TMI-10-100, Submittal of Relief Request RR-10-02 Re Weld Overlay of the Pressurizer Spray Nozzle to Safe-End & Safe-End to Elbow Dissimilar Metal Welds

Submittal of Relief Request RR-10-02 Re Weld Overlay of the Pressurizer Spray Nozzle to Safe-End & Safe-End to Elbow Dissimilar Metal Welds

ML102740532
Person / Time
Site:	Three Mile Island
Issue date:	09/30/2010
From:	Cowan P Exelon Generation Co, Exelon Nuclear
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
TAC MD4191, TAC MD5427, TMI-10-100
Download: ML102740532 (19)

Text

10 CFR 50.55a TMI-10-100 September 30, 2010 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No. 50-289

Subject:

Submittal of Relief Request RR-10-02 Concerning the Weld Overlay of the Pressurizer Spray Nozzle to Safe-End and Safe-End to Elbow Dissimilar Metal Welds

References:

1) Letter from H. K. Chernoff (U.S. Nuclear Regulatory Commission) to C. M.

Crane (AmerGen Energy Company, LLC), "Three Mile Island Nuclear Station, Unit 1 (TMI-1), Relief Request 2007-TMI-01, Regarding Structural Weld Overlays on Pressurizer Surge, Pressurizer Spray, and Hot Leg Decay Heat Drop Line Nozzles, (TAC NO. MD5427)," dated October 17, 2007

2) Letter from R. G. West (AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Pressurizer Weld Overlay Examination Results and Closeout of Confirmatory Action Letter Requirements (TAC NO. MD4191 ),"

dated December 4, 2007

3) Letter from R. G. West (AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Response to Request for Additional Information -

Relief Request 2007-TMI Structural Weld Overlays (SWOLs) of the Pressurizer Surge, Pressurizer Spray, and Hot Leg Decay Heat Drop Line Nozzle Dissimilar Metal Welds including the SWOL of Adjacent Welds," dated August 13,2007 Attached for your review is a relief request associated with the fourth Inservice Inspection (lSI) interval for Three Mile Island Nuclear Station (TMI), Unit 1. TMI, Unit 1 is requesting relief to perform a weld overlay of pressurizer spray nozzle to safe-end and safe-end to elbow dissimilar metal welds. The fourth interval of the TMI, Unit 1 lSI program complies with the 2004 Edition,

Submittal of Relief Request RR~10-02 Concerning the Weld Overlay of Dissimilar Metal Welds September 30, 2010 Page 2 no Addenda, of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code. The fourth lSI interval will begin on April 20, 2011. We request your approval by September 30, 2011.

In the Reference 1 letter, AmerGen Energy Company, LLC (now Exelon Generation Company, LLC (Exelon)) received approval to perform a structural weld overlay of these same pressurizer spray nozzle to safe-end and safe~end to elbow dissimilar metal welds if examination results from the 2007 outage were unacceptable. As discussed in Reference 2, an overlay was not performed because no degradation was detected during the examination. Accordingly, this portion of the relief request was never implemented. The attached relief request is similar to the relief request approved in the Reference 1 letter.

A summary of the regulatory commitments contained in this submittal is provided in Attachment 1.

If you have any questions concerning this letter, please contact Tom Loomis at (610) 765-5510.

Respectfully, P~lmC\l~ B.

Director ~ Licensing & Regulatory Affairs Exelon Generation Company, LLC Attachments: 1) Summary of Commitments

2) Relief Request RR-1 0~02 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, TMI USNRC Project Manager, TMI

ATTACHMENT 1 Summary of Commitments

The following table identifies commitments made in this document. (Any other actions discussed in the submittal represent intended or planned actions. They are described to the NRC for the NRC's information and are not regulatory commitments.)

