bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear Concentration Effects on Radionuclide Diffusion and Mobility in Compacted Bentonite.
Authors: Anderson Harold M. , Chiao Frank S. 
Published: March 2011

AbstractThis paper examines some previously reported experimental results on the migration behavior of selected radionuclides in compacted bentonite and demonstrates that a much better agreement between observed and theoretically predicted migration behavior can be obtained when the model considers nonlinear concentration effects. The radionuclide transport model used in this study employs a semianalytic, integral equation approach to the solution of the diffusion equation with nonlinear retardation mechanisms. The effect of radionuclide concentration on species mobility is modeled as a highly nonlinear Freundlich isotherm.Several empirical correlations using the Freundlich isotherm form for retardation are presented and are shown to account for the deviation from linearity in the diffusion model for migration behavior. These correlations are then used in further numerical studies of long term backfill barrier performance for 3 and 4 member chain species after a hypothetical canister failure. The overall importance of nonlinear concentration effects to radionuclide migration estimation is discussed.
Ion Implantation Damage Processes in Nuclear Waste Glass and Other Silicate Glasses
Authors: Arnold G. W. 
Published: March 2011

AbstractCantilever beam measurements of induced lateral stress have been made for He, Xe and Pb ion-implantation into the complex borosilicate radioactive waste glasses (PNL 76–68, SRP), a commercial borosilicate (Pyrex), and into fused Si02 (Suprasil 1). For the borosilicate glasses, implantation caused a buildup of stress to a saturation value (∼ 1 × 105 dynes/cm). The maximum occurred at ion fluences greater than those found for maximum stress in fused silica and without a stress relief mechanism. The separate family of stress curves for Pyrex and PNL 76–68 coincide when stress is plotted as a function of energy into electronic processes. Pyrex has 13 wgt.% B2O3 and 81 wgt.% SiO2, while PNL 76–68 and SRP have 10% B2O3, 40% SiO2 and N5 B2O3 and 58% Si0 2, respectively. Pyrex is known to be phase-separated, and Ghe waste glasses are susceptible to phase separation. It is suggested that the B2O3 phase may be more easily compacted than the SiO2 phase. The evidently greater effectiveness of the ionization component of the ion energy in creating damage in borosilicate glasses should be of considerable interest in waste glass studies because of the large amounts of ionization from α-decay (∼ 5 MeV He).
Effects of Alpha Irradiation on Barium Hollandite and Nickel-Iron Spinel
Authors: Weber W. J. 
Published: March 2011

AbstractBarium hollandite and nickel-iron spinel have been irradiated with alpha particles emitted from a PuO2 source in order to simulate the effects from alpha particles emitted in adjacent actinide-containing phases of the SYNROC assemblage. The unit cell of barium hollandite undergoes an apparent volume expansion of several percent and a weak transformation from a tetragonal to a monoclinic structure when irradiated with alpha particles to a fluence of 3 × 1020 alphas/m2 (∼0.05 dpa). The spinel structure, however, is stable with respect to alpha irradiation and the irradiation-induced volume expansion of the unit cell is less than 0.2%. The results are compared with available neutron-irradiation data, and the differences in observed behavior discussed.
Reference and Testing Materials Available from the Materials Characterization Center
Authors: Daniel J. L. , Mellinger G. B. , Barner J. O. 
Published: March 2011

AbstractA major responsibility of the Materials Characterization Center (MCC) is to acquire and distribute reference and testing materials endorsed by DOE, for use in research and development in nuclear waste management. MCC standard materials provide a common basis for data obtained in waste repository development work, thereby assisting in developing a defensible database of known accuracy and precision. Homogeneity of standard materials is of particular importance. MCC emphasizes homogeneity of composition and physical characteristics of the standard materials, using statistical methods in sampling procedures and evaluation of analytical data.Two classifications of standard materials are available from the MCC. Approved Reference Materials (ARMs) are intended as standard reference and calibration materials [similar to the SRMs of the U.S. National Bureau of Standards (NBS)], for field calibration of MCC standard test methods. Each ARM is characterized by MCC and other laboratories such as NBS to a high level of accuracy and precision. Approved Testing Materials (ATMs) are used as common testing materials, representing specific formulations of typical waste forms. Most ATMs are radioactive materials, for which characterization has been conducted on shielded analytical instruments at PNL. More than ten different ATMs (borosilicate glass and spent fuel) are in the MCC inventory.These materials are available without charge, in reasonable amounts, to DOE programs. Other users pay pro-rated production costs. The materials normally are supplied in the form in which they were produced, e.g., glass as-cast bars. In some cases the MCC can supply special specimen forms, e.g., crushed powders or shaped monoliths.
Characterization of Hydrated Surface Layers on Nuclear Waste Glasses by Infrared Reflectance Spectroscopy
Authors: Zellmer Lauren A. , White William B. 
Published: March 2011

