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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Ab initio calculations for void swelling bias in α - and δ -plutonium

Void swelling can develop in materials under persistent irradiation when nonequilibrium vacancy and self-interstitial populations migrate under sufficiently asymmetric interaction biases. In conventional metals, the propensity is determined to the first approximation by comparing point-defect relaxation strains. We thus present DFT-based calculations of structures and formation energies and volumes of point defects in the α and the δ phases of plutonium. Here we discuss the pros and cons of various levels of electronic structure theory: spin polarization, spin-orbit coupling, and orbital polarization. Our results show that lattice defects in δ-Pu, in contrast to most fcc metals, have surprisingly small formation volumes. Equally unexpected are the large defect formation volumes found in the low-symmetry α-Pu phase. Both these unusual properties can be satisfactorily explained from defect-induced spin/orbital moment formation and destruction in the Pu phases. Surprisingly, the point defects in α-Pu are found to induce far larger transformation of the local electronic structure than in δ-Pu. When we use the calculated defect properties to estimate the classic void swelling bias in each of the phases, we find it to be unusually small in δ-Pu but likely much larger in α-Pu. Hence, swelling rates and mechanisms can diverge dramatically between the different phases of Pu. Especially in the transient regime before the formation of large defect clusters, the swelling rate of α-Pu can reliably be expected to be much larger than δ-Pu. However, accurate forecasts over longer times will require the conventional void-swelling theory to be modified to handle the complexities presented by the different Pu phases. As a case in point, we show the possible anomalous temperature dependence of vacancy properties in δ-Pu, caused by entropic contributions from defect-induced spin-lattice fluctuations. Such complications may affect defect-defect interactions and thus alter the void swelling bias.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Adhesion Capabilities of Permanent Foaming Fixatives

DOE-EM have identified an operational requirement for a fixative that can immobilize and/or encapsulate residual contamination in 3D void volumes (pipes, gloveboxes, waste containers, etc.) during D and D activities. Failure to safely and effectively immobilize residual contamination can: Put workers at risk; Contaminate the public and environment; Drive up costs. Commercial-off-the-shelf (COTS) polyurethane (PU) foams is one possible solution and is currently being investigated by Savannah River National Lab (SRNL). Adhesion testing will dictate how well PU foams will adhere and immobilize residual contamination onto a substrate. Results can provide a performance criteria for Section 5 of ASTM E3191: Standard Specification for Permanent Foaming Fixatives Used to Mitigate Spread of Radioactive Contamination. Initial mechanical testing showed intumescent rigid PU foams were best in class (tensile, compression, TGA/DSC) Application of intumescent rigid PU foam in pipe scenario with 'contamination' showed excellent adhesion capabilities as long as foam had contact with pipe. The foam, however, was not able to penetrate 'contamination' but created pockets where the contamination interacted with the substrate. Pretreatment options of pipe were considered to produce better immobilization capabilities. Pretreatment options included COTS products like baking spray, rubber cement, and soap. Foam was still able to immobilize on a global sense, but not a local sense. Essentially acted as a mechanical plug. A tensile tester (MTS Criterion Series 43) was utilized to evaluate the tensile adhesion strength of 6 COTS PU foams. ASTM D1623: Tensile and Tensile Adhesion Properties of Rigid Cellular Plastics. Procedures: PU foams were cured between two smooth 2'' x 2'' 304 stainless steel coupons with hinges glued on plates for gripping support. Parameters Used: Pull rate of 0.1 in/min. Calculations: Tensile adhesion strength, elongation, and ImageJ analysis of how PU foam is left on substrate. Outcome: The PU foam with the best adhesion capabilities would be downselected for further evaluation to be used as a permanent foaming fixative. The rigid PU foams had the best adhesion capabilities with the R1 foam having a max load of 236 N. One of the I-R2 samples reached almost 450 N and another sample reached 2500 N before slipping. The other intumescent foam, I-F4, had the most coverage on the stainless steel coupon's surface from the ImageJ results (61.43% surface coverage). The intumescent foam, I-R2, will be the foam of choice for future testing due its fire retardant and adhesion capabilities. Future directions: Conduct the following experiment in a pipe scenario with the down-selected PU foam. Procedures: PU foam will be cured between in a 304 stainless steel pipe (ID: 4'', OD: 4.5'', Height: 4''). Parameters Used: Compression testing results will be referenced to determine if foam's adhesion strength would be greater its compression strength as its being compressed. Calculations: Compression strength, shear stress, total time elapsed. Conduct further adhesion testing with the down-selected PU foam (I-R2) to be treated as a permanent foaming fixative (PFF). Determine the minimum contact the PFF should have with the substrate for adequate results. Evaluate if PFF's adhesion capabilities is time dependent (3.1.5 of ASTM E3911). Subject PFF to seismic stressors addressed in Safety Basis of Interim Operation documents (SBIO) to further evaluate adhesion capabilities.

