ML20012B474

LER 88-007-01:on 880513,determined That Procedures for Setting Trip Point for Overpower & Overtemp Differential Instrument Loops Did Not Require Setpoints to Be Reset Conservatively.Setpoints recalculated.W/900305 Ltr

ML20012B474
Person / Time
Site:	Wolf Creek
Issue date:	03/05/1990
From:	Bailey J, Mike Williams WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-88-007, LER-88-7, NO-90-0064, NO-90-64, NUDOCS 9003150043
Download: ML20012B474 (6)

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W$LF CREEK NUCLEAR OPERATING CORPORATION John A. Dessy

• • March 5, 1990 No 90-0064 U. S. Nuclear _ Regulatory Comunission ATTN Document Control Desk

. Mail. Station P1-157 P Washington, D. C. 20555 .;

Reference:

Letter ET 88 0082 dated June 13, 1988 from

J. A. Bailey, WCN00, to Document Control Desk, NRC ,

Subject Docket No. 50-482: Licensee Event Report 88-007 01 *]

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Gentlemen n

ll The Reference submitted Licensee Event Report 88-007-00 pursuant to 10 CFR' 50.73 (a)(2)(1) concerning a violation of ~ Technical Specifications. =

Subsequent review of the situation determined that the surveillance tast 1 procedure had satisfied Technical specification 2.2.1. The Reference lo- j being supplemented as a voluntary report to clarify the method of setting the trip setpoints.

Very truly yours,

.,_ /44 . A -

1 John A. Bailey I Vice President .

Nuclear Operations j JABlaem p Attachment cci E. J. Holler (NRC), w/a R. D. Martin (NRC), w/a-D. V. Pickett (NRC), w/a M. E. Skow (NRC), w/a l

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Merlin G. Williams 31I6 1 3161 4 l-l8 i81311 i cowLef t oNE tine ron Acu cowoNINT e Antung otaenieto iN Twis a:Pont ns, cau:S system COMPONENT MANgjac. ajP,oa,1,Agg t cAust syst M coMPoNa NT "'NX,'C' 0

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$UPPLtMENT AL AtPORT S KPICitD (14! MON 1H DAY YEAR SUBMt&510N Yts fitVen, comente lufCtfD SUOnctS$lON DA tt) NO l l l A T Actimi ,e .a.. ,,,,. . ,,a ,,.y.N,.<. ,,.,.. ,nei At 1230 Cttr on May 13, 1988, while reviewing the surveillance test methodology, the utility Reactor Engineering supervisor and a utility Instrument and Cmtrol (IsC) supervisor detemined conservatively that the pMures for setting the trip point for Overpower Differential 'nsperature (OPdT) and Over+==-ature Differential 'D===mture (Onfr) instrument loops did not ocmply with Technical Specifications 2.2.1, Action Statanent "a", by not requiring the trip points to be reset to the conservative side of the required setpoint. Based on this conservative determination, the affected seure was revised, and the trip setpoints were adjusted accordingly.

In August of 1989, upm further review of this situation and a fonnal evaluation and definition of calibration accuracy, it has been concluded that the previous version of the procedure had conplied with the requirunents of the Technical Specification. Consequently the s d aral

.cevision was unn - ry and it is intended to restore the s d ures to the original methodology. The original Licensee Event Report is being supplananted as a voluntary report to clarify the method of setting the trip setpoints.

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0l1 0l2 or 0l5 15x3, . ,=, anc r.,,,, asma v mi INIRCDUCTION At 1230 CDT on May 13, 1988, while reviewing the surveillance test nethodology, the utility Reactor Engineering supervisor and a utility Instrument and Control (IsrC) supervisor conservatively detemined that the kwmiures for setting the trip point for Overtower Differential 'Nuperature (OPdT) and Overtenparature Differential 'nsparature (Cmfr) instrument loops

[JC-AS) contained an error. It was then detamined that the surveillance test gvc dure for the Analog Channel Operatimal Test of the 7300 Process Instrumentation (JC-IA) did not ocmply with %chnical Specifications 2.2.1, cetim statment *a a, which states:

"a. With a Reactor Trip System Instrumentation or Interlock Setpoint less conservative than the value shown in the Trip Setpoint column but nere conservative than the value shown in the Allowable Value colunn of Table 2.2-1, adjust the Setpoint consistent with the Trip Setpoint value."

We unit was operating in )txie 1, Power Operation, at 100 percent power when this problem was identified. Revision 0 of this Licensee Event Report (LER) was submitted pursuant to 10CPR 50.73(a)(2)(1)(B), as a violation of Technical Specification 2.2.1, based an the above determination. Upon further review of the situation in August,1989, it was determined that the surveillance test procedure had satisfied Technical Specification 2.2.1, Acticn Statement 'a' prior to May,1988. We original Licensee Event Report is thebeing supplemented as a voluntary report to clarify the method of setting trip setpoints.

