bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Approach to Analysis of High Level waste Container Performance in an Unsaturated Repository Environment
Authors: Walton John C. , Sridhar Narasi , Cragnolino Gustavo , Torng Tony , Nair Prasad 
Published: March 2011

ABSTRACTOne of the requirements for the performance of waste packages prescribed in 10CFR 60.113 is that the high level waste must be “substantially completely” contained for a minimum period of 300 to 1000 years. During this period, the radiation and thermal conditions in the engineered barrier system and the near-field environment are dominated by fission product decay. In the present U.S design of the engineered barrier system, the outer container plays a dominant role in maintaining radionuclide containment. A quantitative methodology for analyzing the performance of the container is described in this paper. This methodology enables prediction of the evolution of the waste package environment in terms of temperature fields, stability of liquid water on the container surface, and concentration of aggressive ions such as chloride. The initiation and propagation of localized corrosion is determined by the corrosion potential of the container material and critical potentials for localized corrosion. The coiTOsion potential is estimated from the kinetics of the anodic and cathodic reactions including oxygen diffusion through scale layers formed on the container surface. The methodology described is applicable to a wide range of metals, alloys and environmental conditions.
An Accelerated Electrochemical MIC Test for Stainless Alloys
Authors: Gendron T.S. , Cleland R.D. 
Published: March 2011

ABSTRACTPrevious work in our laboratory and elsewhere has suggested that MIC of stainless steels and nickel-base alloys occurs in locally anaerobic regions that support the growth of sulfate reducing bacteria (SRB). The cathodic reaction is provided by oxygen reduction at remote sites. Such a coupling between anode and cathode is difficult to reproduce in the laboratory, but can be simulated indirectly using a double electrochemical cell, as in previous work. A more realistic simulation using a single aerated electrochemical cell has now been developed, in which a second organism (P.aeruginosa)is used to provide an anoxic habitat for SRB growth and possibly a source of organic carbon, within a layer of silt. A bare alloy electrode is used as the oxygen cathode. Tests of this kind using rigorous microbiological procedures have generated pitting corrosion of several alloys in low chloride media simulating freshwater heat exchanger conditions. Similar test procedures are applicable to other environments of interest to this symposium.
The Advantages of a Salt/Bentonite Backfill for Waste Isolation Pilot Plant Disposal Rooms
Authors: Butcher B.M. 
Published: March 2011

ABSTRACTThis paper concludes that a 70 wt% salt/30 wt% bentonite mixture is preferable to pure crushed salt as backfill for disposal rooms in the Waste Isolation Pilot Plant. The performance of two backfill materials is examined with regard to various selection criteria related to compliance with the transuranic radioactive waste standard 40 CFR 191, Subpart B, such as the need for low liquid permeability after closure, chemical stability, strength, ease of emplacement, and sorption potential for brine and radionuclides. Both salt and salt/bentonite are expected to consolidate to a final state of permeability ≤ 10-18 m2, which is adequate for satisfying government regulations for nuclear repositories. The real advantage of the salt/bentonite backfill depends, therefore, on bentonite’s potential for sorbing brine and radionuclides. Estimates of the impact of these properties on backfill performance are presented.
An Experimental study of Granitic Water-Saponitic Bentonite Interaction under Hydrothermal Conditions
Authors: Garralon Antonio , Cuevas Jaime , Leguey Santiago 
Published: March 2011

ABSTRACTThe interaction of a saponitic clay from the Madrid Basin with synthetic groundwater (GW) simulating those from granitic areas is investigated. The experiments performed explore the reaction of clay with GW (1:3 solid to water ratio) at 45, 60 and 90°C. Water extracted from the clay slurries has been analyzed and water of this composition synthesized again to run a new reaction with the original clay (salt concentration process). The clay product of the first reaction was reacted again with GW (leaching process). These reactions were repeated in successive equilibrating steps.Multicationic selectivity coefficients have been calculated. K > Ca > Mg > Na is the order of preference for adsorption by the clay. The selectivity of Ca is highly enhanced in both processes, the clay acting as a true complexing agent for Ca, as calcite controls the carbonate equilibrium. A clear dependence of the exchange constants on temperature with the range explored was not detected. The GW composition evolves from Ca,Na-HCO3 to Na,Mg-HCO3 (leaching) and NaCl (concentration), the solutions being buffered at pH 8.0. Mechanical properties, clay mineralogy and bulk adsorption properties remained virtually unchanged in the successive one month experiments although a slight decrease in BET specific surface area indicated some sepiolite dissolution at 90°C.
Diffusion of Uranium in Compacted Bentonite in the Presence of Carbon Steel
Authors: Idemitsu K. , Furuya H. , Tachi Y. , Inagaki Y. 
Published: March 2011

