Increasing resource use is the primary motivator for the development of technology industries, which is leading to severe consequences, such as the release and disposal of radioactive waste containing radionuclides in the environment. Cesium (137Cs) is one of the most hazardous radionuclides in the environment. In particular, the steel manufacturing process produces hazardous waste in the form of electric arc furnace dust contaminated with 137Cs. In this study, the tolerances of five legume species to different activity concentrations of 137Cs in both seed germination and initial seedling growth were compared. To determine 137Cs tolerance, several parameters related to the growth and development of legumes were measured. Among the five legumes studied, Crotalaria juncea L. was the most 137Cs tolerant at 50,000 Bq·L−1. Sesbania javanica Miq. and Vigna mungo L. Hepper were moderately tolerant to 30,000 Bq·L−1 137Cs. After 10 days, the stress tolerance indices in all legume species decreased by more than 50% at activity concentrations greater than or equal to 20,000 Bq·L−1 137Cs. This approach allows the selection of desirable traits, making more-effective application possible in the phytoremediation of 137Cs through stress tolerance. In conclusion, legumes are promising candidates for the phytoremediation of environmental pollutants.

In this study used Computational Fluid Dynamic analysis to examine NOx reduction in hydrogen combustion, analyzing six conditions with varying air/fuel ratios, temperatures, and concentrations. Results were compared between two combustor shapes and previous experimental data. Findings showed increased air/fuel ratios decreased flame temperature and increased post-combustion O2. NOx emissions peaked at high temperatures and low O2. Numerical results aligned with previous experimental trends, validating the approach. Combustor shape differences, reflecting variations in fuel and air pipes, significantly affected flow rates and combustion positions. This reduced NOx emissions up to a certain air/fuel ratio, but excessive increases diminished this effect. The study highlights the complex relationship between combustor design, operating conditions, and NOx emissions. Further research is needed to optimize NOx reduction by considering pipe numbers and combustion locations. Future studies should explore various combustor geometries, fine-tune air/fuel ratios, and investigate additional parameters influencing NOx formation and reduction in hydrogen combustion systems.

This study involved the heterogenization of a binder pitch (BP) using a small amount of nanocarbon to improve physical properties of the resulting graphite electrode (GE). Heterogenization was carried out by adding 0.5–2.0 wt.% platelet carbon nanofiber (PCNF) or carbon black (CB) to a commercial BP. To evaluate the physical properties of the BPs, we designed a new model graphite electrode (MGE) using needle coke as a filler. The heterogenized binder pitch (HBP) with PCNF or CB clearly increased the coking value by 5–13 wt.% compared to that of the as-received BP. Especially, the model graphite electrodes prepared with HBPs containing 1.0 wt.% PCNF or CB showed significantly improved physical properties compared to the control MGE from the as-received BP. Although the model graphite electrodes prepared with HBPs showed similar properties, they had smaller pore sizes than the control. This indicates that heterogenization of the BP can effectively decrease the pore size in the MGE matrix. Correlating the average pore sizes with the physical properties of the model graphite electrodes showed that, for the same porosity, matrices formed by the HBP with a smaller average pore size can effectively improve the apparent density, tensile strength, and oxidation resistance of the model graphite electrodes.

Working with molten metal has always been and will always be a dangerous workplace. No matter how carefully equipment is designed, workers are trained and procedures are followed, the possibility of an accident can occur in melting workplace. Some primary causes of melt splash and furnace eruptions include wet or damp charge material, dropping heavy charge into a molten bath, wet or damp tools or additives and sealed scrap or centrifugally cast scrap rolls. Induction melting brings together three things (water, molted metal and electricity) that have the potential for concern if the furnace is not properly working. Induction furnace must have a water cooling system built into the coil itself. Water picks up the heat caused by the current as well as heat conducted from the metal through the refractory. The water carries the heat to a heat exchange for removal. Spill pits serve to contain any molten metal spilled as a result of accident, run out or dumping of the furnace in an emergency. If a leak is suspected at any time, cease operation and clear the melt deck area of all personnel and empty the furnace. Molten metal fins can penetrate worn or damaged refractory and come into contact with the coil. A furnace or a close capture hood which suddenly swings down from a tilted position will cause injury or death. Whenever workers are working on a furnace or close capture hood when it is in the tilted position, be sure that it is supported with a structural brace that is strong enough to keep it from dropping if hydraulic pressure is lost. In theory refractory wear should be uniform, however, in practice this never occurs. The most causes of lining failure are improper installation of refractory material, inadequate sintering of refractory material, failure to monitor and record normal lining wear, allowing the lining to become too thin, installation of the wrong refractory, improper preheating of a used cold lining, failure to properly maintain the furnace the sudden or cumulative effects of physical shocks or mechanical stress, and excessive slag or dross buildup. Pouring cradles provide bottom support for crucibles. A crack in the crucible occur below the bottom ring support, the bottom of the crucible can drop and molten metal will spill and splash, possibly causing serious injury or death. To reduce this danger, a pouring cradle that provides bottom support for the crucible must be used. Power supply units must have safety locks and interlocks on all doors and access panels. Workers who work with low voltage devices must be made aware of the risk posed by high levels of voltage and current. The most causes of accidents are introduction of wet or damp material, improper attention to charging, failure to stand behind safety lines, coming into contact with electrically charged components and lack of operator skills and training. Only trained and qualified personnel are to have access to high risk areas. Safety lockout systems are another effective measure to prevent electrical shock

