• Journal of the Korean Society of Radiology
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• v.7 no.5
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• pp.333-338
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• 2013

Generally, it's known fact that intensity of radioactivity satisfies inverse-square law. However, the law was dissatisfied with practical experiment because of limited shape of scintillation detector. Especially, in the case of near distance between the surface of detector and the radioactive source, the difference grows larger. In the present study, reason of this difference was confirmed by experiment with $2^{{\prime}{\prime}}{\times}2^{{\prime}{\prime}}{\phi}$ NaI(Tl) scintillation detector and $^{60}Co$(1.174 MeV, 1.333 MeV)and $^{137}Cs$(0.662 MeV) gamma ray sources. From the experiment, the correction coefficient was obtained with gamma ray detection efficiency and geometrical volume. In the result of the present study, the efficiency difference of the detector was corrected with the coefficient. In the present result, we obtained that the inverse-square law experiment have to consider the efficiency and geometrical value of the detector.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.967-971
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• 1994

The stability constants, log K of the 1 : 1 complexation for IA ions, $Ag^+$, and $Tl^+$ with a series of podands having different aromatic end-groups (I-IV) have been determined conductometrically in methanol at 25.0 $^{\circ}$C. Exceptionally the equivalent conductivity, ${\lambda}_{eq}\;of\;Li^+\;and\;Na^+$ were increased by the addition of I, because the complexed ions are less mobile than solvated ions. The order of log K values for I was $Ag^+{\gg}Tl^+>K^+>Na^+>Rb^+>Cs6+>Li^+$. The log K sequence of the podands for the certain cations was I>II>III${\geq}$IV. And every podands except IV showed the maximum selectivity for $Ag^+$ among the cations. These results were discussed in terms of the aromatic end-group effects, such as hetero-donor atoms or conformational changes by ${\pi}-{\pi}$ stacking interactions. The detailed conformations of ${\pi}-{\pi}$ stacking were also discussed by the observations of upfield shifts of some aromatic protons upon complexation from $^1H$ NMR spectra.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.3043-3050
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• 2022

In Korea, all nuclear power plants (NPPs) participate in annual performance tests including in vivo measurements using the FastScan, a stand type whole body counter (WBC), manufactured by Canberra. In 2018, all Korean NPPs satisfied the testing criterion, the root mean square error (RMSE) ≤ 0.25, for the whole body configuration, but three NPPs which participated in an additional lung configuration test in the fission and activation product category did not meet the criterion. Due to the low resolution of the FastScan NaI(Tl) detectors, the conventional peak analysis (PA) method of the FastScan did not show sufficient performance to meet the criterion in the presence of interfering radioisotopes (RIs), ¹³⁴Cs and ¹³⁷Cs. In this study, we developed an artificial neural network (ANN) to improve the performance of the FastScan in the lung configuration. All of the RMSE values derived by the ANN satisfied the criterion, even though the photopeaks of ¹³⁴Cs and ¹³⁷Cs interfered with those of the analytes or the analyte photopeaks were located in a low-energy region below 300 keV. Since the ANN performed better than the PA method, it would be expected to be a promising approach to improve the accuracy and precision of in vivo FastScan measurement for the lung configuration.

• Journal of Radiation Industry
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• v.17 no.3
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• pp.219-224
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• 2023

A high-efficiency underwater radiation monitoring system, HydroGamma, has been developed for detecting ¹³⁷Cs and ¹³¹I in the event of waterborne radiation contamination. The system consists of a 3-inch NaI (Tl) detector, solar panels for power supply, data acquisition and transmission modules, and batteries. HydroGamma also includes a ⁴⁰K calibration source for remote performance evaluation and energy calibration. In this study, some simulations and experiments were carried out to evaluate the minimum detectable activities (MDA) of HydroGamma. We installed the HydroGamma at Tapjeongho Lake in Nonsan-si and acquired background data since MDA is calculated based on the experimental background data. The results show that the minimum detectable activities for ¹³⁷Cs and ¹³¹I were 1.78Bq L^-1 and 1.81Bq L^-1, respectively even though the gamma rays emitted from ⁴⁰K(1,460 keV) affect the minimum detectable activities for them.

• The Journal of the Korea Contents Association
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• v.14 no.2
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• pp.475-481
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• 2014

The aim of this work was to develop the gamma camera system for small animal gamma imaging and environmental radiation monitoring imaging using a parallel hole collimator and pinhole collimator. The small gamma camera system consists of a CsI(Tl) scintillation crystal with 6 mm in thickness and $50{\times}50mm$ in area coupled with a Hamamatsu H8500C PSPMT, are resistive charge divider, pre-amplifiers, charge amplifiers, nuclear instrument modules (NIMs), an analog to digital converter and a computer for control and display. We have developed a radiation monitoring system composed of a combined pinhole gamma camera and a charge-coupled devices (CCD) camera. The results demonstrated that the parallel hole collimator and pinhole collimator gamma camera designed in this study could be utilized to perform small animal imaging and environmental radiation monitoring system. Consequently in this paper, we proved that our gamma detector system is reliable for a gamma camera which can be used as small animal imaging and environmental radiation monitoring system.

