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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on U(Cr3P2)2 by Materials Project

U(Cr3P2)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. U is bonded to six equivalent Cr and six equivalent P atoms to form distorted UCr6P6 cuboctahedra that share edges with six equivalent CrU2P4 tetrahedra and faces with two equivalent UCr6P6 cuboctahedra. All U–Cr bond lengths are 2.95 Å. All U–P bond lengths are 2.83 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to two equivalent U and four P atoms to form distorted CrU2P4 tetrahedra that share corners with eight equivalent CrU2P4 tetrahedra, edges with two equivalent UCr6P6 cuboctahedra, edges with four equivalent CrU2P4 tetrahedra, and faces with two equivalent CrU2P4 tetrahedra. There are two shorter (2.33 Å) and two longer (2.37 Å) Cr–P bond lengths. In the second Cr site, Cr is bonded in a 5-coordinate geometry to five P atoms. There are four shorter (2.37 Å) and one longer (2.48 Å) Cr–P bond lengths. There are two inequivalent P sites. In the first P site, P is bonded in a 9-coordinate geometry to nine Cr atoms. In the second P site, P is bonded in a 8-coordinate geometry to two equivalent U and six Cr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(Al2Fe)4 by Materials Project

UFe4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U is bonded in a 12-coordinate geometry to eight equivalent Fe and twelve Al atoms. All U–Fe bond lengths are 3.31 Å. There are four shorter (2.97 Å) and eight longer (3.14 Å) U–Al bond lengths. Fe is bonded in a 12-coordinate geometry to two equivalent U, two equivalent Fe, and eight Al atoms. Both Fe–Fe bond lengths are 2.50 Å. There are four shorter (2.52 Å) and four longer (2.63 Å) Fe–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to two equivalent U, four equivalent Fe, and six Al atoms. There are a spread of Al–Al bond distances ranging from 2.68–2.80 Å. In the second Al site, Al is bonded in a 10-coordinate geometry to one U, four equivalent Fe, and five Al atoms. The Al–Al bond length is 2.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(Al2Cr)4 by Materials Project

UCr4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U is bonded in a 12-coordinate geometry to eight equivalent Cr and twelve Al atoms. All U–Cr bond lengths are 3.38 Å. There are four shorter (3.03 Å) and eight longer (3.15 Å) U–Al bond lengths. Cr is bonded to two equivalent U, two equivalent Cr, and eight Al atoms to form a mixture of distorted edge, face, and corner-sharing CrU2Al8Cr2 cuboctahedra. Both Cr–Cr bond lengths are 2.50 Å. There are four shorter (2.56 Å) and four longer (2.67 Å) Cr–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one U, four equivalent Cr, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.73–2.88 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent U, four equivalent Cr, and six Al atoms. Both Al–Al bond lengths are 2.72 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(FeP)2 by Materials Project

U(FeP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent P atoms. All U–Fe bond lengths are 3.01 Å. All U–P bond lengths are 2.93 Å. Fe is bonded to four equivalent U and four equivalent P atoms to form a mixture of distorted edge, face, and corner-sharing FeU4P4 tetrahedra. All Fe–P bond lengths are 2.23 Å. P is bonded in a 9-coordinate geometry to four equivalent U, four equivalent Fe, and one P atom. The P–P bond length is 2.32 Å.

36 MATERIALS SCIENCE↗
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 U(NO7)2 by Materials Project

UNO7NO3(O2)2 crystallizes in the orthorhombic Cmc2_1 space group. The structure is zero-dimensional and consists of eight molecular oxygen molecules, four nitric acid molecules, and four UNO7 clusters. In each UNO7 cluster, U is bonded in a distorted rectangular see-saw-like geometry to six O atoms. There are a spread of U–O bond distances ranging from 1.83–2.45 Å. N is bonded in a trigonal planar geometry to three O atoms. There is one shorter (1.22 Å) and two longer (1.29 Å) N–O bond length. There are five inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one U atom. 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 single-bond geometry to one U and one N atom. In the fourth O site, O is bonded in a single-bond geometry to one N atom. In the fifth O site, O is bonded in a single-bond geometry to one U atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(Al10Cr)2 by Materials Project

U(CrAl10)2 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. U is bonded in a 4-coordinate geometry to four equivalent Cr and twelve equivalent Al atoms. All U–Cr bond lengths are 3.17 Å. All U–Al bond lengths are 3.16 Å. Cr is bonded in a 2-coordinate geometry to two equivalent U and twelve equivalent Al atoms. All Cr–Al bond lengths are 3.08 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded to twelve Al atoms to form a mixture of distorted face, edge, and corner-sharing AlAl12 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.59–2.93 Å. In the second Al site, Al is bonded to twelve Al atoms to form a mixture of face, edge, and corner-sharing AlAl12 cuboctahedra. All Al–Al bond lengths are 2.91 Å. In the third Al site, Al is bonded to one U, two equivalent Cr, and nine Al atoms to form a mixture of distorted face, edge, and corner-sharing AlUAl9Cr2 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.63–3.02 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(H2O3)2 by Materials Project

