PUREX is a nuclear reprocessing method which is the de facto standard aqueous method based on liquid-liquid extraction for the recovery of uranium and plutonium from used nuclear fuel. This process can be used to recover weapon-grade materials as well as reprocessed uranium from spent nuclear reactor fuel, and as such, its component chemicals are monitored. PUREX is an acronym standing for Plutonium and Uranium Recovery by Extraction. The PUREX process is a liquid-liquid extraction method used to reprocess spent nuclear fuel, in order to extract uranium and plutonium, independent of each other, from the fission products.