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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Insights into Tetravalent Np Speciation in HNO 3 through Spectroelectrochemistry and Multivariate Analysis

In situ optical spectroscopy, spectropotentiometry, and multivariate analysis were applied to the Np(IV) nitrate system to better understand speciation and quantify HNO 3 concentration. Thin-layer spectropotentiometry, or spectroelectrochemistry, was leveraged to isolate and stabilize Np(IV) without compromising the solution conditions and generate representative Vis-NIR absorption spectra from 0.5 to 10 M HNO 3 and benchmark the corresponding Np(IV) molar absorptivity coefficients. Spectra were described with principal component analysis (PCA) to identify the purest Np(IV) absorbance spectra among other oxidation states [e.g., Np(V/VI)] at each acid concentration and then to identify the primary sources of variance within each Np(IV) spectrum with respect to Np(IV) nitrate complexes. Then, partial least-squares regression (PLSR) and support vector regression (SVR) models were built to predict HNO 3 concentration from the Np(IV) spectral data. The nonlinear SVR model outperformed the linear PLSR model for the HNO 3 concentration predictions. Finally, the inclusion of spectra collected in edge and center point HNO 3 concentrations in the calibration set was determined to be crucial for producing models with strong predictive capabilities. The multivariate approach used in this study makes it possible to quantify HNO 3 concentration solely based on Np(IV) absorption spectra, which is essential to quantifying processing streams in various online monitoring applications.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Materials Data on Np(SiIr)2 by Materials Project

Np(IrSi)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Np is bonded in a 4-coordinate geometry to eight Ir and eight Si atoms. There are four shorter (3.13 Å) and four longer (3.29 Å) Np–Ir bond lengths. There are four shorter (3.16 Å) and four longer (3.18 Å) Np–Si bond lengths. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded to four equivalent Np and four equivalent Si atoms to form distorted IrNp4Si4 tetrahedra that share corners with twelve equivalent SiNp4Ir4 tetrahedra, edges with two equivalent SiNp4Ir4 tetrahedra, edges with four equivalent IrNp4Si4 tetrahedra, and faces with four equivalent IrNp4Si4 tetrahedra. All Ir–Si bond lengths are 2.44 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Np and five Si atoms. There are one shorter (2.38 Å) and four longer (2.43 Å) Ir–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded to four equivalent Np and four equivalent Ir atoms to form distorted SiNp4Ir4 tetrahedra that share corners with twelve equivalent IrNp4Si4 tetrahedra, edges with two equivalent IrNp4Si4 tetrahedra, edges with four equivalent SiNp4Ir4 tetrahedra, and faces with four equivalent SiNp4Ir4 tetrahedra. In the second Si site, Si is bonded in a 9-coordinate geometry to four equivalent Np and five Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(SO6)2 by Materials Project

Np(SO6)2 is Silicon tetrafluoride-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of four Np(SO6)2 clusters. Np is bonded in a 4-coordinate geometry to six O atoms. There are a spread of Np–O bond distances ranging from 1.77–2.43 Å. S is bonded in a tetrahedral geometry to four O atoms. There are a spread of S–O bond distances ranging from 1.47–1.51 Å. There are seven inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one S atom. In the second O site, O is bonded in a single-bond geometry to one Np atom. In the third O site, O is bonded in a single-bond geometry to one S atom. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one Np and one S atom. In the fifth O site, O is bonded in a single-bond geometry to one Np atom. In the sixth O site, O is bonded in a single-bond geometry to one Np atom. In the seventh O site, O is bonded in a single-bond geometry to one S atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Hydroxypyridinone-based stabilization of Np(IV) enabling efficient U/Np/Pu separations in the Adapted PUREX process

The classical process to recover uranium (U) and plutonium (Pu) from used nuclear fuel using tributyl phosphate (TBP), namely the Plutonium Uranium Redox EXtraction (PUREX) process, is complicated by the persistent presence of neptunium (Np) and thus requires extra purification steps. The concept of Adapted PUREX seeks to achieve Np recovery by adjusting the valence of the metal more effectively, thereby controlling its behavior more precisely. This study introduces the use of an aqueous hydroxypyridinone chelator, 3,4,3-LI(1,2-HOPO) (abbreviated as HOPO), to dictate the behavior of Np for recovery and meanwhile simplify cumbersome reprocessing steps. The interactions between Np and HOPO were probed mechanistically by way of absorption spectrophotometry, in conjunction with cyclic voltammetry. UV–Vis-NIR spectra illustrated the reduction of NpO 2 2+ to Np 4+ , with a fast reaction rate. Cyclic voltammetry revealed quasi-reversible processes between the oxidized and reduced forms of the ligand and its Np complexes. The corresponding heterogeneous rate constants (k 0 ) were estimated from the peak-to-peak separation potentials (ΔE p ), at ~ 4 – 35 μm/s for both HOPO and NpHOPO, with scan rates of 0.01 – 0.4 V/s. Meanwhile, the electromotive force (E MF ) as well as the change of Gibbs free energy (ΔG) were assessed from the half-wave potential (E 1/2 ), demonstrating the completeness of NpO 2 2+ reduction to Np 4+ by HOPO. The cumulative formation constant of the resulting NpHOPO complex (logβ 101 ) was determined by metal competition titration to be 42.0 ± 0.6, corroborating the extraordinarily high affinity of HOPO to tetravalent metal ions. Here, the prowess of valence control by HOPO and the high stability of the formed complex resulted in enhanced separations of Np from U and of Pu from U, with a maximum separation factor of ~7000 for both, nearly 90- and 10300-fold higher, respectively, than the values obtained using conventional PUREX formulae.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Solvation Structure of 237 Np 4+ in a Noncomplexing Environment

