ML090710008

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Request for Alternative Jaf RR-7, Rev 1 to Install a Weld Overlay on N2C Nozzle to Recirculation Inlet Piping Safe-end Dissimilar Metal Weld
ML090710008
Person / Time
Site: FitzPatrick Constellation icon.png
Issue date: 04/01/2009
From: Mark Kowal
Plant Licensing Branch 1
To:
Entergy Nuclear Operations
vaidya b k
References
JAF RR-7, Rev 1, TAC MD9780
Download: ML090710008 (14)
v • d • e


Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Apr; 1 1, 2009 Vice President, Operations Entergy Nuclear Operations, Inc.

James A. FitzPatrick Nuclear Power Plant P.O. Box110 Lycoming, NY 13093 SUB~IECT: JAMES A. FITZPATRICK NUCLEAR POWER PLANT - REQUEST FOR ALTERNATIVE JAF RR-7, REV. 1 TO INSTALL A WELD OVERLAY ON N2C NOZZLE TO RECIRCULATION INLET PIPING SAFE-END DISSIMILAR METAL WELD (TAC NO. MD9780)

Dear Sir or Madam:

By letter dated September 26, 2008, as supplemented by letters dated October 1, October 20, and December 17,2008, Entergy Nuclear Operations, Inc. (the licensee) submitted a Request for Alternative, JAF RR-7, Rev. 1, to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI (ASME Code) for the James A.

Fitzpatrick Nuclear Power Plant (JAF) to the U. S. Nuclear Regulatory Commission (NRC) for review and approval. Alternative JAF RR-7, Rev. 1 would permit the installation of a full structural weld overlay on the N2C reactor pressure vessel nozzle-to-recirculation inlet piping safe end dissimilar metal weld at JAF.

The NRC staff has reviewed the licensee's submittal and determined that the proposed alternative will provide an acceptable level of quality and safety. Therefore, pursuant to paragraph 50.55a(a)(3)(i) of Title 10 of the Code of Federal Regulations, the NRC staff authorizes the use of Request for Alternative JAF RR-7, Rev. 1 at JAF for use during the unit's fall 2008 refueling outage (R-18).

The NRC staffs Safety Evaluation is enclosed.

Sincerely, Mark G. Kowal, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-333

Enclosures:

cc w/encls: Distribution via Listserve

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO REQUEST FOR ALTERNATIVE JAF RR-7, REV. 1 INSERVICE INSPECTION PROGRAM REQUEST FOR ALTERNATIVE FOR JAMES A. FITZPATRICK NUCLEAR POWER PLANT ENTERGY NUCLEAR OPERATIONS, INC.

DOCKET NO. 50-333

1.0 INTRODUCTION

By letter dated September 26, 2008, (Agencywide Documents and Management System (ADAMS) Accession No. ML082770071) as supplemented by letters dated October 1, October 20, and December 17, 2008,(ADAMS Accession Nos. ML082810398, ML082970190, and ML083590350 respectively) Entergy Operations, Inc. (the licensee), requested relief from certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) requirements at James A. Fitzpatrick Nuclear Power Plant (JAF). As an alternative to the ASME Code requirements, the licensee proposes to implement a full structural weld overlay (FSWOL) repair in accordance with ASME Code Cases N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW [Gas tungsten arc weld] Temper Bead Technique,Section XI, Division 1," and N-504-3, "Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping,Section XI, Division 1," as modified by the licensee in its submittal letters. The alternatives proposed in Relief Request JAF RR-7, Rev. 1, would be used to perform a FSWOL on the N2C reactor pressure vessel (RPV) nozzle-to-recirculation inlet piping safe end dissimilar metal weld (DMW).

2.0 REGULATORY REQUIREMENTS The NRC staff based its review of the licensee's proposed alternative for the regulatory requirements described in the paragraphs below:

Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(g)(4),

ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, "Rules for Inservice Inspection (lSI) of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 1O-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of ENCLOSURE

-2 Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.

The code of record for the current fourth lSI interval is the 2001 Edition with 2003 Addenda of the ASME Code,Section XI.