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

Materials Data on PuAl3 by Materials Project

PuAl3 is beta Cu3Ti-like 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 twelve Al atoms to form PuAl12 cuboctahedra that share corners with twelve PuAl12 cuboctahedra, edges with eighteen AlPu4Al8 cuboctahedra, faces with six equivalent PuAl12 cuboctahedra, and faces with six AlPu4Al8 cuboctahedra. There are six shorter (2.98 Å) and six longer (3.00 Å) Pu–Al bond lengths. In the second Pu site, Pu is bonded to twelve Al atoms to form PuAl12 cuboctahedra that share corners with six AlPu4Al8 cuboctahedra, corners with nine PuAl12 cuboctahedra, edges with twelve AlPu4Al8 cuboctahedra, faces with seven PuAl12 cuboctahedra, and faces with nine AlPu4Al8 cuboctahedra. There are three shorter (2.97 Å) and nine longer (2.99 Å) Pu–Al bond lengths. There are four inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to four Pu and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.86–3.13 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to four Pu and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.86–3.13 Å. In the third Al site, Al is bonded to four Pu and eight Al atoms to form distorted AlPu4Al8 cuboctahedra that share corners with two equivalent PuAl12 cuboctahedra, corners with ten AlPu4Al8 cuboctahedra, edges with seven PuAl12 cuboctahedra, edges with eight AlPu4Al8 cuboctahedra, faces with four PuAl12 cuboctahedra, and faces with ten AlPu4Al8 cuboctahedra. There are four shorter (2.96 Å) and two longer (3.03 Å) Al–Al bond lengths. In the fourth Al site, Al is bonded to four Pu and eight Al atoms to form distorted AlPu4Al8 cuboctahedra that share corners with two equivalent PuAl12 cuboctahedra, corners with ten AlPu4Al8 cuboctahedra, edges with seven PuAl12 cuboctahedra, edges with eight AlPu4Al8 cuboctahedra, faces with four PuAl12 cuboctahedra, and faces with ten AlPu4Al8 cuboctahedra. The Al–Al bond length is 2.96 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuGa by Materials Project

PuGa crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. there are three inequivalent Pu sites. In the first Pu site, Pu is bonded in a 12-coordinate geometry to eight equivalent Ga atoms. All Pu–Ga bond lengths are 3.13 Å. In the second Pu site, Pu is bonded in a 8-coordinate geometry to eight equivalent Ga atoms. There are four shorter (3.13 Å) and four longer (3.19 Å) Pu–Ga bond lengths. In the third Pu site, Pu is bonded in a 8-coordinate geometry to eight equivalent Ga atoms. There are four shorter (3.12 Å) and four longer (3.20 Å) Pu–Ga bond lengths. Ga is bonded in a distorted q6 geometry to eight Pu and two equivalent Ga atoms. Both Ga–Ga bond lengths are 2.70 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2Ni17 by Materials Project

