CNRO-2005-00001, Request for Alternatives W3-R&R-003 - Proposed Alternative to ASME Requirements for Weld Repairs

Request for Alternatives W3-R&R-003 - Proposed Alternative to ASME Requirements for Weld Repairs

ML050390283
Person / Time
Site:	Waterford
Issue date:	01/31/2005
From:	Burford F Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNRO-2005-00001
Download: ML050390283 (27)

Text

Entergy Operations, Inc.

- Entergy 1340 Echelon Parkway Jackson, Mississippi 39213-8298 Tel 601-368-5758 F. G. Burford Acting Director Nuclear Safety & Licensing CNRO-2005-00001 January 31, 2005 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Request for Alternatives W3-R&R-003 -

Proposed Alternative to ASME Requirements for Weld Repairs Waterford Steam Electric Station, Unit 3 Docket No. 50-382 License No. NPF-38

REFERENCE:

NRC letter to Arizona Public Service Company, "Palo Verde Nuclear Generating Station, Units 1 and 3 - Relief Request No. 28 RE: Temper Bead Welding Processes for Pressurizer Heater Sleeves (TAC Nos.

MC3553 and MC3555)," dated November 3, 2004

Dear Sir or Madam:

Pursuant to 10 CFR 50.55a(a)(3)(i), Entergy Operations, Inc. (Entergy) proposes an alternative to the temper bead welding requirements of ASME Section Xl IWA-4500 and IWA-4530. As documented in Request for Alternative W3-R&R-003 (see enclosure), Entergy proposes to perform ambient temperature temper bead welding repairs to pressurizer heater sleeve and instrument nozzles at Waterford Steam Electric Station, Unit 3 (Waterford 3).

A similar request was recently approved by the NRC staff for Palo Verde Nuclear Generating Station, as documented in the referenced letter.

Entergy requests NRC approval by March 20, 2005 in order to support activities to be performed during Waterford 3's upcoming spring 2005 refueling outage. Should you have any questions regarding this submittal, please contact Guy Davant at (601) 368-5756.

This letter contains no new commitments.

Sincerely, FP.C,. Bu,¢Fd FGB/GHD/ghd

Enclosure:

Request for Alternative W3-R&R-003 0 1-

CNRO-2005-00001 Page 2 of 2 cc: Mr. W. A. Eaton (ECH)

Mr. J. E. Venable (W3)

Dr. Bruce S. Mallet Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 U. S. Nuclear Regulatory Commission Attn: Mr. N. Kalyanam MS 0-7D1 Washington, DC 20555-0001 NRC Senior Resident Inspector Waterford 3 P. 0. Box 822 Killona, LA 70066-0751

ENCLOSURE CNRO-2005-00001 REQUEST FOR ALTERNATIVE W3-R&R-003

ENTERGY OPERATIONS, INC.

WATERFORD STEAM ELECTRIC STATION, UNIT 3 REQUEST FOR ALTERNATIVE W3-R&R-003 COMPONENTS' Component/Number: Pressurizer RC-MPZR-0001

Description:

Pressurizer Heater Sleeves Pressurizer Upper and Lower Head Instrument Nozzles Pressurizer Side Shell Nozzle Code Class: 1

References:

1. ASME Section Xl, 1992 Edition with portions of the 1993 Addenda as listed in Reference 7

2. ASME Section 1II,Subsection NB, 1971 Edition, Summer 1971 'Addenda

3. ASME Section 1II,Subsection NB, 1971 Edition, Summer 1972 Addenda

4. ASME Section III, Subsection NB, 1989 Edition

5. ASME Section Xl Code Case N-638, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique"

6. EPRI Report GC-1 11050, "Ambient Temperature Preheat for Machine GTAW Temper Bead Applications"

7. CEP-ISI-001, "Waterford 3 Steam Electric Station Inservice Inspection Plan" Unit / Inspection Waterford 3 Steam Electric Station (Waterford 3) Second (2nd)

Interval: 10-Year Interval II. CODE REQUIREMENTS Subarticle IWA-4170(b) of ASME Section XI, 1992 Edition states, "Repairs and installation of replacement items shall be performed in accordance with the Owner's Design Specification and the original Construction Code of the component or system.

Later editions and Addenda of the Construction Code or of Section 1II,either in their entirety or portions'thereof, and Code Cases may be used. If repair welding cannot be performed in accordance with these requirements, the applicable requirements of IWA-4200, IWA-4400, or IWA-4500 may be used."

IWA-4500 of ASME Section XI establishes alternative repair welding methods for performing temper bead welding. According to IWA-4500(a), "Repairs to base materials and welds identified in IWA-4510, IWA-4520, and IWA-4530 may be made by welding Page 1 of 24

without the specified pbstweld heat treatment requirements of the Construction Code or Section III, provided the requirements of IWA-4500(a) through (e) and IWA-4510, IWA-4520, or IWA-4530, as applicable, are met."

IWA-4530 applies to dissimilar materials such as welds that join P-No. 43 nickel alloy to P-No. 3 low alloy steels. According to IWA-4530, "Repairs to welds that join P-No. 8 or P-No. 43 material to P-Nos. 1, 3, 12A, 12B, and 12C material may be made without the specified postweld heat treatment provided the requirements of IWA-4530 through IWA-4533 are met. Repairs made to this paragraph are limited to those along the fusion line of a nonferritic weld to ferritic base material where 1/8-inch or less of nonferritic weld deposit exists above the original fusion line after defect removal."

Temper bead repairs are performed in accordance with IWA-4500 and IWA-4530 whenever the repair cavity is within 1/8-inch of the ferritic base materials. When the gas tungsten arc welding (GTAW) process is used in accordance with IWA-4500 and IWA-4530, temper bead welding is performed as follows:

• Only the automatic or machine GTAW process using cold wire feed can be used.

