[kwhitefoot]

Not really. The supply of economically extractable fissile material is limited in just the same way as any other mineral.

If energy prices rise then it will become worthwhile to extract, if they fall then it will be less so. Of course if the number of consumers rises this will also improve the viability of mining. According to this Wikipedia page: https://en.wikipedia.org/wiki/Uranium_mining_in_Australia, it is currently uneconomic to proceed with several mining projects.

Regardless of economic considerations fissile material is a finite resource although it could be that we will never reach the limit.

[Accujack]

Technically, yes.

In practical terms, however, switching nuclear reactors to use the Thorium fuel cycle would allow us to use a supply of fuel that would probably outlast human civilization.