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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Pu2Zn17 by Materials Project

Pu2Zn17 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 12-coordinate geometry to eighteen Zn atoms. There are a spread of Pu–Zn bond distances ranging from 3.07–3.46 Å. In the second Pu site, Pu is bonded in a 8-coordinate geometry to twenty Zn atoms. There are a spread of Pu–Zn bond distances ranging from 3.09–3.42 Å. There are eight inequivalent Zn sites. In the first Zn site, Zn is bonded in a 1-coordinate geometry to one Pu and thirteen Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.71–3.04 Å. In the second Zn site, Zn is bonded to two equivalent Pu and ten Zn atoms to form a mixture of face, edge, and corner-sharing ZnPu2Zn10 cuboctahedra. There are two shorter (2.62 Å) and six longer (2.63 Å) Zn–Zn bond lengths. In the third Zn site, Zn is bonded to two equivalent Pu and ten Zn atoms to form ZnPu2Zn10 cuboctahedra that share corners with eighteen ZnPu2Zn10 cuboctahedra, edges with six ZnPu3Zn9 cuboctahedra, and faces with fourteen ZnPu2Zn10 cuboctahedra. There are four shorter (2.61 Å) and four longer (2.63 Å) Zn–Zn bond lengths. In the fourth Zn site, Zn is bonded in a 12-coordinate geometry to two Pu and ten Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.66–2.77 Å. In the fifth Zn site, Zn is bonded in a 12-coordinate geometry to two Pu and ten Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.66–2.76 Å. In the sixth Zn site, Zn is bonded to two Pu and ten Zn atoms to form a mixture of distorted face, edge, and corner-sharing ZnPu2Zn10 cuboctahedra. There are two shorter (2.71 Å) and two longer (2.75 Å) Zn–Zn bond lengths. In the seventh Zn site, Zn is bonded to three Pu and nine Zn atoms to form a mixture of distorted face, edge, and corner-sharing ZnPu3Zn9 cuboctahedra. There are one shorter (2.52 Å) and one longer (2.54 Å) Zn–Zn bond lengths. In the eighth Zn site, Zn is bonded to three Pu and nine Zn atoms to form a mixture of distorted face, edge, and corner-sharing ZnPu3Zn9 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Plutonium Redox Transformation in the Presence of Iron, Organic Matter, and Hydroxyl Radicals: Kinetics and Mechanistic Insights

Plutonium (Pu) redox and complexation processes in the presence of natural organic matter and associated iron can impact the fate and transport of Pu in the environment. In this work, we studied the fate of Pu(IV) in the presence of humic acid (HA) and Fe(II) upon reaction with H 2 O 2 that may be generated by photochemical and other reactions. A portion of Pu(IV) was oxidized to Pu(V/VI), which is primarily ascribed to the generation of reactive intermediates from the oxidation of Fe(II) and Fe(II)–HA complexes by H 2 O 2 . The kinetics of Pu(IV) oxidation is pH-dependent and can be described by a model that incorporates Pu redox kinetics with published HA-modified Fenton reaction kinetics. At pH 3.5, the presence of HA slowed Pu(IV) oxidation, while at pH 6, HA accelerated Pu(IV) oxidation in the first several hours followed by a reverse process where the oxidized Pu(V/VI) was reduced back to Pu(IV). Analysis of Pu-associated particle size suggests that Pu oxidation state is a major driver in its complexation with HA and formation of colloids and heteroaggregates. Our results revealed the H 2 O 2 -driven oxidation of Pu(IV)–HA–Fe(II) colloids with implications to the transient mobilization of Pu(V/VI) in organic-rich redox transition zones.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Plutonium Co-precipitation with Calcite

