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Title: Multiscale modeling of thermal conductivity of high burnup structures in UO 2 fuels

The high burnup structure forming at the rim region in UO 2 based nuclear fuel pellets has interesting physical properties such as improved thermal conductivity, even though it contains a high density of grain boundaries and micron-size gas bubbles. To understand this counterintuitive phenomenon, mesoscale heat conduction simulations with inputs from atomistic simulations and experiments were conducted to study the thermal conductivities of a small-grain high burnup microstructure and two large-grain unrestructured microstructures. We concluded that the phonon scattering effects caused by small point defects such as dispersed Xe atoms in the grain interior must be included in order to correctly predict the thermal transport properties of these microstructures. In extreme cases, even a small concentration of dispersed Xe atoms such as 10 -5 can result in a lower thermal conductivity in the large-grain unrestructured microstructures than in the small-grain high burnup structure. The high-density grain boundaries in a high burnup structure act as defect sinks and can reduce the concentration of point defects in its grain interior and improve its thermal conductivity in comparison with its large-grain counterparts. Furthermore, an analytical model was developed to describe the thermal conductivity at different concentrations of dispersed Xe, bubble porosities, and grainmore » sizes. Upon calibration, the model is robust and agrees well with independent heat conduction modeling over a wide range of microstructural parameters.« less
 [1] ;  [2] ;  [1] ;  [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States); Pennsylvania State Univ., University Park, PA (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0022-3115; PII: S0022311515303974
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 470; Journal Issue: C; Journal ID: ISSN 0022-3115
Research Org:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
36 MATERIALS SCIENCE; computer modeling of microstructural effects on thermal transport in UO2 fuels
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1359398