ML17296A203

Accident Tolerant Fuel Lead Test Assembly Deployment

ML17296A203
Person / Time
Site:	Byron
Issue date:	10/03/2017
From:	Exelon Generation Co, Westinghouse
To:	Office of Nuclear Reactor Regulation
References
Download: ML17296A203 (19)

Text

Byron Station Accident Tolerant Fuel Lead Test Assembly Deployment (An Exelon/Westinghouse Initiative)

Jack Grobe Director~ Strategic Projects I

Bill Gassmann Byron ATF Project Manager NRC Briefing

• October 3, 2017

@Westinghouse

,J' Exelon Generation~

Agenda

• Introductions and Opening Remarks

• Meeting Purpose

• Project Overview

• Lead Test Assembly/Lead Test Rod Design Change Overview

• Lead Test Assembly/Lead Test Rod Design Change Analysis

• Fuel Reliability, Reactivity, Shipping and Handling

• Reload Analysis Considerations

• 10 CFR 50.46 and Appendix K

• Project Schedule/Milestones

• NRC Questions/Feedback 1

@Westinghouse

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Exelon Generation.

Meeting Purpose

• Describe the Westinghouse Accident Tolerant Fuel (ATF) Lead Test Assembly (LTA) and Lead Test Rod (LTR) design features that will be deployed at Byron Station

• Summarize the safety-related design change process that will demonstrate:

- The Byron Station ATF LTA program is within the Technical Specification 4.2.1 requirements

- The LTAs are compatible with the co-resident Westinghouse fuel; and

- All applicable core safety and licensing basis criteria continue to be met

• Present the milestones and timeline for ATF LTA deployment at Byron Station

• Obtain NRC feedback on the ATF LTA program and plans at Byron Station 2

@Westinghouse *

~

Exelon Generation.

Project Overview

• *After the accident at Fukushima Daiichi, the U.S. Congress mandated the development of nuclear fuels with enhanced accident tolerance to improve performance under beyond design basis accident (BDBA) conditions

• Major expectations for accident tolerant fuel (ATF) designs:

- Improved cladding reaction to high temperature steam

- Reduced hydrogen generation

- Reduced BDBA source term

• Westinghouse ATF concepts satisfy these expectations

• The Byron Station ATF LTA/LTR Program is a joint initiative between Exelon and Westinghouse 3

@Westinghouse

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Exelon Generation.

LTA/LTR Design Change Overview

• Westinghouse has developed a new fuel type and a new cladding type to satisfy ATF requirements:

- Uranium silicide (U3Si2) fuel pellets will replace standard uranium dioxide (U02) fuel pellets

- Coated zirconium alloy cladding will replace standard Optimized ZIRLO cladding

• Chromium is a coating candidate, but R&D continues and other coatings may be considered

~

Exelon Generation.

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@Westinghouse

LTA/LTR Design Change Overview

• Exelon plans to load two LTAs containing up to 20 LTRs in Byron Station, Unit 2 during Cycles 22, 23 and 24 (Cycle 22 begins operation in Spring 2019)

• The LTRs include a combination of:

- Coated zirconium alloy cladding containing standard uranium dioxide fuel pellets or uranium silicide fuel pellets

- Optimized ZIRLO cladding containing uranium silicide fuel pellets

• The 20 L TRs represent 0.04% of the total fuel rods in the core

• The purpose of this LTR Program is to allow Exelon/Westinghouse to collect further data regarding the performance of the Westinghouse accident tolerant fuel rods 5

@Westinghouse

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ExelonGeneration.

LTA/LTR Design Change Analysis

• The Byron Unit 2-Cycle 22 core reload analysis will be a safety related analysis completed under the Westinghouse and Exelon 10 CFR 50, Appendix B engineering change processes

• Core Reload analysis will confirm acceptable safety margin for all LTA/LTR critical parameters and requirements

• Currently licensed fuel design and reload analysis methods for the reactor core do not fully accommodate the LTA/_LTR design and materials

• Methods will be supplemented with additional analysis and evaluations - conservative assumptions will be employed

• 10 CFR 50.59 process applied to the full core reload_ analysis will appropriately consider the allowance in TS 4.2.1 for a limited number of LTAs that have not completed representative testing

- The answer all 10 CFR 50.59 Questions, including Question (viii),

is anticipated to be "No" 6

@Westinghouse

~

Exelon Generation.

LTA/LTR Design Change Analysis

• LTAs will be fully compatible with:

- Co-resident fuel assemblies

- Control rods, inserts and core instrumentation

- Other reactor pressure vessel internals

• LTAs will have no impact on the projected Energy Utilization Plan

- Cycle length and operating capacity factor

- Load following/de-rating and coastdown length

- Cycle extension techniques and outage length

• Neutronic impact of small amount of U3Si2 and coating will be negligible i

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@Westinghouse

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Exelon Generation.

