bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and Electronic Transitions in AgReO4 Under Pressure
Authors: Vassiliou John K. , Otto Jens W. , Porter Richard F. , Ruoff Arthur L. 
Published: March 2011

AbstractThe behavior of AgReO4 under pressure has been studied in a diamond anvil cell. The equation of state determined by synchrotron radiation shows considerable change in compressibility with increasing pressure. X-ray and Raman scattering show a first-order phase transition from the scheelite to an as yet undetermined structure at 13 GPa. Changes in both the internal and external Raman active modes suggest a change in Re coordination. Optical transmission experiments demonstrate that the energy gap in the scheelitephase decreases at the rate of 75 meV/GPa. There is a small jump in the energy gap at 13 GPa, probably related to the structural transition. AgReO4 remains aninsulator to at least 47 GPa.
A Novel Fast Lithium—Ionic Conductor.
Authors: Moreno-Real L. , Ramirez-Cardenas T. , Bruoue S. , Martinez-Lara M. , Ramosbarrado J.R. 
Published: March 2011

AbstractThe lithium derivatives from anhydrous niobium (Y) phosphate were made through NbOPO4.H20 and LiCl by solid state reaction at 200 ºC and subsequentannealed at 500ºC. The solid with the highest lithium content, exhibits the maximum conductivity of all materials prepared. The electrical conductivity of this solid ranges from 10-10 Ω-1 cm-1 at 373K to 3.62.10-3Ω-1cm-1 at 683K.
Preparation and Discharge Characteristics of Solid Redox Polymerization Electrodes Employing Disulfide Polymers and Copolymers.
Authors: Lerner M. M. , Visco S. J. , Ue M. , Doeff M. M. , Dejonghe L C. 
Published: March 2011

AbstractRecent work in our laboratory on polymeric organodisulfides has shown these materials to perform well as positive electrodes in solid-state batteries. The polymeric materials have been named solid redox polymerization electrodes (SRPE's) due to the reversible polymerization/depolymerization reaction that occurs on charge/discharge of the electrode. The cell reaction for SRPE-based cells can be described fora simple case as, 2n M + (SRS)n = n M2SRS, where M is an alkali metal (LiNaK) and R is an organic group. In the broader sense SRPE's can have more than two S groups per monomer R unit, and are reversible to other monovalent and divalent metals. In thefully charged state SRPE's consist of polydisulfide polymers and are depolymerized on discharge by scission of sulfur-sulfur bonds, leading to the formation of dithiolate salts in the fully discharged cell. SRPE's are easy to synthesize, are air stable, and should be very inexpensive in bulk quantities. Depending on the redox potential of the polydisulfide and reaction conditions, manydisulfides can be copolymerized by oxidizing a mixture of dithiols, x HSRSH + y HSR'SH + (x+y) l2 = (SRS)x(SR'S)y + 2(x+y) HI, allowing modification of the physical and/or redox properties of the SRPE's. A series of simple aliphatic dithiols including (HSCH2CH2SH), (HSCH2CH2OCH2CH2 SH), and (HSCH2CH2SCH2CH2SH) have been oxidized to polydisulfides and mixtures of the dithiols have been copolymerized. All of the resulting polymers and copolymers were evaluated in solid-state lithium cells, with some of the new materials demonstrating high levels of performance. The utilization of available capacity in the positive electrode was observed to be independent of electrode thickness for a number of SRPE's at loading levels up to 45% by weight. At 90°C, relatively thick positive electrodes based on (SCH2CH2S)n have been discharged to surface capacities of over 20 coulombs/cm2 at a current density of 0.5 mA/cm2. The discharge profiles for most of the aliphatic polydisulfides are exceedingly flat at slightly over 2 volts versus lithium. Although other polydisulfides such as those derived from the dithiazoles exhibit higher cell voltages, the low equivalent weight of materials such as (SCH2CH2S)n [46 g/equiv] and the low cost of such polymers indicates a potential for commercial application.
Theoretical Aspects of Non-Debye Relaxation in Ionic Conductors
Authors: Dieterich Wolfgang , Loehle B. , Petersen J. , Stiller O. 
Published: March 2011

