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Thermal chemical-mechanical reactive flow model of shock initiation in solid explosives

Description: The three dimensional Arbitrary Lagrange Eulerian hydrodynamic computer code ALE3D with fully coupled thermal-chemical-mechanical material models provides the framework for the development of a physically realistic model of shock initiation and detonation of solid explosives. The processes of hot spot formation during shock compression, subsequent ignition of reaction or failure to react, growth of reaction in individual hot spots, and coalescence of reacting hot spots during the transition to detonation can now be modeled using Arrhenius chemical kinetic rate laws and heat transfer to propagate the reactive flow. This paper discusses the growth rates of reacting hot spots in HMX and TATB and their coalescence during shock to detonation transition. Hot spot deflagration rates are found to be fast enough to consume explosive particles less than 10 mm in diameter during typical shock duration times, but larger particles must fragment and create more reactive surface area in order to be rapidly consumed.
Date: August 26, 1998
Creator: Nicholls, A. L., III & Tarver, C. M.
Partner: UNT Libraries Government Documents Department

Oxidation of coal and coal pyrite mechanisms and influence on surface characteristics. Final report

Description: Coal oxidation has been studies extensively in previous work. However, there is still no general agreement concerning the mechanisms of oxidation. Moreover, the oxidation behavior of coal and mineral matter have generally been regarded as separate processed. There is appreciable evidence that organic and inorganic oxidation process are actually coupled, consequently the changes in their surface properties induced by oxidation are difficult to predict. This makes the effectively of coal cleaning processes highly sensitive to the extent of weathering and oxidation that the coal has experienced. The objective of this research was to investigate the oxidation behavior of coal and coal pyrite, and to correlate the intrinsic physical and chemical properties of these minerals, along with changes resulting from oxidation, with these surface properties that would influence the behavior in physical cleaning processes.
Date: January 26, 1996
Creator: Doyle, F.M.
Partner: UNT Libraries Government Documents Department

Thermal decomposition of UO{sub 3}-2H{sub 2}0

Description: The first part of the report summarizes the literature data regarding the uranium trioxide water system. In the second part, the experimental aspects are presented. An experimental program has been set up to determine the steps and species involved in decomposition of uranium oxide di-hydrate. Particular attention has been paid to determine both loss of free water (moisture in the fuel) and loss of chemically bound water (decomposition of hydrates). The influence of water pressure on decomposition has been taken into account.
Date: February 26, 1998
Creator: Flament, T.A.
Partner: UNT Libraries Government Documents Department

Workshop for coordinating South Carolina`s pre-college systemic initiatives

Description: The goal of the South Carolina Statewide Systemic Initiative (SC SSI) is to provide quality and effective learning experiences in science and mathematics to all people of South Carolina by affecting systemic change. To accomplish this goal, South Carolina must: (1) coordinate actions among many partners for science and mathematics change; (2) place the instruments of change into the hands of the effectors of change - teachers and schools; and (3) galvanize the support of policy makers, parents, and local communities for change. The SC SSI proposes to establish a network of 13 regional mathematics and science HUBs. The central idea of this plan is the accumulation of Teacher Leaders at each HUB who are prepared in special Curriculum Leadership Institutes to assist other teachers and schools. The HUB becomes a regional nexus for delivering services to schools who request assistance by matching schools with Teacher Leaders. Other initiatives such as the use of new student performance assessments, the integration of instructional technologies into the curriculum, a pilot preservice program, and Family Math and Family Science will be bundled together through the Teacher Leaders in the HUBs. Concurrent policy changes at the state level in teacher and administrator certification and recertification requirements, school regulations and accountability, and the student performance assessment system will enable teachers and schools to support instructional practices that model South Carolina`s new state Curriculum Frameworks in Mathematics and Science.
Date: March 26, 1997
Partner: UNT Libraries Government Documents Department

