bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental Study of Diopside for Use as Implant Material
Authors: Nonami Toru
Published: March 2011

Diopside was prepared sintering a powder compact of composition CaMgSi2O6 at 1573K for 2 hours. The bending strength of this sintered body was 300MPa and fracture toughness was 3.5MPam1/2. Diopside was soaked in a simulated body fluid at 309.5K. Three days later diopside formed hydroxyapatite (Hap) all over the surface [1]. Diopside implanted in rabbits came in close contact with the newly grown bone. EPMA spectral diagrams show a change of composition across the junction from the diopside to the newly grown bone [2].
Dielectric Response of a Chain of Disordered Polarizable Spheres: Numerical Simulation and Theory
Authors: VillaseiÑor-Gonzalez Pedro , Noguez Cecilia , Barrera Ruben G.
Published: March 2011

We applied to a one-dimensional system (1D) a recently developed diagrammatic formalism, in order to calculate the effective dielectric response of a chain of polarizable spheres embeded in an homogeneous host. The effective response is calculated within the dipolar, quasi-static approximation, through the summation of selected classes of diagrams. We compared our results with a numerical simulation, where the position of each sphere was generated at random and the induced dipole moment of each sphere was calculated by solving a set of linear equations through matrix inversion and using periodic boundary conditions.
Effects of Multiple Scattering on Ultrasonic Velocity, Attenuation and Backscattering Noise in Polycrystals
Authors: Bruce Thompson R. , Rose James H. , Ahmed S.
Published: March 2011

Understanding the propagation of ultrasonic waves in polycrystals is important in nondestructive evaluation, both for the purpose of properly detecting or interpreting signals scattered from discrete flaws and for characterizing the microstructure itself. In this paper, the use of the unified theory for elastic wave propagation, developed by Stanke and Kino and based on the second order Keller approximation, is first discussed. After a brief review of the general formalism, recent extensions to the case of polycrystals with preferred grain orientation and elongation are presented. Particular attention is placed on a case commonly found in stainless steels in which the [001] crystallographic axes are aligned and the grains are elongated in the same direction. Techniques to predict the backscattered noise, based on single scattering approximation are then discussed and data motivating the need for extension to include multiple scattering is described. Finally, ways in which these theories can be used to provide improved characterizations of microstructures is indicated.
Multiple Scattering Theory with Space Filling Potentials
Authors: Butler W. H.
Published: March 2011

A brief account of the current state or our understanding of full cell multiple scattering theory is given. The development of this understanding is also briefly outlined.
Variational. Principies for Fuil-Potentiai. Muiltiple Scattering Theory
Authors: Nesbet R. K.
Published: March 2011

The variational principle of Kohn and Rostokcr (KR) implies that the determinant of a product of matrices vanishes at energy eigenvalues. The standard KKR method uses square matrices appropriate to a truncated spherical harmonic expansion, and sets the determinant of one matrix in this product to zero. For general nonspherical potentials in space-filling local cells, the KR variational principle requires these matrices to be rectangular, since the intermediate sum should extend over a complete set of solid harmonic functions. If extended in this way, the intermediate sum can be replaced by a Wronskian surface integral over the interfaces of adjacent space-filling atomic cells, as formulated in the variational principle of Schlosser and Marcus. E-quivalence of these two different variational principles is established here in the limit of completeness of the intermediate sum. The practical implication is that the standard KKR method is not well founded for the full-potential problem. Improved results for low-order basis function expansions can be obtained by including a Wronskian interface integral in full-potential ACO calculations, as a variational completion of the truncated intermediate K KR sum. A revision of CPA alloy theory is proposed that avoids dependence on this intermediate sum.
Alloy Theory Through the Ages
Authors: Gonis A.
Published: March 2011

Man has always been fascinated with the quest to understand the inner workings of nature at a fundamental level. According to Embedocles[1], a philosopher in ancient Greece, all material things consist of four basic elements (he called them “roots”), namely earth, water, air, and fire. Modern mail's interpretation of that statement is that earth, water and air refer to the three states of matter, i.e., solids, liquids and gasses, with fire designating a process for transforming one of those states into the other. Be that as it may, Embedocles' statement could be conceived as the first attempt to construct an alloy theory, i.e., a predictive capability of the behavior of composite systems.
Real Space Multiple Scattering Description of Alloy Phase Stability
Authors: Turchi P. E. A. , Sluiter M.
Published: March 2011

We present a brief overview of the advanced methodology which has been recently developed to study phase stability properties of substitutional alloys, including order-disorder phenomena and structural transformations. The approach is based on the real space version of the Generalized Perturbation Method, first introduced by Ducastelle and Gautier, within the Korringa-Kohn- Rostoker multiple scattering formulation of the Coherent Potential Approximation. Temperature effects are taken into account with a generalized meanfield approach, namely the Cluster Variation Method. The viability and the predictive power of such a scheme will be illustrated by a few examples, among them: (1) the ground state properties of alloys, in particular the ordering tendencies for a series of equiatomic bcc-based alloys, (2) the computation of alloy phase diagrams with the case of fcc and bcc-based Ni-Al alloys, (3) the calculation of antiphase boundary energies and interfacial energies, and (4) the stability of artificial ordered superlattices.
Ground State Searches in Fcc Intermetallics
Authors: Wolverton C. , Ceder G. , Fontaine D. De , Dreyssé H.
Published: March 2011

