bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell Adhesion to Ion Implanted Titanium
Authors: Grabowski K. S. , Gossett C. R. , Young F. A. , Keller J. C.
Published: March 2011

This preliminary investigation evaluates the influence of ion implantation on tissue adhesion by measuring the tendency of fibroblasts to attach to the surface of ion implanted Ti. For this work, polished specimens of commercially pure Ti were implanted with ions of Ti, Ca, C, or N to produce a surface concentration of the implanted element up to about 25 at. %. Unimplanted and ASTM treated Ti, and tissue culture plate specimens were prepared as controls. Specimens were sterilized, then exposed for 15 min. to a culture medium containing about 100,000 fibroblasts. The solution and loose fibroblasts were rinsed away and the fibroblasts counted to determine those left attached. The influence of the different implantation protocols on fibroblast adhesion to Ti will be described. Analysis of the structure and composition of the ion implanted surfaces was obtained by scanning electron microscopy, x-ray photoelectron spectroscopy, and elastic backscattering spectrometry of energetic He ions.
Complement Activation Resulting from Blood-Material Interactions
Authors: Johnson Richart J. , Chenoweth Dennis E.
Published: March 2011

Recently there has been a growing awareness of the importance of the interactions of the human complement system with biomaterials which largely stems from the understanding that complement-materials interactions may result in the production of inflammatory mediators, termed C3a and C5a anaphylatoxins, that can produce significant pathopysiologic alterations in the exposed patient. This presentation will review studies of complement activation produced by various hemodialysis membranes. our current data suggests that hemodialysis membranes may be roughly divided into three categories. The first type of membrane displays a high complement-activating potential as judged by measurements of C3a antigen levels produced during dialysis. These membranes also liberate sufficient quantities of C5a to induce both significant granulocytopenia and cardiopulmonary effects. The second group of membranes exhibits a moderate capacity to activate complement, with the amount of C3a antigen produced by these devices being about half that seen with the highly activating dialyzers. Dialyzers in this intermediate group produce only enough C5a to provoke a modest degree of leukopenia and they generally fail to induce cardiopulmonary manifestations. The third type of device fails to produce significant amounts of either free C3a or C5a and does not produce significant granulocytopenia. Factors that could affect the propensity of a material to activate complement include the density and type of surface nucleophiles, and the presence of surface dcarge which may facilitate the interaction of regulatory components and the adsorbtion of both active and bystander proteins.
Plasma Protein Fractionation by Membrane Filtration in Therapeutic Plasmapheresis
Authors: Horiuchi Takashi , Malchesky Paul S. , Nosé Yukihiko
Published: March 2011

Synthetic polymer membranes which have a nominal pore size (NPS) of 0.03 to 10 microns were evaluated at varying filtration temperatures to separate pathologic macromolecules such as immune complexes, cryoprecipitable proteins and low density lipoproteins (LDL) from essential plasma proteins. At low temperatures (4 to 10°C) cryoprecipitable proteins were selectively removed from cryoglobulinemic plasmas with membranes of 3 micron NPS. However, severe membrane plugging occurred with membranes of smaller pore sizes. In addition, decreased albumin sieving occurs. Above 37°C, increased albumin sieving and prolonged membrane plugging occurs. In the selective removal of low density lipoproteins from hypercholesterolemic plasmas, membranes with NPS of 0.03 microns were found to be suitable at high operating temperatures. Given the proper combination of membrane and temperature control, disease related pathological macromolecules can be treated effectively by selective macromolecule removal.
ProsorbaRTreatment Column: A Device that Removes Circulating Immune Complexes (CIC), IgG, and Autoimmune Antibodies From Patient Plasma
Authors: Balint Joseph P. , Jones Frank R. , Snyder Harry W. ,   Prosorba Column Clinical Trial Group.
Published: March 2011

Selective removal of molecular moieties from plasma of patients can result in tumor regression, auto-antibody clearance, and immune modulation. The ProsorbaRColumn consists of highly purified protein A isolated from Staphylococcus and covalently linked to inert silica housed in a polycarbonate device. Protein A acts as an immunoadsorbent to selectively remove immunoglobulin G (IgG) and IgG containing CIC via specific binding to the Fc fragment of IgG. Columns were sterile, disposable devices that remove approximately one gram of IgG from plasma per treatment. As part of a multicenter clinical trial, 8 of 22 (36%) end stage breast cancer patients exhibited objective antitumor responses. Treatment of 24 patients with immune thrombocytopenia resulted in 14 (58%) of patients having objective increases in platelet counts and clearance or significant reduction of anti-platelet antibody. The mechanism of action of this device is unknown at present but may be selective removal of IgG and CIC, and activation of factors such as the complement system which results in enhanced reticuloendothelial system (RES) clearance of CIC. In addition, immune modulation may result due to the stimulation of anti-idiotypic antibodies and selective clonal deletion of auto-antibody producing lymphocyte sub-populations.
Plasticizer Interaction with Stored Blood Produces a Toxic Metabolite, Mono(2-Ethylhexyl)Phthalate
Authors: Rock G. , Labow R. S. , Franklin C. , Burnett R. , Tocchi M.
Published: March 2011

