AEP-NRC-2008-25, Use of Weld Inlays as an Alternative Repair Technique for Reactor Vessel Safe End-to-Primary Nozzle Alloy 82/182 Welds

Use of Weld Inlays as an Alternative Repair Technique for Reactor Vessel Safe End-to-Primary Nozzle Alloy 82/182 Welds

ML083010238
Person / Time
Site:	Cook
Issue date:	10/07/2008
From:	Jensen J Indiana Michigan Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
AEP-NRC-2008-25
Download: ML083010238 (23)

Text

INDIANA' MICHIGAN POWER Indiana Michigan Power Company Nuclear Generation Group One Cook Place Bridgman, MI 49106 aep.com AEP-NRC-2008-25 10 CFR 50.55a October 7, 2008 Docket No. 50-315 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop O-P1-17 Washington, DC 20555-0001

SUBJECT:

Donald C. Cook Nuclear Plant Unit 1 Use of Weld Inlays as an Alternative Repair Technique for Reactor Vessel Safe End-to-Primary Nozzle Alloy 82/182 welds

Dear Sir or Madam:

Pursuant to 10 CFR 50.55a(a)(3)(i), Indiana Michigan Power Company (I&M), the licensee for Donald C. Cook Nuclear Plant Unit 1, hereby requests Nuclear Regulatory Commission approval of the following request for the third ten-year interval inservice inspection testing program:

Relief Request ISIR-28 for use of weld inlays as an alternate repair technique for Reactor Vessel Safe End-to-Primary Nozzle Alloy 82/182 welds. The proposed alternative provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(a)(3)(i).

The details of the 10 CFR 50.55a requests are attached.

The enclosure to this relief request provides a General Process Description that includes the Alternative Requirements for welding using the remote machine gas tungsten-arc welding process and using the ambient temperature temperbead method.

I&M requests approval by September 8, 2009, to allow use of the alternatives during the Unit 1 Cycle 23 refueling outage.

This letter contains no new or revised commitments.

Should you have any questions, please contact John A. Zwolinski, Manager of Regulatory Affairs, at (269) 466-2478.

S i ncerel SiyiP d

6o e oh esen bDort Services Vice President RSP/jen

Attachment:

ISIR-28

Enclosure:

Weld Inlay And Potential Repair Weld Inlays For Reactor Vessel Safe End-To Primary Nozzle Alloy 82/182 Dissimilar Metal Welds Mitigative/Repair Inlay

U. S. Nuclear Regulatory Commission Page 2 c:

T. A. Beltz - NRC Washington, DC J. L. Caldwell - NRC Region III K. D. Curry - AEP Ft. Wayne J. T. King - MPSC MDEQ - WHMD/RPS NRC Resident Inspector AEP-NRC-2008-25

Attachment to AEP-NRC-2008-25 Page 1 10 CFR 50.55a REQUEST Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

USE OF WELD INLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE

1.0 ASME Code Components Affected

Code components associated with this request are Class 1 NiCrFe dissimilar metal welds (DMWs) with Alloy 82/182 weld metal in the reactor vessel (RV) safe end-to-primary nozzle butt welds, exposed to reactor coolant (RC) that are susceptible to Primary Water Stress Corrosion Cracking (PWSCC). There are a total of eight (8) DMWs, four (4) hot leg (HL) nozzles and four (4) cold leg (CL) nozzles, that are scheduled to have inlay welds applied to the inside surface of the DMWs. The weld inlays, using nickel alloy ERNiCrFe-7A (Alloy 52M) filler metal, will extend from the stainless steel safe end, across the DMW, to the stainless steel cladding on the inside surface of the HL and CL nozzles, protecting the DMWs from the RC. The safe end-to-nozzle welds are scheduled for mitigation/repair during refueling outage U1C23 that is currently scheduled to commence in October 2009.

1.1 Category and System Details Code Class:

Reference:

Class 1 ASME Code, Section Xl, 1989, no Addenda ASME Code Case N-416-1 ASME Section III, 1965 Edition, including Addenda through Winter 1966 (Original Construction Code)

ASME Section III, 1989 Edition (Modification Design Code)

ASME Code Case N-638-1 ASME Code Case N-695 (Preservice/Inservice Inspection Qualification Requirements)

ASME Section III, 1998 Edition, including Addenda through 2000 (Construction Code Nondestructive Examination)

Examination Categories: B-F Item Number:

B5.10 System Welds:

Reactor Coolant System 1.2 Component Descriptions The application of this alternative is to apply inlay welds on eight (8) safe end-to-primary nozzle DMWs. The inlays will extend outward from the stainless steel cladding on the ferritic low alloy steel RV nozzles, across the adjacent DMWs, to the stainless steel safe ends. The applicable weld identification numbers are listed in Table 1. The general configuration for the nozzle locations is shown in Figures 1 and 2.

Attachment to AEP-NRC-2008-25 Page 2 TABLE 1 WELD NUMBERS BY ISI DESIGNATION Item 2

3 4

5 6

7 8

Location N.ozzle-to-Safe End ".Hot L-eg"_

Nozzle-to-Safe End "Cold Leg" Nozzle-to-Safe End "HotLeg" Nozzle-to-Safe End "Cold Leg" Nozzle-to-Safe End "Hot Leg" Nozzle-to-Safe End "Cold Leg" Weld Number by ISI Designation DMW ID RPV-01 1-RPV-1-02

........................ ! R V : : !...........................................

