Spectrophotometric Determination of Simultaneously Present Neptunium,Americium, and Plutonium in Aqueous Solutions

A spectrophotometric method was developed for determining simultaneously present Np, Am, and Pu in sulfuric and perchloric acid solutions. The molar extinction coefficients ε were determined. In the concentration ranges 1.0 × 10^?4?2.0 × 10^?3 M for Pu and Am and 5.0 × 10^?4?1.0 × 10^?2 M for Np, the overall error does not exceed 5%. The detection limits are 3.0 × 10^?5 M for Pu and Am and 1.0 × 10^?4 M for Np.

     

Comparison of Methods for Assessing Plutonium Speciation in Environmental Objects

Several methods for Pu speciation study are compared using the same sample of bottom sediment. Data on Pu distribution among different soil fractions (water-soluble, exchangeable and readily soluble, mobile, associated with organic matter, including humic and fulvic acids, and also with amorphous hydroxides, primarily of iron and manganese) are reported. The major fraction of plutonium is associated with the organic matter. The experimental results on the Pu speciation, obtained by different methods, show satisfactory agreement.     

Photochemical Reactions of Plutonium Ions in Perchloric Acid Solutions

Photochemical reactions of Pu(V), Pu(VI) in 0.01-1.00 M HClO₄ and of Pu(III), Pu(VI) in 9.4 M HClO₄ were studied. In the course of UV irradiation Pu(III) and Pu(V) are oxidized and Pu(VI) is reduced. With increasing acid concentration the oxidation rate increases, whereas the reduction rate decreases. The reaction mechanisms involving formation of excimers, i.e., dimers of plutonium ions occurring in the excited and ground states, are discussed.     

Plutonium Contamination Level and Isotopic Composition in Soils around St. Petersburg

Plutonium isotopic composition including ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, and ²⁴¹Pu and the Pu contamination level are determined in soils around St. Petersburg using an advanced procedure involving radiochemical separation stage followed by the -ray spectrometric and mass spectrometric determination. The Pu specific activity in surface horizons (0-25 cm) ranges from 0.2 to 0.44 Bq kg^-1. The mean ²³⁸Pu/239,240Pu activity ratio is found to be 0.033±0.007. The Pu contamination level of the surface horizon (0-25 cm) is 62±5 Bq m^-2. The ²³⁸Pu/²³⁹Pu, ²⁴⁰Pu/²³⁹Pu, and ²⁴¹Pu/²³⁹Pu isotopic ratios are (2.0±0.5)×10^-4, 0.172±0.004, and 0.003±0.002, respectively. These ratios are close to the values typical of plutonium from the global radioactive fallout due to nuclear weapons tests in the atmosphere. The effect of the Chernobyl accident and regional potential contamination sources, including the Leningrad NPP, on the Pu isotopic composition and contamination level in the soil is insignificant.     

Effect of Bacteria on Plutonium Behavior in Seawater

Heterotrophic bacteria are demonstrated to assimilate effectively plutonium in seawater, from time to time changing its content and speciation.     

Radionuclide Speciation in Soils Contaminated by the Chernobyl Accident

A critical review of the modern concepts of the radionuclide speciation in soil is made. It is shown that subdivision of radionuclides in soil into the water-soluble, exchangeable, mobile, and fixed species is not scientifically valid. New experimental results show that Cs radionuclides exist in soil as ionic (molecular) species irrespective of the distance from the Chernobyl NPP.     

Extraction of Rare-Earth Elements and Americium from Nitric Acid Solutions with Polyphosphine Oxides

Extraction of HNO₃ and microamounts of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Am from solutions of NH₄NO₃ and HNO₃ with solutions of polyphosphine oxides containing o-oxyphenylenemethylene fragments in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the apparent extraction constants were calculated. As the number of phosphoryl groups in the extractant molecule is increased, the extraction of cerium-group lanthanides increases and that of yttrium-group lanthanides decreases.     

化学镀铜液中铜离子型体分布和络合剂的作用

用热力学平衡方法研究了ＢａＴｉＯ３系陶瓷作了ＰＴＣＲ化学沉积金属电极时在酒石酸盐－铜郭子和乙二胺四乙酸钠盐－铜离子体系化学镀铜溶液中各种型体铜离子的分布状况。结果表明,酒石酸盐和乙二胺四乙酸钠盐络合剂会使化学镀铜速度明显下降,其可能的原因是空间的位阻。研究表明,选择合适的络合剂对于化学镀铜的稳定操作十分重要。     

Speciation of Fe(III) Radionuclides in Aqueous Solutions

Fe(III) radionuclide speciation in aqueous solutions at pH ranging from 1 to 12 and Fe(III) concentration, from 1 ×10^{- 7} to 1 ×10^{- 2} M was studied. At trace Fe(III) concentrations (1 ×10^{- 7} M), the sorption colloids, so-called pseudocolloids, are formed within pH range 3-12. At pH within 0.7-1.5, Fe(III) exists in the form of hydrated cations Fe(H₂O)₆ ^{3 +}, which are hydrolyzed at pH > 1.5 (K _h = 3.7 ×10^{- 3}) to form mononuclear Fe(OH)^{2 +} hydroxo complexes. At Fe(III) concentration exceeding 1 ×10^{- 4} M, Fe₂(OH)5.70.3+ binuclear hydroxo complexes are formed.     

