bluuebunny/crossref_metadata_2025 huggingface dataset:
Relation Between Strength, Pore Structure and Associated Properties of Slag-Containing Cementitious Materials
Authors: Roy Della M. , Idorn G. M.
Published: March 2011

Substantial increases of the strength of cement paste and mortars may be obtained in conventional processing by optimizing the materials components, the rheology and the curing, and thereby improving the microstructures. Cementitious materials with high proportions of granulated blast-furnace slag have been investigated. Higher strengths of ASTM C 109 mortars were obtained with 40 to 65% substitution of portland cement by slag, than with ordinary mix compositions and processing.

For one set of mixtures, 28 day strengths ≥ 100 MPa (some as high as 240 MPa) were consistently attained after curing at temperatures ranging from 27 to 250°C. The slag substitutions developed finer pore structures as revealed by intrusion porosimetry measurements, than those with pure portland cement. This is believed to be a major reason for their enhanced durability. At each stage from 3 to 28 days, increase of curing temperatures from 27 to 90°C decreased porosity and increased the strength, reflecting an increased maturity.

Implications for practice and suggestions for further work are discussed.
Production of High Strength Pastes, Mortars, and Concretes
Authors: Carrasquillo Ramon L.
Published: March 2011

For concrete, a grossly heterogeneous material, guidelines for selection of materials for its production, especially high strength concrete, should consider the interactions of its different components under load. Materials selection and production techniques for achieving concretes, mortars and cement pastes with strengths in excess of 10,000 psi are discussed. Emphasis is placed on the production of concretes having a compressive strength in the range of 10,000 to 15,000 psi using readily available materials and conventional production techniques. Emphasis is placed on the practical and technical significance of the factors involved in the selection of the materials and their proportions to achieve uniform, economical, high quality concrete. Selection of the concrete ingredients and their proportions is discussed in terms of their relative contribution to the compressive and flexural strength, elastic properties and observed failure mode of the paste, mortar and concrete. Production of concretes having compressive strengths in excess of 15,000 psi using exotic materials and special production techniques is also discussed.
Properties of High Strength Concrete for Structural Design
Authors: Ahmad Shuaib H. , Shah S. P.
Published: March 2011

The current ultimate strength design practice is based on experimental information obtained from concretes of compressive strengths in the range of 21 to 42 Mpa. For developing a satisfactory procedure for design of structures using higher strength concretes, additional considerations, and validation or modification of existing strength design methods may be necessary.
Very High Strength Cfment-Based Materials – a Prospective
Authors: Diamond Sidney
Published: March 2011

An attempt is made to provide a prospective on new very high strength cement based materials. The mechanical properties of concrete and of conventional cement pastes are considered, and limitations on the behavior of paste set by the Griffith concept of a critical crack explored. Evidence is cited confirming that spherical air voids do indeed act as critical Griffith flaws in undried pastes; however it is suggested that shrinkage cracks dominate the behavior of cement paste exposed to drying. Very high strength systems.must avoid both large air voids and other pores and also be resistant to shrinkage cracking. Streams of development leading to “DSP” (Aalborg) and “MDF” (ICI) systems are described, and details of the functioning of the two classes of product are described. Current and potential commercial developments are briefly noted, and possible interrelations with the emerging areas of “high technology ceramics” mentioned. Finally, a brief summary of relevant mechanical properties is provided.
The Properties and Potential Applications of Macro-Defect-Free Cement
Authors: Alford N McN , Birchall J D
Published: March 2011

The properties of Macro-Defect-Free (MDF) cements are reviewed. Combinations of these properties place MDF cements in a unique position in the materials field, a position which makes direct replacement of current engineering materials such as metals plastics and ceramics a viable proposition. Perhaps of more importance is the invention of devices and components hitherto unavailable because of the property-restricted nature of available materials. Examples are given of unusual uses for cement. These include applications in the fields of cryogenics, ballistic protection, electromagnetic radiation screening and acoustics.
Slurry Infiltrated Fiber Concrete (SIFCON): Properties and Applications
Authors: Lankard David R.
Published: March 2011

