Cold Crucible Induction Research Articles

Coupled 3-D Analysis Employing FEM and Particle Method—Experimental Verification of Cold Crucible Induction Melting

This paper proposes a coupled 3-D finite element method (FEM) and particle method for the analysis of cold crucible induction melting. In this method, the magnetic field is calculated by FEM and the fluid motion equation and the heat equation of a molten metal are calculated by the particle method. The effectiveness of this method is verified through the analysis of the molten metal behavior in the crucible.

Structural study of the complex perovskite Ba4(Ba2Nb2)O11

Structural investigations of single crystals of the complex perovskite Ba4(Ba2Nb2)O11 synthesized by the cold crucible induction melting method were carried out in the present study. The material was studied in the as prepared, dry and hydrated states. In dry and as prepared state, based on the observations both in TEM and XRD, a body centered tetragonal (BCT) structure having the space group I4/mmm (no. 80) and cell dimensions a≈8.75Å and c≈17.1Å was proposed. In hydrated state a hexagonal structure having the space group P6¯m2 (no. 187) and cell dimensions a=6.038Å and c=18.0383Å was proposed. Contrary to previous observations, this sample showed considerable water uptake when compared to sample with the same composition prepared by solid state reaction technique. The thermogravimetric (TG) curve also indicated a phase transition during water uptake.

Analysis of technical development of vitrification radioactive waste in cold crucible induction melter

Analysis of technical development of vitrification radioactive waste in cold crucible induction melter

Towards Increased Waste Loading in High Level Waste Glasses: Developing a Better Understanding of Crystallization Behavior

A number of waste components in US defense high level radioactive wastes (HLW) have proven challenging for current Joule heated ceramic melter (JCHM) operations and have limited the ability to increase waste loadings beyond already realized levels. Many of these “troublesome” waste species cause crystallization in the glass melt that can negatively impact product quality or have a deleterious effect on melter processing. Recent efforts at US Department of Energy laboratories have focused on understanding crystallization behavior within HLW glass melts and investigating approaches to mitigate the impacts of crystallization so that increases in waste loading can be realized. Advanced glass formulations have been developed to highlight the unique benefits of next-generation melter technologies such as the Cold Crucible Induction Melter (CCIM). Crystal-tolerant HLW glasses have been investigated to allow sparingly soluble components such as chromium to crystallize in the melter but pass out of the melter before accumulating. The Hanford site AZ-101 tank waste composition represents a waste group that is waste loading limited primarily due to high concentrations of Fe2O3 (with higher Al2O3). Systematic glass formulation development utilizing slightly higher process temperatures and higher tolerance to spinel crystals demonstrated that an increase in waste loading of more than 20% could be achieved for this waste composition, and by extension higher loadings for wastes in the same group.

Indian Program for Vitrification of High Level Radioactive Liquid Waste

Nuclear Power Programme in India is based on “closed fuel cycle”. Closed fuel cycle involves reprocessing and recycling of Spent Nuclear Fuel (SNF) coming out of nuclear reactors. During reprocessing, uranium &plutonium, constituting bulk of the SNF are separated and subsequently recycled. The remaining small portion constitutes high level radioactive waste containing most of the fission products and minor actinides. A three-step strategy involving immobilization, interim storage followed by ultimate disposal has been adopted in India for management of High Level Waste (HLW). Borosilicate glass matrix has been identified for immobilization of HLW owing to optimal waste loading, adequate leach resistance and long term stability of the product. Glass formulations are developed by suitable addition of modifiers to accommodate compositional variation in the waste. Detailed characterization studies are carried out to understand the structural modifications in the three dimensional network of incorporation of waste constituents followed by product characterization to ascertain the properties of the conditioned vitrified waste product (VWP). On the strength of these indigenous developments, Indian vitrification facilities are in operation at Trombay, Tarapur and Kalpakkam. Different types of melters like metallic, Joule Heated Ceramic Melter (JHCM) have been successfully deployed on industrial scale for vitrification of HLW. A Cold Crucible Induction Melter (CCIM) has also been developed. An interim storage facility is in operation for storage and surveillance of VWP. A site selection programme has been initiated to identify a few suitable geological domains for identifying a candidate disposal site for high level and long lived radioactive wastes. Presently granites have been studied extensively as a host rock & as a natural barrier. Long term evaluation of vitrified high level waste under geological conditions and its comparison with natural analogues (basaltic & obsidian) is being pursued in India.

