Self-absorption Correction Factors Research Articles

Gross Alpha Activity Measurements: Investigating the Crucial Role of Self-Absorption Correction Factors

Gross Alpha Activity Measurements: Investigating the Crucial Role of Self-Absorption Correction Factors

Gamma-ray Spectrometry and X-ray Fluorescence Analysis for Natural Radioactivity Evaluation Associated with Radiation Hazard in Construction Materials

Abstract: This paper had threefold objectives: 1) to evaluate the natural radioactivity using the gamma spectrometry technique, 2) to correct the gamma self-absorption using the transmission method, and 3) to perform mineralogical analysis using the X-ray fluorescence (XRF) analyzer in seven different types of construction materials. The transmission method was used to measure the linear attenuation coefficient µ(E) of the samples as well as their standards at different energetic points. Next, the µ(E) coefficients were used to calculate the self-absorption correction factors (Cauto), and then they were introduced in a simplified formula to correct the fraction of the attenuated gamma radiation inside the traveled medium. Moreover, the quantitative assessment of natural radioactive elements (238U, 232Th, and 40K) was done in different geological matrices. The results have shown that the mean absorbed dose and the annual average dose received by these materials are 40.65 nGy.h-1and 0.2 mSv.y-1, respectively. According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the obtained values in no way pose a risk to human health. For compositional analysis, the X-ray fluorescence (XRF) analyzer was used to determine the concentrations of the major oxides (SiO2, CaO, CO2, and Al2O3) along with other oxides in all collected samples. The compositional results show that the self-absorption correction factors varied depending on the density and chemical composition of a sample. The XRF data shows that the mineralogical compositions are within their recommended limit. Thus, from a health safety perspective, the composition of the minerals does not pose any significant risks. Keywords: Gamma Spectrometry, Natural Radioactivity, Construction Materials, Radiological Hazard, Self-Absorption. PACS NaI(Tl): Sodium iodide (NaI) detector activated by thallium (Tl), XRF: X-Ray Fluorescence.

Determination of Self-absorption Correction Factors of Some Algae Samples: An Experimental study

The purpose of this study to examine experimentally self-absorption correction factors (SACFs) of some algae samples using gamma-ray spectrometry. Various algae samples were collected from Boğaçay in Antalya, Turkey. Collected algae samples were dried, and masses of the samples were calculated. Then densities of the samples were calculated. Each of algaes was counted with and without point sources which are 22Na, 60Co, 133Ba, and 137Cs about 1000 seconds using high purity germanium detector. The SACFs of algae samples were calculated between 80 keV and 1332 keV gamma-ray energies. As a result, SACFs of studied algae samples generally reduce as gamma-ray energy enhances. SACFs of some algae samples are nearly steady because of the densities and elemental contents of the studied algaes.

Effect of atomic number and pressure on plasma pinch properties and characteristic soft x-ray emission in PF1000

In this study, the Lee code is used to compute the characteristics soft x-ray yield (Ysxr) production for nitrogen (N2), oxygen (O2), neon (Ne), and argon (Ar) and bremsstrahlung radiation for hydrogen (H2), deuterium (D2), and helium (He) with pressure variation in PF1000 of 2.5–2.6 MA for D2. In the calculation of characteristic soft x-ray, the corresponding temperature windows of the said gases are set into the code at which they are ionized to their H-like and He-like levels. The focus pinch parameters such as radius ratio (minimum radius of plasma pinch column/anode radius), ion density, specific heat ratio, pinch energy density, self-absorption correction factor, and maximum induced voltage are computed at the optimum pressure of each gas. The obtained pinch plasma temperature range (1.2–2.2) × 106 K of H2, D2, and He is sufficiently high for fully ionized plasmas and the resulting bremsstrahlung radiation (14 J) for He is significantly larger than for H2 (0.26 J) and D2 (0.62 J). The optimum Ysxr of Ne(∼9314 J) at 0.51 Torr with pinch energy density (PED) (∼26 × 108 Jm−3) is found to be the highest whilst for Ar(∼7 J) at 0.019 Torr with (∼1.2 × 108 Jm−3) is the lowest. It is found that the radius ratio (∼0.05) of Ne is 3-fold smaller than that (∼0.16) in Ar. This enhancement of compression in pinch of Ne increases the ion density significantly by a factor of 253 than in Ar gas. Thus, the results show a strong correlation of plasma pinch properties with Ysxr for various gases.

