Engineering Commons^™

A Site-Wide Perspective On Uranium Geochemistry At The Hanford Site, John M. Zachara, C. Brown, J. Christensen, J.A. Davis, E. Dresel, Chongxuan Liu, S. Kelly, James Mckinley, J. Serne, W. Um

US Department of Energy Publications

Uranium (U) is an important risk-driving contaminant at the Hanford Site. Over 200,000 kg have been released to the vadose zone over the course of site operations, and a number of vadose zone and groundwater plumes containing the uranyl cation [UO₂²⁺, U(VI)] have been identified. U is recognized to be of moderate-to-high mobility, conditions dependent. The site is currently making decisions on several of these plumes with long-lasting implications, and others are soon to come.

Uranium is one of nature’s most intriguing and chemically complex elements. The fate and transport of U(VI) has been studied over the …

Scenarios Of Greenhouse Gas Emissions And Atmospheric Concentrations, Leon Clarke, James Edmonds, Henry Jacoby, Hugh Pitcher, John Reilly, Richard Richels

US Department of Energy Publications

This and a companion report constitute one of twenty-one Synthesis and Assessment Products called for in the Strategic Plan for the U.S. Climate Change Science Program. These studies are structured to provide high-level, integrated research results on important science issues with a particular focus on questions raised by decision-makers on dimensions of climate change directly relevant to the U.S. One element of the CCSP’s strategic vision is to provide decision support tools for differentiating and evaluating response strategies. Scenario-based analysis is one such tool. The scenarios in this report explore the implications of alternative stabilization levels of anthropogenic greenhouse …

Global-Change Scenarios: Their Development And Use, Edward Parson, Virginia Burkett, Karen Fisher-Vanden, David Keith, Linda Mearns, Hugh Pitcher, Cynthia Rosenzweig, Mort Webster

US Department of Energy Publications

A scenario is a description of potential future conditions produced to inform decision-making under uncertainty. Scenarios can help inform decisions that involve high stakes and poorly characterized uncertainty, which may thwart other, conventional forms of analysis or decision support. Originally developed to study military and security problems, scenarios are now widely used for strategic planning and assessment in businesses and other organizations, and increasingly to inform planning, analysis, and decision-making for environmental issues, including climate change.
Scenarios can serve many purposes. They can help inform specific decisions, or can provide inputs to assessments, models, or other decision-support activities when these …

Controlled Covalent Functionalization Of Multiwalled Carbon Nanotubes Using [4 + 2] Cycloaddition Of Benzocyclobutenes, Georgios Sakellariou, Haining Ji, Jimmy W. Mays, Nikos Hadjichristidis, Durairaj Baskaran

US Department of Energy Publications

Surface modification of carbon nanotubes (CNTs) through covalent functionalization is vital for the development of high-performance composite materials, chemosensors, nanoelectronics, photovoltaic devices, as well as for a range of biomedical applications. Several methods have been developed to functionalize CNTs. The introduction of acid groups by acid digestion disrupts the structural integrity of CNTs. Apart from shortening the tubes, oxidatively generated acid groups are inhomogenously located at the tips of broken CNTs and, hence, functionalization using acid groups as precursors does not give a statistical distribution of functional groups throughout the surface of the CNTs.

Biostimulation Of Iron Reduction And Subsequent Oxidation Of Sediment Containing Fe-Silicates And Fe-Oxides: Effect Of Redox Cycling On Fe(Iii) Bioreduction, John Komlos, Ravi K. Kukkadapu, John M. Zachara, Peter R. Jaffe

US Department of Energy Publications

Sediment containing a mixture of iron (Fe)-phases, including Fe-oxides (mostly Al-goethite) and Fe-silicates (illites and vermiculite) was bioreduced in a long-term flow through column experiment followed by re-oxidation with dissolved oxygen. The objective of this study was (a) to determine the nature of the re-oxidized Fe(III), and (b) to determine how redox cycling of Fe would affect subsequent Fe(III)-bioavailability. In addition, the effect of Mn on Fe(III) reduction was explored.⁵⁷Fe-Mössbauer spectroscopy measurements showed that biostimulation resulted in partial reduction (20%) of silicate Fe(III) to silicate Fe(II) while the reduction of goethite was negligible. Furthermore, the reduction of Fe …

Influence Of Calcium On Microbial Reduction Of Solid Phase Uranium(Vi), Chongxuan Liu, Byong-Hun Jeon, John M. Zachara, Zheming Wang

