• Journal of Radiation Protection and Research
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• 제43권4호
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• pp.137-142
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• 2018

Background: Gamma-ray detectors having a thin window of a material with low atomic number can increase the true coincidence summing effects for radionuclides emitting X-rays or gamma-rays. This effect can make efficiency calibration or spectrum analysis more complicated. In this study, a Cu shield was tested as an X-ray filter to neglect the true coincidence summing effect by X-rays and gamma-rays in gamma-ray spectrometry, in order to simplify gamma-ray energy spectrum analysis. Materials and Methods: A Cu shield was designed and applied to an n-type high-purity germanium detector having an $X-{\gamma}$ summing effect during efficiency calibration. This was tested using a commercial, certified mixed gamma-ray source. The feasibility of a Cu shield was evaluated by comparing efficiency calibration results with and without the shield. Results and Discussion: In this study, the thickness of a Cu shield needed to avoid true coincidence summing effects due to $X-{\gamma}$ was tested and determined to be 1 mm, considering the detection efficiency desired for higher energy. As a result, the accuracy of the detection efficiency calibration was improved by more than 13% by reducing $X-{\gamma}$ summing. Conclusion: The $X-{\gamma}$ summing effect should be considered, along with ${\gamma}-{\gamma}$ summing, when a detection efficiency calibration is implemented and appropriate shielding material can be useful for simplifying analysis of the gamma-ray energy spectra.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4472-4476
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• 2023

In this study, it has been shown that the true coincidence summing correction factor can be obtained for the first time using the PHITS Monte Carlo program. Determining this correction factor using different methods and tools in each laboratory to increase the possibility of achieving high-efficiency measurement conditions is still popular in gamma-ray spectrometry. By using ¹³³Ba, ¹⁵²Eu, ¹³⁴Cs, and ⁶⁰Co point sources, the true coincidence summing factor was investigated in both near and far counting geometries for 15 different energy values. GESPECOR software was used to validate the results obtained with PHITS. A remarkable agreement was obtained between PHITS and GESPECOR, with a discrepancy of less than 3%. With this study, a new tool has been proposed to obtain the true coincidence summing factor, which is one of the significant correction factors investigated/calculated in gamma-ray spectrometric studies.

• Nuclear Engineering and Technology
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• 제52권6호
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• pp.1266-1270
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• 2020

A code is developed to correct for the coincidence summing effect in detecting a voluminous gamma source, and this code is applied to a¹⁵²Eu standard source as a test case. The source is 1000 mL of liquid in a cylindrical shape. To calculate the coincidence summing effect, the cylindrical source is considered as 10(radial) × 8(height) sectional sources. For each sectional source, the peak efficiency and total efficiency are obtained by Monte Carlo simulation at each energy for 10 energies between 50 keV and 2000 keV. The efficiencies of each sector are then expressed as polynomials of gamma energy. To calculate the correction coefficients for the coincidence summing effect, the KORSUM code is used after modification. The magnitudes of correction are 4%-17% for the standard ¹⁵²Eu source measured in this study. The relative deviation of 4.7% before the coincidence correction is reduced to 0.8% after the correction is applied to the efficiency based on the measured gamma line. Hence, this study has shown that a new method has been developed that is applicable for correcting the coincidence effect in a voluminous source, and the method is applied to the measured data of a standard ¹⁵²Eu cylinder source.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1754-1759
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• 2022

The activity of gamma-ray emitting nuclides is calculated assuming that each gamma-ray is detected individually; thus, the magnitude of the coincidence summing signal must be considered during activity calculations. Here, the correction factor for the coincidence summing effect was calculated, and the detection efficiencies of two HPGe detectors were compared. The CANBERRA Inc. GC4018 high-purity Ge detector provided an estimate for the peak-to-total ratio using a point source to determine the coincidence summing correction factor. The ORTEC Inc. GEM60 high-purity Ge detector uses EFFTRAN in LVis to obtain the parameters of the detector and source model and the gamma-gamma and gamma-X match estimates, in order to determine the coincidence summing correction factor. Nuclide analyses, radioactivity comparisons, and analyses of reference material samples were performed utilizing certified reference materials to accurately determine the detection efficiencies. For both Co-60 and Y-88, the detection efficiency for a point source increased by an average of at least 12-13%, whereas the detection efficiency determined using LVis increased by an average of at least 13-15%. The calculated radioactivity values of the certified reference material and reference material samples were accurate to within 3% and 6% of the measured values, respectively.