Development of a computer code for the calculation of self-absorption correction factors in γ-spectrometry applications

In γ-spectroscopy applications, one of the main effects that needs to be considered is the self absorption of the photons – especially of low energy – within the photon source, which may be significantly different between the calibration standard and the sample analyzed. This effect is highly dependent on material composition and density and sample thickness. A common way of dealing with the self-absorption issue is by using Efficiency Correction Factors (ECF), to take into consideration the different absorbing properties between the calibration standard and the sample. This work presents the on-going development of a MATLAB code for ECF calculation. The code calculates ECF for a variety of material matrices and compositions, focusing on Naturally Occurring Radioactive Materials (NORM), which may have high density and contain high Z elements. The results of the code were compared with other methods of ECF calculation, such as Monte-Carlo simulation.

Estimation of radiation protection ability of borate glass system doped with CdO, PbO, and TeO2

This report presents the gamma-rays and neutron interacting parameters of the newly developed xCdO – 20PbO–10TeO2 – (69-x) B2O3–1CuO glass system with the view to applying them for nuclear protection uses. The glasses were coded as CdPTBCu1 – 4 representing molar concentration of CdO form 0–15%. The mass attenuation coefficient (MAC) of the glasses at gamma radiation energies 662–2506 keV were estimated using FLUKA. Monte Carlo simulation and NIST library. The simulation results compared well with that of NIST library within 2% margin. The MAC declines with energy but generally increases as CdO concentration increases in the glasses. At 0.284 MeV, the MAC values of CdPTBCu1, CdPTBCu2, CdPTBCu3, and CdPTBCu4 were equal to 2.459×10−1, 2.458×10−1, 2.457×10−1, and 2.447×10−1 cm2/g, respectively. While at 2.51 MeV, the values were 4.023×10−2, 4.023×10−2, 3.982×10−2, and 3.994×10−2 cm2/g, respectively. Other photon shielding factors like the effective atomic layer, transmission factor, self-absorption correction factor, and mean free path show that the increase in CdO content improves the photon shielding abilities of CdPTBCu specimens. Furthermore, the fast neutron removal cross section (ΣR) and their total thermal neutron cross section (σT) of the glasses were estimated. ΣR increased from 0.10211 to 0.10775 cm−1 while σT grew from 111.21 to 442.73 b. The increase in CdO content had a positive impact on the photon, fast, and thermal neutron shielding ability of the CdPTBCu glasses. Comparatively, the photon and neutron shielding ability of the present glass system is superior to some conventional and recently studied glass shields. The CdPTBCu glasses are thus potentially useful as photon and neutron absorbers for nuclear radiation protection applications.

Meta-Study of Particulate Detection Losses on Radioactive Air Sample Filters

Several mathematical relationships between air sample filter mass loading and the correlated analytical self-absorption factor were developed using data from other published research in this meta-study. Gross-alpha and -beta applications are addressed for this research. As filter media becomes loaded with particulate matter, there is potential for measurement losses due to self-absorption by mass loading. Components contributing to absorption include particulate dust, radioactive particulates, and filter material. Standards indicate a correction factor should be used when the penetration of radioactive material into the collection media or self-absorption of radiation by the material collected would reduce the detection rate by more than 5%. Previously, losses due to self-absorption have been reported up to 100% over a range up to ~10 mg⋅cm-2 mass loading. These absorption losses then can be used to determine a correction factor for sample results. For low mass loadings (e.g., ≤0.1 mg⋅cm-2) corrections factors in the 0.85 - 1 range have been recommended and used, while at higher mass loadings nearer to 10 mg⋅cm-2 correction factors closer to 0 (representing near 100% losses) are used. Based on data from published studies, the different methods for relating percent loss due to self-absorption to mass loading include linear, exponential, quadratic, and trinomial derived functions. Where applicable, both forced zero and non-forced zero results were evaluated. From the derived functions evaluated, the trinomial function provided the best fit. Once the sample filter mass loading is known, the trinomial function can be applied to estimate losses and the corresponding self-absorption factor. When applied to routine operating conditions for radiological facility stacks monitored at the Pacific Northwest National Laboratory for an average sample filter mass loading of 0.09 ± 0.12 (2σ) mg⋅cm-2 (excluding negative values and outliers) and a range from 0 - 0.24 mg⋅cm-2, the estimated trinomial function nominal self-absorption losses are less than 5% at 0.09 mg⋅cm-2 and less than 10% at 0.24 mg⋅cm-2. The trinomial function is one method that may be used to adjust the activity results of an air sample when the sample-specific mass loading is determined. The application of no correction factor when the ANSI/HPS N13.1-2021 guidance of a 5% threshold for loss is not reached with typical stack sample mass loadings may be reasonable in high-efficiency particulate air filtered systems. For simplicity, it would be conservative in assigning the self-absorption correction factor at the 5% threshold (i.e., 0.95) for general uses but in cases of heavy mass loading to calculate the factor.

