Two predominance-region diagrams for plutonium

Two predominance-region diagrams for plutonium are illustrated. One diagram plots the pH vs. the equilibrium fraction of hexavalent plutonium. The other diagram plots the equilibrium fraction of tetravalent plutonium vs. the plutonium oxidation number. Both diagrams define the boundaries of the regions where tri-, tetra-, penta-, and hexavalent plutonium are the predominant species. In each diagram, the two principal triple points are located at the intersections of three predominance-region boundary lines.Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy under Contract No. W-7405-ENG-36.     

Triangular predominance-region diagrams for plutonium

Two predominance region diagrams can be prepared by plotting the equilibrium fractions of hexavalent vs. trivalent plutonium. The diagrams are differentiated by the species that predominate near their origins. Both diagrams have a curved boundary that separates permissible from forbidden oxidation-state combinations.     

Empirical method for preparing a plutonium predominance-region diagram

An empirical method for preparing a plutonium predominance-region diagram is illustrated by an example. The method estimates the boundaries of the forbidden, unique, and ambiguous regions as defined by the equilibrium fraction of hexavalent plutonium and the plutonium oxidation number.     

Plutonium and intrinsic predominance-region diagrams

Four intrinsic predominance-region diagrams for aqueous plutonium are described. They are easily prepared from an existing diagram by changing the oxidation-state fractions on the axes of the diagram and renaming the predominance regions. Not all combinations of oxidation-state fractions can be used to prepare the diagrams.     

Rearrangement equations for plutonium

The percents of all oxidation states produced by Pu disproportionation, including unreacted starting material, can be obtained by new equations that are easy to apply. The equations are useful for quantifying the extent and the stoichiometry of disproportionation, the consequences of complexation, and the effects of temperature changes on the composition of the oxidation-state mixture.     

Work integrals for plutonium

Free energy changes in Pu disproportionation reactions can be measured by integrating the reaction isotherm with respect to one of the reaction products. Separate integrations can be made for the isotherms of the component reactions contributing to the equilibrium.Mound is operated for the U.S. Department of Energy by EG&G Mound Applied Technologies Incorporated under contract No. DE-AC04-88DP43495.     

Surprising coordination for plutonium in the first plutonium(III) borate

The first plutonium(III) borate, Pu(2)[B(12)O(18)(OH)(4)Br(2)(H(2)O)(3)]·0.5H(2)O, has been prepared by reacting plutonium(III) with molten boric acid under strictly anaerobic conditions. This compound contains a three-dimensional polyborate network with triangular holes that house the plutonium(III) sites. The plutonium sites in this compound are 9- and 10-coordinate and display atypical geometries.     

Charge balance equations for plutonium

Charge balance equations can be used to obtain relationships among oxidation states in plutonium solutions. These equations are prepared from the initial conditions in the solution; they can be checked using equations of mass and charge conservation.Mound is operated for the U. S. Department of Energy by EG&G Mound Applied Technologies, Inc., under Contract No. DE-AC04-88DP43495.     

Work surface for soluble plutonium

Summary A three-dimensional work surface for aqueous plutonium is illustrated. It is constructed by means of estimating work as a function of the ambient pH and redox potential in a plutonium solution. The surface is useful for illustrating the chemistry of disproportionation reactions. Work expressions are easier to use than work integrals.     

General disproportionation equations for plutonium

Disproportionation equations are illustrated for two oxidation numbers (N) and for the general case of any N. The new method illustrates the effect of N on the coefficients in disproportionation equations. An estimate of the equilibrium constant for the first hydrolysis reaction of tetravalent plutonium is obtained by a new approach. The estimated value agrees with many previous results.     

Alpha coefficients for tetravalent plutonium

The complexation of tetravalent plutonium in aqueous solutions derives from several sources including counterions, hydrolysis, additives, and impurities. A quantitative tool accounting for all such effects, known and unknown, is the alpha coefficient. It can be expressed in six ways by means of the equilibrium fractions of two Pu oxidation states.     

Intrinsic predominance region diagram for plutonium

Summary A predominance-region diagram for aqueous plutonium can be prepared by plotting the equilibrium fractions of tetra- and hexavalent plutonium. An example illustrates how the triple points can be used to estimate hydrolysis constants.     

New fecal method for plutonium and americium

A new fecal analysis method that dissolves plutonium oxide was developedat the Westinghouse Savannah River Site. Diphonix Resin . (Eichrom Technologies),is used to pre-concentrate the actinides from digested fecal samples. A rapidmicrowave digestion technique is used to remove the actinides from the DiphonixResin ., which effectively extracts plutonium and americium from acidic solutionscontaining hydrofluoric acid. After resin digestion, the plutonium and americiumare recovered in a small volume of nitric acid that is loaded onto small extractionchromatography columns, TEVA Resin and TRU Resin (Eichrom Technologies). Themethod enables complete dissolution of plutonium oxide and provides high recoveryof plutonium and americium with good removal of thorium isotopes such as ²²⁸Th.     

Sources of misinterpretation for environmental plutonium measurements

Analytical and statistical uncertainties associated with low-level measurements may lead to spurious conclusions regarding the behavior of some plutonium isotopes. The general aspect of the methodology used in sample collection, preparation, radiochemical separation and alpha spectroscopy analysis of plutonium is considered. Biases and experimental artifacts that may produce inaccurate results and improper conclusions are discussed with examples from our research and from the open literature.     

Development of rapid bioassay method for plutonium

For the internal dosimetry of plutonium, a urine bioassay method is very useful but requires several days to obtain the result of the analysis. To shorten the time required for the urine bioassay, a rapid method for plutonium analysis using the ICP-MS system was developed. In this chemical procedure, a microwave oven was applied for sample digestion, and an extraction chromatography resin was used for the separation of plutonium. The measurement time was extremely reduced by application of the ICP-MS as compared to alpha-spectrometry. The total analysis time was about 12 hours and the detection limit was 0.3 mBq/sample. The short analysis time and the low detection limit indicate that this method is useful not only for special monitoring but also for routine monitoring.     

Dosage du plutonium dans les alliages plutonium aluminium par fluorescence-x

An X-ray fluorescence method is described for the determination of plutonium in Pu-Al alloys. In order to obtain satisfactory reproducibility, the alloy is first dissolved in a nitric acid-mercury (II) nitrate mixture. The Lα emission of plutonium is measured, to eliminate matrix effects, an internal standard with a wavelength near that of the Pu emission is used. Equipment and sample preparation are described. Extension of the method to other determinations is discussed.     

Airborne plutonium monitoring

Methods of monitoring low plutonium concentration in the inner and outer atmosphere are analyzed and compared. It is shown that monitors based on the gross alpha counting of air filters are not sensitive enough to measure reliably plutonium activities below 1 MPC. A spectrometric discontinuously operating monitor using a gridded ionization chamber and a membrane filter having 70 cm² active area is described. Plutonium activities of the order of 0.01 MPC /1 mBq.m^–3/ can be measured by the spectrometer at 1 h sampling and 1 h counting time.