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At least 1,783 records · Page 99
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Fracture behavior of irradiation induced nanocrystalline UO 2 studied by in-situ mechanical testing in transmission electron microscopy

Uranium Dioxide (UO 2 ) is widely used as a fuel in current light water reactors (LWRs). Upon accumulation of radiation damage, LWR UO 2 fuel pellets start to develop a different microstructure at the pellet periphery when fuel burnup exceeds 45–50 GWd/tHM. The resulting porous, nanocrystalline microstructure is one of the most prominent microstructural changes occurring in such fuel. Its fracture mechanisms, which causes fuel fine fragmentation, could impact safety limits when the cladding breaches. Direct measurements of these properties are challenging, therefore a surrogate obtained via ion irradiation can be used. In this study, multiple microcantilevers were fabricated by focused ion beam from both fresh UO 2 and UO 2 irradiated with 84 MeV Xe 26+ ions to a peak dose of 1357 displacements per atom (dpa). Further, the irradiation produced a pseudo high burnup structure approximately 2 µm below the surface. In-situ nano-mechanical bending tests were conducted to investigate the fracture behavior and the effect of the surrogate UO 2 high burnup structure on local fracture properties. Fresh UO 2 fuel was observed to fracture in transgranular mode without nucleation or movement of dislocations. However, the Xe-irradiated nanocrystalline microcantilevers fractured along the grain boundaries, with no influence from the pre-existing micro-cracks in the microcantilever. Fracture toughness for this type of surrogate high burnup UO 2 structure is reported for the first time in literature. Both the fracture stress and toughness show degradation for UO 2 as a result of Xe-irradiation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Status of Triso fuel irradiations in the advanced test reactor supporting high-temperature gas-cooled reactor designs - 18468

The Advanced Gas Reactor (AGR) Fuel Development and Qualification Program is irradiating up to seven experiments on low-enriched uranium tri-structural isotropic (TRISO) particle fuel. Irradiations and fuel development are being accomplished at Idaho National Laboratory s Advanced Test Reactor to support development of the next generation of reactors in the United States. The experiments are being irradiated over several years to demonstrate and qualify new TRISO-coated particle fuel for use in high-temperature gas reactors, with goals of providing irradiation performance data to support fuel process development, qualifying fuel for normal operating conditions, supporting development and validation of fuel performance and fission product transport models and codes, and providing irradiated fuel and materials for post-irradiation examination and safety testing. The experiments are irradiated in an inert sweep gas atmosphere, with individual online temperature monitoring and control of each capsule and online fission product monitoring of effluent to track individual capsule fuel performance. The first experiment (AGR-1) started irradiation in December 2006 and was completed in November 2009. The second experiment (AGR-2) started irradiation in June 2010 and completed in October 2013. The third and fourth experiments have been combined into a single experiment (AGR-3/4), which started its irradiation in December 2011 and completed in April 2014. Because the purpose of this experiment was to provide data on fission product migration and retention in the next generation reactor, the design of this experiment was significantly different from the first two experiments. The final experiment (AGR-5/6/7) is scheduled to begin irradiation in early summer 2017. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

High-throughput screening identifies small molecules that bind to the RAS:SOS:RAS complex and perturb RAS signaling

K-RAS is mutated in approximately 30% of human cancers, resulting in increased RAS signaling and tumor growth. Thus, RAS is a highly validated therapeutic target, especially in tumors of the pancreas, lung and colon. Although directly targeting RAS has proven to be challenging, it may be possible to target other proteins involved in RAS signaling, such as the guanine nucleotide exchange factor Son of Sevenless (SOS). We have previously reported on the discovery of small molecules that bind to SOS1, activate SOS-mediated nucleotide exchange on RAS, and paradoxically inhibit ERK phosphorylation. In this paper, we describe the discovery of additional, structurally diverse small molecules that also bind to SOS1 in the same pocket and elicit similar biological effects. We tested>160,000 compounds in a fluorescence-based assay to assess their effects on SOS-mediated nucleotide exchange. X-Ray structures revealed that these small molecules bind to the CDC25 domain of SOS1. Compounds that elicited high levels of nucleotide exchange activity in vitro increased RAS-GTP levels in cells, and inhibited phospho ERK levels at higher treatment concentrations. The identification of structurally diverse SOS1 binding ligands may assist in the discovery of new molecules designed to target RASdriven tumors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Extracting structural motifs from pair distribution function data of nanostructures using explainable machine learning

