ML072220228

Relief Requests CMP-022 and CMP-023 Regarding Use of Weld Overlays as an Alternative Repair Technique

ML072220228
Person / Time
Site:	North Anna
Issue date:	12/19/2007
From:	Marinos E NRC/NRR/ADRO/DORL/LPLII-1
To:	Christian D Virginia Electric & Power Co (VEPCO)
Lingam, Siva NRR/DORL 415-1564
References
CMP-022, Rev 1, CMP-023, Rev 1, TAC MD3903, TAC MD3904
Download: ML072220228 (23)

Text

December 19, 2007Mr. David A. ChristianPresident and Chief Nuclear Officer Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

NORTH ANNA POWER STATION, UNIT NOS. 1 AND 2 - RELIEF REQUESTSCMP-022 AND CMP-023 REGARDING USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE (TAC NOS. MD3903 AND MD3904)

Dear Mr. Christian:

By letter dated January 3, 2007, and as supplemented by letters dated March 13, May 16,June 15, July 25 and October 1, 2007, Virginia Electric and Power Company (the licensee) submitted Alternative Relief Requests CMP-022, Revision 1, and CMP-023, Revision 1, concerning the preemptive weld overlay and inspection of pressurizer dissimilar and similar metal welds at North Anna Power Station, Unit Nos. 1 and 2 (North Anna 1 and 2), respectively.

The licensee proposed the use of full structural preemptive weld overlay with temper bead welding for repair and the Performance Demonstration Initiative program for inspection as alternatives to the requirements of American Society of Mechanical Engineers, Boiler and Pressure Vessel Code,Section XI.The Nuclear Regulatory Commission (NRC) staff has reviewed and evaluated the licensee'ssubmittal and concludes that the proposed alternatives provide an acceptable level of quality and safety. Therefore, pursuant to Title 10 of the Code of Federal Regulations, Part 50,Section 50.55a(a)(3)(i), the proposed alternatives are authorized for the repair and examination of the subject welds for each unit's third 10-year inservice inspection (ISI) interval, which ends April 30, 2009, for North Anna 1 and December 13, 2010, for North Anna 2.The NRC staff provided verbal authorization for the subject relief request for North Anna 1 and2 during a teleconference with the licensee on March 29, 2007. The alternative was authorized for each unit's third 10-year ISI, which ends April 30, 2009, for North Anna 1 and December 13, 2010, for North Anna 2.Sincerely, /RA/Evangelos C. Marinos, ChiefPlant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor RegulationDocket Nos. 50-338 and 50-339

Enclosure:

Safety Evaluationcc w/encl: See next page December 19, 2007Mr. David A. ChristianPresident and Chief Nuclear Officer Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

NORTH ANNA POWER STATION, UNIT NOS. 1 AND 2 - RELIEF REQUESTSCMP-022 AND CMP-023 REGARDING USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE (TAC NOS. MD3903 AND MD3904)

Dear Mr. Christian:

By letter dated January 3, 2007, and as supplemented by letters dated March 13, May 16,June 15, July 25 and October 1, 2007, Virginia Electric and Power Company (the licensee) submitted Alternative Relief Requests CMP-022, Revision 1, and CMP-023, Revision 1, concerning the preemptive weld overlay and inspection of pressurizer dissimilar and similar metal welds at North Anna Power Station, Unit Nos. 1 and 2 (North Anna 1 and 2), respectively.

The licensee proposed the use of full structural preemptive weld overlay with temper bead welding for repair and the Performance Demonstration Initiative program for inspection as alternatives to the requirements of American Society of Mechanical Engineers, Boiler and Pressure Vessel Code,Section XI.The Nuclear Regulatory Commission (NRC) staff has reviewed and evaluated the licensee'ssubmittal and concludes that the proposed alternatives provide an acceptable level of quality and safety. Therefore, pursuant to Title 10 of the Code of Federal Regulations, Part 50,Section 50.55a(a)(3)(i), the proposed alternatives are authorized for the repair and examination of the subject welds for each unit's third 10-year inservice inspection (ISI) interval, which ends April 30, 2009, for North Anna 1 and December 13, 2010, for North Anna 2.The NRC staff provided verbal authorization for the subject relief request for North Anna 1 and2 during a teleconference with the licensee on March 29, 2007. The alternative was authorized for each unit's third 10-year ISI, which ends April 30, 2009, for North Anna 1 and December 13, 2010, for North Anna 2.Sincerely,/RA/Evangelos C. Marinos, ChiefPlant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor RegulationDocket Nos. 50-338 and 50-339

Enclosure:

Safety Evaluationcc w/encl: See next pageDistribution:RidsAcrsAcnwMailCenter RidsRgn2MailCenter(EGuthrie)PUBLICRidsNrrPMSLingam (hard copy)RidsNrrCpnb(TChan)

LPL2-1 R/FRidsNrrLAMO'Brien (hard copy)RidsNrrCpnb(DTarantino)RidsOgcRpRidsNrrLpl2-1 (EMarinos)SCampbell, EDO Rgn II RidsNrrCpnb(JTsao)RidsNrrPMRJervey (hard copy)

ADAMS ACCESSION NO.: ML072220228 *Per SE dated 11/26/07 ML0733100851 OFFICENRR/LPL2-1/PMNRR/LPL2-1/PMNRR/LPL2-1/LANRR/CPNB/BCOGCNRR/LPL2-1/BCNAMESLingamRJerveyMO'BrienTChan*JAdler NLOEMarinos EnclosureDATE 12/10 /07 12/10 /07 12/10 /07 11/26 /07 12/14/07 12 /19/07OFFICIAL RECORD COPYSAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIONRELIEF REQUESTS CMP-022 AND CMP-023NORTH ANNA POWER STATION, UNIT NOS. 1 AND 2VIRGINIA ELECTRIC AND POWER COMPANYDOCKET NOS. 50-338 AND 50-33

91.0 INTRODUCTION

By letter dated January 3, 2007 (Agencywide Documents Access and Management System(ADAMS) Accession No. ML070040490), Virginia Electric and Power Company (the licensee) submitted Alternative Relief Requests (RR) CMP-022 and CMP-023 for North Anna Power Station, Unit Nos. 1 and 2 (North Anna 1 and 2), respectively, to the repair requirements of American Society of Mechanical Engineers (ASME), Boiler and Pressure Vessel Code (Code),Section XI. The licensee's January 3, 2007, alternative repair was based on Code Case N-740, "Dissimilar Metal Weld Overlay for Repair of Class 1, 2, and 3 Items,Section XI, Division 1,"

modified by Appendix VIII, Supplement 11, "Qualification Requirements for Full StructuralOverlaid Wrought Austenitic Piping Welds." The licensee submitted revised Alternative RR CMP-022, Revision 1(CMP-022R1), and CMP-023, Revision 1 (CMP-023R1), for North Anna 1 and 2, respectively, by letter dated March 13, 2007 (ADAMS Accession No. ML070730563). The licensee responded to the Nuclear Regulatory Commission (NRC) staff's request for additional information (RAI) by letters dated May 16, 2007 (ADAMS Accession No. ML071410300), June 15, 2007 (ADAMS Accession No. ML071700268) and July 25, 2007 (ADAMS Accession No. ML072070356). The revised RR added additional information to address the NRC staff's review questions. In addition, the licensee submitted a change to the CMP-022R1 proposal as a result of physical inspection of the affected welds in North Anna 1 on October 1, 2007 (ADAMS Accession No.

