Deuterium separation processes water distillation

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. 

A rough idea of the requirements of the water distillation process may be derived from a representative separation factor of 1.05. The minimum number of theoretical plates (Wmin) needed to enrich deuterium from the natural concentration of xp = 0.000149 atom fraction to product concentration of Xp = 0.998 is... 

The electrolysis is continued until 90% of the liquid has been converted into O2 and H2 most of the residual liquid is then neutralized with CO2, and the water distilled and added to the remaining electrol5fie. This process is repeated to give <99.9% D2O. In the later stages of the separation, the gas evolved at the cathode is burned to yield partially enriched deuterium oxide that can be electrolysed further. Cheap electrical power is, of course, essential for the economic concentration of D2O by this method. 

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). 

This chapter describes processes most suitable for separation of isotopes of light elements on an industrial scale. Principal emphasis is on separation of deuterium through production of heavy water, but some information on separation of isotopes of other light elements is also given. Processes to be discussed include distillation, electrolysis, and chemical exchange. 

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