ML12181A195
| ML12181A195 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 06/22/2012 |
| From: | O'Grady B J Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2012064, TAC ME7875 | |
| Download: ML12181A195 (6) | |
Text
NNebraska Public Power DistrictAlways there when you need us50.55aNLS2012064June 22, 2012U.S. Nuclear Regulatory CommissionAttention: Document Control DeskWashington, D.C. 20555-0001Subject:Response to Nuclear Regulatory Commission Request for Additional InformationRe: Request for Relief for the Fourth 10-Year Inservice Inspection Program (TACNo. ME7875)Cooper Nuclear Station, Docket No. 50-298, DPR-46References: 1.Letter from Lynnea E. Wilkins, U. S. Nuclear Regulatory Commission, toBrian J. O'Grady, Nebraska Public Power District, dated June 11, 2012,"Cooper Nuclear Station -Request for Additional Information Re:Request for Relief for the Fourth 10-Year Inservice Inspection Program(TAC No. ME7875)"2. Letter from Brian J. O'Grady, Nebraska Public Power District, to the U.S.Nuclear Regulatory Commission, dated January 16, 2012, "10 CFR 50.55aRequest RI-07, Revision 0"Dear Sir or Madam:The purpose of this letter is for Nebraska Public Power District to submit a response to requestsfor additional information (RAI) from the Nuclear Regulatory Commission (NRC) (Reference1). The RAI requested information in support of NRC's review of a request for relief (RI-07)from certain in-service inspection (ISI) requirements of the American Society of MechanicalEngineers Boiler and Pressure Vessel Code (Code) for Cooper Nuclear Station (CNS) pursuantto Section 50.55a of Title 10 of the Code of Federal Regulations (Reference 2).Responses to the specific RAI questions are provided in the Attachment to this letter. Noregulatory commitments are made in this submittal.The information submitted by this response to the RAI does not change the conclusions or thebasis of the evaluation provided by Reference 2.COOPER NUCLEAR STATIONP.O. Box 98 / Brownville, NE 68327-0098Telephone: (402) 825-3811 / Fax: (402) 825-5211www.nppd.com NLS2012064Page 2 of 2If you have any questions concerning this matter, please contact David Van Der Kamp,Licensing Manager, at (402) 825-2904.Sincerely,Brian J.O Gr)dyVice President -Nuclear andChief Nuclear Officer/emAttachment: Response to Nuclear Regulatory Commission Request for Additional InformationRe: Request for Relief for the Fourth 10-Year Inservice Inspection Program (TACNo. ME7875)cc: Regional Administrator w/ attachmentUSNRC -Region IVCooper Project Manager w/ attachmentUSNRC -NRR Project Directorate IV-1Senior Resident Inspector w/ attachmentUSNRC -CNSNPG Distribution w/o attachmentCNS Records w/ attachment NLS2012064AttachmentPage 1 of 4AttachmentResponse to Nuclear Regulatory Commission Request for Additional InformationRe: Request for Relief for the Fourth 10-Year Inservice Inspection Program(TAC No. ME7875)Cooper Nuclear Station, Docket No. 50-298, DPR-46NRC Question #1Please describe the materials of construction of components RHR-CA-2A and RHR-CB-1Aincluding the base metal and weld materials.Response #1a. RHR-CA-2A(1) Vessel Material = SA-516-70(2) Distributor Ring Material = SA-516-70(3) Weld Material = E7018 Stick Weldb. RHR-CB-1A(1) Nozzle Material = SA-106-B(2) Shell Material = SA-516-70(3) Weld Material = E7018 Stick WeldNRC Question #2Please clarify the difference in technique between the examinations conducted during theprevious ISI interval and those conducted during the current interval. In addition, pleaseexplain why the coverage percentages differed so much between intervals.Response #2Previous exams were performed in 1995 and 2001. Previous examination coverages werecredited using less conservative calculation techniques. For these particular exams, fullcoverage credit requires that the weld and applicable base material be examined in twodirections axially (beams are perpendicular to the weld axis) and two directionscircumferentially (beams are parallel to the weld axis). Although the previous data did notfully document how coverage was determined, the following compares the previous andcurrent examinations:(1) RHR-CA-2AM (1995) axial scans were performed from both sides of the weld and fullcoverage credit was claimed on all but a small portion