Chemical separation process

One feature of reprocessing plants which poses potential risks of a different nature from those ia a power plant is the need to handle highly radioactive and fissionable material ia Hquid form. This is necessary to carry out the chemical separations process. The Hquid materials and the equipment with which it comes ia contact need to be surrounded by 1.5—1.8-m thick high density concrete shielding and enclosures to protect the workers both from direct radiation exposure and from inhalation of airborne radioisotopes. Rigid controls must also be provided to assure that an iaadvertent criticahty does not occur. 

Although the outline of a chemical separation process could be obtained by tracer-scale investigations, the process could not be defined with certainty until study of it was possible at the actual separation plants. Therefore, the question in the summer of 1942, was as follows How could any separations process be tested at the concentration of plutonium that would exist several years later in the production plants when, at this time, there was not even a microgram of plutonium available This problem was solved through an unprecedented series of experiments encompassing two major objectives. First, it was decided to attempt the production... 

Using chemical separation processes can require significant amounts of energy. What makes aluminum so ideal for recycling ... 

A primary goal of chemical separation processes in the nuclear industry is to recover actinide isotopes contained in mixtures of fission products. To separate the actinide cations, advantage can be taken of their general chemical properties [18]. The different oxidation states of the actinide ions lead to ions of charges from +1 (e.g., NpOj) to +4 (e.g., Pu" " ) (see Fig. 12.1), which allows the design of processes based on oxidation reduction reactions. In the Purex process, for example, uranium is separated from plutonium by reducing extractable Pu(IV) to nonextractable Pu(III). Under these conditions, U(VI) (as U02 ) and also U(IV) (as if present, remain in the... 

This prompted a review of the chemical separation process then in use and the development of the process described in this paper. 

Nonetheless, the United States and other nations have been developing additional chemical separation processes to bring about these goals. Strontium and cesium can be removed from HLW by extraction with crown ethers, such as ditertiarybutyl-dicyclohexanone-18-crown-6, which can also extract 99Tc. In the United States,... 

Asakura, T., Sato, M., Matsumura, M., Morita, Y. 1999. Simulation code of chemical separation process of spent fuel reprocessing Tool for process development and safety research. Proc. 2nd NUCEF Intern. Symp. NUCEF 98. JAERI Report. JAERI-Conf 99-004 Part I. 

Sasaki, Y., Suzuki, S., Tachimori, S., Kimura, T. 2003. An innovative chemical separation process (ARTIST) for treatment of spent nuclear fuel. GLOBAL 2003, New Orleans, LA, November 16-20. 

Many different separation and detection systems have been used for speciation. For example, size fractionation and ultra-filtration have been used for separation with the separated species then being determined by neutron activation (Tanizaki et al., 1992). These physico-chemical separation processes are, however, time consuming and the species have to be collected and then determined separately. Although the techniques are invaluable for certain types of speciation where the interaction of the species with colloids and sediments is important, hybrid or coupled techniques are usually preferred. 

Only the first factor is influenced by the physico-chemical separation process (the selectivity), while the other two factors are determined by the column and the operating conditions, respectively. If C is a continuous criterion (see table 4.7), then both C and C, can be transferred from one column to another. Both column dimensions and flow rate have trivial effects on the analysis time tm. However, if the final analysis is to be run on a different (optimized) column, then it is more logical to use the dimensionless, column-independent factor (1 + km) in eqn.(4.31) instead of tm ... 

The modem microstmcture applications led to increased interest in convection heat transfer in micro conduits. Huid transport in micro channels has found applications in a number of technologies such as biomedical diagnostic techniques, thermal control of electronic devices, chemical separation processes, etc. 

This paper reports the results of investigations of the complex formation between actinide or lanthanide ions and azide or orthophenanthroline. The aim of this work was first to confirm whether these relatively soft ligands give complexes of different stabilities with the trivalent lanthanide and actinide ions, as a consequence of the broader extension of 5f orbitals as compared with 4f. Secondly, we attempted to use the results in actinide chemical separation processes. 

Solvent dewaxing is a chemical separation process in which no chemical reactions occur. Therefore the composition of the dewaxed oil is completely dependent on that of the waxy feed and represents the subtraction of the wax composition. Solvent dewaxing works because it exhibits a preference to crystallize out the highest carbon number n-paraffins, followed by isoparaffins and... 

