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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

An Experimental and Theoretical Investigation into the Chemical Properties of Uranium and Thorium Ions STL-19-13, Year 3 of 3

Presentation describes project to develop an instrument that embeds a variable-temperature, high-pressure drift/reaction cell between two quadrupole mass analyzers for the purpose of investigating gas-phase interactions of uranium (U) and thorium (Th) ions with neutral reactant species, with the overall aim of probing the interactions of U and Th ions in the gas phase.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Influence of Irradiation-induced Microstructural Defects on Thermal Transport in Single Crystal Thorium Dioxide

Microstructural defects formed as a result of fission fragment damage are known to drastically alter thermal conductivity, a fuel property that governs the efficiency of a nuclear reactor. A fundamental understanding of radiation-induced effects on thermal transport is critical for the development of advanced fuels. Ion-irradiation has widely been used to simulate the effects of neutron-irradiation by seeding atomic-to-nanoscale defects of controllable size and density. In this work, we investigate the influence of microstructural defects, induced by ion-irradiation, on the thermal properties of single crystal thorium dioxide samples grown using the hydrothermal technique. The samples were irradiated using 2 MeV protons at room temperature. A laser-based modulated thermoreflectance technique was used to measure the thermal diffusivity and conductivity within the damaged ThO2 region. The experimentally measured thermal properties were compared with Boltzmann Transport Equation predictions, to determine the impact of various defect types on the thermal properties of ThO2.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Conceptual design of thorium-fuelled Mitrailleuse accelerator-driven subcritical reactor using D-Be neutron source

A distributed accelerator is a charged-particle accelerator that uses a new acceleration method based on repeated electrostatic acceleration. This method offers outstanding benefits not possible with the conventional radio-frequency acceleration method, including: (1) high acceleration efficiency, (2) large acceleration current, and (3) lower failure rate made possible by a fully solid-state acceleration field generation circuit. A 'Mitrailleuse Accelerator' is a product we have conceived to optimize this distributed accelerator technology for use with a high-strength neutron source. We have completed the conceptual design of a Mitrailleuse Accelerator and of a thorium-fuelled subcritical reactor driven by a Mitrailleuse Accelerator. This paper presents the conceptual design details and approach to implementing the subcritical reactor core. We will spend the next year or so on detailed design work, and then will start work on developing a prototype for demonstration. If there are no obstacles in setting up a development organization, we expect to finish verifying the prototype's performance by the third quarter of 2015. (authors)

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Core loading pattern optimization of thorium fueled heavy water breeder reactor using genetic algorithm

In this work genetic algorithm was proposed to solve fuel loading pattern optimization problem in thorium fueled heavy water reactor. The objective function of optimization was to maximize the conversion ratio and minimize power peaking factor. Those objectives were simultaneously optimized using non-dominated Pareto-based population ranking optimal method. Members of non-dominated population were assigned selection probabilities based on their rankings in a manner similar to Baker's single criterion ranking selection procedure. A selected non-dominated member was bred through simple mutation or one-point crossover process to produce a new member. The genetic algorithm program was developed in FORTRAN 90 while neutronic calculation and analysis was done by COREBN code, a module of core burn-up calculation for SRAC. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2025

Phonon-Spin Scattering from Unpaired f-electrons in U atoms and It’s Influence on Thermal Transport in Uranium-doped Thorium Dioxide Single Crystals

In this work, impact of low level of uranium (U) atom substitution on thermal conductivity of thorium dioxide (ThO2) is investigated. ThO2 is an electronic insulator with a wide optical band-gap and no unpaired electrons whose thermal transport is governed by phonons. U-substitution introduces unpaired f-electrons resulting in paramagnetic behavior of U-ThO2 at room temperature, which significantly suppresses its thermal conductivity. A single crystal of U-ThO2 with graded composition of U is grown using a hydrothermal synthesis method, and thermal conductivity measurements are performed in regions with uniform composition of U at levels of 0%, 6%, 9% and 16%. Measured thermal conductivity profiles over 77–300 K temperature range are analyzed using an analytical expression for phonon-mediated thermal transport based on Klemens-Callaway model. Temperature dependent thermal conductivity is found to deviate significantly from the Rayleigh scattering trend expected for a simple substitutional point defect with a small perturbation to mass and interatomic forces. With the resonant scattering term, observed large suppression of thermal conductivity at low temperatures can be closely reproduced. Additionally, the extracted phonon-spin coupling constants imply a nonlinear relation of phonon-spin interaction intensity with respect to U doping percentage. Our study reveals how phonon-spin scattering contributed by unpaired f-electrons in U atoms influences thermal transport in the U-ThO2 system.

