ML20309B020

Proposed Relief Request Associated with N-16A Reactor Pressure Vessel Instrument Nozzle Repairs

ML20309B020
Person / Time
Site:	Peach Bottom
Issue date:	11/04/2020
From:	David Helker Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML20309B020 (16)

Text

200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.55a November 4, 2020 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station, Unit 2 Renewed Facility Operating License No. DPR-44 NRC Docket No. 50-277

Subject:

Proposed Relief Request Associated with N-16A Reactor Pressure Vessel Instrument Nozzle Repairs In accordance with 10 CFR 50.55a, "Codes and standards," paragraph (z)(2), Exelon Generation Company, LLC (EGC) requests approval of the attached relief request associated with the repair of a 2-inch instrument line nozzle (N-16A) on the Reactor Pressure Vessel (RPV). This relief request, contained in Attachment 2, applies to one operating cycle for the fifth 10-year Inservice Inspection (ISI) interval. The fifth 10-year ISI interval for Peach Bottom Atomic Power Station (PBAPS), Unit 2 began on January 1, 2019 and will conclude December 31, 2028. The fifth 10-year ISI interval complies with the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, 2013 Edition.

On October 29, 2020, PBAPS, Unit 2 performed a Class 1 system leakage test in accordance with IWB-5210(a). Leakage was observed between the RPV wall and the N-16A 2-inch instrument line nozzle. EGC intends to repair the nozzle by installing a weld pad using Ambient Temperature Temper Bead (ATTB) welding in accordance with ASME Code Case N-638-7, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1" and installing a half nozzle to the weld pad.

In support of the flaw evaluation and applicable acceptance criteria, ASME Code Paragraphs IWB-3420 and IWB-3600 require characterization of the flaw in the penetration.

Currently, there is not a Performance Demonstration Initiative (PDI) qualified technique to perform volumetric Non-Destructive Examination (NDE) of the partial penetration weld in this configuration that can be used to accurately characterize the location, orientation, or size of a flaw in the weld. As an alternative to performing the NDE required to characterize the flaw in instrument penetration N-16A, EGC is proposing to analyze a maximum postulated flaw that bounds the range of flaw sizes that could exist in the original J-groove weld and nozzle, as discussed in Attachment 2.

In accordance with 10 CFR 50.55a(z)(2), EGC proposes the following alternative on the basis that performing a Code required repair results in a hardship without a compensating increase in quality and safety. EGC concludes that the proposed alternative provides an acceptable level of quality and safety.

Peach Bottom Atomic Power Station, Unit 2 Proposed Relief Request Associated with N-16A RPV Instrument Nozzle Repairs November 4, 2020 Page 2 EGC requests approval of the proposed alternative in order to support the return to service from the current PBAPS, Unit 2 refueling outage (P2R23). EGC is requesting approval of this relief request by November 7, 2020. Relief is requested for the duration of PBAPS, Unit 2 Cycle 24 which is currently expected to conclude in the Fall of 2022. contains a summary of commitments.

If you have any questions or require additional information, please contact Tom Loomis at 610-765-5510.

Respectfully, David P. Helker Sr. Manager - Licensing & Regulatory Affairs Exelon Generation Company, LLC Attachments: 1) Summary of Commitments

2) Relief Request I5R-14 cc: USNRC Region I, Regional Administrator USNRC Senior Resident Inspector, PBAPS USNRC Project Manager, PBAPS W. DeHass, Pennsylvania Bureau of Radiation Protection

Peach Bottom Atomic Power Station, Unit 2 Proposed Relief Request Associated with N-16A RPV Instrument Nozzle Repairs November 4, 2020 Page 3 bcc: Senior Vice President - Mid-Atlantic Operations Vice President - Nuclear Security, Licensing and Regulatory Site Vice President - PBAPS Plant Manager - PBAPS Director, Operations -PBAPS Director, Site Engineering - PBAPS Director, Site Training - PBAPS Manager, Regulatory Assurance - PBAPS Director, Licensing - KSQ Sr. Manager, Licensing - KSQ PA DEP BRP Inspector - PBAPS Commitment Coordinator - KSQ B. Watkins - PSEG

ATTACHMENT 1 Summary of Commitments

Summary of Commitments Page 1 of 1 Summary of Commitments The following table identifies commitments made in this document. (Any other actions discussed in the submittal represent intended or planned actions. They are described to the NRC for the NRC's information and are not regulatory commitments.)

