bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Temperature Tensile Behavior Of Free-Standing Gold Films
Authors: Emery R. , Simons C. , Mazin B. , Povirk G. L. 
Published: April 2011

ABSTRACTA method for tensile testing thin films at elevated temperatures is presented. Freestanding tensile specimens were prepared by evaporating 2.1 μm of gold onto a patterned oxidized silicon wafer. Tensile tests were performed at various temperatures up to 600°C. The ultimate tensile strengths of the films decreased as temperature increased, and ductility increased with increasing temperature. Films tested at high temperatures (≥ 400 °C) exhibited significant strain rate-dependence, while films tested at low temperatures (≤ 200 °C) were found to be virtually rate-independent. At higher temperatures and strain rates, stress-enhanced grain growth was observed.
Dislocation-Based Models of Stress-Strain Behavior in Multilayered Thin Films†
Authors: Anderson Peter M. , Kreidler Eric R. 
Published: April 2011

ABSTRACTElementary dislocation arrays are applied to multilayered thin films to predict the critical stress required to propagate dislocation loops within individual layers and to study the tendency for deformation to be uniform or localized. The analyses suggest that shearing normal to layers is a mechanically unstable, softening process while stretching parallel to layers produces substantial hardening. Further, films with smaller layer thickness, h, require larger plastic strains to initiate pile-up modes of slip. Although the initial stress required to propagate an isolated loop within a single layer scales as ln(h)/h, there is a minimum h below which the critical stress is predicted to depend only on the resistance of the interface to dislocation transmission.
Structure Determination of B4C and SiC Thin Films Via Synchrotron High-Resolution Diffraction
Authors: Hershberger J. , Kustas F. , Rek Z. U. , Yalisove S. M. , Bilello J. C. 
Published: April 2011

ABSTRACTThin films of B4C and SiC deposited by magnetron sputtering as components of multilayers have the potential to provide significant property improvements over current wear resistant coating technology. B4C and SiC have previously been found to be amorphous and possibly nanocrystalline under the deposition conditions used. This study reports results of synchrotron x-ray scattering experiments providing information on the degree of crystallinity, strain, average density, and coordination number in 2000 Å films of these compounds on Si substrates. Radial distribution functions from B4C and SiC thin films were obtained and used to model the structure. Strain results are compared with Double Crystal x-ray Diffraction Topography (DCDT) results as a means for establishing a standard strain state.
Practical Limitations to Indentation Testing of Thin Films
Authors: Schneider J. A. , McCarty K. F. , Heffelfinger J. R. , Moody N. R. 
Published: April 2011

ABSTRACTA method that is becoming increasingly common for measuring the mechanical behavior of thin films is low-load indentation testing. However, there can be complications in interpreting the results as many factors can affect hardness and moduli measurements such as surface roughness and determination of the indentation contact area. To further our understanding, the mechanical properties of thin (50 nm) films of AlN on sapphire substrates were evaluated using a scanning force microscopy (SFM) based pico-indentation device to allow imaging of the surface and indentations. Our primary emphasis was the types of problems or limitations involved in testing very thin, as deposited films in which properties are desired over indentation depths less than 50 nm.
Safety Analysis for the Loviisa Low- and Intermediate-Level Radioactive Waste Repository
Authors: Eurajoki T. , Outa S. , Routamo T. 
Published: April 2011

ABSTRACTThe Loviisa low and intermediate level radioactive waste repository is located in southern Finland, at Loviisa NPP site on Hästholmen island, where two VVER-440 reactor units are operated by Imatran Voima Oy (IVO). The repository is excavated in the bedrock, 110 meters below the sea level.
A Mechanistically-Based Model for Spallings Releases at the Waste Isolation Pilot Plant
Authors: Hansen F.D. , Knowles M.K. , Thompson T.W. 
Published: April 2011