Manual GTAW cannot be used.

• A minimum preheat temperature of 300OF is established and maintained throughout the welding process. Interpass temperature cannot exceed 4500F.

• The weld cavity is buttered with at least six (6) layers of weld metal.

• Heat input of the initial six layers is controlled to within +/-10% of that used for the first six (6) layers during procedure qualification testing.

• After the first six weld layers, repair welding is completed with a heat input that is equal to or less than that used in the procedure qualification for weld layers seven and beyond.

• Upon completion of welding, a postweld soak or hydrogen bake-out at 450°F - 550°F for a minimum of four (4) hours is required.

• Preheat, interpass, and postweld soak temperatures are monitored using thermocouples and recording instruments.

• The repair weld and preheated band are examined in accordance with IWA-4533 after the completed weld has been at ambient temperature for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

Ill. PROPOSED ALTERNATIVE A. Background The Waterford 3 pressurizer lower head, upper head, and side shell were manufactured from SA533, Grade B, Class 1 low alloy steel (P-Number 3, Group 3 material). The pressurizer heater sleeves, upper and lower head instrument nozzles, and side shell nozzle were all originally manufactured from Alloy 600 material. Alloy 600 has a demonstrated sensitivity to primary water stress corrosion cracking (PWSCC).

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During previous refueling outages, the Waterford 3 pressurizer upper head instrument nozzles were repaired by replacing the original Alloy 600 nozzles with new Alloy 690 nozzles. In addition, one of the thirty heater sleeves was also previous plugged using Alloy 690. During Refueling Outage -13 in spring 2005, Waterford 3 plans to proactively replace all remaining Alloy 600 heater sleeves and instrument nozzles.

This request for alternative is specific to each of the following pressurizer repair welding activities that involve welding using a proposed ambient temperature temper bead technique:

• Heater Sleeve Mid-Wall Repair In this repair, the new Alloy 690 heater sleeve is welded directly to the pressurizer bore using the proposed ambient temperature temper bead process. Details of this repair are shown in Figure 1, Section 'A-A" and Figure 2, Section "C-C".

• Heater Sleeve Repair Using an Outside Diameter Weld Pad In this repair, an Inconel weld pad is welded to the outside diameter (OD) of the pressurizer lower head using the proposed ambient temperature temper bead process. The new Alloy 690 heater sleeve is welded to the Inconel weld pad using a non-temper bead welding process. A typical detail of this repair is shown in Figure 2, Section "D-D". Note: This alternative repair option will only be used in the unlikely circumstance where the mid-wall repair cannot be implemented.

• OD Weld Pad Repair of Lower Head Instrument Nozzles Inthis repair, an Inconel weld pad is welded to the OD of the pressurizer lower head using the proposed ambient temperature temper bead process. The new Alloy 690 nozzle is welded to the Inconel weld pad using a non-temper bead welding process. A detail of this repair is shown in Figure 1, Section "B-B".

• OD Weld Pad Repair of Side Shell Instrument Nozzle In this repair, an Inconel weld pad is welded to the OD of the pressurizer side shell using the proposed ambient temperature temper bead process. The new Alloy 690 nozzle is welded -to the Inconel weld pad using a non-temper bead welding process. A detail of this repair is shown in Figure 3.

OD Weld Pad Repair of Previously Repaired Upper Head Instrument Nozzles Two Inconel 52 weld pads were previously welded to the OD of the pressurizer upper head using the temper bead process. Alloy 690 instrument nozzles were welded to the weld pads with A-182 filler metal. In this repair, the existing nozzles and associated attachment welds will be removed by grinding and new Alloy 690 nozzles will be installed using Inconel 52 filler metal. In the unlikely event that grinding results in a repair cavity that is within 1/8-inch of the ferritic base materials, ambient temperature temper bead welding will be performed. A typical detail of this repair is shown in Figure 4.

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-I - 5 B. ProDosed Alternative Pursuant to 10 CFR 50.55a(a)(3)(i), Entergy proposes alternatives to the GTAW-machine temper bead welding requirements of IWA-4500 and IWA-4530 of ASME Section Xi. Specifically, Entergy proposes to perform ambient temperature temper bead welding in accordance with Attachment 1, "Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique."

Entergy is planning to use this proposed alternative for mid-wall repairs of the pressurizer heater sleeves and OD weld pad repairs of the pressurizer instrument nozzles as described in Section III.A above. However, where mid-wall repairs for pressurizer heater sleeves cannot be performed, an alternative OD weld pad repair will be performed. Although a contingency, this alternative OD weld pad repair for the heater sleeves is unlikely.

Entergy has reviewed the proposed ambient temperature temper bead welding techniques of Attachment 1 against the GTAW-machine temper bead welding requirements of IWA-4500 and IWA-4530. This review was performed to identify differences between Attachment I and IWA-4500 and IWA-4530. Based upon this review, Entergy proposes alternatives to the following ASME Section Xl requirements of IWA-4500 and IWA-4530:

1. IWA-4500(a) specifies that repairs to base materials and welds identified in IWA-4530 may be performed without the specified postweld heat treatment of the construction code or ASME Section III provided the requirements of IWA-4500 and IWA-4530 are met. IWA-4530 includes temper bead requirements applicable to the shielded metal arc welding (SMAW) and the machine or automatic GTAW processes. As an alternative, Entergy proposes to perform temper bead weld repairs using the ambient temperature temper bead technique described in Attachment 1. Only the machine or automatic GTAW process can be used when performing ambient temperature temper bead welding in accordance with Attachment 1.

