L-2012-307, Approval Request for Use of Heat of Wire with Chromium Content Different than That Approved in Revision 1 of RR-2, Fourth Ten-Year Interval Revision 2 of Relief Request 2: Difference between revisions

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#REDIRECT [[L-2012-307, St. Lucie Plant, Unit 1, Approval Request for Use of Heat of Wire with Chromium Content Different than That Approved in Revision 1 of RR-2, Fourth Ten-Year Interval Revision 2 of Relief Request 2]]
| number = ML12229A049
| issue date = 08/08/2012
| title = Approval Request for Use of Heat of Wire with Chromium Content Different than That Approved in Revision 1 of RR-2, Fourth Ten-Year Interval Revision 2 of Relief Request 2
| author name = Jensen J
| author affiliation = Florida Power & Light Co
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000335
| license number = DPR-067
| contact person =
| case reference number = L-2012-307
| document type = Letter type:L
| page count = 43
| project =
| stage = Request
}}
 
=Text=
{{#Wiki_filter:0 FPL.August 8, 2012 L-2012-307 10 CFR 50.4 10 CFR 50.55a U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Re: St. Lucie Plant Unit 1 Docket No. 50-335 Renewed License No. DPR-67 In-Service Inspection Plans Submittal for Use of Heat of Wire with Chromium Content Different Than That Approved in Revision I of RR-2 Fourth Ten-Year Interval Unit 1 Revision 2 of Relief Request 2
 
