ML20065S869

Draft Setpoint Calculation for RPS Turbine Control Valve Fast Closure Trip Function

ML20065S869
Person / Time
Site:	Quad Cities
Issue date:	11/16/1990
From:	Fleischman B, Green W, Leong J COMMONWEALTH EDISON CO.
To:
Shared Package
ML20065S863	List: ML20065S861 ML20065S864 ML20065S869
References
EDE-40-1190, EDE-40-1190-DRFT, NUDOCS 9012260127
Download: ML20065S869 (5)

Text

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EDE-40 1190

- DRF C71 00086 November 16. 1990 ENCLOSURE L '

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Setpoint Calculation for I Reactor Protection System 1 Turbine Control Valve Fast Closure Trip Function Prepared for Commonwealth Edison Company l

Quad Cities Nuclear Statior.

Prepared byt WYhne Date: 4$'4/90 W. K. Green - Principal Engineer ' ' ~

Verified by: [/ /,% 2

@ L. Leopg - Senior Engineer Date: //-/6 to Approved by: C # M N l

VB F. Fleischman - Manager Date: //-/4 - 9M ~

' Reactor Protection Systems Application Engineering 9012260127 901218

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1.0 Objectives The objective of this calculation is to determine the setpoint to be used for the Reactor Protection System (f.PS) Turbine control Valve Fast closure-(TCVFC These p)ressure switches are Part Ntaber 184C4815P001. This information- Trip function was obtained via telecon with Rob Xorneta of Commonwealth Edison on-November 6,1990.. The new pressure switches are being installed as part '

of turbine vendor Thesignalsfromth(GE)recoseendedmodificationstotheturbinesystem.

ese switches will replace the signals that originally came from contacts on the turbine system fast acting solenoids.

1,. 0 Nothodology :

p'NEDC 31336. " General Electric Instrument Setpoint Methodology,"

October 1986. This is a proprieta document that was developed under contract between BE and certain ers of the Licensing Reytow Group Instrumant Setpoint Methodology owners Group, i

3.0. Asstaptions This calculation makes the following assumptions:

The individual-error terms represent a two signa yalue (g8 percent 4 probability of the value being correct).

Primary Element Accuracy

. are considered negligible (PEA)ofand because theProcess Measurement, short instrument lines and Accuracy (P because the pressure switches are measuring the process directly.

is conservatively estimated to be The Calibration one percent 1%) ofAccuracy full range. tem (C)Since this-value is a function of the instrumen(tation and procedures used for calibration this value must be verified to be conservative by Quad Cities perso,nnel. If_it is found to be non-conservative the results of this report must be o recalculated to reflect the larger value. ,

Instrument Drift Accuracy (A) since(D) therefor is anosix month value given interval is equal for drift to Instrument on drawing L

' 184C4815'. This is consistent with'NEDC-31336. Driftisassumedto be random for the subsequent intervals.

The probability t e avoiding a License Event Report (LER) event should be greater than 90 percent. This is consistent with NEDC-t 31336.

The probability for Spurious Trip Avoidance-(STA) should be granter than 96_ percent. This is consistent with NEDC 31336.

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4.0 -Inputs to Calculation The pressuti switches to which this calculation ap>1ies are measuring-directly,the trip oil pressure that causes the turnine control valves to close in a rapid manner. According to-information in Desi n Record File (DRF)C7100017 this oil pressure a normally about 1500 t 1600 psig, and the control valve can't start-to close until the pressure drop; to 400

-psig. During normal operation of the control valves it is considered t possible to inve transients that would cause the trip system pressure to drop momentarily to about 740 psig. On the basis of this informatica the following values are derived:

Analytical Limit (AL) - 400 psig by the time the oil ressure Thecrossure-switchmusttri!oensurethatatrip reaches this level in order ignal will be generated within 30 milliseconds after start of control valve fast closure.

OperationalLimit(0L)=740psig The Nominal Trip setpoint must be far enough from this value so as to minimize the probability of tripping during normal operational transients.

Drawing 184C4815 indicates that the accuracy of this pressure switch is two percent ( 'of full ran e. Since the full: range of part one (P001)

, is 3000 psig, e accuracy is then 260 psig. Tliis value is assumed to apply over the full range o o)perating temperatures since no information regarding temperature effect on accuracy is given.

'A sumstry of the inputs to be used-in the calculations is as follows:

InstrumentAccuracy(A)=160psig CalibrationAccuracy(C)at30psig .

-Instrument Drift. (0) t60 psig (assume 6 me.)- = *104 psig (18 me.)

Analytical Limit (AL) 400 psig  %~'

OperationalLimit-(0L)=-740ps'ig e

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-. 5.0 Results The following are the results based on the methodology, assumptions, and inputs as given in sections 2.0 3.0, and 4.0 respectively:  ;

paramatar Calculated Reconnended '

Valua value AllowableValue(AV) 456 psig 460 psig or Tech. Spec.Value(TSV)

NominalTripSetpoint(NTSP) 540 psig 550 psig Probability for License 92% N/A

-EventReport(LER) Avoidance .

(Using recommended values)

Probability of S urious ~ 99% N/A l

TripAvoidance(TA)

(Using recossend d va lues)

The NTSP now needs to be adjusted for the practicalities of plant calibration procedures.- The Required Limit the NTSP must ot be found in order that to assure (RL)-is the~ AV is the value be not exceeded.

The RL safunction-ofaccuracy(A)andcalibrationaccuracy(C)as follows 2' I RL = AV + (A + C )l/I Information received on 11 Edison indicates that the /4/90 from Erryl Mendenhall of Commonwealth calibration for this setpoint is accomplished using a Heise pressure gauge measuring 0 to 1000 psig with an accuracy of-1 psi. If one assumes an equal error when calibrating the Heise gauge and another 1 psi error when reading it, the total error is then:

CT " (1 +1 +1)/ = (3) / = 1.732 psi Use CT

= 2 psi I 2 Then RL = 460+(60.+2)1/2 - 520 psig However, this value is less than t'he value requ' ired for 90 percent probability of LER avoidance. -Therefore, use 540 psig as the RL.- ,

In order to obtain an STA probability of 95 percent or greater the NTSP

-should never exceed 638 psig. Therefore, select the NTSP to be midway betweenRL(540psig)Jand638psig.

HTSP=540+(638-540)/2=589psig Use NTSP = 590 nmic with As-Left and Leave Alone tolerances of *20 psi.

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1600 PSI F.A.S T.C. FLUtD TRIP CONTROLLED O-50 PS$ F.C.D FlutD DRAIN TO COOLER F.J S. F. A.S.T C 1600 PS3 F.J S FLUID JET SUPPLY Figure 1. Steam Control Valves Nos.1 through 4, and Intercept Valves Nos.1,3. and 5 (Fluid Flow Diagram)