Concentrations Of Th Research Articles

Study on the Radioactivity Levels of Metal Tailings in the Lhasa Area of Tibet

The main purpose of this study was to determine the natural radioactivity level of raw radionuclides in the metal tailings of a mine in Lhasa, Tibet, and to conduct sampling and detection in 17 typical metal tailing mines in Lhasa, Tibet. The specific activity concentrations of 226Ra, 232Th, and 40K in the samples were calculated. The total αβχγ radiation, radon concentration, and outdoor absorbed dose rate in the air 1.0 m above the ground were measured. The γ radiation levels affecting miners and their surrounding residents were assessed. The results show that the radiation dose ranges from 0.08 μSv/h to 0.26 μSv/h, and the radon concentration ranges from 10.8 Bq/m3 to 29.6 Bq/m3, which does not exceed the national radiation-related standards, and the environmental hazard risk is low. The specific activity concentration of 226Ra ranged from 8.91 Bq/kg to 94.61 Bq/kg, the specific activity concentration of 232Th ranged from 2.90 Bq/kg to 89.62 Bq/kg, and the specific activity concentration of 40K was less than MDA to 762.89 Bq/kg. The average absorbed dose rate (DO) of the 17 mining areas was 39.82 nGy/h, the average annual effective dose rate (EO) was 0.057 mSv/y. The average external risk index of the 17 mining areas was 0.24, the average internal risk index was 0.34, and the average γ index was 0.31, all of which were less than the maximum permissible limit. This means that the metal tailings from all 17 mining areas were within the limit for γ radiation and, therefore, can be used in bulk as major building materials without posing a significant radiation threat to the residents of the study area.

Radiation Risk Among Children due to Natural Radioactivity in Breakfast Cereals

Breakfast cereal is one of the common foods for children’s nutrition. It is made from sugar, barley, calcium carbonate, salt, maize, peanuts, molasses, and honey. Therefore, assessing the levels of radioactivity in breakfast cereal is essential for children’s health. Gamma-ray spectrometry NaI(Tl) was used to measure the radiation hazard in ten samples collected from the Iraqi market. The corresponding radiation dose quantities and hazard indices were also calculated. The average concentrations of 226Ra, 232Th, and 40K were found to be 18.195, 20.965, and 796.500 (Bq.kg-1). The annual effective dose equivalent (AEDEin), annual ingestion dose (AID), and the risk of cancer incidence (ELCR) were all seen to be within the accepted levels, except the annual gonadal equivalent dose (AGED). Radiation hazard index values (i.e., Iγ, Iα, and Hin) were noticed to be lower than unity, except Iγ was much higher than the internationally permissible limits for the samples of BGF5, BGF6, and BGF7 recommended by UNSCER2000. Therefore, the study findings reveal that this type of cereal can be considered a safe feeding material for children’s health.

Radiological and environmental hazards of granitic rocks in Wadi Faliq El Sahl and El Waar area, North Eastern Desert, Egypt

Chronologically, the main exposures in the study area include; tonalite, granodiorite, adamellite, Hammamat Sediments, monzogranite, syenogranite, rapakivi syenogranite, alkali feldspar granite and dykes. This work aims to determine the suitability of the granitic rocks for using as ornamental stones through detecting their radiological and ecological impacts. The studied samples were measured radiometrically by using Na-I detector for determination of 226Ra, 232Th and 40K concentrations. External hazard indices (Hex) in some samples are more than unity, also, the (Raeq) are higher than the exemption limits (370 Bq.kg−1) exceeds the upper limit of exposure. The hierarchical cluster analysis (HCA) was applied to investigate the correlation between the radionuclides and the corresponding radiological hazard variables. Based on the statistical analysis, 232Th and 226Ra mainly contribute to the radioactive risk of the studied rocks. Regarding ecological indices, 42.1% of younger granite samples have Pollution load index values greater than 1, indicating deterioration, while the majority of older granite samples are lower than 1 suggesting perfection samples. Where, some sample from the older granitoids and younger granites have many radiological and ecological parameters greater than the recommended international limits, so, these samples should not be used in construction for safety reasons.