COMMITMENT TYPE COMMITTED DATE COMMITMENT One-Time Action Programmatic OR "OUTAGE" (Yes/No) (Yes/No)

The final one-cycle Within 14 days Yes No flaw analytical following the end of evaluation, evaluation the current PBAPS, of repair, and Unit 2 refueling corrosion evaluation outage.

will be submitted within 14 days following the end of the current Peach Bottom Atomic Power Station (PBAPS), Unit 2 refueling outage.

ATTACHMENT 2 Peach Bottom Atomic Power Station, Unit 2 Proposed Relief Request Associated with N-16A Reactor Pressure Vessel Instrument Nozzle Repairs RELIEF REQUEST I5R-14

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1. ASME CODE COMPONENTS AFFECTED Code Class: 1

Reference:

IWB-2500, Table IWB-2500-1 Exam Category: B-P Item Number: B15.10

Description:

Reactor Pressure Vessel (RPV) Instrument Nozzle inch Nominal Pipe Size Component Number: N-16A

2. APPLICABLE CODE EDITION AND ADDENDA The current edition for the Inservice Inspection (ISI) interval is the American Society of Mechanical Engineers (ASME) Code,Section XI, 2013 Edition. The code of construction for the RPV is the ASME Code Section III, 1965 Edition with Addenda to and including Winter 1965 Addenda.

3. APPLICABLE CODE REQUIREMENTS Flaw Removal IWA-4412 states "Defect removal shall be accomplished in accordance with the requirements of IWA-4420."

IWA-4611.1(a) states "Defects shall be removed in accordance with IWA-4422.1. A defect is considered removed when it has been reduced to an acceptable size."

IWA-5250(a)(3) states "Components requiring corrective action shall have repair/replacement activities performed in accordance with IWA-4000 or corrective measures performed where the relevant condition can be corrected without a repair/replacement activity."

N-528 of Section Ill, 1965 Edition with Addenda to and including Winter 1965, requires repair of weld defects including removal of defects detected by leakage tests.

Flaw Evaluation IWB-3142.1(b) states "A component whose visual examination detects the relevant conditions described in the standards of Table IWB-3410-1 shall be unacceptable for continued service, unless such components meet the requirements of IWB-3142.2, IWB-3142.3, or IWB-3142.4."

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IWA-3300(a) states, in part, "Flaws detected by the preservice and inservice examinations shall be sized ... "

IWA-3300(b) states, in part, "Flaws shall be characterized in accordance with IWA-3310 through IWA-3390, as applicable ... "

IWB-3420 states "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."

IWB-3522.1 states, in part, "A component whose visual examination (IWA-5240) detects any of the following relevant conditions shall meet IWB-3142 and IWA-5250 prior to continued service ... "

IWB-3610(b) states, in part, "For purposes of evaluation by analysis, the depth of flaws in clad components shall be defined in accordance with Fig. IWB-3610-1 ... "

The implementing reply of N-749 states It is the opinion of the Committee that, in lieu of IWB-3610 and IWB-3620, flaws in ferritic steel components operating in the upper shelf temperature range may be evaluated using the following acceptance criteria. The methods and criteria of N-749 are based on the methods of elastic-plastic fracture mechanics (EPFM).

4. REASON FOR REQUEST Following a routine refueling outage on October 29, 2020, leakage was observed between the RPV wall and the N-16A, a 2-inch water level instrument line nozzle, during the pre-startup system leakage testing of the Peach Bottom Atomic Power Station (PBAPS), Unit 2 RPV (See ).

As a result of the leakage indication at instrument nozzle N-16A, Exelon Generation Company, LLC (EGC) is planning to partially replace the existing nozzle assembly with a nozzle that is resistant to Intergranular Stress Corrosion Cracking (IGSCC).

EGC is proposing to apply a welded pad on the Outer Diameter (OD) of the RPV using IGSCC resistant nickel Alloy 52M (ERNiCrFe-7A) filler metal. The new weld pad will be welded using the machine Gas Tungsten Arc Welding (GTAW) Ambient Temperature Temper Bead (ATTB) welding technique. EGC is proposing to attach an IGSCC resistant nozzle to the new weld pad with a partial penetration weld using a non-temper bead manual welding technique and IGSCC resistant nickel Alloy 52M filler metal.