US Department of Energy Publications

The effect of calcium on the dissolution and microbial reduction of a representative solid phase uranyl [U(VI)], sodium boltwoodite (NaUO₂SiO₃OH •1.5H₂O), was investigated to evaluate the rate-limiting step of microbial reduction of the solid phase U(VI). Microbial reduction experiments were performed in a culture of a dissimilatory metal-reducing bacterium (DMRB), Shewanella oneidensis strain MR-1, in a bicarbonate medium with lactate as electron donor at pH 6.8 buffered with PIPES. Calcium increased the rate of Na-boltwoodite dissolution and U(VI) bioavailability by increasing its solubility through the formation of a ternary aqueous calcium-uranyl-carbonate species. The ternary …

Hanford Site Vadose Zone Studies: An Overview, G. W. Gee, M. Oostrom, M. D. Freshley, M. L. Rockhold, John M. Zachara

US Department of Energy Publications

Large quantities of radioactive and chemical wastes resulting from Pu production for nuclear weapons are located in the vadose zone at the USDOE’s Hanford Site, north of Richland, WA. The vadose zone here is characterized by often highly stratified glacial-fluvial sediments that give rise to complex subsurface-flow paths that contribute to uncertainty of contaminant fate and transport. Research efforts have focused on answering questions of contaminant transport from the viewpoint of geologic, biologic, geochemical, and hydrologic controls. This special section highlights key research topics concerning vadose zone problems at the Hanford Site. Research indicates that some of the contaminant species …

Respiration Of Metal (Hydr)Oxides By Shewanella And Geobacter: A Key Role For Multihaem C-Type Cytochromes, Liang Shi, Thomas C. Squier, John M. Zachara, James K. Fredrickson

US Department of Energy Publications

Dissimilatory reduction of metal (e.g. Fe, Mn) (hydr)oxides represents a challenge for microorganisms, as their cell envelopes are impermeable to metal (hydr)oxides that are poorly soluble in water. To overcome this physical barrier, the Gram-negative bacteria Shewanella oneidensis MR-1 and Geobacter sulfurreducens have developed electron transfer (ET) strategies that require multihaem c-type cytochromes (c-Cyts). In S. oneidensis MR-1, multihaem c-Cyts CymA and MtrA are believed to transfer electrons from the inner membrane quinone/quinol pool through the periplasm to the outer membrane. The type II secretion system of S. oneidensis MR-1 has been implicated in the reduction of metal …

Convergence Of Peridynamics To Classical Elasticity Theory, S. A. Silling, R. B. Lehoucq

US Department of Energy Publications

The peridynamic model of solid mechanics is a nonlocal theory containing a length scale. It is based on direct interactions between points in a continuum separated from each other by a finite distance. The maximum interaction distance provides a length scale for the material model. This paper addresses the question of whether the peridynamic model for an elastic material reproduces the classical local model as this length scale goes to zero. We show that if the motion, constitutive model, and any nonhomogeneities are sufficiently smooth, then the peridynamic stress tensor converges in this limit to a Piola-Kirchhoff stress tensor that …

Peridynamic States And Constitutive Modeling, S. A. Silling, M. Epton, O. Weckner, J. Xu, E. Askari

US Department of Energy Publications

A generalization of the original peridynamic framework for solid mechanics is proposed. This generalization permits the response of a material at a point to depend collectively on the deformation of all bonds connected to the point. This extends the types of material response that can be reproduced by peridynamic theory to include an explicit dependence on such collectively determined quantities as volume change or shear angle. To accomplish this generalization, a mathematical object called a deformation state is defined, a function that maps any bond onto its image under the deformation. A similar object called a force state is defined, …

Efficiency Of Gene Silencing In Arabidopsis: Direct Inverted Repeats Vs. Transitive Rnai Vectors, Sergei A. Filichkin, Stephen P. Difazio, Amy M. Brunner, John M. Davis, Zamin K. Yang, Udaya C. Kalluri, Renee S. Arias, Elizabeth Etherington, Gerald A. Tuskan, Steven H. Strauss