Transfer Factor of Radionuclides from Soil to Leafy Vegetables in Iraq Using Gamma Ray Spectroscopy

The activity concentration of natural radioactivity levels, of artificial cesium and transfer factor from soil to plants in agricultural areas at Al- Yusiefya region were determined by using NaI (Tl) detector spectrometer. Ten species of leafy plants have been selected: Spinach, Parsley, Watercress, Lettuce, Rashad, Radish, Green onion, Turnip green, Green beet and Mint. The mean activity concentrations of 238U, 232Th, 40K and 137Cs in leafy vegetable samples were 12.4±3.8, 14.8±4.7, 283±93 and 1.06±0.99 Bg/kg, and in soil samples were 15.9±4.3, 16.1±5.2, 298.5±3.9, and 1.11±0.37 Bq/kg. The radiation hazard indices were evaluated (radium equivalent, external hazard index, annual effective dose, absorbed dose rate) were within the permissible values except for excess lifetime cancer risk. The mean transfer factor values of 226 Ra, 232Th, 40K, and 137Cs were 0.89±0.2, 0.9±0.2 , 1.02±0.3, and 0.77±0.25. The leafy vegetable are safe for consumption and the studied area does not pose a considerable radiological threat .

Environmental radioactivity assessment of the Brunei Darussalam coastline of the South China Sea

Radioactivity levels of naturally occurring radionuclides at the coast of Brunei Darussalam were evaluated along with their dose rates. Twenty-six berm and intertidal sediment samples were measured using gamma-ray spectrometry. The mean activity concentrations of 226Ra, 232Th and 40K in berm sediments were 10.07 ± 1.02 Bq/kg, below the minimum detectable activity, and 21.44 ± 1.23 Bq/kg, respectively, whereas for intertidal sediments they were 7.01 ± 0.87, 1.67 ± 0.15 and 4.99 ± 0.42 Bq/kg, respectively. With respect to the radiological health risk, the average hazard indices, absorbed gamma dose rate, effective dose equivalent, and excess lifetime cancer risk were found to be less than the global average. Calculation of the activity ratio showed that 40K is the main source of radiation in the coastal sediments. Furthermore, the difference in radioactivity levels between the berm sediments and intertidal sediments collected at the same location was investigated. Finally, a standard geological terminology of the littoral zone profile is proposed for describing coastal samples for universal communication among researchers.

Vertical distributions of radionuclides along the tourist-attractive Marayon Tong Hill in the Bandarban district of Bangladesh.

This is the first attempt in the world to depict the vertical distribution of radionuclides in the soil samples along several heights (900 feet, 1550 feet, and 1650 feet) of Marayon Tong hill in the Chittagong Hill Tracts, Bandarban by HPGe gamma-ray spectrometry. The average activity concentrations of 232Th, 226Ra, and 40K were found to be 37.15 ± 3.76 Bqkg-1, 19.69 ± 2.15 Bqkg-1, and 347.82 ± 24.50 Bqkg-1, respectively, where in most cases, 232Th exceeded the world average value of 30 Bqkg-1. According to soil characterization, soils ranged from slightly acidic to moderately acidic, with low soluble salts. The radium equivalent activity, outdoor and indoor absorbed dose rate, external and internal hazard indices, external and internal effective dose rates, gamma level index, and excess lifetime cancer risk were evaluated and found to be below the recommended or world average values; but a measurable activity of 137Cs was found at soils collected from ground level and at an altitude of 1550 feet, which possibly arises from the nuclear fallout. The evaluation of cumulative radiation doses to the inhabitants via periodic measurement is recommended due to the elevated levels of 232Th.This pioneering work in mapping the vertical distribution of naturally occurring radioactive materials (NORMs) can be an essential factual baseline data for the scientific community that may be used to evaluate the variation in NORMs in the future, especially after the commissioning of the Rooppur Nuclear Power Plant in Bangladesh in 2024.

Thorium‐Doped Lithium Fluoride Single Crystal: A Potential Promising Candidate for Solid State Nuclear Optical Clock Materials

AbstractThe solid‐state nuclear optical clock based on 229Th‐doped crystal has great advantages in frequency stability, excitation and detection of nuclear transition, miniaturization, commercialization, and spaceborne ability of nuclear optical clock. Here, the potential of LiF crystal as a host for Th ions is predicted by theoretical calculation, and on this basis, the Th:LiF crystal is successfully grown experimentally for the first time. The theoretical results demonstrate that although the challenges of charge nonconservation and ion radius mismatch between Li+ and Th4+ ions exist, effective doping of thorium can still be achieved via energetically favorable charge compensation mechanisms in an F‐rich environment, and the transmittance of Th:LiF crystal in nuclear transition band will only have a slight decrease, smaller than that of pure LiF crystal. The experimental results prove that the doping concentration of Th:LiF crystal can reach about 8.3 × 1018 cm−3 and the transmittances of 1 mm thick Th:LiF and pure LiF crystal samples grown in similar conditions are ≈68% and 72% at 152.7 nm, respectively. The Th:LiF crystal with high doping concentration, high transmittance, and low background luminescence is expected to be a promising candidate for solid‐state nuclear optical clock materials.

