• Journal of Korean Society of Environmental Engineers
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• v.38 no.1
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• pp.42-46
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• 2016

The radioactive iodine ($^{131}I$) presents in the environment through the excrete process of nuclear medicine patients. In the detecting of low level of $^{131}I$ in the public water, the counting uncertainty has an effect on the accuracy and reliability of detecting $^{131}I$ radioactivity concentration. In this study, the contribution of sample amount, radioactivity concentration and counting time to the uncertainty was investigated in the case of public water sample. Sampling points are public water and the effluents of a sewage treatment plant at Sapkyocheon stream, Geumgang river. In each point, 1, 10 and 20 L of liquid samples were collected and prepared by evaporation method. The HPGe (High Purity Germanium) detector was used to detect and analyze emitted gamma-ray from samples. The radioactivity concentration of $^{131}I$ were in the range of 0.03 to 1.8 Bq/L. The comparison of the counting uncertainty of the sample amount, 1 L sample is unable to verify the existence of the $^{131}I$ under 0.5 Bq/L radioactivity concentration. Considering the short half-life of $^{131}I$ (8.03 days), a method for measuring 1 L sample was used. However comparing the detecting and preparing time of 1, 10 L respectively, detecting 10 L sample would be an appropriate method to distinguish $^{131}I$ concentration in the public water.

• 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.

• Food Science and Preservation
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• v.19 no.2
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• pp.249-256
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• 2012

The changes in the volatile organic compounds in plum after its electron beam irradiation and storage were determined using the simultaneous distillation extraction method and gas chromatograph-mass spectrometry. There were 44, 46, 45, 47, and 38 volatile compounds in the 0-, 0.25-, 0.5-, 0.75-, and 1 kGy irradiated samples, respectively. Also, the volatile flavor components of the plum that was stored for 30 days were identified as 48, 40, 40, 39, and 40 components. The compositions of the volatile compounds of the control and irradiated samples showed a similarity after the storage. Especially, the more important volatile flavor of the plum was identified as hexanal of the C6compounds, (E)-2-hexenal and (Z)-3-hexenal. In particular, hexanal, (E)-2-hexenal, and (Z)-3-hexen-1-ol increased in all the doses, where as hexanol and (E)-2-hexen-1-ol decreased. Among the lactone compounds, ${\gamma}$-hexalactone, ${\gamma}$-octalactone, and ${\gamma}$-decalactone were identified during the storage period in the raw samples. Hexanonic acid and 2-hexenoic acid were not identified during the storage of the samples, and 2-methylprrole was detected only when the storage samples were irradiated at a dose higher than 0.5kGy. Therefore, it was shown that there was no effect on the variation of the volatile organic component suntil 1 kGy in the plum was irradiated with an electron beam.

• Food Science and Preservation
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• v.24 no.3
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• pp.394-405
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• 2017

This study was conducted to confirm the usefulness of essential oil components in yuzu and kumquat cultivated in Korea for comparison with those in lemon and lime. The volatile flavor compounds in citrus fruits (yuzu, kumquat, lemon and lime) were extracted for 3 h with 100 mL redistilled n-pentane/diethylether (1:1, v/v) mixture, using a simultaneous steam distillation and extraction apparatus (SDE). The volatile flavor compositions of the samples were analyzed by gas chromatography-mass spectrometry (GC-MS). The aroma compounds analyzed were 104 (3,713.02 mg/kg) in yuzu, 87 (621.71 mg/kg) in kumquat 103 (3,024.69 mg/kg) in lemon and 106 (2,209.16 mg/kg) in lime. Limonene was a major volatile flavor compound in four citrus fruits. The peak area of limonene was 35.03% in yuzu, 63.82% in kumquat, 40.35% in lemon, and 25.06% in lime. In addition to limonene, the major volatile flavor compounds were ${\gamma}$-terpinene, linalool, ${\beta}$-myrcene, (E)-${\beta}$-farnesene, ${\alpha}$-pinene and ${\beta}$-pinene in yuzu, and ${\beta}$-myrcene, ${\alpha}$-pinene, (Z)-limonene oxide, (E)-limonene oxide, geranyl acetate and limonen-10-yl acetate in kumquat. Furthermore, ${\gamma}$-terpinene, ${\beta}$-pinene, ${\beta}$-myrcene, geranyl acetate, neryl acetate and (Z)-${\beta}$-bisabolene in lemon and ${\gamma}$-terpinene, ${\beta}$-pinene, (Z)-${\beta}$-bisabolene, neral, geranial and neryl acetate in lime were also detected. As a result, it was confirmed that the composition of volatile flavor compounds in four citrus fruits was different. Also, yuzu and kumquat are judged to be worthy of use alternatives for lemon and lime widely used in the fragrance industry.

• Analytical Science and Technology
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• v.30 no.5
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• pp.252-261
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• 2017

Naturally occurring radioactive materials (NORMs) increase radiation exposure to the public as these materials are concentrated through artificial manufacturing processes by human activities. This study focuses on the development of a method for the quantitative analysis of $^{232}Th$, $^{235}U$, and $^{238}U$ in building materials. The accuracy and precision of inductively coupled plasma mass spectrometry (ICP-MS) for determination of digestion processes was evaluated for certified reference materials (CRMs) digested using various mixed acid (e.g., aqua regia, hydrofluoric acid, and perchloric acid) digestions and a $LiBO_2$ fusion method. The method validation results reveal that a $LiBO_2$ fusion and $Fe(OH)_3$ co-precipitation should be applied as the optimal sample digestion process for the quantitative analysis of radionuclides in building materials. The radioactivity of $^{232}Th$, $^{235}U$, and $^{238}U$ in a total of 51 building material (e.g., board, brick, cement, paint, tile, and wall paper) samples was quantitatively analyzed using an established process. Finally, the values of $^{238}U$ and $^{232}Th$ radioactivity were comprehensively compared with those from the indirect method using ${\gamma}$-spectrometry.

