Microstructures of Columnar Grains in Uranium Dioxide

Configurational analysis of uranium-doped thorium dioxide

While thorium dioxide is already used industrially in high temperature applications, more insight is needed about the behaviour of the material as part of a mixed-oxide (MOX) nuclear fuel, incorporating uranium. We have developed a new interatomic potential model, commensurate with a prominent existing UO2 potential, to conduct configurational analyses of uranium-doped ThO2 supercells. Using th...

Molten uranium dioxide structure and dynamics.

Uranium dioxide (UO2) is the major nuclear fuel component of fission power reactors. A key concern during severe accidents is the melting and leakage of radioactive UO2 as it corrodes through its zirconium cladding and steel containment. Yet, the very high temperatures (>3140 kelvin) and chemical reactivity of molten UO2 have prevented structural studies. In this work, we combine laser heating,...

Molecular dynamics analysis of diffusion of uranium and oxygen ions in uranium dioxide

Diffusion behaviours of oxygen and uranium were evaluated for bulk and grainboundaries of uranium dioxide using the molecular dynamics (MD) simulation. It elucidated that oxygen behaved like liquid in superionic state at high temperatures and migrated on sublattice sites accompanying formation of lattice defects such as Frenkel defects at middle temperatures. Formation energies of Frenkel and S...

Surface Electrochemistry of Uranium Dioxide in Acidic Hydrogen Peroxide Solutions

The electrochemical reduction of H2O2 on SIMFUEL was investigated over the pH range 1 to 4. The mechanism at pH 4 is known to occur on U species incorporated into a surface layer of U1-2xU2xO2+x. However, below pH 3, reduction occurs on an adsorbed UO2(OH) state which is unstable and oxidizes to insulating U before dissolving as UO2. Both schemes are observed at intermediate pH’s. The presence ...

Mathematical Modeling of Fluorination Reaction of Uranium Dioxide and Evaluation of Existing Gas-Solid Reaction Models