Search Results (1,121)

This study systematically investigates the influence of temperature on the defect formation mechanisms in uranium nitride (UN) crystals using first-principles calculations. The formation energies and lattice distortion characteristics of various defects at 0 K and 1780 K were calculated by constructing models of perfect crystals as well as vacancy, interstitial, antisite, and divacancy defects. The results demonstrate that elevated temperatures significantly reduce defect formation energies, with interstitial and divacancy defects exhibiting negative formation energies at 1780 K, indicating a tendency for spontaneous formation. The U interstitial defect induces the most pronounced lattice expansion of 5.1% at 0 K. Furthermore, interstitial defects cause the most significant lattice distortions, while Schottky defects exhibit the lowest formation energy. The current study provides theoretical insights into the defect behavior of UN fuel under high-temperature service conditions and offers valuable guidance for optimizing sintering process parameters. Full article

Groundwater used for drinking in settlements located near decommissioned uranium mining facilities may contain elevated naturally occurring radioactive materials, posing long-term public-health concerns. The purpose of this study was to evaluate the radiological quality of groundwater used for drinking in the Saumalkol settlement by applying gross alpha–beta screening and isotope-specific analysis of ²²⁶Ra and ²²⁸Ra to identify the main contributors to groundwater radioactivity and estimate the associated radiation dose from water consumption. Groundwater samples were analyzed using gross alpha–beta screening and isotope-specific determination of ²²⁶Ra and ²²⁸Ra by radiochemical separation and low-background counting, and ingestion doses were estimated using international dose coefficients. Gross alpha activity averaged 2.26 ± 0.96 Bq/L, with most samples exceeding the WHO screening value of 0.5 Bq/L, while gross beta activity averaged 0.65 ± 0.17 Bq/L. Mean activity concentrations of ²²⁶Ra and ²²⁸Ra were 0.17 ± 0.03 Bq/L and 1.47 ± 0.9 Bq/L, respectively, with significantly higher ²²⁸Ra in deep boreholes and a systematic predominance of ²²⁸Ra over ²²⁶Ra (p < 0.05), indicating a thorium-controlled geochemical signature in fractured crystalline aquifers. The estimated annual committed effective ingestion dose from radium isotopes was 0.46 mSv, exceeding the reference level of 0.1 mSv for drinking-water exposure. These findings demonstrate that groundwater radioactivity in Saumalkol is dominated by radium from the thorium series and highlight the need for sustained radionuclide-specific monitoring and targeted water management strategies in uranium-affected regions. Full article

This review examines the renewed strategic relevance of uranium within the evolving global energy system, emphasizing uranium market dynamics, emerging nuclear technologies, and geopolitical realignments. Moving beyond traditional perspectives that treat uranium primarily as a cyclical commodity or focus narrowly on reactor design, the article frames uranium as a critical strategic resource at the intersection of energy security, decarbonization, and industrial transformation. The analysis integrates market fundamentals with technological developments, particularly small modular reactors (SMRs) and advanced high-temperature reactor systems, and regional policy strategies to provide a holistic perspective largely absent from the existing literature. Quantitative evidence indicates a structurally tightening uranium market, with global reactor demand of approximately 67,500 tU per year and mine production historically meeting only 74–90% of annual requirements. Uranium prices have rebounded from below $20 lb⁻¹ U₃O₈ in 2016 to above $80 lb⁻¹ by late 2023, reflecting supply concentration, long development timelines for new mines, and renewed political commitments to nuclear energy. Demand projections suggest an increase of around 28% by 2030 and the potential for a doubling by mid-century under high-nuclear deployment scenarios. From a technological perspective, while SMRs and advanced reactors may increase uranium consumption per unit of electricity, they substantially expand nuclear energy deployment into new domains, including remote power systems, industrial heat applications, and large-scale low-carbon hydrogen production. Overall, the study highlights a qualitative shift in uranium’s role, positioning it as both a foundational component and a key enabler of integrated low-carbon energy systems spanning electricity, heat, and hydrogen production. Full article

