Thorium Alloys Research Articles

First Principles Study of the Structure and Elastic Properties of Thorium Metal

ABSTRACTThorium has long been considered a possible source of fuel for use in power generating nuclear reactors. While much attention and interest have focused on thorium oxide, metallic thorium alloys were investigated in the past as fuel candidates for fast and thermal breeder reactors. In this work, thorium’s two solid allotropes (face centered cubic α and body centered cubic β) are modelled using Density Functional Theory (DFT). The Vienna Ab Initio Simulation Package (VASP) is used to determine structural and elastic properties, as well as the density of states. The Voigt-Reuss-Hill approximations are used to predict the phases’ bulk moduli, shear moduli, Young’s moduli, and Poisson’s ratios. Four exchange-correlation potentials are used and compared. These are the LDA, the PBE-GGA, the RPBE, and the PBEsol. All potentials showed relatively good accuracy when predicting the lattice constant. The RPBE was the most accurate, slightly over predicting by < 0.2%. The RPBE and the PBE-GGA were the most accurate in predicting elastic properties, performing almost equally, while slightly over predicting most values.

Microstructural evolution of as-cast Th–U alloys

Microstructural evolution of as-cast (arc-melted) microstructures of selected compositions of Th–U alloys is investigated. Characterizations are done using XRD, optical microscopy, SEM, TEM and hardness measurement. Microstructures vary from single phase to biphasic with increase in uranium content in thorium. Uranium is present as spheroids (<1 μm) or islands (∼7 μm) in high thorium (<10.7 wt.% U) alloys. With further increase in uranium content it forms an interconnected network of uranium rich phase and gets interspersed with similar network of thorium rich phase. High uranium Th–U alloys has dendrites of thorium dispersed in uranium rich phase. Grain size refinement of thorium rich phase is effective up to ≤10.7 wt.% uranium addition. Hardness of Th–U alloys increases with increase in uranium content. Comparatively lower hardness observed in Th–96U is due to presence of softer eutectic colonies in the microstructures. High thorium alloys have potentials for being utilized as dispersion type fuel with fissile uranium spread in thorium matrix.

Peculiarities of fuel cycle with advanced composite fuel for thermal reactors

The use of dispersion type fuel elements, with high uranium content such as, U–Mo, U–Nb–Zr, U3Si, with a Zr alloy matrix (“advanced metmet”), is considered instead of a UO2 base type fuel for thermal reactors. Such fuels were fabricated and post-preparation analysed. In addition, composite, (U,Th)–PuO2 fuels were considered based on depleted uranium (or uranium, thorium alloy) and dioxide plutonium powder as the dispersion phases (a “cermet” analogue of heterogeneous MOX). Such fuel elements could be used in thermal reactors as low temperature fuels.Subsequently, a novel reprocessing strategy for composite fuel is proposed. This would allow the separation of uranium from burnt plutonium as well as the newly generated fissile plutonium from the burnt portion without chemical processes, with repeated use in CANDU/RBMK reactors. This would simplify the closure of the nuclear fuel cycle. By sequential use of the composite fuel, the generated Pu in spent fuel could be recycled in a more pragmatic way, reducing drastically the waste flow.

Thorium in tungsten: construction of interatomic EAM potentials from ab initio data

The interatomic interaction potential of tungsten and thorium crystals and those of hypothetical tungsten and thorium alloys within the embedded atom approach are considered. The corresponding Ansatz functions are fitted against full potential linear augmented plane wave data of real tungsten- and thorium- and hypothetical tungsten-thorium-crystals. The result is interatomic potentials, ready for use within classical molecular dynamics schemes. A cross check of the resulting force scheme derived by comparison of ab initio and classical molecular dynamics data is provided. Furthermore, we used the potentials to calculate the phonon dispersion relations, which then serve as an additional check.

Laser from Atomic Nuclei

A laser that emits visible light using atomic nuclei, rather than electrons, could be made from a thorium alloy. It could be a first step toward a gamma-ray laser.