Characterization of material structure with X-ray or neutron scattering using e.g. Pair Distribution Function (PDF) analysis most often rely on refining a structure model against an experimental dataset. However, identifying a suitable model is often a bottleneck. Recently, automated approaches have made it possible to test thousands of models for each dataset, but these methods are computationally expensive and analysing the output, i.e. extracting structural information from the resulting fits in a meaningful way, is challenging. Our Machine Learning based Motif Extractor (ML-MotEx) trains an ML algorithm on thousands of fits, and uses SHAP (SHapley Additive exPlanation) values to identify which model features are important for the fit quality. We use the method for 4 different chemical systems, including disordered nanomaterials and clusters. ML-MotEx opens for a type of modelling where each feature in a model is assigned an importance value for the fit quality based on explainable ML.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Proton structure functions at small x

Proton structure functions are measured in electron-proton collision through inelastic scattering of virtual photons with virtuality Q on protons; x denotes the momentum fraction carried by the struck parton. Proton structure functions are currently described with excellent accuracy in terms of scale dependent parton distribution functions, defined in terms of collinear factorization and DGLAP evolution in Q. With decreasing x however, parton densities increase and are ultimately expected to saturate. In this regime DGLAP evolution will finally break down and non-linear evolution equations w.r.t x are expected to take over. In the first part of the talk we present recent result on an implementation of physical DGLAP evolution. Unlike the conventional description in terms of parton distribution functions, the former describes directly the Q dependence of the measured structure functions. It is therefore physical insensitive to factorization scheme and scale ambiguities. It therefore provides a more stringent test of DGLAP evolution and eases the manifestation of (non-linear) small x effects. It however requires a precise measurement of both structure functions F 2 and F L , which will be only possible at future facilities, such as an Electron Ion Collider. In the second part we present a recent analysis of the small x region of the combined HERA data on the structure function F 2 . We demonstrate that (linear) next-to-leading order BFKL evolution describes the effective Pomeron intercept, determined from the combined HERA data, once a resummation of collinear enhanced terms is included and the renormalization scale is fixed using the BLM optimal scale setting procedure. We also provide a detailed description of the Q and x dependence of the full structure functions F 2 in the small x region, as measured at HERA. As a result, predictions for the structure function F L are found to be in agreement with the existing HERA data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Design and Testing of a Scaled Demonstrator Turbine at the National Wind Technology Center: Preprint

This paper discusses the design, manufacturing, and planned testing of a scaled demonstrator turbine as part of the Segmented Ultralight Morphing Rotor (SUMR) project funded by the Advanced Project Research Agency - Energy (ARPA-E). The scaled demonstrator (SUMR-D) is based off of a downwind, 13.2 MW SUMR design. This scaled rotor will be tested on the CART2 turbine at the National Wind Technology Center to verify the scaling methodology and planned control scheme. The design was done in an iterative fashion among six teams focused on aerodynamics, structures, and controls. This process included extensive load analysis, modification for manufacturability, adaptations required for testing on the CART2, and ground proof loading. The details of this process are presented here, concluding with planned testing and expectations of performance.

17 WIND ENERGY↗
DOE OSTI2016

Creating a Tiny Human Body on a Chip

LLNL science communicator Maren Hunsberger takes us "Inside the Lab" to learn about the iChip (In-vitro Chip-based Human Investigational Platform) project at Lawrence Livermore National Laboratory. "One application of the iChip system would be to develop new pharmaceutical drugs," explains Dave Soscia, LLNL postdoc. "When you test in a mouse for example, it's not as close to the human system as you can get. If we can take human cells and put them on devices and actually mimic the structure and function of the organ systems in the human, we can actually replace animal testing and even make a better system for testing pharmaceutical drugs."

