• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.769-770
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• 2005

This study aims to demonstrate the practical value of radioscopic differentiation of materials. The dual energy method is proposed for identifying materials according to atomic numbers. The differentiation of materials is achieved by comparing the attenuation ratio of low and high energy photons. We used gamma-rays of 0.662 MeV and 1.25 MeV and NaI(Tl) scintillation detector with a Multi-channel Analyzer (MCA). We also carried out the Monte Carlo simulation for the case of bremsstrahlung radiation from dual electron beams of 4 MeV and 9 MeV.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2557-2562
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• 2024

A type of integrated multiple-single-channel analyzer (IMSCA) is described. The IMSCA works with an input pulse of 2-20 pC, and it can be directly connected to a scintillation detector, which eliminates the need for a linear amplifier. It consists of 64 input ports, so 1-64 detectors can be set by users according to different requirements. Two energy regions for each input channel can be simultaneously analyzed. Another advantage of the IMSCA is that it integrates with a high-speed pulse signal acquisition card and transmits data to the computer through the network. The maximum pulse through-rate is 1.4 MHz, and linearity can reach 0.1%. This IMSCA has been successfully used in enrichment detecting of nuclear fuel rod.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.2
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• pp.98-111
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• 2008

This review introduces advances in clinical and pre-clinical single photon emission computed tomography (SPECT) and positron emission tomography (PET) providing noninvasive functional images of biological processes. Development of new collimation techniques such as multi-pinhole and slit-slat collimators permits the improvement of system spatial resolution and sensitivity of SPECT. Application specific SPECT systems using smaller and compact solid-state detector have been customized for myocardial perfusion imaging with higher performance. Combined SPECT/CT providing improved diagnostic and functional capabilities has been introduced. Advances in PET and CT instrumentation have been incorporated in the PET/CT design that provide the metabolic information from PET superimposed on the anatomic information from CT. Improvements in the sensitivity of PET have achieved by the fully 3D acquisition with no septa and the extension of axial field-of-view. With the development of faster scintillation crystals and electronics, time-of-flight (TOF) PET is now commercially available allowing the increase in the signal-to-noise ratio by incorporation of TOF information into the PET reconstruction process. Hybrid PET/SPECT/CT systems has become commercially available for molecular imaging in small animal models. The pre-clinical systems have improved spatial resolution using depth-of-interaction measurement and new collimators. The recent works on solid state detector and dual modality nuclear medicine instrumentations incorporating MRI and optical imagers will also be discussed.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.474-482
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• 2002

One dimensional Radiometric scanning system was fabricated and tested as a filmless radiographic inspection system, which could be applied to the evaluation of the corrosion and deposits in the pipeline. This system is composed of the single radioactive source of the collimated focusing beam, and single scintillation detector of BGO, and the mechanical scanning system to transport and align the source and detector, and the operating software to automatically control the mechanical scan system. The performance of the system was simulated using GEANT4 software. This system is applied to one specimen having an artificial falw(flat bottom hole) in the pipe and the other specimen with thickness variation. For the inspection by using the radioactive source in the pipeline, it is possible to evaluate the corrosion and deposits in real time and without film.

• Journal of Radiation Protection and Research
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• v.41 no.3
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• pp.185-190
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• 2016

Background: In order to measure neutron energy spectra, the conventional Bonner Sphere Spectrometers (BSS) are widely used. In this spectrometer, several measurements with different size Bonner spheres are required. Operators should, therefore, place these spheres in several times to a measurement point where radiation dose might be relatively high. In order to reduce this effort, novel neutron energy spectrometer using an onion-like single Bonner sphere was proposed in our group. This Bonner sphere has multiple sensitive spherical shell layers in the single sphere. In this spectrometer, a band-shaped thermal neutron detection medium, which consists of a LiF-ZnS mixed powder scintillator sheet and a wavelength-shifting (WLS) fiber readout, was looped to each sphere at equal angular intervals. Amount of LiF neutron converter is reduced near polar region, where the band-shaped detectors are concentrated, in order to uniform the directional sensitivity. The LiF-ZnS mixed powder has an advantage of extremely high light yield. However, since it is opaque, scintillation photons cannot be collect uniformly. This type of detector shows no characteristic shape in the pulse height spectrum. Subsequently, it is difficult to set the pulse height discrimination level. This issue causes sensitivity fluctuation due to gain instability of photodetectors and/or electric modules. Materials and Methods: In order to solve this problem, we propose to replace the LiF-ZnS mixed powder into a flexible and Transparent RUbber SheeT type $LiCaAlF_6$ (TRUST LiCAF) scintillator. TRUST LiCAF scintillator can show a peak shape corresponding to neutron absorption events in the pulse height spectrum. Results and Discussion: We fabricated the prototype detector with five sensitive layers using TRUST LiCAF scintillator and conducted basic experiments to evaluate the directional uniformity of the sensitivity. Conclusion: The fabricated detector shows excellent directional uniformity of the neutron sensitivity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1519-1527
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• 2020

AGeneral radiation measuring devices have been developed in the form of spatial dose rate detection devices that measure dose rates to radioactive contaminant and 2D or 3D imaging devices for radioactive contamination information. Each of these radiation detection techniques has advantages. The advantages of both detection devices are necessary to minimize personal injury and rapid decontamination in the area of a radioactive accident. In this paper, we proposed a technique that can measure the dose rate and direction information about the radioactive pollutant source in real time using a detection sensor, a rotating body, and a directional shield for radioactive pollutant detection. The rotational-based detection device is configured to check the dose rate and direction using the location information of the rotator and measurement value. We proposed a measurement technique for vertical and horizontal directions through multiple holes. It was confirmed that the measurement error for direction information was less than 1% when detected in the horizontal direction.

