Search Results (599)

Some of nuclear power’s primary detractors are the unique environmental challenges and impacts of radioactive wastes generated during fuel cycle operations. Key benefits of spent fuel reprocessing (SFR) are reductions in primary high active waste (HAW) masses, volumes, and lengths of radiotoxicity at the expense of secondary waste generation and high capital and operational costs. By employing advanced waste management and resource recovery concepts in SFR beyond the existing standard PUREX process, such as minor actinide and fission product partitioning, these challenges could be mitigated, alongside further reductions in HAW volumes, masses, and duration of radiotoxicity. This work assesses various current and proposed SFR and fuel cycle options as base cases, with further options for fission product partitioning of the high heat radionuclides (HHRs), rare earths, and platinum group metals investigated. A focus on primary waste outputs and the additional energy that could be generated by the reprocessing of high-burnup PWR fuel from Gen III(+) reactors using a simple fuel cycle model is used; the effects of 5- and 10-year spent fuel cooling times before reprocessing are explored. We demonstrate that longer cooling times are preferable in all cases except where short-lived isotope recovery may be desired, and that the partitioning of high-heat fission products (Cs and Sr) could allow for the reclassification of traditional raffinates to intermediate level waste. Highly active waste volume reductions approaching 50% vs. PUREX raffinate could be achieved in single-target partitioning of the inactive and low-activity rare earth elements, and the need for geological disposal could potentially be mitigated completely if HHRs are separated and utilised. Full article

Background/Objectives: This study aimed to assess the long-term clinical performance of full-arch fixed restorations made of fiber-reinforced composite (FRC) supported by four ultra-short implants (4.0 × 5.0 mm) in patients with edentulous, atrophic mandibles. Methods: Ten patients were treated at Sapienza University of Rome and monitored over a 10-year period. Each case involved the placement of four plateau-design implants with a pure conometric connection and a calcium phosphate-treated surface. The final prostheses were fabricated using CAD/CAM-milled Trinia^® fiber-reinforced composite frameworks. Clinical parameters included implant and prosthesis survival, marginal bone level (MBL), peri-implant probing depth (PPD), and patient-reported outcome measures (PROMs). Results: Implant and prosthesis survival reached 100% over the 10-year follow-up. MBL data showed a minor bone gain of approximately 0.11 mm per 5 years (p < 0.0001). PPD remained stable under 3 mm, with a minimal increase of 0.16 mm over the same period (p < 0.0001). PROMs reflected sustained high patient satisfaction. No technical complications, such as chipping or framework fracture, were observed. Conclusions: Rehabilitation of the edentulous mandible with ultra-short implants and metal-free FRC prostheses proved to be a minimally invasive and long-lasting treatment option. The 10-year follow-up confirmed excellent implant and prosthetic outcomes, favorable peri-implant tissue health, and strong patient satisfaction. Nonetheless, further studies with larger sample sizes are needed to confirm these encouraging results and strengthen the clinical evidence. Full article

This study aims to assess the ecological and human health risks associated with four heavy metals (Cd, Cr, Cu, and Zn) in the soil of a dumpsite in Targuist city, Morocco. In total, 16 surface soil samples were collected from the dumpsite and its nearby areas following leaching drain flows. The pollution load index (PLI), geo-accumulation index (Igeo), and potential ecological risk index (RI) were subsequently determined. In addition, hazard quotient (HQ) and health index (HI) were used to assess the non-carcinogenic and carcinogenic risks associated with the soil heavy metal contents. The PLI indicated significant contamination by the studied heavy metals. On the other hand, the Igeo values suggested no Cr contamination, moderate contamination by Cu and Zn, and severe contamination by Cd. The RI indicated a dominant contribution from Cd, with minor contributions from Cu, Zn, and Cr accounting for 92.47, 5.44, 1.11, and 0.96%, respectively, to the potential ecological risk in the study area. The non-carcinogenic health risks associated with exposure of the nearby population to the soil heavy metals at the dumpsite and burned solid waste-derived air pollution were below the threshold value of 1 for both children and adults. Although carcinogenic risks were observed in the study area, they were acceptable for both children and adults according to the United States Environmental Protection Agency (USEPA). However, carcinogenic risks associated with Cr were unacceptable according to the Italian Legislation. Finally, strategies to mitigate the risks posed by the dumpsite were also discussed in this study. Full article