2. IWA-4500(d)(2) specifies that if repair welding is to be performed where physical obstructions impair the welder's ability to perform, the welder shall also demonstrate the ability to deposit sound weld metal in the positions, using the same parameters and simulated physical obstructions as are involved in the repair. This limited accessibility demonstration applies when manual temper bead welding is performed using the Shielded Metal Arc Welding (SMAW) process. It does not apply to "welding operators" who perform machine or automatic GTAW welding from a remote location. (This distinction is clearly made in IWA-4500 and IWA-4530.) Because the proposed ambient temperature temper bead technique described in Attachment 1 utilizes a machine GTAW welding process, limited access demonstrations of 'welding operators" are not required. Therefore, the requirement of IWA-4500(d)(2) does not apply.

3. IWA-4500(e)(2) specifies that the weld area plus a band around the repair area of at least 1%times the component thickness or 5 inches, whichever is less, shall be preheated and maintained at a minimum temperature of 3000F for the GTAW process during welding; maximum interpass temperature shall be 450 0F. As an alternative, Entergy proposes that the weld area plus a band around the repair area IPage 4 of 24

of at least 1I times the component thickness or 5 inches, whichever is less, shall be preheated and maintained at a minimum temperature of 500F for the GTAW process during welding. The maximum interpass temperature shall be 3500 F regardless of the interpass temperature during qualification.

4. IWA-4500(e)(2) specifies that thermocouples and recording instruments shall be used to monitor process temperatures. Entergy will not employ thermocouples or recording instrumentation since there will be no elevated preheat. Because of the large heat sink provided by the pressurizer, the interpass temperature is not expected to approach 3500F. This was verified by mockup testing.

5. IWA-4500(e)(2) specifies that thermocouple attachment and removal shall be performed in accordance with ASME Section 111.Because Entergy will not use thermocouples, the thermocouple attachment and removal requirements of IWA-4500(e)(2) do not apply.

6. IWA-4532.1 establishes procedure technique requirements that apply when using the SMAW process. Because the proposed ambient temperature temper bead technique of Attachment 1 utilizes the machine or automatic GTAW welding process, the SMAW temper bead technique requirements of paragraph IWA-4532.1 do not apply.

7. IWA-4532.2(c) specifies that the repair cavity shall be buttered with six layers of weld metal in which the heat input of each layer is controlled to within +1-10% of that used in the procedure qualification test, and heat input control for subsequent layers shall be deposited with a heat input equal to or less than that used for layers beyond the sixth in the procedure qualification. As an alternative, Entergy proposes to deposit the weld area with a minimum of three layers of weld metal to obtain a minimum thickness of 1/8-inch. The heat input of each weld layer in the 1/8-inch thick section shall be controlled to within +/-1 0% of that used in the procedure qualification test. The heat input for subsequent weld layers shall not exceed the heat input used for layers beyond the 1/8-inch thick buttered section (first three weld layers) in the procedure qualification.

8. IWA-4532.2(c) specifies that the completed weld shall have at least one layer of weld reinforcement deposited and then this reinforcement shall be removed by mechanical means. As an alternative, Entergy's proposed ambient temperature temper bead technique does not include a reinforcement layer.

9. IWA-4532.2(d) specifies that,'after at least 3/16-inch of weld metal has been deposited, the weld area shall be maintained at a temperature of 4500F - 5500F for a minimum of four (4) hours (for P-No. 3 materials). As an alternative, Entergy's proposed ambient temperature temper bead technique does not include a postweld soak.

10. IWA-4532.2(e) specifies that after depositing at least 3/16-inch of weld metal and performing a postweld soak 4500 F - 5500 F, the balance of welding may be performed at an interpass temperature of 350 0F. As an alternative, Entergy proposes that an interpass temperature of 3500F may be used throughout the welding process without a postweld soak.

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11. IWA-4533 specifies the following examinations shall be performed after the completed repair weld has been at ambient temperature for at least 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />s: (a) the repair weld and preheated band shall be examined by the liquid penetrant method; (b) the repaired region shall be volumetrically examined by the radiographic method, and if practical, by the ultrasonic method. As an alternative to the IWA-4533, Entergy proposes to perform the following examinations of the new mid-wall repair weld and OD weld pad:

a. A liquid penetrant examination of the completed repair weld shall be performed in accordance with NB-5000 of ASME Section III, 1989 Edition. Acceptance criteria shall comply with NB-5350.

b. The completed repair weld shall be ultrasonically examined in accordance with NB-5000 of ASME Section III, 1989 Edition. Acceptance criteria shall comply with NB-5330.

IV. BASIS FOR PROPOSED ALTERNATIVE The pressurizer upper and lower heads and side shell were manufactured from P-No. 3, Group 3 low alloy steel. If repairs are performed in accordance with ASME Section 1II, Entergy would have two options:

1. Perform a weld repairthat includes a postweld heat treatment at 1,1000F - 1,2500 F in accordance with NB-4622.1; or

2. Perform a temper bead repair using the SMAW process in accordance with NB-4622.1 1.

Each option is discussed below.

1. Postweld Heat Treatment Postweld Heat Treatment (PWHT) of the pressurizer head is impractical. PWHT could cause ovalization and misalignment of heater sleeves, which would permanently damage the head including the heater support assembly. NB-4600 requires PWHTto be performed at 1,100F- 1,2500 F.