Most medical devices utilized in blood storage and transfusion, as well as in many medical and surgical procedures, are manufactured with polyvinylchloride (PVC) plastic containing the plasticizer di(2-ethylhexyl)phthalate (DEHP). During exposure of blood to the plastic surface, the DEHP is leached into the plasma where it is converted to mono(2-ethylhexyl)phthalate (MEHP) by a plasma enzyme in vivo or ex vivo during storage in plastic containers. The toxic effects of MEHP when infused into rats were investigated. The amount of MEHP infused was based on MEHP levels found in a variety of stored blood products (>6 ug/mL in red cell concentrates) and values actually measured during exchange transfusion (5 ug/mL) and cardiopulmonary bypass surgery (2.7 ug/mL). When the circulating level of MEHP in the rat's blood was >125 ug/mL, a greater than 50% decrease in heart rate and blood pressure was observed. This represents a margin of safety of only 25 fold higher than levels measured in humans during exchange transfusions. Although DEHP and MEHP have low oral toxicity, acute exposure by infusion may have lethal effects.
Peripheral Neve Regeneration in Vivo with Tubular Prostheses
Authors: Madison Roger
Published: March 2011

We have developed a quantitative model which allows assessment of the number of primary motor and sensory neurons which regenerate an axon through a tubular prosthesis bridging a 4–5 mm gap of peripheral nerve (1). Labeled somas of motor and sensory neurons are quantified following retrograde transport of horseradish peroxidase (HRP) applied to the distal stump beyond the bridged transection site. The number of myelinated axons at mid-guide level is also quantified. We have studied biodegradable and nin-biodegradable materials as well as the effects on nerve regeneration of basement membrane materials, and specific proteins added to the nerve guide., Adding a laminin-oontaining gel (Matrigel, Collaborative Research, MA) to the lumen of polyethylene tubes increases the rate of nerve regeneration as well as the maximum distance that can be successfully bridged. Similar effects are seen with collagen-based nerve guides when the laminin-cxitaining gel is incorporated into the tube wall. Addition of highly purified acidic fibroblast growth factor (aFGF) to the lumen of polyethylene tubes filled with collagen significantly increases the number of myelinated axons at mid-tube level and the number of primary sensory neurons labeled with HRP.

We coxpared collagen-based nerve guides of different wall porosities. Tubes freely permeable to bovine serum albumin (BSA) contain significantly more myelinated axons (4 week survival) than identical collagen tubes permeable to glucose-size molecules. These and additional experiments demonstrate that manipulation of the extracellular microenvironment of regenerating PNS axons can significantly enhance the early regenerative response.
Improvement and Use of Empirical Estimates of 29Si Chemical Shifts in Zeolites
Authors: Newsam J. M. , Melchior M. T. , BEYERLEIN R. A.
Published: March 2011

29Si chemical shifts, δ, are for aluminosilicate zeolites expressed as δSi-4Al (which can be estimated from the T-O-T angles observed crystallographically) plus terms involving b1 and b2, the quantitative influences of first and second neighbor aluminum atoms. The former, b1, is assumed to be the sum of a fixed electrostatic component, α, and a framework-specific angular term, β(0 < β < 0.9 ppm), that reflects the generally smaller Si-O-Al angles compared to Si-O-Si. The compositional dependence of δ is approximated by an equal influence, b2, per added second neighbor aluminum atom, the concentration of which is assumed to vary linearly with composition. Values of δS-nAl; n=0-3 for representative L (LTL-framework) and omega (MAZ) zeolites calculated on this basis agree well with those observed. Applying this description of the compositional dependence to as-synthesized and dealuminated CSZ-1 zeolites enables the measurement of framework aluminum contents in this four T-site case.
Synthesis and Structural Characterization of a Hydrated Gallosilicate Zeolite with the Nat-Framework
Authors: Xie D. , Newsam J. M. , Yang J. , Yelon W. B.
Published: March 2011

Gallosilicate NAT-framework zeolites have been synthesized from Na2O:TMA2O:Ga2O3:SiO2:H2O gels and characterized by chemical analysis and powder X-ray diffraction. The structure of a hydrated material (Orthorhombic, Fdd2, a = 18.423(4) Å, b = 18.826(3) Å, c = 6.652(1) Å) was determined using powder neutron diffraction. The framework Si:T ratio, Si-Ga segregation and non-framework cation and water configurations are similar to those in the analogous aluminosilicates. The geometrical effects of framework gallium substitution are consistent with those observed for other zeolite framework topologies.
Comparative Studies of the Degradation of Several Zeolites Under Electron Irradiation
Authors: Acosta D. R. , Guzman O. , Angel P. Del , Dominguez J.
Published: March 2011

High resolution electron microscopy has proven to be a powerful technique to determine structural characteristics of zeolites (l–2),symmetry variations and identification of several kind of defects.Together with ideal projected potential images, the microscopist usually finds in electron micrographs the influence of electro-optical parameters and alterations of the crystallinity of the material under electron irradiation. One of the purposes of this workis to contributetothe understanding of the degradation process of zeolites under electron irradiation in the electron microscope and in this way, discriminate when it is possible, what is reliable information recorded in the images obtained in high resolution conditions.
The Effect of Support Composition on Platinum Crystallite Agglomeration in Oxygen
Authors: Morrissey Michael F. , Kitazumi Shoko , Hicks Robert F.
Published: March 2011