US Department of Energy Publications

We investigated the efficiency of RNA interference (RNAi) in Arabidopsis using transitive and homologous inverted repeat (hIR) vectors. hIR constructs carry self-complementary intron-spliced fragments of the target gene whereas transitive vectors have the target sequence fragment adjacent to an intron-spliced, inverted repeat of heterologous origin. Both transitive and hIR constructs facilitated specific and heritable silencing in the three genes studied (AP1 , ETTIN and TTG1 ). Both types of vectors produced a phenotypic series that phenocopied reduction of function mutants for the respective target gene. The hIR yielded up to fourfold higher proportions of events with strongly manifested reduction …

Phosphate Imposed Limitations On Biological Reduction And Alteration Of Ferrihydrite, Thomas Borch, Yoko Masue, Ravi K. Kukkadapu, Scott Fendorf

US Department of Energy Publications

Biogeochemical transformation (inclusive of dissolution) of iron (hydr)oxides resulting from dissimilatory reduction has a pronounced impact on the fate and transport of nutrients and contaminants in subsurface environments. Despite the reactivity noted for pristine (unreacted) minerals, iron (hydr)oxides within native environments will likely have a different reactivity owing in part to changes in surface composition. Accordingly, here we explore the impact of surface modifications induced by phosphate adsorption on ferrihydrite reduction by Shewanella putrefaciens under static and advective flow conditions. Alterations in surface reactivity induced by phosphate changes the extent, decreasing Fe(III) reduction nearly linearly with increasing P surface coverage, …

Reduction Of Pertechnetate [Tc(Vii)] By Aqueous Fe(Ii) And The Nature Of Solid Phase Redox Products, John M. Zachara, Steve M. Heald, Byong-Hun Jeon, Ravi K. Kukkadapu, Chongxuan Liu, James P. Mckinley, Alice C. Dohnalkova, Dean A. Moore

US Department of Energy Publications

The subsurface behaviour of ⁹⁹Tc, a contaminant resulting from nuclear fuels reprocessing, is dependent on its valence (e.g., IV or VII). Abiotic reduction of soluble Tc(VII) by Fe(II)_(aq) in pH 6–8 solutions was investigated under strictly anoxic conditions using an oxygen trap (<7.5 · 10^-9 atm O₂). The reduction kinetics were strongly pH dependent. Complete and rapid reduction of Tc(VII) to a precipitated Fe/Tc(IV) form was observed when 11 µmol/L of Tc(VII) was reacted with 0.4 mmol/L Fe(II) at pH 7.0 and 8.0, while no significant reduction was observed over 1 month at pH 6.0. Experiments conducted …

Uranium(Vi) Release From Contaminated Vadose Zone Sediments: Estimation Of Potential Contributions From Dissolution And Desorption, Deborah L. Bond, James A. Davis, John M. Zachara

US Department of Energy Publications

A key difficulty in developing accurate, science-based conceptual models for remediation of contaminated field sites is the proper accounting of multiple coupled geochemical and hydrologic processes. An example of such a difficulty is the separation of desorption and dissolution processes in releasing contaminants from sediments to groundwaters; very few studies are found in the literature that attempt to quantify contaminant release by these two processes. In this study, the results from several extraction techniques, isotopic exchange experiments, and published spectroscopic studies were combined to estimate the contributions of desorption and dissolution to U(VI) release from contaminated sediments collected from the …

Kinetics Of Reductive Dissolution Of Hematite By Bioreduced Anthraquinone-2,6-Disulfonate, Chongxuan Liu, John M. Zachara, Nancy Foster, Janae Strickland

US Department of Energy Publications

The reductive dissolution of hematite (α-Fe₂O₃) was investigated in a flow-through system using AH2DS, a reduced form of anthraquinone-2,6-disulfonate (AQDS), which is often used as a model electron shuttling compound in studies of dissimilatory microbial reduction of iron oxides. Influent flow rate, pH, and Fe(II) and phosphate concentrations were varied to investigate the redox kinetics in a flow-through reactor. The hematite reduction rates decreased with increasing pH from 4.5 to 7.6 and decreased with decreasing flow rate. The rates also decreased with increasing influent concentration of Fe(II) or phosphate that formed surface complexes at the experimental …

Spectroscopic Evidence For Uranium Bearing Precipitates In Vadose Zone Sediments At The Hanford 300-Area Site, Yuji Arai, M. A. Marcus, N. Tamura, J. A. Davis, John M. Zachara

