bluuebunny/crossref_metadata_2025 huggingface dataset:
ELASTIC PROPERTIES OF METAL SUPERLATTICES
Authors: JANKOWSKI A.F. , TSAKALAKOS T.
Published: March 2011

The elastic properties of modulated structure materials are presented. An enhanced modulus effect has been observed in several composition modulated thin film systems containing short wavelength modulations.8-10nm. The foils were produced by vapor deposition using two or three source evaporator. As compared with homogeneous foils of the same average composition, the modulated foils exhibited an appreciable increase (up to 300%) in modulus. The dependence of various moduli on the modulation parameters (wavelength, composition and amplitude) are described. The plastic behavior, breaking and microhardness of these foils are also presented as a function of the modulation parameters. Current theories based on electronic and strain effects on the elastic constants of metals are also presented to explain the origin of the supermodulus effect.
UPPER CRITICAL FIELD OF Mo-Ni HETEROSTRUCTURES
Authors: UHER CTIRAD , WATSON W.J. , COHN J.L. , SCHULLER IVAN K.
Published: March 2011

Upper critical field and its anisotropy have been measured on two very short wavelength Mo-Ni heterostructures of different degrees of perfection, λ = 13.8Å (disordered structure) and X = 16.6Å (layered structure). In both cases the parallel critical field has an unexpected temperature dependence, a large and temperature dependent anisotropy, and over 60% enhancement over the Clogston-Chandrasekhar limit. Data are fit to the Werthamer-Helfand-Hohenberg theory and the spin-orbit scattering times are found to be 1.79 × 10−13 sec and 2 × 10−13 sec, respectively.
PHOTOLUMINESCENCE AND ELECTRICAL PROPERTIES OF EPITAXIAL GaAs GROWN BY CLOSE SPACE VAPOR TRANSPORT
Authors: MIMILA J. , BOURGOIN J.C. , LEGROS R. , HUBER A
Published: March 2011

The growth of epitaxial GaAs layers on semi-insulating substrates, using high purity GaAs as source material has been obtained by the so-called lose Space Vapor Transport technique. The thermodynamical conditions of the growth, the effect of the growth parameters : source and substrate temperatures, pressure of transporting gas (water vapor) on the growth rate were investigated. Then, the variations of the optical, electrical and deep levels properties of the layers were studied as a function of the growth parameters in order to determine the values of these parameters for which the layers present the best electronic properties. Here, we describe i) the evolution of the photoluminescence spectra versus the substrate and source temperatures, the water vapor pressure being kept constant at its best value; ii) a secondary ion mass spectroscopy analysis of the main impurities contained in the layers. The results demonstrate that the layers are homogeneously Si and S doped, the doping being slightly compensated, the layer-substrate interface is clean and the PL is characteristic of a defect free material.
SOLID PHASE EPITAXIAL GROWTH OF Ge ON GaAs
Authors: Palmstrom C.J. , Galvin G.J. , Schwarz S.A. , Cooman B.C. De , Mayer J.W.
Published: March 2011

Solid phase epitaxial growth of electron beam evaporated Ge layers on unheated GaAs has been demonstrated. The amorphous Ge layers grow epitaxially on the GaAs surface during anneals at 400°C. A technique for growing these epitaxial layers without the need for in-situ heat treatment of the GaAs prior to Ge deposition is described.
ANTIPHASE DOMAIN FREE EPITAXIAL GROWTH OF GaAs ON (100)Ge
Authors: Shinoda Y. , Ohmachi Y.
Published: March 2011

High-quality single domain GaAs epitaxial layers were successfully grown on (100)Ge substrates. Growth was carried out using conventional metalorganic chemical vapor deposition at atmospheric pressure. Antiphase domain free GaAs epitaxial layers were obtained by thermal etching of the Ge surface just prior to growth. Mosaic surface morphology and antiphase boundaries characteristic of domain structures were completely absent in epi-layers following thermal etching. Photoluminescence revealed that domain free epi-layers exhibited characteristics comparable to those of GaAs homoepitaxial layers.
Rapidly Solidified Alloys for Permanent Magnets
Authors: Hadjipanayis G.C.
Published: March 2011

The magnetic and structural properties of melt-spun Fe-R-B alloys are reviewed. The hard magnetic properties of these alloys are attributed to the presence of a highly anisotropic tetragonal phase Fe14R2B which in the case of ribbons occurs in very fine grains. The interachoot of domain walls with this fine microstructure leads to the observed high coercivities. The effects of partial substitution of iron, rare-earth and boron on the formation of Fe14R2B and on its magnetic properties are also discussed.
Magnetic Effect on the Phase Equilibria of FCC(Fe,Ni) Alloys at Low Temperatures
Authors: Lin Jen-Chwen , Chuang Ying-Yu , Chang Y. Austin
Published: March 2011

Phase stabilities of iron alloys at low temperatures are strongly infuenced by magnetic effect. The appearance of certain type of equilibria is often due entirely to magnetic contribution to the Gibbs energy of the pertinent phase. The appearance of the stable and metastable equilibria in fcc(Fe,Ni) alloys are discussed in terms of the magnetic interaction.
Tensile and Creep Properties of Rapidly Solidified Titanium Alloys Containing Complex Matrices and Fine Dispersoids
Authors: Gigliotti M.F.X. , Rowe R.G. , Wasielewski G.E. , Scarr G.K. , Williams J.C.
Published: March 2011

Titanium alloys containing alpha matrices with various rare earth compound dispersions were prepared by melt extraction. The melt extracted material was HIPped, extruded, and thermally exposed to yield various microstructures including transformed beta and equiaxed alpha. Tensile and creep tests were conducted on material in the different microstructural conditions. Trends in mechanical behavior as a function of alloy chemistry and process history are discussed. The alloys with a transformed beta microstructure had superior creep resistance. Alloys containing dispersoids had better tensile ductilities compared with those which did not contain a dispersoid.

