W3F1-2012-0102, Supplemental Response to an NRC Request for Additional Information (RAI) Associated with W3-ISI-020, Request for Alternative to ASME Code Case N-770-1 Baseline Examination

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Supplemental Response to an NRC Request for Additional Information (RAI) Associated with W3-ISI-020, Request for Alternative to ASME Code Case N-770-1 Baseline Examination
ML12352A172
Person / Time
Site: Waterford Entergy icon.png
Issue date: 12/16/2012
From: Rich C
Entergy Operations
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
W3F1-2012-0102, TAC ME9801
Download: ML12352A172 (13)
v • d • e


Text

{{#Wiki_filter:Entergy Operations, Inc. 17265 River Road Killona, LA 70057-3093 Tel 504 739 6496 Fax 504 739 6698 crich@entergy.com Carl E. Rich, Jr. Nuclear Safety Assurance Director Waterford 3 W3F1-2012-0102 December 16, 2012 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Waterford 3 Supplemental Response to an NRC Request for Additional Information (RAI) associated with W3-ISI-020, Request for Alternative to ASME Code Case N-770-1 Baseline Examination [TAC No. ME9801] Waterford Steam Electric Station, Unit 3 Docket No. 50-382 License No. NPF-38

References:

1. Entergy letter dated October 16, 2012, Waterford 3 Request for Alternative W3-ISI-020, ASME Code Case N-770-1 Baseline Examination Request for Alternative (W3F1-2012-0085)

(ML12296A241)

2. NRC email dated November 5, 2012, RAI on Waterford 3's "Request for Alternative W3-ISI-020, ASME Code Case N-770-1 Baseline Examination Request for Alternative. [TAC ME9801]

(ML12310A454)

3. Entergy letter dated November 15, 2012, Response to an NRC Request for Additional Information (RAI) associated with W3-ISI-020, Request for Alternative to ASME Code Case N-770-1 Baseline Examination (W3F1-2012-0096) (ML12324A170)

Dear Sir or Madam:

Entergy Operations, Inc. requested NRCs approval of Request for Alternative W3-ISI-020 for the Waterford Steam Electric Station, Unit 3 (Waterford 3) in Reference 1. The request is associated with the use of an alternative to the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Code Case N-770-1 as conditioned in 10 CFR 50.55a(g)(6)(ii)(F)(3). The NRC has authorized a similar proposed alternative at Arkansas Nuclear One, Unit 2.

W3F1-2012-0102 Page 2 Waterford 3 received a request for additional information (RAI) as documented in Reference 2. Entergy responded to the NRC's RAI in order to complete the review of Request for Alternative W3-ISI-020 as documented in Reference 3. Subsequent to the submittal of Reference 3, it was recognized that additional information was needed relative to one of the questions in the original NRC request for additional information. This specifically deals with Question 3.c.i, which has been discussed during teleconferences between the NRC staff and Entergy. Additionally, during preparation of this supplemental response, it was identified that there is stainless steel butter applied to the safe end of the welds. This stainless steel butter was not factored in the weld volume information in the weld data table previously provided in Reference 3. Please disregard the Updated Weld Data Table contained in Attachment 3 of Reference 3. It has been verified that it is not necessary to forward a corrected copy of the table to the NRC. Condition Report CR-WF3-2012-07464 has been issued within the Waterford 3 Corrective Action Program to address the incorrect information previously provided. Please find Waterford 3's supplemental response to the request for additional information in Attachments 1 through 3. This letter contains no new commitments. If you have any questions or require additional information, please contact the licensing Manager, Chester Fugate, at (504) 739-6685. Sincerely, CRlRJP Attachments: 1. Supplemental Response to Request for Additional Information - Use of ASME Code Case N-770-1 Baseline Examination

2. Weld Data Table
3. RCP Cold Leg Dissimilar Metal Weld Design Drawings

W3F1-2012-0102 Page 3 cc: Mr. Elmo E. Collins, Jr. RidsRgn4MailCenter@nrc.gov Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 E. Lamar Blvd. Arlington, TX 76011-4511 NRC Senior Resident Inspector Marlone.Davis@nrc.gov Waterford Steam Electric Station Unit 3 Dean.Overland@nrc.gov P.O. Box 822 Killona, LA 70066-0751 U. S. Nuclear Regulatory Commission Kaly.Kalyanam@nrc.gov Attn: Mr. N. Kalyanam Mail Stop O-07D1 Washington, DC 20555-0001

