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{{#Wiki_filter:De cembe r 19 , 20 06                                                                                                        M r. D. E. Gri ss e tt e Vi ce Pre si den t So uthe rn N ucl ear Operati ng  Co mpan y , Inc.P.O. B o x 1 2 9 5Bi rmin gham, AL 35 201-129 5
{{#Wiki_filter:December 19, 2006 Mr. D. E. Grissette Vice President Southern Nuclear Operating Company, Inc.
P.O. Box 1295 Birmingham, AL 35201-1295


==SUBJECT:==
==SUBJECT:==
VOGTLE ELECTRIC GENERATING PLANT, UNIT 1 (VOGTLE) -


VOG T LE ELECTRI C GENERAT ING PLANT, UNIT 1 (VOG T LE) - SUM M ARY OF CONFERENCE CALL REGARDING THE 2006 FALL O UT AGE ST EAM GENE RA TO R TUBE IN SP EC TIO NS (TAC N O. M D3 371)De ar M r. Gris sette:On Octob er 1 8, 2 006 , the N ucl ear Re gula tory C ommis si on (NR C) staff pa rtic ip ated i n a con f eren ce cal l w ith S outh ern Nu cl ear Operati ng Co mpan y , Inc., rep rese ntati v es regardi ng ste am gen erat or inspect ion f inding s during the f all 2006 ref ueling outag e. T he NRC staf f is f orw ardi ng the en cl ose d s ummary for y our in f ormati on.
==SUMMARY==
Sin ce r ely,/R A/
Ro bert M arti n, 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 I-1 D i v i s i o n o f O p e r a t i n g R e a c t o r L i c e n s i n g Of f ic e o f N ucl ear Re acto r R egul ati on Do cket No. 50-424 E n cl o su re:  Oc to b e r 1 8 C o n fere n ce C a l l S u mma ry c c w/e n c l:  S e e n e x t p a ge De cembe r 19 , 20 06                                                            M r. D. E. Gri ss e tt e Vi ce Pre si den t So uthe rn N ucl ear Operati ng  Co mpan y , Inc.P.O. B o x 1 2 9 5Bi rmin gham, AL 35 201-129 5


==SUBJECT:==
OF CONFERENCE CALL REGARDING THE 2006 FALL OUTAGE STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD3371)
 
==Dear Mr. Grissette:==
 
On October 18, 2006, the Nuclear Regulatory Commission (NRC) staff participated in a conference call with Southern Nuclear Operating Company, Inc., representatives regarding steam generator inspection findings during the fall 2006 refueling outage. The NRC staff is forwarding the enclosed summary for your information.
Sincerely,
                                            /RA/
Robert Martin, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-424
 
==Enclosure:==
 
October 18 Conference Call Summary cc w/encl: See next page
 
ML063390165                                              NRR-106 OFFICE          NRR/LPL2-1/PM      NRR/LPL2-1/LA            NRR/LPL2-1/BC NAME            RMartin            MOBrien                  EMarinos DATE            12 /11 /06          12 /18 /06                12 / 19 /06 OCTOBER 18, 2006, CONFERENCE CALL
 
