ML13063A018

Browns Ferry Nuclear Plant, Unit 2, Response to Request for Additional Information Regarding Relief Request 2-ISI-28 (TAC No. ME8779)

ML13063A018
Person / Time
Site:	Browns Ferry
Issue date:	02/27/2013
From:	Shea J W Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2-ISI-28, TAC ME8779
Download: ML13063A018 (9)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402February 27, 201310 CFR 50.41OCFR 50.55aATTN: Document Control DeskU.S. Nuclear Regulatory CommissionWashington, D.C. 20555-0001Browns Ferry Nuclear Plant, Unit 2Renewed Facility Operating License No. DPR-52NRC Docket No.50-260Subject: Response to Request for Additional Information Regarding ReliefRequest 2-ISI-28 (TAC NO. ME8779)References: 1. Letter from TVA to NRC, "American Society of MechanicalEngineers,Section XI Code, Inservice Inspection Program for theUnit 2 Third Ten-Year Inspection Interval, Request for Relief2-ISI-28," dated May 24, 20122. Letter from NRC to TVA, "Browns Ferry Nuclear Plant, Unit 2 -Request for Additional Information Regarding Relief Request2-ISI-28 (TAC NO. ME8779)," dated November 2, 2012(ADAMS No. ML12306A352)On May 24, 2012, the Tennessee Valley Authority (TVA) submitted "American Societyof Mechanical Engineers, Section Xl Code, Inservice Inspection Program for the Unit 2Third Ten-Year Inspection Interval, Request for Relief 2-1SI-28 (Reference 1). By NRCletter dated November 2, 2012 (Reference 2), TVA received a Request for AdditionalInformation (RAI) regarding Relief Request 2-ISI-28 for Browns Ferry Nuclear Plant(BFN) Unit 2. The NRC requested the response within 90 days from the date ofissuance. Per email dated January 30, 2013, TVA requested and was granted a21-day extension for the response to the RAI letter. Per email datedFebruary 15, 2013, TVA requested and was granted a 7-day extension for theresponse to the RAI letter. Therefore, the response is due 118 days from date ofissuance, i.e., by February 27, 2013.4DY47Printed on recycled paper U.S. Nuclear Regulatory CommissionPage 2February 27, 2013The enclosure to this letter provides the TVA response to the NRC RAI letter.This letter does not include any new regulatory commitments. Please direct anyquestions concerning this matter to Tom Hess at (423) 751-3487.NRespectfuJ. W. SheaVice President, Nuclear LicensingEnclosure:TVA Response to NRC Request for Informationcc: (Enclosure):NRC Regional Administrator -Region IINRC Senior Resident Inspector -Browns Ferry Nuclear PlantAlabama State Department of Public Health Response to Request for Additional Information Regarding Relief Request 2.1SI.28TVA Response to NRC Request for InformationNRC Request for Additional Information Question 1The Table on page E-6 indicates that the request is for two welds. For each sketch provided,identify the weld(s) that relief is being requested by using standard American Welding Society weldsymbols pointing to each weld face to identify that weld. If a weld face contains more than oneweld designation, identify this on each sketchTVA ResponseRequest for Relief 2-1SI-28 requests relief from weld examination coverage requirements for onereactor pressure vessel nozzle-to-vessel full penetration weld and nozzle inside radius section.Attachment 1 shows the nozzle to vessel weld (N 10-NV), including the requested weld symbols. A builtup pad machined to form a socket for connection of Standby Liquid Control (SLC) piping is present onthe inner radius of the nozzle forging. Details of the inner radius configuration are provided inAttachment 2.NRC Request for Additional Information Question 2Identify the American Society of Mechanical Engineers material designation for each part of eachweld. If a material is clad with Stainless Steel or other metal, clearly identify that material.TVA ResponseThe SLC nozzle is located in the lower head upper segment of the bottom head assembly. TheSLC nozzle forging is fabricated from ASTM A 508, Class 2 manganese-molybdenum steelconforming to ASME Code Case 1332-2 and welded to the lower head using E9016-G. The lowerhead upper segment is clad with E309L.NRC Request for Additional Information Question 3Provide specific details of the basis that 100 percent ultrasonic testing cannot be accomplished,such as the specific design and the conditions that prevent the welds from being examined 100percent by the ultrasonic testing technique.TVA ResponseSpecifically, the limitations are due to the radius of curvature in the transition area between thenozzle and the vessel shell, and geometric design configurations limiting access to a single side ofthe weld. In order to meet the Code requirements, the nozzles and/or subject vessels would haveto be modified to facilitate access for ultrasonic search units.E-1 NRC Request for Additional Information Question 4Address whether any indications, detected on the RPV nozzle-to-vessel welds, were evaluated tobe either relevant or nonrelevant indications. If any indications were detected, discuss thedisposition of these indications.TVA ResponseThere were no recordable indications identified during the inspection of Welds N10-NV and N10-1R.NRC Request for Additional Information Question 5Address how the coverage for the NIO-IR inner radius examination was calculated. Provide acoverage map showing the areas that were missed.TVA ResponseModeling report IR-2004-43 was developed by the EPRI NDE Center. The essential geometricparameters of the Browns Ferry Standby Liquid