AbstractTracer diffusion as well as collective transport properties of ionic conductors are investigated within a lattice-gas model of charged particles. Results obtained from Monte Carlo simulations support the conclusion that the interplay of Coulomb-interactions among diffusing ions and structural disorder in the material provides a general mechanism for non-Debye relaxational effects commonly observed by experiment.
Mineralogical, Textural and Compositional Data on the Alteration of Basaltic Glass From Kilauea, Hawaii to 300°C: Insights to the Corrosion of a Borosilicate Glass Waste-Form
Authors: Smith David K. 
Published: March 2011

ABSTRACTMineralogical, textural and compositional data accompanying greenschist facies metamorphism (to 300°C) of basalts of the East Rift Zone (ERZ), Kilauea, Hawaii may be evaluated relative to published and experimental results for the surface corrosion of borosilicate glass. The ERZ alteration sequence is dominated by intermittent palagonite, interlayered smectite-chlorite, chlorite, and actinolite-epidote-anhydrite. Alteration is best developed in fractures and vesicles where surface reaction layers root on the glass matrix forming rinds in excess of 100 microns thick. Fractures control fluid circulation and the alteration sequence. Proximal to the glass surface, palagonite, Fe-Ti oxides and clays replace fresh glass as the surface reaction layer migrates inwards; away from the surface, amphibole, anhydrite, quartz and calcite crystallize from hydrothermal fluids in contact with the glass. The texture and composition of basaltic glass surfaces are similar to those of a SRL-165 glass leached statically for sixty days at 150°C. While the ERZ reservoir is a complex open system, conservative comparisons between the alteration of ERZ and synthetic borosilicate glass are warranted.
Effects of Composition Variations on Microstructure and Chemical Durability of West Valley Reference Glass.
Authors: Buechele A. C. , Feng X. , Gu H. , Muller I. S. , Wagner W. , Pegg I. L. 
Published: March 2011

ABSTRACTGlasses suitable for high-level nuclear waste vitrification must meet a number of requirements including processability, durability, and phase stability. Our new data indicate that the West Valley Reference 5 composition meets these requirements: it is phase stable over the expected range of melter temperatures and residence times, and only minimal (<2 vol %) secondary phase formation, consisting predominantly of iron-group spinels, is expected in the canister cooled glass. Leach tests have shown that the durability of Reference 5 is significantly less sensitive to spinel formation than the earlier Reference 4. However, natural process variations during production will result in a range of glass compositions around the nominal composition. In this paper we report on the effects of composition changes around Reference 5 on the phase stability upon heat treatment and the consequent effects on chemical durability. Since variations in the waste-stream levels of most major components can be accommodated by adjusting the quantities of the glass-forming additives we focus here on a group of components for which this is generally not the case: Ca, Ce, Cr, Mn, Ni, S, and Fe. While many of these components are present at below 1 wt % they could have potentially significant indirect effects on product durability due to enhancement of secondary phase formation. The results provide a data base to support broad (≥300%) tolerance ranges to variation of levels of most of these components. Viscosity data are also reported.
Key Parameters of Glass Dissolution in Integrated Systems
Authors: Vernaz Etienne Y. , Godon Nicole 
Published: March 2011

ABSTRACTLeaching cells were designed to test the alterability of nuclear waste glasses under conditions closely simulating an actual geological repository. This paper summarizes the results of twenty long-duration tests simulating a variety of storage conditions. The effects of the backfilling materials, the canister, glass cracking and crystallization, a activity and the nature of the host rock are discussed. Moreover, an experiment has been in progress for over seven years in a granite medium; after three years the corrosion rate dropped to about 2 × 10−3 g m−2 d−1, and is sustained only by the water renewal due to sampling at regular intervals. These results constitute a valuable data base on R7T7 glass alteration in geological media at 90°C. Glass alteration mechanisms described in pure water appear to be applicable to a hard rock medium. In clay and salt, however, considerable work remains to be done before environmental factors can be taken into account in an overall dissolution model.
Simfuel Dissolution Studies in Granitic Groundwater at 25°C
Authors: Sandino Amaia , Casas I. , Ollila K. , Bruno J. 
Published: March 2011

ABSTRACTThe dissolution of a non-radioactive chemical analogue of spent nuclear fuel (SIMFUEL) has been studied as a function of two different synthetic groundwaters at 25°C. The cumulative release of U, Mo, Ba, Y and Sr is presented after 170 days of total leaching time.The results obtained show the potential usefulness of SIMFUEL to ascertain the kinetics and mechanisms of dissolution of the minor components of spent fuel. In the case of Sr, a good correlation is found with the dissolution of this minor component measured in spent fuel leaching experiments.
High-Temperature Annealing of Natural UO2+x
Authors: Janeczek J. , Ewing R. C. 
Published: March 2011