Portions of this work were carried out under Air Force Contract F33615-83-C-5034.
Mechanical Properties of Rapidly Solidified High Carbon Iron Base Alloys
Authors: Burchards D. , Kainer K.U. , Mordike B.L.
Published: March 2011

High carbon content iron base alloys (2–4 wt%) with various alloying additions,eg., Cr, Ni, Si or Te were produced in powder form by water atomisation. Depending on the alloying addition the powder particles solidify, microcrystalline with either dendritic or cellular microstructures with supersaturated solid solution and eutectic. The proportion of carbide is dependent on the composition and atomizing conditions. The powder, after suitable preparation, was consolidated by extrusion or hot isostatic pressing. The consolidation behaviour of the powders is influenced by the composition and particle size distribution. The microstructures and hardness values of the powder in the as quenched state are compared with those of the consolidated state with particular emphasis on the thermal stability. The mechanical properties of extruded powders are compared with those for hot isostatically pressed.
Structural Relaxation in Fe-B Glasses
Authors: Altounian Z. , Strom-Olsen J.O. , Olivier N.
Published: March 2011

We present results on structural relaxation in Fe-B glasses. Relaxation effects were studied through measurements of the Curie temperature (Tc) of the glasses annealed at different temperatures (Ta). We observe a monotonic increase in Tc with Ta in all alloys due to irreversible structural relaxation. This increase continues till the start of surface/ bulk crystallization. The observed decrease in Tc upon further annealing is attributed to the strain introduced in the partially glassy system. We see no evidence for reversible structural relaxation in Fe-B glasses.
Hydrogen in Silicon-Unanswered Questions
Authors: Pearton S. J.
Published: March 2011

The study of hydrogen in crystalline Si has enjoyed a resurgence of interest in recent times, principally because hydrogen is a common constituent of many semiconductor reagents, and also because of its ability to passivate the electrically activity of shallow acceptor dopants, and many deep contaminating centers in Si. This enables its use as a sensitive probe of the defect chemistry occurring in Si at relatively low temperatures – the presence of hydrogen can be detected electrically through the passivation of impurities and defects, and isotopic substitution with deuterium enables chemical analysis by secondary ion mass spectrometry.
New Optical Transition at Thermal Donors in Silicon
Authors: Weber J. , Queisser H. J.
Published: March 2011

We detect new luminescence lines in Czochralski-grown silicon after prolonged heat treatments at 450°C. The properties of the new optical transition are well explained by a thermal donor-free hole recombination. From the IR-absorption spectra measured on the same samples, we have evidence for an inhomogeneous distribution of the thermal donors. The spatial fluctuations of the thermal donors appear to be necessary for the new luminescence spectrum to emerge.
A Perspective on Nitrogen in Silicon
Authors: Stein Herman J.
Published: March 2011

This is the first symposium to explicitly include nitrogen in discussions on nondopant light impurities in Si. Ordering of the impurity listing (oxygen, carbon, hydrogen and nitrogen) deserves examination. It is obvious that the impurities are not listed alphabetically nor are they listed in the order they appear in the periodic table. Presumably the ordering does not simply reflect a bias of the organizing chairmen. The impurities are, in fact, listed in an order of recognition on a chronological scale of their importance in Si technology. Equilibrium solid solubility for the different impurities, as well as concentrations of the impurities in the processing environment, probably determined the chronology. Based upon published literature, the importance of oxygen was recognized in the mid 50's, carbon in the mid 60's and hydrogen in the mid 70's. Now in the mid 80's nitrogen is receiving increased attention as an impurity in Si.
Nitrogen-Carbon Interactions in Optical Defects in Silicon
Authors: Dörnen A. , Sauer R. , Pensl G.
Published: March 2011

We report five photoluminescence lines N1 through N5 in silicon which emerge after sequential nitrogen and carbon implantation. Studied is in particular the 0.7456 eV (N1) electronic-vibronic spectrum. Single nitrogen and carbon atoms in the defect are identified by isotope shifts of the no-phonon transition and of a local mode satellite with vibration quantum energy ħω= 122.9 meV. Uniaxial stress or Zeeman measurements yield monoclinic I (C1h) or trigonal (C3v) symmetry, respectively, of the optical defect. Comparing the energy of the local mode and its isotope effects with recent literature data on the nitrogen 963 cm−1 IR vibrational absorption line we discuss a defect model involving a substitutional nitrogen atom modified by an interstitial carbon atom.
Alkoxide Derived Amorphous Solids as an Alternate Nuclear Waste Popm
Authors: Pope J. M. , Harrison D. E.
Published: March 2011

Nitric acid waste can be immobilized in an amorphous aluminosilicate matrix that is produced by polymerization of metal alkoxides [1]. Unlike vitreous aluminosilicate host matrices obtained by melting, neither alkalies, alkaline earths, nor borates are required since no melting is involved. Instead, the alkoxide glass formers and radionuclides react directly to form a randomly cross-linked structure of silica and alumina polyhedra. Structurally, the amorphous product formed through chemical polymerization is similar to a true glass except that it has not experienced melting. As a result, neither a glass transition temperature nor a specific volume temperature dependence would be expected in such an amorphous material. As a chemically durable waste form, the "gel-glass" product should be substantially better than ordinary waste glass because it can be made without the addition of either alkalies or boron.
Immersion and Leach Tests on Solidified Decontamination Wastes From Dresden Unit 1
Authors: Barletta Robert E. , Adams Jay W. , Davis Richard E.
Published: March 2011

In order to provide technical support to the NRC, Brookhaven National Laboratory has performed leach tests and immersion tests using organic liquids and organic saturated water of concentrated decontamination waste solidified using a vinyl ester-styrene binder.