Pu2Ni17 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 in a 12-coordinate geometry to eighteen Ni atoms. There are a spread of Pu–Ni bond distances ranging from 2.89–3.21 Å. In the second Pu site, Pu is bonded in a 2-coordinate geometry to twenty Ni atoms. There are a spread of Pu–Ni bond distances ranging from 2.79–3.11 Å. There are four inequivalent Ni sites. In the first Ni site, Ni is bonded in a 12-coordinate geometry to two Pu and ten Ni atoms. There are a spread of Ni–Ni bond distances ranging from 2.37–2.72 Å. In the second Ni site, Ni is bonded in a 2-coordinate geometry to one Pu and thirteen Ni atoms. There are a spread of Ni–Ni bond distances ranging from 2.40–2.59 Å. In the third Ni site, Ni is bonded to two equivalent Pu and ten Ni atoms to form NiPu2Ni10 cuboctahedra that share corners with fourteen NiPu2Ni10 cuboctahedra, edges with six equivalent NiPu3Ni9 cuboctahedra, and faces with ten NiPu2Ni10 cuboctahedra. All Ni–Ni bond lengths are 2.40 Å. In the fourth Ni site, Ni is bonded to three Pu and nine Ni atoms to form a mixture of distorted edge, face, and corner-sharing NiPu3Ni9 cuboctahedra. Both Ni–Ni bond lengths are 2.39 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2Co17 by Materials Project

Pu2Co17 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 in a 12-coordinate geometry to eighteen Co atoms. There are a spread of Pu–Co bond distances ranging from 2.93–3.27 Å. In the second Pu site, Pu is bonded in a 2-coordinate geometry to twenty Co atoms. There are a spread of Pu–Co bond distances ranging from 2.87–3.13 Å. There are four inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to two Pu and ten Co atoms. There are a spread of Co–Co bond distances ranging from 2.36–2.68 Å. In the second Co site, Co is bonded to two equivalent Pu and ten Co atoms to form CoPu2Co10 cuboctahedra that share corners with fourteen CoPu3Co9 cuboctahedra, edges with six equivalent CoPu3Co9 cuboctahedra, and faces with ten CoPu2Co10 cuboctahedra. There are four shorter (2.39 Å) and two longer (2.54 Å) Co–Co bond lengths. In the third Co site, Co is bonded to three Pu and nine Co atoms to form distorted CoPu3Co9 cuboctahedra that share corners with fifteen CoPu3Co9 cuboctahedra, edges with eight CoPu3Co9 cuboctahedra, and faces with ten CoPu2Co10 cuboctahedra. There are two shorter (2.44 Å) and one longer (2.59 Å) Co–Co bond lengths. In the fourth Co site, Co is bonded in a 2-coordinate geometry to one Pu and thirteen Co atoms. The Co–Co bond length is 2.35 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuNi4 by Materials Project

PuNi4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 9-coordinate geometry to fourteen Ni atoms. There are a spread of Pu–Ni bond distances ranging from 2.82–2.91 Å. In the second Pu site, Pu is bonded in a distorted hexagonal planar geometry to eighteen Ni atoms. There are a spread of Pu–Ni bond distances ranging from 2.81–3.17 Å. There are four inequivalent Ni sites. In the first Ni site, Ni is bonded to four Pu and eight Ni atoms to form a mixture of corner, edge, and face-sharing NiPu4Ni8 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.43–2.50 Å. In the second Ni site, Ni is bonded to four Pu and eight Ni atoms to form a mixture of corner, edge, and face-sharing NiPu4Ni8 cuboctahedra. There are two shorter (2.45 Å) and two longer (2.50 Å) Ni–Ni bond lengths. In the third Ni site, Ni is bonded in a 12-coordinate geometry to three equivalent Pu and nine Ni atoms. There are one shorter (2.79 Å) and two longer (2.83 Å) Ni–Ni bond lengths. In the fourth Ni site, Ni is bonded in a 12-coordinate geometry to four equivalent Pu and eight Ni atoms. There are a spread of Ni–Ni bond distances ranging from 2.45–2.88 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuGa by Materials Project

PuGa 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 in a 5-coordinate geometry to one Pu and eight equivalent Ga atoms. The Pu–Pu bond length is 2.29 Å. There are four shorter (2.93 Å) and four longer (3.25 Å) Pu–Ga bond lengths. In the second Pu site, Pu is bonded in a 8-coordinate geometry to eight equivalent Ga atoms. All Pu–Ga bond lengths are 3.00 Å. Ga is bonded in a 10-coordinate geometry to eight Pu and two equivalent Ga atoms. Both Ga–Ga bond lengths are 2.55 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Circular Reprocessing of Thermoset Polyurethane Foams

