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Discovered in 1829, thorium, CASRN 7440-29-1, is a naturally occurring radioactive metal with no stable isotopes. It is about as abundant as lead. Soil commonly contains an average of about six parts of thorium per million parts of soil. Ingestion of liquid, inhalation of dust or gas, and percutaneous absorption are the routes of exposure. Acute exposure results in dermatitis. Thorium is a carcinogen and developmental toxin. The removal of thorium from the body has been achieved by the use of chelating agents. Studies of thorium workers have shown that breathing thorium dust may cause an increased chance of developing lung disease and cancer of the lung or pancreas many years after being exposed.

We analyzed long-term incidence trends in liver cancer (including hepatocellular carcinoma and intrahepatic cholangiocarcinoma) with an aim to interpret the changes in terms of known risk factors and hypothesize that historical exposure to Thorotrast, a radiographic contrast medium emitting alpha particles, has changed population rates. The NORDCAN database was used to collect cancer registry data from Denmark (DK), Finland (FI), Norway (NO) and Sweden (SE), which we used from 1953 (DK, FI and NO) and 1960 (SE) through 2019. Thorotrast, which caused a 100-fold risk of liver cancer was used in DK and SE, and probably also in FI between 1930 and 1950, but not in NO. The incidence trend for liver cancer showed a broad maximum at around 1980, most prominent and statistically significant in SE and DK men and women, and in all countries, a steadily increasing trend towards the end of follow-up. Incidence for NO was lower than for the other countries and the rates showed no peaking at around 1980. Birth cohort analysis identified a transient risk which could be dated to a period between 1930 and 1950 in countries other than NO. Considering a lag time between Thorotrast use and liver cancer appearance, the large incidence peak around 1980 in DK and DE was probably contributed by Thorotrast but considering the ecological nature of the findings, the association should be considered cautiously as hypothesis generating. The late increase in liver cancer risk is most likely lifestyle related and largely preventable.

We report the synthesis of four homoleptic thorium(iv) amidate complexes as single-source molecular precursors for thorium dioxide. Each can be sublimed at atmospheric pressure, with the substituents on the amidate ligands significantly impacting their volatility and thermal stability. These complexes decompose via alkene elimination to give ThO2 without need for a secondary oxygen source. ThO2 samples formed from pyrolysis of C-alkyl amidates were found to have higher purity and crystallinity than ThO2 samples formed from C-aryl amidates.

Cancers of the gallbladder and extrahepatic bile ducts (called here "GBC" because gallbladder cancer is the main component) are rare in Europe, including the Nordic countries. Their incidence has varied for unknown reasons and we hypothesize that Thorotrast, a previously used carcinogenic radiographic contrast medium, has contributed to the incidence trends. We obtained incidence and survival data from the NORDCAN database, which includes cancer registry data from Denmark (DK), Finland (FI), Norway (NO) and Sweden (SE), which are globally the oldest national cancer databases, starting from 1943 in DK, 1953 in FI and NO and 1960 in SE, and extending to 2016. The incidence trend for GBC showed a broad maximum around 1980 in men (close to 3/100 000) and women (4/100 000), except for NO, where this phenomenon was not seen. In 1955, FI and NO incidence rates were equal but FI rates peaked and later declined similar to DK and SE rates. By 2010, the incidence was similar in all Nordic countries, for both men and women, at close to 2.0/100 000. Birth cohort analysis showed strong effects for countries other than NO. Relative 1-year survival increased for men from 20% to about 50% and similarly for women although at a 5 percentage points lower level. Survival in NO was better than in other countries in the 1980s. Thorotrast, causing a high risk of GBC, was extensively used in the Nordic countries between 1930 and end of 1940s, with the exception of NO, where these was no documented use. These data suggest that Thorotrast influenced GBC epidemiology and probably worsened survival in certain periods.

Radioactive contrast agent introduced in 1928 and mainly used for cerebral angiography until the 1950s.

An alert indicating the formation of salt deposits in the pipelines of oil and gas production complexes reduces the financial losses associated with the removal of these deposits and the loss of production. A method of taking into account the presence of the native radionuclide 232Th and its decay product 208Tl in the deposits is proposed for performing radiation diagnostics of pipelines. The appearance of the deposits is identified according to the 2.614 MeV γ-rays. The thickness of the deposits is determined according to the attenuation of the γ-rays from an external thorium dioxide source placed on the outer surface of a pipe. Calculations confirmed the presence of 1–2 mm thick deposits with probability 0.9 and a false positive rate of 0.01 in 1 h measurements with background 3 counts/sec. A 232Th-based external source with activity 105 and 106 Bq makes it possible to determine deposit thicknesses 2.5–3 and 1–2 mm, respectively, with measurement time 1 h and error about 15%.