Various radioactive metal wastes are generated during operation and decommissioning of nuclear facilities. Radioactive metal wastes with complex geometries or volumetric contamination can be difficult to decontaminate and disposal costs may increase. To solve these problems, the radioactive metal wastes can be treated by melting method. In this study, we designed a melting furnace system of air induction melting type, which is widely utilized due to its advantages of good thermal efficiency, uniform heating and guaranteed safety for radioactive material. By utilizing the melting furnace system, volatile radionuclides existed in the base material can be captured in the form of gas or dust by the filter. The radionuclides whose chemical properties can easily form metal oxides present as slag. For this reason, the specific radioactivity of the base material can be reduced. Radionuclides that are difficult to transport to slag and dust are uniformly distributed in the base material. A dedicated power supply and a transformer were necessary to be included in the melting furnace system since the induction furnace uses high-frequency currents. In addition, a hood is placed on top of the furnace to capture fumes generated during melting, and additional hoods were installed around the furnace to remove airborne dust. In particular, a dust collection unit consisting of a cyclone and a HEPA filter were constructed to effectively collect dust containing radionuclides. During the melting process, the slag is removed and accumulated separately, and the ingot production system was designed to produce the ingot using molten metal. The furnace was constructed for tilting the molten metal by moving the furnace using hydraulic system. The water cooling system and cooling tower were prepared to cool off the equipment with high temperature during melting is cooled off. The above process was specified in the operating procedure developed for this melting furnace system, and the operator shall operate and inspect according to the prescribed procedures. The radioactivity concentration in the sample taken in the step of tilting shall be analyzed whether they meet clearance level for self-disposal determined and publicly announced by the Commission. We can conduct self-disposal for the product of melting furnace system confirmed by the Commission as having the radioactivity concentration by nuclide not exceeding the value determined by the Commission.

In general, systems are developed by repeatedly performing the processes of design, analysis, manufacturing, and performance testing. In particular, systems with temperature, pressure, and flow rate often utilize computational fluid dynamics tools at the design stage. In this paper, we aim to verify the reliability of the analysis results of Solidworks Flow Simulation, which is widely used in heat flow analysis at the design stage. A tube furnace was manufactured, various experiments were performed, and a study was conducted to compare the analysis results. The details of the experiment are as follows. First, an experiment was conducted in which the heater was heated to 900°C without insulating the exposed part of the tube. The detailed contents of the experiment are as follows; - Heating heater and measuring temperature without supplying flow inside the tube, - Tube flow supply (25°C, 15 lpm air) and heater heating/temperature measurement. Second, an experiment was performed in which the exposed part of the tube was insulated (thickness 50 mm) and the heater was heated to 900°C. The detailed contents of the experiment are as follows; - Insulate the outside of the tube except for the flanges at both ends of the tube, and heat the heater and measure the temperature without supplying flow inside the tube. - Insulate the outside of the tube except for the flanges at both ends of the tube, supply flow rate inside the tube (25°C, 15 lpm air) and measure heater heating/temperature. - Insulate the flange of the flow supply section, heat the heater and measure temperature without supplying flow inside the tube. - Insulate the flange of the flow supply section, heat the supply air (277°C, 15 lpm) and measure the temperature using a heating gun without heating the heater. - Insulate the flange of the flow supply section, supply heated air (277°C, 15 lpm) and measure heater heating/temperature. - Insulate the flange of the flow supply section and measure temperature according to heater heating (900°C) and supply temperature (25°C, 277°C 15 lpm). The following results were derived from the experimental and analysis results. - When the exposed part of the tube is insulated, the temperature inside the tube increases and the steady-state power decreases compared to non-insulated. - In areas with insulation, the temperature error between experiment and analysis results is not large. - When flow rate is supplied, there is a large temperature error in experiment and analysis results. - The temperature change after the center of the heater is not large for a temperature change of 15 lpm flow rate. From these results, it can be seen that Solidworks Flow Simulation has a significant difference from the experimental results when there is a flow rate in the tube. This was thought to be because the flow rate acts as a disturbance, and this cannot be sufficiently accounted for in the analysis. In the future, we plan to check whether there is a way to solve this problem.

