Nuclear Reactor Research Articles

Parametric Optimisation of Wire Electrical Discharge Machining of 15CDV6 HSLA Steel Using Taguchi Method

15CDV6 steel is a high strength bainitic High Strength Low Alloy (HSLA) steel with low concentrations of chromium, molybdenum, and vanadium as the main alloying constituents. This steel is very robust and well-tempered i.e., it has High strength and good toughness. It is used in the manufacture of transformers, electric motors, nuclear reactors, and its application to the aerospace industry for the manufacture of rocket motor cases is immense. Simplifying any process of machining is very difficult, since it basically includes forecasts of machining parameters and working requirements that are unpredictable and extremely non-linear in nature which influence the overall production Quality and costs. A key component of producing novel products, particularly for the automotive and aerospace sectors, is wire electro discharge machining (Wire-EDM). This technology got success and offers unique advantages for specific applications, such as working with hard, super-tough, brittle, or difficult-to-machine materials, producing intricate shapes, or achieving high precision. The high degree of the obtainable accuracy and the fine surface quality makes Wire-EDM valuable. The right selection of the process parameters or input variables is the considered as most important task in Wire Electro Discharge Machining of 15CDV6 HSLA steel material. The present work concentrates on optimisation of various process parameters are Pulse-on Time, Pulse-off Time, Water pressure and sensitivity on work material 15CDV6 HSLA steel, the output responses considered are Material Removal Rate (MRR), Surface Roughness (Ra), and Power Consumption (PC). Taguchi Method technique used on experimental results for optimisation and same results are analysed using Analysis of Variance (ANOVA) for identify percentage contribution of process parameters. This work helps in analysing the suitable process parameters and machining performance for machining of 15CDV6 steel and also reveals the research work area in which maximum research work can be done in future.

Generation of shear flows induced by AE / EPM in LHD plasma

Abstract The generation of shear flows (SFs) by Alfven Eigenmodes (AEs) and energetic particle modes (EPMs) have important effects on the operation of future nuclear fusion reactors, because SFs regulate the saturation of the AEs/EPMs, the transport of EPs and thermal plasma, as well as the formation of transport barriers among other consequences. The aim of this study is the analysis of SFs generation during the saturation phase of AEs and EPMs in LHD plasma. Experiments performed in the 23rd and 24th LHD experimental campaigns are dedicated to explore the destabilization of AEs/EPMs in discharges with different heating patterns, thermal plasma and magnetic field configurations. In particular, the shots 176490 and 179697 show the destabilization of MHD bursts and energetic-ion-driven resistive interchange modes (EIC), respectively. Charge exchange spectroscopy measurements in both discharges indicate that the generation of SFs by AE/EPM is uncorrelated with the perturbation induced by the neutral beam injector (NBI). Nonlinear simulations performed using the gyro-fluid code FAR3d show the generation of zonal structures, especially SFs, induced during the saturation phase of Toroidal Alfven Eigenmodes (TAEs) triggered in the MHD burst as well as by the 1 / 1 EIC in the bursting phase. The simulations indicate that SFs are caused by the radial electric fields powered by energy transfers from the unstable AE/EPM towards the thermal plasma. The strongest SFs are measured during the EIC bursting phase once the 1 / 1 EPM overlaps with nearby resonances at the plasma periphery. Likewise, the largest SFs during the MHD burst are observed once TAEs radially overlap in the inner-middle plasma region.

Comparison of Radionuclide Drug Conjugates With Boron Neutron Capture Therapy: An Overview of Targeted Charged Particle Radiation Therapy.

Targeted charged alpha- and beta-particle therapies are currently being used in clinical radiation treatments as newly developed methods for either killing or controlling tumor cell growth. The alpha particles can be generated either through a nuclear decay reaction or in situ by a nuclear fission reaction such as the boron neutron capture reaction. Different strategies have been employed to improve the selectivity and delivery of radiation dose to tumor cells based on the source of the clinically used alpha particles. As a result, the side effects of the treatment can be minimized. The increasing attention and research efforts on targeted alpha-particle therapy have been fueled by exciting results of both academic research and clinical trials. It is highly anticipated that alpha-particle therapy will improve the efficacy of treating malignant tumors. In this overview, we compare radionuclide drug conjugates (RDC) with boron neutron capture therapy (BNCT) to present recent developments in targeted alpha-particle therapy.