© 2019, The Minerals, Metals & Materials Society. A convenient recycling loop is one of the key factors that will help to implement the thorium-based nuclear fuel cycle in the future. Herein, a study is presented concerning the recycling loop of thoria production scrap using dissolution with trifluoromethanesulfonic (triflic) acid and recovery by precipitation with oxalic acid. The kinetics of thoria powders and pellet dissolution was assessed and compared with the THOREX process. The effect of the triflic acid concentration on the recovery yield of thorium during oxalate precipitation was examined, as well as the behavior of radium during this reaction. Finally, the effect of the triflic acid concentration on the recovered thoria morphology was investigated. The triflic acid has minimal effect on the recovery yield during oxalate precipitation even in the case of high acid concentrations. In general, the solubility of radium(II) oxalate is higher than for thorium(IV) and has a maximum at a triflic acid solution of 4 M. An interesting observation was that a stable dihydrate of thorium(IV) oxalate is formed in solution of high triflic acid concentration. It might be explained by the hygroscopic medium during precipitation of the oxalate. All above mentioned observations confirm the benefits of usage of the triflic acid-based closed recycling loop for thorium dioxide-based nuclear fuel. ispartof: JOURNAL OF SUSTAINABLE METALLURGY vol:5 issue:1 pages:118-126 status: published

Thorium oxide thin films were successfully prepared by direct UV irradiation of amorphous films composed of thorium(IV) β-diketonate precursor complexes on Si(100) and quartz substrates. The ThO2 films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). The X-ray diffraction patterns showed that the films that annealed at T° below 550 °C were amorphous. The films that annealed at 550 °C and above exhibited a preferred orientation along the (111) plane. Both the as-photodeposited and annealed ThO2 films exhibited a good optical quality with transparency in the visible region better than 85%. Photoluminescence of ThO2 thin films was reversibly quenched when exposed to 60 ppm of CO at room temperature.

An incremental approach to introducing thorium to the conventional pressure-tube heavy-water reactor natural uranium fuel cycle is investigated. The approach involves the replacement of the centre fuel element of the bundle with an element of thorium dioxide. Increasing the operating margin of a key safety parameter, the coolant void reactivity, is a prime motivating factor. The analyses showed that the simple use of a single pin of thorium is unlikely to be economically advantageous due to a large burnup penalty and increased fuel costs. However, a slight reduction in the void reactivity is observed, and this approach does allow the exploitation of the energy potential available in thorium as an alternative nuclear fuel resource through the development of a U-233 resource. This bundle concept may also be advantageous from a fuel disposal point of view, as the fuel requires less time in storage before emplacement in a deep geological repository.

The effect of fission product (FP) defects and porosity on thermo-mechanical properties of ThO2 within 300–1500 K has been investigated using molecular dynamics (MD) simulations. We consider two typical FPs: Xe and Kr (0–2% defect). Our results indicate that these FPs reduce the thermal expansion (α) at low temperature; however, α of the defected system is similar to that of pure ThO2 at the elevated temperature. For porous ThO2 (0–5% porosity), α is within 5% of that of pure system at all studied temperature. The elastic modulus at finite temperature decreases linearly with the increase in the concentration of Xe, Kr and porosity. The degree of reduction (R) in elastic modulus follows the trend R X e > R K r > R P o r o s i t y for all the studied concentration of defects. The MD derived changes in the elastic modulus by FPs and porosities can be well described by the affine functions. We report that the porous ThO2 shows higher reduction in elastic properties than porous UO2. A detail calculation of 0 K properties as a function of defect concentration is presented.

For the first time, we report the preparation of thorium dioxide with nanofibrous morphology by the electrospinning method. Two approaches were employed with different electrospun solution compositions and inorganic precursors. Thorium nitrate with polyvinyl alcohol (PVA) as a supporting polymer was successfully electrospun from an aqueous solution resulting in green composite fibers that were calcined at 773 K to pure ThO2 nanofibers of diameter 76 ± 25 nm. Another precursor solution was based on organic solvents and thorium acetylacetonate complex with polyvinylpyrrolidone (PVP). Green fibers were calcined at 673 K to porous nanofibers of ThO2 with an average diameter of 34 ± 18 nm and surface area of 85 m2 g-1 . The prepared materials were characterized by TGA-DSC, SEM, TEM, PXRD, and BET methods., This research has been financially supported by the MEYS CR under the project CEITEC 2020 (LQ1601) and the Horizon 2020 Research and Innovation Program under the grant agreement no. 810626 (SINNCE). CIISB research infrastructure project LM2018127 funded by the MEYS CR is gratefully acknowledged for the financial support of the measurements at the CEITEC MU CF X-ray Diffraction and Bio-SAXS and the CF Cryo-electron Microscopy and Tomography.

Hydrothermal conversion of thorium oxalate, Th(C2O4)2·nH2O, into thorium dioxide was explored through a multiparametric study, leading to some guidelines for the preparation of crystallized samples with the minimum amount of impurities. As the formation of the oxide appeared to be operated through the hydrolysis of Th4+ after decomposition of oxalate fractions, pH values typically above 1 must be considered to recover a solid phase. Also, because of the high stability of the thorium oxalate precursor, hydrothermal treatments of more than 5 h at a temperature above 220 °C were required. All the ThO2·nH2O samples prepared presented amounts of residual carbon and water in the range 0.2-0.3 wt % and n ≈ 0.5, respectively. A combined FTIR, PXRD, and EXAFS study showed that these impurities mainly consisted of carbonates trapped between elementary nanosized crystallites, rather than substituted directly in the lattice, which generated a tensile effect over the crystal lattice. The presence of carbonates at the surface of the elementary crystallites could also explain their tendency to self-assembly, leading to the formation of spherical aggregates. Hydrothermal conversion of oxalates could then find its place in different processes of the nuclear fuel cycle, where it will provide an interesting opportunity to set up dustless routes leading from ions in solution to dioxide powders in a limited number of steps.

