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Abstract  

Distillation and condensation characteristics of LiCl-KCl eutectic salts containing rare earth precipitates were investigated and a conversion of the rare earth oxychlorides to oxides was performed. The distillation flux was increased by about 1,000 times by reducing the pressure from 760 Torr to 0.5 Torr. The composition of the recovered salts was changed according to the condensed spot. The conversion temperature of the multicomponent oxychlorides was decreased when compared to that of a single component. It was found that the concentration of the chloride gas in the flue gas is an index to establish whether the conversion is completed or not.

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Abstract  

The Korea Atomic Energy Research Institute (KAERI) completed the High-flux Advanced Neutron Application Reactor (HANARO) in 1995 and the radioisotope production facilities(RIPF) in 1997. Many devices and handling tools were developed and applied for the production of radioisotopes. Emphasis on RI production plan was placed on the development of new radiopharmaceuticals, the development of new radiation sources for industrial use and the steady production of selected radioisotopes. The selected items are 166Ho-based pharmaceuticals, fission 99Mo/99mTc generators, and products of 131I and 192Ir and 60Co sources for industrial use. Now KAERI regularly produces radioisotopes (131I, 99mTc, 166Ho, 192Ir, 60Co etc.) and labeled compounds including 99mTc cold kits. Newly developed therapeutic agents are a 166Ho-chitosan complex for liver cancer treatment, a 166Ho patch for skin cancer treatment and devices such as the stent and balloon for the prevention against restenosis of the coronary artery. Feasibility studies on the installation of a 99mTc generator loading facility and on 60Co production for food irradiation were finished. The 192Ir sealed source assembly for NDT has been supplied to domestic users since May 2001. The fission moly process, separation process of non-sealed sources (125I, 33P, 89Sr, 153Sm, 188Re) and fabrication process of sealed sources (169Yb, 75Se) are also under development. For the quality assurance of our final products, we obtained ISO certification in 2000. We are carrying out a feasibility study on a new research reactor for the stable supply of radioisotopes in Korea.

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Abstract  

The oxidizing reaction of some rare-earth chlorides (Pr/CeCl3) in an eutectic (LiCl-KCl) salt was studied by O2 injection. In this study, oxychlorides (REOCl) or oxides (REO2) were formed as reaction products. The results conformed to the thermodynamic equilibrium data calculated by HSC-Chemistry 5.1 software. The conversion ratio of the rare-earth chlorides to insoluble precipitates was over 0.999, after injecting O2 for 7 hours at 650 °C for the eutectic salt temperature.

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Abstract  

For the instrumental neutron activation analysis of trace impurities in high purity silicon wafer, a modified single comparator method has been applied. The energy distribution of the neutrons at the irradiation position was measured using the two flux monitors, Au and Co, and elemental contents were calculated using the silicon matrix in the wafer as a comparator. This has advantage of reducing the cross contamination from an external monitor during sample preparation and irradiation, the uncertainties from the non-homogeneity of the neutron flux and the error on the weight of comparators. Determination limits for 49 elements were presented under the condition of 72 hours irradiation at a neutron flux of 3.7·1013 n·cm-2·s-1 and 4000 s measurement. The analytical results obtained by this method and the conventional single comparator method were compared and were found to agree well within 5%.

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Abstract

We examine how strategic partnership affects external learning of technology descendants from emerging markets under the context of Taiwan's flat panel display industry. The study takes patent citation as a trail of knowledge flow, and incorporates 1,726 pairs relations of the cited and citing firms. Our empirical evidence shows positive pattern of external learning through strategic technology partnership. After controlling the quality factor of the knowledge, technology descendants do learn more from their alliance partners than other non-allied firms; particularly, trading type of partnerships characterized by the asymmetric relations appears to bring more impact. Furthermore, a focused approach in extrapolating knowledge from strategic partners seems to be the dominant practice.

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Abstract  

This report describes the environmental sample treatment techniques for14C measurement with liquid scintillation counter. The groundwater sample of about 80 liters was collected from well and inorganic carbon was removed by acidification and recirculated gas stripping with the extraction efficiency of more than 98%. The biological samples were freeze-dried and combusted to carbon dioxide in high pressure combustion unit with a combustion efficiency of nearly 99%. The14CO2 in the stack effluents was collected by an air bubbler with a collection efficiency of more than 99% for a sampling time of two weeks. Sampling of14C in reduced form also has been done by passing the gases through a tube furnace with Pt/Al and Pd/Al catalyst. Active and passive sampling methods for atmospheric14C measurements were compared in detail, and it could be concluded that the uncertainty associated with passive sampling method was quite acceptable for environmental monitoring. The CO2 trapped in NaOH was precipitated as BaCO3, and subsequently reconverted to CO2 for environmental samples and transferred to Carbo-Sorb ETM for liquid scintillation counting. In case higher precision is the deciding factor, benzene synthesis would be employed with home-made benzene synthesizer.

