature Actuation System (ESFAS) Instrumentation, WBN TS Base 3.7.3, Main Feedwater Isolation Valves (MFIVs), Note (ji) of SQN Units 1 and 2 TS Table 3.3.2-1, Functions 5.a and 5.b, and Note (k) of TS Table 3.3.2-1, and Functions 5a and 5b of the Westinghouse Standard TS (NUREG-1431, Revision 5.0). The proposed changes do not change the technical content of Note (f) of WBN Unit 1 TS Table 3.3.2-1, Functions 5a and 5b and Note (h) of WBN Unit 2 TS Table 3.3.2-1, Functions 5a and 5b. The current verbiage of Note (f) of WBN Unit 1 TS Table 3.3.2-1, Functions 5a and 5b and Note (h) of WBN Unit 2 TS Table 3.3.2-1, Functions 5a and 5b is the same as the initial issuance of the WBN Unit 1 TS (NRC Accession Number ML052930169) and the WBN Unit 2 TS (NRC Accession Number ML15251A587).
Revision to the Enclosure to Reference 1 CNL-25-028 E1-2 of 2 2.3 Description of the Proposed Change The proposed license amendment would add the following note to SQN Units 1 and 2 and WBN Units 1 and 2 TS 3.3.2, Table 3.3.2-1, Functions 5a and 5b for Modes 1, 2, and 3:
Turbine trip function is not required when all turbine stop valves or all governor valves are closed and are incapable of opening.
The remaining footnotes in TS 3.3.2, Table 3.3.2-1 are renumbered accordingly.
The proposed license amendment also revises Note (f) of WBN Unit 1 TS Table 3.3.2-1, Functions 5a and 5b and Note (h) of WBN Unit 2 TS Table 3.3.2-1, Functions 5a and 5b as follows:
Except when all MFIVs, MFRVs, and associated bypass valves are closed and de-activated or isolated by a closed manual valve.
Revision to the Enclosure to Reference 1 CNL-25-028 Revised Proposed Technical Specification Changes (Mark-Up) for WBN Units 1 and 2
ESFAS Instrumentation 3.3.2 Watts Bar-Unit 1 3.3-36 Amendment 23, Table 3.3.2-1 (page 3 of 7)
Engineered Safety Feature Actuation System Instrumentation FUNCTION APPLICABLE MODES OR OTHER SPECIFIED CONDITIONS REQUIRED CHANNELS CONDITIONS SURVEILLANCE REQUIREMENTS ALLOWABLE VALUE NOMINAL TRIP SETPOINT 4.
Steam Line Isolation (continued) c.
Containment 1, 2(c), 3(c) 4 E
SR 3.3.2.1 2.9 psig 2.8 psig Pressure-SR 3.3.2.4 High High SR 3.3.2.9 SR 3.3.2.10 d.
Steam Line Pressure (1)
Low 1, 2(c), 3(a) (c) 3 per steam D
SR 3.3.2.1 666.6(b) psig 675(b) psig line SR 3.3.2.4 SR 3.3.2.9 SR.3.2.10 (2)
Negative 3(d) (c) 3 per steam D
SR 3.3.2.1 108.5(e) psi 100(e) psi Rate-High line SR 3.3.2.4 SR 3.3.2.9 SR 3.3.2.10 5.
Turbine Trip and Feedwater Isolation a.
Automatic 1(i), 2(f)(i), 3(f)(i) 2 trains H
SR 3.3.2.2 NA NA Actuation Logic SR 3.3.2.3 and Actuation SR 3.3.2.5 Relays b.
SG Water 1(i), 2(f)(i), 3(f)(i) 3 per SG I
SR 3.3.2.1 83.1%
82.4%
Level-High SR 3.3.2.4 High(P-14)
SR 3.3.2.9 SR 3.3.2.10 (h) c.
Safety Refer to Function 1 (Safety Injection) for all initiation Injection functions and requirements.
d.
North MSV Vault 1, 2(f), (g) 3/vault O
SR 3.3.2.6 5.31 inches 4 inches Room Water Room SR 3.3.2.9 Level - High e.
