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Evaluation of need for integral fuel oxidation tests

Description: This document establishes the need for an integral fuel oxidation test which can give confidence to the predictions made by the OXIDE computer code for fuel and core damage during water ingress events in the Modular High Temperature Gas Cooled Reactor (MHTGR). This testing will provide clear engineering evidence to demonstrate that the core of the MHTGR can survive a moisture ingress incident with minimum investment risk and without danger to the reactor personnel or to the public. In particular, these tests will determine the degree of particle debonding and compact stack densification as a function of the fractional compact matrix burnoff. Also included in the document is a description of the proposed tests, and, a test matrix of the planned experiments. 3 refs., 1 fig., 1 tab.
Date: February 1, 1987
Creator: Montgomery, F.C.
Partner: UNT Libraries Government Documents Department

Research in chemical kinetics. Annual report

Description: Accomplishments to date are described for the four projects which make up this investigation. The project titles are: (1) photochemistry of phosphine as studied by FTIR spectroscopy; (2) photolytic studies with radioactive tracers; (3) heterogeneous atmospheric reactions; and (4) reactions of tritium, {sup 38}Cl and {sup 18}F from nuclear recoil. Details of the study and results are presented for the first two projects.
Date: December 31, 1986
Creator: Rowland, F. S.
Partner: UNT Libraries Government Documents Department

Leach testing of waste forms: interrelationship of ISO- and MCC-type tests

Description: Leach testing experiments were conducted on SYNROC-D material to examine the parameters which affect leaching results and to measure the activation energy for leaching of elements from SYNROC-D. Measured leach rates were found to be controlled by precipitation of insoluble phases for those tests where the sample surface area to volume of leachant (SA/V) multiplied by leaching time (t) exceeded 0.3 cm{sup -1}d for leach tests at 90{sup 0}C. In these cases the apparent activation energy for leaching was approximately 10 kcal/mole based on Na and Si data. For leach tests at 90{sup 0}C with (SA/V)(t) less than 0.2 cm{sup -1}d, the activation energy for Na and Si dissolution was 18.5 kcal/mole for sample S29 and 14.5 kcal/mole for sample LS04. These activation energies are in agreement with values reported by Tole and Lasaga (1981) for nepheline dissolution. The effect of sample geometry was investigated by leaching a series of crushed samples of different grain size. The results support the view that geometric surface area should be used in leach rate calculations rather than gas adsorption BET surface area. Comparison of results on S29 leaching of crushed samples and monoliths show that data from MCC-1 and ISO type leach tests may be directly compared when the data are examined at constant (SA/V)(t).
Date: May 14, 1982
Creator: Oversby, V.M.
Partner: UNT Libraries Government Documents Department

Assessment report on the kinetics of radionuclide adsorption on Yucca Mountain tuff

Description: The kinetics of sorption was measured by observing the uptake of radionuclides by tuff wafers and crushed tuff as a function of time. In addition, the broadening of breakthrough curves for cations eluted through crushed-tuff columns was interpreted in terms of adsorption kinetics. The results of these measurements are consistent with a diffusion-limited adsorption mechanism for simple cations, such as strontium, cesium, and barium. The adsorption kinetics for these simple cations is sufficiently fast so that equilibrium can be assumed for the retardation of these chemical species in the groundwater velocities that would be reasonable for most release scenarios. The actinides, in particular plutonium, exhibited a slow time dependence for adsorption. 23 refs., 61 figs., 12 tabs.
Date: July 1, 1987
Creator: Rundberg, R.S.
Partner: UNT Libraries Government Documents Department

Plan for waste package environment for NNWSI [Nevada Nuclear Waste Storage Investigations]

Description: The purpose and objective of the Waste Package Environment task is to establish and characterize the environmental processes affecting the near-field repository host rock after waste package emplacement. These processes, which reflect the perturbation induces in the environment by engineering effects and by the waste package decay heat and radiation, will influence chemical, mineralogical and hydrological features of the environment. The thermal and radiation output of the waste packages will change with time, resulting in an environment in which the chemical, mineralogical and physical attributes may also change through time. To assure that waste package design considerations reflect the characteristics of this evolving environment, it is necessary to determine the range of conditions that may develop in the pre- and post-emplacement waste package environment. To assure that the emplacement configurations do not compromise the lifetime of the repository or the waste packages, the design of the emplacement configuration must also consider the environmental features. Recognition of these requirements resulted in the development of the issue an information needs. 20 refs.
Date: February 1, 1988
Creator: Glassley, W.E.
Partner: UNT Libraries Government Documents Department

