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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Challenges in correlating oxygen stable isotope ratios of hydrates on uranium ore concentrates to process waters

Exchange of oxygen stable isotopes (δ 18 O values) between precipitation waters and uranium oxides is governed by thermodynamics or kinetics. It has been assumed that meteoric waters can be related to precipitation waters in uranium ore concentrates and their calcination and reduced uranium oxide products. With this assumption, the δ 18 O values of uranium materials could provide forensic signatures that identify the production history and geolocation of nuclear materials. To further exploit the potential of δ 18 O values in nuclear material analysis, this study examines the oxygen stable isotope exchange in two UOCs, magnesium diuranate (MDU) and sodium diuranate (SDU). MDU and SDU were synthesized from solutions of uranyl nitrate hexahydrate using precipitation waters with unique oxygen isotope compositions. The structures of the MDU and SDU were analyzed using powder X-ray diffraction (p-XRD) and thermal mass loss curves, while the δ 18 O values of waters generated during thermal decomposition were analyzed using a thermogravimetric analyzer coupled to an isotope ratio infrared spectrometer (TGA-IRIS). By p-XRD, the MDU was uniform and amorphous across all syntheses with residual crystalline material incorporated as a minor component. Combined with the TGA results, all of the MDU is likely amorphous MgU 2 O 7 ·3H 2 O with MgO impurities present throughout. In contrast, the SDU synthesis resulted in multiple phases with many samples exhibiting crystalline phases including a combination of Na(UO 2 ) 4 O 2 (OH) 5 ·5H 2 O and Na 2 (UO2) 6 O 4 (OH) 6 ·8H 2 O with a Na 2 U 2 O 7 minor phase. A small fraction of the SDU samples were amorphous with no crystalline XRD peaks observed. Mass loss curves of the SDU samples revealed that the amorphous samples contained inclusions of similar crystalline phases compared to the crystalline materials. The uniformity of the MDU samples enabled highly reproducible measurements of δ 18 O values of the water vapor yielded for two dehydration events at 170 °C and 500 °C. In contrast, the multiphase composition of the SDU samples resulted in poor reproducibility in δ 18 O values. In conclusion, neither system revealed any correlation between the δ 18 O values of precipitation water, and the waters released during dehydration of the UOCs.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Materials Data on U2V2O11 by Materials Project

(UO2)2(V2O7) crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. U6+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of U–O bond distances ranging from 1.79–2.61 Å. V5+ is bonded to four O2- atoms to form corner-sharing VO4 tetrahedra. There are a spread of V–O bond distances ranging from 1.71–1.80 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one U6+ and one V5+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent U6+ and one V5+ atom. In the third O2- site, O2- is bonded in a linear geometry to two equivalent V5+ atoms. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent U6+ and one V5+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one U6+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one U6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(HO2)2 by Materials Project

UO2(OH)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. U6+ is bonded to six O2- atoms to form corner-sharing UO6 octahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of U–O bond distances ranging from 2.00–2.32 Å. H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.72 Å) H–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent U6+ and one H1+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(HO2)2 by Materials Project

UO2(OH)2 crystallizes in the orthorhombic Cmce space group. The structure is zero-dimensional and consists of four pitchblend, uranium(iv) oxide, uranium(iv) dioxide, uranium dioxide molecules and eight water molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(HO2)2 by Materials Project

UO2(OH)2 crystallizes in the orthorhombic Cmc2_1 space group. The structure is zero-dimensional and consists of four pitchblend, uranium(iv) oxide, uranium(iv) dioxide, uranium dioxide molecules and eight water molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2U2MoO10 by Materials Project

K2(UO2)2(MoO4)O2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of K–O bond distances ranging from 2.78–2.95 Å. In the second K1+ site, K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.75–3.19 Å. There are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of U–O bond distances ranging from 1.85–2.42 Å. In the second U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with two equivalent MoO4 tetrahedra and an edgeedge with one UO7 pentagonal bipyramid. There are a spread of U–O bond distances ranging from 1.84–2.62 Å. Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with two equivalent UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.77–1.83 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three K1+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three U6+ atoms. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one K1+, one U6+, and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one K1+ and three U6+ atoms. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one U6+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one U6+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one U6+ atom. In the ninth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one U6+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UH14(NO2)4 by Materials Project