ML072750064). This alternative will be used in lieu of the requirements contained in the 1989 edition of theASME Code for North Anna 1 and the 1995 edition through 1996 addenda for North Anna 2 of ASME Code,Section XI, IWA-4000, and in the 1998 edition through 2000 addenda for North Anna 1 and 2 of Section XI, Appendix VIII, Supplement 11. The revised RR references Code Case N-740-1 with modifications. It is described inAttachment 2 of the letter to the NRC dated March 13, 2007, under Enclosure 1, "Alternative Requirements for Dissimilar Metal Weld Overlays," as modified by the licensee's October 1, 2007 letter. The RR would be used to perform full structural preemptive weld overlays (PWOL) onpressurizer spray, relief, safety, and surge nozzle safe ends. This request was verbally approved on March 29, 2007. Industry issues with the PWOL technique and North Anna 2 results were discussed in the context of this review during development of this safety evaluation which postponed its completion. Subsequent in-plant work during the North Anna Unit 1 fall outage led to the discovery of a weld configuation which also affected the request. The NRC staff has completed the review of Alternative RRs CMP-022R1 and CMP-023R1 (CMP-022R1/023R1), for North Anna 1 and 2, respectively, and it is addressed as follows.

2.0REGULATORY EVALUATION

Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section50.55a(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 In-service 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 testsconducted 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) twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The ASME Codes of Record for the current, third 10-year ISI interval at North Anna 1 and 2, are the 1989 edition and the 1995 edition through 1996 addenda, respectively.Pursuant to 10 CFR 50.55a(a)(3)(i), alternatives to requirements may be authorized by the NRCif the licensee demonstrates that the proposed alternatives provide an acceptable level of quality and safety.The licensee submitted RRs CMP-022R1/023R1, pursuant to 10 CFR 50.55a(a)(3)(i), whichproposes alternatives to the implementation of ASME Code,Section XI, IWA-4000 and Appendix VIII, Supplement 11. The licensee's alternative is based on Enclosure 1 to theirMarch 13, 2007, letter, "Alternative Requirements for Dissimilar Metal Weld Overlays," (Code Case N-740-1, with modifications) for the deposition of full structural preemptive weld overlay (PWOL) and the Performance Demonstration Initiative (PDI) program implementation of Appendix VIII, Supplement 11, as modified by the licensee's October 1, 2007, letter whichaddressed weld inspection limitations found in Unit 1.3.0PROPOSED ALTERNATIVE REQUEST CMP-022R1/023R13.1Licensee's Reason for Requesting the Alternative Dissimilar metal welds (DMWs) primarily consisting of nickel based Alloy 82/182 weld metal arefrequently used in pressurized water reactors (PWR) construction to connect stainless steel pipe and safe ends to vessel nozzles, generally constructed of carbon or low alloy ferritic steel.

These welds have shown a propensity for primary water stress corrosion cracking (PWSCC) degradation, especially in components subjected to higher operating temperatures, such as the pressurizer.This relief request includes six Class 1 DMWs located on the pressurizer for North Anna 1 and2 which will have full structural PWOL applied. During the recent spring 2007 outage at North Anna 2, verbal approval was granted for the use of the alternative to address PWOL technique.

This RR covers the verbal approval and includes North Anna 1 and 2. Repair/replacement activities associated with PWOL repairs are required to address thematerials, welding parameters, as low as reasonably achievable (ALARA) concerns, operational constraints, examination techniques and procedure requirements for repairs. Comprehensive and generic NRC-approved criteria are not currently available for application of PWOL repairs to DMWs constructed of Alloy 82/182 weld material for mitigation of potential PWSCC.The welding will be performed using a remote machine gas tungsten-arc welding (GTAW)process and using the ambient-temperature temper-bead method with ERNiCrFe-7A (Alloy 52M) weld metal. Manual GTAW, using ERNiCrFe-7 (Alloy 52) or Alloy 52M will be used if local repairs of weld defects are necessary or additional weld metal is required locally to form the final PWOL contour in locations at least 3/16 inch away from the low alloy steel (LAS) nozzles.3.2System/Components for Which the Alternative Is Requested The licensee states that ASME Code components associated with this request are the highsafety significant (HSS) Class 1 DMWs with Alloy 82/182 weld metal believed to be susceptible to PWSCC. There are six welds intended to have full structural PWOL applied. The application of this alternative to apply PWOL on the six potentially PWSCC susceptible safe end-to-pressurizer nozzle welds will also involve extending the weld overlay across the adjacent stainless steel (SS) safe end-to-reactor coolant system (RCS) piping similar metal welds (SMWs). The examination categories are R-A and the welds are included in the Risk-Informed InserviceInspection (RI-ISI) Program. The six DM and SM welds scheduled for full structural PWOL at North Anna 1 and 2 are listed as follows:NORTH ANNA - UNIT 1Apply PWOL on six safe end-to-pressurizer nozzle DMW extending across the adjacent SSpipe/fitting/elbow-to-safe end SMW.WELDNUMBERSIZE (OD)DESCRIPTIONCOMMENT(1-5)SW-5114-InchSurge Nozzle-to-Safe End ReducerLAS nozzle/Alloy 82-182 weld/SSsafe end 39Safe End Reducer-to-Pipe (14-RC-10-2501R-Q1)SS safe end/SS weld/SS pipeSW-306-InchSafety Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end 21Safe End-to-Elbow (6-RC-38-1502-Q1)SS safe end/SS weld/SS pipe(elbow)SW-316-InchSafety Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end 17Safe End-to-Elbow (6-RC-39-1502-Q1)SS safe end/SS weld/SS pipe(elbow)SW-386-InchSafety Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end 25Safe End-to-Elbow (6-RC-37-1502-Q1)SS safe end/SS weld/SS pipe(elbow)SW-646-InchRelief Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end304-InchSafe End-to-ConcentricReducer (4-RC-34-1502-Q1)SS safe end/SS weld/SS pipe (6 x 4concentric reducer)SW-714-InchSpray Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end 11Safe End-to-Pipe (4-RC-15-1502-Q1)SS safe end/SS weld/SS pipe NORTH ANNA - UNIT 2Apply PWOL on six safe end-to-pressurizer nozzle DMW extending across the adjacent SSpipe/fitting/elbow-to-safe end SMW.WELDNUMBERSIZE (OD)DESCRIPTIONCOMMENT(1-5)SW-514-InchSurge Nozzle-to-Safe End ReducerLAS nozzle/Alloy 82-182 weld/SSsafe end 1Safe End Reducer-to-Pipe (14-RC-410-2501R-Q1)SS safe end/SS weld/SS pipeSW-66-InchSafety Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end 1Safe End-to-Elbow (6-RC-437-1502-Q1)SS safe end/SS weld/SS pipe(elbow)SW-96-InchSafety Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end 1Safe End-to-Elbow (6-RC-438-1502-Q1)SS safe end/SS weld/SS pipe(elbow)SW-176-InchSafety Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end 1Safe End-to-Elbow (6-RC-439-1502-Q1)SS safe end/SS weld/SS pipe(elbow)SW-406-InchRelief Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end14-InchSafe End-to-ConcentricReducer (6-RC-434-1502-Q1)SS safe end/SS weld/SS pipe (6 x 4concentric reducer)SW-624-InchSpray Nozzle-to-Safe EndLAS nozzle/Alloy 82-182 weld/SSsafe end 42Safe End-to-Pipe (6-RC-415-1502-Q1)SS safe end/SS weld/SS pipe(1)LAS Nozzle = Low Alloy Steel, SA-508 Class 2, (P-3, Group 3)(2)Alloy 82/182 = Safe End-to-Nozzle weld and buttering, (F-43)

(3)SS Safe End = Wrought Stainless Steel, SA-182 GR F316L, (P-8)

