bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Situ TEM Observations of Surface Roughening and Defect Formation in Lattice Mismatched Heteroepitaxial Thin Films
Authors: Ozkan Cengiz S. , Nix William D. , Gao Huajian 
Published: April 2011

ABSTRACTThis paper focuses on in-situ transmission electron microscopy observations of surface roughening and defect formation in heteroepitaxial Sil−xGex thin films. Annealing experiments have been carried out in-situ in the microscope under a high vacuum environment. We comment on the sample preparation procedure for in-situ TEM experiments and explain the importance of having a sufficiently thick sample to have the stress state in the film unaltered. Experimental results of in-situ surface roughening are presented for suberitically and supercritically thick Sil−xGex films. We found that, in a vacuum environment, the kinetics of surface roughening and the resulting surface morphology are much different than in a hydrogen environment.
Polycapillary X-Ray Optics for Thin Film Strain and Texture Analysis
Authors: Hofmann F. A. , Gibson W. M. , Lee S. M. , Macdonald C. A. , Ullrich J. B. , GAO N. 
Published: April 2011

ABSTRACTPolycapillary optics, shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, can be used to redirect, collimate, or focus x-ray beams from conventional, laboratory-based sources. Multifiber polycapillary collimating optics were placed without system optimization into a number of diffractometer systems. Strain and texture measurements were performed. Measurements on thin films with and without the lens yielded gains of 8–100. Gains are higher in comparison with systems employing pinhole rather than one-dimensional slit collimation. The collimation also resulted in peak symmetrization, which simplified peak shape analysis.Focused beam optics provide even larger gains. Gains of 100 have been demonstrated using polycapillary optics with spot sizes as small 20 μm. This is of particular significance for providing spatial resolution for low signal applications such as thin films. The inverse dependence of the critical angle for total external reflection on photon energy also results in suppression of high energy photons. This suppression of Bremsstrahlung can allow use of higher tube potentials to increase characteristic line emission. Background suppression from a polycapillary optic ″soller slit″ is also enhanced due to the two dimensional collimation and much smaller acceptance angle of the polycapillary optics. Polycapillary optic alignment is also faster and more convenient than the usual parafocusing geometry. The combination of background suppression, intensity gain and increased tube emission by employing polycapillary optics greatly increases the signal to noise ratio for thin film stress analysis.
Effects of Interface Nonplanarity on the Interface Fracture Energy of the TiN/SiO2System
Authors: Lane Michael , Ni Winnie , Dauskardt Reiner , Ma Qing , Fujimoto Harry , Krishna Nety 
Published: April 2011

ABSTRACTFracture mechanics models indicate that nonplanarity of the interface should have a significant effect on the measured fracture energy [1–5]. Previous work on a typical interconnect structure (Fig 1) has demonstrated that two thin film systems with nominally the same composition, but processed under different conditions exhibited different SiO2/TiN interface fracture energies [6,7]. pon investigation via crosssectional TEM, it was found that the stronger interface was significantly rougher than the weaker interface. These results indicate that small changes in processing conditions can significantly effect both interface morphology and adhesion. Accordingly, in this study, samples differing in the flow rate of Ar to a plasma arc during deposition of a TIN layer were chosen in order to investigate the effects on the interface morphology and the resulting interface fracture energy.
Tem Study of Yielding in Polycrystalline Gold Thin Films
Authors: Owusu-Boahen Kwame , King Alexander H. 
Published: April 2011

ABSTRACTWe have used transmission electron microscopy (TEM) to study the microstructure of thin gold films which were grown on 〈100〉 rock salt. The samples were annealed on the rock salt substrate or on a gold TEM specimen grid. Films annealed on rock salt had a larger mean grain size than those annealed on TEM grids. All of the annealed films have a 〈111〉 preferred orientation. Several cracks are observed in the film annealed on rock salt. Plastic yielding of the film was identified by the presence of dislocations, and is caused by tensile stress derived from grain growth. In spite of the uniform texture of the films, the observed dislocations were concentrated only in some individual grains, while their surrounding grains remained dislocation-free. Yielded grains showed no difference of orientation that would lead to higher Schmid factors, so other predictors of yielding must be considered.
Surface Stress Effects On The Critical Thickness Of Thin Film Superlattices
Authors: Cammarata R. C. , Sieradzki K. 
Published: April 2011

