bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Segmented Anisotropic-Isotropic Poly(Aryl Ester)Poly(Arylene Ether) Copolymers
Authors: McGratn J. E. , Cooper K. L. , Waehamad W. , Huang H. , Wilkes G. L. 
Published: March 2011

AbstractCarboxyl functional poly(arylene ether) oligomers of controlled number average molecular weight were synthesized via nucleophilic aromatic substitution step polymerization using p-hydroxy benzoic acid as the molecular weight and end group controlling reagents. The subsequent functionalized polyarylene ethers were copolymerized with acetoxy benzoic acid or acetoxyphenoxy benzoic acid via melt acidolysis procedures. Successful copolymers were generated using chlorobenzene as a solvent for the first s age of the reaction followed by melt reaction at temperatures as high as 325°C. Resulting copolymer composition and segment size were investigated. It was possible to prepare improved solvent resistant copolymers through incorporation of the liquid crystal polyester (LCP) segment. Extraction tests using boiling chloroform showed that a high percentage of segmented copolymer were generated. Swelling characteristics were also noted and were observed to decrease as a function of the LCP concentration utilized. Multiple transitions were observed in differential scanning calorimetry consistent with Tg's, Tm's and possibly with liquid crystal transitions. Optical microscopy showed an ordered microstructure developed which is consistent with the presence of liquid crystalline phases. The materials were successfully compression molded to afford tough coherent films at all compositions, implying the likelihood of improved compressive strength relative to the LCP homo- or copolyesters.
Nature of the Chemical Bonds in Polymer-Salt Complexes: Raman and IR Studies
Authors: Nazri Gholamabbas , MacArthur Donald M. 
Published: March 2011

AbstractPolymer electrolytes are attracting interest because of potential use in ‘solid state’ batteries and electrochromic windows. In this work the nature of the chemical bonds and ion association in polymer-salt complexes were studied. The fundamental vibrational frequencies of LiClO4− were calculated using valence force constants which are obtained from the ClO4− anion. The calculated frequencies and the band assignments agree quite well with the observed frequencies. Raman and IR spectroscopy were used to investigate the interaction of Li+ and ClO4− with the PEO chains. Lithium ion interacted with the negatively charged oxygen of PEO and C104 interacted electro- statically with the positively charged hydrogens. The strong electrostatic interactions induced changes in the intensity of the Raman bands and IR absorption bands of the polymer. The Raman and IR spectra of the polymer-salt complexes clearly show the existence of ‘free’ ions, ionpairs and salt clusters at various concentrations of the lithium salt. The maximum concentration of “free” ions deduced from the spectroscopy is in excellent agreement with the salt concentration required to obtain maximum ionic conductivity.
Estimation of Longevity of Portland Cement Grout Using Chemical Modeling Techniques
Authors: Alcorn S. R. , Coons W. E. , Gardiner M.A. 
Published: March 2011

ABSTRACTPortland cement has been identified as a likely candidate seal material by programs investigating the deep burial of nuclear waste as a disposal mechanism. The longevity of performance of cement grout is currently being investigated, along with bentonite, under the auspices of the Stripa Project. Coordinated laboratory, field, and modeling studies are underway to produce fundamental data, practical experience, and estimates of long-range performance, respectively. Long-term performance of cement grout is of particular concern. Since most of the solid phases of which grout is comprised are metastable, it is likely that grout performance will decrease with time. The question is whether performance will still be acceptable after this decrease. This issue is being addressed with the coupled use of geochemical and permeability modeling. For a simplified cement system, two mechanisms for chemical degradation have been considered: phase change and dissolution. For dissolution, both equilibrium (slow flow) and open (fast flow) systems have been analyzed as bounding scenarios. Granitic terrain groundwaters ranging from fresh to saline have been used in the analyses. To assess the consequences in terms of flow, an empirical relation between cement permeability and porosity has been developed. Performance changes with time have been predicted by making conservative estimates of local hydraulic head conditions for successive periods of repository history. For the granitic rock environments considered, preliminary results indicate that cement grout performance may be acceptable for tens of thousands to millions of years, providing its initial hydraulic conductivity is on the order of 10−12 m/s. Other conditions favoring long-term performance include minimizing the ettringite content of the grout, and emplacement at a site where the groundwater has an elevated TDS, and where the local hydraulic gradient is flat or repository resaturation times are short.
Dissolution Kinetics of a Simple Analogue Nuclear Waste Glass as a Function of Ph, Time and Temperature
Authors: Knauss Kevin G. , Bourcier William L. , McKeegan Kevin D. , Merzbacher Celia I. , Nguyen Son N. , Ryerson Frederick J. , Smith David K. , Weed Homer C. , Newton Leon 
Published: March 2011

