SBK-L-07120, Request for Use of Structural Weld Overlays as an Alternative Repair Technique

Request for Use of Structural Weld Overlays as an Alternative Repair Technique

ML071990104
Person / Time
Site:	Seabrook
Issue date:	07/03/2007
From:	St.Pierre G Florida Power & Light Energy Seabrook
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
SBK-L-07120
Download: ML071990104 (22)

Text

FPL Energy Seabrook Station FPL Energy P.O. Box 300 Seabrook, NH 03874 Seabrook Station (603) 773-7000 JUL 3 2007

,..Docket No. 50-443 SBK-L-07120 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Seabrook Station Request for Use of Structural Weld Overlays as an Alternative Repair Technique Pursuant to 10 CFR 50.55a(a)(3)(i), FPL Energy Seabrook, LLC (FPL Energy Seabrook) requests approval to use the American Society of Mechanical Engineers (ASME) Code Case N-740-1, "Dissimilar Metal Weld Overlay for Repair of Class 1, 2, and 3 ItemsSection XI, Division 1," draft May 2007, to apply dissimilar metal weld overlays for repair/replacement activities. This request contains alternative requirements for the inservice inspection (ISI) program for structural weld overlays (SWOLs) that are planned to mitigate the potential for primary water stress corrosion cracking (PWSCC) susceptibility at Seabrook Station Unit 1. Attachment 1 contains FPL Energy Seabrook's Alternative Request and Enclosure 1 to Attachment 1 contains the PDI Program Modifications to American Society of Mechanical Engineers (ASME) Code, Appendix VIII, Supplement 11. Enclosure 2 provides details on the use of a barrier layer.

This is the initial phase of the control and remediation plan for Alloy 600/82/182 dissimilar metal piping butt welds susceptible to potential PWSCC at Seabrook Unit 1, and SWOLs for mitigation of potential PWSCC susceptible areas are scheduled for the cycle 12 refueling outage and no pre-weld overlay UT examinations are planned. FPL Energy Seabrook will use the alternatives in this request to implement the Electric Power Research Institute's Materials Reliability Program (EPRI/MRP) and the Primary System Piping Butt Weld Inspection and Evaluation Guideline (MRP-139) under the ISI program and the risk-informed ISI (RI-ISI) program.

FPL Energy Seabrook requests review and approval of this proposal be expedited to support the Seabrook Unit 1 refueling outage in the spring of 2008. Similar alternatives have been submitted for NRC review and approval and are referenced in the attached request. FPL Energy Seabrook is submitting this request based on the recent ASME Subcommittee XI approval of Code Case N-740-1. Details of the design analysis for the planned weld overlays are being developed to support the Seabrook Unit 1 spring 2008 an FPL Group company

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 2 refueling outage. The analysis will be available at Seabrook Station for NRC review at the beginning of OR12.

If you have any questions regarding this submittal, please contact Mr. James M. Peschel, Regulatory Programs Manager, at (603) 773-7194.

Very truly yours, FPL Energy Seabrook, LLC Gene St. Pierre Site Vice President cc: S. J. Collins, NRC Region I Administrator G. E. Miller, NRC Project Manager W. J. Raymond, NRC Resident Inspector to SBK-L-07120 U. S. Nuclear Regulatory Commission SBK-L-07120I Page 1 ATTACHMENT 1 10 CFR 50.55a REQUEST Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE

1.0 ASME Code Components Affected

Code components associated with this request are high safety significant (HSS) Class 1 dissimilar metal welds (DMWs) with Alloy 82/182 weld metal in the pressurizer that are believed to be susceptible to Primary Water Stress Corrosion Cracking (PWSCC). There are six (6) welds that are scheduled to have preemptive full structural weld overlays (SWOLs) applied. In addition, the SWOLs will extend across the six (6) adjacent stainless steel pipe-to-safe end similar metal welds. These welds are scheduled to have SWOLs applied during refueling outage 12 (OR12) that is currently scheduled to commence in April 2008.

