Radionuclide Research Articles

Biological assessment and radiological impact in Keana, North Central Nigeria: environmental implication and metabolites production.

The objective of the research was to examine microbial characteristics, metabolites produced, and the potential radiological risks present in mining soils located in Keana, North Central Nigeria. Soil samples were collected from various locations within Keana, Nasarawa State. Bacterial isolation was carried out, and molecular techniques were employed to characterize the bacteria found in the collected soil samples. Additionally, the susceptibility of these isolates to antibiotics was determined, and the bacteria screened for their ability to produce metabolites. The isolated bacteria were classified into three groups: Actinobacteria, Firmicutes, and Proteobacteria. The analysis of the spectra revealed that 1595 compounds were produced, including carboxylic acids, nitro compounds, aldehydes, anhydrides, esters, ketones, amides, phenols, alcohols, alkanes, alkenes, alkynes, and arenes. Some of the metabolites produced were oleic acid, 1,3-dioxolane, linoelaidic acid and oleic acid, 1-nonadecene, butylated hydroxytoluene, diisooctyl phthalate, bis(2-ethylhexyl) phthalate among others, and 1,2-benzenedicarboxylic acid (85.32%) as the most produced metabolite. Among the antibiotics tested, levofloxacin and ciprofloxacin exhibited the strongest antibacterial properties against the isolates. Airborne gamma-ray spectrometry analysis identified elevated levels of potassium, thorium, and uranium in the soils, indicating potential environmental hazards. However, no significant correlation was found between the presence of bacteria and radioactive elements. These findings emphasize the importance of comprehensive environmental monitoring in Keana to address potential health risks associated with microbial contamination and radioactive materials. Additionally, the study highlighted the role of microbial diversity in Keana soils in promoting the production of secondary metabolites with potential applications in pharmaceutical and industrial sectors..

Improved Production of Novel Radioisotopes with Custom Energy Cyclone® Kiube

The implementation of the Variable Energy (VE) feature in the previously fixed-energy IBA Cyclone® Kiube cyclotron is presented as an upgrade enabling the production of novel radioisotopes with improved radionuclidic purity and production yields. The possibility of easily decreasing the energy of the extracted proton beam, from 18 down to 13 MeV, allows us to avoid the use of degraders and/or thick target windows, thus preventing related beam current limitations. The immediate application of the Variable Energy feature is proven by presenting the improved results obtained for the production of 68Ga from the irradiation of liquid targets simultaneously in terms of radionuclidic purity and activity produced.

Studies on uranium concentration in groundwater samples and its associated health hazards to the residents of surrounding regions of Manchanabele reservoir, Bengaluru, Karnataka, India.

Uranium occurs naturally in groundwater and surface water. Being a radioactive element, high uranium concentration can cause impact on human health. The health effects associated with consumption of uranium through water includes increased cancer risk and kidney toxicity. In view of this, an attempt was made in the present study to establish the level of radiological and chemical toxicity of uranium. Radiological toxicity was evaluated in terms of lifetime cancer risk and chemical toxicity through hazard quotient. For the said purpose, groundwater samples from the selected villages of the surrounding region of the Manchanabele reservoir, southwest of Bengaluru, were collected. The collected groundwater samples were analysed for Uranium mass concentration using Light emitting diode (LED) fluorimeter and is found to range from 0.88 to 581.47ppb with a GM of 20.82ppb. The result reveals that ~ 66% of the samples show concentration of uranium within the safe limit of 30ppb as set by the World Health Organisation. The radiological risk estimated in terms of lifetime cancer risk is in the range of 0.0028 × 10-3 to 1.85 × 10-3 with a GM of 0.066 × 10-3. The chemical toxicity risk measured as lifetime annual daily dose is found to range from 0.03 to 21.65μg per kg per d with a GM of 0.77μg per kg per d.