==Reference:==
 
(1) G.L. Johnston (FPL) to U.S. Nuclear Regulatory Commission (L-2008-098), "In-Service Inspection Plans; Submittal for the Use of Structural Weld Overlays as an Alternative Repair Technique; Fourth Ten-Year Interval Unit I Relief Request 2", April 29, 2008, Accession Number ML081230619 (2) B.L. Mozafari (NRC) to J.A. Stall (FPL), "Request for Additional Information
-St. Lucie Plant, Unit 1 -Relief Request for Structural Weld Overlays (TAC No.MD9256)", September 18, 2008, Accession Number ML082610507 (3) E.S. Katzman (FPL) to U.S. Nuclear Regulatory Commission (L-2008-210), "In-Service Inspection Plans; RAI Reply for Fourth Ten-Year Interval Unit 1 Relief Request 2", September 25, 2008, Accession Number ML082740274 (4) T.H. Boyce (NRC) to J.A. Stall (FPL), "St. Lucie, Unit 1 -Safety Evaluation of Relief Request to Use Structural Weld Overlay and Alternative Examination Techniques on Safe End Dissimilar Metal Welds (TAC No. MD9256)", November 3, 2008, Accession Number ML082960546 By letter L-2008-08 dated April 29, 2008 [Reference 1], Florida Power & Light Company (FPL) submitted Relief Request Number 2 (RR-2) as an alternative to the repair requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XI, for St. Lucie Unitl. In response to the U.S. Nuclear Regulatory Commission (NRC) request for additional information dated September 18, 2008 [Reference 2], FPL revised RR-2 as Revision I (RR-2, Rev. 1) in letter L-2008-210 Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957 L-2012-307 Page 2 of 2 dated September 25, 2008 [Reference 3]. By letter dated November 3, 2008 [Reference 4], the USNRC approved RR-2, Rev. 1.The Reference I and 2 Relief Requests, as well as the Reference 4 Safety Evaluation, indicated that the same heat of weld wire, or wire heat with equal or greater chromium (Cr) content than that used in qualification, would be used in situ for the first weld layer as was used in the mockup for the first layer. However, as a result of review by the NRC during the 2012 Permanent Plant Modification Inspection, it was determined that heats of weld wire with Cr content different than that in the mockup had been used in situ.FPL hereby requests approval for use of a heat of wire with chromium content different than that approved in RR-2, Rev. 1. Enclosure I and the supporting attachments contain Revision 2 of RR-2 Should you have any questions regarding this submittal, please contact Mr. Scott Boggs at 561-694-4207.
Very tr ly yours, St. Lucie Plant Enclosure JJ/kdr L-2012-307 Enclosure I Page 1 of4l St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)
Alternative Provides Acceptable Level of Quality and Safety USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE 1.0 ASME Code Components Affected Code components associated with this request are three (3) Class I safe end-to-nozzle dissimilar metal welds (DMWs) with Alloy 82/182 weld metal that are believed to be susceptible to Primary Water Stress Corrosion Cracking (PWSCC). Preemptive full structural weld overlays (SWOLs) are planned to be applied to these DMWs. In addition, the SWOLs will extend across the three (3) adjacent stainless steel pipe elbow-to-safe end similar metal welds. These welds had SWOLs applied during the St. Lucie Unit 1 SLI-22 refueling outage (Fall 2008).1.1 Category and System Details: Code Class: Class 1 System Welds: Reactor Coolant System Examination Categories:
R-A**As submitted by St. Lucie Unit 1, 4 10-year ISI Program Relief Request 1 1.2 Component Descriptions:
The application of this alternative is to apply SWOLs on two (2) safe end-to-hot leg shutdown cooling outlet nozzle welds (one in each hot leg) and one (1) safe end-to-hot leg B surge nozzle weld. The SWOLs will also extend outward from the nozzle across the adjacent stainless steel pipe elbow-to-safe end welds. The applicable weld identifications are as follows in Table 1.
L-2012-307 Enclosure 1 Page 2 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 TABLE I Weld Nos.Nozzle-to-Safe End Safe End-to-Item Location Weld Pipe Elbow 1 Surge Line to Hot Leg B Pipe Nozzle RC-6-509 RC-108-FW-3 2 Shutdown Cooling Outlet to Hot Leg 'A' Pipe 10-509-B RC-162-FW-1 Nozzle 3 Shutdown Cooling Outlet to Hot Leg 'B' Pipe 10-509-A RC-147-FW-1 Nozzle 1.3 Component Materials:
The specific materials are shown in Table 2:
L-2012-307 Enclosure I Page 3 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 TABLE 2 Materials Item Location Nozzle Safe End Pipe Elbow Buttering Pipe Elbow-to-Safe End Weld Surge Line P-No. 1 Group P-No.8 Cast P-No.8 Cast F-No. 43 E308L or to Hot Leg 2 Carbon Steel Stainless Steel Stainless Steel Alloy 82/182 ER308L'B' Pipe SA-105 Grade SA-351 CF8M. SA-351 CF8M.Nozzle II 2 Shutdown P-No. 1 Group P-No.8 Cast P-No. 8 SA- F-No. 43 E308 or Cooling 2 Carbon Steel Stainless Steel 312 TP304 Alloy 82/182 E308L or Outlet to Hot SA-105 Grade SA-351 CF8M. Stainless Steel ER308 or Leg 'A' Pipe II ER308L Nozzle 3 Shutdown P-No. 1 Group P-No.8 Cast P-No. 8 SA- F-No. 43 E308 or Cooling 2 Carbon Steel Stainless Steel 312 TP304 Alloy 82/182 E308L or Outlet to Hot SA-105 Grade SA-351 CF8M. Stainless Steel ER308 or Leg 'B' Pipe II ER308L Nozzle 1.4 Justification for Revision Revision 2 of Relief Request Number 2 provides justification for use of a heat of wire with chromium content different than that approved in Revision 1 of the relief request (Reference ML082960546, Section 3.4.2). Mockup work using the same welding parameters and a weld filler material heat with 29.86% Cr, which bounds the St. Lucie in-situ SWOLs, provided greater than 24% Cr for the first layer deposit. Therefore, the first layer of alloy 52M weld overlay can be credited in the thickness of the structural weld overlay.2.0 Applicable Code Edition and Addenda St. Lucie Unit 1 is currently in the 4 th 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 is Section XI, 2001 Edition, including Addenda through 2003 (Reference
: 1) and 2001 Edition for Appendix VIII. The L-2012-307 Enclosure I Page 4 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 2001 Edition with Addenda through 2003 is applicable 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, 2001 Edition including Addenda through 2003 (Reference 1), IWA-4410(a), IWA-4611.1(a) and Section XI, 2001 Edition with 2001 Edition, Appendix VIII Supplement 11.IWA-4410(a) states in part the following: "Welding, brazing, defect removal, and installation activities shall be performed in accordance with IWA-4420 or IWA-4430, and the other requirements of this Subarticle
........IWA-46 11.1 (a) states in part the following: "Defects shall be removed or reduced in size in accordance with this Paragraph." 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 Dissimilar metal welds (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, generally constructed of carbon or low alloy ferritic steel. These welds have shown a propensity 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," September 2005 (Reference 2).For the upcoming SL1-22 refueling outage, three (3) DMWs located on the hot leg piping are currently scheduled to have SWOLs applied. Repair/replacement activities associated with SWOL repairs are required to address the materials, welding parameters, ALARA concerns, operational constraints, examination techniques and procedure requirements for repairs.
L-2012-307 Enclosure 1 Page 5 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 ASME Code, Section XI, 2001 Edition including Addenda through 2003 (Reference 1), IWA-44 10(a) and IWA-46 11.1 (a) do not address 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.
Also 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.In addition, ASME Code Section XI, 2001 Edition including Addenda through 2003 (References I & 6), and 2001 Edtion of Appendix ViII Supplement 11 cannot be implemented as written for ultrasonic examination of a structural weld overlay repair.Attachment 1 includes a discussion of the Performance Demonstration Initiative (PDI)Program alternatives and their bases with respect to Appendix VIII Supplement 11 requirements.
The alternative described in Section 5.0 is proposed to permit the implementation of SWOLs at St. Lucie Unit 1, as an alternative for the repair/replacement requirements of the ASME Code Section XI, 2001 Edition, including Addenda through 2003 (Reference 1), IWA-4410(a), IWA-461 1.1(a) and 2001 Edition, Appendix VIII, Supplement 11.5.0 Proposed Alternative and Basis for Use This proposal requests the use of the Alternative Requirements shown in Attachment 2 for implementing the three (3) scheduled SWOLs for potentially PWSCC susceptible safe end-to-nozzle welds of the reactor coolant hot leg piping. These SWOLs will include the three (3) adjacent stainless steel pipe elbow-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 SL1-22 Fall 2008 refueling outage.This proposed alternative (Attachment
: 2) is the result of industry's experience with weld overlay modifications for flaws suspected or confirmed to be caused by PWSCC and directly applies to the Alloy 52 or 52M weld material that is primarily being used for these SWOLs.The ultrasonic examination of the completed SWOLs will be accomplished with personnel and procedures qualified in accordance with ASME Code, Section XI, 2001 Edition, including Addenda through 2001 (Reference 5 and 6) Appendix VIII, Supplement 11 (as specified in Attachment 2, Section 3 therein), with the alternatives L-2012-307 Enclosure 1 Page 6 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 used for complying with the PDI Program. See Attachment I for the PDI Program changes to Appendix VIII Supplement 11.5.1 Structural Weld Overlay (SWOL) Design The SWOLs satisfy all the structural design requirements of the pipe as specified in the Alternative Requirements shown in Attachment 2 for the original safe end-to-nozzle welds and the pipe elbow-to-safe end welds. As shown 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 elbow-to-safe end weld. The SWOLs extend around the entire circumference of the nozzle. Alloy 52M and 52 filler metals are compatible with all the wrought and cast base materials and the DMW and similar metal welds that will be covered by the SWOL.The SWOLs will be designed as full structural overlays.
Postulated 100% through-wall flaws shall be assumed as specified in 2(b)(5), Attachment 2, for SWOL length and thickness sizing per 2(b)(6) Attachment
: 2. No ultrasonic examination will be performed prior to SWOL application.
For flaw growth evaluations, since no ultrasonic examination will be performed prior to SWOL application, and the post SWOL ultrasonic examination is not qualified for flaw detection and sizing in cast stainless steel base material on some of the nozzles, postulated 100% through-wall flaws will be assumed as specified in 2(a)(2) and 2(a)(2)(a), Attachment 2, for the welds on all nozzle locations where SWOLs will be applied. Planar flaws detected during the acceptance examination will be characterized and flaw growth calculations performed using the flaw(s) detected plus the postulated 100% through-wall flaws.Note that the details surrounding the design analysis for the SWOLs are being developed to support the St. Lucie Unit 1 Fall 2008 refueling outage and our vendor has committed to supplying this analysis to FPL. The analysis will be available at the plant for NRC review at the beginning of the SL1-22 refuel outage.Paragraph 3(a)(3) of Attachment 2 states that "for planar indications outside this examination volume, the nominal wall thickness shall be "t 2" as shown in Fig 1 (c) for volumes A-E-H-D and F-B-C-G." For the cast stainless steel material, UT is not currently qualified to examine the base metal following weld overlay installation.
Initial 100%through-wall axial and circumferential flaws are assumed for both SWOL design and flaw growth evaluations at all nozzle locations where SWOLs will be installed. "t 2" is '/2 in. outside the PWSCC susceptible DMW. The portion of the pipe, safe end or nozzle material outside the PWSCC susceptible material is assumed unflawed.
These volumes are also outside any other Section XI ISI volume other than associated with the original weld ISI as shown in Figure IWB-2500-8(c) so service related flaws therein are not L-2012-307 Enclosure I Page 7 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 expected to occur. Surface examination is also performed on these areas before the SWOLs are applied to verify absence of surface flaws. The volume of the overlay which is more than 1/ inch from the susceptible region is treated as a cross section which is the SWOL thickness plus the original underlying base metal wall thickness.