A cluster expansion is used to predict the fcc groutnd states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. TFile internetallic structures are not assumed, but derived rigorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearizedmuffin- tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.
Comparison of Ni-Pt and Co-Pt Alloys Aided by Multiple-Scattering Calculations of Local Electronic Structure
Authors: Pisanty Alejandro , Martinez-Carrillo Miguel Angel , Amador Carlos
Published: March 2011

The interaction between atomic and magnetic order is very strong in Ni-Pt alloys, whereas Co-Pt alloys show local magnetic properties which are independent of the composition and state of order of the system. A multiple-scattering calculation on Ni-Pt alloys is used in this paper, together with band structures for ordered compounds of both Ni-Pt and Co-Pt, to discuss the origin of the difference in properties between both alloy systems.
Phase Diagram of Ni-Pt from Linear Muffin-Tin Orbitals Total Energy Calculations
Authors: Amador C. , Lambrecht W. R. L. , Segall B.
Published: March 2011

Progress in the calculation of the phase diagram of the Ni-Pt compounds from "first-principles" is reported. Our procedure consists of: (1) calculating total energies for ordered structures as a function of volume and including internal relaxations by means of the linear muffin-tin orbitals method within the atomic sphere approximation; (2) mapping these results onto an Ising model with effective interaction parameters; and (3) calculating the phase diagram by means of the cluster variation method. We identify the elastic energy related to the difference in the Ni and Pt lattice constant as one of the major problems in this system and discuss the convergence of the cluster expansion of the energy.
Relativistic Multiple Scattering Theory
Authors: Gyorffy B. L.
Published: March 2011

The symmetry properties of the Dirac equation, which describes electrons in relativistic quantum mechanics, is rather different from that of the corresponding Schr6dinger equation. Consequently, even when the velocity of light, c, is much larger than the velocity of an electron Vk, with wave vector, k, relativistic effects may be important. For instance, while the exchange interaction is isotropic in non-relativistic quantum mechanics the coupling between spin and orbital degrees of freedom in relativistic quantum mechanics implies that the band structure of a spin polarized metal depends on the orientation of its magnetization with respect to the crystal axis. As a consequence there is a finite set of degenerate directions for which the total energy of the electrons is an absolute minimum. Evidently, the above effect is the principle mechanism of the magneto crystalline anisotropy [1]. The following session will focus on this and other qualitatively new relativistic effects, such as dichroism at x-ray frequencies [2] or Fano effects in photo-emission from non-polarized solids [3].
Application of Multiple Scattering Theory to Surfaces and Extended Defects
Authors: Cooper Bernard R.
Published: March 2011

This article presents a brief overview of applications of multiple scattering theory to surfaces and extended defects. Discussion is given of some key issues and their practical status, and this discussion is related to the papers in the session which covered this topic at Symposium V.
Effective Cluster Interactions at Disordered Surfaces
Authors: Drchal V. , Kudrnovsky J. , Udvardi L. , Weinberger P. , Pasturel A.
Published: March 2011

Effective cluster interactions (ECI) at surfaces of substitutionally disordered alloys are determined using the generalization of the TB-LMTO-CPA method to inhomogeneous systems. Illustrative results are reported for the (Ag,Pd) alloy system.
Full—Potential Lmto Calculation of Brittle Fracture in Titanium Carbide
Authors: Price D.L. , Cooper B.R.
Published: March 2011

The refractory transition metal—carbides commonly fail under stress by brittle fracture and the properties and nature of the fracture process are consequently of practical interest. We have calculated the fracture properties of titanium carbide under tensile stress using our full—potential LMTO method, a methodology which is closely related to multiple scattering theory (and includes a true interstitial region). The fracture calculation is accomplished by employing a repeated slab (or repeated cleavage separation) geometry. Within this geometry, the fracture process is simulated most simply by uniformly increasing the gap separation from zero to a distance on the order of a few atomic radii. A more sophisticated search for fracture instability involved stretching the ideal crystal and examining the separation energetics of the strained system.

Results of these calculations will be reported both for the ideal, stoichiometric titanium carbide crystal and also for systems containing carbon vacancies. We will discuss therole of such defects in modifying the bonding behavior at the cleavage plane and the resulting effect on resistance to fracture.
Real-Space Multiple Scattering Theory Method: Formalism and Applications
Authors: Zhang X.-G.
Published: March 2011

Different forms of the real-space multiple scattering theory (RS-MST) formalism are compared in order to understand its convergence behavior with respect to truncation in the angular momentum expansions. In particular the so-called “folding method” or (1,n) mode is considered, in which the renormalized t-matrix T of the semi-infinite system has the dimension of n (n > 1) repeating units and the self-consistent equation for T is constructed by adding and contracting one such unit. It has been demonstrated in previous studies of layered structures that the folding method converges rapidly in both angular momentum (L) and site (n) indices and yields accurate results. The convergence behavior is an important factor to be considered in applying the various forms of the RS-MST method to layered structures as well as other systems with extended defects.
Scattering and Multiple Scattering in Disordered Materials, an Overview
Authors: Weaver Richard L. , Butler W. H.
Published: March 2011

