Showing papers by "Pacific Northwest National Laboratory published in 1987"

Thunderstorms: An Important Mechanism in the Transport of Air Pollutants

Abstract: Acid deposition and photochemical smog are urban air pollution problems, and they remain localized as long as the sulfur, nitrogen, and hydrocarbon pollutants are confined to the lower troposphere (below about 1-kilometer altitude) where they are short-lived. If, however, the contaminants are rapidly transported to the upper troposphere, then their atmospheric residence times grow and their range of influence expands dramatically. Although this vertical transport ameliorates some of the effects of acid rain by diluting atmospheric acids, it exacerbates global tropospheric ozone production by redistributing the necessary nitrogen catalysts. Results of recent computer simulations suggest that thunderstorms are one means of rapid vertical transport. To test this hypothesis, several research aircraft near a midwestern thunderstrom measured carbon monoxide, hydrocarbons, ozone, and reactive nitrogen compounds. Their concentrations were much greater in the outflow region of the storm, up to 11 kilometers in altitude, than in surrounding air. Trace gas measurements can thus be used to track the motion of air in and around a cloud. Thunderstorms may transform local air pollution problems into regional or global atmospheric chemistry problems.

Chromate adsorption on amorphous iron oxyhydroxide in the presence of major groundwater ions.

Abstract: Chromate adsorption on amorphous iron oxyhydroxide was investigated in dilute iron suspensions as a single solute and in solutions of increasing complexity containing CO2(g), SO4S (aq), H4SiO4(aq), and cations (K , MgS , CaS (aq)). In paired-solute systems (e.g., CrO4S -H2CO3*), anionic cosolutes markedly reduce CrO4S adsorption through a combination of competitive and electrostatic effects, but cations exert no appreciable influence. Additionally, H4SiO4 exhibits a strong time-dependent effect: CrO4S adsorption is greatly decreased with increasing H4SiO4 contact time. In multiple-ion mixtures, each anion added to the mixture decreases CrO4S adsorption further. Adsorption constants for the individual reactive solutes were used in the triple-layer model. The model calculations are in good agreement with the CrO4S adsorption data for paired- and multiple-solute systems. However, the model calculations underestimate CrO4S adsorption when surface site saturation is approached. Questions remain regarding the surface interactions of both CO2(aq) and H4SiO4. The results have major implications for the adsorption behavior of CrO4S and other oxyanions in subsurface waters.

Solvent Extraction Recovery of Byproduct 137Cs and 90Sr from HNO3 Solutions—A Technology Review and Assessment

Abstract: A principal purpose of this paper is to call out what is perceived to be a timely need for increased research to develop improved and new solvent extraction technology for recovery of 137Cs and 90Sr from strong (≥ 0.5M HNO3) acid media, technology which can be quickly scaled up to routine plant-scale operation with highly radioactive waste solutions when needed. The present and forseeable future (2020) U.S. inventory of 137Cs and 90sr is listed; much of this inventory is expected to be available only in strongly acidic nuclear waste solutions. Comparison of available methods-precipitation and ion exchange as well as solvent extraction—for recovering 137 Cs and 90Sr from alkaline and acid media demonstrates, as expected, that very limited technology is available for use with strongly acidic solutions. Solvent extraction procedures which employ either macrocyclic polyethers (crown ethers) or dicarbolide. H+{[π-(3)-1, 2-B9C2H11Cl2±2Co}−, to extract 137Cs and 90Sr from ≥ 0.5M HNO3 solutions have rece...

Mediated electrochemical reduction of CO2. Preparation and comparison of an isoelectronic series of complexes

Abstract: The preparation and characterization of complexes of the type (M(triphos)L)(BF/sub 4/)/sub 2/ are described (for M = Ni, L is P(OMe)/sub 3/ and PEt/sub 3/; for M = Pd, L is CH/sub 3/CN, P(OMe)/sub 3/, PEt/sub 3/, P(CH/sub 2/OH)/sub 3/, and PPh/sub 3/; for M = Pt, L is PEt/sub 3/; triphos is PhP(CH/sub 2/CH/sub 2/PPh/sub 2/)/sub 2/). On the basis of cyclic voltammetry and bulk electrolysis experiments, the Pd complexes are shown to catalyze the electrochemical reduction of CO/sub 2/ to CO in acidic acetonitrile solutions. The analogous Ni and Pt complexes are not catalysts for CO/sub 2/ reduction under the same conditions. Kinetic studies have been carried out on (Pd(triphos)(PEt/sub 3/))(BF/sub 4/)/sub 2/ and a mechanism for the reduction of CO/sub 2/ is proposed.

