ML070850915

Relief, Request for Alternative ANO1-R&R-010 to Use Proposed Alternative to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code Requirements for Pressurizer Nozzle Weld Overlay Repairs, MD4019

ML070850915
Person / Time
Site:	Arkansas Nuclear
Issue date:	04/06/2007
From:	Terao D NRC/NRR/ADRO/DORL/LPLIV
To:	Mitchell T Entergy Operations
Saba F, NRR/DORL/LPL4, 301-415-1447
References
TAC MD4019
Download: ML070850915 (19)

Text

April 6, 2007 Mr. Timothy G. Mitchell Vice President, Operations Arkansas Nuclear One Entergy Operations, Inc.

1448 SR 333 Russellville, AR 72802

SUBJECT:

ARKANSAS NUCLEAR ONE, UNIT 1- REQUEST FOR ALTERNATIVE ANO1-R&R-010 TO USE PROPOSED ALTERNATIVE TO THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS BOILER AND PRESSURE VESSEL CODE REQUIREMENTS FOR PRESSURIZER NOZZLE WELD OVERLAY REPAIRS (TAC NO. MD4019)

Dear Mr. Mitchell:

By letter dated January 12, 2007, as supplemented by letters dated March 6 and March 22, 2007, Entergy Operations, Inc., submitted for staff review and approval Request for Alternative ANO1-R&R-010 for the installation of full structural weld overlays on dissimilar metal welds of pressurizer nozzles at Arkansas Nuclear One, Unit 1 (ANO-1).

The Nuclear Regulatory Commission (NRC) staff has reviewed the licensees submittal and determined that the proposed alternatives to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 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 ANO1-R&R-010 for the installation of full structural weld overlays on the dissimilar metal welds of the pressurizer nozzles at ANO-1. The effective period of the proposed alternative is the third inservice inspection interval, which ends on May 31, 2007.

The NRC staff's safety evaluation is enclosed. This completes the NRC staffs review under TAC No. MD4019. If you have any questions concerning this matter, please call Farideh Saba of my staff at 301-415-1447.

Sincerely,

/RA/

David Terao, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-313

Enclosure:

Safety Evaluation cc w/encl: See next page

April 6, 2007 Mr. Timothy G. Mitchell Vice President, Operations Arkansas Nuclear One Entergy Operations, Inc.

1448 SR 333 Russellville, AR 72802

SUBJECT:

ARKANSAS NUCLEAR ONE, UNIT 1- REQUEST FOR ALTERNATIVE ANO1-R&R-010 TO USE PROPOSED ALTERNATIVE TO THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS BOILER AND PRESSURE VESSEL CODE REQUIREMENTS FOR PRESSURIZER NOZZLE WELD OVERLAY REPAIRS (TAC NO. MD4019)

Dear Mr. Mitchell:

By letter dated January 12, 2007, as supplemented by letters dated March 6 and March 22, 2007, Entergy Operations, Inc., submitted for staff review and approval Request for Alternative ANO1-R&R-010 for the installation of full structural weld overlays on dissimilar metal welds of pressurizer nozzles at Arkansas Nuclear One, Unit 1 (ANO-1).

The Nuclear Regulatory Commission (NRC) staff has reviewed the licensees submittal and determined that the proposed alternatives to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 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 ANO1-R&R-010 for the installation of full structural weld overlays on the dissimilar metal welds of the pressurizer nozzles at ANO-1. The effective period of the proposed alternative is the third inservice inspection interval, which ends on May 31, 2007.

The NRC staff's safety evaluation is enclosed. This completes the NRC staffs review under TAC No. MD4019. If you have any questions concerning this matter, please call Farideh Saba of my staff at 301-415-1447.

Sincerely,

/RA/

David Terao, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-313

Enclosure:

Safety Evaluation cc w/encl: See next page DISTRIBUTION:

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ADAMS Accession No.: ML070850915

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NAME FSaba:DT for FS LFeizollahi** GGeorgiev for TChan JRund** DTerao DATE 4/6/07 3/27/07 3/26/07 4/5/07 6/6/07 OFFICIAL AGENCY RECORD

Arkansas Nuclear One cc:

Executive Vice President Section Chief, Division of Health

& Chief Operating Officer Emergency Management Section Entergy Operations, Inc. Arkansas Department of Health and P.O. Box 31995 Human Services Jackson, MS 39286-1995 4815 West Markham Street, Slot 30 Little Rock, AR 72205-3867 General Manager Plant Operations Senior Resident Inspector Entergy Operations, Inc. U.S. Nuclear Regulatory Commission Arkansas Nuclear One P.O. Box 310 1448 SR 333 London, AR 72847 Russellville, AR 72802 Regional Administrator, Region IV Director, Nuclear Safety Assurance U.S. Nuclear Regulatory Commission Entergy Operations, Inc. 611 Ryan Plaza Drive, Suite 400 Arkansas Nuclear One Arlington, TX 76011-8064 1448 SR 333 Russellville, AR 72802 County Judge of Pope County 100 W. Main Street Manager, Licensing Russellville, AR 72801 Entergy Operations, Inc.

Arkansas Nuclear One Vice President, Operations Support 1448 SR 333 Entergy Operations, Inc.

Russellville, AR 72802 P.O. Box 31995 Jackson, MS 39286-1995 Director, Nuclear Safety & Licensing Entergy Operations, Inc.

1340 Echelon Parkway Jackson, MS 39213-8298 Section Chief, Division of Health Radiation Control Section Arkansas Department of Health and Human Services 4815 West Markham Street, Slot 30 Little Rock, AR 72205-3867 February 2007

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST TO USE PROPOSED ALTERNATIVE TO ASME CODE REQUIREMENTS FOR PRESSURIZER NOZZLE WELD OVERLAY REPAIRS ENTERGY OPERATIONS, INC.

