弥散型燃料中陶瓷燃料颗粒裂纹的愈合机理

Due to the stable irradiation behaviour, high inherent safety, deep burnup and long life time, the dispersion fuel is one of nuclear fuels which will be widely used in future. In the process of manufacture, the ceramic-fuel particle will be craze because of the rolling pressure. But the crack will be healed in the process of irradiation. Crack healing affects the irradiation behaviour of the dispersion fuel evidently. Revealing the healing mechanism is quite significant to the development of the research of the dispersion fuel..This fund will use the existing irradiated dispersion fuel sample, observe the phenomena of crack healing, analyse the element and the morphology of grain position in the crack healing region. Then the molecular dynamic (MD) method will be used to simulate the deposition behaviors of the fission fragment and the bonding behaviors between the crack surface and the fuel. With MD simulation, it will make the crack healing mode clear. Finally, the crack healing mechanism of ceramic-fuel particle in dispersion fuel with irradiating will be obtained and the influencing factors of crack healing will be showed. The research results are propitious to understand the abnormal swelling of the dispersion fuel in detail. This is fairly important to promote the safety-running temperature and extend the life time of dispersion fuel. Meanwhile，this research will consummate the ceramic crack healing mechanism during the irradiation and the lower temperature condition.

弥散型燃料辐照稳定性好，固有安全性高，燃耗深，使用寿期长，是一种应用前景广阔的核燃料。在制备过程中，陶瓷燃料颗粒因承受轧制压力引起开裂，堆内辐照时裂纹会发生自愈。裂纹愈合对陶瓷燃料的后续开裂行为有显著影响，揭示其愈合机理，对弥散型燃料的研究发展意义重大。.本基金拟利用现有弥散型燃料辐照样品，在热室统计观察裂纹愈合情况，分析裂纹区域的物质成分和晶粒位形特征；利用分子动力学模拟手段，模拟裂变碎片元素在裂纹处的沉积行为及燃料相元素与裂纹面的键合行为，明确裂纹愈合方式，探明裂纹愈合随温度、燃耗深度变化的规律；最终建立弥散型燃料陶瓷燃料颗粒的裂纹愈合机理。研究结果对深入认识弥散型燃料的起泡行为、提高燃料元件的安全运行温度、延长其使用寿期有重要的促进作用，同时该机理的认识将丰富和完善陶瓷材料在辐照和较低温度区间等极端条件下的裂纹愈合机理。

弥散型燃料辐照稳定性好，固有安全性高，燃耗深，使用寿期长，是一种应用前景广阔的核燃料，也是世界上舰船反应堆的主要核燃料。在制备过程中，陶瓷燃料颗粒因承受轧制压力引起开裂，堆内辐照时裂纹会发生自愈。裂纹愈合对陶瓷燃料的后续开裂行为有显著影响，揭示其愈合机理，对弥散型燃料的研究发展意义重大。.本项目利用已有弥散型燃料辐照样品在热室分析裂纹愈合情况，分析裂纹区域的物质成分和晶粒特征，结合利用分子动力学方法模拟裂变碎片对裂纹及紧邻区域进行冲击的过程，分析了裂纹宽度、燃耗深度、温度、损伤能量等因素对裂纹愈合行为的影响，建立了弥散型燃料陶瓷燃料颗粒的裂纹愈合机理。.弥散型燃料陶瓷燃料的裂纹愈合行为是由裂变反应引起的裂变碎片对裂纹区域及裂纹周边区域的冲击造成的，有两种模式，一种是裂变碎片冲击进入裂纹区域被捕获而沉积在裂纹区域，在裂纹区域形成局部团簇；另一种是裂变碎片冲击裂纹边缘区域，引起燃料基体相原子离开原有位置，进入裂纹区域对裂纹进行填充。温度对该类型的裂纹愈合影响不明显。.研究结果对深入认识弥散型燃料的起泡行为、提高燃料元件的安全运行温度、延长其使用寿期有重要意义，同时该机理的认识将为特殊环境下使用的陶瓷材料提供了一种较低温度的连接方法和途径。