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| issue date = 05/02/2007
| issue date = 05/02/2007
| title = Evaluation of the 2005 Steam Generator Tube Inspections Performed During the Refueling Outage (1RF11)
| title = Evaluation of the 2005 Steam Generator Tube Inspections Performed During the Refueling Outage (1RF11)
| author name = Thadani M C
| author name = Thadani M
| author affiliation = NRC/NRR/ADRO/DORL/LPLIV
| author affiliation = NRC/NRR/ADRO/DORL/LPLIV
| addressee name = Blevins M R
| addressee name = Blevins M
| addressee affiliation = TXU Power
| addressee affiliation = TXU Power
| docket = 05000445
| docket = 05000445
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=Text=
=Text=
{{#Wiki_filter: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:
{{#Wiki_filter:May 2, 2007 Mr. M. R. Blevins Senior Vice President &
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.
Chief Nuclear Officer TXU Power Attn: Regulatory Affairs Department P. O. Box 1002 Glen Rose, TX 76043
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  
==SUBJECT:==
COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 -
EVALUATION OF THE 2005 STEAM GENERATOR TUBE INSPECTIONS PERFORMED DURING THE REFUELING OUTAGE (1RF11) (TAC NO. MD1837)
 
==Dear Mr. Blevins:==
 
By letters dated November 7, 2005, and February 3, March 1, and June 12, 2006, TXU Generation Company LP (the licensee) submitted information summarizing the results of the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station, Unit 1. These inspections were performed during the eleventh refueling outage (1RF11).
In addition, the U.S. Nuclear Regulatory Commission (NRC) staff previously summarized additional information concerning the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station, Unit 1, in a letter dated May 18, 2006.
Based on a review of the information provided and the May 18, 2006, NRC staff summary, the NRC staff concludes that the licensee provided the information required by its technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action since the licensees inspections appeared to be consistent with the objective of detecting potential tube degradation, and the inspection results appeared to be consistent with industry operating experience at similarly designed and operated units.
Sincerely,
                                                /RA/
Mohan C. Thadani, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing
 
Office of Nuclear Reactor Regulation Docket No. 50-445
 
==Enclosure:==
As stated cc w/encl: See next page
 
May 2, 2007 Mr. M. R. Blevins Senior Vice President &
Chief Nuclear Officer TXU Power Attn: Regulatory Affairs Department P. O. Box 1002 Glen Rose, TX 76043
 
==SUBJECT:==
COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 - EVALUATION OF THE 2005 STEAM GENERATOR TUBE INSPECTIONS PERFORMED DURING THE REFUELING OUTAGE (1RF11) (TAC NO. MD1837)
 
==Dear Mr. Blevins:==
 
By letters dated November 7, 2005, and February 3, March 1, and June 12, 2006, TXU Generation Company LP (the licensee) submitted information summarizing the results of the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station, Unit 1.
These inspections were performed during the eleventh refueling outage (1RF11).
In addition, the U.S. Nuclear Regulatory Commission (NRC) staff previously summarized additional information concerning the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station, Unit 1, in a letter dated May 18, 2006.
Based on a review of the information provided and the May 18, 2006, NRC staff summary, the NRC staff concludes that the licensee provided the information required by its technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action since the licensees inspections appeared to be consistent with the objective of detecting potential tube degradation, and the inspection results appeared to be consistent with industry operating experience at similarly designed and operated units.
Sincerely,
                                                      /RA/
Mohan C. Thadani, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-445