A hybrid adsorption / ultrafiltration membrane process for removal of Cs-137 from radioactive wastewater using natural clay adsorbent

The removal of radioactive cesium element (Cs-137) from wastewater is relatively challenging due to its high diffusion coefficient, short hydration radius, and the similarity between its chemical behavior to other alkali metals having high background concentrations, leading to a competition that reduces the removal efficiency of cesium (Cs-137). This study introduces an innovative treatment process using a submerged membrane adsorption hybrid system (SMAHS) using natural Iraqi clay minerals as adsorbents. The operational conditions were studied using the (SMAHS) continuous flow operation in stirred filtration mode experiments. The maximum operational conditions were achieved for the initial radioactivity concentration of Cs-137 at 7201.8 Bq/L, clay dose 1 g/L, the stirring speed at 700 rpm, pH =6, the transmembrane pressure (TMP) under 2 bar, and temperature at 25 °C. The SMAHS rejection percentage of Cs-137 was 93.6 % and the permeate flux was 105.6 L/m2.h at the best operational conditions. This study demonstrates that utilizing raw bentonite which is both environmentally friendly and locally available as an adsorbent in the SMAHS has proven its effectiveness for removing Cs-137 from wastewater. The hybrid method effectively immobilizes radioactive waste by converting it from liquid to solid state, leading to an extended and safer storage time.

Development and Verification of Sampling Code NECP-SOUL for Evaluated Nuclear Data Files in ENDF-6 Format

A code called NECP-SOUL is developed to generate samples of evaluated nuclear data files in the ENDF-6 format. The motivation for the development is to obtain more accurate uncertainty quantification results based on the covariance data given in evaluated nuclear data files than the sampling method based on multigroup covariances. NECP-SOUL can handle all covariance data in ENDF-6 files, including average fission neutron multiplicities, resonance parameters, cross sections, angular distributions, energy distributions, and cross sections for the production of radioactive nuclides. In this work, samples of ENDF-6 files are input to the nuclear data processing code to generate A Compact ENDF (ACE)-formatted libraries, and these ACE-formatted libraries are used by the Monte Carlo code. Through statistical analysis, the uncertainty of the neutronics results can be obtained. NECP-SOUL is verified against another similar code, SANDY. In addition, the advantage of sampling ENDF-6 files is analyzed by comparing the uncertainty quantification results with those obtained by sampling multigroup covariance matrices. Moreover, the covariances of cross sections and angular distributions newly provided in ENDF/B-VIII.0 are used to analyze their effect on the uncertainty qualification results.

Efficient removal of U(VI) by graphene-based electrode modified with amidoxime: Performance and mechanism

The burgeoning interest in nuclear energy as a sustainable power source brings to the fore significant environmental and human health concerns associated with wastewater from uranium mining. This study presented the successful synthesis of amidoxime modified graphene-based electrode materials (PAO-N-rGO/CF) designed for treating uranium containing wastewater. The influencing factors of PAO-N-rGO/CF during the electrokinetic restoration process were systematically investigated, exploring the mechanisms of adsorption and electrochemical reduction from the perspectives of establishing adsorption theoretical models, evaluating electrochemical performance, and characterizing reduction products. According to the results, the optimal removal efficiency for U(VI) by PAO-N-rGO/CF reached 99.93 % under conditions of an applied voltage of 5 V, an electrification duration of 20 min, and a pH of 7. Compared to Ca2+, K+, and Mg2+, PAO-N-rGO/CF exhibited strong selectivity for UO22+. Whether dissolved oxygen was present or not, PAO-N-rGO/CF maintained its excellent electrochemical performance. After undergoing 10 cycles of reuse, the removal efficiency for U(VI) only decreased by 8.75 %. The establishment of the adsorption model demonstrated the presence of a chemical bond between uranium and amidoxime groups. The electrochemical performance tests evidenced that PAO-N-rGO/CF exhibited superior electron transfer capability. The reduction of (UO2)3(OH+)5 to UO2 in wastewater at a pH = 7 was verified by analysis of the reduction products. The successful development and mechanistic study of the novel and efficient electrode material provide theoretical support for the control of radioactive nuclide pollution and possess practical value for engineering applications in treating uranium containing wastewater.

