ML20036C179

Forwards Preliminary ASP Evaluations for 921231 Dual Trip & Loss of Offsite Power to Safeguards Buses & 921217 Inoperability of RHR Pump When Emergency Diesel Generator Out of Svc.Lers Also Encl

ML20036C179
Person / Time
Site:	Sequoyah
Issue date:	06/10/1993
From:	Labarge D Office of Nuclear Reactor Regulation
To:	Medford M Tennessee Valley Authority
References
NUDOCS 9306150148
Download: ML20036C179 (35)

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3 UNITED STATES i

j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 0001 June 10, 1993 Docket Nos. 50-327 and 50-328 Tennessee Valley Authority ATTN: Dr. Mark O. Medford, Vice President Technical Support 3B Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801

SUBJECT:

PRELIMINARY ACCIDENT SEQUENCE PRECURSOR (ASP) ANALYSIS FOR SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 Enclosed are preliminary Accident Sequence Precursor (ASP) evaluations for two Sequoyah events that occurred in 1992.

loss of offsite power to the safeguards buses on DecemberOne event was the dual un 31, 1992, and the other was inoperability of a Residual Heat Removal pump when an emergency diesel generator was out of service.

The Licensee Event Reports that formed the basis for the analysis are also enclosed.

This information is included as.

Your review and coment on the analyses of these events would be appreciated.

In particular, coments on the characterization of possible plant responses, given the occurrence of the events, is sought. We are also interested in coments concerning whether the individual descriptions and analyses reasonably represent plant safety equipment configurations and capabilities that existed at the time of the events.

In addition, coments on the analyst's assumptions regarding equipment recovery probabilities are also sought.

We recognize that the enclosed analysis for the loss of offsite power event is different from an analysis that was performed for previous discussions on this event, in that the enclosed analysis does not consider the consequences of loss of cooling water to the reactor coolant pump seals.

For this analysis it is felt that, since offsite power was lost for such a short duration in relation to the time that seal damage would have occurred, seal damage would not have occurred before compensatory action was taken. Therefore, the enclosed analysis more closely represents the conditional core damage probability for a loss of'offsite power event. See Enclosure 2 for a more thorough discussion.

q As discussed with Mr. Jim Smith of your staff, we are requesting that your coments be provided in writing by June 25, 1993. We will review your coments and revise the final ASP analysis as appropriate.

If you have any 0,

questions regarding this matter, please contact me at (301) 504-1472.

9306150148 930610

., - r T: V DR ADOCK 0500 7

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Dr. Mark 0. Medford June 10, 1993 This request is covered by Office of Management and Budget Clearance Number 3150-0011, which expires June 30, 1994. The estimated average number of burden hours is 80 person hours per owner response, including the time required to assess the new recommendations, search data sources, gather and analyze the data, and prepare the required letter.

Comments on the accuracy of the estimate and suggestions to reduce the burden may be directed to the Desh Officer, Office of Information and Regulatory Affairs (3150-0011),

NE0B-3019, Office of Management and Budget, Washington, DC 20503, and to the U.S. Nuclear Regulatory Commission, Information and Records Management Branch (MNBB 7714), Division of Information Support Services, Office of Information and Resources Management, Washington, DC 20555.

Sincerely, Original signed by:

David E. LaBarge, Senior Project Manager Project Directorate 11-4 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation

Enclosures:

1.

ASP Reports 2.

RCP Seal LOCA Modeling For LOOP Analysis cc w/ enclosures:

See next page Distribution Docket File NRC & Local PDRs SQN Reading S. Varga G. Lainas F. Hebdon D. LaBarge B. Clayton 0GC ACRS (10)

E. Merschoff, RII P. Fredrickson, RII J. Crlenjak, RII cc:

Plant Service list 0FC:

PDII-4/LA PDII-4/P C f/

PDIl_-4/D NAME:

BClayton [

DLaBargef/

F$bd'on b

7/93 6 /.e/93 DATE:

(p /%/93

/

DOCUMENT NAME: ASP.LTR

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Tennessee Valley Authority Sequcyah Nuclear Plant ATTN: Dr. Mark 0. Medford cc:

Mr. W. H. Kennoy, Director County Judge Tennessee Valley Authority Hamilton County Courthouse ET 12A Chattanooga, Tennessee 37402 400 West Summit Hill Drive Knoxville, Tennessee 37902 Regional Administrator U.S.N.R.C. Region II Mr. R. M. Eytchison, Vice President 101 Marietta Street, N.W.

Nuclear Operations Suite 2900 Tennessee Valley Authority Atlanta, Georgia 30323 3B Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801 Mr. William E. Holland Senior Resident Inspector Sequoyah Nuclear Plant Mr. M. J. Burzynski, Manager U.S.N.R.C.

Nuclear Licensing and Regulatory Affairs 2600 Igou Ferry Road Tennessee Valley Authority Soddy Daisy, Tennessee 37379 SB Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801 Mr. Jack Wilson, Vice President Sequoyah Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, Tennessee 37379 TVA Representative Tennessee Valley Authority 11921 Rockville Pike Suite 402 Rockville, Maryland 20852 Ms. Marci Cooper, Site Licensing Manager l

Sequoyah Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, Tennessee 37379 Mr. Michael H. Mobley, Director Division of Radiological Health 3rd Floor, L and C Annex 401 Church Street Nashville, Tennessee 37243-1532 General Counsel Tennessee Valley Authority ET 11H' 400 West Summit Hill Drive Knoxville, Tennessee 37902

q ENCLOSURE 1 i

1 PRELIMINARY B.18 LER Number 327/92-027 fi "i

a Event

Description:

Loss of Offske Power to Saferwds Busses at Sequoyak Date of Event:

Dh 31,1992 i

i Plant:

Sequoyah 1 & 2 i

B.18.1 Smaunary 1

Shonly after a switchyard breaker was installed, it fadted and caused an - '7? ;- a=dirir= la the swhchyard. This resuhed la the tripping of boek unha hous 1005 power as loss of cities power (LOOP). Became of the m ='=#;

condition as the safugnants buses, the saastgency diesel generssors started and loaded. The conditional core danese probsidiky estimmend br this event is 1.8 x 10-* per unit. The relative significance of this event compared to other paandw events at Segnoyah is abown in Fig. B.36.

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Ratative event sigudficance of LER 327/92 027 compared wish asher Sequoyah I

& 2 poesseine eveses.

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B.18.2 Event Description 9

On Doommber 31,1992, wie both units at 1005 power, work was progressing on the lastallation of a 500 kV/161-kV swhchyard imeer46e breaker. For tendag purycoss, the primary relay preessalos for 6e breaker was dissided. At 2148 hours0.0249 days <br />0.597 hours <br />0.00355 weeks <br />8.17314e-4 months <br />,11 mis aAur the breaker was placed is earvies, bot embs tripped became of a rammar anoima pump amiervoings signet. The undervoames was comed by an imernal fauk LER NO: 32752427

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i PRELIMINARY I

in the inner de bresbar tha resulted in decreased voltage throughout the estare switchyard. After tbs switchyard fault was cleared (in 88 cycles), offsite power was available ao the station.

Following the plast tripe and aba clesnag of the swisdyard fault, loads==ma-aeirally transferred frosa the unit sesion service transioneers to the commmon astion service transiemers, a designed. However, became of the - ~ '4 asased on the shutdown (sedegaards) buses, Ibo aussrgsasy dismal gamerssors staned and loaded. At 2313 hours0.0268 days <br />0.643 hours <br />0.00382 weeks <br />8.800965e-4 months <br /> the safeguards buses were rasligned to oftbito power. By 0013 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> on Jammary 1,1993, both units were stabilised in bot abundown, i

B.18.3 AMisianal Erant-Lamend Infonnation he Segnoyab switchyard consists of a 50HV section and a 1614V secdos. Unit I is diremly opemecesd!

so the 5004V swiesyard and unit 2 is diready commened to the 1614V pardon of the yasd. De two

=*iaan arsjoined by the inser<le transimmar. Power cartmut breaker 5058 commsets oss of the 50HV buses to the immer<ie treesiocuser. Dunng startup and abuedown, power to both units is supplied by '

1614V systema via the commmon stanos savice transimners.

B.18.4 Modeums Amumptions Sinos the 140P was caused by a =d==rias fanit, this event was =ad=Ind a a ptsme coutered LOOP.

Probabilities for LOOP noarecovery (short tena), failure to recover ac power prior to bemary depletim, and remmor coolant pump asel LOCA probabuities were revised to reSem values sonorisand widi a po; camared LOOP (see ORNUNRC/L1189/11, ArWand LOOP Asemary and FIPR JestIACd Mod.n y.;

August 1989). De event was modeled ist a singis amit. The event sequence was essendeuy the saem j

for both units.

i B.18.5 Analysis Results ne meditionsi probability of core desesse ei== -f for this event is 1.8 x 10-* pse unit. m dominant oore damage sagesen, highlighted on the event tree in Fig. B.37, imotves iblimre of senergency j

.j power resesrusion numiting in a ressor acciant pump sesi LOCA.