==SUMMARY==
 
STEAM GENERATOR TUBE INSPECTIONS VOGTLE ELECTRIC GENERATING PLANT, UNIT 1 DOCKET NO. 50-424 On October 18, 2006, the Nuclear Regulatory Commission (NRC) staff participated in a conference call with Southern Nuclear Operating Company, Inc., representatives, to discuss steam generator (SG) inspection activities at Vogtle Electric Generating Plant, Units 1 and 2, (Vogtle Unit 1 and Vogtle Unit 2), particularly those activities during the Vogtle Unit 1 fall refueling outage (designated 1R13). A summary of the information discussed during the call along with some background information is provided below.
Vogtle Unit 1 has four model F SGs designed and fabricated by Westinghouse. Each SG contains 5626 thermally treated Alloy 600 tubes with an outside diameter of 0.688 of an inch and a nominal wall thickness of 0.040 of an inch. The tubes are hydraulically expanded for the full depth of the tubesheet at each end and are supported by a number of stainless steel tube supports. In the U-bend region, the tubes are supported by anti-vibration bars. The tubes are arranged in a square pitch.
Vogtle Unit 1 SGs began commercial operation in 1987. In 2002, there was an inadvertent addition of phosphate to the Unit 1 and Unit 2 SGs. In the spring of 2004, Vogtle Unit 2 pulled two tubes to investigate crack-like indications at the expansion transition. A laboratory non-destructive examination of both of these tubes indicated that there was no cracking at the expansion transition. Destructive examination of one of these tubes confirmed there was no cracking at the expansion transition. In the spring of 2005, Vogtle Unit 1 identified cracking in bulges within the tubesheet. No crack-like indications were found during the fall 2005 inspection in Vogtle Unit 2. During the recently completed fall 2006 SG tube inspections at Vogtle Unit 1, crack-like indications were identified at the expansion transition. These findings are discussed below. The next Vogtle Unit 2 SG tube inspections are scheduled for the spring of 2007.
During the 1R13 outage, 100 percent of the tubes in SGs 2 and 3 were inspected with a bobbin coil. In addition, the U-bend region of 50 percent of the row 1 and 2 tubes, and 100 percent of the dings and dents greater than 5 volts in the hot leg in SGs 2 and 3 were inspected with a rotating probe. The SGs were chemically cleaned before the tube inspections and the SGs operate at a hot leg temperature of 618 o F.
During 1R13, +Point' inspections of the top of the tubesheet region were planned for 50 percent of the tubes in SGs 2 and 3. During this initial sample, indications of outside diameter stress corrosion cracking were found in several tubes at the bottom of the expansion transition region in both SGs. As a result of finding these indications, the scope of inspection at the top of the tubesheet was expanded to include 100% of the tubes in SGs 2 and 3 and 25 percent of the tubes in SGs 1 and 4. The extent of this inspection was from 3 inches above to 3 inches Enclosure
 
below the top of the tubesheet. As a result of finding indications in the initial sample inspection in SGs 1 and 4, the scope of the inspection at the top of the tubesheet was expanded to include 100 percent of the tubes. At the time of the conference call, 10 indications had been identified:
3 in SG 1, 2 in SG 2, 3 in SG 3, and 2 in SG 4. The licensee indicated that evaluations for other possible indications, some in the sludge pile region, were still ongoing in SG 4.
For SGs 1, 2 and 3, the indications are predominantly located in low row, high column tubes along the periphery (between rows 1 through 6 and between columns 103 through 119).
In order to confirm the indications, five different inspection methods were used: +Point',
Ghent, 3 Coil Delta, and the 0.080 and 0.115 pancake coil. All of the inspection methods confirmed the indications with the exception that some of the small amplitude signals were not identified with the 0.080 pancake coil. Given these results, the licensee concluded that these indications are cracks.
The largest crack-like indication was measured to have a circumferential extent of 180 degrees.
The maximum reported depth was 67 percent throughwall. The indication with the largest circumferential extent was not the same indication that had the maximum depth. The voltages associated with the indications were approximately 0.2 volts, although there were two indications that had voltages of 0.60 volts and 0.73 volts. A historical review of the +Point' data for the tubes in which the ODSCC indications were detected this outage was performed.
This review did not identify any precursor signals in these tubes.
The licensee stated that it had alerted the industry (other licensees of pressurized-water reactors) regarding this issue.
All tubes with crack-like indications will be plugged and stabilized. The licensee considered pulling a tube or tubes, but due to a major tube-pull project overseas, the licensee was not able to pull a tube given its outage schedule. The licensee will evaluate pulling a tube during the next refueling outage. Due to the location of the tubes with crack-like indications in relation to the divider plate, it is not clear whether pulling a tube is feasible. With respect to similar operating experience, the licensee indicated that Comanche Peak Unit 1 had first detected outside diameter circumferential cracks in a similar region of the tube bundle.
The licensee also stated there were indications near the top of the tubesheet that were identified with the +Point' probe but not confirmed with the Ghent, 3 Coil Delta probe or the 0.080 coil. These indications had voltages of approximately 0.06 volts to 0.08 volts.
In addition to crack-like indications found during the inspection, a volumetric flaw above the cold leg flow distribution baffle measuring 42 percent through-wall was detected in one tube.
The indication was attributed to a loose part. +Point' inspections were performed at this elevation for a 2-tube buffer surrounding this volumetric flaw. No possible loose parts were identified during this inspection. Given the location of the indication, visual inspections could not be performed. Other volumetric indications were observed in SG 2, however, they measured less than 10-percent through-wall.
Inspections were performed on a sample of bulges and overexpansion in the tubesheet region (i.e., from the top of the tubesheet to 17 inches below the top of the secondary face of the tubesheet). No indications were found during these inspections.
Based on the information provided, the NRC staff did not identify any technical issues that warranted follow-up action at this time.