(4)SS Surge Line Pipe, Safety Line Elbows, Relief Line Reducer and Spray Line Pipe = Wrought Seamless SS, (P-8)(5)SS welds = Stainless Steel (A-8)3.3Code RequirementsNorth Anna 1 is currently in the third 10-year ISI interval (May 1, 1999 through April 30, 2009). The ASME Code of record for the current 10-year ISI interval isSection XI, 1989 edition. This is also the version used for the Repair/Replacement Program.North Anna 2 is currently in the third 10-year ISI interval (December 14, 2001 throughDecember 13, 2010). The ASME B&PV Code of record for the current 10-year ISI interval isSection XI, 1995 edition, including addenda through 1996. This is also the version used for the Repair/Replacement Program. The alternative described in Section 3.4 below is proposed to permit the implementation ofPWOL at North Anna 1, as an alternative for the repair/replacement requirements of the ASME Code,Section XI, 1989 edition, IWA-4000 and at North Anna 2, as an alternative for the repair/replacement requirements of the ASME Code,Section XI, 1995 edition, including addenda through 1996, IWA-4000.The alternative proposed by this RR is required because IWA-4000 for the year and addenda inuse at North Anna 1 and 2 does not address all the necessary requirements to adequately implement this type of repair. In the proposed alternative, the ultrasonic (UT) examination of the completed PWOL will be accomplished based on the ASME Code,Section XI, 1998 edition including addenda through 2000 for North Anna 1 and for North Anna 2, Appendix VIII, Supplement 11, as modified to comply with the PDI program as listed in Attachment 2, of the letter to the NRC dated March 13, 2007, and further explained by the RAI response dated July 25, 2007.3.4Licensee's Proposed Alternatives and Basis As described in the revised RR, the mitigative weld overlay shall be applied by deposition ofweld reinforcement (weld overlay) on the outside surface of the piping, component, or associated weld, including ferritic materials when necessary, provided the requirements as stated in Enclosure 1, "Alternative Requirements for DMW Overlays," are met. This alternative is the result of the industry's experience with mitigative weld overlay repairs for flaws suspected or confirmed to be from PWSCC and for the first time directly applies to the Alloy 52 or 52M weld material primarily being used for these overlay repairs.A full structural PWOL (designed for the worst case flaw) will be applied in accordance with therequirements of Enclosure 1 followed by a UT examination upon completion

. This proposedalternative is requested for implementing the six scheduled full structural PWOL for the potentially PWSCC susceptible safe end-to-nozzle welds of the pressurizer. The PWOL will include the adjacent stainless steel elbow/pipe/reducer-to-safe-end welds. The request applies to each of the welds listed in Section 2.2 and generically depicted in Figure 1 of the revised RR.3.4.1Full Structural PWOL Assembly The ferritic materials of the nozzles are P-3, Group 3, material; the safe ends andpipe/elbow/reducers are wrought SS, P-8 material. The existing weld filler material is Alloy 82/182 (F-43).The ASME Committee has indicated that the inside diameter (ID) compressive stress levelsremain essentially the same between 100 square inches and 500 square inches in relation to weld overlay applications. The RR allows for the installation of the PWOL using temper-bead welding for up to 500 square inches over the ferritic material. The justification entitled, "Bases for 500 Sq. In. Weld Overlay Over ferritic Material," was provided to the NRC staff in the January 10, 2007, meeting (ADAMS Accession No. ML070470565). Additional justification is provided in Electric Power Research Institute (EPRI) Report 1014351, "Repair and Replacement Applications Center: Topical Report Supporting Expedited NRC Review of CodeCases for DMW Overlay Repairs, December 2006." The full structural weld overlay satisfies all the structural design requirements of the pipeassuming no strength is contributed by the original safe end-to-nozzle DMWs or the elbow/pipe/reducer-to-safe-end SMWs. The mitigative weld overlay is designed to meet structural requirements as if the original welds were removed. As shown in Figure 1 of the alternate request, this structural weld overlay (weld reinforcement) will completely cover the existing Alloy 82/182 DMWs extending onto the ferritic and austenitic SS material on each end of the weld, including the adjacent pipe/elbow/reducer-to-safe-end SMWs. The weld overlay extends the full 360-degrees around the nozzle.The Procedure Qualification Reports (PQR) for qualification of the temper-bead portion of thewelds and for overlay of the buttered P3 nozzle material were performed using ERNiCrFe-7 (Alloy 52) or ERNiCrFe-7A (Alloy 52M) filler metal. Both filler materials have 28.0 to 31.5%

chromium (Cr) and the Alloy 52M filler metal will be used for the production overlays.Furthermore, paragraph 1(e) of the revised RR (Enclosure 1), states that "a diluted first layermay be credited toward the required thickness, provided the portion of the layer over the austenitic base material, austenitic filler material weld and the associated dilution zone from an adjacent ferritic base material contains at least 24% Cr and the Cr content of the deposited weld metal is determined by chemical analysis of the production weld or of a representative coupon taken from a mock-up prepared in accordance with the Weld Procedure Specification (WPS) for the production weld." The licensee's PWOL vendor has prepared representative coupons taken from mock-ups prepared in accordance with the WPS (including use of Alloy 52M filler metal) for the production weld. Where the representative coupons provide a first layer Cr content less than 24%, the production weld overlay procedure will deposit a sacrificial layer of Alloy 52M filler metal over the material responsible for the excessive dilution. The sacrificial layer will not count as a structural layer of the PWOL; the layer covering the sacrificial layer will be the first layer credited as a structural PWOL layer. Where the representative coupons provide a first layer Cr content equal to or greater than 24%, a sacrificial layer of Alloy 52M will not be used and the weld layer will count as a structural layer of the PWOL.Thermocouples will be used to monitor welding preheat and interpass temperatures duringapplication of the weld overlay. After completion of the overlay, the thermocouples will be removed, the thermocouple attachment areas will be ground, and the ground areas will be subjected to a surface examination.3.4.2Weld Overlay Design The PWOL will be designed as mitigating full structural overlays (assumed worst-case flaw) inaccordance with Enclosure 1, Section 2 of the letter to the NRC dated March 13, 2007. Crack growth calculations will be performed to demonstrate that the crack growth in the weld overlay or base metal is acceptable and that residual stress distribution in the weld overlay and original weld result in a favorable stress distribution. This is true for all nozzle structural mitigation weld overlay analyses except the portion of the ASME Code,Section III analysis for the surge lineweld overlay that addresses the insurge/outsurge transients. This portion of the analysis will be addressed with an engineering evaluation of insurge/outsurge transients that will use data from a D.C. Cook, ASME Code,Section III analysis that will qualify the design for seven heat-upsand cool-downs with thirty insurge/outsurge cycles. (This is an excerpt from the licensee's letter of March 13, 2007, and is understood to frame conservative engineering judgement in evaluation of stress caused by transient cycles). The D.C. Cook analysis is representative of the North Anna situation since the nozzles are very similar in configuration and the worst casetransient severity is bounded (i.e., the D.C. Cook transient is considered more severe than the North Anna 1 and 2 transient).The seven heat-ups and cool-downs with thirty insurge/outsurge cycles represent a veryconservative limit placed on interim operation and are associated with the interim analysis.

Interim measures are not meant to correlate with a specific operating cycle. These limiting insurge/outsurges are not expected to occur in the next seven operating cycles based on one heat-up and one cool-down per cycle. The North Anna 1 and 2 specific ASME Code,Section III analysis will be completed by December 31, 2007, at which time the seven heat-ups and cool-downs with thirty insurge/outsurge cycle restrictions will be resolved. The number of heat-ups and cool-downs are currently monitored and recorded by procedure. The North Anna 1 and 2 ASME Code,Section III analysis will be an elastic-plastic analysis based on the definednumber for life of plant transients.A weld shrinkage evaluation will be performed to ensure the effect of weld shrinkage on othercomponents or supports is acceptable. This evaluation will also address increased stiffness at the joint due to increased thickness in the localized area, increased weight due to the increased thickness in the localized area, and the impact on the piping due to thermal contraction caused by the weld cooling process. In addition to the weld shrinkage evaluation, mock-up testing will be used to demonstrate piping movements as a result of the weld overlay application.

