Text

Proposed Alternative to ASME Section XI Requirements for Application of a Weld Overlay (RR-ENG-2-43)
	ML061280504
Person / Time
Site:	South Texas
Issue date:	05/01/2006
From:	Berg M; South Texas
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	NOC-AE-06002000, RR-ENG-2-43, STI: 31999766
	Download: ML061280504 (27)
	v • d • e

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Nuclear Operating Company South Tess Pt/d Ekdctk Gwma1ft Ston PROgr28.9 Mlwfdlk ras 77483 May 1, 2006 NOC-AE-06002000 File No.: G25 10 CFR 50.55a U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Units 1 and 2 Docket No. STN 50-498, STN 50-499 Proposed Alternative to ASME Section Xi Requirements for Application of a Weld Overlay (RR-ENG-2-43)

In accordance with the provisions of 10 CFR 50.55a(a)(3)(i), the South Texas Project requests NRC approval of an alternative approach to the requirements of ASME Boiler and Pressure Vessel Code, Section Xl, "Rules for Inservice Inspection of Nuclear Power Plant Components."

Approval will allow application of full structural weld overlays in pressurizer nozzle safe end welds which diverge from the requirements of the ASME Section Xl code. The affected code requirements are:

ASME Section Xl, Code Case 504-2

ASME Section Xi, Code Case 638-1

ASME Section Xl, Appendix Vil, Supplement 11

ASME Section Xl, Nonmandatory Appendix 0

ASME Section Xl, Code Case N-416-2 The proposed alternative approach will provide an acceptable level of quality and safety.

The proposed structural weld overlay is intended as a preventive measure against flaw development or means of repair for flaws similar to those that have occurred at other nuclear power facilities. The overlay will be applied during the South Texas Project Unite1 Fall 2006 and Unit 2 Spring 2007 refueling outages. The discussion in Attachment 1 provides the basis and justification for the proposed alternative. To suppqrt preparation for the upcoming outages, the NRC is requested to approve this proposed alternative by July 31, 2006.

Similar requests have been made for use of overlays to repair flaws in nozzle safe end welds.

Examples are:

Three Mile Island (TAC No. MC1201) (approved by the NRC on July 21, 2004)

Millstone (TAC No. MC8609) (approved by the NRC on January 20, 2006)

Donald C. Cook (TAC No. MC6704) (approved by the NRC on December 21, 2005)

STI: 31999766 Project Manager on Behalf of the Participants In the South Texas Project

NOC-AE-06002000 Page 2 of 3 There are no commitments included in the attached request.

If there are any questions, please contact either Mr. P. L. Walker at (361) 972-8392 or me at (361) 972-7030.

M. J. Berg Manager Testing/Programs PLW

Attachment:

Proposed Alternative to ASME Section Xl Requirements for Application of a Weld Overlay (RR-ENG-2-43)

NOC-AE-06002000 Page 3of3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Mohan C. Thadani U. S. Nuclear Regulatory Commission Richard A. Ratliff Steve Winn Bureau of Radiation Control Christine Jacobs Texas Department of State Health Services Eddy Daniels 1100 West 49th Street NRG South Texas LP Austin, TX 78756-3189 C. Kirksey City of Austin Senior Resident Inspector J. J. Nesrsta U. S. Nuclear Regulatory Commission R. K. Temple P. 0. Box 289, Mail Code: MN1 16 E. Alarcon Wadsworth, TX 77483 City Public Service C. M. Canady Jon C. Wood City of Austin Cox Smith Matthews Electric Utility Department 721 Barton Springs Road Austin, TX 78704

Attachment NOC-AE-06002000 Page 1 of 24 SOUTH TEXAS PROJECT PROPOSED ALTERNATIVE TO ASME SECTION Xi REQUIREMENTS FOR APPLICATION OF A WELD OVERLAY (RELIEF REQUEST RR-ENG-2-43)

1.0 ASME Code Components Affected

System: Reactor Coolant System Identifiers: Unit 1 16"RC1 412NSS (Pressurizer Surge Line Nozzle Safe End Welds) 6"RC1 003BB1 (Pressurizer Spray Line Nozzle Safe End Welds) 6"RC1004NSS (Pressurizer Safety Line Nozzle Safe End Welds) 6"RC1 009NSS (Pressurizer Safety Line Nozzle Safe End Welds) 6"RC1012NSS (Pressurizer Safety Line Nozzle Safe End Welds) 6"RC1 01 5NSS (Pressurizer Relief Line Nozzle Safe End Welds)

Unit 2 16"RC2412NSS (Pressurizer Surge Line Nozzle Safe End Welds) 6"RC2003BB1 (Pressurizer Spray Line Nozzle Safe End Welds) 6"RC2004NSS (Pressurizer Safety Line Nozzle Safe End Welds) 6"RC2009NSS (Pressurizer Safety Line Nozzle Safe End Welds) 6"RC2012NSS (Pressurizer Safety Line Nozzle Safe End Welds) 6"RC2015NSS (Pressurizer Relief Line Nozzle Safe End Welds)

Function: There are six low alloy steel nozzles for each pressurizer. Each has an Alloy 82/182 weld connecting the low alloy steel nozzle to an austenitic stainless steel (SS) safe end, and an SS weld connecting the safe end to SS piping. The nozzle configuration is shown in Figure 1. One nozzle located on the bottom of the pressurizer connects the surge line from the Loop 4 hot leg to the pressurizer. One nozzle at the top of the pressurizer receives flow from the Loop 1 and Loop 4 cold legs for pressurizer spray.

