bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Transformations on Aging Cu-Al-Ni β Phase Alloys
Authors: Husain S. W. , Clapp P. C. , Ahmed M.
Published: March 2011

The phase transformations occurring on quenching and subsequent aging of a Cu-Al-Ni β phase alloy have been studied using transmission electron microscopy, x-ray diffraction and optical microscopy. Quenching produces an ordered solid solution, β1, based on the DO3structure of Cu3A1. X-ray and electron diffraction show satellite diffraction peaks. On aging, these satellite peaks disappear and the parent phase undergoes a martensitic transformation. It is suggested that the parent phase undergoes a process of phase separation through the mechanism of spinodal decomposition before the martensitic transformation occurs. The martensitic transformation shows isothermal kinetics for which a transformation diagram is presented. Prolonged aging results in the formation of equilibrium phases.
Precipitation Hardening in The 90W-5Ni-5Fe Heavy Alloy
Authors: Posthill J.B. , Edmonds D.V.
Published: March 2011

Precipitation hardening in the W-phase of the 90W-5Ni-5Fe alloy has been identified and monitored by transmission electron microscopy and mechanical tests. Deformation of the alloy prior to aging is observed to accelerate the precipitation reaction. Possible precipitate origin and geometry are discussed in terms of the TEM observations.
The Influence of Oxygen-Rich Inclusions on the Nature of Austenite Decomposition Products of Weld Metal Deposits
Authors: Ferrante M. , Akune K.
Published: March 2011

Recent studies carried out on weld metal have called attention to the role of oxygen-rich inclusions on austenite decomposition. This investigation describes some evidences of the catalytic effect of dislocations upon the γ → α transformation. These defects are generated at the matrix inclusion interface and its presence has been ascertained by TEM. Estimates of the stresses arising from differences in thermal contraction between inclusion and matrix on cooling confirm microstructural observations.
The Effect of Step Quenching on the Kinetics of Bainite Formation in Ferrous Alloys
Authors: Umemoto M. , Igarashi M. , Tamura I.
Published: March 2011

The bainite reactions in the direct and in the step quenched conditions were compared using Fe–7.6Ni–0.48C and Fe–3.6Ni–1.45Cr–0.50C alloys. It was found that in both alloys the bainite reactions were markedly accelerated by step quenching to temperatures even in the stable austenite range prior to the transformation to bainite. Optical microscope observation revealed that this acceleration was caused by the enhanced nucleation of bainite at grain boundaries. This enhanced nucleation by step quench treatment was considered to be due to either the formation of carbon poor areas or the formation of ferrite embryos at the grain boundaries during holding at intermediate temperatures.
Phase Transition Between Matrix and Inclusions in Polymeric Composites
Authors: Theocaris P.S.
Published: March 2011

The influence of boundary layer on the coefficient of adhesion between fibers and matrix in polymer composites was investigated. A multilayer model was introduced consisting of the two main-phases of the composite,that is the elastic inclusion and the viscoelastic matrix and a third intermediate phase consisting of a series of cylindrical layers of mechanical and physical properties varying between the limit values of the matrix and inclusion. The extent of the interlayer between main phases may be determined from the overall properties of the composite and the matrix. The model proved to be very flexible and describes conveniently the behaviour of the material. Moreover, the model allowed the definition of an adhesion coefficient, convenient to describe the quality of adhesion of the component materials and the introduction of an improved expression for the law of mixtures in polymeric composites.
Structural Dynamics of Polymer Electrolytes
Authors: Nazri G-A. , MacArthur D.M. , O'Gara J.F.
Published: March 2011

The structure of polyethylene oxide doped with lithium perchlorate was studied. The macroscopic structure of the polymer-salt complexes was studied by thermal analysis and xray diffraction. The microscopic structure and polymer dynamics were studied by infrared, Raman and nuclear magnetic resonance spectroscopy. Thermal analysis and x-ray diffraction studies clearly revealed the change of crystalline phase to an amorphous phase by the addition of salt. The vibrational analysis showed a conformational transformation of the polymer chain by the addition of salt. Vibrational analysis also showed clearly the formation of free ion, ion-pair and salt cluster in the polymer as the concentration of the salt increased.
New Oxide-Ion Electrolytes
Authors: Goodenough J.B. , Zhen Y.S.
Published: March 2011

Strategic considerations for the design of new O2--ion solid electrolytes are presented, and preliminary measurements of the oxide-ion conductivity σo = (B/T) exp (-EA/kT) and transport number tO = σO/σ are reported for several oxides with perovsldte-related structures. Ba2In2O5 exhibits a first-order transition at Tt ∼ 930°C from the brownmillerite structure to a cubic perovskite with disordered oxygen vacancies and fast O2-ion conduction. Ba3In2MO8 (M = Ce, Zr, or Hf) contains oxygen vacancies ordered into every second BO2 (001) plane. An octahedralsite preference of the disordered M(IV) cations makes incomplete the oxygen-vacancy ordering, so a high extrinsic σo with EA ∼ 0.6 eV is found for T ≤ 400 °C. The transport properties of Ba3In2ZrO8 at 400 °C are equivalent to those of the stabilized zirconias at 800 °C. BagIn6O17 consists of an intergrowth of (BaO)2 rocksalt and Ba3In3O7.5 oxygen-deficient perovskite layers. Although there is no evidence of long-range ordering of the oxygen vacancies, nevertheless an EA = 1.06 eV and transport properties equivalent to stabilized zirconia indicate retention of short-range correlations to at least 950 °C. Attempts to prepare Bag Y6O17 yielded a mixture of hexagonal Ba3Y4O9 and unidentified phases. An EA = 0.45 eV above a Tt=370 °C gives a remarkable O2--ion conductivity at temperatures T > Tt in both the mixed-phase and pure Ba3Y4O9 at temperatures T > 370 °C, but the samples are extremely hygroscopic.
A Thin Film Solid State Nicrobattery for Use in Powering Nicrosensors
Authors: Jones Steven D. , Akridge James R. , Humphrey Susan G. , Liu Chung-Chiun , Sarradin J.
Published: March 2011

