| Autor: |
Yücel, Haluk, Ergin, İ., Çetiner, M. Atıf, Demirel, Halil, Tan, M., Özmen, Atilla |
| Přispěvatelé: |
TAEK-ANAEM |
| Jazyk: |
angličtina |
| Rok vydání: |
2000 |
| Předmět: |
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| Popis: |
I. Avrasya Nükleer Bilimler ve Uygulamaları Konferansı : 23-27 Ekim 2000. İzmir, Türkiye. A gamma spectrometric method is described for the direct “absolute” determination of uranium contents in solid samples. To obtain the exact information about the measurement of 238U in samples by gamma-ray spectroscopy, it is essential that any one of the daughters of 238U should exist in radioactive equilibrium with 238U. This condition is mainly fulfilled by one of the first two daughters, namely, 234Th (24.1 d) and 234mPa (1.17 min) because these daughters are very short-lived compared with 238U. Therefore, the present analytical method employs direct determination of U via the 63.3 keV gamma emission from Th and via the 1001 keV gamma emission from 234mPa. The absolute photopeak efficiency data in the range of 40 keV to 2000 keV for the reverseelectrode Germanium(REGe) detector used is measured using a powder radioactive standard source. The certified uranium samples were prepared in thin thicknesses to minimize the selfabsorption of gamma rays. They are counted for the the time predetermined between 75,000 s and 125,000 s. The measured activities of 238U of the samples via the 63.3 keV (234Th ) and via the 1001 keV (234mPa) are corrected for self-absorption effects due to changes in composition of standard reference materials in a given sample-detector geometry. The self-absorption factors applied to the 46.5 keV(210Pb) peak and the 63.3 keV(234Th) peak results ranged from 10.5% to 33.1% and from 4.9% to 18.4%, respectively. For the 1001 keV(234mPa) gamma emission, the necessary self-absorption factors varied between 0.1% and 3.9%. The results obtained from the 46.5 keV of Pb being far distant member of U and those of the 63.3 keV from 234Th are used to check whether the equilibrium exist in the uranium samples. The results of U via the 63.3 keV peak of Th for the uranium standards agreed to within 0.1 to 6.9% with the certified values of 238U in the samples with uranium concentration ranging from 0.022±001 to 1.02±0.01 wt%. The results of 238U via the 1001 keV peak of 234mPa agreed well to within 0.01 to 4.7% with the certified activity values of 238U of the same samples. When the measurements of the uranium are carried out in a REGe detector system, the results indicate that the uranium concentrations in the samples can be determined to the average 7% error by using the 63.3 keV(234Th) gamma emission with appropriate corrections for self-absorption effects. The 1001 keV peak of 234mPa gives also accurate results for the determination of 238U in the same samples and the need for self absorption correction for the 1001 keV emission seems to be negligible, except in case of thicker samples than that of 1.5 cm thick. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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