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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Impact of fission product inclusion on phase development in U 3 Si 2 fuel

Due to its high thermal conductivity and uranium density, U 3 S i2 has been considered as a candidate for use as an accident tolerant fuel (ATF). In order to fully assess its suitability and performance as a fuel, the impact of fission products (FPs) on the stability and performance of U 3 Si 2 must be investigated. The interactions of FPs and U 3 Si 2 have had relatively little study until now and require experimental and computational examination. U 3 Si 2 was doped with individual FPs to explore U-Si-FP interactions and phase equilibria that may impact the performance of the ATF during irradiation. Elemental Ce, Mo, Y, or Zr were used to individually dope U 3 Si 2 at a concentration of 5 wt% FP. A diffusion couple of a 1:1 Mo:Zr alloy and U 3 Si 2 was heated to 1200 °C in order to consider the impacts of multiple FPs on the stability and structure of the fuel. Samples were characterized for FP solubility and secondary phase formation using electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. First principles density functional theory calculations complemented the experimental effort to understand FP behavior. Experimental and computational findings were used in the development of a thermodynamic database containing 8 major FPs and their associated silicide phases. Finally, fuel compositions generated from depletion calculations were used to thermodynamically model the equilibrium phases of the fuel undergoing burnup.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Molecular Models of Atomically Dispersed Uranium at MoS 2 Surfaces Reveal Cooperative Mechanism of Water Reduction

Single atoms of uranium supported on molybdenum sulfide surfaces (U@MoS 2 ) have been recently demonstrated to facilitate the hydrogen evolution reaction (HER) through electrocatalysis. Theoretical calculations have predicted uranium hydroxide moieties bound to edge-sulfur atoms of MoS 2 as a proposed transition state involved in the HER process. However, the isolation of relevant intermediates involved in this process remains a challenge, rendering mechanistic hypotheses unverified. The present work describes the isolation and characterization of a uranium-hydroxide intermediate on molybdenum sulfide surfaces using [(Cp* 3 Mo 3 S 4 )UCp*], a molecular model of a reduced uranium center supported at MoS 2 . Mechanistic investigations highlight the metalloligand cooperativity with uranium involved in the water activation pathway. The corresponding uranium-oxo analogue, [(Cp* 3 Mo 3 S 4 )Cp*U(═O)], was also accessed from the hydroxide cluster via hydrogen atom transfer and from [(Cp* 3 Mo 3 S 4 )UCp*] through an alternative direct oxygen atom transfer. These results provide an atomistic perspective on the reactivity of low-valent uranium at molybdenum sulfide surfaces toward water, modeling key intermediates associated with the HER of U@MoS 2 catalysts.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2021

Recovery of high specific activity molybdenum-99 from accelerator-induced fission on low-enriched uranium for technetium-99m generators

Abstract A new process was developed to recover high specific activity (no carrier added) 99 Mo from electron-accelerator irradiated U 3 O 8 or uranyl sulfate targets. The process leverages a novel solvent extraction scheme to recover Mo using di(2-ethylhexyl) phosphoric acid following uranium and transuranics removal with tri- n -butyl phosphate. An anion-exchange concentration column step provides a final purification, generating pure 99 Mo intended for making 99 Mo/ 99m Tc generators. The process was demonstrated with irradiated uranium targets resulting in more than 95% 99 Mo recovery and without presence of fission products or actinides in the product.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Materials Data on CsNa3U4(MoO10)2 by Materials Project

CsNa3U4(MoO10)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Cs1+ is bonded in a 2-coordinate geometry to eight O2- atoms. There are a spread of Cs–O bond distances ranging from 3.04–3.65 Å. There are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.47–2.82 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.38–2.89 Å. There are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded to seven O2- atoms to form distorted edge-sharing UO7 pentagonal bipyramids. There are a spread of U–O bond distances ranging from 1.87–2.48 Å. In the second U6+ site, U6+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of U–O bond distances ranging from 1.85–2.59 Å. Mo6+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Mo–O bond distances ranging from 1.75–2.35 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Cs1+, one U6+, and two equivalent Mo6+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+ and three U6+ atoms. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+ and one U6+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Na1+ and one U6+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two U6+ and one Mo6+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to two Na1+ and one U6+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to three U6+ atoms. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to one Cs1+, one Na1+, and one U6+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+, one U6+, and one Mo6+ atom. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to one Cs1+, one Na1+, and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Elemental analysis of air-sensitive frozen molten salt samples using an inert transfer chamber for LIBS/LA-ICP-TOF-MS analysis

