Search Results (926)

Irradiation embrittlement occurs in the cladding materials of fusion reactors during irradiation. Determining the ductile–brittle transition temperature via Charpy impact testing is the primary method for evaluating irradiation embrittlement. Standard-sized V-shaped Charpy impact specimens (CVN) are too large in size and have high induced radioactivity. Small-sized specimens (KLST) can solve these problems, but the performance data measured from small-sized specimens are different from those of standard specimens. In other words, there is a size effect in impact performance. The notch size and hammer impact speed of KLST specimens are different from those of CVN specimens. The influence of these factors on impact performance requires further study. In response to these issues, on the basis of the previous experiments conducted by the research group, GTN damage models of CVN specimens and KLST specimens are constructed using the inverse operation method. Numerical simulation of the impact on the upper platform area is carried out for KLST specimens and variable-sized KLST specimens. Compared with the test results, the numerical simulation results are in good agreement, verifying the accuracy and reliability of the model. The results show that the notch angle and radius have little influence on the plastic zone. The cross-sectional area of the notch has a significant impact on the plastic zone. The impact velocity within the range of 3.8 m/s to 5.24 m/s affects the impact response process, but does not affect the load–displacement curve, the length of the non-plastic deformation zone, or the volume of the plastic zone. Full article

A cascade deep learning approach is proposed for optimizing the design and control of a dual-frequency induction heating system used in semiconductor manufacturing. The system is composed of two independent power inductors, fed at different frequencies, to achieve a homogeneous temperature profile along a graphite susceptor surface, crucial for enhancing layer quality and integrity. The optimization process considers both electrical (current magnitudes and frequencies) and geometrical parameters of the coils, which influence the power penetration and subsequent temperature distribution within the graphite disk. A two-step procedure based on deep neural networks (DNNs) is employed. The first step, namely optimal design, identifies the optimal operating frequencies and geometrical parameters of the two coils. The second step, namely optimal control, determines the optimal current magnitudes. The DNNs are trained using a database generated through finite element (FE) analysis. This deep learning-based cascade approach reduces computational time and multiphysics simulations compared to classical methods by reducing the dimensionality of parameter mapping. Therefore, the proposed method proves to be effective in solving high-dimensional multiphysics inverse problems. From the application point of view, achieving thermal uniformity (±7% fluctuation at 1100 °C) improves layer quality, increases efficiency, and reduces operating costs of epitaxy reactors. Full article

Pyrolysis is a promising thermochemical conversion process for transforming biomass waste into valuable products like bio-oil, syngas, and biochar. Understanding the thermodynamic efficiency of this process is important for optimizing its design and operation conditions. This study presents a novel approach for analyzing lignocellulosic biomass pyrolysis, including flax straw, by using conventional and advanced exergy techniques at different operating temperatures. Using Aspen Plus software, the pyrolysis process was accurately simulated, and system inefficiencies and possible areas for improvement were identified by performing both conventional and advanced exergy analysis. This study addresses the requirements to maximize the yield of valuable products, such as biochar, bio-oil, and biogas, while minimizing exergy losses. The pyrolysis reactor, cyclone, and flash were the main sources of exergy destruction, accounting for 32.2%, 31.8%, and 18.7% of the total exergy destruction, respectively. An advanced exergy analysis revealed that endogenous exergy, which is attributable to internal system irreversibilities, was the primary contributor to exergy destruction within the flax straw pyrolysis process. Notably, 35.6% of the total exergy loss can be potentially mitigated. The findings further suggest that temperature optimization has the potential to significantly reduce exergy destruction by 31.7% via enhancing reaction kinetics and overall conversion efficiency. Full article

