Texte remanié de: Thèse--Sc. nat.--Nancy I, 1971. / Extrait de "Mineralium deposita" 5, 1970, pp. 145-156. Conservé sous la cote: [4° THS. Pièce. 514].

Th. doct.-ing.--Génie géol. et minier--Nancy--I.N.P.L., 1980.

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.

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M.Phil. / In the pricing of nuclear fuel, the cost of the uranium enrichment has the biggest portion. In addition, characteristics of enrichment technologies, the structure of the international market, and the balance of supply and demand are considered to be three main determinant factors for the cost of uranium enrichment. This study attempts to examine the determinant factors of uranium enrichment costs and to try to forecast the future trends of the price of uranium enrichment by examining the current market situation and present projections of uranium enrichment prices. The analysis indicates that while the development of the enrichment techniques allows the enrichers to produce with a lower cost, the structure of the market causes the prices to rise. Moreover, the supply and demand balance of the present market is very fragile and there is a need for an expansion in the market to make and sustain a stronger balance. It is the prediction of this study that the enrichment prices are likely to increase because of the reflection of the constructions of the new enrichment facilities and new ventures in the market.

Uranium exists in carbonate solution in its hexavalent state as the complex ion U0₂(C0₃)₃---- . In most ores uranium occurs as pitchblende (U₃0₈). It has been found possible to dissolve uranium in carbonate-bicarbonate solutions from these ores by leaching them in the presence of oxygen. The overall reaction is as follows: U₃O₈ + ½0₂+ 3C0₃ˉ˭ + 6HCO₃- → 3U0₂(C0₃)₃---- + 3H₂0 The objective of the present research was to examine the kinetics of this reaction with a view to determining the mechanism of the reaction and to establish the variables upon which the rate depends. Two series of experiments were conducted on two types of materials: (a) Pitchblende specimens of measured surface area were suspended in a solution containing sodium carbonate and sodium bicarbonate. Above the solution a desired pressure of oxygen was maintained. (b) A pulp of low grade pitchblende ore in carbonate, solutions was agitated in an autoclave, in the presence of oxygen maintained at the desired pressures. The rate of solution of uranium was measured by sampling and analyzing the solutions at regular time intervals. The effect of oxygen pressure, temperature, and reagent concentration on the rate was studied in each series. The kinetic results were examined by the methods of the absolute reaction rate theory. The following conclusions were drawn from the leaching tests: (1) The absolute reaction rates are about the same for all the materials studied. (2) The reaction rate varies as the square root of the absolute oxygen pressure. (3) The activation energy is about 12,000 - 3000 calories per gram mole. (4) Minimum amounts of carbonate and bicarbonate are necessary to dissolve the oxidized uranium. Further increases beyond this minimum amount result in only minor increases in the rate of the reaction. A mechanism for the leaching rate is proposed in which the oxidation is the rate controlling step. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

This paper deals with a new method of separating uranium from pitchblende. The main feature of this separation is the use of an ion exchange resin, Amberlite IRC-50. The purity of the uranium has been checked, chemically and spectrographically. By this method, uranium of high purity can be obtained even in the presence of large quantities of impurities. / Science, Faculty of / Chemistry, Department of / Graduate