The original partial penetration attachment weld and a remnant of the original nozzle will remain in place. A flaw evaluation will demonstrate the acceptability of leaving the original partial penetration attachment weld, with a maximum postulated flaw, in place for one cycle (see "Flaw Analytical Evaluation" below). IWA-4412 and IWA-4611 contain requirements for the removal of, or reduction in size of defects. The defect on N-16A will not be removed; therefore, relief is sought from these requirements.

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IWB-3400 and IWB-3600 were written with the expectation that volumetric Non-Destructive Examination (NDE) techniques such as Ultrasonic Testing (UT) would be used to determine the flaw size and shape. In support of the flaw evaluation, the ASME Code paragraphs IWB-3420 and IWB-3610(b) require characterization of the flaw in the leaking nozzle. Although demonstrated, there is not a Performance Demonstration Initiative (PDI) qualified technique to perform NDE of the partial penetration weld in this configuration that can be used to accurately characterize the location, orientation, or size of a flaw in the weld.

The flaw evaluation methods presented in IWB-3610 and Appendix A of Section XI are based on Linear Elastic Fracture Mechanics (LEFM) methods. Code Case N-749 was developed to provide criteria for the use of Elastic-Plastic Fracture Mechanics (EPFM) methods as acceptable alternatives to the LEFM methods currently contained in IWB-3610 and Appendix A, for operating conditions where ferritic vessel materials are operating on the material toughness upper shelf. This Code Case is Conditionally Accepted in Revision 19 of NRC Regulatory Guide 1.147.

NB-4620 requires all welds to be post-weld heat treated except as otherwise permitted in NB-4622.7. EGC is proposing to install a welded pad using ATTB welding in accordance with ASME Code Case N-638-7. The NRC has conditionally approved ASME Code Case N-638-7 to allow ATTB welding of dissimilar materials.

5. PROPOSED ALTERNATIVE AND BASIS FOR USE In accordance with 10 CFR 50.55a, "Codes and standards," paragraph (z)(2), EGC proposes the following alternative to the requirements specified in Section 3 above on the basis that performing a Code required repair results in a hardship without a compensating increase in quality and safety. A repair in accordance with the ASME Code, which would remove the flaw from the inner portion of the vessel, would require a full core offload to access the repair location, result in significant risk associated with the inclusion of loose parts and foreign material, and result in significant increase in radiological exposure. These areas of concern result in a significant hardship over the proposed modification.

In lieu of the ASME Code compliant repair, the following alternatives are proposed:

As an alternative to flaw removal or reduction in size to meet the applicable acceptance standards per IWA-4412 and IWA-4611, EGC proposes to implement an OD repair of the RPV instrument nozzle N-16A utilizing an OD weld pad and half nozzle as described in the repair of nozzle penetration section below.

As an alternative to performing the NDE required to characterize the flaw under IWB-3420 and IWB-3610(b) in penetration N-16A, EGC proposes analyzing a maximum postulated flaw that bounds the range of flaw sizes that could exist in the original J-groove weld and nozzle.

As an alternative to NB-4620, EGC is proposing to install a welded pad using ATTB welding in accordance with ASME Code Case N-638-7. The NRC has conditionally approved ASME Code Case N-638-7 to allow ATTB welding of dissimilar materials.

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Basis for Use A. Background The PBAPS, Unit 2 RPV is manufactured from SA-302, Grade B, modified by ASME Code Case 1339 Paragraph 1, steel that is clad with stainless steel. The reactor vessel water instrument nozzles are fabricated with Alloy 600 material (SB-166). See Enclosure 1 for a sketch of N-16A.

During refueling outage P2R23 (Fall 2020), EGC discovered leakage between the RPV wall and the N-16A 2-inch instrument line nozzle. Visual examination detected active leakage at the nozzle interface (annular gap) with the RPV OD during the Class 1 system leakage test. EGC intends to repair the N-16A based on the discussion provided in the following sections.