A novel inert sample transfer system was developed and employed to enable, for the first time, the analysis of air-sensitive salt samples in a two-volume ablation cell using simultaneous laser-induced breakdown spectroscopy (LIBS) and laser ablation (LA)-inductively coupled plasma (ICP)-time-of-flight (TOF)-mass spectrometry (MS) analysis. Molten salts are of growing interest as a medium for advanced nuclear reactors and nuclear fuel reprocessing technologies continue to be developed around their use. However, compositional analysis of molten salt samples can be challenging because of their air-sensitive nature and varying solubilities leading to inaccurate measurements when digested. LA-based analysis provides an alternate method to digestion and can provide rapid elemental information with little sample preparation. In this study, LIBS and LA-ICP-TOF-MS were used to analyze the Ce content in frozen salt samples taken from a series of electrochemical experiments. Calibrations were built for each technique, and the resulting limits of detection for Ce were estimated to be 107 and 58 µg g −1 for LIBS and LA-ICP-TOF-MS, respectively. Test samples from the electrochemical experiments were analyzed using these calibrations. The results matched bulk digestion-based ICP-optical emission spectroscopy values, and daily trends in Ce concentration changes were identified. Additionally, the LIBS and LA-ICP-TOF-MS analysis was demonstrated for identifying microgram per gram levels of components and detecting trace contaminants. The impurities detected by LIBS included Al, Mg, Ca, and Na. The impurities detected by LA-ICP-TOF-MS included W, Ag, Al, Fe, Ni, Mo, Nd, Sm, Th, and U.

Andrews, Hunter B. [Oak Ridge National Laboratory ↗
DOE OSTI2021

Evaluation of Niowave's Proposed Solvent Washing Approach

Niowave, Inc., is a domestic supplier of medical and industrial isotopes from uranium (U) and radium (Ra). The company has recently entered into a cooperative agreement with the U.S. Department of Energy’s National Nuclear Security Administration (NNSA) and plans to deploy a superconducting electron accelerator (LINAC) to fission U for molybdenum-99 ( 99 Mo) production without the need for a nuclear reactor or highly enriched uranium (HEU). NNSA provided funding to the Savannah River National Laboratory (SRNL) to support Niowave in this effort. SRNL evaluated the application of the solvent washing process for Niowave.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1985

Thermal regimes in the detachment fault environment as deduced from fluid inclusions

Extensional tectonism, which dominates middle- and late-Tertiary geology in western Arizona, southeastern California, and southern Nevada, is characterized by normal regionally extensive, low-angle detachment faults. The decollement movement of Fupper plate rocks relative to lower plate assemblages created extensive zones of dilatency, including synthetic and antithetic listric normal faults, tear faults, tectonic crush breccias, shatter breccias, and gash veins in lithologic units above and below the detachment. The tectonically enhanced permeability above and below the detachment fault permitted mass migration of large volumes of hydrothermal solutions along the fault zone during and following upper plate movement. Major quantities of MgO, CaO, K2O, FeO/Fe2O3, SiO2 and CO2 were added to rocks in and near the detachment and related structures. Also introduced were varying amounts of trace elements including Mn, Cu, S, Mo, Ba, Au, Pb, Zn, U and/or Ag. Minerals containing fluid incusions were collected from all of these loci at locations in detachment faulted terranes in western Arizona and southeastern California.

