Membrane processes in nuclear technology - application for liquid radioactive waste treatment

Membrane methods can be considered as the most energy-saving separation tec hniques. Separation abilities of membranes allow the elimination of many no n-effective and energy consuming methods and their replacement by new, mode rn technologies, friendly environment friendly. An application of membrane methods for liquid radioactive wastes treatment requires solving many probl ems connected with the proper selection of the membranes, membrane modules and other equipment according local conditions: chemical and radiochemical composition of the effluents treated, their activity and total salinity. Th e installations working in nuclear industry have to fulfil very strict requ irements. They ought to be reliable, constructed from special materials def ined by separate regulations. Only small number of manufacturers of membran e devices has for their products the certificates of International Atomic E nergy Agency. Reverse osmosis (RO) as a method for liquid waste treatment h as been examined at laboratory and pilot plant installations. The experienc e with the process led to design and construction of the industrial plant, 1 m(3) capacity, composed BE the re RO stages. The plant will be included i nto the system for liquid radioactive wastes purification operating at Inst itute of Atomic Energy in Swierk near Warsaw, treating the liquid waste fro m all of Poland. Membrane distillation (MD) can be an alternative for liqui d radioactive waste concentration. On the basis of previous laboratory test s a pilot plant for liquid radioactive wastes concentration employing direc t contact MD was constructed. Pilot plant experiments showed MD is interest ing solution for liquid low-level radioactive waste treatment. As MD is cha racterised by high retention, large decontamination factors were obtained i n separation of radionuclides, which are present in liquid low-level radioa ctive wastes mainly in an ionic form. The RO and MD plants for liquid low l evel radioactive wastes treatment are presented in the paper and the evalua tion of both methods, as well. (C) 2001 Elsevier Science B.V. All rights re served.