bluuebunny/crossref_metadata_2025_split huggingface dataset:
R7T7 Nuclear Waste Glass Behavior in Moist Clay: Role of the Clay Mass/Glass Surface Area Ratio
Authors: Godon N. , Vernaz E. 
Published: March 2011

ABSTRACTR7T7 glass alteration was investigated in the presence of various moist clays. In contact with smectite 4a, selected in France as a potential engineered barrier material, the glass was significantly corroded: after 6 months the glass corrosion rate was practically the same as the initial alteration rate in double-distilled water. Substantially lower alteration was observed in contact with bentonite 6 activated by sodium carbonate.Smectite 4a consumes silicon released by glass corrosion, and thus retards the rise to high silicon concentrations in solution at which the glass corrosion rate diminishes. Glass can therefore in some cases be altered as much in moist clay as in water with high renewal rates. Other experiments with smaller quantities of smectite 4a showed that the phenomenon becomes less important in time: its duration is proportional to the ratio between the clay mass (C) and the glass surface area (SA). Comparing the results of studies at different C/SA ratios indicates that low glass corrosion rates are obtained more slowly at higher C/SA ratios.Tests with 239Pu-doped R7T7 glass also showed that the radionuclide retention factor in the alteration film at the glass surface is only 6, compared with a factor of nearly 50 in double-distilled water.
Comparison of Surface Layers Formed on Synthetic Basaltic Glass, French R7T7 and HMI Borosilicate Nuclear Waste form Glasses - Materials Interface Interactions Tests, Waste Isolation Pilot Plant
Authors: Jercinovic Michael J. , Kaser Stacy A. , Ewing Rodney C. , Lutze Werner 
Published: March 2011

ABSTRACTMaterials Interface Interaction Test results for up to 2 years indicate that surface layers formed on synthetic basaltic glass in brine are predominantly Mg-chloride or oxychloride. Layers formed on HMI and R7T7 borosilicate glass are Mg-silicates. Layer thickness increases from 1 year to 2 years for basaltic glass and HMI borosilicate glass. Mg-silicate contains Ni and Zr in amounts that are generally related to the composition of associated glass, but layers formed on basaltic glass also contain Ni and Zr, elements not present in the glass. Ni and Zr are, in part externally derived, however, Ti appears to be completely immobile, and is not found in layers formed on Ti-free glass (R7T7). Some chemical components of the surface layers are derived, in part, from alteration of glass but major components of the layers are from the brine.
Grouts and Concretes for the Waste Isolation Pilot Project (WIPP)
Authors: Wakeley Lillian D. 
Published: March 2011

ABSTRACTThe Structures Laboratory of the U.S. Army Engineer Waterways Experiment Station has conducted research on cement-based composites for the Waste Isolation Pilot Project (WIPP) since 1977, in cooperation with Sandia National Laboratories. Field testing requirements guided initial development of grouts. Concurrent and later laboratory studies explored the chemical stability and probable durability of these mixtures. Beginning in 1985, a series of small-scale seal performance tests at the WIPP prompted development of an expansive salt-saturated concrete. Important lessons learned from this ongoing work include: (1) carefully tailored mixtures can tolerate phase changes involving Ca, Al, and S04, without loss of structural integrity; (2) handling and placement properties are probably more crucial to the mixtures than is exact phase composition; and (3) for the environment of a geologic repository, demonstrated chemical durability will be the best indicator of long-term performance.
A Corrosion Localization Assessment of the Mild Steel Used for Nuclear Waste Package
Authors: Akashi Masatsune , Fukuda Takanori , Yoneyama Hiroshi 
Published: March 2011

ABSTRACTThis paper describes a study of corrosion behavior of a mild steel as a candidate of the high-level nuclear waste package in the geological disposal situations, conducted to establish a model for estimating the corrosion allowance requirement to achieve the 1,000 year lifetime for the package. In several series of galvanostatic tests, the maximum penetration depth and the depth distribution were measured for each specimen with a sophisticated ultrasonic inspection technique. The Gumbel distribution model was successfully used in analyzing each set of data for the maximum penetration depth. Relations among the average penetration depth, the maximum penetration depth, and the corrosion allowance requirement were discussed.
Analytic Studies of Colloid Transport in Fractured Porous Media
Authors: Hwang Y. , Chambré P. L. , Lee W. W.-L. , Pigford T. H. 
Published: March 2011

