ML092870739

Relief Request RR-89-61, Revision 2, Regarding the Use of Weld Overlays as an Alternative Repair

ML092870739
Person / Time
Site:	Millstone
Issue date:	10/15/2009
From:	Chernoff H Plant Licensing Branch 1
To:	Heacock D Dominion Nuclear Connecticut
Sandeers, Carleen, NRR/DORL, 415-1603
References
TAC ME1765, FOIA/PA-2011-0115
Download: ML092870739 (15)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 15, 2009 Mr. David A. Heacock President and Chief Nuclear Officer Dominion Nuclear Connecticut, Inc.

Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

MILLSTONE POWER STATION, UNIT NO.2-RELIEF REQUEST RR-89-61, REVISION 2, REGARDING THE USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR (TAC NO. ME1765)

Dear Mr. Heacock:

By letter dated October 4, 2007, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML072780147), as supplemented by letters dated April 11, and April 17,2008 (ADAMS Accession Nos. ML081060130 and ML081140081, respectively), Dominion Nuclear Connecticut, Inc. (DNC or the licensee), submitted Request for Alternative RR-89-61, Revision 1, for Millstone Power Station, Unit NO.2 (MPS2). Specifically, the Relief Request sought approval to use an alternative to the relevant requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, related to weld overlay repairs and preemptive type weld overlay applications for mitigation of primary water stress corrosion cracking. By letter dated May 8,2008 (ADAMS Accession No. ML081150692), the Nuclear Regulatory Commission (NRC) authorized the use of Request for Alternative RR-89-61, Revision 1, for the installation of full structural weld overlays (SWOLs) on 15 dissimilar and similar metal welds at MPS2.

By letter dated July 23,2009 (ADAMS Accession No. ML092090215), as supplemented by letter dated October 9, 2009, DNC submitted Request for Alternative RR-89-61, Revision 2 for MPS2.

The proposed Relief Request would reduce the thickness of certain dissimilar metal structural overlays. This reduction would not change the applicable ASME Code requirements for an SWOL and inspectability as approved by the NRC for RR-89-61, Revision 1. Request for Alternative RR-89-61, Revision 2 will apply to nine dissimilar and similar metal welds at MPS2.

The NRC has reviewed the licensee's analysis in support of this Relief Request and has determined that the proposed alternative provides an acceptable level of quality and safety.

Therefore, pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a(a)(3)(i), the NRC staff authorizes the use of Request for Alternative RR-89-61, Revision 2, for the installation of full structural weld overlays on welds identified in the enclosed safety evaluation during the Cycle 19 refueling outage at MPS2. Request for Alternative RR-89 61, Revision 2, is subject to conditions identified in the enclosed safety evaluation. The effective

D. Heacock -2 period of Request for Alternative RR-89-61, Revision 2, is the third inservice inspection interval whlch ends on March 31,2010.

If you have any question, please contact Carleen Sanders at (301) 415-1603.

/P~R Harold K. Chernoff, Chief Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-336

Enclosure:

Safety Elevation cc w/encls: Distribution via ListServ

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION REQUEST FOR ALTERNATIVE RR-89-61, REVISION 2 USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR AND MITIGATION TECHNIQUE MILLSTONE POWER STATION, UNIT NO.2 DOCKET NUMBER 50-336

1.0 INTRODUCTION

By letter dated October 4,2007, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML072780147), as supplemented by letters dated April 11, and April 17, 2008 (ADAMS Accession Nos. ML081060130 and ML081140081, respectively),

Dominion Nuclear Connecticut, Inc. (DNC or the licensee), submitted Request for Alternative RR-89-61, Revision 1, for the application of preemptive full structural weld overlays (SWOL) over fifteen dissimilar and similar metal welds at Millstone Power Station, Unit NO.2 (MPS2).

The proposed approach is an alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, IWA-4000.

The April 17, 2008, letter contained Westinghouse reports, "Millstone Unit 2 RCS [reactor coolant system] Surge, Spray, Shutdown Cooling, Safety Injection, Charging Inlet, and Letdown/Drain Nozzles Structural Weld Overlay Qualification" (Proprietary and non-proprietary).

The reports described the geometries of the SWOLs, provided the technical basis for the application of the SWOLs, summarized the associated analyses and provided the methodology used to demonstrate the acceptability of the SWOLs design qualifications.

