bluuebunny/crossref_metadata_2025 huggingface dataset:
Second Order Nonlinear Optics and Polymer Physics of Corona Poled, Doped Polymer Materials
Authors: Hampsch Hilary L. , Yang Jian , Wong George K. , Torkelson John
Published: March 2011

Doped glassy polymers have been examined as potential materials for nonlinear optical (NLO) device applications[l-Il1]. In these systems, dopants with excellent nonlinear optical capabilities are dispersed in glassy polymer matrices with good physical properties to make versatile and efficient NLO materials[1-4]. The optical technique of second harmonic generation (SHG), conversion of light of frequency to to light of frequency 2o, is performed as a function of time to examine the temporal stability of NLO dopant orientation in the polymer matrix[I-4]. Through the use of poling, the NLO dopants are aligned into the noncentrosymmetric orientation required for SHG to occur[1-4,7]. Polymeric NLO materials have a number of advantages over the current commercial inorganic crystals, including ease of fabrication and processability, low laser damage, low cost, and excellent chemical and physical resistance[8-10]. Due to the relaxation behavior characterizing glassy polymers even at temperatures well below the glass transition temperature Tg, the dopants can disorient as a function of time following poling[1-4,12,13]. This results in a loss of optical performance with time. The purpose of this work is to examine the basic polymer physics that govern the temporal stability of the dopant orientation and disorientation and related optical behavior as a function of the local microenvironment surrounding the NLO dopants. Systems studied include bisphenol-A-polycarbonate (PC), polystyrene (PS) and poly(methyl methacrylate) (PMMA) doped with well characterized NLO dyes such as 4-dimethylamino-4′- nitrostilbene (DANS) and 4-amino-4′-nitroazobenzene (or disperse orange 3, D03).
Optical Characterization of Polydiacetylene Langmuir Blodgett Film on Silicon Substrates
Authors: Miller P. , Rahman A. K. M. , Broude S. V. , Tripathy S.
Published: March 2011

A bilayer of a surfactive polydiacetylene (15–8 PDA) has been deposited by Langmuir-Blodgett technique on a smooth Silicon substrate using a commercial Lauda film balance [1] . The morphology of the deposited film has been studied by cross-polarized optical microscopy, and laser light scattering microscopy. Usual crystalline domains with size ranging from 5 to 50 μm can be seen between cross polarizers. Nonuniformities and voids in the film are observed by imaging the scattered light from a visible laser beam incident at grazing angle onto the film.

Raman scattering study on these bilayers have been carried out to investigate their vibronic structure. Information about vibronic levels from PDA has been used to define the extent of disorder and crystalline phase of the bilayer.
Theoretical Calculations on Nonlinear Susceptibilities of Organic Crystals
Authors: Itoh Yuzo , Hamada Tomoyuki , Kakuta Atsushi , Mukoh Akio
Published: March 2011

Theoretical calculations on nonlinear susceptibilities of organic crystals are made. Under the oriented gas model approximation, nonlinear susceptibility of a crystal can be calculated both from the molecular hyperpo1arizability and crystal structure data. Molecular hyperpolarizabilities are calculated by an ab initio molecular orbital (MO) method and the energy minimum crystal structures are obtained by an empirical atom-atom pairwise potential method. Finally the effect of intermolecul ar interactions on molecular hyperpolarizabilities, which is neglected in the above approximation, is investigated quantitatively by using a “super molecule” method of ab initio MO calculations.
Efficient Second Harmonic Generation in Hydrazone, Derivatives of Substituted Aromatic Aldehydes
Authors: Potember Richard S. , Hoffman Robert C. , Stetyick Karen A.
Published: March 2011

Hydrazone, 1,1-dimethylhydrazone, methylhydrazone, phenylhydrazone and p-nitrophenyl hydrazone derivatives of substituted aromatic aldehydes were prepared and screened for second harmonic generation using the Kurtz powder technique. One compound, 4-nitro-3-methoxybenzaldehyde hydrazone exhibited a second harmonic signal up to 32 times that of ammonium dihydrogen phosphate (ADP) and 4-nitrobenzaldehyde hydrazone exhibited a second harmonic signal five times higher than previously reported, up to 40 times that of ADP. 3-methyl-4-nitrobenzaldehyde hydrazone, 4-nitrobenzaldehyde phenylhydrazone, 1-naphthaldehyde phenylhydrazone, 1-pyrenecarboxaldehyde phenylhydrazone exhibited second harmonic signals 25, 2.5, 5 and 20 times that of an ADP standard.
Calcium Phosphate Precipitation in Liposomal Suspensions
Authors: Eanes Edward D.
Published: March 2011

Artificial lipid vesicles (liposomes) provide anin vitroapproach for microencapsulating calcium phosphate precipitation reactions in a manner similar to that which occurs in matrix vesicles, the initial loci for extracellular mineralization in many skeletal tissues. Apatitic precipitates readily form within the aqueous interiors of liposomes prepared from phosphatidylcholine, dicetylphosphate, and cholesterol when the liposomal membranes enclosing pH 7.4 buffered PO4solutions are made permeable to external Ca2+with ionophores. If the external Ca solution is rendered metastable with PO4, the apatitic precipitates rapidly expand to outside the liposomes as well. The present paper describes the basic features of liposomal mineralization and presents some specific examples on how compositional alterations in the liposomal membrane and external Ca solution can affect the progress of this mineralization.
The Bernal Icosahedral Spiral
Authors: Vazquez-Polo G. , Jose-Yacaman M.
Published: March 2011

