ML17325A029: Difference between revisions

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| issue date = 04/01/1987
| issue date = 04/01/1987
| title = LER 87-001-00:on 870303,spurious Signal from Source Range Instrument Channel N-31 Resulted in ESF Actuation.Caused by Malfunction of Detector.Source Range Instrument Detector Removed,Replaced & Declared Operable on 870314
| title = LER 87-001-00:on 870303,spurious Signal from Source Range Instrument Channel N-31 Resulted in ESF Actuation.Caused by Malfunction of Detector.Source Range Instrument Detector Removed,Replaced & Declared Operable on 870314
| author name = BLIND A A
| author name = Blind A
| author affiliation = INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
| author affiliation = INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
| addressee name =  
| addressee name =  
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=Text=
=Text=
{{#Wiki_filter:NRCForm368(84)3)LICENSEEEVENTREPORTHLER)U.S.NUCLEARREOULATORYCOMMISSIONAPPAOVEDOMBNO.31500104EXPIAES:8/31/88FACILITYNAME(I)DC.CookNuclearPlntUnit2DOCKETNUMBER(21050003PAE3I1OFpESFActuation(InadvertentOpeningofReactorTripBreakers)DuetotheFailureofaSourceRaneNuclearInstrumentationDEVENTDATEI5)LERNUMBER(6)REPORTDATE(7)OTHERFACILITIESINVOLVED(8)MONTHDAYYEARYEARSEQUENTIALNUMBERREVISION8'NNUMBERMONTHDAYYEARFACILITYNAMESDOCKETNUMBER(SI050000303878700100040105000OPERATINOMODE(0)POWERLEVELppp20.402(B)20.405(~)(1)D)20A05(s)(1)(E)20,405(s)(1)(ill)20.405(s)(1)(Iv)20,405(~)(1)(v)20.405(c)60.35(c1(I)50.38(cl(2)50.73(~l(2)li)5073(~)(2)lii)50.73(~l(2)(iiBLICENSEECONTACTFORTHISLEA(12)60,73(s)(2)liv)50,73(s)(2l(v)50.73(s)I2)(vii)50.73(sl(2)(vill)(A)60,73(v)(2)(vlii)IS)50.73(~)(2)(x)0THEREOUIREMENTSOF10CFR():(Chockoniormoriofthtfollovflnpl(11)THISREPORTISSUBMITTEDPUASUANTT73.71(b)73.71(c)oTHERIsptcifyInAbstractbtlovvtnd/nTits,IVIICForm3BEAJNAMEA.A.Blind-AssistantPlantManagerTELEPHONENUMBERAREACODE616465-901COMPLETEONELINEFOREACHCOMPONENTFAILUREDESCRIBEDINTHISREPORT(13)CAUSESYSTEMCOMPONENTIGDETMANUFAC.TURERW1,20EPOATABLE'ymTONPRDS?.2A..QgSYSTEMCOMPONENTMANUFAC.TUREREPORTABLE"TONPROS:i'~in~$nQgg'&MÃSUPPLEMENTALREPORTEXPECTED(14(YESflfyts,complitiEXPECTEDSUShllSSIOIVDATE)NOABSTRACTfLImltto/400sptcts,lt.,tpprorrlmtttlyflfttinslntlisptctryptvvrlttinllnisl(18)EXPECTEDSUBMISSIONDATE(16)MONTHDAYYEAROnMarch3,1987,at1511hours,aspurioussignalfromasourcerangeinstrumentchannel(N-31)resultedinanEngineeredSafetyFeatures(ESF)actuation(inadvertentopeningofthereactortripbreakers).Thereactorwassubcriticalatthetime.TheautomaticESFresponseswereverified,allequipmentfunctionedasdesigned.IFollowinginvestigation,andreviewofpostactuationdata,itwasconcludedthatthesignalfromN-31wasspuriousandduetoamalfunctionofthedetector,andnotanincreaseinthecoreneutronlevel.Thesourcerangeinstrumentdetectorwasremoved,replacedanddeclaredoperableonMarch14,1987at2223hours.8704070471870401PDRADOCK0500031(LSPDRNRCForm385 NRCForm356A(983)LICENSEEEVENTREPORTHLER)TEXTCONTINUATIONU.S.NUCLEARREGULATORYCOMMISSIONAPPROVEOOMBNO.3150&l04EXPIRES:8/31/88FACILITYNAME(1)~OOCKETNUMBER(2)LERNUMBER(6)PAGE(3)YEAR4)5SEQUENTIALNUMBERREVISIONNUMBERD.C.CookNuclearPlant,Unit2TEXT//F/rroroSFoco/4r/O/ror/Iroo/I/OI/4////IC%%dnrr35//AB/(IT)p5ppp316870010002OF04ConditionsPriortoEventUnit2inMode3(HotStandby),at1.0E4cpswithaunitshutdowninprogress.DescritionofEventOnMarch3,1987,at1511hours,aspurioussignalfromasourcerangeinstrumentchannel(N-31)(EIIS/CHA)resultedinanEngineeredSafetyFeatures(ESF)actuation[inadvertentopeningofthereactortripbreakers(EIIS/BKR)].Thereactorwassubcriticalatthetimewithallcontrolrodbanks(EIIS/ROD),andoneshutdownrodbank(D),fullyinserted.Anothershutdownrodbank(C)wasbeinginsertedwhentheeventoccurred.OperationspersonnelimmediatelyimplementedEmergencyOperatingProcedure1OHP4023.E-Otoverifyproperresponseoftheautomaticprotectionsystem(EIIS:JC)andtoassessplantconditionsforinitiatingappropriaterecoveryactions.TheN-31sourcerangeinstrumentchannelwasreturnedtoserviceonMarch14,1987at2223hoursfollowingdetectorreplacement.TheautomaticESFresponseswereverified,allequipmentfunctionedasdesigned.However,sincetheunitwasinHotStandbyandshutdown;themainfeedwaterpumps(EIIS/P)werepreviouslyremovedfromservice',theturbine/generator(EIIS/TRB-GEN)wasinatrippedcondition,nosteamdump/pressurereliefwasnecessary,andtheauxiliaryfeedwaterpumpswereinservice.System/Equipmentresponsesthatdidoccurincluded;theopeningofthereactortripbreakersandtheinsertionoftheshutdownrodsremainingtobeinserted.Reactorcoolantpump(EIIS/P)operationwasmaintainedthroughouttheeventandnoabnormaloccurrenceswerenoted.Therewerenostructures,components,orsystemsinoperableatthestartofthiseventwhichcouldhavecontributedtothisESFactuation,withtheexceptionofthesubjectsourcerangemalfunction.CauseofEventFollowinginvestigation,andreviewofpostactuationdata,itwasconcludedthatthesignalfromN-31wasspuriousandduetoamalfunctionofthedetector(EIIS/DET)andnotanincreaseinthecoreneutronlevel.Currentcharacteristicscurveswereobtainedforthedetectorand,basedontheWestinghouseManual,itwasdeterminedthatthedetectorfailedduetoairin-leakage.NRCFORM3SSA(94)3I*U.S.GPO:19880824538/455 NRCForm388A(983ILICENSEEEVENTREPORTHLER)TEXTCONTINUATIONU.S.NUCLEARREGULATORYCOMMISSIONAPPROVEDOMBNO,3')50-0104EXPIRES:8/31/BBFACILITYNAME(I)DOCKETNUMBER(2)YEARLERNUMBERl6)SECVENTIALNUMBERREYIEloNNVMERPAGE(3)D.C.CookNuclearPlant,Unit2T)D(T///moro4/rooo/4Eo//rrr/Irwa//rr/one/HRCForm358AB/(IT)050003167001003oF04AnalsisofEventThiseventisbeingreportedpertherequirementsof10CFR50.73(a)(2)(IV),asaneventthatresultedinautomaticactuationofanyEngineeredSafetyFeatureincludingtheReactorProtectionSystem.Thesourcerangeinstrumentationmonitorsthecoreneutronfluxlevelduringreactorshutdownandtheinitialstagesofreactorstartup.Thesourcerangechannelsprovidereactorprotectionbyinitiatingareactortripatarelativelylowneutroncountratetoterminatealowpower/highstartuprateaccident.Theactuationcoincidenceis1of2channels>1.0E5cps.DuringreactorstartupthesourcerangetripsareblockedabovepermissiveP-6(approximately6.0E-llampsontheintermediaterangenuclearinstrumentation).ThesourcerangechannelprotectionisautomaticallyreinstatedwhenreactorpowerdecreasesbelowP-6duringshutdowns.Priortothisevent,bothsourcerangechannelshadre-energizedwhenreactorpowerhaddecreasedbelowP-6.Sincealowpower/highstartuprateconditiondidnotexistduringthisevent,andallreactorProtectionsystemsfunctionedasdesigneduponthereceiptoftheactuationsig'nal,ithasbeenconcludedthatthehealthandsafetyofthepublicwerenotjeopardized.NRCPOllM388A194)3)-oU.S.CPO;19880824538/455 