PUREX

PUREX, short for Plutonium-Uranium Extraction, is a chemical method used to reprocess spent nuclear fuel to recover uranium and plutonium for reuse in nuclear reactors and, historically, for weapons production. It is the most widely used reprocessing technology in civilian nuclear fuel cycles. The process centers on solvent extraction with tributyl phosphate (TBP) dissolved in a hydrocarbon diluent.

Spent fuel is first dissolved in nitric acid to form an aqueous phase containing uranium, plutonium, fission products, and other actinides. In the organic phase, TBP forms stable complexes with uranyl and plutonium nitrates, co-extracting uranium and plutonium from the aqueous solution. The loaded organic phase is then scrubbed to remove impurities, after which the two elements are separated by selective redox steps and washings. A typical sequence uses reduction-oxidation chemistry to move plutonium between the organic and aqueous phases, allowing uranium to be recovered in one stream and plutonium in another. Uranium is usually stripped from the organic phase with a dilute acid to yield a uranyl nitrate solution, while plutonium is subsequently stripped and converted to a plutonium nitrate product.

Historically developed in the mid-20th century, PUREX became the standard method for reprocessing in many facilities worldwide, including civilian and defense programs. It remains the baseline technology for recovering uranium and plutonium from spent fuel, though variations and enhancements have been introduced to improve safety, efficiency, and proliferation resistance.

Safety and regulatory considerations are central to PUREX, given its radiological hazards, chemical toxicity, and the potential for plutonium diversion. Modern plants emphasize containment, criticality safety, waste management, and safeguards compliance.