高温气冷堆大晶粒二氧化铀核芯研究

摘要

Large grain UO2 fuel kernels are expected to reduce fission gas release which can achieve extended burn up and life of reactor.The UO2 fuel kernels of HTGR were prepared by sol-gel method, and doped with Al(NO3)3 · 9H2O to increase their grain sizes.Microstructure of UO2 fuel kernels of HTGR and the relations of the O ions released by the dissociation of Al(OH)3 and the diffusion coefficient of U ions were studied.The effect of dopant content on the grain sizes of UO2 fuel kernels was investigated.It indicates that the grain sizes are increased from 18 μm to 30 μm.The sintering mechanism of UO2 fuel kernels by the addition of Al(NO3)3 · 9H2O shows that the grain sizes of UO2 are affected by the diffusion of vacancy.%大晶粒的UO2核芯可更有效地阻止反应堆运行时裂变气体的释放,实现反应堆燃耗的加深和延长反应堆燃料元件的运行寿命.采用溶胶凝胶工艺制备高温气冷堆燃料元件的UO2核芯,在胶液中加入含有Al的化合物Al(NO3)3·9H2O,以增大核芯晶粒尺寸.研究了添加剂对核芯晶粒尺寸的影响及烧结过程中分解的O离子与核芯U离子的扩散系数之间的关系.通过添加含有Al的化合物,UO2核芯的平均晶粒尺寸由18 μm增加到30μm.对添加Al(NO3)3·9H2O的UO2核芯的烧结机理研究表明,UO2核芯晶粒的长大主要受空位扩散机制的影响.