ARKANSAS NUCLEAR ONE, UNIT 1 DOCKET NUMBER 50-313

1.0 INTRODUCTION

By letter dated January 12, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML070180170), Entergy Operations, Inc. (the licensee), submitted for staff review and approval Request for Alternative ANO1-R&R-010 to the requirements of American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME) Code,Section XI, IWA-4330 for mitigating primary water stress-corrosion cracking (PWSCC) on dissimilar metal welds (DMWs) of pressurizer nozzles using full structural weld overlays at Arkansas Nuclear One, Unit 1 (ANO-1). By letters dated March 6 and March 22, 2007 (ADAMS Accession Nos. ML070740471 and ML070880684, respectively), the licensee submitted the response to the NRCs request for additional information and the revised Request for Alternative ANO1-R&R-010, which includes a change to the start time of the 48-hour hold period for the ultrasonic examination of the weld overlay.

A DMW is defined as a weld that joins two pieces of different type of metals. In the proposed alternative, the dissimilar metal weld joins the ferritic (i.e., carbon steel) pressurizer nozzle to the austenitic stainless steel safe end, valve flange, or piping. The DMW itself is made of nickel-based Alloy 82/182. The proposed weld overlay repair is a process by which weld filler metal that is resistant to stress corrosion cracking is deposited on the outside surface of the degraded pipe including the original pipe weld.

2.0 REGULATORY REQUIREMENTS 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 pre-service examination requirements, set forth in the ASME Code,Section XI, Rules for Inservice Inspection (ISI) 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 10-year interval and

subsequent intervals comply with the requirements in the latest edition and addenda of 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.

Pursuant to 10 CFR 50.55a(a)(3) alternatives to requirements may be authorized by the Nuclear Regulatory Commission (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.

ANO-1 is in the third inspection interval. The current ASME Code edition and addenda for ANO-1 are the 1992 Edition with portions of the 1993 Addenda of the ASME Code,Section XI.

In addition, as required by 10 CFR 50.55a, the licensee will use Appendix VIII, Performance Demonstration for Ultrasonic Examinations of the 1995 Edition through 1996 Addenda of the ASME Code,Section XI, for ultrasonic examination of the weld overlay.

3.0 LICENSEES PROPOSED ALTERNATIVE

3.1 ASME Code Components Affected

The licensee will install a full structural weld overlay on the following seven DMWs.

The pressurizer spray line has two alloy 82/182 DMWs, which will be weld overlaid; weld ID 18-001 joining the nozzle and safe-end weld, and weld ID 18-001A joining the safe-end and piping. The carbon steel (P-No. 1) pressurizer nozzle is welded to an Inconel 600 (P-No. 43) safe end, which is, in turn, welded to stainless steel (P-No. 8) pipe. The two DMWs are located close to each other; therefore, a single weld overlay will be installed across both welds.

There are two (2) pressurizer safety valves. Each valve has an alloy 82/182 DMW joining the carbon steel (P-No. 1) pressurizer nozzle and stainless steel (P-No. 8) valve flange: weld ID 05-040 and ID 05-042.

The pressurizer electromatic relief valve has one alloy 82/182 DMW, ID 05-041, joining the carbon steel (P-No. 1) pressurizer nozzle and stainless steel (P-No. 8) valve flange.

The pressurizer surge line has one alloy 82/182 DMW, ID 16-012A, joining the carbon steel (P-No. 1) pressurizer nozzle and a stainless steel (P-No. 8) safe end.

The hot-leg-to-surge line has one alloy 82/182 DMW, ID 16-001, joining the carbon steel (P-No. 1) hot-leg nozzle and stainless steel (P-No. 8) piping.

3.2 Code Requirements Subarticle IWA-4170(b) of the ASME Code,Section XI, requires that repairs and the installation of replacement items be performed in accordance with the Owners Design Specification and the original Construction Code of the component or system. Alternatively, Subarticle IWA-4170(b) of the ASME Code,Section XI, allows for use of later Editions and Addenda of the Construction Code or ASME Code,Section III.

Subarticles IWA-4300 and IWA-4500 of the ASME Code,Section XI, provide defect removal and alternative welding methods when the requirements of IWA-4170(b) cannot be met.

Subarticle IWA-4800 of the ASME Code,Section XI, requires the performance of pre-service 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 ISI 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 Proposed Alternative Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee proposes the following as alternatives to the Code requirements specified above.

The licensee will install pre-emptive full structural weld overlays in accordance with the proposed alternatives specified in Attachments 2 and 3 to Request for Alternative ANO1-R&R-010 dated March 6, 2007. These alternatives are based on the methodology of ASME Code,Section XI, Code Case N-740. The alternative to design, fabrication, examination, pressure testing, and ISI of pre-emptive full structural weld overlays is described in Attachment 2 of the March 6, 2007 submittal. The alternative applicable to ambient temperature temper bead welding is described in Attachment 3 of the March 6, 2007 submittal. The Attachment 3 alternative will be applied to the six DMWs identified above as an alternative to the post-weld heat treatment requirements of the ASME Code,Section III.

The licensee will perform ultrasonic examinations of the proposed pre-emptive full structural weld overlays in accordance with Appendix VIII, Supplement 11 of the 1995 Edition through 1996 Addenda of ASME Code,Section XI, except as modified by the Performance Demonstration Initiative (PDI) Program. The proposed PDI alternatives to Appendix VIII, Supplement 11 are specified in Attachment 6 of the March 6, 2007 submittal.

3.4 Duration Of the Alternative Request for Alternative ANO1-R&R-010 is applicable for the third inspection interval at ANO-1, which began on June 1, 1997, and ends on May 31, 2007.

4.0 NRC STAFF EVALUATION to Request for Alternative ANO1-R&R-010 contains requirements for the design and nondestructive examination (NDE) of the weld overlay. Attachment 3 to Request for Alternative ANO1-R&R-010 contains requirements for the ambient temperature temper bead welding technique. The proposed methodology and associated requirements for the weld overlay are similar to Code Case N-740, Dissimilar Metal Weld Overlay for Repair of Class 1, 2, and 3 ItemsSection XI, Division 1 of the ASME Code,Section XI. Code Case N-740 combines the requirements in Code Case N-504-2, Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Section XI, Division 1, and N-638-1, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW [gas tungsten arc welding] Temper

Bead Technique Section XI, Division 1. The staff has endorsed Code Cases N-504-2 and N-638-1, but not Code Case N-740. Therefore, the staff evaluates the acceptance of Request for Alternative ANO1-R&R-010 based on the requirements of Code Case N-504-2 and N-638-1.