1 -RPV-2-01

! R _ V

_: :. 2......................................

1 -RPV-2-02 1 -RPV-3-01 1 -RPV-3-02 1.-RPV-4-01 1 -RPV-4-02 1.3 Component Materials The applicable materials are depicted in Table 2.

TABLE 2 HOT LEG AND COLD LEG NOZZLE MATERIALS N Nozzle Nozzle Cladding (P-No. 3, Gr 3)

(a-no

(-No. 8 Type SA-508, CI 2 308, 309, and 312 Safe End-to-Nozzle DMW (F:=-No. 43)

Alloy 82/182 Nozzle DMW Buttering (F-No. 43)

Alloy 182 Safe End (P-No. 8, Gr.

Safe End Cladding

1),

(A-No. 8 and F-No. 43)

SA-182, Type 312L (OD & ID)

Gr F316 Alloy 82 (OD & ID) 2.0

Applicable Code Edition and Addenda

Donald C. Cook Nuclear Plant (CNP) Unit 1 is currently in the Third Inservice Inspection (ISI) interval, scheduled to end on February 28, 2010.

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) of record for the current ISI interval isSection XI, 1989 Edition, no Addenda (Reference 8.2) for the Repair/Replacement Program.

3.0

Applicable Code Requirement

The applicable ASME Code requirements for which relief is requested are:

1. ASME Section XI Case N-638-1 (Reference 8.1) with condition as specified in Regulatory Guide 1.147 Revision 15 Code Case N-638-1 (Reference 8.1) provides requirements for ambient temperature machine gas tungsten-arc dissimilar metal welding using the temperbead technique that is applicable for welding on ferritic low alloy steel.

Attachment to AEP-NRC-2008-25 Page 3 4.0

Reason for Request

Indiana Michigan Power Company (I&M), CNP Unit 1, is proposing to take a proactive approach and apply weld inlays (see Figure 1) and potential repair weld inlays (see Figure 2) on the RV safe end-to-primary nozzle DMWs to prevent the potential occurrence of PWSCC, or remove associated flaws and mitigate the potential for recurrence of PWSCC. During U1C23, eight (8)

DMWs, four (4) on the HL and four (4) on the CL, located at the RV primary nozzles are scheduled for weld inlays.

The enclosure to this relief request provides a General Process Description that includes the Alternative Requirements for welding using the remote machine gas tungsten-arc welding (GTAW) process and using the ambient temperature temperbead method.

DMWs, primarily consisting of Alloy 82/182 weld metal, are frequently used in pressurized water reactor (PWR) construction to connect stainless steel safe ends-to-vessel nozzles that are typically constructed of low alloy ferritic steel. These welds have shown a tendency for PWSCC degradation due to exposure to the RC environment. [See Material Reliability Program: Primary System Piping Butt Weld Inspection and Evaluation Guideline (MRP-1 39), EPRI, Palo Alto, CA:

2005 (Reference 8.3), for DMW repair classification/examination category based on PWSCC susceptibility and mitigation actions.]

Based on application of weld inlays and potential repair weld inlays, I&M requests code relief from the following ASME Section XI Code Case N-638-1 items:

1. Code Case N-638-1, Paragraph 1.0(a); The maximum area of an individual weld based on the finished surface shall be 100 square inches (sq. in.), and the depth of the weld shall not be greater than one-half of the ferritic base metal thickness.

2. Code Case N-638-1, Paragraph 1.0(c); If a defect penetrates into the ferritic base material, repair of the base material, using a non-ferritic weld filler material, may be performed in accordance with the Code Case, provided the depth of repair in the base material does not exceed 3/8 inch (in.).

3. Code Case N-638-1, Paragraph 3.0(d) and 4.0(c); The maximum interpass temperature for field applications shall be 350 degrees Fahrenheit (OF) regardless of the interpass temperature during qualification, and areas from which weld-attached thermocouples have been removed shall be ground and examined using a surface examination method.

4. Code Case N-638-1, Paragraph 4.0(b); The final weld surface and the band around the area defined in paragraph 1.0(d) shall be examined using a surface and ultrasonic methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The ultrasonic examination shall be in accordance with Appendix 1.

Attachment to AEP-NRC-2008-25 Page 4 5.0 Proposed Alternative and Basis for Relief

1. The maximum area of an individual weld based on the finished surface shall be 500 sq. in.,

and the depth of the weld shall not be greater than 2.0 in.

ASME Section XI Code Case N-638-4 specifies a maximum finished surface area of 500 sq.

in.

The maximum depth of flaw removal is 2.0 in.

This exceeds the one-half depth requirement by approximately 0.58 in. The weld residual stress analysis shows no adverse effects of this repair welding (Reference 8.4).

