ML20031E700

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Westinghouse Reactor Protection Sys ESF Actuation Sys Setpoint Methodology. Proprietary Info Deleted
ML20031E700
Person / Time
Site: McGuire 
Issue date: 04/30/1981
From: Miller R, Sharp D, Tuley C
WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
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PROC-810430, NUDOCS 8110160316
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{{#Wiki_filter:P Of 'O WESTINGHOUSE CLASS 3 1 WESTINGHOUSE REACTOR PROTECTION SYSTEM / ENGINEERED SAFETY FEATURES ACTUATION SYSTEM SETPOINT METHODOLOGY DUKE P0llER C0fiPANY, McGUIRE UNIT 1 50-309 C. R. Tuley D. R. Sharp R. 8. Miller APRIL, 1981 This document contains in formation proprietary to Westinghouse Electric Corporation; it is submitted in con fidence and is to be used solely for the purpose for which it is furnished and returned upon request. This document and such information is not to ba reproduced, transmitted, disclosed or used otherwise in whole or in part without authorization of Westinghouse Electric Corporation, Nuclear Energy Systems. 4 WESTINGHOUSE ELECTRIC Nuclear Energy Systems P. O. Box 355 Pittsburgh, Pennsylvania 15230 A KO

o o t 3 TABLE OF CONTENTS Section Ti tle Pace

1.0 INTRODUCTION

1-1 2.0 COMBINATION OF ERROR COMPONENTS 2-1 2.1 Methodology 2-1 2.2 Sensor Allowances 2-2 2.3 Rack Allowances 2-4 3.0 RESPONSE TO NRC QUESTIONS 3-1 3.1 Approacn 3-1 3.2 De finitions for Protection System 3-1 Setpoint Tolerances 3.3 NRC Questions 3-5 4.0 TECHNICAL SPECIFICATION USAGE 4-1 4.1 Current Use 4-1 4.2 New Westinghouse Proposed STS A-1 Setpo' int Approach 4.2.1 Rack Allowance 4-2 4.2.2 Sensor Allowance 4-3 4.2.3 Implementation of the 44 Westinghcuse Proposed Setpoint methodology 4.3 Conclusion 4-6 Appendix A SMPLE STS SETPOINT TECHNICAL SPECIFICATIONS A-1 i

e a i LIST OF TABLES Taole Title Page 3-7 3-1 Tavg Channel Accuracy 3-8 3-2 * . 0vertemperature aT Channel Accuracy 3-10 3-3 Overpower AT Channel Accuracy 3-12 ' 34 Reactor Protection System / Engineered Safety Features Actuation System ? Channel Error Allowances c' 3-13 ~ Notes for Table 3-4 4-7 4-1 Examples of Current STS Setpoint Philosophy s 4-7 4-2 Examples of Proposed STS Rack Allowance 4 s g s. l .r s et T ~

  • m g'&

.A \\ -b m +y e NON+ =w '%D..e 4 6 e N ahm -TWC r 6 h-meg, e e + e ~.- 'e-

i t t i LIST OF ILLUSTRATIONS l F1curc Title Page 4-8 4-1 flUREG-0452 Rev. 2 Setpoint Error Breakdown 4-9 '4-2 Westinghouse STS Setpoint Error 't Breakdown i 4 1 4 [ i i l I I 3 i t i. e s 1 i i 1! I i i i ? 4 [ 4 i i I-1 r 4 i fit i I __nn__-,w, ,,.m -w e n, ,,wv_ _mm,, n ,m,--

1.0 INTRODUCTION

In March of 1977, the NRC requested several utilities with Westinghouse Nuclear Steam Supply Systems to reply to a series of questions concern-ing the methodology for determining instrument setpoints. This document contains the Westinghouse response to those questions with a correspond-ing defense of the technique used in determining the overall allowance for each setpoint. The information desired pertains to the various instrument channel com-ponents' analysis assumptions, i.e., a channal breakdown and values, for the Reactor Protection System (RPS) and the Engineered Safety Features Actuation System (ESFAS). Some of the information requested is already available in public documents, e.g., Chapters 15 and 16 of the Safety Analysis Report. The rest of the information has not been released and is drawn from equipment specifications or analysis assumptions. This information is considered proprietary and is noted as such. The basic underlying assumption used by Westinghouse is that several of the error components and their parameter assumpt' ions act independently, e.g.,[ ']ta,c, This allows the use of a statistical summation of the various breakdown components instead of a strictly arithmetic summation. A direct benefit of the use of this technique is increased margin in the total allow-ance. For those parameter assumptions known to be interactive, the technique uses arithmetic sunnation, e.g, [- ]ta,c The explanation of the overall approach is provided in Section 2. Section 3 presents the information requested along with three examples of individual channels, Tavg, Overtemperature AT, and Overpower AT. Also located in this section are descriptions, or definition, of the 1-1

various parameters used. This insures a clear understanding of the breakdown presented, in nearly all cases a significant margin exists between the statistical summation and the total allowance. Finally, Secticn 4 of this report notes the current philosophy for set-l f points in the Westinghouse generic Standard Technical Specifications (W STS). Also presented in this section is a proposal with examples of a anilosophy utilizing a five column table allowing for rack "as mea-ne sured" parameter drift and sensor "as measured" parameter drift. This l new philosophy is based on the methods of verifying setpoints in the plant and reflects the 31 day and 18 month surveillance requirements. O e S e 2