A thin film solid state microbattery has been used to power an O2 microsensor. The microbattery was fabricated using RF magnetron sputtering for the solid oxide/sulfide electrolyte and the TiS2 cathode. Vacuum evaporation was used for the deposition of LiI and Li anode. rhe microbattery is approximately 10 µm in thickness. The microbattery has an OCV of 2.4-2.5 V and shows close to 100% utilization to a 1.8 V cutoff when discharged between 10 and 135 µA/cm2. The microbattery is capable of supplying 2 second pulses of greater than 2 mA/cm2. The microbattery is rechargeable with over 200 cycles of 70% utilization to a 1.8 V cutoff at current densities up to 135 µA/cm2.

The O2 microsensor consists of a silk-screened Au working and Ag electrode. The Ag electrode was anodized to provide an Ag/AgCl counter electrode. The current produced at the sensor is proportional to the dissolved O2 concentration of an aqueous solution upon application of 0.6 V between the two electrodes.
Fundamental Considerations Relating to the Insertion of Hydrogen Isotopes into Mixed Conductors at High Activities
Authors: Huggins Robert A.
Published: March 2011

Some features of the electrochemical insertion of hydrogen isotopes into mixed conductors under dynamic electrolytic conditions are discussed. Unusual magnitudes of thermodynamic parameters in both the surface region and the bulk can be obtained under some conditions. These can vary greatly, depending upon the surface composition, as well as experimental conditions. It is thus possible to obtain species distributions and related phenomena inside solids during electrolysis at atmospheric pressure that are equivalent to those that would be present if there were a very high external pressure of one of the components.

The transport of hydrogen isotope interstitial species is very microstructure - dependent. Readily visible microstructural changes occur upon insertion and deletion of these species. This leads to the very sporadic nature of structure - dependent phenomena often observed. These considerations may play an important role in the apparent irreproducibility of experimental observations of the ‘cold fusion’phenomenon.
Ion Transport in Single Crystals of the Clay-Like Aluminosilicate, Vermiculite
Authors: Maraqah Hatem , Li Junxiang , Whittingham M. Stanley
Published: March 2011

We have made an investigation of the ion transport properties of single crystals of the naturally occurring clay vermiculite in order to elucidate the mechanism of conductivity including the predominant charge carrier. Measurements of the ion conductivity, magnetic susceptibility and x-ray lattice parameters of ion-exchanged samples strongly suggest that the native cations and not protons are the major current carriers. We have synthesized the hydrogen form and found that it is a much preferred precursor for ion-exchange by other cations allowing the time necessary for ion-exchange to be reduced from several months to around a week.
Optical Efficiency of the Electrochromic Windows Based on Solid Polymer Electrolytes
Authors: Shabrang M. , Murray D.P.
Published: March 2011

Interest in the electrochromics research in the 80's was mainly directed towards potential applications for variable light transmission windows. Even though large-area electrochromic cells incorporating liquid electrolytes are being investigated, we focused on solid state devices. Such devices offer fewer fabrication problems in large-area applications. The solid electrolyte layer is a key component in the fabrication of the solid state windows. This layer must be transparent, electrochemically stable and display adequate ionic conductivity. Optical efficiencies of asymmetric solid state devices based on tungsten oxide as the electrochromic material and commercially available ionomers and polyelectrolytes - Naflon, poly(styrene sulfonic acid), and poly(2-acrylamido-2-methylpropanesulfonic acid), as the solid electrolyte layer are presented at room temperature and 90 C. Impedance behavior of this asymmetric system is discussed and compared with the behavior observed in other systems.
Synthesis, Diffusion and Ion-Exchange in Open Structure Sodium Tungstates and Ybacu Tungstates
Authors: Reis Kenneth P. , Ramanan A. , Gloffke W. , Whittingham M. Stanley
Published: March 2011

Critical to the effectiveness of any solid state device is the reactivity of its components. In solid state ionics one desires certain atoms or ions to show high ionic mobility; yet, at the same time one does not want these atoms or ions to participate in side reactions. These reactions are a function of the crystalline structure of the material, of the way in which it was synthesized and of it's thermodynamic stability relative to the environment. This paper describes the synthesis of a variety of tungsten oxides which exhibit ionic mobility, and the determination of their crystalline structure and reactivity. The reactivity of the 123 superconductor with tungsten oxides is described in terms of the phases formed; none of these phases exhibited superconductivity. Both of these structurally related materials react with lithium and oxygen in a reversible manner, and these reactions are critically important in determining their properties and potential commercial application.
Electrochemical Modification of Bi2Sr2CaCu208+δ and La2CuO4
Authors: Scholz G.A. , Olfert M.
Published: March 2011

