ML071070371

Evaluation of the 2005 Steam Generator Tube Inspections Performed During the Refueling Outage (1RF11)

ML071070371
Person / Time
Site:	Comanche Peak
Issue date:	05/02/2007
From:	Thadani M C NRC/NRR/ADRO/DORL/LPLIV
To:	Blevins M R TXU Power
Thadani, M C, NRR/DORL/LP4, 415-1476
References
TAC MD1837
Download: ML071070371 (6)

Text

May 2, 2007 Mr. M. R. B le v in s S e n io r V ic e P re s id e n t & Chi ef N uclear O ffi cer T XU Po w er At tn: Regul atory A ffai rs D epartm ent P. O. B ox 1002 Gl en Rose, TX 76043 SUB JECT:

CO MA NC HE PEA K STEA M ELEC TRI C STA TIO N, UN IT 1 -EVA LUA TIO N O F THE 200 5 S T E AM G E NE RAT OR T UBE INS P E CT ION S P E RF ORME D DUR ING T HE RE F UE L ING OUT AGE (1R F11) (TA C N O. MD 1837) Dear Mr. Blevin s: By lett ers dated N ovember 7, 2005, and Febr uary 3, Mar ch 1, and June 12, 2006 , TXU Gene rati on Co mpan y LP (the l ic ens ee) sub mitted i nformatio n s ummari z in g the resu lts of the 20 05 stea m genera tor tu be in spe cti ons at Co manch e P eak S team El ectri c S tati on, U n i t 1. Th e se i n sp e ct i o n s w e re p e rfor me d d u ri n g th e e l e v e n th r e fue l i n g o u ta ge (1 R F 1 1). In a ddi tio n, th e U.S. Nu cl ear Re gula tory C ommis si on (NR C) staff pre v io usl y su mmariz ed add iti ona l in f ormati on con cern in g the 200 5 s team genera tor tu be in spe cti ons at Co manch e P eak Ste am E le ctri c S tati on, Un it 1, i n a l etter date d M ay 18 , 20 06.Ba sed on a rev ie w of the i nformatio n p rov id ed and the M ay 18 , 20 06, NR C staff su mmary , the NR C staff co ncl ude s th at th e l ic ens ee prov id ed the in f ormati on requi red by i ts te chn ic al spe ci f ic ati ons. In ad di tio n, th e N RC sta f f co ncl ude s th at th ere are no tech ni cal i ssu es that w arran t foll ow-up acti on si nce the l ic ens ee's i nsp ecti ons ap pea red to b e c ons is tent w ith the obje cti v e o f de tecti ng po tenti al tub e d egrada tio n, a nd the in spe cti on resu lts ap pea red to b e con si sten t w ith i ndu stry op erati ng ex peri enc e a t si mil arl y de si gned and op erate d u ni ts.

Sin ce rely ,/RA/M oha n C. Thad ani , Seni or Proj ect M anager P l a n t L i ce n si n g B ra n ch I V Di v is io n o f Ope rati ng Re acto r Li cen si ng

Of fi ce of N uclear R eactor R egulati on Docket No. 50-445

Enclosure:

As st ated cc w/encl: See next page M ay 2, 200 7 M r. M. R. B le v in s Senior Vice President

& C hi ef Nuc le ar Off ic er TX U Po w er Attn: R egul atory A f f ai rs D epa rtment P. O. Bo x 10 02 Gle n R ose , TX 76 043 S U B JE C T:

C OM A N C H E P E A K S TE A M E L E C TR IC S TA TION , U N IT 1 - E V A L U A TION OF T HE 2005 STEAM GENERAT OR T UBE INSPECT IO NS PERFORM ED DURING TH E R E F U E L IN G OU TA GE (1 R F 1 1) (TA C N O. M D 1 8 3 7) De ar M r. B le v in s: B y l e tt e rs d a te d N o v e mb e r 7 , 2 0 0 5 , a n d F e b ru a ry 3 , M a rc h 1 , a n d J u n e 1 2 , 2 0 0 6 , TXU Genera tio n C ompa ny LP (the l ic ens ee) sub mitted i nformatio n s ummari z in g the resu lts of the 2 0 0 5 s te a m ge n e ra to r tu b e i n sp e ct i o n s a t C o ma n ch e P e a k S te a m E l e ct ri c S ta ti o n , U n i t 1. The se i n sp e ct i o n s w e re p e rfor me d d u ri n g th e e l e v e n th r e fue l i n g o u ta ge (1 R F 1 1). In a ddi tio n, th e U.S. Nu cl ear Re gula tory C ommis si on (NR C) staff pre v io usl y su mmariz ed add iti ona l in f ormati on con cern in g the 200 5 s team genera tor tu be in spe cti ons at Co manch e P eak Ste am E le ctri c S tati on, Un it 1, i n a l etter date d M ay 18 , 20 06.Ba sed on a rev ie w of the i nformatio n p rov id ed and the M ay 18 , 20 06, NR C staff su mmary , the NR C staff co ncl ude s th at th e l ic ens ee prov id ed the in f ormati on requi red by i ts te chn ic al spe ci f ic ati ons. In ad di tio n, th e N RC sta f f co ncl ude s th at th ere are no tech ni cal i ssu es that w arran t foll ow-up acti on si nce the l ic ens ee's i nsp ecti ons ap pea red to b e c ons is tent w ith the obje cti v e o f de tecti ng po tenti al tub e d egrada tio n, a nd the in spe cti on resu lts ap pea red to b e con si sten t w ith i ndu stry op erati ng ex peri enc e a t si mil arl y de si gned and op erate d u ni ts.

