An Evaluation of the Thermophysical Properties of Stoichiometric CeO₂ in Comparison to UO₂ and PuO₂

Abstract

The thermal conductivity of stoichiometric CeO2 was determined through measurement of thermal expansion from 313 to 1723 K, thermal diffusivity from 298 to 1473 K, and specific heat capacity from 313 to 1373 K. The thermal conductivity was then calculated as the product of the density, thermal diffusivity, and specific heat capacity. The thermal conductivity was found to obey an (A + BT)−1 relationship with A = 6.776×10−2 m·K·W−1 and B = 2.793 × 10−4 m·W−1. Extrapolations of applied models were made to provide suggested data for the specific heat capacity, thermal diffusivity, and thermal conductivity data up to 1723 K. Results of thermal expansion and heat capacity measurements agreed well with the limited low‐temperature data available in the literature. The thermal conductivity values provided in the current study are significantly higher than the only high‐temperature data located for CeO2. This is attributed to the tendency of CeO2 to rapidly reduce at elevated temperatures given the available partial pressure of O2 in air at ambient pressure. The CeO2 data are compared to literature values for UO2 and PuO2 to evaluate its suitability as a surrogate in nuclear fuel systems where thermal transport is a primary criterion for performance

Thermodynamic assessment of the oxygen rich U–Ce–O system

“…Venkata et al [37], and Arita et al [14] to the C p versus temperature curves computed using the model for U 1Ày Ce y O 2.00 . Good agreement is seen with the results of [14] and [1]; however, the data from Venkata et al [37] are too high and deviate from the trend of decreasing C p with increasing Ce content. The model for U 1Ày Ce y O 2±x predicts higher C p values with decreasing O/M; since sealed aluminum crucibles were used in Refs.…”

“…A literature review revealed studies reporting oxygen potentials ðm O2 Þ for U 1Ày Ce y O 2±x [4e13], which are summarized in Table 1, along with molar heat capacity (C p ) measurements for stoichiometric U 1Ày Ce y O 2.00 [1,14,15]. Lorenzelli and Touzelin [8], Markin et al [16], and Hoch and Furman [6] used X-ray diffraction (XRD) to determine the phase relations in the vicinity of the fluorite U 1Ày Ce y O 2±x solution.…”

“…In the CeeO and PueO binaries, Ce forms many more stoichiometric compounds with O than does Pu. Finally, Nelson et al [1] compared the thermophysical properties of CeO 2 to PuO 2 in Ref. [1] and showed and these exhibit significant differences.…”

“…Cerium is a high yield fission product (FP) that dissolves extensively in the UO 2 matrix in turn affecting many of its properties. The UeCeeO system is also of interest since Ce may be used as a surrogate for Pu for studying mixed oxide (MOX) fuel CeO 2 and PuO 2 are isostructural, the 3þ and 4þ oxidation states predominate for both Ce and Pu, and the two have comparable ionic radii [1]. The rationale is Ce and Pu dissolved in urania, i.e.…”

Development of Xe and Kr empirical potentials for CeO2, ThO2, UO2and PuO2, combining DFT with high temperature MD

“…It is, therefore, important to consider how such changes to the host lattice could alter fission gas behaviour and impact fuel performance. The use of Ce as a surrogate for Pu [10] or U [11] means CeO 2 is also of interest.…”