ML17347B267

LER 89-006-00:on 890713,intake Cooling Water Flow to Component Cooling Water HXs Degraded Below Design Basis Flow Rate for 15 Minutes.Caused by Failure of Header Isolation Valve 4-50-308.Valve Replaced & Pin removed.W/890814 Ltr

ML17347B267
Person / Time
Site:	Turkey Point
Issue date:	08/14/1989
From:	Herrin D, Woody C FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-89-280, LER-89-006-01, LER-89-6-1, NUDOCS 8908220230
Download: ML17347B267 (9)

Text

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.REGULATORY INFORMATXON DISTRIBUTION SYSTEM (RIDS)

,ACCESSION NBR.8908220230 '. DOC RATE= '.89/08/14 NOTARIZED. "NO, '..DOCKET FACIL:50-251 .Tur3cey Point 'Plant, Unit 4',=-ZMeida Power and Light C 05000251 AUTH. NAME AUTHOR AFFILIATION HERRXN,'D.W. ."Florida -Power & Light Co.

WOODY,C."O. ~':Florida':Power & Light Co.

,-';;RECIP.NAME ~ RECIPIENT AFFILIATION

..'-..;..SUBJECT,: .=LER 89-006-00:on 890713~,degraded:intake cooling water. flow

...;conditionto..-,component:cooling water. heat exchangers.

.W/8 D

'",; DISTRIBUTION .CODE: -" IE22T COPIES RECEIVED. LTR C ENCL "': 'IZE. 8

TITLE:--50.73/50.9 Licensee; Event Report (LER), Inciden Rpt, etc.

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,S FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 40 ENCL 40

P.O. Box14000, Juno Beach, FL 33408-0420 "AUGUSX -1 4" 1989

.'.-.Ir-'89-280

';,":.MO.'FR %0. 73

=-.:,uU S.. Nuclear Regulatory,'ommission

.;-"'Attn". Document Control Desk

,.;<<l; ., Washington,-..D.

- C..20555

."Gentlemen:

'.":Re:. "-.Turkey" Point Unit'A

'"'Docket No.; 50'-251 Reportable Event: 89-06 .

...,. Date .of- Event;: .July .13,. 1989

'*. -'- Degraded Intake Cooling Water Flow'Condition Co Component Cooling Water Heat Exchangers and Unit Shutdown Required b Technical S ecifications due to Valve Failure The attached Licensee Event Report is being submitted pursuant to the requirements of 10 CFR 50.73 to provide" notification of the subject event.

Very truly yours, Acting Senior Vice President Nuclear COW/JRH/cm Attachment cc: Stewart D. Ebneter, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Plant MO8220230 qPOejp PDR ADOCK 0:-OO02=.i PDC an FPL Group company ~E2.>

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NRC form $ 50 U.S. NUCLEAR REGULATORY COMMIS)ON (90$ )

APPROVKO OMS NO. $ 1500109 LICENSEE EVENT REPORT {LER) ~ XPIRKS: 5/$ 1ISS fACILITYNAME tll OOCÃtT NUMSSR (2) ~A IA$

Turkey Point Unit 4 0 5 0 0 0 5 1 > o('0 5 7"LEISegraded Intake Coo1ing Water F1ow Condition to Component Coo1ing Water Heat Exchangers and Unit Shutdown Re uired b Techni'ca1 S cifications due to Valve Failure EVENT OATS Itl Lth NUMSth (5) REPORT OATS (7) OTHER SACILITIKS INVOLVEO Itl OAY YEAR YEAR y'$( $ 54USNTIAL vga nowoN MONTH O*Y YEAR ~ ACIUTY NAMES OOCXET NUMSKRISI MONTH IIC NUMOSR .cv NUMOOR 0 5 0 0 0 0 13 898 006 0 0 14 89 0 5 0 0 0 THIS h SPORT IS SVNAITTKO PURSUANT 7 0 THt RtoUIhtMSNTs os 10 csh (I: tcneeo ono or mom oe Ine losornef) I11)

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LICENSEE CONTACT SOR THIS Lth (12)

NAME TELEPHONE NVM4ER Oennis W. Herrin, Regulation and Compliance Engineer AREA COOK 305 24 6-6 749

~ETK ONS LINt SOR EACH COMPONENT fA)LURE OESCRIStO IN THIS REPOhT (1$ )

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AssTRAcT (Limit lo 1400 roeeee, i.e., epoeorlmemif /lheee einRorooee lyfeen(Nn I/ecol (15)