Thermal Earth model for the conterminous United States using an interpolative physics-informed graph neural network

This study presents a data-driven spatial interpolation algorithm based on physics-informed graph neural networks used to develop a thermal Earth model for the conterminous United States. The model was trained to approximately satisfy Fourier’s Law of conductive heat transfer by simultaneously predicting subsurface temperature, surface heat flow, and rock thermal conductivity. In addition to bottomhole temperature measurements, we incorporated other spatial and physical quantities as model inputs, such as depth, geographic coordinates, elevation, sediment thickness, magnetic anomaly, gravity anomaly, gamma-ray flux of radioactive elements, seismicity, electrical conductivity, and proximity to faults and volcanoes. With a spatial resolution of 18km2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$18 \\ km^2$$\\end{document} per grid cell, we predicted heat flow at surface as well as temperature and rock thermal conductivity across depths of 0-7km\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0-7 \\ km$$\\end{document} at an interval of 1km\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1 \\ km$$\\end{document}. Our model showed temperature, surface heat flow and thermal conductivity mean absolute errors of 6.4∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6.4^\\circ C$$\\end{document}, 6.9mW/m2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6.9 \\ mW/m^2$$\\end{document} and 0.04W/m-K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.04 \\ W/m-K$$\\end{document}, respectively. This thorough modeling of the Earth’s thermal processes is crucial to understanding subsurface phenomena and exploiting natural underground resources. Our thermal Earth model is available as web application at https://stm.stanford.edu, feature layers on ArcGIS at https://arcg.is/nLzzT0, and tabulated data on the Geothermal Data Repository at https://gdr.openei.org/submissions/1592.

Radioactive Attenuation Using Different Types of Natural Rocks.

Humans benefit from nuclear technology, but it also generates nuclear radiation that is bad for both the environment and human health. The serious issue of radiation leakage affects many technological applications. Shielding is required to protect both users and the environment from negative side effects. This work describes the radioactive attenuation properties of some natural rocks, such as claystone, bentonitic claystone, bentonitic shale, sandstone, and basalt using a NaI(Tl) detector. The mass attenuation coefficients μm of these rocks at various photon energies, half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP) were determined. The validation of obtained values of μm was carried out against the theoretical calculations from the XCOM program, and the correlation factor and relative deviation between the two methods were evaluated. It was noted that basalt samples exhibit superior shielding parameters when compared to other rock samples. Also, the concentrations of naturally occurring radioactive elements (238U, 226Ra, 232Th, and 40K) were measured, allowing for the calculation of environmental hazard indices and assessment of attenuation (%) efficiency for certain natural rocks, such as bentonite, sandstone, and basalt. The results revealed that increasing the thickness of Basalt-AZ from 1.5 cm to 2 cm results in an approximate 11% rise in attenuation percentage, with values reaching 77.12%, 67.2%, 67.65%, and 59.8% for NMA-U, IAEA-Th, IAEA-Ra, and IAEA-K, respectively.

Spectroscopic techniques for detecting naturally occurring radioactive nuclides in geology and water: A comprehensive review and health implications

Spectroscopic techniques for detecting naturally occurring radioactive nuclides in geology and water: A comprehensive review and health implications

The thermal structure of the Colombian lithosphere: A regional and basin-scale analysis

It is well-established that the thermal state of the lithosphere strongly influences various regional and local geological processes, including crustal deformation, hydrocarbon maturation, hydrogen generation, and geothermal phenomena. Moreover, the thermal structure exhibits high sensitivity to tectonic features, a property of particular significance in Colombia, where three main tectonic plates converge, and lithospheric tearing has been documented. In this contribution, we focus on elucidating the impact of plate architecture on the thermal field in central-eastern Colombia at both shallow and deep levels. To accomplish this, we constructed a series of two-dimensional profiles and derived a numerical solution of the heat equation using the conservative finite difference method. As constraints, we incorporate an inferred distribution of rocks in the deep crust and upper mantle based on global and local lithospheric thickness models. Material parameters for the various rocks, both exposed and inferred, were obtained from the literature. Additionally, we used superficial heat flow estimates and apparent geothermal gradients compiled by the Colombian Geological Survey.Our results suggest a significant influence of the lithospheric Caldas tear on the thermal state of Colombia, with the breaking off occurring in the Nazca plate under the Eastern Cordillera range around 5°N. The modeled asthenospheric heat flow remains approximately 25 mWm−2, except in the northern Eastern Cordillera range, where the background heat flow increases rapidly to 40 mWm−2. Consequently, our model predicts partial melting in the lower crust to the north and a thermally unstable lower crust to the south of the Caldas tear. The material parameters that best fit the surface data suggest the presence of a basement moderately enriched in radioactive elements in the Eastern Llanos basin. After accounting for compaction, we also confirm a strong influence of the tectonic setting on the thermal state of sedimentary basins.