The acceptance standard for a flaw in the SWOL from Table IWB-3514-2 is thus based on" t 2". The approach is consistent with other examinatidns in Section XI including pipe to pipe welds where the examination volume does not include the entire thickness but the acceptance criteria does. Furthermore indications in the overlay will be required to be sized. This requirement will assure that the indications which may extend into the base metal are not excluded.5.2 Welding The welding will be performed in accordance with Attachment 2 using a 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 may 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 or carbon steel nozzles.During recent dissimilar metal weld (DMW) overlay activities, where ERNiCrFe-7A (Alloy 52M) and ERNiCrFe-7 (Alloy 52) have 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 flaw characteristics observed above are indicative of hot cracking.
This phenomenon has not been observed on the ferritic steel or ENiCrFe-3 (Alloy 182) DMW portions of the assemblies when welding Alloy 52M thereon.Further studies have determined that this problem may occur when using Alloy 52M filler metal on austenitic stainless steel materials with high sulfur content.Extensive tests and field experience from WSI indicate that hot cracking can be a concern when the sulfur and phosphorus content in the diluted weld puddle equals or exceeds 0.014%. The impurity hot cracking threshold level is a function of both the composition of the weld filler materials and the welding parameters that are used because these two factors control the dilution of the solidified weld deposit. This suggests that a combined sulfur plus phosphorus content of the base material approximately 0.046% will represent a threshold for hot cracking with the weld parameters WSI will use at St. Lucie.
L-2012-307 Enclosure I Page 8 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 St. Lucie Unit I will use the barrier layer on all the stainless steel items prior to overlay.The barrier layer will use ER308L or ER309L on the stainless steel and may incorporate Alloy 82 on the stainless steel near the DMW to stainless steel fusion zone only.The barrier layer will not be used in the structural analysis.
The inside diameter of the portion of the SWOL over the barrier layer will be the outside diameter of the barrier layer that is applied over the stainless steel material beneath the SWOL. See Attachment 3 for more information.
The Cr content of the 1 st layer was verified by direct measurement of weld overlay deposits on ASTM A106 Grade B mockups. Welding was performed using a double up progression (starting at the bottom and welding upward to the top on each side) for 5G and 6G mockups and orbital progression for 2G mockups. The Cr content was measured at 90 degree intervals.
All welding parameters were recorded and the 24% minimum Cr value specified in l(e), Attachment 2, was attained in all cases. The attainment of the minimum 24% Cr threshold level has been demonstrated many times on similar mockups using the same WSI welding parameters.
A heat of wire with equal or greater chrome content than the lowest Chrome content of 29.86% used in qualification mockups, will be used in situ for the first layer and the same welding parameters will be specified in the WPS as was used in the mockup for the first layer. It should be noted that the deposition of Alloy 52M over base material already having significant Cr content will have higher deposited Cr content.The SWOL will require welding on more than 100 square inches of surface on the hot leg surge nozzle and shutdown cooling ferritic carbon steel nozzles but less than 300 square inches which is permitted in Appendix I, I-1(b), Attachment
: 2. The SWOL will extend toward the hot leg onto the ferritic steel nozzle base material for a sufficient length so that qualified ultrasonic examination of the required volume can be performed after the SWOL is applied.There have been a number of temper bead SWOLs applied to safe end-to-nozzle welds in the nuclear industry, and SWOLs having more than 100 square inch surface area on the nozzle ferritic steel surfaces have been used. The ASME Committee has indicated the inside diameter compressive stress levels remain essentially the same for both 100 square inches and 500 square inches related to SWOL applications.
The justification entitled"Bases for 500 Sq. In. Weld Overlay Over Ferritic Material", was provided to the NRC staff in the January 10, 2007 meeting (Accession No. ML070470565).
Additional justification is provided in Appendix F of EPRI Report 1014351, Repair and Replacement Applications Center: Topical Report Supporting Expedited NRC Review of Code Cases for Dissimilar Metal Weld Overlay Repairs" December 2006 (Reference 4).
L-2012-307 Enclosure I Page 9 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 The thickness of the SWOLs may exceed V 2 the carbon and low alloy ferritic steel nozzle base metal thickness as specified in Code Case N-638-1. The requirement therein applies to excavated cavities in the ferritic steel base material that are subsequently welded flush.This requirement is not applicable to SWOLs since they are applied to the nozzle surface and limited to 3/8 in. depth into the ferritic steel as specified in Attachment 2, Appendix 1, 1-1(d). Additional justification is provided in Appendix F of Reference 4.1-3.0(d), Appendix I, Attachment 2, specifies the maximum interpass temperature shall be limited to 350 OF maximum, even though the maximum interpass temperature is limited to 150 OF maximum for the first three layers in the test assembly specified in 1-2.1(c).This is greater than the maximum 100 OF interpass temperature increase permitted by QW-406.3.
The following is a clarification of the intent of Code Case N-638-1 that has been included in Code Case N-638-2. The limitation on the procedure qualification maximum interpass temperature (150 OF) is to ensure the cooling rates achieved during procedure qualification are more severe than those encountered during field welding (i.e., are not slower than those achievable during field welding).
The higher interpass temperature is permitted during field welding because it would only result in slower cooling rates which could be helpful in producing more ductile transformation products in the ferritic steel heat affected zone (HAZ). Additional justification information is also included in Reference 4.For applicable cases where paragraph l(c)(1), Attachment 2 applies, the final SWOL ultrasonic and surface examination will be performed after completion of welding since temper bead welding would not be required.
The clarifications in this paragraph are conservative with respect to the intent of the Construction Code post weld heat treatment (PWHT) exemption requirements
[Table NB-4622.7(b)-I]
since all weld overlays are deposited on the surfaces of the ferritic steel nozzles instead of partial or complete through thickness welds applicable for the cases described in the Construction Code.5.3 Examination ASME Section XI, Appendix VIII, Supplement 10 ultrasonic examination will not be performed on the DMWs prior to the SWOLs being applied. Since the structural integrity at the DMW locations will be restored by the SWOLs the ultrasonic examination of the DMWs prior to SWOL application is unnecessary and the increased personnel dose that would be incurred performing the examinations is also undesirable and not consistent with good ALARA practice.
All welds have postulated 100% through-wall cracks for both the SWOL design and for the flaw growth evaluations.
L-2012-307 Enclosure 1 Page 10 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 The ultrasonic and surface examinations will be performed on the temper bead portion of the SWOLs no sooner than 48 hours after completion of the third temper bead layer as specified in 3(a)(2) and 3(a)(3), Attachment 2.The 48 hour delay is intended to provide time for potential delayed hydrogen cracking occurrence.
Attachment 2, Appendix 1 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 welding electrodes and bare wire filler metal with no flux to absorb 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 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 HAZ resulting in achievement of lower hardness and tempered martensite.
This further reduces susceptibility to hydrogen induced cracking.EPRI Report 1013558, Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding, Technical Update, December 2006 (Reference
: 3) provides justification for reducing the 48 hour hold time on P-No. 3 Group No. 3 ferritic steel base material to start after completion of the third temper bead layer.Report 1013558 addresses microstructural issues, hydrogen sources, tensile stress and temperature, and diffusivity and solubility of hydrogen in steels.The base materials studied in the EPRI report are primarily P-No. 3. The hot leg piping nozzle base materials at St. Lucie Unit 1 are P-No. 1 Group No. 2. The concerns associated with hydrogen assisted cracking are generally more significant for P-No. 3 than P-No. I base materials due to the P-No. 3 base material's increased hardenability.
Also, post weld heat treat exemptions shown in ASME Section II1, Table NB-4622.7(b)-I are provided for P-No. 1 Group No. 2 materials, including temper bead welding, whereas no post weld heat treat exemptions, other than temper bead welding, are permitted for P-No. 3 Group No. 3 materials.
L-2012-307 Enclosure I Page 11 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 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 hour hold NDE or subsequent in-service inspections.
Code Case N-638-4, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique Section XI Division 1," specifies NDE to be performed on the final weld no sooner than 48 hours after completion of the third temper bead layer.All examinations will meet the requirements of Attachment 2, excluding qualification of the ultrasonic examination for the completed SWOLs. The ultrasonic examination qualification will be in accordance with ASME Code Section XI, 2001 Edition including Addenda through 2001 (References 5 & 6), Appendix VIII, Supplement II with the alternatives that are used to comply with the PDI Program. See Attachment 1 for the PDI Program changes to Appendix VIII Supplement
: 11. Inservice inspection will be performed as specified in Attachment 2 with the exceptions that: 1) the limitations associated with the cast stainless steel safe end material will adversely affect the examinations and 2) the ultrasonic examination procedures and personnel will be qualified in accordance Appendix VIII, Supplement 11 as modified by the PDI Program as specified in Attachment 1.The cast stainless steel base material of the applicable safe ends and the surge line pipe at the surge line elbow at the hot leg B surge nozzle are not currently within the scope of PDI qualified ultrasonic examination procedures.
Qualified representative mockups are not currently available, and examination procedures and personnel have not yet been demonstrated for the cast material.
In these cases, an Appendix III ultrasonic examination will be performed, using the existing PDI qualified personnel and procedures as shown in Attachment
: 1. As stated previously, 100% through-wall flaws are assumed for both the SWOL design and the flaw growth evaluations at all nozzle locations where SWOLs are being applied.The final ultrasonic examination report will be submitted to the NRC within 60 days after completion thereof. Any flaws detected that exceed the acceptance standards of Table IWB-3514-2 will be reported to the NRC as soon as possible.
A discussion and reason for any SWOL or base metal repairs will be provided.The ultrasonic examination requirements specified in NRC'Regulatory Guide 1.147 Revision 15 as conditional acceptance of Code Case N-638-1 are not applicable to SWOLs. UT of the SWOLs will be performed in accordance with Section XI, Appendix L-2012-307 Enclosure 1 Page 12 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 VIII, Supplement 11 qualified procedures and personnel as modified by PDI and the limitations due to the underlying cast stainless steel base material.
The PDI modifications are shown in Attachment
: 1. Supplement 11 was prepared to be specifically applicable to weld overlays.
The ultrasonic examination requirements in Section 3, Attachment 2, are similar to the ultrasonic examination requirements provided in Appendix Q which have been developed specifically for austenitic weld overlays.
The UT examination to be performed, in conjunction with the surface examinations to be performed, as specified in Section 3 Attachment 2 are based on the latest industry experience and practice and completely satisfactory for the SWOL application.
 