6 2.0 COMBINATION OF ERROR COMPONENTS 2.1 Methodolocy The methodology used to combine the error components for a channel is basically the appropriate statistical comoination of those groups of comoonents which are statistically independent, i.e., not interactive. Those errors which are not independent are added arithmetically into The groups themselves are independent ef fects which can then be groups. systematically combined. The methodology used for this combination is not new. Basically it is ]ta,c.e which has been the[ utilized in other Westinghouse reports. This technique, or other sta-tistical approaches of a similar nature, have been used in WCAP- ~ 9180(1) and WCAP-8567(2)It should be noted that WCAP-8567 has been approved by the NRC Staff thus' noting the acceptability of statis-tical techniques for the application requested. It should also be re-cognized that the Instrument Society of America approves o f the use of statistical techniques in determing safety-related instrumentation set-points (3) Thus is can be seen that the use o.f statistical approaches in analysis techniques is becoming more ar.d more widespread. The relationship between the error components and the total statistical error allowance for a channel is, ~ ta,C F (1) Little, C.C., Kopelic, S. D., and Chelemer, H., " Consideration of Uncertainties in the Speci fication of Core Hot Channel Factor WCAP-9180 (Proprietary), WCAP-9181 (Non-proprietary), Limits." September, 1977. (2) Chelsner, H., Bowman, L. H., and Sharp, D. R., " Improved Thermal Design Procedure," WCAP-8567 (Proprietary), WCAP-8763 (Non-pro-prietary), July,1975. (3) Instrument Society o f America, proposed standard SP67.04, "Setpoints for Safety-Related Instrumentation used in Nuclear Power Plants." 2-1

7-. where: ta c As can be seen in Equation 2.1, [ ]ta,c allowances are interactive and thQs not independent. The [ ]ta c is not neccessarily considered interactive with all other parameters, but as an added degree of conservatism is added arithmetically to the statistical sum. 2.2 Sensor Allowances Four parameters are considered to be sensor allowances, [ ]ta,c (see Table 3-4). Of these four parameters, two are considered to be statistically independent, [ ]ta,c, and two are considered interactive [ ]ta,c, { .]ta,c are considered to be independent due to the manner in which the instrumentation is checked, i.e., the instrumentation is [ and drift determined under conditions in which pressure and temperature ]ta,c An example of this would be as follows; + a,c 2-2

a,c pa,c are considered to be interactive for the same reason that [ ]ta,c are considered independent, i.e., due to the manner in which the instrumentation is checked. [ ] tac Based on this reasoning, [ ]ta,c have been ~ added to form an independent group which is then factored into Equation 2.1. An example of th's impact of this treatment is; for Pressurizer Water Level-High (sersor parameters only): 'ta,b,c i using Equation 2.1 as written gives a total of; 1 ta,c - 1.66 percent 2-3 ,-w-- e p ,m,-w -,-,-..--e,---- -,,e ,---.---------.v.-

+.,,--r.,--,.-----,,--r--

p..

S Assuming no interactive effects for any of the parameters gives the following results: ta.c I (Eq. 2.2) = 1.32 percent Thus it can be seen that the approach represented by Equation 2.1 which accounts for interactive parameters results in a more conservative sum-mation of the allowances. 2.3 Rack Allowances Four parameters, as noted by Table 3-4, are considered to be rack allow-ances,[ ]ta',c Three of these parameters are considered to be interactive (for much the same reason outlined for sensors in 2.2), [ ]ta,c [ t3 a,c, Sased on this logic, these three factors have been added to form an inoependent group. This group is then factored into Equation 2.1. The impact of this approach (formation of an independent group based on interactive components) is significant. For the same channel using thc same. approach outlined in Equations 2.1 and 2.2 the following results are reached: 2-4

e o ta,b,c using Equation 2.1 the result is; ta,c 1.82 percent Assuming no interactive effects for any of the parameters yields the following less conservative result; ~ _ta.c (Eq. 2.3) 1.25 percent Thus the impact o f the use of Equation 2.1 is even greater in the area of rack effects than for the sensor. Therefore, accounting for inter-active effects in the statistical treatment o f these allowances insures a conservative result. Finally, the [ ]"'C parameters ar3 considered to be independent o f both sensor and rack paramr.ters. [ ]ta,c Thus, these parameters have been statistically factored into Equation 2.1. 2-5 w w 9-g.w-g -T-- p--

p rw T-

+ w t- --trw---- p +gwg pm -T-r T y-+

3.0 RESPONSE TO NRC OUESTIONS 3.1 Acaroach As noted in Section One, Westinghouse utilizes a statistic 1 summation of the various components of the channel breakdown. This aproach is valid where no dependency is present. An arithmetic summa ion is ~ required where an interaction between two parameters exist, Section Two Th equation provides a more detailed explanation of this approach. used to determine the margin, and thus the acceptability c the param-eter values used, is: ta,c where: [ ] a,c, and all other parameters are as defined for Equation 21. Tables 3-1 through 3-3 provide examples of individual char el breakdowns verpower AT. and margin calculations for Tavg, Overtemperature aT, and use takes It should be noted that only those channels which Westingt For credit for in the analysis are provided with detailed brei downs. those channels not assumed to be primary trips, there are o Safety etermined. Analysis Limits, thus no Total Allowance or Margin can be 3.2 Definitions for Protection System Setpoint Tolerance: To finsure a clear understanding of the channel breakdown ed by West-ed: inghouse in this gort, the following definitions are no 3-1

e 1. Trio Accuracy The tolera.:e band containing the highest expected value of the difference tetween (a) the desired trip point value of a process variable and (b) the actua'l value at which a comparator trips (and thus actuates some desired result). This is the tolerance band, in percent of span, within which the' complete channel must perform its intended trip function. It includes comparator setting accuracy, channel accuracy (including the sensc-) for each input, and environ-mental effects on the rack-mounted electronics. It comprises all instrumentation errors; however, it does not include process 1 measurement accuracy. 2. Process Measurement Accuracy Ir.cludes plant variable measurement errors up to but not including the sensor. Exarples 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.aeasurement accuracy such as fluio stratification. It also assumes a controlled environment for the readout device. 3-2

