Results for “CONVERSION” — Page 32

DOE OSTI2013

Development of Integrated Online Monitoring Systems for Detection of Diversion at Natural Uranium Conversion Facilities

Recent work at Oak Ridge National Laboratory (ORNL) has focused on some source term modeling of uranyl nitrate (UN) as part of a comprehensive validation effort employing gamma-ray detector instrumentation for the detection of diversion from declared conversion activities. Conversion, the process by which natural uranium ore (yellowcake) is purified and converted through a series of chemical processes into uranium hexafluoride gas (UF6), has historically been excluded from the nuclear safeguards requirements of the 235U-based nuclear fuel cycle. The undeclared diversion of this product material could potentially provide feedstock for a clandestine weapons program for state or non-state entities. Given the changing global political environment and the increased availability of dual-use nuclear technology, the International Atomic Energy Agency has evolved its policies to emphasize safeguarding this potential feedstock material in response to dynamic and evolving potential diversion pathways. To meet the demand for instrumentation testing at conversion facilities, ORNL developed the Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility to simulate the full-scale operating conditions of a purified uranium-bearing aqueous stream exiting the solvent extraction process in a natural uranium conversion plant. This work investigates gamma-ray signatures of UN circulating in the UNCLE facility and evaluates detector instrumentation sensitivity to UN for safeguards applications. These detector validation activities include assessing detector responses to the UN gamma-ray signatures for spectrometers based on sodium iodide, lanthanum bromide, and germanium detectors. The results of measurements under static and dynamic operating conditions at concentrations ranging from 10-90g U/L of naturally enriched UN will be presented. A range of gamma-ray lines was examined and self-attenuation factors were calculated, in addition to attenuation for transmission measurement of density, concentration and enrichment. A detailed uncertainty analysis will be presented providing insights into instrumentation limitations to spoofing.

Dewji, Shaheen A↗

DOE OSTI2013

Semiconductor nanowires for photovoltaic and photoelectrochemical energy conversion

Semiconductor nanowires (NW) possess several beneficial properties for efficient conversion of solar energy into electricity and chemical energy. Due to their efficient absorption of light, short distances for minority carriers to travel, high surface-to-volume ratios, and the availability of scalable synthesis methods, they provide a pathway to address the low cost-to-power requirements for wide-scale adaptation of solar energy conversion technologies. Here we highlight recent progress in our group towards implementation of NW components as photovoltaic and photoelectrochemical energy conversion devices. An emphasis is placed on the unique properties of these one-dimensional (1D) structures, which enable the use of abundant, low-cost materials and improved energy conversion efficiency compared to bulk devices.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Syngas Conversion to Hydrocarbon Fuels through Mixed Alcohol Intermediates

Synthesis gas (syngas) can be used to synthesize a variety of fuels and chemicals. Domestic transportation and military operational interests have driven continued focus on domestic syngas-based fuels production. Liquid transportation fuels may be made from syngas via four basic processes: 1) higher alcohols, 2) Fischer-Tropsch (FT), 3) methanol-to-gasoline (MTG), and 4) methanol-to-olefins (MTO) and olefins-to-gasoline/distillate (MOGD). Compared to FT and higher alcohols, MTG and MTO-MOGD have received less attention in recent years. Due to the high capital cost of these synthetic fuel plants, the production cost of the finished fuel cannot compete with petroleum-derived fuel. Pacific Northwest National Laboratory has recently evaluated one way to potentially reduce capital cost and overall production cost for MTG by combining the methanol and MTG syntheses in a single reactor. The concept consists of mixing the conventional MTG catalyst (i.e. HZSM-5) with an alcohol synthesis catalyst. It was found that a methanol synthesis catalyst, stable at high temperature (i.e. Pd/ZnO/Al2O3) [1], when mixed with ZSM-5, was active for syngas conversion. Relatively high syngas conversion can be achieved as the equilibrium-driven conversion limitations for methanol and dimethyl ether are removed as they are intermediates to the final hydrocarbon product. However, selectivity control was difficult to achieve as formation of undesirable durene and light hydrocarbons was problematic [2]. The objective of the present study was thus to evaluate other potential composite catalyst systems and optimize the reactions conditions for the conversion of syngas to hydrocarbon fuels, through the use of mixed alcohol intermediates. Mixed alcohols are of interest as they have recently been reported to produce higher yields of gasoline compared to methanol [3]. 1. Lebarbier, V.M., Dagle, R.A., Kovarik, L., Lizarazo-Adarme, J.A., King, D.L., Palo, D.R., Catalyst Science & Technology, 2012, 2, 2116-2127. 2. Zhu, Y., Jones, S.B., Biddy, M.J., Dagle, R.A., Palo, D.P., Bioresource Technology, 2012, 117, 341-351. 3. Gujar, A.C., Guda, V.K., Nolan, M., Yan W., Toghiani, H., White, M.G., Applied Catalysis A: General, 2009, 363, 115-121.

