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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Arrhenius Rate: constant volume burn

A constant volume burn occurs for an idealized initial state in which a large volume of reactants at rest is suddenly raised to a high temperature and begins to burn. Due to the uniform spatial state, there is no fluid motion and no heat conduction. This reduces the time evolu tion to an ODE for the reaction progress variable. With an Arrhenius reaction rate, two characteristics of thermal ignition are illustrated: induction time and thermal runaway. The Frank-Kamenetskii approximation then leads to a simple expression for the adiabatic induction time. For a first order reaction, the analytic solution is derived and used to illustrate the effect of varying the activation temperature; in particular, on the induction time. In general, the ODE can be solved numerically. This is used to illustrate the effect of varying the reaction order. We note that for a first order reaction, the time evolution of the reaction progress variable has an exponential tail. In contrast, for a reaction order less than one, the reaction completes in a nite time. The reaction order also affects the induction time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1991

Final design of a free-piston hydraulic advanced Stirling conversion system

Under the US Department of Energy's (DOEs) Solar Thermal Technology Program, Sandia National Laboratories is evaluating heat engines for solar distributed receiver systems. The final design is described of an engineering prototype advanced Stirling conversion system (ASCS) with a free-piston hydraulic engine output capable of delivering about 25 kW of electric power to a utility grid. The free-piston Stirling engine has the potential for a highly reliable engine with long life because it has only a few moving parts, has noncontacting bearings, and can be hermetically sealed. The ASCS is designed to deliver maximum power per year over a range of solar input with a design life of 30 years (60,000 h). The system includes a liquid Nak pool boiler heat transport system and a free-piston Stirling engine with high-pressure hydraulic output, coupled with a bent axis variable displacement hydraulic motor and a rotary induction generator.

Wallace, D. A.↗
NASA NTRS2001

Cool Flame Quenching

Cool flame quenching distances are generally presumed to be larger than those associated with hot flames, because the quenching distance scales with the inverse of the flame propagation speed, and cool flame propagation speeds are often times slower than those associated with hot flames. To date, this presumption has never been put to a rigorous test, because unstirred, non-isothermal cool flame studies on Earth are complicated by natural convection. Moreover, the critical Peclet number (Pe) for quenching of cool flames has never been established and may not be the same as that associated with wall quenching due to conduction heat loss in hot flames, Pe approx. = 40-60. The objectives of this ground-based study are to: (1) better understand the role of conduction heat loss and species diffusion on cool flame quenching (i.e., Lewis number effects), (2) determine cool flame quenching distances (i.e, critical Peclet number, Pe) for different experimental parameters and vessel surface pretreatments, and (3) understand the mechanisms that govern the quenching distances in premixtures that support cool flames as well as hot flames induced by spark-ignition. Objective (3) poses a unique fire safety hazard if conditions exist where cool flame quenching distances are smaller than those associated with hot flames. For example, a significant, yet unexplored risk, can occur if a multi-stage ignition (a cool flame that transitions to a hot flame) occurs in a vessel size that is smaller than that associated with the hot quenching distance. To accomplish the above objectives, a variety of hydrocarbon-air mixtures will be tested in a static reactor at elevated temperature in the laboratory (1g). In addition, reactions with chemical induction times that are sufficiently short will be tested aboard NASA's KC-135 microgravity (mu-g) aircraft. The mu-g results will be compared to a numerical model that includes species diffusion, heat conduction, and a skeletal kinetic mechanism, following the work on diffusion-controlled cool flames by Fairlie et,al., 2000.

Pearlman, Howard↗
DOE OSTI2022

Length and Seed Current Scaling of a Mark X HG driven, 8 inch PBX9501 RancheroS FCG system: II

