nuclear fuel cycle
Think of nuclear fuel not as a one-time tank of gasoline but as a long supply chain with a beginning, a middle, and a stubborn tail — from rock in a mine to a glowing fuel pellet in a reactor to radioactive waste that must be kept safe for a very long time. That whole journey of uranium (and the plutonium made along the way) is the nuclear fuel cycle, and it is held together by a great deal of inorganic chemistry.
The front end is chemistry of separation and conversion. Uranium ore is dissolved and purified, usually through the uranyl ion, into 'yellowcake' (U3O8). Because natural uranium is over 99 percent uranium-238 and only about 0.7 percent the fissile uranium-235, the next step is enrichment: the uranium is converted to uranium hexafluoride UF6, a compound chosen precisely because it turns to gas just above room temperature, and the slightly lighter U-235-bearing molecules are concentrated by centrifuge. The enriched uranium is then turned back into solid uranium dioxide UO2 and pressed into fuel pellets. In the reactor, U-235 fissions to release energy, while some U-238 captures neutrons and becomes plutonium-239, which also fissions and contributes power. At the back end, the spent fuel is intensely radioactive; it can either be stored and disposed of (the 'once-through' cycle) or chemically reprocessed — separating recoverable uranium and plutonium from the fission-product waste, the famous job of the PUREX process, which exploits the actinides' different oxidation states.
Why it matters is the whole debate over nuclear power. The fuel cycle is where chemistry, engineering, economics, and security all collide: reprocessing recovers fuel but also separates weapons-usable plutonium; the long-lived actinide waste is the central disposal problem; and enrichment technology is the same whether the goal is fuel or a bomb. The honest framing belongs to this glossary's scope: here we care about the inorganic chemistry — the uranyl purification, the choice of volatile UF6, the redox separations of PUREX — and treat the nuclear physics of fission only as the reason these chemical steps exist.
The PUREX reprocessing of spent fuel is pure actinide redox chemistry: the spent fuel is dissolved in nitric acid, then an organic extractant (tributyl phosphate) pulls out uranium(VI) and plutonium(IV) together; reducing the plutonium to Pu(III), which the extractant no longer holds, lets it drop back into the water and part company from the uranium.
PUREX separates U from Pu by changing plutonium's oxidation state.
The choice of uranium hexafluoride for enrichment is a piece of clever chemistry, not an accident: fluorine has only one isotope, so every mass difference between UF6 molecules comes from the uranium alone, and UF6 conveniently becomes a gas just above room temperature.