ABSTRACTFour powdered samples of natural UO2+x (uraninite) were annealed in a reducing atmosphere up to 1200°C. The initial unit cell parameters ranged from ao=0.5463 to 0.5385 nm. Small amounts of UO2.25 occur in all samples after annealing. Annealing curves show the effects of recovery of point defects in the oxygen sublattice, ordering of U4+ and U6+, vacancy migration in the cation sublattice, and second order phase transformations. The difference in the annealing behavior of UO2+x with x < 0.15 as compared to x = 0.25 between 400 and 700°C is due to ordering of U4+ and U6+. Density increased after annealing except for one sample in which a large number of cavities (1–2 μm in size) formed. Oxidation and chemical composition have a more dramatic effect on the structural state of natural UO2+x than self-irradiation caused by a-decay damage.
Repassivation Method to Predict Long Term Integrity of Low Alloy Titanium for Nuclear Waste Package
Authors: Tsujikawa Shigeo , Kojima Yoichi 
Published: March 2011

ABSTRACTLong term corrosion resistance is evaluated for G-2 and G-12 titanium as a candidate of the high-level nuclear waste packages. The repassivation potential for crevice corrosion, ER, in comparison with the well known spontaneous potential, ESP, of a metal passivated in given environment, allows conclusions to be drawn whether it performs “permanent” or does not. This repassivation method is extended to determine critical conditions in terms of NaCl concentration and temperature for specimens kept at an electrode potential which is more noble than ER and is included in ESP ranges. Thus obtained NaCl concentration - temperature - crevice corrosion map could predict critical conditions for the titanium used in geologic formations.
Hydrogen Evolution From Corrosion of Iron and Steel in Intermediate Level Waste Repositories
Authors: Grauer R. , Knecht B. , Kreis P. , Simpson J.P. 
Published: March 2011

ABSTRACTThe production of hydrogen from the anaerobic corrosion of iron or steel is an important issue in low/intermediate level nuclear waste repositories where large quantities of iron and steel (e.g. as drums and reinforcing steel) accompany the waste.Most of the iron in intermediate level repositories is in a cemen-titious environment. A review of the literature on the corrosion of iron and steel at high pH values, in particular in cementitious environments, points to hydrogen evolution rates between 22 and 220 mmol(H2)m−2a−1. There is some indication that the rates might be lower but for normal engineering applications there has been no practical need to demonstrate this, and hence a lower rate cannot be assumed on current evidence.In the present work a volumetric method was used to measure hydrogen evolution rates over several thousand hours under conditions relevant to intermediate level waste repositories. The sensitivity of this method (0.4 mmol(H2)m−2a−1) is sufficient to detect hydrogen evolution rates lower than those predicted for iron and steel in concrete.Hydrogen evolution rates in highly alkaline cement pore water were below 0.4 mmol m−2a−1 and almost 1 mmol m−2a−1 for a pore water representative of an aged cement; no decrease was observed even after 12000 h. In general hydrogen evolution rates in alkaline media were observed to take several thousand hours before approaching a constant rate.
Corrosion of Copper-Based Materials in Irradiated Moist air Systems
Authors: Reed Donald T. , Van Konynenburg Richard A. 
Published: March 2011

ABSTRACTThe atmospheric corrosion of oxygen-free copper (CDA-102), 70/30 copper-nickel (CDA-715), and 7% aluminum bronze (CDA-613) in an irradiated moist air environment was investigated. Experiments were performed in both dry and 40% RH (@90°C) air at temperatures of 90 and 150°C. Initial corrosion rates were determined based on a combination of weight gain and weight loss measurements. Corrosion products observed were identified. These experiments support efforts by the Yucca Mountain Project (YMP) to evaluate possible metallic barrier materials for nuclear waste containers.
Thermodynamic Modelling and Aqueous Chemistry in the CaO-Al2O3-SiO2-H2O System
Authors: Atkinson A. , Hearne J. A. , Knights C. F. 
Published: March 2011

