ML18041A134

LER 86-003-00:on 860603,reactor Trip Occurred Due to Loss of Power on White Instrument Bus.Caused by Trip of White Inverter Output Breaker.Procedures for Placing Inverter on Line Will Be revised.W/860703 Ltr

ML18041A134
Person / Time
Site:	Point Beach
Issue date:	07/03/1986
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	Keepler J, James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
CON-NRC-86-59 LER-86-003-01, LER-86-3-1, VPNPD-86-288, NUDOCS 8607090090
Download: ML18041A134 (24)

Text

FORM 1 LER SCSS DATA 09-23-91 DOCKET YEAR LER NUMBER REVXSION DCS NUMBER NSIC EVENT DATE 266 1986 003 0 8607090090 199975 06/03/86 DOCKET:266 POINT BEACH 1 TYPE:PWR REGION: 3 NSSS:WE ARCHITECTURAL ENGINEER: BECH FACILITY OPERATOR: WXSCONSIN ELECTRIC POWER CO.

SYMBOL: WEP COMMENTS STEPS 38-43: COMPLETE DESCRXPTXON OF UNIT 2 EVENT GIVEN IN LER 301/86-003.

WATCH 975 TRANSIENT INITIATED ON BOTH UNITS DUE TO SINGLE FAILURE.

WATCH-LIST CODES FOR THIS LER ARE:

975 POSSIBLE SIGNIFICANT EVENT REPORTABILITY CODES FOR THIS LER ARE:

13 10 CFR 50.73(a)(2)(iv): ESF actuations.

REFERENCE LERS 1 301/86-003 ABSTRACT POWER LEVEL 100~os ON 6 3 86i UNIT 1 AT POINT BEACH NUCLEAR PLANT EXPERIENCED A REACTOR TRIP DUE TO THE LOSS OF POWER ON THE WHITE INSTRUMENT BUS. THE POWER LOSS WAS DUE TO THE TRIP OF THE WHITE INVERTER (1DY03) OUTPUT BREAKER FEEDING THE WHITE INSTRUMENT BUS. THE BREAKER TRIP WAS CAUSED WHEN'FTER MAINTENANCEi THE SWING INVERTER (DYOC) WAS INCORRECTLY RESTORED TO OPERATION ON THE DC BUS FEEDING THE WHITE INVERTERS TO BOTH UNIT 1 AND UNIT 2 (1DY03 AND 2DY03 RESPECTIVELY). THE WHITE INSTRUMENT BUS SUPPLIES A CHANNEL OF POWER RANGE NUCLEAR INSTRUMENTATION. WHEN POWER WAS INTERRUPTED, THIS INSTRUMENTATION GENERATED A 204 LOAD REFERENCE TURBINE RUNBACK FROM ITS DROPPED ROD DETECTION CIRCUITRY. THE STEP DECREASE IN POWER CAUSED THE STEAM DUMP SYSTEM TO ARM. BECAUSE THE WHITE BUS ALSO SUPPLIES POWER TO THE TREF XNSTRUMENTi TREF FAILED LOW GENERATING A TEMPERATURE DEVIATION SIGNAL WHICH CAUSED THE STEAM DUMPS TO GO FULL OPEN AND CONTROL RODS TO STEP IN AT MAXIMUM SPEED. THESE EVENTS CREATED A PRIMARY SYSTEM COOLDOWN WHICH CAUSED PRXMARY SYSTEM PRESSURE TO DECRESE BELOW THE REACTOR TRIP SETPOINT. THE REACTOR TRIPPED.

THE PRIMARY SYSTEM CONTINUED TO COOL DOWN AFTER THE REACTOR TRIP WHEN THE AUXILIARY FEEDWATER SYSTEM AUTOMATICALLY STARTED. THIS COOLDOWN RESULTED IN ACTUATION OF THE SAFETY INJECTION SYSTEM. ALL SAFETY SYSTEMS FUNCTIONED AS DESIGN. PLANT SYSTEMS WERE STABILIZED AND SAFEGUARDS CIRCUITS RESET.

'OCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 311 1982 145 1 8301250373 181466 11/29/82 DOCKET:311 SALEM 2 TYPE:PWR REGION: 1 NSSS WE ARCHITECTURAL ENGINEER: PSEG FACILITY OPERATOR: PUBLIC SERVICE ELECTRIC & GAS CO.

SYMBOL: PEG ABSTRACT ON NOVEMBER 29'982'OLLOWING A SHIFT OF NO ~ 2B VITAL BUS POWER SOURCE IN PREPARATION FOR PLANNED MAINTENANCE ON NO. 1 STATION POWER TRANSFORMERS THE CONTROL ROOM OPERATOR OBSERVED THAT THE P 250 COMPUTER HAD SHUT DOWN. SINCE IT UTILIZES THE COMPUTER DATA AND MEMORY, THE REACTOR COOLANT SYSTEM (RCS) SUBCOOLING MONITOR WAS RENDERED INOPERABLE, AND ACTION STATEMENT 3.3.3.7A WAS ENTERED.

REDUNDANT WIDE RANGE RCS PRESSURE AND TEMPERATURE INDICATION AND STEAM TABLES WERE AVAILABLE, AND THE EVENT CONSTITUTED OPERATION IN A DEGRADED MODE IN ACCORDANCE WITH TECH SPEC 6.9.1.9.B. INVESTIGATION REVEALED THAT THE COMPUTER HAD SHUT DOWN DUE TO FAILURE OF THE INVERTER POWER SUPPLY. THE POWER SUPPLY PROBLEM RESULTED FROM A FAILED OSCILLATOR CIRCUIT BOARD. THE BOARD WAS REPLACED, THE COMPUTER WAS RESTORED TO OPERATION AND THE ACTION STATEMENT WAS TERMINATED.

II DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 361 1990 016 0 9101140111 220676 12/06/90 DOCKET:361 SAN ONOFRE 2 TYPE:PWR REGION: 5 NSSS:CE ARCHITECTURAL ENGINEER: BECH FACILITY OPERATOR: SOUTHERN CALIFORNIA EDISON CO.

SYMBOL: SCE COMMENTS STEP 2: REM MANUFACTURED BY CORNELL-DUBLIER ELECTRIC, PART NO. CDE KBXK1056P OR SCI 020138. STEP 17: PART NO. SCX PC201. STEP 9: CAUSE IX MOMENTARY LOSS OF POWER. STEP 16: COMP MSC TRANSISTOR. STEP 11: COMP MSC MECHANICAL LINKAGE. STEP 25: COMP XR SEQUENCE OF EVENTS RECORDER.

WATCH-LIST CODES FOR THIS LER ARE:

20 EQUIPMENT FAILURE 34 DESIGN ERROR OR INADEQUACY 913 UPDATE NEEDED REPORTABILITY CODES FOR THIS LER ARE:

13 10 CFR 50.73(a)(2)(iv): ESF actuations.

REFERENCE LERS:

1 362/89-001 ABSTRACT POWER LEVEL 100'T 2200 ON DECEMBER 6i 1990i UNIT 2 AUTOMATICALLY TRIPPED FROM 1004 POWER ON A REACTOR PROTECTION SYSTEM LOSS OF LOAD (LOL) SIGNAL. THE LOL SIGNAL WAS CAUSED BY A TURBINE TRIP, WHXCH OCCURRED AS A RESULT OF A MOMENTARY LOSS OF POWER FROM THE NON-1E UNXNTERRUPTIBLE POWER SYSTEM (UPS)g MOMENTARILY DE ENERGIZING BUS Q-069. EMERGENCY FEEDWATER ACTUATION SYSTEM (EFAS) 1 AND EFAS 2 ACTUATIONS PROPERLY OCCURRED. ONE 6.9 KV BUS DID NOT AUTOMATICALLY TRANSFER TO OFFSITE POWER FOLLOWING THE TRXPg DE ENERGIZING 2 REACTOR COOLANT PUMPS (RCPS); TWO OTHER RCPS CONTINUED TO PROVIDE FORCED CIRCULATION'PPROXIMATELY 1 TO 2 MINUTES FOLLOWING THE TRIPg A COMPLETE LOSS OF POWER ON Q-069 OCCURRED. APPROPRIATE ACTIONS WERE INITIATED IN ACCORDANCE WITH PROCEDURES TO COMPENSATE FOR THE OPERATION OF CONTROL SYSTEMS WHICH WERE AFFECTED BY THE LOSS OF POWER ON Q-069. ONE MAIN STEAM SAFETY VALVE FOR EACH STEAM GENERATOR MAY HAVE LIFTED FOR A SHORT TIME AND PROPERLY RESEATED. BUS Q-069 POWER WAS RESTORED AT 2220 VIA THE MANUAL BYPASS SWITCH. RECOVERY OF THE PLANT OTHERWISE PROCEEDED NORMALLY. IT IS POSTULATED THAT FAILURE OF