Fuel bundle end power peaking in pressure tube heavy water reactors (PT-HWRs), particularly considering advanced reactor fuels (such as thorium-based fuels), was evaluated and a mitigation method was assessed. For bundles containing all the same fuel pellets, power is greatest at the bundle ends due to higher thermal neutron flux there. A method to achieve a flatter axial power profile along a bundle by downblending the fissile content in the end pellets with thorium dioxide was evaluated. The method was shown to be effective, and only a slight reduction in fresh fuel reactivity was observed.

Additive manufacturing of thorium dioxide has been investigated using a commercially available stereolithography-based 3D printer and photopolymer resin. Three-dimensional thorium dioxide objects have been printed with good dimensional accuracy. High-density thorium dioxide parts (>90% theoretical density) were achieved by sintering the 3D-printed parts. Despite significant shrinkage, the overall shape of the objects was maintained during sintering with slight distortion. Additive manufacturing is seen to have potential application for advanced nuclear fuel concepts with complex geometries.

A series of 2-D lattice physics calculations with depletion were carried with WIMS-AECL Version 3.1 out as part of exploratory scoping studies to evaluate various thorium-based fuel bundle concepts for potential application in pressure tube heavy water reactors (PT-HWRs). Fuel bundles concepts investigated consisted of a cluster of 35 fuel elements arranged in two rings (14 + 21), and surrounding a central graphite displacer rod. The fuel is comprised of thorium dioxide mixed with a fissile driver of reactor-grade plutonium (∼67 wt% Pu fissile /Pu; 3.5–4.5 wt% PuO 2 /(Pu,Th)O 2 ), low enriched uranium (5 wt% 235 U/U; 40–50 wt% LEUO 2 /(LEU,Th)O 2 ) or uranium–233 (1.8 wt% 233 UO 2 /( 233 U,Th)O 2 ). Estimates of burnup-averaged fuel temperature coefficients (FTC) and coolant void reactivity (CVR) were found to be lower than those for conventional natural uranium dioxide (NUO 2 ) PT-HWR fuel in a 37-element bundle. A low-burnup option for using (LEU,Th)O 2 fuel in a PT-HWR is found to be attractive as a means for extracting energy from thorium, while also generating stockpiles of 233 U, and demonstrating enhanced safety characteristics with reduced CVR and FTC relative to NUO 2 .

In this research, the reverse non-equilibrium molecular dynamics is employed to investigate the effect of vacancy and substitutional defects on the thermal transport in thorium dioxide (ThO2). Vacancy defects are shown to severely alter the thermal conductivity of ThO2. The thermal conductivity of ThO2 decreases significantly with increasing the defect concentration of oxygen vacancy; the thermal conductivity of ThO2 decreases by 20% when 0.1% oxygen vacancy defects are introduced in the 100 unit cells of ThO2. The effect of thorium vacancy defect on the thermal transport in ThO2 is even more detrimental; ThO2 with 0.1% thorium vacancy defect concentration exhibits a 38.2% reduction in its thermal conductivity and the thermal conductivity becomes only 8.2% of that of the pristine sample when the thorium vacancy defect concentration is increased to 5%. In addition, neutron activation of thorium produces uranium and this uranium substitutional defects in ThO2 are observed to affect the thermal transport in ThO2 marginally when compared to vacancy defects. This indicates that in the thorium fuel cycle, fissile products such as 233U is not likely to alter the thermal transport in ThO2 fuel.

In this research paper, the thermal transport in thorium dioxide is investigated by using nonequilibrium molecular dynamics. The thermal conductivity of bulk thorium dioxide was measured to be 20.8 W/m-K, confirming reported values, and the phonon mean free path was estimated to be between 7 and 8.5 nm at 300 K. It was observed that the thermal conductivity of thorium dioxide shows a strong dependency on temperature; the highest thermal conductivity was estimated to be 77.3 W/m-K at 100 K, and the lowest thermal conductivity was estimated to be 4.3 W/m-K at 1200 K. In addition, by simulating thorium dioxide structures with different lengths at different temperatures, it was identified that short wavelength phonons dominate thermal transport in thorium dioxide at high temperatures, resulting in decreased intrinsic phonon mean free paths and minimal effect of boundary scattering while long wavelength phonons dominate the thermal transport in thorium dioxide at low temperatures. Keywords: Molecular Dynamics Simulation, Nuclear Fuel, Thermal Transport, Thorium Dioxide

We precipitated thorium in a two-step process with ammonia and carbonates. In contrast to single step ammonia or carbonate precipitation, the two-step process precipitates >99.9% of Th and removes >99.5% of Ra alongside. Filterability is strongly affected by pH variations in the ammonia step, and under well-controlled conditions, the precipitated ThO2 filters quickly and calcines to crystalline ThO2 at low temperatures. As-precipitated ThO2 contains significant quantities of adsorbed H2O and CO2, which are removed during calcination. The calcination temperature greatly affects the green density of produced pellets, but for all calcination temperatures investigated, the sintered densities are in excess of 96% with grain sizes within the range applied for nuclear fuels at 10–16 μm.