Ionization and charge transfer in He 2 + –rare-gas collisions. II

Abstract: New measurements of absolute cross sections for multiple ionization of helium, neon, argon, and krypton by 50--500-keV/amu ${\mathrm{He}}^{2+}$ impact are presented. By measuring projectile-ion--target-ion coincidences, these cross sections are obtained for the direct ionization as well as the single- and double-electron-capture channels. The present data are combined with previous measurements by the author that covered the energy range between 5 and 67 keV/amu in order to provide a broader description of ${\mathrm{He}}^{2+}$ impact ionization of atomic targets. The earlier measurements were found to require reevaluation in order to correct ion detection efficiencies used in that study. An analysis of the direct-multiple-ionization cross sections demonstrates that a simple impact-parameter, independent-electron model can be used to describe these cross sections over a broad range of low to intermediate impact energies. In particular, this analysis, when applied to fully stripped ion (1\ensuremath{\le}Z\ensuremath{\le}8) impact on helium, yields a single universal curve in the velocity range investigated here.

Fundamentals and practice of supercritical fluid chromatography‐mass spectrometry

Abstract: Aspects et proprietes de chromatographe a fluide supercritique relie a un spectrometre de masse. Description des interfaces possibles et facteurs restrictifs

Sorption of binary mixtures of aromatic nitrogen heterocyclic compounds on subsurface materials.

Abstract: Single and binary solute sorption of pyridine, quinoline, and acridine has been investigated on two low organic carbon subsurface materials with similar properties but different equilibrium pH when saturated with water. Single solute sorption for all compounds is higher in the acidic soil as compared to the basic soil, reflecting stronger sorption of the protonated organic cations. The protonated species exhibit high selectivity for the exchange complex at low aqueous concentration with selectivity increasing with ring number. Binary sorption experiments with quinoline/pyridine and quinoline/acridine demonstrate that competitive sorption occurs between compounds in the acidic subsoil where the protonated compounds species predominate in solution. In contrast, competition is minimal in the basic subsoil when the compounds are neutral. The competition between compounds is consistent with their measured single solute sorption and suggests mass action on a common set of high-affinity surface sites. A simplified model based on ideal absorbed solution theory (IAS) is used to provide simulations of binary solute sorption that are in good qualitative agreement with experimental results. It is suggested that competition between ionized solutes may significantly influence transport of organic mixtures when the groundwater pH is near the pK/sub a/ of the compounds. 31 references, 7 figures,more » 6 tables.« less

Laboratory limits on solar axions from an ultralow-background germanium spectrometer.

Abstract: Laboratory bounds on the couplings to electrons of light pseudoscalars such as axions, familons, Majorons, etc., are set with an ultralow-background germanium spectrometer using a realistic model for the Sun. In particular Dine-Fischler-Srednicki axion models with F/2${x}_{e}^{\mathcal{'}}$\ensuremath{\lesssim}0.5\ifmmode\times\else\texttimes\fi{}${10}^{7}$ GeV are excluded. It should be emphasized that this is a laboratory bound. It does not rely on a detailed understanding of the dynamics and evolution of red giants, white dwarfs, or other stars as do the more speculative astrophysical bounds which are competitive with our laboratory bound. The lower limit should be improved to F/2${x}_{e}^{\mathcal{'}}$g1.8\ifmmode\times\else\texttimes\fi{}${10}^{7}$ GeV in the near future. It is shown that semiconducting Ge detectors for axions could eventually set limits F/2${x}_{e}^{\mathcal{'}}$${g10}^{8}$ GeV. If discovered, axions or other light weakly interacting bosons would not only allow us to study physics at energies beyond the reach of accelerators but would also provide a new laboratory tool to study the deep interior of stars.

Measurement of SEU Thresholds and Cross Sections at Fixed Incidence Angles

Abstract: Current SEU testing and analysis techniques have as basic assumptions that the charge deposited at a junction depends linearly on the linear energy transfer (LET) of the ion and the pathlength of the ion through an imagined parallelepiped that represents the depletion region. This study tests these assumptions for two bipolar parts, AMD 27LSOO and Fairchild 93L422, by irradiating at fixed angles while varying the LET of two ion species. It was found that the 27LSOO shows a pronounced ion species dependence, and may show a deviation of deposited charge from the usual inverse-cosine times a fixed depletion depth, while the 93L422 exhibited the expected inverse-cosine dependence and no ion species dependence.

