Distribution Of Uranium Research Articles

Effect of genetic properties of Khiagda uranium deposits on the choice of in-situ leaching technologies

Hydrogenous uranium deposits of Khiagda ore field have no equal among commercial uranium reserves recovered by the in-situ leaching (ISL) technology. Khiagda JSC carries out ISL of uranium from four uranium deposits in Khiagda field, namely, Khiagda, Vershinnoe, Istochnoe and Kolichkan. As compared to ore occurrences in alluvium in large paleovalleys and in syneclise-type and grabensyncline type artesian basins in Uzbekistan, Southern Kazakhstan, South Australia and in the TransUrals, Khiagda ore field differs by the fact that uranium sources in the catchment area locate at a distance of a few tens of kilometers from the uranium concentration zones in the reducing geochemical barriers. At the Vitim deposits, the zones of uranium removal from the Vitimkan Complex granite by surface water and groundwater and the zones of uranium concentration under the action of syngenetic and epigenetic reducers in the alluvium–proluvium deposits in paleovallyes are very closely spaced at tens and hundreds of meters to a few kilometers. Some other differences include the mostly phosphate rather than oxide and silica composition of uranium minerals and the near-modern age of ore—1.5–12.5 million years. The breakthrough mining technologies are proposed, such as: nonregular accessing of ore bodies with the nonuniform distribution of uranium; use of sodium nitrite as a uranium oxidizer; groundwater resources management in mining of weakly watered deposits; direct determination of uranium content of ore using the method of neutron–neutron logging. These technologies enhance efficiency of ISL. The further research aimed to improve the process designs is proposed to be focused on optimization of ISL borehole patterns as well as on improvement of groundwater resources management in mining weakly watered deposits.

Source, mobilization and distribution of uranium in a complex aquifer system: a spatial and temporal evaluation using geochemical, statistics and GIS approach

Source, mobilization and distribution of uranium in a complex aquifer system: a spatial and temporal evaluation using geochemical, statistics and GIS approach

Importance of accessory minerals for the vertical distribution of uranium and thorium in soil profiles: A case study of durbachite from the Třebíč Pluton (Czech Republic)

The mineralogical character of a parent rock strongly affects the uranium (U) and thorium (Th) contents of soils. We have selected five representative soil profiles developed on amphibole–biotite to biotite durbachites in the Třebíč Pluton (eastern part of the Czech Republic) to characterize the radioactivity and variable-intensity weathering. The Endoskeletic Cambisols with a silt loam to loamy sand texture and a well-developed subsurface Bw horizon represented the most common product of the pedogenetic processes on durbachites. All studied soil profiles showed the evidence of pedogenetic alteration with intrasoil weathering. They were moderately deep (70–80 cm) with high rock-fragment concentrations within the B and C horizons. The predominant grain size fractions were silt (12% to 83%) or sand (8% to 87%), and the percentage of clay was up to 15%. A feldspar–quartz–vermiculite (biotite)–amphibole–kaolinite–Fe–Mn (oxy) hydroxide assemblage was typical for the most weathered parts of the profiles. Variation in the U and Th contents within the studied soil profiles resulted predominantly from the changes in the amounts of primary accessory minerals at different depth levels. Uraninite, monazite, thorite, allanite, zircon, thorogummite, REE-(Rare Earth Elements) fluorocarbonates, and minerals of the rhabdophane group were the main carriers of radioactive elements in the parent durbachite and overlying soil profiles. The gamma-ray spectrometry, geochemical and mineralogical analyses show that uraninite was stable only in the parent durbachite and disappeared at the rocks–C horizon interface. This process was followed by the gradual alteration of allanites, thorites, brabantites and secondary U- and Th-rich minerals (e.g., thorogummite, bastnäsite) toward the soil surface.