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l PRELIMINARY m

LICENSEE EVENT REPORT (LER)

FACIIJTY NAME: Sequoysh Nuclear Plant, Unit I DOCKET NO: 327 TTILE: Raarent Tn'ps as a Result of a Switch Power Circuit Braskar Fault and a Unit 2 Entry laso Lieuting Condition for Opennon O) 3.0.3 When Both CentriAngal Charging Pmaps Waro Removed Froan Service EVENT DATE: 12/31/9f LER#: 92-027-00 REPORT DATE: 02/01/93 OTHER FACI!JTIES INVOLVED: Sequoysk, Unit 2 DOCKET NO: 05000328 l

l OPERATINO MODE: 1 POWER LEVEL: 100 THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR SECTION:

50.73(aX2XI) 4 50.73(aX2)(lv) 50.73(aX2Xv)

J UCENSEE CONTACT FOR THIS LER:

Jan Bajras swski, Complianos Licensing l

1TLEPHONE: (615) 843-7749 COMPONENT FAILURE DESCRIPT10N:

I CAUSE: X SYSTEM: EL COMPONENT: 52 MANUFACTURER: 8455 REPORTABLE NPRDS: N i

Q SUPPLEMENTAL REPORT EXPECIED: NO ABSTRACT:

On h 31,1992, a spyroximusely 2144 Esmera standard time (EST), wink Ushs I and 2 la power operanos at approxiassamly 100 percent, bash mains reesived a reamar trip signal because of reactor coolant pump bus - - %? ; ne rescer trips wers idiowed by anties trips. Underwahngs on ibe l

6.94V shmadown bosnis initimed board load aripping, dismal genermor (D/0) sorts, and tWQs tytag osso absir respanin shmadows hand, Bearical loads were approprisedy angasmond back a the bosnia. Mais i

feedweer isoissed and -m y sandwaar pasps amned. Loss of power e a radiados nommer resulted la as auxillery bulkung isolation. Witi ihmised sesning in the Unit 2 mais enumet room, rwxrvery evoludoms Air Unit 2 ruuuhed is isoission of courtfhgal charging pump smados and removal of boek casertibgel darging pumps tem servica. Unit 2 senered ILO 3.0.3 det appuosimmsty one mimme satil a sucdos now pak was rummabihhsd. Tbs cause of abs event was an inssrust fissit is a swischyard power cartakbreakerrundting9am*-.Jg ^ issdes"-R4-J. Correcdvsactionsincludestre*N of swindyant anaerois and increasing =3=l== Operations control' room sesNing.

I. PLANTCONDITIONS Unia I and 2 were in power opension a approxisestely 100 percent power.

IER NO:327/92427 J

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i PRELIMINARY II. DESCRIPT10N OF EVENT A.

Even On December 31,1992, arapproximusely 2148 Eamers standed skas (EST), bodi unks russived a renc trip signal because of reamor coolant pump bus --- t-~e *7 (EDS Code EA). De undervohags condition resuhad hos an imernal fadt la a now swadyard power cirania breaker (PCB) (EIIS Cod the had base is servios appenzimady 11 =l==am,.

Bedse the sweet, swindyard crews wars la the procams of placing abs PCB'in service. De PCB (PCB 5058) was la the 50lHV swiedyard e isaarne tramsAmmar posittoa. Primary protscsive relays applicalde as the PCB had bass disabled by opa

==ariand trip naout swades to enciliens difhramtial relay cinmit phasing.

%s rescaer trips wars followed by turbias trips. Undervokass on the 6.9 kV shutdown (5/D) boa (EES Code EB) initisand dissal gemorator (D/G) (EDS Code EK) stans and loading ones their l

S/D boards. De S/D based loads wars stripped and upos D/G loading, inada wese "

j segnamond back so the bonnes wth ibs anespelos of the theressi barrier boesaar poses did mot renamet. Main feedwseer isolmed and auxiliary feedwaar (APW) (EDS Code BA) pump Imss of power to a radl=na= manhor (EDS Code E.) resuhad is as muillary building isoholas. De dealt i

was cleared whhis 88 cycles, and oilkies power to the start busses we rumored. Fouowing the trip renceor coolana pumps (RCPS) transistral hem the unit maism servios transAmmar (USBT) as saation servios trummiormer (CSST) as designed; 4 meed semisor[aM, ems, @

During the transiset, Unit 2 removery,. evolutions remiend is

. etasW Unit 2 enamed Lhaklug =aada%

j Cods CB).ammion and bodi pasmos being, removed tem

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'7 Operation (140) 3.0.3 for appensi==ady one asimmes until a section flow pedi was ressuht" ' "

darging asui Sow was act in earvios during this tien, Appscalemsfy 20 assands has statG_ths 11sars mammuy senes as gnnise actsmukng enoug

%s tr%'as syssum astwork cousins of a 50lRV and a 1614V swis& yard a segnoyd Nacisar Plant (SQN). Unit 1 is commened to the $0lRV antwork and Unit 2 is aimascasd to the 1614 hans two entworks arejoined by the insanis transAmmar (Imennis Bank 5 - ses pues 16 af LER). PCB 5058 ces be assi as an immenlegrenstrear PCB and/or a sysre44ms PCB. Produred sienric power to the amargency buess and to start up and shut down abs generadsg unks a SQN is agipued by circuits toss the 1614V swiedyard.

B.

Isopersade seamans, compensam, or sysans not Comeribend h the Event Immnad of die somonience widi design). De wars shed $silowing the loss of ofikles power imucation, as designed. However, as a resuk of the handswiss position, the 1BBPs did not reload upos D/O loading.

C. Dans and Appsoaimmes Timass of Makr Oomrrences b

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PRELIMINARY i

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-s November 20,1992 Switchyard PCBs inadvertently tripped dunag tests to locats a ground on the 254voit direct current control wiring. Two phases of one PCB closed autoauncally because of a malfuncuos and loss of air pressure. De remainag phase did not close. The PCB thee failed.

1 Novensber 23,1992 De decision was made to replace PCB 5058 with a new 554PM type ABB breaker.

A PCB that had base purchased for the Jackson, Tennesses 50lMV==h==iaa was choses as the replacesset PCB. ABB was coetacted to obtain the necessary mformanoe to install the breaker at SQN.

i November 30,1992 De r=plara== PCB arrived at SQN fross Jackson, Tennesses. A design change I

notice and work order were prepared and sqiproved to lastall the breaker.

December 14,1992 PCB 5058 installation began under the guidance of a TVA-ABB fhcapry4 rained l

power =i==== ara specialist.

nacm.h., 29,1992 De Owa=ange load coordiassor was lafonned that PCB 5058 would be ready to

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• be placed in service os Deoseber 31,1992. De bauskar was My facaory and field tasted (the breaker had not beam energised) as required by abs work order.

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Dae-her 31,1992 Following review and approval of the switching order and testing M-RWi y b

at 2137 EST the assim control room (MCR) staff, PCB 5058 was placed is asevios to be followed by verification of phasing on the difflarestial relay circuit. De primary trip cut out swindies were placed la the opse possion and provided so primary relay protscuon for PCB 5058 dunas this taaserseas. Secondary daisyed relay praescnon was avadable and did operans aAar approximasmiy 88 cycles.

December 31,1992 PCB 5058 faultad laternally, resulting la breaker fallers. Frems the ammunciator primeout, the first alanes to come is indicased cecillograph aparation and openmg i

of PCB $074 (Plant Bowen line). De condemner circulattag weser pump motors j

tripped $silowed by alarnas for overcurrent as Osmansor i escient fisid,161-kV l

l supply voltage inDurs, stanos fW excessive error, and uniervoltage on the l

4 RCP bus.

Additional events during this first minues included:

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Opening of the 50RV swachyard PCBs and the intertis PCBs la the 161-kV switchyard.

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2)

Undervoltage on the 6.MV S/D bosnis resultad la the approprises relays scripping the mapr equipment flrom abe boants. This laciuded the centrifIngal charging pumps (COs) on both unas, which subesgesudy nauhad la landown iealmiana 3)

Both amies reesived a rencear trip signal became of RCP bus undervoltage. De rumster trips wwe lbilowed by turbine trips and 161-kV bus voltage 4 milers alarms. Ammmatis transfer Arom USST N NO:327m27

l PRELIMINARY to CSST was

===41, and the 6.9-kV unit boards ramaiaad energized from offsies power.

l Undervoltage on the four 6.MV S/D boards initssted transfer to the D/Gs. The four D/Gs stanad; feede breakers closed and energized their respective S/D boards.

4)

An engineered safety feature (ESF) maxiliary building isolation acerated because of a loss of pow to 0-RM 90101.