ABSTRACTThe chemical properties of the CaO-Al2O3-SiO2-H2O system are important for understanding and predicting the behaviour of Portland cements in cementitious wasteforms and radioactive waste repositories. Solids of known average composition in this system have been synthesised by the co-hydrolysis of mixed alkoxides. The solids have been equilibrated with water at 25°C and the composition of the aqueous phase characterised. A thermodynamic model for the system has been developed by extending an earlier model of solid solutions in amorphous gels to include aluminium compounds. The model accounts for most of the experimental data and predicts that the main influence of aluminium is to form a hydrogarnet solid solution of general composition C3AH6−2xSx The model can be used to predict the chemistry of hydrated cements and the interaction of cements with groundwaters.
The Effects of Calcite Solid Solution Formation on the Transient Release of Radionuclides from Concrete Barriers
Authors: Smith Robert W. , Walton John C. 
Published: March 2011

ABSTRACTThe wealhering of concrete by carbonation causes the formation of calcite solid solutions that can significantly improve concrete as a barrier to the migration of divalent radionuclide cations. Example calculations for 90Sr and 60Co indicate that release rates from carbonated concrete are five orders of magnitude lower than for intact, unweathered concrete and that the thin carbonated zone is a significant sink for these radionuclides.
The Effects of Moisture Content, Salinity and Temperature on the Load-Bearing Capability of a Dense Clay-Based Backfill
Authors: Cheung Steven. C.H. , Gray M.N. , Yong R.N. , Mohamed A.M.O. 
Published: March 2011

ABSTRACTTo predict the mechanical performance of earthen backfill in a nuclear fuel waste disposal vault, the effects of temperature and moisture content on the backfill load-deformation characteristics must be known. Modified California Bearing Ratio (CBR) tests were used to obtain these data. The results show that the load-bearing capability of the backfill is not likely affected by water salinity. The load-bearing capability decreases with increasing temperature and water content or decreasing dry density. The effects of temperature, dry density, and moisture transport processes on load-bearing capability were found to be relatively small compared to those of moisture content. Under the expected Canadian vault environment, the backfill should retain sufficient bearing capacity to satisfy its mechanical design function, which is principally to limit expansion of swelling buffer material.
Modelling Studies of the Sorption of Uranium and Plutonium in the far Field of A Nuclear Waste Repository
Authors: Bond K.A. , Haworth A. , Sharland S.M. , Smith A.C. , Tweed C.J. 
Published: March 2011

ABSTRACTModels of the transport of sorbing radioelements through geological materials have been developed. These models couple a surface-complexation model of sorption processes with transport simulations in the CHEQMATE code. The chemical model has been shown to reproduce trends observed in batch sorption experiments. This approach may ultimately be used to investigate possible limitations to the use of models using simple Kds in repository safety-assessments. The main aim of the study reported in this paper is to increase confidence in the use of the coupled models. Simulations of through-diffusion experiments of uranium with London clay and plutonium with sandstone are presented. In both cases gluconate is present, as a simulant of organic degradation products of cellulose likely to be present in a low- or intermediate-level waste repository.
Influence of Micro Environments and Microorganisms on the Transport Properties of Redox-Sensitive Elements (E.G. Technetium)
Authors: Brühl Hanskarl , Pekdeger Asaf , Winkler Andreas 
Published: March 2011

ABSTRACTIn laboratory experiments immobilisation of Tc under oxic conditions was observed. The transport behaviour of redox-sensitive elements is not only controlled by the geochemical “frame conditions” which can be measured within the macro environment. Immobilisation behaviour of Tc strongly depends on micro environments and on microbial metabolism. Micro environments which may develope on the mineral surfaces can detoriate the mobility of Tc, furthermore the fixation of Tc is influenced by microbial activities.
Characteristics of Migration of 85Sr and 137Cs in Alkaline Solution Through Sandy Soil
Authors: Ohnuki Toshihiko 
Published: March 2011