After final installation of the pressurizer weld overlays, the actual shrinkage will be compared to the value assumed in the evaluation to ensure consistency. The North Anna 1 and 2 pressurizer surge line nozzle-to-safe-end and safe end-to-pipe weldsare not included as part of the approved leak-before-break analysis.3.4.3Examinations As stated in the licensee's July 25, 2007, letter, the examinations will meet the requirements ofEnclosure 1 of the revised RR. The UT examination of the completed full structural PWOL will be performed based on ASME Code,Section XI, 1998 edition including addenda through 2000 for North Anna 1 and for North Anna 2, Appendix VIII, Supplement 11. This conforms to themodified PDI program as listed in Table 1 of Enclosure 1 to Attachment 2 of letter dated March 13, 2007. UT examination requirements for the weld overlays are provided in Section 3 of Enclosure 1 ofthe revised RR, which specifies that UT examination is to be performed in accordance with Section XI of the ASME Code. Unlike ASME Code,Section III, the ASME Code,Section XI, UTexamination is qualified for use based on PDI for both personnel and procedures, and it has been proven to be capable for this application. Therefore, for this application, UT examination in accordance with ASME Code,Section XI requirements for UT are more appropriate than UT examination using ASME Code,Section III requirements. Surface examination requirements ofNB-5300 for the weld overlay and NB-2500 for the base material are required for this application. (ASME Code,Section III requirements are intended for construction activity andSection XI is intended for repair.)The current configuration and geometric limitations of these welds does not permit an effectiveUT examination that will obtain the coverage (examination volume) as required by ASME Code, Section XI, Appendix VIII, Supplement 10. As documented in the licensee's January 31, 2007,letter, four of the six DM welds on each unit have examination coverage estimates of significantly less than the required examination volume (50% - 65%). The remaining two DM welds are estimated as capable of achieving approximately 75% to 80% of the required examination coverage. It is estimated that approximately 0.6 Rem per unit would be expended to perform the UT examinations for these two welds for a total of 1.2 Rem.It is proposed that North Anna 1 and 2 will apply a full structural PWOL in accordance withEnclosure 1 of the alternate request designed for a worse-case through-wall flaw that is 360 degrees in circumference. Therefore, none of the identified welds will receive a pre-weld overlay UT examination. The NRC staff has determined that this provides an acceptable level of quality and safety and does not require the licensee to receive an additional dose from UT examination of these welds prior to application of the PWOL. In addition, if the welds are found with PWSCC or other unacceptable flaws during the post-weld overlay UT examination, no additional examination expansions will be performed because there are no remaining DM welds associated with the pressurizer environment not previously mitigated by application of a PWOL.As described in the licensee's letter to the NRC, dated October 1, 2007, during the North AnnaUnit 1 refueling outage, fall 2007, a PWOL was applied to the pressurizer safety nozzle in accordance with RR CMP-022R1. However, less than 100% volumetric examination coverage was obtained following application of the PWOL, due to a localized fabrication repair in the original DMWs buttering region of 'A' safety valve nozzle PWOL. In addition, the calculated composite coverage of the required examination volume is 99.8%. Therefore, a revision to the NDE requirements of RR CMP-022R1 is provided for the North Anna Unit 1 'A' safety valve nozzle PWOL. The revision modifies Sections 3(b) preservice and 3(c) inservice examination requirements of Enclosure 1 to Attachment 2 of the letter to the NRC, dated March 13, 2007, and provides a detailed basis for requesting the reduced examination volume.i) The examination volume is extended 0.30 inches towards the nozzle taper for 114 degrees ofthe circumference of the weld. The interface of the alloy 600 to low alloy steel defining the examination boundary was confirmed by acid etching. The qualified UT examination procedure requires an examination of the volume to include an additional beam angle of 45 degrees to provide effective coverage of the outer 25% of the existing weld and base material for 1/2 inch on each side of the weld. This angle is required to provide coverage of 100% of this volume. In addition, the outer 25% of the existing weld and base material volume can be effectively examined in three of the required four beam directions. The downstream axial beam direction is limited to 99.2% of the required examination volume due to the restriction of the nozzle taper.

This does not allow access to scan the transducer the required distance from the weld to obtain coverage of the lower near corner of the examination volume. The limited examination volume is located at least 0.25 inches from the alloy 600 buttering material and is effectively examined in the three other required beam directions. The calculated composite coverage of the required examination volume is 99.8%.ii) Several different options were considered to resolve the examination coverage issue. Oneoption was to apply additional overlay material (approximately 1/2 inch) parallel to the PWOL.

However, the addition of material would require a considerable additional dose expenditure andnew PDI qualified transducers that are not readily available. Another option was to apply an additional overlay at a 6-degree slope. Even though this option results in less weld material being added, it would still involve considerable dose expenditure (2 manrem) and an additional qualified transducer that is not readily available. The final option was machining of thepressurizer nozzle to provide additional scan surface for the transducer. This option reduced the strength of the nozzle by increasing the cumulative usage factor by at least a factor of four.

The option also required a significant additional dose (0.750 manrem).iii) The volume of material that will be un-inspectable by UT lies entirely in the low alloy steel,SA508 CL 2, of the pressurizer nozzle. This zone of material is 0.25 inches or more from the alloy 82/182 butter on the nozzle. There is no likelihood of primary water stress corrosion crack initiation or propagation in the low alloy steel material itself and no likelihood of propagation of a postulated primary water stress corrosion crack from the alloy 82/182 butter into the low alloy steel. Consequently, there is no likelihood of any undetectable cracking occurring in the small zone of material with no UT inspection coverage. Furthermore, the PWOL was designed to accommodate a 360-degree through-wall crack in the repaired area with no failure, which bounds the case of a crack that might be postulated to exist in the un-inspectable material.Additionally, if the small volume of this base metal contained a flaw, the flaw would onlypotentially reduce the strength of the nozzle by an insignificant amount. However, cutting a transition in the nozzle in order to facilitate 100% inspection coverage will create a small but real reduction of strength of the nozzle. The reduction of strength for this small improvement in inspection coverage may be acceptable, but will constitute a deliberate reduction of strength in the nozzle to address a potential reduction of strength due to an inability to inspect the nozzle for an additional 0.2%. See Sections 3(b) and 3(c) of Enclosure 1 to Attachment 2 of the letter to the NRC, dated March 13, 2007. 3.4.4Required Activities The preliminary stress analysis required by the alternative request will be performed prior to therefueling outage (RFO) for which the PWOL are scheduled for installation and will be available for NRC review on site. The final stress analysis and the engineering evaluation of insurge/outsurge transients will be submitted to the NRC prior to entry into Mode 4. Also, the final plastic/elastic analysis, which includes the engineering evaluation of insurge/outsurgetransients for the surge line on North Anna 2, will be completed and submitted to the NRC by December 31, 2007.If flaw growth in the weld overlay occurs and the acceptance standards of Table IWB-3514-2cannot be met, a determination will be made to prove if the flaw is not PWSCC. If the cause is determined to be PWSCC or the cause of the flaw cannot be determined, North Anna 1 and 2 will repair the flaw and will not use IWB-3600, IWC-3600, or IWD-3600 of ASME Code,Section XI, to accept these types of flaws.North Anna 1 and 2 have provided: (1) the examination results of the weld overlays, (2) adiscussion of any repairs to the overlay material and/or base material, and the reason for the repair within 14 days after the completion of the UT examination of full structural PWOL installations.3.4.5Use of a Barrier Layer to Mitigate Potential Hot Cracking The licensee states that the most recent industry experience involves the hot cracking of nickelAlloy 52M weld overlay deposits on SS base materials with higher levels of sulfur in the austenitic SS base metal. The licensee plans to apply a weld build-up (barrier layer)approximately 0.065-inch thick of ER309L SS weld metal for the majority of the length of the PWOL build-up. The final tie-in to the existing nickel Alloy 82/182 DMWs will be performed with nickel Alloy 82 weld metal. The barrier layer will provide an improved base layer for application of the full structural PWOL that has been demonstrated by mock-up testing to significantly reduce the susceptibility to hot cracking of the first layer of the PWOL. This application of weld build-up is not counted as part of the full structural PWOL. The weld build-up will be performed in accordance with the requirements of the North Anna 1 and 2, ASME Code,Section XI Repair/Replacement program and ASME Code,Section III.Weld filler material ER309L helps to promote primary solidification of the weld metal as ferrite inlieu of austenite. Also, this approach has been fully qualified in an ASME Code,Section IX structural welding procedure qualification (PQ). The licensee's vendor performed a PQ with ER309L (0.01 weight percent Sulfur) deposited on a high sulfur (greater than 0.01 weight percent Sulfur) austenitic SS base material with a single layer of ER309L deposited in the bottom half of the groove and a single layer of E309L deposited in the top half of the groove.

