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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Molybdenum-99 from Molten Salt Reactor as a Source of Technetium-99m for Nuclear Medicine: Past, Current, and Future of Molybdenum-99

Technitium-99m ( 99m Tc), a widely used radioisotope, is used in tens of millions of medical diagnostic procedures annually. However, it is hard to store and must be immediately used upon production due to its short half-life (i.e., 6 h); thus, it is currently produced from 99 Mo, which itself is a result of 235 U fission. The majority of 99 Mo supplies to U.S. patients are currently provided by foreign producers and produced using highly enriched uranium (HEU). In order to minimize the proliferation risks of HEU-based medical isotope production, the U.S. Department of Energy’s National Nuclear Security Administration has funded a program to accelerate the development of technologies to produce 99 Mo without the use of HEU. Today, the global supply of 99 Mo depends on a limited number of nuclear reactors, and production has been interrupted unexpectedly since 2009 due to the fleet’s advanced age. Herein, alternative options for 99 Mo production are discussed, and one potential option is to obtain 99m Tc from molten salt reactors (MSRs). A MSR is a nuclear fission reactor that can operate at or close to atmospheric pressure with liquid fuel, which allows for producing isotopes in a timely manner. In this paper, the past and current production of 99 Mo via nuclear reactors is described, and the future of 99 Mo production by MSRs is discussed. The behavior and chemical properties of molybdenum in fluoride salts in MSRs and the possible extraction methods are also examined in addition to the limitation of current studies.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1985

Evaluation and prediction of long-term environmental effects of nonmetallic materials

The properties of a number of nonmetallic materials were evaluated experimentally in simulated space environments in order to develop models for accelerated test methods useful for predicting such behavioral changes. Graphite-epoxy composites were exposed to thermal cycling. Adhesive foam tapes were subjected to a vacuum environment. Metal-matrix composites were tested for baseline data. Predictive modeling designed to include strength and aging effects on composites, polymeric films, and metals under such space conditions (including the atomic oxygen environment) is discussed. The Korel 8031-00 high strength adhesive foam tape was shown to be superior to the other two tested.

Papazian, H.↗
DOE OSTI2024

New insights on the effects of chemistry and temperature on α’ precipitation during aging of FeCrAl alloys

Here, the effect of Al on α' precipitation in FeCrAl alloys was studied through thermal aging of several model binary FeCr and FeCrAl alloys with Cr content of 13 wt.%, 17 wt.%, and 25 wt.% with and without 5.5 wt.% Al. Aging was performed up to 1,000h at varying temperatures from 400-500°C. At 400°C no age hardening was observed due to slow kinetics at this temperature. For both the 17Cr and 25Cr alloys, the addition of Al shows a lowering of the miscibility gap, consistent with other reports in literature. Interestingly, however, for the 25Cr alloys the addition of Al in the FeCrAl ternary alloy accelerated α' precipitation below the miscibility gap. Such enhanced precipitation has also been predicted by our atomistic kinetic Monte Carlo (AKMC) simulations. While previous literature has often focused on Al suppressing α', here we show that while Al can lower the miscibility gap in the Fe-Cr ferritic system thermodynamically, it may also enhance the kinetics of precipitation.

36 MATERIALS SCIENCE↗
NASA NTRS2015

A Methodology to Assess the Capability of Engine Designs to Meet Closed-loop Performance and Operability Requirements

Designing a closed-loop controller for an engine requires balancing trade-offs between performance and operability of the system. One such trade-off is the relationship between the 95% response time and minimum high-pressure compressor (HPC) surge margin (SM) attained during acceleration from idle to takeoff power. Assuming a controller has been designed to meet some specification on response time and minimum HPC SM for a mid-life (nominal) engine, there is no guarantee that these limits will not be violated as the engine ages, particularly as it reaches the end of its life. A characterization for the uncertainty in this closed-loop system due to aging is proposed that defines elliptical boundaries to estimate worst-case performance levels for a given control design point. The results of this characterization can be used to identify limiting design points that bound the possible con- troller designs yielding transient results that do not exceed specified limits in response time or minimum HPC SM. This characterization involves performing Monte Carlo simulation of the closed-loop system with controller constructed for a set of trial design points and developing curve fits to describe the size and orientation of each ellipse; a binary search procedure is then employed that uses these fits to identify the limiting design point. The method is demonstrated through application to a generic turbofan engine model in closed- loop with a simplified controller; it is found that the limit for which each controller was designed was exceeded by less than 4.76%. Extension of the characterization to another trade-off, that between the maximum high-pressure turbine (HPT) entrance temperature and minimum HPC SM, showed even better results: the maximum HPT temperature was estimated within 0.76%. Because of the accuracy in this estimation, this suggests another limit that may be taken into consideration during design and analysis. It also demonstrates the extension of the characterization to other attributes that contribute to the performance or operability of the engine. Metrics are proposed that, together, provide information on the shape of the trade-off between response time and minimum HPC SM, and how much each varies throughout the life cycle, at the limiting design points. These metrics also facilitate comparison of the expected transient behavior for multiple engine models.