VOG T LE ELECTRI C GENERAT ING PLANT, UNIT 1 (VOG T LE) - SUM M ARY OF CONFERENCE CALL REGARDING THE 2006 FALL O UT AGE ST EAM GENE RA TO R TUBE IN SP EC TIO NS (TAC N O. M D3 371)De ar M r. Gris sette:On Octob er 1 8, 2 006 , the N ucl ear Re gula tory C ommis si on (NR C) staff pa rtic ip ated i n a con f eren ce cal l w ith S outh ern Nu cl ear Operati ng Co mpan y , Inc., rep rese ntati v es regardi ng ste am gen erat or inspect ion f inding s during the f all 2006 ref ueling outag e. T he NRC staf f is f orw ardi ng the en cl ose d s ummary for y our in f ormati on.
Vogtle Electric Generating Plant, Units 1 & 2 cc:
Sin ce r ely,                                                                    /RA/
Mr. Laurence Bergen Mr. D. E. Grissette, Vice President          Oglethorpe Power Corporation Southern Nuclear Operating Company, Inc.     2100 East Exchange Place P.O. Box 1295                                P.O. Box 1349 Birmingham, AL 35201-1295                    Tucker, GA 30085-1349 Mr. N. J. Stringfellow                        Arthur H. Domby, Esquire Manager, Licensing                            Troutman Sanders Southern Nuclear Operating Company, Inc.     Nations Bank Plaza P.O. Box 1295                                600 Peachtree Street, NE Birmingham, AL 35201-1295                    Suite 5200 Atlanta, GA 30308-2216 Mr. T. E. Tynan, General Manager Vogtle Electric Generating Plant              Resident Inspector Southern Nuclear Operating Company, Inc.     Vogtle Plant 7821 River Road                              8805 River Road Waynesboro, GA 30830                          Waynesboro, GA 30830 Mr. Jeffrey T. Gasser                        Office of the County Commissioner Executive Vice President                      Burke County Commission Southern Nuclear Operating Company, Inc.     Waynesboro, GA 30830 P.O. Box 1295 Birmingham, AL 35201-1295 Mr. Steven M. Jackson Senior Engineer - Power Supply Municipal Electric Authority of Georgia 1470 Riveredge Parkway, NW Atlanta, GA 30328-4684 Mr. Reece McAlister Executive Secretary Georgia Public Service Commission 244 Washington St., SW Atlanta, GA 30334 Mr. Harold Reheis, Director Department of Natural Resources 205 Butler Street, SE, Suite 1252 Atlanta, GA 30334 Attorney General Law Department 132 Judicial Building Atlanta, GA 30334}}
Ro bert M arti n, 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 I-1 D i v i s i o n o f O p e r a t i n g R e a c t o r L i c e n s i n g Of f ic e o f N ucl ear Re acto r R egul ati on Do cket No. 50-424 En cl osu re: Oc to b e r 1 8 C o n fere n ce C a l l S u mma ry c c w/e n c l:  S e e n e x t p a ge DIST RIBUT IO N:P U B L IC P D II-1 R/FR i d sN rr L A M O'B ri e n R i d sN rr D o rl L p l 2-1 (E M a ri n o s) Ri dsOGCR p Ri dsA crsA cnw M ai lC ente rNrr DciCsg b(YDiaz-Cast ill o)
