Radioactive Processes and Applications

Chapters 16 (waste disposal). Chapter 17 (radioactive materials transportation), and Chapter 18 (decontamination and decommissioning) are related to many radioactive processes and materials. Radioactive waste is generated wherever radioactive materials are handled and used. This includes medical applications of radioactive isotopes and their production, as well as the facilities and processes involved in nuclear power. This waste must be stored and/or disposed of in a way that isolates it from the environment until the radioactive materials decay. 

One hundred years after the discovery of radioactivity and fifty years after the dawn of the nuclear age, society continues to debate the benefits and costs of nuclear technology. Understanding nuclear transformations and the properties of radioactivity is necessary for intelligent discussions of the nuclear dilemma. In this chapter, we explore the nucleus and the nuclear processes that it undergoes. We describe the factors that make nuclei stable or unstable, the various types of nuclear reactions that can occur, and the effects and applications of radioactivity. 

Until the advent of modem physical methods for surface studies and computer control of experiments, our knowledge of electrode processes was derived mostly from electrochemical measurements (Chapter 12). By clever use of these measurements, together with electrocapillary studies, it was possible to derive considerable information on processes in the inner Helmholtz plane. Other important tools were the use of radioactive isotopes to study adsorption processes and the derivation of mechanisms for hydrogen evolution from isotope separation factors. Early on, extensive use was made of optical microscopy and X-ray diffraction (XRD) in the study of electrocrystallization of metals. In the past 30 years enormous progress has been made in the development and application of new physical methods for study of electrode processes at the molecular and atomic level. 

Once the radionuclides reach the sediments they are subject to several processes, prime among them being sedimentation, mixing, radioactive decay and production, and chemical diagenesis. This makes the distribution profiles of radionuclides observed in the sediment column a residuum of these multiple processes, rather than a reflection of their delivery pattern to the ocean floor. Therefore, the application of these nuclides as chrono-metric tracers of sedimentary processes requires a knowledge of the processes affecting their distribution and their relationship with time. Mathematical models describing some of these processes and their effects on the radionuclide profiles have been reviewed recently [8,9,10] and hence are not discussed in detail here. However, for the sake of completeness they are presented briefly below. 

IAEA, Application of Ion Exchange Processes for the Treatment of Radioactive Waste and Management of Spent Ion Exchangers, Technical Reports Series No. 408, International Atomic Energy Agency (IAEA), Vienna (2002)... 

Horwitz, E.P., Schulz, W.W. 1990. The TRUEX process A vital tool for disposal of US defense nuclear wastes. Conference on New Separation Chemistry for Radioactive Waste and Other Specific Applications, May, Rome, Italy. 

The renewable energy processes will be monitored and controlled by small, fast, and economical detectors, and fiber optics will play a major role in their designs. The operation and applications of fiber-optic probes have already been discussed in connection with Figure 3.2, so only a brief summary is provided here. Fiber-optic probes can be installed in situ, whereas their readout instruments can be several hundred meters from the probe. The probe can be located in toxic, corrosive, radioactive, explosive, high- or low-temperature/ pressure, and noisy environments. Because the measurement signal is optical, the cables are immune to microwave or electromagnetic interference. 

Plasma torch—based applications for waste treatments include fly ash from incineration processes, asbestos-containing waste, sanitary waste, waste containing organo-halogenated compounds, low-level radioactive waste, and even traditional RDF. In particular, plasma applications represent a very interesting technical solution for the treatment of fly ash from MSW/RDF incineration because the solid by-product, with its extremely low tendency to leaching, can be disposed off as a... 

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. 

The real application of this process is the recalcination of lime sludges from water treatment plants, coking of heavy residues and tars from petroleum refinery operations, concentration and volume reduction of liquid, radioactive wastes, and treatment of refinery sludges containing hydrocarbons, phosphorus, and compounds of calcium, magnesium, iron, and aluminum. 

Like many other specialities, electrodialysis plants are purchased as complete packages from a few available suppliers. Membrane replacement is about 10% per year. Even with prefiltering the feed, cleaning of membranes may be required at intervals of a few months. The comparative economics of electrodialysis for desalting brackish waters is discussed by Belfort (1984) for lower salinities, elecfrodialysis and reverse osmosis are competitive, but for higher ones elecfrodialysis is inferior. Elecfrodialysis has a number of important unique applications, for removal of high contents of minerals from foods and pharmaceuticals, for recovery of radioactive and other substances from dilute solutions, in electro-oxidation reduction processes and others. 

Analytical applications have been found for all parts of the electromagnetic spectrum ranging from microwaves through visible radiation to gamma (y) rays (Table 1). The emission and absorption of electromagnetic radiation are specific to atomic and molecular processes and provide the basis for sensitive and rapid methods of analysis. There are two general analytical approaches. In one, the sample is the source of the radiation in the other, there is an external source and the absorption or scattering of radiation by the sample is measured. Emission from the sample may be spontaneous, as in radioactive decay, or stimulated by thermal or other means, as in flame photometry and fluorimetry. Both approaches can be used to provide qualitative and quantitative information about the atoms present in, or the molecular structure of, the sample. 

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. 

Examples of Application of NF for Liquid Radioactive Wastes Processing and Isotopes Separation... 

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