The leach tests measured the release of Fe, Ni, and Co from these forms in deionized water, groundwater, and seawater. After 64 days, the mean fraction released normalized by V/S for iron was 5.1 ± 1.9 × 10−3 cm in deionized water, 7.1 ± 1.1 × 10−3 cm in groundwater, and 9.0 ± 3.2 × 10−3 cm in seawater. For nickel, 64 day release rates observed were 4.6 ± 1.6 × 10−3 cm, 4.6 ± 1.0 × 10−3 cm, and 5.9 ± 0.6 × 10−3 cm in deionized water, groundwater, and seawater, respectively. After 50 days, the 59 Fe release rates were 5.9 ± 0.7 × 10−3, 4.8 ± 2.4 × 10−3, and 2.8 ± 1.0 × 10−3 cm in deionized water, groundwater, and seawater, respectively. For 60Co, the 50 day releases in the three respective leaching media were 6.0 ± 1.7 × 10−3 cm, 6.8 ± 1.0 × 10−3 cm, and 2.3 ± 0.2 × 10−3 cm.

Immersion tests of waste forms prepared at a solidification demonstration held at the Dresden Nuclear Power Station were conducted in toluene, xylene, and water saturated with toluene and xylene. During immersion of samples in the pure organics, large changes in sample volume and weight were observed. Total weight changes of 9.6 ± 0.3% and 21.6 ± 0.7% were observed after 839 hours of immersion in xylene and toluene, respectively. Air drying of the samples led to an overall weight loss of 23.5 ± 0.7% for xylene and 35.6 ± 0.6% for toluene. Qualitatively, similar changes were observed for immersion tests using organic saturated water. Severe sample deterioration was observed in this case, however. The cause of this deterioration is not known.
Site Characterization for Field Radionuclide Migration Studies in Climax Granite
Authors: Isherwood Dana , Raber Ellen , Stone Randolph
Published: March 2011

Radionuclide migration experiments in fractured granite at the Climax Stock, Nevada Test Site, are needed to compare field and laboratory measured retardation factors to determine whether laboratory studies accurately reflect in situ conditions. Initial field activities have concentrated on hydrological investigations to determine whether the fractures in Climax granite are suitable for migration experiments. A critical question was whether we could isolate a single vertical fracture between two boreholes and establish flow along that fracture from an upper to a lower borehole. Of the ten fractures tested, one fracture would not take water at pressures up to 200 psig for 24 hours. Several fractures were so permeable they accepted water at a rate which exceeded the pumping capacity of the equipment. Other fractures failed to show a connection between the two boreholes. In two fractures, we were able to establish a circulating system with up to 95 percent of the injected water being recovered. Constant pressure injection tests were conducted. Intrinsic permeabilities of 33 and 75 (μm)2 were estimated using a radial nonsteady flow model. These values correspond to effective fracture apertures of 20 and 30 μm respectively. Concurrent with the hydraulic testing activities is a study of the Climax ground-water chemistry. Our analyses show the natural water to be very different in composition from the granite equilibrated water used in laboratory sorption studies. This paper includes the results of the hydrogeological and geochemical investigations, and describes the overall experimental design plans for the radionuclide migration experiments.
Predicting Pu Concentrations in Solutions Contacting Geologic Materials
Authors: Strickert Richard G. , Rai Dhanpat
Published: March 2011

Knowledge of Pu solid phases present in nuclear wastes is important for predicting the geochemical behavior of Pu. Thermodynamic data and experimental measurements using discrete Pu compounds, Pu-doped borosilicate glasses (simulating a high-level waste form), and Pu contaminated sediments suggest that PuO2(c) is very stable and is expected to be present in the repository. The solubility of the stable phase, such as PuO2(c), can be used to predict the maximum Pu concentration in solutions for long-term safety assessment of nuclear waste repositories.
A Natural Analogue for Storage of Radwaste in Crystalline Rocks
Authors: Brookins Douglas G. , Abashian Mark S. , Cohen Lewis H. , Wollenberg Harold A.
Published: March 2011