The influence of cooling rate on condensation of iron, aluminum, and uranium oxide nanoparticles

Fundamental observations of particle size distributions are needed to develop models that predict the fate and transport of radioactive materials in the atmosphere following a nuclear incident. The extent of material transport is influenced by the time scales of particle formation processes (e.g., condensation, coagulation). In this study, we investigated the influence of cooling time scales on size distributions of uranium, aluminum, and iron oxide particles that are synthesized separately under identical run conditions inside the controlled environment of an argon plasma flow reactor. Two distinct temperature distributions are imposed along the flow reactor by varying the argon flow rate downstream of the plasma torch. The vaporized reactants of uranium, aluminum, and iron are cooled from about 5000 K to 1000 K before they are collected on silicon wafers for ex situ scanning electron microscope analysis. The microscope images show that the sizes of the largest aluminum and iron oxide particles heavily depend on the cooling time scales, whereas significant size variation with cooling rate is not observed for uranium oxide particles. In addition, the size distribution of aluminum oxide particles exhibits the broadest range among all three metal oxides studied. We performed simulations of particle size distributions using a kinetic model that couples gas phase oxidation chemistry with particle formation processes, including nucleation, condensation, and coagulation. The model results demonstrate the strong sensitivity of particle size distribution to different cooling histories (i.e., temperature vs residence time) along the flow reactor. The kinetic model also helps identify directions for future research to improve the predictions.

Refining the conceptual model for radionuclide mobility in groundwater in the vicinity of a Hungarian granitic complex using geochemical modeling

Groundwater is an important freshwater resource, which can be affected by geogenic radionuclide contamination. To make decisions regarding the use and management of groundwater, understanding the controls of radionuclide mobility is critical. In the southern foreland of a granitic outcrop in Hungary, high gross alpha activity concentration was measured in drinking water wells, related probably to the presence of uranium. It has been suggested that understanding of the groundwater flow system may be a key aspect to understand uranium mobility in groundwater. The goal of the present work was to elucidate the conceptual model of radionuclide mobility in the study area, focusing in particular on the geochemical controls of uranium. For this purpose, water samples were collected and nuclide-specific measurements for 226Ra and radon isotopes were carried out, in addition to 234U+238U measurements, to increase the range of radionuclides and better understand their mobility. A geochemical modeling analysis involving redox-controlling kinetic reactions and a surface complexation model was developed to support the conceptual model. The results from the sampling indicate that excess of 234U+238U (3–753 mBq L−1) contribute to the natural radioactivity measured in drinking water to a large degree. 226Ra was measured in relatively low activity concentrations (<5–63 mBq L−1) with the exception of three specific wells. Notable radon activity concentration was measured in the springwaters from Velence Hills (1.01–3.14 × 105 mBq L−1) and in interrelation with the highest (285–695 mBq L−1) 226Ra activity concentrations. The geochemical model suggests that uranium distribution is sensitive to redox changes in the aquifer. Its mobility in groundwater depends on the residence time of groundwater compared to the reaction time controlling the consumption of oxidizing species. The longer the flow path from the recharge point to an observation point where U is measured, the more likely it is that reducing conditions will be found in the aquifer and the elemental concentration U will be low.

Distribution and Storage of Uranium, and its Decay Products, in Floodplain Sediments

Distribution and Storage of Uranium, and its Decay Products, in Floodplain Sediments

SPATIAL DISTRIBUTION OF URANIUM IN GROUNDWATER AND ITS HEALTH RISK ASSESSMENT IN HARYANA, INDIA

Uranium contamination is reported in the groundwater of Haryana but the data of its occurrence is utterly scattered. In the present study, the data related to the distribution of uranium in Haryana was compiled and a contour map was generated. The map showed average uranium concentration in groundwater of Fatehabad (22.3 ppb), Jind (16.76 ppb), Rohtak (15.49 ppb), Mahendargarh (18.87 ppb), Gurgaon &amp; Sohna (22.09 ppb), Rewari (14.4 ppb) below the prescribed limit of WHO while in Hisar (33.9 ppb), Sonipat (57.43 ppb), Panipat (49.42 ppb), Sirsa (49 ppb), Jhajjar (53.01 ppb) and Bhiwani (30.15 ppb) districts higher than the standard limit of 30 ppb of WHO, but below the standard limit of 60 ppb issued by AERB. The AED (Annual Effective Dose) in all districts was found to be less than 100 µSv/y; ECR (Excess Cancer Risk) was found to be less in all districts except Hisar, Panipat, Sonipat, Sirsa, Fatehabad, Sohna, Gurugram, Rewari, Jhajjar and Bhiwani districts, where ECR was higher than the prescribed limit of 1.67 × 10-4 as per AERB.