5) no alana for the Unit 1 ice mada=aar lower inlet doors opening was recorved.

6)

Nonaccident equipment sequenced back on the S/D boards. Both CCPs restarted as sect unit.

UnitIat no opersoor took manual coesrol of AFW (anishmuni average tempersenre (T aub avg]

2150 EST was 542 degrees Fahrenhak [FD by reducing the speed of the turbinsMirives auxiliary l

foodwater pump (IDAFWP) and ma===lly throaling the amoeur<irtvem auxHiery disedwater pump (MDAFWP) level control valves (LCVs). De leakpwa onfices were reopened followed by reestabliabing the stesaHlump operation. After the lannumsat==*==W J

(IMs) checked the P-4 cossacts for the renceor trip breakers, the floodwater isolation was reset and steams generaeor blowdown was established.

Unk 2 at De opennor epok manual control of the TDAFWP to bring the pump to mia&==== speed.

2151 EST Unit 2 at no T sub avg teaupersaire had decreased so less than 540 degrees P. De assistaat m

approx.

shift operations supervisor (ASOS) desennimod that boration was regnized. He

.j 2155 EST dirocand baration through the blender a grosser them 10 smuous per misses (gym) with high comosserneios bonsion. He opersoor them took sammal comrol of the MDAFWP LCVs em casemt the tempermuro decrease.

j Unk2a Section to the CCPs swapped over fross the voluans metrol tank (VCI) to the refusing l

2208 EST j

weemr morage task (RWST) becomes level la the VCT had decreased to 7 penant. At that j

thas, the ASOE realised tha leadown had been prwiously isolaned. De ASOS directed ihan one CCP be snapped. Simm ibew-+a= relays were sealed in, she pump wm placed is, " M-(P-T-L).

i Unit 2 at IAndown was reestablished.

/

2209 EST Unit 2 at Ahur the reactor opernear (RO) and ASOS venfled dif5cient VCT level, the i

2211 EST VCr autist valves were opened. De opensor them closed the RWST valves. De opermor observed the the VCT omaist valves were traveling closed. He ascend CCP was snapped and landown =ma-ade=Ily inntsens Whh boek CCPn met is earvion, LCO 3.0.3 was asesred. Appr=imanaly 20 seconds aAmr the ascend CCP was stopped, the 3~

akit apersions supervisor (SOS) saaned the 'IBSPs. The Unk I m were then stoned aesr the Unit 2 TBSPa.

~

I2R NO: 327/92427 M

l

~

1 PRELIMINARY m

]

1 i

Unit 2 VCT valves were opened, the second CCP was started, and letdown was reemablished.

at 2212 EST De handswaches for both tbs VCT and RWST valves were saber placed la or verified to be in AP AUTO position. LCO 3.0.3 was exited.

Unit 2 at The 6.9-kV S/D boards were returned to normal offsite power.

2313 EST January 1,1993 Unit 2' was stabilized in Mode 3.

at 0011 EST l

January 1,1993 Unit I was stabilized in Mode 3.

i at 0013 EST l

D.

Other Systems or Secondary Functions Affected t

The low voltage condition resulted in the Units I and 2 condenser circulming water (CCW) pumps l

tripping. De loss of these pumps is not considered abnormal for this event. De unit boards sustained i

a voltage drop that would came a drop la escantion voltage and result la a speed deviation trip or a power-factor deviation trip. CCW flow is necessary to malarmia coarianmar vacumn and so provide an enable signal for steam dump controls.

E.

Mahod of Discovery De swachyard bussars, reactor trips, and blackout sequence alanes were===== dame 4 on the MCR panels. Oscillograph daarts ' tentifled that a fault had occurred la the CW of PCB 5053, whide was u

in the process of being placed in service.

F.

Operator Actions i

4 De operamrs promptly dingscoed the plant conditioes and look assions aarmanary so stabilise the units is the hot stan6y e-liria= (Mode 3).

Unit 1 MCR persommel (one A308 and two ROs) responded as prescribed by assergemey procedures.

De====dery side of the plant was secured, and the operneors smok ammasi commoi of the TDAFWP and i

placed the motorwirives auxBiery MDAFWP LCVs in mammel bypese' mode. De plant responded as l

aspemed and the operaars partbreed abs designated actions of the proosdans.

t Unit 2 MCR pessommet Sima A305 and one RO) proceeded thrfough the actions described by the muergsacy procedars. Wie only one RO, securing of the assondary side was daisyne De RO took mammal control of the TDAPWP and reduced ks speed a minimumt De MDAPWP LCVs were left in the ano posidos resulting la twice the AFW flow of that im Unit !, resulting in a grosser cooldown rate.

]

Wish blowdown isoised, feedwater pumps tripped, main turbine tripped, and assam dumps not avadable.

the offset of the higher AFW flow cased Unit 2 m cooldown so about 537 dagens F. De ASOS recosamed that RCS berules was required if T sub avg was less than 540 dagten F and made the i

LER NO: 327/92427 '

l l

S.3)$.

~

d

{

PRFHMINARY decision to leave es MDAFJfP EVsja get and infhThe ASOS as(AO tHapusse(which flow Path was to be usedu %g=mseg bannies pask,was,shossggesammah====h spangige,1,ges opermor imervesdiiinand manierise_ema.estesurssesy pedis De ASOS mads es deemian a bonne through the blender and directed the RO to insissa 135 gallons of high conosurados (20,000 parts per 1

miama) boration a grossar than 10 gym. Den ASOldtidass sentes: semen w basis wsak procedure aniowed barmios emagh es pse chassa. De pronmens required nonsion emmusk est emergamey barstion pah. The normal boration path was allowed only if flow could not be achieved through the emergency borados path. De darisiaa 80 borate tiuough the normal rater than emergency path, as required by the procedura, set up the sequence of events ultimasely leading to the loss of both CCPs and charging RCP seal injecdos.

The ASOS had noemd early in the transient that the component cooling symma (CC3)Midd ant 4

68y start aAer the D/Os emergized the S/D boards. De ASOS did not diras mammel starting j

of the TB8Ps a that thee because he did not have the resources a6 eN hypehen D/G:

i W

At the time of the reactor trip, the undervoltage condition had resulted la load aripping of the 6.9-kV j

S/D boards. De load shedding tnpped off the runaang CCP. Wie ao CCPs running, a lsadown isolaios j

Wly occurred. After the. ASOS insisted boration_and.inamuel control o(thajdDAFE LCVs, ay anommene swayover from the VCT e the RWST'osauned as the.im%lpen VGEsesshed1paron$

i At this time, the ASOS realised tha leadown wm isoissed, and normal borados we only providing j

approxiassesly 10 span makeup. After swapover, the ASOS diressed the opssessague esens CCP.

1 De handswitch was placed in the P-T-L posidos to ensure that k would not'immediassey restart, since the w.,+

reisys had not boss remet. no SOS, ASOS, and RO had verined en ao condklos siisted

-fg that would indicam the need for operation of both CCPs. Senpping the CCP was based on adeques RCS i

invessary, tendown i an=ria=, and pomatial for ognipment (CCPs and whengnamigACF.egelslAusses as a aset ed now indicssed as y om es CCPs and no remaing DBPs. DerASOS diressed the RO i

e mestabliek landown now e remore VCT i. val.

i ns RO and ASOs obeenquevei_iadi,*ia incream and aseed est.asygr we capabis of l

supporting sustained tramer of es CCP anstlos trom the RWFT be$tgest3 Mas remore monaal madirians Handswitches for the VCT outlet valves were takaa m A-Ammo, so the OPEN posidos. Whos the RO oboarved the valves reaching the fall open posaios (red lighes), he took the handswisches m tbs l

AP-Amm posklas. De RO than mok the RWST oudet valve handswintes to A-Ames and to the of wr1 position. De RQatW the valves readilag the AsE cioged posidae (gross lighes). k is believed tha n6s were laa in h A,ema semiilgetnas evotados nook place is approx-y is====da based on prianoess.

At this point, the RO rarmilad Ibs RWST valves being closed apd M M neRO samed that as he looked swqntom.43.)andswaches,.hs andeseganiagMystem, indicahs its valves moveensdame De murr vehes rumstems seassesrie asut#slas. Wie *e RWST valve handswitches leR in the A-Auss rater them the AP-Asse W bask

= es Rwrr dit est osame when es VCT sueves nuvend skism no RO cased out es aa-aia m the ASOS. Not knowing whssher the VCT valves were perdy domed or almost Asily domed, the RO LER NO: 32732427 V

n1m r;TafivTimre

PRFUMINARY m

prepared to map the rummag 2A-A CCP. With concern for possatial i===== Aulure o(6e CCP os loss of succoa, the ASOS directed the RO to stop the 2A-A CCP. De RO beid the pump handswitch in the STOP position (not in P-T-L). When told by the ASOS tha the second CCP was being snopped, the SO mammauy started the TBBPs apprealamely 20 aarands aRar the 2A-A CCP was asopped De VCT outlet valves wars reopened and renamed open, the handswnch for the 2A A CCP was released, and the p romaned approaimanaly one aunnes aAer being stopped. Leadown was reestablished and the system stabilised.

