• Proceedings of the Mineralogical Society of Korea Conference
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• 2003.05a
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• pp.67-67
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• 2003

The chemical compositions and textural relationships of the Nb-Zr oxide minerals including pyrochlore [ideally (Ca,Na)$_2$Nb$_2$O$\sub$6/(OH,F), with up to 24% UO$_2$ and 16% Ta$_2$O$\sub$5/] and baddeleyite [ideally ZrO$_2$, with up to 6% Nb$_2$O$\sub$5/] in the Sokli carbonatite complex, Kola Peninsula, Arctic are described. These two minerals in carbonatites are the major hosts for the HFSEs such as U, Th, Ta, Nb, Zr and Hf and thus are interest both economically and petrologically. The Sokli carbonatite complex (360-370 Ma) in Northern Finland, which forms a part of the Paleozoic Kola Alkaline Province (KAP), is mainly composed of multi-stages of carbonatite and phoscorite associations (P1-C1 P2-C2, P3-C3, D4 and D5) surrounded by altered ultramafic rocks (olivinite and pyroxenite) and cut by numerous small dikes of ultramafic lamprophyre. The Sokli complex contains the highest concentration in niobium and probably in tantalum, which are economically very important to modern steel technology, among the ultramafic-alkaline complexes of the KAP. Pyrochlore and baddeleyite mostly concentrate in the phoscorites. Pyrochlores in the Sokli complex are generally rounded octahedra and cubes in shape, red brown to grey yellow in color, and 0.2 to 5 mm in size. They are found in all calcite carbonatites, phoscorites and dolomite carbonatites, except P1-C1 rocks. These pyrochlores display remarkable zonations which depend on host rock compositions, and have significant compositional variations with evolution of the Sokli complex. The common variation scheme is that (1) early pyrochlore is highly enriched in U and Ta; (2) these elements decrease abruptly in the intermediate stage, while Th and Ce increase, and (3) late stage pyrochlore is low in U, Ta, Th, and Ce, and correspondingly high in Nb. Baddeleyites in the Sokli complex occur in the early P1-C1 and P2-C2 rocks and rarely in P3. They crystallized earlier than pyrochlores, and occasionally show post-magmatic corrosion and replacement. The FeO and TiO$_2$ contents of baddeleyites are much lower than those of the other terrestrial and lunar baddeleyites, whereas Nb$_2$O$\sub$5/ and Ta$_2$O$\sub$5/ contents are the highest among the reported compositions. Ta/Nb and Zr/Nb ratios of pyrochlores and baddeleyites decrease towards later stage facies, which is in accordance with the whole rock compositions. The variation of Ta/Nb and Zr/Nb ratios of pyrochlores and baddeleyites is considered to be a good indicator to trace an evolution of the carbonatite complexes.

• Nuclear Engineering and Technology
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• v.49 no.7
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• pp.1547-1554
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• 2017

VESTA (Verification of Ex-vessel corium STAbilization) and VESTA-S (-small) test facilities were constructed at the Korea Atomic Energy Research Institute in 2010 to perform various corium melt experiments. Since then, several tests have been performed for the verification of an ex-vessel core catcher design for the EU-APR1400. Ablation tests of an impinging $ZrO_2$ melt jet on a sacrificial material were performed to investigate the ablation characteristics. $ZrO_2$ melt in an amount of 65-70 kg was discharged onto a sacrificial material through a well-designed nozzle, after which the ablation depths were measured. Interaction tests between the metallic melt and sacrificial material were performed to investigate the interaction kinetics of the sacrificial material. Two types of melt were used: one is a metallic corium melt with Fe 46%, U 31%, Zr 16%, and Cr 7% (maximum possible content of U and Zr for C-40), and the other is a stainless steel (SUS304) melt. Metallic melt in an amount of 1.5-2.0 kg was delivered onto the sacrificial material, and the ablation depths were measured. Penetration tube failure tests were performed for an APR1400 equipped with 61 in-core instrumentation penetration nozzles and extended tubes at the reactor lower vessel. $ZrO_2$ melt was generated in a melting crucible and delivered down into an interaction crucible where the test specimen is installed. To evaluate the tube ejection mechanism, temperature distributions of the reactor bottom head and in-core instrumentation penetration were measured by a series of thermocouples embedded along the specimen. In addition, lower vessel failure tests for the Fukushima Daiichi nuclear power plant are being performed. As a first step, the configuration of the molten core in the plant was investigated by a melting and solidification experiment. Approximately 5 kg of a mixture, whose composition in terms of weight is $UO_2$ 60%, Zr 10%, $ZrO_2$ 15%, SUS304 14%, and $B_4C$ 1%, was melted in a cold crucible using an induction heating technique.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.444-453
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• 2011