==Enclosure:==
==Enclosure:==
As stated cc w/encl: See next page DISTRIBUTION PUBLIC                                RidsNrrPMMThadani LPLIV Reading                          RidsNrrLALFeizollahi                RidsNrrDorlLpl4 RidsOgcRp                              RidsRgn4MailCenter                  RidsNrrDciCsgb RidsAcrsAcnwMailCenter                        KKarwoski, NRR ACCESSION NO: ML071070371 OFFICE      NRR/LPL4/PM        NRR/LPL4/LA        NRR/CSG/BC        NRR/LPL4/BC NAME        MThadani            LFeizollahi        AHiser            THiltz DATE        4/19/07            4/19/07            4/30/07          5/1/07
OFFICIAL RECORD COPY Comanche Peak Steam Electric Station cc:
Senior Resident Inspector            Mr. Richard A. Ratliff, Chief U.S. Nuclear Regulatory              Bureau of Radiation Control Commission                          Texas Department of Health P.O. Box 2159                        1100 West 49th Street Glen Rose, TX 76403-2159            Austin, TX 78756-3189 Regional Administrator, Region IV    Mr. Brian Almon U.S. Nuclear Regulatory              Public Utility Commission Commission                          William B. Travis Building 611 Ryan Plaza Drive, Suite 400      P.O. Box 13326 Arlington, TX 76011                  1701 North Congress Avenue Austin, TX 78701-3326 Mr. Fred W. Madden, Director Regulatory Affairs                  Ms. Susan M. Jablonski TXU Generation Company LP            Office of Permitting, Remediation P.O. Box 1002                        and Registration Glen Rose, TX 76043                  Texas Commission on Environmental George L. Edgar, Esq.                Quality Morgan Lewis                        MC-122 1111 Pennsylvania Avenue, NW        P.O. Box 13087 Washington, DC 20004                Austin, TX 78711-3087 County Judge                        Terry Parks, Chief Inspector P.O. Box 851                        Texas Department of Licensing Glen Rose, TX 76043                  and Regulation Boiler Program Environmental and Natural            P.O. Box 12157 Resources Policy Director          Austin, TX 78711 Office of the Governor P.O. Box 12428 Austin, TX 78711-3189 December 2004
==SUMMARY==
OF STAFFS REVIEW COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 2005 STEAM GENERATOR TUBE INSPECTIONS TAC NO. MD1837 DOCKET NO. 50-445 By letters dated November 7 2005, and February 3, March 1, and June 12, 2006 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML053200044, ML060410171, ML060670445, ML061720032, respectively), TXU Generation Company LP (the licensee) submitted information summarizing the results of the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station (Comanche Peak), Unit 1. These inspections were performed during the eleventh refueling outage (1RF11).
In addition, the U.S. Nuclear Regulatory Commission (NRC) staff previously summarized additional information concerning the 2005 steam generator tube inspections at Comanche Peak, Unit 1, in a letter dated May 18, 2006 (ADAMS Accession No. ML061100059).
Comanche Peak, Unit 1, has four Westinghouse model D4 recirculating steam generators.
Each steam generator contains 4,578 mill annealed Alloy 600 tubes. Each tube has a nominal outside diameter of 0.75 inch and a nominal wall thickness of 0.043 inch. Approximately 90 percent of the tubes are hardroll-expanded for the full depth of the tubesheet at each end, and the remaining 10 percent of the tubes were explosively expanded (with the WEXTEX process) for the full depth of the tubesheet at each end. The tubes are supported by a number of carbon steel tube support plates with circular-shaped holes and V-shaped chrome-plated Alloy 600 anti-vibration bars. The licensee is authorized to implement the voltage-based tube repair criteria for degradation at the tube support plates (as discussed in Generic Letter 95-05),
and an F-star (F*) tube repair criteria for degradation observed below the expansion transition for the tubes that have been hardroll-expanded into the tubesheet.
ENCLOSURE
A total of 736 tungsten inert gas (TIG)-welded sleeves were installed during the 1RF9 outage (fall 2002) in steam generators 2, 3, and 4. No TIG-welded sleeves were installed during 1RF10 (spring 2004); however, a total of 547 Alloy 800 leak-limiting sleeves were installed during 1RF10. Approximately one-half (270) of the tubes sleeved during 1RF10 were previously out-of-service and were de-plugged prior to sleeving. No sleeves were installed during 1RF11 (fall 2005).
The Westinghouse model D4 steam generators have since been replaced at the ongoing refueling outage (1RF12) expected to be completed in April 2007.
The licensee provided the scope, extent, methods, and results of their steam generator tube inspections in the documents referenced above. In addition, the licensee described corrective actions (i.e., tube plugging) taken in response to the inspection findings. All four steam generators were inspected during 1RF11.
As a result of the review of the reports, the NRC staff has the following comments/observations:
A number of TIG-welded sleeves were found to be ovalized during the 1RF10 (spring 2004) inspections. The tubes with these potentially collapsed sleeves were plugged (approximately 60 tubes). During 1RF11, an additional 7 TIG-welded sleeves were found to be collapsed. None of the Alloy 800 sleeves were found to be collapsed. The licensee indicated that the internal pressure that results in sleeve collapse is not sufficient to pull the sleeve away from the tube in the expanded region of the lower sleeve joint since the material is cold worked by the expansion process and the resultant stiffness and residual contact forces present in the joint will preclude sleeve collapse in the expanded region of the lower sleeve joint. The basis for these statements was not provided.
It was indicated that one tube had significantly higher +PointTM amplitudes than another tube and thus the flaw depths were deeper. In research sponsored by the NRC, there is data that indicates that the deepest part of a flaw does not necessarily correspond to the peak amplitude in the eddy current signal. As a result, it is important to understand the limitations in sizing flaws when determining their acceptability (for continued service, for in-situ pressure testing, and for confirming that the performance criteria were satisfied). In the case of Comanche Peak, two tubes were selected for in-situ pressure testing during 1RF11: the longest flaw and the flaw with the largest +PointTM amplitude.
Although the staff did not review the condition monitoring acceptance limits or the tube integrity assessment methodology in detail, the limits and the general approach appeared reasonable.
Although the primary water stress-corrosion cracking was observed in the U-bend region of a row 13 tube in 1RF10 (spring 2004), the largest radius tube in which primary water stress corrosion cracking was identified in the U-bend region during 1RF11 (fall 2005) was in row 5.
The number of tubes identified with circumferential outside diameter stress-corrosion cracking during 1RF11 was less than that observed during the prior outage. Similarly, the number of tubes identified with outside diameter stress-corrosion cracking at dings during 1RF11 was less than that observed during the prior outage. The number of tubes identified with free-span outside diameter stress-corrosion cracking, however, increased when compared to the prior outage. All three of these degradation mechanisms were plugged on detection.
One tube was identified with an axially oriented outside diameter stress-corrosion crack approximately 2.5 inches below the top of the tubesheet. Given that the tube is expanded to the top of the tubesheet, the licensee questioned the validity of the indication.
Since this indication was below the F* distance, it was permitted to remain in service.
In response to an NRC request for additional information (refer to the response to question 3 in the June 12, 2006 letter), the licensee indicated the term upper bound was defined by the probability and confidence level applied to the particular evaluation. In follow-up communications, it was clarified that although the probability and confidence levels were high, the actual reported burst pressure was a lower bound burst pressure with a high probability/confidence level, which is conservative.
Based on a review of the information provided and the May 18, 2006, NRC staff summary, the NRC staff concludes that the licensee provided the information required by its technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action since the licensees inspections appeared to be consistent with the objective of detecting potential tube degradation, and the inspection results appeared to be consistent with industry operating experience at similarly designed and operated units.


