CNL-17-026, Application to Modify Technical Specification 3.3.1, Reactor Protection System Instrumentation, Turbine Trip Function on Low Fluid Oil Pressure (390-WBN-TS-17-04)
| ML17075A229 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 03/16/2017 |
| From: | James Shea Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 390-WBN-TS-17-04, CNL-17-026 | |
| Download: ML17075A229 (27) | |
Text
Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-17-026 March 16, 2017 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390
Subject:
Application to Modify the Watts Bar Nuclear Plant Unit 1 Technical Specification 3.3.1, Reactor Protection System Instrumentation, Turbine Trip Function on Low Fluid Oil Pressure (390-WBN-TS-17-04)
In accordance with the provisions of Title 10 of the Code of Federal Regulations (10 CFR) 50.90, "Application for amendment of license, construction permit, or early site permit," Tennessee Valley Authority (TVA) is submitting for Nuclear Regulatory Commission (NRC) approval, a request for an amendment to Facility Operating License No. NPF-90 for the Watts Bar Nuclear Plant (WBN) Unit 1.
The proposed change revises Technical Specification (TS) 3.3.1, Table 3.3.1-1, Reactor Trip System Instrumentation, Function 14.a. Turbine Trip - Low Fluid Oil Pressure, as follows.
Increases the nominal trip setpoint (NTSP) from 45 pounds per square inch gauge (psig) to 800 psig, and the allowable value from greater than or equal to () 43 psig to 710 psig.
Adds new footnotes (g) and (h) to assess channel performance during testing that verifies instrument channel setting values established by TVAs setpoint methodology.
The proposed change to the TS are due to the replacement and relocation of the pressure switches from the low pressure auto-stop trip fluid oil header that operates at a nominal control pressure of 80 psig to the high pressure turbine electrohydraulic control (EHC) oil header that operates at a nominal control pressure of 2000 psig. The changes to the NTSP and allowable value are needed due to the higher EHC system operating pressure.
Relocation of the initiating pressure switches to the high pressure turbine EHC header is
U.S. Nuclear Regulatory Commission CNL-17-026 Page 2 March 16, 2017 needed to accommodate a modification to the EHC turbine control system while maintaining the function of transmitting the trip signal to the reactor protection system (RPS). This change does not affect any RPS trip functions.
The proposed change to the NTSP is consistent with NUREG-1431, Revision 4, Standard Technical Specifications Westinghouse Plants. The proposed change in the allowable value is based on TVAs setpoint calculation methodology for the specific pressure switches used for the WBN low oil pressure application.
The proposed change also incorporates Technical Specification Task Force (TSTF) Traveler TSTF-493-A, Revision 4, "Clarify Application of Setpoint Methodology for LSSS Functions,"
Option A for the affected turbine trip on low fluid oil pressure function setpoints only. TVAs setpoint calculation procedure incorporates the TSTF-493-A methodology for determining the allowable value. Notes are added that require the evaluation of channel performance for the condition where the as-found setting for the channel setpoint is outside its as found tolerance but conservative with respect to the allowable value, and the establishment of an appropriate as-found tolerance for each channel. These Notes are similar to TSTF-493-A Notes 1 and 2.
The enclosure provides a description of the proposed changes, technical evaluation of the proposed changes, regulatory evaluation, and a discussion of environmental considerations.
Attachments 1 and 2 to the enclosure provide the existing TS and Bases pages marked-up to show the proposed changes. Attachments 3 and 4 to the enclosure provide the existing TS and Bases pages retyped to show the proposed changes.
Changes to the existing TS Bases are provided for information only and will be implemented under the Technical Specification Bases Control Program.
TVA requests approval of the proposed TS change within 12 months of the date of this letter. The proposed TS change is currently planned to be implemented in conjunction with the modifications to the low lube oil pressure switches to be performed in the WBN Unit 1 R15 outage scheduled for Fall 2018. TVA also plans to submit a similar LAR for WBN Unit 2 later this year.
TVA has determined that there are no significant hazards considerations associated with the proposed amendments and Technical Specification changes. The proposed amendments and Technical Specification changes qualify for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9). Additionally, in accordance with 10 CFR 50.91(b)(1), TVA is sending a copy of this letter and attachments to the Division of Radiological Health - Tennessee State Department of Environment and Conservation.
U.S. Nuclear Regulatory Commission CNL-17-026 Page 3 March 16, 2017 There are no new regulatory commitments associated with this submittal. Please address any questions regarding this request to Mr. Edward D. Schrull at (423) 751-3850.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 16th day of March 2017.
Respectfully,
~~
J. W . Shea Vice President, Nuclear Licensing
Enclosure:
Evaluation of Proposed Change cc (Enclosure):
NRC Regional Administ rator- Region II NRC Resident Inspector - Watts Bar Nuclear Plant NRC Project Manage r- Watts Bar Nuclear Plant Director, Division of Radiological Health - Tennessee State Department of Environment and Conservation
Enclosure Evaluation of Proposed Technical Specification Change
Subject:
Application to Modify the Watts Bar Nuclear Plant Unit 1 Technical Specification 3.3.1, Reactor Protection System Instrumentation, Turbine trip function on Low Fluid Oil Pressure (390-WBN-TS-17-04)
CONTENTS 1.0 Summary Description ......................................................................................................... 2 2.0 Detailed Description ........................................................................................................... 2 2.1 Proposed Changes ..................................................................................................... 2 2.2 Condition Intended to Resolve .................................................................................... 3 2.3 Variations .................................................................................................................... 3
3.0 TECHNICAL EVALUATION
............................................................................................... 5 3.1 System Description ..................................................................................................... 5 3.1.1 Existing Pressure Switch Configuration .................................................................. 5 3.1.2 Proposed New Pressure Switch Configuration ....................................................... 5 3.2 Technical Analysis ...................................................................................................... 6 3.2.1 Incorporation of TSTF-493 Option A for the Low Fluid Oil Pressure Trip Function ........................................................................................................... 8 3.2.2 Conclusion ................................................................................................................ 11
4.0 REGULATORY EVALUATION
......................................................................................... 11 4.1 Applicable Regulatory Requirements/Criteria ........................................................... 11 4.1.1 Regulations ........................................................................................................... 11 4.1.2 General Design Criteria ......................................................................................... 11 4.2 Precedent.................................................................................................................. 13 4.3 Significant Hazards Consideration ............................................................................ 14 4.4 Conclusions .............................................................................................................. 16
5.0 ENVIRONMENTAL CONSIDERATION
........................................................................... 16 ATTACHMENTS
- 1. Proposed TS Changes Mark-Ups for WBN Unit 1
- 2. Proposed TS Bases Page Changes (Mark-Ups) for WBN Unit 1(For Information Only)
- 3. Proposed TS Changes (Final Typed) for WBN Unit 1
- 4. Proposed TS Bases Changes (Final Typed) for WBN Unit 1 (For Information Only)
CNL-17-026 E1-1 of 16
Enclosure Evaluation of Proposed Technical Specification Change 1.0
SUMMARY
DESCRIPTION This evaluation supports a request to amend Facility Operating License No. NPF-90 for the Tennessee Valley Authority (TVA) Watts Bar Nuclear Plant (WBN), Unit 1. The proposed change revises Technical Specification (TS) 3.3.1, Table 3.3.1-1, Reactor Trip System Instrumentation, Function 14.a. Turbine Trip - Low Fluid Oil Pressure, to increase the values for the nominal trip setpoint (NTSP) and the allowable value. The proposed change also adds new footnotes (g) and (h) to assess channel performance during testing that verifies instrument channel setting values established by TVAs setpoint methodology.