2. TemDer Bead Repair Using SMAW NB-4622.1 I provides temper bead rules for repair welding dissimilar materials using the SMAW process. Because NB-4622.11 does not include temper bead rules for the machine or automatic GTAW process, a manual SMAW temper bead process must be used. However, a manual SMAW temper bead repair is not a desirable option due to radiological considerations. First, resistance heating blankets, thermocouples, and insulation must be installed. Secondly, the manual SMAW temper bead process is a time and dose intensive process. Each weld layer is manually deposited in a high dose and high temperature (350 0F) environment. The manual SMAW process also requires the weld crown of the first weld layer to be mechanically removed by grinding. Upon completing repair welding, resistance heating blankets, thermocouples, and insulation must be removed. Thermocouples and heating blanket-mounting pins must be removed by Page 6 of 24

grinding. The ground areas must be subsequently examined by either magnetic particle or liquid penetrant examination techniques.

Entergy is not requesting an alternative to NB-4600; rather this request proposes an alternative to IWA-4500 and IWA-4530. Owners are allowed by ASME Section Xl IWA-4170(b) and IWA-4500(a) to perform temper bead repairs of dissimilar materials.

IWA-4170(b) and IWA-4500(a) provide requirements and controls for performing such repairs.

IWA-4500 and IWA-4530 of ASME Section Xl establish requirements for performing temper bead welding of 'dissimilar materials". According to [WA-4530, either the automatic or machine GTAW process or SMAW process may be used. When using the machine GTAW process, a minimum preheat temperature of 300OF must be established and maintained throughout the welding process while the interpass temperature is limited to 450 0F. Upon completion of welding, a postweld soak is performed at 4500 F - 550 0F for a minimum of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

The IWA-4500 and IWA-4530 temper bead welding process is a time and dose intensive process. Resistance heating blankets are attached to the pressurizer base material; typically a capacitor discharge stud welding process is used. Thermocouples must also be attached to the pressurizer base material using a capacitor discharge welding process to monitor preheat, interpass, and postweld soak temperatures. Prior to heatup, thermal insulation is also installed. Upon completion of repair welding (including the postweld soak), the insulation, heating blankets, studs, and thermocouples must be removed from the pressurizer base material. Thermocouples and stud welds are removed by grinding. Ground removal areas are subsequently examined by the liquid penetrant or magnetic particle method. A significant reduction in dose could be realized by utilizing an ambient temperature temper bead process. Therefore, Entergy proposes an alternative welding technique based on the methodology of ASME Code Case N-638.

Suitability of Proposed Ambient Temperature Temper Bead Technique A. Evaluation of the Ambient Temperature Temper Bead Technique Research by the Electric Power Research Institute (EPRI) and other organizations on the use of an ambient temperature temper bead operation using the machine GTAW process is documented in EPRI Report GC-1 11050. According to the EPRI report, repair welds performed with an ambient temperature temper bead procedure utilizing the machine GTAW welding process exhibit mechanical properties equivalent or better than those of the surrounding base material. Laboratory testing, analysis, successful procedure qualifications, and successful repairs have all demonstrated the effectiveness of this process.

The effects of the ambient temperature temper bead welding process of Attachment 1 on mechanical properties of repair welds, hydrogen cracking, and restraint cracking are addressed below.

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1. Mechanical Properties The principal reasons to preheat a component prior to repair welding is to minimize the potential for cold cracking. The two cold cracking mechanisms are hydrogen cracking and restraint cracking. Both of these mechanisms occur at ambient temperature. Preheating slows down the cooling rate resulting in a ductile, less brittle microstructure thereby lowering susceptibility to cold cracking. Preheat also increases the diffusion rate of monatomic hydrogen that may have been trapped in the weld during solidification. As an alternative to preheat, the ambient temperature temper bead welding process utilizes the tempering action of the welding procedure to produce tough and ductile microstructures. Because precision bead placement and heat input control is characteristic of the machine GTAW process, effective tempering of weld heat affected zones is possible without the application of preheat.

According to Section 2-1 of EPRI Report GC-1 11050, "MTlhe temper bead process is carefully designed and controlled such that successive weld beads supply the appropriate quantity of heat to the untempered heat affected zone such that the desired degree of carbide precipitation (tempering) is achieved.

The resulting microstructure is very tough and ductile."

The IWA-4530 temper bead process also includes a postweld soak requirement. Performed at 4500F - 5500F for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (P-No. 3 base materials),

this postweld soak assists diffusion of any remaining hydrogen from the repair weld. As such, the postweld soak is a hydrogen bake-out and not a postweld heat treatment as defined by the ASME Code. At 4500F - 550 0F, the postweld soak does not stress relieve, temper, or alter the mechanical properties of the weldment in any manner.

Section 2.1 of Attachment I establishes detailed welding procedure qualification requirements for base materials, filler metals, restrain, impact properties, and other procedure variables. The qualification requirements of Section 2.1 provide assurance that the mechanical properties of repair welds will be equivalent or superior to those of the surrounding base material.

2. Hydrogen Cracking Hydrogen cracking is a form of cold cracking. It is produced by the action of internal tensile stresses acting on low toughness heat affected zones. The internal stresses are produced from localized build-ups of monatomic hydrogen. Monatomic hydrogen forms when moisture or hydrocarbons interact with the welding arc and molten weld pool. The monatomic hydrogen can be entrapped during weld solidification and tends to migrate to transformation boundaries or other microstructure defect locations. As concentrations build, the monatomic hydrogen will recombine to form molecular hydrogen - thus generating localized internal stresses at these internal defect locations. If these stresses exceed the fracture toughness of the material, hydrogen induced cracking will occur. This form of cracking requires the presence of hydrogen and low toughness materials. It is manifested by intergranular cracking of susceptible materials and normally occurs within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of welding.

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IWA-4500 establishes elevated preheat and postweld soak requirements. The elevated preheat temperature of 3000 F increases the diffusion rate of hydrogen from the weld. The postweld soak at 4500F - 5500F was also established to bake-out or facilitate diffusion of any remaining hydrogen from the weldment.