The groove was subsequently filled with ERNiCrFe-7A (Alloy 52M). The intent of the PQ was to fully qualify the layer of ER309L between high sulfur SS and Alloy 52M to ASME Code,Section IX structural requirements. The 0.01 weight percent sulfur ER309L layer supported tensile tests that resulted in ultimate tensile strengths of 83 and 82.8 ksi with failures being of a ductile nature in the base material. Four transverse side bends were also performed with no indications. In addition to the PQ described above, the licensee's vendor performed mock-up testing using the same heat of filler metal as used for the PQ and plans to use the same for North Anna 1 and 2 PWOL. The mock-up tests were also satisfactory.The nozzle is LAS which involves a different alloy composition as opposed to SS. In carbonsteel, the addition of manganese ties up sulfur in manganese sulfide (MnS). MnS virtually eliminates the formation of low melting point iron sulfides that contribute to the solidification cracking. To date the licensee has not seen this problem on low alloy steel welded with ERNiCrFe-7A (Inconel Alloy 52M).The phrase "structural weld layers" as it relates to chromium content is used as part of CodeCase N-740-1 and the licensee's Enclosure 1 to require weld overlay deposited material with sufficient Cr to prevent SCC. For pressurized water reactors (PWR), to mitigate/repair Alloy 82/182 weld deposit at least 24% Cr is required in the PWOL deposit. When applying the first layer of nickel Alloy 52M PWOL over the base metal with less than 24% Cr (austenitic SS, Alloy 82/182) or almost no Cr (low alloy steel nozzle), the weld dilution from these materials may lower the first layer chemistry slightly below 24%. When this happens, the first layer cannot be credited as a structural layer (i.e., PWSCC resistant) and it is termed a "sacrificial layer."

The second and all subsequent layers of the Alloy 52M full structural PWOL deposit will exceed 24% Cr and will be counted as structural weld layers.The term "barrier layer" is not referenced in either ASME Code,Section III or Enclosure 1 (Code Case N-740-1). It is a licensee phrase used to describe a layer of weld metal build-up applied to the austenitic SS pipe and safe end to reduce the amount of sulfur available for pick-up when applying the subsequent Alloy 52M full structural PWOL. Final NDE of the barrier layer will utilize the methods and acceptance criteria of ASME Code,Section III. The barrierlayer uses filler materials expected to result in a first layer deposit analysis containing less than 24% Cr, and from a functional standpoint, it is considered similar to the sacrificial layer described above. The barrier layer will increase the pipe and safe end thickness and will not beutilized as part of the full structural PWOL. Following application of the full structural PWOL, the barrier layer will be examined by PDI UT in accordance with Enclosure 1 of the alternate request as part of the outer 25% of the pipe through-wall thickness.3.4.6Duration of the Proposed Request The licensee states that the alternative requirements of CMP-022R1/023R1 will be applied forthe duration of up to and including the last outage of the current, third 10-year ISI interval. This includes inservice examination requirements for the six applied PWOL locations for each unit identified in Section 3.2 above and will be applied in accordance with Enclosure 1 of Alternative Requests CMP-022R1 and CMP-023R1.4.0NRC STAFF'S EVALUATIONAlternative Requests CMP-022R1/023R1, consist of 3 parts: (1) Attachment 1, "Use of aBarrier Layer to Mitigate potential Hot Cracking," (2) Attachment 2, "Use of Weld Overlays as an Alternative Repair Technique," which includes Table 1, "PDI Program Modifications to Appendix VIII, Supplement 11," and (3) Enclosure 1, "Alternative Requirements for DissimilarMetal Weld Overlays," including Mandatory Appendix I, "Ambient Temperature Bead Welding,"

as modified by the licensee's October 1, 2007, letter. Currently, the NRC staff has endorsed the use of Code Cases 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," in Regulatory Guide 1.147, Revision 14. The NRC staff has not endorsed the use of Code Cases N-740, N-740-1, or N-638-2. Therefore, the NRC staff used the requirements of Code Cases N-504-2 and N-638-1 to aid in the evaluation of Alternative Requests CMP-022R1/023R1 as NRC-approved criteria associated with similar full structural PWOL applications.Enclosure 1 of the alternate request is based on Code Case N-740-1, "Dissimilar Metal WeldOverlay for Repair of Class 1, 2, and 3 Items,Section XI, Division 1," with modifications.

