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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Designing an impedance-based technique for studying corrosion on cladding materials

In nuclear cladding materials, changes in structure and chemistry over the lifetime of claddings can have a significant impact on fuel and reactor performance. Currently, chemical evolution over the lifetime of the fuel and cladding materials can only be inferred using post-irradiation examination. As an alternative to post-irradiation measurements, electrochemical impedance spectroscopy (EIS) can provide an in-pile measurement of changes in chemistry in oxides and hydrides. The objective of this study is to develop an impedance based sensing technology for measuring spatial- and time-resolved in-pile changes in cladding chemistry in order to understand the mechanisms of hydride formation, hydride dealloying and associated cladding corrosion so that a mitigation strategy and technology can be developed for reactor safe operation. Two prototype impedance-based sensors were designed and assembled using Zr-4 as working electrode and Pt as counter and reference electrode. One sensor is tubular type and the other one is plate-type. These sensors will be tested in static autoclave to investigate the effects of various environmental conditions (including temperature, pressure, and water chemistry) on cladding material corrosion mechanisms. These in-situ EIS sensors would provide corrosion-layer parameters in high-temperature water, such as (1) total layer thickness, (2) the evolution of oxide structures as uniform layer dielectric or sublayer(s), and (3) the possible electrochemistry of the volume corrosion process and the solid/liquid interface, such as the cyclic nature of corrosion of Zr alloys in high-temperature water. This work was focused on electrochemical sensor development, targeting cladding oxides/hydrides under thermodynamic equilibria; characterization of samples using Kelvin probe force microscopy (SKPFM), Raman spectroscopy, and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) to provide high-resolution co-localized characterization of zirconium oxide and metal/oxide interface.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Using spatio-temporal graph neural networks to estimate fleet-wide photovoltaic performance degradation patterns

Accurate estimation of photovoltaic (PV) system performance is crucial for determining its feasibility as a power generation technology and financial asset. PV-based energy solutions offer a viable alternative to traditional energy resources due to their superior Levelized Cost of Energy (LCOE). A significant challenge in assessing the LCOE of PV systems lies in understanding the Performance Loss Rate (PLR) for large fleets of PV systems. Estimating the PLR of PV systems becomes increasingly important in the rapidly growing PV industry. Precise PLR estimation benefits PV users by providing real-time monitoring of PV module performance, while explainable PLR estimation assists PV manufacturers in studying and enhancing the performance of their products. However, traditional PLR estimation methods based on statistical models have notable drawbacks. Firstly, they require user knowledge and decision-making. Secondly, they fail to leverage spatial coherence for fleet-level analysis. Additionally, these methods inherently assume the linearity of degradation, which is not representative of real world degradation. To overcome these challenges, we propose a novel graph deep learning-based decomposition method called the Spatio-Temporal Graph Neural Network for fleet-level PLR estimation (PV-stGNN-PLR). PV-stGNN-PLR decomposes the power timeseries data into aging and fluctuation components, utilizing the aging component to estimate PLR. PV-stGNN-PLR exploits spatial and temporal coherence to derive PLR estimation for all systems in a fleet and imposes flatness and smoothness regularization in loss function to ensure the successful disentanglement between aging and fluctuation. We have evaluated PV-stGNN-PLR on three simulated PV datasets consisting of 100 inverters from 5 sites. Experimental results show that PV-stGNN-PLR obtains a reduction of 33.9% and 35.1% on average in Mean Absolute Percent Error (MAPE) and Euclidean Distance (ED) in PLR degradation pattern estimation compared to the state-of-the-art PLR estimation methods.

14 SOLAR ENERGY↗
DOE OSTI2026

Forensic characterization of surrogate nuclear explosion debris: radiochemical and spectroscopic strategies for method validation

Surrogate nuclear explosion debris (SNED) has emerged as a critical platform for advancing post-detonation nuclear forensic analysis in the absence of readily accessible historic materials. SNED enables controlled investigation and validation of analytical methodologies used to interrogate the chemical, isotopic, radiological, and microstructural signatures preserved in nuclear explosion debris. This review presents an integrated assessment of destructive and non-destructive analytical techniques commonly employed within decision-driven nuclear forensic workflows. Each technique is discussed individually while highlighting how it contributes to different stages of post-detonation analysis. Core methods – including gamma and alpha spectrometry, ICP-MS, TIMS, SIMS, SEM-EDS, XRF, LIBS, vibrational spectroscopy, and X-ray absorption spectroscopy – are critically evaluated with respect to forensic maturity, information content, and matrix limitations. Emphasis is placed on the role of SNED in benchmarking multi-modal workflows and identifying gaps in reproducing heterogeneity, fractionation, and radiation-driven evolution relevant to forensic attribution.