By letter dated May 8,2008 (ADAMS Accession Number ML081150692) the NRC approved Request for Alternative RR-89-61, Revision 1.

By letter dated July 23,2009 (ADAMS Accession No. ML092090215), as supplemented by letter dated October 9,2009, DNC submitted Request for Alternative RR-89-61, Revision 2, which provided Revision 2 to the Westinghouse reports, "Millstone Unit 2 RCS Surge, Spray, Shutdown Cooling, Safety Injection, Charging Inlet, and Letdown/Drain Nozzles Structural Weld Overlay Qualification," (Proprietary and non-Proprietary). These reports provided updated geometries, technical basis and associated analyses for five nozzle locations including three safety injection nozzles and two RCS spray nozzles. The result of these updates is a reduction in the necessary weld thickness. This reduction in thickness reduces the time required to complete the weld overlays, which reduced the exposure to workers facilitating as low as reasonably achievable (ALARA) dose exposure to workers.

Request for Alternative RR-89-61, Revision 2 is proposed for nine welds, which MPS2 plans to install SWOL to during the MPS2 Cycle 19 refueling outage. In all other respects, Request ENCLOSURE

-2 for Alternative RR-89-61, Revision 2, is the same as the previously approved RR-89-61, Revision 1. Therefore, this safety evaluation has limited changes from that issued in our letter dated May 8,2008 ..

Request for Alternative RR-89-61, Revision 2 is designed to mitigate primary water stress-corrosion cracking (PWSCC) on dissimilar metal welds (DMWs) using full structural weld overlays at MPS2. The weld overlay will also be installed on the similar metal welds that are located adjacent to the DMWs to facilitate ultrasonic examination of the DMWs.

A DMW is a weld that joins two pieces of metal that are not of the same material. In the proposed alternative, the dissimilar metal weld joins the ferritic (i.e., carbon steel) nozzle to the safe end that is fabricated with either austenitic stainless steel or cast austenitic stainless steel.

The DMW itself is made of nickel-based Alloy 82/182. The proposed preemptive weld overlay is a process by which weld filler metal that is resistant to stress corrosion cracking is deposited on the outside surface of the pipe including the original pipe weld.

The licensee proposed the alternative for the current third inservice inspection interval which ends on March 31,2010.

2.0 REGULATORY EVALUATION

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 Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-mont~1 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 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 code of record for MPS2 Repair/Replacement activities for the current third lSI interval is the 1998 Edition with No 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 LICENSEE'S PROPOSED ALTERNATIVE The licensee has requested approval to use an alternative to the relevant requirements of the ASME Code,Section XI, related to weld overlay repairs and preemptive type weld overlay applications for mitigation of PWSCC.

-3

3.1 ASME Code Components Affected

The licensee proposes to install a preemptive full structural weld overlay on the 15 DMWs and similar metal welds identified in the Table below from RR 89-61, Revision 1. The table below has been updated to reflect the changes in RR 89-61, Revision 2:

Nozzle Material Identification Type Nozzle DMWweid Safe end lSI Weld Pipe/fitting (carbon (stainless steel) steel)

Hot Leg Surge A-105, Gr 2 BPS-C-1001 SA-351, BPS-C-1003 SA-351 GR Line, 12 inch NPS (P1 ) Gr CF8M CF8M (P8)

(1) (P8)

Hot Leg to SDC A-105, Gr.2 BSD-C-2001 SA-351, BSD-C-2003 SA-376,316 line, 12 inch NPS (P1 ) GrCF8M (P8)

(1) (P8)

RCS Cold Leg SI A-182, F1 BSI-C-1001 SA-351, BSI-C-1003 SA-403 WP Loop 1A, 12 inch (P3) GrCF8M 316(P8)

NPS (2) (P8)

RCS Cold Leg SI A-182, F1 BSI-C-3000 SA-351, BSI-C-3002 SA-403 WP Loop 1B, 12 inch (P3) Gr CF8M 316 (P8)

NPS (2) (P8)

RCS Cold Leg SI A-182, F1 BSI-C-2001 SA-351, BSI-C-2003 SA-403 WP Loop 2A, 12 inch (P3) Gr CF8M 316 (P8)