Ion and Neutral Species in C(2)F(6) and CHF(3) Dielectric Etch Discharges

Description: Relative concentrations of reactive ions, neutral radicals, resist and substrate etch products have been measured in dielectric etch chemistries using an uncollided beam mass spectrometer / ion extractor from Hiden Analytical. Analysis techniques employed include both electron impact ionization and dissociative ionization of neutral gas, and potential bias extraction of positive ions from the reactor discharge volume. Measurements were made in C{sub 2}F{sub 6} and CHF{sub 3} discharges in an inductively coupled plasma (ICP-GEC) research reactor operating with power densities, pressures, gas compositions and wafer materials typical of those found in etch processing tools. Wafer substrates investigated included blanket silicon wafers and silicon wafers with varying amounts of photo-resist coverage of the surface (20%, 80% and 100%). In C{sub 2}F{sub 6} discharges CF{sub 3}{sup +} was consistently the dominant fluorocarbon ion present, in agreement with published cross sections for dissociative ionization [ 1,2.3,4.5,6]. Smaller concentrations of CF+, CF{sub 2}{sup -}, and C{sub 2}F{sub 5}{sup +}, were also observed, though the dissociative ionization production of C{sub 2}F{sub 5}{sup +} was a factor of five smaller than would be expected from published cross section values. The presence of photo-resist, even in small amounts, was found to produce marked changes in the discharge composition. For example in C{sub 2}F{sub 6} discharges, concentrations of SiF{sub x} etch products relative to concentrations of C{sub x}F{sub y} species were notably diminished and larger concentrations of water vapor were observed when resist was present. In CHF{sub 3} discharges, CF{sub 3}{sup +} and CHF{sub 2}{sup +} were found to be the main species present, along with smaller concentrations of CF{sub 2}{sup +}, CF{sup +}, CHF{sup +}, CH{sup +} and F{sup -}.
Date: January 26, 1999
Creator: Hebner, G.; Jayaraman, R.P. & McGrath, R.T.
Partner: UNT Libraries Government Documents Department

The transuranium elements: From neptunium and plutonium to element 112

Description: Beginning in the 1930`s, both chemists and physicists became interested in synthesizing new artificial elements. The first transuranium element, Np, was synthesized in 1940. Over the past six decades, 20 transuranium elements have been produced. A review of the synthesis is given. The procedure of naming the heavy elements is also discussed. It appears feasible to produce elements 113 and 114. With the Berkeley Gas-filled Separator, it should be possible to reach the superheavy elements in the region of the spherical Z=114 shell, but with fewer neutrons than the N=184 spherical shell. 57 refs, 6 figs.
Date: July 26, 1996
Creator: Hoffman, D.C.
Partner: UNT Libraries Government Documents Department


Description: Three saltcake samples taken from Tank 41H on July 12-13, 1993 have been analyzed for chemical and radiochemical content, identification of crystalline phases, and solubility in inhibited water and compared to the results for the earlier sample taken in March 1993.
Date: January 26, 1994
Creator: Hobbs, D.T. & Coleman, C.J.
Partner: UNT Libraries Government Documents Department

Anion exchange separation of plutonium from various solutions stored at PFP

Description: Nitrate anion exchange has been demonstrated to effectively separate plutonium from other metals in solution. Specific PFP solutions types will be tested to determine if they are suitable candidates for anion exchange. Reillex HPQ resin is used to separate Pu(IV) from nitric acid solutions.
Date: February 26, 1996
Creator: Jones, S.A.
Partner: UNT Libraries Government Documents Department

Research on computed tomography reconstructions from one or two radiographs: A report and the application to FXR radiography

