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CONTAMINATION OF GROUNDWATER BY ORGANIC POLLUTANTS LEACHED FROM IN-SITU SPENT SHALE

Description: The potential for contamination of groundwater by organic pollutants leached from in-situ spent shale was studied in a series of laboratory leaching experiments. Both batch-mode and continuous-flow column experiments were conducted to study the leaching phenomenon. Experimental variables included retorting characteristics of spent shale, leaching time, initial quality of leach water, temperature of leach water, and particle size of spent shale. Several unique samples of spent shale were examined during the eaching experiments, including spent shale samples produced during combustion retorting, inert gas retorting, and combustion retorting employing recycle gas. The solid-phase organic carbon content of spent shale samples ranged from 0.2 to 3.9 percent by weight. Leachate derived from the batch-mode experiments was analyzed for organic carbon, organic nitrogen, phenols, and acid/base/netral fractions. The highest levels of organic carbon were detected in leachate derived from spent shale produced during either inert gas retorting or combstion retorting using recycle gas. The highest levels of phenols were observed in leachate obtained from spent shale produced during inert gas retorting; significant levels of organic nitrogen were also detected in various leachate samples. The most predominant organic fraction measured in leachate samples was the neutral fraction associated with spent shale produced during inert gas retorting. Batch-mode experimental results describing equilibrium conditions were analyzed according to the Freundlich and langmuir isotherm models. Those models were found to be appropriate for describing equilibrium relationships between leachate and spent shale produced during inert gas retorting. To a somewhat lesser extent, these same models were found to be appropriate for modeling equilibrium relationships involving combustion-retorted spent shale. A kinetic analysis of results derived from the continuous-flow column experiments was conducted in an attempt to identify a rate-controlling mass transfer mechanism. Internal diffusion appeared to be the most likely rate-limiting mechanism for leaching from combustion-retorted spent shale. In ...
Date: June 1, 1978
Creator: Amy, Gary L.
Partner: UNT Libraries Government Documents Department

Finite difference solution of the time dependent neutron group diffusion equations

Description: In this thesis two unrelated topics of reactor physics are examined: the prompt jump approximation and alternating direction checkerboard methods. In the prompt jump approximation it is assumed that the prompt and delayed neutrons in a nuclear reactor may be described mathematically as being instantaneously in equilibrium with each other. This approximation is applied to the spatially dependent neutron diffusion theory reactor kinetics model. Alternating direction checkerboard methods are a family of finite difference alternating direction methods which may be used to solve the multigroup, multidimension, time-dependent neutron diffusion equations. The reactor mesh grid is not swept line by line or point by point as in implicit or explicit alternating direction methods; instead, the reactor mesh grid may be thought of as a checkerboard in which all the ''red squares'' and '' black squares'' are treated successively. Two members of this family of methods, the ADC and NSADC methods, are at least as good as other alternating direction methods. It has been found that the accuracy of implicit and explicit alternating direction methods can be greatly improved by the application of an exponential transformation. This transformation is incompatible with checkerboard methods. Therefore, a new formulation of the exponential transformation has been developed which is compatible with checkerboard methods and at least as good as the former transformation for other alternating direction methods. (auth)
Date: August 1, 1975
Creator: Hendricks, J.S. & Henry, A.F.
Partner: UNT Libraries Government Documents Department

High statistics study of omega$sup 0$ production at 6 GeV/c

Description: The spin-projected cross sections for $omega$$sup 0$ production at 6 GeV/ c were measured in a counter-spark chamber experiment at the Zero Gradient Synchrotron of Argonne National Laboratory. Results are presented for a sample of 25,000 $omega$$sup 0$ events, and critical tests are shown for any residual background. The reaction is dominated by the s-channel natural-parity helicity one projection (rho$sub 11$ + rho/sub 1-1) dsigma/dt which shows a turnover in the forward direction and no strong dip at t = 0.6 (GeV/c)$sup 2$. The unnatural- parity helicity-zero cross section rho$sub 00$ dsigma/dt shows no forward turnover suggesting a sizeable helicity-nonflip contribution. Comparisons are made with the predictions of a Regge exchange model with absorptive corrections. (auth)
Date: January 1, 1975
Creator: Shaevitz, M.H.
Partner: UNT Libraries Government Documents Department

