Tritium Diffusion Pathways in y-LiAlO2 Pellets Used in TPBAR: A First-Principles Density Functional Theory Investigation

Journal Article · Thu May 10 00:00:00 EDT 2018 · Journal of Physical Chemistry C

DOI:https://doi.org/10.1021/acs.jpcc.8b01108· OSTI ID:1576574

Paudel, Hari ^[1]; Lee, Yueh-Lin ^[1]; Senor, David J. ^[2]; Duan, Yuhua ^[1]

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1. National Energy Technology Laboratory
2. BATTELLE (PACIFIC NW LAB)

With superior thermophysical and thermochemical properties, gamma-LiAlO2 has high compatibility with other blanket materials and is used in the form of an annular pellet in tritium-producing burnable absorber rods (TPBARs) to produce tritium by thermal neutron irradiation of Li-6. In radiation damaged gamma-LiAlO2, different types of vacancies, defects of its constituent elements, and other trapping sites hinder the diffusion process of tritium. In this study, the first-principles density functional theory approach is used to study the diffusion mechanisms of tritium defect and its species, such as interstitial and substitutional tritium defects, oxygen-tritium vacancy defects, and interaction of tritium with oxygen vacancies in defective and nondefective gamma-LiAlO2. The obtained results provide an understanding of how such defects hamper the diffusivity and solubility of tritium. By calculating several different diffusion pathways, our results show that the smallest activation energy barrier is 0.63 eV for substitutional tritium diffusion with a diffusion coefficient of 3.25 X 10(-12) m(2)/s. The smallest oxygen-tritium diffusion barrier is found to be 2.17 eV, which is around 3.5 times higher than the tritium diffusion barrier alone.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1576574
• Report Number(s): PNNL-SA-136350
• Journal Information: Journal of Physical Chemistry C, Vol. 122, Issue 18
• Country of Publication: United States
• Language: English