ML20151R055

Nonproprietary Calculation of Steam Generator Level Low & Lo-Lo Trip Setpoints W/Use of Rosemount 1154 Transmitter

ML20151R055
Person / Time
Site:	Diablo Canyon
Issue date:	03/31/1988
From:	Tuley C WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML16341E618	List: ML20151R055
References
WCAP-11785, NUDOCS 8804270228
Download: ML20151R055 (24)

Text

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?[ ' WESTINGHOUSE CLASS 3

4 WCAP-11785 I

T CALCULATION OF STEAM GENERATOR LEVEL LOW & LOW-LOW TRIP SETPOINTS WITH USE OF A ROSEMOUNT 1154 TRANSMITTER DIABLO CANYON UNITS 1 & 2 i

. March, 1988 C. R. Tuley 4

WESTINGHOUSE ELECTRIC CORPORATION Power Systems

, P. O. Box 355 Pittsburgh, Pennsylvania 15230 8804270228 880418 l PDR ADOCK 05000275 p ,

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TABLE OF CONTENTS Section lillt Eggg

1.0 INTRODUCTION

1 2.0 COMBINATION OF ERROR COMPONENTS 2.1 Methodology 2 2.2 Margin Calculation 4 2.3 ' Definitions for Protection System 5 Setpoint Tolerances 2.4 Westinghouse Setpoint Methodology 11 2.5 Elimination of Margin License Condition 12 2.6 Conclusion 13 L

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LIST OF TABLES Table Iltle ELqt 2-1 Miscellaneous Calculations 14 2-2 Steam Generator Level - Low Low (Feedbreak) 15 2-3 Steam Generator Level - Low-Low (Mass & Energy Release outside of containment) 16 2-4 Steam Generator Level Density Variations 17

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t LIST OF TABLES ,

Table Title EASA 2-1 Miscellaneous Calculations 14 2-2 Steam Generator Level - Low Low (Feedbreak) 15-2-3 Steam Generator Level - Low Low (Mass & Energy Release outside of containment) 16 2-4 Steam Generator Level Density Variations 17 I

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1.0 INTRODUCTION

Westinghouse was requested by Pacific Gas and Electric to evaluate the impact of a Steam Generator Level transmitter changeout, removal -

of the Barton 764, installation of the Rosemount ll54DP4R. The reason for this change is the very significant reduction in the Environmental Allowanco (EA) term, [ ]+a,c for the Barton and 1.4 % Upper Range Level (2.0 % span) for the Rosemount (as identified by Pacific Gas and Electric). This allows a large reduction in the Nominal Trip Setpoint for the Steam Generator Level Low reactor trip and Low-Low reactor trip and auxiliary feedwater initiation. The current trip setpoint is 2 15.0 % span, while using the Rosemount transmitter with the Westinghouse setpoint methodology results in a revised trip setpoint of 1 7.2 % span. This change would result in a significant decrease in the probability of a inadvertent trip.

A brief description of the Westinghouse setpoint methodology is provided in Sections 2.1 through 2.4. The detailed calculational assumptions and results are noted in Tables 2-1 through 2-3. The .

conclusions of this work are provided in Section 2.6.

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2.0 COMBINATION OF ERROR COMPONENTS 2.1 METHODOLOGY The methodology used to combine the error components for a channel is an appropriate combination of those groups which are statistically independent, i.e., not interactive. Those errors which are not 1

independent are placed arithmetica11y into groups that are and can then be systematically combined.  !

The methodology used is the "square root of the sum of the squares" which has been utilized in other Westinghouse reports. This technique, or others of a similar nature, have been used in WCAP-10395(1) and WCAP-8567(2). WCAP-8567 is approved by the NRC noting acceptability of statistical techniques for the application requested. Also, various ANSI, American Nuclear Society, and Instrument Society of America standards approve the use of probabilistic and statistical techniques in determining safety-related setpoints(3)(4). The methodology used in this report is essentially the same as that used for V. C. Summer in August, 1982; approved in NUREG 0717, Supplement No. 4(5),

(1) Grigsby, J. M., Spier, E. M., Tuley, C. R., "Statistical Evaluation of LOCA Heat Source Uncertainty", WCAP-10395 (Proprietary), WCAP-10396 (Non-Proprietary), November,1983. '

(2) Chelemer, H., Boman, L. H., and Sharp, D. R., "Improved Thermal Design Procedure," WCAP-8567 (Proprietary), WCAP-8568 (Non-Proprietary), July,1975.