Multiple-ionization channels in proton-atom collisions

Abstract: A detailed investigation of multiple ionization of He (ionization charge states q = 1,2), Ne (q = 1--3), and Ar and Kr (q = 1--4) is presented for proton impact energies ranging from 10 keV to a few MeV. Absolute cross sections for various ionization pathways have been obtained by combining some new measurements with previously published experimental results and, in certain cases, with existing theoretical information. It is shown how each of these pathways contribute to the various stages of target ionization that are observed after the collision and how these experimentally measured quantities are related to the cross sections for initial inner- and outer-shell vacancy production. Areas where additional data are required or where the existing data are not internally consistent are pointed out. In general, it is shown that the existing data are sufficient to describe the ionization of helium as well as the lower levels of ionization of neon, argon, and krypton. However, for the higher degrees of ionization, particularly for Kr, our understanding is hampered by substantial gaps in the available inner-shell ionization data: both in cross-section and branching-ratio information. Nevertheless, the data are sufficient to indicate the relative importance of the various pathways. Formore » all targets, direct multiple outer-shell cross sections were extracted. Analyzing the energy dependences of these cross sections provided some hints as to how to calculate multiple-ionization cross sections, e.g., information as to where the multiple ionization is dominated by the first-order or by a higher-order term in the perturbation expansion of the proton-target interaction is obtained.« less

Proton transfer from metal hydrides to metal alkynyl complexes. Remarkable carbon basicity of (C5H5) (PMe3)2Ru-C≡C-CMe3

Abstract: The reactions of transition-metal hydrides with metal alkynyl compounds are virtually unexplored. The only previous systematic study is Lukehart's synthesis of bridging vinylidene complexes from formal addition of a Pt-H bond across the carbon-carbon triple bond of several metal alkynyl compounds. Davison and Selegue have shown that unsaturated carbon ligands bonded to late transition metals generally undergo ..beta..-attack by electrophiles and ..cap alpha..-attack by nucleophiles. This suggested that metal vinylidene complexes might be formed by proton transfer from metal hydrides to metal alkynyl complexes. This communication reports the first kinetic and thermodynamic measurements on this type of reaction and provides evidence that certain ruthenium alkynyl complexes are remarkably strong carbon-centered bases.

Heterogeneous Dissolution of Refractory Oxides in Molten Calcium-Aluminum Silicate

Abstract: La dissolution de Al 2 O 3 , MgAl 2 O 4 , Y 3 Al 5 O 12 , MgO et d'autres oxydes refractaires dans des silicates de Ca-Al fondus est heterogene pour des domaines significatifs de temperature et de composition des silicates, avec formation d'au moins un produit de reaction solide a l'interface oxyde-silicate

Hydrogen atom transfer reactions of transition-metal hydrides. Utilization of a radical rearrangement in the determination of hydrogen atom transfer rates

Abstract: The reaction of a transition-metal hydride with an unsaturated substrate is a critical step in several catalytic reactions. Commonly accepted mechanisms for homogeneous hydrogenation and hydroformylation have traditionally involved even-electron intermediates conforming to the 16- and 18-electron rule. Recently, kinetic and spectroscopic (CIDNP) evidence has been reported in support of odd-electron pathways for reactions of metal hydrides with substituted styrenes, anthracenes, allenes, and conjugated dienes, all of which form stabilized (benzylic or allylic) radicals. The authors report a new approach, in which metal hydrides are reacted with vinylcyclopropanes, which contain a radical clock.

Implementation of a Real-Time Ultrasonic Saft System for Inspection of Nuclear Reactor Components

Abstract: In recent years, the Pacific Northwest Laboratory has been developing the Synthetic Aperture Focusing Technique for Ultrasonic Testing (SAFT-UT) for the U.S. Nuclear Regulatory Commission (NRC). The program objective has been to develop and validate the SAFT-UT technology for inservice inspection of nuclear power plant components. This technique utilizes the full three-dimensional SAFT algorithm computed in the time domain. The project has included development of a field-usable, real-time SAFT-UT imaging system, and also enhancement of the SAFT-UT algorithm to achieve real-time rates. This paper discusses techniques that have been employed to achieve these goals, including a description of the system, system performance data, and a discussion of a real-time SAFT processor peripheral device for performing the computer-intensive SAFT algorithm computations. An overall view of the SAFT-UT system itself will also be discussed.