Finite element method for neutron diffusion problems in hexagonal geometry

Description: The use of the finite element method for solving two-dimensional static neutron diffusion problems in hexagonal reactor configurations is considered. It is investigated as a possible alternative to the low-order finite difference method. Various piecewise polynomial spaces are examined for their use in hexagonal problems. The central questions which arise in the design of these spaces are the degree of incompleteness permissible and the advantages of using a low-order space fine-mesh approach over that of a high-order space coarse-mesh one. There is also the question of the degree of smoothness required. Two schemes for the construction of spaces are described and a number of specific spaces, constructed with the questions outlined above in mind, are presented. They range from a complete non-Lagrangian, non-Hermite quadratic space to an incomplete ninth order space. Results are presented for two-dimensional problems typical of a small high temperature gas-cooled reactor. From the results it is concluded that the space used should at least include the complete linear one. Complete spaces are to be preferred to totally incomplete ones. Once function continuity is imposed any additional degree of smoothness is of secondary importance. For flux shapes typical of the small high temperature gas-cooled reactor the linear space fine-mesh alternative is to be preferred to the perturbation quadratic space coarse-mesh one and the low-order finite difference method is to be preferred over both finite element schemes. (auth)
Date: June 1, 1975
Creator: Wei, T.Y.C. & Hansen, K.F.
Partner: UNT Libraries Government Documents Department

Nucleus--nucleus total cross sections for light nuclei at 1.55 and 2.89 GeV/ C/nucleon

Description: Total cross sections have been measured for protons, deuterons, alphas, and $sup 12$C on hydrogen, deuterium, helium, and carbon targets at 1.55 and 2.89 GeV/c/nucleon using the ''good geometry'' transmission method. In addition, the inelastic cross sections and elastic slope parameters were measured for reactions initiated by deuterons, alphas, and $sup 12$C. The factorization relation sigma/ sub T/(AA) = sigma/sub T/(AB)$sup 2$/sigma/sub T/(BB) is violated for some of these reactions. The results generally agree with Glauber theory predictions except in their detailed energy behavior. It is found that sigma/sub T/ approximately equal to 144 (A/sub T//sup $sup 1$/$sub 3$/ + A/sub P//sup $sup 1$/ $sub 3$/ - 1.48)$sup 2$ and sigma/sub IN/ approximately equal to 78 (A/sub T//sup $sup 1$/$sub 3$/ + A/sub P//sup $sup 1$/$sub 3$/ - 1.25)$sup 2$, where A/sub T/(A/ sub P/) is the atomic mass number of the target (projectile) and the cross sections are given in mb. (auth)
Date: November 1, 1975
Creator: Jaros, J.A.
Partner: UNT Libraries Government Documents Department

Influence of microstructure on stress corrosion cracking of mild steel in synthetic caustic-nitrate nuclear waste solution

Description: The influence of alloy microstructure on stress corrosion cracking of mild steel in caustic-nitrate synthetic nuclear waste solutions was studied. An evaluation was made of the effect of heat treatment on a representative material (ASTM A 516 Grade 70) used in the construction of high activity radioactive waste storage tanks at Savannah River Plant. Several different microstructures were tested for susceptibility to stress corrosion cracking. Precracked fracture specimens loaded in either constant load or constant crack opening displacement were exposed to a variety of caustic-nitrate and nitrate solutions. Results were correlated with the mechanical and corrosion properties of the microstructures. Crack velocity and crack arrest stress intensity were found to be related to the yield strength of the steel microstructures. Fractographic evidence indicated pH depletion and corrosive crack tip chemistry conditions even in highly caustic solutions. Experimental results were compatible with crack growth by a strain- assisted anodic dissolution mechanism; however, hydrogen embrittlement also was considered possible. (auth)
Date: December 1, 1975
Creator: Sarafian, P.G.
Partner: UNT Libraries Government Documents Department

Oxygen potential of uranium--plutonium oxide as determined by controlled- atmosphere thermogravimetry

Description: The oxygen-to-metal atom ratio, or O/M, of solid solution uranium- plutonium oxide reactor fuel is a measure of the concentration of crystal defects in the oxide which affect many fuel properties, particularly, fuel oxygen potential. Fabrication of a high-temperature oxygen electrode, employing an electro-active tip of oxygen-deficient solid-state electrolyte, intended to confirm gaseous oxygen potentials is described. Uranium oxide and plutonium oxide O/M reference materials were prepared by in situ oxidation of high purity metals in the thermobalance. A solid solution uranium-plutonium oxide O/M reference material was prepared by alloying the uranium and plutonium metals in a yttrium oxide crucible at 1200$sup 0$C and oxidizing with moist He at 250$sup 0$C. The individual and solid solution oxides were isothermally equilibrated with controlled oxygen potentials between 800 and 1300$sup 0$C and the equilibrated O/ M ratios calculated with corrections for impurities and buoyancy effects. Use of a reference oxygen potential of -100 kcal/mol to produce an O/M of 2.000 is confirmed by these results. However, because of the lengthy equilibration times required for all oxides, use of the O/M reference materials rather than a reference oxygen potential is recommended for O/M analysis methods calibrations. (auth)
Date: October 1, 1975
Creator: Swanson, G.C.
Partner: UNT Libraries Government Documents Department

