bluuebunny/crossref_metadata_2025_split huggingface dataset:
Devitrification Behavior of SRL Defense Waste Glass
Authors: Bickford Dennis F. , Jantzen Carol M. 
Published: March 2011

ABSTRACTSimulated SRL waste was prepared with compositions varying in iron and aluminum content. Two batches with similar composition were produced with different amounts of reducing agent added. Samples were isothermally heat treated and used to derive time-temperature-transformation diagrams. Supplementary samples were cooled in a manner programmed to simulate the cooling curves of production canisters. Less than 10% total devitrification occurs during normal processing. However, when waste glass 165 was purposely devitrified, un to 30 volume percent total spinel and acmite formed. Formation of these species had minor effect on leachability in MCC-1 and accelerated leach tests.
Diffusion of Colloids and Other Waste Species in Brine–Saturated Backfill Materials
Authors: Nowak E. J. 
Published: March 2011

ABSTRACTThe diffusion of plutonium (IV) and pertechnetate and the migration of colloidal gold in brine-saturated bentonite was measured. High ionic strength brine characterizes potentially intruding groundwater for radioactive waste repositories in salt. Plastic diffusion cells containing cylindrical diffusion columns were used for low density bentonite. Metal diffusion cells constructed entirely from Hastelloy C-276 were used for the diffusion of pertechnetate in highly compacted bentonite. Apparent distribution coefficients calculated from plutonium diffusion in two columns of low density bentonite are 2 m3/kg and 3 m3/kg. These values are in good agreement with the value of 3m3/kg that was calculated from previous batch sorption data. Pertechnetate anions migrated out of a brine-saturated high density bentonite diffusion column at rates that are too large to be rationalized with a simple diffusion theory. Additional measurements that take into account possible channeling of pertechnetate are required. Colloidal gold was excluded from low density brine-saturated bentonite, but colloidal gold may have channeled between the bentonite and the wall of the diffusion cell. These results support the effectiveness of brine-saturated bentonite as an engineered barrier to plutonium. The results also highlight the need for additional measurements of pertechnetate and gold transport in bentonite. Needs for transport measurements that take into account site-specific materials interactions are also described.
Leach Testing of Waste Glasses Under Near-Saturation Conditions
Authors: Grambow B. , Strachan D. M. 
Published: March 2011

ABSTRACTTwo waste glasses, MCC 76-68 and C31-3, were leached in deionized water and 0.001 M MgCl2 for periods up to 158 days. At 57 days the gel layer was removed from some of the specimens and leaching continued for up to 100 days. Results from leaching in deionized water showed that the gel layer was not protective. Results from leaching in 0.001 M MgCl2 are in good agreement with the predicted results obtained from the use of the PHREEQE geochemical code and with sepiolite [Mg2Si306(OH)4] as the Mg-bearing precipitate. Both B and Si were predicted and observed to increase with increasing glass dissolution while maintaining sepiolite solubility. Both MCC 76-68 and C31-3 glasses showed increased leaching in 0.001 M MgCl2 upon removal of the layer. This suggests that the leaching mechanism is a function of the difference in the silica chemical potential between the glass and the gel layer.
Leach Behavior of SRL TDS-131 Defense Waste Glass in Water at High&Low Flow Rates
Authors: Barkatt Aaron , Sousanpour William , Barkatt Alisa , Boroomand Morad A. , Macedo Pedro B. 
Published: March 2011

ABSTRACTLeach tests carried out on SRL TDS-131 Defense Waste Class indicate that at high flow rates the controlling mechanism is simple corrosion. The matrix elements (Si, Al) are leached out at rates similar to those of the leaching of the alkalis and of boron, and the leaching process is nearly linear with time. At slow flow rates (below 1 m/yr) leaching becomes controlled by the build-up of a protective layer. Al and most of the Si remain in the leached surface layer. The leach rates decrease in the course of the test before leveling off at constant values which are almost inversely proportional to the contact time, indicating that leachate concentrations have become solubility-limited. The low concentrations observed at this stage indicate the formation of alteration products.
Effects of Metals and Metal Oxides on the Leaching of Nuclear Waste Glasses
Authors: Barkatt Aaron , Sousanpour William , Barkatt Alisa , Boroomand Morad A. 
Published: March 2011

