• Analytical Science and Technology
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• v.19 no.1
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• pp.18-30
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• 2006

This paper describes the cumulative deposition of fallout Pu in soil and lichen at the present time and give the characteristics of fallout Pu deposits in the soil. In the soil of the forest, the accumulated depositions of $^{239,240}Pu$ were estimated to be in the range of 34.0 to $101.2Bq\;m^{-2}$ with an average value of $65.3{\pm}21.6Bq\;m^{-2}$. The average inventory of $^{239,240}Pu$ in the forest was calculated to be two times higher than that in the hill. Also, the deposited activities of $^{239,240}Pu$ in cultivated soil were significantly lower than those in the hill or forest. However, the cumulative depositions of fallout Pu in the volcanic ash soil on Cheju Island were much higher than those in the forest and hill soils. The measured activity concentrations of Pu isotopes in lichens and mosses showed large variations, due to characteristics of species and life span of lichen and moss colonies. From depth profiles, it was found that most of the fallout Pu has been accumulated in upper 10 cm layer of soil. Except for a few cases, the concentrations of $^{239,240}Pu$ in soil tended to decrease exponentially with increasing soil depth. Among parameters affecting the cumulative deposition of fallout Pu, organic substances and rainfall play an important role in the retention and relative mobility of fallout Pu in the soil. However, pH showed a weak correlation with the deposition of fallout Pu in the soil. From sequential leaching experiments, Pu was found to be associated predominantly with the "organic" and "oxy-hydroxy" fractions. Both the activity ratios of $^{238}Pu/^{239,240}Pu$ and $^{241}Pu/^{239,240}Pu$ in soils, lichens and mosses and the atomic ratios of $^{240}Pu/^{239}Pu$ in soils are close to those observed in the cumulative deposit global fallout from nuclear weapon testings. The results obtained from this research make it possible to interpret and predict the behavior of fallout Pu under natural conditions.

• Analytical Science and Technology
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• v.20 no.5
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• pp.419-423
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• 2007

Environmental low level tritium analysis was studied using liquid scintillation counter(LSC) and electrolytic enrichment method. To obtain low level blank count, various counting vials were investigated. Among them, teflon coated PE vial had a lower blank count rate (1.86 cpm) and we obtained 2.01 Bq/L detection and tritium separation factor was above 20. LSC counting efficiency obtained $28.70{\pm}0.27%$ using the NIST tritium standard water sample.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1538-1543
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• 2024

The importance of determining the radon exhalation rate from water surface is emphasized by the increased use of radon and its daughter products as tracers in large-scale circulation studies of the atmosphere. There were many methods to measure radon exhalation from water surface. With the development of radon exhalation rate measurement methods and instruments on the surface of the soil, the rock and building materials, so the radon exhalation rate from water surface can be more accurately measured by applying these improved methods and instruments. In this paper, a cuboid accumulation chamber surrounded by foam boards and a RAD7 were used to measure the radon exhalation rate on the water surface at three different positions by Yixin lake. Each measurement was performed 2 h. The radon exhalation rate from the water surface was about 6 × 10^-3 Bq m^-2s^-1. The thoron exhalation rate from the water surface also can be estimated, it is about 0.16 Bq m^-2s^-1. These results hint that the radon transmission from the lake bottom soil to water and then into the atmosphere.

• Journal of Radiation Industry
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• v.18 no.3
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• pp.155-166
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• 2024

In this study, a liquid scintillation spectrometer was developed for online continuous monitoring of tritium nuclides in water. The device consists of two photoelectron multiplier tubes (PMT), a simultaneous counting circuit, and a signal processing unit including a multi-channel analyzer (MCA). As a method to verify the performance of the equipment developed in this study, samples were prepared using a standard source, and the spectrum of tritium was measured to evaluate the detector characteristics such as efficiency, background (BKG), and minimum detectable activity (MDA). To evaluate the effect of pretreatment on tritium radioactivity measurement results, the MDA of water (seawater and groundwater) samples before and after pretreatment was calculated and compared. The results of the evaluation confirmed the satisfaction of the reference values of the Nuclear Safety Commission's "Discharge Control Standard in Drainage Water" and the World Health Organization's (WHO) "Tritium Radioactivity Concentration for Drinking Water Standards". The liquid scintillation spectrometer developed in this study, with or without pretreatment, confirmed detection performance equivalent to 1/100th of the discharge control standard for drainage water (40,000 Bq L^-1) and the WHO's drinking water standard for tritium radioactivity (10,000 Bq L^-1).