The effects of temperature of oxygen exposure on metal dispersion were determined for platinum deposited on Al2O3, ZrO2, 12 wt% Y2O3–ZrO2, and MgO. Platinum on zirconia and on magnesia showed higher thermal stability than platinum on alumina.
Mössbauer Analysis of Iridium in Pt-Ir/SiO2 Catalysts
Authors: Sawicki J. A. , Wagner F. E. , Rolston J. H.
Published: March 2011

The state of iridium in highly dispersed bimetallic Pt-Ir catalysts supported on amorphous silica was studied by 193Ir Mössbauer spectroscopy, after deposition via ion exchange, as well as after calcination, reduction in hydrogen, and on exposure to carbon monoxide. Characteristic patterns and relative contributions of adsorbed [Ir(NH3)5Cl] complexes, IrCl3, IrO2 and Pt-Ir alloy particles have been identified. The composition of bimetallic particles indicates a strong tendency for segregation of Pt and Ir.
Adsorption and Acidic Properties of Clays Pillared With Oxide Sols
Authors: Yamanaka S. , Nishihara T. , Hattori M.
Published: March 2011

Interlayers of montmorillonite were pillared with TiO2, SiO2-TiO2and SiO2-Fe2O3sols. The pillared structures were thermally stable at least up to 500°C and retained unusually large basal spacings in the range of 24–45Å and surface areas as high as 300–500 m2/g. The TiO2pillared clay showed Type IV adsorption isotherm for nitrogen. Although SiO2-TiO2and SiO2-Fe2O3pillared clays had basal spacings much larger than that of TiO2pillared clay, these mixed oxide pillared clays had small pores and exhibited Type I isotherm. The acidic strength distributions were determined by a titration method using n-butylamine and Hammett indicators. All of the pillared clays had large acidities, but the acidic strength decreased in the following order: TiO2- SiO2» SiO2-Fe2O3pillared clays. Temperature-programmed desorption (TPD) spectra of ammonia were measured and interpreted in relation to the acidity distribution. Infrared spectra of pyridine adsorbed on TiO2pillared clay indicated that the acidity predominantly arises from Lewis acid sites.
Study of Model Copper-Based Catalysts by Simultaneous Differential Scanning Calorimetry, X-Ray Diffraction and Mass Spectrometry
Authors: Newman Robert A. , Blazy Joseph A. , Fawcett Timothy G. , Whiting Larry F. , Stowe Robert A.
Published: March 2011

Recently, a new materials characterization instrument and technique employing simultaneous differential scanning calorimetry/X-ray diffraction/mass spectrometry (DSC/XRD/MS) have been developed at Dow. Use of this technology can be illlustrated by the study of various materials such as polymers, organics/pharmaceuticals, inorganics, and catalysts.

Presented here is the use of the DSC/XRD/MS instrument to study the thermostructural behavior of four model copper-based catalyst systems during activation and regeneration. The instrument allows simultaneous generation of thermal, structural and chemical data in real-time during temperature programmed analysis and provides useful insights into the chemical and physical processes occurring. In addition, the calorimetry data yield qualititative information on the magnitude and rate of heat flow, while the diffraction data provide structural dynamics of reduction, oxidation and crystallite growth.

The results of this study conclusively show cuprous oxide as an intermediate in the reduction of the copper oxide portion of each of the model catalysts. However, such features as the onset temperature and copper surface area varied widely among the four catalysts in response to the same chemical event conducted under similar experimental conditions. On the other hand, oxidation runs on the reduced catalysts were all similar to each other, first producing cuprous oxide from copper metal over a broad range of temperature, followed by the oxidation of cuprous oxide to copper oxide at even higher temperatures.
Carbon Formation on Supported Metal Catalysts
Authors: Baker R. T. K.
Published: March 2011

The potential for carbon formation exists in any system in which hydrocarbons undergo thermal decomposition. It is well known that certain metals can increase the carbon yield by catalyzing the growth of both filamentous and graphitic types of deposit. The highest catalytic activity for carbon deposition is exhibited by the ferromagnetic metals and in particular, iron.

We have used a combination of controlled atmosphere and high resolution electron microscopy techniques to study the formation of the various types of carbon on metal surfaces. In this paper the emphasis is placed on the fundamental aspects surrounding the growth of filamentous carbon. The qualitative and quantitative data obtained from these studies have enable us to develop a mechanism for the growth of filamentous carbon and also provided insights into methods of inhibiting the growth of this form of carbon. Continuous observation of many filamentous carbon growth sequences has shown that both the addition of a second metal to the catalyst and also the strength of the metal-support interaction can have a profound effect on the mode by which carbon filaments grow.
Diffusion in High Occupancy Zeolites
Authors: Wei James
Published: March 2011

Diffusion of small molecules in zeolites most often takes place in the configurational diffusion region, where the molecular diameter is approximately the same or slightly greater than the channel diameter. Since two molecules may not pass each other in a pore, the random walk based diffusion equation does not apply under high occupancy conditions in zeolites with one-dimensional pores.

