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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Probing the Surface Structure of Semiconductor Nanoparticles by DNP SENS with Dielectric Support Materials

Surface characterization is crucial for understanding how the atomic-level structure affects the chemical and photophysical properties of semiconducting nanoparticles (NPs). Solid-state nuclear magnetic resonance spectroscopy (NMR) is potentially a powerful technique for the characterization of the surface of NPs, but it is hindered by poor sensitivity. Dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) has previously been demonstrated to enhance the sensitivity of surface-selective solid-state NMR experiments by 1–2 orders of magnitude. Established sample preparations for DNP SENS experiments on NPs require the dilution of the NPs on mesoporous silica. Using hexagonal boron nitride ($h$-BN) to disperse the NPs doubles DNP enhancements and absolute sensitivity in comparison to standard protocols with mesoporous silica. Alternatively, precipitating the NPs as powders, mixing them with $h$-BN, and then impregnating the powdered mixture with radical solution leads to further 4-fold sensitivity enhancements by increasing the concentration of NPs in the final sample. This modified procedure provides a factor of 9 improvement in NMR sensitivity in comparison to previously established DNP SENS procedures, enabling challenging homonuclear and heteronuclear 2D NMR experiments on CdS, Si, and Cd 3 P 2 NPs. These experiments allow NMR signals from the surface, subsurface, and core sites to be observed and assigned. For example, we demonstrate the acquisition of DNP-enhanced 2D 113 Cd– 113 Cd correlation NMR experiments on CdS NPs and natural isotropic abundance 2D 13 C– 29 Si HETCOR of functionalized Si NPs. These experiments provide a critical understanding of NP surface structures.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Using Multiple Geophysical Methods to Refine a Stratigraphic Conceptual Site Model at a Nuclear Waste Site

At contaminated sites, there is a critical reliance on conceptual site models of which a key component is the geologic framework model (GFM), which is used to build predictive fate and transport modeling in support of remediation goals. Here, we detail an ongoing study at a nuclear waste site (Hanford Site, Washington, USA) where surface geophysical methods were used to complement existing borehole information and to help site new boreholes to update and refine the GFM. Ground-based electrical resistivity tomography (ERT), time-domain electromagnetics (TEM), and seismic data was acquired on the Hanford Site’s Central Plateau, where the presence of a hydraulically transmissive subsurface feature, or paleochannel, was suspected but uncertain based on contaminant concentrations at sparsely located boreholes. To assess and compare ERT, TEM, and seismic geophysical datasets, co-located data was acquired in an area where the existing GFM was more certain. Surrounding the suspected paleochannel, ERT and seismic refraction tomography showed similar subsurface structures consistent with a channelized feature. While TEM interpretation was limited in the suspected paleochannel area due to a thick resistive top layer and high electromagnetic noise, TEM showed greater utility in a different area where these factors were less prevalent. Based on the results of quasi-3D ERT inversions, we propose updates to the GFM, including identifying a paleochannel. Further, we evaluate the utility of geophysical methods and examine lessons learned that will be used as a basis for continued characterization efforts to support site management decisions and implementation efforts.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Effect of Formation Heterogeneity on CO 2 Dissolution in Subsurface Porous Media

Dissolution trapping is one of the most dominant mechanisms for the secure storage of CO 2 injected in porous subsurface formations saturated with brine. This trapping mechanism is enhanced by convective mixing, which occurs due to the gravitational instability between the different fluid layers in the aquifer. The reservoir permeability also plays a crucial role in the dissolution rate and overall fluid flow dynamics during the density-driven convection in porous media. Herein this study investigates the role of complex heterogeneity, i.e., irregular permeability distribution in CO 2 dissolution, using a novel experimental approach to create medium permeability heterogeneity in Hele–Shaw cells. Complex subsurface transport phenomena such as a preferential dissolution path, CO 2 sweep efficiency, changes in finger morphology, and CO 2 concentration distribution are visualized by creating heterogeneous media. Experimental results showed that reservoir permeability heterogeneity causes significant channeling effects and poor sweep efficiency. A scaling relationship between average finger growth rate (Gr) and permeability (k) was obtained as Gr [m s –1 ] = 266.8k [m 2 ] + 1.20 × 10 –6 . Furthermore, the mass of CO 2 dissolved is calculated using the spectrophotometric method to characterize the convective instability. The convective flux was analyzed by comparing the experimental dissolution flux with the theoretical diffusion flux, calculating a maximum Sherwood number of 6.8. The study’s findings improve the current understanding of the CO 2 convection morphology in heterogeneous media, allowing better assessment of long-term CO 2 storage.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

