ML17325A029

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
Issue date:	04/01/1987
From:	Blind A INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:
Shared Package
ML17325A028	List: ML17325A027 ML17325A029 ML17325A030
References
LER-87-001-01, LER-87-1-1, NUDOCS 8704070471
Download: ML17325A029 (5)

Text

NRC Form 368 (84)3)LICENSEE EVENT REPORT HLER)U.S.NUCLEAR REOULATORY COMMISSION APPAOVED OMB NO.31500104 EXPIAES: 8/31/88 FACILITY NAME (I)D C.Cook Nuclear Pl nt Unit 2 DOCKET NUMBER (21 0 5 0 0 0 3 PA E 3I 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 NUMBER REVISION 8'N NUMBER MONTH DAY YEAR FACILITY NAMES DOCKET NUMBER(SI 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 MODE (0)POWE R LEVEL p p p 20.402(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(c 1 (I)50.38(cl(2) 50.73(~l(2)li)5073(~)(2)lii)50.73(~l(2)(iiB LICENSEE CONTACT FOR THIS LEA (12)60,73(s)(2)liv) 50,73(s)(2 l(v)50.73(s)I 2)(vii)50.73(sl(2)(vill)(A) 60,73(v)(2)(vlii)

IS)50.73(~)(2)(x)0 THE REOUIREMENTS OF 10 CFR (): (Chock oni or mori of tht follovflnpl (11)THIS REPORT IS SUBMITTED PUASUANT T 73.71(b)73.71(c)oTHER Isptcify In Abstract btlovvtnd/n Tits, IVIIC Form 3BEAJ NAME A.A.Blind-Assistant Plant Manager TELEPHONE NUMBER AREA CODE 61 646 5-901 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)CAUSE SYSTEM COMPONENT IG DET MANUFAC.TURER W1,2 0 EPOATABLE'ym TO NPRDS?.2 A..Qg SYSTEM COMPONENT MANUFAC.TURER EPORTABLE" TO NPROS:i'~in~$nQgg'&MÃSUPPLEMENTAL REPORT EXPECTED (14(YES flf yts, compliti EXPECTED SUShllSSIOIV DATE)NO ABSTRACT fLImlt to/400 sptcts, lt., tpprorrlmtttly flfttin slntli sptct ryptvvrlttin llnisl (18)EXPECTED SUBMISSION DATE (16)MONTH DAY YEAR 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 functioned as designed.I 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, 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 (983)LICENSEE EVENT REPORT HLER)TEXT CONTINUATION U.S.NUCLEAR REGULATORY COMMISSION APPROVEO OMB NO.3150&l04 EXPIRES: 8/31/88 FACILITY NAME (1)~OOCKET NUMBER (2)LER NUMBER (6)PAGE (3)YEAR 4)5 SEQUENTIAL NUMBER REVISION NUMBER D.C.Cook Nuclear Plant, Unit 2 TEXT//F/rroro SFoco/4 r/O/ror/Iroo/I/OI/4////IC%%dnrr 35//AB/(IT)p 5 p p p 3 1 6 8 7 0 0 1 00 02 OF 04 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 (94)3 I*U.S.GPO:1988 0 824 538/455 NRC Form 388A (983 I LICENSEE EVENT REPORT HLER)TEXT CONTINUATION U.S.NUCLEAR REGULATORY COMMISSION APPROVED OMB NO, 3')50-0104 EXPIRES: 8/31/BB FACILITY NAME (I)DOCKET NUMBER (2)YEAR LER NUMBER l6)SECVENTIAL NUMBER REYIEloN NVM ER PAGE (3)D.C.Cook Nuclear Plant, Unit 2 T)D(T///moro 4/rooo/4 Eo//rrr/Irw a//rr/one/HRC Form 358AB/(IT)0 5 0 0 0 3 1 6 7 001 0 0 3 oF 0 4 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, it has been concluded that the health and safety of the public were not jeopardized.

NRC POllM 388A 194)3)-oU.S.CPO;1988 0 824 538/455 NRC FI>>)II 3MA (94)3)LICENSEE EVENT REPORT (LER)TEXT CONTINUATION U.S.NUCLEAR AEGULATOAY COMMISSION APPROVEO OMB NO.3(50&104 EXPIRES: 8/31/SB FACILITY NAME (11 OOCKET NUMBER (2)YEAR LER NUMBER (6)SEGVENTIAL NVMSSR REVISION NVMSSR PAGE (3)D.C.Cook Nuclear Plant, Unit 2 TEXT/Fmo>>4P>>c>>/4/sq>>kaf, uds//I/d>>4/NRC FamI 36843/(IT) o s o o o 3 1687 001 0 0 4 QF 0 4 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 983)*U.S.GPO:1986.0-824 538/455