Thorium Nitrate Solution Research Articles

Separation of lead-212 from natural thorium solution utilizing novel sulfonamide dibenzo-18-crown-6.

The extraction of lead-212 (212Pb) from radioactive thorium (Th) waste is immensely important, as it serves to mitigate environmental risks associated with radioactive waste and provides a vital source for medical isotopes. To economically extract 212Pb from thorium, we synthesized a novel extractant known as 2,13-disulfonyldiethylamine dibenzo-18-crown-6 (DSADB18C6). We assessed its performance in isolating Pb(II) by employing stable lead and optimizing the parameters of the extraction system. The results showcased an exceptional ability to extract Pb(II) efficiently. Within 10 minutes, using 20 mmol of DSADB18C6 and under conditions of 10 mg L-1 lead concentration (HNO3 = 0.5 mol L-1), the extraction efficiency reached up to 96.1%. Even after four rounds of stripping with 0.4 mol L-1 ammonium citrate, the efficiency remained at 90.2%. Moreover, the extraction stoichiometry and thermodynamics revealed that DSADB18C6 exhibited superior extraction performance compared to the commercial extractant 4',4'',(5'')-di-(tert-butyldicyclohexano)-18-crown-6 (DtBuDC18C6), in line with the density functional theory (DFT) calculation result. Furthermore, we successfully separated 212Pb from the thorium nitrate solution, maintaining radioactive equilibrium with its progeny. Gamma-spectroscopy confirmed a recovery yield of extraction exceeding 85.7%. This study presents a viable approach, underscoring the potential of DSADB18C6 as a promising extractant for the effective separation of 212Pb from radioactive thorium sources.

Isolation of 212Pb from natural thorium for targeted alpha-therapy

Targeted alpha-therapy (TAT) is increasingly attractive due to its extraordinary antitumor efficacy. However, the supply of α-emitters for TAT is insufficient and under control by a limited number of countries. 212Pb is a promising α-emitter with an optimal half-life (10.6 h) and favored decay chain. Of interest, 212Pb can be extracted directly from natural thorium, which may be abundant in the mining waste of rare-earth, uranium, etc. Indeed, radioactive thorium waste has been a longstanding environmental challenge that needs immediate action. Developing an on-demand and facile process to isolate 212Pb from natural thorium would be ideal to meet the above challenges, yet is difficult. In theory, the ratio of 212Pb to natTh is below 10−13 in commercially available thorium salts. As a pilot study, 2.2 MBq of 212Pb was successfully extracted from a 5 L solution of thorium nitrate by using a Pb-selective resin. The radiochemical purity of 212Pb is over 99.9% according to gamma-ray analysis. The purified 212Pb was applied to radiolabel a couple of peptides used in clinics (i.e. PSMA, TATE and FAPI-04), and the radiochemical yields are >85%. Of note, 212Pb can be repeatedly separated from the thorium solution every 2 days. In summary, a practical and scalable method was developed to isolate 212Pb for potentially clinical use, which may be of great importance as it does not require either cyclotron or nuclear reactor.

Gas cell studies of thorium using filament dispensers at IGISOL

Filament-based dispensers of thorium have been investigated at the IGISOL facility, Jyväskylä, for potential use as a thorium ion source for future collinear laser spectroscopy experiments. Several different filaments were manufactured in the Institute of Atomic and Subatomic Physics of TU Wien, with 232Th and 229Th prepared on tantalum substrates either by drying thorium nitrate solution or via molecular plating, while adding a layer of zirconium for oxide reduction. The filaments were characterized in a helium-filled gas cell by performing selective and efficient in-gas-cell resonance laser ionization and by analyzing the resulting ion beams by mass spectrometry. Additionally, the in-gas-cell laser ionization process of thorium was further characterized by wavelength scans, saturation measurements and by recording the temporal behavior of extracted ion pulses. Although an ion source was successfully created with mass-separated intensities over 106 ions/s, the required high filament temperature resulted in significant contributions from interfering impurities and deterioration of the filament structure.