AbstractThe reaction between aqueous solutions and borosilicate glasses designed for commercial or defense waste immobilization produces a hydrated layer on the surface of the glass which can be characterized by infrared reflectance spectroscopy. Specular reflectance curves, obtained by Fourier transform infrared spectroscopy, can be deconvoluted by Kramers-Kronig analysis to obtain true absorption spectra. The pattern of Si-O stretching modes changes for alkali silicate glass, indicating changes in the network polymerization. The characteristic intense band of the borosilicate glasses simply changes intensity in a way that scales with degree of hydration. The progressive hydration of the glass surface also appears as a broad OH band which can be extracted from the reflectance curve by the deconvolution process.
Standardized Waste Form Test Methods
Authors: Slate Steven C. 
Published: March 2011

AbstractThe Materials Characterization Center (MCC) is developing standard tests to characterize nuclear waste forms. Development of the first thirteen tests was originally initiated to provide data to compare different high-level waste (HLW) forms and to characterize their basic performance. The current status of the first thirteen MCC tests and some sample test results are presented: The radiation stability tests (MCC-6 and 12) and the tensile-strength test (MCC-11) are approved; the static leach tests (MCC-1, 2, and 3) are being reviewed for full approval; the thermal stability (MCC-7) and microstructure evaluation (MCC-13) methods are being considered for the first time; and the flowing leach test methods (MCC-4 and 5), the gas generation methods (MCC-8 and 9), and the brittle fracture method (MCC-10) are indefinitely delayed. Sample static leach test data on the ARM-I approved reference material are presented.Established tests and proposed new tests will be used to meet new testing needs. For waste form production, tests on stability and composition measurement are needed to provide data to ensure waste form quality. In transportaion, data are needed to evaluate the effects of accidents on canisterized waste forms. The new MCC-15 accident test method and some data are presented. Compliance testing needs required by the recent draft repository waste acceptance specifications are described. These specifications will control waste form contents, processing, and performance.
Solubility Data for U(VI) Hydroxide And Np(IV) Hydrous Oxide:Application of MCC-3 Methodology
Authors: Krupka Kenneth M. , Rai Dhanpat , Fulton Robert W. , Strickert Richard G. 
Published: March 2011

AbstractExperiments based on a modified MCC-3S test method were conducted to investigate the solubility of U(VI) hydroxide (the mineral schoepite) and Np(IV) hydrous oxide at ambient temperature. The solubility of U(VI) hydroxide was investigated in carbonate-free, oxidizing aqueous solutions in the pH range of 3 to 11. The measured concentrations of dissolved U confirm the amphoteric behavior of U(VI) hydroxide solid and the importance of anionic U(VI) hydroxyl complexes in accurately calculating the solubilities of U(VI) solids under basic pH conditions. The effect of fluoride complexation on the solubility of Np(IV) hydrous oxide was studied in carbonatefree, near-neutral to alkaline solutions that contained 100 ppm total F. For solutions in which sodium dithionite (Na2 S2O4) and metallic Fe were used as reducing agents, the addition of 100 ppm F had no measurable effect on the solubility of Np(IV) hydrous oxide.
The Effect of Radial Temperature Gradients on Glass Fracture in Simulated High-Level Waste Canisters
Authors: Farnsworth Richard K. , Chan M. K. W. , Slate S. C. 
Published: March 2011

