[en] A relativistic density functional description of the electronic structure of Tc2O7 has been evaluated by comparison with solid state 99Tc and 17O NMR spectroscopic data (the former isotope a weak beta-emitter). Every site in the molecule can be populated by a nucleus with favorable NMR characteristics, providing the rare opportunity to obtain a comprehensive set of chemical shift and electric field gradient tensors for a small molecular transition metal oxide. NMR parameters were computed for the central molecule of a (Tc2O7)17 cluster, using standard ZORA optimized all-electron QZ4P basis sets for the central molecule and DZ basis sets for surrounding atoms. The magnitudes of the predicted tensor principal values appear to be uniformly larger than observed experimentally, but discrepancies were within the accuracy of the approximation methods used. The convergence of calculated and measured NMR data suggests that the theoretical analysis has validity for the quantitative understanding of structural, magnetic, and chemical properties of Tc(VII) oxides.

[en] The speciation of Tc(VII) in 12 M sulfuric acid was studied by NMR, UV-visible and XAFS spectroscopy, experimental results were supported by DFT calculation and were in agreement with the formation of TcO₃OH(H₂O)₂. In summary, the speciation of heptvalent technetium has been investigated in sulfuric acid. In 12 M H₂SO₄, a yellow solution is observed, and its ⁹⁹Tc NMR spectrum is consistent with a heptavalent complex. The yellow solution was further characterized by EXAFS spectroscopy, and results are consistent with the formation of TcO₃(OH)(H₂O)₂. No technetium heptoxide or sulfato- complexes were detected in these conditions. The molecular structure of TcO₃(OH)(H₂O)₂ has been optimized by DFT techniques, and the structural parameters are well in accordance with those found by XAFS spectroscopy. The experimental electronic spectra exhibit ligand-to-metal charge transfer transitions that have been assigned using TDDFT methods. Calculations demonstrate the theoretical electronic spectrum of TcO₃(OH)(H₂O)₂ to be in very good agreement with the experimental one. Recent experiments in 12 M H₂SO₄ show the yellow solution to be very reactive in presence of reducing agents presumably forming low valent Tc species. Current spectroscopic works focus on the speciation of these species.

[en] Uranium mononitride (UN), sesquinitride (U2N3) and dinitride (UN2) were characterized by extended X-Ray absorption fine structure spectroscopy. Analysis on UN indicate the presence of three uranium shells at distances of 3.46(3), 4.89(5) and 6.01(6) A and a nitrogen shell at a distance of 2.46(2) A . For U2N3, two absorbing uranium atoms at different crystallographic positions are present in the structure. One of the uranium atoms is surrounded by nitrogen atoms at 2.28(2) A and by uranium atoms at 3.66(4) and 3.95(4) A . The second type of uranium atom is surrounded by nitrogen atoms at 2.33(2) and 2.64(3) A and by uranium atoms at 3.66(4), 3.95(4) and 5.31(5) A . Results on UN2 indicate two uranium shells at 3.71(4) and 5.32(5) A and two nitrogen shells at 2.28(2).

[en] The U.S. Department of Energy (DOE) national laboratories use their expertise in nuclear science and technology (S&T) to support a robust national nuclear S&T enterprise from the ground up. Traditional academic programs do not provide all the elements necessary to develop this expertise, so the DOE has initiated a number of supplemental programs to develop and support the nuclear S&T workforce pipeline. This document catalogs existing workforce development programs that are supported by a number of DOE offices (such as the Offices of Nuclear Energy, Science, Energy Efficiency, and Environmental Management), and by the National Nuclear Security Administration (NNSA) and the Naval Reactor Program. Workforce development programs in nuclear S&T administered through the Department of Homeland Security, the Nuclear Regulatory Commission, and the Department of Defense are also included. The information about these programs, which is cataloged below, is drawn from the program websites. Some programs, such as the Minority Serving Institutes Partnership Programs (MSIPPs) are available through more than one DOE office, so they appear in more than one section of this document.

[en] Quadruply bonded rhenium(III) dimers with the stoichiometry Re₂L₄F₂ (1, L = hexahydro-2H-pyrimido[1,2a]pyrimidinate (hpp^–); 2, L = diphenyl formamidinate (dpf^–)) were prepared from the solid-state melt reactions (SSMRs) between (NH₄)₂[Re₂F₈]·2H₂O and HL. Then those compounds were characterized in the solid state by single-crystal X-ray diffraction and in solution by UV–visible spectroscopy and cyclic voltammetry. The compound [Re₂(hpp)₄F₂]PF₆ (3) was prepared from the one-electron oxidation of Re₂(hpp)₄F₂ with [Cp₂Fe]PF₆. Compounds 1–3 are isostructural with the corresponding chloro derivatives. In summation, compound 1 undergoes two one-electron oxidations. Comparison with its higher halogen homologues reveals that Re₂(hpp)₄F₂ (1) is more easily oxidized than its chloro and bromo analogues.

