Fuel Particles Research Articles

Development and demonstration of a BISON–Griffin modeling framework for the design of targeted TRISO transient experiments in the Transient Reactor Test Facility

Uranium oxycarbide (UCO)-bearing tri-structural isotropic (TRISO) particle fuels are expected to be used in numerous U.S. commercial reactor applications within the next decade. In this work, we reviewed historical particle fuel transient experiments to identify gaps in TRISO fuel performance transient testing. A BISON–Griffin modeling framework was then developed to conduct preliminary TRISO transient analyses and begin to address these gaps. The framework was demonstrated using limiting-case transient conditions from a prototypic high-temperature gas-cooled reactor (HTGR). It was then applied to develop a matrix of experiments that could be performed in the Transient Reactor Test Facility (TREAT) to (1) evaluate UCO-fueled particle performance at moderate and high heat rates, (2) assess whether historical testing involving UO2-fueled particles is applicable to modern UCO-fueled particles, (3) deconvolute the impacts of temperature and heat rate on particle transient response, and (4) collect the data needed for fuel performance model validation and/or further development.

Optimized Dropping and Rolling and Virtual Surface Method for High Packing Fraction of Dispersed Fuel Particles in Annular Container

Because of their favorable thermal conductivity and commendable fuel performance, dispersed fuel elements have been widely adopted in research reactors. However, the geometric complexity resulting from the high packing density of dispersed fuel poses challenges to current geometric modeling methods. Various implicit and explicit modeling techniques have been implemented in Monte Carlo codes. Implicit methods struggle to achieve the correct packing fraction and, therefore, lack accuracy. In this paper, we introduce the Optimized Dropping and Rolling and Virtual Surface method for precise and efficient geometric modeling of such structures. Simultaneously, we apply this novel method to the packing process of an annular container. Test results across various packing fraction cases demonstrate that our modified Optimized Dropping and Rolling method significantly enhances packing efficiency, surpassing the Distinct Element Method hundreds of times.

Numerical Simulation of CO Generation and Combustion Efficiency in Sintering Process: Effect of Solid Fuel Particle Size

For sintering pot productive process with various fuel particle size distributions, a transient numerical simulation sintering model based on the computational fluid dynamics approach is developed using Fluent 2021R1. The model combines chemical reaction, mass and heat transfer, Euler–Euler model, and fluid flow in porous media. In this study, CO is employed as the combustion's intermediate product, which is further oxidized by secondary combustion in the high‐temperature zone. Through calculations, the solid fuel combustion behavior of the sintering is explained collectively with the changing bed temperature, CO emission, and solid fuel combustion efficiency of the process under various fuel particle size distribution. In the sintering process, the fuel particle size distribution is crucial for lowering CO emissions and increasing combustion efficiency. The combustion efficiency shows a tendency of increasing initially before decreasing with the reduction of solid fuel particle size, while CO emissions show a trend of reducing first and then increasing. It is advantageous to lower the CO emission in the sintering process, and the combustion efficiency of the sintering process is greatly boosted by 5.13% when the proportion of solid fuel with 5 mm particle size decreases and the proportion of solid fuel with 3 mm particle size increases.

Experimental Combustion of Different Biomass Wastes, Coals and Two Fuel Mixtures on a Fire Bench

When designing settlements according to the “Green Building” principle, it is necessary to develop a heating system based on climatic conditions. For example, in areas with a sharply continental climate (cold and prolonged winters), it is sometimes necessary to use solid fuel boilers (in the absence of gas). However, to use these, it is necessary to use biomass or biomass-coal blends as fuel to increase their combustion heat. The addition of biomass waste to coal can be aimed at achieving various objectives: utilization of biomass waste; reduction of solid fossil fuel consumption; improvement of environmental performance at coal-fired boiler houses; improvement of the reactivity of coals or to improve the technical and economic performance of heat-generating plants due to the fact that biomass is a waste from various types of production, and its cost depends only on the distance of its transportation to the boiler house. In this work, combustion of various biomass wastes, including sewage sludge, was carried out on a fire bench emulating the operation of a boiler furnace. Fuel particles were ignited by convective heat transfer in a stream of hot air at a velocity of 5 m/s in the temperature range of 500–800 °C, and the experimental process was recorded on a high-speed, color video camera. The obtained values were compared with the characteristics of different coals used in thermal power generation (lignite and bituminous coal). The aim of the work is to determine the reactivity of various types of biomass, including fuel mixtures based on coal and food waste. The work presents the results of technical and elemental analysis of the researched fuels. Scanning electron microscopy was used to analyze the fuel particle surfaces for the presence of pores, cracks and channels. It was found that the lowest ignition delay is characteristic of cedar needles and hydrolyzed lignin; it is four times less than that of lignite coal and nine times less than that of bituminous coal. The addition of hydrolysis lignin to coal improves its combustion characteristics, while the addition of brewer’s spent grain, on the contrary, reduces it, increasing the ignition time delay due to the high moisture content of the fuel particles.

