ML17277B734

Rev 0 to 22A5261, Instrument Setpoints & Tech Spec Limits.

ML17277B734
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Issue date:	12/02/1977
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References
22A5261, TAC-55579, NUDOCS 8505140470
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Text

EIS ID:"NT: IhST SETPttTS t'E TECH LttTS EEVI"'OE STlLTUS'EEET

. '2A5261 COkT OM SHffT 2 QS EEO.

NUCLEAR EHERGY DIVISION ItlSTPUHEttT St:.POIllTS.Alto TECHltICAL SPECIFICATION LIthi S OOCUI'EIIT TITLE Q~ ECIFICAllCtl QORA YAK.'O C3 OTHEII TYPE I ttFI1R'.RTI 0't OOC't1ENT FVF+-" =~A LEGE'4O OII OESCRIFTIOII OF OAOUPS tt/A

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GEf'! ERAL i+j) ELEI:TRfC 22A5261 sH. pro. 2 NOCLEAR ENERGY DIVISION 0 REU

1. SCOPE 1.1 Pur ose: This docurr nt has been prepared to record appropriate methods for the establis ment of recoIIrrended instrurrent nominal trip setpoints and technical specifi "ation limits in a consistent and repeatable manner.

1.2 Setooints Covered: The setpoints considered are those associated with the System and Rod Withdrawal Block. InstrI.mentation.

2 APPLICABLE DOCUNEHTS 2.1 General Ele tric Company Docurents 2.1.1 Suooortina Docu.ments. Hone 3 SYSTEH C SIGH REgUIREt<EHTS s

3.1 C neral: System design requirerents are corcained in the appropriate design docur; ntacion Tn.ey are u.ili ed har , when necessary, to insure that the nominal trip'etpoint r coII'ndations do not resu'.t in violation of syst m design requimaants.

3.2 Definitions

The definition of terIrs used in this document are those contained in IEEc Stanoard 100-1972, IEEE Standard Dictionary of Electrical and Electronic Terms, as further defined in this document.

3.2.1 Pnalvt'.c limit A.L. : the value of the sensed prccess variable established as pa t o ~".e sarety ana ysis, pr'ior to which,a desired action is to be initiated to prevent the process variable from reaching the associated design safety limit.

3.2.2 'Cali"ration accuracy: th quality of freedom from error to which the trip calibration instrum ntation accuracies a

an4 calibration procedure allowances.

3.2.3 Con. ormitv independent: the mat:-durum deviation of the actual chara"teristic (average o~ upscare ana ownscale readiny) -from a specified curve, so positioned as to minimize the a'~ximum deviation.

necessary to r asonaoly protect the integrity of physical 'arriers that guaro against uncontrolled release of radioactivity.

EEHEEAL', i) ELECTRIC NUCLEAR ENEflGY OtVISlON 22A5251 sH. pdo, 3 REV, 0 3.2.l cx:re~ .'. ad s:ata ooeratio~value: the e::trere value of the proc ss val iable anticipated curing nor'sa steady st-te operation. This value may be either a maximum or a minimum value depending upon the process variable.

3.2e6 irstrumnt accurac: the quality of freedom from error of the complete instrument channe from t e sensor input through the trip unit output incl ding the combined conformity, hysteresis and repeatability errors.

3.2.7 Instrurent dri.t: the change in the value of the process variable, at which the trip action will actually~ occur, between the time the nominal trip sotpoint is cal'.brated and a subsequent surveillance test, due to all cause's, as m asured in term of the ins: Jwentation indicator'cale. The value of the process variable at which the trip action will actually occur at the tim of calibration is taken to be the intended nominal trip setpoint value.

3,2.8 Licensina Event Re'port LiRQ: a report which must be filed with the United States tiuc ear Regula.ory Co~>sslon by the power plant operator, (Utility) when a technic 1 specification limit is exceeded, e.g., when a trip se.point value is found to h ve exceeded the corresponding technical specifica ion limit; 3.2eg Limitina normal ooeratino transient:.:he mcst severe ensed process vari-able transient antic:pated dursrg norral operation for which initiation.o. the trip .

action associated with the instruaantation monitoring he process is not anticipated.