NRCFI>>)II3MA(94)3)LICENSEEEVENTREPORT(LER)TEXTCONTINUATIONU.S.NUCLEARAEGULATOAYCOMMISSIONAPPROVEOOMBNO.3(50&104EXPIRES:8/31/SBFACILITYNAME(11OOCKETNUMBER(2)YEARLERNUMBER(6)SEGVENTIALNVMSSRREVISIONNVMSSRPAGE(3)D.C.CookNuclearPlant,Unit2TEXT/Fmo>>4P>>c>>/4/sq>>kaf,uds//I/d>>4/NRCFamI36843/(IT)osooo31687001004QF04CorrectiveActionsThesourcerangeinstrumentdetectorwasremoved,replacedanddeclaredoperableonMarch14,1987at2223hours.FailedComonentIdentificationSourceRangeNuclearInstrumentationDetector(plantdesignationN-31).Manufacturer:WestinghouseModelNumber:WL23706EIIS:DETPreviousSimilarEventsNopreviouseventshaveoccurred.NRCFOAMSSSA983)*U.S.GPO:1986.0-824538/455}}
{{#Wiki_filter:NRC Form 368                                                                                                                                          U.S. NUCLEAR REOULATORY COMMISSION (84)3)
APPAOVED OMB NO. 31500104 EXPIAES: 8/31/88 LICENSEE EVENT REPORT HLER)
FACILITY NAME (I)                                                                                                                       DOCKET NUMBER (21                                PA  E  3I D    C. Cook Nuclear Pl nt Unit 2                                                                                0    5      0    0      0    3            1  OFp ESF    Actuation (Inadvertent Opening of Reactor Trip Breakers)                                                                 Due      to the Failure of a    Source Ran e Nuclear Instrumentation D EVENT DATE I5)                       LER NUMBER (6)                           REPORT DATE (7)                         OTHER FACILITIES INVOLVED (8)
MONTH      DAY      YEAR      YEAR          SEQUENTIAL          REVISION MONTH        DAY        YEAR        FACILITYNAMES                            DOCKET NUMBER(SI NUMBER      8'N NUMBER 0    5    0    0    0 030            3 8 7        8 7            0 0 1                0 0      04 01                                                                            0    5    0    0    0 OP E RAT I NO THIS REPORT IS SUBMITTED PUASUANT T 0 THE REOUIREMENTS OF 10 CFR (): (Chock oni or mori                  of tht follovflnpl (11)
MODE (0)                   20.402(B)                                                                                                                          73.71(b) 20.405(c)                           60,73(s)(2)liv)
POWE R                          20.405( ~ )(1)D)                             60.35(c 1 (I)                       50,73(s) ( 2 l(v)                               73.71(c)
LEVEL p p p            20A05(s)(1)(E)                               50.38(cl(2)                         50.73(s) I 2) (vii)                               oTHER Isptcify In Abstract btlovvtnd /n Tits, IVIICForm 20,405(s)(1)(ill)                           50.73( ~ l(2)li)                   50.73(sl(2)(vill)(A)                             3BEAJ 20.405(s)(1) (Iv)                           5073( ~ )(2)lii)                   60,73(v)(2)(vlii) IS) 20,405( ~ )(1)(v)                            50.73( ~ l(2)(iiB                  50.73( ~ )(2)(x)
LICENSEE CONTACT FOR THIS LEA (12)
NAME                                                                                                                                                          TELEPHONE NUMBER AREA CODE A. A.       Blind         Assistant                Plant Manager                                                              61 646                      5-             901 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
CAUSE    SYSTEM      COMPONENT          MANUFAC.           EPOATABLE      'ym                            SYSTEM  COMPONENT MANUFAC.            EPORTABLE    "
TO NPRDS                                                                                            TO NPROS:i TURER
                                                                                          ?. 2  A.. Qg TURER                                    '~in~ $
nQgg'&MÃ IG DET                      W1,2            0 SUPPLEMENTAL REPORT EXPECTED (14(                                                                                       MONTH      DAY        YEAR EXPECTED SUBMISSION DATE (16)
YES  flfyts, compliti EXPECTED SUShllSSIOIV DATE)                                       NO ABSTRACT fLImlt to /400 sptcts,   lt., tpprorrlmtttly flfttinslntli sptct ryptvvrlttin llnisl (18)
On    March 3, 1987, at 1511 hours, a spurious signal from a source range instrument channel (N-31) resulted in an Engineered Safety Features (ESF) actuation (inadvertent opening of the reactor trip breakers). The reactor was subcritical at the time. The automatic ESF responses were verified, all equipment        I functioned as designed.
Following investigation, and review of post actuation data, concluded that the signal from N-31 was spurious and due to a malfunction it    was of the detector, and not an increase in the core neutron level.
The source range instrument                                  detector was removed, replaced                                  and declared operable on March 14, 1987                                at 2223 hours.
870407047                1  870401 PDR        ADOCK 0500031(L S                                      PDR NRC Form 385
 