Biofuels, such as biodiesel, bioethanol, and biohydrogen produced from organic waste, constitute a sustainable alternative to non-renewable fuels and drive the energy transition. In this work, the inherent safety methodology was implemented to quantify and evaluate the intrinsic risks of obtaining hydrogen from African palm stems through direct gasification with Selexol. The methodology indicators were calculated with reference to databases, the literature, and safety data sheets, considering critical stages of the process. The total inherent safety index (I_SI) was 38, classifying the process as intrinsically unsafe, with the chemical component scoring 21 points, with hydrogen being the main chemical risk (8 points), along with hazards generated by chemical reactions. Likewise, high temperature and pressure conditions indicate the presence of potentially unsafe equipment such as reactors and heat exchangers, giving the process index 17 points. Based on the results, it is recommended to reduce raw material inventories and optimize operating conditions to reduce the potential for hazardous events and improve overall inherent safety. Full article

To achieve a substantial enhancement in thermodynamic efficiency, Generation IV nuclear reactors are designed to operate at significantly elevated temperatures compared to conventional reactors. Moreover, they typically employ a fast neutron spectrum, characterized by higher neutron energy and flux. This combination results in a considerably more intense radiation environment within the core relative to traditional thermal neutron reactors. Therefore, the measurement of neutron flux in the core of Generation IV nuclear reactors faces the challenge of a high-temperature and high-radiation environment. Conventional neutron flux monitoring equipment—including fission chambers, gas ionization chambers, scintillator detectors, and silicon or germanium semiconductor detectors—faces considerable challenges in Generation IV reactor conditions. Under high temperatures and intense radiation, these sensors often experience severe performance degradation, significant signal distortion, or complete obliteration of the output signal by noise. This inherent limitation renders them unsuitable for the aforementioned applications. Consequently, significant global research efforts are focused on developing neutron detectors capable of withstanding high-temperature and high-irradiation environments. The objective is to enable accurate neutron flux measurements both inside and outside the reactor core, which are essential for obtaining key operational parameters. In summary, the four different types of neutron detectors have different performance characteristics and are suitable for different operating environments. This review focuses on 4H-SiC, diamond detectors, high-temperature fission chambers, and self-powered neutron detectors. It surveys recent research progress in high-temperature neutron flux monitoring, analyzing key technological aspects such as their high-temperature and radiation resistance, compact size, and high sensitivity. The article also examines their application areas, current development status, and offers perspectives on future research directions. Full article

A modified Enzyme Action Optimizer (mEAO) is proposed to tune a Fractional-Order Proportional–Integral–Derivative (FOPID) controller for precise temperature regulation of a nonlinear continuous stirred tank reactor (CSTR). The nonlinear reactor model, adopted from a standard benchmark formulation widely used in CSTR control studies, is employed as the simulation reference. The tuning framework operates in a simulation-based manner, as the optimizer relies solely on the time-domain responses to evaluate a composite cost function combining overshoot, settling time, rise time, and steady-state error. Comparative simulations involving EAO, Starfish Optimization Algorithm (SFOA), Success History-based Adaptive Differential Evolution with Linear population size reduction (L-SHADE), and Particle Swarm Optimization (PSO) demonstrate that the proposed mEAO achieves the lowest cost value, the fastest convergence, and superior transient performance. Further comparisons with classical tuning methods, Rovira 2DOF-PID, Ziegler–Nichols PID, and Cohen–Coon PI, confirm improved tracking accuracy and smoother actuator behavior. Robustness analyses under varying set-points, feed-temperature disturbances, and measurement noise confirm stable temperature regulation without retuning. These findings demonstrate that the mEAO-based FOPID controller provides an efficient and reliable optimization framework for a nonlinear thermal-process control, with strong potential for future real-time and multi-reactor applications. Full article