The Effect of Fuel Quality on Cavitation Phenomena in Common-Rail Diesel Injector—A Numerical Study

Plastic is one of the most widely used materials worldwide. The problem with plastic arises when it becomes waste, which needs to be treated. One option is to transform plastic waste into synthetic fuels, which can be used as replacements or additives for conventional fossil fuels and can contribute to more sustainable plastic waste treatment compared with landfilling and other traditional waste management processes. Thermal and catalytic pyrolysis are common processes in which synthetic fuels can be produced from plastic waste. The properties of pyrolytic oil are similar to those of fossil fuels, but different additives and plastic stabilizers can affect the quality of these synthetic fuels. The quality of fuels and the permissible particle sizes and number density are regulated by fuel standards. Particle size in fuels is also regulated by fuel filters in vehicles, which are usually designed to capture particles larger than 4 μm. Problems can arise with the number density (quantity) of particles in synthetic fuels compared to that in fossil fuels. The present work is a numerical study of how particle size and number density (quantity) influence cavitation phenomena and cavitation erosion (abrasion) in common-rail diesel injectors. The results provide more information on whether pyrolysis oil (synthetic fuel) from plastic waste can be used as a substitute for fossil fuels and whether their use can contribute to more sustainable plastic waste treatments. The results indicate that the particle size and number density slightly influence cavitation phenomena in diesel injectors and significantly influence abrasion.

Contrail Modeling of ECLIF2/ND‑MAX flights: Effects of nvPM Particle Numbers and Fuel Sulfur Content

Contrail Modeling of ECLIF2/ND‑MAX flights: Effects of nvPM Particle Numbers and Fuel Sulfur Content

Uncertainty Quantification of Engineering Parameters for a Nuclear Reactor Loaded with Dispersed Fuel Particles

Owing to their high intrinsic safety, dispersed fuel particles are an important fuel pattern for fourth-generation nuclear reactors. Due to the unique cladding layers and the random dispersion characteristics, dispersed fuel particles significantly differ from pressurized water reactors regarding operation-induced uncertainty. This study quantitatively analyzed overall uncertainty while considering a random distribution of dispersed fuel particles, material thickness, and fuel enrichment. The results demonstrated that, for all packing fractions, the uncertainty induced by the random dispersion of dispersed fuel particles was below 0.03%. For every packing fraction, the differences between the results obtained by the regular and the random distribution models increased, and then decreased, until reaching its maximum (1.297%) at 15%. Keff decreased as the radius of the UO2 kernel increased; Keff increased as the thickness of the cladding layer increased; the uncertainty of Keff was 1.003% when a random distribution of particles, material thickness, and fuel enrichment were taken into consideration; the uncertainty of the power distribution of reactor core assemblies was maximized (1.495%) at the edge of the reactor core. Quantitative analysis of uncertainty provides references for the optimization of design and safety margin analysis for reactors.

Experimental Study on Effects of Different Factors on Continuous Detonation of Superfine Lignite: Particle Size and Fuel Equivalent Ratio