The Bryan-Eldora stock (Colorado) intruded the Precambrian Idaho Springs Formation metamorphic rocks 58 million years ago. Geochronologic-geochemical work by Hart et al. (1) has demonstrated that the heat from the cooling intrusive rocks was sufficient to affect mineral isotopic systematics up to 2,000 m. from the contact, and the nature of these isotopic perturbations can be explained by a simple diffusion model in turn based on various heat flow models. Our new studies are focused on elemental exchange between stock and intruded rock as a function of distance from the contact; the assumption is made that the stock is a very large, high heat source analogous to a waste form emplaced in the metamorphic rocks without benefit of canister or engineered backfill. Data for U, Th and the REE indicate actinide and lanthanide immobility except perhaps in the 0–2m. contact zone where some infiltration of the country rocks by stock-derived fluids occurred. Beyond 4 m. no stock-derived U, Th, REE or *Pb are noted. Further, whole rock Rb-Sr and stable 0 isotopic data indicate conductive cooling as opposed to convective, water-induced cooling. The intruded rocks possess low porosity and permeability; this helped prevent elemental migration during the 105 − 106 years of stock crystallization. The petrographic and geochemical studies show that the Idaho Springs (or equivalent) metamorhpic rocks are well suited for radwaste storage.
Diffusion of Neptuiyl(V)- and Pertechnetate Ions in Marine Sediments
Authors: Schreiner F. , Fried S. , Friedman A.
Published: March 2011

The diffusion of the 235NpO2+ and 95m TCo4− -ions has been measured directly in sample cylinders of two different sediments from the floor of the deep sea. In smectiterich sediment not shielded from contact with atmospheric oxygen the following values were obtained for the effective diffusion coefficients of neptunyl- and pertechnetateions, respectively: Deff(NpO2+) = 1.5 × 10−12 m2 s−1 and Deff(TcO4−) = 3.2 × 10−10 m2 s−1. Under anoxic conditions in sediment with known reducing properties, the pertechnetate ion appears to undergo slow reduction and the effective diffusion coefficient of the reduced species of Deff(Tc,red)= 1.1 × 1014 m2 s−1 reflects a substantial decrease of the mobility of the lower-valent technetium.
Mechanisms of Dissolution of Radioactive Waste Storage Glasses and Caesium Migration From a Granite Repository
Authors: Chapman Neil A. , Mckinley Ian G. , Savage David , West Julia M.
Published: March 2011

Experimental and theoretical data are used to compare the effect of three possible leach mechanisms for borosilicate glass waste buried in a granite host-rock on the release and subsequent migration of 135Cs. Protracted release episodes and variations of up to an order of magnitude in groundwater transport times and five orders in output concentrations are possible.
Evaluation of Ceramic Materials to Immobilize ICPP Calcines
Authors: Staples B. A. , Cole H. S. , Mittl J. C.
Published: March 2011

Various ceramic materials as well as Formula 127 glass have been developed to immobilize ICPP zirconia calcine. Tailored, titanate and matrix encapsulated ceramics were prepared by cold pressing and sintering reactants, while glass-ceramics were prepared by melting in a manner similar to that of preparing the glass. X-ray diffraction techniques were used to determine the presence of radionuclide and calcine matrix element host phases in each ceramic material. The aqueous leachability, practical loading capacity and the incorporation of waste elements into host phases was investigated and compared to those of Formula 127 glass through application of the Soxhlet and MCC-1 static leach tests. Potential process requirements for each material were evaluated based on the number of steps needed for laboratory-scale preparation.
Reference Laboratory Testing For Backfill
Authors: Chung Riley M. , Yokel Felix Y.
Published: March 2011

Relatively high magnitude of swelling and low hydraulic conductivity are two of the performance requirements for the backfill placed around the radioactive waste package for the underground nuclear waste storage scheme. Some studies have been conducted in U.S. national laboratories and in other countries where the candidate backfill materials were tested under many different conditions to determine the expected range of these properties. This paper briefly examines the variables that were found to be significant in the evaluation of swelling and hydraulic conductivity and special emphasis is placed on the compaction method, compaction effort, and the moisture content at the time of compaction, which do not receive much consideration in ongoing test programs.
Backfill-Waste Interactions in Repository Simulating Tests
Authors: Sasaki Noriaki , Komarneni Sridhar , Scheetz Barry E. , Roy Rustum
Published: March 2011

Candidate backfill materials such as montmorillonite and clinoptilolite with and without the presence of simulated nuclear waste solids such as borosilicate glass, glass ceramic, sintered ceramic and supercalcine ceramic were investigated under repository simulating conditions (=300°C and 30 MPa). Experiments were conducted under semi-wet as well as wet repository conditions.

Montmorillonite and clinoptilolite did not seem to alter under both semi-wet and wet repository conditions as determined by XRD. However, the above backfill materials reacted extensively with wastes under both conditions. They altered to feldspar (oligoclase) in the presence of borosilicate glass and to analcime in the presence of particular ceramics under both semi-wet and wet repository conditions. Alteration of montmorillonite could not be detected either in the presence of the glass ceramic or supercalcine ceramic under both repository conditions. However, clinoptilolite altered to analcime in the presence of glass ceramic or supercalcine ceramic under wet repository conditions. Reactions of backfill materials with simulated wastes immobilized waste elements such as Cs, Mo, etc., by forming new phases such as analcime, oligoclase and powellite. In fact, analyses of product solutions from interaction runs indicated that the presence of backfill materials during the alteration of waste solids served to drastically reduce the concentration of some radionuclides in solutions. These results suggest that properly selected backfills can provide the simplest and most effective chemical (or thermodynamic) engineered barrier in an intelligently designed multibarrier system. Moreover, they indicate that the μ, P, and T in the usual leach tests (e.g. Paige, IAEA, etc.) are such that results of such tests cannot have any value in evaluating waste form behavior under repository conditions.
Iron-Enriched Basalt and its Application to Three-Mile Island Radioactive Waste Disposal
Authors: Kelsey P. V. , Schuman R. P. , Welch J. M. , Owen D. E. , Flinn J. E.
Published: March 2011

