COMPREHENSIVE INVESTIGATION OF SELECTED ENHANCED ACCIDENT TOLERANT NUCLEAR FUELS

核事故说明了与目前设计的反应堆有关的风险，这些反应堆基于纯氧化铀燃料，其导热率低，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，并可释放出高度爆炸性的氢气。 在开发不可再生能源的可持续替代品方面，对能够长期承受冷却剂损失的增强型事故耐受核燃料的创新研究正在取得势头。EATF材料必须具有较高的导热系数（？）以防止熔毁、减慢氢产生速率和改进裂变产物的保留。我们证明了高导热性核燃料由于减少了热应变而更安全和更持久。 这项研究的总体目标是鉴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（与？随着温度的增加）使用我们的研究小组开发的软件和先进的从头算方法，具有预测能力，现在正在通过全球合作构思。为了防止错误并使工程专业的学生更容易获得最先进的代码，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EATF在正常运行条件下和极端事故条件下的反应堆中的未知性能。我们研究了结构缺陷和氧化对新的进化（氧化铬掺杂的氧化铀）和选定的革命性金属（氮化铀（UN））EATF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）将被用来占点缺陷，大缺陷，和晶界。将研究UO2与UN中晶粒尺寸对氧化速率的相反影响。开发的燃料，无论是纯的和有缺陷的热导率的相关性，将被用于我们的安全分析软件，以调查在燃料棒的温度分布和梯度。研究结果将通过实验数据进行验证。通过与洛斯阿拉莫斯国家实验室的合作，从头算紧密约束代码（Latte）将用于开发新的CMD潜力，以帮助获得领先EATF的资格：碳化硅，其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，通过实验研究电子结构。这项研究将建立一个研究核材料特性的知识库，并培养高素质的人才，以维持加拿大的核工业。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.