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Positronium in Solids: Computer Simulation of Pick-Off and Self-Annihilation

Description: Positronium (Ps) is simulated using Path Integral Monte Carlo (PIMC). This method can reproduce the results of previous simple theories in which a single quantum particle is used to represent Ps within an idealized pore. In addition, the calculations treat the e{sup -} and e{sup +} of Ps exactly and realistically model interactions with solid atoms, thereby correcting and extending the simpler theory. They study the pick-off lifetime of o-Ps and the internal contact density, {kappa}, which cont… more
Date: August 1, 2003
Creator: Bug, A.; Muluneh, M.; Waldman, J. & Sterne, P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Can hydrous minerals account for the observed mid-latitude water on Mars?

Description: Great interest was generated with the discovery by the Odyssey spacecraft OC heterogeneously distributed hydrogcn at martian mid-latitudes, suggesting that large areas of the near-equatorial highlands contain near-surface deposits of 'chemically and/or physically bound 1120 and/or OH' in amounts up to 3.8% equivalent H20. More recent interpretations of the Odyssey data using new calibrations suggest that some near-equatorial areas, such as Arabia Terra, contain up to 8.5f I .3% water-equivalent… more
Date: January 1, 2003
Creator: Bish, D. L. (David L.); Vaniman, D. T. (David T.); Fialips, C. I. (Clair I.); Carey, J. W. (James W.) & Feldman, W. C. (William C.)
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Water-bearing minerals on mars: source of observed mid-latitude water?

Description: The Odyssey spacecraft documented the existence of heterogeneously distributed hydrogen at martian mid-latitudes, suggesting that large areas of the near-equatorial highlands contain near-surface deposits of 'chemically and/or physically bound H20 and/or OH' in amounts up to 3 .8% equivalent H20. Shallow occurrences of water ice are not stable near the martian equator, making the hydrogen deposits at these latitudes somewhat enigmatic. Clay minerals and zeolites have both been proposed as possi… more
Date: January 1, 2003
Creator: Bish, D. L. (David L.); Carey, J. W. (James W.) & Fialips, C. I. (Clair I.)
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Anionic sorbents for arsenic and technetium species.

Description: Two sorbents, zirconium coated zeolite and magnesium hydroxide, were tested for their effectiveness in removing arsenic from Albuquerque municipal water. Results for the zirconium coated zeolite indicate that phosphate present in the water interfered with the sorption of arsenic. Additionally, there was a large quantity of iron and copper present in the water, corrosion products from the piping system, which may have interfered with the uptake of arsenic by the sorbent. Magnesium hydroxide has … more
Date: September 1, 2003
Creator: Lucero, Daniel A.; Moore, Robert Charles; Bontchev, Ranko Panayotov; Hasan, Ahmed Ali Mohamed; Zhao, Hongting; Salas, Fred Manuel et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOSTS

Description: The focus of this project is to improve the catalytic performance of zeolite Y for petroleum hydrocracking by synthesizing nanoparticles of the zeolite ({approx}20-25 nm) inside nanoporous silicate or aluminosilicate hosts. The encapsulated zeolite nanoparticles are expected to possess reduced diffusional path lengths, hence hydrocarbon substrates will diffuse in, are converted and the products quickly diffused out. This is expected to prevent over-reaction and the blocking of the zeolite pores… more
Date: September 3, 2003
Creator: Ingram, Conrad
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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SELECTIVE REDUCTION OF NOX IN OXYGEN RICH ENVIRONMENTS WITH PLASMA-ASSISTED CATALYSIS: CATALYST DEVELOPMENT AND MECHANISTIC STUDIES

Description: The control of NOx (NO and NO2) emissions from so-called ''lean-burn'' vehicle engines remains a challenge. In recent years, there have been a number of reports that show that a plasma device combined with a catalyst can reduce as high as 90% or more of NOx in simulated diesel and other ''lean-burn'' exhaust. In the case of propylene containing simulated diesel exhaust, the beneficial role of a plasma treatment is now thought to be due to oxidation of NO to NO2, and the formation of partially o… more
Date: August 24, 2003
Creator: Peden, C.; Barlow, S.; Hoard, J.; Kwak, J.; Balmer-Millar, M.; Panov, A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Prediction of Coupled Thermal, Hydrological and Chemical Processes at the Proposed Yucca Mountain Nuclear Waste Repository: An Integrated Approach

Description: An integrated modeling approach was developed to investigate long-term coupled thermal, hydrological, and chemical (THC) processes that could take place around nuclear waste emplacement tunnels (drifts). The approach involves the development of process models, followed by numerical implementation and validation against field and laboratory experiments before conducting long-term predictive simulations. An outcome of this work was the refinement and validation of an existing reactive transport n… more
Date: October 17, 2003
Creator: Spycher, N.; Sonnenthal, E.; Kneafsey, T. & Dobson, P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Treatment of Produced Waters Using a Surfactant Modified Zeolite/Vapor Phase Bioreactor System

