Information Notice 2007-06, Potential Common Cause Vulnerabilities in Essential Service Water Systems

Potential Common Cause Vulnerabilities in Essential Service Water Systems

ML062840608
Person / Time
Site:	Point Beach, South Texas
Issue date:	02/09/2007
From:	Michael Case NRC/NRR/ADRA/DPR
To:
Richard Laura, NRR/DIRS/IOEB
References
IN-07-006
Download: ML062840608 (6)

UNIT ED STAT ES N U C L E A R R E GU L A TOR Y C OM M IS S ION OF F IC E OF N U C L E A R R E A C TOR R E GU L A TION W AS HIN GT ON, D.C. 205 55-0 001 Feb ruary 9, 200 7 NRC INFORMATI

ON NO T ICE 2007-06:

POT ENT IAL CO M M ON CAUSE

VULNERABILI

T IES IN ESSENT

IAL SERVICE

W A T E R SY S T E MS A DDRESSEES All hol de r s o f ope r at ing lice ns ee s f or nuc lea r powe r re ac t or s, exce pt th os e who have perman entl y ce ase d o pera tio ns and ha v e c erti f ie d th at fuel ha s b een pe rmanen tly remo v ed f rom the reac tor v essel.

PURPOSE

The U.S. N u cl e a r R e gul a to ry C o mmi ss i o n (N R C) i s i ss u i n g th i s i n form a ti o n n o ti ce (IN) to a l e rt add ress ees of the i mportan ce of main tai ni ng ess enti al se rv ic e w ater (ES W) sy stems in a ma n n e r th a t p re cl u d e s th e d e v e l o p me n t o f po te n ti a l c o mmo n c a u se fai l u re v u l n e ra b i l i ti e s d u e t o pi pi ng or hea t ex cha nger d egrada tio n. It i s e x pec ted that reci pi ents w il l rev ie w the i nformatio n for a p p l i ca b i l i ty t o t h e i r fac i l i ti e s a n d c o n si d e r a ct i o n s, a s a p p ro p ri a te , to a v o i d s i mi l a r p ro b l e ms. How ever, sug g est ions conta

ined in this IN ar

e not NRC req

uirem ents; the ref ore, no specif

ic acti on or w ritte n re spo nse i s re quire d.DESCRIPTION O

F CIRCUMSTA

NCES There hav e b een tw o e v ents at f orei gn op erati ng rea ctors in w hi ch ex terna l corro si on of pi pi ng lo c a t e d in va u lt s ha s ca u s e d a c a t a s t r o p h ic lo s s of on e t r a in of t h e ES W sy s t e m. T h e s e t wo e v e n t s a l s o h a d c o m m o n c a u s e f a i l u r e a s p e c t s t h a t w e r e i d e n t i fi e d a s p a r t o f t h e e x t e n t-o f-condit ion revi ew s. T he f irst f oreig n ev ent occ urr ed at a press

urized-water re

act or (PW R)des igne d b y W esti nghou se, that began co mmerci al op erati on in 19 88. On Au gust 25 , 20 04, w hile operating