The suitability of 347H stainless steel (SS347H) for chloride salt environments is critical in selecting materials for next-generation concentrated solar power (CSP) systems. This study investigated the corrosion behavior of SS347H in a ton-scale purification system with continuously flowing chloride salt under three conditions: exposure to NaCl-KCl-MgCl₂ molten salt vapor, immersion in molten salt, and at the molten salt surface interface. Results revealed that corrosion was most severe in the molten salt vapor, where HCl steam facilitated Cl⁻ reactions with Fe and Cr in the metal, causing dissolution and forming deep corrosion pits. At the interface, liquid Mg triggered displacement reactions with Fe²⁺/Cr²⁺ ions in the salt, depositing Fe and Cr onto the surface, which reduced corrosion intensity. Within the molten salt, Mg’s purification effect minimized impurity-induced corrosion, resulting in the least damage. In all cases, the primary corrosion mechanism involves the dissolution of Fe and Cr, with the formation of minor MgO. These insights provide valuable guidance for applying 347H stainless steel in chloride salt environments. Full article

The structural, elastic, electronic, magnetic, and half-metallic properties of full-Heusler ${\mathrm{Fe}}_2$LiSi and ${\mathrm{Fe}}_2$LiGe compounds were investigated using first-principles calculations. Among the studied configurations, the cubic XA structures in the ferromagnetic state for both compounds are the most stable. They exhibit mechanical stability, elastic anisotropy, and ductility. Compared to ${\mathrm{Fe}}_2$LiGe, ${\mathrm{Fe}}_2$LiSi demonstrates higher stability, stronger anisotropy, greater brittleness, higher Debye and melting temperatures, and a smaller Grüneisen parameter. Both compounds exhibit metallic majority-spin channels and semiconducting minority-spin channels. At the equilibrium lattice constant, ${\mathrm{Fe}}_2$LiSi and ${\mathrm{Fe}}_2$LiGe exhibit half-metallic gaps of 0.141 eV and 0.179 eV, respectively. Both compounds exhibit 100% spin-polarization ratio in specific lattice constant ranges. The total magnetic moment per formula unit (3.000 ${\mu }_{\mathrm{B}}$) follows the generalized Slater–Pauling rule and depends on Fe atomic magnetic moments. These properties indicate that ${\mathrm{Fe}}_2$LiSi and ${\mathrm{Fe}}_2$LiGe hold promise for spintronic applications. Full article

This study presents a comprehensive mathematical model of a semiconductor structure based on vanadium dioxide (VO₂), specifically in its conductive phase. The model was developed using the finite element method (FEM), enabling detailed simulation of the formation of a conductive channel under the influence of low-frequency alternating voltage (50 Hz). The VO₂ structure under investigation exhibits pronounced electric field concentration at the surface, where the field strength reaches approximately 5 × 10⁴ V/m, while maintaining a more uniform distribution of around 2 × 10⁴ V/m within the bulk of the material. The simulation results were validated experimentally using a test circuit. Minor deviations—no greater than 8%—were observed between the simulated and measured current values, attributed to magnetic core saturation and modeling assumptions. A distinctive feature of the model is its ability to incorporate the nonlinear dependencies of VO₂’s electrical properties on frequency. Analytical expressions were derived for the magnetic permeability and resistivity of VO₂, demonstrating excellent agreement with experimental data. The coefficients of determination (R²) for the frequency dependence of magnetic permeability and resistance were found to be 0.9976 and 0.9999, respectively. The current version of the model focuses exclusively on the conductive phase and does not include the thermally induced metal–insulator phase transition characteristic of VO₂. The study confirms that VO₂-based structures exhibit high responsiveness and nonlinear switching behavior, making them suitable for applications in electronic surge protection, current limiting, and switching elements. The developed model provides a reliable and physically grounded tool for the design and optimization components based on VO₂ in power electronics and protective circuitry. Full article