Steel fiber reinforced concretes (SFRC) are typically prepared by adding the fiber along with the other concrete ingredients in the mixing operation. At fiber contents in excess of 2 volume percent, the SFRC becomes difficult or impossible to mix and place. Inasmuch as improvements in concrete properties attributed to the fibers increase as a function of increasing fiber content, this situation places a limit on the ultimate property development in SFRC prepared using the premix approach. Recently, a procedure has been developed wherein steel fiber contents up to 20 volume percent have been provided. Slurry Infiltrated Fiber Concrete (SIFCCN) composites possess outstanding strength, ductility, and crack/spall resistant properties. Equally:important, the ability to construct with SIFCON has been demonstrated.
Microsilica Concrete: A Technological Breakthrough Commercialized
Authors: Radjy Farrokh F. , Loeland Kjell E.
Published: March 2011

With the advent of microsilica concrete, a new generation of high to ultra high strength and high durability concretes have become commercially feasible and are now being specified and used internationally. Microsilica concrete is produced by incorporating microsilica (beneficiated condensed silica fume) additives in conventional concrete mixes, using conventional materials and equipment. Flowing microsilica concretes with strengths as high as 17000 psi have become field realizable, also benefiting by durability improvements expressible by factors, not percents.

Properties of microsilica concrete are reviewed, and property improvements qualitatively linked to a much refined micropore structure of the binder phase.

Some recent and rapidly developing field and laboratory experience both in the U.S. and overseas are presented.
A Measure for the Fracture Toughness of Cement Based Materials
Authors: Jenq Y. S. , Shah S. P.
Published: March 2011

It is frequently reported that the higher the strength of cement based materials, the more brittle is their behavior. It could he useful to quantitatively express the degree of brittleness. Many attempts [1–13] have been made to use linear elastic fracture mechanis (LEFM) to quantitatively express the degree of brittleness. For example, by testing notched beams one can calculate, using the formulas developed from LEFM, a quantity called fracture toughness and termedKICfrom the measured maximum load and the initial notch-length. Unfortunalely, it has been observed thatKthus calculated is dependent on the dimension of the beams. Many researchers have attempted to analyze this size dependency. Such approaches are usually quite cumbersome and are often based on expensive nonlinear finite element programs. In this paper a direct method is suggested to calculate two size-independent fracture toughness parameters from the experimental results. The method was developed based on tests on notched-beams of different mix proportions and different sizes.
A Nuclear Reaction Analysis Technique to Determine The Penetration of Hydrogenic Species into Glasses Exposed to Leaching Solutions
Authors: Gignac L. M. , Altstetter C. J. , Brown S. D.
Published: March 2011

Nuclear reaction analysis is discussed as a method for determining the distribution of deuterium beneath the surfaces of glasses exposed to heavy water solutions for various times and temperatures. Limited examples of both conventional depth profiling for deuterium and a new technique for deuterium mapping are presented. The possible use of deuterium mapping for investigating the kinetics and mechanisms of the leaching of glasses is discussed.
International Waste Glass Study – Composition and Leachability Correlations
Authors: Wicks George G. , Rankin Duncan W. , Gore Sherry L.
Published: March 2011

The International Waste Glass Study found important similarities, based on correlations of composition and leaching performance, among many different defense and commercial waste glass compositions being studied worldwide. In addition, the beneficial effect of waste on glass performance was confirmed for the systems evaluated.
One-Year Leaching of Three SRL Glasses in Granite
Authors: Zhu Bing-Fu , Clark D. E. , Hench L. L. , Wicks G. G. , Werme Lars
Published: March 2011

Three Savannah River Laboratory (SRL) simulated nuclear waste glasses were buried in granite boreholes 345 meters deep. Included in the same boreholes were other potential waste package components including stainless steel and bentonite. Samples were maintained at either ambient mine temperature (8–10°C) or 90°C. Differences in glass leaching performances were observed among the three compositions, with SRL 165 being more durable than SRL 131, both with 29.8% TDS waste. Likewise, the presence of some package components affected the leaching performances. Bentonite resulted in accelerated attack on the glass while the presence of stainless steel did not appear to have much effect. Results obtained through one year of burial are presented in this paper.
Electrokinetics, Adsorption and Colloid Study of Simulated Nuclear Waste Glasses Leached in Aqueous Solutions
Authors: Lee Cheng T. , Clark D. E.
Published: March 2011

