Oxygen self and chemical diffusion coefficients in

Breitung, W.

doi:10.1016/0022-3115(78)90527-5

Cited by 66 publications

(24 citation statements)

References 18 publications

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“…An oxygen concentration gradient is set up between the sample and the reacting medium, and the kinetics are followed by monitoring the weight change or change in conductivity of the sample (Marin, 1968;Lay, 1970). A comparison of oxygen self-diffusion and chemical diffusion coefficients in UO 2 shows that chemical diffusion is several of orders of magnitude faster than self-diffusion (Breitung, 1978). This is because the chemical diffusion coefficient describes the movement of oxygen in the presence of an oxygen concentration gradient.…”

Section: Oxygen Diffusionmentioning

confidence: 99%

“…1016/j.gca.2011.03.040 extensively studied, especially at high temperatures (>600°C), because understanding oxygen diffusion is important in nuclear fuel oxidation and reduction processes (e.g., Bayoglu and Lorenzelli, 1984;Hayward et al, 1997;Sabioni et al, 2000). The results of these studies have been summarized in several reviews (Belle, 1969;Breitung, 1978;Knorr et al, 1989;Meachen, 1989) and show that diffusion coefficients are dependent on temperature and stoichiometry and that there is a range in the data, depending on the experimental method used (Fig. 1).…”

Section: Introductionmentioning

confidence: 98%

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O and H diffusion in uraninite: Implications for fluid–uraninite interactions, nuclear waste disposal, and nuclear forensics

Fayek

Anovitz

Cole

et al. 2011

Geochimica et Cosmochimica Acta

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Section: Oxygen Diffusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

O and H diffusion in uraninite: Implications for fluid–uraninite interactions, nuclear waste disposal, and nuclear forensics

Fayek

Anovitz

Cole

et al. 2011

Geochimica et Cosmochimica Acta

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“…Experimental data on UO 2 transport properties are known for temperatures below 1500 K [6][7][8][9], which correspond to its crystalline state with relatively low concentration of lattice defects. These data do not directly describe processes of superionic transition, during which anionic defect concentration grows exponentially and then saturates at temperatures above 2600 K [10].…”

Section: Introductionmentioning

confidence: 99%

High-precision molecular dynamics simulation of UO2–PuO2: Anion self-diffusion in UO2

Potashnikov

Boyarchenkov

Nekrasov

et al. 2013

Journal of Nuclear Materials

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h i g h l i g h t s" We perform MD simulation of oxygen diffusion in UO2 (up to 50 000 ions and 1 ls time)." We reached 1400 K and 10 À12 cm 2 /sec, which allowed direct comparison to experiments." S-shaped T-dependence of activation energy and k-peak of its derivative were obtained. " Continual superionic phase transition (rather than first or second order) was proved. t r a c tOur series of articles is devoted to high-precision molecular dynamics simulation of mixed actinide-oxide (MOX) fuel in the approximation of rigid ions and pair interactions (RIPI) using high-performance graphics processors (GPU). In this article we study self-diffusion mechanisms of oxygen anions in uranium dioxide (UO 2 ) with the 10 recent and widely used sets of interatomic pair potentials (SPP) under periodic (PBC) and isolated (IBC) boundary conditions. Wide range of measured diffusion coefficients (from 10 À3 cm 2 /s at melting point down to 10 À12 cm 2 /s at 1400 K) made possible a direct comparison (without extrapolation) of the simulation results with the experimental data, which have been known only at low temperatures (T < 1500 K). A highly detailed (with the temperature step of 1 K) calculation of the diffusion coefficient allowed us to plot temperature dependences of the diffusion activation energy and its derivative, both of which show a wide ($1000 K) superionic transition region confirming the broad k-peaks of heat capacity obtained by us earlier. It is shown that regardless of SPP the anion self-diffusion in model crystals without surface or artificially embedded defects goes on via exchange mechanism, rather than interstitial or vacancy mechanisms suggested by the previous works. The activation energy of exchange diffusion turned out to coincide with the anti-Frenkel defect formation energy calculated by the lattice statics.

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“…D U i is the "intrinsic" diffusion coefficient for uranium interstitials on the uranium sublattice and so on; see e.g. [40,21,22,51]. Substi- (9)- (11) in (12)- (15), gives the dopant concentration dependent diffusion coefficients in the (U 1−y ,M y )O 2±x compound.…”

Section: Diffusion Coefficientsmentioning

confidence: 99%

Effect of additives on self-diffusion and creep of UO 2

Massih

Jernvist

2015

Computational Materials Science

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The creep of UO 2 doped with Nb 2 O 5 and Cr 2 O 3 has been assessed using a point defect model based on the law of mass action, and the diffusional creep according to the Nabarro-Herring mechanism, which relates the creep rate to the lattice self-diffusivity, the inverse of grain area and the applied stress. The self-diffusion coefficients of cation (U) and anion (O) are directly proportional to the concentrations of ions, which in turn are functions of dopant concentrations. The model has been used to evaluate past creep experiments on UO 2 doped with Nb 2 O 5 and Cr 2 O 3 in concentrations up to about 1 mol.%, with a varying grain size at different temperatures and applied stresses. The creep rate increases significantly with the dopant concentration and the putative model, after a modification of the creep rate coefficient, retrodict the measured data satisfactorily. A number of factors affecting creep rate and thereby our model computations are discussed.

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Oxygen self and chemical diffusion coefficients in

Cited by 66 publications

References 18 publications

O and H diffusion in uraninite: Implications for fluid–uraninite interactions, nuclear waste disposal, and nuclear forensics

O and H diffusion in uraninite: Implications for fluid–uraninite interactions, nuclear waste disposal, and nuclear forensics

High-precision molecular dynamics simulation of UO2–PuO2: Anion self-diffusion in UO2

Effect of additives on self-diffusion and creep of UO 2

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