• Korean Journal of Food Science and Technology
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• v.42 no.6
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• pp.699-704
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• 2010

Rapeseed oil was stored under different conditions such as in the dark, with UV treatment, and with prooxidantscytochrome C and copper ion. The rapeseed oils stored at different temperatures were analyzed by a mass spectrometrybased electronic nose and discriminant function analysis (DFA). Volatile components in the rapeseed oil increased with storage time, and the discriminant function first score (DF1) moved from a positive position to a negative position as storage time increased. Changes in DF1 were higher under UV treatment than under the dark condition (DF1: $r^2$=0.9481, F=307.03). The different DF1 values (F1) under the dark condition were 0.099, 0.187, and 0.278 as storage temperature increased. The different values under UV treatment were 0.554, 0.588, and 0.542, as storage temperature increased from 4 to $26^{\circ}C$. As concentrations of prooxidants copper ion and cytochrome C increased, amounts of volatile components also increased. These were confirmed by DFA. Furthermore, changes in responses at each ion fragment agreed with reported results for GC/MS, which formed after rancidity of the oil, including pentane, pentanal, 1-pentanol, hexanal, n-octane, 2-hexenal, heptanal, 2-heptenal, decane, 2-octenal, undecane, and dodecane.

• 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 Chemical Society
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• v.17 no.1
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• pp.20-24
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• 1973

The average fission neutron cross sections were determined for the following reactions, $^{93}Nb(n,\alpha)^{90}Y$, $^{90}Zr(n,p)^{90}Y$,$^{93}Nb(n,\alpha)^{90m}Y$and$^{90}Zr(n,p)^{90m}Y$. The cation exchange column was used for the quantitative separation of the product nuclides using $\alpha-$hydroxyisobutyric acid as the eluent. The absolute activites of $^{90m}Y$ and $^{90}Y$were determined by the gamma ray spectrometry and a calibrated $2\pi$gas flow counter, respectively. The cross sections of $^{93}Nb(n,\alpha)^{90}Y$, $^{90}Zr(n,p)^{90}Y$,$^{93}Nb(n,\alpha)^{90m}Y$and $^{90}Zr(n,p)^{90m}Y$ reactions were found to be$0.14\pm0.01mb$, $0.83\pm0.02mb$, $0.018\pm0.02mb$ and $0.33\pm0.02mb$, respectively. The possible use of $^{90m}Y$ instead of $^{90}Y$ was discussed as a better means for the determination of niobium.

• Journal of the Korean Society of Radiology
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• v.12 no.5
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• pp.557-563
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• 2018

Coincidence summing correction effects are known to be greater as the efficiency of the detector increases and as the distance between the source and the detector increases. A point source($^{60}Co$) was used to vary the distance in the direction of the detector's center axis and in the radial direction to obtain the P/T ratio for Coincidence summing correction calibration. In this study, values for coincidence summing corrected calibration of the values in the central and radial directions were applied to the mixed volume source(450 ml CRM source) to compare the overall peak efficiency change according to P/T with Geant4. In addition, the efficiency obtained from the mapping method is applied to the seaweed, a marine sample, and the compatibility of the P/T ratio with the detector and sample very dose together. The efficiency corrected to 1,836 keV was applied to the energy zone affected by the efficiency of 500 keV and the relative error of the measured and corrected values was well matcched by the 3.2 % peak efficiency correction. As with 450 mL CRM source, the larger the volume, the lower the P/T ratio was by ${\pm}5%$. This is due to the increased scattering of gamma-rays emitted as the source becomes farther away from the detector, and this change in P/T has been confirmed to affect the Coincidence summing corrected peak efficiency.

• Applied Biological Chemistry
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• v.37 no.1
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• pp.1-8
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• 1994

This study was carried out to investigate the changes in volatile constituents concerning with the flavor of the green ginger (Zingiber officinale Roscoe) during storage in underground pit ($15^{\circ}C$, RH 95%). And the constituents of essential oil of etiolated shoots formed on the mother rhizomes during the five months storage in the dark under same conditions were compared with those of mother rhizomes. The essential oils of Korean domestic ginger (Bong-dong cultivar) were isolated by simultaneous steam distillation and extraction method (SDE). Then the compositions of the essential oils were analysed by GC and GC-MS spectrometry. The major compounds of essential oil from the fresh rhizomes were zingiberene, $citronellol+{\beta}-sesquiphellandrene$, ${\beta}-phellandrene$, camphene, geranial, ${\gamma}-bisabolene$, ar-curcumene+geranyl acetate, ${\alpha}-pinene$, ${\beta}-gurjunene$, limonene and neral. The content of monoterpene hydrocarbons increased with a concomitant lowering in the amounts of sesquiterpene hrdrocarbons and oxygenated sesquiterpenes during storage of rhizomes although contents of the oxygenated monoterpens changed little or slightly during the storage. During the storage the content of such monoterpenes as camphene, ${\beta}-phellandrene$ and citral (neral and geranial) increased whereas the content of such sesquiterpenes as zingiberene and $citronellol+{\beta}-sesquiphellandrene$ decreased. The composition of shoot oil differed from that of mother rhizome oil in having higher content of terpene hydrocarbons and also in the higher content of bornyl acetate, ${\beta}-gurjunene$ and ar-curcumene+geranyl acetate and lower in citral (neral and geranial).