This report is intended to examine the ultimate operating limits of the combined Pt. 88 capacitor bank (CB) + MarkX Helical Generator (HG) driving a RancheroS Flux Compression Generator (FCG) with various physics experiment load inductances. As such, many degradation mechanisms are neglected in this study. In actual use, degradation of the HG output current delivered to the FCG will probably occur. Internal changes in the HG can occur due to both Ohmic heating in the generator leading to a time varying series resistance [R(t)] such as that seen in the first trial (Shot 0) of the MarkX, as well as any misbehavior, such HG internal turn to turn shorts such as seem to have occurred in subsequent MarkX tests. Both reduce the output current from the HG that is used to seed the FCG. The results discussed here are intended to probe the limits of the RancheroS driving various loads, in an ideal situation in which none of the HG or system degradation mechanisms prior to the FCG armature first motion (FM) reduce the seed current. The HG is modeled simply as a time varying inductance [L(t), as measured in Shot 0], with a constant internal resistance [R(t) = 0.2mOhm]. The RancheroS itself is fully modeled, including all FCG and load degradation mechanisms, thus probing the ultimate capabilities of the full system, independent of problems upstream of the FCG.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Novel mutant P277 peptide VP to ameliorate atherogenic side-effects and to preserve anti-diabetic effects in NOD mice

Highlights: • VP deleted B epitope and reduced atherosclerosis. • VP maintained anti-T1DM function. • VP maintained β cell function and anti-inflammatory. P277 is a 24 amino-acids peptide, residues 437–460 of human heat shock protein 60 (HSP60). P277 or sequence repeated 6 × P277 was previously found showing potency preventive and therapeutic anti-diabetes functions in NOD mice, but aroused atherosclerosis due to the induction of anti-HSP65 autoantibodies as reported. To determine the intrinsic B epitope sequence, we screened P277 with pepscan method and then proved by detection of sera IgG from peptide fragments vaccinated mouse and rabbits. Results indicated HSP60 443–448 (ALLRCI) is potential intrinsic B epitope sequence of P277. We modified P277 by deleting the former three amino acids of ALLRCI (VP) or replacing these six with alanine (AP). The detection of serum lipid parameter in NOD mice and aorta endothelial damage levels in high-cholesterol diets fed rabbits demonstrated that VP induced higher anti-diabetes efficacy and caused less arteriosclerosis-liked diseases separately. With less TLR2/4 activation of dendritic cells and macrophages, VP treatment reduced Th1 related P277 specific pro-inflammatory cytokines production and increased regulatory immune responses both in vivo and in vitro. These results indicated that optimized VP peptide might serve as a promising candidate for mouse type 1 diabetes therapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Melanogenesis stimulation in B16-F10 melanoma cells induces cell cycle alterations, increased ROS levels and a differential expression of proteins as revealed by proteomic analysis

Considering that stimulation of melanogenesis may lead to alterations of cellular responses, besides melanin production, our main goal was to study the cellular effects of melanogenesis stimulation of B16-F10 melanoma cells. Our results show increased levels of the reactive oxygen species after 15 h of melanogenesis stimulation. Following 48 h of melanogenesis stimulation, proliferation was inhibited (by induction of cell cycle arrest in the G1 phase) and the expression levels of p21 mRNA were increased. In addition, melanogenesis stimulation did not induce cellular senescence. Proteomic analysis demonstrated the involvement of proteins from other pathways besides those related to the cell cycle, including protein disulfide isomerase A3, heat-shock protein 70, and fructose biphosphate aldolase A (all up-regulated), and lactate dehydrogenase (down-regulated). In RT-qPCR experiments, the levels of pyruvate kinase M2 mRNA dropped, whereas the levels of ATP synthase (beta-F1) mRNA increased. These data indicate that melanogenesis stimulation of B16-F10 cells leads to alterations in metabolism and cell cycle progression that may contribute to an induction of cell quiescence, which may provide a mechanism of resistance against cellular injury promoted by melanin synthesis. -- Highlights: Black-Right-Pointing-Pointer Melanogenesis stimulation by L-tyrosine+NH{sub 4}Cl in B16-F10 melanoma cells increases ROS levels. Black-Right-Pointing-Pointer Melanogenesis inhibits cell proliferation, and induced cell cycle arrest in the G1 phase. Black-Right-Pointing-Pointer Proteomic analysis showed alterations in proteins of the cell cycle and glucose metabolism. Black-Right-Pointing-Pointer RT-qPCR analysis confirmed alterations of metabolic targets after melanogenesis stimulation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

An experimental study of waveguide coupled microwave heating with conventional multicusp negative ion sources