• Journal of radiological science and technology
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• v.38 no.3
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• pp.305-313
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• 2015

After Fukushima Daiichi nuclear disaster in 2011, study and maintenance of monitoring systems have been made at home and abroad. As concerns about radioactive contamination of water have increased in Korea, update of maintenance of managing radioactive materials in water is being made mainly by Ministry of Environment. In this study, we analysed current state of monitoring system modification in Japan, the country directly involved and neighboring country. According to the result, Japan modified the legislations first. Then Ministry of Education, Culture, Sports, Science and Technology (MEXT) provides theoretical background of radiological monitoring. And Ministry of the Environment actually watches state of water pollution in public waters and underground water. Finally related agencies like local government are monitoring current state of radioactive contamination in water environment. By region, local monitoring stations share the investigation of the whole country. Also, additional monitoring is running around nuclear facilities. After Fukushima disaster, monitoring for area near Fukushima is added. Among the reference levels, management target value of drinking water and tap water is 10 Bq/kg, and those of public water and underground water are 1 Bq/L. Measuring intervals varied from every hour to once a year, regularly or irregularly depending on the investigation. The main measuring items are air dose rate, gross ${\alpha}$, gross ${\beta}$, ${\gamma}$ radionuclide, Cs-134, Cs-137, Sr-89, Sr-90, I-131, and so on. In comparison, regulations about general public water in Korea need to be modified, while those about area near nuclear facility and drinking water are organized well. In future, therefore, domestic system would be expected to be modified with making reference to the guidelines like WHO's one. As good case of applying international guideline to domestic environment, Japanese system could be a reference when general standard of radioactivity in public water is made in Korea.

• Analytical Science and Technology
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• v.31 no.4
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• pp.149-160
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• 2018

A large number of functional living products are being produced for eco-friendly or health-promoting purposes. In the manufacturing process, such products could be adulterated with raw materials with high radioactivity, such as monazite and tourmaline. Thus, it is essential to manage raw materials and products closely related to the public living. For proper management, an accurate radioactivity data of the processed products are needed. Therefore, it is essential to develop a rapid and validated analytical method. In this study, the concentration of the radioactive $^{238}U$ and $^{232}Th$ in building materials (e.g., tile, cement, paint, wall paper, and gypsum board) and living products (e.g., health products, textiles, and minerals) were determined and compared by ED-XRF and ICP-MS. By comparing the results of both methods, we confirmed the applicability of the rapid screening and precise analysis of ED-XRF and ICP-MS. In addition, $^{238}U$ and $^{232}Th$ levels were relatively lower in building materials than in living products. Particularly, $^{232}Th$ content in 6 of 47 living products exceeded (maximum $8.2Bq{\cdot}g^{-1}$) the standard limit of $^{232}Th$ content in raw material ($1.0Bq{\cdot}g^{-1}$).

• Analytical Science and Technology
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• v.28 no.6
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• pp.377-384
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• 2015

A survey of the artificial radionuclides in rivers and lakes was conducted to investigate their levels in surface water. Water samples were collected at 60 points and analyzed by gamma-ray spectrometry with a measurement time of 10,000 seconds for ¹³⁴Cs, ¹³⁷Cs, and ¹³¹I. The obained values were lower than MDA for all points, except one point for ¹³¹I that was 0.533±0.058 Bq/L. ¹³¹I is known as a radioactive material that occurs frequently in sewage treatment plants. Because it is often used for medical treatments and subject to spreading into the environment due to the excretion from the patients. For the point where ¹³¹I was detected, we conducted additional investigation on the upstream river point and the effluent points of nearby sewage treatment plant to find the source of ¹³¹I. ¹³¹I was not detected at the upstream points of one of the upstream sewage treatment plants but found at the downstream points with the level being 0.257±0.034 to 0.799±0.051 Bq/L, proving the sewage treatment plant was the ¹³¹Isource.

