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Diffusion of oxygen in hypostoichiometric uranium dioxide nanocrystals. A molecular dynamics simulation

K. A. Nekrasov, A. E. Galashev, D. D. Seitov, S. K. Gupta


A molecular dynamic simulation of diffusion of intrinsic oxygen anions in the bulk of hypostoichiometric UO2-x nanocrystals with a free surface was carried out. The main diffusion mechanism turned out to be the migration of oxygen by the anionic vacancies. It is shown that in the range of values of the non-stoichiometry parameter 0.05 £x £ 0.275 the oxygen diffusion coefficient D is weakly dependent on temperature, despite the uniform distribution of the vacancies over the model crystallite. The reliable D values calculated for the temperature T = 923 K are in the range from 3×10-9 to 7×10-8 cm2/s, in quantitative agreement with the experimental data. The corresponding diffusion activation energy is in the range from 0.57 eV to 0.65 eV, depending on the interaction potentials used for the calculations.


uranium dioxide; hypostoichiometry; oxygen diffusion; nanocrystals

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Choi E-Y, Kim J-K, Im H-S, Choi I-K, Na S-H, Lee JW, Jeong SM, Hur J-M. Effect of the UO2 form on the electrochemical reduction rate in a LiCl–Li2O molten salt. J Nucl Mater. 2013;437:178–87. doi:10.1016/j.jnucmat.2013.01.306

Hur J-M, Hong S-S, Lee H. Electrochemical reduction of UO2 to U in a LiCl–KCl-Li2O molten salt. J Radioanal Nucl Chem. 2013;295:851–4. doi:10.1007/s10967-012-2258-0

Sakamura Y, Kurata M, Inoue T. Electrochemical reduction of UO2 in molten CaCl2 or LiCl. J Electrochem Soc. 2006;153(3):D31–9. doi:10.1149/1.2160430

Choi E-Y, Won CY, Cha J-S, Park W, Im HS, Hong SS, Hur J-M. Electrochemical reduction of UO2 in LiCl–Li2O molten salt using porous and nonporous anode shrouds. J Nucl Mater. 2014;444:261–9. doi:10.1016/j.jnucmat.2013.09.061

Willit JL, Miller WE, Battles JE. Electrorefining of uranium and plutonium - A literature review. J Nucl Mater. 1992;199:229-49. doi:10.1016/0022-3115(92)90515-M

Sakamura Y, Omori T. Electrolytic Reduction and Electrorefining of Uranium to Develop Pyrochemical Reprocessing of Oxide Fuels. Nuclear Technology. 2017;171(3):266-75. doi:10.13182/NT10-A10861

Bayoglu AS, Lorenzelli R. Oxygen diffusion in fcc fluorite type nonstoichiometric nuclear oxides MO2±x. Solid State Ionics. 1984;12:53–66. doi:10.1016/0167-2738(84)90130-9

Kim KC, Olander DR. Oxygen diffusion in UO2−x. J Nucl Mater. 1981;102:192–9. doi:10.1016/0022-3115(81)90559-6

Murch GE, Catlow CRA. Oxygen diffusion in UO2, ThO2 and PuO2. A Review. J Chem Soc, Faraday Trans 2. 1987;83:1157–69. doi:10.1039/F29878301157

Hayward PJ, George IM, Kaatz RA, Olander DR. Measurement of 2000–2100°C oxygen diffusion coefficients in hypostoichiometric UO2. J Nucl Mater. 1997;244:36–43. doi:10.1016/S0022-3115(96)00722-2

Moore E, Gueneau C, Crocombette J-P. Diffusion model of the non-stoichiometric uranium dioxide. J Solid State Chem. 2013;203:145–53. doi:10.1016/j.jssc.2013.04.006

Li Y, Liang T, Sinnott SB, Phillpot SR. A charge-optimized many-body potential for the U–UO2–O2 system. J Phys Condens Matter. 2013;25:505401. doi:10.1088/0953-8984/25/50/505401

Li Y. A fundamental understanding of the structures of oxygendefect clusters in UO2+x, U4O9 and U3O7: from the perspective of Tetris cubes. Acta Materialia. 2020;194:482–95. doi:10.1016/j.actamat.2020.05.032

Emre C, Govers K., Lamoen D, Labeau P-E, Verwerft M. Atomic scale analysis of defect clustering and predictions of their concentrations in UO2+x. J Nucl Mater. 2020;541:152403. doi:10.1016/j.jnucmat.2020.152403

Morelon N-D, Ghaleb D, Delaye J-M, Van Brutzel L. A new empirical potential for simulating the formation of defects and their mobility in uranium dioxide. Phil Mag. 2003;83:153355. doi:10.1080/1478643031000091454

Potashnikov SI, Boyarchenkov AS, Nekrasov KA, Kupryazhkin AY. High-precision molecular dynamics simulation of UO2–PuO2: Anion self-diffusion in UO2. J Nucl Mater. 2013;433:215-26. doi:10.1016/j.jnucmat.2012.08.033

Yakub E, Ronchi C, Staicu D. Computer simulation of defects formation and equilibrium in non-stoichiometric uranium dioxide. J Nucl Mater. 2009;389:119–26. doi:10.1016/j.jnucmat.2009.01.029

Govers K, Lemehov S, Hou M, Verwerft M. Molecular dynamics simulation of helium and oxygen diffusion in UO2±x. J Nucl Mater. 2009;395:1319. doi:10.1016/j.jnucmat.2009.10.043

Goel P, Choudhury N, Chaplot SL. Atomistic modeling of the vibrational and thermodynamic properties of uranium dioxide, UO2. J Nucl Mater. 377;2008:438. doi:10.1016/j.jnucmat.2008.03.020

Potashnikov SI, Boyarchenkov AS, Nekrasov KA, Kupryazhkin AY. High-precision molecular dynamics simulation of UO2–PuO2: Pair potentials comparison in UO2. J Nucl Mater. 2011;419:217–25. doi:10.1016/j.jnucmat.2011.08.033

Govers K, Lemehov S, Hou M, Verwerft M. Comparison of interatomic potentials for UO2: Part II: Molecular dynamics simulations. J Nucl Mater. 2008;376:66–77. doi:10.1016/j.jnucmat.2008.01.023

Balboa H, Van Brutzel L, Chartier A, Le Bouar Y. Assessment of empirical potential for MOX nuclear fuels and thermomechanical properties. J Nucl Mater. 2017;495:67–77. doi:10.1016/j.jnucmat.2017.07.067

Busker G, Ph.D. thesis, Imperial College, London; 2002.

Matzke H. Atomic Transport Properties in UO2 and Mixed Oxides (U, Pu)O2. J Chem Soc, Faraday Trans 2. 1987;83:1121-42. doi:10.1039/F29878301121

Berthinier C, Rado C, C. Chatillon C, Hodaj F. Thermodynamic assessment of oxygen diffusion in non-stoichiometric UO2±x from experimental data and Frenkel pair modeling. J Nucl Mater. 2013;433:265–86. doi:10.1016/j.jnucmat.2012.09.011

Basak CB, Sengupta AK, Kamath HS. Classical molecular dynamics simulation of UO2 to predict thermophysical properties. J Alloys Compd. 2003;360:210–6. doi:10.1016/S0925-8388(03)00350-5

Thermophysical properties database of materials for light water reactors and heavy water reactors, IAEA (2006).

Nekrasov KA, Seitov DD, Pomosova AA, Kupryazhkin AY, Gupta SK, Usseinov AB. Sputtering of material from the surface of PuO2 crystals by collision cascades impact. A molecular dynamics study. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2020;475:39–43. doi:10.1016/j.nimb.2020.04.034

Seitov DD, Nekrasov KA, Kupryazhkin AY, Gupta SK, Usseinov AB. The impact of the collision cascades on the xenon and helium clusters in PuO2 crystals. A molecular dynamics simulation. A molecular dynamics study. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2020;476:26–31. doi:10.1016/j.nimb.2020.04.040


Copyright (c) 2021 Kirill A. Nekrasov, Alexander E. Galashev, Dastan D. Seitov, Sanjeev K. Gupta

© Chimica Techno Acta, 2014-2021
ISSN 2411-1414 (Online)

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