Cold Crucible Induction Melter Research Articles

Hot corrosion behavior of the rotating kiln thermowell from a cold crucible induction melter system

A thermowell dissembled from an on-going high-temperature rotating kiln part from a cold crucible induction melter (CCIM) system was characterized, and the underlying mechanism governing its hot corrosion and degradation behavior was further studied. Results indicate that the high-temperature interaction between the thermowell and the nuclear waste stream leading to the formation of oxides with different valence states mainly composed of FeCrO2, Fe2O3, FeO and NiO, with the diffusion of the simulated radionuclides into the lattice structure The on-site corrosion and phase degradation are thermodynamically driven by the outward growth of the oxidation film.

Cold Crucible Induction Melting for the Fabrication of Fe–xTiC In Situ Metal Matrix Composites: Alloying Efficiency and Microstructural Analysis

Fe–xTiC in situ metal matrix composites (MMCs) are fabricated utilizing a cold crucible inductive melting (CCIM) technique with varying TiC amounts (2, 3.5, and 5 wt%). Steel blocks and pure Ti plates are remelted in a water‐cooled copper crucible. The subsequent solidification of [Ti]‐ and [C]‐rich melt yields TiC reinforcement particles in an ingot. The holding time varies between 5 and 30 min, whereas the holding temperature alters depending on the amount of TiC, ranging from 1380 to 1620 °C for Fe‐5TiC and Fe‐2TiC, respectively. Alloying efficiency for TiC‐forming elements is estimated for all fabricated Fe–xTiC ingots by comparing [Ti] and [C] target values with measured ones. The lower TiC amounts and shorter holding times result in decreased [Ti] and [C] losses. SEM analysis of three cross‐section samples representing different TiC amounts reveals two distinct morphologies of TiC in situ reinforcements: primary blocky/cubic and eutectic plate‐like precipitates. The blocky precipitates appear slightly finer with a decrease in TiC amount (4.4 ± 1.2 μm for Fe‐5TiC and 3.8 ± 0.7 μm for Fe‐2TiC), whereas the length of plate‐like precipitates noticeably decreases in the samples with lower TiC amounts (11.0 ± 7.0 μm for Fe‐5TiC and 6.8 ± 3.6 μm for Fe‐2TiC).

Radioactive-Waste Vitrification by Cold-Crucible Induction Melting in a Bottom-Heated Furnace

Radioactive-Waste Vitrification by Cold-Crucible Induction Melting in a Bottom-Heated Furnace

Refinement of the eutectic composition in the LaB6–VB2 system

The LaB6–VB2 alloy with the eutectic structure was obtained by cold crucible induction melting followed by crystallization. The mole ratio of components in the initial powder mixture was 35 : 65. The structure and composition of the LaB6–VB2 material were studied by X-ray diffraction, scanning electron microscopy, and X-ray microanalysis. The composition of the alloy is represented by two boride phases — cubic LaB6 and hexagonal VB2. Two-phase eutectic regions up to 500 μm in size represent a LaB6 matrix filled with 0.8–2.0 μm thick VB2 fibers (filamentary, rod crystals). VB2 fibers are predominantly oriented along the direction of the temperature gradient that appeared when cooling the melt, i.e. from the outer surface of the sample to its center. The integrated phase area analysis was used to determine the eutectic composition: 42 Ѓ} 1 mol% LaB6 and 58 Ѓ} 1 mol% VB2.

Экспериментальные и теоретические исследования индукционных печей с холодными тиглями и донным нагревом для остекловывания радиоактивных отходов

The paper describes the development of a concept for bottom-heated induction melting in cold crucible (CCIM-BH) applied for radioactive waste vitrification purposes. It presents experimental and theoretical research data that can be used in the design development of industrial high-performance radioactive waste vitrification facilities. The paper provides experimental data involving electrical and energy characteristics of the melters. Based on 2D simulation of electromagnetic and hydrodynamic processes, the study evaluates the distributed parameters of induction systems demonstrating CCIM-BH features and advantages.

