ML13078A297

Enclosure 1, Inservice Inspection (ISI) Relief Request REP-1 U2, Revision 2 in Accordance with 10 CFR 50.55a(a)(3)(i)

ML13078A297
Person / Time
Site:	Diablo Canyon
Issue date:	03/05/2013
From:	Pacific Gas & Electric Co
To:	Office of Nuclear Reactor Regulation
Shared Package
ML130780374	List: DCL-13-021, Performance Demonstration Initiative (POI) Program Alternatives and Their Bases with Respect to ASME Code Section Xi, Appendix Viii Supplement 11 Requirements ML13078A291 ML13078A292 ML13078A293 ML13078A294 ML13078A297
References
DCL-13-021
Download: ML13078A297 (43)

Text

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 INSERVICE INSPECTION (lSI) RELIEF REQUEST REP-1 U2, Revision 2 In Accordance with 10 CFR SO.SSa(a)(3)(i)

USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE

--Alternative Provides Acceptable Level of Quality and Safety--1. ASME Code Component Affected Code components associated with this request are high safety significant Class 1 dissimilar metal welds (DMWs) with Alloy 82/182 weld metal in the pressurizer nozzle-to-safe end connection that are susceptible to primary water stress corrosion cracking (PWSCC). There are six dissimilar metal welds that have had preemptive full structural weld overlays (SWOLs) applied in accordance with Revision 1 of this Relief Request. In addition, the SWOLs extend across the six adjacent stainless steel pipe-to-safe end similar metal welds. These welds had SWOLs applied during the Diablo Canyon Power Plant (DCPP) Unit 2 Fourteenth Refueling Outage (2R 14) in 2008. 1.1 Category and System Details: Code Class: ASME Class 1 System Welds: Reactor Coolant System Examination Categories:

B-F (Risk-informed Category R-A) Note: Following weld overlay installation, inservice inspections (lSI) during the third inspection interval will be performed in accordance with the requirements of this relief request. 1.2 Component Descriptions:

The application of this alternative is to apply SWOLs on one potentially PWSCC-susceptible safe end-to-pressurizer surge nozzle DMW, three safe end-to-safety nozzle DMWs, one safe end-to-relief nozzle DMW, and one safe end-to-spray nozzle DMW. The SWOLs extend outward across the adjacent stainless steel pipe-to-safe end welds. The applicable weld identification is as follows: a) Weld No. WIB-439SE Safe End -To-Surge Nozzle Weld and adjacent Pipe-to-Safe End Weld No. WIB-438 Line Identifier 2-*-16-14SPL (Surge Nozzle) 1 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled

..

Enclosures 3 and 4 contain Propri e tary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 b) Weld N o. W IB-369 S E S a f e E nd-to-80 1 O A S afe t y No zzle W e ld and adjacent Pipe-to-Safe End Weld No. WIB-369 Line Identifier 2-S6-729-6 (Safety Nozzle A) c) Weld No. WIB-423SE Safe End-to-8010B Safety Nozzle Weld and adjacent Pipe-to-Safe End Weld No. WIB-423 Line Identifier 2-S6-728-6 (Safety Nozzle B) d) Weld No. WIB-359SE Safe End-to-8010C Safety Nozzle Weld and adjacent Pipe-to-Safe End Weld No. WIB-359 Li ne Identifier 2-S6-72 7 -6 (Safety Nozzle C) e) Weld No. WIB-380SE Safe End-to-Relief Nozzle Weld a nd adjacent Pipe-to-Safe End Weld No. WIB-380 Line Identifier 2-S6-730-6 (PORV Nozzle) f) Weld No. WIB-345SE Safe End-to-Spray Nozzle Weld and adjacent Pipe-to-Safe End Weld No. WIB-345 Line Identifier 2-S6-15-4SPL (Spray Nozzle) 1.3 Component Materials:

a) Nozzles are Low Alloy Steel SA-508 CL2 (P-No. 3 Group No.3) b) Safe End-to-Nozzle Welds and Buttering are Alloy 82/182 (F-No.43) c) Safe Ends are Wrought Stainless Steel SA-182 GR F316L (P-No.8) d) Attached Pipe is Wrought Seamless Stainless Steel SA-376 Type 316 (P-No. 8) and Welds are Stainless Steel (A-No.8) e) Pre-SWOL barrier layers were applied as follows: ER309L for the stainless steel base and weld metal, and ERNiCr-3 (Alloy 82) used locally at the interface between the Alloy 182 DMW and the stainless steel. f) SWOL consisting of ERNiCrFe-7 A (Alloy 52M) weld metal. The welding was performed to the requirements of Revision 1 using a remote machine gas tungsten arc welding (GTAW) process and the ambient temperature temper bead method. The materials listed above apply to all pressurizer nozzles. 2. Applicable Code Edition and Addenda DCPP Unit 2 is currently in the third 10-year lSI interval.

The ASME Boiler and Pressure Vessel Code (Code) of record isSection XI, 2001 Edition, including Addenda through 2003 (Reference 8.1) for the current 10-year lSI interval and the Repair/Replacement and lSI Program. ASME Code Section XI, 2001 Edition,'no Addenda, Appendix VIII, Supplement 11 , 2 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is de c ontrolle d.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 (R efe r e n ce 8.2) as i m ple m ente d by t he Perfor m a n ce D e mon stratio n Initiative (POI) Program, is used for ultrasonic examination qualification f or SWOLs. ASME Code Section XI, Appendix Q, 2004 Edition with 2005 Addenda (Reference 8.5) is used for SWOL lSI requirements for the remainder of the third inspection interval, nominally scheduled to end March 13, 2016. 3. Applicable Code Requirement The applicable Code requirement for which relief is requested is ASME Code Section XI, 2001 Edition, including Addenda through 2003, IWA-4410 and IWA-4611 (Reference 8.1), and ASME Code Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement

11. (Reference 8.2) IWA-4410 states, in part, the following: "Welding, brazing, defect removal, ..... and installation shall be performed in accordance with this Subarlicle." IWA-4611.1 (a) states, in part, the following: "Defects shall be removed in accordance with IWA-4422.1.

A defect is considered removed when it has been reduced to an acceptable size." IWA-4611.2(a) states, in part, the following: "After final processing, the affected surfaces, including surfaces of cavities prepared for welding, shall be examined by the magnetic parlicle or liquid penetrant method to ensure that the indication has been reduced to an acceptable size in accordance with IWB-3500." 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. Reason for Request DMWs, primarily consisting of Alloy 82/182 weld metal, were frequently used in pressurized water reactor (PWR) construction to connect stainless steel safe ends to vessel nozzles, which are constructed of carbon or low alloy ferritic steel. These welds have shown a potential for PWSCC degradation, especially in components subjected to high operating temperatures such as the pressurizer.

See EPRI MRP-169 "Technical 3 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 Basis fo r Pr eemp t ive Wel d O ver l ays f or A ll oy 8 2/1 8 2 Butt W el ds i n PWRs," O ctober 2005 (Refere n ce 8.3). During 2R14, 6 DMWs located on the pressurizer had SWOLs applied in accordance with Revision 1. 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. ASME Code Section XI, 200 1 Edition, including Addenda through 2003 (Reference 8.1), IWA-4410 and IWA-4611, 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 for mitigation of potential PWSCC are not currently available for application of SWOL repairs to DMWs constructed of Alloy 82/182 weld material.

