Radioactive wastes liquid membranes

FIGURE 25.19 A scheme of the pilot plant for radioactive waste concentration (1) MD module, (2) distillate reservoir, (3) feed tank, (4, 5) pumps, (6) heater, (7, 8) heat exchangers, and (9, 10) prefilters. (Reprinted from J. Membr. ScL, 163, Zakrzewska-Trznadel, G., Harasimowicz, M., and Chmielewski, A.G., Concentration of radioactive components in liquid low-level radioactive waste by membrane distillation, 257-264, Copyright 1999, with permission from Elsevier.)... 

Harasimowicz, M., and Chmielewski, A.G., Concentration of radioactive components in liquid low-level radioactive waste by membrane distillation, 257-264, Copyright 1999, with permission from Elsevier. 

Cell harvesters were developed to capture multiple samples of cells on membrane filters, wash away unincorporated isotopes, and prepare samples for liquid scintillation counting on special equipment developed to process and count multiple samples. Despite miniaturization and improvements in efficiency of this technique, the disadvantages of multiple liquid handling steps and increasing costs for disposal of radioactive waste materials severely limit its usefulness. Although specific applications require measuring DNA synthesis as a marker for cell proliferation, much better choices are available for detecting viable cell number for HTS. 

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. 

IAEA Technical Reports Series No. 431. 2005. Application of Membrane Technologies for Liquid Radioactive Waste Processing, pp. 1-145. Consultants Pabby A.K., Kohout R. (Canada), and TapseU G. (AustraUa) [http /www.iaea.org/Publications/index.html]. 

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. 

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. 

Membrane Processes Employed for Liquid Radioactive Waste Treatment.850... 

Liquid Radioactive Waste Processing by Membrane Processes Advantages and Limitations.872... 

For the treatment of conventional, nonradioactive liquid waste the predicted lifetime of membranes is 4—5 years. The effective lifetime depends on the conditions in which the membrane is used the characteristics of solutions treated, pressure, and temperature. While selecting the membrane for radioactive waste processing, one has to remember about its resistance and... 

MEMBRANE PROCESSES EMPLOYED FOR LIQUID RADIOACTIVE WASTE TREATMENT... 

Liquid radioactive waste was directed from the waste storage tank to the 8 m feed reservoir. After pretreatment with PP depth filters and injection of antisealant, the wastes were directed to the first stage of RO. The retentate from this stage was concentrated in the third RO unit. The concentrated solution could be directly solidified if the concentration of the total solute was appropriate (<250 g/dm ). The salt concentration is limited by the conditions of concrete solidification. If the concentration was not sufficient, the further concentration took place in the evaporator. Permeate from the first and third stages was directed to the permeate reservoir before the second RO unit. The product from the membrane installation (permeate from the second stage) was of required radiochemical purity and after the control of specific activity and salinity was discharged to the communal sewage. 

FIGURE 30.12 Decontamination of the sample of liquid radioactive waste in UF/complexation process with a use of different complexing agents, CeRam Inside membrane, 15 kDa. (Reprinted from Zakrzewska-Trznadel, G., J. Membr. Sci., 225, 25, 2003. Copyright [2003] with permission from Elsevier.)... 

Despite of some technical and process limitations, membrane techniques are very useful methods for the treatment of different types of effluents. They can be applied in nuclear centers processing low- and intermediate-level liquid radioactive wastes or in fuel reprocessing plants. All the methods reported in the chapter have many advantages and can be easily adapted for actual, specific needs. Some of them are good pretreatment methods the other can be used separately as final cleaning steps, or can be integrated with other processes. Membrane methods can supplement or replace techniques of distillation, extraction, adsorption, ion exchange, etc. Evaluation of membrane processes employed for liquid radioactive waste treatment is presented in Table 30.17. 

International Atomic Energy Agency, Application of Membrane Technologies for Liquid Radioactive Waste Processing, Technical Report Series No. 431, IAEA, Vienna, 2004. 

Chmielewski, A.G., Harasimowicz, M., and Zakrzewska-Trznadel, G., Membrane technologies for liquid radioactive waste treatment, Czech. J. Phys., 49, 979, 1999. 

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. 

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. 

Advancement in Membrane Methods for Liquid Radioactive Waste Processing... 

Membrane Methods for the Treatment of Liquid Radioactive Waste.666... 

MEMBRANE METHODS FOR THE TREATMENT OF LIQUID RADIOACTIVE WASTE... 

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