• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.13 no.2
• /
• pp.113-122
• /
• 2015

⁵⁵Fe and ⁶³Ni are key factors in deciding the proper handling of the decommissioning of radioactive waste from nuclear facilities. For determining beta emitting radionuclides, the dismantled waste samples should be completely decomposed and separated from the sample matrix. This study reports the comparison results of the recovering efficiencies of Iron and Nickel with wet digestion methods that use various acids and alkali-fusion methods. Various matrices of NIST SRMs (1646a, 1944, 8704, 2709a, and 1633c), the recovering efficiencies of using alkali-fusion methods ranged from 95.3 to 98.3% for Iron, and from 86.6 to 88.1% for Nickel within about 2% of relative standard deviation. On the other hand, those using one of the three wet digestion methods ranged from 77.9 to 105.3% for Iron and from 40.1 to 78.5% for Nickel with over 10% of relative standard deviation. Therefore, one may draw the conclusion that the analytical results derived from Iron and Nickel using alkali-fusion methods are fairly reliable due to the recovering efficiencies observed.

• Analytical Science and Technology
• /
• v.31 no.3
• /
• pp.134-142
• /
• 2018

The uranium isotopic ratio in environmental samples around nuclear facilities is important because it reveals information regarding illegal activities or anthropogenic pollution. Determination of uranium isotopes, however, is a challenging task requiring much labor and time because of the complex separation procedures and lengthy process. In this study, a rapid determination method for uranium isotopes in environmental samples was developed using. The sample was completely decomposed using the alkali fusion method. The separation procedure using extraction chromatography (UTEVA) was simplified in a single step without any further removal process for Si and major matrix elements. The established method can be completed within 3 h from sample dissolution to ICP-MS measurement. Most matrix elements and uranium isotopes in the soil samples were well separated and purified. Five types of were used to assess the method's accuracy and precision for a rapid uranium analysis method. The analytical accuracy for all CRM samples ranged from 95.1 % to 97.8 %, and the relative standard deviation was below 3.9 %. From the analytical results, one may draw conclusions that the evaluated method for uranium isotopes using alkali-fusion, the extraction chromatography process, and ICP-MS measurements is fast and fairly reliable owing to its recovering efficiencies. Thus, it is expected that the evaluated method can contribute to the improvement of environmental monitoring ability.

• Journal of the Korean Chemical Society
• /
• v.38 no.6
• /
• pp.411-417
• /
• 1994

For the analysis of fine ceramics, which is one of the new materials difficult to be dissolved, the methods of sample pretreatments such as alkali fusion and high pressure acid digestion were studied using inductively coupled plasma-atomic emission spectrometer(ICP-AES). For the Al2O3 powder sample, the results from high pressure acid digestion method showed better reproducibility than those obtained by alkali fusion technique. In the case of the analysis of SiC powder using the former method, impurities of the powder in the range of ppm were determined without matrix interference by removing Si as Si-F volatilization. Japan Certified Reference Materials (JCRM022 and JCRM023) were analyzed by this method for ultra fine powder and the results showed high accuracy and good reproducibility.

• The Journal of the Petrological Society of Korea
• /
• v.3 no.1
• /
• pp.41-48
• /
• 1994

Three USGS rock standards (G-2, W-2, and BHVO-1) are decomposed by three different methods, such as open beaker, microwave oven, and alkali fusion method, to compare the effect of decomposition methods for trace elememt analysis in the rock samples. Solubilized trace elements are measured with inductively coupled plasma mass spectrometer (ICP-MS). Generally the analytical results of trace elements between open beaker and microwave digestion method are not different. In case of alkali fusion method, some volatile elements such as Pb, Cu, and Rb are considerably lost. Using acid digestion method, Zr and Hf concentrations are lowered in case that these elements are concentrated in refractory minerals. The concentrations of rare earth elements are generally consistent with the recommended values, but due to large dilution factor, there are some analytical problems in alkali fusion method.

• Journal of the Korean Applied Science and Technology
• /
• v.32 no.2
• /
• pp.240-247
• /
• 2015

Zeolite A was prepared from coal fly ash upon NaOH fusion treatment, followed by hydrothermal treatment. The effects of treatment conditions such as NaOH/ash ratio, fusion temperature, the amount of sodium aluminate added, hydrothermal treatment temperature and time on the type and the crystallinity of zeolites were investigated. The optimal NaOH/ash weight ratio and fusion temperature to produce high crystalline zeolite A were 1.2 and $550^{\circ}C$, respectively. The dissolution of $Si^{4+}$ and $Al^{3+}$ from the fused fly ash was not affected by stirring time. The type of synthetic zeolites was found to be dependent on the amount of sodium aluminate added. The low amount of sodium aluminate favored zeolite X, while a single phase zeolite A was produced by increasing the amount sodium aluminate. Zeolite A was transformed into hydroxysodalite with increasing hydrothermal treatment time and temperature. A high crystalline zeolite A could be obtained by decreasing the temperature increasing time up to the reaction temperature.