Europa Surface Radiation Environment for Lander Assessment

The Jovian magnetospheric particle environment at Europa's surface is critical to assessment of landed astrobiological experiments in three respects: (1) the landing site must be chosen for the best prospects for detectable organic or inorganic signs of Life, e.g. regions of freshly emergent flows from the subsurface; (2) lander systems must reach the surface through the Jovian magnetospheric environment and operate long enough on the surface to return useful data; (3) lander instrumentation must be capable of detecting signs of life in the context of the local environmental radiation and associated chemistry. The Galileo, Voyager, and Pioneer missions have provided a wealth of data on energetic particle intensities throughout the Jovian magnetosphere including from many flybys of Europa. cumulative radiation dosages for spacecraft enroute to Europa can be well characterized, but knowledge of the surface radiation environment is very limited. Energetic electrons should primarily impact the trailing hemisphere with decreasing intensity towards the center of the leading hemisphere and are the most significant radiation component down to meter depths in the surface regolith due to secondary interactions. Observed surface distribution for sulfates is suggestive of electron irradiation but may have alternative interpretations. Having much-larger magnetic gyroradii than electrons, energetic protons and heavier ions irradiate more of the global surface. The particular orientations of electron, proton, and ion gyromotion would project into corresponding directional (e.g., east-west) anisotropies of particle flu into the surface. Particular topographic features at the landing site may therefore offer shielding from part of the incident radiation.

Cooper, John F.↗
DOE OSTI2019

Characterization of Oxygenaceous Species Formed by Exposure of Ag(111) to Atomic Oxygen

The uptake and chemical speciation of oxygen in and on Ag(111) surface is described herein. An Ag(111) surface was exposed to gas-phase oxygen atoms under ultrahigh vacuum compatible conditions at various surface temperatures. The O uptake was quantified using temperature-programmed desorption measurements and showed that oxygen exposures at temperatures above 500 K yielded only surface-adsorbed oxygen in a single surface reconstruction. At temperatures below 500 K, O uptake continued past O surface saturation, and a maximum in the uptake with respect to exposure temperature was observed at 450 K. A model where O atoms must diffuse out of subsurface absorption sites to free room for further O describes this observation. The chemical speciation of the oxygenaceous species formed under these conditions was achieved using X-ray photoelectron spectroscopy. These data show that a single O species initially formed on the surface, but at higher coverages, a new, three-dimensional oxygenaceous phase developed. Because of the importance of silver in heterogeneously catalyzed partial oxidation reactions, these results show that oxygen species embedded below the surface plane must be incorporated into accurate models of Ag-surface catalyzed reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2003

An Automated, Low Mass, Low Power Drill for Acquiring Subsurface Samples of Ground Ice for Astrobiology Studies on Earth and on Mars

As a project that is part of NASA s Astrobiology Technology & Instrument Development Program (ASTID), we are developing a low mass (approx.20kg) drill that will be operated without drilling fluids and at very low power levels (approx.60 watts electrical) to access and retrieve samples from permafrost regions of Earth and Mars. The drill, designed and built as a joint effort by NASA JSC and Baker-Hughes International, takes the form of a down-hole unit attached to a cable so that it can, in principle, be scaled easily to reach significant depths. A parallel laboratory effort is being carried out at UC Berkeley to characterize the physics of dry drilling under martian conditions of pressure, temperature and atmospheric composition. Data from the UCB and JSC laboratory experiments are being used as input to a drill simulation program which is under development to provide autonomous control of the drill. The first Arctic field test of the unit is planned for May 2004. A field expedition to Eureka on Ellesmere Island in Spring 2003 provided an introduction for several team members to the practical aspects of drilling under Arctic conditions. The field effort was organized by Wayne Pollard of McGill University and Christopher McKay of NASA ARC. A conventional science drill provided by New Zealand colleagues was used to recover ground ice cores for analysis of their microbial content and also to develop techniques using tracers to track the depth of penetration of contamination from the core surface into the interior of the samples.