1) A CAPACITOR IN THE NON-1E UPS INVERTER OUTPUT AND 2) A TRANSXSTOR IN THE STATIC SWITCH TRANSFER LOGIC CONTROL CIRCUIT COMBINED TO CAUSE THE LOSS OF POWER ON BUS Q-069 (BOTH AT THE ONSET OF THE EVENT AND AT 1-2 MINUTES POST-TRIP). THE ROOT CAUSE EVALUATION IS CONTINUING.

DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 362 1991 001 0 9104220351 221467 03/15/91 DOCKET:362 SAN ONOFRE 3 TYPE:PWR REGION: 5 NSSS:CE ARCHXTECTURAL ENGINEER: BECH FACILITY OPERATOR: SOUTHERN CALIFORNIA EDISON CO.

SYMBOL: SCE COMMENTS STEP 2: PART NO. CDE KBXK1056PX OR SCI 020138.

NATCH-LIST CODES FOR THXS LER ARE:

20 EQUIPMENT FAILURE REPORTABXLITY CODES FOR THIS LER ARE:

13 10 CFR 50.73(a)(2)(iv): ESF actuations.

REFERENCE LERS:

1 361/86-029 2 361/90-016 3 362/89-001 ABSTRACT POWER LEVEL 100~os AT 0938 ON MARCH 15'991i UNIT 3 AUTOMATICALLY TRIPPED FROM 100~o POWER ON A REACTOR PROTECTION SYSTEM LOSS OF LOAD (LOL) SIGNAL THE LOL SIGNAL WAS CAUSED BY A TURBINE TRIPi WHICH OCCURRED AS THE RESULT OF A MOMENTARY INTERRUPTION IN POWER FROM THE NON-lE UNINTERRUPTIBLE POWER SYSTEM (UPS), DE-ENERGIZING BUS 3Q069.

EMERGENCY FEEDWATER ACTUATION SYSTEM (EFAS) 1 AND EFAS 2 ACTUATIONS PROPERLY OCCURRED. ONE NON-1E 4.16 KV (3A03) BUS DID NOT AUTOMATICALLYTRANSFER FROM ITS NORMAL POWER SOURCE TO ITS ALTERNATE POWER SOURCE RESULTING IN THE LOSS OF THE ALTERNATE POWER SUPPLY (3B012) TO THE NON-1E BUS 3Q069. ONE MAIN STEAM SAFETY VALVE LIFTED FOR A SHORT TIME AND PROPERLY RESEATED. AT 1000, WHEN 3A03 WAS MANUALLY REENERGIZEDi POWER WAS RESTORED TO 3Q069 ~ APPROPRIATE ACTIONS WERE TAKEN IN ACCORDANCE WITH PROCEDURES TO COMPENSATE FOR THE OPERATION OF CONTROL SYSTEMS WHICH WERE AFFECTED BY THE LOSS OF POWER TO THE NON-1E UPS. POST-TRIP PLANT RECOVERY OTHERWISE PROCEEDED NORMALLY. AN OUTPUT CAPACITOR IN THE CONSTANT VOLTAGE TRANSFORMER (CVT) SECTION OF THE NON-1E UPS INVERTER FAILED CAUSING THE MOMENTARY INTERRUPTION IN POWER FROM THE NON-1E UPS. ALL CAPACITORS IN THE UNITS 2 AND 3 NON-1E UPS WERE REPLACED WITH AN UPGRADED MODEL. THE UNIT 3 INSTRUMENT BUSSES POWERED BY THE NON-1E UPS WERE MODIFIED SUCH THAT POWER WILL BE MAINTAINED TO CRITICAL COMPONENT SYSTEMS.

DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 369 1984 024 0 8412010048 192511 08/21/84 DOCKET:369 MCGUIRE 1 TYPE PWR REGION: 2 NSSS:WE ARCHITECTURAL ENGINEER: DUKE FACILITY OPERATOR: DUKE POWER CO.

SYMBOL: DPC COMMENTS STEP 16: CAUSE XX VOLTAGE SPIKE. STEP 6 COMP RLX CONTROL OUTPUT RELAY.

NATCH-LIST CODES FOR THIS LER ARE:

975 POSSIBLE SI GNIFXCANT EVENT REPORTABILITY CODES FOR THIS LER ARE:

14 10 CFR 50.73(a)(2)(v): Event that could have prevented fulfillment of a safety function.

ABSTRACT POWER LEVEL 100'T 2400 ON 8 20 84i THE MCGUIRE SWITCHYARD COMPUTER WAS REPORTED INOPERABLE. ON 8-21-84, COMPUTER AND INVERTER MAINTENANCE PERSONNEL PERFORMED CORRECTIVE MAINTENANCE ON THE SWXTCHYARD COMPUTER AND STATIC INVERTER. AT 2114, THE SWITCHYARD COMPUTER WAS RE STARTEDi CHECKED FOR OPERABXLITYi AND RETURNED TO SERVICE. AT 2148, WHEN THE SWITCHYARD OPERATOR RE-ENABLED THE I I COMPUTER CONTROL OUTPUTS g 3 0 POWER C RCU T BREAKERS ( PCBS ) AND ASSOCIATED DISCONNECTS OPENED i RESULTING XN MCGUIRE UNIT 1 REACTOR TRIP AND TURBINE TRIP, LOSS OF UNIT 1 OFFSITE AC POWER, AND STARTUP OF UNIT 1 DGS A AND BE UNIT 1 WAS IN MODE 1 AT 100+o POWER AT THE TIME THIS INCIDENT IS CLASSIFIED AS A COMPONENT MALFUNCTION/FAILURE BECAUSE THE CONTROL CIRCUITS WERE CHANGED TO AN UNDESIRABLE STATE WITHOUT A COMMAND FROM THE COMPUTER, DURING COMPUTER AND INVERTER MAINTENANCE. DESIGN DEFICIENCY ALSO CONTRIBUTED BECAUSE THE COMPUTER PROGRAM DID NOT INCLUDE A FUNCTXON TO RESET THE COMPUTER OUTPUT CONTROL CIRCUITS TO A PREDETERMINED STATE WHEN THE COMPUTER IS RESTARTED. THE BEHAVIOR AND CONTROL OF THE TRANSIENT WHICH RESULTED FROM THE REACTOR AND TURBINE TRIP WERE AS COULD BE EXPECTED.

FORM 6 LER SCSS DATA 09-23-91

• • • • • • • • • • • • • • • • • • • • • • • • 4**************************************

DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 373 1989 009 1 8907110299 214561 03/02/89 DOCKET:373 LA SALLE 1 TYPE:BWR REGION: 3 NSSS:GE ARCHITECTURAL ENGINEER: SLXX FACILITY OPERATOR: COMMONWEALTH EDISON CO.

SYMBOL: CWE COMMENTS STEPS 2,3: MODEL NO. 9L11MHA264.

WATCH-LIST CODES FOR THIS LER ARE:

942 UNUSUAL EVENT 20 EQUIPMENT FAILURE REPORTABILITY CODES FOR THIS LER ARE:

13 10 CFR 50.73(a)(2)(iv): ESF actuations.