X-ray spectroscopic methods↗
DOE OSTI2022

Simulated tree recruitment at PA-BCI under four precipitation scenarios

Simulated recruitment rates are provided for four tropical tree plant functional types (PFTs) which vary in drought and shade tolerance, at Barro Colorado Island, Panama (PA-BCI). Recruitment rates are predicted using the Tree Recruitment Scheme (TRS; Hanbury-Brown et al., 2022) and model data output from the Ecosystem Demography model version 2 with hydrodynamics (ED2; Medvigy et al., 2009, Powell et al., 2018). Predictions of recruitment are provided under four precipitation scenarios: “BASE” = recycled 2008-2014 observed meteorology (Faybishenko & Paton, 2021), “SYN-ENSO” = two exceptionally strong El Niño events within 30 years (Powell et al., 2018), “WET” = 30% increase in precipitation compared to BASE, and DRY-DS = dry season (January–April) precipitation reduced by 75% compared to BASE. In addition to recruitment rates, this dataset provides TRS predictions of PFT-specific seed bank and seedling pool dynamics (tracked in units of carbon) and ED predictions of understory photosynthetically active radiation and soil matric potential at 6 cm soil depth.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Chemical and physical transformations of carbon-based nanomaterials observed by liquid phase transmission electron microscopy

This article addresses recent advances in liquid phase transmission electron microscopy (LPTEM) for studying nanoscale synthetic processes of carbon-based materials that are independent of the electron beam—those driven by nonradiolytic chemical or thermal reactions. In particular, we focus on chemical/physical formations and the assembly of nanostructures composed of organic monomers/polymers, peptides/DNA, and biominerals. The synthesis of carbon-based nanomaterials generally only occurs at specific conditions, which cannot be mimicked by aqueous solution radiolysis. Carbon-based structures themselves are also acutely sensitive to the damaging effects of the irradiating beam, which make studying their synthesis using LPTEM a unique challenge that is possible when beam effects can be quantifi ed and mitigated. With new direct sensing, high frame rate cameras, and advances in liquid-cell holder designs, combined with a growing understanding of irradiation effects and proper experimental controls, microscopists have been able to make strides in observing traditionally problematic carbon-based materials under conditions where synthesis can be controlled, and imaged free from beam effects, or with beam effects quantified and accounted for. These materials systems and LPTEM experimental techniques are discussed, focusing on nonradiolytic chemical and physical transformations relevant to materials synthesis.

