ML14027A326
| ML14027A326 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 01/22/2014 |
| From: | Gatlin T D South Carolina Electric & Gas Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MF1848 | |
| Download: ML14027A326 (8) | |
Text
Thomas D. GatlinVice President, Nuclear Operations803.345.4342A SCANA COMPANYU.S. Nuclear Regulatory CommissionDocument Control DeskWashington, DC 20555-0001January 22, 2014Dear Sir I Madam:Subject: VIRGIL C. SUMMER NUCLEAR STATION (VCSNS), UNIT 1DOCKET NO. 50-395OPERATING LICENSE NO. NPF-12RESPONSE TO REQUEST FOR ADDITIONAL INFORMATIONCONCERNING RELIEF REQUEST NO. RR-II-10 (TAC NO. MF1848)Reference:1. Thomas D. Gatlin, SCE&G Letter to Document Control Desk, Request Relieffrom ASME Code Requirements in VCSNS 3r Ten Year Inservice InspectionInterval, dated May 6, 2013 [ML13129A178]2. Thomas D. Gatlin, SCE&G Letter to Document Control Desk, Response toRequest for Additional Information Concerning Relief Request No. RR-III- 10(TAC No. MF1848), dated October 11, 2013 [ML1 3289A1 83]3. Shawn Williams, NRC Letter to Thomas D. Gatlin, SCE&G, Request forAdditional Information Concerning Relief Request No. RR-111-1O (TAC No.MF1848), dated December 11, 2013 [ML13340A377]South Carolina Electric & Gas Company (SCE&G) received an NRC letter dated December 11,2013 (Reference 3), requesting additional information (RAI) regarding thee Virgil C. SummerNuclear Station Unit 1 relief request from ASME code requirements in the VCSNS 3rd Ten YearInservice Inspection Interval (Reference 1) and supplement dated October 11, 2013 (Reference2). SCE&G has reviewed the request for additional information and hereby submits theattached response.If you have any questions or require additional information, please contact Mr. Bruce Thompsonat (803) 931-5042.Very truly yours,TS/TDG/wm Thomas D. GatlinEnclosure -Response to Follow-up RAI Concerning Relief Request No. RR-III-10(TAC No. MF1848) [ML13340A377]Attachmentc: K. B. MarshS. A. ByrneJ. B. ArchieN. S. CarnsJ. H. HamiltonJ. W. WilliamsW. M. CherryV. M. McCreeS. A. WilliamsNRC Resident InspectorK. M. SuttonNSRCRTS (CR-12-05348)File (810.19-2)PRSF (RC-14-0006)AO~Virgil C. Summer Station , Post Office Box 88
- Jenkinsville, SC .29065 .F (803) 941-9776 Document Control DeskEnclosureCR-12-05348RC-14-0006Page 1 of 3VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1DOCKET NO. 50-395OPERATING LICENSE NO. NPF-12ENCLOSUREVIRGIL C. SUMMER NUCLEAR STATION, UNIT NO. I -RESPONSE TO FOLLOW-UPREQUEST FOR ADDITIONAL INFORMATION CONCERNING RELIEF REQUESTNO. RR-III-10 (TAC NO. MF1848) [ML13340A377]
Document Control DeskEnclosureCR-12-05348RC-14-0006Page 2 of 3REQUEST FOR ADDITIONAL INFORMATION REGARDINGVIRGIL C. SUMMER NUCLEAR STATION UNIT 1.SOUTH CAROLINA ELECTRIC & GAS CO.RELIEF REQUEST NO. RR-111-10DOCKET NO. 50-395 (TAC NO. MF1848)The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided bySouth Carolina Electric & Gas Co. (SCE&G, the licensee) for Virgil C. Summer Nuclear Station,Unit 1 (VCSNS) Relief Request No. RR-111-10 in its letter dated May 6, 2013 (AgencywideDocuments Access and Management System (ADAMS) Accession No. ML 13129A1 78), assupplement dated October 11, 2013 (ADAMS Accession No. ML 13289A1 83) and hasdetermined that additional information is necessary to complete the review of Relief RequestNo. RR-III-10.Regulatory Basis:10 CFR 50.55a(g) requires the use of ASME Code, Section Xl for in-service inspection (ISI)examinations. The relevant requirements of the ASME Code,Section XI for the pressurizersurge nozzle examination are that essentially 100% of the nozzle-to-vessel shell weld beexamined. Code Case N-460, which is approved for use by the NRC in Regulatory Guide 1.147,Revision 16, "Inservice Inspection Code Case Acceptability, ASME Section Xl, Division 