at 100 perce

nt power, an ESW

sy ste m m anhole pipe brok

e circum f eren tially prompti ng a pl ant shu tdow n from the

tota l lo ss of the B trai n o f the E SW sy stem. The e v ent w as of g reat con cern for pl ant safety be cau se it cou ld ha v e l ed to a co mmon c aus e fai lu re i n a sy stem th at i s th e u lti mate hea t si nk f or mo st s afety l oad s. The E SW pi pes are bu rie d a nd use manh ol es at c ertai n i nterv al s to al lo w for i nsp ecti on and mai nten anc e. The E SW pi pi ng i s a B ON N A d e si gn th a t u se s a s te e l p i p e l i n e d w i th c e me n t o n b o th s i d e s to p re v e n t co rr o si o n. The man hol e fil le d w ith su rf ace w ater and co rrode d th e e x pos ed carb on stee l manh ol e p ip in g nec k. The b reak res ul ted f rom e x terna l corro si on due to imp rope r i nsta ll ati on of ex terna l cemen t pi pe coa tin g. The l ic ens ee ex tent-o f-con di tio n re v ie w found co rrosi on at tw o o ther E S W ma n h o l e n e cks t h a t a l so r e qui re d s i gni fic a n t re p a i r. The s eco nd f orei gn ev ent occ urred at a P W R, des igne d b y F ramatome , tha t be gan co mmerci al ope rati on in 19 88. On De cembe r 11 , 19 98, w hi le op erati ng at 75 perc ent pow er, a n E SW pi pe ruptu red and floo ded the pi pi ng gall ery w ith se a w ater. S in ce the B trai n o f the E SW sy stem w as lo st, th e o pera tors shu tdow n th e p la nt. The p ip e i s c ompo sed of pre stress ed, in ner and M L06 284 060 8 IN 200 7-06 P a g e 2 o f 5 oute r co ncre te p ip es w ith emb edd ed stri ngs an d s teel pi pe. A v is ual i nsp ecti on of the f ai le d p i p e r e v e a l e d a 3.3 foo t l o n g b y 2.8 i n ch e s w i d e t h ro u gh-w a l l r u p tu re. Th e p re st re ss e d w i re and ste el cy li nde r w ere f oun d to be se v erel y co rrode d. The p ip e i s l oca ted in an un dergroun d gall ery tha t ha s v ery hu mid co ndi tio ns. The li cen see de termin ed that con den sati on got i nsi de a sm a l l c ra ck o n t h e s u rfac e o f th e p i p e c a u si n g c o rr o si o n o f th e s te e l w i re. Th e l i ce n se e e x te n t-o f-co n d i ti o n r e v i e w i d e n ti fie d 1 6 o th e r p i p e s p o o l s th a t w e re a l so r e p l a ce d. There al so hav e b een tw o e v ents at dome sti c o pera tin g reacto r pl ants tha t ex peri enc ed si gnifica nt i ntern al de gradati on of criti cal E SW co mpon ents tha t ha d th e p oten tia l f or c ommon cau se f ai lu res. On Jun e 2 7, 2 005 , at the So uth Tex as Pro ject, U ni t 2, a th ree gall ons/hou r throu gh-w al l le ak w as id enti f ie d i n Trai n 2 A, ess enti al co ol in g w ater (EC W) sy stem p ip in g f la nge. The p ip e i s 3 0 i nch es in di ameter, compo sed of an al umi num-bro nz e, a nd is l oca ted immed ia tel y do w nstre am o f an E CW retu rn th rottl e (b utterfly) v al v e. Su bse quent li cen see inv est iga tion f ound cavitation pitt

ing , circ um f eren tial pipe crack

ing , and pipe-t

o-en d f lang e w eld sep arati on in the pi pe. On Au gust 15 , 20 05, as part of thei r ex tent-o f-con di tio n re v ie w , the li cen see i nsp ecte d Trai n 2 B of the EC W sy stem a nd dete rmin ed that a s imi la r do w nstre am fla n ge h a d a n a p p ro x i ma te l y 3 0 i n ch e s-l o n g b y t h re e i n ch e s-w i d e s e gme n t o f th e a l u mi n u m-bron z e p ip e th at b roke free.

Train 2B of the E CW sy stem w as dec la red in ope rabl e for th e same reas ons as E CW Trai n 2 A and w as repo rted to th e N RC as a common-c aus e in ope rabi li ty of i nde pen den t trai ns (Li cen see E v ent Re port No. 49 9/20 050 04, Agenc y w id e Do cumen ts A cce ss and M ana gement S y stem (A DA M S) Acc ess io n N o. M L05 263 003 1). The licensee dete

rm ined the cause

of the dam ag e w as cavitation imping

em ent f rom the heavil

y throttl ed butte rf ly v al v e. The ro ot c aus e w as the f ai lu re to i nco rpora te re quisi te i nsp ecti on acti v iti es f or E CW pi pi ng i nto stati on programs.On M arch 20 , 20 05, at P oi nt B eac h N ucl ear Pl ant, Un it 1, th e G-0 1 e mergency di ese l genera tor (ED G) be came in ope rabl e d ue to a thro ugh-w al l le ak i n th e e ndb el l of the ED G coo li ng sy stem h e a t e x ch a n ger (In sp e ct i o n R e p o rt 5 0-2 6 6/2 0 0 5-0 1 0 , A D A M S A cc e ss i o n N o. M L 0 5 3 0 0 0 2 3 7).Licensee inspec

