Thorium Dioxide Research Articles

Neutronic characteristics and feasibility analysis of micro-heterogeneous duplex ThO2-UO2 fuel pin in PWR

The shortage of natural uranium resources, nuclear waste disposal and nuclear proliferation issues are important constraints to the development of nuclear energy. The development and utilization of thorium fuel is an effective way to solve these problems. This paper analyses the neutron physical properties of micro-heterogeneous duplex fuel and compares them with UO2 fuel in terms of burnup depth, reactivity coefficients and radioactive waste. Additionally, the best grid of duplex fuel is explored as well.Results from this study show that the ThO2-UO2 duplex fuel can match the discharge burnup of UO2 fuel with the 235U enrichment greater than 5% but less than 20%. The reactivity was calculated at different levels of thorium dioxide fuel, and the rate of decrease in reactivity is lower for duplex fuel than for uranium dioxide fuel. Fuel temperature coefficient (FTC) and moderator temperature coefficient (MTC) are within the acceptable range specified for pressurized water reactors. Production of both weapons-grade plutonium and minor actinides are greatly reduced and the effect of fission nuclides breeding is significant. When the volume ratio of moderator to fuel is 3.27, the duplex fuel performs the best in burnup and the cycle burnup is greatly increased. It also has good performance on safety and nonproliferation issues under such grid condition.Physical calculations of assembly size were performed for 20% ThO2 duplex fuel at a volume ratio of moderator to fuel of 3.27 and compared them with the UO2 assembly calculations. Duplex fuel has higher cycle burnup and economy. Moreover, The negative FTC and MTC and the high control rod value of duplex fuel enable the reactor to be safe. Duplex fuel has a lower power peaking factor and a more uniform power distribution which are good for reactor operation.

Ultra-safe nuclear thermal rockets using lunar-derived fuel

Rocket launch failure rate is slightly higher than five percent. Concerned citizens are likely to protest against private-sector launches involving fission reactors. Yet, fission reactors can power long-duration lunar operations for science, observation, and in situ resource utilization. Furthermore, fission reactors are needed for rapid transport around the solar system, especially considering natural radiation doses for crews visiting Mars or an asteroid. A novel approach is to create nuclear fuel on the Moon. In this way, a rocket launched from the earth with no radioactive material can be fueled in outer space, avoiding the risks of spreading uranium across Earth's biosphere. A solution is to harvest fertile thorium on the lunar surface, then transmute it into fissile uranium using the gamma ray fog which pervades the deep sky. It is only at lunar orbit, at the very edge of cislunar space, that the Earth-launched machine becomes a nuclear thermal rocket (NTR). Thorium is not abundant, but can be concentrated by mechanical methods because of its very high specific density relative to the bulk of lunar regolith. Thorium dioxide (ThO2) has an extremely high melting point, such that skull crucible heating can be used to separate it from supernatant magma. When filled into a graphite-lined beryllium container (brought from Earth) and set out on the lunar surface, high-energy gamma rays will liberate neutrons from the Be. After moderation by the graphite, these thermal neutrons are captured by the thorium nucleus, which is transmuted into protactinium (Pa91). This element can be extracted using the THOREX process, and will then decay naturally into U-233 within two or three lunar days. The uranium is oxidized and packed into fuel pellets, ready to be inserted into a non-radioactive machine, which now becomes an NTR. Additionally, hydrogen can be extracted from deposits in permanently-shadowed regions on the Moon, providing reaction mass for the NTR. A novel method of solid-state hydrogen storage, which can be entirely fabricated using in situ resources, can deliver said hydrogen to the fission reactor to provide high and efficient propulsive thrust. These combined operations lead to an ultra-safe (for the Earth) means for private sector, commercial transport and power generation throughout the Solar System. With the hydrogen storage material used as radiation shielding for crewed spacecraft, and greatly-reduced transit times relative to chemical rocketry, this innovative approach could fundamentally transform how humans work, play, and explore in outer space.

Theoretical study of ThO2 by first principles calculations

In this paper, the thermodynamic, structural properties and vibrational spectrum of thorium dioxide have been studied using the Density Functional Perturbation Theory (DFPT) and Density Functional Theory (DFT) in the framework of first principles calculations. Quantum espresso software, which is an open source computing code, has been used in order to compute the kohn-Sham equations to obtain the minimum total energy of crystal. The vibrational spectrum of the thorium dioxide was examined along various symmetrical directions, and the results showed the dynamical stability of the crystal system. The quasi-harmonic Debye-Einstein model as implemented in GIBBS2 Code was used to calculate the thermodynamic properties of thorium dioxide at high temperatures and pressures. The simulation results showed that the Debye temperature of thorium dioxide decreased with increasing temperature at a constant pressure and increased with increasing pressure at a constant temperature. Increasing the Debye temperature indicated an increase in the crystal stiffness and the average sound velocity. It was observed that the volumetric thermal expansion coefficient and gruneisen parameter decreased exponentially with increasing pressure at a constant temperature, while increased with increasing temperature at a constant pressure, indicating an increase in heat transfer in the crystal lattice