Briggs, G. A.↗
DOE OSTI2019

Support for Next-Generation Ecosystem Experiments (NGEE Arctic) Field Campaign Report

An important challenge for Earth System Models (ESMs) is to represent land surface and subsurface processes and their complex interactions in a warming climate. This is especially important for arctic ecosystems where permafrost extent, topography, hydrology, vegetation, disturbance, and biogeochemistry are inextricably linked. The implications of such linkages include permafrost thaw and deepening of the active layer, microbial decomposition of vulnerable soil organic matter, altered productivity and migration of tall woody shrubs, and watershed-scale changes in surface and groundwater transport and storage. Although ESMs describe some of these interactions for high-latitude ecosystems, their representation requires extensive confrontation with field and laboratory observations to test and improve models, and to use those models to inspire new observations and experiments. The Next-Generation Ecosystem Experiments (NGEE Arctic) is a 10-year project (2012 to 2022) to improve our predictive understanding of carbon-rich arctic system processes and feedbacks to climate. This is achieved through experiments, observations, and synthesis of existing data sets that strategically inform model process representation and parameterization, and that enhance the knowledge base required for model initialization, calibration, and evaluation. One question of special interest to the NGEE Arctic project addresses how above- and below-ground plant functional traits might change across environmental gradients, and what are the consequences for arctic ecosystem C, water, and nutrient fluxes? Arctic plant traits, and their variation in response to changing environmental conditions, will play a key role in the response of tundra ecosystems to warming, permafrost thaw, and the wetter or drier conditions expected in the future. The appropriate representation of these functional traits in models is necessary to accurately represent ecosystem C, water, and nutrient cycling in tundra ecosystems, now and in the future. We characterized the variation in above- and below-ground plant traits in response to varying edaphic and environmental conditions in Utqiaġvik (formerly Barrow), Alaska. These new data, combined with remote-sensing and synthesis activities across the Arctic and the globe, have been used to inform model structure and parameterization of key processes such as photosynthesis, nutrient dynamics, and trait variation across the landscape.

North Slope of Alaska, arctic processes (meteorolo↗
DOE OSTI2022

Development of coated heat flux gauges for fast responding measurements

Thermal systems often exhibit transient behaviors that have important implications for the operation of the system and can be difficult to predict. For these reasons, experimental testing is often required to ensure system durability requirements are achieved. One important parameter governing the survivability of components in hot, high-stress environments is the heat flux into the part that dictates the temperature distribution for the component. However, sensors required to experimentally characterize heat fluxes in extreme environments must also be resilient. Here, this study presents the development of coated heat transfer gauges capable of robust, high-frequency measurements in turbine research facilities. The addition of a protective coating increases the durability of the gauge, but inherent of that coating is the attenuation of high-frequency temperature penetrations. As a result, this study first outlines the use of analytical solutions to define a gauge design for a specific frequency range and heat transfer, ensuring that subsurface signals can be rectified to surface conditions through inverse methods. Then, the fabrication of polyimide substrate sensors with a parylene-F coating is described. Micro surface heaters added to the custom sensors were used to determine important geometric and thermal properties necessary to calculate accurate surface heat flux. Ultimately, this work shows increased sensor robustness in a turbine test bed and experimentally validates that the frequency response of the fabricated sensors meet the design intent.

47 OTHER INSTRUMENTATION↗
DOE OSTI2013

Field Test Design Simulations of Pore-Water Extraction for the SX Tank Farm

A proof of principle test of pore water extraction is being performed by Washington River Protection Solutions for the U.S. Department of Energy, Office of River Protection. This test is being conducted to meet the requirements of Hanford Federal Facility Agreement and Consent Order (HFFACO) (Ecology et al. 1989) Milestone M 045-20, and is described in RPP-PLAN-53808, 200 West Area Tank Farms Interim Measures Investigation Work Plan. To support design of this test, numerical simulations were conducted to help define equipment and operational parameters. The modeling effort builds from information collected in laboratory studies and from field characterization information collected at the test site near the Hanford Site 241-SX Tank Farm. Numerical simulations were used to evaluate pore-water extraction performance as a function of the test site properties and for the type of extraction well configuration that can be constructed using the direct-push installation technique. Output of simulations included rates of water and soil-gas production as a function of operational conditions for use in supporting field equipment design. The simulations also investigated the impact of subsurface heterogeneities in sediment properties and moisture distribution on pore-water extraction performance. Phenomena near the extraction well were also investigated because of their importance for pore-water extraction performance.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Processing and Characterization of Fe-Mn-Cu-Sn-C Alloys Prepared by Ball Milling and Spark Plasma Sintering

In this work, Fe-Mn-Cu-Sn-C alloys were prepared by means of powder metallurgy (PM). Powder mixtures were ball-milled for 8, 30 and 120 h and densified to < 1% porosity using spark plasma sintering (SPS) at 900 °C and 35 MPa. After consolidation, all samples of the Fe alloys were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), hardness and flexural strength tests. Resistance to abrasive wear was evaluated in both three-body abrasion and two-body abrasion tests. The SEM observations revealed an evident dependence of grain size and microstructural homogeneity on milling time. The XRD analysis showed a marked increase in austenite content in the as-sintered specimens with milling time. Although the proportion of deformation-induced martensite was small, the strengthening effect of abrasion on the subsurface layer of the investigated alloys was clearly indicated by Knoop hardness measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A method to generate small-scale, high-resolution sedimentary bedform architecture models representing realistic geologic facies

