Laser melting of nano-crystalline uranium dioxide

The present work is focused on the investigation of possible melting temperature depression of nanocrystalline UO2. The behaviour of nano-crystalline refractory oxide of this kind has been studied above 1500 K for the first time here. The technique used is based on sub-second laser heating and fast pyrometry. Nano-crystalline UO2 with grains of (30 20) nm underwent fast oxidation due to the high specific surface. The measured melting point depression (up to over 300 K below 3120 K, the melting temperature of micrometer-sized UO2) was thus mostly attributable to a non-negligible oxygen-to-metal molar ratio increase and, possibly, only to a much lesser extent to a real grain-size effect.