ABSTRACTThe effects of the presence of various metals and metal oxides on the leaching of nuclear waste glasses in water can be considerable even under rapid flow conditions. The systems studied here include SRL TDS-131 glass in the presence of lead and stainless steel, and PNL 76-68 glass in the presence of aluminum, alumina and their mixtures. Lead specifically suppresses dissolved silica, but does not inhibit dissolution of defense waste glass as a whole. Stainless steel specifically reduces the levels of dissolved Ca and Sr. Al and Al2 O3 exercise a general reducing effect on the rates of dissolution of commercial waste glass and the presence of alumina may have a beneficial role in enhancing waste package durability.
The Waste Package Materials Field Test in S.E. New Mexico Salt
Authors: Molecke Martin A. , Torres Teresa M. 
Published: March 2011

ABSTRACTA six-part, waste package materials field test was conducted in a halite horizon of a potash mine in southeastern New Mexico. The primary purposes of this test were to evaluate the thermophysical and geochemical performance of candidate HLW-package backfill materials emplaced in rock salt and the corrosion behavior of candidate waste canister or overpack alloys. This field test series also served as a precursor to forthcoming Waste Isolation Pilot Plant (WIPP) in situ waste package performance experiments on simulated defense high-level waste packages, serving to develop applicable testing, instrumentation, and sampling techniques. The backfill materials tested (individually, in one- to five-month tests) were: low-density bentonite clay; low-density bentonite (70 wt.%)-silica sand (30 wt.%) mixtures, both dry and brine-injected; high-density bentonite-sand annular compacts; trapped air; and finely-crushed WIPP salt. The in situ measured thermal conductivities (at a maximum canister-heater surface temperature of 150° or 250°C) for the backfills ranged from 0.25 W/mK for pure bentonite to about 1.25 W/mK for the high-density bentonite-sand. No significant backfill material degradation products were detected in post-test analyses. No appreciable corrosion of the titanium-, nickel-, or iron-based alloys embedded in the hot backfill was found; potentially significant pitting corrosion of 2 1/4 Cr-1 Mo steel and copper was detected.
Activity Diagrams for Calcium/Hydrogen, Sodium/Hydrogen, and Potassium/Hydrogen, and H4SiO4and Their Relation to Reactions in Systems Containing Radioactive Waste Forms, Cement, and Rock in the Presence of Water
Authors: Barnes Mary W. , Roy Della M. 
Published: March 2011

ABSTRACTIn order to identify reactions which can occur in systems containing nuclear waste forms, cement, and repository rock in the presence of water, activity diagrams were calculated from free energies for aluminosilicates and calcium silicates. Log (calcium activity)/(hydrogen activity)2was plotted against log (H4SiO4activity) for reactions among calcium aluminum silicates for which free energies are available in the literature. Similar diagrams were made for sodium/hydrogen activity, and potassium/hydrogen activity. For calcium an activity diagram was constructed for the silicates.Groundwater compositions from candidate repository sites in the Palo Duro Basin of Texas, the Delaware Basin of New Mexico, and the Nevada Test Site were plotted on these diagrams. Essentially all of these are shown to be in the calcium zeolite field as shown on the diagram for calcium in the absence of other cations. When considerable Mg and Fe are present in the water, other phases may replace the calcium zeolite in the pertinent region of the diagram. Chlorite is shown to be stable in this region at the Mg and pH level of the Ogallala if the chlorite is high in iron, and at the Mg and pH level of the Wolfcamp low- or high-Fe chlorites are stable. Potassium and sodium mineralrelationships fall in two categories, dilute waters and saline waters. Of the dilute waters, that from the Ogallala aquifer in the Palo Duro Basin, and most of the Nevada Test Site waters, including that from the proposed radwaste repository horizon, are in equilibrium with Na-beidellite and kaolinite. Boreholes at Yucca Flat and Mercury Valley at the Nevada Test Site, and shallow ground water from the Rolling Plains north and east of the Palo Duro Basin are in equilibrium with kaolinite. Of the saline waters, that from the Castile (deep in the Delaware Basin) is a kaolinite water. The brines from the Salado and Rustler formations are in equilibrium with kaolinite and possibly also with sodium-potassium zeolite and illite.Leachates of cement and water, and cement, waste, and water were plotted on the calcium silicate activity diagram. These solutions are in equilibrium with calcium silicate hydrate hydrolysis reactions, with grossular and possibly with Ca-zeolites. Among the calcium silicates, calciumsilicate-hydrate gel (C-S-H gel) and tobermorite are the most likely candidates, but the thermodynamic data are not adequate to distinguish all the possibilities. The underlying assumptions are discussed.
Stability of Radioactive Waste Glasses Assessed from Hydration Thermodynamics
Authors: John Plodinec M. , Jantzen Carol M. , Wicks George G. 
Published: March 2011