(3) ANSI /ANS Standard 58.4-1979, "Criteria for Technical I Specifications for Nuclear Power Stations."

(4) ISA Standard S67.04,1982, "Setpoints for Nuclear Safety-Related Instrumentation Used in Nuclear Power Plants."

4 (5) NUREG-0717, Supplement No. 4, "Safety Evaluation Report related to the Operation of Virgil C. Summer Nuclear Station, Unit No.

1", Docket No. 50 395, August, 1982.

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I The relationship between the error components and the total error for a channel is noted in Equation 2.1, .

CSA = ((PHA)2 + (PEA)2 + (SCA + SMTE + SD)2 + (SPE)2 + (STE)2 + '

(RCA + RMTE + RCSA + RD)2 + (RTE)2)l/2 + EA (Eq.2.1) where:

CSA = Channel Statistical Allowance PHA = Process Measurement Accuracy PEA - Primary Element Accuracy SCA = Sensor Calibration Accuracy SMTE - Sensor Measurement and Test Equipment Accuracy SD = Sensor Drift SPE - Sensor Pressure Effects STE = Sensor Temperature Effects RCA - Rack Calibration Accuracy RMTE - Rack Measurement and Test Equipment Accuracy RCSA - Rack Comparator Setting Accuracy RD = Rack Drift .

RTE = Rack Temperature Effects EA - Environmental Allowance As can be seen in the equation, drift and calibration accuracy allowances are interactive and thus not independent. The environmental allowance is not necessarily considered interactive with all other parameters, but as an additional degree of conservatism is added to the statistical sum. It should be noted that for this document, it is assumed that the accuracy effect on a channel due to cable degradation in an accident environment is less than 0.1 % of span. This magnitude of impact is considered negligible and is not factored into the calculations. An error due to this cause, in excess of 0.1 % of span is directly added as an environmental error. .

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2.0 COMBINATION OF ERROR COMPONENTS 2.1 METHODOLOGY '

The methodology used to combine the error components for a channel is an appropriate combination of those groups which are statistically independent, i.e., not interactive. Those errors which are not independent are placed arithmetically into groups that are and can then be systematically combined.

The methodology used is the "square root of the sum of the squares" which has been utilized in other Westinghouse reports. This technique, or others of a similar nature, have been used in WCAP-10395(1) and WCAP-8567(2). WCAP-8567 is approved by the NRC noting acceptability of statistical techniques for the application requested. Also, various ANSI, American Nuclear Society, and Instrument Society of America standards approve the use of probabilistic and statistical techniques in determining safety-related setpoints(3)(4). The methodology used in this report is essentially the same as that used for V. C. Summer in August,1982; approved in NUREG-0717, Supplement No. 4(5),

(1) Grigsby, J. M., Spier, E. M., Tuley, C. R., "Statistical Evaluation of LOCA Heat Source Uncertainty", WCAP-10395 (Proprietary), WCAP-10396 (Non-Proprietary), November, 1983.

(2) Chelemer, H., Boman, L. H., and Sharp, D. R., "Improved Thermal Design Procedure," WCAP-8567 (Proprietary), WCAP 8568 (Non-Proprietary), July,1975.

(3) ANSI /ANS Standard 58.4-1979, "Criteria for Technical Specifications for Nuclear Power Stations."

(4) ISA Standard S67.04,1982, "Setpoints for Nuclear Safety-Related Instrumentation Used in Nuclear Power Plants."