G.

Safety System Responses Safety systems performed and plant parameters iW as expected for the reamor and turbine trips.

Detads of spec Sc safety system responses are as follows: Upon reempt of the trip signals, the S/D and control beak rods for both units dropped into the core and reecsor power rapedly decreened as

• Wad.

The RCPs for both units were in service during the transient and forced Sow was maumained.

Mais feedwser flow for both units terminmed on the reassor trips. The AFW peeps for both units started as designed, and steam Sow contioned to the TDAFW pumps. The operanor of each unit took mammal control of the TDAFW pumps and MDAFW pumps as the transiset progressed.

De auxiliary building vest radiation anonieor lost power at the start of the event. His espdyment is powered fross the instrument power distribution pensi, which is not backed by the ElmRE vital inverters. His condition resulted la a control room alarm

• Auxiliary Buikling Vent Monsor Hi Rad" m' '

and was not a residt of as assaal high radistion condition. De equipment performed as espected.

De mornaal feeder to the 6.9-kV S/D boards is designed to opes when is undervokass relays sense less than 30 poroset vohage fbr mors than 0.5==nnada. AAer the 6.9-kV S/D board voltage had decreased to less than 70 percumt

' - ' n a D/G start signal was generated. De load shedding occurred as expected. AAar each D/G reached the appropriate speed and voltage, the breaker that cosassa each D/G to the S/D board closed, and the load sequencing timers started. Lands were thus =mammically W for a monaccidset loading sequence. Dunng this event, the load shed/lood sequence logic fhacriaamd as designed on the trur S/D boards, with the saception of the TBBPS.

Ther TBBPs thBed to matt foBowing S/D board raiondias. De 505 epok mammal acsion to restart the TBBPS. Parther investigations isso the finiture to start revealed that thaf handswishes for the pumps had been placed in the A-Ammo position is accordance with procedura. Wkk the headswiach in this position, the pumps wW mot start sqion acesstion of the blachout relays.11gs handswach position described by procedure was Sound to be incorrea relative to design.

During the time that the S/D boards were without power, a control power alans was reasived on D/G 1 A-A and a low lube ou pressure alans was racerved on the ibur D!Gs. De low labs oil pressure alarm was especssd for the event and was cleared. De control 9wer alans was rwiewed and doemd to be the result of the test pushbutaan being depressed or isomenerti!y shorted. Dis comution was evahsated and no D/G operability concerns were identiSed.

LER NO: 32732427 v

w FfUUTiW N

• f r

PRELIMINARY Dunag this trambat, Unit 1 RCS temperamres ramaland above the analysis va C'

relanvs a S/D marga. N FSAR or technical speedication (TS) repiremens were not veimed.

During this transient, Unit 2 RCS tamperamres dropped to appen=hamanly 537 desress F. De cooldown on Unit 2 was grenser than Unit I becesse of a delay la taking mammal cossrol of AFW as desenbod in Section F. A borados of 10 syss through the blender was lasiased and was rapissed by RW.TT warar on VCT swapover.

r'aladeria== show that approximately 600 ppe boros was regnired to maincus adegusas S/D margia for as RCS tempermurs of 537 desress F. Boros concemension before tbs event was 735 ppe. De PSAR or TS regaremenu wars not violated.

Unit 1 pressuriser level was connant at appromhmanaly 57 percent before the event, sharply dec 33 percent (expected ihr the reactor trip while under load), and thee asalad to appromismusely 29 De 29 percent level was r==aaaahle ibr pressurser level widt two CCPs rumming, and leadown

~i isolmed. Actaal and programuned levels returned to agreement upos stabilization of the plant and to nonnat hot standby naadiriaam Unit 2 pressuriser level was coastant at approximasely 59 percent before the event and thes decreased

[

upon the reacnor trip'to approximately 33 percent. Level==h==Wy incrossed to apprealmstely 48 percent. Leadown was isoissed when both CCPs were anopped as a reunit of 5/D beesd load stripping again laser whom both CCPs were stopped by opermor action. Acmal levels, posarip, ressaimed well abov prograsumed levels principenly because of the operation of bosit CCPs and the dorados for which leadown was isolmed. No challenges e any FSAR analysis limie wars observed.

Except for a temporary upward trend as the Unit I upper comaimuseet radiation monieors, ao b.s' r;

pararbations wars observed la an=rmi====r pressure, tempeners, or radiados. De enact cause ibr the 3

lacreens in the perdcolaes count rass could not be delsrunmad Two pismaihie espismations of the rue increase are: (1) preesisting particaises activsy that was dimurbed upon restart of to radiation monnor i

(RM) pump, or (2) the remert of the upper cosuperument cooling ihms ator reloading on the S/D boards.

• ' + ' =

"y, three Unit I lower ice a=d== mar doors opened during the transiset. De most likely cause for ice condomsar door operation is the restart of the three lower comparamsas coolers (LCCS) after loading back on the S/D boards. De Unit 2 doors did not open; however, only two LCCs were restarted.

Whsm the Unit:2 G3h assa4the red leur oil presumes llWLibumimame:ca each of the pway 4

3 handswithms. Dess low ou pressero lights remained illuminnend wheMes CCPs were ruuming. Dee lishes cleared aest abe blackout relays were reest. As operasor was dispached a check the oil pressurs on the CCPs lomEy. When he arrived, oss CCP was is servim and the oil pressure for that pamp was i

nonmal. Troubleshooting,verdled abat the ciraniary assocised wie ehtimatet psensualW was immalled la asememum wieremism ispinemas, and es maxiliary oil pasp and light for 6. CCP worked as designed. An independset review was performed amLmo esisdagApipummt dadel=ywanidenned j

• st comid impen CCP operahEky.

I i

IJt2 NO: 32732 027 A

PRELIMINARY

m. CAUSE OF EVENT i

A.

Immediate Case The launediate case of the event (ESF and RPS acmances) was an internal fait h

PCB that was being placed in service. This fault dropped bus voltages for both uniss through the intertiej transionner below the undervoltage prorareiam setpoints.

De immediate cause of the LCO 3.0.3 entry was the loss of CCP sucaos and the reunoval of both CCP from service.

j 4

B.

Root Case The toot cause analysis for the innarnal ',imit of the PCB doesnained that the fadt was the result of parncie ~=e==i==eia= of the gas insulaing systems. During breaker timing tasm, the breaker appears to have been " pumped" (the breaker was in motion toward opening widi a closure signal initiated). The pumping action resula is the producuos of metallic particles the allowed Sashower in the resistor assembly area. Breaker thning test methodology did not provide guidance to susure that breaker pumping would be provessed. The syssam coanguration and testing " ',,, of bypassing primary breaker preenctios~ was the case of the extent of =d==y==r undervokage raadiria== ce bodt units. His undervol age eaadeia= resulted la activanos of undervoltage pratarrias, precipstating the dual unit trips, t

load shedding, and D/o mart.

~

7 Ahhough =lan=== T3 stadhug was maintaland, effective consrol of the transiset br Unit 2 was hampered by the thcs the only ces licensed opermor was ce duty. Tbs other scheduled opermor had called la sick and the Operations amperimeandent made the decision act as hold another operator over. As a result of the asessa of the spec Sc event (i.e., rencear trips and undervehage ce bosh amis combined with a major upset en the ofbies electrical dheribados symmm), oubar MCR personest wars not availshie to assist is i

the Unit 2 resposes. During the transiset, the Unit 2 opennor was delayed is securing the secondary plant and taking saammal coasrol of the MDAFW LCVs. His assion precipinand the unit osoidown, bonsion 1

evolution, and evammut LCO 3.0.3 entry.

C.

