L-PI-07-054, CFR 50.55a Request: Proposed Alternatives for Application of Structural Weld Overlay to the Pressurize Surge Nozzle Weld (2-RR-4-81)

CFR 50.55a Request: Proposed Alternatives for Application of Structural Weld Overlay to the Pressurize Surge Nozzle Weld (2-RR-4-81)

ML071760332
Person / Time
Site:	Prairie Island
Issue date:	06/25/2007
From:	Wadley M Nuclear Management Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-PI-07-054
Download: ML071760332 (37)

Text

Prairie lsland Nuclear Generating Plant Operated by Nuclear Management Company, LLC June 25,2007 L-PI-07-054 10 CFR 50.55a U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie lsland Nuclear Generating Plant Unit 2 Docket 50-306 License No. DPR-60 10 CFR 50.55a Request: Proposed Alternatives for Application of Structural Weld Overlav to the Prairie lsland Nuclear Generating Plant Unit 2 Pressurizer Surae Nozzle Weld (2-RR-4-81 Pursuant to 10 CFR 50.55a(a)(3)(i), Nuclear Management Company, LLC (NMC) requests Nuclear Regulatory Commission (NRC) approval for relief from applicable requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, as detailed in the attached 10 CFR 50.55a request. This request is for Prairie lsland Nuclear Generating Plant (PINGP) Unit 2 RepairIReplacement program, as established by the ASME Section XI Code, and involves a proposed alternative to ASME Section XI requirements for use of a weld overlay. The PINGP is currently in its fourth ten-year Inservice Inspection (ISI) interval.

NMC proposes to implement alternative requirements to ASME Section XI to provide for the installation and examination of a full structural weld overlay (FSWOL) for the pressurizer surge line nozzle-to-safe end dissimilar metal and safe end-to-reducer stainless steel butt welds. The overlay is a pre-emptive measure addressing primary water stress corrosion cracking concerns identified by the industry for welds associated with Alloy 600/82/182 components exposed to primary coolant. NMC has determined the proposed alternative requirements are appropriate for installation and examination of the FSWOL and will provide an acceptable level of quality and safety as required by 10 CFR 50.55a(a)(3)(i). Enclosure 1 contains the 10 CFR 50.55a request. Enclosure 2 contains additional industry information supporting this request.

NMC requests approval by June I , 2008, based on the next PINGP Unit 2 refueling outage scheduled for Fall 2008. A June I , 2008, approval allows NMC to sufficiently plan and prepare the pre-emptive weld overlay activities in advance of the refueling 1717 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1121

Document Control Desk Page 2 outage. If you have questions regarding this 10 CFR 50.55a request, please contact Lynne Gunderson at 715-377-3430.

Summarv of Commitments This letter contains no revisions to existing commitments. A summary of new commitments is included in Enclosure 3 of this letter.

Michael D. Wadley Site Vice President, Prairie lslan clear Generating Plant Nuclear Management Company, LLC Enclosures (3) cc: Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC Chief Boiler Inspector, State of Minnesota

Enclosure 1 Prairie Island Nuclear Generating Plant Unit 2 10 CFR 50.55a Request No. 2-RR-4-8, Rev. 0 Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

--Alternative Provides Acceptable Level of Quality and Safety--

1.0 ASME Code Components Affected

==

Description:==

Nozzle-to-safe end dissimilar metal (DM) Alloy 821182 butt weld and safe end-to-reducer stainless steel (SST) butt weld on surge line connection to the pressurizer. See Table 1 for detail.

Table 1 : Pressurizer Surge Nozzle Safe End Welds Code Exam Item Code Code Weld ID Class Category Number Category Item Weld Description Number 1 R-A R1.15-2 B-F B5.40 14" surge nozzle-to-safeend W-I 7 1 R-A R1.I 1-2 B-J B9.11 14" surae nozzle safe end-to-reducer W-16 2.0 Applicable Code Edition and Addenda ASME Section XI:

The Prairie Island Nuclear Generating Plant (PINGP) Unit 2 Fourth Ten-Year Interval lnservice Inspection (ISI) program is based on the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code,Section XI, 1998 Edition with 2000 Addenda. The fourth ten-year interval began December 21,2004 and ends December 20,2014.

ASME Section Ill:

ASME Boiler and Pressure Vessel Code, Section Ill Class A, Nuclear Vessels, 1965 Edition Winter 1966 Addenda (PINGP Unit 2 Pressurizer original code of construction)

USAS-B31. I .O-1967, USA Standard Code for Pressure Piping - Power Piping (PINGP Unit 2 reactor coolant system (RCS) piping original code of construction) 3.0 Applicable Code Requirement 3.1 Applicable ASME Code Requirements IWA-4420 and IWA-4520(a) of ASME Section XI (Ref 8.1) require repairlreplacement activities to be performed in accordance with the Owner's Requirements and the original Construction Code for the affected component or system. IWA-4430 and IWA-4600 provide for alternative welding methods. As an alternative to existing ASME Section XI Page 1 of 31

requirements for piping weld selection and examination volumes, Nuclear Management Company (NMC) has implemented 10 CFR 50.55a request number 2-RR-4-5, "Risk Informed Examination of Class 1 and 2 Piping Welds (code case N-578 and EPRl TR-1 12657),11Revision 0. Request 2-RR-4-5 was approved by the Nuclear Regulatory Commission (NRC) on January 5, 2006 (reference 8.12). Request 2-RR-4-5 implements the risk informed inservice inspection (RI-ISI) program for PlNGP Unit 2 in lieu of Table IWB-2500-1.

Section XI, Appendix VIII, Supplement 11 (reference 8.2) specifies the performance demonstration requirements for ultrasonic examination including requirements for ultrasonic testing (UT) procedures, equipment, and personnel for UT of completed weld overlays (WOLs).

3.2 Applicable ASME Code Cases ASME Code Case N-504-2, "Alternative Rules for Repair of Class I , 2, and 3 Austenitic Stainless Steel Piping,Section XI, Division 1 (reference 8.3) allows use of a WOL to

,I' enhance pipe integrity. This code case has been conditionally accepted in NRC Regulatory Guide (RG) 1.147, Revision 14 (reference 8.4), for use with the condition that the provisions of Section XI, Nonmandatory Appendix Q (reference 8.5) must also be met.

ASME Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temperbead Technique,Section XI, Division 1,"

(reference 8.6) describes the process for welding similar and dissimilar metals using ambient temperature machine gas tungsten arc weld (GTAW) temperbead technique.

This code case has also been conditionally accepted in NRC RG 1.147, Revision 14.

However, based on the modifications proposed in this 10 CFR 50.55a request for application of N-638-1, the conditions imposed in RG 1.I47 on use of this code case are not applicable for the intended application.

Code Cases N-504-2 and N-638-1 cannot be used without applying certain provisions and modifications. The provisions and modifications are explained in Section 5.0 and associated Tables 2 and 3 of this 10 CFR 50.55a request.

4.0 Reason for Request Primary water stress corrosion cracking (PWSCC) of nickel alloy base materials and weld metals exposed to pressurized water reactor (PWR) primary coolant is a concern in the nuclear industry. In particular, Alloy 821182 welds exposed to elevated temperatures, similar to the PlNGP Unit 2 pressurizer surge line dissimilar metal nozzle-to-safe end weld, are believed to pose a heightened propensity to PWSCC.

Nuclear Management Company has concluded that the application of a full structural weld overlay (FSWOL) to the PlNGP Unit 2 pressurizer surge nozzle DM weld is the most appropriate course of action in order to ensure RCS pressure boundary integrity.

The FSWOL of the DM nozzle-to-safe end weld would preclude future examination of Page 2 of 31

the SST safe end-to-reducer weld due to the close proximity of the two welds.

Therefore, the FSWOL will extend from the ferritic carbon steel nozzle across both butt welds to the SST pipe reducer to allow examination of both welds.

Weld overlays have been used for over 20 years for repair and mitigation of intergranular stress corrosion cracking in boiling water reactors and more recently for repair of PWSCC in pressurized water reactors. FSWOLs arrest propagation of existing flaws (if present) by inducing favorable residual compressive stress in the susceptible portion of the original DM weld.

The PlNGP Unit 2 pressurizer nozzle-to-safe end weld was most recently examined in November 2006. The weld was examined per ASME Section XI, Appendix VI II, Supplement 10 using qualified procedures, personnel, and equipment. The examination had a composite coverage of 94.1 percent (91 percent axial scans, 97.3 percent circumferential scan). Per MRP-139 (reference 8.7) at least 90 percent is required for the axial scans. This PlNGP Unit 2 examination met the ASME Section XI and MRP-139 requirements for exam coverage. No PWSCC indications were detected.