Semiconducting Bi2Sr2CaCu208 and La2CuO4 can be made superconducting following their oxidation in an electrochemical cell. Experimental evidence suggests that the deintercalation of copper, ie. the oxidation of the copper oxide planes is responsible. Intercalation, ie. reduction, reverses the above trends. The mechanism controlling superconductivity is therefore sensitive to the Cu/O ratio, which can be reversibly controlled at room temperature.
Diffusion in Materials with Ionic and Electronic Disorder
Authors: Maier Joachim
Published: March 2011

Besides some necessary reviewing of conventional diffusion theory, this paper deals with the modification of the mass and charge transport equations originating from the occurence of internal defect-chemical reactions (especially valence changes of the defects) which can be considered to be in local equilibrium. It is shown how the phenomenological transport coefficients for chemical diffusion, tracer diffusion and ionic conduction depend on the individual defect diffusivities under such general conditions. Moreover, the evaluation formulae of well-known electrochemical techniques such as Wagner-Hebb polarization and concentration cell experiments have to be modified. Application is made to the influence of trapping effects in doped SrTi03, to the valence changes in YBa2Cu3O6+x as well as to the mixed conduction in orthorhombic PbO.
Thin Film Amorphous Electrolytes: The Li2O-SiO2-P2O5 System
Authors: Bates J. B. , Dudney N. J. , Sales B. C. , Robertson J. D. , Zuhr R. A. , Gruzalski G. R. , Luck C. F.
Published: March 2011

Thin film amorphous electrolytes with compositions xLi2O:ySiO2:zP2O5 were deposited by single and dual source rf magnetron sputtering and their compositions determined by electron and ion beam techniques. Films containing P but no Si were composed of mainly orthophosphate and some linear chain phosphate anions, whereas single phase films containing Si and P were evidently composed of branched and possibly cyclic and extended network structures. Films with Si/P > 1 appeared to contain two or more amorphous phases. In the range of compositions investigated, the lithium ion conductivity depends mainly on the lithium ion mobility which is sensitive to the structure of the films. An open circuit voltage from 1 to 3 V measured between blocking metal contacts on the electrolyte thin films suggests that the films mightbe electrets.
Spuiter Deposition of Lithium Silicate — Lithium Phosphate Amorphous Electrolytes
Authors: Dudney N. J. , Bates J. B. , Robertson J. D. , Luck C. F.
Published: March 2011

Thin films of an amorphous lithium-conducting electrolyte were deposited by rf magnetronsputtering of ceramic targets containing Li4SiO4and Li3PO4. The lithium content of the films was found to depend more strongly on the nature and composition of the targets than on many other sputtering parameters. For targets containing Li4SiO4, most of the lithium was found to segregate away from the sputtered area of the target. Codeposition using two sputter sources achieves a high lithium content in a controlled and reproducible film growth.
Ionic Displacements and Piezoelectric Constants of AgGaS2 from X-Ray Diffraction of a Crystal in an External Electric Field.
Authors: Graafsma Heinz , Majewski Jarek , Cahen David , Coppens Philip
Published: March 2011

We have determined the displacements of the ions and the changes in cell parameters which occur on application of an electric field to a crystal of AgGaS2, using a three-step modulation method. The shifts in Bragg angle of 14 reflections, due to a fieldof 2.6 x 106 V/m applied nearly parallel to [221], were used to refine the change in cell parameters. The resulting piezo-electric coefficients are d14=d25 =8.8 (0.9) 10-12 C/N and d36=7.6 (1.8) 10-12 C/N. This leads to a value of 4.8 (0.5) pC/Nfor the piezoelectric constant in the [221] direction which compares well with a value of 5-6 10-12 C/N determined by other methods. The ionic displacements were studied on a second sample, with E=2.6x 106 V/m in adirection parallel to [110]. Very small, but significant a and b directiondisplacements were observed for all atoms, whereas the displacements in the c direction were negligible as expected. Relative to the sulfur framework, the Ga ion displacement is considerably larger than that of the Ag ions.
Simultaneous Measurement of the Electronic and Ionic Conductivity of a Solid Electrolyte
Authors: Riess I. , Safadi R.
Published: March 2011

We describe a method for a simultaneous measurement of the total and electronic conductivities of solid electrolytes (SE). The total conductivity is determined by a four probe method and the electronic (electron/hole) conductivity is determined simultaneously by a two probe method, for samples having the van—der—Pauw configuration.
A Study of the Optical Band Gap of Lithium Tungsten Trioxide Thin Films
Authors: Berera G. , Goldner R.B. , Amtz F.O. , Wong K.K. , Ciaccia A. , Welch M. , Haas T.E. , Jauniskis L.
Published: March 2011

The insertion of lithium (lithiation) into tungsten trioxide results in the formation of the tungsten bronze LixWO3. Polycrystalline, rf sputter deposited thin films of LixWO3 were investigated for their application in Smart Window Devices. The optical band gap studies of these films revealed the narrowing of the intrinsic band gap as a consequence of lithium insertion. The results suggest that the rigid band model, which is generally adopted in interpreting the electronic structure of the tungsten bronzes may not be applicable in Lix WO3.
Technical Bases for the Dwpf Testing Program
Authors: Plodinec M. J.
Published: March 2011

The Defense Waste Prsocessing Facility (DWPF) at the Savannah River Site (SRS) will be the first production facility in the United States for the immobilization of high-level nuclear waste. Production of DWPF canistered wasteforms will begin prior to repository licensing, so decisions on facility startup will have to be made before the final decisions on repository design are made. The Department of Energy’s Office of Civilian Radioactive Waste Management (RW) has addressed this discrepancy by defining a Waste Acceptance Process. This process provides assurance that the borosilicate-glass wasteform, in a stainless-steel canister, produced by the DWPF will be acceptable for permanent storage in a federal repository. As part of this process, detailed technical specifications have been developed for the DWPF product.

