ML20029D767

LER 94-002-00:on 940404,performance of Surveillance Check Power Distibution Breaker Alignment & Power Availability Verification Resulted in Entry Into LCO 3.0.3.Caused by Procedure Error.Procedures revised.W/940503 Ltr

ML20029D767
Person / Time
Site:	Crystal River
Issue date:	05/03/1994
From:	Boldt G, Ken Wilson FLORIDA POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
3F0594-04, 3F594-4, LER-94-002, LER-94-2, NUDOCS 9405100057
Download: ML20029D767 (6)

Text

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3 Florida 1 Power CORPORATION 1

l Crystal Rever Urut 3 l Docket No.60-302 l

hd5h(db U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555

Subject:

Licensee Event Report (LER) 94-002-00

Dear Sir:

Attached is Licensee Event Report (LER) 94-002-00 which is submitted in accordance with 10 CFR 50.73.

Sincerely,

?

G.L. B ldt Vice President Nuclear Production GLB/JAF:rp attachment xc: Regional Administrator, Region II ,

NRR Project Manager '

Senior Resident Inspector l 1

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100U13 CRYSTAL RIVER ENERGY COMPLEX: 167so W. Power Line Street

• Crystal Rivee, Florida 34428-6708

• 1904) 796-6406 '

A fkmde Ivogren Company  ? s7 L' I

9405100057 940503 PDR S

ADOCK 05000302 l PDR

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NRC [C?tM 388 U.S. NCLEAR NOG 1ATORY COM MISSION APfEDVED OMB NO.3160-0104

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OFFICE OF MANAGEMENT AND BUDGET, WASHI TON DC 2u603.

F ACCLITY NAME (1) DOCKET NUMBER (2) P AGE (3)

CRYSTAL RIVER UNIT 3 (CR-3) ol5lo]olol310l2 1 lOFl 0 l 5 TITLE (4)

Perforrnance of Surveillance to Check Power Distribution Breaker Alignrnent and Power Availability Verification Results in Entry into LCO 3.o.3 l EVENT DATE (6) LER NUMHER (5) REPOH1 DATE (7) OTHER FAC6LiTIES INVOLVED (8)

FACILrrY NAMES SEQUENTIAL REVISION DOCKET NUMBEFMS)

MONTH DAY YEAR YEAR NUMDER NUMBER MONTH DAY YEAR N/A 0l 6l 0l ol ol l l ol4 ol4 o 4 ol4 -

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o[o ols 0l3 ol4 wA olsjalolol l l 4AT Tins KFORT IS SUBMfTTED PURSUANT TO THE KOUIREMENTS OF to CFR 6: icurex ofvr on adonE OF THE FOf.Lowwcil O l) 20.402(b) 20.405(c) 60.73(aX2)0v) 73.71(b)

R 20.405(aX1)0) 60.36(cXI) 60.73(aX2)(v) _

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50.73(aX2Xvil) _

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LICENSEE CONT ACT FOR THis LER (12)

NAME TELEPHONE NUMBER AREA CODE K. R. Wilson, Managor, Nuclear Licensing ol0l4 6l 6 l 3 l- l 4l 5 l 4 l 0 COMPLETE ONE LINE FOR EACH COMPONENT FAJLURE IN Ties REPORT (13)

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CAUSE SYST E M COMPONENT MANUFAC- REPORTABLE CAUSE SYSTEM COMPONENT MANUFAC. REPORTABLE TURER TO NPRDS TURER TO NPRDS I l l \ l l l l l l l l l 1 I I l l l I I I I I I l l l SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONT H DAY YEAR SUBMISSION

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On April 4,1994, Florida Power Corporation's Crystal River Unit 3 was in MODE 1 (POWER OPERATION), operating at 76% reactor power. During performance of a pcwer availability verification surveillance, at 2145, the voltage on Engineered Safeguards (ES) 4160 Volt Alternating Current (VAC) bus A and ES 4160 VAC bus B was observed to be 4350 VAC. This value exceeded the surveillance procedure limit of 4300 VAC. The shift supervisor entered Improved Technical Specification Limiting Condition for Operation (LCO) 3.0.3. The System Dispatcher was requested to reduce the grid voltage affecting the 230 Kilovolt (KV) switchyard, which feeds the 4160 VAC ES busses via the Offsite Power and the Back-Up ES transformers.

By 2210, the ES 4160 VAC A and B bus voltages were observed to be less than 4300 VAC. No reactor shutdown was initiated since the elevated voltage condition existed for less than one hour. During this event, no loss of function occurred and no measurable damage or degradation was experienced by any associated system 1 or component. The cause of this event was the overly conservative upper voltage limits specified in the surveillance procedure. Corrective actions include the performance of no-load voltage drop calculations, revision of applicable procedures to reflect the allowable bus voltage limits, and an evaluation of an upper bus voltage alarm installation.