ZPPR progress report: September 1988--December 1988

Description: Further results are presented from the JUPITER-III program. Calculation models and k-effective results are given for the three configurations of the large, homogeneous assembly ZPPR-18. Reaction rate results, including sodium activation are given for ZPPR-18A. Also included are spatial decoupling results from ZPPR-18. As a successor to JUPITER-III, the Io program investigated the effects of uranium fuel distribution in mixed uranium and plutonium fueled assemblies. The ZPPR-19A and 19B assemblies which made up the Io program are described.
Date: January 20, 1989
Creator: Brumbach, S.B. & Collins, P.J.
Partner: UNT Libraries Government Documents Department

Preliminary results on the hydrolysis and carbonate complexation of dioxoplutonium(V)

Description: The hydrolysis and carbonate complexation reactions of dioxoplutonium (V) were studied in near neutral aqueous systems. These experiments involved the addition of hydroxide or carbonate to Pu(V) in a perchorate medium. Change in the electronic adsorption spectra provided information about the chemical properties of Pu(V). The results indicate the Pu(V) does not hydrolyze below pH 7.15. In the carbonate complexation studies, log {beta}{sub 11} was measured to be 4.4 +- 0.7. 5 figs., 3 tabs.
Date: November 1, 1987
Creator: Bennett, D.A.; Hoffman, D.C.; Nitsche, H. & Silva, R.J.
Partner: UNT Libraries Government Documents Department

FFTF (Fast Flux Test Facility) Reactor Characterization Program: Absolute Fission-rate Measurements

Description: Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, {sup 237}Np, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.
Date: May 1, 1981
Creator: Fuller, J.L.; Gilliam, D.M.; Grundl, J.A.; Rawlins, J.A. & Daughtry, J.W.
Partner: UNT Libraries Government Documents Department

Rate of Pu(IV) polymer formation in nitric acid solutions. A parametric study

Description: The kinetics of Pu(IV) polymer formation has been examined with the intent of developing a simple mathematical equation that would predict the appearance of polymer. The fundamental polymerization rate has been found to be dependent on [Pu(IV)]{sup 1} {sup 2} and [HNO{sub 3}]{sup -6}. The activation energy for polymer formation is real temperature dependent, varying from 66.9 kJ/mol (16 kcal/mol) at 25{sup 0}C to 150.5 kJ/mol (36 kcal/mol) at 105{sup 0}C. These relationships have guided the developement of an empirical model that gives time to form 2% polymer in hours, t = [Pu/sub T/]/sup a/[HNO{sub 3}]/sup b/ Ae/sup c/T/, where a = -1.6, b = 4.6, c = 12.300 K, and A = 7.66 x 10{sup -16} h M{sup -3}; [Pu/sub T/] is the total plutonium concentration, mol/L; and [HNO{sub 3}] is the makeup nitric acid concentration, mol/L. 11 references, 26 figures, 1 table.
Date: July 1, 1984
Creator: Toth, L.M. & Osborne, M.M.
Partner: UNT Libraries Government Documents Department

Corrosion processes of austenitic stainless steels and copper-based materials in gamma-irradiated aqueous environments

Description: The US Department of Energy is evaluating a site located at Yucca Mountain in Nye County, Nevada, as a potential high-level nuclear waste repository. The rock at the proposed repository horizon (above the water table) is densely welded, devitrified tuff, and the fluid environment in the repository is expected to be primarily air-steam. A more severe environment would be present in the unlikely case of intrusion of vadose groundwater into the repository site. For this repository location, austenitic stainless steels and copper-based materials are under consideration for waste container fabrication. This study focuses on the effects of gamma irradiation on the electrochemical mechanisms of corrosion for the prospective waste container materials. The radiolytic production of such species as hydrogen peroxide and nitric acid are shown to exert an influence on corrosion mechanisms and kinetics.
Date: September 1, 1985
Creator: Glass, R.S.
Partner: UNT Libraries Government Documents Department