Zirconium and its alloys are widely used in nuclear power engineering due to their favorable physical and mechanical properties and their low thermal-neutron absorption cross-section. Their high corrosion resistance in aqueous and steam environments at elevated temperatures is essential for the reliable operation of fuel assemblies and is associated with the formation of a stable, compact ZrO₂ oxide layer. However, under reactor conditions, the presence of hydrogen, iodine and other fission products can reduce corrosion resistance, making detailed corrosion assessment necessary. Manufacturing technology, alongside alloy composition, also plays a decisive role in determining corrosion behavior. This study presents corrosion test results for a Zr-1%Nb alloy processed under thermomechanical conditions corresponding to rolling in a special type of three-roll skew rolling–Radial-Shear Rolling (RSR). The applied rolling technology ensured the formation of a pronounced ultrafine-grained (UFG) structure in the near-surface layers, with an average grain size below 0.6 µm. EBSD and TEM observations revealed a largely equiaxed microstructure with refined grains and increased grain boundary density. The corrosion testing was performed in high-temperature steam vessels at 400 °C and 10.3 MPa for 72, 336, 720 and 1440 h. The results demonstrate that RSR processing is an efficient alternative to conventional multi-pass normal bar rolling with vacuum heat treatments, allowing a significant reduction in processing steps and eliminating the need for expensive tooling and intermediate thermal or chemical treatments. Bars manufactured using this method meet the ASTM B351 requirements. The specific weight gain did not exceed 22 mg/dm² after 72 h and 34.5 mg/dm² after 336 h. After 1440 h, the samples exhibited a continuous, uniform dark-grey oxide layer with an average thickness below 5.3 µm. Full article

The urgent need for cleaner energy sources has driven exploration into innovative and sustainable solutions. This study investigates the potential of the invasive aquatic plant, the water hyacinth, to contribute to energy recovery and support the preservation of blue carbon ecosystems through biomass removal. Employing slow pyrolysis, this study examines the influence of temperature (300–500 °C) and residence time (30–90 min) on bio-oil and biochar production in a fixed-bed reactor. Results revealed that residence time was the key operational parameter significantly influencing total liquid condensate yield, which peaked at 34.34 wt% at 400 °C after 90 min. Moisture content reveals an actual organic bio-oil yield of approximately 3.4–4.8 wt%. In contrast, biochar yield (max. 43.74 wt%) was not significantly affected by the tested parameters. The resulting bio-oil exhibited a high heating value of up to 25.84 MJ/kg, suggesting its potential as a renewable fuel. This study concludes that slow pyrolysis of invasive water hyacinth provides a dual-benefit pathway: it co-produces renewable bio-oil for energy recovery alongside a stable biochar, offering a tangible route for blue carbon sequestration. This integrated approach transforms an environmental liability into valuable resources, contributing to a cleaner environment and a more sustainable future. Full article

Oxy-fuel combustion technology is a critical pathway for carbon capture in the cement industry. However, the high-concentration CO₂ atmosphere significantly alters multiphysics coupling in the calciner and systematic studies on its comprehensive effects remain limited. To address this, a Computational Particle Fluid Dynamics (CPFD) model using the MP-PIC method was implemented using the commercial software Barracuda Virtual Reactor 22.1.2 to simulate an industrial-scale oxy-fuel cement calciner and validated against industrial data. Under oxy-fuel combustion with 50% oxygen concentration in the tertiary air, simulations showed a 38.4% increase in the solid–gas mass ratio compared to conventional air combustion, resulting in a corresponding 37.7% increase in total pressure drop. Flow resistance was concentrated primarily in the constriction structures. Local temperatures exceeded 1200 °C in high-oxygen regions. The study reveals a competition between the inhibitory effect of high CO₂ partial pressure on limestone decomposition and the promoting effect of elevated overall temperature. Although the CO₂-rich atmosphere thermodynamically suppresses calcination, the higher operating temperature under oxy-fuel combustion effectively compensates, achieving a raw meal decomposition rate of 92.7%, which meets kiln feed requirements. This research elucidates the complex coupling mechanisms among flow, temperature, and reactions in a full-scale oxy-fuel calciner, providing valuable insights for technology design and optimization. Full article

