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Title: A First-Principles Density Function Theory Study of Tritium Diffusion in Li 2ZrO 3: Application for Producing Tritium

Abstract

The ceramic material Li 2ZrO 3 has superior thermo-physical and thermo-chemical properties and is highly compatible with other blanket materials used in nuclear reactors. Like LiAlO 2, it could be used in the form of an annular pellet in tritium-producing burnable absorber rods (TPBARs) to produce tritium( 3H) upon thermal neutron irradiation of lithium isotope ( 6Li). The radiation damaged pellet crystal contains vacancies, defects of its constituent elements, and several other trapping sites which hinder the 3H diffusion process and releasing behavior. In this study, we investigate the diffusion mechanisms of 3H and O 3H species in Li 2ZrO 3 ceramic pellet in order to understand the effects on diffusion barriers and diffusion coefficients due to the presence of interstitial and substitutional Li defects, hydroxide (O– 3H) vacancy defect, and of the interactions of 3H with O-vacancies in the radiation damaged Li 2ZrO 3 crystal. We consider several possible diffusion pathways of interstitial and substitutional 3H and its species in a defective supercell and calculate the activation energy barrier profiles. We find that the smallest activation energy barrier is 0.3 eV and corresponding diffusion coefficient at 600 K is 1.93 × 10 –9 m 2/s for 3H substitutional diffusion.more » The smallest 3H interstitial diffusion barrier and diffusion coefficient are found to be 0.34 eV and 3.25 × 10 –9 m 2/s. By examining several channels for diffusion, our results show the most likely diffusion mechanism of 3H migration is occurring along the c-direction by exchange of 3H within and between different Li sites. Here, our calculated results reveal that the smallest energy barrier for O 3H diffusion is 0.75 eV which is when O 3H is diffusing to the O–Li vacancy pair and the corresponding diffusion coefficient is 6.31 × 10 –13 m 2/s. In terms of 3H diffusion, the obtained results indicate that the performance of Li 2ZrO 3 could be better than γ-LiAlO 2, a widely used ceramic material in TPBAR for producing 3H.« less

Authors:
 [1]; ORCiD logo [1]
  1. National Energy Technology Lab. (NETL), Pittsburgh, PA (United States)
Publication Date:
Research Org.:
National Energy Technology Lab. (NETL), Pittsburgh, PA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1573894
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 50; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Paudel, Hari P., and Duan, Yuhua. A First-Principles Density Function Theory Study of Tritium Diffusion in Li2ZrO3: Application for Producing Tritium. United States: N. p., 2018. Web. doi:10.1021/acs.jpcc.8b05810.
Paudel, Hari P., & Duan, Yuhua. A First-Principles Density Function Theory Study of Tritium Diffusion in Li2ZrO3: Application for Producing Tritium. United States. doi:10.1021/acs.jpcc.8b05810.
Paudel, Hari P., and Duan, Yuhua. Mon . "A First-Principles Density Function Theory Study of Tritium Diffusion in Li2ZrO3: Application for Producing Tritium". United States. doi:10.1021/acs.jpcc.8b05810. https://www.osti.gov/servlets/purl/1573894.
@article{osti_1573894,
title = {A First-Principles Density Function Theory Study of Tritium Diffusion in Li2ZrO3: Application for Producing Tritium},
author = {Paudel, Hari P. and Duan, Yuhua},
abstractNote = {The ceramic material Li2ZrO3 has superior thermo-physical and thermo-chemical properties and is highly compatible with other blanket materials used in nuclear reactors. Like LiAlO2, it could be used in the form of an annular pellet in tritium-producing burnable absorber rods (TPBARs) to produce tritium(3H) upon thermal neutron irradiation of lithium isotope (6Li). The radiation damaged pellet crystal contains vacancies, defects of its constituent elements, and several other trapping sites which hinder the 3H diffusion process and releasing behavior. In this study, we investigate the diffusion mechanisms of 3H and O3H species in Li2ZrO3 ceramic pellet in order to understand the effects on diffusion barriers and diffusion coefficients due to the presence of interstitial and substitutional Li defects, hydroxide (O–3H) vacancy defect, and of the interactions of 3H with O-vacancies in the radiation damaged Li2ZrO3 crystal. We consider several possible diffusion pathways of interstitial and substitutional 3H and its species in a defective supercell and calculate the activation energy barrier profiles. We find that the smallest activation energy barrier is 0.3 eV and corresponding diffusion coefficient at 600 K is 1.93 × 10–9 m2/s for 3H substitutional diffusion. The smallest 3H interstitial diffusion barrier and diffusion coefficient are found to be 0.34 eV and 3.25 × 10–9 m2/s. By examining several channels for diffusion, our results show the most likely diffusion mechanism of 3H migration is occurring along the c-direction by exchange of 3H within and between different Li sites. Here, our calculated results reveal that the smallest energy barrier for O3H diffusion is 0.75 eV which is when O3H is diffusing to the O–Li vacancy pair and the corresponding diffusion coefficient is 6.31 × 10–13 m2/s. In terms of 3H diffusion, the obtained results indicate that the performance of Li2ZrO3 could be better than γ-LiAlO2, a widely used ceramic material in TPBAR for producing 3H.},
doi = {10.1021/acs.jpcc.8b05810},
journal = {Journal of Physical Chemistry. C},
number = 50,
volume = 122,
place = {United States},
year = {2018},
month = {11}
}

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