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Abstract  

Solvent extraction was described for determining of the americium content in the liquid samples. Arylesters of imidodiphosphoric, imidothiodiphosphoric, imidodithiodiphosphoric acids and tetraphenylimidodithiodiphosphine are used as representatives of bidentate organophosphoric extractants. From the group of tridentate agents, pentaphenyldiimidotriphosphate, was used. The extraction properties of tetraphenyl imidodiphosphates and their sulphur analogues for trivalent americium in 0.1 mol L−1 HNO3 into toluene also in the presence of tri-n-octylphosphine oxide (TOPO) were investigated. The dependences of equilibrium ratios of the americium on analytical or equilibrium concentration of chelating agents, pH, initial concentration of nitric acid and initial concentration of TOPO were studied. The structures of the complexes in the organic phase were determined and the values of extraction constants were calculated. The extracted species were AmA3, AmA3 (HA), the addition of TOPO induced synergistic extraction of AmA3 TOPO. The utilization of sulphur analogues was marginal.

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Abstract  

This paper describes the development of a separation method for americium from the effluents emanating from anion exchange column, used for the recovery of plutonium from analytical waste solutions. The waste contained uranium, sodium, calcium and iron as the major impurities as estimated by ICP-AES method. ~99% pure americium was obtained by three separation steps using solvent extraction and extraction chromatography techniques. In the first step, uranium was quantitatively separated by giving five contacts of equal volumes of 30% TBP in n-dodecane. Fe and Na were separated in the next step using 0.1 M TODGA + 0.5 M DHOA as the extractant. In the last step, Am was separated from the co-extracted Ca (about 76%) using CMPO loaded extraction chromatographic column. The overall recovery was >80% with decontamination factor (D.F.) from the impurities being >3000 while the purity of the product was 99%.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Svetlana Ovsiannikova, Maryna Papenia, Katsiaryna Voinikava, Justin Brown, Lindys Skipperud, Galina Sokolik, and Sergey Svirschevsky

Abstract  

The physicochemical forms of radionuclides in soils determine the processes of their entry into the soil solutions, redistribution in the soil profile, soil–plant and soil–ground or surface waters transfer as well as spreading outside the contaminated area. The vertical distribution of plutonium and americium and their physicochemical forms in soils of Polessie State Radiation-Ecological Reserve (PSRER) were studied with the aim of establishing the potential for radionuclide migration. Samples of alluvial soddy-podzolic and peaty soils with a low (1–3%) and relatively high (~80% of dry sample mass) content of organic matter have been selected for investigation. A method employing sequential selective extraction has been used for analysis of radionuclide physicochemical forms in the soils. Activity concentrations of 238Pu, 239,240Pu and 241Am in the samples were determined via radiochemical analysis with alpha-spectrometric identification of radionuclides. The results indicate that the main proportion of plutonium and americium remains in the 0–20 cm soil layer. The inventories of mobile and biologically available forms of plutonium and americium, expressed as a percentage of the total radionuclide content in soil, lie in the ranges of 1.1–9.4 and 2.7–29% respectively. Greater proportions of mobile and biologically available forms of radionuclides appear to be associated with mineral soil as compared to organic soil. In both mineral and organic soils, the portion of mobile americium is higher than plutonium. The inventories of mobile forms of plutonium and americium increase with the depth of soils.

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Abstract  

Due to the scarcity of good quality uranium resources, the growth of nuclear technology in India is dependent on the utilization of the vast thorium resources. Therefore, Advance Heavy Water Reactor is going to acquire significant role in the scenario of Indian nuclear technology, where (Th, Pu)O2 will be utilized as fuel in the outermost ring of the reactor core. This will lead to a complex matrix containing thorium as well as americium, which is formed due to β- decay of plutonium. The amount of americium is dependent on the burn up and the storage time of the Pu based fuels. In the present case, attempt was made to develop a method for the determination of americium as well as thorium by ICP-AES. Two emission lines of americium were identified and calibration curves were established for determination of americium. Though the detection limit of 283.236 nm line (5 ng mL−1) of americium was found to be better than that of 408.930 nm (11 ng mL−1), the former line is significantly interfered by large amount of thorium. Three analytical lines (i.e. 283.242, 283.730 and 401.913 nm) of thorium were identified and calibration curves were established along with their detection limits. It was observed that 283.242 and 401.913 nm line are having similar detection limits (18 and 13 ng mL−1, respectively) which are better than that of 283.730 nm (60 ng mL−1). This can be attributed to the high background of 283.273 nm channel of thorium. The spectral interference study revealed that even small amount of americium has significant contribution on 283.242 nm channel of thorium while the other two channels remain practically unaffected. Considering both these facts, spectral interference and analytical performance (detection limits and sensitivity), it was concluded that 401.913 nm line is the best analytical line out of the three lines for determination of thorium in presence of americium.