• Journal of Radiation Protection and Research
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• v.29 no.4
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• pp.257-261
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• 2004

A coded-aperture gamma camera was developed to increase the sensitivity of a pin hole camera made with a pixellated CsI(Tl) scintillator and a position-sensitive photomultiplier tube. The modified round-hole uniformly redundant array of pixel size $13{\times}11$ was chosen as a coded mask considering the detector spatial resolution. The performance of the coded-aperture camera was compared with the pin hole camera using various forms of Tc-99m source to see the improvement of signal-to-noise ratio or the improvement of the sensitivity. The image quality is much improved despite of a slight degradation of the spatial resolution. Though the camera and the test were made for low energy case, but the concept of the coded-aperture gamma camera could be effectively used for the radioactive environmental monitoring and other applications.

• Journal of Radiation Protection and Research
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• v.42 no.2
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• pp.91-97
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• 2017

Background: A gamma energy identifying algorithm using spectral decomposition combined with smoothing method was suggested to confirm the existence of the artificial radio isotopes. The algorithm is composed by original pattern recognition method and smoothing method to enhance the performance to identify gamma energy of radiation sensors that have low energy resolution. Materials and Methods: The gamma energy identifying algorithm for the compact radiation sensor is a three-step of refinement process. Firstly, the magnitude set is calculated by the original spectral decomposition. Secondly, the magnitude of modeling error in the magnitude set is reduced by the smoothing method. Thirdly, the expected gamma energy is finally decided based on the enhanced magnitude set as a result of the spectral decomposition with the smoothing method. The algorithm was optimized for the designed radiation sensor composed of a CsI (Tl) scintillator and a silicon pin diode. Results and Discussion: The two performance parameters used to estimate the algorithm are the accuracy of expected gamma energy and the number of repeated calculations. The original gamma energy was accurately identified with the single energy of gamma radiation by adapting this modeling error reduction method. Also the average error decreased by half with the multi energies of gamma radiation in comparison to the original spectral decomposition. In addition, the number of repeated calculations also decreased by half even in low fluence conditions under $10^4$ ($/0.09cm^2$ of the scintillator surface). Conclusion: Through the development of this algorithm, we have confirmed the possibility of developing a product that can identify artificial radionuclides nearby using inexpensive radiation sensors that are easy to use by the public. Therefore, it can contribute to reduce the anxiety of the public exposure by determining the presence of artificial radionuclides in the vicinity.

• Korean Journal of Optics and Photonics
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• v.20 no.4
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• pp.201-206
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• 2009

In this study, we have fabricated a fiber-optic radiation sensor for detection of tritium using inorganic scintillators and optical fibers. We have tested various kinds of inorganic scintillators such as $Gd_2O_2S$ : Tb, $Y_3Al_5O_{12}$ : Ce, and CsI : Tl to select the most effective sensor tip. In addition, we have measured the scintillating lights using a photomultiplier tube as a function of distance between sensor tips to the source with the different activities of hydride tritium. The final results are compared with those which are obtained using a surface activity monitor.

• Journal of Sensor Science and Technology
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• v.26 no.6
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• pp.427-431
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• 2017

In this study, a foods radioactivity monitoring sensor was developed as a part of basic research for household radioactivity monitoring, and its performance was evaluated using a calibration source. The prototype of the sensor was based on a CsI:Tl scintillator using a crystal light guide and Si photomultiplier. The light guide was introduced to improve gamma-ray detection efficiency. For quantitative evaluation, tests were conducted using $^{134}Cs$ liquid source. In the performance evaluation, It was confirmed that analysis of $^{134}Cs$: 100 Bq/L(kg) was possible. Thus, result of this study is expected to contribute to research in the development of the household foods radioactivity monitoring system.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2640-2645
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• 2021

We report the development of a gamma-ray imaging device, named Large-Area Hybrid Gamma Imager (LAHGI), featuring high imaging sensitivity and good imaging resolution over a broad energy range. A hybrid collimation method, which combines mechanical and electronic collimation, is employed for a stable imaging performance based on large-area scintillation detectors for high imaging sensitivity. The system comprises two monolithic position-sensitive NaI(Tl) scintillation detectors with a crystal area of 27 × 27 cm² and a tungsten coded aperture mask with a modified uniformly redundant array (MURA) pattern. The performance of the system was evaluated under several source conditions. The system showed good imaging resolution (i.e., 6.0-8.9° FWHM) for the entire energy range of 59.5-1330 keV considered in the present study. It also showed very high imaging sensitivity, successfully imaging a 253 µCi ¹³⁷Cs source located 15 m away in 1 min; this performance is notable considering that the dose rate at the front surface of the system, due to the existence of the ¹³⁷Cs source, was only 0.003 µSv/h, which corresponds to ~3% of the background level.