RidsNrr PM RM art in R i d sR gn2 M a i l C tr (S S h a e ff e r) AD AM S Acc ess io n N o.: M L06 339 016 5 NR R-1 06 OF FICE NRR/LPL2-1/PM NRR/LPL2-1/LA NRR/LPL2-1/BC NA M E RM arti n M O'B rie n EM ari nos DA TE 12  /11 /06 12 /18 /06 12 / 1 9 /0 6 OFFICIAL RECORD CO PY Enclo sure OCT OBER 18, 2006, CO NFERENCE CALL SUM M ARY ST EAM GENERAT OR T UBE INSPECT IO NS V OG TL E E L E C TR I C G E N E R A TI N G P L A N T, U N I T 1 DOCK ET N O. 50-4 24 On Octob er 1 8, 2 006 , the N ucl ear Re gula tory C ommis si on (NR C) staff pa rtic ip ated i n a con f eren ce cal l w ith S outh ern Nu cl ear Operati ng Co mpan y , Inc., rep rese ntati v es, to d is cus s stea m genera tor (S G) i nsp ecti on acti v iti es at V ogtle E le ctri c Gen erati ng Pl ant, Un its 1 and 2, (Vog tle Unit 1 and Vogt le Uni t 2), part icularly thos e activities during the Vog tle Unit 1 f all ref ueling outag e (desig nate d 1R13). A summ ary of the inf orm ation discus sed dur ing the call a lo n g wit h so m e ba c k g r o u n d in f o r m a t io n is pr o vi d e d be lo w.Vog tle Unit 1 has f our m odel F SGs desig ned and f abrica ted by W est ing house. Each SG con tai ns 562 6 th ermal ly trea ted Al lo y 60 0 tu bes w ith an ou tsi de di ameter of 0.688 of an i nch and a nomi nal w al l thi ckness of 0.040 of an i nch. The tub es are hy drau li cal ly ex pan ded for the f ul l dep th o f the tub esh eet at e ach en d a nd are sup porte d b y a numb er o f sta in le ss stee l tube su p p o rt s. In t h e U-b e n d r e gi o n , th e t u b e s a re s u p p o rt e d b y a n ti-v i b ra ti o n b a rs. Th e t u b e s a re arran ged i n a square pi tch.Vo gtle Un it 1 S Gs be gan co mmerci al op erati on in 19 87. In 200 2, th ere w as an in adv erten t add iti on of pho sph ate to th e U ni t 1 and U ni t 2 SGs. In the spri ng of 200 4, V ogtle U ni t 2 pul le d tw o tu bes to in v esti gate cra ck-li ke i ndi cati ons at the ex pan si on trans iti on. A l abo ratory no n-des tructi v e e x ami nati on of both of these tub es in di cate d th at th ere w as no crac king at the ex pan si on trans iti on. D estru cti v e e x ami nati on of one of the se tube s c onfirmed the re w as no cra ck ing at the expansion tra nsition. In th e spring of 2005, Vog tle Unit 1 identif ied crack ing in bul ges w ith in the tub esh eet. N o c rack-li ke i ndi cati ons w ere f oun d d uri ng the fall 20 05 in spe cti on in V ogtle U ni t 2. D uri ng the rec entl y co mpl eted fall 20 06 SG tu be in spe cti ons at V o gt l e U n i t 1 , c r a c k-l i ke i n d i c a t i o n s w e r e i d e n t i fi e d a t t h e e x p a n s i o n t r a n s i t i o n. Th e s e fi n d i n gs are di scu sse d b el ow. The ne x t V ogtle U ni t 2 SG tu be in spe cti ons are sc hed ul ed f or th e spri ng of 200 7.During the 1R13 outag e, 100 per cent of the tube s in S Gs 2 and 3 w ere inspec ted wi th a bobbin coi l. In add iti on, the U-b end regi on of 50 perc ent of the row 1 and 2 tube s, a nd 100 pe rcen t of the di ngs an d d ents greate r tha n 5 v ol ts i n th e h ot l eg i n S Gs 2 and 3 w ere in spe cted w ith a ro ta ti n g p ro b e. Th e S Gs w e re c h e mi ca l l y c l e a n e d b e fore t h e t u b e i n sp e ct i o n s a n d t h e S Gs ope rate at a ho t l eg tempe rature of 61 8 F. o Du rin g 1R1 3, +P oi ntŽ i nsp ecti ons of the top of the tub esh eet regio n w ere pl ann ed f or 5 0 perc ent of the tube s i n S Gs 2 and 3. D uri ng thi s i ni tia l sampl e, i ndi cati ons of ou tsi de di ameter stress co rrosi on crac king w ere f oun d i n s ev eral tub es at th e b ottom o f the ex pan si on trans iti on regio n i n b oth SGs. A s a