Deuterium separation processes

In a two-component mixture, the separation factor a is defmed as the fraction of desired component in the phase in which it concentrates divided by the fraction of desired component in the other phase. Deuterium, the isotope principally discussed in this chapter, almost always concentrates in the liquid phase. For such deuterium separation processes, the deuterium separation factor a is given by... 

As the oceans of the world contain about 10 kg of deuterium and resources of lithium minerals are of comparable magnitude, it is clear that if this fusion reaction could be utilized in a practical nuclear reactor, the world s energy resources would be enormously increased. Although intensive research is being conducted on confinement of thermonuclear plasmas, it is not yet clear whether a practical and economic fusion reactor can be developed. If fusion does become practical, isotope separation processes for extracting deuterium from natural water and for concentrating from natural lithium will become of importance comparable to the separation of U from natural uranium. 

Oose-sepaiation case. In many multistage isotope separation processes a — 1 < 1, so that / — 1 1 and 7 — 1 < 1. The gaseous diffusion process for separating uranium isotopes and the water distillation process for enriching deuterium are examples. 

Process requirements. Distillation of water for deuterium separation differs from all other industrial distillation processes in the extremely small difference in normal boiling point between the key components, O.T C between HjO and HDD. This, coupled with the very low natural abundance of deuterium, leads to an extraordinarily high reboil vapor ratio, so that the heat consumption per unit of DjO product is enormous. 

Discussion of processes for industrial separation of uranium isotopes cannot be as complete as the discussion of deuterium separation in Chap. 13. The detailed technology of the most economical and most promising processes is subject to security classification and to proprietary restrictions. Nevertheless, processes for enriching uranium can be described in sufficient detail to make their principles clear and to illustrate the similarities and differences between them and processes for separating isotopes of light elements. 

Two basic types of the LC separation processes can be distinguished. By adsorption chromatography on classic column or straight phase HPLC, usually ordinary (unlabeled) compounds elute first, i.e., the separation factor is less than unity. (a = i/ 2capacity factor). As mentioned above, deuterated or tritiated compounds are more polar and thus are more strongly bound to polar stationary phases. 

Since the stable isotopes that will be discussed are naturally occurring (the natural abundances are H, 0.015 C, 1.1 N, 036 0, 0.04 0, 0.2%), they are not m themselves alien to animal systems. However, questions of toxicity inevitably arise. Althou there are no radiation hazards associated with the isotopes themselves, the cotiunonly available deuterium compounds may contain a significant amount of tritium which is simultaneously enriched in the separation process. Carbon-14 does not currently present an analogous problem since most of the world supplies of carbon-13 use a geological source of carbon as feedstock for their separation processes. In the case of nitrogen and oxygen, with only very short-lived radioisotopes, the problem does not arise. 

Erdey-Gruz and Volmer and Butler/ to whom we owe a rate expression for charge transfer processes. Later, Frumkin " took into account the potential distribution at the electrode-electrolyte interface and its influence upon the process of discharge of ions. Experimentally observable quantities other than the Tafel constants have also been employed since then in elucidating the mechanism. For example, experimental observations of and attempts of theoretical interpretation of the electrolytic hydrogen-deuterium separation factor were presented by Topley and Eyring, Horiuti, " and others, " as briefly reviewed elsewhere. ... 

Since 1952, most of the tritium measured in the atmosphere originates from thermonuclear explosions. Like hydrogen, deuterium and tritium also exhibit molecular isomerism. Because of the important differences between the relative atomic masses of the three isotopes, their physical properties (e.g., density, enthalpy of vaporization) differ greatly. This allows an easier isotopic separation than for any other element. Several separation processes are used for the enrichment and separation of hydrogen isotopes. Most of these processes use isotopic exchange reactions (e.g., H D-H O or NH3-HD) and to a lesser extent fractional distillation and water electrolysis (e.g., Norway, Canada). 

DifficultSepa.ra.tions, Difficult separations, characterized by separation factors in the range 0.95 to 1.05, are frequentiy expensive because these involve high operating costs. Such processes can be made economically feasible by reducing the solvent recovery load (260) this approach is effective, for example, in the separation of m- and -cresol, Hnoleic and abietic components of tall oil (qv), and the production of heavy water (see Deuteriumand TRITIUM, deuterium). 

Distillation of Hquid hydrogen as a method for separating deuterium received early consideration (10,58) because of the excellent fractionation factor that can be attained and the relatively modest power requirements. The cryogenic temperatures, and the requirement that the necessarily large hydrogen feed be extremely pure (traces of air, carbon monoxide, etc, are soHds at Hquid hydrogen temperature) have been deterrents to the use of this process (see... 

In this method, each gas is produced in a separate compartment so they have high purity. In this process, deuterium oxide, D20, is electrolyzed more slowly so the water becomes enriched in the heavier isotope. The other electrolytic process that produces hydrogen is the electrolysis of a solution of sodium chloride. 

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