05000423/LER-1993-012

LER 93-012-00:on 930805,piece of Plywood Discovered in Train a of Sws.Caused by Inadequate Work Control During 1991 Outage to Repair Sws.Plywood Removed & Increased Attention Being Paid to Matl Exclusion in Critical sys.W/930903 Ltr

ML20056H461
Person / Time
Site:	Millstone
Issue date:	09/03/1993
From:	Scace S, Temple W NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:
References
LER-93-012-01, LER-93-12-1, MP-93-709, NUDOCS 9309090371
Download: ML20056H461 (6)

LER-2093-012,

Event date:
Report date:
4232093012R00 - NRC Website

text

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rereast usat.es ser.iee cmca, N:rt mas: Nx,ea E. .wey company HARTFORD. CONNECTICUT 06141-0270 (2031605-5000 l September 3, 1993 {

MP-93-709 i Re: 10CFR*0.73(a)(2)(i) j I

U.S. Nuclear Reculatorv Commission Document Contrh1 Desk Washington, D.C. 20555

Reference:

Facility Operating License No. NPF-49 Docket No. 50-423 Licensee Event Report 93-012-00  ;

Gentlemen:

This letter forwards Licensee Event Report 93-012-00 required to be submitted within I thirty (30) days pursuant to 10CFR50.73(a)(2)(i).

Very truly yours, l NORTHEAST NUCLEAR ENERGY COMPANY .

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' Step ed E. Scace ta o

, Vice President - Millstone Station I r

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Attachment:

LER 93-012-00 i cc: T. T. Martin. Region 1 Administrator P. D. Swetland. Senior Resident inspector, Millstone Unit Nos.1. 2 and 3  :

V. L. Rooney, NRC Project Manager. Millstone Unit No. 3 .

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'r . c p,.,mc r r_ v::: z w , n een : w Vmam J. Temp!e, Site Ucensing (203) 437-5904 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) i as rcn e.:.: I REr 39 T Asl p _5 E.5 E c Dr e cv '- r. .W:A:vE n *c'r;;s C A;$E SvETEV c;ycONEN" MANJ AC'URER TO N:;DE SUPPLEMENTAL REPORT EXPECTED (14) gxpEcygo U ON' O.* v VE A:i T.cc _ susM:esion DATE M5) 11 15 93 i

7l Ces m.m t wE c rE e w ssON c cr, ABSTRACT: p 4 v sarn .e am a rey E s,; e-s: ace tweem vs m s)

On August 5.1%3 at la unh the plant m \1 ode t a piece of plywood uas discovered in the " A" tram of I the Stmce Water Sutenn Two das s later another piece was discovered m another part of the " A" tram. Tlns had the ;30tt rmal to make the " A" n am moperable. No actual flow oistrucnons were observed. The ply w ood i wa< cmanered donn; m-pecnon of tne Sertne Water System at the beginning of the urut's refueling outage. l The root cau e of th9 es ent u: madequate work control during the 1"1 outage to repair the Seruce Water Si tem. A tout cause anani s is beir conducted to determme uh3 sarious barners f aded uhich could hate s

prn ented <:arur.g up .uth the ply wood dmm m place.

lo prnent f ew rence. mcreau d attention is bemg paid to material ex !unon m the Seroce Water Spiem. l Apph;ahnny la other ty4cnw tind other un:ts at Slihuone is under cormderation I

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1. Descmnon of Event I On August 5,1493 at 1730 with the plant m Mode 5 (41 psia and 97 degrees Fahrenhen), the A"  !

train of the Semce Water System was bemg mspected as part of the unit's refuehng outape. A 25.5 "

round piece of plvuood was discovered uedged mio the downstream side of a tee m the 30" supply.

The W branch hne supphes the Contamment Recirculauon (RSS) heat exchangers. The 30" mam  ;

header supphes normal loads consistmg of Reactor Plant Component Coohng Water fCCP). Reactor Plant Ventilauon (HVR) and Charpmg Pump coolers (CCE). See attached sketch. i Two days later. on August 7.1093 at 2115, a 24.5" round piece of plywood was discovered m the 26" l Semce Water supply to the A~ tram RSS heat exchangers. The disk was wedged honzontally and was  !

downstream of the branch supph connecuon to the Engmeered ( et) Features Buildmg Venti!auon system (HVO) and safety Injection Pump Coohng System (CCI).  ;

Immediate correcuve acuon was removal of the plywood and performing an evaluauon to determine the .

cause. ,

In the event of a Loss of Coolant Accident (LOCA), this portion of the Semce Water System is required to suppiy cochng water 'a the following loads:

the RSS heat exchangers t

air condiuoners for Residual Heat Removal pump and RSS pump emergenc3 venulation i Safety injecuon Pump Coohng l Motor Comrol Center and Rod Control area ventilanon coolers  ;

Nc. autornatic or manually mitiated safety response was required or mitiated.

