ML042440425
| ML042440425 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 08/06/2004 |
| From: | Rich Smith Entergy Nuclear South, Entergy Operations |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| W3F1-2004-0073 | |
| Download: ML042440425 (37) | |
Text
Attachment 4 To W3FI-2004-0073 Additional Information Regarding EPU Steam Generator Pressure - Low Setpoint Development
DRN No. 04-1235 Pages CALCULATION Init. Doc.: ER-W3-2003-0353-000 COVER PAGE El DRN Superseded: 03-551 El Calculation El DRNs Voided:
[9 DRN E Calculation SupersededNoided:
E1 As-BulltINo ICN Required l PendingliCN Required (verify current status In IDEAS)
Reason For Pending Status: (ER. T.S.. Change. etc.)
ER-W3-2003-0353-000 Calculation No: ECI92-019 Revision: 3
Title:
Plant Protection System Indicating and Recording Instrumentation Loop Uncertainty Calculation System: PPS Componentltqulpment Identifier: N/A Safety Code: Caic Code:
0 Yes (ANO/GGNS Only)
El No Study Calc:
El Quality YocEs No 10CFR50.59 Review Structure:
§ Addrosced in: ER-W3-2003-0353-000 Bm aEev.l Room______ Wall_ __
O Attached Coordinates:a El No LBD Impact R-Type: B13.16 Org. Code: (ANO/GGNS/RBS Only)
Keywords: None Topical Codes: (ANO Only)
, ,VIEWS 3 i /4204 Dv an8/412004 (NamerSignaturetDate) (Name/Signature/Date)
(Name/Signature/Date) 0 Design Verifier SupervisorlApproval Responsible Engineer il Reviewer Checker (Only As-Built OComments Attached DRNs Included in Revision)
E Comments Attached
CALCULATION CALCULATION NO: EC192-01 9 REFERENCE SHEET REVISION: o
- 1. DRNs INCORPORATED:
- 1. RELATIONSHIPS:
Document No. Sht Rev Input Output Impact DRNJTracking No.
Doc Doc YIN ECI01-006, DRN 03-1409 0 ED 0l N MI-005-463 El 0 y ER-W3-2003-0353-000 FSAR El 0 Y DRN 04-363 Tech. Specifications EJ 0 Y ER-W3-2001-1149-000 Passport CDB Ol 0 Y ER-W3-2003-0353-000 DBD-12 El 0 Y ER-W3-2003-0353-000 SD-PPS E 0 Y ER-W3-200343534000l OP-903-107 0 0 y ER-W3-2003-0353-000 OP-500-009 0 0 y ER-W3-2003-0353-000 OP-009-007 0d 0 Y ER-W3-2003-0353-000 El El O El I- 171 El O El El1 O O O O3 Ill. CROSS
REFERENCES:
1.I El El.
IV. SOFTWARE USED:
Title:
NIA Version/Release: DiskClCD N o .-
DISK/CDS INCLUDED:
Tite: NIA Version/Release: Disk/CD No.
V. OTHER CHANGES:l
Cale. No. EC192-019 l
[ I-ENTERGY Page ivl Revision Record Of Affected No. Revision Pages DRN 04- Revised Low Pressure setpoint, allowable value and alarm, DRN based on revised analysis limit. The Low SG Pressure 2, 4,28.
6, 8, 15, 1235 Variable Setpoint Step value is also revised. 22, 120, Corrected error in calculating SG Low Press PTE. Ref.: CR- 121, 122, WF3-2004-02388 125,126, 127 Supersedes DRN 03.551.
DESIGN VERIFICATION RECORD Page 1 of 2 Document Number _ECI92-019 Revision 3 METHOD Verification methods to be used:
X DesIgn Revlew Qualification Testing
- Alternate Calculations DOCUMENT(S) REVIEWED: (Attach Additional Sheet(s), if needed)
Document Noimher Revision Document Title ECI92-019 DRN 041235 PPS Setooint Uncertaintv
SUMMARY
OF REVIEW: (Attach Additional Sheet(s), it needed)
Design Verification Completed By UAL-T- LJA Date: a( rfk(
Comment Resolutions Accepted By A1/A Date: .
Engineering Supervisor Zfe . JeM#vAR73aQ/t Date:
DESIGN VERFiCAnON RECORD Page 2 of 2 Document Number _EC192019 Revision 3 CMNT ACPT I INITID NO. COMMENT I RESOLUTION IY/N ATE I None All comments and questions were resolved without requiring documentation.
Plant Protoction Systom Sotpolnt EC192-019 Uncertainty Calculation Page 2 of 163 E t~ei y Revision 3
2.0 CONCLUSION
TABLE
2.0 CONCLUSION
S
SUMMARY
PARAMETER ENG. UNITS VDC WO LEVEL LOW TRIP 21.40% 2.a9t ALLOWABLE VALUE 26.48 % 2.059 PRE-TRIP ALARM 29.70 % 2.188 HIGH TRIP 87.70% 4.508 ALLOWABLE VALUE 88.62% 4.545 PRE-TRIP ALARM 85.40% 4.418 RCS FLOW LOW TRIP 19.00 PSID 3.800 ALLOWABLE VALUE 18.47 PSID 3.694 PRE-TRIP ALARM NIA NIA PZR. PRESS.(NR) HIGH TRIP 2350.0 PSIA 4.400 ALLOWABLE VALUE 23592 PSIA 4.437 PRE-TRIP ALARM 2310.0 PSIA 4.240 PZR. PRESS. (WR) LOW TRIP 1684.0 PSIA 3.245 LOWABLE VALUE 1649.7 PSIA 3.200 PRE-TRIP ALARM 1788.0 PSIA 3.384 CONT. PRESS.(NR) HIGH TRIP 17.1 PSIA 3.280 ALLOWABLE VALUE 17.4 PSIA 3.317 PRE-TRIP ALARM 16.4 PSIA 3 1R7 CONT. PRESS. (WR) HIGH TRIP 17.7 PSIA 3.360 ALLOWABLE VALUE 18.0 PSIA 3.397 PRE-TRIP ALARM 18.8 PSIA .240 1l SIG PRESSURE LOW TRIP 602.0 PSIA 3207 ALLOWABLE VALUE 648.4 PSIA 3.162 PRE TRIP ALARM 0P -