Sin ce r ely,/R A/

M oha n C. Thad ani , S eni or P roject M ana ger P l a n t L i ce n si n g B ra n ch I V Di v is io n o f Ope rati ng Re acto r Li cen si ng Of f ic e o f N ucl ear Re acto r R egul ati on Do cket No. 50-445 En cl osu re: As state d c c w/e n c l: S e e n e x t p a ge DIS T RIB UT ION P U B L ICRi dsN rrPM M Thada niLP LIV R ead in gRi dsN rrLA LFe iz ol la hiRidsNrr DorlLpl4R i d s Og c R p R i d s R gn 4 M a i l C e n t e r R i d s N r r D c i C s gb Ri dsA crsA cnwM ail Cent er K K a r w o s ki , NR RAC CE SS ION N O: M L07 107 037 1 OF FICE NRR/LPL4/PM NRR/LPL4/LA NRR/CSG/BC NRR/LPL4/BC N A M E M Tha d a n i L F e i z o l l a h i A H i se r TH i l tz DA TE 4/19/07 4/19/07 4/30/07 5/1/07 OFFI CI AL R ECO RD CO PY De cembe r 20 04 Com anche Peak Steam Elect ri c Stati on cc: Senior R esident Inspector U.S. Nuc lea r Reg ula tory Com mi ssion P.O. B ox 2159 Gl en Rose, TX 76403-2159 Regio na l Adminis trat or, Re gio n IV U.S. Nuc lea r Reg ula tory Com mi ssion 611 Ryan Pl aza Dr ive, Suite 400 Ar li ngton, TX 76011 Mr. Fred W. M adden, D ir ector Regu lato ry Affa irs TXU Gener ati on Com pany LP P.O. B ox 1002 Gl en Rose, TX 76043 Geor ge L. Edgar, Esq.Mo rg a n L e wi s 1 1 1 1 P e n n s y lv a n ia Av e n u e , NW Washi ngton, D C 20004 Count y Judge P.O. B ox 851 Gl en Rose, TX 76043 E n v ir o n me n ta l a n d Na tu ra l Resour ces Poli cy Di rector Of fi ce of the G overnor P.O. B ox 12428 Aus ti n, TX 78711-3189 Mr. R ichard A. R atl if f, Chi ef Bur eau of R adiati on Cont rol Te xa s Dep artme nt o f Hea lth 1100 West 49t h Street Aus ti n, TX 78756-3189 Mr. B ri an Al mon Publi c Ut il it y C omm issi on Wi ll iam B. Travi s B uil ding P.O. B ox 13326 1701 Nor th C ongress A venue Aus ti n, TX 78701-3326 Ms. Susan M. Jablonski Of fi ce of Perm it ti ng, R emedi ati on and Regi str ati on Texas Com mi ssion on Envir onmental Qua lity MC-122 P.O. B ox 13087 Aus ti n, TX 78711-3087 Terry Par ks, C hief Inspector Texas Depar tm ent of Li censing and Regul ati on Boi ler Program P.O. B ox 12157 Aus ti n, TX 78711 ENCLOSURESUM MA RY OF STA FF'S R EVI EWCO MA NC HE PEA K STEA M ELEC TRI C STA TIO N, UN IT 12 0 0 5 S T E AM G E NE RAT OR T UBE IN S P E CT ION STAC NO. M D1837DO CK ET NO. 50-445 By lett ers dated N ovember 7 2005, and February 3, Mar ch 1, and June 12, 2006 (Agenc y w id e D ocu ments Acc ess an d M ana gement S y stem (A DA M S) Acc ess io n No s. M L0 53 20 00 44 , M L0 60 41 01 71 , M L0 60 67 04 45 , M L0 61 72 00 32 , re sp ec t ively), T XU Gener ati on Com pany LP (the l icensee) submi tted i nform ati on summ ari zing t he resul ts of t he 2005 steam generat or tube i nspecti ons at C omanche Peak Ste am E lec tric S tatio n (Co man ch e P ea k), Un it 1. T he se ins pe ctio ns were p e rf o rm e d d u ri n g th e e le v e n th re fu e li n g o u ta g e (1 RF 1 1). In a d d it io n , t h e U.S. Nu c le a r R e g u la to ry Co mm is s io n (N RC) s ta ff p re v io u s ly summ ari zed additi onal i nform ati on concerning t he 2005 steam generat or tube in s p e c ti o n s a t C o ma n c h e P e a k , Un it 1 , i n a le tt e r d a te d Ma y 1 8 , 2 0 0 6 (A DAMS Acce ssio n No. ML0 61 10 00 59).Com anche Peak, U nit 1, has four West inghouse m odel D 4 recir culati ng steam ge ne rato rs.Each steam gener ator cont ains 4, 578 mi ll annealed A ll oy 600 tubes. Each tu b e h a s a n o mi n a l o u ts id e d ia me te r o f 0.7 5 in c h a n d a n o mi n a l w a ll th ic k n e s s o f 0.0 4 3 in c h. Ap p ro x im a te ly 9 0 p e rc e n t o f t h e tu b e s a re h a rd ro ll-expanded for the f ull depth of the t ubesheet at each end, and t he remai ning 10 percent of t he tubes wer e explosi vely expanded (w it h the WEX TEX pro ce ss) for the full d ep th o f the tub es he et a t ea ch en d. T he tub es are su pp orte d b y a nu mbe r of ca rbo n s tee l tub e s up po rt p late s with circ ula r-shaped holes and V-shaped chrom e-pl ated A ll oy 600 anti-vibr ati on bars. The li censee is author ized t o im plem ent the vol tage-bas ed tube repai r cri teri a for de gra da tion at t he tub e s up po rt p late s (a s d isc us se d in Gen eric Le tter 95-05), and an F-star (F*) tube repai r cri teri a for degr adation obser ved below the expansion tr ansit ion for the tubes t hat have been hardrol l-expanded into t he tub es he et.

