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Article Dans Une Revue Journal of Nuclear Materials Année : 2015

In situ high temperature X-Ray diffraction study of the phase equilibria in the UO 2 –PuO 2 –Pu 2 O 3 system

Résumé

The region of the U–Pu–O phase diagram delimited by the compounds UO2–PuO2–Pu2O3 is known to exhibit a miscibility gap at low temperature. Consequently, MOX fuels with a composition entering this region could decompose into two fluorite phases and thus exhibit chemical heterogeneities. The experimental data on this domain found in the literature are scarce and usually provided using DTA that is not suitable for the investigation of such decomposition phenomena. In the present work, new experimental data, i.e. crystallographic phases, lattice parameters, phase fractions and temperature of phase separation, were measured in the composition range 0.14 < Pu/(U + Pu) < 0.62 and 1.85 < O/(U + Pu) < 2 from 298 to 1750 K using a novel in situ high temperature X-ray diffraction apparatus. A very good agreement is found between the temperature of phase separation determined from our results and using the thermodynamic model of the U–Pu–O system based on the CALPHAD method. Also, the combined use of thermodynamic calculations and XRD results refinement proved helpful in the determination of the O/M ratio of the samples during cooling. The methodology used in the current work might be useful to investigate other oxides systems exhibiting a miscibility gap.
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Dates et versions

hal-01815818 , version 1 (14-06-2018)

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Renaud Belin, Michal Strach, Thibaut Truphémus, Christine Guéneau, Jean-Christophe Richaud, et al.. In situ high temperature X-Ray diffraction study of the phase equilibria in the UO 2 –PuO 2 –Pu 2 O 3 system. Journal of Nuclear Materials, 2015, 465, pp.407 - 417. ⟨10.1016/j.jnucmat.2015.06.034⟩. ⟨hal-01815818⟩
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