Tobias Chemnitz, Christian Reiter, Florian Kraus
et al.
This paper provides a unique and to the best of our knowledge first-of-a-kind attempt to develop chemical processes that may contribute to the volume reduction of SMR TRISO-based fuels and aims at the eventual ability to reprocess the spent fuel. To this end, the etching behavior of two materials, silicon carbide, SiC and pyrolytic carbon, PyC, that are generally used for the different barrier layers of a TRISO particle has been investigated. Either F/NFx or O radicals were used as etching agents and were obtained from NF3 and molecular O2, respectively, using a microwave plasma generated in a remote plasma source RPS. Laser heating of the sample materials of up to 1200 °C allowed for determination of etching rates. The results of these experiments show that chemical processing of TRISO particles via plasma-assisted etching is possible and complete removal of the encapsulation and TRISO layers can be achieved. Additional research on the waste streams and off-gases, in particular the possibility of introducing intermediate steps to reduce the CO2 formed in the chemical reactions is needed.
Agricultural residues represent a vast, underutilized resource for renewable energy. This study combines empirical analysis from 179 countries with a case study of a pelletization facility to evaluate the global potential of agricultural pelletization for fossil fuel replacement. The findings estimate a technical availability of 1.44 billion tons of crop residues suitable for pellet production, translating to a 4.5% potential displacement of global fossil fuel energy use, equating to 22 million TJ and equivalent to 917 million tons of coal annually. The economically optimized scenario projects annual savings of $163 billion and a reduction of 1.35 billion tons of CO2 equivalent in emissions. Utilizing the custom-developed CLASP-P and RECOP models, the study further demonstrates that agricultural pellets can achieve competitive pricing against conventional fossil fuels in many markets. Despite logistical and policy challenges, agricultural pelletization emerges as a scalable, market-driven pathway to support global decarbonization goals while fostering rural economic development. These results reinforce the need for targeted investment, technological advancement, and supportive policy to unlock the full potential of agricultural pellets in the renewable energy mix.
David Salvador-Jasin, A Duncan Walker, Jon F Carrotte
As a direct consequence of liquid kerosene injection, aeroengine combustors may be categorized as non-premixed combustion systems, characterized by a swirl-stabilized and highly complex flow field. In addition to the flow of air through the fuel injector, there are a large number of other features through which oxidizer can enter the heat release region. These can have an impact on local fuel-air mixing, inducing strong spatial and temporal variations in stoichiometry, thereby affecting emissions and combustion system performance. This paper discusses a novel statistical methodology, based on Principal Component Analysis (PCA) and K-means clustering, that aims to improve understanding of fuel-air mixing in realistic aeroengine combustors. The method is applied in a postprocessing step to data sampled from a Large Eddy Simulation (LES), where every chamber inflow has been tagged with a unique passive scalar, which allows it to be traced across space and time. PCA is used to construct a low-dimensional, visually interpretable representation of a spatially localized fuel-air mixing process, while K-means clustering is employed to produce an unsupervised discretization of the flow field into regions of similar fuel-air mixing characteristics. The proposed methodology is computationally inexpensive, and the easily interpretable outputs can help the combustion engineer make better informed decisions about combustor design.
During irradiation, phenomena such as kernel swelling and buffer densification may impact the performance of tristructural isotropic (TRISO) particle fuel. Post-irradiation microscopy is often used to identify these irradiation-induced morphologic changes. However, each fuel compact generally contains thousands of TRISO particles. Manually performing the work to get statistical information on these phenomena is cumbersome and subjective. To reduce the subjectivity inherent in that process and to accelerate data analysis, we used convolutional neural networks (CNNs) to automatically segment cross-sectional images of microscopic TRISO layers. CNNs are a class of machine-learning algorithms specifically designed for processing structured grid data. They have gained popularity in recent years due to their remarkable performance in various computer vision tasks, including image classification, object detection, and image segmentation. In this research, we generated a large irradiated TRISO layer dataset with more than 2,000 microscopic images of cross-sectional TRISO particles and the corresponding annotated images. Based on these annotated images, we used different CNNs to automatically segment different TRISO layers. These CNNs include RU-Net (developed in this study), as well as three existing architectures: U-Net, Residual Network (ResNet), and Attention U-Net. The preliminary results show that the model based on RU-Net performs best in terms of Intersection over Union (IoU). Using CNN models, we can expedite the analysis of TRISO particle cross sections, significantly reducing the manual labor involved and improving the objectivity of the segmentation results.
Rahman Matee Ur, Abbas Ghazanfar, Hussain Syed Baqar
et al.