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Abstract  

This paper describes new approaches to digestion, accurate separation and determination of americium in soil samples by alpha spectrometry. The soil samples were obtained from surface and at a depth of 40 cm in a residential area. They were digested on a hot plate or in closed vessels heated in a microwave oven. The effect of decomposition methods on accuracy and reproducibility has been investigated. An extraction chromatography column is used to separate the americium from other actinide elements and interfering substances in the soil matrix. Prior to the determination of very low amounts of americium (100 ng g−1), electrodeposition at a current of 800 mA and a plating time of 150 min in the pH range of 2–3 has been applied. The typical recovery of Am from the samples is 88 % when dissolution occurs in a microwave oven. This is higher than the typical recovery of 83 % that is observed when the samples are heated on a hot plate.

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Abstract  

Two Americium–Beryllium neutron sources were dismantled, sampled (sub-sampled) and analyzed via inductively coupled plasma mass spectrometry (ICP-MS). Characteristics such as “age” since purification, actinide content, trace metal content and inter and intra source composition were determined. The “age” since purification of the two sources was determined to be 25.0 and 25.4 years, respectively. The systematic uncertainties in the “age” determination were ±4% 2σ. The amount and isotopic composition of U and Pu varied substantially between the sub-samples of Source 2 (n = 8). This may be due to the physical means of sub-sampling or the way the source was manufactured. Source 1 was much more consistent in terms of content and isotopic composition (n = 3 sub-samples). The Be–Am ratio varied greatly between the two sources. Source 1 had an Am–Be ratio of 6.3 ± 52% (1σ). Source 2 had an Am–Be ratio of 9.81 ± 3.5% (1σ). In addition, the trace element content between the samples varied greatly. Significant differences were determined between Sources 1 and 2 for Sc, Sr, Y, Zr, Mo, Ba and W.

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Abstract  

For the first time, the complexation of americium(III) with salicylic acid was studied at trace metal concentrations using a 2.0 m Long Path Flow Cell for UV–vis spectroscopy. The detection limit of Am(III) in aqueous solution at pH 3.0 was found to be 5 × 10−9 M. Two Am(III)-salicylate complexes were formed at pH 5.0 in 0.1 M NaClO4, indicated by a clear red shift of the absorption maximum. The absorption spectra obtained from spectrophotometric titration were analyzed by means of factor analysis and complex stabilities were calculated to be log β110 = 2.56 ± 0.08 and log β120 = 3.93 ± 0.19.

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Abstract  

During the simultaneous extraction of plutonium and uranium using anion exchange chromatographic technique from analytical waste in hydrochloric acid medium, 241Am which is invariably present in the plutonium bearing fuel samples remains in the effluent. A two step separation scheme was developed for the recovery and purification of Am from the assorted waste to facilitate the disposal of large volume of aqueous waste and the purified Am solution was utilized for spectroscopic investigation. The separation scheme involved solvent extraction using 0.1 M TODGA + 0.5 M DHOA for separation of americium from Fe, Pb, Ni and Na followed by extraction chromatographic technique using CMPO on inert support as stationary phase for separation of Ca from Am. A systematic study on the extraction behavior of Am from hydrochloric acid medium revealed that out of four extraction systems well known for actinide partitioning namely 0.1 M TODGA + 0.5 M DHOA, 1 M DMDBTDMA, 0.2 M CMPO + 1.2 M TBP and 30% TRPO, only 0.1 M TODGA + 0.5 M DHOA extracts americium from 7.5 M HCl feed acidity. A comparative study involving CMPO solvent extraction and column chromatographic technique revealed that elution of Am from column is satisfactory as compared to inefficient stripping of Am from organic phase in solvent extraction technique using 0.1 M HNO3. The purity of the final solution was checked for 17 elements of interest and was found to be 98% pure, while the overall recovery of this two step separation scheme was found to be 95%.

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Abstract  

A new sorbent, thorium oxalate incorporated in silica gel matrix was prepared. This material was characterized by X-ray, Thermo-gravimetric Analysis, surface area and porosity analysis. The material was obtained in the form of granular particles in the mesh size range of 80–150 American Standard of Testing Materials, yielding good liquid flow, when packed in ion exchange column. This sorbent was investigated for the sorption of americium from various aqueous media such as nitric acid, oxalic acid and sulphuric acid by distribution coefficient studies. Column experiments were carried out to study the practical application of this sorbent for removal of americium from oxalic acid-nitric acid solutions. Elution studies were also carried out for the recovery of americium.

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Abstract  

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B) in the presence of 1,2-(diphenylphosphino)ethane dioxide (DPPEtDO, L) has been investigated. The equilibrium data have been explained assuming that the species HL+, HL2 +, ML2 3+ and ML4 3+ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability constants of the corresponding complexes EuLn 3+ and AmLn 3+, where n = 2, 4 and L is DPPEtDO, in water-saturated nitrobenzene are comparable.

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