For zeolites with multi-dimensional pores, such as ZSM-5 and A, one sometimes encounters the counter-intuitive result that diffusivity dramatically rises with occupancy. There are two explanations for this behavior: one from irreversible thermodynamics and the Darken equation, which predicts that diffusivity will always rise with occupancy; the other from a Markov model of random activated jumps between low energy positions, such as pore crossings, which predicts that diffusivity will increase with occupancy if the activation energy of diffusion decreases with occupancy– such as due to swelling.
Temperature Dependence of Copper (II) Catalyzed Oxidation of Propylene on X Zeolite: Relation To Copper (II) Migration
Authors: Yu Jong-Sung , Kevan Larry
Published: March 2011

The copper(II) catalyzed oxidation of propylene on CuK-X zeolite was studied over the temperature range of 150 to 400°C in a flow system. Arrhenius activation energies could be obtained at less than 30%conversion from 160 to 210°C and were found to decrease with increasing copper(II) content. These results are correlated with electron spin resonance studies of the migration of copper(II) within the zeolite lattice at the reaction temperature. The change in activation energy with copper(II) content shows that a substantial part of the total activation energy is due to copper(II) migration.
Active Sites in Oxide-Promoted Metal Catalysts – Evidence for the Significance of Perimeter Sites in AlOx and MnOx/Ni(lll) Catalysts
Authors: Zhao Yong-Bo , Lin Tzer-Shen , Chung Yip-Wah
Published: March 2011

MnOx (0.2 < × < 0.5) and AlOx (0.5 < × < 1.1) /Ni(lll) model catalysts were prepared by depositing the oxides onto clean Ni(111) surfaces under ultrahigh vacuum conditions, with the average oxide coverage varying from 0 to 1.3 monolayers (ML) for MnOx and 0 to 2.8 ML for AlOx. CO chemisorption over these catalysts at 200 K was used to titrate different adsorption sites. Thermal desorption showed the usual prominent CO desorption peak at 415 K from the clean Ni(111) surface. This 415 K peak decreases with increasing oxide coverage in an almost linear fashion, indicating a siteblocking effect by the oxide. At the same time, a new thermal desorption peak appears at 305 K from MnOx/Ni(111) and 300 K from AlOx/Ni(111), reaching maximum intensity at some intermediate oxide coverage. For MnOx/Ni(111), this coincides with the appearance of a new C-0 stretching mode at 1620 cm−1, which disappears upon heating the surface to 325 K for a few minutes, suggesting that both the 305 K thermal desorption peak and the 1620 cm−1 loss peak represent the same adsorbed CO state. This is attributed to CO adsorbed on MnOx/Ni perimeter sites. Results from Monte Carlo simulation and scanning tunneling microscopy are presented and compared with CO chemisorption data. The significance of perimeter sites in strong metal-support interaction is discussed.
Influence of Potassium on the Oxidation Rate of Carbon
Authors: Sjövall Peter , Hellsing Bo , Keck Karl-Erik , Kasemo Bengt
Published: March 2011

The influence of K, deposited on a carbon surface, on the oxidation of carbon in O2 was investigated. Reaction rate measurements, carried through in a UHV-system by use of AES, showed that potassium increases the reaction rate by up to ∼ 104 times. A theoretical model, based on the assumption that O2 dissociation is the rate limiting step, has been developed. The model shows that a charge transfer mechanism can explain the observed rate increase. Results from TPD/TPR-measurements indicate that the sticking probablility for O2 on a graphite surface with predeposited K is approximately independent on K coverage for coverages down to 0.5 × 1014 cm−2, corresponding to an effective radius of K of ∼ 7.3 Å.
A Single Turnover (STO) Characterization of Supported Palladium Catalysts
Authors: Augustine Robert L. , Baum David R.
Published: March 2011

While the STO catalyst characterization procedure has been applied to a variety of supported Pt catalysts, application of this technique to the characterization of supported Pd catalysts showed that there were several significant differences between the Pt and the Pd catalysts. Under STO reaction conditions each surface site on a Pt catalyst reacts only once so there is a 1:1 relationship between the product composition and the densities of the various types of active sites present. With Pd catalysts under these same conditions, alkene isomerization takes place so readily that the amount of isomerized product formed depends on the contact time of the reactant pulse with the catalyst so there is no direct relationship between the amount of isomerization and the number of isomerization sites present. On Pt there are some direct saturation sites present on which H2 is rather weakly held. Such sites are not present on Pd catalysts. The reactive surface of supported Pt catalysts remains constant on long exposure to air. With Pd catalysts exposure to air results in a decrease in saturation site densities which can be reversed by re-reduction of the surface with H2 under ambient conditions but not completely under what can be termed “reaction conditions” where the extent of surface re-reduction decreases with catalyst age.
Secondary Cation Effects On Sodium And Potassium Zeolite Syntheses at Si/Al2 = 9: Part 1- Phase Development in the Sodium System
Authors: Vaughan David E. W.
Published: March 2011