ABSTRACTAssessment of the geologic performance of radioactive waste glasses requires extrapolation of finite tests to very long times. Hydration thermodynamics provides a means to compare the stability of waste glasses to natural analogues and to ancient synthetic glasses. The glass composition is separated into structural components of known free energy of hydration. These are then summed to provide a discrete measure of the stability of a given glass to aqueous attack. Hydration thermodynamics can be used to extend the results of laboratory tests of Savannah River waste glass to the repository environment.
Kinetics of the Adsorption of Radionuclides on Tuff From Yucca Mountain
Authors: Rundberg R. S. 
Published: March 2011

ABSTRACTThe sorption of simple cations in tuff is dominated by adsorption on aluminosilicates that have charged surfaces, suc as zeolites and clays. The most significant sorbing minerals present in Nevada tuff are clinoptilolite, heulandite, mordenite, and montmorillonite. The kinetics of sorption on tuffs containing the minerals clinoptilolite and montmorillonite has been determined by studying the uptake of strontium, cesium, and barium on thin tuff wafers. The rate constants for uptake of these elements on tuff are consistent with a model of sorption that is diffusion limited but where diffusion occurs in two stages. First the cations diffuse into the rock through the water-filled pore space. Next, the cations must diffuse into the much narrower channels within the aluminosilicate crystals. After they are within the zeolite framework o between the clay planes, the cations may rapidly sorb on the negatively charged surfaces. The actinide elements have a time constant for the apparent sorption that is inconsistent with this model and may have a radically different mechanism o removal from solution.
A Natural Analogue Study of Radionuclide Migration in Clays
Authors: Mckinley Ian G. , Mackenzie Angus B. , West Julia M. , Scott R. D. 
Published: March 2011

ABSTRACTThe use of sediment laid down in a Scottish loch during the Flandrian marine transgression as a source term for a “natural analogue” study of elemental migration in clays over a timescale of 103 − 104 y has been investigated. Depth profiles of over 20 elements have been measured which illustrate varying post depositional behaviour ranging from effectively total immobility to complete redistribution throughout the sediment profile. These results are contrasted with laboratory batch sorption data for a range of nuclides on samples of this sediment.
Disproportionation and Polymerization of Plutonium(IV) in Dilute Aqueous Solutions
Authors: Newton T. W. , Rundberg V. L. 
Published: March 2011

ABSTRACTThe rates of polymerization and disproportionation of Pu(IV) have been studied using low concentrations: (1.7 − 10) × 10−6M Pu, (0.8 − 12) × 10−4M HCI and 0.01M ionic strength. Osmium(II) complexes such as the tris−4,41−2,21−bipyridine complex were found to react rapidly with Pu(IV) but very slowly, if at all, with Pu(IV) polymer, Pu(lll), or Pu(V). Thus, it is possible to determine unreacted Pu(IV) in the presence of reaction products by using Os(II) complexes. Disproportionation reaction products, Pu(IlI) and Pu(V), were determined using their reactions with Ce(IV) sulfate. We find −d[Pu(IV)]/dt = k'[Pu(IV)]2 at constant pH. Log k1 varies from about 4.25 at pH 3 to about 7.0 at pH 4.1 (units for k1 are M−1min−1). The [H+] dependence varies from about −2 to −3 over the pH range studied. The measured rate is the sum of those for polymerization and disproportionation; the latter reaction amounts to about 75% of the total at pH 3 and 20% at pH 4. The second-order rate constants for disproportionation are very much larger than expected on the basis of extrapolation from 0.2 to 1.OM HClO, solutions. The products of the reaction do not affect the rate, but U(VI), aged Pu(IV) polymer, and CO2 increase the rate.
Permeability and Pore-Fluid Chemistry of the Topopah Spring Member of the Paintbrush Tuff, Nevada Test Site, in a Temperature Gradient – Application to Nuclear Waste Storage
Authors: Morrow C. A. , Moore D. E. , Byerlee J. D. 
Published: March 2011

