ThO2 Research Articles

Molecular Transformations for Direct Synthesis of Thorium Dioxide Films

New Th(IV) complexes with high volatility were synthesized and applied as molecular single‐source precursors for chemical vapor deposition (CVD) of ThO2 thin films. The change in the steric profile of alkoxide ligands and concomitant reduction in the molecular weight of [Th(L)2(OR)2] (1‐OR, R = iso‐propyl (1‐OiPr) or tert‐butyl (1‐OtBu), L = N‐(4,4,4‐trifluorobut‐1‐ene‐3‐one)‐methoxyethylamide)) had a profound effect on the vapor pressure (at 10‐5 mbar) evident in the drop in sublimation temperature to 100 °C for the iso‐propoxide derivative against 130 °C observed for the tert‐(1‐OtBu). Hirshfeld surface analysis of both complexes showed different degrees of intermolecular H⋅⋅⋅F interactions responsible for the observed differences in the volatilities of the two complexes. Both mixed‐ligand compounds (1‐OiPr, 1‐OtBu) were applied in the CVD process to deposit thorium oxide thin films without any carrier or reactive gas that verified their suitability as single‐source precursors to ThO2 coatings. Thin films of ThO2 were grown at 500 °C and 600 °C on Si/SiO2 substrates, which showed presence of C, N, and F presumably originating from the incorporation of ligand fragments in the growing CVD deposits. Subsequent calcination of CVD‐grown ThO2 films at 800 °C in air led to phase pure ThO2 coatings with uniform morphology.

Multilateral evaluation of the effects of utilizing thorium oxide in the Bushehr VVER-1000 reactor

Abstract The use of thorium oxide in thermal reactors is currently being explored due to its promising outcomes. One primary concern is how to reduce the pollution of core components and nuclear waste. The inclusion of 232Th in the reactor leads to the production of 233U and decreases the formation of minor actinides. On the other hand, 238U increases the production of 239Pu, a toxic and strategically significant isotope, along with minor actinides. Therefore, the potential of thorium to reduce the production of 239Pu, one of the most harmful isotopes, can be assessed in the Bushehr VVER-1000 reactor. This study involved replacing some uranium in the Bushehr VVER-1000 reactor with 232Th. The research focused on examining the environmental impact of nuclear waste, including activity, chain reactions, and isotope levels, over a two-year period. The impact of the new fuel substitution was evaluated in the Bushehr reactor, which has a power of 3,000 MWth, in three scenarios: thorium addition to 1.6 % enriched assemblies, thorium addition to 2.4 % enriched assemblies, and thorium addition to 3.6 % enriched assemblies. These changes were analyzed in terms of nuclear waste contamination, plutonium production, fuel burn-up, and conversion ratio, and compared to the reactor using UO2 fuel. The simulation was conducted using the MCNPX 2.6.0 computational code and heterogeneous geometry. The results indicate that nuclear waste pollution decreased when thorium was added to the 1.6 % and 2.4 % enriched assemblies, but increased when added to the 3.6 % assemblies. Additionally, fuel burn-up increased with the addition of thorium in the 1.6 % and 2.4 % assemblies, but decreased in the 3.6 % assemblies. However, the conversion ratio increased in all cases. The fuel temperature coefficient (FTC), moderator temperature coefficient (MTC), and void coefficient (VC) were calculated and evaluated.

Inorganic metal oxide‐reinforced polymer‐based flexible inorganic nanocomposite for UV shielding applications

AbstractThis investigation reveals the successful incorporation of strontium‐doped thorium oxide (SrThO3) NPs into polyvinyl alcohol (PVA) polymer nanocomposites. The fabrication process of these PVA nanocomposites entails utilizing varying amounts (0.5, 1.0, 2.0, and 4.0 wt%) of SrThO3 nanofillers through a straightforward solution casting technique. The microstructure and overall structure of the resulting polymer nanocomposites were analyzed using powdered x‐ray diffraction for crystalline structure and Fourier transform infrared (FTIR) spectroscopy for molecular composition. The introduced SrThO3 nanofiller demonstrates a strong affinity for the hydroxyl groups present in the PVA polymer, a phenomenon validated through FTIR spectroscopy. In order to comprehend the impact of doping, the surface morphology of the PVA polymer nanocomposites underwent examination via scanning electron microscopy. The absorption and transmission of light were quantitatively assessed using UV–visible spectroscopy. The excitation and emission behaviors of electrons in both the PVA and SrThO3‐doped PVA nanocomposites were scrutinized through photoluminescence spectroscopy. Furthermore, the extent of UV light absorption was investigated by studying the degradation of methylene blue dye, a substance known for its sensitivity to UV light. Results indicate that the intentional incorporation of SrThO3 NPs significantly enhances UV stability.

