Membrane processes for environmental protection: applications in nuclear technology

Membrane processes are considered as potential methods useful in clean technologies that minimize the use of raw materials, rationalize energy consumption and reduce waste production. They are capable to solve many environmental problems, among them problems related to nuclear technology field. Membrane processes have been already applied for liquid radioactive waste processing in many nuclear centres around the world. Reverse osmosis (RO) was implemented at the Institute of Atomic Energy (IAE) at Świerk for liquid low-level radioactive waste concentration. A 3-stage RO plant supplements the existing waste processing system based on an evaporator giving the possibility of initial concentration of liquid waste or final polishing of the condensate after evaporation. Intensive studies on ultrafiltration (UF) enhanced by sorption on inorganic sorbents or complexation with chelating polymers were carried out. Ceramic membranes made of alumina, titania and zirconia were used in the experiments. Such membranes show a high chemical, temperature and radiation resistance. Thermal process, namely membrane distillation with the use of resistant porous membranes from PTFE was proposed and tested for radioactive waste concentration. The results collected in laboratory and pilot plant experiments allowed to consider the process usable for small installations operated with utilization of cheap energy sources or waste heat. Other methods like liquid membranes and electric processes with ion-exchange membranes as possible applications in nuclear industry are under development. Membrane methods were considered as alternative solutions for reclamation of different materials that can be recycled and reused. Some of them allow minimizing the total energy consumption by various energy recovery systems and utilization of cheap energy sources.