• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.397-410
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• 2018

When considering the long-term safety assessment of spent-nuclear fuel management, americium is one of the most radio-toxic actinides. Although spectroscopic methods are widely used for the study of actinide chemistry, application of those methods to americium chemistry has been limited. Herein, we purified $^{241}Am$ to obtain a highly pure stock solution required for spectroscopic studies. Quantitative and qualitative analyses of purified $^{241}Am$ were carried out using liquid scintillation counting, and gamma and alpha radiation spectrometry. Highly sensitive absorption spectrometry coupled with a liquid waveguide capillary cell and time-resolved laser fluorescence spectroscopy were employed for the study of Am(III) hydrolysis and oxalate (Ox) complexation. $Am^{3+}$ ions under acidic conditions exhibit maximum absorbance at 503 nm, with a molar absorption coefficient of $424{\pm}8cm^{-1}{\cdot}M^{-1}$. $Am(OH)_3(s)$ colloidal particles formed under near neutral pH conditions were identified by monitoring the absorbance at around 506-507 nm. The formation of ${Am(Ox)_3}^{3-}$ was detected by red-shifts of the absorption and luminescence spectra of 4 and 5 nm, respectively. In addition, considerable enhancements of the luminescence intensities were observed. The luminescence lifetime of ${Am(Ox)_3}^{3-}$ increased from 23 to 56 ns, which indicates that approximately six water molecules are replaced by carboxylate ligands in the inner-sphere of the Am(III). These results suggest that ${Am(Ox)_3}^{3-}$ is formed through the bidentate coordination of the oxalate ligands.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.341-347
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• 2013

The n-type and p-type silicon samples were exposed by 40.0, 3.98 MeV proton beams ranging between 0 to $20.0{\times}10^{13}protons/cm^2$. Coincidence Doppler Broadening Positron Annihilation Spectroscopy (CDBPAS) were applied to study of defect characteristics of p type and n type silicon samples. In this investigation the numerical analysis of the spectra was employed to the determination of the shape parameter, S, defined as the ratio between the amount of counts in a central portion of the gamma spectrum and the total counts of whole gamma spectrum. The S-parameter values strongly depend on the irradiated proton beam that indicated the defects generate more, rather than the energy intensity. 40 MeV irradiated proton beam in the n-type silicon at $20.0{\times}10^{13}protons/cm^2$ was larger defects than 3.98 MeV irradiated proton beam. It was analysis between the proton irradiation beams and the proton intensities of the irradiation. Because of the Bragg peak, SRIM results shows mainly in a certain depth of the sample to form the defect by the proton irradiation, rather than the defects to appear for the entire sample.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.968-973
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• 1998

The critical micelle concentrations($CMC^*$) of the mixed surfactant systems of cationic surfactant cetylpyridinium chloride(CPC) and nonionic surfactant Triton X-100(TX-100) in aqueous solutions of salts(KCl and $Na_2CO_3$) and isomeric butanols(tert-butanol, iso-butanol and n-butanol) were determined by UV spectroscopy method. The various thermodynamic values in aqueous solutions of salts and isomeric butanols were compared with the values in pure water, calculated by means of the equation derived from the pseudo-phase separation model. Thermodynamic parameters($X_1$, $\beta$, ${\gamma}i$, $ai^M$, $C_i$ and ${\Delta}H_{mix}$) were found to have great effects of salts and isomeric butanols on the mixed micellization of CPC/TX-100 mixtures, and also in good agreements with the nonideal mixed micelle model. They showed all negative deviations from the ideal mixed micellar behavior.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.10
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• pp.1454-1459
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• 2012

An improved detection of radiation-induced paramagnetic faults was developed to identify the irradiation status of basil and clove. The effectiveness of different sample pretreatments, including freeze-drying (FD), oven-drying (OD), alcoholic-extraction (AE), and water-washing and alcoholic-extraction (WAE), were examined. All non-irradiated samples showed a single central signal ($g_0$=2.006), whereas radicals representing two additional side peaks ($g_1$=2.023 and $g_2$=1.986) with a mutual distance of 6 mT were detected in the irradiated samples. AE and WAE produced the best results for irradiated clove in terms of intensities of radiation-specific ESR signals and their ratios to the central signal. However, FD provided the highest intensities of radiation-specific ESR signals for basil, whereas their ratios to the major signal were better in the cases of AE and WAE. Signal noise, particularly due to $Mn^{2+}$ signals, was observed, whereas it decreased in AE and WAE pretreatments. Based on our results, AE and WAE can improve the detection conditions for radiation-specific ESR signals in irradiated samples.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.643-649
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• 2016

When a cyclotron produces $^{18}F^-$, accelerated protons interact with metal parts of the cyclotron machine and induces radioactivity. Especially, the target window and chamber of the target assembly are the main parts where long-lived radionuclides are generated as they are incident by direct beams. It is of great importance to identify radionuclides induced in the target assembly for the safe operation and maintenance of a cyclotron facility. In this study, we analyzed major radionuclides generated in the target assembly by an operation of the Cyclotron 18/9 machine and measured dose rates after the operation to establish the radiation safety guideline for operators and maintenance personnel of the machine. Gamma spectroscopy with HPGe was performed on samples from the target chamber and Havar foil target window to identify the radionuclides generated during the operation for production of $^{18}F^-$- isotope and their specific activity. Also, the dose rates from the target were measured as a function of time after an operation. These data will help improve radiological safety of operating the cyclotron facilities.

