After the Fukushima-Daiichi incident, the emergence of accident-tolerant fuel (ATF) cladding materials became essential; henceforth, numerous research studies have been conducted, especially by AREVA NP and DOE, USA, and CEA & ED, France. Zr-based ATF claddings are real-time solutions due to their advantageous built-in characteristics. In the recent era, chromium-coated Zr-claddings have been developed to improve further neutron economy and the cladding resistance under accidental scenarios. This work uses deep eutectic solvents (DES) to electroplate eco-friendly and efficient Cr coatings over Zr-4 alloy, utilizing Cr(III)/DES electrolyte. Since the growth mechanism and kinetics of the Cr-coating on Zr-alloy are not well established, this work provides a detailed discussion of the electrochemical kinetics and growth mechanism involved in forming Cr over Zr-4 alloys. Surface engineering of the as-coated samples was studied through various spectroscopic techniques. The initial experimental findings suggest their potential as ATF cladding materials in LWRs to enhance safety and reliability.

The advancement of Accident-Tolerant Fuel (ATF) technologies has led to the introduction of novel cladding materials that exhibit superior oxidation resistance and enhanced thermal and mechanical properties compared to conventional zirconium-based alloys. The options being studied are chromium-coated zirconium-based alloys, silicon carbide, and iron-based alloys. These innovative materials are designed to improve safety margins and minimize hydrogen production during severe accident scenarios. Their unique thermal and neutronic properties may significantly influence core neutronic parameters. This study offers a comparative evaluation of the impact of ATF cladding on CR worth and reactivity coefficients, employing 3D whole core simulations for an APR-1400. The reactivity coefficients studied are the isothermal temperature coefficient, moderator temperature coefficient, Doppler coefficient, boron coefficient, and power coefficient. The CASMO-4E/SIMULATE3 code system is utilized to carry out the calculations needed. This study reveals the safety and performance effects of integrating ATF cladding materials into nuclear reactors. Gaining a comprehensive understanding of these effects is crucial for optimizing control strategies and bolstering the accident tolerance of contemporary nuclear systems.

The Collision Probability Method (CPM) offers elegant geometric flexibility for neutron transport, but its quadratic memory footprint has severely restricted its scalability. While Tensor Train (TT) formats have recently broken the curse of dimensionality in differential transport formulations, their potential to compress the fully-coupled, dense integral operators of the CPM remains largely unexplored. This work presents QUANTRA, establishing the algorithmic foundation for a tensor-train formulation of the collision probability method (TT-CPM) applied to the k-eigenvalue neutron-transport problem. By benchmarking the framework on one-dimensional geometries, we isolate and quantify the massive runtime and memory gains achievable through the tensorization of dense integral kernels. The solver uses TT rounding via truncated SVD to control ranks and employs GMRES as the inner linear solver within each power iteration. We assess one-dimensional criticality problems in slab, cylindrical, and spherical geometries for finite and infinite media, including monoenergetic, two-group, and six-group configurations. For 1D benchmark problems, QUANTRA’s TT-CPM achieves up to 541.02× end-to-end speedup while preserving keff and flux fidelity, and reduces peak memory by up to 917.90× across the benchmark suite.

This study explores the integration of artificial neural networks (ANNs) with a simulated annealing (SA) algorithm to optimize nuclear reactor core loading patterns. By employing ANNs to predict critical reactor parameters, such as reactivity, power peaking factor (PPFmax), and cycle length in days, and combining them with the SA algorithm for optimization, the study addresses the multi-objective challenge of enhancing reactor efficiency and safety. The fitness function, defined as the ratio of cycle length to PPFmax, serves as the optimization objective, enabling the SA algorithm to identify loading patterns that maximize operational cycle length and minimize the power peaking factor. The methodology incorporates a high-dimensional design space with factorial complexity and leverages the predictive accuracy of ANNs to guide optimization. Results demonstrate the framework’s ability to improve reactor performance metrics, achieving longer operational cycles and reduced safety constraints. The findings underscore the potential of integrating advanced machine learning and heuristic optimization techniques in reactor design.