Workplaces with natural radionuclides – investigation results from Bavaria

Abstract Since the amendment of the German Radiation Protection Ordinance in the year 2001 special workplaces with increased exposure due to natural terrestrial radiation have been subject to legal regulations. After the Radiation Protection Ordinance came into force the Bavarian Environment Agency informed all water supply facilities, breweries, dairies, mineral water manufactures, operators of underground workplaces and radon spas that the annual radon exposure of their staff has to be estimated. In Bavaria approximately 3330 companies with workplaces with exposure to radon were investigated. Herein the water supply facilities represented the largest group with 2550 companies. In about 96 % of all investigated companies the radon exposure of the staff is below the action level of 6 mSv per year. In 75 water supply facilities and two mines the radon exposure of the staff exceeded the action level (6 mSv/a) or the annual limit (20 mSv/a). Workplaces with increased exposure due to uranium and thorium are of secondary importance in Bavaria. Within the scope of a research project 13 companies were found, that still use thoriated welding electrodes. Only a few facilities use thoriated mantles, thorium alloys or natural thorium and uranium. The effective dose of all examined workers was below the action level of 6 mSv per year.

Flow-Through Dissolution of Uranium-Thorium Ore Dust, Uranium Concentrate, Uranium Dioxide, and Thorium Alloy in Simulated Lung Fluid

Flow-Through Dissolution of Uranium-Thorium Ore Dust, Uranium Concentrate, Uranium Dioxide, and Thorium Alloy in Simulated Lung Fluid

Flow-Through Dissolution of Uranium-Thorium Ore Dust, Uranium Concentrate, Uranium Dioxide, and Thorium Alloy in Simulated Lung Fluid

Flow-Through Dissolution of Uranium-Thorium Ore Dust, Uranium Concentrate, Uranium Dioxide, and Thorium Alloy in Simulated Lung Fluid

Superconductivity in amorphous actinide alloys

Superconductivity has been studied in amorphous binary alloys of actinides containing Co, Fe, and Ni. Amorphous thorium alloys have critical temperatures of up to 3.8 K and electronic properties similar to other transition-metal amorphous alloys. By contrast, amorphous uranium alloys have critical temperatures below 1.0 K and exhibit two unusual electronic properties: (1) The temperature coefficient of resistivity is quite large and negative (\ensuremath{\lesssim}-1.3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$/K) which is generally not found in other low resistivity (&lt;90\ensuremath{\mu}\ensuremath{\Omega} cm) amorphous alloys containing transition metals; (2) the upper critical-field gradient is the highest observed in bulk amorphous superconductors, up to 44 kOe/K. Based on the resistivity and critical-field gradient we estimate the renormalized density of states to be two to three times that of 4d and 5d amorphous superconductors. The possibility of strong spin fluctuation in these materials is discussed.

The electronic structure of glassy uranium and thorium alloys

We have studied the electronic structure of glassy Fe34U66, Co40U60, Ni33U67, Ni40U60 and Fe45Th55 by photoelectron spectroscopy and X-ray emission spectroscopy. The uranium alloys exhibit a narrow 5f band which remains pinned to the Fermi level. Also the binding energy shifts of the U 4f core levels on alloying are rather small. Therefore, we conclude that uranium has the same electronic configuration (5f3) in these U rich alloys as in U metal. Similarly to pure thorium, no occupied 5f states have been observed in Fe45Th55.

Methanol synthesis catalysts from thorium-copper intermetallics. Preparation and evaluation

Bureau of Mines research into the use of intermetallic compounds as catalytic materials has shown catalysts prepared from binary alloys of copper and thorium to be active for the synthesis of methanol from carbon monoxide and hydrogen. Activation of the alloys resulted in oxidation of the thorium yielding high surface area catalysts containing copper interspersed on thoria. For example, catalysts prepared from ThCu/sub x/ alloys by air oxidation at 400/sup 0/C had surface areas as high as 35 m/sup 2//g and produced up 6.7 times as much methanol as a traditional Cu/ZnO/Al/sub 2/O/sub 3/ catalyst from 16H/sub 2/:CO synthesis gas in a continuous-flow microreactor at 280/sup 0/C and 60 atm pressure. Standard inlet space velocity was 31,000 h/sup -1/.