The influence of Group 1A elements, and various alkyl ammonium cations, on a metastable faujasite synthesis at a silica/ alumina ratio of 9 are reported. Co-crystallization of faujasite, gmelinite and gismondine (P) occurs in reactions with Li+, K+ and Rb+, but the trapping of Cs+ in the FAU sodalite cage (CSZ-1/ CSZ-3) inhibits subsequent reactions to GIS, and blocks the formation of GME. Morphological effects of these cations include platelet formation and the promotion of small crystals. TMA addition promotes mazzite analogues; and DEDM stabilizes FAU, and at 140°C., induces the crystallization of ECR-1. The derivation of all these phases from a restricted number of secondary building units is
discussed.
Near-Field Mass Transfer in Geologic Disposal Systems: a Review
Authors: Pigford T. H. , Chambré P. L.
Published: March 2011

A primary purpose of performance assessment of geologic repositories for radioactive waste is to predict the extent to which radioactive species are released from the waste solids and are transported through geologic media to the environment. Reliable quantitative predictions must be made of rates of release of radionuclides from the waste into the rock, transport through the geologic media, cumulative release to the accessible environment, and maximum concentrations in ground water and surface water. Here we review theoretical approaches to making the predictions of near-field release from buried waste solids, which provide the source terms for far-field release. The extent to which approaches and issues depend on the rock media and on regulatory criteria is discussed.
Laboratory Radionuclide Migration Experiments at a Scale of 1 m
Authors: Vandergraaf Tjalle T. , Grondin D. M. , Drew D. J.
Published: March 2011

Results are presented from a migration experiment carried out in a natural fracture in a 1 m × 1 m × 0.6 m quarried granite block. Near-uniform flow in the fracture was achieved by controlling the groundwater flow from the fracture laterally across the exit face of the fracture. The longitudinal dispersion was determined from the elution profile of uranine, a non-sorbing tracer. The effect of matrix diffusion was determined by reducing the linear velocity of the transport solution from approximately 3 to 0.75 cm/h. The velocity of a sorbing tracer, Cs-137, was compared to that of non-sorbing I-131 and with that calculated from data obtained for Cs-137 in static sorption experiments on similar fracture surfaces. Information on channeling in the fracture was obtained by autoradiographing the fracture surface of the separated block after the termination of the experiment. Quantitative information on the sorbed Cs-137 inventory by two-dimensional gamma scanning of the fracture surfaces is underway.
Channeling and its Potential Consequences for Radionuclides Transport
Authors: Moreno Luis , Neretnieks Ivars
Published: March 2011

Radionuclide transport through fractured media is usually calculated assuming that water flows in most of the fractures. Several observations in the field and the laboratory show that flow is very unevenly distributed in fractured crystalline rock. These observations indicate that most of the water flow takes place in a limited number of channels. The channels are seldom wider than a few meters and are often much narrower. This means that the surface of the fracture in contact with the flowing water (wetted surface) is less than one might expect.

This low value of the wet surface of the fracture may considerably influence the transport of radionuclides through fractured media. If the channels do not intersect over a certain distance, then the channels may be modelled as a bundle of independent channels. Channels with a large flow and small sorption surface will carry the tracer rapidly and in large amounts.

Calculations are performed for cases where channeling is assumed to take place. The most important entities to assess are the water flow distribution in the different channels, the wetted surface of the channels, the diffusivity into the rock matrix, and the sorption coefficient in the matrix. Experimental data for the water flow distribution are used and the transport of nuclides is calculated for the different channels. From these values the concentration of the effluent is determined. The results show that the retardation for the nonsorbing nuclides is negligible. Retardation is only important for the nuclides which are strongly sorbed on the granitic rock. Calculations are also done assuming other channel frequencies and other overall water flowrates.
State-of-the-Art Evaluation of Repository Sealing Materials and Techniques.
Authors: Gnirk Paul
Published: March 2011

Under the auspices of the OECD/NEA Stripa Project, a state-of-the-art evaluation of repository sealing materials and techniques has been undertaken with particular application to crystalline rock. The objectives of the evaluation were (1) to review progress to date in the development of repository sealing materials and emplacement techniques; (2) to identify priority materials for sealing narrow aperture fractures in crystalline rock, including issues of technical concern to the long-term effectiveness of such materials; and (3) to provide a framework for advancing an in situ fracture-sealing test program that can be designed and implemented at the Stripa Mine.

The classes of sealing materials that were considered included cementitious materials, natural clay materials, chemical grouts, fracture-filling synthetic minerals, ceramics, and metals. Of these, cementitious materials and natural clay materials were recommended as high-priority materials for further study because they can be designed to meet desired repository performance characteristics, there is considerable history of successful use in similar engineering applications, and there is indirect evidence that they will continue to perform as expected for long periods of time. Techniques for the emplacement of these sealing materials in rock fractures include pressure injection, dynamic (or vibratory) injection, and electrophoresis.
Size and Density of A 242Pu Colloid
Authors: Rundberg Robert S. , Mitchell Alan J. , Triay Ines R. , Torstenfelt N. Börje
Published: March 2011