Polymerization of Pu(IV) in aqueous nitric acid solutions

Description: The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to establish the influence of large UO{sub 2}(NO{sub 3}){sub 2} concentrations on the polymerization rates and, more generally, to review the influence of the major parameters on the polymer reaction. Typically, experiments have been performed at 50{sup 0}C and with 0.05 M Pu in nitric acid solutions that vary in acidity from 0.07 to 0.4 M. An induction period usually precedes the polymer growth stage during which time nucleation of primary hydrolysis products occurs. Uranyl nitrate retards the polymerization reaction by approximately 35% in spite of the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation, expressed as d(percent polymer)/dt, has been shown to depend on the total plutonium concentration in reactions where the Pu(IV) concentration remained constant; and it is therefore suggested that the polymer reaction rate is not first order with respect to the concentration of plutonium as was previously thought. It has been shown further that accurate acid determinations on stock reagents are essential in order to obtain reliable polymerization experiments. Satisfactory procedures for these analyses did not exist, so appropriate modifications to the iodate precipitation methods were developed. The most ideal plutonium reagent material has been shown to be crystalline Pu(IV) nitrate because it can be added directly to acid solutions without the occurrence of unintentional hydrolysis reactions.
Date: October 1, 1980
Creator: Toth, L.M.; Friedman, H.A. & Osborne, M.M.
Partner: UNT Libraries Government Documents Department

Disproportionation and polymerization of plutonium(IV) in dilute aqueous solutions

Description: The rates of polymerization and disproportionation of Pu(IV) have been studied using low concentrations: (1.7 - 10) x 10{sup -}M Pu, (0.8 - 12) x 10{sup -}M HCl and 0.0iM ionic strength. Osmium(II) complexes such as the tris-4,4`-2,2`-bipyridine complex were found to react rapidly with Pu(IV) but very slowly, if at all, with Pu(IV) polymer, Pu(III), or Pu(V). Thus, it is possible to determine unreacted Pu(IV) in the presence of rection products by using Os(II) complexes. Disproportionation reaction products, Pu(III) and Pu(V), were determined using their reactions with Ce(IV) sulfate. We find -d[Pu(IV)]/dt = k`[Pu(IV)]{sup 2} at constant pH. Log k` varies from about 4.25 at pH 3 to about 7.0 at pH 4.1 (units for k` are M{sup -1}min{sup -1}). The [H{sup +}] dependence varies from about -2 to -3 over the pH range studied. The measured rate is the sum of those for polymerization and disproportionation; the latter reaction amounts to about 75% of the total at pH 3 and 20% at pH 4. The second-order rate constants for disproportionation are very much larger than expected on the basis of extrapolation from 0.2 to 1.0M HC10{sub 4} solutions. The products of the reaction do not affect the rate, but U(VI), aged Pu(IV) polymer, and CO{sub 2} increase the rate.
Date: December 31, 1983
Creator: Newton, T.W. & Rundberg, V.L.
Partner: UNT Libraries Government Documents Department

Transport and reaction kinetics at the glass:solution interface region: Results of repository-oriented leaching experiments

Description: Repository-oriented leaching experiments involving Savannah River Laboratory (SRL) 165 type glass under a {gamma}-radiation field (1 = 0.2 x 10{sup 4} R/h) have been performed by the Nevada Nuclear Waste Storage Investigations (NNWSI) project. In this communication, we discuss glass surface analyses obtained by SEM, nuclear resonance profiling, and SIMS together with leachate solution data in relation to a mechanism that couples diffusion, hydrolysis (etching and gelation), and precipitation to qualitatively describe the release of different glass components to the leachant solutions. The release of mobile (e.g., Li) and partly mobile (e.g., B) species is controlled primarily by interdiffusion with water species across the interdiffusion zone. Glass components that are immobile in the interdiffusion zone are released to the solution by etching. For prediction of long-term steady-state concentrations of glass components with low solubility, the relative rates of release from the glass and secondary mineral precipitation must be taken into account.
Date: December 31, 1986
Creator: Abrajano, T.A. Jr. & Bates, J.K.
Partner: UNT Libraries Government Documents Department