3.2.10 maximum desicn instr;m ntation 'drift: the maximum drift permitted by the instrumentation design and procuremert specifica ',ons for the complete instrur<nt channel from t". sensor through the tr'ip unit, inclusive. The maximum drift represents t o standard deviations of the probeability d',stribution of inst 'ut"ent drift. The.saxi;:,um drift is specified for a period of ti~:: equivalsent to or grea' than the surveillance test interval.

3.2.11 Operational limit: the o'perational value established by the limiting nornal operating trans> ent.

3.2.12 t(cminal Tri" Se.point l(.T.S, ): the intended calibration point at which a .rip act>on ~s set trip operation.

to operate, cod..denly t¹ center of an acceptable rance of 3.2.13 Reoeat bilitv: the closeness nf agreement s-among a number of consecutive m asurencnts oi she ou ,'ut ior the same value of the input under the sare cperat ng condiuons, approachng from the same direction, for full range traverses.',2.14 Technical Specification Limit tT.S.L.: th limit prescribed as a license condition on an inpornnt process variable.

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-1 EHEP,AL <~"l ELECTR) 0 22A5261 sx.xo; 4 NUCLEAR ENERGY DIV!SlOM Rav. O 3.3 Limit Relationships: The relationsh!p between the nomina< setpoint and the PROCESS VARIABLE CJ W

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4. PSSURN<CE PROV I 5IO,'rdaIIce with the current GE-HED engineer'.ng design rev'ew procedures.

5. HAHDi.IhG, SHIFPIHG AliD STORAGE - hot appl icable.

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6. RECOtPKHDAT IC'iS

6.1 General

In order to provide a consistent and ~oeatable m thod for estab >sning inst: nrwnt nomina> trip setpoint nd tcchnical specification limit value recommendations th pro"edures described in the appendices have been developed.

Due to the general characteristics of the instIuIn ntation and processes involved it has been necessary to provide three (3) different m.thods. Th se three (3) methods are based ori computation, engineering judgment. and historical data. The methods are to be applied independently. Hcwever, portions of the computational

~ thcd mav be incorpo.ated into the other two r>ethods. Each of the methods is xplained in a sewrate appendix. The method and associated appendix are as follows:

a. =Corautational Apperdix 10

b. Engineering t udgment Appendix 20

c. Histrica 1 Data Appendix 30 6~2 Soecific SI'tooiirt Re sI "endations: Specific nominaI trip setpoint and technTi~asp ci rTcacicn>>ms t reco~rdacions along wi "h the analytic limits are delineated in plant uniqu data sheet.".

GEMERAL (':::..) ELEl:TPIC 22A5251 SH. No. 6 r UcLEAR raw=ace oiws(oN REV. 0 APPEt(DIX 10

10. METHOO FOR ESTABLISHIt(G TRIP SETPG[((TS A'(0 TECHNICAL SPECIFICATIOt( LIMITS BY COviPUTATIG!(

10.1 Ceeeral 10.1.1 Vien sufficient information'is available regarding a dynamic proi".ess and the

<<ssocia ed instrumentation, it is possible to establish the nominal trip setpoint c nd t chnical specification limit valves utilizing the following procedure. This

(:rocedul-e does not atterqt to apply a rigorous s.atistical evaluation of the instrumentation parameters. The analytic limit is established through tte me of computational models which include combired margins for related instrmentation parameters but do rot necessarily include separate rrargins for each individual i "istruwnt characteristic. Consequently, it s not practical to remove the instru-

'ment related margins rom .he models used to es>zblish the analytic limits. Ir

• order to separately account for instrumentation accuracy and calibration accuracy it is. therefor necessary to in d dundancv irito the technical specification limit; establishments.