The size and density of a 242Pu colloid has been measured by autocorrelation photon spectrometry. The sedimentation rate of the colloid was determined by ultraspeed centrifugation. From the concentration profiles of 242Pu in the centrifuged test tubes, a standard sedimentation formula was used to calculate the density; the size of the colloid was known from the light scattering experiments. The determined density of the 242Pu colloid was only slightly lower than the estimated density of crystalline PuO2.
Analysis Of Congruent Matrix Release, Precipitation, And Time-Distributed Containment Failure On Spent Fuel Performance
Authors: Apted Michael J. , Engel David W.
Published: March 2011

The Analytical Repository Source-Term (AREST) code has been developed for source-term evaluation of spent fuel as a final waste form in geologic repositories. AREST contains a set of analytical equations for the timedependent diffusional mass transport of both solubility-limited and inventory-limited radionuclides from a spent fuel in a failed container surrounded by a shell of packing or other porous material imbedded in a porous host rock. Three factors that affect release performance are examined: 1) congruent dissolution of the UO2 matrix, 2) chemical instability of the UO2 matrix, with precipitation of a more stable uranium phase within the waste package, and 3) the attenuation of release rate by distribution of containment failures with time.

For congruent matrix dissolution, the release rates of included nuclides are proportional to the product of solubility-limited release of uranium and the fractional abundance of the nuclide. For certain conditions, congruent release rates are calculated to be up to 10 orders of magnitude lower than release rates assuming individual solubility-limits. Precipitation of a more stable, lower solubility uranium phase within the waste package is shown to increase release rates from the UO2 matrix compared to the non-precipitation case, in agreement with previous calculations. During the first 300 to 1000 years after repository closure, the distribution of containment failures with time will act to attenuate the peak average release rates of soluble, longlived nuclides, such as iodine-129, to values smaller than release rates below regulatory limits. However, for soluble nuclides with short half-lives, such as cesium-137, a broader distribution of containment failure with constant mean time of failure can actually cause an increase In the peak average release rates.
A Vault Model for the Assessment of Used Fuel Disposal in Canada
Authors: Garisto N. C. , Leneveu D. M.
Published: March 2011

The environmental assessment of the geological disposal of used nuclear fuel involves the assimilation of experimental results to produce an estimate of the potential impact of a disposal vault on man and the environment. In this paper we briefly outline the assessment methodology and expand upon one aspect of the data assimilation process, namely, the incorporation of research results on the performance of engineered barriers into assessment models.

The model to be discussed represents (i) failure modes for titaniumbased containers, including short-term failures due to undetected manufacturing defects and long-term failures due to uniform and local corrosion; (ii) release of radionuclides from used fuel, including relatively fast release of soluble fission products from gap and grain boundaries and slow, congruent release controlled by the dissolution of the fuel matrix itself; and (iii) mass transport of released radionuclides through the clay-based sealing materials surrounding the waste container, including diffusion, convection and radionuclide storage (sorption or retardation) effects.
Preliminary Geochemical/Geophysical Model of Yucca Mountain
Authors: Cederberg Gail A. , Greenwade L. Eric
Published: March 2011

As part of the Nevada Nuclear Waste Storage Investigations (NNWSI) Project, a comprehensive geochemical/geophysical model is being compiled. This model incorporates the current and relevant stratigraphic, petrologic, hydrogeologic, geochemical, and material data associated with a candidate repository at Yucca Mountain, Nevada. In this report the known repository data are compiled and unknown parameter values are estimated based on the available data. More data are needed before the geochemical/geophysical model of Yucca Mountain can be regarded as satisfactory and a suitable base for multidimensional predictive flow and transport simulations. Recommendations for future studies concerning site characterization and data aquisition are presented.
The Natural Chimical Background Conditions In Crystalline Rocks
Authors: Wikberg Peter
Published: March 2011

Equipment for sampling and analyses of groundwater has been developed and operated. The results from the chemical characterization is used to group the waters into different classes mainly with respect to origin and residence time. The most important process affecting the chemistry of the groundwater is the carbon dioxide weathering.
Numerical Simulation of Alteration of Sodium Bentonite by Diffusion of Ionic Groundwater Components
Authors: Jacobsen J. S. , Carnahan C. L.
Published: March 2011

Because of its ability to retard the movement of radionuclides, sodium bentonite is being considered as a packing and backfilling material in a number of nuclear waste isolation programs. Few studies, however, have considered how the chemical properties of the bentonite backfill will vary with distance from the canister and change in time as groundwater constituents diffuse through the bentonite. Of particular importance is the conversion of sodium bentonite to calcium bentonite by ion exchange, which will in turn affect the migration of cationic radionuclides, such as Cs+and Sr2+, leaking from a waste canister.

