Publication Laka-library:
The enrichment of radioactive isotopes by thermal diffusion (1956)
| Author | A.E.De Vries |
| Date | September 1956 |
| Classification | 6.01.2.25/04 (URANIUM - ENRICHMENT) |
| Front | 
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From the publication:
INTRODUCTION The properties of isotopes are very similar. The separation of two or more isotopes is therefore a difficult matter and the change in concentration ratio, caused by one elementary process like distillation, electrolysis, diffusion etc. is very small. Thus, to get a significant change in concentration ratio the process has to be repeated several times. This is usually done in one apparatus of which the active part therefore has a rather great volume. The amount of material necessary in order to get a separation, i.e. the quantity filling the active part of the apparatus, is called the hold-up. As the hold-up itself cannot be separated it is not negligible in the case of small samples. Thermal diffusion is one of the most advantageous methods in this respect because only gases are used. The elementary effect is multiplied by means of a column, in a way analogous to the way one uses rectification columns in order to repeat the elementary distillation process. The only drawback in the application of thermal diffusion columns is, that the diameter is coupled to the pressure of the gas in such a way that the hold-up is more or less fixed. Clusius, who specialises in separating isotopes, that is producing stable isotopes in more than 99% purity, performs these separations quantitatively by adding a compound X to the mixture of isotopes A and B. While A and B concentrate at the top and at the bottom of the column respectively, X is chosen such that it concentrates somewhere in the column. As in thermal diffusion gases ordinarily concentrate according to their masses, the lighter molecule at the top and the heavier one at the bottom, this means that as a rule the added compound X must have a mass intermediate to that of A and B.
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