engine control↗
NASA NTRS2015

A Methodology to Assess the Capability of Engine Designs to Meet Closed-Loop Performance and Operability Requirements

Designing a closed-loop controller for an engine requires balancing trade-offs between performance and operability of the system. One such trade-off is the relationship between the 95 percent response time and minimum high-pressure compressor (HPC) surge margin (SM) attained during acceleration from idle to takeoff power. Assuming a controller has been designed to meet some specification on response time and minimum HPC SM for a mid-life (nominal) engine, there is no guarantee that these limits will not be violated as the engine ages, particularly as it reaches the end of its life. A characterization for the uncertainty in this closed-loop system due to aging is proposed that defines elliptical boundaries to estimate worst-case performance levels for a given control design point. The results of this characterization can be used to identify limiting design points that bound the possible controller designs yielding transient results that do not exceed specified limits in response time or minimum HPC SM. This characterization involves performing Monte Carlo simulation of the closed-loop system with controller constructed for a set of trial design points and developing curve fits to describe the size and orientation of each ellipse; a binary search procedure is then employed that uses these fits to identify the limiting design point. The method is demonstrated through application to a generic turbofan engine model in closed-loop with a simplified controller; it is found that the limit for which each controller was designed was exceeded by less than 4.76 percent. Extension of the characterization to another trade-off, that between the maximum high-pressure turbine (HPT) entrance temperature and minimum HPC SM, showed even better results: the maximum HPT temperature was estimated within 0.76 percent. Because of the accuracy in this estimation, this suggests another limit that may be taken into consideration during design and analysis. It also demonstrates the extension of the characterization to other attributes that contribute to the performance or operability of the engine. Metrics are proposed that, together, provide information on the shape of the trade-off between response time and minimum HPC SM, and how much each varies throughout the life cycle, at the limiting design points. These metrics also facilitate comparison of the expected transient behavior for multiple engine models.

systems analysis↗
DOE OSTI2023

Comparative Analysis of Hotspot Stress Endurance in Pristine and Thermal Cycled Prestressed Glass–Glass Photovoltaic Modules

Hotspots pose a significant long-term reliability challenge in photovoltaic (PV) modules that can have a detrimental impact on the efficiency, safety, and financial viability of a PV system. This paper aims to evaluate the endurance of hotspot stress in pristine and prestressed glass–glass (GG) modules. The accelerated prestressing was conducted for 600 thermal cycles (TC600) to represent decades of field exposure. GG modules are quickly becoming an alternative to the traditional glass–backsheet (GB) modules that have been the industry standard. Unlike other conventional studies that subject only pristine modules to hotspot stress, this paper evaluates the performance of an accelerated/simulated field-aged GG module (using TC600) and a pristine GG module. Pre- and post-characterizations were performed before and after each test to determine changes in electrical performance and observe any defects in GG modules. During the hotspot test, an approximately 200 °C maximum cell temperature was observed with a cell shading of 25% (the worst-case shading ratio). After the hotspot test, electroluminescence imaging indicated that most cells in the prestressed GG module exhibited severe damage whereas no significant defects were evident in the pristine GG module where the prestressed GG module degraded 8.2% and the pristine GG module degraded 1.5% in maximum power. These findings are critical for the industry, considering that GG bifacial modules will dominate the market.