The papers papers in this section were presented at a joint session of symposium V on Applications of Multiple Scattering Theory and of Symposium P on Disordered Systems. They show that the ideas of scattering theory can help us to understand a very broad class ofphenomena.
Diffusing Wave Spectroscopy: The Dynamics of Multiply Scattering Media
Authors: Weitz D. A. , Pine D. J. , Durian D. J. , Zhu J. X.
Published: March 2011

When light is very strongly multiply scattered by a medium, its propagation can be well described by a diffusion approximation. This allows important, measurable quantities to be calculated theoretically and interpreted. Thus, for example the total light transmitted through a sample can be used to determine the transport mean free path which characterizes the diffusive transport of the light. In addition, the distribution of path lengths followed by the diffusing light can be determined. This distribution can in turn be used to interpret the temporal fluctuations of the scattered intensity that arise due to the motion of the scattering medium. Therefore, traditional quasielastic, or dynamic, light scattering can be extended to the strongly multiple scattering limit. This technique is called Diffusing Wave Spectroscopy (DWS), and allows useful information about the dynamics of the medium to be determined. Furthermore, new physical processes can be studiedusing DWS. For example, DWS is sensitive to very small motions of colloidal particles: motion of 1 pm diameter particles can be resolved on lengths of∼ 5 Å using light with a wavelength of 0.5 μm. New physical phenomena are probed when motion on these length scales is observed. In particular, the time evolution of the hydrodynamic interaction between concentrated colloidal particles can be resolved. In addition, DWScan also probe spatially rare events since the light paths sample a large volume of the sample. This allows DWS to probe very slow dynamics, making it useful for the study of materials such as foams. This talk reviews the fundamentals of DWS and highlights some ofits unique applications.
First-Principles Angle-Resolved Photoemission Intensity Calculations in Y Ba2Cu3O7
Authors: Lindroos M. , Bansil A. , Campuzano J. C.
Published: March 2011

We discuss the application of the multiple scattering theory to obtain first-principles predictions of angle-resolved photoemission intensities (ARPES) in the high-Tc superconductors. In this connection, we have generalized and implemented the ‘one-step’ photoemission approach to treat systems with an arbitrary number of atoms in the layer unit cell. We illustrate the methodology with results for the r-S symmetry direction for the (001)-surface of orthorhombic YBa2Cu3O7. Our computations give insight into the effects of surface termination, and of polarization of incident light on photoemission intensities.
Hierarchical Structure of a Natural Composite: Insect Cuticle
Authors: Gunderson Stephen L. , Gunnison Katie E. , Sawvel John W.
Published: March 2011

The insect cuticle is an excellent example of a natural, fiber-reinforced, polymeric composite consisting of chitin fibers embedded in a protein matrix. Optical and electron microscopy have been used to examine the structure and interaction of the constituents of the bessbeetle (Odontotaenius disjunctus) cuticle from the molecular to the macroscopic levels.

Molecular chains of the polysaccharide chitin (N-acetylglucosamine) are grouped together to form “fibrils” which are either dispersed throughout the matrix or combined to form larger “fibers”. The fibers are unidirectionally oriented within individual sheets or laminae which are stacked on top of one another at various angles forming a laminated structure.

The protein matrix is ductile upon initial deposition but then undergoes a crosslinking process which increases its shear stiffness, thereby improving load transfer between fibers. The matrix is bound to the chitin via beta linkages holding it together at both the fibril and fiber levels. The matrix has a fibrous morphology which provides adequate toughness in spite of the high degree of crosslinking.

Reference is made to designs observed in the bessbeetle cuticle which could be applied to man-made composites for improved performance primarily in the areas of damage tolerance and strength and stiffness coupled with low weight. For these designs to be implemented using synthetic materials, new or modified processing and fabrication methods are needed.
Self-Organization (Assembly) in Biosynthesis of Silk Fibers - A Hierarchical Problem
Authors: Kaplan David L. , Fossey Stephen , Viney Christopher , Muller Wayne
Published: March 2011

In natural systems, structural macromolecules undergo prescribed recognition and assembly steps during synthesis and processing. These associations lead to more complex assemblies that exhibit useful multifunctional properties. Many of these processes are not well understood. Some aspects of these processes are presented using the fibrous protein polymer silk as an example. Issues such as polymer chain biosynthesis, chain interactions, processing into fibrils, and complex engineering into supra-assemblies are addressed and biochemical, spectroscopic and modeling studies are reviewed. Genetic level controls of chain composition, crystalline/amorphous domain distribution, chain aggregation, chain registry, silk I-silk II phase transitions, nematic liquid crystalline phase, loss of water, global molecular alignment, and solution spinning are some of the characteristics of this biological system that are addressed. Although some information is available at the molecular and macro-scale levels, a key issue is the paucity of information at the meso-scale level to fully understand the role of structural hierarchy in the silk fiber assembly process.
Hierarchical Structure and Light Scattering in the Cornea
Authors: Farrell R. A. , Freund D. E. , McCally R. L.
Published: March 2011