ABSTRACTIn a high-level waste repository, a carbon steel overpack will be corroded by consuming oxygen trapped in the repository after closure. This will create a reducing environment in the vicinity of repository. Reducing conditions are expected to retard the migration of redox-sensitive radionuclides such as uranium.The apparent diffusivities of uranium were measured in compacted bentonite (Kunigel VI®, Japan) in contact with carbon steel under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusivities of uranium were 3.5 × 10-14 to 1.1 × 10-13 m2/s under reducing conditions and 9.0 × 10-13 to 1.4 × 10-12 m2/s under oxidizing conditions. There was no significant effect of dry density (1.6 to 1.8 g/cm3) and silica sand (0 or 40%) on the apparent diffusivities.Since the bentonite pore water would be buffered at a pH between 8 and 9, uranium in the bentonite pore water would probably exist as a neutral hydroxide complex under reducing conditions and as an anioníc carbonate or hydroxide complex under oxidizing conditions. The anion exclusion theory cannot explain the difference of diffusivities between the two conditions. The uranium concentrations in bentonite under oxidizing conditions were one order of magnitude higher than those under the reducing conditions. The uranium concentration in the bentonite pore water under the reducing condition is estimated to be two orders of magnitude lower than that under the oxidizing conditions under the assumption of diffusion in porous media.
Estimation of Static Fatigue Behavior of Ceramic Materials as Candidate Overpack Materials
Authors: Obata Masamichi , Honda Akira , Ishikawa Hirohisa , Mano Tadashi 
Published: March 2011

ABSTRACTStatic fatigue behavior is one of the important factors for life prediciton of ceramic materials. In this study, SCG (slow crack growth) parameters were measured under atmosphere conditions, and the static fatigue behavior of alumina, PSZ (partially stabilized zirconia), and titanium oxide was examined.According to the results of the evaluatin of the static fatigue behavior, the destruction probability after 1,000 years would be less than 1/40,000 when tensile stresses occurring in the material were less than 79.4, 241.3, 8.0 MPa for alumina, PSZ, and titanium oxide, respectively. However titanium oxide could not be used because of the wall thickness that would be needed to accomplish this stress. The life prediction method includes only tht effect of preexisting flaws so the method to estimate the effect of localized corrosion is required for the future examination of the application of ceramic materials.
Potential Resources from Coal Fly Ash
Authors: Watson J. S. 
Published: March 2011

AbstractRecent studies at Oak Ridge National Laboratory (ORNL) and elsewhere have identified various chemical processes for recovering useful materials, such as alumina and iron oxides, from coal combustion fly ash. Based on certain assumptions, each of these processes can yield useful products at economical prices. Most processes leave a residual solid waste with a volume only slightly less than that of the original waste. This residue may not present a serious hazard, but its volume alone makes disposal difficult for utilities with limited land available for disposal sites. Characteristics of some of the residues are being studied to determine possible beneficial uses or applications of these by-products.
Characterization of a Lignite Ash from the Metc Gasifier I. Mineralogy
Authors: McCarthy Gregory J. , Keller Lindsay P. , Stevenson Robert J. , Galbreath Kevin C. , Steinwand Aaron L. 
Published: March 2011

AbstractUtilization or disposal of gasification ash requires detailed characterization of its chemistry and phase formation (mineralogy). A North Dakota lignite ash produced in the Morgantown Energy Technology Center (METC) gasifier has been studied in detail by x-ray diffraction and electron microprobe analysis. The ash was coarse (84% of grains larger than 1.0 mm) but a typical grain was composed of a dozen or more crystalline phases with dimensions on the micrometer scale as well as less abundant glass phases. Hard centimeter-size clinkers suggested partial melting followed by crystallization. Silicates (dicalcium silicates (C2S), merwinite, Ca-Na-silicate (CNS), quartz), aluminosilicates (melilite, nepheline, carnegieite), oxides (ferrite spinels, periclase, hematite), calcite and minor zeolites comprised the dominant mineralogy. Microprobe analyses were obtained for large numbers of grains of the C2S phases, CNS, merwinite, melilite, ferrite spinels and calcite. The remaining phases had crystal sizes too small for analysis. A model is proposed for the genesis of this ash based on the inorganic constituents of lignite and the gasifier operating conditions.
Characterization of a Lignite Ash from the METC Gasifier III. Correlations of Leaching Behavior and Mineralogy
Authors: Hassett D. J. , McCarthy G. J. , Henke K. R. , Korynta E. D. 
Published: March 2011

