Text

TSTF-573-T, Correct RPS Bases for MSIV and TSV Functions
	ML20302A220
Person / Time
Site:	Technical Specifications Task Force
Issue date:	10/27/2020
From:	Michelle Honcharik; Office of Nuclear Reactor Regulation
To:	; Technical Specifications Task Force
	Honcharik,M., NRR/DSS, 301-4151774
Shared Package
ML20302A210	List: ML20302A217; ML20302A218; ML20302A219; ML20302A220; ML20302A221;
References
	BWROG-138, Rev. 0, TSTF-573-T, Rev. 0
	Download: ML20302A220 (32)
	v • d • e

BWROG-138, Rev. 0 TSTF-573-T, Rev. 0 Technical Specifications Task Force Improved Standard Technical Specifications Change Traveler Correct RPS Bases for MSIV and TSV Functions NUREGs Affected: 1430 1431 1432 1433 1434 2194 Note: This "T" Traveler has been reviewed and approved by the Technical Specification Task Force and is made available as a template for plant-specific license amendments. This Traveler has not been reviewed and approved by the Nuclear Regulatory Commission.

Classification: 2) Bases Only Change Recommended for CLIIP?: No Correction or Improvement: Correction NRC Fee Status:

Changes Marked on ISTS Rev 4.0 See attached.

Revision History OG Revision 0 Revision Status: Active Revision Proposed by: BWROG Revision

Description:

Original Issue Owners Group Review Information Date Originated by OG: 10-May-18 Owners Group Comments Comments received and incorporated.

Owners Group Resolution: Approved Date: 01-Jul-18 TSTF Review Information TSTF Received Date: 18-Jul-18 Date Distributed for Review 18-Jul-18 TSTF Comments:

(No Comments)

TSTF Resolution: Approved for Use Date: 06-Aug-18 Affected Technical Specifications S/A 3.3.1.1B Bases RPS Instrumentation NUREG(s)- 1433 1434 Only S/A 3.3.1.1A Bases RPS Instrumentation NUREG(s)- 1433 1434 Only Action 3.3.1.1B.C Bases RPS Instrumentation NUREG(s)- 1433 1434 Only Action 3.3.1.1A.C Bases RPS Instrumentation NUREG(s)- 1433 1434 Only 06-Aug-18 Copyright(C) 2018, EXCEL Services Corporation. Use by EXCEL Services associates, utility clients, and the U.S. Nuclear Regulatory Commission is granted. All other use without written permission is prohibited.

TSTF-573, Rev. 0

1.

SUMMARY

DESCRIPTION The Bases for the Boiling Water Reactor (BWR) Standard Technical Specifications (STS) TS 3.3.1.1, "Reactor Protection System (RPS) Instrumentation," describe the arrangement of the logic of the Main Steam Isolation Valve (MSIV) - Closure Function (Function 5 in NUREG-1433 and Function 6 in NUREG-14341). The Bases state that the RPS logic is arranged such that either the inboard or outboard MSIV on at least three main steam lines (MSLs) must close in order for a scram to occur. This description was inappropriately carried forward as a requirement in Required Action C.1 to necessitate both MSIV channels in three MSLs to be operable in both RPS trip systems (not necessarily the same MSLs for both trip systems) in order to assure RPS trip capability. This is unnecessarily restrictive as trip capability is maintained with at least one trip system logic in each trip system having both MSIV channels operable for two MSLs. These Bases sections are revised to reflect the plant design.

An analogous condition occurs for the Turbine Stop Valve (TSV) - Closure Function (Function 8 NUREG-1433) and TSV Closure, Trip Oil Pressure - Low Function (Function 9 NUREG-1434) in that the Bases state that three channels are required per trip system to maintain RPS trip capability. Under the design, trip capability is maintained with at least one trip system logic in both trip systems having two operable TSV channels. These Bases sections are revised to reflect the plant design.

2. DETAILED DESCRIPTION 2.1. Current Requirements The Applicable Safety Analyses, LCO, and Applicability Bases of TS 3.3.1.1, Function 5 (NUREG-1433) and Function 6 (NUREG-1434) state, in part:

MSIV closure signals are initiated from position switches located on each of the eight MSIVs. Each MSIV has two position switches; one inputs to RPS trip system A while the other inputs to RPS trip system B. Thus, each RPS trip system receives an input from eight Main Steam Isolation Valve - Closure channels, each consisting of one position switch. The logic for the Main Steam Isolation Valve - Closure Function is arranged such that either the inboard or outboard valve on three or more of the main steam lines must close in order for a scram to occur.

The Applicable Safety Analyses, LCO, and Applicability Bases of TS 3.3.1.1, Function 8 (NUREG-1433) states, in part:

Turbine Stop Valve - Closure signals are initiated from position switches located on each of the four TSVs. Two independent position switches are associated with each stop valve.

One of the two switches provides input to RPS trip system A; the other, to RPS trip system B. Thus, each RPS trip system receives an input from four Turbine Stop Valve -

1 NUREG-1433 is based on the BWR/4 plant design, but is also applicable of the BWR/2, BWR/3, and, for some requirements, to the BWR/5 plant designs. NUREG-1434 is based on the BWR/6 plant design, and is applicable, for some requirements, to the BWR/5 plant design.

1

TSTF-573, Rev. 0 Closure channels, each consisting of one position switch. The logic for the Turbine Stop Valve - Closure Function is such that three or more TSVs must be closed to produce a scram.

Eight channels of Turbine Stop Valve - Closure Function, with four channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function even if one TSV should fail to close.

The Applicable Safety Analyses, LCO, and Applicability Bases of TS 3.3.1.1, Function 9 (NUREG-1434) states, in part:

Turbine Stop Valve Closure, Trip Oil Pressure - Low signals are initiated by the electrohydraulic control (EHC) fluid pressure at each stop valve. Two independent pressure transmitters are associated with each stop valve. One of the two transmitters provides input to RPS trip system A; the other, to RPS trip system B. Thus, each RPS trip system receives an input from four Turbine Stop Valve Closure, Trip Oil Pressure -

Low channels, each consisting of one pressure transmitter. The logic for the Turbine Stop Valve Closure, Trip Oil Pressure - Low Function is such that three or more TSVs must be closed to produce a scram.

Eight channels of Turbine Stop Valve Closure, Trip Oil Pressure - Low Function, with four channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function even if one TSV should fail to close.