Four nozzles at the top of the pressurizer provide a relief path to the pressurizer relief tank for overpressure protection. The pressurizer configuration is shown in Figure 2.

Code Class: Class 1

2.0 Applicable Code Edition and Addenda

The South Texas Project Inservice Inspection program for the second ten-year interval complies with the requirements of ASME Boiler and Pressure Vessel Code, Section Xl, 1989 Edition and the 1995 Edition with 1996 Addenda for application of Section Xl, IWA-2300, Appendix I, Appendix VII, and Appendix Vill.

Design and fabrication are in accordance with ASME Section III, 1974 Edition.

Attachment NOC-AE-06002000 Page 2 of 24 3.0 Applicable Code Requirements ASME Section Xl, Article 4000, specifies requirements for repair and replacement of pressure-retaining components. Certain requirements of IWA-4000 can be accomplished using the methodology of Code Case N-504-2, "Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping, Section Xl, Division 1," and the methodology of Code Case N-638-1, "Similar and Dissimilar Metal Welding using Ambient Temperature Machine GTAW (Gas Tungsten Arc Welding) Temper Bead Technique, Section Xl, Division l."

ASME Code Case N-504-2 allows use of a weld overlay (WOL) to enhance pipe integrity. This Code Case has been endorsed in Nuclear Regulatory Commission (NRC)

Regulatory Guide 1.147, Revision 14, for generic use with the condition that the provisions of Section Xl, Nonmandatory Appendix Q, 'Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments," must also be met.

ASME Code Case N-638-1 provides for welding dissimilar metals. This Code Case has been endorsed in NRC Regulatory Guide 1.147, Revision 14, for generic use with the condition that ultrasonic examination (UT) shall be demonstrated for the repaired volume using representative samples which contain construction-type flaws. The acceptance criteria of NB-5330 of Section III edition and addenda approved in 10 CFR 50.55a apply to all flaws identified within the repaired volume.

ASME Section Xl, Appendix VilI, "Performance Demonstration for Ultrasonic Examination Systems," provides requirements for UT procedures, equipment, and personnel for UT of the completed WOL.

ASME Code Case N-416-2 allows use of a system leakage test, in conjunction with specified non-destructive examination (NDE), in lieu of a system hydrostatic test. N-416-2 has been approved by the NRC for use at the South Texas Project (reference 9.5).

4.0 Reason for Request Given the location and thickness of the welded zones and the availability of Code Case N-504-2, removal of flaws prior to applying the overlay material would be a difficult task with no net benefit to the station. In addition, examination by UT of the safe end welds prior to the weld overlay is unnecessary because, if flaws are present, they will be mitigated by the WOL.

A WOL is to be applied over each pressurizer nozzle safe end weld using machine GTAW. ASME Code Case N-638-1 allows application without the use of elevated temperature pre-heat and without post-weld heat treatment following completion of GTAW. Both elevated temperature pre-heat and post-weld heat treatment require that the components be drained prior to pre-heat or post-weld heat treatment, which may be impractical for operational and radiological reasons.

Appendix Vil provides UT performance qualification requirements for a completed structural WOL application. In lieu of these ASME Code UT requirements, alternative techniques are proposed for UT examination of the full structural WOL. The specified requirements in Appendix Vil need clarification in part, and in some cases are not compatible with the implementation by the Performance Demonstration Initiative (PDI).

5.0 Proposed Alternatives The South Texas Project proposes a full structural WOL for the nozzle safe end welds using Alloy 52 weld metal. References to Alloy 52 weld metal in the relief request are

Attachment NOC-AE-06002000 Page 3 of 24 intended to apply to use of Alloy 52, 52M, or 152 weld metal. The WOL will extend around the full circumference of the existing nozzle safe end Alloy 82/182 welds, overlapping the neighboring sections of low alloy steel nozzle and stainless steel piping.

A typical WOL configuration to be applied is shown in Figure 1.

5.1 Code Case N-504-2 and Section Xi Nonmandatory Appendix Q ASME Section Xl Code Case N-504-2, "Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping," provides for reducing defects in austenitic stainless steel piping to an acceptable size by deposition of weld reinforcement material on the outside surface of the pipe. The WOL will be designed in accordance with NRC-approved Code Case N-504-2, "Alternative Rules for Repair of Classes 1, 2, and 3 Austenitic Stainless Steel Piping," with some exceptions. The provisions of Section Xl Nonmandatory Appendix Q, "Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments," are imposed by NRC Regulatory Guide 1.147, Revision 14, as a condition for acceptance of Code Case N-504-2.