Inhalation represents the most prevalent route of exposure with Thorium-232 compounds (Th-nitrate/Th-dioxide)/Th-containing dust in real occupational scenario. The present study investigated the mechanism of Th response in normal human alveolar epithelial cells (WI26), exposed to Th-nitrate or colloidal Th-dioxide (1–100 μg/ml, 24–72 h). Assessment in terms of changes in cell morphology, cell proliferation (cell count), plasma membrane integrity (lactate dehydrogenase leakage) and mitochondrial metabolic activity (MTT reduction) showed that Th-dioxide was quantitatively more deleterious than Th-nitrate to WI26 cells. TEM and immunofluorescence analysis suggested that Th-dioxide followed a clathrin/caveolin-mediated endocytosis, however, membrane perforation/non-endocytosis seemed to be the mode of Th internalization in cells exposed to Th-nitrate. Th-estimation by ICP-MS showed significantly higher uptake of Th in cells treated with Th-dioxide than with Th-nitrate at a given concentration. Both Th-dioxide and nitrate were found to increase the level of reactive oxygen species, which seemed to be responsible for lipid peroxidation, alteration in mitochondrial membrane potential and DNA-damage. Amongst HSPs, the protein levels of HSP70 and HSP90 were affected differentially by Th-nitrate/dioxide. Specific inhibitors of ATM (KU55933) or HSP90 (17AAG) were found to increase the Th- cytotoxicity suggesting prosurvival role of these signaling molecules in rescuing the cells from Th-toxicity.

The present study aims to investigate the optimum parameter in producing high-purity thorium dioxide (ThO2) using Di-2-ethylhexyl phosphoric acid (D2EHPA) and Aliquat-336 as solvent materials. The extraction and purification process was performed using [Th-RE](OH)4 compound which was selectively precipitated from the monazite leach solution. Several parameters such as types of acid (HCl, HNO3 and H2(SO4)), acid molarity (1M–6M), and solvent ratio (10%–30%) were investigated. The findings indicate that different solvents require a distinctive aqueous medium to extract thorium. The optimum concentrations of D2EHPA and Aliquat-336 in extracting thorium were identified to be at 1M H2(SO4) and 4M HNO3 with 30% and 20% ratio, respectively. The multi-stage extraction process was successfully extracted and purified thorium at a purity of 96.8% (D2EHPA) and 98.0% (Aliquat-336). Subsequent conversion to ThO2 yielded a high-purity thorium dioxide at 99.1%. In general, the study elucidates that both solvents have the potential to be utilized as thorium extracting agents in preference to the conventional tri-butyl phosphate (TBP).

Thorium dioxide (thoria, ThO2) is used in refractory applications and as nuclear fuel. Its melting temperature, the highest of any binary oxide, makes it a difficult system to process. Here we report on the effects of flash sintering on the densification of thoria. We found 95% of theoretical density is obtained at ~950 °C (~30% of the melting temperature) with an electric field of 800 V/cm. Variation in power density had a minimal effect on the densification. Scanning electron microscopy images show the effects of flash sintering on grain size as a function of electric field.

The stability and clustering behavior of fission products (Zr, Mo, Ru, and Rh) in thorium dioxide have been investigated by density functional theory. The calculations were performed considering the possible insertion sites in ThO2, including interstitial sites, thorium vacancies, oxygen vacancies, the oxygen–thorium divacancy, and three types of Schottky defect. The thorium vacancy is the most energetically favorable trap site for all of these fission products. Zr and Mo can exist as oxide precipitates whereas Rh and Ru tend to form metallic clusters in ThO2. Moreover, Ru and Rh dimers are the most stable clusters in the Schottky defect in ThO2, suggesting that metal clusters in ThO2 may be formed of these dimers trapped in Schottky defects.

Oxidation of a ∼1000 A sputter-deposited thorium thin film at 150 °C in 100 ppm of flowing oxygen in argon produces the long-sought solid form of thorium monoxide. Changes in the scattering length density (SLD) distribution in the film over the 700-min experiment measured by in-situ, dynamic neutron reflectometry (NR) shows the densities, compositions and thickness of the various thorium oxides layers formed. Screened, hybrid density-functional theory calculations of potential thorium oxides aid interpretation, providing atomic-level picture and energetics for understanding oxygen migration. NR provided evidence of the formation of substoichiometric thorium oxide, ThOy (y

PURPOSE: Studies of ionizing radiation effects through the archiving of data began with standardizing medical treatments in the early 1900s shortly after the discovery of X-rays. Once the breadth of the delayed effects of ionizing radiation was recognized, the need for long-term follow up became apparent. There are now many human archives of data from nuclear disasters and accidents, occupational exposures, and medical procedures. Planned animal irradiation experiments began around the time of the Cold War and included a variety of doses, fractions, dose rates, and types of ionizing radiation. The goal of most of these studies was to supplement information coming from human data; carefully planned experimental conditions and immediate and uninterrupted data collection were the basis for this hope. This review aims to highlight major archives that have shaped the field of radiation biology and provide a broad range of the types of archives currently available. CONCLUSIONS: By preserving all of these data and tissue sets, radiation biologists can combine databases and conduct large-scale analyses of detailed existing data and perform new assays with cutting edge scientific approaches.