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
Principal Contributor: K. Karwoski Date: May 2, 2007}}
&    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}}

Latest revision as of 08:20, 23 November 2019

Evaluation of the 2005 Steam Generator Tube Inspections Performed During the Refueling Outage (1RF11)
ML071070371
Person / Time
Site: Comanche Peak Luminant icon.png
Issue date: 05/02/2007
From: Thadani M
NRC/NRR/ADRO/DORL/LPLIV
To: Blevins M
TXU Power
Thadani, M C, NRR/DORL/LP4, 415-1476
References
TAC MD1837
Download: ML071070371 (6)
v • d • e


Text

May 2, 2007 Mr. M. R. Blevins Senior Vice President &

Chief Nuclear Officer TXU Power Attn: Regulatory Affairs Department P. O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 -

EVALUATION OF THE 2005 STEAM GENERATOR TUBE INSPECTIONS PERFORMED DURING THE REFUELING OUTAGE (1RF11) (TAC NO. MD1837)

Dear Mr. Blevins:

By letters dated November 7, 2005, and February 3, March 1, and June 12, 2006, TXU Generation Company LP (the licensee) submitted information summarizing the results of the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station, Unit 1. These inspections were performed during the eleventh refueling outage (1RF11).

In addition, the U.S. Nuclear Regulatory Commission (NRC) staff previously summarized additional information concerning the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station, Unit 1, in a letter dated May 18, 2006.

Based on a review of the information provided and the May 18, 2006, NRC staff summary, the NRC staff concludes that the licensee provided the information required by its technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action since the licensees inspections appeared to be consistent with the objective of detecting potential tube degradation, and the inspection results appeared to be consistent with industry operating experience at similarly designed and operated units.