The weld reinforcement material is to be Alloy 52 or equivalent applied as a WOL to the existing austenitic stainless steel safe ends, the low alloy steel nozzles, stainless steel piping, and the Alloy 82/182 and austenitic stainless steel weld material joining them.

The WOL will be designed as a full structural overlay consistent with the requirements of Code Case N-504-2 and Appendix 0. The WOL design assumes there is no contribution to structural integrity from the original section of pipe. The structural WOL will completely cover the existing Alloy 82/182 weld metal and extend onto the ferritic and austenitic stainless steel (SS) material at each end. The specific thickness and length of the WOL to be applied will be designed according to the guidance provided in the code case.

The methodology of Code Case N-504-2 and provisions of Appendix Q will be followed with modifications described in Table 1. Applicable requirements not listed will be met as described in Code Case N-504-2 and Appendix 0.

5.2 Code Case N-638-1 Application of the WOL requires welding on the low alloy steel nozzle material with Alloy

52. Temper bead welding will be used for this purpose using the guidance of Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique." Code Case N-638-1 describes the process for welding similar and dissimilar metals using ambient temperature machine gas tungsten arc weld (GTAW) temper bead method. GTAW will be performed in accordance with Code Case N-638-1, with some exceptions. Code Case N-638-1 was conditionally approved for generic use in NRC Regulatory Guide 1.147, Revision 14, and was developed for welding similar and dissimilar metals using ambient temperature machine GTAW temper bead technique.

Code Case N-638-1 specifies a limit of 100 square inches for a temper bead weld. This applies to the surge line nozzles (16-inch diameter), safety and relief line nozzles (6-inch diameter), and spray line nozzles (6-inch diameter). The intent of the code case is clarified to limit the area of an individual weld over the ferritic material. The weld surface areas over ferritic material are expected to be approximately 144 square inches, 52 square inches, and 26 square inches, respectively. Electric Power Research Institute Technical Report 1003616 (reference 9.4) provides justification for a maximum area of 500 square inches. The surge line nozzle weld area can be assumed to not exceed 200 square inches.

Attachment NOC-AE-06002000 Page 4 of 24 The methodology of Code Case N-638-1 will be followed for any welding on ferritic material where the Construction Code requires post-weld heat treatment with the modifications proposed in Table 2. Applicable requirements not listed will be met as described in Code Case N-638-1.

5.3 ASME Section XI, Appendix Vill, Supplement 11 UT of the completed structural WOL will be accomplished in accordance with ASME Section Xl, Appendix Vill, Supplement 11 modified to comply with the Performance Demonstration Initiative (PDI), as described in Table 3. PDI has developed a program for qualifying equipment, procedures, and personnel for WOL examinations in accordance with the UT criteria of Appendix Vil, Supplement 11. Applicable requirements not listed will be met as described in Appendix Vil Supplement 11.

5.4 ASME Section Xl, Code Case N416-2 Application of Code Case N-416-2 for a system leakage test in lieu of a system hydrostatic test requires performance of NDE in accordance with the methods and acceptance criteria of the applicable Subsection of the 1992 Edition of ASME Section IlIl.

The NDE requirements of Nonmandatory Appendix Q will be followed for the required NDE in lieu of ASME Section IlIl.

6.0 Basis for Use 6.1 ASME Section XI Code Case N-504-2 and Section XI Nonmandatory Appendix 0 Table 1 addresses the specific changes and the bases justifying the proposed modifications.

6.2 ASME Code Case N-638-1 Table 2 addresses the specific changes and the bases justifying the proposed modifications.

Some of the reasons for the 100-square-inch limit are distortion of weld and base metal, cracking in weld and base metal, and large residual stresses. Since the nozzle-to-safe-end welds and the weld overlays are fabricated from austenitic materials with inherent toughness, no cracking in the overlays is expected to occur due to the shrinkage associated with the weld overlay. Many temper bead weld overlays have been applied in the nuclear industry to these nozzle-to-safe end locations. There has not been any reported cracking due to the weld overlay application. The stiffness and high toughness inherent in the nozzle material are expected to protect against cracking and limit any distortion that might occur in the nozzle. Axial shrinkage will be measured and evaluated for impact on the nozzle and safe end materials and on the piping system in accordance with ASME CC N-504-2. Also, any cracking would be detected by the final NDE of the weld overlay.

6.3 ASME Section XI, Appendix Vill, Supplement 11 Table 3 addresses the specific changes and the bases justifying the proposed modifications.

6.4 ASME Section XI Code Case N-416-2 ASME Section IlIl Subsection NB Article 5000 for Examination does not address the structural weld overlay type configuration and appropriate NDE cannot be determined adequately. In the absence of clearly defined NDE requirements, application of

Attachment NOC-AE-06002000 Page 5 of 24 Nonmandatory Appendix Q addresses specific NDE with appropriate references to ASME Sections IlIl and Xi for acceptance criteria.

6.5 Leak-Before-Break WCAP-1 0489, "Technical Bases for Eliminating Pressurizer Surge Line Ruptures as the Structural Design Basis for the South Texas Project," provides technical justification for eliminating pressurizer surge line breaks based on fracture mechanics analysis.