ABSTRACTThe Topopah Spring Member of the Paintbrush Tuff from the Nevada Test Site is being investigated by the Nevada Nuclear Waste Storage Investigations project (NNWSI) as a possible nuclear waste repository host rock. Changes with time of the permeability and fluid chemistry of the Topopah Spring Member have been measured in samples subjected to a temperature gradient. Maximum temperatures of the imposed gradients ranged from 90° to 250°C; minimum temperatures were 36° to 83°C. Confining and pore pressures simulated a depth of about 1.2 km, which is greater than the proposed repository depth, but chosen for comparison with previous studies at these pressures. Pore fluid used in the experiments was groundwater from the Nevada Test Site; the direction of pore-fluid flow was from the high- to the low-temperature side of the tuffs.Initial permeabilities of the tuff samples ranged from 3 to 65 μdarcys, the wide range in values resulting from differences in the void and fracture geometries of the samples. Heating the tuffs produced no change in permeability in tne lowest temperature experiment and only small changes at higher temperatures. The fluids discharged from the tuffs were dilute waters of nearneutral pH that differed only slightly from the original groundwater composition.Since proposed burial in the Topopah Spring Member would be in the unsaturated zone, the high initial permeabilities and the absence of permeability change with heating may be desirable, because downward-percolating waters would be able to drain into deeper formations and not collect at the repository level. in addition, any fluids that may come in contact with waste canisters wlll not have acquired any potentially corrosive characteristics through interaction with the tuff.
The Use of Natural Radionuclides to Predict the Behavior of Radwaste Radionuclides In Far-Field Aquifers
Authors: Hubbard N. , Laul J. C. , Perkins R. W. 
Published: March 2011

ABSTRACTIn appropriate aquifers the natural radionuclides of the U and Th decay series are important sources of information about the behavior of radwaste radionuclides in far-field aquifers. The Wolfcamp Carbonate, Pennsylvanian Carbonate and Granite Wash aquifers in the Palo Duro Basin of the Texas Panhandle are prime examples of such aquifers. Sampling and analysis for key radionuclides in the ground waters of these aquifers are quite feasible and have been accomplished. Key early results are: (1) Ra does not appear to be retarded by sorption, (2) Th appears to be strongly sorbed, (3) kinetics seem to be different on time scales of days to months than on ones of hundreds of thousands of years, and (4) U and Th behave similarily when the time scales (half-lives) are similar, leading to the suggestion that uranium is in the +4 valence state in these aquifers.
Mechanisms for the Interaction of Americium(III) and Neptunium(V) with Geologic Media
Authors: Allard B. 
Published: March 2011

ABSTRACTThe sorption of americium(III) and neptunium(V) on geologic media has been measured under oxic conditions. The aqueous phase was generally a synthetic groundwater. The solid phase was a pure mineral, representative of crystalline granitic rocks. Altogether 40 minerals and rocks were used. The effects of parameters such as pH and ionic strength of the aqueous phase as well as cation exchange capacity and surface/mass ratio of the solid sorbent are discussed. The sorption mechanism in the environmental pH-range can be denoted as physical adsorption process, which is largely governed by pH and the speciation in the aqueous phase and to a less extent by the exchange capacity of the solid.
The Basalt/Water System: Considerations for a Nuclear Waste Repository
Authors: Lane D.L. , Apted M.J. , Allen C.C. , Myers J. 
Published: March 2011

ABSTRACTHigh-level nuclear Waste emplaced in a repository in basalt will lead to elevated temperatures and chemical reactions between the basalt and repository groundwater. The resultant changes in groundwater chemistry and the formation of secondary minerals will affect radionuclide release rates from the repository. In this study, Grande Ronde Basalt and synthetic groundwater were reacted at temperatures of 100°, 150°, and 300°C at a pressure of 30 MPa. Dickson-type sampling autoclaves were used to follow solution composition changes with time. Solution PH remained weakly alkaline, while steady state concentrations of F-, Cl-, SO4-2, and total Carbon were similar to or lower than initial values. Alteration assemblages at 300°C included silica, zeolites, potassium feldspar, and iron smectite. These assemblages are metastable, and prediction of alteration in the basalt and packing material depends on “accelerated” tests results and must be supplemented by study of metastable assemblages in natural analog systems and by tests in open systems with varying flow rates. Experimental data are consistent with rapid adjustment of Eh to reducing values; however, more work on reaction rates and buffering capacity is in progress.
Chemical Migration by Contact Metamorphism between Pegmatite and Country Rocks: Natural Analogs for Radionuclide Migration
Authors: Laul J. C. , Walker R. J. , Shearer C. K. , Papike J. J. , Simon S. B. 
Published: March 2011