Currently, there are no generically accepted guidance or criteria for applying a nickel alloy FSWOL to a DM weld that is constructed of Alloy 821182 weld material and is believed to be susceptible to PWSCC. Pursuant to 10 CFR 50.55a(a)(3)(i), NMC requests relief from the requirements of the ASME code and proposes alternative requirements for installation and examination of the pre-emptive FSWOL that is to be applied to the pressurizer nozzle-to-safe end DM weld. The proposed alternative uses methodologies and requirements similar to those in ASME Code Cases N-504-2 and N-638-1, but is requested with certain provisions and modifications.

5.0 Proposed Alternative and Basis for Use NMC proposes to apply a FSWOL to the PlNGP Unit 2 pressurizer nozzle-to-safe end DM weld using a high-chromium nickel alloy weld metal that is resistant to PWSCC.

The FSWOL will extend around the full circumference of the existing nozzle safe end Alloy 821182 and SST welds and will overlap the neighboring sections of the low-alloy ferritic steel nozzle and SST reducer. The PlNGP Unit 2 pressurizer surge nozzle FSWOL configuration is shown in Figure 1.

Included as part of this request (Enclosure 2) is a discussion addressing recent industry experience concerning hot cracking of the Alloy 52M weld overlay on austenitic SST base materials with high levels of sulfur.

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FIGURE 1 PlNGP UNIT 2 PRESSURIZER SURGE NOZZLE OVERLAY DIAGRAM THERMAL SLEEVE

/"- SA-240, TYPE 304 STAINLESS STEEL WELD OVERLAY ALLOY 52M OR EQUIVALENT 14" SCH 160 X 10" SCH 140 CONCENTRIC REDUCER A-403, GRADE WP.

TYPE 316, STAINLESS STEEL Page 4 of 31

5.1 Code Case N-504-2 and Section XI, Nonmandatory Appendix Q ASME Section XI Code Case N-504-2 allows a flaw in austenitic SST piping to be reduced to an acceptable size through the deposition of weld reinforcement on the outside surface of the pipe without flaw removal. The provisions of Section XI Nonmandatory Appendix Q are imposed by NRC RG 1.147, Revision 14, as a condition for acceptance of Code Case N-504-2.

For the design of the FSWOL it is conservatively assumed that a 360 degree circumferential through-wall flaw is present in the original Alloy 821182 weld and in the original SST weld. Thus, the FSWOL will extend around the full circumference of the nozzle-to-safe end weld location and the safe end-to-reducer weld location as required by ASME Code Case N-504-2. The weld reinforcement material is to be Alloy 52M, or equivalent, and applied as a FSWOL to the existing ferritic carbon steel nozzle, austenitic SST safe end, SST pipe reducer, and the Alloy 821182 and austenitic SST weld material joining them.

The WOL will be designed as a FSWOL consistent with the requirements of ASME Code Case N-504-2 and Section XI Nonmandatory Appendix Q. The FSWOL design assumes there is no contribution to structural integrity from the original section of pipe.

The FSWOL thickness and length will be designed according to the guidance provided in Code Case N-504-2.

The design and repair methodologies of Code Case N-504-2 and provisions of Nonmandatory Appendix Q will be followed with modifications. These modifications and their bases are summarized in Table 2. All other applicable requirements not listed in Table 2 will be met as described in Code Case N-504-2 and Nonmandatory Appendix Q.

Weld overlay examination, preservice of the completed repair, and inservice inspections will be performed in accordance with Code Case N-504-2, ASME Section XI, Nonmandatory Appendix Q, Subarticles Q-4100, Q-4200 and (2-4300, and ASME Section XI, Appendix VIII, Supplement 11 with the modifications noted in Section 5.3 and Table 4 of this 10 CFR 50.55a request. These examinations will meet the applicable code and code case requirements as modified by this request.

Any FSWOL preservice ultrasonic indications characterized as weld flaws in the FSWOL weld metal that exceed the acceptance standards of IWB-3514-2 will be removed or reduced to an acceptable size. Indications located in the outer 25 percent of the base metal that are characterized as cracks will meet the design analysis requirements as specified in Nonmandatory Appendix Q, Q-3000.

5.2 Code Case N-638-1 Application of the FSWOL requires welding on the ferritic steel nozzle material with Alloy 52M. Temperbead welding will be used for this purpose using the guidance of Code Case N-638-1. Code Case N-638-1 describes the process for welding similar and Page 5 of 31

dissimilar metals using ambient temperature machine GTAW temperbead method. Gas tungsten arc welding will be performed in accordance with Code Case N-638-1, with some modifications. As noted previously, Code Case N-638-1 was conditionally accepted in NRC RG 1.147, Revision 14, and was developed for welding similar and dissimilar metals using ambient temperature machine GTAW temperbead technique.

However, based on the additional modifications proposed for application of this code case (Table 3), the conditions imposed by RG 1.I47 on use of this code case are not applicable for the intended application.

The methodology of Code Case N-638-1 will be followed for welding on ferritic material where the Construction Code requires post-weld heat treatment, with modifications.

The proposed modifications to Code Case N-638-1 specifically address the draining requirement, weld area limit of 100 square inches, ultrasonic examination thickness, 48-hour post-weld hold criteria prior to nondestructive examination (NDE), and the use of nonattached temperature measuring devices for temperbead welding. These specific changes and the basis justifying each proposed modification to the methodologies specified in Code Case N-638-1 are addressed in Table 3. Applicable requirements not listed will be met as described in the code case.

5.3 ASME Section XI, Appendix VIII, Supplement 11 Ultrasonic testing of the completed FSWOLs will be accomplished in accordance with ASME Section XI, Appendix VIII, Supplement 11, modified to comply with the Performance Demonstration Initiative (PDI), as described in Table 4. PDI has developed a program for qualifying equipment, procedures, and personnel for WOL examinations in accordance with the UT criteria of ASME Appendix VIII, Supplement

11. Table 4 addresses the specific modifications made to the requirements of Appendix VI II, Supplement 11. The basis for each modification is provided as well.

ASME Section XI, Appendix VIII, Supplement 11 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, it does not produce a useable axial flaw in austenitic materials because the sound beam, which normally passes only through base material, must now travel through weld material on at least one side, producing an unrealistic flaw response. To resolve this issue the PDI program made revisions to allow use of alternative flaw mechanisms under controlled conditions.

For example, alternative flaws shall be limited to cases when implantation of cracks precludes obtaining an effective ultrasonic response, flaws shall be semi elliptical with a tip width of less than or equal to 0.002 inches, and at least 70 percent of the flaws in the detection and sizing test shall be cracks and the remainder shall be alternative flaws.

Applicable requirements not listed or addressed in Table 4 will be met as described in ASME Section XI, Appendix VIII, Supplement 11.

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5.4 Implementation The FSWOL is currently planned for installation during the PlNGP Unit 2 Fall 2008 refueling outage as a preventive measure against flaw development in the DM weld.

NRC approval is requested by June 1, 2008 to support scheduling for completion of activities during the outage.

5.5 Conclusion The pre-emptive FSWOL will be installed in accordance with Code Case N-504-1, ASME Section XI Nonmandatory Appendix Q, and Code Case N-638-1 as modified by Tables 2 and 3. Ultrasonic testing of the completed FSWOLs will be accomplished in accordance with ASME Section XI, Appendix VI II, Supplement 11, modified to comply with the PDI, as described in Table 4. NMC has determined the proposed alternative provides an acceptable level of quality and safety and requests the NRC staff authorize the proposed alternative in accordance with 10 CFR 50.55a(a)(3)(i).

6.0 Duration of Proposed Alternative The proposed alternative is requested for the design life of the FSWOL, as determined by the required evaluation in Paragraph (g) of Code Case N-504-2 and the corresponding requirements in Nonmandatory Appendix Q. lnservice Inspection (ISI) requirements beyond the current interval will be evaluated and established by the PlNGP Unit 2 RI-IS1 Program.

7.0 Precedents Similar 10 CFR 50.55a requests have been submitted to the NRC with several obtaining approval:

7.1 Letter from L. Raghavan, NRC, to Mano K. Nazar, "Donald C. Cook Nuclear Plant, Unit 2 (DDCNP-2) -Alternative Regarding Use Of Preemptive Weld Overlays On Certain Dissimilar Metal Welds (TAC No. MD9305)," dated March 1,2007 (ML070460121).