ABSTRACTWe have measured the dissolution rate of a simple five-component borosilicate glass (Na2O, CaO, Al2O3, B2O3, SiO2) using a flow-through system. The experiments were designed to measure the dissolution rate constant over the interval pH 1 through pH 13 at 3 temperatures (25°, 50° and 70°C). Dilute buffers were used to maintain a constant pH. Analyses of solutions and solid surfaces provided information that is used to develop a kinetic model for glass dissolution.Under all conditions we eventually observed linear dissolution kinetics. In strongly acidic solutions (pH 1 to pH 3) all components but Si were released in their stoichiometric proportions and a thick, Si-rich gel was formed. In mildly acidic to neutral solutions the gel was thinner and was both Si- and Al-rich, while the other components were released to solution in stoichiometric proportions. In mildly to strongly alkaline solutions all components were released to solution in stoichiometric proportions. By varying the flow rate at each pH we demonstrated a lack of transport control of the dissolution rate.The dissolution rates were found to be lowest at near-neutral pH and to increase at both low and high pH. A rate equation based on transition-state theory (TST) was used to calculate dissolution rate constants and reaction order with respect to pH over two pH intervals at each temperature. At 250C between pH 1 and pH 7 based on the Si release rate the log rate constant for glass dissolution (g glass/m20d) was −0.77 and the order with respect to pH was −0.48. Between pH 7 and pH 13 the log rate constant for glass dissolution was −8.1 and the order with respect to pH was +0.51. The measured simple glass dissolution rate constants compare very well with constants estimated by fitting the same TST equation to experimental results obtained for SRL-165 glass and to dissolution rate estimates made for synthetic basaltic glasses.
Immobilization in Cement of Ion Exchange Resins
Authors: Bescop P. Le , Bouniol P. , Jorda M. 
Published: March 2011

ABSTRACTRecent studies were carried out in France to improve ion exchange resin solidification in cement-based matrices. Work is conducted on different types of waste - cationic, anionic and mixed-bed resins - under regenerated and loaded states. The main objective is to increase the waste incorporation rate up to roughly 50% (in volume). Hydraulic cement formulas are developed taking into account waste chemistry, in particular the presence of ions which inhibit setting.
Chemistry of Glass Corrosion in High Saline Brines
Authors: Grambow B. , Müller R. 
Published: March 2011

ABSTRACTExperimental data were obtained for conventional pH values corrected for liquid junction, amorphous silica solubility and glass corrosion in concentrated salt brines. The data were interpreted with a geochemical model. The brine chemistry was described with the Pitzer formalism [1] using a data base which allows calculation of brine compositions in equilibrium with salt minerals at temperatures up to 200°C.In MgCl2 dominated brines Mg silicates form and due to the consumption of Mg the pH decreases with proceeding reaction. A constant pH (about 4) and composition of alteration products is achieved, when the alkali release from the glass balances the Mg consumption. The low pH results in high release of rare earth elements REE and U from the glass. In the NaCl dominated brine MgCl2 becomes exhausted by Mg silicate formation. As long as there is still Mg left in solution the pH decreases. After exhaustion of Mg the pH rises with the alkali release from the glass and analcime is formed.
Comparison of the Layer Structure of Vapor Phase and Leached SRL Glass by Use of AEN
Authors: Biwer Bruce M. , Bates John K. , Abrajano Teofilo A. , Bradley John P. 
Published: March 2011