US Department of Energy Publications

Uranium (U) solid-state speciation in vadose zone sediments collected beneath the former North Process Pond (NPP) in the 300 Area of the Hanford site (Washington) was investigated using multi-scale techniques. In 30 day batch experiments, only a small fraction of total U (~7.4%) was released to artificial groundwater solutions equilibrated with1% pCO₂. Synchrotron-based micro-X-ray fluorescence spectroscopy analyses showed that U was distributed among at least two types of species: (i) U discrete grains associated with Cu and (ii) areas with intermediate U concentrations on grains and grain coatings. Metatorbernite (Cu[UO₂]₂[PO₄]₂•8H …

Cation Exchange Reactions Controlling Desorption Of 90sr2+ From Coarse-Grained Contaminated Sediments At The Hanford Site, Washington, James Mckinley, John M. Zachara, Steven Smith, Chongxuan Liu

US Department of Energy Publications

Nuclear waste that bore ⁹⁰Sr²⁺ was accidentally leaked into the vadose zone at the Hanford site, and was immobilized at relatively shallow depths in sediments containing little apparent clay or silt-sized components. Sr²⁺, ⁹⁰Sr²⁺, Mg2+, and Ca²⁺ was desorbed and total inorganic carbon concentration was monitored during the equilibration of this sediment with varying concentrations of Na⁺, Ca²⁺. A cation exchange model previously developed for similar sediments was applied to these results as a predictor of final solution compositions. The model included binary exchange reactions for the four …

Geochemical Controls On Contaminant Uranium In Vadose Hanford Formation Sediments At The 200 Area And 300 Area, Hanford Site, Washington, James Mckinley, John M. Zachara, Jiamin Wan, David Mccready, Steven M. Heald

US Department of Energy Publications

Long-term historic spills of uranium at the 300 Area fuel fabrication site (58,000 kg of disposed uranium over 32 yr) and at the 200 East Area BX tank farm (7000 kg of spilled uranium in one event), both within the Hanford formation in the Hanford Site, Washington State, were investigated by subsurface sampling and subsequent microscale investigations of excavated samples. The 200 Area sediments contained uranyl silicate mineralization (sodium boltwoodite) in restrictive microfractures in granitic clasts, in the vadose zone over a narrow range in depth. Well logging and column experiments indicated that tank wastes migrated deeper than observed in …

Geochemical Processes Controlling Migration Of Tank Wastes In Hanford’S Vadose Zone, John M. Zachara, Jeff Serne, Mark Freshley, Fred Mann, Frank Anderson, Marcus Wood, Tom Jones, Dave Myers

US Department of Energy Publications

Nuclear wastes from Hanford’s processing for separation of plutonium are stored in massive, buried, single-shell tanks in 18 tank farms. These so-called tank wastes were initially thermally hot because of radioactive decay, and many exhibited extreme chemical character in terms of pH, salinity, and radionuclide concentration. At present, 67 of the 149 single shell tanks are suspected to have released over 1.9 million L of tank waste to the vadose zone, with most leak events occurring between 1950 and 1975. Boreholes have been placed through the largest vadose zone plumes to define the extent of contaminant migration and to develop …

Generation Of Electron Bunches At Low Repetition Rates Using A Beat-Frequency Technique, M. Poelker, J. Grames, J. Hansknecht, R. Kazimi, J. Musson

US Department of Energy Publications

Even at a continuous wave facility such as CEBAF at Jefferson Lab, an electron beam with long time intervals (tens of ns) between individual bunches can be useful, for example, to isolate sources of background via time of flight detection or to measure the energy of neutral particles that cannot be separated with a magnetic field. This paper describes a demonstrated method to quickly and easily deliver bunches with repetition rates of 20 to 100 MHz corresponding to time intervals between 50 and 10 ns (respectively). This is accomplished by changing the ON/OFF frequency of the photogun drive laser by …

Development Of A High Average Current Polarized Electron Source With Long Cathode Operational Lifetime, C. K. Sinclair, P. Adderley, B. M. Dunham, J. C. Hansknecht, P. Hartmann, M. Poelker, J. S. Price, P. M. Rutt, W. J. Schneider, M. Steigerwald

US Department of Energy Publications

Substantially more than half of the electromagnetic nuclear physics experiments conducted at the Continuous Electron Beam Accelerator Facility of the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory) require highly polarized electron beams, often at high average current. Spinpolarized electrons are produced by photoemission from various GaAs-based semiconductor photocathodes, using circularly polarized laser light with photon energy slightly larger than the semiconductor band gap. The photocathodes are prepared by activation of the clean semiconductor surface to negative electron affinity using cesium and oxidation. Historically, in many laboratories worldwide, these photocathodes have had short operational lifetimes at high average current, and have …

