bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Water Vapor and Oxygen in the Processing Environment on the Properties of Sputtered a-Si:H Films
Authors: Wang Cheng , Parsons G. N. , Lucovsky G. 
Published: March 2011

ABSTRACTA systematic study of the effect of the trace impurity of oxygen and water vapor in the processing environment on the infra-red (IR), optical and electrical properties, and defect density of sputtered a-Si:H films is reported. The results are that small contents of water introduced into the argon plasma extract H-atoms from the growth surface, thereby reducing total hydrogen content and polyhydride formation in films deposited at low substrate temperatures, <150°C. This leads to a decrease of the defect density, and hence, to improvements in the photoconductivity (Δσ) and the associated quantum efficiency-mobility-lifetime(ημτ) product.
Plasma Diagnostic of a TCDDC System Using a Quadropole Mass Spectrometer
Authors: Vieira M. , Maçarico A. , Martins R. , Ferreira I. , Guimarāes L. 
Published: March 2011

ABSTRACTSpecies formed during the decomposition of silane-methane-hydrogen mixtures ([SiH4]x:[CH4]y:[H2]z), by spatial plasma separation technique using the TCDDC (Two Consecutive Decomposition and Deposition Chambre) systeml, are evaluated by mass spectrometric analysis and related with the structural and electro-optical properties for either amorphous (a-) or microcrystalline (μc-) thin films. Results obtained show that in the plasma region, the main reaction is the direct fragmentation of SiH4 by electron impact whilst near the growing surface, the main detected species are excited. The kind of species and their intensity depend strongly on the power density (dp), mixture gas ratio (g = CH4 /SiH4+CH4), static electromagnetic (ξ, B) fields and r.f. frequency (f), used. Since CH4 has a threshold decomposition higher than that one of SiH4, the species presented at the plasma region are, mainly, methyl, dimethyl and CH2-CH2 graphitic-like chains depending, mostly, on dp and on g. By diluting the mixture in H2, we observe the existence of active H2 species that, for high dp, may lead to a transition from the amorphous to microcrystalline phase, as well as a carbon incorporation in the amorphous tissue as graphitic-like bonds. This allow us to infer the merit of the TCDDC system in producing a-/μc-thin films that can be applied to photovoltaic and other applications.
A Single Phase ([Nzp]) Ceramic Radioactive Waste Form
Authors: Roy Rustum , Yang L.J. , Alamo J. , Vance E.R. 
Published: March 2011

ABSTRACTIt has been shown that between 10 and 20% of a simulated PW–4b radwaste composition can be incorporated into a single nhase with the NZP (= ‘MaZr2 P3 o12’) structure. By changing the P/Na and Zr/Na molar ratios (i.e., adjusting the crystal chemical model of where each ion is located in the structure) it has been possible to outline a very ‘forgiving’ compositional regime both at the 10% and the 20% waste loading level within which one obtains one ([NZP]) or two ([NZP] and [monazite]) phases. We have also succeeded in substituting Tio2 for Zro2 in making a TiO2-rich [NTP] waste form analogous to the [NZ]] materials.Thus we have succeeded in creating monophasic and diphasic ceramic waste forms which can be sintered below 1000° C. Only preliminary leach data have been obtained at 25° and 300°C, and they place this material with good ceramic forms.
Comparison of the Leachability of Three TRU Cement Waste Forms
Authors: Ross Wayne , Westsik Joseph , Roberts Frank , Harvey Clark 
Published: March 2011

ABSTRACTCement waste forms prepared by three processes, casting, cold pressing, and FUETAP (Formed Under Elevated Temperatures and Pressure) have been compared for their leachability by using the MCC-1 leach test. The results indicate that releases of plutonium are not controlled by the waste form matrix and that there is no significant overall advantage to any of the three cement processes from a leachability viewpoint.
Preferential Dissolution Phenomena of Nuclear Waste Materials
Authors: Clarke D. R. , Flintoff J. F. 
Published: March 2011

ABSTRACTPreferential dissolution of polyphase nuclear waste materials in short term leach tests can exaggerate radionuclide release rates when extrapolated to the lifetime of the waste form. Possible preferential leach phenomena are associated with the presence of cracks, intergranular phases and readily soluble phases. The rate of dissolution and the microstructural connectivity of the most soluble phase determine the period over which perferential dissolution is observable. The connectivity of phases is amenable to control during processing by altering the starting green density of the precursor powders.
Evaporite Dissolution Relevant to the Wipp Site, Northern Delaware Basin, Southeastern New Mexico
Authors: Lambert Steven J. 
Published: March 2011