Assessment of occupational radiation exposure of NORM scales residues from oil and gas production

Radiological hazards from external exposure of naturally occurring radioactive materials (NORM) scales residues, generated during the extraction process of oil and gas production in southern Algeria, are evaluated. The activity concentrations of 226Ra, 232Th, and 40K were measured using high-purity gamma-ray spectrometry (GeHP). Mean activity concentration of 226Ra, 232Th and 40K, found in scale samples are 4082 ± 41, 1060 ± 38 and 568 ± 36 Bq kg−1, respectively. Radiological hazard parameters, such as radium equivalent (Raeq), external and internal hazard indices (Hex, Hin), and gamma index (Iγ) are also evaluated. All hazard parameter values were greater than the permissible and recommended limits and the average annual effective dose value exceeded the dose constraint (0.3 mSv y−1). However, for occasionally exposed workers, the dose rate of 0.65 ± 0.02 mSv y−1 is lower than recommended limit of 1 mSv y−1 for public.

MAGMA COMPOSITION AND FORMATION CONDITIONS OF ALKALI-SALIC ROCKS OF THE EARLY MESOZOIC ADAATSAG BIMODAL ASSOCIATION OF THE KHARKHORIN RIFT ZONE OF CENTRAL ASIA (DATA FROM THE STUDY OF MELT INCLUSIONS IN MINERALS)

Based on the method of investigation of melt inclusions using electron and ion microprobe, the magma composition and formation conditions of comendites of the Early Mesozoic Adaatsag volcanic association (Mongolia) were studied. The mechanisms leading to the accumulation of rare and rare earth elements in them were determined. Melt and fluid inclusions are found in quartz from the comendites, collected from different parts of the volcanic sequence. The melt inclusions consist of glass, a gas bubble and daughter minerals represented by fluorite, polylithionite and potassium feldspar. The use of the Raman spectroscopy method made it possible to study the composition of the gas phase in melt inclusions. It is determined that the predominant components of the gas phase are water and hydrogen. Fluid inclusions are represented by aqueous solutions that correspond to KF in composition. The concentration of KF in the solution reach up to 4.0–4.1 wt. %. Thermometric experiments with melt inclusions and analysis of the composition of glasses of homogenized melt inclusions in quartz of the comendites showed that the crystallization of magmas of these rocks occurred from water-saturated rare-metal melts with high contents of Li, Zr, F, Rb, Nb, Y and Th at temperatures of 880–930°C and at a pressure of 1000 bar at a depth of ~3.5 km and was accompanied by degassing processes. Comparison of the obtained data on the study of melt inclusions in the phenocrysts of the alkali-salic rocks of the same age volcanic associations Adaatsag, Dzarta-Кhuduk and Sant, developed within the Kharkhorin rift zone, revealed general patterns of their magma evolution. This allowed us to propose a similar mechanism of their formation, involving the accumulation of many rare and rare-earth elements, as well as volatile components (F, H2O) in the process of crystallization differentiation. Subsequently, a salt melt rich in Li, F and water could be separated from such comendite magmas. The detection of fluoride aqueous inclusions in quartz allows us to suppose the further evolution of the salt melt leading to the appearance of a concentrated aqueous fluid and the possible participation of the latter in metasomatic processes.