DESCRIPTION We subject surveillance test procedure tests the setpoint for each of the reactor trip signals generated by the 7300 Process Instrumentation. We general methodology used therein is to inject a test signal at the detector and to note the trip point of the applicable bistable. For each trip function, there is listed a desired value, a tolerance range and an allowable value. %e relationship of these three are shown in Figure 1.

The desired value corresponds to the Trip Setpoint of %chnical Specifications, Table 2.2-1; the tolerance range is conservative with respect to the desired value and the allowable value of the procedure corresponds to the Allowable Value Colunn of Table 2.2-1. During calibration the trip point of each bistable is reset to the tolerance range unless it is found already in the tolerance range.

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011 013 00 0 15 ft vtxT , . < wc ,,,,, mm mm FIGURE 1  !

Desired Allowable I value value 1

'Iblatance  !

Conservative Ranoe Nonconservative  !

Because of the ocuplexity of the Optfr and the ORIT instruaunt loops the l gw iare calibrated each instnanent loop in three sections. Figure 2 provides a sinplified block diagrera of one instrument loop. 'Ihe bistables  :

for the OPdT and OntT instrumsnt loops have two inputs; one cou+. ling to i the differential tenparature and the other corresponding to a calculated . l trip setpoint. The surveillance test suc=iore calibrated the OPc0 and ORIT bistables by supplying a test signal at the two inputs to the bistables (labeled "a" and *b" on Figure 2) and setting the trip in the nonnal nenner. Each of the input instruments feeding the bistable was calibrated

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to a plus or minus tolerance on either side of the ncminal value.

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_ Differential

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Bistable Output S _ Setpoint

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_ Instrunent b Mhr 1988 AlmLYSIS In May of 1988, it was believed that the procedure assumed that a perfect l signal would be supplied at "a" and "b" and set the bistable trip point l accordingly. It was further concluded that the kw lure failed to recognize that instrument error in the two input instruments would affect i the instrument loop trip point. 'Ibe resultant error for the instrument loop l is the sum of the bistable error plus the error in each input instrument. l Since the resultant error could be ncnoonservative, this sveuiure allowed 1 l the instrument loop trip setpoint of OPdT and OIdT instruments to be less conservative than the value shown in the Trip Setpoint colunns of 'Ibchnical l Specifications Table 2.2-1, resulting in violation of action statanent "a". .

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Oll Ol4 OF 015 I TEXT Idr more spece e sevassf. use seineonet MC Fonn JesCs A (176 AUGUST 1989 AIRLYSIS Upon further review of the situation in August,1989, it was recogni. zed that ,

the Bases for 'mchnical Specification 2.2.1 states that "%e Setpoint for a >

Reactor Trip System or interlock function is considered to be adjusted consistent with the ncminal value when the 'as measured' setpoint is within the band allowed for calibration accuracy".

% e calibration accuracy has been evaluated and specifically defined. It provides a tolerance range enempassing the Trip Setpoint value. Therefore, following perfonence of the calibration p1.ocadure, the bistable setpoint -i should be left at the Trip Setpoint value plus or minus the calibration .

accuracy for emplinnce with this Technical Specification 2.2.1, Action Statement "a".

Consequently it is planned to revise the method of calibration to the original method.

ADDITIGAL IIGGMM'IW This surveillance test procedure is done monthly when the unit is in 2de 1 (Power Operation) or E de 2 (Startup). % ere are four OPdT instrment loops and four cidT instrument loops that are calibrated each time the surveillance test procedure is arvr=nHshed.

It should be pointed out that the specific setpoint has always been within L the Trip Setooint value column cf Technical Specifications Table 2.2-1. We

!~ OFtfr and OIth' instrument loops are very stable. Se anount of drift noted during the nunthly surveillance test has never been enough to require any adjustment. Werefore, the instruments were always considered operable. If a condition had occurred that required these instruments to trip, they would have done so within the values analyzed in the Accident Analysis.

Therefore, there was no adverse safety significance as a result of this event. %ere was no damage to plant equipent or release of radioactivity .

as a result of this event. At no time did conditions develop that nny have posed a threat to the health and safety of the public.

ACTIW 'INGN -

Following the original determination that an error existed, the nost recently ocmpleted surveillance test g.wedure was examined to determine which instruments were left with nonconservative trip points. It was determined that two OPdT and three OIdT instrument loops were affectcri. New

, setpoints were then calculated and a tmporary procedure was approved for 1: resetting the bistable trip setpoint for each of these. The affected l- feRC f enn 308A (649)

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inxire - a m anscre w . inn bistable trip setpoints wem s%-ly adjusted by 2056 CDI' on May 13, 1988.

All rMums that verified the other setpoints of 'Dochnical Specifications Table 2.2-1 wem reviewed to ensure this error did not exist in other setpoints. Uhe surveillance test g& ares were revised to pmvent further OcCurIences.

Based on the formal definition of calibration accuracy, it has been determined that this gMural revisicn was unnecessary and it-is intended to revise the pMure accordingly.

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NflC Form SOSA (649)

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