The Bases of Required Action C.1 state, in part:

Required Action C.1 is intended to ensure that appropriate actions are taken if multiple, inoperable, untripped channels within the same trip system for the same Function result in the Function not maintaining RPS trip capability. A Function is considered to be maintaining RPS trip capability when sufficient channels are OPERABLE or in trip (or the associated trip system is in trip), such that both trip systems will generate a trip signal from the given Function on a valid signal. For the typical Function with one-out-of-two taken twice logic and the IRM and APRM Functions, this would require both trip systems to have one channel OPERABLE or in trip (or the associated trip system in trip). For Function 5 (Main Steam Isolation Valve - Closure), this would require both trip systems to have each channel associated with the MSIVs in three main steam lines (not necessarily the same main steam lines for both trip systems) OPERABLE or in trip (or the associated trip system in trip).

For Function 8 (Turbine Stop Valve - Closure) [Function 9 Turbine Stop Valve Closure, Trip Oil Pressure - Low], this would require both trip systems to have three channels, each OPERABLE or in trip (or the associated trip system in trip).

2.2. Reason for the Proposed Change There have been several reportable events (e.g., Fermi 2 LER 2017-001 and Monticello LER 2017-006) involving the use of a test box during the conduct of Channel Functional Testing that 2

TSTF-573, Rev. 0 would defeat either the MSIV channels of two MSLs in one RPS trip logic, or two TSV channels in one RPS trip logic due to the parallel configuration of those channel output contacts in the trip logic. Although trip capability was maintained (as described in Section 3), the minimum number of channels per trip system described in the Bases for Required Action C.1 was not met (three MSLs or TSV channels per trip system). These events prompted a review by the BWR Owners Group of the accuracy and clarity of the Bases for these functions and Required Action C.1.

2.3. Description of the Proposed Change The Applicable Safety Analyses, LCO, and Applicability Bases of TS 3.3.1.1, Function 5 (NUREG-1433) and Function 6 (NUREG-1434) are revised as follows (underlined text indicates additions, struck-through text indicates removal):

MSIV closure signals are initiated from position switches located on each of the eight MSIVs. Each MSIV has two position switches; one inputs to RPS trip system A while the other inputs to RPS trip system B. Each inboard and outboard MSIV inputs to a main steam line channel in each trip system, and each of the two trip logics within each RPS trip system receive parallel inputs from two of the four main steam lines. Thus, each RPS trip system receives an input from eight Main Steam Isolation Valve - Closure channels, each consisting of one position switch. The logic for the Main Steam Isolation Valve -

Closure Function is arranged such that either the inboard or outboard valve on both three or more of the main steam lines in one of the two trip logics in each RPS trip system must close in order for a scram to occur.

The Applicable Safety Analyses, LCO, and Applicability Bases of TS 3.3.1.1, Function 8 (NUREG-1433) is revised to read:

Turbine Stop Valve - Closure signals are initiated from position switches located on each of the four TSVs. Two independent position switches are associated with each stop valve.

One of the two switches provides input to RPS trip system A; the other, to RPS trip system B. Each of the two trip system logics within each RPS trip system receive parallel inputs from two of the four turbine stop valves. Thus, each RPS trip system receives an input from four Turbine Stop Valve - Closure channels, each consisting of one position switch. The logic for the Turbine Stop Valve - Closure Function is such that two three or more TSVs in one of the two trip logics in each RPS trip system must be closed to produce a scram.

Eight channels of Turbine Stop Valve - Closure Function, with four channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signal even if one TSV should fail to close.

3

TSTF-573, Rev. 0 The Applicable Safety Analyses, LCO, and Applicability Bases of TS 3.3.1.1, Function 9 (NUREG-1434) is revised to read:

Turbine Stop Valve Closure, Trip Oil Pressure - Low signals are initiated by the electrohydraulic control (EHC) fluid pressure at each stop valve. Two independent pressure transmitters are associated with each stop valve. One of the two transmitters provides input to RPS trip system A; the other, to RPS trip system B. Each of the two trip system logics within each RPS trip system receive parallel inputs from two of the four turbine stop valves. Thus, each RPS trip system receives an input from four Turbine Stop Valve Closure, Trip Oil Pressure - Low channels, each consisting of one pressure transmitter. The logic for the Turbine Stop Valve Closure, Trip Oil Pressure - Low Function is such that two three or more TSVs in one of the two trip logics in each RPS trip system must be closed to produce a scram.

Eight channels of Turbine Stop Valve Closure, Trip Oil Pressure - Low Function, with four channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signal even if one TSV should fail to close.

The NUREG-1433 and NUREG-1434 Bases of Required Action C.1 are revised to read:

Required Action C.1 is intended to ensure that appropriate actions are taken if multiple, inoperable, untripped channels within the same trip system for the same Function result in the Function not maintaining RPS trip capability. A Function is considered to be maintaining RPS trip capability when sufficient channels are OPERABLE or in trip (or the associated trip system is in trip), such that both trip systems will generate a trip signal from the given Function on a valid signal. For the typical Function with one-out-of-two taken twice logic and the IRM and APRM Functions, this would require both trip systems to have one channel OPERABLE or in trip (or the associated trip system in trip). For Function 5 [6] (Main Steam Isolation Valve - Closure), this maintaining RPS trip capability would require at least one trip logic in both trip systems to have each channel associated with the MSIVs in two three main steam lines (at least three different main steam lines total for both trip systems not necessarily the same MSLs for both trip systems) OPERABLE or in trip (or the associated trip system in trip).

For Function 8 (Turbine Stop Valve - Closure) [Function 9 Turbine Stop Valve Closure, Trip Oil Pressure - Low], this maintaining RPS trip capability would require at least one trip system logic in both trip systems to have two three channels (at least three different turbine stop valves total for both trip systems), each OPERABLE or in trip (or the associated trip system in trip).

The proposed change is a change to the TS Bases. These changes are applicable to the Bases for RPS Instrumentation both with and without a setpoint control program (B 3.3.1.1A and B). Title 10 of the Code of Federal Regulations (10 CFR), Part 50.36, states, "A summary statement of the bases or reasons for such specifications, other than those covering administrative controls, shall 4

TSTF-573, Rev. 0 also be included in the application, but shall not become part of the technical specifications." A licensee may make changes to the TS Bases without prior NRC review and approval in accordance with the Technical Specifications Bases Control Program.