ABSTRACTMathematical models of coupled migration of colloids and solute in fractured, porous medium are presented, for two types of colloid-solute interaction. When the colloid-solute interaction is by dissolution, solute that normally has greater retardation than colloids is accelerated by colloid dissolutions. For sorption interaction, the apparent migration speed of pseudocolloids can be greater or less than the solute migration speed without interaction, depending on the choice of parameters.
Migration of Anionic Species of Radioactive Cobalt through Soil
Authors: Ohnuki Toshihiko , Robertson David E. 
Published: March 2011

ABSTRACTThe migration of an anionic species of 60Co through soil has been examined utilizing data on the migration of radionuclides leached from an aqueous waste disposal site. Correlation coefficients between concentrations of the anionic species of 60Co and those of the particulate, cationic and non-ionic species of 60Co reveal that the anionic species of 60Co was not interconverted from the other species during migration. The cross correlations of changes in the concentrations of the anionic species of 60Co with time between three different down gradient positions give a calculated retardation factor of the anionic species of 60Co of approximately 19, being 1200 times lower than the results of laboratory measurements. The average concentration distribution of the anionic species of 60Co suggests that the migration of the anionic species of 60Co consists of two migration fractions which were driven by different migration mechanisms.
Effective Diffusivity of Carbon Dioxide and Iodine through “G” Tunnel Tuff
Authors: Bardakci Tevfik , King Franklin G. , Sein Maung K. 
Published: March 2011

ABSTRACTThe effective diffusivity of carbon dioxide and iodine through “G” tunnel tuff were determined using a steady-state method and an unsteady-state method respectively. Results show that the effective diffusivity of carbon dioxide and iodine through dry tuff increased with temperature. The effective diffusivity of carbon dioxide decreased as the moisture content of the “G” tunnel tuff increased. An emprical correlation was obtained to estimate the effective diffusivity of carbon dioxide as a function temperature and the percent saturation. Specific surface area and pore volume of tuff was determined using a mercury porosimeter. A scanning electron microscope was utilized to further characterize the porous structure of the tuff samples.
Transport of Gaseous 14C in a Partially Saturated, Fractured, Porous Medium
Authors: Light W. B. , Chambré P. L. , Lee W. W.-L. , Pigford T. H. 
Published: March 2011

ABSTRACTWe predict the transport of 14C from the proposed nuclear waste repository at Yucca Mountain using a porous medium model. Use of this model is justified if the Peclet number, which indicates equilibrium between gas in fractures and liquid in rock pores, is much less than unity. For the assumed release rates, maximum predicted concentrations of 14CO2 in rock near the ground surface are comparable to the USNRC limit for unrestricted areas. Furthermore, dilution near the ground surface as the 14CO2 enters the atmosphere will lower the concentrations by several orders of magnitude. Travel times from the repository to the surface are predicted to be hundreds to thousands of years. For a wide range of the parameters, the release rate from the source has negligible effect on the maximum concentrations at the ground surface.
Analysis of Mass Transport in an Engineered Barriers System for the Disposal of Used Nuclear Fuel
Authors: Garisto Nava C. , Leneveu Dennis M. 
Published: March 2011

ABSTRACTThe Vault Model has been developed to assess the performance of engineered barriers in a conceptual geological disposal vault for used nuclear fuel. It represents container failure, release of radionuclides from used fuel and mass transport of released radionuclides through the clay-based sealing materials surrounding the waste containers. This paper focusses on mass-transport processes represented by the Vault Model, including diffusion, convection and retardation.In particular, we present results of several scoping calculations carried out with the Vault Model. We consider cases where the clay-based barriers are represented by either a one- or a two-layer system adjacent to an intact rock and a case where the two clay-based barriers are adjacent to a highly fractured rock. These calculations provide insight into the model and produce test cases for comparison with both relatively simple analytical estimates and similar computer codes, as they become available. The analytical estimates generally support the Vault Model results and thus enhance our confidence in the accuracy of the Vault Model calculations.
The Effect of Pressure on the Critical Temperature of Four-Component Microemulsioms
Authors: Goyette Jacques , Bose T. K. , Thoen J. , Lalanne J. R. 
Published: March 2011