Description: Co-produced water from the oil and gas industry accounts for a significant waste stream in the United States. It is by some estimates the largest single waste stream in the country, aside from nonhazardous industrial wastes. Characteristics of produced water include high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component, and chemicals added during the oil-production process. While most of the produced water is disposed via re… more
Date: April 1, 2003
Creator: Katz, Lynn E.; Kinney, Kerry A.; Bowman, R. S. & Sullivan, E. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Treatment of Produced Waters Using a Surfactant Modified Zeolite/Vapor Phase Bioreator System

Description: Co-produced water from the oil and gas industry is by some estimates the largest single waste stream in the country, aside from nonhazardous industrial wastes. Characteristics of produced water include high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component, and chemicals added during the oil-production process. While most of the produced water is disposed via reinjection, some of them must be treated to remove organic constit… more
Date: October 1, 2003
Creator: Katz, Lynn E.; Kinney, Kerry A.; Bowman, R. S. & Sullivan, E. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Caustic Waste-Soil Weathering Reactions and Their Impacts on Trace Contaminant Migration and Sequestration

Description: We are studying Cs, Sr and I uptake and release during clay mineral weathering under conditions representative of caustic tank waste leachate. Cesium sorption after 1 year reaction was the greatest in the order of vermiculite, illite, montmorillonite and kaolinite. Vermiculite showed highest Sr sorption, followed by kaolinite, montmorillonite and illite. Secondary phase products were feldspathoid sodium aluminum nitrate silicate, sodium aluminum nitrate silicate hydrate, Na-Al chabazite and zeo… more
Date: June 1, 2003
Creator: Chorover, Jon D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Colloid-Facilitated Transport of Radionuclides Through the Vadose Zone

Description: Given that there is a wide range of chemical compositions of Hanford Tank Waste, we have studied mineral formation and transformation by systematically varying anion composition and OH concentrations of simulated tank solutions in presence and absence of Cs. The feldspathoids and zeolite formed in the presence of Cs were analyzed with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and solid state NMR. The presence of Cs in the simula… more
Date: June 1, 2003
Creator: Flury, Markus
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Evaluation of the Incorporation of Uranium into Sodium Aluminosilicate Phases

Description: This report describes batch laboratory experiments performed to determine the relative amounts of uranium incorporated in aluminosilicate structures during synthesis. The findings summarized here are based on laboratory experiments, which involved the synthesis of sodium aluminosilicates (NAS) structures, amorphous, zeolites A and sodalite phases in the presence of depleted uranium and the analytical search for incorporated uranium in NAS internal structures after synthesis. These studies will … more
Date: March 26, 2003
Creator: Oji, L.N.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Ceramic Membranes for Hydrogen Production From Coal Annual Report: 2002

Description: The objective of this project is to develop ceramic membranes for hydrogen separation from fuel gas or synthesis gas at temperatures 400-500 C. The membrane chosen for this purpose consists of a dense silica layer coated on a porous support by chemical vapor depositrion (CVD). The support used during the reporting period was zeolite silicalite grown on macroporous alumina tubes. Chemical vapor deposition was carried out using alternating exposure of the support to silicon tetrachloride (SiCl{su… more
Date: March 18, 2003
Creator: Gavalas, George R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Characterization of Water and CO2 Adsorption by Stores 3A Desiccant Samples Using Thermal Gravimetric Analysis and Fourier Transform Infrared Spectroscopy

Description: Two lots of manufactured Type 3a zeolite samples were compared by TGA/IR analysis. The first lot, obtained from Davidson Chemical, a commercial vendor, was characterized during the previous study cycle for its water and water-plus-CO{sub 2} uptake in order to determine whether CO{sub 2} uptake prevented water adsorption by the zeolite. It was determined that CO{sub 2} did not hamper water adsorption using the Davidson zeolite. CO{sub 2} was found on the zeolite surface at dewpoints below -40 C,… more
Date: February 1, 2003
Creator: RIVERA, DION A.; ALAM, M. KATHLEEN; MARTIN, LAURA & BROWN, JASON R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Corrosion tests with uranium- and plutonium-loaded ceramic waste forms.

Description: Tests were conducted with ceramic waste form (CWF) materials that contained small amounts of uranium and plutonium to study their release behavior as the CWF corroded. Materials made using the hot isostatic press (HIP) and pressureless consolidation (PC) methods were examined and tested. Four different materials were made using the HIP method with two salts having different U:Pu mole ratios and two zeolite reagents having different residual water contents. Tests with the four HIP U,Pu-loaded CW… more
Date: January 9, 2003
Creator: Morss, L. R.; Johnson, S. G.; Ebert, W. L.; DiSanto, T.; Frank, S. M.; Holly, J. L. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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BIFUNCTIONAL CATALYSTS FOR THE SELECTIVE CATALYTIC REDUCTION OF NO BY HYDROCARBONS

Description: Novel bifunctional catalysts combining two active phases, typically Cu-ZSM-5 and a modifier, were prepared and tested for the selective catalytic reduction of nitrogen oxides using propylene in order to overcome the hindering effects of water typically seen for single-phase catalysts such as Cu-ZSM-5. The catalysts were made by typical preparation techniques, but parameters could be varied to influence the catalyst. The physical characterization of the materials showed that the modification pha… more
Date: August 24, 2003
Creator: Neylon, M.; Castagnola, M.; Kropf, A. & Marshall, C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Current Ansto Research on Wasteform Development