• Economic and Environmental Geology
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• v.38 no.6 s.175
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• pp.689-697
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• 2005

Mineralogical composition, $^{137}Cs$ activity, total organic carbon (TOC), and particle size of marine sediments near Wuljin Nuclear Powerplant were analyzed and the relationships among those components were investigated. The particle sizes of sediments were equivalent to sand size and in the range of $-0.48\~3.6\;Md\phi$. TOC contents and $^{137}Cs$ activities were in the range of $0.06\~1.75\%$ and minimum detectable activity (MDA) $\~4.0Bq/kg-dry$ with the average value of $1.15{\pm}0.62$ Bq/kg-dry, respectively. The sediments in study area were characterized by large particle size and small TOC contents, and $^{137}Cs$ activity compared with other marine sediments. The main mineral components were quartz and feldspar (albite, microcline, and small amount of orthoclase) with small amount of pyroxene, calcite, hornblende. Minerals with $10{\AA}$ XRD peak (mainly biotite) and chlorite were also identified. Among those minerals, biotite shows the linear relationship with $^{137}Cs$ content probably due to the frayed edge site (FES) on biotite or small amount of mixed illite. However, TOC content shows most linear relationship with $^{137}Cs$ content because no significant amount of clay minerals, which can adsorb significant amount of Cs, were observed in the study area, indicating that the distribution of $^{137}Cs$ in this study area was more significantly affected by the TOC content than mineral composition.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.1
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• pp.38-43
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• 2012

Purpose: Patients injected with FDG use the bathroom that Measured surface contamination level and spatial dose rate. This study about the effect that result affects workers in same part. Materials and Methods: Group1 is St. Vincent' s hospital's 60case. Group 2 is Bucheon St. Mary's hospital's 50case. Last case is lower the average daily number of patients than group 2. Measured time is 8:00, 10:00, 13:00, 15:00 and 17:00. Measured part is 4 point of toilet, basin and wastepaper basket, also measured accumulation dose of toilet during 3 month. Hospitals is installed PET/CT ware surveyed on presence of bathroom that used only by patient and worker has been using the bathroom. Results: The highest average surface contamination level of toilet is group1($8.38{\pm}4.56$), but the highest spatial dose rate is group3. Cumulative exposure dose measured by TLD during 3months is St.Vincent's hospital 0.78 mSv and Bucheon St.Mary's hospital 0.37 mSv. And result of survey is 16.12% worker using the bathroom. Conclusions: The more daily number of patient, the higher surface contamination level of bathroom. Especially, wastepaper basket's surface contamination level is exceed the reference value $4Bq/cm^2$. Based on This survey, Bathroom require special attention and proper decontamination.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.1
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• pp.86-90
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• 2012

Purpose: Quantification of myocardial blood flow (MBF) using dynamic PET imaging has the potential to assess coronary artery disease. Rb-82 plays a key role in the clinical assessment of myocardial perfusion using PET. However, MBF could be overestimated due to the underestimation of left ventricular input function in the beginning of the acquisition when the scanner has non-linearity between count rate and activity concentration due to the scanner dead-time. Therefore, in this study, we evaluated the count rate linearity as a function of the activity concentration in PET data acquired in list mode. Materials & methods: A cylindrical phantom (diameter, 12 cm length, 10.5 cm) filled with 296 MBq F-18 solution and 800 mL of water was used to estimate the linearity of the Biograph 40 True Point PET/CT scanner. PET data was acquired with 10 min per frame of 1 bed duration in list mode for different activity concentration levels in 7 half-lives. The images were reconstructed by OSEM and FBP algorithms. Prompt, net true and random counts of PET data according to the activity concentration were measured. Total and background counts were measured by drawing ROI on the phantom images and linearity was measured using background correction. Results: The prompt count rates in list mode were linearly increased proportionally to the activity concentration. At a low activity concentration (<30 kBq/mL), the prompt net true and random count rates were increased with the activity concentration. At a high activity concentration (>30 kBq/mL), the increasing rate of the prompt net true rates was slightly decreased while the increasing rate of random counts was increased. There was no difference in the image intensity linearity between OSEM and FBP algorithms. Conclusion: The Biograph 40 True Point PET/CT scanner showed good linearity of count rate even at a high activity concentration (~370 kBq/mL).The result indicates that the scanner is useful for the quantitative analysis of data in heart dynamic studies using Rb-82, N-13, O-15 and F-18.