ML18058A381

LER 92-024-00:on 920327,inadvertent Opening of Station Power Breaker Resulting in ESF Actuation & Interruption of Shutdown Cooling.Caused by Supervisor Allowing Work to Proceed on C Bus.Event Discussed w/maint.W/920427 Ltr

ML18058A381
Person / Time
Site:	Palisades
Issue date:	04/27/1992
From:	Hillman C, Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-024, LER-92-24, NUDOCS 9205010265
Download: ML18058A381 (7)

Text

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consumers

• Power *

• o. G B* Slade

. General Manager POWERlNli lllllCHlliAN-S PROlillESS .

• Palisades Nuclear Plant:

• 27780 .Blue Star Meinc>ria~. Highway. Covert. Ml 49043 April 27, 1992

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Nuclear. Regulatory Commission*

'Document Control Desk *.  :*.

WashiDgton, .DC 20~55 * *.'

LICENSE *DPR"'20 "'_. Oi>A~rsADEs !>.LANT*~

• DOC.KET .50-255 . * * ,.

. L.ICENSEE EVENT REPORT 92'-024 ~-- INADVERTENT' OPENING OF* THE STATiON POWER* ..

• BREAKER. RESULTING IN AN ESF ACTUATION .AND iNT_ERRUPTION OF SHUTDOWN COOLING *. **.:. -

• f.* *.

Li,~en'see Event Report. ( LER) 92--024 is. attached.<*...Thi's event* is* rep.ortabl e *i rf..-. *. *. *. :~...* .*

• . -accordanc.e w*ith 10CFR50. 73 ( a)(2H iv)' as an* eveh(that -res~lted, in ari 'automa't i c *. * .

~ctuation'*of an engineered- safety *feature. *: * * * * * *

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NRC: Res'ident Inspector *Pali sades* \,

Attachment" 9205'010265 920427 PDR ADOCK 05000255 S PDR . A CM5 ENERGY COMPANY

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I :1 I On March 27~ 1992, at 2226 ho~rs, with the plant in cold shutdown, s~utdo~n cooling flow ~as interrupted ~hen ~he 'C' bus ~u,plyirig power to t~e operating

• shutdown cooling pump was de-energized as a resu t of reaker testing on the station powet breaker. Und~rvoltage on the 'C~ bus resulted in both diesel generators starting. The interruption of shutdown coolinJ lasted for .. _ .

a~proximately four minutes. Durin~ the shtitdown cooling luw ihterrµption, t e core exit temperature increase approximately stx degrees fahrenheit.

• 1wo root causes for this event f:!X*ist. . The Shift Supervisor allowed work to proceed on the 'C' bus despite the ~ufdance provided. to him b{ the Operations Scheduler, and contrary to information provided in the ~enera operating procedures. In addition, *work proteeded beyond that whic~ was .authorized by the* Shi ft Sup.ervi sor. , * . * . ** .

Corrective action for this event included-immediate action to discuss the event with all mainten~nce and operations work shifts emphasizing the problems associated with deviating from procedures and approved work scope. Further corrective action includes evaluating the use of a more formal communications policy within the maintenance departments, training electrical repairman and supervisors on the breaker testing requirements .stated in administrative grocedures~ defining expectations for th~ responsibility of operating * .

reakers, relocating the taution placards to a more visible location within the breaker cubicle, evaluate modifyin~ the start-up and station safe~uards breakers to prevent operation in the -" est pas it ion, and modifying t e .

• 11 general operating prqcedure '

as necessary.

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- LICENSEE -NT AEP()AT ILIA> TEXT CONTINUA-N Palisades Plant T1llT ,. _ . . . ._._. __ _ _ltl/C ,,..,.._ ...." 1111

• EVENT DESCRIPTION On March.27, 1992, at 2226 hours0.0258 days <br />0.618 hours <br />0.00368 weeks <br />8.46993e-4 months <br />, with the plant in cold ~hutdown, shutdown cooling was temporari.ly interrupted when the 'C' bus su~plying power to the

-0perating shutdown cooling pump [B~;P] was de-energized as a result ~f breaker testing on the station power breaker [FK;BKR]. Undervoltage on the

• c bus 1 1 resulted in both diesel- generators starting. The interruption of shutdown*

~ooling lasted for approximately four minutes. During the interrupti~n of shutdown. tooling, the pr.iniary coolant system (PCS) [AB] temperature increased.