The mobility of plutonium (Pu) in the environment is affected by Pu–mineral interactions, such as adsorption–desorption and structural incorporation. Calcite (CaCO 3 ) is a common secondary phase in near surface environments and a major component of many rocks and soils and is expected to form as an alteration product of cement-based materials planned for use in geological repositories. The reactivity of the calcite surface and its ability to tolerate significant variations in its chemical composition through substitution of Ca for other cations make calcite a potentially important sink for environmental contaminants. Here, single crystals of calcite were synthesized from aqueous solutions in equilibrium with air containing Pu as either Pu(VI) or Pu(IV) and characterized using a combination of laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) and X-ray absorption spectroscopy (XAS). These data are used to assess the amount, structure, and oxidation state of Pu co-precipitated into calcite, providing insight into the potential for Pu sequestration in calcite precipitates. Overall, the XAS and LA–ICP–MS data support the co-precipitation of plutonyl [Pu(VI/V)] in the bulk calcite, although the exact nature of the co-precipitated Pu complex is difficult to elucidate in the synthesized material. Co-precipitated plutonyl could be incorporated in either distorted Ca lattice sites or defect sites, and we provide evidence to suggest that Pu(VI) is reduced mainly to Pu(V) in the precipitated solid. LA–ICP–MS additionally shows that the co-precipitation of Pu(VI/V) is favored over the co-precipitation of Pu(IV). Altogether, our results suggest that Pu sequestration in calcite under environmental conditions could immobilize Pu and isolate it from groundwater interactions in contaminated environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Thermodynamics of gallium-stabilized delta-plutonium: A high-temperature drop calorimetry study

Throughout the Cold War (1947–1991), both the United States and the former Soviet Union independently derived a phase diagram for the Pu-Ga system that has different implications on Pu phase stability. In the phase diagram produced by the United States, the Pu δ-phase is thermodynamically stable at room temperatures when Ga content is between 2 and 9 at. %. The diagram produced by the Soviet Union shows the δ-phase undergoing an eutectoid decomposition into the α-Pu + α-Pu 3 Ga at 7.9 at. % Ga and 370 K. This would suggest that Ga-stabilized δ-Pu is metastable with respect to α-Pu + α-Pu 3 Ga at 298 K. To investigate this, and the thermodynamic behavior of Ga in the FCC lattice of δ-Pu, we have utilized high-temperature drop calorimetry to study the enthalpy of formation of two δ-Pu 1−x Ga x compositions. In doing so, mixing models (regular and subregular) were developed to understand the thermodynamic behavior of Ga in the FCC lattice of δ-Pu and found a strong departure from ideal conditions, which suggests Ga ordering in the FCC lattice of δ-Pu. Overall, it was found that δ-Pu 1−x Ga x is enthalpically metastable with respect to α-Pu + Pu 3 Ga at 298 K.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Plutonium Oxidation State Distribution in the Presence of WIPP-Relevant Organics and Iron Corrosion Products

The oxidation state and solubility of plutonium (Pu) in high ionic strength synthetic WIPP (Waste Isolation Pilot Plant) brines as a function of pC H+ in the presence and absence of WIPP-relevant organic ligands (EDTA [Ethylenediaminetetraacetic acid], oxalate, citrate, acetate) and iron corrosion products (magnetite and metallic iron) at 𝑇 = 23 ± 2 ∘C was thoroughly studied by long-term batch solubility experiments (between approximately 800-1,100 days) from an undersaturation approach. The oxidation state of Pu in the WIPP environment has been a topic of interest since the initial Compliance Certification Application (CCA). This study aims to investigate the solubility of Pu under the expected WIPP conditions and to determine the oxidation state of the solid phase that will control the solubility. One of the most important results of this study is that the Pu oxidation state was analyzed both from the surface area of the corrosion products and in the precipitated solid. The analysis of the Pu oxidation state on the surface of the iron mineral from the ongoing undersaturated experiments is more relevant to the performance assessment of nuclear waste disposal than short term batch (plutonium-iron phase) experiments. The X-ray Absorption Near-Edge Spectroscopy (XANES) analysis showed that Pu oxidation state is different on the metal surface and in the precipitated solid. Pu(III) is the dominant oxidation state in the metallic iron (Fe 0 ) system in the presence and absence of organics. Pu(IV) is the dominant oxidation state in the magnetite system in the presence and absence of organics. Also, organics stabilize Pu(IV) in the magnetite system. Analysis of Pu in the precipitated solid by Extended X-ray Absorption Fine Structure (EXAFS) analysis showed that Pu formed an inner-sphere complex with iron with minor amounts of PuO 2 present. X-ray diffraction (XRD) results indicate that metallic iron and magnetite did not oxidize in three years in the alkaline and high ionic strength system. Under these conditions (8 < pC H+ < 10 at T = (22 ± 2) °C under nitrogen atmosphere, the solubility of Pu changes by up to three orders of magnitude (10 -5 and 10 -8 M). The spread in solubility is highest at pC H+ = 9. Pu(III) and Pu(IV) showed different solubility behavior in the synthetic WIPP brine. A summary of the data collected in this report will be submitted to Sandia National Laboratories as part of a parameter update report which will outline the changes to the OXSTAT parameter for the 2026 Compliance Recertification Application (CRA-2026). The experiments performed were done according to the U.S. Department of Energy (DOE) approved Test Plan entitled “Effects of Radiolysis, Organic Complexation, and Redox Conditions on the Speciation and Oxidation State Distribution of Pu(III/IV)” (LCO-ACP-25). All data reported were obtained under the Los Alamos National Laboratory-Carlsbad Office (LANL-CO) Quality Assurance Program, which is compliant with the DOE Carlsbad Field Office, Quality Assurance Program Document (CBFO/QAPD).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on Pu3Al by Materials Project

