bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Target Structure on Film Stress in WTI Sputtering
Authors: Lo Chi-Fung , Wang Hong , Gilman Paul 
Published: April 2011

ABSTRACTIn this report, the effect of sputtering target microstructure on the deposited film stress was investigated. By controlling the metallurgical process, two types of W-10wt%Ti target constituents, namely single-phase and multiple-phase WTi, were prepared. The former one was composed of W-rich (βTi,W) phase only, the latter one was with W, W-rich (βTi,W) and Ti-rich (βTi,W) phases. The stress of the films deposited on 12.7 cm diameter silicon oxide wafers from the single-phase target tends to be more compressive than that from the multiple-phase target. By increasing wafer temperature, the compressive stress was linearly decreased. In addition, the level of film stress was also affected by the film thickness and other sputtering parameters. To understand the causes for the differences in film stress between the multiple-phase and singlephase derived films, an evaluation of the film structure using a field-emission scanning electron microscope (FE-SEM) and mechanical testing using a nano-indentation instrument were performed. Finer domains with denser laminar structure were observed on the films deposited from the single-phase target. However, no significant difference in mechanical properties was found between these two from the nano-indentation measurements. It is envisioned that the more uniform solid solution between the W and Ti in the films obtained by sputtering the single-phase targets generates a higher compressive stress when deposited on the silicon oxide wafers resulting in a higher compressive stress.
Interfacial Strain Reliefs in Epitaxial YBa2Cu3O7–δ Thin Films Grown on SrTiO3 Buffered MGO Substrates
Authors: Cui Xingtian , Chen Q. Y , Guo Yongxiang , Chu W. K. 
Published: April 2011

ABSTRACTHigh quality YBa2Cu3O7–δ, (YBCO) epitaxial thin films grown on MgO substrate with a strainrelieved SrTiO3 (STO) buffer layer have been investigated by Rutherford backscattering spectrometry (RBS), ion channeling and high resolution cross sectional transmission electron microscopy (XTEM). The in-situ growth of STO buffer layer along with the YBCO films was carried out by pulsed laser ablation. In this work, minimum yield of channeling measurements have shown that a very thin STO buffer layer is sufficient to grow highly crystalline YBCO thin films on MgO substrates. TEM studies showed that the STO layers were strain-relieved by an array of periodic edge dislocations. The YBCO films on STO buffer, as in those grown directly on an STO substrate, evolved from a strained layer to a largely dislocation free area.
Measurement of Residual Stress in Thin Films Using the Optical Microprobe
Authors: Atkinson A. , Clarke D. R. , Jain S. C. , Pinardi K. , Webb S. 
Published: April 2011

ABSTRACTThe laser optical microprobe is a powerful tool for studying the spatial variation of residual stress exploiting the sensitivity of Raman and luminescence spectra to the local stress. Here, using two different examples, we consider some issues determining the depth and lateral resolution of these techniques and their use in stress mapping in thin films. The first example involves Raman microprobe studies of a strained GeSi alloy quantum wire structure. The second example involves stress mapping using chromium ion luminescence in alumina films grown by high temperature thermal oxidation of NiAl single crystals.
Microstructures and Mechanical Properties of Sputtered Cu/Cr Multilayers
Authors: Misra A. , Kung H. , Mitchell T. E. , Jervis T. R. , Nastasi M. 
Published: April 2011

ABSTRACTThe microstructures and mechanical properties of Cu/Cr multilayers prepared by sputtering onto {100} Si substrates at room temperature are presented. The films exhibit columnar grain microstructures with nanoscale grain sizes. The interfaces are planar and abrupt with no intermixing, as expected from the phase diagram. The multilayers tend to adopt a Kurdjumov- Sachs (KS) orientation relationship: {110}Cr //{111}Cu, <111>Cr //<110>Cu. The hardness of the multilayered structures, as measured by nanoindentation, increase with decreasing layer thickness for layer thicknesses ranging from 200 nm to 50 nm, whereas for lower thicknesses the hardness of the multilayers is independent of the layer thickness. Dislocation-based models are used to interpret the variation of hardness with layer periodicity. The possible effects of factors such as grain size within the layers, density and composition of films and residual stress in the multilayers are highlighted. Comparisons are made to the mechanical properties of sputtered polycrystalline Cu/Nb multilayers which, like Cu/Cr, exhibit sharp fcc/bcc interfaces with no intermixing and a KS orientation relationship, but have a small shear modulus mismatch.
Mechanical Characterization of Sub-Micron Polytetrafluoroethylene (PTFE) Thin Films
Authors: Lucas B. N. , Rosenmayer C. T. , Oliver W. C. 
Published: April 2011

