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The VVER-1200/AES-2006 is recognized as a leading Gen III+ nuclear reactor design, meeting stringent international safety standards. This study evaluates the use of a novel PuO 2 -ThO 2 duplex fuel, incorporating weapon-grade plutonium (WgPu) and thorium, for a hypothetical VVER-1200 assembly. The research also explores incorporating minor actinides (MAs) for transmutation, comparing two methods: MAs coated on WgPuO 2 and MAs mixed with WgPuO 2 as integral fuel burnable absorber rods. Neutronic properties of these fuels are compared to those of LEU-fueled assemblies. The results show a 135% higher burnup for the duplex fuel compared to LEU, with extended criticality, reduced reactivity swings, and lower Pu-239 concentrations upon discharge. While Np-237 and Am-241 concentrations decrease, Am-243, Cm-244, and Cm-245 increase, but overall radiotoxic waste is reduced. Enhanced safety coefficients are also observed, within acceptable LWR ranges.

The increasing threat of terrorism involving Radiological Dispersal Devices (RDDs) necessitates comprehensive evaluation and preparedness strategies, especially in densely populated public areas. This study aims to assess the potential consequences of RDD detonation, focusing on the effective doses received by individuals and the ground deposition of radioactive materials in a hypothetical urban environment. Utilizing the HotSpot code, simulations were performed to model the dispersion patterns of 137Cs and 241Am under varying meteorological conditions, mirroring the complexities of real-world scenarios as outlined in recent literature. The results demonstrate that 137Cs dispersal produces a wider contamination footprint, with effective doses exceeding the public exposure limit of 1 mSv at distances up to 1 km, necessitating broad protective actions. In contrast, 241Am generates higher localized contamination, with deposition levels surpassing cleanup thresholds near the release point, creating long-term remediation challenges. Dose estimates for first responders highlight the importance of adhering to operational dose limits, with scenarios approaching 100 mSv under urgent rescue conditions. Overall, the findings underscore the need for rapid dose assessment, early shelter-in-place orders, and targeted decontamination to reduce population exposure. These insights provide actionable guidance for emergency planners and first responders, enhancing preparedness protocols for RDD incidents in major urban centers.

This article investigates alternate fuel options for Pressurized Water Reactors (PWRs), focusing on thorium use to address safety, efficiency, and waste issues associated with standard UO 2 fuel. Challenges in thorium utilization, such as the lack of a fissile isotope, are handled using approaches such as homogeneous mixtures and heterogeneous arrangements, promoting the exploration of (Th- 233 U- 235 U)O 2 fuel in various assembly configurations. According to recent research, the annular dual-cooled assembly design has promising results in terms of fuel efficiency and safety while lowering the requirement for higher fissile enrichment levels. Studies additionally demonstrate that annular dual-cooled duplex fuel configurations can produce higher discharge burnup and lower power peaking factors than traditional UO 2 fuel. The purpose of this work is to analyze and compare the performance of (Th- 233 U- 235 U)O 2 fuel in various configurations against conventional UO 2 fuel, focusing on key characteristics such as reactivity change, criticality, discharge burnups, and reactivity feedback coefficients.

This study investigates the performance and safety characteristics of (Th- 233 U- 235 U)O 2 fuel in various cladding materials, including SiC and a sandwich cladding system combining SiC with SS-310, in comparison to traditional UO 2 fuel with Zirlo™ cladding. Utilizing a dual-cooled annular assembly design, the (Th- 233 U- 235 U)O 2 fuel demonstrates significant enhancements in cycle length, outperforming conventional UO 2 assemblies. The radial power distribution analysis reveals that (Th- 233 U- 235 U)O 2 fuel reduces maximum radial power, contributing to uniform power distribution and enhanced reactor safety. Reactivity feedback coefficients, including Fuel Temperature Coefficients (FTCs) and Moderator Temperature Coefficients (MTCs), are consistently negative for (Th-233U- 235 U)O 2 fuel with advanced claddings, indicating improved inherent safety.

This study presents a comprehensive neutronic analysis of dual-cooled annular duplex fuel assemblies incorporating UO 2 -ThO 2 composition for application in advanced pressurized water reactors (PWRs). The investigation employs a 13 × 13 fuel assembly configuration to evaluate the operational enhancement potential of modern reactor systems. The research methodology focuses on the comparative assessment of burnup characteristics across varying uranium enrichment levels, benchmarking the neutronic performance of dual-cooled duplex fuel against conventional solid 17 × 17 and dual-cooled 13 × 13 UO 2 assemblies. The results demonstrate that the proposed UO 2 -ThO 2 dual-cooled duplex fuel configuration with 7 wt.% U-235 achieves discharge burnup equivalent to that of conventional solid UO 2 assemblies. Safety analysis encompasses the quantification of plutonium isotope production and minor actinide generation, revealing that dual-cooled duplex assemblies produce significantly reduced quantities of plutonium isotopes and lower concentrations of minor actinides, including neptunium (Np), americium (Am), and curium (Cm), relative to conventional all-UO₂ assemblies. Reactivity coefficient analysis confirms that both the fuel temperature coefficient (FTC) and moderator temperature coefficient (MTC) maintain consistently negative values throughout the operational cycle. These coefficients not only satisfy but exceed the established safety criteria for PWR operations, thereby demonstrating the enhanced safety margins and operational performance characteristics inherent to the dual-cooled duplex fuel assembly design.

Nuclear energy sustainability and deployment flexibility can be significantly enhanced through Small Modular Reactors (SMRs) technology. Critical to their operational success is the thorough assessment of thermal-hydraulic characteristics, especially when incorporating advanced fuel design concepts. This research conducts an extensive thermal-hydraulic analysis examining various thorium-based fuel formulations, including (Th- 235 U)O 2 , (Th- 233 U)O 2 , and an innovative (Th- 233 U- 235 U)O 2 composition, benchmarked against standard UO 2 fuel. The investigation encompasses both solid fuel arrangements and dual-cooled annular assembly designs, focusing on safety optimization and operational efficiency enhancement. The analysis focuses on key safety parameters, including pressure drop, coolant enthalpy, fuel centerline temperature, and Departure from Nucleate Boiling Ratio (DNBR). Results for solid fuel configurations reveal that thorium-based fuels exhibit reduced pressure drop, more efficient enthalpy distribution, lower peak fuel temperatures, and higher DNBR values compared to conventional UO 2 , highlighting improved thermal stability and safety margins. The (Th- 233 U- 235 U)O 2 mixture demonstrates a balanced performance by mitigating the limitations of other thorium compositions. In annular configurations, all fuel types benefit from enhanced heat removal due to the dual cooling surfaces, resulting in further reductions in pressure drop and peak temperatures, as well as a significant increase in DNBR values. The highest DNBR, reaching up to 3.051, confirms the annular geometry’s superior safety performance against boiling crises.