Pursuant to 10 CFR 50.55a(a)(3) alternatives to requirements may be authorized by the NRC if the licensee demonstrates that: (i) the proposed alternatives provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The licensee submitted the subject relief request, pursuant to 10 CFR 50.55a(a)(3)(i), which proposed an alternative to the implementation of the ASME Code,Section XI requirements based on ASME Code Cases N-740, N-638-1 and N-504-3 as modified by the licensee for the deposition of a FSWOL for the remaining service life of the identified components. Regulatory Guide (RG) 1.147, "Inservice Inspection Code Case Acceptability, ASME Code,Section XI, Division 1," lists the code cases that are acceptable to the NRC for application in licensees' ASME Code,Section XI lSI programs. A licensee may use a code case specified in the RG without prior approval by the NRC if it meets the conditions specified for the code case.

3.0 LICENSEE'S PROPOSED ALTERNATIVE The licensee's proposed alternative is described in Enclosure 1, Attachment 2 of its submittal dated October 1,2008, and is based on ASME Code Case N-740. The ASME Code Case N 740 has been accepted by the ASME Code Committee. However, it has not been accepted by the NRC and therefore, it is not considered in the NRC staff review of this request. The licensee's submittal dated October 1, 2008, also provided the comparison of the proposed alternative with ASME Code Cases N-504-3, N-638-1, and ASME Section XI, Non-Mandatory Appendix O. The scope of NRC staff evaluation of the licensee's proposed alternative in Sections 3.6 and 3.9 of this Safety Evaluation is limited to the evaluation of the differences, modifications and exceptions from the ASME Code Cases N-504-3 and N-638-1, ASME Section XI, Non-Mandatory Appendix 0, and Compliance with RG 1.147.

3.1 ASME Code Component Affected During ultrasonic examination of the lSI Weld N-2C-SE, N2C RPV nozzle-to-recirculation inlet piping safe end dissimilar metal weld, an axial indication approximately 0.8" long with a 0.5" (approximately 40%) through-wall depth was detected. Due to the high intergranular stress corrosion cracking (IGSCC) crack growth rate, the DMW with the axial indication cannot be accepted by an ASME Code,Section XI, IWB-3600 analytical evaluation. As a result, Entergy proposed to repair the subject DMW by installing a full structural weld overlay.

3.2 ASME Code Requirements Subarticle IWA-4411 (a) of the ASME Code,Section XI requires that repairs and the installation of replacement items be performed in accordance with the Owner's Requirements and the original Construction Code of the component or system. Alternatively, Subarticle IWA-4411 (a) and (b) of the ASME Code,Section XI allows for the use of later Editions and Addenda of the Construction Code or ASME Code,Section III, either in their entirety or portions thereof, and Code Cases.

-3 Subarticles IWA-4411(e) and IWA-4600 of the ASME Code,Section XI provide defect removal and alternative welding methods when the requirements of IWA-4411 cannot be met.

Subarticle IWA-4530(a) of the ASME Code,Section XI requires the performance of preservice examinations based on IWB-2200 of the ASME Code,Section XI for Class 1 components.

The ASME Code,Section XI, Table IWB-2500, Categories B-F and B-J prescribes lSI requirements for Class 1 butt welds.

Appendix VIII, Supplement 11 of the ASME Code,Section XI, specifies performance demonstration requirements for ultrasonic examination of weld overlays.

3.3 Duration of the Alternative The repair performed using this Relief Request is applicable to the fourth 10-Year lSI interval for JAF which began March 1,2007, and will end December 31,2016, and for the period of extended operation which expires October 17, 2034. The licensee implemented the request during the unit's fall 2008 refueling outage (R-18).

3.4 Licensee's Proposed Modifications and Exceptions for the use of ASME Code Case N-504-3 The following paragraphs describe the licensee's proposed exceptions and alternatives for the use of ASME Code Case N-504-3:

3.4.1 ASME Code Case N-504-3, Paragraph (b) requires that the FSWOL be low carbon (0.035% maximum) austenitic stainless steel. An alternative was required since a nickel-based filler (Alloy 52M) has been selected to be used.

