Browsing by All Authors "Tan, M."
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Item A gamma spectrometric method for direct measurement of uranium contents in solid samples(Turkish Atomic Energy Authority, 2000-10) Yücel, Haluk; Ergin, İ.; Çetiner, M. Atıf; Demirel, Halil; Tan, M.; Özmen, Atilla; 3905; TAEK-ANAEMA 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.Item Determination of rare-earth elements by radioisotope x-ray fluorescence technique(Turkish Atomic Energy Commission, Ankara Nuclear Research Center, 1974-06) Şaplakoğlu, A.; Özoğlu, İ.; Tan, M.; Erdoğan, H.; AEK-Ankara Nükleer Araştırma MerkeziToprak numunelerinde Nadir Toprak Elementlerinin konsantrasyonları enerji dispersiv analiz ve Radyoizotop X-Işını Floresans Metodu ile bu laboratuvarda geliştirilen bir hesap yöntemi kullanılarak tespit edilmiştir. Ölçü ve hesap neticeleri 1 % civarındaki konsantrasyonlar için hatanın 95 % emniyet sınırı ile ± % 5 olduğunu göstermektedir. 0.2 % civarındaki konsantrasyonlar için hata sınırı ± 15 % olup, tayin edilebilecek en küçük konsantrasyon değeri milyonda 100 olarak hesaplanmıştır.Item Measurement of thermal neutron cross section and Resonance integral for 139La(n,γ) 140La reaction by activation method using cadmium ratios(National Nuclear Center of the Republic of Kazakhstan / Institute of Nuclear Physics, 2003) Yücel, Haluk; Karadağ, Mustafa; Çetiner, M. Atıf; Tan, M.; Özmen, Atilla; 3905; TAEK-ANAEMThermal neutron cross section and resonance integral for the 139La(n,γ)140La reaction was measured by the activation method. The experimental samples with and without a cylindrical Cd shield case in 1 mm wall thickness were irradiated in an isotropic neutron field of the 241Am-Be neutron source. The extent of the nonideality of the epithermal neutron spectrum(i.e., α- shaping factor for 1 E1+α epithermal distribution) at the sample irradiation position was experimentally determined by the two-detector(Au and W foils) method, and it was found to be 0.560±0.002. The induced activities in the samples were measured by high resolution γ-ray spectrometry with a calibrated n-type Ge detector. Thermal neutron cross section for 2200 m/s neutrons and resonance integral for the 139La(n,γ)140La reaction has been obtained relative to the reference values, σ0=13.3±0.1 b and I0=14.0±0.3 b for the 55Mn(n,γ)56Mn reaction as a single comparator. The results corrected for gamma attenuation, thermal neutron and resonance neutron self-shielding effects and the effect of α- shaping factor on the resonance integral value of the (n,γ) reactions. For the conversion of the measured infinite dilution resonance integral, I(α) to the I0 for 1/E ideal epithermal neutron spectrum, the concept of effective resonance energy, Er described by De Corte for the Ryves’ method[1] has been used. By defining Cd cut-off energy 0.55 eV, the results obtained were: σ0=9.27 ± 0.37 b and I0=12.16 ± 0.60 b for the 139La(n,γ)140La reaction. These results are discussed and compared with previous measurements and the evaluated data in JEF-2.2, IAEA and JENDL-3.2. Thermal neutron cross section for 139La(n,γ)140La reaction is in good agreement with the recent measurements. There existed the discrepancies between present results and some of old experimental data for thermal cross section and resonance integral for this reaction is within about 6-40%.