As discussed above, Request for Alternative ANO1-R&R-010 dated March 6, 2007, is the same as the version dated March 22, 2007, except that weld overlay using ambient temperature temper bead welding changed from one DMW to six DMWs. The major revisions to Request for Alternative ANO-1-R&R-010 appear in the March 6, 2007, submittal. The weld overlay requirements of Attachments 2 and 3 in the March 6, 2007, submittal and in the March 22, 2007, submittal are the same. Also, the licensee provided a response to the staff request for additional in the March 6, 2007, submittal. Therefore, the staffs evaluation below will be based on March 6, 2007 submittal, unless otherwise identified. However, for the purpose of approval, the staff will use Request for Alternative ANO-1-R&R-010 dated March 22, 2007.

4.1 General Requirements Section 1.0, General Requirements, of Attachment 2 to Request for Alternative ANO1-R&R-010 provides requirements for the specification of the base metal (carbon steel, stainless steel, and Alloy 82/182) and weld overlay filler metal (Alloy 52M), surface condition of the base metal, and chromium content of the weld overlay deposits.

As discussed above, the licensee will apply a weld overlay to the flange of the two safety valves and the relief valve. The staff asked the licensee to clarify whether the weld shrinkage from the weld overlay on the flange would cause distortion resulting in leakage of the valve flange or exert unanalyzed forces on the flange bolting. In the March 6, 2007 letter, the licensee responded that during the welding operation, the safety and relief valves will be unbolted and removed from the piping system. Therefore, the welding operation will not affect the seating surfaces of the valves or mating surfaces of the flanges. The welding operation will also not result in unanalyzed forces on the flange bolting.

The licensee clarified further that weld shrinkage due to the weld overlay should not result in misalignment or leakage of the valve. The expected axial and radial shrinkage due to welding should be symmetric in nature since the overlay regions of the nozzles/flanges are also symmetric. Because the pressurizer nozzles and flanges are relatively thick members in relation to the thickness and length of the deposited weld overlays, the weld overlays should not substantially distort the flanges.

The licensee stated that Welding Services Inc., the contracted welding vendor for the ANO-1 weld overlays, installed weld overlays on the safety relief valve DMWs at Oconee Unit 1 in the fall of 2006. As part of the Oconee Unit 1 project, a scaled mock-up was welded. Distortion and shrinkage measurements were taken during the mock-up welding and field installation of the weld overlays at Oconee. The maximum deflection of the flanges was measured to be approximately 0.05 inch, and the maximum sealing surface flatness change was measured to be less than 0.01 inch. These changes are minimal and did not result in any valve installation problems or leakage issues. The ANO-1 relief valve nozzle designs are similar to the Oconee Unit 1 safety relief valve nozzle design. The weld overlay designs for ANO-1 are also similar to the Oconee Unit 1 design. Therefore, the effects of welding on the flanges and sealing surfaces at ANO-1 are expected to be similar to those measured at Oconee Unit 1.

The licensee stated that a mockup of the weld overlay design for the ANO-1 emergency relief valve (ERV) nozzle DMW is also being performed. During the mock-up, distortion and shrinkage measurements will be taken to evaluate angular deflection and sealing surface flatness of the flange. Distortion and shrinkage measurements will also be taken during field installation activities. Finally, Request for Alternative ANO1-R&R-010 requires the performance of a system leakage test in accordance with Subarticle IWA-5000 of the ASME Code,Section XI, to verify that there is no unacceptable leakage from the flanged connections.

The staff finds that the weld overlay of the flanges of the safety valves and ERV is acceptable because the licensee has considered the weld shrinkage as part of mock-up and will remove the valve body when installing weld overlay to minimize distortion on the valve flange.

The staff asked the licensee whether the proposed alternative would allow a new weld overlay be installed over the top of an existing weld overlay. The staff's position is that the weld overlay is a single application, not multiple applications, on any one dissimilar metal weld. In the March 6, 2007 letter, the licensee responded that the proposed alternative is not intended to allow a new weld overlay to be installed over an existing weld overlay. The licensee has clarified this position by adding paragraph 1.0(e) to Attachment 2 to Request for Alternative ANO1-R&R-010, which requires that: "A new weld overlay shall not be installed on top of an existing weld overlay that has been in service." The staff finds that paragraph 1.0(e) is acceptable because the weld overlay will not be installed on an existing weld overlay more than one time.

In the March 6, 2007 letter, the licensee stated that ambient temperature temper bead welding is only applicable to the pressurizer nozzle-to-surge line DMW and none of the other DMWs require the use of ambient temperature temper bead welding. In the March 22, 2007, the licensee revised the submittal to require the use of ambient temperature temper bead welding on the six DMWs joining ferritic material. The DMW (Weld ID 18-001A) in the pressurizer spray line, which joins alloy 600 safe-end and stainless steel piping, will not be welded with ambient temperature temper bead welding because the safe end and piping are not ferritic material. The ambient temperature temper bead welding is applicable to ferritic material. The licensee will install the weld overlay on weld ID18-001A in accordance with the ASME Code,Section III, requirements. The staff finds the revision in March 22, 2007, submittal acceptable because the licensee will be applying ambient temperature temper bead welding to the six DMWs joining ferritic material and the ASME Code,Section III, welding to the non-ferritic material of weld ID 18-001A.

4.2 Crack Growth Considerations and Design Section 2, Crack Growth Considerations and Design, of Attachment 2 to Request for Alternative ANO-1-R&R-010 provides the requirements for weld overlay design, design-basis flaw size, and the crack-growth calculation. The crack-growth calculation assures that the growth of the crack in the base metal will be mitigated or minimized by the installation of the weld overlay.

The licensee stated that the design basis for full structural weld overlays is to maintain the original design margins with no credit taken for the underlying PWSCC-susceptible weldments.

The assumed design-basis flaw for the purpose of sizing the weld overlays is 360° and 100 percent through the original wall thickness of the DMWs. Regarding the crack-growth

analysis for the pre-emptive full structural weld overlay, a flaw originating from the inside diameter with a depth of 75 percent and a circumference of 360° will be assumed. A 75-percent through-wall flaw is the largest flaw that could remain undetected in the base metal.