Dewaxing of paraffinic lube stocks is an essential step in the production of lubricants which will remain fluid and permit machinery to operate at winter temperatures. The next two chapters outline the technologies that have been developed for this purpose (except solvent dewaxing, which was discussed in Chapter 6). These processes reflect the historical development of dewaxing chemical knowledge during this century, first using chemical separation processes and more recently, chemical conversion. 

Table 10.1 lists the principal types of pyrometallurgical processes on which experimental work has been conducted. These have been grouped into physical separation processes, in which no chemical reactions take place, and chemical separation processes. 

The common sources of indium are the minerals dark sphalerite, christophite, and marmatite. Indium is also found in small amounts in manganese, tungsten, zinc, and tin ores. Rarely found as a free element, indium is commonly associated with gallium in tin and zinc ores. The main commercial source for indium is from zinc smelter flue dusts (Smith etal. 1977). Enrichment of indium from zinc residues is performed by acid leaching followed by chemical separation processes. Aqueous electrolysis of indium salts yields a final metal of 99.9% purity. Canada has the greatest resources of indium with approximately 27% of the world s reserves (based on estimated indium content of zinc reserves) and the United States has about 12% of the world reserves (Brown 2000). In recent years, there have been major improvements in the recovery, refining and recycling of... 

Different uses of supercritical fluid (SCF) solvents in chemical separation processes have been of considerable research interest since the 1970s. The basic principles of SCF extraction engineering and a number of applications for this technology are described in several review papers [1,2]. As a new field related to SCF technology, the application of supercritical solvents as reaction media attracts increasing attention, especially for catalytic reactions. In such processes, the SCF may either actively participate in the reaction or function solely as the solvent for the reactants, catalysts, and products. 

As discussed in 19.10, Pu has been formed in natural uranium reactors at a later stage of the earth s evolution. Many thousands of tons of plutonium has been synthesized in commercial and military reactors the annual global production rate in nuclear power reactors in the year 2000 was 1000 tons/y, contained in the spent fuel elements. The nuclear reactions and chemical separation processes are presented in Chapters 19 and 21. The build-up of heavier elements and isotopes by n-irradiation of Pu in nuclear reactors is illustrated in Figures 16.2 and 16.3. The accumulated amount of higher actinides within the European commimity is many tons for Np, Pu and Am, and himdreds of kg of Cm the amounts in the United States and Russia are of the same magnitude. 

In the future, mass spectrometry (see Chapter 17) may supersede radiochemical analysis for long-lived radionuclides and require a different set of chemical separations. This trend is opposed to a certain extent by chemical separation processes introduced to achieve ever lower minimum detectable activity requirements and by the continued interest in identifying newly created radioelements. 

With regard to application, we will apply our tools to optimize a force field specific for fluorinated alcohols. Fluorinated alcohols are highly relevant in industrial applications (e.g., as solvents used in chemical separation processes). Their attractiveness is that they can be extracted firom the reaction medium and be reused, which makes them both environmentally friendly and economically attractive [90]. The challenge in optimizing such a force field arises frrom the lack of experimental data and lacks previously published parameters that can be used as an initial input [91-93]. The goal will be to fit both vapor-liquid equilibrium data (e.g., saturated liquid density, vapor pressure) and transport properties (e.g., diffusion coefficients) simultaneously and at different temperatures. Hence, not only parallelization over different substances but also over different ensembles and temperatures are required. 

Numerous applications involve coupling liquid-phase chemiluminescence detection to physical or chemical separation processes. Conversely, adequate selectivity can also be achieved for particular analytes in a range of sample matrices through a judicious selection of reagent and reaction conditions. Successful detection strategies have been employed for HPLC, flow analysis, electrophoresis, immunoassay labels, DNA probes, and enzyme reactions. 

A scheme of activation analysis usually includes a chemical separation process or the addition of a carrier . It is sometimes desirable to remove chemically, before activation, any elements which would cause interference. For example, the presence of sulphur or chlorine in the sample could cause inaccuracies in the estimation of phosphorus content due to reactions (13.216) and (13.217) taking place and providing extra radioactive phosphorus. In a similar manner silicon can also cause interference with the phosphorus estimation owing to the side reaction. 

A somewhat similar but high-tech process, the magnetically assisted chemical separation process, is discussed in section 2.2. 

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