Influence of chemical effects on the Li (i = 1–3) subshell X-ray spectra for 79Au compounds

The influence of chemical effects on intensity ratios i.e. ILi/ILα (i = l, β1, β15,2,3 and β5/2), ILα2/ILα1, ILj/ILβ1 (j = η, γ1 and γ5), ILk/ILγ4 (k = β6,4, β10,9/1 and γ2,3,6) and ILβ1/ILγ1 and chemical shift of Ll and Lγ1 X-ray emission peaks for 79Au compound has been investigated using polychromatic high resolution wavelength dispersive X-ray fluorescence (WDXRF). The measured intensity ratios of L X-ray emission spectra were corrected for spectrometers detector efficiencies and self-absorption correction factors. The experimental values of intensity ratios have been compared with the theoretical values evaluated using different set of available fractional emission rates, fluorescence and Coster-Kronig yields. The measurements also report significant energy shift (∼1–7 eV) in Ll and Lγ1 X-ray peaks of 79Au compounds relative to pure elemental form. The discrepancies in measured intensity ratios and shift in L X-ray emission spectra of 79Au compounds from the theoretical predicated values can be attributed to chemical effects due to core-valence exchange interactions and crystal effects of different ligands attached to central 79Au atom.

Self-absorption Correction Factors: Applying A Simplified Method to Analysis of Lead-210 in Different Environment Samples by Direct Counting of Low-energy Using HPGe Detector

This study aimed to determine the self-absorption correction factors of lead-210 (210Pb) in various Syrian environment samples. Seven sediments, five soils, and four plant samples were analysed by Gamma Spectroscopy using simple and direct analysis method called Cutshall. The method is based on measuring the penetration of gamma which emitted from a standard source, prepared in the laboratory by deposition of QCYB40 Standard Solution on stainless steel disk. The source was placed on top of the studied sample and the reference air sample during the measurement. The purpose was to study the self-absorption inside each sample by calculation of its self-absorption factors without knowing its chemical composition. The self-absorption correction results for the sediment samples SE3, SE6 and SE8 ranged between 36% and 45%, and 34% to 42% for the soil samples S5 and S1, respectively. Also, for the four plant samples, it recorded variance range from 4% to 18%. This is due to the difference in the density of the G4 sample, which appeared to be very low. However, the self-absorption correction factors CF were set for the different environmental samples, and the results show that the density factor of the sample is not the only influent factor in the CF values for low energies measurement, the sample chemical composition (sample matrix) is also more effective in addition to the samples’ particle sizes.

Determination of correction factor of self-absorption for lead-210 in environment samples using spike method

In environment radiation measurement, calculation the correction factors are critical, especially for low energy measurement because of self-absorption phenomena. In this work the main purpose is to determination the self-absorption correction factors of lead-210 (210Pb) energy (46.5keV) in various environment samples (7 sediments, 5 soil) using an experimental method called Spike Method. The samples were collecting from different places in Syrian. They were prepared according to the laboratory producers starting from collecting, cleaning, drying, grounding, hemogenic and calculating the appearance density. Low-energy gamma spectroscopy HPGe was used for radiation analysis which available at the laboratories of the Protection and Safety Department - Syrian Atomic Energy Commission – Syria. The spike method depends on adding a quantity of a standard solution with a known activity which contains lead isotope 210Pb and added to the studied samples. Self-absorption correction factors (CF) calculated by the ratio of the count rate or activity of spiked and unspiked samples. The CF for sediment samples were between 29% to 54% and for soil samples, the CFs were between 38% to 56% recording correction higher than sediment samples. The results showed a relatively high self-absorption and CFs values because of the chemical composition changeable between the spiked and unspiked samples. For that, it is better to adopt other methods less expensive, give results faster, higher accuracy and do not make change in the chemical composition. The results were also showed the density factor is the most influential factor in self-absorption phenomena.