ABSTRACTSurface stress represents the reversible work per unit area to elastically stretch a solid surface, and can be associated with interfaces between two solid phases as well as free solid surfaces. The effects of surface stresses on the critical thickness for epitaxy in thin film superlattices is given.
Determination of the Mechanical Properties of Polysilicon Thin Films Using Bulge Testing
Authors: Jayaraman S. , Edwards R. L. , Hemker K. J. 
Published: April 2011

ABSTRACTUsing standard deposition and micromachining techniques, silicon substrates with square and rectangular windows covered with membranes of polycrystalline silicon (polysilicon) have been fabricated. Pressure-displacement curves obtained during the bulge testing of membranes with the above geometries have been used to determine the elastic constants E and v of the polysilicon. The results obtained (E = 162± 4 GPa and v = 0.19±0.03) are in good agreement with literature values for bulk polycrystalline silicon.
The Effects of Residual Stress on Modulus Measurements by Indentation
Authors: Bahr D. F. , Crowson D. A. , Robach J. S. , Gerberich W. W. 
Published: April 2011

ABSTRACTContinuous indentation has been used to evaluate the mechanical response of chromium and platinum films deposited on silicon and glass substrates. The traditional method of analysis of indentation data to determine modulus and hardness is sensitive to residual stress in the film, thereby suggesting that modulus measurements may be used to gauge residual stresses. Evaporated metal films, which are under residual tension, tend to show a lower modulus (using standard calculation methods) than the bulk materials. However, a sputtered platinum film exhibits an apparently higher modulus than the bulk material. These data suggest that differences between the calculated and expected modulus using indentation tests cannot be used to unequivocally determine the stress state in a thin film.
Probabilistic Modeling of Gas Transport in a Plugged Repository in Salt Rock
Authors: Höglund L O , Wiborgh M , Arens G. 
Published: April 2011

ABSTRACTSince 1981 the former rock salt mine Bartensleben near Morsleben (former GDR) ERAM has been in operation as a repository for low and intermediate level radioactive waste. As a result of the reunification and the changed licensing situation a new closure concept for the repository has to be developed. In the course of this work, the optimal design of the plug is currently being evaluated considering also gas escape and exchange of potentially contaminated brine through the plug.
A Regulatory Authority's Needs for R&D to Develop Competence in Assessing Nuclear Waste Management Safety
Authors: Norrby Sören 
Published: April 2011

ABSTRACTA regulatory authority in the field of nuclear waste management will not be responsible for the waste management itself. The regulator will however be responsible for reviewing the safety of the waste management activities proposed and performed by nuclear power plant owners or special organisations set up to manage and dispose of nuclear waste. In this paper the regulator's need for R&D to develop competence in the assessment of nuclear waste management safety is discussed.
Source Trends for Performance Assessment of HLW Glass and Spent Fuel as Waste Forms
Authors: Grambow B. 
Published: April 2011

ABSTRACTwith respect to the state of validation for source term development. Consequences of the various mechanism on mass half lives of the waste forms are calculated with analytical equations. For glass the largest uncertainty stems from the yet unclear dissolution mechanism under silica saturated conditions. Source terms based on silica solubility coupled to Si-mass transfer are probably neither conservative nor realistic. For spent fuel the largest uncertainty is in the extrapolation of radiolytic fuel oxidation for long periods of time. Considering the uncertainties involved, reaction rates cannot yet be extrapolated reliably to values much lower than the lowest reliable experimental measurements.
Chemical Durability of Aluminosilicate Glasses Containing Low Solubility Chemical Elements
Authors: Leturcq G. , Berger G. , Advocat T. , Fillet C. , Halgand C. , Vernaz E. 
Published: April 2011