3.4.2 ASME Code Case N-504-3, Paragraph (e) requires the first two layers of the FSWOL to have as-deposited delta ferrite measurements of at least 7.5 FN (Ferrite Number) for the weld reinforcement. Since the nickel alloy filler (Alloy 52M) is a fully austenitic material and does not contain ferrite, this requirement is not applicable.

3.4.3 ASME Code Case N-504-3, Paragraph (h) specifies that a system hydrostatic test be performed in accordance with ASME Code,Section XI, IWA-5000 if the flaw penetrates the original pressure boundary. As an alternative, leak testing in accordance with IWA - 5000 will be performed.

3.4.4 ASME Code Case N-504-3 has been conditionally approved by the NRC in Regulatory Guide 1.147, Revision 15, with the additional condition that the provisions of ASME Code,Section XI, Non-Mandatory Appendix Q, "Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldment," (Appendix Q) must also be met when using ASME Code Case N-504-3. Appendix Q pertains to Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments. Since the FSWOL is being performed with a nickel-based filler (Alloy 52M) over a DMW, not ferritic material, the

- 4 licensee will comply with Appendix Q as well as ASME Code Case N-504-3, as they apply to this type of weldment (nickel-based filler (Alloy 52M) over a DMW).

3.5 Licensee's Basis for Proposed Modifications and Exceptions for the use of ASME Code Case N-504-3 The following paragraphs describe the licensee's basis for proposed exceptions and alternatives for the use of ASME Code Case N-504-3:

3.5.1 The weld overlay will be deposited with ERNiCrFe-7 (Alloy 52M) filler metal. This material has been included in ASME Code,Section IX as an F-No. 43 filler metal.

Containing 28.0 - 31.5% chromium, this filler metal has excellent resistance to IGSCC.

Where welding is performed on ferritic nozzles, an ambient temperature temperbead Welding Procedure Specification (WPS) will be used. The weld overlay is applied 360 degrees around the circumference of the nozzle safe end dissimilar metal weld, and will be deposited using a WPS Paragraph for groove welding, qualified in accordance with the Construction Code and Owner's requirements and identified in the Repair/Replacement Plan.

3.5.2 ASME Code Case N-504-3, Paragraph (e) requires the first two layers of the FSWOL to have as-deposited delta ferrite measurements of at least 7.5 FN for the weld reinforcement. Since the nickel alloy filler (Alloy 52M) is a fully austenitic material and does not contain ferrite, this requirement is not applicable.

3.5.3 ASME Code Case N-504-3, Paragraph (h) specifies that a system hydrostatic test be performed in accordance with ASME Code,Section XI, IWA-5000 if the flaw penetrates the original pressure boundary. Leak testing in accordance with ASME Code,Section XI (2001 Edition with the 2003 Addenda), IWA-5000 will be performed. The pressure testing requirements of Section 4.0 of Attachment 1 are similar to paragraph (h) of ASME Code Case N-504-3 except that only a system leakage test per IWA-5000 is required.

3.5.4 For the lSI and subsequent additional examinations of the FSWOL, ASME Code Case N-504-3 does not require implementation of Appendix Q of the ASME Code,Section XI.

RG 1.147, Revision 15 imposed the following condition for using Code Case N-504-3:

"The provisions of [ASME Code] Section XI, Non-Mandatory Appendix Q, Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldment, must also be met." The licensee's submittal stated that the lSI and subsequent additional examinations of the FSWOL in the proposed alternative would meet the associated requirements contained in Appendix Q as well as ASME Code Case N-504-3, as they apply to a nickel-based filler (Alloy 52M) over a DMW weldment.

3.6 Staff Evaluation of Licensee's Proposed Modifications and Exceptions for the use of ASME Code Case N-504-3 Under the rules of ASME Code,Section XI, IWA-4411 repairs shall be performed in accordance with the licensee's design specification and the original Construction Code. Later editions and

-5 addenda of the Construction Code or of ASME Code,Section III, either in their entirety or portions thereof, and ASME Code Cases may be used. In addition to the above, defects shall be removed or reduced in size in accordance with ASME Code,Section XI, IWA-4400. ASME Code Case N-504-3, as modified by the identified alternatives, will be used by the licensee to perform a FSWOL on the N2C RPV nozzle-to-recirculation inlet piping safe end DMW. ASME Code Case N-504-3 was conditionally approved by the NRC staff for use under Regulatory Guide (RG) 1.147, Revision 15. Therefore, the use of ASME Code Case 1\1-504-3 as an alternative to the mandatory ASME Code repair provisions is acceptable to the staff, provided that all conditions and provisions specified in RG 1.147, Revision 15 are complied with.

