Development of Melting System for Measurement of Trace Elements and Ions in Ice Core

홍상범,이광현,허순도,홍성민,Tseren-Ochir Soyol-Erdene,김선미,정지웅,전승준,강창희 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.4

We present a titanium (Ti) melting head divided into three zones as an improved melting system for decontaminating ice-core samples. This system was subjected to performance tests using short ice-core samples (4 × 4 cm2, ~5 cm long). The procedural blanks (PBs) and detection limits of ionic species, with the exception of NO 3 − , were comparable with published values, but for elements the experimental procedures should be refined to obtain valid Zn concentrations due to the PB of ~90.0 ± 16.2 ng/L. The improved melting system efficiently decontaminated the samples, as verified by the concentration profiles of elements and ions in the melted samples from the three melting-head zones. The recovery of trace elements in ice-core samples was ~70–120% at ~100 ng/L in artificial ice cores. Because of the memory effects between ice-core samples melted in series, the melting system should be rinsed at least 5–6 times (in a total volume of ~2.5 mL deionized water) after each melting procedure. Finally, as an application of this technique, trace elements were measured in ice-core samples recovered from the East Rongbuk Glacier, Mount Everest, (28°03′N, 86°96′E, 6518 m a.s.l.), and the concentrations of trace elements following mechanical chiseling and the melting method were compared.

Assembly processes of moss and lichen community with snow melting at the coastal region of the Barton Peninsula, maritime Antarctic

김석철,김준석,홍보람,홍순규,김지희,이규송 한국생태학회 2016 Journal of Ecology and Environment Vol.40 No.1

Background: In this article, it was analyzed how snow melting affects the assembly of lichen and moss communities in a small area of the coastal region of Barton Peninsula, which is in maritime Antarctic. In the small area, even though there is a huge gap of difference of the environment between the snow-filled area and snow-melt one, the latter did not have distinctive environmental gradients. Results: Depending on the snow melting time, coverage and species diversity of lichens and mosses tend to increase remarkably. For species with significant changes depending on the snow-covered period, there are Andreaea regularis, crustose lichens, Placopsis contortuplicata, Usnea aurantiaco-atra, and snow algae. In this area, the process of vegetation assembly process has shown the directional development in the order of snow algae→crustose, lichen sub-formation→fruticose lichen, moss cushion sub-formation (Andreaea sociation)→fruticose lichen, and moss cushion sub-formation (Usnea sociation), according to the order of snow melting. These directional development stages are shown in gradual change in small area with the snow melting phenomena. However, in the snow-free area, where water is sufficiently supplied, it is expected that moss carpet sub-formation (Sanionia sociation) will be developed. Vegetation development in the small area with the snow melting phenomena, depending on differences of resistance on snow kill and moisture settled by species in according to the time of snow melting, tolerance model to form community is followed. Conclusions: The research results explain the development of vegetation in the Antarctic tundra and its spatial distribution according to the period for growth of lichens and mosses in the summer time by differences of snow melting in the small area. In the future, if research for the community development process in a large scale will be done, it will be helpful to figure out temporal and spatial dynamic of vegetation in the Antarctic tundra where snow and glaciers melt rapidly due to climatic warming.

Assembly processes of moss and lichen community with snow melting at the coastal region of the Barton Peninsula, maritime Antarctic

Kim, Seok Cheol,Kim, Jun Seok,Hong, Bo Ram,Hong, Soon Gyu,Kim, Ji Hee,Lee, Kyu Song The Ecological Society of Korea 2016 Journal of Ecology and Environment Vol.40 No.1

