• Nuclear Engineering and Technology
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• 제16권1호
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• pp.18-20
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• 1984

붕소의 사전 농축후 포획감마선 계측법에서 자연 리티움 벽돌을 Ge(Li) 검출기 앞에 설치하므로서 붕소의 검출한계를 더욱 낮출 수 있었다. 실험상 검출한계는 알루미늄, 철강, 이산화우라늄 그리고 그라파이트 시료에 대해서 각각 0.30ppm, 0.18ppm, 0.045ppm 고리고 0.090ppm이었다. 또한 계측 중 중성자 속의 변화에 의한 오차를 없애기 위하여 교대로 계측하는 방법을 사용하였다.

• 대한의용생체공학회:의공학회지
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• 제18권3호
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• pp.291-299
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• 1997

As a microimaging device detecting gamma rays emitted from small lesions or tumors during operation, the intraoperative surgical probe has been proposed and is now under development. We have designed a multipurpose portable gamma prove system and evaluated the performance both for the absolute counting purpose of residual radioactivities and for the localizing capability of gamma events using the NaI(Tl) crystal and two types of photomultiplier tubes(PMTs). Counting efficiencies in the range of routine clinical use of radiation dose were measured using the assembly of single channel PMTs and 0.5 inch thick NaI(Tl) crystal of 1 inch diameter. The positioning of gamma events for imaging purpose requires the multiple channel PMTs with appropriate positioning electronics. We have designed a simple and reliable positioning circuit based on the concept of modified Anger. In preliminary experiments using the multiple channel PMT of 3 inch diameter and the dim lighth source, we were able to trace and localize the correct position with reduced positioning error by the use of two multiplier/divider chipset and simplified peripherals. The energy resolutions for the counting gamma probe measured as full width at half maximum(FWHM) for Cs-137, F-18, Tc-99m were 12%, 13%, and 36%, respectively. The spatial resolution for the imaging gamma probe measured as FWHM for green LED was 2.9 mm. The results indicate that the currently developing probe is very promising and could be very useful for many applications in nuclear medicine. Future studies will include developing collimators, improving interface hardwares, and evaluating the system with clinical data.

• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3798-3807
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• 2021

Tritium extraction from radioactively contaminated cement mortar samples was performed using heating and liquid scintillation counting methods. Tritiated water molecules (HTO) can be present in contaminated water along with water molecules (H₂O). Water is one of the primary constituents of cement mortar dough. Therefore, if tritium is present in cement mortar, the buildings and structures using this cement mortar would be contaminated by tritium. The radioactivity level of the materials in the environment exposed to tritium contamination should be determined for their disposal in accordance with the criteria of low-level radioactive waste disposal facility. For our experiments, the cement mortar samples were heated at different temperature conditions using a high-temperature combustion furnace, and the extracted tritium was collected into a 0.1 M nitric acid solution, which was then mixed with a liquid scintillator to be analyzed in a liquid scintillation counter (LSC). The tritium extraction rate from the cement mortar sample was calculated to be 90.91% and 98.54% corresponding to 9 h of heating at temperatures of 200 ℃ and 400 ℃, respectively. The tritium extraction rate was close to 100% at 400 ℃, although the bulk of cement mortar sample was contaminated by tritium.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.3925-3934
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• 2023

The importance of fast neutron detection for nuclear safeguards purposes has increased due to its potential advantages such as reasonable cost and higher precision for larger sample masses of nuclear materials. Pulse-shape discrimination (PSD) is inevitably used to discriminate neutron- and gamma-ray- induced signals from organic scintillators of very high gamma sensitivity. The light output (LO) threshold corresponding to several MeV of recoiled proton energy could be necessary to achieve fine PSD performance. However, this leads to neutron count losses and possible distortion of results obtained by neutron multiplicity counting (NMC)-based nuclear material accountancy (NMA). Moreover, conventional PSD techniques are not effective for counting of neutrons in a high-gamma-ray environment, even under a sufficiently high LO threshold. In the present work, PSD performance (figure-of-merit, FOM) according to LO bands was confirmed using a conventional charge comparison method (CCM) and compared with results obtained by convolution neural network (CNN)-based PSD algorithms. Also, it was attempted, for the first time ever, to reject fake neutron signals from distorted PSD regions where neutron-induced signals are normally detected. The overall results indicated that higher neutron detection efficiency with better accuracy could be achieved via CNN-based PSD algorithms.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3380-3389
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• 2022

We evaluated the performance of an improved hybrid median filter (IHMF) applied to X-ray computed tomography (CT) images obtained using a high-resolution photon-counting cadmium zinc telluride (CZT) detector. To study how the proposed approach improves the image quality, we measured the noise levels and the overall CT-image quality. We established a CZT imaging system with a detector length of 5.12 cm and thickness of 0.3 cm and acquired phantom images. To evaluate the efficacy of the proposed filter, we first modeled two conventional median filters. Subsequently, we were able to achieve a normalized noise power spectrum result of ~10^-8 mm², and furthermore, the proposed method improved the contrast-to-noise ratio by a factor of ~1.51 and the coefficient of variation by 1.55 relative to the counterpart values of the no-filter image. In addition, the IHMF exhibited the best performance among the three filters considered as regards the peak signal-to-noise ratio and no-reference-based image-quality evaluation parameters. Thus, our results demonstrate that the IHMF approach provides a superior image performance over conventional median filtering methods when applied to actual CZT X-ray CT images.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2057-2062
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• 2024

