bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Alignment of Carbon Nanofibers in Polymer Composites
Authors: Shi Donglu , He Peng , Lian Jie , Chaud Xavier , Beaugnon Eric , Wang Lumin , Ewing Rodney C. , Tournier Robert 
Published: April 2011

ABSTRACTCarbon nanofibers were well aligned in polymer composite magnetically at moderate fields up to 3 T. Due to the NiO-coating, carbon nanofibers exhibited strong magnetic moments that lead to alignment. Both TEM and SEM results showed the well-aligned nano-fibers in a polymer matrix. Mechanical testing showed a pronounced anisotropy in tensile strength in directions normal (12.1MPa) and parallel (22MPa) to the applied field, resulting from the well-aligned nanofibers in the polymer matrix. The mechanism of magnetic alignment due to coating of NiO on the nano fiber surface is discussed.
Band Engineering of Partially Exposed Carbon Nanotube Field-Effect Transistors
Authors: Liu Xiaolei , Luo Zhicheng , Han Song , Tang Tao , Zhang Daihua , Zhou Chongwu 
Published: April 2011

ABSTRACTWe present a new approach to engineer the band structure of carbon nanotube field-effect transistors via selected area chemical gating. By exposing the center part or the contacts of the nanotube devices to oxidizing or reducing gases, a good control over the threshold voltage and subthreshold swing has been achieved. Our experiments reveal that NO2 shifts the threshold voltage higher while NH3 shifts it lower for both center-exposed and contact-exposed devices. However, modulations to the subthreshold swing are in opposite directions for center-exposed and contact-exposed devices: NO2 lowers the subthreshold swing of the contact-exposed devices, but increases that of the center-exposed devices; In contrast, NH3 reduces the subthreshold swing of the center-exposed devices, but increases that of the contact-exposed devices. A model has been developed based on Langmuir isotherm, and the experimental results can be well explained.
Competitive Etching and Oxidation of Vicinal Si(100) Surfaces
Authors: Albao Marvin A. , Liu Da-Jiang , Choi Cheol H. , Gordon Mark S. , Evans J. W. 
Published: April 2011

ABSTRACTExposure of a vicinal Si(100) surface to oxygen at around 550 C produces etching-mediated step recession. In addition, some oxide islands are formed which locally pin receding steps. We develop an atomistic lattice-gas model for this process which accounts for the interplay between oxygen surface chemistry (adsorption, diffusion, oxide formation, and etching via SiO desorption) and the silicon surface and step dynamics (anisotropic diffusion and aggregation of di-vacancies formed by etching, and ad-dimer attachment-detachment dynamics at steps incorporating anisotropic energetics). Kinetic Monte Carlo simulation of this model produces step morphologies retaining some qualitative but not quantitative features of their equilibrium structure (alternating rough SB steps and smooth SA steps), except for pinning which produces protruding “fingers”. These features are seen in Scanning Tunneling Microscopy studies.
Droplet Behaviour in Inkjet Printing
Authors: Stringer Jonathan E , Smith Patrick J , Derby Brian 
Published: April 2011

ABSTRACTThe interaction of an inkjet printed droplet with a substrate is of importance when determining the final size and shape of deposits. A simple model is proposed that relates droplet diameter, printed dot pitch and equilibrium contact angle to as-printed track width. Reasonable agreement was found between the model and final track width, with slight over-prediction accounted for by removal of the organic component of the ink during heat treatment. Immediately after droplet impact, the drop may spread to a considerably greater extent than predicted by equilibrium because of the kinetic energy of the droplet in flight. Simulations of droplet impact showed that the maximum droplet spread decreased linearly with equilibrium contact angle. Recoil of these droplets towards their equilibrium shape occurred above a threshold contact angle. This threshold was greater than expected, suggesting an energy barrier preventing recoil or the kinetics of recoil being too slow for recoil to occur within the timeframe of this study.
Repository performance assessment and advanced fuel cycle models for input to decision making of options for nuclear waste and resource management
Authors: Small J.S. , Zimmerman C.H. , Parker D.R. , Robbins C. , Bond A.E. , Stevens G.A. 
Published: April 2011

