Stability evaluation of fluorite structure phase in PuO2–UO2–ZrO2 system by thermodynamic modelling

Thermodynamics of Fluorite-Structured Oxides Relevant to Nuclear Energy: A Review

“…Thermodynamic modeling of the PuO 2 −UO 2 −ZrO 2 system showed that the fluorite phase of the PuO 2 −ZrO 2 subsystem is more stable than that of the UO 2 −ZrO 2 subsystem at lower temperatures and vice versa at higher temperatures. 231 A study of CeO 2 −Gd 2 O 3 −CoO solid solutions using CALPHAD calculations allowed the evaluation of phase stability in this system below liquidus temperatures. 232 In recent years, a new multicomponent class of so-called "high entropy materials" has drawn a large amount of attention.…”

“…EMF studies were performed on UO 2 –ZrO 2 –LnO 2– x (Ln = La, Nd, Ce) systems, showing that the solubility of oxygen in UO 2± x is increased much more significantly by the lanthanides than by zirconium. Thermodynamic modeling of the PuO 2 –UO 2 –ZrO 2 system showed that the fluorite phase of the PuO 2 –ZrO 2 subsystem is more stable than that of the UO 2 –ZrO 2 subsystem at lower temperatures and vice versa at higher temperatures . A study of CeO 2 –Gd 2 O 3 –CoO solid solutions using CALPHAD calculations allowed the evaluation of phase stability in this system below liquidus temperatures …”

Dissolution behavior of (U,Zr)O2-based simulated fuel debris in nitric acid

“…The localized erosion could be a result of the formation of minor U-rich phases that can leach faster than the Zr-rich phase. However, according to the UO 2 -PuO 2 -ZrO 2 pseudo-ternary phase diagram [26], the equilibrium phase composition is unlikely to change notably even if the Pu content rises up to 4%. Therefore, non-equilibrium factors, such as the difference in the cooling rate during solidification, could cause the inhomogeneous nature of the solid surface and lead to the difference in the values of IDRs between MOX-SIMDEBRIS and U-SIMDEBRIS.…”

The influences of Pu and Zr on the melting temperatures of the UO2–PuO2–ZrO2pseudo-ternary system

“…In addition, it is important for the prediction of the debris states because the central part of the debris is expected to have been in a molten state for a long time because of its decay heat. The melting temperatures and phase states of the U-Zr-O system have been evaluated from experimental and thermodynamic viewpoints [1][2][3][4][5][6][7][8][9]. For the melting temperatures of the U-Pu-Zr-O system, however, only a thermodynamic calculation of the phase diagram of * Corresponding author.…”

“…For the melting temperatures of the U-Pu-Zr-O system, however, only a thermodynamic calculation of the phase diagram of * Corresponding author. Email: morimoto.kyoichi@jaea.go.jp the UO 2 -PuO 2 -ZrO 2 pseudo-ternary system has been conducted [9] and no experimental evaluation has been done.…”