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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

The impact of feedstock size and composition on the hydrothermal growth of (U,Th)O 2

Bulk crystal growth of refractory oxides requires unique approaches, and the U x Th 1-x O 2 solid solution is no exception. Hydrothermal transport reactions of U 0.1 Th 0.9 O 2 onto ThO 2 seeds with feedstocks comprised of U 0.1 Th 0.9 O 2 or mixtures of UO 2 and ThO 2 with a nominal composition of U 0.1 Th 0.9 O 2 are investigated with µ-Raman spectroscopy and X-ray fluorescence. In each case, the trends in stoichiometry as a function of distance from the seed are analyzed and the deviations from the nominal stoichiometry discussed. When the feedstock is composed of mixed oxides, the particle surface area’s influence on the feedstock dissolution rate is the dominant factor and can produce U-rich stoichiometries as high as U 0.75 Th 0.25 O 2 . When composed solely of U 0.1 Th 0.9 O 2 , the total growth amount depends on the particle size, but the obtained stoichiometry is the product of differing solubilities. Although the U0.1Th0.9O 2 feedstock produces the most homogeneous growth, the ending growth of the smallest particle UO 2 /ThO 2 mixture yields the stoichiometry closest to U 0.1 Th 0.9 O 2 . How to obtain desired stoichiometries from mixtures by matching the particle size and solubilities is briefly discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2022

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–1 Th + –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.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Enrichment of the Galactic disc with neutron-capture elements: Gd, Dy, and Th

The study of the origin of heavy elements is one of the main goals of nuclear astrophysics. In this paper, we present new observational data for the heavy r-process elements gadolinium (Gd, Z= 64), dysprosium (Dy, Z= 66), and thorium (Th, Z= 90) in a sample of 276 Galactic disc stars (–1.0 < [Fe/H] < + 0.3). The stellar spectra have a high resolution of 42 000 and 75 000, and the signal-to-noise ratio higher than 100. The LTE abundances of Gd, Dy, and Th have been determined by comparing the observed and synthetic spectra for three Gd lines (149 stars), four Dy lines (152 stars), and the Th line at 4019.13 Å (170 stars). For about 70 percent of the stars in our sample, Gd and Dy are measured for the first time, and Th for 95 percent of the stars. Typical errors vary from 0.07 to 0.16 dex. This paper provides the first extended set of Th observations in the Milky Way disc. Here together with europium (Eu, Z= 63) data from our previous studies, we have compared these new observations with nucleosynthesis predictions and Galactic Chemical Evolution simulations. We confirm that [Gd/Fe] and [Dy/Fe] show the same behaviour of Eu. We study with GCE simulations the evolution of [Th/Fe] in comparison with [Eu/Fe], showing that unlike Eu, either the Th production is metallicity dependent in case of a unique source of the r-process in the Galaxy, or the frequency of the Th-rich r-process source is decreasing with the increase in [Fe/H].

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Laser Excitation of the Th-229 Nucleus

The 8.4 eV nuclear isomer state in Th-229 is resonantly excited in Th-doped CaF 2 crystals using a tabletop tunable laser system. A resonance fluorescence signal is observed in two crystals with different Th-229 dopant concentrations, while it is absent in a control experiment using Th-232. The nuclear resonance for the Th 4 + ions in Th: CaF 2 is measured at the wavelength 148.3821(5) nm, frequency 2020.409(7) THz, and the fluorescence lifetime in the crystal is 630(15) s, corresponding to an isomer half-life of 1740(50) s for a nucleus isolated in vacuum. These results pave the way toward Th-229 nuclear laser spectroscopy and realizing optical nuclear clocks. Published by the American Physical Society 2024

Physics↗
DOE OSTI2020

Materials Data on Th(GeAu)2 by Materials Project

Th(AuGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Au and eight equivalent Ge atoms. All Th–Au bond lengths are 3.46 Å. All Th–Ge bond lengths are 3.37 Å. Au is bonded to four equivalent Th and four equivalent Ge atoms to form a mixture of distorted edge, face, and corner-sharing AuTh4Ge4 tetrahedra. All Au–Ge bond lengths are 2.64 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Th, four equivalent Au, and one Ge atom. The Ge–Ge bond length is 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(FeGe)2 by Materials Project

Th(FeGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent Ge atoms. All Th–Fe bond lengths are 3.21 Å. All Th–Ge bond lengths are 3.21 Å. Fe is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ge atoms. All Fe–Ge bond lengths are 2.35 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Th and four equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(GePt)2 by Materials Project

Th(PtGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Pt and eight equivalent Ge atoms. All Th–Pt bond lengths are 3.34 Å. All Th–Ge bond lengths are 3.36 Å. Pt is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ge atoms. All Pt–Ge bond lengths are 2.54 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Th, four equivalent Pt, and one Ge atom. The Ge–Ge bond length is 2.47 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(GeRh)2 by Materials Project