In-situ observation of the alpha/beta cristobalite transition using high voltage electron microscopy

Description: A high temperature water vapor phase is expected to persist in the vicinity of high level radioactive waste packages for several hundreds of years. The authors have begun an investigation of the structural and chemical effects of water on cristobalite because of its abundance in the near field environment. A high voltage transmission electron microscope (HVEM) investigation of bulk synthesized {alpha}-cristobalite to be used in single phase dissolution and precipitation kinetics experiments revealed the presence {beta}-cristobalite, quartz and amorphous silica, in addition to {alpha}-cristobalite. Consequently, this apparent metastable persistence of {beta}-cristobalite and amorphous silica during the synthesis of {alpha}-cristobalite was investigated using a heating stage and an environmental cell installed in the HVEM that allowed the introduction of either dry CO{sub 2} or a CO{sub 2} + H{sub 2}O vapor. Preliminary electron diffraction evidence suggests that the presence of water vapor affected the {alpha}-{beta} transition temperature. Water vapor may also be responsible for the development of an amorphous silica phase at the transition that may persist over an interval of several tens of degrees. The amorphous phase was not documented during the dry heating experiments. 20 refs., 7 figs., 5 tabs.
Date: October 1, 1989
Creator: Meike, A. & Glassley, W.
Partner: UNT Libraries Government Documents Department

Photodecomposition of energetic nitro compounds

Description: The photodecomposition of energetic nitrocompounds depends on the excitation energy, the light intensity which determines the mono-, bi- or multiphotonic character of the initial process and their gaseous, liquid or solid state. The initial processes of the photodecomposition of nitromethane and nitroalcanes are reviewed and their relevance to the initiation of energetic nitrocompounds detonation is discussed. The case of nitramines (dimethylnitramine and tutorial) is also briefly introduced.
Date: March 14, 1989
Creator: Mialocq, J.C.
Partner: UNT Libraries Government Documents Department

Fundamental study of the mechanism and kinetics of cellulose hydrolysis by acids and enzymes. Final report, June 1, 1978-January 31, 1981

Description: There are three basic enzymes (e.g., endoglucanase (C/sub x/), exoglucanase (C/sub 1/) and cellobiase) comprising the majority of extracellular cellulase enzymes produced by the cellulolytic mycelial fungi, Trichoderma reesei, and other cellulolytic microorganisms. The enzymes exhibited different mode of actions in respect to the hydrolysis of cellulose and cellulose derived oligosaccharides. In combination, these enzymes complimented each other to hydrolyze cellulose to its basic constituent, glucose. The kinetics of cellobiase were developed on the basis of applying the pseudo-steady state assumption to hydrolyze cellobiose to glucose. The results indicated that cellobiase was subjected to end-product inhibition by glucose. The kinetic modeling of exoglucanase (C/sub 1/) with respect to cellodextrins was studied. Both glucose and cellobiose were found to be inhibitors of this enzyme with cellobiose being a stronger inhibitor than glucose. Similarly, endoglucanase (C/sub x/) is subject to end-product inhibition by glucose. Crystallinity of the cellulose affects the rate of hydrolysis by cellulases. Hence, the changes in crystallinity of cellulose in relation to chemical pretreatment and enzyme hydrolysis was compared. The study of cellulase biosynthesis resulted in the conclusion that exo- and endo-glucanases are co-induced while cellobiase is synthesized independent of the other two enzymes. The multiplicity of cellulase enzymes are the end results of post-translational modification during and/or after the secretion of enzymes into growth environment.
Date: February 1, 1981
Creator: Gong, C.S. & Chang, M.
Partner: UNT Libraries Government Documents Department

Heterogeneous kinetics of coal gasification. Quarterly technical progress report, 1 May 1982-31 July 1982. [Equipment design]