(5) NUREG-0717, Supplement No. 4, "Safety Evaluation Report related to the Operation of Virgil C. Summer Nuclear Statirn, init No.

1", Docket No. 50 395, August, 1982.

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1 The relationship between the error components and the total error for a channel is noted in Equation 2.1, .

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CSA - ((PMA)2 + (PEA)2 + (SCA + SMTE + SD)2 + (SPE)2.+ (STE)2 + '

(RCA + RMTE + RCSA + RD)2 + (RTE)2)l/2 + EA (Eq.2.1) l I

1 i where:

CSA = Channel Statistical Allowance

= Process Measurement Accuracy f PMA PEA - . Primary Element Accuracy SCA = Sensor Calibration Accuracy ,

SMTE - Sensor Measurement and Test Equipment Accuracy ,

SD = Sensor Drift j SPE - Sensor Pressure Effects STE - Sensor Temperature Effects .

RCA = Rack Calibration Accuracy  ;

RMTE - Rack Measurement and Test Equipment Accuracy l

RCSA - Rack Comparator Setting Accuracy j RD = Rack Drift . .

RTE = Rack Temperature Effects EA = Environmental Allowance i

l As can be seen in the equation, drift and calibration accuracy allowances are interactive and thus not independent. The  :

environmental allowance is not necessarily considered interactive with all other parameters, but as an additional degree of

) conservatism is added to the statistical sum. It should be noted that for this document, it is assumed that the accuracy effect on a j channel due to cable degradation in an accident environment is less <

than 0.1 % of span. This magnitude of impact is considered i

negligible and is not factored into the calculations. An error due to this cause, in excess of 0.1 % of span is directly added as an .

' environmental error.  ;

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f The Westinghouse setpoint methodology results in a value with a 95 %

probability with a high confidence level. With the exception of Process Measurement Accuracy and Rack Drift, all uncertainties assumed are the extremes of the ranges of the various parameters, i.e., are better than two sigma values, or are the calculated values based on the design specifications. Rack Drift is assumed, based on a survey of reported plant LERs, and with Process Measurement Accuracy, is considered a conservative value.

2.2 MARGIN CALCULATION t

As noted, Westinghouse utilizes the square root of the sum of the squares for summation of the various components of the channel breakdown. This approach is valid where no dependency is present.

An arithmetic summation is required where an interaction between two parameters exists. The equation used to determine the margin, and thus the acceptability of the parameter values used, is:

Margin - TA - ((PMA)2 + (PEA)2 + (SCA + SMTE + S0)2 + (SPE)2 +

(STE)2 + (RCA + RMTE + RCSA + RD)2 + (RTE)2)l/2 - EA (Eq.2.2) where:

TA = Total Allowance (Safety Analysis Limit - Nominal Trip Setpoint),

all other parameters are as defined for Equation 2.1.

Using Equation 2.1, Equation 2.2 may be simplified to:

i Margin - TA - CSA (Eq. 2.3) P i

Table 21 provides the calculation of the Rosemount SPE, STE, SD and EA terms, based on Rosemount and Pacific Gas & Electric specifications. Tables 2-2 and 2 3 provide individual channel breakdown and CSA, TA,1 T , T2 and margin calculations for two different cases. The first is based on the Safety Analysis Limit 4

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W used for loss of Normal Feedwater, Feedbreak, and Station Blackout.

The second is based on the Safety Analysis Limit used for Mass and ~

Energy Release Outside of Containment. Westinghouse evaluates both cases when a setpoint study is performed. In most cases the .

Feedbreak results are most limiting and determine the Nominal Trip Setpoint and Allowable Value noted in the plant Technical Specifications. However, due to the significant reduction in the transmitter temperature error and the relatively small error for reference leg heatup in adverse environmental conditions, this is no longer the most limiting case. For Diablo Canyon, with the changeout of the transmitters, the most limiting case is now the Mass and Energy Release Outside of Containment.

2.3 DEFINITIONS FOR PROTECTION SYSTEM SETPOINT TOLERANCES To insure a clear understanding of the channel breakdown used in this report, the following definitions are noted. The uncertainty values provided in these definitions are typical for Westinghouse .

supplied equipment.