1.1 Category and System Details:

Code Class: Class 1 System Welds: Reactor Coolant System Examination Categories: R-A*

• Welds are included in the Risk Informed Inservice Inspection Program 1.2 Component Descriptions:

The application of this alternative to apply SWOLs on one (1) potentially PWSCC susceptible safe end-to-pressurizer surge nozzle DMW, three (3) safe end-to safety nozzle DMWs, one (1) safe end-to-relief nozzle DMW and one (1) safe end-to-spray nozzle DMW. The SWOLs will extend outward across the adjacent stainless steel pipe-to-safe end welds. The applicable weld identifications are shown in Table 1. The general configuration for the different nozzle locations is shown in Figure 1.

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 2 TABLE 1 WELD NUMBERS BY ISI DESIGNATION Weld Number by ISI Desianatio Item Location Safe End to Nozzle Pipe to Safe End Weld Weld 1 Pressurizer Spray Nozzle RC E-10 SP-SE RC 0048-03 06 2 Pressurizer Relief Nozzle B RC E-10 B-SE RC 0080-0101 3 Pressurizer Safety Nozzle A RC E-10 A-SE RC 0074-0101 4 Pressurizer Safety Nozzle C RC E-10 C-SE RC 0075-0101 5 Pressurizer Safety Nozzle D RC E-10 D-SE RC 0076-0101 6 Pressurizer Surge Nozzle RC E-10 S-SE RC 0049-0105 1.3 Component Materials:

The applicable materials are depicted in Table 2.

TABLE 2 MATERIALS Nozzle (Noz Nozzle 3Safe End to Safe End (P-No. 8 Pipe to Safe Pipe Location (P-No. 3 Group Buttering (F-No. 43) Buttering Weld Group 1) End Weld

(-o ) (P-No. 8 Gop1

3) Wed(A-No. 8) Group 1)

Spray cSA-508 Alloy 182 Alloy SA-182 ER308/E308 SA-376 Spay Cl 2a 82/1 82 GR F316L ER0/38TP316 Safety& SA-508 Alloy 182 Alloy SA-182 ER308/E308 SA-376 Cl 2a 82/182 GR F316L with ER308L TP316 Root Insert SA-508 Alloy 182 Alloy SA-182 SA-376 Surge Cl 2a 82/182 GR F316L ER308/E308 TP304

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 3 2.0 Applicable Code Edition and Addenda Seabrook Station is currently in the 2 nd 10-year Inservice Inspection (ISI) interval. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) of record for the current 10-year ISI interval isSection XI, 1995 Edition, including Addenda through 1996 (Reference 1) for the Repair/Replacement Program.

3.0 Applicable Code Requirement The applicable Code requirement for which the relief is requested is ASME Code Section XI, 1995 Edition including Addenda through 1996 (Reference 1), IWA-4410, IWA-4611 and Appendix VIII, Supplement 11.

IWA-4410(a) states:

"Repair/replacement activities shall be performed in accordance with the Owner's Requirements and the original Construction Code of the component or system, except as provided in IWA-4410(b), (c), and (d)."

IWA-4410(c) states in part the following:

"Alternatively, the applicable requirements of IWA-4600 may be used for welding....."

IWA-46 11.1 (a) states in part the following:

"Defects shall be removed or reduced in size in accordance with this Paragraph."

IWA-4611. 1(b) states:

The original defect shall be removed:

IWA-461 1.1 (b)(2) states:

"when welding is required in accordance with IWA-4630 or IWA-4640 and the defect penetrates the base material."

IWA-4611.4(a) states in part the following:

"After final grinding, the affected surfaces, including surfaces of cavities prepared for welding, shall be examined by the magnetic particle or liquid penetrant method to ensure that the indication has been reduced to an acceptable size in accordance with IWA-3000...."

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 4 Appendix VIII provides requirements for performance demonstration for ultrasonic examination systems. Supplement 11 provides qualification requirements for full structural overlaid wrought austenitic piping welds.

4.0 Reason for Request DMWs, primarily consisting of Alloy 82/182 weld metal are frequently used in pressurized water reactor (PWR) construction to connect stainless steel pipe and safe ends to vessel and pipe nozzles that are typically constructed of carbon or low alloy ferritic steel. These welds have shown a tendency for PWSCC degradation, especially in components subjected to higher operating temperatures, such as the pressurizer. See EPRI MRP-169 "Technical basis for Preemptive Weld Overlays for Alloy 82/182 Butt Welds in PWRs", October 2005 (Reference 2).