SummaryThe Waste Isolation Pilot Plant (WIPP) is an underground facility operated by the US Department of Energy (DOE) for permanent disposal of transuranic waste. The compliance of the WIPP to the US Environmental Protection Agency regulations, as assessed by the performance assessment process, is demonstrated by comparison of potential releases to the regulatory limits. In the Compliance Certification Application the potential for solids release to the surface exists only for “disturbed” scenarios, whereby the repository is intersected by an exploratory borehole at some time during the regulatory period of 10,000 years. Releases for this scenario are dominated by three mechanisms associated with the hypothetical scenario. These mechanisms are “cuttings”; the removal of solid materials by the action of drilling, “cavings”; the removal of solids by erosion by the circulating mud, and “spallings”; the removal of solids by a gas-driven blow-out.
Modeling of Glass Dissolution and Transport With the Code SUGAR
Authors: Small J.S. , Trivedi D.P. , Abraitisti P.K. 
Published: April 2011

ABSTRACTSUGAR (Simplified Understading of Glass And environment Reactions) is a one dimensional (lD) reactive transport code which sequentially couples dissolved chemical species transport and sorption with, chemical speciation, mineral precipitation and kinetic controlled glass dissolution. SUGAR also has the capability to model radioactive decay and steel corrosion. This paper describes the computer model and presents results of model testing against experimental data. The capabilities of the model are demonstrated by a preliminary investigation of the geochemical evolution of glass in crystalline rock formations.
Further Studies of Synroc Immobilization of HLW Sludges and Tc for Hanford Tank Waste Remediation
Authors: Vance E.R. , Hart K.P. , Carter M.L. , Hambley M.J. , Day R.A. , Begg B.D. 
Published: April 2011

ABSTRACTSynroc/glass composites were designed for simulated Hanford HLW sludges containing U (the current “All-Blend” formulation). The composite contained ∼ 50 wt% of simulated HLW (oxide equivalent), to which ∼ 6, 10, 10, and 24 wt% of CaO, Al2O3, TiO2 and SiO2 were added, and melted under an argon atmosphere at 1350°C. The phase assemblage consisted of zirconolite, perovskite, spinel, nepheline, whitlockite and glass as major phases. Seven-day PCT tests yielded values of < 0. 1 g/m2 for all elements studied. The PCT results were tolerant to changes of ∼ 20% of the inventories of the additives, and to variations in redox conditions.Technetium separated out during decontamination of liquid Hanford wastes can be incorporated as metal in hot-pressed Synroc prepared under reducing conditions, and its leach resistance is good (∼ 10∼3 g/m2/day at 70°C), and can be improved by alloying with iron group metals. With a choice of “neutral” (P(O2) ∼ 10−4 atm., near the Ni/NiO buffer) hot-pressing conditions, Tc can also be incorporated as Tc4+, substituting for Ti4+ in the ceramic phases, and in this form, it should be highly leach resistant also.
High-Level Nuclear Waste Management: How Physics Can Help
Authors: Salvatores M. , Zaetita A. 
Published: April 2011

ABSTRACTThe potential value of Partitioning/Transmutation (P/T) strategies for high-level nuclear waste management has been investigated (one would be tempted so say “periodically”) since 1970. The basic physics phenomena are well understood, and scenarios for the fuel cycle can be imagined. However, the criteria to judge the impact of P/T are matter for discussion (and controversy). Moreover the relation to disciplines other than reactor physics can be significant (e.g. innovative fuels and Actinide chemistry).A number of key issues are revisited here and will be discussed in some detail.
Large-Scale Model Testing of a Concrete Silo EBS for Low- and Intermediate-Level Waste Disposal
Authors: Konishi K. , Ukaji K. , Fujiwara A. , Endo T. , Tsuji Y. 
Published: April 2011

ABSTRACTThis study focuses on demonstrating the feasibility of constructing a large reinforced concrete silo for the disposal of low- and intermediate-level radioactive waste. In a large-scale model test, the results of temperature (from heat of hydration) and thermal stress analyses were confirmed, as was the practicality of countermeasures to prevent thermal cracking. After one year, the average permeability of the model silo was estimated to be below 1×10−11m/s.
Scientific Progress Toward Meeting R&D Needs: Autobahns and Wanderwegs
Authors: Hadermann J. , Berner U. , Pearson F.J. 
Published: April 2011