A baseline of natural radionuclides in water and sediment of a pristine coastal ecosystem: The Xcalak and Mahahual coral reef lagoons in the western Caribbean

In ecosystems, natural radionuclides are present in the environment and living organisms. The 238U natural decay chain produces multiple radioactive elements, such as 234U, 226Ra, 210Pb, and 210Po. These radionuclides can be found in air, water, rocks, soil, and other biotic and abiotic components, mainly derived from minerals, such as zircon and apatite. In this study, we determined the activity concentration of radionuclides from the 238U decay chain in the sediment of a coastal ecosystem on the southern Mexican coast in the western Caribbean, an ecosystem minimally affected by industrial activities. Methods included high-resolution gamma-ray spectrometry and alpha-particle spectrometry. Results showed that the sediment samples had an activity concentration range of 18.2–36.6 Bq/kg for 238U, 25.0–41.4 Bq/kg for 234U, 10.1–37.3 Bq/kg for 210Pb, and 29.9–46.0 Bq/kg for 210Po. Water samples ranged between 17.9 and 36.3 mBq/L and 27.9–66.0 mBq/L for 238U and 234U, respectively. The activity concentration of these radionuclides in the sediment and water of this area is compared with that of other coral reefs worldwide, providing a radiometric baseline for comparison purposes.

Radiometric and petrographic characterization of El-Yatima granite: Evaluating radiological risks and mineralogical features

The current investigation aims to assess the potential of El-Yatima granitic pluton as a decorative stone by examining its natural radioactivity and mineralogical elements. Specifically, the study aims to determine the concentrations of radionuclides 40K, 232Th, and 226Ra, perform petrographic analyses, and evaluate the associated radiological risks to determine the safety and usability of the granite in construction and decoration, as well as to assess the potential of these granitic rocks as a safe and effective decorative stone for various applications. It has a 12 km2 surface area of 812 m above sea level. It is situated in the Eastern Central Desert. Its hypidiomorphic texture, medium-to-coarse grain size, and predominant composition of K-feldspars, quartz, and plagioclase are observed, along with minute amounts of muscovite and biotite. By employing NaI (Tl) gamma-ray spectroscopy, the natural radionuclide concentrations of 40K, 232Th, and 226Ra in El-Yatima granitic rocks were ascertained. Additionally, radiological concerns were identified for the materials that were examined. The average concentrations of radionuclides 40K, 232Th, and 226Ra are 178 Bqkg−1, 44 Bqkg−1, and 41 Bqkg−1, respectively. The following are the computed values: 117 Bqkg−1, 0.43, 0.32, 53 nGyh−1, average radium equivalent (Raeq), hazard indices (Hin and Hex) and dose rate (D), respectively. When compared to levels typically indicated, it was discovered that its values were within the worldwide standard. The study's findings could be a starting point for radiometric data for upcoming surveillance and epidemiological research.

Research progress on microbial adsorption of radioactive nuclides in deep geological environments.

Due to the development and utilization of nuclear energy, the safe disposal of nuclear waste needs to be urgently addressed. In recent years, the utilization of microorganisms' adsorption capacity to dispose of radioactive waste has received increasing attention. When compared with conventional disposal methods, microbial adsorption exhibits the characteristics of high efficiency, low cost, and no secondary pollution. In the long term, microbial biomass shows significant promise as specific chemical-binding agents. Optimization of biosorption conditions, identification of rare earth element binding sites, and studies on the sorption capacities of immobilized cells provide compelling reasons to consider biosorption for industrial applications in heavy metal removal from solutions. However, the interaction mechanism between microorganisms and radioactive nuclides is very complex. This mini-review briefly provides an overview of the preparation methods, factors affecting the adsorption capacity, and the mechanisms of microbial adsorbents.

Synthesis and Characterization of Silver-Modified Nanoporous Silica Materials for Enhanced Iodine Removal.