Photoionization And Electron-Impact Ionization Of Ar5+, Jing Cheng Wang, M. Lu, D. A. Esteves, M. Habibi, G. Alna’Washi, R. A. Phaneuf, A. L. D. Kilcoyne

US Department of Energy Publications

Absolute cross sections for photoionization and electron-impact ionization of Ar⁵⁺ have been measured using two different interacting-beams setups. The spectra consist of measurements of the yield of products due to single ionization as a function of electron or photon energy. In addition, absolute photoionization and electron-impact ionization cross sections were measured to normalize the measured Ar⁶⁺ product-ion yield spectra. In the energy range from 90 to 111 eV, both electron-impact ionization and photoionization of Ar⁵⁺ are dominated by indirect 3s subshell excitation-autoionization. In the energy range from 270 to 285 eV, resonances due to 2p …

Small Wind Electric Systems: A Nebraska Consumer’S Guide

US Department of Energy Publications

Can I use wind energy to power my home? This question is being asked across the country as more people look for affordable and reliable sources of electricity. Small wind electric systems can make a significant contribution to our nation’s energy needs. Although wind turbines large enough to provide a significant portion of the electricity needed by the average U.S. home generally require one acre of property or more, approximately 21 million U.S. homes are built on one-acre and larger sites, and 24% of the U.S. population lives in rural areas.

A small wind electric system will work for you …

Oxygenated Interface On Biomass Burn Tar Balls Determined By Single Particle Scanning Transmission X-Ray Microscopy, Alexei V. Tivanski, Rebecca J. Hopkins, Tolek Tyliszczak, Mary K. Gilles

US Department of Energy Publications

Carbonaceous particles originating from biomass burning can account for a large fraction of organic aerosols in a local environment. Presently, their composition, physical and chemical properties, as well as their environmental effects are largely unknown. Tar balls, a distinct type of highly spherical carbonaceous biomass burn particles, have been observed in a number of field campaigns. The Yosemite Aerosol Characterization Study that took place in summer 2002 occurred during an active fire season in the western United States; tar balls collected during this field campaign are described in this article. Scanning transmission X-ray microscopy and near-edge X-ray absorption fine structure …

Controlled Covalent Functionalization Of Multiwalled Carbon Nanotubes Using [4 + 2] Cycloaddition Of Benzocyclobutenes, Georgios Sakellariou, Haining Ji, Jimmy W. Mays, Nikos Hadjichristidis, Durairaj Baskaran

US Department of Energy Publications

Surface modification of carbon nanotubes (CNTs) through covalent functionalization is vital for the development of high-performance composite materials, chemosensors, nanoelectronics, photovoltaic devices, as well as for a range of biomedical applications. Several methods have been developed to functionalize CNTs. The introduction of acid groups by acid digestion disrupts the structural integrity of CNTs. Apart from shortening the tubes, oxidatively generated acid groups are inhomogenously located at the tips of broken CNTs and, hence, functionalization using acid groups as precursors does not give a statistical distribution of functional groups throughout the surface of the CNTs.

Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry Characterization Of Primary Amine End-Functionalized Polystyrene And Poly(Methyl Methacrylate) Synthesized By Living Anionic Polymerization Techniques, Haining Ji, Georgios Sakellariou, Jimmy W. Mays

US Department of Energy Publications

The reaction of living anionic polymers with 2,2,5,5-tetramethyl-1-(3-bromopropyl)-1-aza-2,5- disilacyclopentane (1) was investigated using coupled thin layer chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Structures of byproducts as well as the major product were determined. The anionic initiator having a protected primary amine functional group, 2,2,5,5-tetramethyl- 1-(3-lithiopropyl)-1-aza-2,5-disilacyclopentane (2), was synthesized using all-glass high-vacuum techniques, which allows the long-term stability of this initiator to be maintained. The use of 2 in the preparation of well-defined aliphatic primary amine R-end-functionalized polystyrene and poly(methyl methacrylate) was investigated. Primary amino R-end-functionalized poly(methyl methacrylate) can be obtained near-quantitatively by reacting 2 with 1,1-diphenylethylene in tetrahydrofuran …