NRC Form 356A                                                                                                                U.S. NUCLEAR REGULATORY COMMISSION (983)
LICENSEE EVENT REPORT HLER) TEXT CONTINUATION                                            APPROVEO OMB NO. 3150&l04 EXPIRES: 8/31/88 FACILITYNAME (1)           ~                                                     OOCKET NUMBER (2)                 LER NUMBER (6)                     PAGE (3)
REVISION YEAR 4)5 SEQUENTIAL NUMBER        NUMBER D. C. Cook Nuclear                        Plant, Unit                2        p  5  p  p    p  3 1  6 8 7      0  0  1        00 02          OF    04 TEXT //F/rroro SFoco /4 r/O/ror/ Iroo /I/OI/4/ ///IC %%dnrr 35//AB/ (IT)
Conditions Prior to Event Unit      2  in    Mode 3            (Hot Standby), at 1.0          E4 cps    with  a unit shutdown            in progress.
Descri tion of Event On    March 3, 1987, at 1511 hours, a spurious signal from a source range instrument channel (N-31) (EIIS/CHA) resulted in an Engineered Safety Features (ESF) actuation [inadvertent opening of the reactor trip breakers (EIIS/BKR)]. The reactor was subcritical at the time with      all control rod banks (EIIS/ROD), and one shutdown rod bank (D),
fully inserted. Another shutdown rod bank (C) was being inserted when      the event occurred.                         Operations personnel immediately implemented Emergency Operating Procedure                              1 OHP 4023.E-O to verify proper response of the automatic protection system (EIIS:JC) and to assess plant conditions for initiating appropriate recovery actions. The N-31 source range instrument channel was returned to service on March 14, 1987 at 2223 hours following detector replacement.
The automatic ESF responses were verified,                                   all  equipment functioned as designed.                   However, since the unit was in Hot Standby and shutdown; the main feedwater pumps (EIIS/P) were previously removed from service',
the turbine/generator (EIIS/TRB-GEN) was in a tripped condition, no steam dump/pressure relief was necessary, and the auxiliary feedwater pumps were in service.
System/Equipment                      responses that did occur included; the opening of the reactor trip breakers and the insertion of the shutdown rods remaining to be inserted. Reactor coolant pump (EIIS/P) operation was maintained throughout the event and no abnormal occurrences were noted.
There were no                  structures, components, or systems inoperable at the start of this event which could have contributed to this ESF actuation, with the exception of the subject source range malfunction.
Cause        of Event Following investigation, and review of post actuation data,                                         it  was concluded that the signal from N-31 was spurious and due to a malfunction of the detector (EIIS/DET) and not an increase in the core neutron level.
Current characteristics                              curves were obtained for the detector and, based on the Westinghouse                              Manual, it  was determined that the detector failed                      due      to  air in-leakage.
NRC FORM 3SSA                                                                                                                            *U.S.GPO:1988 0 824 538/455 (94)3 I
 