Pu3Al is Uranium Silicide structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded to eight equivalent Pu and four equivalent Al atoms to form PuPu8Al4 cuboctahedra that share corners with twelve equivalent PuPu8Al4 cuboctahedra, edges with eight equivalent AlPu12 cuboctahedra, edges with sixteen equivalent PuPu8Al4 cuboctahedra, faces with four equivalent AlPu12 cuboctahedra, and faces with fourteen PuPu8Al4 cuboctahedra. All Pu–Pu bond lengths are 3.09 Å. All Pu–Al bond lengths are 3.14 Å. In the second Pu site, Pu is bonded to eight Pu and four equivalent Al atoms to form distorted PuPu8Al4 cuboctahedra that share corners with twelve equivalent PuPu8Al4 cuboctahedra, edges with eight equivalent AlPu12 cuboctahedra, edges with sixteen PuPu8Al4 cuboctahedra, faces with four equivalent AlPu12 cuboctahedra, and faces with fourteen PuPu8Al4 cuboctahedra. All Pu–Pu bond lengths are 3.14 Å. All Pu–Al bond lengths are 3.09 Å. Al is bonded to twelve Pu atoms to form AlPu12 cuboctahedra that share corners with twelve equivalent AlPu12 cuboctahedra, edges with twenty-four PuPu8Al4 cuboctahedra, faces with six equivalent AlPu12 cuboctahedra, and faces with twelve PuPu8Al4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmPu3 by Materials Project

Pu3Tm is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded to eight equivalent Pu and four equivalent Tm atoms to form PuTm4Pu8 cuboctahedra that share corners with four equivalent TmPu12 cuboctahedra, corners with fourteen equivalent PuTm4Pu8 cuboctahedra, edges with six equivalent TmPu12 cuboctahedra, edges with twelve equivalent PuTm4Pu8 cuboctahedra, faces with four equivalent TmPu12 cuboctahedra, and faces with sixteen PuTm4Pu8 cuboctahedra. There are a spread of Pu–Pu bond distances ranging from 3.37–3.48 Å. There are two shorter (3.42 Å) and two longer (3.43 Å) Pu–Tm bond lengths. In the second Pu site, Pu is bonded to eight equivalent Pu and four equivalent Tm atoms to form PuTm4Pu8 cuboctahedra that share corners with four equivalent TmPu12 cuboctahedra, corners with fourteen PuTm4Pu8 cuboctahedra, edges with six equivalent TmPu12 cuboctahedra, edges with twelve equivalent PuTm4Pu8 cuboctahedra, faces with four equivalent TmPu12 cuboctahedra, and faces with sixteen PuTm4Pu8 cuboctahedra. There are a spread of Pu–Pu bond distances ranging from 3.37–3.48 Å. There are two shorter (3.42 Å) and two longer (3.43 Å) Pu–Tm bond lengths. Tm is bonded to twelve Pu atoms to form TmPu12 cuboctahedra that share corners with six equivalent TmPu12 cuboctahedra, corners with twelve PuTm4Pu8 cuboctahedra, edges with eighteen PuTm4Pu8 cuboctahedra, faces with eight equivalent TmPu12 cuboctahedra, and faces with twelve PuTm4Pu8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaPu3 by Materials Project

