It is an acronym standing for Plutonium-URanium EXtraction-- "de facto" standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel.
It is an acronym standing for Plutonium URanium EXtraction. PUREX is the "de facto" standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used ("spent ", or"depleted") nuclear fuel.