In addition, ASME Code Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement 11 (Reference 8.2), cannot be implemented as written for ultrasonic examination of a SWOL repair. Enclosure 2 includes a discussion of the POI Program alternatives and their bases with respect to Appendix VIII, Supplement 11 requirements.

Section 5.0 provides alternatives to the repair/replacement requirements of the ASME Code Section XI, 2001 Edition, including Addenda through 2003 (Reference 8.1), IWA-4410 and IWA-4611 and ASME Code Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement

11. (Reference 8.2) 5. Proposed Alternative and Basis for Use This request proposes the use of the alternative requirements included in Attachment 1, for the 6 SWOLs for PWSCC-susceptible safe nozzle welds of the pressurizer.

These SWOLs include the 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. Installation of the proposed alternative was performed during 2R14 in February 2008. Revision 1 of this proposed alternative is the result of industry experience with weld overlay modifications for potentia l or known flaws caused by 4 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decont r olle d.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 PWSCC , and directly applies to the Alloy 52 or 52M weld material that was primarily used for these SWOLs. Revision 2 of this proposed alternative addresses newly detected fabrication-related flaws identified in four of the SWOLs during Unit 2's seventeenth refueling outage (2R17), as described in Table 1. The ultrasonic examination of the completed SWOLs was accomplished with personnel and procedures qualified in accordance with ASME Code Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement 11 (Reference 8.2), as implemented by the POI program. 5.1 SWOL Design The SWOLs satisfy all the structural design requirements of the pipe, as specified in the alternative requirements in Attachment

1. As shown in Figure 1, the SWOLs completely cover the existing Alloy 82/182 weld and 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 extend around the entire circumference of the nozzle. Alloy 52M and 52 filler metals are compatible with all the wrought base materials and the DMWs and similar metal welds that are covered by the SWOL. The SWOLs are designed as full structural overlays to repair the assumed worst case flaw in accordance with the alternative requirements in Attachment

1. The design analyses for the preemptive structural weld overlays are available at the plant for NRC review. 5.2 Welding The welding was performed in accordance with the alternative requirements in Attachment 1 using a remote machine gas tungsten-arc welding (GTAW) process and 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 inch away from the low alloy steel nozzles. Industry experience through 2007 from weld overlay activities using ERNiCrFe-7A (Alloy 52M) and ERNiCrFe-7 (Alloy 52) revealed a potential for flaws in the first layer deposited on the austenitic stainless steel portions (safe ends, pipe etc.) of the assemblies.

5 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter OCL-13-021 The flaw characteristics observed in the first layer are indicative of hot cracking.

This phenomenon has not been observed on the ferritic steel or ENiCrFe-3 (Alloy 182) OMW portions of the assemblies when Alloy 52M is used for the first layer. 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 performed through 2007 have concluded that welding with Alloy 52M on stainless steel base material with 0.020 wt% sulfur results in cracking.

Conversely, welding on stainless steel base materials with less than 0.010 wt% has resulted in no cracking.

OCPP Unit 2 material composition records indicate that the possibility of hot cracking due to the influence of sulfur in existing base materials could not be ruled out. In order to minimize the occurrence of hot cracking, one or more barrier layers were applied to all stainless steel items prior to Alloy 52M overlay. The barrier layer(s) are ER309L for the stainless steel base and weld metal, and Alloy 82 for the OMW fusion zone and adjacent stainless steel heat affected zone. The barrier layer is not credited in the structural analysis or in the crack growth analysis.

See Attachment 2 for additional barrier layer information.

5.3 Examination

The original configuration of the pre-overlay OMWs did not permit an ASME Code Section XI, Appendix VIII Supplement 10 ultrasonic examination to obtain greater than 90 percent coverage of the required examination volume. Therefore, none of the welds received a pre-weld overlay ultrasonic examination.

All overlay examinations have met the alternative requirements in Attachment

1. The ultrasonic examination qualification was in accordance with ASME Code Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement 11 (Reference 8.2), as implemented by the POI Program. See Enclosure 2 for a comparison of differences between Appendix VIII and the POI program. 6 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021

5.4 Considerations

for Hydrogen Cracking Ultrasonic and surface examinations of the completed overlay were performed on the temper bead portion of the SWOLs at least 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 Paragraphs 3(a)(2) and 3(a)(3), Attachment

1. The 48-hour delay provided time for delayed hydrogen cracking occurrence.

Attachment 1, 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 is inherently free of hydrogen.

The GTAW process relies on a bare welding electrode 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 were used to ensure the base metal, shielding gas, welding electrodes, filler metal and weld region were 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 resulting in achievement of lower hardness and tempered martensite.

This further reduces susceptibility to induced cracking.

EPRI Report 1013558, "Temperbead Welding Applications, 48-Hour Hold Requirements for Ambient Temperature Temperbead Welding," Technical Update, December 2006 (Reference 8.4), provides justification for allowing 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. EPRI Report 1013558 addresses microstructural issues, hydrogen s*ources, tensile stress and temperature, and diffusivity and solubility of hydrogen in steels. Furthermore, past industry experience with the use of the machine or automatic GTAW process has resulted in no detection of hydrogen-7 Enclosures 3 and 4 contain Proprietary Informat i on When separated from Enclosures 3 and 4 , this document is decontrolle

d.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 induced crack ing after the 48-hour hold nondestructive examination (NDE) or subsequent lSI. Code C ase 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 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. 5.5 Acceptance and Preservice Examinations and Results All nozzles received acceptance examinations (including liquid penetrant examinations) and preservice examinations upon installation in 2008 using the following qualified conventional ultrasonic techniques:

Axial direction:

• O-degree (straight beam)

• OD "creeping wave"

• 70 degree refracted longitudinal beam (RL),

• 60 degree RL

• 45 degree RL Circumferential direction

• 00 "creeping wave"

• 60 degree RL

• 45 degree RL

• 70 degree RL (surge nozzle only)

• 40 degree RL (Spray Line) These examinations recorded acceptable laminar reflectors in Safety Nozzle A characterized as lack of bond at the SWOL interface with the nozzle low alloy steel base metal and no other recordable indications were identified.

5.6 Continuing

Inservice Inspections and Results During DCPP's Unit 2 fifteenth refueling outage (2R15) in October 2009, all the nozzles received lSI ultrasonic examinations of the lSI volume using the following qualified conventional techniques:

Axial direction:

• 45-degree RL

• 60-degree RL Circumferential direction (all nozzles) 8 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021

• 45 degree RL Circumferential direction additional scans Spray nozzle:

• 40 degree RL and 60 degree RL scans Surge nozzle

• 60 degree RL scans. 100 percent of the lSI volumes were reported to be covered and no reportable flaw indications were detected.

In Safety Nozzle A SWOL, two indications were detected outside the lSI volume that were recorded as unchanged from the preservice examination data after SWOL installation.

During DCPP's 2R17, the Safety Nozzle B SWOL was scheduled for lSI examination.

The lSI examination of Safety Nozzle B was conducted using Section XI, Appendix VIII, Supplement 11 qualified phased array ultrasonic techniques in lieu of the qualified discrete angle conventional ultrasonic techniques used during previous examinations.

The phased array examinations use inclusive angles from approximately O-degrees through 85 degrees simultaneously and have enhanced sensitivity to reflectors oriented off-normal compared to the discrete angles used in conventional ultrasonic techniques.