Attachment 1 to W3F1-2012-0102 Supplemental Response to Request for Additional Information Use of ASME Code Case N-770-1 Baseline Examination to W3F1-2012-0102 Page 1 of 3 Request for Additional Information Use of ASME Code Case N-770-1 Baseline Examination

3. Section 5 of the proposed alternative, Proposed Alternative and Basis for Use, states that the SI-UT-130 Rev. 3 UT procedure has been successfully qualified for single-sided axial scan examination, per the requirements of the ASME Code, Section XI, Appendix VIII
c. Provide data for the circumferential scan coverage of the susceptible material for the inner 1/3 of wall thickness of each of the subject welds
i. For each weld where the circumferential scan coverage of the susceptible material is less than 100 percent, please provide an axial cross sectional map indicating the unexamined zone and the size of largest potential flaw in the susceptible material within the unexamined zone Circumferential Scan Coverage for Axial Flaws- Structural Integrity Associates performed the Waterford 3 PDI examinations for the RCP cold leg suction and discharge nozzle welds and associated safety injection nozzle welds in accordance with the Performance Demonstration Qualification Summary (PDQS) for SI-UT-130 provided in Reference 3. For weld profiles that have a tapered surface, the PDQS states that the procedure is not qualified to detect axial flaws on the far side (stainless steel side) of a single sided access. This would limit the qualified exams from the near side (carbon steel side) to the weld centerline including the PWSCC susceptible weld material scanned within this detectable region. The tapered weld surface qualification process was based on the ability of the detection methods to use both electronic and mechanical (manual) skewing. The procedure PDQS requires both mechanical and 10 degrees of electronic skewing in both directions to provide assurance that all susceptible material was examined. The application of both mechanical and electronic skewing established the ability of the detection methods to identify flaws in the susceptible material for the areas for which the procedure is qualified.