In the present work we study the means to produced icosahedral and decahedral spiral structures based on the ideas of Mackay and Bernal. It is found that indeed it is possible to generate spirals with five-fold or ten fold symmetry axes which might be structural unit for Quasicrystals. These types of structures are already present in many biological systems
Biomineralization: New Routes to Crystal Engineering
Authors: Mann Stephen , Heywood Brigid R. , Didymus Jon M. , Rajam Sundara , Wade Vanessa J. , Walker Justin B. A.
Published: March 2011

This paper discusses the principal features of biomineralization in relation to the controlled crystallization of inorganic materials, and the modelling of these conceptsin vitro. The biological strategies adopted in the regulation of nucleation and growth are; (a) the use of constrained reaction environments, (b) the synthesis of chemically and structurally specific organic macromolecules, and (c) the secretion of tailor-made additives of low and high molecular weight. Underlying these strategies is the concept of molecular recognition at interfaces comprising organic and inorganic surfaces. The structural, electrostatic and stereochemical aspects of these interfacial interactions in systems involving supramolecular asemblies, Langmuir monomolecular films and tailored additives will be described.
Dental Enamel Biomineralization: A Prospectus
Authors: Slavkin Harold C. , Snead Malcolm L. , Zeichner-David Margarita , Lau Eduardo C. , Fincham Alan G.
Published: March 2011

It is becoming increasingly evident that recombinant DNA technology, physical-chemistry and selected biological processes can be coupled leading to the development of new “synthetic” biomaterials. This summary and prospectus will highlight selected features related to dental enamel biomineralization towards the development of human dental enamel as a restorative biomaterial.
The Effects of Particle Size and Solution Chemistry on the Formation of Hydroxyapatite
Authors: Fulmer Mark , Brown Paul W.
Published: March 2011

The effects of varying the particle sizes of particulate reactants which form hydroxyapatite by a dissolution-precipitation reaction is considered. The effect of Mg2+ ion, known to inhibit hydroxyapatite formation in vivo. on the reaction to form hydroxyapatite is discussed.
Biomimetic Routes to Thin Film Ceramics
Authors: Calvert Paul , Broad Andy
Published: March 2011

The aim of this work is to produce dense, fired thin sheets of barium titanate less than 30μm thick via flexible green bodies produced by in situ precipitation of BaTiO3 in polymer films, with burnout of the polymer followed by sintering of the mixed oxide powder film.
Synthetic Surfaces as Models for Biomineralization Substrates
Authors: Rieke Peter C. , Bentjen Susan B. , Tarasevich Barbara J. , Autrey Thomas S. , Nelson David A.
Published: March 2011

Polyethylene and oxide substrates were derivatized with functional groups commonly associated with biomineralization substrates. These groups include carboxylate, phosphate, hydroxy, sulfonate, thiol, and amine. FTIR, XPS, and contact angle wetting were used to identify and characterize the products at each step. The efficacy of these groups toward inducing mineralization will be compared with naturally occurring substrates.
Nanocomposites — the Multifunctional Family of Materials
Authors: Roy Rustum
Published: March 2011

This paper starts by discussing the concept of multifunctional materials. Multifunctionality can be achieved in a single phase in a composite or a mixture. While a few exceptional single phase materials such as diamond, Al2O3, CaSrZr4P6O24 exhibit peak values of more than one function, it will be argued that the “invention” of the nanocomposite class of materials made by solution sol-gel processing has opened up the potential for designing several multifunctional materials.

Examples will be drawn from our recent results—both successes and failures—in trying to design and synthesize nanocomposites of two or more ceramic phases for various chemical, thermal, and electrical functions.
Multifunctional Ferroic Nanocomposites
Authors: Newnham R. E. , McKinstry S. E. , Ikawa H.
Published: March 2011

As trends towards miniaturized components and systems continue in many fields, there has been a rapid development in similarly scaled-down composites. In the electronics industry, these nanocomposites (and especially active nanocomposites based on ferroic elements) form a basis for many of the recent advances in both information and charge storage. While the overall properties of some of these composites can be explained as straightforward extrapolations from the bulk properties, in other instances the small size of the ferroic phase has important consequences on the macroscopic behavior of the composite. This paper reviews some of the recent developments in small-scale ferroic nanocomposites and details the relation between component size and the resultant properties.
Designing Pore-Size in Silica Gels: [H2O] – [TMOS] System
Authors: Kido H. , Malla P. B. , Komarneni S.
Published: March 2011

A series of microporous silica gels were synthesized by hydrolyzing tetramethylorthosilicate (TMOS) with varying amounts of water. No catalyst or alcohal was added. The gels were characterized by water sorption isotherms, the BET nitrogen surface area measurements, and differential thermal analysis. Although the gelation time for all H2O/TMOS molar ratios (R) was approximately the same (about 3 hr), the pore-size (pore diameter) and sorption capacity were found to be minimum in the R range 4.96–5.37 but increased with both increasing and decreasing R. Water sorption isotherms measured at 25°C after degassing at 200°C of gels prepared with R = 4.96–5.37 exhibited moderate Type I (Brunauer classification) isotherm which changed to intermediate between Type I and Type IV with decreasing or increasing R. These results indicated that the amount of organic or water which was not utilized in the reaction and the degree of cross-linking apparently played a role for the observed variations in pore-size or shape of water isotherms.
Synthesis and Properties of Comb-Like Liquid Crystalline Polymers with Electrooptically Active Mesogenic Side Groups
Authors: Maeda M. , Kumar R.S. , Blumstein A. , Tripathy S.K. , Sixou P. , Faubert F.
Published: March 2011

In an attempt to synthesize side chain liquid crystalline polymers containing NLO active moieties, a number of psubstituted aromatic azomethine phenols with donor-acceptor substituents such as N≡C and NO2 were prepared and incorporated into a polymer chain as side groups.