36 - MATERIALS SCIENCE↗
DOE OSTI2019

A Thorium Metal‐Organic Framework with Outstanding Thermal and Chemical Stability

Abstract A new thorium metal‐organic framework (MOF), Th(OBA) 2 , where OBA is 4,4′‐oxybis(benzoic) acid, has been synthesized hydrothermally in the presence of a range of nitrogen‐donor coordination modulators. This Th‐MOF, described herein as GWMOF‐13, has been characterized by single‐crystal and powder X‐ray diffraction, as well as through a range of techniques including gas sorption, thermogravimetric analysis (TGA), solid‐state UV/Vis and luminescence spectroscopy. Single‐crystal X‐ray diffraction analysis of GWMOF‐13 reveals an interesting, high symmetry (cubic Ia d ) structure, which yields a novel srs‐a topology. Most notably, TGA analysis of GWMOF‐13 reveals framework stability to 525 °C, matching the thermal stability benchmarks of the UiO‐66 series MOFs and zeolitic imidazolate frameworks (ZIFs), and setting a new standard for thermal stability in f‐block based MOFs.

Carter, Korey P.↗
DOE OSTI2025

Thorium Bis‐Salophen Trimers as Anion Detectors and Binding Agents

Bis‐salophen ligands are the condensation product of a tetramine and a salicylaldehyde derivative. They feature two binding sites, both of which are tetradentate with mixed O/N donor atoms. Reaction with the ligand precursor and thorium nitrate tetrahydrate forms a 3:3 metal‐to‐ligand trimer with a ΔΔΔ‐chirality confirmed by X‐ray crystallography of a racemic single crystal. The structure has a pore in the center of the triangular structure measuring 6.22 Å at its narrowest point. This compound is air‐ and water‐stable as well as soluble in organic solvents. Here, this compound was screened with a series of tetrabutyl ammonium halide salts, and tetrabutylammonium (TBA) chloride showed the strongest binding to the complex. After the addition of 2 equivalents of TBACl, the complex and salt precipitate out of solution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Thermophysical Properties of Mixtures of Thorium and Uranium Nitride

Abstract The miscibility, lattice parameter, and thermophysical properties of (Th 0.2 U 0.8 )N and (Th 0.5 U 0.5 )N have been investigated. It is shown that additions of thorium nitride (ThN) to uranium nitride (UN) increases the thermophysical performance of the mixed nitride fuel form in comparison to reference UN. In the more dilute limit, additions of ThN serve as a burnable neutronic poison and reduces the change in k eff over the lifecycle of the fuel. At higher concentrations, additions of ThN serve as a significant fertile source of 233 U. Where appropriate, comparisons to previous work on UN + PuN mixtures are made, as this is a comparable fuel form for potential fast reactor concepts, and a suitable point of contrast in the possible design space afforded by mixed (Th x U 1 − x )N fuel forms. The data from this work are the input parameters for finite element modeling of the temperature distribution in a compact reactor. The results of modeling and simulation of this core design are shown for the case of steady-state operation and during double, adjacent heat pipe failure.