===5.4 Conclusion===
The proposed alternative shown in Attachment 2 has been developed to cover the most recent operating experience and NRC approved criteria that are associated with similar SWOL applications.
Similar NRC approved requests have been used to produce acceptable weld overlays when applied to dissimilar metal welds with Alloy 82/182 weld material.
Therefore FPL considers that Attachment 2 and the PDI Program provides an acceptable level of quality and safety, consistent with provisions of 10 CFR 50.55a(a)(3)(i).
L-2012-307 Enclosure I Page 13 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 6.0 Precedents Similar requests have been submitted and approved to address the issues that are contained in this request. Florida Power & Light (FPL) submitted Relief Request #10 for St. Lucie Unit 2, on September 24, 2007 and received NRC's approval December 12, 2007 (TAC NO. MD5114, ADAMS Accession No. ML073400022) which included the application of full structural SWOLs to pressurizer and hot leg connection dissimilar metal butt welds.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, Unit 1, 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)7.0 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 4th 10-year ISI interval which includes inservice examination requirements of Attachment 2 for any applied weld overlays.
Future inservice examinations of weld overlays at St. Lucie Unit I beyond this inspection interval will be as required by the NRC in the regulations.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.MCI201), dated: July 21, 2004, (ADAMS Accession No. ML041670510).
(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-9-01F at the Donald C. Cook Nuclear Plant Unit 1, Docket No. 50-315, (TAC No.MC8807), dated February 10, 2006, (ADAMS Accession No. ML060240355).
L-2012-307 Enclosure I Page 14 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 8.0 References
: 1. ASME Code, Section XI, 2001 Edition, including Addenda through 2003 2. EPRI MRP-169 "Technical Basis for Preemptive Weld Overlays for Alloy 82/182 Butt Welds in PWRs," September 2005.3. EPRI Report 1013558, Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding, Technical Update, December 2006.4. EPRI Report 1014351, Topical Report Supporting an Expedited NRC Review of the Content of the Code Case needed for Dissimilar Metal Weld Overlay Repairs, Final Report, July 2006 5. 10CFR50.55a, Nuclear Regulatory Commission Federal Register part II, Vol. 72, No. 243, effective date January 8, 2008, 10 CFR part 50 Industry Codes and Standards; Amended Requirements; Final Rule.6. ASME Code, Section XI, 2001 Edition, for Appendix VIII, Supplement 11 examinations as modified by I OCFR50.55a(b)(2)(xxiv).
 