3. TECHNICAL EVALUATION The RPS logic for the MSIV - Closure Function is shown on Figure 1 (although it is from the Hatch Final Safety Analysis Report, it is representative of the logic for the BWR designs). The A and B RPS trip systems each have two trip logics. Each trip logic contains output contacts from two of the four MSL channels (The vendor design documentation refers to the MSLs as channels) configured in parallel. The logic is 1-out-of-2-taken twice, which means one of the two trip logic relay closing coils must de-energize in each trip system trip to product a scram.

Having any three MSL channels operable in both trip systems will ensure trip capability. From the vendor design documentation, the basis for this arrangement is to allow one MSL to be taken out of service (i.e., the MSL is isolated) without either causing or preventing a scram. This is unrelated to the single failure criteria. There is no single failure that would cause any single MSL to not isolate on a valid signal. However, it should be noted that with one MSL out of service, the RPS trip system is no longer single failure proof. This design feature was inappropriately described in the Bases of Required Action C.1 as requiring three operable MSL channels per trip system (not necessarily the same MSL in each trip system) as the minimum functional capability.

The problems with these Bases statements are: 1) it was never part of the logic design feature that different MSLs could be operable in both trip systems, and 2) this creates an implication over and above the single failure criterion that trip capability requires the postulation of any single MSL to close. This is not required by IEEE-279-1971, Criteria for Protection Systems for Nuclear Generating Stations, and is overly restrictive. It can readily be seen on Figure 1 that only two MSL channels associated with one trip logic in each trip system are required to maintain trip capability. However, the proposed parenthetical statement in the Bases describes the design feature that the closure of at least three MSLs are required to produce a scram.

Similarly, the RPS logic for the NUREG-1433 TSV - Closure and the NUREG-1434 TSV Closure, Trip Oil Pressure - Low Functions is shown on Figure 2. The A and B RPS trip systems each have two trip logics. Each trip logic contains output contacts from two of the four TSV channels configured in parallel. The logic is 1-out-of-2-taken twice, which means one of the two trip logic relay closing coils must de-energize in each trip system trip to produce a scram.

Having any three TSV channels operable will ensure trip capability, although this configuration is no longer single failure proof. This design feature was described in the Bases of Required Action C.1 as requiring three operable TSV channels per trip system as the minimum functional capability. This would be valid if the single failure criteria were applicable. However, as stated in the C.1 Bases, this Required Action is for conditions where multiple, inoperable, untripped channels in one trip system exist. Under such conditions, single failure criteria is not applicable (i.e., the time spent in this condition is limited by the TS Action). Absent considerations of single failure, it can be seen on Figure 2 that only two TSV channels associated with one trip logic in each trip system is required to maintain trip capability. Consistent with the MSIV - Closure Function, a parenthetical statement is inserted in the Bases to describe the design feature that the closure of at least three TSVs are required to produce a scram.

5

TSTF-573, Rev. 0 TSTF-231, "Reword Bases for Turbine Stop Valve (TSV) Closure function of RPS Instrumentation LCO," approved by the NRC on June 13, 2000 and incorporated into Revision 2 of the STS, revised the wording for NUREG-1433, Function 8, and NUREG-1434, Function 9:

Eight channels of Turbine Stop Valve - Closure [Turbine Stop Valve Closure, Trip Oil Pressure - Low] Function, with four channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function even if one TSV should fail to close.

This wording is subject to misinterpretation, as it can be read to imply that trip capability is maintained with a failure of a TSV to close combined with an additional single instrument failure. It can seen on Figure 2 that trip capability is not assured with that combination of failures. The wording is revised to be consistent with the analogous discussion of the MSIV -

Closure function.

Conclusion The proposed Bases change is made under the provisions of the TS Bases Control Program.

This change removes incorrect information regarding the number of MSLs and TSV channels needed to be operable in order to maintain RPS trip capability.

4. REGULATORY EVALUATION A regulatory evaluation is not required for a TS Bases change.

5. REFERENCES None 6

TSTF-573, Rev. 0 Figure 1 RPS Logic for the MSIV - Closure Function 7

TSTF-573, Rev. 0 Figure 2 RPS Logic for the TSV - Closure Function 8

TSTF-573, Rev. 0 Bases Markup 9

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

Four channels of Reactor Vessel Water Level - Low, Level 3 Function, with two channels in each trip system arranged in a one-out-of-two logic, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signal.

The Reactor Vessel Water Level - Low, Level 3 Allowable Value is selected to ensure that during normal operation the separator skirts are not uncovered (this protects available recirculation pump net positive suction head (NPSH) from significant carryunder) and, for transients involving loss of all normal feedwater flow, initiation of the low pressure ECCS subsystems at Reactor Vessel Water - Low Low Low, Level 1 will not be required.

The Function is required in MODES 1 and 2 where considerable energy exists in the RCS resulting in the limiting transients and accidents. ECCS initiations at Reactor Vessel Water Level - Low Low, Level 2 and Low Low Low, Level 1 provide sufficient protection for level transients in all other MODES.

5. Main Steam Isolation Valve - Closure MSIV closure results in loss of the main turbine and the condenser as a heat sink for the nuclear steam supply system and indicates a need to shut down the reactor to reduce heat generation. Therefore, a reactor scram is initiated on a Main Steam Isolation Valve - Closure signal before the MSIVs are completely closed in anticipation of the complete loss of the normal heat sink and subsequent overpressurization transient.

However, for the overpressurization protection analysis of Reference 5, the Average Power Range Monitor Fixed Neutron Flux - High Function, along with the S/RVs, limits the peak RPV pressure to less than the ASME Code limits. That is, the direct scram on position switches for MSIV closure events is not assumed in the overpressurization analysis.

Additionally, MSIV closure is assumed in the transients analyzed in Reference 8 (e.g., low steam line pressure, manual closure of MSIVs, high steam line flow). The reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the ECCS, ensures that the fuel peak cladding temperature remains below the limits of 10 CFR 50.46.

MSIV closure signals are initiated from position switches located on each of the eight MSIVs. Each MSIV has two position switches; one inputs to RPS trip system A while the other inputs to RPS trip system B. Each inboard and outboard MSIV inputs to a main steam line channel in each trip system, and each of the two trip logics within each RPS trip system receive parallel inputs from two of the four main steam lines. Thus, each channels, each consisting of one position switch. The BASES RPS trip General Electric BWR/4 STS B 3.3.1.1A-14 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued) system receives an input from eight Main Steam Isolation Valve - Closure channels, each consisting of one position switch. The BASES logic for the Main Steam Isolation Valve - Closure Function is arranged such that either the inboard or outboard valve on boththree or more of the main steam lines in one of the two trip logics in each RPS trip system must close in order for a scram to occur.