The complex hierarchical structure of the cornea of the eye as it is known from light and electron-microscopy is reviewed. Microscopy depicts the cornea as a layered structure with each layer parallel to the cornea's surfaces. The middle 90% of the cornea is a connective tissue layer called the stroma, which in turn is comprised of 2 μm thick sheets (lamellae) of collagen fibrils embedded in a ground substance. Fibrils within a given lamella have their axes parallel to one another, while fibril axes in adjacent lamellae make large angles with one another. Predictions of light scattering theory are then used to show how light scattering measurements made on fresh tissue can test these structures for possible artifacts due to preparative procedures. With unpolarized light, the total scattering cross-section depends on the fibrillar ultrastructure, but not on the lamellar structure. Angular scattering depends on both levels of hierarchical organization. The lamellar level of organization is especially significant for the propagation and scattering of polarized light. To date the structural implications of scattering measurements are in accord with structures seen in electron micrographs.
Eukaryotic Signal Transduction Pathways And Man-Made Systems Compared
Authors: Bayley Hagan
Published: March 2011

The components of biological signal transduction pathways have been compared with those of electronic circuits. Indeed, attempts are being made to incorporate biomolecules into electronic devices. However, man-made biomolecular devices do not yet mimic several important features of naturally occurring systems, especially those of eukaryotes. It is well known that the polypeptide components of biological signal transduction pathways include subunits of receptors, regulatory proteins, enzymes and channels. It is less well appreciated that each component often exists in many functionally related but not redundant forms. When proteins are hetero-oligomers, numerous combinations of these forms may be permitted yielding large arrays of signal transduction molecules with overlapping properties. Further, the organization of these molecules within the cell Is highly complex. Especially alien to the materials scientist are the findings that signal transductlon proteins can translocate between regions of cells in response to stimuli and change in concentration as a consequence of breakdown and resynthesis. These features, as well as the interactions between signal transduction pathways, produce far more complex and fluid signalling networks than those presently used in man-made devices. Is anything to be gained by mimicking such complexity or are we on the right track in designing relatively simple, structurally rigid devices using biomolecular components?
Characterization of the Complex Matrix of theMytilus EdulisShell and the Implications for Biomimetic Ceramics
Authors: Keith J. A. , Stockwell S. A. , Ball D. H. , Muller W. S. , Kaplan D. L. , Thannhauser T. W. , Sherwood R. W.
Published: March 2011

The macromolecular matrix present in the composite shell of the blue mussel,Mytilus edulis, accounts for less than 1% of the shell by weight but is theorized to play a significant role in controlling the growth, morphology, and orientation of the CaCO3that makes up the shell. The presence of several proteins in this matrix, only some of which have affinity for calcium, suggests a hierarchical structural model for the shell. Proteins were isolated under denaturing, reducing conditions and separated by centrifugation, gel electrophoresis, and high performance liquid chromatography. The major matrix proteins, both soluble and insoluble, were evaluated for amino acid composition, calcium binding, and glycosylation. Some N-terminal sequence data was collected. Non-proteinaceous components of the matrix were also analyzed. Comparison of the mussel shell matrix with the protein matrix of other molluscan systems suggests that this complexity is not unique to the mussel and may provide a key to the understanding of more generic biomineralization processes necessary for such applications as biomimetic ceramics.
Self-Assembly of Bacterial Macrofibers: A System Based Upon Hierarchies of Helices
Authors: Mendelson Neil H.
Published: March 2011

Cylindrical-shaped cells of Bacillus subtilis (0.7 by 4 μm) are the building blocks of macrofibers, highly organized, helically twisted, multifilament structures millimeters to centimeters in length. The forces responsible for self-assembly and the cylinder-helix deformation trace to the assembly of cell wall polymers and restraint of the motions generated by cell growth. An hierarchical relationship exists involving: (i) molecular level events associated with cell surface assembly, which in turn govern, (ii) cellular level events concerned with motions that accompany cell growth, and these in turn drive, (iii) multicellular level events such as the folding and plying of cell filaments to form a mature macrofiber. Cell growth generates new material and engenders twisting of the cell cylinder along a screw axis as it elongates. The helix hand and degree of twist at the cellular level eventually dictate the hand and twist of the mature multifilament macrofiber. Although several different routes can lead to the initiation of macrofiber production, once initiated a repetitive cycle of folding and plying becomes established. The self-assembly proceeds until mechanical and geometrical factors preclude further folding cycles.
An Alternate Mechanism for Porous Si Photoluminescence: Recombination in SiHx Complexes
Authors: Prokes S. M. , Glembocki O. J. , Bermudez V. M. , Kaplan R. , Friedersdorf L. E. , Searson P. C.
Published: March 2011