2R17 lSI of Safety Nozzle B The phased array examination detected three narrow aligned reflectors transverse to the pipe axis at the upstream (nozzle) end of the lSI volume. The reflectors were not recorded during the acceptance examination nor the 2R15 lSI ultrasonic examination that used qualified conventional ultrasonic techniques.

The recorded phased array indications are required to be aggregated in conformance with Section XI, IWA-3360-1, resulting in reported dimensions (corrected and length reduced for outside diameter/indication plane diameter ratio) of 4.7 inches by 0.25 inches as identified in Table 1. The combined reflector is characteristic of, and is evaluated as, incomplete bond between the SWOL and low alloy steel base metal and associated incomplete inter-bead fusion in the SWOL application.

The portion of Safety Nozzle B containing the indications was also examined using qualified conventional O-degree ultrasonic techniques and equipment essentially identical to those used during the 2R 14 acceptance examinations.

This examination was focused on the identified indications area. Laminar type indications of low amplitude, generally corresponding to those identified by phased array but of shorter length, were identified.

These indications were determined to be recordable, however the shorter 9 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 length did not require aggregation per Section XI, IWA-3360-1 and thus were acceptable to Revision 1. As a result of the indications detected in Safety Nozzle B, the lSI scope was ultimately expanded to include qualified ultrasonic phased array examinations of the remaining SWOLs. A summary of the phased array examination results applicable to this Relief Request Revision 2 are shown in Table 1. Following any qualified phased array examinations that identified new indications in the remaining nozzles, additional partial examinations were performed using essentially identical conventional O-degree equipment and techniques as those used during the initial acceptance examinations.

These partial examinations were performed for additional information only, to determine if the new indications could have been detectable during the original acceptance examinations.

These scans did not constitute a qualified examination per Section XI, Appendix VIII, Supplement 11 as implemented by POI, and results of those scans are discussed here for information only. 2R17 Additional lSI of the PORV Nozzle and Surge Nozzle During the expanded scope qualified phased array examinations, the PORV Nozzle and Surge Nozzle SWOLs were confirmed to have no recordable indications.

2R17 Additional lSI of Safety Nozzle A Safety Nozzle A had acceptable laminar reflectors recorded during the original acceptance examination using qualified conventional O-degree and 45 degree ultrasonic techniques with the 45 degree results confirmed unchanged during the 2R15 lSI examination.

During the 2R17 phased array examination, additional lengths of the previously recorded reflectors and three spot reflectors were detected.

The indications are also oriented transverse to the pipe axis on the upstream (nozzle) side of the lSI volume, but farther upstream (at the original nozzle surface geometric transition, outside of the lSI volume) than those on Safety Nozzle B. Figure 1 of Attachment 1 shows the acceptance examination volume does not extend to include the nozzle geometric transition where part of the indication is located. Although that portion of the reflector may lie outside the acceptance examination volume, it is conservatively included in the acceptance analysis.

The overall dimensions of the combined reflectors (corrected and length reduced for relative diameters) is 16.3 inches by 0.40 inches as identified in Table 1. The combined reflector is characteristic of, and is evaluated as, incomplete bond between the 10 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decon t rolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E letter DCl-13-021 SWOl and low alloy steel base metal and associated incomplete bead fusion in the SWOl application.

During the informational

' conventional O-degree scans of Safety Nozzle A, laminar type indications corresponding to the phased array indications were detected and estimated to be recordable when using the criteria of Revision 1. It is estimated these indications in Nozzle A would be similar to though shorter than those detected by phased array. 2R17 Additional lSI of Safety Nozzle C Safety Nozzle C had no recordable indications identified prior to 2R17. The phased array examination detected a laminar reflector located wall in the SWOl, 0.30 inches below the surface. The reflector is located in the lSI volume of the SWOl, over the original stainless steel safe-end and is oriented circumferentially.

The reflector dimensions (corrected and reduced for relative diameters) are 1.85 inches by 0.25 inches. A separate laminar type reflector transverse to the pipe axis at the upstream edge of the original nozzle surface geometric transition and outside of the lSI volume, at or near the interface between the SWOl and low alloy steel base metal with corrected length of 0.68 inches and width of 0.25 inches was also detected, as were two spot indications.

All these reflectors are characteristic of and are evaluated as incomplete inter-bead fusion in the SWOl application.

These indications have been evaluated to meet the acceptance criteria of Revision 1 of this relief request. During the informational conventional O-degree scans of Safety Nozzle C, laminar indications corresponding to the phased array indications were detected and estimated to be recordable when using the criteria of Revision 1. It is estimated the indications in Safety Nozzle C are similar in size and location to those identified using the qualified phased array techniques and thus would meet the criteria in Revision 1. 2R17 Additional lSI of the Spray Nozzle The Spray Nozzle had no recordable indications identified prior to 2R 17. The ultrasonic phased array examination detected discrete and intermittent indications as recorded on the examination reports. Indication 1 is seen intermittently for 20.1 inches around the circumference and indication 4 is observed concurrently for 1.72 inches, as identified in Table 1. The indications are on the downstream (nozzle) side of the SWOl near the geometric transition in the original low alloy steel nozzle profile. The combined width of the two indications 11 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-02 1 is 0.42 inches. This combined reflector is characteristic of, and is evaluated as, incomplete bond between the SWOL and low alloy steel base metal and associated incomplete inter-bead fusion in the SWOL application.

Although the indications could be further resolved to reduce the recordable length, the overall length is conservatively used in Section 5.8 below. Indications 2 and 3 are observed concurrently as a laminar reflector

0.8 inches

long by 0.312 inches wide oriented circumferentially at the interface between the SWOL and the underlying stainless steel pipe weld. This indication is characteristic of, and evaluated as, incomplete bond with the stainless steel and associated incomplete inter-bead fusion in the SWOL. These indications are acceptable to Revision 1 and are not included in Table 1. During the informational conventional O-degree scans of the Spray Nozzle, laminar indications corresponding to the phased array indications were detected and estimated to be recordable when using the criteria of Revision 1. It is estimated the indications in the Spray Nozzle would be similar to though shorter than those detected by phased array. As a result, the 360 degree intermittent reflectors may resolve into more numerous but smaller aggregated flaws. 5.7 Engineering Basis For Characterizion of 2R17 Flaws As Overlay Lack of Bond/lnterbead Lack of Fusion A review of 2R17 SWOL phased array ultrasonic testing (UT) examinations concluded that the indications are characteristic of "Lack of Bond" (LOB) or "Interbead Non Fusion" (ILOF). The factors that lead to this determination are noted below:

• LOB and ILOF are common overlay flaws

• A common location for these type of flaws is at the interface of the weld overlay and the base material

• The majority of the flaws are located over the low alloy nozzle base material.

No potential for PWSCC flaws exists at that location.

• These type flaws are primarily laminar and may contain some very small planar content

• The vendor has experienced issues with LOB between the overlay and base material during similar overlay installations

• UT phased array signal responses are prevalent at lower angles of interrogation.

12 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolle

d.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021

• No through wall dimensions can be measured in any of the indicat ions. Conserva tive assignment of through-wall dimensions were assigned for "stacked" laminar indications.

• Indications are circumferential, following installation bead paths

• Indications have limited width, sized conservatively at 0.25 inches, which equates to the expected large phased array UT transducer oversizing of the approximate width of one bead (0.150 inches).

• Indications can be recorded with conventional UT zero degree transducer, which would only be sensitive to reflectors with surfaces primarily parallel to outside surface of weld overlay.