Pu3La is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded to eight equivalent Pu and four equivalent La atoms to form PuLa4Pu8 cuboctahedra that share corners with four equivalent PuLa4Pu8 cuboctahedra, corners with eight equivalent LaPu12 cuboctahedra, edges with twenty-four PuLa4Pu8 cuboctahedra, faces with six equivalent LaPu12 cuboctahedra, and faces with twelve PuLa4Pu8 cuboctahedra. All Pu–Pu bond lengths are 3.48 Å. All Pu–La bond lengths are 3.47 Å. In the second Pu site, Pu is bonded to eight Pu and four equivalent La atoms to form PuLa4Pu8 cuboctahedra that share corners with twelve equivalent PuLa4Pu8 cuboctahedra, edges with eight equivalent LaPu12 cuboctahedra, edges with sixteen PuLa4Pu8 cuboctahedra, faces with four equivalent LaPu12 cuboctahedra, and faces with fourteen PuLa4Pu8 cuboctahedra. All Pu–Pu bond lengths are 3.47 Å. All Pu–La bond lengths are 3.48 Å. La is bonded to twelve Pu atoms to form LaPu12 cuboctahedra that share corners with four equivalent LaPu12 cuboctahedra, corners with eight equivalent PuLa4Pu8 cuboctahedra, edges with eight equivalent LaPu12 cuboctahedra, edges with sixteen equivalent PuLa4Pu8 cuboctahedra, faces with four equivalent LaPu12 cuboctahedra, and faces with fourteen PuLa4Pu8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Influences on Subsurface Plutonium and Americium Migration

Plutonium (Pu) has been released to the environment worldwide, including approximately 1.85 × 1015 Bq (200 kg) of Pu from process waste solutions to unconfined soil structures at the Hanford Site in Washington State. The subsurface mobility of Pu is influenced by complex interactions with sediments, groundwater, and any co-contaminants within the waste stream. Previous investigations at Hanford have shown that Pu exists as discrete PuO 2 particles forming before or after disposal, as secondary solid phases formed from waste interactions with sediments as adsorbed/incorporated species, and/or as dissolved species. In this research, new evidence is presented for the existence of PuO 2 , PuO 2 -Bi 2 O 3 composites, and particles from burnt Pu metal in near-surface sediments where Pu-laden acidic process waste was disposed to sediments. Pu and americium (Am) L3 X-ray absorption spectroscopy and density functional theory suggest that, in larger, more crystalline PuO 2 particles, Am formed from radioactive decay is retained in the Pu IV O 2 structure as Am IV . The Pu and Am that were disposed of in an acidic waste stream have since migrated deeper into the subsurface with detection to at least 37 meters below ground surface. In contrast, Pu deposited near the ground surface from neutral pH waste is found to be homogeneously distributed and relatively immobile. Groundwater extractions performed on contaminated sediments indicate that both Pu and Am are recalcitrant, with Am being fractionally less extractable than Pu on a molar basis. These results suggest that the more mobile fraction of Am has migrated from the near-surface and may be present in the deeper sediments as a different phase than Pu. From these results, it is suggested that Pu and Am deposited from acidic wastes were initially mobile and became significantly less mobile as wastes were neutralized within the soil profile.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Materials Data on Pu5Ir4 by Materials Project

Pu5Ir4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Pu sites. In the first Pu site, Pu is bonded in a 6-coordinate geometry to six Ir atoms. There are a spread of Pu–Ir bond distances ranging from 2.63–3.20 Å. In the second Pu site, Pu is bonded in a 6-coordinate geometry to six Ir atoms. There are a spread of Pu–Ir bond distances ranging from 2.67–2.91 Å. In the third Pu site, Pu is bonded in a 7-coordinate geometry to seven Ir atoms. There are a spread of Pu–Ir bond distances ranging from 2.77–3.23 Å. There are three inequivalent Ir sites. In the first Ir site, Ir is bonded in a 5-coordinate geometry to eight Pu and one Ir atom. The Ir–Ir bond length is 2.78 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to eight Pu and one Ir atom. In the third Ir site, Ir is bonded in a 5-coordinate geometry to eight Pu and one Ir atom. The Ir–Ir bond length is 2.91 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu5Os3 by Materials Project

Pu5Os3 crystallizes in the orthorhombic Fmmm space group. The structure is three-dimensional. there are three inequivalent Pu sites. In the first Pu site, Pu is bonded to four Os atoms to form distorted edge-sharing PuOs4 tetrahedra. There are two shorter (2.71 Å) and two longer (2.72 Å) Pu–Os bond lengths. In the second Pu site, Pu is bonded in a 6-coordinate geometry to six Os atoms. There are a spread of Pu–Os bond distances ranging from 2.94–3.19 Å. In the third Pu site, Pu is bonded in a 6-coordinate geometry to six Os atoms. There are a spread of Pu–Os bond distances ranging from 2.93–3.19 Å. There are three inequivalent Os sites. In the first Os site, Os is bonded in a 10-coordinate geometry to eight Pu and two equivalent Os atoms. Both Os–Os bond lengths are 2.77 Å. In the second Os site, Os is bonded in a 10-coordinate geometry to ten Pu atoms. In the third Os site, Os is bonded in a 10-coordinate geometry to ten Pu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuGaRh by Materials Project

