A gamma spectrometric method for direct measurement of uranium contents in solid samples
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Date
2000-10
Journal Title
Journal ISSN
Volume Title
Publisher
Turkish Atomic Energy Authority
Abstract
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.
Description
I. Avrasya Nükleer Bilimler ve Uygulamaları Konferansı : 23-27 Ekim 2000. İzmir, Türkiye.
Keywords
Gamma spectrometric method, Gamma spektrometrik yöntem, Direct measurement of uranium contents, Uranyum içeriğinin doğrudan ölçümü, Solid samples, Katı örnekler
Citation
Yücel, H. ... [ve arkadaşları]., (2000). A gamma spectrometric method for direct measurement of uranium contents in solid samples. I. Eurasia Conference on Nuclear Science and Its Application, Presentations, Vol 2, (s. 798-816). 23-27 October 2000. İzmir, Turkey.