This study investigates vortex-induced vibrations (VIV) in tandem cylinders, modeling basic configurations relevant to reactor fuel rods. Utilizing Reynolds-Averaged Navier–Stokes (RANS) equations with the Shear Stress Transport (SST) k-ω turbulence model, it examines how cylinder spacing ratios ( Sx/D = 2, 3, 5, 9 ) and reduced velocities ( Ur = 2 to 14 ) influence vibrational and vortex dynamics. Mesh and timestep sensitivity analyses confirm computational reliability, with discrepancies under 2

A numerical framework leveraging finite element analysis is established to examine the thermomechanical behavior and burst safety of a novel accident-tolerant fuel (ATF) cladding design. This design incorporates a thin niobium (Nb) liner positioned between two layers of silicon carbide ceramic matrix composites (SiC-CMC). The burst safety is assessed through a probabilistic failure analysis utilizing Weibull theory, accounting for the scatter in the apparent strength of SiC-CMC and the associated size effect. By examining variations in Nb layer thickness and pellet-clad gap thickness, the primary focus is on assessing the burst safety of the sandwich claddings in an APR1400 fuel system under both steady operation and loss-of-coolant accident (LOCA) scenarios. The findings indicate sandwich claddings are likely to function without fracture or leakage for both the original thickness (82.5 mu m) and reduced gap thicknesses of up to 70 mu m. However, a further reduction to 57.5 mu m in gap thickness is likely to lead to cladding failure during steady operation. This research leverages computational modeling to gain a foundational insight into the thermomechanical performance of SiC-CMC/Nb sandwich claddings in nuclear fuel rods and provides predictive tools aimed at augmenting the safety and reliability of next-generation nuclear power plants.

The hybrid review paper meticulously examines crucial research on tandem cylinders across a broad range of Reynolds (Re) numbers, extending up to 170,000 for Strouhal (St) and 300,000 for pressure coefficients (CP). By consolidating findings on various flow parameters, including Strouhal number, drag (CD), lift (CL), and pressure coefficients (CP), the paper advocates the use of experimental and three-dimensional numerical data, exclusively omitting two-dimensional numerical data, especially at higher Re numbers. To this end, the predictive performance of different machine learning techniques-such as XGBoost, genetic optimization, ensemble modeling, and Random Forest-was evaluated using numerical simulations and data sourced from literature. The results demonstrate that, given a sufficiently large dataset, these techniques can accurately predict flow variables like Strouhal number and pressure coefficients with minimal computational cost. However, it is crucial to use only three-dimensional datasets for such analyses. The study identifies Random Forest and XGBoost models as the most accurate in forecasting flow-induced oscillations and pressure distributions around the cylinders, exhibiting the lowest mean squared errors for Strouhal number and pressure coefficient predictions.

The United Arab Emirates (UAE) launched its nuclear energy program in 2008, achieving notable outcomes with the ‘UAE Policy on the Peaceful Use of Nuclear Energy’ program. This initiative is dedicated to ensuring the operational safety, reliability, and efficient operation of its advanced nuclear reactor (APR-1400) power plants. In the aftermath of the Fukushima incident, the global nuclear fuel research and development community shifted toward developing accident-tolerant fuels (ATFs). ATFs are purposefully engineered and manufactured to withstand delayed periods of core cooling system disruption, thereby significantly enhancing safety compared to conventional fuel systems while maintaining or improving normal operational performance. This research investigates the feasibility of implementing ATFs as the primary nuclear fuel source within APR-1400 nuclear reactor and evaluates their potential effect on the operational parameters and safety. In order to accomplish this objective, comprehensive review and assessments of the potential ATFs, including neutronics, thermal-hydraulic, thermomechanical/chemical, and fuel performance evaluations, were conducted, encompassing multiple candidate ATF concepts. This research aims to overview ongoingresearch efforts and prospective ATF concepts for near-future implementation within APR-1400 nuclear power plants.

This study aims to develop the KAFKA code, built on the ABAQUS™ framework, to conduct detailed simulations of Accident Tolerant Fuel (ATF) cladding coated on both the inner and outer surfaces, in order to evaluate the thermal and mechanical performance of coated cladding under different operational conditions. The KAFKA code allows for advanced simulations of fuel rod behaviors, accounting for temperature- and burnup-dependent material properties, fuel swelling, densification, fission gas release, as well as the mechanical responses of cladding and coatings. The results from fully coupled multiphysics modeling demonstrated that Cr and FeCrAl coatings delayed gap closure and reduced hoop stress on the Zr-4 substrate, mitigating failure mechanisms like fatigue, stress corrosion cracking, and creep rupture under steady-state and daily load-following conditions. These findings indicate that the use of coupled multiphysics code enables a more precise evaluation of coated ATF cladding and nuclear fuel performance, contributing to the safer operation of nuclear reactors.

