• 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%).

• Nuclear Engineering and Technology
• /
• 제54권5호
• /
• pp.1606-1615
• /
• 2022

For investigating whether the MARSSIM nonparametric test has sufficient statistical power when a site has a specific contamination distribution before conducting a final status survey (FSS), a novel approach was proposed to predict the release probability of the site. Five distributions were assumed: lognormal distribution, normal distribution, maximum extreme value distribution, minimum extreme value distribution, and uniform distribution. Hypothetical radioactivity populations were generated for each distribution, and Sign tests were performed to predict the release probabilities after extracting samples using Monte Carlo simulations. The designed Type I error (0.01, 0.05, and 0.1) was always satisfied for all distributions, while the designed Type II error (0.01, 0.05, and 0.1) was not always met for the uniform, maximum extreme value, and lognormal distributions. Through detailed analyses for lognormal and normal distributions which are often found for contaminants in actual environmental or soil samples, it was found that a greater statistical power was obtained from survey units with normal distribution than with lognormal distribution. This study is expected to contribute to achieving the designed decision error when the contamination distribution of a survey unit is identified, by predicting whether the survey unit passes the statistical test before undertaking the FSS according to MARSSIM.

• 대한방사선기술학회지:방사선기술과학
• /
• 제44권2호
• /
• pp.109-115
• /
• 2021

In this study, a physical evaluation of internal radiation exposure in children was conducted using nuclear medicine test(Renal DTPA Dynamic Study) to simulate the distribution and effects of the radiation throughout the tracer kinetics over time. Monte Carlo simulations were performed to determine the internal medical radiation exposure during the tests and to provide basic data for medical radiation exposure management. Specifically, dose variability based on changes in the tracer kinetic was simulated over time. The internal exposure to the target organ (kidney) and other surrounding organs was then quantitatively evaluated and presented. When kidney function was normal, the dose to the target organ(kidney) was approximately 0.433 mGy/mCi, and the dose to the surrounding organs was approximately 0.138-0.266 mGy/mCi. When kidney function was abnormal, the dose to the surrounding organs was 0.228-0.419 mGy/mCi. This study achieved detailed radiation dose measurements in highly sensitive pediatric patients and enabled the prediction of radiation doses according to kidney function values. The proposed method can provide useful insights for medical radiation exposure management, which is particularly important and necessary for pediatric patients.

• Nuclear Engineering and Technology
• /
• 제55권9호
• /
• pp.3401-3408
• /
• 2023

In this study, we used the Monte Carlo N-Particle program to simulate the gamma-ray spectra obtained from plastic scintillators holes filled with bismuth nanoparticles. We confirmed that the incorporation of bismuth nanoparticles into a plastic scintillator enhances its performance for gamma-ray spectroscopy using the subtraction method. The subtracted energy spectra obtained from the bismuth-nanoparticle-incorporated and the original plastic scintillator exhibit a distinct energy peak that does not appear in the corresponding original spectra. We varied the diameter and depth of the bismuth-filled holes to determine the optimal hole design for gamma-ray spectroscopy using the subtraction method. We evaluated the energy resolutions of the energy peaks in the gamma-ray spectra to estimate the effects of the bismuth nanoparticles and determine their optimum volume in the plastic scintillator. In addition, we calculated the peak-to-total ratio of the energy spectrum to evaluate the energy measuring limit of the bismuth nanoparticle-containing plastic scintillator using the subtraction method.

• Nuclear Engineering and Technology
• /
• 제55권12호
• /
• pp.4678-4684
• /
• 2023

Using the Monte Carlo method, the impact of the angular distribution of the electron source on the dose distribution for the 2.5 MeV ELV electron accelerator was explored. The experiment measured the 3-D dose distribution in the irradiation chamber for electron energies of 1.0 MeV and 2.5 MeV. The simulation used the MCNP6.2 code to evaluate three angular distribution models of the source: a mono-directional beam, a cone shape, and a triangular shape. Of the three models, the triangular shape with angles θ = 30°, φ = 0° best represents the angle of the scan hood through which the electron beam exits. The MCNP6.2 simulation results demonstrated that the triangular model is the most accurate representation of the angular distribution of the electron source for the 2.5 MeV ELV electron accelerator.

• Nuclear Engineering and Technology
• /
• 제56권5호
• /
• pp.1845-1853
• /
• 2024

The setpoint of the reactor trip system shall be set to consider the measurement uncertainty of the instrument channel and provide a reasonable and sufficient margin between the analytical limit and the trip setpoint. A comparative analysis was conducted to find out an appropriate uncertainty combination method through an example problem. The four methods were evaluated; 1) ISA-67.04.01 method, 2) the GUM95 method, 3) the modified GUM method developed by Fotowicz, and 4) the modified IEC61888 method proposed by authors for the pressure instrument channel presented in ISA-RP67.04.02 example. The appropriateness of each method was validated by comparing it with the result of Monte Carlo simulation. As a result of the evaluation, all methods are appropriate when all measurement uncertainty elements are normally distributed as expected. But ISA-67.04 method and GUM95 method overestimated the channel uncertainty if there is a dominant input element with rectangular distribution among the uncertainty input elements. Modified GUM95 methods developed by Fotowicz and modified IEC61888 method by authors are able to produce almost the same level of channel uncertainty as the Monte Carlo method, even when there is a dominant rectangular distribution among the uncertainty components, without computer-assisted simulations.