Description: During the reporting period significant progress was made on two fronts: (1) the steam addition system for transient steam-char kinetic experiments; and (2) the automated data acquisition system for rapid mass programming (control) of the mass spectrometer and data logging. Steam Addition System: Although it is a relatively straightforward matter to produce steam for the reactor, we found that it is quite a challenge to develop a system capable of maintaining a steady and accurately-known flow rate of steam-argon mixtures at high pressure and temperature in alternate flow circuits (i.e., the reactor and purge lines), while simultaneously protecting downstream valving and instrumentation. Thus, the scheme originally proposed has been modified to eliminate potential operating problems associated with the preliminary design. Automated Data Acquisition System: Although the CO/sub 2/ gasification data were obtained manually, the ultimate objective of the project to develop a quantitative understanding of the complete gasification rate process in the complex synthesis gas milieux calls for automated programming (control) of the mass spectrometer. In addition, the current mass spectrometer signal processing technique requires the use of a lock-in amplifier to extract the modulated portion of the total signal due to the beam species only, in an analog mode. In order to allow fast scanning of a number of species, the characteristic dwell time required by the lock-in amplifier on a particular mass peak must be decreased. These requirements are being met by implementing automated mass programming and data collection, and direct digital, phase-sensitive pulse counting.
Date: August 1, 1982
Creator: Calo, J.M.
Partner: UNT Libraries Government Documents Department

Development of processes for the production of solar grade silicon from halides and alkali metals. Phase II. Fourth quarterly report, 1 July-30 September 1980

Description: The objective of this program is to characterize the kinetics and mechanism of the formation and growth of silicon particles from the decomposition of silane at high temperatures. The experiments are aimed at determining the rates at which gas-phase species form silicon particle precursors, the time required for silane decomposition to produce silicon particles, and the competing rate of growth of silicon seed particles injected into a decomposing silane environment. An AeroChem high-temperature fast-flow reactor (HTFFR) was modified to study the decomposition of silane. Experiments are being performed at pressures from 5-760 Torr, temperatures from 600 to 1300/sup 0/C, and average gas velocities of 1-100 m s/sup -1/ (i.e., reaction times from about 0 to 300 ms). A cooled inlet is used to inject room temperature silane into any part of the uniform temperature zone of the HTFFR and a fluidized bed feed system will be used to inject silicon seed particles. The basic experiment consists of varying the position of the cooled inlet and measuring scattered light intensity in the observation plane to determine the particle size as a function of time available for silane decomposition. The techniques under consideration to measure average particle density and particle size distribution are turbidity, 90/sup 0/ scattering, polarization, forward scattering, and Mie resonances. The apparatus has been assembled and tested. Preliminary observations of turbidity and 90/sup 0/ scattering on Si particles formed from SiH/sub 4/ decomposition have been made. These observations indicate that the apparatus and optical systems are capable of providing the detailed particle density and size measurements necessary to describe the SiH/sub 4/-to-particle kinetics.
Date: October 1, 1980
Creator: Dickson, C.R.; Felder, W. & Gould, R.K.
Partner: UNT Libraries Government Documents Department

Direct observation of electron transfer across a lipid bilayer: laser photolysis of an asymmetric vesicle system containing chlorophyll, methyl viologen, and EDTA

Description: Electron transfer across lipid bilayer vesicle walls was examined by laser flash photolysis to determine the mechanisms of charge transport across the membrane. The discussion is restricted to vesicles whose walls contain phosphatidylcholine, chlorophyll a, and valinomycin. (ACR)
Date: January 1, 1980
Creator: Ford, W.E. & Tollin, G.
Partner: UNT Libraries Government Documents Department

Effects of preignition on pulverized coal combustion. First quarterly report, September 19-December 31, 1980. [Reactivity optimization]

Description: The theoretical task of optimizing pore structure with respect to char reactivity has indicated that the total porosity and the distribution of porosity are the most important char characteristics to consider when trying to optimize char oxidation above 800/sup 0/K. The bench scale experiment designed to achieve the optimum char structure has been designed and will be constructed during the next quarter.
Date: January 1, 1981
Creator: Simons, Girard A. & Kothandaraman, G.
Partner: UNT Libraries Government Documents Department

Environmental effects on electron transfer from chlorophyll triplet to quinone: role of dielectric constant, viscosity and quinone structure in cellulose acetate films

