Isotope separation
Isotope separation is the general term for processes with which the isotopes contained in a natural chemical element can be separated from one another. It does not have to be radioisotopes .
The separation process practically never results in a pure isotope, but the process divides the original amount of substance into two partial amounts (fractions), one of which is enriched in the isotope of interest and the other is correspondingly depleted . By repeating the respective process several times with the enriched subset, higher degrees of enrichment can be achieved.
The isotopes of one and the same element hardly differ from one another in chemical terms. The isotope separation processes are therefore almost always based on physical processes. The only exceptions to this are very light elements such as hydrogen and lithium , where the relative mass difference of the atoms is so great that it becomes noticeable in the chemical behavior.
Procedure
The following methods can be used to separate isotopes:
- Mass spectrometry (for analytical purposes)
- Centrifugation with gas centrifuges
- Gas diffusion process based on the membrane process
- Separation nozzle process
- fractional distillation (e.g. mercury isotopes , heavy water )
- Electrolysis (e.g. enrichment of deuterium )
- Photochemically via the selective excitation of isotopes in a mixture with laser light , whereby the excited isotopes are more reactive and can be removed via subsequent reactions.
- Thermophoresis , thermal diffusion, Clusius and Dickel separating tube
Applications
By far the most important isotope separation in terms of quantity is uranium enrichment , the increase in the content of uranium-235 for the production of nuclear fuel for nuclear power plants . Lithium is also enriched with lithium-6 for nuclear weapons purposes. For nuclear fusion reactors also enriched lithium is needed in the in the long Blanket the fusion fuel tritium to erbrüten. Here it is also necessary to separate the hydrogen isotopes protium , deuterium and tritium from one another.
There are other applications of (almost) pure isotopes or isotopically enriched substances for research purposes. As part of the Avogadro project , mass standards are produced from silicon , which is highly enriched in silicon-28.
See also
Individual evidence
- ^ Römpp: Basislexikon Chemie, Georg Thieme Verlag 1998, ISBN 3-13-115711-9
- ↑ Hans Güsten: I sotopentrennung by laser photochemistry, chemistry in our time , the 11th year of birth 1977, No. 2, p. 33,. ISSN 0009-2851