Decontamination of groundwater using membrane-assisted solvent extraction

This report describes the development of a new process to remove volatile organic compounds at dilute concentrations (VOCs) from groundwater was recently begun at Argonne. This process consists of membrane-assisted solvent extraction and membrane-assisted distillation stripping (MASX/MADS). The use of membranes is the solvent extraction and distillation stripping units improves mass transfer by increasing the interfacial surface area, thus allowing the process to be performed efficiently at high throughputs. The thermodynamics of the separation process and regions of applicability of this process are discussed

Decontamination of groundwater using membrane-assisted solvent extraction

This report describes the development of a new process to remove volatile organic compounds at dilute concentrations (VOCs) from groundwater was recently begun at Argonne. This process consists of membrane-assisted solvent extraction and membrane-assisted distillation stripping (MASX/MADS). The use of membranes is the solvent extraction and distillation stripping units improves mass transfer by increasing the interfacial surface area, thus allowing the process to be performed efficiently at high throughputs. The thermodynamics of the separation process and regions of applicability of this process are discussed

Progress in alkaline peroxide dissolution of low-enriched uranium metal and silicide targets

This paper reports recent progress on two alkaline peroxide dissolution processes: the dissolution of low-enriched uranium metal and silicide (U{sub 3}Si{sub 2}) targets. These processes are being developed to substitute low-enriched for high-enriched uranium in targets used for production of fission-product {sup 99}Mo. Issues that are addressed include (1) dissolution kinetics of silicide targets, (2) {sup 99}Mo lost during aluminum dissolution, (3) modeling of hydrogen peroxide consumption, (4) optimization of the uranium foil dissolution process, and (5) selection of uranium foil barrier materials. Future work associated with these two processes is also briefly discussed

The use of a centrifugal contactor for component concentration by solvent extraction

Theoretical and experimental work was undertaken to explore the use of the Argonne design centrifugal contactor as a concentrating device for metal ions in solutions such as transuranic-containing waste streams and contaminated groundwater. First, the theoretical basis for operating the contactor as a concentrator was developed. Then, the ability of the contactor to act as a concentrating device was experimentally demonstrated with neodymium over a wide range of organic-to-aqueous (O/A) flow ratios (0.01 to 33). These data were also used to derive a correlation for the effect of O/A flow ratio on extraction efficiency

TRUEX processing of plutonium analytical solutions at Argonne National Laboratory

The TRUEX (TRansUranic EXtraction) solvent extraction process was developed at Argonne National Laboratory (ANL) for the Department of Energy. A TRUEX demonstration completed at ANL involved the processing of analytical and experimental waste generated there and at the New Brunswick Laboratory. A 20-stage centrifugal contactor was used to recover plutonium, americium, and uranium from the waste. Approximately 84 g of plutonium, 18 g of uranium, and 0.2 g of americium were recovered from about 118 liters of solution during four process runs. Alpha decontamination factors as high as 65,000 were attained, which was especially important because it allowed the disposal of the process raffinate as a low-level waste. The recovered plutonium and uranium were converted to oxide; the recovered americium solution was concentrated by evaporation to approximately 100 ml. The flowsheet and operational procedures were modified to overcome process difficulties. These difficulties included the presence of complexants in the feed, solvent degradation, plutonium precipitation, and inadequate decontamination factors during startup. This paper will discuss details of the experimental effort

Review and Evaluation of Extractants for Strontium Removal using Magnetically Assisted Chemical Separation

A literature review on extractants for strontium removal was initially performed at Northern Illinois University to assess their potential in magnetically assisted chemical separation. A series of potential strontium extractants was systematically evaluated there using radioanalytical methods. Initial experiments were designed to test the uptake of strontium from nitric acid using several samples of magnetic extractant particles that were coated with various crown ether ligands. High partition coefficient (K{sub d}) values for stimulant tank waste were obtained. Further studies demonstrated that the large partitioning was due to uncoated particles

Sabotage in Contests: A Survey

A contest is a situation in which individuals expend irretrievable resources to win valuable prize(s). ‘Sabotage’ is a deliberate and costly act of damaging a rival’s' likelihood of winning the contest. Sabotage can be observed in, e.g., sports, war, promotion tournaments, political or marketing campaigns. In this article, we provide a model and various perspectives on such sabotage activities and review the economics literature analyzing the act of sabotage in contests. We discuss the theories and evidence highlighting the means of sabotage, why sabotage occurs, and the effects of sabotage on individual players and on overall welfare, along with possible mechanisms to reduce sabotage. We note that most sabotage activities are aimed at the ablest player, the possibility of sabotage reduces productive effort exerted by the players, and sabotage may lessen the effectiveness of public policies, such as affirmative action, or information revelation in contests. We discuss various policies that a designer may employ to counteract sabotage activities. We conclude by pointing out some areas of future research

Is Promiscuity Associated with Enhanced Selection on MHC-DQα in Mice (genus Peromyscus)?

Reproductive behavior may play an important role in shaping selection on Major Histocompatibility Complex (MHC) genes. For example, the number of sexual partners that an individual has may affect exposure to sexually transmitted pathogens, with more partners leading to greater exposure and, hence, potentially greater selection for variation at MHC loci. To explore this hypothesis, we examined the strength of selection on exon 2 of the MHC-DQα locus in two species of Peromyscus. While the California mouse (P. californicus) is characterized by lifetime social and genetic monogamy, the deer mouse (P. maniculatus) is socially and genetically promiscuous; consistent with these differences in mating behavior, the diversity of bacteria present within the reproductive tracts of females is significantly greater for P. maniculatus. To test the prediction that more reproductive partners and exposure to a greater range of sexually transmitted pathogens are associated with enhanced diversifying selection on genes responsible for immune function, we compared patterns and levels of diversity at the Class II MHC-DQα locus in sympatric populations of P. maniculatus and P. californicus. Using likelihood based analyses, we show that selection is enhanced in the promiscuous P. maniculatus. This study is the first to compare the strength of selection in wild sympatric rodents with known differences in pathogen milieu