1. Trio Accuracy The tolerance band containing the highest expected value of the difference between (a) the desired trip point value of a process variable and (b) the actual value at which a comparator trips (and thus actuates some desired result). This is the tolerance band, in %

of span, within which the complete channel must perform its intended trip function. It includes comparator setting accuracy, channel accuracy (including the sensor) for each input, and environmental effects on the rack-mounted electronics. It comprises all instrumentation errors; however, it does not include process measurement accuracy.

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2. Process Measurement Accuraev Includes plant variable measurement errors up to but not including the sensor. Examples are the effect of fluid stratification on temperature measurements and the effect of changing fluid density on level measurements.

3. Actuation Accuracy Synonymous with trip accuracy, but used where the word "trip" does not apply.

4. Indication Accuracy The tolerance band containing the highest expected value of the difference between (a) the value of a process variable read on an indicator or recorder and (b) the actual value of that process variable. An indication must fall within this tolerance band. It includes channel accuracy, accuracy of readout devices, and rack environmental effects, but not process measurement accuracy such as fluid stratification. It also assumes a controlled environment for the readout device.

5. Channel Accuracy The accuracy of an analog channel which includes the accuracy of the primary element and/or transmitter and modules in the chain where calibration of modules intermediate in a chain is allowed to compensate for errors in other modules of the chain. Rack environmental effects are not included here to avoid duplication due to dual inputs, however, normal environmental effects on field mounted hardware is included.

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6. Sensor Allowable Deviation 7

The accuracy tnat can be expected in the field. It includes drift, temperature effects, field calibration and for the case of d/p ,

transmitters, an allowance for the effect of static pressure variations.

The tolerances (with typical values for Westinghouse supplied equipment) are as follows:

d. Reference (calibration) accuracy - [ ]+a,c unless other data indicates more inaccuracy. This accuracy is the SAMA reference accuracy as defined in SAMA standard PMC 20.1-1973(1).

b. Measurement and Test Equipment accuracy - usually included as an integral part of (a), Reference (calibration) accuracy, when less than 10 % of the value of (a). For equipment (DVM, pressure gauge, etc.) used to calibrate the sensor with larger uncertainty values, a specific allowance .

is made,

c. Temperature effect - ( )+a,c based on a nominal temperature coefficient of ( )+a,c/100 0F and a 0 F, maximum assumed change of 50

d. Pressure effect - usually calibrated out because pressure is constant. If not constant, a nominal [ ]+a,c j3 used. Present data indicates a static pressure effect of approximately [ ]+a,c/1000 psi.

(1) Scientific Apparatus Manufacturers Association, Standard PliC 20.1-1973, "Process Measurement and Control Terminclogy" -

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e. Drift - change in input-output relationship over a period of time at reference conditions (e.g., constant temperature -

[ ]+a,c ofspan).

7. Rack Allowable Deviation  ;

The tolerances (with typical values for Westinghouse supplied equipment) are as follows:

a. Rack Calibration Accuracy i

The accuracy that can be expected during a calibration at reference conditions. This accuracy is the SAMA reference )

accuracy as defined in SAMA standard PMC 20.1-1973(1).

This includes all modules in a rack and is a total of

( ]+a,c of span, assuming the chain of modules is tuned to this accuracy. For simple loops where a power supply (not used as a converter) is the only rack module, l

this accuracy may be ignored. All rack modules individually must have a reference accuracy within [ ]+a,c,

b. Measurement and Test Equipment Accuracy Is usually included as an integral part of (a), Reference (calibration) accuracy, when less than 10 % of the value of (a). For equipment (DVM, current source, voltage source, etc.) used to calibrate the racks with larger uncertainty values, a specific allowance is made.

l (1) Scientific Apparatus Manufacturers Association, Standard PMC I

, 20.1-1973, "Process Measurement and Control Terminology".