A general function for determining mass attenuation coefficients to correct self-absorption effects in samples measured by gamma spectrometry

This work is focused on obtaining a general function for calculating the mass attenuation coefficients of samples whose compositions are known such as waste, biota or NORM (Naturally Occurring Radioactive Materials) samples. After determining the general function, it is possible to assess the self-absorption effects by the self-absorption correction factor, which is really important to consider for samples measured by gamma spectrometry. In order to obtain a general function of the mass attenuation coefficients dependent on the gamma emission energy (Eγ) and the chemical elements (Zi) with their respective concentrations (xi), it was necessary to fit the tabulated values of the mass attenuation coefficients versus gamma energy in the range of 20 keV–2000 keV for each chemical element. This is the energy range for the majority of gamma emissions of natural radionuclides. Once those fittings for each chemical element, Z, from 1 (H) to 92 (U) were done, the parameters, that resulted from those fittings, were fitted versus the atomic number, Z. This provides a general function that allows to calculate the mass attenuation coefficient by knowing the gamma emission energy and the sample composition. Finally, both the general function for calculating the mass attenuation coefficient and the self-absorption correction factor, which is used in gamma spectrometry with coaxial Ge detectors, were validated by comparisons made with the values provided by databases for several samples with widely different known densities, compositions and activity concentrations.

Experimental and Simulation Results of the Self-Absorption Correction Factors of Some Chemical Fertilizers in the Energy Range from 80 to 1332 keV

The purpose of this study is to calculate self-absorption correction factors of some chemical fertilizers used in Antalya in Turkey. Eight different types of chemical fertilizers with densities varying from 1.043 to 1.485 g cm–3 were investigated by Monte Carlo simulations and experimentally using the Transmission Method. Self-absorption correction factors of some chemical fertilizers were calculated experimentally using point sources which are 133Ba, 137Cs, 22Na and 60Co in the energy range from 80 to 1332 keV. The point source emissions were counted for 1000 seconds using a high purity germanium (HPGe) detector. Spectra were analyzed using computer software. Self-absorption correction factors versus energy graphics were obtained and compared with those of air and ultrapure water. The self-absorption correction factor versus energy graphics were obtained and fitted. Experimental and simulation results of the self-absorption correction factors of some chemical fertilizers were obtained and compared in the energy range from 80 to 1332 keV.

Effects of element composition in soil samples on the efficiencies of gamma energy peaks evaluated by the MCNP5 code

In this work, self-absorption correction factor related to the variation of the composition and the density of soil samples were evaluated using the p-type HPGe detector. The validated MCNP5 simulation model of this detector was used to evaluate its Full Energy Peak Efficiency (FEPE) under the variation of the composition and the density of the analysed samples. The results indicates that FEPE calculation of low gamma ray is affected by the composition and the density of soil samples. The self-absorption correction factors for different gamma-ray energies which was fitted as a function of FEPEs via density and energy and fitting parameters as polynomial function for the logarithm neper of gamma ray energy help to calculate quickly the detection efficiency of detector. Factor Analysis for the influence of the element composition in analysed samples on the FEPE indicates the FEPE distribution changes from non-metal to metal groups when the gamma ray energy increases from 92 keV to 238 keV. At energies above 238 keV, the FEPE primarily depends only on the metal elements and is significantly affected by aluminium and silicon composition in soil samples.

Angular distribution of characteristic X-ray emission from Fe and V following photoionization