Thorium isotope evidence for glacial–interglacial dust storminess and productivity in the North Pacific gyre

The flux of dust deposition to the ocean and its impact on marine biological productivity are outstanding issues of the Earth’s climate system. The North Pacific gyre (NPG) is the Earth’s largest ecosystem and is important for marine nitrogen fixation, which is sensitive to Asian dust-regulated surface nutrient stoichiometry. Meanwhile, it is one of the least studied regions in the global ocean during the late Pleistocene, because of the extremely slow sediment accumulation and lack of biological material preservation. 232Th and 230Th concentrations recorded by hydrogenetic ferromanganese crusts in the deep NPG provide a novel and quantitative proxy of dust deposition and export productivity in this region. For this purpose, we have established an in situ U–Th isotope analytical technique on hydrogenetic ferromanganese crusts collected from the deep NPG. Iron, Mn, and Co of our samples have also been analyzed to constrain the impact of dust dissolution on the Fe geochemical cycle. Remarkably, variability of the 232Th-based dust flux over the last ∼900 ky exhibits a striking resemblance to grain-size records of the Chinese loess deposits and sea-level reconstructions but clearly decouples from the global temperature evolution. On orbital time scales, dust storms over the NPG are apparently sensitive to effects related to continental ice sheet sizes but decoupled from major global cooling during the early glaciation. While our 232Th data indicate a 2- to 3-fold variability of glacial–interglacial dust flux, scavenging of Fe, Mn, and Co in the deep NPG is much less variable through the late Pleistocene. We suggest that variable dust fluxes have a limited impact on the inventory of dissolved Fe in the deep waters of NPG, even though the scavenging of Fe has likely been regulated by glacial–interglacial paleoceanography. The paired 230Th-scavenging-based biological productivity tracks gyre sea surface temperature rather than dust flux during the last glacial cycle. We observe no correlation between dust flux and export productivity in the NPG, indicating that dust-derived Fe is not the productivity-limiting factor on orbital time scales in this region. Instead, these results imply that changes in gyre mixing and mode water formation might have led to increased supply of phosphorous and thus enhanced glacial biological carbon sequestration, with potentially stronger nitrogen fixation under higher eolian input.

Estimation of indoor gamma radiation dose rate from concrete blocks constructed from tin mine tailings

The use of building materials made from geological sources contributes greatly to the indoor radiation exposure of human. As a result, it is critical for public health that building materials be screened for elevated radionuclide concentrations. This research measures the primordial radionuclide content of concrete blocks derived from mine tailings and also estimates the indoor annual effective dose rate (AEDR) and associated parameters. Furthermore, it presents a simple empirical relationship for evaluating dose rate per unit specific activity due to radionuclides from a wall of arbitrary dimensions. Twelve concrete blocks constructed using tin mine tailings as fine aggregates were collected locally and analyzed for 235U, 232Th and 40K content using gamma spectrometry analysis. The concentration of 238U ranged from 86.29 to 197.73 Bq/kg with a mean of 120.93 Bq/kg. Also, the specific activity of 232Th and 40K is within the limits: 99.01–353.67 Bq/kg and 500.71–1021.77 Bq/kg with mean values of 248.31 Bq/kg and 635.10 Bq/kg, respectively. Obtained dose rate per unit specific activity agreed well with data from literature. Using the derived values of dose rate per unit specific activity, the annual effective dose rate (AEDR) obtained from a typical Nigerian room varies significantly from that obtained from equations in referenced documents where a different room configuration was used. The mean AEDR from the realistic Nigerian room (3.6 × 3.6 × 3 m3) was higher than the world average value but less than the recommended safety limit of 1 mSvy−1. Some of the blocks with AEDR more than the safety limits were recommended for use in superficial quantities for building construction. The model derived in this study can be applied to calculate dose rates within any room configuration.

Assessing the radiological risks associated with primarily natural radioactivities of coastal seawater in northen Vietnam using the Erica software

The activity concentrations of naturally occurring radionuclides 226Ra, 232Th, and 238U were determined in marine sediments, seawaters and seafood along the Gulf of Vietnam to establish baseline data for future environmental monitoring at a surface water depth of 0–3 cm. The concentration of uranium, thorium and radium were determined using a low background gamma spectrum as well as activity ofy of 238U(214Bi), 232Th(228Ac) and 226Ra. The mean radioactivity concentrations of 226Ra, 232Th, and 238U were found to be 8.59 ± 0.54, 1.31 ± 0.15, and 6.91 ± 0.64 Bq m−3, respectively, in seawater samples and 32.96 ± 1.90, 37.64 ± 1.91, and 39.28 ± 1.96 Bq kg−1, respectively, in marine sediments, 0.21 ± 0.03, 0.69 ± 0.11, and 0.19 ± 0.03 Bq kg−1, respectively, in fish samples and 0.23 ± 0.041, 0.41 ± 0.06, and 0.31 ± 0.06 Bq kg−1, respectively, in clam samples. The radioactivity concentrations in seawater are higher than those in sediment and compared with those reported in other countries. The mean values of distribution coefficient (L/kg) is 0.53, 0.13, and 0.23, respectively, in fish samples and 0.19, 0.16 and 0.13, respectively, in clam samples at Hai Phong, Quang Ninh and Ha Tinh. Moreover, the ecological dose at Hai Phong, Quang Ninh and Ha Tinh are 0.03, 0.02 and 0.02 µGy h−1, respectively, in fish and 0.02, 0.03, and 0.03 µGy h−1, respectively, in clams and the mean human’s seafood consumers dose rate is 1.13×10-6 Sv/yrs. Results were discussed and compared with those reported in similar studies and with internationally recommended values within limits recommended by UNSCEAR.

