ML103430156

Relief Request ANO1-R&R-013, Proposed Alternative to Requirements Associated with Repair of Components, for Duration of ANO-1 Spring 2010 Refueling Outage 1R22

ML103430156
Person / Time
Site:	Arkansas Nuclear
Issue date:	01/10/2011
From:	Markley M Plant Licensing Branch IV
To:	Entergy Operations
Kalyanam N, NRR/DORL/LPL4, 415-1480
References
TAC ME3701
Download: ML103430156 (20)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 January 10, 2011 Vice President, Operations Arkansas Nuclear One Entergy Operations, Inc.

1448 SR. 333 Russellville, AR 72802

SUBJECT:

ARKANSAS NUCLEAR OI'JE, UI'JIT NO.1 - REQUEST FOR ALTERNATIVE AN01-R&R-013, FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL REPAIRS TO THE PRESSURIZER INSTRUMENTATION PENETRATIONS (TAC I'JO. ME3701)

Dear Sir or Madam:

By letter dated April 5, 2010, as supplemented by letters dated April 12, 2010, and January 6, 2011, Entergy Operations. Inc. (Entergy, the licensee), requested U.S. Nuclear Regulatory Commission (NRC) staff review and approval of Relief Request AN01-R&R-013, to allow weld repairs during the spring 2010 refueling outage (1 R22) at Arkansas Nuclear One, Unit 1 (ANO 1). The relief request would provide alternatives to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI requirements.

Specifically, Entergy has proposed to repair the penetration by installing a welded pad using Ambient Temperature Temper Bead welding in accordance with ASI\\/IE Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW [Gas Tungsten Arc Welding] Temper Bead Technique," and, as an alternative to performing the Code Case N-638-1 surface and ultrasonic examinations at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the completed weld has reached ambient temperature, Entergy has proposed to perform the surface and ultrasonic examinations at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the third weld layer is completed. Additionally, as an alternative to performing the non-destructive examination required to characterize the flaw in penetration RC-1001 AlB, Entergy proposed analyzing a maximum postulated flaw that bounds the range of flaw sizes that could exist in the J-groove weld and nozzle.

The NRC staff has reviewed the licensee's submittal, as supplemented, and determined that AN01-R&R-013, will provide an acceptable level of quality and safety. Therefore, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3)(i), the NRC staff authorizes the use of the AI'J01-R&R-013 for weld repairs at ANO-1. The relief is authorized for the duration of the ANO-1 spring 2010 refueling outage 1R22 to support the repair of the pressurizer instrumentation nozzle RC-1 001 AlB.

Due to the immediate need of this relief request, verbal authorization for the use of this relief request, AN01-R&R-013, was granted on April 12, 2010.

- 2 All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.

The bases for the NRC staff's conclusions are contained in the enclosed Safety Evaluation. If you have any questions, please contact Kaly N. Kalyanam at (301) 415-1480 or by email at kaly.kalyanam@nrc.gov.

Sincerely, A4-t~ ~Uz; Michael 1. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-313

Enclosure:

As stated cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST AN01-R&R-013, PROPOSED ALTERNATIVES TO THE REQUIREMENTS OF ASME CODE ASSOCIATED WITH REPAIR OF PRESSURIZER INSTRUMENTATION PENETRATION ENTERGY OPERATIONS, INC.

ARKANSAS NUCLEAR ONE, UNIT 1 DOCKET NO. 50-313

1.0 INTRODUCTION

By letter dated April 5, 2010, as supplemented by letters dated April 12, 2010, and January 6, 2011 (Agencywide Documents Access and Management System (ADAMS)

Accession Nos. ML100950255, ML101050404, and ML110070413, respectively), Entergy Operations, Inc. (Entergy, the licensee), submitted relief request (RR) AN01-R&R-013 for the U.S. Nuclear Regulatory Commission (NRC) review and approval. RR AN01-R&R-013 proposed alternatives to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, associated with repair of an instrument penetration nozzle of the Arkansas Nuclear One, Unit 1 (ANO-1) pressurizer.

During the ANO-1 spring 2010 refueling outage 1R22, the licensee discovered, by visual examinations, signs of leakage consisting of rust-colored stains and boron residue at pressurizer instrumentation penetration nozzle, RC-1001 AlB, used for measuring the water level in the pressurizer. This observation necessitated the repair of this penetration nozzle during the refueling outage 1R22.

The licensee requested the NRC authorization for the use of RR AN01-R&R-013 in order to support the spring 2010 refueling outage 1R22. On April 12, 2010, the NRC staff granted verbal authorization for the use of RR AN01-R&R-013 for the repair of pressurizer instrumentation penetration nozzle RC-1001 AlB at ANO-1 for the spring 2010 refueling outage 1R22 (ADAMS Accession No. ML103570333).

2.0 REGULATORY REQUIREMENTS Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g) specifies that inservice inspection (lSI) of nuclear power plant components shall be performed in accordance with the requirements of the ASME Code,Section XI, except where specific written relief has been Enclosure

- 2 granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). The regulations in 10 CFR 50.55a(g)(6)(i) state that the Commission may grant such relief and may impose such alternative requirements as it determines is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the pUblic interest, given the consideration of the burden upon the licensee. The regulations in 10 CFR 50.55a(a)(3) state that alternatives to the requirements of paragraph (g) of 10 CFR 50.55a may be used, when authorized by the NRC, if (i) the proposed alternatives would 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 regulations in 10 CFR 50.55a(g)(5)(iii) state that if the licensee has determined that conformance with certain code requirements is impractical for its facility, the licensee shall notify the Commission and submit, as specified in 10 CFR 50.4, information to support the determinations.

Pursuant to 10 CFR 50.55a(g)(6)(ii)(E), "Reactor coolant pressure boundary visual inspections,"

all licensees of pressurized-water reactor (PWR) plants shall augment their lSI program by implementing ASME Code Case N-722, "Additional Examinations for PWR Pressure Retaining Welds in Class 1 Components Fabricated With Alloy 600/82/182 Materials," subject to the conditions specified in paragraphs (1) through (4) of 10 CFR 50.55a(g)(6)(ii)(E).