Liquid crystalline properties of intermediate compounds composed of such moieties were explored separately and in mixtures. Phase diagrams were established. These intermediate compounds of M2C8 and M5C8 show interesting mesogenic properties.

Methacrylic esters with such moieties were also synthesized. Homopolymer and copolymer systems with donor-acceptor substituents were obtained. Such copolymers also display liquid crystalline properties.
Silicone Containing Liquid Crystalline Polyurethanes and Polyesters
Authors: Kosfeld Robert , Braun F. , Willner L. , Heb M.
Published: March 2011

Series of poly(urethanes) were prepared in which the spacer groups between the rigid segments contained siloxanes. The conditions for the appearence of liquid crystallinity and a fair thermal stability were investigated and compared to those of corresponding esters.
Microphase Separation in Triblock Copolymer Melts
Authors: Mayes Anne M. , Cruz Monica Olvera De La
Published: March 2011

Phase diagrams of the microphase morphologies for triblock copolymer melts are calculated for the weak segregation limit. The diagrams are found to be highly asymmetric with block copolymer composition.
Multi-Functional Device Applications of Nonlinear Optical Polymer Materials.
Authors: Lytel R. , Lipscomb G.F.
Published: March 2011

Recent developments in the application of electro-optic polymer materials to perform multi-functional roles in integrated optic device applications are summarized and future requirements for practical field operation are discussed.
Study on Diopside Whiskers Precipitation Type Hydroxyapatite
Authors: Nonami Toru
Published: March 2011

A biomedical material for use as artificial bone and dental root is provided which takes the form of a sintered composite body comprising a Hydroxyapatite(HAP) and diopside whisker. The mixed powder of HAP and diopside was heated to make this composite material. The sintering of HAP and the precipitation of diopside whisker were examined, to find a method of making them occur simultaneously. Also, diopside was added to HAP and sintering at 1200°C for 2hr. was done. As a result of these investigations, diopside whisker of aspect ratio 101˜15 was formed. Moreover the intermediate layer of CaO-SiO2-P2O5-MgO system was generated at the interface of HAP and whisker. The bending strength of this sintered body was 300MPa and fracture toughness was 3.2MPa ·m1/2. These values were higher by about 2times or 3times than those of matrix HAP respectively. The increase in bending strength was attributed to an increase in fracture toughness, caused by an increase in fracture surface energy.
Assessment of the Performance of Cement-Based Composite Material for Radioactive Waste Immobilization
Authors: Atkins M. , Cowie J. , Glasser F.P. , Jappy T. , Kindness A. , Pointer C.
Published: March 2011

The problem of predicting the future performance of cement-based systems is complicated by a poor understanding of the behaviour of cement systems at long ages, as well as of the complex interactions which can occur between cement and waste components - active as well as inactive - and with cement blending agents including fly ash, glassy slags and natural pozzolans. The progress achieved in developing a predictive capability is reviewed. Considerable success has been achieved in modelling the chemically-related features of cement based systems in terms of pH, Eh, and of element partition between solid and aqueous phases. The behaviour of model radwaste elements - iodine and uranium - has been studied in depth and indicates that both sorption and precipitation occur. U(VI), in particular, forms solubilitylimiting compounds, e.g. uranophane. But in general, presently-available data are inadequate to predict many cement-waste stream teractions; future progress in modelling is likely to rely heavily on additions to the data base.

The repository environment will also condition chemical exchanges in cement-based systems. Progress is being made in predicting the impact of CO2, a common ground water component, on the performance of cement systems.
Encapsulation of Radioiodine in Cementitious Waste Forms
Authors: Atkins M. , Glasser F.P.
Published: March 2011

Risk assessment models applied to radioactive waste repository design disclose that iodine is one of the nuclides causing most concern. Computer calculations for these scenario studies assume that iodine, in the form of I−, is poorly sorbed on most geological materials. Therefore it is important that iodine be retained at source, ie. within the vault, for as long as is practicable.

In the UK context, cements are likely to form a major part of the waste package for low and medium active wastes, and of engineered vault structures. These cements are likely to be blends of one form or another, including Portland cement blended with blast furnace slag, or fly ash. It is therefore important to assess the effect of Portland cement and blending agent on iodine speciation and uptake by the constituent solid phases. Data are presented on the uptake of I− on specific phases: Ca(OH)2, calcium aluminate sulphate hydrates, hydrotalcite and calcium silicate hydrogel (C-S-H). Combining this with a model for predicting phase assemblages in well-aged slag cements, yields an optimum blend for immobilising radioiodide, on ageing.