SIG DIP HIGH TRIP 123.00 PSID 0.410 ALLOWABLE VALUE 134.02 PSID 0.447 PRE-TRIP ALARM 90.04 PSID 0.329 UNEAR POWER HIGH TRIP 108.00 % 5.400 ALLOWABLE VALUE 108.76% 5.438 PRE-TRIP ALARM 1U3.0 0% 5.150 LOG POWER HIGH TRIP 0.257% 7.109 OWABLE VALUE 0.280% 7.147 PRE-TRIP ALARM 0.001% 4.699 RWSP LEVEL LOW TRIP 10.00% 1.400 ALLOWABLE VALUE 09.08% 1.383 PRE-TRIP ALARM 15.00 % 1.600
Plant Protection System Setpolnt EC192-019 Uncertainty Calculation Page 4 of 163 2 Ente C M RevIsion 3 2.1.6 WIDE RANGE CONTAINMENT PRESSURE 59.00 % SPAN 3.360 VOLTS DC 17.7 PSIA 2.1.7 LOW STEAM GENERATOR PRESSURE
% SPAN (3.207 VOLTS DC 2 PSIA 2.1.8 STEAM GENERATOR DIFFERENTIAL PRESSURE 10.25 % SPAN 0.410 VOLTS DC 123.0 PSID 2.1.9 LINEAR POWER 54.00 % SPAN 5.400 VOLTS DC 108.0 % POWER 2.1.10 LOG POWER
.71.09 % SPAN 7.1 US VoLrs DC
-0.590 LOG % POWER 0.257 % POWER 2.1.11 REFUELING WATER STORAGE POOL LEVEL 10.00 % SPAN 1.400 VOLTS DC 10.00% LEVEL
59.92 % SPAN 3.397 VOLTS DC 10.0 PSIA 2.2.7 LOW STEAM GENERATOR PRESSURE 540 % SPAN 3.162 VOLTS DC 648. PSIA 2.2.8 STEAM GENERATOR DIFFERENTIAL PRESSURE 11.17 % SPAN 0.447 VOLTS DC 134.0 PSID 2.2.9 LINEAR POWER 54.38 % SPAN 5.438 VOLTS DC 108.70 % POWER 2.2.10 LOG POWER 71.47 % SPAN 7.147 VOLTS DC
-0.552 LOG % POWER 0.280 % POWER 2.2.11 REFUELING WATER STORAGE POOL LEVEL 9.08 % SPAN 1.363 VOLTS DC 9.08 % LEVEL
Plant Protection System Satpoint EC192-019 Uncertainty Calculation Page 8 of 163 2.36ID RTRevision 3 2.3.6 WIDE RANGE CONTAINMENT PRESSURE 56.00 % SPAN 3.240 VOLTS DC 16.8 PSIA 2.3.7 LOW STEAM GENERATOR PRESSURE 6.0% SPAN 3.400 VOLTS DC 720.0 PSIA 2.3.8 STEAM GENERATOR DIFFERENTIAL PRESSURE 8.22 % SPAN 0.329 VOLTS DC 98.6 PSID 2.3.9 LINEAR POWER 51.50 % SPAN 5.150 VOLTS DC 103.00 % POWER 2.3.10 LOG POWER 46.99 % SPAN 4.699 VOLTS DC
-3.000 LOG % POWER 0.001 % POWER 2.3.11 REFUELING WATER STORAGE POOL LEVEL 15.00 %SPAN 1.600 VOLTS DC 15.0 % LEVEL
2.4 CHANNEL
SUMMARY
(continued) 2.4.7 LOW STEAM GENERATOR PRESSURE
SUMMARY
PPS Input Range . 1.000 to 5.000 vDC Loop Span : 0.00 to 100 % SPAN Transmitter Span : 1200.0 PSIA The loop errors for Steam Generator Pressure Loops A, B, C and Dare as follows:
REF PPSo = i 1.28 %SPAN NOR PPSo _ 1.85 % SPAN
- 1.78 % SPAN ACC PPSo - 4 6.44 % SPAN
- 5.82 % SPAN The setpoints for these instrument loops arc:
VALUE VOLTS EU Trip/Actuation Setpoint 32 6 The allowable values for these instrument loops are:
VALUE VOLTS EU Allowable Value jt.03 y =162 648 The pretrip setpoint for these instrument loops are:
VALUE VOLTS EU Pretrip Setpoint l3720.0
PARAMETER LIMITING ANALYSIS ACCIDENT SETPOINT Low S/G Lcvol MSLB 5% Loval High SIG Level N/A 90% Level Low Reactor Coolant Flow MSLB wlth LOOP 70% Flow Hligh Pressurizer Pressure FWLB 2422 PSIA Low Pressurizer Pressure LOCA, CEA Ejection 1560 PSIA High Containment Pressure MSLB 19.7 PSIA High-High Cont. Pressure MSLB, LOCA 19.7 PSIA Low S/G Pressure MSLB, FWLB 576 PSIA High SIG Delta Pressure MSLB 230 PSID I
High Linear Power Level MSLB 115% Power High Logarithmic Power CEA Withdrawal 0.760% Power 15.201 Low RWSP Level LOCA 7.00% Level [4.17]
I
Plant Protection System Setpoint EC192-019
___ Uncertainty Calculation Page 28 of 163
-e Revision 3
3.0 REFERENCES
(continued) 3.39 Letter C. Sweeney (EBASCO) to W. Mawhinney (CE), LW3-1434-77, dated 7122/77 "LOUISIANA POWER & LIGHT COMPANY WATERFORD SES UNIT NO. 3 CONTAINMENT OVER-PRESSURE ANALYSIS".
3.40 CE Interoffice Correspondence M. F.Strollo to R. 0. Allen, C-PSAE-82-020, dated July 22,1982, "Steam Generator Low Level Setpoint Used InWaterford-3 FSAR".
3.41 CE Interoffice Correspondence M. F. Strollo to R. 0. Allen, C-PSAE-82-016, dated June 30, 1982, "Setpoint and Response Time Used in the Chapter 15 Analysis for Waterford-3 FSAR".
3.42 CE Interoffice Correspondence C. R. Lehmann to R. 0. Allen, C-TM-034, dated November 4, 1981, "Analysis Setpolnts and Response Tlmes".
3.43 CE Interoffice Correspondence M F. Strollo to R. 0. Allen, C-PSS-81-020, dated November 10, 1981, "Setpolntr and Operability Time tmnts Req'.ii used in Chapter 15 Analysis for Waterford-3 FSAR".