ABSTRACTA methodology and computer software is described which can be used to track the inventory of radionuclides as they are affected by various nuclear, physical and chemical processes during reactor, storage, effluent and disposal phases of the nuclear fuel cycle. Such a model is required to provide an assessment of economic, environmental and societal performance indicators which underpin decisions regarding options for the use and management and nuclear materials. An example generic deep repository model is described which can be used to provide an indicator of environmental performance of vitrified high level waste and UO2 and mixed oxide (MOX) spent fuels. The assessment models highlight the significance of the I-129 fission product which necessitates the use of appropriate dose assessment models to be considered for each process step of the nuclear fuel cycle in order that a complete environmental assessment of process options can be determined.
Sorption of Molybdenum(VI) on Synthetic Magnetite
Authors: Rovira Miquel , de Pablo Joan , Ignasi Casas I. , Giménez Javier , Clarens Frederic , Martinez-Lladó Xavier 
Published: April 2011

ABSTRACTIn this study we experimentally investigated the interaction of Mo(VI) with magnetite, which is a corrosion product of steel. The work was conducted with commercial magnetite, and we studied the influence of pH, pe and solid/liquid ratio on Mo sorption. A Surface Complexation Model (SCM) has been applied tothe experimental data, allowing to explain the results using the Diffuse Layer Model (DLM) and by considering the formation of the monodentate complex: >FeOMo(OH)5. At pH 2, experimental data were satisfactorily fitted to a a Langmuir isotherm.
Field Test of Ethanol/Bentonite Slurry Grouting into Rock Fracture
Authors: Asada Motoyuki , Nakashima Hitoshi , Ishii Takashi , Horiuchi Sumio 
Published: April 2011

ABSTRACTCrystalline rocks have fractures which may cause unexpected routes of groundwater seepage. Cement grouting is one of the most effective methods to minimize seepage; however, cement materials may not be suitable for the purpose of extra-long durability, because cement is neutralized or degraded by chemical and physical influence of chemical reaction.Natural clay like bentonite is one of the most promising materials for seepage barrier; however, water/bentonite grout is so viscous that enough amount of bentonite can not be grouted into rock fractures. To increase bentonite content in grout with low viscosity, the utilization of ethanol as a mixing liquid was studied. Ethanol suppresses bentonite swelling, and more bentonite can be injected more than that of water/bentonite slurry. In this paper, grouting into in-situ rock mass fracture from the ground surface was tested to investigate the barrier performance and workability of ethanol/bentonite slurry as a grouting material.
Development of the Supercontainer Design for Deep Geological Disposal of High-Level Heat Emitting Radioactive Waste in Belgium
Authors: Bel Johan J.P. , Wickham Stephen M. , Gens Robert M.F. 
Published: April 2011

ABSTRACTONDRAF-NIRAS has recently selected a Supercontainer with a Portland Cement (PC) buffer as the preferred new reference design for disposal of HLW and spent fuel. The selection process involved a multi-criteria analysis of alternative design options, which were evaluated against a range of long-term safety and feasibility criteria. A PC concrete has been chosen for the buffer because this will provide a highly alkaline chemical environment, which will last for thousands of years. In this environment the external surface of the overpack will be passivated and overpack corrosion will be inhibited. The concrete buffer also has low-hydraulic conductivity to slow the infiltration of external fluids to the overpack surface, and provides radiological shielding.ONDRAF-NIRAS has made a preliminary evaluation of the viability of the reference Supercontainer design. The following areas were reviewed and investigated: radiolysis, thermo-hydraulic (TH) behaviour of the concrete buffer, metal corrosion, the chemical and mineralogical evolution of the concrete buffer, and relevant industrial experience. This paper describes the main findings, and identifies remaining design and performance uncertainties. Prioritisation and recommendations for future work are also given.
Development of an Uncertainty Analysis Methodology Associated with the Characterization of the Geological Environment: Study on its Applicability in the Tono area
Authors: Yanagizawa K. , Takeda S. , Osawa H. , Suyama Y. , Takase H. , Toida M. , Metcalfe R. 
Published: April 2011