Conventional solid oxide fuel cells (SOFCs) work at high operating temperatures (800–1,000°C). Lowering the operating temperature of SOFCs reduces the open-circuit voltage (OCV) and performance. Herein, a scheme was established to boost the voltage of the developed SOFC using a DC-DC voltage booster. The LTspice technique was used to develop a DC-DC booster, and the code was generated with a minimum of 0.7 V. For experimental evidence, BixAg1.00Fe1−x
Zn2O7+δ
(BAFZ oxide) materials were synthesized to investigate anodic properties. UV-vis and Fourier transform infrared spectroscopy techniques were used to determine the band gaps and functional groups. The vibrational modes of composite materials were studied via Raman spectroscopy. A slight peak shift toward a higher wavenumber was noted in the BAFZ oxide sample attributed to the addition of bismuth trioxide (Bi2O3). The conductivity was measured and found to be 1.2 S/cm at 600°C in a H2 atmosphere. Fuel cell performance was also measured in the temperature range of 400–620°C, and a maximum OCV of 1.1 V was achieved at 620°C. Finally, the boosted voltage was recorded at 2.2 V under the same circumstances using a DC-DC booster.
Rahul Kumar, Kamlesh Sahoo, Manish Kumar Singh
et al.
Developing bulk high entropy alloys (HEAs) with good strength and ductility combinations is challenging. Many of the currently reported HEAs are prepared from pure metals. The current study selected a multicomponent CoCrFeMn alloy and prepared it using scrap, ferroalloys, and pure elements. Further improvement in the properties of as-cast alloys is done by minute solute addition. The Thermo-Calc® simulation studies identified the maximum amount of minute solute elements that can be added without any new phase formation. The studied master alloy and modified compositions show a multiphase structure with FCC and HCP phases. The detailed microstructural analysis confirms that the secondary dendritic arm spacing was reduced while adding trace elements, and Cu-containing alloys showed a reduction of ∼44.44 %. The effect of the casting condition was studied by varying the heat transfer condition via different mould geometries. The mechanical properties, such as the tensile test and Vickers microhardness, show remarkable improvement with minute additions of solutes and by varying heat transfer conditions. The master alloy and Cu containing alloy show a maximum strength of ∼429 MPa and ∼562 MPa, respectively. The Cu-containing alloy shows an outstanding strength-ductility combination, and the detailed TEM-STEM analysis confirms the formation of Fe-rich clusters and Cu-rich phases. The current study shows a cost reduction of ∼1/10 compared with the alloys formed by pure elements.
For the transition to emission-free or low-emission energy, hydrogen is a promising energy carrier and fuel of the future with the possibility of long-term storage. Due to its specific properties, it poses certain safety risks; therefore, it is necessary to have a comprehensive understanding of hydrogen. This review article contains ten main chapters and provides, by synthesizing current findings primarily from standards and scientific studies (predominantly from 2023 to 2024), the theoretical basis for further research directed toward safe hydrogen infrastructure.
The continued transition towards electric mobility will decrease energy tax revenues worldwide, which has substantial implications for government funds. At the same time, demand for transportation is ever increasing, which in turn increases congestion problems. Combining both challenges, this paper assesses the effectiveness of congestion pricing as a sustainable revenue stream to offset fuel tax loss in 2030 while simultaneously enhancing efficiency in the transport sector. A congestion-based toll that is road-and-time-variant is simulated for the greater Berlin area in Germany using the multi-agent transport simulation (MATSim) software. Through the simulation results, this paper quantifies the impacts of the toll on the governmental revenue, traffic management, environment, social welfare, and the distribution effects. We find that the revenue from congestion tolls in a metropolitan area can compensate the reduction in passenger car fuel tax. Furthermore, a remarkable welfare surplus is observed. The toll also successfully incentivises transport users to adjust their travel behaviour, which reduces traffic delay time by 28%. CO2 emissions as a key metric for decarbonisation of the transport sector decrease by more than 5%. The analysis of the distribution effects suggests that a redistribution plan with a focus on the middle-low-income residents and the outer boroughs could help the policy gain more public acceptance.
Jean-Christophe Perrin, Assma El Kaddouri, Laouès Guendouz
et al.
As programs to support efficient and sustainable energy sources are expanding, research into the potential applications of the hydrogen vector is accelerating. Proton exchange membrane fuel cells are electrochemical converters that transform the chemical energy of hydrogen into electrical energy. These devices are used today for low- and medium-power stationary applications and for mobility, in trains, cars, bicycles, etc. Proton exchange membrane fuel cells use a polymer membrane as the electrolyte. The role of the membrane is multiple: it must separate gases, be an electronic insulator and a very good ionic conductor. In addition, it must resist free-radical chemical attack and have good mechanical strength. Nafion-type perfluorinated membranes have all these properties: the fluorinated backbone is naturally hydrophobic, but the hydrophilic ionic groups give the material excellent water sorption properties. The water adsorbed in the structure is extremely mobile, acting as a transport medium for the protons generated at the anode. Although it has been studied for a long time and has been the subject of a large number of papers perfluorinated membranes are still the reference membranes today. This article reviews some contributions of Nuclear Magnetic Resonance methods in liquid state to the study of water properties in the structure of Nafion-type perfluorinated membranes.
