Rolando Lastra

Comparison of Uranium Recovery by Ion Exchange from Sulfuric Acid Liquor in Iodide and Chloride Media

ABSTRACT Uranium is normally leached from its ores with sulfuric acid, separated from impurities using solvent extraction or ion exchange, and precipitated to yield a commercial product known as “yellow cake.” This research has investigated the use of sodium chloride and potassium iodide with the sulfuric acid leach to recover the uranium, mercury and cesium from the cemented waste. Sulfuric leaching using KI improves the solubilization of Hg by a combination of acidification, complexation, and oxidation and form a mercury tetraiodide complex. Mercury and cesium were recovered selectively using thiourea resin and solid potassium cobalt hexacyanoferrate respectively with removal efficiencies reaching 99%. The U recovery from sulfuric liquor using the chelating resin Lewatit TP260 is very efficient. The loading curve for U recovery in iodide media shows a better uptake than in chloride media and the resulting breakthrough is delayed. High purity yellow cake was obtained by precipitation as sodium diuranate.

OPTIMIZATION AND VALIDATION OF A CHEMICAL PROCESS FOR URANIUM, MERCURY AND CESIUM LEACHING FROM CEMENTED RADIOACTIVE WASTES

Canadian Nuclear Laboratories (CNL) is developing a treatment and long-term management strategy for a legacy cemented radioactive waste that contains uranium, mercury, and fission products. Extracting the uranium would be advantageous for decreasing the waste classification and reducing the cost of long-term management. The chemical leachability of 3 key elements (U, Hg, and Cs) from a surrogate cemented waste (SCW) was studied with several lixiviants. The results showed that the most promising approach to leach and recover U, Hg, and Cs is the direct leaching of the SCW with H2SO4 in strong saline media. Operating parameters such as particle size, temperature, pulp density, leaching time, acid and salt concentrations, number of leaching/washing steps, etc. were optimized to improve key elements solubilization. Sulfuric leaching in saline media of a SCW (U5) containing 1182 ppm of U, 1598 ppm of Hg, and 7.9 ppm of Cs in the optimized conditions allows key elements solubilisation of 98.5 ± 0.4%, 96.6 ± 0.1...