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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on U(HO)8 by Materials Project

U(HO)8 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. U is bonded to eight O atoms to form distorted edge-sharing UO8 hexagonal bipyramids. There are a spread of U–O bond distances ranging from 1.83–2.43 Å. There are four inequivalent H sites. In the first H site, H is bonded in a distorted linear geometry to two O atoms. There is one shorter (1.01 Å) and one longer (1.66 Å) H–O bond length. In the second H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the third H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the fourth H site, H is bonded in a single-bond geometry to two O atoms. There is one shorter (1.00 Å) and one longer (1.75 Å) H–O bond length. There are four inequivalent O sites. In the first O site, O is bonded in a 4-coordinate geometry to two equivalent U, one H, and one O atom. The O–O bond length is 1.45 Å. In the second O site, O is bonded in a single-bond geometry to one U atom. In the third O site, O is bonded in a distorted water-like geometry to one U and two H atoms. In the fourth O site, O is bonded in a distorted water-like geometry to three H atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoUTe4 by Materials Project

UHoTe4 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. U5+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of U–Te bond distances ranging from 3.06–3.22 Å. Ho3+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ho–Te bond distances ranging from 3.06–3.25 Å. There are three inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent U5+ and two equivalent Ho3+ atoms to form a mixture of distorted edge and corner-sharing TeHo2U2 trigonal pyramids. In the second Te2- site, Te2- is bonded to two equivalent U5+ and two equivalent Ho3+ atoms to form a mixture of distorted edge and corner-sharing TeHo2U2 trigonal pyramids. In the third Te2- site, Te2- is bonded in a 6-coordinate geometry to two equivalent U5+ and two equivalent Ho3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U2CuAs2(HO)24 by Materials Project

U2CuAs2(HO2)8(H2O)8 crystallizes in the tetragonal P4/nnc space group. The structure is three-dimensional and consists of sixteen water molecules and one U2CuAs2(HO2)8 framework. In the U2CuAs2(HO2)8 framework, U6+ is bonded to six O2- atoms to form UO6 octahedra that share a cornercorner with one CuO6 octahedra and corners with four equivalent AsO4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (1.82 Å) and four longer (2.31 Å) U–O bond lengths. Cu2+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with two equivalent UO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (1.94 Å) and two longer (2.51 Å) Cu–O bond lengths. As5+ is bonded to four equivalent O2- atoms to form AsO4 tetrahedra that share corners with four equivalent UO6 octahedra. The corner-sharing octahedral tilt angles are 45°. All As–O bond lengths are 1.72 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cu2+ and two equivalent H1+ atoms. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+ and one As5+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one U6+ and one Cu2+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one U6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U2CuP2(HO)24 by Materials Project

U2CuP2(HO2)8(H2O)8 crystallizes in the tetragonal P4/nnc space group. The structure is three-dimensional and consists of sixteen water molecules and one U2CuP2(HO2)8 framework. In the U2CuP2(HO2)8 framework, U6+ is bonded to six O2- atoms to form UO6 octahedra that share a cornercorner with one CuO6 octahedra and corners with four equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (1.82 Å) and four longer (2.32 Å) U–O bond lengths. Cu2+ is bonded to six O2- atoms to form distorted CuO6 octahedra that share corners with two equivalent UO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (1.92 Å) and two longer (2.59 Å) Cu–O bond lengths. P5+ is bonded to four equivalent O2- atoms to form PO4 tetrahedra that share corners with four equivalent UO6 octahedra. The corner-sharing octahedral tilt angles are 42°. All P–O bond lengths are 1.56 Å. H1+ is bonded in a distorted single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cu2+ and two equivalent H1+ atoms. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+ and one P5+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one U6+ and one Cu2+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one U6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Isomeric and beta-decay spectroscopy of 173,174 Ho

β-decay spectroscopy of 173,174 Ho (Z = 67, N = 106,107) was conducted at Radioactive Isotope Beam Factory at RIKEN by using in-flight fission of a 345-MeV/u 238 U primary beam. A previously unreported isomeric state at 405 keV with half-life of 3.7(12) μs and a spin and parity of (3/2 + ) is identified in 173 Ho. Moreover, a new state with a spin and parity of 9 - was discovered in 174 Er. The experimental log ft values of 5.84(20) and 5.25(18) suggest an allowed-hindered β decay from the ground state of 174 Ho to the K π = 8 - isomeric state in 174 Er. Configuration-constrained potential energy surface (PES) calculations were performed and the predictions are in reasonable agreement with the experimental results.