Description: This report documents some cooperative research into volumetric image reconstruction from single radiographs. Imaging dynamic events is the most important application for this type of work, but the techniques have possible extensions. Two general objectives guide this work. The first objective is to gain an understanding of the assumptions and limitations of single-view methods for representing internal features. Second, we endeavor to obtain and/or develop techniques for performing image reconstructions with FXR radiographs. If possible, we seek to obtain some quantitative measure of the accuracy of this class of image reconstructions in two respects: (i) in terms of the dimensional accuracy of feature boundaries, and (ii) as pertains to the accuracy of the voxel intensities. Dynamic events are not always self-calibrating, and it is important to establish the reconstruction accuracy of single-view methods for placing bounds on the kinds of conclusions which can be advanced from single-view reconstructed images. Computed tomographic image reconstructions provide dimensional detail of internal structures of objects and provide a measure of the per-voxel attenuation of material in the object. When assumptions behind a reconstruction algorithm are not satisfied, or are satisfied in a limited way, the accuracy of the reconstructed image is compromised. It is the goal of Cr analysis to discern the {open_quotes}real{close_quotes} features of the internals of an object in the midst of a certain level of artifactual content in the image. By understanding the ways in which CT reconstructions from a single radiograph can produce misleading results we hope to develop some measure of the benefits and limitations of single view techniques. 31 refs., 20 figs.
Date: January 26, 1995
Creator: Back, N.; Schneberk, D.; McMillan, C.; Azevedo, S. & Gorvad, M.
Partner: UNT Libraries Government Documents Department

X-ray, K-edge measurement of uranium concentration in reactor fuel plates

Description: Under the Characterization, Monitoring, and Sensor Technology Crosscutting Program, the authors have designed and built a K-edge heavy-metal detector that measures the level of heavy-metal content inside closed containers in a nondestructive, non-invasive way. They have applied this technique to measurement of the amount of uranium in stacks of reactor fuel plates containing nuclear materials of different enrichments and alloys. They have obtained good agreement with expected uranium concentrations ranging from 60 mg/cm{sup 2} to 3,000 mg/cm{sup 2}, and have demonstrated that the instrument can operate in a high radiation field (> 200 mR/hr).
Date: November 26, 1997
Creator: Jensen, T.; Aljundi, T.; Whitmore, C.; Zhong, H. & Gray, J.N.
Partner: UNT Libraries Government Documents Department

Effect of tetralin on polymer degradation in solution. [Quarterly report, January--March 1995]

Description: The effect of a hydrogen-donor solvent (tetralin) on the thermal degradation of poly(styrene-allyl alcohol) in solution was investigated in a steady-state tubular flow reactor at 1000 psig (6.8 MPa), at various tetralin concentrations (0--50%), polymer concentrations (1--4 g/L), and temperatures (130--200 C). The molecular weight distributions of the effluent at each condition were examined as a function of residence time by gel permeation chromatography. In the presence of tetralin, the polymer degrades by deploymerization to specific low molecular weight compounds and by random chain scission. No reaction was observed in the solvent 1-butanol in the absence of tetralin. The experimental data were interpreted with a rate expression first-order in polymer concentration based on continuous mixture kinetics, and rate coefficients were determined for the specific and random degradation processes. Activation energies were in the range of 5--10 kcal/mol for specific degradation and 33 kcal/mol for the random degradation process. A plot of rate coefficients versus tetralin concentration indicates a first-order rate at low tetralin concentrations and a zero-order dependence at high tetralin concentrations.
Date: April 26, 1995
Creator: Madras, G.; Smith, J.M. & McCoy, B.J.
Partner: UNT Libraries Government Documents Department

Studies of supported hydrodesulfurization catalysts. Final technical report

Description: This report describes a series of studies on the following: Mo/titania and Mo/alumina catalysts for thiophene hydrodesulfurization; absorption of metal oxyanion on alumina; particle size effects for Co/silica catalyst for CO hydrogenation; correlation of Mo oxidation states with benzene hydrogenation activity; factor analysis for curve fitting Mo ESCA spectra; and quantitative Raman and ESCA characterization of W/titania catalysts. 27 refs.
Date: October 26, 1995
Creator: Hercules, D. M.
Partner: UNT Libraries Government Documents Department

An experimental method for investigating phase transformations in the heat affected zone of welds using synchrotron radiation

