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Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
Results of microbalance, pressure-volume-temperature, and mass spectrometric measurements show that a higher oxide of plutonium, PuO{sub 2+x}, and hydrogen are formed by reaction of plutonium dioxide with water at 25 C to 350 C. PuO{sub 2+x} has an intense green color consistent with the presence of Pu(VI). An oxide composition in excess of PuO{sub 2.25} is identified, but the maximum value of x is undefined. Reaction rates derived from linear mass-time and pressure-time data are described by an Arrhenius relationship that yields an activation energy of 9.4 " 0.6 kcal/mol for the PuO2 + H2O reaction. X-ray diffraction data for PuO{sub 2+x} shows that the oxide has a fluorite-related structure consistent with substitution of Pu(VI) on cationic lattice sites and accommodation of additional oxygen on interstitial sites. The cubic lattice parameter has a low, but well-defined, linear dependence on the O:Pu ratio, suggesting that PuO{sub 2+x} forms as a continuous solid solution. The failure of earlier attempts to prepare higher oxides of plutonium is attributed to slow oxidation kinetics and insensitivity of diagnostic techniques. Similarities of the PuO{sub 2+x} and UO{sub 2+x} phase are examined and relevance of the results to plutonium technology and environmental issues is discussed.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
Results of microbalance, pressure-volume-temperature, and mass spectrometric measurements show that a higher oxide of plutonium, PuO{sub 2+x}, and hydrogen are formed by reaction of plutonium dioxide with water at 25 C to 350 C. PuO{sub 2+x} has an intense green color consistent with the presence of Pu(VI). An oxide composition in excess of PuO{sub 2.25} is identified, but the maximum value of x is undefined. Reaction rates derived from linear mass-time and pressure-time data are described by an Arrhenius relationship that yields an activation energy of 9.4 " 0.6 kcal/mol for the PuO2 + H2O reaction. X-ray diffraction data for PuO{sub 2+x} shows that the oxide has a fluorite-related structure consistent with substitution of Pu(VI) on cationic lattice sites and accommodation of additional oxygen on interstitial sites. The cubic lattice parameter has a low, but well-defined, linear dependence on the O:Pu ratio, suggesting that PuO{sub 2+x} forms as a continuous solid solution. The failure of earlier attempts to prepare higher oxides of plutonium is attributed to slow oxidation kinetics and insensitivity of diagnostic techniques. Similarities of the PuO{sub 2+x} and UO{sub 2+x} phase are examined and relevance of the results to plutonium technology and environmental issues is discussed.
Author: Publisher: ISBN: Category : Languages : en Pages : 22
Book Description
Identification of products formed by the reaction of plutonium metal with liquid water at 23°C indicates that the plutonium-oxygen phase diagram is similar to the cerium-oxygen and praseodymium-oxygen diagrams. Quantitative measurements of H2 formation and analytical data suggest that a sequence of hydrolysis reactions produces oxide hydrides of trivalent plutonium, Pu2O3, mixed-valent oxides and PuO2. The intermediate oxides are the n = 7, 9, 10 and 12 members of the Pu{sub n}O{sub 2n-2} homologous series. Properties of the residue formed by thermal decomposition of the initial hydrolysis product, plutonium monoxide monhydride (PuOH), are consistent with the formation of metastable plutonium monoxide. Crystal-chemical, thermodynamic, and kinetic factors are evaluated, but definitive assignment of the equilibrium Pu-O diagram is not possible. 22 refs., 6 figs., 1 tab.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The kinetic and equilibrium behavior of the Pu + O + H system has been studied by measuring the production of hydrogen gas formed by a sequence of hydrolysis reactions. The kinetic dependence of the Pu + H2O reaction on salt concentration and temperature has been defined. The metal is quantitatively converted to a fine black powder which has been identified as plutonium monoxide monohydride, PuOH. Other hydrolysis products formed in aqueous media include a second oxide hydride, Pu--O9H3, and the oxides Pu2O3, Pu--O12, Pu9O16, Pu10O1, Pu12O22, and PuO2. Thermal decomposition products of PuOH include Pu2O2H and PuO. A tentative phase diagram for Pu + O + H is presented and structural relationships of the oxide hydrides and oxides are discussed. 10 figures, 5 tables.
Author: Publisher: ISBN: Category : Languages : en Pages : 12
Book Description
Based on a thermochemical model of defect formation, the concentration of various types of defects and the non-stoichiometry of PuO{sub 2-x} are calculated as functions of temperature and partial pressure of oxygen. The model is able to predict oxygen diffusivity for temperatures in the (900, 1400) C range and oxygen pressure (1,10−25) atm. Comparison with experimental data shows that the model describes non-stoichiometry and oxygen diffusivity well. The calculated free energy of non-stoichiometric plutonia is used to derive the high oxygen, high temperature, region of the Pu-O phase diagram, which is still subject of controversy. The thermochemistry of PuO{sub 2+x}, if any, is also discussed. Thermochemical models of PuO{sub 2-x} are necessary for prediction of oxidation-reduction of Pu-based alloys and for the design of better oxide nuclear fuels. The type and defect formation mechanism determine the alloy performance while kinetic properties of point defects govern radiation tolerance and fission gas release. Oxygen diffusion is also important in optimizing surface properties. Together with the phase stability, diffusion governs the non-stoichiometry of the alloy. Modeling the defects and the mobility of oxygen opens a path to the modeling of the more complex phenomena, such as ageing. Although the Ce-O and Pu-O phase diagrams are still controversial in the high temperature region, there is a consensus regarding the existence of fluorite (f.c.c.) phases in the region x
Author: Publisher: ISBN: Category : Languages : en Pages : 22
Book Description
Chemistry and kinetics of air reactions with plutonium monoxide monohydride (PuOH) and with mixtures of the oxide hydride and plutonium metal are defined by results of pressure-volume-temperature (PVT) measurements. Test with specimens prepared by total and partial corrosion of plutonium in 0.05 M sodium chloride solution show that reaction of residual water continues to generate H2 after liquid water is removed by evacuation. Rapid exposure of PuOH to air at room temperature does not produce a detectable reaction, but similar exposure of a partially corroded metal sample containing Pu and PuOH results in hydride (PuH(subscript x))-catalyzed corrosion of the residual Pu. Kinetics of he first-order reaction resulting in formation of the PuH(subscript x) catalyst and of the indiscriminate reaction of N2 and O2 with plutonium metal are defined. The rate of the catalyzed Pu+air reaction is independent of temperature (E{sub a} = 0), varies as the square of air pressure, and equals 0.78 " 0.03 g Pu/cm2 min in air at one atmosphere. The absence of pyrophoric behavior for PuOH and differences in the reactivities of PuOH and PuOH + Pu mixtures are attributed to kinetic control by gaseous reaction products. Thermodynamic properties of the oxide hydride are estimated, particle size distributions of corrosion products are presented, and potential hazards associated with products formed by aqueous corrosion of plutonium are discussed.
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Author: Luis A. Morales
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Author: David F. Bowersox
Author: R. G. Gutmacher
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Author: M. Kasha![Thermochemistry of Defects and Phase Stability in Plutonium Dioxide (PuO[2-x]. PDF](https://books.google.com/books/content/images/frontcover/v-VxAQAACAAJ?fife=w80-h100)
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Author: R. E. Skavdahl
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