S°F; based on one ~ore exit thermocouple, 7°F, based.on ariothet core exit thermocouple, and 1°F based on the s*hutdown cooling heat exchanger in let temperature t~ermocouple .. The .initial PCS temperature wa~ approximately 82°F.

This event is reportable to the NRC in a~co~dance with 10CFR50~73la)(~)(iv) as an ~vent that resulted *in an automatic actuation of an engineered safety .

feature (diesel generators).

CAUSE OF THE EVENT Two root causes for th{s event ~xist~:The Shift Supervisor.allowed work to proceed on the 'C' bus despite the guidance provided to *him by the Operations

• Scheduler, and contrary to information provided in the general' operating.

procedures.. In aqdition*, work pro~eeded beyond that which was authorized by the Shift Supervisor.*. * *

• This event does not involve the failure of any equi pm~nt i_mportant to safety.

ANALYSIS OF THE EVENT The P~lisades ~afety related Electr~cal Distribution System consist~ of two 2400V electrical buses which supply power to numerous loads in the plant, including the low pressure safety injection (LPSI) pumps which ~erve as the .

. Shutdown Cooling pumps. Each of these buses are normally powered by one of the following incciming breakers:* _:

• Start~up Power.

• Station Safeguards Power

• Diesel.Power These breakers have three possible positions wfthin their cubicles~ 1.

• • Disconnect position - is the position in which the control power is disconnect~d from the breaker, the interlocks are not connected, and the

.breaker cannot be connected to a load. 2. Test position - in: this position

.control power* is conn~cted to the breaker, the interlocks are connected, and the breaker cannot be connected to i load. 3. Connect position - in which the control power is connected to the breaker, the interlocks are connected, and the breaker can be connected to a load.

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.It .is normal plant policy during shutdown cooling operations to maintain two independent power sources available to each of the two safety related buses,

'C' and 'D'. This is controlled via the operating proced~res. Also, the Operations Scheduling Supervisor communicates these requirements to the operating crews via the following:

• A Shutdown Cooling ~quipment Ava*lability list, and

• A Shutdown Cooling Risk Assessment list which augments th* equi~ment

• availability list.* *

• This infor~atiori is tontained in general operating procedure (GOP) 14, "Shutdown Cooling Operations;" Step 6.5.a and band is the ~ethod used to control equipment status with respect to Shutdown Risk Management iss~es.

Earlier in the 1992 Refueling Outage, the station safeguards supply breaker charging motor failed to stop when requ.ired. A spare breaker was placed in the breaker cubicle on the 'C.' bus and maintenance was performed on the normal

• breaker. On the "day~ shift of March 27~ 1992, the spare breaker was.replaced with the.normal breaker and subsequent testing indicated that the problem still existed with the normal breaker. As a result, the normal breaker was again .removed from the cubicle and the spare was put back in the 'C' bus. .

• This work was performed with all loads, including the operating shutdown cooling pump P-67A, po~er~d from 'D' bus. At. the end of the "day" shift on* .

March 27, 1992,. the safety related electrical distribution system was aligned with 'C' bus supplying all loads .. At that time, *'C' bus'. was powered from the.

itation safeguards power supply breaker;_ The 'D'. bu~ was not supplying loads because* testing on the 'D' bus was scheduled for *the _foll owing day.

Early ~n t~e "afternoon" shift of March 27, 199~, electrical mai~tenance

• finished work on the normai station safeguards breaker charging*motor. The

• breaker was successfully tested five times outside of the.cubicle. Based on the result~ of the succe~sf~l tests, the electrical repairman in charge

~equested that the spare ~reaker be removed from the cubicle and the normal breaker installed. The *shift Supervisor discussed the request with 'the Shift

• Enginee~ and dete~mined that the work could b~ compl~ted ~ith mini~um risk.

The Shift Supervisor and Shift Engineer discussed two options to complete the

• job: * * .*

• Transfer all loads to*'D' bus, or;

• Trarisfer. 'C~ bus supply power from the station safeguards breaker to the start-up breaker (the alternate power supply).