ABSTRACTThis paper summarises the last talk given at the conference. Its contents were prepared during the first four days of the symposium with the goal of comparing the R+D needs as specified by three invited lectures with the actual scientific work as given in oral and poster contributions by symposium participants. We first present some general conclusions and then address specific aspects of the individual sessions. Finally, the main conclusions from the six workshops are given.
Ionic Transport in Compacted Bentonite: Preliminary Equilibrium Results
Authors: Lehikoinen J. , Muurinen A. , Olin M. 
Published: April 2011

ABSTRACTAn attempt is made to decompose some quantities, most commonly integrated over the chemical composition, the structure of the pore network and the time scale, into their differential counterparts. Into this category typically fall, say, the apparent diffusivities of ionic species. To serve this objective, a two-dimensional unsteady molecular-level electrokinetic transport model for ionic species in bentonite clays will be developed. The model incorporates additional features to the conventional Gouy-Chapman (GC) theory: ionic hydration, dielectric saturation, and the volume exclusion of ions. The governing equations for the flow of electrolyte solution through the pores are solved by an iterative numerical scheme to relate the characteristics of the flow to the characteristics of the pores and to the composition of the external solution in contact with the clay. The pore geometry of the clay is modelled as an array of non-interconnected tortuous channels with no parallel or serial-type non-uniformities along the pathway. This roughly corresponds to the picture of clay particles of infinite extent aligned in parallel and spaced apart by a constant distance. The model aims to simulate and interpret equilibrium and transport experiments for bentonite clays containing different types of background electrolytes at various compactions. Specifically, emphasis is placed on quantifying the extent of co-ion exclusion and understanding the postulated surface diffusion mechanism on the basis of the well-established electric double-layer (EDL) theory. This contribution presents and discusses some preliminary results, based on the modified Boltzmann statistics, for the equilibrating part of the model.
Geochemical Modeling of the Interaction of HLW Glass With Boom Clay Media
Authors: Lolivier Ph. , Lemmens K. , Iseghem P. Van 
Published: April 2011

ABSTRACTA geochemical model has been developed to describe the interactions of the main elements released from the COGEMA R7T7 SON68 glass with the Boom Clay environment and predict the formation of secondary phases which may influence the glass corrosion. It is based on two submodels: a model describing the interaction between the clay and its porewater, and a model for glass corrosion in groundwater. According to the calculations, no secondary minerals are predicted to precipitate when glass dissolves in the Boom Clay. The oncentrations of the main elements released from the glass are controlled by stable phases present in the Boom Clay (a.o. Si, Al) or by cation exchange reactions (e.g. Na). The concentration of silica in solution can be maintained below the glass silicon solubility limit. Therefore, the Boom Clay can suppress the saturation of silica, explaining the enhancing effect of Boom Clay on glass corrosion. The influence of the presence of clay on the other components of the glass is also discussed.
The Influence of Thermal Gradients on the Long-Term Evolution of the Near-Field Environment of High-Level Nuclear Wastes Disposal
Authors: Poinssot C. , Toulhoat P. , Goffé B. 
Published: April 2011

ABSTRACTThe initial stage of some HLW disposal systems will be characterised by a large thermal pulse in the near-field environment, due to the heat of the radioactivity decay. This will lead to the development of a transient spatial thermal gradient between the hot canister and the cold geological medium, which could significantly affect the composition and the elemental distribution within the near-field environment. A coupled experimental and modelling work is presented in order to determine the influence of a thermal gradient on water-rock interaction processes. First experiments with a simulated nuclear glass evidenced mass transfer processes leading to chemical differentiation in the solid phases between the hot and the cold end of the system. The relevance of these experimental results to the case of a HLW disposal is strongly supported by in-situ experiments at Stripa, in which a realistic EBS under thermal gradient developed exactly the same mass transfers.In order to understand the driving force of these processes, we tried to model simplified experiments by using a mixing cell geochemical model built upon the geochemical code EQ3/EQ6. The discrepancies between modelling and experiments indicate the existence of coupled processes involving irreversible precipitation.Finally, thermal gradients were applied in nuclear glass-clay interaction experiments to enhance elemental migrations. The main results are: (i) a re-crystallisation of the initial clay toward a more silicic one through incorporation of elements released by the glass, (ii) a strong influence of clay chemistry on the nuclear glass secondary phases.
Corrosion of Ti99.8-Pd Under Gamma Irradiation in MgC12-Rich Brine
Authors: Smailos E. , Schild D. , Gompper K. 
Published: April 2011