Numerical study of noble metals sedimentation during vitrification of high-level radioactive waste in a cold crucible induction melter

Numerical study of noble metals sedimentation during vitrification of high-level radioactive waste in a cold crucible induction melter

Melting and draining tests on glass waste form for the immobilization of Cs, Sr, and rare-earth nuclides using a cold-crucible induction melting system

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

Characterization of municipal solid-waste incinerator fly ash, vitrified using only end-waste glass

The possibility of vitrifying the fly ash generated from municipal solid-waste incinerators and the immobilisation effect of toxic elements were investigated using several batches of fly ash and two kinds of common waste glass (waste glass from end liquid crystal display device and soda lime silicate waste glass). Fly ash could be vitrified by melting at 1300 °C prior to the introduction of a minimum of 30 wt% waste glass to each batch. Leaching tests were performed using the TCLP (Toxicity Characteristic Leaching Procedure) for three types of glass to identify the concentrations of five harmful elements (Pb, Ba, As, Cd, Cr) in the extraction fluid and a surface analysis using SIMS (Secondary Ion Mass Spectrometry) was performed to reveal the elemental distribution of the glass. The results confirmed that the regulatory levels (Pb < 5, Ba<100, As<5, Cd < 1 and Cr < 5 ppm) set by the US EPA (Environmental Protection Agency) were satisfied, while the elemental distribution on the glass surface, before and after TCLP, differed only in the amount of Cr. Two melt properties (σ: electrical conductivity, η: viscosity) at around 1300 °C were examined for simulated glass melts assuming the application of CCIM (Cold-Crucible Induction Melting) technology and discussed in terms of their constraint values (σ: 0.1–1.0 S/cm, η: 10–100 dPas) for CCIM and the effect of their composition. To obtain the desired both melt properties, it is suggested that the present glasses should contain 2–4 wt% Na 2 O. Additionally, the economic and environmental effects of the waste glass recycling on fly ash vitrification were discussed from the view point of energy saving and CO 2 reduction. • Fly ash is completely vitrified with only common waste glasses. • Leaching tests and surface analysis indicate excellent chemical durability. • Some fly ash batches are suitable for cold crucible induction melting. • Use of waste glass lowers melting temperature of fly ash batch.

Fluxes for the Slag Melting of Metallic Radioactive Wastes to Return Fissionable Materials to a Nuclear Fuel Cycle

The possibility of flux fabrication for processing metallurgical radioactive wastes by melting the components into a slag agglomerate aimed at returning fissionable materials to a nuclear fuel cycle is shown. The proposed compositions contain no components used in nonferrous and ferrous metallurgy, namely, silica, fluorides, and boron compounds. Fluxes based on the systems Al2O3–MnO, Al2O3–MnO–Na2O, Al2O3–MnO–CaO, and Al2O3–MgO–CaO–Fe2O3 are synthesized by cold crucible induction melting. Their thermochemical properties and phase compositions are studied.

Eloboration of Methods for Determination on Content of the Oxygen, Nitrogen, Hydrogen Admixtures in Titanium Aluminides

Titanium intermetalides (TiAl and Ti3 Al) and alloys on theirs bases applies in air — and spacetechnology and automobile industry.&#x0D; Physical and mechanical properties there alloys is better, then at classical Ti — or Ni — alloys, that are utilized in aeroplanes and rocets.&#x0D; Alloys, based on TiAl and Ti3Al, are made with utilization vacuum — arc, plasma — arc, induction- garnisage, magnetoperating electroslag melting, electron — beam melting with intermediate capacity, electroslag melting in inert atmosphere under «active» fluxes with metallic calcium, induction melting in muchsectional crystallizator and cold crucible, argon — arc melting with unexpended tungsten electrode in copper watercooling crucible.&#x0D; For connection of the details, that were made from these alloys, there were used welding by pressure, contact, electron — beam, diffusion welding.&#x0D; Alloys, based on titanium aluminide, have essential defects — high brittleness and low plasticity, viscosity and resistance thermal impact strength.&#x0D; Autors a lot of articles explaines these descriptions by structural special features of titanium aluminides and alloys on their bases, but does not consider possibilities of the influence by oxygen nitrogen, hydrogen admixtures.&#x0D; In literature information about methods of determination gaseous admixtures (O, N, H) contents in titanium aluminides and alloys on their bases are absented.&#x0D; Methods of determination oxygen, nitrogen, hyd­rogen contents in titanium aluminides on ana­lysers TC436, RO316, TN114, RH402 are created. Parameters of these methods are described in this article (temperatures of heating on graphite crucibles, times, masses of analytical samples).