14 SOLAR ENERGY↗
DOE OSTI2021

Assessment of Aging Degradation Mechanisms of Alloy 709 for Sodium Fast Reactors

This project was initiated in October 2015 to investigate the creep and creep-fatigue behavior of Alloy 709 for structural components in Gen IV sodium cooled fast spectrum reactors. The goal of this project is to develop an understanding of the mechanisms responsible for the behavior of austenitic stainless steel alloy 709 under accelerated testing conditions to confidently predict long term creep and creep-fatigue behavior at the times (500,000 hours) and temperatures (550°C) of interest for fast reactor structural applications. Alloy 709 has exhibited significantly better creep resistance than Alloy 316H, which is currently specified in design of fast reactor structural components. However, the alloy has not been code qualified for elevated temperature nuclear design. The elevated temperature microstructure stability and creep and creep-fatigue behavior need to be better understood so service life can be accurately predicted. Alloy 709 was developed for fossil boiler applications, which operate at a higher temperature than the nuclear components. Thus, there is a strong need to characterize its creep and creep-fatigue behavior at these lower temperatures and corresponding longer service lifetimes. The overall objective of this project is to develop sufficient understanding of the mechanisms responsible for behavior of Alloy 709 under accelerated testing conditions to confidently predict long term creep and creep-fatigue behavior at the times (500,000 hours) and temperatures (550°C) of interest for fast reactor structural applications. The following report summarizes the findings of the creep-fatigue and creep behavior with respect to the research questions identified during the course of the project. Additionally, the training and professional development that occurred through the project and the products resulting from the project are summarized.

36 MATERIALS SCIENCE↗
NASA NTRS1994

The cost of access to space

Nearly four decades into the space age, our biggest problem is still the high cost of transportation to space. Close behind are the relatively infrequent flight opportunities and high risk of the transportation systems we have. These problems are of course not independent; rather, they are interrelated measures of the difficulty of accelerating a payload through an ideal velocity increment of over 9 km/s and a height of 200 km or more in just a few minutes. These difficulties are not unrecognized, and the demand for newer, cheaper, more reliable, more frequently flying launch systems has been unending. Hundreds, maybe thousands of studies have been done on various approaches offering improved access to space, and each approach has its ardent supporters, convinced that no other approach can work as well. In the government, hardly a year passes without the attempted initiation of a new program to lower the cost and improve the reliability of space transportation. This paper does not attempt to decide the merits and demerits of various transportation concepts but examines the cost of access to space from a slightly different perspective, and attempts to use that perspective to reach some conclusions about characteristics that a next-generation system must have to yield lower cost, regardless of its design.

Griffin, Michael D.↗
NASA NTRS1977

The age of the galactic cosmic rays derived from the abundance of Be-10

Satellite measurements of the abundance of the Be-10 isotope in galactic cosmic rays are used to determine the cosmic-ray lifetime for escape. The data are analyzed by employing a technique based on an extensive calibration of a cosmic-ray telescope with the aid of high-energy Be beams accelerated in a bevatron. It is found that the Be-10/Be abundance ratio at 80 MeV/nucleon is 0.028 + or - 0.104. A comparison of this result with calculations based on a homogeneous steady-state model of galactic cosmic-ray confinement and propagation yields an average interstellar density of 0.18 (+0.18, -0.11) atom/cu cm and a corresponding cosmic-ray lifetime of 17 (+24, -8) million years after solar modulation is taken into account. The low average density traversed by the cosmic rays is shown to suggest that the particles may be spending the major part of their existence in regions of very low matter density. The consequences of these results are discussed for models of cosmic-ray propagation in the Galaxy, including such alternatives as propagation in a galactic halo or in regions of interstellar space where the interstellar gas density is very low.

Garcia-Munoz, M.↗
DOE OSTI2021

Impact of limestone fineness on cement hydration at early age

This study compares the influence of two limestone fineness on strength development and cement hydration. The replacement of clinker by 20% of fine limestone (d{sub v,50} = 2 μm and SSA = 4,21 m{sup 2}/g) gives similar strength development to PC up to 7 days. Fine limestone enhances cement hydration and offsets the dilution effect caused by the decrease of clinker amount. The accelerating effect of the limestone was explained by a higher degree of undersaturation with respect to C{sub 3}S. The influence of coarse limestone (d{sub v,50} = 130 μm and SSA = 0,46 m{sup 2}/g) on cement hydration is limited to dilution effect. The combination of fine and coarse limestone was also studied. A linear correlation was obtained between strength and gel space ratio for all investigated systems. Furthermore, the results showed that despite the similarity of specific surface area, limestone is more effective than quartz for the enhancement of cement hydration.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Graphene Oxide Nanoribbons for High Early-Strength Cement Concrete