However, while hydrogen cracking is a concern for SMAW, which uses flux covered electrodes, the potential for hydrogen cracking is significantly reduced when using the machine GTAW welding.

The machine GTAW welding process is inherently free of hydrogen. Unlike the SMAW process, GTAW welding filler metals do not rely on flux coverings that may be susceptible to moisture absorption from the environment. Conversely, the GTAW process utilizes dry inert shielding gases that cover the molten weld pool from oxidizing atmospheres. Any moisture on the surface of the component being welded will be vaporized ahead of the welding torch. The vapor is prevented from being mixed with the molten weld pool by the inert shielding gas that blows the vapor away before it can be mixed. Furthermore, modern filler metal manufacturers produce wires having very low residual hydrogen. This is important because filler metals and base materials are the most realistic sources of hydrogen for automatic or machine GTAW temper bead welding. Therefore, the potential for hydrogen-induced cracking is greatly reduced by using the machine GTAW process.

3. Cold Restraint Cracking Cold restraint cracking generally occurs during cooling at temperatures approaching ambient temperature. As stresses build under a high degree of restraint, cracking may occur at defect locations. Brittle microstructures with low ductility are subject to cold restraint cracking. However, the ambient temperature temper bead process is designed to provide a sufficient heat inventory so as to produce the desired tempering for high toughness. Because the machine GTAW temper bead process provides precision bead placement and control of heat, the toughness and ductility of the heat affected zone will typically be superior to the base material. Therefore, the resulting structure will be appropriately tempered to exhibit toughness sufficient to resist cold cracking.

In conclusion, no elevated preheat or postweld soak above ambient temperature is required to achieve sound and tough repair welds when performing ambient temperature temper bead welding using the machine GTAW process. This conclusion is based upon strong evidence that hydrogen cracking will not occur with the GTAW process. In addition, automatic or machine temper bead welding procedures without preheat will produce satisfactory toughness and ductility properties both in the weld and weld heat affected zones. The results of previous industry qualifications and repairs further support this conclusion. The use of an ambient temperature temper bead welding procedure will improve the feasibility of performing localized weld repairs with a significant reduction in radiological exposure.

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B. Evaluation of Proposed Alternatives to IWA-4500 and IWA-4530

1. According to IWA-4500(a), repairs may be performed to dissimilar base materials and welds without the specified postweld heat treatment of ASME Section III provided the requirements of IWA-4500 and IWA-4530 are met.

The temper bead rules of IWA4500 and IWA-4530 apply to dissimilar materials such as P-No. 43 to P-No. 3 base materials welded with F-No. 43 filler metals. When using the GTAW-machine process, the IWA-4500 and IWA-4530 temper bead process is based fundamentally on an elevated preheat temperature of 3000F, a maximum interpass temperature of 4500F, and a postweld soak of 4500F - 5500F. The proposed alternative of Attachment I also establishes requirements to perform temper bead welding on dissimilar material welds that join P-No. 43 to P-No. 3 base materials using F-No. 43 filler metals. However, the temper bead process of Attachment 1 is an ambient temperature technique that only utilizes the GTAW-machine or GTAW-automatic process. The suitability of the proposed ambient temperature temper bead technique is evaluated in this section. The results of this evaluation demonstrate that the proposed ambient temperature temper bead technique provides an acceptable level of quality and safety.

2. According to IWA-4500(e)(2), the weld area plus a band around the repair area of at least 1-1/2 times the component thickness or 5 inches, whichever is less, shall be preheated and maintained at a minimum temperature of 300OF for the GTAW process during welding while the maximum interpass temperature is limited to 450 0F. The ambient temperature temper bead technique of Attachment 1 also establishes a preheat band of at least 1%times the component thickness or 5 inches, whichever is less. However, the ambient temperature temper bead technique requires a minimum preheat temperature of 500 F and a maximum interpass temperature of 3500F. The suitability of an ambient temperature temper bead technique with reduced preheat and interpass temperatures is addressed in Section IV.A.

-3. According to IWA-4500(e)(2), thermocouples and recording instruments shall be used to monitor process temperatures. The use of thermocouples and recording instruments is only required by ASME Sections III and Xl when performing either PWHT operations or traditional temper bead welding operations with elevated preheat and postweld soak temperatures. The use of thermocouples and recording instrumentation is not required by ASME Section Xl Code Case N-638 for monitoring welding process temperatures.

Per Paragraph 1(d) of Attachment 1, the minimum welding temperature is 500F. The containment temperatures are not expected to be less than 50°F during the welding operations. However, the Welding Procedure Specification requires that the minimum temperature be verified prior to welding.

4. According to IWA-4532.2(c), the repair cavity shall be buttered with six layers of weld metal in which the heat input of each layer is controlled to within

+/-10% of that used in the procedure qualification test, and heat input control for subsequent layers shall be deposited with a heat input equal to or less than that used for layers beyond the sixth in the procedure qualification. As an alternative to IWA-4532.2, Entergy proposes to butter the ferritic base material Page 10 of 24

i, J ..- { .X j with at least three layers of weld metal to obtain a minimum butter thickness of 1/8-inch. The heat input of each layer in the 1/8-inch thick buttered section shall be controlled to within +/-10% of that used in the procedure qualification test. The heat input for subsequent weld layers shall not exceed the heat input used for layers beyond the 1/8-inch thick buttered section (first three weld layers) in the procedure qualification. When using the ambient temperature temper bead technique of Attachment 1,the machine GTAW process is used.