The following paragraphs discuss the NRC staff's evaluation of these compliances:

3.6.1 In its submission, the licensee stated that Paragraph (b) of ASME Code Case N-504-3 requires that the reinforcement weld material shall be low carbon (0.035% maximum) austenitic stainless steel. The proposed alternative to the ASME Code Case N-504-3 provisions involves the use of a nickel-based alloy weld material rather than the low carbon austenitic stainless steel. In lieu of the stainless steel weld material, Alloy 52M, a consumable welding wire, which is highly resistant to Stress Corrosion Cracking (SCC), was proposed for the overlay weld material. The NRC staff noted that the use of the 52M material is consistent with weld materials used to perform similar FSWOLs at other operating Boiling Water Reactor facilities. The NRC staff also noted that the licensee is proposing to perform the subject FSWOL on dissimilar metal welds made of Alloy 82/182 material. For material compatibility in welding, the NRC staff believes that Alloy 52M is a better choice of filler material than austenitic stainless steel material for this weld joint configuration. Alloy 52M contains about 30% chromium which would provide excellent resistance to SCC if exposed to the reactor coolant environment. This material is identified as F-No. 43 filler metal and has been previously approved by the NRC staff for similar applications. Therefore, the NRC staff finds that the licensee's proposed use of Alloy 52M for the FSWOL as an alternative to the requirements of ASME Code Case N-504-3, Paragraph (b) is acceptable as it will provide an acceptable level of quality and safety.

3.6.2 Paragraph (e) of ASME Code Case N-504-3 requires as-deposited delta ferrite measurements of at least 7.5 FN for the weld reinforcement. The licensee proposed that delta ferrite measurements will not be performed for this overlay because the deposited Alloy 52M material is 100% austenitic and contains no delta ferrite due to the high nickel composition (approximately 60% nickel). ASME Code Case N-504-3 is intended for FSWOL repair of austenitic stainless steel piping. Therefore, the material requirements regarding the carbon content limitation (0.035% maximum) and the delta ferrite content of at least 7.5 FN, as delineated in ASME Code Case N-504-3, Paragraphs (b) and (e),

apply only to an austenitic stainless steel FSWOL material to ensure its resistance to SCC. These requirements are not applicable to Alloy 52M, a nickel-based material which would be used for the FSWOL. Therefore, the NRC staff finds that the requested alternative will provide an acceptable level of quality and safety.

3.6.3 The licensee's proposed modification to Paragraph (h) of ASME Code Case N-504-3 is to perform leak testing in accordance with ASME Code,Section XI (2001 Edition with the 2003 Addenda), IWA-5000. Use of a leak test at normal operating temperature and

-6 pressure in lieu of a hydrostatic test has been incorporated in ASME Code,Section XI beginning in the 1998 Edition with the 1999 Addenda. JAF is currently in its fourth 10-year lSI interval and the lSI Code of record for the fourth 10-year lSI interval is the ASME Code,Section XI, 2001 Edition, including Addenda through 2003. The NRC staff finds that the licensee's alternative is consistent with the current practice, and therefore acceptable.