s 5. Channel Accuracy The accuracy of an analog channel which includes the accuracy of the primary e,er.ent anc/or transmitter and mocules in the enain where calibration of modules intermediate in a chain is allowed to compen-sate for errors in other modules o f the chain. Rack environmental ef fects are not included here to avoid cuplication due to cual inputs, however, normal environmental e f fects on field mounted hard-ware is included. 6. Sensor Allowable Deviation The accuracy that can be expected in the field. It includes drift, temperature e ffects, field calibration and for the case of d/p trans-mitters, an allowance for the e f fect o f static pressure variations. The tolerances are as follows: Re ference (calibration) accuracy - [ ]tabc percent unless a. other data indicates more inaccuracy. This accuracy is the SAMA re ference accuracy as de fined in SAMA standard PMC-20-1-1973III. b. Temperature e f fect - [ ]tabc percent baswd in a nominal temperature coef ficient of [ ]tabc ercent/*.00 F and a 0 maximum assumed change o f 50 F. Pressure a ffect - usually calibrated out because pressure is c. con stant. If not constant, nominal [ ] abc percent is used. Present data indicates a static pressure ef fect of approximately ]tabc percent /1000 psi. d. Dr.. - chtnge in input-output relationship over a period of time at reference conditions (e.g., [ ] a,c [ ] #DC of span. 3-3

.~. 7. Rack Allowable Deviatior The tolerances are as follows: a. Rack Calibration Accuracy The accuracy that can be expected during a' calibration 6t refer-ence conditions. 'This accuracy is the SAMA referca.: sccuracy as defined in SAMA standard PMC-20-1-1973(1) This it.cludes all modules in a rack and is a total of [ ]tabc ercent of span assuming the 'n of modules is tuned to this accuracy. For simple loops x .e a power supply (not used as a converter) is the only rack module, this accuracy may be igncred. All rack modules individually must have a reference accuracy within -[ ] abc percent. b. Rack Environmental Effects Includes effects of temperature, humidity, voltage, and frequency changes of which temperature is the most significant. An accuracyof[ ]tabc percent is used which considers a 0 0 nominal ambient temperature of 70 F with extremes to 40 5 and 120 F for short periods of time. c. Rack Drift (instrument channel drift) - change in input-output relationship over a period of time at reference ccnditions (e.g., [ ]ta,c +1 percent of span, d. Comoarator Settino Accuracy Assuming an exact electronic input, (Note thi the channel accuracy" takes care of deviations from this i 11),the (1) Scientific Apparatus Manufacturers Association, Standard PMC-20-1-1973, " Process Measurement and Control Terminology." 3-4

( 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 ar r as follows: (a) Fixed setpoint with a single input - [ ] abc percent This assumes that comparator nonlinearities are accuracy. compensated by the setpoi.it. (b) Qual input - an additional [ ]tabc percent must be added for comparator nonlinearities between two inputs. Totai[ ]tabc percent accuracy. Note: The following four definitions are currently use in the Standardized Technical Specifications (STS). 8. Nominal Safety System Setting The desired setpoint ' the variable. Initial calibration and subsequent recalibrations should be made at the nominal safety system setting (" Trip Setpoint" in STS). 9. Limiting Safety System Setting A setting chosen to prevent exceeding a Cafety Analysis Limit (" Allowable Values" in STS). (violation of this setting represents an STS violation).

10. Allowance for Instrument Channel Drift The difference between (8) nd (9) taken in the conservative direc-tion.

5

I

11. Safety Analysis Limit The setpoint value assumed in safety analyses.
12. Total Allowable Setooint. Deviation scme definition as 9, but the difference between 8 and 12 encompasses

[ ],ta,c 3.3 NRC Questions T'e information requested by the NRC for each channel is: 1. What is the technical specification trip setpoint value ? 2. What is the technical specifi, cation allowable value ? 3. What instrument drift is assumed to occur during the interval between technical specificr.'. ion surveillance tests ? What are the components of the cumulative instrument bics (e.g., 4. instrument calibration error, instrument drift, instrument acror, etc.) ? 5. What is the margin between the sum of the channel instrumentation error allowances and the total instrumentation error allowance assumed in the accident analysis ? The Westinghouse response to these questions is: The response to Question 1 will be found as Column 14 of Table a. 3 4 in this section. 3-6 wm g- - - - -.p.3 y y-p 9-e, ,__..,47-, 7 -,y-r-- a. _-,7

L __- b. Column 13 of Table 3 4 provides the information requested in Question 2. The instrument drift assumed is the difference between the trip c. setpoint and the allowable value in the technical specifications, this can be found as Column 11 of Table 3 4 d. The bulk of Table 3-4 provides the breakdown values required by Question 4. The margin requested by Question 5 is noted in Column 17 of Table e. 34. It should be remembered that Westinghouse is providing responses only for those channels for which credit is taken in the accident analysis. Again this is due to the f act that Question 5 cannot be answered if the channel is rat a primary trip. 1 3-7

..--w. --+.<<-,...-,..e w m -== = ~ * * = * ~ ' ' ~ ' " * '

  • ~ ~ '

TABLE 3-1 Tavg Channel Accuracy Parameter Allowance * ~ tabc

  • in percent of span.

The' margin, based on Equatio:, 3.1, is calculated as follows: -tabc =[ )Pabc The Total Allowance is 4.0%, tnus the margin is [ ]ta,b,c of span. 3-8

) i i l TABLE 3-2 Overtemperature AT Channel Accuracy Allowance

  • Parameter tabc f

I O i \\ 1, ) i f i

  • in percent of span, (1000F span - 150 % power) 3,9

TABLE 3-2 (Continued) Tne Margin, basad on Equation 3.1, is calculated as follows: .'a,b. C ~ =[ ] a,c. The Total Allowance is 6.0%, tnus the margin is [ ]ta,c of span. 3-10

j ) 7 t I TABLE 3-3 i i Overoower AT Channel Accuracy Allowance

  • Parameter i

tabc i k t 4j L r I; j c t v i .e b i P 4 l d I I 2 I, t E i i f 0

  • in percent of span,~(100 F span - 150% power)-

i I 3-11 h' k i %ev,v e-e e --

  • w-e m..