• 한국방사선학회논문지
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• 제12권5호
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• pp.557-563
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• 2018

동시 합성 보정 효과는 검출기의 효율이 향상할 때 그리고 선원과 검출기 사이의 거리가 가까울수록 크게 나타나는 것으로 알려져 있다. 점 선원($^{60}Co$)을 사용하여 검출기 중심축 방향 및 방사상 방향에서 거리에 따른 변화를 주어 P/T 비를 구하여 동시합성 보정을 하였다. 따라서 본 연구에서는 중심축 및 방사상 방향에서 동시합성 보정한 값들을 혼합부피선원(450 mL CRM source)에 적용하여 P/T에 따른 전체 피크효율 변화를 Geant4과 비교하였다. 또한 검출기와 시료가 아주 밀착된 상태에서 맵핑법에서 구한 효율을 환경시료 중에서 해양 시료인 미역에 적용하여 P/T 비의 적합성을 평가하고자 한다. 500 keV 이상의 효율의 영향을 받는 에너지 영역에 1,836 keV로 보정한 효율을 적용한 결과 측정값과 보정값의 상대오차는 3.2 % peak 효율이 보정되어 잘 일치하였다. 450 mL CRM source처럼 부피가 커질수록 P/T 비는 ${\pm}5%$까지 감소하였다. 이것은 검출기로부터 선원이 멀어짐에 따라 방출된 감마선의 산란이 많아지기 때문이며, 이처럼 P/T 변화는 동시합성 보정 피크 효율에 영향을 줌을 확인하였다.

• 대한전자공학회논문지
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• 제13권1호
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• pp.1-10
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• 1976

원자로의 안전계통에 이용되는 2-out of-3 내시회로 및 파고선별기에 관해 인술하고 상세한 해석을 하였다. 1-out of-m 동시회로의 안전신뇌도 및 확사비상정지신뇌도에 관한 식을 유도하여 적정한 1의 값을 구하였다. 2-out of-3 동시유로는 펄스 합산 방법을 이용하여 설계하였으며 매우 간단한 원리로 동작한다. 파고선별기는 전 선렬영역에 걸쳐 좋은 직선성 및 threshold 안정도를 가진다. A 2-out of-3 coincidence circuit and a discriminator to be used in the safely systems in nuclear reactors are described and analyzed in detail. The expressions for the reliability and the spurious scram reiliability of 1·out of-m coincidence logic in general are derived and the optimum value of 1 is assessed. The coincidence circuit is designed by making use of the pulse-summing method and is very simple in principle. The discriminator has good linearity in in the whole discrimination range and good threshold stability.

• 대한방사선방어학회:학술대회논문집
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• 대한방사선방어학회 2009년도 춘계 학술발표
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• pp.230-231
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• 2009

• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3421-3430
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• 2021

Spherical NaI(Tl) detectors are used in gamma-ray spectrometry, where the gamma emissions come from the nuclei with energies in the range from a few keV up to 10 MeV. A spherical detector is aimed to give a good response to photons, which depends on their direction of travel concerning the detector center. Some distortions in the response of a gamma-ray detector with a different geometry can occur because of the non-uniform position of the source from the detector surface. The present work describes the calibration of a NaI(Tl) spherical detector using both an experimental technique and a numerical simulation method (NSM). The NSM is based on an efficiency transfer method (ETM, calculating the effective solid angle, the total efficiency, and the full-energy peak efficiency). Besides, there is a high probability for a source-to-detector distance less than 15 cm to have pulse coincidence summing (CS), which may occur when two successive photons of different energies from the same source are detected within a very short response time. Therefore, γ-γ ray CS factors are calculated numerically for a ¹⁵²Eu radioactive cylindrical source. The CS factors obtained are applied to correct the measured efficiency values for the radioactive volumetric source at different energies. The results show a good agreement between the NSM and the experimental values (after correction with the CS factors).

• 대한방사선방어학회:학술대회논문집
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• 대한방사선방어학회 2009년도 춘계 학술발표
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• pp.250-251
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• 2009

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.778-784
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• 2016

HyperGam-U was recently developed to determine uranium enrichment based on ${\gamma}$- and X-ray spectroscopy analysis. The $XK_{\alpha}$ region of the uranium spectrum contains 13 peaks for $^{235}U$ and $^{238}U$ and is used mainly for analysis. To describe the X-ray peaks, a Lorentzian broadened shape function was used, and methods were developed to reduce the number of fitting parameters for decomposing the strongly overlapping peaks using channel-energy, energy-width, and energy-efficiency calibration functions. For validation, eight certified reference material uranium samples covering uranium enrichments from 1% to 99% were measured using a high-resolution planar high-purity germanium detector and analyzed using the HyperGam-U code. When corrections for the attenuation and true coincidence summing were performed for the detection geometry in this experiment, the goodness of fit was improved by a few percent. The enrichment bias in this study did not exceed 2% compared with the certified values for all measured samples.