Exploring geochemical distribution of potentially toxic elements (PTEs) in wetland and agricultural soils and associated health risks.

This study is carried out to understand the degree of soil pollution, transport mechanism, and distribution pattern of potentially toxic elements (PTEs), including the exposure effects on human health. Towards this, topsoil samples were collected from the Saman wetland and surrounding agricultural fields in the Gangetic plain, India. The results show that the mean concentration of Cu, Hg, Zn, Pb, Th, As, U, and Cd of both soil types exceed the natural background values. The multivariate analysis suggests the soils are moderately contaminated with As, Cd, Zn, Pb, and Hg (possibly from anthropogenic sources) and heavily contaminated with Th and U, likely ascended from geogenic sources. The GIS-based geostatistical plots coupled with principal component analysis (PCA) and hierarchical cluster analysis (HCA) apportion the sources of these toxic elements, which vary greatly and are closely correlated to the geogenic processes and local anthropogenic sources like pesticides and agrochemicals. The health risk assessment revealed that the cumulative hazard index (HI) values of PTEs are lower than the safe level, suggesting no significant noncarcinogenic effect for adults and children. However, excess cancer risk (ECR) values exceed the permissible limit (1 × 10-6), signifying that exposure to the toxic element concentration may cause cancer in the exposed population, most probably in the children subpopulation. Thus, this study highlights the importance of local compliance, ensuring the quality checks and management policies in using pesticides and other agrochemicals containing PTEs to control the imposed cancer risks.

Measurements of natural radioactivity and evaluation of radiation hazard indices in soils around the Manyoni uranium deposit in Tanzania

Pre-mining natural radioactivity levels in soils over a 27.96 km2 site around the Manyoni Uranium Project in Tanzania were determined by a high purity germanium detector. The mean activity concentrations of 226Ra, 232Th, and 40K in soils were 227.43 ± 38.79 Bq/kg, 65.22 ± 3.70 Bq/kg, and 107.32 ± 23.07 Bq/kg, respectively. The average radium equivalent activity (Raeq), external hazard index (Hex), and internal hazard index (Hin) at these concentrations were 328.95 Bq/kg, 0.89, and 1.50, respectively. The mean absorbed dose rate in air at 1 m above the ground (Da) was 148.94 nGy/h, and the mean outdoor annual effective dose (Ed) was 0.18 mSv/y. Additionally, natural radioactivity levels in soils over a 0.71 km2 site, which is inside the 27.96 km2 site, which is prone to mine dust pollution above healthy levels, were also determined. The mean activity concentrations of 226Ra, 232Th, and 40K in the soils from this site were 380.4 ± 59.93 Bq/kg, 78.69 ± 8.99 Bq/kg, and 70.40 ± 7.91 Bq/kg, respectively. The corresponding means for Raeq, Hex, and Hin were 498.35 Bq/kg, 1.35, and 2.37, respectively. The mean Da and Ed were 226.21 nGy/h and 0.28 mSv/y, respectively. The average values of Ed at both sites were less than the public exposure limit of 1 mSv/y. This means that the sites have normal background radiation levels that do not endanger people's health when they engage in outdoor activities. When mining begins, the natural radioactivity levels obtained in this study, rather than national or global averages, can be used by mine owners or government agencies to assess the environmental effects of mining. Even after mining and during decommissioning, these baseline levels can also be used to measure how well the land has been restored.