..vw ewytyw w _. _,ww-w m m egperg+wwwy-q +,w av'*W-T w r-N f uer. -.. Wws,, -. ..--w.-r*7v vem'* W psw-*v f e-

  • w*v T

TABLE 3-3 (Continued) The margin based on Equation 3.1 is calculated as follows: . tabc -[ ]tabc. The total Allowance is 4.2%, thus the margin is [ ]tabc of span. o e 3-12

-m.... -..s NOTES FOR TABLE 3-4_ l. All values in percent span. 2. As noted in Table 15.1-3 of.SAR. 3. As noted in Table 2.2-1 and 3.3-4 of Westinghouse STS. ]ta.c 4. [ 5. Not used in the Safety Analysis. 6. As noted in Figure 15.1-1 of SAR. 7. As noted in Notes 1 and 2 of Table 2.2-1 of Westinghouse STS. 8. [ ]ta,c 9. Note found in Table 15.1-3 of SAR but used in Safety Analysis. 10. Not Westinghouse scope. 11. As noted in Table 2.2-1 of Westinghouse STS. 12. Trip Setpoint function of note (11) plus 10%. 3 ** 13. [ 3.*** 14. Included in [ I i ..,...-__m, ,e_.-,,-, - ~ _, _, _, _ _ _.., _..-_.,.,.,_;.--..,.,,,,__,,,.

4.0 TECHNICAL SPECIFICATION USAGE I. ~. CURRENT USE 'he Standard Technical Soecifications (STS) as used for Westinghouse type plant designs (see NUREG-0452, Revision 2) utilizes a two column

  1. ormat for the RPS and ESF system. This format recognizes that the

~ setooint channel breakdown, as presented in Figure 1-1, allows for a certain amount of rack drift. The intent of this format is to reduce the number of Licensee Event Reports (LERs) in the area of instru-mentation setpoint drift. It appears that this approach has been successful in achieving its goal. However, the approach utilized is fairly simplistic [ ~ ta,c ~ g The use of the statistical swunation technique described in Section Two of this report allows for a natural extension of the two column approach. [ ]ta,c and also allows for a more flexible approach in reporting LERs. Also'of significant benefit to the plant is the incorporation of sensor drift parameters on an 18 month basis (or more of ten if necessary). 4-1 4 e j , ~, _, -. _ _ _,,. _, _

4.2 NEW WESTINGHOUSE PROPOSED STS SETPOINT APPROACH Recognizing that besides rack drift the plant also experiences sensor drift, Westinghouse now proposes an approach to technical specification setpoints that is somewhat more sophisticated than that used today. This new methodology-accounts for two additional f actors seen in the plant during periodic surveillance,1) sensor drift effects, and, 2) interactive effects for both sensors and rack. 4.2.1 RACK ALLOWANCE The first that will be covered is item 2, the interactive effects. Westinghouse has known for some time that when an instrument technician looks for [ ] tac he is seeing more than that. This inter-action has been noted several times and is handled in Equations 2.1 and 3.1 by { ]ta,c To account for this interaction at the rack level, Westinghouse proposes that the difference between the STS Trip Setpoint and the STS Allowable Value be a [ statistically determined]ta,c " trigger value" as shown in Figure 4-2. This value is determined by the following equation: [ ]ta,c (Eq. 4.1) where: the "as measured" rack trip setpoint R = ta,c [ 3 4-2

t3ac [ ]andallotherparametersareasdefinedforEquations2.1and + a,c 3.1. This means that all the instrument technician has to do during~the 31 day periodic surveillance is determine the value of the bistable trip 59tpoint, verify that it is less than the STS Allowable value, and does not have to account for any additional effects. The same approach is used for the sensor, i.e., the "as mea:ared" value is used when required. Tables 4-1 and 4-2 show the current STS setpoint philosophy and the Westinghouse proposed rack allowance (for use on 31 day sur-veillance only). A comparison of the two different Allowable Values will show the net gain of the proposed version. 4.2.2 SENSOR ALLOWANCE To account for the sensor allowance, i.e., drift, is somewhat more com-plicated. If the approach used by Westinghouse was a straight arith-metic sum, sensor allowances for drift would also be straight forward, i.e., a three column setpoint methodology. However, the use of the statistical summation requires a somewhat more complicated approach. This methodology, as proposed by Westinghouse and demonstrated in Sec-tion 4.2.3, Implementation, can be used quite readily by any operator whose plant's setpoints are based on statistical sumation. The method-ology is based on the use of the following equation. [ ]ta.c (Eq.4.2) 4-3 ..,---,--.r--nm,,.., .n., ,,--.yv,._,.--_,,.,,, ,-n ,.,,,.,w,,,,,,,,a-,.,-,_,,,-_,, ,._,.,w,,,,,,m...,e,.,,,,,,,.w,,,. ,,,,,,,,,.,,,_mm._,

r wnere: t the "as measured sensor value" [ J a,c S and all other parameters are as de fined in Equation 4.1 Ecaation 4.2 can be reduced fbrther, for use in the STS to: Z + R + S < TA (Eq. 4.3) where: t [ Ja,c Equation 4.3 would be used in two instances,1) when the "as measured" rack setpoint value exceeds the rack " trigger value" a3 de fined by the STS Allowable Value, and, 2) when determining that the "as measured" sensor value is within acceptable values as utilized in the various Safety Analyses and verified every 18 months. 4.2.3 IMPLEMENTATION OF THE WESTINGHOUSE PROPOSED SETPOINT METHODOLOGY Implementation of this new methodology is reasonably straight forward, Appendix A provides a proposed text and sample table for use in the STS. An example of how the speci fication would be used for the Steam Generator Water Level - Low-Low reactor trip is as follows. Every 31 days, as required by Table 4.3-1, a (Unctional test would be per formed on the channels o f this trip function. During this test the bistable trip setpoint would be determined for each channel. If the "as measured" bistable trip setpoint error was found to be less than or equal to that required by the STS Allowable Value, no action would be necessary by the plant staff. The Allowable Value is determined by Equation 4.1 as follows: 4-4