The development of 228Ac isotopic generator

The paper describes a method of recovery of 228Ac tracer from an old thorium salt through sequential separation of 228Ra by sorption onto the MnO2-CTA disk from thorium solution followed by Ac/Ra separation using the Axionit 507 extraction chromatographic resin. It was shown that the optimal conditions of radium separation from thorium nitrate solution are pH 4.7–6.1 and EDTA as a complexing agent for thorium stabilization as Th4+ form at Th/EDTA molar ratio of 1:1. Since both 228Ra and 224Ra are separated from thorium solution, 25 days were calculated as the minimal time necessary for obtaining pure fraction of 228Ra. Separation of 228Ac from 228Ra generator solution by the Axionit 507 resin is possible at pH 2.4–2.9; actinium desorption can be performed by 4–10 mL of any mineral acid solution at pH 1–1.5. High selectivity of the Axionit 507 resin provided additional decontamination of 228Ra generator solution from 228Th. The 228Ac eluate with the average radionuclide purity of 98.8% containing no organic compounds and/or complexing agents was obtained.

Solid State Chemistry of Ten-Fold Coordinate Thorium(IV) Complexes with Oxalates in the Presence of Ammonium and Hydrazinium Ions

Double and triple thorium oxalates have been synthesized by successive evaporation of a solution of thorium nitrate, ammonium, or hydrazinium oxalate and hydrogen peroxide. Compounds M6Ca2Th2(C2O4)9·nH2O (M = NH4+, N2H5+) (1) were first accidentally obtained due to the unexpected presence of calcium as impurities in the thorium nitrate used. Further evaporation led to the M2Th2(C2O4)5·nH2O (M = NH4+, N2H5+) (2) precipitation. After an additional evaporation of 2 weeks, compounds (2) transform into M4Th(C2O4)4·nH2O (M = NH4+, N2H5+) (3). In the three compounds, thorium is coordinated by five bidentate oxalate ions. In (1) Th(C2O4)5 entities share an oxalate ion to form dimeric units further connected by Ca(C2O4)5 (M = NH4+) or Ca(C2O4)5(H2O) (M = N2H5+) entities to build three-dimensional (3D) frameworks. Compounds (2) exhibit a 3D honeycomb thorium oxalate framework. Compounds (3) contain chains of oxalate-shared Th(C2O4)5 entities, whereas, in solution, the compound (NH4)2Th2(C2O4)5·1.5H2O (2) reacts with oxalate ions and turns into compound (NH4)4Th(C2O4)4·4H2O (3); in the solid state the chains of the compound (3) condense to form the 3D framework of the compound (2) and release solid ammonium oxalate.

Homogeneous hydrolysis of thorium by thermal decomposition of urea

Abstract Thorium was precipitated homogeneously from a thorium nitrate solution by the thermal decomposition products of urea. The kinetics of the hydrolysis were studied at 90 and 100°C by pH measurement during the initial 5 h and the precipitation efficiencies of thorium and radium were measured over a 24 h period. Precipitation of the radium daughters was closely followed with the aim of co-precipitation of radium with thorium. The CO2 formed during urea decomposition dissolved in the solution, forming CO3 2− during the experiment upon reaching a sufficiently high pH level (>7). This allowed radium to co-precipitate partially, thus reducing the activity of the filtrate. After filtration or centrifugation, the precipitate is composed of nanocrystalline thorium dioxide (crystallite size ~10 nm), with weakly bound H2O and CO2.

The effect of precipitation and calcination parameters on oxalate derived ThO2 pellets

Thorium oxalate is easy to prepare, but the derived oxide powders retain the platelet morphology of the primary oxalate. This negatively impacts packing and sintering. If powder milling is to be avoided, powder synthesis needs to be optimized. That is the goal of this paper, where different precipitation strategies were used and their effect on powder characteristics and pellet synthesis was investigated. Oxalates prepared by adding a thorium nitrate solution to an oxalic acid solution proved most promising. Further optimizing of the calcination temperature revealed that with increasing calcination temperature the packing density improved significantly. This came at the cost of decreased early stage sintering and a higher frequency of end-capping during compaction. The calcination temperature at which the highest final density can be reached was dependent on the sintering cycle. Furthermore, the ThO2 powders had less surface area and thus adsorbed less gases during storage when calcined at higher temperatures.