Thermal transport is a key performance metric for thorium dioxide in many applications where defect-generating radiation fields are present. An understanding of the effect of nanoscale lattice defects on thermal transport in this material is currently unavailable due to the lack of a single crystal material from which unit processes may be investigated. In this work, a series of high-quality thorium dioxide single crystals are exposed to 2 MeV proton irradiation at room temperature and 600 °C to create microscale regions with varying densities and types of point and extended defects. Defected regions are investigated using spatial domain thermoreflectance to quantify the change in thermal conductivity as a function of ion fluence as well as transmission electron microscopy and Raman spectroscopy to interrogate the structure of the generated defects. Together, this combination of methods provides important initial insight into defect formation, recombination, and clustering in thorium dioxide and the effect of those defects on thermal transport. These methods also provide a promising pathway for the quantification of the smallest-scale defects that cannot be captured using traditional microscopy techniques and play an outsized role in degrading thermal performance.

Thorium has been considered a potential nuclear fuel for decades. To develop evaluation method for high-temperature properties of thorium dioxide as a candidate nuclear fuel, we perform first-principles molecular dynamics. The calculated enthalpy and thermal expansion agree well with the observed data. The Bredig transition temperature also coincides with experiments. Our results indicate that this method can provide reliable data of thermal properties of nuclear fuels.

Thorium based fuels offer several benefits compared to uranium based fuels thus they might be an attractive alternative to conventional fuel types. This study is devoted to the synthesis and the characterization of small thorium dioxide microspheres (O

The effect of thorium addition on the thermophysical properties of uranium dioxide has been systematically investigated by molecular dynamics (MD) simulation technique in the whole concentration range of thorium and in the temperature range from 300 K to 2100 K. The Born-Mayer-Huggins (BMH) interatomic potential with the partially ionic model (PIM) was used and the potential parameters of thorium ion are derived from the experimental lattice constants data of thorium dioxide by the three point method. The predicted lattice parameter, thermal expansion coefficient, enthalpy, specific heat capacity, and thermal conductivity for the U1-yThyO2 solid solution all agree well with the available experimental data. The results indicate a significant effect of thorium content on the thermophysical properties of the U1-yThyO2 solid solution. The lattice parameters are increasing with the thorium content and closely followed Vegard's law, while the thermal expansion coefficient and enthalpy as well as specific heat capacity decrease very clearly with the thorium content. On the other hand, it is found that the U1-yThyO2 solid solution exhibits lower thermal conductivity than both the pure UO2 and ThO2. Additionally, a series of consistent equations for the thermophysical properties of U1-yThyO2 solid solution are recommended based on the MD data. Keywords: U1-yThyO2 solid solution, MD, Thermophysical properties

In this research, two different types of sinterable ThO2 nanopowders were synthesized by surfactant assisted sol–gel process using thorium nitrate as a starting material, and Triton X100 and Polysorbate 80, as two different structure directing agents. Both of the prepared gels were dried and characterized by thermogravimetry–differential scanning calorimetry (TGA–DSC) and X-ray diffraction (XRD). The dried gels were finally calcined and, the produced powders were subjected to XRD, Brunauer–Emett–Teller (BET), Barret–Joyner–Halenda (BJH) analyses and SEM studies. Detailed analyses show that thorium dioxide powders of different crystallite sizes, surface areas, pore volumes and sizes and sinterabilities were prepared using two different surfactants. This synthesizing route yielded the well crystallite nano-sized ThO2 powders with relatively high surface area and good sinterability at low temperature of 1400 °C. The powder synthesized using Triton X100 surfactant exhibited higher surface area, pore volume, pore size and crystallite size. It contained some aggregated particles along with the smaller seeds. Furthermore, the pellet which is fabricated by powder synthesized using Triton X100 had a higher density and better grain growth, to some extent.

WOS: 000388432000001, Nuclear spent fuel management is one of the top major subjects in the utilization of nuclear energy. Hence, solutions to this problem have been increasingly researched in recent years. The basic aim of this work is to examine the fissile breeding and transuranic fuel transmutation potentials of a gas cooled accelerator-driven system. In line with this purpose, firstly, the conceptually designed system is optimized by using several target materials and fuel mixtures, from the point of neutronic. Secondly, three different material compositions, namely, pure lead bismuth eutectic (LBE), LBE+natural UO2, and LBE+ 15 % enrichment UO2, are considered as target material. The target zone is separated to two sub-zones but as one within the other. The outer sub-zone is pure LBE target, and the inner sub-zone is either UO2 or pure LBE target.The UO2 target sub-zone is cooled with helium gas. Finally, the thorium dioxide mixed with transuranic dioxides, discharged from PVVR-MOX spent fuel, in pebbles composed of graphite and TRISO-coated spherical fuel particles, is used for breeding fissile fuel and transmuting transuranic fuels. Three different thorium-transuranic mixtures, (Th, Pu)O-2, (Th, Cm)O-2, (Th, Pu, MA)O-2, are examined with various mixture fractions. The packing fractions of the fuel pebbles in the transmutation core and the tristructural-isotropic coated fuel particles in a pebble are assumed as 60 % and 29 %, respectively. The transmutation core is also cooled with a high-temperature helium coolant. In order to produce high-flux neutrons that penetrate through the transmutation core, the target is exposed to the continuous beams of 1 GeV protons. The computations have been carried out with the high-energy Monte Carlo code MCNPX using the LA150 library. The numerical outcomes show that the examined accelerator-driven system has rather high neutronic data in terms of the energy production and fissile fuel breeding., Research Fund of the Erciyes University [FDK-2015-5811], This study is supported by the Research Fund of the Erciyes University, Project no. FDK-2015-5811.