ABSTRACTThis study reports the results of an investigation of the mechanical properties of polytetrafluoroethylene (PTFE) thin films on silicon substrates in the 0.5 to 15 μm thickness regime using frequency specific depth-sensing indentation. All measurements were conducted at an excitation frequency of 45 Hz using a constant (1/P dP/dt) load ramp of 0.1 s−1. The modulus of the PTFE at a depth of 5% of the film thickness was measured to be approximately 1 GPa (v = 0.46) independent of film thickness. These values are somewhat higher than the values obtained from free-standing 15 μm film measurements of 0.4 GPa for the tensile modulus and 0.49 GPa for the storage modulus @ 1.1 Hz. The film hardness at these depths was observed to range between 30 and 55 MPa with no correlation observed between the hardness and respective film thickness. While reliability modeling for interconnects currently uses interlayer dielectric mechanical properties data determined from free-standing films with thicknesses of several microns, these insitu results should more closely mimic the constrained deformation that occurs during service and perhaps lead to a better understanding of the electromigration resistance of PTFE.
Transport and Retention Within the Fracturing Network of an Indurated Argillaceous Formation (Tournemire Site, France)
Authors: Windt L. De , Cabrera J. , Boisson J.-Y. 
Published: April 2011

ABSTRACTThe characteristics of indurated argillaceous formations, considered as potential host media for high level radioactive waste disposal, differ in many aspects from plastic clays or crystalline rocks. In order to develop generic research on the containment properties of such formations, the French Institute for Protection and Nuclear Safety (IPSN) selected the Tournemire site ]1]: a sub-horizontal claystone layer (250 m thick, argilites and marls from Toarcian and Domerian formations) located between two limestone aquifers. Water circulations seem to be of very minor importance in the claystones, with a main diffusive component for transport ]1]. However, since a few weak water inflows occur in fracturing networks induced by tectonics, one of the key issues in the site characterisation is to adequately identify the water flows and the related transport and retention features within these specific water-conducting features. It is the purpose of the authors to present some insights in such a complex topic, using informations acquired in the framework of the Tournemire Project.
Simulation of Steady-State Groundwater Flow in the Gorleben Area
Authors: Genteri M. , Klemenz W. , Ludwig R. , Wollrath J. 
Published: April 2011

ABSTRACTThe Gorleben salt dome, near the river Elbe at the border between Lower Saxony and Brandenburg in Germany, is under investigation as a candidate site for the final disposal of radioactive waste. The diapir is crossed by an Elsterian subglacial erosion channel, which forms the lowest aquifer in the salt dome area and contains saturated brines. The salt dome is bounded in the North and the South by pronounced structural depression zones, with deepening of the Tertiary and Quaternary layers. At the bottom the aquifer system is bounded by a thick clay layer (Rupelton). Saltwater is also present in the lowermost part of the aquifer system outside of the salt dome area. The area between the infiltration zone in the South (Gartower Tannen) and the exfiltration zone in the North, West and South-West covers approximately 350 km2 (see figure 1). The field investigations in the Southern part are completed, whereas the area North of the Elbe river is currently under investigation.
The Assessment of Radionuclide Retardation in Fractured Crystalline Rocks
Authors: Alexander W. Russell , Ota Kunio , Frieg Bernhard , Mckinley Ian G. 
Published: April 2011

