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Kahee Jeong,Sooyeon Lim,Ji Eun Park,Wook sohn 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
Many radionuclides emit two or more gamma rays in a cascade once they decay. At this time, gamma rays are detected at the same time, and the signals are overlapped and measured as one added signal. This is called the summing coincidence effect, and it causes an error of more than 10% depending on the detection efficiency, measurement conditions, and target nuclide. It is known to be greater as the efficiency of the detector increases and as the distance between the source and the detector decreases. It is necessary to consider the summing coincidence effect since the efficiency of the HPGe detector owned by the KHNP CRI is as high as 65%. In this study, We would like to propose an appropriate gamma nuclide analysis method for radioactive waste generated from NPP by evaluating the influence on the summing coincidence effect.
Evaluation of Gross Alpha Radioactivity of Radioactive Sludge Samples
Kahee Jeong,Sooyeon Lim,Ji-Eun Park,Wook Sohn 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
In order to establish disposal plans for sludge, which is one of the untreated waste materials from domestic nuclear power plants, it is necessary to determine the radioactivity concentration of radioactive isotopes. In this study, we aim to evaluate the gross alpha radioactivity of sludge containing radioactive contaminants after pre-treatment, in order to assess the level of sludge waste and obtain analytical data for discussing disposal methods. Samples of sludge generated from nuclear power plants were pre-treated, solutionized, and prepared as analysis samples for evaluating the gross alpha radioactivity.
Determining the Optimal Conditions for the Sample Quantity of Radioactive Sludge
Kahee Jeong,Sooyeon Lim,Ji-Eun Park,Wook Sohn 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
Typically, the bottom of the effluent treatment facility at a nuclear power plant contains sediment, which is low-contamination waste consisting of sludge, gravel, sand, and other materials from which radioactive contaminants have been removed. Among these sediments, sludge is an irregular solid form consisting of small particles that are coagulated together, with radioactive isotopes containing cobalt attached. Currently, there is a record of disposing of dry active waste from domestic nuclear power plants, and efforts are underway to gather basic data for the disposal of untreated waste such as sludge, spent filter, and spent resin. In particular, the classification and disposal methods of waste will be determined based on the radioactivity concentration. Therefore, plans are being made to determine the radioactivity concentration of radioactive isotopes and establish disposal plans for sludge samples. In this study, pre-treatment and solutionization were carried out for the analysis of radioactive isotopes in sludge sampels from nuclear power plants. The deviation of the gamma radioisotope analysis results was derived to obtain an optimal sample quantity that represents the sludge.
Kahee Jeong,Ji-eun Park,Soo Yeon Lim,Wook Sohn 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1
For the final disposal of radioactive waste generated during the operation of nuclear power plants, concentrations of 14 radionuclides including gross alpha have to be determined to meet nuclear regulatory requirements. In order to determine the gross alpha radioactivity in radioactive waste, the sample must be preprocessed into a solution which is usually a strong acid. When this solution is used to prepare the gross alpha measurement sample, it produces a lot of salt, which makes an accurate measurement difficult. Also it causes corrosion of a planchet, which causes problems in the disposal of waste in the future. For these reasons, an acid treatment of the solution was added to the existing preprocess procedure, which is also expected to improve the measurement error. Although the gross alpha measurement is known to be easy to perform and able to give rapid results, it cannot be used for quantitative analysis. This is because the energies emitted by the individual alpha nuclides are assumed to be produced from a single alpha emitted by the individual alpha nuclides are assumed to be produced from a single alpha emitter used as the standard calibration source. Also, due to self-absorption of alpha particles a counting rate depends on the thickness (or weight) of the residues on the planchet. In this study, we compared gross alpha radioactivity with and without an acid treatment to prepare gross alpha measurement samples. The weights of the treated samples increased by at most 5% after about 12 hours of evaporation to dryness, and then saturated or slightly decreased, while the weights of the untreated samples increased up to 20% over time. In addition, the radioactivities of the untreated samples were about two times those of the treated samples. This is considered to be due to differences both in the geometric shapes of the samples and the weights of their residues which resulted from whether acid treatment was applied or not. The results of this study showed that an acid treatment was beneficial in reducing both production corrosion and salts which could result in more reliable and constant measurements of gross alpha activity. The results showed that acid treatment was beneficial in reducing corrosion and measurement errors.
Stable Isotope Analysis of Northern Pintail (Anas acuta) Feathers Wintering on Junam Reservoir
Jeong, Kahee,Bae, In-Ae,Kim, Jong-Yun,Song, Kyuseok,Lee, Si-Wan,Kang, Tae-Han Chemic Publishing Company 2014 Asian Journal of Chemistry Vol.26 No.13
<P>For the first time in Korea, stable isotope ratio mass spectroscopic analysis method was introduced as an alternative method to track the movement of the migratory birds. Hydrogen isotope ratio (delta H-2) and oxygen isotope ratio (delta O-18) of the feather samples were collected from northern pintail, which were captured in Junam Wetland Park and were measured using a continuous flow-isotope ratio mass spectrometer. The delta H-2 values of all feathers show a bimodal frequency distribution with a wide range of delta H-2 values (-30 % to -120 %), while the range of delta O-18 values was relatively very small (ca. 6-18 %). The difference between the two modes in the frequency distribution of delta H-2 values for male was more than that for female. Although the two-dimensional plot of delta H-2 versus delta O-18 can provide the information on the breeding ground of the migratory wild birds. The northern pintails captured in Junam Wetland Park have more than two geographical origins.</P>