Thermal transport at (001) twist grain boundaries in UO{sub 2}
- Department of Physics, Missouri University of Science and Technology, Rolla, MO 65409 (United States)
- Department of Computer Science, Montana Tech of the University of Montana, Butte, MT 59701 (United States)
- Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States)
The thermal conductivity of the nuclear fuels critically affects performance and safety of the nuclear reactor and thus continues to attract interest of engineers and researches. In spite of the large volume of experimental data on the thermal transport properties in UO{sub 2}, new discoveries in recent years include anisotropic thermal conductivity, and unexpectedly large contribution of the optical phonons to thermal transport. On the other hand, advances in computer power allow to simulate directly from atomic level the effect of structural defects such as grain boundaries, dislocations and pores on the thermal conductivity in UO{sub 2}. Unfortunately, such simulations do not provide detailed information about phonon scattering processes, which are important for the complete understanding of the thermal transport and generation of the physics-based thermal transport models in nuclear performance codes. In this work, we apply phonons wave-packet (PWD) molecular dynamics simulation technique in order to elucidate the individual phonons contribution to the thermal transport through the grain boundaries (GB) in UO{sub 2}. In this work we elucidated the effect of the grain boundary atomic structure on the details of the thermal conductance through the interface. Namely, we demonstrated that transmission coefficient as a function of the wave vector is a strong function of the disorder at the interface: for ideally structured GBs it has sharp peaks and pronounced valleys. Such structure disappears upon introduction of the disorder near the interface, and as a result transmission coefficients behave very similarly between GBs of different misorientation, but the same degree of disorder. Kapitza conductance through these GBs is also nearly identical. It is unlikely for experimentally observed GBs to be atomically sharp, and thus Kapitza conductance in polycrystalline UO{sub 2} can be considered misorientation independent with good accuracy, and it does not to be accounted for in physics-based thermal transport model for fuel performance codes. (authors)
- OSTI ID:
- 22992118
- Journal Information:
- Transactions of the American Nuclear Society, Vol. 114, Issue 1; Conference: Annual Meeting of the American Nuclear Society. Embedded topical meeting 'Nuclear fuels and structural material for the next generation nuclear reactors', New Orleans, LA (United States), 12-16 Jun 2016; Other Information: Country of input: France; 12 refs.; Available from American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 United States; ISSN 0003-018X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
97 MATHEMATICAL METHODS AND COMPUTING
ACCURACY
ANISOTROPY
DISLOCATIONS
GRAIN BOUNDARIES
INTERFACES
MOLECULAR DYNAMICS METHOD
NUCLEAR FUELS
PHONONS
POLYCRYSTALS
REACTORS
SAFETY
SCATTERING
SIMULATION
THERMAL CONDUCTIVITY
TRANSPORT THEORY
URANIUM DIOXIDE
WAVE PACKETS