A pre-service volumetric examination will be performed after application of the weld overlay using an ASME Section XI, Appendix VIII (as implemented through PDI) examination procedure. This examination will verify that there is no cracking in the upper 25 percent of the base material. The preservice examination will also demonstrate that the assumption of a 75-percent through-wall crack is conservative. The PDI procedure is not qualified to examine lower 75 percent of the pipe wall thickness. Therefore, a conservative approach is that a 75-percent through-wall crack is assumed to exist in the lower 75 percent of the pipe wall thickness.

The licensee stated that if no flaws were identified in the upper 25 percent of the original weld, the flaw depth for crack-growth calculation would be 75 percent through-wall in the original weld. If any crack-like flaws are found during the pre-service examination in the upper 25 percent of the original weld or base metal, an analyzed flaw (the postulated 75 percent through-wall flaw plus the portion of the as-found flaw in the upper 25 percent) would be used for the crack-growth calculation. The staff finds that the proposed flaw size for the crack-growth calculation is conservative and, therefore, is acceptable.

As part of the weld overlay design, the licensee will perform the following analyses. The licensee will perform nozzle-specific stress analyses to establish a residual stress profile in each pressurizer nozzle. Severe weld repairs will be assumed in these analyses that effectively bound any actual weld repairs that may have occurred in the pressurizer nozzles. The analyses will then simulate application of the weld overlays to determine the final residual stress profiles.

Post-weld overlay residual stresses at normal operating conditions will be shown to result in beneficial compressive stresses on the inside surface of the components, assuring that further crack initiation due to PWSCC is highly unlikely.

The license will also perform fracture mechanics analyses to predict crack growth for postulated flaws. Crack growth due to PWSCC and fatigue will be analyzed for the original DMW. The crack-growth analyses will consider all design loads and transients, plus the post-weld overlay and through-wall residual stress distributions. The analyses will demonstrate that the postulated cracks will not grow beyond the design basis for the weld overlays. The licensee will demonstrate by analysis that the weld overlay does not impact the conclusions of the existing stress reports for the pressurizer nozzles. The stress and fatigue criteria of ASME Code,Section III, will be met for regions of the overlays remote from assumed cracks.

The licensee will measure shrinkage during the overlay application. Shrinkage stresses at other locations in the piping systems arising from the weld overlays will be demonstrated not to have an adverse effect on the systems. Clearances of affected support and restraints will be checked after the overlay repair, and will be reset within the design ranges as required.

Lastly, the licensee will evaluate the total added weight on the piping systems due to the overlays for potential impact on piping system stresses and dynamic characteristics. The as-built dimensions of the weld overlays will be measured and evaluated to demonstrate that they meet or exceed the minimum design dimensions of the overlays.

The staff finds that the licensee proposed analyses and shrinkage measurement are consistent with paragraph (g) of Code Case N-504-2 and are, therefore, acceptable.

In the March 6, 2007 submittal, the licensee stated that Alloy 52M weld metal has demonstrated sensitivity to certain impurities, such as sulfur, when deposited onto austenitic stainless steel base metal. Therefore, should this condition exist, a butter layer of austenitic stainless steel filler metal will be applied across the austenitic stainless steel base metal prior to installing weld overlay. The staff asked the licensee to discuss any potential welding problems (e.g., lack of fusion) associated with overlaying the Alloy 52M on the butter layer. In the March 6, 2007 letter, the licensee responded that it does not expect welding problems if an austenitic stainless steel weld butter layer is applied onto a stainless steel base material such as A-376, TP316. The weld butter will be applied with the GTAW process using an austenitic stainless steel weld filler metal that has chemical, mechanical, and metallurgical properties that are equivalent (or similar) to those of the austenitic stainless steel base materials. Austenitic stainless steel filler metals are specifically manufactured for joining, building-up, overlaying, or buttering austenitic stainless steel base materials. The welding procedure for applying the austenitic stainless steel butter layer will be qualified in accordance with ASME Code,Section IX, for the applicable base materials, filler metals, and welding variables. The licensee noted that the austenitic stainless steel butter layer will not be deposited onto the existing Alloy 82/182 weld or carbon steel base material of the pressurizer nozzle. The butter layer will only be applied onto austenitic stainless steel base materials.

The licensee clarified further that the deposition of an Alloy 52M weld overlay onto austenitic stainless steel weld metal (i.e., the butter layer) is also not expected to be a problem. From a welding perspective, Alloy 52M weld metal can be deposited over austenitic stainless steel weld metal just as easily as it can be deposited over an austenitic stainless base material. The welding procedure that will be used to apply the Alloy 52M weld overlay onto the austenitic stainless steel base materials and butter layer will be qualified in accordance with ASME Code,Section IX, and the requirements of Request for Alternative ANO1-R&R-010, Attachment 2.

The licensee will prepare a mock-up(s) to validate the process for the applications to be encountered at ANO-1. In the mock-up(s), a stainless steel butter layer will be applied to the stainless steel base material prior to deposition of the Alloy 52 weld metal. The mock-up will provide information for the licensee to assure that sound welds will be made in the field application. The thickness of the butter layer will be typical of that used for structural weld overlay layers (0.080 to 0.100 inch), with specific welding parameters to be defined during the welding procedure qualification and mock-up programs.

Because the coefficients of thermal expansion for the austenitic stainless steel weld metal and austenitic stainless steel base material are essentially the same, the differential thermal expansion between the weld overlay (Alloy 52M) and base metal (stainless steel) versus that of the weld overlay (Alloy 52M) and butter layer (stainless steel) will be the same. Therefore, the deposition of an austenitic stainless steel butter layer onto an austenitic stainless steel base material prior to deposition of the Alloy 52M weld overlay will have no adverse affect on weld shrinkage. Nonetheless, if the stainless steel butter layer is applied, the effect of the butter layer on the weld overlay will be reconciled in the weld overlay design and residual stress analyses.

The licensee stated that if an austenitic stainless steel butter layer is installed, it will not be included in or credited to the structural weld overlay design thickness. Additionally, the austenitic stainless steel butter layer will not adversely affect the ability to ultrasonically examine the weld overlay or base metal.