Parker, S. S. (ORCID:000000018597440X)↗
DOE OSTI2017

A new thorium-229 reference material

A new reference material was characterized for 229 Th molality and thorium isotope amount ratios. This reference material is intended for use in nuclear forensic analyses as an isotope dilution mass spectrometry spike. The reference material value and expanded uncertainty (k = 2) for the 229 Th molality is (1.1498 ± 0.0016)×10 -10 mol g -1 solution. The value and expanded uncertainty (k = 2) for the n( 230 Th)/n( 229 Th) ratio is (5.18 ± 0.26)×10 -5 and the n( 232 Th)/n( 229 Th) ratio is (3.815 ± 0.092)×10 -4 .

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

Thermal conductivity suppression in uranium-doped thorium dioxide due to phonon-spin interactions

In this work, impact of low level of uranium (U) atom substitution on thermal conductivity of thorium dioxide (ThO 2 ) is investigated. ThO 2 is an electronic insulator with a wide optical band-gap and no unpaired electrons whose thermal transport is governed by phonons. U-substitution introduces unpaired f-electrons resulting in paramagnetic behavior of U-ThO 2 at room temperature, which significantly suppresses its thermal conductivity. A single crystal of U-ThO 2 with graded composition of U is grown using a hydrothermal synthesis method, and thermal conductivity measurements are performed in regions with uniform composition of U at levels of 0%, 6%, 9% and 16%. Measured thermal conductivity profiles over 77–300 K temperature range are analyzed using an analytical expression for phonon-mediated thermal transport based on Klemens-Callaway model. Temperature dependent thermal conductivity is found to deviate significantly from the Rayleigh scattering trend expected for a simple substitutional point defect with a small perturbation to mass and interatomic forces. With the resonant scattering term, observed large suppression of thermal conductivity at low temperatures can be closely reproduced. Additionally, the extracted phonon-spin coupling constants imply a nonlinear relation of phonon-spin interaction intensity with respect to U doping percentage. Our study reveals how phonon-spin scattering contributed by unpaired f-electrons in U atoms influences thermal transport in the U-ThO 2 system.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Impact of Noncovalent Interactions on the Structural Chemistry of Thorium(IV)-Aquo-Chloro Complexes

Five novel tetravalent thorium (Th) compounds that consist of Th(H 2 O) x Cl y structural units were isolated from acidic aqueous solutions using a series of nitrogen-containing heterocyclic hydrogen (H) bond donors. Taken together with three previously reported phases, the compounds provide a series of monomeric Th IV complexes wherein the effects of noncovalent interactions (and H-bond donor identity) on Th structural chemistry can be examined. Seven distinct structural units of the general formulas [Th(H 2 O) x Cl 8–x ] x-4 (x = 2, 4) and [Th(H 2 O) x Cl 9–x] x-5 (x = 5–7) are described. The complexes range from chloride-deficient [Th(H 2 O) 7 Cl 2 ] 2+ to chloride-rich [Th(H 2 O) 2 Cl 6 ] 2– species, and theory was used to understand the relative energies that separate complexes within this series via the stepwise chloride addition to an aquated Th cation. Electronic structure theory predicted the reaction energies of chloride addition and release of water through a series of transformations, generally highlighting an energetic driving force for chloride complexation. To probe the role of the counterion in the stabilization of these complexes, electrostatic potential (ESP) surfaces were calculated. Finally, the ESP surfaces indicated a dependence of the chloride distribution about the Th metal center on the pK a of the countercation, highlighting the directing effects of noncovalent interactions (e.g., Hbonding) on Th speciation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Influence of Substituents on the Electronic Structure of Mono- and Bis(phosphido) Thorium(IV) Complexes