In this study, numerical modeling on the gas flow and off-gases in the low temperature carbonization furnace for carbon fiber was analyzed. The furnace was designed for testing carbonization process of carbon fibers made from various precursors. Nitrogen gas was used as a working gas and it was treated as an incompressible ideal gas. Three-dimensional computational fluid dynamics for steady state turbulent flow was used to analyze flow pattern and temperature field in the furnace. The off-gas mass fraction and cumulative emission gas of species were incorporated into the CFD analyses by using the user defined function(UDF). As a results, during the carbonization process, the emission of CO2 was the dominant among the off-gases, and tow moving made the flow in the furnace be uniform.

In this paper, a basic study was conducted to observe the temperature inside the tube according to the heating temperature of the tube furnace. In a tube furnace, a tube is inserted, and the air space outside the tube is heated to increase the temperature of the gas inside the tube through conduction of the tube. Tube furnaces are widely used in research to capture volatile nuclides. In this case, a volatile nuclide capturing filter is inserted inside the tube, and an appropriate temperature is required to capture it. Since the tube furnace heats the air space outside the tube to the target temperature, a difference from the temperature inside the tube occurs. In particular, if a flow of gas occurs inside the tube, a larger temperature difference may occur. In order to confirm this temperature difference, an experimental device was constructed, and basic data was produced through several experiments. The following studies were conducted to produce data. First, the temperature of the air layer of the heating unit and the temperature inside the tube were measured in real time in the absence of gas flow inside the tube. Second, the temperature of the air layer of the heating unit and the temperature inside the tube were measured in real time while air having a certain temperature was flowing inside the tube. As a result of the experiment, when there is no flow inside the tube, when the heating target temperature is low, the temperature inside the tube is significantly lower than the target temperature, and when the target temperature is high, the temperature inside the tube approaches the target temperature. It was found that when there is about 20°C air flow inside the tube, the temperature inside the tube is significantly lowered even if the heating target temperature is high. In the future, additional research on changing the temperature of the gas flowing inside the tube will be conducted, and the results of this study are expected to greatly contribute to the design of a tube furnace that captures volatile nuclides.

The optimum vitrification conditions of the radioactive waste using high-temperature furnace and HIP (Hot Isostatic Press) were studied for the successful reduction of the solidification volume, radioactive level, satisfying the disposal criteria such as leaching rate and compressive strength. Vitrification is receiving attention for the solidification disposal of intermediate and low-level radioactive wastes for its chemical-physical stability and leachability. Its principle is to trap the radioactive material in a fixed structure of the glass type materials, such as Boron Trioxide, Silicon Dioxide and Phosphorus Pentoxide. Sludge targeted in this study is assembly of materials while sludge is stored in the stainless-steel tank before disposal, which consists of Fe3O4 (14.9wt%), Fe2O3 (3.8wt%), and Cr2O3 (6.3wt%), cement paste (25wt%) and detergent/shower sludge (50wt%). The detergent/shower sludge generated from the washing the clothes that were worn during the work at the laboratory and nuclear power plant contains organic materials that are vulnerable to chemical reactions, therefore, immobilization of organic material by the incinerating step, which can also immobilize the radioactive substance, was applied. Its composition – containing Cs-133 and Co-59 substitution for Cs-134 and Co-60 that are radioactive – was analyzed by XRD before and after the mineralization of the sludge using high temperature furnace in different temperature, to identify the remaining element and the features of the mineralized sludge. Targeted sludge was vitrificated using Hot Isostatic Press in with different pressure and temperature conditions, to find out the optimum vitrification conditions. Vitrificated waste was evaluated in many aspects - leaching evaluation following ANS16.1, compressive strength evaluation of 3.44 MPa (waste disposal criteria), volume reduction before and after the sequence.

In this study, gas flow pattern and temperature distribution in a laboratory scale low temperature furnace for carbonization were numerically analyzed. The furnace was designed for testing carbonization process of carbon fibers made from polyimide(PI) precursor. Nitrogen gas was used as a working gas and it was treated as an ideal gas. Three-dimensional computational fluid dynamics analysis for steady state turbulent flow was used to analyze flow pattern and temperature field in the furnace. The results showed that more uniform velocity profile and axisymmetric temperature distribution could be obtained by varying mass flow rate at the inlets.

