Uranium Isotopes In Environmental Samples Research Articles

Determination of Uranium Isotopes in Environmental Samples Using Different Analytical Techniques: A Comparison

Determination of Uranium Isotopes in Environmental Samples Using Different Analytical Techniques: A Comparison

Determination of uranium isotopes in environmental samples by anion exchange in sulfuric and hydrochloric acid media

Method for determination of uranium isotopes in various environmental samples is presented. The major advantages of the method are the low cost of the analysis, high radiochemical yields and good decontamination factors from the matrix elements, natural and man-made radionuclides. The separation and purification of uranium is attained by adsorption with strong base anion exchange resin in sulfuric and hydrochloric acid media. Uranium is electrodeposited on a stainless steel disk and measured by alpha spectrometry. The analytical method has been applied for the determination of concentrations of uranium isotopes in mineral, spring and tap waters from Bulgaria. The analytical quality was checked by analyzing reference materials.

Novel method for determination of uranium isotopes in environmental samples by liquid–liquid extraction with triisooctylamine in sulfuric and hydrochloric acid media

Novel and robust method for determination of uranium isotopes in various environmental materials is presented. The method is based on total decomposition of the solid materials by the use of closed vessels microwave acid digestion systems and pre concentration of uranium from the liquid samples. The separation of uranium from interfering radionuclides and stable matrix elements is attained by liquid–liquid extraction with triisooctylamine/xylene in sulfuric and consecutively in hydrochloric acid media. Purified uranium is electrodeposited on a stainless steel disks and then measured by alpha spectrometry. The critical steps in the method were examined. The analytical method has been successfully applied to the determination of uranium isotopes in mineral and tap waters, as well as in soils from Northwestern Bulgaria. The analytical quality was checked by analyzing reference materials with different matrices.

Determination of uranium isotopes in environmental samples

The determination of isotopes of uranium by alpha spectrometry in different environmental components (sediments, soil, water, plants and phosphogypsum) is presented and discussed in this paper. The alpha spectrometry is a very convenient and good technique for activity concentration of natural uranium isotopes (234U, 235U, 238U) in environmental samples and provides the most accurate determination of isotopic activity ratios between 234U and 238U. The analysis were provided information about possible sources of high concentrations of uranium in the examined sites determined by anthropogenic sources. The calculation of values 234U/238U in all analyzed samples was applied to identifying natural or anthropogenic uranium origin. Activity concentration of uranium isotopes in analyzed environmental samples shows that measurement of uranium levels is of great importance for environmental and safety assessment especially in contaminated areas (phosphogypsum waste heap).

Method for determination of uranium isotopes in environmental samples by liquid–liquid extraction with triisooctylamine/xylene in hydrochloric media and alpha spectrometry

Alternative method for determination of uranium isotopes in various environmental samples is presented. The method is based on total decomposition of the solid materials and preconcentration of liquid samples. The separation of uranium from interfering radionuclides and stable matrix elements is attained by liquid–liquid extraction with triisooctylamine/xylene in hydrochloric media. After the additional removal of stable iron by extraction with diisopropyl ether, purified uranium is electrodeposited on stainless steel disks and measured by alpha spectrometry. The analytical method has been successfully applied to the determination of uranium isotopes in water and bottom sediments from the rivers Danube, Ogosta and Tzibritza in Northwestern Bulgaria. The analytical quality was checked by analyzing reference materials with different matrices.

반응속도론적 인광 분석기를 이용한 환경 시료 중 우라늄 동위원소 분석에 대한 연구

본 논문에서는 반응속도론적 인광 분석기(Kinetic Phosphorescence Analyzer, KPA)를 이 용하여 환경 시료 중의 우라늄 동위원소 분석에 대한 연구를 기술하였다. 극초단파 산분해 기술을 이용하여 토양 및 유리 재질 시료로부터 우라늄 성분을 추출한 후, UTEVA 수지를 통해서 우라늄 동위원소를 순수하게 분리하였고 KPA로 우라늄 농도를 정량하였다. 우라늄 표준용액을 사용하여 KPA를 이용한 우라늄 측정법에 대한 선형성 및 재현성 실험을 수행하였다. 우라늄 표준용액, 지하수 및 인증 표준시료에 대해 KPA를 사용하여 우라늄 농도를 측정하여 KPA를 이용한 우라늄 분석법에 대한 신뢰도를 검증하였다. In this paper, the study of analysis of uranium isotopes in environmental samples with a kinetic phosphorescence analyzer (KPA) was described. After leaching uranium fraction from soil and glass material with microwave acid digestion technology, uranium isotopes were purified with UTEVA column, and then measured using KPA. Linearity and repeatability tests for measurement of uranium isotopes were carried out in the uranium standard solution with KPA. The reliability for analytical method of uranium with KPA was validated by its application to uranium standard solution, ground water, IAEA and NIST reference samples.