Here, the solvation structure of an Np 4+ ion in an aqueous, noncomplexing and nonoxidizing environment of trifluoromethanesulfonic (triflic) acid was investigated with X-ray absorption spectroscopy (XAS) combined with ab initio molecular dynamics (AIMD) and time-dependent density functional theory (TDDFT) calculations. Np L III -edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data were collected for Np 4+ in 1, 3, and 7 M triflic acid using a laboratory-scale spectrometer and separately at a synchrotron facility, producing data sets in excellent agreement. TDDFT calculations revealed a weak pre-edge feature not previously reported for Np L III -edge XANES. AIMD modeling results showed differences in the hydration shell of the Np 4+ ion at different concentrations of triflic acid; these results are supported by the experiment. EXAFS fit models to the experiment resulted in similar coordination of Np 4+ in noncomplexing aqueous media as reported in the literature for 1 M perchloric acid but, together with calculations, revealed more than one distance between Np and O atoms in 7 M triflic acid. These results imply monodentate coordination with sulfonate groups in 7 M triflic acid and suggest the possibility of proto-neptunyl species in relatively low-concentration Np 4+ acid solutions.

Boglaienko, Daria V. [Pacific Northwest National L↗
DOE OSTI2020

Materials Data on Np(Al2Cu)4 by Materials Project

Np(CuAl2)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 12-coordinate geometry to eight equivalent Cu and twelve Al atoms. All Np–Cu bond lengths are 3.37 Å. There are four shorter (3.04 Å) and eight longer (3.18 Å) Np–Al bond lengths. Cu is bonded in a 12-coordinate geometry to two equivalent Np, two equivalent Cu, and eight Al atoms. Both Cu–Cu bond lengths are 2.54 Å. There are four shorter (2.56 Å) and four longer (2.68 Å) Cu–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Np, four equivalent Cu, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.73–2.84 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Np, four equivalent Cu, and four equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The Natural Products Magnetic Resonance Database (NP-MRD) for 2025

The Natural Products Magnetic Resonance Database or NP-MRD (https://np-mrd.org) is a comprehensive, freely accessible, web-based resource for the deposition, distribution, extraction and retrieval of nuclear magnetic resonance (NMR) data on natural products. The NP-MRD was initially established to support compound de-replication and data dissemination for the natural products community. However, that community has now grown to include many users from the metabolomics, microbiomics, foodomics and nutrition science fields. Indeed, since its launch in 2021, the NP-MRD has expanded enormously in size, scope and popularity. The current version of NP-MRD now contains nearly 7X more compounds (281,859 vs. 40,908) and 7X more NMR spectra (5.1 million vs. 817,000) than the first release. More specifically, an additional 4.6 million predicted spectra and another 11,000 spectra simulated from experimental chemical shifts were deposited into the database. Likewise, the number of NMR raw spectral data depositions has grown from a 165 spectra per year to more than 10,000 per year. As a result of this expansion, the number of monthly webpage views has grown from 55 to 20,000 and the number of monthly visitors has increased from 7 to 2500. To address this growth and to better support the expanding needs of its diverse community of users, many additional improvements to the NP-MRD have been made. These include significant enhancements to the data submission process, important improvements to the visualization and display of NMR spectra, notable updates to the database’s spectral search utilities and useful additions to support better NMR spectral analysis/prediction. Significant efforts have also been undertaken to remediate and update many of NP-MRD’s database entries. This manuscript describes these database improvements and expansion efforts, along with how they have been implemented and what future upgrades to the NP-MRD are planned.