3.6.4 The NRC staff reviewed the licensee's proposed alternative described in the Attachment 2 of the Enclosure 1 of the licensee's submittal dated October 1, 2008, and noted the following:

  • ASME Code,Section XI, Non-Mandatory Appendix Q, "Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments," provides an alternative to the requirements of IWA-4420, IWA-4520, IWA-4530, and IWA-4600 for making repairs to, and the examination of, Class 1, 2, and 3 austenitic stainless steel pipe weldments by deposition of a weld overlay on the outside surface of the pipe.
  • In approving the use of ASME Code Case N-504-3, RG 1.147, Revision 15 imposed the condition that the requirements of Non-Mandatory Appendix Q for the lSI and subsequent additional examinations of the FSWOL must also be satisfied.
  • The NRC staff finds that the licensee's proposed alternative described in the Attachment 2 of the Enclosure 1 of the licensee's submittal dated October 1, 2008, meets all the requirements of Non-Mandatory Appendix Q, as they apply to a nickel based filler (Alloy 52M) over DMW weldments, as well as meets or exceeds the corresponding requirements of ASME Code Case N-504-3.
  • Additionally, the Attachment 4 to Enclosure 1 in the licensees submittal dated October 1, 2008, discussed the comparison of the proposed alternative with the requirements of ASME Code Case N-504-3 and Non-Mandatory Appendix Q.

Specifically, it shows that the licensee's proposed alternative, Section 2.0, "Crack Growth Considerations and Design," and Section 3.0, "Examination and Inspection,"

of which concern with design considerations, evaluation of the repaired weldment, and nondestructive examination (NDE), including preservice inspection, inservice inspection and additional examinations of the repair area, meet or exceed the pertinent requirements of ASME Code Case N-504-3 and the requirements of Non Mandatory Appendix Q.

Based on the above discussion, the NRC staff finds that the licensee's implementation of proposed alternative for the lSI and subsequent additional examinations of the FSWOL will provide an acceptable level of quality and safety.

-7 3.7 Licensee's Proposed Modifications and Exceptions for the use of ASME Code Case N-638-1 The following paragraphs describe the licensee's proposed exceptions and alternatives to ASME Code Case N-638-1:

3.7.1 ASME Code Case N-638-1, Paragraph 1.0(a) limits the maximum area of an individual weld to 100 square inches. As an alternative, the maximum area of finished surface of the weld shall be limited to 500 square inches over the ferritic material.

3.7.2 ASME Code Case N-638-1, Paragraph 2.1 (j) specifies acceptance criteria for Charpy V - notch tests of the heat affected zone (HAl). According to paragraph 2.1 U), the "average values of the three HAl impact tests shall be equal to or greater than the average values of the three unaffected base metal tests." Although not explicitly stated, the average values referred to in paragraph 2.1 U) are the average lateral expansion values of the HAl and base material specimens. Because this is the case, the acceptance criteria for Charpy V-notch testing of the HAl is also based on average lateral expansion values in the proposed alternative.

3.7.3 ASME Code Case N-638-1, Paragraph 3.0(c) requires the deposition and removal of at least one weld reinforcement layer for "similar materials" (i.e., ferritic materials). The licensee will not perform these activities.

3.7.4 ASME Code Case N-638-1, Paragraph 4.0(b) specifies that the final weld surface shall be examined using surface and ultrasonic testing (UT) examinations no sooner than 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after the weld reaches ambient temperature. As an alternative, the licensee would perform surface and volumetric examinations 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after the third weld layer is installed.

3.7.5 ASME Code Case N-638-1, Paragraph 4.0(c), specifies that the area from which weld-attached thermocouples have been removed (after completion of the weld repair),

shall be ground and examined using a surface examination method. Thermocouples will not be used. Instead, preheat and interpass temperatures will be monitored by calibrated contact pyrometers.

3.8 Licensee's Basis for Proposed Modifications and Exceptions for the use of ASME Code Case N-638-1 The following paragraphs describe the licensee's basis for proposed exceptions and alternatives to ASME Code Case N-638-1:

3.8.1 ASME Code Case N-638-1, Paragraph 1.0(a) specifies that the maximum area of finished surface of the weld shall be limited to 100 square inches. As an alternative, the licensee stated that the surface area will be limited to 500 square inches over the ferritic material. The licensee stated that ASME Code Case N-638-3 has been approved by the ASME and that residual stress analyses performed in support of ASME Code Case N 638-3 show that stresses for 100 square inch through 500 sq uare inch surface area overlays are very similar. The licensee indicated that there is extensive field experience

-8 with temperbead weld overlays on ferritic material. Several overlays have been applied with low alloy steel coverage significantly greater than the 100 square inches. These overlays have been examined with Performance Demonstration Initiative (PDI) qualified techniques, in some cases multiple times, and none have shown any signs of new cracking or growth of existing cracks.