We present the concept of an ultracold neutron (UCN) source with a superfluid He-4 (SF ⁴He) converter located in the thermal column of the WWR-K research reactor at the Institute of Nuclear Physics (INP) in Almaty, Kazakhstan. The conceptual design is based on the proposal of accumulating UCNs in the source and effectively transporting them to experimental setups. We propose to improve the UCN density in the source by separating the heat and UCN transport from the production volume and decreasing the temperature of the SF ⁴He converter to below about 1 K. To obtain operation temperatures below 1 K, we plan to use a He-3 pumping cryogenic system and minimize the thermal load on the UCN accumulation trap walls. Additional gain in the total number of accumulated UCNs can be achieved through the use of a material with a high critical velocity for the walls of the accumulation trap. The implementation of such a design critically depends on the availability of materials with specific UCN and cryogenic properties. This paper describes the conceptual design of the source, discusses its implementation methods and material requirements, and plans for material testing studies. Full article

Powered by high-efficiency thermophotovoltaics and developed through economics-by-design analysis, a promising, optimized design was selected for the radiantly integrated TPV–microreactor system. However, the novelty of the conversion system, the connection between the TPV and critical reactor core, requires a proper degree of reliability analysis to develop confidence in this technology. This is made difficult by the lack of computational tools that capture the full suite of physics and feedback mechanisms present in the RITMS design. This paper outlines the methods utilized to capture power, temperature, and reactivity variation and feedback mechanisms through time, utilizing lumped conditions, point kinetics equations, and the determination of temperature reactivity coefficients. The computational package was applied to a series of accident-driven transient scenarios, demonstrating the RITMS design’s ability to return to a safe operating equilibrium without active interference. In the case of high positive reactivity insertion accidents, design solutions were demonstrated that would mitigate risk. Full article

In this study, a three-dimensional computational fluid dynamic (CFD) model was constructed and validated against experimental data. The oxygen injection methods—specifically the primary air flow and secondary air flow—were investigated. The results demonstrate that primary air flow is the dominant factor in combustion. An increase of primary air from an φ of 0.20 to 0.75 lead to a rise in combustion peak temperature from 892.17 K to 1321.02 K, while simultaneously expending the flame combustion zone and enhancing the conversion of C₁₀H₈ and CH₄. Conversely, increasing the secondary air flow from 1 L/min to 7 L/min reduced the centrally measured temperatures form 886.09 K to 856.07 K due to irregular flow patterns, which expanded the central low-temperature region. While secondary air flow promoted more uniform reactant conversion and slightly suppressed intermediate products (e.g., soot, C₆H₆), its overall effect was secondary to that of the primary air. This research reveals a critical design insight: using primary air injection to introduce oxygen into the reactor is a reasonable approach. The findings provide valuable guidance for optimizing partial oxidation burner design and operating conditions to maximize tar conversion while maintaining reactor integrity. The study also establishes a rigorously validated CFD framework for analyzing complex reacting flows in tar thermochemical conversion reactors. Full article

Growing environmental awareness has renewed interest in thorium as a nuclear fuel, underscoring the need for further studies to evaluate how reactors perform when conventional fuels are replaced with thorium-based alternatives. In this study, thermal hydraulics and solid mechanics computations were simulated using COMSOL multiphysics to investigate the safe operating conditions of a heavy water reactor with thorium-based fuel. The thermo-mechanical analysis of the fuel rod under transient heating conditions provides critical insights into strain, displacement, stress, and coolant flow behavior at elevated volumetric heat sources. After 3 s of heating, the strain distribution in the fuel exhibits a high-strain core surrounded by a low-strain rim, with peak volumetric strain increasing nearly linearly from 0.006 to 0.014 as heat generation rises. Displacement profiles confirm that radial deformation is concentrated at the outer surface, while axial elongation remains uniform and scales systematically with power. The resulting von Mises stress fields show maxima at the outer surface, increasing from ~0.06 to 0.15 GPa at the centerline with higher heat input but remaining within structural safety margins. Cladding simulations demonstrate nearly uniform axial expansion, with displacements increasing from ~0.012 mm to 0.03 mm across the investigated power range, and average strain remains negligible (≈10⁻⁴), while mean stresses increase moderately yet stay well below the yield strength of zirconium alloys, confirming safe elastic behavior. Hydrodynamic analysis shows that coolant velocity decreases smoothly along the axial direction but maintains stability, with only minor reductions under increased heat sources. Overall, the coupled thermo-mechanical and fluid-dynamic results confirm that both the fuel and cladding remain structurally stable under the studied conditions. By using COMSOL’s multiphysics capabilities, and unlike most legacy codes optimized for uranium-based fuel, this work is designed to easily incorporate non-traditional fuels such as thorium-based systems, including user-defined material properties, temperature-dependent thermal polynomial formulas, and mechanical response. Full article