Code Case N-740-1 was developed as the result of industry's need to repair (reduce or mitigate) flaws (suspected or confirmed) generated from Primary Water Stress Corrosion Cracking (PWSCC) via application of weld overlay. Also, the code case offers relief from post weld heat treatment (PWHT) by allowing the use of a temper-bead weld process. Code Case N-740-1 is essentially a combination of Code Cases N-504-2 and N-638-2.The licensee's alternative request is intended as a proactive approach to mitigate potentialeffects of PWSCC by means of a full structural PWOL, to fulfill the surface and geometric requirements of ASME Code,Section XI, Appendix VIII and permit the use of a PDI qualified UT examination. The proposed alternative will be employed at North Anna 1 and 2 during each unit's current third 10-year ISI interval. The full structural PWOL will be applied to the DMW Alloy 82/182 between LAS nozzles and SS safe ends. Nickel base Alloy 82/182 filler metal has been discovered to be susceptible to environmentally assisted cracking when exposed to reactor plant primary water (PW), a phenomenon referred to as PWSCC. In general, some damaging factors that may possess a strong influence on the SCC behavior of nickel-based alloys have been identified as PW hydrogen partial pressure, alloy chromium content, carbide precipitation, grain-boundary properties and temperature. Structural weld overlays have been used for several years on piping of both boiling water reactors (BWR) and PWRs to inhibit thegrowth of flaws while establishing a new structural pressure boundary. The structural weld overlay will control growth in PWSCC flaws and maintain weld integrity by producing compressive stress in the DM weld. The full structural weld overlay will be sized to meet all structural requirements independent of the existing weld. Furthermore, the overlay will produce a UT examinable surface. Due to their close proximity, adjacent stainless steel RCS piping-to-stainless steel safe end SMW will be incorporated into the area of the weld overlay.The basis for the licensee's proposed alternatives are provided in Alternative Requests CMP-022R1/023R1, dated March 13, 2007 and modified by the licensee's letter dated October 1, 2007. The licensee proposed to use Enclosure 1 of the alternate request, with modifications, to install the full structural PWOL. The PWOL is proposed as an alternative to the ASME Code,Section XI, IWA 4000 requirements. For inspection of the full structural PWOL, the licensee proposed using the PDI program as an alternative to the ASME Code requirements of Section XI, Appendix V III, Supplement 11. The NRC staff has evaluated thelicensee's basis for the proposed alternatives and notes that Enclosure 1, based on Code Case N-740-1, is not approved for use by the NRC in RG 1.147, Revision 14. However, the NRC staff recognizes that Code Case N-740-1 (currently not endorsed by the NRC) does provide alternatives to the ASME Code equivalent to those approved in Code Cases N-504-2 and N-638-1. The NRC staff's evaluation of the proposed alternatives to ASME Code,Section XI, IWA-4000 and Appendix VIII, Supplement 11 are provided as follows.As stated in Section 4.3.1, Required Activities, of Alternative Requests CMP-022R1/023R1, ofthe letter to the NRC, dated March 13, 2007, the licensee provided the following: 1) results within 14 days, of the completion of UT examinations on installed PWOL, and 2) a discussion including the reason for any repairs to the weld overlay and/or base metals. 4.1General Requirements Code Case N-504-2 and/or Appendix Q of ASME Code,Section XI, require certainspecifications and surface conditions of the applicable base metal (carbon steel, SS, and Alloy 82/182), the weld overlay filler metal (Alloy 52M) and the chromium content of the weld overlay deposits to be met to allow use of the PWOL technique. Section 1.0 of Enclosure 1 of revised RR CMP-022R1 and CMP-023R1, provides corresponding requirements to those in N-504-2 and Appendix Q. The licensee will deposit a barrier layer of ER309L SS filler metal on the base metal as a contingency for preventing possible hot cracking, which may result from high sulfur content in austenitic SS base material. The tendency of certain metals to exhibit hot cracking is caused by the segregation at grain boundaries of low-melting constituents (e.g., sulfur) in the weld metal. This may result in grain-boundary tearing under thermal contraction stresses. Hot cracking may be minimized by employing low impurity welding metals.The licensee will install the barrier layer, ER309L, on the austenitic SS pipe and safe end onlyand stop short of the Alloy 82/182 weld material. The final tie-in to the existing nickel Alloy 82/182 weld will be performed with nickel Alloy 82 weld metal. Acid etching may be employed to identify the original Alloy 82/182 weld joint-to-safe-end interface as a precaution against weld over of the DMW with ER309L. Welding over the nickel base ENiCrFe-3 (Inconel 182) joint with an iron based ER309L electrode may cause cracking in the ER309L. The Alloy 82 will be welded from the tie-in to the mid point (approximately) of the Alloy 82/182 weld joint and completed with weld overlay Alloy 52M. An informational liquid penetrant (LP) examination willbe performed on the relevant portion (the SS safe end) of the PWOL first layer. If indications of hot cracking are identified, as determined by the welding engineer, the suspect nickel alloy weld metal will be completely removed along with any indications in the underlying base metal of the SS safe end. Complete removal of the nickel alloy weld metal shall be verified by acid etch and the resulting cavity will be LP inspected. Next, a weld build-up will be applied to the cavity using SS weld material for the bulk of the build-up with the final tie-in to the existing nickel alloy weld being performed using nickel alloy weld metal. This weld build-up will serve two purposes: (1) to restore the SS base metal to its original contour, and (2) to provide an improved base layer for application of the PWOL by reducing the amount of sulfur available for pick-up when applying the subsequent Alloy 52M full structural PWOL thereby reducing susceptibility to hot cracking.The licensee reported that the PQ reports for qualifying the temper-bead section of the weldreinforcement and for overlay of the buttered P3 nozzle material were performed using austenitic nickel alloy ERNiCrFe-7 (Alloy 52 UNS N06052) or ERNiCrFe-7A (Alloy 52M, UNSN06054) filler metals. These filler materials were selected for their enhanced resistance to PWSCC. The Cr content of Alloy 52 and 52M is identical at 28-31.5%, providing superior corrosion resistance. Alloy 52M will be used for the full structural PWOL. Alloy 52M contains a higher Niobium content (0.5-1%), which acts as a stabilizer providing resistance to intergranular corrosion. Its chemistry acts to pin grain boundaries inhibiting separation between grains andhot tearing during weld puddle solidification. Also, the difference in composition improves weldability. Moreover, Alloy 52M exhibits ductile properties and toughness similar to austenitic SS piping welds at PWR operating temperature. These filler materials are suitable for welding over the ferritic nozzle, the Alloy 82/182 weld, and the adjacent austenitic SS elbow/pipe/reducer-to-safe end welds and components.Delta ferrite (FN) measurements are not required per Enclosure 1 of the alternate request forweld overlay repairs made of Alloy 52/52M weld metal. The staff finds this acceptable because welds of Alloy 52/52M are 100% austenitic and contain no FN due to their high nickel composition (approximately 60% nickel).4.2Crack Growth Consideration and Design Code Case N-504-2 and/or Appendix Q of ASME Code,Section XI, provide requirements forthe weld overlay design and crack growth calculations. Section 2 of Enclosure 1 of CMP-022R1/023R1 provides the corresponding requirements. The proposed mitigative full structural weld overlays are designed to contain the assumed flaw in the underlying base material or weld and is based on the limiting case of the two as follows: (a) 100-percent through-wall for the entire circumference, or (b) 100-percent through-wall for1.5 inches or the combined width of the weld plus buttering, whichever is greater, in the axialdirection for the entire circumference.Section 2(a) of Enclosure 1 of the revised RR states that flaw characterization and evaluationrequirements shall be based on the UT examination results. Section 4.3 of the alternative request states that the licensee will not perform a UT examination on the DMW prior to weld overlay installation. The NRC staff observes that the condition of the original welds may not be known without conducting a UT examination of the DMW prior to weld overlay installation. This observation is based on UT examination being qualified to detect only the outer 25 percent ofthe original weld (or base metal) following installation of the overlay. The condition of the remaining inner 75 percent of the original weld would not be known.However, Section 2(a)(2) of Enclosure 1 requires for mitigative overlays, that initial postulatedflaw size assumptions for crack growth calculations shall be consistent for various pre-installation examination situations such as, an axial flaw 100 percent though the original wall thickness set at length of 1.5-inches, or the combined width of the weld plus buttering, whichever is greater, be used for the crack growth calculations. In addition, Section 2(a)(2)(b) requires that if no UT examination is performed prior to the application of the overlay, a postulated 360-degree circumferential flaw 100 percent though the original wall thickness shall be assumed for the crack growth calculations. Any actual flaw would not exceed the depth of these assumptions and would be detectable by the qualified post weld overlay UT examinations. The NRC staff finds that Section 2(a)(2)(b) is acceptable because the assumed flaw size for the crack growth calculation is a conservative assumption, which cannot be exceeded by any actual flaw.Paragraphs g(2) and g(3) of Code Case N-504-2 require evaluations of residual stresses andflaw growth of the repaired weldments. Similar evaluations are required in Section 4.2 of Alternative Request CMP-022R1/023R1 which fulfill these required evaluations. For example, Section 2(b)(8) of Enclosure 1 of the revised RR states that the effects of any changes in applied loads, as a result of weld shrinkage from the entire overlay on other items in the piping system shall be evaluated. The report will include crack growth calculations to illustrate that crack growth in the weld overlay or base metal is acceptable and residual stress distribution in the weld overlay as well as the original weld demonstrate favorable stress distribution. The licensee stated that this stress evaluation conclusion is true for all nozzle structural mitigative weld overlay assessments except the portion of the ASME Code,Section III analysis dealingwith the surge line overlay, which will address the insurge/outsurge transients. This portion of the analysis will utilize an engineering evaluation of these transients applying data from a DC Cook ASME Code,Section III analysis that qualified the design for seven heat-up and cool-down plus thirty insurge/outsurge cycles. The licensee will perform the preliminary analysis prior to the outage for which the overlays are scheduled for installation and will be available on site for NRC review. The seven heat-ups and cool-downs with thirty insurge/outsurge cycles represent a very conservative limit placed on interim operation and are associated with the interim analysis. Interim measures are not meant to correlate with an operating cycle-specific number. These limiting insurge/outsurges are not expected to occur in the next seven operating cycles based on one heat-up and one cool-down cycle. The North Anna 1 and 2 specific ASME Code,Section III analysis will be completed by December 31, 2007, at whichtime the seven heat-ups and cool-downs with thirty insurge/outsurge cycle restrictions will be resolved. The number of heat-ups and cool-downs are currently monitored and recorded by procedure. The NRC staff finds that the licensee will provide timely stress analyses of the nozzles as a result of PWOL, and, therefore, this issue is closed.4.3Examination and Inspection The ASME Code, Code Case N-504-2 allows the use of weld overlay repair by deposition ofweld reinforcement on the outside surface of the pipe in lieu of mechanically reducing a defect to an acceptable flaw size. Both Code Case N-504-2 and/or Appendix Q of ASME Code,Section XI require specificacceptance, pre-service and in-service examinations of the installed weld overlay. Section 3 of of CMP-022R1 and CMP-/023R1 provides corresponding requirements.4.3.1Acceptance Examination Section 3(a)(2) of Enclosure 1 of CMP-022R1/023R1 requires surface examinations of installedfull structural PWOL and adjacent base material shall comply with the acceptance criteria of the Construction Code or NB-5300 of ASME Code,Section III. Section 3(a)(2) also requires UTexaminations of the installed weld overlay to assure adequate fusion/bond with base metal and to detect welding flaws. The required acceptance examination surface volume and thickness are defined in Figure 1 of Enclosure 1. Planar flaws detected in the weld overlay acceptance examination shall meet the preservice examination standards of Table IWB-3514-2.The proposed acceptance criteria are consistent with Code Case N-504-2 and Appendix Q of Section XI, except as follows: Section 3(a)(2) of Enclosure 1of the alternate request, requires that "For planar indications outside this examination volume, the nominal wall thickness shall be

