ML21102A063

ONS Slides for Pre-Application Meeting to Discuss Proposed Relief Request Related to Code Case N-853

ML21102A063
Person / Time
Site:	Oconee
Issue date:	04/14/2021
From:	Duke Energy Carolinas
To:	Plant Licensing Branch II
Zachery Stone-NRR/DORL 301-415-0615
References
Download: ML21102A063 (15)

Text

Duke Energy Pre-Submittal Meeting - April 14, 2021 Oconee Alloy 600 PWSCC Mitigation Acceptance Criteria

Participants Dave Peltola, Engineering - Duke Energy Steve Roe, Engineering - Duke Energy Art Zaremba, Fleet Licensing Manager - Duke Energy Josh Duc, Fleet Licensing - Duke Energy Jim Axline - Structural Integrity Chris Lohse - Structural Integrity 2

Objectives for This Meeting:

Brief NRC on Dukes reason for proposed request, proposed alternative, basis for use, and proposed timeline Ensure common understanding for Duke Energys request and technical scope Obtain NRC feedback prior to formal submittal 3

Agenda I. Reason for Request II. Components Affected III. ASME Code and Regulatory Requirements IV. Proposed Alternative V. Basis for Relief VI. Precedents VII. Conclusion 4

I. Reason for Request CC N-853 requires volumetric ultrasonic examination in accordance with Construction Code or ASME Section III, with NB-5330 acceptance criteria.

ASME Section XI, IWB-3514 acceptance criteria is proposed in lieu of the NB-5330 acceptance criteria.

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II. Components Affected Components Affected:

Reactor coolant system (RCS) hot/cold leg nozzles Piping Nozzles (Unit 3 ONLY)

Resistance Temperature Element (RTE) Nozzles (All 3 Units)

Susceptible to primary water stress corrosion cracking (PWSCC)

Alloy 600 nozzles, Alloy 82/182 welds Preemptive PWSCC mitigation via reinforcing pad and replacement nozzle in accordance with CC N-853 6

II. Components Affected Sketch of Example Existing Nozzle Configuration Sketch of Example Existing Fast RTE Nozzle Configuration 7

II. Components Affected Sketch of Example Repaired Nozzle Configuration with Code Case N-853 J Groove Weld 8

II. Components Affected Sketch of Example Repaired Nozzle Configuration with Alternative (Previously Approved) Full Penetration Corner Weld 9

III. ASME Code Edition and Requirements ASME Section XI Code of Record is the 2007 Edition with 2008 Addenda Fifth 10-year inspection interval ending July 15, 2024 ASME Section XI, Code Case (CC) N-722-1 ASME Section XI, CC N-853 NRC approval for ONS February 26, 2020 (ML20055F571) 10

IV. Proposed Alternative RCS nozzle / weld PWSCC mitigation per CC N-853 CC N-853 requires volumetric ultrasonic examination in accordance with Construction Code or ASME Section III, with NB-5330 acceptance criteria which, similar to the radiographic acceptance standards, allows for no indications (cracks, lack of fusion, or incomplete penetration).

ASME Section XI, IWB-3514 acceptance criteria is proposed in lieu of NB-5330, as it is based on ultrasonic examination which will avoid potential outage re-work that provides no safety or quality benefit Duration of Alternative Implementation allowed for the remainder of the current interval Once implemented, physical repair duration is for the life of each Unit 11

V. Basis for Relief Alternative provides acceptable level of quality and safety - 10 CFR 50.55a(z)(1)

NB-5330 acceptance criteria is similar to the radiographic examination criteria and would reject many flaws that are not significant to the weld pad structural integrity IWB-3514 has been used since the 1980s for inspecting planar flaws in IWB-2500 inspected components with a good service history Other welded repairs already allow the use of IWB-3514 examination criteria Correction of rejected flaw would require Remove portion of pad, reweld and reexamine Removal/rewelding significantly alters residual stress field, potentially producing less optimal stress field for arresting PWSCC crack growth Correcting a NB-5330 structurally insignificant flaw would detrimentally impact the pad stress field used to protect the pressure boundary Avoids unnecessary risk to personnel safety during outage (dose, injuries, etc.)

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VI. Precedents The weld pads are similar to Full Structural Weld Overlays (FSWOs), used to mitigate stress corrosion cracking in dissimilar metal piping butt welds Both the FSWOs and the CC N-853 weld pads are deposited using 52M weld wire and the Gas Tungsten Arc Welding (GTAW) weld process.

The material and weld process for both applications are subjected to the same potential fabrication issues Pre-service examination of FSWOs at ONS used IWB-3514 from 2006 - 2010 Oconee FSWOs (RR ML062430314, SER ML071280781)

Approved acceptance criteria of ASME Code,Section XI, Code Case N-504-2 and Nonmandatory Appendix Q in lieu of those of NB-5330 of ASME Code,Section III Discusses in detail the concerns with utilizing ASME Code,Section III acceptance criteria based on radiography 13

VII. Conclusion For the reasons discussed in this presentation, Duke Energy believes that the proposed alternative provides an acceptable level of quality and safety.

Duke Energy plans to submit no later than May 2021.

Upcoming Fall 2021 and Spring 2022 outages could benefit by use of this relief 14

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