Parent, Lucas R.↗
DOE OSTI2020

Materials Data on Li7Ti12O24 by Materials Project

Li7Ti12O24 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are seven inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–9°. There are a spread of Li–O bond distances ranging from 2.00–2.38 Å. In the second Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–14°. There are a spread of Li–O bond distances ranging from 2.00–2.35 Å. In the third Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–13°. There are a spread of Li–O bond distances ranging from 2.00–2.31 Å. In the fourth Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Li–O bond distances ranging from 2.00–2.43 Å. In the fifth Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Li–O bond distances ranging from 2.01–2.37 Å. In the sixth Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Li–O bond distances ranging from 2.01–2.36 Å. In the seventh Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Li–O bond distances ranging from 2.01–2.36 Å. There are twelve inequivalent Ti+3.42+ sites. In the first Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four TiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–19°. There are a spread of Ti–O bond distances ranging from 1.98–2.14 Å. In the second Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four equivalent LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–18°. There are a spread of Ti–O bond distances ranging from 2.00–2.08 Å. In the third Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four TiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–19°. There are a spread of Ti–O bond distances ranging from 1.95–2.15 Å. In the fourth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four equivalent LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–14°. There are a spread of Ti–O bond distances ranging from 2.01–2.07 Å. In the fifth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of Ti–O bond distances ranging from 2.00–2.08 Å. In the sixth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four TiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–19°. There are a spread of Ti–O bond distances ranging from 1.99–2.13 Å. In the seventh Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 12–13°. There are a spread of Ti–O bond distances ranging from 1.88–2.17 Å. In the eighth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are a spread of Ti–O bond distances ranging from 2.00–2.09 Å. In the ninth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Ti–O bond distances ranging from 2.00–2.08 Å. In the tenth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–12°. There are a spread of Ti–O bond distances ranging from 2.01–2.04 Å. In the eleventh Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four TiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–19°. There are a spread of Ti–O bond distances ranging from 1.98–2.13 Å. In the twelfth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four equivalent LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. There are a spread of Ti–O bond distances ranging from 2.00–2.12 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to three Li1+ and three Ti+3.42+ atoms to form OLi3Ti3 octahedra that share corners with four equivalent OLi3Ti3 octahedra, a cornercorner with one OLi2Ti3 square pyramid, edges with two equivalent OLi3Ti3 octahedra, and edges with six OLi2Ti3 square pyramids. The corner-sharing octahedra tilt angles range from 2–3°. In the second O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share corners with four equivalent OLi2Ti3 square pyramids, edges with six OLi3Ti3 octahedra, and edges with two equivalent OLi2Ti3 square pyramids. In the third O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form a mixture of edge and corner-sharing OLi2Ti3 square pyramids. In the fourth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the fifth O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share corners with four equivalent OLi2Ti3 square pyramids, edges with six OLi3Ti3 octahedra, and edges with two equivalent OLi2Ti3 square pyramids. In the sixth O2- site, O2- is bonded to three Li1+ and three Ti+3.42+ atoms to form OLi3Ti3 octahedra that share corners with four equivalent OLi3Ti3 octahedra, a cornercorner with one OLi2Ti3 square pyramid, edges with two equivalent OLi3Ti3 octahedra, and edges with six OLi2Ti3 square pyramids. The corner-sharing octahedra tilt angles range from 3–8°. In the seventh O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share a cornercorner with one OLi3Ti3 octahedra, corners with four equivalent OLi2Ti3 square pyramids, and edges with four equivalent OLi2Ti3 square pyramids. The corner-sharing octahedral tilt angles are 0°. In the eighth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the ninth O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share a cornercorner with one OLi3Ti3 octahedra, corners with four equivalent OLi2Ti3 square pyramids, and edges with four equivalent OLi2Ti3 square pyramids. The corner-sharing octahedral tilt angles are 0°. In the tenth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the eleventh O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share corners with four equivalent OLi2Ti3 square pyramids, edges with six OLi3Ti3 octahedra, and edges with two equivalent OLi2Ti3 square pyramids. In the twelfth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the thirteenth O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form a mixture of edge and corner-sharing OLi2Ti3 square pyramids. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Li1+ and three Ti+3.42+ atoms. In the fifteenth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the sixteenth O2- site, O2- is bonded to three Li1+ and three Ti+3.42+ atoms to form OLi3Ti3 octahedra that share corners with four equivalent OLi3Ti3 octahedra, a cornercorner with one OLi2Ti3 square pyramid, edges with two equivalent OLi3Ti3 octahedra, and edges with six OLi2Ti3 square pyramids. The corner-sharing octahedra tilt angles range from 1–2°. In the seventeenth O2- site, O2- is bonded to three Li1+ and three Ti+3.42+ atoms to form OLi3Ti3 octahedra that share corners with four equivalent OLi3Ti3 octahedra, a cornercorner with one OLi2Ti3 square pyramid, edges with two equivalent OLi3Ti3 octahedra, and edges with six OLi2Ti3 square pyramids. The corner-sharing octahedral tilt angles are 2°. In the eighteenth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the nineteenth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the twentieth O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share a cornercorner with one OLi3Ti3 octahedra, corners with four equivalent OLi2Ti3 square pyramids, and edges with four equivalent OLi2Ti3 square pyramids. The corner-sharing octahedral tilt angles are 0°. In the twenty-first O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the twenty-second O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share corners with four equivalent OLi2Ti3 square pyramids, ed

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li10Sn(PSe6)2 by Materials Project