~ a 10.1.2. The differential between the nominal tr'.p setpoint value and the technical specification limit is established as the maximum drift jermitted by the associated instrurertation specif'.cation. This dif erential allows for the maximum drift between calibraticns without compromising the analytic limit sine tl'.ere will still be sufficient margin to account for instrum.ntation and:calibration accuracies.

10.1.3 Once the rominal trip setpoint and technical specification limit values have been establi hed using 10.2 below, tney ar heckad to insure they will not result in an unacceptable level of Licensing Event Reports (LER) or trips due to nort.al operatio,.al transients. If the nom.'nal trip setpoint and technical specificat!on limit values are not acceptab'.e there are,everal alternatives available. One alternative is to establish tho se values using a more rigorous statis ic-', evaluation and taking credit for instrurent channel redundancies.

Another alternative is to replace .he instrumntation design specification data with actual operational data'nd estab'.ish the nominal trip setpoint and technical specification limit values based on this data.

10.1.4 It is recommended that the instrurentation parareters utilized in establisih-ing the nominal trio setooints and techn'.cal specification limits be monitored during operation. then sufficient operational data has been gathered, the rcminal trip s tpoints and technical specification '.imsts should be recomputed to improve plar.t operational:rargins arid further minimize LERs.

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0 E fI E 8 I L i,';.:rrj E e F. CTR t0 22A5261 SH. NO. 7 t(UCLEAR ENERGY OIYISION Rcv, 0 10.2 procedure for Establishing Hominal Trio Setooint afld Technical Soecif>ca:>on Lic> t 10.2.1 Data :.eot;ired: Tne following data is required to establish the nominal trip setpoin-. ano technical specification limit.

a. 'Analytic Limit (A. L.).

b. Instrumentation accuracy.

c. Calit ation accuracy.

d. I'aximum design instrumentation drift.

10.2.2 Technical Soecification Limit 10.2.2.1 The technical specification limit {T.S.L.} is established so there ~s at

'ieast a 0.9772 probability of providing the trip action before the process variable reaches the analvtic limit in .he case where the maximum drift has'occurred as sho~n on Figure i0. 1. The raximum drift being the instruttf ntation design maximum drift (D).

10. 2.2.2 The instrumentaticn parareters involved in establishing the technical specification limit are the instrumentation accuracy and the calibration accuracy.

Instrumentation accuracy is the specified design accuracy and is assumed to represent bio =tandard deviations (2"a) of the instrunentation indica':,on aC th trip level oi the process variable.

10.2.2e3 It is assuoed that the plant operator will calibrat the instrunen ation with an accu.acy equivalent to the irstrumentation resolution. This asswrption is necessary since specific data related to the plant operators calisbr'tion procedures, calibration equipwnt and calibratior. equipn r. maint.:narce are not available. The inst"umntaticn resolutior is taken to represent one stant'arif deviation (ac) nf the in'trumentation calibration at the trip level o": the process variable. The instru-tentavion includes the sensor, signaI condi io~.ing circuitry and trip unit.

I'2.2.2e4 . In order to obtain the desired Oe9772 probability, for a ore sided normal distribution, the:echnical pecification limit must be set, two (2) standard devia-tions flam the analytic limit. In this case the standard deviation is determined as th 'statis.ical coebination of ihe instr santa"tion accuracy and t ra cal'ibr tier.

acruracy, i.es s oa + oc . T.S.L. = A.L. - 2 yoa e+scca, for process variables

",hat i,".crea e toward the A.Lss or T.S.L. = A.L. + 2 yoaa + oca , for Proce's I

variables that decrease toward the P;.L.

10.2.2.5 'fihen actual calibration accuracy. data becores available .he technical specification limit can be adjusted using this procedure and the new calibration accuracy standard deviation.

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0Ef'ERAL <"'> ELECTBt C 22A5261 Fw No.