Thermal impacts on nondestructive analysis measurements of uranium hexafluoride

A series of nondestructive assay measurements were performed before, during, and after localized heating of an industrial standard 12B cylinder of uranium hexafluoride to replicate dose variations previously observed on commercial 30B cylinders. While cylinders represent a closed system, enrichment measurements may be impacted by altered uranium and daughter product distributions due to sublimation. A series of measurements were performed to examine localized heating impacts on dose rates, ratios of uranium and daughter product distributions, and measured 235U enrichment as calculated by two different approaches. The less complex enrichment meter approaches were found to be more robust and less prone to deviation than isotope ratio approaches such as FRAM, but the impact can be minimized by using observable dose changes to avoid impacted areas.

Quantitative appraisal of spatiotemporal uranium distribution, quality of groundwater, and associated risks in Kapurthala, Jalandhar, and Hoshiarpur districts of northern Punjab, India.

Groundwater samples from Kapurthala (45), Jalandhar (70), and Hoshiarpur (70) districts from northern Punjab, India, were studied for seasonal variation (pre-monsoon and post-monsoon) of uranium distribution and physicochemical parameters, quality and suitability for drinking purposes, source apportionment, and health risks. The average uranium concentration (in μg L-1) in Kapurthala, Jalandhar, and Hoshiarpur districts was 12.7, 18.8, and 7.0, respectively, in pre-monsoon and 8.0, 17.3, and 5.6, respectively, in post-monsoon. In both seasons, uranium concentration was below WHO limit (30 μg L-1) in more than 90% of groundwater samples, and it was found to exhibit positive correlation majorly with TDS, EC, and total alkalinity. Principal component analysis revealed dissolution of rocks/minerals contributing to mineralization of associated aquifers in addition to some anthropogenic activities such as excessive application of fertilizers/pesticides and dumping of domestic waste followed by their seepage into the groundwater table. All groundwater samples fall in very good to good drinking groundwater quality and its quality is more improved in post-monsoon season owing to dilution of various inorganic salts during groundwater recharge in monsoon season. Average Hazard Index (HI) values due to ingestion of U, F-, and NO3- via drinking water for both adults and children were found to be marginally greater than safe limit of 1 with major contribution from F-. It is advisable to local government/public that regular monitoring of groundwater and proper management policies or strategies should be adopted followed by their implementation to control groundwater pollution in three districts.

Phase distribution of uranium in matrices obtained by co-melting basalt and uranium-containing aluminum oxide

Safe disposal of nuclear waste is key to sustainable use of nuclear energy. Exploring safe and reliable disposal methods for nuclear waste has become a research hotspot. The phase distribution of uranium in matrices obtained by co-melting basalt and uranium-containing Al2O3 was examined for the development of a potential material for radioactive waste immobilization. The co-melting of basalt with UO3-containing Al2O3 produced matrices containing glass, plagioclase, and spinel as major phases. The highest uranium content (97 mass % UO3) was observed on the non-dissolved fragment of the Al2O3 grains. The titanium-containing complex oxide phase, supposedly, ilmenite, contained up to 62 mass % UO3. The glass phase exhibited an uneven distribution of uranium, with its content ranging ~ 5 to ~ 10 mass % UO3. Data on the leaching of uranium into H2O from the co-melt of basalt and UO3-containing Al2O3 were obtained.