NPS (1) (P8)

RCS Cold Leg SI A-182, F1 BSI-C-4000 SA-351, BSI-C-4002 SA-403 WP Loop 2B, 12 inch (P3) GrCF8M 316(P8)

NPS (2) (P8)

Hot Leg drain A-105, Gr.2 BPD-C-1001 SA-182, BPD-C-1003 SA-376,316 line, 2 inch NPS (P1 ) TP-316 (P8)

(3) Loop 1 (P8)

RCS Cold Leg A-105, Gr.2 BCH-C-1001 SA-182, BCH-C-1003 SA-376,316 Charging Line, 2 (P1 ) TP-316 (P8) inch NPS (1) (P8)

Loop 1A

-4 RCS Cold Leg A-105, Gr.2 BCH-C-2001 SA-182, BCH-C-2003 SA-376,316 Charging Line, 2 (P1 ) TP-316 (P8) inch NPS (2) (P8)

Loop 2A RCS Cold Leg A-105, Gr.2 BPD-C-4000 SA-182, BPD-C-4002 SA-376,316 Letdown Line, 2 (P1 ) TP-316 (P8) inch NPS (3) (P8)

Loop 2B RCS Cold Leg A-105, Gr.2 BPY-C-1001 SA-182, BPY-C-1003 SA-376,316 Spray Line, 3 inch (P1 ) TP-316 (P8)

NPS (2) Loop 1A (P8)

RCS Cold Leg A-105, Gr.2 BPY-C-3000 SA-182, BPY-C-3002 SA-376,316 Spray Line, 3 inch (P1 ) TP-316 (P8)

NPS (2) Loop 1B (P8)

RCS Cold Leg A-105, Gr.2 BPD-C-1017 SA-182, BPD-C-1019 SA-376,316 Drain Line, 2 inch (P1 ) TP-316 (P8)

NPS (2) Loop 1A (P8)

RCS Cold Leg A-105, Gr.2 BPD-C-3000 SA-182, BPD-C-3002 SA-376,316 Drain Line, 2 inch (P1 ) TP-316 (P8)

NPS (2) Loop1 B (P8)

RCS Cold Leg A-105, Gr.2 BPD-C-2001 SA-182, BPD-C-2003 SA-376,316 Drain Line, 2 inch (P1) TP-316 (P8)

NPS (2) Loop 2A (P8)

(1) SWOLs installed on these welds during Cycle 18 refueling outage using Alternative RR-89-61, Revision 1 (2) SWOLs are to be installed in accordance with Alternative RR-89-61, Revision 2 (3) SWOLs no longer planned for these locations

=

I\lPS nominal pipe size; SDC shutdown cooling; SI Safety Injection 3.2 Code Requirements By letter dated September 13,1995 (ADAMS Accession No. ML052210033), the NRC staff approved the use of the 1998 Edition of the ASME Code for MPS2. The ASME Code,Section XI 1998 Edition, no Addenda, IWA-4000 is used for the MPS2 repair/replacement program which does not include the needed requirements for the weld overlay repair. By letter dated September 13, 1995 (ADAMS Accession No. ML052210033), the NRC staff approved the use of the 1998 Edition of the ASME Code.

The ASME Code requirements for which relief is requested are contained in the following: (1) 1998 Edition with no Addenda of the ASME Code,Section XI, IWA-4000, and (2) 1995 Edition with the 1996 Addenda of the ASME Code,Section XI, Appendix VIII, Supplement 11.

-5 The licensee proposes Request for Alternative RR-89-61, Revision 2, to permit the implementation of scheduled SWOLs at MPS2, as an alternative to the repair/replacement requirements of the ASME Code,Section XI, 1998 Edition with No Addenda, IWA-4000.

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 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 proposed alternatives are applicable to 15 DMWs and adjacent stainless steel welds identified in Section 3.1 above. MPS2 installed four SWOLs during Cycle 18 (2R18) (spring 2008) using the Alternative RR-89-61, Revision 1. Nine of the remaining SWOLs are proposed to be installed utilizing Alternative RR-89-61, Revision 2. Two welds were found to be inspectable and no SWOLs are planned for these welds at the current time.