Study on optimization of actinide oxalate precipitation process in a vortex flow reactor

ABSTRACTOxalate precipitation process is globally accepted and is the current choice for conversion of actinide nitrates to their oxides. A vortex flow reactor with magnetic stirrer is found to be a better option for a hassle-free operation of batch as well continuous actinide reconversion process. Utilization of magnetic stirrer as an alternate for the conventional mechanical stirrer eliminates corrosion-related issues as none of the metal parts are in contact with nitric acid as well as oxalic acid solution. Moreover, this alternative system ensures a maintenance-free process. Optimization of various process conditions in a vortex reactor was accomplished using cerium nitrate as a surrogate for actinide nitrate and the results obtained were compared with that of pitched blade mechanical stirrer. About 40 L of thorium nitrate solution was successfully precipitated by the optimized procedure in a vortex reactor.

Formation of local thorium silicate compound by electrochemical deposition from an acetone solution of thorium nitrate

The results of the study of local formation (diameter of deposited area is about 100 μm) of thorium oxide coatings on SiO2/Si(001) surface by electrochemical deposition are presented. It was found that the electrochemical deposition of thorium atoms from an acetone solution of Th(NO3)4 on silicon surface lead to the formation of thorium-based films. The results of surface analysis by local X-ray photoelectron spectroscopy and X-ray photoemission indicate that these films contain of thorium-, silicon-, oxygen- and carbon-based compounds. After 30 h of annealing at 1350 °C in atmosphere carbon pulled completely, and the compound transforms into thorium silicate films ThSiO4 (Huttonite). Our primary study of ThSiO4 compound by reflection electron energy loss spectroscopy showed that this system have energy gap ~7.7 eV and can be useful for further research of «nuclear clocks» as well as for «nuclear battery».

UxTh1-x(C2O4)2 Solid Characterisation Studies

Many advanced reprocessing schemes under development are aimed at co-processing and co-conversion of actinides, unlike current reprocessing plants that produce separate uranium and plutonium products. The most well developed option for the co-conversion stage is probably oxalate co-precipitation, followed by the thermal co-conversion to a mixed oxide product. It is thus envisaged that future processes will avoid separation of plutonium from uranium and instead allow part of the uranium to flow with the plutonium, resulting in co-precipitation as the oxalate, and finally co-conversion to a mixed uranium-plutonium oxide (MOX), which can be fabricated into recycled nuclear fuel for further energy generation.The co-crystallisation of uranium (IV) and plutonium (III) into a single oxalate structure ensures the homogenous distribution of the two actinides at the molecular scale. The joint conversion of uranium and plutonium to the oxide form makes it possible to remove the complicated step of blending and grinding the two distinct oxide powders, as currently employed for the purposes of MOX fuel fabrication. This concept can also be extended to other actinides, including minor actinides from partitioning processes such as SANEX (Selective Actinide Extraction) and GANEX (Grouped Actinide Extraction) processes or even a thorium containing product from recycle of thorium based fuels.A selection of UxTh1-x(C2O4)2 solids at varying concentrations of uranium and thorium were prepared by oxalate co-precipitation. Uranium (VI) was conditioned electrochemically at -0.7 V to uranium (IV), in the presence of hydrazine. The reduced uranium (IV) in nitric acid was mixed with thorium nitrate solutions at different concentration ratios with oxalic acid. The mixed tetravalent uranium-thorium oxalate solid products have been characterised by Raman and IR spectroscopies. The influence of thorium substituted into the uranium oxalate structure was evaluated. Several vibrational modes were found to be affected by the variation in ionic radius appearing to be metal sensitive and therefore, provide the initial indication in the evaluation of the chemical composition.