Machine GTAW is a low heat input process that produces consistent small volume heat affected zones. -Subsequent GTAW weld layers introduce heat into the heat affected zone produced by the initial weld layer. The heat penetration of subsequent weld layers is carefully applied to produce overlapping thermal profiles that develop a correct degree of tempering in the underlying heat affected zone. When welding dissimilar materials with nonferritic weld metal, the area requiring tempering is limited to the weld heat affected zone of the ferritic base material along the ferritic fusion line.

After welding the ferritic base material to Alloy 690 with at least 1/8-inch of weld metal (first 3 weld layers), subsequent weld layers should not provide any additional tempering to the weld heat affected zone in the ferritic base material.

Therefore, less restrictive heat input controls are adequate after depositing the 1/8-inch thick weld section.

5. According to lWA-4532.2(c), at least one layer of weld reinforcement shall be deposited on the completed weld and with this reinforcement being subsequently removed by mechanical means. In the proposed alternative of Attachment 1, the deposition and removal of a reinforcement layer is not required. A reinforcement layer is required when a weld repair is performed to a ferritic base material or ferritic weld using a ferritic weld metal. On ferritic materials, the weld reinforcement layer is deposited to temper the last layer of untempered weld metal of the completed repair weld. Because the weld reinforcement layer is untempered (and unnecessary), it is removed. However, when repairs are performed to dissimilar materials using nonferritic weld metal, a weld reinforcement layer is not required because nonferritic weld metal does not require tempering. When performing a dissimilar material weld with a nonferritic filler metal, the only location requiring tempering is the weld heat affected zone in the ferritic base material along the weld fusion line. However, the three weld layers of the 1/8-inch thick weld section are designed to provide the required tempering to the weld heat affected zone in the ferritic base material. Therefore, a weld reinforcement layer is not required.

While Entergy recognizes that IWA-4532.2(c) does require the deposition and removal of a reinforcement layer on repair welds in dissimilar materials, Entergy does not believe that is necessary for repair using a nonferritic filler material. This position is supported by the fact that ASME Code Case N-638 only requires the deposition and removal of a reinforcement layer of a similar filler material (ferritic) when performing repair welds on similar (ferritic) materials. Repair welds on dissimilar materials using nonferritic filler materials are exempt from this requirement in Code Case N-638.

Page 11 of 24

6. According to IWA-4532.2(d), the weld area shall be maintained at a temperature of 4500 F - 5500F for a minimum of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (for P-No. 3 materials) after at least 3/16-inch of weld metal has been deposited. In the proposed alternative of Attachment 1, a postweld soak is not required. The suitability of an ambient temperature temper bead technique without a postweld soak is addressed in Section IV.A.

7. According to IWA-4532.2(e), after depositing at least 3/16-inch of weld metal and performing a postweld soak at 300 0F, the balance of welding may be performed at an interpass temperature of 350 0F. As an alternative, Entergy proposes that an interpass temperature of 3500F may be used throughout the welding process without a postweld soak. The proposed ambient temperature temper bead process of Attachment 1 is carefully designed and controlled such that successive weld beads supply the appropriate quantity of heat to the untempered heat affected zone such that the desired degree of carbide precipitation (tempering) is achieved. The resulting microstructure is very tough and ductile. This point is validated during weld procedure qualification.

Based on Charpy V-notch testing of the procedure qualification test coupon, impact properties in weld heat affected zone will be demonstrated to be equal to or better than those of the unaffected base material. The suitability of an ambient temperature temper bead technique without a postweld soak is addressed in Section IV.A.

8. IWA-4533 specifies that the repair weld and preheated band shall be volumetrically examined by the radiographic method, and if practical, by the ultrasonic method after the completed repair 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 />. IWA-4533 specifies the following examinations shall be performed after the completed repair weld has been at ambient temperature for at least 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />s: (a) the repair weld and preheated band shall be examined by the liquid penetrant method; (b) the repaired region shall be examined by the radiographic method, and if practical, (c) by the ultrasonic method. Entergy will perform the liquid penetrant examination of the completed repair weld. As an alternative to the radiographic examination of IWA-4533, Entergy proposes ultrasonic examination of the repair weld.

Radiography of the welds is not practical based on the inability to place film to get a meaningful radiograph. The acceptance criteria for the ultrasonic examination are contained in Attachment 1.

9. IWA-4533 specifies that (a) the repair weld and preheated band shall be examined by the liquid penetrant method; (b) the repaired region shall be volumetrically examined by the radiographic method, and if practical, by the ultrasonic method. As an alternative to the IWA-4533, Entergy proposes to perform the following examinations:

a. Liquid penetrant examination shall be performed in accordance with NB-5000 of ASME Section III, 1989 Edition. Acceptance criteria shall comply with NB-5350.

Suitability: When using an ambient temperature temper bead technique, an elevated preheat temperature is not used. As a result, there is no preheated band. Therefore, the proposed alternative to only examine the Page 12 of 24

new mid-wall repair weld and OD weld pad (including weld heat affected zones) is acceptable.

b. The completed repair weld shall be ultrasonically examined in accordance with NB-5000 of ASME Section III, 1989 Edition. Acceptance criteria shall comply with NB-5330.

Suitability: Radiographic examination is impractical since the pressurizer vessel inside diameter is inaccessible for positioning the gamma source.

As an alternative to radiographic examination, an ultrasonic examination of the new mid-wall repair weld and OD weld pad will be performed.

Ultrasonic examination of temper bead repair welds is an acceptable option according to ASME Section XI, IWA-4630 in the 1995 Edition, 1996 Addenda and later (approved by NRC through the 2001 Edition, 2003 Addenda). Ultrasonic examination of repair welds is also required in Code Case N-638. The proposed ultrasonic examination will be performed in accordance with ASME Section 1II, NB-5000 which includes acceptance criteria that is appropriate for fabrication type flaws.