1,"clarifies "essentially 100 percent" to be greater than 90 percent coverage of the examinationvolume, or surface area, as applicable. Since the licensee's examination of the pressurizersurge nozzle-to-vessel shell weld only obtained 51% coverage, the NRC needs to understandclearly how that coverage was achieved in order to satisfy the requirements of 10 CFR50.55a(a)(3), which states, in part, that alternatives to the requirements of paragraph (g) maybe used, when authorized by the NRC, if the applicant demonstrates that: (i) the proposedalternatives would provide an acceptable level of quality and safety, or (ii) compliance with thespecified requirements would result in hardship or unusual difficulty without a compensatingincrease in the level of quality and safety.Follow-up RAI 6.c response on October 11, 2013The licensee's response to RAI6(c) did not provide the specifics necessary for the NRCto fully understand how the value of 51% coverage was determined. Describe how thevalue of 51% was determined. Provide the calculation and an illustration as necessaryfor clarity. From the information previously provided, it appears that the coverage from450 and 600 probes should be different, and coverage may also be different from eachscan direction, especially in light of the fact that the vendor appears to be taking creditfor capturing additional coverage from performing the examination in the gaps betweenthe heater penetrations on the head side. Specifically, describe how coverage from each Document Control DeskEnclosureCR-12-05348RC-14-0006Page 3 of 3of the transducers and scan directions were credited in determining the 51% coveragevalue. Address whether credit may be given for one angle only, or if coverage with bothangles is required for credit.SCE&G ResponseVCSNS vendor WesDyne International, who performed the ultrasonic examination of nozzle toshell weld # 1-2100A-8 during Refueling Outage 20, has provided additional informationregarding the ultrasonic examination of the weld in question. The examination of thepressurizer surge nozzle to the shell weld was limited due to one sided access (nozzle side)and heater tube penetrations (shell side) that prevented unobstructed scanning. No credit forcoverage was taken for either angle below the 60 degree metal path plot, and no credit wastaken for areas that achieved coverage with just one angle.The top portion of the weld was the only area where both angles (45 degrees and 60 degrees)achieved complete coverage; therefore, that was the number that was reflected in the previousweld material coverage calculation (i.e., 51 percent in References 1 and 2 listed in the coverletter). With a holistic analysis of the ultrasonic examination for nozzle to shell weld # 1-2100A-8, new results are being provided for the top portion of the weld where both angles achievedcomplete coverage (provided in attachment). The percentage for the shell side is now 46percent, instead of 51 percent, while the percentage for the nozzle side is now 58 percent,instead of 51 percent. The combined coverage from both directions for the axial scanning wasconservatively recorded as 51 percent originally, and is shown to be 52 percent in the attachedcalculations. Calculations provided by the vendor were based on total area of the weld scannedversus total area of weld covered with both angles per direction. The enclosed attachmentprovides full detail of WesDyne International's analysis.In addition, WesDyne International explained why oscillating the transducers to make anattempt to scan around the penetrations on the shell side to provide a small increase in totalcoverage was not considered. Assumptions needed for that option would not be easilydefendable. This is also discussed in the enclosed attachment.