Porous silicon layers have been formed which exhibit photoluminescence (PL) peaks that do not blueshift with increasing porosity. Hydrogen desorption experiments have been performed in vacuum under anneals between 230°C–390°C. Simultaneous, in-situ PL measurements show that the PL intensity decreases and disappears with decreasing hydrogen content. Infrared spectroscopy (IR) measurements also show loss of hydride species in the same temperature range. These results indicate that hydrogen is important in the PL process. We suggest that silicon hydrides are the source of PL in porous SI.
Structural Studies, Surface Properties, and Photoluminescence Behaviour of Silicon Nanocrystals
Authors: Heath J. R. , Jasinski J. M.
Published: March 2011

A method for synthesizing crystalline and/or amorphous silicon nanoparticles (3 – 30 nm diameter) is discussed. The photoluminescence (PL) behaviour of these particles is studied as crystallinity, size, surface stoichiometry, and excitation frequency are varied. Orange-red photoluminescence (PL), similar to that reported for “porous silicon,” is observed. The wavelength dependence of this PL is not a function of size, but rather particle crystallinity. A separate PL feature, near 430 nm, is reported. No size dependent effects are observed for this feature.
Photoluminescence and Structure of Chemically Etched Si
Authors: Shih S. , Jung K. H. , Hsieh T. Y. , Sarathy J. , Tsai C. , Li K.-H. , Campbel J. C. , Kwong D. L.
Published: March 2011

We demonstrate for the first time that chemical etching of Si in HF-HNO3-based solution without applying bias can produce a room temperature photoluminescent porous Si layer. Scanning electron microscope studies reveal a surface morphology similar to that of the conventionally anodized porous Si. The formation mechanism of the chemically etched (CE) film can be explained by a local anodization concept. X-ray diffraction studies on the luminescent CE porous Si show a broad amorphous peak.
Visible Light Emission from Silicon Nanoparticles
Authors: Zhang D. , Kolbas R. M. , Mehta P. , Singh A. K. , Lichtenwalner D. J. , Hsieh K. Y. , Kingon A. I.
Published: March 2011

Orange-red light emission has been observed for the first time from crystalline silicon nanoparticles produced by gas phase synthesis in a non-thermal microwave plasma. The size and crystalline nature of the particles have been confirmed by transmission electron microscopy and X-ray diffraction. Photoluminescence at 300 K and 77 K has been measured and analyzed. The emission spectra are consistent with quantum mechanical calculations based on a quantum box.
Light-Emitting Porous Silicon in High Magnetic Fields
Authors: Zheng X. L. , Chen H. C. , Wang W. , Heiman D.
Published: March 2011

Photoluminescence from porous silicon was studied in a helium atmosphere and at high magnetic fields. In a magnetic field, the spectral peak had a negligible shift, amounting to +0.2 ±0.5 meV at B= 18T. If quantum confinement is the major effect, then the conduction electron would be confined to a diameter of less than 3.5 nm.
R717 Glass Alteration in the Presence of Mortar: Effect of the Cement Grade
Authors: Andriambololona Z. , Godon N. , Vernaz E.
Published: March 2011

R717 glass alteration was investigated in the presence of four mortars prepared from four different cement grades: “CPA” Portland cement (mortar M1), CPA with pozzolana additive (M2), CPA with amorphous silica additive (M3) and “CLK” blast furnace slag cement (M4). Glass specimens were also altered in Volvic mineral water and in a cement effluent. Glass corrosion in the cement media was greater than in Volvic water, but well below what could be expected from the high pH (approx 12.5). The relatively low alteration was probably related to the protective action of the calcium-enriched gel layer that formed at the glass surface. The glass corrosion rate was 2 to 3 times lower with cement containing pozzolana or silica gel additives or with CLK cement than with CPA cement alone.
Microstructure of Simulated High-Level Waste Glass Doped with Short-Lived Actinides, 238Pu and 244Cm
Authors: Inagaki Y. , Furuya H. , Idemitsu K. , Banba T. , Matsumoto S. , Muraoka S.
Published: March 2011

The microstructural changes of a simulated waste glass irradiated with doping of 238pu and 244Cm were observed by use of a preshadowed carbon replica technique in combination with scanning electron microscopy (SEM). The irradiated glass was annealed and its microstructural changes after annealing were observed by use of the sametechnique.

In the glass irradiated at a dose of 2.75x1025 α-decays/m3, bubbles with a radius from 0.15μrm to 0.35μm were observed. The average bubble radius and the bubble density were 0.23μm and 1x1017 bubbles/m3, respectively. Using these observed values, the volume change of the glass resulting from the bubble formation was estimated to be + 0.51 %. This valuoof + 0.51 % was close to the volume change of the irradiated glass measured in our previous study, which suggests a large portion of the volume change by α-irradiation results from bubble formation. In the glass annealed after irradiation the average bubbleradius was observed to decrease with annealing time. The bubble radius as a function of annealing time was analyzed on the basis of the helium diffusion model with two chemicalprocesses, i.e. trapping at bubbles and re-solution from bubbles into glass matrix. The values of the diffusion coefficient of helium, the trapping parameter and the re-solution parameter, which had been obtained experimentally in our previous study on the helium release, were applied to the calculation. The calculated curve was in good agreement with the observed data.
Remote Monitoring of Molten Radioactive Glass
Authors: Schneider Alfred , Li Kang-Wen K. , Schumacher Ray F.
Published: March 2011