150 ≤ A ≤ 189↗
DOE OSTI2025

Formation of U(VI) peroxide nanoclusters from cascade reactions with a persulfate radical initiator

Radiolysis of water in high radiation fields generates a variety of reactive oxygen species that influence the chemical behavior and complexation of hexavalent uranium. This study investigates the behavior of interaction of a uranyl cation (UO 2 2+ (VI)) with a series of free radicals that are formed in situ via activation of the free radical initiator persulphate (S 2 O 8 2− ), which releases both SO 4 ˙ − and ˙OH species in the solution. Electron Paramagnetic Resonance (EPR) and Raman spectroscopy were used to evaluate the presence of the hydroperoxyl radical (HO 2 ˙) and superoxide radicals (O 2 ˙ − ) that are formed within the solution through radical cascade reactions. In addition, a uranyl peroxide cluster solid (NaU 24 ) was crystallized and characterized using single crystal X-ray diffraction (SCXRD), vibrational spectroscopy, and EPR spectroscopy. The presence of the hydroperoxyl radical (HO 2 ˙) and superoxide radicals (O 2 ˙ − ) was also observed in the solid-state compound, but spectroscopic evidence suggests that it was associated with the Na + network and not the cluster itself. Density functional theory (DFT) calculations were also utilized to further confirm the radical species produced and determine the potential stabilization of radicals detected within the cluster and lattice.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Westinghouse advanced fuel management strategies leveraging high enrichment and high burnup fuel to optimize PWR economics

In the US, nuclear power plants have been focused on increasing electricity generation for over three decades via longer operating cycles, reduced number of outages and duration, and the implementation of power up-rates. The potential for zero-carbon emission credits and other carbon-reduction initiatives further makes nuclear power utilities to focus on increasing generation capability. Longer operating cycles provide increased energy generation and enable economic savings to nuclear utilities when the increase in fuel loading required to achieve the extended cycle energy target and resulting increase in total fuel cost is offset by the savings from outage avoidance and reduced replacement power costs. For the current licensed limits of 5 w/o {sup 235}U enrichment and 62 GWd/tU peak pin burnup, higher power density PWR plants, which are prevalent in the PWR fleet, require an excessively penalizing fraction of feed fuel assemblies to operate for the extended cycle duration, with inevitably poor fuel use and fuel cycle economics that cannot be counterbalanced by the savings on outage cost avoidance. To overcome this barrier, the nuclear industry is pursuing development of high enrichment/high burnup fuel technology ({sup 235}U enrichment up to 8 w/o and peak pin burnup up to 75 GWd/tU) which increases fuel energy generation capability and can enable high power density plants to achieve positive economics on 24-month cycle of operation. This paper presents advanced fuel management strategies developed by Westinghouse to enable transition of PWR reactors from 18-month to 24-month cycle of operation, with and without a core thermal power uprate, which are then used as basis to assess the economics of a direct transition from 18 to 24-month cycles with high enrichment/high burnup fuel. The results show that these fuel management strategies, especially if coupled with thermal power up-rates, present the opportunity for substantial economic benefits to utilities. The systematic review of fuel management strategies presented can provide an illustrative reference for decision makers as they consider how to maximize nuclear energy generation economically. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

First Sagittarius A* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole

We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium toward the Galactic center. Mitigation of the rapid intraday variability that characterizes Sgr A* has been carried out through the addition of a “variability noise budget” in the observed visibilities, facilitating the reconstruction of static full-track images. Our static reconstructions of Sgr A* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions and a small cluster that contains diverse nonring morphologies. Based on our extensive analysis of the effects of sparse (u,v)-coverage, source variability, and interstellar scattering, as well as studies of simulated visibility data, we conclude that the Event Horizon Telescope Sgr A* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of ∼50 μas, consistent with the expected “shadow” of a 4 × 10$^{6}$ M $_{⊙}$ black hole in the Galactic center located at a distance of 8 kpc.

79 ASTRONOMY AND ASTROPHYSICS↗