COMMITMENT TYPE COMMITTED COMMITMENT DATE OR ONE-TIME Programmatic "OUTAGE" ACTION (Yes/No)

(Yes/No)

Exelon Generation Company, Within 30 days Yes No LLC commits to providing the after the completion results of the ultrasonic of the last exam ination of the structural ultrasonic weld overlay on the TMI, Unit 1 exam ination of the Pressurizer Spray Nozzle welds weld overlays PR-009BM and SP-021 BM. during the Fall 2011 TMI, Unit 1 The results will include: T1 R19 refueling

• A list of the 1

indications outage.

detected ,

• The disposition of all the indications using the standards of ASME Section XI, Nonmandatory Appendix Q,

• The type and, if possible, nature of the indications2.

Also included in the results will be a discussion of any repairs to the overlay material.

1The recording criteria of the ultrasonic examination procedure to be used for the examination of the TMI, Unit 1 pressurizer overlay SI-UT-126 requires that all indications, regardless of amplitude, be investigated to the extent necessary to provide accurate characterization, identity and location. Additionally, the procedure requires that all indications, regardless of amplitUde, that cannot be clearly attributed to the geometry of the weld or overlay configuration, be considered flaw indications.

2Ultrasonic examination procedure SI-UT-126 requires that all suspected flaw indications are to be plotted on a sectional drawing of the weld and that the plots should accurately identify the specific origin of the reflector.

ATTACHMENT 2 Relief Request No. RR*10*02

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 1 of 14)

Request for Relief for Alternative Requirements of Full Structural Weld Overlays (SWOLs) of the Pressurizer Spray Dissimilar Metal Welds in Accordance with 10 CFR 50.55a(a)(3)(i) 1.0 ASME CODE COMPONENT(S) AFFECTED Code Class: 1

Reference:

IWA-4000, "Repair/Replacement Activities" Examination Category: R-A Item Number: See Table 1A for listing

Description:

Full SWOLs of the Pressurizer Spray Dissimilar Metal Welds Component Number(s): See Table 1A for listing Drawing Number(s): 1D-ISI-RC-005 1D-ISI-RC-012 2.0 APPLICABLE CODE EDITION AND ADDENDA

1. American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 2004 Edition, no Addenda.

2. Pressurizer Code of Construction, ASME Code Section III, 1965 Edition, through Summer 1967 Addenda.

3. USAS B31.7, Nuclear Power Piping, February 1968 Draft Including June 1968 Errata.

4. USAS B31.1, Power Piping, 1967 Edition.

3.0 APPLICABLE CODE REQUIREMENT

1. American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 2004 Edition no Addenda, IWA-4000, "Repair/Replacement Activities".

2. Nuclear Regulatory Commission (NRC) conditionally approved Code Case N-504-3, "Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping,Section XI, Division 1," with condition as specified in Regulatory Guide (RG) 1.147, Revision 15.

3. NRC conditionally approved Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 2 of 14)

Section XI, Division 1,"with condition as specified in Regulatory Guide (RG) 1.147, Revision 15.

4. ASME Code,Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement 11, "Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds".

4.0 REASON FOR REQUEST Dissimilar metal welds on U.S. Pressurized Water Reactor (PWR) Reactor Coolant Systems (RCS) often consist of Alloy 82/182 weld material to connect stainless steel pipe and safe-ends to vessel and piping nozzles, which are generally constructed using carbon or low alloy ferritic steel. These welds have shown a propensity for Primary Water Stress Corrosion Cracking (PWSCC) degradation, especially in components subjected to higher operating temperatures, such as the pressurizer or hot leg.

Three Mile Island Nuclear Station (TMI), Unit 1 plans to install a full structural weld overlay (SWOL) on the pressurizer (PZR) spray nozzle to safe-end and safe-end to elbow dissimilar metal welds during the T1 R19 refueling outage in Fall 2011.

Exelon Generation Company, LLC (Exelon) is taking a proactive approach in addressing Alloy 600 PWSCC degradation by applying a preemptive SWOL to the pressurizer spray nozzle to safe-end and safe-end to elbow dissimilar metal welds.