7.2 Letter from L. Raghavan, NRC, to Mano K. Nazar, "Donald C. Cook Nuclear Plant, Unit 1 (DDCNP-1) - Alternative Regarding Use Of Preemptive Weld Overlays (PSOLs) On Certain Dissimilar Metal Welds (TAC No. MD2119)," dated April 26,2007 (ML070720021).

7.3 Letter from Darrell J. Roberts, NRC, to David A. Christian, Dominion Nuclear Connecticut, Inc., "Millstone Power Station, Unit No. 3 - Issuance of Relief from Code Requirements (TAC No. MC8609)," dated January 20, 2006 (ML053260012).

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Letter from Keith D. Young to NRC Document Control Desk, "Docket Number 50-483, Union Electric Company, Callaway Plant, 10 CFR 50.55a Request For Relief From ASME Section XI Repair And Replacement Requirements Proposed Alternatives For Application Of Structural Weld Overlays To Pressurizer Nozzle Welds," dated August 14, 2006 (ML062360200).

Letter from David T. Fitzgerald to NRC Document Control Desk, "Docket Number 50-483, Union Electric Company, Callaway Plant, Response To Request For Additional Information Regarding 10CFR 50.55a Request For Relief From ASME Section XI Repair And Replacement Requirements: Proposed Alternatives For Application Of Structural Weld Overlays To Pressurizer Nozzle Welds," dated March 26,2007 (ML070990115).

Letter from Russell G. West to NRC Document Control Desk, "Relief Request No. 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 May 1, 2007 (ML071220466 ).

References ASME Code,Section XI, 1998 Edition through 2000 Addenda, IWA-4000, "RepairIReplacementActivities."

ASME Code,Section XI, 1998 Edition through 2000 Addenda, Appendix VIII, Supplement 11 "Qualification Requirements For Full Structural Overlaid Wrought Austenitic Piping Welds."

ASME Code Case N-504-2, "Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping,Section XI, Division 1".

U.S. Nuclear Regulatory Commission Regulatory Guide 1.147, Revision 14, "Inservice lnspection Code Case Acceptability, ASME Section XI, Division 1,"

August 2005.

ASME Code Section XI, 2004 Edition through 2006 Addenda, Nonmandatory Appendix Q, "Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments."

ASME Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temperbead Technique,Section XI, Division 1."

Electric Power Research Institute Technical Report 1010087, "Materials Reliability Program: Primary System Piping Butt Weld Inspection and Evaluation Guidelines (MRP-139)," August 2005.

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8.8 Electric Power Research lnstitute Topical Report 1013036, "Topical Report Supporting an Expedited NRC Review of the Content of the Code Case Needed for Dissimilar Metal Weld Overlay Repairs," January 2006.

8.9 Electric Power Research lnstitute Technical Report 1003616, "Additional Evaluations to Expand Repair Limits for Pressure Vessels and Nozzles," March 2004.

8.10 Electric Power Research lnstitute GC-111050, "Ambient Temperature Preheat for Machine GTAW Temperbead Applications, November 1998.

8.1 1 Electric Power Research lnstitute Report 1013558, "Temperbead Welding Applications 48-Hour Hold Requirements for Ambient Temperature Temperbead Welding," December 2006.

8.12 Letter from NRR to NMC, "Prairie Island Nuclear Generating Plant, Units 1 and 2

- Issuance of Relief Request for the Risk-Informed Inservice Inspection Program (TAC NOS. MC5644 and MC5645)," dated January 5,2006 (ML053270079).

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TABLE 2: MODIFICATIONS TO ASME CODE CASE N-504-2 AND SECTION XI, NONMANDATORY APPENDIX Q Current Requirements Modification and Basis Code Case N-504-2, Reply: It is the opinion of the Committee Modification: Permit Code Case N-504-2 and Section XI that, in lieu of the requirements of IWA-4120 in Editions and Nonmandatory Appendix Q for the installation of a nickel alloy Addenda up to and including the 1989 Edition with the 1990 FSWOL to mitigate the potential of PWSCC in Pressurizer Addenda, in IWA-4170(b) in the 1989 Edition with the 1991 nozzle-to-safe-end DM weld as modified herein.

Addenda up to and including the 1995 Edition, and in IWA-4410 in the 1995 Edition with the 1995 Addenda and later Editions and Code Case N-504-2, Reply: It is the opinion of the Committee Addenda, defect in austenitic stainless steel piping may be that Code Case N-504-2 and Section XI Nonmandatory Appendix reduced to a flaw of acceptable size in accordance with IWB- Q, 2005 Addenda, may be used for the application of Alloy 3640 from the 1983 Edition with the Winter 1985 Addenda, or 52152M full structural weld overlays of the ferritic (P-No.1 Group later Editions and Addenda, by deposition of weld reinforcement 2) nozzle material, nickel alloy (F-No.43) weld material, and (weld overlay) on the outside surface of the pipe, provided the austenitic stainless steel (P-No. 8) safe end and pipe base following requirements are met: material and (A-No.8) weld materials, to mitigate the potential of PWSCC in nozzle-to-safe-end DM weld as modified herein.

Nonmandatory Appendix Q, Scope: This Appendix provides an alternative to the requirements of IWA-4420, IWA-4520, IWA- Basis: The FSWOL will be sized to meet all structural 4530, and IWA-4600 for making repairs to, and subsequent requirements without considering the structured component of examination of Class 1, 2, and 3 austenitic stainless steel pipe the existing Alloy 821182 and SST weldments. Industry operating weldments with stress corrosion cracking, by deposition of weld experience has shown that propagation of PWSCC in Alloy reinforcement (weld overlay) on the outside surface of the pipe. 821182 weld metal will arrest at the SST base metal, ferritic base After a weld overlay has been installed in accordance with this metal, or Alloy 52152M interface. The 360 degree FSWOL will Appendix, the inservice examinations identified in Q-4300 shall thus control propagation of PWSCC and maintain joint integrity.

be performed as long as the repair remains part of the pressure boundary.

Code Case N-504-2, Paragraph (b): Reinforcement weld metal Modification: Nickel alloy weld filler metal may be used in lieu of shall be low carbon (0.035% max.) austenitic stainless steel low carbon austenitic filler metal.

applied 360 deg. around the circumference of the pipe, and shall be deposited in accordance with a qualified welding procedure Code Case N-504-2, Paragraph (b): Reinforcement weld metal specification identified in the Repair Program. shall be a PWSCC resistant nickel alloy filler material applied 360 Nonmandatory Appendix Q, Q-2000 Paragraph (a): degrees around the circumference of the pipe, and shall be Reinforcement weld metal shall be low carbon (0.035% max.) deposited in accordance with a qualified welding procedure Page 10 of 31

TABLE 2: MODIFICATIONS TO ASME CODE CASE N-504-2 AND SECTION XI, NONMANDATORY APPENDIX Q Current Requirements Modification and Basis austenitic stainless steel applied 360 deg around the specification.

circumference of the pipe, and shall be deposited using a Welding Procedure Specification for groove welding, qualified in Basis: The FSWOL weld metal will be ERNiCrFe-7A (Alloy 52M, accordance with the Construction Code and Owner's UNS N06054). Repairs, if required, may be ERNiCrFe-7A or Requirements and identified in the RepairlReplacement Plan. ERNiCrFe-7 (Alloy 52). ERNiCrFe-7A and ENiCrFe-7 are assigned F-No. 43 by ASME Section IX, 2006 Addenda. The requirements of ASME Section Ill, NB-2400 will be applied to all filler material as required by ASME Section XI.

Alloys 52M and 52 contain about 30% Cr (significantly higher than Alloy 821182), imparting excellent PWSCC resistance. Alloy 52M and 52 are fully austenitic and have ductile properties and toughness similar to austenitic SST piping welds at PWR operating temperature. Furthermore, these filler materials are suitable for welding to the ferritic nozzle, Alloy 811182 weld, and the austenitic SST pipe, welds, and safe end materials.