Santeri Saariokari, Peter Dendooven, Mounia Laassiri
et al.
We are evaluating the performance of a Passive Gamma Emission Tomography (PGET) device equipped with 3D position-sensitive cadmium zinc telluride (CZT) gamma-ray detectors when used for inspecting spent nuclear fuel assemblies (SFAs). Recent advancements in imaging detector technology may offer a method to extend the capabilities of such devices beyond standard safeguards applications, allowing an efficient non-invasive way to accurately characterise the properties of nuclear fuel assemblies. The efficiency of the currently used small CZT detectors is restricted by the limited likelihood of full gamma-ray absorption, which is needed for optimal imaging information. Employing larger CZT detectors would increase the probability of capturing the full energy of gamma rays, thereby enhancing the sensitivity of the PGET device and the quality of the reconstructed images. Large CZT detectors need to be position-sensitive to determine through which collimator slit a gamma ray travelled. Position sensitivity results from the pixelated readout of the CZT crystals. Pixelation potentially increases the spatial resolution of the system, which is currently determined by the collimator used. Pixelation allows resolving the position of arrival up to (readout pitch)/$\sqrt{12}$. We are additionally exploring the potential of utilising Compton imaging to provide information on the origin of gamma rays along the SFA. A simulation is created using Geant4 to compare the full photon absorption efficiency of large and current, small, crystals. Gamma rays of energy 661.7 keV and 1274 keV are targeted to the model describing the approved apparatus now equipped with 22 mm x 22 mm x 10 mm crystals of CZT. It is observed that the efficiency for photon absorption in this case is greatly increased when compared to the existing detectors.
Viviana Mancuso, Mihail N. Popescu, William E. Uspal
Many biological microswimmers are capable of chemotaxis, i.e., they can sense an ambient chemical gradient and adjust their mechanism of motility to move towards or away from the source of the gradient. Synthetic active colloids endowed with chemotactic behavior hold considerable promise for targeted drug delivery and the realization of programmable and reconfigurable materials. Here we study the chemotactic behavior of a Janus particle, which converts ``fuel'' molecules, released at an axisymmetric chemical patch located on a planar wall, into ``product'' molecules at its catalytic cap and moves by self-phoresis induced by the product. The chemotactic behavior is characterized as a function of the interplay between the rates of release (at the patch) and the consumption (at the particle) of fuel, as well as of details of the phoretic response of the particle (i.e., its phoretic mobility). Among others, we find that, under certain conditions, the particle is attracted to a stable ``hovering state'' in which it aligns its axis normal to the wall and rests (positions itself) at an activity-dependent distance above the center of the patch.
Uranium silicide (U<sub>3</sub>Si<sub>2</sub>) is regarded as a viable fuel option for improving the safety of nuclear power plants. In the present work, phase-field simulations were employed to investigate grain growth phenomena, encompassing both isotropic and anisotropic grain growth. In simulations of isotropic grain growth, it is commonly assumed that the energy and mobility of the grain boundaries (GBs) remain constant, represented by average values. The calculated grain growth kinetic rate constant, <i>K</i>, exhibits a close correspondence with the experimental measurements, indicating a strong agreement between the two. In simulations of anisotropic grain growth, the values of GB energy and mobility are correlated with the angular disparity between GBs. The simulation results demonstrated that the growth rate of U<sub>3</sub>Si<sub>2</sub> can be influenced by both the energy anisotropy and mobility anisotropy of GBs. Furthermore, the anisotropy in mobility results in a greater prevalence of low-angle GB distribution in comparison to high-angle GBs. However, the energy anisotropy of GBs does not impact the frequency distribution of the angle difference between GBs.
