ML20024J247

LER 94-009-00:on 940909,EDG G-02 Inadvertently Started & Station Battery Charger D-08 Tripped Off Due to Blown Fuse. Caused by Inadequate Procedure.Blown Fuse Replaced & Electrical Distribution Sys Restored to normal.W/941006 Ltr

ML20024J247
Person / Time
Site:	Point Beach
Issue date:	10/06/1994
From:	Castell C, Link B WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-94-073, CON-NRC-94-73 LER-94-009, LER-94-9, VPNPD-94-106, NUDOCS 9410130065
Download: ML20024J247 (7)

Text

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Wisconsin l

1Electnc

- POWER COMPAth' l 231 W Michigan Po Box 2046. Milwoukee WI 53201-2046 (414)221-2345 VPNPD-94-106  ;

NRC-94-073  ;

October.6, 1994 l i

Document Control Desk U.S. NUCLEAR REGULATORY COMMISSION Mail Station P1-137 I Washington, DC 20555 Gentlemen: l

, , s. -. ., . s. ,.

DOCKETS 50-266 AND 50-301 LICENSEE EVENT REPORT 94-009-00 INADVERTENT EMERGENCY DIESEL START AND LOSS OF A STATION BATTERY CHARGER POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 Enclosed is Licensee Event Report 94-009-00 for Point Beach Nuclear ,

Plant, Units 1 and 2. This report is being submitted in accordance I with the requirements of 10 CFR 50.73 (a) (2) (1) (B) , "Any operation I or condition prohibited by the plant's Technical Specifications" and 10 CFR 50.73 (a) (2) (iv) , "Any event or condition that resulted ,

in a manual or automatic actuation of any Engineered Safety Feature l (ESF), including the reactor protection system (RPS)." This report describes a situation that caused a blown fuse in the metering and relaying circuit for the 2A-06 4160 Volt emergency bus.

Please contact us if there are any questions.

Sincerely,

/

Bo Li k Vice President Nuclear Power CAC/jg { gg rj { g Enclosure cc: NRC Regional Administrator, Region III NRC Resident Inspector 7410130065 941006 PDR ADOCK 05000266 f, S PDR ,,g g m.g g y m,g gg. p,pg , /) l

o .

NRC F0itM 366 U.S. MUCLEAR REGULATORY Cupet!SSION APPROVED BY Opm No. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH LICENSEE EVENT REPORT (LER) $3pn"EI, "S RE RDING BUR EN h5 I " "

TE i)

THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, (See reverse for required number of digits / characters for each block) WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET. WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) PAGE (3)

POINT BEACH NUCLEAR PLANT, UNIT 1 05000266 1 OF 6 TITLE (4)

INADVERTENT EMERGENCY DIESEL START AND LOSS OF A STATION BATTERY CHARGER EVENT DATE (5) lER NLSWER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

SEQUENTIAL REVISION FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NUMBER PBNP UNIT 2 05000301 94 '# " * "#*' "'I "

09 09 94 -- 009 --

00 10 06 94 O 0 OPERATING TH IS RrP RT IS SUBMITTED PURSUANT TO THE REQUIREIENTS OF 10 CFR i: (Check one or more) (11)

N ODE (9) 20.402(b) 20.405(c) X 50.73(a)(2)(iv) 73.71(b)

POWER 20.405(a)(1)(1) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c) 100%

LEVEL (10) 20.405(e)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vil) OTHER 20.405(a)(1)(lii) X 50.73(a)(2)(1) 50.73(a)(2)(vill)(A) (Specify in s ow 20.405(a)(1)(tv) 50.73(a)(2)(ll) 50.73(a,)(2)(vill)(B) 20.405(a)(1)(v) 50.73(a)(2)(ill) 50.73(a)(2)(x) NRC Form 366Aj LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

CURTIS A. CASTELL, SENIOR ENGINEER-LICENSING 414-221-2019 COMPLETE ONE LINE FOR EACH CGEPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER 0 P DS A EF FU X999 N SUPPLEMENTAL REPORT EXPECTFD (14) EXPECTED MONTH DAY YEAR YES SUBMISSION (If yes, complete EXPECTED SUBMIS$10N DATE). X No DATE (15) 5STRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On September 9, 1994 at about 1114 hours0.0129 days <br />0.309 hours <br />0.00184 weeks <br />4.23877e-4 months <br />, with both units at full power, a fuse in the Unit 2, B train, 4160V emergency bus 2A-06 metering and relaying circuit blew during modifications to Control Board C-02 for the installation of additional emergency diesel generators. The blown fuse caused a 2A-06 undervoltage signal to be generated. The undervoltage signal caused the normal power supply breaker for 2A-06 to open and deenergize the bus. Emergency Diesel Generator G-02 immediately started and reenergized the 2A-06 bus. One of the four station battery chargers (D-08) tripped off, as expected, during the momentary loss of power to the Unit 2, B train. D-08 was restored at 1129 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.295845e-4 months <br />. The DC buses for PBNP are shared by both units; therefore, this event affected both units.