Biological material itself appears with poor contrast in electron microscopy (EM), due to its composition mostly of light elements. Classical staining agents such as osmium tetroxide, uranyl acetate, and lead citrate preserve and/or stain cellular structures such as membranes, cytoplasm, and organelles well for EM. However, extracellular polymeric substances (EPS) show no or only poor contrast with these staining agents. The endothelial glycocalyx in blood vessels consists mainly of proteoglycans. It can be visualized by EM only by additional staining with heavy metal ions such as copper (Alcian blue, cupromeronic blue), ruthenium (ruthenium red), or lanthanum. Best results are achieved by combined perfusion of fixative and stain. Cationic hydrous thorium dioxide colloids (named here cThO2) trace acidic groups in EPS. We describe here the use of cThO2 to visualize the glomerular endothelial glycocalyx in the mouse kidney. cThO2 shows high electron density and binds to a continuous layer of up to a few hundred nanometers thickness on the glomerular endothelium, as well as on epithelia in other blood vessels in perfused animals. The observed staining pattern gives rise to periodic densities, with a spacing varying between 50 and 200 nm, depending on the overall layer thickness, which varies between below 50 up to 300 nm. Due to high electron density of the used cThO2 particles, the introduced method allows distinct imaging and precise fine structural analysis of the endothelial glycocalyx.

Thorium is most commonly precipitated as oxalate, because of the high efficiency regardless of precipitation conditions. Thorium oxalate readily decomposes into fine-grained ThO2 during heating, but keeps the macrostructure of the oxalate platelets. To assess the effects of precipitate macrostructure on the sintering behavior, different platelet morphologies were prepared and sintered. There are two factors which influence the sintering: the presence of holes within the platelets and the size of the platelets. Small platelets or precipitates with holes generally sinter to thorium dioxide pellets of a higher density and smaller grain size.

Thorium (Th) is a natural radioactive element present in the environment and has the potential to be used as a clean nuclear fuel. Relatively little is known about the aquatic toxicity of Th, especially in nanoparticulate form, which may be the main chemical species of Th in the natural waters. In this study, impacts of ThO

A 69-year-old man presented with sudden onset of pain in the right upper abdomen. An enlarged liver and jaundice were found by his family physician and he was referred to our University Hospital. In 1936, 49 years previously, he underwent angiography of the left forearm with a contrast medium of undocumented type for evaluation of fracture in a hospital of the Imperial Army. Laboratory data revealed elevated bilirubin (total 3.8 mg/dl, direct 2.7 mg/dl), elevated liver enzyme (AST 215KU, ALT 93 KU), anemia (RBC 332 × 10, Hb 11.0 g/dl, WBC 8600), platelet count 23.6 × 10, negative AFP, negative HBsAg and HBsAb, total protein 5.7 g/dl, erythrocyte sedimentation rate 22/h, and serum creatinine 1.6 mg/ml. On physical examination a small amount of ascites was noted. The liver was enlarged and palpated 3 finger-breadths below his right costal margin. The patient expired soon after radiography and CT with no further examinations. Radiography of the abdomen revealed enlarged liver and atrophic spleen containing radiopaque material (Fig. 1). Non-enhanced CT of the upper abdomen showed a large low-density mass in the liver, containing irregular streaky densities. Reticular high densities were also seen in the other areas of liver parenchyma. There were spotty increased densities at the hepatic port and around the pancreas. The spleen was markedly dense and atrophic, consistent with Thorotrast deposition (Fig. 2a–c). CT of the abdomen after administration of contrast medium showed irregularly enhanced areas in the round low-density mass in the right lobe of the liver, consistent with a solid neoplasm (Fig. 3d, e). There was also a moderate amount of ascites around the liver (Fig. 3f). Introduction

Uranium dioxide (urania, UO2) and thorium dioxide (thoria, ThO2) doped with gadolinium oxide (gadolinia, Gd2O3) were prepared via solid-state synthesis. For Gd2O3-doped ThO2, also an alternative, semi-dry process (“suspension coating”) was applied in which Gd2O3-coated ThO2 powder was produced via suspension drying followed by calcination. The microstructure and homogeneity of the materials were investigated by ceramography, EPMA and XRD. Solid-state synthesis is a convenient method to produce Gd2O3-doped UO2. However, this route was found to be inappropriate to obtain Gd2O3-doped ThO2 with an acceptable microstructure and homogeneity. The suspension coating process reported in this work is a simple and practical method to overcome these issues.