On July 13, 1989, Intake Cooling Water (ICW) flow to the Unit 4 Component Cooling Water (CCW) heat exchangers degraded to below the design basis flow rate for fifteen minutes while backwashing the 4A--ICW/CCW basket-. strainer'CW flow was'estored within five minutes of recognizing the degraded flow condition. On July 15, 1989 the same condition occurred but ICW flow was maintained above the design basis flow. On July 16, 1989, the 4B ICW header was taken out of service for investigation. The cause of these condi,tions was initially believed to be clogging of the 4B ICW/CCW basket strainer and/or a malfunction of its differential pressure gauge . Subsequent evaluation indicated flow obstruction in or around 4B ICW header isolation valve 4-50-308. Due to the frequency of cleaning ICW/CCW basket strainers, a management decision was made not to continue power operations with only one header of ICW operable. Unit 4 was placed in Mode 3 on July 17, 1989 'alve 4-50-308 was replaced and the 4B ICW header was returned to" service on July 20, 1989. The initial degraded ICW flow condition did not affect any other plant equipment .

NRC Sone $ 54 I9 5$ )

VX, HUCL'SAh 'hSOUL'ATOAY'COMMISSION APPRQVSQ QMS NQ 3150&IOA RT.QXRl'TBCT;CQNTlNU ATION SXPI ASSI S/31 I!8 OQCKST HUMSSh I31 LSh HUMSSh ISl PAOS I3I fACILITYHAMS III 4.T, SSOVSNTIAl ASV tSION Y SAN NUM NUM ~N

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.,;3heeriytion 4lf+,tbe" event

,"At 1625 on. July '13 '.I'989, with Unit 4 in,"Mode 1 at 25K power, the 4A Intake

',,"Cooling Water (ICW)/Component Cooling .Water (CCW)'asket strainer (EIIS system 3I,; component

3SKT)-was. taken. out, of,service for:cleaning. (See simplified

.drawing of the .ICW system attached,*),'t 1635:,the Nuclear Operator, observed a

'degraded flow condition on the CCW heat exchangers (EIIS System: CC,, compon-

.~;".,>I;- ent: HX) and immediately notified.the Control Room operator. The Nuclear

', Operator was instructed to valve the 4A ICW/CCW basket strainer back. in

'ervice ht 1640 ICW flow was'estored,:,to the CCW heat exchangers. The .Oper-

","'.",'ations personnel believed the source of reduced ICW flow to the CCW heat ex-

"

. "'I.'Lchangers to be clogging of. the 4B ICW/CCW basket strainer. Between,1725 and 2125 the 4B ICW/CCW basket strainer wai out of service for cleaning 'The

. basket strainer;.was..found to be, more clogged than normal

.At >pproximatel'y 2200 en,'.July 14', .1989- the -onsite Technical Department was

- " directed to perform an evaluation of the ICW degraded flow condition.'t

'0800 'on July 15, '1989,. the Techni'cal. Department. system engineer notified

" Operations Department;,personnel Chat.-an, analysis of the degraded 'ICW flow

.condition on July.13, 1989 revealed that the ICV,flow,to -~ CCW heat

'exchangers tms. 'below;the. design -basis. flow rate from 1625 to '1640 on July 13 9 1989 ~

At 1824 on July 15, 1989, an attempt was made to valve out the 4A ICW/CCW basket strainer for cleaning when ICW flow to the CCW heat exchangers de-creased . The strainer was returned to a normal alignment while ICW flow was maintained above 15,400 gpm. Since the 4B ICW/CCW basket strainer had previously been cleaned and showed a differential pressure decrease to approximately 1.0 psid, Operations personnel suspected the strainer to be clogged and the differential pressure gauge to be in error.

At 1425 on July 16, 1989, with Unit 4 in Mode 1 at 100X power, the 4B ICW/

CCW basket strainer was taken out of service in accordance with Technical Specification 3.4.5.b.l for cleaning and to inspect for obstructions. The inspection showed no significant blockage . Subsequent evaluation of the degraded ICW flow condition by the System Engineer indicated probable flow restriction in or around 4B ICW header isolation valve 4-50-308.

Due to the frequency of cleaning ICW/CCW basket strainers, a management decision was made not to continue operation with only one header of ICW operable . Therefore, at 0325 on July 17, 1989, a Unit 4 shutdown was initi-ated and at 0607 Unit 4 was placed in Mode 3 (hot standby).

