COMPREHENSIVE INVESTIGATION OF SELECTED METAL OXIDES WITH APPLICATION FOR CLEAN ENERGY

这项建议涉及核级和原子级的多尺度建模的应用。这项工作是独一无二的，因为它结合了核模拟和材料建模。虽然要使用的技术已经很好地确定了，但它们从未像这里建议的那样结合在一起。这项工作将应用最先进的第一原理(预测)和改进的建模来研究新型和核材料的结构、光学、机械和热物理性质。这项研究的总体目标是对新型核材料的性质有一个基本的了解。今后三年的短期目标主要集中在：(1)联合模拟辐射源和核材料的原子分子动力学模型，以更好地从根本上了解辐射的影响；(2)利用从头算、预测和半经验方法，大规模研究辐射引起的缺陷对材料性能的影响；(3)通过模拟确定各种核燃料的结构、机械和热物理性质；(4)研究鳗系氧化物的光学和电学性质(重点是U3O8)；以及(5)为反应堆安全课程编写互动代码。 铀氧化物的半导性引起了人们的兴趣，因为这些氧化物的介电常数(e~20)比SiO_2(3.5)高得多。贫铀氧化物可以从核废料中回收，并在太阳能电池和电子产品中有潜在的应用。它们也是生产浓缩铀的副产品。U3O8是最稳定的铀氧化物，但目前还没有关于光学带隙的实验数据。我们拥有所需的专业知识来研究U3O8的电子结构和带隙，包括实验(在加拿大光源)和理论上。萨斯卡通的Cameco公司可以为我们提供可以安全检查的耗尽的U3O8样品。一旦带隙被确定，光学和机械性质将从第一性原理计算中准确地确定。它们将被用来评估U3O8在太阳能电池板中的潜在应用。这将为萨斯喀彻温省铀氧化物的新应用奠定基础，使其超越目前的铀矿石出口。关于U3O8的机械和结构性能的准确数据将使人们能够预测在反应堆或废物储存室发生事故期间由于氧化而导致铀矿体积增加时的应力。 我们已经从理论上研究了各种核燃料，特别是具有高热导率的本质安全的Thoria，它通过更有效的散热来防止燃料熔化。然而，燃料导热系数的实验数据显示出很大的差异，燃耗引起的降解的影响还不是很清楚。蒙特卡罗程序将被用来模拟燃料棒在运行过程中的原子位移，并将评估物理燃耗。经典分子动力学程序中的参数将利用第一性原理计算进行调整，并将用于评估物理燃耗对导热系数的退化。将对二氧化铀和二氧化钛的燃料行为进行比较。 开发的纯燃料和包含缺陷的导热系数关联式将用于新的交互软件，用于多学科调查核反应堆安全和调查类似福岛事故中的燃料熔化。对于设计更安全的反应堆来说，获得模拟铀氧化物和新的更安全燃料(Thoria，UC)性质的新方法是至关重要的。

This proposal concerns the application of multi-scale modeling at both nuclear and atomistic levels. This work is unique because it combines nuclear simulations with materials modeling. Although the techniques to be used are well established, they have never been coupled together as proposed here. This work will apply state of the art, first principles (predictive) and improved modeling to investigate structural, optical, mechanical, and thermo-physical properties of novel and nuclear materials. The overall objective of this research is to develop a fundamental understanding of the properties of novel and nuclear materials. The short-term objectives over the next three years focus on (1) use of combined simulation of the radiation sources and atomistic molecular dynamics modeling of nuclear materials to achieve a better, fundamental understanding of the effects of radiation; (2) use of ab initio, predictive, and semiempirical methods to study the effect of radiation induced defects on the properties of materials on a large scale; (3) determining structural, mechanical, and thermo-physical properties for various nuclear fuels from simulations; (4) investigating optical and electronic properties of actinide oxides (with emphasis on U3O8); and (5) preparing interactive code for a reactor safety course. The semiconductive properties of uranium oxides are of interest since these oxides have dielectric constants much higher (e ~ 20) than SiO2 (3.5). Depleted uranium oxides can be recovered from nuclear waste and have potential application in solar cells and electronics. They are also a by-product of the production of enriched uranium. U3O8 is the most stable uranium oxide but there are no experimental data available about optical band gap. We have the required expertise to investigate the electronic structure and the band gap of U3O8, both experimentally (at Canadian Light Source) and theoretically. Cameco Inc. in Saskatoon can provide us with samples of depleted U3O8 that can be safely examined. Once the band gap has been determined both the optical and mechanical properties will be accurately determined from first principles calculations. They will be used to evaluate the potential application of U3O8 in solar panels. It will lay the groundwork for new applications for uranium oxides in the province of Saskatchewan beyond the current export of uranium ore. Accurate data on the mechanical and structural properties of U3O8 would allow the prediction of stresses when urania volume increases due to oxidation during an accident in a reactor or waste storage compartment. We have studied various nuclear fuels theoretically, especially inherently safe thoria with high thermal conductivity that prevents fuel melting by more efficient heat dissipation. However the experimental data for thermal conductivity of fuel show big differences and implications of burn-up-induced degradation is not well known. Monte Carlo code will be used to simulate the atoms displacements in fuels in operating fuel rods and a physical burnup will be evaluated. The parameters in classical molecular dynamics code will be tuned up using the first principles calculations and it will be used to evaluate the degradation of the thermal conductivity by the physical burnup. The comparison between urania and thoria fuel behaviours will be investigated. The developed thermal conductivity correlations for pure fuel and with inclusion of defects will be used in the new interactive software for multidisciplinary investigation of nuclear reactor safety and investigation of fuel melting in an accident similar to Fukushima. It is critical for the design of safer reactors to have access to new methods of simulating the properties of uranium oxides and new safer fuels (thoria, UC).