An on-line method is described for the near-continuous monitoring of the composition of a molten radioactive waste glass or, alternatively, for signaling a deviation from the target composition of a waste glass. The principle of this method, proposed by A. Schneider in 1986, is founded on the relation between two specific physical properties and composition in a ternary system. Most glasses currently considered as waste forms can be represented as pseudo-ternary systems. The pair of properties especially well suited for this purpose are the viscosity and density of the molten glass. A novel viscometry method was developed which uses the remotely determined rise velocity of carefully metered gas bubbles. The monitoring method was tested successfully with simulated Savannah River waste glasses. An integrated probe was conceived for a Joule-heated melter for the on-line determination of viscosity, temperature, density, and liquid level. A computer program calculates the glass composition from the measured data, using information from a previously developed data base.
An Aluminumsilicate Ceramic Nuclear Waste Form
Authors: Loida A.
Published: March 2011

Aluminum silicate based ceramics were studied as matrix materials for the immobilizationof real TRU—wastes, as well as simulated high-level and TRU—waste mixtures. As observed by XRD and electron microscopy, isolation of radionuclides is achieved either by encapsulation of radiophases by aluminumsilicate matrix phases and by incorporation into host phases in the matrix. TRU—leach rates were found to be on the order of 5*10–3 and 1*10–2 gm–2 d–1 at room temperature after one year in MgCl2 —rich salt solution. By doping the ceramic matrix with 20 weight percent PuO2 an accumulated α-dose of 8.33*109 Gy (1*1019 α-decays*g–1) was reached after 3 years. The microstructure and the lattice constants ofthe matrix phases were not affected by a-irradiation.
Europium and Cesium Ion Immobilization in Crystalline Hosts with Magnetoplumbite or Related Type Structures
Authors: Thery J. , Borel C. , Vivien D.
Published: March 2011

This study deals with the incorporation of Eu3+ ions in aluminates with magnetoplumbite (MP) or mixed β alumina - MP type structure. The synthesis procedure is the coprecipitation from a nitric solution. Partial substitution of Eu3+ byLa3+ increases the thermal stability range of the phases. In these structuresEu3+ occupies several sites and in the case of Na+ containing phases, Eu3+ and Na+ coexist at some mirror planes. Some results concerning Cs+ ion immobilization in mixed β - MP structures, by ionic exchange in molten salt are also reported.
The Importance of Transuranium Solids in Solubility Studies for Nuclear Waste Repositories
Authors: Nitsche Heino
Published: March 2011

Solids obtained from laboratory solubility experiments in two different groundwaters from the Yucca Mountain region, Nevada, are described. The solubility study provided limiting solubility concentrations for neptunium(V), plutonium(IV), and americium(III) in groundwaters from Wells J-13 and UE-25p#l. The solubility-controlling solids are compared to relevant radionuclide compounds that are reported in the literature. The preparations and some characteristics of published solids that possibly may form in actinide-groundwater systems are described. The solids formed in the experiments are sodium neptunium(V) carbonates, polymeric Pu(IV) that contained small amounts of carbonate, and hexagonal or orthorhombic americium(III) hydroxycarbonates.
The Effects of the Degradation of Organic Materials in the Near Field of a Radioactive Waste Repository
Authors: Greenfield B.F. , Moreton A.D. , Spindler M.W. , Williams S.J. , Woodwark D.R.
Published: March 2011

UK Nirex Ltd are seeking to develop a deep underground repository for the disposal of solid ILW and LLW in the UK. The formation of water-soluble complexants from the degradation of the solid organic polymers and cellulosic materials present in such wastes may influence the solubility and sorption properties of a number of radioelements. A number of materials have been chemically degraded under alkaline, anaerobic conditions representative of the near field of the repository. Measurements of plutonium solubility in the leachates obtained show that the degradation of cellulose is of particular concern; the effects on the solubility can be several orders of magnitude greater than those of other organic materials. Products formed from the degradation of ion-exchange resins were found to have little effect. Solubilities of a number of other radioelements in aerobically degraded cellulose leachates are also given. The effect of reducing the ratio of celluloseto cement in the degradation experiments results in a decrease in plutonium solubility in the corresponding leachate. Several of the likely degradation products of cellulose have been individually synthesised including isosaccharinic acid, a key degradation product of cellulose. Enhanced plutonium solubilities have been measured in 10-3M solutions of these compounds. Sorption of plutonium onto cement from leachates obtained by the degradation of 10% cellulose in cement is reduced by about two orders of magnitude. Interaction with cement removes significant concentrations of complexants from solution. Thermodynamic modelling studies show that hydroxyl groups present in the compounds which result from the alkaline degradation of cellulose can strongly complex with plutonium.
Is Geological Disposal the Only Answer?
Authors: Teillac Jean
Published: March 2011