ABSTRACTThe joint Nagra/PNC Radionuclide Migration Programme has been running for over ten years in Nagra‘s Grimsel Test Site in the central Swiss Alps. The programme is specifically aimed at the further development of conceptual models of radionuclide transport in the geosphere, rigorously testing the applicability of current transport codes to quantify radionuclide migration in situ and assessing how successfully laboratory sorption data (specifically, Kd values) may be extrapolated to in situ conditions to predict radionuclide retardation in the geosphere [1]. A large series of field tracer migration experiments was carried out in a hydrologically well characterised water-bearing, complex fracture (or shear zone), increasing in complexity from simple, nonsorbing fluoresceine (a fluorescent dye), 3H, 3,4He, 82Br and 123I through weakly sorbing 22.24Na,85Sr and 86Rb to a final, long-term experiment with moderately sorbing 134,137Cs. The radionuclides were injected into a dipole flow field where the flowpath length, dipole width or shape and groundwater flow velocity were all varied. After a considerable learning period, generally good fits could be obtained between transport code predictions and subsequent field tracer breakthrough curves, suggesting that the transport codes tested were a reasonable representation of in situ conditions.
Kinetics of Reduction and Precipitation of U(VI) in the Dissolution of UO2(s) Under Anoxic Conditions in NaCl 5 mol kg−1. Influence of Metallic Iron
Authors: Giménez J. , Molera M. , Casas I. , Torrero M.E. , de Pablo J. 
Published: April 2011

ABSTRACTExperiments of spent fuel dissolution performed in presence of iron show, for uranium as well as for some radionuclides, lower final concentrations than measured in similar experiments but in absence of iron. So far, only the final concentrations obtained in these experiments have been published. In this work, we have focused our study on the reduction of uranium (VI) due to the presence of iron and the subsequent precipitation of Uranium (IV) due to its lower solubility. This behavior has been confirmed using a Scanning Electron Microscope by observing an uranium phase precipitated on the iron surface and assuming, under the experimental conditions, that it most likely corresponds to U02(s). We have modeled this process assuming a first-order kinetic.
Corrosion Mechanisms of Spent Fuel Under Oxidizing Conditions
Authors: Finn P. A. , Finch R. , Buck E. , Bates J. 
Published: April 2011

ABSTRACTThe release of99Tc can be used as a reliable marker for the extent of spent oxide fuel reaction under unsaturated high-drip-rate conditions at 90°C. Evidence from leachate data and from scanning and transmission electron microscopy (SEM and TEM) examination of reacted fuel samples is presented for radionuclide release, potential reaction pathways, and the formation of alteration products. In the ATM-103 fuel, 0.03 of the total inventory of99Tc is released in 3.7 years under unsaturated and oxidizing conditions. Two reaction pathways that have been identified from SEM are 1) through-grain dissolution with subsequent formation of uranyl alteration products, and 2) grain-boundary dissolution. The major alteration product identified by X-ray diffraction (XRD) and SEM, is Na-boltwoodite, Na[(UO2)(SiO3OH)]H20, which is formed from sodium and silicon in the water leachant.
Study of Uranium Incorporation Into Zircon: Solubility Limits and Durability of Fixation
Authors: Ioudintsev S.V. , Omelianenko B.I. , Lapina M.I. 
Published: April 2011

ABSTRACTResearch on synthetic zircons fabricated in system ZrO2-UO2-SiO2 at T = 400 - 750° C, PH20 = 100-200 MPa, and Ni-NiO oxygen buffer was made in order to estimate the limits of uranium incorporation into the phase's structure. It was shown that up to 27 wt.% of uranium may locally enter into the synthetic zircons. SEM/EDS study of the samples has showed that the element is uniformly distributed within the zircon crystals. Incorporation of U into zircon increases its unit-cell dimensions up to α = 6.70 A and c = 6.00 A relative to 6.60 and 5.98 A for a pure phase without impurities.After thermal high temperature treatment of the samples under 1400° C, in air, for 6 hours inhomogeneous distribution of uranium within the zircon grains was revealed. Very small uranium rich spots probably corresponding to a newly formed phase were observed in the zircon crystals. Contents of the element throughout the grains decreased to about 10 wt.%. It is probably caused by destruction of zircon-coffinite solid solution formed at hydrothermal conditions in the course of its re-heating.Study of interaction of natural zircons with alkaline carbonate solution at 100° C shows that U release from the phase can reach up to 6 % of total uranium in the samples even under relatively short term interaction. Loss of uranium rises with the element content (or amorphisation degree) and run duration, as well as with grain size reduction. Research on uranium distribution in natural zircons picked up from altered and weathered rocks is characterised by strong depletion of U at grain margins relative to the centre of the crystals. These results indicate that zircon may lose some uranium and, probably, the other actinides with time due to its lattice destruction under radioactive decay followed by hot water attack.
Leaching of Spent Fuel and Simulated Fuel in the Presence of Environmental Materials: Integral Experiments
Authors: Le Lous K. , Constantin S. , Paul J.L. , Sambugaro D. , Vernaz E. 
Published: April 2011