Among photon counting detector (PCD)-based technologies, the K-edge subtraction (KES) method has a very high material decomposition efficiency. Yet, since the increase in noise in the X-ray image to which the KES method is applied is inevitable, research on image quality improvement is essential. Here, we modeled a block-matching and 3D filtering (BM3D) algorithm and applied it to PCD-based X-ray images with the improved KES (IKES) method. For PCD modeling, Monte Carlo simulation was used, and a phantom composed of iodine substances with different concentrations was designed. The IKES method was modeled by adding a log term to KES, and the X-ray image used for subtraction was obtained by applying the 3.0 keV range based on the K-edge region of iodine. As a result, the IKES image using the BM3D algorithm showed the lowest normalized noise power spectrum value. In addition, we confirmed that the contrast-to-noise ratio and no-reference-based evaluation results when the BM3D algorithm was applied to the IKES image were improved by 29.36 % and 20.56 %, respectively, compared to the noisy image. In conclusion, we demonstrated that the IKES imaging technique using a PCD-based detector and the BM3D algorithm fusion technique were very efficient for X-ray imaging.

• Nuclear Engineering and Technology
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• 제6권2호
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• pp.80-88
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• 1974

Amiel의 지발중성자 계측법을 사용한 분석과정을 다소 수정하여 지질학적 시료중의 우라륨 및 토륨의 동시 정량을 시도하였다. 본 분석과정은 넓은 범위의 두원소의 함량비에서 정화하게 적용할 수 있었다. 개발과정중 수행한 세력사항을 기술하였으며 나아가 본 분석법을 평가하였던 바 우라늄의 감도는 0.1$\mu\textrm{g}$이하였고 토륨의 감도는 약 5$\mu\textrm{g}$이었다.

• 핵의학기술
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• 제21권1호
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• pp.70-75
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• 2017

방사성 요오드 갑상선 섭취율 검사는 방사성 요오드를 투여하고 일정 시간 후 갑상선의 요오드 방사능치를 측정하여 전반적인 기능 상태를 알아보는 검사법이다. 검사에 영향을 미치는 인자는 매우 다양하다. 본 연구에서는 갑상선의 길이나 두께, 부피에 따른 기하학적 요인이 계수율에 주는 영향을 관찰하고자 한다. 액체상태의 $^{131}I\;185kBq$ ($5{\mu}Ci$)을 지름이 0.5, 1, 1.5, 3 cm 인 주사기에 넣고 길이를 1 cm 간격으로 생리식염수를 추가하여 증가시켰다. 선원을 장비로부터 25 cm 거리에서 횡축방향과 종축방향으로 위치하였을 때 각각의 계수율을 측정하였다. 횡축 방향으로 위치하였을 때, 선원의 길이가 변화하여도 대부분 유의한 차이를 보이지 않았다. 종축 방향으로 위치하였을 때, 곡선추정 회귀분석 결과 복합모형곡선과 높은 상관관계를 보였고($$R^2{\geq_-}0.941$$), 선원의 길이가 증가할수록 계수율은 감소하였다. 따라서 갑상선 섭취율 검사 시, 갑상선의 가로나 세로 방향의 차이에 따른 섭취율의 오차는 적을 것으로 예상되어 지며, 단순한 부피의 차이보다 갑상선의 두께 및 투여 전 선량측정 시의 비커에 따라서 오차가 생길 수 있다고 예상된다. 따라서 오차를 줄이기 위해서는 초음파 등의 영상을 참고하여 두께를 구해 섭취율 수치에 적용하거나, 결과에서 구한 복합방정식을 통해 오차를 예측, 갑상선과 섭취율 장비의 거리를 변화시킨다면 비교적 정확한 계수율을 구할 수 있을 거라 사료 된다.

• 분석과학
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• 제18권4호
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• pp.298-308
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• 2005

사용후핵연료시료 중에 함유된 탄소-l4와 트리튬을 회수 및 정량하였다. $CO_2$ 운반체($CaCO_3$)를 포함한 사용후핵연료시료를 $90^{\circ}C$에서 8M $HNO_3$ 용액으로 용해하면서 휘발된 $^{14}CO_2$를 1.5 M NaOH 용액을 포함한 포집관에 수집하였다. 용해 중 휘발되는 방사성 요오드는 Ag-silica gel 흡착체를 담은 포집 관으로 사전제거하였다. 핵연료 용해용액 중에 남아있는 트리튬(HTO)를 정량하기 위하여 양이온과 음이온 교환수지 혼합물 및 무기이온교환체를 이용한 뱃치 및 분리관법으로 용해용액을 탈이온화시켜 간섭이온을 제거하였다. 포집용액 중의 탄소-14와 탈이온화수 중의 트리튬을 액체섬광계수법으로 정량하였다.

• Journal of Radiation Protection and Research
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• 제34권3호
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• pp.121-128
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• 2009

국내 원전의 계획예방정비기간중에 원자로계통의 개방과정에서 원자로건물내 공기 중으로 누설된 $^{131}I$의 채내 흡입으로 원전 종사자의 내부피폭이 발생하였다. 이에 따라 원전에서 보유하고 있는 전신계측기(Whole Body Counter)를 이용하여 방사선작업 종료 후 즉시 원전종사자의 체내에 침적된 내부방사능을 측정하였고, 수일 경과 후 재측정하였다. 이러한 전신계측결과를 이용한 섭취량 산정 값을 원전종사자가 출입한 원자로 건물 내 공기 중의 $^{131}I$ 방사능 농도 측정결과와 원자로건물 출입기록에 근거하여 계산된 $^{131}I$ 채내 섭취량과 비교 평가하였다. 그 결과 전신계측기를 이용한 채내 방사능측정 결과와 공기중 농도를 이용한 섭취량 산정 결과는 비교적 잘 일치하는 것으로 평가되였다.