Cold crucible induction melter studies for making glass ceramic waste forms: A feasibility assessment

Glass ceramics are being developed to immobilize fission products, separated from used nuclear fuel by aqueous reprocessing, into a stable waste form suitable for disposal in a geological repository. This work documents the glass ceramic formulation at bench scale and for a scaled melter test performed in a pilot-scale (∼1/4 scale) cold crucible induction melter (CCIM). Melt viscosity, electrical conductivity, and crystallization behavior upon cooling were measured on a small set of compositions to select a formulation for melter testing. Property measurements also identified a temperature range for melter operation and cooling profiles necessary to crystallize the targeted phases in the waste form. Bench scale and melter run results successfully demonstrate the processability of the glass ceramic using the CCIM melter technology.

Numerical Analysis of Cold Crucible Induction Melting Employing FEM and MPS Method

This paper proposes a coupled method of 3-D finite element method (FEM) and moving particle semi-implicit (MPS) method for the analysis of cold crucible induction melting. In this method, the magnetic field is calculated by FEM and the fluid motion equation of the molten metal and the thermal distribution in the molten metal are calculated by the MPS method. In this paper, the phase transformation of the metal is not considered. The effectiveness of this method is verified through the analysis of the molten metal behavior in the crucible.

파이로그린공정 희토류폐기물 유리화 타당성 연구

파이로그린공정의 염폐기물처리과정에서 발생되는 주요 산화물 형태의 폐기물에는 희토류폐기물이 있으며 주요 구성 핵종은 Y, La, Ce, Pr, Nd, Sm, Eu, Gd 등 8종이다. 최종적인 희토류폐기물의 형태는 산화물 형태로 발생된다. 본 연구에서는 붕규산 유리계 내에서 희토류 산화물의 유리화 타당성을 평가 하기 위하여 6종의 유리조성을 개발하였다. 희토류 8핵종 혼합에 대한 solubility는 <TEX>$1,200^{\circ}C$</TEX>에서 25wt% 미만, <TEX>$1,300^{\circ}C$</TEX>에서 30wt% 미만 waste loading으로 온도 상승에 따라 증가하는 것으로 나타났으며 liquidus temperature는 균질한 유리가 형성된 20wt% waste loading에서 <TEX>$950^{\circ}C$</TEX> 이하로 평가되었다. 희토류 산화물의 유리매질 내 solubility 이상에서는 희토류-oxide-silicate 결정이 생성된 유리세라믹을 이차상으로 형성하였으며 20~25wt% waste loading의 표면균질성이 양호한 유리는 용융온도 <TEX>$1,200{\sim}1,300^{\circ}C$</TEX> 범위에서 점도 100 poise 이하, 전기전도도 1 S/cm 이상으로 유도가열식 저온용융로설비에서의 운전 용이성이 매우 양호한 것으로 평가되었다. 개발된 유리조성에 대한 기타 물리 화학적 특성 평가를 위한 실험들이 향후 수행될 예정이다. The rare earth oxide wastes consisting of major 8 nuclides Y, La, Ce, Pr, Nd, Sm, Eu and Gd, are generated during the salt waste treatment of PyroGreen process. The final form of the rare earth is generated as the oxide state. In this study, six candidate glasses were developed to evaluate the feasibility for vitrifying the rare earth oxide wastes within the borosilicate glass system. The solubilities of the mixture of the rare earth oxide waste showed less than 25wt% at <TEX>$1,200^{\circ}C$</TEX>, less than 30wt% at <TEX>$1,300^{\circ}C$</TEX>, respectively. It means that solubility is increased with the temperature increment. The liquidus temperature of the homogeneous glass with 20wt% waste loading was determined as less than <TEX>$950^{\circ}C$</TEX>. In more than solubility of rare earth oxides glass, formation of rare earth-oxide-silicate crystal in glass-ceramic occurred as the secondary phase. As their viscosity at melting temperature <TEX>$1,200{\sim}1,300^{\circ}C$</TEX> was less than 100 poise, electrical conductivity was higher than 1 S/cm, 20~25wt% waste loading glasses with good surface homogeneity are judged to have good operability in cold crucible induction melter. Other physicochemical properties of the developed glasses are going to be experimented in the future.

