Plutonium metal standards exchange program for actinide measurement quality assurance (2001–2007)

Plutonium metal exchange programs operated by the Rocky Flats Plant were conducted from 1956–1989 to ensure quality and to compare measurements in a plutonium metal matrix. Los Alamos National Laboratory (LANL) re-established the program in 2001 to assess the quality of analytical chemistry capabilities that support special nuclear material characterization. It is the only program of its kind for the preparation and distribution of plutonium metal reference materials with a range of impurity contents to multiple laboratories for destructive measurements of elemental concentration, isotopic abundance, and both metallic and non-metallic impurity levels. This program provides independent verification of analytical measurement capabilities for each of the seven currently participating laboratories, and allows any technical problems with analytical measurements to be identified and corrected. This paper focuses on basic program elements and presents a summary of methods and results for plutonium, uranium, neptunium, and americium, measurements.     

Metal dicarbides as intermediate species in thermal ion formation mechanisms

Lanthanide elements (lanthanum to lutetium) and actinide elements (uranium and plutonium) adsorbed onto resin beads and mounted on rhenium filaments were studied as thermal ionization sources. Temperatures at which these ion sources gave maximum intensities were measured for each of these elements. The temperature trends correlate with the dissociation energies of the corresponding metal dicarbide compounds. The metal dicarbide functions as a carrier to take the lanthanide and actinide elements to higher temperatures than would be attainable otherwise. This results in release of the atomic species at a higher temperature where ionization probability is significantly increased.     

The Coordination Chemistry of f-Block Elements in Molten Salts

The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties.     

Transfer of selected heavy metals and radionuclides from calcareous peat to saw sedge (Cladium mariscus) in eastern Poland

Summary The level of artificial and natural radionuclide concentration as well as heavy metal content were determined in samples of saw sedge and peat collected in the Special Protection Area of peat bogs near Chelm (Poland). Gamma- and alpha-spectrometry with proper sample preparation were used to determine natural gamma-emitters, artificial ¹³⁷Cs and alpha-radiating plutonium (²³⁸Pu and ^239,240Pu). Non radioactive elements were determined by AAS. Rather low level of heavy metal concentration in all samples was found, however, the transfer factors were significant. Peat contamination with artificial radionuclides (¹³⁷Cs and plutonium) was low. Contrary, the concentration of these isotopes in saw sedge was higher than normally observed in non contaminated areas, what is a result of a significant transfer factor.     

锕系元素在熔盐体系中的电化学及萃取特性研究进展

熔融盐是一类非水溶剂,分为高温熔盐、室温熔盐和低温熔盐。 作为反应介质和电解介质,因其优良性能,可以溶解很多难溶于水的活泼金属。 近年来,该领域的研究热点是将熔盐作为干法后处理的电解质分离和回收锕系元素。 本文综述了锕系元素在高温熔盐中的电化学行为、热力学等物理特性,介绍了近几年室温离子液体(RTILs)的研究进展及锕系元素在RTILs中萃取特性的最新研究成果,展望了熔盐体系未来的研究方向。     

A Bulk Resin Bead Procedure To Obtain Uranium And Plutonium From Radioactive Solutions For Mass Spectrometric Analysis

Abstract

A method is described for extracting representative uranium and plutonium samples from highly radioactive solutions for isotopic mass spectrometric analysis. Anion resin beads in the nitrate form are used to effect separation from fission products and other actinides. Conditions required to achieve separation are proper adjustment of the uranium and nitric acid concentrations. Once uranium and plutonium are adsorbed, each bead serves as a sample for mass spectrometric analysis, with plutonium and uranium being run sequentially from the same bead. Quantitative determination of the two elements is effected through the technique of isotopic dilution.     

Capillary driven molten metal flow over topographically complex substrates

A theoretical model of a capillary driven flow of liquid metal through topography features of rough surfaces has been verified by a study of molten solder (Sn-Pb) spreading over Cu(6)Sn(5)/Cu(3)Sn/Cu intermetallic (IMC) substrates. Flow through microgrooves over a rough IMC substrate is considered as spreading through an isotropic porous medium featuring a network of open microgrooves having predefined free-flow area cross sections. The relative margin of deviation between theoretically predicted and empirically determined locus of points of triple line locations is within the range of 5-15%. This margin supports the validity of the developed, analytically formulated square root power law model for a whole spreading domain in terms of (i) geometry of topographical features of the rough surface (i.e., effective intrinsic permeability, porosity/tortuosity, and microchannel cross section geometry), (ii) wetting/spreading features (equilibrium contact angle and filling factor), and (iii) molten metal/substrate properties (viscosity and surface tension). Experimental data involving triple line kinetics represent the data set of locations of the triple line versus time obtained by in situ monitoring of the spreading of molten metal systems over IMC substrates by using the controlled atmosphere hot stage microscopy.     

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.     