3.44 CE Interoffice Correspondence F. K. Chiang to R. 0. Allen, C-LOCA-81-017, dated November 9, 1981, "Waterford Unit 3 ECCSA'S Data Response for Setpoint Analysis".
3.45 CE Interoffice Correspondence R. L. Kim to E. Anavim, C-PSAE-82-040, dated November 18, 1982, "Revised Waterford Unit 3 RPS Requirements for SLB and FWLB Events".
3.46 CE Interoffice Correspondence W. G. Dove to R. 0. Allen, C-PSA-261, dated March 28, 1983, "Waterford Plant: MSLB Containment Temperatures @ 6.5 psig (512962)".
3.47 Louisiana Power & Light Co. Waterford SES Unit No. 3 drawing LOU-5817, 075A, "Line List Document Revision 19 Page 172".
3.48 ENTERGY Inter-Office Correspondence J. B. Holman to R. H. O'Donnell, W3C1-93-0024, dated July 15,1993, "Post-MSLB Reference Leg Water Temperature".
3.49 ABBICE Calculation 9270-ICE-36182, Rev. 2, PPS Setpoint Analysis 3.50 FCIOI-006, Rev. 0. Determination of Secondary Systems Measurement s Functonal Safety Significance.
3.51 Letter PO-95-281 from ABB/CE to J.P. Johnson dated May 19, 1995 'ESR 95-004, Design Basis for RAS Response Time and Setpolnr 3.52 Calculation EC-M91-011 Revision 0 ONPSH for Safeguard Pumps in Recirculation Mode with Valve SI-106A(B) Failed Open"
Plant Protection System Setpoint EC192-Ol9 Uncertainty Calculation Page 120 of 163
- nteigU Revision 3 7.7 STEAM GENERATOR PRESSURE (continued)
- The output uncertainty terms for the bistable (PPSo) and the variable setpoint card after the transmitter and the PAC are given as follows.
REF PPSo = (PACoA2 4 ePPSA2 1 ePPVA2)A0.5
= 1.28 %SPAN NOR PPSos = + (PACoA2 + ePPSA2 + ePPVA2)A0.5
=_ 1.63 % SPAN NOR PPSo = + PPSos + ePPSb + ePPVb
=+ 1.63 % SPAN + 0.07 % SPAN ACC PPSos = * (PACosA2 + ePPSA2 + ePPVA2)A^.5
=*: 5.82 % SPAN ACC PPSo = +/- ACC PPSos + IRb + ACC ePPSb + ACC ePPVb
=-_ 5.82 % SPAN + 0.63 % SPAN The periodic test error includes the bistable card uncertainties and the variable setpoint card uncertainties.
PERIODIC TEST ERROR = _ (PPS(RA) A2 + PPS(MTE)A2 + PPS(DR)A2+
PPV(RAPPV(MTE)A2 + PPV(DR)J2)AO.5 PTE + Qp % SPAN
Plant Protection System Setpoint EC192-019 Uncertainty Calculation Page 121 of 163
.Enlfefg Revision 3 7.7 STEAM GENERATOR PRESSURE (continued) 7.7.3 Calculated Trip Setpoint and Allowable Value The purpose of the low stArm generator pressure function is to provide a reactor trip to assist the ESF system In a Steam Line Break event.
The reactor trip and main steam isolation functions are credited with limiting the consequences of the Steam line break, feedwater line break with or without loss of AC, and Steam Bypass Malfunction event.
( The limiting analysis setpoint of 576 psia (48.00% span) from Reference 3.50 is used as the basis for the following setpoint determinations.
The low SIG pressure setpoint is a variable setpoint. This means that the setpoint is automatically set to a certain step value below actual SIG pressure. As SIG pressure increases, the variable trip setpoint is increased to maintain the adjusted step difference up to a calIbrated maximum setpofnt.
At this point, further increases in S/G pressure do not affect the trip /
actuation setpoint. This maximum trip setpoint is the value that is calculated
/ determined beluw.
7.7.3.1 TriplActuation Setpoint To determine the most conservative uncertainty, the positive bias error is added to the highest analysis low setpoint:
PPS Trip/Actuation Setpoint = PPS/ESFAS Analysis Setpoint + ACC PPSo
= 8 % SPAN + 6.44 % SPAN (54b4 % SPAN The PPS Trip/Actuation Setpoin f Low SG Pres must therefore be set a v W reater than or equal to 382PSP A5454%4.The setpoint is set at psi)
T(55.17=)
PPS Trip/Actuation Setpoint % SPAN
7.7.3.2 Allowable Value PPS Allowable Value = Trip/A on Setpoint - PPSYIE_
= 55.17 ) %SPAN -l.J14) % SPAN
= % SPAN 7.7.3.3 Alarm Setpolnts There are no safety analysis requirements for the pretrip (alarm) setpoints.
The following value may be changed as required, provided that Section 7.7.5 (below) is onsidered in the change rocess. The pretri (alarm) set oint is 7.74 Vy 3.49. f Eerence PPS Alarm Value =Trip/Actuation Setpoint + 58 PSI
\ = 55.17 % SPAN +4.84 %SA
> . - 0.00 %SPAN A 7.7.4 Voltage Equivalents for Setpoints and Allowable Values The PPS Cabinet input ranges from 1.000 to 5.000 vDC Equivalent process range 0.00 to 100 % SPAN Based on these end points the following equation is derived:
V = (%SPAN/ 25.00 ) + 1.00 PPS Trip/Actuation Setpoint 55.17 % 3.2070 volts Allowahle Values 54.03 % )3.162 volts Pretrip Setpoint 60.00 3.400 volts 7.7.5 Basis for Variable Setpoint Step Value There are four design considerations that need to be accommodated in the selection of the Low S/G Pressure Variable Setpoint Step Value. These considerations are discussed below, then the overall design basis for the selected step value is procntcd.
Plant Protection System Setpolnt EC192-019
£ Uncertainty Calculation Page 125 of 163 7 W EAM GRRevision 3 7.7 STEAM GENERATOR PRESSURE (continued) variations during both startup and normal operations. Since the existing step value of 184 PSIA reflects the current field setting, the years of operating history show that a atop value of 184 PSIA ic within the range of adjuctmont of the equipment. Therefore, a step value of 184 PSIA satisfies the requirements of DC1 and DC4.