Li10Sn(PSe6)2 is Aluminum carbonitride-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are twenty inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 5-coordinate geometry to five Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.67–2.85 Å. In the second Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.64–3.30 Å. In the third Li1+ site, Li1+ is bonded to six Se2- atoms to form distorted LiSe6 octahedra that share a cornercorner with one LiSe6 octahedra, corners with two equivalent PSe4 tetrahedra, corners with three LiSe4 tetrahedra, corners with two equivalent LiSe5 trigonal bipyramids, an edgeedge with one SnSe4 tetrahedra, an edgeedge with one PSe4 tetrahedra, and edges with three LiSe4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. There are a spread of Li–Se bond distances ranging from 2.67–3.28 Å. In the fourth Li1+ site, Li1+ is bonded to six Se2- atoms to form LiSe6 octahedra that share corners with two equivalent PSe4 tetrahedra, corners with four LiSe4 tetrahedra, an edgeedge with one LiSe6 octahedra, an edgeedge with one SnSe4 tetrahedra, an edgeedge with one PSe4 tetrahedra, edges with four LiSe4 tetrahedra, and an edgeedge with one LiSe5 trigonal bipyramid. There are a spread of Li–Se bond distances ranging from 2.73–3.00 Å. In the fifth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two equivalent LiSe6 octahedra, corners with two equivalent LiSe4 tetrahedra, corners with two PSe4 tetrahedra, an edgeedge with one LiSe6 octahedra, an edgeedge with one LiSe4 tetrahedra, an edgeedge with one SnSe4 tetrahedra, and an edgeedge with one LiSe5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 18–63°. There are a spread of Li–Se bond distances ranging from 2.49–2.67 Å. In the sixth Li1+ site, Li1+ is bonded in a 4-coordinate geometry to five Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.67–3.37 Å. In the seventh Li1+ site, Li1+ is bonded to four Se2- atoms to form distorted LiSe4 tetrahedra that share a cornercorner with one LiSe6 octahedra, corners with two PSe4 tetrahedra, corners with four LiSe4 tetrahedra, corners with two LiSe5 trigonal bipyramids, an edgeedge with one LiSe6 octahedra, and an edgeedge with one SnSe4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Li–Se bond distances ranging from 2.55–2.69 Å. In the eighth Li1+ site, Li1+ is bonded to six Se2- atoms to form LiSe6 octahedra that share a cornercorner with one LiSe6 octahedra, corners with two PSe4 tetrahedra, corners with six LiSe4 tetrahedra, an edgeedge with one LiSe6 octahedra, an edgeedge with one LiSe4 tetrahedra, an edgeedge with one SnSe4 tetrahedra, and an edgeedge with one PSe4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. There are a spread of Li–Se bond distances ranging from 2.68–3.24 Å. In the ninth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two LiSe6 octahedra, a cornercorner with one SnSe4 tetrahedra, a cornercorner with one PSe4 tetrahedra, corners with two equivalent LiSe4 tetrahedra, an edgeedge with one LiSe4 tetrahedra, and an edgeedge with one PSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–71°. There are a spread of Li–Se bond distances ranging from 2.51–2.65 Å. In the tenth Li1+ site, Li1+ is bonded to five Se2- atoms to form LiSe5 trigonal bipyramids that share corners with two equivalent LiSe6 octahedra, a cornercorner with one PSe4 tetrahedra, corners with two equivalent SnSe4 tetrahedra, corners with four LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one PSe4 tetrahedra, and edges with two LiSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–37°. There are a spread of Li–Se bond distances ranging from 2.58–3.04 Å. In the eleventh Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with four LiSe6 octahedra, a cornercorner with one SnSe4 tetrahedra, a cornercorner with one PSe4 tetrahedra, corners with two equivalent LiSe4 tetrahedra, an edgeedge with one LiSe4 tetrahedra, and an edgeedge with one PSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 9–68°. There are a spread of Li–Se bond distances ranging from 2.51–2.75 Å. In the twelfth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two LiSe6 octahedra, corners with two PSe4 tetrahedra, corners with four LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one SnSe4 tetrahedra, and an edgeedge with one LiSe5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 53–73°. There are a spread of Li–Se bond distances ranging from 2.65–2.80 Å. In the thirteenth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two SnSe4 tetrahedra, corners with three LiSe4 tetrahedra, corners with three LiSe5 trigonal bipyramids, edges with two LiSe6 octahedra, and an edgeedge with one PSe4 tetrahedra. There are a spread of Li–Se bond distances ranging from 2.58–2.66 Å. In the fourteenth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two equivalent LiSe4 tetrahedra, corners with two PSe4 tetrahedra, corners with two equivalent LiSe5 trigonal bipyramids, an edgeedge with one LiSe6 octahedra, an edgeedge with one LiSe4 tetrahedra, and an edgeedge with one SnSe4 tetrahedra. There are a spread of Li–Se bond distances ranging from 2.55–2.76 Å. In the fifteenth