Sincerely,

/RA/

Mohan C. Thadani, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing

Office of Nuclear Reactor Regulation Docket No. 50-445

Enclosure:

As stated cc w/encl: See next page

May 2, 2007 Mr. M. R. Blevins Senior Vice President &

Chief Nuclear Officer TXU Power Attn: Regulatory Affairs Department P. O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 - EVALUATION OF THE 2005 STEAM GENERATOR TUBE INSPECTIONS PERFORMED DURING THE REFUELING OUTAGE (1RF11) (TAC NO. MD1837)

Dear Mr. Blevins:

By letters dated November 7, 2005, and February 3, March 1, and June 12, 2006, TXU Generation Company LP (the licensee) submitted information summarizing the results of the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station, Unit 1.

These inspections were performed during the eleventh refueling outage (1RF11).

In addition, the U.S. Nuclear Regulatory Commission (NRC) staff previously summarized additional information concerning the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station, Unit 1, in a letter dated May 18, 2006.

Based on a review of the information provided and the May 18, 2006, NRC staff summary, the NRC staff concludes that the licensee provided the information required by its technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action since the licensees inspections appeared to be consistent with the objective of detecting potential tube degradation, and the inspection results appeared to be consistent with industry operating experience at similarly designed and operated units.

Sincerely,

/RA/

Mohan C. Thadani, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-445

Enclosure:

As stated cc w/encl: See next page DISTRIBUTION PUBLIC RidsNrrPMMThadani LPLIV Reading RidsNrrLALFeizollahi RidsNrrDorlLpl4 RidsOgcRp RidsRgn4MailCenter RidsNrrDciCsgb RidsAcrsAcnwMailCenter KKarwoski, NRR ACCESSION NO: ML071070371 OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/CSG/BC NRR/LPL4/BC NAME MThadani LFeizollahi AHiser THiltz DATE 4/19/07 4/19/07 4/30/07 5/1/07

OFFICIAL RECORD COPY Comanche Peak Steam Electric Station cc:

Senior Resident Inspector Mr. Richard A. Ratliff, Chief U.S. Nuclear Regulatory Bureau of Radiation Control Commission Texas Department of Health P.O. Box 2159 1100 West 49th Street Glen Rose, TX 76403-2159 Austin, TX 78756-3189 Regional Administrator, Region IV Mr. Brian Almon U.S. Nuclear Regulatory Public Utility Commission Commission William B. Travis Building 611 Ryan Plaza Drive, Suite 400 P.O. Box 13326 Arlington, TX 76011 1701 North Congress Avenue Austin, TX 78701-3326 Mr. Fred W. Madden, Director Regulatory Affairs Ms. Susan M. Jablonski TXU Generation Company LP Office of Permitting, Remediation P.O. Box 1002 and Registration Glen Rose, TX 76043 Texas Commission on Environmental George L. Edgar, Esq. Quality Morgan Lewis MC-122 1111 Pennsylvania Avenue, NW P.O. Box 13087 Washington, DC 20004 Austin, TX 78711-3087 County Judge Terry Parks, Chief Inspector P.O. Box 851 Texas Department of Licensing Glen Rose, TX 76043 and Regulation Boiler Program Environmental and Natural P.O. Box 12157 Resources Policy Director Austin, TX 78711 Office of the Governor P.O. Box 12428 Austin, TX 78711-3189 December 2004

SUMMARY

OF STAFFS REVIEW COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 2005 STEAM GENERATOR TUBE INSPECTIONS TAC NO. MD1837 DOCKET NO. 50-445 By letters dated November 7 2005, and February 3, March 1, and June 12, 2006 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML053200044, ML060410171, ML060670445, ML061720032, respectively), TXU Generation Company LP (the licensee) submitted information summarizing the results of the 2005 steam generator tube inspections at Comanche Peak Steam Electric Station (Comanche Peak), Unit 1. These inspections were performed during the eleventh refueling outage (1RF11).

In addition, the U.S. Nuclear Regulatory Commission (NRC) staff previously summarized additional information concerning the 2005 steam generator tube inspections at Comanche Peak, Unit 1, in a letter dated May 18, 2006 (ADAMS Accession No. ML061100059).

Comanche Peak, Unit 1, has four Westinghouse model D4 recirculating steam generators.

