• 분석과학
• /
• 제20권6호
• /
• pp.460-467
• /
• 2007

자연계에 존재하는 $^{238}U$, $^{235}U$, $^{232}Th$ 그리고 $^{40}K$의 감마선과 베타선에 대해 토양의 흡수선량을 평가하기 위한 유효 흡수선량 환산인자를 계산하였다. 이 때 감마선과 베타선에 대한 붕괴당 에너지, 반감기, 분기율등의 핵자료들은 National Nuclear Data Center (NNDC)의 최근 자료들을 이용하였다. 본 연구에서 계산한 흡수선량 인자 및 이를 이용하여 얻은 $^{238}U$, $^{232}Th$ 그리고 $^{40}K$의 베타선과 감마선에 유효흡수선량은 1998년 Aitken의 결과와 비교적 잘 일치하였지만, $^{235}U$의 경우는 많은 차이가 있음을 확인하였다. 한국 충북 청원군 오성에 있는 선사유적지(만수리) 내의 토양에 대해 고 분해능 감마선 분광 분석 장치(HP Ge 검출기)로 지각 방사선의 감마선 스펙트럼을 측정하고, 계산된 유효 흡수선량 환산인자를 이용하여 연간방사선량을 평가하였는데, 연간방사선량이 3.8~5.9 mGy/year으로 평가되었다. 또한 Rn 이하의 붕괴 핵종을 포함하여 연간방사선량을 평가하는 경우와, 이를 포함하지 않고 연간방사선량을 평가하는 경우는 9~30 % 차이를 나타내었다. 이 흡수선량 환산인자로 토양에 존재하는 자연 방사성 동위원소들의 베타선과 감마선에 대한 유효 흡수선량 평가법이 확립하였다.

• 제어로봇시스템학회논문지
• /
• 제9권4호
• /
• pp.296-303
• /
• 2003

A personal portable type electronic dosimeter using silicon PIN photodiode and small GM tube is recently attracting much attention due to its advantages such as an immediate indication function of dose and dose rate, alerting function, and efficient management of radiation exposure history and dose data. We designed and manufactured a semiconductor radiation detector aimed to directly measure X-ray and v-ray irradiated in silicon PIN photodiode, without using high-priced scintillation materials. Using this semiconductor radiation detector, we developed an active electronic dosimeter, which measures the exposure dose using pulse counting method. In this case, it has a shortcoming of over-evaluating the dose that shows the difference between the dose measured with electronic dosimeter and the dose exposed to the human body in a low energy area. We proposed an energy compensation filter and developed a dose conversion algorithm to make both doses indicated on the detector and exposed to the human body proportional to each other, thus enabling a high-precision dose measurement. In order to prove its reliability in conducting personal dose measurement, crucial for protecting against radiation, the implemented electronic dosimeter was evaluated to successfully meet the IEC's criteria, as the KAERI (Korea Atomic Energy Research Institute) conducted test on dose indication accuracy, and linearity, energy and angular dependences.

• Imaging Science in Dentistry
• /
• 제44권1호
• /
• pp.21-29
• /
• 2014

Purpose: To determine the conversion coefficients (CCs) from the dose-area product (DAP) value to effective dose in cone-beam CT. Materials and Methods: A CBCT scanner with four fields of view (FOV) was used. Using two exposure settings of the adult standard and low dose exposure, DAP values were measured with a DAP meter in C mode ($200mm{\times}179mm$), P mode ($154mm{\times}154mm$), I mode ($102mm{\times}102mm$), and D mode ($51mm{\times}51mm$). The effective doses were also investigated at each mode using an adult male head and neck phantom and thermoluminescent chips. Linear regressive analysis of the DAP and effective dose values was used to calculate the CCs for each CBCT examination. Results: For the C mode, the P mode at the maxilla, and the P mode at the mandible, the CCs were 0.049 ${\mu}Sv/mGycm^2$, 0.067 ${\mu}Sv/mGycm^2$, and 0.064 ${\mu}Sv/mGycm^2$, respectively. For the I mode, the CCs at the maxilla and mandible were 0.076 ${\mu}Sv/mGycm^2$ and 0.095 ${\mu}Sv/mGycm^2$, respectively. For the D mode at the maxillary incisors, molars, and mandibular molars, the CCs were 0.038 ${\mu}Sv/mGycm^2$, 0.041 ${\mu}Sv/mGycm^2$, and 0.146 ${\mu}Sv/mGycm^2$, respectively. Conclusion: The CCs in one CBCT device with fixed 80 kV ranged from 0.038 ${\mu}Sv/mGycm^2$ to 0.146 ${\mu}Sv/mGycm^2$ according to the imaging modes and irradiated region and were highest for the D mode at the mandibular molar.