Code Case N-504-2, Paragraph (e): The weld reinforcement Modification: Delta ferrite (FN) measurements will not be shall consist of a minimum of two weld layers having as- performed when using Alloy 52Ml52 filler material. The FSWOL deposited delta ferrite content of at least 7.5 FN. The first layer deposit shall instead meet the following requirements:

of weld metal with delta ferrite content of least 7.5 FN shall constitute the first layer of the weld reinforcement design Code Case N-504-2, Paragraph (e): The austenitic nickel alloy thickness. Alternatively, first layers of at least 5 FN may be weld overlay shall consist of at least two weld layers deposited acceptable based on evaluation. [Similar to Q-2000(d)] from a filler material with a Cr content of at least 28%. The first layer of weld metal deposited may not be credited toward the required WOL structural design thickness. Alternatively, the as-Nonmandatory Appendix Q, Q-2000 Paragraph (d): The weld deposited first layer may be credited toward the required reinforcement shall consist of at least two weld layers having as- structural design thickness, provided the diluted layer applied deposited delta ferrite content of at least 7.5 FN. The first layer over the austenitic base material, austenitic weld metal and of weld metal with delta ferrite content of at least 7.5 FN shall ferritic carbon steel base material contains at least 24% Cr. The Page 11 of 31

TABLE 2: MODIFICATIONS TO ASME CODE CASE N-504-2 AND SECTION XI, NONMANDATORY APPENDIX Q Current Requirements Modification and Basis constitute the first layer of the weld reinforcement that may be Cr content of the first layer may be determined by chemical credited toward the required thickness. Alternatively, first layers analysis of the production weld or may be demonstrated by a of at least 5 FN are acceptable, provided the carbon content of representative coupon taken from a mockup prepared in the deposited weld metal is determined by chemical analysis to accordance with the production welding procedure specification be less than 0.02%. (WPS). The welding parameters demonstrated on the mockup to achieve 24% Cr on the first layer shall be used for the production weld first layer.

Basis: Alloy 52Ml52 weld metal is fully austenitic and contains no delta ferrite due to the high nickel (-60%) content. As-deposited delta ferrite content is therefore not applicable for Alloy 52Ml52 weld metal. Alloy 52Ml52 with as-deposited first layer chromium content greater than or equal to 24% provides acceptable PWSCC resistance.

EPRI Topical Report 1013036, Appendix B, "White Paper-Effect of Chromium Content on Nickel-Base Allow SCC Resistance,"

(Ref 8.8) shows that 24% Cr provides acceptable resistance to PWSCC in PWR applications. As-deposited first layer chemistry will be verified either by field chemistry measurements or by prior mockup demonstration using production WPS parameters.

When first-layer chemistry meets or exceeds 24% Cr, this initial layer will be credited toward FSWOL design thickness. If the first-layer Cr is less than 24%, the first layer will be considered sacrificial and will not be credited toward FSWOL design thickness.

Code Case N-504-2 Paragraphs (0 and (g) Code Case N-504-2, Modifications: The provisions of N-504-2 (f) and (g), Q-3000 in the 2005 Addenda of Section XI, and Nonmandatory Appendix Q, Q-3000 Paragraph (b): The design corrections to Q-3000 published in the 2006 Addenda of Section Page 12 of 31

TABLE 2: MODIFICATIONS TO ASME CODE CASE N-504-2 AND SECTION XI, NONMANDATORY APPENDIX Q Current Requirements Modification and Basis of the weld overlay shall satisfy the requirements of the XI will be used, with the following modifications:

Construction Code and Owner's Requirements in accordance with IWA-4221 and the following, using the assumptions and flaw Nonmandatory Appendix Q, 4-3000 Paragraph (b): The design characterization restrictions in Q-3000(a). The design analysis of the weld overlay shall be in accordance with IWA-4221 and the required by Q-3000(b)(l) - (4) shall be completed in accordance following, using the assumptions and flaw characterization with IWA-4311. restrictions in Q-3000(a). The design analysis required by Q-3000(b)(l)-(4) shall be completed in accordance with IWA-4311.

The analysis required under N-504-2(g)(2) and (g)(3) are currently in development and will be completed prior to entering Mode 4 Startup following the refueling outage FSWOL installation.

Nonmandatory Appendix Q, Q-3000 Paragraph (b) (3): The overlay design thickness of items meeting Q-3000(a)(2), (3), or (4) shall be based on the measured diameter, using the thickness of the weld overlay as restricted by Q-2000(d). The wall thickness at the weld overlay, any planar flaws in the weld overlay and the effects of any discontinuity (e.g., another weld overlay or reinforcement for a branch connection) within a distance of 2.5 d ~fromt the toes of the weld overlay, shall be evaluated and shall meet the requirements of IWB-3640.

Basis: The 2005 Addenda of Section XI incorporated Code Case N-504-2 as Nonmandatory Appendix Q. Unfortunately, inadvertent consequences of modified wording caused problems with implementation. Nonmandatory Appendix Q was revised in the 2006 Addenda to more accurately incorporate the provisions of Code Case N-504-2. A correction to Q-3000(b) deleted the requirement for the design of the WOL to satisfy the Page 13 of 31

TABLE 2: MODIFICATIONS TO ASME CODE CASE N-504-2 AND SECTION XI, NONMANDATORY APPENDIX Q Current Requirements Modification and Basis requirements of the Construction Code and Owner's requirements. There was no similar wording in Code Case N-504-2. This wording was inappropriate because meeting the requirements of the construction Code required the absence of cracks. A fundamental purpose of Code Case N-504-2 was to repair cracks (reduce to an acceptable size) by installation of a WOL. The appropriate requirements for maintaining Section Ill (i.e., the Construction Code) limits were properly transferred from Case N-504-2 into Q-3000(b)(l) in the initial issue of Nonmandatory Appendix Q and the deletion of Q-3000(b) in the 2006 Addenda of Nonmandatory Appendix Q resolved the problem.

Regarding the correction in Q-3000(b)(3), "overlay design thickness" is more appropriate than "pressure design", which is incorrect and was not used in Code Case N-504-2. Overlay design thickness is based on other loads in addition to pressure.

Code Case N-504-2, Paragraph (h): The completed repair shall Modification: In lieu of a hydrostatic test, a system leakage test be pressure tested in accordance with IWA-5000. If the flaw will be performed in accordance with Section XI, IWA-5000 of the penetrated the original pressure boundary prior to welding, or if 2000 Addenda.

any evidence of the flaw penetrating the pressure boundary is observed during the welding operation, a system hydrostatic test Code Case N-504-2, Paragraph (h): The completed repair shall shall be performed in accordance with IWA-5000. If the system be pressure tested in accordance with IWA-5000.

pressure boundary has not been penetrated, a system leakage, inservice, or functional test shall be performed in accordance with Basis: A system hydrostatic test at normal operating temperature IWA-5000. and at 1.02 times the Class 1 reactor coolant system operating pressure (as specified by IWA-5000 and IWB-5000) provides no more assurance of the structural condition of the FSWOL than a system leakage test performed at RCS operating pressure. The Page 14 of 31

TABLE 2: MODIFICATIONS TO ASME CODE CASE N-504-2 AND SECTION XI, NONMANDATORY APPENDIX Q Current Requirements Modification and Basis 1993 Addenda of ASME Section XI eliminated Class 1 system hydrostatic tests for inservice inspection. Furthermore, the 1999 Addenda of ASME Section XI, which is accepted in 10CFR50.55a, permits a system leakage test in lieu of a system hydrostatic test for all repairlreplacement activities.

Page 15 of 31

TABLE 3: MODIFICATIONS TO ASME CODE CASE N-638-1 Current Requirements Modification and Basis Reply: It is the opinion of the Committee that repair to P-No. 1, 3, Modification: Permit installation of the FSWOL with or without the 12A, 12B, and 12c1, except SA-302 Grade B, material and their Pressurizer and associated surge nozzle piping drained.

associated welds and welds joining P-No. 8 or P-No. 43 material to P-Nos. 1, 3, 12A, 12B, and 12c1, except SA-302 Grade B, Reply: It is the opinion of the Committee that repair to P-No. 1, 3, material may be made by the automatic or machine GTAW 12A, 12B, and 12c1, except SA-302 Grade B, material and their temperbead technique without the specified preheat or postweld associated welds and welds joining P-No. 8 or P-No. 43 material heat treatment of the Construction Code, when it is impractical to to P-Nos. 1, 3, 12A, 12B, and 12c1,except SA-302 Grade B, drain the component or impractical for radiological reasons. The material may be made by the automatic or machine GTAW nondestructive examination requirements of the temperbead technique without the specified preheat or postweld Construction Code need not be met, provided the requirements heat treatment of the Construction Code with or without draining of paras. 1.0 through 5.0, and all other requirements of IWA- the system or component. The nondestructive examination 40002, are met. requirements.. .

Basis: As part of plant refueling, the surge nozzle and associated piping will be drained below the overlay location for brief periods during FSWOL installation.