res ul t of f in di ng the se in di cati ons , the sc ope of i nsp ecti on  at the top of the tube she et w as ex pan ded to in cl ude 10 0% o f the tub es in S Gs 2 and 3 and 25 pe rcen t of the tube s i n S Gs 1 and 4. The ex tent of thi s i nsp ecti on w as f rom 3 i nch es abo v e to 3 in che s  bel ow the top of the tub esh eet. A s a res ul t of f in di ng i ndi cati ons i n th e i ni tia l sampl e i nsp ecti on in S Gs 1 and 4, the sco pe of the in spe cti on at th e to p o f the tub esh eet w as ex pan ded to in cl ude 100 pe rcen t of the tube s. At the time of the co nference ca ll , 10 i ndi cati ons ha d b een i den tifie d: 3 i n S G 1, 2 i n S G 2, 3 i n S G 3, and 2 in S G 4. The li cen see i ndi cate d th at e v al uati ons for othe r po ssi bl e i ndi cati ons , so me i n th e s lu dge p il e re gion , w ere sti ll on goin g in S G 4.For SGs 1, 2 an d 3 , the i ndi cati ons are pre domi nan tly l oca ted in l ow row , hi gh col umn tube s a l o n g th e p e ri p h e ry (b e tw e e n r o w s 1 t h ro u gh 6 a n d b e tw e e n c o l u mn s 1 0 3 t h ro u gh 1 1 9).In o rder to c onfirm th e i ndi cati ons , fiv e d iff eren t i nsp ecti on method s w ere use d: +P oi ntŽ, Ghent, 3 C oi l De lta , an d th e 0.080 an d 0.115 pa nca ke coi l. A ll of the i nsp ecti on method s con f irme d th e i ndi cati ons w ith the ex cep tio n th at s ome of the smal l ampl itu de si gnal s w ere not id enti f ie d w ith the 0.0 80 pan cake c oi l. Gi v en thes e re sul ts, th e l ic ens ee con cl ude d th at th ese i n d i ca ti o n s a re c ra cks. The l argest c rack-li ke i ndi cati on w as measu red to h av e a ci rcumferenti al ex tent of 180 de grees.The max imu m rep orted de pth w as 67 perc ent throu ghw al l. The in di cati on w ith the l argest ci rcumferenti al ex tent w as not the same in di cati on that had the max imu m de pth. The v ol tages a s s o c ia t e d wit h t h e in d ic a t io n s wer e ap p r o xi m a t e ly 0.2 vo lt s , al t h o u g h t h e r e wer e t wo i n d i ca ti o n s th a t h a d v o l ta ges o f 0.6 0 v o l ts a n d 0.7 3 v o l ts. A h i st o ri ca l r e v i e w o f th e +P o i n tŽd a ta for t h e t u b e s i n w h i ch t h e OD S C C i n d i ca ti o n s w e re d e te ct e d t h i s o u ta ge w a s p e rfor me d. This rev ie w di d n ot i den tify an y pre curs or s igna ls i n th ese tub es. The l ic ens ee state d th at i t ha d a le rted the in dus try (oth er l ic ens ees of pre ssu riz ed-w ater re a ct o rs) re gar d i n g th i s i ss u e. Al l tube s w ith cra ck-li ke i ndi cati ons w il l be pl ugg ed and sta bi li z ed. The li cen see co nsi dere d pulling a tube or tubes, but due to a maj or tu be-p ull proj ect ov ers eas, the licensee w as not able to p ul l a tu be giv en its ou tage sc hed ul e. The l ic ens ee w il l ev al uate pu ll in g a tu be duri ng the n e x t re fue l i n g o u ta ge. D u e t o t h e l o ca ti o n o f th e t u b e s w i th c ra ck-l i ke i n d i ca ti o n s i n r e l a ti o n t o the di v id er p la te, i t i s n ot c le ar w heth er p ul li ng a tube i s feasi bl e. W ith res pec t to si mil ar ope rati ng ex peri enc e, th e l ic ens ee in di cate d th at C oman che P eak U ni t 1 had first d etec ted outs