SRS has developed detailed strategies for demonstrating compliance with each of the Waste Acceptance Process specifications. An important part of the compliance is the testing which will be carried out in the DWPF. In this paper, the bases for each of the tests to be performed in the DWPF to establish compliance with the specifications are described, and the tests are detailed. The results of initial tests relating to characterization of sealed canisters are reported.
UO2. Matrix Dissolution Rates and Grain Boundary Inventories of Cs, Sr, and Tc in Spent Lwr Fuel
Authors: Gray W. J. , Strachan D. M.
Published: March 2011

Experimental methods have been developed for measuring the grain-boundary inventories of radionuclides and for determining whether the UO2 matrix of spent light-water reactor fuel dissolves congruently. Both methods depend upon first separating the fuel into individual grains. With the grain boundaries thus exposed, the associated inventories of radionuclides can be completely dissolved and measured. To determine whether the UO2 matrix of spent fuel dissolves congruently, the fuel grains were placed in a flow-through column and water was pumped through the column at a rate sufficient to maintain the concentration of U in the column effluent far below saturation. Once the grain-boundary material has dissolved, the forward dissolution rate of the UO2 matrix can be measured and, by measuring the concentrations of other radionuclides in the column effluent, the degree of congruency of the dissolution process can be determined. Data obtained to date indicate that the grain-boundary inventories of Cs, Tc, and Sr are approximately equal to gap inventories and that the fractional dissolution rate of Cs from the U02 matrix is approximately equal to that of U, i.e., the Cs and U dissolved nearly congruently. In addition, the data appear to show a gradient in the concentrations of Cs and Sr across the individual UO2 grains.
Radiation Induced Dissolution of UO2
Authors: Christensen Hilbert
Published: March 2011

In order to be able to model the effect of water radiolysis on the dissolution of fuel in the disposal vault it is essential to study the oxidation mechanism. Radiolysis of water produces radicals and molecules, amongst them the oxidizing species H2O2 and OH radicals, and, in aerated solutions, O2- as well. These species are probably responsible for the oxidation and dissolution of UO2 observed in a number of experiments. In the present investigation the effect of the oxidizing species has been studied separately using suitable scavengers. A polished specimen of UO2 was immersed in water and irradiated at ambient temperature with Co-60 gamma radiation. After irradiation the amount of uranium which had dissolved, or deposited elsewhere than the sample surface, was measured, and the oxidation of the surface was determined, using ESCA and SIMS. In 50 mM H2O2 (without irradiation) the corrosion rate was 5±3 μg.cm−2d−1 after 6 d exposure at pH 8. Corresponding rates for oxidation by O2- and OH radicals were about 3 μg.cm−2d−1, (dose rate 600±90 Gy/h.)
The Solubility of Unirradiated UO2In Both Perchlorate And Chloride Test Solutions. Influence of the Ionic Medium
Authors: Torrero M. E. , Casas I. , Aguilar M. , De Pablo J. , Gimenez J. , Bruno J.
Published: March 2011

The solubility of a crystalline unirradiated UO2(s) has been studied under reducing conditions at 25°C in three different ionic media: 0.008 mol dm–3NaCIO4, 1 and 5 mol dm-3NaCl+. The species responsible for the solubility in perchlorate medium are U(OH)3and U(OH)4, with the stability constants log β13= -0.4(±0.2) and log β14= -5.7(±0.1), respectively. The solubility in both1! and 5 M chloride media is explained at pH values higher than 6 by the species U(OH)4with log β14= -5.5(±0.2) while at lower pH values an abnormal behaviour is observed, with higher uranium concentrations in solution and a proton independent solubility for pH values lower than 4. The XPS observations of the reacted solids do not show the presence of solid surface phases other than uranium dioxide, with an upper oxidation state of UO2.1.
Effect of Compacted Bentonite on the Corrosion behavior of Carbon Steel as Geological Isolation Overpack Material
Authors: Honda A. , Teshima T. , Tsurudome K. , Ishikawa H. , Yusa Y. , Sasaki N.
Published: March 2011

The corrosion rate of carbon steel in compacted bentonite was evaluated with regard to the test period length, temperature, chemicals of solution and bulk density of compacted bentonite.

The average corrosion rate decreased gradually with increasing test period up to 180 days in immersion tests. The corrosion rate of carbon steel in compacted bentonite at a dry density of 1.32g/cm3 was estimated to be about 0.01 mm/y which was one order of magnitude lower than that in bentonite slurry. No significant influence of temperature on corrosion rates was observed in compacted bentonite in the range of 50∼180 °C. Variation of kinds and concentration of anion(chloride, floride, sulfate, and carbonate)in aqueous solution did not have much influence on the corrosion rate of carbon steel.