Background: In this article, it was analyzed how snow melting affects the assembly of lichen and moss communities in a small area of the coastal region of Barton Peninsula, which is in maritime Antarctic. In the small area, even though there is a huge gap of difference of the environment between the snow-filled area and snow-melt one, the latter did not have distinctive environmental gradients. Results: Depending on the snow melting time, coverage and species diversity of lichens and mosses tend to increase remarkably. For species with significant changes depending on the snow-covered period, there are Andreaea regularis, crustose lichens, Placopsis contortuplicata, Usnea aurantiaco-atra, and snow algae. In this area, the process of vegetation assembly process has shown the directional development in the order of snow algae${\rightarrow}$crustose, lichen sub-formation${\rightarrow}$fruticose lichen, moss cushion sub-formation (Andreaea sociation)${\rightarrow}$fruticose lichen, and moss cushion sub-formation (Usnea sociation), according to the order of snow melting. These directional development stages are shown in gradual change in small area with the snow melting phenomena. However, in the snow-free area, where water is sufficiently supplied, it is expected that moss carpet sub-formation (Sanionia sociation) will be developed. Vegetation development in the small area with the snow melting phenomena, depending on differences of resistance on snow kill and moisture settled by species in according to the time of snow melting, tolerance model to form community is followed. Conclusions: The research results explain the development of vegetation in the Antarctic tundra and its spatial distribution according to the period for growth of lichens and mosses in the summer time by differences of snow melting in the small area. In the future, if research for the community development process in a large scale will be done, it will be helpful to figure out temporal and spatial dynamic of vegetation in the Antarctic tundra where snow and glaciers melt rapidly due to climatic warming.

CaO 도가니에 의한 Ti-6Al-4V 합금의 용해와 주조결함

內田省壽,鎌田動也,田中直裕,柳澤平 한국주조공학회 2004 한국주조공학회지 Vol.24 No.6

The CaO crucible is expected to serve as a useful tool for melting Ti and its alloys due to its thermodynamic stability. However, tjere still remain problems that need to be resolved in the melting of Ti and its alloys to enable commerical use. The cause of the defects of Ti-6Al-4V alloy castings melted in the CaO crucible were examined and compared with induction skull melting. The key factors of the melting technique using the CaO crucible, affecting the quality of Ti-6Al-4V alloy castings, were investigated. Defects of the Ti-6Al-4V alloy castings are caused by the chemical reduction of CaO by Ti. Pressurizing with argon gas in a vacuum induction chamber is effective for reducing the defects. Preheating of the charged material in the crucible and quick pouring into a mold of lower temperature, just after melting down, are important for produsing sound Ti-6Al-4V castings.

Multi-Cellular Natural Convection in the Melt during Convection- Dominated Melting

Kim, Sin,Kim, Min-Chan The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.1

Convection-dominated melting in a rectangular cavity is analyzed numerically with particular attention to the multi-cellular flows in the melt. At the earlier stage of the melting, the melt region is quite similar to a cavity with high aspect rati71, where the multi-cellular natural convection appears. Numerical results show that the formation and evolution of the multiple flow cells in the melt region is approximately similar to t]tat of a single-phase flow in a tall cavity with the same aspect ratio; however, the continuous change of the melt region due to the melting affects the detailed process. Also, numerical aspects for the prediction of the detailed flow structure in the melt are discussed.

Fluid-present disequilibrium melting in Neoarchean arc-related migmatites of Daeijak Island, western Gyeonggi Massif, Korea

Lee, Y.,Cho, M. Universitetsforlaget ; Elsevier Science Ltd 2013 Lithos Vol.179 No.-