O e [ ] t a,c where: ~ ta,c ~ [ tya,c Now let's assume that one bistable has " drifted" more than that allowed by the STS for 31 day surveillance. According to the proposed ACTION statement "A", the plant staff must verify that Equation 2.2-1 is met. Going to the proposed Table 2.2-1, the following values are noted: 2'. ^ 12.18 and the Safety Allowance (TA) - 15.0. I.et's assume that the "as measured" rack setpoint value is 2.25 percent low and the "as measured" sensor value is 1.5 percent. Equation 2.2-1 now looks like: I + T + 5 < TA '2.18 +-2.25 + 1.5 < 15.0 15.9 15.0 4-5

.. ~ _ _ _ _.. _.. - _ _.. _ _ _ _.. _ _. _ _. As can be seen,15.9 percent is not less than 15.0 percent thus the plant staf f must follow ACTION statement "B" (declare channel inoperable and place in the " tripped" condition). If the sam of R + S was about one percent less e.g., R = 2.0 percent, S 0.75 percent thus R + 5 - 2.75 percent, then the sum o f Z + R + 5 = would be less than 15 percent. Under this condition, the olant staff should recalibrate the instrumentation, as good engineering practice suggests, but the incident is not reportable, even though the " trigger valued is exceeded, because Equation 2.2-1 was satis fied. Table 4.3-1 also requires that a calibration be per formed every re fuel-ing (approximately 18 months). To satis fy this requirement, the plant sta ff would determine the bistable trip setpoint (thus determining the "as measured" rack value at that time) and the ' sensor "as measured" value. Taking these two "as measured" values and using Equation 2.2-1 again the plant staff can determine that the tested channel is in fact 4 within the Sa fety Analysis allowance.

4.3 CONCLUSION

Using the above proposed methodology, the plant gains added operational flexibilty and yet remains within the allowances acccur.ted for in the various accident analyses. In addition, the methodology allows for a sensor dri ft factor and an increased rack dri ft factor. These two gains should signi ficantly reduce the problems associated with channel drift and thus decrease the number of LERs while allowing plant operation in a safe manner. 9 4-6

(- TABLE 4-1 EXAMPLES OF CURRENT STS SETPOINT PHILOSOPHY r s Power Range Pressurizer Neutron Flux - High Pressure - High i Safety Analysis Limit 118% 2410 psig STS Allowable value 110% 2395 psig i STS Trip Setpoint 109 % 2385 psig 4 i TA8LE 4-2 EXAMPLES OF PROPOSED STS RACK ALLOWANCE Power Range Pressurizer Neutron Flux - High Pressure - High Safety Analysis Limit 118% 2410 psig STS Allowable Value 111.2 % 23% psig (Trigger Value) STS Trip Setpoint 109 % 2335 psig 4-7 I ,,---.,-,,e ,-,-,-,-.-e-- -,.- - - -.. - - + -, ,-.-,-.-----.,.-...w...--,.

Figure 4-1 +'a,c Actual Calib-ation Setpoint Figure 4-1 NUREG-0452 Rev. : 5etpoint Error Breakdown

Figure 4-1 ,'a,c l Table 4-2 Westinghouse STS Setpoint Error Breakdown

APPENDIX A SAMPLE STS SETPOINT TECHNICAL SPECIFICATIONS 2.2 LIMITING SAFETY SYSTEM SETTINGS INSTRUMENT SETPOINTS REACTOR TRIP SYSTEM 2.2.1 The Reactor Trio System instrumentation setpoints shall be set consistent with the Trip Setpoint values shown in Table 2.2-1. APPLICABILITY: As shown for each channel in Table 3.3-1. ACTION: A. With a reactor Trip System instrumentation channel setpoint (for rack components only) less conservative than the value shown in the Allowable values column of Table 2.2-1, determine that the following equation is met for the affected channel: I + R + S < TA (Eq. 2.2-1) where: l Z = the value from column Z of Table 2.2-1 for the a ffected

channel, R = the "as measured" value (in percent) of rack drift for the a ffected channel, 5 = either the "as measured" value (in percent) of the sensor dri ft, or the value in column S of Table 2.2-1 for the affected channel, and TA = the value from column TA of Table 2.2-1 for the a ffected channel.

8. With the requirements of Equation 2.2-1 not met, declare the channel inoperable and apply the applicable ACTION statement requirement of specification 3.3.1.1 until the channel is restored to OPERABLE Status with its trip setpoint adjusted consistert with tP.a Trip Setpoint value.

t-O -. - = - - =. - o se l g -t .8 4 ~ ns g L. =E

==

  • 3 "..

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E 3 e. g a s a 2 a - [ y =U 3

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3 A1

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e N g = - -- en a

== C O "s - g f *. R. 'R. L $ e m5 ~$ 1< 1 . a i E ~.

e. e e is.

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== 41 - At est p.= g-g a - e o e m =.

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e. :

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~ s; < " _ ' 3-

, S, #,S i

F t, -i m '. c e e =

== o.

e.., ~. ~.

. =. e .e. .e e o. o. 1 - - e c ~ - a r. ~.- r + .. e e e e. me EI 2^ g, C .I -4 s enl %J' w, 4 '? g' I r E 9 4 e e e e - -. e e. e. E e e ~ = e e -. -. ~ ~ ~ (*

== -e i I. k es. .e of e ._e g 3 3 O -} p 3 u a m 4 g 3 =. =.=.

== w w ~I g + n ns. e- = E E =& 2

  • 4 E

3. w

t. e wg t-h.

E .E-8' 6 6 me E as S Un e e e p 3= "g C =* 3 = g = C &E E = 2 3 C .=. g w w g t =

3. g.

- - +es t me L g, g& g g 6 g a 6 a. 3 -= . T. -{ 3 .m k ee 3 m a> g a

3 p.I

.e** g P te 9 4 6 6 6 a=3 k E.