• Baseline conventional UT zero degree data also recorded a similar indication on nozzle A. This indicates flaw was introduced during installation; this reflector has UT signal envelope information similar to the others.

• Time encoded phased array data was reviewed by industry experts who concur with the characterization (Reference EPRI Internal Report IR-2013-541, "Review of Ultrasonic Examinations Performed at Diablo Canyon Nuclear Power Plant during the Inservice Examination of Emptive Weld Overlays During 2R17," dated February, 2013 * " Industry research by sectioning weld overlay test specimens has noted laminar flaws with varying amounts of interbead non fusion. This type of "crescent" shaped flaw will return the signal characteristics that were recorded on these indications.

5.8 2R17 Inservice Inspection Volume Coverage The potential for the reflectors detected by phased array to mask a portion of the lSI volume from ultrasonic examinations was also evaluated.

Attachment 1, Section 3(a)3(b) requires that the reduction in coverage of the examination volume due to laminar flaws shall be less than 10 percent. Figure 2 depicts typical techniques used to determine accessible percentages of inspection areas and volumes. In general, scaled drawings for both axial and circumferential orientations are made from outside diameter (00) surface contours measured before and after the SWOLs are installed.

Ultrasonic thickness measurements are used to determine inside diameter location and relative geometric positions.

The required examination volumes and any ultrasonic reflectors that may occlude a portion of the volume are then plotted on these drawings.

Scan angles are projected through the required volumes as accessible to determine coverage.

13 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 For Safety Nozzle A, no part of the lSI volume is occluded from ultrasonic exam inatio n by the laminar reflector and is thus acceptable, as identified in Table 1. For Safety Nozzle B, the area occluded by th e laminar reflector from ul trasonic examination in either axial or transverse directions is less than 2 percent of the required examination volume and is thus acceptable, as identified in Table 1. For Safety Nozzle C, the area occluded by the laminar reflector from ultrasonic examination in either axial or transverse directions is less than 1 percent of the required examination volume and is thus acceptable, as identified in Table 1. For the Spray Nozzle, the larger laminar reflectors do not occlude any part of the lSI volume from ultrasonic examination.

For the small reflector located above the stainless steel weld, the area occluded by the laminar reflector in either axial or transverse directions is less than 1 percent of the required examination volume and is thus acceptable, as identified in Table 1. 5.9 Evaluation of Indications Exceeding the Criteria of Revision 1 All recordable indications from Safety Nozzle A, Safety Nozzle B, Safety Nozzle C, and Spray Nozzle were evaluated in accordance with the acceptance criteria contained in Section 3 of Attachment

1. Some indications did not fully meet the Acceptance Examination criteria contained in Section 3(a), of Attachment 1; these indications are listed in Table 1 and discussed below. AREVA Calculation 32-9199937-000, "DCPP Unit 2 -Evaluation of Laminar Indications in Pressurizer Nozzles" and AREVA Calculation 32-9199805-000, "Diablo Canyon Power Plant Unit 2 Pzr Safety and Spray Nozzles Planar Flaw Analysis" provide additional technical details to support the conclusions below. Safety Nozzle A Indications 1 and 1A were evaluated against Section XI, Table IWB-3514-3 with a surface area of 4.9 in 2 vs. an allowable of 7.5 in 2 and found to be acceptable.

Indications 1 and 1A, while being primarily laminar in nature, were conservatively assumed to have a 0.080 inch through-wall dimension, and evaluated against Section XI, Table IWB-3514-2 and found to be acceptable.

14 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 Indications 1 and 1 A have a length of 16.3 inches compared to an allowable of 3.0 inches. The Safety No zzle A geometry and SWOL length excluding these i ndications have been evaluated and determined to be sufficient to transfer the load through shear back to the base metal, conservatively considering a 100 percent through wall crack in the PWSCC susceptible material.

A conservative criterion for maximum allowable shear stress from ASME III, NB-3227.2 was utilized.

These indications are acceptable as-is due to the ample amount of structural integrity margin in the remaining weld overlay. AREVA Calculation 32-9199937-000 provides a quantitative and conservative assessment of this margin. Safety Nozzle B Indications 1, 2, and 3 were evaluated against ASME Section XI, Table IWB-3514-3 with a surface area of 0.9 in 2 vs. an allowable of 7.5 in 2 and found to be acceptable.

Indications 1, 2, and 3 have a combined length of 4.7 inches compared to an allowable of 3.0 inches. The Safety Nozzle B geometry and SWOL length excluding these indications have been evaluated and determined to be sufficient to transfer the load through shear back to the base metal, conservatively considering a 100 percent through wall crack in the PWSCC susceptible material.

A conservative criterion for maximum allowable shear stress from ASME III, NB-3227.2 was utilized.

These indications are acceptable as-is due to the ample amount of structural integrity margin in the remaining weld overlay. AREVA Calculation 32-9199937 -000 provides a quantitative and conservative assessment of this margin. Spray Nozzle Indications 1 and 4 were evaluated against Section XI, Table IWB-3514-3 with a surface area of 6.3 in 2 vs. an allowable of 7.5 in 2 and found to be acceptable.

Indications 1 and 4 have a combined length of 20.1 inches compared to an allowable of 3.0 inches. The Spray Nozzle geometry and SWOL length excluding these indications have been evaluated and determined to be sufficient to transfer the load through shear back to the base metal, conservatively considering a 100 percent through wall crack in the PWSCC susceptible material.

A conservative criterion for maximum allowable shear stress from ASME III, NB-3227.2 was utilized.

These indications are acceptable as-is due to the ample amount of structural integrity margin in the remaining weld overlay. AREVA 15 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decon tro lle d.

Enc l osures 3 and 4 contain Proprietary Information

-W i thhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter OCL-13-021 C alculatio n 3 2-91999 37-000 p ro v id es a q u ant i ta t iv e assessment of th i s margi n. 5.10 Apparent C ause of I ncomplete Weld Bond and Incomplete In t erbead Fusion The indications identified during the 2R17 outage lSI examination exhibited characteristics similar to LOB and or ILOF. This section discusses apparent causes fo r these types of weld dis con tinuitie s. Filler metals with 30 percent chromium, such as Alloy 52M, are recognized as being very sluggish (low fluidity) filler metals to weld. This sluggishness is due to its higher viscosity creating an inherent slower response of the filler metal to changes normally occurring during welding. This sluggishness is more noticeable on first layer welds due to the dilution of the low alloy steel substrate of the component, and may even be apparent on the second layer until the weld chemistry becomes more consistent on the third and remaining layers of the SWOL. Even though more welding discontinuities might be expected when welding out of position and when using Alloy 52M filler metal, discontinuities may occur regardless of welding position.

A typical overlay contains hundreds of weld beads and the small, incomplete fusion (i.e., minimal through thickness dimension) discontinuities are not detrimental to the structural integrity of the SWOL and are mitigated through the robust overlay design criteria.

In summary, to address these concerns, overlays are designed to ensure these small, laminar type (i.e., minimal through thickness dimension) . discontinuities are not detrimental to the structural integrity of the SWOL and are mitigated through robust design. The UT acceptance criteria allows for permissible laminar type flaws to address the welding challenge of the 30 percent chromium alloys. 5.11 Apparent Cause of Original Acceptance Examination Indications Not Recorded There are inherent differences between the conventional UT techniques and the phased array techniques used to examine these weld overlays.