Glasses for immobilization of low- and intermediate-level radioactive waste

Reprocessing of spent nuclear fuel (SNF) for recovery of fissionable elements is a precondition of long-term development of nuclear energetics. Solution of this problem is hindered by the production of a great amount of liquid waste; 99% of its volume is low- and intermediate-level radioactive waste (LILW). The volume of high-level radioactive waste (HLW), which is characterized by high heat release, does not exceed a fraction of a percent. Solubility of glasses at an elevated temperature makes them unfit for immobilization of HLW, the insulation of which is ensured only by mineral-like matrices. At the same time, glasses are a perfect matrix for LILW, which are distinguished by low heat release. The solubility of borosilicate glass at a low temperature is so low that even a glass with relatively low resistance enables them to retain safety of under-ground LILW depositories without additional engineering barriers. The optimal technology of liquid confinement is their concentration and immobilization in borosilicate glasses, which are disposed in shallow-seated geological repositories. The vitrification of 1 m3 liquid LILW with a salt concentration of ∼300 kg/m3 leaves behind only 0.2 m3 waste, that is, 4–6 times less than by bitumen impregnation and 10 times less than by cementation. Environmental and economic advantages of LILW vitrification result from (1) low solubility of the vitrified LILW in natural water; (2) significant reduction of LILW volume; (3) possibility to dispose the vitrified waste without additional engineering barriers under shallow conditions and in diverse geological media; (4) the strength of glass makes its transportation and storage possible; and finally (5) reliable longterm safety of repositories. When the composition of the glass matrix for LILW is being chosen, attention should be paid to the factors that ensure high technological and economic efficiency of vitrification. The study of vitrified LILW from the Kursk nuclear power plant with high-power channel reactors (HPCR; equivalent Russian acronym, RBMK) and the Kalinin nuclear power plant with pressurized water reactors (PWR; equivalent Russian acronym VVER) after their 14-yr storage in the shallow-seated repository at the MosNPO Radon testing ground has confirmed the safety of repositories ensured by confinement properties of borosilicate matrix. The most efficient vitrification technology is based on cold crucible induction melting. If the content of a chemical element in waste exceeds its solubility in glass, a crystalline phase is formed in the course of vitrification, so that the glass ceramics become a matrix for such waste. Vitrified waste with high Fe; Na and Al; Na, Fe, and Al; Na and B is characterized. The composition of frit and its proportion to waste depends on waste composition. This procedure requires careful laboratory testing.

