COMPREHENSIVE INVESTIGATION OF SELECTED ENHANCED ACCIDENT TOLERANT NUCLEAR FUELS

核事故说明了目前以纯铀(UO2)燃料为基础的反应堆设计的风险，这种燃料的导热系数很低，在高温和进一步氧化时会恶化。锆合金覆层在高温下与水迅速反应，释放出极具爆炸性的氢气。在开发可持续替代不可再生能源的背景下，对能够长期承受冷却剂损失的增强型事故容忍核燃料(EATF)的创新研究正在获得势头。EATF材料必须具有较高的导热系数(？)以防止熔化，降低氢气生成速度，并提高裂变产物的保留率。我们证明，由于减少了热应变，高导热核燃料更安全、更持久。这项研究的总体目标是鉴定和发展对选定的进化性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(与？使用我们研究小组开发的软件和具有预测能力的先进从头算方法)，这些方法现在正通过全球合作构思。为了防止错误，并使最新的代码更容易为工科学生所接受，我们开发了一个界面，该界面将进一步更新。在这项研究中，我们评估了反应堆中EATF在正常运行条件和极端事故条件下的未知性能。我们研究了结构缺陷和氧化对新的进化型(掺铬的二氧化铀)和选定的革命性金属(氮化铀(UN))EATF导热系数的影响。计算技术，如密度泛函理论和经典分子动力学(CMD)将被用来解释点缺陷、大缺陷和晶界。我们将研究UO2和UN中颗粒大小对氧化速率的相反影响。开发的纯燃料和含缺陷燃料的导热系数关联式将用于我们的安全分析软件，以调查燃料棒中的温度分布和梯度。这一发现将得到实验数据的验证。通过与洛斯阿拉莫斯国家实验室的合作，从头算紧束缚代码(LATE)将被用于开发新的CMD潜力，以帮助获得领先的EATF：碳化硅的资格，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研究核材料性质的知识库和高素质的人员，以支持加拿大的核工业。EATF可以重振铀工业，因为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.