Immersion tests of carbon steel in compacted bentonite at a dry density of 0.69 ∼ 1.32 g/cm3, which was mixed with an aqueous solution(synthetic sea water and distilled water), were carried out. The corrosion rate in compacted bentonite decreased from 0.04 to 0.005mm/y as the density of bentonite increased.

This result suggests that the corrosion rate of carbon steel in compacted bentonite is governed by the diffusivity of corrosive materials. In general, oxygen is the dominate factor affecting corrosion rate, therefore prediction of the average corrosion rate of carbon steel was carried out on the basis of the diffusion behavior of dissolved oxygen in compacted bentonite. The prediction agreed with experimental results.
Overview of Chemical Modeling of Nuclear Waste Glass Dissolution
Authors: Bourcier William L.
Published: March 2011

Glass dissolution takes place through metal leaching and hydration of the glass surface accompanied by development of alteration layers of varying crystallinity. The reaction which controls the long-term glass dissolution rate appears to be surface layer dissolution. This reaction is reversible because the buildup of dissolved species in solution slows the dissolution rate due to a decreased dissolution affinity. Glass dissolution rates are therefore highly dependent on silica concentrations in solution because silica is the major component of the alteration layer.

Chemical modeling of glass dissolution using reaction path computer codes has successfully been applied to short term experimental tests and used to predict long-term repository performance. Current problems and limitations of the models include a poorly defined long-term glass dissolution mechanism, the use of model parameters determined from the same experiments that the model is used to predict, and the lack of sufficient validation of key assumptions in the modeling approach. Work is in progress that addresses these issues.
Corrosion Products And Mechanisms in Long-Term Corrosion of Copper
Authors: McNeil M. B. , Little B. J.
Published: March 2011

Copper and copper alloys are frequently used in environments where short-term laboratory testing indicates that they should be resistant to corrosion. However, in long-term service, copper and its alloys show degradation mechanisms which have not been replicated in the laboratory. In this paper, corrosion mechanisms for copper alloys will be examined from the standpoint of corrosion product thermodynamics and corrosion kinetics, with particular reference to microbiologica11y influenced corrosion (MIC). Comparison will be made to the corrosion behavior of high-iron and high-nickel alloys.
An Advanced Cold Process Canister Design for Nuclear Waste Disposal
Authors: Raiko Heikki , Salo Jukka-Pekka
Published: March 2011

An advanced cold process canister design, ACPC-design, is introduced in this paper. The cold process canister consists of a steel canister as a load bearing element, with an outer corrosion shield of copper, Fig. 1 - Fig. 4. The canister will be rilled with granular material, such as lead shots, glass beads or quartz sand.

The conditions for the canister design are presented: dimensioning against radiation, allowed heat loads, strains, corrosion and leak tightness etc. The mechanical dimensioning of the copper/steel canister is made according to the Finnish standards (SFS) for pressure vessels.
Stainless Steel Welds in Containers of Nuclear Waste
Authors: Menendez H. A. , Willis C. F. , Devine T. M.
Published: March 2011

The as-welded microstructure of 308 stainless steel is usually a mixture of austenite and ferrite phases. The morphology of the duplex structure is a function of the composition of the weld. The resistance to sensitization is proportional to the amount and distribution of austenite-ferrite boundary area and the probability of precipitation of embrittling phases such as σ and α′ is proportional to the volume fraction of ferrite phase. Consequently, the properties of 308 stainless steel welds are strong functions of their microstructures. These, in turn, are primarily determined by the composition of the weld. Accordingly, to maximize the properties of welds of canisters of nuclear waste may require a restriction of the compositional limits of 308 stainless steel in order to preclude the formation of microstructures that are particularly susceptible to sensitization and/or mechanical embrittlement.
R7T7 Glass Initial Dissolution Rate Measurements Using a High-Temperature Soxhlet Device
Authors: Delage Fabienne , Dussossoy J.L.
Published: March 2011

The corrosion of glasses in aqueous media is described by the general rate equation proposed by Grambow. In its simplest form, this equation may be written as: V = Vo [1-a(H4SiO4)/a*(H4SiO4)]. The purpose of this investigation was to measure the initial dissolution rate (Vo) of R7T7 nuclear waste glass at temperatures between 90 and 250°C, and to determine activation energies of reaction.

Leaching solutions were maintained far from equilibrium using a dynamic leaching apparatus: the High-Temperature Soxhlet device. The corrosion rates were defined by weight loss measurements and by silicon, boron, sodium and lithium analysis in the leachate. Throughout the test temperature range, the normalized mass losses were linear with time. The initial dissolution kinetics calculated from weight loss (before and after scraping off the surface layer) and from Si, B, Na and Li release, followed an Arrhenius relation. Activation energies range from 58 to 60 kJ·mol−1 depending on the element. This slight discrepancy is attributed to a more pronounced retention factor for certain elements In the alteration layer as the temperature rises. The mean activation energy of reaction (about 59 kJ·mol−1) Is typical of a surface-controlled reaction. This energy is unique in the temperature range investigated.
Hygrothermal Performance of an Engineered Clay Barrier
Authors: Selvadurai A.P.S. , Cheung S.C.H.
Published: March 2011

