The environmental dependence of redox energetics of PuO2 and \alpha-Pu2O3: A quantitative solution from DFT+U calculations

We report a comprehensive density functional theory (DFT) + $U$ study of the energetics of charged and neutral oxygen defects in both PuO$_{2}$ and $\alpha$-Pu$_{2}$O$_{3}$, and present a quantitative determination of the equilibrium compositions of reduced PuO$_{2}$ (PuO$_{2-x}$) as functions of environmental temperature and partial pressure of oxygen, which shows fairly agreement with corresponding high-temperature experiments. Under ambient conditions, the endothermic reduction of PuO$_{2}$ to $\alpha$-Pu$_{2}$O$_{3}$ is found to be facilitated by accompanying volume expansion of PuO$_{2-x}$ and the possible migration of O-vacancy, whereas further reduction of $\alpha$-Pu$_{2}$O$_{3}$ is predicted to be much more difficult. In contrast to the endothermic oxidation of PuO$_{2}$,\ the oxidation of $\alpha$-Pu$_{2}$O$_{3}$ is a stable exothermic process.Comment: 5 PLA pages, 4 figure

Thermodynamic systematics of oxides of americium, curium, and neighboring elements

Recently-obtained calorimetric data on the sesquioxides and dioxides of americium and curium are summarized. These data are combined with other properties of the actinide elements to elucidate the stability relationships among these oxides and to predict the behavior of neighboring actinide oxides. 45 references, 4 figures, 5 tables

Cerium neodymium oxide solid solution synthesis as a potential analogue for substoichiometric AmO 2 for radioisotope power systems

The European Space Agency (ESA) is sponsoring a research programme on the development of americium oxides for radioisotope generators and heater units. Cubic AmO2-(x/2) with an O/Am ratio between 1.65 and 1.75 is a potentially suitable compound for pellet sintering. C-type (Ia-3) Ce1-xNdxO2-(x/2) oxides with 0.5 &lt; x &lt; 0.7 could be used as a surrogate for some Ia-3 AmO2-(x/2). A new Ce1-xNdxO2-(x/2) production process has been investigated where a nominally selected x value of 0.6 was targeted: Ce and Nd nitrates and oxalic acid were added drop-wise into a vessel, where they continuously reacted to create oxalate precipitates. The effect of temperature (25 °C, 60 °C) of the reactants (mixed at 250 revolutions per minute) on oxalate particle shape and size were investigated. Oxalates were calcined at 900 °C to produce oxide particles. Oxalate particle properties were characterised as these are expected to influence oxides particle properties and fuel pellet sintering.</p

Ceramics in nuclear waste management

Seventy-three papers are included, arranged under the following section headings: national programs for the disposal of radioactive wastes, waste from stability and characterization, glass processing, ceramic processing, ceramic and glass processing, leaching of waste materials, properties of nuclear waste forms, and immobilization of special radioactive wastes. Separate abstracts were prepared for all the papers. (DLC