"t 2" as shown in Fig 1(c) of Enclosure 1 for volumes A-E-H-D and F-B-C-G." Volumes A-E-H-Dand F-B-C-G are defined in Figure 1(c) and refer to the portion of the weld overlay that is 1/2 inch away from the original weld. The NRC staff notes that a UT examination is not qualified to examine the inner 75 percent of the base metal after weld overlay installation. Therefore, the

"t 2" dimension, which is the weld overlay thickness plus pipe thickness, should not be aparameter for the acceptance criteria of IWB-3514-2 because the "t 2" dimension includes the75-percent depth of the base metal. Furthermore, larger flaws would be permitted to remain in service within the weld overlay if the "t 2" dimension were used establishing a non-conservativeapplication.The NRC staff notes that the pressurizer LAS nozzles and SS safe ends have not had a historyof PWSCC. However, Alloy 600 DM weld material has had a history of PWSCC and the purpose of the weld overlay is to mitigate flaws suspected or confirmed from PWSCC of the DM weld. Volumes A-E-H-D and F-B-C-G as defined in Figure 1(c), pertain to the portion of the weld overlay that is not required to support the pressure boundary function of the PWOL or base metal. If larger flaws are allowed to remain in service in this portion of the weld overlay, the structural integrity of the portion of the PWOL that covers the original weld will not be adversely affected. Therefore, the NRC staff finds that the use of the "t 2" dimension isacceptable because the base metal of the pressurizer nozzle and safe ends at North Anna 1 and 2 are not susceptible to PWSCC, as indicated by their history.4.3.2Preservice ExaminationSection 3(b) of Enclosure 1 of CMP-022R1/023R1 requires a pre-service UT examination of theinstalled weld overlay and the upper (outer) 25 percent of the original pipe wall thickness. The required examination volume is defined in Figure 2 of Enclosure 1of the alternative request.As stated in Section 3(b)(2) of Enclosure 1, if a flaw is detected in the outer 25 percent of thebase metal or original weld during the pre-service examination, the as-found flaw size would be used for the crack growth evaluation. The NRC staff does not believe this is a conservative assumption for the crack growth calculation if the original weld was not examined prior to installing the PWOL. The current UT examination is qualified only to detect flaws in the outer25 percent of the pipe base metal after a weld overlay is applied. With the limited UT qualification, the condition of the inner 75 percent of the pipe base metal would not be known.A conservative assumption would be to assume existence of a crack of 75-percent through-walldepth in the inner 75-percent pipe base metal. The 75-percent depth flaw should be added to the depth of the crack found in the outer 25 percent of the pipe base metal. This worst-case crack (the sum of two flaws) should be used to calculate crack growth. The licensee shall only use the actual UT determined through-wall dimension in the crack growth analysis for flaws that are detected by the qualified UT examination to be entirely within the outer 25 percent and do not breach the interface between the outer 25 percent and inner 75 percent of the original base metal or weld metal thickness. However, in Section 2(a)(2)(b) the licensee states that 100%

original through-wall thickness shall be used satisfying this conservative assumption. In addition, the NRC staff finds that Section 3(b)(3) adequately addresses a conservative flaw size to be used in the crack growth calculation by not allowing the use of ASME Code acceptance criteria that exceed the preservice examination standards of Section 3(b)(2). Therefore, the proposed pre-service examination requirements in Section 3(b) of Enclosure 1 of Alternative Requests CMP-022R1/023R1 are acceptable.In the letter dated October 1, 2007, the licensee stated that due to a localized fabrication repairin the original DMW buttering region of 'A' safety valve nozzle PWOL, at North Anna Unit 1, the examination resulted in less than the required volume shown in Figure 2 of Enclosure 1 to of the letter of March 13, 2007. The calculated composite coverage of the required examination volume is 99.8%. To achieve 100% coverage would require modification or machining of the nozzle area. In this configuration the composite coverage is sufficient to provide early indication of any flaws introduced through operational effects without additional modification. The staff concludes, based on the preceding discussion, that compliance with the ASME Coderequired preservice and in-process examinations for the North Anna Unit 1 'A' safety valve nozzle PWOL provides an acceptable level of quality and safety. 4.3.3Inservice Examination Section 3(c) of Enclosure 1 the revised RR provides requirements for UT inserviceexaminations with the examination volume defined in Figure 2 of Enclosure 1. Section 3(c)(4)allows flaws in PWOL to be accepted by IWX-3640 of ASME Code,Section XI. The NRC staff agrees with use of the acceptance criteria of IWB-3600 for flaws in the weld overlay if the flaw growth is caused by fatigue. However, flaw growth caused by PWSCC is considered of greater risk and the NRC staff finds such a growth mechanism in PWOL unacceptable. Section 4.3.1 of the alternate request added the following requirement:If flaw growth in the weld overlay occurs and the acceptance standards of IWB-3514-2cannot be met and the cause is determined to be PWSCC or cannot be determined, North Anna 1 and 2 will repair the flaw and will not use IWB-3600, IWC-3600, or IWD-3600 to accept these types of flaws.The NRC staff finds the above requirement acceptable because the licensee will not use IWX-3600 to accept suspected PWSCC flaws in PWOL. 4.4 Mandatory Appendix 1--Ambient Temperature Temper-Bead WeldingCode Case N-638-1 provides requirements for ambient temperature temper bead welding. Mandatory Appendix 1 of Enclosure 1 of CMP-022R1 and CMP-023R1 is based on Code Case N-638-2. The major difference between the two documents is discussed below.Paragraph 1(b) of Mandatory Appendix 1 states that the maximum area of the weld overlaybased on the finished surface over the ferritic base material shall be 500 square inches.