High-altitude mine wastelands in Southwest China present formidable challenges for ecological rehabilitation due to extreme climatic stressors and multi-element contamination. Ecological restoration is closely related to soil environment. However, the mechanism by which parent material-induced heterogeneity governs spontaneous vegetation succession is still poorly understood. We established 36 plots (216 quadrats) to investigate the soil physical and chemical properties and vegetation restoration of propylite, porphyry and siltstone in the Xifanping Copper Mine, Sichuan Province. Furthermore, fifteen metal/metalloid elements (Au, Ag, Mo, W, Cu, Pb, Zn, Hg, As, U, Se, Cr, Sn, Ti, Total Fe₂O₃), soil pollution and vegetation structure were evaluated. The study area exhibited severe composite pollution (mean Nemerow integrated pollution index = 8.09), primarily driven by Au, Ag, Mo, W, and Cu. Vegetation surveys identified 34 vascular plant species from 12 families. Propylite-derived substrates supported significantly higher species richness, Shannon–Wiener diversity, and soil organic matter than porphyry and siltstone. Redundancy analysis (RDA) identified soil organic matter (SOM) and bulk density (BD) as dominant environmental filters, with SOM explaining 14.03% of community variance (p < 0.01). Two native pioneers, Potentilla supina and Cynoglossum wallichii, were identified as specialized uranium (U) accumulators with bioconcentration factors of 13.39 and 4.49, respectively. Lithological inheritance dictates early successional trajectories by influencing edaphic structure and nutrient bioavailability. The identified U-accumulating species provide a valuable genetic resource for implementing Assisted Natural Regeneration (ANR) and developing sustainable phytoremediation strategies in contaminated alpine ecosystems. Full article

The Yaojia Formation in the northeastern Songliao Basin is a primary target horizon for sandstone-type uranium mineralization in the area. Understanding its provenance, composition, and depositional paleoclimate is of great significance for uranium exploration in the region. This study analyzed 58 sandstone and mudstone samples using petrographic thin-section observation, elemental geochemistry, and detrital zircon U-Pb geochronology. The results show that Yaojia Formation sandstones are feldspathic lithic quartzose sandstone (averaging 47% lithics, 32% quartz, and 21% feldspar, mainly K-feldspar), with moderate sorting and predominantly angular to subangular grains, indicating rapid denudation in the source area, medium- to short-distance transport, and rapid deposition. The chemical weathering index (CIA, 52–68) and the index of compositional variation (ICV, 0.83~1.26) are generally low, indicating moderate chemical weathering. Rb/Sr, Sr/Cu, Al₂O₃/MgO, CIA, MgO/CaO ratios indicate that the Yaojia Formation was deposited under predominantly arid–semiarid conditions, with later stages being wetter than earlier ones. Rare earth element (REE) characteristics indicate light REE enrichment, heavy REE depletion, and significant negative Eu anomalies. Combined with A-CN-K diagrams and discriminant plots such as La/Th-Hf and Co/Th-La/Sc, the provenance is primarily derived from felsic magmatic rocks in a post-orogenic extensional tectonic setting. Detrital zircon U-Pb ages are mainly concentrated at 119–153 Ma (64%), 160–183 Ma (14%), and 318.3–327.7 Ma (6%), showing the highest similarity to zircon age spectra from magmatic rocks in the Great Xing’an Range. The comprehensive results indicate that the clastic rocks of the Yaojia Formation in the study area were mainly sourced from Early Cretaceous felsic magmatic rocks in the Great Xing’an Range and have undergone short- to medium-distance transport and sedimentation under arid to semi-arid paleoclimatic conditions. Full article

Sandstone uranium deposits exhibit stratabound mineralization and strong vertical heterogeneity in geological space, which complicates the identification of uranium anomaly layers and their integration into deposit-scale 3D models using borehole datasets. In this paper, we propose a UAPC Fourier layer identification (UFLI) method for uranium anomaly layer identification. The method is based on multi-log feature construction, random forest-based estimation of a depth continuous uranium anomaly probability curve (UAPC), and improved Fourier vertical variation analysis. We used 19 boreholes arranged on four exploration lines (ZKA-ZKD) of the Daying uranium deposit in the northern Ordos Basin (north central China), for the validation. The proposed UFLI method identified 51 uranium anomaly layers at a 5 m sampling interval, forming discrete vertical clusters within the drilled successions. The results indicate that anomalies are overwhelmingly concentrated in the Middle Jurassic Zhiluo Formation, particularly within the lower Zhiluo member, with an anomaly-bearing depth range of approximately 550–745 m. Comparison with known mineralization records shows that both industrial and ordinary mineralization intervals are captured within the anomaly layers. Then, based on inter-borehole continuity of anomaly layers, we reconstructed five uranium orebodies (orebodies 1–5) and describe their distribution characteristics. The proposed method provides a technical means for subsurface visualization and exploration targeting in sandstone uranium systems. Full article