The high burn-up structure evolution in polycrystalline UO2: Phase-field modeling investigation

Abstract Understanding the evolution of microstructure in nuclear fuels under high burn-up conditions is a critical concern aimed at extending fuel refueling cycles and enhancing nuclear reactor safety. In this study, a phase-field model has been proposed to examine the evolution of high burn-up structures in polycrystalline UO2. The formation and growth of recrystallized grains were initially investigated. It was demonstrated that recrystallization kinetics adhere to the KJMA equation, and recrystallization represents a process of free energy reduction. Subsequently, the microstructure evolution in UO2 was analyzed as burn-up increased. Gas bubbles acted as additional nucleation sites, thereby augmenting recrystallization kinetics, while the presence of recrystallized grains accelerated bubble growth by increasing the number of grain boundaries. The observed variations in recrystallization kinetics and porosity with burn-up closely align with experimental findings. Furthermore, the influence of grain size on microstructure evolution was deliberated upon. Larger grain sizes were found to decrease porosity and the occurrence of high burn-up structures.

Bidimensional Gegenbauer Polynomials for Variable‐Order Time‐Fractional Integro‐Partial Differential Equation With a Weakly Singular Kernel

ABSTRACTIn this paper, a pseudo‐operational collocation method based on Gegenbauer polynomials is presented to solve a category of variable‐order time‐fractional integro‐partial differential equations with singular kernels. The applications of these functional equations can be revealed in the theory of elasticity, hydrodynamics, heat conduction, and nuclear reactor theory. The pseudo‐operational matrices are constructed utilizing bivariate Gegenbauer polynomials to approximate the solution of the mentioned equation. Then, using the collocation method and resultant matrices, the main equation is converted into a system of algebraic equations that can be solved by Newton's iteration method. Besides presenting a fast and accurate method, an error bound is determined in a Gegenbauer‐weighted space for the residual function obtained from the proposed approach. Finally, several test examples are performed to confirm the reliability and efficiency of the proposed method.

Coal-to-nuclear modernization of an existing power plant with a IV-th generation nuclear reactor

The paper presents an analysis of a transition from a coal-fired power plant to a nuclear unit. The main focus is set on the extensive usage of the existing parts of the already operating system. The key problem is the correct matching of a nuclear reactor and the steam island. It is assumed here that the reactor module operates under nominal conditions and the steam turbine is adapted to fit the reactor. The paper describes the numerical model of the steam turbine cycle for the off-design simulations. The developed model allows us to determine the changes in the steam cycle in order to match the required water and steam temperature values at the inlets and the outlets of the steam generator. The paper presents the suggested modifications and the evaluation of the operation after the transition.

Impact of MHD mixed convection on heat and mass transfer in a typical DCLL breeder blanket

Abstract A typical dual-coolant lead lithium (DCLL) liquid blanket employs eutectic liquid lithium lead alloy (PbLi) as coolant and tritium breeder for Tokamak nuclear fusion reactor, and is responsible for transporting heat and tritium. The blanket is subjected to both strong magnetic field and strong radially non-uniform neutron volume heating. The flow of liquid metal is influenced by the combined effects of magnetohydrodynamics (MHD), buoyancy, and inertial effects, resulting in a complex MHD mixed convection phenomenon. This study employs direct numerical simulation (DNS) based on finite volume method to analyze the flow, heat transfer, and mass transfer within blanket unit. The results demonstrate that mixed convection has a significant impact on the MHD pressure drop and flow characteristics. The complex MHD mixed convection gives rise to a considerable number of vortices, particularly in regions of the turn and the downward poloidal duct. The formation of low-speed zones and jets within the blanket has the potential to significantly impact heat and mass transfer, leading to the accumulation of heat and tritium. On the other hand, the markedly elevated tritium production rate is a significant contributing factor to the obviously elevated tritium concentration in the vicinity of the first wall.

Dielectric Barrier Discharge Reactors for Plasma‐Assisted CO2 and CH4 Conversion: A Comprehensive Review of Reactor Design, Performance, and Future Prospects

Dielectric barrier discharge (DBD) plasma is a promising technology for catalysis due to its low‐temperature operation, cost‐effectiveness, and silent operation. This review comprehensively analyzes the design and operational parameters of DBD plasma reactors for three key catalytic applications: CH4 conversion, CO2 splitting, and dry reforming of methane (DRM). While catalyst selection is crucial for achieving desired product selectivity, reactor design and reaction parameters such as discharge power, electrode gap, reactor length, frequency, dielectric material thickness, and feed gas flow rate, significantly influence discharge characteristics and reaction mechanisms. This review also explores the influence of less prominent factors, such as electrode shape and applied voltage waveforms. Additionally, this review addresses the challenges of DBD plasma catalysis, including heat loss, temperature effects on discharge characteristics, and strategies for enhancing overall efficiency.