Artifical Intelligence↗
DOE OSTI2023

Np-237 LoD Measurement by TIMS-Multi-Ion Counting Total Evaporation [Poster]

Requests for ultra-low-level 237 Np analyses highlight the importance of a robust chemical purification and measurement technique for Np. In FY2022, LANL is quantifying the instrumental 237 Np LoD. Need to incorporate a chemical purification procedure for TIMS-MICTE sample preparation. What is the recovery of the chemical purification procedure? What is the ultimate detection limit that can be achieved while incorporating a chemical purification procedure? We have adapted and refined the Pu TIMS-MICTE method for Np analyses. We have determined expected uncertainties for 237 Np TIMS-MICTE measurements. We have increased sensitivity through technique improvements. We have improved method reliability for Np analyses and increased throughput. Apply knowledge gained from progress made in FY2022 to further develop Np sample purification and analyses by TIMSMICTE.

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

Materials Data on Np(GePd)2 by Materials Project

Np(PdGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Ge atoms. All Np–Pd bond lengths are 3.38 Å. All Np–Ge bond lengths are 3.21 Å. Pd is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing PdNp4Ge4 tetrahedra. All Pd–Ge bond lengths are 2.53 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Pd, and one Ge atom. The Ge–Ge bond length is 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(GeRh)2 by Materials Project

Np(RhGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Ge atoms. All Np–Rh bond lengths are 3.35 Å. All Np–Ge bond lengths are 3.18 Å. Rh is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted edge, corner, and face-sharing RhNp4Ge4 tetrahedra. All Rh–Ge bond lengths are 2.47 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Rh, and one Ge atom. The Ge–Ge bond length is 2.56 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(SiRh)2 by Materials Project

Np(RhSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Si atoms. All Np–Rh bond lengths are 3.22 Å. All Np–Si bond lengths are 3.05 Å. Rh is bonded to four equivalent Np and four equivalent Si atoms to form a mixture of distorted edge, corner, and face-sharing RhNp4Si4 tetrahedra. All Rh–Si bond lengths are 2.41 Å. Si is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Rh, and one Si atom. The Si–Si bond length is 2.34 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(CuGe)2 by Materials Project

Np(CuGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Np–Cu bond lengths are 3.29 Å. All Np–Ge bond lengths are 3.08 Å. Cu is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing CuNp4Ge4 tetrahedra. All Cu–Ge bond lengths are 2.43 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(MnGe)2 by Materials Project

Np(MnGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Mn and eight equivalent Ge atoms. All Np–Mn bond lengths are 3.24 Å. All Np–Ge bond lengths are 3.10 Å. Mn is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of edge, face, and corner-sharing MnNp4Ge4 tetrahedra. All Mn–Ge bond lengths are 2.37 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.55 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(CoGe)2 by Materials Project

Np(CoGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Co and eight equivalent Ge atoms. All Np–Co bond lengths are 3.15 Å. All Np–Ge bond lengths are 3.10 Å. Co is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing CoNp4Ge4 tetrahedra. All Co–Ge bond lengths are 2.33 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Co, and one Ge atom. The Ge–Ge bond length is 2.47 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(Al2Fe)4 by Materials Project

NpFe4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 12-coordinate geometry to eight equivalent Fe and twelve Al atoms. All Np–Fe bond lengths are 3.32 Å. There are four shorter (2.97 Å) and eight longer (3.15 Å) Np–Al bond lengths. Fe is bonded in a 12-coordinate geometry to two equivalent Np, two equivalent Fe, and eight Al atoms. Both Fe–Fe bond lengths are 2.51 Å. There are four shorter (2.52 Å) and four longer (2.64 Å) Fe–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to two equivalent Np, four equivalent Fe, and six Al atoms. There are a spread of Al–Al bond distances ranging from 2.70–2.80 Å. In the second Al site, Al is bonded in a 10-coordinate geometry to one Np, four equivalent Fe, and five Al atoms. The Al–Al bond length is 2.75 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(NiGe)2 by Materials Project

Np(NiGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Np–Ni bond lengths are 3.21 Å. All Np–Ge bond lengths are 3.12 Å. Ni is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted edge, face, and corner-sharing NiNp4Ge4 tetrahedra. All Ni–Ge bond lengths are 2.36 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.52 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(FeGe)2 by Materials Project

Np(FeGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent Ge atoms. All Np–Fe bond lengths are 3.13 Å. All Np–Ge bond lengths are 3.09 Å. Fe is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing FeNp4Ge4 tetrahedra. All Fe–Ge bond lengths are 2.32 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Fe, and one Ge atom. The Ge–Ge bond length is 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Measurement of the Effective Capture Cross Section of 238 Np in the High Flux Isotope Reactor

The cross sections of 237 Np and 238 Np are important for accurate modeling and simulation of 238 Pu in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). Uncertainties in these cross sections can impact the ability to predict and optimize the target design and loading for 238 Pu production targets. The effective capture cross section of 237 Np in the location of pneumatic tube 1 in HFIR was measured as a first step in the measurement of the 238 Np capture and fission cross sections. Here, we describe the flux measurements, 237 Np experiments, and data analysis of the 237 Np capture cross section in HFIR.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