B. Cause of Leakage After discovery of the leak from the RPV OD, an EVT-1 visual examination was performed of the N-16A wetted surfaces from the inside diameter (ID) of the RPV with a color camera. The internal visual examination did identify an apparent surface crack approximately 1.15 in length at the 6 oclock position extending radially from the inside edge of the Alloy 600 nozzle into the Alloy 182 J-groove weld. This surface cracks location is consistent with the location of leakage observed on the exterior of the RPV at the N-16A nozzle during the bare metal visual leakage inspection (VT-2).

After completion of the internal visual exam, a nozzle plug with a face plate seal was installed in the inside diameter of the N-16A nozzle to facilitate the half nozzle repair (see Enclosure 2).

Following plug installation, no leakage was observed coming through or around the nozzle and a demonstrated volumetric ultrasonic examination (UT) was performed from the RPV exterior surface for informational purposes (see "Examination of the J-groove Weld" below).

During the UT examination, a single planar radial-axial indication was detected and noted to be present throughout the entire J-groove cross sectional area, but no penetration into the ferritic vessel base metal was detected. The ultrasonic indication was located at the nozzle 6 oclock position, which correlates to the reported flaw location from the visual examinations. In addition, no circumferential indications in either the J-groove weld or adjacent low alloy steel base material were detected. The ultrasonic inspection report also noted that the weld image showed the J-groove weld at a larger depth into the RPV base material than the 9/16 inch minimum specified in the design drawing. This could be indicative that a repair(s) was made to this weld during fabrication, though no fabrication records have been found to date that confirm this possibility.

The combined and spatially correlated internal and external visual and ultrasonic results suggest that the most probable cause of the external leakage observed coming from the N-16A nozzle is that a single radial-axial oriented IGSCC flaw initiated in the J-groove weld and then propagated through the J-groove weld until it reached a depth where a leak path in the annulus between the nozzle and reactor vessel penetration existed.

A search of fabrication records for the N-16A nozzle and J-groove weld, to date, has not identified any anomalous material conditions or process deviations that could have contributed

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(Page 5 of 10) to the IGSCC indication observed; however, it is possible that subsurface fabrication defects could have existed to further propagate the flaw through the J-groove weld.

C. Extent of Condition The leakage between the RPV wall and the N-16A instrument nozzle was identified during the Class 1 system leakage test. As part of the Class 1 system leakage test, a bare metal VT-2 was performed on the five other additional RPV instrument nozzles (N-11A, N-11B, N-12A, N-12B, and N-16B), and there was no evidence of leakage on any of the nozzles during examination.

D. Examination of the J-groove Weld A visual examination was performed from the RPV ID using a color camera at the N-16A location. The exam volume encompassed the Alloy 182 J-groove weld, outer portions of the Alloy 600 nozzle bore, and the inside surface of the RPV immediately adjacent to the N-16A location. The visual examination was performed before and after the area was hydrolazed. The visual examination revealed a surface crack at the 6 oclock position beginning on the vertical nozzle face and extending down the wall approximately 1.15 inches. The indication does not appear to extend beyond the radius into the horizontal portion of the nozzle bore.

A volumetric (UT) examination was performed on the N-16A J-groove weld from the RPV OD in accordance with BWRVIP-03, Rev. 19. This examination was conducted to supplement visual examinations performed from the RPV ID. This volumetric examination technique has been demonstrated to provide crack detection, length sizing, and depth sizing of flaws that initiate within the partial penetration J-groove weld material and to detect planar flaw indications in the low alloy vessel material, but has not been qualified in accordance with ASME Section XI, Appendix VIII. The exam volume included the J-groove weld and the RPV low alloy steel interface. The UT exam identified one flaw indication in the J-groove weld material recorded in both the clockwise and counterclockwise scan directions. The position of the flaw was in the same area as recorded during the visual examination from the RPV ID. No reflectors extending into the RPV base material were observed; thus, this UT exam provides reasonable confidence that the flaw has not propagated into the RPV low alloy steel.

E. Flaw Analytical Evaluation A flaw evaluation for one cycle of operation in accordance with IWB-3610 (LEFM method), as well as per Code Case N-749 (EPFM method) will be performed. Code Case N-749 will be used with all applicable conditions stated in Table 2 of Reg. Guide 1.147, Revision 19. The flaw evaluation will be based on the following:

Conservatively assume that the entire as-left Alloy 182 J-groove weld is initially flawed;

- Both the circumferential and radial-axial flaw orientations will be considered. The analysis will be performed for the worst case flaw orientation based on the higher stresses perpendicular to the orientation of the flaw.

