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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Commonly Overlooked Material Attractiveness Issues [Slides]

SG-Pu, WG-Pu, FG-Pu, RG-Pu, HEU, and Np should not be ignored in safeguards or security discussions: Nation states prefer SG-Pu and WG-Pu for missile delivery. Terrorists and some nation states will prefer FG-Pu and RG-Pu to minimize the mass that must be stolen/diverted and to minimize the risk of detection. Terrorists and some nation states will prefer HEU to eliminate the need for testing. A nation state with reprocessing capabilities might prefer 237 Np because the IAEA doesn’t require it to be safeguarded. Terrorists might prefer 237 Np if the nation state does not provide adequate safeguards and security for it.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuB2Rh3 by Materials Project

PuRh3B2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Pu is bonded in a 12-coordinate geometry to two equivalent Pu, twelve equivalent Rh, and six equivalent B atoms. Both Pu–Pu bond lengths are 2.93 Å. All Pu–Rh bond lengths are 3.18 Å. All Pu–B bond lengths are 3.26 Å. Rh is bonded in a distorted square co-planar geometry to four equivalent Pu and four equivalent B atoms. All Rh–B bond lengths are 2.19 Å. B is bonded in a 6-coordinate geometry to three equivalent Pu and six equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuB7IO14 by Materials Project

Pu(BO2)7I crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four hydriodic acid molecules and one Pu(BO2)7 framework. In the Pu(BO2)7 framework, Pu is bonded in a 3-coordinate geometry to three O atoms. There are a spread of Pu–O bond distances ranging from 1.82–2.05 Å. There are seven inequivalent B sites. In the first B site, B is bonded in a trigonal planar geometry to three O atoms. All B–O bond lengths are 1.37 Å. In the second B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.43–1.55 Å. In the third B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.44–1.49 Å. In the fourth B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.43–1.51 Å. In the fifth B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.36–1.39 Å. In the sixth B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.34–1.41 Å. In the seventh B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.35–1.40 Å. There are fourteen inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the second O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the third O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the fourth O site, O is bonded in a trigonal planar geometry to three B atoms. In the fifth O site, O is bonded in a distorted bent 120 degrees geometry to two B atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to two B atoms. In the seventh O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the eighth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the ninth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the tenth O site, O is bonded in a bent 150 degrees geometry to one Pu and one B atom. In the eleventh O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the twelfth O site, O is bonded in a single-bond geometry to one Pu atom. In the thirteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the fourteenth O site, O is bonded in a single-bond geometry to one Pu atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu3Si2 by Materials Project

Pu3Si2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a square co-planar geometry to four equivalent Si atoms. All Pu–Si bond lengths are 2.90 Å. In the second Pu site, Pu is bonded in a 6-coordinate geometry to six equivalent Si atoms. There are two shorter (2.90 Å) and four longer (3.00 Å) Pu–Si bond lengths. Si is bonded in a 9-coordinate geometry to eight Pu and one Si atom. The Si–Si bond length is 2.38 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce4Pu by Materials Project