In simulator runs and drills, operators have been trained to respond to Design Basis Accidents, including SGTR events. During recovery from an SGTR, operators are Alerted to manually reduce the Low SIG E~sure setpoint upon actuation of the Pretrip a which first actuates atPSIA. At this time, S/G pressure Is at I72OPSIA, so the trip set olnt Is reduced to a value 184 PSIA below the existing SIG pressure, or5SIA. C qcident with the setpoint reduction, the pretrip value is also reduced to 4PSIA maintaining the normal differential between the pretrip setpoint and the trip setpoint of 58 PSIA. As the rapid cooldown (to below 5001F) continues, eventually the reduced pretrip setpoint 5PSIA) will be reached, and its actuation will again prompt the operator to manually redbud the variable setpoint. At this point the reduc, trip setpoint will be 0 SIA and the rduced pretrip setpoint will beP SIA. The saturation tempefaturt Lr68)PSIA is approximately 6 so the operator can cooldown to460D witi only two setpoint reductions and without constant attention (due to the prompting by the pretrip alarm). Since this Is the limiting scenario, the preceding discussion illustrates that the existing step value satisfies the requirements of DC3.
In summary, the existing step value (184 PSI) satisfies the requirements of DC1, DC3, and DC4, while administrative controls are in place to minimize the olgnifioanco of DC2. In addition, the existing stop value is consistent with the value stated in Technical Specification Table 2.2-1, S 200 PSI.
Therefore, the existing step value of 184 PSIA is appropriately chosen.
7.7.6 Basis for Variable Setpolnt Minimum Trip Setting Acrident analyses credit the MSIS ESFAS function throughout the range of S/G pressures (from 0 to 1200 PSiA and from 1200 to 0 PSIA). Therefore, the minimum trip setpoint is set outside the range, i.e. less than 0 PSIA.
Setting the minimum trip value less than 0 PSIA ensures that the minimum trip setting will not affect operation of the MSIS function at any time.
Therefore the existing minimum trip value of "less than zero" PSIA is Approprlately cosen.
Plant Protection System Setpoint EC192-019 Uncertainty Calculation Page 126 of 163 M-nteigy Revision 3 7.7 STEAM GENERATOR PRESSURE (continued) 7.7.7 Basis for Variable Setpoint Low' Annunciator Setpoint Since the Low S/I Pressure Trip I Actuation Setpoint is a variable setpoint that is automatically Increased as S/G pressure increases, an annunciator has been provided to alert the operator If the tracking function should fail. This avoide the need for constant nperator attention to the setpoint indicators to ensure that the setpoint is tracking properly. Note that the setpoint is a differential setpolnt that is actuated by an adjusted deviation between SIG pressure and the Low SIG Pressure Trip I Actuation setting. Three design considerations form the basis for the setting of the 'Variable Setpoint Low' annunciator. These are described below as DC1 and DC2, and DC3.
Design Consideration 1 (DC1):
The trip setting tracks the increasing SIG pressure by an amount equal to the step value (184 PSIA) plus or minus some variation due to equipment uncertainty. To prevent operation of the Low Setpoint Annunciator when there is no equipment malfunction, the step value provides the basis for the minimum annunciator setting. That Is, the annunciator 5etpoint should be set greater than 184 PSIA deviation.
Design Curosideration 2 (DC2):
The minimum annunciator setting is also based on avoiding annunciator actuation during ctartup or normal oerations. The maximum setting of the Low S/I Pressure Trip Bistable is(643PSlA {Reference Section 7.7.3.1 above). The r urn SIG pressure during startup or normal operations is approximately ) PSIA (Reference 3.58). To avoid annunciator actuation at 10005PSIA, the Low Setoint Annunciator'setting must be great than theference betweenCt)PSIA and the maximum trip setpoln4~662 PSIA). Therefore the annunciator setpoint must be greater than lA deviation.
Plant Protection System Setpolnt EC192-019 Calculation Page 127 of 163 MEnterg
__Uncertainty Revision 3 7.7 STEAM GENERATOR PRESSURE (continued)
Design Consideration 3 (DC3):
Tho Low Annunciator Sotpoint should be low enough that a faulty tracking function is detected before the deviaiton between the trip setpoint and SIG pressure becomes large enough to compromise the protective actions.
Basis Summary:
Based on DC1. DC2, and DC3, the Low Annunciator setpoint should meet the following criteria:
- Setpoint must be >1 PSI deviation (from DC1).
Setpoint must be 1t3 PSI deviation (from DC2).
Setpoint should be small enough that a malfunction Is detected in a timely I
manner to ensure continuous protection (from DC3).
Evaluating the existing Low Annunciator setting (301 PSIA deviation between SIG pressure and the current setting of the trip I actuation setpointl against the desi n considerati thatDC1 is satisfied but Is not. Therefore, tme existing ow Annunciator setting of 301 PSI deviation is not adequate. The setpoint should be changed to 345 PSI deviation to satisfy DC1, DC2 and DC3.
to W3F1 -2004-0073 Section 7.7 of Calculation EC-192-019, Revision 3
_Plant Protection Systemn Setpolnt EC192-019 Uncertainty Calculation Page II11 of 163 EntergyRevision3 7.7 STEAM GENERATOR PRESSURE MEASUREMET TRANSMfTTER BISTBLE PPSo eTR ePPS SG IPT1O13A,B,CD ICECP25.26,27,28 CP-10 BLOCK DIAGRAM STEAM GENERATOR No. 1 PRESSURE LOOPS A, B, C, and D MEASUREMENT TRANSMITTER eTRXeP 3~ eISACL SG IPT1023A,B,CD ICECP25.26,27.28 CP-10 BLOCK DIAGRAM STEAM GENERATOR No. 2 PRESSURE LOOPS A, B, C, and D
Plant Protection System Setpoint EC192-019 Uncertainty Calculation Page 112 of 163
-Jflery Revision 3 7.7 STEAM GENERATOR PRESSURE (continued) 7.7.1. Functional Description The Steam Generator Pressure function of the Plant Protection System (PPS) provides a reactor trip on Low Steam Generator Pressure.
During plant cooldown the Low Steam Generator Pressure trip setpoint can be manually decreased to 200 PSI below the existing pressure. During plant startup the setpoint is automatically increased and remains 200 PSI below steam generator pressure.
The Steam Generator Pressure transmitter is calibrated from 0 to 1200 PSIA and outputs a 4 to 20 maDC signal proportional to the process variable. A 250 ohm resistor develops a 1 to 5 vDC signal for input to the PPS bistable.
