• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.351-357
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• 2003

Transuranic elements such as Pu, Am and Cm in synthetic solution of spent nuclear fuel samples were determined by electrodeposition followed by alpha-spectrometry after separation using anion exchange and extraction chromatography in order to determine the transuranic elements in radwaste samples from nuclear power plants. Plutonium was separated by 12M HC1-0.1M HI as an eluent on anion exchange column. As a second step Am and Cm were separated in a group by DTPA-Lactic acid as the eluent on HDEHP coated column. The nuclides of $^{239}Pu$, $^{241}Am$및 $^{244}Cm$ separated were determined by alpha-spectrometry after electrodeposition in 0.1M $NaHSo_4$-0.53M $Na_2SO_4$buffer solution as an electrolyte. The recovery yields of $^{239}Pu$, $^{241}Am$및 $^{244}Cm$ were 83.8%, 85.2% and 86.3%, respectively, from the synthetic solution containing uranium and non-radioactive metal elements.

• Nuclear Engineering and Technology
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• v.10 no.3
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• pp.153-163
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• 1978

The problems of solid waste disposal into the ground in connection with environmental aspects in the vicinity of a site would be very significant, though ground disposal for solid waste is safe and economical method. Studies of the waste-movement and migration of radionuclides (Sr-90 and Cs-137) for the disposal into the ground were performed under laboratory and field conditions. Affinity of the soils for radionuclide solution was higher than that in the acid solution. The sorption of radionuclides by the soils showed a time-dependent reation. The migration rates of radiostrontium and radiocesium were a range of 3.73$\times$10$^{-3}$ to 10.9$\times$10$^{-3}$ cm/day. The nuclides in the soil migrate much more slowly than the water, probably due to its high exchange capacity. The observed distribution of tritium was compared with that calculated by a mathematical model based on diffusivity. This study suggests that the tritiated water can be used to trace the movement of ground water.

• Journal of Soil and Groundwater Environment
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• v.28 no.6
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• pp.58-70
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• 2023

The improper management of radioactive waste or accidents caused by natural disasters can result in the release of radioactive materials into the surrounding environment, potentially leading to soil and groundwater contamination by radionuclides. In this study, adsorption-desorption behaviors of the radionuclides (cobalt and strontium) in natural soil, montmorillonite, Mn-PILC, Fe-PILC, and fishbone were investigated. Several models were used to predict adsorption isotherms of radionuclides on various absorbents. Adsorption isotherms of cobalt and strontium in several adsorbents were examined at pH 5.5. The amount of sorbed cobalt and strontium were represented fishbone > natural soil > Mn-PILC > Fe-PILC > montmorillonite and natural soil > Mn-PILC > fishbone > Fe-PILC > montmorillonite, respectively. Adsorption datas were fitted with several models such as Freundlich, Langmuir, Sips, Redlich-Peterson, Khan, and Generalized model. The results of curve fitting showed R²> 0.98 in all of adsorption models, except Sr²⁺ adsorption onto montmorillonite. For modified clays (Mn-PILC, Fe-PILC), it is suggested that, unlike natural soils and fish bones, there are not only single adsorption mechanisms but also adsorption mechanisms based on chemical adsorption and surface charge. In the case of fish bones, due to the relatively higher adsorption capacity than modified clays and its characteristic of significant desorption, it is expected more suitable for the removal of radionuclides in aquatic environments than for the immobilization of radionuclides in soil.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.3
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• pp.332-344
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• 1996

The vertical profiles of the natural $^{210}Po,\;^{210}Pb\;and\;^{234}Th$, activities were measured at the upper 150 m or 200 m of water column from west-east intersection in the east-southern coastal area of the Korea Peninsula during the period from 26 to 29 April 1994 to compare the removal rates (residence time) and removal processes for $^{210}Po\;and\;^{234}Th$. At the inshore stations, the $^{210}Po$ activity was generally higher in the thermocline and its under layer than in the surface mixed layer, while represented the reversed pattern at the offshore stations. However, the $^{210}Pb$ activity decreased generally with depth. Also, the activity of $^{210}Po$ relative to its parent $^{210}Pb$ was deficient in the water column above the main thermocline, but was slightly excess or close to equilibrium in the thermocline and its under layer. The vertical profiles for the activity of $^{210}Pb$ relative to its parent $^{226}Ra$ showed the reversed pattern with the vertical variation of $^{210}Po$ excess (or deficiency). The $^{234}Th$ activity was significantly lower in the surface mixed layer and thermocline than in the deeper layer. The residence time of $^{210}Po$ ranged from 1 to 4 years at the five stations except station E8 that showed yet long residence time (approximately 10 years). The long residence time at the station E8 may resulted from the thicker surface mixed layer and subsequent the vertical mixing of $^{210}Po$ which was recycled in the lower surface mixed layer compared to at the other stations. Also, the residence time of $^{210}Po$ was shorter at the inshore stations than at the offshore stations. However, the residence time of $^{234}Th$ ranged from 52 to 74 days at all station without the significant variation, was very much shorter relative to the residence time of $^{210}Po$. The correlation between the removal rate of dissolved $^{234}Th$ and the concentration of total suspended matter (TSM) was generally positive. Therefore, it seems that the major route of the removal mechanism of $^{234}Th$ from seawater in the surface mixed layer is via adsorption onto suspended particle surfaces (most likely inorganic particles) and subsequent settling to the bottom layer. Between the removal rate of dissolved $^{210}Po$ and the concentration of chlorophyll-a was positively good correlation. Consequently, most likely the removal of $^{210}Po$ may be occurred by uptake to organisms (mainly such as planktonic debris or fecal pellets) and subsequent settling.