Control nozzle and the qualified procedureessential variables were input into the EPRI software to calculate the coverage obtained.'Attachment 3 provides the coverage map for the limited volume of coverage.NRC Request for Additional Information Question 6From the Coverage Data Sheets (CDSs), CDS-01 shows that the 60-degree probe can approachvery close to the edge of the fillet. In CDS-02, the drawing shows that the 50-degree probe stopsmuch earlier and the line labeled "50°0' appears to be drawn with an angle of 60 degrees. Provide adrawing that shows the regions inspected by the 50-and 60-degree probes.TVA ResponseThe area of limitation, calculated in CDS-01, is based on the index point of the 60 degreetransducer, when the front (nose) is butted up against the outside nozzle radius. The indexpoint location, in this case, can be marked by the extrapolation of the dashed arrow that isdepicted exiting the Code Required Volume of Coverage (CRV). Note that the solid arrow thatpoints to the vessel toe of the outside radius is for reference only, and does not apply to thetransducer exit point, nor was used in the calculation of the achieved volume. The depiction oftransducer angles presented in CDS-02 are representative of the compound angles of skew(+/- 13 to 40 degrees) coupled with the angle of propagation (50 degree shear) within thematerial, at the minimum and maximum radial transducer positions. This results in a parallax.However, the two-dimensional (single-slice) drawing depicts that the 50 degree sheartransducer at the maximum radial position with a skew of +/- 40 degrees strikes the ID at theouter limit (vessel side of weld) of the CRV. Likewise, the 50 degree shear transducer at theminimum radial position with a skew of +/- 13 degrees strikes the ID at the inner limit (nozzleside of weld) of the CRV. Modeling report IR-2003-31 was developed by the EPRI NDE Centerutilizing modeling software. The essential geometric parameters of the Browns Ferry StandbyLiquid Control nozzle and the qualified procedure essential variables were input into thesoftware to calculate the coverage obtained. The coverage plot on CDS-02 combines theE-2 details of the modeling report IR-2003-31, Figure 2-4 and Figure 2-5, for the calculation of theextent of circumferential coverage.NRC Request for Additional Information Question 7In CDS-02, showing the circumferential examination for axial flaws, the drawing appears to showthat the weld was inspected using a 50-and 60-degree skew. This drawing appears to be a drawingof the axial inspection. Please verify the skew angles used to calculate the coverage of thecircumferential examination.TVA ResponseThe depiction in CDS-02 uses compound angles (incident angle plus skew angles) resulting in aparallax, as rendered in the two-dimensional drawing. However, the skew angles used for the 50degree shear transducer were +/- 13 degrees to +/- 40 degrees, which results in a maximummisorientation angle of 0 degrees (perpendicular to an axial flaw), for the circumferential exam.CDS-02 is correctly identified as circumferential exam coverage.NRC Request for Additional Information Question 8For Weld NIO-NV, the calculation for circumferential ultrasonic examination coverage gives ahigher weight to the lower 15 percent than the upper 85 percent. From the CDSs, it appears thatthe Composite Axial plus Circumferential Coverage is 81.7 percent, not 86.2 percent. Confirm thatthe Composite Axial plus Circumferential Coverage is 86.2 percent. If not, address thediscrepancy.TVA ResponseThe correct value of the Composite Axial plus Circumferential Coverage is 81.7 percent. Thecalculation in the examination report determined the percentage of coverage obtained. But, duringcalculation of the circumferential coverage of the upper 85% of thickness (T), the calculation didnot include the appropriateweighting factor of 85% (0.85). The value should have been multipliedby 85% (0.85) prior to composite. This error has been entered into TVA's Corrective ActionProgram.E-3 ATTACHMENTS:1. Detail B, Drawing 122858E-1 1, Lower Head Upper Segment Drawing2. Detail B, Drawing 151863E, Modification of 2" Liquid Control Nozzle3. IR 2004-43, Figures 4 and 5E-4 Attachment 1Detail B, Drawing 122858E-1 1, Lower Head Upper Segmelnt Drawing _..I IIJ t'VL xBE 7.4L& 3 Attachment 2Detail B, Drawing 151863E, Modification of 2" Liquid Control Nozzle'MontF#. .4b as --j-.1- A=,`/ I 7Vj RWR I IIOWFA)~*.w0bIA Attachment 3IR 2004-43, Figures 4 and 5Figure 4 shows the minimum and maximum probe radial positions and the portion of theexamination volume covered by the vessel shell detection technique, 70/(2 to 23)v, forprobes scanned at the azimuth angle of 00.Browns Ferry Standby Liquid Control Nozzle (N10);70/(2 to 23)vs134between the dottedlines represents 130the non inspected zarea. I A0 2 48R10 12 14 16Figure 4. Browns Ferry Standby Liquid Control Nozzle (N 10): Probe Scan Limits andExamination Coverage for Vessel Shell Detection Technique, 70/(2 to 23)v.Figure 5 shows the minimum and maximum probe radial positions and the portion of theexamination volume covered by the vessel shell detection technique, 65/(1 to 1O)v, forprobes scanned at the azimuth angle of 0'.Browns Ferry Standby Liquid Control Nozzle (N10);651(1 to 1O)vs134Z048R10 12 14 16Figure 5. Browns Ferry Standby Liquid Control Nozzle (N 10): Probe Scan Limits andExamination Coverage for Vessel Shell Detection Technique, 65/(1 to 10)v.6