The Main Steam Isolation Valve - Closure Allowable Value is specified to ensure that a scram occurs prior to a significant reduction in steam flow, thereby reducing the severity of the subsequent pressure transient.

Sixteen channels of the Main Steam Isolation Valve - Closure Function, with eight channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude the scram from this Function on a valid signal. This Function is only required in MODE 1 since, with the MSIVs open and the heat generation rate high, a pressurization transient can occur if the MSIVs close. In MODE 2, the heat generation rate is low enough so that the other diverse RPS functions provide sufficient protection.

6. Drywell Pressure - High High pressure in the drywell could indicate a break in the RCPB. A reactor scram is initiated to minimize the possibility of fuel damage and to reduce the amount of energy being added to the coolant and the drywell.

The Drywell Pressure - High Function is a secondary scram signal to Reactor Vessel Water Level - Low, Level 3 for LOCA events inside the drywell. However, no credit is taken for a scram initiated from this Function for any of the DBAs analyzed in the FSAR. This Function was not specifically credited in the accident analysis, but it is retained for the overall redundancy and diversity of the RPS as required by the NRC approved licensing basis.

High drywell pressure signals are initiated from four pressure transmitters that sense drywell pressure. The Allowable Value was selected to be as low as possible and indicative of a LOCA inside primary containment.

Four channels of Drywell Pressure - High Function, with two channels in each trip system arranged in a one-out-of-two logic, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signal. The Function is required in MODES 1 and 2 where considerable energy exists in the RCS, resulting in the limiting transients and accidents.

General Electric BWR/4 STS B 3.3.1.1A-15 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued) 7a, 7b. Scram Discharge Volume Water Level - High The SDV receives the water displaced by the motion of the CRD pistons during a reactor scram. Should this volume fill to a point where there is insufficient volume to accept the displaced water, control rod insertion would be hindered. Therefore, a reactor scram is initiated while the remaining free volume is still sufficient to accommodate the water from a full core scram. The two types of Scram Discharge Volume Water Level -

High Functions are an input to the RPS logic. No credit is taken for a scram initiated from these Functions for any of the design basis accidents or transients analyzed in the FSAR. However, they are retained to ensure the RPS remains OPERABLE.

SDV water level is measured by two diverse methods. The level in each of the two SDVs is measured by two float type level switches and two thermal probes for a total of eight level signals. The outputs of these devices are arranged so that there is a signal from a level switch and a thermal probe to each RPS logic channel. The level measurement instrumentation satisfies the recommendations of Reference 9.

The Allowable Value is chosen low enough to ensure that there is sufficient volume in the SDV to accommodate the water from a full scram.

Four channels of each type of Scram Discharge Volume Water Level -

High Function, with two channels of each type in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from these Functions on a valid signal. These Functions are required in MODES 1 and 2, and in MODE 5 with any control rod withdrawn from a core cell containing one or more fuel assemblies, since these are the MODES and other specified conditions when control rods are withdrawn. At all other times, this Function may be bypassed.

8. Turbine Stop Valve - Closure Closure of the TSVs results in the loss of a heat sink that produces reactor pressure, neutron flux, and heat flux transients that must be limited. Therefore, a reactor scram is initiated at the start of TSV closure in anticipation of the transients that would result from the closure of these valves. The Turbine Stop Valve - Closure Function is the primary scram signal for the turbine trip event analyzed in Reference 8. For this event, the reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the End of Cycle Recirculation Pump Trip (EOC-RPT) System, ensures that the MCPR SL is not exceeded.

General Electric BWR/4 STS B 3.3.1.1A-16 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

Turbine Stop Valve - Closure signals are initiated from position switches located on each of the four TSVs. Two independent position switches are associated with each stop valve. One of the two switches provides input to RPS trip system A; the other, to RPS trip system B. Each of the two trip logics within each RPS trip system receives parallel inputs from two of the four turbine stop valves. Thus, each RPS trip system receives an input from four Turbine Stop Valve - Closure channels, each consisting of one position switch. The logic for the Turbine Stop Valve - Closure Function is such that twothree or more TSVs in one of the two trip logics in each RPS trip system must be closed to produce a scram. This Function must be enabled at THERMAL POWER 30% RTP. This is normally accomplished automatically by pressure transmitters sensing turbine first stage pressure; therefore, to consider this Function OPERABLE, the turbine bypass valves must remain shut at THERMAL POWER 30% RTP.

The Turbine Stop Valve - Closure Allowable Value is selected to be high enough to detect imminent TSV closure, thereby reducing the severity of the subsequent pressure transient.

Eight channels of Turbine Stop Valve - Closure Function, with four channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signaleven if one TSV should fail to close. This Function is required, consistent with analysis assumptions, whenever THERMAL POWER is 30% RTP. This Function is not required when THERMAL POWER is < 30% RTP since the Reactor Vessel Steam Dome Pressure -

High and the Average Power Range Monitor Fixed Neutron Flux - High Functions are adequate to maintain the necessary safety margins.

9. Turbine Control Valve Fast Closure, Trip Oil Pressure - Low Fast closure of the TCVs results in the loss of a heat sink that produces reactor pressure, neutron flux, and heat flux transients that must be limited. Therefore, a reactor scram is initiated on TCV fast closure in anticipation of the transients that would result from the closure of these valves. The Turbine Control Valve Fast Closure, Trip Oil Pressure - Low Function is the primary scram signal for the generator load rejection event analyzed in Reference 8. For this event, the reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the EOC-RPT System, ensures that the MCPR SL is not exceeded.

Turbine Control Valve Fast Closure, Trip Oil Pressure - Low signals are initiated by the electrohydraulic control (EHC) fluid pressure at each control valve. One pressure transmitter is associated with each control valve, and the signal from each transmitter is assigned to a separate RPS General Electric BWR/4 STS B 3.3.1.1A-17 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES ACTIONS (continued) inoperable channels are all in different Functions). The decision of which trip system is in the more degraded state should be based on prudent judgment and take into account current plant conditions (i.e., what MODE the plant is in). If this action would result in a scram or RPT, it is permissible to place the other trip system or its inoperable channels in trip.

The 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months Completion Time is judged acceptable based on the remaining capability to trip, the diversity of the sensors available to provide the trip signals, the low probability of extensive numbers of inoperabilities affecting all diverse Functions, and the low probability of an event requiring the initiation of a scram.