ABSTRACTEvaluation of the threat of natural dissolution of host evaporites to the integrity of the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico has taken into consideration (1) the volume of “missing” rock salt, (2) the occurrence (or not) of characteristic dissolution brines, (3) geomorphic features, some of which are unrelated to dissolution, and (4) the time intervals over which dissolution may have been active. Even under the assumption that all “missing” halite was originally present and has been removed by dissolution, there is no evidence of active preferential removal of the lower Salado Formation halite by any geologically reasonable process. The geologic record contains evidence of dissolution in the Triassic and Jurassic; to constrain all removal of basinal halite to the late Cenozoic yields an unrealistically high rate of removal. Application to the lower Salado of a stratabound mechanism known to be active in Nash Draw, a near-surface feature within the Basin, allows a minimum survival time of 2,500,000 years to be predicted for the subsurface facility for storage of radioactive waste at WIPP. This calculation is based on an analysis of all known dissolution features in the Delaware Basin, and takes into account the wetter (pluvial) climate during the past 600,000 years.
Radionuclide Migration into Natural Fracture Surfaces of Granitic Rock
Authors: Torstenfelt B. , Eliasson T. , Allard B. , Andersson K. , Hoglund S. , Ittner T. , Olofsson U. 
Published: March 2011

ABSTRACTThe uptake of cesium on natural fracture surfaces taken from granitic bedrock has been studied as well as the depth penetration into the underlying rock. The fracture minerals usually exhibit good sorptive properties with respect to cesium (with the exception of calcite). The surface coatings do not act as physical diffusion barriers and do not prevent a migration into the underlying rock. A considerable depth penetration into the rock (several mm over a period of three months) was observed. The dominating pathways into the rock matrix were the high-capacity minerals in grains or in microfissures. The calculated diffusivity in the rock matrix was of the order of 10−13 m2/s.
Salt Creep Design Consideration for Underground Nuclear Waste Storage
Authors: Li William T. , Wu Ching L. , Antonasc Nicholas J. 
Published: March 2011

ABSTRACTThis paper summarizes the creep consideration in the design of nuclear waste storage facilities in salt, describes the non-linear analysis method for evaluating the design adequacy, and presents computational results for the current storage design. The application of rock mechanics instrumentation to assure the appropriateness of the design is discussed.It also describes the design evolution of such a facility, starting from the conceptual design, through the preliminary design, to the detailed design stage The empirical design method, laboratory tests and numerical analyses, and the underground in situ tests have been incorporated in the design process to assure the stability of the underground openings, retrievability of waste during the operating phase and encapsulation of waste after decommissioning.
Studies on Speciation of Americium, Technetium and Neptunium in Simulated Vitrified-Waste Leachates
Authors: Bidoglio G. , De Plano A. , Chatt A. 
Published: March 2011

ABSTRACTPhysico-chemical forms of several radionuclides are being investigated in order to characterize the migrating species in a deep geologic repository. Under ground water bicarbonate and carbonate concentration levels, Am(CO3)2 has been observed to be the most important complex while the formation of Am(OH)(CO3)22− has been indicated, stability constants of Am-complexes have been calculated, and a distribution diagram of Am(III) species as a function of pH is presented. Speciation of Tc has been studied using radiochemical and electromigration methods in oxic and anoxic environments; in effective diffusion coefficient of 1.37 × 10−5 cm2 S−1 for ToO4− has been obtained. Preliminary studies on Np(V) indicate that NpO2+ does not form strong complexes with carbonate and bicarbonate ions at ground water concentrations.
Waste Classification System for Low-Level Radioactive Wastes
Authors: Wickham L. E. , Rope S. K. 
Published: March 2011

ABSTRACTSome low-level radioactive waste represents both a chemical and radiological hazard, and it is desirable that management practices take this into account. This paper describes a waste classification system that could provide guidance on how mixed wastes could be separated for disposal, and the degree of disposal isolation each waste material or shipment needs. An example of the system's use is provided.
Leach Tests of Simulated Low-Level Transuranic Waste Forms Containing Transuranic Elements
Authors: Welch Jane M. , Sill Claude W. , Flinn John E. 
Published: March 2011