Demonstration tests were performed on iron-enriched basalt (IEB), a dissolution and immobilization medium for TMI radioactive wastes. Zeolite of the type used for cesium and strontium decontamination of TMI containment water was mixed with 20 wt% additives and melted at 1500°C to form IEB. Cesium volatility from the IEB melts was low. Leaching tests in 90°C deionized water showed leach rates of 6 μg/cm2 d for both cesium and strontium. IEB melts were used to dissolve Type 304 SS pellets and UO2 pellets clad with zircaloy in order to simulate immobilization of TMI core debris. Bubbling air through the melts greatly enhanced the dissolution of these components.
Migration of Radionuclide Chains In Subseabed Disposal
Authors: Ray A. K. , Nuttall H. E.
Published: March 2011

In this study of subseabed disposal, the two dimensional (axial and radial) migration of radionuclide chains released from a canister located in a sedimentary layer bounded at the top by the ocean and at the bottom by an impermeable basalt zone is analyzed to determine the escape rate of radlonuclides into the seawater. Analytical solutions have been derived to represent the transient concentration profiles within the sediment, flux and discharge rates to the water column of each member present in a decay chain. Using the properties of chain members present in actinide decay systems, the effects of half-life, adsorption equilibrium and other relevant parameters are elucidated.
Formulation and Processing of Polyphase Ceramics for High Level Nuclear Waste
Authors: Harker Alan B. , Morgan Peter E. D. , Clarke David R. , Flintoff John F.
Published: March 2011

Two basic crystalline phase assemblages have been developed for incorporating the full range of Savannah River Plant waste compositions into polyphase ceramic forms. Both phase assemblages provide crystalline host phases, with stable mineral analogues, for all radionuclides in the waste. The first, an alumina based assemblage, immobilizes the radioactive elements in solid solutions of magnetoplumbite and uraninite with the bulk non-radioactive waste elements being present in spinel and nepheline. The second assemblage uses the titanate based “zirconolite” type fluorite structure and the alumina/iron based magnetoplumbite phases to host the radioactive nuclei with spinel and nepheline, again providing crystalline hosts for the non-radioactive elements. Both phase assemblages can be consolidated to a fine grain ceramic by hot isostatic pressing at 1040°C pressures from 20,000 to 30,000 psi. Redox control during processing, just sufficient to reduce uranium to the tetravalent state, is used.
On-Line Measurements of the Volatilization of Ruthenium in a Vitrification Process
Authors: Odoj R. , Schwitz M.
Published: March 2011

The studies were performed using Ru–103 as a tracer. The volatilization of Ru from ruthenium containing liquids, like HAW-solutions, is about 15%. A chemical denitration of these solutions with HCHO or HCOOH reduces the volatilization to about 2%. Additional catalytic reduction with Fe-powder lowers the volatilization to about 4 ‰. The carry over of Ru seems to depend on the aerosol production rate and not the vapor pressure. Only RuO2 could be detected in the off-gas.
Behavior of Radionuclides During the Smelting of Noncombustible Solid Wastes
Authors: Osaki Makoto , Yokoi Shinji , Miyagawa Minoru
Published: March 2011

The melting process of noncombustible solid wastes seems to be one of the most promising processes for volume reduction and immobilization. This melting process needs a high temperature of around 1500° C, but the behavior of radionuclides in such a process and at such a temperature has not been fully examined. We melted small contaminated samples to examine the behavior of radionuclides. Melted products were subjected to leaching tests.

Many assorted samples were melted, and we found that the vapour pressure of the radionuclide determined the distribution between melted products and dusts. The standard free energy of oxide formation and the quantity of stable nuclide of the radionuclide determined the distribution between metal and slag products. The leaching rate of melted products was sufficiently low.
Vitrification of High-Level Radioactive Waste in a Small-Scale Joule-Heated Ceramic Melter
Authors: Woolsey Gerald B. , John Plodinec M.
Published: March 2011

Vitrification is the reference process for the immobilization of radioactive waste from the production of defense materials at the Savannah River Plant (SRP). Since 1979, a small vitrification facility (1 Ib/hr) has been operated at the Savannah River Laboratory using actual SRP waste. In previous studies. dried waste was fed to this smaller melter. This report discusses direct feeding of actual liquid-waste slurries to the small melter. These liquidfeeding tests demonstrated that addition of premelted glass frit to the waste slurry reduces the amount of material volatilized. Results of these tests are in accord with results of large-scale tests with actual waste.
Metastable Liquid Immiscibility in Nuclear-Waste-Glasses
Authors: Engell John E. , Roed GjerlØff
Published: March 2011

For glass systems related to two potential nuclear-wasteglasses, ABS–39 and ABS–41, the 600°C isotherm of the metastable immiscibility field has been located experimentally. Both glasses are in the one phase glass field down to temperatures below 600°C. ABS–39 and ABS–41 are Na2O-B2O3-SiO2 glasses containing 1.66 wt% UO2 and 9 wt% of simulated fission products. Additional components in ABS–39 are Al2O3 and Fe2O3. In ABS–41 these two oxides are partly substituted with ZnO and Li2O. This substitution causes an extension of the metastable immiscibility field relative to the ABS–39 system.
Interim Waste Forms for High-Level Radioactive Wastes: Processing and Properties
Authors: Bandyopadhyay G.
Published: March 2011