The staff finds that the installation of a butter layer on the base metal is acceptable because the austenitic stainless steel butter layer will not cause adverse chemical or metallurgical interaction on the austenitic stainless steel base metal or Alloy 52M weld overlay metal.

Paragraph 2.0(b)(4) of Attachment 2 to Request for Alternative ANO1-R&R-010 states that

...any planar flaws in the weld overlay...shall be evaluated and shall meet the requirements of IWB-3640... The NRCs position is that the acceptance criteria of Subarticle IWB-3640 of the ASME Code,Section XI, are not acceptable for the planar flaw in the weld overlay. Any planar flaws in the weld overlay rejected by the standards of Subarticle IWB-3514 of the ASME Code,Section XI, need to be removed.

In the March 6, 2007 letter, the licensee responded that it agrees with the NRCs position and will not accept planar flaws in the weld overlay based on the analytical evaluation provisions of IWB-3640. The licensee clarified that paragraphs 3.0(a) and (b) of Attachment 2 to Request for Alternative ANO1-R&R-010 require that any planar flaws identified during the acceptance and pre-service examinations of the weld overlay must meet the acceptance standards of IWB-3514.

Therefore, if a planar flaw is identified in the weld overlay that exceeds the acceptance standards of IWB-3514, the planar flaw will be rejected and removed.

The licensee clarified further that the intent of paragraph 2.0(b)(4) of Attachment 2 to Request for Alternative ANO1-R&R-010 is not to specify acceptance standards for the weld overlay examination because weld overlay examination acceptance standards are addressed by paragraphs 3.0(a) and (b) of Attachment 2. The licensee stated that the intent of paragraph 2.0(b)(4) is to address two specific design issues: (1) design thickness of the weld overlay; and (2) compliance of the weld overlay design with IWB-3640. With respect to the design thickness of the weld overlay, no structural credit can be taken for the original weld (i.e.,

flaws in the original weld are assumed to be 100-percent through-wall for the entire circumference), while the weld overlay thickness credited in the design must consist of weld layers that contain at least 24-percent chromium. Regarding the applicability of IWB-3640 to the weld overlay design, paragraph 2.0(b)(4) ensures that the combined wall thickness at the weld overlay (i.e., wall thickness of the pipe at the original weld and weld overlay thickness) meets the requirements of IWB-3640 when evaluating the following anomalies in the weld overlay region:

• Planar flaws identified during the acceptance and pre-service examinations of the weld overlay. Although considered in the paragraph 2.0(b)(4) evaluation, these planar flaws must also meet the acceptance standards of IWB-3500 according to paragraphs 3.0(a) and (b) of Attachment 2 of Request for Alternative ANO1-R&R-010.

• Postulated flaws assumed in the original weld for the purpose of design. The flaws were assumed to be 100-percent through-wall for the entire circumference.

• Discontinuities within a distance of 2.5%Rt from the toes of the weld overlay. Examples of discontinuities include another weld overlay or reinforcement for a branch connection.

The licensee concluded that planar flaws identified in the weld overlay must first meet the acceptance standards of IWB-3500 as required by paragraphs 3.0(a) and (b) of Attachment 2 to Request for Alternative ANO1-R&R-010. However, when evaluating the combined wall thickness at the weld overlay in accordance with IWB-3640, planar flaws accepted by Subarticle

IWB-3500 per paragraphs 3.0(a) and (b) must also be considered in the paragraph 2.0(b)(4) evaluation.

The licensee added a note to paragraph 2.0(b)(4) of Attachment 2 to Request for Alternative ANO1-R&R-010 to clarify the examination acceptance criteria for the planar flaws. The staff finds that the note is acceptable because it clarifies that any planar flaws detected in the weld overlay will satisfy the acceptance standards of IWB-3514, not IWB-3600.

4.3 Examination and Inspection Section 3, Examination and Inspection, of Attachment 2 to Request for Alternative ANO1-R&R-010 provides requirements for the acceptance examination, pre-service examination, and inservice examination after weld overlay is installed. The length, surface finish, and flatness requirements of the weld overlay are specified in the weld overlay design to provide for required examination volume of the weld overlay as shown in Figures 1 and 2 of Attachment 2 to Request for Alternative ANO1-R&R-010.

The ultrasonic examinations performed in accordance with the proposed alternative are in accordance with ASME Code,Section XI, Appendix VIII, Supplement 11, as implemented through the PDI. These examinations are considered more sensitive for detecting fabrication and service-induced flaws than the ASME Code,Section III, radiographic or ultrasonic examination methods. Furthermore, construction-type flaws have been included in the PDI qualification sample sets for evaluating procedures and personnel.

Appendix VIII, Supplement 11 of the 1995 Edition through 1996 Addenda of ASME Code,Section XI, specifies requirements for performance demonstration of ultrasonic examination procedures, equipment, and personnel used to detect and size flaws in full structural overlays of wrought austenitic piping welds. The current ultrasonic examination technology cannot meet the requirements of Appendix VIII, Supplement 11. Therefore, the industry initiated the PDI Program as an alternative to satisfy the requirements of ASME Code,Section XI, Appendix VIII.

The licensee proposed to use the PDI program as indicated in Attachment 6 to Request for Alternative ANO1-R&R-010 to satisfy the Appendix VIII, Supplement 11, qualification requirements. Therefore, the PDI initiatives will be used for qualification of ultrasonic examinations to detect and size flaws in the pre-emptive full structural weld overlays of this request. The staff has endorsed the industrys PDI program. The staff finds that the licensee proposed PDI program is consistent with the industrys PDI program and, therefore, is acceptable.

4.3.1 Acceptance Examination Section 3(a), Acceptance Examination of the Overlay, of Attachment 2 to Request for Alternative ANO1-R&R-010 requires a surface examination of an installed weld overlay and the acceptance criteria will be based on NB-5300 of the ASME Code,Section III.

Per Section 3.0(a)(3) of Attachment 2 to Request for Alternative ANO1-R&R-010, any planar flaws found during either the acceptance or pre-service examination are required to meet the requirements of Table IWB-3514-2. This approach was previously determined to be acceptable in the NRC Safety Evaluation Report (SER) for Three Mile Island, Unit 1, dated July 21, 2004.