ABSTRACTJNC has developed an uncertainty analysis methodology for application to the spatially heterogeneous characteristics of a geological environment. The developed methodology adopts a new approach that identifies all the possible options in concepts and parameter ranges that cannot be excluded in the light of evidence available. This approach enables uncertainties associated with the understanding at a given stage of the site characterization to be made explicit, using probability theory and possibility theory. The uncertainties could be reduced by screening, to exclude concepts and parameter ranges that can be denied in the light of additional evidence obtained in subsequent investigation stages. This paper describes an outline of the developed methodology and its applicability in the Tono area.
Europium migration in Argilaceous Rocks : on the use of Micro Laser-Induced Breakdown Spectroscopy (micro LIBS) as a Microanalysis Tool
Authors: Menut Denis , Descostes Michael , Meier Patrick , Radwan Jean , Mauchien Patrick , Poinssot Christophe 
Published: April 2011

ABSTRACTEu migration in a Callovo-Oxfordian argilite sample was studied using the micro LIBS technique. Quantitative elemental mapping were made by micro LIBS that showed the actual distribution of the various micro areas observed on the Callovo-Oxfordian sample's surface. Calcite, dolomite, alumino-silicates, quartz, pyrite and iron oxides were identified and their statistical distribution was determined. Experimental Eu profiles observed are consistent with diffusion process accompanied by heterogeneous sorption on alumino-silicate surface.
Research in actinide geochemistry: Do we need speciation information at the molecular level?
Authors: Geckeis Horst 
Published: April 2011

ABSTRACTRadionuclide sorption to rock or sediment surfaces in the vicinity of a nuclear waste reposi-tory contributes significantly to the overall safety performance of a given disposal concept. State-of-the-artspeciation techniques as laser - and X-ray spectroscopy are becoming more and more involved into the elucidation of sorption mechanisms and to the quantification of surface speciation. They are extremely valuable tools to gain fundamental understanding as a basis for the development of geochemical sorption models which in turn are needed to predict ra-dionuclide behaviour in the environment.
Carbon Steel Canister Performance Assessment: Iron Transfer Study
Authors: Vokál Antonín , Lukin Dmitrij , Vopálka Dušan 
Published: April 2011

ABSTRACTCarbon steel has been chosen in the Czech disposal concept of spent fuel disposal in a granite host rock as a reference material for disposal canisters. On the basis of the results of performance assessment studies, it could be decided whether this material is suitable or whether a more corrosion resistant, and also more expensive, material should substitute it. A number of papers have convincingly shown that iron transfer constraints contribute to a significant decrease in corrosion rate, but no study hasso far been devoted to modeling this process. In this paper the effects of initial corrosion rate, corrosion product solubility and porosity and other repository parameters on the transfer of iron to the host rock are modeled using a numerical transport computer code. It was found that the critical parameter for iron transfer is the solubility of corrosion products, considerably affecting the steady state corrosion rate. The initial corrosion rate of carbon steel and the sorption properties of bentonite primarily affect the time needed to achieve a steady state of corrosion. The results of the calculations strongly suggest that the constraints on iron transfer from the canister surface will govern the corrosion rate of carbon steel canisters, whose lifetime, owing to this effect, can stretch to millions of years.
Corrosion of Copper Canisters Through Microbially Mediated Sulphate Reduction
Authors: Sidborn Magnus , Neretnieks Ivars 
Published: April 2011