An integrated experimental and computational investigation of defect and microstructural effects on thermal transport in thorium dioxide

Advanced nuclear reactor concepts aim to use fuels that must withstand unprecedented temperature and radiation extremes. In these fuels, thermal energy transport under irradiation is directly related to fuel longevity, reactor safety, and is arguably one of the most important performance metrics. Here we provide a comprehensive, first-principles-informed treatment of phonon mediated thermal transport in a defect-bearing actinide oxide with direct comparison to experimental measurements. Pristine and proton irradiated thorium dioxide was chosen as a model system to treat the complexity of thermal transport in the presence of lattice defects. A thermal transport model is implemented using the linearized Boltzmann transport equation (LBTE) with input from first principles calculations and defect evolution models. Density functional theory is used to calculate phonon dispersion in thorium dioxide and used as an input to calculate both intrinsic and extrinsic, defect-induced relaxation times. In addition, a defect evolution model is benchmarked using microstructure characterization of as-irradiated thorium dioxide using a combination of electron microscopy and optical spectroscopy. The output of the LBTE is compared directly to mesoscopic measurements of thermal conductivity on length scales commensurate with defect accumulation. Parametric measurements of conductivity with irradiation dose and temperature suggest a saturation in the reduction of thermal conductivity with increasing defect generation, which is partially captured in our defect evolution model and LBTE framework. This comprehensive, atomistic- to meso-scale treatment provides the necessary basis to investigate thermal transport under irradiation in more complex systems that exhibit strong electron correlation.

Production of high-purity ThO2 from monazite ores for thorium fuel-based reactor

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).

Two-step alkaline thorium dioxide precipitation A low waste method for highly sinterable ThO2

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 ThO 2 filters quickly and calcines to crystalline ThO 2 at low temperatures. As-precipitated ThO 2 contains significant quantities of adsorbed H 2 O and CO 2 , 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.

Thorium amidates function as single-source molecular precursors for thorium dioxide.

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.

Influence of field conditions on quantitative analysis of single crystal thorium dioxide by atom probe tomography

Atom probe tomography (APT), a 3D microscopy technique, has great potential to reveal atomic scale compositional variations, such as those associated with irradiation damage. However, obtaining accurate compositional quantification by APT for high bandgap materials is a longstanding challenge, given the sensitivity to field evaporation parameters and inconsistent behaviors across different oxides. This study investigates the influence of APT laser energy and specimen base temperature on compositional accuracy in single crystal thoria (ThO2). ThO2 has a broad range of applications, including advanced nuclear fuels, sensors, lasers and scintillators, electrodes, catalysis, and photonics and optoelectronics. The expected stoichiometry of ThO2 is achieved at APT base temperature of 24 K and laser energy of 100 pJ. To overcome mass resolution limitations associated with significant thermal tails, Bayesian methods are applied to deconvolute ion identity within the mass spectra. This approach affirms that the parameters chosen are appropriate for APT analysis of ThO2.

Insight into thorium dioxide could provide new energy applications

Microscale defects in thorium dioxide were found to have large effects on its thermal transport.

The influence of lattice defects, recombination, and clustering on thermal transport in single crystal thorium dioxide

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.