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall 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 of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of 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 of the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.

3.0 TECHNICAL EVALUATION

3.1 ASME Code Components Affected

Code Class:

Class 1 Component:

Instrumentation Penetration Nozzle System:

Reactor Coolant System, Pressurizer Examination Category:

PWR Components Containing Alloy 600/82/182 Code Item No.:

B15.180 in Table 1 of ASME Code Case N-722 The component for which relief is requested is listed below.

System I Component Component No.

Component Material Reactor Coolant System, Pressurizer; Instrumentation Penetration Nozzle and Attachment Weld RC-1001 AlB Alloy 600/82/182

- 3 The RC-1001 AlB pressurizer instrumentation nozzle is a 1.0-inch piping connection used for measuring the water level in the pressurizer. The subject instrumentation nozzle is identified as RC-1001 AlB because the first two components on the piping from this penetration are valves with tag numbers RC-1001A and RC-1001B. The instrumentation nozzle RC-1001 AlB and the associated attachment weld serve as a portion of the pressure boundary for the pressurizer.

3.2

Applicable Code Edition and Addenda

The current Code of record for the fourth 10-year lSI interval at ANO-1 is the 2001 Edition through 2003 Addenda of the ASME Code,Section XI, which is scheduled to end on June 1, 2017.

The original Construction Code of record for the ANO-1 pressurizer is the 1965 Edition through 1967 Addenda of the ASME Code,Section XI.

The 2002 Addenda of the ASME Code,Section XI, is used to comply with the regulatory requirements of 10 CFR 50.55a(b)(2)(xx).

The 1992 Edition and no Addenda of the ASME Code,Section III, is used to comply with the provisions of IWA-4540(a)(2) of the 2002 Addenda of the ASME Code,Section XI.

The 1989 Edition and no Addenda of the ASME Code,Section III, is used for the design of the new instrumentation penetration configuration and the nondestructive examination (NDE) of the new instrumentation nozzle attachment weld (i.e., partial penetration J-groove weld).

3.3 Applicable Code Requirements Pursuant to 10 CFR 50.55a(b)(2)(xx), "System leakage tests," the NDE provision in IWA 4540(a)(2) of the 2002 Addenda of the ASME Code,Section XI, must be applied when performing system leakage tests after repair and replacement activities performed by welding.

According to IWA-4540(a)(2) of the 2002 Addenda of the ASME Code,Section XI, all welds and weld areas sUbject to a system leakage test shall be nondestructively examined in accordance with the methods and acceptance criteria of the 1992 Edition or later of the ASME Code,Section III. To comply with 10 CFR 50. 55a(b)(2)(xx), the NDE methods and acceptance criteria of the 1992 Edition and no Addenda of the ASME Code,Section III is used.

The new instrumentation penetration configuration is designed in accordance with the 1989 Edition and no Addenda of the ASME Code,Section III. The NDE of new instrumentation nozzle attachment weld (i.e., partial penetration J-groove weld) is performed in accordance with the 1989 Edition and no Addenda of the ASME Code,Section III.

The regulatory requirements in 10 CFR 50.55a(g)(6)(ii)(E), "Reactor coolant pressure boundary visual inspections," require all licensees of PWR plants to augment their lSI program by implementing ASME Code Case N-722, "Additional Examinations for PWR Pressure Retaining Welds in Class 1 Components Fabricated With Alloy 600/82/182 Materials," subject to the conditions specified in paragraphs (1) through (4) of 10 CFR 50.55a(g)(6)(ii)(E). ASME Code Case N-722 requires that, in addition to the examination requirements of the ASME Code,Section XI, Table IWB-2500-1, the examination requirements of ASME Code Case N-722,

- 4 Table 1, shall be performed for the PWR plants having partial or full penetration welds in Class 1 components containing Alloy 600/82/182 material. The inspection requirements of ASME Code Case N-722 do not apply to components with pressure retaining welds fabricated with Alloy 600/82/182 materials that have been mitigated by weld overlay or stress improvement.

ANO-1 has adopted ASME Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW [Gas Tungsten Arc Welding]Temper Bead Technique,"

for its lSI program which establishes requirements for performing ambient temperature temper bead welding as an alternative to the preheat and post-weld heat treatment requirements of the Construction Code. ASME Code Case N-638-1 has been conditionally approved for use by the NRC in Regulatory Guide (RG) 1.147, Revision 15, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1" (ADAMS Accession No. ML072070419), with the following condition: "UT [ultrasonic testing] examinations shall be demonstrated for the repaired volume using representative samples which contain construction type flaws. The acceptance criteria of NB-5330 of Section III edition and addenda approved in 10 CFR 50.55a apply to all flaws identified within the repaired volume."

The 2001 Edition through 2003 Addenda of the ASME Code,Section XI, IWB-3522, provides acceptance criteria for the visual examinations performed in accordance with the ASME Code Case N-722, Table 1, Examination Categories Class 1 PWR Components Containing Alloy 600/182/82, Item No. B15.180.

The 2001 Edition through 2003 Addenda of the ASME Code,Section XI, IWB-3522.1, states that the relevant conditions that may be detected during the conduct of system pressure tests shall require correction to meet the requirements of IWB-3142 and IWA-5250 prior to continued service.

The 2001 Edition through 2003 Addenda of the ASME Code,Section XI, IWB-3142.1(b), states that a component whose visual examination detects the relevant conditions described in the standards of Table IWB-341 0-1 shall be unacceptable for continued service, unless such components meet the requirements of IWB-3142.2, IWB-3142.3, or IWB-3142.4.

The 2001 Edition through 2003 Addenda of the ASME Code,Section XI, IWB-3142.4, states that a component containing relevant conditions is acceptable for continued service if an analytical evaluation demonstrates the component's acceptability. The evaluation analysis and evaluation acceptance criteria shall be specified by the owner. A component accepted for continued service based on analytical evaluation shall be subsequently examined in accordance with IWB-2420(b) and IWB-2420(c).