The Shift Superv*isor elected to swap the 'C' bus supply from the station

. safeguards ~upply breaker to the start-up supply breaker. This transfer ~as successfully crimpleted. However, the electrical configuration did not comply ~ .

with* the Shutdown Cooling Equipment Availability sheets provided to the

Control Room by the Operations Scheduling Supervisor per General Operating Procedures (GOP) 14; "Shutdown Cooling Operations."

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~** ...._...... . **o* JI Palisades Plant T'DT_1*~-* .... -~~_,..,.J!lllll'.~1171 The Shift Supervisor directed an Auxiliary Operator (AO).remove the 'spare' station safeguards supply.breaker from 'C' bus and replace it with the*normal breaker as the electrical repair-worker had requested; The Shift Supervisor directed the AO to leave.the normal breaker in the "conned" position with the chargirig.motor fuses installed. The control power fuses were not installed.

This would ~llow racking in the breaker but not allow breaker operation. The Shift Supervisor did not give permission to either the AO or the. electrical

.repair-worker*to do anything else with the breaker in the cubicle other than leave* it in the. "connect" position with charging motor fuses installed. The

• AO completed the work as di.rected by the Shift Supervisor .. During this time P-67A, _the operating shutdown ~o~ling pump, was powered from the 'C' bus,* ,

which in turn was supplied from the start-up power supply breaker.

• . Th~ Electri~al Mai~tenance Supervisor requested the electrical repair-worker and the AO to place the brea~er in the "test" position and to close the .

• breaker to test the charging motor. The Electrical Maintenance Supervisor

• wanted to ensure the charg,ing motor functioned properly and, therefore,. felt

• this action was w~rranted~

• Neither the AO or the electriccil repair-worker questioned the req~est based on their understanding of the approved ~ork scope.: .Caution signs* existed fn twtr areas. One on. the inside .of the start-:UP and stati oii safeguards breaker cu bi cl es to warri operators not to close the *

. breakers whjle the b~e~ker was in the "test"* position. These signs ara*poorly * *'

Jocated and are not rea~ily visib_le .. A second_ tautior:i sign js.on the outside . **,.*

of the breaker panel stating testing shall be done per Administrative Procedure 4w02. Wheri ~he breaker ~as .closed while in the "test" position, th~,

start-up power supply breaker opened and 'C' bus de-energized. The relay logic fo~ the start-up breakers and the Station* safeguards breakers on 'C' and

'D' bus is such that the.-bus. cannot be supplied from two power sources... Since the operating ~hutdown cooling pump was supplied from 'C' bus,* shutdown cooling was iriterrupted. * * .

RESPONSE_ TO EVENT Both di eselS gene.raters started* as a result of 1ow voltage on 'C' ,bus. The 1-1 diesel generator *did not synchronize to 'C' bus because the control power.

fuses were r:ibt installed iri the station safeguards breaker. This allowed the

• diesel generator logic to respond as. if.the station safeguards breaker was c.losed .to the bus. The .'D' bus was already powered from station* safeguards, the~efore, the 1-2 diesel generate~ did not synchronize to the bus~ The operator's responded using the Off-Normal* Operating Procedure (ONP} 17, "Loss

• of Shutdown* Cooling," and.manually latched the synchroniiing relay, allowing the. 1-1 diesel generator to synchronize to 'C' bus. The automatic load *

• sequencers then placed loads -0n 'C' bus. -LPSI pump P-678 was started after throttling closed.the injection.valves and shutdown cooling was restored less that 4 minutes after the ~C' bus initially de-energized. PCS temperature increased approximately seven d~grees fahrenheit. .

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On Monday, March 30, 1992, a Management .Review Board (MRB) was he_ld to review the Loss of 'C' b~s. and interruption of Shutdown Cooling incident which occurred on Friday, March 27, 1992. Th~ MRB was convened and clarified the following facts presented in the "Plant Personnel *statements" contained in the

• .Post-Trip Review Report.

• The Shift Supervisor releas~d the ~ork to th~ electric~1 repair-worker to test the breaker charging .motor in the 11

~onnect 11 position while the breaker was in the cubitle.

