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Title: Thermophysical properties of urania-zirconia (U,Zr)O2 mixed oxides by molecular dynamics

Abstract

Molecular dynamics simulations were used to investigate the thermophysical properties of (U,Zr)O2 between 300 K and 3500 K. For compositions with <25% UO2 the tetragonal phase is stable but beyond 25% the cubic fluorite phase becomes stable for all temperatures. Thermal expansion, heat capacity and thermal conductivity have been predicted. The addition of ZrO2 to UO2 causes a reduction in thermal conductivity however this effect decreases with increased temperature and, beyond 1000 K, becomes insignificant. Thermal expansion of (U,Zr)O2 mixtures with >25% UO2, which are in the cubic fluorite phase, is similar to that of the pure UO2 end member. A superionic transition is observed in cubic (U,Zr)O2 at temperatures between 1500 K and 3000 K, occurring at progressively lower temperatures with increasing ZrO2 content. Here, the heat capacity of these mixed oxides increases from 80 J/mol.K up to 130 J/mol.K at temperatures relevant to accident conditions, possibly retarding heating in fuels with a significant pellet-clad bonding layer.

Authors:
 [1];  [2]; ORCiD logo [3];  [1];  [1]
  1. Univ. of New South Wales (Australia). School of Mechanical Engineering; Australia's Nuclear Science and Technology Organisation (ANSTO) (Australia)
  2. Univ. of New South Wales (Australia). School of Mechanical Engineering
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1574000
Alternate Identifier(s):
OSTI ID: 1693656
Report Number(s):
LA-UR-19-25917
Journal ID: ISSN 0022-3115; TRN: US2001315
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 528; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; UO2; ZrO2; Thermal expansion; Thermal conductivity; Nuclear fuel

Citation Formats

Frost, Dillon G., Galvin, Conor O. T., Cooper, Michael William Donald, Obbard, Edward G., and Burr, Patrick A. Thermophysical properties of urania-zirconia (U,Zr)O2 mixed oxides by molecular dynamics. United States: N. p., 2019. Web. doi:10.1016/j.jnucmat.2019.151876.
Frost, Dillon G., Galvin, Conor O. T., Cooper, Michael William Donald, Obbard, Edward G., & Burr, Patrick A. Thermophysical properties of urania-zirconia (U,Zr)O2 mixed oxides by molecular dynamics. United States. doi:10.1016/j.jnucmat.2019.151876.
Frost, Dillon G., Galvin, Conor O. T., Cooper, Michael William Donald, Obbard, Edward G., and Burr, Patrick A. Tue . "Thermophysical properties of urania-zirconia (U,Zr)O2 mixed oxides by molecular dynamics". United States. doi:10.1016/j.jnucmat.2019.151876. https://www.osti.gov/servlets/purl/1574000.
@article{osti_1574000,
title = {Thermophysical properties of urania-zirconia (U,Zr)O2 mixed oxides by molecular dynamics},
author = {Frost, Dillon G. and Galvin, Conor O. T. and Cooper, Michael William Donald and Obbard, Edward G. and Burr, Patrick A.},
abstractNote = {Molecular dynamics simulations were used to investigate the thermophysical properties of (U,Zr)O2 between 300 K and 3500 K. For compositions with <25% UO2 the tetragonal phase is stable but beyond 25% the cubic fluorite phase becomes stable for all temperatures. Thermal expansion, heat capacity and thermal conductivity have been predicted. The addition of ZrO2 to UO2 causes a reduction in thermal conductivity however this effect decreases with increased temperature and, beyond 1000 K, becomes insignificant. Thermal expansion of (U,Zr)O2 mixtures with >25% UO2, which are in the cubic fluorite phase, is similar to that of the pure UO2 end member. A superionic transition is observed in cubic (U,Zr)O2 at temperatures between 1500 K and 3000 K, occurring at progressively lower temperatures with increasing ZrO2 content. Here, the heat capacity of these mixed oxides increases from 80 J/mol.K up to 130 J/mol.K at temperatures relevant to accident conditions, possibly retarding heating in fuels with a significant pellet-clad bonding layer.},
doi = {10.1016/j.jnucmat.2019.151876},
journal = {Journal of Nuclear Materials},
number = ,
volume = 528,
place = {United States},
year = {2019},
month = {11}
}

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