Liquid radioactive waste treatment, membrane application

Zakrzewska-Trznadel, G., Harasimowicz, M., Chmielewski, A.G., Membrane processes in nuclear technology— Application for liquid radioactive waste treatment, Sep. Purif. Technol. 22-23, 617, 2001. 

This section aims to explain the unique features of membrane separation methods, their superior performance in contaminant removal, and their operational sensitivities and limitations. We focus particularly on the factors that need to be carefully assessed when the membrane technology to be used in the treatment of liquid radioactive waste is being considered. These include membrane configuration and arrangement, process application, operational experience, data related to key performance parameters, and plant and organizational impacts. 

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. 

It has been demonstrated that membrane separation processes can be successfully used in the removal of radioactive substances, with some distinct advantages over conventional processes. Following the development of suitable membrane materials and their long-term verification in conventional water purification, membrane processes have been adopted by the nuclear industry as a viable alternative for the treatment of radioactive liquid wastes [1]. In most applications, membrane processes are used as one or more of the treatment steps in complex waste treatment systems, which combine both conventional and membrane treatment technologies. These combined systems have proved more efficient and effective for similar tasks than conventional methods alone. 

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. 

Some research groups worldwide are currently working on the application of membrane technology to the treatment of radioactive liquid wastes with different levels of activity, from low to high activity waste. Research is mainly focused on wastes from the nuclear industry. However, the nuclear industry is not the only source of radioactive wastes medical and research applications of radioisotopes also generate radioactive wastes. 

Since 1995, the Chemical and Nuclear Engineering Department of the Polytechnic University of Valencia in Spain has been working on the application of membrane technology to the treatment of low and medium level radioactive liquid wastes. In this chapter, we describe two practical cases of radioactive liquid waste treatment using membrane processes the treatment of Cs-contaminated water generated after a radioactive incident in a stainless steel production factory, and the treatment of 1 liquid wastes from nuclear medicine services at hospitals. 

Calix[4]-W5-crowns 1-7 are used as selective cesium-carriers in supported liquid membranes (SLMs). Application of the D esi diffusional model allows the transport isotherms of trace level Cs through SLMs (containing calix[4]-6/5-crowns) to be determined as a function of the ionic concentration of the aqueous feed solutions. Compound 5 appears to be much more efficient than mixtures of crown ethers and acidic exchangers, especially in very acidic media. Decontamination factors greater than 20 are obtained in the treatment of synthetic acidic radioactive wastes. Permeability coefficient measurements are conducted for repetitive transport experiments in order to determine the SMLs stability with time. Very good results (over 50 days of stability) and high decontamination yields are observed with l,3-calfac[4]-Aw-crowns 5 and 6. 

Dulama, M., Pavelescu, M., Deneanu, N., Dulama, C.N., Application of indigenous inorganic sorbents in combination with membrane technology for treatment of radioactive liquid waste from decontamination processes, Radiochim. Acta 98, 413, 2010. 

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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