The proposed change to the TS are due to the replacement and relocation of the pressure switches from the low pressure auto-stop trip fluid oil header that operates at a nominal control pressure of 80 pounds per square inch gauge (psig) to the high pressure turbine electrohydraulic control (EHC) oil header that operates at a nominal control pressure of 2000 psig. The changes to the NTSP and allowable value are needed due to the higher EHC system operating pressure. Relocation of the initiating pressure switches to the high pressure turbine EHC header is needed to accommodate a modification to the EHC turbine control system while maintaining the function of transmitting the trip signal to the reactor protection system (RPS). This change does not affect any RPS trip functions. Relocation of the pressure switches to the high pressure EHC header requires a new turbine trip NTSP and allowable value for low fluid oil pressure and consequently, a change to WBN Unit 1 Technical Specification Table 3.3.1-1.
The proposed change to the NTSP is consistent with NUREG-1431, Revision 4, Standard Technical Specifications Westinghouse Plants. The proposed change in the allowable value is based on TVAs setpoint calculation methodology for the specific pressure switches used for the WBN low oil pressure application.
The proposed change also incorporates Technical Specification Task Force (TSTF) Traveler TSTF-493-A, Revision 4, "Clarify Application of Setpoint Methodology for LSSS Functions,"
Option A for the affected turbine trip on low fluid oil pressure function setpoints only. TVAs setpoint calculation procedure incorporates the TSTF-493-A methodology for determining the allowable value. Notes are added that require the evaluation of channel performance for the condition where the as-found setting for the channel setpoint is outside its as found tolerance but conservative with respect to the allowable value, and the establishment of the appropriate as-found tolerance for each channel. These Notes are similar to TSTF-493-A Notes 1 and 2.
2.0 DETAILED DESCRIPTION 2.1 Proposed Changes The proposed change revises TS 3.3.1, Table 3.3.1-1, Function 14.a. as follows:
Increases the NTSP from 45 psig to 800 psig, and the allowable value from greater than or equal to () 43 psig to 710 psig.
Adds new footnote (g) that states, If the as found channel setpoint is outside its predefined as found tolerance, then the channel shall be evaluated to verify that it is functioning as required before returning the channel to service.
CNL-17-026 E1-2 of 16
Enclosure Evaluation of Proposed Technical Specification Change Adds new footnote (h) that states, The instrument channel setpoint shall be reset to a value that is within the as left tolerance around the Nominal Trip Sepoint (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.
Attachments 1 and 2 to this enclosure provide the existing TS and Bases pages marked-up to show the proposed changes. Attachments 3 and 4 to the enclosure provide the existing TS and Bases pages retyped to show the proposed changes.
Changes to the existing TS Bases are provided for information only and will be implemented under the Technical Specification Bases Control Program.
2.2 Condition Intended to Resolve The proposed changes to the TS are due to the replacement and relocation of the pressure switches from the low pressure auto-stop trip fluid oil header that operates at a nominal control pressure of 80 psig to the high pressure turbine EHC oil header that operates at a nominal control pressure of 2000 psig. The changes to the NTSP and allowable value are needed due to the higher EHC system operating pressure. Relocation of the initiating pressure switches to the high pressure turbine EHC header is needed to accommodate a modification to the EHC turbine control system while maintaining the function of transmitting the trip signal to the RPS. This change does not affect any RPS trip functions.
2.3 Variations TVA is proposing the following minor variations for the notes added to the TS Table 3.3.1-1, Function 14.a. to Notes 1 and 2 in TSTF-493-A, Revision 4. These variations do not affect the applicability of TSTF-493-A or the NRC staffs safety evaluation of the proposed license amendment.
2.3.1 The WBN Unit 1 TS utilize different numbering than the Standard Technical Specifications for which TSTF-493-A, Revision 4 is based. The following table summarizes the differences between the WBN Unit 1 TS numbering and the TSTF-493-A, Revision 4 numbering.
TSTF-493-A, Revision 4 WBN Unit 1 TS Table 3.3.1-1 NUREG-1431, Westinghouse Plants Reactor Trip System Instrumentation Specification 3.3.1 Reactor Trip System Instrumentation
- 16. Turbine Trip 14. Turbine Trip
- a. Low Fluid Oil Pressure a. Low Fluid Oil Pressure CNL-17-026 E1-3 of 16
Enclosure Evaluation of Proposed Technical Specification Change 2.3.2 The footnotes added to WBN Unit 1 TS Table 3.3.1-1 utilize different numbering than from the TSTF-493-A, Revision 4 Notes 1 and 2. In addition, the WBN Unit 1 TS footnote (h) does not include the following statement from TSTF-493-A, Revision 4 Note 2:
Setpoints more conservative than the NTSP are acceptable provided that the as-found and as-left tolerances apply to the actual setpoint implemented in the Surveillance procedures (field setting) to confirm channel performance.
The last sentence in TSTF-493-A, Revision 4 Note 2 is also modified for the WBN Unit 1 TS footnote. The wording of the WBN Unit 1 footnotes are identical to the previously NRC approved WBN Unit 2 TS Table 3.3.1-1 footnotes. The following table summarizes the differences between the WBN Unit 1 TS footnote numbering and wording, and the TSTF-493-A, Revision 4, Notes 1 and 2.
TSTF-493-A, Revision 4 for Option A WBN Unit 1 TS Table 3.3.1-1 NUREG-1431, Westinghouse Plants Note 1: Footnote (g):
Table 3.3.1-1 Footnote (c) - Insert 1 If the as found channel setpoint is outside "If the as-found channel setpoint is outside its predefined as found tolerance, then the its predefined as-found tolerance, then the channel shall be evaluated to verify that it is channel shall be evaluated to verify that it is functioning as required before returning the functioning as required before returning the channel to service.
channel to service."