The 2001 Edition through 2003 Addenda of the ASME Code,Section XI, IWA-5250(a)(3), states that components requiring correction shall have repair and replacement activities performed in accordance with IWA-4000.

The 2001 Edition through 2003 Addenda of the ASME Code,Section XI, IWB-361 O(b) states that for purposes of evaluation by analysis, the depth of flaws in clad components shall be defined in accordance with Figure IWB-3610-1.

- 5 The 2001 Edition through 2003 Addenda of the ASME Code,Section XI, IWB-3420, states that each detected flaw or group of flaws shall be characterized by the rules of IWA-3300 to establish the dimensions of the flaws. These dimensions shall be used in conjunction with the acceptance standards of IWB-3500.

The 2001 Edition through 2003 Addenda of the ASME Code,Section XI, IWA-4411 (a), states that later editions and addenda of the Construction Code, or a later different Construction Code, either in its entirety or portions thereof, and ASME Code Cases may be used provided the substitution is as listed in IWA-4221 (c).

3.4 Licensee Proposed Alternatives The licensee proposes the following alternatives to the 2001 Edition through 2003 Addenda of the ASME Code,Section XI, requirements:

a.

As an alternative to IWB-3420 and IWB-3610(b) requirements, to perform the NOE to characterize the flaw in the instrumentation nozzle RC-1001 AlB, the licensee proposes analyzing a maximum postulated flaw that bounds the range of flaw sizes that could exist in the J-groove weld and the nozzle base materials.

b.

As an alternative to IWB-3142.4 requirements, to perform the subsequent NOE examinations to assess potential growth of the flaw in the instrumentation nozzle RC-1001 AlB, the licensee proposes analyzing a maximum postulated flaw that bounds the potential growth of the existing flaw.

c.

As an alternative to the requirements in paragraph 4.0(b) of ASME Code Case N-638-1, to perform the surface and UT examinations of the final weld surface and the band around the area defined by paragraph 1.0(d) at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the completed weld has reached ambient temperature, the licensee proposes to perform surface and UT examinations at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the third weld layer is completed.

3.5 Licensee Basis for Use of Proposed Alternatives The licensee stated that the ANO-1 pressurizer was manufactured from SA-516, Grade 70, carbon steel with a stainless steel clad. The instrumentation nozzles of the pressurizer were fabricated with Alloy 600 and the associated J-groove dissimilar metal (OM) welds were made with nickel-based Alloy 82/182 weld materials. The subject Alloy 600/182/82 components that are exposed to the primary coolant water and the elevated operating temperatures can pose a propensity for primary-water stress-corrosion cracking (PWSCC). The licensee discovered by the visual examinations a leak in level tap instrumentation nozzle RC-1001 AlB located on the pressurizer upper side shell during the spring 2010 refueling outage 1R22. This observation has necessitated the repair of the level tap instrumentation nozzle RC-1001 AlB.

- 6 To repair the leaking nozzle RC-1001 NB, the licensee utilized the "half-nozzle" repair technique and replaced a portion of the existing penetration nozzle RC-1001 NB assembly with an Alloy 690 nozzle resistant to the PWSCC, as shown below in Figure 1.

+0000" Iti----lrtll 1.455" -0,'005" Replacement Nozzle r~~'/1 0.815" +/-0.010" Replacement Weld

...--'/ !SQuare Weld Padl 0.4" min.

0.5" min.

01875' min.

.~--

Progressive PT DETAIL C Vessel 00

~L-------"".urIj V I4-- B 0'* 1 460* +0.010" ore. la..

-0.000" Original Partial Penetration Weld Vessel 10 Figure 1. Licensee schematic diagram of the replacement penetration nozzle, the remnant of original (existing) nozzle, and the associated attachment welds The Alloy 690 penetration nozzle consisted of the application of a welded pad to the outside diameter (00) of the pressurizer using Alloy 52M (ENiCrFe-7A) filler metals resistant to the PWSCC and was welded using the machine gas tungsten arc welding (GTAW) ambient temperature temper bead (ATIB) technique. The Alloy 690 replacement nozzle was attached to the new weld pad with a partial penetration attachment weld using the manual GTAW welding non-temper bead technique.

Repair and Replacement Process and NDE Examinations The licensee stated that the "half-nozzle" technique and the 00 weld pad were utilized to repair the leaking nozzle RC-1001 NB. The process for repair and examination is as follows:

a.

The existing nozzle RC-1001 NB is cut at or near the 00 surface of the pressurizer and then removed by machining to a depth near the pressurizer mid wall. To facilitate installation of the new half nozzle, the bore diameter is reestablished by machining. The remnant of existing nozzle RC-1001 NB and the original partial penetration attachment weld that contained the flaw are left in place and the flaw is not removed.

- 7

b.

The visual examinations are performed on the nozzle base material and bore area to ensure unacceptable corrosion has not occurred. In addition, the surface and UT examinations are used to inspect the base metal prior to application of the weld pad.

c.

A non-ferritic weld pad utilizing Alloy 52M weld filler metal is installed on the 00 of the pressurizer using the machine GTAW ATTB welding process as illustrated in Figure 1. The weld pad is examined in accordance with ASME Code Case N-638-1. As an alternative to performing the surface and UT examinations at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the completed weld has reached ambient temperature, the licensee proposes to start the 48-hour time clock after the third weld layer is completed. The UT examinations are performed on the weld pad after the 48-hour hold.

d.

A new partial penetration weld preparation is machined into the welded pad on the pressurizer.

e.

The new nozzle is welded to the pad.

f.

The new partial penetration attachment weld is examined in accordance with the Construction Code which includes the progressive penetrant testing (PT) examinations.

g.

Fracture mechanics evaluation in accordance with IWB-3600 is performed on the original (10 surface) partial penetration weld as an alternative to the required volumetric examinations because the weld cannot be volumetrically examined.

For fracture mechanics evaluation, the weld is assumed to be completely cracked, as a worse case, to ensure that the flaw in the original weld will not adversely affect the pressurizer.

