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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

MANTRA: An Integral Reactor Physics Experiment to Infer Actinide Capture Cross-sections from Thorium to Californium with Accelerator Mass Spectrometry

The principle of the proposed experiment is to irradiate very pure actinide samples in the Advanced Test Reactor at INL and, after a given time, determine the amount of the different transmutation products. The determination of the nuclide densities before and after neutron irradiation will allow inference of effective neutron capture cross-sections. This approach has been used in the past and the novelty of this experiment is that the atom densities of the different transmutation products will be determined using the Accelerator Mass Spectrometry technique at the ATLAS facility located at ANL. It is currently planned to irradiate the following isotopes: 232Th, 235U, 236U, 238U, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 243Am, 244Cm and 248Cm.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Why reconsider the thorium fuel cycle?

In this paper we have endeavored to present the available technical information on the potential use of Th in nuclear fuel cycle (FC) applications as compared to U without subjective evaluations. Where helpful, we have compared the technical attributes of Th-232 as a fertile isotope and U-233 as a fissile isotope with other similar isotopes (i.e., U-238, and U-235 and Pu-239, respectively). In addition, we have summarized (a) experience gained to-date with fabricating and reprocessing of Th-232/U-233 fuels, (b) factors concerning Th fuel irradiation in both test reactors and power reactors, and (c) differences in the backend of the FC with emphasis on repository risks. As might be expected, many technical aspects of Th vs. U have not changed since the sixties. However, there are some factors elaborated in this paper that have changed. Changes potentially encouraging Th use are: (a) the ability to recover large amounts of Th as a byproduct with small attendant costs and environmental impacts, (b) the potential to produce fewer minor actinides (MA) and less Pu during power production, and (c) increased concerns about proliferation which might be somewhat mitigated by the high radioactivity and amenability to isotopic dilution of U-233. Changes challenging Th utilization are: (a) obtaining sufficient experience handling Th/U-233 fuels, (b) the existence of large inventories of depleted U and continuing discovery of large U resources, and (c) recognition that the extent to which U-233 might mitigate proliferation concerns is not as large as originally hoped.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

An experimental study of the solubility and speciation of thorium in chloride-bearing aqueous solutions at temperatures up to 250 °C

In this study, the solubility and speciation of Th in Cl-bearing solutions saturated in ThO2 was investigated experimentally at 150, 175, 200, 225 and 250°C, and saturated water vapor pressure. At these experimental conditions (pH 25°C < 3.8, mNaCl < 2.5), Th-chloride complexation is insignificant, and the solubility of Th is controlled by hydrolysis. The two main species in solution were identified as Th(OH) 2 2+ and Th(OH) 4 ° and formed via the reactions Th 4+ + 2OH - ↔ Th(OH)$2+\atop{2}$ and Th 4+ + 4OH - ↔ Th(OH)$0\atop{4}$. The logarithms of the formation constants determined for the first reaction are 23.91 ± 0.05, 24.79 ± 0.07, 25.78 ± 0.05, and 25.85 ± 0.05 for 175, 200, 225 and 250°C, respectively, and 42.18 ± 0.06, 43.50 ± 0.07, 43.17 ± 0.08, and 43.74 ± 0.11 for the second reaction at the same temperatures. Formation constants could not be determined reliably for 150 °C. Extrapolations of our formation constants to 25°C are in excellent agreement with the values determined at 25 °C by Neck and Kim (2001) and Ekberg et al. (2000). Finally, for natural systems buffered by thorianite (ThO 2 ), the solubility determined in our study likely reflects a minimum, as the presence of additional ligands would lead to higher solubility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Homoleptic 1,2-benzenedithiolate complexes of thorium and uranium

Reaction of 4 equiv. of [Li(TMEDA)] 2 [1,2-S 2 C 6 H 4 ] with [ThCl 4 (DME) 2 ] or [UCl 4 (THF) 3 ] in THF results in formation of [Li(THF) 2 ] 4 [An(1,2-S 2 C 6 H 4 ) 4 ] (An = Th, 1; An = U, 2), whereas reaction of 4 equiv. of [Li(TMEDA)] 2 [1,2-S 2 C 6 H 4 ] with UCl 4 in Et 2 O results in formation of [Li(TMEDA)] 4 [U(1,2-S 2 C 6 H 4 ) 4 ] (3). Complexes 1–3 represent the first reported benzenedithiolate complexes of the actinides. Here, they were characterized by NMR spectroscopy and X-ray crystallography. In the solid state, complexes 1–3 exhibit triangular dodecahedral geometries about their actinide centers. Additionally, their Li + cations are bound by two sulfur atoms of adjacent [1,2-S 2 C 6 H 4 ] 2− ligands, in addition to two solvent donor atoms. In solution, complexes 2 and 3 exhibit spectral data consistent with S 4 symmetry (and non-exchanging Li + sites), whereas complex 1 exhibits spectral properties consistent with labile Li + cations.