• Journal of Radiation Protection and Research
• /
• v.40 no.2
• /
• pp.101-109
• /
• 2015

Alpha spectrometry is typically used for the assessment of uranium particle concentrations and its accuracy can be directly related to the accuracy in which the radiochemical pre-treatment is conducted. Ashing and alkali fusion methods are typically used but the ashing method requires longer analysis time and the alkali fusion method is extremely costly. Therefore, a new pre-treatment method using ultrasonic cleaning was developed and its experimental result was compared against the two conventional methods in terms of pre-treatment time, convenience, cost, and recovery rate of a target material. The results that were obtained by the conventional methods(ashing and alkali fusion) and the new method were compared. Consequently, even though the shorter pre-treatment time was required, the new technique showed almost same recovery rate comparing with two conventional methods. The new method was also featured by its relatively lower cost and a simpler process than two conventional methods.

• Proceedings of the IEEK Conference
• /
• 2001.10a
• /
• pp.357-361
• /
• 2001

The possibility of producing Cr$_2$O$_3$powder from waste magnesia-chromium refractory was investigated by sulfuric acid reaction, alkali fusion, water leaching & purification and heat treatment. The effects of temperature, the amount of NaOH added and the flow rate of air on chromium extraction efficiency in an alkali fusion step were investigated. The fusion product was leached with methanol to solve free-NaOH, and then leached with water to produce a Na$_2$CrO$_4$solution. The purity of chrome(Ⅵ) oxides, prepared both from monochromate with an impurity content and monochromate purified with $CO_2$were also examined. The purified monochromate solution was reduced from Cr(Ⅵ) to Cr(III) with NaHSO$_3$solution. The reduced solution was neutralized with NaOH to produce Cr(OH)$_3$. Water washing was treated to eliminate Na$_2$SO$_4$from neutralized Cr(OH)$_3$slurry. The washed Cr(OH)$_3$was dried and thermally treated to produce Cr$_2$O$_3$powder. The properties like lightness and hue of Cr$_2$O$_3$fabricated in this study were L=47.47, a=-14.40 and b=17.21.

• Journal of Korea Society of Waste Management
• /
• v.35 no.7
• /
• pp.640-646
• /
• 2018

Biomass-fired power plants produce electricity and heat by burning biomass in a boiler. However, one of the most serious problems faced by these plants is severe corrosion. In biomass boilers, corrosion comes from burnt fuels containing alkali, chlorine, and other corrosive substances, causing boiler tube failures, leakages, and shorter lifetimes. To mitigate the problem, various approaches implying the use of additives have been proposed; for example, ammonium sulfate is added to convert the alkali chlorides (mainly KCl) into the less corrosive alkali sulfates. Among these approaches, the high temperature corrosion prevention technology based on ammonium sulfate has few power plants being applied to domestic power plants. This study presents the results obtained during the co-combustion of wood chips and waste in a circulating fluidized bed boiler. The aim was to investigate the characteristics of pollution load in domestic biomass power plants with ammonium sulfate injection. By injecting the ammonium sulfate, the KCl content decreased from 68.9 to 5 ppm and the NOx were reduced by 18.5 ppm, but $SO_2$ and HCl were increased by 93.3 and 68 ppm, respectively.

• Journal of the Korean earth science society
• /
• v.42 no.1
• /
• pp.1-10
• /
• 2021

Silicon (Si) is the second most abundant element in the crust and consists of three stable isotopes, 28Si (92.23%), 29Si (4.67%), and 30Si (3.10%). Si isotopes are widely studied worldwide as a proxy for the biogeochemical cycle of Si to reconstruct the paleoenvironment and paleoclimate. However, in Korea, there have been no studies on biogenic silica using Si isotopes. In this study, we carried out Si isotope measurements of giant diatoms, summarizing the previously reported alkali fusion methods and establishing the best Si separation method for biogenic silica. Samples were completely digested using alkali fusion at high temperatures, effectively separating Si using an AG® 50W-X8 cation exchange resin. To evaluate the precision and accuracy of our measurements, Si isotope standard material (NBS-28) and USGS reference materials (AGV-2, GSP-2, BHVO-2) were analyzed. The results are in excellent agreement with the reported values within the acceptable error. The Si isotope measurement method developed in this study is expected to help in understanding the paleoclimate and paleoenvironment by tracing the Si cycle.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.5 no.1
• /
• pp.27-30
• /
• 1981

The change of physical properties of polyester yarn treated with sodium hydroxide solution for making polyester silk like was investigated. The tenacity of polyester yarn was reduced by increasing alkali concentration and temperature. Degree of polymerization of polyester was decreased slightly but the heat of fusion was not changed appreciably.