Flaw Evaluation The licensee stated that the ASME Code,Section XI, IWB-3600, fracture mechanics analysis is performed on the original partial penetration weld to confirm the acceptability of the postulated bounding 10 flaw in the instrumentation nozzle RC-1001 AlB. Because the J-groove weld cannot be volumetrically examined, the weld is assumed to be completely cracked as a worse case. This ensures that the flaw in the original weld will not adversely affect the pressurizer.

The evaluations showed that the potential remnant defects in the pressurizer J-groove weld assumed for the instrumentation nozzle RC-1001 AlB were acceptable based on either the linear-elastic fracture mechanics (LEFM) or elastic-plastic fracture mechanics (EPFM) principles of Section XI of the ASME Code. For those flaw sizes and load cases that did not meet the acceptance criteria for LEFM, additional analysis using EPFM was performed which indicated that the flaw was acceptable. Fatigue crack growth analyses showed that the postulated remnant flaws in the remnant pressurizer instrumentation nozzle RC-1001 AlB evaluated herein were acceptable for a 60-year plant operating period.

- 8 The licensee stated that the finite element models using ANSYS, were developed for the stress intensity factor calculations and determination of the residual stresses for the nozzle repair. The models facilitates the simulation of the deposition of weld beads, the post-weld heat treatment, the installation of the nozzle and associated J-groove weld, and the hydrotest. The model includes the pressurizer shell, the cladding, the replacement nozzle, the existing nozzle remnant, the original J-groove weld, and the 00 pad repair with associated J-groove and cover fillet repair welds. For the flaw evaluation, three crack fronts were modeled representing a flaw at the weld to carbon-steel interface, and two slightly larger flaws penetrating into the carbon steel to evaluate fatigue growth of the postulated flaw in the weld.

The licensee stated that the initial flaw assumes that the J-groove weld is completely cracked.

Crack tip elements are created along the contour of the existing J-groove weld. The crack tip elements are created such that the resulting crack is in the axial plane with respect to the pressurizer vessel because the vessel hoop stress is typically the dominant stress. Additional crack tip paths are also included, assuming self-similar crack growth from the J-groove weld.

Under the self-similar crack growth assumption, the crack aspect ratio (depth-to-Iength) remains constant and the crack front retains its shape as the crack propagates into the base metal. The initial flaw is then grown into the carbon-steel base metal of the pressurizer shell by fatigue.

The methodology of the 2001 Edition through 2003 Addenda of the ASME Code,Section XI, Subarticle A-4300, was used to perform the fatigue crack growth evaluation. Fatigue crack growth analyses show that the postulated remnant flaw in the remnant pressurizer instrumentation nozzle RC-1001 NB is acceptable for a 60-year plant operating period.

The licensee stated that the actual flaw is considered to be the result of PWSCC. The PWSCC cracking is limited to Alloy 600 material and Alloy 82/182 weld metal materials, and is typically limited to that portion of the component where the stress levels will support the PWSCC. The maximum-size PWSCC flaw is limited to Alloy 600 material because the carbon steel is not susceptible to PWSCC. The ASME Code,Section XI, allows evaluation of the actual flaw size with subsequent examination to monitor crack growth. As an alternative, this flaw evaluation qualified the largest PWSCC flaw that the crack could grow to, and then qualified additional fatigue crack growth into the carbon steel. By using the bounding flaw size, the flaw analysis demonstrates that the repair would provide an acceptable level of quality and safety.

3.6 Duration of Relief RR AN01-R&R-013 is submitted for approval for the duration of the ANO-1 spring 2010 refueling outage 1R22 to support the repair of pressurizer instrumentation penetration nozzle.

4.0 STAFF EVALUATION As required by 10 CFR 50.55a(g)(6)(ii)(E), the licensee preformed the visual examinations of all pressurizer instrumentation nozzles in accordance with ASME Code Case N-722 every refueling outage. A leak was discovered by the visual examinations in the level tap of one instrumentation nozzle, identified with component no. RC-1001 NB, located on the pressurizer upper side shell during the ANO-1 spring 2010 refueling outage 1R22. This observation necessitated the repair of the leaking nozzle RC-1001 NB during this refueling outage for which the licensee requested NRC authorization for the use of RR AN01-R&R-013 in order to support

- 9 the spring 2010 refueling outage. On April 12, 2010, the NRC staff granted verbal authorization for the use of RR AN01-R&R-013 during the ANO-1 spring 2010 refueling outage 1R22.

ASME Code Case N-638-1 establishes requirements for performing ambient temperature temper bead welding as an alternative to preheat and post-weld heat treatment requirements of the Construction Code. ASME Code Case N-638-1 requires that the final weld surface and the band around the area defined in paragraph 1.0(d) shall be examined using a surface and UT methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

ANO-1 has adopted ASME Code Case N-638-1 for its lSI program. ASME Code Case N-638-1 has been conditionally approved for use by the NRC in RG 1.147, Revision 15, with the condition that the UT examinations shall be demonstrated for the repaired volume using representative samples which contain construction type flaws, and the acceptance criteria of NB-5330 of Section III edition and addenda of the ASME Code approved in 10 CFR 50.55a apply to all flaws identified within the repaired volume.

Repair and Replacement and NOE Examinations of Nozzle RC-1001 AlB The NRC staff notes that the A1\\l0-1 pressurizer is made of carbon steel and its inside surface is clad with stainless steel. The pressurizer instrumentation nozzles and the attachment J-groove OM welds are fabricated from Alloy 600/82/182 and exposed to the primary coolant water and the elevated operating temperatures, therefore, are susceptible to PWSCC. To repair the leaking nozzle RC-1001 AlB, the licensee utilized the "half-nozzle" repair technique where a portion of the existing nozzle assembly at or near the 00 surface of the pressurizer was cut and removed by machining to a depth near the pressurizer mid-wall, and replaced with the Alloy 690 nozzle resistant to the PWSCC, as shown in Figure 1. The Alloy 690 replacement nozzle consisted of the application of a welded pad to the 00 of the pressurizer using Alloy 52M filler metal resistant to the PWSCC. The Alloy 52M welded pad was welded on the carbon-steel vessel using the machine GTAW ATTB technique in accordance with ASME Code Case N-638-1. The Alloy 690 replacement nozzle was attached to the new weld pad with a partial penetration weld using a non-temper bead manual welding technique. The remnant of existing nozzle RC-1001 AlB and the original partial penetration attachment weld that contained the flaw was left in place.