Code Case N-638-1 requires 350°F interpass temperature for the first three layers and all subsequent layers. The 350°F interpass on the first three layers provides adequate control to ensure tempered martensite with adequate toughness in the ferritic carbon steel nozzle material, and the 350°F interpass for all subsequent layers ensures the SST weld and base material are not sensitized. The interpass temperature controls of N-638-1 are therefore adequate to ensure acceptable mechanical properties and structural integrity of the overlay weldment.

Paragraph l.O(a): The maximum area of an individual weld Modifications: The area of the ferritic carbon steel nozzle base based on the finished surface shall be 100 sq. in., and the depth material covered by the FSWOL may exceed 100 sq. in. The of the weld shall not be greater than one-half of the ferritic base one-half base metal thickness limitation applies to weld repair of metal thickness. base metal excavations and is not applicable to FSWOLs.

Page 16 of 31

TABLE 3: MODIFICATIONS TO ASME CODE CASE N-638-1 Current Requirements Modification and Basis Paragraph l.O(a): The maximum ferritic carbon steel base material surface area covered by weld overlay shall be 300 sq.

in.

Basis: The requirements of N-638-1 are applied to the FSWOL material installed on the ferritic carbon steel nozzle base material. The area of the FSWOL covering the ferritic base material for the PlNGP Unit 2 surge nozzle is approximately 140 sq. in. which will exceed the 100 sq. in. limit of surface covered by the FSWOL imposed by Code Case N-638-1. In order for the FSWOL to satisfy structural requirements, additional weld material may be necessary in the axial direction on the ferritic carbon steel nozzle to facilitate the required post-overlay ultrasonic examination and/or to achieve an acceptable overlay blend transition into the nozzle. The maximum ferritic carbon steel base material covered by the FSWOL will be limited to 300 sq. in.

Extensive experience exists in BWR and PWR WOL applications where the ferritic base material covered by WOL exceeded the 100 sq. in. limitation without any damage or long-term detrimental effects. EPRl Technical Report 1003616, "Additional Evaluations to Expand Repair Limits for Pressure Vessels and Nozzles," (Ref.

8.9) provides justification for WOL areas up to 500 sq. in. Finite element analyses of the ambient temperature temperbead repair process show that residual stresses are not detrimentally affected by increasing the allowable repair area. In fact, analyses show that in some cases increasing the allowable repair area improves the residual stress distribution in the weldment.

Page 17 of 31

TABLE 3: MODIFICATIONS TO ASME CODE CASE N-638-1 Current Requirements Modification and Basis ASME published Code Case N-638-3, which permits a repair area up to 500 sq. in., in Supplement 9 to the 2004 Edition of ASME Section XI. The Committee white paper basis for this N-638 revision indicates that the 100 sq. in. limitation was arbitrarily established and that repair areas up to 500 sq. in. would have no adverse effect.

Paragraph 4.0(b): The final weld surface and the band around Modification: In lieu of the requirements of Paragraph 4.0(b),

the area defined in para. 1.O(d) shall be examined using a examination of the final FSWOL will be in accordance with the surface and ultrasonic methods when the completed weld has requirements of Code Case N-504-2 and Nonmandatory been at 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 Appendix Q, as modified in this relief request. The 48-hour hold ultrasonic examination shall be in accordance with Appendix 13. time prior to final NDE may start following completion of the third temperbead layer and is applied only to FSWOL section that 3 ~ e f etor the 1989 Edition with the 1989 Addenda and later covers and/or adjoins the ferritic carbon steel nozzle base Editions and Addenda. material.

Paragraph 4.0(b): The final weld overlay shall be examined in accordance with Code Case N-504-2 and Nonmandatory Appendix Q, as modified. The volume and area requiring examination by Code Case N-504-2 and Nonmandatory Appendix Q are adequate for detection of hydrogen delayed cracking that occurs in the ferritic carbon steel heat affected zone (HAZ). Examination of the weld overlay covering the ferritic base material and examination of the adjacent ferritic base material shall be performed no sooner than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after completion of the third temperbead layer over the ferritic base material.

Basis: Examination of a band width 1.5 times the component thickness or 5 in. which ever is less, around the repair area after 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> at ambient temperature is for detection of delayed HAZ cracking that may occur due to inadvertent introduction of deleterious monatomic hydrogen into a hardened base metal Page 18 of 3 1

TABLE 3: MODIFICATIONS TO ASME CODE CASE N-638-1 Current Requirements Modification and Basis HAZ microstructure that was not adequately tempered. The ferritic nozzle base material HAZ due to the first Alloy 52M layer is the only region susceptible to potential hydrogen delayed cracking. The volume and area requiring examination by Code Case N-504-2 and Nonmandatory Appendix Q are therefore adequate for detection of hydrogen delayed cracking that occurs in vicinity of the first layer HAZ and the excessive examination band region specified by Paragraph 4.0(b) is not necessary.

Hydrogen contamination to deleterious levels from outside sources is unlikely when applying the ambient temperature temperbead machine GTAW process with the associated methodologies specified for welding control, cleanliness, and examination. As compared to flux type welding processes, machine GTAW with argon shielding is an inherently low-hydrogen process that provides optimum temperbead welding controls to ensure adequately tempered base metal HAZ with high fracture toughness. The low hydrogen and tempering characteristics of the machine GTAW process are well documented in EPRl GC-111050, "Ambient Temperature Preheat for Machine GTAW Temperbead Applications," (Ref. 8.10).

Code Case N-504-2 and Nonmandatory Appendix Q require liquid penetrant examination (PT) prior to installation of the FSWOL. Cleaning the base metal for PT provides assurance, in addition to typical welding process controls, that deleterious hydrogen from surface contamination is not introduced in the first layer of the FSWOL.

The high affinity of fully austenitic Alloy 52M filler metal for monatomic hydrogen combined with a low diffusion coefficient keeps diffusion of deleterious hydrogen into the ferritic carbon Page 19 of 3 1

TABLE 3: MODIFICATIONS TO ASME CODE CASE N-638-1 Current Requirements Modification and Basis steel base material to negligible levels. Furthermore, only welding in contact with the ferritic carbon steel base material has potential of introducing deleterious monatomic hydrogen into a hardened untempered HAZ region. Each successive temperbead layer has a decreasing propensity for introducing hydrogen into the ferritic base material due to increasing distance from the susceptible base metal HAZ. After three layers the temperbead process adequately tempers the martensite formed in the ferritic base material by the first layer. Adequate tempering by the third weld layer decreases the hardness and increases the fracture toughness in the potentially susceptible ferritic base material HAZ thus mitigating susceptibility to delayed hydrogen cracking.

In addition, the use of the machine GTAW temperbead process provides precise control of heat input, bead placement, bead size and contour. The very precise control over these factors afforded by the machine GTAW process provides effective tempering of the nozzle ferritic steel HAZ resulting in achievement of lower hardness and tempered martensite. This further reduces susceptibility to hydrogen induced cracking.

EPRl Report 1013558, Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding, Technical Update, December, 2006 (Reference 8.11) 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 Page 20 of 31

TABLE 3: MODIFICATIONS TO ASME CODE CASE N-638-1 Current Requirements Modification and Basis 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 and provides the technical justification therein.

The 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> delay provides time after welding for delayed hydrogen cracking occurrence.

The base materials studied in the EPRl report are primarily P-No. 3. The pressurizer surge nozzle ferritic carbon steel base material is P-No. 1 Group No. 2. The concerns associated with hydrogen assisted cracking are generally more significant for P-No. 3 than P-No.1 Group No. 2 base materials due to P-No. 3 base materials increased hardenability.

Also, post weld heat treat exemptions shown in ASME Section Ill, Table NB-4622.7(b)-1 are provided for P-No. 1 Group No. 2 materials including temperbead welding, whereas no post weld heat treat exemptions, other than temperbead welding, are permitted for P-No. 3 Group No. 3 materials. It is noted that temperbead welding may only be required on the carbon steel nozzle taper where the thickness is greater than 1-112 in.

depending on the final FSWOL thickness.

Based on past and recent NDE experience on temperbead weld overlays, hydrogen cracking of these welds was not identified during the initial NDE after a 48-hour hold time or subsequent inservice inspection examinations.

In summary, the inherent low hydrogen nature of the prescribed ambient temperature temperbead machine GTAW process and methodology, the relatively low susceptibility of hydrogen induced Page 21 of 31

TABLE 3: MODIFICATIONS TO ASME CODE CASE N-638-1 Current Requirements Modification and Basis cracking in ferritic base material HAZ when using nickel alloy filler metals, and performance of the Nonmandatory Appendix Q and N-504-2 final examination (as modified) 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after completion of the third layer over the ferritic base material provides substantial assurance against the potential for delayed hydrogen cracking in the ferritic base material HAZ.