• 한국의학물리학회지:의학물리
• /
• 제18권3호
• /
• pp.126-133
• /
• 2007

세기조절방사선치료(Intensity modulated radiation therapy, IMRT) 선량의 정확도를 원격으로 점검할 수 있는 시스템 구축을 목적으로, 두경부용 팬텀을 제작하였다. 팬텀은 공기 및 뼈 구조물의 교체 장착을 통해, 균질 혹은 비균질 팬텀으로 이용할 수 있다. 일차적으로 단일 빔 및 세 빔의 조사에 대한 몬테칼로(Monte Carlo, MC) 전산모사를 시행하고, 이온 전리함 및 열형광선량계(thermoluminescent dosimeter, TLD)를 이용한 측정과 비교하였다. TLD의 판독은 독립된 두 기관에서 수행하였다. 단일 빔의 경우, 균질 및 비균질 팬텀에 대한 이온 전리함 측정 결과는 MC전산모사 결과와 대체로 2% 수준에서 일치하였으며, TLD 의 경우에는 기관에 따라 2% 혹은 7%수준의 차이를 보였다. 세 빔을 이용한 비교의 경우에는, 이온 전리함은 -5% 수준, TLD의 경우에는 $+2{\sim}+3%$ 수준의 차이를 보였다. 원격 선량 검증을 위해서는 TLD 판독의 신뢰도 향상이 필요한 것으로 판단되었다. MC 전산모사는 새로운 팬텀 개발 시에, 선량 측정값의 신뢰도 확보에 이용될 수 있다.

• Journal of Radiation Protection and Research
• /
• 제29권4호
• /
• pp.269-273
• /
• 2004

고계수율 환경에서의 G-M 계수기의 가용 범위를 확장하기 위하여 두 가지 불감시간(연장가능 및 연장불능)을 채택한 복합 모형이 개발되었으며, 이 복합모형 참 계수율과 실측 계수율간의 상관관계를 보다 정확히 설명한다. 이 논문에서는 몬테칼로 모사법에 근거한 G-M 계수기 불감효과 분석 프로그램 GMSIM을 개발하여 연장가능 불감시간 모형 및 연장불능 불감시간 모형에 적용하여 그 정확도를 확인하였다. GMSIM을 이용하여 복합 불감시간 모형을 따르는 G-M 계수기의 계수 통계 특성을 분석한 결과, 두 가지 이상적 모형의 중간적 특성을 보였다. 향후 GMSIM은 세 가지 모형의 불감시간 특성을 분석하는데 사용될 수 있다.

• 방사선산업학회지
• /
• 제7권2_3호
• /
• pp.115-119
• /
• 2013

The density profile measurement technology by gamma transmission has been widely used to diagnose processes in the field of refinery and petrochemical industry. This technology can reveal a clue and position of abnormal phenomenon of industrial processes during their operation. In this paper, the feasibility of the gamma transmission technology for detecting changes in the amount of fluid in a distillation column was evaluated by using Monte Carlo simulations. The simulations assumed that $^{60}Co$ (1.17, 1.33 MeV) sources and NaI (Tl) detectors (${\Phi}5{\times}5cm$) are located in opposite sides of a column and it concurrently moves in vertical direction. To determine the dependency of a spatial resolution on aperture size of a collimator, the simulation model for a tray in a column were simulated with the aperture sizes of 1 and 2 cm. The thickness of the high density area including a tray and fluid was 7.6 cm in the simulation. The spatial resolution of the tray was 8.2 and 8.5 cm, respectively. As a result, it was revealed that the conventional density profile measurement technique is not able to show the deviation of liquid level on a tray in a column.

• 한국콘텐츠학회논문지
• /
• 제15권4호
• /
• pp.350-356
• /
• 2015

본 연구의 목적은 몬테칼로 모사방법을 이용하여 소동물 전용 양전자방출단층촬영 시스템의 모듈 내 섬광체 배열 수에 따른 특성평가를 하는 것이다. 이 연구에서 제안한 소 동물 전용 양전자방출단층촬영 시스템은 모듈 내 섬광체 수를 1 ~ 8개로 구성하였으며, 섬광체 크기는 $2.0{\times}2.0{\times}10.0mm^3$ 크기의 LSO섬광결정을 사용하였고 스캐너의 직경은 100 mm로 설계하였다. 몬테칼로 시뮬레이션 방법중에 하나인GATE 코드를 이용하여 선원은 511 keV 점선원을 이용하였으며 동시계수 측정된 좌표값을 이용하여 민감도 및 사이노그램을 획득하였다. 모듈 내 섬광체 수가 적을수록 모듈 별 틈새가 줄어들어 민감도가 향상되는 결과를 보였으며, 사이노그램 결과에서도 불완전한 데이터(missing data)가 발생하지 않는 것을 알 수 있었다. 이 연구 결과는 모듈 안 섬광체 수가 적을수록 민감도 향상 및 불완전한 데이터 획득이 줄어드는 것을 증명함으로써, 소동물 전용 양전자방출단층촬영 시스템의 성능 개선을 위한 새로운 접근법을 제시한다.