ABSTRACTWe present results for the pressure dependence of the critical temperature (dTc/dP) for several microemulsions of n-dodecane, water, n-pentanol and sodium dodecylsulfate with critical points along a criticial line ending at a critical end point (CEP). The variation of dTc/dP as a function of the water to surfactant ratio X shows a nonlinear behavior, with large changes near the CEP, and similar to the X dependence previously observed for the correlation length amplitude ξo. From the negative sign of dTc/dP we also conclude that a possible anomaly in the density must be opposite to the anomaly recently reported for the refractive index.
Phase Diagram for Reversibly-Assembled Rod-Like Aggregates: Nematic, Columnar and Crystalline Ordering
Authors: Taylor Mark P. , Herzfeld Judith 
Published: March 2011

ABSTRACTAqueous solutions of amphiphilic molecules which reversibly assemble into well defined polydisperse rod-like aggregates display a characteristic sequence of lyotropic mesophases including translational as well as orientational ordering. We have developed a model for such systems which incorporates a phenomenological description of aggregate assembly with a scaled particle calculation of the configurational entropy in the fluid dimensions and a cell theory description of the configurational entropy in the translationally ordered dimensions. The model reproduces many of the features seen in the experimental phase diagrams, including regions of isotropic, nematic, columnar and crystalline stability. In addition to the calculated phase diagram, related aggregate size distributions are reported.
Nonequilibrium X-Ray Study of the Nematic to Smectic-a Transition Under Shear Flow
Authors: Safinya C. R. , Sirota E. B. , Piano R. , Lei N. 
Published: March 2011

ABSTRACTWe report on synchrotron x-ray scattering studies of the microscopic structure of the nematic (N) and the smectic-A (SmA) phases in the liquid crystal 8CB under dynamic “steady state” shear flow conditions carried out in an x-ray Couette cell. These measurements directly probe length scales less than 100 Å and as large as 104 Å in the vicinity of the N-SmA phase transition away from equilibrium. The N-SmA transition corresponds to the onset of a one-dimensional mass density wave. In the nematic phase close to the smectic-A phase, there are very large pretransitional smectic-A fluctuations because the transition is almost second order. Under shear flow, we find that the nematic director undergoes a series of abrupt transitions between different orientational states of the director. We discuss the stability regimes of these orientational states by considering the fluctuation induced renormalization of one of the nematic shear viscosities and the fluctuation induced torque on the nematic director.
Formulation and Processing of Colloidal Dispersions
Authors: Russel William B. 
Published: March 2011

ABSTRACTColloidal dispersions are encountered during the processing of chemicals and materials in a number of contexts, generally requiring control of macroscopic properties such as the phase behavior and rheology through the manipulation of the chemistry. This paper surveys several applications, including the fabrication of advanced ceramics and the formulation of coatings, and attempts to identify the limiting science in each case.
The Mechanical Properties of Thixotropic Gels and their Effect on Attenuation in Optical Fiber Communication Cables
Authors: Taylor Carl R. , Overton Bob J. , Tu Ching Fang 
Published: March 2011

ABSTRACTFumed silica/oil gels exhibiting rheological properties characterized by a yield stress followed by shear thinning behavior have been studied for application as waterblocking filling compounds for fiber optic cable. It is found that added signal attenuation in optical fibers after processing into a filled fiber optic ribbon cable is a function of the yield stress of the filling gel. We derive experimentally and apply a model of the relationship to formulate an optimum fumed silica/oil filling gel for fiber optic ribbon cables.
Dehydration of Protein Polymers in Concentrated Nematic Solutions
Authors: Hentschke Reinhard , Herzfeld Judith 
Published: March 2011

