A two-cycle process using O Phi CMPO and HDEHP as extractants to achieve an alpha decontamination factor of HLLW greater than 10(3) together with a reduction of the lanthanides/americium weight ratio by a factor of about 200 is considered. Experimentally measured distribution ratios have been employed as input data of a suitable computer code to define operating conditions and MIS stage numbers of a process flow-sheet able to meet the above-mentioned objectives.