Thermal Properties of UO2 by Molecular Dynamics Simulation

Abstract

Molecular dynamics (MD) simulation was performed to investigate thermal expansion, specific heat and thermal conductivity of UO 2 . For thermal expansion, experimental measurements were made and compared with MD simulation results. These thermal expansion values and other reported data were in good agreement with the MD thermal expansion value. Effects of Schottky defects on thermal properties were evaluated. For thermal expansion, the effect was negligible. For specific heat, the constant volume term of specific heat increased with increasing Schottky defect concentration. But the dilation term of specific heat was nearly-unchanged. Thermal conductivity decreased with increasing Schottky defect concentration. It was considered that the increasing constant volume term was caused by increasing internal energy which was attributed to the Schottky defects. Calculated thermal conductivity values corresponded to experimental data when the supercell contained Schottky defects. It was thought that a perfect crystalline supercell caused high thermal conductivity and the defect structure scattered phonon vibrations and decreased the thermal conductivity.

Development of a multiscale thermal conductivity model for fission gas in UO2

“…MD simulations for pure UO 2 were carried out using the potential from Busker et al [24], at temperatures ranging from 200 K to 1500 K. These MD results consistently overpredict the thermal conductivity of UO 2 , as has been previously observed in the literature [25,26]. This is primarily due to resonant scattering of phonons by spins in the paramagnetic phase of UO 2 [23,27], which is not captured by the MD simulations.…”

Thermal expansion measurement of (U,Pu)O2-x in oxygen partial pressure-controlled atmosphere

“…4 shows the Pu content dependence of thermal expansion for (U,Pu)O 2.00 . The data of UO 2 and PuO 2 were measured with the same apparatus as in previous reports [12,18]. In the high temperature range above 1500 K, U 0.7 Pu 0.3 O 2 had the highest thermal expansion.…”

“…(5), and coefficients a 0 , a 1 , a 2 and a 3 were obtained. Uchida et al [12,18] and Kato et al [19] reported thermal expansion and derived the equations for UO 2 and PuO 2 . Their data were reassessed by Eq.…”

Mikrostruktur Dan Komposisi Fasa Pelet Sinter UO2 Dengan Penambahan Dopan Logam Zirkonium

“…Konduktivitas panas suatu material dipengaruhi oleh struktur kristal dan kesempurnaannya, dinamika kisi, kestabilan struktur, porositas dan ukuran butir [10,[14][15][16][17][18]. Hasil perhitungan dispersi phonon dengan simulasi molekular dinamis pada struktur elektronik UO 2 , mengungkapkan bahwa konduktivitas panas UO 2 yang rendah merupakan efek dari ketidakharmonisan struktur yang besar pada optical modes dari phonon sebagai pembawa panas [14].…”