Measurement of oxygen chemical diffusion in PuO_2‐x and analysis of oxygen diffusion in PuO_2‐x and (Pu,U)O_2‐x

Abstract

All available oxygen potential-temperature-composition data for the calcium fluorite-structure <PuO 2-T >** phase were retrieved from the literature and utilized in the development of a binary solid solution representation of the phase. The data and phase relations are found to be best described by a solution of [Pui^C^] and [PuO 2 ] with a temperature dependent interaction energy. The fluorite-structure <U 1 _ z Pu z 0 w > is assumed to be represented by a combination of the binaries' <PuO 2 _ x > and CUO^^, and thus treated as a solution of [Pu^/302], [PuO 2 ], [UO 2 ], and either [U 2 0i,.5] or [U3O7]. The resulting equations well reproduce the large amount of oxygen potential-temperature-composition data for the mixed oxide system, all of which were also retrieved from the literature. These models are the first that appear to display the appropriate oxygen potential-temperature-composition and phase relation behavior over the entire range of existence for the phases.

Defect Chemistry and Basic Properties of Non-Stoichiometric PuO₂

“…In the PuO 2-x , it is reported that sources of electrical conductivity is not ions but electrons and holes [10]. The electrical conductivity 𝝈 is written by, 𝝈 = 𝝈 𝒆 𝝈 𝒉 = 𝝁 𝒆 𝐡 𝝁 𝒉 (14) with 𝝈 = 𝝁 and 𝝈 𝒉 = 𝐡 𝝁 𝒉 , where 𝝁 and 𝝁 𝒉 are electrons and holes mobility, respectively. Since = 𝟐 𝐎 , Equation 15 is derived using Eqs.…”

“…Experimental data on the oxygen chemical diffusion coefficient 𝐷 ̃ in PuO 2−x is limited. Bayoglu and Lorenzelli [13] reported 𝐷 ̃ to be about 1×10 −6 cm 2 /s at 1353 K. Kato et al [14] obtained the value of 10 −7 cm 2 /s at temperatures in the range of 1473-1873 K. A large difference was observed between the reported data. Bayoglu and Lorenzelli [13] measured 𝐷 ̃ during the oxidation process.…”

“…Bayoglu and Lorenzelli [13] measured 𝐷 ̃ during the oxidation process. Kato et al [14] attempted to measure 𝐷 ̃ during both the oxidation and reduction processes. They found that the oxidation curve was not dominated by the diffusion controlled process.…”

“…3. Relationship between oxygen diffusion coefficients and P O2 [14] Defect and Diffusion Forum Vol. 375…”

New insights into the process of intrinsic point defects in PuO2

“…10,12,13 The stoichiometry of PuO 2 is known to have a signicant impact on important physical properties like lattice parameters, thermodynamical stability, and melting temperature. 14 Therefore, it is essential to investigate the characteristics of defects in non-stoichiometric PuO 2 composition to understand the variation in its physical properties.…”