NUCLEAR ENERGY iilVl iota AKV, 0 10.2.3 tic~inal Ti io Setooint 10.2.3.1 The nominal t'rip setpoint (N.T.S.) value is established by the ma.".imu.'.i

'esign initrumentation drift (0). The nor.;inal trip setpoint '.s offset fro..l the techliical specification limit by an amount equal to the naximum desi,n instrumenta-tion drift expected during tie surve'11ance test interval. As noted in tile establishment of t'nL technical specification limit this will provide an assurance of required trip actions in;lie case where the rzximum drift has occurred.

H.T.S. ~ T.S.L. - 0, for process 'variables that increase toward the A.L., or H.T.S. = T.S.L. + D, for process variables tnat decrease tm ard the A.L.

10.2.3.2 Actual observed drift will d': ffel from plant to plant due to environmental factors, rainten=nce procedures and trip setpoint surveillance. frequencies. Also,

he actual observed dri ft cha~acteristic may include a statistically significan .

bias. Consequently, as actual drift data '.s accumulated, includ ng confirried, statistically si<,.nificant bias data, the rominal trip setpoint can be adjusted to reflect the inst; umentation performance.

i0.3 0 eratiohal Transient Trio Avoidance r

10,3.1 In order to evaluate the imoac. of 'the nominal trip setpoint value (Xs) on plant availabil ty one of two simple tests can be applied. These ta".ts are.

based on a distr>bution of differ"nce calculation and are used here to evaluate the probability of a trip occurring due to the spectrum of norral operating transients or due to:he '.imiting normal operating transient when no safe.y constraints are ccmpromiised. The caiculations establish the probability of avoiding a trip under safe conditions. Five (5) factors, not previously used, are utilized in these tests.

They are predicted e .treme steady state operating value for ti e variable (Xo), the limiting predicted normal operating transient, the standard deviation associated with the limit;ng operating transient (ii<), t:ie ruquired trip avoidance probability during the limiting transient and the va~iue of the standard deviation (."d) associated with the instrumentation oriit. In the absence of actual observed drift data the standard deviation (cd) for drift is taken as one half of the maximum design instrunantr ticn dri ft (9).

10.3.2 The test to evaluate the operational transient trip avoidance associated wi:h the spectrum of normal 'ooerating tra".sients is based on the nominal trip set-point distribution and tne operational process variable distribution as shown in Figure 10.2.

f Technical Operati onal Process Hominal Trip Setpoints ,.Specification Variable Dl:,t.ribution Distribution, N.T.S. 'Limit, T.S.L.

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Extreme llominal Trip Steady State Setpoint, X Operating Value,= X Area represent',ng Area representing the probabil i ty tho probability of of an LER.

an undersirable trip.

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yO GEHEtiAL g".:g ELECTR fC 22A5261 sH. rro. 11 t(UcLEAk E!IERQY r'! vtstoM AKV. 0 10.3.'Z.l The extreme steady state operating value (Xo) is utilized as the rr an of the operational variable distribution and the predicted norrral process variable chanoe of the limitirg transient. is taken as the standard deviation (ct) of the operational process variable dis".ributicn. Obviously, this is an oversimplifica-tion of the operational variable distribution. However, if this test is successful it will not be necessary to perform a more rigorous i:est.

10.3.2.2 The setpoint distribution utilizes the nomina'1 trip setpoint value (Xs) as a .-,~an. The standard deviation (ci) is corputed as tire statistical combination of the instrumentation drift stanoard deviation (cd), instrumentation accuracy (ca) and calibration accuracy (cc), i.e.,

a ~ c 2 + c 2 + c 2 i a c d 10.3.2.3 A one sided probability of tr'p avoidance based on a non.al distribution is obtained from a standard textbook su+istical tabre for areas under the standard ror al curve, from - to Z, where Z = X/a, i.e., probability and Statis ics for Engineers, Hiller and Freud, Prentice-Hall, Table III. For the delta distribution

. case, X. is the difference between the means of the two distribut~ons. The delta standard de~iation (c.) is the statistical corbination of the two distribution standard deviations, i.e.,

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There fore, X -X c 2 c,2 t 1 i

when Xo is greater than X, and X <<X Zg 2 +d when X is less .han Xs . The probability of trip avoidance is the normal distribution statistical able value corresponding to Z..