Alternately, if it is not desired to place the inoperable channels (or one trip system) in trip (e.g., as in the case where placing the inoperable channel or associated trip system in trip would result in a scram [or RPT]),

Condition D must be entered and its Required Action taken.

C.1 Required Action C.1 is intended to ensure that appropriate actions are taken if multiple, inoperable, untripped channels within the same trip system for the same Function result in the Function not maintaining RPS trip capability. A Function is considered to be maintaining RPS trip capability when sufficient channels are OPERABLE or in trip (or the associated trip system is in trip), such that both trip systems will generate a trip signal from the given Function on a valid signal. For the typical Function with one-out-of-two taken twice logic and the IRM and APRM Functions, this would require both trip systems to have one channel OPERABLE or in trip (or the associated trip system in trip). For Function 5 (Main Steam Isolation Valve - Closure), thismaintaining RPS trip capability would require at least one trip system logic in both trip systems to have each channel associated with the MSIVs in twothree main steam lines (at least three different main steam lines total for both trip systemsnot necessarily the same main steam lines for both trip systems) OPERABLE or in trip (or the associated trip system in trip).

For Function 8 (Turbine Stop Valve - Closure), thismaintaining RPS trip capability would require at least one trip system logic in both trip systems to have twothree channels (at least three different turbine stop valves total for both trip systems), each OPERABLE or in trip (or the associated trip system in trip).

The Completion Time is intended to allow the operator time to evaluate and repair any discovered inoperabilities. The 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Completion Time is General Electric BWR/4 STS B 3.3.1.1A-21 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A acceptable because it minimizes risk while allowing time for restoration or tripping of channels.

General Electric BWR/4 STS B 3.3.1.1A-22 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (With Setpoint Control Program)

B 3.3.1.1B BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

Four channels of Reactor Vessel Water Level - Low, Level 3 Function, with two channels in each trip system arranged in a one-out-of-two logic, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signal.

The Reactor Vessel Water Level - Low, Level 3 Allowable Value is selected to ensure that during normal operation the separator skirts are not uncovered (this protects available recirculation pump net positive suction head (NPSH) from significant carryunder) and, for transients involving loss of all normal feedwater flow, initiation of the low pressure ECCS subsystems at Reactor Vessel Water - Low Low Low, Level 1 will not be required.

The Function is required in MODES 1 and 2 where considerable energy exists in the RCS resulting in the limiting transients and accidents. ECCS initiations at Reactor Vessel Water Level - Low Low, Level 2 and Low Low Low, Level 1 provide sufficient protection for level transients in all other MODES.

5. Main Steam Isolation Valve - Closure MSIV closure results in loss of the main turbine and the condenser as a heat sink for the nuclear steam supply system and indicates a need to shut down the reactor to reduce heat generation. Therefore, a reactor scram is initiated on a Main Steam Isolation Valve - Closure signal before the MSIVs are completely closed in anticipation of the complete loss of the normal heat sink and subsequent overpressurization transient.

However, for the overpressurization protection analysis of Reference 5, the Average Power Range Monitor Fixed Neutron Flux - High Function, along with the S/RVs, limits the peak RPV pressure to less than the ASME Code limits. That is, the direct scram on position switches for MSIV closure events is not assumed in the overpressurization analysis.

Additionally, MSIV closure is assumed in the transients analyzed in Reference 8 (e.g., low steam line pressure, manual closure of MSIVs, high steam line flow). The reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the ECCS, ensures that the fuel peak cladding temperature remains below the limits of 10 CFR 50.46.

MSIV closure signals are initiated from position switches located on each of the eight MSIVs. Each MSIV has two position switches; one inputs to RPS trip system A while the other inputs to RPS trip system B. Each inboard and outboard MSIV inputs to a main steam line channel in each trip system, and each of the two trip logics within each RPS trip system receive parallel inputs from two of the four main steam lines. Thus, each RPS trip system receives an input from eight Main Steam Isolation Valve General Electric BWR/4 STS B 3.3.1.1B-14 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (With Setpoint Control Program)

B 3.3.1.1B BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

- Closure channels, each consisting of one position switch. The logic for the Main Steam Isolation Valve - Closure Function is arranged such that either the inboard or outboard valve on boththree or more of the main steam lines in one of the two trip logics in each RPS trip system must close in order for a scram to occur.

The Main Steam Isolation Valve - Closure Allowable Value is specified to ensure that a scram occurs prior to a significant reduction in steam flow, thereby reducing the severity of the subsequent pressure transient.

Sixteen channels of the Main Steam Isolation Valve - Closure Function, with eight channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude the scram from this Function on a valid signal. This Function is only required in MODE 1 since, with the MSIVs open and the heat generation rate high, a pressurization transient can occur if the MSIVs close. In MODE 2, the heat generation rate is low enough so that the other diverse RPS functions provide sufficient protection.

6. Drywell Pressure - High High pressure in the drywell could indicate a break in the RCPB. A reactor scram is initiated to minimize the possibility of fuel damage and to reduce the amount of energy being added to the coolant and the drywell.

The Drywell Pressure - High Function is a secondary scram signal to Reactor Vessel Water Level - Low, Level 3 for LOCA events inside the drywell. However, no credit is taken for a scram initiated from this Function for any of the DBAs analyzed in the FSAR. This Function was not specifically credited in the accident analysis, but it is retained for the overall redundancy and diversity of the RPS as required by the NRC approved licensing basis.

High drywell pressure signals are initiated from four pressure transmitters that sense drywell pressure. The Allowable Value was selected to be as low as possible and indicative of a LOCA inside primary containment.

Four channels of Drywell Pressure - High Function, with two channels in each trip system arranged in a one-out-of-two logic, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signal. The Function is required in MODES 1 and 2 where considerable energy exists in the RCS, resulting in the limiting transients and accidents.

General Electric BWR/4 STS B 3.3.1.1B-15 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (With Setpoint Control Program)

B 3.3.1.1B BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued) 7a, 7b. Scram Discharge Volume Water Level - High The SDV receives the water displaced by the motion of the CRD pistons during a reactor scram. Should this volume fill to a point where there is insufficient volume to accept the displaced water, control rod insertion would be hindered. Therefore, a reactor scram is initiated while the remaining free volume is still sufficient to accommodate the water from a full core scram. The two types of Scram Discharge Volume Water Level -

High Functions are an input to the RPS logic. No credit is taken for a scram initiated from these Functions for any of the design basis accidents or transients analyzed in the FSAR. However, they are retained to ensure the RPS remains OPERABLE.