The conventional technique utilizes 6 discrete and fixed examination angles (0°, 40°,45°,60°,70° and 00 creeping wave), whereas the 16 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 phased a r ray technique generate s every ang l e rangi n g fr om 0° throu g h 85°. Additionally there is a significant difference in examination sensitivity used for detecting lack of fusion/bond flaws in the overlay material.

The phased array technique examination sensitivity is generally twice (+6dB) that of the conventional technique.

This can result in the phased array having increased sensitivity to small flaws detected with 0° through 25° angle range as compared to the 0° conventional techniques.

This increased sensitivity can also result in small flaws being more readily detectable with the phased array technique versus the conventional technique.

The flaw present in the subject weld overlays generally has a small cross section, and limited in through-wall extent and axial (width) dimension to one weld bead or less in size. Due to the small size, the reflective area of this flaw type is limited and thus produces conventional UT responses that are relatively low level and at times difficult to discriminate from the inherent background signal noise associated with performing UT on weld material.

Based on the characteristics and sizes of these flaws it is likely that the conventional 0° UT technique applied during the original acceptance examinations may not have produced a significant enough flaw response to alert the NDE examiner to the presence of these flaws. This is substantiated by the fact that a portion of the flaw(s) identified in Safety Nozzle A was detected during the acceptance examination; however an increased flaw length dimension was reported with the phased array technique.

Additionally, it is concluded that due to the characteristics and orientations of the flaws, the phased array techniques are more likely to produce readily recognizable UT responses over a larger surface scanning area thereby increasing the probability of flaw detection by the NDE examiner.

This conclusion is substantiated by the fact that the flaw indications obtained with the phased array technique produced responses with angles ranging from approximately 15° through 30°. This range of angles is not present in the conventional UT technique.

Both the conventional UT and phased array UT techniques have been qualified for use through the POI program's implementation of Section XI, Appendix VIII requirements.

As such both techniques have met the same qualification acceptance criteria and level of qualification rigor. Both of 17 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this documen t is de c on tro lle d.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 these UT techniques have been widely used by the nuclear industry and both techniques have demonstrated the ability to readily detect and characterize flaws of safety significance, during multiple qualifications.

Based on the previous discussion Pacific Gas and Electric Company (PG&E) has concluded that the apparent cause for the subject flaws not being identified during the original NDE acceptance examinations is directly related to flaw size and orientation, the differences in the applied NDE examination technology, and the examination sensitivity used. When using the conventional technique, the physical manipulation necessary to develop recordable indications is more demanding than that required when using the phased array technique with its additional angles. Additional rigor was required in order to obtain the responses, which could be the contributing cause for the examiners not reporting the flaws during the acceptance examination.

5.13 Potential Hardship Consideration of material removal and localized repair welding of the structural overlays may result in redistribution of the stress profiles and would result in undue hardship.

Additionally, the spray and relief nozzle overlays are all located on the top of the pressurizer which creates additional personnel hazards. Work at this location requires personnel to ascend to an elevated platform and would require rigging of equipment to the work location.

The small elevated platform is congested with nozzles, piping, structural elements and other plant equipment located in close proximity.

To assure safety of personnel and adjacent plant equipment, adequate time is needed to assure proper job planning.

Effective dose rates in this area are 4.5 mr/hr. Personnel requirements for the welding, inspection and associated support activities for the anticipated duration of this work will result in approximately 2.6 Rem additional exposure to individuals involved.

5.14 Subsequent Inspections In addition to the scheduled future inservice inspections of the pressurizer nozzle SWOLs, all nozzles except the PORV Nozzle and Surge Nozzle will be reexamined during DCPP Unit 2's next three lSI periods'in accordance with Section XI, IWB-2420 using qualified phased array techniques to assure the identified reflectors have not increased in size. Note: The lSI Program Plan selected Safety Nozzles A and B for scheduled examinations.

18 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is dec o ntrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 5.15 Related Additional Inspections The Pressurizer Nozzles are subject to VT-2 examination during pressure test associated with startup every refueling outage. 5.16 Conclusion NRC approved requests have been used to produce acceptable weld overlays when applied to Alloy 82/182 DMWs at other facilities (see Section 6). The proposed alt.ernative in Attachment 1 has been developed to cover operating experience and NRC-approved criteria that are associated with similar SWOL applications at the time the SWOLs were applied. Indications identified with the enhanced sensitivity phased array ultrasonic techniques have been evaluated and found to meet the design requirements stated in this relief request Revision 2. Therefore, PG&E considers that Attachment 1, and the previously NRC-approved POI Program ultrasonic examination qualification alternative to ASME Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement 11, provide an acceptable level of quality and safety, consistent with provisions of 10 CFR 50.55a(a)(3)(i).

6. Precedents Relief requests have been submitted by other utilities to address the PWSCC susceptibility of Alloy 82/182 weld issues that are contained in this request. The following relief requests have been approved by the NRC: 6.1 AmerGen Energy Company, Three Mile Island Nuclear Station, Unit 1, on July 21, 2004, in NRC letter, "Three Mile Island Nuclear Station, Unit 1 (TMI-1) Request for Relief from Flaw Removal, Heat Treatment, and Nondestructive Examination Requirements for the Third 10-year Inservice Inspection (lSI) Interval, (TAC No. MC1201)," (ADAMS Accession No. ML041670510).

6.2 Constellation

Energy's Calvert Cliffs Nuclear Power Plant, Unit 2, on July 20, 2005, in NRC letter, "Calvert Cliffs Nuclear Power Plant, Unit Nos. 2 -Relief Request for Use Weld Overlay and Associated Alternative Inspection Techniques (TAC Nos. MC6219 and MC6220)," (ADAMS Accession No. ML051930316).

6.3 Millstone

Unit 3, on January 20, 2006, in NRC letter, "Millstone Power Station, Unit No.3 -Issuance of Relief from Code 19 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 Requirements (TAC No. MC8609)," (ADAMS Accession No. ML053260012).

6.4 Indiana

Michigan Power Company, Donald C. Cook Unit 1, on February 10, 2006, in NRC letter, "Donald C. Cook Nuclear Plant, Unit 1 (DCCNP-1)

-Alternatives Regarding Repair of Elbow Weld 1-RC-9-01 F (TAC No. MC8807)," (ADAMS Accession No. ML060240355).

6.5 Indiana

Michigan Power Company , Donald C. Cook Unit 2, on March 1,2007, in NRC letter, "Donald C. Cook NuClear Plant, Unit 2 (DCCNP-2)

-Alternative Regarding Use of Preemptive Weld Overlays on Certain Dissimilar Metal Welds (TAC No. MC9305)," (ADAMS Accession No. ML070460121).

7. Du ration of Proposed Alternative The alternative requirements of this request will be applied to installation of weld overlays during the current third 1 O-year lSI interval.

Overlay installation and acceptance requirements are applicable for the expected life of the overlay, which is 20 years beyond the current license expiration date of August 26, 2025. Overlay lSI examination requirements stated in this request are applicable for the remainder of the third inspection interval, nominally scheduled to end March 13,2016. Successive lSI examinations of Safety Nozzle A, B, and C and the Spray Nozzle will extend into and be performed during the first and second periods of the fourth inspection interval, in accordance with Section XI, IWB-2420.