Each steam generator contains 4,578 mill annealed Alloy 600 tubes. Each tube has a nominal outside diameter of 0.75 inch and a nominal wall thickness of 0.043 inch. Approximately 90 percent of the tubes are hardroll-expanded for the full depth of the tubesheet at each end, and the remaining 10 percent of the tubes were explosively expanded (with the WEXTEX process) for the full depth of the tubesheet at each end. The tubes are supported by a number of carbon steel tube support plates with circular-shaped holes and V-shaped chrome-plated Alloy 600 anti-vibration bars. The licensee is authorized to implement the voltage-based tube repair criteria for degradation at the tube support plates (as discussed in Generic Letter 95-05),

and an F-star (F*) tube repair criteria for degradation observed below the expansion transition for the tubes that have been hardroll-expanded into the tubesheet.

ENCLOSURE

A total of 736 tungsten inert gas (TIG)-welded sleeves were installed during the 1RF9 outage (fall 2002) in steam generators 2, 3, and 4. No TIG-welded sleeves were installed during 1RF10 (spring 2004); however, a total of 547 Alloy 800 leak-limiting sleeves were installed during 1RF10. Approximately one-half (270) of the tubes sleeved during 1RF10 were previously out-of-service and were de-plugged prior to sleeving. No sleeves were installed during 1RF11 (fall 2005).

The Westinghouse model D4 steam generators have since been replaced at the ongoing refueling outage (1RF12) expected to be completed in April 2007.

The licensee provided the scope, extent, methods, and results of their steam generator tube inspections in the documents referenced above. In addition, the licensee described corrective actions (i.e., tube plugging) taken in response to the inspection findings. All four steam generators were inspected during 1RF11.

As a result of the review of the reports, the NRC staff has the following comments/observations:

A number of TIG-welded sleeves were found to be ovalized during the 1RF10 (spring 2004) inspections. The tubes with these potentially collapsed sleeves were plugged (approximately 60 tubes). During 1RF11, an additional 7 TIG-welded sleeves were found to be collapsed. None of the Alloy 800 sleeves were found to be collapsed. The licensee indicated that the internal pressure that results in sleeve collapse is not sufficient to pull the sleeve away from the tube in the expanded region of the lower sleeve joint since the material is cold worked by the expansion process and the resultant stiffness and residual contact forces present in the joint will preclude sleeve collapse in the expanded region of the lower sleeve joint. The basis for these statements was not provided.

It was indicated that one tube had significantly higher +PointTM amplitudes than another tube and thus the flaw depths were deeper. In research sponsored by the NRC, there is data that indicates that the deepest part of a flaw does not necessarily correspond to the peak amplitude in the eddy current signal. As a result, it is important to understand the limitations in sizing flaws when determining their acceptability (for continued service, for in-situ pressure testing, and for confirming that the performance criteria were satisfied). In the case of Comanche Peak, two tubes were selected for in-situ pressure testing during 1RF11: the longest flaw and the flaw with the largest +PointTM amplitude.

Although the staff did not review the condition monitoring acceptance limits or the tube integrity assessment methodology in detail, the limits and the general approach appeared reasonable.

Although the primary water stress-corrosion cracking was observed in the U-bend region of a row 13 tube in 1RF10 (spring 2004), the largest radius tube in which primary water stress corrosion cracking was identified in the U-bend region during 1RF11 (fall 2005) was in row 5.

The number of tubes identified with circumferential outside diameter stress-corrosion cracking during 1RF11 was less than that observed during the prior outage. Similarly, the number of tubes identified with outside diameter stress-corrosion cracking at dings during 1RF11 was less than that observed during the prior outage. The number of tubes identified with free-span outside diameter stress-corrosion cracking, however, increased when compared to the prior outage. All three of these degradation mechanisms were plugged on detection.

One tube was identified with an axially oriented outside diameter stress-corrosion crack approximately 2.5 inches below the top of the tubesheet. Given that the tube is expanded to the top of the tubesheet, the licensee questioned the validity of the indication.

Since this indication was below the F* distance, it was permitted to remain in service.

In response to an NRC request for additional information (refer to the response to question 3 in the June 12, 2006 letter), the licensee indicated the term upper bound was defined by the probability and confidence level applied to the particular evaluation. In follow-up communications, it was clarified that although the probability and confidence levels were high, the actual reported burst pressure was a lower bound burst pressure with a high probability/confidence level, which is conservative.

Based on a review of the information provided and the May 18, 2006, NRC staff summary, the NRC staff concludes that the licensee provided the information required by its technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action since the licensees inspections appeared to be consistent with the objective of detecting potential tube degradation, and the inspection results appeared to be consistent with industry operating experience at similarly designed and operated units.

Principal Contributor: K. Karwoski Date: May 2, 2007

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