UO2(NH2O)2(NH2OH)2(H2O)2 crystallizes in the orthorhombic Pbca space group. The structure is zero-dimensional and consists of eight hydroxyammonium molecules; eight hydroxylamine molecules; four pitchblend, uranium(iv) oxide, uranium(iv) dioxide, uranium dioxide molecules; and eight water molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UH16C4(NO3)4 by Materials Project

UO2(NH4)3(CO2)4NH2OH2O crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of twelve ammonium molecules; sixteen formic acid molecules; four hydroxylamine molecules; four pitchblend, uranium(iv) oxide, uranium(iv) dioxide, uranium dioxide molecules; and four water molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UH12(NO7)2 by Materials Project

UO2(NO3)2(H2O)6 crystallizes in the orthorhombic Cmc2_1 space group. The structure is zero-dimensional and consists of eight nitric acid molecules; four pitchblend, uranium(iv) oxide, uranium(iv) dioxide, uranium dioxide molecules; and twenty-four water molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on UBr4(NO2)2 by Materials Project

UO2(NO)2(Br)4 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of one 1,3,2,4-dioxadiazetidine molecule; four hydrobromic acid molecules; and one pitchblend, uranium(iv) oxide, uranium(iv) dioxide, uranium dioxide molecule.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(C2O5)2 by Materials Project

UO2(CO2)4 crystallizes in the orthorhombic Ccce space group. The structure is zero-dimensional and consists of sixteen formic acid molecules and four pitchblend, uranium(iv) oxide, uranium(iv) dioxide, uranium dioxide molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs3U2PO10 by Materials Project

Cs3(UO2)2(PO4)O2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 5-coordinate geometry to eight O2- atoms. There are a spread of Cs–O bond distances ranging from 3.12–3.60 Å. In the second Cs1+ site, Cs1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cs–O bond distances ranging from 3.02–3.18 Å. There are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded to six O2- atoms to form UO6 octahedra that share corners with two equivalent UO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are a spread of U–O bond distances ranging from 1.88–2.42 Å. In the second U6+ site, U6+ is bonded to six O2- atoms to form UO6 octahedra that share corners with two equivalent UO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are a spread of U–O bond distances ranging from 1.89–2.30 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four UO6 octahedra. The corner-sharing octahedra tilt angles range from 34–53°. There is two shorter (1.55 Å) and two longer (1.57 Å) P–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to two Cs1+, one U6+, and one P5+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to three Cs1+ and one U6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+, one U6+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Cs1+ and two U6+ atoms. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to three Cs1+ and one U6+ atom.

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 UC3N4O11 by Materials Project

UO2(N2)2(CO3)3 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of sixteen ammonia molecules; twelve carbonic acid molecules; and four pitchblend, uranium(iv) oxide, uranium(iv) dioxide, uranium dioxide molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Optical Vibrational Spectroscopic Investigation of Natural and Synthetic Analogs of Uranyl Oxyhydroxyhydrate Minerals