Cs(+) Speciation on Soil Particles by TOF-SIMS Imaging

Soil particles exposed to CsI solutions were analyzed by imaging time-of-flight secondary ion mass spectrometry and also by scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). The results showed that Cs(+) could be detected and imaged on the surface of the soil particles readily at concentrations down to 160 ppm, which corresponds to 0.04 monolayer. Imaging revealed that most of the soil surface consisted of aluminosilicate material. However, some of the surface was more quartzic in composition, primarily SiO(2) with little Al. It was observed that adsorbed Cs(+) was associated with the presence of Al on the surface of the soil particles. In contrast, in high SiO(2) areas of the soil particle where little Al was observed, little adsorbed Cs(+) was observed on the surface of the soil particle. Using EDS, Cs(+) was observed only in the most concentrated Cs(+)-soil system, and Cs(+) was clearly correlated with the presence of Al and I. These results are interpreted in terms of multiple layers of CsI forming over areas of the soil surface that contain substantial Al. These observations are consistent with the hypothesis that the insertion of Al into the SiO(2) lattice results in the formation of anionic sites, which are then capable of binding cations.     

Development of a Sorption Technique for the Selective Separation of Plutonium and Americium from Nitric Acid Intermediate-Level Wastes of Chemical and Metallurgical Production

Radiochemistry - The sorption extraction of Pu and Am from nitric acid simulation solutions were studied on a solid extractant (TVEX) AXIONIT MND 40T in a static mode. It is shown that the...     

On the Highest Oxidation States of Plutonium in Alkali Solutions in the Presence of Ozone

During ozonation of Pu(VI) alkaline solutions, the highest oxidation state of Pu is formed in an oscillatory reaction. This plutonium species is reduced with Pu(VI) or Fe(III). Ferrate ion is also reduced with Pu(VI). It was assumed that in alkali solution plutonium is partially oxidized with ozone to Pu(VIII).     

Effect of Intense Self-Irradiation on the Phase Composition of Metallic Plutonium

The crystal structure of film samples of "high-level" (based on ²³⁸Pu) and low-level (based on ²³⁹Pu) metallic plutonium during their prolonged (up to 343 days) storage (self-irradiation) at room temperature was studied by X-ray diffraction. In the samples of high-level plutonium, the -Pu and -Pu lattices coexist. In the period of 40-60 days, the other known crystal modifications of plutonium (-Pu, -Pu, -Pu, and -Pu) are also present. Low-level plutonium had only the -Pu lattice. A possible origin of this phenomenon is discussed.     

Stereochemistry of Americium and Curium in Oxygen-Containing Compounds

Coordination of the Am and Cm atoms in the crystal structures of oxygen-containing compounds was analyzed using Voronoi–Dirichlet polyhedra (VDPs). These actinides (An) form coordination polyhedra AnO_n (6 ≤ n ≤ 9) of eight types. At a fixed oxidation state of An, the volume of the corresponding VDP is virtually independent of the coordination number n. Analysis of the characteristics of atomic VDPs in the An sublattices revealed compounds with binding An–An 5f interactions in the crystals.     

Speciation and Migration Behavior of Pu and Am in Floodplain Soils and Bottom Sediments of the Yenisei River

Am and Pu speciation in floodplain soils and bottom sediments of the Yenisei River is studied. Pu is more tightly associated with amorphous hydroxides as compared to Am. Am associated with organic matter is potentially more mobile than Pu. Model experiments showed that fulvic acids decelerate Am sorption from water to floodplain soil.     

Extraction of Americium and Neodymium from Perchloric and Hydrochloric Acid Solutions with Neat Diphenyl(dibutylcarbamoylmethyl)phosphine Oxide

Interaction of solid diphenyl(dibutylcarbamoylmethyl)phosphine oxide (Ph₂Bu₂) with perchloric and hydrochloric acid solutions was studied. On contact with the acids, this agent forms a liquid substance (liquid reagent, LR) exhibiting extractive power. The conditions of LR formation and extraction of Am(III) from HCl solutions with LR in the absence of organic diluent were studied. The solubility of Ph₂Bu₂ in 3 M HClO₄ is 2.5 mg l^{- 1}. The composition of the LR formed in HClO₄ solutions is 2Ph₂Bu₂·HClO₄·nH₂O. Perchloric acid is quantitatively backwashed from the LR phase with water. Formation of an Nd(III) complex with LR in HClO₄ solutions is accompanied by cementation (solidification) of the compound. The resulting complex has the 3 : 1 [Ph₂Bu₂ : Nd(III)] composition and mp 120°C. According to the IR spectrum, the coordination of Ph2Bu2 with the HClO₄ molecule is monodentate, and with the Nd(III) ion (in the absence of organic diluent) it is bidentate.     

Synthesis and Study of Americium Intermetallides with Gold

Radiochemistry - Samples of 241Am alloys with gold were synthesized for the first time. The alloys were obtained by the condensation of americium metal vapor on a flat gold substrate. The results...