Heat content op uranium dioxide from 1200 to 3100 °K

Heat capacity anomaly in UO2 in the vicinity of 1300K: an improved description based on high resolution X-ray and neutron powder diffraction studies

“…1): below 1300 K, a classical Debye behavior is reported, but above this temperature, C p strongly increases and at 2600 K it equals twice the value of the Dulong-Petit plateau [10][11][12][13][14][15][16][17]. That behavior was observed both in the non-irradiated material [10][11][12][13][14][15][16] and in the irradiated one [18]. It is not yet clear, whether the electronic disorder, detected by electrical measurements, completely drives this C p anomaly.…”

“…The nature of this singularity is still debated. In the literature, four contributions are usually taken into account: the U 4C crystal fields [14,15,17], the thermal expansion [10][11][12][13][14][15][16][17], the electronic disorder [16,17,[19][20][21] and also the oxygen anti-Frenkel disorder [11,12,16,17,[19][20][21]. By adjusting these different contributions, C p was fitted over a wide range of temperature.…”

Thermal variation of the optical absorption of UO2: determination of the small polaron self-energy

“…Among the different physical properties, the electrical and thermal properties have received special attention since they exhibit singular behaviour in the vicinity of 1300 K which is the typical temperature of UO 2 pellets in normal PWR operation. Around this range of temperature, it is observed, indeed, that electrical conductivity and heat capacity both present a drastic change in their temperature dependence [1][2][3][4][5][6][7]. This abnormal behaviour has been attributed either to the emergence of intrinsic electronic charge carriers [8,9], or to simultaneous electronic and oxygen anti-Frenkel pair disorder [10].…”

Thermophysical properties and oxygen transport in the (U ,Pu1−)O2 lattice

“…For UO 2 there is a deviation from linear thermal expansion and a classical Debye description of the constant pressure specific heat above 1300 K [11][12][13][14][15][16][17][18][19][20]. At 2670 K (0.85T m ) there is a peak in the specific heat due to a premelting transition or superionic transition as seen in other fluorite structures [11].…”