PUREX

The PUREX process is a physico- chemical process, which is used in the reprocessing of spent fuel to separate the fissile material contained uranium and plutonium from the unusable radioactive waste. The abbreviation PUREX stands for " Plutonium Uranium Recovery by Extraction".

In principle, the PUREX process is a form of extraction ( specifically the solvent countercurrent extraction ), in which an aqueous phase ( fuel solution ) and an organic phase ( extractant) are brought into close contact and then issue another again. Serves as an extractant, a phosphoric acid ester ( tri-n -butyl phosphate, short name: TBP), which is diluted with 70 % kerosene. Therefore, the extractant is also shortly called TBP 30.

When reprocessing the fuel rods are cut and the fuel dissolved with all components in hot nitric acid. The TBP -30 then triggers the formation of complexes selectively nitrates of uranium and plutonium from the nitrate fuel solution out while the nitrates of fission products remain in the aqueous phase. In order to achieve the highest possible extraction rates to each other countercurrently out liquids must be mixed well together. Subsequently, TBP and the aqueous phase set again automatically from one another, so that the uranium and plutonium -laden organic phase and the aqueous phase in which the nitrates of fission products are, can be easily separated from each other.

Since the separation effect of a single extraction step is not sufficient to achieve the required degree of purity, this operation is repeatedly carried out in the mixing apparatus, which are arranged one behind the other. As mixers come pulse columns or mixer-settlers are used.