ABSTRACTProtein fibers (e.g., actin filaments, microtubules, and sickle cell hemoglobin polymers), formed by reversible association of quasispherical protein monomers, contain substantial solvent. At high concentrations, solutions of these fibers become non-ideal due to interactions between the elongated particles. One manifestation of this non-ideality is the spontaneous alignment of the fibers. Model calculations, involving simple intra- and inter aggregate interactions leading to polymerization and alignment, agree well with osmotic pressure measurements of sickle cell hemoglobin solutions in the region of the phase transition. However, at higher concentrations the theory cannot fit the experimental data unless solvent is gradually squeezed out of the fiber under osmotic stress. We find that a linear potential for the fiber dehydration gives osmotic pressure results consistent with the experimental data. Under these conditions, substantial fiber dehydration occurs with increasing protein concentrations beyond the alignment transition. This indicates that particle interactions sufficient to cause alignment are also sufficient to squeeze significant amounts of solvent out of the sickle cell hemoglobin fibers.
Statistical Thermodynamics of Phase Transitions in Surfactant Monolayer Films
Authors: Cantor Robert S. 
Published: March 2011

ABSTRACTA lattice statistical mechanical method has recently been developed and used to predict structural and thermodynamic properties of fluid phases of surfactant monolayer films of uniform chain length. This mean-field approach is extended here to examine films of mixed chain length. As in the earlier work, a fluid-fluid (LC-LE) phase transition is predicted to occur at high surface densities. This transition is found to exhibit non-ideal mixing behavior, ranging from positive azeotropy to phase separation (in the LC phase) as the difference in chain lengths increases. In contrast, the phase diagram in the liquid-gas (LEG) transition region is predicted to exhibit almost ideal behavior, with a nearly linear bubble-point curve.
X-Ray Studies of the Liquid/Vapor Interface: Water and Polymer and Fatty Acid Monolayers on Water
Authors: Schlossman M. L. , Schwartz D. K. , Kawamoto E. H. , Kellogg G. J. , Pershan P. S. , Ocko B. M. , Kim M. W. , Chung T. C. 
Published: March 2011

ABSTRACTX-ray specular reflectivity is used to study the liquid-vapor interface of pure water and of fatty acid and polymer monolayers at that interface. For the pure water surface the reflectivity was measured for three different spectrometer resolutions and simultaneous fits with only one free parameter to all of the data are in excellent agreement with the prediction of capillary wave theory for the RMS surface roughness. Diffuse scattering away from the specular condition, at wavevectors corresponding to those of the capillary waves, yields intensities and line shapes in agreement with theory with no significant adjustable parameters. Reflectivity from separate monolayers of co-poly 1,2-butadiene/butyl alcohol (50% random substitution) and lignoceric acid (CH3(CH2)22COOH) at the water/vapor interface are interpreted to obtain profiles of the average electron density ρ(z) as a function of distance z along the surface normal. For the polymer monolayer we find the following: 1) a local maximum in the electron density approximately 10% larger than that of the bulk polymer and 2) the RMS roughness of the vapor/polymer interface agrees with capillary wave theory predictions for the lower surface pressures. For the highest surface pressure the RMS roughness exceeds the value predicted by the capillary wave model. Measurements of reflectivity from a lignoceric acid monolayer, as a function of surface pressure throughout an isotherm (near room temperature), reveal the following behavior: 1) the overall thickness of the monolayer increases with increasing pressure and 2) the head groups occupy a progressively larger region along the surface normal as the pressure increases, indicating that they rearrange normal to the interface.
Dynamics of Flexible Polyions in Solution: Ionic Strength Effects
Authors: Mattoussi Hedi , Langley Kenneth H. , Karasz Frank E. 
Published: March 2011

ABSTRACTMeasurements of the collective diffusion coefficient, for polyelectrolyte solutions at high ionic strength and in the dilute regime, are reported. The data are discussed within the framework of a persistent chain with electrostatic contribution to account for the Coulomb interactions.
Class F Fine Fly Ash
Authors: Sheu T. C. , Quo L. W. , Kuo S. T. 
Published: March 2011