ABSTRACTThe combined influence of gamma radiation (10 Gy/h) and high temperature (150 °C) on the corrosion of the promising HLW container material Ti99.8-Pd was investigated in an MgCl2-rich brine, and the corrosion surface films formed were characterized by XPS. For comparison, specimens without irradiation were also examined.Under the test conditions used, the alloy Ti99.8-Pd is resistant to local corrosion and its general corrosion is negligible low. The thin corrosion films formed on the surface of unirradiated specimens and in the crevices of specimens exposed to radiation consist of TiO2. However, outside the crevices of irradiated specimens, a surface layer consisting of Mg (main component of the brine) and Si (impurity in the brine) oxide is built up over the TiO2 layer. Comparable TiO2 layer thicknesses (30 - 65 nm, depending on the experimental conditions) are found for unirradiated and irradiated laboratory specimens. The TiO2 layer formed on the in-situ corrosion specimens (33 nm / 5.3 years) is thinner than that of the laboratory specimens (58 nm / 191 days) indicating less aggressive conditions in the field experiments. In view of these results, the alloy Ti99.8-Pd continues to be considered as a strong candidate container material and will be further investigated.
Flow Versus Transport Property: Stochastic Approach for Estimation of Its Effective Values in Heterogeneous Media
Authors: Ando K. , Vomvoris S. 
Published: April 2011

ABSTRACTFlow and transport in a fractured rock is often conceptualized as flow between parallel plates and/or flow in tubes. For simple conceptual models, such as parallel plates or tube, it has been shown theoretically that the increase in effective porosity for transport is proportional to the variability (roughness) of the fracture aperture or tube radius. This paper focus on a tube model and estimates transport properties which are consistent with the estimated measured hydraulic properties from well tests in deep boreholes.
A Modest Proposal: A Robust, Cost-Effective Design for High-Level Waste Packages
Authors: Apted M.J. 
Published: April 2011

ABSTRACTAn alternative waste-package design for the geological disposal of high-level waste (HLW) glass is presented. In conventional designs, a massive buffer of compacted bentonite is placed around a thick-walled, mild-steel overpack; in the revised design, a much thinner buffer is placed within a thin-walled, mild-steel overpack. This simple expedient eliminates certain performance concerns in existing waste-package designs, while not necessitating the study of any new materials. This integrated waste package (IWP) design has comparable release-rate performance as current package designs for HLW. In addition, the 1WP design requires far-less rock excavation, permits significantly higher temperatures for longer periods, leads to a 20-50% reduction in repository area, and is more cost efficient than previous designs.
Scenario Analysis and Conceptual Model Development Using FANFARE
Authors: Kelly M , Billington D.E. 
Published: April 2011

ABSTRACTA computer programme (FANFARE) for facilitating scenario analysis and conceptual model development is discussed. FANFARE implements a systematic methodology, based on the use of Directed Diagrams, that makes the assessment of comprehensiveness of FEPs and scenarios a tractable problem. Coupled with its ability to store a traceable audit trail of judgments and decisions, this makes FANFARE a useful tool for carrying out FEP analysis, scenario analysis and conceptual model development for performance assessments of radiological disposal facilities. It can also be applied to other systems that require consideration of the underlying phenomena to determine system performance.
Site Characterization Strategy and Its Role in Post Closure Performance Assessment
Authors: Littleboy A.K. , Degnan P.J. , Mcleod R.S. , Norris S. 
Published: April 2011