PuCe4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Pu is bonded to six equivalent Pu and six equivalent Ce atoms to form PuCe6Pu6 cuboctahedra that share corners with six equivalent PuCe6Pu6 cuboctahedra, corners with six CeCe12 cuboctahedra, edges with six equivalent PuCe6Pu6 cuboctahedra, edges with eighteen CeCe9Pu3 cuboctahedra, faces with six equivalent PuCe6Pu6 cuboctahedra, and faces with twelve equivalent CeCe9Pu3 cuboctahedra. All Pu–Pu bond lengths are 3.21 Å. All Pu–Ce bond lengths are 3.14 Å. There are eight inequivalent Ce sites. In the first Ce site, Ce is bonded to three equivalent Pu and nine Ce atoms to form CeCe9Pu3 cuboctahedra that share corners with twelve CeCe9Pu3 cuboctahedra, edges with six equivalent PuCe6Pu6 cuboctahedra, edges with eighteen CeCe9Pu3 cuboctahedra, faces with six equivalent PuCe6Pu6 cuboctahedra, and faces with twelve CeCe9Pu3 cuboctahedra. There are six shorter (3.21 Å) and three longer (3.30 Å) Ce–Ce bond lengths. In the second Ce site, Ce is bonded to twelve Ce atoms to form CeCe12 cuboctahedra that share corners with three equivalent PuCe6Pu6 cuboctahedra, corners with nine CeCe9Pu3 cuboctahedra, edges with three equivalent PuCe6Pu6 cuboctahedra, edges with twenty-one CeCe9Pu3 cuboctahedra, and faces with eighteen CeCe9Pu3 cuboctahedra. There are six shorter (3.21 Å) and three longer (3.29 Å) Ce–Ce bond lengths. In the third Ce site, Ce is bonded to twelve Ce atoms to form CeCe12 cuboctahedra that share corners with three equivalent PuCe6Pu6 cuboctahedra, corners with nine CeCe9Pu3 cuboctahedra, edges with three equivalent PuCe6Pu6 cuboctahedra, edges with twenty-one CeCe9Pu3 cuboctahedra, and faces with eighteen CeCe9Pu3 cuboctahedra. There are six shorter (3.21 Å) and three longer (3.30 Å) Ce–Ce bond lengths. In the fourth Ce site, Ce is bonded to twelve Ce atoms to form CeCe12 cuboctahedra that share corners with three equivalent PuCe6Pu6 cuboctahedra, corners with nine CeCe9Pu3 cuboctahedra, edges with three equivalent PuCe6Pu6 cuboctahedra, edges with twenty-one CeCe9Pu3 cuboctahedra, and faces with eighteen CeCe9Pu3 cuboctahedra. There are a spread of Ce–Ce bond distances ranging from 3.21–3.30 Å. In the fifth Ce site, Ce is bonded to twelve Ce atoms to form CeCe12 cuboctahedra that share corners with three equivalent PuCe6Pu6 cuboctahedra, corners with nine CeCe9Pu3 cuboctahedra, edges with three equivalent PuCe6Pu6 cuboctahedra, edges with twenty-one CeCe9Pu3 cuboctahedra, and faces with eighteen CeCe9Pu3 cuboctahedra. There are six shorter (3.21 Å) and three longer (3.30 Å) Ce–Ce bond lengths. In the sixth Ce site, Ce is bonded to twelve Ce atoms to form CeCe12 cuboctahedra that share corners with three equivalent PuCe6Pu6 cuboctahedra, corners with fourteen CeCe12 cuboctahedra, edges with three equivalent PuCe6Pu6 cuboctahedra, edges with nineteen CeCe9Pu3 cuboctahedra, and faces with twenty-one CeCe9Pu3 cuboctahedra. There are a spread of Ce–Ce bond distances ranging from 3.21–3.30 Å. In the seventh Ce site, Ce is bonded to sixteen Ce atoms to form CeCe16 cuboctahedra that share corners with three equivalent PuCe6Pu6 cuboctahedra, corners with nineteen CeCe9Pu3 cuboctahedra, edges with three equivalent PuCe6Pu6 cuboctahedra, edges with twenty-one CeCe9Pu3 cuboctahedra, and faces with thirty-four CeCe12 cuboctahedra. There are a spread of Ce–Ce bond distances ranging from 3.21–6.42 Å. In the eighth Ce site, Ce is bonded to three equivalent Pu and nine Ce atoms to form CeCe9Pu3 cuboctahedra that share corners with seventeen CeCe9Pu3 cuboctahedra, edges with six equivalent PuCe6Pu6 cuboctahedra, edges with sixteen CeCe9Pu3 cuboctahedra, faces with six equivalent PuCe6Pu6 cuboctahedra, and faces with fifteen CeCe16 cuboctahedra. All Ce–Pu bond lengths are 3.14 Å. All Ce–Ce bond lengths are 3.21 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu3I by Materials Project