PURPOSES : This paper presents the experimental results of tests conducted on concrete produced with air-cooled (AS) and water-cooled (WS) ground blast-furnace slag exposed to multi-deterioration environments of carbonation and scaling. METHODS : Carbonated and uncarbonated concrete specimens were regularly monitored according to the ASTM C 672 standard to evaluate the durability of concrete exposed to both scaling and combined carbonation and scaling conditions. Additionally, mechanical properties, such as compressive strength, flexural strength, and surface electric resistivity, were analyzed. RESULTS : It was found that concrete specimens produced with AS and WS had a beneficial effect on the mechanical properties because of the latent hydraulic properties of the AS and WS mineral admixtures. Moreover, carbonated concrete showed good scaling resistance in comparison to uncarbonated concrete, particularly for concrete produced with AS and WS. CONCLUSIONS : The improved scaling resistance of carbonated concrete showed that AS is a suitable option for binders used in cement concrete pavements subjected to combined carbonation and scaling.

Geopolymers have many advantages over Portland cement, including energy efficiency, reduced greenhouse gas emissions, high strength at early age and improved thermal resistance. Alkali activated geopolymers made from waste materials such as fly ash or blast furnace slag are particularly advantageous because of their environmental sustainability and low cost. However, their durability and functionality remain subjects for further study. Geopolymer materials can be used in various applications such as fire and heat resistant fiber composites, sealants, concretes, ceramics, etc., depending on the chemical composition of the source materials and the activators. In this study, we investigated the thermal properties and microstructure of fly ash and blast furnace slag based geopolymers in order to develop eco-friendly construction materials with excellent energy efficiency, sound insulation properties and good heat resistance. With different curing times, specimens of various compositions were investigated in terms of compressive strength, X-ray diffraction, thermal property and microstructure. In addition, we investigated changes in X-ray diffraction and microstructure for geopolymers exposed to 1,000 oC heat.

This study was performed in order to obtain the effect of the compressive strength of the cured product with manufacturing conditions (amounts of fine aggregate and different types of alkali activator). Material which is the basis of the cured product was used for the blast furnace slag, which has a latent hydraulic activity. Consequently, when using sodium hydroxide as the alkali activator, it is possible to obtain a higher compressive strength than using the calcium hydroxide. And also, it can be added a 10% of fine aggregate with blast furnace slag to improve the compressive strength.

PURPOSES: This study investigates the mechanical performance of carbon-capturing concrete that mainly contains blast furnace slag. METHODS: The mixture variables were considered; these included Portland cement content, which was varied from 10% to 40% of the blast furnace slag by weight. The specimens were exposed to different conditions such as high N2 and O2 concentrations, laboratory conditions and high CO2 conditions. Mechanical performances, including compressive and flexural strengths and carbon-capturing depth, were evaluated. RESULTS : The slump, air content and unit weight were not affected significantly by the variation in cement content. The strength development when the specimens were exposed to high purity air was slightly greater than that when exposed to high CO2. As the cement content increased the compressive and flexural strength increased but not considerably. The carbon-capturing capacity decreased as the cement content increased. The specimens exposed in the field for 70 days had flexural strength greater than 3 MPa. CONCLUSIONS : The results indicate that cement content is not an important parameter in the development of compressive and flexural strengths. However, the carbon-capturing depth was higher for less cement content. Even after field exposure for 70 days, neither any significant damage on the surface nor any decrease in strength was observed.

고로슬래그는 유동성 장기강도 및 내구성이 좋고 수화열을 낮아 경화체를 제조함에 따른 적용성이 우수하지만, 몇 가지 문제점을 갖는다. 시공시간이 증가하고 회전속도가 늦고 초기강도가 낮다. 본 연구에서는 알칼리활성화를 이용한 경화체 제조에 있어 필요한 알칼리 수용액을 해수담수화 과정에서 발생하는 농축수의 전기분해를 통하여 공급하였으며. 알칼리 수용액을 이용하여 고로슬래그와 경화체를 제작하였다. 결과는 다음과 같이 요약할 수 있다 : 모르타르의 압축강도는 NaOH 2%이하일 때는 감소하고, 6% 이하까지는 증가한다. 그리고 NaOCl의 함량이 증가할수록 압축강도도 증가한다. 그러나 NaCl이 모르타르에 존재하면 초기강도보다 재령 28일차 강도는 감소하게 된다.