bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dissolution of Irradiated Fuel Under Hydrothermal Conditions
Authors: Johnson Lawrence H. , Joling Henry H. 
Published: March 2011

ABSTRACTUranium dioxide, the major component of irradiated CANDU fuel, shows good hydrothermal stability under the appropriate redox conditions. The thermodynamic stability of UO2in low ionic strength granite groundwater at 150°C under oxidizing and reducing conditions is briefly reviewed in order to provide a basis for discussion of the results of irradiated fuel dissolution experiments. Fuel chemistry characteristics that influence the kinetics of fission product release are also discussed.Experimental studies demonstrate the influence of redox chemistry on irradiated fuel dissolution behaviour. Undero9 trongly reducing conditions, both uranium and99Tcconcentrations in solution decrease to the detection limit, whereas appreciable concentrations of both elements accumulate under oxidizing conditions. The release of some fission products, such as90Sr and137Cs, does not seem to be strongly affected by changes in redox chemistry. Under oxidizing conditions, the rate of90Sr release to solution increases by a factor of ten to twenty between 25 and 150°C.These studies indicate the need for further work in certain areas, in particular on the relative amounts of important fission productsreleased by leaching versus matrix dissolution, and on the effect of the products of α–radiolysis of water on the dissolution of irradiated fuel.
Dod Applications of Implantation-Modified Materials
Authors: Hubler G. K. 
Published: March 2011

ABSTRACTThis paper reviews areas under investigation within DoD involving the application of ion implantation to problems in wear, friction, corrosion, and fatigue. Specific results on the modification of metal fatigue in Ti turbine blade alloys and the modification of sliding wear of steels are reviewed and discussed in terms of the mechanisms which are thought to be acting to improve the metal properties.
Development of Engineered Structural Barriers For Nuclear Waste Packages
Authors: Westerman R. E. , Pitman S. G. , Elmore R. P. , Nelson J. L. 
Published: March 2011

ABSTRACTThe development of structural barriers for nuclear waste packages involves selection of candidate materials, their screening by mechanical and corrosion testing, rigorous accelerated testing, and evaluation and comparison with other package elements. This document presents results from work conducted on titanium and cast steels.
Strontium-Basalt Reactions Under Nuclear Waste Repository Conditions
Authors: Komarneni Sridhar 
Published: March 2011

ABSTRACTHydrothermal interactions of Sr as strontium chloride or hydroxide with basalts or basalt phases were investigated at 300°C for 4 and/or 12 weeks under a confining pressure of 30MPa. The nature and extent of Sr immobilization varied with the Sr source and with the basalt or basalt phase which immobilized up to 99.99% of the added Sr. The main mechanism of Sr fixation with basalts seems to be ion exchange when SrCl2 was the Sr source. Among the basalt phases, basalt glass was the most effective for SrCl2 immobilization by probably forming new strontium mineral phases. However, when Sr(OH)2 reacted with basalts or basalt phases Sr was immobilized by the crystallization of strontium aluminosilicates such as SrAl2Si2O8 . These results of Sr-nearfield interactions in a basalt repository indicate that basalt can be a good barrier for Sr migration from nuclear wastes.
Chemical, Physical and Engineering Characterization Of Candidate Backfill Clays and Clay Admixtures for a Nuclear Waste Respository-Part I
Authors: Singh Sudesh K. 
Published: March 2011

ABSTRACTFourteen Canadian clays and clay admixtures were subjected to simulated nuclear waste repository environments. The present work is concerned with the montmorillonite-dominant materials only. The montmorillonite-dominant samples showed significant leaching on interaction with deionized water. On heating the samples at 200°C for 500 hours, montmorillomites lost intermicellar water completely and acquired cusp-like to cylindrical morphologies. The loss of water and the morphological changes in montmorillonites significantly altered the engineering characteristics. Permeability, shrinkage limits, compactability and shear strength varied in response to the dominant exchange cation in the structure of montmorillonites and the presence of other mineral components in the materials. The synthetic granite water reacted with montmorillonites and led to changes in chemical and mineralogical compositions, crystalline state and engineering properties.
Stochastic Analysis of Groundwater Flow and Contaminant Transport in a fractured Rock System
Authors: Schwartz F.W. , Smith L. , Crowe A.S. 
Published: March 2011