Document Control DeskAttachmentCR-12-05348RC-14-0006Page 1 of 4VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT IDOCKET NO. 50-395OPERATING LICENSE NO. NPF-12ATTACHMENTWESDYNE LETTER TO VCSNS, DATED DECEMBER 6, 2013, REGARDING ULTRASONICEXAMINATION OF NOZZLE TO SHELL WELD # 1-2100A-8 DURINGREFUELING OUTAGE RF20
~WESDynlEA Westinghouse Electric CompanyDecember 6, 2013V.C. Summer Nuclear Power StationSubject: Ultrasonic examination of nozzle to shell weld # 1-2100A-8 during RF20Examination of the pressurizer surge nozzle to shell weld # 1-2100-8 was limited due toone sided access (nozzle side) and heater tube penetrations (shell side) preventingunobstructed scanning.Scanning to the maximum extent practical was performed in four directions i.e. bothdirections perpendicular to the weld and both directions parallel to the weld utilizing 450and 600 shear wave angles. Scanning for indications lying perpendicular to the weld wasaccomplished by scanning tangential to the weld and oscillating the transducer +/- 15'-20o.A ring of heater penetrations prevented complete access from the shell side of the weld.This ring consisted of 20 (-1.5" diameter) penetrations separated by approximately 3.0inches with one 18.5 inch gap at one quadrant (vessel O°). The gap between the tubes wasnot enough to pass the search units (1/2" x 1.0") through and still maintain grip and control.The obstructions (nozzle on one side of the weld and penetrations on the other) preventedthe search units from getting back away from the weld far enough to reach the bottomportion of the weld. (see attached sketch Figure 1)Basically no credit was taken for either angle below the 600 metal path plot in areas on theshell side, in front of the penetrations and on the nozzle side where the transducers wereunable to scan back due to the nozzle blended radius. Areas that got coverage with justone angle were conservatively not credited for coverage. Single angle coverage credit wasnot considered. The top portion of the weld is the only area where both angles getcomplete coverage and therefore it is that number that is reflected in the calculation.Calculations are based on total area of weld versus total area of weld covered with bothangles in both directions. WesDyne considers the CW and CCW coverage to be completeand therefore 100%. Perpendicular weld coverage with both angles combined wasconservatively estimated to be 52%. Calculated as 4 independent scans, the totals are:Noz Side = 58% Shell Side = 46% CW = 100% CCW = 100%304 /4 = 76%"A powerful part of your team" Fq1WESDynEAWastinghouse Electnc CompanyWeld coverage based on % of weld material scannedfrom both dkedions wih both tansducersMpepdmular and parWal to fe weld (4 d,&ecboks)Assumes no scannV between penetrationsWed ldl (CtO) -2.0"Wsjdcvt-yrWed Ana I Vbkame -4.0 sqin 1314in'TnAi40e -.Wx-?6'12-.W4uoInThu~e It- 2r *A712 -,100sq hiTft)3s. sq inTrmngeE- 2ra1.0rIZ-.14Ssqkirsed F- r t 2r *OS6qinTr~ov G. -W x.T 12 -.O97aq inlrtk t,1 $a in£ -ýD eoAwWGOdDeaNoz Side 58% coverageShd Side 46% coverageCW Scan = 100%% corageCCW Scan 1NS.coeragTOTAL COVERAGE30414 -76%Noz We. owna -2S% or SO% ft w eftsStag Side coverage -23% or 46% ftor "li W&9Wded -bloat thud 6dsg uiV Ww is te aemaltege tmwe come"g Walid aa**WNOT TO SCALEFigure 1"A powerful part of your team" AWostmnghouse Elect&i CompanyThere is an argument that if we oscillate the transducers and attempt to scan around thepenetrations on the shell side, we could get more coverage. This is probably true butseveral assumptions would have to be made. Because of the difference in circumferencebetween the penetration row diameter and the smaller weld circumference diameter, itcould be possible to assume coverage of the weld area without the typical transduceroverlap at the penetration ring. Additionally, transducer oscillation +/- 200 and beam spread(not normally credited) could conceivably provide additional coverage between thepenetrations. If these considerations are viable then the coverage on the shell side of theweld could increase to approximately 83%. (see Figure 2)Weld coverage based an % of weld manwial scannedWon bolth dukecions with both ransducersperpenducidr and Parae So the weld (4 drecions)Asmes addina coverageby scatewi between Pene~aionsNoz Sids 6=% coverageShlle Sid 74.8% coverageCW Scan = 100%% coverageCCW scan = j00covenageTOTAL. COVERAGE332.14 -832%Adtion ShelSde Qsa C alve atio"9 spames 1.S"ea =285S3A Gap in heater ring @0 deg -ILEmerWeld Ckvcunernce =Tr47177=61% of100% coveragePh tus ,e ntanetg30" had 46%coverage 13.8%13.8%+61%- 7428%Weld width (00) = 2.06Wel wdth (ID) -.e"Weld Cuc -77" N Side aWeldrAa IVokorm Red D- 76'x 108 = 810sqin4,08qm1314in3 TrangleE- 27xl.OI2= 145*qin125-TVP RecdF a -3" x 2r .066 sq inTriangleG- .AS"x.3"I2 =.097sqinC. AR. Totals 1.19sqin32S TV.p 1.1912.04 = 56%TranducerFigure 2Michael McKaigWesDyne NDE Level III"A powerful part of your team "