ABSTRACTSimulations of waste forms that might be produced by slagging pyrolysis incineration of low-level transuranic (TRU) wastes stored at the Idaho National Engineering Laboratory (INEL) have been fabricated containing the transuranic isotopes 237Np, 239pu, 24lAm, 244Cm at levels of approximately 1 μCi per gram of each.Leach tests were performed using frit and vitrified monolithic specimens of average INEL TRU waste, portland cement monoliths made with frit as aggregate, and vitrified monoliths of INEL soil and simulated Rocky Flats sludge. Static leach tests were performed at 90, 70, 40, and 25°C in deionized water for up to 364 days. Leachates were analyzed for the TRU elements by alpha spectrometry. The following generalizations can be made:1. Cemented frit and vitrified sludge waste forms produce leachates with the highest pHs (>11) and have the lowest TRU leach rates, 10−4 g/m2.d at 90°C.2. Neptunium has a higher leach rate than the other three TRU elements by as much as two orders of magnitude for all waste forms tested except cemented frit.3. Only the vitrified soil samples display a marked temperature dependence for leach rates of all four TRU elements.
Electric Arc Furnace Melting of Simulated Transuranic Wastes
Authors: Nafziger R. H. , Oden L. L. 
Published: March 2011

ABSTRACTAs part of an interagency agreement between the Bureau of Mines, U.S. Department of the Interior, and the U.S. Department of Energy through its contractor, EG&G Idaho, Inc., the Bureau conducted six melting tests at its Albany Research Center to assess the feasibility of melting transuraniccontaining wastes. The tests were conducted with simulated wastes in a conventional refractory-lined electric arc furnace. Charge materials included concrete, soil, metal, wood, CaO- and Na2O-containing chemical waste sludges, cement, and polyethylene mixed in various proportions in both unburned and partially incinerated forms. The investigation showed that it is possible to melt these materials in a 1-metric-ton conventional electric arc furnace and separate the slag and metal provided that suitable fluxes are added to condition the silicious slags. However, the electric arc furnace cannot be considered an efficient incinerator. The molten slags were poured into 210-liter steel drums having a 0.64-cm-thick steel chill plate on the bottom. All slags were tapped from the furnace satisfactorily. The concrete and sludge materials required the most energy for melting (2.2 to 2.6 kwhr/kg). The highest electrode consumption occurred when the sludges were melted (0.04 kg/kg product). A high alumina-chrome refractory is satisfactory for use as a furnace lining in melting these wastes. Offgases and particulates from all of the tests were sampled and analyzed. The greatest amounts of particulate matter in the offgas streams were obtained from melting sludges and incinerated wastes.It is recommended that if a conventional electric arc furnace is used to melt transuranic waste that it (1) be fed slowly to prevent excessive fumes and flames and (2) be operated continuously to minimize startup problems and improve efficiency.
Thermal Conductivity of Bentonite/Quartz High-Level Waste Package Backfill
Authors: Moss Marvin , Molecke Martin A. 
Published: March 2011

ABSTRACTA mixture of bentonite clay and quartz sand is being considered for use as a waste-package backfill, the material placed between a radioactive-waste canister and the repository host rock. Compacts of bentonite/quartz with weight-percent ratios of 100/0, 70/30, 50/50 and 30/70 were made at room temperature under a pressure of 100 MPa (15 ksi). Upon initial heating, the thermal conductivity of the 70/30 compact rose from 1.20 W/m·K at 298 K to 1.32 W/m·K at 373 K. After further heating to 473 K, it fell to 1.10 W/m·K, reflecting the loss of interlamellar water from the bentonite. The conductivity of the now-dehydrated compact was reproducible through several heating and cooling cycles, varying from 1.15 W/m·K at 573 K to 1.03 W/m·K at 298 K. The other mixtures were qualitatively similar to the 70/30: the 100/0, 50/50 and 30/70 dehydrated compacts displayed conductivities of 0.59, 1.06 and 0.83 W/m.K,respectively, at 298 K. Measured densities ranged from 1.98 to 2.12 g/cc. Combined geometric-mean and Maxwell models for thermal conduction in composite systems predict the measured results reasonably well. An analysis of the impact of backfills on high-level waste (HLW) package design indicates that no significant thermal penalty is imposed.
Inertial Effects in Transport of Radioactive Waste Through Engineered Barriers
Authors: Carnahan C. L. 
Published: March 2011