• Korean Journal of Food Science and Technology
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• v.41 no.2
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• pp.131-135
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• 2009

The identification characteristics of irradiated commercial Ramen soup were investigated depending on radiation sources and doses by electron spin resonance (ESR) spectroscopy. Two commercial powder soups (RS-1, RS-2) were irradiated at 0 to 20 kGy under ambient conditions by both a Co-60 gamma irradiator and an electron beam (EB) accelerator, respectively. Crystalline sugar-induced multi-component signals with g-values of 2.010/2.011, 2.006, 2.002 and 1.999 were detected in the irradiated Ramen soup (RS-1, RS-2), whereas $Mn^{2+}$ signals were observed in non-irradiated samples, thereby distinguishing each other. Under the same analytical conditions, the intensity of ESR signals was higher in EB-irradiated samples than the gamma-irradiated ones. Determination coefficients ($R^2$) between irradiation doses and corresponding ESR responses were above 0.9665 in all the samples, and the magnetic field of specified g-value remained constant. The predominant ESR signals of $g_2$ (2.010-2.011) and $g_3$ (2.002) increased with corresponding doses of irradiation ($R^2$= 0.9750-0.9981).

• The Korean Journal of Mycology
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• v.35 no.2
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• pp.96-100
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• 2007

In order to select ${\gamma}-Linolenic$ acid (GLA)-producing fungi, a total of forty-four strains of 4 genera such as Phytophthora, Pythium, Mucor and Rhizopus were obtained from Koran Agricultural Culture Collection (KACC) and then analysed by using GC-FID and GC-MS. GLA was detected on 39 fungal strains, and the highest rate of GLA was found as 24.8% of total fatty acids on Mucor hiemalis f. sp. hiemalis KACC 40264. Total GLA content of Zygomycota was comparatively high - Mucor (14.2%) and Rhizopus (14.3%), whereas that of Oomycetes was low - Phytophthora (3.3%) and Pythium (3.0%). Moreover, total fatty acids of the Zygomycota fungi such as Mucor (15.4 mg/100 ml) and Rhizopus (7.1 mg/100 ml) were higher compared with the Oomycetes such as Phytophthora (2.6 mg/100 ml) and Pythium (4.5 mg/100 ml). Thus, two genera such as Mucor and Rhizopus have higher potential as an useful microbial resource. The total fatty acid content varies even within the strains of the same genus e.g. Mucor. M. blumbeus KACC 40935 showed the highest values on productivity (18.2%) of GLA and total fatty acid contents (50.8 mg/100 ml liquid medium).

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.435-441
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• 2012

The direct conversion of cellulose into polyols in $H_2$ was examined over Pt catalysts supported on various zeolites, viz., mordenite, Y, ferrierite, and ${\beta}$. For comparison, Pt catalysts supported on ${\gamma}-Al_2O_3$, $SiO_2-Al_2O_3$, and $SiO_2$ were also tested. The physical properties of the catalysts were probed with $N_2$ physisorption. The surface acidity was measured with temperature programmed desorption of ammonia ($NH_3$-TPD). The Pt content was quantified with inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The Pt dispersion was determined with CO chemisorptions and transmission electron microscopy (TEM). The conversion of cellulose appeared to be mainly dependent on the reaction temperature and reaction time because it depends on the concentration of $H^+$ ions reversibly formed in hot water. Pt/H-mordenite (20) showed the highest yield to polyols among the tested catalysts. Pt/H-zeolite was superior to Pt/Na-zeolite for this reaction. The polyol yield was dependent on the surface acid density and the external surface area.

• Geophysics and Geophysical Exploration
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• v.22 no.3
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• pp.149-159
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• 2019

Borehole elemental concentration logging, measuring neutron-induced gamma rays by inelastic scattering and neutron capture interactions between neutron and formation, delivers concentrations of the most common elements found in the minerals and fluids of subsurface formation. X-ray diffraction and X-ray fluorescence analysis from core samples are traditionally used to understand formation composition and mineralogy, but it represents only part of formations. Additionally, it is difficult to obtain elemental analysis over the whole intervals because of poor core recovery zones such as fractures or sand layers mainly responsible for groundwater flow. The development of borehole technique for in situ elemental analysis plays a key role in assessing subsurface environment. Although this technology has advanced consistently starting from conventional and unconventional resources evaluation, it has been considered as exclusive techniques of some major service company. As regards domestic research and development, it has still remained an unexplored field because of some barriers such as the deficiency of detailed information on tools and calibration facility for chemistry and mineralogy database. This article reviews the basic theory of spectroscopy measurements, system configuration, calibration facility, and current status. In addition, this article introduces the domestic researches and self-development status on borehole elemental concentration tools.

• Nuclear Engineering and Technology
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• v.41 no.5
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• pp.723-728
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• 2009

The response property of the CZT detector ($5{\times}5{\times}5\;mm^3$), widely used in photon spectroscopy, was evaluated by considering the charge collection efficiency, which depends on the interaction position of incident radiation, A quantitative analysis of the energy spectra obtained from the CZT detector was also performed to investigate the tail effect at the low energy side of the full energy peak. The collection efficiency of electrons and holes to the two electrodes (i.e., cathode and anode) was calculated from the Hecht equation, and radiation transport analysis was performed by two Monte Carlo codes, Geant4 and MCNPX. The radiation source was assumed to be 59.5 keV gamma rays emitted from a $^{241}Am$ source into the cathode surface of this detector, and the detector was assumed to be biased to 500 V between the two electrodes. Through the comparison of the results between the Geant4 calculation considering the charge collection efficiency and the ideal case from MCNPX, an pronounced difference of 4 keV was found in the full energy peak position. The tail effect at the low energy side of the full energy peak was confirmed to be caused by the collection efficiency of electrons and holes. In more detail, it was shown that the tail height caused by the charge collection efficiency went up to 1000 times the pulse height in the same energy bin at the calculation without considering the charge collection efficiency. It is, therefore, apparent that research considering the charge collection efficiency is necessary in order to properly analyze the characteristics of CZT detectors.