AbstractThe Pacific Northwest Laboratory performed experiments on canisters of simulated high-level waste (HLW) glass to estimate the effects of radial temperature gradients on the degree of glass fracture in actual HLW canisters. Glass cracking may result in an increased amount of fine glass particles that are of concern in transportation and repository safety analyses. A test matrix was developed to examine the effect of air cooling, water quenching, and internal fins on canister cooling rates, radial temperature gradients, glass cracking levels, and particle size distributions. The data shows the reduction of radial temperature gradients to be important in reducing the amount of waste glass fracture. Cracking profiles show that internal carbon steel fins significantly decrease the degree of fracture. Different cooling rates only affect the amount of particles above a certain size. The amount of particles below that size depends on the interaction between the glass and canister.
Leaching of Saltstone
Authors: Barnes Mary W. , Langton Christine A. , Roy Della M. 
Published: March 2011

AbstractA modified IAEA leach test was used to evaluate the relative performance of potential saltstone formulations. The effects of sample size and leach rates for specific ions were determined. Leaching mechanisms were determined for NO3−, NO2−, SO4−2, Na+, Ca+2 and Si.NO2−, NO3−, Na+ and SO4−2 are listed in order of decreasing leach rates. These ions exhibited high initial leach rates which decreased rapidly with time. High initial rates were attributed to surface wash off and diffusion. Within 10 days leach rates stabilized and can be explained by diffusion. Effective diffusivities for nitrite, nitrate, sodium, and sulfate were calculated from the leaching data. They are 6.4 × 10−10, 4.1 × 10−10, 3.2 × 10−10, and 0.9 × 10−10 cm2 /sec, respectively.Negative leach rates were measured for Ca+2 and Si in some formulations. This was attributed to precipitation of CaCO3 and hydrated calciumsilicate phases on the surfaces of the samples.
Nuclear Glass Corrosion Mechanisms Applied to the French LWR Reference Glass
Authors: Nogues J. L. , Vernaz E. Y. , Jacquet-Francillon N. 
Published: March 2011

AbstractThe French LWR reference glass was leached under different experimental conditions. Analysis of the leachate together with electron microscopic examination of the leached surfaces led us to the following conclusions. The corrosion of the nuclear glasses is congruent at the hydration front, but only a fraction of the elements enters the solution ; the other elements contribute to the formation of the surface layer resulting in incongruent dissolution from the standpoint of the entire sample. The leaching rate in static experiments was observed to decrease sharply in time. Specific experiments were performed to assess the protective role of the hydrolyzed layer with respect to the silica solubility limit, and the predominant effect of the solubility limit was clearly demonstrated.
Leaching of Warm-Pressed CsZp-Cement Composite Waste Forms
Authors: Fajun Wei , Grutzeck Michael W. , Roy Della M. 
Published: March 2011

AbstractCesium zirconium phosphate [CsZr2 (PO4)3 or CsZP] has been mixed with various cement matrix materials, warm pressed, cured and leached at different temperatures. Although hydrated portland cement minerals can immobilize most of U, La and Nd (as proxies for transuranics) they are less effective in immobilizing Cs, Sr or Ba under ordinary conditions. Earlier published work showed favorable immobilization of Cs in CsZP-cement composite waste forms which compared rather favorably with many other waste forms with respect to Cs leachability. By using warm pressing combined with suitable admixtures rates of 28 to 60 day Cs leachability or the composites have been substantially reduced, attaining values of less than 0.20 g/m2. d.
Leachability of Decontamination Reagents From Cement Waste Forms.
Authors: Piciulo P. L. , Davis M. S. , Adams J. W. 
Published: March 2011

AbstractBrookhaven National Laboratory, in order to provide technical information needed by the U.S. Nuclear Regulatory Commission to evaluate the adequacy of near-surface disposal of decontamination wastes, has begun to study the leachability of organic reagents from solidified simulated decontamination wastes. Laboratory scale cement waste forms containing EDTA, picolinic acid or simulated (low oxidation metallic ion) decontamination reagent were leach tested. Samples containing an organic reagent on either mixed bed ion-exchange resins or anion exchange resins were tested. A fixed interval leach procedure was used, as well as the ANS 16.1 standard procedure. The leachability indices measured for the release of the acid from resin/cement composites are: 10.1 for EDTA on mixed bed resins; 9.1 for picolinic acid on mixed bed resins; 9.2 for picolinic acid on anion exchange resins; 8.8 for picolinic acid in forms containing simulated LOMI reagent on mixed bed resins and 8.7 for picolinic acid in forms containing simulated LOMI reagent on anion exchange resins. The leachability indices measured varied with leach time and the data indicate that a simple diffusion model may not be adequate for defining release from these waste forms.
A Transport Code for Radiocolloid Migration: With an Assessment of an Actual Low-Level Waste Site
Authors: Travis Bryan J. , Nuttall H. E. 
Published: March 2011