Note 2: Footnote (h):
Table 3.3.1-1 Footnote (d) - Insert 2 The instrument channel setpoint shall be The instrument channel setpoint shall be reset to a value that is within the as left reset to a value that is within the as-left tolerance around the Nominal Trip Setpoint tolerance around the Nominal Trip Setpoint (NTSP) at the completion of the surveillance; (NTSP) at the completion of the otherwise, the channel shall be declared surveillance; otherwise, the channel shall inoperable. The methodologies used to be declared inoperable. Setpoints more determine the as found and as left conservative than the NTSP are acceptable tolerances for the NTSP are specified in provided that the as-found and as-left FSAR Section 7.1.2.
tolerances apply to the actual setpoint implemented in the Surveillance procedures (field setting) to confirm channel performance. The Nominal Trip Setpoint and the methodologies used to determine the as-found and the as-left tolerances are specified in [insert the facility FSAR reference or the name of any document incorporated into the facility FSAR by reference]."
CNL-17-026 E1-4 of 16
Enclosure Evaluation of Proposed Technical Specification Change
3.0 TECHNICAL EVALUATION
3.1 System Description The reactor trip system (RTS) initiates a unit shutdown, based on the values of selected unit parameters, to protect against violating the core fuel design limits and reactor coolant system (RCS) pressure boundary during anticipated operational occurrences (AOOs) and to assist the engineered safety features (ESF) systems in mitigating accidents.
The protection and monitoring systems have been designed to assure safe operation of the reactor. This is achieved by specifying limiting safety system settings (LSSSs) in terms of parameters directly monitored by the RTS, as well as specifying limiting conditions for operation (LCOs) on other reactor system parameters and equipment performance.
The turbine trip low fluid oil pressure trip Function anticipates the loss of heat removal capabilities of the secondary system following a turbine trip. This trip Function acts to minimize the pressure/temperature transient on the reactor. The reactor trip on a turbine trip is actuated by two-out-of-three logic from low oil pressure signals or by closed signals from all four turbine steam stop valves. The circuitry associated with the pressure switches is independent of the turbine control system and does not perform any turbine control functions.
A turbine trip causes a direct reactor trip above the P-9 setpoint of approximately 50 percent
(%) power. Any turbine trip from a power level below the P-9 setpoint will not directly trip the reactor, but will allow the reactor control system to bring the reactor to zero power utilizing steam dump to the condenser as an artificial load. The reactor trip on turbine trip provides additional protection and conservatism beyond that required for the health and safety of the public. This trip is included as part of good engineering practice and prudent design. No credit is taken in the accident analyses for this trip.
3.1.1 Existing Pressure Switch Configuration Three pressure switches are located on the low pressure fluid oil header (also referred to as the auto-stop trip (AST) system). The three low oil pressure switches have two output contacts that provide redundant inputs to each of the three RPS protection channels I, II and III (two-out-of-three logic). This signal initiates a reactor trip on a turbine trip if reactor power is above the P-9 power range neutron flux interlock (approximately 50% of full power). The low pressure AST fluid oil header operates at a nominal control pressure of approximately 80 psig. The existing NTSP is 45 psig and the allowable value is 43 psig.
3.1.2 Proposed New Pressure Switch Configuration The proposed modifications to the EHC system remove the AST oil header where the existing low oil pressure switches were located. To support this modification, the RPS trip function will now be performed by three new pressure switches located on the high pressure turbine EHC trip header. As with the original pressure switches, the three new pressure switches have two output contacts that provide redundant inputs to each of the three RPS protection channels I, II and III (two-out-of-three logic). The RPS logic is not affected by the change and the signal will still initiate a reactor trip on a turbine trip if reactor power is above the P-9 power range neutron flux interlock (approximately 50% of full power).
CNL-17-026 E1-5 of 16
Enclosure Evaluation of Proposed Technical Specification Change The EHC system supplies hydraulic control oil fluid to the turbine stop, governor, intercept and reheat valves. The EHC fluid is provided by skid-mounted hydraulic pumps that maintain operating pressure at approximately 2000 psig. The changes to the NTSP and allowable value are needed due to the higher EHC system operating pressure. The operation of the turbine is dependent on maintaining proper EHC system pressure. On a turbine trip initiation signal, EHC dump valves connected to the EHC fluid header are signaled to open draining the EHC fluid from the piping. The EHC header pressure is rapidly decreased, closing the turbine stop valves and tripping the turbine.
The decreased EHC fluid pressure is sensed by the new low fluid oil pressure switches.
When the decreased pressure is sensed by the pressure switches, a reactor trip signal is initiated by two-out-of-three RPS channels. The circuitry associated with the pressure switches and the RPS is independent of the new turbine control system.
3.2 Technical Analysis The low pressure AST fluid oil header pressure switches provides inputs to each of the three RPS protection channels I, II and III (two-out-of-three logic) to initiate a reactor trip on a turbine trip if reactor power is above the P-9 power range neutron flux interlock. This trip anticipates the loss of heat removal capabilities of the secondary system following a turbine trip and acts to minimize the pressure/temperature transient on the RCS.
The reactor trip on turbine generator trip is an anticipatory trip that provides additional protection and conservatism beyond that required for the health and safety of the public.
The accident analyses do not credit this direct reactor trip on a turbine trip for any core protection function. WBN Unit 1 is designed to withstand a complete loss of load and not sustain core damage or challenge the RCS pressure limitations. Core protection is provided by the high pressurizer pressure and over temperature T trip functions. RCS integrity is ensured by the pressurizer safety valves.
The turbine protection system consists of the low pressure auto-stop oil system, and the stop valve and control valve emergency trip fluid systems in the high-pressure EHC fluid control system. On a turbine trip signal, solenoid valves open to depressurize the auto-stop oil system, which causes an interface emergency trip valve to open, depressurizing the high pressure EHC header. Loss of the EHC pressure causes the stop valve emergency trip fluid systems to trip closed, tripping the turbine.
When the low oil pressure condition is sensed below the setpoint following a turbine trip by two-out-of-three pressure switches RPS Channel I, II, and III, the RPS initiates a reactor trip signal.
The new configuration will allow the RPS trip function to be performed by three new pressure switches in a different location but with the same function. The new pressure switches are located on the high pressure turbine EHC trip header. Consistent with the original pressure switches, the three new pressure switches have two output contacts that provide redundant inputs to each of the three RPS protection channels I, II and III (two-out-of-three logic). The RPS logic is not affected by the change and the signal will still initiate a reactor trip on a turbine trip if reactor power is above the P-9 power range neutron flux interlock (approximately 50% of full power).