id e d ia meter c irc umf eren tia l crac ks in a si mil ar re gion of the tub e b und le.The l i ce n se e a l so s ta te d t h e re w e re i n d i ca ti o n s n e a r th e t o p o f th e t u b e sh e e t th a t w e re id enti f ie d w ith the +P oi ntŽ p robe bu t no t co nfirmed w ith the Ghe nt, 3 C oi l De lta pro be or th e 0.08 0 c oi l. Thes e i ndi cati ons ha d v ol tages o f ap prox ima tel y 0.0 6 v ol ts to 0.0 8 v ol ts.In addit ion to crac k-lik e indications f ound dur ing the inspect ion, a v olume tr ic f law above the cold le g f lo w di stri buti on baff le mea suri ng 42 pe rcen t thro ugh-w al l w as dete cted i n o ne tube.T he indication w as att ribut ed to a loose part.  +PointŽ inspections w ere per f orm ed at this e l e v a ti o n for a 2-t u b e b u ff e r su rr o u n d i n g th i s v o l u me tr i c fla w. N o p o ss i b l e l o o se p a rt s w e re identif ied during this inspect ion. Given the location of the indication, v isual i nspec tions could not be performed.
Other v ol umetri c i ndi cati ons w ere obs erv ed in S G 2, how ev er, th ey me asur ed less than 10-perc ent t hrou g h-wall.Insp ecti ons w ere performed on a s ampl e o f bu lges and ov erex pan si on in the tub esh eet regio n (i.e., from the top of the tube she et to 17 i nch es bel ow the top of the se con dary face o f the tube she et). No i ndi cati ons w ere f oun d d uri ng the se in spe cti ons.Ba sed on the i nformatio n p rov id ed, the NR C staff di d n ot i den tify an y tec hni cal i ssu es that w arran ted f ol lo w-up acti on at th is ti me.
Vog tle Electr ic Gener ating Plant, Units 1 & 2 cc: M r. D. E. Gri sse tte, V ic e P resi den t So uthe rn N ucl ear Operati ng Co mpan y , Inc.P.O. B ox 12 95 Bi rmin gham, AL 352 01-1 295 M r. N. J. Stri ngf el lo w M ana ger, Li cen si ng So uthe rn N ucl ear Operati ng Co mpan y , Inc.P.O. B ox 12 95 Bi rmin gham, AL 35 201-129 5M r. T. E. Tyn an, Genera l M ana ger Vo gtle El ectri c Gen erati ng Pl ant So uthe rn N ucl ear Operati ng Co mpan y , Inc.782 1 R iv er R oad W ay nes boro , GA 30 830 M r. Je f f rey T. Gasse r Ex ecu tiv e V ic e P resi den t So uthe rn N ucl ear Operati ng Co mpan y , Inc.P.O. B ox 12 95 Bi rmin gham, AL 352 01-1 295 M r. S tev en M. Ja ckson Senior Eng ineer - Power Supply M unicipal El ect ric Autho rity of Geor g ia 1470 Riv ered g e Park w ay, NW Atl anta , GA 30 328-468 4 M r. R eec e M cAl is ter E x e cu ti v e S e cr e ta ry Georgia P ubl ic S erv ic e C ommis si on 244 W ashing ton St., SW Atl anta , GA 30 334 M r. H arol d R ehe is , D ire ctor De partmen t of Na tural R eso urce s 205 B utl er S treet, SE , S ui te 1 252 Atl anta , GA 30 334 Attorn ey Gen eral Law D epa rtment 132 Ju di ci al B ui ld in g Atl anta , GA  30 334 M r. La uren ce Be rgen Og le thorp e P ow er C orpo rati on 210 0 E ast Ex cha nge P la ce P.O. B ox 13 49 Tucker, GA 300 85-1 349 A rt h u r H. D o mb y , E squ i re Tro u tma n S a n d e rs Na t ion s Ba nk Pla za 600 Peacht ree St reet , NE Su ite 52 00 Atl anta , GA  30 308-221 6 Re si den t Ins pec tor Vo gtle Pl ant 880 5 R iv er R oad W ay nes boro , GA  30 830 Of f ic e o f the C oun ty C ommis si one r Bu rke Co unty C ommis si on W ay nes boro , GA 30 830}}

