ML090970285
| ML090970285 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 04/02/2009 |
| From: | Morris J Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML090970285 (17) | |
Text
Duke JAMES R. MORRIS, V/CE PRESIDENT PrEnergy. Duke Energy Carolinas, LLC Carolinas Catawba Nuclear Station 4800 Concord Road / CN01 VP York, SC 29745 803-701-4251 803-701-3221 fax April 2, 2009 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555
Subject:
Duke Energy Carolinas, LLC (Duke)
Catawba Nuclear Station, Unit 2 Docket Number 50-414 Request for Relief Number 09-CN-002 Request to Utilize Alternative to the Requirements of ASME Code Case N-638-1 Pursuant to 10 CFR 50.55a(a) (3) (i), please find attached Request for Relief 09-CN-002. This request for alternative is being submitted to obtain NRC approval to utilize an alternative to certain requirements of the subject Code Case to apply weld buildup on three of the four reactor vessel hot leg nozzles.
Enclosure 1 contains the request for alternative. Duke requests approval of this request for alternative by April 13, 2009.
There are no NRC commitments in conjunction with this request for alternative.
If you have any questions concerning this material, please call L.J. Rudy at (803) 701-3084.
Very truly yours, James R. Morris LJR/s Enclosure (740 WU31 www. duke-energy.com
Document-Control Desk Page 2 April 2, 2009 xc (with enclosure):
L.A. Reyes, Regional Administrator U.S. Nuclear Regulatory Commission, Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303 A.T. Sabisch, Senior Resident Inspector U.S. Nuclear Regulatory Commission Catawba Nuclear Station J.H. Thompson, Project Manager (addressee only)
U.S. Nuclear Regulatory Commission Mail Stop 8-G9A Washington, D.C. 20555-0001
Document Control Desk Page 3 April 2, 2009 bxc (with enclosure):
R. D. Hart L. J. Rudy D. L. Ward D. H. Llewe.llyn J. M. ShupiJng N. I. Mohr T. L. Bradl ey K. Douthit K.L. Ashe RGC File Document Control File 801.01 ELL-EC050 NCMPA-1 NNCEMC PMPA
Enclosure 1 Request for Relief 09-CN-002
Enclosure 1 ProposedAlternative In Accordance with 10 CFR 50.55a(a)(3)(i)
--Alternative Provides Acceptable Level of Quality and Safety--
Duke Energy Corporation Catawba Nuclear Station Unit 2 Relief Request 09-CN-002 REFERENCE CODE: The American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME),Section XI, 1998 Edition through 2000 Addenda.
1.0 ASME Code Components Affected
The ASME Code components associated with this request are the Class 1 Reactor Pressure Vessel (RPV) hot leg nozzles. The 2B, 2C, and 2D RPV hot leg nozzles will receive weld buildup during the Catawba Nuclear Station - Unit 2 (CNS2) EOC 16 (Spring 2009) outage.
1.1 Category and System Details:
Code Class: Class 1 System Welds: Reactor Coolant System Examination Categories:
Category B-P for reactor vessel Code Item Numbers:
B 15.10 for pressure retaining boundary No relief is being requested from the pressure retaining boundary testing requirements.
1.2 Component Descriptions:
This alternative is to apply weld buildup on the three reactor vessel hot leg nozzles. The applicable items and descriptions are:
Catawba Unit 2 Description- Attached Safe-End Size Comment .
Nominal 29"ID with 2 5/8" LAS nozzle/Alloy 82-182 weld/SS safe RV Nozzle B Loop wall / end RV Nozzle C Loop Nominal 29"ID with 2 5/8" LAS nozzle/Alloy 82-182 weld/SS safe RVNozzle _ C Loopwall end Nominal 29"ID with 2 5/8" RV Nozzle D Loop wall ILAS end 'nozzle/Alloy 82-182 weld/SS safe 1
Request No. 09-CN-002 1.3 Component Materials:
- 1. Low Alloy Steel (LAS) nozzles are SA-508 Class 2 (P-3).