Analytical Method Validation of Thorium in Ore Sample Using UV-Vis Spectrophotometer

Monazite contains several rare earth elements (REE) along with radioactive elements, i.e., thorium (Th) and uranium (U). Thorium content in monazite is several times higher than uranium. Monazite contains around 12% thorium oxide, but the thorium content in this mineral varies depending on location. To determine the thorium content in monazite, an appropriate and validated analytical method is needed so that the reliability of the test results can be trusted. Apart from that, method validation is one of the clauses in SNI ISO/IEC 17025:2017 that must be fulfilled by the laboratory to be certified and produce reliable data. This research aims to validate analytical methods for non-standard and modified methods that are likely to be used outside the scope. In this research, the method used to digest and analyze thorium in mineral samples refers to the ASTM E2941-14 method with several modifications. Therefore, the analysis method needs to be validated. Validation of the analytical method is carried out by testing several parameters such as linearity and working range tests, accuracy, precision (repeatability), Limit of Detection (LOD), and Limit of Quantitation (LOQ). The results of linearity, accuracy, and repeatability tests that meet the acceptance requirements can be used as a method of validation evaluation. The results of the method validation parameter test met the acceptance requirements, with the linearity test showing a coefficient of determination (R2) of 0.997, the accuracy test showing % a recovery value of 106.22%, and the precision (repeatability) test showing %RSD of 3.76% with LOD value is 0.650 mg/L, and LOQ is 0.724 mg/L. Based on the results of these parameter tests, the method for analyzing thorium in mineral samples was validated.

Preliminary analysis of the core design for Indonesia Micro Reactor (IMR-13)

The development of microreactor technology can meet the energy needs of specific regions of Indonesia’s underdeveloped, foremost, and outermost areas. One of the latest microreactor designs is the Indonesia Micro Reactor (IMR-13), which has seed and blanket fuel and 5MWt power generation. The IMR-13 reactor has characteristic design features for operation for as many as ten years without refuelling. The reactor core comprises integral fuel elements consisting of a heat pipe, fuel matrix, fuel cladding, and graphite moderator. There are two fuel element types: seed fuel elements with 19.75 % low-enriched uranium oxide and blanket fuel elements with thorium oxide – graphite reflectors on the bottom, sides, and top surround the reactor core. Side reflectors have moving parts that function to regulate reactor power. There are no active components in this reactor. Heat transfer occurs by natural circulation in the heat pipe to the molten salt pool and then from the molten salt pool to the steam generator. This research focuses on the neutronic aspect of the reactor, particularly in calculating the seed and blanket ratio to allow the reactor to operate for ten years with minimal power peaking factor. The selected variant model has 979 seeds and 294 blankets. The variation model has a value of excess reactivity at the beginning of the life of 937 pcm. Each value of the shutdown margin for system first and system second sequentially is 3020 pcm and 2994 pcm. The temperature reactivity coefficient is negative, implying inherent safety. At the end of life, the burnup value was achieved at 4.97 GWd/MTU with an excess reactivity of 271 pcm. A parameter analysis of the burnup characteristics will follow in the selected variant model. The parameters examined were the core power distribution, delayed neutrons, the fast fission factor, conversion ratio, and decay heat.