PuRhGa crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 5-coordinate geometry to five Rh and six Ga atoms. There are four shorter (2.87 Å) and one longer (2.88 Å) Pu–Rh bond lengths. There are two shorter (3.07 Å) and four longer (3.19 Å) Pu–Ga bond lengths. In the second Pu site, Pu is bonded in a 5-coordinate geometry to five Rh and six Ga atoms. There are two shorter (2.87 Å) and three longer (2.88 Å) Pu–Rh bond lengths. There are two shorter (3.06 Å) and four longer (3.19 Å) Pu–Ga bond lengths. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to six Pu and three Ga atoms. There are two shorter (2.66 Å) and one longer (2.67 Å) Rh–Ga bond lengths. In the second Rh site, Rh is bonded in a 9-coordinate geometry to three Pu and six Ga atoms. All Rh–Ga bond lengths are 2.62 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 4-coordinate geometry to six Pu and four Rh atoms. In the second Ga site, Ga is bonded in a 4-coordinate geometry to six Pu and four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuAlCo by Materials Project

PuCoAl crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 5-coordinate geometry to five Co and six Al atoms. There are one shorter (2.73 Å) and four longer (2.78 Å) Pu–Co bond lengths. There are two shorter (2.94 Å) and four longer (3.12 Å) Pu–Al bond lengths. In the second Pu site, Pu is bonded in a 5-coordinate geometry to five Co and six Al atoms. There are a spread of Pu–Co bond distances ranging from 2.73–2.78 Å. There are a spread of Pu–Al bond distances ranging from 2.94–3.12 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 9-coordinate geometry to six Pu and three Al atoms. All Co–Al bond lengths are 2.49 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to three Pu and six Al atoms. All Co–Al bond lengths are 2.53 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to six Pu, four Co, and two equivalent Al atoms. Both Al–Al bond lengths are 2.63 Å. In the second Al site, Al is bonded in a 4-coordinate geometry to six Pu, four Co, and two Al atoms. The Al–Al bond length is 2.63 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2ReB6 by Materials Project

Pu2ReB6 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Pu+4.50+ sites. In the first Pu+4.50+ site, Pu+4.50+ is bonded in a 2-coordinate geometry to fourteen B2- atoms. There are a spread of Pu–B bond distances ranging from 2.65–2.79 Å. In the second Pu+4.50+ site, Pu+4.50+ is bonded in a 12-coordinate geometry to twelve B2- atoms. There are a spread of Pu–B bond distances ranging from 2.63–2.70 Å. Re3+ is bonded in a 10-coordinate geometry to ten B2- atoms. There are a spread of Re–B bond distances ranging from 2.36–2.40 Å. There are six inequivalent B2- sites. In the first B2- site, B2- is bonded in a 8-coordinate geometry to six Pu+4.50+ and two B2- atoms. There is one shorter (1.71 Å) and one longer (1.72 Å) B–B bond length. In the second B2- site, B2- is bonded in a 3-coordinate geometry to four equivalent Pu+4.50+, two equivalent Re3+, and three B2- atoms. There are a spread of B–B bond distances ranging from 1.79–1.83 Å. In the third B2- site, B2- is bonded in a 3-coordinate geometry to four Pu+4.50+, two equivalent Re3+, and three B2- atoms. The B–B bond length is 1.80 Å. In the fourth B2- site, B2- is bonded in a 9-coordinate geometry to four Pu+4.50+, two equivalent Re3+, and three B2- atoms. There is one shorter (1.76 Å) and one longer (1.84 Å) B–B bond length. In the fifth B2- site, B2- is bonded in a 3-coordinate geometry to four Pu+4.50+, two equivalent Re3+, and three B2- atoms. The B–B bond length is 1.80 Å. In the sixth B2- site, B2- is bonded in a 9-coordinate geometry to four Pu+4.50+, two equivalent Re3+, and three B2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuGaNi by Materials Project