Some phases in ternary alloys of thorium and uranium with the Al 4Ba-ThCu 2SI 2-type structure

The geometrical characteristics of Al 4Ba-ThCu 2Si 2-type phases are discussed briefly in terms of reduced cell parameters ( a R A ) . Special reference is made to those ternary compounds of Th and U which have this type of structure; the data already known from the literature and those now obtained for 21 new compounds are considered.

Thermodynamic properties of liquid alloys of thorium with aluminum

Thermodynamic properties of liquid alloys of thorium with aluminum

Alloys of thorium with certain transition metals VI. The constitution of thorium-nickel alloys containing 50–96% nickel

The thorium-nickel system has been studied over the composition range 50–96% nickel∗ at temperatures between 1000 ° and 1500 °C, or the liquidus where this was below 1500 °C, by metallographic and X-ray methods. A few alloys were annealed at 800 °C. Two intermetallic compounds not previously reported were observed at 63.5 ± 0.5% nickel (ThNi x ) and at 80.5 ± 0.5% nickel (ThNi 4). ThNi x forms by a peritectic reaction at 1037 ± 12 °C while ThNi 4 forms peritectically at 1212 ± 12 °C. Eutectics between ThNi and ThNi x and between ThNi 2 and ThNi 4 occur at 60 ± 0.5% and 69 ± 0.5% nickel, respectively. The eutectic temperatures are both in the range 1025°–1050 °C. There is some evidence to suggest that ThNi x decomposes at a temperature between 800° and 1000 °C but it was not possible to investigate this fully. ThNi 2 is an off-stoichiometric compound occurring at 64.75 ± 0.5% nickel and forms directly from the melt at 1062 ± 12 °C. The compound ThNi 5 occurs over a composition range of approximately 83.5–86.5% nickel at 1300 °C decreasing to 83.5–85.5% nickel at 1100 °C. The congruent melting of ThNi 5 above 1500 °C and the peritectic formation of Th 2Ni 17 were confirmed, the peritectic temperature being between 1300° and 1325 °C. Th 2Ni 17 forms a eutectic with nickel at 94 ± 0.5% nickel; this eutectic temperature was also between 1300° and 1325 °C.

Alloys of thorium with certain transition metals V. The ThOs 2ThIr 2 pseudo-binary system and some additional results on the thorium-iridium system

The ThOs 2ThIr 2 pseudo-binary system has been studied by X-ray and metallographic methods. The composition range of stability of the cubic C15-type phase was investigated and some information was obtained on the stability of other phases in the ternary system. Some new metallographic results on binary ThIr alloys containing 66–83% Ir ★ ★ All compositions are given as atomic percentages. are also reported.

Corrosion of thorium and thorium alloys and reactions with the environment

The published literature on reactions between metallic thorium and oxygen, nitrogen, air, hydrogen, and water vapor is briefly reviewed. For reactions with oxygen and nitrogen the reaction rate follows a parabolic-rate law at low temperatures, but is linear at higher temperatures. The change in reaction kinetics is apparently due to the process being diffusion controlled in the temperature range where the reaction layer is continuous but controlled by the reaction at the surface-layer base-metal interface at higher temperatures. The reaction rate between thorium and air was found to be linear from 100 to 900°C, while the reaction rate between thorium and hydrogen was parabolic up to 700°C. Observed reactions between thorium and its alloys and water vapor, acids, molten metals, organic coolants, and fluorine compounds are briefly reviewed. In addition several topics of interest to fuel-element designers such as the corrosion of defected fuel elements, and the compatibility of thorium alloys with cladding materials are summarized.

Magnetic Properties of Some Alloys of Thorium with Holmium and Erbium

Neutron diffraction studies have been carried out on a number of alloys of thorium with the heavy rare-earth metals Ho and Er, as part of an investigation of the nature of the exchange interaction in these materials. At room temperature, the heavy rare earths in question crystallize in the simple hcp structure; thorium, in the ccp structure. Alloys containing more than about 80 at. % rare earth are found in the hcp structure, and those with less than about 50 at. % are found in the ccp arrangement. The three outer electrons of the rare-earth metals (5d16s2) are presumed to form conduction bands, and it is generally accepted that magnetic coupling in the rare-earth metals occurs via an indirect interaction involving a polarization of the conduction electrons. Thorium, a tetravalent diluent (outer electron configuration 6d27s2), provides a means of changing the effective number of conduction electrons on alloying of the rare earths. In contrast to the effect of trivalent yttrium and lutetium as diluents, small additions of thorium tend to stabilize the ferromagnetic state in the hcp structure. Attempts at correlation of the results with the Ruderman-Kittel-Kasuya-Yosida theory have been made but with indifferent success.