V. CONCLUSION 10 CFR 50.55a(a)(3) states:

"Proposed alternatives to the requirements of (c), (d), (e), (f), (g), and (h) of this section or portions thereof may be used when authorized by the Director of the Office of Nuclear Reactor Regulation. The applicant shall demonstrate that:

(i) The proposed alternatives would provide an acceptable level of quality and safety, or (ii) Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety."

Entergy believes that compliance with the repair rules as stated in ASME Section Xl (Reference 1) and as described in Section II of this request would result in unwarranted damage to the pressurizer head assembly. Additionally, the work required to meet the current Code repair method, automatic or machine GTAW temper bead with 3000F minimum preheat and 4500 F - 5500F postweld hydrogen bake-out, would be extremely difficult and personnel radiation exposure resulting from set-up, monitoring, and removing the required equipment is not justified.

Entergy also believes that the proposed alternative provides an acceptable level of quality and safety without exposing the pressurizer to potential distortion of the sleeves and heater support structure, as discussed in Section IV. Therefore, Entergy requests that the NRC staff authorize the proposed alternative in accordance with 10 CFR 50.55a(a)(3)(i).

Page 13 of 24

24' 161 o £xIati ng a.Sleeve Existing Nozzle max.2750.1251 min.

E HeSate Seeve Bor Max.5;W, 5 Hole (see Note 7)

See Detail A on Figure 2 T \, _- Replacement n Replacementwi 3leeet-fl. o 30 38 *, -0.614-i0.030 221 B4l4 24-1/4' Section A-ASeto B-Notes: 1. Break all sharp corners to leave a smooth transition.

2. Replacement sleeves and nozzles are Alloy 690 material.

3. Replacement weld metal is Alloy 52/152.

4. Replacement sleeve and nozzle length defined by WSI.

5. Potential MNSA/mid-wall repair interaction shown on Figure 2.

6. There is no requirement as to the radius of the replacement weld connecting the pad to the replacement nozzle/sleeve.

7. The slope of the replacement weld shown is a maximum slope. Other slopes, such as 1:3 where the first dimension is the pad thickness. are acceptable.

9. MNSA holes will not be plugged.

Figure 1 Sections Showing Heater Sleeve and Instrument Repair Page 14 of 24

Existing Sleeve IZZZZ 0.125' min.

Instrument Nozzle:

Heater Sleeve:

Replacement - 4° Sleeve See Detail A 1.300

- / ' (See Note 6 on V-4 Instrument Nozzle: 0.16- min.

Heater Sleeve: 0.13' min.

Detail A Secion D-Dl (One sleeve has this geometry)

Section C-C MNSA/Mid-Wall Repair Layout (Two sleeves have this geometry)

Figure 2 Sections Showing Heater Sleeve and Instrument Repairs at Previous MNSA and OD Pad Locations Page 15 of 24

1.315't0.005 Replacement -I Nozzle 0.815si0.015 0.5*

min.

See Detail A II*

0.1875 I.1 (See Note 6) min.

C.5 :

-! E min.

4- Existing Nozzle ' 2JALA SECTIOl A-A Notes: 1. Break all sharp corners to leave a smooth transition.

2. Replacement nozzle is Alloy 690 material.

3. Replacement weld metal is Alloy 52/152.

4. Replacement nozzle length defined by wsr.

5. There is no requirement as to the radius of the replacement weld connecting the pad to the replacement nozzle.

6. The slope of the replacerent weld shown is a maximum slope. Other slopes, such as 1:3 where the first dimension is the pad thickness. are acceptable.

Figure 3 Section Showing Side Wall Instrument Repair Page 16 of 24

Cladding Weld Pad J-Groove Weld J-Groove Weld Pressurizer Wall Figure 4 Pressurizer Upper Head Instrument Nozzle Repair Page 17 of 24

REQUEST NO. W3-R&R-003 ATTACHMENT 1 DISSIMILAR METAL WELDING USING AMBIENT TEMPERATURE MACHINE GTAW TEMPER BEAD TECHNIQUE Page18 of 24

Attachment I to Request for Alternative W3-R&R-003 1.0 GENERAL REQUIREMENTS:

(a) The maximum area of an individual weld based on the finished surface will be less than 100 square inches, and the depth of the weld will not be greater than one-half of the ferritic base metal thickness.

(b) Repair/replacement activities on a dissimilar-metal weld are limited to those along the fusion line of a nonferritic weld to ferritic base material on which 1/8-inch or less of nonferritic weld deposit exists above the original fusion line.

Repair/replacement activities on nonferritic base materials where the repair cavity is within 1/8-inch of a ferritic base material may also be performed.

(c) If a defect penetrates into the'ferritic base material, repair of the base material, using a nonferritic weld filler material, may be performed provided the depth of repair in the base material does not exceed 3/8-inch.

(d) Prior to welding, the temperature of the area to be welded and a band around the area of at least 1%times the component thickness (or 5 inches, whichever is less) will be at least 500F.

(e) Welding materials will meetthe Owner's Requirements and the Construction Code and Cases specified in the'repair/replacement plan. Welding materials will be controlled so that they are identified as acceptable until consumed.

(fe The area prepared for welding shall be suitably prepared for welding in accordance with a written procedure.

2.0 WELDING QUALIFICATIONS The welding procedures and the welding operators shall be qualified in accordance with Section IX and the requirements of paragraphs 2.1 and 2.2.

2.1 Procedure Qualification:

(a) The base materials for the welding procedure qualification will be the same P-Number and Group Number as the materials to be welded. The materials shall be post weld heat treated to at least the time and temperature that was applied to the material being welded.