2.0 Applicable Code Edition and Addenda
Catawba Nuclear Station - Unit 2 (CNS2) is currently in the third 10-year Inservice Inspection (ISI) interval. The American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (Code) of record for the current 10-year ISI interval isSection XI, 1998 Edition through 2000 Addenda (Reference 1). This is also the edition used for the Repair/Replacement Program.
3.0 Applicable Code Requirement
ASME Boiler and Pressure Vessel Code,Section XI, 1998 Edition through 2000 Addenda, Article IWA-4000, "Repair/Replacement Activities" ASME Section XI, Division 1 Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique" ASME Boiler and Pressure Vessel Code,Section III, 1974 Edition, no Addenda for Catawba Unit 2 Class 1 piping ASME Boiler and Pressure Vessel Code,Section III, 1971 Edition through Winter 1972 Addenda for Catawba Unit 2 Reactor Vessel design and fabrication ASME Boiler and Pressure Vessel Code,Section III, 1989 Edition No Addenda - Duke Welding Program for all units at all sites
4.0 Reason for Request
Duke previously proposed to perform pre-emptive mitigation of the RPV hot leg nozzle dissimilar metal welds for the EOC 16 (Spring 2009) outage. During implementation Duke decided to suspend this mitigation and implement qualified ultrasonic examinations (UT) to satisfy industry commitments. To facilitate a qualified examination any applied weld deposit over the dissimilar metal weld (DMW) must be removed to allow access from the outside diameter (OD). To minimize excessive personnel dose, it is desirable to leave a portion of the deposited weld metal on the external surface of the RPV nozzle.
ASME Code Section XI, 1998 Edition through 2000 Addenda and Code Case N-638-1 provide rules for the application of weld metal utilizing the temperbead technique. This Code Case has been conditionally approved by the NRC for use; however it contains 2
Request No. 09-CN-002 several limitations that if implemented would cause additional dose. Therefore, Duke proposes the following alternative.
5.0 Proposed Alternative Pursuant to 10CFR 50.55a (a) (3) (i), an alternative to certain requirements listed in Section 3.0 above is requested on the basis that the proposed alternative will provide an acceptable level of quality and safety. Attachment 1, included as a part of this request for relief, provides details of relief requested from each of these requirements.
Weld Deposit SS Weld SS Pipe]I Notes:
- 2. Safe end is SA-182 Type 316 (P-8).
- 3. LAS Nozzle is SA-508 Class 2 (P-3).
Figure 1. Schematic Configuration for RPV Hot Leg Nozzle at Catawba Unit 2 (Loops B, C, and D) 6.0 Basis for Use The weld buildup will meet applicable design rules of ASME Section XI and the Construction Code as required by IWA-4000. Welding and examination requirements for the weld deposits will meet the requirements of ASME Code Case N-638-1 with the exceptions discussed in Attachment 1. Based on the following discussion, the alternative provides an acceptable level of quality and safety.
Suitability of Proposed Ambient Temperature Temper Bead Technique The weld buildup addressed by this Relief Request will be performed using ambient temperature temper bead welding in lieu of Post Weld Heat Treatment, in accordance with Reference 5. Research by the Electric Power Research Institute (EPRI) and other organizations on the use of an ambient temperature temper bead process using the 3
Request No. 09-CN-002 machine Gas Tungsten Arc Welding (GTAW) process is documented in EPRI Report GC-1 11050 (Reference 3). 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 to 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 on mechanical properties of repair welds, hydrogen cracking, cold restraint cracking, and extent of weld deposit coverage of ferritic base metal are addressed in the followingparagraphs.
Mechanical Properties The principal reason 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 are utilized in 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 111050, "the 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-4630 temper bead process also includes a postweld soak requirement.
Performed at 300'F 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 300'F, the postweld soak does not stress relieve, temper, or alter the mechanical properties of the weldment in any manner.
The alternative establishes detailed welding procedure qualification requirements for base materials, filler metals, restraint, impact properties, and other procedure variables. The qualification requirements provide assurance that the mechanical properties of repair welds will be equivalent to or superior to those of the surrounding base material.
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Request No. 09-CN-002 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.
IWA-4630 establishes elevated preheat and postweld soak requirements. The elevated preheat temperature of 300'F increases the diffusion rate of hydrogen from the weld.