In reviewing the response to the NRC staff's request to explain the process of non-temper bead welding performed (e.g., by which edition and addenda of the ASME Code the non-temper bead welding procedure is qualified, what filler weld material is used, and discussions on the welding process), the staff has determined that the licensee applied the new partial penetration attachment weld between the new Alloy 690 nozzle and the weld pad utilizing a manual GTAW technique and a welding procedure specification qualified in accordance with NB-4000 of the 1989 Edition and no Addenda of the ASME Code,Section III, and the ASME Code,Section IX, requirements. The Alloy 52M (ERNiCrFe-7A) weld filler material conforms to the requirements of Part C SFA 5.14 of the 2004 Edition through 2006 Addenda of the ASME Code,Section II, and NB 2400 of the 1989 Edition and no Addenda of the ASME Code,Section III. The new partial penetration attachment weld was examined progressively by PT according to the requirements of NB-5245 of the 1989 Edition and no Addenda of the ASME Code,Section III.

- 10 Based on the licensee's response to the NRC staff's request to (a) clarify whether the weld pad is a metal plate welded to the 00 surface of pressurizer or a pad fabricated by depositing weld layers at the penetration on the 00 surface of pressurizer, and (b) provide the dimensions (e.g.,

length and width) of the weld pad, the staff has determined that the weld pad installed by the licensee to the 00 of the pressurizer is 100 percent deposited weld metal, built up by installing multiple layers of weld passes. Installing the Alloy 52M weld pad allows welding of the Alloy 690 nozzle to the Alloy 52M weld pad without the need for post-weld heat treatment of the attachment weld. The installed weld pad is a square shape with as-built dimensions at the full thickness of 3.375 inches by 3.3125 inches, and as built dimensions at the interface with the carbon steel of 4.6875 inches by 4.6875 inches. The as-built thickness of the pad is 0.5875 inches. The maximum area of the weld pad adjoining the surface of the pressurizer is less than 100 square inches and complies with paragraph 1.0(a) of ASME Code Case N-638-1 requirements.

From the licensee's response to the issues such as extent of surface area and volume examined and UT qualifications, the NRC staff has determined that the licensee performed the ASME Code Case N-638-1 required NOE examinations, prior to welding, of the area to be welded and a band around the area of at least 1 'Y2 times the component thickness or 5 inches, whichever is less. Figure 2 below shows the schematic diagram of the area and volume examined by the surface (PT) and volumetric (UT) examinations. The PT examinations of the base material of the weld pad footprint and 5 inches around the weld pad location include the examination area E-F-G-H as shown in Figure 2. The UT examinations of base material of the weld pad footprint and 5 inches around the pad location using the phased array laminar examination technique (-150 to +150 sectorial scan) include the examination volume A-B-C-O E-F-G-H as shown in Figure 2. The UT examination procedure was qualified by demonstration to the Authorized Nuclear Inservice Inspector and the licensee's NOE Level III using representative samples which contain the construction type flaws (the condition required by the NRC in RG 1.147, Revision 15, for use of ASME Code Case N-638-1).

- 11

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Figure 2. Licensee schematic diagram of the NDE examinations area and volume (weld pad and base metal area around the weld pad).

The licensee further stated that the visual examinations of the penetration bore on nozzle RC-1001 NB was performed after a portion of the original nozzle was removed by the machining operations. The machining operations performed did not involve defect removal, however, they were performed to (a) partially remove the existing nozzle and (b) reestablish the bore diameter to facilitate installation of the new half-nozzle in accordance with the ASME Code,Section III, design requirements. NB-4121.3 of the 1989 Edition and no Addenda of the ASME Code,Section III, states that the component surfaces requiring machining shall be reexamined by the magnetic particle or PT examinations when (a) a surface examination was originally required by NB-2500 and (b) the amount of material removed from the surface exceeds the lesser of 10 percent of the minimum required thickness or 1/8 inch, whichever is less. The licensee stated that the amount of material removed during the machining operation of RC-1001 NB nozzle bore was approximately 0.040 inch which is significantly below the NB 4121.3 thickness criteria. Prior to installing the new Alloy 690 nozzle, the penetration bore was cleaned by a combination of air nozzle vacuum and wiped down with a damp cloth.

Based on the licensee's response on post-weld inspection of the weld pad and associated welding including the acceptance criteria and the UT qualification, the NRC staff has determined that the licensee performed the post-weld NDE examinations of the weld pad, the base metal area around the weld pad, and the partial penetration attachment weld. The weld pad and the base metal area around the weld pad were examined (a) by the volumetric examinations using the aforementioned UT procedure and qualification and (b) by the surface examinations using

- 12 PT as described above. According to the condition required by the NRC in RG 1.147, Revision 15, for use of ASME Code Case N-638-1, the ultrasonic acceptance criteria of NB-5330 of the 1998 Edition through 2000 Addenda of the ASME Code, Section ",, applies to all flaws identified within the repaired volume. The new attachment weld was examined by surface examination using PT in accordance with NB-5245 of the 1989 Edition and no Addenda of the ASME Code,Section III. The acceptance criteria of NB-5350 of the 1989 Edition through 1989 Addenda of the ASME Code,Section III, and the 1992 Edition with no Addenda of the ASME Code,Section III, requires surface examination of the new attachment weld.