The postulated initial flaw size geometry assumes that the Alloy 182 J-groove weld is completely cracked, no credit is taken for any remaining life of this material, and flaw growth in this material is not required;

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The maximum postulated flaw size will be evaluated by further extending the flaw into the low alloy steel (LAS) RPV shell to account for the appropriate stress corrosion crack growth rate, using BWRVIP-60-A, over the next 2-year fuel cycle; Weld residual stresses will conservatively be based on room temperature yield strength of the Alloy 182 J-groove weld material; and The fracture mechanics evaluation for the as-left Alloy 182 J-groove weld will use the stresses of the LAS shell from the 2-D axisymmetric finite element analysis of instrument nozzle N-16A with the LAS shell that includes the nozzle repair design configuration to be installed.

The ASME Section XI flaw evaluation requires a projection of crack growth for the flaw in the Alloy 182 J-groove weld of the remnant nozzle being abandoned in-place, and potentially into the RPV LAS material. The potential crack propagation is into the RPV LAS by fatigue and stress corrosion cracking. Prediction of fatigue crack growth requires the weld residual and design basis transient event through-wall stresses for the RPV shell at the nozzle. For this fracture mechanics analysis a conservative evaluation will be performed. This evaluation will be used to demonstrate compliance with a combination of IWB-3610 and Code Case N-749 (as conditioned in Table 2 of Regulatory Guide 1.147, Revision 19), as applicable. This one-cycle flaw evaluation will be submitted to the NRC. Refer to Summary of Commitments section (Attachment 1) for timing of submittal of the flaw evaluation.

F. Repair of Nozzle N-16A EGC is planning to replace this existing nozzle assembly with a nozzle penetration that is resistant to IGSCC, using ASME Section XI, Code Case N-638-7 as conditionally approved by the NRC in Regulatory Guide 1.147, Revision 19, and ASME Section III. See Enclosure 2 for a sketch of the planned RPV instrument nozzle repair. A welded pad will be applied to the OD of the RPV using IGSCC resistant nickel Alloy 52M filler metal and will be welded using the machine GTAW ATTB welding technique. The IGSCC resistant nozzle will be attached to the new weld pad with a partial penetration weld using a non-temper bead manual welding technique and IGSCC resistant filler metal. The original partial penetration attachment weld and a remnant of the original nozzle are planned to remain in place.

The planned steps of the proposed repair are described below. This plan may change due to varying conditions present during the work. Changes to the plan detailed below will remain in compliance with applicable Code requirements.

1. Install sealing plug into nozzle N16-A from the ID of the RPV.

2. Detach piping near reducing coupling.

3. Cut the existing nozzle outboard of the RPV.

4. Grind the nozzle flush with the vessel shell outer surface.

5. Install/attach capacitor discharge studs for welding and boring tools.

6. Perform surface and volumetric examinations on the RPV OD in preparation for the new weld pad.

7. Install the weld dam.

8. Deposit the weld pad, in accordance with Code Case N-638-7 (start 48-hr hold after completion of 3rd tempering layer).

9. Perform post weld grinding of the weld pad.

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10. Perform dimensional inspection of weld pad.

11. 48-hr hold ends.

12. Perform a surface examination of weld pad.

13. UT of weld pad.

14. Machine the weld pad to remove the weld dam.

15. Machine final weld pad bore.

16. Measure and perform a surface examination of the final bore.

17. Machine, inspect, and perform a surface examination of the replacement nozzle.

18. Weld new reducing coupling to nozzle.

19. Inspect and perform a surface examination of the reducing coupling to nozzle weld.

20. Machine J-prep in weld pad.

21. Inspect and perform a surface examination of the J-groove.

22. Replacement nozzle installation and welding.

23. Inspect and perform a progressive surface examination of the nozzle weld.

24. Remove capacitor discharge studs attached to RPV.

25. Perform surface examination of RPV at capacitor discharge stud attachment locations in accordance with ASME Section III.

26. Attach piping to new reducing coupling.

27. Remove sealing plug.

The repair discussed in the above plan will be performed in accordance with ASME Code Section XI, 2013 Edition. Additionally, NDE is planned as described in the list of operations above. The new weld pad is examined with PT and UT examinations following completion as required by ASME Code Case N-638-7. These examinations will verify there are no unacceptable indications (cracking or fabrication) in the newly installed weld pad or original base metal material.