3.8.2 Paragraph 2.1 U) of ASME Code Case N-638-1 states, "The average of the three HAZ impact tests shall be equal to or greater than the average values of the three unaffected base metal tests." However, the Charpy V-notch test acceptance criteria in ASME Code Case N-638-1 is misleading and inconsistent in comparison with the specified acceptance criteria in ASME Code,Section XI applicable to other Class 1 components, since it implies that all three parameters, i.e., lateral expansion, absorbed energy, and percent shear fracture, must be equal to or exceed the base material values. ASME Code Case N-638-2 corrected Paragraph 2.1 (j) to state that Charpy V-notch acceptance criteria is based on the average lateral expansion values rather than the average of all three values. This change clarified the intent of the code case and aligned its Charpy V notch acceptance criteria with that of ASME Code Sections III and XI as demonstrated in: ASME Code,Section III, NB-4330, "Impact Test Requirements," ASME Code,Section XI, IWA-4620, "Temperbead Welding of Similar Materials," and ASME Code,Section XI, IWA-4630, "Temperbead Welding of Dissimilar Materials."

3.8.3 The requirement of Paragraph 3.0(c) of ASME Code Case N-638-1 which requires the deposition and removal of at least one weld reinforcement layer for "similar materials" (i.e., ferritic materials) is only applicable when welding is performed using ferritic filler weld metal. When temperbead welding is performed with ferritic filler metal, each ferritic weld layer must be tempered by the heat supplied from a subsequent weld layer.

Because the final layer of a completed weld or weld repair would be untempered, Paragraph 3.0(c) requires the deposition and removal of an additional layer (weld reinforcement) to ensure that the final layer of the completed weld is tempered.

Since only austenitic filler metal (i.e., Alloy 52M) will be used to fabricate the proposed weld overlays (not ferritic filler weld metal, for "similar materials"), depositing and removing a weld reinforcement layer is not required.

3.8.4 ASME Code Case N-638-1, Paragraph 4.0(b) specifies that the final weld surface shall be examined using surface and LIT examinations no sooner than 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after the weld reaches ambient temperature. As an alternative, the licensee would perform surface and volumetric examinations 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after the third layer is installed. Based on research and industry experience, The Electric Power Research Institute (EPRI) has provided a technical basis for starting the 48-hour hold after completion of the third temperbead weld layer rather than waiting for the weld overlay to cool to ambient temperature. Weld layers beyond the third layer are not designed to provide tempering to the ferritic HAZ during ambient temperature temperbead welding. EPRI has documented their technical basis in Technical Report 1013558, "Temperbead Welding Applications - 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding" (ADAMS Accession No. ML070670060). The technical data provided by EPRI in their report is based on testing performed on SA-508, Class 2 low-alloy steels, which is the nozzle material being overlaid at JAF. After evaluating all of the issues relevant to hydrogen cracking such as microstructure of susceptible materials, availability of

-9 hydrogen, applied stresses, temperature, and diffusivity and solubility of hydrogen in steels, EPRI concluded that: "There appears to be no technical basis for waiting the 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after cooling to ambient temperature before beginning the NDE of the completed weld. There should be no hydrogen present, and even if it were present, the temperbead welded component should be very tolerant of the moisture."

3,8.5 In its submission, the licensee stated that ASME Code Case N-638-1, Paragraph 3.0 does not specifically address monitoring or verification of welding interpass temperatures, however, ASME Code Case N-638-1, Paragraph 4.0(c) specifies that the area from which weld-attached thermocouples have been removed (after completion of the weld repair), shall be ground and examined using a surface examination method.

The licensee states that thermocouples will not be used. Instead, a contact pyrometer will be used to measure the preheat and interpass temperatures. The proposed interpass temperature controls are based on field experience with depositing weld overlays. Interpass temperature beyond the third layer has no impact on the metallurgical properties of the low alloy steel HAZ. The licensee further described in its submission that, in the first three layers, the interpass temperature will be measured every three to five passes and after the first three layers, interpass temperature measurements will be taken every six to ten passes for the subsequent layers. Also, the licensee stated that the contact pyrometers will be calibrated in accordance with approved calibration and control program documents.

