Tritium Accommodation and Diffusion in Li₈PbO₆ from First-Principles Simulations.

Area of Science:

• Nuclear Engineering
• Materials Science
• Computational Physics

Background:

• Lithium lead oxide (Li8PbO6) is a candidate material for fusion reactor breeding blankets.
• Tritium breeding and recovery are critical processes in fusion energy technology.
• Understanding tritium's behavior within the blanket material is essential for efficient recovery.

Purpose of the Study:

• To investigate tritium accommodation in Li8PbO6 using computational methods.
• To determine the migration mechanisms and energy barriers for tritium in Li8PbO6.
• To assess the implications of tritium migration on blanket performance and aging.

Main Methods:

• Density Functional Theory (DFT) to model tritium interactions with Li8PbO6.
• Nudged Elastic Band (NEB) method to calculate migration barriers.
• Analysis of tritium binding sites and defect migration pathways.

Main Results:

• Tritium preferentially binds to oxygen ions, forming hydroxyl groups, rather than occupying interstitial sites.
• Anisotropic migration barriers for tritium interstitials were predicted (0.27 eV in xy-plane, 0.69 eV along z-axis).
• Escape from lithium vacancy traps requires 0.76-0.85 eV, with whole trap migration at 0.67-1.18 eV.

Conclusions:

• Tritium accommodation in Li8PbO6 is primarily through hydroxyl formation.
• Low migration energies suggest that blanket aging will have a reduced impact on tritium release compared to other materials.
• These findings support Li8PbO6 as a promising material for fusion reactor blankets.