ABSTRACTThe chemical durability of aluminosilicate glasses was investigated experimentally between 90 and 200°C. In order to evaluate their potential for containment of minor actinides, these glasses were doped with Nd (to simulate the presence of trivalent actinides) or U. The proportions of the glass network formers, Si and Al, were near those found in basaltic glasses (tholeitic end members). The differences between the chemical compositions allow the clarification of the influence of glass network modifier elements on the chemical durability of silica glasses. More precisely, we tested the ability of Ti, Zr, Nd and N to potentially improve the chemical durability.Two types of leach tests were conducted:Dynamic leach tests to determine the initial dissolution rates at 90, 150 and 200°C and the activation energy (Ea) of the glass dissolution reaction;Static leach tests at high SA/V (200 cm−1) and 90°C to determine the long-term alteration rates and the apparent silica solubility.For all the glass compositions tested, the initial dissolution rates at nearly neutral or weakly basic pH are similar at the same temperature. Consequently all aluminosilicate glasses have the same activation energy, 60 kJ/mol. This suggests that the initial hydrolysis mechanism is controlled by the breakdown of Si-O and/or Al—O bonds, whatever the nature of glass network modifier elements.On the other hand, modifier elements have major effects on the formation of protective films at the glass surface. The nature of this protective film depends on the chemical composition of the glass. A phenomenon similar to metal passivation, has been observed on a glass highly enriched with Nd (53.8 oxide wt%) which may lead to alteration rates in undersaturated media up to two orders of magnitude lower than those observed for basaltic glasses. This “passivation” effect disappears when a sodium sulfate solution (a Nd complexing agent) is used as a leachant. Nitrogen does not improve the chemical durability of aluminosilicate glasses. Finally, all these glasses have the same low dissolution rate (10−4 g/m2/day) under saturated conditions.
Chemical Composition, Geochemical Alteration, and Radiation Damage Effects in Natural Perovskite
Authors: Lumpkin Gregory R. , Colella Michael , Smith Katherine L. , Mitchell Roger H. , Larsen Alf Olav 
Published: April 2011

ABSTRACTPreliminary analytical and transmission electron microscopy (AEM and TEM) results for a small suite of natural perovskites are reported in this paper and discussed in relation to previous work. We show that perovskite compositions in Synroc and tailored ceramics plot within the known fields of natural perovskite compositions. AEM analyses and electron diffraction work on selected samples indicate that they are predominantly stoichiometric variants of the cubic perovskite structure. Geochemical alteration was observed in one sample of loparite from Bratthagen, Norway. The primary result of this alteration was leaching of Na from the A-site. Although sufficient alpha-decay dose levels for complete amorphization are not realized in this suite of samples, the available data bracket the beginning of the crystalline-amorphous transformation at doses that are ∼ 2-4 times greater than those of zirconolite of similar age. These results may be due to fundamental differences in the damage annealing rates of perovskite and zirconolite.
Apatitic Waste Forms: Process Overview
Authors: Carpena J. , Audubert F. , Bernache D. , Boyer L. , Donazzon B. , Lacout J.L. , Senamaud N. 
Published: April 2011

ABSTRACTOur study is concerned with the different apatitic waste forms which can be produced with processes ranging from high-temperatures to ambient temperature synthesis. The different processes developped allow to take into account the nature of the waste and the application targeted, from specific conditioning of separated wastes, encapsulating of mixed wastes, solid or liquid wastes, to filling materials for direct storage of spent fuel, interim storage, surface storage or deep repository.
Nd-Doped Zirconolite Ceramic and Glass Ceramic Synthesized by Melting and Controlled Cooling
Authors: Advocat T. , Fillet C. , Marillet J. , Leturco G. , Boubals J.M. , Bonnetier A. 
Published: April 2011