South MSV Vault 1, 2(f), (g) 3/vault O
SR 3.3.2.6 4.56 inches 4 inches Room Water Room SR 3.3.2.9 Level - High (continued)
(a)
Above the P-11 (Pressurizer Pressure) interlock.
(b)
Time constants used in the lead/lag controller are t1 50 seconds and t2 5 seconds.
(c)
Except when all MSIVs are closed and de-activated.
(d)
Function automatically blocked above P-11 (Pressurizer Interlock) setpoint and is enabled below P-11 when safety injection on Steam Line Pressure Low is manually blocked.
(e)
Time constants utilized in the rate/lag controller are t3 and t4 50 seconds.
(f)
Except when all MFIVs, MFRVs, and associated bypass valves are closed and de-activated or isolated by a closed manual valve.
(g)
MODE 2 if Turbine Driven Main Feed Pumps are operating.
(h)
For the time period between February 23, 2000, and prior to turbine restart (following the next time the turbine is removed from service), the response time test requirement of SR 3.3.2.10 is not applicable for 1-FSV-47-027.
(i)
Turbine trip function is not required when all turbine stop valves or all governor valves are closed and are incapable of opening.
ESFAS Instrumentation 3.3.2 Watts Bar-Unit 1 3.3-38 Amendment 1, 75, 104, 148, 154, Table 3.3.2-1 (page 5 of 7)
Engineered Safety Feature Actuation System Instrumentation FUNCTION APPLICABLE MODES OR OTHER SPECIFIED CONDITIONS REQUIRED CHANNELS CONDITIONS SURVEILLANCE REQUIREMENTS ALLOWABLE VALUE NOMINAL TRIP SETPOINT 6.
Auxiliary Feedwater (continued) c.
Safety Refer to Function 1 (Safety Injection) for all initiation functions and requirements.
Injection d.
Loss of Offsite 1, 2,3 4 per bus F
Refer to Function 4 of Table 3.3.5-1 for Power SRs and Allowable Values e.
Trip of all Main Feedwater Pumps (1)
Turbine Driven Main Feedwater Pumps 1( ij ), 2 1 per pump J
SR 3.3.2.8 SR 3.3.2.9 SR 3.3.2.10 43.3 psig 50 psig and (2)
Standby Main Feedwater Pump 1, 2 1
P SR 3.3.2.8 SR 3.3.2.10 SR 3.3.2.12 NA NA f.
Auxiliary Feedwater Pumps Train A and B Suction Transfer on Suction Pressure - Low 1, 2, 3, 4(k) 3 B
SR 3.3.2.6 SR 3.3.2.9 SR 3.3.2.10 A) 0.5 psig A) 1.2 psig B) 1.33 psig B) 2.0 psig 7.
Automatic Switchover to Containment Sump a.
Automatic 1, 2, 3, 4 2 trains C
SR 3.3.2.2 NA NA Actuation Logic SR 3.3.2.3 and Actuation SR 3.3.2.5 Relays (continued)
( ij )
Entry into Condition J may be suspended for up to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> when placing a Turbine Driven Main Feedwater (TDMFW) Pump in service or removing a TDMFW pump from service.
( j )
Deleted.
( k )
When steam generators are relied on for heat removal.
ESFAS Instrumentation 3.3.2 SURVEILLANCE REQUIREMENTS (continued)
Watts Bar - Unit 2 3.3-37 Amendment 55, Table 3.3.2-1 (page 4 of 9)
Engineered Safety Feature Actuation System Instrumentation FUNCTION APPLICABLE MODES OR OTHER SPECIFIED CONDITIONS REQUIRED CHANNELS CONDITIONS SURVEILLANCE REQUIREMENTS ALLOWABLE VALUE NOMINAL TRIP SETPOINT 5.
Turbine Trip and Feedwater Isolation a.
Automatic Actuation Logic and Actuation Relays 1(j), 2 (h)(j), 3 (h)(j) 2 trains H
SR 3.3.2.2 NA NA SR 3.3.2.3 SR 3.3.2.5 b.