Description: Although welding is an established technology used in many industrial settings, it is least understand terms of the phases that actually exist, the variation of their spatial disposition with time, and the rate of transformation from one phase to another at various thermal coordinates in the vicinity of the weld. With the availability of high flux and, more recently, high brightness synchrotron x-radiation sources, a number of diffraction and spectroscopic methods have been developed for structural characterization with improved spatial and temporal resolutions to enable in-situ measurements of phases under extreme temperature, pressure and other processing conditions not readily accessible with conventional sources. This paper describes the application of spatially resolved x-ray diffraction (SRXRD) for in-situ investigations of phase transformations in the heat affected zone (HAZ) of fusion welds. Results are presented for gas tungsten (GTA) welds in commercially pure titanium that show the existence of the high temperature bcc {beta}-phase in a 3.3 {plus_minus} 0.3 mm wide HA band adjacent to the liquid weld pool. Phase concentration profiles derived from the SRXRD data further show the co-existence of both the low temperature hcp ({alpha}-phase and the {beta}-phase in the partially, transformed region of the HA. These results represent the first direct observations of solid state phase transformations and mapping of phase boundaries in fusion welds. SRXRD experiments of this type are needed as experimental input for modeling of kinetics of phase transformations and microstructural evolution under the highly non-isothermal conditions produced during welding.
Date: May 26, 1995
Creator: Elmer, J.W.; Wong, J.; Froba, M.; Waide, P.A. & Larson, E.M.
Partner: UNT Libraries Government Documents Department

Tank 241-BY-103 headspace gas and vapor characterization results for samples collected in May 1994 and November 1994

Description: Significant changes have been made to all of the original vapor characterization reports. This report documents specific headspace gas and vapor characterization results for all vapor sampling events to date. In addition, changes have been made to the original vapor reports to qualify the data based on quality assurance issues associated with the performing laboratories
Date: September 26, 1995
Creator: Bratzel, D.R.
Partner: UNT Libraries Government Documents Department

Pion correlations as a function of atomic mass in heavy ion collisions

Description: The method of two pion interferometry was used to obtain source-size and lifetime parameters for the pions produced in heavy ion collisions. The systems used were 1.70 {center dot} A GeV {sup 56}Fe + Fe, 1.82 {center dot} A GeV {sup 40}Ar + KCl and 1.54 {center dot} A GeV {sup 93}Nb + Nb, allowing for a search for dependences on the atomic number. Two acceptances (centered, in the lab., at {approximately} 0{degrees} and 45{degrees}) were used for each system, allowing a search for dependences on the viewing angle. The correlation functions were calculated by comparing the data samples to background (or reference) samples made using the method of event mixing, where pions from different events are combined to produce a data sample in which the Bose-Einstein correlation effect is absent. The effect of the correlation function on the background samples is calculated, and a method for weighting the events to remove the residual correlation effect is presented. The effect of the spectrometer design on the measured correlation functions is discussed, as are methods for correcting for these effects during the data analysis. 58 refs., 39 figs., 18 tabs.
Date: November 26, 1989
Creator: Chacon, A.D.
Partner: UNT Libraries Government Documents Department

The hydrothermal stability of cement sealing materials in the potential Yucca Mountain high level nuclear waste repository

Description: Cementitious materials, together with other materials, are being considered to seal a potential repository at Yucca Mountain. A concern with cementitious materials is the chemical and mineralogic changes that may occur as these materials age while in contact with local ground waters. A combined theoretical and experimental approach was taken to determine the ability to theoretically predict mineralogic changes. The cementitious material selected for study has a relatively low Ca:Si ratio approaching that of the mineral tobermorite. Samples were treated hydrothermally at 200{degrees}C with water similar to that obtained from the J-13 well on the Nevada Test Site. Post-test solutions were analyzed for pH as well as dissolved K, Na, Ca, Al, and Si. Solid phases formed during these experiments were characterized by scanning electron microscopy and X- ray diffraction. These findings were compared with predictions made by the geochemical modeling code EQ3NR/E06. It was generally found that there was good agreement between predicted and experimental results.
Date: November 26, 1991
Creator: Krumhansl, J.L.; Hinkebein, T.E. & Myers, J.
Partner: UNT Libraries Government Documents Department