Li1+ site, Li1+ is bonded to four Se2- atoms to form distorted LiSe4 tetrahedra that share a cornercorner with one SnSe4 tetrahedra, a cornercorner with one PSe4 tetrahedra, corners with two equivalent LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, and an edgeedge with one PSe4 tetrahedra. There are a spread of Li–Se bond distances ranging from 2.53–2.60 Å. In the sixteenth Li1+ site, Li1+ is bonded to five Se2- atoms to form distorted LiSe5 trigonal bipyramids that share a cornercorner with one PSe4 tetrahedra, corners with two SnSe4 tetrahedra, corners with seven LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, an edgeedge with one LiSe4 tetrahedra, and an edgeedge with one PSe4 tetrahedra. There are a spread of Li–Se bond distances ranging from 2.61–3.07 Å. In the seventeenth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two equivalent LiSe6 octahedra, corners with two SnSe4 tetrahedra, corners with four LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, and an edgeedge with one PSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–25°. There are a spread of Li–Se bond distances ranging from 2.58–2.68 Å. In the eighteenth Li1+ site, Li1+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.56–2.80 Å. In the nineteenth Li1+ site, Li1+ is bonded in a 5-coordinate geometry to five Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.57–3.13 Å. In the twentieth Li1+ site, Li1+ is bonded to four Se2- atoms to form distorted LiSe4 tetrahedra that share a cornercorner with one SnSe4 tetrahedra, a cornercorner with one PSe4 tetrahedra, corners with three LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, an edgeedge with one PSe4 tetrahedra, and an edgeedge with one LiSe5 trigonal bipyramid. There are a spread of Li–Se bond distances ranging from 2.64–2.71 Å. There are two inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share corners with four LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, and edges with two LiSe4 tetrahedra. There are a spread of Sn–Se bond distances ranging from 2.54–2.57 Å. In the second Sn4+ site, Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share corners with four LiSe4 tetrahedra, corners with three LiSe5 trigonal bipyramids, edges with two LiSe6 octahedra, and edges with two LiSe4 tetrahedra. There are a spread of Sn–Se bond distances ranging from 2.53–2.58 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with three LiSe6 octahedra and corners with five LiSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–55°. There are a spread of P–Se bond distances ranging from 2.20–2.26 Å. In the second P5+ site, P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with three LiSe6 octahedra, corners with three LiSe4 tetrahedra, edges with two LiSe4 tetrahedra, and edges with two LiSe5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 27–57°. There are a spread of P–Se bond distances ranging from 2.21–2.25 Å. In the third P5+ site, P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with two LiSe4 tetrahedra, corners with two LiSe5 trigonal bipyramids, and edges with two LiSe4 tetrahedra. There are one shorter (2.23 Å) and three longer (2.24 Å) P–Se bond lengths. In the fourth P5+ site, P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with two LiSe4 tetrahedra, edges with three LiSe6 octahedra, and edges with two LiSe4 tetrahedra. There are three shorter (2.23 Å) and one longer (2.24 Å) P–Se bond lengths. There are twenty-four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the second Se2- site, Se2- is bonded to four Li1+ and one P5+ atom to form distorted SeLi4P square pyramids that share a cornercorner with one SeLi4P square pyramid, corners with two SeLi4P trigonal bipyramids, a cornercorner with one SeLi3P trigonal pyramid, an edgeedge with one SeLi4Sn square pyramid, and edges with two SeLi4P trigonal bipyramids. In the third Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the fifth Se2- site, Se2- is bonded in a 6-coordinate geometry to five Li1+ and one P5+ atom. In the sixth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the seventh Se2- site, Se2- is bonded to four Li1+ and one P5+ atom to form distorted SeLi4P trigonal bipyramids that share corners with two SeLi3P trigonal pyramids, an edgeedge with one SeLi4P square pyramid, and edges with two SeLi4P trigonal bipyramids. In the eighth Se2- site, Se2- is bonded in a distorted see-saw-like geometry to three Li1+ and one P5+ atom. In the ninth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one Sn4+ atom. In the tenth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one Sn4+ atom. In the eleventh Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the twelfth Se2- site, Se2- is bonded to three Li1+ and one P5+ atom to form SeLi3P trigonal pyramids that share corners with two SeLi4Sn square pyramids, a cornercorner with one SeLi4Sn trigonal bipyramid, and an edgeedge with one SeLi3P trigonal pyramid. In the thirteenth Se2- site, Se2- is bonded to four Li1+ and one P5+ atom to form distorted SeLi4P trigonal bipyramids that share corners with two SeLi4Sn square pyramids, a cornercorner with one SeLi4Sn trigonal bipyramid, ed