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

A RADIAL VELOCITY TEST FOR SUPERMASSIVE BLACK HOLE BINARIES AS AN EXPLANATION FOR BROAD, DOUBLE-PEAKED EMISSION LINES IN ACTIVE GALACTIC NUCLEI

One of the proposed explanations for the broad, double-peaked Balmer emission lines observed in the spectra of some active galactic nuclei (AGNs) is that they are associated with sub-parsec supermassive black hole (SMBH) binaries. Here, we test the binary broad-line region hypothesis through several decades of monitoring of the velocity structure of double-peaked Hα emission lines in 13 low-redshift, mostly radio-loud AGNs. This is a much larger set of objects compared to an earlier test by Eracleous et al. and we use much longer time series for the three objects studied in that paper. Although systematic changes in radial velocity can be traced in many of their lines, they are demonstrably not like those of a spectroscopic binary in a circular orbit. Any spectroscopic binary period must therefore be much longer than the span of the monitoring (assuming a circular orbit), which in turn would require black hole masses that exceed by 1–2 orders of magnitude the values obtained for these objects using techniques such as reverberation mapping and stellar velocity dispersion. Moreover, the response of the double-peaked Balmer line profiles to fluctuations of the ionizing continuum and the shape of the Lyα profiles are incompatible with an SMBH binary. The binary broad-line region hypothesis is therefore disfavored. Other processes evidently shape these line profiles and cause the long-term velocity variations of the double peaks.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Computational Assessment of Hydrodynamic Loads on Rockeries for River Bank Protection

Colorado experienced an extreme flooding event in September of 2013 that ravaged canyon roadways southeast of Estes Park, CO. Central Federal Lands was asked to rebuild SH 34 and CO 43 after the floods. To minimize river encroachments in narrow canyons, roadway fill embankments must be over steepened. Using a rockery to stabilize the roadway embankment rather than traditional vertical, concrete structures was the solution. However, no analytical techniques were available for evaluating the hydraulic stability of such structures. Argonne National Laboratory was employed to estimate the hydrodynamic forces by using advanced, computational fluid dynamics (CFD). An investigation was conducted on a section of a model rockery comprised of large boulders exposed to a variety of hydraulic flow conditions. A repeatable geometric section of a typical rockery structure was modeled and used to create boundaries for the CFD model. The test case matrix covers computer simulations of various rockery and channel geometries. The geometrical parameters taken into account are: rockery height, outside face batter angle of the rockery, rockery base width, river bed width, and the hydraulic parameters are: flow depth, flow velocity, and hydraulic angle of attack. Two failure mechanisms of rockery structures, sliding and overturning, are considered. The existing design equations for both modes are modified by addition of hydrodynamic force terms. The new terms were calculated for a parametric set of geometry and condition variation using the CFD model. Moreover, formulas for dimensionless hydraulic force coefficients are proposed that can be used in the design of new rockeries or in evaluation of existing dry-stack rockeries in river environments.

42 ENGINEERING↗
DOE OSTI2025

Toward Standardized Microscale Tensile Testing for Two‐Photon Polymerization‐Fabricated Materials in Liquid