PuNiGa crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 11-coordinate geometry to five Ni and six Ga atoms. There are four shorter (2.83 Å) and one longer (2.88 Å) Pu–Ni bond lengths. There are two shorter (3.07 Å) and four longer (3.17 Å) Pu–Ga bond lengths. In the second Pu site, Pu is bonded in a 11-coordinate geometry to five Ni and six Ga atoms. There are two shorter (2.84 Å) and three longer (2.85 Å) Pu–Ni bond lengths. There are a spread of Pu–Ga bond distances ranging from 3.05–3.18 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 9-coordinate geometry to six Pu and three Ga atoms. There are a spread of Ni–Ga bond distances ranging from 2.64–2.68 Å. In the second Ni site, Ni is bonded in a distorted q6 geometry to three Pu and six Ga atoms. There are four shorter (2.55 Å) and two longer (2.57 Å) Ni–Ga bond lengths. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded to six Pu, four Ni, and two equivalent Ga atoms to form distorted face-sharing GaPu6Ga2Ni4 cuboctahedra. Both Ga–Ga bond lengths are 2.84 Å. In the second Ga site, Ga is bonded in a 12-coordinate geometry to six Pu, four Ni, and two Ga atoms. The Ga–Ga bond length is 2.79 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuAlNi by Materials Project

PuNiAl crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 5-coordinate geometry to five Ni and six Al atoms. There are one shorter (2.77 Å) and four longer (2.81 Å) Pu–Ni bond lengths. There are two shorter (2.97 Å) and four longer (3.16 Å) Pu–Al bond lengths. In the second Pu site, Pu is bonded in a 5-coordinate geometry to five Ni and six Al atoms. There are a spread of Pu–Ni bond distances ranging from 2.79–2.81 Å. There are a spread of Pu–Al bond distances ranging from 2.96–3.18 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 9-coordinate geometry to six Pu and three Al atoms. There are two shorter (2.52 Å) and one longer (2.53 Å) Ni–Al bond lengths. In the second Ni site, Ni is bonded in a 9-coordinate geometry to three Pu and six Al atoms. All Ni–Al bond lengths are 2.56 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 4-coordinate geometry to six Pu, four Ni, and two equivalent Al atoms. Both Al–Al bond lengths are 2.66 Å. In the second Al site, Al is bonded in a 4-coordinate geometry to six Pu, four Ni, and two Al atoms. The Al–Al bond length is 2.66 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Influence of ethylenediaminetetraacetic acid on the long-term oxidation state distribution of plutonium

Here, spectrophotometry was used to study the effect of EDTA on plutonium oxidation state distribution as a function of time, pH, and ligand-to-metal ratio (L/M) under anoxic conditions. Novel Pu(V)-EDTA absorption bands were identified at 571, 993, 1105, and 1150 nm with molar absorption coefficients of 15 ± 1, 6 ± 1, 10 ± 1, and 10 ± 1 cm –1 M –1 , respectively. Pu(V)-EDTA spectral changes occurred at L/M < 1, indicating only Pu V O 2 (EDTA) 3- formed with logK = 3.6 ± 0.3. Time-resolved experiments showed EDTA drastically increased the Pu(V/VI) reduction rate, which we propose is driven by amine lone-pair electron donation and the oxidative decarboxylation of EDTA. Oxidation of Pu(III)-EDTA to Pu(IV)-EDTA occurred on a slower time scale (110–237 days) than previously reported (<15 min) and is hypothesized to be radiolysis driven. Pu(V/VI)-EDTA and Pu(III)-EDTA both approached Pu(IV)-EDTA stabilization over time, yet Pu(V/VI)-EDTA solubility data was ≥ 1.0 log 10 units higher than predicted by Pu(IV)-EDTA solubility models, indicating that current thermodynamic models are incomplete. Ultimately, the data show EDTA preferentially stabilizes Pu(IV) over time regardless of initial oxidation state, but Pu(V)-EDTA can persist under environmentally-relevant conditions, emphasizing the need to continue investigating redox reactions, speciation, and behavior of these complexes to support the transuranic waste disposal and surface remediation/containment efforts.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Materials Data on Pu3Sc by Materials Project

Pu3Sc is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a distorted body-centered cubic geometry to four equivalent Pu and four equivalent Sc atoms. All Pu–Pu bond lengths are 3.07 Å. All Pu–Sc bond lengths are 3.07 Å. In the second Pu site, Pu is bonded in a 8-coordinate geometry to eight equivalent Pu and six equivalent Sc atoms. All Pu–Sc bond lengths are 3.55 Å. Sc is bonded in a distorted body-centered cubic geometry to fourteen Pu atoms.

36 MATERIALS SCIENCE↗