AbstractLignite gasification ash from the Morgantown Energy Technology Center (METC) gasifier was subiected to two short-term leaching treatments. The cnncentrations of regulated elements in the EPA EP procedure leachate from the bulk METC ash did not exceed the “EP Trigger Limits.” A modification of this procedure that uses a basic synthetic groundwater instead of the acid EP extractant was also performed on the bulk ash and its eleven size fractions. Water equilibria modeling was used to explain the concentrations of major elements in solution. Corcentrations of minor and trace elements in solution after leaching with synthetic groundwater were also below “EP Trigger Limits.”
Investigation of Leachability of Subbituminous Fly Ash Enhanced Road Base Materials
Authors: Garcez Ivan , Tittlebaum Marty E. 
Published: March 2011

AbstractEnormous amounts of coal fly ash produced by the utilities industry create a significant disposal problem. The abundance of fly ash along with its self-hardening properties led the Louisiana Department of Transportation and Development (LA DOTD) to use fly ash as a soil stabilizer for road bases. However, the LA DOTD is primarily concerned with the strength of the material and has not studied its leaching characteristics. In this study, a total of three samples, a 30 percent subbituminous fly ash/soil mixture, subbituminous fly ash, and soil, were leached following the EPA multiple extraction procedure and analyzed by Inductively Coupled Argon Plasma Spectrometry (ICAP). Results indicate that little change in leachate quality of subbituminous fly ash was caused by the soil stabilization process. The insignificant change is attributed to the low cation exchange capacity of the soil. ICAP analysis revealed that levels of toxic metals in the leachates are well within RCRA standards.
Characterization of Fly Ash and its Reactions in Concrete
Authors: Roy Della M. , Luke Karen , Diamond Sidney 
Published: March 2011

AbstractFly ashes are currently being produced that are much more widely different from each other in composition and other characteristics than had been previously experienced, owing to the widespread use of low rank subbituminous and lignitic coals. The current ASTM classifications into Class F and Class C pozzolan categories are not adequate to describe all their important properties. Current characterization methods are reviewed, including physical characterization by particle size distribution, shape, apparent specific gravity, content of hollow grains and of residual coal fragments, etc., chemical procedures of various kinds, and SEM, EDXA, XRD, and other methods for the determination of mineralogical content and glass character. Etching and chemical dissolution procedures are particularly important. The state of these various methods, current results of their use in rly ash characterizations, and the relations of these to reactivity and performance of fly ashes in cement and concrete are discussed.
Scanning Electron Microscopy and X-Ray Diffraction Analysis of Various Size Fractions of Fly Ash
Authors: Joshi R. C. , Natt G. S. , Day R. L. , Tilleman D. D. 
Published: March 2011

AbstractX-ray diffraction and scanning electron microscopic analyses have been performed on the various Western Canadial fly ash fractions and on mixtures of cement and fly ash fractions. The ash mineralogy of hydrated and unhydrated fly ash samples was examined by x-ray diffraction. Results from a study of the morphology of ash particles etched in dilute hydrofluoric acid are also included. Scanning electron microscopy indicates that most of the reactive portion of the ash is on the particle surface. Also, as the fly ash particle size increases, the amount of crystalline SiO2 increases but the quantity of calcium containing compounds decreases. Crys~alline SiO2 (the majority of which is present in the +75 μm fraction) does not take part in self-hardening reactions but does appear to take part in pozzolanic reactions.
Technical Note on the Determination of Free Lime (CaO) in Fly Ash
Authors: Schlorholtz Scott , Demirel Turgut 
Published: March 2011