Thorium based nuclear fuel is of immense interest to India by virtue of the abundance of Thorium and relative shortage of Uranium. Thorium metal tubes were being cold drawn using copper as cladding to prevent die seizure. After cold drawing, the copper was removed by dissolution in nitric acid. Thorium does not dissolve being passivated by nitric acid. Initially the copper cladding was carried out by inserting copper tubes inside and outside the thorium metal tube. In an innovative development, the mechanical cladding with copper was replaced by electroplated copper with a remarkable improvement in thorium tube acceptance rates. Oxalate derived thoria powder was found to require lower compaction pressures compared to ammonium diuranate derived urania powders to attain the same green compact density. However, the green pellets of thoria were fragile and chipped during handling. The strength improved after introducing a ball milling step before compaction and maintaining the green density above the specified value. Alternatively, binders were used later for greater handling strength. Magnesia was conventionally being used as dopant to enhance the sinterability of thoria. The normal sintering temperature for magnesia doped thoria was 1600℃ - 1700℃, which was achieved in electrically heated molybdenum element sintering furnaces with reducing atmosphere. 0.25 mole percent addition of niobia to the thoria was found to bring down the sintering temperature to 1150℃. Sintering could be done in ordinary furnaces in air atmosphere using silicon carbide or Kanthal heating elements. Electrical conductivity was measured for both magnesia and niobia doped sintered thoria and used in interpreting differences in sintering behavior.

International audience; The synthesis of original crystalline thorium aspartate tetrahydrate, Th(C4NO4H6)4.4H2O, was performed using two different wet-chemistry routes, involving either L-asparagine or L-aspartic acid as complexing agent. Characterization of this compound through 13C NMR and PXRD led to confirm the terminal coordination mode of the aspartate group and to suggest a potential cubic lattice (Pn-3 space group). Vibrational spectroscopy data were also collected. The conversion of thorium aspartate tetrahydrate into thorium dioxide was further performed through classical high temperature heat treatment or under hydrothermal conditions. On the one hand, thermal treatment provided a pseudomorphic conversion which retained the starting morphology, and favored the increase of the average crystallite size, as well as the complete elimination of the residual carbon content. On the other, hydrothermal conversion could be used to tune the morphology of the final oxide, ThO2.nH2O microspheres being prepared when starting from L-asparagine.

Thorium-based nuclear reactors use thorium as fuel through breeding to uranium-233. The analysis of boron level in thorium fuels is essential due to the stringent specifications for boron. A method has been developed for the determination of trace boron in high-purity ThO2 powders. About 0.4000 g of ThO2 powder was added to a mixture of 4 mL concentrated HNO3 and a few drops of 0.5 % HF, then dissolved in a microwave digester. The solution was then heated to evaporate surplus HNO3 and HF, and then an amount of 3 M HNO3 was added and the solution was subsequently used for the chemical separation. By spiking a known amount of boron before the evaporation process, it was observed that recoveries of boron were near 100 % in this open heating step. 50 % (v/v) tri-n-butyl phosphate (TBP) using carbon tetrachloride as the diluent was used as the extractant. The number of extractions was optimized to reduce the thorium concentration in the aqueous phase to avoid spectral interference of thorium in the determination of boron by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The results of blank experiments showed that the limit of detection of the developed method was about 0.03 µg B/g ThO2. Samples of a high-purity ThO2 powder (ThO2 > 99.99 % by weight) were analyzed, and the results showed that the boron level was about 0.24 µg/g ThO2 and that the relative standard deviation (RSD) was about 10.5 % (n = 6). By spiking 0.10 µg boron (corresponding to 0.25 µg/g ThO2) into the ThO2 powders before digestion, it was found that the recoveries were in the range of 88–108 % (n = 6). These results indicated that the proposed method could meet the requirements for the determination of trace boron in high-purity ThO2 powders.

We report a facile method to synthesize monodisperse, uniform and size-controllable thorium dioxide nanoparticles via a hydrothermal precursor synthesis and a subsequent calcination treatment. Highly uniform spherical precursor nanoparticles with a tunable diameter of 38–274 nm and monodisperse irregular precursor nanoparticles with a size range of 20–45 nm can be successfully synthesized using thorium nitrate pentahydrate, urea and glycerol as the metal source, nucleation agent, and size-controlling agent, respectively. The chemical composition, growth process, and size control of the precursor nanoparticles have been systematically investigated, and a probable formation mechanism of these nanoparticles was also proposed. Calcination of precursor nanoparticles at 800 °C leads to the formation of uniform thorium dioxide nanoparticles without any morphological deformation. Furthermore, the size and shape effects of thorium dioxide nanoparticles on the uptake of dye molecules have been studied. The corresponding adsorption behaviors of as-prepared samples can be elucidated very well by the nitrogen adsorption–desorption analysis.

Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear light water reactors. Thorium can be found in pristine as well as irradiated MOX samples. In normal conditions this element is only present in one oxidation state (IV), therefore its characterization can be used as a solid base for later studies of other actinides with the same oxidation state. In this work, the atomic structure and nearest-neighbor environment of thorium within pristine and irradiated MOX samples were analyzed by micro-X-ray absorption fine structure (μ-XAFS) spectroscopy measured in fluorescence mode. To serve as a reference, spectra of pure thoria (ThO 2 ) powder samples were recorded. It was found that thorium is only present in its most common state (tetravalent) in both pristine and irradiated fuels. The structure of the thorium dioxide and MOX samples was modeled and their respective spectra were calculated. This modeling is consistent with the experimental conclusions.

Raman spectroscopic investigations were carried out on proposed nuclear fuel thorium dioxide–uranium dioxide (ThO2–UO2) solid solutions and simulated fuels based on ThO2–UO2. Raman spectra of ThO2–UO2 solid solutions exhibited two-mode behavior in the entire composition range. Variations in mode frequencies and relative intensities of Raman modes enabled estimation of composition, defects, and oxygen stoichiometry in these compounds that are essential for their application. The present study shows that Raman spectroscopy is a simple, promising analytical tool for nondestructive characterization of this important class of nuclear fuel materials.