Assessment using fracture mechanics demonstrated that small flaws or leakage cracks will remain stable and will be detected either by in-service inspection or by leakage monitoring systems long before such flaws can grow to a critical size (leak-before-break

[LBB]).

In accordance with 10 CFR 50.12(a), the South Texas Project applied for an exemption from the requirements of 10 CFR 50, Appendix A, General Design Criterion 4 (GDC 4) for the treatment of pressurizer surge line pipe breaks. The exemption request was approved by the NRC in Supplement 7 to the South Texas Project Safety Evaluation Report (NUREG-0781).

MRP-140, "Materials Reliability Program: Leak-Before-Break Evaluation for PWR Alloy 82/182 Welds," addresses this issue. The LBB evaluation, conservatively including consideration of Pressurized Water Stress Corrosion Cracking (PWSCC) morphology, indicates that the margins in NUREG-1061, Volume 3 and draft Standard Review Plan 3.6.3 can be met for the relatively larger lines even after considering leak rate reduction resulting from PWSCC crack morphology. Assessment of leak detection capabilities concludes that action would be taken long before the Technical Specification leakage limit of 1 gpm. This is consistent with the leakage detection capability of 1 gpm used in the LBB submittals. Even with inclusion of PWSCC, there is ample time (more than one year) before leakage would increase to a point at which corrective action is necessary.

In the context of this submittal, only the pressurizer surge lines are included in LBB. The pressurizer spray, safety, and relief lines are not included under LBB. Effect of the overlay on pressurizer surge line LBB criteria is assessed during the overlay design process pursuant to 10 CFR 50.59.

6.6 NRC Bulletin 2004-01 Pursuant to NRC Bulletin 2004-01, "Inspection of Alloy 82/182/600 Materials Used in the Fabrication of Pressurizer Penetrations and Steam Space Piping Connections at Pressurized-Water Reactors," (reference 9.1), the South Texas Project has inspected the steam space nozzles during recent refueling outages.

In addition to the ASME Section Xi-required examinations, Bare Metal Visual (BMV) inspections were performed on all steam space nozzles during the Unit 2 refueling outage in March 2004. There was no evidence indicating any pressure boundary leakage from the pressurizer nozzle safe ends, nor was there any evidence of corrosion or wastage (reference 9.2).

As noted in a supplemental response to NRC Bulletin 2004-01, dated June 9, 2005 (reference 9.3), BMV inspections were performed on all steam space nozzles during the Unit 1 refueling outage that began in March 2005 (1RE12). A complete BMV examination was performed at each of the pressurizer nozzle safe ends. There was no evidence indicating pressure boundary leakage from these nozzle safe ends, nor was there evidence of corrosion or wastage.

Attachment NOC-AE-06002000 Page 6 of 24 6.7 Pressure Testing The NRC previously approved Code Case N-416-2, "Alternative Pressure Test Requirement for Welded Repairs, Fabrication Welds for Replacement Parts and Piping Subassemblies, or Installation of Replacement Items by Welding, Class 1, 2, and 3," for use at the South Texas Project. The code case allows use of a system leakage test, in conjunction with specified NDE, in lieu of a system hydrostatic test to detect leakage from welded repairs, fabrication welds for replacement parts and piping subassemblies, or welds for installation of replacement items. For a system leakage test to be used, Code Case N-416-2 requires:

Performance of NDE in accordance with the methods of Non-Mandatory Appendix Q and acceptance criteria of the applicable Subsection of the 1992 Edition of Section III (as described in Section 5.4).

Performance of a visual examination (VT-2) prior to or immediately upon return to service in conjunction with a system leakage test, using the 1992 Edition of Section Xl, in accordance with IWA-5000, at nominal operating pressure and temperature.

Documentation of use of this Case on an NIS-2 Form.

6.8 Welder Qualification and Welding Procedures All welders, welding operators, and welding procedures will be qualified in accordance with ASME Code Section IX, any special requirements from Section Xl, and applicable code cases. If necessary, a manual shielded metal arc procedure will be qualified to facilitate localized repairs and to provide a seal weld prior to depositing the overlay over the existing F43 weld deposit material. This procedure uses shielded metal arc weld electrodes consistent with the requirements of ASME Section Xl.

7.0 Duration of Proposed Alternative This proposed alternative is for application as needed during the remainder of the current inspection interval which ends September 24, 2010 for Unit 1 and October 8, 2010 for Unit 2. The duration of the proposed alternative is the remaining service life of the affected components.

8.0 Implementation The structural WOL will be installed during the South Texas Project Unit 1 Fall 2006 and Unit 2 Spring 2007 refueling outages as a preventive measure against flaw development or means of repair for any flaws that may be present in the dissimilar metal welds. NRC approval is requested by July 31, 2006, to support scheduling for completion of activities during the outage.