The burnup, initial enrichment, and cooling time of spent nuclear fuel collectively determine the activities of key gamma-emitting nuclides (e.g., ¹³⁴Cs, ¹³⁷Cs, ¹⁵⁴Eu). In safeguards verification, a non-destructive assay (NDA) using radiation detectors can directly acquire the gamma-ray emission signatures associated with these characteristic nuclides. Previous studies have reported empirical relationships between the activities of nuclides such as ¹³⁴Cs, ¹³⁷Cs, and ¹⁵⁴Eu and the assembly burnup. However, the non-uniform axial power distribution in fuel assemblies leads to variations in axial-segment burnup. Accordingly, this study utilizes a nuclide sample database of a typical pressurized water reactor (PWR) assembly generated by OpenMC 0.15.3 depletion calculations. The calculated results are analyzed, and a sensitivity analysis of the hydrogen-to-uranium atomic ratio (H/U) on the characteristic nuclides is presented, confirming the necessity of incorporating the H/U ratio as an input parameter to improve the cross-condition generalization of the surrogate models. Subsequently, MLP and CNN based on PyTorch 2.9.1 (CUDA 13.0 build: 2.9.1+cu130), and XGBoost 3.0.2 models are implemented to invert axial-segment burnup, initial enrichment, and the number densities of selected actinides under various discrete operating conditions based on characteristic nuclide activities. A comparative analysis of the prediction results from different feature inversion methods is provided. The results indicate that the MLP model performs best with Method A, which incorporates absolute ¹³⁷Cs activity and the ¹⁵⁴Eu/¹³⁷Cs ratio, achieving a relative prediction deviation of only 5.2% for initial enrichment. Under Method C, the XGBoost model attains a relative prediction deviation of only 0.9% for axial-segment burnup (BU_zone). Full article

Nuclear energy has become a promising substitute for traditional fossil fuels (e.g., coal, oil, and natural gas) by reason of its ultra-high energy density, firm power generation, and near-zero carbon emissions. However, the shortage of uranium resources is threatening the sustainable development of nuclear power, and meanwhile the nuclear fuel front-end cycle inevitably causes radioactive uranium-bearing wastewater discharge, resulting in severe environmental pollution. Nowadays, the extraction and enrichment of uranium in seawater and uranium-containing wastewater offer a prospective avenue to secure the long-term viability of nuclear power with environmental conservation. Among numerous strategies, photocatalytic extraction of soluble hexavalent uranyl (U(VI)) over graphitic carbon nitride (g-C₃N₄), a conjugated polymer semiconductor, is increasingly attracting widespread attention due to its high solar energy utilization, environmental friendliness, high selectivity, good stability, and low cost. A comprehensive overview that pinpoints research directions for novice researchers is urgently required. Herein, the development progress of g-C₃N₄-mediated photocatalytic U(VI) extraction is briefly introduced. Subsequently, the possible mechanisms are discussed with the assistance of advanced characterization techniques, and the influential factors for catalytic efficiency are also discussed. Moreover, multiple applications of g-C₃N₄-based catalysts on photocatalytic U(VI) reduction and extraction are elaborated, especially for modularization approaches on a large scale. At length, the future challenges and prospects in photocatalytic uranium extraction from water bodies are proposed. This review aims to offer fundamental insights into designing and exploring novel g-C₃N₄-based photocatalysts for soluble U(VI) enrichment in water bodies, especially opening up new avenues for the future development of sustainable uranium extraction technologies in practice. Full article