A series of laboratory experiments was conducted to establish the heat-induced moisture movement in a bentonitic clay buffer. The buffer material is proposed as an engineered barrier to isolate a heat-emitting high-level nuclear fuel waste container from its emplacement borehole located in a deep rock repository. In the experimental simulation, the hygrothermal phenomena are initiated by a cylindrical heater placed within the compacted buffer material in a borehole centrally located in a granite block. The experimental results illustrate the time-dependent distribution of temperatures within the rock mass and the residual moisture distribution at the termination of the experiment.
Compression Behaviour of Clay-Based Backfill Under Large Hydraulic Loading
Authors: Chan H.T. , Crawford A.M. , Lau K.C.
Published: March 2011

A one-dimensional analytical model has been developed to describe the compressive behaviour of clay-based shaft backfills under large hydraulic loads. The analytical model has been calibrated with results from a compression test on a partially saturated swelling clay backfill mix in the high-pressure compression cell constructed at Ontario Hydro.
The Application of Positron Emission Tomography to the Study of Mass Transfer in Fractured Rocks
Authors: Gilling D. , Jefferies N. L. , Fowles P. , Hawkesworth M. R. , Parker D. J.
Published: March 2011

Water flow in hard rocks takes place dominantly in fractures. In order to predict the transport of dissolved radioelements through a fractured rock it is necessary to take into account both the geometry of the fracture network and the hydraulic properties of the individual fractures. This paper describes a technique for studying mass transfer in a single fracture. The technique is positron emission tomography (PET) and it offers the potential for visualising quantitatively the migration of dissolved tracers. Preliminary experiments have been undertaken involving the flow of Na-22 and F-18 labelled solutions through artificial fractures. The results demonstrate that PET is well suited to this application.
Nonideality Effects on the Ion Exchange Behavior of the Zeolite Mineral Clinoptilolite
Authors: Pabalan Roberto T.
Published: March 2011

The presence of laterally-extensive zones of zeolitized tuff underlying the proposed high-level nuclear waste repository at Yucca Mt., Nevada, has focused attention on the potential role of zeolite minerals, particularly clinoptilolite, in sorbing radionuclides and thereby retarding their migration. Ion exchange between zeolites and aqueous solutions depends on factors including compositions of the aqueous and zeolite phases and solution concentration. In addition, the thermodynamic stability of zeolite minerals and their susceptibility to diagenetic alteration also depend on aqueous and solid phase compositions. Therefore, spatial variations in zeolite compositions which have been observed at Yucca Mt., as well as natural or repository-induced changes in groundwater chemistry, may result in variations in the effectiveness of the zeolite minerals as retardation agents.

Ion exchange experiments were conducted to obtain isotherm data and to evaluate the use of thermodynamic models in describing and predicting the solid solution and ion exchange properties of clinoptilolite. The experimental data were interpreted using excess Gibbs energy models for the aqueous solution and zeolite phases to account for nonideality in the system. The results indicate that the thermodynamic models allow predictions of clinoptilolite ion exchange behavior at ionic strengths and relative concentrations for which data are absent, and provide a foundation for the interpretation of ion exchange equilibria in multicomponent geochemical systems.
Hydrolysis of R7T7 Nuclear Waste Glass in Dilute Media: Mechanisms and Rate as a function of Ph
Authors: Advocat T. , Crovisier J. L. , Vernaz E. , Ehret G. , Charpentier H.
Published: March 2011

R7T7 nuclear waste glass dissolution in highly dilute aqueous media under static conditions at 90°C occurs according to two different mechanisms depending on the solution acidity. In acid media (pH 4.8 and 5.5), preferential extraction of glass network modifiers results in the formation of an alkali metal-depleted surface region on which amorphous and crystallized (phosphate) compounds rich in transition elements precipitate. Steady-state dissolution conditions are not reached, as attested by variable normalized SI, B and Na mass losses. Glass dissolution is stoichiometric in basic media (pH 7 to 10): the strong bonds of the silicated network are broken at a rate that increases with the pH: the glass dissolution rate increases by a factor of 15 between pH 7 and 10. Under these conditions, alteration products at the glass/solution interface do not constitute a short-term kinetic barrier against the release of the major glass components.
Diffusion Porosity and Diffusivity of Radionuclides in Granitic Rocks. Part II: Diffusivity and Electrical Resistivity Measurements in Rock Matrix Around Fractures
Authors: Kumpulainen Heikki , Muurinen A. , Uusheimo K.
Published: March 2011

The microfracturing of rock matrix around fractures was studied experimentally by determining the diffusion properties of a non-sorbing tracer. The diffusivities were measured by tracer techniques using 36C1 isotope as a tracer and 0.0044 M or 1 M NaCl solutions. The diffusivities were also determined by measuring the electrical resistivities of the samples saturated with 1 M NaCl solution. The rock samples were granite around a partially filled carbonate fracture and gneiss around a slickenside fracture.

The apparent diffusivities of all the studied samples were approximately of the same order of magnitude. None of the variables, i.e. salt concentration of the solution, rock and fracture type or distance from the fracture surface, had any significant effect on the apparent diffusivities.

