ORNL is managed by UT-Battelle, LLC for the US Department of Energy

Activities in HALEU/HBU/ATFPresenter: W. Wieselquist

Contributors:R. BellesJ. ClarityR. CumberlandR. HallG. IlasW.J. MarshallU. MertyurekR. Sweet

SCALE Users’ Group WorkshopAugust 4-6, 2021

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Outline• Past Activities

– Phase 1 of NRC HALEU/HBU/ATF preparedness• Transportation package criticality safety• Lattice physics/depletion

• Current Activities– Phase 2 of NRC HALEU/HBU/ATF preparedness

• Initial core-level• Additional front-end and back-end

– VALID validation basis extension– R&D in validation "extrapolation"

• Future Activities– NRC Phase 3 (January 2022)

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Phase 1 HALEU+HBU+ATF Activities• 4 main reports

(fuel cycle stage focus areas)1. TM on HALEU in the Front

End (E1,T1,T2)2. TM on PWR lattice

HALEU+HBU (U2)3. TM on BWR lattice

HALEU+HBU (U2)4. TM on Near-term ATF for

PWRs and BWRs (U2)

• Development activities informed by those analyses – to be deployed in 6.3.0 – and used in Phase 2

E1 – UF6 enrichmentT1 – transportation of UF6/UO2(powder) to f uel f abrication f acilityF1 – f abrication of UO2 f uel pelletsF2 – f abrication of LWR f uel assembliesT2 – transportation of f resh f uel assemblies to the plantU1 – f resh f uel staging and loadingU2 – power productionU3 – spent f uel pool/shuf f le operationsU4 – on-site dry cask storageT3 – transportation of spent f uel to of f-site storageS1 – of f-site storage

Enrichment Fabrication Utilization StorageMining & Milling Disposal

E1 T1 F1 F2 T2 U1 U2 U3 T3 S1U4

1. Enhance NRC staff competency in the expected behavior and impacts of these concepts 2. Provide training to NRC staff in approaches to performing independent reviews including the development of baseline approaches for the evaluation of these concepts 3. Extend existing computational tools, data, developing validation basis, and uncertainty analysis to support efficient reviews

LWR Fuel Cycle

Overarching Goals

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HALEU Front End TM-2020/1725

DN-30 UF6 package

Contributors: Robert Hall, B.J. Marshall, William A. Wieselquist

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PWR lattice TM-2020/1833

Modeled Lattice Designs5, 6.5, 8 wt% W17x17 with 104 IFBA up to 80GWD/MTU burnup and 10,000 days of cooling

Findings• Lattice physics results overall showed no

unusual, unexpected, or adverse code performance trends

• Higher enrichment with same power level means lower flux level

• Soluble boron and control rod worth reduced due to harder spectrum

• No increase in uncertainties of the calculated QOI are observed.

Challenges• Need core calculation to assess some

reactivity effects

• Investigated further in Phase 2

Contributors: Robert Hall, Riley Cumberland, William A. Wieselquist

Control Rod Worth(pcm)

Other comparisons include decay heat, soluble boron worth, moderator temperature coefficient, Doppler temperature coefficient, etc.

NOTE: difference when comparing EOL for each design

EOL

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BWR lattice TM-2020/1835

Modeled Lattice Designs5 wt% max-4.5wt % average enrichment to 10 wt% max-7.5wt % average enrichment DOM and VAN lattices with 10-70% void fraction up to 80 GWD/MTU burnup and 10,000 days of cooling

Findings• Lattice physics results overall showed no unusual,

unexpected, or adverse code performance trends

• Core average DTC and β-eff are not expected to change substantially due to the offsetting effects of increased enrichment and increased burnup

• Trends are in general in good agreement with PWR fuel

• No increase in uncertainties of the calculated QOI are observed.

Challenges• Predicting lattice design for HALEU BWR fuel

• Investigated further in Phase 2

Contributors: Riley Cumberland, Ryan Sweet, Ugur Mertyurek, Robert Hall, William A. Wieselquist

Moderator Void Coefficient (pcm/%Void)

Other comparisons include decay heat, control blade worth, moderator void coefficient, Doppler temperature coefficient, etc.

NOTE: Small difference when comparing EOL for each design

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ATF lattices TM-2021/1961

Modeled Lattice DesignsPWR and BWR designs from HALEU+HBU reports but with near-term ATF concepts: chromium coating, chromium dopant, and FeCrAl cladding

Findings• Chromium coating small overall change (~300 pcm

reactivity penalty)

• Chromium dopant negligible change (due to slight increase in fuel density)

• FeCrAl requires design choices due to high reactivity penalty and thinner clad, changes depend on those choices

• For PWR, determined enrichment/burnup change for 1824 month cycle prediction and enrichment penalty for chromium options (0.15 wt%) and FeCrAl (0.6-0.8 wt%)

Challenges• BWR design options with HALEU+HBU compounded with

FeCrAl optionsdifficult to assess enrichment penalty

Contributors: Robert Hall, Ryan Sweet, Randy Belles, William A. WieselquistControl Blade Worth Difference for BWR with FeCrAl and 10 wt%

max pin enrichment

Other comparisons include decay heat, moderator void coefficient, Doppler temperature coefficient, etc.

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Summary

• All Phase 1 TM reports are available on SCALE website

– https://www.ornl.gov/scale/scale/reactor-physics-reports

– https://www.ornl.gov/scale/scale/criticality-safety-reports

– Additionally, all models from these reports (and future models) will be available on https://code.ornl.gov/scale/analysis

• Phase 2– Ugur Mertyurek is leading

Polaris+PARCS core-level studies– Justin Clarity is leading front-

end/back-end studies

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Reference List• Robert Hall, B.J. Marshall, William A. Wieselquist, Assessment of Existing Transportation Packages for

Use with HALEU, ORNL/TM-2020/1725, UT-Battelle, LLC, Oak Ridge National Laboratory (September 2020) [supporting files]

• Robert Hall, Ryan Sweet, Randy Belles, and William A. Wieselquist, Extended-Enrichment Accident-Tolerant LWR Fuel Isotopic and Lattice Parameter Trends, ORNL/TM-2021/1961, UT-Battelle, LLC, Oak Ridge National Laboratory (March 2021). [supporting files]

• Riley Cumberland, Ryan Sweet, Ugur Mertyurek, Robert Hall, and William A. Wieselquist, Isotopic and Fuel Lattice Parameter Trends in Extended Enrichment and Higher Burnup LWR Fuel Vol. II: BWR Fuel, ORNL/TM-2020/1835, UT-Battelle, LLC, Oak Ridge National Laboratory (March 2021). [supporting files]

• Robert Hall, Riley Cumberland, Ryan Sweet, and William A. Wieselquist, Isotopic and Fuel Lattice Parameter Trends in Extended Enrichment and Higher Burnup LWR Fuel Vol. I: PWR Fuel, ORNL/TM-2020/1833, UT-Battelle, LLC, Oak Ridge National Laboratory (February 2021). [supporting files]