syngas, catalysis, mixed alchohols, biomass, fossi↗

DOE OSTI2017

Considerations for Using FGE Conversion Factors in Type A Shipping Packages at the Savannah River Site

Contact Handled-Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC) conversion factors are typically used as fissile gram equivalent (FGE) values in systems such as transuranic waste at the Savannah River Site (SRS). Publicly available technical justifications for CH-TRAMPAC conversion factors are lacking. Special considerations are needed to justify the use of the CH-TRAMPAC conversion factor for 235 U to 239 Pu, over the full range of Pu and U densities for Type A shipping packages in the K-Area Complex (KAC) at SRS. It is important to understand the limitations and the area of applicability for using these conversion factors.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Conversion of biomass by efficient base-catalyzed decarboxylation reaction

Highly efficient and universal biomass conversion methods are described. Methods utilize a base-catalyzed decarboxylation reaction in a conversion process carried out in the presence of excess base to overcome carbonate formation from CO2. Methods can efficiently convert all components of a biomass feedstock to liquid hydrocarbons and carbon dioxide byproduct. The process has several versions: hydrolysis and alcoholysis, etc. The chemical process can be carried out with nearly 100% conversion for any type of biomass feedstock and requires no expensive or complicated pretreatment. The conversion reactions can be carried out at moderate temperatures of 170-300° C. and form a product that can include a mixture of hydrocarbons and oxygenated hydrocarbons, including alcohols and phenol derivatives.

09 BIOMASS FUELS↗

DOE OSTI2023

2.3.4.104 - Lignin Conversion to Sustainable Aviation Fuel Blendstocks

The Lignin Conversion to Sustainable Aviation Fuel Blendstocks (LigSAF) project focuses on the conversion of lignin-rich streams to deoxygenated aromatic and cycloalkane blendstocks in the jet fuel range. This work is done in close collaboration with the BETO-funded Lignin-First Biorefinery Development project and industrial scale-up partners, and the work is closely guided by analysis to develop cost-effective and sustainable routes to produce lignin-based SAF blendstocks. To date, we have demonstrated the continuous catalytic conversion of a lignin oil from poplar to deoxygenated aromatic products at -85% C-mol yield. This hydrodeoxygenation process uses a stable, earth-abundant catalyst and requires no solvent. We have also established a baseline process model and associated techno-economic analysis and life cycle assessment that together demonstrate the potential to achieve cost parity with fossil carbon-based jet fuel at -70% reduction in greenhouse gas emissions. Current work is focused on expanding the slate of feedstocks for hydrodeoxygenation to include lignin oils from softwoods, agricultural residues, and grasses as well as from hydrolysis lignin substrates from biochemical conversion and pulp-and-paper processes. We are also undertaking catalyst development efforts to tune the reaction selectivity from aromatic compounds to cycloalkanes. Lastly, we are investigating reaction engineering strategies to slurry solids for hydrodeoxygenation reactions.

aromatics↗

DOE OSTI2016

Conceptual Phase Neutronic and Thermal Analyses for the LEU Conversion of the Transient Reactor Test Facility (TREAT)

The Transient Reactor Test Facility (TREAT) is an experimental reactor designed for transient testing of nuclear reactor fuels and other materials. TREAT is located at the Idaho National Laboratory (INL). It was operated from 1959 until 1994, when it was placed on nonoperational standby. Preparations for the restart of TREAT are now underway. Simultaneously, work is being performed to support the conversion of TREAT from its current high enriched uranium (HEU) fuel to low enriched uranium (LEU, defined as uranium with less than 20% {sup 235}U) fuel, under the support of the Department of Energy (DOE) National Nuclear Security Administration (NNSA) Material Management and Minimization (M{sup 3}) reactor conversion program. Following the pre-conceptual phase of the TREAT conversion project (which included assessments of conversion feasibility, including LEU fuel element fabrication feasibility), conceptual phase work was performed to evaluate potential LEU fuel element designs for TREAT. Simultaneously, activities including scale-up development work for fuel fabrication and mock-up element production were performed by the INL Fuel Engineering and Design (FED) team. Utilizing the lessons learned in the analysis and fabrication work, an LEU conceptual design description was collaboratively established and evaluated in detail. A summary of this work and corresponding example results are presented here. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2017