The postweld soak at 300'F was also established to bake-out or facilitate diffusion of any remaining hydrogen from the weldment. However, while hydrogen cracking is a concern for Shielded Metal Arc Welding (SMAW), which uses flux covered electrodes, the potential for hydrogen cracking is significantly reduced when using the machine GTAW process.
The machine GTAW process is inherently free of hydrogen. Unlike the SMAW process, GTAW 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, modem 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 the automatic or machine GTAW temper bead process. Therefore, the potential for hydrogen-induced cracking is greatly reduced by using the machine GTAW process. Extensive research has been performed by EPRI (Reference 4) which provides a technical basis for starting the 48-hour hold after completing the third temper bead weld layer rather than waiting for all weld deposit to cool to ambient temperature. This approach has been previously reviewed and approved by the NRC for pressurizer and hot leg surge nozzle overlays.
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Request No. 09-CN-002 Cold Restraint Cracking Cold 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.
Area Limitation IWA-4630 and early versions.of Code Case N-638 through Revision 2 for temper bead welding contained a limit of 100 square inches for the surface area of temper bead weld over the ferritic base metal. The associated limitation proposed in Attachment 1 is 500 square inches, consistent with ASME approved Code Case.N-638-3. However,,Code Case N-63 8-3 has not been approved by the NRC in Regulatory Guide 1.147 Revision 15.
An ASME white paper (Reference 2) describes the technical justification for allowing increased overlay areas up to 500 square inches. The white paper notes that the original limit of 100 square inches in Code Case N-638-1 was arbitrary. It cites evaluations of a 12 inch diameter nozzle weld overlay to demonstrate adequate tempering of the weld heat affected zone (Section 2a of the white paper), residual stress evaluations demonstrating acceptable residual stresses in weld overlays ranging from 100 to 500 squareinches (Section 2b of the white paper), and service history in which weld repairs exceeding 100 square inches were NRC approved and applied to DMW nozzles in several BWRs and PWRs (Section 3c of the white paper). Some of the cited repairs are greater than 15 years old, and have been inspected several times with no evidence of any continued degradation.
It is important to note that the above theoretical arguments and empirical data havebeen verified in practice by extensive field experience with temper bead weld overlays, with ferritic material coverage ranging from less than 10 square inches up to and including. 325 square inches. Table 1 below provides a partial list of such applications. It is seen from this table that the original DMW weld overlay was applied over 20 years ago, and WOLs with low alloy steel (LAS) coverage in the 100 square inch range have been in service for
.5 to 15 years. Several overlays have been applied with LAS coverage significantly greater than the 100 square inches. Relief requests for these large overlays have been previously approved. These overlays have been examined with PDI qualified techniques, 6
Request No. 09-CN-002 in some cases multiple times, and none have shown any signs of new cracking or growth of existing cracks.
7.0 Duration of Proposed Alternative This proposed alternative is for application as needed during the remainder of the current Catawba Nuclear Station - Unit 2 (CNS2) third inspection interval which ends August 19, 2016.
8.0 Implementation The weld deposit will be installed during the Catawba Nuclear Station - Unit 2 (CNS2)
EOC 16 (Spring 2009) outage. NRC approval is requested by 04/13/2009, to support the schedule for completion of activities during-the outage.
9.0 Precedents Similar requests have been submitted to address the issues that are contained in this request. The technical approach and basis for the proposed alternative in this request is similar to the request from Duke Energy Corporation's McGuire Nuclear Station Unit I and Catawba Nuclear Station Unit 2 for application of FSWOLs to their pressurizer nozzle DMWs in letter titled "Duke Power Company LLC d/b/a Duke Energy Carolinas, LLC, (Duke) McGuire Nuclear Station, Unit I Docket Number 50-369 Catawba Nuclear Station, Unit 2 Docket Number 50-414 Relief Request 07-GO-00,1" (ADAMS Accession, Number ML070310367), dated January 24, 2007. This relief request was approved by the NRC through the NRC Letter to Duke, Catawba Nuclear Station, Unit 2, and McGuire Nuclear Station, Unit 1, Relief 07-GO-001 for Use of Preemptive Weld Overlay and Alternative Examination Techniques on Safe End Welds (TAC Nos. MD4671 and MD4672), November 27, 2007.