In aquatic environments, the presence of iodine species, including radioactive isotopes like 129I and I2, poses significant environmental and health concerns. Iodine can enter water resources from various sources, including nuclear accidents, medical procedures, and natural occurrences. To address this issue, the use of natural occurring nanoporous minerals, such as zeolitic materials, for iodine removal will be explored. This study focuses on the adsorption of iodine by silver-modified zeolites (13X-Ag, 5A-Ag, Chabazite-Ag, and Clinoptilolite-Ag) and evaluates their performance under different conditions. All materials were characterized using scanning electron microscopey (SEM), energy-dispersive X-ray spectroscopy (EDS), powdered X-ray diffraction (P-XRD), Fourier-transform infrared spectrometry (FTIR), and nitrogen adsorption studies. The results indicate that Chabazite-Ag exhibited the highest iodine adsorption capacity, with an impressive 769 mg/g, making it a viable option for iodine removal applications. 13X-Ag and 5A-Ag also demonstrated substantial adsorption capacities of 714 mg/g and 556 mg/g, respectively, though their behavior varied according to different models. In contrast, Clinoptilolite-Ag exhibited strong pH-dependent behavior, rendering it less suitable for neutral to slightly acidic conditions. Furthermore, this study explored the impact of ionic strength on iodine adsorption, revealing that Chabazite-Ag is efficient in low-salinity environments with an iodine adsorption capacity of 51.80 mg/g but less effective in saline conditions. 5A-Ag proved to be a versatile option for various water treatments, maintaining its iodine adsorption capacity across different salinity levels. In contrast, Clinoptilolite-Ag exhibited high sensitivity to ionic competition, virtually losing its iodine adsorption ability at a NaCl concentration of 0.1 M. Kinetic studies indicated that the pseudo-second-order model best describes the adsorption process, suggesting chemisorption mechanisms dominate iodine removal. Chabazite-Ag exhibited the highest initial adsorption rate with a k2 value of 0.002 mg g-1 h-1, emphasizing its superior adsorption capabilities. Chabazite and Clinoptilolite, naturally occurring minerals, provide eco-friendly solutions for iodine adsorption. Chabazite superior iodine removal highlights its value in critical applications and its potential for addressing pressing environmental challenges.

Assessment of radon in traditional building materials using polymeric nuclear track detector

Natural uranium deposits decay into radon gas, a radioactive element that is produced spontaneously. It is a radioactive gas that adversely affects the human population because it can be ingested and inhaled internally, contaminating living tissue, especially DNA, through the ionizing process that increases free radical bodies and increases the risk of cancer. The present study is carried out to determine the radon concentration for some traditional building materials in Egypt by using the nuclear track detector (CR-39). The values of radon concentrations measured by CR-39 ranged from 40.5 ± 3 to 593.2 ± 13 with an average value of 180 ± 6 (Bqm−3). The average values of both surface and mass exhalation rates are 6.3E-04 (Bqm−2h−1) and 7.01E-06 (Bqkg−1h−1) respectively. Pearson’s correlation analysis shows a direct and great correlation between 222Rn, and all variables indexed particularly the annual effective dose with significance at 0.01. The current study helps to create baseline data to assess any anomalies in the level of background radioactivity at Egyptian houses. In addition to applying radiation protection strategies for public and occupational regarding the permissible and recommendation limits by ICRP, and IAEA.

Distribution, risk evaluation, and source allocation of cesium and strontium in surface soil in a mining city.

Radioactive nuclides cesium (Cs) and strontium (Sr) possess long half-lives, with 135Cs at approximately 2.3 million years and 87Sr at about 49 billion years. Their persistent accumulation can result in long-lasting radioactive contamination of soil ecosystems. This study employed geo-accumulation index (Igeo), pollution load index (PLI), potential ecological risk index (PEPI), health risk assessment model (HRA), and Monte Carlo simulation to evaluate the pollution and health risks of Cs and Sr in the surface soil of different functional areas in a typical mining city in China. Positive matrix factorization (PMF) model was used to elucidate the potential sources of Cs and Sr and the respective contribution rates of natural and anthropogenic sources. The findings indicate that soils in the mining area exhibited significantly higher levels of Cs and Sr pollution compared to smelting factory area, agricultural area, and urban residential area. Strontium did not pose a potential ecological risk in any studied functional area. The non-carcinogenic health risk of Sr to the human body in the study area was relatively low. Because of the lack of parameters for Cs, the potential ecological and human health risks of Cs was not calculated. The primary source of Cs in the soil was identified as the parent material from which the soil developed, while Sr mainly originated from associated contamination caused by mining activities. This research provides data for the control of Cs and Sr pollution in the surface soil of mining city.