Pu3I is Uranium Silicide-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 four equivalent I atoms to form a mixture of distorted edge and corner-sharing PuI4 cuboctahedra. All Pu–I bond lengths are 3.28 Å. In the second Pu site, Pu is bonded in a square co-planar geometry to four equivalent I atoms. All Pu–I bond lengths are 3.17 Å. I is bonded to twelve Pu atoms to form a mixture of edge, corner, and face-sharing IPu12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuB2Ir3 by Materials Project

PuIr3B2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Pu is bonded in a 12-coordinate geometry to two equivalent Pu, twelve equivalent Ir, and six equivalent B atoms. Both Pu–Pu bond lengths are 3.12 Å. All Pu–Ir bond lengths are 3.15 Å. All Pu–B bond lengths are 3.16 Å. Ir is bonded in a distorted square co-planar geometry to four equivalent Pu and four equivalent B atoms. All Ir–B bond lengths are 2.22 Å. B is bonded in a 6-coordinate geometry to three equivalent Pu and six equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Chapter 6: TEA and LCA of Bio-Based Polyurethanes

For bio-based polyurethane (PU) to replace its conventional petroleum-based counterpart, it must be cost-competitive while providing a positive environmental benefit. Techno-economic analysis (TEA) and life cycle assessment (LCA) provide tools to quantify the economic and environmental viability of bio-based PU and to identify key drivers. Here we describe TEA and LCA methodologies for assessing bio-based PU, including an example case study for producing a flexible PU foam. This process has the potential to be cost-competitive with traditional PU based on a published study using a linseed oil proxy feedstock. Bio-based PU also demonstrates environmental advantages in some categories considered but faces challenges in others compared to petroleum-based PU. Further TEA and LCA beyond the case study may enable assessment for alternative product and process variations that are possible for bio-based PU.

bio-based polyurethane↗
DOE OSTI2024

Plutonium Speciation and Oxidation State Distributions in the Presence of Citrate

We explored the speciation and kinetics of the Pu(VI)-citrate and Pu(III)-citrate systems (pH m = 2.5–11.0, I = 0.1 M NaCl, T = 23 °C, O 2 (g) < 2 ppm) using ultraviolet–visible–near-infrared (UV–vis–NIR) spectrophotometry, solvent extraction, and PHREEQC modeling. Formation constants were determined for PuO 2 (HcitH)(aq) (log K° 1,1 = 1.09 ± 0.05) and PuO 2 (HcitH)(citH) 3– (log K° 1,2 = -0.20 ± 0.07), and evidence for (PuO 2 ) m (citH –k ) n (OH) x 2m(3+k)n–x was identified under alkaline conditions. Pu(VI) species were found to be less stable in the presence of citrate than in the absence of citrate (t ≤ 168 days); the rate of reduction increased with increasing pH. Further, the direct reduction of Pu(VI) to Pu(IV) was required to fit experimental data in the presence of citrate but did not improve the fit for Pu in the absence of citrate. We also observed increased Pu(III) stability in the presence of citrate (t ≤ 293 days), with higher concentrations of Pu(III) favored at lower pH. Finally, we provide evidence of a radiolysis-driven mechanism for the citrate-mediated reduction of plutonium that involves electron transfer from the oxidative breakdown of citrate. Our work highlights the need to investigate the redox effect of organic ligands on plutonium oxidation states under repository-relevant conditions.

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

Computational Investigation of the Chemical Bond between An(III) Ions and Soft-Donor Ligands