Detection of gadolinium deposits in patients who have repeatedly been administered intravenous gadolinium chelates have given rise to concern regarding the long-term safety of magnetic resonance imaging (MRI) contrast media. Nevertheless, negative long-term clinical effects have not yet been observed. In some publications parallels have been drawn to the sequelae of thorotrast that was formerly used for arterial angiography. In this article the history of thorotrast use is briefly described and in particular why, despite warnings, this substance was used frequently and worldwide. A brief summary of the results of the German Thorotrast Study revealed that high excess rates were only observed for primary malignant liver tumors after a 15-year or longer latency period and to a lesser degree of leukemias, as well as for severe local complications due to paravascular injections, particularly in the neck region. Based on this historical review, we will venture to take stock of the outcome from the "success story" of this contrast agent.

A self-consistent model of thorium dioxide and its dilute alloys with cerium is developed. Thermal and elastic properties of ThO2 and several variations of Ce[Formula: see text]Th[Formula: see text]O2 synthesized by various techniques (powder processing and pelletization (POP) and coated agglomerate pelletization process (CAP) and using two different atmospheres, i.e., air or Ar[Formula: see text]H2 mixture) are simulated. The influence of porosity on degree of phonon anharmonicity and on the lattice properties (in particular, thermal conductivity) of the considered systems is analyzed.

Undoped and ThO2:Ln3+ (Ln = Nd, Ho, and Er) were synthesized by wet chemical route and characterized using X-ray diffraction (XRD). PAS was used to investigate electronic absorption of Nd3+, Ho3+ and Er3+ in thorium dioxide as well as of pure rare earth oxide powder Ln2O3 (Ln = Nd, Ho, and Er). PA spectra were also obtained for aqueous solution of lanthanides for evaluating various covalency parameters. Various covalency parameters like nephelauxetic ratio (β), covalency factor (b1/2) and Sinha parameter (δ) were evaluated for pure oxide powder and for rare earth doped thoria for all these system from their individual PA spectra.

Thorium dioxide doped with oxides of magnesium and calcium was prepared from deagglomerated mixed oxalates. The influence of the dopant oxide concentration (0.1, 0.25 and 0.5 mol% MO, M = Mg, Ca) on the powder properties was studied. The dependence of bulk density, specific surface area, X-ray crystallite size, residual carbon content and distribution of particle size on the dopant concentrations was investigated in detail. The transmission electron microscopy (TEM) investigations revealed that the powders comprised cuboidal agglomerates with a nanocrystalline substructure (10 nm). It was found that 0.5 mol% calcia doped thoria exhibits better sinterability than pure thoria and magnesia doped thoria at a temperature as low as 1673 K. Further, it was demonstrated for the first time that doping nanocrystalline thoria with calcia helps reduce the de-sintering phenomena.

Quantitative leaching of Sr from homogeneous and calcined (Th,Sr) O(2) in dilute perchloric acid medium suggests the possibility of reducing the hazardousness of discharged nuclear fuel by separation of (90)Sr, a prominent fission product at dissolution stage itself rather than the conventional approach of its recovery from high level nuclear waste. Apart from mitigating the radiotoxicity of the nuclear waste, recovered (90)Sr can be employed as a compact heat source and as parent radionuclide for (90)Y (used in therapy radiopharmaceuticals), provided it can be made available at desired high purity. Leaching behavior of few other fission products was also investigated to quantify their contamination in leached Sr. Feasibility of employing extraction chromatography using Sr selective resin was explored in perchloric acid medium. In this context, the distribution coefficients of (85)Sr(II), Th (IV), Zr(IV), Y(III), Pd(II) as well as (152)Eu(III) and (137)Cs (I) were determined under varying nitric acid/perchloric acid concentration and under varying loading conditions of metal ions. Perchloric acid medium appears better than nitric acid medium for preferential leaching of Sr from (Th,Sr)O(2) as well as for uptake of Sr by Sr selective chromatographic resin.

India is one of the few countries committed to expansion of nuclear power. In view of the abundance of thorium relative to uranium, thorium cycle is under serious development and implementation. Both ThO2 and (U,Th)O2 are used. Fine powders of the same are mostly prepared through the aqueous chemical route, pressed and sintered. Extrusion and hot impact densification are also being used. Sol-gel method and other alternatives are also being pursued with the advantage of automation and remote operation. Relevant papers on the thorium cycle with emphasis on processing methods and related aspects are reviewed here.

Two novel thoria (ThO2) nanoparticles-carbon paste electrodes were used to evaluate an anodic stripping voltammetric method for the direct determination of arsenite and total inorganic arsenic (arsenite plus arsenate) in water samples. The effect of Ag((I)), Cu((II)), Hg((II)), Sb((III)) and Se((IV)) ions on the electrochemical response of arsenic was assayed. The developed electroanalytical method offers a rapid procedure with improved analytical characteristics including good repeatability (3.4%) at low As((III)) concentrations, high selectivity, lower detection limit (0.1 μg L(-1)) and high sensitivity (0.54 μA μg(-1) L). The analytical capability of the optimized method was demonstrated by the determination of arsenic in certified reference materials (trace elements in natural water, trace elements in water and coal fly ash).