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

Nuclear waste management. Quarterly progress report, July-September 1980

Research is reported on: high-level waste immobilization, alternative waste forms, TRU waste immobilization and decontamination, krypton solidification, thermal outgassing, /sup 129/I fixation, unsaturated zone transport, well-logging instrumentation, waste management system and safety studies, effectiveness of geologic isolation systems, waste/rock interactions, engineered barriers, backfill material, spent fuel storage (criticality), barrier sealing and liners for U mill tailings, and revegetation of inactive U tailings sites. (DLC

Hanford Works Report HW-63574

In support of the Plutonium Recycle Program at Hanford, the properties of PuO2 are being investigated. This paper reports sintering studies on PuO2 and PuO2-UO2 mixtures and solid solutions; melting studies on PuO2 and UO2; thermal expansion data to 1000 C; and irradiation data on PuO2-UO2 mixtures. The existence of a continuous series of solid solutions formed during sintering has been established for the system UO2-PuO2. A linear relation between lattice parameter and composition exists. Extensive sinterability data on the isomorphous compound UO2 and PuO2 and their intermediate compositions has been obtained. The effect on sintered density of temperature, time, and concentration for both physical additions of PuO2 and additions of UO2-PuO2 solid solutions to UO2 have been studied. Evaluation data are supported by microscopic examination and X-ray diffraction