However, within the same SER, the NRC had concerns regarding the application of

Table IWB-3514-3 to laminar flaws in a weld overlay. The SER stated, Applying Table IWB-3514-3 to a weld overlay exposes several inherent oversights. For instance, the acceptance of a laminar flaw size is independent of the weld overlay size, and the acceptance criteria are silent on the inaccessible volume beneath the lamination, which may hide other flaws beneath the lamination. The licensee addressed the staffs concerns in paragraph 3.0(a)(3), as follows:

• Per Section 3.0(a)(3)(i) of Attachment 2, Table IWB-3514-3 has been restricted so that the total laminar flaw shall not exceed 10 percent of the weld surface area and no linear dimension of the laminar flaw shall exceed 3 inches.

• Per Section 3.0(a)(3)(ii) of Attachment 2, the reduction in coverage due to laminar flaws shall be less than 10 percent. The dimensions of the un-inspectable volume are based on the coverage obtained by angle beam examinations of the weld overlay.

• Per Section 3.0(a)(3)(iii) of Attachment 2, any un-inspectable volume in the weld overlay shall be assumed to contain the largest radial planar flaw that could exist within that volume. This assumed flaw shall meet the inservice examination standards of Table IWB-3514-2. Alternately, the assumed flaw shall be evaluated and meet the requirements of IWB-3640. Both axial and circumferential planar flaws shall be assumed.

The staff finds that the above requirements to limit the size of the laminar flaws and the potential flaws in the un-inspectable volume have addressed the staffs concerns regarding the laminar flaws in the weld overlay and are acceptable.

Regarding hydrogen cracking concerns, the licensee stated that NDE required by paragraphs 3.0(a)(2) and 3.0(a)(3) of Attachment 2 is capable of detecting hydrogen cracking in ferritic materials. If hydrogen cracking were to occur, the licensee stated that it would occur in the heat-affected zone (HAZ) of the ferritic-base material either below or immediately adjacent to the weld overlay. Therefore, it is unnecessary to examine the entire 1.5T (T is the wall thickness of piping) band defined in paragraph 1.0(e) of Attachment 3. Hydrogen cracking is not a concern in austenitic materials. If it occurs in the ferritic-base material below the weld overlay, it will be detected by the ultrasonic examination, which will interrogate the entire weld overlay including the interface and HAZ beneath the weld overlay. If hydrogen cracking occurs in the ferritic-base material immediately adjacent to the weld overlay, it will be detected by the liquid penetrant examination which is performed at least one-half inch on each side of the weld overlay.

Paragraphs 3.0(a)(2), 3.0(a)(3), and 3.0(b)(1) of Attachment 2 to Request for Alternative ANO1-R&R-010 require that when ambient temperature temperbead welding is performed over ferritic materials, the liquid penetrant and ultrasonic examinations will not be performed until at least 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after completing of the third layer of the weld overlay. This requirement deviates from Code Case N-638-1, which requires that the liquid penetrant and ultrasonic examinations not be performed until at least 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after the weld reaches the ambient temperature.

This 48-hour hold time is specified to allow sufficient time for hydrogen cracking to occur (if it is to occur) in the HAZ of ferritic materials prior to performing NDE so that if hydrogen cracking does occur, NDE would be able to detect it. However, based on extensive research and industry experience, the Energy Power Research Institute (EPRI) has provided a technical basis

for starting the 48-hour hold after completion of the third temper bead 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 when performing ambient temperature temper bead welding. EPRI has documented their technical basis in Technical Report 1013558, Temper Bead Welding Applications - 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding (ADAMS Accession No. ML070670060). Although the technical data provided by EPRI in their report is based on testing performed on SA-508, Class 2 low-alloy steels and other P-Number 3, Group 3 materials, the conclusions are bounding and applicable to P-Number 1 materials such as SA-508, Class 1, which have a lower carbon equivalent and lower hardenability. The ANO-1 pressurizer nozzles are manufactured from SA-508, Class 1, carbon steel.

After evaluating all of the issues relevant to hydrogen cracking such as microstructure of susceptible materials, availability of hydrogen, applied stresses, temperature, and diffusivity and solubility of hydrogen in steels, EPRI concluded that: ...[t]here appears to be no technical basis for waiting 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 temper bead welded component should be very tolerant of the moisture... EPRI also notes that over 20 weld overlays and 100 repairs have been performed using temper bead techniques on low-alloy steel components over the last 20 years. During this time, there has never been an indication of hydrogen cracking by the NDE performed after the 48-hour hold or by subsequent ISI.

In addition, the ASME Code,Section XI, Committee published a White Paper to support the 48-hour hold time alternative. The ASME White Paper (ADAMS Accession No. ML070790679) points out that the introduction of hydrogen to the ferritic HAZ is limited to the first weld layer since this is the only weld layer that makes contact with the ferritic-base material. While the potential for the introduction of hydrogen to the ferritic HAZ is negligible during subsequent weld layers, these layers provide a heat source that accelerates the dissipation of hydrogen from the ferritic HAZ in non-water backed applications. Furthermore, the solubility of hydrogen in austenitic materials such as Alloy 52M is much higher than that of ferritic materials while the diffusivity of hydrogen in austenitic materials is lower than that of ferritic materials. As a result, hydrogen in the ferritic HAZ tends to diffuse into the austenitic weld metal, which has a much higher solubility for hydrogen. This diffusion process is enhanced by heat supplied in subsequent weld layers. The ASME White Paper concludes that there is sufficient delay time to facilitate the detection of potential hydrogen cracking when NDE is performed 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after completion of the third weld layer.

The staff finds that 48-hour hold time after the third weld layer is acceptable because the licensee has provided sufficient technical justification to show that hydrogen cracking in the weld overlay would not likely to occur under the proposed alternative.

4.3.2 Pre-Service Examination Section 3.0(b), Preservice Inspection, of Attachment 2 to Request for Alternative ANO1-R&R-010 requires an ultrasonic examination of the installed weld overlay and the upper (outer) 25 percent of the original pipe-wall thickness. The required examination volume is defined in Figure 2 of Attachment 2 to ANO-1-R&R-010. Paragraph 3.0(b)(2) requires that the acceptance standards of Table IWB-3514-2 be met for the weld overlay. This means that any flaws in the

weld overlay that cannot satisfy the acceptance standards of Table IWB-3514-2 of the ASME Code,Section XI, will be removed. The staff finds that the pre-service examination requirements are acceptable because they are consistent with the staff position on the disposition of the pre-service flaws in the weld overlay.

