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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Crosslinked anion exchange membranes with connected cations

The selective transport of ions has crucial importance in biological systems as well as modern-day energy devices, such as batteries and fuel cells, and water purification membranes. Control over ion movement can be exerted by ligation, ion channel dimensions, solvation, and electrostatic interactions. Polyelectrolyte hydrogels can provide aligned pathways for counter ion transport but lack mechanical integrity, while polyelectrolyte membranes typically suffer from the absence of an ion transport channel network. To develop polymer membranes for improved ion transport, we present the design of a novel material that combines the advantages of aligned pathways found in polyelectrolyte hydrogel and mechanical robustness in conventional membranes. The ionic species were organized via controlled copolymerization of a quaternizable monomer. Additionally, dimensional stability was then incorporated through a cast/crosslinking method to lock in the network of connected cationic groups. This strategy resulted in dramatically enhanced ion transport, as characterized by ionic conductivities (>80 mS/cm for Cl-, and approximate to 200 mS/cm for OH-).

Zhang, Wenxu↗
DOE OSTI2017

Ion transport properties of mechanically stable symmetric ABCBA pentablock copolymers with quaternary ammonium functionalized midblock

Anion exchange membranes (AEMs) are a promising class of materials for applications that require selective ion transport, such as fuel cells, water purification, and electrolysis devices. Studies of structure–morphology–property relationships of ion-exchange membranes revealed that block copolymers exhibit improved ion conductivity and mechanical properties due to their microphase-separated morphologies with well-defined ionic domains. While most studies focused on symmetric diblock or triblock copolymers, here, the first example of a midblock quaternized pentablock AEM is presented. A symmetric ABCBA pentablock copolymer was functionalized to obtain a midblock brominated polymer. Solution cast films were then quaternized to obtain AEMs with resulting ion exchange capacities (IEC) ranging from 0.4 to 0.9 mmol/g. Despite the relatively low IEC, the polymers were highly conductive (up to 60 mS/cm Br- at 90 °C and 95%RH) with low water absorption (<25 wt %) and maintained adequate mechanical properties in both dry and hydrated conditions. X-ray scattering and transmission electron microscopy (TEM) revealed formation of cylindrical non-ionic domains in a connected ionic phase.

Ertem, SP↗
DOE OSTI2020

Electrowetting‐Mediated Transport to Produce Electrochemical Transistor Action in Nanopore Electrode Arrays

Abstract Understanding water behavior in confined volumes is important in applications ranging from water purification to healthcare devices. Especially relevant are wetting and dewetting phenomena which can be switched by external stimuli, such as light and electric fields. Here, these behaviors are exploited for electrochemical processing by voltage‐directed ion transport in nanochannels contained within nanopore arrays in which each nanopore presents three electrodes. The top and middle electrodes (TE and ME) are in direct contact with the nanopore volume, but the bottom electrode (BE) is buried beneath a 70 nm silicon nitride (SiN x ) insulating layer. Electrochemical transistor operation is realized when small, defect‐mediated channels are opened in the SiN x . These defect channels exhibit voltage‐driven wetting that mediates the mass transport of redox species to/from the BE. When BE is held at a potential maintaining the defect channels in the wetted state, setting the potential of ME at either positive or negative overpotential results in strong electrochemical rectification with rectification factors up to 440. By directing the voltage‐induced electrowetting of defect channels, these three‐electrode nanopore structures can achieve precise gating and ion/molecule separation, and, as such, may be useful for applications such as water purification and drug delivery.

Kwon, Seung‐Ryong↗
DOE OSTI2019

Subsystem complexity and holography

As a probe of circuit complexity in holographic field theories, we study sub-system analogues based on the entanglement wedge of the bulk quantities appearing in the “complexity = volume” and “complexity = action” conjectures. We calculate these quantities for one exterior region of an eternal static neutral or charged black hole in general dimensions, dual to a thermal state on one boundary with or without chemical potential respectively, as well as for a shock wave geometry. We then define several analogues of circuit complexity for mixed states, and use tensor networks to gain intuition about them. In the action approach, we find two possible cases depending on an ambiguity in the definition of the action associated with a counterterm. In one case, there is a promising qualitative match between the holographic action and what we call the purification complexity, the minimum number of gates required to prepare an arbitrary purification of the given mixed state. In the other case, the match is to what we call the basis complexity, the minimum number of gates required to prepare the given mixed state starting from a minimal complexity state with the same eigenvalue spectrum. One way to fix this ambiguity is to choose an action definition such that UV divergent part is positive, in which case the best match to the action result is the basis complexity. In contrast, the holographic volume does not appear to match any of our definitions of mixed-state complexity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Recovering the QNEC from the ANEC