2. The depth into the base material is based on flaw removal up to 2 in.

It was assumed that flaw removal up to 2-in depth, near the buttering-to-nozzle fusion zone, results in a maximum depth of nozzle low alloy ferritic steel material being replaced by the Alloy 82/52M weld as shown in Figure 2. Analysis shows that the nozzle low alloy ferritic steel that is replaced by the Alloy 82/52M weld material does not adversely affect the structural integrity of the DMW region (Reference 8.4).

3. Use of heat flow analysis or 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 using the maximum permitted heat input specified on the applicable.welding procedure specification.

ASME Section XI Code Case N-638-4 specifies these alternatives in lieu of direct interpass temperature measurement, as a clarification, when thermocouples are not used.

4. Acceptance nondestructive examination (NDE) (ultrasonic testing and liquid pentrant testing and/or eddy current) will be performed 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after.the third temperbead layer is deposited over the ferritic steel nozzle. No NDE of the ferritic steel nozzle preheated band after welding.

Acceptance NDE 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the third temperbead layer is deposited over the ferritic steel nozzle is sufficient to verify the integrity of the weld and adjacent heat-affected-zone (Reference 8.5).

The purpose of the weld inlay is to provide PWSCC and corrosion resistant weld material over the inner surface of the DMW so that the PWSCC susceptible Alloy 82/182 material is not exposed to the reactor coolant system water environment. The application of the proposed alternatives are equal to or surpass the requirements of ASME Section Xl Code Case N-638-1 items for which relief is requested. Therefore, the use of the proposed alternative will continue to provide an acceptable level of quality and safety consistent with provisions of 10 CFR 50.55a(a)(3)(i).

6.0 Precedents'

1) Weld inlay or corrosion resistant clad on Arkansas Nuclear One Unit 1 RV safe end-to-core flood nozzle DMWs (ML070040338).

Attachment to AEP-NRC-2008-25 Page 5

2) For temperbead welding, 500 sq. in. of weld surface has been approved by the Nuclear Regulatory Commission in a letter to Arkansas Nuclear One, Unit 1 (ML0811301738).

7.0 Duration of Proposed Alternative The duration of the proposed alternative is the remaining service life of the components including the period of extended operation.

8.0 References 8.1 Code-Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique," dated February 13, 2003.

8.2 ASME Boiler & Pressure Vessel Code,Section XI, 1989 Edition, No Addenda.

8.3 Materials Reliability Program: Primary System Piping Butt Weld Inspection and Evaluation Guidelines (MRP-139), EPRI, Palo Alto, CA: 2005.

8.4 Areva Engineering Information Record, Document Identifier 51-9082202-000, Weld Inlay Analytical Justification.

8.5 Temperbead Welding Applications:

48-Hour Hold Requirements for Ambient Temperature Temperbead Welding, EPRI, Palo Alto, CA:.2006,

Attachment to AEP-NRC-2008-25 Page 6 DMW ALLOY 82/182 NOZZLE SA-508. CL2 CLADDING TYPE 312L Figure 1 -

SAFE END INLAY SA-182, CLADDING GR F316 ALLOY 52M TYPE 308, 309 AND 312 Typical Weld Inlay Configuration DMW ALLOY 82/11

'CLADDING

-TYPE 308, 309, AND 312 Figure 2 - Typical Weld Inlay Repair Configuration (1/8 in. and more than one layer minimum thick Alloy 52M cover on inner surface over all Alloy 82)

Enclosure to AEP-NRC-2008-25 Page 1 WELD INLAY AND POTENTIAL REPAIR WELD INLAYS FOR REACTOR VESSEL SAFE END-TO PRIMARY NOZZLE ALLOY 82/182 DISSIMILAR METAL WELDS MITIGATIVE/REPAIR INLAY General Process Description The following describes the overall process.

Ultrasonic Testing (UT) will be performed on the dissimilar metal welds (DMW) prior to commencing with modification activities. The UT is performed to satisfy the Section Xl, IWB-2000 requirement for inservice examination and to provide information to determine the extent of additional machining required in the event that flaws are detected.

Based on the UT results, and after determination of the DMW boundaries exposed to the reactor coolant (RC), a cavity will be machined around the full inside circumference of the DMW and a liquid penetrant testing (PT) performed. The final cavity configuration will be dependent on the flaws detected in the DMW and the minimum cavity width will be sufficient to provide for the weld inlay to completely cover the exposed DMW inner surface with more than one layer and at least 1/8 inch (in.) final thickness using nickel alloy ERNiCrFe-7A (Alloy 52M).

Welding of the cavity will be performed with Alloy 52M.

The final weld inlay inner,.surface contour will be essentially equivalent with the original DMW surface contour and blended with the, adjacent surrounding surfaces (see Figure 1).

For DMWs where flaws with significant through-wall depths are removed, ERNiCr-3 (Alloy 82) may be used to partially fill theý cavity; however, Alloy 52M will be used on at least the inner 1/8 in. and more than one layer of the final inlay thickness (see Figure 2).

Acceptance PT will be performed on the weld inlay and acceptance UT and preservice UT on the final modified DMW, including the weld inlay, will be performed.