Additionally, ASME published Code Case N-638-3, which does not require examination of the band around the repair area, in Supplement 9 to the 2004 Edition of ASME Section XI. Also, the Boiler and Pressure Vessel Main Committee in August 2006 approved a revision to N-638-3 which permits start of the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold following completion of the third temperbead layer (Reference ASME Code Committee tracking no. BC06-134).

Therefore, final FSWOL examination will not include base metal at 1.5T distance beyond the overlay weld as specified in N-638-1.

The final NDE of the temperbead portion of the weld over the ferritic carbon steel nozzle will be performed no sooner than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after completion of the third temperbead layer.

Paragraph 4.0(c): Areas from which weld-attached Modification: Provide for use of non-attached temperature thermocouples have been removed shall be ground and measuring devices.

examined using a surface examination method.

Paragraph 4.0(c): Process temperatures may be monitored with non-attached type devices, such as contact pyrometers, which will enable manual recording of process temperatures.

Instruments used will be calibrated in accordance with approved calibration and control program requirements. If weld-attached thermocouples are used, the local area where thermocouples were attached shall be ground and examined using a surface examination method.

Page 22 of 31

! TABLE 3: MODIFICATIONS TO ASME CODE CASE N-638-1 Current Requirements Modification and Basis I

Basis: Process temperature monitoring is performed to ensure compliance with the applicable Welding Procedure Specification preheatlinterpass temperature requirements during overlay welding. lnterpass temperature, temperature of a previously deposited weld pass prior to depositing a subsequent weld pass, must be measured at the start location of the successive weld pass prior to commencement of welding. Attached thermocouples are not practical for this application because they must be fixed at specific location(s). The accuracy of temperature measurements from a contact pyrometer and attached thermocouple are comparable. Use of non-attached temperature measuring devices is adequate for controlling and monitoring temperatures during ambient temperature temperbead machine GTAW.

NRC conditions for use of Code Case N-638-1 specified in With the modifications described above, the NRC RG 1.147, Regulatory Guide 1.147 Revision 14, conditions for use of N-638-1 are not applicable and therefore will not be applied.

Page 23 of 31

Modifications t o ASME Section XI Appendix VIII, Supplement 11 (Table 4)

Appendix Vlll Supplement 11 of Section XI cannot be used without modification for nondestructive examination (NDE) qualifications of a FSWOL. Relief is requested to use the PDI program implementation of Appendix Vlll Supplement 11.

A detailed comparison of Appendix Vlll Supplement 11 and PDI requirements is summarized below in Table 4. The bases for the proposed alternatives to Supplement 11 are noted in Table 4 except as described in the following paragraph (for broader alternatives affecting several Supplement 11 paragraphs).

To avoid confusion several instances of the term "cracks" or "cracking" were changed to the term "flaws" because of the use of alternative flaw mechanisms. The PDI program revised paragraph 2.0 to allow the overlay fabrication and base metal flaw tests to be performed separately. The PDI program also allows closer spacing of flaws provided they don't interfere with detection or discrimination. The specimens used to date for qualification to the Tri-party NRC, Boiling Water Reactor Owners Group (BWROG) and Electric Power Research Institute (EPRI) agreement have a flaw population density greater than allowed by current Code requirements. These samples have been used successfully for all previous qualifications under the Tri-party agreement program. To facilitate their use and provide continuity from the Tri-party agreement program to Supplement 11, the PDI program has merged the Tri-party test specimens into their weld overlay program.

TABLE 4: MODIFICATIONS TO SECTION XI APPENDIX VIII, SUPPLEMENT 11 Current Requirements Modification and Basis 7 . 7 General. Paragraph (b): The specimen set shall consist of at 7 . 7 General. Paragraph (b): The specimen set shall consist of at least three specimens having different nominal pipe diameters least three specimens having different nominal pipe diameters and overlay thicknesses. They shall include the minimum and and overlay thicknesses. They shall include the minimum and maximum nominal pipe diameters for which the examination maximum nominal pipe diameters for which the examination procedure is applicable. Pipe diameters within a range of 0.9 to procedure is applicable. Pipe diameters within a range of 0.9 to 1.5 times a nominal diameter shall be considered equivalent. If 1.5 times a nominal diameter shall be considered equivalent. If the procedure is applicable to pipe diameters of 24 in. or larger, the procedure is applicable to pipe diameters of 24 in. or larger, the specimen set must include at least one specimen 24 in. or the specimen set must include at least one specimen 24 in. or larger but need not include the maximum diameter. The larger but need not include the maximum diameter.

specimen set must include at least one specimen with overlay thickness within -0.1 in. to +0.25 in. of the maximum nominal The specimen set shall include specimens with overlays not overlay thickness for which the procedure is applicable. thicker than 0.1 in. more than the minimum thickness, nor thinner Page 24 of 31

I TABLE 4: MODIFICATIONS TO SECTION XI APPENDIX VIII, SUPPLEMENT 11 Current Requirements Modification and Basis I

than 0.25 in. of the maximum nominal overlay thickness for which the examination procedure is applicable.

Basis: To avoid confusion, the overlay thickness tolerance contained in the last sentence was reworded.

1.I General. (d) Flaw Conditions (1): Base metal flaws. All flaws 1.I General. (d) Flaw Conditions (I): Base metal flaws. All flaws must be cracks in or near the butt weld heat-affected zone, open must be in or near the butt weld heat-affected zone, open to the to the inside surface, and extending at least 75% through the inside surface, and extending at least 75% through the base base metal wall. Flaws may extend 100% through the base metal wall. Intentional overlay fabrication flaws shall not interfere metal and into the overlay material; in this case, intentional with ultrasonic detection or characterization of the base metal overlay fabrication flaws shall not interfere with ultrasonic flaws. Specimens containing IGSCC shall be used when detection or characterization of the cracking. Specimens available. At least 70 percent of the flaws in the detection and containing IGSCC shall be used when available. sizing tests shall be cracks and the remainder shall be alternative flaws. Alternative flaw mechanisms, if used, shall provide crack-like reflective characteristics and shall be limited by the following:

Paragraph (d) ( I )(a): The use of Alternative flaws shall be limited to when the implantation of cracks produces spurious reflectors that are uncharacteristic of actual flaws.

Paragraph (d) ( I ) (b): Flaws shall be semi elliptical with a tip width of less than or equal to 0.002 inches.

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, it does not produce a useable axial flaw in austenitic materials because the sound beam, which normally passes only through base material, must now travel through weld material on at least one side, producing an unrealistic flaw response. To resolve this issue, the PDI program revised this paragraph to allow use of alternative flaw Page 25 of 31

TABLE 4: MODIFICATIONS TO SECTION XI APPENDIX VIII, SUPPLEMENT 11 Current Requirements I Modification and Basis I mechanisms under controlled conditions. For example, alternative flaws shall be limited to when implantation of cracks precludes obtaining an effective ultrasonic response, flaws shall be semi elliptical with a tip width of less than or equal to 0.002 inches, and at least 70% of the flaws in the detection and sizing test shall be cracks and the remainder shall be alternative flaws.

I . I General. (e) Detection Specimens (I): At least 20% but less I . I General. (el Detection Specimens (I): At least 20% but less than 40% of the flaws shall be oriented within 520 deg. of the than 40% of t'hh base metal flaws shall'be oriented within 520 pipe axial direction. The remainder shall be oriented deg. of the pipe axial direction. The remainder shall be oriented circumferentially. Flaws shall not be open to any surface to circumferentially. Flaws shall not be open to any surface to which the candidate has physical or visual access. The rules of which the candidate has physical or visual access.

IWA-3300 shall be used to determine whether closely spaced flaws should be treated as single or multiple flaws. Basis: The requirement for axially oriented FSWOL fabrication flaws was excluded from the PDI Program as an improbable scenario. WOLs are typically applied using automated GTAW techniques with the filler metal applied in a circumferential direction. Because resultant fabrication induced discontinuities would also be expected to have major dimensions oriented in the circumferential direction axial FSWOL fabrication flaws are unrealistic.

The requirement for using IWA-3300 for proximity flaw evaluation was excluded. Instead indications will be sized based on their individual merits.

I . 1 General. (e) Detection Specimens (2): Specimens shall be I . 1 General. (e) Detection Specimens (2): Specimens shall be divided into base and overlay grading units. Each specimen shall divided into base metal and overlay fabrication grading units.

contain one or both types or grading units. Each specimen shall contain one or both types of grading units.

