热压烧结UN陶瓷芯块的性能

UN燃料具有铀密度高、熔点高、热导率高、热膨胀系数低、辐照稳定性好等优点，是未来空间核电源、核火箭、快堆和ADS的重要候选燃料。本文采用金属铀粉与氮气在300～400℃直接发生化合反应，制得单相U₂N₃粉末。粒度为38.3 μm的U₂N₃粉末在1 600 ℃真空热压烧结，制得相对密度为93.5%、存在少量金属铀相的UN陶瓷；而18.1 μm的U₂N₃粉末在1 550 ℃真空热压烧结，制得相对密度为96.1%、不残留金属铀相的UN陶瓷，U与N的总质量分数为99.57%，每个金属杂质含量均低于50 μg/g，氧含量为1 048 μg/g，碳含量为502 μg/g。U₂N₃在1 027 ℃以上将会完全分解成UN，UN在1 627 ℃以上也会发生分解。

Property of Uranium Nitride Ceramic Pellet by Hot Press Sintering

Uranium nitride nuclear fuel has lots of advantages, such as high uranium density, high melt point, high thermal conductivity, low thermal expansion coefficient and high irradiation stability, so it is an important candidate fuel for the future nuclear energy systems including space nuclear reactor, nuclear rocket, fast reactor and ADS. In this research, U₂N₃ powders were fabricated by nitriding reaction of nitrogen and uranium powders. UN ceramic pellets with density of 93.5%TD (theory density) have a little residual metal uranium when U₂N₃ powders with median particle size of 38.3 μm were hot press sintered in vacuum at 1 600 ℃. But UN ceramic pellets can be vacuum hot press sintered to 96.1% TD at 1 550 ℃ by 18.1 μm U₂N₃ powders, without residual uranium, in which the total mass content of U and N is 99.57%, the impurity content of each heavy metal is less than 50 μg/g, the oxygen content is 1 048 μg/g, and the carbon content is 502 μg/g. U₂N₃ will completely be decomposed into UN above 1027 ℃, and UN will also be decomposed above 1 627 ℃。