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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The extraction of Uranium by some trisubstituted phosphine oxides and sulphides

Wang, Martha T. January 1961 (has links)
Thesis (M.A.)--Boston University / The extraction of uranium with O.lM trioctylphosphine oxide in cyclohexane in the presence of hydroxyethylethylenediaminetriacetic acid was shown to be most effective in the pH range from 0.5 to 1.5. A pH of 1.0 has been chosen as the working level for the extraction. It was found that under the above conditions uranium(VI) can be extracted quantitatively. The method used for the determination of uranium was based on the colorimetric method given by Horton and White in which dibenzoylmethane was used to form a colored complex in the presence of pyridine as a buffer agent in ethyl alcohol. The absorbances at the wave length 405 mu were measured. An interference study at a uranium concentration level of 0.050 mg. per ml. was made to find the tolerance level of various diverse ions of 0.500, 0.050 and 0.005 mg. per ml. concentrations. The metal ions that were studied were: aluminium(III), barium(II), bismuth(III), cadmium(II), cerium(III), chromium(III), cobalt(II), copper(II), iron(II), iron(III), lead(II), magnesium(II), manganese(II), nickel(II), potassium(I), silver(I), sodium(I), thorium(IV), zinc(II), and zirconium( IV). It was found that cerium (III), lead(II), thorium(IV) and zirconium(IV) interfered with the extraction of uranium under the above conditions. Triphenylphosphine sulfide was prepared, as described by Michaelis, by the direct addition of elementary sulfur to triphenylphosphine. Attempts were made to use triphenylphosphine sulfide as an extractant for the following metal ions: aluminium(III) bismuth(III), chromium(VI), copper(II), magnesium(II), manganese( VII), mercury(II), tin(II), and zinc(II). The results obtained indicated that triphenylphosphine sulfide did not extract the above metals.
2

Modeling energy consumption in the mining and milling of uranium

Tavrides, Emily Loree 16 February 2011 (has links)
A family of top-down statistical models describing energy consumption in the mining, milling, and refining of uranium are formulated. The purpose of the models is to estimate the energy-to-grade dependence for uranium extraction, while defining a minimum grade that can be feasibly mined and produced. The results serve as a basis for understanding the factors governing energy consumption in the production of U3O8. The models are applied to a considerably larger data set of operating mines than in any previous effort. In addition, the validity of the modeling approach is established by modeling energy for two other commodities, gold and copper, thereby showing it can be applied to other metals. Statistical measures of explanatory power show that the models the energy-to-grade relationship is well-described for both uranium and gold. For copper, there was insufficient data over a broad range of ore grades to obtain a model that passed statistical confidence measures. The results show that mining of lower-grade deposits of uranium is likely to be less energy-intensive than previous investigators concluded. It is shown that the uncertainty in the results is dominated by the contribution of the grade-independent component of energy consumption. / text
3

SOFT-TEMPLATING SYNTHESIS OF MESOPOROUS SILICA-BASED MATERIALS FOR ENVIRONMENTAL APPLICATIONS

Gunathilake, Chamila Asanka 19 April 2017 (has links)
No description available.
4

Safeguards for Uranium Extraction (UREX) +1a Process

Feener, Jessica S. 2010 May 1900 (has links)
As nuclear energy grows in the United States and around the world, the expansion of the nuclear fuel cycle is inevitable. All currently deployed commercial reprocessing plants are based on the Plutonium - Uranium Extraction (PUREX) process. However, this process is not implemented in the U.S. for a variety of reasons, one being that it is considered by some as a proliferation risk. The 2001 Nuclear Energy Policy report recommended that the U.S. "develop reprocessing and treatment technologies that are cleaner, more efficient, less waste-intensive, and more proliferation-resistant." The Uranium Extraction (UREX+) reprocessing technique has been developed to reach these goals. However, in order for UREX+ to be considered for commercial implementation, a safeguards approach is needed to show that a commercially sized UREX+ facility can be safeguarded to current international standards. A detailed safeguards approach for a UREX+1a reprocessing facility has been developed. The approach includes the use of nuclear material accountancy (MA), containment and surveillance (C/S) and solution monitoring (SM). Facility information was developed for a hypothesized UREX+1a plant with a throughput of 1000 Metric Tons Heavy Metal (MTHM) per year. Safeguard goals and safeguard measures to be implemented were established. Diversion and acquisition pathways were considered; however, the analysis focuses mainly on diversion paths. The detection systems used in the design have the ability to provide near real-time measurement of special fissionable material in feed, process and product streams. Advanced front-end techniques for the quantification of fissile material in spent nuclear fuel were also considered. The economic and operator costs of these systems were not considered. The analysis shows that the implementation of these techniques result in significant improvements in the ability of the safeguards system to achieve the objective of timely detection of the diversion of a significant quantity of nuclear material from the UREX+1a reprocessing facility and to provide deterrence against such diversion by early detection.

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