Thermoset polyurethane (PU) foams are widely used in industrial applications, but they cannot be recycled by conventional melt reprocessing because of their cross-linked structures. The introduction of carbamate exchange catalysts converts thermoset PU into covalent adaptable networks (CANs), which are amenable to reprocessing at elevated temperatures. However, this approach has produced solid PU films, which have fewer uses and lower commercial demand. In this work, simultaneous reprocessing and refoaming of thermoset PU foams is demonstrated by leveraging the melt-processability of PU CANs and allowing cell growth by gas generation in a twin-screw extruder. The optimal operating temperature of the refoaming process is determined through chemical, thermal, and structural analysis of PU foam extrudates. The foam-to-foam extrusion process produces controllable, continuous, and uniform foam structures, as characterized by cell diameter and cell number density. Low-density PU foams are obtained through a process simulating injection molding. The compression properties of reprocessed PU foam are compared with as-synthesized PU foam to demonstrate efficacy of the refoaming processes. These results demonstrate that PU foams can be prepared through recycling while maintaining microstructural and chemical integrity. In the future, this strategy may be applied to thermoset PU foams of various chemical compositions and shows promise for scalability.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Plutonium mobilization from contaminated estuarine sediments, Esk Estuary (UK)

Since 1952, liquid radioactive effluent containing 238-242 Pu, 241 Am, 237 Np, 137 Cs, and 99 Tc has been released with authorization from the Sellafield nuclear complex (UK) into the Irish Sea. This represents the largest source of plutonium (Pu) discharged in all western Europe, with 276 kg having been released. In the Eastern Irish Sea, the majority of the transuranic activity has settled into an area of sediments (Mudpatch) located off the Cumbrian coast. Radionuclides from the Mudpatch have been re-dispersed via particulate transport in fine-grained estuarine and intertidal sediments to the North-East Irish Sea, including the intertidal saltmarsh located at the mouth of the Esk Estuary. Saltmarshes are highly dynamic systems which are vulnerable to external agents (sea level change, erosion, sediment supply, and freshwater inputs), and their stability remains uncertain under current sea level rise projections and possible increases in storm activity. In this work, we examined factors affecting Pu mobility in contaminated sediments collected from the Esk Estuary by conducting leaching experiments under both anoxic and oxic conditions. Here, leaching experiments were conducted over a 9-month period and were periodically sampled to determine solution phase Pu via multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS), and to measure redox indicators (Eh, pH and extractable Fe(II)). Microbial community composition was also characterized in the sediments, and at the beginning and end of the anoxic/oxic experiments. Results show that: 1) Pu leaching is about three times greater in solutions leached under anoxic conditions compared to oxic conditions, 2) the sediment slurry microbial communities shift as conditions change from anoxic to oxic, 3) Pu leaching is enhanced in the shallow sediments (0–10 cm depth), and 4) the magnitude of Pu leached from sediments is not correlated with total Pu, indicating that the biogeochemistry of sediment-associated Pu is spatially heterogeneous. These findings provide constraints on the stability of redox sensitive Pu in biogeochemically dynamic/transient environments on a timescale of months and suggests that anoxic conditions can enhance Pu mobility in estuarine systems.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Structural and Spectroscopic Characterization of Plutonium and Other Tetravalent Metals Complexed to a Keggin Ion

Here, we report the isolation of the first plutonium(IV) complex with a Keggin ion chelator: Cs 20 [Pu(PW 11 O 39 ) 2 ] 2 ·13H 2 O. Single crystal XRD and solid-state UV–vis absorbance analysis demonstrate the stabilization of Pu 4+ by the Keggin ligand. The unit cell contains two [Pu(PW 11 O 39 ) 2 ] 10– complexes (Pu(PW 11 ) 2 ) bridged by Cs + . Raman and 31 P NMR spectra of Pu(PW 11 ) 2 are consistent with the analogous Zr 4+ , Hf 4+ , Ce 4+ , and Th 4+ complexes. The Pu–O bond distances at the two Pu sites are 2.35(3) and 2.34(3) Å, matching the value extrapolated from the bonding trend built with the other 8-coordinated tetravalent cations. However, the long-range arrangement of the Pu(PW 11 ) 2 complexes within the lattice is unique in the series of M IV (PW 11 ) 2 compounds: pairs of Pu(PW 11 ) 2 are organized perpendicular to each other. Based on solution-state UV–visible absorbance, small-angle X-ray scattering (SAXS), and 31 P NMR, the tetravalent cations quantitatively form the 1:2 species in solution ([Pu(PW 11 O 39 ) 2 ] 10– (aq) ) and no 1:1 species ([Pu(PW 11 O 39 )(H 2 O) x ] 3– (aq) ). Finally, a linear correlation exists between the metal–oxygen distances in the M IV (PW 11 ) 2 compounds and the corresponding metal dioxides, allowing for extrapolation for Pa 4+ , Am 4+ , and Bk 4+ . The results indicate that our microscale POM approach represents a viable pathway to probe properties of rare actinide ions in discrete molecules, beyond the traditional oxide extended solids.

