The high-temperature heat capacity of the (Th,U)O<sub>2</sub> and (U,Pu)O<sub>2</sub> solid solutions

Journal article (2017)

Authors

S.O. Valu RST/Applied Radiation & Isotopes - AS , European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe
O. Beneš European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe
D Manara European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe
R. Konings European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe, RST/Reactor Physics and Nuclear Materials - AS
M. W.D. Cooper Imperial College London, Los Alamos National Laboratory
R. W. Grimes Imperial College London
C Guéneau CEA-Saclay
Research Group
RST/Reactor Physics and Nuclear Materials (AS) (TU Delft)
Heat capacity Calorimetry Actinide mixed oxides
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Published Date

01-02-2017

Language

English

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Faculty

Applied Sciences

Department

RST/Radiation, Science and Technology

Research Group

RST/Reactor Physics and Nuclear Materials

Abstract

The enthalpy increment data for the (Th,U)O2 and (U,Pu)O2 solid solutions are reviewed and complemented with new experimental data (400–1773 K) and many-body potential model simulations. The results of the review show that from room temperature up to about 2000 K the enthalpy data are in agreement with the additivity rule (Neumann-Kopp) in the whole composition range. Above 2000 K the effect of Oxygen Frenkel Pair (OFP) formation leads to an excess enthalpy (heat capacity) that is modeled using the enthalpy and entropy of OFP formation from the end-members. A good agreement with existing experimental work is observed, and a reasonable agreement with the results of the many-body potential model, which indicate the presence of the diffuse Bredig (superionic) transition that is not found in the experimental enthalpy increment data.