36 MATERIALS SCIENCE↗
DOE OSTI2022

In Situ Plasma Processing of Superconducting Cavities at JLab

Jefferson Lab has an ongoing R&D program in plasma processing which is close to going into production pro-cessing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient[1]. The initial focus of the effort is processing C100 cavities by injecting RF power into the HOM coupler ports. The goal will be to improve the operational gradients and the energy margin of the CEBAF linacs by processing cryomodules in situ. Results from processing cryomodule in the cryomodule test bunker as well as vertical test results will be present-ed. This work will describe the systems and methods used at JLAB for processing cavities using an argon oxygen gas mixture. Before and after plasma processing results will also be presented.

Powers, T.↗
DOE OSTI2023

Geometry Optimization for a Quadrupole Resonator at Jefferson Lab

The quadrupole resonator (QPR) is a sample characterization tool to measure the RF properties of superconducting materials using the calorime-try method at different temperatures, magnetic fields, and frequencies. Such resonators are cur-rently operating at CERN and HZB but suffer from Lorentz force detuning and modes overlap-ping, resulting in higher uncertainties in surface resistance measurement. Using the two CERN's QPR model iterations, the geometry was opti-mized via electromagnetic and mechanical simu-lations to eliminate these issues. The new QPR version was modelled for an increasing range of magnetic fields. The magnetic field is concentrat-ed at the center of the sample to reduce the un-certainty in surface resistance measurements sig-nificantly. This paper discusses the QPR geome-try optimization for the new version of QPR, which is now progressing toward fabrication.

Bira, S.↗
DOE OSTI2023

IN SITU PLASMA PROCESSING OF SUPERCONDUCTING CAVITIES AT JLAB, 2023 UPDATE

Jefferson Lab has an ongoing R&D program in plasma processing which just completed a round of production processing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient. The initial focus of the effort was processing C100 cavities by injecting RF power into the higher order mode (HOM) coupler ports. Results from processing cryomodules in the CEBAF accelerator as well as vertical test results will be present-ed. The goal of in-situ processing is to improve the operational gradients and the energy margin of the linacs. This work will describe the systems and methods used at JLAB for processing cavities using an argon-oxygen gas mixture as well as a helium-oxygen gas mixture. Before and after plasma processing results will also be presented.

Powers, Thomas↗
DOE OSTI2020

Dimer description of the SU(4) antiferromagnet on the triangular lattice

In systems with many local degrees of freedom, high-symmetry points in the phase diagram can provide an important starting point for the investigation of their properties throughout the phase diagram. In systems with both spin and orbital (or valley) degrees of freedom such a starting point gives rise to SU(4)-symmetric models. Here we consider SU(4)-symmetric "spin" models, corresponding to Mott phases at half-filling, i.e. the six-dimensional representation of SU(4). This may be relevant to twisted multilayer graphene. In particular, we study the SU(4) antiferromagnetic "Heisenberg" model on the triangular lattice, both in the classical limit and in the quantum regime. Carrying out a numerical study using the density matrix renormalization group (DMRG), we argue that the ground state is non-magnetic. We then derive a dimer expansion of the SU(4) spin model. An exact diagonalization (ED) study of the effective dimer model suggests that the ground state breaks translation invariance, forming a valence bond solid (VBS) with a 12-site unit cell. Finally, we consider the effect of SU(4)-symmetry breaking interactions due to Hund's coupling, and argue for a possible phase transition between a VBS and a magnetically ordered state.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Analysis Of The Sludge Batch 7b (Macrobatch 9) DWPF Pour Stream Glass Sample (Rev. 1)