Design The mitigative/repair weld inlay will satisfy the requirements specified in the Alternative Requirements (Appendix 1), using Primary Water Stress Corrosion Cracking (PWSCC) resistant Alloy 52M filler metal. The weld is deposited into a cavity that is machined across.the entire inner surface of the DMW that is exposed to the RC (see Figure 1). For cases using repair weld inlays at depths greater than 1/8 in., Alloy 82 may be used to partially fill the cavity; however, Alloy 52M will be used on at least the inner 1/8 in. and more than one layer of the final inlay thickness (see Figure 2).

Enclosure to AEP-NRC-2008-25 Page 2 Stress Analyses Primary and secondary stress and fatigue analyses for. both the inlet and outlet nozzles are performed in accordance with NB-3200,Section III (Reference 1) for the modified DMW to show compliance therewith. The stress analyses consider. the following final modified configurations:

1) 0.13 in. deep cavity requiring more than one layer and at least 1/8 in. thick weld inlay of Alloy 52M for the full inner circumference (see Figure 1).

2) 2 in. deep local repair weld inlay (see Figure 2) using Alloy 82 or Alloy 52M with at least 1/8 in. and more than one layer of the final inlay thickness of Alloy 52M weld inlay applied thereon.

Flaw Growth Analyses Flaw growth analyses for postulated flaws are performed in accordance with IWB-3640.

Minimal flaw growth occurs for the assumed design life of the modified DMWs and flaw growth in the weld inlay is significantly less than its 1/8 in. minimum thickness, such that the Alloy 82/182 material would not be exposed to the RC during its design life.

Residual stresses for the modified DMW are calculated based on the original DMW configuration. This analysis also assumes a full circumferential 50% through-wall weld repair from the inside surface of the DMW has previously occurred. Also, the residual stress analysis takes into account the effects of the safe end-to-pipe weld.

For the mitigative,,,inlay

,configuration, a 3/16 in. deep cavity is machined in the DMW and the surrounding material- (see Figure 1), A..single layer of Alloy 82 is deposited therein, then the cavity is filled with Alloy',.52M.

material. For the 2 in. repair configuration, a 2 in. deep cavity (see Figure 2) is machined and filled. back with Alloy 82 material with at least 1/8 in. thick and more than one layer Alloy 52M'.

material at the inside surface.

Planar flaws are postulated to exist in the newly applied weld inlay and in the original DMW.

Both circumferential and axial flaws are evaluated in conjunction with the maximum size flaw permitted by the inservice examination acceptance standards of Table IWB-3514-2:

For the 1/8 in. Weld Inlay Design Case:

Postulated flaws in weld inlay:

1) Circumferential surface flaw of 1/16 in. depth through the inlay weld thickness, inside diameter (ID) surface connected for the entire circumference of the inlay.

2) Axial surface flaw of 1/16 in. depth through the inlay weld thickness, ID surface connected for the entire width (axial length) of the inlay.

Postulated flaws in the original DMW:

1) Full circumferential subsurface flaw of 3/8 in. depth in the remaining DMW, originating at the weld inlay/DMW interface for the entire circumference of the inlay.

2) Axial subsurface flaw of 3/8 in. depth in the remaining DMW, originating at the weld inlay/DMW interface for the entire width (axial length) of the inlay.

Enclosure to AEP-NRC-2008-25 Page 3 For the Repair Weld Design Case:

Postulated flaws in weld inlay:

1) Circumferential surface flaw of 1/16 in. depth through the inlay weld thickness, ID surface connected for the entire circumference of the inlay.

2) Axial surface flaw of 1/16 in. depth through the inlay weld thickness, ID surface connected for the entire width (axial length) of the inlay.

Postulated flaws in the original DMW:

1) Full circumferential surface flaw postulated to exist from the outside surface of the DMW to the 2-in. boundary depth of the newly deposited weld material.

2) Axial surface flaw postulated to exist from the outside surface of the DMW to the 2-in.

boundary depth of the newly deposited weld material for the entire width (axial length) of the inlay.

Leak-Before-Break (LBB) Evaluation Since the original geometry and loads are not significantly modified by the weld inlay (see Figure 1), or repair weld inlay (see Figure 2), when applicable, and the replacement weld inlay material (Alloy 52M) has equal or superior fracture toughness than the existing materials, LBB remains applicable at these locations. Furthermore, gas tungsten-arc welding (GTAW) is used for the weld inlay and repair weld inlay. GTAW exhibits higher fracture toughness properties, with either Alloy-82 or Alloy 52M than the shielded metal arc welding process which.was the; process used for the original DMWs at these locations.

Evaluation of Weld Shrinkage Effects The axial weld shrinkage caused by the weld inlay (see Figure 1) and repair weld inlay (see.

Figure 2) has a negligible effect on the attached piping.

The radial weld shrinkage has a negligible effect on the nozzle configuration.

Welding The welding will be performed in accordance with the Alternative Requirements using the remote machine GTAW process and using the ambient temperature temperbead method (Appendix 1 and 2).

During recent DMW overlay activities, where Alloy 52M was used for the filler metal, there were some cases where flaws occurred in a portion of the first layer of the overlay deposited on the austenitic stainless steel items (safe ends, pipe, etc.). The flaw characteristics observed are indicative of hot cracking.

This phenomenon has not been observed on the ferritic steel or ENiCrFe-3 (Alloy 182) DMWs when welding Alloy 52M thereon.