Vortex-induced vibration (VIV) poses significant challenges in engineering. Structures subjected to fluid flows necessitate effective suppression mechanisms to avoid vibrations. This study investigates the ability of a nonlinear energy sink (NES) system to reduce VIV under a variety of reduced velocities (Ur). Over 3,000 scenarios were examined to assess the impact of NES properties; mass ratio (β=0.01−0.5), spring ratio (γ=0.01−2.0), and damping ratio (ξ=0.01−2.0) on the vibrational response of structures using computational fluid dynamics (CFD) simulations utilizing Reynolds-averaged Navier–Stokes (RANS) turbulence models. The numerical simulations were validated using experimental data demonstrating excellent agreement with the literature. Vibrational contour maps were developed from the CFD predictions over a wide range of Ur,β,γ,andξ. Our findings indicate that the process of tuning the NES parameters (β, γ, and ξ) can either diminish vibrational amplitudes (Ay/D), or if not carefully optimized, can amplify them. With optimal NES parameter tuning, an amplitude reduction of 94% was found to be possible. Furthermore, Sobol sensitivity analysis was performed, which revealed that while Ay/D highly depends on Ur, proper tuning of the β in combination with γ is critical, especially in regimes where parameter interactions become significant. While global optimization is challenging, it is recommended that the optimized NES parameters for the lock-in region differ from those for the lower-branch vibration region.

Recent research has faced challenges in achieving high specific capacitance and cycle stability with carbon nanofibers (CNFs) as supercapacitor electrodes. This study employs calcination/activation techniques to modify the electrochemical and structural properties of electrospun sulfur/nitrogen (S, N)-enriched CNFs. Combining the electrospinning process with these methods produces CNFs with a high energy density, enhancing non-faradaic processes. The 3D interconnected morphology of S, N-enriched CNFs possesses an appropriate surface area of 104.1 m2/g at 77 K with the high porous nature. Due to the excellent synergistic effect of nitrogen and sulfur atoms, the as-prepared porous CNFs showed excellent electrochemical performance in a three-electrode assembly. Under a neutral medium, the symmetric two-electrode cell displayed an outstanding electrochemical performance with a specific capacitance of 186F/g, an energy density of 25.8 Wh kg-1 , a power density of 500 W kg-1 and excellent capacitance retention of 88.2 % over 3000 charge-discharge cycles. The findings strongly indicate that the as-prepared CNFs have the potential to advance significantly energy storage technology, surpassing other reported carbon materials.

This study provides an in-depth examination of the initial, transition, and equilibrium cycles of the APR-1400 reactor core, focusing on reference fuel cladding and ATF cladding systems. This research highlights the importance of in-core fuel management strategies, particularly checkerboard configuration, in maintaining safe and efficient reactor operations. The radial peaking factor (RPF) is an essential parameter in evaluating the core configuration, and a study demonstrated that the RPF can be effectively controlled below the threshold of 1.85 through careful fuel reshuffling and introducing new fuel assemblies. Key findings indicate that the RPF values vary across different cycles but remain within safe limits. Specifically, the RPFs for the initial, first transition, second transition, and equilibrium cycles are 1.36, 1.21, and 1.23; 1.43, 1.38, and 1.30; 1.64, 1.44, and 1.31; and 1.29, 1.33, and 1.66, respectively, measured at the beginning, middle, and end of each cycle. These results underscore the effectiveness of the proposed fuel management strategies in maintaining a stable and safe power distribution within the reactor core. This study also underscores the potential benefits of ATF cladding materials, such as chromium-coated zirconium, which offer enhanced resistance to high-temperature oxidation, thereby improving reactor safety under normal and accident conditions. The implementation of ATFs could lead to significant improvements in safety margins, operational efficiency, and overall reactor performance. This research contributes valuable insights into optimizing in-core fuel management practices for the APR-1400 reactor. This study lays a foundation for future studies and practical applications that could further enhance the safety and efficiency of nuclear power plants. By demonstrating the advantages of ATFs and effective fuel management, this study supports the continued development and deployment of advanced nuclear technologies, promoting greater public confidence in nuclear energy as a reliable and safe power source.