REFERENCE LERS:

1 373/87-003 2 373/87-014 3 374/84-020 ABSTRACT POWER LEVEL 0860 'N 3/2/89i AT 2302 HRS A PHASE TO GROUND FAULT OCCURRED AT t'C" PHASE LIGHTNING ARRESTOR ON THE PRIMARY SIDE OF THE UNIT 2 SYSTEM AUX. TRANSFORMER. FAULT WAS AUTOMATICALLY ISOLATED BY THE TRIPPING OF SWITCHYARD OIL CIRCUIT BREAKERS (OCB) 4-6 AND 6-1 AND UNIT 2 FEEDER BREAKERS. ALL LOADS BEING FED FROM THE SAT TRANSFERRED TO UNIT 2 UNIT AUX. TRANSFORMER EXCEPT FOR BUS 243 WHICH WAS SUPPLIED BY 2B DIESEL GENERATOR WHICH SATISFACTORILY AUTO-STARTED ON UNDERVOLTAGE. UNIT 2 REMAINED ON-LINE AFTER THE INCIDENT. AS A RESULT OF TRANSIENT ON THE 345 KV SYSTEM, UNIT 1 GENERATOR PROTECTIVE RELAYING SENSED A HIGH GENERATOR DIFFERENTIAL CURRENT ON PHASE A AND ISOLATED UNIT 1 GENERATOR. UNIT 1 TURBINE TRIPPED ON LOAD REJECTION RESULTING IN A REACTOR SCRAM FROM TURBINE CONTROL VALVE FAST CLOSURE.

UNIT 1 PROCEEDED INTO NORMAL POST-SCRAM CONDITIONS WITH THE EXCEPTION OF TEMPORARY LOSS OF THE SERVICE AIR COMPRESSOR AND PLANT PROCESS COMPUTER. PROBLEMS WERE ALSO ENCOUNTERED WITH THE RESETTING OF THE SCRAM LOGIC. CAUSE OF THIS EVENT WAS THE PHASE TO GROUND FAULT THAT OCCURRED FROM THE LIGHTNING ARRESTOR TOP CAP TO A SPARGER HEAD ON THE TRANSFORMER DELUGE SYSTEM. THIS WAS EVIDENT FROM ARC BURNING IDENTIFIED AT TOP OF LIGHTNING ARRESTOR AND AT SPARGER HEAD. FAULT WAS CAUSED BY DEBRIS THAT HAD BLOWN ONTO THE LIGHTNING ARRESTOR LEAD.

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DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 395 1988 001 0 8803070227 208519 02/04/88 DOCKET:395 SUMMER 1 TYPE:PWR REGION: 2 NSSS:WE ARCHITECTURAL ENGINEER: GLBT FACILITY OPERATOR: SOUTH CAROLINA ELECTRIC & GAS CO.

SYMBOL: SCC COMMENTS STEP 5: COMP MEI PERIMETER CAMERAS. STEP 10: COMP MEI PORTAL ACCESS CONTROLLER UNITS. STEP 11: COMP MSC ELECTRIC DOOR STRIKES. STEP 12: PSYS SW UNKNOWN VITAL AREAS. STEP 9: PART NUMBERS 200140 AND 200569 SPM/E E/D WATCH-LIST CODES FOR THIS LER ARE:

34 DESIGN ERROR OR INADEQUACY 946 PHYSICAL SECURITY/SAFEGUARDS REPORTABILITY CODES FOR THIS LER ARE:

20 10 CFR 73.71(c): Physical security system threatened.

ABSTRACT POWER LEVEL 100~os AT APPROXIMATELY 0830 HOURSi FEBRUARY 4~ 1988'WO PLANT ELECTRICIANS CRIMPED AN ELECTRICAL LEAD WHILE REPLACING AN ELECTRICAL DISTRIBUTION PANEL COVER. THE CIRCUIT SHORTED TO GROUND AND TRIPPED A CIRCUIT BREAKER WHICH RESULTED IN A LOSS OF THREE PERIMETER CAMERAS. SIMULTANEOUSLY, THE CURRENT TO GROUND SITUATION CAUSED THE ASSOCIATED INVERTER TO TEMPORARILY OVERLOAD CREATING A MOMENTARYi BUT SIGNIFICANT REDUCTION IN VOLTAGE THAT RESULTED IN SIX ELECTRIC DOOR STRIKES FAILING IN THE UNLOCKED (ENERGIZED) POSITION.