NRC Form 388A                                                                                                          U.S. NUCLEAR REGULATORY COMMISSION (983 I LICENSEE EVENT REPORT HLER) TEXT CONTINUATION                                    APPROVED OMB NO, 3')50-0104 EXPIRES: 8/31/BB FACILITY NAME (I)                                                             DOCKET NUMBER (2)             LER NUMBER l6)                     PAGE (3)
YEAR    SECVENTIAL      REYIEloN NUMBER        NVM ER D. C. Cook Nuclear                          Plant, Unit          2        0  5  0  0    0 3 1 6    7      001            0          0  3 oF    0    4 T)D(T ///moro 4/rooo /4 Eo//rrr/ Irw a//rr/one/HRC Form 358AB/ (IT)
Anal sis            of Event This event              is being reported per the requirements of 10CFR50.73 (a)(2)(IV),               as an event that resulted in automatic actuation of any Engineered                  Safety Feature including the Reactor Protection System.
The source              range instrumentation monitors the core neutron flux level during reactor shutdown and the initial stages of reactor startup. The source range channels provide reactor protection by initiating a reactor trip at a relatively low neutron count rate to terminate a low power/high startup rate accident. The actuation coincidence is 1 of 2 channels > 1.0 E5 cps. During reactor startup the source range trips are blocked above permissive P-6 (approximately 6.0 E-ll amps on the intermediate range nuclear instrumentation).
The source range channel                          protection is automatically reinstated            when reactor power decreases                          below P-6 during shutdowns.       Prior to this event, both source range channels had re-energized when reactor power had decreased below P-6.
Since        a  low power/high startup rate condition did not exist during this event,               and all reactor Protection systems functioned as designed upon the receipt of the actuation sig'nal, concluded that the health and safety of the public were not it  has been jeopardized.
NRC POllM 388A                                                                                                                    -oU.S.CPO;1988 0 824 538/455 194)3)
 