SWOLs have been used for several years on both Boiling Water Reactors (BWR) and PWRs to arrest existing (or postulated) flaws from propagating while establishing a new structural pressure boundary. In some cases, SWOLs have been used to reestablish structural integrity of a dissimilar metal weld containing through wall leaking flaws. In addition to proactively mitigating PWSCC in the dissimilar metal weld, the SWOL can provide an acceptable geometry that allows ultrasonic examination in accordance with Performance Demonstration Initiative (POI),

Materials Reliability Program (MRP) (Reference 6), and ASME Section XI requirements.

The welding will be utilizing a mechanized Gas Tungsten Arc Welding (GTAW) process and the ambient temperature temper bead method with ERNiCrFe-7A (referred to as Alloy 52M in subsequent discussion in this document) weld metal.

When temper bead welding is not required, manual GTAW with Alloy 52M may be used if local repairs of weld defects are necessary or if additional weld metal is required locally to form the final SWOL contour. Shielded metal arc welding (SMAW), using Alloy 152 (ENiCrFe-7), would only be used to repair indications in the existing dissimilar metal welds prior to overlay initiation.

10 CFR 50.558 RELIEF REQUEST RR-10-02 Revision 0 (Page 3 of 14)

As discussed herein, there is no comprehensive criterion for a licensee to apply a SWOl repair to a dissimilar metal weld that is constructed of Alloy 82/182 weld material. The American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 2004 Edition, no Addenda, IWA-4000, is used for the TMI, Unit 1 Section XI Repair/Replacement Program, but it does not contain the needed requirements for this type of weld overlay repair.

Repair/replacement activities associated with weld overlays of this type are required to address materials, welding parameters, personnel radiation exposure concerns, operational constraints, examination techniques, and procedural requirements.

5.0 PROPOSED ALTERNATIVE AND BASIS FOR USE Pursuant to 10 CFR 50.55a(a)(3)(i), Exelon proposes applying a SWOl designed in accordance with Code Case N-504-3 (Reference 1) including NRC conditions identified in Regulatory Guide 1.147, Revision 15 (References 2 and 4) with the modifications proposed in Table 2 of this relief request. In addition, Code Case N-638-1 (Reference 3) (including NRC conditions identified in Regulatory Guide 1.147 (Reference 2)) for temper bead welding will be used with modifications proposed in Table 3 of this relief request. Final ultrasonic (UT) examination of the finished SWOl will be performed using Electric Power Research Institute (EPRI) POI demonstrated ultrasonic examination procedures and personnel in lieu of the ASME Section XI, Appendix VIII, Supplement 11 (Reference 5) as proposed in an associated relief request (Reference 13).

Code Case N-504-3 is currently approved for use in RG 1.147, Revision 15 with additional conditions that ASME Code Section XI, 2004 Edition with 2005 Addenda, Appendix Q, be applied to use of the Code Case. The PZR spray nozzle SWOl, described herein, will extend around the full circumference of the dissimilar metal welds as required by Code Case N-504-3. The specific thickness and length will be determined according to the guidance provided in Code Case N-504-3 and Regulatory Guide 1.147, Revision 15. The SWOl will completely cover the dissimilar metal welds, Inconel 600 safe-end, ferritic steel nozzle, and adjacent stainless steel material with Alloy 52M material to the extent that PWSCC susceptible material is mitigated and examination capability is maintained for adjacent welds. The purpose for this SWOl approach is to produce a single weld overlay covering both welds thereby also providing the weld geometry required to perform the final volumetric examinations and obtain the required examination volume coverage.

Prior to installation of the SWOl, TMI, Unit 1 will complete a bare metal visual examination of the nozzle to safe-end and safe-end to elbow dissimilar metal welds immediately after the insulation is removed in the area around the nozzle and

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 4 of 14) dissimilar metal weld areas to ensure that no through-wall cracks exist prior to applying the overlay. The visual examination will be completed in accordance with 10 CFR 50.55a(g)(6)(ii)(E). Exelon intends to complete a POI qualified UT examination of the dissimilar metal welds prior to application of this overlay.