ABSTRACT The Rotating Detonation Engine (RDE) is garnering attention for its high thermal cycle efficiency. In order to explore the detonation evolution of lignite/gas/oxygen gas-solid two-phase fuel in RDE, self-developed RDE(L:1000 mm) was used to study the detonation characteristics of lignite dust with ultra-fine particle size in methane/oxygen atmosphere, and the effects of ultra-fine particle size and equivalent ratio on detonation characteristics were explored, achieving stable propagation of rodtating detonation waves (RDW) with durations between 0.611 and 0.684s. The results indicate that the introduction of lignite dust significantly enhances the detonation effects compared to pure methane fuel. An increase in the overall equivalence ratio boosts the propagation velocity of RDW in methane-solid fuels, while a larger lignite dust particle size slows it down. Among ultrafine lignite powder sizes, a 1 μm particle size achieved the highest detonation wave speed. In terms of RDW propulsion, the impact of particle size and methane-solid fuel equivalence ratio on thrust mirrors their effect on detonation wave velocity. At a global equivalence ratio (GER) of 1.8, the specific impulse under different particle sizes was about 0.6 times that at a GER of 1.0, suggesting that an excess of fuel can reduce detonation effectiveness. The optimal specific impulse results were obtained with a lignite powder addition rate of 6 g/s, particle size of 1 μm, and GER of 1.0, reaching 4.6 kN·s·kg−1. The research results reveal the detonation process and detonation propagation law of lignite in methane/oxygen, especially for the future application of lignite in detonation energy release engineering.

Phase field modeling of irradiation-induced shrinkage fracture in TRISO fuel particle

With the features in retaining fission products and maintaining structural stability, TRISO fuel particle has been widely implemented and studied in the development of advanced nuclear fuel element. During service, however, the key silicon carbide (SiC) layer of TRISO may fail due to irradiation-induced shrinkage fracture of inner pyrolytic carbon (IPyC) layer. Hence, it has great significance to analyze the fracture characteristics of TRISO for its application in engineering. This work presents a phase field model of brittle fracture for the shrinkage cracking, which is capable of simulating the propagation of IPyC crack and interfacial crack between IPyC and SiC naturally. At first, the physical model of TRISO and phase field model have been verified respectively. Subsequently, the crack evolution has been investigated under different parameters, including the Bacon Anisotropy Factor (BAF) of IPyC, fuel temperature and density of IPyC. Simulation results reveal that increasing the BAF or decreasing the density and temperature, the fracture of IPyC will be accelerated and the crack deflection may also occur subsequently. In contrast, the fracture of IPyC can be put off and relieve the stress concentration in SiC. The combination effect of shrinkage and stress relaxation from creep ultimately determines the crack evolution, which in turn influences the stress distribution within SiC.

Thermal conductivity of SiC and PyC coatings in spherical nuclear fuel particles measured by nanosecond time domain thermoreflectance

TRi-structural ISOtropic (TRISO) nuclear particle fuels are intended for application in several designs of advanced high temperature nuclear reactors. Nanosecond time domain transient thermoreflectance has been applied to the silicon carbide (SiC) and the inner and outer pyrolytic carbon (PyC) coatings of surrogate TRISO particles, measuring mean thermal conductivities of 166 ± 18 W∙m−1K−1, 11.1 ± 1.9 W∙m−1K−1, and 8.6 ± 2.1 W∙m−1K−1, respectively, for each layer. The applicability of the analytical heat diffusion model used to fit the measured traces was examined and it was found that the boundary effect at the SiC/PyC interface becomes perceptible at a lateral distance approximately equal to the thermal penetration depth of SiC (7.1 µm). In addition, steady-state thermal modelling showed that the radial thermal resistance of the particle is dominated by the porous buffer layer. The thermal resistance will likely increase significantly upon circumferential detachment of the porous buffer carbon coating with irradiation. Implications for fuel design and reactor performance are discussed.

Meta-heuristic Adaptive Equivalent Consumption Minimization of a Fuel Cell Vehicle Incorporating Fuzzy Inference and Particle Swarm Optimization

Meta-heuristic Adaptive Equivalent Consumption Minimization of a Fuel Cell Vehicle Incorporating Fuzzy Inference and Particle Swarm Optimization

Pressureless sintering of large sized fully ceramic microencapsulated fuel pellets

Large-sized fully ceramic microencapsulated (FCM) nuclear fuel pellets were fabricated by a novel tape casting process in this study. The process involved producing a single layer of FCM fuel green tapes embracing TRISO particles by tape casting with silicon carbide ceramic as the matrix. The resulting tapes were stacked vertically and made into green bodies through cold isostatic pressing. Large-sized FCM fuel pellet with diameters over 86 mm was then successfully prepared by pressure-less sintering with AlN-Y2O3-Sc2O3−MgO as sintering additives. The FCM fuel pellets obtained through this method exhibited a dense structure, flat surface, and no cracks. Thus, the integrated formation of the fuel-free zone and fuel-filled zone could be realized by precisely controlling the fuel-free zone thickness. The TRISO particles were regularly and uniformly distributed in a triangular shape and remained structurally intact. By adjusting the spacing of the TRISO particles in the FCM fuel pellets to a range of 500 to 1500 μm, the volume fraction of fuel particles in the FCM fuels was controlled between 12.8 and 31.7 vol.%.