Extension of the Plutonium Oxide Nanocluster Family to Include {Pu16} and {Pu22}

Plutonium(IV) oxide nanoclusters represent an interesting scientific problem regarding structure-function relationships and are also relevant to global concerns surrounding plutonium reprocessing, the remediation of plutonium-contaminated soils, and the storage or disposal of plutonium-containing wastes. Here we report the synthesis of five unique Pu^IV oxide nanoclusters containing 38, 22, or 16 metal centers and capped only with inorganic ligands, such as chlorine and water, which prevent formation of the extended PuO₂ structure. The products are interrogated through single-crystal X-ray diffraction, bond valence calculations, and comparisons to other known metal-oxide nanoclusters. Of particular interest is the incorporation of hydroxide linkages into the smaller plutonium oxide nanoclusters, which underscores previous observations and hypotheses regarding the formation of plutonium polymers and colloids.     

Synthesis of Al Nanopowders in an Anodic Arc

Nanopowders of metals and metal oxides have been produced using an arc operated between a refractory rod anode and a hollow cathode (J. Haidar in A method and apparatus for production of material vapour, Australian Patent No. 756273, 1999). the arc attachment to the anode is through a small region of molten metal located at the tip of the rod anode. Heat from the arc evaporates the molten metal and the vapour is passed through the arc plasma before condensing into sub-micron particles downstream of the cathode. A precursor metal is continuously fed onto the tip of the anode to maintain the molten metal region and compensate for losses of materials due to evaporation. The particle size of the produced powder depends on the pressure in the arc chamber and for production of nanoparticles in the range below 100 nm we use a pressure of 100 torr. Aluminium has been used as a precursor material, leading to production of aluminium metal nanopowders when the arc is operated in argon and to aluminium oxide nanopowders for operation in air. For operation in air, the products are made of γ-Al₂O₃.     

Extraction of plutonium from sulphuric acid by TOA in toluene

The extraction of plutonium(VI) and plutonium(III) from sulphuric acid by TOA in toluene has been studied as a function of the acid and tri-octyl amine concentration. A comparison of the extraction properties of plutonium with those of uranium(VI) and uranium(IV) has been made. It was found that the extraction properties of plutonium(VI) are very similar to those of uranium(VI) and that TOA is a relatively poor extractant for plutonium(III). Uranium(IV) shows better extraction properties than plutonium(III). The results obtained are considered in the light of the stabilities of the complexes formed by these elements in the organic and aqueous phase. A method of separation of both elements by solvent extraction based on changing their oxidation states is suggested.     

Ion microscopes and microprobes in marine pollution research

Secondary-ion mass spectrometry (ion microscope and ion microprobe) and x-ray spectrometry (electro microprobe) are used to identify elements taken up from sea water by marine organisms. Several species of fish, molluscs and crustacea are shown to accumulate lithium, aluminium, silver, lead, rare-earth elements, uranium and plutonium. The main storage tissues are the digestive tract and the exoskeleton. Sphrerocrystals and lysosomes play prominent roles in metal accumulation and elimination.     

Fractional sublimation of various metal acetylacetonates

A simple fractional sublimator is described which possesses a continuous temperature gradient along its length. Samples are placed in the high temperature end of the tube and volatilized at 1-mm pressure. The gases are moved through the tube with air as a carrier. The metal chelates recrystallize on the walls of the tube in discrete and reproducible temperature zones. Characteristic recrystallization zones are reported for 21 metal acetylacetonates. The chelates can be grouped according to zone temperatures into 6 fairly distinct groups over the range 15 to 200°, which makes many separations possible. Separations of mixtures of Mg, Al and Be ; Ni, Fe and Be ; and, Cu and Fe were studied quantitatively. The separations achieved compared favorably with those reported by gas chromatography. The method offers real promise for the purification of a number of metals but appears especially good as a method for beryllium and certain platinum group metals.     

Recent progress in actinide borate chemistry

The use of molten boric acid as a reactive flux for synthesizing actinide borates has been developed in the past two years providing access to a remarkable array of exotic materials with both unusual structures and unprecedented properties. [ThB(5)O(6)(OH)(6)][BO(OH)(2)]·2.5H(2)O possesses a cationic supertetrahedral structure and displays remarkable anion exchange properties with high selectivity for TcO(4)(-). Uranyl borates form noncentrosymmetric structures with extraordinarily rich topological relationships. Neptunium borates are often mixed-valent and yield rare examples of compounds with one metal in three different oxidation states. Plutonium borates display new coordination chemistry for trivalent actinides. Finally, americium borates show a dramatic departure from plutonium borates, and there are scant examples of families of actinides compounds that extend past plutonium to examine the bonding of later actinides. There are several grand challenges that this work addresses. The foremost of these challenges is the development of structure-property relationships in transuranium materials. A deep understanding of the materials chemistry of actinides will likely lead to the development of advanced waste forms for radionuclides present in nuclear waste that prevent their transport in the environment. This work may have also uncovered the solubility-limiting phases of actinides in some repositories, and allows for measurements on the stability of these materials.     

Bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) acetamide [BenzoDODA]—first selective extractant for plutonium(IV) recovery (SEPUR) from acidic media

A novel extractant, namely, Benzodioxodiamide (BenzoDODA) has been synthesized and evaluated for its extraction behaviour towards plutonium and other elements present in the spent nuclear fuel. High separation factors for plutonium over other elements were observed, indicating the high selectivity of the extractant for plutonium. The extractant is quite promising for the selective separation of plutonium from dissolver solution and various acidic waste streams.     

The determination of plutonium by mass spectrometry using a [242]-plutonium tracer

An isotopic dilution method is described for the determination ot plutonium in samples of irradiated uranium using a ²⁴²Pu tracer. An aliquot of tracer is added to the sample and the mixture treated to ensure isotopic exchange; plutonium is then separated by an ion exchange procedure and an isotopic analysis made using an M.S.5. mass spectrometer. The precision (3 σ) for an aliquot containing 0.1 μg plutonium is 0.6%. A possible application of the method would be its use for control analyses of the feed solution in a chemical plant processing natural uranium fuel elements as, for example, the Windscale primary separation plant.     

Luminescent determination of microamounts of plutonium

Determination of microamounts of plutonium isotopes by luminescent radiation in the infra-red region of PbMoO₄ crystallophosphors activated by plutonium is proposed. The determination is possible against the background of subtantial amounts of uranium, iron, rare earths and other elements. The detection limit of plutonium is 10^–9 g in the samples tested. The accuracy is 0.1 for a confidence level of 0.95.     

Synthesis and characterization of manganese-, nickel-, and cobalt-containing carbonate precursors for high capacity Li-ion battery cathodes

Mn-rich transition metal (Mn, Ni, Co) carbonate precursor was precipitated as the precursor for Li- and Mn-enriched composite material used as advanced cathode for lithium-ion battery. The pH zone that favors carbonate precipitation reactions for transition metals (Co, Ni, Mn) was predicted by taking into account the chemical equilibriums between metal elements Me (Co, Ni, Mn) and ammonia bicarbonate. The physical properties of the precursor and the final lithiated cathode material were characterized in detail, and the electrochemical properties of the prepared Li_1.2Ni_0.12Co_0.12Mn_0.56O₂ powder were evaluated. The study aids in understanding the precipitation and yields an optimal precipitation condition for the system.     

Plutonium Activity Ratios in Plankton: New Evidence of Hold-Up Time in Irish Sea Sediments

The determination of activity ratios for radioisotopes of different half-lives can be used to estimate transit times from a point source to locations further away. For conservative elements, this time is approximately equivalent to the net hydrological transport. However, for non-conservative elements such as plutonium, the additional influence of biogeochemical processes decreases the net transport time. In this study, ²⁴¹Pu and ^239,240Pu concentrations in Irish Sea plankton samples, collected in May 1994, were determined and the ²⁴¹Pu/^239,240Pu ratios calculated. Plutonium-239,240 was measured using a standard method by ion exchange chromatography and alpha counting, and ²⁴¹Pu was determined by liquid scintillation counting using the disk-supported technique. The latter showed some methodological problems, which are briefly discussed. The ²⁴¹Pu/^239,240Pu ratios gave an estimate of the "transit time" from Sellafield to the different sampling points. In fact, this time represents the age of plutonium in plankton, i.e., the time lag between release from Sellafield and detection at the different sampling stations. The mean plutonium age was 17±2 years (n = 10) and 18.6±0.8 years (n = 13) in phytoplankton and zooplankton, respectively. The spatial distribution was reasonably homogeneous over the Irish Sea. The assimilation-elimination processes of plutonium in plankton are rather rapid. Therefore, it may be assumed that, in this time scale, the plutonium concentrations were in equilibrium with surrounding waters. Thus, it is concluded that plutonium was rather old because resuspension-sedimentation processes had occurred that delayed its transport within the Irish Sea. Therefore, the age of plutonium in plankton represented the hold-up time of plutonium in the sediments from the Irish Sea.     

A spectrophotometric method for the determination of neptunium and plutonium in process solutions

A method is described for the determination of neptunium and plutonium in process solutions. This involves the separation of these elements followed by their spectrophotometric determination as Arsenazo III complexes. Neptunium(IV) and plutonium(IV) are separated using TTA extraction method and the separated Np(IV) and Pu(IV) are then determined as their Arzenazo III complexes in 5M HNO₃. A few solutions obtained by dissolving irradiated fuels were analysed for plutonium and neptunium using this method and the results were compared with those obtained by other methods. An attempt was made to use Arsenazo III to determine uranium in the plant solutions.