• Nuclear Engineering and Technology
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• v.14 no.3
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• pp.103-109
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• 1982

An empirical formula for determining water content as functions of uranium concentration and nitric acid normalities in uranyl nitrate solutions has been derived from a least-squares analysis of experimental data, i.e., uranium concentration, nitric acid normalities and solution densities for a large number of UO$_2$(NO$_3$)$_2$ solutions. The formula derived is Q=1-0.3628C-0.0327H$^{+}$ where Q, C, and H$^{+}$ stand for water content (g/cc), uranium concentration (g/cc), ana nitric acid normality, respectively. Atom number densities and nuclear criticality for hypothetical uranyl nitrate solutions have been calculated by using the empirical formula, ana compared with the results obtained on the basis of uranium concentration, nitric acid normality, and solution density. The empirical formula derived in this study seems to be useful in uranium concentrations ranging from 0.295g/cc down to 0.004g/cc and nitric acid normality from 5.06 to 1.00..00.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.83-90
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• 2011

Removal of dissolved uranium by D. baculatum, a sulfate-reducing bacterium, and effects of trace metals such as manganese, copper, nickel, and cobalt were investigated. Total concentrations of dissolved uranium and trace metals were used by $50\;{\mu}M$ and $200\;{\mu}M$, respectively. Most dissolved uranium decreased up to a non-detectable level (< 10 ppb) MS during the experiments. Most of the heavy metals did nearly not affect the bioremoval rates and amounts of uranium, but copper restrained microbial activity. However, it is found that dissolved uranium rapidly decreased after 2 weeks, showing that the bacteria can overcome the copper toxicity and remove the uranium. It is observed that nickel and cobalt were readily coprecipitated with biogenic mackinawite.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.4
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• pp.196-203
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• 2004

To understand the geochemical processes in the Han River Estuary, distributions and behaviors of nutrients, dissolved organic matters, and uranium were investigated and analyzed during estuarine tidal mixing in June 2000 and February 2001. The distribution of inorganic nutrients showed very dynamic distributional patterns implying an apparent nitrification process and a concave non-conservative mixing along the salinity gradient. Dissolved organic carbon was high in the upstream region and decreased sharply in the low salinity region of around 5 psu. The 3-D fluorescence characteristic of dissolved organic matter showed two distinct fluorophores in the study area. Biomacromolecules originated mainly from the indigenous biochemical processes and geomacromolecules from terrestrial humic materials. In the study area, the distribution of geomacromolecule showed a concave non-conservative property along the salinity gradient presumably due to the flocculation and removal processes in the estuary. Meanwhile, distribution of the dissolved uranium, mainly in the form of stable uranium carbonate complex, also showed a concave non-conservative property along the salinity gradient in the Han River Estuary. From this study, the removal rate of dissolved uranium in the Han River Estuary was estimated to be about 7.1 ton per year.

• Journal of Radiation Protection and Research
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• v.11 no.1
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• pp.22-28
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• 1986

Densities of a large number of mixed uranyl nitrate-thorium nitrate solutions were measured with pycnometer. By the least squares analysis of the experimental result, an empirical formula for determining water content of mixed uranyl nitrate-thorium nitrate solutions as functions of uranium concentration, thorium concentration and nitric acid normality is derived; $W=1.0-0.358\;C_u-0.4538\;C_{Th}-0.0307\;H^+$ where $W,\;C_u,\;C_{Th},\;and\;H^+$ stand for water content(g/cc), uranium concentration (g/cc), thorium concentration (g/cc), and nitric acid normality, respectively. Water contents of the mixed uranyl nitrate-thorium nitrate solutions are calculated by using the empirical formula, and compared with the values calculated by Bouly's equation in which an additional data, solution density, is required. The two results show good agreements within 2.7%.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.1
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• pp.33-38
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• 2009

An experiment for uranium sorption onto fresh and weathered biotites was performed. After centrifugation, concentrations of uranium in the supernatants were analyzed using ICP-MS, and biotite samples were investigated using XRD and SEM. With powdered biotites (<3 mm in size), we have conducted uranium sorption experiments about fresh and weathered biotites to obtain uranium sorption amounts in various pH conditions. The uranium sorption was not high at a low pH (e.g., pH 3), but increased with increasing pH. There were lower uranium sorption by the weathered biotites than by the fresh ones, and the difference was much larger at higher pH (e.g., pH 11). The lower sorption values of uranium by the weathered biotites may be caused by a change of mineral surfaces and a chemical behavior of surrounding dissolved elements. It seems that the uranium-mineral interaction has been diminished, especially, in the weathered biotite by a destruction and dissolution of preferential sorption sites on the mineral surfaces and by the colloidal formation from dissolved elements.