The normal configuration of the other equipment that was affected was re-established. The blown fuse was replaced at about 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> and the normal configuration of the electrical distribution system was re-established at 1429 hours0.0165 days <br />0.397 hours <br />0.00236 weeks <br />5.437345e-4 months <br />. The blown fuse was the result of an inadequate procedure because the procedure did not contain the proper equipment isolation for the work being performed.

NRC FORM 366 (5 92) l

MRC FC'D 366A U.S. NUCLEAR REGJLATORY C(sellSSION APPROWED BY Ole 3150-0106 (5 92) EXPIRES 5/3t/95 ESTIMATED BURDEN PER RESPONSC TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

LICENSEE EVENT REPORT (LER) EE INFdMA E A[RECNDS NAGE BRAN TEXT CONTINUATION (MNB8 T/14), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK l

REDUCTION PROJECT (3150-0104), OFFICE OF )

MANAGFMENT AND PUDGET, WASHINGTON, DC 20503.  ;

FACILITY NAfE (1) DOCKET IR3eER (2) LER IR3eER (6? PAGE (3)

YEAR SEQUENTIAL REVISION POINT BEACH NUCLEAR PLANT 05000266 94 00 2 OF 6 '

-- 0 0 9 -- j TEXT (if more space is reouired. use additional copies of NRC Form 366AJ (17)

EVENT DESCRIPTION On September 9, 1994, at about 1114 hours0.0129 days <br />0.309 hours <br />0.00184 weeks <br />4.23877e-4 months <br />, with both units at full power, a fuse in the Unit 2, B train, 4160V emergency bus 2A-06 metering and relaying circuit blew during modifications to Control Board C-02 for the installation of additional emergency diesel generators. The blown fuse resulted in a 2A-06 undervoltage signal because the undervoltage protectihn relays are in that circdiY.* The unde 2Rioltac}e' signal caused the normal power supply breaker for 2A-06 to open and deenergize the bus.

Emergency Diesel Generator G-02 immediately started and reenergized the 2A-06 bus.

Other equipment affected by momentary loss of voltage on the 2A-06 bus included:

Battery Charger D-08 tripped.

2A-06 synchronization circuitry was lost due to the blown fuse and as a consequence of isolation of the circuitry for performance of the modification.

Letdown isolation occurred due to the loss of power to Letdown Isolation Valve RC-00427.

Non-safety related Motor Control Center B-21 Feeder Breaker 2B52-28C tripped due to the undervoltage.

The B train service water pumps were sequenced on due to the l undervoltage and restoration of voltage by the emergency diesel I generator. i Normal configuration of this equipment was re-established. The blown fuse was replaced at about 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> and the normal configuration of the i electrical distribution system was re-established at 1429 hours0.0165 days <br />0.397 hours <br />0.00236 weeks <br />5.437345e-4 months <br />.

Technical Specification 15.3.7.A.1.h states, "Four battery chargers  !

are operable with one charger carrying the DC loads on each main DC l distribution bus: D01, D02, D03, and D04." The battery charger D-08 is the normal battery charger for D02. Technical Specification 15.3.7.A.1.h does not provide a limiting condition of operation (LCO) action statement for operation with less than 4 battery chargers. Therefore, Technical Specification 15.3.0, 3-hour limiting condition for operation was entered as required for this situation. Battery Charger D-08 was restored at i 1129 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.295845e-4 months <br /> and the Technical Specification 15.3.0, 3-hour limiting I condition for operation, was exited. The DC buses for PBNP are shared by l both units; therefore, this LCO was applicable to both units. i NRC FORM 366A (5-92) I 1