Negative ion production with conventional multicusp plasma chambers utilizing 2.45 GHz microwave heating is demonstrated. The experimental results were obtained with the multicusp plasma chambers and extraction systems of the RF-driven RADIS ion source and the filament driven arc discharge ion source LIISA. A waveguide microwave coupling system, which is almost similar to the one used with the SILHI ion source, was used. The results demonstrate that at least one third of negative ion beam obtained with inductive RF-coupling (RADIS) or arc discharge (LIISA) can be achieved with 1 kW of 2.45 GHz microwave power in CW mode without any modification of the plasma chamber. The co-extracted electron to H{sup −} ratio and the optimum pressure range were observed to be similar for both heating methods. The behaviour of the plasma implies that the energy transfer from the microwaves to the plasma electrons is mainly an off-resonance process.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2012

Development and Testing of a Green-Propellant Micro-Hybrid Thruster with Electrostatic Ignition

As early as 1937 German scientists at Peenemunde experimented with highly unstable fuel blends of nitrous oxide (N2O) and ethanol. These early tests mostly resulted in explosions and destroyed rocket engines. More recently several companies have developed experimental nitrous oxide fuel blends (NOFB) with Isp exceeding 300 sec. Although NOFBx has recently been cleared for tests on the International Space Station, this propellant remains highly experimental and has not been cleared for commercial transport by the US DOT. Recent work by Karabeyoglu et al. has raised concerns about the safety risks of mixing hydrocarbons with N2O. Liquid oxidizer/fuel blends are highly explosive and require extreme care in transport and servicing. By adding small amounts of a liquid organic fuel such as alcohol or a hydrocarbon, the odds of an explosive decomposition event are significantly increased.iv The proposed solution mitigates the explosion hazards of NOFB by separating the oxidizer from the hydrocarbon fuel formed as of a small cylindrical section of ABS thermoplastic. As N2O vapor flows across the grain segment, current enters a 1000 VDC high-tension lead in the ABS fuel grain and produces an inductive spark that vaporizes a small amount of the material. The ablated fuel vapor plus residual energy from the spark seed a localized exothermic N2O dissociation that produces sufficient heat to initiate combustion. The process is also effective when gaseous oxygen is used. A low TRL (2-3) prototype demonstrating the feasibility of controlled hydrocarbon-seeding was recently tested at Utah State University.v The unit features a miniature 2.5 cm ABS fuel grain fabricated using a Stratasys Dimension 3-D printer. The 9-N thruster was pulse-fired up to 27 consecutive times on a single ABS grain segment. Ignition was achieved by as little as 12-15 Joules energy input. This value is contrasted with the typical 30-minute pre-heat requirement for the ECAPS LMP-103S ADN-based monopropellant, requiring an energy input of 14,850 Joules for catalytic dissociation. The hydrocarbon-seeded micro-hybrid was also adapted as a non-pyrotechnic ignitor for a 900 N (200-lbf) thrust hybrid motor. The motor was successfully ignited 4 consecutive times with no hardware swaps or propellant additions. The amount of ABS seed material that can be fit into the injector cap is the only limit to the number of available repeat firings. This series of tests marks the first time a hybrid motor was ever ignited by other than a solid-propellant pyrotechnic charge or bi-propellant flame ignitor. Nitrous oxide hybrid motors are typically difficult to ignite and usually require multiple solid-propellant charges to initiate combustion, so this nonpyrotechnic ignition is a significant accomplishment. The controlled hydrocarbon-seeding approach is fundamentally different from all other green propellant solutions offered by the aerospace industry. Although the proposed system is more correctly a hybrid technology; the system retains all the simple features of a monopropellant design. To date no optimization study has been performed to identify the best grain geometry for electrostatic ignition. Fortunately, because the grain segments are fabricated using rapid-prototyping technology, changing the grain geometry is as simple as modifying the 3-D printer CAD-file. Vacuum Isp exceeding 270 seconds has been demonstrated (Ref v), a value significantly higher than those offered by competing green monopropellant options. The propellants of choice, N2O/GOX and ABS are 100% non-toxic, non-explosive, and environmentally benign. Because the inert oxidizer and fuel components are mixed only within the combustion chamber, the system retains the inherent safety of a hybrid rocket and can be piggy-backed as a secondary payload with no overall mission risk increase to the primary payload, an excellent characteristic for secondary launch systems.