Beane, R. E.↗
DOE OSTI2021

Determination of Thermal Expansion, Defect Formation Energy, and Defect-Induced Strain of α-U Via ab Initio Molecular Dynamics

Uranium (U) is often alloyed with molybdenum (Mo) or zirconium (Zr) in order to stabilize its high-temperature body-centered cubic phase for use in nuclear reactors. However, in all metallic fuel forms, the α phase of U remains in some fraction. This phase decomposition due to temperature or compositional variance can play an outsized role on fuel performance and microstructural evolution. Relatively little is known about fundamental point defect properties in α -U at non-zero temperatures, from either computational or experimental studies. This work performs the first thorough evaluation of the α phase of U via ab initio molecular dynamics (AIMD). A number of thermophysical properties are calculated as a function of temperature, including equilibrium lattice parameters, thermal expansion, and heat capacity. These results indicate a two-region behavior, with the transition at 400 K. The thermal expansion/contraction in the a / b direction occurs rapidly from 100 up to 400 K, after which a more linear and gradual change in the lattice constant takes place. The volumetric expansion matches experiments quantitatively, but the individual lattice constant expansion only matches experiments qualitatively. Point defect formation energies and induced lattice strains are also determined as a function of temperature, providing insight on defect populations and the fundamentals of irradiation growth in α -U. Interstitials induce significantly more strain than vacancies, and the nature of that strain is highly dependent on the individual lattice directions. The direction of point defect-induced lattice strain is contrary to the irradiation growth behavior of α -U. This work shows that isolated point defects cannot be the primary driving force responsible for the significant irradiation-induced growth of α -U observed experimentally.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Materials Data on U5(B12Mo5)2 by Materials Project

U5(Mo5B12)2 crystallizes in the orthorhombic Pmmn space group. The structure is three-dimensional. there are three inequivalent U+3.20+ sites. In the first U+3.20+ site, U+3.20+ is bonded in a 11-coordinate geometry to fourteen B+1.50- atoms. There are a spread of U–B bond distances ranging from 2.61–2.84 Å. In the second U+3.20+ site, U+3.20+ is bonded in a 10-coordinate geometry to ten B+1.50- atoms. There are a spread of U–B bond distances ranging from 2.63–2.92 Å. In the third U+3.20+ site, U+3.20+ is bonded in a 8-coordinate geometry to thirteen B+1.50- atoms. There are a spread of U–B bond distances ranging from 2.72–3.19 Å. There are six inequivalent Mo2+ sites. In the first Mo2+ site, Mo2+ is bonded in a 9-coordinate geometry to nine B+1.50- atoms. There are a spread of Mo–B bond distances ranging from 2.28–2.34 Å. In the second Mo2+ site, Mo2+ is bonded in a 9-coordinate geometry to nine B+1.50- atoms. There are a spread of Mo–B bond distances ranging from 2.27–2.32 Å. In the third Mo2+ site, Mo2+ is bonded in a 9-coordinate geometry to nine B+1.50- atoms. There are a spread of Mo–B bond distances ranging from 2.26–2.61 Å. In the fourth Mo2+ site, Mo2+ is bonded in a 9-coordinate geometry to nine B+1.50- atoms. There are a spread of Mo–B bond distances ranging from 2.26–2.37 Å. In the fifth Mo2+ site, Mo2+ is bonded in a 8-coordinate geometry to eight B+1.50- atoms. There are a spread of Mo–B bond distances ranging from 2.28–2.37 Å. In the sixth Mo2+ site, Mo2+ is bonded in a 6-coordinate geometry to six B+1.50- atoms. There are four shorter (2.38 Å) and two longer (2.41 Å) Mo–B bond lengths. There are fourteen inequivalent B+1.50- sites. In the first B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to two equivalent U+3.20+, four Mo2+, and three B+1.50- atoms. There is one shorter (1.79 Å) and two longer (1.83 Å) B–B bond length. In the second B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to two equivalent U+3.20+, five Mo2+, and two equivalent B+1.50- atoms. Both B–B bond lengths are 1.89 Å. In the third B+1.50- site, B+1.50- is bonded in a 3-coordinate geometry to three equivalent U+3.20+, three equivalent Mo2+, and three B+1.50- atoms. There is two shorter (1.82 Å) and one longer (1.83 Å) B–B bond length. In the fourth B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to three U+3.20+, three Mo2+, and three B+1.50- atoms. Both B–B bond lengths are 1.83 Å. In the fifth B+1.50- site, B+1.50- is bonded in a 3-coordinate geometry to three U+3.20+, three Mo2+, and three B+1.50- atoms. The B–B bond length is 1.80 Å. In the sixth B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to two equivalent U+3.20+, four Mo2+, and three B+1.50- atoms. There is two shorter (1.84 Å) and one longer (1.91 Å) B–B bond length. In the seventh B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to three U+3.20+, three Mo2+, and three B+1.50- atoms. Both B–B bond lengths are 1.82 Å. In the eighth B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to two U+3.20+, five Mo2+, and two equivalent B+1.50- atoms. In the ninth B+1.50- site, B+1.50- is bonded in a 3-coordinate geometry to three U+3.20+, three Mo2+, and three B+1.50- atoms. In the tenth B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to two U+3.20+, five Mo2+, and two equivalent B+1.50- atoms. In the eleventh B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to four equivalent U+3.20+, two equivalent Mo2+, and three B+1.50- atoms. The B–B bond length is 1.77 Å. In the twelfth B+1.50- site, B+1.50- is bonded in a 3-coordinate geometry to three equivalent U+3.20+, three equivalent Mo2+, and three B+1.50- atoms. Both B–B bond lengths are 1.83 Å. In the thirteenth B+1.50- site, B+1.50- is bonded in a 3-coordinate geometry to four equivalent U+3.20+, two equivalent Mo2+, and three B+1.50- atoms. Both B–B bond lengths are 1.78 Å. In the fourteenth B+1.50- site, B+1.50- is bonded in a 2-coordinate geometry to two equivalent U+3.20+, four equivalent Mo2+, and two equivalent B+1.50- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2U(MoO4)3 by Materials Project