In its supplement dated April 12, 2010, the licensee stated that there is a gap with a minimum separation of 0.125 inch between the replacement nozzle and the remnant of original nozzle RC-1001 AlB. This gap will allow the borated primary coolant water to come in contact with the carbon steel in the area of the annulus between the new Alloy 690 nozzle and the pressurizer carbon-steel base metal. The licensee also stated that the potential for carbon-steel degradation due to contact with the primary coolant water and the corrosion rates have previously been evaluated for similar modifications. As an example of actual industry experience, San Onofre Nuclear Generating Station repaired a hot-leg nozzle in 1993 using the half-nozzle repair technique that included a gap between the new nozzle and the remnant of original nozzle which exposed the carbon-steel base metal to the primary coolant. The new nozzle at San Onofre was removed after 5 years to inspect the carbon steel for corrosion and determined that the corrosion rate was limited to 0.001 - 0.002 inches per year. Another example includes the nozzle from the ANO-1 pressurizer penetration that was also repaired using the half-nozzle repair technique during the ANO-1 1R9 refueling outage (almost 20 years ago). This nozzle also included a gap between the new nozzle and the remnant of original nozzle which exposed the carbon-steel base metal to the borated primary coolant. During the current ANO-1 refueling outage (1 R22), the licensee removed this nozzle and inspected for carbon-steel base metal corrosion. It was determined that after nearly 20 years in service, there was no measurable corrosion of the exposed carbon steel. Based on these calculations and the actual results from industry experience, only minimal corrosion of the carbon-steel base metal is expected to occur during the remaining life of the ANO-1 plant.

Regarding the lSI of the repaired nozzle (e.g., inspection method and frequency, and the acceptance criteria), the licensee stated that the pressure retaining weld on the repair instrumentation nozzle RC-1001 AlB will no longer contain Alloy 600/82/182 materials.

Therefore, the requirements of 10 CFR 50.55a(g)(6)(ii)(E) to implement ASME Code Case N-722 will no longer be applicable. The repaired nozzle RC-1001 AlB will be examined in accordance with the 2001 Edition through 2003 Addenda of the ASME Code,Section XI, Table IWB-2500-1, Examination Category B-P, Item No. B15.10. Additionally, the licensee confirmed that all instrumentation nozzles on the ANO-1 pressurizer were examined in accordance with the requirements of 10 CFR 50.55a(g)(6)(ii)(E) during the current ANO-1 spring 2010 refueling outage 1R22. The regulations in 10 CFR 50.55a(g)(6)(ii)(E) require that the licensee augment its lSI program by implementing ASME Code Case N-722 SUbject to conditions specified in paragraphs (2) through (4) of 10 CFR 50.55a(g)(6)(ii)(E). As a result of the examinations, one penetration nozzle, RC-1001 AlB, was found to be leaking.

By letter dated April 12, 2010, the licensee clarified that at the start of the current ANO-1 refueling outage 1R22, the only unmitigated Alloy 600/82/182 penetrations were the nine instrumentation penetrations. All of the other ANO-1 pressurizer nozzles that had

- 13 Alloy 600/82/182 DM butt welds had been mitigated by full structural weld overlays. These nine pressurizer instrumentation nozzles consist of:

The 1.5 inch thermowell nozzle attached to the pressurizer by a partial penetration weld on the ID surface of the pressurizer.

Six 1-inch nozzles (level taps, spares, vent and sample tap, sample tap) attached to the pressurizer by a partial penetration weld on the ID surface of the pressurizer.

Two previously repaired nozzles (1 inch thermowell (TE-1002A1B) and 1 inch level tap (RC-1 001 AlB)) had OD diameter pads replaced with resistant material and the nozzles were also replaced using resistant material. It should be noted that TE-1002A1B is one nozzle and RC-1001A1B is one separate nozzle.

Once these nine penetrations are mitigated at refueling outage 1R22, there will be no unmitigated Alloy 600/82/182 penetrations left on the ANO-1 pressurizer.

The licensee further stated that a relief is not required for the eight pressurizer nozzles that have undergone the preemptive half-nozzle modifications because none of the eight nozzles exhibited any evidence of a defect (e.g., boric acid leakage or build-up) in the attachment welds or nozzle at the time of installation. The NRC staff notes that the preemptive half-nozzle modifications are not repairs and does not fall under the jurisdiction of IWA-4340 of ASME Code,Section XI, since they are not being installed to mitigate a defect. In addition, the licensee stated that for these eight pressurizer nozzles, the surface and UT examinations are performed according to paragraph 4.0(b) of ASME Code Case N-638-1 which is at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the completed weld has reached ambient temperature. Also, these eight nozzles are not part of the subject relief request.

Proposed 48 Hours Hold for Ambient Temperature Temper Bead Welding The licensee's proposed alternative to the requirements in paragraph 4.0(b) of ASME Code Case N-638-1 is to perform the NDE (i.e., surface and UT) examinations at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the third weld layer is completed. Whereas paragraph 4.0(b) of ASME Code Case N-638-1 provision requires the surface and UT examinations to be performed when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The 48-hour delay between welding completion and cooling to ambient temperature and the final NDE examinations of the fully welded component is provided so that any delayed hydrogen cracking or cold cracking that may occur can take place prior to the final NDE of the temper bead weld and surrounding area.

The NRC staff notes that Electric Power Research Institute (EPRI) in Technical Report 1013558, "Temperbead Welding Applications, 48-Hour Hold Requirements for Ambient Temperature Temperbead Welding," dated December 2006 (ADAMS Accession No. ML070670060), has documented the industry and regulatory technical concerns and the technical bases for changing the requirements for the 48-hour delay. EPRI evaluated two primary degradation mechanisms of cold cracking of high-restraint geometries (weld shrinkage induced) and hydrogen-assisted cracking (hydrogen-delayed cracking) that are of concern for low-alloy steel welding at ambient temperatures. EPRI concluded that (a) there appears to be

- 14 no technical basis for waiting the 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after cooling to ambient temperature before beginning the NDE of the completed weld and (b) even in the very unlikely case that cracking was to occur, it would not be structurally significant. In addition, the EPRI report stated that over 20 weld overlays and 100 repairs have been performed using temper bead techniques on low-alloy steel components over the last 20 years. During this time, there has never been an indication of hydrogen cracking by the NDE performed after the 48-hour hold or by subsequent lSI.