A t otal of 736 tungst en inert gas (TIG)-wel ded sleeves w ere ins tal led duri ng the 1R F9 outage (f all 2002) in st eam generat ors 2, 3, and 4. N o TIG-w elded sleeves w ere ins tal led duri ng 1RF10 (spri ng 2004); how ever, a total of 547 All o y 8 0 0 le a k-l im it in g s le e v e s we re in s ta ll e d d u ri n g 1 RF 1 0. Ap p ro x im a te ly on e-h alf (2 70) of the tub es sle ev ed du ring 1RF1 0 we re p rev iou sly ou t-of-servi ce and were de-plugged pri or to sl eeving. No sl eeves wer e inst all ed du ring 1RF1 1 (fa ll 20 05).The Westi nghouse model D 4 steam gener ators have si nce been replaced at the ongoing r efuel ing outage (1RF12) expected to be compl eted in A pri l 2007.The li censee provided t he scope, extent , m ethods, and result s of thei r steam generator tube inspect ions i n the document s refer enced above. In addi ti on, th e li c e n s e e d e s c ri b e d c o rr e c ti v e a c ti o n s (i.e., tu b e p lu g g in g) t a k e n in res po ns e to the ins pe ctio n fin din gs. All fou r ste am g en era tors were inspect ed during 1R F11. As a result of the r eview of the r eports, the N RC staff has the fol low ing co mmen ts/o bs erv atio ns:A num ber of TI G-wel ded sleeves w ere found t o be ovali zed duri ng the 1RF1 0 (s prin g 2 00 4) in sp ec tion s. T he tub es with th es e potenti all y coll apsed sleeves w ere plugged (approxim atel y 60 tub es). Durin g 1 RF11 , an ad ditio na l 7 T IG-welde d s lee ve s we re found to be col lapsed. None of the A ll oy 800 sleeves w ere found to b e c olla ps ed. Th e lic en se e in dic ate d th at t he inte rna l pre ssu re tha t re su lts in sle ev e c olla ps e is no t su fficie nt t o p ull th e s lee ve awa y fro m the tub e in the ex pa nd ed reg ion of t he lowe r sle ev e join t sin ce the mate rial is co ld wo rke d b y th e e xp an sio n p roc es s a n d th e re s u lt a n t s ti ff n e s s a n d re s id u a l c o n ta c t f o rc e s p re s e n t i n the joi nt w il l precl ude sleeve col lapse i n the expanded region of the low er sl eeve joi nt. The basis for these stat ements was not provi ded.It w as indi cated that one tube had signi fi cantly higher +Point TM amp litud es tha n a no the r tu be an d th us the flaw d ep ths were deeper. I n research sponsor ed by the N RC , t here is data that in d ic a te s th a t t h e d e e p e s t p a rt o f a fl a w d o e s n o t n e c e s s a ri ly co rres po nd to t he pe ak amp litud e in the ed dy cu rren t sig na l. As a re s u lt , i t i s im p o rt a n t t o u n d e rs ta n d th e li mi ta ti o n s in s iz in g fl a ws when deter mi ning thei r acceptabi li ty (f or conti nued servi ce, for in-sit u pressure t esti ng, and for confir mi ng that t he perfor mance cri teri a wer e sati sfi ed). In the case of C omanche Peak, t wo t ubes wer e selected f or in-sit u pressure t esti ng during 1R F11: the longest fl aw and the f law wi th the l argest +Point ampl it ude.TMAl though the st aff di d not revi ew t he conditi on moni tori ng acceptance li mi ts or t he tube int egri ty assessm ent met hodology in detai l, the li mi ts and the general approach appeared reasonable.

