Computational Molecular Analysis for Thorium Fuels

Thorium oxide has a set of physical and chemical properties which make it an excellent fertile nuclear fuel matrix. For such fuels to receive safety 'qualification', their safe performance needs to be demonstrated using a combination of physical testing and computer modelling. To support this work, there is a need for more detailed knowledge of the fundamental material properties of thorium fuel materials, (Th,Pu)O2 and (Th,U)O2, and for ThO2 itself. In many cases, these properties (such as gas diffuss ion rates through the oxide lattice) cannot be measured and so reliable computed values are sought. This is a major challenge, but one that modern molecular dynamics tools are becoming able to meet. An important first step toward building this capabilit y is to establish the computational parameters through a series of high level 'first principles' calculations on the various thorium oxide materials. This will be done through a program of calculating the structures and energies of ThO2, (Th,Pu)O2, and ( Th,U)O2. The density of electronic states, the energies of various defect structures will be computed and form a useful database serving dynamic property estimation in future work. This work will be challenging and extend the boundaries of application o f the computational tools to new material types. It will require the intelligent adaptation of methods to compensate for special features of ThO2, relativistic effects and f-electron localisation. The predictive capability for ThO2 properties that is bui lt during this project will enable us to make greater use of the data is generated in physical testing programs. This will maximise the value of these expensive tests ultimately help in building the safety case for thorium fuels. The application of these computational techniques on ThO2 materials has potential spin-off relevence to the metallurgical industry and the development of specialized products such as next-generation inorganic solar cells