CNL-17-026 E1-6 of 16
Enclosure Evaluation of Proposed Technical Specification Change On a turbine trip initiation signal, EHC dump valves connected to the EHC fluid header are signaled to open draining the EHC fluid from the piping. The EHC header pressure is rapidly decreased closing the turbine stop valves and tripping the turbine. The decreased EHC fluid pressure is sensed by the new low fluid oil pressure switches. When the decreased pressure is sensed by the pressure switches, a reactor trip signal is initiated by two out of the three RPS channels if reactor pressure is above the P-9 power range neutron flux interlock (approximately 50% of full power). The circuitry associated with the pressure switches and the RPS is independent of the new turbine control system.
Because the reactor trip on turbine trip function of the low fluid oil pressure is not credited in the accident analysis, the pressure switches are quality related, non-seismic devices. The switches are similar to switches used in similar EHC applications at the Browns Ferry Nuclear Plant (BFN) on the turbine stop valves. The new switches are designed for consistent, dependable operation at the higher EHC fluid oil pressure. Operational experience at BFN has shown this style of switch to be reliable. The piping connecting the switches to the EHC header is capable of withstanding the system pressure. Postulated pipe breaks in the EHC header do not need to be considered in the design, as no safety-related equipment would be adversely impacted. A break would result in closure of the associated turbine valves and actuation of the pressure switches.
The low pressure setpoint provides an unambiguous, non-spurious indication of turbine trip status. The calculated setpoint uncertainties are determined for normal conditions because the switches are not credited for operation under accident conditions; therefore, the switches will not be exposed to adverse environmental conditions before or during the time they are needed to function.
The purpose of the switches is to actuate a reactor trip in response to a turbine trip event, not as a direct result of an accident such as a loss of coolant accident (LOCA) or a main steam line break (MSLB). The safety analyses do not credit the operation of the reactor trip on turbine trip function of the low fluid oil pressure switches; therefore, there is not an associated analytical limit (AL) or safety limit. Therefore, the low fluid oil pressure setpoint is not a limiting setpoint used to protect a design or licensing basis limiting condition. The low fluid oil pressure setpoint represents the turbine tripped and not tripped physical condition.
NUREG-1431, Revision 4, provides the referenced NTSP for Turbine Trip on low fluid oil pressure as 800 psig. This value is consistent with the EHC operating system pressure range associated with this parameter for WBN Unit 1. The setpoint value of 800 psig was based on the minimum required EHC fluid oil pressure, the expected calibration tolerance and frequency of the switches, and the expected time-based drift of the pressure switches.
The new low fluid oil pressure setpoint allows for operator recovery actions from a decreasing EHC system pressure occurrence prior to a turbine trip (e.g., EHC system leakage). The EHC system low pressure alarm setpoint will have sufficient margin from the system trip setpoint. The high pressure EHC fluid "Low Pressure Alarm" occurs on decreasing pressure at 1600 psig and alerts the operator in the control room that the EHC fluid oil pressure is decreasing. The "Main Pump Auto Start" is initiated on decreasing pressure at 1500 psig and starts the backup EHC fluid oil pump to maintain pressure in the high pressure header to prevent a turbine trip. An EHC fluid "Low-Low Pressure Alarm" occurs on decreasing pressure at 1350 psig and alerts the operator in the control room.
This alarm allows for operator action to recover the EHC fluid oil pressure in response to the CNL-17-026 E1-7 of 16
Enclosure Evaluation of Proposed Technical Specification Change low pressure alarm and main pump auto start action. If EHC fluid oil pressure is not recovered by the time the pressure drops below 800 psig, the turbine will trip (as sensed by the two-out-of-three pressure switches) and the new low oil pressure switch contacts will open to send a trip signal to the RPS if reactor power is above the P-9 power range neutron flux interlock (approximately 50% of full power).
The setpoint is offset from the allowable value such that the limit will not be exceeded due to instrument uncertainties expected to be present between calibrations. NUREG-1431, Revision 4 lists an allowable value for turbine trip on low fluid oil pressure as greater than or equal to 750 psig. WBN Unit 1 has evaluated and confirmed as described in section 3.2.1 below that the WBN allowable value of 710 psig was sufficient to account for uncertainties for the pressure switches being used at WBN in accordance with TVA Branch Technical Instruction BTI-EEB-TI-28, Setpoint Calculations.
BTI-EEB-TI-28 incorporates methodologies for the determination of setpoints for nuclear safety-related instrumentation in ISA Standard ISA-S67.04-1982 and 1994, Setpoints for Nuclear Safety-Related Instrumentation Used in Nuclear Power Plants, as endorsed in Regulatory Guide (RG) 1.105, Revisions 2 and 3, respectively. Although the pressure switches are considered non-safety related, the new turbine trip setpoint on low fluid oil pressure has been determined in accordance with BTI-EEB-TI-28. Instrument uncertainties such as calibration error, and drift were considered in determining a total device uncertainty for the pressure switches.
In order to ensure that the instrument channel is capable of performing its specified function, WBN Unit 1 performs testing of this channel in accordance with current station procedures that govern the control of calibration requirements (including as-found and as-left tolerances), and the evaluation of out-of-tolerance instruments. Calibration accuracy is defined in the applicable instrument design output documents.
3.2.1 Incorporation of TSTF-493 Option A for the Low Fluid Oil Pressure Trip Function As noted in Section 1.0, TVAs setpoint calculation procedure incorporates the setpoint methodologies described in TSTF-493-A. However, WBN Unit 1 has not incorporated the setpoint methodologies described in TSTF-493-A for all of the instrumentation in Unit 1.
TVA has chosen to perform the Technical Analysis and Allowable Value determination for the WBN Unit 1 low fluid oil pressure instrumentation using the methodologies described in TSTF-493-A as referenced in the NRC Notice of Availability published in the Federal Register on May 11, 2010 (75 FR 26294). A discussion of the TVA TSTF-493-A setpoint methodology is provided in the UFSAR section 7.1.2 for WBN Unit 2. The NRCs review of the TVA implementation of the TSTF-493-A setpoint methodology used for WBN Unit 2 is contained in NUREG-0847 Supplement 23, Safety Evaluation Report Related to the Operation of Watts Bar Nuclear Plant Unit 2. In the WBN Unit 2 SER Supplement 23, the NRC concluded that the TVA methodology meets the relevant guidance of NRC Regulatory Issue Summary 2006-17, "NRC Staff Position on the Requirements of 10 CFR 50.36, Technical Positions, Regarding Limiting Safety System Settings During Periodic Testing and Calibration of Instrument Channels," and RG 1.105. The same NRC approved setpoint methodology for WBN Unit 2 is used for the evaluation of the low fluid oil pressure trip function for WBN Unit 1 in accordance with BTI-EEB-TI-28.
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Enclosure Evaluation of Proposed Technical Specification Change Plant-specific information related to the Technical Analysis is described below to document that the content of TSTF-493-A, Revision 4, Option A, is applicable to WBN Unit 1 for this parameter only.