Band structure and decay channels of thorium‐229 low‐lying isomeric state for ensemble of thorium atoms adsorbed on calcium fluoride

AbstractThe results are presented on the study of the electronic structure of thorium atoms adsorbed by the liquid atomic layer deposition from aqueous solution of thorium nitrate on the surface of CaF2. The chemical state of the atoms and the change of the band structure in the surface layers of Th/CaF2 system on CaF2 substrate were investigated by XPS and REELS techniques. It was found that REELS spectra for Th/CaF2 system include peaks in the region of low energy losses (3‐7 eV) which are missing in the similar spectra for pure CaF2. It is concluded that the presence of the observed features in the REELS spectra is associated with the chemical state of thorium atoms and is caused by the presence of uncompensated chemical bonds at the Th/CaF2 interface, and, therefore, by the presence of unbound 6d‐ and 7s‐electrons of thorium atoms. Assuming the equivalence of the electronic configuration of thorium‐229 and thorium‐232 atoms, an estimate was made on the time decay of the excited state of thorium‐229 nuclei through the channel of the electron conversion. It was found that the relaxation time is about 40 μs for 6d‐electrons, and about 1 μs for 7s‐electrons. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Local Electrochemical Deposition of Thorium on SiO2/Si(111) Surface

The paper presents the results of the study of local formation of thorium oxide coatings on SiO2/Si(111) surface by electrochemical deposition. It was found that the electrochemical deposition of thorium atoms from thorium nitrate solution of Th(NO3)4 with the presence of water on silicon surface results in local formation of thorium compounds. The results of surface analysis by local XPS indicate that these compounds represent a thorium-, silicon-, oxygen- and carbon-based compounds. After 6hours annealing at 600°C at atmosphere carbon pulled completely, and the cluster formed film consists of oxygen and thorium only. It was shown that this system can be promising for further research of nuclear low-lying isomeric transition in 229Th isotope when irradiated by an electron beam.

Preparation technique of thorium films by electrochemical deposition for nuclear optical frequency standard based on thorium-229

The increase of the accuracy of optical frequency standards by means of the development of nuclear clocks a novel frequency standard based on the nuclear transition to the long-living isomer nuclear state of Th-229 with energy ~7.6 eV is of great interest. The main problem is the fact that there are no experimental data on the direct measurement of the energy of the isomeric transition in Th-229, and the above result was obtained only by indirect measurements, and has great uncertainty. Low energy ion scattering spectroscopy might be used for more precision investigations of the isomeric transition in Th-229. It is caused by the fact that ion scattering spectra exhibit the fine structure determined by the target surface electronic structure. In the case of low energy nuclear transition it can give the information about the isomer nuclear state of Th-229. To prove this supposition it is necessary to prepare high quality samples with a high thorium surface coverage. An original preparation technique of the thorium films by electrochemical deposition from thorium nitrate solution on Si(111) substrate is reported. It was found that electrochemical deposition of Th on the semiconductor substrates leads to the formation of ThSiOx island films. The origin of the observed thorium films formation and the results on the investigation of 229Th and 232Th films on Si(111) surface by X-ray photoelectron spectroscopy and low energy ion spectroscopy discussed.

Apparent molar volumes and viscosity B-coefficients of caffeine in aqueous thorium nitrate solutions at T = (298.15, 308.15, and 318.15) K

Apparent molar volumes ϕ V and viscosity B-coefficients for caffeine in (0.00, 0.03, 0.05, and 0.07) mol · dm −3 aqueous thorium nitrate, Th(NO 3) 4, solutions were determined from solution density and viscosity measurements over the temperature range (298.15 to 318.15) K as function of concentration of caffeine and the relation: ϕ V ∘ = a 0 + a 1 T + a 2 T 2 , have been used to describe the temperature dependence of the standard partial molar volumes ϕ V ∘ . These results have been used to deduce the standard volumes of transfer Δ ϕ V ∘ and viscosity B-coefficients of transfer Δ B for caffeine from water to aqueous Th(NO 3) 4 solutions for rationalizing various interactions in the ternary solutions. The structure-making or breaking ability of caffeine has been discussed in terms of the sign of ( δ 2 ϕ V ∘ / δ T 2 ) P . The Friedman–Krishnan co-sphere model was used to explain the transfer volume of caffeine with increasing Th(NO 3) 4 molarity. The activation parameters of viscous flow for the ternary solutions were also discussed in terms of transition state theory.