SG Water Level -
High High (P-14) 1(j), 2 (h)(j), 3 (h)(j) 3 per SG I
SR 3.3.2.1 83.1%
82.4%
SR 3.3.2.4 (b) (c)
SR 3.3.2.9 (b) (c)
SR 3.3.2.10 c.
Safety Injection Refer to Function 1 (Safety Injection) for all initiation functions and requirements.
d.
North MSV Vault Room Water Level - High 1, 2 (h)(i) 3 per vault room O
SR 3.3.2.6 5.31 inches 4 inches SR 3.3.2.9 e.
South MSV Vault Room Water Level - High 1, 2 (h)(i) 3 per vault room O
SR 3.3.2.6 4.56 inches 4 inches SR 3.3.2.9 (continued)
(b)
If the as found channel setpoint is outside its redefined as found tolerance, then the channel shall be evaluated to verify that it is functioning as required before returning the channel to service.
(c)
The instrument channel setpoint shall be reset to a value that is within the as left tolerance around the Nominal Trip Setpoint (NTSP) at the completion of the surveillance; otherwise, the channel shall be declared inoperable. The methodologies used to determine the as found and as left tolerances for the NTSP are specified in FSAR Section 7.1.2.
(h)
Except when all MFIVs, MFRVs, and associated bypass valves are closed and de-activated or isolated by a closed manual valve.
(i)
MODE 2 if Turbine Driven Main Feed Pumps are operating.
(j)
Turbine trip function is not required when all turbine stop valves or all governor valves are closed and are incapable of opening.
ESFAS Instrumentation 3.3.2 SURVEILLANCE REQUIREMENTS (continued)
Watts Bar - Unit 2 3.3-39 Amendment 55, Table 3.3.2-1 (page 6 of 9)
Engineered Safety Feature Actuation System Instrumentation FUNCTION APPLICABLE MODES OR OTHER SPECIFIED CONDITIONS REQUIRED CHANNELS CONDITIONS SURVEILLANCE REQUIREMENTS ALLOWABLE VALUE NOMINAL TRIP SETPOINT 6.
Auxiliary Feedwater (continued) d.
Loss of Offsite Power 1, 2, 3 4 per bus F
Refer to Function 4 of Table 3.3.5-1 for SRs and Allowable Values. Notes (b) and (c) are applicable to SR 3.3.5.2 for this function.
e.
Trip of all Main Feedwater Pumps (1)
Turbine Driven Main Feedwater Pumps 1 (jk), 2 1 per pump J
SR 3.3.2.8 (b)(c) 43.3 psig 50 psig SR 3.3.2.9 (b)(c)
SR 3.3.2.10 and (2)
Standby Main Feedwater Pumps 1, 2 1
P SR 3.3.2.8 NA NA SR 3.3.2.10 SR 3.3.2.12 f.
Auxiliary Feedwater Pumps Train A and B Suction Transfer on Suction Pressure - Low 1, 2, 3, 4(ml) 3 B
SR 3.3.2.6 A) 0.5 psig A) 1.2 psig SR 3.3.2.9 (b) (c)
SR 3.3.2.10 B) 1.33 psig B) 2.0 psig (continued)
(b)
If the as found channel setpoint is outside its redefined as found tolerance, then the channel shall be evaluated to verify that it is functioning as required before returning the channel to service.
(c)
The instrument channel setpoint shall be reset to a value that is within the as left tolerance around the Nominal Trip Setpoint (NTSP) at the completion of the surveillance; otherwise, the channel shall be declared inoperable. The methodologies used to determine the as found and as left tolerances for the NTSP are specified in FSAR Section 7.1.2.
(jk)
Entry into Condition J may be suspended for up to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> when placing a Turbine Driven Main Feedwater (TDMFW) Pump in service or removing a TDMFW pumps from service.
(k)
Deleted.
(ml)
When steam generators are being relied on for heat removal.