Adopting mobile robots for high voltage (HV) live-line operations can mitigate personnel casualties and enhance operational efficiency. However, conventional mechanical arms cannot inspect concealed spaces in the power cable tunnel because their joint integrates metallic motors or hydraulic serial-drive mechanisms, which limit the arm’s length and insulation performance. Therefore, this study proposes a 7-degree-of-freedom (7-DOF) bionic mechanical arm with rigid-flexible coupling, mimicking human arm joints (shoulder, elbow, and wrist) designed for HV live-line operations in concealed cable tunnels. The arm employs a tendon-driven mechanism to remotely actuate joints, analogous to human musculoskeletal dynamics, thereby physically isolating conductive components (e.g., motors) from the mechanical arm. The arm’s structure utilizes dielectric materials and insulation-optimized geometries to reduce peak electric field intensity and increase creepage distance, achieving intrinsic self-insulation. Furthermore, the mechanical design addresses challenges posed by concealed spaces (e.g., shield tunnels and multi-circuit cable layouts) through the analysis of joint kinematics, drive mechanisms, and dielectric performance. The workspace of the proposed arm is an oblate ellipsoid with minor and major axes measuring 1.25 m and 1.65 m, respectively, covering the concealed space in the cable tunnel, while the arm’s quality is 4.7 kg. The maximum electric field intensity is 74.3 kV/m under 220 kV operating voltage. The field value is less than the air breakdown threshold. The proposed mechanical arm design significantly improves spatial adaptability, operational efficiency, and reliability in HV live-line inspection, offering theoretical and practical advancements for intelligent maintenance in cable tunnel environments. Full article

Spinel-structured hausmannite (Mn(II)Mn(III)₂O₄) is a vital intermediate in Mn mineralogy and a key player in redox chemistry in the environment. Its transformation into other Mn oxides is a critical factor in controlling its environmental occurrence and reactivity. Yet structural impurities and solution pH, as well as the fate of impurities during transformation, which influence hausmannite transformation processes and products, remain largely unknown. In the present work, we address this knowledge gap by investigating pristine and metal-substituted hausmannite, specifically nickel (Ni) or cobalt (Co), equilibrated at two time periods (8 h and 30 days) and three different pH levels (4, 5, and 7). Solution chemistry data revealed that both the equilibration period and pH had a significant impact on hausmannite dissolution rates and the concomitant repartitioning of Ni or Co. Hausmannite with Ni or Co substitution exhibited lower dissolution rates than pristine mineral under acidic conditions. Mineralogy and crystal chemistry data indicated that hausmannite was the major host phase after 30-day equilibration, followed by minor transformed products, including birnessite and manganite. Although minor, birnessite became more abundant than manganite at low pHs. Analytical high-resolution transmission electron microscopy (HRTEM) analyses revealed a poorly crystalline, nano-scaled MnO₂ formed from hausmannite and the majority of metal impurities remaining in the host hausmannite. Yet Co was associated with both hausmannite and the newly formed birnessite, whereas Ni was only found with hausmannite, indicating the strong sequestration of Co by Mn(II/III) and Mn(IV) mineral phases. This study highlights the significant impacts of metal impurities and pH on the stability of hausmannite and its transformation into birnessite, as well as the control of Mn-oxide minerals on the solubility and sequestration of transition metals in the environment. Full article

In recent years, extensive attention has been paid to advanced oxidation processes (AOPs) with peracetic acid (PAA), a widely used disinfectant, using transition metal ions for the degradation of organic contaminants within water environments. Mn(II) has been widely used as an effective homogeneous transition metal catalyst for oxidant activation, but it has shown poor performances with PAA. Since the stability of manganese species can be enhanced through the addition of ligands, this study systematically investigated a novel AOP for the oxidation of carbamazepine (CBZ) using an Mn(II)/PAA system with several different ligands added. The reactive species were explored through UV-vis spectrometry, scavengers, and probe compounds. The results suggest that Mn(III)–ligand complexes and other high-valent Mn species (Mn(V)) were generated and contributed obviously toward efficient CBZ oxidation, while radicals like CH₃CO₂^• and CH₃CO₃^• were minor contributors. The oxidation efficiency of Mn(II)/PAA/ligands depended highly on ligand species, as ethylene diamine tetraacetic acid (EDTA) and oxalate (SO) could promote the oxidation of CBZ, while pyrophosphate (PPP) showed modest enhancement. The results obtained here might contribute to the removal of residue pharmaceuticals under manganese-rich waters and also shed light on PAA-based AOPs that could help broaden our present knowledge of manganese chemistry for decontamination in water treatment. Full article