Small-scale (mm to m) sedimentary structures (e.g. ripple lamination, cross-bedding) have received a great deal of attention in sedimentary geology. The influence of depositional heterogeneity on subsurface fluid flow is now widely recognized, but incorporating these features in physically-rational bedform models at various scales remains problematic. The current investigation expands the capability of an existing set of open-source codes, allowing generation of high-resolution 3D bedform architecture models. The implemented modifications enable the generation of 3D digital models consisting of laminae and matrix (binary field) with characteristic depositional architecture. The binary model is then populated with petrophysical properties using a textural approach for additional analysis such as statistical characterization, property upscaling, and single and multiphase fluid flow simulation. One example binary model with corresponding threshold capillary pressure field and the scripts used to generate them are provided, but the approach can be used to generate dozens of previously documented common facies models and a variety of property assignments. An application using the example model is presented simulating buoyant fluid (CO 2 ) migration and resulting saturation distribution.

58 GEOSCIENCES↗
NASA NTRS2004

On the Dielectric Properties of the Martian-like Surface Sediments

We have undertaken laboratory electromagnetic characterization of the total set of minerals identified by TES on the Martian surface in order to investigate experimentally the dielectric properties of the sediments covering it in the frequency range from 1 to 30 MHz. Volcanic Rocks with a well defined mineralogy and petrology from potential terrestrial analogues sites have also been included in the study. Our primary objective is to evaluate the range of electrical and magnetic losses that may be encountered by the various Radar sounding and imaging experiments dedicated to map the Martian subsurface searching for underground water. The electromagnetic properties of these Mars-like materials will be presented as a function of various geophysical parameters, such as porosity, bulk density and temperature. The secondary objective, is to locate regions were surface dielectric conditions are suitable for subsurface sounding.

Heggy, E.↗
DOE OSTI2018

Exploiting Knowledge of Technetium in the Subsurface to Develop Remediation Strategies – 18223

Technetium-99 (Tc) contamination remains a major environmental problem at legacy nuclear reprocessing sites, such as the Hanford Site in south-central Washington state, where the total inventory of released Tc is estimated at 700 Ci. The environmental risk associated with Tc is due to its long half-life (213,000 years) and the high mobility of the oxidized anionic pertechnetate species (Tc(VII)O4-). Thus, there is a critical need to resolve scientific and technical issues underpinning the ability to safely, cost-effectively, and efficiently remediate Tc-contaminated vadose zone sediments and groundwater. Developing enhanced attenuation strategies for released Tc that reduce contaminant migration, while mitigating risk to human health and the environment, requires characterization of any retardation processes and mass flux. The current conceptual model for Tc transport in the vadose zone assumes that Tc is predominantly present in its oxidized form as TcO4-, which is highly soluble and mobile. However, under certain conditions, Tc can become entrained in solid phases. Characterization of Tc-containing mineral phases from sediment cores extracted from various Hanford waste disposal sites were analyzed to determine Tc present in vadose zone sediments as (i) TcO4- that remains in water films associated with fine-grained sediments; (ii) Tc co-precipitated with other lanthanides in phosphate mineral phases; and (iii) Tc present as TcO2•nH2O in localized reducing zones. These results will be used to develop improved long-term Tc remediation strategies that are most likely to succeed during field application, through stimulation of conditions that enhance Tc attenuation.

Pearce, Carolyn I.↗
DOE OSTI2021

Utilizing distributed acoustic sensing and ocean bottom fiber optic cables for submarine structural characterization

The sparsity of permanent seismic instrumentation in marine environments often limits the availability of subsea information on geohazards, including active fault systems, in both time and space. One sensing resource that provides observational access to the seafloor environment are existing networks of ocean bottom fiber optic cables; these cables, coupled to modern distributed acoustic sensing (DAS) systems, can provide dense arrays of broadband seismic observations capable of recording both seismic events and the ambient noise wavefield. Here, we report a marine DAS application which demonstrates the strength and limitation of this new technique on submarine structural characterization. Based on ambient noise DAS records on a 20 km section of a fiber optic cable offshore of Moss Landing, CA, in Monterey Bay, we extract Scholte waves from DAS ambient noise records using interferometry techniques and invert the resulting multimodal dispersion curves to recover a high resolution 2D shear-wave velocity image of the near seafloor sediments. We show for the first time that the migration of coherently scattered Scholte waves observed on DAS records can provide an approach for resolving sharp lateral contrasts in subsurface properties, particularly shallow faults and depositional features near the seafloor. Our results provide improved constraints on shallow submarine features in Monterey Bay, including fault zones and paleo-channel deposits, thus highlighting one of many possible geophysical uses of the marine cable network.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Simulations of Water Flow in Relation to a Steady Criticality in an Unsaturated Alluvial Repository