9.0 References 9.1 NRC Bulletin 2004-01, Inspection of Alloy 82/182/600 Materials Used in the Fabrication of Pressurizer Penetrations and Steam Space Piping Connections at Pressurized-Water Reactors," dated May 28, 2004 9.2 Correspondence from T. J. Jordan to Document Control Desk, Response to NRC Bulletin 2004-01, Inspection of Alloy 82/182/600 Materials Used in the Fabrication of Pressurizer Penetrations and Steam Space Piping Connections at Pressurized-Water Reactors," dated July 27, 2004 (NOC-AE-04001762)

Attachment NOC-AE-06002000 Page 7 of 24 9.3 Correspondence from T. J. Jordan to Document Control Desk, "Response to NRC Bulletin 2004-01, "Inspection of Alloy 82/182/600 Materials Used in the Fabrication of Pressurizer Penetrations and Steam Space Piping Connections at Pressurized-Water Reactors," dated June 9, 2005 (NOC-AE-05001890) 9.4 Electric Power Research Institute Technical Report 1003616, "Additional Evaluations to Extend Repair Limits for Pressure Vessels and Nozzles," March 2004 9.5 Correspondence from Robert A. Gramm, Nuclear Regulatory Commission, to William T.

Cottle, "Request for Approval to Use American Society of Mechanical Engineers (ASME)

Code, Section Xl, Code Case N-416-2, Relief Request RR-ENG-2-20 (TAC Nos.

MB0382 and MB0383), dated February 16,2001

Attachment NOC-AE-06002000 Page 8 of 24 TABLE 1 DESIGN/MATERIAUNONDESTRUCTIVE EXAMINATION Modifications to ASME Code Case N-504-2 and ASME Section Xi Appendix 0 Code Case N-504-2 and Modification/Basis ASME Section Xi Appendix M Current Requirements It is the opinion of the Committee that, in lieu of Code Case N-504-2 will be used for weld overlay the requirements of IWA-4120 in Editions and (WOL) repairs or mitigation to the ferritic (P3) and Addenda up to and including the 1989 Edition with nickel alloy (F43/P43) base material as well as the the 1990 Addenda, in IWA-4170(b) in the 1989 austenitic stainless steel (P8) base material.

Edition with the 1991 Addenda up to and including the 1995 Edition, and in IWA-4410 in the 1995 Basis: Code Case N-504-2 is accepted for use Edition with the 1995 Addenda and later Editions along with Nonmandatory Appendix Q in NRC and Addenda, defect in austenitic stainless steel Regulatory Guide 1.147 Rev. 14. For the WOL, the piping may be reduced to a flaw of acceptable size base material will be ferritic material (P3) with in accordance with IWB-3640 from the 1983 existing nickel alloy weld metal (F43) to which an Edition with the Winter 1985 Addenda, or later austenitic stainless steel (P8) safe end is welded.

Editions and Addenda, by deposition of weld Industry operational experience has shown that reinforcement (weld overlay) on the outside PWSCC in Alloy 82/182 will blunt at the interfaces surface of the pipe, provided the following with stainless steel base metal, ferritic base metal, requirements are met. [Essentially the same and Alloy 52 weld metal.

scope of Appendix Qu:

Application of a 3600 full structural WOL will mitigate any potential PWSCC crack and maintain weld integrity. The WOL will induce compressive stress in the weld, thus potentially impeding initiation or growth of any reasonably shallow cracks. The WOL will be sized to meet all structural requirements independent of the existing weld.

Weld Metal (b) Reinforcement weld metal shall be low carbon In lieu of austenitic stainless steel filler material, the (0.035% max.) austenitic stainless steel applied reinforcement weld metal will be a nickel alloy.

3600 around the circumference of the pipe, and shall be deposited in accordance with a qualified Basis: Alloy 52, 52M and 152 may be used as weld welding procedure specification identified in the metal. The requirements of ASME Section III, NB-Repair Program. [Essentially the same as Q- 2400 will be applied to all filler material.

2000(a)]

These filler materials were selected for their improved resistance to PWSCC. Alloys 52, 52M and 152 all contain about 30% chromium which imparts excellent corrosion resistance. The existing Alloy 82/182 weld and the Alloy 52 WOL are austenitic

Attachment NOC-AE-06002000 Page 9 of 24 and have ductile properties and toughness similar to austenitic stainless steel piping welds at pressurized water reactor operating temperatures. These filler materials are suitable for welding over the ferritic nozzle, Alloy 82/182 weld, and the austenitic stainless steel piping or safe ends.

Delta Ferrite Content (e) The weld reinforcement shall consist of a Delta ferrite (FN) measurements will not be minimum of two weld layers having as-deposited performed for WOL made of Alloy 52 weld metal.

delta ferrite content of at least 7.5 FN. The first layer of weld metal with delta ferrite content of Basis: Alloy 52 welds are 100% austenitic and least 7.5 FN shall constitute the first layer of the contain no delta ferrite due to the high nickel content weld reinforcement design thickness. Alternatively, (approximately 60% nickel).

first layers of at least 5 FN may be acceptable based on evaluation. [Same as 0-2000(d)]

Pressure Testing (h) The completed repair shall be pressure tested If a flaw or evidence of a flaw is observed, in lieu of in accordance with IWA-5000. If the flaw hydrostatic testing, a system leakage test and an penetrated the original pressure boundary prior to ultrasonic examination (UT) of the weld overlay will welding, or if any evidence of a flaw penetrating be performed consistent with ASME Code Case N-the pressure boundary is observed during the 416-2, as modified by Nonmandatory Appendix Q.

welding operation, a system hydrostatic test shall be performed in accordance with IWA-5000. If the Basis:

system pressure boundary has not been Application of Code Case N-416-2 for a system penetrated, a system leakage, inservice, or leakage test in lieu of a system hydrostatic test functional test shall be performed in accordance requires performance of NDE in accordance with the with IWA-5000. methods and acceptance criteria of the applicable Subsection of the 1992 Edition of ASME Section 1II.