Considerations for Using FGE Conversion Factors in Type A Shipping Packages at the Savannah River Site

Contact Handled-Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC) conversion factors are typically used as fissile gram equivalent (FGE) values in systems such as transuranic waste at the Savannah River Site (SRS). Publicly available technical justifications for CH-TRAMPAC conversion factors are lacking. Special considerations are needed to justify the use of the CH-TRAMPAC conversion factor for {sup 235}U to {sup 239}Pu, over the full range of Pu and U densities for Type A shipping packages in the K-Area Complex (KAC) at SRS. It is important to understand the limitations and the area of applicability for using these conversion factors.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2014

Applicability of ICRP 116 dose conversion coefficients to Korean pediatric population exposed to external photons - Paper 25

In the event of a radiological accident or attack, the estimation of organ dose is crucial to determine the possible health effect to general public. To that end, International Commission on Radiological Protection (ICRP) published a comprehensive set of organ dose conversion coefficients derived from the adult stylized (or mathematical) computational phantoms. More recently, ICRP updated the conversion coefficients based on their new reference computational phantoms, adult male and female voxel phantoms, exposed to a variety of radiation types and irradiation geometries. The adult voxel phantoms represent the organ mass and body dimensions of the Caucasian population. It is known that children generally receive greater radiation dose to organs compared to adults for external irradiation due to their smaller body size. that may provide less shielding to internal organs than adults. However, only a few studies investigated if the organ dose conversion coefficients developed for adults can be used for children and how much dose discrepancy needs to be expected. In this study, we adopted a Korean 7-year-old whole body voxel phantom to calculate a comprehensive organ dose conversion coefficients when the phantom is exposed to external photon irradiation geometries. We also compared the results with the data provided in the ICRP Publication 116, which is based on the ICRP adult voxel phantoms. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2026

Optimizing Neutrino Flavor Conversion Measurements through Machine Learning

The phenomenon of neutrino flavor conversion whereby the flavor of a neutrino particle can change between its time of production and later detection was the first definitive evidence of physics beyond the Standard Model. Some of the oscillation parameters used to describe this conversion are not yet well measured, leaving important questions still open regarding flavor conversion both in vacuum and as neutrinos travel through matter. NOvA is a long-baseline neutrino oscillation experiment that uses Fermilab's predominantly $\nu_\mu$ NuMI beam. A 14 kton oil-based liquid scintillator far detector 810 km away is used to measure neutrino oscillation through the $\nu_\mu$ disappearance and $\nu_e$ appearance channels. Super-K is a 50 kton water Cherenkov detector, which measures the disappearance of $\nu_e$ produced during solar fusion. The high density environment of the sun decreases the $\nu_e$ survival probability at higher energies observable in Super-K compared to the vacuum-dominated oscillations at lower energies. However, the transition region is overshadowed by radioactive background in the detector. In both of these experiments, the separation of neutrino detection events from background and classification of neutrino flavor are crucial tasks that benefit from the introduction of machine learning. Chapter 1 gives an overview of neutrinos and the context under which flavor conversion is measured in this dissertation. Chapters 2-7 present the results of a Bayesian sampling approach for the latest NOvA 3-flavor oscillation analysis with $26.6 \times 10^{20}$ protons on target in neutrino mode and $12.5 \times 10^{20}$ in antineutrino mode collected over 10 years. Chapters 8-13 present the results of extending the Super-K solar analysis to lower energies during its fourth phase with 2970 days of livetime.

Yankelevich, Alejandro Jaime [UC, Irvine]↗

DOE OSTI2026

Optimizing Neutrino Flavor Conversion Measurements through Machine Learning

The phenomenon of neutrino flavor conversion whereby the flavor of a neutrino particle can change between its time of production and later detection was the first definitive evidence of physics beyond the Standard Model. Some of the oscillation parameters used to describe this conversion are not yet well measured, leaving important questions still open regarding flavor conversion both in vacuum and as neutrinos travel through matter. NOvA is a long-baseline neutrino oscillation experiment that uses Fermilab's predominantly $\nu_\mu$ NuMI beam. A 14 kton oil-based liquid scintillator far detector 810 km away is used to measure neutrino oscillation through the $\nu_\mu$ disappearance and $\nu_e$ appearance channels. Super-K is a 50 kton water Cherenkov detector, which measures the disappearance of $\nu_e$ produced during solar fusion. The high density environment of the sun decreases the $\nu_e$ survival probability at higher energies observable in Super-K compared to the vacuum-dominated oscillations at lower energies. However, the transition region is overshadowed by radioactive background in the detector. In both of these experiments, the separation of neutrino detection events from background and classification of neutrino flavor are crucial tasks that benefit from the introduction of machine learning. Chapter 1 gives an overview of neutrinos and the context under which flavor conversion is measured in this dissertation. Chapters 2-7 present the results of a Bayesian sampling approach for the latest NOvA 3-flavor oscillation analysis with $26.6 \times 10^{20}$ protons on target in neutrino mode and $12.5 \times 10^{20}$ in antineutrino mode collected over 10 years. Chapters 8-13 present the results of extending the Super-K solar analysis to lower energies during its fourth phase with 2970 days of livetime.