The chemical bonding of actinide ions with arene and borohydride ligands is explored via quantum chemical methods to understand how the transuranium elements interact with softdonor ligands. Specifically, the [An(C 6 Me 6 )(BH 4 ) 3 ] complexes (An = U, Np, and Pu) and their reduced congeners are studied. Density functional theory (DFT) shows that the metal–ligand interactions in the neutral complexes are governed by electrostatic interactions. Both DFT and complete active space (CASSCF) results show that as one moves from U to Pu, the 5f-orbitals are stabilized leading to a poorer energy match with the ligand orbitals. This contributes to progressively weaker metal-arene and metal-borohydride interactions across the series due to a decrease in energy-driven covalency. A reduction in orbital contributions to bonding is obtained for the transuranium-arene interactions as well. Upon reduction, the arene is reduced, forming a δ-bond. This causes the An–arene distances to contract by 0.1–0.2 Å compared to the neutral complexes. The ground state is assigned as the intermediate-spin state where the arene radical is antiferromagnetically coupled to the metal-centered f-electrons in Np and Pu. On the other hand, the ferromagnetically and antiferromagnetically coupled states are close in energy in the uranium complex, but do not mix when spin– orbit coupling is included using a state-interaction approach (SO-CASPT2). The population of the CASSCF δ*-antibonding natural orbital increases from U to Pu consistent with the increased An–arene distances, weaker interactions, and decreasing covalency across the series. Although the An–B distance increases by ca. 0.06 Å upon reduction, both the neutral and reduced species involve an An(III)–borohydride bond and as such are qualitatively similar. The Np complexes can be assigned to have slightly weaker bonding than the uranium analogs but are overall “uranium-like”. The Pu complexes are predicted to have less covalent contributions to bonding in both the Pu–arene and Pu–borohydride interactions; however, the Pu–arene interaction is predicted to be particularly weak.

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

Actinide 5f Occupations: The Case of PuO 2

In actinide chemistry, the formal number of open-shell 5f electrons, n open , is a well-defined quantity with an integer value. The effective 5f occupation, n f , additionally takes donation and back-donation into account, generally has a non-integer value, and has varying numerical definitions. The present study explores the important distinction between n f and n open in actinide chemistry with the example of PuO2, by using electronic structure methods with a relativistic Hamiltonian in combination with experimental Pu M 5 -edge high-energy-resolution X-ray absorption and emission spectroscopic data. The total donation to the metal in PuO 2 is between 3.1 and 2.4 electrons, depending on the type of calculation, most of which is to the Pu 6d and 5f shells. The donation into 5f is sensitive to the approximations in the electronic structure model but likely amounts to 1.6/0.8 electrons when the diffuse regions of the 5f shell are included/excluded. Valence band resonant inelastic X-ray scattering experiments demonstrate that Pu 5f electron density is present in the valence band; thus, there is a clear experimental signature of covalent bonding in PuO 2 . Pu M 5 -edge and M 3 -edge high-energy-resolution X-ray absorption near-edge structures for Pu 3+ and Pu 4+ in an aqueous solution are compared to PuO 2 , showing that Pu in PuO 2 has an nf closer to Pu 4+ (aq).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Correlation strength and orbital differentiation across the phase diagram of plutonium metal

We compare the trends on the strength of electronic correlations across the different phases of elemental Pu focusing on its site and orbital dependence, using a combination of density functional theory (DFT) and dynamical mean-field theory (DMFT) calculations within the vertex corrected one crossing approximation. We find that Pu-5f states are more correlated in δ -Pu, followed by some crystallographic sites in α and β phases. In addition, we observe that Pu-5f 5/2 and Pu-5f 7/2 orbital differentiation is a general feature of this material, as is site differentiation in the low-symmetry phases. The Pu-5f 5/2 states show Fermi liquid like behavior, whereas the Pu-5f 7/2 states remaining incoherent down to very low temperatures. We correlate the correlation strength in the different phases to their structure and the Pu-5 f occupancy of their crystallographic sites.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Plutonium Dedicated Surface Probe Microscopy Capability