• Nuclear Engineering and Technology
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• v.5 no.4
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• pp.291-309
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• 1973

Exposure rates due to leakage gamma-rays from operating reactors TRIGA Mark II and III were measured in a horizontal plane by means of scintillation spectrometry using a 3"$\times$3" cylindrical Nal(T1) detector associated with a 400 channel pulse height analyzer under varied conditions of reactor operation. In determining exposure rate due to the leakage gamma-rays at each point of measurement, Moriuchi's spectrum-exposure rate conversion theory was applied instead of using conventional responce matrix method which necessitates very complicated procedures to convert a spectrum into exposure rate. The results show that a basic pattern of "typical" spectrum of the reactor leakage gamma-rays is neither affected by thermal output of the reactor, nor influenced by overall attenuation in radiation intensity. It was indicated that he attenuation of the leakage gamma-rays in air in terms of exposure rate as a whole follows an exponential law, and the total exposure rate due to the leakage gamma-rays at a certain point is nearly proportional to thermal output of the reactor. The complexity in spectrum measured for a movable core reactor, TRIGA Mark III, was analyzed through spectrum resolution, and proper judgement of the leakage gamma-rays in a complex spectrum was discussed.ctrum was discussed.

• Journal of Radiation Protection and Research
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• v.48 no.3
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• pp.131-143
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• 2023

Background: This study examined the detection limit of thyroid screening monitoring conducted at the time of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011 using a Monte Carlo simulation. Materials and Methods: We calculated the detection limit of a NaI(Tl) survey meter to measure ¹³¹I accumulation in the thyroid gland of children. Mathematical phantoms of 1- and 5-year-old children were developed in the simulation of the Particle and Heavy Ion Transport code System code. Contamination of the body surface with eight radionuclides found after the FDNPP accident was assumed to have been deposited on the neck and shoulder area. Results and Discussion: The detection limit was calculated as a function of ambient dose rate. In the case of 40 Bq/cm² contamination on the body surface of the neck, the present simulations showed that residual thyroid radioactivity corresponding to thyroid dose of 100 mSv can be detected within 21 days after intake at the ambient dose rate of 0.2 µSv/hr and within 11 days in the case of 2.0 µSv/hr. When a time constant of 10 seconds was used at the dose rate of 0.2 µSv/hr, the estimated survey meter output error was 5%. Evaluation of the effect of individual differences in the location of the thyroid gland confirmed that the measured value would decrease by approximately 6% for a height difference of ±1 cm and increase by approximately 65% for a depth of 1 cm. Conclusion: In the event of a nuclear disaster, simple measurements carried out using a NaI(Tl) scintillation survey meter remain effective for assessing ¹³¹I intake. However, it should be noted that the presence of short-half-life radioactive materials on the body surface affects the detection limit.

• Progress in Medical Physics
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• v.8 no.2
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• pp.67-76
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• 1997

We studied optical behavior of scintillation light generated in NaI(TI) crystal using Monte Carlo simulation method. The simulation was performed for the model of NaI(TI) scintillator (size: 60 mm ${\times}$ 60 mm ${\times}$ 6 mm) using an optical tracking code. The sensitivity as a function of surface treatment (Ground, Polished, Metal-0.95RC, Polished-0.98RC, Painted- 0.98RC) of the incident surface of the scintillator was compared. The effects of NaI(TI) scintillator thickness and the refractive index of light guide optically coupling between the NaI(TI) scintillator and photomultiplier tube (PMT) were simulated. We also evaluated intrinsic position resolution of the system by calculating the spread of scintillation light generated. The sensitivities of the system having the surface treatment of Ground, Polished, Metal-0.95RC, Polished-0.98RC and Painted-0.98RC were 70.9％, 73.9％, 78.6％, 80.1％ and 85.2％, respectively, and the surface treatment of Painted-0.98RC allowed the highest sensitivity. As increasing the thickness of scintillation crystal and light guide, the sensitivity of the system was decreased. As the refractive index of light guide increases, the sensitivity was increased. The intrinsic position resolution of the system was estimated to be 1.2 mm in horizontal and vertical directions. In this study, the performance of NaI(TI)-PMT detector system was evaluated using Monte Carlo simulation. Based on the results, we concluded that the NaI(TI)-PMT detector array is a favorable configuration for small gamma camera imaging breast tumor using Tc-99m labeled radiopharmaceuticals.

• Journal of Radiation Protection and Research
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• v.39 no.3
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• pp.150-158
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• 2014

Radiation-related practitioners and radiation-treated patients at medical institutions are inevitably exposed to radiation for diagnosis and treatment. Although standards for maximum doses are recommended by the International Commission on Radiological Protection (ICPR) and the International Atomic Energy Agency (IAEA), more direct and available measurement and analytical methods are necessary for optimal exposure management for potential exposure subjects such as practitioners and patients. Thus, in this study we developed a system for real-time radiation monitoring at a distance that works with existing portable device. The monitoring system comprises three parts for detection, imaging, and transmission. For miniaturization of the detection part, a scintillation detector was designed based on a silicon photomultiplier (SiPM). The imaging part uses a wireless charge-coupled device (CCD) camera module along with the detection part to transmit a radiation image and measured data through the transmission part using a Bluetooth-enabled portable device. To evaluate the performance of the developed system, diagnostic X-ray generators and sources of $^{137}Cs$, $^{22}Na$, $^{60}Co$, $^{204}Tl$, and $^{90}Sr$ were used. We checked the results for reactivity to gamma, beta, and X-ray radiation and determined that the error range in the response linearity is less than 3% with regard to radiation strength and in the detection accuracy evaluation with regard to measured distance using MCNPX Code. We hope that the results of this study will contribute to cost savings for radiation detection system configuration and to individual exposure management.