Al though the pri mar y wat er str ess-cor rosi on cracking w as observed i n the U-bend regi on of a row 13 tube in 1R F10 (spri ng 20 04), the larg es t ra diu s tu be in wh ich prima ry wa ter stre ss corrosi on cracking w as identi fi ed in the U-bend regi on during 1RF11 (fal l 2005) w as in row 5. The number of tubes ident if ied w it h circum ferent ial outsi de diam eter st ress-corrosi on cracking dur ing 1R F11 was l ess than that obser ved during t he prior outage. Si mi lar ly, the number of tubes i dentif ied w it h outsi de diam eter st ress-corrosi on cracking at dings dur ing 1R F11 was l ess than that observed duri ng the pri or outage.

The number of t ubes identi fi ed wi th fr ee-span outsi de diam eter st ress-corrosi on cracking, however , i ncreased whe n c omp are d to the prio r ou tag e. All th ree of t he se degradati on mechanis ms w ere plugged on detect ion.One t ube was i dentif ied w it h an axiall y ori ented outsi de diam eter str ess-cor rosi on crack approxim atel y 2.5 i nches below the top of the tubesheet. G iven t hat the t ube is expanded to the t op of the tu b e s h e e t, th e li c e n s e e q u e s ti o n e d th e v a li d it y o f t h e in d ic a ti o n. Since thi s indi cati on was bel ow t he F* dist ance, i t w as permi tted to rem ain i n servi ce.In re sp on se to a n NRC req ue st fo r ad ditio na l info rmatio n (re fer t o the response t o question 3 i n the June 12, 2006 let ter), t he li censee indi cated the ter m "upper bound" was def ined by the probabil it y and confidence l evel appl ied to t he parti cular evaluat ion. In fol low-up com muni cati ons, i t w as clar if ied that alt hough the probabil it y and confidence l evels w ere high, the ac tua l rep orte d b urs t pr es su re wa s a "lowe r bo un d" bu rst p re s s u re wi th a h ig h p ro b a b il it y/c o n fi d e n c e le v e l, wh ic h is conservati ve.Ba s e d o n a re v ie w o f t h e in fo rm a ti o n p ro v id e d a n d th e Ma y 1 8 , 2 0 0 6 , NR C staf f sum mar y, t he NR C s taff concludes that the li censee provided t he in fo rm a ti o n re q u ir e d b y it s te c h n ic a l s p e c if ic a ti o n s. I n a d d it io n , t h e NRC staf f concludes t hat ther e are no technical issues t hat w arrant fol low-up acti on since the l icensee's inspect ions appeared t o be consistent wi th the ob jec tive of d ete ctin g p ote ntia l tub e d eg rad atio n, a nd the ins pe ctio n re su lts a p p e a re d to b e c o n s is te n t w it h in d u s tr y o p e ra ti n g e x p e ri e n c e a t s im il a rl y de sig ne d a nd op era ted un its. P r i n c i p a l C o n t r i b u t o r: K. K a r w o s ki Da te: M ay 2, 200 7