During OR12, six (6) DMWs located on the pressurizer are scheduled to have SWOLs applied. ASME Code Section XI, 1995 Edition, including Addenda through 1996 (Reference 1), IWA-4410 and IWA-46 11, does not provide all the needed requirements for this type of repair since potential existing defects will not be removed or reduced in size and weld overlay of potential existing flaws in DMWs will be performed. In addition, ASME Code Section XI, 1995 Edition, including Addenda through 1996 (Reference 1), Appendix VIII, Supplement 11 cannot be implemented as written for ultrasonic examination of a structural weld overlay repair. Enclosure 1 includes a discussion of the Performance Demonstration Initiative (PDI) Program alternatives and their bases with respect to Appendix VIII, Supplement 11 requirements. Comprehensive and generic NRC approved criteria are not currently available for application of SWOL repairs to DMWs constructed of Alloy 82/182 weld material for mitigation of potential PWSCC.

The alternative described in Section 5.0 is proposed to permit the implementation of SWOLs at Seabrook Station, as an alternative for the repair and replacement requirements of the ASME Code Section XI, 1995 Edition including Addenda through 1996 (Reference 1), IWA-4410, IWA-46 11 and Appendix VIII, Supplement 11.

5.0 Proposed Alternative And Basis for Use The ASME Subcommittee XI has recently approved Section XI Code Case N-740-1, "Dissimilar Metal Weld Overlay for Repair of Class 1, 2, and 3 Items" Draft May 2007 (Reference 3). This Draft Code Case is the result of the industry's experience with weld overlay repairs for flaws suspected or confirmed to be from PWSCC and for the first time directly applies to the Alloy 52M weld material that is primarily being used for these overlay repairs.

This application requests the approval to use Code Case N-740-1, Draft May 2007 (Reference 3) for implementing the six (6) scheduled SWOLs for potentially PWSCC susceptible safe end-to-nozzle welds of the pressurizer. These SWOLs will include the

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 5 six (6) adjacent stainless steel pipe-to-safe end welds. This request applies to each of the welds listed in Section 1.2, which are generically depicted in Figure 1. The proposed alternative is scheduled to be performed during the OR12 in April 2008.

The ultrasonic examination of the completed SWOLs will be accomplished in accordance personnel and procedures qualified in accordance with ASME Code Section XI, 1995 Edition, including Addenda through 1996 (Reference 1), Appendix VIII, Supplement 11 as specified in Code Case N-740-1 Draft May 2007 (Reference 3) Section 3 therein with the alternatives used for complying with the PDI Program. See Enclosure 1 for the PDI Program changes to Appendix VIII, Supplement 11.

5.1 SWOL Design The SWOLs will be designed in accordance with ASME Section XI Code Case N-740-1 Draft May 2007 (Reference 3). The detailed design analysis for the SWOLs is being developed to support OR12 in April 2008 outage by AREVA, the design and welding contractor. The analysis will be available at Seabrook Station for NRC review at the beginning of OR12.

The SWOLs will satisfy all the structural design requirements of the pipe with the assumption that no strength is contributed by the original safe end-to-nozzle welds or the pipe-to-safe end welds, as if the welds were removed. As depicted in Figure 1, the SWOLs will completely cover the existing Alloy 82/182 weld and will extend onto the ferritic nozzle and austenitic stainless steel material on each end of the weld, including the adjacent pipe-to-safe end weld. The SWOLs will extend around the entire circumference of the nozzle. Alloy 52M and Alloy 52 filler metals are compatible with all the wrought base materials and the DMWs and similar metal welds that will be covered by the SWOL.

5.2 Welding The welding will be performed in accordance with Code Case N-740-1, Draft May 2007 (Reference 3) using a remote machine gas tungsten-arc welding (GTAW) process and using the ambient temperature temper bead method with ERNiCrFe-7A (Alloy 52M) weld metal. Manual GTAW, using ERNiCrFe-7 (Alloy 52) or Alloy 52M will be used if local repairs of weld defects are necessary or additional weld metal is required locally to form the final SWOL contour in locations at least 3/16 in. away from the low alloy steel nozzles.

