• Journal of the Korean Ceramic Society
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• v.52 no.2
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• pp.92-102
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• 2015

Current plans for legacy nuclear wastes stored in underground tanks at the U.S. Department of Energy's Hanford Site in Washington are that they will be separated into high-level waste and low-activity waste fractions that will be vitrified separately. Formulating optimized glass compositions that maximize the waste loading in glass is critical for successful and economical treatment and immobilization of these nuclear wastes. Glass property-composition models have been developed and applied to formulate glass compositions for various objectives for the past several decades. Property models with associated uncertainties combined with composition and property constraints have been used to develop preliminary glass formulation algorithms designed for vitrification process control and waste-form qualification at the planned waste vitrification plant. This paper provides an overview of the current status of glass property-composition models, constraints applicable to Hanford waste vitrification, and glass formulation approaches that have been developed for vitrification of hazardous and highly radioactive wastes stored at the Hanford Site.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11b
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• pp.176-181
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• 2005

The electrolytic reduction process and the electrorefining process, which are being developed at the Korea Atomic Energy Research Institute (KAERI), are to generate molten waste salts such as LiCI salt and LiCI-KCI eutectic salt, respectively. Our goal in waste salt management is to minimize a total waste generation and fabricate a very low­leaching waste form such as a ceramic waste form. Zeolite has been known to one of the most desirable media to immobilize waste salt, which is water soluble and easily radiolyzed. Zeolite can be also used to the removal of fission products from the spent waste salt. Molten LiCI salt is mixed with zeolite A at $650^{\circ}C$ to form a salt-loaded zeolite, and then thermally treated in above $900^{\circ}C$ to become an immobilized product with crystal phase of $Li_{8}Cl_{2}$-Sodalite. In this work, a crystal phase changes of immobilization medium, zeolite, during immobilization of molten LiCI salt using zeolite A is introduced.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.4
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• pp.509-516
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• 2020

An important property of glass and ceramic solid waste forms is processability. Tellurite materials with low melting temperatures and high halite solubilities have potential as solid waste forms. Crystalline TiTe3O8 was synthesized through a solid-state reaction between stoichiometric amounts of TiO2 and TeO2 powder. The resultant TiTe3O8 crystal had a three-dimensional (3D) structure consisting of TiO6 octahedra and asymmetric TeO4 seesaw moiety groups. The melting temperature of the TiTe3O8 powder was 820℃, and the constituent TeO2 began to evaporate selectively from TiTe3O8 above around 840℃. The leaching rate, as determined using the modified American Society of Testing and Materials static leach test method, of Ti in the TiTe3O8 crystal was less than the order of 10-4 g·m-2·d-1 at 90℃ for durations of 14 d over a pH range of 2-12. The chemical durability of the TiTe3O8 crystal, even under highly acidic and alkaline conditions, was comparable to that of other well-known Ti-based solid waste forms.

• Journal of Ceramic Processing Research
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• v.19 no.6
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• pp.472-478
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• 2018

In this study, the sintering mechanism of woodceramics (WCs) from cashew nut shell waste (CNSW) was studied by analyzing chemical reactions and structural changes during the sintering process of of CNSW powder, liquefied wood and green bodies of WCs at $900^{\circ}C$ for 60 minutes in the $CO_2$ atmosphere. The chemical and structural properties of the products were investigated by X-ray diffraction (XRD), Raman spectroscopy, Fourier Transform Infrared (FTIR), and scanning electron microscope (SEM). The results showed that the decomposition reactions of liquefied wood and CNSW occurred simultaneously to form the hard carbon and the soft carbon at high temperature. The sintering mechanism of WCs has been presented.

• Journal of Powder Materials
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• v.23 no.3
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• pp.221-227
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• 2016

Waste oyster shells create several serious problems; however, only some parts of them are being utilized currently. The ideal solution would be to convert the waste shells into a product that is both environmentally beneficial and economically viable. An experimental study is carried out to investigate the recycling possibilities for oyster shell waste. Bulk ceramic bodies are produced from the oyster shell powder in three sequential processes. First, the shell powder is calcined to form calcium oxide CaO, which is then slaked by a slaking reaction with water to produce calcium hydroxide $Ca(OH)_2$. Then, calcium hydroxide powder is formed by uniaxial pressing. Finally, the calcium hydroxide compact is reconverted to calcium carbonate via a carbonation reaction with carbon dioxide released from the shell powder bed during firing at $550^{\circ}C$. The bulk body obtained from waste oyster shells could be utilized as a marine structural porous material.