• Journal of the Mineralogical Society of Korea
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• v.23 no.2
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• pp.107-115
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• 2010

Removal and mineralization of dissolved uranium by bacteria in KURT (KAERI Underground Research Tunnel), Korea Atomic Energy Research Institute (KAERI) was investigated. Two different bacteria, IRB (iron-reducing bacteria) and SRB (sulfate-reducing bacteria) was used, and minerals formed by these bacteria were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Compared to uranyl ions, ferric ions were preferentially reduced by IRB, showing that there is no significant reduction and removal of uranium. However, uranium concentration considerably decreased by addition of Mn(II). Results show that a sulfide mineral such as mackinawite (FeS) is formed by SRB respiration through combination of Fe(II) and S without manganese sulfide formation. In the presence of Mn(II), however, uranium is removed effectively, suggesting that the sorption and incorporation of uranium could be affected by Mn(II) onto the sulide minerals.

• Economic and Environmental Geology
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• v.43 no.3
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• pp.223-233
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• 2010

The effects of extracellular polymeric substances (EPS) of Pseudomonas aeruginosa on adsorption and redox state alteration of dissolved As, Cr and U were investigated through batch experiments. Surfaces of bacterial cells were either vigorously washed or unwashed. Solutions of As(V), Cr(VI) and U(VI) were inoculated with the bacterial cells under no nutrient condition, and total aqueous concentrations and redox state alteration were monitored over time. No As adsorption occurred onto bacteria or EPS; however, unwashed bacteria reduced about 60% As(V) to As(III). Unwashed bacteria also led to removal of 45% total dissolved Cr and reduction of 64% Cr(VI). About 80% U(VI) was removed from solution with unwashed bacteria as well. Such electrochemical reduction of the elements was likely due to reducing capacity of EPS itself or detoxifying reduction of the bacteria which kept their viability under protection of EPS. The results indicated that bacterial biofilm may significantly control the redox state and subsequent mobility of As, Cr and U in natural geologic settings.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.1
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• pp.63-72
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• 2020

Dissolved hexavalent uranium can exist in the form of several different chemical species. Furthermore, species distributions depend on the pH value of the aqueous solution. Representatively, UO₂²⁺, UO₂OH⁺, (UO₂)₂(OH)₂²⁺, and (UO₂)₃(OH)₅⁺ species coexist in solutions at acidic and circumneutral pH values. When amorphous silica particles are suspended in an aqueous solution, the dissolved chemical species are easily adsorbed onto silica surfaces. In this study, it was examined whether the species distribution of the adsorbed U(VI) on a silica surface followed that of the dissolved U(VI) in an aqueous solution. Time-resolved luminescence spectra of three different dissolved species (UO₂²⁺, UO₂OH⁺, and (UO₂)₃(OH)₅⁺) and two different adsorbed species (≡SiO₂UO₂, ≡SiO₂(UO₂)OH^-, or ≡SiO₂(UO₂)₃(OH)^5-) were measured in the pH range 3.5-7.5. The spectral shapes of these chemical species were compared by changing the pH value; consequently, it was confirmed that the species distribution of the adsorbed U(VI) species was different from that of the dissolved U(VI) species.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.4
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• pp.347-352
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• 2005

This research was focused on the distribution of Uranium-238 concentration in the Han River. Also, six water treatment plants in Seoul have been investigated to find out the behaviour and the removal capability of uranium. The uranium concentrations were ranged $0.02{\sim}0.54{\mu}g/L$ in the Han River. The relationship between conductivity and total dissolved solids shows that uranium concentration is positively related with conductivity and total dissolved solids. In addition, it has been founded that there was no relevance between uranium concentration and geological structure, because most of the sampling area are Banded Gneiss. The average uranium concentration in six water treatment plants was determined to $0.134\;{\mu}g/L$ in raw water, $0.050\;{\mu}g/L$ in coagulated water, $0.029\;{\mu}g/L$ in settled water, $0.020\;{\mu}g/L$ in filtered water, $0.019\;{\mu}g/L$ in finished water. After filtration in the treatment process, uranium concentration level was maintained lower than $0.029\;{\mu}g/L$. The average uranium removal efficiency compared to the raw water was 63% after coagulation, 15% after sedimentation, 8% after filtration and disinfection. The analysis shows that 78% of uranium in the raw water was removed during coagulation and sedimentation processes. However, 8% of that was removed through filtration and chlorination processes.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.77-85
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• 2018

There would be a possibility of uranium contamination around the nuclear power plants and the underground waste disposal sites, where the uranium could further migrate and diffuse to some distant places by groundwater. It is necessary to understand the biogeochemical behaviors of uranium in underground environments to effectively control the migration and diffusion of uranium. In general, various kinds of microbes are living in soils and geological media where the activity of microbes may be closely connected with the redox reaction of nuclides resulting in the changes of their solubility. We investigated the adsorption and precipitation behaviors of dissolved uranium on some solid materials using hydrogen gas as an electron donor instead of organic matters. Although the effect of hydrogen gas did not appear in a batch experiment that used granite as a solid material, there occurred a reduction of uranium concentration by 5~8% due to hydrogen in an experiment using bentonite. This result indicates that some indigenous bacteria in the bentonite that have utilized hydrogen as the electron donor affected the behavior (reduction) of uranium. In addition, the bentonite bacteria have showed their strong tolerance against a given high temperature and radioactivity of a specific waste environment, suggesting that the nuclear-biogeochemical reaction may be one of main mechanisms if the natural bentonite is used as a buffer material for the disposal site in the future.