ABSTRACTWe have designed an apparatus which simulates the conditions of a deep geological repository in order to study the behaviour of spent fuel under leaching. A spent fuel and a Simfuel have thus been leached by synthesized clayey or granitic groundwater in sandy clay (90 % sand) or granite, in reducing conditions, at 90°C and 40 bars.The apparent leach rate for spent fuel in clayey water is 3.33 µg.m−2.dr−1in the presence of clay and 3.37 µg.m-−2.d−1in the presence of granite. The apparent leach rate in granitic water is slower, being 0.37 µg.m−2d−1in the presence of clay and 0.74 µg.m−2d−1in the presence of granite.For Simfuel, the apparent leach rate in clayey water is 7.4 µg.m−2.d−1in the presence of clay and 1. 1 µg.m−2.d−1in the presence of granite, which is the same order of magnitude as that for spent fuel. In granitic water, the apparent leach rate is 20 to 40 times greater than that for spent fuel. It is 14.8 µg.m−2.d−1in the presence of clay and 18.5 µg.m−2.d−1in the presence of granite.
Scientific Studies on the Immobilization of Pu by ISV in Field Trials at Maralinga, Australia
Authors: McGlinn P.J. , Hart K.P. , Day R.A. , Harries J.R. , Weir J.A. , Thompson L.E. 
Published: April 2011

ABSTRACTANSTO has studied material resulting from an In Situ Vitrification (ISV) trial on contaminated soil from the Maralinga nuclear weapons test range in Australia. The investigations included determining the distribution of Pu and α-activity in the intermediate scale melt, leach testing of sub-samples from the melt, and physical characterisation of the ISV material, prior to and after leaching. The results show that Pu is well mixed though the whole vitrified/ceramic block from the ISV trials at Maralinga and the durability of the vitrified/ceramic product ensures that the Pu is satisfactorily encapsulated.
Synthesis of Ce-Doped Zircon by a Sol-Gel Process
Authors: Ushakov S.V. , Burakov B.E. , Garbuzov V.M. , Anderson E.B. , Strykanova E.E. , Yagovkina M.M. , Helean K.B. , Guo Y.X. , Ewing R.C. , Lutze W. 
Published: April 2011

ABSTRACTZircon, ZrSiO4, is a prospective durable host material for the immobilization of excess weapons plutonium. Using cerium as a chemical analogue for plutonium, the experiments on the synthesis of Ce-doped zircon were conducted by sintering of sol-gel precursors in air and vacuum. The results showed that cerium substantially promotes zircon formation from sol-gel precursors and sintering in air is preferable for cerium incorporation in zircon structure. Based on measured lattice constants, solid solution compositions (Zr0.96Ce0.04)SiO4 and (Zr0.98Ce0.02)SiO4 were formed in samples sintered in air at 1400°C and 1600°C, respectively. The solubility limits of cerium and actinides in zircon and mechanism of zircon formation are discussed.
R&D in Support of Repository Implementation Do We Need Any More?
Authors: Mccombie Charles 
Published: April 2011

ABSTRACTIs there any need for further scientific and technical development work in the field of waste management? Radically different views on this provocative question have been put forward by opposing sides in the nuclear debate. P. Slovik [1] quotes various leaders on the nuclear community who for years have been claiming that waste management has no unsolved technical problems. At the recent public hearing in England [2], on the other hand, Greenpeace and others convinced the Inspector that, despite a GBP 200 million site characterisation programme with many deep boreholes, UK-Nirex still knew too little about the deep hydrogeology to justify even the sinking of an exploratory shaft at Sellafield. Where does the truth lie?
Diffusion of Cs and Sr in Compacted Bentonites Under Reducing Conditions and in the Presence of Corrosion Products of Iron
Authors: Idemitsu K. , Tachi Y , Furuya H. , Inagaki Y. , Arima T. 
Published: April 2011

