• Journal of Radiation Protection and Research
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• v.42 no.3
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• pp.158-165
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• 2017

Background: Nuclear facilities in South Korea have generally adopted pressurized ion chambers to measure ambient gamma ray exposure rates for monitoring the impact of radiation on the surrounding environment. The rates assessed with pressurized ion chambers do not distinguish between natural and man-made radiation, so a further step is needed to identify the cause of abnormal variation. In contrast, using NaI(Tl) scintillation detectors to detect gamma energy rates can allow an immediate assessment of the cause of variation through an analysis of the energy spectra. Against this backdrop, this study was conducted to propose a more effective way to monitor ambient gamma exposure rates. Materials and Methods: The following methods were used to analyze gamma energy spectra measured from January to November 2016 with NaI detectors installed at the Korea Atomic Energy Research Institute (KAERI) dormitory and Hanbat University. 1) Correlations of the variation of rates measured at the two locations were determined. 2) The dates, intervals, duration, and weather conditions were identified when rates increased by $5nSv{\cdot}h^{-1}$ or more. 3) Differences in the NaI spectra on normal days and days where rates spiked by $5nSv{\cdot}h^{-1}$ or more were studied. 4) An algorithm was derived for automatically calculating the net variation of the rates. Results and Discussion: The rates measured at KAERI and Hanbat University, located 12 kilometers apart, did not show a strong correlation (coefficient of determination = 0.577). Time gaps between spikes in the rates and rainfall were factors that affected the correlation. The weather conditions on days where rates went up by $5nSv{\cdot}h^{-1}$ or more featured rainfall, snowfall, or overcast, as well as an increase in peaks of the gamma rays emitted from the radon decay products of $^{214}Pb$ and $^{214}Bi$ in the spectrum. This study assumed that $^{214}Pb$ and $^{214}Bi$ exist at a radioactive equilibrium, since both have relatively short half-lives of under 30 minutes. Provided that this assumption is true and that the gamma peaks of the 352 keV and 1,764 keV gamma rays emitted from the radionuclides have proportional count rates, no man-made radiation should be present between the two energy levels. This study proved that this assumption was true by demonstrating a linear correlation between the count rates of these two gamma peaks. In conclusion, if the count rates of these two peaks detected in the gamma energy spectrum at a certain time maintain the ratio measured at a normal time, such variation can be confirmed to be caused by natural radiation. Conclusion: This study confirmed that both $^{214}Pb$ and $^{214}Bi$ have relatively short half-lives of under 30 minutes, thereby existing in a radioactive equilibrium in the atmosphere. If the gamma peaks of the 352 keV and 1,764 keV gamma rays emitted from these radionuclides have proportional count rates, no man-made radiation should exist between the two energy levels.

• Journal of Radiation Protection and Research
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• v.15 no.2
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• pp.51-56
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• 1990

The dispersing model of radioactive plume in the atmosphere was assumed to form finite ellipseshaped volumes rather than a single plume and gamma absorbed doses from the plume were computed using the proposed model. The results obtained were compared with those computed by the Gaussian plume and the circular approximation models. The results computed by the proposed ellipse-shaped approximation model were close to those by the Gaussian plume model. and more accurate than those by the circular approximation model. The computing time for the proposed approximation model was one fortieth of that for the Gaussian plume model.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4002-4018
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• 2023

An integrated neutron interrogation system has been developed for non-destructive assay of highly-radioactive special nuclear materials, to accumulate knowledge of the method through developing and using it. The system combines a differential die-away (DDA) measurement system for the quantification of nuclear materials and a prompt gamma-ray analysis (PGA) system for the detection of neutron poisons which disturb the DDA measurements; a common D-T neutron generator is used. A special care has been taken for the selection of materials to reduce the background gamma rays produced by the interrogation neutrons. A series of measurements were performed to test the basic performance of the system. The results show that the DDA system can quantify plutonium of as small as 20 mg and it is not affected by intense neutron background up to 1.57 × 10⁷ s^-1 and gamma ray of 4.43 × 10¹⁰ s^-1. The gamma-ray background counting rate at the PGA detector was reduced down to 3.9 × 10³ s^-1 even with the use of the D-T neutron generator. The test measurements show that the PGA system is capable of detecting 0.783 g of boron and about 86.8 g of gadolinium in 30 min.

• Journal of Radiation Protection and Research
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• v.40 no.3
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• pp.124-131
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• 2015

Radiation exposure to humans can be caused by the gamma rays emitted from natural radioactive elements(such as uranium, thorium and potassium and any of their decay products) of Naturally Occurring Radioactive Materials(NORM) or Technologically Enhanced Naturally Occurring Radioactive Materials(TENORM) added consumer products. In this study, assume that activity of radioactive elements is $^{238}U$, $^{235}U$, $^{232}Th$ $1Bq{\cdot}g^{-1}$, $^{40}K$ $10Bq{\cdot}g^{-1}$ and the gamma rays emitted from these natural radioactive elements radioactive equilibrium state. In this study, reflected End-User circumstances and evaluated annual exposure dose for products based on ICRP reference voxel phantoms and ICRP Recommendation 103 using the Monte Carlo Method. The consumer products classified according to the adhere to the skin(bracelet, necklace, belt-wrist, belt-ankle, belt-knee, moxa stone) or not(gypsum board, anion wallpaper, anion paint), and Geometric Modeling was reflected in Republic of Korea "Residential Living Trend-distributions and Design Guidelines For Common Types of Household.", was designed the Room model($3m{\times}4m{\times}2.8m$, a closed room, conservatively) and the ICRP reference phantom's 3D segmentation and modeling. The end-user's usage time assume that "Development and Application of Korean Exposure Factors." or conservatively 24 hours; in case of unknown. In this study, the results of the effective dose were 0.00003 ~ 0.47636 mSv per year and were confirmed the meaning of necessary for geometric modeling to ICRP reference phantoms through the equivalent dose rate of belt products.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.233-238
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• 2003