An atomic force microscope (AFM) equipped with gas dosing capabilities and a scanning tunneling microscope (STM) housed within a vacuum chamber with Pu sputtering capabilities and the potential for rapid heating via electron bombardment have been devised for investigations of Pu surface aging (such as oxidation, corrosion, and self-irradiation damage), reactivity, and rapid heating. These instruments are capable of probing Pu surface areas ranging from a fractions of nm2 (STM) to hundreds of μm2 (AFM) to obtain three dimensional imaging of surface microstructure and morphology, as well as mapping of the local electronic structure (i.e., the occupied and unoccupied electronic states), surface chemical, and mechanical properties. A detailed description of our surface probe microscopy (SPM) capability, specifically designed for handling of Pu coupons is given in the references. In FY20, four tasks have been undertaken: Resumed maintenance of Pu AFM and modification of STM capabilities including calibration, annual measurement of Pu surface, and implementation of additional instrumentation for rapid heating effort; Analyzed AFM FY19 gas dosing experiment data of 7 at% gallium-stabilized δ-phase Pu (δ-Pu) coupon; Determined the direction of future gas dosing experiments to investigate reversibility of surface features; and, Published a paper titled "Effects of ion sputtering on plutonium surfaces" in the Journal of Nuclear Materials.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

C136A and C138A Report of Analysis

In this work the isotopic ratios and weight percentages of 238 Pu, 239 Pu, 240 Pu, 241 Pu and 242 Pu were determined using Isotope Dilution Mass Spectrometry. Two samples of C136A and C138A were sent to the Analytical Research laboratories by the National Nuclear Security Administration Nuclear Reference Material Program. The four samples were dissolved in concentrated hydrochloric acid. From the parent solutions, eight aliquots were taken, diluted, spiked with 244 Pu and submitted to separations. After the samples were separated, they were analyzed using Multicollector Inductively Coupled Plasma Mass Spectrometry. Along with the samples, two C126A Quality Control Samples were analyzed each day. Mass bias standards were also analyzed at the beginning, during and at the end of the analysis. GUM Workbench Pro software Version 2.4.1.406 was used to calculate the isotopic ratios relative to 239 Pu, and total Pu mass and the correlated expanded uncertainties.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2020

Materials Data on PuGa5Co by Materials Project

PuCoGa5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Pu is bonded to twelve Ga atoms to form PuGa12 cuboctahedra that share corners with four equivalent PuGa12 cuboctahedra, faces with four equivalent PuGa12 cuboctahedra, and faces with four equivalent GaPu4Ga8 cuboctahedra. There are eight shorter (2.94 Å) and four longer (2.98 Å) Pu–Ga bond lengths. Co is bonded in a body-centered cubic geometry to eight Ga atoms. All Co–Ga bond lengths are 2.48 Å. There are five inequivalent Ga sites. In the first Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Pu, two equivalent Co, and seven Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.62–2.98 Å. In the second Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Pu, two equivalent Co, and seven Ga atoms. There are two shorter (2.94 Å) and four longer (2.98 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Pu, two equivalent Co, and seven Ga atoms. There are one shorter (2.62 Å) and two longer (2.94 Å) Ga–Ga bond lengths. In the fourth Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Pu, two equivalent Co, and seven Ga atoms. Both Ga–Ga bond lengths are 2.94 Å. In the fifth Ga site, Ga is bonded to four equivalent Pu and eight Ga atoms to form GaPu4Ga8 cuboctahedra that share corners with four equivalent GaPu4Ga8 cuboctahedra, faces with four equivalent PuGa12 cuboctahedra, and faces with four equivalent GaPu4Ga8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuCu6 by Materials Project

PuCu6 is Bergman Structure: Mg32(Al,Zn)49 Bergman-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Pu is bonded in a 6-coordinate geometry to nineteen Cu atoms. There are a spread of Pu–Cu bond distances ranging from 2.86–3.38 Å. There are five inequivalent Cu sites. In the first Cu site, Cu is bonded in a 10-coordinate geometry to four equivalent Pu and ten Cu atoms. There are a spread of Cu–Cu bond distances ranging from 2.47–3.02 Å. In the second Cu site, Cu is bonded to three equivalent Pu and nine Cu atoms to form a mixture of edge, face, and corner-sharing CuPu3Cu9 cuboctahedra. There are a spread of Cu–Cu bond distances ranging from 2.45–2.59 Å. In the third Cu site, Cu is bonded in a 11-coordinate geometry to three equivalent Pu and eight Cu atoms. There are two shorter (2.50 Å) and one longer (2.82 Å) Cu–Cu bond lengths. In the fourth Cu site, Cu is bonded in a 12-coordinate geometry to three equivalent Pu and nine Cu atoms. There are a spread of Cu–Cu bond distances ranging from 2.44–3.00 Å. In the fifth Cu site, Cu is bonded to three equivalent Pu and nine Cu atoms to form a mixture of edge, face, and corner-sharing CuPu3Cu9 cuboctahedra. There are one shorter (2.45 Å) and one longer (2.57 Å) Cu–Cu bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Exploring constituent redistribution in irradiated U-19Pu-14Zr fuel via electron probe microanalysis