ABSTRACTIt has been possible to develop a stochastic model for groundwater flow and mass transport in a fractured rock system. A large number of statistically independent realizations of a fracture network are generated from a set of probability distributions for parameters defining the fracture geometry. By solving for hydraulic head at the fracture intersections and using data on apertures and porosities, seepage velocities may be calculated and the transport equation solved for each trial of a Monte Carlo simulation. Model output consists of distributions of moving particles and various mass exit times. Applications illustrate the types of model results and the skewed character of particle distributions.
Performance of Asphalt and Clay Liners as a Uranium Mill Tailings Leachate Barrier
Authors: Buelt James , Barnes Steve 
Published: March 2011

ABSTRACTPacific Northwest Laboratory is evaluating the long-term effectiveness of various asphalt and clay liner materials as a radionuclide and process chemical barrier from uranium mill tailings. A field test is being conducted by monitoring asphalt and clay liners installed at the Grand Junction, Colorado tailings site. In addition eight prospective liners have undergone three months exposure to accelerated conditions to predict their behavior over a 1000 year period. High calcium leachates have been forced through thin layers of clay to determine the ability of the clay to resist ion exchange, which reduces its swelling capabilities. Asphalt liners have been exposed to elevated temperatures and increased strengths of oxidizing agents to accelerate their aging process. The permeability coefficients measured during this exposure were then used to predict each liners stability with time. The analyses thus far show that clay soils with bentonite amendments and most asphalt compositions have good long-term performance characteristics.
A Comparative Assessment of Tru Waste Forms and Immobilization Processes
Authors: Ross W. A. , Harvey C. O. , Lokken R. O. , May R. P. , Roberts F. P. , Timmerman C. L. , Treat R. L. , Westsik J. H. 
Published: March 2011

ABSTRACTSix alternative TRU waste forms and seven waste immobilization processes are comparatively assessed on the basis of both product properties and process costs and risks. The waste forms are characterized for their leachability, mechanical strength, and thermal and radiation stability. The processes are evaluated in terms of costs (for processing, transportation, and repository disposal) and in terms of occupational exposure, industrial hazard, and quality assurance. Cast cement is recommended for immobilization of defense TRU wastes. A glass system, either borosilicate or aluminosilicate, is recommended for immobilization of commercial TRU wastes.
Low-Level Waste Disposal Analysis
Authors: Ensminger Daniel , Koplik Charles , Oston Steven , Kaplan Maureen , Nalbandian James 
Published: March 2011

ABSTRACTThe safety of low-level radioactive waste disposal sites is analyzed using the computer code LOTRAN. Radiation doses to off-site individuals and to future land reclaimers are computed for a generic disposal site located in a humid Eastern environment. The predicted doses are compared to illustrative performance criteria developed under this project. Results provide insight into those characteristics of low-level waste disposal systems most important to public safety and will allow analyses of tradeoffs among natural and engineered features.
Immobilization and Leakage of Krypton Encapsulated in Zeolite or Glass
Authors: Christensen A. B. , Del Debbio J. A. , Knecht D. A. , Tanner J. E. 
Published: March 2011

ABSTRACTKrypton and other gases are readily adsorbed in zeolite 5A molecular sieve or porous Vycor “thirsty glass” and may be trapped there by sintering 2–4 hours at 700° or 900°C, respectively. Encapsulation in these materials is the basis of a method to “immobilize” krypton-85 for storage. Amounts of gas trapped are approximately proportional to gas density, and are about 50 and 40 cc(standard conditions = STP)/cc of solid at 1000 atm, for zeolite 5A and glass, respectively. Based on tests of a few months duration a leakage of 0.3% of the krypton is predicted for 10 years at 400°C for either material.
Cementitious Radioactive Waste Hosts Formed Under Elevated Temperatures and Pressures (Fuetap Concretes)
Authors: Dole L. R. , Moore J. G. , Rogers G. C. , West G. A. , Devaney H. E. , Morgan M. T. , Mcdaniel E. W. , Kessler J. H. 
Published: March 2011