Precipitation of I as AgI during cementation and radiolytic effects on I are also discussed. The production of gaseous radioiodine (I2) is potentially a serious problem.
Durability of Blended Cements in Contact with Sulphate-Bearing Ground Water
Authors: Duerden S L , Majumdar A J , Walton P L
Published: March 2011

In the concept of radioactive waste disposal developed in the UK, OPC blended with pulverised fuel ash or ground granulated blastfurnace slag is being considered for encapsulation of waste forms, as a material for backfilling and sealing a repository, and for concrete in repository construction.

This paper describes a laboratory study of the long term durability of such cements in contact with sulphate-bearing ground water under accelerated exposure conditions. Mineralogical analysis of the cements over the exposure period, carried out with the aid of scanning electron microscope observations and x-ray diffraction studies, provides an indication of the stability of cementitious phases exposed to an aggressive environment.

It is shown that for intact cement blocks there is minimal interaction between cement and sulphate-bearing ground water. Sulphate minerals produced by the reaction are accommodated in voids in the cement with no adverse effect on the cement structure. However, crystallisation of C-S-H and sulphate minerals along cracks in hardened cement specimens causes expansion of fracture surfaces resulting in a more accessible route for ground water intrusion and radionucleide migration.

The reaction of cement with ground water is greatly accelerated by the use of powdered material. Ettringite formed in the reaction is found to be unstable under these conditions. The mineralogical assemblage after exposure for 1 year is calcite, hydrotalcite, C-S-H and quartz.
A Comparison of the Behaviour of Vitrified HLW in Repositories in Salt, Clay and Granite. I: Experimental
Authors: Mertens L. A. , Lutze W. , Marples J. A. C. , van Iseghem P. , Vernaz E.
Published: March 2011

Laboratories from 11 countries participated in a ‘Round Robin’ comparative test excercise using the European Commission's Repository Systems Simulation Test [1,5]. The compulsory core part of this exercise involved testing an inactive simulant of the French high-level waste glass (SON68) in containers in which the conditions were similar to those that might occur after disposal of vitrified waste in a future repository. There were three options for the test, representing repositories in clay, granite and salt. Fifteen laboratories, mostly from within the European Community, but including laboratories from USA, Canada and Japan took part in the Round Robin. Most of the laboratories only covered one option: clay, 3, granite, 10, and salt 6. The test procedure was closely specified by the European Communities. This contribution and a companion paper [2] summarize the acquired information.

The HLW borosilicate glass SON68 (R7T7), to be returned to and eventually disposed of in various geological repositories by Cogema's reprocessing customers, was tested in a stainless steel autoclave developed and provided by CEA, Marcoule. The glass was prepared and delivered by CEA; together with crushed granite, sand, smectite and groundwater for the granite option. SCK-Mol provided the clay, smectite, sand and the recipe for claywater, HMI-Berlin the recipe for the rock salt composition. The analytical method was the only variable to be chosen by the participants. After termination of the experiments (duration 14-364d, temperature 90°C), the concentrations of the glass constituents Si, B, Mo, Li, in solution had to be determined. The data base was used to evaluate the test procedure and to identify analytical problems.
Nuclear Waste Immobilization in Cement-Based Materials: Overview of French Studies
Authors: Atabek Rosemarie , Bouniol Pascal , Revertegat Eliane , Oliver Jean , Gegout Philippe , Jorda Michel
Published: March 2011

An overview of the different problems to be solved for waste form disposal in a shallow-land burial site is presented. Examples of cementbased materials used to immobilize concentrates are given in relation to cement chemistry. Experimental studies, undertaken to assess concrete durability, obviously indicate that pH is the starting parameter of chemical degradation reactions. It is found that blended cement (CLC) has a better cesium retention ability and a stronger resistance to chloride and sulfate attack than Portland cement.
Growth Rate of Alteration Layer and Elemental Mass Losses During Leaching of Borosilicate Nuclear Waste Glass
Authors: Banba T. , Murakami T. , Isobe H.
Published: March 2011

MCC-1 static leaching experiments were carried out for a simulated waste glass in deionized water for up to 364 days at 90°C in order to examine the relationship between alteration layer thickness and elemental mass losses. The thickness of the layer increased linearly at a rate of 0.63,μm/day for the first 91 days, and thereafter it remained constant (about 60 μm) independent of time. The change in normalized elemental mass losses of B, Na, and Si with time shows the same trend as that of the change in the layer thickness. It is also demonstrated that the growth rate of the layer can be calculated from the released boron in the leachates. The shrinkage of the alteration layer during air-drying is not significant in spite of the porous structure of the layer, which results from the depletion of cations and the recrystallization reported previously. Although the apparent release of elements almost ceases after a 91-day leaching experiment, reactions in the layer such as crystal growth continue.
Effects of Surface Area-to-Solution Volume Ratio on Chemical Durability of Nuclear Waste Glasses
Authors: Feng X. , Pegg I. L. , Guo Y. , Barkatt AA. , Macedo P. B.
Published: March 2011