NRC FCSM 366A U.S. NUCLEAR REGULATORY CupOllSSION APPROWED BY Ole No. 3150-0104 (5 92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE INFORMATION AND RECORDS MANAGEMENT BRANCH TEXT CONTINUATION (MN88 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001 AND TO THE PAPERWORK REDUCTION PROJECT (315IO-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY IIAE (1) DOCKET IE5WER (2) LER IRAeER (6? PAGE (3)

YEAR SEQUENTIAL REVISION POINT BEACH NUCLEAR PLANT 05000266 3 OF 6 94 -- 0 09 -- 00 TEXT (if more space is reauired, use additional copies of NRC Form 366A) (17)

This event resulted from work performed in the control room in Control Board C-02, in accordance with an installation work plan procedure, IWP 91-116*V1, "New EDG Project Pre-U2R20 Control Board Work." As part of this procedure, the 2A52-72, 2A-05/2A-06 bus tie breaker, control switch, and the associated synchronization switch, SS/2A52-72, were being removed.

The synchronization switch #

was removed and the associated wires were cut.

The maintenance eleiitricians noticed that one of th*8 cut wires was connected to another synchronization switch that was not part of the isolation boundary. The electricians notified the control operator that several synchronization switches may be disabled. The responsible engineer determined that synchronization switches for the following breakers were disabled:

A52-26 2A-01 Supply Breaker ,

A52-44 2A-01 to 2A-03 Bus Tie Breaker A52-45 2A-03 Supply Breaker A52-66 Emergency Diesel (G-02) Output Breaker to 1A-06 A52-67 Emergency Diesel (G-02) Output Breaker to 2A-06 A52-76 2A03 to 2A-05 Supply Breaker The responsible engineer initiated a procedure change to install a wire that would restore operability to the synchronization switches that had been unintentionally disabled. After the wire was installed, the l synchronization switches were checked again. It was determined that i the synchronization switch for the A52-67 breaker was still disabled.  !

Another procedure change was initiated by the responsible engineer to install two additional wires. During the preparation of the second wire which was not expected to be live, the wire inadvertently contacted a metal part of the control board, which caused a short circuit to ground in the 2A-06 metering and relaying circuitry. The short circuit caused a blown fuse in the metering and relaying circuitry, which subsequently caused the loss of voltage relays to actuate.

CAUSES . ,

4 A root cause of this event was an inadequate procedure. The procedure was inadequate because the installation work plan did not include proper isolation of the circuits being worked on or appropriate precautions for working on equipment that was not isolated. In addition, the isolations that were performed disabled more equipment than expected.

N2C FORM 366A (5-92)

NRC FC3M 366A U.S. NUCLEAR REEJLATOY CapellSSION APPROWE3 BY Ole uo. 3150-0104 (5 92) EXPIRES 5/31/95 ESilMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

LICENSEE EVENT REPORT (LER) E INFONf0h ANh^ REC DS NAGE BRAN TEXT CONTINUATION (MNBB 7714), U.S. NUCLEAR REGULATORY COFMISSION, WASHINGTON, DC 20555 0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY leAfE: (1) DOCKET IRABER (2) LER lasmER (6? PAGE (3) ,

l YEAR SEQUENTIAL REVISION POINT BEACH NUCLEAR PLANT 05000266 94 4 OF 6 I

__ g o g __ 00 YEXT (If more soace is reauired. use additional copies of NRC Form 366A) (17) l l

The cause of the inadequate procedure is considered to be inadequate  !

preparation and technical review of the procedure.

1 CORRECTIVE ACTIONS The immediate corrective actions included replacement of the blown  ;

fuse and restoration of the electrical distribution system to normal.  ;

Additionally. the procedure was reviewed and the appropriate isolations ~~ ~~

for the modification were established. l A root cause evaluation of this event is being performed to determine if any longer-term programmatic corrective actions are necessary.

COMPONENT AND SYSTEM DESCRIPTION I

The 2A-06 emergency bus provides power for Train B safety-related and i some non-safety-related equipment. The undervoltage protection and metering circuitry for the 2A-06 bus is used to monitor voltage on the i 2A-06 bus and provide initiation of the undervoltage protection which includes automatic disconnection of the bus from off-site power and I restoration of power by the emergency diesel generator. The undervoltage )

protection and metering circuitry is powered from potential transformers (PT) on the 2A-06 bus. The secondaries of these PT circuits are protected by 6 amp fuses, which is one of fuses that blew.