Oak Ridge National Laboratory (ORNL) is examining the conditions under which a criticality event could be ruled out for large packages placed in an unsaturated alluvial repository. This work specifically examines the water level in a stylized waste package that is assumed (1) to fail on the top, and (2) to empty as water is driven away—not by boiling—but by fluid flow phenomena driven by thermal gradients. This analysis uses the PFLOTRAN code package. Specifically, this year’s work includes examination of the heat rate at which water is driven away for various percolation rates using the same assumptions listed in the 2022 annual report. The STANDARDS (formerly UNF-ST&DARDS) package has predicted dual-purpose canister (DPC) neutron multiplication factors (k-effectives) ranging above 1.1 (unitless) with failed components. The DPC designs were not created with the intent to use for disposal purposes. Emplacing such packages may be worth consideration if it can be shown that criticality is either extremely unlikely or of very low consequence to the repository’s safety case. This work aims to help establish hydrologic boundary conditions for a highly hypothetical, highly stylized subsurface criticality event. The approach to critical is assumed to be slow, producing steady heating rates under a few kilowatts. For a DPC containing capillary media, the simulated power required for dry-out was proportional to the percolation rate but was unaffected by the size of a large breech on top of the DPC. Results for single cases with no capillary media in the DPC suggest that higher infiltration rates may be required in those cases to cause flooding. Bounding mechanisms and assumptions must be identified and characterized further by performing additional perturbations to various input parameters to demonstrate robustness of the results. This might be accomplished by examining responses to power pulses to determine the system transfer function required to enable a reduced order feedback model.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Remediation Technologies Screening Report for the Deep Vadose Zone, Hanford's Central Plateau - 12414

Deep Vadose Zone contamination is a significant issue because it represents a potential source for continued release of contamination to the groundwater and associated receptors. This contamination, which is the result of past waste disposal practices on the Hanford Site Central Plateau, occurs deep in the subsurface and is not easily remediated by typical surface remedies. The Deep Vadose Zone is defined as the sediment below the limit of typical surface-based remedies (such as, excavation or caps), but above the water table. The Central Plateau Deep Vadose Zone begins at a depth of approximately 15 m (50 ft) below ground surface and extends to a depth of approximately 76 m (250 ft) below ground surface. Cleanup of the Deep Vadose Zone is challenging because contamination is difficult to access and expensive to characterize; contaminants occur at different depths and soil types; conventional, surface-based remedies have limited effectiveness; and remedy performance is difficult to predict, test, and monitor. Typically, remedial technologies for Deep Vadose Zone contamination are less developed than for the shallow soil contamination or saturated groundwater contaminants. In addition, few remediation technologies have been tested in the field, and fewer still have been successfully implemented as full remedial actions. These challenges, along with the limited number of potentially applicable remediation technologies, complicate the decision-making process for evaluating and selecting Deep Vadose Zone remedial alternatives. The Deep Vadose Zone remediation technologies pre-screening involved a comprehensive review of potentially applicable technologies for remediating Deep Vadose Zone contamination in the Hanford Site's Central Plateau. The list of remediation technologies was developed from previous Hanford Site studies, science and technology databases, as well as other cleanup projects across the country that have similar conditions. The list of remediation technologies was shared with the public and stakeholders to provide an opportunity to identify additional technologies. From these efforts, 59 technologies that may support future remediation of the Deep Vadose Zone were identified. The initial list of 59 potential technologies were then screened in order to identify viable or potentially viable technologies whose implementation would benefit from further investigation and evaluation during the remedial investigation/feasibility study activities. This approach eliminated five technologies from further consideration because they either would not be ready to support remediation within the next 3 to 5 years or were not applicable for Deep Vadose Zone remediation. Eleven (11) technologies were identified as viable, requiring no further testing or investigation during the RCRA Facility Investigation/Remedial Investigation activities. The remaining 43 potentially applicable technologies were identified as requiring additional testing or investigation to determine whether they should be considered further in the selection of a remedial alternative for the 200-DV-1 Operable Unit. The results of this pre-screening effort will be used to plan and scope the appropriate field investigation, treatability study, and feasibility study tasks during development of the 200-DV-1 Operable Unit Work Plan. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