RELIABILITY OF USING 238U/235U AND 234U/238U RATIOS FROM ALPHA SPECTROMETRY AS QUALITATIVE INDICATORS OF ENRICHED URANIUM CONTAMINATION

Alpha spectrometry is a commonly used technique for the measurement of uranium isotopes in environmental samples because it is widely available at a relatively low cost. For natural uranium the (234)U to (238)U activity ratio should be 1 and the (238)U to (235)U activity ratio should be 21.7. However, a lower (238)U to (235)U ratio is usually observed in alpha spectrometric analysis of environmental soil samples. This observation has led to the conclusion that soils from nuclear weapons facilities were contaminated with highly enriched uranium. This study was undertaken to test the reliability of using activity ratios from alpha spectrometry to infer the presence of highly enriched uranium in soil samples. The results of these experiments indicate that the (238)U to (235)U activity ratio is not a reliable indicator, but that the (234)U to (238)U activity ratio can be used to qualitatively indicate the presence of highly enriched uranium at concentrations near 10 ng g(-1) and above.

An improved method for the determination of uranium isotopes in environmental samples by alpha-spectrometry

In order to improve the selectivity of the uranium isotopes determination in environmental samples, further studies have been carried out, including (1) interference of 210Po with uranium isotope determination, (2) distribution coefficients of polonium between 5% TOPO in toluene and aqueous hydrochloric and nitric acids, (3) decontamination factor of uranium from polonium of the recommended procedure, and (4) leaching effect comparison of two different leaching procedures in a lichen sample. Based on the new findings, a more accurate extraction chromatographic/ a-spectroscopy method has been developed. For the method's validation, four kinds of reference materials supplied by the IAEA have been tested. It is observed that nearly all the 238U, 234U and 235U concentrations obtained are in good agreement with the recommended or information values, showing that the method can give reliable results. A comparison with existing uranium determination methods has also been made. It is concluded that due to involving preconcentration and chemical separation, the extraction chromatographic/a-spectroscopy method is a more selective, very sensitive and accurate, and low cost method.

Determination of uranium isotopes in environmental samples by alpha-spectrometry

A new and accurate method for the determination of uranium isotopes (238U, 234U and 235U) in environmental samples by alpha-spectrometry has been developed. Uranium is preconcentrated from filtered water samples by coprecipitation with iron(III) hydroxide at pH 9-10 using an ammonia solution and the precipitate is dissolved in HNO3 and mineralized with H2O2 and HF; uranium in biological samples is ashed at 600 °C, leached with Na2CO3 solution and mineralised with HNO3, HF and H2O2; uranium in soil samples is fused with Na2CO3 and Na2O2 at 600 °C and leached with HCl, HNO3 and HF. The mineralized or leaching solution in 2M HNO3 is passed through a Microthene-TOPO (tri-octyl-phosphine oxide) column; after washing, uranium is directly eluted into a cell with ammonium oxalate solution, electrodeposited on a stainless steel disk and measured by alpha-spectrometry. The lower limits of detection of the method is 0.37 Bq.kg-1 (soil) and 0.22 mBq.l-1 (water) for 238U and 234U and 0.038 Bq.kg-1 (soil) and 0.022 mBq.l-1 (water) for 235U if 0.5 g of soil and 1 litre of water are analyzed. Five reference materials supplied by the IAEA have been analyzed and reliable results are obtained. Sample analyses show that, the 238U, 234U and 235U concentrations are in the ranges of 0.30-103, 0.49-135 and 0.02-4.82 mBq.l-1 in waters, of 1.01-7.14, 0.85-7.69 and 0.04-0.32 Bq.kg-1 in mosses and lichens, and of 25.6-53.1, 26.4-53.8 and 1.18-2.48 Bq.kg-1 in sediments. The average uranium yields for waters, mosses, lichens and sediments are 74.5±9.0%, 80.5±8.3%, 77.8±4.9% and 89.4±9.7%, respectively.

Optimization of a radioanalytical procedure for the determination of uranium isotopes in environmental samples

A radiochemical procedure is described for the fast and sensitive measurement of uranium isotopes in gaseous and liquid effluents of nuclear facilities. Equally, this procedure is suitable to measure uranium isotopes in all kinds of environmental samples. Uranium is leached from ashed sample materials with HNO3, HF, and Al(NO3)3 solution and separated from matrix elements by extraction with trioctylphosphinic oxide and backextraction with NH4F. After radiochemical cleaning by coprecipitation with LaF3 and anion exchange, uranium isotopes are electroplated on stainless steel discs from HCl/oxalate solution. The preparation is measured by alpha-spectrometry using surface barrier detectors. The detection limit for 1000 minutes of counting time is 2 mBq per sample and nuclide, the chemical yield is in the range of 50 to 80%.