The licensee will install preemptive full structural weld overlays in accordance with the proposed alternatives specified in Enclosure 1 to Request for Alternative RR-89-61, Revision 1, as modified by letter dated July 23, 2009. These alternatives are based on the methodology of ASME Code,Section XI, Code Case N-740, "Dissimilar Metal Weld Overlay for Repair of Class 1, 2, and 3 ItemsSection XI, Division 1." The alternative to design, fabrication, examination, pressure testing, and lSI of preemptive full structural weld overlays is described in Attachment 2, Enclosure 1 of the April 11, 2008, letter. The alternative applicable to ambient temperature temper bead welding is described in Attachment 2, Appendix I to Enclosure 1 of the April 11, 2008, letter. The ambient temperature temper bead welding will be applied to the welds 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 preemptive 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 Enclosure 2 of the April 11, 2008, letter.

3.4 Duration of the Alternative The licensee's proposed alternative is applicable to the third 10-Year Interval at MPS2. MPS2 is currently in the third 10-year lSI interval which began on April 1, 1999, and has been extended to end on March 31, 2010. The license intends to implement the request during refueling outage 2R19.

-6 4.0 TECHNCIAL EVALUATION The licensee states that, Alternative RR-89-61, Revision 1, is based on Code Case N-740.

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 NRC staff has endorsed Code Cases N-504-3 and N-638-1 in Regulatory Guide 1.147, Revision 15, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1," but not Code Case N-740.

RG 1.147, as incorporated by reference into 10 CFR 50.55a(3)(b), identifies Code Cases with any identified limitations or modifications that the NRC has determined to be acceptable alternatives to applicable parts of Section XI. As identified in RG 1.147, Code Case N-504-3 is conditionally accepted stating that the provisions of Section XI, Appendix Q to the ASME Code must also be met.

The NRC staff evaluated the acceptability of Request for Alternative RR-89-61, Revision 1 based on the requirements of Code Case N-504-3 and N-638-1. The staff endorsed the use of N-504-3 in Regulatory Guide 1.147, Revision 15, during the same time period it was reviewing the MPS2 submittal. Therefore, some of the issues that the NRC staff raised during the review of the licensee's submittal were based on N-504-2 and the discussion below will contain references to N-504-2. The NRC staff notes that the licensee's submittal has considered the differences between N-504-2 and N-504-3.

4.1 General Requirements Section 1.0, "General Requirements," of Attachment 2, Enclosure 1 to Alternative RR-89-61, Revision 1 dated April 11, 2008, 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. The proposed alternative is consistent with N-504-3 and N-638-1 and Appendix Q to the ASME Code,Section XI.

In the October 4, 2007, letter, the licensee stated that it would apply a butter (transitional) layer of austenitic stainless steel filler metal across the austenitic stainless steel base metal.

Paragraph (e) of Code Case N-504-3 requires specific delta ferrite content in the weld layer when austenitic stainless steel weld metal is used. The April 11, 2008, letter, states that for the 2R19 outage the austenitic stainless steel filler metal for the transitional layer will be qualified by the vendor and approved by DNC and will be either ER 308/308L or ER 309/309L with a delta ferrite content of 7.5 FN to 20 FN.

The licensee stated further that the transitional weld layer will be deposited with a welding procedure that has been qualified in accordance with the ASME Code,Section IX. Liquid penetrant (PT) examinations will be performed prior to deposition of the butter layer.

The NRC staff finds that the requirements of the licensee's proposed alternative provide an acceptable level of quality and safety, as the licensee will deposit the transitional layer on the pipe and perform examination in accordance with the requirements of the ASME Code and Code Case N-504-3.

-7 4.2 Crack Growth Considerations and Design Section 2, "Crack Growth Considerations and Design," of Attachment 2, Enclosure 1 to Request for Alternative RR-89-61, Revision 1 dated April 11, 2008, 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 Section 2 requirements are consistent with N-504-3 and Appendix Q to the ASME Code,Section XI. The NRC staff reviewed the technical reports submitted with Request for Alternative RR-89-61, Revision 2 which provided updated geometries, technical basis and associated analyses for five nozzle locations including three safety injection nozzles and two RCS spray nozzles, sections pertaining to the RCS surge, shutdown cooling, charging inlet and letdown/drain nozzles remained unchanged from Revision

1. The significant issues are discussed below.

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 0 and 100 percent through the original wall thickness of the DMWs. Regarding the crack-growth analysis for the preemptive full structural weld overlay, the licensee stated that a 100 percent through-wall flaw has been postulated for the crack growth calculations.

