bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractWe 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

AbstractWe 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

AbstractThe 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

ABSTRACTThe 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

ABSTRACTExperimental 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

ABSTRACTIn 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTGlass 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

ABSTRACTCopper 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

ABSTRACTAn 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTA 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

ABSTRACTA 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

ABSTRACTWater 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

ABSTRACTThe 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

ABSTRACTR7T7 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

ABSTRACTThe 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

ABSTRACTRadionuclides 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

ABSTRACTA 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.