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c. Rack Environmental Effects Includes effects of temperature, humidity, voltage and frequency changes of which terperature is the most ,

significant. An accuracy of ( ]+a,c, is used which considers a nominal ambient temperature of 70 0F with extremes to 40 Of and 120 0F for short periods of time,

d. Rack Drift Instrument channel drift - change in input-output relationship over a period of time at reference conditions (e.g., constant temperature) - 1.0 % of span,

e. Rack Comparator Setting Accuracy Assuming an exact electronic input, (note that the "channel accuracy" takes care of deviations from this ideal), the ~

tolerance on the precision with which a comparator trip value can be set, within such practical constraints as time '

and effort expended in making the setting.

The tolerances assumed for Diablo Canyon are as followt:

(a) Fixed setpoint with a single input - ( ]+a,c accuracy. This assumes that comparator nonlinearities are compensated by the setpoint.

(b) Dual input - an additional ( ]+a,c must be added for comparator nonlinearities between two inputs.

Total accuracy is [ ]+a c, t

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Note: The following four definitions are currently used in the Standardized Technical Specifications (STS).

8. Nominal Safety System Settina The desired setpoint for the variable. Initial calibration and subsequent recalibrations should be made at the nominal safety system setting ("Trip Setpoint" in STS).

9. limitina Safety System Settina A setting chosen to prevent exceeding a Safety Analysis Limit

("Allowable Values" in STS).

10. Allowance for Instrument Channel Drift The difference between (8) and (9) taken in the conservative '

direction.

11. Safety Analysis Limit The setpoint value ascumed in safety analyses.

12. Total Allowable Setooint Deviation Maximun setpoint deviation from a nominal due to instrument (hardware) effects.

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2.4 WESTINGHOUSE SETPOINT METHODOLOGY .,

Recognizing that Diablo Canyon does not use the Westinghouse five column approach for the protection function Technical Specification ,

requirements, calculations were performed to determine the Allowable Value. In the simplistic sense, the Allowable Value may be the arithmetic sum of the various rack calibration and drift uncertainties, this is defined as:

(Eq. 2.4)

Ti = (RCA + RMTE + RCSA + RD)

.However, this ignores the fact that the Total Allowance may be insufficient in magnitude to substantiate such a large value when Sensor Orift and calibration uncertainties are accounted for in a more rigorous statistical manner. A second calculation is defined by the extraction of the sensor uncertainties and those parameters for which there is no surveillance possible on any periodic basis:

(Eq.2.5)

T 2 = TA - ((A) + (S)2)l/2 - EA where:

A = (PMA)2 + (PEA)2 + (SPE)2 + (STE)2 + (RTE)2 S = (SCA + $HTE + SD)

EA, TA and all other parameters are as defined for Equation 2.1.

It should be noted that these two equations are the same as those used by Westinghouse for the five column approach, but without the flexibility of evaluating the current sensor condition in the determination of channel acceptability. For this plant, a violation of the Allowable Value is considered a determination of the unacceptability of the channel and the channel must be placed in the Tripped Condition or returned to an operable condition within six hours. This is really not operationally significant since typically, .

the channel can be returned to an operable condition by the 11

a recalibration of the rack modules in a reasonably short period of time. For the determination of the Allowable Value in the 13chnical Specifications for the Steam Generator Level - Low and Low-Low

, functions, the smaller of the two values, T1 or T2 is used. '

2.5 ELIMINATION OF MARGIN LICENSE CONDITION In NUREG-0675 Supplement No. 9(1) the NRC staff required that the instrument channel uncertainty for the Steam Generator Level -