3.9 Staff Evaluation of Proposed Modifications and Exceptions for the use of ASME Code Case N-638-1 The following paragraphs discuss the NRC staff's evaluation of the exceptions and alternatives for the use of ASME Code Case N-638-1 :

3.9.1 The licensee is applying a 360-degree, full structural weld overlay to maintain weld integrity. The full structural weld overlay will fulfill all structural requirements, independent of the existing weld. Operational experience has also shown that SCC in Alloy 82/182 will blunt at the interface with stainless steel base metal, carbon steel base metal, or Alloy 52 weld metal.

To eliminate the need for preheat and post-weld heat treatment under the Construction Code, the industry developed requirements for implementation of a temperbead welding technique which were published in ASME Code Case N-638-1. The NRC endorsed Code Case N-638-1 in RG 1.147, Revision 15. The temperbead technique carefully controls heat input and bead placement which allows subsequent welding passes to stress relieve and temper the HAZ of the low alloy or carbon steel base material and preceding weld passes. The welding is performed with low hydrogen electrodes under a blanket of inert gas. The inert gas shields the molten metal from moisture and hydrogen.

Therefore, the NRC staff finds that the need for the preheat and post-weld heat treatment specified by the ASME Construction Code is not necessary to produce a sound weld using a temperbead welding process which meets the requirements of ASME Code Case N-638-1.

- 10 3.9.2 ASME Code Case N-638-1, Paragraph 1.0(a) requires that the maximum area of an individual weld, based on the finished surface, will be limited to 100 square inches and the depth of the weld will not exceed one-half of the ferritic base metal thickness. This condition will not be met because the design for the weld overlay covers an area up to approximately 500 square inches on the ferritic component, which exceeds the limitations of ASME Code Case N-638-1. The EPRI Technical Report 1003616 provides technical justification for exceeding the size of the temperbead repairs up to a finished area of 500 square inches over the ferritic material. Results of industry analyses and testing performed to date have indicated that there is no direct correlation between the amount of surface area repaired and residual stresses generated using temperbead welding. Residual stresses associated with larger area repairs (> 100 square inches) remain compressive at an acceptable level. Based on the preceding discussion, the NRC staff finds that the modification to increase the weld overlay area to as much as 500 square inches provides an acceptable level of quality and safety.

3.9.3 The licensee has adequately demonstrated in its submittal, that Paragraph 2.1(j) of ASME Code Case N-638-1 clearly intended that the Charpy V-notch test acceptance criteria in ASME Code Case N-638-1 be based on the average lateral expansion value rather than the average of all three values (lateral expansion, absorbed energy, and percent shear fracture). The licensee has also shown that all of the governing documents, i.e., ASME Code,Section III, NB - 4330, "Impact Test Requirements," ASME Code,Section XI, IWA-4620, "Temperbead Welding of Similar Materials," and ASME Code,Section XI, IWA-4630, "Temperbead Welding of Dissimilar Materials" and ASME Code Case N-638-2 use the average lateral expansion value criterion. Therefore, the NRC staff finds that the licensee's proposed alternative to use the average lateral expansion value criterion for Charpy V-notch test acceptance criteria provides an acceptable level of quality and safety.

3.9.4 ASME Code Case N-638-1, Paragraph 3.0(c) requires the deposition and removal of at least one weld reinforcement layer for "similar materials" (i.e., ferritic materials). Since this weld is a dissimilar metal weld with an austenitic filler metal (i.e., Alloy 52M) for the proposed weld overlays, The NRC staff finds it acceptable that depositing and removing a weld reinforcement layer is not required.