The melting process of meta-igneous rocks was investigated via field, petrographic and geochemical analyses of the Neoarchean (~2.51Ga) migmatite complex in Daeijak Island, western Gyeonggi Massif. This complex consists primarily of garnet-free amphibolites and tonalitic migmatites, both of which contain hornblende, plagioclase and quartz as major constituents. Neosomes and leucosomes in the migmatite have dioritic-tonalitic and tonalitic-trondhjemitic compositions, respectively. Compositions of hornblende (X<SUB>Fe</SUB>=0.39-0.42) and plagioclase (An<SUB>24-27</SUB>) vary little between the neosomes and leucosomes. The amphibolites show distinct depletions in Nb, Ta, Zr, and Ti relative to large ion lithophile elements, suggesting an arc-related origin for their basaltic protolith. Leucosomes have lower contents of K<SUB>2</SUB>O, MgO, FeO<SUP>@?</SUP>, TiO<SUB>2</SUB>, Zr, Rb, and rare earth elements (REE) than amphibolites and neosomes, but are higher in SiO<SUB>2</SUB>, Na<SUB>2</SUB>O, and Sr contents. Leucosomes and neosomes have positive [(Eu/Eu<SUP>@?</SUP>)<SUB>N</SUB>=1.32-7.26] and negative (0.71-0.97) Eu anomalies, respectively, which are attributed to the variable degree of plagioclase fractionation during the partial melting. The P-T condition for the migmatite formation was estimated to be ~700-730<SUP>o</SUP>C and 4.7-5.5kbar, primarily based on the hornblende-plagioclase thermobarometry and phase equilibria. Various lines of textural evidence, such as the channel flow of melt along migmatitic layers and the segregation of melt into shear bands or boudin necks suggest a syn-deformation crystallization of melt. Chemical disequilibrium in migmatites is documented not only by petrographic and geochemical data but also by the REE modeling between melt product and source rock. Disequilibrium process is most likely attributed to the rapidity of melt extraction or migration, compared to chemical diffusion rate. In summary, the fluid-present disequilibrium melting of dioritic-tonalitic protoliths has produced tonalitic-trondhjemitic leucosomes in a dynamic arc environment prevalent in the Neoarchean crust of the Korean Peninsula as well as the Shandong Peninsula, North China Craton.

Considerations on Event Sequence and Consequences of Critical Hazards Generated From Operation of a Melting Facility for Metal Radioactive Waste

KwanSeong Jeong,KeunYoung Lee,SeungJoo Lim,HwanSeo Park,JaeYoung Pyo 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

The critical hazards generated from operation of a melting facility for metal radioactive waste are mainly assumed to be such as vapor explosion, ladle breakthrough and failure in the hot-cell or furnace chamber using remote equipment. In case of vapor explosion, material containing moisture and/or enclosed spaces may, due to rapid expansion of gases when heated, cause an explosion and/or violent boiling. The rapid expansion of gases may lead to ejection of molten radioactive metal from the furnace into the furnace hall. If there is a large amount of liquid the explosion may damage or destroy technical barriers such as facility walls. The consequences for the facility ranges from relatively mild to very severe depending on the force of the explosion as well as the type of waste being melted. Nonradiological consequences may be physical damage or destruction of equipment and facility barriers, such as walls. Due to the radiological consequences a longer operational shutdown would likely be required. Cleanup efforts would include cutting of solidified metal in a problematic radiological environment requiring use of remote technology before damage and repair requirements can be assessed. Even though there is a risk for direct physical harm to operators for example in the control room and hot-cell, this analysis focuses mainly on the radiological impact. The extent to which remote equipment could be used in the decontamination effort will largely determine the health consequences to the workers. It is reasonable to assume that there will be a need for workers to participate manually in the effort. Due to the potentially large dose rates and the physical environment, it is possible that the maximum allowable dose burden to a worker will be reached. No major consequence for the environment is expected as most of the radioactivity is bound to the material. In case of ladle breakthrough, a ladle breakthrough involves loss of containment of the melt due to damage of the ladle. This may be caused e.g. by increased wear due to overheating in the melt, or from physical factors such as mechanical stress and impact from the waste. A ladle breakthrough may lead to spread of molten metal in the furnace hall. Molten metal coming into contact with the surrounding cooling equipment may cause a steam explosion. The consequences of a ladle breakthrough will depend on the event sequence. The most severe is when the molten metal comes into contact with the cooling system causing a vapor explosion. The basic consequences are assumed to be similar to those of the vapor explosion above. While the ejection of molten metal is likely more local in the ladle breakthrough scenario, the consequences are judged to be similar. In case of failure in the hot-cell or furnace chamber using remote equipment, the loss of electric supply or technical failure in the furnace causes loss of power supply. If not remedied quickly, this could lead to that the melt solidifies. A melt that is solidified due to cooling after loss of power cannot be removed nor re-melted. This may occur especially fast if there is not melted material in the furnace. An unscheduled replacement of the refractory in the furnace would be required. It could be unknown to what degree remote equipment can be used to cut a solidified melt. It is therefore assumed that personnel may need to be employed. This event could not have any impact on environment