A.

= -**a= 8.= t. L 9

    • t.
1. p 475 1 m..-

L=== W L 4 2 &, 3 J 4 Erte .e .. s 4-8 46 %I -v5 m5 - c t "y 33 3.I I k k 5 : - 2g g 3. g - 4 g-z > 3 3 ? i ALE ga 4 g: eI r-r E < < < w = - w = - w E - - g0 'a - ig j g > f s - s 2 2 a - se a t a-2 2 .T g. C g, a s. 6

== = - a."m e 4

  • K e

a e e. g 4. K .r e. .m f% t.. !

TABLE 2.2-1 (continued) REACTOR TRIP SYSTEM INSTRtMENTATION TRIP SEIPOINIS NOIATION 5 1+1 5 NOTE 1: Overtemperature aT (3,T1 + Tg ) (3, ' 5)-T 1 + K (W P') - f (al)l g 4 i 3 g 3 l * '5 '6 p 3 1+T5 3 Where: - Lead-lag compensator on measured aT 3 - Time constants utilized in the lead-lag controller for aT, Tg - 8 secs., T g, Tp 7 - 3 secs. 1 I - Lag compensator on measured AT g, - Time constant utilized in the lag compensaton for aT,1 3 - 2 secs. d 1 3 aTo = Indicated AT at RATED THERHAL POWER K1 - 1.198 - 0.0133 K2 1+T 5 - The function generated by the lead-lag controller for Tavg dynamic compensation j 4 1+ 5 - Time constants utilized in the lead-lag controller for Tavg, T4 - 28 secs., 14,15 5 = 4 secs. T T - Average temperature *F 1- - Lag compensator on measured Tavg 1+T b 6 t O

~ TABLE 2.2-1 (continued) REACTOR TRIP SYSTEM INSTRUNENTATION TRIP SEIPOINTS NOTAll0N NOTE 1: (con tinued) T6 - Time constant utilized in the measured Tavg lag compensator, T6 - 2 secs. T' < 590.8'F (Nomin31 Tavg at RATED TilERMAL POWER) i - 0.000647 K3 P = Pressurizer pressure, psig P' - 2235 psig (Nominal RCS operating pressure) 5 - Laplace trans form operator 33 -); and f (al) is a function of the indicated dif ference between top and bottom detectors of 1 the power range nuclear ton chambers; with gains to be selected based on measured instru-ment response during plant startup tests such that: (i) for qt - pb between -43 percent and -6.5 percent (1(al) = 0 (where qt and qb are percent RATED THERMAL POWER in the top and bottom halves of the core respectively, and qt + qb is total THERMAL POWER in percent of RATED THERMAL POWER). (ii) for each percent that the magnitude of (qt - qb) exceeds -43 percent, the aT trip setpoint shall be automatically reduced by 2 percent of its value at RATED TilERMAL POWER. (iii) for each percent that the magnitude of (qt - qb) exceeds -6.5 percent, the al trip setpoint shall be automatically reduced by 1.641 percent of its value at RATED THERMAL POWER. t NOTE 2: The channel's maximum trip setpoint shall not exceed its computed trip point by more than 4.0 percent. l tf f

r l l 0 TABLE 2.2-1 (continued) REACTOR TRIP SYSTEM INSTRLNENTATION 1 RIP SETP0'91S NOTATION I+t S T S I 6 k +'6 N)TE 3: Overpower al ( g,

3) (p,
3) < aTg (K4 5 (1 + 1 5} Il+1S

-K 2 7 6 1+t S g Where: - as defined in Note 1 I+1 5 7 l f T),12 - as defined in Note I t I - as defined in Note 1 y g, 3 l 9 T

  • 85 d'II"*d I" " l' I l

3 aTo - as defined in Note 1 = 1.163 K4 - 0.02/~F for increasing average temperature and 0 for decreasing average tem-KS perature 1 5 7 - The function generated by the lead-lag controller for Tavg dynamic compensation l 3, g 7-10 secs. 1 - Time constant utilized in the lead-lag controller for Tavg, 1 l 7 l = as defined in Note 1 g 16 - as de fined in Note 1 l I O

I TABLE 2.2-1 (continued) REACTOR TRIP SYSTEM INSTRUMENTATION TRIP SETPOINTS NOTATION NOTE 3: (con tinued) - 0.00126/*F for T > T" and K6 - 0 for T < T" K6 T - as defined in Note 1 T" - Indicated Tavg at RATED THERMAL POWER (Calibration temperature for aT instrumen-tation, < 59G.8'F) S - as de fined in Note 1 f (al) - 0 for all al 2 NOTE 4: The channel's maximum trip setpoint shall not exceed its computed trip point by more than 2.8 percent. i h is 4 0 5

c 2.2 LIMITING SAFETY SYSTEM SETTINGS INSTRUMENTATION SETPOINTS ENGINEERED 5AFETY FEATURE ACTUATION SYSTEM 2.2.2 The Engineered Sa fety Feature Actuation System (ESFAS) instrumen-tation setpoints snall be set consistent with the Trip Setpoint values shown in Table 2.2-2. APPLICABILITY: As shown 6or each channel in Table 3.3-3. ACTION: A. With an ESFAS instrumentation channel setpoint (for rack components only) less conservative than the value shown in the Allowable Values column of Table 2.2-2, determine that equation 2.2-1 is met for tne a f fected channel: where: the value from column I of Table 2.2-2 for the af fected Z =

channel, R

the "as measured" v,alue (in percent) of rack drift 6cr = the af fected channel, either the "as measured" value (in percent) of the sen-S = sor dri ft, or the value in column S of Table 2.2-2 for the a f fected channel, and the value from colunn TA of Table 2.2-2 for the affected TA = Channel. Wi th the requirements of Equation 2.2-1 not met, declare tne channel B. inoperable and apply the applicable ACTION statement requirement of Speci fication 3.3.2.1 until the channel is restored to OPERABLE status with its trip setpoint adjusted consistent with the Trip Setpoint value. k'$

