The above both assume no development of technology that allows waste to be re-used as fuel (which I've seen discussed, but have no idea if is actually practical)
There are two things you can do:
1. Process part-used fuel and extract the unused fuel from the fission products to make new fuel (i.e. concentrate it). This is a good thing and a bit of a no-brainer ... but some of those byproducts are toxic, dangerous to handle, and require careful (and costly) storage and disposal.
2. Incorporate some isotope in the fuel that turns into (maybe another sort of) fuel as the reactor runs (as 238U is added to Uranium fuel in a fast breeder reactor so that as the 235U is used up to generate power the 238U turns into 239Pu (which is also a fissile material and so can be used as a nuclear fuel)).
The trouble with this is that Plutonium and its decay byproducts are rather more dangerous than Uranium and its byproducts. When the nuclear industry was young the production of Plutonium was seen as a good thing because it could be used as a fuel and in the manufacture of atomic bombs. Nowadays ... not so much.
Biting the hand that feeds IT