유리섬유 및 알루미늄 금속 혼합물 유리조성 개발

원전에서 발생되는 방사성폐기물에 대한 고화처리 방법 중 하나인 유리화기술이 일부 가연성폐기물에 대해 적용되고 있다. 국내외적으로 중저준위 방사성폐기물의 효과적인 감용과 안정적인 처분을 위해 다양한 폐기물에 대한 유리화기술 적용방안이 확대 연구되고 있으며, 최근에는 가연성폐기물 뿐만 아니라 알루미늄 금속과 같은 비가연성폐기물에도 유리화 연구가 활발하게 진행되고 있다. 공기조화계통 (HVAC)에는 주로 필터가 이용되고 있으며, 사용 후 필터는 여과재 (유리섬유 및 알루미늄)를 이용하여 배기체를 흡착하기 때문에 방사성폐기물로 처리가 되어야 한다. 본 연구는 필터에 대한 처리기술 연구를 위해 유도가열식 저온용융로 (Cold Crucible Induction Melter: CCIM)를 이용한 유리화 타당성 연구를 수행하였다. 사용후 필터에 대한 유리화 (Vitrification)는 먼저 유리섬유 및 알루미늄 함량을 고려한 최적의 유리조성을 개발 하였으며, 개발된 유리 조성을 이용하여 최적의 폐기물 저감을 위한 용융변수와 최종 생성된 유리고화체의 특성을 분석하였다. 사용후 필터 유리화용 조성유리는 주로 <TEX>$SiO_2$</TEX>와 <TEX>$B_2O_3$</TEX>로 구성되어 있다. 전기로를 이용한 용융물 특성시험에서는 폐기물 투입률 및 최종 생성물인 유리고화체의 특성이 검토되었다. 본 연구에서는 알루미늄 금속과 유리섬유로 구성된 필터에 대한 유리조성 개발과 이를 통해 생성된 유리고화체의 물리화학적 특성을 검토하고 유리화 타당성을 확인하였다. Vitrification technology has been widely applied as one of effective processing methods for wastes generated in nuclear power plants. The advantage of vitrifying for low- and intermediate-level radioactive wastes has a large volume reduction and good durability for the final products. Recently, a filter using on HVAC(Heating Ventilating & Air Conditioning System) is composed with media (glass fiber) and separator (aluminum film) has been studied the proper treatment technology for meeting the waste disposal requirement. Present paper is a feasibility study for the filter vitrification that developing of the glass compositions for filter melting and melting test for physicochemical characteristic evaluation. The aluminum metal of film type is preparing with 0.5 cm size for proper mixing with glass frit, glass fiber is also preparing with 1 cm size within crucible. The glass compositions should be developed considering molten glass are related with wastes reduction. Glass compositions obtained from developing on glass formulation are mainly composed of <TEX>$SiO_2$</TEX> and <TEX>$B_2O_3$</TEX> for aluminum metal. A variety of factors obtained from the glass formulation and melting test are reviewed, which is feeding rate and glass characteristics of final products such as durability for implementing the wastes disposal requirement.

Corrosion study of a highly durable electrolyzer based on cold crucible technique for pyrochemical reprocessing of spent nuclear oxide fuel

The application of the cold crucible technique to a pyrochemical electrolyzer used in the oxide-electrowinning method, which is a method for the pyrochemical reprocessing of spent nuclear oxide fuel, is proposed as a means for improving corrosion resistance. The electrolyzer suffers from a severe corrosion environment consisting of molten salt and corrosive gas. In this study, corrosion tests for several metals in molten 2CsCl–NaCl at 923K with purging chlorine gas were conducted under controlled material temperature conditions. The results revealed that the corrosion rates of several materials were significantly decreased by the material cooling effect. In particular, Hastelloy C-22 showed excellent corrosion resistance with a corrosion rate of just under 0.01mm/y in both molten salt and vapor phases by controlling the material surface at 473K. Finally, an engineering-scale crucible composed of Hastelloy C-22 was manufactured to demonstrate the basic function of the cold crucible. The cold crucible induction melting system with the new concept Hastelloy crucible showed good compatibility with respect to its heating and cooling performances.

A simplified mathematical model of glass melt convection in a cold crucible induction melter