Here, a series of metallocene thorium complexes with mono- and bis(phosphido) ligands have been investigated with varying hues: (C 5 Me 5 ) 2 Th(Cl)[P(Mes) 2 ] (Mes = mesityl = 2,4,6-(CH 3 ) 3 C 6 H 2 ; dark red-purple), (C 5 Me 5 ) 2 Th[P(Mes)(CH 3 )] 2 (dark red-purple), (C 5 Me 5 ) 2 Th(CH 3 )[P(Mes) 2 ] (dark red-purple), (C 5 Me 5 ) 2 Th(CH 3 )[P(Mes)(SiMe 3 )] (orange), (C 5 Me 5 ) 2 Th(Cl)[P(Mes)(SiMe 3 )] (orange), (C 5 Me 5 ) 2 Th[P(Mes)(SiMe 3 )] 2 (orange), and (C 5 Me 5 ) 2 Th[PH(Mes)] 2 (pale yellow). While all of these complexes bear a mesityl group on phosphorus, the electronic structure observed differs depending on the other substituent (mesityl, methyl, trimethylsilyl, or hydrogen). This sparked an investigation of the electronic structure of these complexes using 31 P NMR and electronic absorption spectroscopy in concert with time-dependent density functional theory calculations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Monomeric and Trimeric Thorium Chlorides Isolated from Acidic Aqueous Solution

Two thorium(IV) compounds, [Th(H 2 O) 4 Cl 4 ]·2 (HPy·Cl) ( 1 ) and (HPy) 3 [Th 3 (H 2 O) 2 Cl 10 (OH) 5 ]·4(HPy·Cl) ( 2 ) (HPy = pyridinium), were isolated from acidic aqueous solution. The compounds were synthesized at room temperature and subsequently characterized using single crystal X-ray diffraction along with Raman and IR spectroscopies. Whereas compound 1 is built from discrete mononuclear Th(H 2 O) 4 Cl 4 units, compound 2 consists of a novel hydroxo-bridged trimeric [Th 3 (OH) 5 ] 7+ core. Such species are largely absent from discussions of Th solution and solid-state chemistry and their isolation may be attributed to outer coordination sphere interactions that help stabilize the structural units; extensive hydrogen bonding and $π–π$ stacking interactions are present in 1 and 2 . Density functional theory calculations were performed to predict the respective vibrational frequencies of the structural units, and their relative stability was predicted at the correlated molecular theory level. Small-angle X-ray scattering analysis of [Th 3 (OH) 5 ] 7+ in water indicates that the trimeric structural unit remains intact and that it is indeed an important species that necessitates consideration in geochemical models and for design of Th materials from water.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

From Thorium to Plutonium: Trends in Actinide(IV) Chloride Structural Chemistry

A series of eighteen actinide (IV) compounds were synthesized from acidic aqueous media containing thorium, uranium, or plutonium. The metal cation adopts a variety of different structural units with the general formula [An(H 2 O) x Cl y ] 4-y (x=4-7, y=2-4) or AnCl 6 2- charge balanced by protonated nitrogen-containing heterocycles. Compound identities were classified by single crystal X-ray diffraction and subsequently characterized by Raman, IR, and optical absorption spectroscopies. Discrepancies across the early actinides were observed in this family of An(IV)-chlorides, with Th adopting exclusively Th-aquo-chloro species, Pu forming only PuCl 6 2- , and U residing somewhere in between, crystallizing both as U-aquo-chloro and UCl 6 2- monomeric units. Reports of An-H 2 O-Cl species are largely absent from tetravalent An solid state discussions despite their identification in chloride solutions. Here, the isolation of unique An(IV)-chlorides may be attributed to nonbonding interactions provided by outer coordination sphere counter-ions that could play a role in stabilizing these structural units. Differences in the structural chemistry of Th, U, and Pu also demonstrate a break in the series despite their common oxidation state and nearly identical synthetic procedures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Guided Ion Beam and Quantum Chemical Investigation of the Thermochemistry of Thorium Dioxide Cations: Thermodynamic Evidence for Participation of f Orbitals in Bonding