Nominal Trip Setpoint (NTSP)
The NTSP is the nominal value at which the instrument is set when it is calibrated. Because most instruments cannot be set to an exact value, the instrument is set to the nominal setpoint within an allowed tolerance band defined as Acceptable As Left (AAL).
NUREG-1431, Revision 4, Standard Technical Specifications Westinghouse Plants, provides the referenced NTSP for Turbine Trip on low fluid oil pressure as 800 psig.
Analytical Limit (AL)
The AL represents the parameter value at which a safety action is assumed in the accident analysis to be initiated to ensure that the safety limits either are not exceeded during accidents or anticipated operational occurrences. Note that the safety analyses in Chapter 15 of the WBN UFSAR do not credit the operation of the reactor trip on turbine trip function of the low fluid oil pressure switches. Therefore, an AL or safety limit is not defined for the low oil pressure trip function.
Allowable Value An allowable value is the limiting value of the as-found trip setting used during surveillance testing for the portion of the channel being tested, beyond which the channel is inoperable.
The allowable value ensures that sufficient margin exists to the AL to account for unmeasurable uncertainties such as process effects to ensure that the protective action is performed under worst case conditions before the AL is exceeded when the channel is reset to within the acceptable as left (AAL) tolerance. The safety analyses in Chapter 15 of the WBN UFSAR do not credit the operation of the reactor trip on turbine trip function of the low fluid oil pressure. Therefore, an AL or safety limit is not defined for the low oil pressure trip function. The allowable value is derived from the NTSP in accordance with BTI-EEB-TI-28.
Because analog instruments cannot be set to an exact value, a calibration tolerance is established around the NTSP. Therefore, an instrument adjustment is considered successful if the AAL instrument setting is within the setting tolerance (i.e., a range of values around the NTSP). The field setting is the NTSP with margin added and is at least as conservative as the NTSP.
Proposed Notes (g) and (h)
The proposed Notes (g) and (h) for Function 14.a. of TS Table 3.3.1-1 for low fluid oil pressure are based on this Function being an automatic protective device related to variables having a significant safety function as delineated by 10 CFR 50.36(c)(1)(ii)(A).
These Notes are similar to TSTF-493-A Notes 1 and 2.
Proposed Note (g) for Function 14.a. of TS Table 3.3.1-1 states: "If the as found channel setpoint is outside its predefined as found tolerance, then the channel shall be evaluated to verify that it is functioning as required before returning the channel to service."
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Enclosure Evaluation of Proposed Technical Specification Change This Note requires evaluation of channel performance for the condition where the as-found setting for the channel setpoint is outside its as found tolerance but conservative with respect to the allowable value. Evaluation of channel performance will verify that the channel will continue to perform in accordance with safety analysis assumptions and the channel performance assumptions in the setpoint methodology. The purpose of the assessment is to ensure confidence in the channel performance prior to returning the channel to service.
Verifying that a trip setting is conservative with respect to the allowable value when a surveillance test is performed does not by itself verify the instrument channel will operate properly in the future. Although the channel was operable during the previous surveillance interval, if it is discovered that channel performance is outside the performance predicted by the plant setpoint calculations for the test interval, then the design basis for the channel may not be met, and proper operation of the channel for a future demand cannot be assured.
Proposed Note (g) formalizes the establishment of the appropriate as-found tolerance for each channel. This acceptable as found tolerance is applied about the NTSP or about any other more conservative setpoint. The acceptable as found tolerance ensures that channel operation is consistent with the assumptions or design inputs used in the setpoint calculations and establishes a high confidence of acceptable channel performance in the future. Because the as-found tolerance allows for both conservative and non-conservative deviation from the NTSP, changes in channel performance that are conservative with respect to the NTSP will also be detected and evaluated for possible effects on expected performance.
Proposed Note (h) for Function 14.a. of TS Table 3.3.1-1 states: "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."
To implement surveillance Note (h), the acceptable as left tolerance for some instrumentation Function channels is established to ensure that realistic values are used that do not mask instrument performance. Setpoint calculations assume that the instrument setpoint is left at the NTSP within a specific acceptable as left tolerance (e.g., 25 psig +/- 2 psig). A tolerance band is necessary because it is not possible to read and adjust a setting to an absolute value due to the readability and/or accuracy of the test instruments or the ability to adjust potentiometers. The acceptable as left tolerance is normally as small as possible considering the tools and the objective to meet an as low as reasonably achievable calibration setting of the instruments. The acceptable as left tolerance is considered in the setpoint calculation. Failure to set the actual plant trip setpoint to the NTSP (or more conservative than the NTSP), and within the acceptable as left tolerance, would invalidate the assumptions in the setpoint calculation because any subsequent instrument drift would not start from the expected as-left setpoint.
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Enclosure Evaluation of Proposed Technical Specification Change Note (g) for Table 3.3.1-1, Function 14.a. (TSTF-493-A Note 1), results in a more restrictive requirement in that an evaluation of the channel performance is required for the condition where the acceptable as found setting for a channel setpoint is outside its as-found tolerance, but conservative with respect to the allowable value. In addition, incorporation of surveillance Note (h) for Table 3.3.1-1, Function 14.a. (TSTF-493-A Note 2) results in a more conservative requirement in that the allowance for the trip setpoints to be set more conservative than the NTSP explicitly requires that the as-found and acceptable as left tolerances apply to the actual setpoint implemented in the surveillance procedures to confirm channel performance.
3.2.2 Conclusion The proposed changes revise Technical Specification (TS) 3.3.1, Table 3.3.1-1, Reactor Trip System Instrumentation, Function 14.a. Turbine Trip - Low Fluid Oil Pressure, to increase the values for the nominal trip setpoint (NTSP) and the allowable value. The proposed change also adds new footnotes (g) and (h) to assess channel performance during testing that verifies instrument channel setting values established by TVAs setpoint methodology. These proposed TS changes do not impact or change any assumptions contained in the plant safety analyses. Therefore, the Margin of safety related to the ability of the fission product barriers to perform their design functions during and following accident conditions is not affected. These barriers include the fuel cladding, the reactor coolant system, and the containment system. The performance of these barriers is not significantly degraded by the proposed changes.
4.0 REGULATORY EVALUATION
4.1 Applicable Regulatory Requirements/Criteria 4.1.1 Regulations 10 CFR 50.36 sets forth the regulatory requirements for the content of the TSs. This regulation requires, in part, that the TS contain Surveillance Requirements (SRs).
10 CFR 50.36(c)(3), states that SRs to be included in the TS are those relating to test, calibration, or inspection, which assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the TS LCO will be met.