AT APPROXIMATELY 0840 HOURS, SECURITY PROCEDURES WERE IMPLEMENTED TO COMPENSATE FOR THE LOSS OF THE CAMERAS AND TOTAL LOSS OF THE SECURITY COMPUTER SYSTEM AT APPROXIMATELY 0907 HOURS'LEVEN ADDITIONAL SECURITY FORCE PERSONNEL REPORTED FOR DUTY FROM THE TRAINING AUGMENTATION TO COMPENSATE FOR THE LOSS OF ALARM CAPABILITY AND LOCKING MECHANISMS AT THE VITAL AREAS AFFECTED BY THE OUTAGE.

OPERATIONAL TESTS WERE CONDUCTED ON ALL VITAL DOORS AND PERIMETER INTRUSION DETECTION SEGMENTS AFFECTED. ALL TESTS WERE SATISFACTORILY COMPLETED AT 1243 HOURS, FEBRUARY 4, 1988. COMPENSATORY POSTS AT EACH VITAL AREA REMAINED IN EFFECT UNTIL EACH DOOR WAS OPERATIONALLY TESTED.

DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 423 1987 027 0 8707090095 205195 06/05/87 DOCKET:423 MILLSTONE 3 TYPE PWR REGION: 1 NSSS:WE ARCHITECTURAL ENGINEER: SWXX FACILITY OPERATOR: NORTHEAST NUCLEAR ENERGY CO.

SYMBOL: NNE WATCH-LIST CODES FOR THIS LER ARE:

31 ACCIDENTAL ACTION 941 REPORT ASSOCIATED WITH 10 CFR 50.72 REPORTABILITY CODES FOR THIS LER ARE:

13 10 CFR 50.73(a)(2)(iv): ESF actuations.

ABSTRACT POWER LEVEL 100+os AT 1323 ON JUNE 5) 1987) WITH THE PLANT AT 100+o POWERi THE NORMAL SUPPLY BREAKER TO TRAIN nA>> VITAL BUS 34C WAS TRIPPED OPEN. THE MAIN STEAM ISOLATION VALVES IMMEDIATELY CLOSED ON LOSS OF 120VAC TO THEIR SOLENOID TEST CONTROL CIRCUITRY. A REACTOR TRIP FOLLOWED ON LOW-LOW STEAM GENERATOR LEVELS, WHICH SIGNALED A TURBINE TRIP. A TRAIN "A" LOSS OF POWER SIGNAL WAS GENERATED, THE EMERGENCY DIESEL GENERATOR STARTED AND SUCCESSFULLY ENERGIZED VITAL LOADS. THE MAIN STEAM ATMOSPHERIC RELIEF VALVES AND STEAM GENERATOR CODE SAFETIES OPENED AS DESIGNED A TRAIN itAti CONTROL BUILDING ISOLATION, AND TRAIN 'tA't AND "B" FEEDWATER ISOLATION RESULTED FROM THE EVENT ~ THE PLANT WAS IN HOT STANDBY (MODE 3 ) BY 1 600 HOURS ~ JUNE 5 i 1 9 8 7 ~ THE CAUSE OF BUS 3 4 C TRI P WAS A RESULT OF PERSONNEL ERROR i DUE TO AN OPERATOR DROPPING A RACKING MOTOR ONTO THE 4.16KV SWITCHGEAR.

~ t 0

DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 424 1990 023 0 9101220420 220828 12/18/90 DOCKET 424 VOGTLE 1 TYPE:PWR REGION: 2 NSSS:WE ARCHITECTURAL ENGINEER: BESS FACILITY OPERATOR: GEORGIA POWER CO.