ASME Section III Subsection NB Article 5000 for Examination does not address the structural weld overlay type configuration and appropriate NDE cannot be determined adequately. The NDE requirements of Nonmandatory Appendix Q will be followed for the required NDE in lieu of ASME Section 1II.

Attachment NOC-AE-06002000 Page 10 of 24 TABLE 2 AMBIENT TEMPER BEAD WELDING Modifications to Code Case N-638-1 Code Case N-638-1 Modification/Basis Weld Area 1.0(a) The maximum area of an individual weld The maximum area of an individual weld based on based on the finished surface shall be 100 sq. in., the finished surface over the ferritic material shall and the depth of the weld shall not be greater than not exceed 200 square inches, and the depth of the one-half of the ferritic base metal thickness. WOL shall not be greater than one-half of the ferritic base metal thickness Basis: The maximum finished area of the WOL for the surge line nozzle will exceed 100 sq-in over the ferritic material. EPRI Technical Report 1003616 justifies extending the size of the temper bead repairs up to a finished area of 500 sq-in over the ferritic material. The area of the finished overlays will be substantially less than this.

Examination 4.0(b) The final weld surface and the band around The UT coverage area will be defined using Code the area defined in para. 1.0(d)* shall be Case N-504-2 and Appendix Q instead of that examined using a surface and ultrasonic methods defined by Code Case N-638-1. The band around when the completed weld has been at ambient the welded area will only receive a surface temperature for at least 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months . The ultrasonic examination, not a UT examination. Examinations examination shall be in accordance with Appendix will be performed after the completed weld has been I. Refer to the 1989 Edition with the 1989 at ambient temperature for at least 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months .

Addenda and later Editions and Addenda.

Basis: The ultrasonic examination requirements of N-638-1 are developed for repair activities involving excavation and repair' wherein the repair weld and

1.0(d) Prior to welding the area to be welded and adjacent base material(s) typically require volumetric a band around the area of at least 1112 times the examination. These requirements for volumetric component thickness or 5 in., whichever is less examination are not considered suitable for shall be at least 50 0F. pressurizer nozzle surfaces adjacent to the structural weld overlay, since the existing nozzle configuration is not conducive to effective ultrasonic examination.

For structural weld overlays, Code Case N-504-2 has been developed specifically for installation of structural weld overlays, and contains NDE requirements consistent with structural weld overlay configurations. For this application, any major base material cracking is expected to take place in the heat affected zone directly below the WOL or in the underlying weld deposit and not in the band of

Attachment NOC-AE-06002000 Page 11 of 24 material outside the WOL. UT of the finetl weld surface should identify such cracks if thf ay are present.

This Code Cas e applies to any type of vwelding where a temper bead technique is employed and is not specifically awritten for WOL applications.. For structural weld overlays, Code Case N1-504-2 specifically appli es to structural weld overlay's, and includes NDE re( juirements consistent with structural WOL configuraticons.

Attachment NOC-AE-06002000 Page 12 of 24 TABLE 3 ALTERNATIVES TO APPENDIX Vill, SUPPLEMENT 11 ASME Section Xl Appendix Vill Supplement 11 - Qualification Requirements for Modification/Basis Full Structural Weld Overlaid Wrought Austenitic Piping Welds 1.0 SPECIMEN REQUIREMENTS 1.1(b) The specimen set shall consist of at least 1.1(b) The specimen set shall consist of at least three specimens having different nominal pipe three specimens having different nominal pipe diameters and overlay thicknesses. They shall diameters and overlay thicknesses. They shall include the minimum and maximum nominal include the minimum and maximum nominal pipe diameters for which the examination pipe diameters for which the examination procedure is applicable. Pipe diameters within a procedure is applicable. Pipe diameters within a range of 0.9 to 1.5 times a nominal diameter range of 0.9 to 1.5 times a nominal diameter shall shall be considered equivalent. If the procedure be considered equivalent. If the procedure is applicable to pipe diameters of 24 inches or is applicable to pipe diameters of 24 inches or larger, the specimen set must include at least one larger, the specimen set must include at least one specimen 24 inches or larger but need not specimen 24 inches or larger but need not include the maximum diameter. The specimen include the maximum diameter. The specimen set must include at least one specimen with set shall include specimens with overlays not overlay thickness within -0.1 inches to +0.25 thicker than 0.1 inch more than the minimum inches of the maximum nominal overlay thickness, nor thinner than 0.25 Inch of the thickness for which the procedure is applicable, maximum nominal overlay thickness for which the examination procedure is applicable.