Low-Low include a margin of 3.0 % span. This was based upon the Safety Analysis Limit of 0.0 % span (used in the Feedbreak analysis) and the staff perception that the instrument channel (specifically the transmitter) exhibited some undesirable characteristics when indicating near the low level tap. Based on past indication of Rosemount 1153 transmitters in other plants (the base design for the 1154), Westinghouse believes the revised trip setpoint noted on Table 2-3 is acceptable for use. Westinghouse has no indication that the 1153 or 1154 transmitters exhibit any unexpected enaracteristics in the level region near the bottom tap. These transmitters would be in I the upper range (18 to 20 mA) when the Steam Generator level was approacning the bottom tap (0 % span). Westinghouse has not noted any of the following: (1) that the transmitter is any more difficult I

to calibrate for this region of operation, (2) that the transmitter exhibits any significant non-linearity not already accounted for and (3) that the stability of the output of the transmitter in this range is any different than in the mid-range. Based on the above, the available margin noted on Tables 2-2 and 2 3 and the limiting case Safety Analysis Limit, Westinghouse believes the NRC requirement for maintaining the 3.0 % margin in the determination of the Trip Setpoint is not necessary and contributes to inadvertent trips on indicated low-Low level.

(1) NUREG 0675, Supplement No. 9, "Safety Evaluation Report related  ;

to the operation of Diablo Canyon Nuclear Power Station, Units i and 2", Docket Nos. 50-275 and 50 323, June, 1980, i

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2.6 CONCLUSION

S As can be seen from the results noted on Tables 2-2 and 2-3, the most limiting case for the determination of the revised Steam Generator .

Level - Lcw and Low Low Trip Setpoints is Mass and Energy Release Outside of Containment. For both analysis cases, there is margin available with a Trip Setpoint of 7.2 % span. The most limiting value for the Allowable Value is also based on the Mass and Energ)

Release Outside of Containment and is 6.2 % span.

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TABLE 2 1

, MISCELLANEOUS CALCULATIONS SPE = ((0.2 % URL)2 + (0.5 % SPAN)2)l/2

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= (((0.002)(150 in H2 O))2 + ((0.005)(106 in H2 O))2)l/2(ion g)

(106 in H20)

! STE = (0.75 % URL + 0.5 % span)/(100 0)*

F for a 50 O f change '

=

0.0075)(150 in H2 O) + (0.005)(106 in H 2O)(50 0F)(100 %)

(106 in H 20)(100 UF)

SD = (0.25 % URL)/(6 months)

• for an 18 month interval i

= (0.0025)(150 in H O)(18 2 months)(100 %)

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(6 months)(106 in H 2O)

EA = 1.4 % URL per Pacific Gas and Electric specif4 cation

, = (0.014)(150 in H O)(100 2  %)

(106 in H20)

SPE = 0.57 % span STE = 0.78 % span SD = 1.06 % span EA = 1.98 % span per Rosemount Product Data Sheet 2514, 1984 i

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TABLE 2-2 STEAM GENERATOR LEVEL - LOW-LOW (FEEDBREAK) .

Ear 3 meter Allowance

• Process Measurement Accuracy .

Density variations with load due to recirculation -- - +a,c ratio changes **

Primary Element Accuracy Sensor Calibration Accuracy Heasurement & Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects Sensor Orift Environnental Allowance Transmitter Reference Leg Heatup Rack Calibration Measurement & Test Equipment Accuracy Rack Comparator Setting Accuracy One input Rack Temperature Effects Rack Drift Total Allowance - 7.2 % span

-- -- +a,c Channel Statistical Allowance -

Margin =

Ti T2 "

Safety Analysis Limit = 0.0 % span Nominal Trip Setpoint 2 7.2 % span Allowable Value 2 5.6 % span -

• In % instrument span (100 % Level)

• • See Table 2-4 '

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D TABLE 2-3 STEAM GENERATOR LEVEL - LOW-LOW (MAtti and ENERGY RELEASE)

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Parameter Allowance

• Process Measurement Accuracy Density variations with load due to recirculation - -

+a,c ratio changes **

f Primary Element Accuracy Sensor Calibration Accuracy l Measurement & Test Equipment Accuracy

{

Sensor Pressure Effects Sensor Temperature Effects l Sensor Drift Environmental Allowance

} Transmitter Reference Leg Heatup Rack Calibration Measurement & Test Equipment Accuracy I i Rack Comparator Setting Accuracy One input i