The NRC staff also notes that the NRC recently approved the use of the 48-hour hold time after the third weld layer for Davis-Besse Nuclear Power Station, Unit 1, in a letter dated January 21, 2010 (ADAMS Accession Number ML100080573). Therefore, the staff accepts the licensee's proposed alternative to the requirements in paragraph 4.0(b) of ASME Code Case N-638-1, which is to perform the NDE (i.e., surface and UT) examinations at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the third weld layer is completed.

Proposed Flaw Evaluation The NRC staff has reviewed the three proprietary flaw evaluation reports, ANO-34Q-326, Revision 1, ANO-43Q-301, Revision 2, and ANO-34Q-330, Revision 0, submitted to the NRC with RR AN01-R&R-013. The licensee's flaw evaluation used an initial maximum postulated flaw as an alternative to:

1)

The ASME Code,Section XI, IWB-3420 and IWB-3610(b), requirements which is to perform the NDE examinations to characterize the flaw in the instrumentation nozzle RC-1001 AlB.

2)

The ASME Code,Section XI, IWB-3142.4, requirements which is to perform the subsequent NDE examinations to assess the potential growth of the flaw in the instrumentation nozzle RC-1001 AlB.

The licensee proposed the flaw evaluation as an alternative to the above two requirements because there are no qualified and demonstrated volumetric examination techniques currently available to accurately size and characterize the flaw left in-place in the instrumentation nozzle RC-1001 AlB. The NRC staff notes that the assumptions of the ASME Code,Section XI, IWB-3600, are that cracks are fully characterized in order to compare the calculated parameters to the allowable parameters addressed in IWB-3500.

The licensee stated that because the original nozzle RC-1001 AlB J-groove weld has not been and will not be volumetrically examined, it is assumed to have an unacceptable flaw. In the flaw evaluation, the maximum postulated flaw is conservatively assumed, e.g., the entire original J-groove weld and the cladding are initially cracked, extending to the J-groove and pressurizer interface, and through-wall in the remnant of the original nozzle RC-1001 AlB base metal. The postulated flaw is assumed to be oriented in the axial direction because the hoop stresses are typically higher than the axial stresses. The postulated flaw oriented in the circumferential direction is not analyzed because the dominant applied stress in the pressurizer vessel wall is in the hoop direction that drive axially oriented flaw growth. The NRC staff notes that this is consistent with the approach taken for all small bore nozzle repairs including the reactor pressure vessel top head control rod drive mechanism repairs which the axial flaw is assumed.

- 15 By letter dated January 6, 2011, the licensee responded to the NRC staff question regarding the use of buttering between the J-groove attachment weld and the pressurizer carbon-steel shell at the nozzle location. The licensee stated that from the review of the vendor documentation and plant drawings a weld butter was not used between the J-groove attachment weld and the pressurizer carbon-steel shell at the nozzle location in the construction of the welds.

The licensee analyzed three separate as-modeled postulated flaws. Flaw 1 is modeled as "initial flaw," Flaw 2 is modeled as "extended flaw," and Flaw 3 is modeled as "final flaw." The licensee included the residual stresses in its flaw evaluation, along with operating pressure and thermal loads, and the full safety factors for normal operating conditions. The stress intensity factors along the crack front of each flaw are calculated for pressure, residual stress, steady stress thermal conditions, heat-up, cool-down with insurge, cool-down with high-pressure injection test (HPI), and loss-of-coolant accident (LOCA) transient conditions.

The NRC staff's review of the licensee's flaw evaluation, documented in the ANO-34Q-326, Revision 1, report (non-proprietary version in ADAMS Accession No. ML101050370), indicates that the calculated stress intensity factor "K" values using the principles of LEFM are within the ASME Code,Section XI, allowable limits for the heat-up and the LOCA transients. However, the stress intensity factor "K" values exceed allowable limits for the steady state conditions with maximum pressure, the cool-down with insurge, and the cool-down with HPI transients. The staff notes that the licensee performed flaw evaluation based upon the principles of EPFM to take advantage of the ductility of the pressurizer material in the upper shelf temperature region for the cases the allowable limits exceeded.

The NRC staff's review of the licensee's flaw evaluation based upon the principles of EPFM, documented in the proprietary report ANO-43Q-301, Revision 2, indicates that there exist large margin to instability for both the penetration bore and the clad and vessel (clad/vessel) interface flaw locations. Therefore, it is concluded from the fracture mechanics results that the potential remnant cracking is acceptable in accordance with the flaw evaluation principles of the ASME Code,Section XI.

The NRC staff's review of the licensee's fatigue crack growth analysis, documented in ANO-34Q-330, Revision 0, (non-proprietary version in ADAMS Accession No. ML101050371),

indicates that the maximum end-of-evaluation period crack growth is 0.274 inch at the penetration bore and 0.216 inch at the pressurizer base metal and clad interface location for the 60-year plant operating period. For this analysis, the licensee implemented the methodology of A-4300 of Appendix A of the 2001 Edition through 2003 Addenda of the ASME Code,Section XI, at the bounding locations for 60 years of crack growth. The licensee stated that the EPFM analysis was performed for the cases where the allowable stress intensity factor "K" limits were exceeded in the LEFM analysis to take advantage of the ductility of the pressurizer material in the upper shelf temperature region. The staff notes that the fatigue crack growth analysis shows the postulated remnant flaw in the pressurizer nozzle RC-1 001 AlB is acceptable for a 60-year plant operating period.

