Advanced microstructure investigations of the high-burnup structure (HBS) in UO₂ produced by high-dose 84 MeV Xe ion irradiation are reported. Spark plasma sintered micro-grained UO₂ was irradiated to 1357 dpa at 350 °C. The characteristic nano-grains and micro-pores of the HBS were formed. The grain size and grain boundary misorientation distributions of the HBS were measured using transmission electron microscopy based orientation imaging microscopy. Grain polygonization due to accumulation of radiation-induced dislocations was found to be the mechanism of nano-crystallization. The morphology of Xe bubbles was quantitatively investigated. This study provides crucial references for advanced fuel performance modeling of high-burnup UO₂.

报告了由高剂量84 MeV Xe离子辐照产生的UO _2中高燃点结构（HBS）的高级微观结构研究。将火花等离子体烧结的UO ₂微粒在350°C下辐照至1357 dpa。形成了HBS的特征性纳米颗粒和微孔。使用基于透射电子显微镜的取向成像显微镜来测量HBS的晶粒尺寸和晶界取向不良分布。发现由于辐射引起的位错的积累而引起的晶粒多角化是纳米晶化的机理。定量研究了Xe气泡的形态。该研究为高燃耗UO _2的先进燃料性能建模提供了关键参考。