UO2(OH)4 crystallizes in the orthorhombic Pnma 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 1.80–2.44 Å. There are two inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to two O atoms. There is one shorter (1.00 Å) and one longer (1.76 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. There are four inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one U atom. 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 4-coordinate geometry to two equivalent U, one H, and one O atom. The O–O bond length is 1.45 Å. In the fourth O site, O is bonded in a distorted water-like geometry to one U and two H atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(NO7)2 by Materials Project

UO8(NO3)2 crystallizes in the orthorhombic Cmc2_1 space group. The structure is zero-dimensional and consists of eight nitric acid molecules and four UO8 clusters. In each UO8 cluster, U is bonded in a 4-coordinate geometry to six O atoms. There are a spread of U–O bond distances ranging from 1.81–2.79 Å. There are five inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.24 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 single-bond geometry to one U atom. In the fourth O site, O is bonded in a single-bond geometry to one U atom. In the fifth O site, O is bonded in a water-like geometry to one U and one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(NO5)2 by Materials Project

UNO8NO2 crystallizes in the monoclinic Cm space group. The structure is one-dimensional and consists of two nitrous acid molecules and two UNO8 ribbons oriented in the (0, 1, 0) direction. In each UNO8 ribbon, U is bonded in a distorted see-saw-like geometry to six O atoms. There are a spread of U–O bond distances ranging from 1.83–2.81 Å. N is bonded in a 4-coordinate geometry to four O atoms. There is two shorter (1.19 Å) and two longer (1.98 Å) N–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one U atom. 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 single-bond geometry to one N atom. In the fourth O site, O is bonded in a single-bond geometry to one N atom. In the fifth O site, O is bonded in a bent 150 degrees geometry to one U and one O atom. The O–O bond length is 1.23 Å. In the sixth O site, O is bonded in a distorted bent 150 degrees geometry to one U and one N atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(Al2Cu)4 by Materials Project

UCu4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U is bonded in a distorted square co-planar geometry to four equivalent Cu and sixteen Al atoms. All U–Cu bond lengths are 3.04 Å. There are eight shorter (3.33 Å) and eight longer (3.36 Å) U–Al bond lengths. Cu is bonded in a 10-coordinate geometry to one U, one Cu, and eight Al atoms. The Cu–Cu bond length is 2.62 Å. There are a spread of Cu–Al bond distances ranging from 2.70–2.91 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to two equivalent U, four equivalent Cu, and six Al atoms. There are four shorter (2.57 Å) and two longer (2.70 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent U, four equivalent Cu, and six Al atoms. Both Al–Al bond lengths are 2.75 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Measurement of low energy characteristic X-rays emitted present in U-10Mo HALEU alloy fuel

Advance high density monolithic alloy HALEU fuels have been scanned with a silicon drift detector scanning system to measure low-energy characteristic X-rays emitted by uranium daughters, as well as zirconium present as a foil diffusion barrier. Four peaks were measured across the surfaces of three plates, and are consistent with other thorium and protactinium peaks present in depleted uranium samples that are induced by the decay of 235 U and 238 U. Of the four peaks detected, three are dominated by the decay of 235 U, and one peak at 15.70 keV covers two characteristic X-rays from the zirconium diffusion barrier (Kα 1 ) and from a 231 Th 15.62 keV X-ray induced by 235 U α-decay. The low energies of these lines suggest that they are mostly emitted from the fuel meat surface, and the poor counting statistics caused by strong self-attenuation make these data a poor candidate for 235 U/ 238 U ratio analysis. We suggest, then, that these X-rays could be used for passive measurement of variations in the cladding thickness of these fuels to complement manual thickness measurement methods.