7 l 4 l i f l IABtt 2.2-2 l tNGINEERED SAFEIV f f AluRE ACIUA'110N SYSTEM lNSIRIN(NIAll0N IRIP 5tifulNi$ See.sor I f unc t {nn.a,{ tall Igtal Al_lywang j lA) { Drl!L J5) !r ip _Se tpi>Jul Allowe.fr v a lue-l i 1. 541 1 V INJFCil0N, IURBIN[ 1 RIP AND Fl((WAl[R 150l All0N l { A. Manual Inillation M NA NA NA Na t

8. Au t 3ma t ic Ac tua t inn l ogic NA NA NA NA NA t

C. Cnntainment Pressere - lligh 3.0 0.71 1.5 < 4.7 psig - 5.(> pse9 O. Pressur izer Pressure - tow 13.0 10.71 1.5 i 1900 psig }

f. Steamline Pressure - Low 17.9 10.71 1.5 i 600 psig

- 1809 psig sin psig INoir *. ) T. Dif ferential Pressure G. Steam Flow in Iwo Steamlines - 100 psi - 109 psi Between Steamlines - High 3.0 0.87 2(l.5) e l - liigh 20.0 13.16 2(l.5) < A function de fined as < A funi t sim eh t one 1 4. Tollows: A aP (orresponding follows: A al' (ne s e-spesiilinis j to 40% of full steam f l e=a to 42.5% o f hell s t esa l leiw between 01 and 20% load and between ut.n d /07 I n..:.m. then a aP increasing linearly then a aP anc r ea.ing l en..n l y to a aP corresponding to 110% to a ar (in s espearlinis lie 11/.$1 o f full s team finw at full of full s traus l i nw.i t tull Inad ined l q lt. l av y - l ow -l ow 4.0 1.12 0.2 -> 543*F '> 540.5"I i ? l 2. E.ONIAINHINI SPRAV I i A. Manual Initiation NA NA NA NA NA D. A4tomatic Actuation logic NA NA NA NA NA + f (. Con t a inmen t Pres sur e - liigh -fligh 3.0 0.71 1.5 < 23.5 psig 5 74.4 psea f J. filNIAlfMINI 1501 All0N 5 i } A. Phase "A" Isolation

l. Manual NA NA NA NA NA
2. f rom Sa fety injectinn Automatic Ac tualinn logic NA NA NA NA NA 1

l R. Phase "B" Isola t inn j

l. Manual M

NA NA NA NA j j

2. Aufomatic Attuatinn NA NA NA NA NA i
1. f.on ta inmen t Pres sur e -

liigh-liigh 3.0 0.71 1.5 < 23.5 psig 5 24.4 esa p I r. Con t a inmen t V en t ila t irm Isolatinn I

1. Manual NA NA NA NA NA

' d*

2. I rtwa Sa fet y injer tinn Au t oma t ir Ac tu a t inn i ngir NA NA NA NA I4A

{

l. I nnta inment Raillo-

.u liv ity Itiqh (10) (10) (10) (10) II'd a ) i i i

I I r I 1 l 1ABtf 2y ( NGI N.I.E R E D. _S A.f.f l Y _F_t_A.llm..t_ AC lUAl l0N _S_Y_ S_IE M .I. N_5_1_R_IN.I_N I Al_l. D_N_ _IR. IP _Si lPU I N.I 5_ f, Sensor l functional tinit total Alleuant.e (IA) l Drlft y ) Ir,,p 5etpoint_ Allew4hle v.elen-l i i 4. N il /M I I NI 1504All0N i i A. Manual M NA NA NA NA L R. Aut<wnatic Actuation logic NA NA NA NA NA C. (nntalement Pressure - I3 l /4.4 psey I :s i fligh liigh 3.0 0.11 1.5 < 23.5 pseg j, (). Steamline Pressure - I rw 11.9 10.11 1.5 > 600 psig > 51H ps i., ( N..t.. s ) i}j i { f. Negat ive Steam Pressur e g Ill.S pst (ten t e fi l 3 Rale.lligh H.0 0.11 1.5 < -100 pst l S. tilHil! Nt IRIP ANO fillWAllH 1%8All0N l . y!i i A. Steam Generator Water j I h:, level - High-iligh 13.0 2.18 1.5 < 61% o f narr ow r an ge < 68.H1 of narrow range 3 Instrument span Instruaent sp.us '1 [ ll5 l 6. AtlIll l ARY f fIDWAllR A. Steam Generator Water U w l evel - t ow-t <w 15.0 12.10 1.5 g)l-15% of narrow range > 13.21 a f narro-r.une-t M instrument spae Ins t r esewn t sp in O. Safety injection See I abeve (all 51 setpoints) k '! l' C. Station Riackout (10) (10) (10) (10) (10) h D. Ir Ips of Main Feedwater j Piseps NA NA NA NA NA L{ g. 6 4 l l 0 'h Li i i h] Note 5: lime s onstants utilized in the le,$d-lag runtroller for Steam Pressure-itw are ij > $0 setunds and 17 < 5 winnels. Jj q Note 6: Ihe time tonstant utillied in the e ate-lag controller for Negat ive Steam Preuure Rate.High. 50 sei s. l( ij. t 5 1 l, 'd'E 4 a. i 1 f l 4 i 1 1

r v 4 . _ _. _ _ _ _ _.._-...___._ s. ~ SAFE Y LIMITS f.ND LIMITING SAFETY SYSTEM SETTINGS 2.2 _IMITING SAFETY SYSTEM SETTINGS REACTOR TRIP / ENGINEERED SAFETY FEATURE ACTUATION SYSTER INTERLOCKS 2.2.3 The Reactor Trip System and Engineered Safety Feature Actuation System interlock setpoints shall be consistent with the Trip Setpoint values shown in Table 2.2-3. APDL*CABILITY: As shown for each channel in Table 3.3-5. ACTION: Witn a reactor trip system or engineered safety feature actuation system interlock set' oint less conservative than the value 'shown in the Allow-p able value column of Table 2.2-3 declare the channel inoperable and apply the applicable ACTION statement o f Table 3.3-5 until the channel is restored to OPERABLE status with its trip setpoint adjusted consis-tent with the Trip Setpoint value. e A-lO