Neutronic evaluation for different external neutron sources in a Small-Subcritical fast reactor

This study proposes an optimized small-sized subcritical fast reactor with an external neutron source for actinide transmutation. The reactor integrates features of Accelerator Driven Systems (ADS) and Fusion-Fission Systems (FFS) based on Tokamak technology. Both external neutron sources were evaluated, one from fusion reactions and the other from spallation reactions in the designed small subcritical fast reactor. The analysis assessed neutron flux and actinide transmutation rates through fuel burnup simulations at 1200 K. The results underscore the significance of external neutron sources in subcritical systems, with the fusion-fission source presenting high actinide transmutation. The SSFR utilizes thorium oxide as fuel and Lead-Bismuth Eutectic (LBE) as coolant. Neutronic parameter comparisons between FFS and ADS neutron sources were conducted, showing advantages for actinide transmutation in the system with the FFS neutron source, which enhances transmutation, minimizing radiotoxicity. The neutronic parameters were obtained using the MCNP, while the MONTEBURNS code, which links the MCNP and the ORIGEN depletion code, was utilized to perform the fuel burnup simulations. The cross-section libraries were generated by the NJOY-2012 using the nuclear data library JEFF-3.3.

Investigating the effect of bedrock temperature on the design of a Brazilian deep geological repository for LEU and reprocessed fuel

The final stage of the nuclear fuel cycle involves the design of a disposal repository for spent fuel or high-level waste from reprocessing operations. Focusing on the back-end fuel cycle, this study investigated the impact of bedrock temperature on the disposal of traditional low-enriched fuel and two reprocessed fuels, in a hypothetical design of a Brazilian Deep Geological Repository (DGR). The reprocessed fuels taken into consideration in this study were transuranic fuel spiked with thorium oxide and a plutonium/uranium fuel mix. For all fuels, interim storage had previously taken place for 50 years. The appropriate spacing between adjacent canister was determined, and the effect of increasing the bedrock temperature until the maximum allowed temperature at the canister surface were estimated using the ANSYS code. Results showed a linear relationship between the two temperatures. The transuranic fuel cannot be disposed of under assumed conditions, while the plutonium/uranium fuel requires larger disposal areas than traditional low-enriched fuel. We estimated the total area of disposal required for different amounts of spent fuel and identified six regions for further studies based on simulation results, mean bedrock temperature data, and population density, primarily in the southeastern part of Brazil.

Evaluation of the acid leaching technique for recovery of U3O8 and ThO2 in niobium/tantalum slag

This study presented the recovery of uranium oxide and thorium oxide from aluminothermic slag from the metallurgical processing of columbite – a niobium/tantalum mineral with the presence of U3O8 and ThO2 – from a mining-industrial facility. The methodology consisted of sampling, comminution, and leaching using sulfuric acid. The head sample showed contents of (1.78 + 0.14) % for U3O8 and (3.66 + 0.04) % for ThO2. The metallurgical recovery reached values above 80% for the uranium oxide and above 70% for the thorium oxide for pH < 1.5 and process time greater than eight hours.

Optimization of 200 MWt HTGR with ThUN-based fuel and zirconium carbide TRISO layer

Abstract TRISO fuel particle using ZrC has better strength and resistance to high temperatures than SiC. Previous studies show that the ZrC layer, as a substitution of SiC within the TRISO layer of coated fuel particles, has an insignificant difference in the performance of the neutronic aspect. Further neutronic studies are required to obtain the best combination of thorium-based fuel with ZrC coating for HTGR. This study analyzed the neutronic performance of three types of thorium-based fuels, oxide, carbide, and nitride, for HTGR. The reactor design refers to the High-Temperature Test Reactor with some axial and radial fuel configuration adjustments. This reactor is designed to operate at 200 MWt and has been modified to use a ZrC layer as a substitute for the SiC layer on the coated fuel particles. The neutronic study is carried out using SRAC2006 code with JENDL 4.0 nuclear data library. Neutronic parameters analyzed include multiplication factor, power peaking factor, and neutron spectrum. Neutronic analysis results show that thorium nitride fuel’s multiplication factor (k eff) is better than other compared fuel types with k-eff 1.050, higher than thorium carbide, 1.004. At the same time, thorium oxide has been sub-critical. The power-peaking value of all materials is close to the ideal peaking value that is one. Other neutronic aspects, such as the neutron spectrum for three compared fuel types, have a similar trend.

