• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.119-120
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• 2004

A study on the selective adsorption of uranium(VI) from a high concentration of chemical salts has tern peformed to investigate the uranium removal mechanisms and the application conditions of the electrosorption technique using the activated carbon fiber(ACF) as a good conductive electrosorption adsorbent. Electrosorption test were carried out using an electrochemical cell.(omitted)

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.2
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• pp.129-138
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• 2011

Performance changes of an anode-supported tubular SOFC including current collectors are analyzed at different current collecting methods using numerical simulation. From the two dimensional numerical model of the solid oxide fuel cell with nickel felts as anodic current collectors and silver wires as cathodic ones, the performance curves and the distributions of temperature, concentration, current density are obtained. Also, the voltage loss of the cell is divided into three parts: activation loss, concentration loss and ohmic loss. The results show that the performance change of the cell is dominantly influenced by the ohmic loss. Although the temperature and concentration distributions are different, the total activation loss and concentration loss are nearly same. And the ohmic loss is divided into each parts of the cell components. The ohmic loss of the anodic current collectorreaches about 60~80% of the cell's total ohmic loss. Therefore, the reduction of the ohmic loss of the anodic current collector is very important for stack power enhancement. It is also recommended that the load should be connected to the both ends of the anodic current collector.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.3
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• pp.367-386
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• 2021

The overestimation and underestimation of the radioactivity concentration of difficult-to-measure radionuclides can occur during the implementation of the scaling factor (SF) method because of the uncertainties associated with sampling, radiochemical analysis, and application of SFs. Strict regulations ensure that the SF method as an indirect method does not underestimate the radioactivity of nuclear wastes; however, there are no clear regulatory guidelines regarding the overestimation. This has been leading to the misuse of the SF methodology by stakeholders such as waste disposal licensees and regulatory bodies. Previous studies have reported instances of overestimation in statistical implementation of the SF methodology. The analysis of the two most popular linear models of the SF methodology showed that severe overestimation may occur and radioactivity concentration data must be dealt with care. Since one major source of overestimation is the use of minimum detectable activity (MDA) values as true activity values, a comparative study of instrumental techniques that could reduce the MDAs was also conducted. Thermal ionization mass spectrometry was recommended as a suitable candidate for the trace level analysis of long-lived beta-emitters such as iodine-129. Additionally, the current status of the United States and Korea was reviewed from the perspective of overestimation.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.314-314
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• 2016

In this paper, the effects of carrier concentration on dielectric constant of ITO films were investigated by spectroscopic ellipsometry. From SE results, we find the pronounced shift of the ${\varepsilon}1$ peaks toward high energy with concentration; while contrarily, the ${\varepsilon}2$ values at low energy region increases with decreasing concentration. These shifts are attributed to the Burstein-Moss and free-carrier absorption effects within ITO films. With increases carrier concentration, the values of extinction coefficients show quite different behaviors in range of wavelength from 200 to 1200 nm. The reduction in k at ${\lambda}{\leq}500nm$, while increasing at ${\lambda}{\geq}500nm$ was observed. The QE of HJ solar cells behaviors can be roughly classified into two regions: short-wavelengths (${\leq}650nm$) and long-wavelengths region (${\geq}650nm$). With increasing carrier concentration as well as energy band gap, QE shows improvement at short-wavelength, while at long-wavelength QE shows opposite trend. Widening band gap energy due to Burstein-Moss shift is the key to improve QE in short-wavelength; simultaneously FCA effect due to optical scattering is attributed to the reduction in QE at long-wavelength. In spite of band gap extension, Jsc calculated from QE decreases from 34.7 mA/cm2 to 33.2 mA/cm2 with increasing carrier concentration. It demonstrated that FCA effect may more govern Jsc in the HJ solar cells.