<sec> The de-excitation process of vacancy in the inner shell of the target atom caused by collision ionization produces the characteristic X-ray or Auger electrons. The precise measurement of ionization cross sections plays an important role in many basic research fields, as well as in practical fields, such as chemical analysis of Particle Induced X-ray Emission (PIXE), atomic and nuclear processes, and X-ray fluorescence (XRF) spectroscopy. As we know, when ionization cross sections are measured precisely, whether the emission of X-ray is isotropic in collision process must be considered. However, there have been few experimental results for angular dependence of <i>K</i><sub>β</sub>/<i>K</i><sub>α</sub> intensity ratios in the literature until now. Therefore, this study aims to verify that the <i>K</i><sub>α</sub> and <i>K</i><sub>β</sub> X-rays originated from filling of the <i>K</i> shell vacancies with total angular momentum quantum number 1/2 (<i>J</i> = 1/2) are isotropic.</sec><sec> In this work, the typical <i>K</i>-shell X-ray spectra for Fe and V, which induced by bremsstrahlung with central energy of 13.1 keV, have been measured at emission angles varied from 120° to 170° at intervals of 10°. The characteristic X-ray spectra obtained by the detector are fitted by Gauss function, where the absorption of incident X-rays by the detector, the absorption of emitted X-rays by the atmosphere and the self-absorption correction factor of incident and emitted X-rays by the target are all taken into account.</sec><sec> The experimental results of <i>K</i><sub>β</sub>/<i>K</i><sub>α</sub> intensity ratio in this experiment coincide with those of theoretical calculation, as well as the Ertuğral’s experimental result. The experimental results show that the intensity ratio of <i>K</i><sub>β</sub>/<i>K</i><sub>α</sub> is a constant at different detection angles. Therefore it can be concluded that the emission of <i>K</i><sub>α</sub> and <i>K</i><sub>β</sub> is isotropic in the detection range. Since the <i>K</i> shell has no sub-shell, there is no Coster-Kronig transition in the collision ionization process. In the process of photoionization, the vacancies in the <i>K</i> shell are produced by direct ionization. As a result, the cross section ratio of <i>K</i> shell X-ray generation is independent of the <i>K</i> shell photoionization cross section. In addition, the experimental results show that the <i>K</i><sub>β</sub>/<i>K</i><sub>α</sub> characteristic X-ray intensity ratio of target Fe is 8% higher than that of target V, which are consistent with the theoretical analysis results that the characteristic X-ray intensity ratio depends on the target atomic number <i>Z</i>.</sec>

Calculation of self-absorption and coincidence summing correction factors for the extended sources using GEANT4

A detailed study of the full energy peak efficiency of a high purity germanium (HPGe) detector including the effect of source self-absorption and coincidence summing was performed using Monte Carlo simulation, as it is difficult and time-consuming to measure the full energy peak efficiency experimentally. Cylindrical water composition source was simulated with different characteristics, covering the energy range from 60 to 1836 keV. Self-absorption correction factors (SAFcal) were calculated for two source volumes and obtained good agreement with the experimental results except for (60Co and 88Y) nuclides. The simulation was performed for various samples with different densities and observed their effects on the full energy peak efficiency value of the detector. In the case of extended volumetric source, the coincidence summing correction factors (CSFcal) for two nuclides (60Co and 88Y) were estimated with the GEANT4 simulation toolkit. The effect of correction factors on different cylindrical source volumes was also investigated. With the self-absorption and coincidence summing effect, the best agreement was achieved between simulated and experimental results with discrepancy less than 2% for all of the radionuclides included in two source volumes.

Calibration of HPGe Detector Efficiencies With Self-Absorption Correction of Gas Sphere Sources

Several types of radioactive gases are released from the nuclear reactor. In order to measure the activity of such gases, it is necessary to calculate the accurate efficiency. Practically, efficiency calibration with gaseous sources is not very easy because of the low half-lives of the noble gases. For this purpose, Monte Carlo (MC) simulation was performed to study the full energy peak efficiency of two n-type high-purity Germanium (HPGe) detectors. Two spheres of xenon and krypton composition sources with two nuclides (Xe133 and Kr85) and two-point sources were simulated, covering the energy range from 81 keV to 604 keV. Self-absorption correction factors were calculated with GEANT4 for two gas sphere samples and obtained good efficiency agreement with the experimental results. The simulation was performed for various gas samples with different densities and observed their effects on the full energy peak efficiency value of two detectors. The corresponding self-absorption correction factors were calculated for each gaseous sample and investigated that the self-absorption correction factors not only depend on the sample characteristics but also on the detector geometry and source to detector distance. The dependence of the full energy peak efficiency on the side cap wall material and their thicknesses were also carried out for some particular photon energies.

