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  • Author or Editor: H. Salar Amoli x
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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  

This paper describes our development of an accurate determination of uranium by alpha spectrometry using various kinds of sample digestion methods. The sample preparation techniques employed an acid digestion with HNO3, and microwave oven digestion either by HNO3 or by combination of HNO3 and HF. The samples were obtained from surface and in depth(40 cm) soils from residential area. An extraction chromatography column has been used to separate the uranium from interference matrix and elements. Results show that the microwave method significantly speeds up the analysis time, reduces the volume of acids used and eliminates a large fraction of acid vapour emission. Compared with the uranium recoveries it was shown that microwave HNO3+HF achieved greater recovery (83%) than microwave HNO3 (78%), while less obtained by HNO3 digestion using hot plate (75%). Various kind of digestion methods have been applied (24 times) for two kind of soil sample. The reproducibility was acceptable and the average precision (coefficient of variation) was between 4 to 5. No significant differences between the precision of the methods have been observed. Acid volume required for the microwave procedures are a fraction of 5 times lower and the analysis time 6 times lower than traditional digestion by hot plate technique.

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Summary  

A simple method was used to design and set up an electrodeposition device for the alpha-emitting nuclides. The designed electroplating facility is leak proof and simple in operation and dismantled. The effect of current, pH of electrolyte, and the plating time on the electrodeposition efficiency have been investigated in a sodium bisulphate, sulphuric acid electrolyte in order to determine the optimum conditions. It was shown that a current of 900-1000 mA, plating time of 80-90 minutes and pH range of 2-2.3 are the best conditions for deposition of nano-scale uranium and plutonium. In these circumstances, it was possible to deposit 0.004 ng . g-1 Pu and 60 ng . g-1 U in an electroplating planchette. The device and modified procedures were successfully applied for soil samples. Prior to electrodeposition of the elements, a column extraction chromatography has been used to separate the Pu and U and eliminate most matrix and interferences in environmental samples.

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