This review relates the kinetics of anaerobic digestion (AD) to energy outcomes, including typical ranges of methane yields and volumetric methane productivities (down to hourly g L⁻¹ h⁻¹ scales relevant for industrial plants). It further translates these relationships into practical control principles that support stable, high methane productivity. Evidence spans substrate selection and co-digestion with emphasis on carbon/nitrogen (C/N) balance, pretreatment strategies, and reactor operation, linking process constraints with operating parameters to identify interventions that raise performance while limiting inhibition. Improving substrate accessibility is the primary step: pretreatment and co-digestion shift limitation beyond hydrolysis and allow safe increases in organic loading. Typical mesophilic operation involves hydraulic retention times of about 10–40 days for food waste and 20–60 days for different types of livestock manure and slowly degradable energy crops, with stable performance achieved when the solids retention time (SRT) is maintained longer than the hydraulic retention time (HRT). Stability is further governed by sustaining a low hydrogen partial pressure through hydrogenotrophic methanogenesis. Temperature and pH define practicable operating ranges; meanwhile, mixing should minimise diffusion resistance without damaging biomass structure. Early-warning indicators—volatile fatty acids (VFAs)/alkalinity, the propionate/acetate ratio, specific methanogenic activity, methane (CH₄)% and gas flow—enable timely adjustment of loading, retention, buffering, mixing intensity and micronutrient supply (Ni, Co, Fe, Mo). In practice, robust operation is generally associated with VFA/alkalinity ratios below about 0.3 and CH₄ contents typically in the range of 50–70% (v/v) in biogas. The review consolidates typical feedstock characteristics and biochemical methane potential (BMP) ranges, as well as outlines common reactor types with their advantages and limitations, linking operational choices to energy yield in combined heat and power (CHP) and biomethane pathways. Reported pretreatment effects span approximately 20–100% higher methane yields; for example, 18–37% increases after mechanical size reduction, around 20–30% gains at 120–121 °C for thermal treatments, and in some cases nearly a two-fold increase for more severe thermal or combined methods. Priorities are set for adaptive control, micronutrient management, biomass-retention strategies, and standardised monitoring, providing a coherent route from kinetic understanding to dependable energy performance and explaining how substrate composition, pretreatment, operating parameters, and kinetic constraints jointly determine methane and energy yield, with particular emphasis on early-warning indicators. Full article

This study investigates a shielded reactor coolant pump (RCP) using a thermo-fluid–structure interaction approach to numerically simulate the internal flow characteristics, impeller forces, and rotor vibration modes during rapid start-up following a loss of power accident under high-temperature and high-pressure conditions. A three-dimensional fluid–structure coupling model was established, employing the SST k-ω turbulence model and a one-way fluid–structure interaction method. The effects of three different start-up acceleration rates on pump head, pressure pulsation, vortex structures, turbulent kinetic energy distribution, and dynamic stress on the impeller were systematically analyzed. The results indicate that the medium-acceleration scenario (4.5 s start-up time) exhibits the most favorable performance in terms of pressure pulsation control, vorticity suppression, and stress distribution, effectively avoiding cavitation and structural resonance while ensuring a smooth and reliable start-up process. Modal analysis reveals that the rotor system is predominantly characterized by bending vibrations with satisfactory torsional stiffness and appropriately set critical speeds, presenting no resonance risks. This research provides theoretical foundations and engineering references for the safe restart of RCPs under extreme operational conditions. Full article