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Title: The high-temperature heat capacity of the (Th,U)O 2 and (U,Pu)O 2 solid solutions

The enthalpy increment data for the (Th,U)O 2 and (U,Pu)O 2 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. Here, 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.
Authors:
ORCiD logo [1] ;  [2] ;  [2] ; ORCiD logo [1] ; ORCiD logo [3] ;  [4] ;  [5]
  1. Joint Research Centre, Karlsruhe (Germany); Delft Univ. of Technology, Delft (The Netherlands)
  2. Joint Research Centre, Karlsruhe (Germany)
  3. Imperial College, London (United Kingdom); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Imperial College, London (United Kingdom)
  5. CEA, DANS, DPC, SCCME, LM2T, Gif-sur-Yvette Cedex (France)
Publication Date:
Report Number(s):
LA-UR-16-20239
Journal ID: ISSN 0022-3115
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 484; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Actinide mixed oxides; Calorimetry; Heat capacity
OSTI Identifier:
1375163