Experiments measuring the movement of trace amounts of radionuclides through compacted bentonite have typically used unaltered bentonite. Models based on experiments such as these may not lead to accurate predictions of the migration through altered or partially altered bentonite of radionuclides that undergo ion exchange. To address this problem, we have modified an existing transport code to include ion exchange and aqueous complexation reactions. The code is thus able to simulate the diffusion of major ionic groundwater components through bentonite and reactions between the bentonite and groundwater. Numerical simulations have been made to investigate the conversion of sodium bentonite to calcium bentonite for a reference groundwater characteristic of deep granitic formations.
The Effects of Changes in pH within a Clay Surrounding a Cementitious Repository
Authors: Jefferies Nicholas L. , Tweed Cherry J. , Wisbey Simon J.
Published: March 2011

The effect of a concrete-based repository on local geological conditions and properties has been explored. As part of a complete description of repository behaviour, a static model of clay-alkali interactions has been set up. Parallel experiments have demonstrated the buffering capacity of clays, and are indicating the chemical and physical changes that may occur when an alkali plume interacts with a clay host rock.
Aqueous Corrosion of the French LWR Solution Reference Glass First Generation Model
Authors: Mouche E. , E. Vernaz
Published: March 2011

Experiments have been performed on the aqueous dissolution of French LWR solution reference glass that have identified key dissolution mechanisms to be considered in modeling. The physical hypotheses on which the model relies are a dissolution rate governed by the silica concentration in solution according to a first order kinetic law, congruent release of the mobile elements at the gel-glass interface, and diffusion of silicic acid in the gel interstitial solution. A comparison of theoretical results obtained by a semi-analytical solution to the model and experimental results suggests some modifications to develop a more advanced model.
A Comparative Experimental Study of Glass Stability in Seawater and Distilled Water
Authors: Zhou Zhihong , Fyfe W. S.
Published: March 2011

Both PNL76−68 and ABS-118 glasses show greater stability in seawater (SW) than in distilled and deionized water (DDW), in the MCC-1 90°C corrosion test. After 180 days of corrosion, the boron release from PNL76- 68 and ABS-118 glasses is about five and two times lower respectively in SW than in DDW. Seawater leachates show less increase in pH than DDW leachates. Glass corroded in SW shows little or no total weight loss. Significant amounts of Mg from SW have been added to the surface layers of both types of glass. Mg-silicates were found in surface layers formed in SW, whereas Zn- and Fe-silicates in surface layers formed in DDW. Shortterm leaching tests in D2O, NaCl and MgCl2 solutions suggested that high salt content in leachant can impede glass hydration. Both silica saturation and Mg diffusion may be responsible for greater stability of the glasses in SW than in DDW.
Modelling of the Near-Field Chemical Environment
Authors: Grenthe Ingmar
Published: March 2011

A review of chemical phenomena of importance for the conceptual near-field modelling of nuclear waste repositories is given. The emphasis is on thermodynamic modelling and the coupling of chemical processes mediated through ground water.
Impact of Phase Stability on the Corrosion Behavior of the Austenitic Candidate Materials For NNSWI.
Authors: Bullen Daniel B. , Gdowski Gregory E. , McCright R. Daniel
Published: March 2011

The Nuclear Waste Management Program at Lawrence Livermore National Laboratory is responsible for the development of the waste package design to meet the Nuclear Regulatory Commission licensing requirements for the Nevada Nuclear Waste Storage Investigations (NNWSI) Project. The metallic container component of the waste package is required to assist in providing substantially complete containment of the waste for a period of up to 1000 years. Long term phase stability of the austenitic candidate materials (304L and 316L stainless steels and alloy 825) over this time period at moderate temperatures (100–250°C) can impact the mechanical and corrosion behavior of the metal barrier.

A review of the technical literature with respect to phase stability of 304L, 316L and 825 is presented. The impact of martensitic transformations, carbide precipitation and intermediate (σ. χ, and η) phase formation on the mechanical properties and corrosion behavior of these alloys at repository relevant conditions is discussed. The effect of sensitization on intergranular stress corrosion cracking (IGSCC) of each alloy is also addressed. A summary of the impact of phase stability on the degradation of each alloy in the proposed repository environment is included.
A Study of the Hydrothermal Stability of Copper for Use as a Container Material for Nuclear Waste
Authors: Lazaar Paul I. , Ulmer G. C. , Grandstaff D. E.
Published: March 2011

The hydrothermal stability of copper has been studied to assess its suitability as a container material for disposal of nuclear waste in the proposed repository site at Hanford, Wa. The experiments (Cohassett basalt, synthetic Grande Ronde #4 groundwater, and copper powder with a water:rock:Cu-powder mass ratio of 20:1:1) were conducted at 300°C, 30 MPa, using Dickson rocking autoclaves for periods up to 3000 hours. Redox was calculated from dissolved H2 measured by gas chromatograph and He-ionization detector.

After ca. 100 hours the solution Cu concentration stabilized at 2–3 ppm, near Cu saturation, and did not vary significantly during the remainder of the experiment. The in situ solution pH was slightly alkaline. The copper powder showed little evidence of etching. The Cu concentration did not reflect oxide-coating spallation effects such as those described by Johnston et al.[15]. Within 48 hours, the log fO2 values decreased rapidly toward the magnetite-hematite phase boundary (−31 at 300°C); this is well within the stability field of native copper. SEM and EDX analysis of the reaction products revealed a copper-iron sulfide. One experiment used copper powder containing ca. 5% cuprite. Oxygen released by the cuprite overwhelmed the buffering capacity of the basalt. The resulting log fO2 values stabilized near the copper-cuprite phase boundary (−23.1 at 300°C) with the solution remaining within the copper stability field. Copper purity is important as oxygen contamination or oxidation of the copper containers may strongly affect the repository redox and mobility of radionuclides.
A Method for Measuring the Self-Cementing Characteristics of Fly Ash Pastes
Authors: Malek R. I. A. , Roy D. M.
Published: March 2011

The development of an improved method of trimethylsilylation [1] made possible the assessment of different polysilicate fractions in hydrated cement pastes, as a means of structural characterization. Several laboratories have presented various gas-liquid chromatographic data on the polysilicate derivatives of C-S-H [2–5]. Identification of the different molecular weight fractions has been made, in most laboratories, by matching the gasliquid chromatographic peaks with the gel permeation chromatographic peaks. The success of this matching process is always dependent on type of instruments, length of columns and temperature range.