Latest revision as of 21:51, 13 March 2020

(Vogtle), Unit 1 - Summary of Conference Call Regarding the 2006 Fall Outage Steam Generator Tube Inspections
ML063390165
Person / Time
Site: Vogtle Southern Nuclear icon.png
Issue date: 12/19/2006
From: Martin R
NRC/NRR/ADRO/DORL/LPLII-1
To: Grissette D
Southern Nuclear Operating Co
Martin R, NRR/DORL, 415-1493
References
TAC MD3371
Download: ML063390165 (5)
v • d • e


Text

December 19, 2006 Mr. D. E. Grissette Vice President Southern Nuclear Operating Company, Inc.

P.O. Box 1295 Birmingham, AL 35201-1295

SUBJECT:

VOGTLE ELECTRIC GENERATING PLANT, UNIT 1 (VOGTLE) -

SUMMARY

OF CONFERENCE CALL REGARDING THE 2006 FALL OUTAGE STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD3371)

Dear Mr. Grissette:

On October 18, 2006, the Nuclear Regulatory Commission (NRC) staff participated in a conference call with Southern Nuclear Operating Company, Inc., representatives regarding steam generator inspection findings during the fall 2006 refueling outage. The NRC staff is forwarding the enclosed summary for your information.

Sincerely,

/RA/

Robert Martin, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-424

Enclosure:

October 18 Conference Call Summary cc w/encl: See next page

ML063390165 NRR-106 OFFICE NRR/LPL2-1/PM NRR/LPL2-1/LA NRR/LPL2-1/BC NAME RMartin MOBrien EMarinos DATE 12 /11 /06 12 /18 /06 12 / 19 /06 OCTOBER 18, 2006, CONFERENCE CALL

SUMMARY

STEAM GENERATOR TUBE INSPECTIONS VOGTLE ELECTRIC GENERATING PLANT, UNIT 1 DOCKET NO. 50-424 On October 18, 2006, the Nuclear Regulatory Commission (NRC) staff participated in a conference call with Southern Nuclear Operating Company, Inc., representatives, to discuss steam generator (SG) inspection activities at Vogtle Electric Generating Plant, Units 1 and 2, (Vogtle Unit 1 and Vogtle Unit 2), particularly those activities during the Vogtle Unit 1 fall refueling outage (designated 1R13). A summary of the information discussed during the call along with some background information is provided below.

Vogtle Unit 1 has four model F SGs designed and fabricated by Westinghouse. Each SG contains 5626 thermally treated Alloy 600 tubes with an outside diameter of 0.688 of an inch and a nominal wall thickness of 0.040 of an inch. The tubes are hydraulically expanded for the full depth of the tubesheet at each end and are supported by a number of stainless steel tube supports. In the U-bend region, the tubes are supported by anti-vibration bars. The tubes are arranged in a square pitch.

Vogtle Unit 1 SGs began commercial operation in 1987. In 2002, there was an inadvertent addition of phosphate to the Unit 1 and Unit 2 SGs. In the spring of 2004, Vogtle Unit 2 pulled two tubes to investigate crack-like indications at the expansion transition. A laboratory non-destructive examination of both of these tubes indicated that there was no cracking at the expansion transition. Destructive examination of one of these tubes confirmed there was no cracking at the expansion transition. In the spring of 2005, Vogtle Unit 1 identified cracking in bulges within the tubesheet. No crack-like indications were found during the fall 2005 inspection in Vogtle Unit 2. During the recently completed fall 2006 SG tube inspections at Vogtle Unit 1, crack-like indications were identified at the expansion transition. These findings are discussed below. The next Vogtle Unit 2 SG tube inspections are scheduled for the spring of 2007.

During the 1R13 outage, 100 percent of the tubes in SGs 2 and 3 were inspected with a bobbin coil. In addition, the U-bend region of 50 percent of the row 1 and 2 tubes, and 100 percent of the dings and dents greater than 5 volts in the hot leg in SGs 2 and 3 were inspected with a rotating probe. The SGs were chemically cleaned before the tube inspections and the SGs operate at a hot leg temperature of 618 o F.

During 1R13, +Point' inspections of the top of the tubesheet region were planned for 50 percent of the tubes in SGs 2 and 3. During this initial sample, indications of outside diameter stress corrosion cracking were found in several tubes at the bottom of the expansion transition region in both SGs. As a result of finding these indications, the scope of inspection at the top of the tubesheet was expanded to include 100% of the tubes in SGs 2 and 3 and 25 percent of the tubes in SGs 1 and 4. The extent of this inspection was from 3 inches above to 3 inches Enclosure

below the top of the tubesheet. As a result of finding indications in the initial sample inspection in SGs 1 and 4, the scope of the inspection at the top of the tubesheet was expanded to include 100 percent of the tubes. At the time of the conference call, 10 indications had been identified:

3 in SG 1, 2 in SG 2, 3 in SG 3, and 2 in SG 4. The licensee indicated that evaluations for other possible indications, some in the sludge pile region, were still ongoing in SG 4.