4.3.3 Inservice Examination Section 3(c) of Attachment 2 to Request for Alternative ANO1-R&R-010 requires inservice examination be conducted ultrasonically and the examination volume is defined in Figure 2 of to Request for Alternative ANO1-R&R-010.

Paragraph 3.0(c)(3) of the original alternative dated January 12, 2007, states that if the weld overlay does not meet the standards of Table IWB-3514-2, it can be accepted by IWB-3600.

The staff would accept the acceptance criteria of IWB-3600 to disposition flaws in the weld overlay if the flaw growth is caused by thermal fatigue, which would be insignificant. However, flaw growth by PWSCC could be significant. Therefore, the staff finds that PWSCC or PWSCC-induced flaw growth in the weld overlay is unacceptable. In the March 6, 2007 letter, the licensee clarified that it does not intend to perform an IWB-3600 analytical evaluation of PWSCC in weld overlays. By letter dated March 6, 2007, the licensee revised paragraph 3.0(c)(3) of Attachment 2 to ANO1-R&R-010 to include the following requirement:

"flaws identified as primary water stress corrosion cracking cannot be accepted by an IWB-3600 analytical evaluation." The staff finds that the revised paragraph 3.0(c)(3) prohibits the use of analytical evaluation of IWB-3600 to disposition PWSCC-induced flaws, which is consistent with the NRC staffs position and, therefore, is acceptable.

The weld overlay will be ultrasonically examined during the first or second refueling outage following application. If the first ISI examination after installation show no indication, no crack growth, or no new cracking in the weld overlay, the subject weld will be placed into a population group for each unit to be examined on a sample basis in the future. If a planar indication is detected in the weld overlay during the first ISI and is accepted per Table IWB-3514-2, the weld overlay will be re-examined in the future refueling outage(s) per paragraph 3.0(c)(5) of to Request for Alternative ANO1-R&R-010.

The successive examination requirements of Section 3.0(c) of Attachment 2 to Request for Alternative ANO1-R&R-010 ensure that cracks identified by ISIs are appropriately monitored.

Section 3.0(c) of Attachment 2 requires that the weld overlay be reexamined during the first or second refueling outage following discovery of the growth or new cracking. If additional crack growth or a new crack is discovered during a successive examination, then the successive examination of the weld overlay would be re-performed within the next two refueling outages.

However, if the successive examination of the weld overlay reveals no additional indication of crack growth or new cracking, the weld overlay shall be placed into a population to be examined on a sample basis. Twenty-five percent of this population shall be examined once every 10 years. The licensee stated that the successive examination schedule is identical to that specified in paragraph Q-4300 of ASME Code,Section XI, Appendix Q, which has been imposed as a condition to using Code Case N-504-2 by the NRC in Regulatory Guide 1.147.

The staff finds the successive examination requirements of Section 3.0(c) is consistent with Appendix Q to the ASME Code,Section XI, and, therefore, is acceptable.

4.4 Pressure Testing

Section 4, Pressure Testing, of Attachment 2 to Request for Alternative ANO1-R&R-010 requires a system leakage test be performed in accordance with IWA-5000 after a weld overlay is installed. The staff finds this requirement acceptable because it is consistent with paragraph (h) of Code Case N-504-2.

4.5 Documentation Section 5, Documentation, of Attachment 2 to Request for Alternative ANO1-R&R-010 requires that use of the proposed alternative be documented on ASME Form NIS-2, Owners Report for Repairs or Replacements. The staff finds this requirement acceptable because it is consistent with paragraph (m) of Code Case N-504-2.

4.6 Proposed Ambient Temperature Temper Bead Welding The requirements for the proposed ambient temperature temper beading welding are discussed in Attachment 3 to Request for Alternative ANO1-R&R-010 and are based on Code Case N-638-1 with the following exceptions. The staff evaluation of the exceptions is discussed below:

Paragraph 1.0(a) of Code Case N-638-1 limits the maximum area of an individual weld to 100 square inches on the ferritic-base material using temper bead welding. However, the proposed alternative allows the weld surface area up to 300 square inches on the ferritic-base material. The licensee stated that technical justification for allowing weld overlays on ferritic materials with surface areas up to 500 square inches is provided in the White Paper supporting the changes in ASME Code Case N-638-3 and EPRI Report 1011898, Justification for the Removal of the 100 Square Inch Temper bead Weld Repair Limitation (Reference 1). The EPRI report cites evaluations of a 12-inch diameter nozzle weld overlay to demonstrate adequate tempering of the weld HAZ, residual stress evaluations demonstrating acceptable residual stresses in weld overlays ranging from 100 to 500 square inches, and service history in which weld repairs exceeding 100 square inches were NRC approved and applied to DMW nozzles in several boiling-water reactor and pressurized-water reactor applications. Some of the cited repairs are greater than 15 years old, and have been inspected several times with no evidence of any continued degradation. The above theoretical arguments and empirical data have been 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.

The staff finds that the proposed 300-square inch weld area on the ferritic material is acceptable because the stress analysis presented in EPRI Report 1011898 shows that the structural integrity of ferritic material is not adversely affected by a 300-square inch weld overlay area.

Also, the staff has previously approved 300-square inch weld area for the Susquehanna Nuclear Plant (Reference 2).

Paragraph 2.1(g) of Attachment 3 to Request for Alternative ANO1-R&R-010 requires that

...[t]he average lateral expansion value of the three HAZ Charpy V-notch specimens shall be equal to or greater than the average lateral expansion value of the three unaffected base metal specimens... The proposed requirement deviates from Code Case N-638-1, paragraph 2.1(j),

which requires that ...average values of the three HAZ impact tests shall be equal to or greater than the average values of the three unaffected base metal tests...