A barrier weld will be used on all the stainless steel items prior to welding being performed. The barrier layer will use ER309L on the stainless steel and ERNiCr-3 (Alloy 82) on the stainless steel near the DMW to stainless steel fusion zones and on the adjacent DMW surfaces.

Enclosure to AEP-NRC-2008-25 Page 4 The weld inlay filler metal covering the Alloy 82 barrier welds and the balance of the DMW surface, including deep weld repairs where Alloy 82 is used, will be Alloy 52M. The minimum as-deposited Cr content for at least the final 1/8 in. and more than one layer of the weld inlay thickness will be 24%.

The Alternative Requirements (Appendix 1) specifies the maximum finished surface area of the weld inlay over the low alloy ferritic steel base material to be 500 square inches (sq. in.), which exceeds the 100 sq. in. maximum surface area specified in Code Case N-638-1 (Reference 2),

Paragraph 1.0(a).Section XI Code Case N-638-4 specifies a maximum finished surface area of 500 sq. in. over the ferritic material.

The Alternative Requirements (Appendix 1) specifies the maximum cavity depth for weld repair is 2 in. That exceeds the depth of low alloy ferritic steel of 1/2 the ferritic steel thickness at the nozzle interface permitted by Code Case N-638-1 (Reference 2), Paragraph 1.0(a), for temperbead welding. Analysis shows that the nozzle low alloy ferritic steel that is replaced by the Alloy 82/52M weld material does not adversely affect the structural integrity of the DMW region.

The Alternative Requirements (Appendix 1) does not specify the maximum permitted depth into the low alloy ferritic steel for weld repair using nonferritic weld material, whereas the maximum depth into the low alloy ferritic steel nozzle material is 3/8 in. permitted by Code Case N-638-1 (Reference 2), Paragraph 1.0(c), for temperbead welding. It was assumed that flaw removal up to a 2 in. depth, near the buttering-to-nozzle fusion zone, resulting in a maximum depth of nozzle low alloy ferritic steel material being replaced by the Alloy 82/52M weld. Analysis shows that the nozzle low-alloy.ferritic steel that is replaced by the Alloy 82/52M weld material does not adversely affect the structural integrity of the DMW region.

Code Case N-63871 (Reference 2), Paragraph 3.0(d) specifies a maximum interpass temperature of 350 degrees Fahrenheit (OF) and implies temperature monitoring by thermocouples may be required by Paragraph 4.0(c). Since direct temperature measurement methods will be impractical to perform during welding operations from inside the nozzle, the Alternative Requirements (Appendix 1) specifies interpass temperature shall be determined by either:

a) performing heat flow calculations using the variables listed therein; or b) 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 using the maximum permitted heat input specified on the applicable welding procedure specification.

Section XI Code Cases N-638-2 through -4 specify these alternatives in lieu of direct interpass temperature measurement.

Examination Prior to machining, UT will be performed on the DMW in accordance with Section XI (Reference 3) and procedures, personnel, and equipment that have been qualified in accordance with Code Case N-695 (Reference 4).

The results of this examination will determine if there are PWSCC related flaws or other adverse pre-existing conditions.

Enclosure to AEP-NRC-2008-25 Page 5 Following machining and prior to inlay welding (see Figure 1) and repair welding (see Figure 2),

PT will be performed in accordance with NB-5000,Section III (Reference 1).

IWB-3514-2,Section XI (Reference 3), acceptance criteria will be applicable.

Following welding, acceptance/preservice PT and/or eddy current (see Figure 1) will be performed thereon in accordance with NB-5000,Section III (Reference 1) and IWA-2222,Section XI (Reference 3).

Because ambient temperature temperbead welding is used, the examination will be conducted at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the completion of the third temperbead layer over the lowalloy ferritic steel base material. The acceptance criteria of NB-5352,Section III (Reference 1) will apply with the additional requirement that rounded indications with major dimensions greater than 1/16 in. are unacceptable. For areas outside of the inlay, the inservice examination acceptance standards of Table IWB-3514-2 shall apply.

Acceptance UT will be performed on the weld inlay (see Figure 1) in accordance with Section V (2004 Edition), Article 4, Cladding - Technique One, using calibration blocks in accordance with Figure T-434.4.2.2.

Because ambient temperature temperbead welding is used, the examination will be conducted at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the completion of the third temperbead layer over the low alloy ferritic steel base material.

The acceptance criteria will be in accordance with NB-5330,Section III (Reference 1). When deep repair welding is performed (see Figure 2), acceptance UT of the repair weld below the weld inlay will be performed in accordance with Section V (2004 Edition), Article 4, and the acceptance criteria will be in accordance with NB-5330,Section III (Reference 1).

The requirement for NDE of the 1-1/2T band in Code Case N-638-1 (Reference 2) is specified to assure all flaws in the area of the repair have been removed or addressed, since these flaws may be associated with the original flaw and may have been overlooked. In this case, the repair welding is being performed as a result of PWSCC concerns occurring in the DMW and not for defects in the nozzle ferritic steel.

Preservice UT of the modified DMW, including the weld inlay (see Figure 1) and repair weld/weld inlay (see Figure 2), when applicable, will be performed in accordance with Section Xl (Reference 3) and procedures, personnel, and equipment that have been qualified in accordance with Code Case N-695 (Reference 5).