ABSTRACTAddition of an inertial term to the constitutive relation for mass flux leads to a mass transport equation which is hyperbolic and describes propagation of a distorted wave with a finite velocity. This approach eliminates the “instantaneous propagation paradox” inherent in parabolic transport equations based on Fick's law. Analytical solutions of the wave transport equation have been derived and have the properties that the leading edge of a solute front propagates at a finite, predictable velocity and is truncated by a step function which decreases in magnitude exponentially with time. The inertial effects on computed solute fronts are most evident near the leading edge, and have potential significance in the prediction of engineered barrier performance.
Corrosion of Ticode-12 in A Simulated Waste Isolation Pilot Project (Wipp) Brine
Authors: Ahn T. M. , Lee B. S. , Woodward J. , Sabatini R. L. , Soo P. 
Published: March 2011

ABSTRACTThe corrosion behavior of TiCode-12 (Ti-0.3 Mo-0.8 Ni) high level nuclear waste container alloy has been studied for a simulated WIPP brine at a temperature of 150°C or below. Crevice corrosion was identified as a potentially important failure mode for this material. Within a mechanical crevice, a thick oxide film was found and shown to be the rutile form of TiO2, with a trace of lower oxide also present. Acidic conditions were found to cause a breakdown of the passive oxide layer. Solution aeration and increased acidity accelerate the corrosion rate. In hydrogen embrittlement studies, it was found that hydrogen causes a significant decrease in the apparent stress intensity level in fracture mechanics samples. Hydride formation is thought to be responsible for crack initiation. Stress corrosion cracking under static loads was not observed. Attention has also been given to methods for extrapolating short term uniform corrosion rate data to extended times.
Rheological and Physical Properties of Magesium Oxide and Silica Fume-Modified Cement Mortars Cured at High Temperature
Authors: Nakagawa Zenbe-e , White Elizabeth L. , Roy Della M. 
Published: March 2011

ABSTRACTPhysical properties and placement characteristics of cementitious mortars have been studied for their potential as repository sealing materials. They contained various expansive agents and industrial by-products, and were investigated at curing temperatures up to 250° C, the upper limit of an emplacement site or generally of relevance in accelerated reaction studies. An expansive agent, magnesium oxide, and two industrial by-products, silica fume and granulated blast furnace slag have been used at different percentages in the mixtures. Excellent general performance, including very high strengths up to 240 MPa combined with very low intrinsic permeability <10−8 Darcy (μm2) were generated at 175°C on material having a viscosity of 5000 cP (mPa·s) at 38° C. One 1700 cP(mPa·s) material treated at 250°C had compressive strength >180 MPa and also <10−8 Darcy (μm2) permeability. MgO was found to accelerate formation of tobermorite and generally cause expansion; at 250° C expansion was also related to xonotlite formation.
Microanalytical and Structural Characterization of Optical Materials By Electron Microscopy and Related Specitroscopies
Authors: Krishnan Kannan M. 
Published: March 2011

ABSTRACTThe fine probe forming capabilities of an analytical electron microscope combined with the development of related spectroscopies, diffraction and imaging techniques, makes it possible to obtain structural and chemical information from multiphase materials at high spatial resolution. These microanalytical methods are described with relevant examples from our studies of compounds in the A12O3-AIN pseudobinary system, a potential window material, low-pressure synthesized diamond, diamond-like carbon and hydrocarbon films. A comprehensive example of the characterization of a novel AION poltypoid structure (32H), illustrative of both the information content obtainable from these techniques at any particular level of resolution and the need to employ all the complementary methods of analysis, is discussed. Efforts to characterize a variety of diamond-like carbon films by the measurements of both the low-loss plasmon resonances and the fine strcture in the core-loss edges observable in the energy-loss spectrum, to obtain sp3/sp2 ratios are outlined. The electronic structure of thin film diamonds, synthesized by a plasma enhanced chemical vapour deposition method, has been shown to be in agreement with band structure calculations.
Characterization of KNbO3 Thin Films Deposited by Ion Beam Sputtering using a Computer-Controlled Rotating Target Holder
Authors: Ameen M. S. , Graettinger T. M. , Auciello O. , Rou S. H. , Kingon A. I. , Krauss A. R. 
Published: March 2011