AbstractRecently, there is increased concern that radiocolloids may act as a rapid transport mechanism for the release of radionuclides from high-level waste repositories. The role of colloids is, however, controversial because the necessary data and assessment methodology have been limited. To quantitatively assess the role of colloids, the TRACR3D transport code has been enhanced by the addition of the population balance equations. The code was tested against the experimental laboratory column data of Avogadro et al. Next a low-level radioactive waste site was investigated to explore whether colloid migration could account for the unusually rapid transport of plutonium and americium observed. The nature and modeling of radiocolloids are discussed along with site simulation results from the TRACR3D code.
Ion-Beam Modification of Silicided Ti/Si Contacts
Authors: Lester S.D. , Cheung N.W. 
Published: March 2011

ABSTRACTIon-beam mixing studies were performed with arsenic implantation up to a dose of 1015/ cm2 through Ti on n+-Si contacts. Lateral silicide growth of many microns over the contact edges was observed for furnace annealed samples. The lateral growth is greatly enhanced by ion-beam mixing and can be suppressed with silicon nitride capping or using rapid thermal annealing (RTA) with a flash-lamp system. For RTA annealed samples. the implanted arsenic profile measured by RBS showed no snowplowing during the silicide growth process. Hligh contact resistivity was measured in the high-temperature annealed samples. This observation is consistent with the lower dopant concentration at the silicide/Si interface, due to silicide growth consuming the n+-Si layer.
Surface Modification of Soda Glass by Recoil Ion Implantation of In2O3.
Authors: Cadien K. C. , Harbison B. B. 
Published: March 2011

ABSTRACTRecoil ion implantation of In2O3 into soda glass substrates has been investigated. Increased adhesion results, while the optical and electrical properties are altered. Large energy deposition rates can lead to the reduction of the oxide, thus decreasing visible transmission. Thermal annealing in air results in the recovery of optical and electrical properties. The influence of ion energy and dose on the modification of the glass has been examined.
Focussed Ion Beams from Liquid Metal Ion Sources Theory and Applications
Authors: Kingham David R , Mifsud Vincent J 
Published: March 2011

ABSTRACTA theoretical model of liquid metal ion source (LMIS) operation has been developed by Kingham and Swanson. In this paper we consider beams from LMIS on the basis of this model. In particular we consider properties such as angular intensity, energy spread and relative abundance of differently charged species of the ion beam, and the dependence of these properties on source current and elemental composition. The conclusion is that the brightest focussed beam for a given probe size is attainable at the lowest possible source current as previously stated by Swanson. LMIS sources have an onset current of typically 1-2[A and will not operate stably below this current, thus limiting the maximum focussed ion beam brightness. The physical reason for this is discussed. The relevance of these properties to fine focussed ion beam applications, particularly semiconductor processing, is discussed. Useful, and in some cases unique, device manufacturing techniques can be postulated using one or more of the momentum, energy or atomic addition properties inherant tothis type of system. Advanced research tools are discussed, together with some examples of the use of microfocussed ion beams with probe sizes down to less than 50nm. Immediate applications include: high resolution ion imaging and SIMS microanalysis; ion beam machining and microfabrication; ion beam resist exposure and ion beam mask repair.
The Kinetics and Microstructure of Ion Beam Induced Crystallisation of Silicon
Authors: Williams J.S. , Brown W.L. , Elliman R. G. , Knoell R. V. , Maher D.M. , Seidel T.E. 
Published: March 2011