We study the relative entropy in QFT comparing the vacuum state to a special family of purifications determined by an input state and constructed using relative modular flow. We use this to prove a conjecture by Wall that relates the shape derivative of relative entropy to a variational expression over the averaged null energy (ANE) of possible purifications. Furthermore, this variational expression can be used to easily prove the quantum null energy condition (QNEC). We formulate Wall’s conjecture as a theorem pertaining to operator algebras satisfying the properties of a half-sided modular inclusion, with the additional assumption that the input state has finite averaged null energy. We also give a new derivation of the strong superadditivity property of relative entropy in this con- text. We speculate about possible connections to the recent methods used to strengthen monotonicity of relative entropy with recovery maps.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Accounting for Environmental Aspects in Water-Chemistry Optimization of the Second Loop of NPP with VVER

A problem in operating NPP with VVER is that waste solutions containing ethanolamine and ammonia from regeneration of ion-exchange filters from the second loop must be processed. The amount of ammonia in the regeneration solutions is equal to 85% of the total amount of the contaminating substances. The water chemistry regime of the second loop without ammonia or with ammonia replaced by dimethylamine is examined. It is shown that the use of dimethylamine makes it possible to increase the duration of the filtration cycle for ion-exchange filters of the purification systems, decrease the concentration of products of corrosion, reduce the environmental impact, and simplify the waste water purification technology.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2013

Rapid determination of radiostrontium in seawater samples

A new method for the determination of radiostrontium in seawater samples has been developed at the Savannah River National Laboratory (SRNL) that allows rapid preconcentration and separation of strontium and yttrium isotopes in seawater samples for measurement. The new SRNL method employs a novel and effective pre-concentration step that utilizes a blend of calcium phosphate with iron hydroxide to collect both strontium and yttrium rapidly from the seawater matrix with enhanced chemical yields. The pre-concentration steps, in combination with rapid Sr Resin and DGA Resin cartridge separation options using vacuum box technology, allow seawater samples up to 10 liters to be analyzed. The total 89 Sr + 90 Sr activity may be determined by gas flow proportional counting and recounted after ingrowth of 90 Y to differentiate 89 Sr from 90 Sr. Gas flow proportional counting provides a lower method detection limit than liquid scintillation or Cerenkov counting and allows simultaneous counting of samples. Simultaneous counting allows for longer count times and lower method detection limits without handling very large aliquots of seawater. Seawater samples up to 6 liters may be analyzed using Sr Resin for 89 Sr and 90 Sr with a Minimum Detectable Activity (MDA) of 1-10 mBq/L, depending on count times. Seawater samples up to 10 liters may be analyzed for 90 Sr using a DGA Resin method via collection and purification of 90 Y only. If 89 Sr and other fission products are present, then 91 Y (beta energy 1.55 MeV, 58.5 day half-life) is also likely to be present. 91 Y interferes with attempts to collect 90 Y directly from the seawater sample without initial purification of Sr isotopes first and 90 Y ingrowth. The DGA Resin option can be used to determine 90 Sr, and if 91 Y is also present, an ingrowth option with using DGA Resin again to collect 90 Y can be performed. An MDA for 90 Sr of <1 mBq/L for an 8 hour count may be obtained using 10 liter seawater sample aliquots.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2014

Rapid determination of 226 Ra in emergency urine samples

A new method has been developed at the Savannah River National Laboratory (SRNL) that can be used for the rapid determination of 226 Ra in emergency urine samples following a radiological incident. If a radiological dispersive device event or a nuclear accident occurs, there will be an urgent need for rapid analyses of radionuclides in urine samples to ensure the safety of the public. Large numbers of urine samples will have to be analyzed very quickly. This new SRNL method was applied to 100 mL urine aliquots, however this method can be applied to smaller or larger sample aliquots as needed. The method was optimized for rapid turnaround times; urine samples may be prepared for counting in <3 h. A rapid calcium phosphate precipitation method was used to pre-concentrate 226 Ra from the urine sample matrix, followed by removal of calcium by cation exchange separation. A stacked elution method using DGA Resin was used to purify the 226 Ra during the cation exchange elution step. This approach combines the cation resin elution step with the simultaneous purification of 226 Ra with DGA Resin, saving time. 133 Ba was used instead of 225 Ra as tracer to allow immediate counting; however, 225 Ra can still be used as an option. The rapid purification of 226 Ra to remove interferences using DGA Resin was compared with a slightly longer Ln Resin approach. A final barium sulfate micro-precipitation step was used with isopropanol present to reduce solubility; producing alpha spectrometry sources with peaks typically <40 keV FWHM (full width half max). This new rapid method is fast, has very high tracer yield (>90 %), and removes interferences effectively. The sample preparation method can also be adapted to ICP-MS measurement of 226 Ra, with rapid removal of isobaric interferences.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2015

Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

Isotope dilution mass spectrometry (IDMS) is an analytical technique capable of providing accurate and precise quantitation of trace isotope abundance and assay providing measurement uncertainties below 1 %. To achieve these low uncertainties, the IDMS method ideally utilizes chemically pure “spike” solutions that consist of a single highly enriched isotope that is well-characterized relating to the abundance of companion isotopes and concentration in solution. To address a current demand for accurate 137Cs/137Ba ratio measurements for “age” determination of radioactive 137Cs sources, Idaho National Laboratory (INL) is producing enriched 134Ba isotopes that are tobe used for IDMS spikes to accurately determine 137Ba accumulation from the decay of 137Cs. The final objective of this work it to provide a homogenous set of reference materials that the National Institute of Standards and Technology can certify as standard reference materials used for IDMS. The process that was developed at INL for the separation and isolation of Ba isotopes, chemical purification of the isotopes in solution, and the encapsulation of the materials will be described.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

An interlaboratory collaboration to determine consensus 231 Pa/ 235 U model ages of a uranium certified reference material for nuclear forensics

Application of the 231 Pa/ 235 U radiochronometer for nuclear forensic investigations is challenged by a lack of certified reference materials with 231 Pa/ 235 U model purification dates. The Japan Atomic Energy Agency, Los Alamos National Laboratory, and Lawrence Livermore National Laboratory completed an interlaboratory study measuring 231 Pa/ 235 U model ages of New Brunswick Laboratory CRM U100. Results from independent laboratories were combined to calculate a consensus 231 Pa/ 235 U model purification date for CRM U100 of March 26, 1959 ± 237 days. This 231 Pa/ 235 U consensus date for CRM U100 may be used by the nuclear forensic community for quality control of 231 Pa/ 235 U radiochronometry measurements of unknown materials.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2022

Chemical separation of 146 Sm for half-life determination

Here, although methods for the chemical separation of samarium from a rock matrix are well established, chemical separation of samarium from non-natural isotopic impurities for the purpose of 146 Sm half-life measurement requires modifications to these procedures, as well as additional checks for effective separation. This work describes the chemical purification procedures associated with the 146 Sm source and the results from gamma spectroscopy. The purification procedure allowed for the quantitative determination of the number of 146Sm atoms using a modified isotope dilution technique. Alpha-decay counting of the sample will be applied in the future to determine the half-life of 146 Sm.

146Sm↗
DOE OSTI2023

Separation of protactinium from uranium-niobium alloys for 231 Pa– 235 U radiochronometry in nuclear forensic investigations

The isolation and purification of protactinium from uranium materials is essential for 231 Pa– 235 U radiochronometry, but separating Pa from uranium-niobium alloys, a common material in the nuclear fuel cycle, is challenging due to the chemical similarity of Pa and Nb. Here, in this work, we present three resin chromatography separation techniques for isolating Pa from U and Nb which were independently developed by three different laboratories through ad hoc adaptations of standard operating procedures. Our results underscore the need for and value of purification methods suitable for a diversity of uranium-based materials to ensure the operational readiness of nuclear forensics laboratories.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Volume Averaging Study of the Capacitive Deionization Process in Homogeneous Porous Media

Ion storage in porous electrodes is important in applications such as energy storage by supercapacitors, water purification by capacitive deionization, extraction of energy from a salinity difference and heavy ion purification. In this paper, a model is presented to simulate the charge process in homogeneous porous media comprising big pores. It is based on a theory for capacitive charging by ideally polarizable porous electrodes without faradaic reactions or specific adsorption of ions. A volume averaging technique is used to derive the averaged transport equations in the limit of thin electrical double layers. Transport between the electrolyte solution and the charged wall is described using the Gouy–Chapman–Stern model. The effective transport parameters for isotropic porous media are calculated solving the corresponding closure problems. Finally, the source terms that appear in the average equations are calculated using numerical computations. An alternative way to deal with the source terms is proposed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry as a Platform for Characterizing Multimeric Membrane Protein Complexes

Membrane protein characterization is consistently hampered by challenges with expression, purification, and solubilization. Among several biophysical techniques employed for their characterization, native-mass spectrometry (MS) has emerged as a powerful tool for the analysis of membrane proteins and complexes. Here, two MS platforms, the FT-ICR and Q-ToF, have been explored to analyze the homotetrameric water channel protein, AquaporinZ (AqpZ), under non-denaturing conditions. This 97 kDa membrane protein complex can be readily liberated from the octylglucoside (OG) detergent micelle under a range of instrument conditions on both MS platforms. Increasing the applied collision energy of the FT-ICR collision cell yielded varying degrees of tetramer (97 kDa) liberation from the OG micelles, as well as dissociation into the trimeric (72 kDa) and monomeric (24 kDa) substituents. Tandem-MS on the Q-ToF yielded higher intensity tetramer signal and, depending on the m/z region selected, the observed monomer signal varied in intensity. Precursor ion selection of an m/z range above the expected protein signal distribution, followed by mild collisional activation, is able to efficiently liberate AqpZ with a high S/N ratio. The tetrameric charge state distribution obtained on both instruments demonstrated superpositioning of multiple proteoforms due to varying degrees of N-terminal formylation. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Genetic techniques for studies of methyl-coenzyme M reductase from Methanosarcina acetivorans C2A.