ABSTRACTKNbO3 is a strong candidate as a material for use as channel waveguides due to a high electrooptic figure of merit. High quality single crystals are difficult to obtain due to incongruent melting of the compound. Control of cation concentration and oxygen incorporation are problems encountered in current thin film processing routes.In order to overcome the problems discussed above, an ion beam deposition system featuring a computer-controlled rotatable target holder and quartz crystal resonator (QCR) feedback loop has been developed. Multicomponent films are produced via sputtering from elemental or compound targets sequentially exposed to an ion beam. Initial results are presented on the use of this new technique for the deposition of KNbO3. Pressed KNbO3, Nb2O5, and KO2 powders were used as sputtering targets. By varying the programmed thickness of deposited film from each target being sputtered, the ratio of K:Nb could be reproducibly controlled. The variation in sticking coefficients due to substrate temperature was also compensated for in this manner.Thin films were analyzed by X-ray diffraction and TEM to determine phases present and film microstructure. Film morphology and composition has been studied as a function of substrate temperature, layer thickness, and ion beam process parameters. The relation between deposition parameters and film characteristics are discussed.
Structural and Optical Characteristics of Thin Films Deposited by Ionized Cluster Beam
Authors: Yamada Isao 
Published: March 2011

ABSTRACTIn ionized cluster beam (ICB) deposition, crystal properties can be controlled by changing the acceleration voltage and the ionization current. Therefore, the physical and chemical characteristics of the deposited films can be controlled. This controllability in ICB deposition allows one to deposit new optical films. These films are expected to have many new applications over optical range from x-ray to visible. This paper describes film examples for an X-ray mirror with low stray scattering, for an excimer laser mirror with very high damage threshold power and for dielectric optical coatings. These results show that the ICB technique offers much potential for developing new optical thin films in a wide range of applications.
The Effects of Biasing on the Optical and Electrical Properties of RF Sputtered VO2
Authors: Razavi A. , Hughes T. , Bobyak L. 
Published: March 2011

ABSTRACTVanadium dioxide was deposited on sapphire substrates by RF reactive sputtering. Biasing of substrates during deposition was used to alter both resistivity and infrared transmission of VO2 thin films. It has been found that as the negative dc bias potential is increased, films in the metallic state show an increased transmittance of IR wavelengths between 2.5 and 6 μm. Also, the resistivity ratio of the semiconductor to metal phase as a function of bias potential is found to reach a maximum value after which further increases in bias cause degradation of electrical properties. X-ray diffraction analysis was used to study film composition.
Optical Dispersion Relations for “Diamondlike” Carbon Films
Authors: Alterovitz Samuel A. , Sieg Robert M. , Shoemaker Neil S. , Pouch John J. 
Published: March 2011

ABSTRACTEllipsometric measurements on plasma deposited “diamondlike” amorphous carbon (a-C:H) films were taken in the visible, (E = 1.75 to 3.5 eV). The films were deposited on Si and their properties were varied using high temperature (up to 750 °C) anneals. The real (n) and imaginary (k) parts of the complex index of refraction N were obtained simultaneously. Following the theory of Forouhi and Bloomer (Phys. Rev. B34, 7018 (1986)), a least squares fit was used to find the dispersion relations n(E) and k(E). Reasonably good fits were obtained, showing that the theory can be used for a-C:H films. Morever, the value of the energy gap Eg obtained in this way was compared to the Eg value using conventional Tauc plots and reasonably good agreement was obtained.
Nitrogen Doping of ZnO Prepared by Organometallic Chemical Vapor Deposition
Authors: Pan H-C , Wessels B. W. 
Published: March 2011

ABSTRACTZnO layers were grown by organometallic chemical vapor deposition. Films were deliberately doped with nitrogen by incorporating ammonia into the ambient during growth. The resistivity of the films depended strongly on the ammonia partial pressure. The layers were n-type with resistivities in the range of 0.1 − 360 ohm-cm. The films exhibited strong ultraviolet nearbandedge photoluminescent emission. Emission was ascribed to recombination of bound excitons at neutral acceptors, presumably involving substitutional nitrogen.