Optimization of light water reactor High Level Waste disposal scenario in the situation of delayed reprocessing with existing and demonstrated technology

Disposal scenario of High Level Waste (HLW) of Light Water Reactor (LWR) have been optimized to reduce waste volume and repository footprint in geological disposal. The optimization was performed with existing and demonstrated technology in the situation where the reprocessing will be delayed. In general, the scenario with Partitioning and Transmutation (P&T) is optimized to minimize waste package number generated in the situation where the spent fuel will be reprocessed immediately with the minimum cooling time. With considering the delay of reprocessing, it is found that the more simplified and effective optimization with the high-waste-loading glass and cold crucible induction melter technologies and without partitioning. The optimized case can achieve significant reduction of number of waste package generation and the repository footprint to half of those of non-P&T case with 100 years cooling.

Cyclic martensitic transformations and damage evolution in shape memory zirconia: Single crystals vs polycrystals

AbstractIn zirconia‐based shape memory ceramics (SMCs), cracking during the martensitic transformation can be avoided in structures that reduce the relative presence of grain boundaries where high levels of transformation mismatch stress develop. This approach has been well established in single crystals, but only for sample sizes below about 5 microns. In this paper, we extend the strategy of eliminating grain boundaries to bulk specimen scales by fabricating mm‐scale single crystal SMCs via cold crucible induction melting. For 1.5 and 2.0 mol% Y2O3‐ZrO2, we study the cyclic martensitic transformation of both single crystal and polycrystal structures. Whereas single crystals have very repeatable transformation behavior in terms of hysteresis and strain amplitude, polycrystals degrade dramatically as they accumulate cracking damage with repeated cycling. As the polycrystal evolves from a pellet to granular packing of loose single crystals/grains, the energy dissipation converges with that of the single‐crystal structure, and the energy spent on cracking throughout that process is captured by calorimetry analysis. These results verify that grain boundaries play a key role in damage evolution during martensitic transformation and that microstructural control can extend the size‐scale of viable single crystal or oligocrystal SMCs from the micro‐ to the millimeter scale.

In situ process monitoring of nuclear waste glass melts using non-contact microwave sensor

• Non-contact microwave sensor for in situ high temperature measurements. • Algorithms to extract process parameters from SFCW radar measurements. • Demonstration of continuous monitoring of absolute level of glass melt. • In situ identification of thermal steady state of glass melt. • Remote monitoring of all stages in a typical vitrification batch process. A non-contact microwave sensor is presented for in situ process monitoring of nuclear waste glass melts inside a cold crucible induction melting (CCIM) furnace. The level and thermal steady state of the molten glass inside a 1400 °C CCIM furnace were measured during 6-hour long vitrification process using a corrugated horn antenna operating over 20–24 GHz designed for high temperature measurement. The non-contact in situ microwave measurements indicate the ability to measure absolute level, identify thermal steady state of the glass melt, and remotely monitor the vitrification process for safe immobilization of the liquid radioactive waste.

Investigation of silver behavior in the glass melt and its effect on the IMCC conditions in an industrial-scale furnace during vitrification of HLLW simulants

ABSTRACTThe large-scale cold crucible induction melter (CCIM) with productivity of 12 kg/h was created for melting borosilicate glass containing 20 mass. % of high-level liquid wastes (HLLW) simulators. Tests were carried out to study the effect on the CCIM operating parameters during sedimentation of metallic silver, at the content of 3.8 mass. % Ag2O in glass. Post-test analyses of the glass shows the sedimentation of silver in the bottom layers of the molten pool. Experiments have confirmed that the presence of noble metals in the form of undissolved sediments in the bottom layers of furnace leads to a changes in the properties of the melt, the aggravation of its drain conditions, an increase in the thermal conductivity of the skull and heat losses during melting.