ABSTRACTNeodymium-doped zirconolite materials may be synthesized by two melting processes. One involves devitrification of an aluminosilicate parent glass containing titanium, zirconium and neodymium oxides, yielding a glass ceramic comprised of submicron zirconolite needles embedded in a silica-rich glass matrix. The second method consists of melting an oxide mixture with the stoichiometry of a highly Nd-enriched zirconolite, then quickly cooling the melt to produce a ceramic rich in zirconolite crystals several hundred microns long containing a large fraction of the initial neodymium.
An Integrated Testing Program for a Near-Field Radionuclide Migration Code
Authors: Binks P. , Fairhurst A. , Howarth D. , Humphreys P. N. , Johnstone T. , Jones M. , Kelly E. , Lee A. , Mcgarry R. , Randall M. , Smalley D. , Thomson G. , Trivedi D. P. 
Published: April 2011

ABSTRACTThe DRINK code is a 2D, biogeochemical transport code developed as a research tool to simulate the long term evolution of near surface LLW disposal sites and to generate gaseous and liquid source terms for far field studies. The code was recently upgraded to provide a more generic modelling tool with wider application to radionuclide migration scenarios. During the development of this code, the Generalised Repository Model (GRM), an integrated strategy has been employed to ensure the production of a fully tested, verified and quality assured product. This strategy is based around a code development protocol with three main components: quality assurance and documentation, verification and realism testing. Realism testing includes both peer review and model testing, with the latter including: experimental test cases; natural and anthropogenic analogues; field observations and finally uncertainty and sensitivity analysis. This paper describes the successful application of the protocol to the development and testing of the GRM code with specific emphasis upon verification and realism testing.
Simulation of the Evolution of a Clay Engineered Barrier by Interaction With Granitic Groundwater: Dynamics and Characteristic Time Scales
Authors: Cranga M. , Trotignon L. , Martial C. , Castelier E. 
Published: April 2011

ABSTRACTThe chemical evolution of a clay engineered barrier in a deep repository interacting with various groundwaters is predicted using the TRIO-EF code supported by additional models tested against experimental data. Main results of this work are related to the long term evolution of the porewater and the buffering effect of the clay barrier in the presence of ion exchange sites and calcite, when exposed to representative granitic groundwaters or more acidic or alkaline waters.
Application of a 3D-Geoscience Information System Within the Performance Assessment of the Geological Barrier Above the Morsleben Nuclear Waste Repository
Authors: Ehrminger B. , Schindler M. , Hugi M. , Wollrath J. , Kibel H. , Langkutsch U. 
Published: April 2011

ABSTRACTThe application of a 3-dimensional geoscience information system (GSIS) in the performance assessment of the geological barrier of the nuclear waste disposal site Morsleben is presented. A primary objective is the development of a geometrically consistent three-dimensional model, representing all relevant hydrostratigraphic units in the model area. Following the completion of the structural model, Finite-Element mesh generation techniques are applied to derive a threedimensional spatial discretisation for numerical modelling of the regional groundwater movement.
Conditioning of Ash Residue in the Reaction Wave of Glass-Forming Heterogeneous Composition
Authors: Karlina O.K. , Petrov G.A. , Ojovan M.I. , Varlackova G.A. , Dmitriev S.A. 
Published: April 2011

ABSTRACTThe possibility of furnace free vitrification of ash residue was considered by using heat generation by means of exothermal chemical reactions which occur in the mixture of heat generating materials (heating batch), glass forming batch and ash residue.
Model Calculations of Porosity Reduction Resulting From Cement-Tuff Diffusive Interaction
Authors: Lichtner Peter C. , Pabalan Roberto T. , Steefel Carl I. 
Published: April 2011

