33 research outputs found

    Evaluation of Cs/Sr Waste Form for Long Term Storage and Disposal

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    The goal of this project is to examine two potential concerns regarding the long-term performance of a proposed cesium/ strontium waste form. To facilitate long-term storage, up to 300 years, the disposal containers will need to be able to survive for the entire storage interval. The first aspect of the project will explore the potential interaction of the aluminosilicate waste form with the storage canister materials to determine if there is any corrosion or chemical interaction concerns for the storage of the materials. At the end of the storage interval, most of the 137Cs in the waste form will have decayed to its daughter, 137Ba. While this decay provides a significant reduction in the decay heat generated by the waste form, it poses a new concern. Barium is hazardous, and is identified by the U.S. Environmental Protection Agency (EPA) as a hazardous constituent under the Resource Conservation and Recovery Act (RCRA). To dispose of any material containing a RCRA-identified constituent, the material must be demonstrated to be durable enough to prevent the release of the hazardous component or must be treated as hazardous waste. For the Cs/Sr waste stream, failure to contain the barium within the waste form would require disposal as a mixed waste stream, greatly increasing the disposal costs. Understanding the potential impacts of radioactive damage, high storage temperatures, and the crystallographic impacts of the decay transmutation itself on the performance of the waste form 300 years from now poses a significant challenge

    Isothermal Titration Calorimetry and Transmission Electron Microscopy of Main-Chain Viologen Polymer Containing Bromide as Counerions

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    Polyelectrolytes are an important class of macromolecules that contain dissociable ionic groups. When introduced into polar solvent, usually the universal solvent water, dissociation takes place so that electrically charged macromolecule is suspended in solution. The electrostatic interaction is operative between ionized groups inside the macromolecule, between the macromolecules, between the counterions, and between the macromolecule and counterion. Since this interaction is characterized by its long-range nature, the solution exhibits various interesting properties including the polyelectrolyte behavior very different from solutions of neutral polymers

    Time-Dependent Fatigue Crack Propagation Behavior of Two Solid-Solution-Strengthened Ni-Based Superalloys—INCONEL 617 and HAYNES 230

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    The fatigue crack propagation (FCP) as well as the sustained loading crack growth (SLCG) behavior of two solid-solution-strengthened Ni-based superalloys, INCONEL 617 (Special Metals Corporation Family of Companies) and HAYNES 230 (Haynes International, Inc., Kokomo, IN), were studied at increased temperatures in laboratory air under a constant stress-intensity- factor (K) condition. The crack propagation tests were conducted using a baseline cyclic triangular waveform with a frequency of 1 3 Hz. Various hold times were imposed at the maximum load of a fatigue cycle to study the hold time effect. The results show that a linear elastic fracture mechanics (LEFM) parameter, stress intensity factor (K), is sufficient to describe the FCP and SLCG behavior at the testing temperatures ranging from 873 K to 1073 K (600 C to 800 C). As observed in the precipitation-strengthened superalloys, both INCONEL 617 and HAYNES 230 exhibited the time-dependent FCP, steady SLCG behavior, and existence of a damage zone ahead of crack tip. A thermodynamic equation was adapted to correlate the SLCG rates to determine thermal activation energy. The fracture modes associated with crack propagation behavior were discussed, and the mechanism of time-dependent FCP as well as SLCG was identified. Compared with INCONEL 617, the lower crack propagation rates of HAYNES 230 under the time-dependent condition were ascribed to the different fracture mode and the presence of numerous W-rich M6C-type and Cr-rich M23C6-type carbides. Toward the end, a phenomenological model was employed to correlate the FCP rates at cycle/time-dependent FCP domain. All the results suggest that an environmental factor, the stress assisted grain boundary oxygen embrittlement (SAGBOE) mechanism, is mainly responsible for the accelerated time dependent FCP rates of INCONEL 617 and HAYNES 230

    Absolute-energy-scale calibration of ARGO-YBJ for light primaries in multi-TeV region with the Moon shadow observation

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    In 2011 ARGO-YBJ experiment has reported a work to study the absolute rigidity scale of the primary cosmic ray particles based on the Moon's shadow observation. Given the progress in high energy hadronic interaction models with LHC data, in cosmic ray chemical composition measurement and in experimental data accumulation, more updates can be researched. This paper aims to further disentangle the composition dependence in absolute-energy-scale calibration by using specific moon-shadow data which mainly is comprised of light component cosmic rays. Results show that, 17% energy scale error is estimated from 3 TeV to 50 TeV. To validate the performance of this technique, the light component cosmic ray spectrum in the same energy region is shown. (C) 2017 Elsevier B.V. All rights reserved

    Comparison of Different Sample Preparation Techniques in TEM Observation of Microstructure of INCONEL Alloy 783 Subjected to Prolonged Isothermal Exposure

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    INCONEL alloy 783 was annealed and aged following the standard heat treatment procedure. One set of specimens was then isothermally exposed at 500 °C for 3000 h. Mechanical properties were measured at room temperature and 650 °C, and the results showed the prolonged exposure increased the strength and decreased elongation of alloy 783. The microstructures of as-produced and exposed material were examined using optical microscope, SEM and TEM, respectively. Three techniques, jet electro-polishing, ion milling, and focused ion beam, were employed to prepare the TEM samples to observe the variation of microstructure of alloy 783 due to isothermal exposure. TEM images of samples prepared by different methods were analyzed and compared. The results indicate that the jet electro-polishing technique allows the detail microstructure of alloy 783 subjected to different treatments to be well revealed, and thereby the TEM images can be used to explain the enhancement of strength of alloy 783 caused by isothermal exposure

    Effects of nickel-aluminum-beta precipitates on crack growth behavior in INCONEL alloy 783.