NRC FI>>)II 3MA                                                                                              U.S. NUCLEAR AEGULATOAYCOMMISSION (94)3)
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION                                APPROVEO OMB NO. 3(50&104 EXPIRES: 8/31/SB FACILITY NAME (11                                                  OOCKET NUMBER (2)             LER NUMBER (6)                     PAGE (3)
YEAR  SEGVENTIAL        REVISION NVMSSR        NVMSSR D. C. Cook          Nuclear Plant, Unit                  2      o  s  o  o    o 3  1687        001              0        0 4    QF    0    4 TEXT /Fmo>> 4P>>c>> /4/sq>>kaf, uds //I/d>>4/NRC FamI 36843/(IT)
Corrective Actions The source            range instrument detector was removed, replaced and declared operable on March 14, 1987 at 2223 hours.
Failed        Com    onent    Identification Source Range Nuclear Instrumentation Detector                          (plant designation N-31).
Manufacturer:             Westinghouse Model Number:             WL23706 EIIS:DET Previous Similar Events No    previous events have occurred.
NRC FOAM SSSA                                                                                                          *U.S.GPO:1986.0-824 538/455 983)}}

Latest revision as of 06:00, 29 October 2019

LER 87-001-00:on 870303,spurious Signal from Source Range Instrument Channel N-31 Resulted in ESF Actuation.Caused by Malfunction of Detector.Source Range Instrument Detector Removed,Replaced & Declared Operable on 870314
ML17325A029
Person / Time
Site: Cook American Electric Power icon.png
Issue date: 04/01/1987
From: Blind A
INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:
Shared Package
ML17325A028 List:
References
LER-87-001-01, LER-87-1-1, NUDOCS 8704070471
Download: ML17325A029 (5)


Text

NRC Form 368 U.S. NUCLEAR REOULATORY COMMISSION (84)3)

APPAOVED OMB NO. 31500104 EXPIAES: 8/31/88 LICENSEE EVENT REPORT HLER)