Similar relief requests were also previously submitted by Progress Energy's Crystal River NuclearPlant, South Carolina Electric and Gas's Virgil C. Summer Station, and by Entergy for Arkansas Nuclear One. These requests were approved by the NRC through the NRC Letter to Progress Energy's Crystal River Nuclear Plant, Unit 3, Relief Request
- 08-001-RR, Revision 1, to Install a Weld Overlay on the Dissimilar Metal Weld in the Decay Heat Drop Line (TAC NO. MD 8237) May 22, 2008; NRC letter to South Carolina Electric and Gas, Virgil C. Summer Nuclear Station, Unit 1, Proposed Alternative for the Application of Weld Overlay on Dissimilar Metal Welds of Pressurizer Nozzles (TAC NO. MD5665), March 25, 2008; and NRC letter to Entergy, Arkansas Nuclear One, Unit 1 - Request for Alternative to the American Society of 7
Request No. 09-CN-002 Mechanical Engineers Boiler and Pressure Vessel Code Requirements for Pressurizer Nozzle Weld Overlay Repairs (TAC NO. MD4019), April 6, 2007, respectively.
10.0 References
- 1. The American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME),Section XI, 1998 Edition through 2000 Addenda.
- 2. "Justification for the Removal of the 100 Square Inch Limitation for Ambient Temperature Temper Bead Welding on P-3 Material", EPRI-NP-101 1898, February 2005.
- 3. "Ambient Temperature Preheat for Machine GTAW Temperbead Applications",
EPRI Report GC- 111050, November 1998.
- 4. "Temperbead Welding Applications - 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Hold for Ambient Temperature Temperbead Welding", EPRI Report 1013558, December 2006.
- 5. ASME Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique."
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Request No. 09-CN-002 Table 1. Recent Overlay Experience Nozzle Diameter Date Plant Component (in)
December 2007 SCE/SONGS 2 PZR surge nozzle 12 November 2007 Duke/Oconee 3 PZR spray nozzle 4 safety/relief nozzles 4.5 PZR surge nozzle 10 November 2007 APS / Palo Verde 3 PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 12 October 2007 SCE/SONGS 3 PZR surge nozzle 12 October 2007 Duke / Catawba 2 PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 14 October 2007 PSEG/Hope Creek Recirc Inlet nozzle 10 October 2007 TVA Sequoyah 1 PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 12 October 2007 Tai Power / Recirc Inlet nozzle 10 Kuosheng 2 September 2007 Progress / Harris PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 14 June 2007 APS / Palo Verde 1 PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 12 May 2007 Entergy / ANO 1 PZR spray nozzle 4 safety/relief nozzles 4.5 PZR surge nozzle 10 May 2007 Duke / Oconee 2 PZR spray nozzle 4 safety/relief nozzles 4.5 PZR surge nozzle 10 April 2007 Duke / McGuire 1 PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 14 April 2007 STPNOC / South PZR spray nozzle 6 Texas 2 safety/relief nozzles 6 PZR surge nozzle 16 March 2007 FPL / Duane Arnold Recirc. Inlet nozzles 10 March 2007 TPC / Chin Shan Recirc Outlet nozzle 23 March 2007 Entergy / Pilgrim Recirc. Inlet nozzle 10 December 2006 TVA/Sequoyah 2 PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 14 November 2006 SCE/SONGS Unit 3 PZR spray nozzle 5.1875 safety/relief nozzles* 8 PZR surge nozzle 12.75 9
Request No. 09-CN-002 Table 1. Recent Overlay Experience (concluded)
Nozzle Diameter Date Plant Component (in)