ABSTRACTConcretes formed under elevated temperatures and pressures (FUETAP concretes) are effective hosts for transuranic (TRU) and high-level defense and commercial wastes.Tailored cement formulations developed at Oak Ridge National Laboratory (ORNL) use Portland cement, fly ash, sand, and clay additives. These FUETAP concretes are cured under mild autoclave conditions, then the unbound water is removed.This paper summarizes the FUETAP development program. These continuous studies address the major questions concerning the performance of radioactive waste forms.
Mercury Reduction and Removal During High-Level Radioactive Waste Processing and Vitrification
Authors: Eibling Russell E. , fowler John R. 
Published: March 2011

ABSTRACTA reference process for immobilizing the high-level radioactive waste in borosilicate glass has been developed at the Savannah River Plant. This waste contains a substantial amount of mercury from separations processing. Because mercury will not remain in borosilicate glass at the processing temperature, mercury must be removed before vitrification or must be handled in the off-gas system. A process has been developed to remove mercury by reduction with formic acid prior to vitrification. Additional benefits of formic acid treatment include improved sludge handling and glass melter redox control.
Leaching Behaviour of Ion-Implanted Simulated Hlw Glasses and Tentative Prediction of their Alpha-Recoil Aging.
Authors: Dran J.C. , Langevin Y. , Maurette M. , Petit J.C. , Vassent B. 
Published: March 2011

ABSTRACTThe ion implantation-based simulation of α-recoil aging in radwaste glasses has been applied to several simulated HLW glasses. The results are qualitatively described by a new model of leaching for the implanted glasses although several specific features of irradiated surfaces are not clearly understood. This model suggests that for the most likely case of diffusion-controlled corrosion, where the reaction scheme involves several steps (hydration, dissolution of hydrated silica gel, etc…), the kinetics-controlling one would not necessarily be radiation sensitive. Indeed for these more representative glasses, no evidence for a drastic increase in the dissolution rate of the silica gel, induced by ion implantation has been so far detected, whereas the hydration rate seems in some cases more significantly enhanced. However the implications of these observations for the durability of the glasses remain to be assessed.
The Effect of Radiolysis on Leachability of Plutonium and Americium from 76–101 Glass
Authors: Nash K. L. , Fried S. , Friedman A. M. , Susak N. , Rickert P. , Sullivan J. C. , Karim D. P. , Lam D. J. 
Published: March 2011

ABSTRACTOne aspect of the leachability of actinide bearing glass which has not been adequately addressed is the effect of radiolysis of the system (glass-water) on the amount of actinides liberated from the glass. In the present study, we have investigated the leaching of plutonium and americium from 76–101 glass samples (containing 2 mole % plutonium) in the presence of a one megaRad/hour gamma radiation field. The presence of the radiation field was found to increase the leaching rate of both plutonium and americium by a factor of five. Speciation studies of the plutonium in the leachate indicate that the plutonium is present predominantly in the higher oxidation states, Pu(V) and Pu(VI) and that it is significantly associated with colloidal particles. Examination of the glass surfaces with X-ray photoemission spectroscopy, XPS, both before and after leaching was carried out; these studies showed lower surface concentrations of plutonium in the samples of glass leached in the radiation field.
Ion Implantation Studies of Nuclear Waste Forms
Authors: Northrup Clyde J. M. , Arnold George W. , Headley Thomas J. 
Published: March 2011

ABSTRACTThe first observations of physical and chemical changes induced by lead implantation damage and leaching are reported for two proposed U.S. nuclear waste forms (PNL 76–68 borosilicate glass and Sandia titanate ceramics) for commercial wastes. To simulate the effects of recoil nucleii due to alpha decay, the materials were implanted with lead ions at equivalent doses up to approximately 1 × 1019 a decays/cm3 . In the titanate waste form, the zirconolite, perovskite, hollandite, and rutile phases all exhibited a mottled appearance in the transmission electron microscope (TEM) typical of defect clusters in radiation damaged, crystalline solids. One titanate phase containing uranium was found by TEM to be amorphous after implantation at the highest dose. No enhanced leaching (deionized water, room temperature, 24 hours) of the irradiated titanate waste form, including the amorphous phase, was detected by TEM, but Rutherford backscattering (RBS) suggested a loss of cesium and calcium after 21 hours of leaching. The RBS spectra also indicated enhanced leaching from the PNL 76–68 borosilicate glass after implantation with lead ions, in general agreement with the observations of Dran, et al. [6,7] on other irradiated materials. Elastic recoil detection spectroscopy (ERD), used to profile hydrogen after leaching, showed penetration of the hydrogen to several thousand angstroms for both the implanted and unimplanted materials. These basic studies identified techniques to follow the changes that occur on implantation and leaching of complex amorphous and crystalline waste forms. These studies were not designed to produce comparisons between waste forms of gross leach rates.
Study of the Metamict Transformation in α-Quartz Using High-Resolution Electron Microscopy and Convergent Beam Electron Diffraction
Authors: Pascucci M. R. , Hutchison J. L. , Hobbs L. W. 
Published: March 2011