ABSTRACTIn high-level waste repositories, a carbon steel overpack will be corroded by consuming oxygen trapped in the repository after closure. Iron corrosion products are expected to interfere with migration of radionuclides by filling the pore in bentonite and sorbing radionuclides. In this study the apparent diffusion coefficients of cesium and strontium were measured in compacted Na-bentonites (Kunigel VI® and Kunipia F®, JAPAN) contacted with carbon steel and its corrosion products under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusion coefficients of cesium with and without corrosion product were 2.2 to 13 × 10−12m2/s. The apparent diffusion coefficients of strontium with and without corrosion product were 3.1 to 25 × 10−12m2/s. There were significant effects of dry density (0.8 to 2.0 g/cm3) and montmorillonite contents (50% for Kunigel V1 or 100% for Kunipia F). The presence of corrosion product decreased the apparent diffusion coefficients of Cs in both bentonites and that of Sr in Kunigel V1, especially at low dry density. This may be due to corrosion product filling the pore in the bentonite, decreasing the free pore size and density for diffusion.
Influence of Hydromechanical Couplings on the Resaturation of Engineered Barriers
Authors: Lassabatere T. 
Published: April 2011

ABSTRACTThis paper presents a fully coupled model for unsaturated deformable materials like swelling clays of engineered barriers. A thermodynamic framework is adopted which allows to take into account the influence of the mechanical variables (stress and strain tensors) upon the hydraulic part of the state equations (suction - water content relation). So, a fully coupled behaviour formulation is stated which, when combined with « classical » phenomenological relations, makes it possible to study the influence of the mechanical state of the barrier on the kinetics of its resaturation.
Alteration of Repository Structural Materials Within the First Few Years
Authors: West J. M. , Cave M. , Coombs P. , Milodowski A. E. , Rochelle C. A. 
Published: April 2011

ABSTRACTA series of batch laboratory experiments were set up to study the gross effects of microbial activity on repository geochemistry, radionuclide sorption and integrity of repository and host rock materials. The experiments were fully monitored for 550 days and some were continued, under apparently aerobic conditions, for 1700 days. Geochemical modelling of the experiments reproduced many of their features, but showed that the contents were not in chemical equilibrium after 1700 days with redox disequilibrium a likely feature. The models could not predict localised reactions such as enhanced pitting of steel which appeared to be microbially mediated.
The Leaching Behavior of Bituminized Radioactive Waste in the Geologic Disposal Conditions of the Boom Clay Formation
Authors: Sneyers A. , Iseghem P. Van 
Published: April 2011

ABSTRACTAs part of the evaluation of the safety of geologic disposal, the leaching behaviour of two types of bituminized radioactive waste (Eurobitum and CEA bitumen) has been studied as a function of temperature, pressure, leachant composition and bitumen matrix type. Inactive and active bitumen samples were brought into contact with two test media, simulating the geologic disposal environment of the Boom clay formation. At contact with these media, the samples swelled and soluble salts and radionucides were leached. It was found that the leach rate is influenced by temperature, the leachant composition, and the physical characteristics of the bitumen matrix. The release of nitrate is interpreted as a diffusion controlled process, which can however be disturbed by crack formation. The leaching of 60Co, 90Sr, and total β is diffusion controlled. Low leach rates were measured for Pu and Am: the release of Pu and Am is limited by their solubility in the leachant. Pu and Am are preferentially sorbed to the Boom clay, the test container or the bitumen. The leached mobile Pu and Am concentrations are of the order of 10−10 to 1013 M at 23°C. The results of this study suggest that the integrity of bituminized waste packages is seriously affected due to the leaching of soluble salts: a full-size 220 litre Eurobitum drum is predicted to be depleted in NaNO3 in less than 20,000 years.
Comparative Structural Study and Dissolution of Simplified Glasses: A Radioactive Waste Glass (R7T7) and a Basaltic Glass
Authors: Angeli F. , Faucon P. , Charpentier T. , Petit J.C. , Virlet J. 
Published: April 2011

ABSTRACTThe local cation environments in a borosilicate glass (containing the main components of the French nuclear waste glass, R7T7) and of basaltic-like glass are presented on the basis of17A1 and23Na Multi-Quanta Magic-Angle Spinning Nuclear Magnetic Resonance (MQ-MAS NMR) spectroscopies. The chemical and geometrical environment of each nucleus is characterized. Moreover, qualitative information about the distribution of these parameters, characteristic of the disorder level in the structure, is obtained. These results are presented with the characteristics of the Al and Na dissolution in water at 100°C. The relation between the local environments of these cations and their mass loss in solution is discussed.