Actinide Leaching from Waste Glass: Air-Equilibrated Versus Deaerated Conditions

摘要

Leach tests were conducted in aerated and deaerated solutions using glass containing exp 239 Pu, exp 237 Np and exp 238 U, at temperatures of 25 and 75 exp 0 C and in deionized water, 0.03M NaHCO sub 3 and WIPP B salt brine for periods up to 341 days. Neptunium leaching was decreased by factors of 10 to 100 (depending on leach time) in the deaerated solutions at 75 exp 0 C. Plutonium leaching decreased by factors of 3 to 5 due to deaeration, but only in the deionized water leachate at 25 exp 0 C. Uranium leaching in salt brine and deionized water at 25 exp 0 C was decreased by factors of 2 to 5 in deaerated solutions. Time and temperature dependencies were also observed for the leaching of the actinides during the course of this work. After the first leach interval (2 days), the time dependent release curve for Pu was essentially flat or decreasing under all conditions, and maximum Pu solution concentration (at 25 exp 0 C), as implied by release in aerated leachate, agrees with independent solubility data. The low exp 239 Pu releases observed in leach solutions are consistent with accumulation of exp 239 Pu on the leached glass surface. The amounts of uranium and neptunium leached increased with time under most conditions. For Pu leaching, temperature has a small effect in deaerated leachates and negative effect in aerated leachates. Neptunium leaching generally increase with temperature under aerated conditions, but not in proportion to increases of matrix element leaching. In deaerated leachates, Np leaching decreases with temperature. Uranium leaching increases with temperature under aerated and deaerated conditions but not in proportion to matrix element increases. 4 figures, 6 tables. (ERA citation 07:003445)