Two-photon polymerization (TPP) enables the fabrication of intricate 3D microstructures with submicron precision, offering significant potential in biomedical applications like tissue engineering. In such applications, to print materials and structures with defined mechanics, it is crucial to understand how TPP printing parameters impact the material properties in a physiologically relevant liquid environment. Herein, an experimental approach utilizing microscale tensile testing (μTT) for the systematic measurement of TPP-fabricated microfibers submerged in liquid as a function of printing parameters is introduced. Using a diurethane dimethacrylate-based resin, the influence of printing parameters on microfiber geometry is first explored, demonstrating cross-sectional areas ranging from 1 to 36 μm 2 . Tensile testing reveals Young's moduli between 0.5 and 1.5 GPa and yield strengths from 10 to 60 MPa. The experimental data show an excellent fit with the Ogden hyperelastic polymer model, which enables a detailed analysis of how variations in writing speed, laser power, and printing path influence the mechanical properties of TPP microfibers. The μTT method is also showcased for evaluating multiple commercial resins and for performing cyclic loading experiments. Collectively, this study builds a foundation toward a standardized microscale tensile testing framework to characterize the mechanical properties of TPP printed structures.

mechanical characterization↗
DOE OSTI2017

Tracking Internal Temperature and Structural Dynamics during Nail Penetration of Lithium-Ion Cells

Mechanical abuse of lithium-ion batteries is widely used during testing to induce thermal runaway, characterize associated risks, and expose cell and module vulnerabilities. But, the repeatability of puncture or 'nail penetration' tests is a key issue as there is often a high degree of variability in the resulting thermal runaway process. Here, the failure mechanisms of 18650 cells punctured at different locations and orientations are characterized with respect to their internal structural degradation, and both their internal and surface temperature, all of which are monitored in real time. The initiation and propagation of thermal runaway is visualized via high-speed synchrotron X-ray radiography at 2000 frames per second, and the surface and internal temperatures are recorded via infrared imaging and a thermocouple embedded in the tip of the penetrating nail, respectively. The influence of the nail, as well as how and where it penetrates the cell, on the initiation and propagation of thermal runaway is described and the suitability of this test method for representing in-field failures is discussed.

25 ENERGY STORAGE↗
DOE OSTI2019

New interaction potentials for alkali and alkaline-earth aluminosilicate glasses

Here, we apply a recently developed optimization scheme to obtain effective potentials for alkali and alkaline-earth aluminosilicate glasses that contain lithium, sodium, potassium, or calcium as modifiers. As input data for the optimization, we used the radial distribution functions of the liquid at high temperature generated by means of ab initio molecular dynamics simulations and density and elastic modulus of glass at room temperature from experiments. The new interaction potentials are able to reproduce reliably the structure and various mechanical and vibrational properties over a wide range of compositions for binary silicates. Previously, we tested these potentials for various ternary systems and find that they are transferable and can be mixed, thus allowing us to reproduce and predict the structure and properties of multicomponent glasses.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Neutron and Ion Irradiation Studies on Advanced Steels Using the Nuclear Science User Facilities

For nuclear reactor structural materials, irradiation is capable of inducing a series of microstructural modifications, such as dislocation loops/network, selective elemental segregation and precipitation, voids and helium bubbles, leading to the degradation in structural materials' performance through irradiation hardening and embrittlement, swelling, irradiation creep, etc. Since radiation poses challenges for structural applications in nuclear reactors in multiple aspects and the underlying mechanisms are often interconnected, radiation effect studies need well-designed test matrix and proper characterization techniques. The Nuclear Science User Facilities (NSUF) offer extensive capabilities for studying radiation effects in nuclear fuels and structural materials. This research covers both neutron and ion irradiation studies carried out using a variety of instruments through the NSUF. The neutron irradiation ferritic ODS steel MA957 was accomplished utilizing the neutron irradiation capability of the Advanced Test Reactor (ATR) and the post-irradiation examination (PIE) capabilities of the Center for Advanced Energy Studies (CAES). The neutron-irradiated specimens were characterized using transmission electron microscopy (TEM) and atom probe tomography (APT). The in situ TEM ion irradiation study on austenitic stainless steel (SS) 316H was completed using the IVEM-Tandem facility at Argonne National Laboratory.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Electroless nickel – phosphorus coating on crab shell particles and its characterization