• Korean Journal of Environmental Biology
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• v.34 no.4
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• pp.304-313
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• 2016

One of the issues currently facing nuclear power plants is how to store spent nuclear waste materials which are contaminated with radionuclides such as $^{134}Cs$, $^{135}Cs$, and $^{137}Cs$. Bioremediation processes may offer a potent method of cleaning up radioactive cesium. However, there have only been limited reports on $Cs^+$ tolerant bacteria. In this study, we report the isolation and identification of $Cs^+$ tolerant bacteria in environmental soil and sediment. The resistant $Cs^+$ isolates were screened from enrichment cultures in R2A medium supplemented with 100 mM CsCl for 72 h, followed by microbial community analysis based on sequencing analysis from 16S rRNA gene clone libraries(NCBI's BlastN). The dominant Bacillus anthracis Roh-1 and B. cereus Roh-2 were successfully isolated from the cesium enrichment culture. Importantly, B. cereus Roh-2 is resistant to 30% more $Cs^+$ than is B. anthracis Roh-1 when treated with 50 mM CsCl. Growth experiments clearly demonstrated that the isolate had a higher tolerance to $Cs^+$. In addition, we investigated the adsorption of $0.2mg\;L^{-1}$ $Cs^+$ using B. anthracis Roh-1. The maximum $Cs^+$ biosorption capacity of B. anthracis Roh-1 was $2.01mg\;g^{-1}$ at pH 10. Thus, we show that $Cs^+$ tolerant bacterial isolates could be used for bioremediation of contaminated environments.

• Clean Technology
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• v.22 no.2
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• pp.122-131
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• 2016

Caesium radioisotopes, ¹³⁴Cs and ¹³⁷Cs which come from the atmospheric nuclear tests and discharges from nuclear power plants, are very important to study artificial radioactivity. In this work, in order to lower the minimum detection activity (MDA) we investigated environmental radioactivity according to the Environment Measurement Laboratory procedure by ¹³⁷Cs and ¹³⁴Cs which is similar to chemical and environmental behaviors of ¹³⁷Cs. The environmental soils in high mountain areas near nuclear power plant were collected, and an Ammonium Molybdophosphate (AMP) precipitation method, which showed high selectivity toward Cs⁺ ions, was applied to chemically extract and concentrate Caesium radioisotopes. Radioactivity was estimated by a gamma-ray spectrometry. In gamma energy spectrum, with an increasing of ⁴⁰K radioactivity, it increased the MDA of ¹³⁴Cs and ¹³⁷Cs. Therefore, if the natural radionuclides were removed from the soil samples, the MDA of Caesium may be reduced, and the contents of ¹³⁷Cs of in the environmental soils can effectively be estimated. In the standard soil sample of Korea Institute of Nuclear Safety, radioactivity of ⁴⁰K was removed more than 84% on average, and the MDA of ¹³⁴Cs was reduced 2 times. The content of ¹³⁷Cs was recovered over 84%. On the other hand, in environmental soils, AMP precipitation method showed removal ratio of ⁴⁰K up to 180 times, which reduced the MDA about 5 times smaller than those of Direct method. ¹³⁷Cs recovery ratio showed from 54.54% to 70.06%. When considering the MDA and recovery ratio, AMP precipitation method is effective for detection of Caesium radioisotopes in low concentration.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.1
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• pp.8-13
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• 2016

