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Kyunghun Jung,Minyoung Jung,Woojin Jo,Jung Bo Yoo 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
Concrete is the primary building material for nuclear facilities, making it one of the most common forms of radioactive waste generated when decommissioning a nuclear facility. Of the total waste generated at the Connecticut Yankee and Maine Yankee nuclear power plants in the United States, concrete waste accounts for 83.5% of the total for Connecticut Yankee and 52% for Maine Yankee. In order to dispose of the low- to medium-level radioactive concrete waste generated during the decommissioning of nuclear power plants, it is necessary to analyze the radioactivity concentration of gamma nuclides such as Co-58, Co-60, Cs-137, and Ce-144. Gamma-ray spectroscopy is commonly used method to measure the radioactivity concentration of gamma nuclides in the radioactive waste; however, due to the nature of gamma detectors, gamma rays from sequentially decaying nuclides such as Co-60 or Y-88 are subject to True Coincidence Summing (TCS). TCS reduces the Full Energy Peak Efficiency (FEPE) of specific gamma ray and it can cause underestimation of radioactivity concentration. Therefor the TCS effect must be compensated for in order to accurately assess the radioactivity of the sample. In addition, samples with high density and large volume will experience a certain level of self-shielding effect of gamma rays, so this must also be compensated for. The Radioactive Waste Chemical Analysis Center at the Korea Atomic Energy Research Institute performs nuclide analysis for the final disposal of low- and intermediate-level concrete waste. Since a large number of samples must be analyzed within the facility, the analytical method must simultaneously satisfy accuracy and speed. In this study, we report on the results of evaluating the accuracy of the radioactivity concentration correction by applying an efficiency transfer method that appears to satisfy these requirements to concrete standard reference material.
Kyunghun Jung,Minyoung Jung,Jung Bo Yoo,Tae-Hong Park 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
According to the ‘Regulations on the Delivery of Low and Medium Level Radioactive Waste’, Notification No. 2021-26 of the Nuclear Safety and Security Commission, a history of radioactive waste and a total amount of radioactivity in a drum are mandatory. At this time, the inventory of radionuclides that make up more than 95% of the total radioactivity contained in the waste drum should be identified, including the radioactivity of H-3, C-14, Fe-55, Co-58, Co-60, Ni-59, Ni-63, Sr- 90, Nb-94, Tc-99, I-129, Cs-137, Ce-144, and total alpha. Among nuclides to be identified, gamma-emitting nuclides are usually analyzed with a gamma ray spectrometer such as HPGe. When a specific gamma-ray is measured with a detector, several types of peaks generated by recombination or scattering of electrons are simultaneously detected in addition to the corresponding gamma-ray in gamma-ray spectroscopy. Among them, the full energy peak efficiency (FEPE) with the total gamma energy is used for equipment calibration. However, this total energy peak efficiency may not be accurately measured due to the coincidence summing effect. There are two types of coincidence summing: Random and True. The random coincidence summing occurs when two or more gamma particles emitted from multiple nuclides are simultaneously absorbed within the dead time of the detector, and this effect becomes stronger as the counting rate increases. The true coincidence summing is caused by simultaneous absorption of gamma particles emitted by two or more consecutive energy levels transitioning from single nuclide within the dead time of the detector. This effect is independent of the counting rate but affected by the geometry and absolute efficiency of the detector. The FEPE decreases and the peak count of region where the energy of gamma particles is combined increases when the coincidence summing occurs. At the Radioactive Waste Chemical Analysis Center, KAERI, samples with a dead time of 5% or more are diluted and re-measured in order to reduce the random coincidence summing when evaluating the gamma nuclide inventory of radioactive waste. In addition, a certain distance is placed between the sample and the detector during measurement to reduce the true coincidence summing. In this study, we evaluate the coincidence summing effect in our apparatus for the measurement of radioactive waste samples.
Jung Bo Yoo,Kyunghun Jung,Kwang-Soon Choi,Jungweon Choi,Gi Yong Kim,Simon Oh,Hyojin An,Jihyun Kim,Minyoung Jung 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
To achieve permanent disposal of radioactive waste drums, the radionuclides analysis process is essential. A variety of waste types are generated through the operation of nuclear facilities, with dry active waste (DAW) being the most abundant. To perform radionuclides analysis, sample pretreatment technology is required to transform solid samples into solutions. In this study, we developed a dry ashing-microwave digestion method and secured the reliability of the analysis results through a validity evaluation. Additionally, we conducted a comparative analysis of the radioactivity of 94Nb nuclides with and without the chemical separation process, which reduced the minimum detectable activity (MDA) level by more than 65-fold for a certain sample.
정경훈(Kyunghun Jung),이영훈(Younghun Lee),조성국(Seongkook Cho),조경석(Kyungseok Cho),박창호(Changho Park) 한국자동차공학회 2013 한국자동차공학회 지부 학술대회 논문집 Vol.2013 No.5-2
As key industry, the automobile industry is a technology-intensive industry developing rapidly to comply with the demands of consumer. In this paper, the motor development of high voltage cooling fan motor for fuel-cell electric vehicle is presented. In the first place, optimal design of the motor has been conducted. In order to find optimal solution. RSM was used and Output power, Torque-Ripple, Cogging-Torque were considered in optimization process. Also, stress simulation was conducted to prevent the problems in mass production. Finally, through the comparison between simulation results and experimental ones, the validity of design process is verified.
정경훈(Kyunghun Jung),김태완(Taewan Kim),조경석(Kyungseok Cho),박창호(Changho Park) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
As key industry, the automobile industry is a technology-intensive industry developing rapidly to comply with the demands of consumer. In this paper, the motor development of high voltage cooling fan motor for fuel-cell electric vehicle is presented. In the first place, optimal design of the motor has been conducted. In order to find optimal solution, RSM was used and Output power, Torque-Ripple, Cogging-Torque were considered in optimization process. Also, stress simulation was conducted to prevent the problems in mass production. Finally, through the comparison between simulation results and experimental ones, the validity of design process is verified.
정경훈(Kyunghun Jung),조성국(Seongkook Cho),조경석(Kyungseok Cho),박창호(Changho Park) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
As key industry, the automobile industry is a technology-intensive industry developing rapidly to comply with the demands of consumer. In this paper, the motor development of high voltage electric compressor for hybrid car is presented. In the first place, optimal design of the motor has been conducted. In order to find optimal solution, Taguchi method was used and Output power, Torque-Ripple, Cogging-Torque were considered in optimization process. Also, stress simulation was conducted to prevent the problems in mass production. The weight balance was designed and applied to the motor since the high voltage electric compressor has unbalance. Finally, through the comparison between simulation results and experimental ones, the validity of design process is verified.