Study of online measurements techniques of metallic phase spatial distribution into a corium pool

In the context of in-vessel retention (IVR) strategy in order to better assess the risk of reactor vessel failure, the knowledge related to the kinetics of immiscible liquid phases stratification phenomenon needs to be further improved. So far, only one medium-scale experiment (MASCA-RCW, in the frame of the OECD MASCA program) gives direct information regarding the transient relocation of metal below the oxide phase through post-mortem measurements. No experimental characterization of the stratification inversion kinetics when heavy metal becomes lighter and relocates at the top exists. Further investigation of these hydrodynamic and thermochemical processes could be made possible thanks to on line instrumentation enabling to follow displacement of oxidic and metallic phases into the corium pool. At CEA Cadarache, studies are under progress to set up innovative technologies for corium stratification monitoring which would be integrated to a cold crucible induction melting furnace. Based on space and time resolution specifications, three on-line measurements techniques were selected and studied. The first one is an ultrasonic technique using a refractory material waveguide and based on a time-of-flight measurement. We present the feasibility approach with the preliminary results obtained during experiments at high temperature on VITI facility. The second method consists in electromagnetic characterization of the corium pool thanks to an excitation by a magnetic field induced by surroundings coils and measurement of magnetic response by sensors placed around the crucible. A modelling study has enabled to define an appropriate experimental configuration. An experimental set up has also been tested to verify the calculation results. The third technique is 2D X-rays imaging. A feasibility study for a real-time X-ray imagingwith a framerate of 1 image/s has been performed using home-made simulation software MODHERATO, accounting forscattering, based on corium behavior previsions. Results on thedetection of interfaces between different type of corium phases(oxide, light metal, heavy metal) are shown.

Magnetic Transitions in the Co-Modified Mn2Sb System

Mn2Sb is ferrimagnetic below its Curie temperature (TC) and passes through a spin flip transition with decreasing temperature. The Co substitution induces an additional first-order phase transition from the ferrimagnetic (FRI) to an antiferromagnetic (AFM) state. This phase transition is connected to a sizable magnetocaloric effect (MCE). To understand the underlying mechanisms, the temperature dependence of structural and magnetic changes was analyzed. At the same time, the influence of the Co substitution was explored. Three Mn2−xCoxSb (x = 0.1, 0.15, 0.2) compounds were synthesized by cold crucible induction melting. Neutron powder diffraction was performed to determine the magnetic structures and to obtain the individual magnetic moments on both symmetrically independent Mn sites. In combination with the temperature-dependent magnetization measurements, the magnetic phase transition temperatures were identified. In the low-temperature range, additional antiferromagnetic peaks were detected, which could be indexed with a propagation vector of (0 0 ½). In Mn1.9Co0.1Sb at 50 K and in Mn1.8Co0.2Sb at 200 K, a co-existence of the FRI and the AFM state was observed. The pure AFM state only occurs in Mn1.8Co0.2Sb at 50 K.

Interface reaction during titanium alloys investment casting by residue gas in ceramic mold

The chemical reaction between mold material and titanium melt during investment casting was studied intensively. However, the influence of residue gas in ceramic mold on interface reaction remains unclear. In this investigation, the effect of residue gas in Y2O3–silica sol shell mold on interface reaction during Ti–6Al–4V alloy investment casting was investigated. Two groups of shell molds were prepared by adding different kinds of pore formers, i.e., spherical starch particles or nylon fibers, respectively. Ti–6Al–4V alloy was cast under vacuum by gravity casting through cold crucible induction melting (CCIM) method. Porosity of different shell molds was measured based on Archimedean method. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to characterize the micromorphology and composition of the reaction area, respectively. White light interferometer (WLI) was used to obtain the surface topography of the shell mold. The results show that the direct chemical reaction is very weak for all specimens. The release of residue gas in closed pores is the key factor influencing surface defects. However, open pores make nearly no difference on the interface reaction.