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    Recently developed γ-γ′-β three phases governing INCONEL* alloy 783 is the result of an extensive superalloy development program aimed at improving environmental-induced intergranular cracking resistance. Formation of intermetallic nickel aluminide β phase in alloy 783 is essentially resistant for the general oxidation. In this study, commercial alloy 783 was subjected to various metallurgical processing including heat treatments with β aging/without β aging, addition of 3% Cr into alloy, and thermo-mechanical processing (TMP). The corresponding microstructures were evaluated by means of the optical microcopy, SEM and TEM. These processed materials were subjected to the fatigue crack growth and sustained loading crack growth tests to investigate the effects of β precipitates on crack growth process, especially on the time-dependent crack growth behavior. It was found that β precipitates in alloy 783 play a very significant role in controlling SAGBO-induced crack growth process. Properly controlling the microstructure and morphology of β precipitates by different metallurgical processing can improve the resistance to environmental-induced damage. Based on the experimental results, a phenomenological model, which could describe crack growth behavior of alloy 783 subjected to the different metallurgical processing, were developed through introducing a universal time-dependent factor, α(t, T). Combining the physical interpretation of SAGBO-induced degradation mechanism and generated data, a 1-D stress-assisted oxygen diffusion model at crack tip along grain boundaries was proposed. This model was utilized to characterize crack growth behavior and crack incubation time in alloy 783 without β aging under sustained load condition. The good agreement between model prediction and experimental results were obtained. *INCOLOY and INCONEL are trademarks of the Special Metals Corporation. Huntington, West Virginia

    Identification of SAGBO-induced damage zone ahead of crack tip to characterize sustained loading crack growth in alloy 783

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    Sustained loading was applied to alloy 783 subjected to a non-standard heat treatment, annealing plus γ′ aging, at elevated temperature. The existence of damage zone ahead of the crack tip was identified and propagation rate of the damage zone was correlated to the sustained loading crack growth rate. The formation of damage zone was ascribed to stress accelerated grain boundary oxidation

    Reply to comment on “Identification of SAGBO-induced damage zone ahead of crack tip to characterize sustained loading crack growth in alloy 783”

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    The damage zone, formed during sustained loading by stress accelerated grain boundary oxygen embrittlement, is a localized region ahead of the crack tip. Before the crack growth reaches a steady rate, the existence of the crack growth transient period shows that cracking is likely to occur within the damage zone. This is indeed compatible with the dynamic embrittlement model

    State of Charge Estimation and Evaluation of Lithium Battery Using Kalman Filter Algorithms

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    The accurate and rapid estimation of the state of charge (SOC) is important and difficult in lithium battery management systems. In this paper, an adaptive infinite Kalman filter (AUKF) was used to estimate the state of charge for a 18650 LiNiMnCoO2/graphite lithium-ion battery, and its performance was systematically evaluated under large initial errors, wide temperature ranges, and different drive cycles. In addition, three other Kalman filter algorithms on the predicted SOC of LIB were compared under different work conditions, and the accuracy and convergence time of different models were compared. The results showed that the convergence time of the AUKF algorithms was one order of magnitude smaller than that of the other three methods, and the mean absolute error was only less than 50% of the other methods. The present work can be used to help other researchers select an appropriate strategy for the SOC online estimation of lithium-ion cells under different applicable conditions

    Micro-Structural Characterization of Precipitation-synthesized Fluorapatite Nano-material by Transmission Electron Microscopy using Different Sample Preparation Techniques

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    Fluorapatite is a naturally occurring mineral of the apatite group and it is well known for its high physical and chemical stability. There is a recent interest in this ceramic to be used as a radioactive waste form material due to its intriguing chemical and physical properties. In this study, the nano-sized fluorapatite particles were synthesized using a precipitation method and the material was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Two well-known methods, called solution-drop and the microtome cutting, were used to prepare the sample for TEM analysis. It was found that the microtome cutting technique is advantageous for examining the particle shape and cross-sectional morphology as well as for obtaining ultra-thin samples. However, this method introduces artifacts and strong background contrast for high-resolution transmission electron microscopy (HRTEM) observation. On the other hand, phase image simulations showed that the solution-drop method is reliable and stable for HRTEM analysis. Therefore, in order to comprehensively analyze the microstructure and morphology of the nano-material, it is necessary to combine both solution-drop and microtome cutting techniques for TEM sample preparation
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