SDV water level is measured by two diverse methods. The level in each of the two SDVs is measured by two float type level switches and two thermal probes for a total of eight level signals. The outputs of these devices are arranged so that there is a signal from a level switch and a thermal probe to each RPS logic channel. The level measurement instrumentation satisfies the recommendations of Reference 9.

The Allowable Value is chosen low enough to ensure that there is sufficient volume in the SDV to accommodate the water from a full scram.

Four channels of each type of Scram Discharge Volume Water Level -

High Function, with two channels of each type in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from these Functions on a valid signal. These Functions are required in MODES 1 and 2, and in MODE 5 with any control rod withdrawn from a core cell containing one or more fuel assemblies, since these are the MODES and other specified conditions when control rods are withdrawn. At all other times, this Function may be bypassed.

8. Turbine Stop Valve - Closure Closure of the TSVs results in the loss of a heat sink that produces reactor pressure, neutron flux, and heat flux transients that must be limited. Therefore, a reactor scram is initiated at the start of TSV closure in anticipation of the transients that would result from the closure of these valves. The Turbine Stop Valve - Closure Function is the primary scram signal for the turbine trip event analyzed in Reference 8. For this event, the reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the End of Cycle Recirculation Pump Trip (EOC-RPT) System, ensures that the MCPR SL is not exceeded.

General Electric BWR/4 STS B 3.3.1.1B-16 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (With Setpoint Control Program)

B 3.3.1.1B BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

Turbine Stop Valve - Closure signals are initiated from position switches located on each of the four TSVs. Two independent position switches are associated with each stop valve. One of the two switches provides input to RPS trip system A; the other, to RPS trip system B. Each of the two trip logics within each RPS trip system receives parallel inputs from two of the four turbine stop valves. Thus, each RPS trip system receives an input from four Turbine Stop Valve - Closure channels, each consisting of one position switch. The logic for the Turbine Stop Valve - Closure Function is such that twothree or more TSVs in one of the two trip logics in each RPS trip system must be closed to produce a scram. This Function must be enabled at THERMAL POWER 30% RTP. This is normally accomplished automatically by pressure transmitters sensing turbine first stage pressure; therefore, to consider this Function OPERABLE, the turbine bypass valves must remain shut at THERMAL POWER 30% RTP.

The Turbine Stop Valve - Closure Allowable Value is selected to be high enough to detect imminent TSV closure, thereby reducing the severity of the subsequent pressure transient.

Eight channels of Turbine Stop Valve - Closure Function, with four channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signaleven if one TSV should fail to close. This Function is required, consistent with analysis assumptions, whenever THERMAL POWER is 30% RTP. This Function is not required when THERMAL POWER is < 30% RTP since the Reactor Vessel Steam Dome Pressure -

High and the Average Power Range Monitor Fixed Neutron Flux - High Functions are adequate to maintain the necessary safety margins.

9. Turbine Control Valve Fast Closure, Trip Oil Pressure - Low Fast closure of the TCVs results in the loss of a heat sink that produces reactor pressure, neutron flux, and heat flux transients that must be limited. Therefore, a reactor scram is initiated on TCV fast closure in anticipation of the transients that would result from the closure of these valves. The Turbine Control Valve Fast Closure, Trip Oil Pressure - Low Function is the primary scram signal for the generator load rejection event analyzed in Reference 8. For this event, the reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the EOC-RPT System, ensures that the MCPR SL is not exceeded.

Turbine Control Valve Fast Closure, Trip Oil Pressure - Low signals are initiated by the electrohydraulic control (EHC) fluid pressure at each control valve. One pressure transmitter is associated with each control valve, and the signal from each transmitter is assigned to a separate RPS General Electric BWR/4 STS B 3.3.1.1B-17 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (With Setpoint Control Program)

B 3.3.1.1B BASES ACTIONS (continued) inoperable channels are all in different Functions). The decision of which trip system is in the more degraded state should be based on prudent judgment and take into account current plant conditions (i.e., what MODE the plant is in). If this action would result in a scram or RPT, it is permissible to place the other trip system or its inoperable channels in trip.

The 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months Completion Time is judged acceptable based on the remaining capability to trip, the diversity of the sensors available to provide the trip signals, the low probability of extensive numbers of inoperabilities affecting all diverse Functions, and the low probability of an event requiring the initiation of a scram.

Alternately, if it is not desired to place the inoperable channels (or one trip system) in trip (e.g., as in the case where placing the inoperable channel or associated trip system in trip would result in a scram [or RPT]),

Condition D must be entered and its Required Action taken.

C.1 Required Action C.1 is intended to ensure that appropriate actions are taken if multiple, inoperable, untripped channels within the same trip system for the same Function result in the Function not maintaining RPS trip capability. A Function is considered to be maintaining RPS trip capability when sufficient channels are OPERABLE or in trip (or the associated trip system is in trip), such that both trip systems will generate a trip signal from the given Function on a valid signal. For the typical Function with one-out-of-two taken twice logic and the IRM and APRM Functions, this would require both trip systems to have one channel OPERABLE or in trip (or the associated trip system in trip). For Function 5 (Main Steam Isolation Valve - Closure), thismaintaining RPS trip capability would require at least one trip system logic in both trip systems to have each channel associated with the MSIVs in twothree main steam lines (at least three different main steam lines total for both trip systemsnot necessarily the same main steam lines for both trip systems) OPERABLE or in trip (or the associated trip system in trip).

For Function 8 (Turbine Stop Valve - Closure), thismaintaining RPS trip capability would require at least one trip system logic in both trip systems to have twothree channels (at least three different turbine stop valves total for both trip systems), each OPERABLE or in trip (or the associated trip system in trip).

The Completion Time is intended to allow the operator time to evaluate and repair any discovered inoperabilities. The 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Completion Time is General Electric BWR/4 STS B 3.3.1.1B-21 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (With Setpoint Control Program)

B 3.3.1.1B acceptable because it minimizes risk while allowing time for restoration or tripping of channels.

General Electric BWR/4 STS B 3.3.1.1B-22 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

6. Main Steam Isolation Valve - Closure MSIV closure results in loss of the main turbine and the condenser as a heat sink for the Nuclear Steam Supply System and indicates a need to shut down the reactor to reduce heat generation. Therefore, a reactor scram is initiated on a Main Steam Isolation Valve - Closure signal before the MSIVs are completely closed in anticipation of the complete loss of the normal heat sink and subsequent overpressurization transient.