Yankelevich, Alejandro Jaime [UC, Irvine]↗

DOE OSTI2026

Optimizing Neutrino Flavor Conversion Measurements through Machine Learning

The phenomenon of neutrino flavor conversion whereby the flavor of a neutrino particle can change between its time of production and later detection was the first definitive evidence of physics beyond the Standard Model. Some of the oscillation parameters used to describe this conversion are not yet well measured, leaving important questions still open regarding flavor conversion both in vacuum and as neutrinos travel through matter. NOvA is a long-baseline neutrino oscillation experiment that uses Fermilab's predominantly $\nu_\mu$ NuMI beam. A 14 kton oil-based liquid scintillator far detector 810 km away is used to measure neutrino oscillation through the $\nu_\mu$ disappearance and $\nu_e$ appearance channels. Super-K is a 50 kton water Cherenkov detector, which measures the disappearance of $\nu_e$ produced during solar fusion. The high density environment of the sun decreases the $\nu_e$ survival probability at higher energies observable in Super-K compared to the vacuum-dominated oscillations at lower energies. However, the transition region is overshadowed by radioactive background in the detector. In both of these experiments, the separation of neutrino detection events from background and classification of neutrino flavor are crucial tasks that benefit from the introduction of machine learning. Chapter 1 gives an overview of neutrinos and the context under which flavor conversion is measured in this dissertation. Chapters 2-7 present the results of a Bayesian sampling approach for the latest NOvA 3-flavor oscillation analysis with $26.6 \times 10^{20}$ protons on target in neutrino mode and $12.5 \times 10^{20}$ in antineutrino mode collected over 10 years. Chapters 8-13 present the results of extending the Super-K solar analysis to lower energies during its fourth phase with 2970 days of livetime.

Yankelevich, Alejandro Jaime [UC, Irvine] (ORCID:0↗

DOE OSTI2020

Solid-State NMR Studies of Solvent-Mediated, Acid-Catalyzed Woody Biomass Pretreatment for Enzymatic Conversion of Residual Cellulose

Enzymes selectively hydrolyze the carbohydrate fractions of lignocellulosic biomass into corresponding sugars, but these processes are limited by low yields and slow catalytic turnovers. Under certain conditions, the rates and yields of enzymatic sugar production can be increased by pretreating biomass using solvents, heat, and dilute acid catalysts. However, the mechanistic details underlying this behavior are not fully elucidated, and designing effective pretreatment strategies remains an empirical challenge. Herein, using a combination of solid-state and high-resolution magic-angle-spinning NMR, infrared spectroscopy, and X-ray diffractometry, we show that the extent to which cellulase enzymes are able to hydrolyze solvent-pretreated biomass can be understood in terms of the ability of the solvent to break the chemical linkages between cellulose and noncellulosic materials in the cell wall. This finding is of general significance to enzymatic biomass conversion research, and implications for designing improved biomass conversion strategies are discussed. Furthermore, these findings demonstrate the utility of solid-state NMR as a tool to elucidate the key chemical and physical changes that occur during the liquid-phase conversion of real biomass.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Direct conversion of methane to aromatics and hydrogen via a heterogeneous trimetallic synergistic catalyst

Abstract Non-oxidative methane dehydro-aromatization reaction can co-produce hydrogen and benzene effectively on a molybdenum-zeolite based thermochemical catalyst, which is a very promising approach for natural-gas upgrading. However, the low methane conversion and aromatics selectivity and weak durability restrain the realistic application for industry. Here, a mechanism for enhancing catalysis activity on methane activation and carbon-carbon bond coupling has been found to promote conversion and selectivity simultaneously by adding platinum–bismuth alloy cluster to form a trimetallic catalyst on zeolite (Pt-Bi/Mo/ZSM-5). This bimetallic alloy cluster has synergistic interaction with molybdenum: the formed CH 3 * from Mo 2 C on the external surface of zeolite can efficiently move on for C-C coupling on the surface of Pt-Bi particle to produce C 2 compounds, which are the key intermediates of oligomerization. This pathway is parallel with the catalysis on Mo inside the cage. This catalyst demonstrated 18.7% methane conversion and 69.4% benzene selectivity at 710 °C. With 95% methane/5% nitrogen feedstock, it exhibited robust stability with slow deactivation rate of 9.3% after 2 h and instant recovery of 98.6% activity after regeneration in hydrogen. The enhanced catalytic activity is strongly associated with synergistic interaction with Mo and ligand effects of alloys by extensive mechanism studies and DFT calculation.