Per N-504-3, Paragraph (d), a liquid penetrant (PT) examination will be performed of the overlay area with an acceptance criteria that no indication greater than 1/16" is permitted. If any indication is found greater than 1/16", the indication will be removed or reduced below the acceptance criteria, and the PT performed again. If any indication(s) do require repair, the repair will be completed and the area will again have a PT completed for final acceptance. Refer to Question 1 from the Exelon Response to a Request for Additional Information (RAI) concerning additional information on PT examinations (Reference 15).

Per N-504-3, flaw evaluations and shrinkage stress effects analyses will be addressed through the approved overlay designs that are currently in development.

These documents will be completed and approved for use prior to application at TMI, Unit 1. Full structural weld overlays are considered physical plant changes and will be approved in accordance with Exelon procedures.

Monitoring of preheat and interpass temperature is necessary to assure the field welding heat input remains within qualified parameters. Weld preheat and heat input are monitored through the use of calibrated contact pyrometers or thermocouples. The interpass temperature is measured multiple times within each layer.

Subsequent inservice examinations will be scheduled and performed in accordance with the requirements of Nonmandatory Appendix Q or alternate schedules accepted by the NRC (for example adoption of ASME Code Case N-770 as proposed by 75FR24324). If a POI qualified UT examination of welds SP-021 BM and PR-009BM is completed prior to application of the weld overlay and no PWSCC or other indications unacceptable to ASME Section XI are identified, the welds will be considered "uncracked" per Code Case N-770. If a pre-overlay POI qualified UT examination is not completed, or PWSCC is detected, or other ASME Section XI unacceptable indications are identified, then the overlay repaired welds will be considered "cracked" per Code Case N-770. Regardless of pre-overlay UT examination status or results, the applied weld overlay will be a full structural weld overlay (assumed circumferential flaw that is 100% through wall extending around the entire circumference of the weld). The design life flaw growth analysis will assume that a 75% through-wall flaw exists at the time of weld overlay deposit, based on flaw detection capability in the outer 25% through-wall of the original weld.

If a flaw is detected in the outer 25% through-wall of the repaired welds the design life flaw growth analysis will be revised to address the actual flaw condition detected as required by ASME Section XI, Appendix Q. In all cases the overlay design will

10 CFR 50.558 RELIEF REQUEST RR-10-02 Revision 0 (Page 5 of 14) comply with Code Case N-504-3, including ASME Section XI, Appendix Q requirements, as specified in this relief.

Exelon intends to install one or more weld barrier layer(s) to prevent hot cracking in stainless steel materials similar to that installed during the 2007 weld overlays (Reference 15).

6.0 DURATION OF THE PROPOSED ALTERNATIVE The duration of the proposed alternative associated with the SWOL is the remaining service life of the components including future plant life extension. Relief from the fourth ten-year lSI interval ASME Section XI, Appendix VIII, Supplement 11 inspection requirements is addressed in Reference 13 and is applicable to this overlay application. The fourth ten-year lSI interval is scheduled to begin on April 20,2011.

7.0 PRECEDENTS A similar relief request was approved for use in the Reference 14 NRC Safety Evaluation Report. However, this overlay was not performed in the 2007 refueling outage and is being resubmitted for approval.

Additionally, similar relief requests for SWOLs of dissimilar metal weld (both PWR and BWR) have been approved for a number of units throughout the industry (see References 7 through 10). A number of units have submitted relief requests citing similar proposed relief request methodology. These relief requests were associated with welding over detected or postulated flaws outside the acceptance criteria of Section XI utilizing proposed modifications to existing Code Cases N-504 and N-638 and NRC conditions for use.

8.0 REFERENCES

1. ASME Code Case N-504-3, "Alternative Rules for Repair of Classes 1,2, and 3 Austenitic Stainless Steel Piping," dated August 4, 2004.

2. Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1," Revision 15, October 2007.

3. ASME Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,"dated February 13, 2003.

4. American Society of Mechanical Engineers (ASME)Section XI Nonmandatory Appendix Q, "Nonmandatory Appendix Q Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments, 2004 Edition with 2005 II Addenda.