Behavior of Host Materials with Surrogates of the Rare Earth–Actinide Fraction under Ion Irradiation

The behavior of rare earth titanate phases of monoclinic and orthorhombic symmetry under ion irradiation was studied. Three samples contain a set of rare earth elements (REE), and in one sample the high-level waste (HLW) is simulated by neodymium. The samples were prepared by sintering at 1400°С or cold crucible induction melting followed by melt crystallization. The samples were irradiated with 1-MeV Kr2+ ions at temperatures in the range 298–1023 K on a tandem installation consisting of an ion accelerator and a transmission electron microscope. The critical amorphization doses for the samples at 298 K were (1.5–2.5) × 1014 ion cm–2. These values correspond to those for monoclinic titanates Nd2Ti2O7 and La2Ti2O7, are close to those for REE–Ti pyrochlores and brannerite, and are lower by an order of magnitude than those for zirconolites at the same irradiation mode. The critical amorphization temperature of the phases studied (900 K) is comparable to that of Nd2Ti2O7 (920 K), but higher than that of La2Ti2O7 (840 K). Close radiation resistance of the REE2Ti2O7 and REE4Ti9O24 phases in which the rare earth elements are represented by a mixture of elements similar in composition to their set in spent nuclear fuel and liquid HLW from its reprocessing or solely by Nd confirms the assumption that Nd is a suitable surrogate for the whole rare earth–actinide fraction.

Development, characterization and dissolution behavior of calcium-aluminoborate glass wasteforms to immobilize rare-earth oxides

Calcium-aluminoborate (CAB) glasses were developed to sequester new waste compositions made of several rare-earth oxides generated from the pyrochemical reprocessing of spent nuclear fuel. Several important wasteform properties such as waste loading, processability and chemical durability were evaluated. The maximum waste loading of the CAB compositions was determined to be ~56.8 wt%. Viscosity and the electrical conductivity of the CAB melt at 1300 °C were 7.817 Pa·s and 0.4603 S/cm, respectively, which satisfies the conditions for commercial cold-crucible induction melting (CCIM) process. Addition of rare-earth oxides to CAB glasses resulted in dramatic decreases in the elemental releases of B and Ca in aqueous dissolution experiments. Normalized elemental releases from product consistency standard chemical durability test were <3.62·10−5 g·m−2 for Nd, 0.009 g·m−2 for Al, 0.067 g·m−2 for B and 0.073 g·m−2 for Ca (at 90, after 7 days, for SA/V = 2000m−1); all meet European and US regulation limits. After 20 d of dissolution, a hydrated alteration layer of ~ 200-nm-thick, Ca-depleted and Nd-rich, was formed at the surface of CAB glasses with 20 mol% Nd2O3 whereas boehmite [AlO(OH)] secondary crystalline phases were formed in pure CAB glass that contained no Nd2O3.

The effect of synthesis conditions on the phase composition, structure, and chemical durability of uranium-bearing murataite ceramics

The samples of U-bearing ceramics with a composition (wt%) 5 Al2O3, 10 CaO, 55 TiO2, 10 MnO, 5 Fe2O3, 5 ZrO2, 10 UO2 were produced by melting of oxide mixtures in a Pt ampoule, glassy carbon crucibles in a resistive furnace, and cold crucible inductive melting (CCIM). In total 85–95 vol% of the samples produced were composed of murataite polytypes with 5- (5C), 8- (8C), and 3- (3C) fold elementary fluorite unit cell forming respectively core, medium part and rim of the murataite grains. Crichtonite, rutile, and Mn/Fe titanate (pyrophanite/ilmenite) were found to be minor phases. The latter was primarily present in the ceramics produced by melting in glassy carbon crucibles. Cold crucible melted ceramics contained the traces of vitreous phase due to melt contamination with a cold crucible putty material. Average U leach rates from the ceramics measured by SPFT procedure were found to be 10−3 g m−2 d−1 and lower.