[en] Dipotassium pentachloridooxidotechnetate, K_2[TcOCl_5], has been isolated as green single crystals by the dissolution of (NH_4)TcO_4 in 12 M HCl at 0 C and careful precipitation with KCl. The structure of this compound was determined by single-crystal X-ray diffraction analysis [a = 13.0815(9), b = 9.8982(6), c = 6.7623(4) Aa; V = 875.605 Aa"3, orthorhombic, Pnma, Z = 4] and compared with the corresponding molybdenum and rhenium analogues. The structure of K_2[TcOCl_5] was also investigated by density functional theory, and the results are in agreement with the crystallographic data. The oscillator strengths of the electronic transitions in the C_4_v complex anions [TcOCl_5]"2"- and [TcOCl_4]"- were also calculated by using time-dependent density functional theory and compared with the experimental UV/Vis spectra. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Group 7 elements form unique binary oxides with the stoichiometry M₂O₇. The heptoxides of manganese and technetium crystallize as molecular solids while rhenium forms an extended solid with mixed valances, 4 and 6. Unlike manganese and rhenium heptoxides which are used in the chemical industry technetium heptoxide has found very few applications due to its radioactive nature; it has been primarily use as a chemical precursor. While both of the molecular solids, Mn₂O₇³ and Tc₂O₇⁴ can be described by two corner-sharing MO₄ tetrahedron. The most distinctive difference is that the manganese's compound has a metal-oxygen-metal bond angle of 120.7 deg. while the technetium species is 180 deg.. Additionally, Tc₂O₇ has the largest molar volume of the heptoxides which suggest that it will be more susceptible to external stimuli of pressure and temperature than the others heptoxides. A pressure induced twisting has been predicted by Fang et al. Anomalous behavior is seen in the c-axis where below 2 GPa the Van der Waals interactions between the Tc₂O₇ molecules is over come and compression is observed but at higher pressures the twisted distortion forces the lattice to expand. The terminology diagonal-double tetrahedrons (DDTs) is introduced to discuss the molecules of Tc₂O₇. The rigid nature of the DDTs has been attributed to the cause of this twisted distortion mechanism. Recently, the solid state and gas phase behavior of technetium heptoxide was revisited by Childs et al. in light of ⁹⁹Tc being an important dose contributor in the Hanford waste and vitrification being proposed for immobilization of nuclear waste. Technetium heptoxide is one of the proposed volatilized species of technetium found in the vitrification process. In this study the crystal structure of Tc₂O₇ was reported at 100 K and compared to the structure first determined by Krebs at room temperature. Inspection of the metal-oxygen distances revealed the 100 K structure had longer bond lengths for the bridging oxygen than at high temperature. It is suggested that transverse thermal vibrational modes can be used to explain this negative thermal expansion behavior. This describes the average bond length of a central atom (i.e. the bridging oxygen atom) being measured as shorter at higher temperatures due to the larger thermal motion. Diffraction methods that measure the long range average structure are susceptible to observing this shorter average length as opposed to the true bond length, atom position at oscillation node that a method like Pair-Distribution Functional PDF Analysis would yield. In the case of Tc₂O₇, the magnitude of the transverse thermal vibrational mode is at the limit of being detectable by SCXRD and likely not observable by PDF analysis. Here we report the preliminary results of our study on the nature of the thermal expansion behavior of Tc₂O₇. The transverse thermal vibration mode compression mechanism is considered and compared to the pressure induced twisted distortion mechanism predicted at high pressure. (authors)

[en] Actinide nitrides, in particular UN, are being considered as fuel types for advanced reactor systems. Here, we demonstrate a low-temperature synthesis route on uranium that could be developed into a commercial fabrication process for UN and mixed actinide nitride fuels. UN was successfully synthesized from UO₂ by first reacting with NH₄HF₂ in a ball mill at 20 deg. C to form tetravalent ammonium uranium fluorides. Then, reaction with an ammonia atmosphere at 800 deg. C oxidized tetravalent uranium fluorides to hexavalent UN₂. The final product, UN, was obtained by decomposing UN₂ at 1100 deg. C under argon to produce UN through an intermediate phase of U₂N₃