HALEU↗
DOE OSTI2021

Enhancing isotope mixing in U-10Mo downblend castings with electromagnetic stirring

Uranium alloyed with 10 wt percent molybdenum (U-10Mo) is the proposed fuel for use in the United States’ high-performance research reactors. The U-10Mo fuel is fabricated by a two-step casting process that downblends highly enriched uranium with depleted uranium (DU) and/or natural uranium (NU) and subsequently alloys the resulting high-assay low-enriched uranium (HALEU) with Mo. Currently, a two-step casting process is needed to meet the ingots’ U-235 enrichment homogeneity specifications. This work demonstrates the ability to provide more homogeneous U-235 distributions during downblend casting by using zirconia for crucibles rather than graphite. When graphite is used as a crucible, the electromagnetic field produced by the induction heater couples directly with the graphite. Zirconia is nonconducting in this study, and therefore does not couple with the field. The induction field couples directly with the metal, and causes electromagnetic stirring (EMS) in the molten metal pool. Eight downblend casting experiments were carried out in this work. Four were performed with zirconia crucibles and four with graphite crucibles. The U-235 enrichment was measured at nine discrete points in each casting using laser ablation multi-collector inductively coupled mass spectrometry (LA-MC-ICP-MS). The enrichment homogeneity was approximately eight times better in zirconia crucible castings than in graphite crucible castings as measured by the plate enrichment range and enrichment coefficient of variation. The results show a single casting step could be used to meet USHPRR enrichment specifications if electromagnetic stirring is present during casting. A related investigation was carried out to determine whether it is appropriate to measure enrichment on as-cast ingots or whether heat treated specimens should be used to accurately characterize enrichment. The results show that the as-cast microstructure plays a significant role in enrichment homogeneity. It is recommended that all enrichment measurements be done after the homogenization heat treatment typical of U-10Mo processing.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Computational determination of a primary diffusion mode in γ U-10Mo under irradiation

Low enriched uranium (< 20 % 235 U)-molybdenum (U-Mo) monolithic fuel is the primary candidate for high performance research and test reactors, and is in the process of being qualified to replace highly enriched uranium (≥ 20 % 23 5U) fuel. As part of the qualification process, it is critical to understand and predict the behavior of fission gas bubbles under irradiation, which affects fuel swelling and fuel failure. Mechanistic fuel models are being developed that can both reproduce the existing experimental data for fuel swelling, and be further applied to irradiation conditions beyond the experimental scope. Diffusion of species under irradiation conditions is an important parameter in the mechanistic fuel models; however, no temperature-relevant experimental diffusion data exists. In the present work, radiation-enhanced diffusion coefficients of U, Mo, and Xe in λU-10wt.%Mo were calculated in the temperature range between 300 K and 1400 K via rate-theory models and molecular dynamics simulations with an embedded-atom method interatomic potential for the U-Mo-Xe system. Accordingly, total diffusion coefficients under relevant irradiation conditions are determined using previously obtained intrinsic thermal diffusion and radiation-driven diffusion coefficients, as well as the newly calculated radiation-enhanced diffusion coefficients presented herein. Radiation-enhanced diffusion of U and Mo was dominant in the intermediate temperature range, whereas radiation-enhanced diffusion of Xe did not significantly contribute to total diffusion of Xe at the relevant fission rate densities. Radiation-enhanced diffusion of Xe became faster than both intrinsic thermal diffusion and radiation-driven diffusion at a fission rate density of 5 x 10 22 fissions/m 3 /s, which is higher than the typical fission rate density range in research reactors. The temperature regime that radiation-enhanced diffusion of each element dominated was dependent on the fission rate density. Finally, the total diffusion coefficients of U, Mo, and Xe, updated in this work, will be utilized as parameters in the mechanistic fuel models to help predict the behavior of fission gas bubbles under irradiation more accurately.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Performance of a triple-GEM detector with capacitive-sharing 3-coordinate (X–Y–U)-strip anode readout

The concept of capacitive-sharing readout, described in detail in a previous study, offers the possibility for the development of high-performance three-coordinates (X--Y--U)-strip readout for Micro Pattern Gaseous Detectors (MPGDs) using simple standard PCB fabrication techniques. Capacitive-sharing (X--Y--U)-strip readout allows simultaneous measurement of the Cartesian coordinates x and y of the position of the particles together with a third coordinate u along the diagonal axis in a single readout PCB. This provides a powerful tool to address multiple-hit ambiguity and enable pattern recognition capabilities in moderate particle flux environment of collider or fixed target experiments in high energy physics HEP) and nuclear physics (NP). We present in this paper the performance of a 10 cm × 10 cm triple-GEM detector with capacitive-sharing (X--Y--U)-strip anode readout. Spatial resolutions of the order of $\sigma_{x}^{res}$ = 71.6 $\pm$ 0.8 $\mu$m for X-strips, $\sigma_{y}^{res}$ = 56.2 $\pm$ 0.9 $\mu$m for Y-strips and $\sigma_{u}^{res}$ = 75.2 $\pm$ 0.9 $\mu$m for U-strips have been obtained at a beam test at Thomas Jefferson National Accelerator Facility (Jefferson Lab). Modifications of the readout design of future prototypes to improve the spatial resolution and challenges in scaling to large-area MPGDs are discussed.