Based on the qualification work performed on representative mockups, the Chromium content of the initial Alloy 52M layer will be > 24%, therefore an initial Alloy 52M sacrificial layer will not be required.

In the event that a flaw(s), having major dimension exceeding 1/16 in., is/(are) observed on the surfaces to be welded and flaw size reduction to an acceptable size is impractical,

.I -

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 6 a seal weld layer will be applied over these flaw(s) and will not be credited for the required SWOL thickness.

5.3 Barrier Layer to Prevent Hot Cracking in High Sulfur Stainless Steel During recent dissimilar metal weld (DMW) 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. FPL Energy Seabrook will utilize a barrier layer as a precaution to prevent hot cracking in the first layer of Alloy 52 filler metal. Enclosure 2 provides details on the use of a barrier layer.

5.4 Examination Examinations will meet the requirements of the Code Case N-740-1, Draft May 2007 (Reference 3), excluding qualification of the ultrasonic examination for the completed SWOLs. The ultrasonic examination qualification will be in accordance with ASME Code Section XI, 1995 Edition, including Addenda through 1996 (Reference 1),

Appendix VIII, Supplement 11 with the alternatives that are used to comply with the PDI Program. See Enclosure 1 for the PDI Program changes to Appendix VIII, Supplement 11.

The PDI Program 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/BWROG/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 structural weld overlay program.

The current configuration of these DMWs does not permit an ASME Code Section XI, Appendix VIII, Supplement 10 ultrasonic examination to obtain greater than 90%

coverage of the required examination volume without extensive machining. Therefore, none of these welds will receive a pre-weld overlay ultrasonic examination The ultrasonic and surface examinations will be performed on the temper bead portion of the SWOLs 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 temper bead layer as specified in Code Case N-740-1 Draft May 2007 (Reference 3), Paragraphs 3(a)(2). The 48-hour delay provides time for delayed hydrogen cracking to occurr.

Code Case N-740-1 Draft May 2007 requires the machine or automatic GTAW process to be used for temper bead welding thereby eliminating the use of welding processes requiring flux for arc shielding.

The machine GTAW temper bead process uses a welding process that is inherently free of hydrogen. The GTAW process relies on bare wire filler metal with no flux to absorb

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 7 moisture. An inert gas blanket provides shielding for the weld and surrounding metal, which protects the region during welding from the atmosphere and the moisture it, may contain and typically produces porosity free welds. In accordance with the weld procedure qualification, welding grade argon in accordance with SFA-5.32, SG-A is used for the inert gas blanket. To further reduce the likelihood of any hydrogen effects, specific controls will be used to ensure the welding electrodes, filler metal and weld region are free of all sources of hydrogen.

In addition, the use of the machine GTAW temper bead 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 heat affected zone (HAZ) resulting in achievement of lower hardness and tempered martensite. This further reduces susceptibility to hydrogen induced cracking. Furthermore, past industry experience with the use of the machine or automatic GTAW process has resulted in no detection of hydrogen induced cracking after the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold NDE or subsequent in-service inspections.

EPRI Report 1013558, Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding, Technical Update, December 2006 (Reference 4) provides justification for the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold time on P-No. 3 Group No. 3 ferritic steel base material to start after completion of the third temper bead layer as currently specified in Code Case N-740-1 Draft May 2007 (Reference 3). Report 1013558 addresses microstructure issues, hydrogen sources, tensile stress and temperature, and diffusivity and solubility of hydrogen in steels.

In addition, the NRC has approved starting the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold time after the third structural layer has been completed for Arkansas Nuclear One (ANO).

Code Case N-638-4 "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique Section XI, Division 1" (Reference 5) published in Nuclear Code Cases Supplement 11 specifies NDE 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 temper bead layer.

The SWOL ultrasonic examination results will be provided to the NRC within fourteen (14) days after completion of the ultrasonic examinations.

