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Abstract  

Chemical neutron activation analysis was applied to determine trace uranium in estuarine pore water after a simple separation through coprecipitation with hydrated iron(III) oxide. The mean coprecipitation yield of uranium was found to be ~85% under pH ranged from 6 to 8.6. The distributions of uranium in both seawater and pore water were determined alongwith the variations of uranium content in oxidation and reduction conditions. Behaviors of uranium in pore water are also discussed.

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Abstract  

A simple and non-destructive method has been proposed for the routine determination of uranium by epithermal neutron activation analysis in coral skeletons. Using a cadmium capsule, about 0.1-0.2 g samples were irradiated for 6 hours in the Triga Mark II Reactor. Measurements of -ray (239Np via 239U) were performed with each sample and standard after cooling for about three days. Compared with a non-destructive thermal NAA, the present method was found to improve the sensitivity because it reduced the intense Compton background induced by 24Na. We determined uranium in coral standards within 2% of analytical precision. The data obtained for the carbonate standards are mostly consistent with reported values. The present method could be usefully applied to determine uranium contents in fossil corals from the Funafuti Atoll in the Pacific. The distribution of uranium between seawater and coral skeletons is also discussed in order to understand the environmental media in which the coral grew.

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Abstract  

The concentration of rare earths and other elements have been determined in the bed sediment samples of Karnafuli estuarine zone in the Bay of Bengal by instrumental neutron activation analysis (INAA). The samples and the standards soil-5, soil-7, coal fly ash and pond sediment were prepared and simultaneously irradiated for short and long time at the TRIGA Mark-II research reactor facility of Atomic Energy Research Establishment, Savar, Dhaka. The maximum themal neutron flux was of the order of 1013 n·cm–2·s–1. After irradiation the radioactivity of the product nuclides was measured by using a high resolution high purity germanium detector system. Analysis of -ray spectra and quantitative analysis of the elemental concentration were done via the software GANAAS, it has been possible to determine the concentration level of 27 elements including the rare earths La, Ce, Sm, Eu, Tb, Dy and Yb and uranium and thorium.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Raman
,
N. Molla
,
A. Sharif
,
S. Basunia
,
S. Islam
,
R. Miah
,
S. Hossain
,
M. Chowdhury
,
A. Bhuiyan
, and
P. Stegnar
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Summary  

A systematic and non-destructive technique is proposed for the determination of fluorine in coral samples by instrumental neutron activation analysis using the 19F(n,γ)20F reaction. About 50 to 80-mg samples in polypropylene capsules were irradiated for 15 seconds in the pneumatic transfer tube system (PN-3) of JRR-3M reactor. After the irradiation at a thermal neutron flux of 1.5 . 1013 n . cm-2 . s-1, the coral samples and standards were cooled for 6 seconds and the g-rays emitted were measured for 15 seconds with a Ge detector. The sequence from sample irradiation to g-ray counting was performed under a computer-control mode. The analytical precision was ~5% for the JCp-1 coral standard. The present method was applied to the determination of fluorine in corals from Thailand, Okinawa and the Philippines. The advantage of one method over destructive techniques is discussed by comparing the analytical results obtained for the JCp-1 coral standard using INAA, ion chromatography and spectrophotometry. Factors that may control the levels of fluorine in corals are also discussed.

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Summary  

Recently, in our laboratory an intercomparison was made of methods for the annual radiation dose determination (assessed from direct radiation counting and/or from the measurement of the K, Th and U contents) applied to luminescence dating of loess and sand sediment, whereby the emphasis was put on their precision and accuracy. Although these properties are important, the duration of the measurement is also a practically relevant aspect. Indeed, direct alpha, beta and gamma-counting can last a week or more, and the determination of K, Th and U via NAA can take up to three weeks to enable proper gamma-ray spectrometry of the long-lived 233 Th/233Pa. Therefore, in the present work the performance of k 0-based epiCd-NAA (ENAA, with irradiation under a cadmium cover) when applied to sediments is compared to k 0-NAA. As concluded, with the use of k 0-ENAA the analysis turnaround time could be considerably reduced from ~3 weeks to ~ 2.5days, while maintaining satisfactory accuracy, precision and determination sensitivity.

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