ABSTRACTCalculations of risk or dose from the groundwater flow pathway are a central part of the assessment of post closure performance for a deep repository system for radioactive waste. These calculations need to be supported by a knowledge of the various components of the disposal system. Site characterisation provides a site specific geological database which can be used to build, test and refine numerical models of the geosphere and, to some extent, the biosphere components of the disposal system in order to evaluate its future evolution.Site characterisation programmes, and groundwater flow modelling within the performance assessment need to progress in an interactive manner to ensure that both remain focused on the resolution of key uncertainties which impact the overall performance assessment. The data derived from site investigations can be classified in terms of their application within the performance assessment: establishing the framework for numerical models; enabling the parameterisation of numerical models; testing model output; refining models; and demonstrating their credibility. Site characterisation programmes need to be established to provide the appropriate level of information for each of these stages. It is therefore not particularly useful to classify information into the traditional disciplines of geology, hydrogeology and geochemistry.A key issue for developing a geological and hydrogeological database for performance assessment is determining when sufficient information has been obtained. Primarily, this is dictated by the needs and sensitivities of the performance assessment and any regulatory requirements. However, radioactive waste disposal agencies work in a political environment that is strongly influenced by public perception. In order to progress, any programme must attain a broad measure of credibility and acceptability to other key “stakeholders”.The paper draws on examples and experiences from the extensive programme of work which has been performed by Nirex to understand the characteristics of a site near Sellafield in Cumbria, and to develop groundwater flow models to support the assessment of the post closure performance of a potential repository located at that site. Uncertainties important in influencing calculated risk within an interim assessment, published as the “Nirex 95 assessment” were used to develop further site-specific investigations. The resulting site characterisation activities generated an enhanced and refined site-specific geological and hydrogeological database for a subsequent assessment - the “Nirex 97 assessment”.
The Wellenberg K-Model: A Geostatistical Description of Hydraulic Conductivity Distribution in the Host Rock for Site Characterization and Performance Assessment Purposes
Authors: Marschall P. , Vomvoris S. , Jaquet O. , Lanyon G.W. , Vinard P. 
Published: April 2011

ABSTRACTThe Wellenberg K-model describes the distribution of the hydraulic conductivity of the host rock at Nagra's proposed site for a LLW/ILW repository. The description takes the form of the expected value of hydraulic conductivity at a location and the uncertainty around this expected value. The development of the K-model is based on geostatistical concepts and, in particular, on kriging and conditional simulation methods. The model is built of cubes with sides of 100 m. Upscaling of the transmissivity profiles at the borehole locations to effective K-values on the 100 m scale is realised by fracture network modelling. The K-model accounts explicitly for the hydraulic conductivities estimated at each borehole. It is consistent with the hydrogeological conceptualization of the host rock and generates realistic hydraulic conductivity distributions with a degree of variability similar to that observed in the data.
Application of Thermodynamic Sorption Models to Distribution Coefficients of Radionuclides in Bentonite
Authors: Ochs M. , Lothenbach B. , Yui M. 
Published: April 2011

ABSTRACTThe application of thermodynamic models to calculateKdvalues for Sr/Ra and Pb on bentonite is demonstrated. The model discussed here can be used to identify relevant sorption processes, as well as other factors that determineKdvalues, such as impurities contained in bentonite or artifacts (precipitation); i.e. it can be used to conduct sensitivity analyses ofKdvalues.Kdvalues can be modeled over a very wide range, indicating that such models may also be used for an evaluation of experimental data, and for predictive purposes where no such data are available.
Modeling the Chemical Evolution of Porewater in the Palfris Marl, Wellenberg, Central Switzerland
Authors: Pearson F. J. , Waber H. N. , Scholtis A. 
Published: April 2011

ABSTRACTThe chemical evolution of groundwater in the Palfris marl at Wellenberg has been simulated using a reactive transport model. The results were tested against the chemical and stable carbon isotopic composition of water samples from exploratory boreholes. Water chemistry is constrained by mineral and cation exchange equilibria. To reproduce measured CO2(tot) and δ3C values requires H+ ion exchange. Matching measured ratios between Cl– and other dissolved constituents constrains the relative amounts of reacting water and rock to porosities between I and 10%. NaHCO3 waters sampled from the Palfris are formed by replacement of the initial Na-Cl water by one to five pore volumes of infiltrating Ca-HCO3 recharge water. To entirely exhaust the exchange capacity of the formation so that Ca-HCO3 water persists requires several hundred to several thousand pore volumes of flow. The agreement between model results and measured water chemistry demonstrates a quantitative understanding of the geochemical processes controlling the chemistry of water naturally present in the Palfris marl. These processes will also determine the behaviour of material that might emanate from a repository. In addition, the modelling provides water flow information of use in testing groundwater flow models.