Several simulated interim waste forms have been investigated in the laboratory to study their suitability for application in handling and transportation of high-level radioactive wastes to terminal processing sites. In the fused-salt/sludge option, the neutralized supernatant liquid and the precipitated sludge are treated simultaneously to form fused-salt cakes. Silicate-based options, in which sodium silicate or sodium silicate and Ca(OH)2 act as binders for the sludge, require prior separation of the sludge and the soluble radioactive constituents from the supernatant before the waste form can be prepared. The results from tests on simulated fused-salt waste forms indicated that the process simplicity of this option is partially offset by the high water solubility and hygroscopicity of the product, which would necessitate special precautions during transportation and storage. The most promising silicate-based option is the ambienttemperature silicate sludge process, in which the sludge is mixed with sodium silicate [and sometimes with Ca(OH)2] and subsequently exposed to a contrelled-humidity environment at room temperature to form a chemical bond. Solid material containing 75 wt % synthetic calcined sludge, prepared by this process, has sufficient physical, chemical, and mechanical stability for use as an interim waste form.
Effects of Alpha, Gamma, and Alpha-Recoil Radiation on Borosilicate Glass Containing Savannah River Plant Defense High-Level Nuclear Waste
Authors: Bibler Ned E.
Published: March 2011

At the Savannah River Plant, the reference process for the immobilization of defense high-level waste (DHLW) for geologic storage is vitrification into borosilicate glass. During geologic storage for 106y, the glass would be exposed to ∼3 × 1010 rad of β radiation, ∼1010 rad of γ radiation, and 1018 particles/g glass for both α and α-recoil radiation. This paper discusses tests of the effect of these radiations on the leachability and density of the glass. No effect of the radiations was detected that reduced the effectiveness of the glass for long-term storage of DHLW even at doses corresponding to 106 years storage for the actual glass. For the tests, glass containing simulated DHLW was prepared from frit of the reference composition. Three methods were used to irradiate the glass: external irradiations with beams of ∼200 keV or Pb ions, internal irradiations with Cm–244 doped glass, and external irradiations with Co–60 γ rays. Results with both Xe and Pb ions indicate that a dose of 3 × 1013 ions/cm2 (simulating >106 years storage) does not significantly increase the leachability of the glass in deionized water. Tests with Cm–244 doped glass show no increase in leach rate in deionized water up to a dose of 1.3 × 1018 α and α-recoils/g glass. The density of the Cm–244 doped glass has decreased by 1% at a dose of 1018 particles/g glass. With γ-radiation, the density has changed by <0.05% at a dose of 8.5 × 1010 rad. Results of leach tests in deionized water and brine indicated that this very large dose of γ-radiation increased the leach rate by only 20%. Also, the leach rates are 3 to 4 times lower in brine.
Influence of Irradiation With Gamma - Quanta and Beam of Accelerated Electrons on the Sorption Parameters of Clay Minerals of the Montmorillonite Group
Authors: Spitsyn V. I. , Balukova B. D. , Savushkina M. K.
Published: March 2011

The minerals belonging to the montmorillonite group were studied. Under irradiation werp air-dry minerals as well as those in solutions containing 90Sr, which gave us an opportunity to study the irradiation influence on the soprtion accumulation of radionuclides. The analysis of the diffractograms of irradiated and nonirradiated minerals shows that the structure of the minerals belonging to the montmorillonite group remains unchanged, while alumosilicate layers converge which results in a decrease in interplane distance.
The Influence of Gamma Irradiation on the Leaching Behavior of a Modified Synroc-B Ceramic Waste Form
Authors: Solomah A. G.
Published: March 2011

The leaching behavior of a sintered Modified SYNROC-B ceramic waste form containing l0wt% simulated high level radioactive waste, under the influence of γ-irradiation, has been investigated. Similar leaching experiments have been carried out in the absence of γ-irradiation, and the leach rates of Ba and Cs are presented for comparison studies. Acid/Base formation has been monitored through pH measurements of the leachants. A decrease in pH is found with γ-irradiation due to radiolytic nitric acid generation. Higher initial leach rates with a more pronounced subsequent drop in the case of Ba and Cs were observed with γ-irradiation than without irradiation. The results of the study are presented and discussed.
Management of Radioactive Wastes in Europe (Ec) History, Philosophy and Plans for the Next Five Years
Authors: Orlowski S. , Simon R.A
Published: March 2011

Since its first R & D programme on radioactive waste management in 1973, the European Community has been contributing a steadily increasing share of the European research effort in this field. A major part of the programme is devoted to the investigation and evaluation of management concepts for high-level and TRU wastes from the backend of the fuel cycle. Risk analysis studies for the assessment of multi-barrier terminal isolation systems currently have high priority.
Radiation Induced Impurity Precipitation in Mgo
Authors: Clement S. , Hodgson E. R.
Published: March 2011

In MgO irradiated at high dose rates and high temperatures with 1.8 MeV electrons, a suppression of the Fe3+ optical absorption band at 290 nm is observed. This suppression, a function of both dose rate and temperature, is consistent with a reduction process induced by oxygen displacement damage. Both thermal and radiation enhanced diffusion are involved and lead to the formation of iron containing precipitates. Similar results have been obtained for Ni2+.
Electrical Properties and Defect Structures of CoO and MnO at High Defect Content
Authors: Sykora G.P. , Mason T.O.
Published: March 2011