ABSTRACTCharacteristics of the migration of 85Sr and 137cs in a solution of pH 12 through coastal sandy soil have been investigated by both column and batch tests. Desorption behaviors of the 85Sr and 137Cs by the sandy soil in both column and batch tests were examined by sequential extraction techniques, in order to study difference in the adsorption behavior of the 85Sr and 137Cs under dynamic (column) and static (batch) conditions. The dominant components of the sandy soil to the adsorption of the 85Sr ancj 137Cs were tested in batch tests.The adsorption of the 85Sr by the sandy soil was a function of pH, while that of the 137Cs was independent of pH of the solution. Most of the 85Sr was reversively adsorbed with the sandy soil under both static and dynamic conditions. Approximately 85 percent of the 137Cs was irreversibly sorbed by the sandy soil in the column test, which was greater than that in the batch test. The desorption behaviors of the 137Cs adsorbed by kaolinite and by sericite resembled that of the sandy soil. Most of the 85Sr was reversively adsorbed by kaolinite, chlorite, sericite, FeOOH, Ti02 and Mn02 which is similar to the desorption behavior of 85Sr by the sandy soil. The distribution coefficients of the 85Sr for kaolinite, FeOOH, Mn02 and Ti02 were larger by several times than those for the chlorite and the sericite.Therefore, the dominant components of the sandy soil contributing to the adsorption of 137Cs would be sericite, and those of 85Sr would be kaolinite, FeOOH, Ti02 and Mn02.
Immobilization of Radioactive Strontium in Contaminated Soils by Phosphate Treatment
Authors: Kim K.H. , Lee S.Y. , Ammons J.T. 
Published: March 2011

ABSTRACTThe feasibility of in situ phosphate- and metal- (calcium, aluminum, and iron) solution treatment for 90Sr immobilization was investigated. Batch and column experiments were performed to find optimum conditions for coprecipitation of 90Sr with Ca-, Al-, and Fe-phosphate compounds in contaminated soils. Separate columns were packed with artificially 85Sr-contaminated acid soil as well as 90Sr-contaminated soil from the Oak Ridge Reservation. After metal-phosphate treatment, the columns were then leached successively with either tapwater or 0.001 M CaCl2 solution. Most of the 85Sr coprecipitated with the metal phosphate compounds. Immobilization of 85Sr and 90Sr was affected by such factors as solution pH, metal and phosphate concentration, metal-to-phosphate ratio, and soil characteristics. Equilibration time after treatments also affected 85Sr immobilization. Many technology aspects still need to be investigated before field applications are feasible, but these experiments indicate that phosphate-based in situ immobilization should prevent groundwater contamination and will be useful as a treatment technology for 90Sr-contaminated sites.
Diffusion Porosity and Diffusivity of Radionuclides In Granitic Rocks. Part I: Diffusion Interfaces Around Permeable Fractures
Authors: Pirhonen Veijo O. , Front K. , Pitkänen P. 
Published: March 2011

ABSTRACTThis paper addresses the problem of evaluation of radionuclide retardation in fractured rocks. Pore space around permeable fractures was examined by means of the fracture profiling technique which comprises porosity measurements and chemical analyses along the profiles perpendicular to the fracture surfaces.Scanning electron micrographs show that the examined interfaces contain microfractures and tube-like diffusion channels. These are most frequent within 2 - 4 cm from the surface of the examined fractures. Porosity and chemistry of these interfaces are fracture specific. It is possible that diffusion into the rock matrix is restricted into the interfaces around the permeable fractures.
Flow Path Mineralogy: Its Effect on Radionuclide Retardation in the Geosphere
Authors: Ticknor Kenneth V. , Kamineni D. C. , Vandergraaf T. T. 
Published: March 2011

ABSTRACTThe geological formation surrounding a nuclear fuel waste disposal vault is an important barrier to the migration of radionuclides to the biosphere. Field investigations of plutonic rocks in the Canadian Shield have shown that open, water-bearing fractures form the main potential migration paths for radionuclides through the geosphere. Any interaction between the radionuclides in solution and the minerals in these fractures will retard radionuclide movement towards the biosphere. The minerals lining these open fractures are products of rock alteration and have themselves been subject to varying degrees of alteration over time. Accordingly, the fracture mineralogy is quite different from the bulk mineralogy of the intact host rock.The degree to which measured radionuclide sorption varied with mineralogy was examined by laboratory sorption studies using static batch techniques and autoradiography combined with petrography. Fission products (Sr, Cs) and actinides (U, Np, Pu) were among the radionuclides studied. It was found that most fracture-infilling minerals such as hematite, goethite, illite, kaolinite, chlorite, epidote, gypsum and muscovite show preferential sorption for certain radionuclides. Calcite sorbs actinides such as U, Np and Pu from solution, but not ion exchangeable radionuclides such as Cs and Sr. Quartz shows the least affinity for any of the radionuclides studied.It is concluded that variations in the type, amount and composition of fracture-infilling minerals must be considered in the assessment of the suitability of any geological formation as a radioactive wastes disposal site.