Operation Optimization Framework for Advanced Reactors Using a Data-Driven Digital Twin

Abstract To meet future energy demand, while producing safe, reliable, and carbon-free energy, nuclear reactors will be needed. To make next-generation reactors more economically competitive, the Artificial Intelligence and Machine Learning-based operation optimization module of the dynamic operation and maintenance optimization (DyOMO) framework is proposed. The operation optimization module of DyOMO consists of a data-driven digital twin coupled to a genetic algorithm (GA) optimizer to quickly and efficiently search the solution space for optimal control schemes. The digital twin consists of a Bayesian Network (BN) known as MVCBayes to incorporate uncertainty in the optimization and feedforward neural networks (FFNN) as MVCNet with GA to conduct the optimization. Over time as reactor systems are operating, component degradation will cause the system's electrical output to decrease or be shutdown entirely to perform maintenance. To prevent this, the DyOMO operation optimization module aims to prolong system operation until the next scheduled maintenance period using multiple variable control (MVC) that simultaneously perturbs all actuators to better control the reactor. Comparing this approach with traditional single variable control (SVC), MVC can extend reactor operation past 5% degradation while SVC begins to struggle once the pump and turbine degradation surpasses 0.85% for load-following (LF) operation. Given this extra operation time, the system can continue to run while maximizing its safety margin until the next scheduled shutdown and potentially decrease the total number of maintenance actions throughout the license period to decrease operational and maintenance (O&M) costs.

Initial Event Analysis for Turbine Missile Events at Floating Nuclear Power Plants Using the Master Logic Diagram Method

Floating Nuclear Power Plants (FNPP) have become a popular design choice in several countries, including South Korea, China, and Denmark. Safety analysis, including probabilistic safety assessment, must be conducted for every nuclear reactor design. Among the parameters that need to be determined are initiating events. Initiating events is crucial information as it impacts further analyses, such as event and fault tree analyses. Various methods exist for deciding and initiating events, including the Master Logic Diagram (MLD). The determination of initiating events can be based on the potential impact of internal or external hazards on the FNPP. This study aims to demonstrate the application of MLD in determining initiating events in the case of a turbine missile incident on Akademik Lomonosov floating NPP. Turbine missile events are critical due to their potential to damage important safety-related structures, systems, and components in the vicinity. From the analysis, it was found that ten basic events could be candidates for initiating events. After the screening process, four initiating events were identified as the final result: reactor vessel rupture (RVR), loss of feedwater (LOFW), feedwater line break (FWLB), and loss of condenser vacuum (LOCV). Keywords: Floating NPP, safety analysis, initiating event, master logic diagram (MLD)

Design innovative perspectives of thermally radiative flow of chemically reactive magnetized nanofluid capturing bioconvection and Joule heating aspects

The distinguishing thermophysical features of nanofluids make them possibly advantageous in enhancing transfer of heat. The applications of nanofluids in industrial cooling, cooling tower detection, imaging, microelectronic cooling, crossbreed motor proficiency, transparent sunscreen, crack-resistant paint, nuclear reactor cooling, thermal transport, enhanced oil recovery, and architecture have diversified extensively in recent years. Scientific research has shown an enormous spike in fascination with non-Newtonian nanofluids in the past few decades. The stress in non-Newtonian fluids varies nonlinearly with the rate of deformation. These fluids are used in material processing, bioengineering, polymeric fluids, oil reservoir design, and the chemical and nuclear industries. There have been several non-Newtonian models presented forth. The Williamson fluid model is one example of such a model that has a shear-thinning behavior. The current article explanate analysis of (3D) Williamson fluid flow considering various physical features which plays vital role to raise the heat transportation rate. Through transformations procedure the governing physical problem is simplified and then solved via bvp4c in MATLAB. Acquired data are tabulated and graphically presented, and the impacts of relevant parameters on concentration-microorganisms and temperature have been examined numerically. According to the accomplishments, the concentration profile is anticipated to decline as the stretching rate parameter and Brownian motion parameter values grow. By boosting the magnetic parameter, the microorganism profile advances, but the bioconvection Peclet number reveals an opposite tendency.