8. References 8.1 ASME Code,Section XI, 2001 Edition, including Addenda through 2003. 20 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 8.2 ASME Code,Section XI, 2001 Edition, no Addenda, Appendix VIII, Supplement

11. 8.3 EPRI MRP-169 "Technical Basis for Preemptive Weld Overlays for Alloy 82/182 Butt Welds in PWRs," October 2005. 8.4 EPRI Report 1013558, "Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding," Technical Update, December 2006. 8.5 ASME Code Section XI, Appendix Q, 2004 Edition with 2005 Addenda. 21 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021

.55 Pipe T I P31S) SWOL Safe-End (SA.18:2 F316L) -

'LIVe1d A82 RootIAt&2 Bal ce , Figure 1! -Typical SWOl , C*on'fig , uration 22 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Unde r 1 0 C F R 2.390 Figure 2 Illu st ra ti on of Coverage Calculation Nozzle "B" I 0.79" Enclosure 1 PG&E Letter DCL-13-021 l S I Ex a m i n a t i on V ol ume Code Co v er a ge Box 316 SS Pip i ng LI-------Area of lSI Examination Volume Code Coverage Bo x = 0.11" 0.05"

..L' ___ _ ....-----0.04" Axial Exam Coverage (.11 * .11 = .0121) + (.5 * (.05 * .11) = .00275) + (.5 * (.16 + .04) * .15 = .015) = 0.03 sq'/in. (0.03/4.16)

• 100 = 0.7% I ndication length = 5.5" Overlay circumference at flaw = 29.1" (5.5/29.1) = 19% 0.007

• 19 = 0.133% total Area doubled for conservatism

= 2

• 0.133 = 0.27% Coverage = 100 -0.27 = 99.73% N ot t o scale 5.26

• 0.79 = 4.1 6 sq'/in. i 0.15" 23 71.69° 5.8" N ozzle "B" WI B-4 23 Ove rl ay Indicatio n and p hased-a rr a y co ve rage Botto m o f l SI Exami n a t i on Volum e Box Enclosures 3 and 4 contain Proprietary Information 71.69° flaw length 71.69/360

= 20% 0.25" flaw width 5.31" lSI Volume width 0.25/5.31

= 5% 20%of5%= 1% 99% Coverage in circumferential di r ecti When separated from Enclosures 3 and 4 , this documen t is decontroll ed ..

Enclosures 3 and 4 contain Proprietary Information

-Withho l d U nde r 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 Table 1: 2R17 Indications Exceeding Original Acceptance Criteria TAC NO. MD4974 Acceptance Criteria Less than 3.0" Length lind. Ind. Depth sTable or Pa ge# # Orient. Cla ssi fication 4Length Width fromOD IWB-3S14-3 (in 2) L ess than 10"/0 of eirc. Saf e ty Nozzle "A" Examin ed 2-22-13 Lack of BondI Unacceptable:

1 Circ Interbead non-fusion 16.3" 0.4" 0.60" Acceptable:

Lack of BondI 4.9 vs 7.5 Allow 16.3" Actual vs. 3.0" Allow 1A Circ Interbead non-fusion 16.3" 0.4" 0.52" Saf ety Nozzle " B" Examined 2-14-13 Lack of Bondi 1 Circ Interbead non-fusion Combined 0.25" 0.58" Unacceptable:

Lack of Bondi Length Acceptable:

4.7" Actual 2 Circ I nte rbead non-fusion 4.7" 0.25" 0.65" 0.9 vs 7.5 Allow vs. 3.0" Allow Lack of Bondi 3 Circ Interbead non-fusion 0.25" 0.65" Spray Nozzle Examined 2-27-13 Lack of Bondi Unacceptable:

21 Ci r c Interbead non-fusion 1.72" 0.42" 0.46" Acceptable

Lack of Bondi 6.3vs 7.5 Allow 20.1" Actual 4 Circ I nterbead non-fusion 3 20.1" 0.25" 0.43" vs. 3.0" Allow 1 Indicat ion numbers correspond to those on exam data sheets. 2 Indicat ion le n gth acceptable

<< 3"). Included due to proximity to indication

1. 4. 31nd ication intermittent over length of 20.1", see attached rollout for pictorial representation of occurrence.

4 Actua l length of the indication 5 For a given nozzle, all laminar indications combined have a total surface area <10% of the weld surface area Less than 10"/0 reduction in coverage volume Accep t able: 100% Cove rage Acceptable:

98.9 4% Coverage Acceptable

99.33% Coverag e Table IWB-3S14-2 Preservice Examination for Assumed Flaws in W eld Overlay (a/t, %) 6 A ccep ta b le: Ci r c. 2.5 vs. 8.2 Allow A x ial 2.5 vs. 8.5 Al low N/A: Weld Ove r lay Volume Not Occluded N/A: Weld Overlay Volume Not Occluded Dispo si tion Under Revised Acceptance Criteria A c cep t As-Is: Ac c ept As-Is: A cc ept As-Is: 6 Sta cked lam i nar indications 1 and 1A in the Safety Nozzle "An are on the edge of the acceptance volume and have been conservatively evaluated as a planar indication w it h a height of 0.080" to Table IWB-35 14-2 as ACCEPTABLE. 24 Enclosures 3 and 4 contain Proprietary Informati on When separated from Enclosures 3 and 4 , this documen t is d e co n trolled ..

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 Alternative Requirements for Dissimilar Metal Weld Overlays I n lieu of the requirements of IWA-441 0 and IWA-4611, a defect exceeding the applicable acceptance criteria in austenitic stainless steel or austenitic nickel alloy piping, components, or associated welds may be accepted by analysis in accordance with IWB-3640 by 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 the low alloy steel nozzles (P-No. 3) to the safe end (P-No. 8 or 43), inclusive of the N06082 or W86182 weld that joins the two items. The design of the overlay is extended to include the adjacent stainless steel to stainless steel weld joints (P-No. 8 to P-No. 8 with P-No. 6 filler material). (b ) (deleted in Revision 1) (c) Weld overlay filler metal shall be austenitic nickel alloy (28 percent Cr minimum, ERNiCrFe-7 or ERNiCrFe-7A) applied 360 deg. around the circumference of the item, and shall be 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. (d) Prior to deposition of the weld overlay, the surface to be weld overlaid shall be examined by the liquid penetrant method. Indications with major dimension greater than 1/16 in. (1.5 mm) shall be removed, reduced in size, or corrected 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.

25 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled

..

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 (e) (f) (g) (h) (2) If repair of indications ident ified in 1 (d) is required , the area where the weld overlay is to be deposited, including any local 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 1/16 in. (1.5 mm) prior to the application of the structural layers of the weld overlay. Weld overlay deposits shall meet the following requirements.

The austenitic nickel alloy weld overlay shall consist of at least two weld layers deposited from a filler material with a Cr content of at least 28 percent. The first layer of weld metal deposited may not be credited toward the required thickness.

Alternatively, 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 contains at least 24 percent Cr and the Cr content of the deposited weld metal is determined by chemical analysis of the production weld or of a representative coupon taken from a mockup prepared in accordance with the WPS for the production weld. This alternative is only for welding in applications Rredicted not to have exceeded thermal neutron fluence of 1 x 10 7 (E< 0.5 eV) neutrons per cm 2 prior to welding. A new weld overlay shall not be installed over the top of an existing weld overlay that has been in service. Appendix 1 shall be used for ambient-temperature temper bead welding 2. Crack Growth and Design (a) Crack Growth Calculation of Flaws in the Original Weld or Base Metal. The size of. all flaws detected or postulated in the original weld or base material shall be used to define the life of the overlay, which is 20 years beyond the current license expiration date of August 26, 2025. Crack growth in the original weld and base metal, due to both stress corrosion and fatigue shall be evaluated.