The most limiting accident condition (ACC) for a low steam generator pressure trip is a Steam Line Break (SLB).
7.7.2 Process Measurement Errors and Instrument Uncertainties 7.7.2.1 Process Measurement Error The process measurement error is attributed to the vertical section of the water-filled sensing line between the process tap and the pressure transmitter. The transmitters are located below the process taps. Reference 3.24 calculates the transmitter calibration based on the sensing line head above the transmitter at a temperature of 120 ° F. A change in ambient temperature causes a change in sensing line temperature and density.
The process measurement error is calculated for transmitter SGIPT1 01 3B & D which has the largest vertical distance between tap and transmitter. This will result Inthe most conservative error. The density of water in the sensing line during accident conditions is at the temperatures Indicated and a pressure corresponding to an analytical setpoint of 675 PSIA.
SPAN 1200.00 PSI [3.11]
SENSING LINE HEIGHT : 38.1 FEET [3.24]
CALIBRATION TEMPERATURE: 120.00 deg F [3.24]
S.G. c CAL TEMP : 0.9901 [3.24]
DENSITY @ CAL TEMP (Dc) : 61.73 Lbm/Ft 3 [4.16]
NORMAL TEMPERATURE : 120.00 deg F [3.24]
ACC TEMP (SLB) : 350.00 deg F [4.20]
DENSITY @ NOR TEMP (Dn) : 61.73 Lbm/Ft3 DENSITY @ SLB TEMP (Da) : 55.74 Lbm/Ft 3 [3.9]
STATIC HEAD (h) : 16.35 PSI [3.24]
TEMPERATURE EFFECT : h(Da-Dc)/Dc PSI [3.1]
NOR TEMP EFF (TE) : 0.00 PSI ACC TEMP EFF-SLB (ATE) : - 1.58 PSI
.Plant ProtectSon System Setpo(nt EC192-019 EntrgyUncertainvty Calc3ulation Page 114 of 163 7.7 STEAM GENERATOR PRESSURE (continued)
The process measurement errors during accident temperatures are as follows:
ACC SLB PMEb = (ATE/SPAN)*1 00%
= - 0.13 % SPAN Since the Trip/Actuation Setpoint is a 'low" setpoint, only the positive errors are applicable. Therefore, ACC PME will have no effect upon the Trip/Actuation setpoint and need not be considered.
TRANSMITTER TAG NUMBER SG IPT1013A, B, C, D [3.2, 3.10]
SG IPT1023A, B, C, D MANUFACTURER ROSEMOUNT [3.2]
MODEL NUMBER 1154SH9 [3.2]
UPPER RANGE LIMIT (URL) 3000.00 PSIA [3.3b]
SPAN 1200.00 PSIA [3.10]
AMB CAL TEMPERATURE 65.00 deg F [3.6]
AMB NOR TEMPERATURE 120.00 deg F [3.8]
AMB ACC (SLB) TEMP 350.00 deg F [4.20]
REF ACCURACY (RA) 0.25 % [3.3b]
DRIFT (DR) 0.20 % URL [3.3c]
DR (for 22.5 mo.) 0.50 % [4.41 CALIBRATION EFF (CAL) 0.25 % [3.24]
M&TE EFFECT (MTE) 0.14 % [4.13]
NOR TEMP EFF (TE) (0.15%URL+0.35%SPAN)/50 °F [3.3b]
TE 0.80 %
ACC TEMP EFF (ATE) (2.0%URL+0.5%SPAN) [3.3b]
ATE 5.50 %
POWER SUPPLY EFF (PS) N/A [5.3]
POST-SEISMIC (PSE) 0.50 % URL [3.3b]
PSE 1.25 %
ACC RAD EFF (ARE) (0.5%URL+1.0%SPAN) [3.3b]
ARE N/A [5.11]
Plant Protection System Setpolnt EC192-019 I Uncertainty Calculation Page 115 of 163 7 EnteMGy Revision 3 7.7 STEAM GENERATOR PRESSURE (continued)
The transmitter uncertainties (eTRX) for Reference (REF), Normal (NOR) and Accident (ACC) conditions are given as follows:
REF eTRX = i (CAL + MTE) =+/- 0.39 % SPAN NOR eTRX = i ((CAL + MTE)A2 + DRA2 + TEA2 )A^.5 1.02 % SPAN ACC eTRX = +/- ((CAL + MTE)A2 + DRA2 + ATEA2 + PSEA2)AO.5
=+/- 5.68 % SPAN The output uncertainty terms for the Transmitter (TRXo) for Reference (REF), Normal (NOR) and Accident (ACC) are as follows:
REF TRXo = +/- REF eTRX =+/- 0.39 % SPAN NOR TRXo NOR eTRX = 1.02 % SPAN ACC TRXo= ACC eTRX 5.68 % SPAN INSULATION RESISTANCE The transmitter is located within the containment building, and as such, the effects of harsh environment on loop signal cabling must be considered. The accident environment effect is considered for cabling from the transmitter through the containment electrical penetrations. The most conservative of the loops (P101 3D) is used in determining the IR effects.
CABLE LENGTH/MFG : 220 FT/SAMUEL MOORE [3.5]
IRb :+ 0.51 % SPAN [3.4]
Plant Protection System Setpolnt EC192-019 Uncertainty Calculation Page 116 of 163 Revision 3 I
7.7 STEAM GENERATOR PRESSURE (continued)
PAC CABINET TAG NUMBER SG IPCII013A,B, C, D [3.10]
SG IPCII023A,B, C, D MANUFACTURER WESTINGHOUSE MODEL 2837A86G03 DESCRIPTION 250.00 ohm RESISTOR AMB CAL TEMP (AMB) 70.00 deg F [5.2]
MAX NOR TEMP (NOR) 110.00 deg F [5.2]
MAX ACC TEMP (ACC) 110.00 deg F [5.2]
DT (NOR-AMB) 40.00 deg F REFERENCE ACCURACY (RA): + 0.075 OHMS [3.16.a]
RA 0.0375 % SPAN (NEGLIGIBLE)
TEMP COEFF (TE) : 3.00 ppmldeg C [5.8]
TE 0.0083 % SPAN (NEGLIGIBLE) [4.18]
STABILITY (DRIFT) : 35.00 ppmlyear [5.8]
DR (for 22.5 mo.) : 0.0082 % SPAN (NEGLIGIBLE) [4.19]
RA, TE and DR for PAC are < 0.05% and considered negligible per ASSUMPTION 5.1.