Uranyl oxy-hydroxy-hydrate minerals are common alteration products of uraninite (UO2+x) which is chemically and structurally analogous to uranium dioxide nuclear fuel. Therefore, structural and spectroscopic investigations of these alteration minerals and their analogous anthropogenic counterparts can provide insight into the environmental behavior of nuclear fuel cycle materials. Previously, we compiled available vibrational spectroscopic data for uranyl minerals in the Compendium of Uranium Raman and Infrared Experimental Spectra (CURIES) and found that only 37% of known uranyl oxy-hydroxy-hydrate minerals had spectra readily available in the literature and existing databases for inclusion therein. Furthermore, no available infrared spectra for this mineral group were included in CURIES. To expand our understanding of the spectroscopic features of uranyl oxy-hydroxy-hydrates and the structural origins thereof, we collected, and now include in CURIES, Raman and infrared spectra for an additional 12 uranyl hydroxide phases. To better understand the impact of structural and compositional variations of these phases on their spectroscopic features, we compare Raman spectra of different anion sheet topological groups and of analogous phases hosting different counter cations. We identify spectroscopic variations related to differences in equatorial bonding and structural changes as a result of cation substitution. We also prepare a uranyl hydroxide phase via hydrolysis of uranyl fluoride (UO2F2) as an analog of hydrolysis reactions that occur in nuclear fuel cycle materials; and we find that the alteration product of UO2F2, despite chemical and structural similarities to uranyl oxy-hydroxy-hydrate minerals, is readily distinguishable from related mineral phases using Raman spectroscopy. In this work, we provide new insights into the structural origins of spectroscopic features in uranyl oxy-hydroxy-hydrate minerals, improve the average Raman spectrum for this group of minerals, and thereby improve capabilities for identifying these mineral species and related anthropogenic phases using Raman spectroscopy.

Barth, Brodie [ORNL] (ORCID:0000000256142601)↗
DOE OSTI2019

Safety Testing and Destructive Examination of AGR-2 UCO Compact 6-4-3

Post-irradiation examination (PIE) and elevated-temperature safety testing are being performed on tristructural-isotropic (TRISO) coated-particle fuel compacts from the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program’s second irradiation experiment (AGR-2). Details on this irradiation experiment have been previously reported. The AGR-2 PIE effort builds upon the understanding acquired throughout the AGR-1 PIE campaign (Demkowicz et al. 2015) and is establishing a database for the different AGR-2 fuel designs. The AGR-2 irradiation experiment included TRISO fuel particles coated at BWX Technologies (BWXT) with an engineering-scale coater, which had a coating chamber 150 mm in diameter. Two coating batches were tested in the AGR-2 irradiation experiment. Batch G73H-10-93085B had uranium dioxide (UO2) kernels with an average diameter of 508 µm. Batch G83J-14-93073A had UCO kernels with an average diameter of 427 µm; in this kernel design, some of the uranium oxide is converted to uranium carbide during fabrication to provide a getter for oxygen liberated during fission and to limit CO production. Fabrication and property data for the AGR-2 coating batches have been compiled and compared to AGR-1. The AGR-2 TRISO coatings were most like the AGR-1 Variant 3 TRISO deposited in the Oak Ridge National Laboratory (ORNL) laboratory-scale coater, which had a coating chamber 50 mm in diameter (Hunn and Lowden 2006). In both cases, the hydrogen and methyltrichlorosilane coating gas mixture that was used to deposit the SiC was diluted with argon to produce a finer grained, more equiaxed SiC microstructure. In addition to the fact that AGR-1 fuel had smaller UCO kernels that were 350 µm in diameter, other notable differences in the TRISO particle properties included (1) the pyrocarbon anisotropy, which was slightly higher in the particles coated in the engineering-scale coater, and (2) the exposed kernel defect fraction, which was higher for AGR-2 fuel due to the detected presence of particles with impact damage that was introduced during TRISO particle handling.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Safety Testing and Destructive Examination of SGR-2 UCO Compact 2-1-2