Defect studies at high defect content in transition metal monoxides allow for the conduction mechanisms to be established and the nature of defect interactions to be studied. Conductivity and thermopower results in p-type, highly defective MnO are reported and analyzed with a combination of point defects and clusters. A high pressure oxygen apparatus to achieve defect contents up to 5 percent in CoO has been designed and constructed.
Structure-Transport Relationships in Fast Ion Conducting Alkali Borate Glasses
Authors: Fusco F. A. , Tuller H. L. , Uhlmann D. R.
Published: March 2011

The effect of CaO substitutions (between 1 and 10% (CaO)2/Li2O) on the transport and physical properties of two fast ion conducting lithium borate glass systems (37.3 mol % Li20, 62.7 mol % Li2O3 and 50 mol % Li2O, 50 mol % Li2O, 50 mol % B2O3) are investigated. Measurements of electrical conductivity, density and glass transition temperature are reported. The influence of strain effects on carrier mobility is examined. Measurements of electrical conductivity and molar volume are extended to a K2O·2B2O3 glass and compared with existing data for corresponding lithium and sodium diborate glasses.
Electronic Barriers Produced at Zno Surfaces By Ion Implantation And Annealing
Authors: Sonder E. , Zuhr R. A. , Martinelli J. R.
Published: March 2011

Modern varistors are made of polycrystalline ZnO, doped to create Schottky-like barriers at the grain boundaries. To allow the study of tailored single barrier junctions, we have implanted ZnO crystals with Bi, Sb and transition metals. The electrical properties and the distribution of Bi and Sb were measured in the implanted crystals as a function of annealing temperature. After implantation and before heating, no barriers can be observed. After heating to 600–800°C, a high voltage (insulating) barrier is created. Heating to above 1000°C produces a 2-1/2 Volt barrier with high nonlinearity. The temperatures at which these barriers appear correspond, respectively, to temperatures at which motion of Sb and Bi first can be observed by ion backscattering techniques, and at which these elements diffuse freely.
Reactive Sputtering Deposition of Titanium Oxide Films By Means of An RF Triode Sputtering Source
Authors: Yamashita Toru , Robinson J. W. , Yamauchi H.
Published: March 2011

TiOx thin films were fabricated by means of a reactive sputtering technique in an rf triode sputtering-deposition unit. The deposition rate was studied in detail. A ‘phase diagram’ of TiOx was determined. XPS study showed the formation of a Ti02 surface layer on TiOx thin films. Oxygen was removed by the Ar+ bombardment on Ti02 to yield Ti203.
The Influence of Irradiation Temperature on U.V. Induced Defect Creation in Dry Silica
Authors: Devine R. A. B. , Fiori C. , Robertson J.
Published: March 2011

Electron spin resonance measurements have been carried out on samples of Suprasil Wl (dry silica) subjected to ultraviolet laser radiation (λ = 248 nm, E = 5 eV/photon). Studies have been made for fixed irradiation temperature (room) variable accumulated ultraviolet dose and fixed accumulated dose (3000 J/cm2) at various irradiation temperatures in the range 110 K to 335 K. Three principal defect centers are observed. Non-bridging oxygen hole centers are created at all temperatures in the range studied with slightly higher efficiency at room temperature (ration 300 K/150 K ∼ 2.5). Comparison of the dose dependent growth curve of the 4.8 eV absorption and its isochronal annealing curve with those for the oxygen hole center clearly identify the origin of the absorption band with this defect. A threshold temperature ∼ 200 K is found for oxygen vacancy creation consistent with results on single crystalline quartz. Post irradiation annealing at 593 K eliminates the vacancy centers and the peroxy radical resonance appears. Its growth as a function of accumulated ultraviolet dose and irradiation temperature supports the hypothesis that peroxy radicals form by the trapping of diffusing, molecular oxygen at the oxygen vacancy center.
Heavy Metal Fluoride Glasses for Optical Applications
Authors: Sibley W. A. , Yeh D. C. , Suzuki Y. , Quarles G. J. , Powell R. C.
Published: March 2011

Great progress has been made in optical device technology over the past decade. This progress brings a host of new services which include voice, data and visual communications. The realization of low loss optical fibers which give rise to long distance optical communication and the growth in information processing through computer technology will lead to an accelerating growth in the utilization of light guides and light wave communication systems. Heavy metal fluoride glasses have proved to be excellent hosts for both rare earth and 3d transition metal ions. In addition, their potential as light guides is at present unexcelled. This glass is especially promising for optical display devices, laser hosts, and electroluminescence panels. Numerous defects and impurities can be incorporated in the glass which absorb or emit light. Through optical studies of rare earth ions such as Er3+, Ho3+, Nd3+ and Pr3+ it is possible to investigate the multiphonon emission rate for optical transitions in the heavy metal fluoride materials. It is found that these particular materials have a much lower multiphonon rate than oxide glasses. This makes them attractive for room temperature devices. When 3d transition metal ions are incorporated into heavy metal fluoride glasses, the optical properties are similar in many cases to those in crystals. Inhomogeneous broadening of the absorption and emission bands occurs in the glass, but the lifetimes and oscillator strengths of the transitions in glass and crystals are of the same magnitude. Radiation damage of glasses can be detrimental to long range optical communication. It is found that the heavy metal fluoride glasses damage by the photochemical mechanism which is also dominant in highly ionic materials. Optical absorption and electron spin resonance measurements have been utilized to identify the types of radiation induced defects in these materials.
Identification of Transition Metal Sites in Fused SiO2 by X-Ray Absorption Spectroscopy
Authors: Lytle Farrel W. , Greegor Robert B.
Published: March 2011