Whitmore, Stephen A.↗
DOE OSTI2014

Iodine solubility in a low-activity waste borosilicate glass at 1000°C

The purpose of this study was to determine the solubility of iodine in a low-activity waste borosilicate glass when heated inside an evacuated and sealed fused quartz ampoule. The iodine was added to glass frit as KI in quantities of 100–24000 ppm iodine (by mass), each mixture was added to an ampoule, the ampoules were heated at 1000 °C for 2h, and then air quenched. In samples with ≥12000 ppm iodine, low viscosity salt phases were observed on the surface of the melts during cooling that solidified into a white coating upon cooling. These salts were identified as mixtures of KI, NaI, and Na 2 SO 4 with X-ray diffraction (XRD). The iodine concentrations in glass specimens were analyzed with inductively-coupled plasma mass spectrometry and the overall iodine solubility was determined to be 10000 ppm by mass. Several crystalline inclusions of iodine sodalite, Na 8 (AlSiO 4 ) 6 I 2 , were observed in the 24000 ppm specimen as determined by micro-XRD and wavelength dispersive spectroscopy.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2018

The Fusion Driven Rocket: Nuclear Propulsion through Direct Conversion of Fusion Energy

The future of manned space exploration and development of space depends critically on the creation of a dramatically more efficient propulsion architecture for in-space transportation. A very persuasive reason for investigating the applicability of nuclear power in rockets is the vast energy density gain of nuclear fuel when compared to chemical combustion energy. The Fusion Driven rocket (FDR) represents a revolutionary approach to fusion propulsion where the power source releases its energy directly into the propellant, not requiring conversion to electricity. It employs a solid lithium propellant that requires no significant tankage mass. The propellant is rapidly heated and accelerated to high exhaust velocity (> 30 km/s), while having no substantial physical interaction with the spacecraft thereby avoiding damage to the rocket and limiting both the thermal heat load and radiator mass. The key to achieving this stems from research at MSNW and the UW on the magnetically driven implosion of metal foils onto a magnetized plasma target to obtain fusion conditions. A logical extension of this work leads to a method that utilizes these metal shells (or liners) to not only achieve fusion conditions, but to serve as the propellant as well. Several low-mass, magnetically driven metal liners are inductively driven to converge radially and axially and form a thick blanket surrounding the target plasmoid and compress the plasmoid to fusion conditions. Virtually all of the radiant, neutron and particle energy from the plasma is absorbed by the encapsulating, thick metal blanket thereby isolating the spacecraft from the fusion. This energy, in addition to the intense Ohmic heating at peak magnetic field compression, is adequate to vaporize and ionize the metal blanket. The expansion of this hot, ionized metal propellant through a magnetically insulated nozzle produces high thrust at the optimal Isp. The energy from the fusion process, along with the waste heat, is thus utilized at very high efficiency. The basic scheme for FDR is illustrated and described in the report (see Fig. 2) The two most critical issues in meeting challenges introduced employing magneto-inertial fusion as the power source is driver efficiency and “stand-off” – the ability to isolate and protect fusion and thruster from the resultant fusion energy. By employing metal shells for compression, it is possible to produce the desired convergent motion inductively by inserting the metal sheets along the inner surface of cylindrical or conically tapered coils. Both stand-off and energy efficiency issues are solved by this arrangement. 3 This two year effort focused on achieving three key criteria for the Fusion Driven Rocket to move forward for technological development: (1) the physics of the FDR must be fully understood and validated, (2) the design and technology development for the FDR required for its implementation in space must be fully characterized, and (3) an in-depth analysis of the rocket design and spacecraft integration as well as mission architectures enabled by the FDR need to be performed. A subscale, laboratory liner compression test facility was assembled at the University of Washington Plasma Dynamics Laboratory with sufficient liner kinetic energy (~ 0.5 MJ) to reach conditions required for fusion breakeven conditions. Detailed experimental studies of the dynamic behavior of the driven liners as well as liner convergence and magnetic compression were performed. The development of both the 1D liner dynamics code and the full 3D ANSYS® liner calculations was achieved. The characterization of both the FDR and spacecraft as well as a design architecture analysis was conducted that included an examination of a wide range of mission architectures and destinations for which this fusion propulsion system would be enabling or critical. In particular a rapid, single launch manned Mars mission was developed.

