The potential importance of tetraborate complexation on lanthanide(III) and actinide(III) solubility is recognized in the literature but a systematic study of f-element complexation has not been performed. In neodymium solubility studies in WIPP brines, the carbonate complexation effect is not observed since tetraborate ions form a moderately strong complex with neodymium(III). The existence of these tetraborate complexes was established for low and high ionic strength solutions. Changes in neodymium(III) concentrations in undersaturation experiments were used to determine the neodymium with tetraborate stability constants as a function of NaCl ionic strength. As very low Nd(III) concentrations have to be measured, it was necessary to use an extraction pre-concentration step combined with ICP-MS analysis to extend the detection limit by a factor of 50. The determined Nd(III) with borate stability constants at infinite dilution and 25 °C are equal to logβ1=4.55±0.06 using the SIT approach, equal to logβ1=4.99±0.30 using the Pitzer approach, with an apparent logβ1=4.06±0.15 (in molal units) at I=5.6 m NaCl. Pitzer ion-interaction parameters for neodymium with tetraborate and SIT interaction coefficients were also determined and reported.
Bio-mediated reduction of multivalent actinide contaminants plays an important role in their fate and transport in the subsurface. To initiate the process of extending recent progress in uranium biogeochemistry to plutonium, a side-by-side comparison of the bioreduction of uranyl and plutonyl species was conducted with Shewanella alga BrY, a facultative metal-reducing bacterium that is known to enzymatically reduce uranyl. Uranyl was reduced in our system, consistent with literature reports, but we have noted a strong coupling between abiotic and biotic processes and observe that non-reductive pathways to precipitation typically exist. Additionally, a key role of biogenic Fe 2+ , which is known to reduce uranyl at low pH, is suggested. In contrast, residual organics, present in biologically active systems, reduce Pu(VI) species to Pu(V) species at near-neutral pH. The predominance of relatively weak complexes of PuO 2 + is an important difference in how the uranyl and plutonyl species interacted with S. alga. Pu(V) also led to increased toxicity towards S. alga and is also more easily reduced by microbial activity. Biogenic Fe 2+ , produced by S. alga when Fe(III) is present as an electron acceptor, also played a key role in understanding redox controls and pathways in this system. Overall, the bioreduction of plutonyl is observed under anaerobic conditions, which favors its immobilization in the subsurface. Understanding the mechanism by which redox control is established in biologically active systems is a key aspect of remediation and immobilization strategies for actinides when they are present as subsurface contaminants.
Two-photon excitation by a pulsed dye laser was used to prepare the Xe(5p56p[1/2]o, [3/2]2, [5/212) and Xe(5p56p'[1/2]o, [3/2]2) states in the presence of several reagent gases to measure total quenching rate constants at 300 K. The new measurements together with rate constants from the literature provide a general overview of Xe(6p) atom reactivity, especially with halogen-and oxygen-containing molecules. Reactive quenching and/or excitation transfer to the reagent molecule are the dominant quenching mechanisms, rather than intramultiplet transfer to other states of the Xe(6p) manifold. The XeCl(B and D) and XeF(B and D) product state distributions from reactions of the Xe(5~~(~P1,2)6p') states with HC1, Ch, F2, N F 3 , CCL and CClzFz were observed in order to record the degree of conservation of the x e + ( * P~~) core as indicated by XeCl(D) or XeF(D) formation. Except for the HCl reaction, the Xe+(*Pm) core does not have a high degree of conservation in reactions of Xe(6p') atoms. For conditions of low reagent pressure, radiative decay of the Xe(6p) states can produce a high local concentration of metastable Xe(6s) atoms, which subsequently undergo bimolecular, energy-pooling, associative-ionization reactions. The Xe2+ ions subsequently recombine with electrons to generate a variety of excited Xe* states.
Abstract-The TEAM Workshops originated from probknss in fusion reaeareh. Based on his recent observations regarding automotive modeling, the author asks whether TEAM-i&e worksho~and the accompanying cooperation among model= are of vahse in areas of economic competition. I. cO&@ETtTtON AND~PSRATIONIn her study of advanced automotive government-industry cooperative programs, Melissa Polverini [1] compared the Advanced Clean Energy Project in Japan, the Car of Tomorrow in Europe, and the Partnership for a New Generation of Vehicles (PNGV) in the USA. The Advanced Clean Energy Project assigned individual appointments to each company. That meant the companies needed to share little or no research information, The Car of Tomorrow is to come up with only one car design, which will then be put into production. Because of tha~the companies have to share information, which for competitive reasons they don't want to do, resulting in delays for the program. The PNGV attempts something in between. The companies work together on pre-competitive issues, but in the vehicle engineering phase, they act independently.I talked about this earlier this week in my panel presentation on PNGV modeling [2]. This morning let's think about cooperation in competitive industries. In particular, consider what role TEAM or TEAM-like workshops can play in this process. A VOLATfLE MEETINGWhat got me thinking about this was a particular PNGV Technical Team meeting. Each Technical Team has members from the '*BigThree" US automakers, from government agencies, and from the national laboratories [3]. This particular meeting was a meeting of the Systems Analysis Team, who are responsible for developing modeling tools and encouraging the other teams to do modeling. Members of other teams were also present as well as other people with broader responsibilities within PNGV. Every year the Peer Review Panel from the Nationai Research Council [4] recommends cost modeling for PNGV, and every year the automakers demur. But this particular meeting was about modeling somethhg else, modeling that the PNGV secretariat and the US Department of Energy (DOE) had km pushing for. The modeling had finally been done, but was badly flawed because it was based on bad assumptions. Because of these bad assumptions, the results ilom the modeling were a clear-cut "The bigger, the better" or "The smaller, the better." Even if the modeling had been done correctly, the results would be controversial because the different automakers had each been promoting different choices.The modelers and those of us tlom the Systems Analysis Technical Team believed the purpose of the meeting was to provide better assumptions, so the modeling could be redone. Instead, some of the industry people questioned the need for cooperative modeling, saying their in-house, proprietary modeling tools were far better, and could provide all that was needed.This sort of response is not unique to the auto industry. A week ago, representatives of another industry visited Argonne National Laboratory (ANL), and ...
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