On the confluence of ultrafast high‐temperature sintering and flash sintering phenomena

AbstractUltrafast high‐temperature sintering (UHS) and flash sintering are novel methods for rapid sintering of ceramics, often completed in just a few seconds. Here, we show that both also share two additional features: an abrupt rise in electrical conductivity, which is electronic, and electroluminescence. More fundamentally, both are related to phonon physics where MD calculations have shown that proliferation of phonons at the edge of the Brillouin zone can induce Frenkel pairs without the application of electrical fields. Here, we show that, indeed, heating without the application of electric field, can also induce flash: Rapid heating processes of thin films of an oxide‐salt deposited on silk fibers, with a propane torch, are shown to induce electronic conductivity, electroluminescence, and rapid sintering of the oxide. The discussion in this article harkens back to two inventions, more than a century ago, which can now be related to flash and UHS: (i) the Nernst glow lamp circa 1900, made from zirconia, and (ii) the Welsbach mantle, constituted from ceria doped thorium oxide, in the late nineteenth century. Thus, the confluence between high heating rate and electric field induced flash phenomena links the past to the new. The emerging question is how injection of phonons that has been shown to create Frenkels can further induce high electronic conductivity and electroluminescence in oxides. Both electronic conductivity and luminescence are likely related to the generation of electron–hole pairs.

Efficient prevention of cracking of external gelation-made thorium oxide microspheres by hydrothermal treatment

Efficient prevention of cracking of external gelation-made thorium oxide microspheres by hydrothermal treatment

Reactions of Thorium Oxide Clusters with Water: The Effects of Oxygen Content.

Thorium oxide has many important applications in industry. In this article, theoretical calculations have been carried out to explore the hydrolysis reactions of the ThOn (n=1-3) clusters. The reaction mechanisms of the O-deficient ThO and the O-rich ThO3 are compared with the stoichiometric ThO2 . The theoretical results show good agreement with the prior experiments. It is shown that the hydrolysis mainly occurred on the singlet potential surface. The overall reactions consist of two hydrolysis steps which are all favourable in energy. The effects of oxygen content on the hydrolysis are elucidated. Interestingly, among them, the peroxo group O2 2- in ThO3 is converted to the HOO- ligand, behaving like the terminal O2- in the hydrolysis which is transformed into the HO- groups. In addition, natural bond orbital (NBO) analyses were employed to further understand the bonding of the pertinent species and to interpret the differences in hydrolysis.

Facile Preparation of Macro-Microporous Thorium Oxide via a Colloidal Sol-Gel Route toward Safe MOX Fuel Fabrication.

The identification of new colloidal sol-gel routes for the preparation of actinide oxides, which have a homogeneous and accessible porosity that can easily be impregnated by any concentrated actinide solution, opens new perspectives for the preparation of homogeneous nuclear fuel for minor actinide transmutation. This homogeneity allows us to avoid "hot spot" formation due to the local accumulation of more fissile elements. Here, we report the preparation of macro-microporous ThO2 materials by a colloidal sol-gel route. Using a thorium salt with 6-aminocaproic acid as a complexing agent at a controlled pH, we were able to pilot the condensation of thorium hydroxo species forming colloids of tuned nanometric size and thus the sol stability. After a freeze-drying process to concentrate colloids and a thermal treatment allowing complexing agent removal and macroporosity formation by a brutal gas release during combustion, a loose packing of ThO2 nanoparticles with an ordered distribution of interparticular porosity and a fraction of nanometric crystallites, whose size depends on the initial colloidal size, were obtained. The sols, pastes, and final materials were characterized by small- and wide-angle X-ray scattering to determine the colloidal size and the final structure of the materials, which was also confirmed by transmission electron microscopy. The most promising material was finally successfully impregnated by a simulating minor actinide solution and thermally treated to prepare a mixed actinide oxide material. This safe technology, relying on the colloidal sol-gel process and the formulation of complex fluids forming tunable precursors, opens new perspectives for the reuse of nuclear waste solutions as new fuel.

Quantitative analysis of gadolinium in thorium oxide matrix using laser-induced breakdown spectroscopy

Quantitative analysis of gadolinium in thorium oxide matrix using laser-induced breakdown spectroscopy

Sequential Bond Dissociation Energies of Th+(CO)x, x = 3-6: Guided Ion Beam Collision-Induced Dissociation and Quantum Computational Studies.