If the flaw is at or near the boundary of two different materials, evaluation of the flaw growth in both materials is required.

26 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Informat i on -Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 (1) Fo r the DCPP U nit 2 pressurizer repair ov erlays, the initia l flaw size for c r ack growth shall be based on the postulate d flaw, since no pre-overlay ul tr ason i c examination i s performed.

(2) For postulated flaws in the original weld or base metal the axial flaw length shall be set at 1.5 inches (38 mm) or the combined width of the weld plus buttering, whichever is greater. The circumferential flaw length shall be assume d to be 360 degrees. (a) Since no examination is performed prior to application of the overlay, initial inside surface connected planar flaws equal to at least 75 percent through the original wall thickness shall be assumed, in both the axial and circumferential directions, consistent with the overlay inservice inspection volume in Figure 2. (b) In determining the expected life of the overlay, any planar flaw found by the overlay preservice examination of paragraph 3(b), which exceeds the depth of (a) above, shall be used as part of the initial flaw depth in determining the expected life of the overlay. The flaw depth assumed is the detected flaw depth plus the postulated worst-case flaw depth (i.e., 75 percent of original wall) in the unqualified ultrasonic examination region of the pipe wall thickness. (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-4311.

(1) The axial length and end slope of the weld overlay shall cover the weld and the 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, or the Construction Code. Any laminar flaws in the weld overlay shall be evaluated in the analysis to ensure that load 27 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosu r es 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 redistributio n complies with th e above. Th ese r equire m e nts will usually be satisfied if the weld overlay full thickness length extends axially beyond the projected flaw by at leas t O.7SJRi 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 slope of the overlay shall not exceed 30 degrees. A slope of not more than 1:3 is recommended.

(3) For determining the combined length of oriented flaws in the underlying base material or weld, multiple flaws shall be treated as one flaw of length equal to the sum of the lengths of the individual flaws characterized in accordance with IWA-3300.

(4) For circumferentially-oriented flaws in the underlying base material or weld, the flaws shall be assumed to be 100 percent through the original wall thickness of the item for the entire circumference of the item. (5) For axial flaws in the underlying base material or weld, the flaws shall be assumed to be 100 percent through the original wall thickness of the item for the entire axial length of the flaw or combined flaws, as applicable.

(6) For the DCPP Unit 2 full structural overlays, since ultrasonic examination is not performed prior to installation of the overlay, the assumed flaw in the underlying base material or weld is to be based on the limiting case of the two below: (a) 100 percent through wall for the entire circumference, or (b) 100 percent through wall for 1.5 in. (38 mm) or the combined width of the weld plus buttering, whichever is greater, in the axial direction.

(7) 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.SJRi from the toes of the weld overlay, including the flaw size assumptions defined in 2(b)(4), (5), or (6) above, shall be evaluated and shall meet the requirements of IW8-3640.

(8) 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 28 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is dec o ntrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter OCL-13-021 3. Examination l oads, changes in system flexibility and weigh t due to the . weld overlay) shall be evaluated.

Existing flaws previously accepted by analytical evaluation shall be evaluated in accordance with IWB-3640.

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 the POI implementation of ASME Section XI, Appendix VIII, Supplement 11,2001, Edition no Addenda, or as updated requirements are mandated by the NRC. 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 per POI implementation of Appendix VIII requirements.

The weld overlay shall be inspected to verify acceptable configuration.

(2) The weld overlay and the adjacent base material for at least 'Y2-in. (13 mm) from each side of the weld shall be examined using the liquid penetrant method. 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 used, the liquid penetrant 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 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. (3) The acceptance examination volume, A-B-C-O, in Fig.1 (a) plus the heat-affected zone beneath the fusion zone C-O shall be ultrasonically examined to assure adequate fusion (i.e., adequate bond) with the base metal and to detect flaws, such as interbead lack of fusion, inclusions, or cracks. The interface C-O shown between the overlay and the weld includes the bond and the heat affected zone from the overlay. If ambient temperature temper bead welding is used, the ultrasonic 29 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Informat i on -Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 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 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. 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 "t1" 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-O and F-B-C-G. Laminar flaws 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 percent of the weld surface area and that no linear dimension of the laminar flaw area exceeds 3.0 in. (76 mm), or 10 percent of the nominal pipe circumference, whichever is greater. i) During 2R17, the SWOLs at Safety Nozzles A and B, and the Spray Nozzle were examined with enhanced sensitivity phased array ultrasonic techniques and each found to have a narrow fabrication-related laminar flaw oriented circumferentially over the low alloy steel nozzle base material as identified in Table 1. These flaws exceed 3.0 inches in length and shall be subject to quantitative analysis for acceptability.

ii) Quantitative analysis has shown that the structural integrity of the weld overlay in each case is assured as demonstrated in Enclosures 3 and 4 to PG&E Letter DCL-13-021, "ASME Section XI Inservice Inspection Program Relief Request REP-1 U2, Revision 2," dated . March 5, 2013 . Therefore, the indications are acceptable as-is. (b) The reduction in coverage of the examination volume, C-O in Fig. 1 (a) due to laminar flaws shall be less than 10 percent. 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 30 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decon tr olle d.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 exist within t hat volume. This assumed flaw shall meet t he preservice examination 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.

The angle beam shall be directed perpendicular and parallel to the piping axis, with scanning performed in four directions, to locate and size any cracks that might have propagated into the outer 25 percent of the base material, underlying weld, or into the weld overlay. Any uninspectable examination volume in the outer 25 percent of the underlying weld or base material, as applicable, as shown in Fig. 2, shall be assumed to contain the largest circumferential and axial planar flaw within that volume for flaw growth evaluation.

(2) The preservice examination acceptance standards of Table IWB-3514-2 shall be met for the weld overlay. In applying the acceptance standards, wall thickness, t w , shall be the thickness of the weld overlay. Cracks in the outer 25 percent of the base metal*shall meet the design analysis requirements of 2 (b). (3) Planar flaws detected in the outer 25 percent of the underlying weld or base material thickness as depicted in the examination volume of Fig. 2 shall be evaluated in accordance with IWB-3640. c. I nservice Inspection (1) The inservice inspection requirements of ASME Code 2004 Edition, including 2005 Addenda,Section XI, Appendix 0, Subarticle 0-4300 (including 0-4310), shall apply for the third ten-year lSI interval for the weld overlay examination.

The lSI requirements for the weld overlays for the fourth and later lSI intervals shall be those incorporated by reference in Title 10, Code of Federal Regulations, Part 50.55a (10 CFR 50.55a) in effect at that time. (2) 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.

