Liquid radioactive waste treatment, membrane reverse osmosis

Radioactive waste treatment applications have been reported [3-9] for the laundry wastes from nuclear power plants and mixed laboratory wastes. Another interesting application of reverse osmosis process is in decontamination of boric acid wastes from pressurized heavy water reactors (PHWRs), which allows for the recovery of boric acid, by using the fact that the latter is relatively undissociated and hence wdl pass with water through the membrane while most of the radioactivity is retained [10]. Reverse osmosis was evaluated for treating fuel storage pool water, and for low-level liquid effluents from reprocessing plants. 

Ultrafiltration membranes are suitable for the treatment of radioactive liquid wastes, especially as reverse osmosis pretreatment [6]. Therefore, ultrafiltration is used for the removal of the radioactivity associated with the proteins and high-molecular-weight organic compounds, as these species can reduce reverse osmosis performance. 

For radioactive effluent treatment, the relevant membrane processes are microfiltration, ulfrafiltration (UF), reverse osmosis, electrodialysis, diffusion, and Donnan dialysis and liquid membrane processes and they can be used either alone or in conjunction with any of the conventional processes. The actual process selected would depend on the physical, physicochemical, and radiochemical nature of the effluents. The basic factors which help in the design of an appropriate system are permeate quality, decontamination, and VRFs, disposal methods available for secondary wastes generated, and the permeate. 

Some areas of application are the nuclear industry and the treatment of radioactive liquid wastes, with two main purposes reduction in the waste volume for further disposal, and reuse of decontaminated water. Pressure-driven membrane processes (microfiltration, ultrafiltration, nanofiltration, and reverse osmosis [RO]) are widely used for the treatment of radioactive waste. 

This section describes some case studies carried out by the authors, which are related to radioactive liquid waste treatment using membrane processes a study about the influence of radiation on reverse osmosis membranes, a practical case about concentration of I radioactive liquid wastes by ultrafiltration and reverse osmosis processes, and a practical experience about decontamination of Cs liquid waste by reverse osmosis, including a study of radiological protection during the treatment. 

Membrane technologies have a great potential in the treatment of radioactive liquid wastes, as it has been proved throughout this chapter. In this sense, it is expected a growing use of the membrane processes in the radioactive field, with different possibilities alone, combined between them (microfiltration or ultrafiltration and reverse osmosis) or combined with other conventional processes like evaporation or ion exchange. Furthermore, some special membrane processes, like membrane distillation or liquid membranes, could be applied for the specific treatment of radioactive wastes. 

C.S. Pawaskar et al.. Performance evaluation of reverse osmosis with disc tube module for treatment of low level radioactive liquid waste, in S.A. Ansari, A.K. Pandey, P.K. Mohapatra, A. Goswami (eds.). Proceedings of Theme Meeting on Membrane Separation for Fuel Cycle Applications, BARC, Mumbai, India, September 16-18, 2013, p. 43. 

M. Sancho, J.M. Amal, G. Veidu, J. Lora, Reverse osmosis-based treatment of radioactive liquid wastes generated in hospital facility and steel industry Case studies, in A.K. Pabby, S.S.H. Rizvi, A.M. Sastre (eds.). Handbook of Membrane Separations Chemical, Pharmaceutical, and Biotechnological Applications, CRC Press, Boca Raton, EL, 2008, Chapter 32, pp. 919-931. 

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