Determination of Natural Uranium Concentration in Boom Clay: Effect of Different Extraction Techniques

摘要

Natural uranium concentration has been measured in the pore water of Boom Clay extracted by three different techniques: (1) batch leaching of clay suspensions; (2) squeezing of clay cores; (3) collection by piezometers. The results show that the batch and the squeezing techniques extract higher uranium concentrations (up to three orders of magnitudes) than measured in the pore water collected by piezometers. Batch techniques (leaching and squeezing) tend to remobilise natural uranium from clay surfaces as colloids into aqueous phase. As a consequence, the batch distribution coefficient (K_d) may underestimate the retention capability of the clay. The in situ retention mechanisms for natural uranium may involve colloid filtration and/or dissolution of uranium-bearing minerals.