S2690 You Cannot Ignore Abdominal Dropsy: A Rare and a Fateful Presentation

INTRODUCTION: Angiosarcoma (AS) is a rare soft tissue sarcoma known to be one of the aggressive malignancies which carry a poor prognosis with 5- year overall survival reported at <43%. AS mainly originates from the breast (35%) and skin (20%), followed by soft tissue (13%) involvement. Hepatic AS accounts for only 0.5%–2% of primary hepatic malignancies. CASE DESCRIPTION/METHODS: A 56-year-old male presents with abdominal pain and 20-pound weight loss for the past two months. His abdomen appeared tense and distended. Results showed a hemoglobin 6.1 gm/dL, platelet count 63 × 103 /mm3, total bilirubin of 3.2 mg/dL, ALP 315 IU/L, AST 305 IU/L, ALT 209 IU/L, and albumin of 2.6 gm/dL. A CT of the abdomen showed multiple hypodense lesions in the liver, and spleen with the peripheral enhancement of the contrast [Figure 1A] suggestive of metastatic lesions. Colonoscopy was normal and EGD demonstrated multiple erythematous nodular lesions in the gastric body [Figure 1B] and duodenum [Figure 1C], biopsies of which were inconclusive. A CT guided liver biopsy showed small aggregates of anastomosing vascular channels with highly atypical cells suggestive of AS [Figure 2A]. Tumour cells were positive for CD-34 [Figure 2B] and focally positive for Factor VIII [Figure 2C]. The patient deteriorated very rapidly and died 2 weeks later due to cardiac arrest. DISCUSSION: Hepatic AS is more commonly seen in males (3:1) with a median age of the presentation around the 5th- 6th decade. Use of anabolic steroids, oral contraceptives, exposure to radiation, and chemicals like arsenic, vinyl chloride, and thorium dioxide are certain risk factors for the development of hepatic angiosarcoma. Often patients report non-specific symptoms such as abdominal pain, anemia, weight loss, fever, fatigue, however, can present with jaundice and ascites in case of advanced disease. Rare but spontaneous rupture of the liver and intraabdominal bleeding can also occur in patients with hepatic AS. Tumor size, visceral tissue involvement, the presence of necrosis, and metastatic disease at the initial presentation are some of the poor prognostic factors. CT angiography is the preferred imaging modality. Pathological diagnosis is often required. Median survival is approximately 6 months without any treatment. Surgery can be considered if they are localized to a lobe. Chemotherapy can be offered for palliation in cases of advanced and multifocal disease. Because of a high recurrence rate, liver transplant is generally not recommended for hepatic AS.Figure 1.: A. (From top to bottom) CT of the abdomen showed multiple hypodense lesions in the liver. B. EGD demonstrated multiple erythematous nodular lesions in the gastric body. C. EGD demonstrated multiple erythematous nodular lesions in theduodenum.Figure 2.: A: Liver biopsy showed small aggregates of anastomosing vascular channels with highly atypical cells suggestive of AS. B: Tumour cells positive for CD-34. C: Focally positive for Factor VIII.

Hydrothermal Conversion of Thorium Oxalate into ThO2·nH2O Oxide.

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.

Synthesis and Spark Plasma Sintering of Microcrystalline Thorium Dioxide for Nuclear Fuel Products

Thorium dioxide represents a future of the world market of nuclear fuel for fourth generation nuclear reactors. In this regard, the problems of technologies for thorium separation from irradiated fuel, its conversion into fuel raw materials, and fabrication of required quality fuel products need effective solutions. In this work the synthesis of microcrystalline mesoporous ThO2 powders through the deposition of the oxalate complex from nitrate solutions, and its consolidation by spark plasma sintering (SPS) technology has been studied. The influence of the SPS temperature ranging within 1000–1600°С on the ThO2 powder shrinkage dynamics, phase composition, microstructure, and density of pelletized ceramic products has been studied. Vickers microhardness parameters of samples have been determined. The results show that high-speed (minutes-taking) SPS consolidation of powders at 1600°C and 80 MPa can provide ThO2 ceramics with 92.5% theoretical density. Microcrystalline powders with particle sizes averaging 3-4 µm can be used as raw materials instead of less accessible nanoscale materials. The study shows the expediency and prospects of further studies with the view of SPS technology adaptation for the needs of the nuclear industry.

Microscopy and spectroscopy of plutonium dioxide aging under ambient and near-ambient conditions

Characterization of nuclear materials under controlled conditions promotes a better understanding of their chemistry and provides insight into their stability. Of particular importance is identifying how environmental and storage conditions affect both bulk and sub-bulk scale chemical and physical properties. Such data may provide insight for nuclear forensic applications and can help address fundamental safety and storage concerns. In this work, plutonium dioxide (PuO2) and thorium dioxide (ThO2) aging was studied as a function of temperature and relative humidity (RH) while simultaneously observing the effects of fluoropolymer containment. Morphological changes were monitored using scanning electron microscopy and interpreted utilizing a previously-published lexicon of descriptive imaging terminology. Changes in phase were observed using X-ray diffraction measured on a single-crystal X-ray diffractometer to permit sub-bulk scale (< 10 mg) analysis. Ancillary techniques, including energy-dispersive X-ray, infrared, Raman, and X-ray photoelectron spectroscopy, were used to further probe and interpret the observed aging effects. ThO2 materials exhibited no change in macroscopic appearance and microstructure, whereas PuO2 underwent transitions to mixed plutonium dioxide/plutonium fluoride hydrate and mixed plutonium dioxide/ammonium plutonium fluoride phases under ambient temperature at 81% RH and 45 °C at 81% RH, respectively. These results highlight important stability differences between actinide oxides and underpin the belief that further research is needed to elucidate the fundamental chemical and physical properties of many actinide compounds, like PuO2 and ThO2, near ambient temperatures and humidities.