==9.0 Attachments==
Attachment I "PDI Program Modifications to Appendix VIII Supplement 11" Attachment 2 "Alternative Requirements for Dissimilar Metal Weld Overlays" Attachment 3"Barrier Layer to Prevent Hot Cracking in High Sulfur Stainless Steel" L-2012-307 Enclosure 1 Page 15 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 SS Pipe Elbow ISA-312 TP304: Hot Leg Shutdown Cooling Outlet Nozzles;-SA-35 1 CF8: Hot Leg Surge Nozzle)SS Sole End (SA-351 CF8M)Pipe Elbow/SE .Hot Leg B Surge Nozzle & Hot Leg Weld (SS) Shutdown Cooling Outlet Nozzles Weld Buttering (A182)SE/Nozzle Weld A82 Root/A 182 Bolance SWOL (A52/A52M) n Carbon Steel (SA-105 Gr 1I)-Hot Leg B Surge Nozzle &Hot Leg Shutdown iz, Cooling Outlet Nozzles Figure 1 -Typical SWOL Configuration L-2012-307 Enclosure 1 Page 16 of 4l St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Attachment 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 Modification: (b) The specimen set shall consist of least three specimens having different at least three specimens having different nominal nominal pipe diameters and overlay pipe diameters-and overlay thicknesses.
They shall thicknesses.
They shall include the include the minimum and maximum nominal pipe minimum and maximum nominal pipe diameters for which the examination procedure is diameters for which the examination applicable.
Pipe diameters within a range of 0.9 to procedure is applicable.
Pipe diameters
 
===1.5 times===
a nominal diameter shall be considered within a range of 0.9 to 1.5 times a nominal equivalent.
If the procedure is applicable to pipe diameter shall be considered equivalent.
If diameters of 24 inches or larger, the specimen set the procedure is applicable to pipe must include at least one specimen 24 inches or diameters of 24 inches or larger, the larger but need not include the maximum diameter.specimen set must include at least one The specimen set shall include specimens with specimen 24 inches or larger but need not overlays not thicker than 0.1 inches more than the include the maximum diameter.
The minimum thickness, nor thinner than 0.25 inches of specimen set must include at least one the maximum nominal overlay thickness for which specimen with overlay thickness within -0.1 the examination procedure is applicable.
inches to +0.25 inches of the maximum Basis: To avoid confusion, the overlay thickness nominal overlay thickness for which the tolerance contained in the last sentence was procedure is applicable, reworded and the phrase "and the remainder shall be alternative flaws" was added to the next to last sentence in paragraph 1.1 (d) (1).(d) Flaw Conditions (1) Base metal flaws. All flaws must be Modification:
(1) Base metal flaws. All flaws must cracks in or near the butt weld heat- be in or near the butt weld heat-affected zone, open affected zone, open to the inside surface, to the inside surface, and extending at least 75%and extending at least 75% through the through the base metal wall. Intentional overlay base metal wall. Flaws may extend 100% fabrication flaws shall not interfere with ultrasonic through the base metal and into the overlay detection or characterization of the base metal material; in this case, intentional overlay flaws. Specimens containing IGSCC shall be used fabrication flaws shall not interfere with when available.
At least 70% of the flaws in the ultrasonic detection or characterization of detection and sizing tests shall be cracks and the the cracking.
Specimens containing remainder shall be alternative flaws. Alternative IGSCC shall be used when available, flaw mechanisms, if used, shall provide crack-like reflective characteristics and shall be limited by the following:
L-2012-307 Enclosure 1 Page 17 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Appendix VIII, Supplement 11 PDI Modification (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.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 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. To avoid confusion, the overlay thickness tolerance contained in paragraph 1.1(b) last sentence, was reworded and the phrase "and the remainder shall be alternative flaws" was added to the next to last sentence.
Paragraph 1.1(d)(1) includes the statement that intentional overlay fabrication flaws shall not interfere with ultrasonic detection or characterization of the base metal flaws.(e) Detection Specimens (1) At least 20% but less than 40% of the flaws shall be oriented within +20 degrees of the pipe axial direction.
The remainder shall be oriented circumferentially.
Flaws shall not be open to any surface to which the candidate has physical or visual access. The rules of IWA-3300 shall be-1-Modification:
(1) At least 20% but less than 40% of the base metal flaws shall be oriented within+/-20 degrees of the pipe axial direction.
The remainder shall be oriented circumferentially.
Flaws shall not be open to any surface to which the candidate has physical or visual access.Basis: The requirement for axially oriented overlay L-2012-307 Enclosure I Page 18 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Appendix VIII, Supplement 11 PDI Modification used to determine whether closely spaced flaws should be treated as single or multiple flaws.fabrication flaws was excluded from the PDI Program as an improbable scenario.
Weld overlays are typically applied using automated GTAW techniques with the filler metal applied in a circumferential direction.
Because resultant fabrication induced discontinuities would also be expected to have major dimensions oriented in the circumferential direction axial overlay 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.(2) Specimens shall be divided into base (2) Specimens shall be divided into base metal and and overlay grading units. Each specimen overlay fabrication grading units. Each specimen shall contain one or both types of grading shall contain one or both types of grading units.units. Flaws shall not interfere with ultrasonic detection or characterization of other flaws.(a)(1) A base grading unit shall include at Modification: (a)(1) A base metal grading unit least 3 inches of the length of the overlaid includes the overlay material and the outer 25% of weld. The base grading unit includes the the original overlaid weld. The base metal grading outer 25% of the overlaid weld and base unit shall extend circumferentially for at least 1 inch metal on both sides. The base grading unit and shall start at the weld centerline and be wide shall not include the inner 75% of the enough in the axial direction to encompass one half overlaid weld and base metal overlay of the original weld crown and a minimum of 0.50 material, or base metal-to-overlay interface.
inch 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. 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.
Modified to require that a base metal grading unit include at least 1 in.of the length of the overlaid weld, rather than 3 inches.(a)(2) When base metal cracking Modification: (a)(2) When base metal flaws penetrates into the overlay material, the penetrate into the overlay material, the base metal base grading unit shall include the overlay grading unit shall not be used as part of any overlay L-2012-307 Enclosure 1 Page 19 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Appendix VIII, Supplement 11 PDI Modification metal within 1 inch of the crack location, fabrication grading unit.This portion of the overlay material shall not be used as part of any overlay grading unit.(a)(3) When a base grading unit is Modification: (a)(3) Sufficient unflawed overlaid designed to be unflawed, at least 1 inch of weld and base metal shall exist on all sides of the unflawed overlaid weld and base metal grading unit to preclude interfering reflections from shall exist on either side of the base adjacent flaws.grading unit. The segment of weld length Basis: Modified to require sufficient unflawed used in one base grading unit shall not be overlaid weld and base metal to exist on all sides of used in another base grading unit. Base the grading unit to preclude interfering reflections grading units need not be uniformly spaced from adjacent flaws, rather than the 1 inch around the specimen.
requirement.(b)(1) An overlay grading unit shall include Modification: (b)(1) An overlay fabrication grading the overlay material and the base metal-to-unit shall include the overlay material and the base overlay interface of at least 6 metal-to-overlay interface for a length of at least square inches. The overlay grading unit 1 inch.shall be rectangular, with minimum Basis: Modified to require sufficient unflawed dimensions of 2 inches. 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.(b)(2) An overlay grading unit designed to Modification: (b)(2) Overlay fabrication grading be unflawed shall be surrounded by units designed to be unflawed shall be separated unflawed overlay material and unflawed by unflawed overlay material and unflawed base base metal-to-overlay interface for at least metal-to-overlay interface for at least 1 inch at both 1 inch around its entire perimeter.
The ends. Sufficient unflawed overlaid weld and base specific area used in one overlay grading metal shall exist on both sides of the overlay unit shall not be used in another overlay fabrication grading unit to preclude interfering grading unit. Overlay grading units need reflections from adjacent flaws. The specific area not be spaced uniformly about the used in one overlay fabrication grading unit shall specimen.
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 in. at both ends, rather than around its entire perimeter.
L-2012-307 Enclosure I Page 20 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Appendix VIII, Supplement 11 PDI Modification (b)(3) Detection sets shall be selected from Table VIII-S2-1.
The minimum detection sample set is five flawed base grading units, ten unflawed base grading units, five flawed overlay grading units, and ten unflawed overlay grading units. For each type of grading unit, the set shall contain at least twice as many unflawed as flawed grading units.Modification: (b)(3) Detection sets shall be selected from Table VIII-S2-1.
The minimum detection sample set is five flawed base metal grading units, ten unflawed base metal grading units, five flawed overlay fabrication grading units, and ten unflawed overlay fabrication grading units.For 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.(f) Sizing Specimen (1) The minimum number of flaws shall be Modification:
(1) The minimum number of flaws ten. At least 30% of the flaws shall be shall be ten. At least 30% of the flaws shall be overlay fabrication flaws. At least 40% of overlay fabrication flaws. At least 40% of the flaws the flaws shall be cracks open to the inside shall be open to the inside surface. Sizing sets surface. 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 Modification:
(3) Base metal flaws used for length sizing demonstrations shall be oriented sizing demonstrations shall be oriented circumferentially.
circumferentially.
(4) Depth sizing specimen sets shall Modification:
(4) Depth sizing specimen sets shall include at least two distinct locations where include at least two distinct locations where a base cracking in the base metal extends into the metal flaw extends into the overlay material by at overlay material by at least 0.1 inch in the least 0.1 inch in the through-wall direction.
through-wall direction.
 
