Phase-Field Simulation of Spinodal Decomposition in U-50Zr Metallic Nuclear Fuel

Area of Science:

• Materials Science
• Nuclear Engineering
• Physical Chemistry

Background:

• Uranium-Zirconium (U-Zr) fuel undergoes spinodal decomposition during the gamma-delta phase transition, impacting its properties.
• Limited understanding exists regarding the specifics of spinodal decomposition in U-50Zr fuel.

Purpose of the Study:

• To investigate the spinodal decomposition behavior in U-50Zr fuel.
• To analyze the thermodynamic mechanisms driving spinodal decomposition.
• To determine the influence of temperature and grain boundaries (GB) on this process.

Main Methods:

• Utilized the phase-field approach for simulation.
• Thermodynamic analysis of spinodal decomposition mechanisms.
• Examination of temperature and GB effects on decomposition.

Main Results:

• U-rich phase, with up to 90% U concentration, forms during spinodal decomposition.
• The U-rich phase initially appears at GBs, followed by precipitation within grains.
• Ostwald ripening is observed, where larger precipitates absorb smaller ones.
• Temperature significantly affects the coarsening rate and equilibrium time of precipitates.

Conclusions:

• Spinodal decomposition in U-50Zr initiates at grain boundaries and progresses into the grain.
• Temperature is a critical factor controlling the kinetics and final state of spinodal decomposition.
• The findings provide crucial insights into U-Zr fuel behavior under phase transition conditions.