Zeta potentials of SRL-131-29.8% TOS simulated nuclear waste glasses leached in D.I. water, Al, Ca, Mg, and Zn chloride solutions at 90°C were measured as a function of leaching time. For short term leaching, the adsorption of Ca, Mg, Zn and Al reverses the glass surface potential from negative to positive. Colloids were found to be stable in D.I. water and AICl3 solutions after leaching, presumably due to the electrostatic repulsion between the glass surface and similarly charged particles. Colloids were not found in Mg, Zn or Ca chloride solutions after leaching; instead, a relatively thick metasilicate surface layer was formed on glass surfaces leached in these solutions. The concentration of Si in solution is reduced by the formation of these surface layers.
Leaching Savannah River Plant Nuclear Waste Glass in a Saturated Tuff Environment
Authors: Bibler N. E. , Wicks G. G. , Oversby V. M.
Published: March 2011

Samples of SRP glass containing either simulated or actual radioactive waste were leached at 90°C under conditions simulating a saturated tuff repository environment. The leach vessels were fabricated of tuff and actual tuff groundwater was used. Thus, the glass was leached only in the presence of those materials (including the Type 304L stainless steel canister material) that would be in the actual repository. Tests were performed for time periods up to 6 months at a SA/V ratio of 100 m−1. Results with glass containing simulated waste indicated that stainless steel canister material around the glass did not significantly affect the leaching. Based on Li and B (elements not in significant concentrations in the tuff or tuff groundwater), glass containing simulated waste leached identically to glass containing actual radioactive waste. The tuff buffered the pH so that only a slight increase was observed as a result of leaching. Results with glass containing actual radioactive waste indicated that tuff reduced the concentrations of Cs-137, Sr-90, and Pu-238 in the free groundwater in the simulated repository by 10–100X. Also, radiolysis of the groundwater by the glass (approximately 1000 rad/hr) did not significantly affect the pH in the presence of tuff. Measured normalized mass losses in the presence of tuff for the glass based on Cs-137, Sr-90, and Pu-238 in the free groundwater were extremely low, nominally 0.02, 0.02, and 0.005 g/m2, respectively, indicating that the glass-tuff system retained radionuclides well.
Nuclear Waste Glass Interfaces after 1 year Burial in Stripa
Authors: Werme L O , Hench L L , Lodding A
Published: March 2011

Interface reactions between two nuclear waste borosilicate glasses and repository components have been studied in an in-situ burial experiment in Stripa mine, Sweden. Exposures up to one year have been analyzed and are reported.

The results obtained up to date show an increased depth of attack ranging by: increased severity from the glass/granite interfaces, glass/glass interfaces to glass/bentonite interfaces. The rate and extent of surface attack is discussed in terms of ion exchange with species from the groundwater and leached from the repository components.
Effect of Temperature on the Sorption of Chelated Radionuclides
Authors: Maest Ann S. , Crerar David A. , Dillon Edward C. , Trehu Stephen M. , Rountree Tamara N.
Published: March 2011

Temperature effects in the near-field radioactive waste disposal environment can result in changes in the adsorptive capacity and character of the substrate and the chemistry of the reacting fluids. This work examines the effect of temperature on 1) the kinetics of radionuclide sorption onto clays from 25°-75°C and 2) the degradation and metal-binding ability of two organic complexing agents found in chelated radioactive wastes and natural groundwaters. Clay-solution mixtures containing U, Co, Sr and Cs with kaolinite or montmorillonite were sampled over a 100-hour period for kinetic results at 25°, 50° and 75°C with and without EDTA. Three thermal degradation experiments with EDTA and oxalic acid were maintained at 250° for one week. Initial equilibrium concentrations were attained in the kinetics runs within 30 minutes in most cases. Possible sorption/retention mechanisms include ion exchange, physical adsorption and/or precipitation. EDTA decreased U and Co sorption, but slightly enhanced Sr and Cs sorption. Complexing of Al by EDTA may drive Sr and Cs to the clay surface to satisfy the resulting charge imbalance. Adsorption increased with increasing temperature for U, Co without EDTA and Sr, while Cs sorption decreased from 25°-75°C. Primary EDTA degration (at ∼200°C) products were mostly ethyl- and methyl-substituted amines with no metal-binding ability; therefore, to inhibit transport of low-level chelated radioactive wastes thermal or biological degradation is recommended. Interaction of high-level radioactive wastes with naturally-occurring organics in repository groundwaters may enhance migration of the actinides and 60Co.
Transport and Capture of Colloidal Particles in Single Fractures
Authors: Bonano E. J. , Beyeler W. E.
Published: March 2011