Effects on Fuel Reliability

• No issues anticipated

• Investigation of new LTR/LTA attributes continues in test reactors and the laboratory

- No significant issues have been identified or are expected Testing continues in several areas

- Pellet-clad compatibility

- 1*ntegrity of coating

- U3Si2 pellet performance and mechanical design

• Standard fuel reliability concerns are also satisfactorily

• addressed I

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Exelon Generation!

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@Westinghouse I

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Reactivity Management

• U3Si2 pellets will have reduced enrichment

- Rod power similar to symmetric U02 rods

• Coating has negligible neutronic impact

• LTAs will be loaded in non-limiting core locations

- 5% peaking factor reduction will be used

- LTRs will be located in non~limiting locations within the LTAs

• Negligible impact on rod worth, thermal limits, shutdown margin, and reactivity coefficients

• There are no changes to thermal limits or thermal limits monitoring

• No anticipated mixed core concerns

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Fuel Shipping and Handling

• Standard shipping containers will be used

• Standard receipt, handling, and inspection processes will apply

• No changes needed to fuel handling equipment

• Westinghouse taking licensing actions on shipping containers

- Received approval for transport of U3Si2 in June 2017 I

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@Westinghouse*

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Reload Analysis Considerations

• Standard reload deliverables will be provided per the normal reload schedule

• Items required for LTAs beyond the normal reload scope are:

- Thermal-hydraulic Analysis Methods

- Fuel Rod Design

- Neutronics

- Nuclear Design

- Criticality Analyses

- Loss of Coolant Accident Analysis

- Transient Analysis

- Alternate Source Term Exelon GenerationJ 11 @ Westinghouse I

Reload Analysis Considerations - Operating Limits

• Standard reload design margins will be used for non-ATF fuel

- Thermal limits

- Shutdown Margin

- Fuel Exposure

- Hot Excess Reactivity

• Margin to operating limits for non-ATF fuel will be unaffected 12 @Westinghouse i

Exelon Generationl I I i

Reload Analysis Considerations - Fuel Storage

• No significant technical concerns exist

• Westinghouse will perform New Fuel Storage Rack, Spent Fuel Storage Rack, and Fuel Rod Storage Basket criticality evaluations

• Addressing the codes and methods question regarding spent fuel pool analysis is ongoing 13

@)Westinghouse

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Reload Analysis Considerations - Use of Proven Design

• LTRs/LTAs w;ll be of standard 17x17 Optimized Fuel Assembly (OFA) design

• Mechanical, neutronic, and thermal-hydraulic differences from standard 17x17 OFA fuel will be negligible

• Nuclear Fuels Vendor Oversight will focus on pellet/clad fabrication differences and closely monitor fabrication process

• Contingency will be to replace the twenty LTRs with standard U02 and Optimized ZIRLO if unexpected challenges arise 14 @Westinghouse

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Exelon Generation

Reload Analysis Considerations - Model Accuracy

• Currently licensed fuel design and reload analysis methods do not fully accommodate the LTRs/LTA design and materials

• Methods will be supplemented with additional analysis and evaluations, as necessary

• Conservative assumptions will be employed as necessary to ensure appropriate LTR/LTA margin in all aspects of operation

• Methods adequacy will be treated in Exelon Engineering Configuration Change package and recognize TS prov~sion that methods not submitted to NRC are acceptable for LTAs

• LTRs and LTAs will be placed in appropriate locations to maximize fidelity of online core monitoring

- Impact will be negligible

~

Exelon Generation~.

15 @Westinghouse

Need for an Exemption from 10 CFR 50.46 and Appendix K

• . Historically, some licensees implementing LTA programs have requested exemptions for developmental fuel types

• Exelon and Westinghouse are seeking further understanding regarding the need for an exemption to 10 CFR 50.46 and Appendix K

• Based on NRC discussions to date, Exelon proposes tl1at th~

subject LTRs/LTAs may be appropriately inserted in the reactor core with:

- Safety analysis performed under the safety related eng~neering design change processes

- The need for a license amendment request (LAR) for the core reload will be evaluated under the 10 CFR 50.59; an LAR is not anticipated Exemption from 10 CFR 50.46 and Appendix Kare not anticipated 16 @Westinghouse I

Exelon Generation I.

Project Schedule/Milestones

• 4Q2017

• 4Q2017

• 4Q2017

• 4Q2018

• 4Q2018

• 1Q2019

• 2Q2019 NRC Briefing Finalize Regulatory Approach Initiation of Exelon Engineering Change Package Completion of Exelon Engineering Change Evaluation and Documentation Complete LTR Fabrication LTRs Delivered to Byron Station Byron Unit 2 Cycle 22 Startup I

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@Westinghouse I

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NRC Questions/Feedback 18 @ Westinghouse

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