Th(RhGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Ge atoms. All Th–Rh bond lengths are 3.35 Å. All Th–Ge bond lengths are 3.24 Å. Rh is bonded to four equivalent Th and four equivalent Ge atoms to form a mixture of distorted edge, corner, and face-sharing RhTh4Ge4 tetrahedra. All Rh–Ge bond lengths are 2.49 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Th, four equivalent Rh, and one Ge atom. The Ge–Ge bond length is 2.54 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(Al2Cr)4 by Materials Project

ThCr4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to eight equivalent Cr and twelve Al atoms. All Th–Cr bond lengths are 3.43 Å. There are four shorter (3.11 Å) and eight longer (3.22 Å) Th–Al bond lengths. Cr is bonded to two equivalent Th, two equivalent Cr, and eight Al atoms to form distorted CrTh2Al8Cr2 cuboctahedra that share corners with eight equivalent AlTh2Al6Cr4 cuboctahedra, corners with ten equivalent CrTh2Al8Cr2 cuboctahedra, edges with four equivalent CrTh2Al8Cr2 cuboctahedra, edges with four equivalent AlTh2Al6Cr4 cuboctahedra, faces with six equivalent CrTh2Al8Cr2 cuboctahedra, and faces with eight equivalent AlTh2Al6Cr4 cuboctahedra. Both Cr–Cr bond lengths are 2.51 Å. There are four shorter (2.59 Å) and four longer (2.72 Å) Cr–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to two equivalent Th, four equivalent Cr, and six Al atoms to form distorted AlTh2Al6Cr4 cuboctahedra that share corners with eight equivalent CrTh2Al8Cr2 cuboctahedra, corners with ten equivalent AlTh2Al6Cr4 cuboctahedra, edges with three equivalent AlTh2Al6Cr4 cuboctahedra, edges with four equivalent CrTh2Al8Cr2 cuboctahedra, faces with seven equivalent AlTh2Al6Cr4 cuboctahedra, and faces with eight equivalent CrTh2Al8Cr2 cuboctahedra. There are two shorter (2.74 Å) and four longer (2.86 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 10-coordinate geometry to one Th, four equivalent Cr, and five Al atoms. The Al–Al bond length is 2.80 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(NiGe)2 by Materials Project

Th(NiGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Th–Ni bond lengths are 3.21 Å. All Th–Ge bond lengths are 3.22 Å. Ni is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ge atoms. All Ni–Ge bond lengths are 2.39 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Th, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.57 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(SiRh)2 by Materials Project

Th(RhSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Si atoms. All Th–Rh bond lengths are 3.28 Å. All Th–Si bond lengths are 3.17 Å. Rh is bonded to four equivalent Th and four equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing RhTh4Si4 tetrahedra. All Rh–Si bond lengths are 2.44 Å. Si is bonded in a 9-coordinate geometry to four equivalent Th, four equivalent Rh, and one Si atom. The Si–Si bond length is 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(CuGe)2 by Materials Project

Th(CuGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Th–Cu bond lengths are 3.29 Å. All Th–Ge bond lengths are 3.22 Å. Cu is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ge atoms. All Cu–Ge bond lengths are 2.46 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Th, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.51 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(GeOs)2 by Materials Project

Th(OsGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Os and eight equivalent Ge atoms. All Th–Os bond lengths are 3.30 Å. All Th–Ge bond lengths are 3.31 Å. Os is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ge atoms. All Os–Ge bond lengths are 2.48 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Th, four equivalent Os, and one Ge atom. The Ge–Ge bond length is 2.58 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(MoO4)2 by Materials Project

Th(MoO4)2 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are five inequivalent Th4+ sites. In the first Th4+ site, Th4+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are three shorter (2.39 Å) and six longer (2.48 Å) Th–O bond lengths. In the second Th4+ site, Th4+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Th–O bond distances ranging from 2.18–2.74 Å. In the third Th4+ site, Th4+ is bonded to seven O2- atoms to form distorted ThO7 pentagonal bipyramids that share corners with seven MoO4 tetrahedra. There are a spread of Th–O bond distances ranging from 2.36–2.44 Å. In the fourth Th4+ site, Th4+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are three shorter (2.41 Å) and six longer (2.45 Å) Th–O bond lengths. In the fifth Th4+ site, Th4+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are six shorter (2.42 Å) and three longer (2.47 Å) Th–O bond lengths. There are six inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with two equivalent ThO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.76–1.82 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.77–1.84 Å. In the third Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with two equivalent ThO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.76–1.83 Å. In the fourth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with two equivalent ThO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.76–1.82 Å. In the fifth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share a cornercorner with one ThO7 pentagonal bipyramid. There are a spread of Mo–O bond distances ranging from 1.76–1.89 Å. In the sixth Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There is three shorter (1.77 Å) and one longer (1.86 Å) Mo–O bond length. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to one Th4+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted linear geometry to one Th4+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a water-like geometry to one Th4+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to one Th4+ and one Mo6+ atom. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one Th4+ and one Mo6+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Th4+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Th4+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a linear geometry to one Th4+ and one Mo6+ atom. In the ninth O2- site, O2- is bonded in a distorted linear geometry to one Th4+ and one Mo6+ atom. In the tenth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to one Th4+ and one Mo6+ atom. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to one Th4+ and one Mo6+ atom. In the thirteenth O2- site, O2- is bonded in a water-like geometry to one Th4+ and one Mo6+ atom. In the fourteenth O2- site, O2- is bonded in a distorted water-like geometry to one Th4+ and one Mo6+ atom. In the fifteenth O2- site, O2- is bonded in a distorted linear geometry to one Th4+ and one Mo6+ atom. In the sixteenth O2- site, O2- is bonded in a 2-coordinate geometry to one Th4+ and one Mo6+ atom. In the seventeenth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the eighteenth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(BRu)2 by Materials Project