(X-Y-U) strip↗
DOE OSTI2023

Annealing influence on the microstructure of irradiated U-Mo monolithic fuel foils

In this study we compared the microstructure evolution of U-Mo fuel foils produced with and without heat treatment at low burn-up via advanced post-irradiation examination. The aim of this study is to observe after irradiation the ways in which the fabrication processes have influenced fuel behavior at early-stage irradiation, as for very low burn up microstructural studies are lacking. In this work it was observed that the larger grain size detected in the heat-treated samples before irradiation led to decreased grain refinement after irradiation. Grain refinement was associated with the presence of small nano-size bubbles and precipitates. This phenomenon is hypothesized to influence early fuel swelling during reactor irradiation. Grain refinement was also observed to increase in regions where γ-U decomposition was present. Thus, it was enhanced in the samples fabricated without heat treatment. The heat treatment also increased the thickness of the U-Mo/Zr interface, namely of the UZr 2 layer. However, the influence of this layer on fuel performance needs further investigation. On one side, it may contribute to better mechanical bonding; on the other, it may influence swelling and blistering in the interaction layer as porosity increases when this layer is increased. This was observed especially in the presence of increased area containing low Mo concentration, and thus containing a higher fraction of the α-U phase, which is highly susceptible to irradiation induced swelling. Strong evidence of reverse transformation under irradiation (α-U + γ'-U2Mo → bcc γ-U) was observed in these samples. While the precipitates (carbides and oxide) seem to be unaffected by the irradiation at these low burnups. However, further analyses are necessary at higher burn-up to assess the exact impact different heat treatments have on fuel performance.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

U-Pu and Ba-Cs isotopic measurements on Trinitite by laser ablation sampling on the Neoma MC-ICP-MS

In this study we present the results of combined U-Pu and Ba-Cs isotope measurements obtained by laser ablation (LA) sampling of two glassy debris fragments (‘Trinitite’) from the world's first atomic bomb detonation conducted in New Mexico on July 16, 1945. Our primary goal in conducting these measurements was to understand whether examination of the U-Pu and Ba-Cs systematics by direct sampling (e.g. without any chemical separation or purification prior to isotope ratio measurement) could yield meaningful information that would differentiate the Trinitite fragments from glassy material lacking a nuclear fission signature. These measurements were conducted on a ThermoFisher Scientific Neoma multi collector – inductively coupled plasma – mass spectrometer (MC-ICP-MS), which is a relatively new MC-ICP-MS platform, so we also examine the behavior of these isotope systems in standards sampled in solution and via LA. Unsurprisingly, the measurements made on purified solutions of the U, Pu, and Ba isotopic standards produce high precision isotope ratios. Furthermore, this extends to the U-Pu measurements made by LA sampling, with the expected degradation in precision and accuracy related to matrix effects and signal intensity fluctuation. However, the Ba-Cs data acquired by LA is of low precision across all of the matrices examined and bears evidence of complex mass fractionation that will require further investigation to resolve. In total, our results indicate that the observed U-Pu isotope data are of sufficient quality to accurately constrain the U and Pu isotopic composition of glass containing sub-ppm levels of these elements which in turn could be used to differentiate glass containing anthropogenic fission products from natural glass whereas the Ba-Cs LA data cannot be used for this purpose until further methodological refinement is performed.

Ba-Cs↗
DOE OSTI2022

NSTX-U theory, modeling and analysis results

Here, the mission of the low aspect ratio spherical tokamak NSTX-U is to advance the physics basis and technical solutions required for optimizing the configuration of next-step steady-state tokamak fusion devices. NSTX-U will ultimately operate at up to 2 MA of plasma current and 1 T toroidal field on axis for 5 s, and has available up to 15 MW of neutral beam injection power at different tangency radii and 6 MW of high harmonic fast wave heating. With these capabilities NSTX-U will develop the physics understanding and control tools to ramp-up and sustain high performance fully non-inductive plasmas with large bootstrap fraction and enhanced confinement enabled via the low aspect ratio, high beta configuration. With its unique capabilities, NSTX-U research also supports ITER and other critical fusion development needs. Super-Alfvénic ions in beam-heated NSTX-U plasmas access energetic particle (EP) parameter space that is relevant for both α-heated conventional and low aspect ratio burning plasmas. NSTX-U can also generate very large target heat fluxes to test conventional and innovative plasma exhaust and plasma facing component solutions. This paper summarizes recent analysis, theory and modelling progress to advance the tokamak physics basis in the areas of macrostability and 3D fields, EP stability and fast ion transport, thermal transport and pedestal structure, boundary and plasma material interaction, RF heating, scenario optimization and real-time control.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