Thermal expansion of neptunium-uranium mixed oxides

Thermal expansions of NpyU1-yO2 solid solutions were investigated between room temperature and 1273 K by a high temperature X-ray diffraction technique. The lattice parameters of NpyU1-yO2 solid solutions at high temperatures were given in polynomial expressions of temperature. High temperature heat capacities, C-p, of NpyU1-yO2 solid solutions were estimated from the thermodynamic relation using the measured thermal expansions and literature data. The estimated errorsin the calculated C-p of UO2 were less than +/- 5%. (C) 1997 Elsevier Science B.V.