The inservice acceptance standards of IWB-3514.4 (Reference 3) will be applicable.

UT will be performed no sooner than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after completion of the third temperbead layer over the low alloy ferritic steel nozzle base material.

The 48-hour delay is intended to provide time for delayed hydrogen cracking occurrence. The Alternative Requirements (Appendix 1) specifies the machine GTAW process to be used for temperbead welding, thereby eliminating the use of welding processes requiring flux for arc shielding.

The machine GTAW temperbead 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

Enclosure to AEP-NRC-2008-25 Page 6 qualification, welding grade argon is used for the inert gas blanket.

To further reduce the likelihood of 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 temperbead process provides precise control of heat input, bead placement, bead size and contour. The precise control over these factors afforded by the machine GTAW process provides effective tempering of the nozzle low alloy ferritic steel heat-affected zone (HAZ). resulting in achievement of lower hardness and tempered martensite.

This further reduces susceptibility to hydrogen-induced cracking.

Temperbead Welding Applications, 48-Hour Hold Requirements for Ambient Temperature Temperbead Welding, EPRI, Palo Alto, CA: 2006 (Reference 6) provides justification for reducing the 48-hour hold time on P-No. 3, Group No. 3 low alloy ferritic steel base material, starting after completion of the third temperbead layer, as specified in the Alternative Requirements (Appendix 1). This report addresses microstructural issues, hydrogen sources, tensile stress and temperature, and diffusivity and solubility of hydrogen in steels. Past industry experience with the use of the machine GTAW process has resulted in no detection of hydrogen induced cracking after the 48-hour hold nondestructive examination or subsequent inservice inspections.

Inservice examination volumetric and surface examinations will be performed on all modified DMWs as specified in the Alternative Requirements (Appendix 1).

References

1)

ASME Boiler & Pressure Code',Section III, 1989 Edition, No Addenda.

2)

Code Case N-638-1, "Similar-and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique," dated February 13, 2003.

3)

ASME Boiler & Pressure Vessel Code,Section XI, 1989 Edition, No Addenda.

4)

Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds," dated May 21, 2003.

5)

Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds," dated May 21, 2003.

6)

Temperbead Welding Applications:

48-Hour Hold Requirements for Ambient Temperature Temperbead Welding, EPRI, Palo Alto, CA: 2006.

Enclosure to AEP-NRC-2008-25 Page 7 Appendix 1 ALERNATIVE REQUIREMENTS FOR REACTOR REQUIREMENTS FOR REACTOR VESSEL SAFE END-TO-PRIMARY NOZZLE ALLOY 82/182 DISSIMILAR METAL WELD MODIFICATION USING WELD INLAY 1.0 GENERAL

a.

The weld inlay shall be applied on the inside surface of the full penetration circumferential austenitic nickel alloy welds (DMWs) on the low alloy steel components, including nozzles (P-No. 3) to safe ends or piping components (P-No. 8 or 43), inclusive of the UNS N06082 or W86182 DMWs that join the two items.

b.

Appendix 1 shall apply to DMWs and adjacent component nozzles, cladding, piping, and their austenitic stainless steel welds, if applicable, consisting of the following materials and combinations thereof:

i.

P-No. 8 and P-No. 43.

ii.

P-No. 8 or 43 and P-No. 3.

c.

The location of the DMW fusion zones shall be determined.

d.

All welding shall use Welding Procedure Specifications qualified in accordance with Appendix 2.

e.

Ambient temperature temperbead welding shall be performed in accordance with Appendix 2.

f.

The final 1/8 in. inlay thickness shall contain at least 24% Chromium (Cr) as deposited.

The Cr content of the deposited weld metal shall be determined by chemical analysis of a coupon from a mockup representative of the materials on which the inlay will be deposited using the applicable production weld parameters and the same production weld metal classification.

The weld filler metal used for the mockup shall have Cr content no greater than that to be used for the inlay. The results shall be documented.

g.

Welding shall be performed using the machine GTAW process.

ERNiCrFe-7A (Alloy 52M) filler metal shall be used for at least the final 1/8 in. thickness and more than one layer (inlay). ERNiCr-3 (Alloy 82) may be used for repair welding, when applicable, beyond at least 1/8 in. and more than one layer thickness from the inside final surface.

h.

To reduce the potential of hot cracking when applying an austenitic nickel' alloy over P-No. 8 base metal, austenitic stainless steel welds, or cladding, it shall be permissible to apply ER309L austenitic stainless steel filler material and Alloy 82 near the DMW fusion zones, over the austenitic stainless steel material.

The Alloy 82 shall be subsequently covered with at least 1/8 in. thick and more than one layer of Alloy 52M complying with 1.0(f) and (g).

Unless otherwise specified, all Section III and Section Xl references in this Appendix shall be the 1989 Edition, no Addenda.

2.0 DESIGN, STRESS ANALYSES, AND FLAW GROWTH ANALYSES

a.

Design The thickness of the inlay over the exposed portion of the original DMW at the inner surface shall comply with the following.

Enclosure to AEP-NRC-2008-25 Page 8

i.