Examination and repair of the 4-50-308 valve required isolation of the 48 ICW header. Although no degraded flow conditions were indicated for the 4A ICW/

CCW basket strainer, to ensure the maximum flow capability, PPL determined that backwash of the 4A ICW/CCW basket strainer was prudent . However, with the 4B ICW header at reduced flow (approximately 8200 gpm) and therefore, NAC POIIM 3ISA I943 I

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ACILITY NAM% 111 OOOO KT NLNShlh 0) LIh NUMC!h Ie SA44 ISI Y SAN 4~~~" $ 4 4 V 4 N T I AL NVM 1

', ASVISION NVM Turkey Point Unit 4 TgCT /A' SASSS N ~, ~ ~ IlhC 1INIIIJ%4'Sl ISSl o 5 o o o 2 ~'1 9 0 0 6 0 0 030' 5

'"technically inoperables NRC approval was wcquired to .isolate the 4A XCW/CCW basket atraincr ~ On July 18, 1989, the NRC approved a disaretionary enforce-

'.'ment for. a period of time not to exceed one hour to perform the requested back-

, wash of the 4h ICW/CCW basket strainer. This operation took place between

'2000 and,.'2100, on *July 18, 1989.

Valve 4-50-308 was replaced- and the 4B .'ICW header'wae returned to service .at

,~1900 on July 20,,1989. Technical Specific'ation Action Statement time acquire-

,ments associated., with the 4B ICW header 'low flow aonditi'on were met. '

', 'iiCause.zf; the "Eat

'The aausc of the degraded ZCW flow to'the 'CCW heat exahangers was -due.so. fail-

,- .ure of 4B ICW header isolation valve 4-50-308 Upon disassembly, the valve di'sc'as found to be 4n the partially opened position and separated from the valve stem. The tapered pins .(2) which connect the disa to the valve upper "stem failed in the threaded region'. Preliminary indiaations are that the "t'apered pins experienced fatigue failure due to oacillations set,up 4n the

,.valve internals .by .turbulent. flow: aonditgons.-

Analysis of the Event The minimum required total flow to the CCW heat exchangers during power opera-tion was less than the design basis flow from 1625 to 1640 on July 13, 1989.

During this time, the CCW heat exchanger outlet temperature reached a maximum recorded value of approximately" 109 degrees P.

The limiting components in the CCW system from the perspective of operating CCW temperatures are the Reactor Coolant Pumps seals'ased on this limita-tion, the CCW heat exchanger outlet temperature may exceed 105 degrees P up to 125 degrees P for' maximum period of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. Since the CCW heat ex-changer outlet temperature reaahed a maximum recorded value of approximately 109 degrees P during the 15 minutes of degraded ICW flow, it may be concluded that this condition had no significant affect on plant equipment.

The degraded ICW flow to the CCW heat exahangers occurred during the back-washing of the 4A ICW/CCW basket strainer . Within 5 minutes of recognizing the degraded ICW flow aondition, total ICW flow to the CCW heat exahangers was restored to above 15,400 gpm. Had a Design Basis Aaaident oacurred during this time, ICW flow to the CCW heat exchangers aould have been restored in time to acaomodate the heat loads generated by a Large Break Loss of Coolant Accident .

During the time the 4B ICW header was out of service to repair valve 4-50-308, ICW total flow to the CCW heat exahangers was maintained above that required to mitigate the consequences of a Design Basis Accident.

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COMMISSION

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.~Corr(E(@tive.-'katioas 1)""'Caution statements have.been';ailded to.:procedures 3/4-0P-019, "Intake "Cooing Water System," for operators .to ensure that total ICW Slow:to the CCW heat pxchangers- does not drop below 15,400 gpm'while.valyiag- an

,ICW/CCW basket strainer.. out of .service for baekwashing.

', 4),*",While valve 4-50-308 was removed .from the 4B ICW header, a "crawl-through" inspeation was,aondueted to .ensure removal'f any obstructions

."-.to the -4B ICW/CCW basket strainer'),

Valve 4-50-308 was replaced 'After ensuring valve integrity -and opera-

'-bilkty, the 4B,ICW header,was;returned to service

-4) ., A disc/stem .tapered pin from. the .4-50-308 valve has been recovered from

'",the 4B ICW header. ;This pinwill,be .analyzed to determinee Xtss fail a ure

-meel3aaism hdditfena1 Inforaation

'Valve 4-50-308 is a Model Triton XR-70 36" manual butt t e Henry Pratt Company. The replacement val've is a Model RIA 36" manual the rfl l u er y va ve suppliedd by li butterfly valve supplied by the Henry Pratt Co.

So similar Licensee Event Reports could be located.

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