Energy↗
DOE OSTI2021

Characterization of Self-Magnetic Pinch (SMP) radiographic diode performance on RITS-6 at Sandia National Laboratories: 1) Diode Dynamics, DC Heating to extend Radiation Pulse

Radiographic diodes focus an intense electron beam to a small spot size to minimize the source area of energetic photons for radiographic interrogation. The self-magnetic pinch (SMP) diode has been developed as such a source and operated as a load for the RITS-6 Inductive Voltage Adder (IVA) driver. While experiments support the generally accepted conclusion that a 1:1 aspect diode (cathode diameter equals anode-cathode gap) delivers optimum SMP performance, such experiments also show that reducing the cathode diameter, while reducing spot size, also results in reduced radiation dose, by as much as 50%, and degraded shot reproducibility. Analyzation of the effective electron impingement angle on the anode converter with time made possible by a newly developed dose-rate array diagnostic indicates that fast-developing oscillations of the angle are correlated with early termination of the radiation pulse on many of the smaller-diameter SMP shots. This behavior as a function of relative cathode size persists through experiments with output voltages and currents up to 11.5 MV and 225 kA, respectively, and with spot sizes below ~ few mm. Since simulations to date have not predicted such oscillatory behavior, considerable discussion of the angle-behavior of SMP shots is made to lend credence to the inference. There is clear anecdotal evidence that DC heating of the SMP diode region leads to stabilization of this oscillatory behavior. This is the first of two papers on the performance of the SMP diode on the RITS-6 accelerator.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Impact of initial CA dissolution on the hydration mechanism of CAC

Usually, for basic investigations on the hydration behaviour of CA (monocalcium aluminate, CaAl{sub 2}O{sub 4}) preferably pure samples without the presence of other hydraulic phases are used. In the presented study we apply an alternative approach investigating mixes that contain tiny to low amounts of CA (0.5–20 wt%) besides CA{sub 2} (CaAl{sub 4}O{sub 7}) or C{sub 6}AF{sub 2} (Ca{sub 6}Al{sub 2}Fe{sub 4}O{sub 15}). The hydration of the mixes is investigated by isothermal heat flow calorimetry, in-situ XRD and pore solution analysis at 23 °C. A modified thermodynamic database enables the calculation of saturation indices for relevant hydrate phases in the investigated systems. CA similarly influences the hydration of both CA{sub 2} and C{sub 6}AF{sub 2} although the exact impact strongly depends on the initial CA/water ratio in the mixes. Up to a certain amount CA is completely consumed during the first minutes after mixing. Beyond this amount the presence of undissolved CA causes an induction period and retards the hydration of CA{sub 2} or C{sub 6}AF{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Additive Manufacturing Consolidation of Low-Cost Water Atomized Steel Powder Using Micro-Induction Sintering

ORNL worked with Grid Logic Inc to demonstrate micro induction sintering (MIS) and binder decomposition of steel powders. It was shown that MIS effectively emits spatially confined electromagnetic energy that is directly coupled to metallic powders resulting in resistive heating of individual particles. The non-uniformity of particle morphology and distribution of the water atomized steel powders resulted in inefficient transfer of energy. It was shown that adhering the particles together using polymer binders resulted in more efficient coupling. Using the MIS processes, debinding and sintering could be done in a single step. When combined with another system, such as binder-jet, this could reduce the amount of required post-processing. An invention disclosure was filed on hybrid systems that use MIS to reduce the amount of required post-processing.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Hsc70 facilitates TGF-β-induced activation of Smad2/3 in fibroblastic NRK-49F cells

Heat-shock cognate protein 70 (Hsc70), a molecular chaperone constitutively expressed in the cell, is involved in the regulation of several cellular signaling pathways. In this study, we found that TGF-β-induced phosphorylation and nuclear translocation of Smad2/3 were suppressed in fibroblastic NRK-49F cells treated with small interfering RNA (siRNA) for Hsc70. In the cells underexpressing Hsc70, transcriptional induction of connective tissue growth factor (CTGF), a target gene of the TGF-β signaling, was also suppressed in the early phase of TGF-β stimulation. Upon stimulation with TGF-β, Hsc70 interacted with Smad2/3, suggesting functional interactions of Hsc70 and Smad2/3 for the activation of TGF-β-induced Smad signaling. Although the expression of heat-shock protein 70 (Hsp70) was upregulated in the cells treated with Hsc70 siRNA, TGF-β-induced Smad activation was not affected in the cells overexpressing Hsp70. Collectively, these results indicate that Hsc70, but not Hsp70, supportively regulates TGF-β-induced Smad signaling in NRK-49F cells. - Highlights: • Hsc70 siRNA treatment suppressed the expression of Hsc70 but induced the expression of Hsp70 in NRK-49F cells. • Hsc70 siRNA treatment suppressed the activation of Smad2/3 in the cells treated with TGF-β. • Hsc70 interacted with Smad2/3 on stimulation with TGF-β in the cells. • Hsp70 did not influence the TGF-β-induced activation of Smad2/3 in the cells overexpressing Hsp70.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Prediction and Measurement of the Kinetics of Isothermal Crystallization and Devitrification of Mold Powder Slags