The minimum final thickness of the inlay shall consist of at least 1/8 in. of Alloy 52M at the inner surface.

ii.

The minimum thickness of the inlay using Alloy 52M in accordance with 2.0a.i.

shall extend over and beyond the final inner surface DMW fusion zones by at least twice the demonstrated accuracy of the locating technique of 1.0c or 1/4 in.,

whichever is greater.

iii.

The maximum thickness of the repair weld, if required, including the weld inlay shall be 2 in.

iv.

The design life of the modified DMWs shall be 30 additional years and shall be verified by the stress analyses specified in 2.0b and the flaw growth analyses specified in 2.0c considering the postulated flaws.

b.

Stress Analyses

i.

Stress and fatigue analyses shall be performed in accordance with NB-3200. The stress analyses evaluate the following modified DMW configurations.

1. 0.13 in. deep cavity requiring a 0.13 in. thick weld inlay for the full inner circumference.

2. 2 in. thick, local cavity repair weld inlay with weld inlay thereon.

c.

Flaw Growth Analyses

i.

Flaw growth analyses for postulated flaws shall be performed in accordance with IWB-3640. The residual stress analyses shall assume a full circumferential 50%

through-wall weld repair from the inside surface of the original DMW has previously occurred.

ii.

Planar flaws shall be postulated to exist in the newly applied weld inlay and in the original DMW as follows.

1. Circumferential flaw of 1/16'in. depth through the inlay weld thickness, surface connected for the entire circumference of the inlay.

2. Axial flaw of 1/16 in. depth through the inlay weld thickness, surface connected for the entire width (axial length).of the inlay.

3. Circumferential flaw of depth equal to the maximum acceptable flaw depth per Table IWB-3514-2, in the remaining DMW, originating at the weld inlay/DMW interface for the entire circumference of the inlay.

4. Axial flaw of depth equal to the maximum acceptable flaw depth per Table IWB-3514-2, in the remaining DMW, originating at the weld inlay weld inlay/DMW interface for the entire width (axial length) of the inlay.

d.

Any changes in applied loads, as a result of weld shrinkage from the inlay, or deep weld repair, when applicable, on the other items in the piping system (e.g., support loads and clearances and nozzle loads) shall be evaluated. Existing flaws previously accepted by analytical evaluation shall be evaluated in accordance with IWB-3640, as applicable.

3.0 EXAMINATION

a.

General

i.

The examination requirements of this Appendix shall be applicable in lieu of all other examination requirements.

ii.

Nondestructive examination procedures shall be in accordance with NB-5000 for acceptance examinations and IWA-2200 for preservice and inservice examinations and as specified herein.

Enclosure to AEP-NRC-2008-25 Page 9 iii.

Nondestructive examination personnel shall be qualified in accordance with IWA-2300, and as specified herein.

iv.

The final surface of the inlay shall be suitable for surface and volumetric examination.

v.

Examinations required after inlay welding shall be performed no sooner than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after completion of the third temperbead layer over the ferritic steel nozzle.

vi.

All flaws detected that are not associated with the DMW modification activity shall meet the requirements of IWB-3000.

b.

Examination Prior to Application of the Inlay

i.

Prior to machining and inlay welding, the applicable DMW volume shall be ultrasonically examined using procedures, personnel, and equipment that have been qualified in accordance with Code Case N-695.

Ultrasonic examination acceptance criteria shall be in accordance with the inservice examination acceptance standards of IWB-3514.

ii.

After machining and prior to welding, the area to be welded shall be examined using the liquid penetrant examination method. The acceptance criteria shall be in accordance with IWB-3514-2.

c.

Acceptance Examination of the Inlay

i.

The inlay surface, including at least 1/2 in. of adjacent material, shall be examined using the liquid penetrant examination method in accordance with NB-5000.

Acceptance criteria for the weld inlay shall be in accordance with NB-5352 with the additional requirement that rounded indications with major dimension greater than 1/16 in. shall not be permitted. Criteria for the balance of the surface examination area shall be in accordance with the. inservice examination acceptance standards of Table IWB-3514-2.

ii.

The inlay volume, at least 1/8 in. thickness, including the fusion zones shall be ultrasonically examined in accordance with Section V, Article 4, using Cladding Technique One.

Calibration standards shall be in accordance with Figure T-434.4.2.2., The acceptance criteria of NB-5330 shall apply. The repair weld volume, when applicable, shall be ultrasonically examined in accordance with Section V, Article 4. The acceptance criteria of NB-5330 shall apply.

d.

Preservice Examination

i.

Surface examination is required of the inlay surface. Examination requirements and acceptance criteria shall be as specified in 3.0c.i.

ii.

The modified DMW examination volume (see Figure El) shall be ultrasonically examined using procedures, personnel, and equipment that have been qualified in accordance with Code Case N-695.

Ultrasonic examination acceptance criteria shall be in accordance with the inservice examination acceptance standards of IWB-3514.

e.

Inservice Examination

i.

Volumetric and surface examination shall be performed on all the modified DMWs no sooner than the third refueling outage and no later than 10 years following inlay welding.