THE INTERACTION OF THE Eco RI RESTRICTION ENZYME FROM E.coli WITH NUCLEOTIDES

Description: The Eco R1 restriction enzyme can be shown to be inhibited by nucleotides which correspond to any part of its known site of phosphodiesterase activity. A series of di-, tetra-, and hexa-nucleotide fragments were synthesized and their effect on the activity of the enzyme upon superhelical Co1 E1 DNA studied. The inhibition caused by the individual mononucleotides were also studied. In general all the nucleotide fragments showed some form of interaction with the enzyme system. Tetranucleotides were stronger inhibitors than dinucleotides, which in turn were stronger inhibitors than the mononucleotides. Within each category of inhibitors, those containing the phosphodiester bond which is acted upon by the enzyme were the strongest inhibitors. Only those fragments which were consistent with the enzymes site of activity showed competitive inhibition kinetics. Nucleotides which do not fit within the site of phosphodiesterase activity show non-competitive inhibition kinetics.
Date: November 1, 1979
Creator: Hollis, Donald F.
Partner: UNT Libraries Government Documents Department

Analysis and Development of FACE Automatic Apparatus for Rapid Identification of Transuranium Isotopes

Description: A description of and operating manual for the FACE Automatic Apparatus has been written along with a documentation of the FACE machine operating program, to provide a user manual for the FACE Automatic Apparatus. In addition, FACE machine performance was investigated to improve transuranium throughput. Analysis of the causes of transuranium isotope loss was undertaken both chemical and radioactive. To lower radioactive loss, the dynamics of the most time consuming step of the FACE machine, the chromatographic column output droplet drying and flaming, in preparation of sample for alpha spectroscopy and counting, was investigated. A series of droplets were dried in an experimental apparatus demonstrating that droplets could be dried significantly faster through more intensie heating, enabling the FACE machine cycle to be shortened by 30-60 seconds. Proposals incorporating these ideas were provided for FACE machine development. The 66% chemical loss of product was analyzed and changes were proposed to reduce the radioisotopes product loss. An analysis of the chromatographic column was also provided. All operating steps in the FACE machine are described and analyzed to provide a complete guide, along with the proposals for machine improvement.
Date: September 1, 1978
Creator: Sebesta, E.H.
Partner: UNT Libraries Government Documents Department

ELECTROCHEMICAL MACHINING OF CARBIDES AND BORIDES

Description: The use of high rate anodic dissolution (electrochemical machining) for shaping titanium carbide, zirconium carbide, titanium boride and zirconium boride has been investigated in 2N potassium nitrate and 3N sodium chloride under current densities ranging from 20 to 120 A/cm{sup 2} (corresponding to cutting rates of 0.3 to 1.8 mm/min). The dissolution stoichiometry for all these materials is independent of the current density in the range 20 to 120 A/cm{sup 2}. Both titanium and zirconium appear to dissolve in the +4 state, boron in the +3 state and the weight loss measurements indicate that carbon is oxidized to CO and CO{sub 2}. The current voltage curves permit to establish that, over the entire current density and flow range investigated, dissolution occurs in the transpassive state. The surface roughness obtained on TiC and ZrC is within 3-5 {micro}m and is independent of current density, applied voltage or flow rate.
Date: July 1, 1978
Creator: Dissaux, Bernard Antoine; Muller, Rolf H. & Tobias, Charles W.
Partner: UNT Libraries Government Documents Department

REDUCTION OF NITRIC OXIDE BY CARBON MONOXIDE OVER A SILICA SUPPORTED PLATINUM CATALYST: INFRARED AND KINETIC STUDIES

Description: The reduction of nitric oxide by carbon monoxide over a 4.5 weight precent platinum catalyst supported on silica was studied at 300 C. Reaction rate data was obtained together with in situ infrared spectra of species on the catalyst surface. The kinetics of the system were found to exhibit two distinct trends, depending on the molar ratio of CO/NO in the reactor. For net reducing conditions (CO/NO> 1) the catalyst underwent a transient deactivation, the extent of which was dependent on the specific CO/NO ratio during reaction. Reactivation of the catalyst was obtained with both oxidizing and reducing pretreatments. For molar feed ratios of CO/NO less than one, carbon monoxide conversion was typically 95 to 100%, resulting in strongly oxidizing conditions over the catalyst. Under these conditions no deactivation was apparent. Infrared spectra recorded under reaction conditions revealed intense bands at 2075 and 2300 cm{sup -1} , which were identified as carbon monoxide adsorbed on Pt and Si-NCO, respectively. Isocyanate bands formed under reducing conditions were more intense and exhibited greater stability than those formed under oxidizing conditions. A reaction mechanism based on the dissociation of nitric oxide as the rate-limiting step was used to correlate nitric oxide reaction rates and nitrous oxide selectivities observed under reducing conditions. As part of this mechanism it is assumed that nitrous bxide is formed via a Langmuir-Hinshelwood process in which an adsorbed nitrogen atom reacts with an adsorbed nitric oxide molecule. The nitric oxide reaction rate was found to be first order in nitric oxide partial pressure, and inverse second order in carbon monoxide partial pressure. A mechanism is proposed to qualitatively explain the deactivation process observed under reducing conditions. The essential part of this mechanism is the formation of an isocyanate species on the Pt crystallites of the catalyst and the subsequent ...
Date: August 1, 1978
Creator: Lorimer, D.H.
Partner: UNT Libraries Government Documents Department