and nuclear chemistry↗
DOE OSTI2022

Dinuclear Complexes of Uranyl, Neptunyl, and Plutonyl: Structures and Oxidation States Revealed by Experiment and Theory

Dinuclear perchlorate complexes of uranium, neptunium, and plutonium were characterized by reactivity and DFT, with results revealing structures containing pentavalent, hexavalent, and heptavalent actinyls, and actinyl-actinyl interactions (AAIs). Electrospray ionization produced native complexes [(AnO 2 ) 2 (ClO 4 ) 3 ] - for An:An = U:U, Np:Np, Pu:Pu, and Np:Pu, which are intuitively formulated as actinyl(V) perchlorates. However, DFT identified lower-energy structures [(AnO 2 )(AnO 3 )(ClO 4 ) 2 (ClO 3 )] - comprising a perchlorate fragmented to ClO 3 , actinyl(VI) cation An VI O 2 2+ , and neutral AnO 3 . For U:U and Np:Np, and Np in Np:Pu, the coordinated AnO 3 is calculated as actinyl(VI) with an equatorial oxo, [O yl =An VI =O yl ][=O eq ], whereas for Pu:Pu, it is plutonyl(V) oxyl, [O yl =Pu V =O yl ][-O eq • ]. The implied lower stability of Pu VI versus Np VI indicates weaker Pu=O eq versus Np=O eq bonding. Adsorption of O 2 by the U:U complex suggests oxidation of U V to U VI , corroborating the assignment of perchlorate [(An V O 2 ) 2 (ClO 4 ) 3 ] - . DFT predicts the O 2 adducts are [(An VI O 2 )(O 2 )(An VI O 2 )(ClO 4 ) 3 ] - with actinyls oxidized from +V to +VI by bridging peroxide, O 2 2- . In accordance with reactivity, O 2- addition is computed as substantially exothermic for U:U and least favorable for Pu:Pu. Collision-induced dissociation of native complexes eliminated ClO 2 to yield [(AnO 2 )(O) 2 (AnO 2 )(ClO 4 ) 2 ] - , in which fragmented O atoms bridge as oxyl O -• and oxo O 2- to yield uranyl(VI) and plutonyl(VI), or as oxos O 2- to yield neptunyl(VII), [O yl =Np VII =O yl ] 3+ .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Thermal Activation of Zirconium(IV) Acetylacetonate Catalysts to Enhance Polyurethane Synthesis and Reprocessing

Carbamate formation and exchange catalysts enable efficient polyurethane (PU) manufacturing, as well as emerging recycling and reprocessing methods for PU thermosets. Zirconium β-diketonate complexes, such as Zr acetylacetonate [Zr(acac) 4 ], are effective alternatives to toxic organotin catalysts that have been used for PU reprocessing. Here, we report that Zr(acac) 4 undergoes a thermally activated process in the PU network during reprocessing that transforms it into a more active carbamate exchange catalyst. This process is associated with the irreversible loss of acetylacetonate ligands and is not observed for the more sterically hindered Zr 2,2,6,6-tetramethyl-3,5-heptanedione [Zr(tmhd) 4 ] complex. Crossover experiments between PU thermoplastics indicated enhanced carbamate exchange after the thermal activation of Zr(acac) 4 in the presence of one of the PUs, whereas a sample of Zr(acac) 4 activated in the absence of the PU had no catalytic activity. Thermal gravimetric analysis suggested that this process is associated with the loss of one protonated acac ligand. Stress relaxation analysis of PU thermosets indicated a distinct change in the characteristic relaxation time associated with the thermal activation of Zr(acac) 4 at temperatures above 140 °C; no such change was observed for samples reprocessed using Zr(tmhd) 4 . Density functional theory and molecular experiments suggest that irreversible ligand exchange of acac with alkoxide or carbamate reduces the activation energy for urethane formation and reversion. Furthermore, the Zr(acac) 4 catalyst activated in the presence of a PU’s polyol precursor provided more porous and less dense PU foams compared to those made using the unactivated Zr(acac) 4 catalyst. Furthermore, these findings are important for developing improved PU synthesis and recycling processes. Thermally activating a catalyst during reprocessing may provide more nuanced control of the in-use and reprocessing characteristics of PU thermosets.