For SGs 1, 2 and 3, the indications are predominantly located in low row, high column tubes along the periphery (between rows 1 through 6 and between columns 103 through 119).

In order to confirm the indications, five different inspection methods were used: +Point',

Ghent, 3 Coil Delta, and the 0.080 and 0.115 pancake coil. All of the inspection methods confirmed the indications with the exception that some of the small amplitude signals were not identified with the 0.080 pancake coil. Given these results, the licensee concluded that these indications are cracks.

The largest crack-like indication was measured to have a circumferential extent of 180 degrees.

The maximum reported depth was 67 percent throughwall. The indication with the largest circumferential extent was not the same indication that had the maximum depth. The voltages associated with the indications were approximately 0.2 volts, although there were two indications that had voltages of 0.60 volts and 0.73 volts. A historical review of the +Point' data for the tubes in which the ODSCC indications were detected this outage was performed.

This review did not identify any precursor signals in these tubes.

The licensee stated that it had alerted the industry (other licensees of pressurized-water reactors) regarding this issue.

All tubes with crack-like indications will be plugged and stabilized. The licensee considered pulling a tube or tubes, but due to a major tube-pull project overseas, the licensee was not able to pull a tube given its outage schedule. The licensee will evaluate pulling a tube during the next refueling outage. Due to the location of the tubes with crack-like indications in relation to the divider plate, it is not clear whether pulling a tube is feasible. With respect to similar operating experience, the licensee indicated that Comanche Peak Unit 1 had first detected outside diameter circumferential cracks in a similar region of the tube bundle.

The licensee also stated there were indications near the top of the tubesheet that were identified with the +Point' probe but not confirmed with the Ghent, 3 Coil Delta probe or the 0.080 coil. These indications had voltages of approximately 0.06 volts to 0.08 volts.

In addition to crack-like indications found during the inspection, a volumetric flaw above the cold leg flow distribution baffle measuring 42 percent through-wall was detected in one tube.

The indication was attributed to a loose part. +Point' inspections were performed at this elevation for a 2-tube buffer surrounding this volumetric flaw. No possible loose parts were identified during this inspection. Given the location of the indication, visual inspections could not be performed. Other volumetric indications were observed in SG 2, however, they measured less than 10-percent through-wall.

Inspections were performed on a sample of bulges and overexpansion in the tubesheet region (i.e., from the top of the tubesheet to 17 inches below the top of the secondary face of the tubesheet). No indications were found during these inspections.

Based on the information provided, the NRC staff did not identify any technical issues that warranted follow-up action at this time.

Vogtle Electric Generating Plant, Units 1 & 2 cc:

Mr. Laurence Bergen Mr. D. E. Grissette, Vice President Oglethorpe Power Corporation Southern Nuclear Operating Company, Inc. 2100 East Exchange Place P.O. Box 1295 P.O. Box 1349 Birmingham, AL 35201-1295 Tucker, GA 30085-1349 Mr. N. J. Stringfellow Arthur H. Domby, Esquire Manager, Licensing Troutman Sanders Southern Nuclear Operating Company, Inc. Nations Bank Plaza P.O. Box 1295 600 Peachtree Street, NE Birmingham, AL 35201-1295 Suite 5200 Atlanta, GA 30308-2216 Mr. T. E. Tynan, General Manager Vogtle Electric Generating Plant Resident Inspector Southern Nuclear Operating Company, Inc. Vogtle Plant 7821 River Road 8805 River Road Waynesboro, GA 30830 Waynesboro, GA 30830 Mr. Jeffrey T. Gasser Office of the County Commissioner Executive Vice President Burke County Commission Southern Nuclear Operating Company, Inc. Waynesboro, GA 30830 P.O. Box 1295 Birmingham, AL 35201-1295 Mr. Steven M. Jackson Senior Engineer - Power Supply Municipal Electric Authority of Georgia 1470 Riveredge Parkway, NW Atlanta, GA 30328-4684 Mr. Reece McAlister Executive Secretary Georgia Public Service Commission 244 Washington St., SW Atlanta, GA 30334 Mr. Harold Reheis, Director Department of Natural Resources 205 Butler Street, SE, Suite 1252 Atlanta, GA 30334 Attorney General Law Department 132 Judicial Building Atlanta, GA 30334

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