Basis: The proposed alternative provides clarification regarding application of the tolerance.

The tolerance is unchanged for a single specimen set. It clarifies the tolerance for multiple specimen sets by providing tolerances for both minimum and maximum thicknesses. The proposed wording maintains the intent of the overlay thickness tolerance.

1.1(d) Flaw Conditions (1)Base metal flaws. All flaws must be cracks in or (1) Base metal flaws. All flaws must be in or near near the butt weld heat-affected zone, open to the the butt weld heat-affected zone, open to the inside inside surface, and extending at least 75% through surface, and extending at least 75% through the the base metal wall. Flaws may extend 100% base metal wall. Intentional overlay fabrication through the base metal and into the overlay flaws shall not interfere with ultrasonic material; in this case, intentional overlay detection or characterization of the base metal fabrication flaws shall not interfere with flaws. Specimens containing IGSCC shall be used ultrasonic detection or characterization of the when available. At least 70 percent of the flaws cracking. Specimens containing IGSCC in the detection and sizing tests shall be cracks

Attachment NOC-AE-06002000 Page 13 of 24

[intergranular stress corrosion cracking] shall be and the remainder shall be alternative flaws.

used when available. Alternative flaw mechanisms, if used, shall provide crack-like reflective characteristics and shall be limited by the following:

(a) The use of alternative flaws shall be limited to when the Implantation of cracks produces spurious reflectors that are uncharacteristic of actual flaws.

(b) Flaws shall be semi-elliptical with a tip width less than or equal to 0.002 inch.

Basis: This paragraph requires that all base metal flaws be cracks. Implanting a crack requires excavation of the base material on at least one side of the flaw. While this may be satisfactory for ferritic materials, austenitic materials do not provide a realistic flaw response.

To resolve this issue, the PDI developed a process for fabricating flaws that exhibit crack-like reflective characteristics. Use of alternative flaws is limited to when implantation of cracks precludes obtaining an effective ultrasonic response. Fabricated flaws are semi-elliptical with a tip width less than or equal to 0.002 inch. At least 70% of the flaws in the detection and sizing test are cracks and the rest are alternative flaws.

1.1(e) Detection Specimens (1) At least 20% but less than 40% of the flaws (1) At least 20% but less than 40% of the base shall be oriented within +20 deg. of the pipe axial metal flaws shall be oriented within +20 degrees of direction. The remainder shall be oriented the pipe axial direction. The remainder shall be circumferentially. Flaws shall not be open to any oriented circumferentially. Flaws shall not be open surface to which the candidate has physical or to any surface to which the candidate has physical visual access. The rules of IWA-3300 shall be or visual access.

used to determine whether closely spaced flaws should be treated as single or multiple flaws. Basis: The requirement for axially oriented overlay fabrication flaws was excluded from the PDI Program as an improbable scenario. Weld overlays are typically applied using automated GTAW techniques with the filler metal applied in a circumferential direction. Because fabrication-induced discontinuities would also be expected to have major dimensions oriented in the circumferential direction, axial overlay fabrication flaws are unrealistic.

I Used in place of IWA-3300. PDI treats each flaw as

Attachment NOC-AE-06002000 Page 14 of 24 an individual flaw and not as part of a system of closely spaced flaws. PDI controls the flaws used in a test specification set to be free of interfering reflections from adjacent flaws. Spacing the test specimen flaws more closely results in a more challenging performance demonstration.

1.1(e) Detection Specimens (2) Specimens shall be divided into base and (2) Specimens shall be divided into base metal and overlay grading units. Each specimen shall contain overlay fabrication grading units. Each specimen one or both types of grading units. shall contain one or both types of grading units.

Flaws shall not interfere with ultrasonic detection or characterization of other flaws.

Basis: Inclusion of 'metal" and 'fabrication' provides clarification. Flaw identification is improved by ensuring flaws are not masked by other flaws.

1.1(e) Detection Specimens (2)(a)(1) A base grading unit shall include at least 3 (2)(a)(1) A base metal grading unit includes the inches of the length of the overlaid weld. The overlay material and the outer 25% of the original base grading unit includes the outer 25 percent of overlaid weld. The base metal grading unit shall the overlaid weld and base metal on both sides. extend circumferentially for at least 1 inch and The base grading unit shall not include the inner shall start at the weld centerline and be wide 75 percent of the overlaid weld and base metal enough in the axial direction to encompass one overlay material, or base metal-to-overlay half of the original weld crown and a minimum interface. of 0.50 inch of the adjacent base material.

Basis: The PDI program intentionally excludes the phrase "and base metal on both sides," because some of the qualification samples include flaws on both sides of the weld. Several instances of the terms "cracks" and "cracking" were changed to the term "flaws" because of the use of alternative flaw mechanisms.

The proposed change permits the PDI program to continue using test specimens from the existing weld overlay program which have flaws on both sides of the welds. These test specimens have been used successfully for testing the proficiency of personnel for over 16 years. The weld overlay qualification is designed to be a near-side [relative to the weld] examination, and it is improbable that a candidate would detect a flaw on the opposite side of the weld due to the sound attenuation and redirection caused by the weld microstructure.