Na2U(MoO4)3 is Zircon-derived structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.52–2.59 Å. U4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of U–O bond distances ranging from 2.33–2.41 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.76–1.84 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.77 Å) and two longer (1.86 Å) Mo–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Na1+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one U4+, and one Mo6+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Na1+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one U4+, and one Mo6+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one U4+, and one Mo6+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one U4+, and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UMo4PbO16 by Materials Project

UMo4PbO16 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with two equivalent PbO7 pentagonal bipyramids. There are a spread of U–O bond distances ranging from 1.83–2.48 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Mo–O bond distances ranging from 1.74–2.16 Å. In the second Mo6+ site, Mo6+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Mo–O bond distances ranging from 1.73–2.20 Å. Pb2+ is bonded to seven O2- atoms to form PbO7 pentagonal bipyramids that share corners with two equivalent UO7 pentagonal bipyramids. There are a spread of Pb–O bond distances ranging from 2.49–2.64 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mo6+ and one Pb2+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one U6+ and one Pb2+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+ and two Mo6+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+ and two equivalent Mo6+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Mo6+ and one Pb2+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Mo6+ and one Pb2+ atom. In the ninth 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 SrU(MoO4)4 by Materials Project

SrUMo4O16 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. Sr2+ is bonded to seven O2- atoms to form SrO7 pentagonal bipyramids that share corners with two equivalent UO7 pentagonal bipyramids. There are a spread of Sr–O bond distances ranging from 2.48–2.58 Å. U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with two equivalent SrO7 pentagonal bipyramids. There are a spread of U–O bond distances ranging from 1.82–2.47 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a 5-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.74–2.59 Å. In the second Mo6+ site, Mo6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.73–2.58 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Sr2+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a linear geometry to one Sr2+ and one U6+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to two Mo6+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+ and two Mo6+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+ and two equivalent Mo6+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Sr2+ and two equivalent Mo6+ atoms. In the seventh O2- site, O2- is bonded in a single-bond geometry to two Mo6+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Sr2+ and two Mo6+ atoms. In the ninth 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 UTl2(MoO5)2 by Materials Project