Being hydrophilic material, crab shell particles have only a limited number of applications. It is, therefore, necessary to modify the surface of the crab shell particles. To make them useful ever for the applications, the main theme we proposed in this article is to utilize crab shell particles (CSP) with the core coated with nickel phosphorus (NiP) as a shell using the electroless coating process. For dealing with serious environmental problems, utilization of waste bio-shells is always an important factor to be considered. Chelating ability of crab shell particles eliminates the surface activation in this work proceeding to the coating process. The functional group, phase structure, microstructure, chemical composition and thermal analysis of CSP and NiP/CSP were characterized using Fourier transform infra-red spectroscopy (FTIR), x-ray diffraction analyzer (XRD), scanning electron microscope (SEM), energy-dispersive x-ray spectroscopy (EDS), and thermogravimetric analysis (TGA). The combination of an amorphous and crystalline structure was exhibited by CSP and NiP/CSP. NiP/CSP has shown a better thermal stability when compared to uncoated CSP. Stability test, adsorption test, and conductivity test were conducted for the study of adsorption behavior and conductivity of the particles. CSP presented a hydrophilic property in contrast to hydrophobic NiP/CSP. NiP/CSP presented a conductivity of about 44% greater compared to the CSP without any fluctuations. - Highlights: • Utilization of crab shell waste is focused on. • NiP coating on crab shell particle is fabricated using electroless process. • Thermal analysis, stability test, adsorption test and conductivity test were done. • Organic matrix of crab shell particle favors the coating process. • Results demonstrate the characterization of CSP core – NiP shell structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Achievements and Prospects of Global Broadband Seismographic Networks After 30 Years of Continuous Geophysical Observations

Global seismographic networks (GSNs) emerged during the late nineteenth and early twentieth centuries, facilitated by seminal international developments in theory, technology, instrumentation, and data exchange. The mid- to late-twentieth century saw the creation of the World-Wide Standardized Seismographic Network (1961) and International Deployment of Accelerometers (1976), which advanced global geographic coverage as seismometer bandwidth increased greatly allowing for the recording of the Earth's principal seismic spectrum. The modern era of global observations and rapid data access began during the 1980s, and notably included the inception of the GEOSCOPE initiative (1982) and GSN (1988). Through continual improvements, GEOSCOPE and the GSN have realized near-real time recording of ground motion with state-of-art data quality, dynamic range, and timing precision to encompass 180 seismic stations, many in very remote locations. Data from GSNs are increasingly integrated with other geophysical data (e.g., space geodesy, infrasound and Interferometric Synthetic Aperture Radar). Globally distributed seismic data are critical to resolving crust, mantle, and core structure; illuminating features of the plate tectonic and mantle convection system; rapid characterization of earthquakes; identification of potential tsunamis; global nuclear test verification; and provide sensitive proxies for environmental changes. As the global geosciences community continues to advance our understanding of Earth structure and processes controlling elastic wave propagation, GSN infrastructure offers a springboard to realize increasingly multi-instrument geophysical observatories. Here, we review the historical, scientific, and monitoring heritage of GSNs, summarize key discoveries, and discuss future associated opportunities for Earth Science.

58 GEOSCIENCES↗
DOE OSTI2018

Absence of Local Fluctuating Dimers in Superconducting Ir 1-x (Pt,Rh) x Te 2

The compound IrTe2 is known to exhibit a transition to a modulated state featuring Ir-Ir dimers, with large associated atomic displacements. Partial substitution of Pt or Rh for Ir destabilizes the modulated structure and induces superconductivity. It has been proposed that quantum critical dimer fluctuations might be associated with the superconductivity. Here we test for such local dimer correlations and demonstrate their absence. X-ray pair distribution function approach reveals that the local structure of Ir 0.95 Pt 0.05 Te 2 and Ir 0.8 Rh 0.2 Te 2 dichalcogenide superconductors with compositions just past the dimer/superconductor boundary is explained well by a dimer-free model down to 10 K, ruling out the possibility of there being nanoscale dimer fluctuations in this regime. This is inconsistent with the proposed quantum-critical-point-like interplay of the dimer state and superconductivity, and precludes scenarios for dimer fluctuations mediated superconducting pairing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