Methanogenic archaea generate methane as a by-product of anaerobic respiration using CO 2 , C 1 compounds (like methanol or methylated amines), or acetate as terminal electron acceptors. Methanogens are an untapped resource for biotechnological advances related to methane production as well as methane consumption. Yet, key biological features of these organisms remain poorly understood. One such feature is the enzyme methyl-coenzyme M reductase (referred to as MCR), which catalyzes the last step in the methanogenic pathway and results in methane formation. Gene essentiality has limited genetic analyses of MCR thus far. Therefore, studies of this important enzyme have been limited to biochemical and biophysical techniques that are especially laborious and often reliant on sophisticated instrumentation that is not commonly available. In this chapter, we outline our recently developed CRISPR–Cas9-based genome editing tools and describe how these tools have been used for the introduction of a tandem affinity purification tag at the chromosomal mcr locus in the model methanogen, Methanosarcina acetivorans C2A. Moreover, we report a protocol for rapid affinity purification of MCR from M. acetivorans C2A that will enable high-throughput studies of this enzyme in the future.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Preparation of coenzyme F430 biosynthetic enzymes and intermediates

Methyl-coenzyme M reductase (MCR) is the key enzyme in pathways for the formation and anaerobic oxidation of methane. As methane is a potent greenhouse gas and biofuel, investigations of MCR catalysis and maturation are of interest for the development of both methanogenesis inhibitors and natural gas conversion strategies. Here, the activity of MCR is dependent on a unique, nickel-containing coenzyme F430, the most highly reduced tetrapyrrole found in nature. Coenzyme F430 is biosynthesized from sirohydrochlorin in four steps catalyzed by the CfbABCDE enzymes. Here, methods for the expression and purification of the coenzyme F430 biosynthesis enzymes are described along with conditions for the synthesis and purification of biosynthetic intermediates on the milligram scale from commercially available porphobilinogen.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Reactor production of promethium-147

In this paper, we describe the 147 Pm production yields and level of impurities from several targets that consisted of milligram quantities of highly enriched 146 Nd oxide irradiated at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory for durations ranging from 24 to180 h. A comparison between theoretical and experimental data are also presented, and attempts were made to empirically evaluate the neutron capture cross-sections of 41.3-d 148m Pm and 5.4-d 148g Pm. For a one-cycle irradiation (~24 days), 147 Pm yield reaches a maximum value of 101.8 MBq/mg (2.75 mCi/mg) at 60 days after the end of bombardment. Because of large neutron capture cross-sections of 147 Pm, the yield of 147 Pm does not significantly increase with longer irradiation. Our estimates of the thermal neutron capture cross-section and resonance integral for 146 Nd at 1.48 ± 0.05 b and 2.56 ± 0.25 b, respectively, were consistent with the reported values. The effective neutron capture cross-section of 147 Pm to 148m Pm was 53.3 ± 2.7 b - a factor of 2 lower than the 98.7 ± 6.5 b calculated from reported cross-sections. The measured σ eff to the ground state (5.37-d 148g Pm) was 82.0 ± 4.1 b; ~34 % lower than the value of 139 ± 0 b calculated from reported cross-sections. In this work, we also describe the development of a chemical process based on extraction and ion-exchange chromatography for separation of 147 Pm from milligram quantities of 146 Nd and other impurities. Sequential separation of Pm from the Nd target and from other radioisotopic impurities ( 153 Gd and 154&155 Eu, 192 Ir, and 60 Co) was achieved using a LN extraction resin in HCl media followed by further purification of Pm from 60 Co and 192 Ir using a low cross-linking cation exchange resin. Based on these data, we estimated that two rounds of purification under our experimental conditions can provide a mass separation factor of > 104 between Pm and Nd. Our data indicate that curie quantities of 147 Pm with suitable chemical and radioisotopic purity for applications in beta voltaic batteries can be produced by irradiating gram quantities of highly enriched 146 Nd in the flux trap of HFIR for one cycle.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Study of cosmogenic activation above ground for the DarkSide-20k experiment

The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39 Ar. Despite the outstanding capability of discriminating γ / β background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39 Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37 Ar and 3 H are shown not to be relevant due to short half-life and assumed purification methods.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