Science Question 1: What is the impact of 5f electrons on phonon and electron structure in Th1-xUxO2 and UZr alloys?

This question targets the complexities introduced by 5f electrons in electron and phonon dispersion and scattering. This foundational work is necessary to fully consider the more complex problem of transport in the presence of mesoscale defect structures.


Science Question 2: How do intrinsic and irradiation-induced defects self-organize in Th1-xUxO2 and UZr alloys, and what are their impacts on electron and phonon scattering?

This question considers the self-organization mechanisms of prominent non-ordered and ordered structures found in off-stoichiometric oxide fuel, loops and void structures in ion-irradiated oxide and metallic fuel, and grain boundaries in high-burnup structures, as well as the impact of these defect structures on electron and phonon scattering.


Science Question 3: What are the collective effects of defects, defect ordering and defect supersaturation on thermal transport of Th1-xUxO2 and UZr alloys?

This question addresses the collective impacts of electron and phonon scattering by defects on thermal transport on mesoscopic length scales. Validation of model predictions, obtained using the Boltzmann transport formalism, will come from nanometer- and micrometer-scale thermal transport measurements and from in-reactor measurements of thermal conductivity.