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 8 5.5 Conclusion Similar NRC-approved requests have been used to produce acceptable weld overlays when applied to dissimilar metal welds with Alloy 82/182 weld material. The proposed alternative uses ASME Section XI Code Case N-740-1, Draft May 2007 (Reference 3) that has been developed to cover the most recent operating experience and NRC-approved criteria that are associated with similar SWOL applications. Therefore FPL Energy Seabrook considers that this Case and the PDI Program provides an acceptable level of quality and safety, consistent with provisions of 10 CFR 50.55a(a)(3)(i).

6.0 Duration of Proposed Alternative The alternative requirements of this request will be applied for the duration of up to and including the last outage of the current 2"d 10-year ISI interval which includes inservice examination requirements of Code Case N-740-1, Draft May 2007 Draft (Reference 3) for any applied weld overlays. The use of Code Case N-740-1, Draft May 2007 is requested until the NRC publishes the Code Case as a future revision of Regulatory Guide 1.147. Future inservice examinations of weld overlays at Seabrook beyond this inspection interval will be as required by the NRC in the regulations 7.0 Precedents Similar requests have been submitted to address the issues that are contained in this request. These include requests from the Indiana Michigan Power Company's, D. C. Cook Unit 2. NRC verbal approval was received on March 23, 2006, for their request, which included the application of full structural weld overlays applied to their pressurizer nozzle DMWs.

In a letter dated, March 13, 2007, a similar request was submitted for North Anna Units 1 and 2 by Virginia Electric and Power Company (Dominion). NRC verbal approval was received March 29, 2007.

Additionally, the following requests associated with weld overlay repairs have been approved by the NRC: AmerGen Energy Company, Three Mile Island Nuclear Station, Unit 1, on July 21, 2004;(1) Constellation Energy's Calvert Cliffs Nuclear Power Plant, (1) NRC letter, Safety Evaluation of Request for Relief from Flaw Removal, Heat Treatment and Nondestructive Examination (NDE) Requirements for the Third 10-Year Inservice Inspection Interval, Three Mile Island Nuclear Station, Unit 1 (TMI-1), Docket No. 50-289, (TAC No. MC1201), dated: July 21, 2004, (ADAMS Accession No. ML041670510).

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 9 Unit 2, on July 20, 2005;(2) Millstone Unit 3, on January 20, 2006;(3) and Indiana Michigan Power Company, Donald C. Cook Unit 1, on February 10, 2006.(4) 8.0 References

1. ASME Code,Section XI, 1995 Edition, including Addenda through 1996.

2. EPRI MRP-169 "Technical Basis for Preemptive Weld Overlays for Alloy 82/182 Butt Welds in PWRs", October 2005.

3. ASME Code Case N-740-1 Tracking No. BC06-1651, Changes from N-740, SWGER Edits 05-17-2007, "Dissimilar Metal Weld Overlay for Repair of Class 1, 2, and 3 ItemsSection XI, Division 1"

4. EPRI Report 1013558, Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding, Technical Update, December 2006.

5. Code Case N-638-4 "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temperature Bead Technique Section XI, Division 1" (2) NRC letter, Safety Evaluation for Calvert Cliffs Nuclear Power Plant, Unit No. 2, Docket No. 550-318, Relief Request for Use Weld Overlay and Associated Alternative Inspection Techniques (TAC Nos. MC6219 and MC6220), dated July 20, 2005, (ADAMS Accession No. ML051930316).

(3) NRC letter, Safety Evaluation of Relief Request IR-2-39 Pertaining to the Repair and Inspection of Nozzle to Safe End Weld, Weld No. 03-X-5641-E-T at Millstone Power Station Unit No. 3 (MPS3) Docket No. 50-423, (TAC No.

MC8609), dated January 20, 2006, (ADAMS Accession No. ML053260012).

(4) NRC letter, Safety Evaluation of Alternative Regarding Repair of Safe-End-To-Elbow Weld 1-RC-9-01 F at the Donald C. Cook Nuclear Plant Unit 1, Docket No. 50-315, (TAC No. MC8807), dated February 10, 2006, (ADAMS Accession No. ML060240355).