Longitudinal oxidative unzipping of the outer walls of multiwalled carbon nanotubes (MWCNTs) yields graphene oxide nanoribbons (GONRs), which exhibit greater open surface area and functional edge content than MWCNTs. This paper presents a study of the nano-amendment of Portland cement concrete with GONRs in concentrations between 0.05% (in weight of cement, wt%) and 0.0005 wt%, thus up to two orders of magnitude lower than that reported as lower-bound in the archival literature. The dispersibility in aqueous solution as a function of GONR concentration and oxygen weight content (O%) was assessed through dynamic light scattering (DLS) and zeta potential analysis. The results indicated that less effective suspensions were obtained for 0.05 wt% of GONRs and 22.7 O%. Therefore, GONR water suspensions with 30-40% O% were used to manufacture 50 mm × 100 mm cylindrical concrete specimens. After 7 days of curing, results from uniaxial compression tests using four specimens per configuration (MWCNT concentration and O%) showed that the incorporation of GONRs resulted in an average increase in compressive strength up to 45%. Consistent with the DLS and compression test results, SEM micrographs showed well-dispersed GONRs together with accelerated and preferential formation of calcium silicate hydrates (C-S-H) for all GONR concentrations. The results indicate, for the first time, that the incorporation of very small concentrations (as low as 0.0005 wt%) of well-dispersed GONR amendments can significantly enhance the early-age concrete strength. However, such enhancement became insignificant after 28 days of curing.

cement↗
DOE OSTI2023

Photoaging of phenolic secondary organic aerosol in the aqueous phase: evolution of chemical and optical properties and effects of oxidants

Abstract. While gas-phase reactions are well established to have significant impacts on the mass concentration, chemical composition, and optical properties of secondary organic aerosol (SOA), the aqueous-phase aging of SOA remains poorly understood. In this study, we performed a series of long-duration photochemical aging experiments to investigate the evolution of the composition and light absorption of the aqueous SOA (aqSOA) from guaiacyl acetone (GA), a semivolatile phenolic carbonyl that is common in biomass burning smoke. The aqSOA was produced from reactions of GA with hydroxyl radical (•OH-aqSOA) or a triplet excited state of organic carbon (3C∗-aqSOA) and was then photoaged in water under conditions that simulate sunlight exposure in northern California for up to 48 h. The effects of increasing aqueous-phase •OH or 3C∗ concentration on the photoaging of the aqSOA were also studied. High-resolution aerosol mass spectrometry (HR-AMS) and UV–Vis spectroscopy were utilized to characterize the composition and the light absorptivity of the aqSOA and to track their changes during aging. Compared to •OH-aqSOA, the 3C∗-aqSOA is produced more rapidly and shows less oxidation, a greater abundance of oligomers, and higher light absorption. Prolonged photoaging promotes fragmentation and the formation of more volatile and less light-absorbing products. More than half of the initial aqSOA mass is lost, and substantial photobleaching occurs after 10.5 h of prolonged aging under simulated sunlight illumination for 3C∗-aqSOA and 48 h for •OH-aqSOA. By performing positive matrix factorization (PMF) analysis of the combined HR-AMS and UV–Vis spectral data, we resolved three generations of aqSOA with distinctly different chemical and optical properties. The first-generation aqSOA shows significant oligomer formation and enhanced light absorption at 340–400 nm. The second-generation aqSOA is enriched in functionalized GA species and has the highest mass absorption coefficients in 300–500 nm, while the third-generation aqSOA contains more fragmented products and is the least light absorbing. These results suggest that intermediately aged phenolic aqSOA is more light absorbing than other generations, and that the light absorptivity of phenolic aqSOA results from a competition between brown carbon (BrC) formation and photobleaching, which is dependent on aging time. Although photoaging generally increases the oxidation of aqSOA, a slightly decreased O/C of the •OH-aqSOA is observed after 48 h of prolonged photoaging with additional •OH exposure. This is likely due to greater fragmentation and evaporation of highly oxidized compounds. Increased oxidant concentration accelerates the transformation of aqSOA and promotes the decay of BrC chromophores, leading to faster mass reduction and photobleaching. In addition, compared with •OH, photoaging by 3C∗ produces more low-volatility functionalized products, which counterbalances part of the aqSOA mass loss due to fragmentation and evaporation.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1985

Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants

The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium.

Beck, R.↗
DOE OSTI2023

Abstract for CRADA between NETL and Praxair Surface Technologies, Inc. (AGMT-1288)

The National Energy Technology Laboratory (NETL) and Praxair Surface Technologies (Participant) will collaborate in the design and manufacturing of new high-performance thermal barrier coatings (TBCs) for hydrogen gas turbine applications. High-throughput first-principles density functional theory (DFT) calculations will be performed to accelerate novel TBCs discovery with expanded phase field, increased temperature and erosion capabilities, low thermal conductivity, and significant toughness imparted by ferroelastic toughening for the non-transformable tetragonal oxide phase. Down-selected materials will be manufactured using solid state powder processing techniques. Testing will include isothermal aging followed by Raman and x-ray diffraction (XRD) phase analysis, indentation fracture toughness measurements, erosion testing, and thermal conductivity measurements. The collaboration will facilitate the deployment of hydrogen gas turbine technologies that are a key to the decarburization of power generation in the United States.