Alcohols↗
DOE OSTI2025

Plutonium isotope ratio measurements by total evaporation-thermal ionization mass spectrometry (TE-TIMS): an evaluation of uncertainties using traceable standards from the New Brunswick Laboratory

The accuracy and precision of isotope amount ratio measurements using thermal ionization mass spectrometry (TIMS) instrumentation are described, and the measurement of Pu materials is emphasized. The mass fractionation observed for Am, Ga, Pu, and U for isotope amount ratio measurements using the total evaporation (TE) technique is compared with theoretical estimates to demonstrate the advantage of the TE methodology and to investigate systematic biases in the major isotope amount ratios of U and Pu certified reference material (CRM) standards from the U.S. provider of CRMs. The quality of the Pu isotopic data generated by TIMS instruments in an analytical laboratory is demonstrated by the application of the double ratio technique to estimate the 241 Pu half-life. Analytical data on traceable Pu CRMs from the New Brunswick Laboratory (NBL), generated as part of routine measurements supporting various programs, are used for this half-life estimation. Although the 241 Pu abundances in CRMs of 136, 137, 138, and 126-A are approximately 200–2000× smaller than those in the 241 Pu material used in the previous Institute for Reference Materials and Measurements (IRMM) evaluation of the 241 Pu half-life, the half-life value estimated in this work shows excellent agreement with the currently accepted value from the IRMM. This agreement also demonstrates the pedigree of the Pu isotopic standards from the NBL and the quality of the isotope amount ratio measurements using TIMS instrumentation. For both the major and minor Pu isotope amount ratios, this report describes the relative importance of the factors affecting the uncertainty of TIMS measurements, which are considered the gold standard in isotope ratio measurements (LA-UR-24-29199).

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2020

The TRANSCEND University Consortium: Theme 4: Nuclear Materials - 20431

The safe and secure management of Pu is a matter of international concern, with ∼250 t of separated Pu currently stockpiled worldwide. The UK's civil inventory of nuclear materials contains significant stocks of separated Pu from the reprocessing of Magnox and AGR spent fuels. The preferred option for the 138.5 tonnes of Pu is re-use as mixed oxide (MOx) fuel, although 5% is not suitable for re-use and is recommended for direct disposal. However, it will take more than 15 years to implement re-use, requiring that the Pu be kept in interim storage in its current state for that period, i.e. as PuO{sub 2} powder within inert steel storage cans at Sellafield. The focus of the work presented here is thus plutonium storage and the direct disposal of plutonium. The Research and Development needs of both are now pressing: in the case of storage due to it being the current default; in the case of immobilization and disposal because of a comparative lack of Research and Development on Pu conditioning and packaging due to policy uncertainty as to whether it would be disposed of in a Geologic Disposal Facility (GDF). Addressing these needs is complicated by Pu's high radioactivity, decay heat and radiotoxicity, criticality, nuclear safeguard requirements and, for some UK Pu contaminated materials targeted for disposal, poor inventory. Thus, there is also a critical requirement for underpinning research on Pu bearing materials in these two contexts. In response to these needs, the TRANSCEND Consortium (Transformative Science and Engineering for Nuclear Decommissioning, a multi-disciplinary collaboration of 11 universities and 8 key industry partners from across the UK's civil nuclear sector) is seeking to provide technical underpinning to ongoing option development for the UK's civil Pu stockpile. Whilst understanding the behaviour of plutonium during its re-use as MOx is beyond the scope of the TRANSCEND Consortium work plan, the main objectives of the work are: (1) For interim storage: to understand how the surface structure and properties of pristine and radiation damaged PuO{sub 2} change with time in the absence and presence of water; and (2) For immobilization and disposal: to understand the mechanisms of incorporation of Pu into ceramic and glass-ceramic waste-forms, as well as the effect on these of self-induced radiation damage. Each objective is being addressed through separate work packages, the details of which are discussed in this paper. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Materials Data on PuCo3 by Materials Project