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 10

- Pipe/SE Weld (SS)

-SS Safe End (SA-182 F316L)

SE/Nozzle Weld A82 Root/A182 Balance Weld Butfering (A182)

Low Alloy Steel

/ Nozzle (SA-508 Class 2a)

Figure 1 - Typical SWOL Configuration

U. S. Nuclear Regulatory Commission SBK-L-07120 Attachment 1 Page 11 Enclosure 1 PDI Program Modifications to Appendix VIII, Supplement 11 Appendix VIII, Supplement 11 PDI Modification 1.0 SPECIMEN REQUIREMENTS 1.1 General (b) The specimen set shall consist of at least Modification: (b) The specimen set shall consist of at three specimens having different nominal pipe least 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 pipe diameters for which the examination diameters for which the examination procedure is procedure is applicable. Pipe diameters within a applicable. Pipe diameters within a range of 0.9 to range of 0.9 to 1.5 times a nominal diameter 1.5 times a nominal diameter shall be considered shall be considered equivalent. If the procedure equivalent. If the procedure is applicable to pipe is applicable to pipe diameters of 24 inches or diameters of 24 inches or larger, the specimen set larger, the specimen set must include at least must include at least one specimen 24 inches or larger one specimen 24 inches or larger but need not but need not include the maximum diameter.

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

Basis: To avoid confusion, the overlay thickness tolerance contained in the last sentence was reworded and the phrase "and the remaindershall be alternative flaws" was added to the next to last sentence in paragraph1.1 (d) (1).

(d) Flaw Conditions (1) Base metal flaws.

All flaws must be cracks in or near the butt weld Modification: All flaws must be in or near the butt weld heat-affected zone, open to the inside surface, heat-affected zone, open to the inside surface, and and extending at least 75% through the base extending at least 75% through the base metal wall.

metal wall. Flaws may extend 100% through Intentional overlay fabrication flaws shall not interfere the base metal and into the overlay material; in with ultrasonic detection or characterization of the base this case, intentional overlay fabrication flaws metal flaws. Specimens containing IGSCC shall be used shall not interfere with ultrasonic detection or when available. At least 70% of the flaws in the characterization of the cracking. Specimens detection and sizing tests shall be cracks and the containing IGSCC shall be used when available, remainder shall be alternative flaws. 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 of less than or equal to 0.002 inches.

U. S. Nuclear Regulatory Commission SBK-L-07120 Attachment 1 Page 12 Appendix VIII, Supplement 11 PDI Modification Basis: This paragraphrequires that all base metalflaws be cracks. Implanting a crack requires excavation of the base materialon at least one side of theflaw. While this may be satisfactoryforferriticmaterials, it does not produce a useable axialflaw in austenitic materials because the sound beam, which normallypasses only through base material,must now travel through weld materialon at least one side, producingan unrealistic flaw response. To resolve this issue, the PDIProgram revised this paragraphto allow use of alternativeflaw mechanisms under controlledconditions. Forexample, alternativeflaws shall be limited to when implantationof cracks precludes obtainingan effective ultrasonic response,flaws shall be semi ellipticalwith 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 remaindershall be alternativeflaws. To avoid confusion, the overlay thickness tolerance containedin paragraph1.1(b) last sentence, was reworded and the phrase "and the remaindershall be alternativeflaws" was added to the next to last sentence. Paragraph 1.1 (d)(1) includes the statement that intentionaloverlay fabricationflaws shall not interfere with ultrasonic detection or characterizationof the base metal flaws.

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

be used to determine whether closely spaced Basis: The requirementfor axially oriented overlay flaws should be treated as single or multiple fabricationflaws was excludedfrom the PDIProgram as flaws. an improbable scenario. Weld overlays are typically appliedusing automated GTA W techniques with the filler metal appliedin a circumferentialdirection.

Because resultantfabricationinduced discontinuities would also be expected to have major dimensions oriented in the circumferentialdirection axial overlay fabricationflaws are unrealistic. The requirementfor using IWA-3300forproximityflaw evaluation was excluded, instead indicationswill be sized based on their individual merits.

