Variation of the thermal conductivity of (U,Dy)O2 solid solutions as a function of the Dy content

The relationship between the lattice parameter (a) and the Dy content (y) in (U1-yDyy)O-2, 0 <= y <= 0.2, is expressed as a=0.5470 - 0.0215y in this study. When the above relation was applied to the Ohmichi's rule, it was suggested that U5+ existed in preference to U6+ in (U,Dy)O-2 solid solutions. The thermal conductivities of UO2 and (U,Dy)O2 gradually decreased with the temperature, which showed that the temperature dependency of the thermal conductivity up to 1473 K followed the phonon conduction model, K= (A+BT)(-1). The relationship between the thermal conductivity of UO2 and (U,Dy)O-2 could be expressed as K(SS) = K-UO2/(1 + K-UO2 (0.9704y - 0.0006yT)). It was also found that the size effect had a greater influence on the lattice defect thermal resistivity than the mass effect and especially, the size difference between the U4+ and U5+ ions rather than that between the U4+ and Dy3+ played a dominant role in the reduction of the thermal conductivity of (U,Dy)O2. (C) 2006 Elsevier B.V. All rights reserved.