Effect of temperature on lattice parameter and bulk modulus of mixed Uranium-Thorium oxides
Matthew Loyd
Department of Materials Science & Engineering, University of Tennessee
This page shows visualizations of the a UO2 lattice that has been displaced so that the resulting stresses can be used to calculate the bulk modulus. This was done using a modified version of the ELASTIC_T example for the 2018 spring course MSE 614.
Understanding the mechanical properties of actinide oxides at different temperatures has many implications in planning fuel cells and handling spent nuclear fuel. In this work, I investigated a composition that has important in mixed oxide (MOX) fuel cycles, UxTh1-xO2. To do this, I used the EAM potential for this composition [1], and built my own LAMMPS input files. I determined the lattice parameter for UO2, ThO2, and 3 intermediate compositions from 300-1000 K and at 0 GPa pressure. The average linear coefficientof thermal expansion for each composition is included in the table blow
| Composition | Thermal Expansion (x 106 K-1) |
|---|---|
| UO2 | 6.40 |
| U3ThO8 | 6.12 |
| UThO4 | 7.02 |
| UTh3O8 | 5.83 |
| ThO2 | 6.68 |
Next, I used a LAMMPS example that perturbs the simulated atoms and measures resultant stress to calculate the bulk modulus at the same temperatures and pressure. This is simulatied below.
Interactive Structures
Color Legend:
- Blue = Uranium
- Green = Thorium
- Red = Oxygen
References
[1] Atomistic Simulation Group, Library of Potentials, Online, October 2015,http://abulafia.mt.ic.ac.uk/potentiaks
posted: April 2018.
updated: April 2018.