10 CFR 50.558 RELIEF REQUEST RR-10-02 Revision 0 (Page 6 of 14)

5. ASME Code,Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement 11, "Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds".

6. "Material Reliability Program: Primary System Piping Butt Weld Inspection and Evaluation Guidelines (MRP-139, Revision 1),"EPRI Report Number 1015009, Final Report, December 2008.

7. Letter from Richard Laufer (NRC) to Christopher M. Crane (AmerGen Energy Company, LLC), "Three Mile Island Nuclear Station, Unit 1 (TMI-1) Request for Relief From Flaw Removal, Heat Treatment, and Nondestructive Examination Requirements for the Third 10-year Inservice Inspection (lSI) Interval (TAG No.

MG1201), "dated July 21,2004, ADAMS Accession Number ML041670510.

8. Letter from Richard J. Laufer (NRC) to Bryce L. Shriver (PPL Susquehanna),

"Susquehanna Steam Electric Station, Unit 1 - Relief from American Society of Mechanical Engineers, Boiler and Pressure Vessel Gode (ASME Gode),

Section XI Appendix VIII, Supplement 11, Requirements and Gases N-504-2 and N-638 Requirements (TAG Nos. MG2450, MG2451, and MG2594),"dated June 22, 2005, ADAMS Accession Number ML051220568.

9. Richard J. Laufer (NRC) to Michael R. Kansler (Entergy Nuclear Operations, Inc.), "Pilgrim Nuclear Power Station Relief Request No. PRR-9 (TAG No.

MG8292),"dated March 22, 2006, ADAMS Accession Number ML060240055.

10. Michael L. Marshall Jr. (NRC) to Christopher M. Crane (Exelon Generation Company, LLC), "Byron Station, Unit No. 1 - Evaluation of Relief Request 13R-08 Pertaining to Structural Weld Overlays (TAG No. MD1761), "dated January 29,2007, ADAMS Accession Number ML062510169.

11. William H. Bateman (NRC) to Michael Bratton (PDI Chairman) (Entergy Nuclear Southwest), "Weld Overlay Performance Demonstration Administered By POI as an Alternative for Generic Letter 88-01 Recommendations," dated January 15, 2002, ADAMS Accession Number ML020160532.

12. Repair and Replacement Applications Genter: "Temperbead Welding Applications 48-Hour Hold Requirements for Ambient Temperature Temperbead Welding, II EPRI Report Number 1013558, December 2006.

13. Pamela B. Cowan (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, IISubmittal of Relief Requests Associated with the Fourth Inservice Inspection (lSI) Interval, II Relief Request 14R Request for Relief From Qualification Requirements of ASME Section XI, Appendix VIII, Supplement 11, for Examination of Structural Weld Overlays (SWOLs) In Accordance with 10 GFR 50.55a(a)(3)(i), dated August 10, 2010, ADAMS Accession Number ML102290162.

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 7 of 14)

14. Harold K. Chernoff (NRC) to Christopher M. Crane (AmerGen Energy Company, LLC), "Three Mile Island Nuclear Station, Unit 1 (TMI-1), Relief Request 2007- TMI-01, Regarding Structural Weld Overlays on Pressurizer Surge, Pressurizer Spray, and Hot Leg Decay Heat Drop Line Nozzles, (TAG No. MD5427), dated October 17, 2007, ADAMS Accession Number II ML072770051 .

15. Russell G. West (AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Response to Request for Additional Information - Relief Request No. 2007- TMI-01 Structural Weld Overlays (SWOLs) of the Pressurizer Surge, Pressurizer Spray, and Hot Leg Decay Heat Drop Line Nozzle Dissimilar Metal Welds including the SWOL of Adjacent Welds, dated August 13, 2007, II ADAMS Accession Number ML072320404.