tions ident

if ied signif

icant dam ag e to the endbe

ll due to m icrobiolog

ically in duc ed corro si on (M IC). The li cen see mai nten anc e ru le ev al uati on dete rmin ed that the poo r condit ion of the endbells f

rom pitting caused by

M IC w as k nown f or near ly ten years, but

timely and eff ecti v e c orrec tiv e a cti ons w ere not taken. Al so, on Ap ril 22 , 20 05, a th rough-w al l serv ic e w a te r (S W) l e a k o cc u rr e d o n t h e G-0 2 E D G h e a t e x ch a n ger a l te rn a te S W s u p p l y l i n e d u e t o M IC.BA CKGRO UND T he ESW syst em (o r its eq uiva len t) f or U. S. co m m er ci al r ea ct or pla nt s is th e as su r ed , sa f et y-rel ated mea ns of transferrin

g sens ib le an d d eca y he at from the

rea ctor coo la nt s y stem to the ul tima te h eat si nk. The ES W sy stem i s a ls o re li ed upo n for o ther cri tic al sa f ety functi ons , su ch as prov id in g cool in g w ater f or mo st o f the es sen tia l, safety-rel ated equi pmen t us ed f or miti gatin g pl ant acc id ent and tran si ent con di tio ns, reac tor c ool ant pump se al co ol in g, spen t fuel p o o l c o o l i n g, a n d for d i ss i p a ti n g s e n si b l e a n d r e a ct o r d e ca y h e a t d u ri n g s h u td o w n c o n d i ti o n s.

IN 200 7-06 P a g e 3 o f 5 Al so, on PW Rs, the safety rel ated au x il ia ry feedw ater sy stems ty pi cal ly rel y on the E SW sy stem as an emer

g ency mak eup w ater sourc e f or f eeding the ste am gen erat ors. Plant-s

pecif ic prob abi li sti c ri sk asse ssmen ts (P RA s) h av e s how n th at th e l oss of the E SW sy stem may be a si gni fic a n t co n tr i b u to r to t h e p o te n ti a l for a c o re d a ma ge a cc i d e n t. D IS C U S S ION The first

f orei gn ev ent in v ol v ed the f ai lu re to pro perl y pro tect the ex teri or p ip in g surfaces

in the v ic in ity of w el d n eck flanges

that had be en in stal le d to al lo w pe rson nel ac ces s for i nsp ecti ng the i n si d e E S W s y st e m p i p i n g s u rfac e s. The u n p ro te ct e d w e l d n e ck jo i n ts w e re s u b je ct t o corro si on. A ll of the se area s w ere al so sub ject to rou tin e w etti ng of the

unp rotec ted ex teri or surface of w el d n eck are as. In add iti on, NR C staff co ncl ude d th at a funda mental sh ortco min g a s s o c i a t e d w i t h t h e fi r s t fo r e i gn e v e n t w a s t h e u t i l i t y's fa i l u r e t o a d e qu a t e l y t r e n d a n d t a ke app ropri ate corre cti v e a cti on f or a know n d egrade d c ond iti on. D omesti c o pera tin g reacto r pl ants are su bject to Ti tle 10 of the Co de of F ede ral R egu la tio ns (10 CFR) Part 50, Appendix B, Cri teri on XVI, "C orrec tiv e A cti on," w hi ch requi res that prompt and eff ecti v e c orrec tiv e a cti ons be ta ken t o a d d re ss s i gni fic a n t co n d i ti o n s a d v e rs e t o qu a l i ty. The s eco nd f orei gn ev ent al so in v ol v ed the f ai lu re to pro tect the ex teri or p ip in g surface o

f the ES W sy stem. One of the le sso ns le arne d w as to i mpl emen t an i nsp ecti on program th