We report data on the relationship between nuclear waste glass durability, as measured by leachate concentrations and leach rates, and the ratio of glass surface area to solution volume, S/V. The study includes West Valley non-radioactive production glasses (SF6 and SF10), West Valley glasses containing U and Th designed at CUA (WVCM47, WVCM50, and WVCM59), Savannah River SRLTDS-131 glass, and Hanford waste glass HW-39 (for which existing literature data is used). While some of these glasses show departures of leachate concentrations from simple (S/V)t scaling others conform well. The departures are, in all cases, most evident at high values of S/V. It is therefore important, therefore to understand how glass composition determines which corrosion mechanism is dominant in order to assess the region of validity of extrapolations based on (S/V)t scaling. While leach rates show a general tendency to decrease with S/V and time, exceptions are evident for the less durable glasses which show minima and maxima in the S/V-dependence at fixed time.
Simultaneous Evaporation of CS and TC During Vitrification-A Thermochemical Approach
Authors: Migge H.
Published: March 2011

In vitrification of nuclear waste, technetium tends to be lost substantially by evaporation [1,2,3,4,5]. If Cs is not present, 63% of the Tc volatilized from the molten borolilicate glass at 1420K under oxidizing conditions and about 40% under reducing conditions achieved by adding 0.5 wt% graphite to the dried frit mixture[5]. This behaviour could be correlated to thermochemistry in the simple Tc-O system considering the predominance areas of the different oxides and the partial pressures of Tc2O7above them[6]. If Cs is present(0.544 g Cs/l together with 1.61 g Na/l in the synthetic HAW solution), Tc was found to start a genuine volatilization at about 800K which proceeded rapidly in the range 875 to 950K[2]. At 1300K between 60 and 80% of the Tc and 10% of the Cs had volatilized. Because of the ratio Tc:Cs≉7:l volatility by formation of gaseous CsTcO4 was excluded[2]. On the other hand, for the same glass and HAW solution as reported in Ref.[2], Tc was found to produce a synergistic effect on the volatility of Cs[3,4]: between 2 and 5% Cs volatilized without Tc but about 22% in the presence of Tc and temperatures up to 1400K. The amount of volatilized Tc was about 50%. Furthermore[3,4], Tc was identified together with Cs in crystals deposited in the aerosolfilters after continuous heating to about 1170K. Since the aerosol crystals showed a constant ratio of Tc:Cs =1:1 and since the valency of Tc in the crystals was found to be seven the formation and the condensation of gaseous CsTcO4was assumed [3,4]. Gaseous CsTcO4or other gaseous pertechnetates of the alkaline metals have not yet been identified experimentally. Its existence may be concluded, however, from the existence of the gaseous perrhenates which form with every alkaline metal. Solid CsTcO4and other solid alkalipertechnetates are well known [7]. By using the thermochemical data of the alkaliperrhenates, free energies of condensed as well as of gaseous CsTcO4are estimated. Together with the results of the thermochemical treatment of the Tc-O system[6] and experimental data of the Cs-O system[8] they are used to calculate tentative isothermal predominance area diagrams of the ternary Cs-Tc-O system. Isobars of the gases Cs2O,CsO,Tc2O7, and CsTcO4above the different condensed phases are also cal culated and used to understand the experimental results[2,3,4] on the simultaneous evaporation of Cs and Tc during vitrification.
The Effect of Temperature on the Redox Constraints for the Processing of High-Level Nuclear Waste into a Glass Waste Form
Authors: Schreiber Henry D. , Schreiber Charlotte W. , Riethmiller Margaret W. , Downey J. Sloan
Published: March 2011

The oxidation-reduction equilibria of selected multivalent elements in an alkali borosilicate glass melt (Savannah River Laboratory frit #131) were measured as a function of the imposed oxygen fugacity over the temperature range from 950°C to 1350°C. Redox constraints on the processing of high-level nuclear waste into the glass melt require that the prevailing oxygen fugacity be about 10−5 to 10−12 Zatm at 950°C, about 10−2 to 10−9 atm at 1150°C, and about 100 to 10−7 atm at 1350°C. Such conditions circumvent foaming under oxidizing situations and metal/sulfide precipitation if the system becomes too reducing. The defined oxygen fugacity ranges correspond to the previously prescribed range of 0.1 to 0.5 for the [Fe2+]/[Fe3+] ratio in the resulting glass, independent of the processing temperature from 950°C to 1350°C.
Diffusion of Cesium in Sodium Borosilicate Glasses for Nuclear Waste Immobilisation
Authors: Sengersi E.G.F. , Janssen F.J.J.G. , de Waal H.
Published: March 2011

Diffusion of cesium in borosilicate glass for high-level radioactive waste is discussed. For this purpose model glasses with non-radioactive elements are being made, in accordance with the specifications of the reprocessing plants, from which concentration couples are composed. A concentration couple consists of two cylinders of borosilicate glass which contain different amounts of cesium. After heat treatment the couples are studied by means of scanning electron microscopy and X-Ray microanalysis. The model study will provide a basis for predictions of the containment achieved over a longer period of time.
Actinide Speciation in Spent Fuel Leaching Studies
Authors: Choppin Gregory R.
Published: March 2011

The uranium and plutonium chemistry relevant for spent fuel leach studies is discussed. Model calculations are evaluated by comparison with the results of spent UO2fuel leaching obtained in the Swedish SKB program. The thermodynamic data were found to agree sufficiently with the measured solution concentrations that it can be assumed that in oxic natural waters, leachate uranium from spent fuel would be uranyl carbonate complexes in the solution (or hydroxo complexes in the absence of carbonate) while schoepite would be the solubility limiting solid. For plutonium, PuO2+would be the solution species and Pu(OH)4the solubility limiting solid.
Statistical Model for Grain Boundary and Grain Volume Oxidation Kinetics in UO2 Spent Fuel
Authors: Stout R. B. , Shaw H. F. , Einziger R. E.
Published: March 2011