A design analysis is being performed in accordance with the design requirements of ASME Section III. The analysis will confirm that the new nozzle will not eject from the RPV under design conditions. The new design will be reconciled to the original Construction Code and address design and transient loads to ensure all Code requirements are met. A one-cycle evaluation of the repair will be submitted to the NRC. Refer to the Summary of Commitments section (Attachment 1) for timing of the submittal of the evaluation of the repair.

The current accumulated Effective Full Power Years (EFPYs) for PBAPS, Unit 2, is 35.64, but the fluence analysis used a conservative value of 35.7 EFPY. The fast neutron fluence value (E > 1.0 MeV) at 35.7 EFPY for the N-16A nozzle at the outside diameter (1T) is 5.45E+16 neutrons/cm2. This value used the DPA-weighted attenuation method as described in Regulatory Guide 1.99, and is below the threshold level of 1E+17 neutrons/cm2 (E > 1.0 MeV). The material in the area of this repair is not expected to have decreased fracture toughness or ductility associated with damage of low alloy steels in the beltline region; therefore, there is not a weldability concern for the repair.

G. Corrosion Evaluation A corrosion evaluation will be performed to consider potential material degradation due to the repair of the N-16A RPV instrumentation nozzle. The repair will result in the RPV low alloy steel

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(Page 8 of 10) being exposed to the reactor coolant. The corrosion review will address general corrosion, crevice corrosion, and galvanic corrosion of the exposed low-alloy steel (LAS) in the gap.

PBAPS, Unit 2 operation implements On-Line Noble Metal Chemical addition with Hydrogen Water Chemistry to mitigate corrosion. The reactor water chemistry of PBAPS, Unit 2 meets the requirements of the latest BWRVIP Water Chemistry Guidelines (BWRVIP-190, Revision 1).

The corrosion evaluation will be submitted to the NRC. Refer to Summary of Commitments section (Attachment 1) for timing of submittal of the corrosion evaluation.

H. Loose Parts Evaluations Given the original N-16A nozzle will not be entirely removed, EGC completed a lost-parts evaluation to assess the potential for nozzle segments to enter the RPV during power operation.

Two evaluations were completed to address the potential impact on the fuel and the potential impact on internal RPV components. The evaluations determined that the potential for lost parts did not pose any safety concerns. The evaluations considered interfacing systems and other RPV internal components, flow blockage, and adverse chemical reactions.

Conclusion Based on the above, in accordance with 10 CFR 50.55a(z)(2), EGC has concluded that compliance with the ASME Code to perform the repair results in a hardship without a compensating increase in quality and safety. The proposed alternative provides an acceptable level of quality and safety as discussed above.

6. DURATION OF PROPOSED ALTERNATIVE Relief is requested for the duration of the PBAPS, Unit 2 Cycle 24, which is currently scheduled to conclude in the Fall of 2022. A separate relief request will be submitted to justify continued use of the nozzle repair for the life of the plant. This permanent relief request, which will contain the appropriate analyses and justification for the remainder of the plant operating life, will be submitted prior to the end of the upcoming operating cycle.

7. PRECEDENTS A similar relief request was previously approved via a verbal authorization on April 15, 2012 for Quad Cities, Unit 2 (ML12107A472). The NRC Safety Evaluation was subsequently issued on January 30, 2013 (ML13016A454). A second similar relief request was previously approved via a verbal authorization on May 17, 2017 for Limerick, Unit 2 (ML17137A307). The NRC Safety Evaluation was subsequently issued on August 14, 2017 (ML17208A090).

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Enclosure 1 N16-A Figure SS Cladding Alloy 600 A-182 J-groove weld Leak Location SA-302 Gr B Modified

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Enclosure 2 Instrument Nozzle N-16A Half-Nozzle Repair Sketch Temporary Plug Remnant Nozzle RPV Shell SA-302 Gr B Modified 1/16 to 1/8 inch gap between nozzle remnant and new nozzle 3/4 inch thick Alloy 52M weld pad Alloy 52M J-groove weld Alloy 690 nozzle 1/2 inch fillet weld 2 x 1.5 reducing coupling