Introducing the Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations—II: Illustrative Application to Heat and Energy Transfer in the Nordheim–Fuchs Phenomenological Model for Reactor Safety

This work presents an illustrative application of the newly developed “Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations (2nd-FASAM-NODE)” methodology to determine most efficiently the exact expressions of the first- and second-order sensitivities of NODE decoder responses to the neural net’s underlying parameters (weights and initial conditions). The application of the 2nd-FASAM-NODE methodology will be illustrated using the Nordheim–Fuchs phenomenological model for reactor safety, which describes a short-time self-limiting power transient in a nuclear reactor system having a negative temperature coefficient in which a large amount of reactivity is suddenly inserted. The representative model responses that will be analyzed in this work include the model’s time-dependent total energy released, neutron flux, temperature and thermal conductivity. The 2nd-FASAM-NODE methodology yields the exact expressions of the first-order sensitivities of these decoder responses with respect to the underlying uncertain model parameters and initial conditions, requiring just a single large-scale computation per response. Furthermore, the 2nd-FASAM-NODE methodology yields the exact expressions of the second-order sensitivities of a model response requiring as few large-scale computations as there are features/functions of model parameters, thereby demonstrating its unsurpassed efficiency for performing sensitivity analysis of NODE nets.

Shielding factors for a fission-powered mars exploration rover

Background With the advances in compact fission power systems and Stirling converters, the efficiency and portability of electrical energy production systems has increased substantially thanks to NASA’s Kilopower project. These 1-10 kWe-class reactors are compact enough to be transportable by pressurized rovers, allowing an extended human reach across the surface of Mars to produce scientific data at a rate that greatly surpasses the rate of robotic rover data collection. If rovers were to harness fission power while mobile, it is possible for near-limitless range. This capability could allow one crew on Mars for under a “Conjunction” class mission as outlined in NASA’s Mars Design Reference Architecture (DRA) 5.0 to visit many geological sites of interest instead of requiring additional landings to explore distant features of the Martian surface. This study explored the parameters that affected the mass of the shielding required to protect the crew against a fission reactor embedded in the chassis of a pressurized rover. Methods An analytical approach was devised to estimate the required mass of a hypothetical solid tungsten shield under various conditions. Results Power levels below 3.4 kWe were found to be impractical for rover applications. Between 3.4 kWe and 10 kWe would be able to recharge the rover without returning to base camp. The increase in shielding mass from a 3.4 kWe reactor and a 10 kWe reactor was 6%. The reduction between a 10 kWe reactor at 3 m and 6 m was 7%. Varying the shield thickness in accordance with astronaut activities resulted in a 19% reduction. Powering the reactor off before exiting the vehicle resulted in an additional 65% reduction. Conclusions Knowledge of the crew activities and locations had the greatest impact on the required shielding mass and the mission activities should be well-understood and taken into account for shield design.

A Comprehensive Review of Mixed Convective Heat Transfer in Tubes and Ducts: Effects of Prandtl Number, Geometry, and Orientation

This paper presents a comprehensive review of mixed convective heat transfer phenomena involving fluids with varying Prandtl numbers, specifically focusing on their behavior in different geometries and orientations. This study systematically explores heat transfer characteristics for fluids with low, medium, and high Prandtl numbers across a range of tube geometries, including circular, rectangular, triangular, and elliptical cross-sections, and examines their effects in both horizontal and vertical tube orientations. By consolidating existing research findings and analyzing various experimental and numerical studies, this review elucidates the complex interactions between fluid properties, tube geometry, and flow orientation that influence mixed convection heat transfer. Key insights are provided into the mechanisms driving heat transfer enhancements or degradations in different scenarios. In view of the findings from this paper, more than 84% of studies were conducted in a horizontal orientation and circular cross-section with a tendency to use medium-to-high Prandtl numbers as the working fluid for the past 10 years. This paper also identifies critical gaps in current knowledge and suggests future research directions to advance the understanding and application of mixed convective heat transfer in diverse engineering systems. Furthermore, apart from having different geometries applied in industrial applications, there is still room for improvement through the addition of passive methods to the heat transfer system, including helical coils, corrugations, swirl generators, and ribs. Overall, from the literature review, it is found that there are few relevant numerical simulations and experimental studies concentrating on middle Prandtl number fluids. Hence, it is recommended to perform more research on medium Prandtl number fluids that can be used as energy storage systems (ESS) in concentrating solar power plants, nuclear reactors, and geothermal systems.