Cold crucible induction melting is emerging as a promising technology for immobilizing nuclear waste in glass matrices. Since the transport properties such as viscosity and electrical conductivity of molten glass exhibit strong temperature dependencies, performance of the cold crucible induction melter is highly sensitive to the thermal field prevailing in the molten glass pool. A simplified mathematical model was developed to numerically investigate the impact of molten glass properties such as viscosity, thermal conductivity and electrical conductivity on the performance of a cold crucible induction melter meant for high level radioactive waste vitrification. The present investigation of the thermal convection using the simplified model confirms the findings of previous studies. Numerical simulation of thermal convection shows that low electrical conductivity and high viscosity existing in the cooler parts of the molten glass bath can lead to poor electromagnetic induction and localized heating in the present melter-inductor configuration. The stable thermal stratification due to bottom cooling leads to a relatively stagnant fluid layer in the lower part of the glass melt. These features of the thermal convection can limit the heat transfer and mixing in the glass melt which in turn can affect both the melting capacity and product homogeneity adversely. Mechanical stirring using a water-cooled stirrer can overcome these limitations. The present study confirms that mechanical stirring of the glass melt can enhance the electromagnetic induction through thermal homogenization. Mechanical mixing eliminates the relatively stagnant fluid layer observed in thermal convection. Distribution of induced power, temperature and velocity predicted by the simplified model exhibit matching characteristics of the results obtained by other investigators. The simplified model reduces the computational load substantially as it eliminates complex electromagnetic computations.

Glass Formulation Development in Support of Melter Testing to Demonstrate Enhanced High Level Waste Throughput

AbstractThe U.S. Department of Energy (DOE) is currently processing high-level waste (HLW) through a Joule-heated melter (JHM) at the Savannah River Site (SRS) and plans to vitrify HLW and Low activity waste (LAW) at the Hanford Site. Over the past few years at the Defense Waste Processing Facility (DWPF), work has concentrated on increasing waste throughput. These efforts are continuing with an emphasis on high alumina concentration feeds. High alumina feeds have presented specific challenges for the JHM technology regarding the ability to increase waste loading yet still maintain product quality and adequate throughput. Alternatively, vitrification technology innovations are also being investigated as a means to increase waste throughput. The Cold Crucible Induction Melter (CCIM) technology affords the opportunity for higher vitrification process temperatures as compared to the current reference JHM technology. Higher process temperatures may allow for higher waste loading and higher melt rate.Glass formulation testing to support melter demonstration testing was recently completed. This testing was specifically aimed at high alumina concentration wastes. Glass composition/property models developed for DWPF were utilized as a guide for formulation development. Both CCIM and JHM testing will be conducted so glass formulation testing was targeted at both technologies with a goal to significantly increase waste loading and maintain melt rate without compromising product quality.

Experimental analysis of the performance of cold crucible induction glass melter

An engineering scale cold crucible induction glass melter was developed employing a transistor-based induction heating power supply with an operating frequency of 200 kHz. Experimental investigations were carried out to study its electrical and thermal performances during various stages of operations such as start-up heating, batch melting and idling. Sodium borosilicate glass with an electrical conductivity of 1.9 Ω cm and viscosity of 9.4 Poise at 1000 °C was used for the present study. Calorimetric measurements were carried out to determine the electrical and thermal efficiencies of various subsystems involved. An electrical efficiency of 80.4%, a melter efficiency of 20.83% and an over all efficiency of 16.74% were experimentally obtained for batch melting of sodium borosilicate glass in an engineering scale cold crucible induction glass melting system.

Characterization of the glass-ceramic material prepared upon vitrification of an iron-containing surrogate of high-level wastes in a cold crucible

Vitreous materials are prepared by cold crucible induction melting of a surrogate of high-level wastes (from the Savannah River Site, United States) and a borosilicate glass frit taken in mass ratios from 45: 55 to 60: 40. According to the X-ray diffraction and electron microscopic data, the vitreous materials thus produced consist of a glass matrix and a magnetite-type spinel enriched in transition elements. The degree of crystallinity of the materials increases with an increase in the waste oxide content from 6 to 18–20 vol %. The vitreous materials are characterized by a high chemical durability, which decreases only at high contents of the waste oxides (55 wt % and higher) due to the formation of an additional nepheline phase.