Commercialised biodiesel, comprising of methyl esters, have large amounts of oxygenated compounds which cause low calorific value, high viscosity, poor low temperature performance and can only used in blends with petroleum-based diesel. Deoxygenation of these compounds can occur through three reaction pathways which are decarboxylation, decarbonylation, hydrodeoxygenation. The removal of oxygen can improve their fuel properties, and is heavily influenced by the presence of hydrogen (H2). However, given safety issues during transportation and storage of H2, the use of solvents to produce in-situ H2 for the deoxygenation process has been suggested as an alternative. The present work attempts to investigate the addition of solvents (deionised water, methanol, ethanol, 1-propanol, 2-propanol, n-hexane and cyclohexane) on the deoxygenation of methyl oleate to enhance its fuel properties. The experiments were carried out with unreduced bimetallic NiCo impregnated onto TiO2. Incorporation of NiCo onto TiO2 maintained the mesoporous nature of the support while increasing the number of strong acid sites of the catalyst, which can promote C-O bond cleavage during deoxygenation. Under hydrogen-restricted conditions, the deoxygenation is expected to occur mainly through decarboxylation and decarbonylation to produce alkanes and alkenes, with cracking to produce shorter chain methyl esters. The deoxygenation was conducted with 50 g methyl oleate, 40 g solvent, 5 wt% catalyst at 300 °C for 2 h in a pressurised nitrogen atmosphere. GCMS analysis show that the addition of 2-propanol showed the highest methyl oleate conversion (69.08 %) over other solvents, with 12.74 % selectivity for alkane formation. These results indicate the potential of solvent-aided deoxygenation of methyl esters for biofuel use.
Chemical engineering, Computer engineering. Computer hardware
We comment on the note "Low Q nuclear fusion in a volume heated mixed fuel reactor" by Ruhl and Korn in which hydrodynamic life-time considerations are included in estimates of ignition energy for uncompressed fusion fuel targets. For the case of DT fusion, the authors arrive at a required hot-spot energy of 1MJ. We point out that their Q = 1 estimate is not relevant for transition into a thermonuclear fusion regime, and that it is based on DT implanted in a boron-proton matrix without accounting for all consequences. Applying the proper corrections leads to an increase in the needed laser energy to initiate useful fusion power production, even for DT, into the GJ range. The aim of Marvel Fusion is the use of p-11B fusion reactions, which would require already according to Ruhl and Korn's optimistic estimate, a hot-spot energy of 1 GJ. If this were to be provided for by a mixed pBDT fuel or a staged explosion scheme (rather than by laser deposition), it would imply a high associated production rate of fast neutrons, and the need for tritium breeding, and push the energy produced by a single laser pulse into non-manageable dimensions.
Ammonia (NH<sub>3</sub>) has been receiving the attention of researchers as an alternative promising green fuel to replace fossil sources for energy production. However, the high NOx emissions are one of the drawbacks and restrictions of using NH<sub>3</sub> on a broad scale. The current study investigates NO production/consumption for a 70/30 (vol%) NH<sub>3</sub>/H<sub>2</sub> mixture using kinetic reaction mechanism concepts to shed light on the essential reaction routes that promote/inhibit NO formation. Sixty-seven kinetic reaction mechanisms from the literature have been investigated and compared with recently reported measurements at a wide range of equivalence ratios (ϕ) (0.6–1.4), atmospheric pressure and temperature conditions. Both numerical simulations and experimental measurements used the same combustion reactor configuration (premixed stabilized stagnation flame). To highlight the best kinetic model for the predicting of the NO experimental measurements of NO, a symmetric mean absolute percentage error (SMAPE) has been determined as a preliminary estimation by comparing both numerical and experimental measurements. The results found that the kinetic reaction mechanism of Glarborg showed an accurate prediction with a minor error percentage of 2% at all lean and stoichiometric conditions. Meanwhile, the kinetic model of Wang accurately predicted the experimental data with 0% error at ϕ = 1.2 and underestimated the mole fraction of NO at 1.4 ϕ with an error of 10%. The sensitivity analysis and rate of production/consumption of NO mole fractions analysis have also been implemented to highlight the most important reactions that promote/inhibit NO formation. At lean and stoichiometric conditions, Glarborg kinetic model shows that the kinetic reactions of HNO + H ⇌ NO + H<sub>2</sub>, HNO + O ⇌ NO + OH, and NH + O ⇌ NO + H are the most important reaction routes with considerable effect on NO formation for 70/30 (vol%) NH<sub>3</sub>/H<sub>2</sub> mixture. In contrast, the reactions of NH<sub>2</sub> + NO ⇌ N<sub>2</sub> + H<sub>2</sub>O, NH<sub>2</sub> + NO ⇌ NNH + OH, NH + NO ⇌ N<sub>2</sub>O + H, and N + NO ⇌ N<sub>2</sub> + O significantly consume NO to N<sub>2</sub>, NNH, and N<sub>2</sub>O. Further, Wang’s mechanism illustrated the dominant effect of each HNO + H ⇌ NO + H<sub>2</sub>, N + OH ⇌ NO + H, NH + O ⇌ NO + H in NO formation and NH + NO ⇌ N<sub>2</sub>O + H, NH<sub>2</sub> + NO ⇌ NNH + OH, and NH<sub>2</sub> + NO ⇌ N<sub>2</sub> + H<sub>2</sub>O in the consumption of NO mole fractions.