Kinetic energy dependent reactions of ThO + with O 2 are studied using a guided ion beam tandem mass spectrometer. The formation of ThO 2 + in the reaction of ThO + with O 2 is observed to be slightly endothermic and also exhibits two obvious features in the cross section. These kinetic energy dependent cross sections were modeled to determine a 0 K bond dissociation energy of D 0 (OTh + - O) = 4.94 ± 0.06 eV. This value is slightly larger but within experimental uncertainty of less precise previously reported experimental values. The higher energy feature in the ThO 2 + cross section was also analyzed and suggests formation of an excited state of the product ion lying 3.1 ± 0.2 eV above the ground state. Additionally, the thermochemistry of ThO 2 + was explored by quantum chemical calculations, including a full Feller-Peterson-Dixon (FPD) composite approach with correlation contributions up to CCSDT(Q) and four-component spin-orbit corrections, as well as more approximate CCSD(T) calculations including semiempirical estimates of spin-orbit energy contributions. The FPD approach predicts D 0 (OTh + -O) = 4.87 ± 0.04 eV, in good agreement with the experimental value. Analogous FPD results for ThO+, ThO, and ThO 2 are also presented, including ionization energies for both ThO and ThO 2 . The ThO 2 + bond energy is larger than those of its transition metal congeners, TiO 2 + and ZrO 2 + , which can be attributed partially to an actinide contraction, but also to contributions from the participation of f orbitals on thorium that are unavailable to the transition metal systems.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Unprecedented Radiation Resistant Thorium–Binaphthol Metal–Organic Framework

A thorium–organic framework (TOF-16) containing hexameric secondary building units connected by functionalized binaphthol linkers was synthesized, characterized, and irradiated to probe its radiation resistance. Radiation stability was examined using γ-rays and 5 MeV He 2+ ions to simulate α particles. γ-irradiation of TOF-16 to an unprecedented 4 MGy dose resulted in no apparent bulk structural damage visible by X-ray diffraction. To further probe radiation stability, we conducted the first He 2+ ion irradiation study of a metal–organic framework (MOF). Diffraction data indicate onset of crystallinity loss upon approximately 15 MGy of irradiation and total loss of crystallinity upon exposure to approximately 25 MGy of He 2+ ion irradiation. In conclusion, the high radiation resistance observed suggests MOFs can withstand radiation exposure at doses found in nuclear waste streams and highlights the need for a systematic approach to understand and eventually design frameworks with exceptional radiation resistance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

In-Plane Thorium(IV), Uranium(IV), and Neptunium(IV) Expanded Porphyrin Complexes

In our research, we report a first series of in-plane thorium(IV), uranium(IV), and neptunium(IV) expanded porphyrin complexes. These actinide (An) complexes were synthesized using a hexa-aza porphyrin analogue, termed dipyriamethyrin, and the non-aqueous An(IV) precur-sors: ThCl 4 (DME) 2 , UCl 4 , and NpCl 4 (DME) 2 under conditions of in situ sodium bis(trimethylsilyl)amide deprotonation. The molecu-lar and electronic structure of the ligand, each An(IV) complex, and a corresponding uranyl(VI) complex were characterized using NMR and UV-vis spectroscopies, as well as single crystal X-ray diffraction analysis. Computational analyses of these complexes, coupled with their structural features, provide support for the conclusion that a greater degree of covalency in the ligand-cation orbital interactions arises as the early actinide series is traversed from Th(IV) to U(IV) and Np(IV). The axial ligands in the current An(IV) complexes proved labile, allowing for the electronic features of these complexes to be further modified.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

A mesoporous cationic thorium-organic framework that rapidly traps anionic persistent organic pollutants

Many environmental pollutants inherently exist in their anionic forms and are therefore highly mobile in natural water systems. Cationic framework materials that can capture those pollutants are highly desirable but scarcely reported. Here we present a mesoporous cationic thorium-based MOF (SCU-8) containing channels with a large inner diameter of 2.2 nm and possessing a high surface area of 1360 m 2 g –1 . The anion-exchange properties of SCU-8 were explored with many anions including small oxo anions like ReO 4 – and Cr 2 O 7 2– as well as anionic organic dyes like methyl blue and the persistent organic pollutant, perfluorooctane sulfonate (PFOS). Both fast uptake kinetics and great sorption selectivity toward PFOS are observed. The underlying sorption mechanism was probed using quantum mechanical and molecular dynamics simulations. These computational results reveal that PFOS anions are immobilized in SCU-8 by driving forces including electrostatic interactions, hydrogen bonds, hydrophobic interactions, and van der Waals interactions at different adsorption stages.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