In this study, the transport and capture rates of colloidal particles were calculated for a parallel-plate channel simulating a single fracture. The steady-state convective diffusion equation was solved with the particle velocity normal to the walls of the channel being the sum of the external forces acting on the particles. The forces considered were the gravitational, London-van der Waals and electric-double layer forces. The effects of parameters governing these forces and particle production mechanism on the rates of particle capture and transport are determined. The dynamic balance between particle production and capture has a significant effect on the concentration of particles leaving the fracture. The average particle velocity, though higher than the average fluid velocity, seems to be insensitive to phenomena governing particle capture.
Behavior of Carbon-14 in Waste Packages for Spent Fuel in a Repository in Tuff
Authors: Konynenburg R. A. Van , Smith C. F. , Culham H. W. , Otto C. H.
Published: March 2011

Analysis of gas from a heated air-filled canister containing a spent fuel assembly before and after rupture of a fuel rod shows that about 1.5 mCi of 14C from the external surface of the assembly was rapidly oxidized and released as 14CO2 in excess oxygen at 275°C and 104rad/hr. After rupture, an additional 0.3 mCi was released, probably also from the external surface. The total 14C inventory in the entire 15×15 rod assembly including structural hardware is estimated to be 690 mCi. These measurements indicate that account will have to be taken of the time distribution of lifetimes of the canisters, and a broad definition of the “engineered system” may be necessary, in order to meet 1OCFR60 requirements with spent fuel in a repository in tuff.
Thermodynamically Coupled Mass Transport Processes in a Saturated Clay
Authors: Carnahan C. L.
Published: March 2011

Gradients of temperature, pressure, and fluid composition in saturated clays give rise to coupled transport processes (thermal and chemical osmosis, thermal diffusion, ultrafiltration) in addition to the direct processes (advection and diffusion). One-dimensional transport of water and a solute in a saturated clay subjected to mild gradients of temperature and pressure was simulated numerically. When full coupling was accounted for, volume flux (specific discharge) was controlled by thermal osmosis and chemical osmosis. The two coupled fluxes were oppositely directed, producing a point of stagnation within the clay column. Solute flows were dominated by diffusion, chemical osmosis, and thermal osmosis. Chemical osmosis produced a significant flux of solute directed against the gradient of solute concentration; this effect reduced solute concentrations relative to the case without coupling. Predictions of mass transport in clays at nuclear waste repositories could be significantly in error if coupled transport processes are not accounted for.
Extension of the EQ3/6 Computer Codes to Geochemical Modeling of Brines
Authors: Jackson Kenneth J. , Wolery Thomas J.
Published: March 2011

Recent modifications to the EQ3/6 geochemical modeling software package [1–3] provide for the use of Pitzer's [4] equations to calculate the activity coefficients of aqueous species and the activity of water. These changes extend the range of solute concentrations over which the codes can be used to dependably calculate equilibria in geochemical systems, and permit the inclusion of ion pairs, complexes, and undissociated acids and bases as explicit component species in the Pitzer model. Comparisons of calculations made by the EQ3NR and EQ6 computer codes with experimental data confirm that the modifications not only allow the codes to accurately evaluate activity coefficients in concentrated solutions, but also permit prediction of solubility limits of evaporite minerals in brines at 25°C and elevated temperatures. Calculations for a few salts can be made at temperatures up to ∼300°C, but the temperature range for most electrolytes is constrained by the availability of requisite data to values ≤100°C. The implementation of Pitzer's equations in EQ3/6 allows application of these codes to problems involving calculation of geochemical equilibria in brines; such as evaluation of the chemical environment which might be anticipated for nuclear waste canisters located in a salt repository.
Rapid Increases in Permeability and Porosity of Bentonite-Sand Mixtures Due to Alteration by Water Vapor
Authors: Couture Rex A.
Published: March 2011