1. Ultrasonic examination shall be performed using procedures, personnel, and equipment that have been qualified in accordance with Code Case N-695. The inservice examination acceptance standards of IWB-3514 shall be applicable.

Enclosure to AEP-NRC-2008-25 Page 10 ii.

Examination volumes that show no indications of cracking shall be placed into a population to be examined on a sample basis., 25% of this population shall receive a volumetric examination performed from the outside diameter surface, or a volumetric examination and a surface examination performed from the weld ID surface. The 25% sample shall be.added-to the Inservice Inspection Program in accordance with IWB-2410 and shall be examined once each inspection interval.

iii.

If inservice examinations reveal crack growth or new cracking meeting the acceptance standards of IWB-3132.3, the DMW examination volume shall be reexamined during the first refueling outage following discovery of the growth or new cracking.

The weld examination volume shall be subsequently examined during each of the next two refueling outages.

iv.

Any volumetric examinations that reveal crack growth or new cracking meeting the acceptance standards shall also be subject to a surface examination.

The acceptance standards of 3.0c.i. shall be applicable. This surface examination shall also be required in any subsequent examinations required by 3.0e.iii.

1. If the examinations required by 3.0e.iii or 3.0e.iv. reveal that the flaw(s) remain essentially unchanged for three successive examinations, the weld examination schedule may revert to the sample and schedule of examinations.

This DMW shall be included in the 25% sample population.

v.

For volumetric examinations performed from the outside surface if new cracking or the growth of existing cracking is detected, additional surface examinations shall also be performed from the inside surface in the same outage and in subsequent outages as applicable for volumetric examinations.

f.

The 25% sample shall consist of the same welds in the same sequence during successive intervals to the extent practical provided the 25% sample contains the welds that experience the highest operating temperature in the item.

If hot leg and cold leg welds are included in the same item, the initial 25% sample does not need to include the cold leg welds. Those welds not included in the 25% sample shall be examined prior to the end of the evaluation period if the plant is to be operated beyond that time.

4.0 PRESSURE TESTING A system leakage test shall not be required for a weld inlay thickness of 10% or less of the original DMW thickness.

A system leakage test shall be performed in accordance with IWA-5000 for weld inlays greater than 10% of the original DMW thickness.

5.0 DOCUMENTATION Use of Appendix 1 shall be documented on Form NIS-2.

Enclosure to AEP-NRC-2008-25 Page 11 1/4" 1/3t D

t 1/2, F

SURFACE EXAMINATION Figure El - Examination Volume Volumetric Examination A-B-C-D Surface Examination E-F

Enclosure to AEP-NRC-2008-25 Page 12 Appendix 2 AMBIENT TEMPERATURE TEMPERBEAD WELDING 1.0 GENERAL REQUIREMENTS 1.1 The maximum area of an individual inlay weld based on the finished surface over the ferritic base material shall be 500 sq. in.

1.2 Repair/replacement activities on a DMW in accordance with this Appendix shall be limited to those along the fusion line of a nonferritic weld to ferritic base material on which 1/8 in. or less nonferritic weld deposit exists above the original fusion line.

1.3 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., whichever is less, shall be at least 50 0F.

2.0 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 the time and temperature that was applied to the materials to be welded.

b)

The root width included angle of the cavity in the test assembly shall be no greater than the minimum specified for the barrier weld.

c)

The maximum interpass temperature for the first three layers. of the test assembly shall be 1500F.

d)

The test assembly cavity depth shall be at least 1 in. The test assembly thickness shall be at least twice 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. The qualification test plate shall be prepared in accordance with Figure 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 (f), below, but shall be in the base metal.

f)

Charpy V-notch tests of the ferritic HAZ shall be performed at the same temperature as the base metal test of (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 HAZ impact specimens shall be taken transverse to the axis of the weld and

Enclosure to AEP-NRC-2008-25 Page 13 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. 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 SA-370, Figure 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 Reference Temperature for Nil Ductility Transition (RTNDT) 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.

3.1 The area to be welded shall be buttered with a deposit of at least three layers to achieve at least 1/8 in. (3mm) and more than one layer at the final inner surface of inlay weld thickness using Alloy 52M 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 45,000 Joule/inch (1,800 Joule/millimeter) under any conditions. Particular care shall be taken in the placement of the weld layers of the austenitic inlay weld filler material at the toe of the inlay weld 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.

Enclosure to AEP-NRC-2008-25 Page 14 3.2 The maximum interpass temperature for field applications shall be 350°F for all weld layers regardless of the interpass temperature used during qualification. The interpass temperature limitation of QW-406.3 need not be applied.

3.3 The interpass temperature shall be determined by one of the following methods:

a)

Heat flow calculations using the variables listed below as a minimum:

1) welding heat input

2) initial base material temperature

3) configuration, thickness, and mass of the item being welded

4) thermal conductivity and diffusivity of the materials being welded

5) arc time per weld pass and delay time between each pass

6) arc time to complete the weld b)

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.

3.4 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.

Enclosure to AEP-NRC-2008-25 Page 15 HAidJCF

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GENERAL NOITU: Base metI Charpy hmp ct spccimems are not

shovmw, Tiis figure illustiates a simitwr-tal wel, Fig. 1-1 QUALIFICATION TEST PLATE