The licensee performed nozzle-specific stress analyses to establish a residual stress profile in each subject nozzle. Post-weld overlay residual stresses at normal operating conditions were 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 licensee also performed fracture mechanics analyses to predict crack growth for postulated flaws. Crack growth due to PWSCC and fatigue was analyzed for the original DMW. The analyses demonstrated that the postulated cracks will not grow beyond the design basis for the weld overlays. The licensee demonstrated that applying the weld overlay does not impact the conclusions of the existing stress reports. The stress and fatigue criteria of ASME Code,Section III, will be met for regions of the overlays remote from the 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. 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 NRC staff finds the crack growth considerations and deslqn of the licensee's proposed alternative provide an acceptable level of quality and safety as the proposed analyses and shrinkage measurement are consistent with paragraph (g) of Code Case N-504-3 and are, therefore, acceptable.

-8 4.3 Examination and Inspection Section 3, "Examination and Inspection," of Attachment 2, Enclosure 1 to Request for Alternative RR-89-61, Revision 1 dated April 11, 2008, provides requirements for the acceptance examination, pre-service examination, and inservice examination after the weld overlay is installed. The length, surface finish, and flatness requirements of the weld overlay are specified in the weld overlay design to provide the required examination volume of the weld overlay as shown in Figures 1 and 2 of Attachment 2, Enclosure 1 to Request for Alternative RR-89-61, Revision 1.

4.3.1 Acceptance Examination Section 3.0(a), "Acceptance Examination," of Attachment 2 to Request for Alternative RR-89-61, Revision 1 dated April 11,2008, requires a surface and UT examination of an installed weld overlay. The NRC staff finds the requirements of the acceptance examination acceptable because they are consistent with N-504-3 and Appendix Q to the ASME Code,Section XI.

4.3.2 Preservice Examination Section 3.0(b), "Preservice Inspection," of Attachment 2, Enclosure 1 to Request for Alternative RR-89-61, Revision 1, dated April 11, 2008, 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, Enclosure 1 to Request for Alternative RR-89-61, Revision 1. The NRC staff finds the preservice examination requirements acceptable because they are consistent with Code Case N-504-3 and the ASME Code,Section XI, Appendix Q.

4.3.3 Inservice Examination Section 3.0(c) of Attachment 2 to Request for Alternative RR-89-61, Revision 1 dated April 11, 2008, requires inservice examination be conducted ultrasonically with the examination volume defined in Figure 2 of Attachment 2 to Request for Alternative RR-89-61, Revision 1.

The requirements in Section 3.0(c) of Attachment 2 are consistent with the ASME Code,Section XI, Appendix Q with the following exception.

In Section 4.3 of Request for Alternative RR-89-61, Revision 1, dated April 11, 2008, the licensee discussed the inspection issues regarding cast austenitic stainless steel (CASS) which was used to fabricate the safe ends of six of the DMWs identified for application of the SWOLs and the surge line similar metal weld identified in Section 3.1 above. The licensee stated and the NRC staff agrees that the ultrasonic examination has not been qualified in accordance with Appendix VIII, Supplement 11 of the ASME Code,Section XI, in the examination of CASSo The licensee stated further that a flaw with a depth of 100 percent of pipe thickness and circumference of 360 degrees will be assumed in the crack growth calculation for the cast stainless steel safe ends. The subject weld shall be ultrasonically inspected during the first or second refueling outage following the weld overlay installation per Section 3(c)(1) of Attachment 2, Enclosure 1 of Request for Alternative RR-89-61, Revision 1. After the first lSI examination,

-9 the required inspection volume shall be ultrasonically inspected every 10 years from the date of the installation until such time when UT is qualified to examine the CASS portion of the required inspection volume in accordance with new performance demonstration requirements of ASME Code,Section XI, Appendix VIII. After the subject weld is examined by qualified UT for the CASS material and no planar flaws are detected, the weld may be placed in the 25 percent sample inspection population per proposed relief request for Alternative RR-89-61, Revision 1, Section 3(c)(5). The inspection of the overlaid weld shall not be credited to satisfy the requirement of the 25% sample inspection every 10 years of overlaid welds with non-CASS materials.

