ML20006E157

LER 90-001-00:on 900117,unplanned Actuation of ESF Reactor Bldg Standby Ventilation Sys B Occurred,Causing Interlocking Relays in Control Circuits to Deenergize.Caused by Transient Voltage Dip.Procedures Re Bus Loads modified.W/900209 Ltr

ML20006E157
Person / Time
Site:	Shoreham File:Long Island Lighting Company icon.png
Issue date:	02/09/1990
From:	Notaro J, Schnaars G LONG ISLAND LIGHTING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-001, LER-90-1, PM-90-029, PM-90-29, NUDOCS 9002220204
Download: ML20006E157 (6)

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[#4,g LONG 18 LAND LIGHTING COMPANY SHOREHAM NUCLEAR POWER STATION

• P.O. BOX 628

• WADING RIVER, NEW YORK 11792-

. TEL. (516) 929-8300

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February 9, 1990 PM 90-029 l-

-U.S.. Nuclear Regulatory Commission Document' Control-Desk Washington, D.C. 20555

Dear Sir:

l LIn accordance with 10CFR50.73, enclosed is Shoreham Nuclear Power i

Station's-Licensee. Event Report, LER 90-001.

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Sincerely yours,- j i

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~ Jack A.- Notfro Plant Manager

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Enclosure

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William T.' Russell,--Regional Administrator i Institute of Nuclear Power Operations, Records Center -

American Nuclear Insurers  ;

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Shoreham Nuclear power Station Unit 1 0 l5l0l0l0l3 l2l2 i lopl0 l4 Unplanned Actuation of Reactor Building Standby Ventilation System During Test of T--~

Tw e. esA nwne EVENT DAf t 151 LEft NUMSER to) REPORT DATE 17) OTHER F ACILITitS INVO./ED 18)

MONTH DAY YEAR YtAR I'gG 7fy MONTH DAY YEAR ' ACILIT v N AMES DOCnti NUMSERI$)

015lcl0l0l l l nI1 1 17 o n o In nIn h n in 01 2 0 l9 9 l0 0 [5;0 l0 1 0l l l THIS REPORT IS SUDMITTED PURSUANT TO THE RkOUIREMENTS OF 10 CFR l. (Checa one er mere e,,ne ferie .nps (til OPE R ATING . g MODE m 20 402thi to 40 sten to.73telt2Hal 7371N y _

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NAME TELEPHONE NUMSER ARE A COJE '

George D. Schnaars, Operational Compliance Engineer 5l1p 9l2 ; 9; i8 ;3j0j0 I l COMPLETE ONE LINE FOR E ACH COMPONENT F AILURE DESCRISED IN THIS REPORT (136 MA AC. R PORfAB E R PORTA E CAUSE SYSTEM COMPONENT o pn CAUSE SY STE M COMPONENT s M A% AC- pp

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SUPPLEMENTAL REPORT EXPECTED ties MONT k. DAY YEAR SUOMi$$ ION - r Yt$ to, pas eempie,e EXPECTED SUOMISSION DA TEI NO l l l A 1x ACT m,,,a ,e ,*= .me, , e e.,e.-e,*,, ,,,,,,,, ,,,e ,me ,, ,are. ,,,,s., im On January 17, 1990 at 0457~ hours, an unplanned actuation of the Engineered Safety Feature Reactor Building Standby Ventilation System (RBSVS) "B" occurred, This actuation occurred during the performance of a surveillance procedure that tested the ability of Emergency Bus 102 to automatically " fast transfer" from its normal -

to its alternate power supply. The voltage dip during the fast transfer was sufficient to deenergize interlocking relays in the control circuits for 1T46*A0V-35B or 37B (Reactor Building Normal Ventilation Supply and Exhaust Valves). Either one of the A0Vs going closed caused the actuation of RBSVS "B". Testing was stopped and plant management was notified of the event. The event was reportable under 10CFR50.72(b)(2)(ii) and the NRC was notified at

( 0652 hours0.00755 days <br />0.181 hours <br />0.00108 weeks <br />2.48086e-4 months <br />. Corrective actions include changing the surveillance

/ test' procedure to require that if a minimum emergency bus load cannot be achieved, then RBSVS is to be manually initiated.

• Reactor Defueled N;.C form 366 (6-894

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- PLAN't_AED_SYSIEM_IDEHilEICAIl0H General Electric - Boiling Water Reactor Energy Industry Identif.ication System (EIIS) codes are identified j- in-the_ text as [xx].

lIDEBIIFICAIIOfLRE_THE EVENT ,

Unplanned actuation of the Engineered Safety Feature Reactor Building Standby Ventilation System (RBSYS)[BH] "B" during a surveillance test. .