Tl2UO2(MoO4)2 crystallizes in the orthorhombic Pca2_1 space group. The structure is three-dimensional. there are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with five MoO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.83–2.43 Å. In the second U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with five MoO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.83–2.40 Å. There are four inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.77–1.81 Å. In the second Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with two UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.76–1.84 Å. In the third Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with two UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.76–1.84 Å. In the fourth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.76–1.83 Å. There are four inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Tl–O bond distances ranging from 2.84–3.45 Å. In the second Tl1+ site, Tl1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Tl–O bond distances ranging from 2.84–3.13 Å. In the third Tl1+ site, Tl1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tl–O bond distances ranging from 2.84–3.39 Å. In the fourth Tl1+ site, Tl1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tl–O bond distances ranging from 2.72–3.39 Å. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one U6+ and two Tl1+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one U6+ and one Tl1+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and three Tl1+ atoms. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and three Tl1+ atoms. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and three Tl1+ atoms. In the seventh O2- site, O2- is bonded in a distorted linear geometry to one U6+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and two Tl1+ atoms. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the eleventh O2- site, O2- is bonded in a 2-coordinate geometry to one U6+, one Mo6+, and two Tl1+ atoms. In the twelfth O2- site, O2- is bonded in a 1-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the thirteenth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and two Tl1+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and two Tl1+ atoms. In the fifteenth O2- site, O2- is bonded in a single-bond geometry to one U6+ and two Tl1+ atoms. In the sixteenth O2- site, O2- is bonded in a single-bond geometry to one U6+ and one Tl1+ atom. In the seventeenth O2- site, O2- is bonded in a 1-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the eighteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+, one Mo6+, and one Tl1+ atom. In the nineteenth O2- site, O2- is bonded in a 2-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the twentieth O2- site, O2- is bonded in a 2-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U2Tl2Mo3O16 by Materials Project

U2Mo3Tl2O16 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with five MoO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.82–2.45 Å. In the second U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with five MoO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.82–2.38 Å. There are three inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.74–1.84 Å. In the second Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with four UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.78–1.80 Å. In the third Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.75–1.83 Å. There are two inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded in a 2-coordinate geometry to ten O2- atoms. There are a spread of Tl–O bond distances ranging from 2.90–3.59 Å. In the second Tl1+ site, Tl1+ is bonded in a 5-coordinate geometry to nine O2- atoms. There are a spread of Tl–O bond distances ranging from 2.90–3.52 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+, one Mo6+, and one Tl1+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+, one Mo6+, and one Tl1+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one U6+ and one Tl1+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+ and one Mo6+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and one Tl1+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one Mo6+ and one Tl1+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one U6+, one Mo6+, and two Tl1+ atoms. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to one U6+, one Mo6+, and two Tl1+ atoms. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to one U6+ and one Tl1+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one U6+, one Mo6+, and one Tl1+ atom. In the fourteenth O2- site, O2- is bonded in a single-bond geometry to one U6+ and two Tl1+ atoms. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+, one Mo6+, and one Tl1+ atom. In the sixteenth O2- site, O2- is bonded in a single-bond geometry to one U6+ and two Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb2U2Mo3O16 by Materials Project

Rb2U2Mo3O16 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Rb–O bond distances ranging from 2.97–3.58 Å. In the second Rb1+ site, Rb1+ is bonded in a 5-coordinate geometry to eight O2- atoms. There are a spread of Rb–O bond distances ranging from 2.94–3.41 Å. There are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with five MoO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.81–2.44 Å. In the second U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with five MoO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.82–2.41 Å. There are three inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with four UO7 pentagonal bipyramids. There is two shorter (1.79 Å) and two longer (1.80 Å) Mo–O bond length. In the second Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.74–1.83 Å. In the third Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three UO7 pentagonal bipyramids. There are a spread of Mo–O bond distances ranging from 1.75–1.83 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Rb1+, one U6+, and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U6+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Rb1+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+, one U6+, and one Mo6+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to two Rb1+ and one U6+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one Rb1+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to two Rb1+ and one U6+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Rb1+, one U6+, and one Mo6+ atom. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+, one U6+, and one Mo6+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+, one U6+, and one Mo6+ atom. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to one Rb1+, one U6+, and one Mo6+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to one Rb1+, one U6+, and one Mo6+ atom. In the thirteenth O2- site, O2- is bonded in a 1-coordinate geometry to two Rb1+, one U6+, and one Mo6+ atom. In the fourteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+, one U6+, and one Mo6+ atom. In the fifteenth O2- site, O2- is bonded in a distorted single-bond geometry to one Rb1+ and one U6+ atom. In the sixteenth O2- site, O2- is bonded in a distorted single-bond geometry to one Rb1+ and one U6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

p K a of alcohols dictates their reactivity with reduced uranium-substituted thiomolybdate clusters