Influences of geological factors on the distribution of uranium in drinking water limescale in the junction zone of the East European Platform and the Southern Urals

An assessment of uranium contents and distribution in drinking water limescale has been conducted in the Republic of Bashkortostan (RB), Russia. A total of 515 limescale samples from 262 settlements of the RB were analyzed. The spread of U concentration values in limescale samples ranged from 0.01 to 61.0 μg/g.Elevated U concentrations in the West of the RB corresponded with the horsts of the granite-gneiss crystalline basement of the South-Tatar Dome and their Eastern slopes, the areas with the Lower Permian red beds and the oil and gas fields. The U migration from the granite-gneiss basement is attributed to the tectonic factor and hydrocarbons movement. Elevated concentrations of U within the South of the RB are associated primarily with the deposits of the Southern Ural brown coal basin. The Bashkir Trans-Urals anomalies are mainly associated with Lower Paleozoic eclogite complex, Devonian and Carboniferous volcanic-sedimentary, carbonate, intrusive formations, as well as the Jurassic cover of terrigenous marine sediments.The negative anomalies of the spatial distribution of U are located in the area of the Ufimian Plateau mainly composed of limestone.

Distribution, behavior, and erosion of uranium in vineyard soils

Phosphate fertilization contributes to an input of uranium (U) in agricultural soils. Although its accumulation and fate in agricultural soils have been previously studied, its colloidal transport and accumulation along slopes through erosion have been studied to a lesser extent in viticulture soils. To bridge this gap, the contents and potential mobility of U were investigated in vineyard model soils in the Rhineland-Palatinate region, Germany. In addition to elevated U contents, U was expected to associate with colloids and subject to erosion, thus accumulating on slope foots and in soils with fine structure, and reflecting a greater variability. Moreover, another expectation was the favorable erosion/mobility of U in areas with greater carbonate content. This was tested in three regional locations, at different slope positions and through soil horizon depths, with a total of 57 soil samples. The results show that U concentrations (0.48–1.26 ppm) were slightly higher than proximal non-agricultural soils (0.50 ppm), quite homogenous along slope positions, and slightly higher in topsoils. Assuming a homogeneous fertilization, the vertical translocation of U in soil was most probably higher than along the slope by erosion. In addition, carbonate content and soil texture correlated with U concentrations, whereas other parameters such as organic carbon and iron contents did not. The central role of carbonate and soil texture for the prediction of U content was confirmed using decision trees and elastic net, although their limited prediction power suggests that a larger sample size with a larger range of U content is required to improve the accuracy. Overall, we did not observe neither U nor colloids accumulating on slope foots, thus suggesting that soils are aggregate-stable. Lastly, we suggested considering further soil parameters (e.g., Ca2+, phosphorus, alkali metals) in future works to improve our modelling approach. Overall, our results suggest U is fortunately immobile in the studied locations.

Enhanced effects and mechanisms of Syngonium podophyllum-Peperomia tetraphylla co-planting on phytoremediation of low concentration uranium-bearing wastewater

To improve the remediation efficiency of plants on low concentration uranium-bearing wastewater and clarify its strengthening mechanism, Syngonium podophyllum-Peperomia tetraphylla co-planting system was established, the enhanced effects of plants interaction on uranium removal were investigated, the chemical forms, valence states, and subcellular distribution of uranium in plants were confirmed, and the mechanisms of alleviating uranium stress by plants interaction were revealed. In Syngonium podophyllum-Peperomia tetraphylla co-planting system, the total amount of ethanol-extracted uranium and deionized water-extracted uranium with higher toxicity in their roots were reduced by 10.30% and 7.17%, respectively, which reduced the toxicity of uranium to plants. Plants interaction can inhibit the reduction of U(VI) in the root of Peperomia tetraphylla, which is conducive to the transport of uranium from roots to shoots. In addition, uranium in plants mainly existed in the cell wall (54.44%–66.52%) and the soluble fraction (23.85%–32.89%). These results indicated that Syngonium podophyllum and Peperomia tetraphylla co-planting can enhance their effects of uranium removal by alleviating uranium stress with the cell wall immobilization and vacuole compartmentation, improving biomass of plants, increasing bioaccumulation factor and translocation factor of uranium.