The effective diffusivities and porosities, on the other hand, depended strongly on the salt concentration of tha water used to saturate the rock samples. Possible reasons for this could be the alteration of the pore structure or change of the electrical double layer during the saturation of the rock with strong NaCl solution.
Migration of Radionuclides in Fracture Columns
Authors: Hölttä Pirkko , Hakanen Martti , Hautojärvi Aimo
Published: March 2011

Radionuclides transported by ground water flowing through fractures may be delayed by interactions with the fracture surfaces. The migration of radionuclides in fractures was studied under well defined laboratory conditions using tonal-ite drill core columns with a fracture running parallel to the core axis. The hydrodynamic characterization of the columns was performed using tritiated water, pertechnetate and chloride ions as non-sorbing tracers. Strontium and neptunium were used to study the retardation of radionuclides on the fracture surfaces.

The experimental set-up is described, and break-through curves of non-sorbing tracers, strontium and neptunium are presented. The results were interpreted using models for dispersion and diffusion into the rock matrix. From the shape of the break-through curves it was concluded that for non-sorbing tracers there was very little or no diffusion at all into the rock matrix. Retardation of strontium in a column with intact tonalite surfaces indicated a Ka factor identical with that earlier determined by batch experiments. The break-through curve of neptunium indicated a non-sorbing fraction.
Radioactive Tracer Study Performed in a Dipole Geometry in a Highly Conductive Fracture Zone
Authors: Byegård Johan , Skarnemark Gunnar , Skålberg Mats
Published: March 2011

A radioactive tracer experiment has been performed in a highly conductive fracture zone, using a dipole geometry. Anions (131I− and 82Br−) and complexed metal ions (51Cr-EDTA, 58Co-EDTA, 111In-EDTA, 140La-DOTA, 160Tb-EDTA, 169Yb-EDTA and 177Lu-DOTA) have been injected and their properties as non-sorbing tracers were evaluated. Besides, studies of slightlysorbing cations (24Na+, 58Co2+, 86Rb+ and 201T1+) were performed. 99mTcO4 and its chemical analogue 186ReO4 were also injected to study the behaviour of Tc at low redox-potentials. Breakthrough was obtained for Re and for all metal complexes and anions. Some differences in the recovery yields could be seen. No transport of cations, except for Na, could be measured. No breakthrough of Tc could be observed. This indicates that TcO4− was reduced and sorbed.
Assessing the Natural Performance of Felsic Tuffs Using the Rb-Sr and Sm-Nd Systems-A Study of the Altered Zone in the Topopah Spring Member, Paintbrush Tuff, Yucca Mountain, Nevada
Authors: Peterman Zell E. , Spengler Richard W. , Futa Kiyoto , Marshall Brian D. , Mahan Shannon A.
Published: March 2011

Core samples of the Topopah Spring Member of the Paintbrush Tuff from drill hole UE25A#1 were analyzed for Sr and Nd isotopes and selected minor and trace elements to constrain the origin of a zcolitized zone associated with the lower vitrophyre. The Sm-Nd radiogenic isotope system was unperturbed by the alteration, but the Rb-Sr system was severely disturbed in the altered zone. The thick, densely welded high-silica rhyolite is remarkably uniform in composition with only a slight decrease in initial 87Sr/86Sr ratios with depth (0.7129–0.7125). Quartz latite in the upper part of the Topopah Spring has significantly lower initial Sr isotope ratios (0.7095–0.7114). Locally in the altered zone, Sr and Ca were gained in substantial amounts, and K, Rb, and Y were removed. Ti, Zr, Nb, Ba, La, Ce, Sm, and Nd were relatively immobile during the alteration. Sr added to the altered zone had an isotopic composition of 0.7119 ± 0.0002 and was probably derived from dissolution of glass in the bulk Topopah Spring (high silica rhyolite + quartz latite) and transported downward by infiltration.
Natural-Analog Studies for Partial Validation of Conceptual Models of Radionuclide Retardation at the Wipp
Authors: Ward David B. , Brookins Douglas G. , Siegel Malcolm D. , Lambert Steven J.
Published: March 2011

Transport by groundwater within the Culebra Dolomite, an aquifer above the Waste Isolation Pilot Plant (WIPP), is the most probable mechanism for long-term release of radionuclides to the accessible environment. Radionuclides could be retarded by sorption if the groundwater is exposed to sufficient amounts of fracture-lining clays. In this natural-analog study, distributions of U and trace metals have been examined to constrain the strength of clay/solute interactions within the Culebra.

Uranium solid/liquid distribution ratios, calculated from U concentrations of groundwaters and consanguineous fracture-filling clays, range from ∼80 to 800 mℓ/g and imply retardation factors of 60 to 500 using a fracture-flow model. Retardation factors inferred from uranium-series disequilibria and 14C ages in Culebran groundwaters alone are much lower (∼10), implying that clays may contain a significant unreactive component of U. Such a possibility is corroborated by Rb/Sr ages; these imply long-term stability of the clays, with resetting occurring more than 250 Ma ago. Factor analysis and mass-balance calculations suggest, however, that Mg-rich clays are dissolving in Pleistocene-age groundwaters and/or are converting to Na-rich smectites, and that B and Li are taken up from the water by the clays. Apparently, the solution chemistry reflects gradual equilibration of clays with groundwater, but thus far the bulk of the clays remain structurally intact. Measurements of the distribution of U in the Culebra will be more meaningful if the inert and exchangeable components of the U content of the clays can be quantified.
Radionuclides in Hydrothermal Systems as Indicators of Repository Conditions
Authors: Wollenberg H.A. , Flexser S. , Smith A.R.
Published: March 2011