The rate and extent of formation of crystalline phases in the slag film that develops between the mold and the strand in steel continuous casting determine heat transfer and lubrication between them and therefore play crucial roles in shell integrity. In this work, a commercial mold powder for casting medium carbon (MC) thin steel slabs is selected for carrying out detailed comparisons between predicted and experimental results of the rates of isothermal crystallization and devitrification of liquid and glassy slag, respectively. Predictions are obtained with a kinetic model that combines the induction period (of Šimon and Kolman) and the Kissinger methods to evaluate time–temperature–transformation (TTT) diagrams for the devitrification and crystallization reactions associated with the peaks appearing in non-isothermal thermo-analysis traces. To obtain experimental validation of the diagram, a high-temperature confocal laser scanning microscope (HT-CLSM) is used to rapidly heat or cool a sample, ~ 140 mg, of glassy powder or liquid slag, respectively, to selected isothermal conditions, where it is held for a prescribed length of time before quenching. Identification and quantification of the phases present in the quenched samples are done by a quantitative X-ray powder diffraction analysis (QXRPDA) method that uses a PONKCS (partial or not known crystal structure) procedure based on Le Bail and Rietveld strategies for refinement of diffraction patterns. The many experimental results indicate that the predicted TTT diagrams for devitrification and crystallization of the mold slag give a good estimation of the rate of the transformations that take place at different temperatures and reveal the differences in the reactions that occur along both paths.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Lighting system with induction power supply

A system for producing light is provided. The system comprises a sealed enclosure surrounding a porous graphite foam conductor which is exposed to an electromagnetic field generated by an oscillating circuit. When exposed, the foam conductor conducts induced electric current which heats the same to product light. The amount of light is controllable by changing the output of a drive circuit. The oscillating circuit comprises a first inductor and a first capacitor. The first inductor has a first terminal and a second terminal. The output of the drive circuit is controlled by turning a MOSFET OFF and ON. The MOSFET is turned ON when an integrated signal representative of a difference between a voltage proportional to the first terminal and a voltage proportional to the second terminal is between a first voltage threshold and a second voltage threshold and based on a timing signal.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

The effects of glass doping, temperature and time on the morphology, composition, and iron redox of spinel crystals

Precipitation of large crystals/agglomerates of spinel and their accumulation in the pour spout riser of a Joule-heated ceramic melter during idling can plug the melter and prevent pouring of molten glass into canisters. Thus, there is a need to understand the effects of spinel-forming components, temperature, and time on the growth of crystals in connection with an accumulation rate. In our study, crystals of spinel [Fe, Ni, Mn, Zn, Sn][Fe, Cr]₂O₄ were precipitated from simulated high-level waste borosilicate glasses containing different concentrations of Ni, Fe, and Cr by heat treating at 850 and 900°C for different times. These crystals were extracted from the glasses and analyzed with scanning electron microscopy and image analysis for size and shape, with inductively coupled plasma-atomic emission spectroscopy and atom probe tomography for concentration of spinel-forming components, and with wet colorimetry and Mössbauer spectroscopy for Fe²⁺/Fe total ratio. High concentrations of Ni, Fe, and Cr in glasses resulted in the precipitation of crystals larger than 100 µm in just two days. Crystals were a solid solution of NiFe₂O₄, NiCr₂O₄, and -Fe₂O₃ (identified only in the high-Ni-Fe glass) and also contained small concentrations of less than 1 at% of Li, Mg, Mn, and Al.

chemical analysis↗