===2.0 CONDUCT===
OF PERFORMANCE DEMONSTRATION The specimen inside surface and Modification:
The specimen inside surface and identification shall be concealed from the identification shall be concealed from the candidate.
candidate.
All examinations shall be All examinations shall be completed prior to grading completed prior to grading the results and the results and presenting the results to the presenting the results to the candidate.
candidate.
Divulgence of particular specimen Divulgence of particular specimen results or results or candidate viewing of unmasked L-2012-307 Enclosure 1 Page 21 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Appendix VIII, Supplement 11 PDI Modification candidate viewing of unmasked specimens specimens after the performance demonstration is after the performance demonstration is prohibited.
The overlay fabrication flaw test and the prohibited.
base metal flaw test may be performed separately.
 
===2.1 Detection===
 
Test. Flawed and unflawed Modification:
 
===2.1 Detection===
 
Test. Flawed and grading units shall be randomly mixed. unflawed grading units shall be randomly mixed.Although the boundaries of specific grading Although the boundaries of specific grading units units shall not be revealed to the candidate, shall not be revealed to the candidate, the the candidate shall be made aware of the candidate shall be made aware of the type or types type or types of grading units (base or of grading units (base metal or overlay fabrication) overlay) that are present for each that are present for each specimen.specimen.2.2 Length Sizing Test (d) For flaws in base grading units, the Modification: (d) For flaws in base metal grading candidate shall estimate the length of that units, the candidate shall estimate the length of that part of the flaw that is in the outer 25% of part of the flaw that is in the outer 25% of the base the base wall thickness.
metal wall thickness.
 
===2.3 Depth===
Sizing Test. For the depth sizing test, 80% of the flaws shall be sized at a specific location on the surface of the specimen identified to the candidate.
For the remaining flaws, 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.Modification:
 
===2.3 Depth===
Sizing Test.(a) The depth sizing test may be conducted separately or in conjunction with the detection test.(b) When the depth sizing test is conducted in conjunction with the detection test and the detected flaws do not satisfy the requirements of 1.1 (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.
L-2012-307 Enclosure 1 Page 22 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Appendix VIII, Supplement 11 PDI Modification
 
===3.0 ACCEPTANCE===
 
CRITERIA 3.1 Detection Acceptance Criteria.
Modification:
 