Characteristic Features of the Hydrodynamics and Combustion of Fine Fuel Particles in the Vortex Zone of a Cyclone-Grate-Fired Chamber

Characteristic Features of the Hydrodynamics and Combustion of Fine Fuel Particles in the Vortex Zone of a Cyclone-Grate-Fired Chamber

Deterministic Transport Calculation Method for Statistical Geometry with Small Fuel Particles

A deterministic transport calculation method is proposed for the treatment of dispersed fuel particles in a fuel compact/fuel pebble of a typical high-temperature gas-cooled reactor fuel. The random distribution of fuel particles was considered using the statistical geometry (STG) method, which is widely used in the Monte Carlo method. A long-ray trace, which represents a neutron flight path, was considered, and the segment lengths and material distributions on the ray trace were randomly sampled using STG. Then a conventional transport sweep, as used in the method of characteristics, was performed along the ray trace. The proposed deterministic statistical geometry (DSTG) method can calculate the flux spatial distribution in a heterogeneous geometry containing randomly dispersed fuel particles and the surrounding graphite matrix, which is consistent with the STG in a Monte Carlo method. The validity of the DSTG method was confirmed through sensitivity calculations and comparisons with a multigroup Monte Carlo method that utilizes STG. The proposed method can be used for the homogenization of heterogeneous structures inside a fuel compact or fuel pebble as an alternative to conventional deterministic unit cell calculations that consider fuel particles and the surrounding matrix in high-temperature gas-cooled reactor fuels.

Residual stresses in as-manufactured TRISO Coated Particle Fuel (CPF)

TRistructural ISOtropic coated particle fuels (TRISO CPF) have been developed as a possible fuel solution for high temperature nuclear reactors, which offer the possibility of nuclear cogeneration-powered industrial facilities and hydrogen production. A finite element model was developed to simulate the fabrication process of TRISO particles. Understanding the initial stress and bonding state of the layers is crucial in predicting performance and failure in service, however this factor has not received an in depth consideration in the available literature. The simulations of a fully bonded model of TRISO (layers perfectly attached to each other) revealed the presence of high values of tensile hoop stresses in the inner fuel kernel (up to 250 MPa, sufficient to cause fracture in UO2) and even higher compressive stresses (up to 600 MPa) in the silicon carbide layer. Simulations conducted without bonding between kernel and buffer found the residual stress state to be consistently more relaxed with respect to the fully bonded model. This was most evident in the radial stress, which drops to less than 10 MPa (tensile or compressive) throughout the particle. In the hoop direction, compression of 150 MPa remained in the SiC layer. Such results are consistent with the empirical evidence of the occurrence of kernel-buffer debonding during the fabrication of TRISO particles. Finally, a brief investigation of the effect of ovality on the model with kernel-buffer debonding showed an overall increase in the magnitude of the hoop stress in the SiC and PyC layers in a flat spot caused by reduced buffer material.

A Review on Methods Available for Doping of High Energy Boron Particles Into Liquid Fuels