(b) Consideration will be given to the effects of irradiation on the properties of material, including weld material for applications in the core belt line region of the reactor vessel. Special material requirements in the Design Specification will also apply to the test assembly materials for these applications.

(c) The root width and included angle of the cavity in the test assembly will be no greater than the minimum specified for the repair.

Page 19 of 24

Attachment I to Request for Alternative W3-R&R-003 (d) The maximum interpass temperature for the first three layers or as required to achieve the 1/8-inch butter thickness in the test assembly will be 150'F.

For the balance of the welding, the maximum interpass temperature shall be 3500F.

(e) The test assembly cavity depth will be at least one-half the depth of the weld to be installed during the'repair/replacement activity, and at least 1 inch. The test assembly thickness will be at least twice the test assembly cavity depth.

The test assembly will be large enough to permit removal of the required test specimens. The test assembly dimensions surrounding the cavity will be at least the test assembly thickness, and at least 6 inches. The qualification test plate will be prepared in accordance with Figure 1.

(f) Ferritic base material for the procedure qualification test will 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 subparagraph (h) below, but shall be in the base metal.

(g) Charpy V-notch tests of the ferritic weld metal of the procedure qualification shall meet the requirements as determined in subparagraph (f) above. This test is not required when non-ferritic weld metal is used.

(h) Charpy V-notch tests of the ferritic heat-affected zone (HAZ) will be performed at the same temperature as the base metal test of subparagraph (f) above. Number, location, and orientation of test specimens will be as follows:

1. The specimens will be removed from a location as near as practical to a depth of one-half the thickness of the deposited weld metal. The test coupons for HAZ impact specimens will be taken transverse to the axis of the weld and etched to define the HAZ. The notch of the Charpy V-notch specimens will 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 will 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 will be oriented parallel to the principal direction of rolling or forging.

3. The Charpy V-notch test will be performed in accordance with SA-370.

Specimens will be in accordance with SA-370, Figure I1, Type A. The test will consist of a set of three full-size 10 mm x 10 mm specimens.

The lateral expansion, percent shear, absorbed energy, test Page 20 of 24 to Request for Alternative W3-R&R-003 temperature, orientation and location of all test specimens will be reported in the Procedure Qualification Record.

(I) The average values of the three HAZ impact tests will be equal to or greater than the average values of the three unaffected base metal tests.

2.2 Performance Qualification:

Welding operators will be qualified in accordance with ASME 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 using cold wire feed.

(b) Dissimilar metal welds shall be made using F-No. 43 weld metal (QW-432) for P-No. 43 to P-No. 3 weld joints.

(c) The area to be welded will be buttered with a deposit of at least three layers to achieve at least 1/8-inch butter thickness as shown in Figure 2, steps 1 through 3, with the heat input for each layer controlled to within +/- 10% of that used in the procedure qualification test. Particular care will be taken in placement of the weld layers at the weld toe area of the ferritic base material to ensure that the HAZ is tempered. Subsequent layers will be deposited with a heat input not exceeding that used for layers beyond the third layer (or as required to achieve the 1/8-inch butter thickness) in the procedure qualification.

(d) The maximum interpass temperature field applications will be 3500 F regardless of the interpass temperature during qualification.

(e) Particular care will 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.

4.0 EXAMINATION

(a) Prior to welding, a surface examination will be performed in accordance with NB-5000 of ASME Section III on the area to be welded.

- (b) A liquid penetrant examination of the completed repair weld (including weld pads) shall be performed in accordance with NB-5000 of ASME Section 1II.

(c) An ultrasonic examination of the completed repair weld (including weld pads) shall be performed in accordance with NB-5000 of ASME Section III.

(d) NDE personnel performing liquid penetrant and ultrasonic examinations will be qualified and certified in accordance with NB-5500.

Page 21 of 24 to Request for Alternative W3-R&R-003 5.0 DOCUMENTATION Use of Request No. W3-R&R-003 shall be documented on NIS-2. Alternatively, repairs may be documented on Form NIS-2A as described in Code Case N-532 if prior approval is obtained from the NRC.

Page 22 of 24

Attachment I to Request for Alternative W3-R&R-003 Discard Transverse Side Bend Reduced Section Tensile Transverse Side Bend

. -I IlHAZ Charpy

. . < 1V-Notch Transverse Side Bend Reduced Section Tensile Transverse Side Bend Discard Fusion line Weld Metal Hea Afce Zo..,AZ

-I GENERAL NOTE: Base Metal Charpy impact specimens are not shown.

Figure 1 - QUALIFICATION TEST PLATE Page 23 of 24 to Request for Alternative W3-R&R-003 Step 1: Deposit layer one with first layer weld parameters used in qualification.

Step 2: Deposit layer two with second layer weld parameters used in qualification. NOTE:

Particular care shall be taken in application of

\,the second layer at the weld toe to ensure that the weld metal and HAZ of the base metal are tempered.

Step 3: Deposit layer three with third layer weld parameters used in qualification. NOTE:

Particular care shall be taken in application of the third layer at the weld toe to ensure that the weld metal and HAZ of the base metal are tempered.

Step 4: Subsequent layers to be deposited as qualified, with heat input less than or equal to that qualified in the test assembly. NOTE:

Particular care shall be taken in application of the fill layers to preserve the temper of the weld metal and HAZ.

GENERAL NOTE: For dissimilar-metal welding, only the ferritic base metal is required to be welded using Steps 1 through 3 of the temper bead welding technique.

Figure 2 - AUTOMATIC OR MACHINE GTAW TEMPER BEAD WELDING Page 24 of 24