A study of the application of different membrane processes to nuclear technology has been conducted at the Institute of Nuclear Chemistry and Technology (INCT) for many years. One application of membrane methods involves the purification and concentration of liquid low- and medium-level radioactive wastes (LLLRWs and LMLRWs). The separation of radioactive model solutions as well as LLLRW and LMLRW samples has been examined with various reverse osmotic modules equipped with thin-composite polymeric membranes. On the basis of these investigations, membrane modules were selected for the pilot plant processing of liquid wastes from nuclear centers. A three-stage JP3RO reverse osmosis unit was constructed. The installation is described in this paper, and the results of preliminary pilot plant experiments are presented.