344. Application of Monte Carlo techniques to the calibration of airborne radioactivity monitoring systems

Purpose Air monitoring systems are mandatory in all areas potentially contaminated with airborne radioactivity, such as hot laboratories, treatment rooms, and radioactive waste storage areas. The calibration of such systems may be practically complicated or require the application of correction factors, obtained by means of approximated analytical calculations. Monte Carlo techniques provide an effective way to check the calibration and the impact of the approximations used in the calculation. Methods The present work compares two different systems: a continuous air monitoring system, composed by a NaI detector located inside a chimney, and an air pumping system that measures the sample activity in a Marinelli beaker geometry, equipped with NaI detector. This setup allows to calibrate the continuous air monitoring system using the measurements provided by the Marinelli beaker system. A self-absorption correction factor, applied in the calibration of the Marinelli beaker system, is derived for gamma and beta+ radiation and compared with approximated analytical calculation available for gamma [1] . The cross-calibration of the two systems is complicated by the presence of F18 that sticks to the duct’s walls, producing a background that continuously increases during the air flow, therefore the calibration constants are checked using an approximate analytical calculation and a Geant4 simulation. Results Calibration factors are computed for ducts of different sizes and lengths, and validated using the IRST monitoring system. These coefficients represent a useful estimate in the calibration of continuous air monitoring systems in all cases where the cross-calibration of two systems is not possible. Conclusions Monte Carlo techniques help in overcome challenging aspects in the calibration of air monitoring systems, providing reliable results that can be used to cross-check the calibration constants of the system in case of large experimental uncertainties.

Comparison of simulated and experimental values of self-absorption correction factors for a fast and credible adjust in efficiency curve of gamma spectroscopy

Self-absorption correction factors are fundamental in spectroscopy to correct the efficiency of the samples detection whose density is different from the radioactive standard. Mathematical simulations have been widespread as a tool to facilitate the procedure of correction factors calculation. In this paper, LabSOCS was used to calculate the self-absorption correction factor for some geometries and the values found were compared to those obtained in MCNP and experimental values. The percentage deviations found for the self-absorption correction factor calculated by LabSOCS were below 1.6% when compared to experimental values. Deviations were below 1.9% in the curve extrapolation of the experimental procedure found in literature. Results obtained show that the deviations increase proportionally to the difference between the density values of the radioactive standard and the sample. High percentage deviations were also noticed in simulations whose samples had high densities, complex geometries and low energy gamma-rays.

Determination of the HPGe detector efficiency in measurements of radioactivity in extended environmental samples

A combination of experimental measurements and Monte Carlo (MC) calculations was used to determine the full-energy peak efficiency of a HPGe detector employed in environmental measurements. The manufacturer-provided parameters of the detector were corrected by comparing measured values of the efficiency with those obtained by MC simulations. After the adjustment of the active volume of the detector, the simulated and experimentally measured efficiencies agreed within 1%. A full-energy peak efficiency curve for a new distance was obtained by simulation. The efficiency curve for volumetric samples in the 53–1408keV energy range was determined using the efficiency transfer method. Geometric and self-absorption correction factors were estimated by experimental measurements, MC calculations or a combination of the two. In addition, the density of two sediment samples was estimated by a transmission measurement experiment and data simulation. Finally, concentrations of 238U and 232Th in two sediment samples from the Caetité region of Brazil were determined with relative uncertainties of about 5%.

Methodology for determination of correction factors in direct gamma spectrometric measurement of radionuclides in sediments

In this study, the practical methodologies are described for the determination of the factors for the self-absorption effect (Fs), spectral interferences (Fcsi), and true coincidence summing effects (Fcoi), which are used in direct gamma-spectrometric measurement of radionuclides such as 210Pb, 238U, 234Th, 226Ra, 214Pb, 228Ac, 208Tl, 214Bi, 137Cs and 40K in samples. To validate the applied methods, certified reference materials (CRMs) of lake and stream sediments were measured with an n-type Germanium (Ge) detector-calibrated using a multinuclide reference source. The highest self-absorption correction factors ranged from Fs = 1.44–2.10 for 46.5keV peak (210Pb) and Fs = 1.25–1.60 for 63.3keV peak (234Th) lying in the low energy region of the spectrum. The systematic influence was observed for 186.2keV (226Ra) peak due to spectral interferences with the 235U contribution. For this peak, Fcsi is changed from 0.921 to 0.955. Additionally, the present study suggests that true coincidence summing (TCS) effects are not dominant, except for 208Tl and 214Bi for which Fcoi ranged from 1.179 to 1.192 an ranged from 1.140 to 1.151, respectively.