• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1210-1217
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• 2021

The analysis of ⁴¹Ca in concrete generated from the nuclear facilities decommissioning is critical for ensuring the safe management of radioactive waste. An analytical method for the determination of ⁴¹Ca in concrete is described. ⁴¹Ca is a neutron-activated long radionuclide, and hence, for accurate analysis, it is necessary to completely extract Ca from the concrete sample where it exists as the predominant element. The decomposition methods employed were the acid leaching, microwave digestion, and alkali fusion. A comparison of the results indicated that the alkali fusion is the most suitable way for the separation of Ca from the concrete sample. Several processes of hydroxide and carbonate precipitation were employed to separate ⁴¹Ca from interferences. The method relies on the differences in the solubility of the generated products. The behavior of Ca and the interfering elements such as Fe, Ni, Co, Eu, Ba, and Sr is examined at each separation step. The purified ⁴¹Ca was measured by a liquid scintillation counter, and the quench curve and counting efficiency were determined by using a certified reference material of known ⁴¹Ca activity. The recoveries in this study ranged from 56 to 68%, and the minimum detectable activity was 50 mBq g^-1 with 0.5 g of concrete sample.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.200-205
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• 1999

In the ferromagnetic phase with electrons for La$_{1-x}$(Ca or Sr)$_x$MnO$_3$, films, a remnant resistivity of the order of 10$^{-8}$ ${\omega}$m is observed up to 100 K and increases exponentially with temperature up to T$_c$ and above one Tesla as a function of magnetic field strength (a positive magnetoresistivity). The phase below T$_c$ is regarded as a polaronic state with a polaronic tunneling conduction. Possible p-wave condensation (or superconductor) with a parabolic density of states and the phase separation are discussed on the basis of the two-fold degeneracy of ${\varrho}_{\delta}$ orbitals.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.309-310
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• 2005

Some minor elements(Al, B, Ba, Ca, Cd, Co, Cr, Cu, Gd, Mg, Mn, Mo, Nd, Ni, P, Pb, Si, Sn, Sr, Ti, V, Yb, Zn and Zr) in iron compounds such as the S/G sludge of a power plant were separated from iron by anionic and cationic exchange methods. If a ICP-AES or AAS determination follows this method, minor elements of more than 2 or 20 ppm of Fe can be determined with an error less than 20% except Sn and Mo. Alkaline elements were excluded from this study since they can be easily recovered from an anionic exchange. Application to real sludge samples is ongoing.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.84-85
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• 2002

Recently doped perovskite manganites have renewed interest because they exhibit a variety of unique magnetic and electronic behaviors such as colossal magnetoresistance (CMR), percolative phase separation, spin/charge/orbital ordering, and so on. For this reason, fabrication of thin films with the best surface morphology and controlling their magneto transport properties is essential for making magneto-resistive devices. (omitted)

• Analytical Science and Technology
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• v.13 no.5
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• pp.601-607
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• 2000

Lanthanum has been used as one of the burnup monitor in spent nuclear fuel. $U_3Si/Al$ spent nuclear fuel contains small amount of La in high concentration of U and Al. Therefore, chemical separation of La is required to remove matrix elements. At first, ion chromatography (IC) and inductively coupled plasma systems were installed in radiation shielded glove box to handle the radioactive samples. Retention behavior of uranium, aluminum, lanthanum and some interesting fission products (Sr, Zr, Y, Mo, Ru, Pd, Rh, Cs, Ba, Ce, Pr, Nd, Sm, Eu and Cd) was investigated using the CG10 column and ${\alpha}$-HiBA eluent. As all elements were eluted earlier than lanthanum in 0.2 M ${\alpha}$-HiBA eluent, a portion of U and Al was directly passed to waste using a three way valve between the column and the nebulizer. Thus it was possible to determine the lanthanum in a high concentration of U and Al matrix. Retention time of La was about 12 minutes in this separation condition. Optimum range for the determination of La in $U_3Si/Al$ spent nuclear fuel was $1-10{\mu}g/L$ (ppb) with this system and detection limit was $0.25{\mu}g/L$ in case of $200{\mu}L$ of sample volume.

• Analytical Science and Technology
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• v.13 no.4
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• pp.446-452
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• 2000

The simulated nuclear spent fuel (SIMFUEL) containing the platinum group elements which will not be dissolved in a nitric acid was completely dissolved with a acid digestion bomb. The metallic elements separated in the SIMFUEL were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). Because the peaks of metallic elements were spectrally interfered by uranium spectrum, uranium and metallic elements were separated by cation exchange resin for Mo, Pd, Rh and Ru and by anion exchange resin for Ba, Ce, La, Nd, Rh, Sr, Y and Zr, respectively. The recovery of Mo, Pd, Rh and Ru after separation by cation exchange chromatography found to be 99-103% and anion exchange separation showed 96.5-107% of recovery except Y with the simulated solution whose concentration was similar to the spent nuclear fuel. The relative standard deviation of this method showed 1.3-6.7% in the SIMFUEL whose concentrations of metallic elements were between several $10^2-10^3$ppm.