The total PAC uncertainty (ePAC) consists of MTE.
REF ePAC = +/- (RA + MTE) 0.072 %SPAN NOR ePAC = +/- ((RA + MTE)A2 + DRA2 + TEA2)^0.5 0.072 % SPAN ACC ePAC = +/- ((RA + MTE)A2 + DRA2 + TEA2)A0.5 0.072 % SPAN
Plant Protection System Setpoint EC192-019 Uncertainty Calculation Pa 117 f 163 E tffgy Revision 3ge 7.7 STEAM GENERATOR PRESSURE (continued)
The output uncertainty terms for the PAC (PACo) after the transmitter is given as follows:
REF PACo = +/- ((REF TRXo)A2 + (REF ePAC)A2)A0.5
= + 0.39 % SPAN NOR PACo = +/- ((NOR TRXo)A2 + (NOR ePAC)A2)AO.5 1.02 % SPAN ACC PACos = +/- ((ACC TRXos)A2 + (ACC ePAC)A2)AO.5 5.68 % SPAN ACC PACo = +/- ACC PACos + lRb 5.68 %SPAN+ 0.51 %ESPAN
Plant Protection System Setpolnt ECI92-019 I lJuIIUILCIIILY C.aIgvl ull3 Page 118 of 163 J22flntaW ~ Revision 3 7.7 STEAM GENERATOR PRESSURE (continued)
LOW STEAM GENERATOR PRESSURE TRIP BISTABLE MODEL NUMBER 26440 [3.17]
FULL RANGE 0.00 to 10.00 vDC [3.17]
INPUT RANGE 1.00 to 5.00 vDC SPAN 4.00 vDC LINEARITY (LA) : 25.00 mV [3.17]
LA 0.63 % SPAN REPEATABILITY (RP) +/- 0.25 % FULL SCALE [3.17]
RP : 0.63 % SPAN RESOLUTION (RL) : 1.00 mV [3.17]
RL +/- 0.03 % SPAN (NEGLIGIBLE)
M & TE EFFECT(MTE) :_ 0.10 % SPAN [5.9]
DRIFT (DR): : 9.1 mV / 39 days [3.17]
(105 DAYS) : 0.23 % SPAN 14.4]
REFERENCE ACCURACY (RA) = i (LAA2 + RPA2 + RLA2)AO.5 RA = 0.88 % SPAN WORST CASE NORMAL TEMPERATURE EFFECT (+/- TE + TEb):
(for a temperature shift of 20 deg F) [5.10]
TE = 2.81 mV [3.17]
0.070 % SPAN TEb =+ 0.84 mV [3.17]
=+ 0.02 % SPAN The Bistable Comparator Card uncertainties (ePPS) for the Reference (Ref), Normal (Nor), and Accidents (ACC) conditions are as follows:
REF ePPS = +/- (RA + MTE) =+/- 0.98 % SPAN NOR ePPS = +/- ((RA + MTE)A2 + DRA2 +TEA2)AO.5 1.01 % SPAN NOR ePPSb = + TEb =+ 0.02 % SPAN ACC ePPS = i ((RA + MTE)A2 + DRA2 +TEA2)AO.5 1.01 % SPAN ACC ePPSb= +TEb =+ 0.02 % SPAN
Plant Protection System Setpoint EC192-019 Uncertainty Calculation
~Eterg Revision 3 Page 119 of 163 I 0 7.7 STEAM GENERATOR PRESSURE (continued)
LOW STEAM GENERATOR PRESSURE VARIABLE SETPOINT CARD MODEL NUMBER 26480 [3.17]
FULL RANGE 0.00 to 10.00 vDC [3.17]
INPUT RANGE 1.00 to 5.00 vDC SPAN 4.00 vDC ACCURACY (AC) + 25.00 mV [3.17]
AC : 0.63 %SPAN RESOLUTION (RL) : 2.00 mV [3.17]
RL : 0.05 % SPAN M & TE EFFECT(MTE) : 0.10 % SPAN 15.9]
DRIFT (DR): : 9.1 mV /39 days i[3.17]
(105 DAYS) : 0.23 % SPAN [4.4]
REFERENCE ACCURACY (RA) = i (ACA2 + RLA2)^0.5 RA =+/- 0.63 % SPAN WORST CASE NORMAL TEMPERATURE EFFECT (+/- TE + TEb):
(for a temperature shift of 20 deg F) [5.10]
TE = +/- 3.23 mV [3.17]
=i 0.08 % SPAN TEb =+ 1.88 mV [3.17]
+ 0.05 % SPAN The Variable Setpoint Card uncertainties (ePPV) for the Reference (Ref), Normal (Nor),
and Accidents (ACC) conditions are as follows:
REF ePPV = +/- (RA + MTE) =i 0.73 % SPAN NOR ePPV = +/- ((RA + MTE)A2 + DRA2 +TEA2)^0.5 0.77 %SPAN NOR ePPVb = + TEb =+ 0.05 % SPAN ACC ePPV = i ((RA + MTE)^2 + DR^2 +TE^2)^0.5 0.77 % SPAN ACC ePPVb =+ TEb =+ 0.05 % SPAN
Plant Protection System Setpoint EC192-019
~EntergyRevision Uncertainty Calculation 3I Page 120 of 163 7.7 STEAM GENERATOR PRESSURE (continued)
The output uncertainty terms for the bistable (PPSo) and the variable setpoint card after the transmitter and the PAC are given as follows.
REF PPSo = + (PACOA2 + ePPSA2 + ePPVA2)AO.5
=* 1.28 % SPAN NOR PPSos = (PACoA2 + ePPSA2 + ePPVA2)AO.5 1.63 % SPAN NORPPSo=+/- PPSos+ ePPSb + ePPVb 1.63 %SPAN + 0.07 % SPAN ACC PPSos = +/- (PACOsA2 + ePPSA2 + ePPVA2)AO.5 5.82 % SPAN ACC PPSo = +/- ACC PPSos + IRb + ACC ePPSb + ACC ePPVb
+/- 5.82 % SPAN + 0.63 % SPAN The periodic test error includes the bistable card uncertainties and the variable setpoint card uncertainties.
