[en] The rising price of uranium has led uranium producers to increase their plant capacity. The new project proposed to increase capacity is based on processing low-grade uranium by heap leaching. It is necessary to modify the plant, particularly the solvent extraction unit, to handle the increased flow. The goal of our study is to determine the minimal changes necessary to process the whole flow. Several stages have been carried out (i) thermodynamic modelling of the solvent extraction process to determine the capacities of the SX plant and the impact of the modification and (ii) pilot tests at the plant of the different configurations proposed by modelling. This paper presents results of the pilot tests performed at the plant. (authors)