Thermal conductivity of neptunium dioxide

Abstract The thermal diffusivity of neptunium dioxide was measured in the temperature range from 473 to 1473 K by using a laser flash method. The thermal diffusivity slightly decreased with increasing temperature in the temperature range investigated. The heat capacity of NpO 2 was measured in the temperature range from 334 to 1071 K by using a drop calorimetry method. The heat capacity of NpO 2 determined in this study was slightly larger than that of UO 2 and about 7% smaller than that of PuO 2 . The thermal conductivity of NpO 2 was determined from the thermal diffusivity, the heat capacity and the bulk density. It was found that the thermal conductivity of NpO 2 from 873 to 1473 K lay between those of UO 2 and PuO 2 .

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