ABSTRACTComparison of trace element signatures of country rocks as a function of distance from the contact with two pegmatites, Tin Mountain and Etta, in the Black Hills of South Dakota, suggests that some elements such as K, Li, Rb, Cs, As, Sb, Zn and Pb, have migrated to distances of 4 to 40 meters during contact metamorphism. The relative degree of migration varies depending on the element. On the other hand, there is virtually no migration of rare earth elements (REE), Al, Sc, Cr, Hf, U, and Th. Biotite and muscovite are effective trace element traps for Li, Rb and Cs. Biotite has a greater affinity for Rb, Cs and Li than muscovite.
CVD and Characterization of Al-Cu Metallization Thin Films
Authors: Houlding V. H. , Maxwell H. , Crochiere S. M. , Farrington D. L. , Rai R. S. , Tartaglia J. M. 
Published: March 2011

ABSTRACTThe chemical vapor deposition of Al-Cu thin films on Si, SiO2, and TiN substrates was examined in a vertical low pressure cold wall reactor using trimethylamine alane (TMAA1) at 20 C as the Al source. The Cu sources bis-(hexafluoroacetylacetonato)copper(H)(CuHFA), (cyclopentadienyl)copper(I) triethylphosphine (CpCuPEt3), and (hexafluoroacetylacetonato)copper(I) trimethylphosphine (HfaCuPMe3), were compared. The Cu content of the films was controlled up to“5 wt% by simply varying the temperature of the Cu source. Codeposited Al-Cu films with excellent conductivity, purity, and adhesion properties were obtained with all Cu sources. Optimal film smoothness was achieved at∼350 C. The compounds differed in the ease of control over the %Cu in the films. CuHFA exhibited a massive parasitic reaction which made control very difficult. The Cu(I) complexes showed very minor parasitic reactions. Analysis of films with high Cu content by SEM-EDS showed clear segregation of Cu and Al, consistent with the low solubility of Cu in Al. Films with >2% Cu appeared homogeneous on a μm scale by both SEM-EDS and SIMS depth profiling. TEM of film cross sections revealed a polycrystalline Al film with small (20–100 Å) Cu-rich particles dispersed throughout the Al grains. These particles exhibited bright field-dark field contrast characteristic of crystalline material.
Detection of Titanium Silicide Formation and Phase Transformation by Picosecond Ultrasonics
Authors: Lin H. -N. , Stoner R. J. , Maris H. J. , Harper J. M. E. , Cabral C. , Halbout J. -M. , Rubloff G. W. 
Published: March 2011

ABSTRACTPicosecond ultrasonics is employed to study the titanium silicide formation sequence for evaporated Ti films on silicon substrates annealed at temperatures between 300 and 800 °C. The measurements show significant differences in the ultrasonic echo pattern before and after the structural phases C49 and C54 are formed, thus indicating that picosecond ultrasonics is a sensitive non-destructive probe of silicide formation. The longitudinal sound velocity has been found to be (8.3 ± 0.2) × 105 cm/sec for C49 TiSi2, and about 5% lower for the C54 phase.
Air-Bridge Electron-Beam Lithography for Coplanar Millimeter Wave Circuits
Authors: Haydl William H. , Bojko R. J. , Eastman L. F. 
Published: March 2011

ABSTRACTIn the development of air bridges for low capacitance crossovers, resists of 3–6μm thickness a e needed, which calls for special alignment techniques. A technique has been developed for an air bridge tec nology, which is realized entirely by electron beam lithography. Such an all-electron-beam technique for sub-micron devices and ultrahigh frequency circuits, results in a fast turn-around-time in the development of integrated circuits.Gold plated air bridges with 20 to 120 pm span, 5–60 μm width, 2.6 pm height, and 2–4 μm thickness, were realized on GaAs and InP.
Barrier Inhomogeneities at Schottky Contacts: Curved Richardson Plots, Idealities, and Flat Band Barriers
Authors: Werner Jürgen H. , Güttler Herbert H. , Rau Uwe 
Published: March 2011

ABSTRACTEvaluating either curved Richardson plots or temperature-dependent ideality data allows for a quantitative characterization of spatial inhomogeneities at Schottky contacts. Applying the two independent methods to PtSi/Si diodes we obtain a standard deviation around 70mV for the barrier fluctuations. These results agree with those from the comparison of temperature-dependent current and capacitance barriers. We discuss also flat band barrier heights which should be used if one investigates the temperature dependence of fundamental Schottky barrier heights. Their temperature coefficients depend on metallization. For epitaxial NiSi2/Si contacts on (100) oriented Si we find a strong influence of interface crystallography on the temperature coefficients.