at in spe cts f or b oth in terna l and ex terna l corro si on. The li cen see al so pai nted the ou tsi de of the ES W pi pes to min imi z e th e p oten tia l f or c orros io n.Do mesti cal ly , a pote nti al ly si mil ar p robl em w as note d d uri ng an N RC i nsp ecti on at th e P oi nt B e a ch fac i l i ty. L i ke th e fi rs t fore i gn e v e n t, t h e l i ce n se e for P o i n t B e a ch d i d n o t ta ke a p p ro p ri a te co rr e ct i v e a ct i o n t o r e so l v e a kn o w n d e gra d e d c o n d i ti o n u n ti l M IC r e su l te d i n a n a ct u a l fai l u re. Al so, li ke the f irs t forei gn ev ent, M IC attac k of the E DG e ndb el ls rep rese nted a common cau se f ai lu re me cha ni sm tha t co ul d re nde r al l of the ED Gs i nop erab le i f no t pro perl y mon ito red and reso lv ed.E S W s y st e ms for U. S. n u cl e a r p o w e r p l a n ts a re ge n e ra l l y u n i que fro m o n e p l a n t to a n o th e r. Ho w ev er, d omesti c E SW sy stems ty pi cal ly i ncl ude pi pi ng sec tio ns that are buri ed and no t read il y ac ces si bl e for i nsp ecti on. B uri ed sec tio ns of pi pi ng can be su bject to p eri odi c w etti ng f rom sto rms or lo cal floo di ng con di tio ns. E x teri or p rotec tiv e c oati ngs may al so not be f ul ly i ntac t due to imp rope r i nsta ll ati on, age d egrada tio n, o r mai nten anc e p racti ces. It is al so pos si bl e for som e ESW piping sect

ions to be located in v

aults or pipe chases that

are subj ect to periodic

f lo odi ng an d/or hi gh hu mid ity tha t ca n c lo sel y mi mic the f orei gn ev ents.

IN 200 7-06 P a g e 4 o f 5 Al so, at S outh Tex as Pro ject U ni t 2, ES W sy stem d egrada tio n l ed to a thro ugh-w al l le ak that ul tima tel y be came an actu al co mmon c aus e fai lu re v ul nera bi li ty. S imi la r ca v ita tio n d amage w as f oun d i n tw o tra in s o f the E SW sy stem a t U ni t 2. P rope r ap pl ic ati on of the reco mmenda tio ns of NR C Generi c L etter (GL) 89-13, "Se rv ic e W ater Sy stem P robl ems A f f ecti ng Sa f ety-Re la ted Eq uipme nt," and 10 CFR Part 50, Appendix B, Criter

ion XVI , "Cor rec tive A ction," like ly w ould h a v e p re v e n te d t h i s e v e n t.RELEVA NT GENERIC CO

MM UNICA T IO NS NR C GL 8 9-13 , "S erv ic e W ater Sy stem P robl ems A f f ecti ng Sa f ety-Re la ted Equi pmen t," da ted Ju l y 1 8 , 1 9 8 9 , re que st e d s p e ci fic l i ce n se e a ct i o n s to r e so l v e S W s y st e m p ro b l e ms. I n parti cul ar, th is GL reco mmende d th at l ic ens ees en sure by a routi ne in spe cti on and mai nten anc e p rogram f or o pen-cy cl e S W sy stem p ip in g and co mpon ents tha t co rrosi on, eros io n p rotec tiv e c oati ng f ai lu re, s il tin g, and bi ofoul in g cann ot d egrade the pe rf ormanc e o f sa fety r e l a te d s y st e ms s u p p l i e d b y s e rv i ce w a te r.NR C GL 9 0-05 , "Gui dan ce f or P erforming Tempora

ry N on-C ode R epa ir of ASM E Co de Cl ass 1, 2, and 3 Piping," dat ed June 15, 1990 , pro vi des g uidance f or Code Class 3 piping.