ABSTRACTA biogeochemical model was developed with an aim to illustrate the transport and reaction processes that may be involved in copper canister corrosion by sulphide in a deep repository for nuclear waste. Sulphide concentrations in the groundwaters in Sweden are relatively low and are generally considered to be of little importance for corrosion of the copper canisters. Sulphate, however, is present in relatively large amounts (50-700 mg/L) and may be reduced to sulphide by reaction with organic matter. Mediated by microbes, the reduction rate may be increased considerably compared to abiotic reduction. Microbially mediated sulphate reduction occurs in many natural environments, provided that reactive organic matter is available. Groundwater analyses indicate relatively high concentrations of dissolved methane (up to 16 mg/L) which thermodynamically is a suitable reducing agent. This processes could occur in fractures inthe bedrock provided that substrates are continuously supplied and that there is a sink for the reaction products. In the repository, the copper canisters may provide a sink for sulphide that yields a favourable environment for the microbe population. The model domain includes a canister with surrounding backfill material intersected by a hydraulically conductive fracture. Transport of substrates and reaction products in the fracture and backfillas well as microbially mediated reaction at the fracture opening is included in the model. Results indicate that microbially produced sulphide could potentially contribute to canister corrosion.
The Diffusion of Radionuclides through Waste Encapsulation Grouts
Authors: Chambers Adam V. , Green Andrew , Harris Andrew W. , Heath Timothy G. , Hunter Fiona M.I. , Manning Michelle C. , Williams Stephen J. 
Published: April 2011

ABSTRACTUnited Kingdom Nirex Limited develops and advises on safe, environmentally sound and publicly acceptable options for the long-term management of radioactive waste. One option Nirex has developed is a phased geological repository concept for intermediate level waste and some low level wastes that makes use of a combination of engineered and natural barriers. Physical containment of radionuclides would be achieved by immobilisation and packaging of wastes (mostly) in stainless steel containers.Existing models of the migration of dissolved radionuclides from packaged wastes suggest that radionuclide release is determined largely by the rate of diffusion through the encapsulation grout used to immobilise the waste. The use of such models requires diffusion coefficient data for radionuclides in waste encapsulation grouts. This paper describes a programme of through-diffusion experiments, and modelling interpretation, aimed at deriving diffusion coefficients for some radionuclides in two types of encapsulation grout.An intrinsic diffusion coefficient of HTO of around 1×10−13 to 2×10−13 m2s−1 was determined for a 3:1 mix of blast furnace slag to ordinary Portland cement, compared to around 4×10−13 to 5×10−13 m2s−1 for a 3:1 mix of pulverised fuel ash to ordinary Portland cement. These values are lower than that assumed for a non-sorbing radionuclide in an earlier modelling exercise. Porosity values around 0.3 were obtained in each case. For 36Cl as chloride, the experiments showed no significant breakthrough over the experimental timescale of about one year, suggesting an intrinsic diffusion coefficient below 5×10−13 m2s−1. One possibility is that chlorine-containing solids are precipitating in the cement. An intrinsic diffusion coefficient for 137Cs in the 3:1 mix of pulverised fuel ash to ordinary Portland cement of 4×10−15 m2s−1 was estimated, significantly lower than that determined for HTO.The results from three of the sixteen experiments could not be fitted with a simple diffusion model, and for a further five experiments there was some doubt as to whether simple diffusion behaviour had been observed. It is suggested that this may have been due to cracks in the grouts that were sufficiently large to affect the diffusion properties of the grouts, although none was visible to the naked eye. Cracking of the waste encapsulation grouts could provide a mechanism for enhanced migration of radionuclides from waste packages, compared with diffusion in a homogeneous porous medium alone.
Mixed Organic and Mineral Waste Processing by Incineration-Vitrification : Case of Bituminous Media
Authors: Girold Christophe , Pinet Olivier , Lemort Florent 
Published: April 2011