To clarify the current state of heavy metal contamination in the sediments of lakes in China, the data on six heavy metals derived from the sediment samples of 71 lakes across China from 2003 to 2022 are collected in this study through meta-analysis. Uncertainty analysis is conducted using the Monte Carlo method to evaluate the heavy metals against cumulative characteristics, potential ecological risk, and toxicity indicators. The following conclusions are reached. (1) There is severe pollution in lake sediments in China. The concentrations of Cu, Pb, Zn, Ni, and Cd in lakes exceed their corresponding soil background values. Cr heavy metal contamination exceeded the soil background values in 54.5% of lakes. (2) Cd is the major pollutant in lake sediments across China, followed by Cu, Zn, Pb, Ni, and Cr in descending order. Lakes with higher ecological risk are predominantly concentrated in quadrants 2 and 3, indicating an overall high ecological risk status for Chinese lakes and significant potential ecological hazards. Pb and Cr are identified as the most toxic elements in lake sediments, with the lakes of higher toxicity mainly concentrated in quadrants 3 and 4. (3) Heavy metal pollution shows a significant trend of variation by region. The sources of heavy metals in lake sediments differ between the southern, central, and northern regions of China. In the lakes located in northern China, pollution is largely attributed to mining and industrial emissions, with agriculture as a less significant factor. In the central region, surface runoff and domestic sewage are the main contributors, while industrial and agricultural emissions play a minor role. In the south, industrial emission is the major source of pollution, with agricultural emission and natural factors being less significant. Full article

Globally, most skarn deposits show a direct relationship with magmatic activity, indicating a genetic link between the geochemical composition of causative plutons and the metal content of associated skarns. Therefore, this study investigated the Early–Middle Eocene plutonic rocks and their relationship with Fe-Zn skarn deposits in the Esendemirtepe-Koçak and Horoz areas of south-central Türkiye. Despite the regional significance, previous studies have not adequately addressed the petrogenetic evolution of these intrusions and the geochemical characteristics of the related skarns. In particular, the fluid-aided mobility of elements at the contact between the causative plutons and the volcano-sedimentary country rocks remains poorly understood. Therefore, in this study, field studies, petrographic and mineralogical analysis, and whole-rock geochemical analysis were conducted to investigate the genetic link between the plutonic rocks and the skarn deposits. Field studies reveal that the skarn zones are within volcano-sedimentary sequences and marble-schist units intruded by four distinct plutonic bodies: (1) Esendemirtepe diorite, (2) Koçak diorite, (3) Horoz granodiorite, and (4) Çifteköy monzogabbro. These rocks exhibit calc-alkaline, I-type, and metaluminous signatures, except for the Çifteköy monzogabbro, which shows I-type, tholeiitic, and alkaline characteristics. All the plutonic rocks associated with the skarn formation display steep LREE-enriched REE patterns with minor positive Eu anomalies (Eu/Eu* = 0.98–1.35), suggesting a subduction-related volcanic arc setting similar to other granitoids in the Ulukışla Basin. The Horoz skarn exhibits both endoskarn and exoskarn features, while the Esendemirtepe-Koçak deposit is characterized by typical exoskarn features. Dominant ore minerals in both skarn deposits include magnetite, hematite, sphalerite, chalcopyrite, and pyrite, with minor arsenopyrite, galena, and cobaltite. The mineral composition of the skarn also shows the dominance of Na-rich and Mg-rich minerals in both locations. The geochemical compositions of the I-type, metaluminous Esendemirtepe-Koçak, and Horoz plutonic rocks are compatible with Fe-Zn skarn type deposits based on the moderate MgO (0.36–4.44 wt.%) and K₂O (1.38–7.99 wt.%), and Rb/Zr and Sr/Zr ratios. They also show typical volcanic arc features, and the variation in various trace element concentrations shows similarity with Fe-Zn skarn type granitoids. These findings support a strong genetic relationship between the mineralization and the geochemical and mineralogical characteristics of the associated plutonic rocks. Full article

Atomic diffusion additive manufacturing (ADAM) is a specialized extrusion-based metal additive manufacturing (MAM) process where metal parts are produced through a three-stage process of printing, de-binding and sintering. Several scientific facts, such as dimensional error, surface quality, tensile behavior and the internal structure of this process for specific materials for certain conditions, are not well explained in the existing literature. To address these issues, the present manuscript investigates the effect of infill type and shell thickness on 17-4 precipitation-hardened (PH) stainless steels on the dimensional accuracy, surface roughness and mechanical properties of the printed specimens. It was found that the strength (maximum ultimate tensile strength up to 1049.1 MPa) and hardness (290 HRB) of the specimens mainly depend on shell thickness, while infill type plays a relatively minor role. The principle of atomic diffusion may be the reason behind this pattern, as an increase in shell thickness is essentially an increase in the density of material deposited during printing, allowing more fusion during sintering and thus increasing its strength. The two different infill types (triangular and gyroid) contribute towards minimal changes, although it should be noted that triangular specimens exhibited greater ultimate tensile strength, whereas the gyroid had slightly longer elongation at break. Dimensional accuracy and surface roughness for all the specimens remain reasonably consistent. The cross-section of the tensile tested specimens revealed significant pores in the microstructure that could contribute to a reduction in the mechanical properties of the specimens. Full article