Extraction kinetics of lanthanum(III), uranyl(VI), and thorium(IV) nitrates from water-salt solutions using a composite based on a polymeric support and tri-n-butyl phosphate at various temperatures

The extraction kinetics of lanthanum(III), uranyl(VI), and thorium(IV) nitrates from water-salt solutions using a composite based on a polymeric support and tri-n-butyl phosphate (TBP) were studied at 293.15–333.15 K. Interfacial diffusion (the film kinetics) is the rate-controlling stage of extraction. Mass transfer coefficients were determined, and their temperature dependence was used to estimate apparent activation energies Ea. The mass transfer coefficients increase in going from lanthanum(III), uranyl(VI), and thorium(IV) nitrate solutions to water-salt solutions containing 2 mol/L sodium nitrate or with rising temperature. Ea is independent of the metal ion and the supporting electrolyte concentration; Ea = 25 ± 1 kJ/mol. At a fixed temperature, the increasing order of the mass transfer coefficients is as follows: thorium(IV) < uranyl(VI) < lanthanum(III).

An XRD and Fourier-transformed infrared spectroscopy investigation of single and mixed γ-alumina and thorium oxide

Mixed γ-alumina and thorium oxide samples were prepared with various compositions (100, 95, 90, 80, 50, 25, 15, 5 and 0 wt%, respectively) by addition of a solution of thorium nitrate to a slurry solution of aluminum isopropoxide [Al(OC 3H 7) 3] in deionized water. Mixed oxides (slurry solution) were heated at 120 °C (oil bath) for 24 h with mixing (for uniform distribution of oxides and to remove excess water) followed by calcinations at 600 °C for 6 h. New Fourier-transformed infrared spectroscopy (FTIR) absorption bands and the absence of crystallinity demonstrated by XRD analysis clearly show that γ-alumina and thorium oxide are mixed chemically and on atomic scale during the calcination period. The mechanically mixed oxide retained crystallinity and do not show mixing on the atomic scale. The evaluation for the catalytic activity of single or the chemically mixed catalysts for the dehydration of 2-hexanol and 1,2-diphenyl-2-propanol was investigated. The infrared spectrum of γ-alumina calculated by AM1 method show absorption pattern similar to FTIR.

Solubility of crystalline thorium dioxide

SummaryThe solubility of thorium oxides of different crystallinity is investigated at 25°C by different experimental approaches. The dissolution of bulk crystalline ThO2(cr) is a very slow process and the Th(IV) concentrations measured after one year at pH 1-3 in 0.1 and 0.5M HCl-NaCl solutions do not represent equilibrium data. Coulometric titration of thorium nitrate solutions in the low pH range of 1.5-2.5 leads to the formation of microcrystalline ThO2·xH2O(mcr) particles which subsequently agglomerate to a precipitate. The solubility of this solid, in equilibrium with Th4+(aq), is measured from the oversaturation direction. The solubility product is determined to be logK´sp=-49.9±0.4 in 0.5M NaCl corresponding to logK°sp=-53.2±0.4 (converted toI=0 with the SIT). It is close to the thermochemical value for ThO2(cr) and about 6 orders of magnitude lower than that of X-ray amorphous Th(IV) hydroxide or hydrous oxide. The differences in the solubility products are discussed with regard to the particle size and compared with analogous data for U(IV), Np(IV) and Pu(IV).Above the threshold of hydrolysis of Th4+at pH&gt;2.5, the dissolution of microcrystalline ThO2·xH2O(mcr) is found to be irreversible. In near-neutral to alkaline solutions, the measured thorium concentrations approach those of amorphous Th(OH)4(am). Similar results are obtained with crystalline ThO2(cr) in 0.5M NaCl-NaOH solutions. The solubility is not controlled by the bulk crystalline solid but by amorphous fractions on the surface.