AbstractThe Taiwan Power Company's (TPC) coal combustion power plants produced approximately 1 million tons of class F fly ash in 1988 but only 25% of it was effectively utilized. Accordingly, this study investigated the use of separation techniques to improve the quality of the fly ash in order to increase its application. In the experiment, the fly ash was dry-sieved through sieves No. 200, 300 and 400 mesh respectively. The chemical, physical and some of the engineering properties of those classified class F fine fly ashes were ascertained.
The Use of Fly Ash in Concrete - A European View
Authors: Pratt P. L. 
Published: March 2011

AbstractA European view of the use of fly ash in concrete, if there is one, is very confused. Mehta [1] produced figures for the production and utilisation of fly ash in the cement and concrete industries for 1984, ranging from 10% utilisation in the UK where the cement makers are not enthusiastic, to 80% in the Federal Republic of Germany and even 94% in the Netherlands according to Fraay, Bijen, de Haan and Larbi [2]. Looking a little deeper into these figures the CEGB Ash Marketing Board says that it sells over 40% of its production of fly ash of some 14 million tons/year, much of it for landfill, while the figures for Germany relate only to the 2.6–2.9 million tons of ash from black coal; 70% of the German ash comes from brown coal, and all of this is returned to the open-pit mine for dumping. This paper will review some of the European papers in the Third CANMET/ACI International Conference on Fly ash, Silica Fume, Slag and Natural Pozzolans in Concrete held in Trondheim in June 1989 and some more recent work funded by the Ash Marketing Division of CEGB at Imperial College and the Building Research Establishment, Garston. Four specific aspects of the effects of fly ash on concrete will be considered: rheology and workability; the pozzolanic reaction and the effects of curing; the development of microstructure; and the development of strength and some aspects of durability.
Hydraulic Properties of Fluidized Bed Combustion Ashes
Authors: Odler I. , Zysk K. -H. 
Published: March 2011

AbstractSeven fluidized bed combustion ashes of different composition were studied as to their hydraulicity and pozzolanicity. Four of them exhibited hydraulic reactivity and hardened when mixed with water. All of them exhibited a positive effect on strength development if used as constituents of blended cements. However, the presence of significant amounts of Fe2+ and free lime in the ash, as well as excessive amounts of SO3 in the produced cement caused unsoundness associated with the decline of flexural strength after longer hydration times.
Stratlingite and Hydrogarnet from Calcium Aluminosilicate Glass Cements
Authors: MacDowell John F. 
Published: March 2011

AbstractCalcium aluminosilicate glass cements that hydrate directly to stratlingite (2CaO·Al2 O3 SiO2 · 8H2 O) and/or hydrogamet solid solution (3CaO·Al2 O3·XsiO2 ·[16–2X]H2O) are described.Hydrogamet develops rapidly during curing of pastes containing between 12 and 16 wt.% SiO2, while stratlingite grows more slowly in bladed radial spherulites in compositions containing 18 to 25% SiO2Compressive strengths between 35 and 70 MPa, 20–35% porosity, and excellent thermal and chemical stability are characteristic of the cured hydrogamet cements, while the stratlingite pastes have strengths between 70 and 140 MPa and 1–10% porosity.A preferred composition area is described that yields mixtures of the two hydrated phases, resulting in a useful combination of low porosity and high early strength.
Quantum Effects At Gaas/AlxGa1−xJunctions
Authors: Gossard A. C. 
Published: March 2011

Quantum effects occurring at interfaces between GaAs and AlxGa1−x As are reviewed. Electrons and holes can be confined to two-dimensional quantum states in thin semiconductor layers or at semiconductor heterointerfaces. The twodimensional states in GaAs/AlxGa1−xAs structures show strongly modified electrical and optical behavior relative to unconfined material, with the properties strongly dependent on the structural design.Electrons confined in high mobility structures at selectively doped GaAs-AlxGa1−xAs heterointerfaces show a quantized Hall effect with an associated vanishing parallel resistance and, in high magnetic fields, an apparent electron crystallization.Optical transitions between confined electron and hole states in quantum well thin layers form the basis of quantum well luminescence and for new non-linear optical logic structures.All the quantum effects are sensitive to interfacial properties which are closely dependent on the conditions of epitaxial growth.