All wastes are distinguished by their harmful effects: radioactivity in the case of radioactive waste. An advantage of this type of waste is that the harmful effects diminish in time. Pending this radioactive decay, the materials must be contained to avoid human exposure to radiation, which is not difficult; assurance mlust also be provided, however, that the containment is effective for very long durations, consistent with the half-lives of the radionuclides involved.
Instant Release of14C,99Tc,90Sr and137Cs from Used Candu Fuel at 25°C in Distilled Deionized Water
Authors: Stroes-Gascoyne S. , Tait J.C. , Garisto N.C. , Porth R.J. , Ross J.P.M. , Glowa G.A. , Barnsdale T.R.
Published: March 2011

Instant-release fractions were measured for release of14C,99Tc,90Sr and137Cs from segments of clad used CANDU fuels in distilled deionized water at pH 8.5 and 25°C. Measured–instant release values, 0.002 to 0.07% for14C, 0.001 to 0.23% for99Tc and 0.0005 to 0.04% for 9 0 Sr, were one to two orders of magnitude lower than the estimated values currently used in the safety assessment of the Canadian concept of geological disposal of intact used CANDU fuel. The values for14C were also lower than values reported in the literature for PWR fuels.
Movement of the Redox Front at a Uranium Mine at POÇOS De Caldas
Authors: Romero Leonardo , Neretnieks Wars , Moreno Luis
Published: March 2011

In an open pit uranium mine at Pogos de Caldas (PDC) in Brazil, uranium oxide has accumulated at the redox front. The redox front forms and moves by the oxidation of pyrite in the rock by oxygen infiltrating with rainwater. The rock was formed nearly 90 million years ago by volcanic activity. Between 3 and 12 km of rock has eroded away since the formation of the rock. The redox front lies between tens and several hundred meters below the ground surface. The front is uneven and locally there are redox “fingers” which extend to depths of hundreds of meters. The redox fingers are often associated with fractures or fracture zones.
U and Nd Isotopes from the New Oklo Reactor 10 (GABON): Evidence for Radioelements Migration
Authors: Hemond C. , Menet C. , Menager M.T.
Published: March 2011

New isotopic data on daughters of transuranium elements and fission products from the Oklo reactor 10 and its surrounding provide evidences of Nd and U migrations. Whereas Nd was released only along carbonated fissures (NdFp as high as 1.048 in the fissures compared to 1.007 in the neighbouring sandstone), U has migrated through the sandstone as well (abnormal negative 235U anomalies as low as 0.714 in both fissures and surrounding sandstone). Nevertheless the released amount of radioelements is very small and visible in the drop of the concentrations between the reactor and the surrounding sandstone [8]. As consequence, a retention effect is evidenced at the reactor-sandstone boundary.
The Alligator Rivers Analogue Project - Characterisation of the Development of the Uranium Dispersion Fan
Authors: Duerden P.
Published: March 2011

The Koongarra uranium deposit in the Northern Territory (NT) of Australia is being studied to evaluate the processes and mechanisms involved in the hydrological/geochemical alteration of the primary uranium mineralisation and model the formation of the secondary uranium orezone and the dispersion fan. The project includes studies of groundwater flow through the orebody, the chemistry of intersecting groundwaters and the uranium distribution and mineralogy of the orezones. The work has resulted in solid phase and groundwater databases, and hydrological data from field and laboratory measurements. These are being used to test a range of geochemical, hydrological and transport models.
Diffusion of Carbon Dioxide Through Upper Layers of Yucca Mountain
Authors: Singh Ajeet , Tatterson Gary , King Franklin G. , Bardakci Tevfik
Published: March 2011

The effective diffusivities of carbon dioxide through Tiva Canyon tuff and the lower lithophysal zone of the Topopah Spring tuff (outcrop sample of the layer above the proposed nuclear repository site layer) were determined using a steady-state method (counter diffusion). The diffusivity of carbon dioxide through the Tiva Canyon and lithophysal zone tuffs increased with temperature and decreased with percent saturation. The following correlation was obtained to estimate the effective diffusivity of carbon dioxide through the Tiva Canyon tuff as a function temperature and percent saturation.

De = 1.2168×10−2 − 3.7713×10−5 T + 9.9510×10−8 T2 − 4.2220×10−5 × (Percent Saturation)

where De is in cm2/sec and T in K. These units hold for all other correlations in this paper.

The effective diffusivity of carbon dioxide through the lower lithophysal zone of the Topopah Spring tuff (layer right above the proposed repository site) also increased with temperature and decreased with percent saturation. For this layer, the following correlation was obtained to estimate the effective diffusivity of carbon dioxide as a function temperature and percent saturation.