As for the locations of the crack tip of three postulated flaws (Flaw 1, 2, and 3) as well as the flaw orientation, the licensee stated that the crack tip for Flaw 1 is at the interface between the J-groove weld and carbon-steel pressurizer vessel material. Flaw 1 is modeled to encompass

- 16 the entire face of the J-groove weld, the adjacent remnant nozzle RC-1001 NB wall, and the adjacent cladding. The crack tips for Flaw 2 and Flaw 3 follow the shape of Flaw 1, encompass the remnant nozzle RC-1001 NB wall, and penetrate a distance into the carbon-steel pressurizer base metal. Along the nozzle RC-1001 NB bore, Flaw 2 penetrates 0.375 inch into the carbon steel, and Flaw 3 penetrates 0.696 inch into the carbon steel, as measured from the J-groove weld and carbon-steel interface. Along the interface between the cladding and carbon steel, Flaw 2 penetrates 0.388 inch into the carbon steel, and Flaw 3 penetrates 0.721 inch into the carbon steel, as measured from the J-groove weld and carbon-steel interface. Flaws 1, 2, and 3 are in the axial radial plane with respect to the pressurizer nozzle RC-1001 NB, and are oriented in the axial radial plane of the pressurizer shell. Additionally, the licensee clarified that the flaw sizes postulated in the analysis are consistent with the dimensions of the original pressurizer nozzle RC-1001 NB. The remnant nozzle RC-1001 NB has nominal 00 of 1.455 inches, nominal 10 of 0.815 inch, and wall thickness of 0.32 inch. The nominal thickness of cladding is 3/16 inch. Further, the licensee stated that the J-groove length measured from the J-groove and nozzle interface along the free surface of the cladding on the 10 of the pressurizer vessel in the plane that is perpendicular to the axis of the pressurizer and contains the axis of the penetration is 0.900 inch. The J-groove length measured from the 10 surface of the vessel along the penetration nozzle bore at the plane formed by the penetration axis and the pressurizer vessel axis is 0.938 inch. In its supplement dated April 12, 2010, the licensee further clarified that the dimensions shown in Figure 1 of the ANO-34Q-326, Revision 1, report are measured from the interface between the nozzle 00 surface and J-groove weld to a point on the free surface of the cladding on the 10 surface of the pressurizer vessel. These dimensions are appropriate for describing the model geometry. However, for crack growth analysis, the stress intensity factor at the crack tip in the carbon steel, not in the cladding, is of interest. The clad and vessel (clad/vessel) interface dimensions shown in Table 1 of the ANO 43Q-301, Revision 2, report and in table 2 of the ANO-34Q-330, Revision 0, report (proprietary) are representative of locations of the crack tip in the carbon steel, and are measured from the interface between the nozzle 00 surface and the J-groove weld to a point along the interface between the cladding and the carbon-steel vessel material. The two sets of dimensions are correct, but measured at different end points.

Finally, in response to the request from the staff to explain why the total stress intensity factor "Ktotat" for the penetration bore location shown in table 1 of ANO-43Q-301, Revision 2, report (proprietary) is progressively lower from Flaw 1 to Flaw 3, whereas the total stress intensity factor "Ktotal" for the clad/vessel interface location is progressively higher from Flaw 1 to Flaw 3, and also to discuss why the stress intensity factor "KIt" due to thermal and residual stresses for the penetration bore location is gradually lower as the flaw size increases, the licensee stated that the stress intensity factor "KIP" due to pressure increases progressively with larger flaw sizes which is expected at the penetration bore and the clad and vessel (clad/vessel) interface, as shown in table 1 of the ANO-43Q-301, Revision 2, report (proprietary). However, at the bore region, the residual stress effects decrease as the crack tip moves deeper into the vessel thickness from Flaw 1 to Flaw 3, as shown in table 1 of the ANO-43Q-301, Revision 2, report (proprietary). Therefore, this effect accounts for the downward trend of the total stress intensity factor "Ktotal" in the penetration bore region as the flaw gets larger. The NRC staff notes that the high value of the stress intensity factor "Kit" due to residual stress at the bore for Flaw 1 is the result of the triple point effect (Le., the intersection point between the weld, carbon steel, and nozzle materials having different cooling rates). At the clad interface points which are at a constant depth from the 10 surface of the vessel, the stress intensity factor "Kit" due to residual

- 17 stress has little variation. The NRC staff concludes that the variation in stress intensity factor values, as explained by the licensee, is acceptable.

In its review of the licensee's supplement dated April 12, 2020, the staff has determined that the licensee did not use outsurge transient because the pressurizer nozzle RC-1001 NB is located in the steam space above the RCS level, therefore, the insurge and outsurge transients are not applicable. However, for evaluating the cool-down transient a composite transient (a portion of which includes insurge) was conservatively used by the licensee for the flaw evaluation of nozzle RC-1001 NB. In addition, the licensee confirmed that the stresses due to the mechanical loads such as seismic loads are negligible and are not included in the flaw evaluation.

The NRC staff concludes that the licensee's flaw evaluation, as explained above, is acceptable because a conservative initial crack size is assumed and the flaw evaluation has demonstrated that the assumed worst-case crack size will not grow to an unacceptable depth into the carbon steel pressurizer vessel material over the life of the repair. Furthermore, the long-term impact on exposed carbon-steel material to reactor coolant is negligible because operating history of domestic power plants includes many cases where localized exposure of carbon steel to reactor coolant has been confirmed to be very low. As a result, the staff concludes that the licensee's proposed alternative to the requirements of the ASIVIE Code,Section XI, IWB-3420, IWB 3610(b), and IWB-3142.4, provides an acceptable level of quality and safety.

5.0 CONCLUSION

On the basis of review and evaluation of the licensee's submittals, the NRC staff concludes that the proposed alternatives would provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the staff authorizes the use of RR AN01-R&R-013 for the repair of the instrumentation nozzle RC-1001 NB of the ANO-1 pressurizer. The relief is authorized for the duration of the ANO-1 spring 2010 refueling outage 1R22 to support the repair of the pressurizer instrumentation nozzle RC-1001 NB.

All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.

Principal Contributors: A. Rezai J. Tsao Date: January 10, 2011

- 2 All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.

The bases for the NRC staff's conclusions are contained in the enclosed Safety Evaluation. If you have any questions, please contact Kaly N. Kalyanam at (301) 415-1480 or by email at kaly. kalyanam@nrc.gov.

Sincerely, IRA!

Michael 1. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-313

Enclosure:

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