===3.1 Detection===
 
Acceptance Criteria.Examination procedures, equipment, and Examination procedures are qualified for detection personnel are qualified for detection when when: the results of the performance (a) All flaws within the scope of the procedure are demonstration satisfy the acceptance detected and the results of the performance criteria of Table VIII-S2-1 for both detection demonstration satisfy the acceptance criteria of and false calls. The criteria shall be Table VIII-S2-1 for false calls.satisfied separately by the demonstration (b) At least one successful personnel results for base grading units and for demonstration has been performed meeting the overlay grading units. 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 measurements, as compared to the true flaw flaw lengths, is less than or equal to 0.75 lengths, is less than or equal to 0.75 inch. The inch. The length of base metal cracking is length of base metal flaws is measured at the 75%measured at the 75% through-base-metal through-base-metal position.position.(b) All extensions of base metal cracking Modification:
This requirement is omitted.into the overlay material by at least 0.1 inch Basis: The requirement for reporting all extensions are reported as being intrusions into the of cracking into the overlay is omitted from the PDI overlay material.
Program because it is redundant to the 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 weld overlay program consistent with the Supplement 2 depth sizing criteria.
L-201 2-307 Enclosure I Page 23 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Attachment 2 Alternative Requirements for Dissimilar Metal Weld Overlays In lieu of the requirements of IWA-4410 and IWA-4611, a defect in austenitic stainless steel or austenitic nickel alloy piping, components, or associated welds may be reduced to a flaw of acceptable size in accordance with IWB-3640 by the addition of a repair weld overlay. The weld overlay shall be applied by deposition of weld reinforcement (weld overlay) on the outside surface of the piping, component, or associated weld, including ferritic materials when necessary, provided the following requirements are met: 1 GENERAL REQUIREMENTS (a) A full-structural weld overlay shall be applied by deposition of weld reinforcement (weld overlay) on the outside surface of circumferential welds in carbon steel (P-No. 1) to safe ends or piping components (P-No. 8 or 43), inclusive of the UNS N06082 or W86182 welds that join the two items. The design of the overlay may be extended to include the adjacent stainless steel to stainless steel welds (P-No. 8 to P-No. 8).(b) Attachment 2 applies to dissimilar metal welds between P-No. 8 or 43 and P-Nos. 1, 3, 12A, 12B, or 12C 1 materials.
Attachment 2 also applies to dissimilar metal welds between P-No. 8 and P-No. 43 materials joined with austenitic F-No.43 filler metal, and to welds between P-No. 8 and P-No. 8 materials as described in 1(a) above.(c) Weld overlay filler metal shall be austenitic nickel alloy (28% Cr min., ERNiCrFe-7 or ERNiCrFe-7A) applied 360 deg. around the circumference of the item, and deposited using a Welding Procedure Specification (WPS) for groove welding, qualified in accordance with the Construction Code and Owner's Requirements and identified in the Repair/Replacement Plan. As an alternative to the post weld heat treatment (PWHT) requirements of the Construction Code and Owner's requirements, the following provisions may be applied.(1) For P-No. 1 base materials, the Construction Code PWHT exemptions permitted for circumferential butt welds may be applied to exempt the weld 1 P-Nos. 12A, 12B, and 12C designations refer to specific material classifications originally identified in Section Iil and subsequently reclassified in a later Edition of Section IX.
L-2012-307 Enclosure I Page 24 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 overlay from PWHT with the following clarifications: (a) The nominal weld thickness is defined as the maximum overlay thickness applied over the ferritic base material.(b) The base material thickness is defined as the maximum thickness of the ferritic material where the overlay is applied.(2) Appendix I shall be used for ambient-temperature temper bead welding.(d) Prior to deposition of the weld overlay, the surface to be weld overlaid shall be examined using the liquid penetrant method. Indications with major dimension greater than 1/6 in. (1.5 mm) shall be removed, reduced in size, or weld repaired in accordance with the following requirements:
(1) One or more layers of weld metal shall be applied to seal unacceptable indications in the area to be repaired with or without excavation.
The thickness of these layers shall not be used in meeting weld reinforcement design thickness requirements.
Peening the unacceptable indication prior to welding is permitted.
(2) If weld repair of indications identified in 1(d) is required, the area where the weld overlay is to be deposited, including any local weld repairs or initial weld overlay layer, shall be examined by the liquid penetrant method. The area shall contain no indications with major dimension greater than 1A16 in. (1.5 mm) prior to the application of the structural layers of the weld overlay.(e) Weld overlay deposits shall meet the following requirements:
The austenitic nickel alloy weld overlay shall consist of at least two weld layers deposited using 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 thickness.
Alternatively, for PWR applications, a diluted first layer may be credited toward the required thickness, provided the portion of the layer over the austenitic base material, austenitic filler material weld and the associated dilution zone from an adjacent ferritic base material contain at least 24% Cr and the Cr content of the deposited weld metal is determined by chemical analysis taken from a mockup prepared in accordance with the WPS for the production weld.(f) Attachment 2 is only for welding in applications predicted not to have exceeded thermal neutron fluence of 1 x 1017 (E < 0.5 eV) neutrons per cm 2 prior to welding.(g) A new weld overlay shall not be installed over the top of an existing weld overlay that has been in service.2 CRACK GROWTH AND DESIGN (a) Crack Growth Calculation of Flaws in the Original Weld or Base Metal.
L-2012-307 Enclosure I Page 25 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 The size of all flaws postulated in the original weld or base metal shall be used to define the life of the overlay. In no case shall the inspection interval be longer than the life of the overlay. The inspection interval shall be as specified in 3(c).Crack growth in the original weld or base metal, due to both stress corrosion and fatigue, shall be evaluated.
Flaw characterization and evaluation shall be based on the postulated flaw, if ultrasonic examination of the weld and base material is not performed.
(1)For repair overlays, the initial flaw size for crack growth in the original weld or base metal shall be based on the postulated flaw, if no pre-overlay ultrasonic examination is performed.
(2) For postulated flaws in the original weld or base metal the axial flaw length shall be set at 1.5 in. (38 mm) or the combined width of the weld plus buttering, whichever is greater. The circumferential flaw length shall be assumed to be 360 deg.(a) If no examination is performed prior to application of the overlay, initial inside-surface-connected planar flaws equal to 100% through the original wall thickness shall be assumed, in both the axial and circumferential directions, consistent with the overlay examination volume in Fig. 2.(b) In determining the expected life of the overlay, any inside surface connected planar flaw found by the overlay preservice inspection of 3(b) that exceeds the depth of (2)(a) above shall be used as part of the initial flaw depth.The flaw depth assumed is the detected flaw depth plus the postulated worst-case flaw depth in the unqualified ultrasonic examination region of the pipe wall thickness.
An overlay meeting this condition shall be considered a repair.(b) Structural Design and Sizing of the Overlay. The design of the weld overlay shall satisfy the following, using the assumptions and flaw characterization restrictions in 2(a). The following design analysis shall be completed in accordance with IWA-431 1.(1) The axial length and end slope of the weld overlay shall cover the weld and heat-affected zones on each side of the weld and shall provide for load redistribution from the item into the weld overlay and back into the item without violating applicable stress limits of NB-3200. Any laminar flaws in the weld overlay shall be evaluated in the analysis to ensure that load redistribution complies with the above. These requirements will usually be satisfied if the weld overlay full-thickness length extends axially beyond the projected flaw by at least 2.5'1(Rt), where R is the outer radius of the item and t is the nominal wall thickness of the item.(2) Unless specifically analyzed in accordance with 2(b)(1), the end transition taper of the overlay shall not exceed 30 deg. A slope of not more than 1:3 is L-2012-307 Enclosure I Page 26 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 recommended.
(3) For circumferentially oriented flaws, in the underlying base material or weld, the flaws shall be assumed to be 100% through the original wall thickness for the entire circumference of the item.(4) For axial flaws in the underlying base material or weld, the flaws shall be assumed to be 100% through the original wall thickness of the item for the entire axial length of the flaw or combined flaws, as applicable." (5) For full structural overlays, when ultrasonic examination is not performed prior to installation of the weld overlay, the assumed flaw in the underlying base material or weld shall be based on the limiting case of the two below: (a) 100% through-wall for the entire circumference, or (b) 100% through-wall for 1.5 in. (38 mm) or the combined width of the weld plus buttering, whichever is greater, in the axial direction.
(6) The overlay design thickness shall be verified using only the weld overlay thickness conforming to the deposit analysis requirements of 1(e). The combined wall thickness at the weld overlay and the effects of any discontinuities (e.g., another weld overlay or reinforcement for a branch connection) within a distance of 2.54(Rt) from the toes of the weld overlay, including the flaw size assumptions defined in 2(b)(3), (4), or (5) above, shall be evaluated and meet the requirements of IWB-3640 (7) The effects of any changes in applied loads, as a result of weld shrinkage from the entire overlay, on other items in the piping system (e.g., support loads and clearances, nozzle loads, and changes in system flexibility and weight due to the weld overlay) shall be evaluated.
Existing flaws previously accepted by analytical evaluation shall be evaluated in accordance with IWB-3640, IWC-3640, or IWD-3640, as applicable.
3 EXAMINATION In lieu of all other examination requirements, the examination requirements herein shall be met for the life of the weld overlay. Nondestructive examination methods shall be in accordance with IWA-2200, except as specified herein.Nondestructive examination personnel shall be qualified in accordance with IWA-2300. Ultrasonic examination procedures and personnel shall be qualified in accordance with Appendix VIII, Supplement 11.For cast stainless steel materials the applicable volumes shall be examined in accordance with Appendix VIII Supplement 11 qualified procedures and personnel to the maximum extent practicable and the remaining volume may be examined in accordance with Appendix III.
L-2012-307 Enclosure I Page 27 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 (a) Acceptance Examination (1) The weld overlay shall have a surface finish of 250 micro-in.
(6.3 micrometers)
RMS or better and a contour that provides for ultrasonic examination in accordance with procedures qualified in accordance with Appendix VIII. The weld overlay shall be inspected to verify acceptable configuration.
(2) The weld overlay and the adjacent base material for at least 1/2 in. (13 mm) from each side of the weld shall be examined using the liquid penetrant method. Surface examination shall be performed on weld attached thermocouple removal areas in accordance with NB-4435(b)(3).
The weld overlay shall satisfy the surface examination acceptance criteria for welds of the Construction Code or NB-5300. The adjacent base metal shall satisfy the surface examination acceptance criteria for base material of the Construction Code or NB-2500. If ambient-temperature temper bead welding is required, the liquid penetrant examination of the completed weld overlay shall be conducted after the three tempering layers (i.e., layers 1, 2, and 3) have been in place for at least 48 hr after completion of the third temper bead layer over the ferritic steel.(3) The acceptance examination volume A-B-C-D in Fig. 1(a) plus the heat-affected zone beneath the fusion zone C-D shall be ultrasonically examined to assure adequate fusion (i.e., adequate bond) with the base metal and to detect welding flaws, such as interbead lack of fusion, inclusions, or cracks., Cast stainless steel base material heat-affected zones shall be ultrasonically examined to the extent practicable.
If ambient-temperature temper bead welding is required, the ultrasonic examination of the completed weld overlay shall be conducted after the three tempering layers (i.e., layers 1, 2, and 3) over the ferritic steel have been in place for at least 48 hr.Planar flaws detected in the weld overlay acceptance examination shall meet the preservice examination standards of Table IWB-3514-2.
In applying the acceptance standards to planar indications within the volume E-F-G-H, in Fig.1(b), the thickness 1t 1" shall be used as the nominal wall thickness in Table IWB-3514-2. For planar indications outside this examination volume, the nominal wall thickness shall be "t 2" as shown in Fig. 1(c), for volumes A-E-H-D and F-B-C-G.Laminar flaws in the weld overlay shall meet the following: (a) Laminar flaws shall meet the acceptance standards of Table IWB-3514-3 with the additional limitation that the total laminar flaw shall not exceed 10% of the weld surface area and that no linear dimension of the laminar flaw area exceeds 3.0 in. (76 mm) or 10 % of the nominal pipe circumference, whichever is greater.(b) The reduction in coverage of the examination volume A-B-C-D in Fig.
L-2012-307 Enclosure I Page 28 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 1(a), due to laminar flaws shall be less than 10%. The uninspectable volume is the volume in the weld overlay underneath the laminar flaws for which coverage cannot be achieved with angle beam examination.(c) Any uninspectable volume in the weld overlay shall be assumed to contain the largest radial planar flaw that could exist within that volume. This assumed flaw shall meet the preservice examination acceptance standards of Table IWB-3514-2, with nominal wall thickness as defined above for planar flaws.Both axial and circumferential planar flaws shall be assumed.(4) After completion of all welding activities, affected restraints, supports, and snubbers shall be VT-3 visually examined to verify that design tolerances are met.(b) Preservice Inspection (1) The examination volume in Fig. 2 shall be ultrasonically examined, except cast stainless steel base material within the examination volume shall be ultrasonically examined to the extent practicable.
The angle beam shall be directed perpendicular and parallel to the piping axis, with scanning performed in four directions, to locate and size any planar flaws that might have propagated into the upper 25% of the base material or into the weld overlay.(2) The pre-service examination acceptance standards of Table IWB-3514-2 shall be met for the weld overlay. In applying the acceptance standards, wall thickness, tw, shall be the thickness of the weld overlay.(3) The flaw evaluation requirements rules of IWB-3640 shall not be applied to planar flaws identified during pre-service examination that exceed the preservice examination acceptance standards of Table IWB-3514-2.(c) Inservice Inspection (1) The weld overlay examination volume in Fig. 2 shall be added to the inspection plan. The weld overlay inspection interval shall not be greater than the life of the overlay defined in 2(a) above. The weld overlay shall be ultrasonically examined during the first or second refueling outage following application.
(2) Subarticle Q-4300 will be used with exceptions as follows. The cast stainless steel volume beneath the SWOL will be UT examined on a "best effort" basis since qualified UT examination is not achievable at this time. Qualified procedures and personnel will be used in accordance with Appendix VIII, Supplement 11 as modified by the PDI Program. The weld overlay will be examined in accordance with the PDI qualified procedure from both sides to the fullest extent possible.
However, no credit for examination coverage can be given in any portion of the examination volume where the ultrasonic beam passes through the cast stainless steel material.(3) The weld overlay examination volume in Fig. 2 shall be ultrasonically L-2012-307 Enclosure I Page 29 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 examined,.
except cast stainless steel base material within the examination volume shall be ultrasonically examined to the extent practicable, to determine if any new or existing planar flaws have propagated into the outer 25% of the base metal thickness or into the overlay. The angle beam shall be directed perpendicular and parallel to the piping axis, with scanning performed in four directions.