The uranium-substituted thiomolybdate cluster, (Cp* 3 Mo 3 S 4 )UCp*, has been demonstrated as a model for water reduction by single uranium atoms supported on a molybdenum sulfide surface (U@MoS 2 ). In this study, the scope of O–H bond activation is expanded through the investigation of the reactivity of various alcohols with differing pKa values for the –OH proton. The reaction of (Cp* 3 Mo 3 S 4 )UCp* with stoichiometric amounts of methanol, phenol, 2,6-dichlorophenol, and nonafluoro-tert-butyl alcohol affords the corresponding mono-alkoxide species, (Cp* 3 Mo 3 S 4 )Cp*U(OR), via a uranium-metalloligand cooperative activation of the O–H bond. This observed reactivity is analogous to the O–H bond activation reported by (Cp* 3 Mo 3 S 4 )UCp* in the presence of water. However, addition of tert-butanol induces protonolysis of the Cp* ligand on uranium, resulting in the formation of a uranium tris-tert-butoxide cluster, (Cp* 3 Mo 3 S 4 )U(O t Bu) 3 . Independent synthesis of (Cp* 3 Mo 3 S 4 )Cp*U(O t Bu) was possible via an alternative pathway, eliminating sterics as a justification for the observed discrepancy in reactivity. Furthermore, these results offer insight into the role the –OH proton pKa plays in dictating the mechanism of O–H bond activation of alcohols by the uranium-substituted thiomolybdate cluster.

Patra, Kamaless↗
DOE OSTI2022

PNNL's Characterization Summary for MP-2 Experiment

Characterization of as-fabricated fuel was performed at Pacific Northwest National Laboratory (PNNL) in accordance with the characterization plan for the fabrication of U 10Mo plate fuel for the U.S. High Performance Research Reactor conversion program’s Fuel Fabrication Pillar (INL 2021). Similar characterization work is also being performed at Idaho National Laboratory to provide a detailed understanding of the as-fabricated foils that would be irradiated in the Mini-Plate 2 (MP 2) experiment. Under the MP 2 characterization plan, foils are studied that have different fabrication parameters (such as rolling condition, rolling thickness reduction, co-rolling with Zr layers). Similar samples from master foils were sent to both the organizations, so that the testing and analysis can be done independently using similar equipment and standardized measurement and analysis procedures. A final, consolidated report will be prepared based on this work and will summarize all the information obtained from the two laboratories. The MP 2 experiment will provide an opportunity to understand the effects of processing conditions on the final fuel microstructure, to compare results obtained independently, and achieve a two-way validation. In Fiscal Year 2022, PNNL received five MP 2 cast (PD STD2) samples to examine the foils’ chemistry and microstructure. For each cast sample, PNNL received samples from three different locations. PNNL also received and characterized 24 U 10Mo foil samples, by sectioning four pieces/specimens from each foil, in accordance with the MP 2 Characterization Plan (INL 2021). These 24 samples consist of four types of foils from BWX Technologies: 0.047 in. thick hot-rolled and annealed samples with Zr layers; 0.025 in. thick cold-rolled and annealed samples with Zr layers; 0.0105 in. thick cold-rolled and annealed samples with Zr layers. Along with these, PNNL also received four plates with Zr layers that were 0.025 in. and 0.0105 in. thick. This report describes the results of PNNL’s MP 2 foil characterization. Microstructure, Mo homogeneity, carbide fraction and morphology, U 10Mo foil thickness, and Zr thickness were evaluated in both the longitudinal and transverse directions for all the foils of the three different thicknesses.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Lifetime measurements in 102 Mo interpreted in the interacting boson model and the X(5) symmetry

Lifetimes of low-lying excited states in 102 Mo populated in the two-neutron transfer reaction 100 Mo ⁢( 18 O, 16 O)⁢ 102 Mo were measured using the recoil distance Doppler shift method at the IFIN-HH Tandem accelerator. Lifetimes of the $2^+_1$, $0^+_2$, $4^+_1$, $2^+_2$, $2^+_3$, $3^+_1$, $6^+_1$, ($0^+_3$), $4^+_2$, ($3^−_1$), and ($5^−_1$) states were obtained. The deduced electromagnetic transition strengths have been compared to calculations performed in the interacting boson model framework including models representing the U(5) and X(5) symmetries. It is found that 102 Mo lies between the U(5) limit and the X(5) critical point symmetry.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