CARBON-13 NMR STUDIES OF LIQUID CRYSTALS

Description: High resolution, proton decoupled {sup 13}C nmr are observed for a series of neat nematic liquid crystals, the p-alkoxyazoxybenzenes, and a smectic-A liquid crystal, diethylazoxydibenzoate in a magnetic field of 23 kG. The (uniaxial) order parameters S = <P{sub 2}(cos{theta})> are found to be about 0.4 and 0.9 for the nematic and smectic-A phase respectively at the clearing points. The order parameter increases with decreasing temperature in the nematic phase but is constant, or nearly so, with temperature in the smectic-A phase. In the nematic series studied, the ordering exhibits an even-odd alternation along the series and qualitative agreement with a recent theory due to Marcelja is found. In both phases, the spectra show that the molecule rotates rapidly about its long axis. Tentative conclusions about molecular conformational motion and {sup 14}N spin relaxation are presented for both nematic and smectic-A phases. In the smectic-A phase, the sample is rotated about an axis perpendicular to H{sub 0} and the resulting spectra are discussed. The theory of observed chemical shifts in liquid crystals is treated in an appendix. Equations are derived which relate the nmr spectra of liquid-crystals to the order parameters. A model for the smectic-C phase due to Luz and Meiboom and Doane is described and lineshapes are determined on the basis of this model for special cases. Experiments on smectic-C liquid crystals are currently underway for comparison with the theory. Also treated in an appendix is the dependence of the order parameters on the molecular potential which give rise to the various degrees of order in the different liquid crystalline phases. To a good approximation the functional dependence of the order parameters on the molecular potential is shown to be a simple one in the limit of small tilt angle in the smectic-C phase.
Date: June 1, 1975
Creator: Allison, Stuart
Partner: UNT Libraries Government Documents Department

CARBON AND DEUTERIUM NUCLEAR MAGNETIC RESONANCE IN SOLIDS

Description: In Chapter I we present the results on a study of cross polarization dynamics, between protons and carbon-13 in adamantane, by the direct observation of the dilute, carbon-13, spins. These dynamics are an important consideration in the efficiency of proton enhancement double-resonance techniques and they also provide good experimental models for statistical theories of cross relaxation. In order to test these theories we present a comparison of the experimental and theoretical proton dipolar fluctuation correlation time {tau}{sub c}, which is experimentally 110 {+-} 15 {micro}sec and theoretically 122 {micro}sec for adamantane. These double resonance considerations provide the background for extensions to deuterium and double quantum effects discussed in Chapter II. In Chapter II an approach to high resolution nmr of deuterium in solids is described. The m = 1 {yields} -1 transition is excited by a double quantum process and the decay of coherence Q({tau}) is monitored. Fourier transformation yields a deuterium spectrum devoid of quadrupole splittings and broadening. If the deuterium nuclei are dilute and the protons are spin decoupled, the double-quantum spectrum is a high resolution one and yields information on the deuterium chemical shifts {Delta}{omega}. The relationship Q({tau}) {approx} cos 2{Delta}{omega}{tau} is checked and the technique is applied to a single crystal of oxalic acid dihydrate enriched to {approx} 10% in deuterium. The carboxyl and the water deuterium shifts are indeed resolved and the anisotropy of the carboxyl shielding tensor is estimated to be {Delta}{sigma} = 32 {+-} 3 ppm. A complete theoretical analysis is presented. The extension of cross relaxation techniques, both direct and indirect, to proton-deuterium double resonance is also described. The m = 1 {yields} -1 double quantum transition and the m = {+-} 1 {yields} 0 single quantum transitions may all be polarized and we present the derivation of the Hartmann-Hahn cross polarization ...
Date: July 1, 1976
Creator: Shattuck, Thomas Wayne
Partner: UNT Libraries Government Documents Department