Th(RuB)2 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Th is bonded in a 10-coordinate geometry to four equivalent Ru and six equivalent B atoms. All Th–Ru bond lengths are 3.02 Å. There are two shorter (2.88 Å) and four longer (3.08 Å) Th–B bond lengths. Ru is bonded in a 4-coordinate geometry to two equivalent Th and four equivalent B atoms. There are two shorter (2.09 Å) and two longer (2.16 Å) Ru–B bond lengths. B is bonded in a 7-coordinate geometry to three equivalent Th and four equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(BRh)4 by Materials Project

Th(RhB)4 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to twelve equivalent Rh and twelve equivalent B atoms. There are four shorter (3.03 Å) and eight longer (3.21 Å) Th–Rh bond lengths. There are eight shorter (3.07 Å) and four longer (3.21 Å) Th–B bond lengths. Rh is bonded in a 5-coordinate geometry to three equivalent Th and five equivalent B atoms. There are a spread of Rh–B bond distances ranging from 2.24–2.31 Å. B is bonded in a 6-coordinate geometry to three equivalent Th, five equivalent Rh, and one B atom. The B–B bond length is 1.79 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(Mg4Al3)4 by Materials Project

Th(Mg4Al3)4 is alpha-derived structured and crystallizes in the cubic I-43m space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to three equivalent Mg, one Th, and six equivalent Al atoms. All Mg–Mg bond lengths are 3.02 Å. The Mg–Th bond length is 3.36 Å. All Mg–Al bond lengths are 3.23 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to seven Mg and five equivalent Al atoms. There are two shorter (3.11 Å) and four longer (3.18 Å) Mg–Mg bond lengths. There are a spread of Mg–Al bond distances ranging from 2.85–3.19 Å. Th is bonded in a 12-coordinate geometry to four equivalent Mg and twelve equivalent Al atoms. All Th–Al bond lengths are 3.25 Å. Al is bonded in a 11-coordinate geometry to seven Mg, one Th, and three equivalent Al atoms. There are one shorter (2.74 Å) and two longer (2.80 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Preliminary Insights Into the Feasibility of Determining the Purification Date of Enriched Uranium by Direct Measurement of the 230 Th/ 234 U Ratio Using an All-Faraday Detector Configuration on the Neoma MC-ICP-MS

Rationale: Mass spectrometric measurement of the 230 Th/ 234 U ratio to calculate the purification age of enriched uranium is typically conducted via a combination of ion counters and faraday detectors, thus requiring an inter-detector calibration scheme. Here, our aim is to understand whether the pursuit of a simplified measurement scheme involving only faraday detectors is feasible. Methods: We investigate the possibility of determining U-Th model ages for two enriched uranium standards (NBL U630 and U850) by direct measurement of the 230 Th/ 234 U ratio (without chromatographic separation or isotope dilution) on a ThermoFisher Scientific Neoma MC-ICP-MS utilizing both solution and laser ablation (LA)-based sampling techniques and an all-faraday detector configuration. Results: For the solution mode analyses conducted on aliquots containing sub μg/mL total U, we produce composite average 230 Th/ 234 U model dates of May 19, 1988 (± 351 days), and March 26, 1961 (± 2.5 years) using the directly measured 230 Th/ 234 U ratios for the NBL U630 and U850 uranium standards, which have certified purification dates of June 6, 1988 (± 190 days), and December 31, 1957 (± 36.5 days), respectively. The ages produced by LA-based sampling of dried residues of the same standards deposited onto cotton TexWipes are less accurate and of poorer precision (June 23, 2004 ± 8.7 years for U630 and December 21, 1965 ± 7.9 years for U850) but still yield meaningful information in regards to the purification date. Conclusions: We believe that further refinement of the all faraday detector measurement approach to include development of a more robust Th/U relative sensitivity factor determination, signal cutoff selection, and data processing protocols will allow for this approach to be confidently applied to enriched uranium materials with unknown purification histories. Potential advantages of the method include the reduced sample handling and infrastructure requirements as well as the ability to simultaneously generate a broad picture of the uranium isotopic composition in tandem with the U-Th age determination.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