Machine learning (ML) models can complement traditional measurement-based approaches by supporting large-scale screening, spatial analysis, and prioritization of buildings for testing of indoor radon, a leading cause of lung cancer among non-smokers. Originating from uranium decay in soil and rock, radon enters homes via foundation cracks and accumulates indoors, influenced by building characteristics, ventilation, urbanization, and geogenic factors. As part of the Zagreb pilot within the “Evidence Driven Indoor Air Quality Improvement” (EDIAQI) project, this is the first ML application for indoor radon analysis in Croatia. This research evaluates residential indoor radon concentrations in Zagreb using ML applied to a dataset of 80 households. Several linear regression and tree-based ensemble methods were tested. The best-performing model (GBR) achieved an R² of 0.99 on the training set and 0.57 on the test set, with an RMSE of 33 Bq/m³ and MAE of 26 Bq/m³. Although predictive performance was moderate and generalization limited, key building characteristics such as construction year, dwelling type, occupancy details, and floor level were identified as relevant variables. The results suggest that machine learning may support radon risk prioritization in urban environments, but cannot replace direct measurements for regulatory purposes. Full article

High-temperature gas-cooled reactors (HTGRs) employ spherical fuel elements containing thousands of tristructural-isotropic (TRISO) particles, each centered on a UO₂ fuel kernel. The internal gelation process is a key technology for preparing these UO₂ fuel kernels. However, its application is limited by the poor room-temperature stability of conventional broths and the inherent trade-off between broth stability and mechanical strength. In this work, a novel five-component broth system composed of ZrO(NO₃)₂, hexamethylenetetramine (HMTA), urea, acetylacetone (ACAC), and glucose was developed. The synergistic effects of ACAC and glucose on broth stability and gelation kinetics were systematically investigated. An optimal ACAC/glucose molar ratio of 1:1 and an ACAC/ZrO₂⁺ ratio of 1.5 yielded a zirconium broth stable for over 5 h at 25 °C. Yttrium-stabilized zirconia (YSZ) microspheres prepared under optimized conditions exhibited excellent sphericity (1.04 ± 0.01), high density (5.84 g/cm³), and a crushing strength of 8.0 kg sphere⁻¹. Importantly, this stabilization strategy was successfully extended to the uranium broth, increasing its room-temperature stability from minutes to 6 h. The results demonstrate that the synergistic stabilization strategy effectively decouples the trade-off between broth stability and mechanical strength during the internal gelation process, providing an energy-efficient, scalable route for the preparation of nuclear fuel microspheres. Full article

The modern development of the energy and metallurgy industries is accompanied by the increasing use of coal in the form of fuel and raw material. However, at the same time, urgent issues are arising concerning assessments of its radiological and environmental safety. Coal and ashes accumulate natural radionuclides (such as thorium, uranium, and potassium-40), and toxic and rare earth elements (REEs) that are capable of migrating into the environment during the processes of production, burning and ash disposal. Special attention has recently been paid to rare earth elements that are of economic value as critical metals for sophisticated technologies, but these can pose environmental risks. Their presence in coal is becoming an increasingly relevant issue for cross-disciplinary research, at the intersection of geochemistry, radioecology and the sustainable use of natural resources. Moreover, issues regarding the radiological safety of coal deposits and their derivative products are especially crucial for Kazakhstan, Russia, China and other countries with developed coal production industries. Studies demonstrate that ash and slag of thermal power plants can comprise increased concentrations of natural radionuclides that can accumulate in soil, water and the environment. Therefore, the study of rare earth, toxic and radioactive element contents in coal using nuclear analytical methods is of high practical and environmental significance, especially in terms of assessing radiation load on the environment, designing control measures and ash disposal, and the prospect of the selective extraction of REEs from the coals. Full article

Uranium ore preconcentration is a critical step in achieving environmentally sustainable uranium mining and reducing the operational load of hydrometallurgical processing systems. Conventional radioactive sorting systems predominantly employ a “single-ore-particle intermittent measurement” mode. Under continuous ore flow and high-throughput operating conditions, however, the radiation fields of adjacent ore particles inevitably overlap, which results in gamma-counting interference and blurred ore-segment boundaries, thereby limiting sorting accuracy and system capacity. To address these challenges, this study established a convolutional model that describes the relationship between ore-grade distribution and gamma-response characteristics under continuous ore flow conditions. On this basis, a deconvolution-based method for uranium ore grade calculation was proposed, and an adaptive determination strategy for the characteristic parameter α was introduced to improve grade estimation accuracy and enable reliable identification of ore-segment boundaries. The experimental results showed that, for uranium grades ranging from 0.05% to 0.18% and ore-segment lengths of 16–40 cm, the relative errors between the inverted and true grades of individual segments were all less than 10%. Compared with conventional intermittent measurement and identification schemes, the proposed method achieves stable and accurate grade inversion under conditions of overlapping radiation fields in continuous ore segments. Full article