SYMBOL: GPC COMMENTS STEP 2: CLASS AA/FA, 3 PHASE, DRY TYPE TRANSFORMER. STEP 18: MODEL NO.

5HK350-3000.

WATCH-LIST CODES FOR THIS LER ARE:

20 EQUIPMENT FAILURE REPORTABILITY CODES FOR THIS LER ARE:

13 10 CFR 50.73(a)(2)(iv): ESF actuations.

REFERENCE LERS:

1 424/90-016 ABSTRACT POWER LEVEL 100+os ON 12 18 90 AT 1936 CSTi UNIT WAS OPERATING AT 1004 POWER WHEN A 4160/480 VOLT NON-1E TRANSFORMER (1NB1OX)

EXPERIENCED AN INTERNAL FAULT. THIS FAILURE RESULTED IN A LOSS OF POWER FOR THE SPEED CONTROL CIRCUITRY FOR THE 1B MAIN FEEDWATER PUMP (MFP) TURBINE AND CERTAIN SUPPORT SYSTEMS FOR EMERGENCY DIESEL GENERATOR 1 B ~ FEEDWATER PUMP SPEED / FEEDWATER FLOW i AND STEAM GENERATOR (SG) LEVELS DECREASED. THE REACTOR OPERATOR INITIATED A MANUAL REACTOR TRIP AT 1937 CST AFTER EFFORTS TO MAINTAIN SG LEVELS WERE UNSUCCESSFUL. ALL SAFETY RELATED FUNCTIONS OCCURRED PER DESIGN FOLLOWING THE REACTOR TRIP HOWEVERS A NON 1E 4160 VOLT BUS FAILED TO AUTOMATICALLYTRANSFER TO THE RESERVE AUXILIARY TRANSFORMERS CAUSING A TEMPORARY LOSS OF VARIOUS NON-1E HOUSE LOADS. TRANSFER OF THE 4160 VOLT BUS WAS COMPLETED MANUALLY AND NORMAL PLANT CONDITIONS WERE ESTABLISHED FOR HOT STANDBY BY 1956 CST. THE ROOT CAUSE FOR THE TRANSFORMER FAILURE IS INDETERMINATE; HOWEVER, SEVERAL SIMILAR TRANSFORMER FAILURES HAVE OCCURRED AT VEGP (REFERENCE LER 50-424/1990-016). THE INVOLVED TRANSFORMERS ARE GE CLASS AA/FA, THREE PHASE, DRY TYPE TRANSFORMERS. THE FAILED TRANSFORMER HAS BEEN REPLACED AND FURTHER STUDY OF POSSIBLE FACTORS WHICH MAY HAVE LED TO THE FAILURE IS IN PROGRESS.

~ )

DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 455 1987 019 1 8806230261 209583 10/02/87 DOCKET:455 BYRON 2 REGION 3 ARCHITECTURAL ENGINEER: SLXX FACILITY OPERATOR: COMMONWEALTH EDISON CO.

SYMBOL: CWE COMMENTS STEP 6: EQUIPMENT OPERATOR OPENED STATION AUX TRANSFORMER DISCONNECT INSTEAD OF THE MAIN TRANSFORMER DISCONNECT.

WATCH-LIST CODES FOR THIS LER ARE:

35 HUMAN ERROR 942 UNUSUAL EVENT 20 EQUIPMENT FAILURE REPORTABILITY CODES FOR THIS LER ARE:

13 10 CFR 50.73(a) (2)(iv): ESF actuations.