Analysis of Mo-99 production as function of CAMOLYP reactor power

CAMOLYP or critical assembly for molly production is a nuclear reactor based on mixed uranium thorium fuels, which is currently being developed in BATAN Yogyakarta. This study aims to know how much the amount of 99Mo isotope production can be achieved on 6 days reactor operation as function of different power levels. The method is a calculation of reactor physics simulation by using MCNPX computer code. The calculation is done for the reactor core configuration of 23 thorium dioxide fuel rods in the outer ring with the total mass of 73.12 kg and 1.706 kg of 235U in the annulus. The analysis result shows that the CAMOLYP’s 99Mo production can be formulated as linear function of the reactor power level in watt. From the analysis result, it can be concluded that the CAMOLYP reactor can produce 39.91 curie 99Mo at 1000 watts and 6 days operations. This analysis result indicates that the CAMOLYP reactor as a low power reactor has succeeded in producing 99Mo isotope which is sufficient for domestic needs.

Conceptual Process to Produce ThO2 from Monazite

This study level process design represents an economically viable method for extracting thorium dioxide and other rare earth elements from monazite ore. This paper incorporates results from the 2019 capstone project from the honors Design Internship in Green Engineering in Chemical and Biomolecular Engineering. In this activity, senior students in Chemical Engineering at the University of Tennessee (UT) focused on the development and study of a process for the recovery of thorium dioxide and P2O5 from monazite. While not mandated, the process offers rare earth oxides as attractive byproducts. The project focused on recovery of byproducts rather than the creation or addition to waste streams. Additionally, (1) the process economics relied heavily on recovery of rare earth byproducts, (2) thorium handling portions of the process could be effectively segregated from rare earth and phosphate handling portions of the process, and (3) thorium and uranium content of waste streams should be carefully managed and eliminated where possible.

On Top of the Alveolar Epithelium: Surfactant and the Glycocalyx.

Gas exchange in the lung takes place via the air-blood barrier in the septal walls of alveoli. The tissue elements that oxygen molecules have to cross are the alveolar epithelium, the interstitium and the capillary endothelium. The epithelium that lines the alveolar surface is covered by a thin and continuous liquid lining layer. Pulmonary surfactant acts at this air-liquid interface. By virtue of its biophysical and immunomodulatory functions, surfactant keeps alveoli open, dry and clean. What needs to be added to this picture is the glycocalyx of the alveolar epithelium. Here, we briefly review what is known about this glycocalyx and how it can be visualized using electron microscopy. The application of colloidal thorium dioxide as a staining agent reveals differences in the staining pattern between type I and type II alveolar epithelial cells and shows close associations of the glycocalyx with intraalveolar surfactant subtypes such as tubular myelin. These morphological findings indicate that specific spatial interactions between components of the surfactant system and those of the alveolar epithelial glycocalyx exist which may contribute to the maintenance of alveolar homeostasis, in particular to alveolar micromechanics, to the functional integrity of the air-blood barrier, to the regulation of the thickness and viscosity of the alveolar lining layer, and to the defence against inhaled pathogens. Exploring the alveolar epithelial glycocalyx in conjunction with the surfactant system opens novel physiological perspectives of potential clinical relevance for future research.

Preparation of thorium dioxide nanofibers by electrospinning

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.

Preparation of thorium dioxide nanofibers by electrospinning

Preparation of thorium dioxide nanofibers by electrospinning

Infrared-active phonon modes in single-crystal thorium dioxide and uranium dioxide

The infrared-active phonon modes, in single-crystal samples of thorium dioxide (ThO2) and uranium dioxide (UO2), were investigated using spectroscopic ellipsometry and compared with density functional theory. Both ThO2 and UO2 are found to have one infrared-active phonon mode pair [consisting of one transverse optic (TO) and one associated longitudinal optic (LO) mode], which is responsible for the dominant features in the ellipsometric data. At room temperature, our results for the mode pair’s resonant frequencies and broadening parameters are comparable with previous reflectance spectroscopy characterizations and density functional theory predictions. For ThO2, our ellipsometry and density function theory results both show that the LO mode broadening parameter is larger than the TO mode broadening. This signifies mode anharmonicity, which can be attributed to the intrinsic phonon–phonon interaction. In addition to the main mode pair, a broad low-amplitude impurity-like vibrational mode pair is detected within the reststrahlen band for both ThO2 and UO2. Elevated temperature measurements were performed for ThO2 in order to study the mechanisms by which the phonon parameters evolve with increased heat. The observed change in the TO resonant frequency is in excellent agreement with previous density functional calculations, which only consider volume expansion of the crystal lattice. This suggests that the temperature-dependent change in the TO frequency is primarily due to volume expansion. The change in the main mode pair’s broadening parameters is nearly linear within the temperature range of this study, which indicates the intrinsic anharmonic scattering (via cubic anharmonicities) as the main decay mechanism.