PERIODIC TEST ERROR = (PPS(RA) A2 + PPS(MTE)A2 + PPS(DR)^2+
PPV(RA)A2 + PPV(MTE)A2 + PPV(DR)A2)A0.5 PTE =+/- 1.18 % SPAN
Plant Protection System Setpolnt EC192-019 Uncertainty Calculation Page 121 of 163 tew Revision 3 7.7 STEAM GENERATOR PRESSURE (continued) 7.7.3 Calculated Trip Setpoint and Allowable Value The purpose of the low steam generator pressure function is to provide a reactor trip to assist the ESF system in a Steam Line Break event.
The reactor trip and main steam isolation functions are credited with limiting the consequences of the Steam line break, feedwater line break with or without loss of AC, and Steam Bypass Malfunction event.
The limiting FSAR Chapter 15 safety analysis setpoints for the Low Steam Generator Pressure are: a reactor trip and ESFAS actuation at 675 PSIA (56.25% SPAN) for Steam Line Break with or without Loss of Offsite AC and ESFAS at 675 PSIA (56.25% SPAN) for Feedwater Line Break. FSAR Chapter 6 Mass and Energy Release Analysis (for peak containment pressure) for Postulated Secondary System Pipe Ruptures Inside Containment uses an analysis setpoint of 678 PSIA. As this is the most limiting analysis setpoint, 678 PSIA is used as the basis for the following setpoint determinations. These setpoints are taken from References 3.43 and 3.50.
The low SIG pressure setpoint is a variable setpoint. This means that the setpoint is automatically set to a certain step value below actual S/G pressure. As S/G pressure increases, the variable trip setpoint is increased to maintain the adjusted step difference up to a calibrated maximum setpoint. At this point, further increases in SIG pressure do not affect the trip / actuation setpoint. This maximum trip setpoint is the value that is calculated I determined below.
7.7.3.1 TriplActuation Setpoint To determine the most conservative uncertainty, the positive bias error is added to the highest analysis low setpoint:
PPS Trip/Actuation Setpoint = PPS/ESFAS Analysis Setpoint + ACC PPSo
= 56.50 % SPAN + 6.44 % SPAN
- 62.94 % SPAN The PPS Trip/Actuation Setpoint for Low S/G Pressure must therefor be set at a value greater than or equal to 755.28 PSIA (62.94%). The setpoint is set at 764 PSIA (63.67%) Decreasing to retain the existing Technical Specification Setpoint.
PPS Trip/Actuation Setpbint P 63.67 % SPAN
Plant Protection System Setpoint EC192-01 9 Uncertainty Calculation
-aEnteW Revision 3 Page 122 of 163 I 7.7 STEAM GENERATOR PRESSURE (continued) 7.7.3.2 Allowable Value PPS Allowable Value = Trip/Actuation Setpoint - PPS PTE
= 63.67 % SPAN - 1.18 % SPAN
= 62.49 % SPAN 7.7.3.3 Alarm Setpoints There are no safety analysis requirements for the pretrip (alarm) setpoints.
The following value may be changed as required, provided that Section 7.7.5 (below) is considered in the change process. The pretrip (alarm) setpoint is chosen to reflect current field settings, originally provided by Reference 3.49.
Alarm Setpoint = 68.50 % SPAN 7.7.4 Voltage Equivalents for Setpoints and Allowable Values The PPS Cabinet input ranges from 1.000 to 5.000 vDC Equivalent process range 0.00 to 100 % SPAN Based on these end points the following equation is derived:
V = (% SPAN /25.00) + 1.00 Value Voltage PPS Trip/Actuation Setpoint 63.67 3.547 volts Allowable Values 62.49 3.500 volts Pretrip Setpoint 68.50 3.740 volts 7.7.5 Basis for Variable Setpoint Step Value There are four design considerations that need to be accommodated in the selection of the Low S/G Pressure Variable Setpoint Step Value. These considerations are discussed below, then the overall design basis for the selected step value is presented.
Plant Protection System Setpolnt EC192-019 Enters Uncertainty Calculatlon Page 123 of 163 7.7 STEAM GENERATOR PRESSURE (continued)
Design Consideration 1 (DC1):
It is imperative that the step value be large enough that normal (expected)
SIG pressure variations (decreases) during either startup or normal operations will not cause unnecessary protective system alarms, trips, or actuations.
Design Consideration 2 (DC2):
It is desirable that the step value magnitude be limited such that the trip setpoint would not be reduced below the Tech Spec Allowable Value, if the Reset button were depressed during Normal Operating Conditions.
Design Consideration 3 (DC3):
The design of the variable setpoint is such that the setpoint is automatically increased as S/G pressure increases up to a maximum adjustable setpoint.
However, when S/G pressure is decreasing, the setpoint must be manually reset. This is accomplished by manually depressing a Reset button which reduces the variable trip setpoint to a value equal to the current S/G pressure minus the magnitude of the adjusted step value. This action can be repeated as necessary to preserve MSIS protection while decreasing S/G pressure during a shutdown. The magnitude of the step value determines how often (how many times) the setpoint must be manually reset during shutdown I depressurization. The impact of this required action on operators must be considered when choosing the step value.
Desian Consideration 4 (DC4):
The selected step value must be within the adjustment range of the equipment.
Overall Design Basis:
A review of the four design considerations listed above indicates that DC1 and DC4 must be fully accommodated in the selected step value, while DC2 and DC3 require further evaluation.
DC2 is desirable, but not mandatory, since administrative controls are in place to ensure that inadvertent lowering of the Low S/G pressure setpoint (by depressing the Reset button) is detected / avoided. These administrative controls include procedure steps and channel checks of the trip setpoint
indicators. Procedural steps in both Operations and Maintenance surveillance procedures return the variable trip setpoint to its maximum value following performance of these procedures. It is generally agreed that the procedural controls will prevent inadvertent operation with reduced setpoints. This Is further assured by performance of channel checks of the setpoint indicators, which would clearly indicate if reduced setpoints were in effect during normal operation. Based on this discussion, the significance of DC2 is minor.
DC3 is most significant during EOP situations, namely following a Steam Generator Tube Rupture (SGTR) accident. After the affected S/G is identified and Isolated, only one S/G Is available as a heat sink for RCS cooldown / depressurization. It is critical that this heat sink be available to allow the optimum cooldown method. A MSIS at this time would require a less desirable cooldown method / sqenario. Therefore, as the unaffected S/G pressure decreases (as a result of the RCS cooldown), the Low S/G Pressure setpoint must be manually reduced by depressing the Reset button.