• 한국의학물리학회지:의학물리
• /
• 제32권3호
• /
• pp.59-69
• /
• 2021

Purpose: The relationship between computed tomography (CT) number and electron density (ED) has been investigated in previous studies. However, the role of these measures for guiding cancer treatment remains unclear. Methods: The CT number was plotted against ED for different imaging protocols. The CT number was imported into ED tables for the Pinnacle treatment planning system (TPS) and was used to determine the effect on dose calculations. Conversion tables for radiation dose calculations were generated and subsequently monitored using a dosimeter to determine the effect of different CT scanning protocols and treatment sites. These tables were used to retrospectively recalculate the radiation therapy plans for 41 patients after an incorrect scanning protocol was inadvertently used. The gamma index was further used to assess the dose distribution, percentage dose difference (DD), and distance-to-agreement (DTA). Results: For densities <1.1 g/cm³, the standard deviation of the CT number was ±0.6% and the greatest variation was noted for brain protocol conditions. For densities >1.1 g/cm³, the standard deviation of the CT number was ±21.2% and the greatest variation occurred for the tube voltage and head and neck (H&N) protocol conditions. These findings suggest that the factors most affecting the CT number are the tube voltage and treatment site (brain and H&N). Gamma index analyses for the 41 retrospective clinical cases, as well as brain metastases and H&N tumors, showed gamma passing rates >90% and <90% for the passing criterion of 2%/2 and 1%/1 mm, respectively. Conclusions: The CT protocol should be carefully decided for TPS. The correct protocol should be used for the corresponding TPS based on the treatment site because this especially affects the dose distribution for brain metastases and H&N tumor recognition. Such steps could help reduce systematic errors.

• 대한한방내과학회지
• /
• 제20권1호
• /
• pp.167-180
• /
• 1999

Cervus elaphus, being known to reinforce Kidney, have tested to study the effects concerning damages of brain tissue induced by lipid peroxidation. In vitro, the level of lipid peroxide in brain tissue was decreased proportinally according to dose by Cervus elaphus extract solution for aqua-acupuncture (CESAA). It was much more decreased, when lipid peroxidation was induced with Fe(II). And, it was seen proportinally decrease according to the dose of CESAA on xanthine oxidase activities and type conversion ratio. However, I can not find special changes about aldehyde oxidase activities. And, I had observed the effects of CESAA on damages of rat's brain following ischemia and reflow. Before ischemia was caused, CESAA was applied 0.2 ml per 250 g through femoral vein in ischemia and reflow group and normal sailine was applied in normal group. Ischemia was caused by cervical artery's clamp for 30 min and reflowed by clamp remove after 15 min. It was increased on the content of lipid peroxidation, activies and type conversion ratio of xanthine oxidase following ischemia and reflow. However, they were decreased when CESAA was pre-appllied. However, it could not seen special changes on aldehyde oxidase activities, either. In conclusion. CESAA recovers the damage of brain due to ischemia and reflow by decreasing the lipid peroxidation through decreasing of xanthine oxidase activies and type conversion ratio.

• Nuclear Engineering and Technology
• /
• 제54권1호
• /
• pp.301-309
• /
• 2022

This work aims to establish some X-ray qualities recommended by the International Standard Organization (ISO) using the half-value layer (HVL) and H_p(10) dosimetry approaches. The HVL values of the following qualities N-60, N-80, N-100, N-150 and N-250 were determined using various attenuation layers. The obtained results were compared to those of reference X-ray beam qualities and a good agreement was found (difference less than 5% for all qualities). The GAMOS (Geant4-based Architecture for Medicine-Oriented Simulations) radiation transport Monte Carlo toolkit was employed to simulate the production of X-ray spectra. The characteristics HVLs, mean energy and the spectral resolution of simulated spectra have been calculated and turned out to be conform to the ISO reference ones (difference less than the limit allowed by ISO). Furthermore, the conversion coefficients from air kerma to personal dose equivalent for simulated and measured spectra were fairly similar (the maximum difference less than 4.2%).