Revision to the Enclosure to Reference 1 CNL-25-028 Revised Proposed Technical Specification Bases Changes (Mark-Up) for WBN Units 1 and 2 (For Information Only)
ESFAS Instrumentation B 3.3.2 BASES (continued)
Watts Bar-Unit 1 B 3.3-72 Amendment APPLICABLE 5.
Turbine Trip and Feedwater Isolation SAFETY ANALYSES, LCO, and This Function is actuated by SG Water LevelHigh High, MSVV Water APPLICABILITY Level - High, or by a SI signal. The RTS also initiates a turbine trip (continued) signal whenever a reactor trip (P-4) is generated. In the event of SI, the unit is taken off line and the turbine generator must be tripped. The MFW System is also taken out of operation and the AFW System is automatically started. The SI signal was discussed previously. The turbine trip function is not required when all turbine stop valves or all governor valves are closed and are incapable of opening (i.e., turbine tripped).
a.
Turbine Trip and Feedwater Isolation-Actuation Logic and Actuation Relays Automatic Actuation Logic and Actuation Relays consist of the same features and operate in the same manner as described for ESFAS Function 1.b.
b.
Turbine Trip and Feedwater Isolation-Steam Generator Water Level-High High (P-14)
This signal provides protection against excessive feedwater flow.
The ESFAS SG water level instruments provide input to the SG Water Level Control System. Therefore, the actuation logic must be able to withstand both an input failure to the control system (which may then require the protection function actuation) and a single failure in the other channels providing the protection function actuation. Since Watts Bar has only 3 level channels per SG, control/protection interaction is addressed by the use of a Median Signal Selector which prevents a single failure of a channel providing input to the control system requiring protection function action. That is, a single failure of a channel providing input to the control system does not result in the control system initiating a condition requiring protection function action. The Median Signal Selector performs this by not selecting the channels indicating the highest or lowest steam generator levels as input to the control system.
The Function is actuated when the level in any SG exceeds the high high setpoint, and performs the following functions:
Trips the main turbine;
Trips the MFW pumps;
Initiates feedwater isolation; and
Shuts the MFW regulating valves and the bypass feedwater regulating valves.
ESFAS Instrumentation B 3.3.2 BASES (continued)
Watts Bar-Unit 1 B 3.3-73 Amendment APPLICABLE b.
Turbine Trip and Feedwater Isolation-Steam Generator Water SAFETY ANALYSES Level-High High (P-14) (continued)
LCO, and APPLICABILITY Since no adverse control system action may now result from a single, failed protection instrument channel, a second random protection system failure (as would otherwise be required by Reference 4) need not be considered.
The transmitters (d/p cells) are located inside containment.
However, the events that this Function protects against cannot cause a severe environment in containment. Therefore, the Trip Setpoint reflects only steady state instrument uncertainties.
c.
Turbine Trip and Feedwater Isolation-Safety Injection Turbine Trip and Feedwater Isolation is also initiated by all Functions that initiate SI. The Feedwater Isolation Function requirements for these Functions are the same as the requirements for their SI function. Therefore, the requirements are not repeated in Table 3.3.2-1. Instead Function 1, SI, is referenced for all initiating functions and requirements d.
Turbine Trip and Feedwater Isolation - Main Steam Valve Vault Room Water Level - High This signal precludes submergence of equipment that is required for safe shutdown in the event of a MSVV Room flood due to a Main Feedwater line break. MSVV Room Water Level -
High does not provide any control function. Thus, three OPERABLE channels in each Valve Vault Room are sufficient to satisfy the protection requirements with a two-out-of-three logic.
The level switches which are located inside the MSVV Rooms are subjected to adverse environmental conditions during a Main Feedwater line break. The trip setpoint reflects both steady state and adverse environmental instrument uncertainties.
Turbine Trip and Feedwater Isolation Functions - Automatic Actuation Logic and Actuation Relays, Steam Generator Water Level - High High (P-14), and Safety Injection must be OPERABLE in MODES 1, 2, and 3 except when all MFIVs, MFRVs, and associated bypass valves are closed and de-activated or isolated by a closed manual valve when the MFW System is in operation and the turbine generator may be in operation. In MODES 4, 5, and 6, the MFW System and the turbine generator are not in service and this Function is not required to be OPERABLE.