r w b ~~ 9 7 0** m -a 3 C A QJ m W .E = w Cm >= w ww C 3 <2 <2 >== 2 m Cn - c-3 L.3 .Q LM cc C <C e= = 4w QJ l A 64 C c., mA e m C 3 0 6 CL c. QJ n oJ >= QJ - oJ sJ w . L 9 m9 C< c w e 3 3 x ME M-> ME E e w Mm a o N CC N 3= C CE M CK E c- = = N. m .m .m m g c -w v - c. = mw co w O 6 ^l v >- VH w v >- ^ ).- vl ^l ^{ vla Z g axw >= .Z K w p OJ- -a m C QJ e W g C. L .= 4 g E C 3 C C 9 wg @ m wg wa @= gg C >= w Ce >= w >= w C 3 C eC 3 47 43 eC 2 - c-3 O oc C 4 Lw 2O cc C .c w %y A 8 A L C. C 1 A Cn Cn L a C b 3 W W -b e= = 3 @ .g W OJ >= G - OJ O ,J en en W >= 6 m W

  • C en 4 M <E eC CL CL e 3

W ME m Me I M-ME M-> N E Q. OE C3-G3 E C2 m m m C .1 = -w - A3 er w ee w m m m .-e 47 aC N 6 Z E c- = 2 m m 6 g >= ^l V l>= vl= w VP= ^{W ^l vl1 Z y W = 4 >= i >= w La. aC m Cw E M 3 3 y A A C C E C m se e d a >= . mud t 6 g a. W l W L e e L L 9 W O C C 3 3 .C g-CC @ l W L L m m W t CL Ub M M sn L I M 9 4 1 2 3 W QJ @m i cc I WA m L L m-I C E E 'E A A - 4 C QJ x I 3 Q. C. C.

=

w 3 L gC L L .N E l 6 4- @.ad @ G3 cn - QJ e QJ -e 9 -6 3U C 4 C i N .=8 N i >== t

  • a-Q.

c

  • 3 CC 9 C.

9A = C @ C A-3 2 LA L QJ L L EO CQ l i 2 3 I C 3 C .= a L L L L L m i m -e a U QJ

  • QJ CL

@ M @ x m m m .C e U C w 3 3-3= 3 = QJ >= QJ b CJ 4 3 CO O6 O-C- LC 6 9 3 L QJ l 6 =Z JW A6 16 AZ A W WA g l O Y N b m l l Rn1

f I l j RI A: TOR PPDTECT!af. SYSitr/[1:GtttirIO 1 ? 1 I t I= - senwr Protectim thannel Power Range, Neutron Flus - Mign Setpotat Power Range, heutrw T bs - t on Settotet Po=*r Range, neutron Flas. hign Posit ive Rate P=ar Ra+;e, teatron F La - Hio's negative Rate Intermediate Range, heutron Flus Source Aange, teutron F1wa Ove-teewerature AT AT Enannel T Channel avg Pressar tre* Pressure Cnsonel Overpower AT A7 rr. <el Pressuriser Pressure - Los Reactor $D Pressarize Pressure. Hign Pre sswr i ter aster Level - Higa Loss of Flo= !!ew Generator bater Level - Lo.-Low unaervoltag - a' P (10; (10) (10) (10) { 10) iiO) Onoe-f requency. R:e (10) (10) (10) (10) (10) (10) Coct ainmert Pressure - M.gn Pressge ster PMssure. Los Saf ety injettton stessiire Pressv-e - Lo. Contaneent Pressure - M gh-H i o* steam Generator mat ** Level - Higa-ogn hegative $testline eressure Rate N'? e i

i l i TAAE 3-4 aFETY FEATURES ACTUAT70ii 5YSTD; Ctyggt gapoa ALLogggg I 10 11 !? a3 14 15 16 17 3 7 l: Rata seovnt,4 Electroatcs

I t a,c Safety STS STS Analysis Allowable Trts Total Ortf t (1) Limit (2) value (3) 5etpoint (3)

Allowance (1) 1.0 1181 RTP 1101 RTP 1091 RTP 7.5 1.0 355 RTP 261 RTP 255 RTP 8.3 1.0 (5) 5.51 RTP 5.01 RTP 1.0 5) 5.51 RTP 5.01 RTP 4.2 5) 301 RTP 251 RTP 3.0 (5) 1.3 a 105 cps 1.0 a 105 cas 1.0 function (6) function (7) fanction (7) 6.0 1.0 1.0 function (6) functun (7) function (7) 4.2 1.0 1.0 1945 psig (g) 1950 mstg 1960 psig 14.4 1.0 2410 pstg 2395 vstg 2385 psts 3.1 1.0 (?) 931 span 921 spai. 0.8 871 cesign 891 destge 901 destyn 2.5 (10) (10) (10) (10) _ 1.0 function (12) fu ction (11) furction (11) 12.0 n 10) f.5% bus volt. (13) 691 bus voit. 701 bus volt. 5.0 (' ;) (10) (1:; (10) [ a,c 10) 53.9 Hz (16) 56.4 Hz 56.5 Hz 1.3 0.6 1.8 pstg 1.2 pstg 1.1 psig 4.1 1.0 1685 psig 1835 pstg 1845 pstg 20.0 1.0 285 psts 565 psts 585 ps tg 25.0 0.6 3.5 psig 3.0 psic 2.9 psig 3.5 1.0 (5) 851 span 841 span (5) -100 pst -110 pst 5.0 .}}

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