Hydrothermal systems in tuffaceous and older sedimentary rocks contain evidence of the interaction of radionuclides in fluids with rock matrix minerals and with materials lining fractures, in settings somewhat analogous to the candidate repository site at Yucca Mountain, NV. Earlier studies encompassed the occurrences of U and Th in a “fossil” hydrothermal system in tuffaceous rock of the San Juan Mountains volcanic field, CO. More recent and ongoing studies examine active hydrothermal systems in calderas at Long Valley, CA and Valles, NM. At the Nevada Test Site, occurrences of U and Th in fractured and unfractured rhyolitic tuff that was heated to simulate the introduction of radioactive waste are also under investigation. Observations to date suggest that U is mobile in hydrothermal systems, but that localized reducing environments provided by Fe-rich minerals and/or carbonaceous material concentrate U and thus attenuate its migration.
The Redistribution of Uranium Series Radionuclides at Koongarra
Authors: Edis Robert
Published: March 2011

The distribution of 238U, 234U, 230Th and 236Ra in rocks from the Koongarra uranium deposit has been examined. Alpha-spectrometry and ICP-MS were used to estimate elements in “accessible” and “inaccessible” phases, separated by a two-phase extraction scheme; and bulk analyses of visibly distinct zones were made using PIXE-PIGME, DNAA and XRF.

The secondary U dispersion fan of the Koongarra site is characterised by 234U/238U, 230Th/234U and 236Ra/230Th activity ratios (ARs) below unity in the extractable (accessible) phases, and above unity in the non-extractable (inaccessible) phases. The patterns of the ARs suggest zones of different U deposition and leaching rates with the most rapid accumulation at the base of weathering, especially at the extremities of the dispersion fan.
Effects of Chlorite Alteration on Uranium Redistribution in Koongarra, Australia
Authors: Murakami Takashi , Isobe Hiroshi , Edis Robert
Published: March 2011

The relevance of alteration of chlorite, one of the major constituent minerals of the host rock to uranium ore at Koongarra, to the redistribution of uranium in the vicinity of the ore deposit has been examined. The chlorite alteration is produced by weathering; chlorite is transformed to vermiculite, through regularly interstratified chlorite/vermiculite. The Fe released from chlorite reprecipitates to form iron minerals, possibly ferrihydrite. Vermiculite is then replaced by kaolinite (and possibly smectite), further releasing Fe. On the millimeter scale, an alpha autoradiography study has shown that uranium concentrations are qualitatively proportional to the extent of the alteration; altered chlorite grains having higher uranium concentration. On the meter scale, the X-ray diffraction study has revealed that the abundances of chlorite, vermiculite, and kaolinite correspond well to the low, intermediate, and high uranium concentration zones, respectively. These suggest that the interaction of the uraniferous solution with chlorite causes the alteration of chlorite and the precipitation and sorption of uranium in the alteration products from the solution, and thus, the uranium migration is retarded at Koongarra.
Quantitative Interpretation of Halogen Porewater Concentration Profiles in Lake Sediments
Authors: Eberhard Falck W. , Hooker Paul J.
Published: March 2011

Halogen ion migration through clay-rich sediments is particularly well documented in cores from Loch Lomond, Scotland, where distinctive patterns for CI, Br and I have been observed. The sediments are a sequence of marine and limnic silts and clays which cover glacial deposits. The marine band, resulting from a transgression 6900 y B.P. to 5400 y B.P., acts as a source for the halogens.

A 1-D conceptual model and code has been developed taking into account variations in the concentration boundary conditions and the accumulation of sediments. The model has been calibrated against the CI concentration distributions for which boundary conditions can be estimated readily.

The model has been applied to Br and I profiles. Deviations between the Cl-calibrated model and the measured profiles were attributed to reactive processes. Release rates from the marine band for Br and I are deduced. Their sensitivity with respect to system properties, assumptions over boundary and initial conditions and reaction mechanisms is discussed.
Three-Dimensional Visualization: Breakthrough in Analysis and Communication of Technical Information for Nuclear Waste Management
Authors: Alexander Donald H. , Hill E. Richard , Smoot John L. , Smith Dennis R. , Waldo Karen , Cerny Barbara A. , Krupka Kenneth M.
Published: March 2011

Computer graphics systems that provide interactive display and manipulation of three-dimensional data are powerful tools for the analysis and communication of technical information required for characterization and design of a geologic repository for nuclear waste. Greater understanding of site performance and repository design information is possible when performance-assessment modeling results can be visually analyzed in relation to site geologic and hydrologic information and engineering data for surface and subsurface facilities. In turn, this enhanced visualization capability provides better communication between technical staff and program management with respect to analysis of available information and prioritization of program planning.

A commercially-available computer system was used to demonstrate some of the current technology for three-dimensional visualization within the architecture of information systems for nuclear waste management. This computer system was used to interactively visualize and analyze the information for two examples: 1) site-characterization and engineering data for a potential geologic repository at Yucca Mountain, Nevada; and 2) three-dimensional simulations of a hypothetical release and transport of contaminants from a source of radionuclides to the vadose zone. Users may assess the three-dimensional distribution of data and modeling results by interactive zooming, rotating, slicing, and peeling operations. For those parts of the database where information is sparse or not available, the software incorporates models for the interpolation and extrapolation of data over the three-dimensional space of interest.