Comeributing Facsors i

De removal of primary breaker preemssion relays (trip cut <ms relsyspbehre placing the asw PCB in servka provemand early breaker acesation (3.5 cycia) hr prosemica of swiachyard basses and the gameradag unies. Before placing the breaker in service, as assessman was made hr disshimment of relay

(

pecession, and k was daaradmed the failure of the new PCB was4ighly unlikely. His was ibunded as successihl ibceory and field testing. Also, it was considensi that the poemstial br an imeurtle trip ruumiting ikeus saiswiring or heproper phasing might mist without the trip me out relays remioved. It is i

concinded that the testing assehodology did not appropriassly asons posumtial risks levolved and that airmatives were not adapussiy evaeussel. c-between es Tramaminion and Power Service crysmie=ria= ami sies manage===mr was immlegases br asssasing naamgenhaky of inherent risk.

i LER NO: 32782 427 M

rum --

N

i e+

4 PRFUMINARY 4

Additionally, the testing dacumanen did not contain sufficient danil for sits managenset to understandV or assess the potential risks involved.

m Unk 2 opennors failed to follow procedures regarding alignment of the emergency boration push His set up the seguemos of evens ultimately resulting is loss of CCP mcsion and resumag both CCPs from service for appressanely one mismas. k alastappsusest agasens aumtesq$st tsadesshioni ths VCT and RW5T cusist valve headswindumdiremly ruumising.na.lsen af G3 sumimma SesNing facsored into key decisions.made dunas tese evolutions as described in Susion H.P. De magstuds of the event pa== dad by having only one licensed opersoor, resuksd in delisages to the opermore (RO and ASOS). Fross a human facsors standpoint, this sissation heighammed the posumtial fbr medvensat/umrmognised opermor action la me best of the baals. levatigslos reseks conclude ear the RWST bandewisses were immorressly leR in A-Ames and that inadversamt opermostandesappe have remaked in redosure of the VCT valves. While not recalled, the asion could have takse plans unde i

the urgency / pressure of the saastaos and not have been raaein=aly recognised. While the effect of 1

minismus stafflag on this event was apparent, it is considered ihm recovery evolutions could have beam successflally perfonned had procedures besa explicitly fbilowed.

IV. ANALYSIS OF EVENT A C-phens to ground fanit on the 50HV sysessa caused both Umbs I and 2 to trip. De Gumit caused the C-phase vokass is the 50RV switchyard so drop to aero and the 1614V swinchysed CM voltage to dip to appsozimensly 50 percent. De flade caused abe 1614V voltage es dip benmos of the insertie transionner being in servios a abs time of the theit. De isesnie transdarmer ties the 1614V swachyard i

to the 50MV swachyad; therefore, the 1614V swachyard was supplying power as the dumk, whick

^%~!

caused les voltage a dip. Wie a flesis of this mensre and the isonnis transdanner in service, the 1614V

"{

swiedyard reponded as especssd. De reduced voltage on both the 50RV and 1614V sweesyenis is re6easd back to the maillery power symma (APS). De undervehags relays on the RCPs inmess a reactor trip signal in seveseses and oms 4sif cycles when the voltags goes below 5022V (appsozimasely 73 percent). Derebre, and unit's reemor prosession sysset responded to the degrated voltags and tripped. De undervokage relays on the 6.MV S/D boards'sonssi tender brushers trip the breakers if I

ihe voltage dips no ao peromet or less sbr oms 4ait sesons. His would came es 10 percent loss of vohags relsys to sert the D/Os and sequence the loads osso them. De RCPs did not trip since as

' i.. 7 sigast ofless than 56 Hent on abe RCP bus did not occer.

The Unit i unit bosnis that transinned ikans the USST to the C35T b 0mmes of the loss of es 500 kV 9

swechyard. De Unit 2 bosnis dhi mot transfer immediassiy fkom the USSTt as the CSSW since there was not a ihmit la the Umk 2 main gamerasar or any of tbs 1614V somress tied so the genannor. De Unit 2 usk boards transferred appromhmately 30 maaanda aRar the remmat tripped as designed. De reaction of alma APS to the undervoltags for 90 cycles was as expecsad and as designed. De respouse to the event is part of the design basis for SQN.

la addidos, bot embs' DISPs were shed idlowing to loss of oghias weer indismine as designed.

However, upon DA3 raiosding, they wars motisiosdad becamas of the pahlos of the hemdswishes.The RCP marmel barrier hem mensgar thansons e a backup is es and isisassa sysises is essere the hoc LER NO: 32782427

\\

4 I

PRELIMINARY m

RCS water will not enter the RCP beanags and seals in the event of a loss of seal injection. Whue the l

thermal barrier heat exchanger provides a backup fuart=; operation of the RCPs wisit rednood or a CCS Sow e the thermal barrier heat eschanger will not result in damage a the RCP assWer hearing as toeg as aanmal seal injection flow is maintained. 'Ibe operaer rocosmiand during the event that the l

TBBPs had not restarted and waned until D/G loading could be venSed to start the 'IBBPS. Therefore, the opensor at his point maissaiand to primary cooling source br to semis 0.e., darging pumps).

Later in this event, both CCPs br Unit 2 were removed ham service approximasesty 20 seconds before i

auanal start of the TBBP$.

j Evaluation indicated that there is approximately 50-55 gallons of cold weemr contained la the shaA a area of the rencaor coolant pumps. With a monunal lenkeff runs of 3 spas, it is estimated that it would take 10 to 20 mientes br het RCS water to costaa the semis. Although there would be some increase in tempermurs of the waar la the seal ares as k leaks through, any loss of Sow hr a period ofIsas than 10 mh==== is not consklared so have adverse sNoms ce seal condition or perfonments. Theperiod o time wnhout nonnel charging seal injectma or normal tennel barrier cooling was appsesimunesty 20 '

===4

No TBBP high temperature alarms were present dunng this event. There was no RCS invemeory loss outside of the RCS or to interfacmg systems. The capabilky se provide adegases long ear core coollag remnained unkspaired.

Unit I was S/D and stabilized la Mode 3 with no other anosmalies. Plant paramasers -M with the trip Anaction responded as designed and opennor actions were considered appropnans via the emergency Procedures.

m During the event response, Unit 2 RCS T sub avg trended below 540 degrees P and emergency procedures required emergency boration to compensate for potential reduction la S/D smorgia. Given the 4

actual===== of boration regaired and the fact that all rods innened upon reecear trip, no challenge to 4

the FSAR or T3..,.;.

occurred.

During the loss of power, low ou pressure indications were racerved in the MCR br bot of the Unit 2 CCPS. Under S/D boant load sequencing, the CCP auxiliary oil pump is stoned i===themiy whea power is reestand to the S/D bosni. The CCP stans two =amada laser regunBess of oil pressure.

. Assuming that the low ou pressors indicating lights were a tnse indication that no annulary oil peep start had not occurred, the afliscas of operating the CCPs with low oil pressure were evahuand. It was j

concluded thac

/

1.

The low oil pressure condition would have only existed during pump startup. Omos the pump was up a fhlt speed, sufficient ou pressure would have existed to adegumesly lubricate the pump bearings.

2.

If oss of the charging pumps was la anneal operation when the event accorred, suf5cient beanas lubricssion would have been provided if the tiene laturval for which the charging pump was without 4

power was short 0.e., whhis the start-up and wind <iown times). Sufficiset pressars would have exisend a baths the pump bearings whk lobe oil.

M NO:mm27 u.

- J

y i

2 -

PRELIMINARY t

N An investigation iiras performed on the lubs oil light anomaly and no ognipsnas ds6ciency wm found.*#

4 In conclusion, primury safety systems responded as designed during eis transiemL Adequase S/D ma*

weil wisin presenbed safety analysis ilmim, wm --i= d for boe unim. No primary safay systma composes was fauhad or degraded dunng this event. Safury paramasers remained wi6in abs design basis of the plant. His event did not result la adverse raaamp=ne== to plant persommel or the public.

L V.

CORRECTIVE ACTION A.

tam =-$1=ma Corrective Actions i

ne control rooms staff prompdy diagnosed the plant conditions and took actions to ambillas the unit in a nada ca=diria=

Additionally, the nosor-operated d3=an== area for PCB S058 were opened, which completely isolated the PCB ham the bus. Follow-up investigadoes were inithsed for identined anomalies j

and approprisse corrective actions were identified.

B.

Corrective Action to Provent Recurrence De tr====iania= and Power Service Sold test manual has beam rwised to provide speciSc guidance for breaker tindag testing. His guidance ensures that the Asid timing tout does not bypses the aus6 eumping 9

circuit wakin the breaker. Addittomal courois have beam amhiinhed so suengesa -

between the Tr====3==1a= sad Power Service cwamir=*ia= and the she, increase plass visibility of 1

switchyard work, i=pi====* improved risk amma==t =r for disablemmat of prosective releys, and change tasting " -A4,;y to admindse dianhaa==ar of pressceive relays.

,,3 1

Ad=i i==*stive connois have been i=pl=====d m emsnm em consol room andReg wW be==3==3 a

m two ROs ibr and operating unit. De mead ihr addirianal training a dilmand andReg levels (i.e.,

j comanos MCR stafnag mut as skit technical advisor / SOS act available) is being evalmeend.

j

\\

no operssors levolved is abe Unit 2 recovery evolutions have beam commentled am proomdure aeersace i

and are providing the lessoms leermed ham this event to other operamus. Operatoms managenset has met wish the opersoor crews and discussed this event focusing on psocedure seeremos and opermor accons i

l omsskie procedural snaps.

i ne procedure used to positime the TBSP swaches was rwined m/be in agreamsat wish design c,'

Oest MCR handswith positions were reviewed assiumt design requirumanas ao ensure proper positioning. A b= ceder eftert is in psogress to provide overau impsovensass in the comrol of j

comagersionorpisetmyngsme. nisafantincludesspecisc. c lae aamagersioncontroi prooses, rwieur e proper.y idsmary compossets aseding coungsration control, and a sammre that approprime adanniersive coments are in place e renect es rapdred comagazion. nis broad efrort is P-8 by a Sahl coangerados verincation.

