Graphite components are constantly subjected to a combined actions of annealing and irradiation due to high temperatures and thermal spike caused by irradiation when reactors are operating, resulting in complex microstructures along with matching changes in the material properties and dimensions. This study investigates the evolution process of initial irradiation defects at different annealing temperatures, which is difficult to captured by experiment. The findings indicate that 923K reactor-temperature annealing can also quickly restore isolated self-interstitial atoms and small-sized point defect clusters to intralayer locations on the nanosecond scale. However, multi-interlayer penetration damages and localized point defect aggregation from high-energy irradiation can lead to the disappearance of layered structural information, which allows these damage structures to develop into interlayer dislocations during annealing process. These interlayer dislocations further exacerbate the interlayer expansion of graphite crystal and may elucidate the mechanism behind volume expansion in nuclear graphite within reactors. Fully amorphized regions can also regain a layered structure approximately when guided by residual layered structures at 2000K, while chaotic regions or disordered layered structures form in the absence of guidance. These chaotic regions significantly exacerbate the volume expansion of graphite model, which may be related to the rapid volume increase observed in nuclear graphite components at the end of reactor life. The study provides insights into the transformation of initial irradiation defects into different types of defects under different temperatures and damage states, which serve as a critical foundation for assessing the evolution of irradiation defects in nuclear graphite for reactor applications and annealing studies.

中文翻译：

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深入了解辐照后石墨化结构的退火机制


反应堆运行时，由于辐照引起的高温和热尖峰，石墨部件不断受到退火和辐照的联合作用，导致复杂的微观结构以及材料性能和尺寸的匹配变化。本研究研究了不同退火温度下初始辐照缺陷的演变过程，这是实验难以捕获的。研究结果表明，923K 反应堆温度退火还可以将孤立的自填隙原子和小尺寸点缺陷簇快速恢复到纳秒级的层内位置。然而，高能辐照引起的多层层间穿透损伤和局部点缺陷聚集会导致层状结构信息的消失，从而使这些损伤结构在退火过程中发展为层间位错。这些层间位错进一步加剧了石墨晶体的层间膨胀，并可能阐明反应堆内核石墨体积膨胀背后的机制。当在2000K时由残余层状结构引导时，完全非晶化区域也可以大约恢复层状结构，而在没有引导的情况下形成混沌区域或无序层状结构。这些混沌区域显着加剧了石墨模型的体积膨胀，这可能与反应堆寿命结束时在核石墨组件中观察到的体积快速增加有关。 该研究提供了在不同温度和损伤状态下初始辐照缺陷向不同类型缺陷转变的见解，这为评估反应堆应用和退火研究中核石墨辐照缺陷的演变提供了关键基础。