• The Shift Supervisor directed the AD.tQ refuove the e~isting (spare) breaker from the station start-up power breaker cubicle and to install the repaired (nor~al) breaker in the cubicle, leavin~ the.break~~ irr,the "connect" position and with the charging motor fuses installed. (The. *  :

control power fuses were not installed.)

• The discussions with the. AO and the electrical repair:..worker were independent af each other~** The AO was .unaware of the scope cif work for

• .which-the electrical repair-worker was approved. .

• The Ele.ctrical Maintenance Supervisor was not .involved in* either.of the conversations with the.Shift Supervisor and was, therefore, unaware of the approved scope of work. *. * *

• When the normal breaker was i~stalled in the cubicle, only the chargin~

motor .fuses were installed. The contra 1 power fuses were not i nsta 11 ed~.

• Wheh ~he Electrital *Maintenance Supervisor. requested the electrical repair-worker and AO to place the breaker in ~he "test" position and close th~ breaker, neither the electrical ~epair-worker or AO questioned the request based on their understanding of the approved work scope.

• The electrical repair-work.er racked the breaker from the "connect"

• position to the "test" position and closed the breakei. '(Th~ operation of equipment is the responsibility of the Operations Department.)

• The Shift Supervisor did not feel the work he authorfzed (transferring

'C' bus power from the station safeguards supply breaker to the start-up .1 supply breaker and replacing the station start-up breaker while lEaving the breaker in the "connect" position to test the tharging motor) was a

• risk to shutdown safety. *

• T~e-taution signs inside the br~aker cubicles, which had been placed* in the.cubicles as a tesult -0f ~revious similar events, were not clearly visible to the workers.

' ~.

• The caution* signs on the. front of the breaker cubicles, which state that .'

breaket t~sting shall be performed in a~cordance with the requirements of Administrative Protedure 4.02, "Control of Equipment Status," did not stop the event.

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• The* El ectri cal Mai ntehanc;e Super.visor *and e lectri cal . repair-worker were .. *

- ... not aware of previous problems w'ith t-esting these breakers while in the "tes~" position. The AO had trair:iing*on the previou_s~ problems but did not recall the testing problems .. - . -

.*toRRECTI~E ACtibN The follow~ng correitive actions were developed as a result of the*

investigation of thi~*incident: * , *

• _ Immediate ac-t ion .taken by Operat fons* Management~ was. to meet with ::a 11 shifts to dis~us~~the event and ex~ectations for* shutdown risk management. _  :

• _ .. , _

• T~e incident was .als9 djscussed with all maintenahte. shifts emphasiz'ing

• the probl~ms-associated with d~viating from.the .a~pro~ed.w6rk~scope.

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• 'lnvestig~te and evaJuate the use of :a 'more formal. communicatfons.policy.: .

within the maintenanc'e*departmentS. *Consider- the existing operatjons*."-.

,po}icy-in thi*S ev~l.uatio.n '.for.tonsistency. p.ur.poses. * * *

... , ** _1;.  : '

• ~ . Trafn electrical rep.air-worker and :superv*i so rs .on* the breaker testing* ...

requirements stated in Administrative Procedure 4.02: Specifically, ,. __ **

• address* the problems with testing* incoming breakers racked in to t.he *,

"test~ positi4~. Incl~de expectations for breaker operations develop~d . **

by .op_eration~ in this .. traini_ng: . .. .. . - ,

• Define expectations for _breaker operations. Siiec i nca 11 y, . define account ab le depar.tments '*for breaker** <>per at ions in the "connect."; "test",

and "~i~C:onnect".positions.. .. * -:. ... *

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Pla-ce cauti,on placard.s which are:locatedjnside the breaker ¢ubi~les-in*

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a more* vi s_i ble '.locati ori within ..the. br~aker c*ubj cl e. ,, _

• • • Evalu~t.ion. of: a .inodificati.~n to the start-up ,and. stafio_p- safeguards

• breakers to. preven.t 'operation* in the "test" position. * . . . _.*

~, *'

• 'Eyaluate GOP 14, Step 6.5 and Attachment 3 with respect to this event. -

• This evaluatiort:shoul~ ensure Operations Management's e~pectations are

.'clearly defi.ned *to thE? shift SROs via this procedure. *Modify' the *

• • proce.dure-as necessary.: as a result of this evaluation-_.' ..

• • ADDITIONAL INFORMATION None