Transmission electron microscopy characterization of the fuel-cladding chemical interactions in HT9 cladded U-10Zr fuel

Yachun Wang; Brandon D. Miller; Jason M. Harp; Daniele Salvato; Luca Capriotti; Tiankai Yao

doi:10.1016/j.jnucmat.2022.153990

Transmission electron microscopy characterization of the fuel-cladding chemical interactions in HT9 cladded U-10Zr fuel

Yachun Wang, Brandon D. Miller, Jason M. Harp, Daniele Salvato, Luca Capriotti, Tiankai Yao

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

Fuel cladding chemical interaction (FCCI) is a key phenomenon needs to be better understood to establish the design basis for U-10Zr metallic fuel performance. Characterizing the microstructure and chemical composition of FCCI at micron and sub-micron scale is critically important toward a more mechanistic understanding of FCCI phenomenon and its potential effects on cladding integrity and metallic fuel performance. This paper, by using transmission electron microscopy, investigated the FCCI region in HT9 cladded U-10Zr fuel irradiated to 5.7% FIMA burnup at a peak inner cladding temperature of 615 °C in Fast Flux Test Facility (FFTF). Four distinct layers are identified in the FCCI region. The migration of Fe into the fuel side leads to the formation of several U-Zr-Fe ternary phases, including χ-Fe_0.5Zr_0.32U_0.18, ε-Fe_0.3Zr_0.4U_0.3, and λ-Fe_0.06Zr_0.23U_0.71, mingled with UFe₂, U₆Fe, and U phase at various Fe penetration depth up to ∼ 150 µm. On the cladding side, grain coarsening and significant lanthanides infiltration along grain boundaries are observed. Laves phase, (Fe,Cr)₂(Mo,W), which typically does not exist in fresh HT9, is identified in a wide radial range in the cladding. The typical HT9 martensitic lath structure and pre-existing M₂₃C₆ precipitates disappear, partially or completely, depending on the radial distance from the fuel-cladding interface. Those microstructural and compositional changes could cause mechanical degradation in the HT9 cladding. The present characterization results will improve the understanding of FCCI phenomenon and facilitate the development of microstructure-informed FCCI modeling for metallic fuel.

Original language	English
Article number	153990
Journal	Journal of Nuclear Materials
Volume	572
DOIs	https://doi.org/10.1016/j.jnucmat.2022.153990
State	Published - Dec 15 2022
Externally published	Yes

Funding

The authors acknowledge the financial support of the U.S. Department of Energy, Advanced Fuels Campaign of the Fuel Cycle R&D program in the Office of Nuclear Energy for sample preparation and irradiation experiments. The microstructure characterization and phase identification were supported by a Laboratory Directed Research and Development Project (22A1059-094FP) under the U.S. Department of Energy , Office of Nuclear Energy, Idaho Operations Office Contract DE-AC07-051D14517 . Accordingly, the U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so, for U.S. Government purposes. The authors acknowledge the financial support of the U.S. Department of Energy, Advanced Fuels Campaign of the Fuel Cycle R&D program in the Office of Nuclear Energy for sample preparation and irradiation experiments. The microstructure characterization and phase identification were supported by a Laboratory Directed Research and Development Project (22A1059-094FP) under the U.S. Department of Energy, Office of Nuclear Energy, Idaho Operations Office Contract DE-AC07-051D14517. Accordingly, the U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so, for U.S. Government purposes.

Funders	Funder number
U.S. Government
U.S. Department of Energy
Office of Nuclear Energy
Laboratory Directed Research and Development	22A1059-094FP
Idaho Operations Office, U.S. Department of Energy	DE-AC07-051D14517

Keywords

Fuel-cladding chemical interaction (FCCI)
HT9 cladding
Laves phase
Transmission electron microscopy
U-10Zr metallic fuel
U-Zr-Fe ternary phase

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10.1016/j.jnucmat.2022.153990

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@article{099d9e74133f472e9718b9ae6e2aab8f,

title = "Transmission electron microscopy characterization of the fuel-cladding chemical interactions in HT9 cladded U-10Zr fuel",

abstract = "Fuel cladding chemical interaction (FCCI) is a key phenomenon needs to be better understood to establish the design basis for U-10Zr metallic fuel performance. Characterizing the microstructure and chemical composition of FCCI at micron and sub-micron scale is critically important toward a more mechanistic understanding of FCCI phenomenon and its potential effects on cladding integrity and metallic fuel performance. This paper, by using transmission electron microscopy, investigated the FCCI region in HT9 cladded U-10Zr fuel irradiated to 5.7% FIMA burnup at a peak inner cladding temperature of 615 °C in Fast Flux Test Facility (FFTF). Four distinct layers are identified in the FCCI region. The migration of Fe into the fuel side leads to the formation of several U-Zr-Fe ternary phases, including χ-Fe0.5Zr0.32U0.18, ε-Fe0.3Zr0.4U0.3, and λ-Fe0.06Zr0.23U0.71, mingled with UFe2, U6Fe, and U phase at various Fe penetration depth up to ∼ 150 µm. On the cladding side, grain coarsening and significant lanthanides infiltration along grain boundaries are observed. Laves phase, (Fe,Cr)2(Mo,W), which typically does not exist in fresh HT9, is identified in a wide radial range in the cladding. The typical HT9 martensitic lath structure and pre-existing M23C6 precipitates disappear, partially or completely, depending on the radial distance from the fuel-cladding interface. Those microstructural and compositional changes could cause mechanical degradation in the HT9 cladding. The present characterization results will improve the understanding of FCCI phenomenon and facilitate the development of microstructure-informed FCCI modeling for metallic fuel.",