Preparation of highly pure thorium nitrate via thorium sulfate and thorium peroxide

A simple alternative and selective method has been proposed for the preparation of thorium nitrate using as raw material a hydrated crystalline technical grade thorium sulfate. This salt was produced industrially [1] from the alkaline chemical processing of monazite sand in S. Paulo. From a crude thorium hydroxide as the raw material containing uranium and rare earth elements was prepared a technical grade thorium sulfate [Th(SO 4) 2.9H 2O]. A typical analysis of this salt had shown the following composition: ThO 2 47–53%, R 2O 3 (rare earth oxides) 0.5–0.9%, and UO 3 0.01% and minor amounts of iron, titanium, phosphorus, and silicon oxides. The thorium sulfate is dissolved into water and the thorium peroxide is precipitated from acidic medium by addition of hydrogen peroxide. The thorium peroxide is filtered, washed and finally dissolved with nitric acid. Samples of the thorium peroxide were dried and fired to ThO 2 and aliquot of the thorium nitrate solution was evaporated to dryness and calcined to obtain the ThO 2. Both ThO 2 have high purity (>99.5%). The content of total rare earth elements is very low (0.23% as oxide). Uranium was not detected. The great majority of the RE is precipitated and recovered from the filtrate by oxalic acid.

Physical properties of thorium oxalate powders and their influence on the thermal decomposition

Thorium oxalate dihydrate powders were obtained by precipitation from thorium nitrate solution using oxalic acid in the presence of ultrasound and mechanical agitation. Properties measured included particle morphology, particle size and particle size distribution, and specific surface area. The thermal decompositions of the powders were investigated by using thermogravimetry and differential thermal analysis techniques. The result showed that the thermal decomposition stages of the thorium oxalate dihydrate obtained by mechanical and ultrasonic agitation are same. The decomposition reactions of the oxalates precipitated in the presence of ultrasound proceed in a narrower temperature interval, within a shorter period of time. The kinetic parameters for each stage were calculated.

Experimental Determination and Simulation of the Reactivity Effects and Reaction Rate Sensitivity to Different Ranges of Neutron Energy in Homogeneous Heavy Water Solutions of Thorium

The experimental and simulated results of reactivity effects and reaction rate sensitivity to different ranges of neutron energy in heavy water solutions of thorium nitrate are reported. The experiments were carried out at the MAKET critical plant at the Institute for Theoretical and Experimental Physics. The reactivity effects were measured by a critical experimental method using the experimental dependence of lattice reactivity variations as a function of heavy water levels in the core tank. The reaction rates and the functionals were measured in the experimental samples of 27Al, naturCu, and 232Th and of a many-composite Al + 55Mn + naturCu + 197Au + naturLu alloy. The experimental samples were measured using a Canberra comanufactured spectrometer (a GC-2518 Ge detector, a 1510 module, and a 1510 plate with software to emulate a multichannel analyzer on an IBM personal computer).The experimental run yielded macrodistribution of reaction rates R(n,γ)63Cu in the lattice, the reactivity effects induced by different thorium nitrate concentrations in the heavy water solution within the volume of the experimental setup, the reactivity effects induced by different heights of filling the experimental tank with the thorium nitrate solution, distribution of reaction rates R(n,γ)63Cu, R(n,γ)55Mn, R(n,γ)197Au, R(n,γ)176Lu, R(n,α)27Al, and R(n,γ)232Th within the experimental volume, and distributions of the functional σ(n,α)27Al/σ(n,γ)232Th within the experimental volume.All of the experimental data were simulated by the MCU code and partly by the TRIFON-TREC code. Therefore, it is possible to validate the applicability of the codes for simulating blankets of subcritical accelerator-driven facilities with independent circulation of a heavy water solution of thorium such that 233U buildup to replace the transmuted 239Pu can be studied.The results of the experiments and simulation are tabulated and displayed as plots.