Description: Current ANSTO scientific research on wasteform development for mainly high-level radioactive waste is directed towards practical applications. Titanate wasteform products we have developed or are developing are aimed at immobilization of: (a) tank wastes and sludges; (b) U-rich wastes from radioisotope production from reactor irradiation of UO2 targets; (c) Al-rich wastes arising from reprocessing of Al-clad fuels; (d) 99Tc; (e) high- Mo wastes arising from reprocessing of U-Mo fuels and (f) pa… more
Date: February 27, 2003
Creator: Vance, E. R.; Perera, D. S.; Stewart, M. W. A.; Begg, B. D.; Carter, M. L.; Day, R. A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Treatment of Produced Oil and Gas Waters With Surfactant-Modified Zeolite

Description: Co-produced water from the oil and gas industry accounts for a significant waste stream in the United States. It is by some estimates the largest single waste stream in the country, aside from nonhazardous industrial wastes. Characteristics of produced water include high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component, and chemicals added during the oil-production process. While most of the produced water is disposed via re… more
Date: November 1, 2003
Creator: Katz, Lynn E.; Bowman, R. S. & Sullivan, E. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Behavior of Holocarbons in Zeolitic Materials

Description: This report describes results on this grant over the 3 year period, 1999-2002. The emphasis of the work has continued to shift during 2001-2 from halocarbon adsorption in zeolites towards other separation processes in zeolites. These additional areas include (i) work on lithium-containing zeolites for non-cryogenic air separation, and (ii) the study of nickel phosphate molecular sieves for hydrogen storage. Nevertheless, they continued their experimental and computational work on halocarbons in… more
Date: December 8, 2003
Creator: Cheetham, Anthony K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Colloid-Facilitated Transport of Radionuclides Through the Vadose Zone

Description: We have completed the studies on reactions of minerals with caustic Hanford tank waste solutions. Systematic studies on the effects of different anions, cations, and the radionuclide Cs-137 were completed and technical manuscripts on these experiments were submitted for publication. The concentration of NaOH and the type of anion played the dominant roles in determining minerals formed. Increasing NaOH concentration and temperature enhanced the formation of feldspathoids; when NaOH concentratio… more
Date: June 1, 2003
Creator: Flury, Markus; Lichtner, Peter C. & McCarthy, John F.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The Chemistry, Crystallization, Physicochemical Properties and Behavior of Sodium Aluminosilicate Solid Phases: Final Report

Description: The synthesis of sodium aluminosilicate solids phases precipitated from NO{sub 2}/NO{sub 3}-free and NO{sub 2}/NO{sub 3}-rich liquors has been performed. Four sodium aluminosilicate precipitation products were formed. These are (1) X-ray/electron diffraction-indifferent amorphous phase; (2) crystalline zeolite A; (3)NO{sub 2}/NO{sub 3}-rich crystalline sodalite; and (4) NO{sub 2}/NO{sub 3}-rich crystalline cancrinite phase. Characterization of the physicochemical properties for these phases has… more
Date: March 12, 2003
Creator: Rosencrance, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Evaluation of Uranium Co-precipitations with Sodium Aluminosilicate Phases

Description: This paper describes batch laboratory experiments performed to evaluate uranium incorporation into aluminosilicate structures during synthesis. This research was conducted in response to plant problems related to the accumulation of uranium with aluminosilicates in low-level radioactive waste evaporators. We have found that conditions which favor precipitation of aluminosilicates also foster uranium solid precipitation, so it is difficult to attribute problems with uranium accumulation to say j… more
Date: June 24, 2003
Creator: Oji, L.N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Pultonium Colloid-Facilitated Transport in the Environment - Experimental and Transport Modeling Evidence for Plutonium Migration Mechanisms

Description: Natural inorganic colloids (< 1 micron particles) found in groundwater can sorb low-solubility actinides and may provide a pathway for transport in the subsurface. For example, Kerting et al found that Pu, associated with colloids fraction of the groundwater, was detected over 1 km away from the underground nuclear test at the Nevada Test Site (NTS) where it was originally deposited 28 years earlier. However, laboratory experiments have not identified the mechanisms by which Pu may sorb to c… more
Date: February 19, 2003
Creator: Zavarin, M.; Maxwell, R. M.; Kersting, A. B.; Zhao, P.; Sylwester, E. R.; Allen, P. G. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Colloid-Facilitated Transport of Low-Solubility Radionuclides: A Field, Experimental, and Modeling Investigation

Description: For the last several years, the Underground Test Area (UGTA) program has funded a series of studies carried out by scientists to investigate the role of colloids in facilitating the transport of low-solubility radionuclides in groundwater, specifically plutonium (Pu). Although the studies were carried out independently, the overarching goals of these studies has been to determine if colloids in groundwater at the NTS can and will transport low-solubility radionuclides such as Pu, define the geo… more
Date: February 1, 2003
Creator: Kersting, A. B.; Reimus, P. W.; Abdel-Fattah, A.; Allen, P. G.; Anghel, I.; Benedict, F. C. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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