X-ray↗
DOE OSTI2017

Ca(BH 4 ) 2 as a simple tool for the preparation of thorium and uranium metallocene borohydride complexes: First synthesis and crystal structure of (C 5 Me 5 ) 2 Th(η 3 -H 3 BH) 2

Here, calcium borohydride allows for the high-yielding synthesis of (C 5 Me 5 )2An(η 3 -H 3 BH) 2 (An = Th, U) by reaction with (C 5 Me 5 ) 2 AnCl 2 (An = Th, U). While a preparative synthesis of (C 5 Me 5 ) 2 U(η 3 -H 3 BH) 2 has been previously reported in the literature using K(C 5 Me 5 ) and U(BH 4 ) 4 , the use of Ca(BH 4 ) 2 is higher yielding and mild. Full characterization of the novel compound (C 5 Me 5 ) 2 Th(η 3 -H 3 BH) 2 is presented.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Plutonium and minor actinides utilization in Thorium molten salt reactor

FUJI-12 reactor is one of MSR systems that proposed by Japan. The original FUJI-12 design considers Th/{sup 233}U or Th/Pu as main fuel. In accordance with the currently suggestion to stay away from the separation of Pu and minor actinides (MA), in this study we evaluated the utilization of Pu and MA in FUJI-12. The reactor grade Pu was employed in the present study as a small effort of supporting THORIMS-NES scenario. The result shows that the reactor can achieve its criticality with the Pu and MA composition in the fuel of 5.96% or more.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2011

CHEMICAL ABUNDANCES FOR EVOLVED STARS IN M5: LITHIUM THROUGH THORIUM

We present analysis of high-resolution spectra of a sample of stars in the globular cluster M5 (NGC 5904). The sample includes stars from the red giant branch (RGB; seven stars), the red horizontal branch (two stars), and the asymptotic giant branch (AGB; eight stars), with effective temperatures ranging from 4000 K to 6100 K. Spectra were obtained with the HIRES spectrometer on the Keck I telescope, with a wavelength coverage from 3700 A to 7950 A for the HB and AGB sample, and 5300 A to 7600 A for the majority of the RGB sample. We find offsets of some abundance ratios between the AGB and the RGB branches. However, these discrepancies appear to be due to analysis effects, and indicate that caution must be exerted when directly comparing abundance ratios between different evolutionary branches. We find the expected signatures of pollution from material enriched in the products of the hot hydrogen burning cycles such as the CNO, Ne-Na, and Mg-Al cycles, but no significant differences within these signatures among the three stellar evolutionary branches especially when considering the analysis offsets. We are also able to measure an assortment of neutron-capture element abundances, from Sr to Th, in the cluster. We find that the neutron-capture signature for all stars is the same, and shows a predominately r-process origin. However, we also see evidence of a small but consistent extra s-process signature that is not tied to the light-element variations, pointing to a pre-enrichment of this material in the protocluster gas.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Thorium abundances in solar twins and analogs: Implications for the habitability of extrasolar planetary systems

We present the first investigation of Th abundances in solar twins and analogues to understand the possible range of this radioactive element and its effect on rocky planet interior dynamics and potential habitability. The abundances of the radioactive elements Th and U are key components of a planet’s energy budget, making up 30%–50% of the Earth’s. Radiogenic heat drives interior mantle convection and surface plate tectonics, which sustains a deep carbon and water cycle and thereby aides in creating Earth’s habitable surface. Unlike other heat sources that are dependent on the planet’s specific formation history, the radiogenic heat budget is directly related to the mantle concentration of these nuclides. As a refractory element, the stellar abundance of Th is faithfully reflected in the terrestrial planet’s concentration. We find that log ϵ{sub Th} varies from 59% to 251% that of solar, suggesting extrasolar planetary systems may possess a greater energy budget with which to support surface to interior dynamics and thus increase their likelihood to be habitable compared to our solar system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Search for direct detection of thorium-229m nuclear VUV photons