Ceramic thermal barrier coatings with improved corrosion resistance

Abstract: A method for limiting the ingress of corrosive species into physical vapor deposited zirconia thermal barrier coatings by inserting dense ceramic sealing layers into the usual columnar (segmented) ceramic microstructure has been examined. The concept was evaluated by sputtering a series of ZrO 2 -20Y 2 O 3 deposits onto In792 substrates coated with a CoCrAlY bondlayer. In each coating the majority of the ceramic layer was deposited with a porous columnar (segmented) microstructure. This microstructure provided the ceramic with excellent tolerance to thermal cycling. To reduce their permeability to liquid and gaseous species, selected coatings were modified by inserting several dense ceramic sealing layers into the columnar ceramic microstructure. Subsequent thermal cycle and corrosion testing showed that the inclusion of dense ZrO 2 -20Y 2 O 3 interlayers was effective in blocking the ingress of liquid Na 2 SO 4 without degrading the thermal cycle durability of the deposit. Dense ceramic layers of ZrO 2 -20Y 2 O 3 did not, however, appear to reduce the diffusion of oxygen through the coating. This was determined by comparing the oxidation rates of the underlying bondlayers. Inclusion of dense, 3 μm thick layers of either ZrSiO 4 or SiAlON into the middle of ZrO 2 -20Y 2 O 3 deposits also failed to reduce bondlayer oxidation significantly. The use of intermediate sealing layers has been shown to block the infiltration of deleterious species, such as Na 2 SO 4 ; however, methods for significantly slowing the diffusion of oxygen were not identified.

Stimulation of cutaneous mechanoreceptors by 60‐Hz electric fields

Abstract: Chronic exposure of animals to 60-Hz electric fields is known to affect the nervous system in a variety of subtle ways. The mechanism whereby these effects are produced remains unknown. One hypothesis is that the effects are a result of direct interaction between neuronal membranes and induced currents. Alternatively, the effects could be produced indirectly, as a result of sensory stimulation and the resulting low-level stress. To test these hypotheses, a system was developed to expose the surface of an anesthetized cat's paw to surface electric fields up to 600 kV/m while simultaneously measuring, in dorsal root fibers, afferent nerve impulses originating from various receptor types in the exposed paw. Of the 245 receptor units tested, comprising ten cutaneous receptor types, ten responded to the electric field with an increase in firing rate. The most sensitive receptor type was the rapidly adapting field receptor (RAF); eight of 20 (40%) were sensitive to the electric field, with thresholds as low as 160 kV/m. One of 35 rapidly adapting high-frequency receptors and one of 22 type T hair-follicle receptors were also sensitive to the electric field. Follow-up tests on the RAF receptors showed that hair removal reduced but did not eliminate the electric field sensitivity, suggesting that at least one other mechanism was involved in addition to stimulation via hair movement. The most likely mechanism is field-induced vibrations of the skin, since a further reduction in firing rate occurred following application of mineral oil to the depilated paw. Direct interaction with neuronal membranes is not supported by our evidence.

A comparison of the performance of nuclear waste glasses by modeling

Abstract: The reprocessing of spent fuel from nuclear reactors and processing of fuels for defense purposes have generated large volumes of high-level liquid waste that need to be immobilized prior to final storage. For immobilization, the wastes must be converted to a less soluble solid, and, although other waste forms exist, glass currently appears to be the choice for the transuranic-containing portion of the reprocessed waste. Once produced, this glass will be sent in canisters to a geologic repository located some 200 to 500 m below the surface of the earth.

Improving the Performance of Mass-Consistent Numerical Models Using Optimization Techniques

Abstract: This paper describes a technique of using a mass-consistent model to derive wind speeds over a microscale region (about 4 km2) of complex terrain A serious limitation of these numerical models is that the calculated wind field is highly sensitive to certain input parameters, such as that used to simulate the atmospheric stability Because accurate values for these parameters are not usually known, confidence in the calculated winds is low However, values for these parameters can be found by tuning the model to existing wind observations within a microscale area This tuning is accomplished with an optimization procedure that adjusts the unknown parameters so that the discrepancy between the observed winds and model calculations of these winds is minimized The model was verified with eight sets of hourly averaged wind data These data were obtained from measurements made at 28 sites covering a windfarm development in the Altamont Pass area of California When the model was tuned to a small subs

Rare earth element patterns in biotite muscovite and tourmaline minerals

Abstract: Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10−4 g/g to 10−10 g/g. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization.

Strategies for promoting technology transfer to the private sector

Abstract: This article discusses alternative promotion strategies that public policy makers can use to increase the effectiveness and efficiency of technology transfer programs. Three transfer strategies are described; the passive, the role-directed, and the organization-directed strategies. Factors influencing the selection of one of these transfer strategies by policy makers are considered in detail.