of the vessel and NLS2012064AttachmentPage 2 of 4distributor ring side base material and weld. A 45' transducer with a "FullVee Path" calibration was credited as achieving the majority of the twodirection axial scan coverage. Additionally, a supplemental 0' transducerwas used from the face of the filet weld and was credited.M (2001) axial scans were performed using similar exam techniques as usedin 1995 with the exclusion of the 0' transducer. The coverage calculationdocumented was carried over from the 1995 data.M (2011) axial scans were performed from both sides of the weld and fullcoverage credit was limited due to the weld configuration. Current axialcoverage was obtained using a primary 45' transducer with a "Full VeePath" calibration and supplemented with 60' and 70' transducers whereapplicable. The use of a 0' transducer is not a currently accepted techniquefor axial angle beam inspection and therefore was not performed.M (1995) circumferential scans were performed from both sides of the weldusing a 45' transducer in the clockwise and counterclockwise directions inrelation to weld's centerline using a "Full Vee Path" calibration. It alsoappears that the use of the 0' transducer was credited for additionalcoverage.0 (2001) circumferential scans were performed using similar examtechniques as in 1995 with the exclusion of the 0' transducer. Thecoverage calculation documented was carried over from the 1995 data.0 (2011) circumferential scans were performed from both sides of the weldin the clockwise and counterclockwise directions in relation to weld'scenterline using a "Single Vee Path" calibration. The use of a "Full VeePath" calibration using a 45' transducer and the use of a 0' transducerfrom the face of a filet weld are not accepted techniques forcircumferential angle beam inspection and therefore were not performed.(2) RHR-CB-IAN (1995) axial scans were performed from both sides of the weld and fullcoverage credit was claimed on all but a small portion of the nozzle sidebase material. A 45' and 60' transducer with "Full Vee Path" calibrationswere used to credit two directional axial scan coverage.0 (2001) axial scans were performed using similar exam techniques as in1995. The total examination coverage was recalculated to be 90.3%.0 (2011) axial scans were performed using a 45' transducer with a "Full VeePath" calibration and supplemented with 60' and 70' transducers from the NLS2012064AttachmentPage 3 of 4vessel side of the weld as an acceptable single-sided exam technique thatachieves 100% two directional axial scan coverage.M (1995) circumferential scans were performed from the vessel side of theweld using a 45' transducer in the clockwise and counterclockwisedirections in relation to weld's centerline. It appears that the samecoverage calculation techniques that were used to credit axial scancoverage were also used for the circumferential scans.0 (2001) circumferential scans were performed using similar examtechniques as in 1995. The total examination coverage was recalculated tobe 90.3%.0 (2011) circumferential scans were performed from the vessel side of theweld in the clockwise and counterclockwise directions in relation to weld'scenterline using a "Single Vee Path" calibration. The use of a "Full VeePath" calibration using a 45' transducer is not an accepted technique forcircumferential angle beam inspection and therefore was not performed.NRC Question #3Please discuss whether or not alternative beam-angle examinations were attempted. Also,please describe the impact of these alternatives, ifany, on coverage.Response #3a. RHR-CA-2A and RHR-CB- I A(1) For axial scans, 60' and 70' angles were used to increase exam coverage asnoted on the drawing included in Revision 0 of the Relief.(2) For circumferential scans, a 45' transducer using a "Single Vee Path"calibration is the optimal technique for detecting axially oriented flaws inside acurved surface and therefore no additional angles were credited to increasecircumferential scan coverage.NRC Question #4Please provide a diagram of the residual heat removal vessel on which the examinations wereperformed indicating on the diagram where the welds of interest are located.Response #4See following Figure:
NLS2012064AttachmentPage 4 of 4FIGURE