ABSTRACTTest samples of 131 type glass that have been reacted for extended time periods in water vapor atmospheres of different relative humidities and in static leaching solution have been examined to characterize the reaction products. Analytical electron microscopy (AEM) was used to characterize the leached samples, and a complicated layer structure was revealed, consisting of phases that precipitate from solution and also form within the residual glass layer. The precipitated phases include birnessite, saponite, and an iron species, while the intralayer phases include the U-TI containing phase brannerite distributed within a matrix consisting of bands of an Fe rich montmorillonite clay. Comparison is made between samples leached at 40°C for 4 years with those leached at 90°C for 3-1/2 years. The samples reacted in water vapor were examined with scanning electron microscopy and show increasing reaction as both the relative humidity and time of reaction increases. These samples also contain a layered structure with reaction products on the glass surface.
Hydrothermal Leaching of R7-T7 Borosilicate Glass
Authors: Caurel J. , Vemaz E. , Beaufort D. 
Published: March 2011

ABSTRACTThe results of hydrothermal leach tests are intended to be used to predict long-term low-temperature glass dissolution. It is often assumed that data can be extrapolated to other conditions using an Arrhenius-type equation. Hydrothermal leaching mechanisms and their temperature dependence in R7T7 glass were investigated in static experiments lasting from 7 days to 1 year at 150°C and 250°C. Leachates, surface layers and crystalline products were analyzed by ICP, TEM, SEM, EMP, XRD and cathodoluminescence. Unexpectedly, no actual saturation conditions in solutions were reached after one year leaching at 150°C nor at 250°C. The effect of precipitation of alteration products (a silica-enriched amorphous layer and aluminosilicates [smectite at 150°C, smectite and zeolites at 250°C]) is discussed. However, the formation of large cracks in the bulk glass results in a higher glass reacting surface and a higher dissolution rate at 250°C. Arrhenius calculations cannot be used to extrapolate our hydrothermal data to lower-temperatures.
Characterization of Mechanical Strengths for Simulated High-Level Waste Forms
Authors: Igarashi Hiroshi , Takahashi Takeshi 
Published: March 2011

ABSTRACTWaste forms have been developed and characterized at PNC (Power Reactor and Nuclear Fuel Development Corporation)to immobilize high-level liquid waste generated from the reprocessing of nuclear spent fuel.Mechanical strength tests were excecuted on simulated solidified highlevel waste forms which were borosilicate glass and diopside glass-ceramic. Commercial glass was tested for comparison. Measured strengths were three-point bending strength,uniaxial compressive strength,impact strength by falling weight method,and Vickers hardness. Fracture toughness and fracture surface energy were also measured by both notch-beam and indentation technique.The results show that mechanical strengths of waste glass form are similar and that the glass ceramic form has the higher fracture toughness.
Oxidation of UO2 Fuel by Radicals Formed During Radiolysis of Water
Authors: Sunder S. , Shoesmith D.W. , Christensen H. , Miller N.H. , Bailey M.G. 
Published: March 2011

ABSTRACTThe effects of radicals, formed during radiolysis of water, on the oxidation and dissolution of U02 were investigated as a function of dose rate and total dose. The U02 oxidation rate during radiolysis was monitored by recording the corrosion potential of a U02 electrode as a function of time. Changes in the surface of U02 were determined using cathodic stripping voltammetry (CSV) and X-ray photoelectron spectroscopy (XPS). Our studies suggest that the oxidation of U02, in irradiated de-oxygenated solutions consists of two stages. The first stage consists of the growth of a surface film of composition close to U02.33 and of thickness similar to that obtained (over longer exposure periods) in unirradiated oxygenated solutions. The rate of growth of this film appears to be proportional to the square root of the dose rate. The second stage consists of oxidative dissolution of this film (as U02+2). This step mainly occurs at higher doses. Relative rates of oxidation of U02 to U02.33, the first stage, were obtained in four different solutions favouring the formation of selected radicals.
Corrosion Product Identification and Relative Rates of Corrosion of Candidate Metals in an Irradiated Air-Steam Environment
Authors: Reed Donald T. , Swayambunathan V. , Tani B. S. , Van Konynenburg Richard A. 
Published: March 2011