Post-irradiation examination (PIE) and elevated-temperature safety testing are being performed on tristructural-isotropic (TRISO) coated-particle fuel compacts from the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program’s second irradiation experiment (AGR-2). Details on this irradiation experiment have been previously reported. The AGR-2 PIE effort builds upon the understanding acquired throughout the AGR-1 PIE campaign and is establishing a database for the different AGR-2 fuel designs. The AGR-2 irradiation experiment included TRISO fuel particles coated at BWX Technologies (BWXT) with an engineering-scale coater, which had a coating chamber 150 mm in diameter. Two coating batches were tested in the AGR-2 irradiation experiment. Batch G73H-10-93085B had uranium dioxide (UO2) kernels with an average diameter of 508 µm. Batch G83J-14-93073A had UCO kernels with an average diameter of 427 µm; in this kernel design, some of the uranium oxide is converted to uranium carbide during fabrication to provide a getter for oxygen liberated during fission and to limit CO production. Fabrication and property data for the AGR-2 coating batches have been compiled and compared to AGR-1. The AGR-2 TRISO coatings were most like the AGR-1 Variant 3 TRISO deposited in the Oak Ridge National Laboratory (ORNL) laboratory-scale coater, which had a coating chamber 50 mm in diameter (Hunn and Lowden 2006). In both cases, the hydrogen and methyltrichlorosilane coating gas mixture that was used to deposit the SiC was diluted with argon to produce a finer grained, more equiaxed SiC microstructure. In addition to the fact that AGR-1 fuel had smaller UCO kernels that were 350 µm in diameter, other notable differences in the TRISO particle properties included (1) the pyrocarbon anisotropy, which was slightly higher in the particles coated in the engineering-scale coater, and (2) the exposed kernel defect fraction, which was higher for AGR-2 fuel due to the detected presence of particles with impact damage that was introduced during TRISO particle handling.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

TREAT Fuel Motion Summary Report. SETH A-E Experiments

In support of the Accident Tolerant Fuels program, experiment devices are being developed to enable transient testing of pressurized water reactor (PWR) type fuel specimens. In fiscal year 2019 several fueled tests were conducted in the Transient Reactor Test Facility (TREAT) using the Separate Effects Test Holder (SETH). Five different SETH capsules (SETH A-E) were assembled, each holding a 10-pellet rodlet with 4.9% enriched, commercially-produced fresh UO2 pellets in zirconium alloy cladding with pellet dimensions having typical PWR radial dimensions and a total pellet stack length measuring 10.16 cm. The rodlet’s length allows the specimen to be axially positioned in the center of the core with minimal flux variation over the height of the rodlet. The fuel motion monitoring system (FMMS) is located on the north side of the TREAT reactor. Having direct line-of-sight of the core enables the FMMS to collect spatially-resolved data for fast neutrons generated due to fission occurring in experiment specimens. The FMMS contains 360 channels that make up a 10 (horizontal) by 36 (vertical) array of viewing slots; for the SETH A-E test series 96 proton-recoil scintillator (PRS) detectors were installed in the system. The fast neutrons are detected in the PRS detectors from light produced by the recoil of protons interacting with ZnS(Ag) grains in each detector's scintillator button. This report focuses on the FMMS data captured in the SETH A-E experiments, with multiple transients varying in reactivity addition and length. The first three experiments had a total reactor energy of 101 MJ each and were critical in understanding the FMMS field of view, lead shielding, and other TREAT data acquisition systems. SETH-B2 and C had a reactivity addition of almost double the previous transients and served as a demonstration of the detector array behavior under increased reactor energy. The final two SETH experiments (D and E) were aimed at reaching cladding melting temperatures with a reactor energy over 500 MJ for each test. In preparation for the higher energy transients, the FMMS lead shielding was reduced to 0.5 inches from the 6 inches used in SETH A-C. This was expected to saturate the detectors at the peak of the transient in exchange for higher sensitivity at lower energies after the peak, when the motion was expected. SETH-D was clipped at approximately 3 seconds, which was too early for the FMMS to capture any rodlet motion. SETH-E had the same reactivity addition as SETH-D but the transient time was extended to 18 seconds. The FMMS captured the downward motion of the rodlet in SETH-E as the count rate significantly changed for the detectors viewing the specimen. Snapshots taken throughout the transient helped identify the approximate time at which the motion initiated. Further analysis of the individual detector data captured on a per-millisecond time basis resulted in a determination that the approximate time for the onset of the downward motion was 2.84 ± 0.02 seconds. Neutron radiographs confirmed that downward motion occurred for SETH-D and SETH-E. Motion in SETH-D could also have been captured by the FMMS if the transient time had been longer for SETH-D. Ultimately, these final two tests served to demonstrate the FMMS's ability to track fuel motion during transient experiments at TREAT.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