The Yucca Mountain Project of the U.S. Department of Energy is investigating the suitability of a site in the unsaturated zone at Yucca Mountain, NV, for a high-level nuclear waste repository. Most of the waste will consist of UO2 spent fuel in Zircaloy-clad rods from nuclear reactors. If failure of both the waste containers and the cladding occurs within the lifetime of the repository, then the UO2 will be exposed to oxygen in the air and higher oxides of uranium may form. The oxidation state of the spent fuel may affect its dissolution behavior if later contacted by water. A model for the kinetics of spent fuel oxidation under repository-relevant conditions is thus necessary to predict the behavior of the waste form for assessing the performance of the repository with respect to the containment of radionuclides. In spent fuel experiments, the UO2 oxidation front initially propagates along grain boundaries followed by propagation into grain volumes. Thus, the oxidation kinetics is controlled by two processes and the oxidation of spent fuel fragments will depend on the density and physical attributes of grain boundaries. With this in mind, concepts from statistical mechanics are used to define a density function for grain boundaries perunit volume per unit species in a spent fuel fragment. Combining the integral forms of mass conservation and this grain boundary density function, a model for the global rate of oxidation for a spent fuel fragment is obtained. For rapid grain boundary oxidation compared to grain volume oxidation, equations of the model are solved and results compared to existing data.
Measurement of Soluble Nuclide Dissolution Rates from Spent Fuel
Authors: Wilson C. N. , Gray W. J.
Published: March 2011

Gaining a better understanding of the potential release behavior of water-soluble radionuclides is the focus of new laboratory spent fuel dissolution studies being planned in support of the Yucca Mountain Project. Previous studies have suggested that maximum release rates for actinide nuclides, which account for most of the long-term radioactivity in spent fuel, should be solubility-limited and should not depend on the characteristics or durability of the spent fuel waste form. Maximum actinide concentrations should be sufficiently low to meet the NRC annual release limits. Potential release rates for soluble nuclides such as 99Tc, 135Cs, 14C and 129I, which account for about 1-2% of the activity in spent fuel at 1000 years, are less certain and may depend on processes such as oxidation of the fuel in the repository air environment.

Dissolution rates for several soluble nuclides have been measured from spent fuel specimens using static and semi-static methods. However, such tests do not provide a direct measurement of fuel matrix dissolution rates that may ultimately control soluble-nuclide release rates. Flow-through tests are being developed as a potential supplemental method for determining the matrix component of soluble-nuclide dissolution. Advantages and disadvantages of both semi-static and flow-through methods are discussed. Tests with fuel specimens representing a range of potential fuel states that may occur in the repository, including oxidized fuel, are proposed. Preliminary results from flow-through tests with unirradiated UO2 suggesting that matrix dissolution rates are very sensitive to water composition are also presented.
A Study on Fabrication Technology of Ceramic Overpack - A Conceptual Design and Fabrication of a Full-Scale Ceramic Overpack -
Authors: Teshima T. , Karita Y. , Katsumoto K. , Ishikawa H. , Sasaki N.
Published: March 2011

The conceptual design and fabrication test of a full-scale ceramic overpack were performed from the viewpoint of structural barriers as a part of program to evaluate their potential use as overpack under conditions of deep geological disposal.

Materials investigated were porcelain (used for insulators) and A12O3 with high purity of 99.7 %. The selected design consisted of a cylindrical body with hemispherical heads at each end. The design thickness of overpack is the sum of the structural thickness and corrosion allowance. The thickness required to resist the lithostatic pressure was estimated by the basic cylinder buckling formulas and finite element stress analyses in both case of uniform and non-unifom external pressure conditions. These analyses showed that structural thickness of 119 mm was necessary for overpack of porcelain and 40 - for A12O3 under the predicted maximum uniform pressure. In addition, fracture probability of delayed failure, one of significant degradation mode, was estimated for overpack of porcelain.

A full-scale overpack of porcelain, of dimensions 800 mm outer diameter x 2200 mm length x 150mm wall thickness, was fabricated under the ordinary level of fabrication technology.
Leaching/Migration of UO2-Fuel in Compacted Bentonite
Authors: Albinsson Y. , Forsyth R. , Skarnemark G. , Skålberg M. , Torstenfelt B. , Werme L.
Published: March 2011

The release and migration of the fission products cesium, europium and technetium, the actinides plutonium, americium and curium, and the activation product cobalt from spent nuclear fuel pellets in highly compacted bentonite clay has been measured after contact times of 101 and 386 days. Experiments at longer contact times are in progress. In some cases small amounts (0.5–1%) of powdered copper or iron metal, or vivianite (Fe3(PO4)2) have been mixed with the bentonite clay.