ABSTRACTThe metamict transformation under electron irradiation has been studied in α-quartz using transmission electron microscopy (TEM) and convergent-beam electron diffraction (CBD). The transformation occurs in two stages: heterogeneous nucleation of discrete disordered inclusions and a slower homogeneous loss of crystalline order in the surrounding matrix. Both features are attributable to solidstate radiolysis, a mechanism for which is proposed. Ultrahigh resolution TEM structure images and information from zeroth and high order Laue zones in CBD confirm that shortrange correlations are the first to be lost and that longerrange correlations persist well into the metamict transformation. A transformation model is advanced in which progressive disorder evolves from small displacements of individual [SiO4] coordination units, made possible by lowered connectivity, within a framework of long-range ordered material.
Materials Research for the Canadian Nuclear Fuel Waste Management Program
Authors: Cameron Donald J. 
Published: March 2011

ABSTRACTNuclear fuel waste disposal research in Canada is concentrating on hard-rock disposal. The research programs concerned with the man-made components of the disposal system are reviewed. Irradiated fuel and solidified reprocessing wastes are both being researched, as are durable containers, and buffer and backfill materials. This review concentrates mainly on the more scientific aspects of the research, which contribute to the selection of preferred options for the various components of the system, and which support directly or indirectly the safety analysis of the disposal concept. Some technology development is included in the program now, and this is expected to expand as confidence in the acceptability of the disposal concept grows.
The Development and Testing of Synroc C as a High Level Nuclear Waste Form
Authors: Reeve K.D. , Levins D.M. , Ramm E.J. , Woolfrey J.L. , Buykx W.J. 
Published: March 2011

ABSTRACTThe current status of SYNROC C research and development by the Australian Atomic Energy Commission is reviewed. A non-radioactive fabrication demonstration line designed to produce 10 cm o.d., 90 cm long, cylinders of SYNROC canned in stainless steel by the method of in-can hot pressing is being commissioned. Leach tests are proving the excellent leach resistance of SYNROC. Accelerated radiation damage testing using fast neutrons has simulated storage times of up to 6.7×105 years. Thermophysical properties of SYNROC have been measured over the temperature range 20–650°C.
Percolation Transition and Accumulation of Strain in Chalcogenide Glasses
Authors: Murase Kazuo , Fukunaga T. 
Published: March 2011

ABSTRACTNetwork structures and glass forming tendency of g-(Ge1−ySny)1−x(Se, or S)xare discussed in connection with the percolation transition near the Phillips critical composition xc= 0.8, and local or extended topological transitions due to strains induced by compositional changes or applied pressures.
Defect Levels in the Gap of Arsenic Selenide Glasses
Authors: Adriaenssens Guy J. 
Published: March 2011

ABSTRACTThe ideas and energy diagrams of the valence alternation pair model (also: negative-U model) are introduced and matched to the classical steady-state photoconductivity analysis in terms of two discrete recombination levels in the gap. Data from bulk a-As47Se53 serve as example. Negative effective correlation energies Ueff = -0.72 eV for a-As2Se3, −0.61 eV for a-As2Se4 and -0.58 eV for a-As47Se53 are obtained. The positively charged defects are found to be Se3+ with relaxation energies W+ ≃ 0.1 to 0.2 eV, and the negatively charged defects are As2− with relaxation energies W− ≃ 0.3 to 0.6 eV.
The Relation Between Defects and Relaxation in Viscous Liquids
Authors: Brawer S. 
Published: March 2011