Event Date: 01/17/30

. Repo'rt Date: 02/09/90 DONDITIQES PRIOB._ID THE. EVENT Reactor.Defueled - All fuel assemblies stored in the Spent Fuel Pool Mode-Switch - Shutdown RPV Pressure.= 0 psig RPV-Temperature = 85 Degrees F

! . POWER LEVEL - 0 DEliCBIETIQU_QE._IBE_EVIHI On January 17, 1990 Control-Room Operators were performing surveillance test procedure SP 24.301.01,_ Station Power Supply Transfer Test. This test is performed in order to satisfy Technical

- Specifications 4.8.1.1'.1 b and 4.8.1.2. 'The operators were performing' step'58 of this procedure. This step verifies the-operability of the-fast transfer capability of the Emergency Bus 102 switchgear.- At 0457 hours0.00529 days <br />0.127 hours <br />7.556217e-4 weeks <br />1.738885e-4 months <br />, the operators manually tripped the l normal. supply breaker to bus 102 and then verified-that the reserve supply breaker _to~ bus 102 closed automatically as required by the fast transfer scheme. However, during the peri'ormance of this step - <

lan unplanned actuation of the Engineered Safety Feature RBSVG "B" occurred.

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Testing was then stopped and RBSVS "A" and the A and B trains of Control Rnom Air Conditioning were manually initiated. The

. unplanned actuation of an Engineered Safety Feature is reportable per 10CFR50.72(b)(2)(ii). Plant management personnel were notified of the event and the NRC was notified at 0652 hours0.00755 days <br />0.181 hours <br />0.00108 weeks <br />2.48086e-4 months <br />.

CAUSE_DE_IBE EVENI The unplanned actuation of RBSYS "B" was caused by the transient voltage dip on bus 102 which occurred during the fast transfer test of the bus 102 switchgear. Specifically, the voltage dip allowed an ,

interlocking relay to drop out in the control circuit for 1T46*A0V-35B or 37B (Reactor Building Normal Ventilation Supply-and Exhaust Valves). These relays have seal-in contacts that open on relay dropout and prevent them from picking up again after normal voltage is restored. When these relays deenergize they allow their i associated AOV to close (1T46*AOV-35B or 37B) and either AOV closing initiated RBSYS "B".

The fast transfer of an emergency bus from its normal to its alternate power supply in designed to be completed within 10 cycles to prevent-running motors from dropping out of step. Testing determined that this fast transfer is completed in 4.5 to 6 cycles.

This testing was performed while the emergency buses were supplying

. loads consistant with the current plant operating condition.

Additional testing determined that the critical factor in this event is that the magnitude of the voltage dip during the fast transfer is dependent upon the amount of rotating equipment being powered by the bus. For example, during a bus deenergization, the length of I time for the bus voltage to drop low enough for the interlocking' l relays to deenergize was 1 cycle with a bus load of 20 amps. The )

time was 21.5 cycles when additional motors were run to increase the bus load to 140 amps.

Since the emergency bus switchgear complete the fast transfers within'the design requirement, the occurrence of the interlocking relays dropping out (and the RBSVS initiation) is dependent upon the bus-load. The inductive loads being supplied by the bus help E maintain the residual bus voltage during the fast transfer. Without

-sufficient inductive load, the bus voltage decays to a point where the interlocking relays drop out.

The occurrence of an RBSYS initiation during an emergency bus fast  ;

transfer test had never been experienced prior to this event. This I is because the previous fast transfer tests were performed when the emergency bus loads were higher than present.

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TEXT CONTINUATION 1%"n'"48,"rl*MN!'fe5M'%d'Cn, PAPERWO K RE TION 6 1 O IC '

OF MANAQf MENT AND DVDGET,WASHINGTCE, DC 20603. '

PACILITY . FAME til DOCKET UMSER (2) LER NUMSER (St PAGE (31

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Shoreham Nuclear power Station Unit 1 o.l6jol0l0l3l2l2 9 l0 -

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010 0l4 oF 0 l4 Tur a = w w =ac r assaim ANALYSIS _OE_IBE EVENT >

. There was no safety significance to this event. The plant is shutdown and has been defueled since August of 1989. The operators took the proper corrective actions in response to the RBSYS initiation.

Plant. Systems, including the RBSYS and the Bus 102 switchgear,-

performed as designed.

CORREGIlY.E_AGIl0NS

1. Station Procedure 24.301.01, Station Power Supply Transfer Test, has been modified to require operators to start additional rotating equipment so that the emergency bus loads are above a specified minimum load. If this minimum load '

cannot be achieved then the applicable train of RBSVS is to be manually initiated prior to the fast transfer-test of the emergency bus switchgear.

2. Station Procedure 23.309.01, 4160 Emergency Bus Distribution, '

has been changed by adding precautions and instructions to cover the event where the emergency bus fast transfer occurs and RBSVS actuates. i ADDITIONAL _lHEQEMAIl0B

a. Manufacturer and_model_ number __of_ failed _ comp _onent_Lal N/h

b. LEB_ numbers _of_ previous _similar_eyents None i

1 I

I 1

l NRC F.rm 308A (649) -