De imbs oil light anomaly on the Unit 2 CCP lebe oil symme was investigned. no '. 3=%

r=aa====d=*ia== are under evaluation for ibriber action.

LER NO: 327/92427

j p..

f

~

}

L PRFUMINARY i

m.

VI. ADDmONALiNFORMATION l

i A.

Failed Csg-:- __

The failed compoesnt of this event was an Ases Brown Boverl 550-PM power circuk breaker.

B.

Previous Slaular Eveens A rwiew of previous evedas did not idemufy as LER =maelmad wkh failure to pawide adequate relay !

pe during breaker testing, vcr isolation /cCP sucnos isolation, or opermor stamag.

No

' =Minia==l prwious evenes were identined reissive to opersoor error or failure a follow procedures dunas a transient. A prwious event (LER 50 328/88010) was identined associsand with an operseer taidag t i

CCP en the P-T L position. In that event, the respoestde RO did met recogmies that placing the CCP handswindi is the P-T-L position womid result la the CCP being inoperable during plant operation la -

Mode 3. Two LERs (50 327/92018 and 92025) were identined that addressed single sysesenMa=pa===

faDure aNealms bodi unks. Those LERs provided indenmation as wiser leerusion isso die station mmessadas coment air symme and azios air compressor selecaer tesi shamre. The causes and correcdvs acdoms of those events would not have prevented the event descr8:ed by this LER.12Rs wers identined (unts 327/92006,90oop, and 328/90009) asocissed wkh psocedure Wi-involving falhare to property venty RCS Gow, failure to aeners to a precaution rammiting is an amenmade mart of l

the AFW sysema, and failure a property i=Ta==== a surveulance requinumsat.1he broader issues of l

humes psionnamos and comaal of work are being walunged under the sies '7.c plan that is i

curready being developed.

b vii.co -

i Figure oasitted. (no tide wailable)

/

1 P

l i

5 332 PREIAENARY

~.

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~~

PRELIMINARY C

B.19 LER Number 328/92-010 "i

Event Descriptaoa:

EDG Removed from Service with RHR Pmap Isoperable Date of Evesc July 17,1992 Planc Sequoyah Nuclear Plant. Unk 2 B.19.1 Sumanary During; d,.

+ of a survedlance procedure on the 28-B Rasidual Heat Removal (RHR) pump, k was J

found tha the miniSow comuni valve==ei===8y cycled open and closed chan k shouW have ramaiand opened. Whus the pump was inoperable, the 2A-A sumergency dised generssor (EDG) was inoperaMe for 17 h and the 2A-A canadAngal charging pump was inoperable for 6 h. The wh core damage probabilky estimated for this ovest is 8.6 x 10d. 'Ibo raladvs signincamos of this event compared to i

oubar & d events at Sequoyak, Unit 2 is shown

• y Fig. B.38.

i ustsamese n

15 7 154 15 4 154 154 15 4

'-j I

i I

i v

m, e g.

- - hB-p e.marammer-

- Ince Fig. BJ8.

Raistin event sigm6cance of I.ER 328/92410 compared wkh other Supeyak 2 ovens l

/

B.19.2 Enud Deceipdes On July 17,19RE, wkh the unit a 1005 power, a quarterly surveillanes procedure ce the 2MB RHR pump was h During the test, k was discovered tius the pump's miniSow line nosor control valve was % cyciles open and closed whom it should have remudned opea.

LER NO: 328/92 010 s.333 PRELIMINARY

.J 1

PRELIMINARY l

Further investigation revealed tha the valve had bass misweed on July 1,1992, during perf the flow swach quarterly preventive '==taaaaca procedurs. Between July 1,1992 and Ju thers wars 10 insmaces where Train A safety eququasst had boss out of aeruimew Only e instamass wars of a sigencast a==riam EDG 2A-A was out of service for 17 h, and pump (CCP) 2A-A was out of service for 6 h.

t i

no wiring for the a bar RHR trams was verifled to be correct.

B.19.3 Additional Event-Related Inforniation no Segnoyak Uaks have anadlaw lines for each of the RHR.pumqs His Sow pub consists of thei pump, a now sensor, the RHR han sachanger, and a recirculminsLiime that ressus as the pum l

De recirculados time contains a mour.opersed Sow comsmi valvm tha varies hs position, based!

pump discharge dow sigmal, so mahamin antal pump Sow betwess 500 and 1500 gal / min. Idamm and indlemaa of the valve's pos: tine is available is the control rcas.

Durtag an accidaar. the pump would be aligned Ibr rencaor coolant synne (RCS) hgesde the pump would be in the recirculation modo undi RC5 premurs drops below the pump domesl presure, or the synne is restigned a the assay isiention pump smaios during om recircussion phes De valvo does not have any thannel overloeds and may fail aAmr 15 min of custimmo the valve closed and RCS pressure grestar than the RHR pump deseesd pressure, lamm hnama 4

a timondi the pump resuka, windi could possiblydamage the pump besmuse ofoverhandag..W fully open, Sow so the RC5 would be innsinciset so ensure accidset mitigados. Because the valve

^

mari'===ly cycled opened and closed, the actual time a failure of the RHR pump is users difikmit g

3 De two CCPs fulHil part of the amargency cars cooling syssa (ECCS) ibemina. De discharge presure of tim pumps (2610 psig) is grener than monmal RCS pressure. De two hidt preseus s isiection (HPSI) sysans pussps have a discharge pressure of 1650 psig. AM four pumps are imidst injection and dartes long term recuculmios cooling.

B.19.4 Modelleg Assummptions t

De event was modeled summing the258 RHR train sad the 2A-A EDG are inoperable tr 17 h. De i

Accident Segnames Precursor (AEPinodsitdo not assount for aspones Aigt head and lasersmadhes bend sysemus that Sequoyah uses der em BCCS thamion. De models have a single high pressure injection symus. herstes the caertAngst charging pump (CCF) inopershilky was modeled as "f w

iniemian syssum lheurse nis is equivaient a rendering the CCP and HPs! pump is the same train inopenbie.

hree cases were rua. For all cassa, one train of high-pressure recirridariam was inoperaide because of the RHR pump falhas. De first two cases were run for the EDG inopersidlity. De firm was for the lose ofedhias power (LOOP)laitissor and the second we for the transiemt sad loss of%onimmt (LOCA)

LER NO: 328/92410 s-3M PRELDENARY

l i

l l

I PRELIMINARY in%. For the LOOP case the equipment associated with the trais 2 EDG is readered inoperable due f{

to loss of electrical power. For the other rue laelanes, transients and LOCAs, only the EDG is inoperable since the associated equipment will recahm power flross onkins. De thini case was run for the CCP nasvadability la this case one train of high pressero lajection, rectremheios and flead and bleed I

are t -,-- 2 M due to the loss of the CCP, while the other recimdation trais is inoperable due to the RHR Pusup being inoperable.,

B.19.5 Analysis Resuks De==diriand probabuky of core damage==ri===d ibr this ovest is 8.6 x 10d. His consists of 8.3 x 104 the the EDO lapparabuky and 6.3 x 10-* dbr the CCP inoperab8ky. k abould be acted that since the CCP inopernbuky was anodeled a as inoperabilky of boek the CCP and HPSI pumip is the same trais, the remak is very commervadvs for this case. The da=ian=r segmenos, highlighted on the ovest tree la Fig. B.39, lavolves a LOCA lbliowed by the f!silure of high pressure recimdation.

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M l

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Damian=r core damage M-ibt LER 328/92-010 j

IJER NO: 32882414

.L' 3335 PRE'tJMINARY j

s!

l I

PRELIMINARY

.e.

i IXBSITIOe4L CORE DAlthE PaceABILITT CALtiAATIces Event Ishntiffer: 3M/93-018 twent Demeriptien 800 remaued free service vtth 1 Ret pap Ineserehte (LOIP enty) twent setes 07/17/93 Plants Saipanysk 2 (Case 1) t tanAWAILAsILITY, sumafions' 17 eaure j

IICo M00eteAOLE INITIAfleB EVEnf PROBASILIT!ts LOOP 1.58-e6 SEmmam 00 wit 10ERL PalMASILITT Sett End Staterinttfoter Prehuhtitty-LocP 2 u-g l

Teest 2.8E 4 ATWR -

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LER NO: 32882410

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PRELDdINARY fl r.;

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4 LER NO. 328/92414 q;i g

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PRELIMINARY CCIBITiem4L CDEE SMIAE PRCMSILiff CALEIAAfl0E Event Identifferr 3M/M.919 Event tenertption: Se reened fers service with 1 teR pas Insperable (Teams & Lata enty) twent toter 07/T7/M Plants sagseven 2 (Caos 23 usatalLAstliff, gaatteam' 17 news etWN !stTIAf!NE WWWY PGEASILITIES T**8' LOCA 1.M-R.-.