The results indicate as expected a high mobility of cesium. The actinides have a very low mobility. After 386 days, plutonium has diffused less than 0.5 mm away from the fuel, while americium and curium appear to be somewhat more mobile. The behaviour of europium is similar to that of trivalent actinides. Very little technetium has been leached from all samples. Cobalt shows a strong retention in pure bentonite as well as in the presence of vivianite, while the mobility is much larger when iron or copper is added.
The Microstructure of ggbfs/OPC Habdened Cement Pastes and Some Effects of Leaching
Authors: Richardson I.G. , Rodger Sally A. , Groves G.W.
Published: March 2011

Ground granulated blast-furnace slag (ggbfs) /Ordinary Portland cement (OPC) blends are possible materials for use in intermediate and low-level radioactive waste repositories. The microstructural development in neat OPC is described. The effect of increasing the loading of ggbfs on the composition and microstructure of the hardened paste has been examined by a number of techniques, including transmission electron microscopy. The implications for performance are discussed. A ggbfs/OPC 9:1 blend which had been exposed, after normal hydration to aqueous leaching was also examined. Marked changes in the microstructure and composition were observed.
Estimation of Illitization Rate of Smectite from the Thermal History of Murakami Deposit, Japan
Authors: Kamei G. , Arai T. , Yusa Y. , Sasaki N. , Sakuramoto Y.
Published: March 2011

The research on illitization of smectite in the natural environment affords information on the long-term durability of bentonite which is the candidate for buffer material.

Murakaml bentonite deposit in central Japan, where the bentonite and rhyolitic intrusive rock were distributed, was surveyed and the lateral variation of smectite to illite in the aureole of the rhyolite was studied.

The radiometric ages of some minerals from the intrusive rock and the clay deposit were determined. Comparison of the mineral ages ( obtained by K-Ar, Rb-Sr and fission-track methods ) with closure temperature estimated for the various isotopic systems allowed the thermal history of the area. The age of the intrusion was 7.1± 0.5 Ma(; Mega d'annees), and the cooling rate of the intrusive rock was estimated to be approximately 45 °C/Ma.

Sedimentation ages of the clay bed were mostly within the range from 18 to 14 Ma. However, the fission-track age of zircon in the clay containing illite/smectite mixed layers was 6.4±0.4 Ma, which was close to that of the intrusion. The latter value could be explained as the result of annealing of fission-tracks in zircon. The presence of annealing phenomena and the estimated cooling rate concluded that illitization had occured in the period of 3.4 Ma at least under the temperature range from above 240±50 to 105 °C. Illite-smectite mixed layers occured from smectite in the process. The proportion of iliite was about 40 %. Approximately, 29 kcal/mol as a value of activation energy was calculated to the illitization.

The hydrogen isotopic ratio ( D/H ) of constitution water of the illite was determined. The values that were calculated for the water, which was related to the illitization, fell within the range of hydrogen isotopic ratios of seawater.
Authigenic Clay Minerals in the Rustler Formation, WIPP Site Area, New Mexico
Authors: Brookins D. G. , Lambert S. J. , Ward D. B.
Published: March 2011

Transuranic waste is planned for disposal in the Late Permian evaporites of the Delaware Basin, southeastern New Mexico, at the WIPP Site. The disposal horizon is located in the bedded halite of the Salado Formation, which is overlain by the impure halite-anhydrite (gypsum)-siltstone-mudstone of the Rustler Formation. The Rustler Formation also contains two dolomite members, the Magenta and Culebra, which transmit water. The Culebra Member is suspected to have actively interacted with waters at time(s) from the Late Permian to the present, and it is important to assess the reactivity of these waters in conjunction with WIPP stability.

We have investigated the Rb-Sr systematics of clay minerals from the Culebra Member and elsewhere in the Rustler Formation. By separating the less than 0.125 μm size material we are able to deal with presumed true authigenic clay minerals. The authigenic fraction is especially sensitive to chemical and isotopic exchange with waters, and an episodic exposure to a large amount of water will re-set the clay minerals to such a time. Our data yield 259 ± 22 Ma Rb-Sr isochron, which is consistent with the Late Permian age of the Rustler Formation. This age demonstrates that age-determining cations in these clay minerals have preserved their isotopic and chemical integrity since the Late Permian.
Sizing Requirements for Flow-Through Geochemical Tests: Theoretical Considerations and Model Results
Authors: Hoover James D. , Thornton Edward C.
Published: March 2011

A methodology for evaluating test apparatus size requirements has been applied to the sizing of flow-through tests used in the evaluation of coupled reaction and transport processes. The results of the sizing evaluation constrain the apparatus dimensions and test conditions capable of yielding results representative of the processes of interest.

The size requirements of flow-through tests involving a system of simplified granite and groundwater were determined in order to demonstrate the feasibility and implications of sizing evaluations. Reaction path simulations were performed using the E03/6 codes at temperatures of 25°C, 100°C, and 200°C. The determination of reaction path as a function of time was then used to obtain minimum column residence time requirements. Simulation results indicate that column lengths required for development of quasistatic equilibrium reaction zones at 200°C are three times smaller than at 100°C, and over 36 times smaller than at 25°C.