• 방사선산업학회지
• /
• 제17권2호
• /
• pp.161-172
• /
• 2023

Coal-fired power plants handle large quantities of coal, one of the most prominent NORM, and the coal ash produced after the coal is burned can be tens of times more radioactive than the coal. Workers in these industries may be exposed to internal exposure by inhalation of particles while handling NORM. This study evaluated the size, concentration, particle shape and density, and radioactivity concentrations of airborne suspended particles in the main processes of a coal-fired power plant. Finally, the internal radiation dose to workers from particle inhalation was evaluated. For this purpose, airborne particles were collected by size using a multi-stage particle collector to determine the size, shape, and concentration of particles. Samples of coal and coal ash were collected to measure the density and radioactivity of particles. The dose conversion factor and annual radionuclide inhalation amount were derived based on the characteristics of the particles. Finally, the internal radiation dose due to particle inhalation was evaluated. Overall, the internal radiation dose to workers in the main processes of coalfired power plants A and B ranged from 1.47×10^-5~1.12×10^-3 mSv y^-1. Due to the effect of dust generated during loading operations, the internal radiation dose of fly ash loading processes in both coal-fired power plants A and B was higher than that of other processes. In the case of workers in the coal storage yard at power plants A and B, the characteristic values such as particle size, airborne concentration, and working time were the same, but due to the difference in radioactivity concentration and density depending on the origin of the coal, the internal radiation dose by origin was different, and the highest was found when inhaling coal imported from Australia among the five origins. In addition, the main nuclide contributing the most to the internal radiation dose from the main processes in the coal-fired power plants was thorium due to differences in dose conversion factors. However, considering the external radiation dose of workers in coal-fired power plants presented in overseas research cases, the annual effective dose of workers in the main processes of power plants A and B does not exceed 1mSv y^-1, which is the dose limit for the general public notified by the Nuclear Safety Act. The results of this study can be utilized to identify the internal exposure levels of workers in domestic coal-fired power plants and will contribute to the establishment of a data base for a differential safety management system for NORM-handling industries in the future.

• 생명과학회지
• /
• 제14권2호
• /
• pp.269-274
• /
• 2004

불균일상 촉매를 이용한 대두유와 메탄올간의 에스테르화 반응에 대하여 조사하였다. 온도 40∼$65^{\circ}C$에서 대두유와 메탄올 혼합물 내 성분 분배를 측정하였다. NaOH, CaO, Ca(OH)$_2$, MgO, Mg(OH)$_2$, and Ba(OH)$_2$과 같은 촉매에 대하여 반응 혼합물의 글리세린 함량을 측정하였다. 측정된 글리세린 농도로부터 반응 혼합물의 전화율을 계산하였다. 촉매 투여량, 보조용매 그리고 반응온도의 최종전화율에 대한 영향을 조사하였다. 대두유에 대한 메탄올의 용해도는 메탄올에 대한 대두유의 용해도보다 월등히 컸다. 대두유의 에스테르화 반응에 불균일상 촉매를 사용한 경우 최종전화율은 불균일상 촉매의 염기도에 크게 의존하였고, 촉매 금속의 염기도 증가에 따라 증가하였다. 알칼리 금속의 수산화물이 산화물 보다 효과적이었으며, 산화물은 촉매효과를 보이지 않았다. Ca(OH)$_2$를 에스테르화 반응의 촉매로 사용한 경우, 최종전화율의 최대값이 촉매 투여량 4%일 때 측정되었다. 최종전화율과 반응속도는 온도증가에 따라 증가하였으며 5$0^{\circ}C$에서 급격한 증가를 보였다. Ba(OH)$_2$를 촉매로 사용한 경우 보조용매로 HCl$_2$를 투여하면, 투여량 3%일 때 최종전화율의 최대값이 측정되었다.

• Nuclear Engineering and Technology
• /
• 제56권6호
• /
• pp.2190-2194
• /
• 2024

The study investigates the dose-dependent direct X-ray sensing characteristics of Brucinium benzilate (BB) and N-acetylglycine (NAG) organic crystals. BB and NAG were prepared as a slurry and deposited as a thick film on a patterned metal electrode. The X-ray induced photocurrent response was examined for various exposure doses using an intraoral pulsed 70 keV X-ray machine connected to a source meter. Subsequently, the morphological properties and thickness of the thick films were analyzed using scanning electron microscopy (SEM). At a photon energy of 70 keV, the attenuation coefficient values for NAG and BB crystals were determined to be approximately 0.181 and 0.178 cm²/g, respectively. The X-ray stopping power of the crystals was measured using a suniray-2 X-ray imaging system. To evaluate the responsiveness of the sensors, the photocurrent sensitivity and noise equivalent dose rate (NED) were calculated for both thick films. The findings demonstrated a noteworthy capability of sensing low doses (mGy), thereby suggesting the potential application of these organic materials in X-ray sensor development.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 2003년도 춘계학술발표대회 요약집
• /
• pp.342.2-342.2
• /
• 2003