• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1266-1276
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• 2021

The mask parameters of a coded aperture are critical design features when optimizing the performance of a gamma-ray camera. In this paper, experiments and Monte Carlo simulations were performed to derive the minimum detectable activity (MDA) when one seeks a real-time imaging capability. First, the impact of the thickness of the modified uniformly redundant array (MURA) mask on the image quality is quantified, and the imaging of point, line, and surface radiation sources is demonstrated using both cross-correlation (CC) and maximum likelihood expectation maximization (MLEM) methods. Second, the minimum detectable activity is also derived for real-time imaging by altering the factors used in the image quality assessment, consisting of the peak-to-noise ratio (PSNR), the normalized mean square error (NMSE), the spatial resolution (full width at half maximum; FWHM), and the structural similarity (SSIM), all evaluated as a function of energy and mask thickness. Sufficiently sharp images were reconstructed when the mask thickness was approximately 2 cm for a source energy between 30 keV and 1.5 MeV and the minimum detectable activity for real-time imaging was 23.7 MBq at 1 m distance for a 1 s collection time.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.3
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• pp.151-155
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• 1997

In this research, nondestructive test using a radioisotope, $^{241}Am$ gamma-ray, was accomplished in order to evaluate the fiber volume fraction of the accumulated composite layers such as glass fiber/epoxy and carbon fiber/epoxy. Attenuation coefficients of the fiber and resin were measured respectively by NaI(T1) detector The fibers volume fraction was measured for various thickness of composite layers between 2 and 20mm. Fiber volume fraction of the composite layers were also measured for various amount of fibers. The experimental errors from nondestructive test using gamma-ray were in the range of ${\pm}1{\sim}2.5%$ in comparison with those from observation by optical microscopy. By selecting the optimum energy and activity of radioisotope, this method can provide a new means for the evaluation of the fiber volume fraction.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1925-1931
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• 2024

The study conducted in the northwest region of Jordan aimed to assess the levels of natural radioactivity in soil and olive mill pomace (OMP) samples. The researchers used Nal (TI) gamma-ray spectrometry to measure the activity concentrations of ²²⁶Ra, ²³²Th, ⁴⁰K, and ¹³⁷Cs in the samples. The average activity concentrations of ²²⁶Ra, ²³²Th, ⁴⁰K, and ¹³⁷Cs in the soil samples were found to be 18.624 ± 5.82, 12.276 ± 5.728, 518.33 ± 212.57, and 0.140 ± 0.09 (Bq, kg^-1), respectively. In the OMP samples, the average activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were 7.272 ± 4.386, 3.454 ± 1.503, and 169.997 ± 81.873 (Bq kg^-1), respectively, and no ¹³⁷Cs was detected. The study also investigated fundamental parameters associated with radon, specifically the radon emanation coefficient (Rn_EC) and radon mass exhalation rate (E_x). The Rn_EC values ranged from 0.621 to 0.78 (Bq kg^-1), with an average value of 0.71 ± 0.06 (Bq kg^-1). The estimated E_x from the soil samples ranged from 65.83 to 124.86 (mBq kg^-1h^-1), with an average value of 99.74 ± 21.73 (mBq kg^-1h^-1). Regarding radiological hazards, the study examined various parameters, including radium equivalent activity, external and internal hazard indices, gamma and alpha indices, absorbed gamma dose rate, and excess lifetime cancer risk. All of these assessed values were found to be below the worldwide recommended limits for radiological safety. Additionally, the study analyzed the concentrations of gross alpha and gross beta radioactivities in soil and OMP samples. The soil samples had an average gross alpha activity of 4.642 ± 1.04 (Bq kg^-1) and an average gross beta activity of 48.13 ± 14.50 (Bq kg^-1). The OMP samples showed an average gross alpha activity of 0.32 ± 0.27 (Bq kg^-1) and an average gross beta activity of 59.19 ± 12.94 (Bq kg^-1). Overall, the obtained results are crucial for evaluating the radiological risks associated with natural radioactivity in the northwest region of Jordan. The findings establish baseline data for comparison and reference for radioactivity levels in the environment.

• Korean Journal of Environmental Agriculture
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• v.19 no.2
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• pp.142-146
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• 2000

To observe the stimulating effects of low dose ${\gamma}-radiation$ on the seed germination, early growth and physiological activity in the gourd, seeds of three cultivars (Partner, Support, FR Yongja) were irradiated at the dose of $0.5{\sim}30\;Gy$. The hormetic effects of the low dose ${\gamma}-radiation$ on the growth were different from each cultivar. Low dose ${\gamma}-radiation$ had promoting effects on the germination at the optimum dose of 2 Gy and 8 Gy and on the early growth at the optimum dose of 4 Gy, 16 Gy and 20 Gy in Partner and Support cultivar and 1 Gy in FR Yongja cultivar. Irradiation didn't have significant effects on the chlorophyll contents of gourd plantlet. The antioxidant enzyme activity of gourd plantlet and early growth increased in low dose irradiation group.