Metals and metalloids such as Fe, Al, Be, B, Li, Mg, Ti are used as high energy materials as they possess higher gravimetric and volumetric heating values than liquid fuels. Boron possesses the highest volumetric (136 kJ/cm3 ) heating values among most of the preferred metal particles however it is second highest in gravimetric (58 kJ/g) heating values. This review highlights different successful methods of introduction of boron/aluminum particles in liquid fuels maintaining its suspension stability by using various surfactants or functionalization by different groups of ligands. Commercially available boron powder (nominal diameter 800 nm) contains coarser and mixed-size boron particles that require long milling times or a two-step milling process before final sample preparation. Suspension stability of boron particles can be achieved by using various classes of surfactants or techniques involved in surface modification of particles. Surfactants that are commonly used are oleic acid, sorbitanoleate, tween80, etc. Sorbitan oleate is now a days gaining popularity as the best stabilizer for this type of fluid preparation. Another effective ligand (amphiphilic) that is Trioctyl phosphine oxide (TOPO) links with fuel with its hydrophobic chain (long carbon chain) and nanoparticles with its polar head group. Recently some studies employed the capping of nanoparticles with ionic liquids (ILs) like (1-methyl-4-amino-1,2,4-triazoliumdicyanamide ([MAT][DCA]),1-butyl-3-methylimidazoliumdicyanamide ([BMIM][DCA]) and Dicyanamide-based Dicationic Ionic Liquid (DCIL). Capping of nanoparticles with organic chemicals is commonly done by Silane, Polymethyl acrylic acid (PMAA), Octyloxy, etc. An attempt to coat the surface of boron with an energetic polymer (Glycidylazide polymer) was also made recently by many researchers. These methods are some of the best approaches to attain longtime stability of high energy particles dopedliquid fuel. After a thorough study of literature, the available techniques already tried and tested by different research groups have been presented.

Experimental Study on the Effect of Bed Material Amount and Fuel Particle Size on Load Change of Circulating Fluidized Bed

Experimental Study on the Effect of Bed Material Amount and Fuel Particle Size on Load Change of Circulating Fluidized Bed

A Novel Plenoptic Camera-Based Measurement System for the Investigation into Flight and Combustion Behavior of Refuse-Derived Fuel Particles.

In the past several decades, refuse-derived fuels (RDFs) have been widely applied in industrial combustion processes, for instance, in cement production. Since RDF is composed of various waste fractions with complex shapes, its flight and combustion behaviors can be relatively complicated. In this paper, we present a novel plenoptic camera-based spatial measurement system that uses image processing approaches to determine the dwell time, the space-sliced velocity in the depth direction, and the ignition time of various applied RDF fractions based on the obtained images. The image processing approach follows the concept of tracking-by-detection and includes a novel combined detection method, a 2.5D multiple particle tracking algorithm, and a postprocessing framework to tackle the issues in the initial tracking results. The thereby obtained complete spatial fuel trajectories enable the analysis of the flight behaviors elaborated in the paper. The acquired particles' properties (duration, velocity, and ignition time) reversely prove the availability and applicability of the developed measurement system. The adequacy and accuracy of the proposed novel measurement system are validated by the experiments of detecting and tracking burning and nonburning fuel particles in a rotary kiln. This new measurement system and the provided experimental results can benefit a better understanding of the RDF's combustion for future research.

Neutronic and Thermal-Fluidic Analyses for an Additive Manufactured Reactor With SiC Matrix and TRISO Particle Fuel

Abstract Additive manufacturing (AM) is a transformational digital manufacturing technology featured with rapidity, customizability, precision, and economy, which is fundamentally altering the way components are designed and manufactured. AM enables the freedom of design, and makes full use of complexity of geometry which “comes for free”. Applying AM technology to nuclear industry can yield advanced reactor designs with function and structure matched for the best thermal, fluidic and mechanical performance. In this work, an AM-informed reactor core design with silicon carbide (SiC) matrix and tri-structural isotropic (TRISO) particle fuel is proposed and analyzed. The core is an integrated 3D-printed SiC bulk with helical cruciform coolant channels, and the UO2-bearing TRISO fuel particles are dispersed in the bulk. A multiphysics analysis framework for irregular geometry is developed to analyze and further optimize the reactor design. The TRISO particle positions are generated with discrete element method (DEM). The Reactor Monte Carlo code (RMC) and the commercial computational fluid dynamics (CFD) software star-ccm+ are used for the neutronic and thermal-fluidic analyses, respectively. RMC simulates the neutron transport to predict the effective multiplication factor and power distribution. star-ccm+ calculates the flow and heat transfer in coolant channels and heat conduction in solid matrix with the power distribution as the heat source. Preliminary results show that the power peaking factor FQ decreases below 1.65, the heat transfer area increases by 30.3% and the fuel peaking temperature decreases by 25 K. The optimized AM-informed design enjoys better neutronic and thermal-fluidic performance than those with regular geometry.

Mathematical Model of the Ignition of a Gel Fuel Particle in a High-Temperature Air Medium

Mathematical Model of the Ignition of a Gel Fuel Particle in a High-Temperature Air Medium