AbstractMany fly ashes contain free lime (CaO) and periclase (MgO) [1,2]. These two compounds, when present in excessive amounts, are known to cause soundness problems in portland cement [3,4]. Recent work [5] has indicated that the autoclave expansion of portland cement-fly ash pastes is related to the concentration of CaO and MgO in a given paste, free lime typically being more detrimental than periclase. The purpose of this technical note is to briefly discuss two methods that are currently available for determining the free lime content of fly ash, and to suggest a supplement to the autoclave test (described in ASTM C 151). The major drawback of the autoclave test is that it requires approximately two days to complete and therefore it would be helpful to have a quick chemical test that could be used to indicate the soundness properties of a given fly ash.
Characterization of Crystalline Phases in Fly Ash by Microfocus Raman Spectroscopy
Authors: Scheetz Barry E. , White William B. 
Published: March 2011

AbstractThe laser Raman microprobe was used to interrogate individual fly ash particles as small as 1 μm diameter and record “fingerprint” Raman spectra from both crystalline and non-crystalline components.of the fly ash. When compared to reference patterns of known crystalline phases, the Raman spectra can be used to identify crystalline phases and can give some structural information on other phases. Furthermore, because this method characterizes fly ash particles on an individual basis, correlations to both color and morphology of the particles can be made.
Retardation Effects in the Hydration of Cement-Fly Ash Pastes
Authors: Grutzeck Michael W. , Fajun Wei , Roy Della M. 
Published: March 2011

AbstractThe hydration of high-calcium and low-calcium fly ash-cementmixtures was investigated to determine the effect of fly ash upon the hydration of a Type I portland cement, and to determine the associated mechanisms of hydration. When blended with portland cement, both fly ashes retarded the early hydration process, the high-Ca more so than the low-Ca. Analyses of solution compositions and calorimetric (heat of hydration) measurements were made. The retardation and hydration effects are discussed in terms of solution composition data and solid phase characterization. The hydration effects were interpreted and compared with the results of previous work.
Reaction Products in Fly Ash Concrete
Authors: Baker Mark D. , Laguros Joakim G. 
Published: March 2011

AbstractThe setting and strength gaining process of PC concrete containing Class C high lime fly ash were related to the reaction products identified using XRD and SEM. Four fly ash concrete mixes (20, 30, 40, and 50 percent replacement of cement by fly ash) and similar paste mixes were compared to control mixes for curing periods up to one year. Setting time and early compressive strength were adversely affected by the addition of fly ash. Beyond one week all of the fly ash concrete mixes gained strength at a faster rate than the corresponding control mixes. XRD studies suggest that the retardation mechanism may be associated with the high levels of ettringite formed early in the hydration process and its conversion to monosulfoaluminate. A decrease in the level of calcium hydroxide, typical of pozzolanic activity, was not in evidence. SEM micrographs of fly ash spheres in concrete at the various stages of hydration reveal an intricate crystal framework. A simple heat of hydration test is presented which helps explain the strength gains observed.
Autoclave Expansion of Portland Cement-Fly Ash Pastes
Authors: Schlorholtz Scott , Demirel Turgut 
Published: March 2011

AbstractThe influence of the chemical composition of fly ash on the autoclave expansion of portland cement-fly ash pastes has been studied. The autoclave expansion tests were performed as described in ASTM C 151–81. Several of the cement-fly ash pastes tested exhibited severe expansive behavior. Free lime (CaO) was the only single variable that correlated well with the expansion observed in the autoclave tests. A multivariable model was generated in which lime, magnesium oxide, and tricalcium aluminate were the significant variables. The autoclave expansion of portland cement-fly ash pastes appears to be quite sensitive to the amount of free lime present in a given mixture.
Characterization of the Ni/NiO, Interface Region in Oxidized High Purity Nickel by Transmission Electron Microscopy
Authors: Sawhill Howard T. , Hobbs Linn W. 
Published: March 2011

ABSTRACTNi/NiO interface structures were investigated using TEM, and the observed structures were compared with current heterophase interface models. Relative magnitudes of Ni/NiO interfacial energies were obtained from measurements of dihedral angles at triple grain junctions between Ni and NiO grains. Extra reflections in diffraction patterns from oxide grains adjacent to the Ni/NiO interface were compared with kinematical structure factor calculations for several proposed structures.
Interface Study of Mo/GaAs
Authors: Ling Peiching , Chang Jyh-Kao , Lin Min-Shyong , Lou Jen-Chung 
Published: March 2011