(4) The inservice examination acceptance standards of Table IWB-3514-2 shall be met for the weld overlay. If flaw growth in the weld overlay occurs and inservice examination acceptance standards of Table IWB-3514-2 cannot be met, a determination will be made to prove that the flaw is not PWSCC. If the cause is determined to be PWSCC or the cause of the flaw cannot be determined, the flaw shall be repaired and IWB-3600, IWC-3600, or IWD-3600 shall not be used to accept these types of flaws. Flaws due to stress corrosion cracking in the weld overlay that exceed the inservice examination acceptance standards of Table IWB-3514-2 shall not be accepted and result in removal of the weld overlay and the item shall be repaired or replaced.(5) Weld overlay examination volumes in Fig. 2 that show no indication of planar flaw growth or new planar flaws shall be placed into a population to be examined on a sample basis, except as required by 3(c)(1). Twenty-five percent of this population shall be examined at least once during every 10 years.(6) If inservice examinations reveal planar flaw growth, or new planar flaws that meet the inservice examination acceptance standards of IWB-3514 or acceptance criteria of IWB-3600, the weld overlay examination volume shall be reexamined during the first or second refueling outage following discovery of the growth or new planar flaws.(7) For weld overlay examination volumes with unacceptable indications in accordance with 3(c)(4), the weld overlay shall be removed, including the original defective weld, and the item shall be corrected by a repair/replacement activity in accordance with IWA-4000.(d) Additional Examinations.
If inservice examinations reveal unacceptable indications according to 3(c)(4), planar flaw growth into the weld overlay design thickness, or axial flaw growth beyond the specified examination volume, additional weld overlay examination volumes, equal to the number scheduled for the current inspection period, shall be examined prior to return to service. If additional unacceptable indications are found in the second sample, 50% of the total population of weld overlay examination volumes shall be examined prior to return to service. If additional unacceptable indications are found, the entire remaining population of weld overlay examination volumes shall be examined prior to return to service.4 PRESSURE TESTING L-2012-307 Enclosure 1 Page 30 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 A system leakage test shall be performed in accordance with IWA-5000.5 DOCUMENTATION Use of Attachment 2 shall be documented on Form NIS-2.
L-2012-307 Enclosure 1 Page 31 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 A B D c a. Acceptance Examination Volume A-B-C-D 1 /2 in .(m in .) E r -.1/2 in. (min.)(Note 1)ti_4 H \ 4 G b. Thickness (t ) for Table IWB-3514-2
: c. Thickness (t ) for Table IWB-3514-2 Fig. 1 Acceptance Examination Volume and Thickness Definitions Notes: (1) For axial or circumferential flaws, the axial extent of the examination volume shall extend at least Y in.(13 mm) beyond the toes of the original weld.(2) The weld includes the weld end butter, where applied.
L-2012-307 Enclosure I Page 32 of 41 St. Lucie Unit I FOURTH INSPECTION
[NTERVAL RELIEF REQUEST NUMBER 2 Revision 2 I t J1 Examination Volume A-B-C-D NOTES: (1) For axial or circumferential flaws, the axial extent of the examination volume shall extend at least Y in. (13 mm) beyond the as-found flaw and at least Y2 in. (13 mm) beyond the toes of the original weld.(2) The weld includes weld end butter, where applied.Fig. 2 Preservice and Inservice Examination Volume L-2012-307 Enclosure I Page 33 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 MANDATORY APPENDIX I AMBIENT TEMPERATURE TEMPER BEAD WELDING I-1 GENERAL REQUIREMENTS (a) This Appendix applies to dissimilar austenitic filler metal welds between P-Nos. 1, 3, 12A, 12B, and 12C1 materials and their associated welds and welds joining P-Nos. 8 or 43 materials to P-Nos. 1, 3, 12A, 12B, and 1202 materials with the following limitation:
This Appendix shall not be used to repair SA-302 Grade B material unless the material has been modified to include from 0.4% to 1.0% nickel, quenching, tempering, and application of a fine grain practice.(b) The maximum area of an individual weld overlay based on the finished surface over the ferritic base material shall be 300 in.2 (195,000 mm 2).(c) Repair/replacement activities on a dissimilar-metal weld in accordance with this Appendix are limited to those along the fusion line of a nonferritic weld to ferritic base material on which 1/8 in. (3 mm) or less of nonferritic weld deposit exists above the original fusion line.(d) If a defect penetrates into the ferritic base material, repair of the base material, using a nonferritic weld filler material, may be performed in accordance with this Appendix, provided the depth of repair in the base material does not exceed 3'8 in. (10 mm).(e) Prior to welding, the area to be welded and a band around the area of at least 11/2 times the component thickness or 5 in. (130 mm), whichever is less, shall be at least 50'F (100C).(f) Welding materials shall meet the Owner's Requirements and the Construction Code and Cases specified in the Repair/Replacement Plan.Welding materials shall be controlled so that they are identified as acceptable until consumed.(g) Peening may be used, except on the initial and final layers.1-2 WELDING QUALIFICATIONS The welding procedures and operators shall be qualified in accordance with Section IX and the requirements of 1-2.1 and 1-2.2.2 P-Nos. 12A, 12B, and 12C designations refer to specific material classifications originally identified in Section III and subsequently reclassified in a later Edition of Section IX.
L-2012-307 Enclosure I Page 34 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 1-2.1 Procedure Qualification (a) The base materials for the welding procedure qualification shall be of the same P-Number and Group Number as the materials to be welded. The materials shall be post weld heat treated to at least the time and temperature that was applied to the materials being welded.(b) The root width and included angle of the cavity in the test assembly shall be no greater than the minimum specified for the repair.(c) The maximum interpass temperature for the first three layers of the test assembly shall be 150&deg;F (660C).(d) The weld overlay shall be qualified using a groove weld coupon. The test assembly groove depth shall be at least 1 in. (25 mm). The test assembly thickness shall be at least twice the test assembly groove depth. The test assembly shall be large enough to permit removal of the required test specimens.
The test assembly dimensions on either side of the groove shall be at least 6 in. (150 mm). The qualification test plate shall be prepared in accordance with Fig. I-1.
L-2012-307 Enclosure I Page 35 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 GENERAL NOTE: Base metal Charpy impact specimens are not shown.FIG. I-1 QUALIFICATION TEST PLATE (e) Ferritic base material for the procedure qualification test shall meet the impact test requirements of the Construction Code and Owner's Requirements.
If such requirements are not in the Construction Code and Owner's Requirements, the impact properties shall be determined by Charpy V-notch impact tests of the procedure qualification base material at or below the lowest service temperature of the item to be repaired.
The location and orientation of the test specimens shall be similar to those required in 1-2.1(f) below, but shall be in the base metal.(f) Charpy V-notch tests of the ferritic heat-affected zone (HAZ) shall be L-2012-307 Enclosure I Page 36 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 performed at the same temperature as the base metal test of 1-2.1(d) above.Number, location, and orientation of test specimens shall be as follows: (1) The specimens shall be removed from a location as near as practical to a depth of one-half the thickness of the deposited weld metal. The coupons for HAZ impact specimens shall be taken transverse to the axis of the weld and etched to define the HAZ. The notch of the Charpy V-notch specimen shall be cut approximately normal to the material surface in such a manner as to include as much HAZ as possible in the resulting fracture.(2) When the material thickness permits, the axis of a specimen shall be inclined to allow the root of the notch to be aligned parallel to the fusion line.(3) If the test material is in the form of a plate or forging, the axis of the weld shall be oriented parallel to the principal direction of rolling or forging.(4) The Charpy V-notch test shall be performed in accordance with SA-370.Specimens shall be in accordance with SA-370, Fig. 11, Type A. The test shall consist of a set of three full-size 10 mm x 10 mm specimens.
The lateral expansion, percent shear, absorbed energy, test temperature, orientation, and location of all test specimens shall be reported in the Procedure Qualification Record.(g) The average lateral expansion value of the three HAZ Charpy V-notch specimens shall be equal to or greater than the average lateral expansion value of the three unaffected base metal specimens.
However, if the average lateral expansion value of the HAZ Charpy V-notch specimens is less than the average value for the unaffected base metal specimens and the procedure qualification meets all other requirements of this appendix, either of the following shall be performed.
(1) The welding procedure shall be requalified.
(2) An Adjustment Temperature for the procedure qualification shall be determined in accordance with the applicable provisions of NB-4335.2 of Section III, 2001 Edition with 2002 Addenda. The RT NDT or lowest service temperature of the materials for which the welding procedure will be used shall be increased by a temperature equivalent to that of the Adjustment Temperature.
1-2.2 Performance Qualification Welding operators shall be qualified in accordance with Section IX.1-3 WELDING PROCEDURE REQUIREMENTS The welding procedure shall include the following requirements: (a) The weld metal shall be deposited by the automatic or machine GTAW L-2012-307 Enclosure I Page 37 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 process.(b) Dissimilar metal welds shall be made using A-No. 8 weld metal (QW-442)for P-No. 8 to P-No. 1, 3, or 12 (A, B, or C)1 weld joints or F-No. 43 weld metal (QW-432) for P-No. 8 or 43 to P-No. 1, 3, or 12 (A, B, or C)1 weld joints.(c) The area to be welded shall be buttered with a deposit of at least three layers to achieve at least W8 in. (3 mm)- overlay thickness with the heat input for each layer controlled to within +/-10% of that used in the procedure qualification test. The heat input of the first three layers shall not exceed 45 kJ/in. (1.8 kJ/mm)under any conditions.
Particular care shall be taken in the placement of the weld layers of the austenitic overlay filler material at the toe of the overlay to ensure that the HAZ and ferritic base metal are tempered.
Subsequent layers shall be deposited with a heat input not exceeding that used for layers beyond the third layer in the procedure qualification.(d) The maximum interpass temperature for field applications shall be 350&deg;F (180&deg;C) for all weld layers regardless of the interpass temperature used during qualification.
The interpass temperature limitation of QW-406.3 need not be applied.(e) The interpass temperature shall be determined by one of the following methods: (1) Temperature measurement (e.g. contact pyrometers, temperature indicating crayons, or thermocouples) during welding. The interpass temperature shall be monitored to assure Code Compliance to limit radiation dose as follows: Interpass temperature measurements will be taken every three to five passes on the first three layers and every six to ten passes after the first three layers.(2) heat flow calculations using the variables listed below as a minimum: (a) welding heat input (b) initial base material temperature (c) configuration, thickness, and mass of the item being welded (d) thermal conductivity and diffusivity of the materials being welded (e) arc time per weld pass and delay time between each pass (f) arc time to complete the weld (3) measurement of the maximum interpass temperature on a test coupon that is equal to or less than the thickness of the item to be welded. The maximum heat input of the welding procedure shall be used in the weld testing of the test coupon.(f) Particular care shall be given to ensure that the weld region is free of all potential sources of hydrogen.
The surfaces to be welded, filler metal, and shielding gas shall be suitably controlled.
L-2012-307 Enclosure 1 Page 38 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Page is intentionally left blank L-2012-307 Enclosure 1 Page 39 of 41 St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 ATTACHMENT 3 Barrier Layer to Prevent Hot Cracking in High Sulfur Stainless Steel Background 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.Discussion The flaw characteristics observed above are indicative of hot cracking.
This phenomenon has not been observed on the ferritic steel or ENiCrFe-3 (Alloy 182)DMW portions of the assemblies when welding Alloy 52M thereon.Further studies have determined that this problem may occur when using Alloy 52M filler metal on austenitic stainless steel materials with high sulfur content.Extensive tests and field experience from WSI indicate that hot cracking can be a concern when the sulfur and phosphorus content in the diluted weld puddle equals or exceeds 0.014%. The impurity hot cracking threshold level is a function of both the composition of the weld filler materials and the welding parameters that are used because these two factors control the dilution of the solidified weld deposit. This suggests that a combined sulfur plus phosphorus content of the base material approximately 0.046% will represent a threshold for hot cracking with the weld parameters WSI will use at St. Lucie.To reduce the susceptibility of hot cracking occurrence due to welding Alloy 52M on the stainless steel base materials with high sulfur, WSI has selected ER308L or ER309L filler metal as the preferred filler metals to provide a barrier layer between the Alloy 52M and the high sulfur stainless steel base material.
These filler metals are compatible with the base material and promote 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.
These filler L-2012-307 Enclosure 1 Page 40 of 41 St. Lucie Unit I FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 metals are also compatible with the Alloy 52M subsequently welded thereon.However, the barrier layer may consist of ERNiCr-3 (Alloy 82) being used locally at the interface between the Alloy 182 DMW and the stainless steel item.ER308L or ER309L welding on Alloy 182 may result in cracking of the ER308L or ER309L weld. Welding on high sulfur stainless steel with Alloy 82 has not been a concern relevant to hot cracking occurrence.
WSI welded two mockups to evaluate the interactive effects, such as hot cracking and lack of fusion, between the Alloy 82/182 DMW, the stainless steel base material, the ER308L and the subsequent Alloy 52M weld overlay. One mockup assembly consisted of a stainless steel pipe (approximately 0.050 wt%sulfur and phosphorus combined) and an ASTM A106 Grade B pipe with an Alloy 82 groove weld joining them. The second mockup consisted of a stainless steel pipe joined to a cast stainless steel pipe with a stainless butt weld. The other end of the cast stainless steel pipe was joined to a P3 forging using an Alloy 82 groove weld.For both mockups the barrier layer and overlay were welded in the same sequence as performed in the field (barrier layer ER308L to within 1/8" of the joining DMW and then four or more layers of Alloy 52M overlay).
The barrier layer and overlay welding parameters used in the mockup were similar to those used in the field and controlled the weld dilution by controlling the weld heat input and the Power Ratio.The following examinations were performed on the final mockup:* PT was performed on the base materials and joining groove welds* PT was performed on the ER308L barrier layer* PT was performed on the first layer of Alloy 52M overlay and on the final layer of the weld overlay* PDI qualified Phased Array UT was performed on the completed mockup One recordable (not rejectable) planar UT indication of less than 0.200" in length was found on one of the mockups unrelated to the barrier layer. Subsequent metallographic examination found this likely to be porosity.
Metallographic examination was conducted at EPRI searching for any type of discontinuity, flaw or other anomaly. All samples were removed from selected locations in both mockups and revealed no conditions of concern.
L-2012-307 Enclosure 1 Page 41 of 4l St. Lucie Unit 1 FOURTH INSPECTION INTERVAL RELIEF REQUEST NUMBER 2 Revision 2 Conclusion St. Lucie Unit 1 will use the barrier layer on all the stainless steel items prior to overlay. The barrier layer will use ER308L or ER309L on the stainless steel and may use Alloy 82 on the stainless steel near the DMW to stainless steel fusion zone only.Structural credit will not be assumed for the barrier layer in determining the required minimum overlay thickness since the alternative does not address the use of stainless steel filler metal.The barrier layer welding will be performed in accordance with ASME Section IX qualified welding procedure specification(s).
PT 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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