This work investigates the effectiveness of Cr coatings on fuel cladding systems to improve accident tolerance in pressurized water reactors. This study is focused on evaluating the neutronics performance of zirconium alloy claddings coated with Cr (Zr alloy-Cr) and comparing them with the current Zr-U system. The critical parameters related to the performance of such a reactor design, like multiplication factor, neutron spectrum, and radial neutron flux, are assessed by the simulation performed with the Monte Carlo code Serpent 2.1.31.Chromium coatings can significantly enhance the corrosion resistance and thermal conductivity for increased reactor safety. Furthermore, an adhesive layer, such as molybdenum, would further stabilize the coating and solve any problem of interdiffusion occurring at a high temperature.Optimal designs identified are comprised of a 10-mu m-thick Cr overlay with 2.20-mu m-thick molybdenum as the adhesive layer to provide optimal performance while minimizing the negative influence of the neutron economy. This study proves the potential of the Cr-coated cladding system for short- to medium-term solutions in improved safety and efficiency in nuclear reactors, mainly under severe accident conditions.

Extending the fuel cycle from 18 to 24 months in Pressurized Water Reactors (PWRs) using LEU+ fuel (5 % <= U-235 <= 10 %) increases excess reactivity, requiring effective control to ensure safety and performance. This study evaluates various BA concepts-including gadolinia or erbia homogeneously mixed with fuel, ZrB2coatings, and highly intensive gadolinia/alumina burnable absorbers (HIGA)-to minimize CS usage while maintaining a 24-month cycle. Equilibrium core configurations were analyzed using CASMO-4E/SIMULATE-3. Results indicate that a hybrid approach, combining 0.75 w/o erbia homogeneously with fuel and 7 mol% HIGA BA rods, achieves optimal reactivity suppression while fulfilling safety criteria. This configuration effectively lowers CS concentration from 1357 ppm to 1151 ppm compared to a conventional Gd2O3 + UO2BA rod core, maintaining a stable reactivity coefficient range throughout the cycle. These findings support the feasibility of extending the APR-1400 fuel cycle while ensuring reactor safety and performance.

Because of their greater accident tolerance, iron-chromium-aluminum (FeCrAl) alloys hold great promise for applications in nuclear fuel claddings. Here, a finite element-based computational framework is developed to analyze the thermomechanical performance of APR1400 fuel rods with FeCrAl claddings subjected to a typical LOCA condition preceded by 4 years of normal operation. The effect of enhancements in the yield and ultimate strength of FeCrAl on the burst safety of fuel rods is evaluated for various choices of pellet diameters and cladding thicknesses. The pellet diameter is increased by reducing the cladding thickness and/or the pellet-clad gap thickness with the intention of compensating for the additional neutronic penalty of FeCrAl in comparison to the conventional Zircaloy. It is found that a reduction of the pellet-clad gap thickness from 83 to 50 mu m can increase the cladding's burst safety by up to 35%. Additionally, strengthening FeCrAl alloys has significantly improved cladding performance under LOCA (Loss of Coolant Accident) conditions. Specifically, an 80% enhancement in the yield and ultimate strength has been shown to improve the cladding burst safety by 80%. The findings of this study suggest that improved material properties and geometric modifications can significantly improve the burst safety of FeCrAl-based ATF systems, which is an important consideration for their practical implementation.