10,3,3 The test to evaluate the operational transient trip avoidance associated with the limiting normal operating transient is based on the nominal trip setpoint distribution and the distribution of the '.imiting trarsient as she'n in Figure 1G.3.

0 T II I C 22A5'Z61 sH.wo. 12 0 E W E II A I. qadi E LE NUCLEAR ENERGY OIVISIOtl nsv. 0 I'hgnitvde of Hominal Trip the Limiting Limiting Setpoint Technica 1 Transient Trarsient Distribution, Specification Distribution N.T.S. Limit, T.S.L.

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Extreme Nominal Trip Steady Stare Setpoint. X Operating Yalue, X Area Area Representing Representing the Probability of the Probability an Und sirable Trip of an LER FIGglc 10 3

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22A5261 sH. No. 13 NUCI.EAR ENERGY DIYISION nev, 0 10.3.3.1 The mean of 'the limiting operating transient distribution is taken as the extreme steady state operating vaiue (Xo) plus, or minus as appropriate, the rragnii.ud- of the limiting transient {T), i.e., X - <~ + T, where the process variable transient 'in'creases toward the analytic limit ai,'T =

Xo - T , where the process variable decrease toward the analytic ;imit. Tho. standard deviation as. ociated with the limiting operating transieI.t (cm) is toe value used for the standard deviation to be associated with the distribution of XT .

10.3. 3.2 The setpoint distribution and standard aeviation are to be established as stated in Paragraph .10.3.2.2.

10.3. 3.3 Jsing the method of Paragraph 10.3.2.3 but substituting XT for and cm for at provides the probability nf'rip avoidance i.e.,

XT-X T

Z az+c 1

-'iI when Xo =is greater than Xs, and X -XT Z

oz+~z when X is less than XS .:liote, t!Ie selec'.io.. of which eouati:n i" applied depends on the relationship'etween Xo and X,. not on the relationsI ip between XT and Xs .

10.3.4 rigorous In the event an unsatisfactory trio avoidance probability has be~n obta'ined a more rigorous definition c. the operational process variable distribution must be established or the nomiaal trip setpoint value can be adjusted based cn engineer-ing judgment to reduce the interval hetw en it and the ';"chnical specification limit. The alternative chose will deperd on the value of the trip avoidance probabi lity, the function of the trip sigral, and an evaluation of the un'ique plant operating requirements. A definition of the operational process variable distribut'o1 should be based on the noIinal steady state operating value of the process variable as the mean rather than the maximum steady-stat= opei'atinq value.

The standard deviation should be computed in a statistica;:;armer using tho nor a.

operating transient frequency data rather than relying onIy on the limiting nor..al operating transient, 'and instru~ntation redundancy and trip logic shou'Id be included in determining the nominal trip setpoint .statistical di tribution. Mhen considering the trip logic'he fnllowing expressions should be used to comoute the probabilities of :rip and trip avoidance.

10. 3.4.1 Probability of trip avoidance = 1 - probability of trip.

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GENERAL Q ELEilTBiC NUCLEA,R EHaRQY OIVl. CION REV.

22A5261 0

sH. iso. 14 l0.3.4.2 Probability of trip, single ~liannel = P.