ESFAS Instrumentation B 3.3.2 BASES (continued)
Watts Bar - Unit 2 B 3.3-87 Amendment APPLICABLE SAFETY
- ANALYSES, LCO, and APPLICABILITY (continued) 5.
Turbine Trip and Feedwater Isolation The primary functions of the Turbine Trip and Feedwater Isolation signals are to prevent damage to the turbine due to water in the steam lines, and to stop the excessive flow of feedwater into the SGs. These Functions are necessary to mitigate the effects of a high water level in the SGs, which could result in carryover of water into the steam lines and excessive cooldown of the primary system.
The SG high water level is due to excessive feedwater flows.
An additional function of the Turbine Trip and Feedwater Isolation signal is to prevent submergence of safety related equipment in the Main Steam Valve Vault (MSVV) Rooms in the event of a Main Feedwater Line Break.
This Function is actuated by SG Water Level - High High, MSVV Water Level - High, or by an SI signal. The RTS also initiates a turbine trip signal whenever a reactor trip (P-4) is generated. In the event of SI, the unit is taken off line and the turbine generator must be tripped. The MFW System is also taken out of operation, and the AFW System is automatically started.
The SI signal was discussed previously. The turbine trip function is not required when all turbine stop valves or all governor valves are closed and are incapable of opening (i.e., turbine tripped).
a.
Turbine Trip and Feedwater Isolation - Actuation Logic and Actuation Relays Automatic Actuation Logic and Actuation Relays consist of the same features and operate in the same manner as described for ESFAS Function 1.b.
- b.
Turbine Trip and Feedwater Isolation - Steam Generator Water Level-High High (P-14)
This signal provides protection against excessive feedwater flow. The ESFAS SG water level instruments provide input to the SG Water Level Control System. Therefore, the actuation logic must be able to withstand both an input failure to the control system (which may then require the protection function actuation) and a single failure in the other channels providing the protection function actuation. Since Watts Bar has only 3 level channels per SG, control/protection interaction is addressed by the use of a Median Signal Selector which prevents a single failure of a
ESFAS Instrumentation B 3.3.2 BASES (continued)
Watts Bar - Unit 2 B 3.3-89 Amendment APPLICABLE SAFETY
- ANALYSES, LCO, and APPLICABILITY (continued) d.
Turbine Trip and Feedwater Isolation - Main Steam Valve Vault Room Water Level - High This signal precludes submergence of equipment that is required for safe shutdown in the event of a MSVV Room flood due to a Main Feedwater line break. MSVV Room Water Level - High does not provide any control function.
Thus, three OPERABLE channels in each Valve Vault Room are sufficient to satisfy the protection requirements with a two-out-of-three logic.
The level switches which are located inside the MSVV Rooms are subjected to adverse environmental conditions during a Main Feedwater line break. The NTSP reflects both steady state and adverse environmental instrument uncertainties.
Turbine Trip and Feedwater Isolation Functions - Automatic Actuation Logic and Actuation Relays, Steam Generator Water Level - High High (P-14), and Safety Injection must be OPERABLE in MODES 1, 2, and 3 except when all MFIVs, MFRVs, and associated bypass valves are closed and de-activated or isolated by a closed manual valve when the MFW System is in operation and the turbine generator may be in operation. In MODES 4, 5, and 6, the MFW System and the turbine generator are not in service and this Function is not required to be OPERABLE.
Turbine Trip and Feedwater Isolation Function - MSVV Room Water Level - High must be OPERABLE in MODE 1 and in MODE 2 when the Turbine Driven Main Feedwater Pumps are operating. In MODE 2, due to the limited capacity of the Standby Main Feed Pump, and in MODES 3, 4, 5, and 6 a Main Feedwater Line break will not result in flooding which will submerge required safety equipment in the MSVV Rooms, therefore this Function is not required to be OPERABLE.
Partial Revision to the RAI Response of Reference 3 CNL-25-028 E2-1 of 1 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 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.
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: