Thermal expansion and thermal conductivity of (Th,U)O sub(2) mixed oxides: A molecular dynamics and experimental study

Thermal expansion and thermal conductivity of ThO sub(2) and (Th,U)O sub(2) mixed oxides (MOX) have been investigated by using molecular dynamics (MD) simulation and experimental study. MD simulation have been performed to determine lattice thermal expansion of Th sub(1-x)U sub(x)O sub(2) (x = 0 to...

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Bibliographic Details
Published in:Journal of alloys and compounds 2015-11, Vol.650, p.165-177
Main Authors: Ghosh, P S, Somayajulu, P S, Krishnan, K, Pathak, N, Arya, A, Dey, G K
Format: Article
Language:English
Subjects:
Computer simulation
Heat transfer
Lattices
Mixed oxides
Molecular dynamics
MOX
Thermal conductivity
Thermal expansion
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Summary:Thermal expansion and thermal conductivity of ThO sub(2) and (Th,U)O sub(2) mixed oxides (MOX) have been investigated by using molecular dynamics (MD) simulation and experimental study. MD simulation have been performed to determine lattice thermal expansion of Th sub(1-x)U sub(x)O sub(2) (x = 0 to 0.3125) solid-solutions in the temperature range of 300-3000 K using a combination of Coulomb-Buckingham-Morse and many-body potential model with partial ionic charges. Special quasi-random structures were employed to establish solid-solution configurations. Experimental verification of the lattice thermal expansion behavior is carried out on polycrystalline sample of ThO sub(2) -x wt.% UO sub(2) (x = 0, 6, 13, 25 and 30) MOX from room temperature to 1273 K in vacuum using high temperature X-ray diffraction (HT-XRD). Our combined MD simulations and HT-XRD measurements indicate that incorporation of UO sub(2) in ThO sub(2) systematically increases coefficient of thermal expansion but the rate of increase is higher in low UO sub(2) composition range ([< or =]13 wt.%). A comparative evaluation of the thermal properties of ThO sub(2)-6wt.% UO sub(2) pellets prepared by coated agglomerate pelletization (CAP) process and powder metallurgy routes (sintered in Ar-8%H sub(2) atmosphere) have been performed with respect to micro-inhomogeneity, porosity, O/M and trace impurities. The thermal conductivity of ThO sub(2) and ThO sub(2)-6 wt.% UO sub(2) calculated under equilibrium condition by Green-Kubo formalism show good agreement with our experimental measurements.
ISSN:0925-8388
DOI:10.1016/j.jallcom.2015.07.260