Spatiotemporal evolution of U and Th isotopes in a mine effluent highly polluted by Acid Mine Drainage (AMD)

The spatiotemporal evolution of both U and Th isotopes in a mine effluent highly polluted by acid mine drainage (AMD) was evaluated. The acidic tributary, which born from the outflows of an abandoned sulfide mine, flows into the Odiel River. AMD comprises an important source of natural radionuclides, presenting concentrations of 238U and 232Th, two and four orders of magnitude higher, respectively, than the background values of surface continental waters. These natural radionuclides behave conservatively along the mine effluent (pH < 2.5) throughout the hydrological year. Under AMD conditions uranium is in the hexavalent state U(VI) and the main dissolved species are uranyl sulfate complexes. The polluted tributary has a significant impact on the Odiel River acidifying its waters during the low flow season and increasing up to one order of magnitude the activity concentrations of U and Th isotopes. U presented a conservative behavior in the Odiel River during the low flow season (pH ≈ 3), however it is removed from the liquid phase in the wet season (pH ≈ 6), probably due its coprecipitation/adsorption onto Al-phases. Th shows a high sensitivity to small increases of pH, and it is strongly coprecipitated/adsorbed with or onto Fe-oxyhydroxydizes in the river.

Alpha spectrometry isotopic ratios indications in the Paleozoic sedimentary rock of El Gor area, Southwestern Sinai, Egypt: insights on uranium mobility age

The study area is located between longitude 33° 18' 00" − 33° 21' 00" E and latitude 28° 59' − 29° 01' N and covers approximately 700 km2. Uranium and thorium isotopes were determined by alpha spectrometry. The activity concentrations of 238U, 234U and 235U were ranged between 245.5 ± 8.3–465.2 ± 15.2 Bq.kg−1 with an average 345.5 ± 10.4–452.5 ± 9.3 Bq.kg−1 and 890.5 ± 21.3 Bq.kg−1 with an average 632.3 ± 14.9–11.40 ± 0.5 Bq.kg−1 and 21.50 ± 1.4 Bq.kg−1, respectively. The activity concentration of 232Th, 230Th and 228Th were ranged between 153.1 ± 0.3–318.1 ± 2.9 Bq.kg−1, 149.5 ± 0.7–280.8 ± 2.2 Bq.kg−1 and 36.9 ± 0.1–60.5 ± 0.9 Bq.kg−1. The 230Th/232Th activity ratios in all samples were lower than 20, indicating that these samples have been contaminated by detrital 230Th. Th/U ratio varied between 1.3 and 2.1 with an average 1.8; all values were lower than 3.5, indicated enrichment of uranium. 234U/238U activity ratios that higher than unity indicates that an isotope of uranium has migrated within the rock. From the isotopes of uranium and thorium and their activity ratios, the isochron age for the collected samples was about 58.96 ka.

Transfer factor of radionuclides from soil to cereal crops around gold mining and evaluation of corresponding radiological hazard levels Oromia, Ethiopia

ABSTRACT Radionuclide distribution and transfer factors in plants are decisive parameters used to evaluate radioactive contamination in the environment and its radiological health risks to humans. In this study, the activities concentration of 226Ra, 232Th, and 40K were measured using NaI(Tl) gamma-ray spectrometry on soils and on corresponding teff and wheat plant samples analyzed collected from Sakaro gold mining area from Reji kebele, Oromia, Ethiopia. The results of mean activity concentration of 226Ra, 232Th, and 40K samples analyzedzed in soil, teff, and wheat samples were found to be 33.05 ± 0.72, 13.7 ± 0.51 and 220.18 ± 0.61 Bq.kg-1, 3.93 ± 0.4,27 ± 0.61 and 148.3 ± 0.5 Bq.kg-1 and 3.22 ± 0.43, 4.59 ± 0.64 and 229.8 ± 0.5 Bq.kg-1 respectively. Results showed that the activity concentration of radionuclides in this study area was within the limit. The transfer factors from soil to cereal crops (teff and wheat) were compared with the study done in a different country of the world and its values were below unity except for 40K in wheat samples. The absorbed dose rate, annual effective dose rate, external and internal hazards index, lifetime cancer risk, and annual effective ingestion dose were estimated and were also compared with the internationally accepted values. It was found that none of the results exceeded the recommended limit value.