ABSTRACTThe electrical characteristics and the microstructure of Mo/GaAs Schottky diodes fabricated by electron-beam evaporation have been studied. The barrier height, ideality factor, deep trapping levels and intermetallic compounds of these annealed or unannealed Mo/GaAs Schottky diodes are obtained by using the I-V, C-V, Rutherford backscattering spectroscopy (RBS), Auger electron spectroscopy (AES), deep level transient spectroscopy (DLTS) and transmission electron microscopy (TEM) analyses. An obvious interdiffusion at Mo/GaAs interface is observed in Mo/GaAs Schottky diodes annealed above 500°C for 10 min. DLTS results show that there are two electron traps [Ec-(0.52±0.02)'eV and Ec-(0.86±0.02) eV] and one hole trap [Ev+(0.92±0.02) eV] are demonstrated for 300°C, 400°C post-annealed Mo/GaAs diodes. TEM results also indicate that the disappearance of these deep trapping levels may correlated to the formation of intermetallic compounds GaMo3 and MoAs2 existed in Mo/GaAs diodes post-annealed above 500°C. It is believed that the metal-semiconductor interdiffusion and the intermetallic compounds play the major roles for the thermal degradation of Mo/GaAs Schottky diodes.
Defects in Platinum Silicide Formation
Authors: Warburton Michael J. 
Published: March 2011

ABSTRACTFour types of cause related defects in the formation of platinum silicide were examined by scanning Auger Microscopy (SAM). These are: “Dark Platinum”, a dark rough patch on the platinum silicide, “Aqua Regia Attack”, the apparent etch of the platinum silicide by the aqua regia used to remove pure Pt metal, “Spot Defects”, holes in the Pt-Si layer and Ti-W strip defects, the apparent defects left in the Pt-Si by the stripping of a Ti-W overlayer. Elemental Auger maps show that silicide formation was prevented, in the first three cases, by remaining oxide from a masking step. The fourth case was caused by a layer of titanium oxide overlying the Pt-Si.
Auger Electron Analysis of Oxides Grown on a Dilute Zirconium/Nickel Alloy
Authors: Ploc R. A. , Davidson R. D. , Roy J. A. 
Published: March 2011

ABSTRACTAuger electron analysis of oxides grown at 573 K in dried oxygen on the matrix and on precipitates in a 0.5 wt% Ni in zirconium alloy, is part of a larger program to study the effect of second phase particles on the oxidation and hydriding behaviour of Zircaloy-2. The alloy consisted of a zirconium matrix containing randomly distributed Zr2Ni precipitates of up to 10 μM in diameter. Oxidation simultaneously proceeded about the whole periphery of the precipitate and after approximately 50 days exposure was completely oxidized and of nearly uniform composition. The chemical structure of the oxides grown on the matrix and on the free and internal surfaces of the precipitate were determined as a function of depth in the oxide film.
Surface Segregation of Ni-Cr Alloy
Authors: Chen N. Q. , Zhang Q. J. , Hua Z. Y. 
Published: March 2011

ABSTRACTThe surface segregation of a Ni-Cr alloy used for commerciel heating elements hps been examined with a scanning Auger Microprobe (SAM) and other electron spectroscopy. A variety of sample surfaces prepared by different ways, including fracturing, mechanical polishing, electrochemical polishing, annealing, oxidation and their combinptions were investigated.Results showed that on the surface treated with mechanical polishing followed by oxidation, a continuous, hichly chromium-enriched layer would be formed in a few minutes. Three factors, i.e., mechanical polishing, oxygen environment and temperature, have been found all necessary to make this Cr enrichment happen rapidly.Taking the advantage of high spatial resolution of AMH, other experimentol facts have been obtained by comparing SFM image and Auger map. First, the Cr segregated at the area where abrading trace (about few micrometers in width) existed. Second, during the oxidation process at early stage Cr war enriched at the arrin boundaries and soreaded laterally.These results indicate that Cr as diffusing thru the crain boundaries to the surface and the process of mechanical nolishing played, the role for increasing a large number ofcrain boundaries. The chemical driving force of oxygenalso promotes the diffusion unto at a relatively low temperature so is to complet- the orocess in a short period.