ABSTRACTThis paper reviews recent detailed investigations into the crystal growth kinetics and the microstructure of ion-beam-stimulated epitaxial crystallisation of silicon. Beam-induced crystallisation at temperatures between 200-400°C is found to be characterised by an activation energy of 0.24eV. Furthermore, in this temperature regime, crystal growth on (100) silicon is found to be free of extended defects except for a sharp hand of dislocation loops centred about the range of the ions employed to stimulate crystallisation. A higher temperature regime (>400°C) is observed in which the growth kinetics are less well defined but appear to be associated with an apparent activation energy of >0.5eV. In this regime, extended defects are observed to extend from the ion range to the surface. Results are presented which strongly suggest that nuclear energy deposition precisely at the amorphous-crystalline interface is responsible for crystallisation under ion irradiation. It is argued that the major fraction (2.4eV) of the thermal-only activation energy for epitaxial crystallisation of silicon is likely to be associated with the formation of nucleation sites for growth, a step which is achieved athermally under ion irradiation. In addition, the growth rate per unit ion fluence is found to be independent of substrate orientation at temperatures <450°C and independent of doping concentration for temperatures <400°C. These results are consistent with our proposed model for beam-induced crystallisation.
Semiconductor Alloys: Local Bond Lengths, Mixing Enthalpies, and Microclusters
Authors: Chen A.B. , Sher A. 
Published: March 2011

AbstractSeveral recent theoretical studies of the local structure of semiconductor alloys are summarized. First, dilute limit calculations of local bond lengths and mixing enthalpies are discussed. These calculations include effects due to both bond length and bondangle distortions, as well as local chemical rearrangements. Then, a new statistical theory of concentrated alloys is described. Deviations from random alloy distributions (microclusters) are predicted.
The Identification of Lattice Defects in GaAs and AlGaAs
Authors: Weber Eicke R. 
Published: March 2011

AbstractAnion antisite defects are the first convincingly identified intrinsic lattice defect in GaAs. Photo-EPR allowed to determine the energy levels of this double donor, with the single donor level being midgap. This level appears to be very similar to the technologically important “EL2” center in GaAs. However, various evidence indicates that EL2 is not due to ideal, undistorted antisite defects.Fermi level pinning at Schottky contacts on GaAs has been ascribed to intrinsic lattice defects. Antisite defects are a likely candidate for this process.Finally, the microscopic identity of the “DX” center in AlGaAs will be discussed. This defect has been generally identified with a complex of a donor atom and an unknown partner. A number of recent experimental observations indicate that this defect might rather be due to isolated donors, which get deep levels because of the change of bandstructure in the alloy system.
Microscopic Identification of Anion Antisite Defects in GaAs by Optically Detected Magnetic Resonance
Authors: Spaeth J. Martin , Hofmann Detlev M. , Meyer Bruno K. 
Published: March 2011

AbstractAnion antisite defects in GaAs have been identified so far by their electron spin resonance (ESR) spectrum as one specific point defect, which was found in as-grown, plastically deformed and electron and neutron irradiated GaAs. By optical detection of electron nuclear double resonance (ODENDOR),it could be shown that several species of anion antisite defects exist having practically the same ESR spectrum, which cannot any longer be taken as “fingerprint” identification for this defect. Recent results of ODESR and ODENDOR investigations in as-grown, plastically deformed and electron irradiated GaAs are reviewed. It is also pointed out that the spin lattice relaxation time is an important quantity for the microscopic identification and the properties of anion antisite defects.
Defect Aggregates In Silicon
Authors: Corbett James W. , Corelli John C. , Desnica Uros , Snyder Lawrence C. 
Published: March 2011

AbstractIn this brief review we consider the vacancy-related, the vacancy oxygen-related, and the vacancy-hydrogen-related defects. We note the common opportunity for chemically-driven partial dissociation of defects. With this background we briefly survey what is known of the oxygen agglomerates, noting that we favor the ylid ( the saddle-point for oxygen diffusion) as the thermal donor core, but that the (vacancy + di-oxygen) complex can also be a core, and that the latter defect can occur when the strain-energy reaches the.point that a vacancy-interstitial pair can be created, causing interstitial emission from the oxygen agglomerate. We note as well that the emission of Si≡0 is energetically favored versus emission of an unbonded interstitial.