Several types of gamma-ray sensors were constructed by packing different numbers of fibers into aluminum tubes, and tested to detect the $^137Cs$ gamma ray. It has been found from this investigation that tapered fibers can be more efficient to collect the lights produced inside the sensor and transfer them into the transmitting fiber in order to predict the functioning of the tapered fiber, tapered plastic scintillators, composed of polystyrene with minute amount of dPOPOP and PPO or dPBD, were fabricated and tested for the detection of gamma rays from 1.0 1.5 3.0 5.0 ${\mu}Ci$ $^137Cs$ sources, and the pulse hight spectrum and the relationship between the radioactivity and the total counts are analyzed. It has been found from this study that the tapered scintillating optical fiber, if manufactured, can be practically applied to the development of gamma-ray sensors which can be deployed In ${\mu}Ci$-level radiation fields

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.303-308
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• 2001

An objection of this study is to develop a high stable measuring circuits and a analytic system for radioactive pulses. The proposed system consists of a pulse detection units for neutrons and gamma-rays a programmable high voltage supply unit and a digital signal processor. The programmable high voltage supply unit designed can generate DC voltage up to 1,500 V at 5 V input and have a series voltage regulator to maintain the output voltage constantly, resulting in less than 1.63% of voltage regulation. The pulse detection parts consists of an active integrator, a pole-zero circuit, and a 3-stage amplifier of 60 dB, and its frequency bandwidth is from 37 Hz to 300 kHzAlso, pulse height distribution in accordance with pulse counts is important data in analyzing radioactive pulses. In this study, A/D convertor (12bit, 100ms) and DSP (TMS320C31-60) are used to analyze the pulse height, and the analytic system is designed to be operated in PC-base.

• Journal of Radiation Industry
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• v.12 no.4
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• pp.303-310
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• 2018

Since Roentgen discovered X-rays, radiation sources have been utilized for many areas such as agriculture, industry, medicine and fundamental chemical research. As a result, human society has gained lots of benefits. However, if a radioactive material is used for the malicious purpose, it causes serious consequences to humanity and environment. Consequently, international organizations including International Atomic energy Agency (IAEA) have been emphasizing establishment and implementation of security management to prevent sabotage and illicit trafficking of radioactive materials. For this reason, the rule of technical standards of radiation safety management was revised and the public notice of security management regarding radioisotope was legislated in 2015 by Nuclear Safety and Security Commission (NSSC). Several radioactive sources which have to be regulated under the above rule and the public notice have been utilized in Advanced Radiation Technology Institute (ARTI) of Korea Atomic Energy Research Institute (KAERI). In order to control them properly, security management system such as access control and physical protection has been adapted since 2015. In this paper, we have analyzed the public notice of NSSC and its field application case. Based on the results, we are going to draw improvement on the public notice of NSSC and security system.

• The Plant Pathology Journal
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• v.22 no.3
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• pp.295-302
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• 2006

The present study addressed the efficacy of nanosized silica-silver for controlling plant pathogenic microorganisms. The nanosized silica-silver consisted of nano-silver combined with silica molecules and water soluble polymer, prepared by exposing a solution including silver salt, silicate and water soluble polymer to radioactive rays. The nanosized silica-silver showed antifungal activity against the tested phytopathogenic fungi at 3.0 ppm with varied degrees. In contrast, a number of beneficial bacteria or plant pathogenic bacteria were not significantly affected at 10 ppm level but completely inhibited by 100 ppm of nanosized silicasilver. Among the tested plant pathogenic fungi, the new product effectively controlled powdery mildews of pumpkin at 0.3 ppm in both field and greenhouse tests. The pathogens disappeared from the infected leaves 3 days after spray and the plants remained healthy thereafter. Our results suggested that the product developed in this study was effective in controlling various plant fungal diseases.

• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.149-154
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• 2001

Calculational models to evaluate radiation doses resulting from the medical use of high energy beta-ray sources are presented. The radioactive sources considered are Sr-90/Y-90 used as ophthalmic applicator, Re-188 used for treating restenosis of coronary artery, and Ho-166 used for treating hepatic tumors. Typical therapeutic situations which might induce relatively high radiation doses the medical person involved were considered to compute by using MCNP-4C Monte Carlo code the radiation doses. The calculation results suggest that for all of the cases considered, the evaluated radiation doses are negligible compared to the dose limits. It is also found that the effect of Bremsstrahlung radiations on the total dose is insignificant, and hence the conventional lead gown is also effective in shielding beta-rays.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1777-1780
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• 2024

Chemical and thermal characteristics of cation exchange resins were examined after irradiation of gamma rays. The degradation of cation exchange resins was mainly observed at doses of up to 500 kGy, whereas the balance between degradation and cross-linking reactions was sustained at 700 kGy. While the carbon content decreased significantly up to a maximum dose of 500 kGy, it showed an increase at higher doses. Conversely, the oxygen content exhibited a decrease in contrast to the carbon content. The continuous reduction in sulfur content was attributed to the decomposition of sulfonic groups. Gamma-ray irradiation caused a decrease in the initiation temperature of sulfonic groups and PS-DVB, but unlike the chemical properties of cation exchange resins due to gamma-ray irradiation, the thermal properties of resins remained unaffected.