Rack Temperature Effects Rack Drift Total Allowance - 4.0 % span

+a,c Channel Statistical Allowance -

Margin -

T1 T2 Safety Analysis Limit - 3.2 % span Nominal Trip Setpoint 2 7.2 % scan Allowable Value 1 6.2 % span In % instrument span (100 % Level)

, ** See Table 2-4 16

TABLE 2-4 STEAM GENERATOR LEVEL DENSITY VARIATIONS Because of density variations with load due to changes in recirculation, it

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is impossible without some form of compensation to have the same accuracy under all load conditions. The recommended calibration point is at 50 %

power conditions. Approximate errors at 0 % and 100 % water level readings and also for nominal trip points of 10 % and 70 % level are listed below for a typical 50 % power condition calibration. This is a general case and will change somewhat from plant to plant. These errors are only from density changes and do not reflect channel accuracies, trip accuracies or indicated accuracies which have been defined as Delta-P measurements only.(1)

INDICATED LEVEL (50 % Power Calibration) 0% 10% 70% 100% ,

Actual Leve! - - +a,c 0 % Power -

Actual Level 100 % Power (1) Miller, R. B., "Accuracy Analysis for Protection / Safeguards and Selected Control Channels", WCAP-8108 (Proprietary), March 1973.

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APPROVAL FOR RELEASE OF TECHNICAL REPORT Ac.ku e NUMBER: WCAP-11784 W PROPRIETARY CIASS: 2 DIIS te.tuu HAS BEDI REQUESTED BY: C. R. 'IUIEY/WEC E 324/W-284-4343 FIR REIEASE 'IO: PACIFIC GAS & ELECTRIC /NRC FOR ' HIE FOLIfWDG REMON(S): CENTRACIUAL OBLIGATION PREVICUS REIEASE: LONE REFORT TITLE: CAICUIATION OF STEAM GENERAIOR LEVEL ICW-ICW TRIP SETdODTP WTIH USE l OF A ROSDOUNP 1154 TRANSMrITER DIABIO CANYON UNITS 1 & 2 REPORT FUNDED BY: DATE OF ISSUE: MAR. 1988 l l

DATE STARIED ROUrD7G: 03/17/88 l l

SIGRIURE CHECK IDX DATE DO lm REIEASE REIEASE*

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REIURN 'IO: DIEORMATICti RESOURCE CDTTER - WEC E-209.

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IF REAGu IS W PROPRIETARY CIASS 2, 'IHDI SIGRIURE IS ICT RKUIRED AS PER NS-RAW-87-014.

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f IF NDR/IOP REIORT, 'IHDI SIGRIURES ARE LOT RDQUIRED AS PER CE-86-054 AND l NS-RAW-86-018.

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r APPROVAL FOR RELEASE OF TECHNICAL REPORT ic:.loRf NUMBER: WCAP-11785 W PROPRIETARY CLASS: 3

'IHIS REEORP HAS BEDT RD2UESTED BY: C. R. TUIEY/WEC E 324/W-284-4343 .

TOR REIEASE TO: UNRESTRICTED DISTRIBUTION FOR 'IHE 70 LID 4 dig REASON (S):

PREVIOUS REIFJSE: NONE REFORT TITIE: CAICJIATICN OF STCAM GENERAIOR IEVEL IDN-IDW TRIP SETPODE WI'DI USE OF A BOSDOUNT 1154 TRANSMITTER DIABID CANYON UNITS 1 & 2 REFORP EUNDED BY: LATE OF ISSUE: MAR. 1988 DATE SIARTED RCUIDIG: 03/17/88 SIGINME CHECK B3X QLT_S Do NOT REIEASE RELEASE *

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() J/ pg R. A. WIESEMANN PRCUECT MANAGER 2 gg () hhg6 J. C. WWMEL DEUMATION RESCURCE CDTTER ( ) ()

B. A. BURY

• IF APPROVAL IS IM GIVDT, STATE REASON (S) BEIDf. EO IM 00lTTHUE ROUrDUI REIURN 'IO: DIEDBMATION RESOURCE CDTTER - WEC E-209.