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 8 of 14)

TABLE 1A COMPONENT IDENTIFICATION For TMI, Unit 1 PZR Nozzle to Safe-End and Safe-End to Elbow Weld SWOL Scheduled for Overlay Repair During TMI Outage T1 R19 NOZZLE TO NOZZLE ITEM # SIZE SAFE-END TO ELBOW ITEM #

SAFE-END WELD ADJACENT WELD #

Spray PR-009BM R1.15 4" SP-021BM R1.11 B15.150 R1.15 B15.150 Note: Item numbers reflect Risk-Informed classification per RISI Program and ASME Code Case N-722.

R1.11: Elements Subject to Thermal Fatigue.

R1.15: Elements SUbject to Primary Water Stress Corrosion Cracking (PWSCC).

B15.150: Spray nozzle-to-pipe connection (B15.150 is the Code Case N-722 assigned number).

The NRC has not approved Leak Before Break (LBB) application to these welds therefore LBB does not apply to this overlay.

TABLE1B COMPONENT MATERIAL Weld Component Component Component Number PR-009BM Nozzle - P1 Weld - F43 Safe-End - P43 SP-021BM Safe-End P43 Weld- F43 Elbow - P8

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 9 of 14)

TABLE 2 DESIGN/MATERIAUNONDESTRUCTIVE EXAMINATION Modifications to Code Case N-504-3 and ASME Section XI, Appendix Q CODE CASE N-504-3 AND ASME PROPOSED MODIFICATIONS SECTION XI APPENDIX Q N-504-3: "Reply: It is the opinion of the Modification: Code Case N-504-3 and Committee that, in lieu of the requirements of Appendix Q will be used for the weld overlay of IWA-4120 in Editions and Addenda up to and the P1, P8, F43 and/or P43 materials as defined including the 1989 Edition with the 1990 in Table 1B.

Addenda, in IWA-4170{b) in the 1989 Edition with the 1991 Addenda up to and including the Basis: Code Case N-504-3 is accepted for use 1995 Edition, and in IWA-4410 in the 1995 in the current NRC Regulatory Guide 1.147 Edition with the 1995 Addenda up to and Rev. 15, and previous revisions have been used including the1996 Addenda, and in IWA-4420 extensively in BWR primary system piping.

in the 1995 Edition with the 1997 Addenda and More recently, N-504-3 (with modifications later Editions and Addenda, in IWA-4810{a) in approved under relief request submittals) has the 1992 Edition with the 1994 Addenda been applied to PWR applications as a PWSCC through the 1995 Edition, and in IWA-4520{a) mitigation technique. Industry operating in the 1995 Edition with the 1995 Addenda and experience in the area has shown that PWSCC later Editions and Addenda, a defect in in Alloy 82/182 will blunt at the interface with austenitic stainless steel piping may be stainless steel base metal, ferritic base metal, or reduced to a flaw of acceptable size in Alloy 52M weld metal. The 360 deg. full .

accordance with IWB-3640 from the 1983 structural weld overlay will control growth In a Edition with the Winter 1985 Addenda, or later PWSCC crack and maintain RCS integrity. The Editions and Addenda, by deposition of weld applied SWOL will also induce compressive reinforcement (weld overlay) on the outside stress in the existing dissimilar metal welds, surface of the pipe, provided the following thus potentially impeding growth of cracks.

requirements are met" Furthermore, the SWOL will be sized to meet structural requirements without crediting integrity of the existing welds.

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 10 of 14)

TABLE 2 DESIGN/MATERIAUNONDESTRUCTIVE EXAMINATION Modifications to Code Case N-504-3 and ASME Section XI, Appendix Q CODE CASE N-504-3 AND ASME PROPOSED MODIFICATIONS SECTION XI APPENDIX Q N-504-3: "(b) Reinforcement weld metal shall Modification: Weld overlay filler metal shall be be low carbon (0.035% max.) austenitic an austenitic nickel alloy (28% Cr min.) applied stainless steel applied 360 deg. around the 360 deg. around the circumference of the item, circumference of the pipe, and shall be and shall be deposited using a Welding deposited in accordance with a qualified Procedure Specification for groove welding, welding procedure specification identified in qualified in accordance with the the Repair Program." Repair/Replacement Code and Owner's requirements and identified in the Note: This requirement is similar to Repair/Replacement Plan.