The conventional Zircaloy-uranium fuel-cladding system in pressurized water reactors faces challenges such as reduced mechanical strength, stability, and susceptibility to oxidation and embrittlement at high temperatures. The Accident Tolerant Fuel concept, aiming to address these issues, involves replacing or coating cladding with materials exhibiting enhanced corrosion resistance. This study explores the efficacy of ATF using a chromium coating and selecting an adhesive layer material (Niobium or Molybdenum) between cladding and coating. Neutronics analyses, employing the Serpent Monte Carlo 2.31 simulation tool on the APR-1400 reactor, assess the impact on different neutronics parameters. A sensitivity analysis involves varying coating thickness ( 10 mu m, 15 mu m, 20 mu m) and adhesive layer thickness (2.20 mu m, 3.20 mu m, 4.20 mu m) for Zircaloy cladding. Results show that adjusting ATF design parameters can match the original fuel-cladding cycle length. The 10 mu m coating with 2.2 mu m Nb adhesive layer exhibits minimal neutronics impact, suggesting it as an alternative cladding material. In 2D reactor core analysis, Nb outperforms Mo due to a lower reactivity difference and smaller absorption cross-section, enhancing thermomechanical properties with minimal neutronics impact. Implementing Cr- coating with Nb adhesive layers holds promise for enhancing safety and reliability in nuclear power plants, particularly in mitigating risks during high-temperature conditions and loss-of-coolant accidents.

TheUAE's nuclear energy program, which began in 2008 with the publication of the "UAE Policy on the Peaceful Use of Nuclear Energy" document, has prioritized the safe, reliable, and economic operation of its APR-1400 nuclear power plants at Barakah. Following the Fukushima accident, the development of Accident Tolerant Fuels (ATFs) has become a focus in the nuclear fuel research and development community. ATFs are designed to withstand a significant loss of active cooling in the reactor core for a longer period, resulting in increased safety compared to the existing fuel system while maintaining or improving normal operation performance. The purpose of this study is to investigate the feasibility of using ATFs as nuclear fuel in the APR-1400 nuclear power plants (BNPPs) and assess their impact on the plant's safety and operation parameters. To accomplish this goal, a variety of analyses and assessments will be necessary, including neutronics, thermal-hydraulic, thermo-mechanical/chemical, and fuel performance analyses for multiple candidate ATF concepts. The investigation will focus on the APR-1400 reactor, which is the reactor of choice in Barakah plants. The study aims to provide a review of ongoing research and potential ATF concepts for use in the near future in APR-1400 nuclear power plants.

Electrochemical energy storage (EES) devices are much needed due to their improved reliability and sustainability. As a class of EES, supercapacitors (SCs) have exhibited relatively more advantages, including high power density, longer cycle life, rapid charge-discharge speed, and high energy efficiency. Carbon materials are the electrodes of most significant concern in high-performance SCs. Among the carbon materials, the electrospun-derived carbon nanofibers (CNFs) and their composites are of high interest due to their scalable preparative process, high specific surface area (SSA), and porosity, and apt to construct essentially conducting self-standing electrodes for EES devices leading to improved electrochemical performance and energy storage capacitance. Conducting polymers (CPs)-based materials can be used as SCs' electrodes due to their versatility, supreme conductivity, redox property, inherent elasticity, low cost, and facile production. This review aims to provide a precise overview of the recent trends in CPs, especially concentrating on polyaniline (PANI), polythiophene (PTh), polypyrrole (PPy), and poly (3,4-ethylene dioxythiophene) (PEDOT) based electrospun CNFs and their composite as the potential electrodes for high-performance flexible SCs. The review systematically addresses synthesis techniques, design concepts, recent progress, challenges, and future perspectives on developing binder-free, self-standing CPs-derived CNFs/composites-based electrodes for constructing future flexible SCs.

After the 2011 Fukushima nuclear accident, scientists and engineers have been developing accidenttolerant fuel (ATF) concepts to make nuclear reactors safer.To make light-water reactor fuel-cladding systems more resistant to accidents, researchers are proposing solutions to the problem of Zr-based cladding oxidation.Researchers are proposing to improve the accident tolerance of current fuel cladding systems by enhancing Zr-based alloys or coating Zircaloy, or by using new cladding/fuel materials.Neutron physics is essential for evaluating the feasibility of these solutions.It will be used to assess not only their safety but also their economic viability.This review summarises the nuclear industry's efforts to investigate the reactor physics impact of accident-tolerant fuel (ATF) concepts on current and future reactor designs.Important reactor physics parameters that affect safety and economics include reactivity coefficients, cycle length, neutron spectrum, excess reactivity, and control rod worth.This work can serve as a reference for the nuclear community, especially reactor physicists when studying ATF concept implementation.