Process principle for the separation of fission products from the fuels uranium and plutonium as exemplified by the PUREX process. The aqueous solution of fuel and fission products is placed in homogenous contact with an organic solution which is insoluble in water. The organic solvent in the PUREX process consists of a mixture of tributylphosphate (TBP) and kerosene. In extraction according to the PUREX process, advantage is taken of the fact that the substances uranyl nitrate and plutonium nitrate included in the aqueous solution are readily soluble in the mixture of TBP and kerosene whereas the fission products in this organic phase are practically insoluble. The separation is effected in extractors, i.e. apparatuses in which the two phases are collided in countercurrents, intensively mixed and separated again in settling chambers.

Extraction principle