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7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Spark plasma sintering of fuel meats for U 3 O 8 based dispersion fuels

Research and test reactors often use dispersion-type fuel due to its increased thermal conductivity and burn-up capabilities compared to conventional fuel. Al-U 3 O 8 (aluminumtriuranium octaoxide) dispersion fuels have several advantages over their competitors, such as higher service temperature and better stability of oxygen stoichiometry. However, the two-step fabrication of dispersion fuel causes undesirable porosity in cold-pressed fuel meats that is preserved in co-extruded fuel plates. To combat this, spark plasma sintering (SPS) was used for the fabrication of Al-15, 20, and 30 vol% U 3 O 8 and 8 and 12 vol% Mo-U 3 O 8 fuel meats for the Al-U 3 O 8 time. The in situ SPS data was used to construct and validate Master Sintering Curves (MSCs) with accuracies in Al fuels at 0.02 g/cm 3 , and Mo fuels at 0.07 and 0.17 g/cm 3 . The as-sintered fuel meats were characterised using x-ray diffraction (XRD) and scanning electron microscopy (SEM) to understand chemical and physical changes following the SPS process. The pellets exhibited very high relative densities, the U 3 O 8 was observed to undergo reduction to UO 2 .

Aluminium↗
NASA NTRS1973

Nuclear characteristics of a fissioning uranium plasma test reactor with light-water cooling

An analytical study was performed to determine a design configuration for a cavity test reactor. Test section criteria were that an average flux of 10 to the 15th power neutrons/sq cm/sec (E less than or equal to 0.12 eV) be supplied to a 61-cm-diameter spherical cavity at 200-atm pressure. Design objectives were to minimize required driver power, to use existing fuel-element technology, and to obtain fuel-element life of 10 to 100 full-power hours. Parameter calculations were made on moderator region size and material, driver fuel arrangement, control system, and structure in order to determine a feasible configuration. Although not optimized, a configuration was selected which would meet design criteria. The driver fuel region was a cylindrical annular region, one element thick, of 33 MTR-type H2O-cooled elements (Al-U fuel plate configuration), each 101 cm long. The region between the spherical test cavity and the cylindrical driver fuel region was Be (10 vol. % H2O coolant) with a midplane dimension of 8 cm. Exterior to the driver fuel, the 25-cm-thick cylindrical and axial reflectors were also Be with 10 vol. % H2O coolant. The entire reactor was contained in a 10-cm-thick steel pressure vessel, and the 200-atm cavity pressure was equalized throughout the driver reactor. Fuel-element life was 50 hr at the required driver power of 200 MW. Reactor control would be achieved with rotating poison drums located in the cylindrical reflector region. A control range of about 18 percent delta k/k was required for reactor operation.

Whitmarsh, C. L., Jr.↗
DOE OSTI2020

Materials Data on UAl2 by Materials Project

UAl2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. U is bonded in a 12-coordinate geometry to four equivalent U and twelve equivalent Al atoms. All U–U bond lengths are 3.34 Å. All U–Al bond lengths are 3.20 Å. Al is bonded to six equivalent U and six equivalent Al atoms to form a mixture of edge, face, and corner-sharing AlU6Al6 cuboctahedra. All Al–Al bond lengths are 2.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UAl3 by Materials Project

UAl3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. U is bonded to twelve equivalent Al atoms to form UAl12 cuboctahedra that share corners with twelve equivalent UAl12 cuboctahedra, edges with twenty-four equivalent AlU4Al8 cuboctahedra, faces with six equivalent UAl12 cuboctahedra, and faces with twelve equivalent AlU4Al8 cuboctahedra. All U–Al bond lengths are 3.01 Å. Al is bonded to four equivalent U and eight equivalent Al atoms to form AlU4Al8 cuboctahedra that share corners with twelve equivalent AlU4Al8 cuboctahedra, edges with eight equivalent UAl12 cuboctahedra, edges with sixteen equivalent AlU4Al8 cuboctahedra, faces with four equivalent UAl12 cuboctahedra, and faces with fourteen equivalent AlU4Al8 cuboctahedra. All Al–Al bond lengths are 3.01 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UAl4 by Materials Project

UAl4 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. U is bonded in a 9-coordinate geometry to thirteen Al atoms. There are a spread of U–Al bond distances ranging from 3.01–3.13 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 3-coordinate geometry to three equivalent U and ten Al atoms. There are a spread of Al–Al bond distances ranging from 2.86–3.07 Å. In the second Al site, Al is bonded in a 10-coordinate geometry to three equivalent U and seven Al atoms. There are a spread of Al–Al bond distances ranging from 2.61–2.77 Å. In the third Al site, Al is bonded to four equivalent U and eight Al atoms to form a mixture of distorted face, edge, and corner-sharing AlU4Al8 cuboctahedra. Both Al–Al bond lengths are 3.12 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UAl2 by Materials Project

UAl2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent U sites. In the first U site, U is bonded in a 1-coordinate geometry to one U and twelve Al atoms. The U–U bond length is 2.62 Å. There are a spread of U–Al bond distances ranging from 3.09–3.34 Å. In the second U site, U is bonded in a 1-coordinate geometry to one U and twelve Al atoms. The U–U bond length is 2.59 Å. There are a spread of U–Al bond distances ranging from 3.08–3.34 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded to six U and six Al atoms to form a mixture of corner, edge, and face-sharing AlU6Al6 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.65–2.94 Å. In the second Al site, Al is bonded to six U and six Al atoms to form a mixture of corner, edge, and face-sharing AlU6Al6 cuboctahedra. There are two shorter (2.70 Å) and four longer (2.80 Å) Al–Al bond lengths. In the third Al site, Al is bonded to six U and six Al atoms to form a mixture of corner, edge, and face-sharing AlU6Al6 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UAl3 by Materials Project

UAl3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. U is bonded to twelve equivalent Al atoms to form a mixture of corner and face-sharing UAl12 cuboctahedra. There are six shorter (3.02 Å) and six longer (3.09 Å) U–Al bond lengths. Al is bonded in a 10-coordinate geometry to four equivalent U and six equivalent Al atoms. There are two shorter (2.83 Å) and four longer (2.84 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