The licensee stated that the Charpy V-notch test acceptance criteria in Code Case N-638-1 are misleading and inconsistent with the specified acceptance criteria in Section XI applicable to other Class 1 components, because paragraph 2.1(j) of Code Case N-638-1 implies that all three parameters - lateral expansion, absorbed energy, and percent shear fracture - must be equal to or exceed the base material values. Paragraph 2.1(g) of Attachment 3 to Request for Alternative ANO-1-R&R-010 requires that the Charpy V-notch acceptance criteria be based on the average lateral expansion values rather than the average of all three values.

Paragraph 2.1(g) of Attachment 3 to Request for Alternative ANO1-R&R-010 clarified the intent of the code case and aligned its Charpy V-notch acceptance criteria with that of Subarticle NB-4330, Impact Test Requirements, of the ASME Code,Section III and Subarticles IWA-4620, Temperbead Welding of Similar Materials, and IWA-4630, Temperbead Welding of Dissimilar Materials, of the ASME Code,Section XI.

The staff finds that paragraph 2.1(g) of Attachment 3 to Request for Alternative ANO1-R&R-010 is acceptable because the proposed acceptance criteria for Charpy V-notch tests are consistent with those requirements of ASME Code,Section III, NB-4330, and Section XI, IWA-4620 and IWA-4630.

Paragraph 3.0(c) of Code Case N-638-1 requires the deposition and removal of at least one weld reinforcement layer for similar materials (i.e., ferritic materials). This requirement is only applicable when welding is performed using ferritic filler weld metal. Since only austenitic filler metal (i.e., Alloy 52M) will be used to fabricate the proposed weld overlays, depositing and removing a weld reinforcement layer is not required. Therefore, this requirement is not included in the proposed alternative. The staff agrees with the licensee that paragraph 3.0(c) of Code Case N-638-1 is not applicable to the proposed weld overlay.

Paragraph 3.0 of Code Case N-638-1 does not address monitoring or verification of welding interpass temperatures. However, paragraph 3.0(d) of Attachment 3 to Request for Alternative ANO1-R&R-010 requires use of a contact pyrometer to measure preheat and interpass temperature. The paragraph also requires that in the first three layers, the interpass temperature will be measured every three to five passes. 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 licensee stated that 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 staff finds that the proposed interpass temperature measurements are acceptable because they provide adequate monitoring of the weld overlay temperature such that the metallurgical properties of the low alloy steel pressurizer nozzle will not be affected by the temperature of the weld overlay.

In RG 1.1.47, Revision 14, the staff imposes the following condition on Code Case N-638-1:

...UT examinations shall be demonstrated for the repaired volume using representative samples which contain construction type flaws. The acceptance criteria of NB-5330 of Section III edition and addenda approved in 10 CFR 50.55a apply to all flaws identified within the repaired volume... In response to the condition, the licensee clarified that weld overlays for repair of cracks in piping are not addressed by ASME Code,Section III. Section III utilizes NDE procedures and techniques with flaw detection capabilities that are well within the practical limits of workmanship standards for welds. These standards are most applicable to volumetric

examinations conducted by radiographic examination. The licensee stated that radiography of weld overlays is not appropriate because of the potential for radioactive material in the Reactor Coolant System and water in piping and components.Section III acceptance standards are written for a range of fabrication flaws including lack of fusion, incomplete penetration, cracking, slag inclusions, porosity, and concavity. However, experience and fracture mechanics have demonstrated that many of the flaws that are rejected using Section III acceptance standards do not have a significant effect on the structural integrity of the component. Furthermore, utilizing ASME Code,Section III acceptance standards on weld overlays would be inconsistent with years of NRC precedence and is without justification given the evidence of past NRC approvals and operating experience.

The staff finds that the acceptance criteria of ultrasonic examination as required in Request for Alternative ANO-1-R&R-010 are acceptable because (a) the acceptance criteria of the ultrasonic examination provide equivalent, if not better than, the acceptance criteria of radiography of NB-5330 of ASME Code,Section III, and (b) the ultrasonic examination will provide reasonable assurance of integrity of the weld overlays.

4.7 Commitments In Enclosure 3 of the March 6, 2007 letter, the licensee made the following commitments. The licensee will submit the following information to the NRC within 14 days from completing the final ultrasonic examinations of the completed weld overlays: (a) Weld overlay examination results including a listing of indications detected, (b) Disposition of all indications using the standards of ASME Code,Section XI, IWB-3514-2 and/or IWB-3514-3 criteria and, if possible, the type and nature of the indications, and (c) A discussion of any repairs to the weld overlay material and/or base metal and the reason for the repairs.

In addition, prior to entry into Mode 4 from start-up after the completion of twentieth refueling outage (1R20), the licensee will submit to the NRC a stress analysis summary demonstrating that the pressurizer and hot-leg piping nozzles will perform their intended design functions after the weld overlay installation. The stress analysis report will include results showing that the requirements of NB-3200 and NB-3600 of the ASME Code,Section III, are satisfied. The stress analysis will also include results showing that the requirements of IWB-3000 of the ASME Code,Section XI, are satisfied. The results will show that the postulated crack including its growth in the nozzles will not adversely affect the integrity of the overlaid welds.

The NRC staff finds that the commitment to submit weld overlay examination results and stress analysis is acceptable.

5.0 CONCLUSION

The NRC staff has reviewed the licensees submittal and determined that Request for Alternative ANO1-R&R-010 dated March 6, 2007, will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the staff authorizes the use of Request for Alternative ANO1-R&R-010 dated March 6, 2007, for the installation of full structural weld overlay on the dissimilar metal welds of the pressurizer nozzles at ANO-1. The effective period of Request for Alternative ANO1-R&R-010 is the third ISI interval, which ends on May 31, 2007.

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

6.0 REFERENCE

1. Justification for the Removal of the 100 Square Inch Temper Bead Weld Repair Limitation, Electric Power Research Institute Report, 1011898.

2. Letter from NRC to PPL Susquehanna, LLC, Susquehanna Steam Electric Station, Unit 1 - Relief from American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code),Section XI, Appendix VIII, Supplement 11, Requirements and Code Cases N-504-2 and N-638 Requirements (TAC NOS. MC2450, MC 2451 and MC2594) (ADAMS Accession No. ML051220568), dated June 22, 2005.

Principal Contributor: John Tsao Date: April 6, 2007