Estimating indoor radon concentrations based on the uranium content of geological units in South Africa

Very few studies have been done on radon in South Africa, even though South Africa holds nearly a tenth of the global uranium deposits. This study aimed to map and estimate the radon risk for South Africa, and to identify potential hotspots. In this study, the uranium content of the different types of rock was determined and uranium concentrations in geological units were then projected. A uranium distribution map of South Africa was then constructed, and indoor radon concentrations were estimated and mapped based on the uranium levels of areas. Towns in areas where indoor radon measurements were conducted compared well with the estimated radon values. The maps predicted high estimated indoor radon concentrations in areas at several geological structures. Towns in these areas that have not been measured were identified. The south-western and north-eastern regions of South Africa pose the highest radon risk according to this study, and extensive radon measurements in the towns of these regions is proposed.

Distribution and uptake of uranium in rice and wheat from soil samples collected from Al- Diwaniyah, Iraq

Wheat and rice are among the main ingredients on which the Iraqi populations depend. The important part of this is detected knowledge the uptake radionuclide in this cereal, no less in admiration of any personal health harmful. In this study, we measured the concentrations of naturally occurring radioactive nuclides in cereals and the corresponding soil collected from agricultural fields in Al Shamiyah, Al- Diwaniyah governorate in Iraq using nuclear detector of tracks (CR-39). The mean activity concentration of uranium (ppm) in soil, wheat and rice samples were found to be 1.18 ± 0.19, 0.02 ± 0.001 and 0.88 × 10-2 ± 0.00085, respectively. Factors of transfer from soil-to- cereals were limited to be 0.012 and 0.017 for wheat and rice. The results of TFs of 238U were found to be in agreement with previous studies values, these results refer to radionuclides movement were very low in these soils. Results have been shown the uranium concentration to be less than permissible limit (11.7 ppm) proposed by UNSCEAR. On the other side, results noticed there are no pose significant threats to health of human, the edible cereals being safe to consume.

Uranium incorporation in fluorite and exploration of U–Pb dating

Abstract. The age of ore deposits constitutes a decisive element in understanding their formation. Deciphering their precise chronology may be a challenge in the absence of mineral phases that can be dated by conventional geochronometers. Fluorite is very common either as the major or accessory mineral in a wide variety of ores and may provide information regarding the origin and timing of mineralizing fluid flows. In this contribution, we explore U–Pb dating on fluorite crystals from the world-class carbonate strata-bound fluorite ore of Pierre-Perthuis in Burgundy (Morvan massif, France). The uranium distribution within fluorite is mapped using induced fission-track and synchrotron radiation X-ray fluorescence nano-imaging, showing that higher U content is measured in an overgrowth of fluorite (Flog) as a discrete band. Preservation of a micrometer-thick zonation in U, associated with other substituted elements such as Sr, Y, Fe and Zr, implies that neither solid-state diffusion nor dissolution–recrystallization occurred. These U-bearing external fluorite overgrowths contain solid inclusions of about 30 µm globular pyrite crystals with a mean δ34S of −23.6 ± 0.4 ‰V-CDT. We propose that the U incorporation in the fluorite lattice results from the development of a redox front during bacterial sulfate reduction. Flog generation sampled and analyzed by laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS) on four different crystals provides identical U–Pb ages within the limits of analytical uncertainty. Considered altogether, these four crystals yield an age estimate of 40.0 ± 1.7 Ma, not corrected for matrix-related elemental fractionation. Our results show that fluorite LA-ICP-MS U–Pb geochronology has potential for dating distinct crystal growth stages, although further research should be conducted to evaluate its accuracy.

Relative importance of organic- and iron-based colloids in six Nova Scotian lakes

Dissolved organic matter (DOM) concentrations have been increasing in parts of the northern hemisphere for several decades. This process—brownification—often accompanies increasing iron and aluminum, but the metal–DOM interactions these concurrent trends imply are poorly described. Here we used field-flow fractionation with UV and ICP-MS detection to measure the size distribution of colloidal iron, aluminum, manganese, copper, uranium, and chromophoric DOM in six lakes over six months. Five of these lakes have browned to some degree in the past three decades, with linear increases in organic carbon and color ranging from 0.01 to 0.13 mg C L−1 yr−1 and 0.13–1.94 PtCo yr−1. Browning trends were more pronounced and colloids more abundant in lakes with wetlands in their catchments. Iron and aluminum were present in two primary fractions, sized nominally at 1 and 1000 kDa. The 1 kDa fraction included the primary DOM signal, while the 1000 kDa fraction absorbed minimally at 254 nm and likely represents iron-rich (oxyhydr)oxides. Colloidal manganese was sized at 1000+ kDa, whereas colloidal copper and uranium occurred primarily at 1 kDa. These associations fit with a pattern of increasing DOC, iron, aluminum, and color in the region’s lakes. They represent a significant challenge for drinking water treatment systems, especially those in remote communities. Given that browning trends are expected to continue, monitoring plans would better inform treatment process design and operation by characterizing DOM and iron-rich, primarily inorganic colloids that contribute to adverse water quality outcomes.