03 NATURAL GAS↗

DOE OSTI2014

One dimensional full wave analysis of slow-to-fast mode conversion in lower hybrid frequencies

The linear conversion from the slow wave to the fast wave in the lower hybrid range of frequencies is analyzed numerically by using the set of field equations describing waves in a cold plane-stratified plasma. The equations are solved as a two-point boundary value problem, where the polarizations of each mode are set consistently in the boundary conditions. The scattering coefficients and the field patterns are obtained for various density profiles. It is shown that, for large density scale length, the results agree well with the traditional cognitions. In contrast, the reflected component and the probable transmitted-converted component from the conversion region, which are neglected in the usual calculations, become significant when the scale length is smaller than the wavelength of the mode. The inclusion of these new components will improve the accuracy of the simulated propagation and deposition for the injected rf power when the conversion process is involved within a sharp-varying density profile. Meanwhile, the accessibility of the incident slow wave for the low frequency case is also affected by the scale length of the density profile.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Compression of Acoustic Beams at Conversion Reflection in Hexagonal Crystals

It is shown how the entire energy of an acoustic beam incident on a boundary of a hexagonal crystal can be directed into a narrow reflected beam propagating at a small angle to the surface. This process is accompanied by mode conversion: the incident and reflected beams belong to different acoustic branches. The conversion near the total internal reflection is implemented by matching the orientations of the sagittal plane and surface and thereby eliminating the loss for parasitic wave reflection. The found conversion conditions and resonant reflection parameters are expressed in terms of the moduli of elasticity of crystal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2017

Foreshock wave interaction with the magnetopause: Signatures of mode conversion

Our previous hybrid simulation under a radial interplanetary magnetic field (IMF) and a supercritical solar wind Mach number has shown that foreshock compressional waves originated from the quasi–parallel (Q–∥) shock are mode converted to kinetic Alfvén waves (KAWs) at the Alfvén resonance surface of the subsolar magnetopause. In this paper, three–dimensional global dayside mode conversion is investigated for cases under various solar wind conditions using the global hybrid model. The global patterns and propagations of KAWs are distinguished and presented. Under a near–critical Mach number ( M A =3), KAW structures due to mode conversion exhibit a feature of broader excitation regions in the magnetopause boundary layer (MPBL) compared to supercritical Mach number ( M A =5) shocks. For cases with an oblique IMF with supercritical Mach numbers ( M A =5), the amplitude of magnetosheath compressional waves is larger at the quasi–parallel shock (Q–∥) than at the quasi–perpendicular (Q–⊥) shock. Downstream of the Q–∥ shock, there is a general trend that the perturbations of density ( N ) and magnetic field ( B ) change from predominantly in–phase in the magnetosheath to antiphase near the MPBL. While downstream of the Q–⊥ shock, an antiphase relation between N and B is dominant throughout the magnetosheath and magnetopause except near the shock transition. The compressional drivers are found to reach an extended region of the magnetopause due to the combined effects of wave propagation in the plasma frame and flow convection, leading to a broad region of mode conversion at the magnetopause. Subsequently, the resulting KAWs can be carried to the regions downstream of the Q–⊥ shock owing to the flow convection at the magnetopause. Furthermore the KAWs propagate poleward along the geomagnetic field lines and meanwhile are carried tailward by the ambient flows, and they are more intense in the downstream of Q–∥ shocks than downstream of Q–⊥ shocks.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2018

On the Balance of Intercalation and Conversion Reactions in Battery Cathodes

A thermodynamic analysis of the driving forces is presented for intercalation and conversion reactions in battery cathodes across a range of possible working ion, transition metal, and anion chemistries. Using this body of results, the importance of polymorph selection as well as chemical composition on the ability of a host cathode to support intercalation reactions is analyzed. It is found that the accessibility of high energy charged polymorphs in oxides generally leads to larger intercalation voltages favoring intercalation reactions, whereas sulfides and selenides tend to favor conversion reactions. Furthermore, it is observed that Cr-containing cathodes favor intercalation more strongly than those with other transition metals. It is concluded that two-electron reduction of transition metals (as is possible with the intercalation of a 2 + ion) will favor conversion reactions in the compositions studied.

25 ENERGY STORAGE↗