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

I . I General. (e) Detection Specimens (2) (a)(l): A base grading I .1 General. (e) Detection Specimens (2) (a)(l): A base metal unit shall include at least 3 in. of the length of the overlaid weld. grading unit includes the overlay material and the outer 25% of The base grading unit includes the outer 25% of the overlaid the original overlaid weld. The base metal grading unit shall Page 26 of 31

TABLE 4: MODIFICATIONS TO SECTION XI APPENDIX VIII, SUPPLEMENT 11 Current Requirements Modification and Basis weld and base metal on both sides. The base grading unit shall extend circumferentially for at least 1 in. and shall start at the not include the inner 75% of the overlaid weld and base metal weld centerline and be wide enough in the axial direction to overlay material, or base metal-to-overlay interface. encompass one half of the original weld crown and a minimum of 0.50" of the adjacent base material.

Basis: The phrase, "and base metal on both sides," was inadvertently included in the description of a base metal grading unit. The PDI program intentionally excludes this requirement because some of the qualification samples include flaws on both sides of the weld. This paragraph was also modified to require that a base metal grading unit include at least 1 inch of the length of the overlaid weld, rather than 3 inches.

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

used as part of any overlay grading unit.

I .1 General. (e) Detection Specimens (2) (a)(3): When a base I.I General. (e) Detection Specimens (2) (a)(3): Sufficient grading unit is designed to be unflawed, at least 1 in. of unflawed unflawed overlaid weld and base metal shall exist on all sides of overlaid weld and base metal shall exist on either side of the the grading unit to preclude interfering reflections from adjacent base grading unit. The segment of weld length used in one base flaws.

grading unit shall not be used in another base grading unit. Base grading units need not be uniformly spaced around the Basis: This paragraph was also modified to require sufficient specimen. unflawed overlaid weld and base metal to exist on all sides of the grading unit to preclude interfering reflections from adjacent flaws, rather than the 1 inch requirement.

I . 1 General. (e) Detection Specimens (2) (b)(l): An overlay I . I General. (e) Detection Specimens (2) (b)(l): An overlay grading unit shall include the overlay material and the base fabrication grading unit shall include the overlay material and the metal-to-overlay interface of at least 6 sq. in. The overlay base metal-to-overlay interface for a length of at least 1 in.

grading unit shall be rectangular, with minimum dimensions of 2 in. Basis: This paragraph is also modified to define an overlay fabrication grading unit as including the FSWOL material and the Page 27 of 31

TABLE 4: MODIFICATIONS TO SECTION XI APPENDIX VIII, SUPPLEMENT 11 Current Requirements Modification and Basis base metal-to-overlay interface for a length of at least 1 inch rather than the 6 sq. in. requirement.

1.I General. (e) Detection Specimens (2) (b)(2): An overlay I .I General. (e) Detection Specimens (2) (b)(2): Overlay grading unit designed to be unflawed shall be surrounded by fabrication grading units designed to be unflawed shall be unflawed overlay material and unflawed base metal-to-overlay separated by unflawed overlay material and unflawed base interface for at least 1 in. around its entire perimeter. The metal-to-overlay interface for at least 1 in. at both ends.

specific area used in one overlay grading unit shall not be used in Sufficient unflawed overlaid weld and base metal shall exist on another overlay grading unit. Overlay grading units need not be both sides of the overlay fabrication grading unit to preclude 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: Paragraph 1.1 (e)(2)(b)(2) states that overlay fabrication grading units designed to be unflawed shall be separated by unflawed overlay material and unflawed base metal-to-overlay interface for at least 1 inch at both ends, rather than around its entire perimeter.

1.I General. (e) Detection Specimens (2) (b)(3): Detection sets I . I General. (e) Detection Specimens (2) (b)(3): Detection sets shall be selected from Table Vlll-S2-1. The minimum detection shall be selected from Table Vlll-S2-1. The minimum detection sample set is five flawed base grading units, ten unflawed base sample set is five flawed base metal grading units, ten unflawed grading units, five flawed overlay grading units, and ten unflawed base metal grading units, five flawed overlay fabrication grading overlay grading units. For each type of grading unit, the set shall units, and ten unflawed overlay fabrication grading units. For contain at least twice as many unflawed as flawed grading units. each type of grading unit, the set shall contain at least twice as 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.

I .1 General. (I7 Sizing Specimen (I): The minimum number of 1.7 General. (0 Sizing Specimen (1): The minimum number of flaws shall be ten. At least 30% of the flaws shall be overlay flaws shall be ten. At least 30% of the flaws shall be overlay fabrication flaws. At least 40% of the flaws shall be cracks open fabrication flaws. At least 40% of the flaws shall be open to the to the inside surface. inside surface. Sizing sets shall contain a distribution of flaw Page 28 of 31

TABLE 4: MODIFICATIONS TO SECTION XI APPENDIX VIII, SUPPLEMENT 11 Current Requirements Modification and Basis 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.

1.1 General. (0 Sizing Specimen (3): Base metal cracking used I.IGeneral. (0 Sizing Specimen (3): Base metal flaws used for for length sizing demonstrations shall be oriented length sizing demonstrations shall be oriented circumferentially.

circumferentially.

I.IGeneral. (0 Sizing Specimen (4): Depth sizing specimen sets I .I General. (0 Sizing Specimen (4): Depth sizing specimen sets shall include at least two distinct locations where cracking in the shall include at least two distinct locations where a base metal base metal extends into the overlay material by at least 0.1 in. in flaw extends into the overlay material by at least 0.1 in. in the the through-wall direction. through-wall direction.

2.0 CONDUCT OF PERFORMANCE DEMONSTRATION 2.0 CONDUCT OF PERFORMANCE DEMONSTRATION The specimen inside surface and identification shall be The specimen inside surface and identification shall be concealed from the candidate. All examinations shall be concealed from the candidate. All examinations shall be completed prior to grading the results and presenting the results completed prior to grading the results and presenting the results to the candidate. Divulgence of particular specimen results or to the candidate. Divulgence of particular specimen results or candidate viewing of unmasked specimens after the performance candidate viewing of unmasked specimens after the performance demonstration is prohibited. demonstration is prohibited. The overlay fabrication flaw test and the base metal flaw test may be performed separately.

2.1 Detection Test.: Flawed and unflawed grading units shall be 2.1 Detection Test.: Flawed and unflawed grading units shall be randomly mixed. Although the boundaries of specific grading randomly mixed. Although the boundaries of specific grading units shall not be revealed to the candidate, the candidate shall units shall not be revealed to the candidate, the candidate shall be made aware of the type or types of grading units (base or be made aware of the type or types of grading units (base metal overlay) that are present for each specimen. or overlay fabrication) that are present for each specimen.

2.2 Length Sizing Test (d): For flaws in base grading units, the 2.2 Length Sizing Test (d): For flaws in base metal grading candidate shall estimate the length of that part of the flaw that is units, the candidate shall estimate the length of that part of the in the outer 25% of the base wall thickness. flaw that is in the outer 25% of the base metal wall thickness.

2.3 Depth Sizing Test.: For the depth sizing test, 80% of the 2.3 Depth Sizing Test:

flaws shall be sized at a specific location on the surface of the (a) The depth sizing test may be conducted separately or in specimen identified to the candidate. For the remaining flaws, conjunction with the detection test.

the regions of each specimen containing a flaw to be sized shall Page 29 of 31

I TABLE 4: MODIFICATIONS TO SECTION XI APPENDIX VIII, SUPPLEMENT 11 Current Requirements Modification and Basis I

be identified to the candidate. The candidate shall determine the (b) When the depth sizing test is conducted in conjunction with maximum depth of the flaw in each region. the detection test and the detected flaws do not satisfy the requirements of I. I (f), additional specimens shall be provided to the candidate. The regions containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the maximum depth of the flaw in each region.

(c) For a separate depth sizing test, the regions of each specimen containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the maximum depth of the flaw in each region.

3.1 Detection Acceptance Criteria.: Examination procedures, 3.1 Detection Acce~tanceCriteria.:

equipment, and personnel are qualified for detection when the Examination procedures are qualified for detection when the results of the performance demonstration satisfy the acceptance results of the performance demonstration satisfy the following criteria of Table Vlll-S2-1 for both detection and false calls. The criteria.

criteria shall be satisfied separately by the demonstration results for base grading units and for overlay grading units. (a) All flaws within the scope of the procedure are detected and the results of the performance demonstration satisfy the acceptance criteria of Table Vlll-S2-1 for false calls.