Phytoremediation strategies present promising approaches for mitigating metal contamination in soils. This study examines the effectiveness of compost and biochar amendments, applied separately or in combination, in altering the properties of sandy mining waste soils (Sw) and affecting levels of metallic trace elements (MTEs). The research evaluates changes in soil physicochemical parameters, metal concentrations in soil pore water (SPW), and metal accumulation in Phaseolus vulgaris. Compost and biochar addition significantly affected SPW pH, which remained alkaline, while increasing SPW electrical conductivity (EC). A treatment combining 20% compost and 2% biochar (SwC20B2) enhanced soil enzymatic activities, with the highest values observed for FDA and ALP activities. Metal availability in the SPW appeared higher on D(0) compared to D(12), with notable reductions in Pb and Zn concentrations observed in the SwC20B2 treatment. Despite this decline, metal accumulation in plant shoots did not significantly differ from that in plants grown in unamended Sw, although all plants exhibited substantial growth. The minor decrease in SPW pH, likely due to compost, may have enhanced metal mobility at D(0). Notably, SPW Pb and Zn concentrations increased with higher compost rates, with SwC20B2 registering the highest Pb and Zn. Although these amendments did not directly alleviate metal mobility, they show potential for use in phytostabilization strategies by using suitable plant species. Full article

Wastewater reinjection is an important measure for balancing the sustainable development of petroleum resources with environmental protection. However, the polymer-containing wastewater generated after polymer injection presents challenges such as reservoir damage and waterflooded zone identification in oilfields. To address this, this study systematically examined the impact of injection water with varying salinities on the flow characteristics and electrical responses of low-permeability reservoirs, based on rock-electrical and multiphase displacement experiments. Additionally, this study analyzed the factors influencing the damage to reservoirs during polymer-containing wastewater reinjection. Mass spectrometry, chemical compatibility tests, and SEM-based micro-characterization techniques were employed to reveal the micro-mechanisms of reservoir damage during the reinjection process, and corresponding protective measures were proposed. The results indicated the following: (1) The salinity of injected water significantly influences the electrical response characteristics of the reservoir. When low-salinity wastewater is injected, the resistivity–saturation curve exhibits a concave shape, whereas high-salinity wastewater results in a linear and monotonically increasing trend. (2) Significant changes were observed in the pore-throat radius distribution before and after displacement experiments. The average frequency of throats within the 0.5–2.5 µm range increased by 1.894%, while that for the 2.5–5.5 µm range decreased by 2.073%. In contrast, changes in the pore radius distribution were relatively minor. Both the experimental and characterization results suggest that pore-throat damage is the primary form of reservoir impairment following wastewater reinjection. (3) To mitigate formation damage during wastewater reinjection, a combined physical–chemical deblocking strategy was proposed. First, multi-stage precision filtration would be employed to remove suspended solids and oil contaminants. Then, a mildly acidic organic-acid-based compound would be used to inhibit the precipitation of metal ions and dissolve the in situ blockage within the core. This integrated approach would effectively alleviate the reservoir damage associated with wastewater reinjection. Full article

The influence of heat input (HI) on the microstructure, microhardness, electrochemical corrosion performance of cold metal transfer additively manufactured (CMTAM) nickel–aluminum bronze alloys was investigated. The nickel–aluminum bronze exhibited an α-Cu austenite matrix with minor γ₂-Cu₉Al₄ and κ phases. As HI increased, the microstructure coarsened progressively. Electron backscatter diffraction (EBSD) analysis revealed that with increasing HI, the grain size gradually increased and the Schmid factor increased. Consequently, the microhardness declined from 198.3 HV to 171.7 HV. The decrease in microhardness with increasing heat input is primarily attributed to the grain coarsening and the coarsening and uneven distribution of the κ phase. As the heat input (HI) increased from 243.8 J/mm to 644.7 J/mm, the corrosion current density rose significantly from 2.56 ± 0.04 μA/cm² to 7.52 ± 0.07 μA/cm². This result indicates a marked deterioration in the material’s corrosion resistance. This phenomenon can be attributed to the grain coarsening and the distribution of Al solute within the microstructure. The CMTAM nickel–aluminum bronze alloys hold significant potential for enhancing the reliability and long-term protection of marine engineering equipment. Full article