A range of possible combinations of column dimensions and flow rates for a set of model test conditions exist for a given residence time. The most appropriate combinations depend on the purpose of the test, the process of interest, and factors such as test duration, sampling requirements, and engineering limitations. Size and scale evaluations thus provide a technical basis for the design and construction of flow-through tests, and have profound implications for the interpretation of test results.
Sizing and Scaling Requirements of a Large-Scale Physical Model for Code Validation
Authors: Khaleel R. , Legore T.
Published: March 2011

Scaling considerations relevant to porous media flow are reviewed. An analysis approach is presented for determining the sizing requirements of a large-scale, hydrology physical model. The physical model will be used to validate performance assessment codes that evaluate the long-term behavior of the repository isolation system. Numerical simulation results for sizing requirements are presented for a porous medium model in which the media properties are spatially uncorrelated.
A Coupled Chemical-Mass Transport Submodel for Predicting Radionuclide Release from an Engineered Barrier System Containing High-Level Waste Glass
Authors: McGrail B. P. , Apted M. J. , Engel D. W. , Liebetrau A. M.
Published: March 2011

A mechanistic model describing a dynamic mass balance between the production and consumption of silicic acid was coupled to a near-field mass transport model to predict the dissolution kinetics of a high-level waste glass in a deep geologic repository. The effects of interactions between an iron overpack and the glass are described by a time-dependent precipitation reaction for a ferrous silicate mineral. The kinetic model is used to transform radionuclide concentration-versus-reaction progress values, predicted from a geochemical reaction path computer code, to concentration-versus-time values that are used to calculate the rate of radionuclide release by diffusive mass transfer to the surrounding host rock. The model provides for both solubility-limited and kinetically limited release; the rate-controlling mechanism is dependent on the predicted glass/groundwater chemistry.
Thermodynamic Modeling of Cement/Groundwater Interaction as a Tool For Long-Tern Performance Assessment
Authors: Criscenti Louise J. , Serne R. Jeff
Published: March 2011

The chemical behavior of cement in the natural environment is of interest because cement has been suggested as a means of containing low-level radioactive waste and as a barrier between radioactive-waste containers and the surrounding soil or rock. In the past, either experiments or computer modeling have been used independently to predict how cement will leach in the natural environment. In this study, a geochemical model for cement leaching was developed, and predictions by the model were compared to results from a static leach test. Calcium concentrations and pH were adequately predicted by the model; however, other major leachate constituents, such as Al, Si, and S04, were poorly predicted. Additional experimental data and refinement of the model are both required to better predict the observed leachate concentrations. Accurate prediction of experimental results by a geochemical model would increase confidence in the model for use in long-term performance assessment.
Grouted Waste Leach Tests: Pursuit of Mechanisms and Data for Long-Term Performance Assessment
Authors: Serne R. Jeff
Published: March 2011

At Hanford, low-level liquid nuclear waste is being mixed with cementitious materials (grout) to form leach-resistant solid waste. Prior to grouting each liquid waste, an assessment must be performed to evaluate the long-term environmental impact. These predictions rely upon a diffusioncontrolled release model and short-term laboratory leach data on small grout samples. This paper describes size scale-up and inventory scale-up experiments that evaluate whether diffusion does in fact control the release of contaminants. The results of the volume scale-up test suggest that tests on grout cylinders between the sizes 3 cm dia. by 3 cm length and 30 cm dia. by 29 cm length yield comparable results. These data and other available literature suggest that extrapolation of leach results to large blocks of solidified waste is defensible.

The inventory scale-up tests for 125I and selenium show a constant effective diffusivity regardless of the original inventory. This suggests that diffusion processes do in fact control the release of iodide and selenium from grout. The 99Tc effective diffusivities may not remain constant with changes in inventory.
Long-Range Interactions and Rigidity in Surfaces and Lamellar Phases
Authors: Kardar Mehran
Published: March 2011

Recently there has been a large effort to understand the statistical and phase behavior of collections of surfaces and membranes. Experimental activity has focused on the behavior of stacked films in lamellar phases of microemulsions. Here I briefly sumnmarize the role of fluctuations and undulations in four classes of films: fluid, hexatic, solid, and charged.
Scaling Behaviour of the Viscoelastic Properties of a Biopolymer System Near the Gel Point
Authors: Axelos M. A. V. , Kolb M.
Published: March 2011

Rheological measurements have been performed on pectin-calcium systems close to the sol-gel transition. Two different experimental setups - steady state and oscillatory shear measurements - show scaling of the viscoelastic properties. The results of both types of measurements are consistent with each other and with scalar percolation theory.
Dynamics of Concentrated Colloidal Suspensions
Authors: Weitz D. A. , Ye L. , Sheng Ping , Huang J. S. , Pine D. J. , Liu J. , Chaikin P. M. , Pusey P. N.
Published: March 2011

We study the dynamics of concentrated colloidal suspensions by measuring the frequency dependent structure factor, S(q,w), using light scattering techniques. We introduce Diffusing Wave Spectroscopy, which extends dynamic light scattering to the multiple scattering regime, allowing us to study the lower frequency, diffusive modes of S(q,w), which reflect the Brownian motion of the particles. We study the behavior of the higher-frequency, propagating modes of S(q,w), which reflect acoustic waves, using Brillouin scattering. To study S(q,w) at low qa, where q is the scattering vector and a the particle diameter, we use inverted micelles, and find that the interactions between the micelles has a dramatic impact on the speed of sound as the volume fraction of micelles increases. To study S(q,w) at large qa, we use index matched PMMA particles, allowing us to measure the dispersion curve of phonons in a hard sphere colloid system. Together, these results provide a measure of S(q, w) over a wide range of q and of w.