Elastic Constants of Magnesium Thorium Alloy

The longitudinal and shear wave velocities in a polycrystalline sample of magnesium thorium alloy were measured by a pulse transmission technique as a function of temperature. Temperatures ranged from 25 C to about 350 deg C for longitudinal wave measurements and to about 220 deg C for shear measurements. The resulting velocity data were used to calculate various elastic properties of the material, including Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio. The resulting least squares fits for these data are: Longitudinal velocity, cl = 5.749 − 3.987 × 10−4T − 1.139 × 10−6T2mm/μsec; shear velocity, ct = 3.108 − 1.421 × 10−4T − 2.588 × 10−6T2mm/μsec; bulk modulus, B = 3.576 × 10″ − 2.744 × 107T + 1.187 × 105T2 dynes/cm2; Young’s modulus, E = 4.435 × 10″ − 1.415 × 107T = 6.037 × 105T2 dynes/cm2; shear modulus, G = 1.716 × 10″ − 7.994 × 106T − 2.619 × 105T2 dynes/cm2; Poisson’s ratio, σ = 0.293 − 6.459 × 10−6T + 3.392 × 10−7T2.

Alloys of thorium with certain transition metals IV. The systems thorium-iron and thorium-cobalt

The thorium-iron and thorium-cobalt systems have been studied over the whole range of compositions at temperatures between 800°C and the liquidus. In the thorium-iron system the occurrence of four intermetallic compounds is confirmed. Th 7Fe 3, ThFe 3 and ThFe 5 are formed peritectically at 962 ± 12° C, 1200 ± 12° C and 1212 ± 12° C respectively, while Th 2Fe 17 crystallizes directly from the melt at 1462 ± 12° C. Eutectics occur between Th 7Fe 3 and ThFe 3 at 45% iron∗∗ and 875 ± 12° C and between Th 2Fe 17 and iron at 94% iron and 1412 ± 12° C. There is no evidence that any of the compounds exist over a range of compositions. The occurrence of five compounds in the thorium-cobalt system is confirmed. Th 7Co 3, ThCo, ThCo 5 and Th 2Co 17 all crystallize directly from the melt at 1188 ± 12° C, 1137 ± 12° C, 1437 ± 12° C and 1462 ± 12° C respectively, while the composition of the compound previously designated ThCo 2–3 was found to be close to ThCo 3. It forms slowly by a peritectic reaction at 1125 ± 12° C. Eutectics occur at 1100 ± 12° C between thorium and Th 7Co 3, at 1037 ± 12° C between Th 7Co 3 and ThCo, at 975 ± 12° C between ThCo and “ThCo 3”, at 1300 ± 12° C between ThCo 5 and Th 2Co 17 and at 1387 ± 12° C between Th 2Co 17 and cobalt. The compound ThCo 5 occurs over a range of composition of approximately 4% at 1300°C decreasing to 2% at 1100°C.

The body-centred-cubic to face-centred-cubic phase transformation in thorium and some thorium-rich alloys

Abstract The fco (α) → bcc (β) phase transformation of thorium and several thorium-rich alloys has been studied by differential thermal analysis. Indium and silicon had no significant effect on the transformation temperature while aluminium, cerium, hafnium, uranium and zirconium lowered it. The results on thorium-cerium alloys are consistent with an inverse peritectic reaction at about 30 at % cerium and 1300° C and a revised form of the thorium-rich part of the thorium-cerium phase diagram is proposed. Thermal analysis and annealing and quenching results place the thorium/ Th3Si2 eutectic temperature at 1439 ± 8° C . The results on Th-U alloys indicate that uranium lowers the transformation temperature to a eutectoid at 1343 ± 17° C and that the solubility of uranium in α-thorium is approximately 2.7 at % at this temperature.