Appendix Q, Q-2000(a).

Basis: Industry operational experience has shown that PWSCC in Alloy 82/182 will blunt at the interface with stainless steel base metal, ferritic base metal, or Alloy 52M weld metal.

N-504-3: "(e) The weld reinforcement shall Modification: Delta ferrite measurements will consist of a minimum of two weld layers having not be performed for weld overlay repairs using as-deposited delta ferrite content of [at] least Alloy 52M weld metal.

7.5 FN. The first layer of weld metal with delta ferrite content of at least 7.5 FN shall Basis: The deposited Alloy 52M is 100%

constitute the first layer of the weld austenitic and contains no delta ferrite due to reinforcement design thickness. Alternatively, the high nickel composition (approximately 60%

first layers of at least 5 FN may be acceptable nickel). The austenitic nickel alloy weld overlay based on evaluation." shall consist of at least two weld layers deposited from a filler metal with a Cr content of Note: This requirement is similar to Q- at least 28%. When welding over an austenitic 2000(d) except that Q-2000(d) alternatively base material or austenitic filler material weld allows the deposited first layers of weld and the associated dilution zone from an metal have a carbon content of <0.02% and adjacent ferritic base material, a diluted first an FN value of at least 5 FN. layer of at least 24% Cr is acceptable, provided the Cr content of the deposited weld metal is determined by chemical analysis of a representative coupon. Alternatively, the first weld layer may be considered "sacrificial", and will not be credited towards the reinforcement design thickness.

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 11 of 14)

TABLE 2 DESIGN/MATERIAUNONDESTRUCTIVE EXAMINATION Modifications to Code Case N-504-3 and ASME Section XI, Appendix Q CODE CASE N-504-3 AND ASME PROPOSED MODIFICATIONS SECTION XI APPENDIX Q N-504*3: "(h) The completed repair shall be Modification: A system leakage test at system pressure tested in accordance with IWA-5000. nominal operating pressure in accordance with If the flaw penetrated the original pressure IWA-5000 shall be performed in accordance boundary prior to welding, or if any evidence of with the TMI, Unit 1 lSI Program. Prior to the the flaw penetrating the pressure boundary is system leakage test, ultrasonic examination of observed during the welding operation, a the finished SWOL using EPRI POI system hydrostatic test shall be performed in demonstrated weld overlay (Reference 11) accordance with IWA-5000. If the system examination procedures and qualified pressure boundary has not been penetrated, a examiners shall be performed.

system leakage, inservice, or functional test shall be performed in accordance with IWA- Basis: The TMI, Unit 1 fourth interval lSI 5000." program utilizes the 2004 Edition, no Addenda, of ASME Code Section XI (including 10 CFR Nonmandatory Appendix Q: (mandated 50.55a(b)(2)(xx)(B)) for NOE and pressure through Regulatory Guide 1.147, Revision 15 testing of welded repairs and replacements.

as a condition of using Code Case N-504-3) ASME Section XI (including 10 CFR states: 50.55a(b)(2)(xx)(B)) permits a system leakage test in lieu of a hydrostatic test provided NOE is "Ultrasonic examination personnel shall be performed in accordance with IWA-4540(a)(2) of certified in accordance with the Owner's the 2002 Addenda of ASME Section XI. IWA-written practice. Procedures and personnel 4540(a)(2) requires NOE to be performed in shall be qualified in accordance with accordance with the 1992 Edition of ASME Appendix VIII." Code Section III, Subsection NB, however, Subsection NB does not address the structural weld overlay configuration, so the NOE requirements of Nonmandatory Appendix Q performed using EPRI POI demonstrated procedures with qualified examiners will be used.

The use of the EPRI POI demonstration and qualification program in lieu of Appendix VIII is addressed in Reference 13, as part of an associated relief request.