• Journal of Power System Engineering
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• v.18 no.3
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• pp.93-99
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• 2014

The purpose of this paper is to manufacture the non-sintered ceramic used lime and industrial waste. The used materials were basalt powder sludge, calcium hydroxide(Ca(OH)2) and additives such as calcium stearate and $TiO_2$. The mixing ratios between Ca(OH)2 and sludge were 5:5, 6:4 and 8:2, respectively. The ceramic forms were pressured by 100, 200 and 300 bar and cured in 14% CO2 for 12 days. The behaviors of compressive strength, specific gravity, water absorption and pH of ceramic form were investigated. The results were compressive strength of over 36 MPa, water absorption of over 8.8%, pH value of over 12.3. And these results satisfied GR F 4006 and 4031 standard.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.576-581
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• 2002

In order to simultaneously vitrify the ton Exchange Resin(IER) and Dry Active Waste(DAW) generated from the Nuclear Power Plants, a vitrification pilot test was conducted using an induction cold crucible melter. The PCT result evaluating the chemical durability of the vitrified from showed that the final glass was more durable than the benchmark glass. Liquidus temperature for the final vitrified form was 1048 K(775$\^{C}$) fur heat treatment experiments. The value of the compressive strength for the vitrified form was ninety times higher than the regulation limit, 34 kg/㎠. The glasses on bottom, middle and top of the CCM were homogeneous with no secondary phase. The precipitation of the magnetic metal phase was able to be avoided by simultaneously fEeding of DAW with IER containing strongly reducing organics. Volume reduction factor of 74 was achieved through the vitrification Pilot test for mixed waste.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.3
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• pp.313-319
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• 2019

The A-KRS (Advanced Korean Reference Disposal System) is the disposal concept for pyroprocessed waste, which has been developed by the Korea Atomic Energy Research Institute. In this disposal concept, the amount of high-level radioactive waste is minimized using pyrochemical process, called pyroprocessing. The produced pyroprocessed waste is then solidified in the form of monazite ceramic. The final product of ceramic wastes will be disposed of in a deep geological repository. By the way, the decay heat is generated due to the radioactive decay of fission products and raises the temperature of buffer materials in the near field of radioactive waste repository. However, the buffer temperature must be kept below $100^{\circ}C$ according to the safety regulation. Usually, the temperature can be controlled by variation of the canister interdistance. However, KAERI has modelled thermal analysis under the boundary condition, where the waste canisters are in direct contact with each other. Therefore, a reliable temperature analysis in the disposal system may fail because of unknown thermal resistence values caused by the spatial gap between waste canisters. In the present work, we have performed thermal analyses considering the gap between heating elements and canisters at the beginning of canister loading into the radioactive waste repository. All thermal analyses were performed using the COMSOL software package.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.505-510
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• 2012

A study of the recovery of tin and nickel from steel ball scraps for barrel plating was carried out through a physical treatment, a leaching treatment, hydrogen reduction and an electrolysis experiment. The recovery of the iron component was over 95% by the physical treatment. We obtained tin oxide in the form of metastannic acid ($SnO_2{\cdot}xH_2O$) with impurities of less than 5% from the leaching treatment. We also recovered the high-purity metallurgical tin at a rate that exceeded 99.9% by the electrolysis of crude tin obtained from the hydrogen reduction of metastannic acid.

• Journal of the Korean Ceramic Society
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• v.28 no.12
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• pp.996-1004
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• 1991

In this study, we tried to synthesis iron hydroxide suitable for longitudinal magnetic recording media from waste acid, which is a by-product of an iron works factory. Effects of initial pH of reactants, reaction temperature, reaction time for the synthesis of acicular iron hydroxide were studied in relation to particle properties of iron hydroxide and magnetic properties of maghemite powders. As the pH in reactant solution increased, $\beta$-FeOOH(pH=4.5), mixture of $\beta$-FeOOH and $\alpha$-FeOOH(4.5$\alpha$-FeOOH and Fe3O4(6.4$\alpha$-FeOOH (pH>13) was found to from in order. Especially, $\alpha$-FeOOH formed above pH 13 was single phase with superior acicularity. The temperature range over which the single-phase goethite can be formed increased as the initial pH of reactants increased (pH 13:10~5$0^{\circ}C$, pH 13.2:10~7$0^{\circ}C$, pH 13.5:0~8$0^{\circ}C$). The goethite formed between 40~6$0^{\circ}C$ has superior characteristics because the acicularity increased with increasing temperature but at high temperature (>6$0^{\circ}C$) Fe3O4 (pH=13) was found to start to form. Generally, single phase of goethite was found to form after one hour when an optimized condition. The particle size of goethite did not change as the reaction time increased over one hour. Accordingly, the magnetic properties of ${\gamma}$-Fe2O3 produced from goethite were not altered.