4.1.2 General Design Criteria As noted in the WBN dual-unit UFSAR Section 3.1.1, WBN was designed to meet the intent of the "Proposed General Design Criteria for Nuclear Power Plant Construction Permits" published in July 1967. The WBN construction permit was issued in January 1973. The WBN dual-unit UFSAR, however, addresses the NRC General Design Criteria (GDC) published as Appendix A to 10 CFR 50 in July 1971, including Criterion 4 as amended October 27, 1987.
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Enclosure Evaluation of Proposed Technical Specification Change The WBN UFSAR contains these GDC followed by a discussion of the design features and procedures that meet the intent of the criteria. The relevant GDC are described below.
Criterion 20Protection System Functions The protection system shall be designed (1) to initiate automatically the operation of appropriate systems including the reactivity control systems, to assure that specified acceptable fuel design limits are not exceeded as a result of anticipated operational occurrences and (2) to sense accident conditions and to initiate the operation of systems and components important to safety.
Criterion 20 is applicable to this amendment request because the input into the RPS must ensure RPS actuation even if the input component fails. The normal operational state of the existing auto stop low fluid oil pressure switch is contacts closed. The contacts open when the low fluid oil pressure drops below the setpoint. If the pressure switch fails, the contacts would open and therefore provide input to the associated RPS channel. The new low fluid oil header pressure switches are configured in the same manner as the existing auto stop low fluid oil pressure switches with contacts closed when EHC header pressure rises above the reset setpoint and contacts open when EHC header pressure drops below the trip setpoint. Pressure switch failure would result in contact opening and input provided to the associated RPS channel in the same manner as an EHC header pressure drop below the trip setpoint. Criterion 20 is met because the new EHC fluid oil header pressure switches are designed to fail into a safe state.
Further conformance with GDC 20 is described in Section 3.1.2.3 of the WBN dual-unit UFSAR.
Criterion 22Protection System Independence The protection system shall be designed to assure that the effects of natural phenomena, and of normal operating, maintenance, testing, and postulated accident conditions on redundant channels do not result in loss of the protection function, or shall be demonstrated to be acceptable on some other defined basis. Design techniques, such as functional diversity or diversity in component design and principles of operation, shall be used to the extent practical to prevent loss of the protection function.
Criterion 22 is applicable to this amendment request because the input into the RPS must ensure RPS channel separation is maintained to provide protection system independence.
The low pressure AST fluid oil header pressure switches provides inputs to each of the three RPS protection channels I, II and III (two-out-of-three logic) to initiate a reactor trip on a turbine trip if reactor power is above the P-9 power range neutron flux interlock. When the low oil pressure condition is sensed below the setpoint following a turbine trip by two-out-of-three pressure switches RPS Channel I, II, and III, the RPS initiates a reactor trip signal. Separation between the three pressure switches and associated wiring is provided in accordance with IEEE 279-1971 and ensures independence between the RPS channels.
The RPS trip function will now be performed by three new pressure switches located on the high pressure turbine EHC trip header. As with the original pressure switches, the three new pressure switches have two output contacts that provide redundant inputs to each of the three RPS protection channels I, II and III (two-out-of-three logic). The RPS logic is not affected by the change and the signal will still initiate a reactor trip on a turbine trip if reactor CNL-17-026 E1-12 of 16
Enclosure Evaluation of Proposed Technical Specification Change power is above the P-9 power range neutron flux interlock (approximately 50% of full power). Separation between the pressure switches for each RPS channel and associated wiring is maintained in accordance with IEEE 279-1971 and ensures independence between the RPS channels.
Further conformance with GDC 22 is described in Section 3.1.2.3 of the WBN dual-unit UFSAR.
Criterion 23Protection System Failure Modes The protection system shall be designed to fail into a safe state or into a state demonstrated to be acceptable on some other defined basis if conditions such as disconnection of the system, loss of energy (e.g., electric power, instrument air), or postulated adverse environments (e.g., extreme heat or cold, fire, pressure, steam, water, and radiation) are experienced.
Criterion 23 is applicable to this modification to the extent that inputs to the RPS are affected. The RPS and the turbine control systems are independent. A failure of the turbine control system does not affect the input to the RPS from the existing auto stop low fluid oil pressure switches. The low pressure AST fluid oil header pressure switches provides inputs to each of the three RPS protection channels I, II and III (two-out-of-three logic) to initiate a reactor trip on a turbine trip if reactor power is above the P-9 power range neutron flux interlock. The RPS trip function will now be performed by three new pressure switches located on the high pressure turbine EHC trip header. The three new pressure switches have two output contacts that provide redundant inputs to each of the three RPS protection channels I, II and III (two of three logic). The RPS logic is not affected by the change and the signal will still initiate a reactor trip on a turbine trip if reactor power is above the P-9 power range neutron flux interlock (approximately 50% of full power). The new switches have been used in similar EHC Turbine Stop Valve applications at the Browns Ferry Nuclear Plant (BFN) and have a reliable operating history. The new low fluid oil header pressure switches do not provide any input into the turbine control system. The low fluid oil header pressure switches utilize the existing auxiliary relays to communicate with the RPS. The connection to the RPS from the auxiliary relays is not being modified. Criterion 23 is met because the relocation and replacement of the pressure switches maintains system reliability, redundancy, and independence from the turbine control system.
Further conformance with GDC 23 is described in Section 3.1.2.3 of the WBN dual-unit UFSAR.
4.2 Precedent The following precedents are related to the proposed TS change in this submittal:
NRC letter to Indiana Michigan Power Company, Donald C. Cook Nuclear Plant, Unit 2
- Issuance of Amendment Regarding Reactor Trip on Low Turbine Oil Pressure (TAC No. MD3161), dated September 21, 2007 (ML072180639). This amendment modified the turbine control system to replace the control system, which increased the nominal control fluid oil operating pressure from 114 psig to 1600 psig. The control fluid oil pressure provided an input to the RPS via three pressure switches connected to the control fluid header. Due to the relocation of the pressure switches to a new higher CNL-17-026 E1-13 of 16
Enclosure Evaluation of Proposed Technical Specification Change operational pressure system, this amendment revised allowable value for low fluid oil pressure from 57 psig to 750 psig.
NRC letter to Duke Energy Progress, Inc., H. B. Robinson Steam Electric Plant, Unit No. 2 - Issuance of Amendment Regarding Technical Specification 3.3.1, Reactor Protection System Instrumentation Turbine Trip (TAC No. MF3463), dated September 22, 2015 (ML15040A073). This license amendment modified TS 3.3.1, Table 3.3.1- 1, Function 15.a. "Low auto stop Oil Pressure," to reflect a modification to the Unit 2 turbine control system. A change to the turbine control system revised the TS for the RPS instrumentation turbine trip Function on low auto stop oil pressure to a turbine trip function on low fluid oil pressure. In addition, the nominal trip setpoint was changed from 45 psig to 800 psig and the allowable value was revised from 40.87 psig to 769 psig.