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11. f_pe of Event l '1he apparent cause of this esent was inadequal; work control during the 1991 outage to repair the Semce Water Sptem- l 1

Dunng part of 1%I, the unn was shutdown to repair leaks in the Semce Water System. Dunng this  ;

t utage, numerous secuons of the sptem were opened, mspected and repaired. Both plywood disks were i i1 stalled to act as dams for the grit h!asting and coaung of the section of pipe around the tee. j "wo opportumties emted for removal of the dams: l cleanness mntrol mspecuon at completion of the job l quahty control mspecuon at completion of the Job. l A root cause analpn to determine why these barriers failed is in progress. The results will be reponed ,

in a supp'emental repon by November 15, 1993. l 111. Anah ':s r,f Event

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l This report is bemp submitted m accordance wnh 10CFR50.73(a)(2)(i)(B), as a condnion prohibited by Techmcal Specificat: ens.

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Techmcal Specihcauens requ re both trams of the Emergency Core Coolmg Ssstem (ECCS) to be  !

OPLRABLE. As n apphes to the RSS system, at least one heat exchanger m each tram is required to be r 3 OPERABLE. Lackmg endence to the contrary. n must be assumed that the plvwood dam m the Service j Water sur;3h ta the " A" tram heat exchangers potenna!b rendered both of them moperable. Since ths  !

condmon exceeded the ume hmus of an Acuon Statement, a wolauon of Technical Spenhcanons  !

occurred i Techrncal Specshcanons require both trams of CCP to be OPERABLE, Wrule no actual degradauon m l finu was obsened, Sernce Water flow to the heat exchanpers may have had a failure mechanism which the flow tesung was unable to duphcate. Therefore the plywood had the potential to render one train moperable. f i

Techrucal Speahcanons requ:re both Seruce Water loops to be OPERA 53tE. Two of the specified functions of the Sernce Water System are to proude coolms to the RSS heat exchangen and the CCP heat exchangers. Smce proper operanon m an accident condioon cannot be demonstratec, the " A" tram was potennalh moperahie. Smce thn condmon exceeded the ume hmus of an Ar' ion Statement, a i nohmon of Technical Specthcanons occurred. I 2 1 The safety sipruncance of this event is imupated by the followmg factors:

a four hour. high flow post-repan flush of the "A" tram chd not reveal any flou degradation to any l

normal or accident load heat exchanger.

a weekh howrate sunei!!ance n perforrned on each of the normal load heat exchangers. The l results of thu suneihance are reneurd and trended by the engmeer responsible for the Serace Water Sntem 11 an adverse trend is identihed, acuan is required to be taken to resche the decreased flow. No such adserse trends uere idenubed smce the dams were left in place. These tests demonstrate that no actual flow degradation to the normal load heat exchangers uhich could base been unpacted by one of the plywood ciams (CCP. HVR and CCE) has occurred smce the dams urre leh m place i there o no mdicanon that the dams mosed from the posioons in which they were found despne

numerous pump shif ts and pump starn. Therefore, n is unhkely that they would hase mosed durmg an accident to resinct flow.  ;

I j The "B' tram has been mtpected and no smdar condmons were found.  !

lY Corrqm e A cuan I

The immediate correcuse acuan was to remose the plywood and perform an evaluation to determme the '

cause j

4 To prevent recurrence, mcreased attentwn is bemt paid to matenal exclusion m entical splems.

Spenhcally, al! dams used m the Scruce Water Sptem dunng the current refueling outage cre being numbered and sgned m and o'n of a log. In addition, appbcaNhty to other systems with large bore pipmg such as feeduater and circulaung water is bemp evaluated. Renew of material exclusion controls for other safety related sptems determined that sufhc ent c, rols are in place to control dm installation and removal. Milktone recognues the seriousness of this cut and will renew applicabihty to other site uruts.

Once the root cause anahsis of the work control dehaency is completed. further correcure action wdl be perf armed a necewary. As an imenm measure until the root cauie can be determmed, the Service l Water Spiem ud! be mspected prior to closure dunng the current refuehng outage.

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V. Adineful In f ormanon i

1.scensee Event Reports (I.ER) subm:tted which discuss common mode failures resultmp from work  ;

control are as follows:

LER Number T:tle 02-003 Inadsertent Enclosure Buildmp Imegnty Breach Due to inadequate Work l Plannmp LER 92-003 discusses an esent where madequate work comrol dunn; the 1991-92 erosion / corrosion outage resuiicd in removal of a Supplemental Leak Collection and Release System (SLCRS) seal.

because this event took place at approumatdy the same time as the dams were lett m place, the ,

correcute acnon for ths LER would not hase been in place to present the current esent.

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