(2) Specimens shall be divided into base and Modification: (2) Specimens shall (2 Specmn hl be divided into ediie nobs base (2 Spcmn hl edvddinobs n oiiain

U. S. Nuclear Regulatory Commission SBK-L-07120 Attachment 1 Page 13 Appendix VIII, Supplement 11 PDI Modification overlay grading units. Each specimen shall metal and overlay fabrication grading units. Each contain one or both types of grading units. specimen shall contain one or both types of grading units. Flaws shall not interfere with ultrasonic detection or characterization of other flaws.

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

interface. Basis: The phrase "and base metal on both sides, " was inadvertently included in the descriptionof a base metal grading unit, The PDIProgram intentionallyexcludes this requirementbecause some of the qualification samples includeflaws on both sides of the weld. To avoid confusion several instances of the term "cracks" or "cracking" were changed to the term "flaws" because of the use of alternativeflaw mechanisms. Modified to require that a base metal grading unit include at least 1 inch of the length of the overlaid weld, ratherthan 3 inches.

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

material shall not be used as part of any overlay grading unit.

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

either side of the base grading unit. The Basis: Modified to requiresufficient unflawed overlaid segment of weld length used in one base weld and base metal to exist on all sides of the grading grading unit shall not be used in another base unit to preclude interfering reflectionsfrom adjacent grading unit. Base grading units need not be flaws, ratherthan the I inch requirement.

uniformly spaced around the specimen.

(b)(1) An overlay grading unit shall include the Modification: (b)(1) An overlay fabrication grading unit overlay material and the base metal-to-overlay shall include the overlay material and the base metal-to-interface of at least 6 square inches. The overlay interface for a length of at least 1 inch.

overlay grading unit shall be rectangular, with Basis: Modified to requiresufficient unflawed overlaid minimum dimensions of 2 inches. weld and base metal to exist on all sides of the grading unit to preclude interfering reflectionsfrom adjacent flaws, ratherthan the 2 inch requirement.

U. S. Nuclear Regulatory Commission SBK-L-07120 Attachment 1 Page 14 Appendix VIII, Supplement 11 PDI Modification (b)(2) An overlay grading unit designed to be Modification: (b)(2) Overlay fabrication grading units unflawed shall be surrounded by unflawed designed to be unflawed shall be separated by unflawed overlay material and unflawed base metal-to- overlay material and unflawed base metal-to-overlay overlay interface for at least 1 inch around its interface for at least 1 inch at both ends. Sufficient entire perimeter. The specific area used in one unflawed overlaid weld and base metal shall exist on overlay grading unit shall not be used in another both sides of the overlay fabrication grading unit to overlay grading unit. Overlay grading units preclude interfering reflections from adjacent flaws. The need not be spaced uniformly about the specific area used in one overlay fabrication grading unit specimen. shall not be used in another overlay fabrication grading unit. Overlay fabrication grading units need not be spaced uniformly about the specimen.

Basis: Paragraph1.1 (e)(2)(b) (2) states that overlay fabricationgradingunits designed to be unflawed shall be separatedby unflawed overlay materialand unflawed base metal-to-overlay interfacefor at least 1 in. at both ends, ratherthan around its entire perimeter.

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

(f) Sizing Specimen (1) The minimum number of flaws shall be ten. Modification: (1) The minimum number of flaws shall At least 30% of the flaws shall be overlay be ten. At least 30% of the flaws shall be overlay fabrication flaws. At least 40% of the flaws fabrication flaws. At least 40% of the flaws shall be shall be cracks open to the inside surface. 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.

(3) Base metal cracking used for length sizing Modification: (3) Base metal flaws used for length demonstrations shall be oriented sizing demonstrations shall be oriented circumferentially. circumferentially.

(4) Depth sizing specimen sets shall include at Modification: (4) Depth sizing specimen sets shall least two distinct locations where cracking in include at least two distinct locations where a base

U. S. Nuclear Regulatory Commission SBK-L-07120 Attachment 1 Page 15 Appendix VIII, Supplement 11 PDI Modification the base metal extends into the overlay material metal flaw extends into the overlay material by at by at least 0. 1 inch in the through-wall least 0.1 inch in the through-wall direction.

direction.