Formation of medical radioisotope 111In in photonuclear reactions

The possibility of photonuclear production of 111In radioisotope has been investigated. The enriched target 112Sn was irradiated at the linear electron accelerator LUE-75 of A. Alikhanian National Science Laboratory (Yerevan, Armenia) at the bremsstrahlung endpoint energy Eγmax = 55 MeV. The cross section per equivalent quantum for reactions 112Sn(γ,x)111In, 112Sn(γ,n)111Sn, 112Sn(γ,2n)110Sn, 112Sn(γ,3n)109Sn,112 Sn(γ,pn)110mIn, 112Sn(γ,pn)110g110In, 112Sn(γ,p2n)109In have been measured via the method of activation and off-line γ-ray spectrometric technique. The cross section per equivalent quantum of the 111In in photonuclear reaction was compared with its cross section in proton induced reaction on cadmium targets and other possible 111In production routes. It is shown that the photonuclear method can be used for the production of 111In.

Evaluation of the activation of the radiation shielding of the LaDiff neutron triple-axis-spectrometer at FRM-II by simulation/calculation

Neutron radiation is widely used for investigation of matter at research reactors and spallation sources. One undesired side-effect is the production of radioactive nuclides in structure materials of the instruments (e.g. mounting structures and radiation shieldings) due to neutron capture reactions. Hence the structure materials themselves become radiation sources. The knowledge of the activities after a certain time of operation is essential for determination of the accessibility, for modifications of the instrument, for reusing the material and for waste management. It is desirable to have these data in the design phase of the instrument. One possibility to obtain the data is a combination of simulation and calculation. In this paper the simulations/calculations for the LaDiff cold triple-axis neutron spectrometer project at FRM-II (research reactor Munich) are presented. The activities in the shielding house around the experimental area of the instrument made from stainless steel and lead are considered for the cases with and without boron-carbide cover and for different Sb-contents of the lead layer. The influence of the skyshine is also considered.

Hydrostatic pressure-induced transformations and multifunctional properties of Francium-based halide perovskite FrCaCl3: Insights from first-principles calculations

Under varying hydrostatic pressures ranging from 0 to 150 GPa, first-principles calculations were conducted to investigate the structural, electronic, bonding, optical, elastic, and mechanical characteristics of the Lead (Pb)-free halide perovskite FrCaCl3 using both the GGA and hybrid HSE06 parameterized density functional theory (DFT). Since the FrCaCl3 cubic perovskite has not yet been synthesized experimentally, its structural and thermodynamic stabilities are confirmed by the Goldschmidt tolerance factor, the octahedral factor, and the formation energy. The induction of pressure has caused a simultaneous decrease in both the lattice parameters and the electronic band gap. Applying the hybrid HSE06 potential refines the accuracy of the band gap, with values decreasing from 5.705 to 2.618 eV from 0 to 150 GPa pressure, suggesting improved optoelectronic attributes. Employing pressure facilitates the formation of stronger chemical bonds characterized by reduced bond lengths. The investigation of optical functions demonstrates that with increased pressure ranging to 150 GPa, the optical conductivity along with the absorption coefficient is oriented towards the low-energy region. The FrCaCl3 perovskite has the prospect to be used in X-ray imaging and other fields of nuclear medicine and diagnostics as it contains the radioactive element Francium (Fr). Additionally, it is found via the study of mechanical characteristics that FrCaCl3 is mechanically stable under various applied pressure, and adding pressure makes it more ductile as well as more anisotropic.