I IF REPORT IS W PROPRIETARY CLASS 2, THDi SIGIAIURE IS IM REQUIRED AS PER NS-RAW-87-014.

2 IF NIR/EOP REPORT, 'IHDi SIGIATURES ARE IM RD2OIRED AS PER CE-86-054 AND

• NS-RAW-86-018.*

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. _ _ _. .. Z_____._ . _ _

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Pacific Gas and Electric Company 77 Beale Street James D. Shrffer San Francisco,CA 94106 %ce President 415I973 4684 Nuclear Power Generabon TWX 910-372-6587 April 18, 1988 PG&E Letter No.: DCL-88-089 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Hashington D.C. 20555 Re: Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 License Amendment Request 88-03 Revision of Technical Specification 2.2.1, "Reactor Trip System Instrumentation Setpoints" and Associated Bases to Reduce Steam Generator Fater Level Low and Low-Low Setpoints Gentlemen:

Enclosure 1 is an application for amendment to Facility Operating License Nos. DPR-80 and DPR-82. The license amendment request (LAR) proposes to revise Technical Specification 2.2.1 and associated Bases to reduce the steam generator water level low and low-low setpoints from 15 to 7.2 percent of the narrow range span. Reducing the setpoints is a part of PG&E's Trip Reduction Program and is expected to decrease the number of unnecessary reactor trips from (1) steam generator water level low-low and (2) steam generator water level low coincident with steam /feedwater flow mismatch. This will in turn reduce the number of challenges to the reactor protection systems and impose fewer thermal transients on the plant, thus enhancing the long-term safety of the plant.

During the current refueling outage for Unit 1 and the next I refueling outage for Unit 2 (Fall of 1988), PG&E plans to replace the existing Barton 764 steam generator level transmitters with more accurate Rosemount 1154 transmitters. The requested setpoint changes will be made as soon as practical thereafter following issuance of a license amendment by the NRC.

A similar license amendment has been previously issued by the NRC for Salem on May 5, 1983 (Amendment 53 to DPR-70 and Amendment 21 to DPR-75).

Enclosure 2 provides HCAP-il784 "Calculation of Steam Generator l

t Level Low and Low-Low Trip Setpoint Hith Use of A Rosemount 1154 Transmitter," dated March 1988. This HCAP provides the analysis and calculation of the steam generator level setpoints. The methodology used to calculate the setpoints is essentially the same as that used for the V. C. Summer plant, which was approved by the NRC Staff in NUREG-0717, Supplement No. 4, dated August 1982.

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1 l Document Control Desk April 18,1988 As HCAP-ll784 contains information proprietary to Hestinghouse Electric Corporation, it is supported by an affidavit signed by Hestinghousp, the owner of the information. The affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of Section 2.790 of the Commission's regulations. It is respectfully requested that the information which is proprietary to Hestinghouse be withheld from public disclosure in accordance with 10 CFR Section 2.790 of the Commission's regulations. Accordingly, included in Enclosure 2 is a Westinghouse authorization letter (CAH-88-019), proprietary information notice, and accompanying affidavit. Correspondence with respect to the proprietary aspects of the Application for Hithholding or the supporting Hestinghouse affidavit should reference CAH-88-019 and should be addressed to R. A. Hiesemann, Manager Regulatory and Legislative Affairs, Hestinghouse Electric Corporation, P.O. Box 335, Pittsburgh, Pennsylvania 15230-0355.

Pursuant to 10 CFR 170.12(c), an application fee of $150.00 is enclosed.

Kindly acknowledge receipt of this material on the enclosed copy of this letter and return it in the enclosed addressed envelope.

Sincerelyt

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. D. Sh f er cc: J. B. Hartin J. Hickman H. H. Hendonca P. P. Narbut B. Norton H. Rood B. H. Vogler CPUC Diablo Distribution Enclosures 1953S/0056K/RLJ/1823

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