This study investigated the removal of a radioactive cesium ($Cs^+$) in the water at the water treatment processes. Since cesium is mostly present as the $Cs^+$ ion state in water, it is not removed by sand filtration, and coagulation with polyaluminum chloride (PACl), powdered activated carbon (PAC) and mixture of PACl and PAC. However, it is known that the removal rate of cesium increases as the turbidity increases in raw water. As the turbidity was adjusted by 74 NTU and 103 NTU using the surrounding solids near G-water intake and yellow soils, removal rate of cesium was about 56% and 51%, respectively. In case of a GAC filtration with supernatants after jar-mixing/setting was conducted, 80% of cesium is approximately eliminated. The experimental results show that it is efficient to get rid of cesium when the turbidity of the raw water is more than 80 NTU. In case of a GAC filtration, about 60% of cesium is removed and it is considered by the effect of adsorption. Cesium is not eliminated by microfiltration membrane while about 75% of cesium is removed by reverse osmosis.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.3
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• pp.141-148
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• 2011

It is clarified in the radioactive waste transfer regulation that the concentration of radioactive waste for the major radio nuclide has to be examined when radioactive waste is guided to the radioactive waste stores. In case of the low level radioactive waste sample, the analytical results of radioactive waste concentration frequently show a value lower than minimum detectable activity (MDA). Since the MDA value basically depends on the amount of a sample, background value, measurement time, counting efficiency, and etc, it would be necessary to increase a sample amount with a intention of minimizing MDA. In order to measure a concentration of $^{129}I$ in low and medium level radioactive waste, $^{129}I$ was collected by using a distillation technique after leaching the simulated radioactive waste sample with a non-volatile acid. The recovery of $^{129}I$ measured was compared with that measured with column elution technique which is a conventional method using an anion-exchange resin. The recovery of inactive iodide by using the distillation method and column elution were found as $86.5{\pm}0.9%$ and $87.3{\pm}2.7%$, respectively. The recovery and MDA value calculated for distillation technique when 100 g of extracted solution of $^{129}I$ was taken, were found to be $84.6{\pm}1.6%$ and $1.2{\times}10^{-4}Bq/g$, respectively. Consequently, the proposed technique with simplified process lowered the MDA value more than 10 times compared to the column elution technique that has a disadvantage of limited sampling amount.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.235-243
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• 2006

In this study, an experimental study on the sorption properties of uranium(VI) onto a bentonite colloid generated from Gyeongju bentonite which is a potential buffer material in a high-level radioactive waste repository was performed as a function of the pH and the ionic strength. The bentonite colloid prepared by separating a colloidal fraction was mainly composed of montmorillonite. The concentration and the size fraction of the prepared bentonite colloid measured using a gravitational filtration method was about 5100 ppm and 200-450 nm in diameter, respectively. The amount of uranium removed by the sorption reaction bottle walls, by precipitation, and by ultrafiltration was analyzed by carrying out some blank tests. The removed amount of uranium was found not to be significant except the case of ultrafiltration at 0.001 M $NaClO_4$. The ultrafiltration was significant in the lower ionic strength of 0.001 M $NaClO_4$ due to the cationic sorption onto the ultrafilter by a surface charge reversion. The distribution coefficient $K_d$ (or pseudo-colloid formation constant) of uranium(VI) for the bentonite colloid was about $10^4{\sim}10^7mL/g$ depending upon pH and ionic strength of $NaClO_4$ and the $K_d$ was highest in the neutral pH around 6.5. It is noted that the sorption of uranium(VI) onto the bentonite colloid is closely related with aqueous species of uranium depending upon geochemical parameters such as pH, ionic strength, and carbonate concentration. As a consequence, the bentonite colloids generated from a bentonite buffer can mobilize the uranium(VI) as a colloidal form through geological media due to their high sorption capacity.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.709-717
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• 2008

Rhizofiltration for cesium uptake by sunflowers (Helianthus annuus L.) and beans (Phaseolus vulgaris var.) was investigated for groundwater contamination. The cesium removal by sunflowers was greater than 98% of the total cesium in solution, and the uptake by beans was also greater than 99% within 24 hours of the rhizofiltration, showing that the rhizofiltration has a great capability to remove cesium from the contaminated water system. Experiments at various pH of solution indicated that a solution of pH $5{\sim}9$ yielded very high cesium accumulation in two plants. From the results of the analysis for cesium accumulation in plant parts, about 80% of cesium transferred into the plant from solution was accumulated in the root part and less than 20% of cesium existed in the shoot part (including leaves). Results suggest that only the roots of the fully grown plant used for rhizofiltration should be disposed or post-treated and thus the cost and time to treat massive amounts of grown plants could be dramatically reduced when sunflower and bean are used in the real field. The results of SEM and EDS analyses indicated that the most of cesium were accumulated in the root surface as a ionic phase rather than a soil precipitation phase.