Experimental study of natural convection in a glass pool inside a cold crucible induction melter

Cold crucible induction melting is evolving as a promising technology for vitrification of high level radioactive waste because of high temperature availability and long melter life. Natural convection in the inductively heated glass pool plays a significant role in the performance of such melters. Experimental investigations were carried out to study the nature of flow patterns and temperature profiles in a sodium borosilicate glass pool inside an engineering scale cold crucible induction melter. Flow patterns were obtained for power levels in the range of 50 to 110 kW. The average surface velocity was found to vary from 5 mm s −1 at 50 kW to 22.5 mm s −1 at 110 kW. Experimentally measured temperature profiles in the glass pool indicated a well-mixed zone above a thermally stratified layer.

ICONE15-10814 PROSPECTIVE APPLICATIONS OF THE METALLIC COLD CRUCIBLE TECHNOLOGY FOR THE VITRIFICATION OF VARIOUS WASTES

This paper presents a review of the CCIM (Cold Crucible Induction Melter) technology development as led by CEA and gives recent illustrations of prospective applications of a metallic cold crucible technology for various waste treatments obtained with research full scale pilot devices.

Compaction and Cold Crucible Induction Melting of Fine Poly Silicon Powders for Economical Production of Polycrystalline Silicon Ingot

AbstractThe consolidation and casting processes of fine silicon powders, by-product of high purity silicon rods making process in the current method, were systematically investigated for use as economical solar-grade feedstock. Morphology, size, and contamination type of the fine silicon powders were inspected by combined analysis of SEM, particle size analyzer, and FT-IR. Silicon powder compacts were tried to fabricate by a consolidation process without a binding agent and then their density ratio and strength were evaluated. Finally, the electrical resistivity of the specimens prepared by an electromagnetic casting method was examined for purity assessment.

Cold Crucible Vitrification of Defense Waste Surrogate and Vitrified Product Characterization

ABSTRACTIn the framework of the contract “Advanced Melter Technology Application to the Defense Waste Processing Facility (DWPF) –Cold Crucible Induction Heated Melter (CCIM)”, vitrification tests with Savannah River Site defense waste surrogate were performed at the SIA Radon facility. Cold crucible melters with inner diameter of 216 mm and 418 mm were used in the testing. Commercially available (USA) frits 200 and 320 were used as glass-forming additives. In three different test campaigns, waste additive mixtures were fed as slurries with ∼60 wt.%, ∼30 wt.%, and 45 wt.% water content. Maximum slurry capacity and glass productivity under steady-state conditions were 35.4 kg/h and 16.2 kg/h, respectively. Specific glass productivity reached up to ∼3000 kg/(m2×day). The average melt process temperature was 1250- 1350 °C. Waste loadings in glass were 45 wt.% in tests 1 and 2 and 50 wt.% in test 3. The glasses produced were found to be homogeneous but contained a magnetite-type phase with the spinel structure due to high iron and manganese content in waste. Spinel was observed in the glassy matrix as individual regular crystals and their aggregates. All the waste uranium entered the vitreous phase. Infra-red spectra consist of strong absorption bands due to bridging Si-O-Si and non-bridging Si-O- bonds, some weak bands due to B-O bonds, and a number of narrow bands due to occurrence of the crystalline phase. The glassy products demonstrate high leach resistance. Normalized release of major glass elements (Na, Li, B, Si) is by 10 to 50 times lower than the values required for repository disposition by EPA.

Purification of Cobalt, Nickel, and Titanium by Cold-Crucible Induction Melting in Ultrahigh Vacuum

Three separate charges of cobalt 9.2 kg in weight, 3.0 kg nickel and 1.6 kg titanium have been melted in ultrahigh vacuum (UHV) using cold-crucible induction melting (CCIM) furnace, in which UHV of better than 1×10−7 Pa is attainable. The effects of CCIM in UHV on the purification of these metals due to the removal of gaseous impurities, and the characteristics of CCIM in UHV have been investigated by the analysis of the melting conditions such as the total pressure and the mass spectra of gases during CCIM, and analytical results of these ingots. CCIM in the present UHV degree and quality is found to be very effective for the purification due to the removal of gaseous impurities in cobalt and nickel, in particular, for the decrease in oxygen, and very important for melting of ultrahigh-purity titanium without any contamination by gaseous impurities, in particular, oxygen.