The Defense Waste Processing Facility (DWPF) began processing Sludge Batch 7b (SB7b), also referred to as Macrobatch 9 (MB9), in January 2012. SB7b is a blend of the heel of Tank 40 from Sludge Batch 7a (SB7a) and the SB7b material that was transferred to Tank 40 from Tank 51. SB7b was processed using Frit 418. During processing of each sludge batch, the DWPF is required to take at least one glass sample to meet the objectives of the Glass Product Control Program (GPCP), which is governed by the DWPF Waste Form Compliance Plan, and to complete the necessary Production Records so that the final glass product may be disposed of at a Federal Repository. Two pour stream glass samples were collected while processing SB7b. The samples were transferred to the Savannah River National Laboratory (SRNL) where one was analyzed and the other was archived. The following conclusions were drawn from the analytical results provided in this report: The sum of oxides for the official SB7b pour stream glass is within the Product Composition Control System (PCCS) limits (95-105 wt%); The average calculated Waste Dilution Factor (WDF) for SB7b is 2.3. In general, the measured radionuclide content of the official SB7b pour stream glass is in good agreement with the calculated values from the Tank 40 dried sludge results from the SB7b Waste Acceptance Program Specification (WAPS) sample; As in previous pour stream samples, ruthenium and rhodium inclusions were detected by Scanning Electron Microscopy-Electron Dispersive Spectroscopy (SEM-EDS) in the SB7b pour stream sample; The Product Consistency Test (PCT) results indicate that the official SB7b pour stream glass meets the waste acceptance criteria for durability with a normalized boron release of 0.8 g/L, which is an order of magnitude less than the Environmental Assessment (EA) glass; The measured density of the SB7b pour stream glass was 2.70 g/cm 3 ; The Fe 2+ /ΣFe ratio of the SB7b pour stream samples was 0.07.

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

V28 Test Report

The V28 containment vessel was procured by the US Army Recovered Chemical Material Directorate (RCMD) as a replacement vessel for use on the P2 Explosive Destruction Systems. It is the fourth EDS vessel to be fabricated under Code Case 2564 of the ASME Boiler and Pressure Vessel Code, which provides rules for the design of impulsively loaded vessels. The explosive rating for the vessel, based on the Code Case, is nine (9) pounds TNT- equivalent for up to 637 detonations. This report documents the results of explosive tests that were done on the vessel at Sandia National Laboratories in Albuquerque New Mexico to qualify the vessel for explosive use. The primary qualification test consisted of six, 1.5 pounds charges of Composition C-4 (equivalent to 11.25 pounds TNT) distributed around the vessel in accordance with the User Design Specification. This test was repeated due to a lack of proper clamp settings. Two additional tests using less explosive were performed, one identical in configuration to a test performed in the V27 qualification series as a baseline for comparison, and one where the separation distance of the charges was increased to extend the V27 analysis of distributed load effects on the P2 vessel. All vessel acceptance criteria were met.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2020

Highly-Active and Contaminant-Tolerant Cathodes for Durable Solid Oxide Fuel Cells (Final Report)