08 HYDROGEN↗
NASA NTRS2018

Expansion and Age of the X-Ray Synchrotron-Dominated Supernova Remnant G330.2+1.0

We report new Chandra observations of one of the few Galactic supernova remnants whose X-ray spectrum is dominated by nonthermal synchrotron radiation, G330.2+1.0. We find that between 2006 and 2017, some parts of the shell have expanded by about 1%, giving a free-expansion (undecelerated) age of about 1000 yr, and implying shock velocities there of 9000 km/s for a distance of 5 kpc. Somewhat slower expansion is seen elsewhere around the remnant periphery, in particular in compact knots. Because some deceleration must have taken place, we infer that G330.2+1.0 is less than about 1000 yr old. Thus, G330.2+1.0 is one of only four Galactic core-collapse remnants of the last millennium. The large size, low brightness, and young age require a very low ambient density, suggesting expansion in a stellar-wind bubble. We suggest that in the east, where some thermal emission is seen and expansion velocities are much slower, the shock has reached the edge of the cavity. The high shock velocities can easily accelerate relativistic electrons to X-ray-emitting energies. A few small regions show highly significant brightness changes by 10%–20%, both brightening and fading, a phenomenon previously observed in only two supernova remnants, indicating strong and/or turbulent magnetic fields.

Borkowski, Kazimierz J.↗
DOE OSTI2025

Performance studies of the Mu2e cosmic ray veto detector

The cosmic ray veto (CRV) detector of the Mu2e experiment consists of four layers of plastic scintillation counters that surround the detector solenoid. These counters are embedded with wavelength-shifting fibers and are read out by silicon photomultipliers (SiPMs). The performance of a subset of the CRV counters was studied in a cosmic-ray test stand. Here, using data taken over a two-year period, we report the single-layer muon detection efficiency and the rate at which the light yield degrades due to the aging of the plastic scintillation counters.

Aging↗
DOE OSTI2023

Consequences of utilizing a redox-active polymeric binder in Li-ion batteries

Development of new polymeric binders can help enable the use of silicon-rich anodes in Li-ion batteries, by providing stronger adhesion to the active material particles. The compositional features that improve interfacial interactions and mechanical properties can often impart electronic conductivity and redox activity to these polymers, which are generally seen as beneficial to cell performance. Alternatively, it is also possible that the addition of charge-transferring centers to the electrode can accelerate cell degradation. Here, we use an aromatic polyimide (∼320 mA h/g of reversible capacity) to explore how a redox-active conductive polymer can affect cell performance. We demonstrate that the lithiated polymer is less stable than the traditional binders upon storage, leading to increased rates of calendar aging. Furthermore, we determine that the adhesion properties of the polymer deteriorate upon repeated cycling, to an extent that is proportional to the degree of delithiation of the binder. More critically, we establish that progressive degradation of the redox behavior of the polymer leads to the release of “extra” Li + into the cell, which can give the false perception of good performance even under conditions of poor stability. In conclusion, our work suggests that redox-active conductive binders can sometimes be detrimental to cell performance, and that works evaluating new polymers must include careful experimental validation under realistic conditions.

25 ENERGY STORAGE↗
NASA NTRS1998

Pilot study of bone mineral density in breast cancer patients treated with adjuvant chemotherapy

The objective of this cross-sectional study was to determine lumbar spine bone mineral density (BMD) in breast cancer patients previously treated with adjuvant chemotherapy. Sixteen of 27 patients who received adjuvant chemotherapy became permanently amenorrheic as a result of chemotherapy. BMD was measured at the lumbar spine using dual energy X-ray absorptiometry (DEXA). Chemotherapy drugs and dosages along with a history of risk factors for reduced bone density including activity level, tobacco and/or alcohol use, metabolic bone disease, family history, and hormone exposure were identified. Results showed that women who became permanently amenorrheic as a result of chemotherapy had BMD 14% lower than women who maintained menses after chemotherapy. Chemotherapy-treated women who maintained ovarian function had normal BMD. This study suggests that women who have premature menopause as a result of chemotherapy for breast cancer are at increased risk of bone loss and may be at risk for early development of osteoporosis. Women who maintain menses do not appear to be at risk for accelerated trabecular bone loss.

Non-NASA Center↗