November 2006 Duke/Catawba Unit 1 PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 14 November 2006 Duke/Oconee Unit 1 PZR spray nozzle 4.5 safety/relief nozzles 4.5 PZR surge nozzle 10.875 HL Surge Nozzle 10.75 October 2006 Duke/McGuire Unit 2 PZR spray nozzle 4 safety/relief nozzles 6 PZR surge nozzle 14 April 2006 FENOC/Davis Besse Hot leg drain nozzle 4 February 2006 SCE/SONGS Unit 2 PZR spray nozzle 8 safety/relief nozzles 6 November 2005 TPC/Kuosheng Unit 2 Recirculation outlet 22 nozzle April 2004 PPL/Susquehanna Recirc. inlet nozzle 12 Unit 1 Recirc. outlet nozzle 28 November 2003 AmerGen/TMI Unit 1 Surge line nozzle 11.5 October 2003 Entergy/Pilgrim Core spray nozzle 10 CRD return nozzle 5 October 2002 Exelon/Peach Bottom Core spray nozzle 10 Units 2 & 3 Recirc. outlet nozzle 28 CRD return nozzle 5 October 2002 AmerGen/Oyster Recirc. outlet nozzle 26 Creek December 1999 FPL/Duane Arnold Recirc. inlet nozzle 12 June 1999 FENOC /Perry Feedwater nozzle 12 June 1998 CEG/Nine Mile Point Feedwater nozzle 12 Unit 2 March 1996 Progress/Brunswick Feedwater nozzle 12 Units 1 & 2 February 1996 Southern/Hatch Unit 1 Recirc. inlet nozzle 12 January 1991 Entergy/River Bend Feedwater nozzle 12 March 1986 Entergy/Vermont Core spray nozzle 10 Yankee 10
Request No. 09-CN-002 ATTACHMENTS Attachment 1 Modifications to Code Case N-638-1 11
Request No. 09-CN-002 Enclosure I/Attachment 1 Page 1 of 2 Attachment 1 Modifications to Code Case N-638-1 Code Case N-638-1 Modification/Basis Modification: The maximum area of an individual weld based on the Weld Area finished surface over the ferritic materialwill not exceed 500 square inches, and the depth of the weld deposit shall notbe greater than one-1.0(a) The maximum area of an individual weld half of the ferritic base metal thickness based on the finished surface shall be 100 sq. inch, Basis: The maximum area of the weld deposit for the RPV nozzle will and the depth of the weld shall not be greater than be approximately500 square inches over the ferritic material.
one-half of the ferritic base metal thickness. Justificationfor extending the area limitation to 500 square inches is based on the overall conclusions of EPRI Report NP-101 1898 as discussed in Section 6.0 of this Relief Request.
Examination Modification: The required liquid penetrant examination of 4.0(b) will (Referenced below in 4.0(b) para. 1.0(d) Prior to welding the area to be be performed on the weld deposit. The ultrasonic examination will be welded and a band around the area of at least 1.5 times the in accordance with ASME Section XI, Appendix I.
component thickness or 5 inch, whichever is less shall be at least Basis: For the application of the weld deposit addressedin this request 50°F.) the examination methodologies will conform to Appendix I. Code Case N-638-3 has eliminatedthe requirementto examine a band'aroundthe 4.0(b) The final weld surface and a band around the area defined in area to be welded, and specifies requiredpost weld nondestructive para. 1.0 (d) shall be examined using a surface and ultrasonic methods examination of the welded region only. This Code Case applies to any when the completed weld has been at ambient temperature for at least type of welding where a temper bead technique is to be employed and 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 is not specifically written for a weld build up. Furtherrevision, to this Appendix 1.3 Code Case has clarified this. For this application, it is believed that any major base material cracking would take place in the HAZ directly 3
below the weld deposit and not in the band of material out beyond the Refer to the 1989 Edition with the 1989 Addenda and later Editions deposit. Therefore, the ultrasonic examinationof the weld deposit and Addenda would identify if this cracking were -to occur.
Request No. 09-CN-002 Enclosure I/Attachment 1 Page 2 of 2 4.0(c) requires temperature monitoring by welded thermocouples per Modification: Preheatand interpass temperaturesfor the weld pad will IWA-461 0(a) be measured 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.
Basis: Code Case N-638-3 has expanded the options for meeting this requirement. Due to the location of the repairand area radiationdose rate, the placement of welded thermocouples for monitoring weld interpasstemperature is determined to be not beneficial based on dose savings. Therefore, welded thermocouples are not planned for use to monitor interpass temperatureduring welding.