10.3.4.3 Probability of trip for one out of tMo taken twice logic = P> (2 - P)>.

10.3.4.4 Probability of trip for. two out of tl ree logic = 3P2.

10.3.4.5 Probability of trip for two out cf four logic ~ P (3P - SP + 6).

10.3.4.6 Probability of trip for one out of four logic = 1 - (1 - P)".

10.4 Licensina Event Report Avoidance 10.4.1 The probability of avoiding a LER due to ins.rumntation drift is deter-mined by the associated standard deviaaon (ci) of the indication of t'Ke process variable. An LEP. avoidance probability of at least 0.9003 is recorwended. This probability is obtained using o statis ical table for areas urder tie standard normal curve, ficm - to 2, where 2 = X/c, i.e., text reft "enced in Paragraph i0.3.2.3. In this case, th value used for X is the pos tive difference between the nominal setpoin value and the techn'."al specification limit. i.e., the aaxiirum design instrumentation drift (D) as shown in Figure 10 2. The standard deviation value used is the statistical co.hination of the instrum ntaticn drift standard devia ion (cd) , instrument tion accura'cy (ca) , and calibration accuracy (cc)',

i.e., c. ~ ca > + c c ~ + c.> d

. The probability of avoiding LER is the nor,.al distribution -tatistical table value corresponding to Z .

10.4.2 in the event an avo',dance probability of less than 0.9C00 has been o~tained one alternative is to increase the differentia> between the nmainal. setpoint value and the technica'"ecification limit. Such <<n adj'us.rent must be based on eng..'neering j;agmant or. actual operational d'.ift data.

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GE II E B A L ii E LE 0 T II I 0 22A5261 sH.wo. 15 NUCLEAR CNEIiGY Ot VISION nEv. 0 APPEHDIX 20

20. HETFOD FOR ESTkRLISHIHG TRIP SETPOIHTS AHD TECHHICAL SPECIFICATIOH LIHITS BY EiiGIHEEfcIHG JUDr-.iEHT 20.1 General 20.1.1 Mhen it is not practical'to apply the technique outlined in Appendix 10 or when the available data is so conserva ive as to resiJlt in unacceptable operating restric'ions, or when the Lead System Engineer considers it appropriate, engineering judgm nt should be I.sed to establish the nomina'. trip retpoint and technical specificaticn limit vaiues. In order to establish a consistent pattern for the applicaticn of engin e "ing judgn nt suggested guid lines are delineated belou.

20.1.2 The guidelires suggested are those of the zone setting concept. 'A two zone concep.. is suggested nere as adequate to establish the nominal trip setpoint and tec,'>nicai speci "icat.'on limit values. The zones are a range within which +he trip value i'<.'equate for its intended function but must be reported as having compromised t"..e applicabl technical specification value.

20.1.3. Zon concepts erplonng rore than two zones have prev-.dusIy been associated with the establish&e~t of instrumentation setpoints. In particular; zones related to establishing when recalibra ion is, or is not, necessary, are conan, i.e.,

leave alone zone. Since s"ecif',cation of +he recalibration limit is not includeo in this docur. nt These additional zones 'are rot addressed. However, the recalibra-tion '1-imiter. ('ave aione zona) is an important operational consid ration aI.d should be est=-bi>shed, within the acceptable trip. valve zones, ba -d on the unique plant oceratirg requirements.

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20.2 Acc P.able Trio Value Zone: The acceptable trip value zone is a portion of the instr;;,> nest>on trIp range which will have as it's midpoint the nomina trip setpoint., and as it's extr m~';he technical specification limit. Figure 20.1 is a repr'esentat on cf he trip v:;lue and zone relationship., The. acceptable trip value zone should be wice enough to allau for normal instrumentation drift durirg survei 1 lance in terval s.

20.3 'icensina Event Re"ort 1

20.3.1 The XR zone is the portion of th instrumentation trip range beyond the technical speci, ication limit. An LER will be required when the trip value is found within this zone.

20 3 2 The LEF. zone shou i d be establ i shed so that when the maximzm expec.ed d: i . t has occurred su.fic'.ent rargin remains beuieen the technical sp:;cif'.cation limit and analytic '.im)+s .o compensate for ins;r:Imentation and calibration accuracies.

GFHEHAL (':g ELECTRIC 22A5261 sH. ao. 16 NUCLEAR N RGY DlVlslON RGV. 0 Licensing Event Report (LD) zone Technica1 Specification Limit Acceptable Hominal Trip Setpoint Trip Va3ue Zone FIGUoc "0.1

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