This proposed LAR is very similar to this precedent because they both involve an increase in the NTSP and allowable value as the result of increased control fluid oil operating pressure originating from upgrades and/or replacement of the originally installed turbine control systems. In both cases, the pressure switches providing the RPS inputs do not interface with the turbine control system and can be considered independent of the turbine control system modifications.
Additionally, this LAR incorporates TSTF- 493-A, Revision 4, Option A for the turbine trip on low fluid oil pressure function only. The same NRC approved setpoint methodology previously approved for WBN Unit 2 is used for the evaluation of the low fluid oil pressure trip function for WBN Unit 1 in accordance with BTI-EEB-TI-28.
4.3 Significant Hazards Consideration The Tennessee Valley Authority (TVA) is proposing an amendment to revise the Watts Bar Nuclear Plant (WBN) Unit 2 Technical Specifications (TSs) to revise TS 3.3.1, Table 3.3.1-1, Reactor Protection System Instrumentation, Function 14.a. Turbine Trip - Low Fluid Oil Pressure. The proposed amendment revises the Nominal Trip Setpoint (NTSP) for this function from 45 pounds per square inch gauge (psig) to 800 psig and the allowable value from greater than or equal to () 43 psig to 710 psig. The proposed change is due to the replacement and relocation of the pressure switches from the low pressure fluid oil system that operates at a nominal control pressure of 80 psig to the high pressure turbine electrohydraulic control (EHC) header that operates at a nominal control pressure of 2000 psig. The changes to the NTSP and allowable value are needed due to the higher EHC system operating pressure. Relocation of the initiating pressure switches to the high pressure turbine EHC header is necessary to accommodate the modification of the EHC Turbine Control system while maintaining the function of transmitting the trip signal to the Reactor Protection System (RPS).
TVA has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:
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Enclosure Evaluation of Proposed Technical Specification Change
- 1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?
Response: No The proposed change reflects a design change to the turbine control system that results in the use of an increased control oil pressure system, necessitating a change to the value at which a low fluid oil pressure initiates a reactor trip on turbine trip. The low fluid oil pressure is an input to the reactor trip instrumentation in response to a turbine trip event. The value at which the low fluid oil initiates a reactor trip is not an accident initiator. A change in the nominal control oil pressure does not introduce any mechanisms that would increase the probability of an accident previously analyzed. The reactor trip on turbine trip function is initiated by the same protective signal as used for the existing auto stop low fluid oil system trip signal. There is no change in form or function of this signal and the probability or consequences of previously analyzed accidents are not impacted.
The proposed change also adds test requirements to the low fluid oil pressure TS instrument function related to those variables to ensure that instruments will function as required to initiate protective systems or actuate mitigating systems at the point assumed in the applicable setpoint calculation. Surveillance tests are not an initiator to any accident previously evaluated. As a result, the probability of any accident previously evaluated is not significantly increased. The systems and components required by the low fluid oil pressure TS instrument function for which surveillance tests are added are still required to be operable, meet the acceptance criteria for the surveillance requirements, and be capable of performing any mitigation function.
Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
- 2. Does the change create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No The EHC fluid oil pressure rapidly decreases in response to a turbine trip signal. The value at which the low fluid oil pressure switches initiates a reactor trip is not an accident initiator. The proposed TS change reflects the higher pressure that will be sensed after the pressure switches are relocated from the auto stop low fluid oil system to the EHC high pressure header. Failure of the new switches would not result in a different outcome than is considered in the current design basis. Further, the change does not alter assumptions made in the safety analysis but ensures that the instruments perform as assumed in the accident analysis.
Therefore, the proposed change does not create the possibility of a new or different kind of accident from any previously evaluated.
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Enclosure Evaluation of Proposed Technical Specification Change
- 3. Does the change involve a significant reduction in a margin of safety?
Response: No The change involves a parameter that initiates an anticipatory reactor trip following a turbine trip. The safety analyses do not credit this anticipatory trip for reactor core protection. The original pressure switch configuration and the new pressure switch configuration both generate the same reactor trip signal. The difference is that the initiation of the trip will now be adjusted to a different system of higher pressure. This system function of sensing and transmitting a reactor trip signal on turbine trip remains the same. Also, the proposed change adds test requirements that will assure that technical specifications instrumentation allowable values: (1) will be limiting settings for assessing instrument channel operability and; (2) will be conservatively determined so that evaluation of instrument performance history and the as left tolerance requirements of the calibration procedures will not have an adverse effect on equipment operability.
The testing methods and acceptance criteria for systems, structures, and components, specified in applicable codes and standards (or alternatives approved for use by the NRC) will continue to be met as described in the plant licensing basis including the updated Final Safety Analysis Report. There is no impact to safety analysis acceptance criteria as described in the plant licensing basis because no change is made to the accident analysis assumptions.
Therefore, the proposed change does not involve a significant reduction in a margin of safety.
Based on the above, TVA concludes that the proposed amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92 (c), and, accordingly, a finding of no significant hazards consideration is justified.
4.4 Conclusions In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
5.0 ENVIRONMENTAL CONSIDERATION
A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or would change an inspection or surveillance requirement.
However, the proposed amendment does not involve (i) a significant hazards consideration; (ii) a significant change in the types or significant increases in the amounts of any effluents that may be released offsite; or (iii) result in a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment needs to be prepared in connection with the issuance of the amendment.
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Enclosure Evaluation of Proposed Technical Specification Change ATTACHMENT 1 Proposed TS Changes (Mark-Ups) for WBN Unit 1 CNL-17-026
RTS Instrumentation 3.3.1 Table 3.3.1-1 (page 4 of 9)
Reactor Trip System Instrumentation APPLICABLE MODES NOMINAL OR OTHER REQUIRED SURVEILLANCE ALLOWABLE TRIP FUNCTION SPECIFIED CHANNELS CONDITIONS REQUIREMENTS VALUE SETPOINT CONDITIONS
- 13. SG Water Level -- 1, 2 3/SG U SR 3.3.1.1 16.4% of 17% of Low-low SR 3.3.1.7 narrow narrow SR 3.3.1.10 range span range span Coincident with: SR 3.3.1.15 a) Vessel T 1, 2 3 V SR 3.3.1.7 Vessel T Vessel T Equivalent SR 3.3.1.10 variable input variable input to power 52.6% RTP 50% RTP 50% RTP With a time 1.01 Ts Ts (Refer delay (Ts) (Refer to to Note 3, if one steam Note 3, Page 3.3-23) generator is Page 3.3-23) affected or A time delay 1.01 Tm Tm (Refer (Tm) if two (Refer to to Note 3, or more steam Note 3, Page 3.3-23) generators are Page 3.3-23) affected OR b) Vessel T 1, 2 3 V SR 3.3.1.7 Vessel T Vessel T Equivalent to SR 3.3.1.10 variable input variable input power > 50% 52.6% RTP 50% RTP RTP with no time delay (Ts and Tm =
0)
- 14. Turbine Trip (i) (g)(h)
(g) If the as found channel setpoint is outside its predefined as found tolerance, then the channel shall be evaluated to verify that it is functioning as required before returning the channel to service.