NRC Form 3e6 (6-89)

NED FC3M 3e6A U.S. NCLEAH KEOCIAT C3Y COMMtsSION fEPEDVED OMB NO. 3150-0104

. EXPIRES 6/31/96 I

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. OFFICE OF MANAGEMENT AND BUDGER WASHIN TON DC 20503.

F Acu TTY NAME (1) DOOLET NUMBLH (2) LER HUMBER (6) PAGE (3)

SEQUENTIAL REVS 8aON CRYSTAL RIVER UNIT 3 (CR-3) 0l 5l 0l 0l 0l 3l 0l 2 9l4 -

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l EVENT DESCRIPTION: )

On April 4,1994, Florida Power Corporation's (FPC) Crystal River Unit 3 (CR-3) was I in MODE 1 (POWER OPERATION), operating at 76% reactor power. Operators were in the process of performing a power distribution breaker alignment and power availability ,

verification surveillance.

At 2145 on April 4,1994, during the performance of the surveillance, the voltage j on Engineered Safeguards (ES) 4160 Volt Alternating Current (VAC) bus A [EB] and ES 4160 VAC bus B was observed to be approximately 4350 VAC. This value exceeded the surveillance procedure limit of 4300 VAC. The shif t supervisor determined that ,

improved Technical Specification (ITS) Limiting Condition for Operation (LCO) 3.8.9 l condition E applied. This condition is defined as "Two trains with inoperable I distribution subsystems that result in a loss of function". The required action for this condition is immediate entry into LC0 3.0.3. The Energy Control Center (ECC) System Dispatcher was immediately notified and requested to reduce the grid voltage affecting the 230 Kilovolt (KV) switchyard.

The source of Offsite Power to the CR-3 4160 VAC ES busses is the 230 KV switchyard via the Offsite Power Transformer (OPT) and the Back-Up ES Transformer (BEST) (see Attachment - AC DISTRIBUTION SYSTEM - PARTIAL BLOCK DIAGRAM).

4 At 2208, the 230 KV switchyard grid voltage was reduced resulting in an ES 4160 VAC "B" bus voltage of less than 4300 VAC. At that time, LC0 3.0.3 was exited and condition A of LC0 3.8.9 applied. The Required Action for Condition A is to restore the power distribution system parameters to within boundaries within eight hours.

t At 2210, the ES 4160 VAC A bus voltage was observed to be less than 4300 VAC. At that time, LC0 3.8.9 was exited. No reactor shutdown was initiated since the elevated voltage condition existed for less than one hour. This report is submitted in accordance with 10CFR50.73(a)(2)(i)(B).

EVENT EVALUATION I

Previous events involving switchyard grid voltages focused on reduced voltage at the associated equipment and ultimately resulted in the installation of the OPT and the BEST to improve the supplied voltage to the equipment during accident conditions.

NRC Form 366A (6-69)

l NG Forta 366A U.S. NCLEAR GOULATC3Y COMMISSION APPcifED OMD NO. 3160-0 #04 EXPIGS 6/3t/96

. LICENSEE EVENT REPORT (LER) (sTgT,rDjugegP E gg TEXT CONTINUATION ggn,EOyggeUgggggg, Cgs 28t'!P #"s8 = ^CfanenT"th omCE LJ mAANAGEMENT AND BUDGET, WASHIN TON DC 20503.

DOC *IT NUMBEH(2) LER NUMBER (6) PAGE (3)

F ACQJTY NAME (1)

SEQUENTIAL REvi8 SON YEAR NUMBER .. NUMBER CRYSTAL RIVER UNIT 3 (CR-3) 0l 5l 0l 0l 0l 3l 0l 2 9l4 -

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0l0 0 l 3 lOFl 0 l 5 TEXT g more spece e ,.ened use e.Amenes 4AC Form 3 sad e (9 7)

I lhe potential effects of this evolution involve induced equipment stress due to  !

i overvoltage and fault currents present at the equipment in levels greater than those utilized in existing calculations. These calculations typically describe specific accident conditions and do not evaluate normal or reduced bus loading conditions.

The Enhanced Design Basis Document (EDBD) contains the design requirements for piant equipment, based upon the original plant design specifications. Typically, large motors and switchgear associated with the 4160 VAC ES busses were specified for 4000 VAC. Industry standards establish a +/- 10% tolerance on the base value voltage, which translates to an allowable operating voltage range of 3600 to 4400 VAC. Based upon the current 4160 VAC ES bus undervoltage protective relaying, the bus voltage cannot drop below 3970 VAC or actuation of the Second Level Undervoltage Relaying (SLUR) system will occur. ITS Lases address a maximum steady state voltage (industry standard) of 4400 VAC.

The FPC CR-3/0thers Interface Matrix, provides a fr rmal interface ayeement between Nuclear Operations and other FPC departments. Tt.as document specifies that the ECC has the lead responsibility and will be the source of voltage measurements and documentation for the 230 KV switchyard. The ECC has been provided with switchyard operating limits based upon engineering calculations which document acceptable switchyard voltages for CR-3 accident scenarios. The 230 KV switchyard was operating within the established band at the time of the incident.