• The Journal of the Petrological Society of Korea
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• v.15 no.2 s.44
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• pp.106-117
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• 2006

Re-Os isotopic system, based on the long-lived $\beta^-$ transition of $^{187}Os(\lambda=1.67\times10^{-11}year^{-1})$ is being widely used in cosmochemistry and geochemistry. Along with the development of elemental separation and mass-spectrometric technique, the Re-Os isotopic system, like Sm-Nd, Rb-Sr, U-Th-Pb isotopic system, is now conventionally applied as a useful tool for absolute dating and isotoptc tracers. This paper introduces brief principles of Re-Os isotopic system and presents the general methodology fur dating the formation age of the subcontinental lithospheric mantle, based on the Re-Os isotopic data of the mantle xeonliths from South Korea.

• Nuclear Engineering and Technology
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• v.41 no.3
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• pp.319-326
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• 2009

This study was carried out to investigate the high-acidity co-separation of Am and RE from a simulated radwaste solution by a solvent extraction using a mixture of Dimethyldibutyltetradecylmalonamide (DMDBTDMA, as an extractant) and dihexyl octanamide (DHOA, as a phase modifier) diluted with n-dodecane (NDD). All the experiments were conducted as a batch type. First, the environmentally friendly DMDBTDMA and DHOA composed of only CHON atoms were self-synthesized. Then, the conditions for the prevention of a third phase, generated in the organic phase were examined. In addition, the effects of the concentration of nitric acid, DHOA, oxalic acid and $H_2O_2$ on the co-extraction of Am and RE were elucidated. Consequently, the optimum condition of (0.5M DMDBTDMA+0.5M DHOA)/NDD-0.3M $C_2H_2O_4-4.5M$ $HNO_3$ and O/A=2 was obtained through experimental work. Under this condition, the extraction yields were found to be about 80% for Am, more than 70% for RE such as La, Eu, Nd, Ce, etc., 3% for Cs and Sr, 69% for Fe and less than 11% for Mo and Ru. For the co-extraction of Am and RE, Fe should be removed in advance or prevented from a co-extraction with Am by controlling the different extraction rates of Am and Fe. About 95% of the Am and RE in the organic phase were stripped using a 0.5M $HNO_3$.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.115-122
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• 1997

The powder preparation by using emulsion drying method, one of the chemical powder fabrication methods has the advantages; easy to control the chemical stoichiometry and to fabricate homogeneously fine particles. In the present study, the initial morphology and size distribution of the powder fabricated by using emulsion dry-ing method were controlled and were improved the homogeneity. By carefully controlling the mixing ratio of oil phase and aqueous solution and surfactant of preventing emulsion separation, the Bi(Pb)-Sr-Ca-Cu-O su-perconducting powders were prepared. The properties of the superconducting powder fabricated by this method and the microstructures and superconducting properties of the pelletized samples were investigated. The microstructures and electric properties of the tapes prepared by oxide powder-in-tube method were in-vestigated. The fabricated powder was spherical with less than 1$\mu$m but most of them was agglomerated with 2~5$\mu$m in size. The critical temperature of the pelletized sample annealed at 84$0^{\circ}C$ for 72 hours in oxygen par-tial pressure of 1/13atm in Ar atmosphere was 108K. And the critical current of the first and second annealed tapes in air prepared by oxide powder-in-tube process were 0.4A and 1.5A, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.571-580
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• 2016

In this paper, performance of the gas turbine combined cycle(GTCC) using pre-combustion carbon capture technology was comparatively analysed. Steam reforming and autothermal reforming were used. In the latter, two different methods were adopted to supply oxygen for the reforming process. One is to extract air form gas turbine compressor (air blowing) and the other is to supply oxygen directly from air separation unit ($O_2$ blowing). To separate $CO_2$ from the reformed gas, the chemical absorption system using MEA solution was used. The net cycle efficiency of the system adopting $O_2$ blown autothermal reforming was higher than the other two systems. The system using air blown autothermal reforming exhibited the largest net cycle power output. In addition to the performance analysis, the influence of fuel reforming and carbon capture on the operating condition of the gas turbine and the necessity of turbine re-design were investigated.