ML23080A297

Presentation Slides for Information Call on 3/21/23 N2E Recirc Discharge Nozzle Weld Repair Request for Alternative

ML23080A297
Person / Time
Site:	Nine Mile Point
Issue date:	03/21/2023
From:	Tom Loomis Constellation Energy Generation
To:	Richard Guzman NRC/NRR/DORL/LPL1
References
Download: ML23080A297 (1)

Text

Nine Mile Point Unit 1 N2E Recirc Discharge Nozzle Weld Repair Request for Alternative March 21, 2023

N2E Recirc Discharge Safe End-to-Nozzle (32-WD-2008) IGSCC Defect

• Summary of N1R27 Examination

- During automated encoded UT examination of 28-inch dissimilar metal (DM) weld 32-WD-208 (N2E), an ID connected flaw was identified with attributes indicative of intergranular stress corrosion cracking (IGSCC)

- The flaw was determined not to meet the acceptance standards of ASME Section XI (i.e. a defect) and was confirmed with CEG NDES and EPRI to be the result of IGSCC

- The defect is located 14-inches clockwise from top dead center and is in the Alloy 82/182 weld material and adjacent stainless steel safe-end material

- The defect has a length of 1.65-inches and a through-wall dimension of 1.52-inches (~83%)

• Additional Background

- N2E is an IGSCC Category D weld. Per BWRVIP-75A Category D welds are those made of susceptible material that have not been treated with an IGSCC remedy and in which cracks have not been reported.

- NMP Unit 1 has 152 IGSCC Category D welds. During N1R27, 83 IGSCC Category D welds are in scope for examination. Extent of condition exams are being performed per Program requirements 1

N2E Recirc Discharge Safe End-to-Nozzle (32-WD-2008) Configuration 2

Proposed N2E Weld Overlay Relief Request

• Constellation would propose a leakage barrier weld overlay of the defect using Code Case N-740-2, with modifications for overlay sizing per ASME Section XI, Non-Mandatory Appendix Q (formerly Code Case N-504-4)

• It is Constellations intent for this repair to be temporary with a full structural weld overlay being completed during the next refueling outage

• Code Case N-740-2 would be met except for the following items (current list, to be validated as part of relief request development)

-Design

• Sizing of the overlay will use the Appendix Q provisions in Q-3000(a)(5) that would allow a leakage barrier overlay for axial flaws

- Technical basis will be provided for the single flaw in the weld exceeding 1.5-inches in length (1.6-inches actual) as required in Q-3000(a)(5) (For weldments with four or fewer axial flaws, each shorter than 1.5 in. (38 mm), and no circumferential flaws)

- Analysis will demonstrate that sufficient material has been installed to meet ASME Section XI Acceptance Criteria for at least a cycle of operation 3

Proposed N2E Weld Overlay Relief Request

• Code Case N-740-2 would be met except for the following items (continued)

-Acceptance Examination

• Elimination of the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold for acceptance NDE after completion of three tempering layers over the ferritic steel

-Preservice Examination

• The PSI examination volume will be met per N-740-2

- The angle beam shall be directed perpendicular and parallel to the piping axis, with scanning performed in four directions, to locate and size any planar flaws that have propagated into the outer 25% of the base metal thickness or into the weld overlay

- The preservice examination acceptance standards of IWB-3514 shall be met for the weld overlay

• Planar flaws in the outer 25% of the base metal thickness shall meet the design analysis requirements of Q-3000

• Additionally, the reactor vessel shell to nozzle weld existing configuration only allows single sided examination from the reactor vessel side. This limitation will continue with the installation of the weld overlay 4

Proposed N2E Weld Overlay Relief Request

-It is Constellations intent for this repair to be temporary (one operating cycle) and we would install the remaining weld material to satisfy the requirements for a full structural weld overlay at a future outage

• This would be submitted as a separate relief request prior to the next refueling outage 5