ABSTRACT POWER LEVEL 0134 ON OCTOBER 2i 1987i AT 0446i UNIT 2 WAS RETURNING TO SERVICE WHEN UNIT 2 WAS SYNCHRONIZED TO THE GRIDi THE STEAM GENERATOR (SG) LEVELS INCREASED AND CAUSED A HI-2 S/G LEVEL TRIP. THE HI-2 SG LEVEL WAS REACHED ON SG 2C DUE TO EXCESSIVE "LEAK BY" OF THE 2FW530 VALVE. THE HIGH S/G LEVEL CAUSED A TURBINE TRIP AND A SUBSEQUENT REACTOR TRIP BECAUSE REACTOR POWER WAS ABOVE 10+os AN EQUIPMENT OPERATOR (EO) WAS INSTRUCTED TO REALIGN THE SWITCHYARD RING BUS AFTER THE TRIP. THE EO OPENED THE SYSTEM AUX TRANSFORMER DISCONNECTS INSTEAD OF THE MAIN POWER TRANSFORMER DISCONNECTS. THE SAFETY RELATED 4KV BUSES WERE DEENERGIZED CAUSING THE EMERGENCY DIESEL GENERATORS TO STARTi REENERGIZE THE BUSES'ND SEQUENCE THE SAFE SHUTDOWN LOADS. THE ROOT CAUSE OF THE LOSS OF OFFSITE POWER WAS DUE TO PERSONNEL ERROR. THE EO OPENED THE WRONG DISCONNECT. THE CORRETIVE ACTIONS ARE AS FOLLOWS: DISCIPLINARY ACTION WAS TAKEN WITH THE EO; ADMINISTRATIVE PROCEDURES WERE REVISED TO ENSURE THAT NO SWITCHYARD OPERATIONS ARE PERFORMED WITHOUT A SECOND INDIVIDUAL PRESENTi PERMANENTi DESCRIPTIVE LABELS HAVE BEEN PLACED ON MPT & SAT SWITCHYARD DISCONNECTS; A WALK THROUGH OF THE SWITCHYARD WITH DIVISION SUPERINTENDENT OF POWER SUPPLY TO DEMONSTRATE PROPER OPERATIONS AND COMMUNICATIONS WAS CONDUCTED; THE SAT DISCONNECTS ARE LOCKED WITH UNIQUE LOCKS FOR EACH UNIT, ETC.

~ M ~

1 302/87-021 2 3 02/87-025 3 304/86-001 4 311/83-022 5 311/88-014 6 3 16/89-014 7 331/85-031 8 334/85-018 9 335/81-053 10 362/89-001 11 364/81-004 12 382/85-042 13 410/86-015 14 458/90-026

II k

I DOCKET YEAR LER NUMBER REVISION DCS NUMBER NSIC EVENT DATE 335 1981 053 0 8201060355 171810 11/25/81 DOCKET:335 ST. LUCIE 1 TYPE:PWR REGION: 2 NSSS:CE ARCHITECTURAL ENGINEER: EBAS FACILITY OPERATOR: FLORIDA POWER 6 LIGHT COMPANY SYMBOL: FPL COMMENTS WATCH 975 LOSS OF CONTROL ROOM ALARM FUNCTION.

WATCH-LIST CODES FOR THIS LER ARE:

975 POSSIBLE SIGNIFICANT EVENT REFERENCE LERS 1 335/79-028 ABSTRACT I I II B2 STAT ON SERVI CE TRANSFORMER FA LED i DEENERG Z NG THE B2 4 8 OV LOAD CENTER. ABOUT 3 MINUTES LATER THE 2 TIE BREAKERS FEEDING THE AB DC BUS FROM THE B BUS TRIPPED'EENERGIZING THE AB DC BUS ~ LOSS OF THIS CAUSED A LOSS OF AB CONTROL POWER AND 120V VITAL AC WHICH FEEDS ALL CONTROL ROOM ALARMS BUT NOT INSTRUMENTS'HE DC BUSg 120V AC AND ALARMS WERE RESTORED WITHIN 15 MINUTES. SEE LER 335-79-28 FOR RELATED EVENTS. THE B TO AB TIE BREAKERS WERE THOROUGHLY TESTED AND INSPECTED. A LOOSE POWER TERMINATION WAS DISCOVERED ON THE B SIDE BREAKER AND THE INSTANTANEOUS OVER CURRENT TRIP WAS SET ON 'LO'N BOTH BREAKERS. THE TRIP WAS RESET TO HI PER DESIGN AND ALL CONNECTIONS WERE TORQUED. ALL SIMILAR BREAKERS WERE CHECKED.