FACILITY NAME (I) DOCKET NUMBER (21 PA E 3I D C. Cook Nuclear Pl nt Unit 2 0 5 0 0 0 3 1 OFp ESF Actuation (Inadvertent Opening of Reactor Trip Breakers) Due to the Failure of a Source Ran e Nuclear Instrumentation D EVENT DATE I5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQUENTIAL REVISION MONTH DAY YEAR FACILITYNAMES DOCKET NUMBER(SI NUMBER 8'N NUMBER 0 5 0 0 0 030 3 8 7 8 7 0 0 1 0 0 04 01 0 5 0 0 0 OP E RAT I NO THIS REPORT IS SUBMITTED PUASUANT T 0 THE REOUIREMENTS OF 10 CFR (): (Chock oni or mori of tht follovflnpl (11)

MODE (0) 20.402(B) 73.71(b) 20.405(c) 60,73(s)(2)liv)

POWE R 20.405( ~ )(1)D) 60.35(c 1 (I) 50,73(s) ( 2 l(v) 73.71(c)

LEVEL p p p 20A05(s)(1)(E) 50.38(cl(2) 50.73(s) I 2) (vii) oTHER Isptcify In Abstract btlovvtnd /n Tits, IVIICForm 20,405(s)(1)(ill) 50.73( ~ l(2)li) 50.73(sl(2)(vill)(A) 3BEAJ 20.405(s)(1) (Iv) 5073( ~ )(2)lii) 60,73(v)(2)(vlii) IS) 20,405( ~ )(1)(v) 50.73( ~ l(2)(iiB 50.73( ~ )(2)(x)

LICENSEE CONTACT FOR THIS LEA (12)

NAME TELEPHONE NUMBER AREA CODE A. A. Blind Assistant Plant Manager 61 646 5- 901 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFAC. EPOATABLE 'ym SYSTEM COMPONENT MANUFAC. EPORTABLE "

TO NPRDS TO NPROS:i TURER

?. 2 A.. Qg TURER '~in~ $

nQgg'&MÃ IG DET W1,2 0 SUPPLEMENTAL REPORT EXPECTED (14( MONTH DAY YEAR EXPECTED SUBMISSION DATE (16)

YES flfyts, compliti EXPECTED SUShllSSIOIV DATE) NO ABSTRACT fLImlt to /400 sptcts, lt., tpprorrlmtttly flfttinslntli sptct ryptvvrlttin llnisl (18)

On March 3, 1987, at 1511 hours0.0175 days <br />0.42 hours <br />0.0025 weeks <br />5.749355e-4 months <br />, a spurious signal from a source range instrument channel (N-31) resulted in an Engineered Safety Features (ESF) actuation (inadvertent opening of the reactor trip breakers). The reactor was subcritical at the time. The automatic ESF responses were verified, all equipment I functioned as designed.

Following investigation, and review of post actuation data, concluded that the signal from N-31 was spurious and due to a malfunction it was of the detector, and not an increase in the core neutron level.

The source range instrument detector was removed, replaced and declared operable on March 14, 1987 at 2223 hours0.0257 days <br />0.618 hours <br />0.00368 weeks <br />8.458515e-4 months <br />.

870407047 1 870401 PDR ADOCK 0500031(L S PDR NRC Form 385

NRC Form 356A U.S. NUCLEAR REGULATORY COMMISSION (983)

LICENSEE EVENT REPORT HLER) TEXT CONTINUATION APPROVEO OMB NO. 3150&l04 EXPIRES: 8/31/88 FACILITYNAME (1) ~ OOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

REVISION YEAR 4)5 SEQUENTIAL NUMBER NUMBER D. C. Cook Nuclear Plant, Unit 2 p 5 p p p 3 1 6 8 7 0 0 1 00 02 OF 04 TEXT //F/rroro SFoco /4 r/O/ror/ Iroo /I/OI/4/ ///IC %%dnrr 35//AB/ (IT)

Conditions Prior to Event Unit 2 in Mode 3 (Hot Standby), at 1.0 E4 cps with a unit shutdown in progress.

Descri tion of Event On March 3, 1987, at 1511 hours0.0175 days <br />0.42 hours <br />0.0025 weeks <br />5.749355e-4 months <br />, a spurious signal from a source range instrument channel (N-31) (EIIS/CHA) resulted in an Engineered Safety Features (ESF) actuation [inadvertent opening of the reactor trip breakers (EIIS/BKR)]. The reactor was subcritical at the time with all control rod banks (EIIS/ROD), and one shutdown rod bank (D),

fully inserted. Another shutdown rod bank (C) was being inserted when the event occurred. Operations personnel immediately implemented Emergency Operating Procedure 1 OHP 4023.E-O to verify proper response of the automatic protection system (EIIS:JC) and to assess plant conditions for initiating appropriate recovery actions. The N-31 source range instrument channel was returned to service on March 14, 1987 at 2223 hours0.0257 days <br />0.618 hours <br />0.00368 weeks <br />8.458515e-4 months <br /> following detector replacement.