Predicting Critical Heat Flux in Narrow Rectangular Channels: A CFD Approach for Subcooled Flow

The PALLAS-reactor is an advanced nuclear reactor designed for producing medical isotopes and for carrying out research on (medical) nuclear technology. RELAP5 is the primary tool for modeling the accident scenarios relevant to the licensing of this reactor. The Groeneveld Look-Up Tables (LUT) are the default model of RELAP5 for estimating Critical Heat Flux (CHF). Literature has shown that the LUT over-predict CHF inside narrow, rectangular channels such as the cooling channels of the core of the PALLAS-reactor. Empirical correlations such as that of Sudo–Kaminaga or its modified version by Kim et al. (SK-Kim) are better suited for these geometries. However, these correlations are typically implemented in one-dimensional (1D) System Thermal-Hydraulics codes whereby the quantities of interest are averaged-out over the control domains. Computational Fluid Dynamics (CFD) could capture three-dimensional effects that could help reducing unnecessary conservatism embedded in some 1D approaches (e.g. Sudo–Kaminaga or SK-Kim correlations). Therefore, CFD is to be employed to support the Deterministic Safety Analyses of the PALLAS-reactor if there are scenarios in which the SK-Kim correlation predicts CHF. Boiling flows inside round or annular vertical channels have been extensively modeled with CFD. However, attempts at modeling CHF in narrow, rectangular geometries are still scarce. Therefore, this work aims at developing and validating a CFD approach for predicting CHF in rectangular channels. Four combinations of turbulence interaction and turbulent dispersion models are investigated; the results are compared against experiments and the SK-Kim correlation; sensitivity analyses are conducted on the turbulence models as well as the mesh. Certain combinations of turbulence interaction and turbulent dispersion models promote the transport of steam towards the center of the channel, thus increasing CHF, while other cause the steam to remain confined at the wall, thereby lowering the CHF. This study provides several CFD options to estimate CHF depending on the required level of conservatism. Estimating CHF in a conservative manner is crucial for licensing the PALLAS-reactor and other reactors of similar design, thereby securing the production of medical isotopes in Europe and the rest of the world.

Implementation and Performance Evaluation of Intelligent Techniques for Controlling a Pressurized Water Reactor

Pressurized water reactors (PWRs) are the most common and widely used type of reactor, and ensuring the stability of the reactor is of utmost importance. The challenges lie in effectively managing power fluctuations and sudden changes in reactivity that could result in unsafe situations. Reactor power fluctuations can cause changes in behavior. At the same time, the transfer of heat from the fuel to the coolant and reactivity changes resulting from differences in fuel and coolant temperatures can also make the systemunpredictable. The primary goal of a power controller used in a nuclear reactor is to sustain the specified power level, which guarantees the security of the power plant. To address these challenges, this paper presents a dynamic model of a PWR and applies several control techniques to the system for power level control. Specifically, a traditional PID controller, a Neural Network controller, a Fuzzy self-tuned PID controller, and a Neuro-Fuzzy self-tuned PID controller were individually designed and evaluated to enhance the performance of the reactor power control system under constant and variable reference power. In addition, the robustness of each controller was appraised against time delays and external disturbances. The system was tested with various initial power values to evaluate its performance under different conditions. The results demonstrate that the Neuro-Fuzzy self-tuned PID controller has the best performance, as well as the fastest response time compared to the other controllers.Furthermore, the intelligent controllers were found to exhibit good robustness against time delays and external disturbances. The system's stability was not significantly affected by changes in the initial power value, although it had a minor effect on the transient response. Overall,the findings of this study can inform the design and optimization of control systems for PWRs, with the ultimate goal of improving their safety, reliability, and performance.

Featuring the aspects with temperature dependent viscosity of inclined MHD Williamson fluid along with heat source/sink, Soret and Dufour effects: A predictor-corrector approach