I Various loads automatically trip on undervoltage. The Unit 2, B train loads that tripped during this event were: Station Battery Charger D-08 and Motor Control Center B-21. Some safety-related equipment is automatically started by sequencing circuitry following restoration of power to the bus. Service Water Pumps P-032C, P-032D, and P-032E all started automatically by the sequencing circuitry. The loss of voltage to the Letdown Isclation Valve 2RC-00427 caused reactor coolant letdown isolation.

The IEEE Standard 803A-1983 component identifiers for this report are:

Bus BU Voltmeter EI Undervoltage Relay 27 Fuse FU I

N2C FORM 366A (5-92)

NRC FCOM 366A U.S. NUCLEAR REEJLATORY C01911SS10N APPROWED BY CBS NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESilMATE TO LICENSEE EVENT REPORT (LER) THE INFORMATION AND RECORDS MANAGEMENT BRANCH TEXT CONTINUATION (MNas 7714), u.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND RUDGET, WASHINGTON, DC 20503.

FACILITY NAfE (1) DOCKET IRAWER (2) LER IRAWER (6? PAGE (3)

YEAR SEQUENTIAL REVISION NWBER NWBER POINT BEACH NUCLEAR PLANT 05000266 5 OF 6 94 -- 0 0 9 -- 00 TEXT (If more space is reauired, use additional copies of NRC Form 366A) (17)

REPORTABILITY This Licensee Event Report is provided pursuant to the requirements of 10 CFR 50.73 (a) (2) (1) (B) , "Any operation or condition prohibited by the plant's Technical Specifications" and 10 CFR 50.73 (a) (2) (iv) , "Any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESF), including the Reactor Protection System (RPS)." A 4-hour notification to the NRC was made at 1230 hours0.0142 days <br />0.342 hours <br />0.00203 weeks <br />4.68015e-4 months <br /> in accordance with 10 CFR 50.72 (b) (2) (ii) , "Any event or condition that results in manual or automatic actuation of any Engineered Safety Feature (ESF), including the Reactor Protection System (RPS)."

SAFETY ASSESSMENT The undervoltage signal that was generated by the blown fuse caused the actuation of the undervoltage protection for 2A-06. The automatic disconnection from the normal power source, the restoration of power to the bus by Emergency Diesel Generator G-02, and sequencing of the service water pumps functioned properly.

The equipment that was affected by the momentary interruption of power to the Unit 2 emergency bus "B" train was restored in a short time with no adverse safety effects.

The D-06 station battery is normally continuously charged by the D-08 station battery charger. The loss of the D-08 battery charger caused the D-06 station battery to begin discharging. The station batteries are sized to carry the maximum expected DC loads for one hour. The battery charger for D-06 was restored in 15 minutes. Tables 8.2-1 and 8.2-2 of the PBNP FSAR show that the battery charger is restored after the injection phase of the Loss of Coolant Accident which is approximately one half-hour. Therefore, the DC battery system remained operable during this event.

SIMILAR OCCURRENCES:

l The following Licensee Event Reports describe the inadvertent actuation of an Engineered Safety Feature:

Unit 1 or common LER 91-006 Inadvertent Start of Emergency Diesel Generator LER 92-003 Inadvertent Start of Emergency Diesel Generator Due to Personnel Error NRC FORM 366A (5-92)

.< o NRC FCCM 366A U.S. IRJCLEAR REGULATORY CGet!SSIC APPROWED BY G W 110. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH

, THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE INFORMATION AND RECORDS MANAGEMENT BRANCH i TEXT CONTINUATION (MNB8 7714), U.S. NUCLEAR REGULATORY COMMISSION, I WASHINGTON, DC 20555-0001 AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY MAIE- (1) DOCKET IRMBER (2) LER IRBSER (6? PAGE (3)

YEAR SEQUENTIAL REVISION NWBER NWBER POINT BEACH NUCLEAR PLANT 05000266 6 OF 6 94 __ 9 99 __ 00 TEXT (If more space is reautred, use additional cooies of WRC Form 366A) (IT)

LER 93-007 Inadvertent Emergency Diesel Start and Loss of a Station Battery Charger Unit 2 LER 84-005 Inadvertent Start of Emergency Diesel Generator LER 84-006 Inadvertent Start of Emergency Diesel Generator LER 84-007 Inadvertent Start of Emergency Diesel Generator I ER 92-007 Inadvertent ESF Actuation as a Result of Improper Surveillance Testing NRC FORM 366A (5-92)