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Publicatie Laka-bibliotheek:
The enrichment of radioactive isotopes by thermal diffusion (1956)

AuteurA.E.De Vries
Datumseptember 1956
Classificatie 6.01.2.25/04 (URANIUM - VERRIJKING)
Voorkant

Uit de publicatie:

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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