VO(II), ZrO(II), Hf(IV), $UO_2$(II), Sn(II), V(V)$O_3$, Ru(III), Cd(II), Ho(III) and Yb(III) complexes of N'-(2-hydroxybenzyl)-2-(phenylamino)acetohydrazide ($H_2L^1$, 1) and N'-((3-hydroxy-naphthalen-2-yl)methylene)-2-(phenylamino)-acetohydrazide ($H_2L^2$, 13) have been synthesized and characterized by elemental analyses, $^1H$ NMR, IR, UV-Vis, conductance, thermal analyses (DTA and TG). The spectral data showed that the ligands behave as neutral bidentate, monobasic bidentate, monobasic tridentate or bibasic tridentate ligand bonded to the metal ions through the azomethine nitrogen atoms, phenolic hydroxyl group in protonated or deprotonated form and enolic or ketonic carbonyl group. The ligands and their metal complexes exhibit higher antifungal and antibacterial inhibitory effects than parent ligands and the solution of metal ions. Most of metal complexes exhibit higher antifungal activity than standard antifungal drug (amphotricene B). It is also clear that the ligands and their metal complexes have higher antifungal activity than antibacterial activity.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.2
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• pp.69-76
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• 2006

TRISO(tri-isotropic)-coated fuel particle technology is utilized owing to its higher stability at a high temperature and Its efficient retention capability for fission products In the HTGR(high temperature gas-reeled reactor). The typical spherical TRISO fuel panicle with a diameter of about 1mm is composed of a nuclear fuel kernel and outer coating layers. The outer coating layers consist of a buffer PyC(pyrolytic carbon) layer, Inner PyC(1-PyC) layer, SiC layer, and outer PyC(O-PyC) layer Most of the Inspection Items for the TRTSO-coated fuel particle depend on destructive methods. The coating thickness of the TRISO fuel particle can be nondestructively measured by the X-ray radiography without generating radioactive wastel. In this study, the coaling thickness for the simulated TRISO-coated fuel particle with $ZrO_2$ kernel Instead of $%UO_2$ kernel was measured by using micro-focus X-ray radiography with micro-focus X-ray generator and flat panel detector The radiographic image was also enhanced by image processing technique to acquire clear boundary lines between coating layers. The coaling thickness wat effectively measured by applying the micro-focus X-ray radiography The inspection process for the TRISO-coated fuel particles will be improved by the developed micro-focus X-ray radiography and digital image processing technology.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.51-56
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• 2001

Vapor explosion is one of the most important problems encountered in severe accident management of nuclear power plants. In spite of many efforts, a lot of questions still remain for the fundamental understanding of vapor explosion phenomena. Therefore, KAERI launched a real material experiment called TROI using 20 kg of UO2 and ZrO2 to investigate the vapor explosion phenomena. In addition, a small-scale experiment with molten-tin/water system was performed to quantify the characteristics of vapor explosion and to understand the phenomenology of vapor explosion. A number of instruments were used to measure the physical change occurring during the vapor explosion. In this experiment, the vapor explosion generated by molten fuel water interaction is visualized using high speed camera and the pressure behavior accompanying the explosion is investigated.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.109-114
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• 2020

This work presents the results of laboratory scale tests of the CARBOFLUOREX (CARBOnate FLUORide EXtraction) process - a novel technology for the recovery of U and Pu from the solid fluorides residue (fluorination ash) of Fluoride Volatility Method (FVM) reprocessing of spent nuclear fuel (SNF). To study the oxidative leaching of U from the fluorination ash (FA) by Na₂CO₃ or Na₂CO₃-H₂O₂ solutions followed by solvent extraction by methyltrioctylammonium carbonate in toluene and purification of U from the fission products (FPs) impurities we used a surrogate of FA consisting of UF₄ or UO₂F₂, and FPs fluorides with stable isotopes of Ce, Zr, Sr, Ba, Cs, Fe, Cr, Ni, La, Nd, Pr, Sm. Purification factors of U from impurities at the solvent extraction refining stage reached the values of 10⁴-10⁵, and up to 10⁶ upon the completion of the processing cycle. Obtained results showed a high efficiency of the CARBOFLUOREX process for recovery and separating of U from FPs contained in FA, which allows completing of the FVM cycle with recovery of U and Pu from hardly processed FA.

• Economic and Environmental Geology
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• v.30 no.5
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• pp.395-406
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• 1997

