The DIAMEX-SANEX process using the solvent HDEHP/DMDOHEMA/TPH was adapted to manage the separation of neptunium and plutonium along with americium and curium in the second cycle of the GANEX process. Distribution ratios of Np and Pu depending on their initial oxidation states, actinide/lanthanide separation factor and loading capacity of the solvent were measured after batch experiments in order to verify the behaviour of Np and Pu in this process and check their impact on the hydrodynamics. Results show that after some experimental optimizations, the group separation seems possible using this process. A demonstrative test will be carried out on a high active feed in 2008 at CEA Marcoule. (authors)