A gradual Proterozoic transition from an unstable stagnant lid to the modern plate tectonic system

When did plate tectonics begin on Earth, and what preceded it? Published thermo-mechanical mantle evolution models imply that the early history of planets with a composition and size similar to Earth and Venus should be characterized by periodic mantle overturns of 30–100 Myr duration, separated by stable lid phases of 100–300 Myr. This is best described as an unstable stagnant lid because this term captures the Jekyll and Hyde duality of such worlds, which alternate between a stagnant lid sensu stricto phase between mantle overturns, and a mobile lid phase during overturns. Mantle overturn upwelling zones would rework and resurface large tracts of pre-existing Hadean crust and basalt-dominated Archean-style oceanic lithosphere (ASOL). Basal anatexis of ASOL c. 40–50 km thick (or melting within down-drips) could generate tonalite–trondhjemite–granodiorite (TTG) melts and create proto-continental nuclei, while garnet pyroxenite restites delaminate into the mantle. With further reworking, low-K tonalitic rocks would remelt to produce granodiorite and granite, completing the transfer of radioactive elements out of the lower crust. Mantle overturns would generate large-scale lateral currents in the upper mantle that would push against Archean-aged sub-continental lithospheric mantle keels, causing continental drift and orogenesis despite the absence of plate boundary forces such as slab-pull. This is corroborated by the observed displacement of Lakshmi Planum (>1000 km) on Venus, a planet with no arcs nor ridges. Recent models suggest that the Abitibi Greenstone Belt formed as an oceanic tract behind a detached ribbon continent during the partial break-up of the Southern Superior Craton and may be a sample of Archean oceanic lithosphere. The Abitibi Greenstone Belt has c. 50 km of apparent stratigraphy composed of 2–10 Myr mafic–felsic bimodal volcanic cycles that follow assimilation–fractionation trends indicating the contamination of mantle-derived basalts with TTG-like anatectites derived from older basalts. ASOL of this type would be difficult to subduct due to its weakness and buoyancy, but would be fertile and could generate large amounts of second-stage melts. There are no sheeted dykes, precluding a seafloor spreading model, while the absence of basal cumulates or attached mantle means that this type of ASOL should not be called an ophiolite. Archean–Proterozoic unconformities are followed by the deposition of iron formations, clastic and volcanic rocks, which are only rarely affected by sagduction. The increase in siliciclastic input and decreasing sagduction reflect near-global Late Archean emergence of stiffening granitic continents from the oceans due to secular cooling and intra-continental differentiation. Albeit associated with continent-derived siliciclastic debris, many Paleoproterozoic volcanic (and plutonic) rocks resemble Archean rocks geochemically. The similarity of magmatic rocks and hot orogenic styles in the Archean and Paleoproterozoic could imply that the overall geodynamic regime was similar in both. The Siderian–Rhyacian quiet period could therefore represent a stagnant lid phase that followed the 2.5 Ga Archean overturn. When the next mantle overturn ruptured the lid at c. 2.2–2.0 Ga (and again at c. 1.9–1.8 Ga), continents would have been set into motion, forming arcs and ridges. Once initiated, arc and ridge segments needed to multiply and propagate to create a world-girdling system. Mesoproterozoic rocks preserve clear evidence of plate mobility, subduction and orogenesis, but, ophiolites, the geological record of seafloor spreading, are extremely rare prior to 1 Ga. The Earth at 2.0 Ga was probably still largely covered by ASOL, possibly similar to the Abitibi Greenstone Belt, but how and where it was all destroyed and replaced by modern oceanic lithosphere are mysteries. Given the volume of ASOL involved, recognizable by-products of this global-scale reworking process should exist. Voluminous anorthosite–mangerite–charnockite–granite/gabbro suite rocks are mostly of Proterozoic age, requiring either an ephemeral source or a unique process. Trace element inversion models applied to massif anorthosites imply they crystallized from high-La/Yb melts that do not resemble tholeiitic basalts, invalidating the notion that they are flotation cumulates from basaltic underplates. Model anorthosite-forming melts can, however, be explained by high-pressure melting of an ASOL-like basalt source with garnet-bearing residues. I posit that massif anorthosites record the destruction of an ephemeral source (ASOL) at Proterozoic convergent margins. When the last ASOL was crushed between converging continents or consumed by an overprinting arc ( c. 0.8–1 Ga), anorthosite–mangerite–charnockite–granite/gabbro suite rocks ceased to form and the Earth became a modern plate tectonic planet.