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 12 of 14)

TABLE 3 AMBIENT TEMPERATURE TEMPER BEAD WELDING Modifications to Code Case N-638-1 CODE CASE N-638-1 PROPOSED MODIFICATIONS 1.0 General Requirements Modification: The maximum area of an H(a) The maximum area of an individual weld individual weld based on the finished surface based on the finished surface shall be 100 sq. over the ferritic material shall not exceed 300 in., and the depth of the weld shall not be sq. in. If any of the TMI, Unit 1 SWOL repairs greater than one-half of the ferritic base metal exceed 300 sq. in. over the ferritic material, thickness." additional relief will be requested. The one half base metal thickness limitation applies only to excavation and repair and is not applicable to this repair.

Basis: Although the final design for the TMI, Unit 1 SWOL was not completed at the time of development of this relief request, it is possible that the SWOL will require welding on more than 100 sq. in. of surface on the carbon steel base material. The SWOL will extend to the transition taper of the carbon steel nozzle to provide a weld geometry that allows qualified UT examination of the required examination volume.

There have been a number of temper bead SWOL repairs successfully applied to safe-end to nozzle welds in the nuclear industry, and a SWOL repair having a 300 sq. in. area was previously approved for TMI, Unit 1 (Reference 14).

4.0 Examination Modification: For the SWOLs, full UT of the H(b) The final weld surface and the band around 1.5T band will not be performed. UT will be the area defined in para. 1.0(d) shall be performed on the actual weld overlay, meeting examined using a surface and ultrasonic the requirements of ASME Code Section XI, methods when the completed weld has been at Nonmandatory Appendix 0-4100.

ambient temperature for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The ultrasonic examination shall be in accordance When austenitic filler materials are used, the with Appendix 1. 3" final SWOL will be examined using the surface and ultrasonic methods after three tempering H3 Refer to the 1989 Edition with the 1989 weld layers (Le., layers 1, 2, and 3) are Addenda and later Editions and Addenda." completed and have been in place for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 13 of 14)

TABLE 3 AMBIENT TEMPERATURE TEMPER BEAD WELDING Modifications to Code Case N-638-1 CODE CASE N-638-1 PROPOSED MODIFICATIONS Basis: Later editions of the code as well as later revisions to the Code Case (N-638-2 and later) removed the requirement for the 1.5T examination band. This is in line with the less restrictive requirements for UT of the ferritic nozzle because hydrogen cracking away from the temper bead weld is not considered a concern in later editions of the code and Code Case N-638. The code case applies to any type of welding where a temper bead technique is to be employed (which includes weld repairs of excavated flaws) and is not specifically written for a SWOL repair. However, it is believed that for this type of repair, any major base material cracking would take place in the ferritic heat-affected zone directly below or adjacent to the weld overlay and not in the required 1.5T examination band of ferritic material beyond the overlay. If this type of cracking were to occur it should be detected by the NDE of the SWOL and adjacent ferritic steel surfaces.

As supported by EPRI's white paper (Reference

12) providing the technical basis for Code Case N-638-4, the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold time prior to final NDE examinations will start upon completion of the third temper bead weld overlay layer.

Reference 12 addresses previous concerns regarding the 48-hour hold time prior to final NDE examinations. Areas of concern imposing the 48-hour hold time addressed through this report include: material microstructure; sources for hydrogen introduction; tensile stress and temperature; and diffusivity and solubility of hydrogen in steels. The report concludes there is no technical basis for waiting 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the weld overlay cools to ambient temperature before performing final NDE of the completed weld overlay.

10 CFR 50.55a RELIEF REQUEST RR-10-02 Revision 0 (Page 14 of 14)

TABLE 3 AMBIENT TEMPERATURE TEMPER BEAD WELDING Modifications to Code Case N-638-1 CODE CASE N-638-1 PROPOSED MODIFICATIONS Based on past and recent NOE experience on temper bead weld overlays, hydrogen cracking of these welds was not identified during the initial NOE after a 48-hour hold time or subsequent inservice inspection examinations.

Appendix I does not specifically address weld overlay ultrasonic examinations. Ultrasonic examinations shall be performed using EPRI POI weld overlay demonstrated examination procedures with POI qualified inspectors.