As the RCS continues to cooldown (rapidly) to s 500 IF (Reference 3.59),
the setpoint may have to be reduced again and again to avoid MSIS actuation. Because of the demands on operator attention that would exist in the control room following any accident, the number of times the Operators must perform this setpoint reduction should be minimized. Therefore the step value should be large enough to avoid the need for constant attention and action by the operators in this, or any similar circumstances. Proper selection of the step value in conjunction with the selected pretrip value can accommodate these objectives and trigger operator action to manually reduce the Low S/G Pressure setpoint, thus avoiding the need for continuous operator attention. The trigger is the actuation of the pretrip alarm (see below).
Basis Summary Since DC2 would dictate a very small step value and DC3 would be better served with a larger step value, some balance must be reached. Since DC2 has been evaluated to have only minor significance, DC3 considerations should prevail. The existing step value of 184 PSIA shall be evaluated in light of DC1, DC3, and DC4.
Years of operating experience have shown that the existing step value (184 PSIA) is large enough to avoid unwanted protective actions due to pressure
Plant Protection System Setpolnt EC192-019 w~tr yUncertainty Calculation Page 125 of 163 7.7 STEAM GENERATOR PRESSURE (continued) variations during both startup and normal operations. Since the existing step value of 184 PSIA reflects the current field setting, the years of operating history show that a step value of 184 PSIA is within the range of adjustment of the equipment. Therefore, a step value of 184 PSIA satisfies the requirements of DC1 and DC4.
In simulator runs and drills, operators have been trained to respond to Design Basis Accidents, including SGTR events. During recovery from an SGTR, operators are alerted to manually reduce the Low S/G Pressure setpoint upon actuation of the Pretrip alarm, which first actuates at 822 PSIA. At this time, S/G pressure is at 822 PSIA, so the trip setpoint is reduced to a value 184 PSIA below the existing S/G pressure, or 638 PSIA. Coincident with the setpoint reduction, the pretrip value is also reduced to lUndefined Bookmark, RT PSIA maintaining the normal differential between the pretrip setpoint and the trip setpoint of 58 PSIA. As the rapid cooldown (to below 5000 F) continues, eventually the reduced pretrip setpoint (696 PSIA) will be reached, and its actuation will again prompt the operator to manually reduce the variable setpoint. At this point the reduced trip setpoint will be 512 PSIA and the reduced pretrip setpoint will be 570 PSIA. The saturation temperature for 570 PSIA is approximately 480 'F, so the operator can cooldown to 4801F with only two setpoint reductions and without constant attention (due to the prompting by the pretrip alarm). Since this is the limiting scenario, the preceding discussion illustrates that the existing step value satisfies the requirements of DC3.
In summary, the existing step value (184 PSI) satisfies the requirements of DC1, DC3, and DC4, while administrative controls are in place to minimize the significance of DC2. In addition, the existing step value is consistent with the value stated in Technical Specification Table 2.2-1, s 200 PSI.
Therefore, the existina step value of 184 PSIA is appropriately chosen.
7.7.6 Basis for Variable Setpoini Minimum Trip Setting Accident analyses credit the MSIS ESFAS function throughout the range of S/G pressures (from 0 to 1200 PSIA and from 1200 to 0 PSIA). Therefore, the minimum trip setpoint is set outside the range, i.e. less than 0 PSIA.
Setting the minimum trip value less than 0 PSIA ensures that the minimum trip setting will not affect operation of the MSIS function at any time.
Therefore the existing minimum trip value of 'less than zero" PSIA is appropriately chosen.
Plant Protection System Setpoint EC192-019
~EntergyRevision Uncertainty Calculation 3I Page 126 of 163 7.7 STEAM GENERATOR PRESSURE (continued) 7.7.7 Basis for 'Variable Setpoint Low' Annunciator Setpoint Since the Low S/G Pressure Trip / Actuation Setpoint is a variable setpoint that is automatically increased as S/G pressure increases, an annunciator has been provided to alert the operator if the tracking function should fail. This avoids the need for constant operator attention to the setpoint indicators to ensure that the setpoint is tracking properly. Note that the setpoint is a differential setpoint that is actuated by an adjusted deviation between S/G pressure and the Low S/G Pressure Trip / Actuation setting. Three design considerations form the basis for the setting of the 'Variable Setpoint Low' annunciator. These are described below as DC1 and DC2, and DC3.
Design Consideration 1 (DC1):
The trip setting tracks the increasing S/G pressure by an amount equal to the step value (184 PSIA) plus or minus some variation due to equipment uncertainty. To prevent operation of the Low Setpoint Annunciator when there is no equipment malfunction, the step value provides the basis for the minimum annunciator setting. That is, the annunciator setpoint should be set greater than 184 PSIA deviation.
Design Consideration 2 (DC2):
The minimum annunciator setting is also based on avoiding annunciator actuation during startup or normal operations. The maximum setting of the Low SIG Pressure Trip Bistable is 764 PSIA (Reference Section 7.7.3.1 above). The maximum S/G pressure during startup or normal operations is approximately 1050 PSIA (Reference 3.58). To avoid annunciator actuation at 1050 PSIA, the Low Setpoint Annunciator setting must be greater than the difference between 1050 PSIA and the maximum trip setpoint (764 PSIA). Therefore the annunciator setpoint must be greater than 286 PSIA deviation.
_ Plant Protection System Setpoint EC192-019 Uncr ertintsaluaion3 Page 127 of 163 7.7 STEAM GENERATOR PRESSURE (continued)
Design Consideration 3 (DC3):
The Low Annunciator Setpoint should be low enough that a faulty tracking function is detected before the deviaiton between the trip setpoint and S/G pressure becomes large enough to compromise the protective actions.
Basis Summary:
Based on DC1, DC2, and DC3, the Low Annunciator setpoint should meet the following criteria:
Setpoint must be >184 PSIA deviation (from DCl).
Setpoint must be >286 PSIA deviation (from DC2).
- Setpoint should be small enough that a malfunction is detected in a timely manner to ensure continuous protection (from DC3).
Evaluating the existing Low Annunciator setting (301 PSIA deviat ion between S/G pressure and the current setting of the trip / actuation setpoint) against the design considerations shows that DC1 and DC2 are satisfied. DC3 is satisfied since the existing setpoint is very near the minimum setting allowed by DC2 (>286 PSIA).
Therefore, the existing Low Annunciator setting of 301 PSIA deviation is appropriately chosen.