2023 SRNL Aging and Lifetimes Report: Tritium Aging of Welded and Additively Manufactured Austenitic Stainless Steels

This report documents work performed in fiscal year 2023 at Savannah River National Laboratory (SRNL) collaborating with Sandia National Laboratories in support of the Aging and Lifetimes program. This work supports Gas Transfer Systems (GTS) design by measuring the mechanical behavior of structural materials used in GTS. Data on properties in relevant conditions are crucial for GTS lifetime assessments and predictions. To simulate relevant conditions, SRNL, in concert with the Savannah River Site, thermally pre-charges test specimens with tritium and stores them at -80°C to allow the tritium decay product, helium-3, to build up while limiting tritium diffusion. According to test plans based on how much helium-3 has accumulated, specimens are removed from storage and tested. Results from mechanical testing provide an empirical basis for GTS design as well as insight to how these structural materials degrade in a tritium environment.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2016

Monitoring of Double-Stud Wall Moisture Conditions in the Northeast

BSC TO5 Task 2.2 Monitoring of Double Stud Wall Moisture Conditions in the Northeast Field test data available for wood moisture contents, temperature, and relative humidity. STRUCTURE - House - Devens, MA 01432 Three double-stud assemblies were compared: 12-in. ocSPF, 12-in. cellulose, and 5.5-in. ocSPF at the exterior of a double-stud wall (to approximate conventional 2 x 6 wall construction and insulation levels, acting as a control wall). These assemblies were repeated on the north and south orientations, for a total of six assemblies. Data were collected from December 2011 through July 2014, capturing three winters of operation in various states. Winter 2011-2012 was very mild (warm) and the house had very low interior relative humidity (RH) because it was unoccupied. Winter 2012-2013 was colder and the house had very high (40%-50%) interior RH until the ventilation system was put into operation (mid-February 2013). Winter 2013-2014 was very cold, but the ventilation system was operated, resulting in moderate interior RHs. Under "normal" interior conditions (functioning ventilation system, wintertime RH 10%-30%), ocSPF walls (both 12 in. and 5.5 in.) with latex paint as interior vapor control (nominally Class III, but possibly more vapor open) showed low risk; all sheathing moisture contents (MCs) remained lower than 20%. However, the 12-in. cellulose wall had MCs higher than 20% on the north side. In addition, the cellulose wall sheathing-insulation interface had high RH conditions. Under high interior humidity loading (nonfunctional ventilation system, 40%-50% interior RH), all test walls showed MCs and sheathing-insulation interface RHs well into the high risk range. The cellulose walls showed particularly high MCs (sheathing in excess of 30%), while the ocSPF walls showed MCs in the 18%-25% range. In addition, the monitoring showed evidence of liquid water condensation (which can result in quick degradation) in all walls; the condensation was substantial in the cellulose walls. These condensation issues occurred on the north and south sides. But in all walls, during each summer after a winter of wetting, moisture levels fell well into the safe range. Based on the difference between the winters, it is clear that interior RH can have a tremendous effect on the performance of enclosure systems, in terms of interstitial condensation risks, when using more vapor-open interior finishes such as latex paint. The ocSPF walls showed consistently lower MCs and interface RH levels than the cellulose walls. Although air leakage cannot be eliminated as a possibility, it is likely that at the thicknesses applied, the ocSPF provided reasonable vapor control (1.5-3.5 perms when combined with Class III latex paint) under normal loading conditions. The collected data were analyzed in terms of ASHRAE Standard 160 criteria (tabulating hours with RH and temperatures that support mold growth), using the calculated surface RH at the sheathing-insulation interface. All north-facing walls failed through all three winters; in particular, there were large numbers of failure hours during the high humidity winter (2012-2013). Sheathing-insulation interface temperatures and RHs during the high humidity winter showed many hours with mold risk conditions (high humidity and sufficient temperature for mold growth).

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