Development of Slag Composition of Concrete Waste for Plasma Torch Melting System

Sunghoon Hong,Jeongsu Jeong,Seoyong Choi,Mingyu Choi,Cheon-Woo Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

Plasma melting technology has been considered as promising technology for treatment of radioactive wastes. According to the IAEA TECDOC-1527 report (2006), the technology has an advantage that it can treat regardless of waste types which is both combustible and non-combustible wastes. In particular, it is expected that a large amount of concrete, a representative non-combustible wastes, will be generated during the operation and dismantling of nuclear power plants. In order to treat the concrete waste in plasma torch melting system, various factors could be considered like the slag of electric conductivity, viscosity and melting temperature. Above all, as a critical factor, the viscosity of the melt is very important to easily discharge the melt. The viscosity of slag (SiO2-CaO-Al2O3 system) can be lowered by adding a basic oxide such as CaO, Na2O, MgO and MnO. The basic oxides are donors of oxygen ions. These oxides are called notwork breakers, because they destroy the network of SiO2 by reacting with it. In this study, the slag composition of the concrete waste was developed to apply the plasma torch melting. Also, demonstration test was performed with the developed slag composition and 100 kW plasma torch melting system.

P₂O₅-SnO₂계 유리에서 용융분위기에 따른 구조와 물성에 미치는 영향

안용태,최병현,지미정,권용진,배현,황해진,An, Yong-Tae,Choi, Byung-Hyun,Ji, Mi-Jung,Kwon, Yong-Jin,Bae, Hyun,Hwang, Hae-Jin 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.2

In this study, tin phosphate glass system($SnO_2-(1-x)P_2O_5-xB_2O_3$) that occur during the melting of the metal oxide inhibition of the oxidation reaction, and to reduce oxides of high melting temperature in the following three methods were melting. The first is the general way in the atmosphere, and the second by injecting $N_2$ gas under a neutral atmosphere, and finally in the air were melted by the addition of a reducing agent Melt in the atmosphere when the oxidation of the metal oxide is inhibited by low temperatures were melting. In addition, the deposition of crystals within glassy or inhibit devitrification phenomenon is also improved over 80% transmittance. This phenomenon, when the melting of glass, many of $Sn^{4+}$ ions are reduced to the $Sn^{2+}$ was forming oxides SnO, because it acts as a modifier oxide.

Nature of Two-dimensional Melting in Simple Atomic Systems

이상일,Sung Jong Lee 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.7

We investigate the characteristics of two-dimensional melting in simple atomic systems viaisobaric-isothermal (NPT) and isochoric-isothermal (NV T) molecular dynamics simulations with aspecial focus on the effect of the range of the potential on the melting. We find that the system withan interatomic potential of longer range clearly exhibits a region (in the PT plane) with a (thermodynamically)stable hexatic phase. On the other hand, the system with a shorter-range potentialexhibits a first-order melting transition both in the NPT and the NV T ensembles. Melting of thesystem with an intermediate range potential shows a hexatic-like feature near the melting transitionin the NV T ensemble, but it undergoes an unstable hexatic-like phase during melting process in theNPT ensemble, which implies the existence of a weakly first-order transition. The overall featuresrepresent a crossover from a continuous melting transition in the cases of longer-ranged potentialsto a discontinuous (first-order) one in the systems with shorter and intermediate ranged potentials. We also calculate the Binder cumulants, as well as the susceptibility, of the bond-orientational orderparameter.