PuCo3 crystallizes in the trigonal R-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 hexagonal planar geometry to eighteen Co atoms. There are six shorter (2.74 Å) and twelve longer (3.11 Å) Pu–Co bond lengths. In the second Pu site, Pu is bonded in a 12-coordinate geometry to twelve Co atoms. There are a spread of Pu–Co bond distances ranging from 2.79–2.89 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Pu and six equivalent Co atoms to form CoPu6Co6 cuboctahedra that share corners with eighteen CoPu3Co9 cuboctahedra, edges with six equivalent CoPu6Co6 cuboctahedra, and faces with twenty CoPu3Co9 cuboctahedra. All Co–Co bond lengths are 2.46 Å. In the second Co site, Co is bonded to three equivalent Pu and nine Co atoms to form distorted CoPu3Co9 cuboctahedra that share corners with eighteen CoPu6Co6 cuboctahedra, edges with six equivalent CoPu3Co9 cuboctahedra, and faces with twenty-two CoPu6Co6 cuboctahedra. There are a spread of Co–Co bond distances ranging from 2.43–2.74 Å. In the third Co site, Co is bonded to five Pu and seven Co atoms to form CoPu5Co7 cuboctahedra that share corners with twenty-one CoPu6Co6 cuboctahedra, edges with eight equivalent CoPu5Co7 cuboctahedra, and faces with twenty CoPu6Co6 cuboctahedra. There are two shorter (2.36 Å) and two longer (2.39 Å) Co–Co bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu3Pd5 by Materials Project

Pu3Pd5 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 10-coordinate geometry to ten Pd atoms. There are a spread of Pu–Pd bond distances ranging from 2.97–3.23 Å. In the second Pu site, Pu is bonded in a 9-coordinate geometry to nine Pd atoms. There are a spread of Pu–Pd bond distances ranging from 2.82–3.20 Å. There are three inequivalent Pd sites. In the first Pd site, Pd is bonded in a 3-coordinate geometry to six Pu and four Pd atoms. There are a spread of Pd–Pd bond distances ranging from 2.80–3.08 Å. In the second Pd site, Pd is bonded in a 6-coordinate geometry to six Pu and four Pd atoms. There are one shorter (2.85 Å) and one longer (2.88 Å) Pd–Pd bond lengths. In the third Pd site, Pd is bonded in a 5-coordinate geometry to five Pu and six Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuNi3 by Materials Project

PuNi3 crystallizes in the trigonal R-3m 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 twelve Ni atoms. There are a spread of Pu–Ni bond distances ranging from 2.91–3.04 Å. In the second Pu site, Pu is bonded in a distorted hexagonal planar geometry to eighteen Ni atoms. There are six shorter (2.88 Å) and twelve longer (3.21 Å) Pu–Ni bond lengths. There are three inequivalent Ni sites. In the first Ni site, Ni is bonded to five Pu and seven Ni atoms to form a mixture of face, edge, and corner-sharing NiPu5Ni7 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.47–2.54 Å. In the second Ni site, Ni is bonded in a 12-coordinate geometry to three equivalent Pu and nine Ni atoms. All Ni–Ni bond lengths are 2.88 Å. In the third Ni site, Ni is bonded to six equivalent Pu and six equivalent Ni atoms to form NiPu6Ni6 cuboctahedra that share corners with twelve equivalent NiPu5Ni7 cuboctahedra, edges with six equivalent NiPu6Ni6 cuboctahedra, and faces with eighteen equivalent NiPu5Ni7 cuboctahedra.

36 MATERIALS SCIENCE↗