Packed columns of canister packing material containing 25% bentonite and 75% quartz or basalt sand, were exposed to water vapor at temperatures of up to 260°C. The permeabilities of the columns were subsequently measured after complete saturation with liquid water in a pressurized system. Exposure to water vapor caused irreversible increases in permeability by factors of up to 105. After saturation with liquid water, the permeability was nearly independent of temperature. The increases in permeability were due to a large decrease in the ability of the bentonite to swell in water. Calculations suggest that swelling of bentonite exposed to water vapor at 250°C was not sufficient to fill the pore spaces. If the pore spaces are filled, the mixture will form an effective barrier against flow, diffusion, and transport of colloids.

The results suggest that if bentonite-based canister packing material is exposed even briefly to water vapor at high temperatures in a high-level nuclear waste repository, its performance will be seriously impaired. The problem will be less severe if the proportion of bentonite is high and the material is highly compacted. Previous results show significant degradation of bentonite by water vapor at temperatures as low as 150°C. This suggests that in some repositories, backfill in tunnels and drifts may also be affected.
Nonlinear Concentration Effects on Radionuclide Diffusion and Mobility in Compacted Bentonite.
Authors: Anderson Harold M. , Chiao Frank S.
Published: March 2011

This 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

Cantilever 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

Barium 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

A 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

The 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

The 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

Experiments 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

The 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

A 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

The 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

Cesium 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

Brookhaven 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

Recently, 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

Ion-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

Recoil 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

A 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

This 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

Several 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

Anion 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

Anion 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

In 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.
Deep Levels Associated with Oxygen Precipitation in CZ Silicon and Correlation with Minority Carrier Lifetimes
Authors: Chan S. S. , Varker C. J. , Whitfield J. D. , Carpenter R. W.
Published: March 2011

A dominant electron trap in boron-doped CZ silicon at Ec −0.41 ± 0.02 eV with a electron capture cross section >10−14 cm2 has been observed with DLTS in 2-step annealed (16 hrs at 800°C + 16 hrs at 1050°C) seed end wafers where oxygen precipitation is pronounced. A strong correlation between the generation lifetime τg (as calculated from junction reverse generation currents) and the density of this trap is also observed. Electron microscopy showed the dominant precipitates to be {100} plate type containing only Si and 0, with dislocations and punched-out loops in close proximity. Wafers from the center- or tang-sections of the ingot or those given a 1-step anneal (conditions which result in much less oxygen precipitation) contain a low density (<1.2 × 1012 cm−3) of a hole trap at Ev +0.25 eV not correlated with Tg. These wafers contain precipitates with a different morphology with much rower or minimal dislocation densities. Possible origins of the lifetime controlling electron trap is discussed.
Evidence of Lattice Relaxation in Platinum-Doped Silicon
Authors: Mayo Santos , Lowney J. R. , Bell M. I.
Published: March 2011

The photoionization cross section of the platinum-acceptor level in silicon was measured (in relative units) as a function of photon energy. Capacitance transients due to electron emission from this level were studied in a p+n gated photodiode at temperatures of 40, 60, and 80 K. Measurements were made over the wavelength range of 2 to 5 μm with light from a prism monochromator with a constant bandpass of 10 meV. The platinum density in the diode was about 1014 cm−3, providing a ratio of deep to shallow (phosphorus) levels of about 0.1. The data are in good agreement with the Ridley-Amato lattice-coupling model when a Huang-Rhys parameter of S = 0.3 is used, corresponding to a Frank-Condon shift of 15 meV if an average phonon energy of 50 meV is assumed. The electronic energy of the acceptor level was 226 ± 5 meV below the conduction band, independent of temperature and in agreement with previous studies of thermal ionization. The present results provide the first clear experimental evidence of lattice relaxation associated with a deep level in silicon. However, the observed Huang-Rhys parameter is smaller than the theoretical estimates of Lowther (S ≅ 1), suggesting that multiphonon emission may not be the only mechanism for carrier recombination involving this level.