2.0 CONDUCT OF PERFORMANCE DEMONSTRATIONS The specimen inside surface and identification Modification: The specimen inside surface and shall be concealed from the candidate. All identification shall be concealed from the candidate.

examinations shall be completed prior to All examinations shall be completed prior to grading grading the results and presenting the results to the results and presenting the results to the the candidate. Divulgence of particular candidate. Divulgence of particular specimen results specimen results or candidate viewing of or candidate viewing of unmasked specimens after unmasked specimens after the performance the performance demonstration is prohibited. The demonstration is prohibited. 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 Modification: Flawed and unflawed grading units shall randomly mixed. Although the boundaries of be randomly mixed. Although the boundaries of specific specific grading units shall not be revealed to grading units shall not be revealed to the candidate, the the candidate, the candidate shall be made candidate shall be made aware of the type or types of aware of the type or types of grading units (base grading units (base metal or overlay fabrication), that are or overlay) that are present for each specimen. present for each specimen.

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

2.3 Depth Sizing Test.

For the depth sizing test, 80% of the flaws shall Modification:

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

the remaining flaws, the regions of each (b) When the depth sizing test is conducted in specimen containing a flaw to be sized shall be conjunction with the detection test and the detected flaws identified to the candidate. The candidate shall do not satisfy the requirements of 1.1 (f), additional determine the maximum depth of the flaw in specimens shall be provided to the candidate. The each region. 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.

U. S. Nuclear Regulatory Commission SBK-L-07120 Attachment 1 Page 16 Appendix VIII, Supplement 11 PDI Modification 3.0 ACCEPTANCE CRITERIA 3.1 Detection Acceptance Criteria.

Examination procedures, equipment, and Modification: Examination procedures are qualified for personnel are qualified for detection when the detection when:

results of the performance demonstration satisfy (a) All flaws within the scope of the procedure are the acceptance criteria of Table VIII-S2-1 for detected and the results of the performance both detection and false calls. The criteria shall demonstration satisfy the acceptance criteria of Table be satisfied separately by the demonstration VIII-S2-1 for false calls.

results for base grading units and for overlay (b) At least one successful personnel demonstration has grading units. 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 VIII-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.

3.2 Sizing Acceptance Criteria.

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

(b) All extensions of base metal cracking into Modification: This requirement is omitted.

the overlay material by at least 0.1 inch are Basis: The requirementfor reportingall extensions of reported as being intrusions into the overlay cracking into the overlay is omittedfrom the PDI material. Program because it is redundant to the RMS calculations performed in paragraph3.2(c) and its presence adds confusion and ambiguity to depth sizing as requiredby paragraph3.2(c). This also makes the weld overlay program consistent with the Supplement 2 depth sizing criteria.

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 17 ENCLOSURE 2 Barrier Layer to Prevent Hot Cracking in High Sulfur Stainless Steel Back2round During recent dissimilar metal weld (DMW) 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' materials at Seabrook Station (SS) where the full structural weld overlay (SWOL) will be deposited are as follows:

• Pressurizer nozzle safe ends are SA-182 Grade F316L.

" Pressurizer safety, relief and spray piping attached to the corresponding nozzle safe ends are SA-376 TP316.

• Pressurizer surge piping attached to the surge nozzle safe end is SA-376 TP304.

• Pipe to nozzle safe end welds are ER308/E308.

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)

DMWs.

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 have resulted in the conclusion 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 selected 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 DMW and the stainless steel item. ER309L welding on Alloy 182 may result in cracking of the

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 18 ER309L weld. Welding on high sulfur stainless steel with Alloy 82 has not been a concern relevant to hot cracking occurrence.

AREVA welded a mockup to evaluate the interactive effects, such as hot cracking and lack of fusion, between the Alloy 182 DMW, 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 welded 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 00 Transducer with Full Coverage

• 450 Transducer with Full Coverage 0 OD Creeper Transducer with Full Coverage 0 600 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 the 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 The barrier layer would use ER309L on the stainless steel and Alloy 82 on the stainless steel near the DMW to stainless steel fusion zone only.

U. S. Nuclear Regulatory Commission SBK-L-07120 Page 19 Structural credit would not be assumed for the barrier layer in determining the required minimum overlay thickness.

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