Some RE (Zr, Nb, REE) ore deposits are located in the middle part of the Korean peninsula. Geotectonically, the RE ore deposits situated on the Kyemyeongsan Formation of northern margin of the Okcheon geosynclinal belt and in the transitional zone between Kyeonggi massif and Okcheon belt. The rare metal deposits distributed in Kyemyeongsan Formation which consists of schist and alkaline granite. The alkali granite has suffered extensive post-magmatic metasomatism and hydrothermal processes. The ore contains mainly Ce-La, Ta-Nb, Y, Y-Nb, Ti-Nb-(U), Nd-Th group minerals. Fergusonite, one of Nb-Y rich REE minerals belonging to the A-B oxides, is most common mineral in the rare metal deposits. The fergusonite bearing rocks may be devided into four types by occurrence features and mineral association, that is, zircon type, allanite vein, feldspar type, and fluorite type. Fergusonites show wide variations in optical properties, due to part of differences in their chemical composition (depending on the types), but also the degree of crystalinity of the individual specimens. Fergusonite metamicts enclosed in biotite are generally surrounded by well developed pleochroic haloes. Usually, fergusonite is accompanied with zircon and other REE-bearing minerals. Petrographical and chemical data are presented for fergusonites which collected different types. $Nb_2O_3$ and $Y_2O_3$ contents range from 48.51 to 53.01 wt.% and 29.18 to 42.02 wt.% respectively. Also, $ThO_2$, (1.83~6.93), $UO_2$, (0.17~2.84), ${\sum}RE_2O_3$ (except to Y) (1.11~8.73), and $TiO_2$, (0.19~1.19 wt.%) contents show variational compositions according to fergusonite types. The ${\sum}RE_2O_3$ of fergusonites are positive relation with $Y_2O_3$ and negative relaton with $ThO_2$ and $({\sum}{RE_2O_3}-{Y_2O_3})$. The $Nb_2O_3$ is sightly negative relation with $Ta_2O_3$. Back-scattered electron microscope images (BEI) of fergusonite show the mineral composition and textural feature is very complicated. The variation of Nb, Th and REE content of fergusonite and the modes of occurrence of mineral, suggests that REE may have been mobilized during the circulation of hydrothermal fluids related to contact metamorphism (metasomatism). The chemical variation of the fergusonites with occurrences and mineral association can be related to metasomatism of alkaline fluid was probably the dominant ore-forming process in Chungju district.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.669-672
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• 2006

고온가스냉각 원자로에서는 고온 안정성 및 핵분열생성물 차단 성능이 우수한 TRISO(tri-tsotropic) 핵연료를 사용하고 있다. TRISO 핵연료 입자는 직경이 약 1 mm인 구 형태로 입자의 중심에는 직경 $0.5{\mu}m$의 핵연료 커널(kernel)이 포함되며 커널 외곽을 코팅 층이 에워싸고 있다. 이 코팅 층은 완충(buffer) PyC(pyrolytic carbon) 층, 내부 PyC 층, SiC 층, 그리고 외부 PyC 층으로 구성되어 있다. 각 코팅 층의 두께는 수십${\sim}$백 ${\mu}m$ 범위이며, 본 연구에서는 각 코팅 층의 두께를 비파괴적으로 측정하기 위하여 마이크로포커스 X-선 발생장치와 고해상도 X-선 평판(flat panel) 검출기로 구성된 정밀한 X-선 래디오그래피 장치를 구성하고, $UO_2$ 핵물질 대신에 $ZrO_2$를 커널로 사용한 모의 TRISO 핵연료 입자에 대한 래디오그래피 영상을 획득한 후 디지털 영상처리기술을 이용하여 코팅 층 사이의 경계선이 구분 가능하도록 영상을 개선하고 디지털 영상처리 알고리즘을 개발하여 코팅 층의 두께를 측정하였다.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.397-400
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• 2002

Vapor explosion is one of the most important problems encountered in severe accident management of nuclear power plants. In spite of many efforts, a lot of questions still remain. So, KAERI launched a real experimental program called TROI using $UO_{2}$ and $ZrO_{2}$ to investigate the vapor explosion. Besides TROI tests, a small-scale experiment with molten-tin/water system was performed to quantify the characteristics of vapor explosion and to understand the phenomenology of vapor explosion. A vapor explosion was observed while the amount of air bubble and water temperature were systematically varied The mass and temperature of tin are $50\;g\;and\;150^{\circ}C$, respectively. Water temperature is set to $24^{\circ}C\;and\;50^{\circ}C$. The void fraction of air bubble ranges from $0\;to\;10\;{\%}$. The strength of vapor explosion was measured using dynamic pressure sensors attached in reactor tube wall. as a function of void fraction. In addition, a high speed video filming up to 1,000 flame/sec was taken in order to visually investigate the behavior of the vapor explosion .

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.414-419
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• 2003

In the recent TROI experiments, melts of zirconia and two different compositions of corium were used to observe the occurrence of a steam explosion when it came into contact with water at two different depths. The compositions of the corium were 70 : 30 and 80 : 20 in weight percent of $UO_{2}$ and $ZrO_{2}$, and the mass of the corium was about 10kg. The depth of water in the interaction vessel was 67cm and 130cm. A steam explosion did not occur in the interaction between 80 : 20 corium melt and water at 130cm depth, while steam spikes were observed in the interactions between corium melts of two different compositions and water at 67cm depth. A strong steam explosion occurred in the interaction between 5.43kg of zirconia melt and water at 67cm depth. This fact shows that the explosivity of zirconia is much greater than that of corium.