We used two methods to attempt to measure the lifetime and energy level of the 229m Th low-lying nuclear state. Both methods used a 233 U source to implant 229 Th into a VUV transparent substrate. The uranium source had a low concentration of 232 U (0.08 ppm) and was chemically purified one week prior to the start of the experiment. In the first method, the time decay method, sensitive to 229m Th lifetimes from 10 min to 15 h, the VUV substrate was irradiated for 4–36 h to ensure a sufficient transfer of 229m Th ions into the substrate. Then the signal from the substrate was observed using a PMT for 15 h. A bandpass filter was placed between the substrate and PMT to provide a means of measuring the 229m Th photon energy. We used nine filters with center transmissions ranging from 140 to 244 nm. In the second method, direct detection, sensitive to lifetimes from zero to 10 min, the substrate was observed directly with the PMT and filter during the deposition process. For both methods our results were limited by the strong background fluorescence and phosphorescence due to the alphas and betas intrinsic to the decay of the 233 U and its daughters. We did not see unambiguous signs of photons from 229m Th. This may be due to one or more of the following: lifetime of 229m Th too short or too long, branching ratio to produce 229m Th from 233 U is too small, energy of 229m Th transition is outside of our observed range of 5.1–8.9 eV, and/or most likely, 229m Th ions drop to a +1 or 0 charge state, and thus lose their nuclear excitation through non-radiative processes.

229Th↗
DOE OSTI2012

Radium and Thorium Sorption by Monosodium Titanate (MST) and Modified MST (mMST)

A series of tests were planned to examine the removal of Ra and Th by monosodium titanate (MST) and modified monosodium titanate (mMST). Simulated waste solutions were prepared containing Ra and Th, along with Sr, Np, Pu, and U. Following simulant preparation the simulants were filtered through 0.45-m filters. Analysis of the simulants indicated no Th in the filtered solution. This is due to the very low solubility of Th in alkaline solutions. Based on the reported detection limits for 228 Th by gamma analyses, the solubility of Th in the simulant solutions is < 3.0E-10 g/L or < 1.3E-12 M. Therefore, data could not be obtained regarding the removal of Th by MST and mMST; however, testing proceeded to examine the removal of Ra. Sorption testing indicated that Ra, like Sr, is very rapidly removed from solution by both MST and mMST. The Ra concentration in solution fell below the method detection limit (MDL) within 30 minutes of contact with MST, and within 2 hours of contact with mMST, when tested at 25 °C using a 5.6 M Na simulant. Additional testing examined the effects of ionic strength and temperature on the MST and mMST performance. Results from these tests showed that the majority of samples still reached a Ra concentration below the MDL, indicating excellent removal. For the highest ionic strength solution (6.6 M Na), there did appear to be a slight decrease in the Ra removal by mMST, as indicated by a larger number of samples just above the MDL. The effect of temperature on 226 Ra removal is indeterminate for either MST or mMST in the temperature range (25-60 °C) and concentrations studied since the final soluble concentration of Ra remained at or below the detection limits for all tests. Desorption testing was also performed using decontaminated salt solution (DSS) diluted to sodium concentrations of 2 M and 0.5 M, to represent the intermediate and final stages of washing. Results from these tests indicated no desorption of any sorbents, with the exception of Pu from mMST, which desorbed slightly (0.02%). Rather, the testing showed additional sorption of sorbates, likely due to the higher sorbent concentrations in these tests compared to the concentrations used for loading (i.e. 13 g/L vs. 0.4 g/L). SRNL recommends additional testing to confirm the low solubility of Th in a range of simulants representing SRS HLW. We also recommend additional sorption testing with simulants containing a higher concentration of 226Ra, to allow for the determination of actual DF values, rather than the minimum DF values reported here.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Adventures in Actinide Chemistry: A Year of Exploring Uranium and Thorium in Los Alamos

The first part of this collection of slides is concerned with considerations when working with actinides. The topics discussed in the document as a whole are the following: Actinide chemistry vs. transition metal chemistry--tools we can use; New synthetic methods to obtain actinide hydrides; Actinide metallacycles: synthesis, structure, and properties; and Reactivity of actinide metallacycles.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

A Synthetic Strategy to Prepare New Complex Uranium- and Thorium-Containing Oxides: Predictive Solid State Synthesis of New Composition using Radius Ratio Rules and Materials Discovery based on Crystal Growth from High Temperature Solutions

Flux crystal growth and mild hydrothermal crystal growth methods were used to obtain new uranium containing phases in single crystal form and permitted the structural characterization of these new compositions as well as the investigation of their magnetic and optical properties. The report describes the approaches used to obtain crystals of several classes of materials including oxides and oxyhalides, silicates, phosphates, and fluorides. The strategies for obtaining these diverse materials and the specific fluxes used are described and discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Studying f-Electron Contributions in Thorium and Uranium Containing Molecules

The pure rotational spectra of several actinide-containing compounds have been improved upon and, in two cases, been recorded for the first time. The diatomic molecules HfS and ThS have been studied in their ground electronic states but high vibrationally excited states. The results have yielded very accurate locations of the minima of the potential energy curves. The asymmetric molecules OThS and UO2S have been prepared by laser ablation synthesis and their pure rotational spectra recorded for the first time. Precise information pertinent to the geometric and electronic structure of these molecules has been obtained and is compared with other, newly recorded and related species such as OCeS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