Separation of isotopes

Separation of isotopes is an extremely challenging analytical problem. Lucy and McDonald [4] demonstrated the extraordinary separation power of CE by obtaining a baseline resolution of two chloride isotopes, and Counter migration was 

2 ppm each 1 = chloride 2 = sulfate 3 = nitrate 4 = fluoride 5 = formate 6 = phosphate  

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The phenomenon of multiphoton dissociation finds a possible application in the separation of isotopes. For this purpose it is not only the high power of the laser that is important but the fact that it is highly monochromatic. This latter property makes it possible, in favourable circumstances, for the laser radiation to be absorbed selectively by a single isotopic molecular species. This species is then selectively dissociated resulting in isotopic enrichment both in the dissociation products and in the undissociated material. 

H. London, ed.. Separation of Isotopes, George Newnes, Ltd., London, 1961. 

H. W. Savage, Separation of Isotopes in Calutron Units, Oak Ridge, Teimessee, National Nuclear Energy Series Div. 1, Vol. 7, TlD-5233, U.S. AEG Technical Information Service, 1951. 

C. Boorman in H. London, ed.. Separation of Isotopes, George Newnes Ltd., London, 1961, Chapt. 8 D. Massignon, Gaseous Diffusion, in S. ViUani, ed.. Topics in Applied Physics, VoL 35, Springer-Vedag, New York, 1979. 

If a temperature gradient is maintained in a binary gaseous mixture, a concentration gradient is established with the light component collecting preferentially at the hot end and the heavier one at the cold end. This phenomenon, known as the Soret effect, may be used as the basis of a separation technique of commercial significance in the separation of isotopes. 

For difficult separations, requiring many stages such as the separation of isotopes. 

Separation-nozzle method, 25 417 Separation of Isotopes by Laser Excitation (SILEX) technology, 25 416-417 Separation processes enhanced, 27 670-673 foams in, 72 19, 21-22 for supercritical fluids, 24 13-14 sustainable development and, 24 175-176... 

Mulliken, R.S. and Harkins, W.D. (1922). The separation of isotopes. Theory of resolution of isotopic mixtures by diffusion and similar processes. Experimental separation of mercury by evaporation in a vacuum. Journal of the American Chemical Society 44 37-65. 

Fig. 8.6 The principle underlying electromagnetic separation of isotopes. Electrostatically accelerated ions enter at the left. A magnetic field perpendicular to the plane of the paper causes the circular orbits shown in the sketch (See text for further detail)...

Uranium enrichment using LIS has been exhaustively studied and the conceptual outlines of two different methods can be found in the open literature. These methods are multi-photon dissociation of UF6 (SILEX, or Separation of Isotopes by Laser Excitation) and laser excitation of monatomic uranium vapor (Atomic Vapor Laser Isotope Separation, or AVLIS). Following an enormous investment, AVLIS was used by the United States DOE in the 1980s and early 1990s, but due to the present oversupply of separated uranium, the plant has been shut down. 

London, H., 1961 Separation of Isotopes (London, George Newnes)... 

Harold Clayton Urey, 1893-. Professor of chemistry at the Institute for Nuclear Studies at the University of Chicago and at the University of California. In 1931 Dr. Urey and his collaborators discovered deuterium, the heavy isotope of hydrogen. Pie has carried out notable researches on the entropy of gases and on the properties and separation of isotopes and has studied the chemical evidence of the earth s origin. 

Similar results have been obtained for methane 12) and for ethane 19). The values quoted in Table II also illustrate the point that the distribution of deuterium between hydrogen and propane differs from the value expected for a random distribution. With the ratio of pressures used, the expected percentage for the mean deuterium content of the hydrocarbon would be 33.3, which is substantially less than the experimental value of 40.9 %. This type of deviation is also found with other hydrocarbons, but it does not affect the validity of using classical theory for the calculation of the interconversion equilibrium constants in studies of mechanism of exchange reactions. More accurate values for these equilibrium constants are necessary, however, if one is interested in the separation of isotopes by chemical processes. 

The separation of isotopes can be used to show the efficiency of separation by capillary electrophoresis. Moreover, the interfacing of a mass spectrometer to the capillary can be used for the study of biological substances (cf. Fig. 16.7). 

Examples of separations of isotopes are in Table 19.10(b). The concentration of U-235 listed there was accomplished in a cascade of 2100 columns, each with an effective height of 14.6 m, inner tube 5 cm dia, gap 0.25 mm, hot surface 87-143°C, and cold surface 63°C, just above the condensation temperature at the operating pressure of 6.7 MPa. Although the process was a technical success. 

Any process which changes the isotopic ratio in reference to uranium, it is a process that increases the ratio of 5U to J, U in uranium by separation of isotopes. 

HEVESY, GEORG de (1885-1966). A Hungarian chemist who won the Nobel prize in chemistry in 1943, for his work on (he use of isotopes as tracers in the study of chemical processes. He discovered the element hafnium in 192.7. One of his interesting projects involved the calculation of ihc percentages of chemical elements in the universe. He also was involved in research using radioactive lead and phosphorus traces. His work included the separation of isotopes by physical means. His Ph D was granted ai Freiburg in 1908. 

The UF6 gas that passes through the membrane is thus very slightly enriched in the lighter, faster-moving isotope. After repeating the process many thousands of times, a separation of isotopes can be achieved. Approximately 85% of the Western world s nuclear fuel supply—some 5000 tons per year—is produced by this gas diffusion method. 

Gersh, M. E. Improved separation of isotopic hydrogens by gas chromatography. 

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