The automatic ESF responses were verified, all equipment functioned as designed. However, since the unit was in Hot Standby and shutdown; the main feedwater pumps (EIIS/P) were previously removed from service',

the turbine/generator (EIIS/TRB-GEN) was in a tripped condition, no steam dump/pressure relief was necessary, and the auxiliary feedwater pumps were in service.

System/Equipment responses that did occur included; the opening of the reactor trip breakers and the insertion of the shutdown rods remaining to be inserted. Reactor coolant pump (EIIS/P) operation was maintained throughout the event and no abnormal occurrences were noted.

There were no structures, components, or systems inoperable at the start of this event which could have contributed to this ESF actuation, with the exception of the subject source range malfunction.

Cause of Event Following investigation, and review of post actuation data, it was concluded that the signal from N-31 was spurious and due to a malfunction of the detector (EIIS/DET) and not an increase in the core neutron level.

Current characteristics curves were obtained for the detector and, based on the Westinghouse Manual, it was determined that the detector failed due to air in-leakage.

NRC FORM 3SSA *U.S.GPO:1988 0 824 538/455 (94)3 I

NRC Form 388A U.S. NUCLEAR REGULATORY COMMISSION (983 I LICENSEE EVENT REPORT HLER) TEXT CONTINUATION APPROVED OMB NO, 3')50-0104 EXPIRES: 8/31/BB FACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER l6) PAGE (3)

YEAR SECVENTIAL REYIEloN NUMBER NVM ER D. C. Cook Nuclear Plant, Unit 2 0 5 0 0 0 3 1 6 7 001 0 0 3 oF 0 4 T)D(T ///moro 4/rooo /4 Eo//rrr/ Irw a//rr/one/HRC Form 358AB/ (IT)

Anal sis of Event This event is being reported per the requirements of 10CFR50.73 (a)(2)(IV), as an event that resulted in automatic actuation of any Engineered Safety Feature including the Reactor Protection System.

The source range instrumentation monitors the core neutron flux level during reactor shutdown and the initial stages of reactor startup. The source range channels provide reactor protection by initiating a reactor trip at a relatively low neutron count rate to terminate a low power/high startup rate accident. The actuation coincidence is 1 of 2 channels > 1.0 E5 cps. During reactor startup the source range trips are blocked above permissive P-6 (approximately 6.0 E-ll amps on the intermediate range nuclear instrumentation).

The source range channel protection is automatically reinstated when reactor power decreases below P-6 during shutdowns. Prior to this event, both source range channels had re-energized when reactor power had decreased below P-6.

Since a low power/high startup rate condition did not exist during this event, and all reactor Protection systems functioned as designed upon the receipt of the actuation sig'nal, concluded that the health and safety of the public were not it has been jeopardized.

NRC POllM 388A -oU.S.CPO;1988 0 824 538/455 194)3)

NRC FI>>)II 3MA U.S. NUCLEAR AEGULATOAYCOMMISSION (94)3)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO OMB NO. 3(50&104 EXPIRES: 8/31/SB FACILITY NAME (11 OOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR SEGVENTIAL REVISION NVMSSR NVMSSR D. C. Cook Nuclear Plant, Unit 2 o s o o o 3 1687 001 0 0 4 QF 0 4 TEXT /Fmo>> 4P>>c>> /4/sq>>kaf, uds //I/d>>4/NRC FamI 36843/(IT)

Corrective Actions The source range instrument detector was removed, replaced and declared operable on March 14, 1987 at 2223 hours0.0257 days <br />0.618 hours <br />0.00368 weeks <br />8.458515e-4 months <br />.

Failed Com onent Identification Source Range Nuclear Instrumentation Detector (plant designation N-31).

Manufacturer: Westinghouse Model Number: WL23706 EIIS:DET Previous Similar Events No previous events have occurred.

NRC FOAM SSSA *U.S.GPO:1986.0-824 538/455 983)