(b) At least one successful personnel demonstration has been performed meeting the acceptance criteria defined in (c).

(c) Examination equipment and personnel are qualified for detection when the results of the performance demonstration satisfy the acceptance criteria of Table Vlll-S2-1 for both detection and false calls.

(d) The criteria in (b) and (c) shall be satisfied separately by the demonstration results for base metal grading units and for overlay fabrication grading units.

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I TABLE 4: MODIFICATIONS TO SECTION XI APPENDIX VIII, SUPPLEMENT 11 1 Current Requirements Modification and Basis Basis: The PDI program allows procedure qualification to be performed separately from personnel and equipment qualification. Historical data indicate that, if ultrasonic detection or sizing procedures are thoroughly tested, personnel and equipment using those procedures have a higher probability of successfully passing a qualification test. In an effort to increase this passing rate, PDI has elected to perform procedure qualifications separately in order to assess and modify essential variables that may affect overall system capabilities. For a procedure to be qualified, the PDI program requires three times as many flaws to be detected (or sized) as shown in Supplement 11 for the entire ultrasonic system. The personnel and equipment are still required to meet Supplement 11.

3.2 Sizing Acceptance Criteria. (a): The RMS error of the flaw 3.2 Sizing Acceptance Criteria. (a): The RMS error of the flaw length measurements, as compared to the true flaw lengths, is less than or equal to 0.75 inch. The length of base metal cracking is measured at the 75% through-base-metal position.

1 length measurements, as compared to the true flaw lengths, is less than or equal to 0.75 inch. The length of base metal flaws is measured at the 75% through-base-metal position.

3.2 Sizing Acceptance Criteria. (b): All extensions of base metal 3.2 Sizing Acceptance Criteria. (b) This requirement is omitted.

cracking into the overlay material by at least 0.1 in. are reported as being intrusions into the overlay material. Basis: The requirement for reporting all extensions of cracking into the FSWOL is omitted from the PDI Program because it is redundant to the root mean squared (RMS) calculations performed in paragraph 3.2 (c) and its presence adds confusion and ambiguity to depth sizing as required by paragraph 3.2(c).

This also makes the FSWOL program consistent with the Supplement 2 depth sizing criteria.

3.2 Sizing Acceptance Criteria. (c): The RMS error of the flaw 3.2 Sizing Acceptance Criteria. (b): The RMS error of the flaw depth measurements, as compared to the true flaw depths, is depth measurements, as compared to the true flaw depths, is less than or equal to 0.125 in. less than or equal to 0.125 in.

Basis: By omitting the Paragraph 3.2 (b) requirement, Paragraph 3.2 (c) is reformatted and becomes 3.2 (b).

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Enclosure 2 Prairie Island Nuclear Generating Plant Unit 2 10 CFR 50.55a Request No. 2-RR-4-8, Rev. 0 Barrier Layer To Prevent Hot Cracking In High Sulfur Stainless Steel

Background:

During recent dissimilar metal weld (DM) overlay activities, where use of ERNiCrFe-7A (Alloy 52M) and ERNiCrFe-7 (Alloy 52) has been used for the filler metal, flaws in the first layer have occurred in the portion of the overlay deposited on the austenitic stainless steel portions (safe ends, pipe etc.) of the assemblies in some cases.

The applicable stainless steel material at PlNGP Unit 2 for the Pressurizer Surge Nozzle where the full structural weld overlay (FSWOL) will be deposited are as follows (See Enclosure 1 Figure 1):

Pressurizer surge nozzle safe end is SA-182 F316L stainless steel.

Piping reducer is A-403 Grade WP Type 316 stainless steel.

Pressurizer surge nozzle butter weld material is 3091308L stainless steel.

Safe end to reducer weld material is 308 stainless steel.

Discussion:

The characteristics of the flaws described above are indicative of hot cracking. This phenomenon has not been observed on the ferritic steel or ENiCrFe-3 (alloy 182) DM welds.

Further studies have determined that this problem may occur when using Alloy 52M filler metal on austenitic stainless steel materials with high sulfur content.

Limited tests and evaluations recently performed by AREVA concluded that welding with Alloy 52M on stainless steel base material with 0.020 wt% sulfur results in cracking while welding on stainless steel base materials with less than 0.010 wt% have resulted in no cracking.

To reduce the susceptibility of hot cracking occurrence due to welding Alloy 52M on the stainless steel base materials with high sulfur, AREVA has used ER309L filler metal as the preferred filler metal to provide a barrier layer between the Alloy 52M and the high sulfur stainless steel base material. This filler metal is compatible with the base material and promotes primary weld metal solidification as ferrite rather than austenite. The ferrite is more accommodating of residual elements therein and in the underlying base material thereby significantly reducing the susceptibility to hot cracking. ER309L is also compatible with the Alloy 52M. However, the barrier layer will necessarily consist of ERNiCr-3 (Alloy 82) being used locally at the interface between the Alloy 182 DM weld and the Stainless Steel item. ER309L welding on Alloy 182 may result in cracking of the ER309L weld. Welding on high sulfur stainless steel with Alloy 82 has not been a concern relevant to hot cracking occurrence.

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AREVA welded a mockup to evaluate the interactive effects, such as hot cracking and lack of fusion, between the alloy 182 DM weld, the stainless steel base material, the ER309L and Alloy 82 barrier layer, and the subsequent Alloy 52M weld overlay. The mockup assembly consisted of a stainless steel pipe (0.020 wt% sulfur) with an Alloy 182 groove weld. The barrier layer and overlay were welding in the same sequence as performed in the field (barrier layer ER309L and Alloy 82 and then two layers of Alloy 52M overlay). The barrier layer and overlay welding parameters used in the mockup were similar to those used in the field however slightly reduced wire feed rates were used for conservatism.

The following examinations were performed on the final mockup and no recordable indications were detected:

PT examination was performed on the:

High sulfur stainless steel base material Alloy 182 Groove Weld ER309L Barrier Layer Alloy 82 Barrier Layer Alloy 52M Overlay Limited PDI UT examination 0" Transducer with full coverage 45" Transducer with Full coverage OD Creeper Transducer with Full coverage 60" Transducer with limited coverage (Focal depth exceeded UT procedure allowable in places due to overlay being of insufficient thickness. Only two layers of Alloy 52M were deposited.)

Eight (8) specimens were removed from around the overlay circumference at approximately 45 degree intervals. Metallographic examination searching for any type of discontinuity, flaw or other anomaly has been performed. No anomalies were observed.

The barrier layer was been successfully implemented on various nozzle SWOLs at North Anna 2 earlier this year.

Conclusion More tests and evaluations would be necessary to accurately determine the threshold where the base metal sulfur content would require barrier layer welding.

Based on the information herein PlNGP Unit 2 Pressurizer Surge nozzle FSWOL will use a barrier layer prior to overlay on all stainless steel components with sulfur content greater than 0.010 wt% and may opt to use a barrier layer on all stainless steel components. The barrier layer will use ER309L on the stainless steel and Alloy 82 on the stainless steel near the DM weld to stainless steel fusion zone only.

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Structural credit will not be assumed for the barrier layer in determining the required minimum overlay thickness.

The barrier layer welding will be performed in accordance with ASME code Section IX qualified welding procedure specification(s). PT examination will be performed on the barrier layer surface and its volume will be included in the final UT of the overlay.

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Enclosure 3 Prairie Island Nuclear Generating Plant Unit 2 10 CFR 50.55a Request No. 2-RR-4-8, Rev. 0 Summary of Commitments Committed Commitment Commitment Date Type

1. NMC commits to providing the following Within 14 days One time action.

information within fourteen days of after the completion of the final PlNGP Unit 2 completion of the Pressurizer Surge Nozzle full structural weld last ultrasonic overlay ultrasonic examination: examination of the weld overlay.

Weld overlay examination results including a list of indications detected.

Disposition of the indications using the standards of ASME Section XI, Nonmandatory Appendix Q.

The type and, if possible, nature of the indications.

A discussion of any repairs to the weld overlay material and/or base metal and the reason for repairs.

2. NMC will submit to the NRC a stress Prior to entry into One time action.

analysis summary demonstrating that the Mode 4 start-up pressurizer nozzle will perform its intended from outage.

design functions after the full structural weld overlay installation. The stress analysis report will include results showing that the requirements of NB-3200 and NB-3600 of the ASME code, Section Ill are satisfied. The results will show that the postulated crack including its growth in the nozzle will not adversely affect the integrity of the overlaid welds. This information will be submitted prior to Mode 4 start-up.

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