• Journal of the Korean Society of Safety
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• v.10 no.2
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• pp.84-91
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• 1995

The characteristics of critical spontaneous ignition of granulated activated carbon were investigated In atmospheres of differing oxygen concentration. At the same concentration the larger vessels yielded the lower critical spontaneous ignition temperature. At the same vessel, as the concentration of oxygen was reduced, Ignition occurred later and at higher ambient temperature, and critical spontaneous ignition temperature increased. The apparent activation energy calculated from the Frank-Kamenetskii's ignition theory appeared to be the slight different value respectively and the mean apparent activation energy was 19850㎈/㏖.

• Journal of the Korean Society of Radiology
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• v.10 no.3
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• pp.171-180
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• 2016

This study was to evaluate the change in characteristics of concentration of ozone after exposure to high energy radiation in linac room. Background ozone concentration of linac room was measured and compared to ozone concentration around linac room. Background ozone concentration of linac room was mean $17.4{\pm}7.9ppb$. It was 50% of the ozone concentration($36.8{\pm}22.3ppb$) around linac room(p<0.05). The concentration of ozone after exposure to high energy radiation in linac room was elevated to double of background ozone level, intensity after exposure. with exposure time concentration of ozone increased proportionally. It showed maximum level at 130~180seconds and slowed a tendency to saturate. It required more than 10 minutes for ozone concentration in linac room to drop to ozone concentration around linac room. The concentration of ozone after exposure to high energy radiation is high enough to cause specific physical symptoms, such as acute dyspnea or chest pain due to dry cough. Exposure to high concentration of ozone in sealed linac room can aggravate pulmonary disease, so special attention is needed.

• Nuclear Engineering and Technology
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• v.28 no.5
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• pp.500-505
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• 1996

At the reference plant(Wolsong unit No. 1) a manual poison sampling system is provided to periodically sample gadolinium from each tank and analyze it in the laboratory to provide assurance that adequate poison concentration in each tank is maintained. The AECB required a continuous, on-line monitoring system. On Wolsong unit No. 2, process piping adapter and new instrument loops added to the Liquid Injection Shutdown System(LISS) which is part of SDS2. The new instrument loops continuously monitor SDS2 poison conductivity and initiate an alarm when the poison concentration is too low.

• Solar Energy
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• v.19 no.1
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• pp.37-45
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• 1999

As polymer added in flow, the phenomenon of drag reduction effect was found by many experiments and studies. We divided polymer into three molecular weight($2{\times}10^5,\;4{\times}10^5,\;5{\times}10^5$) and into four concentration(1, 5, 10, 20wppm), then we measured the drag reduction effect in the range Reynolds Number with $30000{\sim}60000$. Finally we found that the most effect drag reduction was that molecular weight is $2{\times}10^5$ with 10wppm concentration. Then the concentration was according to PEO molecular weight, and in general DR increase according to Reynolds Number.

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.57-61
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• 2002

This paper presents development of a SEC(Solar Energy Concentration) utilizing the concentrated solar beam radiation for joining engineering thermoplastics such as Acrylonitrile/Butadiene/Styrene(ABS), Polycarbonate(PC) and Polymethylmethacrylate (PMMA). In addition, to study the joining of the materials, necessary experimentation with applying primer was performed. Tensile tests were conducted to determine the bond strength achieved at the specimen Joint interface. Microscopic examinations of the fractured joints were performed in order to analyze the overall bond quality. Finally, the results in terms of bond strength achieved at the joint interface and energy consumed in the process was compared with those obtained with similar thermoplastic joining technique utilizing microwave energy.

• Journal of Radiation Protection and Research
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• v.20 no.2
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• pp.123-128
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• 1995

The concentration of Cs-137 and Sr-90 has been analyzed in soils around Taejon region. A correalation was found between the concentration of Cs-137 and the organic matter content. The mean value of Cs-137 was 14.37Bq/kg-dry and that of Sr-90 was 7.95Bq/kg-dry in undisturbed soils around Taejon region. The concentration ratio of Cs-137/Sr-90 was 1.99. The distribution of Cs-137 and Sr-90 was similar to cumulative fallout level and had been more affected by nuclear weapons test than by the chernobyl accident.