The NRC staff notes that the licensee will perform UT examination during the first or second refueling outage following weld overlay application per Section 3.0(c)(1) in addition to performing UT examinations every 10 years, pending qualified POI techniques for CASSo The licensee further stated that until POI procedures are qualified for CASS materials, it will perform "best effort" preservice and inservice inspections of the CASS components per the ASME Code,Section XI, Appendix VIII.

The NRC staff finds that the licensee's strategy for additional examination of CASS components provides an acceptable level of quality and safety, and is therefore, acceptable.

4.4 Proposed Ambient Temperature Temper Bead Welding The requirements for the proposed ambient temperature temper bead welding are discussed in , Enclosure 1 to Request for Alternative RR-89-61, Revision 1 dated April 11,2008, and are based on Code Case N-638-1. The requirements in Attachment 2, to RR-89-61, Revision 1 are consistent with N-638-1, with one exception as 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 500 square inches on the ferritic-base material. The technical justification for allowing weld overlays on ferritic materials with surface areas up to 500 square inches is provided in the ASME white paper supporting the changes in ASME Code Case N-638-3 and Electric Power Research Institute Report (EPRI) Report 1011898, "Justification for the Removal of the 100 Square Inch Temper Bead Weld Repair Limitation". The ASME white paper notes that the original limit of 100 square inches in Code Case N-638-1 was arbitrary. The white paper cites evaluations of a 12-inch diameter nozzle weld overlay to demonstrate adequate tempering of the weld heat affected zone, 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 OMW nozzles in several BWR and PWR 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. It can be seen from the information provided in the EPRI Report and ASME white paper discussed above that the

- 10 original OMW weld overlay was applied over 20 years ago, and weld overlays with low alloy steel coverage in the 1OO-square inch range have been in service for 5 to 15 years. Several overlays have been applied with low alloy steel coverage significantly greater than the 100 square inches. These overlays have been examined with POI-qualified techniques, in some cases multiple times, and none have shown any signs of new cracking or growth of existing cracks.

The NRC staff notes that the proposed 500-square-inch weld area has also been addressed in EPRI Report 1014351, "Repair and Replacement Applications Center: Topical Report Supporting Expedited NRC Review of Code Cases for Dissimilar Metal Weld Overlay Repairs, December 2006." The technical basis for the 500-square-inch weld area was also presented in slides entitled, "Bases for 500 Square Inch Weld Overlay Over Ferritic Material," in an NRC ASME public meeting held on January 10, 2007, (AOAMS Accession No. ML070470565).

Based on EPRI 1014351, the NRC staff finds that the proposed 500-square inch weld area on the ferritic material is acceptable because the stress analysis presented in EPRI Report 1014351 shows that the structural integrity of ferritic material is not adversely affected by a 500 square-inch weld overlay area.

4.5 Performance Oemonstration Initiative Program 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 POI Program as an alternative to satisfy the requirements of ASME Code,Section XI, Appendix VIII.

To this end, EPRI has developed a program for qualifying equipment, procedures, and personnel in accordance with the UT criteria of Appendix VIII, Supplement 11. Prior to the Supplement 11 program, EPRI was maintaining a performance demonstration program (the precursor to the POI program) for weld overlay qualification under the Tri-party Agreement with the NRC, BWR Owner's Group, and EPRI, as discussed in the NRC letter dated July 3, 1984 (Nuclear Oocument System (NUOOCS) Accession No. ML8407090122). Later, the NRC staff recognized the EPRI POI program for weld overlay qualifications as an acceptable alternative to the Tri-party Agreement in its letter dated January 15, 2002, to the POI Chairman (AOAMS Accession No. ML020160532). The POI program is routinely assessed by the NRC staff for consistency with the current ASME Code and proposed changes The licensee proposed to use the POI program as indicated in Enclosure 2 to Request for Alternative RR-89-61, Revision 1, to satisfy the Appendix VIII, Supplement 11, qualification requirements. The POI initiatives will be used for qualification of ultrasonic examinations to detect and size flaws in the preemptive full structural weld overlays of this request. The NRC staff evaluated the differences between the POI program and Supplement 11 as shown in to Request for Alternative RR-89-61, Revision 1. The NRC staff concludes that the justifications for the differences are acceptable and the POI program provides an acceptable level of quality and safety. Therefore, the proposed MPS2 POI program is acceptable for use in lieu of Supplement 11 of Appendix VIII to the ASME Code,Section XI.