However, the presence of flaws on both sides of

Attachment NOC-AE-06002000 Page 15 of 24 the original weld (outside the PDI grading unit) may actually provide a more challenging examination, as candidates must determine the relevancy of these flaws, if detected.

1.1(e) Detection Specimens (2)(a)(2) When base metal cracking penetrates into (2)(a)(2) When base metal flaws penetrate into the the overlay material, the base grading unit shall overlay material, the base metal grading unit shall include the overlay metal within 1 inch of the not be used as part of any overlay fabrication crack location. This portion of the overlay material grading unit.

shall not be used as part of any overlay grading unit. Basis: Substituted terms provide clarification. The PDI program adjusts for this conservative change.

1.1(e) Detection Specimens (2)(a)(3) When a base grading unit is designed to (2)(a)(3) Sufficient unflawed overlaid weld and base be unflawed, at least 1 inch of unflawed overlaid metal shall exist on all sides of the grading unit to weld and base metal shall exist on either side of preclude interfering reflections from adjacent flaws.

the base grading unit. The segment of weld length used in one base grading unit shall not be Basis: The revised wording addresses the same used in another base grading unit. Base grading concerns as the ASME Code.

units. need not be uniformly spaced around the specimen.

1.1(e) Detection Specimens (2)(b)(1) An overlay grading unit shall Include the (2)(b)(1) An overlay fabrication grading unit shall overlay material and the base metal-to-overlay include the overlay material and the base metal-to-interface of at least 6 square inches. The overlay overlay interface for a length of at least 1 inch.

grading unit shall be rectangular, with minimum The PDI program reduces the base metal-to-dimensions of 2 inches TePIpormrdcstebs overlay interface to at least 1 inch (in lieu ea-o of a minimum of 2 inches) and eliminates the minimum rectangular dimension.

Basis: This criterion is necessary to allow use of existing examination specimens that were fabricated in order to meet NRC Generic Letter 88-

01. This criterion may be more challenging than the ASME Code because of the variability associated with the shape of the grading unit.

1.1(e) Detection Specimens (2)(b)(2) An overlay grading unit designed to be (2)(b)(2) Overlay fabrication grading units unflawed shall be surrounded by unflawed designed to be unflawed shall be separated by overlay material and unflawed base metal-to- unflawed overlay material and unflawed base overlay interface for at least 1 inch around its metal-to-overlay interface for at least 1 inch at both entire perimeter. The specific area used in one ends. Sufficient unflawed overlaid weld and

Attachment NOC-AE-06002000 Page 16 of 24 overlay grading unit shall not be used in another base metal shall exist on both sides of the overlay grading unit. Overlay grading units need overlay fabrication grading unit to preclude not be spaced uniformly about the specimen. interfering reflections from adjacent flaws. The specific area used in one overlay fabrication grading unit shall not be used in another overlay fabrication grading unit. Overlay fabrication grading units need not be spaced uniformly about the specimen.

Basis: Relaxation in the required area on the sides of the specimens, while still ensuring no interfering reflections, may provide a more challenging demonstration than required by the ASME Code because of the possibility for a parallel flaw on the opposite side of the weld.

1.1(e) Detection Specimens (2)(b)(3) Detection sets shall be selected from (2)(b)(3) Detection sets shall be selected from Table VIII-S2-1. The minimum detection sample Table Vill-S2-1. The minimum detection sample set is five flawed base grading units, ten unflawed set is five flawed base metal grading units, ten base grading units, five flawed overlay grading unflawed base metal grading units, five flawed units, and ten unflawed overlay grading units. For overlay fabrication grading units, and ten unflawed each type of grading unit, the set shall contain at overlay fabrication grading units. For each type of least twice as many unflawed as flawed grading grading unit, the set shall contain at least twice as units. many unflawed as flawed grading units. For initial procedure qualification, detection sets shall include the equivalent of three personnel qualification sets. To qualify new values of essential variables, at least one personnel qualification set is required.

Basis: The revised wording addresses the same concerns as the ASME Code. The additional wording for personnel qualification sets enhances the ASME Code requirements.

1.1(f) Sizing Specimen (1) The minimum number of flaws shall be ten. (1) The minimum number of flaws shall be ten.

At least 30% of the flaws shall be overlay At least 30% of the flaws shall be overlay fabrication flaws. At least 40% of the fabrication flaws. At least 40% of the flaws shall be cracks open to the inside surface. flaws shall be open to the inside surface. Sizing sets shall contain a distribution of flaw dimensions to assess sizing capabilities. For initial procedure qualification, sizing sets shall include the equivalent of three personnel qualification sets. To qualify new values of essential variables, at least one personnel qualification set is required.

Attachment NOC-AE-06002000 Page 17 of 24 Basis: The revised wording addresses the same concerns as the ASME Code. The additional wording for personnel qualification sets enhances the ASME Code requirements.

1.1(f) Sizing Specimen (3) Base metal cracking used for length sizing (3) Base metal flaws used for length sizing demonstrations shall be oriented circumferentially. demonstrations shall be oriented circumferentially.