Collision-induced dissociation (CID) of [Th,xC,xO]+, x = 3-6, with Xe is performed using a guided ion beam tandem mass spectrometer (GIBMS). Products are formed exclusively by the loss of CO ligands. Analyses of the kinetic energy-dependent CID product cross sections yield bond dissociation energies (BDEs) of (CO)x-1Th+-CO at 0 K as 1.09 ± 0.05, 0.82 ± 0.07, 0.63 ± 0.05, and 0.70 ± 0.05 eV, respectively. Different structures of [Th,xC,xO]+ were explored using various electronic structure methods, and BDEs for CO ligand loss from precursor [Th,xC,xO]+ complexes were computed. Both experimental and theoretical results corroborate that the structures of [Th,xC,xO]+, x = 3-6, formed experimentally are homoleptic thorium cation carbonyl complexes, Th+(CO)x. The nonmonotonic trend in experimental BDEs is reproduced theoretically, although ambiguities in the spin states of the x = 4-6 complexes (doublet or quartet) remain. BDEs calculated at the coupled cluster with single, double, and perturbative triple excitations (CCSD(T))/cc-pVXZ//B3LYP/cc-PVXZ (X = T and Q) level and a complete basis set (CBS) extrapolation agree reasonably well with the experimental values for all complexes. Thorium oxide ketenylidene carbonyl cations, OTh+CCO(CO)y, y = 1-4, were calculated to be the most stable structures of [Th,xC,xO]+, x = 3-6, respectively; however, these are not observed in our experiment. Potential energy profiles (PEPs) having either quartet or doublet spin calculated at the B3LYP/cc-pVQZ level suggest that the failure to observe OTh+CCO(CO)y, y = 1-4, is the result of a barrier corresponding to the C-C bond formation, making the formation of OTh+CCO(CO)y inaccessible kinetically under the present experimental conditions.

Effect of the thorium oxide content on the leaching of a mixed thorium-uranium oxide fuel

Leaching of uranium from uranium oxide fuel in contact with water can be a radiation hazard problem in the case of fuel cladding failure, either during nuclear reactor operation or in an interim storage, as well as in a final repository. One way to mitigate this is to reduce the solubility of the fuel matrix by the mixing uranium oxide with a compound which is less soluble but otherwise of similar properties. In this paper, the effect of thorium oxide content on the leaching of the uranium oxide matrix is investigated. The method was to study the leaching of the uranium oxide fuel matrix as a function of a varying content of thorium oxide, using materials manufactured by powder co-milling. It was found that the substitution of more than 25% UO2 with ThO2 reduces the matrix leaching by more than one order of magnitude in most of the different leaching solutions investigated. The substitution of 7% UO2 with ThO2 results in a reduction of matrix leaching by 10–90%, depending on the concentration of borate and dissolved oxygen in the leaching solution.

Study on Morphology and Chemical States of Surface Active Layer of Th-W Cathode.

The surface morphology and chemical states of W-2%ThO2 thermionic cathode during vacuum high-temperature treatment were investigated in this research. The W-2%ThO2 thermionic cathode was prepared by a solid-liquid doping method combined with high-temperature sintering. The morphology and distribution of thorium oxide were observed using a transmission electron microscope and scanning electron microscope. The chemical states of elements at different temperatures were analyzed by X-ray photoelectron spectroscopy. Results indicate that the surface morphology and chemical form of the alloy evolve with the increase of temperature. The matrix had a lamellar structure at low temperatures, and the surface was relatively flat. The samples were heated to 500 °C, 1100 °C, and 1300 °C for 1 h. During the heating process, thorium oxide changed from granular to spherical, and the matrix was recrystallized. As the heating temperature rises, diffusion channels appear inside the cathode. As the temperature increases, the high-priced tungsten gradually decreases, and the zero-valent tungsten content increases. The adsorbed oxygen left the cathode surface, and the lattice oxygen increased. The surface oxygen content decreased, and the thorium and tungsten content increased.

Extraction of Thorium Oxide (ThO<sub>2</sub>) from Malaysian Monazite through Alkali Digestion: Physical and Chemical Characterization Using X-Ray Analysis

