PUREX process
The PUREX process is a physico-chemical process in the reprocessing of spent fuel assemblies for separating the contained fissile materials of uranium and plutonium from the no longer usable radioactive waste materials is used. The abbreviation PUREX stands for " P lutonium- U ranium R ecovery by ex traction".
In principle, the PUREX process is a form of extraction (more precisely the solvent countercurrent extraction ) in which an aqueous phase (fuel solution ) and an organic phase ( extractant ) are brought into close contact and then separate from each other again. Serves as an extracting agent organophosphate ( tri-n-butyl-phosphate , abbreviation: TBP), with 70% of the C 12-14 - alkanes (usually kerosene is) diluted. This is why the extractant is also called TBP-30 for short.
During reprocessing, the fuel rods are cut and the fuel and all its components are dissolved in hot nitric acid . The TBP-30 then selectively dissolves the nitrates of uranium and plutonium from the nitric acid fuel solution with complex formation , while the nitrates of the fission products remain in the aqueous phase. In order to achieve the highest possible extraction rates, the countercurrent liquids must be mixed well with one another. The TBP and the aqueous phase then automatically separate from one another, so that the organic phase loaded with uranium and plutonium and the aqueous phase in which the nitrates of the cleavage products are located can easily be separated from one another.
Since the separation effect of a single extraction step is not sufficient to achieve the required degree of purity , this process is carried out repeatedly in mixing devices which are arranged one behind the other. As mixers come pulse columns or mixer-settlers used.
See also
literature
- KernEnergie Information Circle: Basic knowledge of nuclear energy. April 2003, ISBN 3-926956-44-5
- Friedrich-Karl Pickert, Hans-Jürgen Zech: Fuel cycle. German Atomic Forum, 1981, ISBN 3-922798-03-4
Web links
- Refining Uranium by the PUREX Process Pictures and sequence of a PUREX process at laboratory level (2009)