The boundary layer flow analysis of Williamson fluid moving on the stretched cylinder has applications in the polymer processing, drug delivery system, cooling systems, rheology of food products, dyeing, and finishing. The numerical solutions of governing Navier-Stokes equations at different scenarios of thermal and solutal aspects have lots of practical implications, including biomedical engineering, cooling and heating processes, chemical reactors, aerodynamics, environmental science, and thermal storage systems. From these practical applications, the authors were motivated to conduct a study in which the numerical behavior is examined by applying the Adams-Bashforth predictor and corrector approach of numerical analysis for the Williamson fluid model in the presence of varying viscosity, natural convection, and the inclined magnetic field. Furthermore, Joule heating, thermal radiation, and heat source/sink effects are included in the thermal aspects because these are the important concepts in thermal management and engineering and have applications in solar thermal energy systems, combustion engines, heat exchangers, nuclear reactors, thermal imaging, and safety. Apart from thermal aspects, the analysis of mass transfer focuses on the influence of chemical reactions and Soret-Dufour effects. The similarity transformations are adopted to convert partial differential equations into ordinary differential equations. Specifically, the well-known predictor and corrector numerical method named the Adams-Bashforth method in combination with the Runge-Kutta 4th order scheme is used to achieve the numerical solutions. The temperature, concentration, and velocity regions are displayed on the graphical and numerical conducts. A comparison is also made between the results obtained by the shooting method and the numerical findings of skin friction, Nusselt number, and Sherwood number determined by the Adams-Bashforth method. The determining results concluded that the restrictions in the flow of Williamson fluid are caused by variations in the inclination magnetic field, the surface curvature, and the Williamson parameter, whereas the motion of the fluid increases due to convection, which occurs due to thermal phenomena. The determined results indicate that the temperature distribution is enhanced due to the addition of thermal radiation, Eckert number, and magnetic field. The surface curvature, Soret number, and reaction coefficient marks the decrease impact on the concentration region. The temperature-dependent viscosity increases the drag force and friction coefficient. The Nusselt number is amplified by applying thermal radiation to the surface of the cylinder. The chemical reaction is the source of the increment in the Sherwood number.

Novel Nuclear Power and Fossil Fuel Hybrid Propulsion Systems for Long-Endurance Unmanned Aerial Vehicles: Configuration Comparison and Performance Optimization

Aircraft nuclear propulsion system can significantly enhance the endurance, but its large size and weight become disadvantages against the conventional fossil fuel propulsion system. In this paper, a novel nuclear power and fossil fuel hybrid propulsion system, which combines the lithium-cooled fast reactor and the kerosene-fueled turbine engine, is proposed to meet the power requirements of different flight segments. Performance assessment and comparison among different hybrid configurations is performed. Results indicate that the configuration combining the nuclear power module with a high bypass ratio turbofan engine is the most promising for aircraft. The primary optimization shows that there is a trade-off between the weight of the nuclear power module and the specific thrust, and the optimal weight of nuclear power module is 3942 kg, with the specific thrust of 195.8 N·kg-1·s-1. The aircraft equipped with the hybrid propulsion system operates at the maximum altitude of approximately 18.2 km and reaches a maximum Mach number of 0.71, allowing for sustained flight for several months in cruise segment. The turbofan engine, nuclear reactor, ancillary systems, shield, and heat exchanger account for 11%, 23%, 11%, 17% and 1% of the fuel mass of the original unmodified aircraft.

Numerical study of the fuel rod melting and molten material migration behavior using the MPS method

The catastrophic consequences of nuclear reactor core meltdowns necessitate a comprehensive understanding of fuel rod behavior during severe accidents. This study employs the moving particle semi-implicit (MPS) method to simulate fuel rod melting and molten material migration, capturing complex phenomena such as phase changes, chemical reactions, and fluid dynamics. The developed MPS code integrates models for heat transfer, eutectic reactions, and surface tension, allowing for detailed three-dimensional simulations. Validation of the code is achieved through comparisons with analytical solutions and experimental data from the FROMA experiments. Simulations of Al–Zn substitute material rods show accurate temperature responses and phase transitions, highlighting the impact of radiation heat transfer and molten pool depth on melting behavior. Additional simulations of a single rod and a 2 × 2 rod bundle in a pressurized water reactor under extreme conditions reveal the significant role of atomic diffusion. Mass transfer between the cladding and fuel pellet expands the melting area and facilitates the formation of low-melting-point substances. The high-temperature behavior of the rod bundle demonstrates characteristic patterns, including the downward migration of molten zirconium and the dissolution of unmelted cladding. Analysis of molten UO2 migration within the rod bundle channel illustrates the influence of initial temperature and volume on migration dynamics and Zr cladding dissolution rates. This study offers valuable insights into understanding and mitigating the risks associated with core meltdowns, thereby enhancing nuclear reactor safety.

Unraveling the self-regulation mechanism of molecular weight in cross-flow enzymatic membrane reactors for stable oligodextran production

Unraveling the self-regulation mechanism of molecular weight in cross-flow enzymatic membrane reactors for stable oligodextran production