3.9.5 ASME Code Case N-638-1, Paragraph 4.0(b) specifies that the final weld surface shall be examined using surface and UT methods no sooner than 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after the weld reaches ambient temperature. The 48-hour hold is to assure adequate hydrogen removal to avoid hydrogen cracking. Hydrogen cracking is a form of cold cracking. It is produced by internal tensile stresses produced from a localized build up of monatomic hydrogen. Monatomic hydrogen can form 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 can occur within 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> of welding. The EPRI

- 11 Technical Report 1013558, "Temper bead Welding Applications - 48 Hour Hold Requirement for Ambient Temperature Temper bead Welding," has shown that it is not necessary to wait until ambient temperature is reached before initiating the 48-hour hold in order to assure adequate hydrogen removal. No further tempering or potential hydrogen absorption effects will occur after deposition of the third overlay layer.

Therefore, the NRC staff finds that the licensee's proposed alternative to perform the surface and UT examinations no sooner than 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after the third layer of the weld overlay is installed provides an acceptable level of quality and safety.

3.9.6 ASME Code Case 1'J-638-1, Paragraph 4.0(c) specifies that the area from which weld - attached thermocouples have been removed shall be ground and examined using a surface examination method. Thermocouples will not be used. Instead, preheat and interpass temperatures will be monitored by contact pyrometers. These temperature sensing devices will be used to verify preheat temperature and interpass temperature every three to five passes in the first three layers. After the first three layers, interpass temperature measurements will be taken every six to ten passes for the subsequent layers. Contact pyrometers will be calibrated in accordance with approved calibration and control program documents. The NRC staff finds that this method of temperature measurement is equivalent with the required method for the measurement of preheat and interpass temperature in the temperature range of 50 of to 350 of. Therefore, the staff concludes that this type of monitoring of the interpass temperature provides an acceptable level of quality and safety.

4.0 CONCLUSION

Based on the discussion above, the NRC staff concludes that the alternatives proposed in the Relief Request JAF RR-7, Rev. 1 to perform a FSWOL on the N2C nozzle-to-recirculation inlet piping safe end dissimilar metal weld will provide an acceptable level of quality and safety.

Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the Alternative JAF RR 7, Rev. 1 for the installation of a FSWOL on the N2C nozzle-to-recirculation inlet piping safe end dissimilar metal weld. This relief request is authorized for use during fall 2008 refueling outage (R-18) at JAF. The repair performed using this alternative is applicable to the fourth 10-Year lSI interval for JAF which began March 1, 2007, and will end December 31, 2016, and for the period of extended operation which expires October 17, 2034.

All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this alternative remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.

5.0 REFERENCES

5.1. ASME Section XI - 2001 Edition/2003 Addenda except as listed in Reference 2 5.2. ASME Section XI - 2001 Edition to be used for Appendix VIII, "Performance Demonstration for Ultrasonic Examination Systems" 5.3. ASME Section III - 1965 Edition/1966 Addenda

- 12 5.4. ASME Section III, Subsection NB - 2001 Edition/2003 Addenda 5.5 JAF-RPT-06-001, ASME B&PV Code Section X1, Fourth Ten Year Inspection Interval Inservice (lSI) Program Plan 5.6. EPRI Report 1011898, Justification for the Removal of the 100 Square Inch Temperbead Weld Repair Limitation 5.7 EPRI Report GC-1 11050, Ambient Temperature Preheat for Machine GTAW Temperbead Applications 5.8. EPRI Report 1013558, 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 5.9 EPRI Report BWRVIP-75-A, Technical Basis for Revisions to Generic Letter 88-01 Inspection Schedules (1012621) 5.10. ASME Code Case N-740, "Full Structural Dissimilar Metal Weld Overlay for Repair or Mitigation of Class 1, 2, and 3 ItemsSection XI, Division 1, Revision 1" 5.11. ASME Code Case N-504-3, "Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping,Section XI, Division 1" 5.12. ASME Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1."

5.13. Relief Request RR-5, Relief from ASME Section X1 Appendix VII, Supplement 11 Requirements for Structural Weld Overlays (PDI)

Principal Contributor: E. Andruszkiewicz, NRRIDCI/CVIB Date: April 1, 2009

ML090710008 *no substantial changes to SE Input memo OFFICE LPL1-1\PM LPL 1-1\LA NRR/CVIB/BC OGC LPL1-1\BC NAME B. K. Vaidya SUttle MMitchell (*) LSubin MKowal DATE 3/19/09 3/19/09 03/09/09 3130109 4/1109

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