T w o specif ic f la w ev al uati on app roac hes , as di scu sse d i n E ncl osu re 1 to the GL, sh oul d b e c ons id ered , name ly , the "thro ugh-w al l f la w" an d th e "w al l thi nni ng" ap proa che s.NR C IN 92-4 9, "R ece nt L oss Or S ev ere De gradati on Of S erv ic e W ater Sy stems," date d J ul y 2, 199 2, a le rted li cen see s to se v eral se rv ic e w ater rel ated ev ents , i ncl udi ng on e e v ent that resu lte d i n th e l oss of the ul tima te h eat si nk f or a sh ort p eri od of time.NR C IN 94-7 9, "M ic robi ol ogica ll y Influ enc ed Co rrosi on Of E mergency D ie sel Gen erato r S erv ic e W ater Pi pi ng," da ted No v embe r 23 , 19 94, al erted l ic ens ees tha t sta gnant or i ntermi ttent-flow

co n d i ti o n s, a s i n t h e c a se o f em e rge n cy d i e se l s e rv i ce w a te r su p p l y h e a d e rs , a re c o n d u ci v e t o the grow th o f mi croo rgani sms th at c an acc el erate co rrosi on rates. NU RE G-1275 , V ol ume 3, "Ope rati ng Ex peri enc e F eed bac k Rep ort - Se rv ic e W ater Sy stem Fai lu res and D egrada tio ns in Li ght W ater Re acto rs," (N ov embe r 19 88) summari z es and di scu sse s S W sy stem e v ents from 198 0 to ea rly 19 87.NU RE G-1461 , "R egul atory A nal y si s for the R eso lu tio n o f Gen eri c Is sue 15 3: L oss of Es sen tia l S e rv i ce W a te r i n L W R s," (A u gus t 1 9 9 3) p ro v i d e s a r e v i e w o f i n d u st ry e x p e ri e n ce a n d p l a n t-spe ci f ic P RA s a nd in si ghts rel ated to ES W sy stem v ul nera bi li tie s.

IN 200 7-06 P a g e 5 o f 5 CONTA CT This i nformatio n n oti ce requi res no spe ci f ic ac tio n o r w ritte n re spo nse. P le ase di rect any q u e s t io n s ab o u t t h is m a t t e r t o t h e t e c h n ic a l c o n t a c t s li s t e d be lo w./TQuay for MCa se/

M ic hae l J. C ase , D ire ctor

Di v is io n o f P ol ic y an d R ul emakin g

Of f ic e o f N ucl ear Re acto r R egul ati onT echnical Contac

ts:

Richard A.

Laura, NRR/DIRS

301-415-183 7 E-ma i l: ral 1@n rc.gov

Jam es E. T atum , NRR/DSS

301-415-280 5 E-ma i l: jet1@nrc.gov No te: N RC gene ric co mmuni cati ons may be found on the N RC pu bl ic w eb si te,http://w w w.nrc.gov un der El ectro ni c R ead in g Roo m/Doc umen t C ol le cti ons.

IN 200 7-06 P a g e 5 o f 5 CONTA CT This i nformatio n n oti ce requi res no spe ci f ic ac tio n o r w ritte n re spo nse. P le ase di rect any q u e s t io n s ab o u t t h is m a t t e r t o t h e t e c h n ic a l c o n t a c t s li s t e d be lo w./TQuay for MCa se/

M ic hae l J. C ase , D ire ctor

Di v is io n o f P ol ic y an d R ul emakin g

Of f ic e o f N ucl ear Re acto r R egul ati onT echnical Contac

ts:

Richard A.

Laura, NRR/DIRS

301-415-183 7 E-ma i l: ral 1@n rc.gov

Jam es E. T atum , NRR/DSS

301-415-280 5 E-ma i l: jet1@nrc.gov No te: N RC gene ric co mmuni cati ons may be found on the N RC pu bl ic w eb si te,http://w w w.nrc.gov un der El ectro ni c R ead in g Roo m/Doc umen t C ol le cti ons.AD AM S Accessi on N umber: M L0628 40608 OFFICE

DIRS:IOEB

Tech.Edi tor

BC:DSS:SBPB

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PGCB:DPR N A ME

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10/27/2 006 OFFICE

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02/0 9/20 07 OF FICI A L RECORD COPY