ABSTRACTPreviously reported work by others indicates that dicopper trihydroxide nitrate, Cu2NO3(OH)3, forms on copper and copper alloys subjected to irradiated moist air near room temperature. We have performed experiments over a range of temperature and humidity, and have found that this species is formed at temperatures up to at least 150° C if low to intermediate relative humidities are present. At 150°C and 100% relative humidity, only Cu2O and CuO were observed. The relative general corrosion rates of the copper materials tested in 1-month experiments at dose rates of 0.7 and 2.0 kGy/h were Cu > 70/30 Cu-Ni > Al-bronze. High-nickel alloy 825 showed no observable corrosion.
Corrosion Behavior of Zirconium Alloy Nuclear Fuel Cladding
Authors: Fraker Anna C. , Harris Jonice S. 
Published: March 2011

ABSTRACTZircaloy−2 and −4 are used as nuclear fuel cladding. Both alloys are more than ninety-eight percent zirconium and are corrosion resistant to various media. Electrochemical measurements using polarization techniques have been made on these alloys in aqueous media with a pH of 8.5 and varying ionic concentration (1X and 10X) at temperatures of 22°C and 95°C. Results showed that under the test conditions of the study these alloys passivated and had negligible corrosion rates, but there were some variations in passivation due to surface preparation and some crevice corrosion was observed. Data are presented and discussed in terms of passivity, breakdown potential and susceptibility to localized corrosion.
Migration Behavior of Uranium Series Nuclides in Altered Quartz-Chlorite Schist
Authors: Ohnuki T. , Murakami T. , Sekine K. , Yanase N. , Isobe H. , Kobayashi Y. 
Published: March 2011

ABSTRACTThe migration behavior of uranium series nuclides in an altered quartz-chlorite schist has been studied by utilizing data on the activity distributions of uranium series nuclides at Koongarra in the Northern Territory of Australia. The variation of 230Th/234U activity ratios (ARs) with distance along surface (2 m depth), intermediate (16 m) and deep (31 m) layers show different trends in the three layers parallel to the water flow. The relationship between the 234U/238U and 230Th/238U ARs reveals that the mobility of the uranium series nuclides is in order 238U, 234U and 230Th, and that the retardation factors oft 234U are greater than those of 238U by a factor of 1.1, 1.9 and 1.0 in the surface, intermediate and deep layers, respectively. X-ray diffraction patterns show different mineral assemblages, which are the alteration products of chlorite at the three layers. These results imply that the migration behavior of uranium series nuclides at each depth would be related to the alteration of chlorite.
Diffusion of Sodium and Copper in Compacted Sodium Bentonite at Room Temperature
Authors: Muurinen Arto , Olin Markus , Uusheimo Kari 
Published: March 2011

ABSTRACTDiffusion studies were carried out with sodium and copper in sodium bentonite. The experiments were performed at room temperature and densities of the samples varied from 0.8 to 1.8 g/cm3.This paper describes the experimental methods used for the diffusion tests and gives the obtained measurement results. The evaluation of the diffusion mechanisms is at this stage preliminary, however.Diffusion of sodium seems to follow similar mechanisms as has been observed for cesium and strontium in several previous studies. The phenomena could be explained by some kind of diffusion of sorbed ions. The measured apparent diffusivities of sodium varied from 50×10−12 to 300×10−12 m2/s and the effective diffusivities from 80×10−12 to 1.6×10−9 m2/s depending on the density of bentonite and the salt concentration of water solution.Low solubility of copper caused precipitation thus interfering the diffusion experiments. However, the part of copper which did diffuse into bentonite seemed to follow the same type of mechanism as sodium. The measured apparent diffusivities of copper varied from 5×10−12 m2/s.The interaction between the cations in the circulating solutions and the sodium ion in bentonite were essential in this study.
Analytical and Numerical Models of Transport in Porous Cementitious Materials
Authors: Garboczi Edward J. , Bentz Dale P. 
Published: March 2011

ABSTRACTFluid flow under applied pressure gradients and ionic diffusion under applied concentration gradients are important transport mechanisms that take place in the pore space of cementitious materials. This paper describes: 1) a new analytical percolation-theory-based equation for calculating the permeability of porous materials, 2) new computational methods for computing effective diffusivities of microstructural models or digitized images of actual porous materials, and 3) a new digitized-image mercury intrusion simulation technique.
Concrete Barrier Performance in Radioactive Waste Disposal in the Unsaturated Zone
Authors: Walton John C. , Otis Mark D. 
Published: March 2011