ABSTRACTBurnable radioactive waste management options are often in favour of the vitrification due to their volume reduction, resulting in cost saving for transport and storage. More, the interest is also to obtain a best radioactivity immobilization in a long-lasting matrix. Development made on incineration-vitrification process must take into account radioactivity environment in term of process compactness, gas treatment and secondary wastes. A new and simplified equipment, using thermal oxygen plasma coupled with a cold crucible melter, is being developed at the Valrho-Marcoule nuclear centre (France) : SHIVA, for Advanced Hybrid System for Incineration and Vitrification. As part of studies concerning the management of bitumen canisters stored in Marcoule, the feasibility of their treatment in an incineration-vitrification process have been tested. This treatment could concern the most radioactive bituminised waste drums because they have to be sent in a costly storage site in consideration of their radioactivity. The interest of such treatment is first to reduce the volume of wastes in order to appreciably diminish the cost of this storage.
Preservation of Archaeological Materials in Arid Environments: Analogues Relevant to Yucca Mountain
Authors: Chapman Neil , Dansie Amy , McCombie Charles 
Published: April 2011

ABSTRACTThe potential repository at Yucca Mountain in Nevada is in an arid area, in unsaturated volcanic tuff with oxidising conditions, and may be kept open and ventilated for hundreds of years. Existing US work on archaeological material and structural analogues in such conditions has been extended to seek further well-preserved objects in such conditions. The objectives of the study are partly scientific and partly aimed at the public. A wide range of exceptionally wellpreserved glass, metal and organic materials is found in the archaeological record from sites that have been characterised by arid conditions for many thousands of years. Underground preservation environments include those either continuously open (caves) or sealed but not ‘backfilled’ (tombs). Preservation of materials in such openings provides a useful analogue reference point for considering the operation and evolution of the Yucca Mountain repository.
Radiation Damage in Pyrochlore and Related Compounds
Authors: Lumpkin G.R. , Whittle K.R. , Rios S. , Trachenko K. , Pruneda M. , Harvey E.J. , Redfern S.A.T. , Smith K.L. , Zaluzec N.J. 
Published: April 2011

ABSTRACTThe radiation damage properties of synthetic pyrochlore-defect fluorite compounds containing lanthanides on the A-site and Ti, Zr, Sn, and Hf on the B-site have been studied extensively using Kr ion irradiation. Using statistical analysis, we show that the results can be quantified in terms of the critical temperature for amorphization, structural parameters, classical Pauling electronegativity difference, and defect energies. The best current model is able to predict the critical temperature to within about 80 degrees Kelvin. The model indicates that radiation tolerance is correlated with an increase in the X anion coordinate toward the value characteristic of the defect fluorite topology, a smaller unit cell dimension, and lower defect energies. Our analysis also demonstrates that radiation tolerance is promoted by an increase in the Pauling cation-anion electronegativity difference or, in other words, an increase in the ionicity of the chemical bonds. Of the two possible cation sites in ideal pyrochlore, the B-site cation appears to play the major role in bonding. This result is supported, for a subset of pyrochlore compounds, by ab initio calculations, which reveal a correlation between the Mulliken overlap populations of the B-site cation and the critical temperature.
The Effect of Nearfield Constraints on the Corrosion Behavior of High Burnup Spent Fuel
Authors: Loida Andreas , Kelm Manfred , Kienzler Bernhard , Geckeis Horst , Bauer Andreas 
Published: April 2011

ABSTRACTThe long-term immobilization for individual radioelements released from the waste form “spent fuel” in solid phases upon groundwater contact depends strongly on the (geo)chemical constraints prevailing in the repository. Related experimental studies comprise effects induced by the presence of Fe based container material, and near field materials other than Fe for a rock salt environment. The effect of the presence of an argillaceous host rock containing organic matter and pyrite on fuel alteration was studied in addition. The results have shown that oxidative radio-lysis products were found to be consumed at a significant extent by the metallic Fe and by the argillaceous host rock. Under these conditions a decrease at a factor of ca.100 for both the matrix dissolution rates and the solution concentrations of U and Pu was found. There is mutual support between the matrix dissolution rates, the solution concentrations and the amounts of oxygen encountered during the experiments under various conditions controlled by the presence of near field materials under study.