Code Case N-638-1 allows only 100 square inches over the ferritic base material. Section 4.1 of the alternate request added that the ASME committee has indicated inside diameter compressive stress levels remain essentially the same between 100 square inches and 500 square inches in relation to weld overlay applications. The presentation slides entitled, "Bases for 500 Square Inch Weld Overlay Over Ferritic Material," were provided to the NRC staff in a public meeting held on January 10, 2007 (ADAMS Accession No. ML070470565).

Additional justification is provided in Electric Power Research Institute (EPRI) Report 1014351, "Repair and Replacement Applications Center: Topical Report Supporting Expedited NRCReview of Code Cases for Dissimilar Metal Weld Overlay Repairs, December 2006."Based on a review of the information provided, the NRC staff concludes that the 500-square-inch weld area limit over the ferritic base metal is acceptable. The EPRI report provided results of finite element analyses demonstrating that the stresses of a nozzle with the 500-square inch weld area will not adversely affect the integrity of the pressurizer nozzle. In addition, Code Case N-638-1 requirements are based on a groove weld design for which the finished surface area requirement also allows the depth of the weld to be no greater than one-half of the ferritic base metal thickness. The code case is adapted for use with the SWOL design which is a surface design with slight depth of penetration and minimal induced stresses as compared to a groove weld design.The NRC staff finds that the requirements of Enclosure 1 together with Mandatory Appendix 1of the alternate request are consistent with the intent of provisions approved in Code Cases N-504-2 & N-638-1 including Section XI, Appendix Q, of the ASME Code. Therefore, the proposed alternative is acceptable.4.5Modifications to Appendix VIII, Supplement 11The U.S. nuclear utilities created the PDI program to implement performance demonstrationrequirements contained in Section XI, Appendix VIII, of the ASME Code. Moreover, the PDIprogram is designed for qualifying equipment, procedures and personnel to examine weld overlays in accordance with the UT criteria of Appendix VIII, Supplement 11. Preceding theSupplement 11 program, EPRI maintained a performance demonstration program for weld overlay qualification under the Tri-party Agreement

1. In lieu of having two programs with similarobjectives, the NRC staff recognized the PDI program 2 for weld overlay qualifications as anacceptable alternative to the Tri-party Agreement. Although the PDI program was developed for ISI at BWR plants, it is applicable to PWR plants like North Anna 1 and 2, because the application for PWOL use is the same concept. The PDI program is routinely assessed by the NRC staff for consistency with the current ASMECode and proposed changes. The PDI program does not fully comport with the existing requirements of Supplement 11. PDI presented the differences at public meetings in which the NRC participated3, 4. The differences involve flaw location within test specimens and fabricatedflaw tolerances. The changes in flaw location permitted using test specimens from the Tri-party Agreement and the changes in fabricated flaw tolerances provide UT acoustic responses similar to responses associated with intergranular stress corrosion cracking. The differences between the PDI program and Supplement 11 are presented in Table 1, "PDI Program Modifications to Appendix VIII, Supplement 11," of Enclosure 1 of CMP-022R1/023R1.The NRC staff evaluated the differences proposed by the licensee between the PDI programand Appendix V III, Supplement 11 in the licensee's revised RR. The NRC staff concludes that an acceptable level of quality and safety is incorporated into the licensee's proposed RR.

5.0CONCLUSION

S The NRC staff has reviewed the licensee's submittal and has determined RRs CMP-022R1/023R1 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 the Alternative Request CMP-022R1/023R1 in lieu of the requirements contained in the 1989 edition of the ASME Code, for North Anna 1 and the 1995 edition through 1996 addenda for North Anna 2 of ASME Code,Section XI, IWA-4000, and in the 1989 edition for North Anna 1 and 1995 edition through 1996 addenda for North Anna 2 of Section XI, Appendix VIII, Supplement 11, for the following items: 1The Tri-party Agreement is between NRC, EPRI, and the Boiling Water Reactor Owners Group (BWROG), "CoordinationPlan for NRC/EPRI/BWROG Training and Qualification Activities of NDE (Nondestructive Examination) Personnel," July 3, 1984.2US NRC Letter from William H. Bateman to Michael Bratton, "Weld Overlay Performance Demonstration Administered byPDI as an Alternative for Generic Letter 88-01 Recommendations," January 15, 2002 (ML020160532).3US NRC Memorandum from Donald G. Naujock to Terence Chan, "Summary of Public Meeting Held June 12 throughJune 14, 2001, with PDI Representatives," November 29, 2001 (ML013330156).4US NRC Memorandum from Donald G. Naujock to Terence Chan, "Summary of Public Meeting Held January 31 -February 2, 2002, with PDI Representatives," March 22, 2002 (ML010940402).The proposed alternative is approved for the full structural PWOL of the DM and SM welds ofthe pressurizer surge line, safety valve, and relief valve nozzles at North Anna 1 and 2. The PWOL will include the adjacent stainless steel elbow/pipe/reducer-to-safe-end welds. The approval applies to each of the welds listed in Section 2.2 and generically depicted in Figure 1 of RRs CMP-022R1/023R1. A full structural PWOL (designed for the worst-case flaw) will be applied in accordance with the requirements of Enclosure 1 of RR CMP-022R1/023R1, followed by UT examination upon completion. No pre-repair UT will be performed.

The UT examination of the completed PWOL will be accomplished in accordance with ASME Code,Section XI, 1998 edition including addenda through 2000 for North Anna 1 and 2, Appendix VIII, Supplement 11, as modified by the licensee's October 1, 2007, letter and tocomply with the PDI program as listed in Attachment 2, Enclosure 1 of CMP-022R1/023R1. The effective period of Alternative Request CMP-022R1/023R1 will be up to and including thelast outage of the current third 10-year ISI interval which includes the inservice examination requirements of Enclosure 1 of the alternative request for the six applied weld overlay locations for North Anna 1 and 2, which ends on April 30, 2009, and December 13, 2010, respectively.All other ASME Code,Section XI requirements for which relief was not specifically requestedand approved remain applicable, including third-party review by the Authorized Nuclear In-service Inspector.Principal Contributor: D. Tarantino Date: December 19, 2007 North Anna Power Station, Units 1 & 2 cc:

Mr. David A. ChristianSenior Vice President and Chief Nuclear Officer Virginia Electric and Power Company Innsbrooks Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711Mr. C. Lee LintecumCounty Administrator Louisa County Post Office Box 160 Louisa, Virginia 23093Ms. Lillian M. Cuoco, Esq.Senior Counsel Dominion Resources Services, Inc.

120 Tredegar Street, RS-2 Richmond, VA 23219Dr. W. T. LoughVirginia State Corporation Commission Division of Energy Regulation Post Office Box 1197 Richmond, Virginia 23218Old Dominion Electric Cooperative4201 Dominion Blvd.

Glen Allen, Virginia 23060Mr. Chris L. Funderburk, DirectorNuclear Licensing & Operations Support Dominion Resources Services, Inc.

Innsbrook Technical Center 5000 Dominion Blvd.

Glen Allen, Virginia 23060-6711Office of the Attorney GeneralCommonwealth of Virginia 900 East Main Street Richmond, Virginia 23219Senior Resident InspectorNorth Anna Power Station U. S. Nuclear Regulatory Commission P. O. Box 490 Mineral, Virginia 23117Mr. Daniel G. StoddardSite Vice President North Anna Power Station Virginia Electric and Power Company Post Office Box 402 Mineral, Virginia 23117-0402Dr. Robert B. Stroube, MD, MPHState Health Commissioner Office of the Commissioner Virginia Department of Health Post Office Box 2448 Richmond, Virginia 23218 Mr. Mark D. Sartain, DirectorNuclear Safety & Licensing Virginia Electric and Power Company North Anna Power Station P. O. Box 402 Mineral, VA 23117