Thermochemistry of UO2 – ThO2 and UO2 – ZrO2 fluorite solid solutions

Lei Zhang, Anna Shelyug, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


The enthalpies of formation of cubic urania – thoria (c-ThxU1−xO2+y) and urania – zirconia (c-ZrxU1−xO2, x < 0.3) solid solutions at 25 °C from end-member binary oxides (c-UO2, and c-ThO2 or m-ZrO2) have been measured by high temperature oxide melt solution calorimetry. The enthalpies of mixing for both systems are zero within experimental error. The interaction parameters for binary solid solutions MO2 – M′O2 (M, M′ = U, Th, Ce, Zr, and Hf), fitted by regular and subregular thermodynamic models using both calorimetric and computational data, increase linearly with the corresponding volume mismatch. Cubic UO2 – ZrO2 appears to be an exception to this correlation and shows a zero heat of mixing despite large size mismatch, suggestive of some short-range ordering and/or incipient phase separation to mitigate the strain. The incorporation of ZrO2 into UO2 stabilizes the system and makes it a potential candidate for immobilization and disposal of nuclear waste.

Original languageEnglish (US)
Pages (from-to)48-54
Number of pages7
JournalJournal of Chemical Thermodynamics
StatePublished - Nov 2017
Externally publishedYes


  • Calorimetry
  • Nuclear fuel
  • Solid solution thermodynamics
  • ThO
  • UO
  • ZrO

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Physical and Theoretical Chemistry


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