Here, the phenomena of constituent redistribution, wherein a previously homogeneous metallic fuel forms discrete, radially concentric compositional zones upon irradiation was investigated by examining an irradiated U-19Pu-14Zr fuel (where numbers represent wt. %) with a burnup of 11.5 at.% with electron probe microanalysis (EPMA) and quadruple inductively coupled plasma mass spectroscopy (Q-ICP-MS). EPMA-generated U, Pu, and Zr compositional data obtained from a diameter traverse of the sample was converted to mass and was used to: 1) compare the overall fuel element analysis results between the two methods, 2) determine the number of compositionally distinct zones forming as a result of constituent redistribution; and 3) quantify the post-irradiation loss or gain of U, Pu, and Zr atoms in each distinct compositional zone. Weight percent concentrations of U, Pu, and Zr for the overall cross section compare favorably between the two analytical methods, suggesting that the spatially resolved EPMA analysis complements bulk chemical analysis. Among the four identified compositional zones, post-irradiation quantification of U, Pu, and Zr elemental atom content changes shows that the quantity of U atoms lost from the innermost zone is slightly less than the quantity of U atoms gained by the middle two zones, and the quantity of Zr atoms lost from the high-U third zone is slightly less than is gained by the two innermost zones. Pu is lost from all four zones, although the innermost zone and the high-U third zone lose a significantly higher percentage (> 22 %) of their initial Pu atoms than the other two zones. For all three elements, EPMA cannot distinguish between atoms lost due to transport to a different zone from atoms lost due to nuclear processes; however, the insight gained from using this process can be used to experiment with new modeling techniques to predict constituent redistribution in U-Pu-Zr fuels.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Functionalized Polymer Thin Films for Plutonium Capture and Isotopic Screening from Aqueous Sources

The rapid screening of plutonium from aqueous sources remains a critical challenge for nuclear nonproliferation efforts. The determination of trace-level Pu isotopes in water requires offsite sample preparation and analysis; therefore, new methods that combine plutonium purification, concentration, and isotopic screening in a fieldable detection system will provide an invaluable tool for nuclear safeguards. This contribution describes the development and characterization of thin polymer-ligand films for the isolation and concentration of waterborne Pu for direct spectroscopic analyses. Submicron thin films were prepared through spin coating onto Si wafers and consisted of combinations of polystyrene (PS) with dibenzoylmethane, thenoyltrifluoroacetone, and di(2-ethylhexyl)phosphoric acid (HDEHP). Pu uptake studies from solutions at pH from 2.3 to 6.3 indicated that only films containing HDEHP exhibited significant recovery of Pu. High alpha spectroscopy peak energy resolutions were achieved for PS-HDEHP films over a range of film thicknesses from 30 to 250 nm. Furthermore, a separate study was performed to evaluate uptake from a primarily Pu(V) solution where it was observed that doubling the HDEHP loading in the film increased uptake of Pu by an order of magnitude. X-ray photoelectron spectroscopy (XPS) analysis revealed that HDEHP was highly concentrated within the first few nanometers of the film at the higher loading. XPS analysis also revealed that, in the presence of water, HDEHP was stripped from the surface layer of the film at circumneutral pH. While significant losses of ligand were seen in all samples, higher loadings of HDEHP resulted in measurable amounts of ligand retained after a 12-h soak in water. Findings of this study are being used to guide the development of thin-film composite membrane-based detection methods for the rapid, fieldable analysis of Pu in water.

36 MATERIALS SCIENCE↗