De = − 1.119×10−3 + 1.2512×10−5 T + 1.8288×10−9 T2 × 2.0725×10−5 × (Percent Saturation)
Applications of the Carbon-14-Polymethylmethacrylate (PMMA) Impregnation Method in Studies on Porosity and Matrix Diffusion
Authors: Hellmuth K-H. , Shtari-Kauppi M. , Lindberg A.
Published: March 2011

We are presenting applications of a new technique for the study of porosity and diffusivity in rocks employing impregnation with labeled polymethylmethacrylate. We studied samples of different rock types and rock that has undergone various types of alteration. We have focussed special attention on fissures and fissure fillings. Association of porosity with certain mineral phases has been addressed. The spatial distribution of rock porosity exhibits a great diversity. It is a rock-typical parameter. Altered rock is, usually, characterized by inhomogenities in porosity and anisotropy of migration pathways.
Long Term Field Leaching Studies of Simulated Nuclear Waste Glass in Granite and Salt
Authors: Schulz R.L. , Clark D.E. , Lodding A.R. , Wicks G.G.
Published: March 2011

Field leaching studies were carried out in granite at the Stripa site in Sweden and also in salt in the Materials Interface Interaction Test at the Waste Isolation Pilot Plant (MIIT/WIPP) in New Mexico. The goal of these studies is to assess the durability of various glass compositions engineered to isolate high-level nuclear waste from the biosphere. An additional goal of the MIIT study is to determine how the glasses interact with a wide array of proposed materials that may be a part of the multi-barrier waste package. These substances include metals, geological host specimens,, as well as engineered backfill and overpack materials.

Two year data on the SRLY (165/TDS) glass compositions has been extracted from both studies (Stripa and WIPP/MIIT) and five year data has recently become available from the MIIT study. Results from SEM/EDS, SIMS and FTIRRS analyses on glass/glass interfaces are presented in this paper.
Transient Diffusion from the Near-Field, A 3-D Model
Authors: Bengtsson A. , Grundfelt B. , Widén H.
Published: March 2011

A study of near-field radionuclide migration is presented. The study [1] has been performed in the context of the SKB91 study which is a comprehensive performance assessment of disposal of spent fuel. The objective of the present study has been to enable the assessment of which nuclides can be screened out because they decay to insignificant levels already in the near-field of the repository.

A numerical model has been used which describes the transient transport of radionuclides through a small hole in a spent fuel canister imbedded in bentonite clay into a fracture in the rock outside the bentonite. Calculations for more than twenty nuclides, nuclides with both high and low solubility, have been made. The effect of sorption in the bentonite backfill is included. Materials data for bentonite where taken from [2]. The size of the penetration hole was assumed to be constant up to the time when the calculations were terminated, 500 000 years after the deposition. The mass transport rate is controlled by diffusion. The model is three dimensional.

This paper describes the geometry of the modelled system, the assumptions concerning the transport resistances at the boundary conditions, the handling of the source term and obtained release curves.
Release of Radionuclides from the Near Field by Various Pathways. The Influence by the Sorption Properties in the Near Field.
Authors: Romero Leonardo , Neretnieks Wars , Moreno Luis
Published: March 2011

Radionuclides from a damaged canister for spent fuel will leak out through a damage in the canister wall and spread through the surrounding backfill. They will further migrate into water bearing fractures in the rock, up through the backfill into the damaged zone around the drift and into the drift itself. Some substance may also diffuse through the rock to adjacent fracture zones. Underway the nuclides will sorb on the materials along the transport paths. This very complex and variable transport geometry has been modelled using a compartment model which is based on simplifying a full 3 dimensional integrated finite difference model. The simplifications are supplemented by introducing analytical and semianalytical solutions at sensitive locations such as entrances and exits from damages and fractures and in the flowing water. The model has been tested against full 3D solutions with good results. Sample calculations are presented and discussed for a nuclide with the chemical properties of Pu-239.
The Future of the Back End of the Fuel Cycle: Volume and Activity Reduction of Wastes Containing Long Half-Life Radionuclides
Authors: Barré J.Y.
Published: March 2011

The future of the nuclear industry and its acceptance by public opinion depend to a large extent on the development of an acceptable solution for waste management and disposal. The long duration of the hazard presented by certain radionuclides found in nuclear wastes is certainly one of the reasons for public concern over definitive waste disposal.
The Effect of Precipitation Fronts Induced by Radionuclide Chain Decay and Elemental Solubility Limits on Near-Field Mass Transport
Authors: Worcan Karen J. , Apted Michael J.
Published: March 2011

The formation and impact of precipitation fronts on the diffusional mass transport of radionuclides from a high-level nuclear waste canister through a bentonite buffer has been investigated in a series of numerical simulations. The precipitation fronts arise from chain decay and ingrowth, coupled with differences in elemental solubility limits and sorption properties. The fronts influence particularly the behavior of uranium, plutonium and neptunium isotopes. The isotopic concentration profiles across the buffer differ considerably from results obtained with models that employ elemental solubility limits simply as a boundary condition at the waste-bentonite interface.
A Possibility for Hlw Disposal in Very Deep Boreholes
Authors: Byalko A.V.
Published: March 2011

Recently we proposed [1] that high-level nuclear waste be deposited in very deep boreholes, filled with a substance of low melting temperature, of high density, not generating gases and water-insoluble.

The first paper outlined nuclear waste disposal in deep boreholes, discussions of physical and chemical processes in a filled borehole and preliminarily comments on the ecological safety of the disposal. The given paper covers some economical aspects of the new proposal as well as the principal steps of implementation of the R&D program.