ABSTRACTTo determine the potential effects of alkaline plume migration on the near-field environment of the proposed high-level radioactive waste geologic repository at Yucca Mountain, Nevada, calculations are conducted simulating interactions between cement and tuff with pure diffusive transport of solute species. The calculations used the reactive transport submodule GEM of the computer code MULTIFLO [6]. The results suggest that strong alteration of the tuff host rock and of cement in contact with the tuff could result from these interactions. Porosity reduction within the tuff could isolate the matrix from fracture pore water. The model calculations predict calcification of the cement as would be expected. In simulations involving counter-diffusive transport across the cement-tuff contact, calcification is more pronounced in a partially-saturated environment compared to a fully-saturated one.
Criticality in a Repository for Spent Fuel: Lessons From Oklo
Authors: Oversby V. M. 
Published: April 2011

ABSTRACTThe conditions that are needed to achieve criticality in a high level waste repository for spent nuclear reactor fuel are reviewed. The effect of initial enrichment of the fuel, burnup, and of mixed oxide fuels on the conditions for criticality are discussed. The situations that produced criticality at Oklo, Gabon, 2000 million years ago are summarized. A model based on the Oklo conditions is presented for estimating the amount of fissile material that must be assembled to create a critical mass in typical granitic rocks. Mechanisms for movement of uranium and plutonium to achieve a critical configuration are discussed and compared to the conditions that are likely to occur in a repository in granite. The sequences of events needed to produce a critical assemblage are shown to be in conflict with the conditions expected in the repository and, in some cases, to require internally inconsistent assumptions to produce the postulated sequence of events. No credible scenario for achieving criticality in a high level waste repository has been found.
Modeling a Cement Degradation Experiment by a Hydraulic Transport and Chemical Equilibrium Coupled Code
Authors: Pfingsten W. , Shiotsuki M. 
Published: April 2011

ABSTRACTAn experiment degrading a porous cement disc by pure water was modelled by a reactive transport model including chemical reactions, mineral precipitation/dissolution reactions and changing hydraulic properties of the cement. For the early cement degradation or high pH phase, an equilibrium sorption approach is used for the release of alkali metals. Porosity changes of the porous cement disc during degradation induce conductivity changes that are taken into account in the modelling by coupling back transport to geochemical parameters.
Laboratory Measurement of Low-Permeability Rocks With a New Flow Pump System
Authors: Zhang Ming , Takahashi Manabu , Esaki Tetsuro 
Published: April 2011

ABSTRACTNearly impermeable host rocks have been recognized as favorable media for many kinds of underground utilization such as radioactive nuclear waste disposal, storage of oil and LP gas, and CAES. To properly evaluate the ability of a geologic medium to retard transmission of fluids, it is necessary to accurately measure its hydraulic properties, most notably the permeability and specific storage. This paper presents a new flow pump permeability test system capable of testing low-permeability rocks under high confining and high pore pressure conditions, which simulate ground pressures at large depths. The new system was used to test the Inada Granite from Japan. The results of present study show that: 1) both permeability and specific storage of the rock are dependent not only on the confining pressure but also on the pore pressure. They decrease with the increment of the effective confining pressure, i.e., the difference between confining and pore pressures; 2) the permeability and specific storage of Inada Granite range from 10−11 to 10−12 cm/s and 10−6 to 10−7 1/cm, respectively. The flow pump technique with its rigorous theoretical analysis can be used to effectively obtain such low permeabilities within several tens of hours; 3) the storage capacity of flow pump system itself decreases with the increment of fluid pressure within the permeating system.
pH-Dependency of HLW Glass Dissolution and Sorption Behavior of Eu, Th, and U on Glass Corrosion Products
Authors: Luckscheiter B. , Grambow B. 
Published: April 2011

ABSTRACTRadionuclide release rates of HLW glasses in brines are normally orders of magnitude lower than glass corrosion rates. Various mechanisms were invoked to explain the experimental release; they may be controlled by the glass dissolution rate, solubility, sorption, coprecipitation, etc.. Glass matrix corrosion kinetics is described by a first order equation, where pH, S/V ratio, an initial constant rate and affinity term based on orthosilic acid activity are the key parameters. The dissolution rate decreases significantly as dissolved silica accumulates in solution