Thermal oxidation of nuclear graphite and pyrolytic carbon coatings

Bryan Conry; David J. Navarro-Solís; Herwin Hein; Michael Holzhäuser; Rudy Konings; Eddie López-Honorato

doi:10.1016/j.nucengdes.2025.114257

Thermal oxidation of nuclear graphite and pyrolytic carbon coatings

Bryan Conry, David J. Navarro-Solís, Herwin Hein, Michael Holzhäuser, Rudy Konings, Eddie López-Honorato

Advanced Fuel Fabrication

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

Abstract

The oxidation of pyrolytic carbon (PyC) deposited via fluidized bed chemical vapor deposition was characterized and compared with that of standard nuclear-grade graphite. The materials were heated at 700 to 1000 °C in a thermogravimetric analysis system under 20% v/v O₂ flow, allowing for direct comparison of dynamic oxidative mass change in each material. Three different PyC samples fabricated under different conditions exhibited variation in total mass loss and mass loss rate, varying by as much as 709 mg/cm² in total mass loss and 14.2 (mg/cm²)/min in mass loss rate at a single temperature. These variations highlight the correlation between PyC microstructure/defect density and oxidation susceptibility. Additionally, changes in the microstructure and composition between PyC and graphite were characterized via scanning electron microscopy and correlated to the mass loss results. The results of this work have implications toward the safety of tristructural isotropic (TRISO) and other coated particle fuels, especially under off-normal conditions, given the limited information that exists about the oxidation behavior of PyC.

Original language	English
Article number	114257
Journal	Nuclear Engineering and Design
Volume	442
DOIs	https://doi.org/10.1016/j.nucengdes.2025.114257
State	Published - Oct 2025

Funding

The authors wish to acknowledge the financial support provided by the National Council of Science and Technology-Mexico (CONACYT) for a PhD scholarship awarded to David J. Navarro-Solís. David Arregui-Mena of Oak Ridge National Laboratory provided a helpful review of the manuscript. Notice: This manuscript has been authored by UT-Battelle LLC under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US 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 US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

Keywords

Microstructure
Oxidation
Scanning electron microscopy
Thermogravimetric analysis

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10.1016/j.nucengdes.2025.114257

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title = "Thermal oxidation of nuclear graphite and pyrolytic carbon coatings",

abstract = "The oxidation of pyrolytic carbon (PyC) deposited via fluidized bed chemical vapor deposition was characterized and compared with that of standard nuclear-grade graphite. The materials were heated at 700 to 1000 °C in a thermogravimetric analysis system under 20\% v/v O2 flow, allowing for direct comparison of dynamic oxidative mass change in each material. Three different PyC samples fabricated under different conditions exhibited variation in total mass loss and mass loss rate, varying by as much as 709 mg/cm2 in total mass loss and 14.2 (mg/cm2)/min in mass loss rate at a single temperature. These variations highlight the correlation between PyC microstructure/defect density and oxidation susceptibility. Additionally, changes in the microstructure and composition between PyC and graphite were characterized via scanning electron microscopy and correlated to the mass loss results. The results of this work have implications toward the safety of tristructural isotropic (TRISO) and other coated particle fuels, especially under off-normal conditions, given the limited information that exists about the oxidation behavior of PyC.",

keywords = "Microstructure, Oxidation, Scanning electron microscopy, Thermogravimetric analysis",

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doi = "10.1016/j.nucengdes.2025.114257",

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T1 - Thermal oxidation of nuclear graphite and pyrolytic carbon coatings

AU - Conry, Bryan

AU - Navarro-Solís, David J.

AU - Hein, Herwin

AU - Holzhäuser, Michael

AU - Konings, Rudy

AU - López-Honorato, Eddie

PY - 2025/10

Y1 - 2025/10

N2 - The oxidation of pyrolytic carbon (PyC) deposited via fluidized bed chemical vapor deposition was characterized and compared with that of standard nuclear-grade graphite. The materials were heated at 700 to 1000 °C in a thermogravimetric analysis system under 20% v/v O2 flow, allowing for direct comparison of dynamic oxidative mass change in each material. Three different PyC samples fabricated under different conditions exhibited variation in total mass loss and mass loss rate, varying by as much as 709 mg/cm2 in total mass loss and 14.2 (mg/cm2)/min in mass loss rate at a single temperature. These variations highlight the correlation between PyC microstructure/defect density and oxidation susceptibility. Additionally, changes in the microstructure and composition between PyC and graphite were characterized via scanning electron microscopy and correlated to the mass loss results. The results of this work have implications toward the safety of tristructural isotropic (TRISO) and other coated particle fuels, especially under off-normal conditions, given the limited information that exists about the oxidation behavior of PyC.

AB - The oxidation of pyrolytic carbon (PyC) deposited via fluidized bed chemical vapor deposition was characterized and compared with that of standard nuclear-grade graphite. The materials were heated at 700 to 1000 °C in a thermogravimetric analysis system under 20% v/v O2 flow, allowing for direct comparison of dynamic oxidative mass change in each material. Three different PyC samples fabricated under different conditions exhibited variation in total mass loss and mass loss rate, varying by as much as 709 mg/cm2 in total mass loss and 14.2 (mg/cm2)/min in mass loss rate at a single temperature. These variations highlight the correlation between PyC microstructure/defect density and oxidation susceptibility. Additionally, changes in the microstructure and composition between PyC and graphite were characterized via scanning electron microscopy and correlated to the mass loss results. The results of this work have implications toward the safety of tristructural isotropic (TRISO) and other coated particle fuels, especially under off-normal conditions, given the limited information that exists about the oxidation behavior of PyC.

KW - Microstructure

KW - Oxidation

KW - Scanning electron microscopy

KW - Thermogravimetric analysis

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DO - 10.1016/j.nucengdes.2025.114257

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VL - 442

JO - Nuclear Engineering and Design

JF - Nuclear Engineering and Design

M1 - 114257

ER -

Thermal oxidation of nuclear graphite and pyrolytic carbon coatings

Abstract

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Keywords

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