Description: The effects of environmental parameters on chlorophyll triplet quenching and electron transfer to quinones have been investigated in a system consisting of donor and acceptor incorporated into a cellulose acetate film which was subsequently exposed to solvent. Triplet quenching by a diffusional mechanism was found to occur in the dry film, with steric effects being a major determinant of quencher effectiveness. No formation of separated radicals was found under these conditions, probably because the high viscosity prevented separation of the initially formed radical-ion pair. When the film was subsequently exposed to water, triplet quenching became more effective and separated radical production occurred. This is attributed to effects of decreased microviscosity and increased dielectric constant. Both steric effects and quinone redox potential were found to influence radical yields. Rate constants for reverse electron transfer were independent of quinone redox potential. When solvents other than pure water were used, radical yields were observed to increase with the dielectric constant. This is ascribed to an increase in the ease of separation of the radical-ion pair.
Date: January 1, 1981
Creator: Cheddar, G. & Tollin, G.
Partner: UNT Libraries Government Documents Department

Energy dissipation in heavy systems: the transition from quasi-elastic to deep-inelastic scattering

Description: The interaction of medium mass projectiles (A = 28 - 64) with /sup 208/Pb has been studied using a split-pole spectrograph which allows single mass and charge identification. The reaction process in all systems studied so far is dominated by quasi-elastic neutron transfer reactions, especially at incident energies in the vicinity of the Coulomb barrier. In addition to the quasi-elastic component deep inelastic contributions are present in all reaction channels. The good mass and charge separation allows to generate Wilczynski plots for individual channels; for the system /sup 48/Ti + /sup 208/Pb we observe that the transition between the quasi-elastic and deep-inelastic reactions occurs around Q = -(30 to 35) MeV.
Date: January 1, 1984
Creator: Rehm, K.E.; van den Berg, A.; Kolata, J.J.; Kovar, D.G.; Kutschera, W.; Rosner, G. et al.
Partner: UNT Libraries Government Documents Department

Fundamental studies of high-temperature corrosion reactions. Sixth annual progress report. [Cu-6% Ni]

Description: Research was conducted on the sulfidation of pure Mo by sulfur gases at 700 to 950/sup 0/C and on the in-situ oxidation of metals and alloys in the hot-stage SEM. Results on the in-situ oxidation of Cu, Ni, Fe, and Cu-6% Ni up to 930/sup 0/C are reported in detail. 21 figures.
Date: February 1, 1981
Creator: Rapp, R.A.
Partner: UNT Libraries Government Documents Department

Fundamentals of nitric oxide formation in fossil fuel combustion. Progress report, 29 June-28 September 1980

Description: The study of the oxidation kinetics of pyridine was completed in the temperature range of 948 to 1073/sup 0/K and concentration ranges of 1.75 to 7.0 mole % oxygen; 0.25 to 2.0 mole % pyridine. The rate law is rate = k(C/sub 5/H/sub 5/N)/sup 1/2/(0/sub 2/)(..delta..0/sub 2/)/sup 1/2/, where ..delta..0/sub 2/ is oxygen consumed (autocatalysis). The temperature dependence is k = 10/sup 14.7 +- .7/exp(-26600 +- 1600/T)(1/mole s). The yield of HCN appeared insensitive to changes in temperature, concentrations and equivalence ratio, and only trace amounts of nitrogen oxides and ammonia were found. Fuel-rich mixtures produced large amounts of smoke so that a nitrogen balance was not possible but for lean mixtures HCN and N/sub 2/ accounted for the product nitrogen. Increase to 2% pyridine and 14% oxygen produced reduced yields of HCN and increased yields of N/sub 2/, N/sub 2/O, and NO. H/sub 2/ had no influence on the rates of pyrolysis and oxidation of pyridine. At 1073/sup 0/K HCN was oxidized at a measurable rate, added benzene increased the rate of oxidation at low equivalence ratios and reduced it at ratios above 0.9, with no significant nitrogen oxides produced, added acetylene increased the oxidation rate and also produced NO. It is clear that conditions can be found for the oxidation of heterocyclic nitrogen compounds that promote the formation of N/sub 2/ at the expense of NO.
Date: December 1, 1980
Creator: Houser, T. & McCarville, M.E.
Partner: UNT Libraries Government Documents Department