Extraction of thorium oxide (ThO2) from monazite mineral specifically from Perak, Malaysia become a bright opportunity for the new income generation in Malaysia eventhough it is involved complex processing routes and require variety of chemicals. Monazite that is known as monazite-(Ce)-PO4 minerals, not just contain thorium, but it also consist rare earth elements (REE) such as cerium (Ce), neodymium (Nd), lanthanum (La) and gadolinium (Gd) and also associated with thorium (Th) and uranium (U) at about 7 wt% and 0.2 wt% respectively. One of the challenges in this R&D work is to determine the presence of thorium, uranium and REE at each processing step due to its similarities of chemical composition and physical properties. Therefore, the aim of this paper is to use several x-ray characterization techniques to identify elemental composition obtained at each processing route to show the evidence of the presence of ThO2 extracted from Malaysia monazite. This paper focused on the use of wavelength dispersive x-ray fluorescence (WDXRF), field emission scanning electron microscope (FESEM) with energy dispersive x-ray (EDX) and x-ray diffraction (XRD) spectrometer to show evidence of ThO2 formation. Result shows that the final product contain of 85 wt% of ThO2 and it is thorianite with nanorod morphology. Thus, conforming that the feasibility of the current processing route to produce ThO2 from Malaysia monazite.

Experimental and computational investigation of the bond energy of thorium dicarbonyl cation and theoretical elucidation of its isomerization mechanism to the thermodynamically most stable isomer, thorium oxide ketenylidene cation, OTh+CCO.

Collision-induced dissociation (CID) of [Th,2C,2O]+ with Xe is performed using a guided ion beam tandem mass spectrometer (GIBMS). The only products observed are ThCO+ and Th+ by sequential loss of CO ligands. The experimental findings and theoretical calculations support that the structure of [Th,2C,2O]+ is the bent homoleptic thorium dicarbonyl cation, Th+(CO)2, having quartet spin, which is both thermodynamically and kinetically stable enough in the gas phase to be observed in our GIBMS instrument. Analysis of the kinetic energy-dependent cross sections for this CID reaction yields the first experimental determination of the bond dissociation energy (BDE) of (CO)Th+-CO at 0 K as 1.05 ± 0.09 eV. A theoretical BDE calculated at the CCSD(T) level with cc-pVXZ (X = T and Q) basis sets and a complete basis set (CBS) extrapolation is in very good agreement with the experimental result. Although the doublet spin bent thorium oxide ketenylidene cation, OTh+CCO, is calculated to be the most thermodynamically stable structure, it is not observed in our experiment where [Th,2C,2O]+ is formed by association of Th+ and CO in a direct current discharge flow tube (DC/FT) ion source. Potential energy profiles of both quartet and doublet spin are constructed to elucidate the isomerization mechanism of Th+(CO)2 to OTh+CCO. The failure to observe OTh+CCO is attributed to a barrier associated with C-C bond formation, which makes OTh+CCO kinetically inaccessible under our experimental conditions. Chemical bonding patterns in low-lying states of linear and bent Th+(CO)2 and OTh+CCO isomers are also investigated.

Malignant Vascular Tumors of the Head and Neck-Which Type of Therapy Works Best?

Simple SummaryMalignant vascular tumors are extremely rare tumors with variable clinical courses, and few data on their clinical management are available. Diagnosis is difficult due to their wide morphologic appearance. The intent of the present review is to demonstrate the current knowledge and management on malignant vascular tumors of the head and neck area. The mainstay of treatment for malignant vascular tumors is surgery, but radiotherapy and chemotherapy are also parts of the treatment concept especially in angiosarcomas. Targeted therapy, antiangiogenetic drugs and immunotherapy have been studied as new treatment options.Malignant vascular tumors of the head and neck are rare neoplasms with variable clinical presentation, wide age distribution, and variable clinical courses. The heterogeneous presentation of angiosarcomas and epithelioid hemangioendothelioma often leads to misdiagnosis and unsuitable treatment. While risk factors for angiosarcomas are previous radiation, chronic lymphedema, and exposure to arsenic, thorium oxide, or vinyl chloride, there are only limited and retrospective data available on prognostic factors in EHE. In both angiosarcomas and EHE, surgery is the mainstay of treatment. There is limited evidence regarding the role of radiotherapy in EHE, although EHE is considered relatively radiosensitive. In angiosarcomas, adjuvant radiotherapy is recommended according to retrospective case series. A standard medical therapy for metastasized malignant vascular tumors is lacking. Chemotherapy, which is effective in angiosarcoma, is mostly ineffective in EHE. Targeted therapy, antiangiogenetic drugs and immunotherapy have been studied as new treatment options. The goal of this review is to summarize the current data regarding malignant vascular tumors along with their diagnosis and management.