However, for the overpressurization protection analysis of Reference 3, the Average Power Range Monitor Fixed Neutron Flux - High Function, along with the S/RVs, limits the peak RPV pressure to less than the ASME Code limits. That is, the direct scram on position switches for MSIV closure events is not assumed in the overpressurization analysis.

Additionally, MSIV closure is assumed in the transients analyzed in Reference 5 (e.g., low steam line pressure, manual closure of MSIVs, high steam line flow). The reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the ECCS, ensures that the fuel peak cladding temperature remains below the limits of 10 CFR 50.46.

MSIV closure signals are initiated from position switches located on each of the eight MSIVs. Each MSIV has two position switches; one inputs to RPS trip system A while the other inputs to RPS trip system B. Each inboard and outboard MSIV inputs to a main steam line channel in each trip system, and each of the two trip logics within each RPS trip system receive parallel inputs from two of the four main steam lines. Thus, each RPS trip system receives an input from eight Main Steam Isolation Valve

- Closure channels, each consisting of one position switch. The logic for the Main Steam Isolation Valve - Closure Function is arranged such that either the inboard or outboard valve on boththree or more of the main steam lines (MSLs) in one of the two logics in each RPS trip system must close in order for a scram to occur.

The Main Steam Isolation Valve - Closure Allowable Value is specified to ensure that a scram occurs prior to a significant reduction in steam flow, thereby reducing the severity of the subsequent pressure transient.

Sixteen channels of the Main Steam Isolation Valve - Closure Function with eight channels in each trip system are required to be OPERABLE to ensure that no single instrument failure will preclude the scram from this Function on a valid signal. This Function is only required in MODE 1 since, with the MSIVs open and the heat generation rate high, a pressurization transient can occur if the MSIVs close. In MODE 2, the heat generation rate is low enough so that the other diverse RPS functions provide sufficient protection.

General Electric BWR/6 STS B 3.3.1.1A-14 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

7. Drywell Pressure - High High pressure in the drywell could indicate a break in the RCPB. A reactor scram is initiated to minimize the possibility of fuel damage and to reduce the amount of energy being added to the coolant and the drywell.

The Drywell Pressure - High Function is a secondary scram signal to Reactor Vessel Water Level - Low, Level 3 for LOCA events inside the drywell. The value is retained for the overall redundancy and diversity of the RPS as required by the NRC approved licensing basis.

High drywell pressure signals are initiated from four pressure transmitters that sense drywell pressure. The Allowable Value was selected to be as low as possible and be indicative of a LOCA inside primary containment.

Four channels of Drywell Pressure - High Function, with two channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signal. The Function is required in MODES 1 and 2 where considerable energy exists in the RCS, resulting in the limiting transients and accidents.

8.a, 8.b. Scram Discharge Volume Water Level - High The SDV receives the water displaced by the motion of the CRD pistons during a reactor scram. Should this volume fill to a point where there is insufficient volume to accept the displaced water, control rod insertion would be hindered. Therefore, a reactor scram is initiated when the remaining free volume is still sufficient to accommodate the water from a full core scram. However, even though the two types of Scram Discharge Volume Water Level - High Functions are an input to the RPS logic, no credit is taken for a scram initiated from these Functions for any of the design basis accidents or transients analyzed in the FSAR. However, they are retained to ensure that the RPS remains OPERABLE.

SDV water level is measured by two diverse methods. The level in each of the two SDVs is measured by two float type level switches and two transmitters and trip units for a total of eight level signals. The outputs of these devices are arranged so that there is a signal from a level switch and a transmitter and trip unit to each RPS logic channel. The level measurement instrumentation satisfies the recommendations of Reference 9.

The Allowable Value is chosen low enough to ensure that there is sufficient volume in the SDV to accommodate the water from a full scram.

General Electric BWR/6 STS B 3.3.1.1A-15 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

Four channels of each type of Scram Discharge Volume Water Level -

High Function, with two channels of each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from these Functions on a valid signal. These Functions are required in MODES 1 and 2, and in MODE 5 with any control rod withdrawn from a core cell containing one or more fuel assemblies, since these are the MODES and other specified conditions when control rods are withdrawn. At all other times, this Function may be bypassed.

9. Turbine Stop Valve Closure, Trip Oil Pressure - Low Closure of the TSVs results in the loss of a heat sink that produces reactor pressure, neutron flux, and heat flux transients that must be limited. Therefore, a reactor scram is initiated at the start of TSV closure in anticipation of the transients that would result from the closure of these valves. The Turbine Stop Valve Closure, Trip Oil Pressure - Low Function is the primary scram signal for the turbine trip event analyzed in Reference 5. For this event, the reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the End of Cycle Recirculation Pump Trip (EOC-RPT) System, ensures that the MCPR SL is not exceeded.

Turbine Stop Valve Closure, Trip Oil Pressure - Low signals are initiated by the electrohydraulic control (EHC) fluid pressure at each stop valve.

Two independent pressure transmitters are associated with each stop valve. One of the two transmitters provides input to RPS trip system A; the other, to RPS trip system B. Each of the two trip logics within each RPS trip system receives parallel inputs from two of the four turbine stop valves. Thus, each RPS trip system receives an input from four Turbine Stop Valve Closure, Trip Oil Pressure - Low channels, each consisting of one pressure transmitter. The logic for the Turbine Stop Valve Closure, Trip Oil Pressure - Low Function is such that twothree or more TSVs in one of the two trip logics in each RPS trip system must be closed to produce a scram.

This Function must be enabled at THERMAL POWER 40% RTP. This is normally accomplished automatically by pressure transmitters sensing turbine first stage pressure; therefore, to consider this Function OPERABLE, the turbine bypass valves must remain shut at THERMAL POWER 40% RTP. The setpoint is feedwater temperature dependent as a result of the subcooling changes that affect the turbine first stage pressure/reactor power relationship. For RTP operation with feedwater temperature 420°F, an allowable setpoint of 26.9% of control valve wide open turbine first stage pressure is provided by the bypass function.

The allowable setpoint is reduced to 22.5% of control valve wide open turbine first stage pressure for RTP operation with feedwater temperature General Electric BWR/6 STS B 3.3.1.1A-16 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

> 370°F and < 420°F. The Turbine Stop Valve Closure, Trip Oil Pressure

- Low Allowable Value is selected to be high enough to detect imminent TSV closure thereby reducing the severity of the subsequent pressure transient.

