PUREXmenetelmällä

PUREX menetelmällä, often referred to as the Plutonium Uranium Reduction Extraction process, is a hydrometallurgical technique used for reprocessing spent nuclear fuel. It is the most common method employed worldwide for recovering uranium and plutonium from irradiated nuclear reactor fuel. The process is designed to separate these valuable actinides from the fission products and other transuranic elements present in spent fuel.

The PUREX process operates on the principle of solvent extraction. Spent fuel is first dissolved in nitric acid. This acidic solution is then contacted with an organic solvent, typically tributyl phosphate (TBP) dissolved in a diluent like kerosene or dodecane. Uranium and plutonium, in their hexavalent or tetravalent oxidation states, respectively, are preferentially extracted into the organic phase, while the fission products and other actinides remain in the aqueous nitric acid phase.

Following the initial extraction, a series of further separation and purification steps are carried out. The uranium is typically reduced to its tetravalent state, allowing it to be stripped back into an aqueous phase, separate from the plutonium. The plutonium is then stripped from the organic phase into an aqueous solution. Subsequent purification steps are employed to achieve the desired purity of both uranium and plutonium for reuse in fuel fabrication or for other purposes. The PUREX process is highly effective but requires stringent safety measures due to the radioactivity of the materials involved and the chemical hazards associated with the solvents and acids used. Waste streams generated by the process also require careful management and disposal.