The objective of this project is to investigate the fundamental degradation methods occurring in solid oxide fuel cell (SOFC) cathodes when exposed to chromium and carbon dioxide contamination and to rationally design alkaline earth-based catalysts to increase stability and tolerance to contaminate poisoning. With a mechanistic and fundamental understanding of the degradation methods, advanced catalytic surface modifications can be applied to reduce degradation. The specific technical objectives are: (1) To identify/develop new catalysts (alkaline-earth based-) that are compatible chemically with the state-of-the-art cathode materials at high temperatures required for fabrication and with contaminates commonly encountered under operating conditions; (2) To improve the infiltration process for optimal control of the thickness, composition, and uniformity of the catalyst coatings; (3) To evaluate the electro-catalytic activity toward ORR of the chemically-stable materials when exposed to different types of contaminants using electrical conductivity relaxation measurements on bar samples and performance evaluation of catalyst-infiltrated cathodes; (4) To unravel the contamination-tolerant mechanisms of the new catalyst coatings under realistic environmental conditions (with different types of contaminants) using powerful in situ and in operando characterization techniques performed on model cells with thin-film/pattern electrodes, as guided by modeling and simulation; (5) To establish scientific basis for rational design of new catalysts of high tolerance to contaminants; (6) To validate the long term stability of modified LSCF cathodes in commercially available cells/stacks under ROC. Alkaline earth-based catalysts have been systematically explored and tested under various contamination conditions. BaCoO 3-δ (BCO) was shown to produce the best catalytic activity enhancement as well as stability in a variety of contaminating conditions, including CO 2 and chromium. The microstructural evolution was investigated with SEM, EDS, and Raman spectroscopy, showing the BCO catalyst prevents the formation of insulating SrCrO 4 by forming electrically conductive BaCrO 4 . Electrochemical relaxation measurements determined the BCO catalyst coatings increased the surface diffusion coefficient but did not significantly affect the diffusion coefficient and determined an optimum surface modification layer of 100 nm. A novel Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O x (BCFN) catalyst was also shown to have excellent stability in chromium containing atmospheres. A novel surface sol-gel (SSG) surface modification, which offers superior thickness and compositional control, was applied to SOFCs to produce BaO catalyst coatings. SSG BaO coatings were shown to produce conformal coatings on the electrode surface, greatly increasing stability in chromium containing atmospheres. An atomic level mechanistic approach was applied to investigate the stability of PrBa 0.8 Ca 0.2 Co2O 5+δ (PBCC) with respect to a variety of common contaminants, demonstrating thermodynamically its superior stability in CO2 containing atmospheres. Finally, the best catalyst coatings demonstrated in this project, BCO and PBCC, were applied to full cells which demonstrated superior stability for over 300 hours in CO 2 and Cr atmospheres.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Benchmark Solutions for Radiation Transport in Stochastic Media with Inhomogeneous Material Statistics

Accurately solving implicit Monte Carlo (IMC) thermal photon transport problems with mixed material cells is important in realistic applications. The production IMC package at LLNL treats mixed material cells arising from ALE remap and hydrodynamics using the same approximate model. The new Imp IMC thermal photon transport package currently under development has both a material interface reconstruction (MIR) algorithm and a Levermore-Pomraning (LP) stochastic medium algorithm for treating mixed material cells. Existing stochastic medium algorithms for treating mixed material cells in IMC lack a complete theoretical basis. The IMC LP algorithm implementation has been demonstrated to reproduce published deterministic LP solutions for the particular case of spatially homogeneous material statistics. Realistic simulations will include spatially inhomogeneous material statistics (material mean chord lengths). In a previous investigation, the LP-model for transport in binary stochastic media in rod geometry was generalized to accommodate spatially varying material chord lengths, i.e., the mixing statistics were allowed to be nonhomogeneous. Analytical solutions were obtained and used to produce a verifi cation suite for the Imp IMC Levermore-Pomraning implementation for different spatial variations of the chord lengths. However, the accuracy of the LP model when the mixing statistics are nonhomogeneous has not been assessed and leaves open the question of whether local accuracy is improved or further degraded when chord lengths are not uniform. This shortcoming is rectifi ed here by developing benchmark analytic solutions for transport in binary Markovian stochastic mixtures in rod geometry with nonhomogeneous mixing statistics, using spatially varying chord lengths considered in the previous investigation based on the LP model. Methods for sampling a nonhomogeneous Poisson process (NHPP) are first described and used to construct individual realizations of the binary mixtures in rod geometry. Analytic solutions are then obtained for the forward and backward directed fluxes on a given realization, now viewed as a deterministic medium with alternating layers of the two materials with known interface locations. Finally, material averaged scalar fluxes are obtained using these sampling schemes with spatially linear and quadratic chord lengths and used to assess the accuracy of the previously obtained LP-model results.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

MSTAR2019 Code Description and User's Manual

This report describes an ideal cascade model of uranium enrichment that includes side feed and side product streams and flexible input options. It is based on the original MSTAR model developed by Ed Von Halle and implemented in a Visual Basic code. The current version allows the user to specify integer numbers of stages or the stage numbers of external flows instead of assays in those flows. The computational engine is written in FORTRAN-90 and is invoked by a user-friendly GUI written in C++. This version of MSTAR has been demonstrated to operate on Linux, Mac, and Windows platforms, and has undergone significant testing and quality analysis. A number of examples are presented to illustrate the operation of the code and guide the user. The code is extremely fast, and results are returned immediately. The input and output have been specially configured for analysis by the environmental sampling team of the International Atomic Energy Agency (IAEA). A number of additional output features are included to assist the user in visualizing computational results and downloading data to files for use in other analysis software.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