ABSTRACTConcrete barriers are an important component of many designs for disposal of radioactive waste in the unsaturated zone. In order to evaluate the effectiveness of the concrete barriers performance assessment models representing material degradation rates and transport properties must be developed. Models for evaluation of fluid flow and mass transport through partially failed concrete barriers located in the unsaturated zone are presented. Implications for the use of impermeable barriers in vault design are discussed. Concrete of highest quality may not always be desirable for use in all components of waste disposal vaults.
Mass Transfer in Water-Saturated Concretes
Authors: Atkinson Alan , Claisse Peter A. , Harris Andrew W. , Nickerson Allan K. 
Published: March 2011

ABSTRACTCements and concretes are often considered as components of barriers for the containment of radioactive waste. The performance of such materials as mainly physical barriers to the transport of dissolved radionuclides depends on the mass transfer characteristics of the material. In particular the diffusion and sorption behaviour of the radionuclides and the water permeability are important. These parameters also influence how the chemistry of the concrete is imposed on the repository. In addition, the transport of gas through concrete controls the way in which gases escape from the repository.Diffusion and gas transport have been measured in a variety of cementitious materials, covering both structural concretes and cementitious backfills; all possible repository construction materials. Measurements have been made using aqueous iodide, strontium and caesium ions and tritiated water as diffusants. The results show that the diffusion of tritiated water is more rapid than that of other species, whilst the transport of strontium and caesium is hindered by sorption; particularly in materials containing blast furnace slag. The transport of gas in these materials has been found to be very sensitive to the degree of water saturation and is extremely low in fully saturated structural concretes. Cementitious backfills have, nevertheless, been identified that have appreciable gas transport even when almost water saturated.The consequences of the results for the performance of cementitious barriers are discussed.
Rheological and Kinetic Properties of Semi-Dilute Solutions of Elongated Micelles
Authors: Candau Sauveur J. , Waton G. , Merikhi F. , Zana R. 
Published: March 2011

ABSTRACTMeasurements of the breaking time of cylindrical micelles of cetyltrimethylammonium bromide in aqueous solutions have been performed by means of T-Jump experiments with light scattering detection. The results provide an unambiguous test of a recent theoretical model for stress relaxation.
Nondiffusive Brownian Motion Studied by Diffusing-Wave Spectroscopy
Authors: Pine D. J. , Weitz D. A. , Durian D. J. , Pusey P. N. , Tough R. J. A. 
Published: March 2011

ABSTRACTOn a short time scale, Brownian particles undergo a transition from initially ballistic trajectories to diffusive motion. Hydrodynamic interactions with the surrounding fluid lead to a complex time dependence of this transition. We directly probe this transition for colloidal particles by measuring the autocorrelation function of multiply scattered light and observe the effects of the slow power-law decay of the velocity autocorrelation function.
Microemulsion Performance Fluids
Authors: Bock J. , Robbins M. L. , Pace S. J. 
Published: March 2011

ABSTRACTMicroemulsions are thermodynamically stable mixtures of two immiscible fluids, such as oil and water, and one or more surfactants or cosurfactants. These systems have a rich micro-structure and phase behavior which can take the form of a variety of multi-phase and single phase oil- or watercontinuous or bicontinuous fluids with unique and useful properties. The thermodynamic stability, ultra-low interfacial tension, clarity, high solubilization capacity and high interfacial area suggest uses “performance fluids.” The relationship between surfactant ussetsru cfotur reth eansde the phase behavior and properties of microemulsions is the key to their design. Through the proper selection of surfactants, microemulsion phase continuity can be tailored for a variety of applications. Two such applications, coal freeze conditioning and oil spill dispersion, are described in this paper.
Study of Curing Processes in PDMS at Various Stoichiometric Ratios by Longitudinal Ultrasonic Waves
Authors: Shefer A. , Gorodetsky G. , Gottlieb M. 
Published: March 2011

ABSTRACTCuring reactions of linear vinyl terminated poly(dimethylsiloxane) with a four functional hydride silane crosslinker at various stoichiometric ratios, were studied by wave propagation at ultrasonic frequencies. Longitudinal wave velocity was found to be sensitive to the covalent endlinking, and gel point in these systems.The observed changes in longitudinal wave velocity during the reaction are governed by changes in the bulk modulus of the system.