keywords = "Fuel-cladding chemical interaction (FCCI), HT9 cladding, Laves phase, Transmission electron microscopy, U-10Zr metallic fuel, U-Zr-Fe ternary phase",

author = "Yachun Wang and Miller, {Brandon D.} and Harp, {Jason M.} and Daniele Salvato and Luca Capriotti and Tiankai Yao",

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year = "2022",

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doi = "10.1016/j.jnucmat.2022.153990",

language = "English",

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T1 - Transmission electron microscopy characterization of the fuel-cladding chemical interactions in HT9 cladded U-10Zr fuel

AU - Wang, Yachun

AU - Miller, Brandon D.

AU - Harp, Jason M.

AU - Salvato, Daniele

AU - Capriotti, Luca

AU - Yao, Tiankai

PY - 2022/12/15

Y1 - 2022/12/15

N2 - Fuel cladding chemical interaction (FCCI) is a key phenomenon needs to be better understood to establish the design basis for U-10Zr metallic fuel performance. Characterizing the microstructure and chemical composition of FCCI at micron and sub-micron scale is critically important toward a more mechanistic understanding of FCCI phenomenon and its potential effects on cladding integrity and metallic fuel performance. This paper, by using transmission electron microscopy, investigated the FCCI region in HT9 cladded U-10Zr fuel irradiated to 5.7% FIMA burnup at a peak inner cladding temperature of 615 °C in Fast Flux Test Facility (FFTF). Four distinct layers are identified in the FCCI region. The migration of Fe into the fuel side leads to the formation of several U-Zr-Fe ternary phases, including χ-Fe0.5Zr0.32U0.18, ε-Fe0.3Zr0.4U0.3, and λ-Fe0.06Zr0.23U0.71, mingled with UFe2, U6Fe, and U phase at various Fe penetration depth up to ∼ 150 µm. On the cladding side, grain coarsening and significant lanthanides infiltration along grain boundaries are observed. Laves phase, (Fe,Cr)2(Mo,W), which typically does not exist in fresh HT9, is identified in a wide radial range in the cladding. The typical HT9 martensitic lath structure and pre-existing M23C6 precipitates disappear, partially or completely, depending on the radial distance from the fuel-cladding interface. Those microstructural and compositional changes could cause mechanical degradation in the HT9 cladding. The present characterization results will improve the understanding of FCCI phenomenon and facilitate the development of microstructure-informed FCCI modeling for metallic fuel.

AB - Fuel cladding chemical interaction (FCCI) is a key phenomenon needs to be better understood to establish the design basis for U-10Zr metallic fuel performance. Characterizing the microstructure and chemical composition of FCCI at micron and sub-micron scale is critically important toward a more mechanistic understanding of FCCI phenomenon and its potential effects on cladding integrity and metallic fuel performance. This paper, by using transmission electron microscopy, investigated the FCCI region in HT9 cladded U-10Zr fuel irradiated to 5.7% FIMA burnup at a peak inner cladding temperature of 615 °C in Fast Flux Test Facility (FFTF). Four distinct layers are identified in the FCCI region. The migration of Fe into the fuel side leads to the formation of several U-Zr-Fe ternary phases, including χ-Fe0.5Zr0.32U0.18, ε-Fe0.3Zr0.4U0.3, and λ-Fe0.06Zr0.23U0.71, mingled with UFe2, U6Fe, and U phase at various Fe penetration depth up to ∼ 150 µm. On the cladding side, grain coarsening and significant lanthanides infiltration along grain boundaries are observed. Laves phase, (Fe,Cr)2(Mo,W), which typically does not exist in fresh HT9, is identified in a wide radial range in the cladding. The typical HT9 martensitic lath structure and pre-existing M23C6 precipitates disappear, partially or completely, depending on the radial distance from the fuel-cladding interface. Those microstructural and compositional changes could cause mechanical degradation in the HT9 cladding. The present characterization results will improve the understanding of FCCI phenomenon and facilitate the development of microstructure-informed FCCI modeling for metallic fuel.

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KW - HT9 cladding

KW - Laves phase

KW - Transmission electron microscopy

KW - U-10Zr metallic fuel

KW - U-Zr-Fe ternary phase

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DO - 10.1016/j.jnucmat.2022.153990

M3 - Article

AN - SCOPUS:85138453325

SN - 0022-3115

VL - 572

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

M1 - 153990

ER -

Transmission electron microscopy characterization of the fuel-cladding chemical interactions in HT9 cladded U-10Zr fuel

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