Geochronology, mineralogy, and geochemistry of tonsteins from the Pennsylvanian Taiyuan Formation of the Jungar Coalfield, Ordos Basin, North China

Altered volcanic ashes occur worldwide in coal-bearing sequences. The Carboniferous is one of the important coal-forming periods but the altered volcanic ashes within coals in China of this geological age have not been well studied. In this study, the nature of the partings in the No. 9 coal seam of the Pennsylvanian Taiyuan Formation from the Yaogou Mine, Jungar Coalfield, Ordos Basin, North China, was comprehensively investigated. Fifteen partings were identified as altered volcanic ashes based on the typical features, including thin but persistent bands, sharp contacts with the enclosing coals, vermicular and book-like kaolinite, angular quartz, and euhedral primary zircons, while some muscovite and detrital zircon grains in the samples indicate minor contribution of terrigenous debris. Two UPb zircon ages from the altered volcanic ashes at the top and bottom of the No. 9 coal constrain that the Taiyuan Formation in the studied area falls within the Gzhelian Stage of the Late Pennsylvanian. All the altered volcanic ashes were defined as tonsteins due to the relative abundances of kaolinite (> 50%). Furthermore, the TiO2/Al2O3 values suggest that the tonsteins have three magmatic origins, which were mostly felsic, with less intermediate and mafic. The trace elements of the enclosing coals, detrital intra-seam clay beds, floor, and roof were mainly sourced from the felsic-intermediate rocks. However, the elevated concentrations of Li, Ga, Zr, Nb, In, Sn, Hf, Ta, Pb, and Th may be related to the leaching of the tonsteins by (acidic) groundwater or hydrothermal solutions. This is supported by the dominant MREY enrichment patterns with positive Gd anomalies of the coals.

Thorium Concentrations in Terrestrial and Freshwater Organisms: A Review of the World Data

An overview of data on thorium concentrations in terrestrial animals, as well as freshwater organisms is presented. Concentrations of 232Th in both animals and fish vary widely, reflecting environmental thorium concentrations. Thorium concentrations in the regions with a normal thorium background in animal tissues were in a range from 0.9 × 10–4 to 2.1 × 10–2 Bq/kg, and from 3.1 × 10–2 to 1.4 × 10–1 Bq/ kg in the areas with high thorium concentrations in the soil. Significantly higher values were observed in wild animals’ tissues. The highest 232Th concentrations were found to be in the skeleton, followed by lungs, kidneys, liver and finally muscles. It has been shown that thorium accumulation is higher in species occupying a higher position in the trophic chains. In areas with normal thorium background, the concentration of 232Th in fish can reach 1.0 × 10–1 Bq/kg (fresh mass), and in areas of high thorium background this value can be up to 100 times higher. The obtained results show the importance of study on the thorium transfer along the food chains and the need to consider observed regularities when assessing the consequences of radioactive contamination of the environment.

Production of mixed element actinide reference particulates to support nuclear safeguards using THESEUS, an aerosol-based particulate synthetic methodology.

The THermally Evaporated Spray for Engineered Uniform particulateS (THESEUS) production platform was developed to generate highly uniform mixed actinide oxide particles. The particulate synthesis platform builds on previous efforts and utilizes an aerosol-based technology to generate, calcine, characterize, and aggregate a monodisperse oxide phase particle product. In this study, particles comprised of uranium oxide, incorporated with varying compositions of thorium, were produced. Th/U test materials with 232Th concentrations between 1 ppm and 10%, ratioed to 238U, were successfully generated with in situ calcination at 600 °C and characterized by in situ aerodynamic particle size spectrometry and ex situ microanalytical methods. Populations of monodisperse particulates (geometric standard deviation - GSD < 1.15) with an average diameter near 1 μm were generatated and micro-Raman spectroscopy of individual particles identified U3O8 as the primary material phase for the range of Th/U samples analyzed. Single particle measurements and automated particle analyses by secondary ion mass spectrometry (SIMS) were performed. Uniform inter-particle elemental and isotopic homogeneity for uranium and thorium isotopes was characterized by SIMS, and a 232Th/238U relative sensitivity factor of 0.53 was determined. SIMS results demonstrated differences in the 232Th/238U profiling behavior for Th/U particulates with increased Th content (>1%). Despite the observed profiling behavior, single particle measurements of the 10% Th sample indicate inter-particle homogeneity. This work represents the first systematic study of Th/U microparticulate reference materials generated and intended for nuclear safeguards applications and serves as a demonstration of THESEUS to support a sustained capability for the production mixed-element particulate reference materials.