When the vendor performed the examination of these welds, they scanned from the carbon steel side of the weld. In addition to the scanning qualified by the procedure, scanning was also performed from the weld surface in an attempt to provide the maximum insonification of the susceptible weld material possible. Even though not within the qualified coverage of the procedure, UT beams were directed into the far side of the weld centerline to interrogate that area for potential flaws. This provided some additional assurance that a potential flaw would be detected in this region to provide defense in depth. This complete scan approach provides a high degree of assurance that the welds were examined to the maximum extent possible including the unqualified region in accordance with the procedure PDQS. As discussed before, no examinations were performed from the cast austenitic stainless steel (CASS) safe ends due to limitations in UT methods for this material and limited scanning area due to the short safe-end length. contains a table which includes the circumferential scan for axial flaw coverage of PWSCC susceptible welds received with both the PDQS qualified and unqualified examination to W3F1-2012-0102 Page 2 of 3 volumes. The table also indicates if the PDQS taper weld limitation was applicable. In all cases, the full extent of the PDQS qualified detectable area (near side of scan) for the susceptible material is documented, as well as the additional non-qualified exam volumes obtained, which included 100% of the total PWSCC susceptible area. Weld Flaw Location - Both the Reactor Coolant Pump (RCP) suction and discharge dissimilar metals have similar weld preps at the CASS safe-end and ferritic piping. The ferritic piping is buttered with an Alloy 82/182 filler metal. The CASS safe-end is buttered with a 308 Stainless Steel (SS) filler metal. Westinghouse generic industry PWSCC flaw analyses considered an axial flaw in the center of the dissimilar metal (DM) weld as illustrated in the RCP suction and discharge drawings in for the following reasons: The root of these welds requires an inside diameter (ID) backgroove to sound base and weld metal with a subsequent Alloy 82/182 backfill weld out. This process increases the residual stresses at the ID root. In addition, the weldment is diluted with the 308 SS on the stainless steel side. Therefore, if a PWSCC flaw were to initiate, it has a highest probability to occur in the centerline of the ID root weld. With an assumed flaw having a 2 to 1 aspect ratio and a 10% wall initial flaw depth, the assumed flaw would essentially cover the width of the root of the DM weld. This assumed flaw originating at the center of the DM weld is larger than and bounds a flaw originating from the corner near the stainless steel to DM weld root. As the flaw propagates through the weld, the axial length will continue to be conservatively greater than the width of the weld. Whereas if a flaw were assumed to initiate near the stainless steel to Alloy 82/182 weld interface, a corner type flaw would only grow in the direction of the susceptible material, resulting in a smaller flaw than the assumed centerline flaw. Additionally, the neighboring stainless weld has a beneficial effect on the DM weld for PWSCC (compressive residual stress). The only other possible crack initiation site is near Alloy 82/182 to clad interface. The axial flaw will arrest as it radially intersects the carbon steel pipe. Crack propagation beyond the carbon steel ID from the clad would have been readily detected from the past examination. Therefore, the most conservative crack location is at the centerline of the weld root. Weld Flaw Detectability - The procedure is qualified through EPRI/PDI to detect flaws as shallow as 10% of the nominal pipe wall thickness as documented in Supplement 10, paragraph 1.2(c)(1) of Appendix VIII of ASME Section XI. However, Supplement 10 does not mandate a specific aspect ratio for flaws or a minimum or maximum reflective area. A 10% through wall flaw specified in Supplement 10 would have a specific reflective area which could be credited as the minimum detectable reflective area. Although it specifies a minimum flaw depth for detection and sizing, Supplement 10 does not mandate a specific aspect ratio (a/l) for the flaws nor a maximum reflective area. However, Supplement 8, Table VIII-S8-1 for Bolts and Studs does contain requirements for a reflective area. Therefore, using the requirements of ASME XI, Appendix VIII, Table VIII S8-1, a quantitative comparison can be made. This table shows a maximum reflective area of 0.059 in2. The most conservative flaw aspect ratio of ASME Section XI, IWB-3514 would be 2 to 1. For a pipe thickness of 3.25 a 10% through wall flaw would be 0.325. Using the equation Af = 1/4r2 where r is the 10% flaw depth of 0.325, a 0.083 in2 reflective area is determined. When compared to the greater than 4 diameter bolting configuration, there is a conservative margin of 40%. When compared to the 2 to 4 diameter bolting configuration, there is a margin greater than 3 times. A slightly larger flaw having a 3 to 1 aspect ratio would be fully constrained by the CASS backgroove. Such a flaw would produce a much larger reflective area, on the order of 1.5 times the size of a 10% 2 to 1 flaw, within the to W3F1-2012-0102 Page 3 of 3 qualified examination volume, and thus increase the detection margin from the Supplement 8 defined areas proportionally. Therefore, a 10% 2 to 1 flaw is concluded to have sufficient reflective area to support detection within the qualified volume. Entergy has established the weld root cross-sections for the subject welds by use of design drawings and other design documents to properly characterize the expected flaw heights (Attachment 3). Entergy previously provided information in letter 2CAN121201 dated December 4, 2012 [ADAMS Accession ML12340A449] indicating that analyses had concluded a postulated initial flaw that is 16.7% through wall would grow to the ASME Code allowable flaw size of 75% through wall in approximately 54 months from the inspection. The largest undetected flaw that could exist due to the examination limitations is 10% through wall, providing a margin of 6.7%. Based on the completion of the previous inspections in October 2009, the crack growth analysis supports operation of Waterford 3 until the next scheduled refueling outage in the spring of 2014. In conclusion, the weld coverage table included in Attachment 2 shows the circumferential coverage (PDQS qualified and non-qualified) obtained for the Waterford 3 Safety Injection nozzle and RCP cold leg DM welds. In all cases for the RCP cold leg DM welds, the full extent of the PDQS qualified detectable area (near side of scan) for the PWSCC susceptible material was equal to 100% of the circumferential scan for axial flaws. Based on the above it was determined that a 10% axial flaw could potentially be present in the PWSCC material before it could be detected via the qualified exam coverage. Weld profile drawings for the RCP suction and for the discharge lines are provided in Attachment 3. These drawings depict the weld area dimensions associated with each RCP DM weld based on the construction drawings for the end preparations as well as an assumed weld flaw having a 2 to 1 aspect ratio that represents a 10% detectable flaw. This flaw profile is considered appropriate based on the considerations discussed above regarding the potential flaw having enough reflective area for the exam to detect it and the conservative assumptions associated with assuming this flaw would develop at the centerline of the DM weld and be limited to a 2 to 1 aspect ratio. to W3F1-2012-0102 Weld Data Table to W3F1-2012-0102 Page 1 of 2 Weld Data Table MRP-139 Volume N-770-1 Coverage Volume Coverage of PWSCC susceptible material Tapered Weld Fig Component Component Axial Circ Axial PDQS ID Description PDQS qualified Non-PDQS (Note1) Scan for Scan for Scan for Limitation Circ Scan for Axial Qualified Circ Scan Circ Axial Circ Flaws for Axial Flaws Flaws Flaws Flaws 30 RCP 1A Inlet 07-002 Elbow (CS) to Safe- 100% 80% 100% 84.8% 100% Yes 501 end (Cast SS) 30 RCP 1A Outlet 08-014 Safe-end (Cast SS) to 100% 78% 100% 67% 100% Yes 502 Pipe(CS) 30 RCP 1B Inlet 09-016 Elbow(CS) to Safe- 100% 83% 100% 68% 100% Yes 501 end (Cast SS) 30 RCP 1B Outlet 10-002 Safe-end (Cast SS) to 100% 81% 100% 69% 100% Yes 502 Pipe (CS) 30 RCP 2A Inlet 11-002 Elbow (CS) to Safe- 100% 80% 100% 65% 100% Yes 501 end (Cast SS) 30 RCP 2A Outlet 12-012 Safe-end (Cast SS) to 100% 76% 100% 100% 100% No 502 Pipe (CS) 30 RCP 2B Inlet 13-016 Elbow (CS) to Safe- 100% 79% 100% 67.2% 100% Yes 501 end (Cast SS) to W3F1-2012-0102 Page 2 of 2 MRP-139 Volume N-770-1 Coverage Volume Coverage of PWSCC susceptible material Tapered Weld Fig Component Component Axial Circ Axial PDQS ID Description PDQS qualified Non-PDQS (Note1) Scan for Scan for Scan for Limitation Circ Scan for Axial Qualified Circ Scan Circ Axial Circ Flaws for Axial Flaws Flaws Flaws Flaws 30 RCP 2B Outlet 14-002 Safe-end (Cast SS) to 100% 80% 100% 67% 100% Yes 502 Pipe (CS) 12 RCS 1A CL, SI 08-009 Nozzle to Safe-end 100% 100% 100% 100% 100% No N/A (Cast SS) 12 RCS 1B CL, SI 10-008 Nozzle to Safe-end 100% 100% 100% 100% 100% No N/A (Cast SS) 12 RCS 2A CL, SI 12-009 Nozzle to Safe-end 100% 100% 100% 100% 100% No N/A (Cast SS) 12 RCS 2B CL, SI 14-006 Nozzle to Safe-end 100% 100% 100% 100% 100% No N/A (Cast SS) Note 1: 501 refers to Drawing 1201260.501 contained in Attachment 3 502 refers to Drawing 1201260.502 contained in Attachment 3

