what are the processes involved in turning uranium into nuclear fuels?
In: Engineering
Uranium, or any other natural radioactive element, must be refined and (usually) “enriched” before being manufactured into fuel pellets or fuel rods. Refinement is the same as refining any metal ore. You remove the impurities, the non-metal parts, to get pure uranium oxide.
Enrichment is more complicated. There are ways you can “enrich” uranium (and other radioactive materials) by selectively keeping only the highly radioactive isotopes. This process works by turning the uranium into a gas by combining it with fluoride (uranium hexafluoride, UF6) and then running that gas through a centrifuge. Only uranium-235 is useful for most nuclear power applications. The rest is split up for other uses (including, for example, “depleted” uranium, which is still radioactive, but only very slowly decays.)
Once you have ~~mostly pure~~ a high enough concentration of uranium-235, it’s packed into pellets or rods, which are encased in zirconium alloys. Zirconium is used rather than steel or other metals because it doesn’t respond very much to the types of neutrons that interact with the U^235 inside the rod/pellet, and because it is resistant to corrosion or other forms of damage.
(You only need “mostly pure” U^235 if you want nuclear weapons. Nuclear reactors don’t need that much purity, and it would in fact be very dangerous to have the purity too high, as it would make an uncontrolled reaction, aka a nuclear explosion.)
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