In the present investigation, a mass spectrometer, in direct contact with the gas-liquid chromatograph, was used to identify the molecular weight of each of the fractions separated from the chromatograph. The technique was applied to determine the molecular weights and abundances of different polysilicate species in hydrated fly ash pastes.
Characterization of Products of Primary Flue Gas Desulphurization
Authors: Odler I. , Zysk K.-H.
Published: March 2011

In primary flue gas desulphurization lime is introduced into the flame, in addition to modifications of the burners and/or equipment. An ash is thus obtained in which the sulphur present in the fuel becomes chemically bound, rather than leaving the heat-generating unit as gaseous SO2, a constituent of the flue gases. In the present paper the composition, particle shape and size distribution of a series of ashes formed in the primary flue gas desulphurization are reported. The options for their utilization need to be evaluated.
Influence of Physical and Chemical Properties on the Activity of Fly Ashes
Authors: Sybertz F.
Published: March 2011

In an experimental program, the suitability of various methods for testing the pozzolanic activity of fly ash was investigated. The research was conducted on virtually all fly ashes approved as concrete additives in Germany. This paper discusses differences in the particle size distribution and the solubility on dissolution with hydrochloric acid and potassium hydroxide of the fly ashes. It also reports on interrelationships between the physical and chemical properties of the fly ashes and the workability and strength of mortars containing fly ash.
Fly Ash in Bricks and Tiles
Authors: Bacher V. , Ernstsen V. , Jeppesen K. G. , Kristiansen H. , Madsen P.
Published: March 2011

Based on the characterization of 12 clay and 5 fly ash samples, samples were selected for the following laboratory scale experiments: preparation of raw mixes, determination of the correlation between water content and plasticity, rate-controlled sintering in a laser-dilatometer, DTA-TGA-analyses, preparation, firing and testing of bars. Laboratory experiments have shown that it is necessary to bind the soluble sulphates as barium sulphate under acidic conditions and bind the free lime as phosphate when wet production methods are to be used. A full scale experiment has been carried out, resulting in the production of 16,000 red bricks containing 33% fly ash by volume in the raw mix. These fly ash bricks look satisfactory and have 10% higher strength and 2% less density than the corresponding bricks without fly ash. The water extractable matter in the two kinds of bricks were compared. The bricks were used for constructing a wall with the purpose of investigating their weather resistance.
Fly Ash As A Binder in Aggregate Base Courses
Authors: Zenieris Petros , Laguros Joakim G.
Published: March 2011

The benefit of adding up to 35 wt% Class C high calcium fly ash to various types of fine and coarse aggregate pavement mixes is described and quantified. The mixes, which were compacted to maximum dry density at optimum moisture content, had variable compressive strengths during the first 28 days of curing; after that they assumed a relatively uniform pattern of strength gain reaching values as high as 11 MPa (1600 psi). Mixes containing 15% fly ash gave unacceptably low strengths. XRD measurements indicated massive formation of ettringite, transforming to monosulfoaluminate and the poorly crystallized hydrated phases of C-A-H, C-A-S-H and C-S-H. This transformation helps explain the gain in strength of the mixes with extended curing. SEM observations depicted progressive packing and densification of the skeletal matrix as the hexagonal phases and C-S-H gained higher crystallinity and formed aggregated masses. Furthermore, these observations suggest that fly ash acts predominantly as a chemical binder and partly as a filler in the aggregate mixes tested.
The Effect of Fly Ash on the Hydration of Cements At Low Temperature Mixed and Cured in Sea-Water
Authors: Jensen H.-U. , Pratt P. L.
Published: March 2011

The use of fly ash as a partial replacement in cements is widespread because of reduced costs and the reported improvement in performance. Fly ash/cement blends have been used offshore for underbase grouting of gravity platforms, although the cold marine exposure may slow the pozzolanic reaction which is very sensitive to temperature. Sea-water could be used as mixing water under these conditions. This paper looks at how curing at 8°C, the use of sea-water as mixing water, and direct exposure to sea-water, influence the hydration, strength and microstructural development of an OPC and an SRPC with 30% fly ash replacement. The early heat evolution was measured with a conduction calorimeter, while the presence and development of hydration products were identified by DTA, TG and x-ray analysis. Scanning electron microscopy was used in two modes; secondary electron images of fracture surfaces were examined, and a quantitative description of microstructure was made possible by analysis of backscattered electron images of polished sections. The morphology and distribution of hydration products in the wet state was studied using an environmental cell in a high voltage electron microscope.