Sensitivity of thermal transport in thorium dioxide to defects

Phonon Scattering and Thermal Conductivity of Actinide Oxides with Defects

“…In the UO 2 structure with fission gas bubbles, however, the temperature slip is not clearly seen at the hot bath or the cold baths, indicating the diffusive nature of the thermal transport (Figure 8a). As stated in the previous section (Section 3.1) and the authors' previous research [3], this diffusive thermal transport is observed in actinide oxides with uniformly distributed point defects. Considering that the simulation structure in Figure 8 contains only two fission gas bubbles, it is interesting that these two fission gas bubbles (two phonon scattering sources) make the thermal transport across the entire structure highly diffusive.…”

“…The addition or subtraction of larger atoms is expected to cause a greater change in phonon transport in crystalline structures, because it alters the lattice vibration in the simulation structure more abruptly. The authors have identified the same results in their previous research study [3] that investigated thorium vacancies and oxygen vacancies in ThO 2 . Other researchers [22,32,33] also reported the same observations in nanostructured crystalline solids.…”

“…This potential has been used successfully to predict thermal properties of actinide oxides [12]. For example, Rahman et al [17] demonstrated the effectiveness of this model, and the authors estimated the thermal transport properties of actinide oxides with defects using the same force field [3,4]. For the interactions between noble gas-actinide and noble gas-oxygen, parameters developed by Cooper et al [15] are used; during their parameter fitting procedure for the gas interactions with actinide oxides, they used the gas-gas interaction developed by Tang-Toennies [18].…”

“…Point defects in oxide fuels are also considered to have a detrimental effect on the thermal transport in oxide fuels, since they alter the vibrational modes of the crystalline structures [2][3][4]. Point defects are understood as the interruption in the fluorite crystal structures of oxide fuels; point defects exist as single to multi-point vacancies, interstitial species, and substitutional atoms.…”

Structural dynamics of Schottky and Frenkel defects in ThO2: a density-functional theory study

“…A handful of recent studies have investigated the effect of point defects on the phonon scattering in ThO 2 , UO 2 and PuO 2 . 17,18,75 For ThO 2 , non-equilibrium molecular dynamics simulations 75 found that Th and O vacancies affected the lowerfrequency modes with the largest contributions to the thermal Fig. 3 Predicted defect concentrations as a function of temperature for the Sh100i, Sh110i, Sh111i, ThFh111i and OFh133i defects using the calculated defect formation free energies.…”