A combined DGT - DET approach for an in situ investigation of uranium resupply from large soil profiles in a wetland impacted by former mining activities

An in situ methodology combining DET and DGT probes was applied in a wetland soil, downstream of a former uranium mine (Rophin), to evaluate metal resupply by calculating the R ratio (R = [U]DGT/[U]pore water) from a high resolution and large (75 cm) soil profile. Our study confirms its applicability in soil layers with varying properties; only soil layers with low water content or coarse texture appear to be limiting factors. For soil profiles, DET provides new insights of the distribution of Uranium as soluble species (free ions, small inorganic complexes, …) along the pore water profile, whereas DGT highlights the presence of other “DGT labile” species. The pairing of DET and DGT, plus the calculation of the R, highlights two U behaviors in combining results from red-ox sensitive elements (Mn, Fe). First, in the organic topsoil layer, an increase in [U]DET and [U]DGT at 3–4 cm reflects the desorption of U probably trapped onto Fe- and Mn-oxohydroxides in a DGT-labile form. However, the resupply from soil to pore water is close to a diffusion only case (R < 0.2) meaning that a portion of U is certainly tightly bound by OM in soil as non-labile species. Second, a peak in [U]DGT perfectly corresponding to the former mine deposit layer signifies the presence of U under DGT-labile species. Moreover, a maximum R value of 0.87 demonstrates the near complete resupply of U from a labile fraction in this layer, as opposed to other elements like Pb.

Single-Cell Imaging for Studies of Renal Uranium Transport and Intracellular Behavior

Nephrotoxicity is the primary health effect of uranium exposure. However, the renal transport and intracellular behavior of uranium remains to be clearly elucidated. In the present study, the intracellular uranium distribution was examined with the cell lines derived from the S3 segment of mouse renal proximal tubules, which is a toxic target site of uranium, using microbeam-based elemental analysis. Uranium exposure at 100 μM for 24 h (non-toxic phase) was performed in S3 cells. Two types of measurement specimens, including those that are adhesive cell specimens and cryosection specimens, were examined for the positional relationship of the intracellular localization of uranium. Based on the combined results of single-cell imaging from the two types of cell specimens, uranium was distributed inside the cell and localized in the cytoplasm near the cell nucleus. In some cells, uranium was colocalized with phosphorus and potassium. The amount of uranium accumulated in S3 cells was estimated using thin section-standards. The mean uranium content of three adhesive cells was hundreds of femtogram per cell. Thus, we believe that single-cell imaging would be useful for studies on renal uranium transportation and cellular behavior.

Effects of ageing on the occurrence form of uranium in vertical soil layers near an uranium tailing reservoir

Uranium contamination due to mining and metallurgical operations is a serious problem worldwide. Upon entering an ecosystem, uranium poses a high potential threat to humans and other organisms. A better understanding of the distribution and speciation of uranium in contaminated soil is therefore necessary over relevant time scales. In this study, we collected uncontaminated soil samples, including eluvial (E), illuvial (B), and parent-material (C) horizons, from a soil profile near a uranium tailing reservoir in southern China. Four columns were filled with the E, B, and C horizons and three types of mixed soil samples to simulate the behavior of uranium in soil near an uranium tailing reservoir. The atomic-scale mechanisms were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, and other characterization methods. The results show that air, clay minerals, iron and manganese oxides, and other soil properties exert important effects on the forms and mobility of uranium in soil, and that ageing leads to a rearrangement and chemical fractionation of uranium in soil.