Modeling Defect-Mediated Diffusion in Cr-Doped UO 2 using a Variable-Charge Interatomic Potential

Abstract

Chromium doping of uranium dioxide is one of the different strategies for the development of Accident Tolerant Fuels (ATFs), promoting a large-grained microstructure that is anticipated to enhance fission gas retention. However, the underlying atomic-scale mechanisms governing this behavior remain incompletely elucidated. This study aims to clarify these mechanisms by systematically investigating defect energetics and diffusion dynamics in Crdoped UO 2 using a semi-empirical tight-binding (SMTB-QB) potential, benchmarked against Density Functional Theory (DFT) calculations. Our approach combines static calculations for defect incorporation and migration energies with high-temperature molecular dynamics simulations to compute atomic diffusion coefficients. Results show that the SMTB-QB model reproduces the stability hierarchy of defects, identifying uranium substitutional sites as energetically favorable. Notably, our calculations reveal that the presence of chromium lowers the uranium migration barrier by approximately 1 eV, resulting in a 1.5-to 2-fold increase in the uranium diffusion coefficient. These findings provide a direct atomistic explanation for the enhanced uranium diffusion that promotes accelerated grain growth, a mechanism acting in concert with proposed liquid phase effects, thereby validating the SMTB-QB potential as a tool to refine multi-faceted fuel performance models.

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BibTeX RIS

BibTeX

@article{roubille2026modeling,
  title = {{Modeling Defect-Mediated Diffusion in Cr-Doped UO 2 using a Variable-Charge Interatomic Potential}},
  author = {Théo Roubille and Mathieu Gascoin and Roland Ducher and Michel Freyss and Robert Tétot and Yves Pipon},
  journal = {Journal of Nuclear Materials},
  year = {2026},
  month = sep,
  doi = {10.1016/j.jnucmat.2026.157117},
  url = {https://asnr.hal.science/hal-05440680v2},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - Modeling Defect-Mediated Diffusion in Cr-Doped UO 2 using a Variable-Charge Interatomic Potential
AU  - Théo Roubille
AU  - Mathieu Gascoin
AU  - Roland Ducher
AU  - Michel Freyss
AU  - Robert Tétot
AU  - Yves Pipon
PY  - 2026
DA  - 2026/09/30
JO  - Journal of Nuclear Materials
DO  - 10.1016/j.jnucmat.2026.157117
UR  - https://asnr.hal.science/hal-05440680v2
AB  - Chromium doping of uranium dioxide is one of the different strategies for the development of Accident Tolerant Fuels (ATFs), promoting a large-grained microstructure that is anticipated to enhance fission gas retention. However, the underlying atomic-scale mechanisms governing this behavior remain incompletely elucidated. This study aims to clarify these mechanisms by systematically investigating defect energetics and diffusion dynamics in Crdoped UO 2 using a semi-empirical tight-binding (SMTB-QB) potential, benchmarked against Density Functional Theory (DFT) calculations. Our approach combines static calculations for defect incorporation and migration energies with high-temperature molecular dynamics simulations to compute atomic diffusion coefficients. Results show that the SMTB-QB model reproduces the stability hierarchy of defects, identifying uranium substitutional sites as energetically favorable. Notably, our calculations reveal that the presence of chromium lowers the uranium migration barrier by approximately 1 eV, resulting in a 1.5-to 2-fold increase in the uranium diffusion coefficient. These findings provide a direct atomistic explanation for the enhanced uranium diffusion that promotes accelerated grain growth, a mechanism acting in concert with proposed liquid phase effects, thereby validating the SMTB-QB potential as a tool to refine multi-faceted fuel performance models.
SN  - 0022-3115
SN  - 1873-4820
ER  -

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