• Journal of Korean Society on Water Environment
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• v.26 no.6
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• pp.948-953
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• 2010

In this study, degradation of estrone (E1) and $17{\alpha}$-ethynylestradiol (EE2) by gamma-irradiation and subsequent reduction of estrogenic activity as a function of absorbed dose were conducted using the yeast two-hybrid assay. Relative potency of E1 and EE2 compared to estrogenic activity of $17{\beta}$-estradiol (E2) was found to be 0.0144 and 0.1605, respectively. More than 90% of E1 and EE2 (both $5.0{\times}10^{-6}M$) was removed at an absorbed dose of 5 kGy, but more than 40% of estrogenic activity still remained. The addition of $TiO_2$ catalyst appeared to improve the removal efficiency of E1 and decrease estrogenic activity while there was no significant effect for EE2. Additionally, the calculated estrogenic activity of E1 and EE2 based on a regression model was well correlated with the observed activity.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.754-756
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• 1999

In this paper, we have developed a high-sensitivity SNRD(Semiconductor Nuclear Radiation Detector) using silicon PIN photodiode. The SNRD is constructed with silicon PIN photodiode(S3590-05), preamplifier and shaping amplifier. To show the effectiveness of SNRD, nuclear radiation experiments are conducted with $\gamma$-ray Ba-133, Cs-137 and Co-60. The SNRD is different in characteristics of the energy spectrum to scintillation detectors. However, the SNRD have a good linearity on $\gamma$-ray energy and activity. The results of this paper can be applied to electronic personal dosimeter.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2285-2288
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• 2002

Recently, electronic personal dosimeters based upon silicon PIN photodiode or miniature GM tube were developed and have attracted a lot of attention because of the advantages of their nature such as indication of dose rate and the cumulative dose, and facilitation of record keeping. In this paper, we have developed a high-sensitivity electronic personal dosimeter with silicon PIN photodiode. The electronic personal dosimeter is constructed with silicon PIN photodiode, preamplifier, and shaping amplifier. To show the effectiveness of electronic personal dosimeter, we conducted nuclear radiation experiments using $\gamma$-ray Ba-133, Cs-137, and Co-60. The electronic personal dosimeter have a good linearity on $\gamma$-ray energy and activity.

• Journal of radiological science and technology
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• v.13 no.1
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• pp.29-35
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• 1990

In a attempt to find out the effects of the irradiation on the lymphatic organs of birds, a total of 40 chickens(4 week old) were selected at random and alloted to control and experimental groups. The experiments were irradiated Co-60 ${\gamma}-ray/400$ rads, and then the enzyme histochemical activity of Bursa Fabricious(BF), thymus and spleen and hematological changes were compared with those of controls for 30 days(24 hrs., 5, 10, 20 and 30 days). The results obtained were summarized as follows: 1. The activity of acid phosphatase(ACP) of the reticuloendothelial cells of BF, thymus and spleen and the epithelia of BF of the experiments were increased significantly from the early experimental terms and then returned to the same level of controls through the late experimental terms. 2. The activity of nonspecific esterase(NSE) of the constituent cells with exception of the lymphocytes in BF, thymus and spleen of experiments were increased significantly from the early experimental terms and then returned to the same level of control through the late experimental terms. 3. The lymphocyte percentage, total erythrocytes and homoglobin of the experiments were severely decreased from early experimental terms and then increased to the normal levels of them incontrols.

• Geophysics and Geophysical Exploration
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• v.24 no.1
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• pp.20-27
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• 2021

Subsurface rock produces heat from the decay of radioactive isotopes in constituent minerals and gamma-ray emissions, of which the magnitude is dominated by the contents of the major radioactive isotopes (e.g., U, Th, and K). The heat production is generally calculated from the rock density and contents of major isotopes, which can be determined by mass spectrometry of drilled core samples or rock fragments. However, such methods are not easily applicable to deep boreholes because core samples recovered from depths of several hundred meters to a few kilometers are rarely available. A geophysical logging technique for boreholes is available where the U, Th, and K contents are measured from the gamma-ray spectrum. However, this technique requires the density to be measured separately, and the measurement depth of the equipment is still limited. As an alternative method, a normal gamma-ray logging tool was adopted to estimate the heat production from the total gamma activity, which is relatively easy to measure. This technical report introduces the development of the proposed method for evaluating the heat production of a granitic rock mass with domestic commercial borehole logging tools, as well as its application to a ~2 km deep borehole for verification.

• 전기의세계
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• v.30 no.10
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• pp.639-644
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• 1981

PVC is a kind of electric insulation polymer. But we get some deteriorations in electrical characteristics of the PVC, when it is used on the radioactive field. In order to find out the cause of the deterioration, we investigate the surface-resistance, volume-resistance, dielectric constant and dielectric loss angle of the soft and hard PVC which is irradiated by the Co$^{60}$ .gamma. radioactivity. From the experiment, we can conclude the followings 1. Radio-activity proof characteristic in the soft PVC is stronger than in the hard PVC. 2. The resistance of PVC which is irradiated by the radio-activity decrease exponentially. 3. The dielectric constant and the dielectric loss angle of PVC irradiated by Co$^{60}$ .gamma.ray reach maximum value in first few time.