- 11 4.6 Required Activities As part of Request for Alternative RR-89-61, Revision 1, the licensee made the following commitments as shown in Attachment 2 of the April 11, 2008, letter. These commitments remain valid for Request for Alternative RR-89-61, Revision 2.

(1) The licensee will submit the following information to the NRC within 14 days from completing the final UT examinations of the completed weld overlays:

(a) Weld overlay examination results including a listing of indications detected and coverage limitations; (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.

(2) Prior to entry into Mode 4 start-up from MPS2's 2R18 and 2R19 outages, the licensee will submit a preliminary stress analysis summary to the NRC, as described in Paragraphs g(2) and g(3) of ASME Code Case N-504-3 demonstrating that the RCS 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 final evaluation shall be submitted within 60 days of plant restart from the outage in which the PWOLs were installed.

(3) The licensee will perform a "best effort" preservice examination of the cast stainless steel region, following installation of the weld overlays during refueling outage 2R18 and 2R19.

(4) Until POI procedures are qualified to examine the upper 25 percent of the cast stainless steel base material, DNC will perform "best effort" inservice inspections of the region shown in Figure 2 of Attachment 2, Enclosure 1 Request for Alternate RR 89-61, Revision 1. Once qualified, the licensee will implement these POI procedures. Inservice inspection of weld overlays for stainless steel welds is performed at the frequencies required by the MPS2 lSI Program as stipulated in Section 3.c of Attachment 2, Enclosure 1 Request for Alternate RR 89-61, Revision 1.

- 12 The NRC staff finds that the above required activities are acceptable because the weld overlay examination results and stress analysis will provide verification of the condition of the weld overlays after installation.

The NRC staff finds that the requirements of Request for Alternative RR-89-61, Revision 2, with reference to Request for Alternative RR-89-61, Revision 1 to be consistent with the intent of the provisions of ASME Code Cases N-504-3 and N-638-1, and Appendices VIII and Q of ASME Code,Section XI. Therefore, the licensees proposed alternative RR-89-61, Revision 2 is acceptable.

5.0 CONCLUSION

The NRC staff has reviewed the licensee's submittal and determined that Request for Alternative RR-89-61, Revision 2, will provide an acceptable level of quality and safety.

Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the use of Request for Alternative RR-89-61, Revision 2, for the installation of full structural weld overlays on the DMWs and adjacent similar metal welds identified in Table 1 during 2R19 refueling outage at MPS2. Request for Alternative RR-89-61, Revision 2, is subject to the above stated conditions identified in Section 4.6. The effective period of Request for Alternative RR-89-61, Revision 2, is the third lSI interval which ends on March 31, 2010.

ASME Code,Section XI requirements for third-party review by the Authorized Nuclear Inservice Inspector remain applicable.

Principal Contributor: K. Hoffman Date: October 15, 2009

D. Heacock -2 period of Request for Alternative RR-89-61, Revision 2, is the third inservice inspection interval which ends on March 31, 2010.

If you have any question, please contact Carleen Sanders at (301) 415-1603.

Sincerely, Ira! (JHughey for)

Harold K. Chernoff, Chief Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-336

Enclosure:

Safety Elevation cc w/encls: Distribution via ListServ DISTRIBUTION:

PUBLIC Branch Reading RidsAcrsAcnw_MailCTR Resource RidsNrrDorlLpl1-2 Resource RidsNrrDCIResource RidsNrrLAABaxterResource RidsNrrMillstone Resource RidsRgn1 MailCenter Resource LTrocine, EDO R-I KHoffman, NRR ADAMS Accession No.:ML092870739

• via email OFFICE LPL 1-2/PM LPL 1-2/LA DCI/CPNB/BC LPL 1-2/BC NAME CSanders ABaxter

• TChan (by HChernoff w/comments memo dated) (JHuQhey for)

DATE 10/15/09 10/15/09 10/13/09 10/15/09 Official Record Copy