X-ray absorption spectroscopy is used to determine valence and site symmetry for all the 3d transition metals in fused quartz prepared by the flame hydrolysis method. The results are compared with optical data on the same samples with generally good agreement.
Theory of Intrinsic Defects in a-SiO2
Authors: Edwards Arthur H.
Published: March 2011

In this paper we discuss recent advances in the theory of intrinsic defects in amorphous SiO2. We pay particular attention to the E' centers, and to the oxygen-related hole traps.
The Varied Causes of Color in Glass
Authors: Nassau K.
Published: March 2011

All but two of the fifteen physical and chemical mechanisms which are necessary to explain all the varied causes of color apply in one way or another to glass. These fifteen causes of color derive from a variety of physical and chemical mechanisms and are summarized in five groups with concentration on those mechanisms that apply to glass and the related glazes and enamels. Vibrations and simple excitations explain the colors of incandescence (e.g. flames, hot glass), gas excitations (neon tube, aurora), and vibrations and rotations (blue ice, water, glasses based on water). Ligand field effect colors are seen in transition metal compounds (turquoise, chrome oxide green, glasses based on copper sulfate) and impurities (ruby, emerald, many doped glasses). Molecular orbitals explain the colors of organic compounds (indigo, chlorophyll, organic glasses) and charge transfer compounds (blue sapphire, lapis lazuli, “beer-bottle” brown and chromate glasses). Energy bands are involved in the colors of metals and alloys (gold, brass, glassy metals), of semiconductors (cadmium yellow, vermillion, chalcogenide glasses), doped semiconductors (blue and yellow diamond), and color centers (amethyst, topaz, irradiated glass). Geometrical and physical optics are involved in the colors derived from dispersive refraction (rainbow, green flash, glass prism spectrum), scattering (blue sky, blue eyes, red sunset, ruby gold and opal glasses), interference (soap bubbles, iridescent beetles, cracks in glasses, interference filters), and diffraction (the corona aureole, diffraction grating spectrum).
The Mixed Alkali Effect in Sodium Rubidium Germanate Glasses
Authors: Mundy J. N. , Jin G.-L.
Published: March 2011

The lack of general applicability of the many theoretical models for the mixed alkali effect (MAE) in glasses is briefly reviewed. Although the MAE appears to be related to the bonding affinity of alkali ions to charge compensating centers in the glass network, experimental scatter and the difficulty of comparing different glass networks have prevented systematic tests of this relationship. The present paper discusses why the mixed alkali germanate glasses should provide a glass system where the concentration and strength of charge-compensating centers can be systematically varied and the relationship to the MAE tested. Such tests are only possible if the ionic conductivity of a series of mixed alkali germanate glasses can be measured in a reproducible manner. The measurements of the ionic conductivity of two series of X(Na,Rb)2O:(1-X)GeO2glasses, with X = 0.19 and X = 0.29, respectively, suggest the necessary reproducibility can be attained.
Computed Structures of [001] Symmetrical Tilt Boundaries in Covalently Bonded Materials
Authors: Wetzel J. T. , Levi A. A. , Smith D. A.
Published: March 2011

The dependence of the structure of (210) and (310) symmetrical [001] tilt boundaries in silicon, germanium and diamond on the Keating covalent force field (potential) has been investigated by computer modelling. We have found that the sensitivity of grain boundary structure to variations of the Keating potential depends on the local atomic arrangement at the grain boundary.
New Silicon (111) Surface (7×7) Reconstruction Benzene-Like Ring Model
Authors: Hao You Gong , Roth Laura M.
Published: March 2011

A new silicon (111) surface (7×7) reconstruction model is proposed. The model for the unit mesh consists of 13 benzene like rings formed by lowering triples of top layer atoms and 12 raised top layer atoms, with three of the rings combining to give depressed corners. The construction of the model is based on some considerations of the physical properties of the surface and on cluster calculations using the semi-empirical MNDOgeometrical optimization method. A cluster calculations with 9 silicon atoms gave the ring structure as an energy minimized result and also gives evidence that the two halves of the unit mesh should be at different height levels. A 13 silicon atom “flower” cluster calculation gave the height of the raised atoms to be .851A. The structure of the unit mesh resembles two types of (2×2) structure which can be formed from the rings and raised atoms (“flowers”), one of which is readily transformed into pi-bonded chain or molecular structures. The model gives a good qualititative account of the various hills and valleys seen in scanning tunneling microscopy, and since lateral displacement is small, it agrees with low energy channeling experiments. In addition good agreement with Cardillo s helium atom scattering experiment and Yang et al. s LEED experiment is found as the model has different heights for the two halves of the unit mesh and characteristics of a mixture of two types of structure.
Classical Two and Three-Body Interatomic Potentials for Silicon Simulations
Authors: Biswas R. , Hamann D. R.
Published: March 2011

We develop two and three-body classical interatomic potentials that model structural energies for silicon. These potentials provide a global fit to a database of firstprinciples calculations of the energy for bulk and surface silicon structures which spans a wide range of atomic coordinations and bonding geometries. This is accomplished using a new “separable” form for the 3-body potential that reduces the 3-body energy to a product of 2-body sums and leads to computations of the energy and atomic forces in n2 steps as opposed to n3 for a general 3-body potential. Simulated annealing is performed to find globally minimum energy states of Si-atom clusters with these potentials using a Langevin molecular dynamics approach.