COMPREHENSIVE INVESTIGATION OF SELECTED ENHANCED ACCIDENT TOLERANT NUCLEAR FUELS

核事故说明了目前基于纯铀（UO2）燃料的反应堆设计的风险，这种燃料导热性低，在高温下和进一步氧化后会变质。锆合金包层在高温下与水迅速反应，并能释放出高爆炸性的氢气。在开发一种可持续替代不可再生能源的背景下，对能够长时间承受冷却剂损失的增强型耐事故核燃料（EATF）的创新研究正在获得动力。EATF材料必须有更高的热导率（?），以防止熔毁，更慢的氢气生成速率，并改善裂变产物的保留。我们证明了高导热核燃料由于减少了热应变而更安全、更持久。这项研究的总体目标是确定和发展对选定的进化和革命性燃料概念的基本理解。我们将研究陶瓷和金属燃料(用？随着温度的升高)，使用我们研究小组开发的软件和先进的从头算方法，这些方法具有预测能力，现在正在通过全球合作构思。为了防止错误，并使最先进的代码更容易获得工程专业的学生，我们已经开发了一个界面，将进一步更新。在本研究中，我们在反应堆的正常运行条件和极端事故条件下评估了eatf的未知性能。我们研究了结构缺陷和氧化对新进化（铬掺杂铀）和选定的革命性金属（氮化铀（UN））的热导率的影响。计算技术，如密度泛函理论和经典分子动力学（CMD）将用于解释点缺陷，大缺陷和晶界。晶粒尺寸对UO2和UN氧化速率的相反影响将被研究。已开发的燃料（包括纯燃料和含缺陷燃料）的导热系数相关性将用于我们的安全分析软件，以研究燃料棒中的温度分布和梯度。这些发现将由实验数据加以验证。通过与洛斯阿拉莫斯国家实验室的合作，从头开始紧密结合代码（Latte）将用于开发新的CMD势，以帮助鉴定领先的EATF：碳化硅，它与蒸汽的反应速度比锆慢10000倍。我们还将与USask的加拿大光源合作，对电子结构进行实验研究。这项研究将建立一个知识库，以研究核材料的特性和高素质的人员，以维持加拿大的核工业。eatf可以振兴铀工业，因为经过改进的燃料将使反应堆更安全、更经济，从而使加拿大工业更具竞争力。

Nuclear accidents illustrate the risks associated with the present design of reactors based on pure urania (UO2) fuel with its low thermal conductivity that deteriorates at high temperatures and upon further oxidation. Zircaloy cladding reacts rapidly with water at high temperatures and highly explosive hydrogen gas can be released. In the context of developing a sustainable replacement for non-renewable energy sources, innovative research towards enhanced accident-tolerant nuclear fuel (EATF) that can withstand the loss of coolant for a long time is gaining momentum. EATF materials must have higher thermal conductivities (?) to prevent meltdown, a slower rate of hydrogen generation, and improved retention of fission products. We demonstrated that high thermal conductivity nuclear fuel is safer and longer-lasting due to reduced thermal strain. The overall objective of this research is to qualify and develop a fundamental understanding of selected evolutionary and revolutionary fuel concepts. We will investigate ceramic and metallic fuels (with ? increasing with temperature) using the software developed in our research group and advanced ab initio methods with predictive power that are now being conceived through a worldwide collaboration. To prevent errors and make state of the art codes more accessible to engineering students, we have developed an interface, which will be further updated. In this research, we assess the uncharted performance of EATFs under both normal operating conditions and the extreme accident conditions in a reactor. We investigate the effects of structural defects and oxidation on thermal conductivity of new evolutionary (chromia doped urania) and selected revolutionary metallic (uranium nitride (UN)) EATFs. Computational techniques such as density functional theory and classical molecular dynamics (CMD) will be used to account for point defects, large defects, and grain boundaries. The opposite effect of grain sizes on the oxidation rate in UO2 versus UN will be studied. The developed thermal conductivity correlations for fuels, both pure and with defects included, will be used in our software for safety analysis to investigate the temperature profiles and gradients in a fuel rod. The findings will be validated by experimental data. Through a collaboration with Los Alamos National Laboratory, ab initio tight-binding code (Latte) will be used to develop new CMD potentials to help with a qualification of a leading EATF: silicon carbide, which reacts 10000 times slower with steam than zirconium. We will also work with the Canadian Light Source at USask to investigate the electronic structure experimentally. This research will develop a knowledge base to study the properties of nuclear materials and highly qualified personnel to sustain Canada's nuclear industry. EATFs could revive the uranium industry as improved fuels would make reactors safer, more economic and, therefore, the Canadian industry more competitive.