Since there have been no prior overvoltage events, a conservative administrative control of the 4160 VAC ES voltage has provided sufficient protection to assure proper voltage is availaSle to plant equipment. The associated surveillance procedure currently estatlishes an administrative maximum of 4300 VAC on the 4160 VAC ES busses.

Engineering personnel performed a voltage drop calculation and determined that a maximum 4160 VAC ES bus voltage of 4406 VAC would result from a 230 KV switchyard upper limit voltage r,f 243.6 KV in a non-load condition. This calculation assumed no losses anywhere from the 230 KV switchyard to the transformer secondary.

Maintaining the 230 KV switchyard voltage within established limits will provide 4160 VAC ES bus levels within the acceptance levels of the ITS and the EDBD.

The effects of overvoltage on components are cumulative and are based on cyclical loading. The determination of these effects presents substantial difficulty when considering the failure of a particular component, based solely on overvoltage.

Weakened insulation, resulting from a plurality of overvoltage stress events, contributes to increased risk of ground faults, bus flashover and motor failures.

The maximum voltage measured in this excursion was 4350 VAC. This value exceeded the administrative limit of 4300 VAC, but remained less than the ITS maximum and industry standard of 4400 VAC. Since CR-3 has not experienced any prior 4160 ES bus overvoltage events, and the current report addresses exceeding an NC Form 366A (6-49)

l NHC FC3M 3esA U S. NUCLEN4 REGULATCRY COMMISSION APPRDVED OMB NO. 3150-0104 EXPIRIS 5/31/96

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A O L UC N PfKI 10'4). 1 OFFICE OF MANAGEMENT AND BUDGET, Wast N TON DC 20603. l FACIUTY NAME (1) DOCKET NUMBER (2) LEH NUMDEH (6) PAGE (3) bEQUENTn. -

HEVISON YEAR NUMBER NUMBER I CRYSTAL RIVER UNIT 3 (CR-3) 0l 5l 0l 0l 0l 3l 0l 2 9l4 -

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0l0 0 l 4 lOFl 0 l 5 TEXT on mwe wue o renwed vu e munne unc Fore 3064 e (17) administrative limit, it can be concluded that no loss of function occurred and no measurable damage or degradation was experienced by any associated system or component.

CAUSE The primary cause of this event was that the 4160 VAC bus voltage upper limits specified in the surveillance procedure were overly conservative. A contributing i factor was the lack of an appropriate bus voltage limit alarm or operator indication that would provide a warning that a plant limit was being approached.

CORRECTIVE ACTION Corrective actions for this event include the following:

1. The System Dispatcher at the ECC was contacted and the switchyard voltage was reduced to provide bus voltage within specification as determined by the CR-3 main control control board metering.

2. The 230 KV switchyard voltage was cycled in order to determine the useable switchyard voltage range without exceeding the 4160 VAC ES bus maximum voltages.

3. Engineering personnel performed no-load voltage drop calculations to determine the maximum voltage possible on the ES 4160 VAC busses.  !

4. Plant procedures, as required, will be revised to reflect the allowable l bus limits. I

5. An evaluation of an upper bus voltage alarm installation will be performed.

PREVIOUS SIMILAR EVENTS There have been no previous events in which high switchyard voltage resulted in a bus overvoltage condition.

NEO Form 366A (6-89)

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NRC'F Cut 366A U.S. Ntt :LE# REOta ATCM COMMISSION f#PRDVED OMB NO. 3160-0104 (5-c2)

EXPIRES 6/31le6

. , LICENSEE EVENT REPORT (LER) ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS TEXT CONTINUATION '"$$5Ifr"EifA C lM E TO TWRF S AND REPORTS M ANAGEMENT BRANCH MNBB 7714), U 8. NUCLEAR REGULATORY COMMISSION. WASHING ON. DC 20556-0001, l AND TO THE PAPE RWOHK REDUCTION PROJECT (3160-0104), 1 Of FICE OF MANAGEMENT AND BUDGET, WASHINGTON DC 20603. '

FA01 TTY NAME (1) DOCKET NUMBER (2) LER NUMDER to) PAGE (3) stuutNTW. REvifuoN YEAR NW8ER -

WW8ER CRYSTAL RIVER UNIT 3 (CR-3) 0l 5l 0l 0l 0l 3l 0l 2 9l4 -

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ATTACHMENT AC DISTRIBUTION SYSTEM - PARTIAL BLOCK DIAGRAM 4902 4Q00 Offette Power Transformer jg Deookridoe i Line' 230 KILOVOLT 1692 1591 1690 SwlTCHYAAD CR- 3 CR-3 _-

plgng Generator Start-Up Back-up ES Transformer Transformer V

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T r a ns f or mer Id Breaker Closed 3207[] 320$ [] 3211 . 3200 [] 3206 H [] 3212 4160 VAC Es eue A 4160 VAC ES Bue f

/A EGDG B EGOG s NC Form 366A (6-89)