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In NO: 328/92410 4

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m PRRIABNARY 8N"#

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LER NO: 328/92 010 V

nan PRELIMINARY

t I

i PRELIMINARY

~

LICENSEE EVENT REPORT (LER)

FACILI1Y NAME: Sequoyah Nuclear Plant, Unk 2 DOCKET NO: 328 i

Tm E:

Residual Hess Remuwal Pump Isoperable dus to a Miswwed Flow Swied fbr the Miniflow i

Valve i

EVENT DATE: 07/17/92 LER #: 92 01040 REPORT DA11: 08/17/92 1

OTHER PACILmES INVOLVED:

DOCKET NO: 05000 OPERA 11NG MODE: 1 POWER LEVEL: 100 THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENT 3 OF 10 CFR S 50.ww2xo. 50.wa2xio i

LICENSEE CONTACT FOR THIS LER: C. H. Whimemore, Congdianos Licnesing TELEPHONE: (615) 843-7210 COMPONENT FAILURE DESCRIPHON:

CAUSE:

SYSTEM:

COMPONENT:

MANUFACTURER:

REPORTABLE NPRDS:

SUPPLEMENTAL REPORT EXPECTED: NO ABSTRACT:

b On July 17, 1992, wkk Unit 2 in Mode I a 100 partant power operations, persommel perfonsing a v

surveillance instruction 'inatined a Residual Hast Rannovel (RHR) Pussp 258 miniSow valve to be m

malihias. Operations persommel declared the RHR peup inopershie, and Limiting r a.diria== for Operation (LCOs) 3.5.2 and 3.6.2.1 were esaared a 1100 Eastere daylips time (EDT) on July 17,1992.

An investigation doesnaimed the probism to be an immorromly earmissend wire on ihe Gow swind. The wire was correctly innoissend and the Sowswks was ihmetionally essend and resarmed to sewins. LCOs 3.5.2 and 3.6.2.1 were salsed a 2249 EDT on July 17,1992. A % levemigestonines the event identined the root camsudshe misleid wire as being insammtion to detail whh an inadagenes ----- -- _' pT i

vertScstlos. Malmesmemos pomommel have beam briedad on spect8s probleus idussiSed in this event. A ins man admemmes pom seminisemme inst (Pur) also commenned e ihm event. On July 2s,1992, during the review d ihe event by the Phat Event Review Pamel (PERP), it waydiscovered ihst a posumtial issus esiment levolving h RHE synessas being onmide ddesign basis ofihm plant. A one4our telephone call motifytag NRC of the issus was made at 1928 EDT on July 28,1992.

L PLANT CONDmONS Unit 2 was operating a appronhammiy 100 percent raamar thansmi We LER NOt 328/92410 B.340 PREIJMINARY

- - _=- -.. - -. -. -

_ = _ - _. - -

4 A

l A

i PRELIMINARY U. DESCRIPi10N OF EVENTS D

e A.

Event On July 17,1992, widt Umk 2 in Mode 1 and 100$ercent power, Operations persomesi perfbrsming a quarterly residual best remioval (RHR) pussy surveillamos lastruados, ' entined the 28-B RHR (EDS d

Code BP) pump (EBS Code P) mim6ow valve (EDS Code FCV) to be==Iheiaming De mi=an,

vdve was cyding open and closed instead of remaining open. Operations persommet dedared the RHR pump inopershie, and Lindring Condition Air Operados (LCOs) 3.5.2 and 3.6.2.1 were essered a !!00 Easters daylight thus (Elyr). As invemigation revesial the Aow switch der du miniSow valve had been miswired on July 1,1992. k should be noemd that betwess July 1 and Jdy 17,1992, these were 10 instances whers Train A safety eqmpment, i.e., causrifhgal charging pump (CCF), safety-isimmion pump, i

diessi gemarumor (D/G), and 6.9 kilovolt shutdown boards were inoperalds Air short periods of thms. Wida ihe exception of two instances ihm are described in the following peregraph, the periods of inoperabilky ww of shon darsion.

B.

Inoperabis Struaeres, C: -, or Systems hat Contribuend a the Even On July 8,1992, D/G 2A-A was inopermine fbr 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br />.

On July 9,1992, CCP 2A-A was inoperalde for six hours.

C.

Deens and Appronhmana Thess of Maior Occurrences June 30,1992 Plowswindi quanarly prevendvs maisemsam (PM) 0600 Elyr we sanned.

b' Juns30,1992 A work regnant (WR) was wrimum to replans a 0830 EIFT Sowswisek whom a probless was tamed that prwemsed celteration and tasdag.

July 1,1992 A WR was compissed (fkruswitch replaand). 0627 EIFT July 1,1992 A FM was complesed and the RHR pump was declared 0730 EDTopershis.

July 8,1992 Diesel Osmarmor (DN3) 2A-A was inoperable - 0600 EDT ISO 3.8.1.1 was aussred.

July 8,1992 D/0 2A-A was operable - LCO 3.8.1.1 was adead. 2301 EIFT July 9,1992 CCP 2A-A was inoperabis ist =misa====ca,140s 1841 EDT33.2,3.1.2.4, and 3.1.2.2 were einerud.

July 10,1992 CCP 2A-A was operabia, and LCOs 3.5.2,3.1.2.4,0097 EIFT and 3.I.2.2 were smited.

j July 17,1992 Quensdy operabatty surveillamos innrussion 1100 EIFT test Air RRR pump 28-8 I

idemiSes simiSow valve cycling open and closed.

3.5.2 and 3.6.2.1 were entered.

July 17,1992. MintSow valve Sowswieck was found to be 1830 miswired - the wiring was 1

corsussed.

July 17,1992 LCOs 3.5.2.1 sad 3.6.2.1 were amined for 28 5 2349 EDT RER pump.

July 18,1992 He wiring as Unit i Train A and both trains of 0015 EDT Unit 2 RER pump miniflow swiedles was veriSed as correct.

July 28,1992 Panowing management's rwiser of the event in 1928 EIFT tie Plant Event Review Paoel (PERP) noming, NRC was modnad of the condition under 10 CFR 38.72 m passarially having plaout the plant cumids of desi s basis, became of This A asemy egsipment t

andAor compossus out of servios between July I and July 17,1992.

1 IER NOt 32832 010 B 34:

PRELSENARY

_ w l

PRELIMINARY

~

i D.

Other Sysuuss or Secondary Functions Affected

)

Nome E.

Method of Discovery 4 ^ - personesi perdenming a quarterly opershility tout on the 254 RHR pump idamnSad the abnormal operation of the minianw valve. Investigation ines the cause of the abnorusal operation of the valve revented the Sowswitch that controis abe miniSow valve had a fleid wire immorrecely termissend.

j F.

Opennor Actions Operations persommel idsstified that the miniflow valve was malfbamioning and took approprisse anion by declaring the 25-B RHR pump laoperable and for entering LCOs 3.5.2 and 3.6.2.1. A WR was initimed to invesdgets and tr=AI=aaar the cause. Ahar corrective anion was condaded and the miniSow valve was ibactionally verifled as being able so perfbra its lassaded flanction, LCOs 3.5.2 and 3.6.2.1 were asleed.

G. Safety System Raspoem No utsty system resposses were required.

m. CAUSE OF EVENT O

A.

Imanadians Case De wi a= cause of this event wm the incorrecsty tunniassed wire der the asimiSow valve, which readsrud the 2H RHR peg imopershle. De inopershility of opposius trais equipment coasribuesd to the event.

B. Root Camme Ders were thres root camass der the event:

!., t=ad=pana asifdschlag and i=====ria= to detail was the casesA the craAsman to imporreaty tennimms the field who. Dare was only ans wirs removed and runarmissend derhg the Joly 1, 1992, Souswindi cultrados FM.

2.

",,a variendas wm not enhaively implemsmand.,Ds variest ed estidsmify ihm the

=-

Said wire was enresimmend as the omrrect ammimal. De sannimal block was sanealy inhaled and the lahai corresponded to the psoceders and drawing. Ds wise was mistuudmass en a carmimal that was not Inhalet 3.

A thiud root comes der this sweet was that ths W tot FlfF) Gir the maisemmance 4

andvity was insmusive. De WR did est damely spesify regukemmes mesummy as verify that the minieow valve manioned preparty samr the Somewhdi was replaced in ass $ssahm widt the PM.

i LER NOt 338/92414 33a FREEDENARY

l:

^

J i,

l PRELIMINARY O

De PMTas semed in the WR was to property calibrate and hectionally check the Sowswach. De ambiguay in the PMT led the craAsmen to belief that a system fuaniaani tout or C ~

i verificados was not required.