(h) 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.
(i) Above the P-9 (Power Range Neutron Flux) interlock.
Watts Bar-Unit 1 3.3-18 Amendment 7, XX
Enclosure Evaluation of Proposed Technical Specification Change ATTACHMENT 2 Proposed TS Bases Changes (Mark-Ups) for WBN Unit 1 (For Information Only)
CNL-17-026
RTS Instrumentation B 3.3.1 Bases APPLICABLE a. Turbine Trip-Low Fluid Oil Pressure (continued)
SAFETY ANALYSES LCO, and power, will not actuate a reactor trip. Three APPLICABILITY pressure switches monitor the control oil pressure in the Turbine Electrohydraulic Control System high pressure header. A low pressure condition sensed by two-out-of-three pressure switches will actuate a reactor trip. These pressure switches do not provide any input to the control system. The unit is designed to withstand a complete loss of load and not sustain core damage or challenge the RCS pressure limitations. Core protection is provided by the Pressurizer PressureHigh trip Function and RCS integrity is ensured by the pressurizer safety valves.
The LCO requires three channels of Turbine Trip Low Fluid Oil Pressure to be OPERABLE in MODE 1 above P-9.
Below the P-9 setpoint, a turbine trip does not actuate a reactor trip. In MODE 2, 3, 4, 5, or 6, there is no potential for a turbine trip, and the Turbine TripLow Fluid Oil Pressure trip Function does not need to be OPERABLE.
- b. Turbine Trip-Turbine Stop Valve Closure The Turbine TripTurbine Stop Valve Closure trip Function anticipates the loss of heat removal capabilities of the secondary system following a turbine trip from a power level below the P-9 setpoint, approximately 50% power. This action will not actuate a reactor trip. The trip Function anticipates the loss of secondary heat removal capability that occurs when the stop valves close.
Tripping the reactor in anticipation of loss of secondary heat removal acts to minimize the pressure and temperature transient on the reactor. This trip Function will not and is not required to operate in the presence of a single channel failure. The unit is designed to withstand a complete loss of load and not sustain core damage or challenge the RCS pressure limitations. Core protection is provided by the Pressurizer PressureHigh trip Function, and RCS integrity is ensured by the (continued)
Watts Bar-Unit 1 B 3.3-30 Revision 13 Amendment 7, XX
Enclosure Evaluation of Proposed Technical Specification Change ATTACHMENT 3 Proposed TS Changes (Final Typed) for WBN Unit 1 CNL-17-026
RTS Instrumentation 3.3.1 Table 3.3.1-1 (page 4 of 9)
Reactor Trip System Instrumentation APPLICABLE MODES NOMINAL OR OTHER REQUIRED SURVEILLANCE ALLOWABLE TRIP FUNCTION SPECIFIED CHANNELS CONDITIONS REQUIREMENTS VALUE SETPOINT CONDITIONS
- 13. SG Water Level -- 1, 2 3/SG U SR 3.3.1.1 16.4% of 17% of Low-low SR 3.3.1.7 narrow narrow SR 3.3.1.10 range span range span Coincident with: SR 3.3.1.15 a) Vessel T 1, 2 3 V SR 3.3.1.7 Vessel T Vessel T Equivalent SR 3.3.1.10 variable input variable input to power 52.6% RTP 50% RTP 50% RTP With a time 1.01 Ts Ts (Refer delay (Ts) (Refer to to Note 3, if one steam Note 3, Page 3.3-23) generator is Page 3.3-23) affected or A time delay 1.01 Tm Tm (Refer (Tm) if two (Refer to to Note 3, or more steam Note 3, Page 3.3-23) generators are Page 3.3-23) affected OR b) Vessel T 1, 2 3 V SR 3.3.1.7 Vessel T Vessel T Equivalent to SR 3.3.1.10 variable input variable input power > 50% 52.6% RTP 50% RTP RTP with no time delay (Ts and Tm =
0)
- 14. Turbine Trip (i) (g)(h)
(g) If the as found channel setpoint is outside its predefined as found tolerance, then the channel shall be evaluated to verify that it is functioning as required before returning the channel to service.
(h) 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.
(i) Above the P-9 (Power Range Neutron Flux) interlock.
Watts Bar-Unit 1 3.3-18 Amendment 7, XX
Enclosure Evaluation of Proposed Technical Specification Change ATTACHMENT 4 Proposed TS Bases Changes (Final Typed) for WBN Unit 1 (For Information Only)
CNL-17-026
RTS Instrumentation B 3.3.1 Bases APPLICABLE a. Turbine Trip-Low Fluid Oil Pressure (continued)
SAFETY ANALYSES LCO, and power, will not actuate a reactor trip. Three APPLICABILITY pressure switches monitor the control oil pressure in the Turbine Electrohydraulic Control System high pressure header. A low pressure condition sensed by two-out-of-three pressure switches will actuate a reactor trip. These pressure switches do not provide any input to the control system. The unit is designed to withstand a complete loss of load and not sustain core damage or challenge the RCS pressure limitations. Core protection is provided by the Pressurizer PressureHigh trip Function and RCS integrity is ensured by the pressurizer safety valves.
The LCO requires three channels of Turbine Trip Low Fluid Oil Pressure to be OPERABLE in MODE 1 above P-9.
Below the P-9 setpoint, a turbine trip does not actuate a reactor trip. In MODE 2, 3, 4, 5, or 6, there is no potential for a turbine trip, and the Turbine TripLow Fluid Oil Pressure trip Function does not need to be OPERABLE.
- b. Turbine Trip-Turbine Stop Valve Closure The Turbine TripTurbine Stop Valve Closure trip Function anticipates the loss of heat removal capabilities of the secondary system following a turbine trip from a power level below the P-9 setpoint, approximately 50% power. This action will not actuate a reactor trip. The trip Function anticipates the loss of secondary heat removal capability that occurs when the stop valves close.
Tripping the reactor in anticipation of loss of secondary heat removal acts to minimize the pressure and temperature transient on the reactor. This trip Function will not and is not required to operate in the presence of a single channel failure. The unit is designed to withstand a complete loss of load and not sustain core damage or challenge the RCS pressure limitations. Core protection is provided by the Pressurizer PressureHigh trip Function, and RCS integrity is ensured by the (continued)
Watts Bar-Unit 1 B 3.3-30 Revision 13 Amendment 7, XX