Late Permian paleoenvironmental instability and recurrent biotic crises coincided with enhanced marine organic-carbon burial, yet ocean-circulation dynamics have remained underappreciated as a key driver. In particular, for the Wuchiaping Formation along the eastern margin of the Paleo-Tethys Ocean, the presence, variability, and mechanistic impact of upwelling—and its coupling with water-column redox structures—have not been systematically constrained, limiting a process-based understanding of organic-matter enrichment. Here, we integrate sedimentological, mineralogical, and multi-proxy geochemical data to investigate the dominant controls on organic matter enrichment in the Wuchiaping Formation shale succession from the northeastern Sichuan Basin. The Lower Wuchiaping Formation consists mainly of clay-rich shales deposited under oxic, shallow-water, and weakly stratified conditions, as indicated by low Ni/Co ratios (average 1.88), limited uranium enrichment (U_EF = 0.21), low Ba/Al ratios, and sparse biogenic debris. Biomarker indices (gammacerane index = 0.35; Pr/Ph = 1.91) suggest unfavorable preservation conditions, resulting in a low mean TOC of 0.78%. In contrast, the Upper Wuchiaping Formation is dominated by siliceous shales with elevated Ni/Co ratios (average 15.83), moderate uranium enrichment (U_EF = 2.48), abundant framboidal pyrite, radiolarian–planktic foraminiferal assemblages, and laminated apatite. High Ba/Al and Cd/Mo ratios, higher gammacerane values, and low Pr/Ph ratios (<1) indicate enhanced water-column stratification and bottom-water anoxia, leading to efficient organic matter preservation and a high mean TOC of 9.2%. Biomarker compositions reveal a shift from terrestrial-dominated organic matter in the Lower Wuchiaping Formation to algal- and plankton-derived inputs in the Upper Wuchiaping Formation. Collectively, these results indicate that intensified upwelling—rather than tectono-magmatic forcing alone—was the primary driver of enhanced productivity, strengthened redox stratification, and organic matter enrichment in the Upper Wuchiaping Formation. Our findings highlight the importance of upwelling–redox coupling as a key mechanism linking Late Permian ocean-system reorganization to spatially and stratigraphically heterogeneous organic-carbon accumulation along the Paleo-Tethyan margin. Full article

Using factual information on background knowledge, costs, personnel numbers, resources, and facilities from the Manhattan Project, we examine the feasibility of the development of nuclear weapons in Germany in World War II. We conclude that, while for various reasons, a uranium bomb would have been technically and economically out of reach in Germany, a few plutonium bombs might have been possible had a coordinated aggressive project been initiated no later than about mid-1940. However, the German scientists involved never established an understanding of the functioning of an atomic bomb as contained in the Frisch–Peierls memorandum and were never asked to provide such a basis on which a decision on an atomic bomb program could be based. This means that a German atomic bomb program did not fail as is often assumed; rather, it was never started. The German uranium project was never more than a scientific mission to study the possibilities offered by the newly discovered source of nuclear power. Full article

The growing global demand for clean and sustainable energy has reignited interest in nuclear power as a carbon-free alternative to fossil fuels, driving an increase in uranium mining. However, uranium extraction releases radioactive elements along with toxic and heavy metals, posing serious environmental risks. A combined narrative and systematic review was employed to evaluate remediation mechanisms, performance trends, sustainability, and emerging technological advancements. The results indicate that phytoremediation remains the most extensively studied and field-applicable technique, while phycoremediation offers rapid uptake in aqueous systems and mycoremediation demonstrates higher tolerance to extreme conditions. However, limitations such as slow remediation rates, site-specific performance, and scalability challenges restrict their widespread implementation. This study also highlights the emerging role of artificial intelligence and machine learning in optimizing remediation processes, although their application remains limited, particularly in fungal systems. Furthermore, the integration of nature-based solutions into nuclear waste management frameworks, aligned with international safety standards, presents a promising pathway for sustainable remediation. Future research should focus on developing hybrid remediation strategies, establishing performance thresholds under high contamination conditions, and advancing AI-driven, site-specific optimization models to enhance efficiency and scalability. Full article