ABSTRACTIt is shown that defects can be identified in liquids, that they are related to atomic diffusion, and a model is described whereby defects give rise to the observed relaxation behavior of viscous liquids. A review is presented of defects in silicate and fluoroberyllate liquids, as studied by computer simulation. It is found that defects have the form of overcoordinated or undercoordinated atoms, and that atomic diffusion occurs only at the site of defects. The manner in which an Ising model can represent the detect structure of viscous liquids to a first approximation is presented. The results of Monte Carlo simulations of a 2-dimensional kinetic Ising model are described. The behavior of this model is qualitatively the same as that of viscous liquids.
Defects and the Photodarkening Process in the Chalcogenide Glasses
Authors: Taylor P. C. , Liu J. Z. 
Published: March 2011

ABSTRACTIn the chalcogenide glasses the primary defects are thought to involve under- and over-coordinated chalcogen atoms which are diamagnetic under quasiequilibrium conditions because of the presence of a strong electron-lattice interaction. These defects can be optically, or in some cases thermally, excited into metastable paramagnetic configurations which are well described as chalcogen “dangling bonds.” Alloying the chalcogenide elements with group V or group IV atoms produces additional diamagnetic defects which in their excited paramagnetic configurations also appear to be well described as dangling bonds. Some of these defects may play a role in the photodarkening (PD) process which is a metastable shift of the absorption edge to lower energies after irradiation with light of energy greater than or equal to that of the band gap. The PD process requires the presence of a non-bonding plike valence band. The microscopic description of the PD process may involve the creation of defects or the tunneling of chalcogen atoms.
UV-Radiation Induced Color Centers in Optical Fibers
Authors: Simpson J. , Ritger J. , DiMarcello F. 
Published: March 2011

ABSTRACTParamagnetic color centers have been observed in germanium silicate and germanium phosphosilicate multimode optical fiber exposed to broadband ultraviolet light (2–5 eV). These centers are characterized by an ESR and optical absorption similar to 1 meV and 100 keV radiation induced defects and show an apparent saturation as the UV dose approaches 100 J/cm2. The UV induced ESR spectra are not identical to that induced by 60Co radiation however, similar Ge(2) and Ge(3) germanium defect signatures are apparent. For both compositions these centers are characterized by a rapidly increasing loss from 1.0 to 0.5 µm with an additional broad absorption peak at 1.5 µm for the phosphorus containing cores. We suggest that the UV induced optical absorptions for both compositions in the short wavelength range are due in part to the Ge(2) germanium substitutional sites and expect that the 1.5 µm absorption is due to the P1 phosphorus oxygen vacancy.
Electron Paramagnetic Resonance Studies of Intrinsic Bonding Defects and Impurities in SiO2 Thin Solid Films
Authors: Schwartz Robert N. , Clark Marion D. , Chamulitrat Walee , Kevan Larry 
Published: March 2011

ABSTRACTElectron paramagnetic resonance (EPR) spectroscopy has been used to identify paramagnetic intrinsic bonding defects and impurities in as-deposited thin solid SiO2 films. Thin films grown by E-beam vacuum deposition, RF sputtering, thermal oxidation of polysilicon, plasma enhanced chemical vapor deposition (PECVD), and low pressure chemical vapor deposition (LPCVD) techniques have been examined. Some of the growth techniques yield films that have paramagnetic centers similar to those found in bulk radiation-damaged vitreous SiO2. A new temperature dependent EPR center was observed in PECVD SiO2 films and has been assigned to trapped NO2. Slow-motional EPR lineshape theory was used to analyze the temperature dependent spectra.
Cross Sectional Transmission Electron Microscopy Study of Obliquely Evaporated Silicon Oxide thin Films
Authors: Barna A. , Geszti O. , Gosztola L. , Seyfried E. 
Published: March 2011

ABSTRACTThe columnar structure in obliquely evaporated silicon oxide layers was investigated by transmission electron microscope (TEM). For TEM studies of these layers, samples were made by low angle ion-beam thinning of cross-sections, the planes of which were determined by the normal of the film and the direction of evaporation. Increasing the angle of evaporation from 5° to 30° (measured from the plane of the substrate), a change from a well–defined columnar structure to a striated structure was observed, for layers evaporated both under “low-rate” and “high-rate” conditions. There is a clear-cut dependence of the orientation of columns (αc) upon the angle of evaporation (α), however deviating from the “tangent rule” (tanαc=2tanα).