Attachment 3 to W3F1-2012-0102 RCP Cold Leg Dissimilar Metal Weld Design Drawing to W3F1-2012-0102 Page 1 of 2 

                                                                      ~M' SCALf 1 : I RAW lo;t; = .32 in.              L_ .,C, GROOVE TO SOUND METAL At-D WELD.

2T0 1 RATIO

  • NOTES:

I. mE WALK-OOWN DIMENSIONS REPORTED IN THE ADJACENT TABLE ARE LARGER mAN DESIGN waD DIMENSIONS ABOVE DUE TO mE HAl EXTENDING our INTO THE BASE MATERIAL AND waD CAPS INSTAllED PR10R TO GRINDING_

2. DESlGN DRAW ING IS FOR Rep SUCTION DMW. 07-002.

0Il-{)16. ll-002. 13-{)16. to W3F1-2012-0102 Page 2 of 2 SKTlON A-A 

                                                                             ~M" FLAW I~ = _ 32in_

SCALE 1 _I 2101 RATIO L_""e, GROOVE TO SOUND METAL AND waD_

  • i
             '--t-~-~-~-

NOTES: I. m E WALK-DOWN DIMENSIONS REPORIID 8HOW ARE LARGER lHAN DfSlGN WElD DIM ENSlONS ABOVE DUE TO 111 E HAl EXTENDING OUT INTO THE BASE MATERW "I'D WELD CAPS INSTAllED PRIOR TO GRIhONG_

2. DESIGN IS ~ IICP DISCHARGE DMW 00-014. 1().{X)2. 12-<l12 1<<Xl2.
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