IV. ANALYSIS OF EVENT j

This emmt involves a wring ermr that resulted la the miar60w recirculation valve cycling when the valve should have remained open.

De flowswitch that was miswired comemis closure of the recircalation valve whom the RHR pump discharge ascends a seapoint of approximately 1,250 gallons per misses (spm). (Dis asspoint=====

for instrument lanccurucies.) De basis ibe the valve closure is so ensure adegmans now goes to the core whenever reassor coolant synssa (RC3) pressures are now enoudt a supw RHR m isdom.

pump ton heating damage, and abr em vatw no esame a 1,500 spa (increasing) e meurs adegame Sow a me ramesor core abr accidem minission. De reciranistion vwve, which is mome operased, is part of the sallity lajamia= nogic; therudore, it does not use thermal overnoeds. De acenster imoeur is read Ibr insurakemut duty and can fhil aAar approximately Afines ademos of h operation. De pump recircadation requiremmens of 500 spa is a h operation vales. De h cycilms of the l

valve reaped the flow nom aero so approximasesty 750 gym wkh each valve cycia. His may asset the cooling E, '

for h flow through the pump, but the anion puis a threat cyde on the pump impeuer and moor bearings that cremes Wietnaal woor on the pump.

g,!

1 During an accident sinsation, the peg normsHy would be is recirasistion mode during the indoction

~

phme of the accides. ne pump is esa used for as poskin session head (NP5H) boost darug the recircaistion phase unsa me Rcs presume emps benow es pump daneses pnumere. wkh the recircahsion vain open, es pump would operme manneny and compism the sociden midsssion tak a 4

desismed.

no wars. case aossario involves a namn break loss or contam accidset wth me minieow.vdw moeor failles in the finDy closed position. Falling la the closed position, the RRR pump is subjem to j

overhaming and eldass theore. nis scenario, compied wie oppostas armin sesey component umsvalishany, rumbs is a comudos cumkle design basis.

Perther investigados and compmeer elsumissed acamarios revealed that no damage would result nom the vatw cycuss er appamiessey 25 minees. R is abuy espeasd em opensors in es main cannot mom would desa es ahmorant aparados een ammmacissus sisudinges rapid esses at pcmidos of the valve, and en omsendon at es mome asperage. Upon dammios, de RRR peg womed esa be armed odr. nis especadom we demonarased by submaining the pmblem e opermars during rupelincation training. name i--saia-did not cyde she aimeow vdve, mapping the RHR pump rdled as normal SI ear =namia= criesris anmasand is amargsacy procedures. De times ranged betwese 21 and 25 minutes beam, e. RHR pump was removed som aervion nereane, me added indkadoes at posidos amus lights and moeor amps should prompt the opennors se enriier imeervenden.

IJE NO: 328/92 010 g.343 PRELIMINARY

're

-w

~

PRELIMINARY s

)

V.

CORRECHVB ACTIONS A.

Immediate Comcsive Acdoes Operations persommet iemandisedy emeured 140s 3.5.2 and 3.6.2.1 for Unit 2.

Operations persommel asised 140s 3.5.2 and 3.6.2.1 for Unit 2 aAmr the mispleasd wire was correa ter-W and me amminosi amt vwiese se adssow valve personned a desismed.

B.

Corrective Acsions to Prevent Racurremos 1.

Wiring on the other mistSow swishes hr Unit 1 and Unit 2 was chedad and veridad as being w.4 tenniassed.

7 2.

The insenumsat PMs dets packages===adanad wkh abe RNR miniSow valve swiedes have beam rwised to require e vertScation he wire h and also Surjumpers.

3.

uh craAssues, plasmars, and proceders writers have beam briedad on this event wkh as t

emphasis on the need for an adegusse PMT or specifying as W verl8cedos in lies of a Phfr.

4.

Mah== piammers will be trained on the proper way to specify anospeamos criteria der verifying that P com perform their intended W His wiu be accomplished by Saposeber 14, 1992.

n VI. ADDTDONALINFORMATION A. Failed Or;:- _

i Nome B.

Prwions Sheilar Evans A rwiew of the licenses event report das base was condused to idsstify any psevious or alesRar evenu, 4

and if so, as desarmies if conomho anions had home w in prevenhg momeramon Several eveses wars idenstAnd hat were conned by er had osmartsdag hamm missaar a tese assed in the t

investigation of his eyes, i.e., imumanion as dessE, imedegame veranandam, and inadeques FMT.

Amines have been amma is naposse to pewimms evens e ensure est eypommises of masseemse were clearly conveyed, madessand, and somerred wie by working 4evel persommel. PsEowleg his event, as ladspenden asse was mammbhd to waham te vertendos and PWT pmosess and esir im@mamerian Correnho salons been his eyelmselom wlE he pursued as part,of the overd SQN perdermanos impswemmet emmes, t

Yn. CoMMnwBur Mahemmance piammers wtB he trained on the paper way to spedfy asesymmon erheds kr verifying that e can persum esir inasmead ammhus. nas wei he assompuesd by sapessner so,1992.

LERNO:338792414

~

s.us NY i

1

4!

a ENCLOSURE 2 l

ASP Reactor Coolarit. Pump Seal.LOCA Madgitna for the Seouovah L.OOP l

(t ER 397/97 027 12 r31/9?)

General t OOP Mode na -

s The ASP EVNTEVAL computer code is used to determine tne conditional core damage probabilities (CCDPs) of events for the ASP program. For LOOP events the ASP DLACKOUT computer code is used to modify the following parameters used in the EVNTEVAL code-LOOP non rscovery probability seat LOCA probaN!!ty (PWRs only) emergonry power tor nvory (gtven no seal LOCA for PWRs) l t

r.,...esy 9 won a seal LOCA nas occurred (PWRs only) l e

enierges.a po*t To datormine those values the ASP BLACKOUT computer code uses the following plant and event depordent data as inputs-lype of LOOP (Lvent dependent)

Pl.snt Centered Grd Related Severe Weather Related Edsomely Severe Weather Related i

Core Uncoverv Tirne (plant deperdent)

{

e Battery Depletion Time (plant deperdeni) i o

Dieset Generator um.n Hapair rime (plant depe Vent)

Reactor Coolant Pump Seal dedgn (plant deperdant - PWRs only) e The type of LOOP which is usec is cependent on the type of fault that causes the LOOP. The frequency.

ard duration rit a LOOP esent are depercent on the type of LOOP used in the evaluation. The LOOP types are irsted above in decrewnc frequency and increasing length. The seal LOCA probability for PWRs is deformined using inc attactw! figure which shows the cumulatrve seal faaure probabity distributiod Scal LOCA Cons 4pr@qn$ fQt $touovah LOOP (I FR 327117 OQfj Shortly after this event occurred. the hcensee determined a corditional core damage probabihty (CCCP) 2 of 6 3F-3 for this event This value was based on the assumption that the reactor coolant pump (RCP) seats would fail whenever the thermal barrier booster pumps (TDDPs) and the charging pumps were simultaneously lost. Dunng recovery from this partcular event both of the TBBPs and the charging.

pumps were lost for a period of 21 s (The component cooling pumps continued to run and provide some flow to the thermal barrier heat exchangers). The CCDP value initially obtained by the loconsee was highly dependent on the seul failure assumption Subsequently, they performed an analysis which demonstratnd that the flow to tne tnermal bamer heat evNngers from the Cisprx.e6t Cooling Pumps i

9 1

I a o un Nu m -uso.

l 7

The intormanon was preeemed to the NRC ty the neensee et e Maren 3.1983 ormorcorrent coneerence it was proveoed to 3RNL t>v the NRC toe wudaranon amng tres evaswahon.

June 4.1993 1

m

. }

f

}T s

a

-J-j

- *.i

,w

)

alorw is suff6 wit to prowent m twture Thus it was coric.uds: a tna licertbev that the assumption of seal fa#ure was overty conursatr e Roevaluation by the isctri ee determined a CCOP value of 1.0E-4.

The ASP event evaluation nwthudologies do not consder RCP val failue likely untE seal Coolang i

(component cooling ard wal iniection) have been lost for about an houd. In this event, seal C0oling was provded throughout the evwnt During the 21 s when the TBBPs and charging was lost, thermal I

barrier cooling flow was reduced 1o 70% 9 the normal value (based on the licensee analysis). This flow was provided by the component couting ;

sps. The TBBPs were f estarted 215 after they were stopped and one charging pump was resta.ted 41 s later. Therefore the reduction in seal cooling for a briot period time (21 s) would not impact the seal falure probab!!.ty used in the ASP evolustion of this event. TNs is consistent with the reevaluation of the event by the licensee

[

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i f

)

i f

f 1

i 3

Based on NUr E C - U M c.:a June 4.1993 2

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