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Abstract  

The goal of this work was to optimize the liquid scintillation counting techniques for the determination of14C in stack effluent gases and in environmental samples such as biological and air samples. Carbon-14 activities in most environmental samples were measured with the direct CO2 absorption method. The highest figures of merit were found through the variation of Carbosorb E and Permafluor V ratio, and measurement windows. The best condition was an 1:1 volume ratio. Average 2.35 g of CO2 was reproducibly absorbed in the 20 ml mixture within 40 minutes. The counting efficiency determined by repeated analysis of NIST oxalic acid standard and the background count rate were measured to be 58.8±1.4% and 1.88±0.06 cpm, respectively, in case of saturated solution. The correction curves of counting efficiency for partially saturated solutions and for saturated solutions with quenching were prepared, respectively. The overall uncertainty of the sample specific activity for near background levels was estimated to be about 7% for 4 hours counting at 95% confidence level. Stack effluent gas samples were measured by a gel suspension counting method. After precipitation of CO2 in the form of BaCO3, 140 mg of which was mixed with 6 ml H2O and 12 ml of Instagel XF. The counting efficiency was measured to be 71.5±1.7% and the typical sensitivity of this technique was about 510 mBq/m3 for a 100 min count at a background count rate of 4.7 cpm. For the benzene counting method measurements were performed with a mixture of 3 ml benzene and 1 ml of scintillation cocktail (5 g of butyl-PBD in 100 ml of scintillation-grade toluene) in a low potassium 7 ml borosilicate glass vial. The counting efficiency and the background count rate were measured to be 64.3±1.0% and 0.51±0.05 cpm, respectively. The long-term stability of samples has been checked for all the counting techniques over a two week period, during which no apparent change in counting efficiency and background level was found.

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Summary  

Accelerator mass spectrometry (AMS) is the most sensitive, safe and precise analytical method for quantifying long-lived isotope in biomedical research with animals as well as human beings. In Korea, AMS Laboratory has been operating successfully for years measuring especially archeological samples for 14C dating. In this year, a biological sample pretreatment facility was setup and we have also started to work on biomedical applications. As a preliminary study, we have measured the natural background levels of 14C in tissues and blood of humans and rats. The results were agreed with the other reported levels and gave stable and reproducible results within 1-2%.

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The complete chloroplast (cp) genome sequence of Pearl millet (Pennisetum glaucum [L.] R. Br.), an important grain and forage crop in the family Poaceae, is reported in this study. The complete cp genome sequence of P. glaucum is 138,172 bp in length with 38.6% overall GC content and exhibits a typical quadripartite structure comprising one pair of inverted repeat (IR) regions (22,275 bp) separated by a small single-copy (SSC) region (12,409 bp) and a large single-copy (LSC) region (81,213). The P. glaucum cp genome encodes 110 unique genes, 76 of which are protein-coding genes, 4 ribosomal RNA (rRNA) genes, 30 transfer RNA (tRNA) genes and 18 duplicated genes in the IR region. Nine genes contain one or two introns. Whole genome alignments of cp genome were performed for genome-wide comparison. Locally collinear blocks (LCBs) identified among the cp genomes showed that they were well conserved with respect to gene organization and order. This newly determined cp genome sequence of P. glaucum will provide valuable information for the future breeding programs of valuable cereal crops in the family Poaceae.

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Abstract  

We measured the isomeric yield ratios for the photonuclear reactions of 93Nb(γ,4n)89m,gNb and natMo(γ,xnp)95m,gNb by using the activation method. The high-purity 93Nb and natMo metallic foils in disc shape were irradiated with uncollimated bremsstrahlung beams of 50-, 60-, and 70-MeV generated from an electron linear accelerator in Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometry with a calibrated high-purity Germanium (HPGe) detector coupled to a PC-based 4 K multichannel analyzer. The reaction 93Nb(γ,4n)89m,gNb was studied for the first time which has no comparable literature data. The result of 95m,gNb isomeric pair was measured based on (γ,p), (γ,np), and (γ,2np) reactions which is the first measurement at the intermediate energy region of 50–70-MeV with a natMo target.

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