31 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021

4. Pressure Testing A system leakage test shall be performed in accordance with IWA-5000.

5. Documentation Use of this alternative shall be documented on Form NIS-2. 32 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 A D 1/2 in. (min.) E H 1/2 in. (min.) a. Acceptance Examination Volume A*B*C*D 1/2 in. (min.) (Note 1) b. Thickness (t1) for Table IWB*351 4*2 B C 1/2 in. (min.) (Note 1) D H P t2 ____

c. Thickness (t2) 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 }'2 in. (13mm) beyond the toes of the original weld. (2) The weld includes the weld end butter, where applied. 33 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 1/2 in. (min.) A t---.-j 1/2 in. (min.) (N o t e 1)

• 0 C t ______

NOTES: (1 ) (2) Examination Volume A-B-C-D For axial or circumferential flaws, the axial extent of the examination volume shall extend at least Y2 in. (13mm) beyond the as-found flaw and at least Y2 in. (13mm) beyond the toes of the original weld. The weld includes weld end butter, where applied. Fig. 2 Preservice and Inservice Examination Volume 34 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 Appendix 1 Ambient Temperature Temper Bead Welding 1 GENERAL REQUIREMENTS (a) This appendix applies to dissimilar austenitic filler metal welds between P-No. 3 materials and their associated welds and welds joining P-No: 8 or 43 materials to P-No. 3 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 percent to 1.0 percent nickel, quenching and 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 500 sq. in. (325,000 sq. mm). (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. (10mm). (e) Prior to welding the area to be welded and a band around the area of at least 1-1/2 times the component thickness or 5 in. (130 mm), whichever is less, shall be at least 50°F (10°C). (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. 2 WELDING QUALIFICATIONS The welding procedures and the welding operators shall be qualified in accordance with Section IX and the requirements of 2.1 and 2.2. 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 postweld heat treated to at least 35 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled

..

Enclosures 3 and 4 contain Proprietary Informat i on -Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 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 repa i r. (c) The maximum interpass temperature for the first three layers of the test assembly shall be 1 50°F (66°C). (d) The test assembly cavity depth shall be at least 1 in. (25 mm). The test assembly thickness shall be at least tw ice the test assembly cavity depth. The test assembly shall be large enough to permit removal of the required test specimens.

The test assembly dimensions surrounding the cavity shall be at least the test assembly thickness and at least 6 in. (150 mm). The qualification test plate shall be prepared in accordance with Fig. 1-1. (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 2.1 (f) below, but shall be in the base metal. (f) Charpy V-notch tests of the ferritic heat-affected zone (HAl) shall be performed at the same temperature as the base metal test of 2.1 (e) 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 HAl impact specimens shall be taken transverse to the axis of the weld and etched to define the HAl. 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 HAl as possible in the resulting fracture.

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. (2) If the test material is in the form of a plate or a forging, the axis of the weld shall be oriented parallel to the principal direction of rolling or forging. (3) The Charpy V-notch test shall be performed in accordance with SA-370. Specimens shall be in accordance with 36 Enclosures 3 and 4 contain Proprietary Information When separated from Endosures 3 and 4 , this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 SA-370 , Fig. 11 , Type A. The test shall consist of a set of 3 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 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 111,2001 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.

2.2 Performance

Qualification Welding operators shall be qualified in accordance with Section IX. 3.0 WELDING PROCEDURE REQUIREMENTS The welding procedure shall include the following requirements: (a) The weld metal shall be deposited by the automatic or machine GTAW 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) 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) weld joints. (c) The area to be welded shall be buttered with a deposit of at least three layers to achieve at least 118 in. (3mm) overlay thickness with the heat input for each layer controlled to within +/-10 percent of that used in the procedure qualification test. The heat input of the first three layers shall not exceed 45kJ/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 fe rr itic base metal are tempered.

Subsequent layers shall be 37 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 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°F (180°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: (1) . Temperature measurement (e.g., pyrometers, temperature indicating crayons, thermocouples) during welding. When it is impractical to use interpass temperature measurements described in this paragraph due to situations where the weldment area is not accessible, such as internal bore welding or when there are extenuating radiological concerns, either paragraph 3(e)(2) or paragraph 3(e)(3) may be used. (2) Heat flow calculations using the variables listed below as a minimum: (i) welding heat input (ii) initial base material temperature (iii) configuration, thickness, and mass of the item being welded (iv) thermal conductivity and diffusivity of the materials being welded (v) arc time per weld pass and delay time between each pass (vi) 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 welding 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.

38 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Lette r DCL-13-021 OiC .. rd TI'MIIYIfI.8ideBand Rtdl.iCtd Semon Ten.1e TrlnlYlr ... Side lend Tr ....... SJdeIlMd A.dycM SIedo" T.n .... Tr.nsv., .. Side Bend Oi'lCItd 14e-t.l.T

-"t. !!.OIoE( ... .A A HAl Ch.rpv y.NoIcf\ A. GENERAL NOTE: Base metal Charpy impact specimens are not shown. Fig. 1-1 QUALIFICATION TEST PLATE 39 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 Attachment 2 Barrier Layer to Prevent Hot Cracking i n 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 t he first layer have occurred in the portion o f the overlay deposited o n the aus t enitic stainless steel portions (safe ends, pipe etc.) o f the assemblies in some cases. Discussion The flaw characteristics observed above are indicative of hot cracking.

This phenomenon has not been observed when welding Alloy 52M on the ferritic steel or ENiCrFe-3 (Alloy 182) DMW portions of the assemblies.

Further studies have determined that this problem may occur when using Alloy 52M filler metal on austenitic stainless steel materials with high sulfur content. Recent limited tests and evaluations have concluded that welding with Alloy 52M o'n 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, ER309L was selected 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 subsequently welded thereon. However, the barrier layer will necessarily consist of ERNiCr-3 (Alloy 82) being used locally at the interface between the Alloy 182 DMWand the stainless steel item. ER309L welding on Alloy 182 may result in cracking of the ER309L weld. Welding on high sulfur stainless steel with Alloy 82 has not been a concern relevant to hot cracking occurrence.

A mockup assembly was fabricated 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 performed therein. The barrier layer and overlay were welded in the same sequence as performed in the field (barrier layer ER309L and Alloy 40 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this document is deco nt rolle d.

Enclosures 3 and 4 contain Propri e tary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 82 and then two layers of Alloy 52M overlay).

The barrier layer and over lay welding parameters used in the mockup were similar to those used in the field however slightly reduced wire feed rates were used for conservatis

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

Penetrant testing (PT) 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 POI ultrasonic testing (UT)

• O-degree Transducer with Full Coverage

• 45-degree Transducer with Full Coverage

• OD Creeper Transducer with Full Coverage

• 60-degree 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)

Metallographic examination searching for any type of discontinuity, flaw or other anomaly has been performed on 8 specimens that were removed in approximate 45-degree circumferential increments around the pipe. (See Figure 1 for typical photomicrograph).

Final metallography of all the specimens has shown no conditions causing concern. Conclusion More tests and evaluations would be necessary to accurately determine the threshold where the base metal sulfur content would require barrier layer welding. DCPP Unit 2 used the barrier layer on all the stainless steel items prior to overlay. The barrier layer used ER309L on the stainless steel and 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 ER309L filler metal. 41 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4 , this documen t is decon tr olle d.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 The barrier layer welding was performed in accordance with ASME Section IX qualified welding procedure specification(s).

PT was performed on the barrier layer surface and its volume was included in the final UT of the overlay. 42 Enclosures 3 and 4 contain Proprietary Information When separated from Enclosures 3 and 4, this document is decontrolled.

Enclosures 3 and 4 contain Proprietary Information

-Withhold Under 10 CFR 2.390 Enclosure 1 PG&E Letter DCL-13-021 Figure 1; High Sulfur Stainless Pipe Exhibiting Alloy 82 (ERNiCr-3)

Deposit Between Alloy 182 (ENiCrFe-3), ER309L, and Alloy 52M (ERNiCrFe-7A)

Deposits.

When separated from Enclosures 3 and 4, this document is decontrolled.