Eight channels of Turbine Stop Valve Closure, Trip Oil Pressure - Low Function, with four channels in each trip system, are required to be OPERABLE to ensure that no single instrument failure will preclude a scram from this Function on a valid signaleven if one TSV should fail to close. This Function is required, consistent with analysis assumptions, whenever THERMAL POWER is 40% RTP. This Function is not required when THERMAL POWER is < 40% RTP since the Reactor Vessel Steam Dome Pressure - High and the Average Power Range Monitor Fixed Neutron Flux - High Functions are adequate to maintain the necessary safety margins.

10. Turbine Control Valve Fast Closure, Trip Oil Pressure - Low Fast closure of the TCVs results in the loss of a heat sink that produces reactor pressure, neutron flux, and heat flux transients that must be limited. Therefore, a reactor scram is initiated on TCV fast closure in anticipation of the transients that would result from the closure of these valves. The Turbine Control Valve Fast Closure, Trip Oil Pressure - Low Function is the primary scram signal for the generator load rejection event analyzed in Reference 5. For this event, the reactor scram reduces the amount of energy required to be absorbed and, along with the actions of the EOC-RPT System, ensures that the MCPR SL is not exceeded.

Turbine Control Valve Fast Closure, Trip Oil Pressure - Low signals are initiated by the EHC fluid pressure at each control valve. There is one pressure transmitter associated with each control valve, the signal from each transmitter being assigned to a separate RPS logic channel. This Function must be enabled at THERMAL POWER 40% RTP. This is normally accomplished automatically by pressure transmitters sensing turbine first stage pressure; therefore, to consider this Function OPERABLE, the turbine bypass valves must remain shut at THERMAL POWER 40% RTP. The basis for the setpoint of this automatic bypass is identical to that described for the Turbine Stop Valve Closure, Trip Oil Pressure - Low Function.

The Turbine Control Valve Fast Closure, Trip Oil Pressure - Low Allowable Value is selected high enough to detect imminent TCV fast closure.

General Electric BWR/6 STS B 3.3.1.1A-17 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (Without Setpoint Control Program)

B 3.3.1.1A BASES ACTIONS (continued)

The 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months Completion Time is judged acceptable based on the remaining capability to trip, the diversity of the sensors available to provide the trip signals, the low probability of extensive numbers of inoperabilities affecting all diverse Functions, and the low probability of an event requiring the initiation of a scram.

Alternately, if it is not desired to place the inoperable channels (or one trip system) in trip (e.g., as in the case where placing the inoperable channel or associated trip system in trip would result in a scram [or RPT]),

Condition D must be entered and its Required Action taken.

C.1 Required Action C.1 is intended to ensure that appropriate actions are taken if multiple, inoperable, untripped channels within the same trip system for the same Function result in the Function not maintaining RPS trip capability. A Function is considered to be maintaining RPS trip capability when sufficient channels are OPERABLE or in trip (or the associated trip system is in trip), such that both trip systems will generate a trip signal from the given Function on a valid signal. For the typical Function with one-out-of-two taken twice logic and the IRM and APRM Functions, this would require both trip systems to have one channel OPERABLE or in trip (or the associated trip system in trip). For Function 6 (Main Steam Isolation Valve - Closure), thismaintaining RPS trip capability would require at least one trip logic in both trip systems to have each channel associated with the MSIVs in twothree MSLs (at least three different main steam lines total for both trip systemsnot necessarily the same MSLs for both trip systems), OPERABLE or in trip (or the associated trip system in trip).

For Function 9 (Turbine Stop Valve Closure, Trip Oil Pressure - Low),

thismaintaining RPS trip capability would require at least one trip system logic in both trip systems to have twothree channels (at least three different turbine stop valves total for both trip systems), each OPERABLE or in trip (or the associated trip system in trip).

The Completion Time is intended to allow the operator time to evaluate and repair any discovered inoperabilities. The 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Completion Time is acceptable because it minimizes risk while allowing time for restoration or tripping of channels.

D.1 General Electric BWR/6 STS B 3.3.1.1A-21 Rev. 4.0

TSTF-573, Rev. 0 RPS Instrumentation (With Setpoint Control Program)

B 3.3.1.1B BASES APPLICABLE SAFETY ANALYSES, LCO, and APPLICABILITY (continued)

The Function is required in MODES 1 and 2 where considerable energy exists in the RCS resulting in the limiting transients and accidents. ECCS initiations at Reactor Vessel Water Level - Low Low, Level 2 and Low Low Low, Level 1 provide sufficient protection for level transients in all other MODES.

5. Reactor Vessel Water Level - High, Level 8 High RPV water level indicates a potential problem with the feedwater level control system, resulting in the addition of reactivity associated with the introduction of a significant amount of relatively cold feedwater.

Therefore, a scram is initiated at Level 8 to ensure that MCPR is maintained above the MCPR SL. The Reactor Vessel Water Level -

High, Level 8 Function is one of the many Functions assumed to be OPERABLE and capable of providing a reactor scram during transients analyzed in Reference 4. It is directly assumed in the analysis of feedwater controller failure, maximum demand (Ref. 5).

Reactor Vessel Water Level - High, Level 8 signals are initiated from four level transmitters that sense the difference between the pressure due to a constant column of water (reference leg) and the pressure due to the actual water level (variable leg) in the vessel. The Reactor Vessel Water Level - High, Level 8 Allowable Value is specified to ensure that the MCPR SL is not violated during the assumed transient.

Four channels of the Reactor Vessel Water Level - High, Level 8 Function, with two channels in each trip system arranged in a one-out-of-two logic, are available and are required to be OPERABLE when THERMAL POWER is 25% RTP to ensure that no single instrument failure will preclude a scram from this Function on a valid signal. With THERMAL POWER < 25% RTP, this Function is not required since MCPR is not a concern below 25% RTP.

6. Main Steam Isolation Valve - Closure MSIV closure results in loss of the main turbine and the condenser as a heat sink for the Nuclear Steam Supply System and indicates a need to shut down the reactor to reduce heat generation. Therefore, a reactor scram is initiated on a Main Steam Isolation Valve - Closure signal before the MSIVs are completely closed in anticipation of the complete loss of the normal heat sink and subsequent overpressurization transient.

However, for the overpressurization protection analysis of Reference 3, the Average Power Range Monitor Fixed Neutron Flux - High Function, along with the S/RVs, limits the peak RPV pressure to less than the ASME Code limits. That is, the direct scram on position switches for MSIV closure events is not assumed in the overpressurization analysis.

General Electric BWR/6 STS B 3.3.1.1B-13 Rev. 4.0